Oxygen vacancy engineering via doping Sr at the La-site of LaMnO3 to promote the ability for aerobic oxidation of benzyl alcohol

Abstract

Aerobic selective oxidation is a prospective route to synthesize fine chemicals and their intermediates in modern industries, yet the development of an efficient catalyst remains a challenge, due to the limitations in O2 adsorption and activation. Herein, we report a promising La1-xSrxMnO3 (LSMO-x) perovskite oxide for aerobic oxidation of benzyl alcohol (BzOH) to benzaldehyde (BzH) via oxygen vacancy engineering. Through the substitution of Sr at the La-site of LaMnO3, the quantity of oxygen vacancies, which are active site of molecular oxygen, is greatly increased, thereby improving the efficiency for oxygen activation and the reaction activity. The optimal catalyst, LSMO-0.15, shows BzOH conversion of 97.0 % and BzH selectivity of 93.4 %, at 50 °C, for 3 h. The importance of oxygen vacancy for the reaction is verified by DFT calculations, by comparing the adsorption energies of reactants on LaMnO3 containing with and without oxygen vacancy. A reaction mechanism is also proposed, in which the adsorption and activation of O2 occurs on the oxygen vacancy, and that of BzOH occurs on the Mn4+ ions. The activated O2 and BzOH then react with each other to release H2O and yield BzH.