Post-synthetically covalent modification of g-C3N4 to regulate electronic structure and investigation of photocatalytic activity for eliminating antibiotics

Antibiotic residues in water have induced serious environment issues, and semiconductor photocatalysis has been proved as an effective technology for antibiotic elimination. Herein, a post-synthetic strategy was employed to covalently modify g-C3N4 (GCN) with methoxybenzoyl (MOB) via amido bond formation between the terminal amino of GCN and the p-anisoyl chloride. SEM and XRD characterizations indicated the morphologic and structural preservation after MOB modification, and FTIR and XPS results suggested the successful modification of MOB onto the GCN skeleton. Through effectively decreasing the electron cloud density of framework by the amido formation and the grafted MOB, the separation and migration of photogenerated charges were promoted, which were verified by PL and electrochemical measurements. As a result, the MOB/GCN showed greatly improved visible-light-driven photocatalytic activity for MOX degradation compared to the pristine GCN. Reaction parameters, such as synthetic temperature, pH value, photocatalyst dosage and MOX concentration were optimized, and the good photocatalytic durability and applicability in real scenarios were also demonstrated. Finally, the degradation pathway of MOX and the possible mechanism to explain the enhanced photocatalytic performance were proposed. This work demonstrates that covalent modification via the post-synthetic route is a promising approach to meliorate the photocatalytic behavior of GCN.