Structure–Activity Relationship in Periodate Activation by Fe-MOFs: Why MIL-101(Fe) Outperforms Other MIL-Series in Antibiotic Degradation

Antibiotics are emerging pollutants that pose significant risks to environmental and human health. Periodate (PI)-based advanced oxidation processes have shown promise for their effective degradation. In this study, we systematically investigate the structure-activity relationship of four representative Fe-based metal-organic frameworks (Fe-MOFs)—MIL-101(Fe), MIL-88B(Fe), MIL-88A(Fe), and MIL-53(Fe)—as PI activators for tetracycline (TC) degradation. Among them, MIL-101(Fe) exhibited the highest catalytic performance, owing to its unique Fe₃O-OH nodes and mesoporous architecture. The MIL-101(Fe)/PI system achieved 93.3% TC degradation and 55.9% mineralization rate within 60 minutes. Mechanistic studies combining scavenger quenching, sulfoxide probe transformation, X-ray photoelectron spectroscopy, and X-ray absorption fine structure confirmed the generation of multiple reactive oxygen species, and high-valent Fe(IV)=O and O₂^·- played major roles in the tetracycline degradation process. Density functional theory calculations further revealed that MIL-101(Fe) and MIL-88B(Fe) effectively interact with PI to form Fe(III)-superoxide (Fe(III)-O-O^·-), a key intermediate in Fe(IV)=O generation. In contrast, the adsorption energy of MIL-53 (Fe) and MIL-88A (Fe) was relatively weak, with fewer binding sites, resulting in poor performance. The synergy between Fe(III)-O-O^·- formation and the pore accessibility of MIL-101(Fe) accounted for its superior catalytic efficiency. This work not only clarifies the structural factors governing PI activation in Fe-MOFs, but also proposes a mechanistically informed strategy for designing high-performance catalysts for antibiotic degradation.