Self-Induced Oxygen Vacancies on Carboxyl-Rich MIL-121 Enable Efficient Activation and Oxidation of Benzyl Alcohol under Visible Light.

The oxygen vacancies could efficiently drive the photocatalytic oxidation of aromatic alcohol through the activation of reactants. However, the activation between aromatic alcohol and O 2 (oxidant) over oxygen vacancies is rarely studied. Herein, the ZnIn 2 S 4 /MIL-121 heterostructure with abundant surface uncoordinated carboxyl was rationally designed for benzyl alcohol (BA) oxidation under visible light. Oxygen vacancies on catalysts were self-induced after the surface complexation between the uncoordinated carboxyl and BA molecules. Based on the reaction results, it is concluded that the oxygen vacancy activation to BA is more effective than that to O 2 for BA oxidation over ZnIn 2 S 4 /MIL-121 hybrids. Specifically, when the activation fully occurs on BA (reaction in N 2 ), an admirable conversion of 93.9% (corresponding production rate of benzaldehyde: 2348 μmol·g -1 ·h -1 ) is achieved, which is 3.4 times that of pure ZnIn 2 S 4 , whereas an inferior conversion of 45.9% is obtained in O 2 due to the competition effect between O 2 and BA for oxygen vacancies.