Composite inorganic materials are frequently used to catalyze large-scale industrial reactions. Identifying materials that are active and selective for specific reactions is important not only for making improvements to existing chemical processes, but also for designing new routes to a sustainable energy economy. A common structure for solid catalysts is for metal nanoparticles—often considered the active component—to be dispersed onto high-surface area metal oxides. However, it has become increasingly apparent that the role of the metal oxide can often extend far beyond being a simple carrier for the metal nanoparticles; sites at the interface between the metal and metal oxide exhibit much faster rates for processes such as CO2 thermal reduction and upgrading of biomass-derived sugars. The chemistry at metal-metal oxide interfaces is often complex and poorly understood, and mechanisms for achieving additional control over catalyst performance are desired.
One method for gaining an additional lever of control is to functionalize surfaces with organic ligands. Organic ligands are widely employed as surfactants for the synthesis of metal nanoparticles. Recent studies have shown that leaving these ligands in place can often have beneficial effects for catalyst performance, especially related to selectivity toward desired products. As an alternative to depositing organic monolayers on the metal nanoparticles, it is also possible to deposit them on the oxide support. Support modification is especially attractive for reactions in which rates are dominated by sites at the metal – support interface. By varying the structure and chemical functionality of the organic ligands, one can hypothetically improve catalyst activity, selectivity, and stability in reactions such as CO2 hydrogenation and furfural hydrodeoxygenation. In this presentation, we will describe use of different components of the organic ligands—the “head” group that covalently attaches to the support and the “tail” organic function—to control selectivity in reactions at surfaces.
Will Medlin received his BS degree in chemical engineering from Clemson University. He received his PhD from the University of Delaware. After conducting postdoctoral research at Sandia National Laboratories in Livermore, California, he joined the faculty of the University of Colorado, where he now serves as Chair and Denver Business Challenge Endowed Professor in the Department of Chemical & Biological Engineering. His research focuses on the design of solid catalysts for energy and environmental applications. His work has particularly emphasized catalyst surface modification using organic self-assembled monolayers or inorganic thin films to enhance control over catalyst surface and near-surface properties. Prof. Medlin has published approximately 125 peer-reviewed papers. He has received several research and teaching awards, such as the NSF CAREER and AIChE Himmelblau Awards. He has been a visiting professor at ETH-Zurich and the Chalmers University of Technology and is an Associate Editor for the journal Catalysis Science and Technology. He has also been active in producing educational tools for the widely used web site learncheme.com.