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 H 2 O coordinated WO x nanoparticles (H 2 O–WO x, average diameter 2.24 nm) embedded into porous carbon matrix have been obtained via space-confinement pyrolysis with postmodification oxidation approach. The synthesized H 2 O–WO x nanoparticles exhibit high activities toward olefin epoxidation reaction using H 2 O 2 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 WO 3 and peroxide coordinated W-(η 2 -O 2 ) species, the water coordinated H 2 O–WO x can transform to hydroperoxide HOO–WO x in the presence of H 2 O 2, and the HOO–WO x species can be further activated by proton acid to enhance its catalytic activities.