LDHs microsphere-induced restructured lamella-confined ZIF-67 composites for PMS activation in NOR degradation: Coupling mechanism of radical and electron transfer pathways

Constructed MOF-in-LDHs to regulate morphology and anchor active sites. • Ternary metal redox cycles coupled with ETP boosted PMS activation. • Ion resistance and cycling stability enable continuous-flow application. Although the development of catalysts with high activity and stability is still a major problem, advanced oxidation processes based on peroxymonosulfate (PMS-AOPs) show promise for the degradation of antibiotics. In this work, FeCu-LDH with an initial fish-scale embroidered spherical morphology was reconstructed during ZIF-67 growth, forming a unique 3D structure with ZIF-67 nanoparticles confined on lamellar substrates. This structure not only provides ideal anchoring sites for ZIF-67 but also alleviates its self-agglomeration and metal ion leaching via spatial confinement. Under optimized conditions, 2 mg of the catalyst achieved 95.12% norfloxacin (NOR) removal within 30 min; positively charged LDHs stabilized negatively charged PMS, while ZIF-67 Co sites triggered the continual production of reactive oxygen species (ROS). DFT calculations showed ZIF-67/FeCu-LDH efficiently activates PMS by enhancing adsorption and interfacial electron transfer. A continuous-flow reactor with this catalyst maintained >90% NOR removal for 8 h, showing good practical potential. Quenching experiments and EPR confirmed SO 4 ·- , ·OH, ·O 2 − and 1 O 2 generation; electrochemical tests verified the participation of type III electron transfer pathway (ETP(III)), with radical-non-radical coupling promoting NOR degradation. Mechanistically, FeCu-LDH lamellar confinement enhances Fe/Cu/Co redox cycles and accelerates electron transfer, supplying sufficient electrons for PMS activation. This study proposes a potential method for designing MOF-in-LDHs composites, providing a reference for the treatment of water contaminated by antibiotics.