Prolonging charge carrier lifetime in S-scheme heterojunctions via ligand-to-metal charge transfer of Ni-MOF for photocatalytic H2 production and simultaneous benzylamine coupling

Abstract

S-scheme heterojunctions have gained widespread application in photocatalytic reactions due to their distinctive carrier transport mechanism and remarkable redox capabilities. However, a significant challenge persists in extending carrier lifetimes while simultaneously enhancing light absorption, both of which are essential for optimizing photocatalytic activity. Herein, we report the solvothermal synthesis of ultrathin CdS nanosheets grown in situ on two-dimensional (2D) Ni-MOF to construct 2D/2D S-scheme heterojunctions. Comprehensive characterizations reveal that the incorporation of Ni-MOF (metal-organic framework) with ligand-to-metal charge transfer (LMCT) states not only broadens optical absorption but also significantly prolongs carrier lifetimes. This synergistic enhancement, coupled with the S-scheme charge transport mechanism, enables the composite to function as a bifunctional catalyst for photocatalytic hydrogen production and simultaneous benzylamine coupling. The optimal system demonstrates an impressive hydrogen evolution rate of 8.5 mmol g⁻¹ h⁻¹ and an N-benzylidenebenzylamine yield of 4.6 mmol g⁻¹ h⁻¹ without requiring a cocatalyst. This work underscores the potential of integrating MOFs with LMCT states into S-scheme heterojunctions to enhance interfacial charge transfer, offering valuable insights for the design of S-scheme heterojunctions for artificial photosynthesis and related fields.