Theoretical and Experimental Studies of Subnanometer Metal Clusters as Novel Heterogeneous Catalysts

Recent advances in synthetic techniques have permitted the reproducible synthesis of subnanometer metal clusters with a size sensitivity of ±1 atom. These clusters, which are soft-landed on oxide supports, often show catalytic activities significantly higher than the activities of larger nanoparticles. In this study, we first describe a class of alumina-supported subnanometer platinum clusters that show higher activity for the oxidation dehydrogenation of propane than any catalysts previously reported while, at the same time, maintaining high selectivity to propylene; a Density Functional Theory analysis demonstrates that these remarkable properties are due to the highly undercoodinated nature of the Pt atoms in Pt4-10 clusters. We next extend our analyses to a different reaction, that of propylene epoxidation on silver, that is also catalyzed with remarkably high activity by subnanometer clusters. We conclude by generalizing selected results to subnanometer clusters of all Pt-group transition metals.