Selective Degradation of Tetracycline by an Adsorption-Coupled Fe-MOF/H2O2 Heterogeneous Fenton-like System

Selective degradation of antibiotics in complex wastewater is often hindered by the non-selective consumption of reactive oxygen species by coexisting organic matter. In this study, an adsorption-coupled heterogeneous Fenton-like strategy was developed to preferentially enrich tetracycline (TC) at the catalyst interface prior to oxidative degradation. MIL-53(Fe), MIL-101(Fe), and NH2-MIL-101(Fe) were synthesized using a solvothermal method and systematically compared in terms of TC adsorption, catalytic degradation, and degradation selectivity in binary TC/glucose systems. Although MIL-101(Fe) exhibited the highest overall TC degradation efficiency, NH2-MIL-101(Fe) showed the highest selectivity toward TC. At a TC/glucose concentration ratio of 2:2, NH2-MIL-101(Fe) achieved a TC degradation selectivity of 73.1%, compared with 50.2% for MIL-101(Fe). Electron spin resonance and radical scavenging experiments demonstrated that ·OH was the dominant reactive species and that TC oxidation occurred predominantly at or near the catalyst surface. The enhanced selectivity was attributed to preferential TC adsorption followed by surface-localized oxidation and repeated adsorption–degradation cycles. Full-scan LC-MS analysis revealed several transformation-related ions, from which a tentative pathway involving possible N-demethylation, oxidative fragmentation, and ring-cleavage-related transformations was proposed; however, the individual product structures were not definitively identified. After five reuse cycles, the TC degradation efficiency remained above 75%, while the degradation selectivity decreased only from 74.7% to 68.7%. NH2-MIL-101(Fe) also retained preferential TC removal in a TC-spiked domestic wastewater matrix. These results demonstrate that coupling preferential adsorption with localized Fenton-like oxidation provides an effective strategy for enhancing the selective removal of antibiotics from complex aqueous matrices.