Deciphering the dominant interfacial active sites in MOF-derived FeCu@C for peroxydisulfate activation towards sustainable tetracycline detoxification: A combined experimental and DFT study.

Abstract

Tetracycline (TC), a representative emerging organic contaminant, has raised increasing concern owing to its widespread occurrence in aquatic environments and the associated risks to ecosystems and human health. Herein, a bimetallic FeCu@C material derived from MIL-101(Fe,Cu) was synthesized and employed for TC detoxification via the combination of adsorption and peroxydisulfate (PDS)-activated Fenton-like catalysis. The optimal catalyst (800 °C, 5 h) achieved a degradation rate constant (kapp) of 0.2141 min-1, i.e., 3.54 times that of the 600 °C counterpart. Comprehensive characterization and density functional theory (DFT) calculations jointly identify Fe0(110) and FeO(111) as the most probable dominant interfacial active centers, while Cu species and Fe3O4 serve as redox mediators and auxiliary sites, respectively. Fe0(110) chemisorbs TC (Eads = -0.899 eV) and elongates the O-O bond of PDS from 1.497 Å to 3.110 Å, triggering homolytic cleavage to generate SO4•- and OH•. Conversely, FeO(111) leaves the O-O bond essentially unchanged (1.492 Å) yet exhibits strong PDS adsorption (Eads = -4.233 eV), favoring a surface-mediated nonradical pathway inferred to produce 1O2 predominantly. ECOSAR-based toxicity assessment confirmed progressive detoxification of TC, with 68.5% TOC removal after 120 min. The catalyst retained essentially complete TC adsorption after five adsorption-regeneration cycles; although the catalytic degradation efficiency declined to 13.17% after five PDS-activation cycles, it was fully restored to 99.03% by recalcination. This work decouples the distinct roles of Fe0 and FeO in radical versus nonradical routes while clarifying the auxiliary role of Cu species, offering molecular-level insights for designing efficient and environmentally safe remediation systems.

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