Thermo‐Enhanced Photocatalytic Activity in Aerobic Oxidative Coupling of Amines to Imines over Cu‐Doped MIL‐125‐NH2

Abstract

AbstractPhotocatalytic oxidation of raw organic molecules to value‐added chemicals provides a cost‐effective and sustainable strategy in organic synthesis. In this work, a series of Cu‐doped MIL‐125‐NH2 with narrower band gaps were synthesized by a one‐pot hydrothermal method and used as photocatalysts for thermo‐enhanced aerobic oxidative coupling of amines to imines under visible light irradiation. With optimal doping content, the conversion of benzylamine over MIL‐125‐NH2/Cu2% can reach 100% at 60 °C under visible light irradiation for 8 h using molecule oxygen as oxidant. It is proved that doping MIL‐125‐NH2 with a suitable Cu content can broaden the visible light absorption range, promote the separation of photo‐induced charge carriers and improve the photocatalytic performance. Moreover, the increase of reaction temperature of the photocatalytic system promotes the performance. Free radical capture experiments and ESR tests show that holes and superoxide free radicals are the main active species. Such an excellent photocatalytic performance can be attributed to the strong light absorption and more efficient electron‐hole separation efficiency via the Cu‐doping strategy in MIL‐125‐NH2 catalysts.