438651 Nature-Inspired Approaches to Catalytic Materials Design

Sunday, November 8, 2015
Exhibit Hall 1 (Salt Palace Convention Center)
Michael M. Nigra, Department of Chemical Engineering, University College London, London, United Kingdom

The precise location of the active site in a catalytic material, specifically the environment that surrounds the active site, very often directly influences the activity and selectivity of a catalyst. The best examples of this environmental control around catalytic active sites are found in enzymes.  In enzymes, the active sites are frequently located in a nano-confined environment in which there is control of electrostatic interactions, precise placement of chemical functional groups, and control of hydrophobicity/hydrophilicity, to name some common examples. These nano-confinement and ligand effects in different catalytic systems have been explored through various studies.

The first studies used a shell of organic ligands, namely calixarene ligands, to allow for stable (sinter-resistant), accessible (able to bind small probe molecules and reactants), and electronically tunable sites on gold clusters. Further studies used organic ligands on gold nanoparticles to determine site requirements for two different reactions: reduction of 4-nitrophenol and reduction of resazurin. In both systems, only a small fraction of gold catalyst was responsible for the majority of the catalytic activity.

Additional studies investigated metal clusters/complexes as well as enzymes that were immobilized inside of the pores of mesoporous materials, such as SBA-15. These immobilized systems both exhibited enhanced catalytic activities over their measured activities when free in solution under specific reaction conditions.

These examples from both my research as PhD student at UC Berkeley (supervised by Alexander Katz) and as a post-doctoral research associate at University College London (supervised by Marc-Olivier Coppens) will be presented and will form the foundation of future research. These approaches will be used to synthesize novel materials for applications in catalysis, energy, and medicine.

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