Dual-Metal Synergy in Bismuth-Porphyrin Nanosheets for Enhanced Photo-Fenton Degradation of Ciprofloxacin

Abstract

The persistent presence of ciprofloxacin (CIP) in aquatic systems necessitates advanced oxidation technologies with high efficiency and sustainability. Herein, we report a post-metalation strategy to construct a bimetallic Bi-TCPP(Fe) metal-organic layer (MOL) by incorporating Fe3+ into porphyrin cavities, which synergistically modulates charge distribution and band structure. Unlike conventional Bi-TCPP MOFs with limited charge separation efficiency, the Fe3+ centers in Bi-TCPP(Fe) MOL induce localized positive charges on porphyrin rings while maintaining the negative charge of Bi nodes, enabling directional metal-to-ligand charge transfer (MLCT) and reducing electron-hole recombination. Under visible LED irradiation (10 W), Bi-TCPP(Fe)/H2O2 achieves 99.6% CIP removal within 45 min (k = 0.24 min−1), outperforming state-of-the-art catalysts (e.g., MIL-100(Fe): 95.2%/120 min). Remarkably, natural sunlight drives 96.4% degradation within 5 min (k = 0.67 min−1), leveraging UV-enhanced excitation. Theoretical calculations reveal Fe3+ introduction confines electrons to porphyrin rings, increasing the HOMO-LUMO gap by 0.53 eV and promoting ROS generation (·OH dominant, confirmed by EPR). ECOSAR analysis demonstrates reduced ecological toxicity of degradation intermediates. This work provides a paradigm for designing dual-metal photocatalysts through charge distribution engineering.

Keywords: Bi/Fe-based metal-organic layer, Ciprofloxacin, Photo-Fenton, Photocatalysis, Synergistic effect