Ligand-Length Engineering in Isoreticular Fe-MOFs Enables Efficient Ciprofloxacin Degradation

Abstract

Iron-based metal-organic frameworks (Fe-MOFs) are attractive photocatalysts for ciprofloxacin (CIP) degradation in photofenton liked reactions due to their accessible Fe sites and porous structures. However, the role of organic linkers in regulating degradation pathways remains unclear. Here, four Fe-MOFs with identical acs topology (MIL-88A, B, C, D) were synthesised via ligand modulation and evalated for visable-light-driven CIP degradation under ambient conditions. MIL-88A and MIL-88D achieved > 90% degradation efficiency, yet followed distinct mechanisms. Quenching experiments, pH-dependent tests, and thermodynamic/kinetic analyses reveal that MIL-88A operates through a thermodynamically driven pathway enabled by a highly positive valence band, showing weak pH dependance. In contrast, MIL-88D proceeds via a kinetics-dominated photo-Fenton route, where efficient charge speration accelerates the Fe 2+ /Fe 3+ redox cycle, leading to strong pH sensitivity.Degradation kinetic modling further uncovers concentration-dependent dominance and pathway switching between the two routes. This work elucidates ligand-regulated thermodynamic-kinetic competition, offering design principles for advanced Fe-MOFs photocatalysts for pollutant remediation.