Singlet oxygen-driven degradation of organic pollutants via peroxymonosulfate activation by sulfur-doped MOF-derived catalysts

Developing stable and efficient catalysts for peroxymonosulfate (PMS) activation is of critical significance for the remediation of antibiotic-contaminated wastewater, as conventional catalytic systems often suffer from insufficient activity, poor stability, or a narrow pH adaptation range. Herein, sulfur-doped metal-organic framework (MOF)-derived catalysts (Co-BDC@S) were successfully synthesized via a one-step pyrolysis of cobalt(II) 1,4-benzenedicarboxylate (Co-BDC) and sulfur powder. Systematic optimization of the synthesis parameters revealed that the Co-BDC@S-700–4 catalyst (where the subscripts "700" and "4" denote the calcination temperature and sulfur doping amount, respectively) exhibits superior PMS activation performance. Specifically, it achieves 97 % removal of ciprofloxacin (CIP, 20 mg/L) within 30 min, accompanied by an ultrahigh initial apparent rate constant of 0.268 min⁻¹ . The system has excellent pH tolerance (3–10) and maintains > 73 % efficiency after 5 cycles (Co leaching <1.0 mg/L), meeting wastewater discharge standards. Mechanistic studies confirm singlet oxygen (¹O₂) as the dominant reactive species, whose high steady-state concentration (5.24 ×10⁻¹² M) is attributed to the synergistic effect of Co₄S₃ and sulfur vacancies facilitating electron transfer and non-radical pathways. Furthermore, ultra-performance Liquid Chromatography Triple Time-of-Flight Mass Spectrometry (UPLC-Triple-TOF/MS) identified 22 transformation intermediates during CIP degradation, and ecological toxicity assessment via the ECOSAR model confirms their significantly reduced environmental risks. This work provides a stable, eco-friendly catalyst and valuable mechanistic insights for designing advanced oxidation systems.