Improved Catalyst Selectivity through
“Single-Site” Immobilization on Solid-Oxide Supports
Traditional methods for synthesizing heterogeneous catalysts are often harsh and
result in ill-defined mixtures of surface species. On the other extreme,
homogenous catalytic systems regularly have a single active site, but suffer
from competitive solvent coordination and facile decomposition.
Site isolation of organometallic moieties by covalent anchoring to a metal oxide
support is a powerful strategy for the formation of solid-state "molecular"
catalysts. Such a strategy combines the advantages of both heterogeneous
(activity, stability, and recyclability) and homogeneous catalysts (well-defined
structure and tunability). However, the connections between the
structure/activity relationships seen in solution and those of the supported
catalysts are not well understood. This study will identify the key parameters
required to maintain the unique selectivity patterns of organometallic catalysts
seen in solution, while enhancing catalyst stability and longevity by supporting
well defined organometallic moieties on solid-oxides.
We will focus on two separate systems, both of which have a wealth of
structure-activity data in solution to guide the supported catalyst design.
Selective alkane dehydrogenation by iridium(III) complexes and direct oxidation
of alkanes to alcohols using platinum(II) complexes have both been outlined by
BES as “grand challenges” facing science today. This project will use our
expertise in heterogeneous catalyst synthesis, testing, characterization, and
modeling to forge links between the homogenous and the heterogeneous catalyst
literature and to bring a new perspective to the challenging problem of rational
catalyst design.
Our goals are to:
- Enhance the understanding of catalyst-support interactions by
identifying the parameters required to maintain the high selectivity seen in
solution on a supported catalyst and thereby enable more intelligent
catalyst design,
- Develop a single-site iridium(III) catalyst to selectively dehydrogenate
alkanes to olefins, and
- Develop a supported platinum(II) oxidation catalyst that will
selectively convert alkanes to alcohols.
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