Construction of ternary BiOBr/NH2-MIL-101(Fe)/g-C3N4 nanocomposite as an efficient photocatalyst for degradation of tetracycline

A novel dual Z-scheme BiOBr/NH 2 -MIL-101(Fe)/g-C 3 N 4 (BNG) heterojunction was constructed via a simple two-step solvothermal process. NH 2 -MIL-101(Fe) nanoparticles and BiOBr microspheres were uniformly deposited on the surface of g-C 3 N 4 . The prepared BNG exhibited significantly enhanced photocatalytic performance for tetracycline (TC) degradation compared to single catalyst. The optimized BNG-19 composite (with 19% NH 2 -MIL-101(Fe)/g-C 3 N 4 ) achieved 92.38% degradation of TC within 75 min under visible light, which was 2.47, 1.78, and 1.84 times higher than that of pure g-C 3 N 4 , NH 2 -MIL-101(Fe), and BiOBr, respectively. Moreover, the composite exhibited excellent stability with 82.4% removal efficiency after five cycles. The enhanced photocatalytic performance was attributed to the synergistic dual Z-scheme charge transfer mechanism, which was directly evidenced by in-situ irradiated XPS showing opposite directional shifts of Bi 4f (positive) and Fe 2p/N 1s (negative). This unique charge transfer pathway effectively promoted the separation of photogenerated carriers, with •OH and •O 2 ⁻ identified as the dominant reactive species. This work provides a new strategy for constructing g-C 3 N 4 -based dual Z-scheme heterostructures with direct mechanistic evidence for efficient environmental remediation.