Download Hi-Res ImageDownload to MS-PowerPointCite This:J. Am. Chem. Soc. 2020, 142, 45, 19189-19197
Guest-Controlled Incommensurate Modulation in a Meta-Rigid Metal–Organic Framework Material
- Jiangnan LiJiangnan LiDepartment of Chemistry, University of Manchester, Manchester M13 9PL, U.K.More by Jiangnan Li,
- Zhengyang ZhouZhengyang ZhouBNLMS, College of Chemistry & Molecular Engineering, Peking University, Beijing 100871, ChinaMore by Zhengyang Zhou,
- Xue Han ,
- Xinran ZhangXinran ZhangDepartment of Chemistry, University of Manchester, Manchester M13 9PL, U.K.More by Xinran Zhang,
- Yong Yan ,
- Weiyao LiWeiyao LiDepartment of Chemistry, University of Manchester, Manchester M13 9PL, U.K.More by Weiyao Li,
- Gemma L. SmithGemma L. SmithDepartment of Chemistry, University of Manchester, Manchester M13 9PL, U.K.More by Gemma L. Smith,
- Yongqiang ChengYongqiang ChengNeutron Scattering Division, Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United StatesMore by Yongqiang Cheng,
- Laura J. McCormick McPhersonLaura J. McCormick McPhersonAdvanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United StatesMore by Laura J. McCormick McPherson,
- Simon J. TeatSimon J. TeatAdvanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United StatesMore by Simon J. Teat,
- Mark D. FrogleyMark D. FrogleyDiamond Light Source, Harwell Science Campus, Oxfordshire OX11 0DE, U.K.More by Mark D. Frogley,
- Svemir RudićSvemir RudićISIS Facility, STFC Rutherford Appleton Laboratory, Chilton, Oxfordshire OX11 0QX, U.K.More by Svemir Rudić,
- Anibal J. Ramirez-CuestaAnibal J. Ramirez-CuestaNeutron Scattering Division, Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United StatesMore by Anibal J. Ramirez-Cuesta,
- Alexander J. BlakeAlexander J. BlakeSchool of Chemistry, University of Nottingham, Nottingham NG7 2RD, U.K.More by Alexander J. Blake,
- Junliang Sun*Junliang Sun*[email protected]BNLMS, College of Chemistry & Molecular Engineering, Peking University, Beijing 100871, ChinaMore by Junliang Sun,
- Martin Schröder*Martin Schröder*[email protected]Department of Chemistry, University of Manchester, Manchester M13 9PL, U.K.More by Martin Schröder, and
- Sihai Yang*Sihai Yang*[email protected]Department of Chemistry, University of Manchester, Manchester M13 9PL, U.K.More by Sihai Yang
Copyright © 2020 American Chemical Society
ACS AuthorChoice with CC-BY license
Supporting Info (6)»
Abstract
Structural transitions of host systems in response to guest binding dominate many chemical processes. We report an unprecedented type of structural flexibility within a meta-rigid material, MFM-520, which exhibits a reversible periodic-to-aperiodic structural transition resulting from a drastic distortion of a [ZnO4N] node controlled by the specific host–guest interactions. The aperiodic crystal structure of MFM-520 has no three-dimensional (3D) lattice periodicity but shows translational symmetry in higher-dimensional (3 + 2)D space. We have directly visualized the aperiodic state which is induced by incommensurate modulation of the periodic framework of MFM-520·H2O upon dehydration to give MFM-520. Filling MFM-520 with CO2 and SO2 reveals that, while CO2 has a minimal structural influence, SO2 can further modulate the structure incommensurately. MFM-520 shows exceptional selectivity for SO2 under flue-gas desulfurization conditions, and the facile release of captured SO2 from MFM-520 enabled the conversion to valuable sulfonamide products. MFM-520 can thus be used as a highly efficient capture and delivery system for SO2.
Introduction
ARTICLE SECTIONS
Metal–organic framework (MOF) materials are synthetic porous materials constructed from bridging metal centers and organic ligands.(1) MOFs can be either rigid(2) or flexible(3) depending upon the metal–ligand coordination combination, framework topology, and organic functionality. Rigid MOFs retain a well-defined framework structure and pore interior against external variables (e.g., temperature, pressure, and guest inclusion), making them useful for the separation and purification of substrates.(2,4) In contrast, flexible MOFs can undergo reversible breathing transitions between typically two well-defined periodic crystal structures. One form is often described as narrow-pored and the other form is described as large-pored, and these two forms therefore show different porosities and properties.(5−10)
Figure 1 illustrates various structural responses to guest binding within a MOF lattice. Breathing and metastable MOFs show two prevailing types of phase transitions, namely, periodic-to-periodic and periodic-to-amorphous. Beyond that, there is also an intriguing class of mesoporous MOFs, allowing the formation of adsorbate superlattices based upon long-range collective adsorbate–adsorbate interactions.(11) The periodic-to-aperiodic transition observed here for MFM-520 represents a new type of framework flexibility in crystalline porous solids. Superspace group theory(12) has been used to describe the commensurate structure of crystalline zeolite SSZ-57(13) in higher-dimensional space, and this has been applied to interpret the incommensurate modulated structures described here.
Figure 1
Figure 1. Representation of structural transitions in various types of MOFs upon guest inclusion and removal. MOFs and guest molecules are shown by solid lines and shaded spheres, respectively. (a) Rigid MOF showing full retention of the framework structure on gas adsorption and desorption. (b) Flexible MOF showing reversible framework breathing between a narrow-pore phase and a large-pore phase. (c) Metastable MOF showing irreversible framework amorphization. (d) Mesoporous MOF showing the formation of superlattices of adsorbates. (e) Meta-rigid MOF, MFM-520, showing reversible incommensurate modulation of the framework structure on going from (top to bottom) MFM-520·H2O (top) to MFM-520 to MFM-520·CO2 (CO2 represented by blue spheres) to MFM-520·SO2 (SO2 represented by green spheres) (bottom).
Experimental Section
ARTICLE SECTIONS
Synthesis of MFM-520
All reagents were used as received from commercial suppliers without purification. The synthesis of H4L (4,4′-bipyridine-2,6,2′,6′-tetracarboxylic acid) and {[Zn2(L)·4H2O]}∞ (MFM-520·H2O) was carried out using previously reported methods.(14)
In Situ Synchrotron Single-Crystal X-ray Diffraction and Structural Characterization
In situ synchrotron X-ray single-crystal diffraction data were collected on beamline 11.3.1 of the Advanced Light Source using monochromated radiation [λ = 0.7749(1) Å]. After data collection for as-synthesized sample MFM-520·H2O, the same single crystal (0.10 × 0.05 × 0.05 mm3) was placed in a capillary gas handling cell and evacuated in situ under dynamic vacuum and a stream of N2 at 340 K centered on the capillary for 4 h. The single-crystal diffraction data of dehydrated MFM-520 were collected at 290 K. Upon loading of CO2 into MFM-520 at 1.0 bar and 290 K, three diffraction data sets were collected at 270 K to examine the possible dynamic behavior of the structural relaxation (i.e., adsorbate–adsorbent equilibrium and change in the modulation vector). The single crystal was then reactivated under vacuum and heating to remove all adsorbed gases. The in situ single-crystal diffraction data for SO2-loaded MFM-520 were collected using the same method as for the CO2-loaded sample.
The influence of temperature on the periodic-to-aperiodic phase transition was monitored by collecting in situ single-crystal diffraction data for dehydrated MFM-520 at 180–350 K on a Rigaku Oxford XtaLAB diffractometer using Mo-Kα radiation. No change in the modulation vectors of MFM-520 was observed between 180 and 350 K (Table S2), confirming the negligible impact of temperature on the modulation vector of MFM-520.
To examine the reversibility of the periodic-to-aperiodic phase transition observed in MFM-520, a single crystal of rehydrated MFM-520·H2O, formed by the treatment of dehydrated MFM-520 with water, was studied by single-crystal diffraction at 180 K. This experiment confirms the absence of satellite reflections of the rehydrated sample (Figure S6).
In the (3 + 2)D incommensurately modulated structure, each parameter of modulation can be expanded as a Fourier series using eq 1:
(1)where x4 = q1r μ + t, x5 = q2r μ + u, and t and u are initial phases in the range of 0 to 1. The real structural parameters can be expressed as eq 2:
(2)
(1)where x4 = q1r μ + t, x5 = q2r μ + u, and t and u are initial phases in the range of 0 to 1. The real structural parameters can be expressed as eq 2:(2)The average structure parameters paveμ were determined by direct methods and least-squares refinements, and the modulations were refined globally using free variables. All non-hydrogen atoms were refined anisotropically, and hydrogen atoms were placed using a riding model. Given the complexity of the structure, soft constraints on the bond length/angle to both host and guest were applied in the final stage of refinement. All refinements of the crystal structures were performed on the JANA2006 software platform.(15)
Gas Adsorption Isotherms
Gravimetric sorption isotherms for N2, CO2, SO2, CH4, CO, and O2 were recorded at various temperatures on a Hiden Isochema IGA-003 system under high vacuum (10−10 bar) produced by a turbo pumping system. Temperatures were maintained using a programmed water bath. Ultra-pure research grade gases (99.999%) were purchased from BOC or Air Liquide. In a typical gas adsorption experiment, 50 mg of acetone-exchanged MFM-520 was loaded into the IGA system and activated at 393 K under dynamic high vacuum (10–10 bar) for 1 day to give fully desolvated MFM-520. BET surface areas and porosity data were obtained from N2 isotherm data at 77 K.
Gas Separation by Breakthrough Experiments
In the breakthrough experiments, the flow rate of the entering gas mixture was maintained at 50 mL min–1, and the gas concentration, C, of SO2, CO2, and N2 at the outlet was determined by mass spectrometry and compared with the corresponding inlet concentration C0, where C/C0 = 1 indicates complete breakthrough. Breakthrough separation of SO2/CO2 was conducted using a mixture containing SO2 (2500 ppm) and 15% CO2 (v/v) diluted in He through a fixed bed packed with MFM-520 at 298 and 318 K and 1 bar at a flow rate of 50 mL min–1. The final results have been converted to dimensionless plots as shown in Figure 4.
The fixed bed of MFM-520 for the adsorptive removal of low concentrations of SO2 under wet conditions was first exposed to a flow of 1.5% H2O in He until the breakthrough of water. A stream of 0.25% SO2 (i.e., 2500 ppm) diluted in He was then flowed through the packed bed of MFM-520 (approximately 1 g) at a total flow rate of 50 mL min–1 at 298 K and 1.0 bar. Dimensionless breakthrough plots were calculated with the following parameters: bed diameter, d, (7 mm); bed length, L, (120 mm); bed volume (5.0 mL); sample mass (1.0 g); sample framework density (1.55 g/cm3); and flow rate (50 mL/min). The sample occupied a volume of 0.65 mL (assuming 100% purity and no framework collapse), and thus the fractional porosity of the fixed bed, ε, was calculated to be 0.87. The superficial gas velocity, u, at the entrance of the bed corresponded to 0.22 m/s, and the characteristic contact time between the gas and the sample of MFM-520 corresponded to εL/u = 4.82 s. The dimensionless time, τ, was obtained by dividing the actual time, t, by the contact time between the gas and the MFM-520 sample, εL/u (i.e., τ = tu/εL).
Inelastic Neutron Scattering (INS) Experiments
INS spectra were recorded on the TOSCA spectrometer at the ISIS Facility at the STFC Rutherford Appleton Laboratory. TOSCA is an indirect geometry instrument that provides a wide spectral range (−25 to 4000 cm–1) with resolution optimized in the 50–2000 cm–1 range. In this region, TOSCA has a resolution of 1.25% of the energy transfer. The instrument is composed of 130 3He detectors in forward and backscattering geometries located 17 m downstream from a 300 K Gd poisoned water moderator. A temperature of 10 ± 0.2 K was maintained during data collection by two He closed-cycle refrigerators with 30 mbar He as an exchange gas.
A sample of MFM-520 was activated at 120 °C and 1 × 10–7 mbar for 1 day and then placed into an 11-mm-diameter vanadium sample can, which was loaded into a helium closed-cycle refrigerator (CCR) cryostat and cooled to 10 K for data collection. Defined amounts of CO2 and SO2 were introduced by warming the sample to 290 K, and the gas was dosed volumetrically from a calibrated volume. The gas-loaded sample was then cooled to 10 K over a period of 2 h to ensure good mobility of adsorbed gases within the crystalline MFM-520. The sample was retained at 10 K for an additional 30 min before data collection to ensure thermal equilibrium.
Density Functional Theory (DFT) Calculations
DFT calculations were performed using CASTEP (version 19.11).(16) The generalized gradient approximation (GGA) as implemented by Perdew–Burke–Ernzerhof (PBE) was used to describe the exchange-correlation interactions. On-the-fly norm-conserving pseudopotentials were employed to account for the effects of core electrons with the default energy cutoff (∼870 eV) for the plane-wave basis. The unit cell configuration determined by XRD was used as the initial structure for the simulations. The atomic coordinates of the guest molecules were first relaxed by molecular dynamics at 300 K for 10 ps to find the optimal binding sites that are not constrained by symmetry (the MOF structure was fixed during this relaxation). The final configurations (including both the MOF and the guest molecules) were further relaxed using the conjugate gradient method to allow minimization of the potential energy and the interatomic forces. The energy tolerance for the electronic structure calculations was 5 × 10–10 eV, and the energy tolerance for ionic relaxation was 5 × 10–9 eV. The tolerance for the interatomic forces was 1 meV/Å. After convergence, the dynamic matrix was obtained using the linear response method, from which the phonon frequencies and vibrational modes were calculated. The electronic structure calculations were performed on a 3 × 3 × 1 Monkhorst–Pack mesh, and the dynamic matrix was calculated directly on the same mesh and then interpolated on a 7 × 7 × 3 Monkhorst–Pack mesh. The IR intensities were directly computed with CASTEP.(16) The OClimax software(17) was used to convert the DFT-calculated phonon results to the simulated INS spectra.
Conversion of Captured SO2
MFM-520 was activated at 393 K under vacuum overnight. The sample was cooled, and MFM-520 was dosed with SO2 for 1 h to reach adsorption equilibrium. Morpholin-4-amine (128.0 mg, 1.25 mmol) and SO2@MFM-520 (357 mg, equivalent to 1.18 mmol of SO2) were suspended in CH3CN (3 mL) and stirred for 1 h. 4-Methoxy-aryldiazonium tetrafluoroborate (55.0 mg, 0.25 mmol) in CH3CN (1 mL) was added dropwise to the above suspension, and the mixture was stirred at room temperature for 1 h. The mixture was filtered, and the filtrate was evaporated. NMR spectroscopy and preparative thin layer chromatography (TLC) were used to quantify the conversion of 4-methoxy-aryldiazonium tetrafluoroborate and the yield of the sulfonamide. Benzenaldehyde was used as an internal standard.
Results and Discussion
ARTICLE SECTIONS
MFM-520·H2O, [Zn2(L)]·H2O (H4L= 4,4-bipyridyl-3,3′,5,5′-tetracarboxylic acid), adopts a 3D open-framework structure comprising square-based pyramidal five-coordinate Zn(II) centers bridged by the tetracarboxylate linker(14) (Figure S1). Each Zn(II) center binds to the N(pyridyl)-donor of L4– along the c axis, and four bridging carboxylates propagate the structure along the diagonals of the ab plane, thus defining an unusual and rigid sqp topology.(18) MFM-520·H2O exhibits bow-tie-shaped pores with dimensions of 6.6 × 4.0 Å2 which are filled with guest water molecules which assemble into 1D helical chains along the [110] direction. These chains are stabilized by strong intermolecular hydrogen bonds [Ow···Ow = 2.934(11), 2.887(11) Å] (Figure S2). The water molecules are also hydrogen bonded to the framework oxygen center of the ligand [Ow···O2 = 3.064(9) Å] (Figure 2a-IV), inducing the overall structure to crystallize in tetragonal space group P42212 [a = b = 7.0211(6), c = 19.9558(15) Å]. These complementary host–guest and guest–guest hydrogen bonds stabilize the periodic structure of MFM-520·H2O and restrict its freedom for structural relaxation.
Figure 2
Figure 2. Column I: views of in situ synchrotron X-ray diffraction images of the hk0 plane. Column II: views of the corresponding crystal structures of MFM-520 as a function of guest inclusion/removal. 8 × 8 × 2 means the unit cell of the modulated structure is 8 times that of the average structure along the a and b axes and 2 times along the c axis; 7 × 7 × 2 means the unit cell of the modulated structure is 7 times that of the average structure along the a and b axes and 2 times along the c axis. Column III: details of the structure shown in the red box in column II. Column IV: molecular details of host–guest interactions. The MOF framework, zinc, oxygen, carbon, and sulfur are shown in blue, green, red, gray, and yellow, respectively. Bond distances are shown in Å. (a) MFM-520·H2O, (b) MFM-520, (c) MFM-520·CO2, and (d) MFM-520·SO2. A comparison of all in situ synchrotron X-ray diffraction images of the hk0.5 and hk1 planes is shown in Figure S5. The reflection conditions of MFM-520·H2O are 00l: l = 2 × integer and h00: h = 2 × integer. According to superspace group theory,(12) there is a supercentered setting with as = a, bs = b, cs = 2c, Q1 = α(as* + bs*), and Q2 = α(−as* + bs*), which is equivalent to the basic setting a, b, c, q1 = α(a* + b*) + 0.5c*, and q2 = α(−a* + b*) + 0.5c*. Because the tables of (3 + 2)D superspace groups(19) provide only reflection conditions with supercenterd settings, we transformed the basic setting to supercentered settings to determine the reflection conditions. With the supercentered setting, the hk0, hk0.5, and hk1 planes are transformed to HK0, HK1, and HK2, respectively (Figure S5). The reflection conditions of MFM-520, MFM-520·CO2, and MFM-520·SO2 are HKLMN: L + M + N = 2 × integer, HK0MN: M = 2 × integer, HHLM0: L = 2 × integer, HH̅L0N: N = 2 × integer, H0LMM̅: 2H + L + 2M = 4 × integer, and 0KLMM: 2K + L + 2M = 4 × integer, corresponding to (3 + 2)D superspace group 136.2.69.10, adopting the symbol P42/mnm(α, α, 1/2)00qs(−α, α, 1/2)0sq0 with basic settings.
On heating MFM-520·H2O at 340 K under dynamic vacuum, additional satellite reflections appear at positions defined by modulation vectors 0.1240(3)(a* + b*) + 0.5c* and 0.1240(3)(−a* + b*) + 0.5c* on the plane diffraction patterns (Figure 2b-I), indicating that an intriguing structural transition has occurred. The loss of guest water molecules removes the stabilizing network of hydrogen bonding and thus creates voids and freedom for the [ZnO4N] polyhedra to relax. Bond distances Zn–N1, Zn–O1, and Zn–O2 in MFM-520·H2O [2.002(6), 2.214(6), and 1.959(5) Å, respectively] change with the loss of water and lie in ranges of 2.07–2.12, 2.25–2.58, and 1.79–2.11 Å, respectively, for dehydrated MFM-520. This is accompanied by the modulation of the electron density at the Zn(II) center with the formal oxidation state ranging from 1.70(10) to 1.93(10) in MFM-520 as determined by bond valence sum (BVS) calculations(20) for the different Zn(II) centers (Figure 3a). In contrast, those in MFM-520·H2O have the same charge of 1.974(14).
Figure 3
Figure 3. Maps of the bond valence sum (BVS) analyses of the oxidation state of Zn(II) centers as a function of the modulation vector u and t in (a) MFM-520, (b) MFM-520·CO2, and (c) MFM-520·SO2. The coordination geometries of the [ZnO4N] polyhedra for the lowest and highest (highlighted in blue and brown, respectively) BVS analysis maps for MFM-520, MFM-520·CO2, and MFM-520·SO2 are illustrated above the contour maps. Bond distances are in Å. BVS parameters Rij(Zn–O), b0(Zn–O), Rij(Zn–N), and b0(Zn–N) are 1.704, 0.37, 1.72, and 0.37 Å, respectively. MFM-520·H2O has a periodic structure and shows no modulation by BVS analysis; the formal oxidation state of all Zn(II) centers in MFM-520·H2O is 1.974(14).
The resulting structure of dehydrated MFM-520 is aperiodic in 3D space but periodic in (3 + 2)D space, and the two modulated vectors (q1 and q2) are projections of the additional two dimensions along the three directions of 3D reciprocal space. Importantly, all satellite reflections of dehydrated MFM-520 disappear on rehydration to MFM-520·H2O, demonstrating the reversibility of this periodic-to-aperiodic phase transition (Figure S6). No change was observed in the modulation vectors for dehydrated MFM-520 between 180 and 350 K (Table S2). Interestingly, for the periodic-to-aperiodic phase transitions in inorganic materials, metal alloys, and organic compounds, which are induced by changes in temperature and electric and magnetic fields,(21−24) the periodic-to-aperiodic transition observed in MFM-520 is controlled by host–guest interactions, representing the first example of such a phenomenon for an inorganic–organic hybrid material or porous solid.
Dehydrated MFM-520 displays a BET surface area of 313 m2 g–1 and a pore volume of 0.146 cm3 g–1,(14) and single-component adsorption isotherms for SO2, CO2, CH4, CO, O2, and N2 in MFM-520 have been recorded at 273–318 K up to 1.0 bar (Figure 4a, Figures S9–S12). The excess adsorption uptake of SO2 at 298 K and 1.0 bar is 3.38 mmol g–1, which is higher than those of CO2, CH4, CO, O2, and N2 (0.77, 0.71, 0.36, 0.19, and 0.18 mmol g–1, respectively). More significantly, at low pressure (e.g., 0.01 bar, 298 K), where all other gases show negligible uptakes (0.09 mmol g–1 for CO2; <0.01 mmol g–1 for CH4, CO, O2, and N2), MFM-520 displays a notably higher isothermal uptake of SO2 (1.66 mmol g–1), accompanied by fast adsorption kinetics typically within minutes (Figures S13 and S14). The static SO2 uptake of MFM-520 is comparable to those of the best-behaving sorbents but is lower than the dynamic SO2 uptake of SIFSIX-2-Cu-i,(25) which possesses very narrow pores (Table S3). Often, there is a trade-off between high adsorption at low pressure and difficulties in the complete regeneration of narrow-pored MOFs. Facile regeneration of the SO2-saturated MFM-520 can be readily achieved solely via a pressure swing, and no loss of SO2 adsorption capacity or crystallinity of MFM-520 was observed after 75 cycles of SO2 adsorption–desorption (Figure 4b).
Figure 4
Figure 4. Gas adsorption, selectivity, stability, thermodynamic, spectroscopy, and dynamic separation data. (a) Adsorption isotherms for SO2, CO2, CH4, CO, O2, and N2 in MFM-520 at 298 K (solid symbols, adsorption; open symbols, desorption). (b) Comparison of the SO2 adsorption capacity of MFM-520 over 75 cycles at 298 K. (c) Variation of isosteric heats of adsorption (Qst) and adsorption entropy (ΔS) for SO2 and CO2 uptake in MFM-520. (d) Comparison of experimental FTIR spectra for bare and CO2- and SO2-loaded MFM-520. (e) Comparison of DFT-calculated FTIR spectra for bare and CO2- and SO2-loaded MFM-520. (f) Comparison of the difference plots for experimental and DFT-calculated INS spectra of D2O-, CO2-, and SO2-loaded MFM-520 (black, experiment; red, calculation). The discrepancies, particularly for the lattice modes at low energy (<200 cm–1), are due to the limitation that DFT simulations can be conducted only on average unit cells, which does not take the incommensurate modulation into consideration. (g) Dimensionless breakthrough plots for SO2/N2 mixtures under dry (solid lines) and humid (dashed lines) conditions. Dry conditions: 2500 ppm SO2, 99.75% N2, total flow rate 50 mL min–1. Wet conditions: 1.5% H2O, 2500 ppm SO2, 98.25% N2, total flow rate 50 mL min–1. (h) Dimensionless breakthrough plots for SO2/CO2 mixtures at 298 K (15% CO2, 2500 ppm SO2, 84.75% He, total flow rate 50 mL min–1). (i) Dimensionless breakthrough plots for cyclic SO2 adsorption under both dry and humid conditions. Dry conditions: 2500 ppm SO2, 99.75% He, total flow rate 50 mL min–1. Wet conditions: 1.5% H2O, 2500 ppm SO2, 98.25% He, total flow rate 50 mL min–1. For experiments under humid conditions, the bed was first exposed to a flow of 1.5% H2O in He until the breakthrough of water.
Further analysis of the adsorption thermodynamics of MFM-520 reveals that the isosteric heat of adsorption (Qst) for CO2 is 32–48 kJ mol–1 and the entropy of adsorption (ΔS) decreases steadily with increasing surface coverage, consistent with the expected ordering of adsorbed CO2 molecules in MFM-520. In comparison, Qst for SO2 adsorption reaches ∼120 kJ mol–1 at low surface coverage and decreases gradually to 60 kJ mol–1 with increasing loading of SO2. The calculated value of Qst is consistent with the calorimetric measurements of 43 and 96 kJ mol–1 for CO2 and SO2 adsorption, respectively (Figures S15 and S16). The higher value of Qst for SO2 uptake is consistent with the expected stronger interaction between the framework and SO2 compared with CO2. However, the ΔS for SO2 adsorption increases steadily from an initial −260 to −135 J K–1 mol–1 with increasing loading of SO2. This observation is opposite to the prevailing understanding of gas adsorption in porous materials, where ordering of the gas molecules results in a decrease in ΔS on gas loading(26−28) and implies increasing disorder of the system on SO2 loading in MFM-520.
We sought to understand the origin of this intriguing pattern in ΔS and have determined the host–guest structures of CO2- and SO2-loaded MFM-520 by in situ synchrotron X-ray single-crystal diffraction (Table S1). On loading CO2 into MFM-520 at 270 K and 1.0 bar, adsorbed CO2 molecules are clearly observed in the pores, corresponding to a crystallographic uptake of 2.18 mmol g–1, in excellent agreement with the isotherm uptake (2.14 mmol g–1). All guest CO2 molecules in MFM-520·CO2 were found to be incommensurate (Figure 2c). Thus, instead of showing a constant distance between adjacent CO2 molecules, the intermolecular distances range from ca. 6.6 to 7.4 Å (Figure S3), indicating no apparent interaction between adjacent CO2 molecules. The distances between CO2 and phenyl rings (C1···pyridyl ring) and between CO2 and aromatic −CH groups (O3···H1C2–C2) are longer than 3.0 Å (Figure 2c-IV), suggesting only very weak supramolecular interactions between the host framework and CO2. Therefore, MFM-520 experiences no change in structure upon CO2 adsorption, and both the oxidation state of Zn(II) centers [ranging from 1.73(9) to 2.07(9)] and the geometry of [ZnO4N] nodes in MFM-520·CO2 [Zn–N1, Zn–O1, and Zn–O2 bond distances ranging between approximately 2.00 and 2.07, 2.20 and 2.50, and 1.72 and 2.25 Å, respectively] are similar to those of bare MFM-520 (Figure 3b, Figures S7 and S8). Thus, the two modulation vectors [0.1243(3)(a* + b*) + 0.5c* and 0.1243(3)(−a* + b*) + 0.5c*] in MFM-520 remain upon adsorption of CO2.
Upon loading of SO2 into MFM-520 at 270 K and 1.0 bar, a crystallographic uptake of SO2 of 3.16 mmol g–1 is observed, in excellent agreement with the isotherm uptake (3.38 mmol g–1). Since the occupancy of adsorbed SO2 molecules is 0.359(13) in the refined structural model of MFM-520·SO2, half of the closely contacted SO2 molecules (ca. 1.7 to 1.9 Å) were removed, and the remaining SO2 molecules have an intermolecular distance of ca. 3.5 Å (Figure S4), which is shorter than that in MFM-520·CO2, suggesting stronger guest–guest interactions between adsorbed SO2 molecules.
On the other hand, strong MOF–SO2 binding is indicated by the short distances between SO2 and aromatic −CH groups (O3···H1C2–C2: ca. 2.33 to 2.75 Å) and between SO2 and [ZnO4N] polyhedra (S1···O2: ca. 2.78 to 3.34 Å) (Figure 2d-IV, Figures S7 and S8). As a result, the structure of MFM-520 is heavily affected by adsorbed SO2 molecules. The ranges of bond distances Zn–N1, Zn–O1, and Zn–O2 in MFM-520·SO2 vary from 1.97 to 2.14, 1.92 to 2.73, and 1.75 to 2.19 Å, respectively, much wider than those observed in MFM-520 and MFM-520·CO2. The oxidation state of the Zn(II) centers also shows a greater range between 1.79(9) and 2.29(9) (Figure 3c) compared with that in MFM-520 and MFM-520·CO2. In MFM-520·SO2, the modulation vectors become 0.1407(6)(a* + b*) + 0.5c* and 0.1407(6)(−a* + b*) + 0.5c*, demonstrating a unique incommensurately ordered dynamic equilibrium for SO2 adsorption. Interestingly, before reaching this equilibrium state, we also identified a transient structure of MFM-520·SO2 with a corresponding crystallographic SO2 uptake of 0.532 mmol g–1 that has intermediate modulation vectors of 0.1331(4)(a* + b*) + 0.5c* and 0.1331(4)(−a* + b*) + 0.5c* (Table S1). The change in the incommensurate modulation of MFM-520 induced by the uptake of SO2 is a dynamic process as a function of diffusion and the settling of SO2 molecules within the pores of the MOF. This result rationalizes the unusual increase in ΔS on SO2 loading and confirms that it emanates from a subtle increase in the structural flexibility of meta-rigid MFM-520 upon SO2 adsorption.
Overall, the incommensurate modulated structure reported here will stimulate a reassessment of a wider range of host–guest systems with unusual adsorption behavior(29,30) and encourage the search for new structural flexibility in other MOFs and porous solids that otherwise may be regarded as entirely rigid.
The binding dynamics and effects on the structural relaxation of MFM-520 have been analyzed further using in situ synchrotron infrared microspectroscopy, inelastic neutron scattering (INS), and DFT modeling (Figure 4d–f and Figures S19–S30). Dehydrated MFM-520 has a number of characteristic peaks at 3104, 1080, 1689, 1571, and 1390 cm–1 (denoted as I, II, III, IV, and V), which are assigned based upon DFT modeling to the stretching (I) and bending (II) modes of the aromatic C–H groups on the pyridyl ring and the symmetric stretching (III) and asymmetric stretching (IV) modes of C–O and the bending (V) mode of C–H groups, respectively. On dosing CO2 (0–1 bar), peak I shows a blue shift (Δ = 9 cm–1) to 3113 cm–1, indicating a stiffening of the framework as a result of the binding of CO2 molecules to −CH groups. No notable changes occur in peaks II–V on CO2 loading, consistent with the very weak MOF–CO2 interactions. Upon loading SO2, a larger blue shift of 12 cm–1 is observed for peak I, accompanied by near-depletion of this band on increasing SO2 loading, demonstrating a stronger −CH···O═S═O supramolecular interaction. Furthermore, distinct red shifts of peaks III and IV (C–O, carboxyl) to 1682 and 1566 cm–1 (Δ = 6 and 5 cm–1, respectively) and peak V (C–H, pyridyl ring) to 1385 cm–1 (Δ = 5 cm–1) are observed, entirely consistent with the presence of structural distortion as observed in crystallographic studies and DFT-calculated IR spectra (Figure 4e). Difference INS spectra recorded (Figure 4f) between bare and CO2-, SO2-, and D2O-loaded MFM-520 reveal shifts of peaks associated with deformation and twisting modes of the pyridyl rings at low frequencies (200–300 cm–1) as well as C–H bending modes at higher frequencies (900–1300 cm–1), as confirmed by DFT modeling. SO2 and D2O both display notably stronger interactions with MFM-520 than CO2, again consistent with the crystallographic studies.
Unlike conventional once-through FGD (flue gas desulfurization) methods where SO2 permanently binds to sorbent materials to form solid inorganic waste, the SO2 captured by MFM-520 remains available to undergo chemical transformation to valuable products.(31,32) A proof-of-concept experiment was thus conducted by coupling 4-methoxyl-aryldiazonium tetrafluoroborates and hydrazine in a solution containing a suspension of MFM-520·SO2 to synthesize aryl N-aminosulfonamides (Scheme 1).(33) A nearly quantitative conversion of 4-methoxyl-aryldiazonium tetrafluoroborates and an 80% yield of the sulfonamide were achieved. Immobilization and then release of SO2 using a stable MOF can thus be used to drive organic reactions effectively, removing the high risk of the large-scale use of caustic and toxic SO2. In line with the observed structural stability of MFM-520, we have confirmed its reusability for three cycles to produce sulfonamide (Table S6). Thus, MFM-520 represents a stable and efficient platform for the capture, storage, and conversion of SO2.
Scheme 1
Scheme 1. Conversion of Captured SO2 in MFM-520
Conclusions
ARTICLE SECTIONS
The metal–organic framework material MFM-520 exhibits a reversible periodic-to-aperiodic structural transition. The aperiodic crystal structure of MFM-520 has no three-dimensional (3D) lattice periodicity but shows translational symmetry in higher-dimensional (3 + 2)D space. Filling of MFM-520 with CO2 and SO2 reveals that while CO2 has a minimal structural influence, SO2 can further modulate the structure incommensurately. In addition, MFM-520 shows high selectivity for SO2 under flue gas desulfurization conditions, and the facile release of captured SO2 from MFM-520 can be used as an SO2 delivery system for subsequent reactivity.
ARTICLE SECTIONS
The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/jacs.0c08794.
Additional experimental details, diffraction data, views of crystal structures, INS and IR spectroscopy, adsorption isotherms, and IAST selectivity (PDF)
Crystal data for MFM-520·H2O (CIF)
Crystal data for MFM-520 (CIF)
Crystal data for MFM-520·CO2 (CIF)
Crystal data for MFM-520·SO2 intermediate (CIF)
Crystal data for MFM-520·SO2 (CIF)
Terms & Conditions
Electronic Supporting Information files are available without a subscription to ACS Web Editions. The American Chemical Society holds a copyright ownership interest in any copyrightable Supporting Information. Files available from the ACS website may be downloaded for personal use only. Users are not otherwise permitted to reproduce, republish, redistribute, or sell any Supporting Information from the ACS website, either in whole or in part, in either machine-readable form or any other form without permission from the American Chemical Society. For permission to reproduce, republish and redistribute this material, requesters must process their own requests via the RightsLink permission system. Information about how to use the RightsLink permission system can be found at http://pubs.acs.org/page/copyright/permissions.html.
Author Information
ARTICLE SECTIONS
- Junliang Sun - BNLMS, College of Chemistry & Molecular Engineering, Peking University, Beijing 100871, China;
http://orcid.org/0000-0003-4074-0962;
Email: [email protected] - Martin Schröder - Department of Chemistry, University of Manchester, Manchester M13 9PL, U.K.;http://orcid.org/0000-0001-6992-0700;
Email: [email protected]
- Sihai Yang - Department of Chemistry, University of Manchester, Manchester M13 9PL, U.K.;http://orcid.org/0000-0002-1111-9272;
Email: [email protected]
- Yong Yan - Department of Chemistry, University of Manchester, Manchester M13 9PL, U.K.;http://orcid.org/0000-0002-7926-3959
- Yongqiang Cheng - Neutron Scattering Division, Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States;http://orcid.org/0000-0002-3263-4812
- Anibal J. Ramirez-Cuesta - Neutron Scattering Division, Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States;http://orcid.org/0000-0003-1231-0068
J.L. and Z.Z. contributed equally.
The authors declare no competing financial interest.
Acknowledgments
ARTICLE SECTIONS
We thank the EPSRC (EP/I011870), the Royal Society and University of Manchester, the National Basic Research Program (nos. 2013CB933402 and 2016YFA0301004), and the National Natural Science Foundation of China (nos. 21527803, 21471009, 21621061, and 21871009) for funding. This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 Research and Innovation Programme (grant agreement no. 742401, NANOCHEM). We are grateful to the Diamond Light Source and the STFC/ISIS Facility for access to beamlines B22 and TOSCA, respectively. This research used the resources of beamlines 11.3.1 and 12.2.1 at the Advanced Light Source, which is a DOE Office of Science User Facility under contract no. DE-AC02-05CH11231. The computing resources were made available through the VirtuES and ICE-MAN projects, funded by the Laboratory Directed Research and Development Program and the Compute and Data Environment for Science (CADES) at ORNL. J.L., X.Z., and Z.Z. thank the China Scholarship Council (CSC) for funding.
References
ARTICLE SECTIONS
This article references 33 other publications.
- 1Kalmutzki, J. M.; Hanikel, N.; Yaghi, M. O. Secondary building units as the turning point in the development of the reticular chemistry of MOFs. Sci. Adv. 2018, 4, eaat9180, DOI: 10.1126/sciadv.aat9180
- 2Bloch, E. D.; Queen, W. L.; Krishna, R.; Zadrozny, J. M.; Brown, C. M.; Long, J. R. Hydrocarbon separation in a metal-organic framework with open iron(II) coordination sites. Science 2012, 335, 1606, DOI: 10.1126/science.1217544[Crossref], [PubMed], [CAS], Google Scholar2https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XksVyqsLc%253D&md5=d149ed45c3e688d5e4ee63d75629bd4fHydrocarbon Separations in a Metal-Organic Framework with Open Iron(II) Coordination SitesBloch, Eric D.; Queen, Wendy L.; Krishna, Rajamani; Zadrozny, Joseph M.; Brown, Craig M.; Long, Jeffrey R.Science (Washington, DC, United States) (2012), 335 (6076), 1606-1610CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)The energy costs assocd. with large-scale industrial sepn. of light hydrocarbons by cryogenic distn. could potentially be lowered through development of selective solid adsorbents that operate at higher temps. Here, the metal-org. framework Fe2(dobdc) (dobdc4- : 2,5-dioxido-1,4-benzenedicarboxylate) is demonstrated to exhibit excellent performance characteristics for sepn. of ethylene/ethane and propylene/propane mixts. at 318 K. Breakthrough data obtained for these mixts. provide exptl. validation of simulations, which in turn predict high selectivities and capacities of this material for the fractionation of methane/ethane/ethylene/acetylene mixts., removal of acetylene impurities from ethylene, and membrane-based olefin/paraffin sepns. Neutron powder diffraction data confirm a side-on coordination of acetylene, ethylene, and propylene at the iron(II) centers, while also providing solid-state structural characterization of the much weaker interactions of ethane and propane with the metal.
- 3Schneemann, A.; Bon, V.; Schwedler, I.; Senkovska, I.; Kaskel, S.; Fischer, R. A. Flexible metal-organic frameworks. Chem. Soc. Rev. 2014, 43, 6062– 6096, DOI: 10.1039/C4CS00101J[Crossref], [PubMed], [CAS], Google Scholar3https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXht1Slu7nI&md5=b824d2bff6379c9662b50e86739b42f7Flexible metal-organic frameworksSchneemann, A.; Bon, V.; Schwedler, I.; Senkovska, I.; Kaskel, S.; Fischer, R. A.Chemical Society Reviews (2014), 43 (16), 6062-6096CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)A review. Advances in flexible and functional metal-org. frameworks (MOFs), also called soft porous crystals, are reviewed by covering the literature of the five years period 2009-2013 with ref. to the early pertinent work since the late 1990s. Flexible MOFs combine the cryst. order of the underlying coordination network with cooperative structural transformability. These materials can respond to phys. and chem. stimuli of various kinds in a tunable fashion by mol. design, which does not exist for other known solid-state materials. Among the fascinating properties are so-called breathing and swelling phenomena as a function of host-guest interactions. Phase transitions are triggered by guest adsorption/desorption, photochem., thermal, and mech. stimuli. Other important flexible properties of MOFs, such as linker rotation and sub-net sliding, which are not necessarily accompanied by crystallog. phase transitions, are briefly mentioned as well. Emphasis is given on reviewing the recent progress in application of in situ characterization techniques and the results of theor. approaches to characterize and understand the breathing mechanisms and phase transitions. The flexible MOF systems, which are discussed, are categorized by the type of metal-nodes involved and how their coordination chem. with the linker mols. controls the framework dynamics. Aspects of tailoring the flexible and responsive properties by the mixed component solid-soln. concept are included, and as well examples of possible applications of flexible metal-org. frameworks for sepn., catalysis, sensing, and biomedicine.
- 4Han, X.; Godfrey, H. G. W.; Briggs, L.; Davies, A. J.; Cheng, Y.; Daemen, L. L.; Sheveleva, A. M.; Tuna, F.; McInnes, E. J. L.; Sun, J.; Drathen, C.; George, M. W.; Ramirez-Cuesta, A. J.; Thomas, K. M.; Yang, S.; Schröder, M. Reversible adsorption of nitrogen dioxide within a robust porous metal-organic framework. Nat. Mater. 2018, 17, 691– 696, DOI: 10.1038/s41563-018-0104-7[Crossref], [PubMed], [CAS], Google Scholar4https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhtFemtr3K&md5=4e16e7aaf7dc6d94f2e4f95a15bafae7Reversible adsorption of nitrogen dioxide within a robust porous metal-organic frameworkHan, Xue; Godfrey, Harry G. W.; Briggs, Lydia; Davies, Andrew J.; Cheng, Yongqiang; Daemen, Luke L.; Sheveleva, Alena M.; Tuna, Floriana; McInnes, Eric J. L.; Sun, Junliang; Drathen, Christina; George, Michael W.; Ramirez-Cuesta, Anibal J.; Thomas, K. Mark; Yang, Sihai; Schroder, MartinNature Materials (2018), 17 (8), 691-696CODEN: NMAACR; ISSN:1476-1122. (Nature Research)Nitrogen dioxide (NO2) is a major air pollutant causing significant environmental1,2 and health problems3,4. We report reversible adsorption of NO2 in a robust metal-org. framework. Under ambient conditions, MFM-300(Al) exhibits a reversible NO2 isotherm uptake of 14.1 mmol g-1, and, more importantly, exceptional selective removal of low-concn. NO2 (5,000 to <1 ppm) from gas mixts. Complementary expts. reveal five types of supramol. interaction that cooperatively bind both NO2 and N2O4 mols. within MFM-300(Al). We find that the in situ equil. 2NO2 ↔ N2O4 within the pores is pressure-independent, whereas ex situ this equil. is an exemplary pressure-dependent first-order process. The coexistence of helical monomer-dimer chains of NO2 in MFM-300(Al) could provide a foundation for the fundamental understanding of the chem. properties of guest mols. within porous hosts. This work may pave the way for the development of future capture and conversion technologies.
- 5Krause, S.; Bon, V.; Senkovska, I.; Stoeck, U.; Wallacher, D.; Többens, D. M.; Zander, S.; Pillai, R. S.; Maurin, G.; Coudert, F.-X.; Kaskel, S. A pressure-amplifying framework material with negative gas adsorption transitions. Nature 2016, 532, 348– 352, DOI: 10.1038/nature17430[Crossref], [PubMed], [CAS], Google Scholar5https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28Xlsl2hur8%253D&md5=45dbe25185745628dc54bba9dcc564b1A pressure-amplifying framework material with negative gas adsorption transitionsKrause, Simon; Bon, Volodymyr; Senkovska, Irena; Stoeck, Ulrich; Wallacher, Dirk; Toebbens, Daniel M.; Zander, Stefan; Pillai, Renjith S.; Maurin, Guillaume; Coudert, Francois-Xavier; Kaskel, StefanNature (London, United Kingdom) (2016), 532 (7599), 348-352CODEN: NATUAS; ISSN:0028-0836. (Nature Publishing Group)Adsorption-based phenomena are important in gas sepns., such as the treatment of greenhouse-gas and toxic-gas pollutants, and in water-adsorption-based heat pumps for solar cooling systems. The ability to tune the pore size, shape and functionality of cryst. porous coordination polymers -or metal-org. frameworks (MOFs)-has made them attractive materials for such adsorption-based applications. The flexibility and guest-mol.-dependent response of MOFs give rise to unexpected and often desirable adsorption phenomena. Common to all isothermal gas adsorption phenomena, however, is increased gas uptake with increased pressure. Here we report adsorption transitions in the isotherms of a MOF (DUT-49) that exhibits a neg. gas adsorption; i.e., spontaneous desorption of gas (methane and n-butane) occurs during pressure increase in a defined temp. and pressure range. A combination of in situ powder X-ray diffraction, gas adsorption expts. and simulations shows that this adsorption behavior is controlled by a sudden hysteretic structural deformation and pore contraction of the MOF, which releases guest mols. These findings may enable technologies using frameworks capable of neg. gas adsorption for pressure amplification in micro- and macroscopic system engineering. Neg. gas adsorption extends the series of counterintuitive phenomena such as neg. thermal expansion and neg. refractive indexes and may be interpreted as an adsorptive analog of force-amplifying neg. compressibility transitions proposed for metamaterials.
- 6Katsoulidis, A. P.; Antypov, D.; Whitehead, G. F. S.; Carrington, E. J.; Adams, D. J.; Berry, N. G.; Darling, G. R.; Dyer, M. S.; Rosseinsky, M. J. Chemical control of structure and guest uptake by a conformationally mobile porous material. Nature 2019, 565, 213– 217, DOI: 10.1038/s41586-018-0820-9[Crossref], [PubMed], [CAS], Google Scholar6https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXmvFWjs7g%253D&md5=dd3b40f6520113a7f23ad984de97fbd8Chemical control of structure and guest uptake by a conformationally mobile porous materialKatsoulidis, Alexandros P.; Antypov, Dmytro; Whitehead, George F. S.; Carrington, Elliot J.; Adams, Dave J.; Berry, Neil G.; Darling, George R.; Dyer, Matthew S.; Rosseinsky, Matthew J.Nature (London, United Kingdom) (2019), 565 (7738), 213-217CODEN: NATUAS; ISSN:0028-0836. (Nature Research)Metal-org. frameworks (MOFs) are cryst. synthetic porous materials formed by binding org. linkers to metal nodes: they can be either rigid1,2 or flexible3. Zeolites and rigid MOFs have widespread applications in sorption, sepn. and catalysis that arise from their ability to control the arrangement and chem. of guest mols. in their pores via the shape and functionality of their internal surface, defined by their chem. and structure4,5. Their structures correspond to an energy landscape with a single, albeit highly functional, energy min. By contrast, proteins function by navigating between multiple metastable structures using bond rotations of the polypeptide6,7, where each structure lies in one of the min. of a conformational energy landscape and can be selected according to the chem. of the mols. that interact with the protein. These structural changes are realized through the mechanisms of conformational selection (a higher-energy min. characteristic of the protein is stabilized by small-mol. binding) and induced fit (a small mol. imposes a structure on the protein that is not a min. in the absence of that mol.)8. Rotation about covalent bonds in a peptide linker can change a flexible MOF to afford nine distinct crystal structures, revealing a conformational energy landscape that was characterized by multiple structural min. The uptake of small-mol. guests by the MOF can be chem. triggered by inducing peptide conformational change. This change transforms the material from a min. on the landscape that is inactive for guest sorption to an active one. Chem. control of the conformation of a flexible org. linker offers a route to modifying the pore geometry and internal surface chem. and thus the function of open-framework materials.
- 7Gu, C.; Hosono, N.; Zheng, J.-J.; Sato, Y.; Kusaka, S.; Sakaki, S.; Kitagawa, S. Design and control of gas diffusion process in a nanoporous soft crystal. Science 2019, 363, 387– 391, DOI: 10.1126/science.aar6833[Crossref], [PubMed], [CAS], Google Scholar7https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXhs1anu7c%253D&md5=5fc62a634e43f158b42a592c4c6be5e7Design and control of gas diffusion process in a nanoporous soft crystalGu, Cheng; Hosono, Nobuhiko; Zheng, Jia-Jia; Sato, Yohei; Kusaka, Shinpei; Sakaki, Shigeyoshi; Kitagawa, SusumuScience (Washington, DC, United States) (2019), 363 (6425), 387-391CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)Design of the gas-diffusion process in a porous material is challenging because a contracted pore aperture is a prerequisite, whereas the channel traffic of guest mols. is regulated by the flexible and dynamic motions of nanochannels. Here, we present the rational design of a diffusion-regulatory system in a porous coordination polymer (PCP) in which flip-flop mol. motions within the framework structure provide kinetic gate functions that enable efficient gas sepn. and storage. The PCP shows substantial temp.-responsive adsorption in which the adsorbate mols. are differentiated by each gate-admission temp., facilitating kinetics-based gas sepns. of oxygen/argon and ethylene/ethane with high selectivities of ∼350 and ∼75, resp. Addnl., we demonstrate the long-lasting phys. encapsulation of ethylene at ambient conditions, owing to strongly impeded diffusion in distinctive nanochannels.
- 8Goodwin, A. L.; Calleja, M.; Conterio, M. J.; Dove, M. T.; Evans, J. S. O.; Keen, D. A.; Peters, L.; Tucker, M. G. Colossal positive and negative thermal expansion in the framework material Ag3[Co(CN)6]. Science 2008, 319, 794– 797, DOI: 10.1126/science.1151442[Crossref], [PubMed], [CAS], Google Scholar8https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXhsFGhs74%253D&md5=f5490d51f1e9db0f3d7906bb3c215c16Colossal Positive and Negative Thermal Expansion in the Framework Material Ag3[Co(CN)6]Goodwin, Andrew L.; Calleja, Mark; Conterio, Michael J.; Dove, Martin T.; Evans, John S. O.; Keen, David A.; Peters, Lars; Tucker, Matthew G.Science (Washington, DC, United States) (2008), 319 (5864), 794-797CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)We show that silver(I) hexacyanocobaltate(III), Ag3[Co(CN)6], exhibits pos. and neg. thermal expansion an order of magnitude greater than that seen in other cryst. materials. This framework material expands along one set of directions at a rate comparable to the most weakly bound solids known. By flexing like lattice fencing, the framework couples this to a contraction along a perpendicular direction. This gives neg. thermal expansion that is 14 times larger than in ZrW2O8. D. functional theory calcns. quantify both the low energy assocd. with this flexibility and the role of argentophilic (Ag+...Ag+) interactions. This study illustrates how the mech. properties of a van der Waals solid might be engineered into a rigid, useable framework.
- 9Serre, C.; Millange, F.; Thouvenot, C.; Noguès, M.; Marsolier, G.; Louër, D.; Férey, G. Very large breathing effect in the first nanoporous chromium(III)-based solids: MIL-53 or Cr(III)(OH)·{O2C-C6H4-CO2}·{HO2C-C6H4-CO2H}x·H2Oy. J. Am. Chem. Soc. 2002, 124, 13519– 13526, DOI: 10.1021/ja0276974[ACS Full Text
], [CAS], Google Scholar9https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD38XotVegt74%253D&md5=59fd68d1cae2399f56196e58039d3bd5Very Large Breathing Effect in the First Nanoporous Chromium(III)-Based Solids: MIL-53 or CrIII(OH)·{O2C-C6H4-CO2}·{HO2C-C6H4-CO2H}x·H2OySerre, Christian; Millange, Franck; Thouvenot, Christelle; Nogues, Marc; Marsolier, Gerard; Loueer, Daniel; Ferey, GerardJournal of the American Chemical Society (2002), 124 (45), 13519-13526CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)The 1st three-dimensional Cr(III) dicarboxylate, MIL-53as or CrIII(OH)·{O2C-C6H4-CO2}·{HO2C-C6H4-CO2H}0.75, was obtained under hydrothermal conditions (as: as-synthesized). The free acid can be removed by calcination giving the resulting solid, MIL-53ht or CrIII(OH)·{O2C-C6H4-CO2}. At room temp., MIL-53ht adsorbs atm. H2O immediately to give CrIII(OH)·{O2C-C6H4-CO2}·H2O or MIL-53lt (lt: low-temp. form, ht:high-temp. form). Structures, which were detd. by using x-ray powder diffraction data, are built up from chains of Cr(III) octahedra linked through terephthalate dianions. This creates a three-dimensional structure with an array of 1-dimensional large pore channels filled with free disordered terephthalic mols. (MIL-53as) or H2O mols. (MIL-53lt); when the free mols. are removed, this leads to a nanoporous solid (MIL-53ht) with a Langmuir surface area over 1500 m2/g. The transition between the hydrated form (MIL-53lt) and the anhyd. solid (MIL-53ht) is fully reversible and followed by a very high breathing effect (more than 5 Å), the pores being clipped in the presence of H2O mols. (MIL-53lt) and reopened when the channels are empty (MIL-53ht). The thermal behavior of the two solids was studied using TGA and x-ray thermodiffractometry. The sorption properties of MIL-53lt also were studied using several org. solvents. Finally, magnetism measurements performed on MIL-53as and MIL-53lt revealed that these two phases are antiferromagnetic with Neel temps. TN of 65 and 55 K, resp. Crystal data for MIL-53as is as follows: orthorhombic space group Pnam with a 17.340(1), b 12.178(1), c 6.822(1) Å, and Z = 4. Crystal data for MIL-53ht is as follows: orthorhombic space group Imcm with a 16.733(1), b 13.038(1), c 6.812(1) Å, and Z = 4. Crystal data for MIL-53lt is as follows: monoclinic space group C2/c with a 19.685(4), b 7.849(1), c 6.782(1) Å, β 104.90(1)°, and Z = 4. - 10Deria, P.; Gómez-Gualdrón, D. A.; Bury, W.; Schaef, H. T.; Wang, T. C.; Thallapally, P. K.; Sarjeant, A. A.; Snurr, R. Q.; Hupp, J. T.; Farha, O. K. Ultraporous, water stable, and breathing zirconium-based metal-organic frameworks with ftw topology. J. Am. Chem. Soc. 2015, 137, 13183– 13190, DOI: 10.1021/jacs.5b08860[ACS Full Text], [CAS], Google Scholar10https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhsFanurbJ&md5=e49fde249c557fa2ff56727b6f6ec306Ultraporous, Water Stable, and Breathing Zirconium-Based Metal-Organic Frameworks with ftw TopologyDeria, Pravas; Gomez-Gualdron, Diego A.; Bury, Wojciech; Schaef, Herbert T.; Wang, Timothy C.; Thallapally, Praveen K.; Sarjeant, Amy A.; Snurr, Randall Q.; Hupp, Joseph T.; Farha, Omar K.Journal of the American Chemical Society (2015), 137 (40), 13183-13190CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)Breathing metal-org. frameworks (MOFs) are an emerging class of soft porous crystals (SPCs) with potential for high working capacity for gas storage applications. However, most breathing MOFs have low stability and/or low surface area. Here the authors report a H2O-stable, high surface area, breathing MOF of ftw topol., NU-1105. While Zr6-oxo clusters as nodes introduce H2O stability in NU-1105, its high surface area and breathing character stem from its pyrene-based tetracarboxylate (Py-FP) linkers, in which the fluorene units (F) in the FP arms play a key role in promoting breathing behavior. During gas sorption studies, the closed pore (cp) ↔ open pore (op) transition of NU-1105 occurs at a propane pressure of ∼3 bar. At 1 bar, NU-1105 is in its cp form and adsorbs less propane than it would in its op form, highlighting improved working capacity. In situ powder x-ray diffraction during propane sorption was used to track the cp ↔ op transition, and mol. modeling was used to elucidate the structure of the op and cp forms of NU-1105. According to TD-DFT calcns., the proposed conformations of the Py-FP linkers in the op and cp forms are consistent with the measured excitation and emission spectra of the op and cp forms of NU-1105. Similar structural transitions are also obsd. in the porphyrinic MOF NU-1104 depending on the identity of the porphyrin core; the authors obsd. breathing behavior if the constituent Por-PTP linker is nonmetalated.
- 11Sung Cho, H.; Deng, H.; Miyasaka, K.; Dong, Z.; Cho, M.; Neimark, A. V.; Ku Kang, J.; Yaghi, O. M.; Terasaki, O. Extra adsorption and adsorbate superlattice formation in metal-organic frameworks. Nature 2015, 527, 503– 507, DOI: 10.1038/nature15734[Crossref], [PubMed], [CAS], Google Scholar11https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhvVWmsrjL&md5=4666eb877d5a30907bf7854fbb443accExtra adsorption and adsorbate superlattice formation in metal-organic frameworksSung Cho, Hae; Deng, Hexiang; Miyasaka, Keiichi; Dong, Zhiyue; Cho, Minhyung; Neimark, Alexander V.; Ku Kang, Jeung; Yaghi, Omar M.; Terasaki, OsamuNature (London, United Kingdom) (2015), 527 (7579), 503-507CODEN: NATUAS; ISSN:0028-0836. (Nature Publishing Group)Metal-org. frameworks (MOFs) have a high internal surface area and widely tunable compn., which make them useful for applications involving adsorption, such as hydrogen, methane or carbon dioxide storage. The selectivity and uptake capacity of the adsorption process are detd. by interactions involving the adsorbates and their porous host materials. But, although the interactions of adsorbate mols. with the internal MOF surface and also amongst themselves within individual pores have been extensively studied, adsorbate-adsorbate interactions across pore walls have not been explored. Here we show that local strain in the MOF, induced by pore filling, can give rise to collective and long-range adsorbate-adsorbate interactions and the formation of adsorbate superlattices that extend beyond an original MOF unit cell. Specifically, we use in situ small-angle X-ray scattering to track and map the distribution and ordering of adsorbate mols. in five members of the mesoporous MOF-74 series along entire adsorption-desorption isotherms. We find in all cases that the capillary condensation that fills the pores gives rise to the formation of 'extra adsorption domains'-i.e., domains spanning several neighboring pores, which have a higher adsorbate d. than non-domain pores. In the case of one MOF, IRMOF-74-V-hex, these domains form a superlattice structure that is difficult to reconcile with the prevailing view of pore-filling as a stochastic process. The visualization of the adsorption process provided by our data, with clear evidence for initial adsorbate aggregation in distinct domains and ordering before an even distribution is finally reached, should help to improve our understanding of this process and may thereby improve our ability to exploit it practically.
- 12Janssen, T.; Chapuis, G.; Boissieu, M. Aperiodic Crystals: From Modulated Phases to Quasicrystals: Structure and Properties; Oxford University Press: Oxford, 2018.
- 13Baerlocher, C.; Weber, T.; McCusker, L.; Palatinus, L.; Zones, I. S. Unraveling the perplexing structure of the zeolite SSZ-57. Science 2011, 333, 1134– 1137, DOI: 10.1126/science.1207466[Crossref], [PubMed], [CAS], Google Scholar13https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhtVGktr3O&md5=d0c7b3947c1325e5ca4e71f360c81c90Unraveling the Perplexing Structure of the Zeolite SSZ-57Baerlocher, Christian; Weber, Thomas; McCusker, Lynne B.; Palatinus, Lukas; Zones, Stacey I.Science (Washington, DC, United States) (2011), 333 (6046), 1134-1137CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)Crystal structure of the zeolite SSZ-57 has been detd. using advanced crystallog. techniques (structure soln. in four-dimensional space and interpretation of three-dimensional diffuse scattering by Monte Carlo simulation) and crystal chem. considerations applied to high-quality single-crystal X-ray diffraction data. The crystal structure was related to that of ZSM-11 but was commensurately modulated along the c axis (P‾4m2, a = b = 20.091, and c = 110.056 Å) to yield a structure with a 12-ring:10-ring ratio of 1:15. Disorder of the 12-rings resulted in a three-dimensional 10-ring channel system with large isolated pockets. The structure helps to clarify the material's catalytic activity.
- 14Lin, X.; Blake, A. J.; Wilson, C.; Sun, X. Z.; Champness, N. R.; George, M. W.; Hubberstey, P.; Mokaya, R.; Schröder, M. A porous framework polymer based on a zinc(II) 4,4′-bipyridine-2,6, 2′, 6′- tetracarboxylate: synthesis, structure, and “zeolite-like” behaviors. J. Am. Chem. Soc. 2006, 128, 10745– 10753, DOI: 10.1021/ja060946u[ACS Full Text], [CAS], Google Scholar14https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD28XnsF2hu7g%253D&md5=814ce41c31d52c3157a64dacc7681a50A Porous Framework Polymer Based on a Zinc(II) 4,4'-Bipyridine-2,6,2',6'-tetracarboxylate: Synthesis, Structure, and "Zeolite-Like" BehaviorsLin, Xiang; Blake, Alexander J.; Wilson, Claire; Sun, Xue Zhong; Champness, Neil R.; George, Michael W.; Hubberstey, Peter; Mokaya, Robert; Schroeder, MartinJournal of the American Chemical Society (2006), 128 (33), 10745-10753CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)The robust metal-org. framework compd. {[Zn2(L)]·4H2O}∞ (I) was synthesized by hydrothermal reaction of ZnCl2 and 4,4'-bipyridine-2,6,2',6'-tetracarboxylic acid (H4L). Compd. I crystallizes in a chiral space group, P42212, with the chirality generated by the helical chains of H-bonded guest H2O mols. rather than by the coordination framework. Removal of guest H2O mols. from the crystal affords the porous material, [Zn2(L)]∞ (II), which has very high thermal stability and is chem. inert. The N2 isotherm of II at 77 K suggests a uniform porous structure with a BET surface area of 312.7 m2/g and a remarkably strong interaction with N2 mols. (βE0 = 29.6 kJ mol-1). II also exhibits significant gas storage capacities of 1.08% for H2 at 4 bar and 77 K and 3.14% (44.0 cm3/g, 67 vol./vol.) for methane at 9 bar at 298 K. The adsorption behavior of II toward org. solvent vapors also was studied, and isotherms reveal that for different solvent vapors adsorption is dominated by two types of processes, absorbate-absorbate or absorbate-absorbent interactions. The adsorption and desorption kinetic processes in II are detd. mainly by the mol. size of the guest species and their interaction with the host.
- 15Petricek, V.; Dusek, M.; Palatinus, L. Crystallographic computing system JANA2006: general features. Z. Kristallogr. - Cryst. Mater. 2014, 229, 345– 352, DOI: 10.1515/zkri-2014-1737[Crossref], [CAS], Google Scholar15https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXmslyjsbs%253D&md5=6cc7613194f2b2f1d3f14be9a64f76bbCrystallographic Computing System JANA2006: General featuresPetricek, Vaclav; Dusek, Michal; Palatinus, LukasZeitschrift fuer Kristallographie - Crystalline Materials (2014), 229 (5), 345-352CODEN: ZKCMAJ; ISSN:2194-4946. (Oldenbourg Wissenschaftsverlag GmbH)JANA2006 is a freely available program for structure detn. of std., modulated and magnetic samples based on X-ray or neutron single crystal/ powder diffraction or on electron diffraction. The system has been developed for 30 years from specialized tool for refinement of modulated structures to a universal program covering std. as well as advanced crystallog. The aim of this article is to describe the basic features of JANA2006 and explain its scope and philosophy. It will also serve as a basis for future publications detailing tools and methods of JANA.
- 16Clark, S. J.; Segall, M. D.; Pickard, C. J.; Hasnip, P. J.; Probert, M. I. J.; Refson, K.; Payne, M. C. First principles methods using CASTEP. Z. Kristallogr. - Cryst. Mater. 2005, 220, 567– 571, DOI: 10.1524/zkri.220.5.567.65075[Crossref], [CAS], Google Scholar16https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2MXmsVSitbk%253D&md5=edb75e2f9d4df4ad83f4df7db21888e7First principles methods using CASTEPClark, Stewart J.; Segall, Matthew D.; Pickard, Chris J.; Hasnip, Phil J.; Probert, Matt I. J.; Refson, Keith; Payne, Mike C.Zeitschrift fuer Kristallographie (2005), 220 (5-6), 567-570CODEN: ZEKRDZ; ISSN:0044-2968. (Oldenbourg Wissenschaftsverlag GmbH)The CASTEP code for first principles electronic structure calcns. is described. A brief, non-tech. overview is given and some of the features and capabilities highlighted. Some features which are unique to CASTEP are described and near-future development plans outlined.
- 17Cheng, Y. Q.; Daemen, L. L.; Kolesnikov, A. I.; Ramirez-Cuesta, A. J. Simulation of inelastic neutron scattering spectra using OCLIMAX. J. Chem. Theory Comput. 2019, 15, 1974– 1982, DOI: 10.1021/acs.jctc.8b01250[ACS Full Text], [CAS], Google Scholar17https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXislertrk%253D&md5=ab97e508f78304baadfd0af414d79a52Simulation of Inelastic Neutron Scattering Spectra Using OCLIMAXCheng, Y. Q.; Daemen, L. L.; Kolesnikov, A. I.; Ramirez-Cuesta, A. J.Journal of Chemical Theory and Computation (2019), 15 (3), 1974-1982CODEN: JCTCCE; ISSN:1549-9618. (American Chemical Society)Studying the vibration of atoms is of fundamental importance and can provide crit. insight for the understanding of materials behavior, such as structure and phase transition, thermodn., and chem. reactions. The at. vibration can be probed using vibrational spectroscopy with various incident particles such as photons, neutrons, or electrons. A major challenge when applying these techniques is often how to interpret the vibrational spectra and how to make connections to the theory. To this end, methods that can simulate the spectra from atomistic models are highly desired. In this paper, we present a program developed for the simulation of inelastic neutron scattering spectra. It has many new and useful features that were not previously available and will greatly facilitate the anal. and understanding of inelastic neutron scattering data.
- 18Boyer, L. L.; Kaxiras, E.; Feldman, J. L.; Broughton, J. Q.; Mehl, M. J. New low-energy crystal structure for silicon. Phys. Rev. Lett. 1991, 67, 715, DOI: 10.1103/PhysRevLett.67.715[Crossref], [PubMed], [CAS], Google Scholar18https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK3MXlsVOjtL8%253D&md5=6d5d51a5b31a8b02186b5e147975e81aNew low-energy crystal structure for siliconBoyer, L. L.; Kaxiras, Efthimios; Feldman, J. L.; Broughton, J. Q.; Mehl, M. J.Physical Review Letters (1991), 67 (6), 715-18CODEN: PRLTAO; ISSN:0031-9007.A min.-energy path in strain space was detd. which takes cubic Si into itself. Energies are computed using the Stillinger-Weber model potential and first-principles total-energy calcns. The energy along this path has an addnl. min., corresponding to a crystal structure with a body-centered-tetragonal lattice and 5-fold-coordinated atoms. Lattice-dynamics, mol.-dynamics, and elastic-const. calcns. show the structure is stable.
- 19Stokes, H. T.; Hatch, D. M.; Campbell, B. J. ISO(3+d)D, ISOTROPY Software Suite, iso.byu.edu.
- 20Brese, N. E.; O’Keeffe, M. Bond-valence parameters for solids. Acta Crystallogr., Sect. B: Struct. Sci. 1991, 47, 192– 197, DOI: 10.1107/S0108768190011041
- 21Ovsyannikov, S. V.; Bykov, M.; Bykova, E.; Kozlenko, D. P.; Tsirlin, A. A.; Karkin, A. E.; Shchennikov, V. V.; Kichanov, S. E.; Gou, H.; Abakumov, A. M.; Egoavil, R.; Verbeeck, J.; McCammon, C.; Dyadkin, V.; Chernyshov, D.; van Smaalen, S.; Dubrovinsky, L. S. Charge-ordering transition in iron oxide Fe4O5 involving competing dimer and trimer formation. Nat. Chem. 2016, 8, 501– 508, DOI: 10.1038/nchem.2478[Crossref], [PubMed], [CAS], Google Scholar21https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XlsVajtb8%253D&md5=17cff2f037f0d8d1fdf322d2704d7340Charge-ordering transition in iron oxide Fe4O5 involving competing dimer and trimer formationOvsyannikov, Sergey V.; Bykov, Maxim; Bykova, Elena; Kozlenko, Denis P.; Tsirlin, Alexander A.; Karkin, Alexander E.; Shchennikov, Vladimir V.; Kichanov, Sergey E.; Gou, Huiyang; Abakumov, Artem M.; Egoavil, Ricardo; Verbeeck, Johan; McCammon, Catherine; Dyadkin, Vadim; Chernyshov, Dmitry; van Smaalen, Sander; Dubrovinsky, Leonid S.Nature Chemistry (2016), 8 (5), 501-508CODEN: NCAHBB; ISSN:1755-4330. (Nature Publishing Group)Phase transitions that occur in materials, driven, for instance, by changes in temp. or pressure, can dramatically change the materials' properties. Discovering new types of transitions and understanding their mechanisms is important not only from a fundamental perspective, but also for practical applications. Here the authors study a recently discovered Fe4O5 that adopts an orthorhombic CaFe3O5-type crystal structure that features linear chains of Fe ions. On cooling .ltorsim.150 K, Fe4O5 undergoes an unusual charge-ordering transition that involves competing dimeric and trimeric ordering within the chains of Fe ions. This transition is concurrent with a significant increase in elec. resistivity. Magnetic-susceptibility measurements and neutron diffraction establish the formation of a collinear antiferromagnetic order above room temp. and a spin canting at 85 K that gives rise to spontaneous magnetization. Possible mechanisms of this transition and compare it with the trimeronic charge ordering obsd. in magnetite below the Verwey transition temp. are discussed.
- 22Prokeš, K.; Hartwig, S.; Gukasov, A.; Mydosh, J. A.; Huang, Y. K.; Niehaus, O.; Pöttgen, R. Coexistence of different magnetic moments in CeRuSn probed by polarized neutrons. Phys. Rev. B: Condens. Matter Mater. Phys. 2015, 91, 014424, DOI: 10.1103/PhysRevB.91.014424[Crossref], [CAS], Google Scholar22https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXlt1Kht74%253D&md5=28a90a13832829f2fd604a2f7eb48285Coexistence of different magnetic moments in CeRuSn probed by polarized neutronsProkes, K.; Hartwig, S.; Gukasov, A.; Mydosh, J. A.; Huang, Y.-K.; Niehaus, O.; Poettgen, R.Physical Review B: Condensed Matter and Materials Physics (2015), 91 (1), 014424/1-014424/6CODEN: PRBMDO; ISSN:1098-0121. (American Physical Society)We report on the spin densities in CeRuSn detd. at elevated and at low temps. using polarized neutron diffraction. At 285 K, where the CeRuSn crystal structure contains two different crystallog. Ce sites, we observe that a Ce site with larger nearest-neighbor distances is clearly more susceptible to the applied magnetic field, whereas the other is hardly polarizable. This finding clearly documents that different local environment of the two Ce sites causes the Ce ions to split into magnetic Ce3+ and nonmagnetic Ce(4-δ)+ valence states. With lowering the temp., the crystal structure transforms to a structure incommensurately modulated along the c axis. This leads to new inequivalent crystallog. Ce sites resulting in a redistribution of spin densities. Our anal. using the simplest structural approximant shows that in this metallic system Ce ions coexist in different valence states. Localized 4 f states that fulfill the third Hund's rule are found to be close to the ideal Ce3+ state (at sites with the largest Ce-Ru interat. distances), whereas Ce(4-δ)+ valence states are found to be itinerant and situated at Ce sites with much shorter Ce-Ru distances. The similarity to the famous γ-α transition in elemental cerium is discussed.
- 23Sun, Z.; Li, J.; Ji, C.; Sun, J.; Hong, M.; Luo, J. Unusual long-range ordering incommensurate structural modulations in an organic molecular ferroelectric. J. Am. Chem. Soc. 2017, 139, 15900– 15906, DOI: 10.1021/jacs.7b08950[ACS Full Text], [CAS], Google Scholar23https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhs1KnsLrL&md5=2b23441afd78eba7a775e6263dcd1aecUnusual Long-Range Ordering Incommensurate Structural Modulations in an Organic Molecular FerroelectricSun, Zhihua; Li, Jian; Ji, Chengmin; Sun, Junliang; Hong, Maochun; Luo, JunhuaJournal of the American Chemical Society (2017), 139 (44), 15900-15906CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)The incommensurate (IC) behaviors of ferroelecs. have been widely investigated in inorg. oxides as an exciting branch for aperiodic materials, whereas it still remains a great challenge to achieve such intriguing effects in org. systems. Here, we present that successive ordering of dynamic dipoles in an org. mol. ferroelec., N-isopropylbenzylaminium trichloroacetate (1), enables unusual incommensurately modulated structures between its paraelec. phase and ferroelec. phase. In particular, 1 exhibits three distinct IC states coupling with a long-range ordering modulation. That is, the incommensurately modulated lattice is ∼7 times as large as its periodic prototype, and the IC structure is well solved using a (3 + 1)D superspace group with the modulated wavevector q = (0, 0, 0.1589). To the best of our knowledge, 1 is the first org. ferroelec. showing such a long-range ordering IC structural modulation. In addn., structural analyses reveal that slowing down dynamic motions of anionic moieties accounts for its modulation behaviors, which also results in dramatic reorientation of dipolar moments and concrete ferroelec. polarization of 1 (∼0.65 μC/cm2). The combination of unique IC structural modulations and ferroelectricity makes 1 a potential candidate for the assembly of an artificially modulated lattice, which will allow for a deep understanding of the underlying chem. and physics of aperiodic materials.
- 24He, H.; Tan, X. Electric-field-induced transformation of incommensurate modulations in antiferroelectric Pb0.99Nb0.02[(Zr1-xSnx)1-yTiy]0.98O3. Phys. Rev. B: Condens. Matter Mater. Phys. 2005, 72, 024102, DOI: 10.1103/PhysRevB.72.024102[Crossref], [CAS], Google Scholar24https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2MXmvFyktbY%253D&md5=772b89625e5c3d224dc78d01852f5079Electric-field-induced transformation of incommensurate modulations in antiferroelectric Pb0.99Nb0.02[(Zr1-xSnx)1-yTiy]0.98O3He, Hui; Tan, XiaoliPhysical Review B: Condensed Matter and Materials Physics (2005), 72 (2), 024102/1-024102/10CODEN: PRBMDO; ISSN:1098-0121. (American Physical Society)Most antiferroelec. ceramics are modified from the prototype PbZrO3 by adding Sn and Ti in conjunction with small amt. of Nb or La to optimize their properties. These modifiers introduce unique nanoscale structural feature to the ceramics as incommensurate modulations. It was shown previously that the modulation is strongly responsive to a change in chem. compn. or temp. However, its response to an elec. field, the driving force in real applications, was not explored before. The dynamic evolution of the incommensurate modulation during the elec. field-induced antiferroelec.-to-ferroelec. transformation was obsd. with an in situ TEM technique. The incommensurate modulation exists as a transverse Pb-cation displacement wave. The wavelength is quite stable against external elec. stimuli, in sharp contrast to the dramatic change under thermal stimuli reported previously. Probably the appeared incommensurate modulation is an av. effect of a mixt. of two commensurate modulations. The elec. field-induced antiferroelec.-to-ferroelec. transformation proceeds with aligning the Pb-cation displacements, which resembles the process of 90° reorientation and 180° reversal in normal ferroelecs.
- 25Cui, X.; Yang, Q.; Yang, L.; Krishna, R.; Zhang, Z.; Bao, Z.; Wu, H.; Ren, Q.; Zhou, W.; Chen, B.; Xing, H. Ultrahigh and selective SO2 uptake in inorganic anion-pillared hybrid porous materials. Adv. Mater. 2017, 29, 1606929, DOI: 10.1002/adma.201606929
- 26Yang, S.; Liu, L.; Sun, J.; Thomas, K. M.; Davies, A. J.; George, M. W.; Blake, A. J.; Hill, A. H.; Fitch, A. N.; Tang, C. C.; Schröder, M. Irreversible network transformation in a dynamic porous host catalyzed by sulfur dioxide. J. Am. Chem. Soc. 2013, 135, 4954– 4957, DOI: 10.1021/ja401061m[ACS Full Text], [CAS], Google Scholar26https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXktVCkt74%253D&md5=e94870fe12554b0dcc7e1925343d140bIrreversible Network Transformation in a Dynamic Porous Host Catalyzed by Sulfur DioxideYang, Sihai; Liu, Leifeng; Sun, Junliang; Thomas, K. Mark; Davies, Andrew J.; George, Michael W.; Blake, Alexander J.; Hill, Adrian H.; Fitch, Andrew N.; Tang, Chiu C.; Schroder, MartinJournal of the American Chemical Society (2013), 135 (13), 4954-4957CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)Porous NOTT-202a shows exceptionally high uptake of SO2, 13.6 mmol g-1 (87.0 wt.%) at 268 K and 1.0 bar, representing the highest value reported to date for a framework material. NOTT-202a undergoes a distinct irreversible framework phase transition upon SO2 uptake at 268-283 K to give NOTT-202b which has enhanced stability due to the formation of strong π···π interactions between interpenetrated networks.
- 27Yang, S.; Sun, J.; Ramirez-Cuesta, A. J.; Callear, S. K.; David, W. I. F.; Anderson, D. P.; Newby, R.; Blake, A. J.; Parker, J. E.; Tang, C. C.; Schröder, M. Selectivity and direct visualization of carbon dioxide and sulfur dioxide in a decorated porous host. Nat. Chem. 2012, 4, 887– 894, DOI: 10.1038/nchem.1457[Crossref], [PubMed], [CAS], Google Scholar27https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhtlymtbbF&md5=3329e5c8d3c0261f0a7b276837539168Selectivity and direct visualization of carbon dioxide and sulfur dioxide in a decorated porous hostYang, Sihai; Sun, Junliang; Ramirez-Cuesta, Anibal J.; Callear, Samantha K.; David, William I. F.; Anderson, Daniel P.; Newby, Ruth; Blake, Alexander J.; Parker, Julia E.; Tang, Chiu C.; Schroeder, MartinNature Chemistry (2012), 4 (11), 887-894CODEN: NCAHBB; ISSN:1755-4330. (Nature Publishing Group)Understanding the mechanism by which porous solids trap harmful gases, e.g., CO2 and SO2, is essential to design new materials for their selective removal. Materials with amine group functionalization dominate this field, largely due to their potential to form carbamates through H2N(δ-)···C(δ+)O2 interactions, thereby covalently trapping CO2; however, the use of these materials is energy-intensive with significant environmental impacts. A non-amine-contg. porous solid (NOTT-300) in which OH- groups within pores selective bind CO2 and SO2 is reported. In-situ powder x-ray diffraction and inelastic neutron scattering studies in conjunction with modeling showed the OH- groups bind CO2 and SO2 by forming O=C(S)=O(δ-)···H(δ+)-O hydrogen bonds, which are reinforced by weak supra-mol. interactions with C-H atoms on the framework arom. rings. This offers the potential for using easy-on/easy-off capture systems for CO2 and SO2 with fewer economic and environmental penalties.
- 28Bell, J. G.; Morris, S. A.; Aidoudi, F.; McCormick, L. J.; Morris, R. E.; Thomas, K. M. Physisorption-induced structural change directing carbon monoxide chemisorption and nitric oxide coordination on hemilabile porous metal organic framework NaNi3(OH)(SIP)2(H2O)5·H2O (SIP = 5-sulfoisophthalate). J. Mater. Chem. A 2017, 5, 23577– 23591, DOI: 10.1039/C7TA05910H[Crossref], [CAS], Google Scholar28https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhslWrsb3F&md5=4bc517d3d573afdf77ffb83af8f32945Physisorption-induced structural change directing carbon monoxide chemisorption and nitric oxide coordination on hemilabile porous metal organic framework NaNi3(OH)(SIP)2(H2O)5·H2O (SIP = 5-sulfoisophthalate)Bell, Jon G.; Morris, Samuel A.; Aidoudi, Farida; McCormick, Laura J.; Morris, Russell E.; Thomas, K. MarkJournal of Materials Chemistry A: Materials for Energy and Sustainability (2017), 5 (45), 23577-23591CODEN: JMCAET; ISSN:2050-7496. (Royal Society of Chemistry)Structural changes occur during thermal activation of NaNi3(OH)(SIP)2(H2O)5·H2O and NaCo3(OH)(SIP)2(H2O)5·H2O, forming porous framework materials. Activating NaNi3(OH)(SIP)2(H2O)5·H2O at 400° K gave NaNi3(OH)(SIP)2(H2O)2; at 513° K gave NaNi3(OH)(SIP)2. CO adsorption/desorption on NaNi3(OH)(SIP)2(H2O)2 at 348° K and 20 bar was hysteretic, but all CO was desorbed in vacuum. NaNi3(OH)(SIP)2(H2O)2 was exposed to NO to establish the accessibility of unsatd. metal centers; crystallog. results showed NO binds to Ni with bent coordination geometry. CO adsorption characteristics on isostructural NaNi3(OH)(SIP)2 and NaCo3(OH)(SIP)2 were examd. at 268-348° K and pressure up to 20 bar. CO surface excess isotherms for NaNi3(OH)(SIP)2 at 348° K were reversible and non-hysteretic at pressure below the isotherm point of inflection; however, above this point, isotherms had reversible and irreversible adsorption components. The irreversible component remaining adsorbed in ultra-high vacuum at 348° K was 4.9 wt. percent. Subsequent sequential CO adsorption/desorption isotherms were non-hysteretic and fully reversible. Thermal stability and stoichiometry of the product were assessed using in-situ temp. programmed desorption in conjunction with thermogravimetric anal. and mass spectrometry. This gave a discrete CO peak at ∼500° K indicating thermally stable CO bonding to the framework (0.42 × CO/formula desorbed [2.31 wt. percent]); a weaker CO2 peak was obsd. at 615° K. The remaining adsorbed species were desorbed as a mixt. of CO and CO2, overlapping with NaNi3(OH)(SIP)2 framework decompn. CO physisorption induced structural change, which led to CO chemisorption on NaNi3(OH)(SIP)2 above the point of inflection in the isotherm and the formation of a new thermally stable porous framework confirmed by CO2 adsorption at 273°K. Thus, CO chemisorption was attributed to cleaving the hemilabile switchable sulfonate group; framework structural integrity was retained by stable carboxylate linkers. Assessments of CO adsorption on NaCo3(OH)(SIP)2 showed hysteretic isotherms; no evidence of irreversible chemisorption CO was obsd. CO/N2 selectivity for NaNi3(OH)(SIP)2 and NaCo3(OH)(SIP)2 was 2.4-2.85 (1-10 bar) and 1.74-1.81 (1-10 bar), resp. This was the first demonstration of physisorption driving structural change in a hemilabile porous framework material; it demonstrated a transition from physisorption to irreversible thermally stable CO chemisorption.
- 29Dubbeldam, D.; Calero, S.; Maesen, T. L. M.; Smit, B. Incommensurate diffusion in confined systems. Phys. Rev. Lett. 2003, 90, 245901, DOI: 10.1103/PhysRevLett.90.245901[Crossref], [PubMed], [CAS], Google Scholar29https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3sXkvVaktL4%253D&md5=beb5309f2a75ae65cd68fbc109f947b8Incommensurate Diffusion in Confined SystemsDubbeldam, D.; Calero, S.; Maesen, T. L. M.; Smit, B.Physical Review Letters (2003), 90 (24), 245901/1-245901/4CODEN: PRLTAO; ISSN:0031-9007. (American Physical Society)Mol. simulations corroborate the existence of the disputed window effect, i.e., an increase in diffusion rate by orders of magnitude when the alkane chain length increases so that the shape of the alkane is no longer commensurate with that of a zeolite cage. This window effect is shown to be characteristic for mol. sieves with pore openings that approach the diam. of the adsorbate. Furthermore, the phys. compatibility between the adsorbate and the adsorbent has a direct effect on the heat of adsorption, the Henry coeffs., the activation energy, and the frequency factors.
- 30Banerjee, D.; Wang, H.; Gong, Q.; Plonka, A. M.; Jagiello, J.; Wu, H.; Woerner, W. R.; Emge, T. J.; Olson, D. H.; Parise, J. B.; Li, J. Direct structural evidence of commensurate-to-incommensurate transition of hydrocarbon adsorption in a microporous metal organic framework. Chem. Sci. 2016, 7, 759– 765, DOI: 10.1039/C5SC03685B[Crossref], [PubMed], [CAS], Google Scholar30https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhslWktr7P&md5=ba6ba68cf4274027b5bd6dc1575d435aDirect structural evidence of commensurate-to-incommensurate transition of hydrocarbon adsorption in a microporous metal organic frameworkBanerjee, Debasis; Wang, Hao; Gong, Qihan; Plonka, Anna M.; Jagiello, Jacek; Wu, Haohan; Woerner, William R.; Emge, Thomas J.; Olson, David H.; Parise, John B.; Li, JingChemical Science (2016), 7 (1), 759-765CODEN: CSHCCN; ISSN:2041-6520. (Royal Society of Chemistry)The efficiency of physisorption-based sepn. of gas-mixts. depends on the selectivity of adsorbent which is directly linked to size, shape, polarizability and other phys. properties of adsorbed mols. Commensurate adsorption is an interesting and important adsorption phenomenon, where the adsorbed amt., location, and orientation of an adsorbate are commensurate with the crystal symmetry of the adsorbent. Understanding this phenomenon is important and beneficial as it can provide vital information about adsorbate-adsorbent interaction and adsorption-desorption mechanism. So far, only sporadic examples of commensurate adsorption have been reported in porous materials such as zeolites and metal org. frameworks (MOFs). In this work we show for the first time direct structural evidence of commensurate-to-incommensurate transition of linear hydrocarbon mols. (C2-C7) in a microporous MOF, by employing a no. of anal. techniques including single crystal X-ray diffraction (SCXRD), in situ powder X-ray diffraction coupled with differential scanning calorimetry (PXRD-DSC), gas adsorption and mol. simulations.
- 31Han, X.; Yang, S.; Schröder, M. Porous metal-organic frameworks as emerging sorbents for clean air. Nat. Rev. Chem. 2019, 3, 108– 118, DOI: 10.1038/s41570-019-0073-7[Crossref], [CAS], Google Scholar31https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXnsFCltrs%253D&md5=2a088bbd1f6da297a76a65e87fb93e4aPorous metal-organic frameworks as emerging sorbents for clean airHan, Xue; Yang, Sihai; Schroder, MartinNature Reviews Chemistry (2019), 3 (2), 108-118CODEN: NRCAF7; ISSN:2397-3358. (Nature Research)A review. Sulfur dioxide and nitrogen oxides generated by anthropogenic activities are air pollutants that cause serious environmental problems and pose substantial health threats. Although established methods for emission desulfurization and denitrogenation already exist, more efficient and flexible technologies are still required. In this Review, we highlight state-of-the-art examples in which metal-org. frameworks (MOFs), an emerging class of porous sorbents, have been applied to the adsorptive removal of SO2 and NO2. MOFs can simultaneously exhibit superior adsorption capacities and exceptional selectivities for SO2 and NO2 in the presence of other flue and exhaust gases while maintaining their structural integrity. The highly cryst. nature and rich chem. functionality of MOFs have enabled the elucidation of host-guest interactions at a mol. level to afford insights and new knowledge that will inspire and inform the design of new generations of adsorbents.
- 32Wu, W.; Han, B.; Gao, H.; Liu, Z.; Jiang, T.; Huang, J. Desulfurization of flue gas: SO2 absorption by an ionic liquid. Angew. Chem., Int. Ed. 2004, 43, 2415– 2417, DOI: 10.1002/anie.200353437[Crossref], [PubMed], [CAS], Google Scholar32https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2cXktFSgsL4%253D&md5=46c733352d836865894616d6e31b4258Desulfurization of flue gas: SO2 absorption by an ionic liquidWu, Weize; Han, Buxing; Gao, Haixiang; Liu, Zhimin; Jiang, Tao; Huang, JunAngewandte Chemie, International Edition (2004), 43 (18), 2415-2417CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)The ionic liq., (IL) 1,1,3,3-tetramethylguanidinium lactate, can absorb SO2 from simulated flue gas effectively under ambient conditions. Absorbed SO2 can be desorbed under vacuum or by heating, and the IL can be reused. This absorption method might be used for cleaning gases that contain SO2.
- 33Zheng, D.; An, Y.; Li, Z.; Wu, J. Metal-free aminosulfonylation of aryldiazonium tetrafluoroborates with DABCO·(SO2)2 and hydrazines. Angew. Chem., Int. Ed. 2014, 53, 2451– 2454, DOI: 10.1002/anie.201309851[Crossref], [CAS], Google Scholar34https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXhtlGks7c%253D&md5=b9716e9d61f94dff696a6f5e4e887885Metal-Free Aminosulfonylation of Aryldiazonium Tetrafluoroborates with DABCO-(SO2)2 and HydrazinesZheng, Danqing; An, Yuanyuan; Li, Zhenhua; Wu, JieAngewandte Chemie, International Edition (2014), 53 (9), 2451-2454CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)Arylsulfonylhydrazides RSO2NHR1 [R = Ph, 4-MeC6H4, 4-t-BuC6H4, 4-MeOC6H4, 4-ClC6H4, 4-BrC6H4, 4-FC6H4, 4-MeO2CC6H4, 4-O2NC6H4, 2-ClC6H4, 2-MeC6H4, 3-ClC6H4, 3-MeO2CC6H4, 3-MeOC6H4, 2,4,6-Me3C6H2; R1 = 4-morpholinyl, 1-piperidinyl, PhNMe, (S)-3-methoxymethyl-1-pyrrolidinyl, PhNEt, PhCH2NPh, Ph2N] were prepd. in 57-95% yields without added metal catalysts by the coupling of aryldiazonium tetrafluoroborates RN2+•BF4- (R = Ph, 4-MeC6H4, 4-t-BuC6H4, 4-MeOC6H4, 4-ClC6H4, 4-BrC6H4, 4-FC6H4, 4-MeO2CC6H4, 4-O2NC6H4, 2-ClC6H4, 2-MeC6H4, 3-ClC6H4, 3-MeO2CC6H4, 3-MeOC6H4, 2,4,6-Me3C6H2) with the bis(sulfur dioxide) complex of DABCO in MeCN at ambient temp. Reaction of an allyloxyphenyldiazonium tetrafluoroborate with the bis(sulfur dioxide) complex of DABCO and 4-aminomorpholine in MeCN gave a dihydrobenzofuranylmethyl sulfonylhydrazide, while reaction of phenyldiazonium tetrafluoroborate with the bis(sulfur dioxide) complex of DABCO and 4-aminomorpholine in the presence of TEMPO gave a phenoxytetramethylpiperidine as the only product, suggesting the involvement of a free radical process. The free energies and transition state free energies for a radical-based mechanism of the reaction between aryldiazonium tetrafluoroborates, DABCO•2SO2, and hydrazines were calcd.
Cited By
Abstract
Figure 1
Figure 1. Representation of structural transitions in various types of MOFs upon guest inclusion and removal. MOFs and guest molecules are shown by solid lines and shaded spheres, respectively. (a) Rigid MOF showing full retention of the framework structure on gas adsorption and desorption. (b) Flexible MOF showing reversible framework breathing between a narrow-pore phase and a large-pore phase. (c) Metastable MOF showing irreversible framework amorphization. (d) Mesoporous MOF showing the formation of superlattices of adsorbates. (e) Meta-rigid MOF, MFM-520, showing reversible incommensurate modulation of the framework structure on going from (top to bottom) MFM-520·H2O (top) to MFM-520 to MFM-520·CO2 (CO2 represented by blue spheres) to MFM-520·SO2 (SO2 represented by green spheres) (bottom).
Figure 2
Figure 2. Column I: views of in situ synchrotron X-ray diffraction images of the hk0 plane. Column II: views of the corresponding crystal structures of MFM-520 as a function of guest inclusion/removal. 8 × 8 × 2 means the unit cell of the modulated structure is 8 times that of the average structure along the a and b axes and 2 times along the c axis; 7 × 7 × 2 means the unit cell of the modulated structure is 7 times that of the average structure along the a and b axes and 2 times along the c axis. Column III: details of the structure shown in the red box in column II. Column IV: molecular details of host–guest interactions. The MOF framework, zinc, oxygen, carbon, and sulfur are shown in blue, green, red, gray, and yellow, respectively. Bond distances are shown in Å. (a) MFM-520·H2O, (b) MFM-520, (c) MFM-520·CO2, and (d) MFM-520·SO2. A comparison of all in situ synchrotron X-ray diffraction images of the hk0.5 and hk1 planes is shown in Figure S5. The reflection conditions of MFM-520·H2O are 00l: l = 2 × integer and h00: h = 2 × integer. According to superspace group theory,(12) there is a supercentered setting with as = a, bs = b, cs = 2c, Q1 = α(as* + bs*), and Q2 = α(−as* + bs*), which is equivalent to the basic setting a, b, c, q1 = α(a* + b*) + 0.5c*, and q2 = α(−a* + b*) + 0.5c*. Because the tables of (3 + 2)D superspace groups(19) provide only reflection conditions with supercenterd settings, we transformed the basic setting to supercentered settings to determine the reflection conditions. With the supercentered setting, the hk0, hk0.5, and hk1 planes are transformed to HK0, HK1, and HK2, respectively (Figure S5). The reflection conditions of MFM-520, MFM-520·CO2, and MFM-520·SO2 are HKLMN: L + M + N = 2 × integer, HK0MN: M = 2 × integer, HHLM0: L = 2 × integer, HH̅L0N: N = 2 × integer, H0LMM̅: 2H + L + 2M = 4 × integer, and 0KLMM: 2K + L + 2M = 4 × integer, corresponding to (3 + 2)D superspace group 136.2.69.10, adopting the symbol P42/mnm(α, α, 1/2)00qs(−α, α, 1/2)0sq0 with basic settings.
Figure 3
Figure 3. Maps of the bond valence sum (BVS) analyses of the oxidation state of Zn(II) centers as a function of the modulation vector u and t in (a) MFM-520, (b) MFM-520·CO2, and (c) MFM-520·SO2. The coordination geometries of the [ZnO4N] polyhedra for the lowest and highest (highlighted in blue and brown, respectively) BVS analysis maps for MFM-520, MFM-520·CO2, and MFM-520·SO2 are illustrated above the contour maps. Bond distances are in Å. BVS parameters Rij(Zn–O), b0(Zn–O), Rij(Zn–N), and b0(Zn–N) are 1.704, 0.37, 1.72, and 0.37 Å, respectively. MFM-520·H2O has a periodic structure and shows no modulation by BVS analysis; the formal oxidation state of all Zn(II) centers in MFM-520·H2O is 1.974(14).
Figure 4
Figure 4. Gas adsorption, selectivity, stability, thermodynamic, spectroscopy, and dynamic separation data. (a) Adsorption isotherms for SO2, CO2, CH4, CO, O2, and N2 in MFM-520 at 298 K (solid symbols, adsorption; open symbols, desorption). (b) Comparison of the SO2 adsorption capacity of MFM-520 over 75 cycles at 298 K. (c) Variation of isosteric heats of adsorption (Qst) and adsorption entropy (ΔS) for SO2 and CO2 uptake in MFM-520. (d) Comparison of experimental FTIR spectra for bare and CO2- and SO2-loaded MFM-520. (e) Comparison of DFT-calculated FTIR spectra for bare and CO2- and SO2-loaded MFM-520. (f) Comparison of the difference plots for experimental and DFT-calculated INS spectra of D2O-, CO2-, and SO2-loaded MFM-520 (black, experiment; red, calculation). The discrepancies, particularly for the lattice modes at low energy (<200 cm–1), are due to the limitation that DFT simulations can be conducted only on average unit cells, which does not take the incommensurate modulation into consideration. (g) Dimensionless breakthrough plots for SO2/N2 mixtures under dry (solid lines) and humid (dashed lines) conditions. Dry conditions: 2500 ppm SO2, 99.75% N2, total flow rate 50 mL min–1. Wet conditions: 1.5% H2O, 2500 ppm SO2, 98.25% N2, total flow rate 50 mL min–1. (h) Dimensionless breakthrough plots for SO2/CO2 mixtures at 298 K (15% CO2, 2500 ppm SO2, 84.75% He, total flow rate 50 mL min–1). (i) Dimensionless breakthrough plots for cyclic SO2 adsorption under both dry and humid conditions. Dry conditions: 2500 ppm SO2, 99.75% He, total flow rate 50 mL min–1. Wet conditions: 1.5% H2O, 2500 ppm SO2, 98.25% He, total flow rate 50 mL min–1. For experiments under humid conditions, the bed was first exposed to a flow of 1.5% H2O in He until the breakthrough of water.
Scheme 1
Scheme 1. Conversion of Captured SO2 in MFM-520References
ARTICLE SECTIONSThis article references 33 other publications.
- 1Kalmutzki, J. M.; Hanikel, N.; Yaghi, M. O. Secondary building units as the turning point in the development of the reticular chemistry of MOFs. Sci. Adv. 2018, 4, eaat9180, DOI: 10.1126/sciadv.aat9180
- 2Bloch, E. D.; Queen, W. L.; Krishna, R.; Zadrozny, J. M.; Brown, C. M.; Long, J. R. Hydrocarbon separation in a metal-organic framework with open iron(II) coordination sites. Science 2012, 335, 1606, DOI: 10.1126/science.1217544[Crossref], [PubMed], [CAS], Google Scholar2https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XksVyqsLc%253D&md5=d149ed45c3e688d5e4ee63d75629bd4fHydrocarbon Separations in a Metal-Organic Framework with Open Iron(II) Coordination SitesBloch, Eric D.; Queen, Wendy L.; Krishna, Rajamani; Zadrozny, Joseph M.; Brown, Craig M.; Long, Jeffrey R.Science (Washington, DC, United States) (2012), 335 (6076), 1606-1610CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)The energy costs assocd. with large-scale industrial sepn. of light hydrocarbons by cryogenic distn. could potentially be lowered through development of selective solid adsorbents that operate at higher temps. Here, the metal-org. framework Fe2(dobdc) (dobdc4- : 2,5-dioxido-1,4-benzenedicarboxylate) is demonstrated to exhibit excellent performance characteristics for sepn. of ethylene/ethane and propylene/propane mixts. at 318 K. Breakthrough data obtained for these mixts. provide exptl. validation of simulations, which in turn predict high selectivities and capacities of this material for the fractionation of methane/ethane/ethylene/acetylene mixts., removal of acetylene impurities from ethylene, and membrane-based olefin/paraffin sepns. Neutron powder diffraction data confirm a side-on coordination of acetylene, ethylene, and propylene at the iron(II) centers, while also providing solid-state structural characterization of the much weaker interactions of ethane and propane with the metal.
- 3Schneemann, A.; Bon, V.; Schwedler, I.; Senkovska, I.; Kaskel, S.; Fischer, R. A. Flexible metal-organic frameworks. Chem. Soc. Rev. 2014, 43, 6062– 6096, DOI: 10.1039/C4CS00101J[Crossref], [PubMed], [CAS], Google Scholar3https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXht1Slu7nI&md5=b824d2bff6379c9662b50e86739b42f7Flexible metal-organic frameworksSchneemann, A.; Bon, V.; Schwedler, I.; Senkovska, I.; Kaskel, S.; Fischer, R. A.Chemical Society Reviews (2014), 43 (16), 6062-6096CODEN: CSRVBR; ISSN:0306-0012. (Royal Society of Chemistry)A review. Advances in flexible and functional metal-org. frameworks (MOFs), also called soft porous crystals, are reviewed by covering the literature of the five years period 2009-2013 with ref. to the early pertinent work since the late 1990s. Flexible MOFs combine the cryst. order of the underlying coordination network with cooperative structural transformability. These materials can respond to phys. and chem. stimuli of various kinds in a tunable fashion by mol. design, which does not exist for other known solid-state materials. Among the fascinating properties are so-called breathing and swelling phenomena as a function of host-guest interactions. Phase transitions are triggered by guest adsorption/desorption, photochem., thermal, and mech. stimuli. Other important flexible properties of MOFs, such as linker rotation and sub-net sliding, which are not necessarily accompanied by crystallog. phase transitions, are briefly mentioned as well. Emphasis is given on reviewing the recent progress in application of in situ characterization techniques and the results of theor. approaches to characterize and understand the breathing mechanisms and phase transitions. The flexible MOF systems, which are discussed, are categorized by the type of metal-nodes involved and how their coordination chem. with the linker mols. controls the framework dynamics. Aspects of tailoring the flexible and responsive properties by the mixed component solid-soln. concept are included, and as well examples of possible applications of flexible metal-org. frameworks for sepn., catalysis, sensing, and biomedicine.
- 4Han, X.; Godfrey, H. G. W.; Briggs, L.; Davies, A. J.; Cheng, Y.; Daemen, L. L.; Sheveleva, A. M.; Tuna, F.; McInnes, E. J. L.; Sun, J.; Drathen, C.; George, M. W.; Ramirez-Cuesta, A. J.; Thomas, K. M.; Yang, S.; Schröder, M. Reversible adsorption of nitrogen dioxide within a robust porous metal-organic framework. Nat. Mater. 2018, 17, 691– 696, DOI: 10.1038/s41563-018-0104-7[Crossref], [PubMed], [CAS], Google Scholar4https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhtFemtr3K&md5=4e16e7aaf7dc6d94f2e4f95a15bafae7Reversible adsorption of nitrogen dioxide within a robust porous metal-organic frameworkHan, Xue; Godfrey, Harry G. W.; Briggs, Lydia; Davies, Andrew J.; Cheng, Yongqiang; Daemen, Luke L.; Sheveleva, Alena M.; Tuna, Floriana; McInnes, Eric J. L.; Sun, Junliang; Drathen, Christina; George, Michael W.; Ramirez-Cuesta, Anibal J.; Thomas, K. Mark; Yang, Sihai; Schroder, MartinNature Materials (2018), 17 (8), 691-696CODEN: NMAACR; ISSN:1476-1122. (Nature Research)Nitrogen dioxide (NO2) is a major air pollutant causing significant environmental1,2 and health problems3,4. We report reversible adsorption of NO2 in a robust metal-org. framework. Under ambient conditions, MFM-300(Al) exhibits a reversible NO2 isotherm uptake of 14.1 mmol g-1, and, more importantly, exceptional selective removal of low-concn. NO2 (5,000 to <1 ppm) from gas mixts. Complementary expts. reveal five types of supramol. interaction that cooperatively bind both NO2 and N2O4 mols. within MFM-300(Al). We find that the in situ equil. 2NO2 ↔ N2O4 within the pores is pressure-independent, whereas ex situ this equil. is an exemplary pressure-dependent first-order process. The coexistence of helical monomer-dimer chains of NO2 in MFM-300(Al) could provide a foundation for the fundamental understanding of the chem. properties of guest mols. within porous hosts. This work may pave the way for the development of future capture and conversion technologies.
- 5Krause, S.; Bon, V.; Senkovska, I.; Stoeck, U.; Wallacher, D.; Többens, D. M.; Zander, S.; Pillai, R. S.; Maurin, G.; Coudert, F.-X.; Kaskel, S. A pressure-amplifying framework material with negative gas adsorption transitions. Nature 2016, 532, 348– 352, DOI: 10.1038/nature17430[Crossref], [PubMed], [CAS], Google Scholar5https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28Xlsl2hur8%253D&md5=45dbe25185745628dc54bba9dcc564b1A pressure-amplifying framework material with negative gas adsorption transitionsKrause, Simon; Bon, Volodymyr; Senkovska, Irena; Stoeck, Ulrich; Wallacher, Dirk; Toebbens, Daniel M.; Zander, Stefan; Pillai, Renjith S.; Maurin, Guillaume; Coudert, Francois-Xavier; Kaskel, StefanNature (London, United Kingdom) (2016), 532 (7599), 348-352CODEN: NATUAS; ISSN:0028-0836. (Nature Publishing Group)Adsorption-based phenomena are important in gas sepns., such as the treatment of greenhouse-gas and toxic-gas pollutants, and in water-adsorption-based heat pumps for solar cooling systems. The ability to tune the pore size, shape and functionality of cryst. porous coordination polymers -or metal-org. frameworks (MOFs)-has made them attractive materials for such adsorption-based applications. The flexibility and guest-mol.-dependent response of MOFs give rise to unexpected and often desirable adsorption phenomena. Common to all isothermal gas adsorption phenomena, however, is increased gas uptake with increased pressure. Here we report adsorption transitions in the isotherms of a MOF (DUT-49) that exhibits a neg. gas adsorption; i.e., spontaneous desorption of gas (methane and n-butane) occurs during pressure increase in a defined temp. and pressure range. A combination of in situ powder X-ray diffraction, gas adsorption expts. and simulations shows that this adsorption behavior is controlled by a sudden hysteretic structural deformation and pore contraction of the MOF, which releases guest mols. These findings may enable technologies using frameworks capable of neg. gas adsorption for pressure amplification in micro- and macroscopic system engineering. Neg. gas adsorption extends the series of counterintuitive phenomena such as neg. thermal expansion and neg. refractive indexes and may be interpreted as an adsorptive analog of force-amplifying neg. compressibility transitions proposed for metamaterials.
- 6Katsoulidis, A. P.; Antypov, D.; Whitehead, G. F. S.; Carrington, E. J.; Adams, D. J.; Berry, N. G.; Darling, G. R.; Dyer, M. S.; Rosseinsky, M. J. Chemical control of structure and guest uptake by a conformationally mobile porous material. Nature 2019, 565, 213– 217, DOI: 10.1038/s41586-018-0820-9[Crossref], [PubMed], [CAS], Google Scholar6https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXmvFWjs7g%253D&md5=dd3b40f6520113a7f23ad984de97fbd8Chemical control of structure and guest uptake by a conformationally mobile porous materialKatsoulidis, Alexandros P.; Antypov, Dmytro; Whitehead, George F. S.; Carrington, Elliot J.; Adams, Dave J.; Berry, Neil G.; Darling, George R.; Dyer, Matthew S.; Rosseinsky, Matthew J.Nature (London, United Kingdom) (2019), 565 (7738), 213-217CODEN: NATUAS; ISSN:0028-0836. (Nature Research)Metal-org. frameworks (MOFs) are cryst. synthetic porous materials formed by binding org. linkers to metal nodes: they can be either rigid1,2 or flexible3. Zeolites and rigid MOFs have widespread applications in sorption, sepn. and catalysis that arise from their ability to control the arrangement and chem. of guest mols. in their pores via the shape and functionality of their internal surface, defined by their chem. and structure4,5. Their structures correspond to an energy landscape with a single, albeit highly functional, energy min. By contrast, proteins function by navigating between multiple metastable structures using bond rotations of the polypeptide6,7, where each structure lies in one of the min. of a conformational energy landscape and can be selected according to the chem. of the mols. that interact with the protein. These structural changes are realized through the mechanisms of conformational selection (a higher-energy min. characteristic of the protein is stabilized by small-mol. binding) and induced fit (a small mol. imposes a structure on the protein that is not a min. in the absence of that mol.)8. Rotation about covalent bonds in a peptide linker can change a flexible MOF to afford nine distinct crystal structures, revealing a conformational energy landscape that was characterized by multiple structural min. The uptake of small-mol. guests by the MOF can be chem. triggered by inducing peptide conformational change. This change transforms the material from a min. on the landscape that is inactive for guest sorption to an active one. Chem. control of the conformation of a flexible org. linker offers a route to modifying the pore geometry and internal surface chem. and thus the function of open-framework materials.
- 7Gu, C.; Hosono, N.; Zheng, J.-J.; Sato, Y.; Kusaka, S.; Sakaki, S.; Kitagawa, S. Design and control of gas diffusion process in a nanoporous soft crystal. Science 2019, 363, 387– 391, DOI: 10.1126/science.aar6833[Crossref], [PubMed], [CAS], Google Scholar7https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXhs1anu7c%253D&md5=5fc62a634e43f158b42a592c4c6be5e7Design and control of gas diffusion process in a nanoporous soft crystalGu, Cheng; Hosono, Nobuhiko; Zheng, Jia-Jia; Sato, Yohei; Kusaka, Shinpei; Sakaki, Shigeyoshi; Kitagawa, SusumuScience (Washington, DC, United States) (2019), 363 (6425), 387-391CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)Design of the gas-diffusion process in a porous material is challenging because a contracted pore aperture is a prerequisite, whereas the channel traffic of guest mols. is regulated by the flexible and dynamic motions of nanochannels. Here, we present the rational design of a diffusion-regulatory system in a porous coordination polymer (PCP) in which flip-flop mol. motions within the framework structure provide kinetic gate functions that enable efficient gas sepn. and storage. The PCP shows substantial temp.-responsive adsorption in which the adsorbate mols. are differentiated by each gate-admission temp., facilitating kinetics-based gas sepns. of oxygen/argon and ethylene/ethane with high selectivities of ∼350 and ∼75, resp. Addnl., we demonstrate the long-lasting phys. encapsulation of ethylene at ambient conditions, owing to strongly impeded diffusion in distinctive nanochannels.
- 8Goodwin, A. L.; Calleja, M.; Conterio, M. J.; Dove, M. T.; Evans, J. S. O.; Keen, D. A.; Peters, L.; Tucker, M. G. Colossal positive and negative thermal expansion in the framework material Ag3[Co(CN)6]. Science 2008, 319, 794– 797, DOI: 10.1126/science.1151442[Crossref], [PubMed], [CAS], Google Scholar8https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXhsFGhs74%253D&md5=f5490d51f1e9db0f3d7906bb3c215c16Colossal Positive and Negative Thermal Expansion in the Framework Material Ag3[Co(CN)6]Goodwin, Andrew L.; Calleja, Mark; Conterio, Michael J.; Dove, Martin T.; Evans, John S. O.; Keen, David A.; Peters, Lars; Tucker, Matthew G.Science (Washington, DC, United States) (2008), 319 (5864), 794-797CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)We show that silver(I) hexacyanocobaltate(III), Ag3[Co(CN)6], exhibits pos. and neg. thermal expansion an order of magnitude greater than that seen in other cryst. materials. This framework material expands along one set of directions at a rate comparable to the most weakly bound solids known. By flexing like lattice fencing, the framework couples this to a contraction along a perpendicular direction. This gives neg. thermal expansion that is 14 times larger than in ZrW2O8. D. functional theory calcns. quantify both the low energy assocd. with this flexibility and the role of argentophilic (Ag+...Ag+) interactions. This study illustrates how the mech. properties of a van der Waals solid might be engineered into a rigid, useable framework.
- 9Serre, C.; Millange, F.; Thouvenot, C.; Noguès, M.; Marsolier, G.; Louër, D.; Férey, G. Very large breathing effect in the first nanoporous chromium(III)-based solids: MIL-53 or Cr(III)(OH)·{O2C-C6H4-CO2}·{HO2C-C6H4-CO2H}x·H2Oy. J. Am. Chem. Soc. 2002, 124, 13519– 13526, DOI: 10.1021/ja0276974[ACS Full Text], [CAS], Google Scholar9https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD38XotVegt74%253D&md5=59fd68d1cae2399f56196e58039d3bd5Very Large Breathing Effect in the First Nanoporous Chromium(III)-Based Solids: MIL-53 or CrIII(OH)·{O2C-C6H4-CO2}·{HO2C-C6H4-CO2H}x·H2OySerre, Christian; Millange, Franck; Thouvenot, Christelle; Nogues, Marc; Marsolier, Gerard; Loueer, Daniel; Ferey, GerardJournal of the American Chemical Society (2002), 124 (45), 13519-13526CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)The 1st three-dimensional Cr(III) dicarboxylate, MIL-53as or CrIII(OH)·{O2C-C6H4-CO2}·{HO2C-C6H4-CO2H}0.75, was obtained under hydrothermal conditions (as: as-synthesized). The free acid can be removed by calcination giving the resulting solid, MIL-53ht or CrIII(OH)·{O2C-C6H4-CO2}. At room temp., MIL-53ht adsorbs atm. H2O immediately to give CrIII(OH)·{O2C-C6H4-CO2}·H2O or MIL-53lt (lt: low-temp. form, ht:high-temp. form). Structures, which were detd. by using x-ray powder diffraction data, are built up from chains of Cr(III) octahedra linked through terephthalate dianions. This creates a three-dimensional structure with an array of 1-dimensional large pore channels filled with free disordered terephthalic mols. (MIL-53as) or H2O mols. (MIL-53lt); when the free mols. are removed, this leads to a nanoporous solid (MIL-53ht) with a Langmuir surface area over 1500 m2/g. The transition between the hydrated form (MIL-53lt) and the anhyd. solid (MIL-53ht) is fully reversible and followed by a very high breathing effect (more than 5 Å), the pores being clipped in the presence of H2O mols. (MIL-53lt) and reopened when the channels are empty (MIL-53ht). The thermal behavior of the two solids was studied using TGA and x-ray thermodiffractometry. The sorption properties of MIL-53lt also were studied using several org. solvents. Finally, magnetism measurements performed on MIL-53as and MIL-53lt revealed that these two phases are antiferromagnetic with Neel temps. TN of 65 and 55 K, resp. Crystal data for MIL-53as is as follows: orthorhombic space group Pnam with a 17.340(1), b 12.178(1), c 6.822(1) Å, and Z = 4. Crystal data for MIL-53ht is as follows: orthorhombic space group Imcm with a 16.733(1), b 13.038(1), c 6.812(1) Å, and Z = 4. Crystal data for MIL-53lt is as follows: monoclinic space group C2/c with a 19.685(4), b 7.849(1), c 6.782(1) Å, β 104.90(1)°, and Z = 4.
- 10Deria, P.; Gómez-Gualdrón, D. A.; Bury, W.; Schaef, H. T.; Wang, T. C.; Thallapally, P. K.; Sarjeant, A. A.; Snurr, R. Q.; Hupp, J. T.; Farha, O. K. Ultraporous, water stable, and breathing zirconium-based metal-organic frameworks with ftw topology. J. Am. Chem. Soc. 2015, 137, 13183– 13190, DOI: 10.1021/jacs.5b08860[ACS Full Text], [CAS], Google Scholar10https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhsFanurbJ&md5=e49fde249c557fa2ff56727b6f6ec306Ultraporous, Water Stable, and Breathing Zirconium-Based Metal-Organic Frameworks with ftw TopologyDeria, Pravas; Gomez-Gualdron, Diego A.; Bury, Wojciech; Schaef, Herbert T.; Wang, Timothy C.; Thallapally, Praveen K.; Sarjeant, Amy A.; Snurr, Randall Q.; Hupp, Joseph T.; Farha, Omar K.Journal of the American Chemical Society (2015), 137 (40), 13183-13190CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)Breathing metal-org. frameworks (MOFs) are an emerging class of soft porous crystals (SPCs) with potential for high working capacity for gas storage applications. However, most breathing MOFs have low stability and/or low surface area. Here the authors report a H2O-stable, high surface area, breathing MOF of ftw topol., NU-1105. While Zr6-oxo clusters as nodes introduce H2O stability in NU-1105, its high surface area and breathing character stem from its pyrene-based tetracarboxylate (Py-FP) linkers, in which the fluorene units (F) in the FP arms play a key role in promoting breathing behavior. During gas sorption studies, the closed pore (cp) ↔ open pore (op) transition of NU-1105 occurs at a propane pressure of ∼3 bar. At 1 bar, NU-1105 is in its cp form and adsorbs less propane than it would in its op form, highlighting improved working capacity. In situ powder x-ray diffraction during propane sorption was used to track the cp ↔ op transition, and mol. modeling was used to elucidate the structure of the op and cp forms of NU-1105. According to TD-DFT calcns., the proposed conformations of the Py-FP linkers in the op and cp forms are consistent with the measured excitation and emission spectra of the op and cp forms of NU-1105. Similar structural transitions are also obsd. in the porphyrinic MOF NU-1104 depending on the identity of the porphyrin core; the authors obsd. breathing behavior if the constituent Por-PTP linker is nonmetalated.
- 11Sung Cho, H.; Deng, H.; Miyasaka, K.; Dong, Z.; Cho, M.; Neimark, A. V.; Ku Kang, J.; Yaghi, O. M.; Terasaki, O. Extra adsorption and adsorbate superlattice formation in metal-organic frameworks. Nature 2015, 527, 503– 507, DOI: 10.1038/nature15734[Crossref], [PubMed], [CAS], Google Scholar11https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhvVWmsrjL&md5=4666eb877d5a30907bf7854fbb443accExtra adsorption and adsorbate superlattice formation in metal-organic frameworksSung Cho, Hae; Deng, Hexiang; Miyasaka, Keiichi; Dong, Zhiyue; Cho, Minhyung; Neimark, Alexander V.; Ku Kang, Jeung; Yaghi, Omar M.; Terasaki, OsamuNature (London, United Kingdom) (2015), 527 (7579), 503-507CODEN: NATUAS; ISSN:0028-0836. (Nature Publishing Group)Metal-org. frameworks (MOFs) have a high internal surface area and widely tunable compn., which make them useful for applications involving adsorption, such as hydrogen, methane or carbon dioxide storage. The selectivity and uptake capacity of the adsorption process are detd. by interactions involving the adsorbates and their porous host materials. But, although the interactions of adsorbate mols. with the internal MOF surface and also amongst themselves within individual pores have been extensively studied, adsorbate-adsorbate interactions across pore walls have not been explored. Here we show that local strain in the MOF, induced by pore filling, can give rise to collective and long-range adsorbate-adsorbate interactions and the formation of adsorbate superlattices that extend beyond an original MOF unit cell. Specifically, we use in situ small-angle X-ray scattering to track and map the distribution and ordering of adsorbate mols. in five members of the mesoporous MOF-74 series along entire adsorption-desorption isotherms. We find in all cases that the capillary condensation that fills the pores gives rise to the formation of 'extra adsorption domains'-i.e., domains spanning several neighboring pores, which have a higher adsorbate d. than non-domain pores. In the case of one MOF, IRMOF-74-V-hex, these domains form a superlattice structure that is difficult to reconcile with the prevailing view of pore-filling as a stochastic process. The visualization of the adsorption process provided by our data, with clear evidence for initial adsorbate aggregation in distinct domains and ordering before an even distribution is finally reached, should help to improve our understanding of this process and may thereby improve our ability to exploit it practically.
- 12Janssen, T.; Chapuis, G.; Boissieu, M. Aperiodic Crystals: From Modulated Phases to Quasicrystals: Structure and Properties; Oxford University Press: Oxford, 2018.
- 13Baerlocher, C.; Weber, T.; McCusker, L.; Palatinus, L.; Zones, I. S. Unraveling the perplexing structure of the zeolite SSZ-57. Science 2011, 333, 1134– 1137, DOI: 10.1126/science.1207466[Crossref], [PubMed], [CAS], Google Scholar13https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhtVGktr3O&md5=d0c7b3947c1325e5ca4e71f360c81c90Unraveling the Perplexing Structure of the Zeolite SSZ-57Baerlocher, Christian; Weber, Thomas; McCusker, Lynne B.; Palatinus, Lukas; Zones, Stacey I.Science (Washington, DC, United States) (2011), 333 (6046), 1134-1137CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)Crystal structure of the zeolite SSZ-57 has been detd. using advanced crystallog. techniques (structure soln. in four-dimensional space and interpretation of three-dimensional diffuse scattering by Monte Carlo simulation) and crystal chem. considerations applied to high-quality single-crystal X-ray diffraction data. The crystal structure was related to that of ZSM-11 but was commensurately modulated along the c axis (P‾4m2, a = b = 20.091, and c = 110.056 Å) to yield a structure with a 12-ring:10-ring ratio of 1:15. Disorder of the 12-rings resulted in a three-dimensional 10-ring channel system with large isolated pockets. The structure helps to clarify the material's catalytic activity.
- 14Lin, X.; Blake, A. J.; Wilson, C.; Sun, X. Z.; Champness, N. R.; George, M. W.; Hubberstey, P.; Mokaya, R.; Schröder, M. A porous framework polymer based on a zinc(II) 4,4′-bipyridine-2,6, 2′, 6′- tetracarboxylate: synthesis, structure, and “zeolite-like” behaviors. J. Am. Chem. Soc. 2006, 128, 10745– 10753, DOI: 10.1021/ja060946u[ACS Full Text], [CAS], Google Scholar14https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD28XnsF2hu7g%253D&md5=814ce41c31d52c3157a64dacc7681a50A Porous Framework Polymer Based on a Zinc(II) 4,4'-Bipyridine-2,6,2',6'-tetracarboxylate: Synthesis, Structure, and "Zeolite-Like" BehaviorsLin, Xiang; Blake, Alexander J.; Wilson, Claire; Sun, Xue Zhong; Champness, Neil R.; George, Michael W.; Hubberstey, Peter; Mokaya, Robert; Schroeder, MartinJournal of the American Chemical Society (2006), 128 (33), 10745-10753CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)The robust metal-org. framework compd. {[Zn2(L)]·4H2O}∞ (I) was synthesized by hydrothermal reaction of ZnCl2 and 4,4'-bipyridine-2,6,2',6'-tetracarboxylic acid (H4L). Compd. I crystallizes in a chiral space group, P42212, with the chirality generated by the helical chains of H-bonded guest H2O mols. rather than by the coordination framework. Removal of guest H2O mols. from the crystal affords the porous material, [Zn2(L)]∞ (II), which has very high thermal stability and is chem. inert. The N2 isotherm of II at 77 K suggests a uniform porous structure with a BET surface area of 312.7 m2/g and a remarkably strong interaction with N2 mols. (βE0 = 29.6 kJ mol-1). II also exhibits significant gas storage capacities of 1.08% for H2 at 4 bar and 77 K and 3.14% (44.0 cm3/g, 67 vol./vol.) for methane at 9 bar at 298 K. The adsorption behavior of II toward org. solvent vapors also was studied, and isotherms reveal that for different solvent vapors adsorption is dominated by two types of processes, absorbate-absorbate or absorbate-absorbent interactions. The adsorption and desorption kinetic processes in II are detd. mainly by the mol. size of the guest species and their interaction with the host.
- 15Petricek, V.; Dusek, M.; Palatinus, L. Crystallographic computing system JANA2006: general features. Z. Kristallogr. - Cryst. Mater. 2014, 229, 345– 352, DOI: 10.1515/zkri-2014-1737[Crossref], [CAS], Google Scholar15https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXmslyjsbs%253D&md5=6cc7613194f2b2f1d3f14be9a64f76bbCrystallographic Computing System JANA2006: General featuresPetricek, Vaclav; Dusek, Michal; Palatinus, LukasZeitschrift fuer Kristallographie - Crystalline Materials (2014), 229 (5), 345-352CODEN: ZKCMAJ; ISSN:2194-4946. (Oldenbourg Wissenschaftsverlag GmbH)JANA2006 is a freely available program for structure detn. of std., modulated and magnetic samples based on X-ray or neutron single crystal/ powder diffraction or on electron diffraction. The system has been developed for 30 years from specialized tool for refinement of modulated structures to a universal program covering std. as well as advanced crystallog. The aim of this article is to describe the basic features of JANA2006 and explain its scope and philosophy. It will also serve as a basis for future publications detailing tools and methods of JANA.
- 16Clark, S. J.; Segall, M. D.; Pickard, C. J.; Hasnip, P. J.; Probert, M. I. J.; Refson, K.; Payne, M. C. First principles methods using CASTEP. Z. Kristallogr. - Cryst. Mater. 2005, 220, 567– 571, DOI: 10.1524/zkri.220.5.567.65075[Crossref], [CAS], Google Scholar16https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2MXmsVSitbk%253D&md5=edb75e2f9d4df4ad83f4df7db21888e7First principles methods using CASTEPClark, Stewart J.; Segall, Matthew D.; Pickard, Chris J.; Hasnip, Phil J.; Probert, Matt I. J.; Refson, Keith; Payne, Mike C.Zeitschrift fuer Kristallographie (2005), 220 (5-6), 567-570CODEN: ZEKRDZ; ISSN:0044-2968. (Oldenbourg Wissenschaftsverlag GmbH)The CASTEP code for first principles electronic structure calcns. is described. A brief, non-tech. overview is given and some of the features and capabilities highlighted. Some features which are unique to CASTEP are described and near-future development plans outlined.
- 17Cheng, Y. Q.; Daemen, L. L.; Kolesnikov, A. I.; Ramirez-Cuesta, A. J. Simulation of inelastic neutron scattering spectra using OCLIMAX. J. Chem. Theory Comput. 2019, 15, 1974– 1982, DOI: 10.1021/acs.jctc.8b01250[ACS Full Text], [CAS], Google Scholar17https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXislertrk%253D&md5=ab97e508f78304baadfd0af414d79a52Simulation of Inelastic Neutron Scattering Spectra Using OCLIMAXCheng, Y. Q.; Daemen, L. L.; Kolesnikov, A. I.; Ramirez-Cuesta, A. J.Journal of Chemical Theory and Computation (2019), 15 (3), 1974-1982CODEN: JCTCCE; ISSN:1549-9618. (American Chemical Society)Studying the vibration of atoms is of fundamental importance and can provide crit. insight for the understanding of materials behavior, such as structure and phase transition, thermodn., and chem. reactions. The at. vibration can be probed using vibrational spectroscopy with various incident particles such as photons, neutrons, or electrons. A major challenge when applying these techniques is often how to interpret the vibrational spectra and how to make connections to the theory. To this end, methods that can simulate the spectra from atomistic models are highly desired. In this paper, we present a program developed for the simulation of inelastic neutron scattering spectra. It has many new and useful features that were not previously available and will greatly facilitate the anal. and understanding of inelastic neutron scattering data.
- 18Boyer, L. L.; Kaxiras, E.; Feldman, J. L.; Broughton, J. Q.; Mehl, M. J. New low-energy crystal structure for silicon. Phys. Rev. Lett. 1991, 67, 715, DOI: 10.1103/PhysRevLett.67.715[Crossref], [PubMed], [CAS], Google Scholar18https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK3MXlsVOjtL8%253D&md5=6d5d51a5b31a8b02186b5e147975e81aNew low-energy crystal structure for siliconBoyer, L. L.; Kaxiras, Efthimios; Feldman, J. L.; Broughton, J. Q.; Mehl, M. J.Physical Review Letters (1991), 67 (6), 715-18CODEN: PRLTAO; ISSN:0031-9007.A min.-energy path in strain space was detd. which takes cubic Si into itself. Energies are computed using the Stillinger-Weber model potential and first-principles total-energy calcns. The energy along this path has an addnl. min., corresponding to a crystal structure with a body-centered-tetragonal lattice and 5-fold-coordinated atoms. Lattice-dynamics, mol.-dynamics, and elastic-const. calcns. show the structure is stable.
- 19Stokes, H. T.; Hatch, D. M.; Campbell, B. J. ISO(3+d)D, ISOTROPY Software Suite, iso.byu.edu.
- 20Brese, N. E.; O’Keeffe, M. Bond-valence parameters for solids. Acta Crystallogr., Sect. B: Struct. Sci. 1991, 47, 192– 197, DOI: 10.1107/S0108768190011041
- 21Ovsyannikov, S. V.; Bykov, M.; Bykova, E.; Kozlenko, D. P.; Tsirlin, A. A.; Karkin, A. E.; Shchennikov, V. V.; Kichanov, S. E.; Gou, H.; Abakumov, A. M.; Egoavil, R.; Verbeeck, J.; McCammon, C.; Dyadkin, V.; Chernyshov, D.; van Smaalen, S.; Dubrovinsky, L. S. Charge-ordering transition in iron oxide Fe4O5 involving competing dimer and trimer formation. Nat. Chem. 2016, 8, 501– 508, DOI: 10.1038/nchem.2478[Crossref], [PubMed], [CAS], Google Scholar21https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XlsVajtb8%253D&md5=17cff2f037f0d8d1fdf322d2704d7340Charge-ordering transition in iron oxide Fe4O5 involving competing dimer and trimer formationOvsyannikov, Sergey V.; Bykov, Maxim; Bykova, Elena; Kozlenko, Denis P.; Tsirlin, Alexander A.; Karkin, Alexander E.; Shchennikov, Vladimir V.; Kichanov, Sergey E.; Gou, Huiyang; Abakumov, Artem M.; Egoavil, Ricardo; Verbeeck, Johan; McCammon, Catherine; Dyadkin, Vadim; Chernyshov, Dmitry; van Smaalen, Sander; Dubrovinsky, Leonid S.Nature Chemistry (2016), 8 (5), 501-508CODEN: NCAHBB; ISSN:1755-4330. (Nature Publishing Group)Phase transitions that occur in materials, driven, for instance, by changes in temp. or pressure, can dramatically change the materials' properties. Discovering new types of transitions and understanding their mechanisms is important not only from a fundamental perspective, but also for practical applications. Here the authors study a recently discovered Fe4O5 that adopts an orthorhombic CaFe3O5-type crystal structure that features linear chains of Fe ions. On cooling .ltorsim.150 K, Fe4O5 undergoes an unusual charge-ordering transition that involves competing dimeric and trimeric ordering within the chains of Fe ions. This transition is concurrent with a significant increase in elec. resistivity. Magnetic-susceptibility measurements and neutron diffraction establish the formation of a collinear antiferromagnetic order above room temp. and a spin canting at 85 K that gives rise to spontaneous magnetization. Possible mechanisms of this transition and compare it with the trimeronic charge ordering obsd. in magnetite below the Verwey transition temp. are discussed.
- 22Prokeš, K.; Hartwig, S.; Gukasov, A.; Mydosh, J. A.; Huang, Y. K.; Niehaus, O.; Pöttgen, R. Coexistence of different magnetic moments in CeRuSn probed by polarized neutrons. Phys. Rev. B: Condens. Matter Mater. Phys. 2015, 91, 014424, DOI: 10.1103/PhysRevB.91.014424[Crossref], [CAS], Google Scholar22https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXlt1Kht74%253D&md5=28a90a13832829f2fd604a2f7eb48285Coexistence of different magnetic moments in CeRuSn probed by polarized neutronsProkes, K.; Hartwig, S.; Gukasov, A.; Mydosh, J. A.; Huang, Y.-K.; Niehaus, O.; Poettgen, R.Physical Review B: Condensed Matter and Materials Physics (2015), 91 (1), 014424/1-014424/6CODEN: PRBMDO; ISSN:1098-0121. (American Physical Society)We report on the spin densities in CeRuSn detd. at elevated and at low temps. using polarized neutron diffraction. At 285 K, where the CeRuSn crystal structure contains two different crystallog. Ce sites, we observe that a Ce site with larger nearest-neighbor distances is clearly more susceptible to the applied magnetic field, whereas the other is hardly polarizable. This finding clearly documents that different local environment of the two Ce sites causes the Ce ions to split into magnetic Ce3+ and nonmagnetic Ce(4-δ)+ valence states. With lowering the temp., the crystal structure transforms to a structure incommensurately modulated along the c axis. This leads to new inequivalent crystallog. Ce sites resulting in a redistribution of spin densities. Our anal. using the simplest structural approximant shows that in this metallic system Ce ions coexist in different valence states. Localized 4 f states that fulfill the third Hund's rule are found to be close to the ideal Ce3+ state (at sites with the largest Ce-Ru interat. distances), whereas Ce(4-δ)+ valence states are found to be itinerant and situated at Ce sites with much shorter Ce-Ru distances. The similarity to the famous γ-α transition in elemental cerium is discussed.
- 23Sun, Z.; Li, J.; Ji, C.; Sun, J.; Hong, M.; Luo, J. Unusual long-range ordering incommensurate structural modulations in an organic molecular ferroelectric. J. Am. Chem. Soc. 2017, 139, 15900– 15906, DOI: 10.1021/jacs.7b08950[ACS Full Text], [CAS], Google Scholar23https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhs1KnsLrL&md5=2b23441afd78eba7a775e6263dcd1aecUnusual Long-Range Ordering Incommensurate Structural Modulations in an Organic Molecular FerroelectricSun, Zhihua; Li, Jian; Ji, Chengmin; Sun, Junliang; Hong, Maochun; Luo, JunhuaJournal of the American Chemical Society (2017), 139 (44), 15900-15906CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)The incommensurate (IC) behaviors of ferroelecs. have been widely investigated in inorg. oxides as an exciting branch for aperiodic materials, whereas it still remains a great challenge to achieve such intriguing effects in org. systems. Here, we present that successive ordering of dynamic dipoles in an org. mol. ferroelec., N-isopropylbenzylaminium trichloroacetate (1), enables unusual incommensurately modulated structures between its paraelec. phase and ferroelec. phase. In particular, 1 exhibits three distinct IC states coupling with a long-range ordering modulation. That is, the incommensurately modulated lattice is ∼7 times as large as its periodic prototype, and the IC structure is well solved using a (3 + 1)D superspace group with the modulated wavevector q = (0, 0, 0.1589). To the best of our knowledge, 1 is the first org. ferroelec. showing such a long-range ordering IC structural modulation. In addn., structural analyses reveal that slowing down dynamic motions of anionic moieties accounts for its modulation behaviors, which also results in dramatic reorientation of dipolar moments and concrete ferroelec. polarization of 1 (∼0.65 μC/cm2). The combination of unique IC structural modulations and ferroelectricity makes 1 a potential candidate for the assembly of an artificially modulated lattice, which will allow for a deep understanding of the underlying chem. and physics of aperiodic materials.
- 24He, H.; Tan, X. Electric-field-induced transformation of incommensurate modulations in antiferroelectric Pb0.99Nb0.02[(Zr1-xSnx)1-yTiy]0.98O3. Phys. Rev. B: Condens. Matter Mater. Phys. 2005, 72, 024102, DOI: 10.1103/PhysRevB.72.024102[Crossref], [CAS], Google Scholar24https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2MXmvFyktbY%253D&md5=772b89625e5c3d224dc78d01852f5079Electric-field-induced transformation of incommensurate modulations in antiferroelectric Pb0.99Nb0.02[(Zr1-xSnx)1-yTiy]0.98O3He, Hui; Tan, XiaoliPhysical Review B: Condensed Matter and Materials Physics (2005), 72 (2), 024102/1-024102/10CODEN: PRBMDO; ISSN:1098-0121. (American Physical Society)Most antiferroelec. ceramics are modified from the prototype PbZrO3 by adding Sn and Ti in conjunction with small amt. of Nb or La to optimize their properties. These modifiers introduce unique nanoscale structural feature to the ceramics as incommensurate modulations. It was shown previously that the modulation is strongly responsive to a change in chem. compn. or temp. However, its response to an elec. field, the driving force in real applications, was not explored before. The dynamic evolution of the incommensurate modulation during the elec. field-induced antiferroelec.-to-ferroelec. transformation was obsd. with an in situ TEM technique. The incommensurate modulation exists as a transverse Pb-cation displacement wave. The wavelength is quite stable against external elec. stimuli, in sharp contrast to the dramatic change under thermal stimuli reported previously. Probably the appeared incommensurate modulation is an av. effect of a mixt. of two commensurate modulations. The elec. field-induced antiferroelec.-to-ferroelec. transformation proceeds with aligning the Pb-cation displacements, which resembles the process of 90° reorientation and 180° reversal in normal ferroelecs.
- 25Cui, X.; Yang, Q.; Yang, L.; Krishna, R.; Zhang, Z.; Bao, Z.; Wu, H.; Ren, Q.; Zhou, W.; Chen, B.; Xing, H. Ultrahigh and selective SO2 uptake in inorganic anion-pillared hybrid porous materials. Adv. Mater. 2017, 29, 1606929, DOI: 10.1002/adma.201606929
- 26Yang, S.; Liu, L.; Sun, J.; Thomas, K. M.; Davies, A. J.; George, M. W.; Blake, A. J.; Hill, A. H.; Fitch, A. N.; Tang, C. C.; Schröder, M. Irreversible network transformation in a dynamic porous host catalyzed by sulfur dioxide. J. Am. Chem. Soc. 2013, 135, 4954– 4957, DOI: 10.1021/ja401061m[ACS Full Text], [CAS], Google Scholar26https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXktVCkt74%253D&md5=e94870fe12554b0dcc7e1925343d140bIrreversible Network Transformation in a Dynamic Porous Host Catalyzed by Sulfur DioxideYang, Sihai; Liu, Leifeng; Sun, Junliang; Thomas, K. Mark; Davies, Andrew J.; George, Michael W.; Blake, Alexander J.; Hill, Adrian H.; Fitch, Andrew N.; Tang, Chiu C.; Schroder, MartinJournal of the American Chemical Society (2013), 135 (13), 4954-4957CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)Porous NOTT-202a shows exceptionally high uptake of SO2, 13.6 mmol g-1 (87.0 wt.%) at 268 K and 1.0 bar, representing the highest value reported to date for a framework material. NOTT-202a undergoes a distinct irreversible framework phase transition upon SO2 uptake at 268-283 K to give NOTT-202b which has enhanced stability due to the formation of strong π···π interactions between interpenetrated networks.
- 27Yang, S.; Sun, J.; Ramirez-Cuesta, A. J.; Callear, S. K.; David, W. I. F.; Anderson, D. P.; Newby, R.; Blake, A. J.; Parker, J. E.; Tang, C. C.; Schröder, M. Selectivity and direct visualization of carbon dioxide and sulfur dioxide in a decorated porous host. Nat. Chem. 2012, 4, 887– 894, DOI: 10.1038/nchem.1457[Crossref], [PubMed], [CAS], Google Scholar27https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhtlymtbbF&md5=3329e5c8d3c0261f0a7b276837539168Selectivity and direct visualization of carbon dioxide and sulfur dioxide in a decorated porous hostYang, Sihai; Sun, Junliang; Ramirez-Cuesta, Anibal J.; Callear, Samantha K.; David, William I. F.; Anderson, Daniel P.; Newby, Ruth; Blake, Alexander J.; Parker, Julia E.; Tang, Chiu C.; Schroeder, MartinNature Chemistry (2012), 4 (11), 887-894CODEN: NCAHBB; ISSN:1755-4330. (Nature Publishing Group)Understanding the mechanism by which porous solids trap harmful gases, e.g., CO2 and SO2, is essential to design new materials for their selective removal. Materials with amine group functionalization dominate this field, largely due to their potential to form carbamates through H2N(δ-)···C(δ+)O2 interactions, thereby covalently trapping CO2; however, the use of these materials is energy-intensive with significant environmental impacts. A non-amine-contg. porous solid (NOTT-300) in which OH- groups within pores selective bind CO2 and SO2 is reported. In-situ powder x-ray diffraction and inelastic neutron scattering studies in conjunction with modeling showed the OH- groups bind CO2 and SO2 by forming O=C(S)=O(δ-)···H(δ+)-O hydrogen bonds, which are reinforced by weak supra-mol. interactions with C-H atoms on the framework arom. rings. This offers the potential for using easy-on/easy-off capture systems for CO2 and SO2 with fewer economic and environmental penalties.
- 28Bell, J. G.; Morris, S. A.; Aidoudi, F.; McCormick, L. J.; Morris, R. E.; Thomas, K. M. Physisorption-induced structural change directing carbon monoxide chemisorption and nitric oxide coordination on hemilabile porous metal organic framework NaNi3(OH)(SIP)2(H2O)5·H2O (SIP = 5-sulfoisophthalate). J. Mater. Chem. A 2017, 5, 23577– 23591, DOI: 10.1039/C7TA05910H[Crossref], [CAS], Google Scholar28https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhslWrsb3F&md5=4bc517d3d573afdf77ffb83af8f32945Physisorption-induced structural change directing carbon monoxide chemisorption and nitric oxide coordination on hemilabile porous metal organic framework NaNi3(OH)(SIP)2(H2O)5·H2O (SIP = 5-sulfoisophthalate)Bell, Jon G.; Morris, Samuel A.; Aidoudi, Farida; McCormick, Laura J.; Morris, Russell E.; Thomas, K. MarkJournal of Materials Chemistry A: Materials for Energy and Sustainability (2017), 5 (45), 23577-23591CODEN: JMCAET; ISSN:2050-7496. (Royal Society of Chemistry)Structural changes occur during thermal activation of NaNi3(OH)(SIP)2(H2O)5·H2O and NaCo3(OH)(SIP)2(H2O)5·H2O, forming porous framework materials. Activating NaNi3(OH)(SIP)2(H2O)5·H2O at 400° K gave NaNi3(OH)(SIP)2(H2O)2; at 513° K gave NaNi3(OH)(SIP)2. CO adsorption/desorption on NaNi3(OH)(SIP)2(H2O)2 at 348° K and 20 bar was hysteretic, but all CO was desorbed in vacuum. NaNi3(OH)(SIP)2(H2O)2 was exposed to NO to establish the accessibility of unsatd. metal centers; crystallog. results showed NO binds to Ni with bent coordination geometry. CO adsorption characteristics on isostructural NaNi3(OH)(SIP)2 and NaCo3(OH)(SIP)2 were examd. at 268-348° K and pressure up to 20 bar. CO surface excess isotherms for NaNi3(OH)(SIP)2 at 348° K were reversible and non-hysteretic at pressure below the isotherm point of inflection; however, above this point, isotherms had reversible and irreversible adsorption components. The irreversible component remaining adsorbed in ultra-high vacuum at 348° K was 4.9 wt. percent. Subsequent sequential CO adsorption/desorption isotherms were non-hysteretic and fully reversible. Thermal stability and stoichiometry of the product were assessed using in-situ temp. programmed desorption in conjunction with thermogravimetric anal. and mass spectrometry. This gave a discrete CO peak at ∼500° K indicating thermally stable CO bonding to the framework (0.42 × CO/formula desorbed [2.31 wt. percent]); a weaker CO2 peak was obsd. at 615° K. The remaining adsorbed species were desorbed as a mixt. of CO and CO2, overlapping with NaNi3(OH)(SIP)2 framework decompn. CO physisorption induced structural change, which led to CO chemisorption on NaNi3(OH)(SIP)2 above the point of inflection in the isotherm and the formation of a new thermally stable porous framework confirmed by CO2 adsorption at 273°K. Thus, CO chemisorption was attributed to cleaving the hemilabile switchable sulfonate group; framework structural integrity was retained by stable carboxylate linkers. Assessments of CO adsorption on NaCo3(OH)(SIP)2 showed hysteretic isotherms; no evidence of irreversible chemisorption CO was obsd. CO/N2 selectivity for NaNi3(OH)(SIP)2 and NaCo3(OH)(SIP)2 was 2.4-2.85 (1-10 bar) and 1.74-1.81 (1-10 bar), resp. This was the first demonstration of physisorption driving structural change in a hemilabile porous framework material; it demonstrated a transition from physisorption to irreversible thermally stable CO chemisorption.
- 29Dubbeldam, D.; Calero, S.; Maesen, T. L. M.; Smit, B. Incommensurate diffusion in confined systems. Phys. Rev. Lett. 2003, 90, 245901, DOI: 10.1103/PhysRevLett.90.245901[Crossref], [PubMed], [CAS], Google Scholar29https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3sXkvVaktL4%253D&md5=beb5309f2a75ae65cd68fbc109f947b8Incommensurate Diffusion in Confined SystemsDubbeldam, D.; Calero, S.; Maesen, T. L. M.; Smit, B.Physical Review Letters (2003), 90 (24), 245901/1-245901/4CODEN: PRLTAO; ISSN:0031-9007. (American Physical Society)Mol. simulations corroborate the existence of the disputed window effect, i.e., an increase in diffusion rate by orders of magnitude when the alkane chain length increases so that the shape of the alkane is no longer commensurate with that of a zeolite cage. This window effect is shown to be characteristic for mol. sieves with pore openings that approach the diam. of the adsorbate. Furthermore, the phys. compatibility between the adsorbate and the adsorbent has a direct effect on the heat of adsorption, the Henry coeffs., the activation energy, and the frequency factors.
- 30Banerjee, D.; Wang, H.; Gong, Q.; Plonka, A. M.; Jagiello, J.; Wu, H.; Woerner, W. R.; Emge, T. J.; Olson, D. H.; Parise, J. B.; Li, J. Direct structural evidence of commensurate-to-incommensurate transition of hydrocarbon adsorption in a microporous metal organic framework. Chem. Sci. 2016, 7, 759– 765, DOI: 10.1039/C5SC03685B[Crossref], [PubMed], [CAS], Google Scholar30https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhslWktr7P&md5=ba6ba68cf4274027b5bd6dc1575d435aDirect structural evidence of commensurate-to-incommensurate transition of hydrocarbon adsorption in a microporous metal organic frameworkBanerjee, Debasis; Wang, Hao; Gong, Qihan; Plonka, Anna M.; Jagiello, Jacek; Wu, Haohan; Woerner, William R.; Emge, Thomas J.; Olson, David H.; Parise, John B.; Li, JingChemical Science (2016), 7 (1), 759-765CODEN: CSHCCN; ISSN:2041-6520. (Royal Society of Chemistry)The efficiency of physisorption-based sepn. of gas-mixts. depends on the selectivity of adsorbent which is directly linked to size, shape, polarizability and other phys. properties of adsorbed mols. Commensurate adsorption is an interesting and important adsorption phenomenon, where the adsorbed amt., location, and orientation of an adsorbate are commensurate with the crystal symmetry of the adsorbent. Understanding this phenomenon is important and beneficial as it can provide vital information about adsorbate-adsorbent interaction and adsorption-desorption mechanism. So far, only sporadic examples of commensurate adsorption have been reported in porous materials such as zeolites and metal org. frameworks (MOFs). In this work we show for the first time direct structural evidence of commensurate-to-incommensurate transition of linear hydrocarbon mols. (C2-C7) in a microporous MOF, by employing a no. of anal. techniques including single crystal X-ray diffraction (SCXRD), in situ powder X-ray diffraction coupled with differential scanning calorimetry (PXRD-DSC), gas adsorption and mol. simulations.
- 31Han, X.; Yang, S.; Schröder, M. Porous metal-organic frameworks as emerging sorbents for clean air. Nat. Rev. Chem. 2019, 3, 108– 118, DOI: 10.1038/s41570-019-0073-7[Crossref], [CAS], Google Scholar31https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXnsFCltrs%253D&md5=2a088bbd1f6da297a76a65e87fb93e4aPorous metal-organic frameworks as emerging sorbents for clean airHan, Xue; Yang, Sihai; Schroder, MartinNature Reviews Chemistry (2019), 3 (2), 108-118CODEN: NRCAF7; ISSN:2397-3358. (Nature Research)A review. Sulfur dioxide and nitrogen oxides generated by anthropogenic activities are air pollutants that cause serious environmental problems and pose substantial health threats. Although established methods for emission desulfurization and denitrogenation already exist, more efficient and flexible technologies are still required. In this Review, we highlight state-of-the-art examples in which metal-org. frameworks (MOFs), an emerging class of porous sorbents, have been applied to the adsorptive removal of SO2 and NO2. MOFs can simultaneously exhibit superior adsorption capacities and exceptional selectivities for SO2 and NO2 in the presence of other flue and exhaust gases while maintaining their structural integrity. The highly cryst. nature and rich chem. functionality of MOFs have enabled the elucidation of host-guest interactions at a mol. level to afford insights and new knowledge that will inspire and inform the design of new generations of adsorbents.
- 32Wu, W.; Han, B.; Gao, H.; Liu, Z.; Jiang, T.; Huang, J. Desulfurization of flue gas: SO2 absorption by an ionic liquid. Angew. Chem., Int. Ed. 2004, 43, 2415– 2417, DOI: 10.1002/anie.200353437[Crossref], [PubMed], [CAS], Google Scholar32https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2cXktFSgsL4%253D&md5=46c733352d836865894616d6e31b4258Desulfurization of flue gas: SO2 absorption by an ionic liquidWu, Weize; Han, Buxing; Gao, Haixiang; Liu, Zhimin; Jiang, Tao; Huang, JunAngewandte Chemie, International Edition (2004), 43 (18), 2415-2417CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)The ionic liq., (IL) 1,1,3,3-tetramethylguanidinium lactate, can absorb SO2 from simulated flue gas effectively under ambient conditions. Absorbed SO2 can be desorbed under vacuum or by heating, and the IL can be reused. This absorption method might be used for cleaning gases that contain SO2.
- 33Zheng, D.; An, Y.; Li, Z.; Wu, J. Metal-free aminosulfonylation of aryldiazonium tetrafluoroborates with DABCO·(SO2)2 and hydrazines. Angew. Chem., Int. Ed. 2014, 53, 2451– 2454, DOI: 10.1002/anie.201309851[Crossref], [CAS], Google Scholar34https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXhtlGks7c%253D&md5=b9716e9d61f94dff696a6f5e4e887885Metal-Free Aminosulfonylation of Aryldiazonium Tetrafluoroborates with DABCO-(SO2)2 and HydrazinesZheng, Danqing; An, Yuanyuan; Li, Zhenhua; Wu, JieAngewandte Chemie, International Edition (2014), 53 (9), 2451-2454CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)Arylsulfonylhydrazides RSO2NHR1 [R = Ph, 4-MeC6H4, 4-t-BuC6H4, 4-MeOC6H4, 4-ClC6H4, 4-BrC6H4, 4-FC6H4, 4-MeO2CC6H4, 4-O2NC6H4, 2-ClC6H4, 2-MeC6H4, 3-ClC6H4, 3-MeO2CC6H4, 3-MeOC6H4, 2,4,6-Me3C6H2; R1 = 4-morpholinyl, 1-piperidinyl, PhNMe, (S)-3-methoxymethyl-1-pyrrolidinyl, PhNEt, PhCH2NPh, Ph2N] were prepd. in 57-95% yields without added metal catalysts by the coupling of aryldiazonium tetrafluoroborates RN2+•BF4- (R = Ph, 4-MeC6H4, 4-t-BuC6H4, 4-MeOC6H4, 4-ClC6H4, 4-BrC6H4, 4-FC6H4, 4-MeO2CC6H4, 4-O2NC6H4, 2-ClC6H4, 2-MeC6H4, 3-ClC6H4, 3-MeO2CC6H4, 3-MeOC6H4, 2,4,6-Me3C6H2) with the bis(sulfur dioxide) complex of DABCO in MeCN at ambient temp. Reaction of an allyloxyphenyldiazonium tetrafluoroborate with the bis(sulfur dioxide) complex of DABCO and 4-aminomorpholine in MeCN gave a dihydrobenzofuranylmethyl sulfonylhydrazide, while reaction of phenyldiazonium tetrafluoroborate with the bis(sulfur dioxide) complex of DABCO and 4-aminomorpholine in the presence of TEMPO gave a phenoxytetramethylpiperidine as the only product, suggesting the involvement of a free radical process. The free energies and transition state free energies for a radical-based mechanism of the reaction between aryldiazonium tetrafluoroborates, DABCO•2SO2, and hydrazines were calcd.
Supporting Information
ARTICLE SECTIONSThe Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/jacs.0c08794.
Additional experimental details, diffraction data, views of crystal structures, INS and IR spectroscopy, adsorption isotherms, and IAST selectivity (PDF)
Crystal data for MFM-520·H2O (CIF)
Crystal data for MFM-520 (CIF)
Crystal data for MFM-520·CO2 (CIF)
Crystal data for MFM-520·SO2 intermediate (CIF)
Crystal data for MFM-520·SO2 (CIF)
Terms & Conditions
Electronic Supporting Information files are available without a subscription to ACS Web Editions. The American Chemical Society holds a copyright ownership interest in any copyrightable Supporting Information. Files available from the ACS website may be downloaded for personal use only. Users are not otherwise permitted to reproduce, republish, redistribute, or sell any Supporting Information from the ACS website, either in whole or in part, in either machine-readable form or any other form without permission from the American Chemical Society. For permission to reproduce, republish and redistribute this material, requesters must process their own requests via the RightsLink permission system. Information about how to use the RightsLink permission system can be found at http://pubs.acs.org/page/copyright/permissions.html.