Developing Catalysis for Energy and the Environment

Enhancing our understanding of the mechanisms of chemical reactions is critical to improving processes to   interconvert efficiently between chemical and electrical energy or to make chemical products in an environmentally benign way.  The Brown group is addressing this overarching problem through studies in two basic areas. 

The first area of research is in oxidation reactions.  Traditionally, redox reactions mediated by metals involve changes in both oxidation state and bonding that directly involve those metal centers.  We are exploring an alternative mode of redox reactivity, what we term "nonclassical" redox reactions, where bond-making or bond-breaking events occur at a metal center but oxidations or reductions occur not at the metal center but at redox-active ligands attached to the metal.  These processes generate novel species with unusual electronic structure, which may be capable of unusual reactivity.  Furthermore, separating the locus of electron transfer from that of changes in bonding mimics the heterogeneous catalysis involved in fuel cells, suggesting that nonclassical homogeneous reactions may lead to conceptual insights or practical advances in systems for interconverting electrical and chemical energy.

A second area of research is in catalysis directed toward chemical synthesis.  We are interested in elucidating general features of the electronic structure of catalysts that enhance or impede their efficiency.  For example, recent studies have suggested that for a broad class of reactions that involve binding to two sites on a catalyst, the electronic similarity or dissimilarity of the sites can have a marked effect on the efficiency of catalysis.  We then use these principles to design new catalysts for useful transformations.  A recent target is catalyzing the use of the noxious pollutant NO₂ to selectively make nitroorganics from hydrocarbons.