Zeolite-Confined Nano-RuO2:  A Green, Selective, and Efficient Catalyst for Aerobic Alcohol Oxidation

The development of green, selective, and efficient catalysts, which can aerobically oxidize a variety of alcohols to their corresponding aldehydes and ketones, is of both economic and environmental significance. We report here the synthesis of a novel aerobic oxidation catalyst, a zeolite-confined nanometer-sized RuO2 (RuO2−FAU), by a one-step hydrothermal method. Using the spatial constraints of the rigid zeolitic framework, we sucessfully incorporated RuO2 nanoparticles (1.3 ± 0.2 nm) into the supercages of faujasite zeolite. Ru K-edge X-ray absorption fine structure results indicate that the RuO2 nanoclusters anchored in the zeolite are structurally similar to highly hydrous RuO2; that is, there is a two-dimensional structure of independent chains, in which RuO6 octahedra are connected together by two shared oxygen atoms. In our preliminary catalytic studies, we find that the RuO2 nanoclusters exhibit extraordinarily high activity and selectivity in the aerobic oxidation of alcohols under mild conditions, for example, air and ambient pressure. The physically trapped RuO2 nanoclusters cannot diffuse out of the relatively narrow channels/pores of the zeolite during the catalytic process, making the catalyst both stable and reusable.