One-step solvothermal formation of Cu - Doped Cu2WO4(OH)2 nanocatalysts for efficient photocatalytic amine oxidation coupling

The development of economical multiphase photocatalysts is a significant challenge in achieving large-scale industrialization. Rational catalyst design can help in achieving efficient, energy-saving, and green catalytic reactions, making it more feasible to screen potential catalyst candidates. In this paper, we have successfully developed a high-efficiency photocatalyst Cu-doped Cu2WO4(OH)2 (CWOH-y, where y represents the molar ratio of copper tungsten source), which can catalyze the aerobic coupling reaction of amines to produce corresponding imines under visible light irradiation. N-benzylidenebenzylamine is synthesized under visible light at 25 °C with an 89 % yield. Under natural light at around 35 °C (mean light intensity of 50 mW/cm2), 94 % of the benzylamine is converted, and 97 % of the product is N-benzylidenebenzylamine. The catalyst exhibits high efficiency due to the synergistic effect of doped Cu, Cu2WO4(OH)2, and visible light. This combination generates a significant amount of superoxide free radicals and singlet oxygen when exposed to visible light. Furthermore, the catalyst demonstrates universality and stability with a wide range of amine derivatives. This study introduces a new environmentally friendly photocatalytic pathway for the synthesis of imines and emphasizes the potential applications of Cu2WO4(OH)2.