Efficient Olefins Epoxidation on Ultrafine H2O-WOx Nanoparticles with Spectroscopic Evidence of Intermediate Species

Design and synthesis of high-performance heterogeneous catalysts are of immense interest in chemical industries. Herein, ultrafine H2O coordinated WOx nanoparticles (H2O-WOx, average diameter 2.24 nm) embedded into porous carbon matrix have been obtained via spaceconfinement pyrolysis with postmodification oxidation approach. The synthesized H2O-WOx nanoparticles exhibit high activities toward olefin epoxidation reaction using H2O2 as oxidant. In epoxidation of cis-cyclooctene, the turnover frequency of the catalyst can achieve as high as 949 h(-1), an activity comparable to the highest of all reported early transition-metal based catalysts. UV-vis spectra and controlled catalytic experiments have been performed to ascertain the possible active site in the catalyst: compared with traditional WO3 and peroxide coordinated W-(eta(2)-O-2) species, the water coordinated H2O-WOx can transform to hydroperoxide HOO-WOx in the presence of H2O2, and the HOO-WO, species can be further activated by proton acid to enhance its catalytic activities.