(423b) Design Of Multifunctional Hybrid Inorganic-Organic Materials For Heterogeneous Catalysis

Davis, M. E., California Institute of Technology

Enzymes have earned the distinction as nature's greatest catalysts due to their ability to carry out a wide variety of reactions with remarkable selectivity and reaction rate. This feat is achieved through very precise positioning of reactive functional groups immobilized in the active site region by the peptide backbone. By taking clues from how nature performs catalytic reactions, we have designed new heterogeneous catalysts that are immobilized combinations of organic functional groups on mesoporous silica (SBA-15) supports. Through a ?one-pot? preparation using organosilanes, direct synthesis allows for incorporation of the functional groups into structures that can then be used to carry out heterogeneous catalysis. Immobilization of groups such as thiols and sulfonic acids allow for cooperative catalysis to occur in the synthesis of bisphenol A leading to dramatic rate and selectivity enhancements. Furthermore, incompatible acidic and basic functional groups can be immobilized and their independent chemical reactivity maintained while also exhibiting cooperativity in an aldol condensation between acetone and 4-nitrobenzaldehyde. These results demonstrate the dramatic rate and selectivity enhancements that can be achieved upon site-positioned immobilization. At this time, no example of enantioselective catalysis using this approach has been reported. Extensions of the current achiral materials to chiral solids will be discussed.