Construction of Ag2S@CdS p-n heterojunction for efficient visible light photocatalytic oxidative coupling of benzylamines to imines

•Ag2S@CdS p-n heterojunction was synthesized by a simple ion exchange method.•The narrow band gap Ag2S semiconductor was used to sensitize CdS to expand the visible light response range.•The internal electric field of the p-n heterojunction effectively improved the separation efficiency of photogenerated carriers.•The synergistic effect of these advantages leads to the excellent visible light photocatalytic performance of Ag2S@CdS. Semiconductor photocatalytic organic reactions have garnered extensive interest owing to their environmentally friendly and sustainable advantages. Herein, the preparation of Ag2S@CdS p-n heterojunction through in-situ ion exchange reaction for photocatalytic benzylamine coupling is reported. Compared with pure CdS, Ag2S@CdS exhibited significantly enhanced photocatalytic activity for the oxidative coupling reaction of benzylamine. In particular, Ag2S@CdS showed high photocatalytic benzylamine conversion (>99 %) after 90 min under sunlight irradiation. The photocatalytic performance test at different wavelengths shows that the broadening of the light absorption range of Ag2S@CdS effectively improves the utilization of visible light. The photoelectric performance test demonstrates that the internal electric field of the p-n heterojunction effectively enhances the efficiency of separating photogenerated carriers. Moreover, Ag2S@CdS exhibited excellent compatibility with various benzylamine derivatives. The mechanism of photocatalytic benzylamine oxidation by Ag2S@CdS was investigated. This work provides some insights into the design of visible-light photocatalysts for selective organic synthesis. [Display omitted]