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

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.