CuO nanoclusters coated with mesoporous SiO2 as highly active and stable catalysts for olefin epoxidation

A one-pot solvothermal synthetic method to prepare uniform CuO colloidal nanocrystal clusters (CNCs) with sizes of approximately 60 nm was developed. To enhance their stabilities, the CuO CNCs were coated with mesoporous SiO2 shells to form CuO CNCs@meso-SiO2 nanocomposites. The CuO CNCs as well as the CuO CNCs@meso-SiO2 composite catalyst were characterized by transmission electron microscopy, small-angle X-ray diffraction and N-2 adsorption-desorption methods. These results indicate that the SiO2 shells have winding mesoporous channels with an average size of 3.7 nm, which are very favorable for mass transfer and catalytic reactions. This nanocomposite catalyst exhibited excellent activity and stability in olefin epoxidation reactions. The structure of the composite catalyst remained intact after eight consecutive runs, while pure CuO CNCs severely aggregated after only 1 run.