Photo-assisted peroxymonosulfate activation with the heterostructure of ZIF-67@MIL-100(Fe) for ciprofloxacin degradation: Reactivity, stability, and synergistic mechanisms

A dual-metal organic framework (MOF) heterostructure, ZIF-67@MIL-100(Fe), was successfully constructed and employed in a photo-assisted peroxymonosulfate (PMS) activation system for ciprofloxacin (CIP) degradation. The outer wrapping structure of MIL-100(Fe) effectively stabilizes ZIF-67, resulting in minimal Co2+ leaching (<0.32 mg/L). For CIP degradation (10 mg/L), the ZIF-67@MIL-100(Fe) exhibited superior catalytic performance (>95 %) with a rate constant of 0.0438 min−1, attributed to the synergistic interaction between the MIL-100(Fe) shell and ZIF-67 core. It was characterized to be more favorable for light absorption, charge separation, and migration than individual components, fostering redox cycles of Co(III)/Co(II) and Fe(III)/Fe(II). This photo-assisted PMS activation process involved both free radical and non-free radical pathways, with SO4•− and 1O2 playing dominant roles in CIP degradation. Based on seven measured intermediates, two degradation pathways were derived: oxidation of the piperazine ring and hydroxylation. Toxicity Evaluation Software Tool (T.E.S.T.) analysis indicated an overall decrease in ecological toxicity following CIP degradation. Furthermore, the composite exhibited robust stability in five cyclic experiments and real aquatic environments, underscoring the photo-assisted ZIF-67@MIL-100(Fe) activated PMS process as a promising and environmentally friendly approach for eliminating antibiotics from contaminated water.