www.acsprf.org

Heterogeneous catalysts are preferred in industrial applications because of their robustness, but homogeneous and enzymatic catalysts are better for complex catalysis where product selectivity is required.  The crossroad of organometallic chemistry with material science has recently allowed the rational development of catalysts that incorporate some of the basic elements found in homogeneous catalysts.  This area of research has been coined as “surface organometallic” chemistry.

Heterogeneous and homogeneous catalysis have traditionally been two different fields of study.  Bridging the gap in research between these two areas will inevitably generate an unparalleled synergy in the design of the next generation of catalysts. Supported, single-site catalysts offer the unmatched selectivity of the organometallic complexes with the convenience of the solid substrates.  For instance, two major obstacles often encountered with homogeneous catalysts, involving dimerization and separation from products, can be avoided by grafting the catalysts onto solid substrates. A major challenge is the characterization of the complex catalysts produced. The goal of this project is to understand the effect of adding a bulky oxide surface as a ligand on an organometallic complex, incluiding the nature of their electronic and chemical interaction, by investigating the organometallic functionalization of well defined oxide model surfaces.

During the first year of the grant we focus on setting up an ultrahigh vacuum system coupled with a reactor cell where reactions could be follow in-situ by infrared absorption spectroscopy (IRAS). To test the system, we studied the interaction of simple organic molecules, such as carboxylates and carbon monoxide with surfaces. The IRAS system is now working and this effort has resulted in a publication that is in press.

We have initiated studies on the interaction of organometallic precursors with oxide surfaces. A Ru₃(CO)₁₂ precursor was deposited on TiO₂(110) surfaces by chemical vapor deposition (CVD). Upon oxidation of the organometallic precursor, 1D RuO_x structures were formed on top of the TiO₂ substrate. In contrast to the highly stability of bulk RuO₂, the 1D structures of RuO_x in direct contact with the reducible oxide substrate became very reactive. It is possible to reduce the RuO_x structures to Ru⁰ by exposure under moderate conditions to CO and re-oxidize them buck to RuO₂. In catalytic tests, this structures show high activity for CO oxidation, while zero reactivity is obtained from either TiO₂ or RuO₂ samples alone.

A post-doc working in this project is fully funded from the PRF grant since the summer of 2011. An undergraduate student funded by a different fellowship also worked during the summer in the project interacting with the post-doc.