Supported oxides are ubiquitous heterogeneous catalysts, and synthetic control over oxide domains offers to improve our understanding of mechanisms at the atomic level and ultimately to control catalyst activities and selectivities. Two routes are presented to well-defined, supported oxides utilizing precursor inorganic complexes with some of the desired atomic connectivity built in. In the first, calixarene-Ta complexes are synthesized and grafted to SiO 2 for a one-pot route to ligand-capped, isolated sites. These catalysts have higher direct epoxidation selectivity for cyclohexene and less H 2O 2 decomposition than their bare oxide analogues. Epoxide hydrolysis can be lessened by simple capping with octanol. In the second, triazacyclononane manganese oxide catalysts are supported on functionalized surfaces for alkene epoxidation / dihydroxylation. These reactions occur at <25°C and epoxidation vs. dihydroxylation selectivity is controlled by the supported co-catalyst. Spectroscopic (principally XAS and UV-vis) and mechanistic studies give additional insight.
ASJC Scopus subject areas
- Chemical Engineering(all)