Forest Products Laboratory

Title: Equilibrating metal-oxide cluster ensembles for oxidation reactions using oxygen in water

Author: Weinstock, Ira A.; Barbuzzi, Elena M. G.; Wemple, Michael W.; Cowan, Jennifer J.; Reiner, Richard S.; Sonnen, Dan M.; Heintz, Robert A.; Bond, James S.; Hill, Craig L.

Date: 2001

Source: Nature. Vol. 414 (Nov. 8, 2001): Pages 191-195

Description: Although many enzymes can readily and selectively use oxygen in water--the most familiar and attractive of all oxidants and solvents, respectively–-the design of synthetic catalysts for selective water-based oxidation processes utilizing molecular oxygen remains a daunting task. Particularly problematic is the fact that oxidation of substrates by O2 involves radical chemistry, which is intrinsically non-selective and difficult to control. In addition, metallo-organic catalysts are inherently susceptible to degradation by oxygen-based radicals, while their transition-metal-ion active sites often react with water to give insoluble, and thus inactive, oxides or hydroxides. Furthermore, pH control is often required to avoid acid or base degradation of organic substrates or products. Unlike metallo-organic catalysts, polyoxometalate anions are oxidatively stable and are reversible oxidants for use with O2. Here we show how thermodynamically controlled self-assembly of an equilibrated ensemble of polyoxometalates, with the heteropolytungstate anion [AIVVW11O40]6– as its main component, imparts both stability in water and internal pH-management. Designed to operate at near-neutral pH, this system facilitates a two-step O2-based process for the selective delignification of wood (lignocellulose) fibres. By directly monitoring the central Al atom, we show that equilibration reactions typical of polyoxometalate anions keep the pH of the system near 7 during both process steps.

Keywords: Oxidation reactions, metal-oxide cluster ensembles, enzymes, oxidants, catalysts

View and Print this Publication (366 KB)

Publication Notes: 

• We recommend that you also print this page and attach it to the printout of the article, to retain the full citation information.
• This article was written and prepared by U.S. Government employees on official time, and is therefore in the public domain.

 Get the latest version of the Adobe Acrobat reader or Acrobat Reader for Windows with Search and Accessibility

Citation

Weinstock, Ira A.; Barbuzzi, Elena M. G.; Wemple, Michael W.; Cowan, Jennifer J.; Reiner, Richard S.; Sonnen, Dan M.; Heintz, Robert A.; Bond, James S.; Hill, Craig L.  2001.  Equilibrating metal-oxide cluster ensembles for oxidation reactions using oxygen in water.   Nature. Vol. 414 (Nov. 8, 2001): Pages 191-195.