Core–shell-structured Z-scheme CdS@MIL-88(A)Fe heterojunctions for efficient visible light photocatalytic oxidative coupling of benzylamines to imines

Abstract

The photocatalytic oxidative coupling of benzylamines to imines has garnered extensive attention owing to its environmentally friendly and sustainable nature. However, it is profoundly desirable and essential to elaborate the structure of photocatalysts and to develop highly efficient visible-light-responsive photocatalysts for oxidative coupling of amines. Herein, a core–shell-structured Z-scheme CdS@MIL-88(A)Fe nanocomposite was successfully fabricated through a facile solvothermal and liquid deposition method for photocatalytic oxidative coupling of benzylamines to imines in air under visible light irradiation. The results demonstrated that the core–shell structure and Z-scheme heterojunction between CdS and MIL-88A(Fe) expedited the transport and separation of photon-generated carriers. Consequently, the CdS@MIL-88A(Fe) nanocomposite exhibited superior photocatalytic activities for oxidative coupling of benzylamines to imines compared to CdS and MIL-88A(Fe), respectively. Characterization of the microstructural properties and elucidation of the photocatalytic mechanism revealed that the photogenerated holes (h⁺) and superoxide radicals (˙O²⁻) were the primary active species responsible for the reaction. This work highlights the potential of the Z-scheme heterostructure design based on metal–organic frameworks (MOFs) for green photocatalytic organic transformations and provides valuable insights into the development of advanced photocatalysts for sustainable chemical synthesis.