Constructing of Bi2WO6 With Double Active Sites of Tunable Metallic Bi and Oxygen Vacancy for Photocatalytic Oxidation of Cyclohexane to Cyclohexanone

Oxygen-containing organics, which are generated from the selective oxidation of their corresponding hydrocarbons, have high value in the chemical and pharmaceutical industries. However, their oxidation reactions are very challenging as the products are more active than the substrates, especially for the oxidation of cyclohexane (CHA). Herein, we focused on the one-step preparation of Bi2WO6 with double active sites of tunable metallic Bi and oxygen vacancies (OV-Bi/Bi2WO6) by a facile solvothermal treatment. Then, OV-Bi/Bi2WO6 was used as an efficient photocatalyst for the partial oxidation of CHA to cyclohexanone (CHA-one) for the first time. The Bi: Bi2WO6 ratio in the as-prepared OV-Bi/Bi2WO6 heterojunction could be tailored from 0.08 to 8.43 by controlling the solvothermal temperature, and the synergistic effect between DMF and EG could increase the reduction of MDF/EG, promote the production of Bi. Moreover, OV-Bi/Bi2WO6-160 yielded 4.4 and 8.8 times more CHA-one (128.8 μmol) than that of pure Bi2WO6 and metallic Bi, respectively, and achieved a 93.6% selectivity to CHA-one under air as an oxidant in solvent-free conditions. Results revealed that the highly enhanced photocatalytic activity was mainly attributed to the superior specific surface area, outstanding photo-absorption, abundant oxygen vacancies, and efficient electron-hole separation. Moreover, for the unique double active sites in OV-Bi/Bi2WO6, oxygen vacancies can enhance the adsorption and activation capacity of Bi2WO6 for O2, while metallic Bi can improve the adsorption and activation capacity of Bi2WO6 for CHA. Meanwhile, the OV-Bi/Bi2WO6 also exhibited excellent durability due to the strong interaction between metallic Bi and Bi2WO6. The present work provides a flexible approach for tailoring the Bi: Bi2WO6 ratio and outlines an effective method for producing CHA-one from CHA under mild conditions.