Unraveling the photocatalytic electron transfer mechanism in a Ti-MOF/g-C3N4 heterojunction for high-efficient coupling performance of primary amines

Abstract

The ti-MOF/g-C₃N₄ heterojunction is a high-efficient photocatalytic heterojunction, but the synergism between Ti-MOF and g-C₃N₄ has not been elucidated at the molecular level, and the application of these materials in the area of primary amine coupling performance has not been reported. In this study, an efficient Ti-MOF/g-C₃N₄ hetero-structure was prepared by simply mixing the as-obtained 5 wt%Ti-MOF/g-C₃N₄. Compared with NH₂-MIL-125(Ti) and g-C₃N₄ themselves, the 5 wt%Ti-MOF/g-C₃N₄ composite shows superior activity in the photocatalytic coupling of benzylamine under irradiation with the highest imine yield of 88% within 3 h, which results in the best performance compared with the published results and is attributed to an improved photogenerated charge formation and transfer efficiency that was confirmed from DFT calculations. The matched energy bands, the Fermi levels, and work functions allowed the formation of the S-scheme heterojunction, and the built-in electric field provided the reaction driving force. VB-XPS analyses also revealed that these materials performed S-scheme staggered configuration and facilitated the charge transfer. Radical quenching experiments suggest that O₂˙⁻ is responsible for the imine formation under aerobic conditions, and our method shows that 5 wt%Ti-MOF/g-C₃N₄ is a new high-efficient photo-catalyst for the coupling of primary amines.