Dual Promotion of Electron Transfer and Polarization by Organic Ligands for Microwave Catalysis over an Iron-Based Metal–Organic Framework

This study employs a competitive coordination modification strategy using salicylic acid (SA) to precisely regulate the coordination environment and electronic structure of Fe-BDC, constructing a “grape-like” modified Fe-BDC material (Fe-BDC/SA1.2) with mixed Fe3+/Fe2+ valences for highly efficient microwave-catalyzed degradation of tetracycline (TC) in wastewater. Experimental results demonstrate that the carboxyl and phenolic hydroxyl groups of SA synergistically modulate the electronic structure of Fe: the carboxyl group stabilizes the framework and induces ligand-to-metal charge transfer (LMCT), while the phenolic hydroxyl group weakens the coordination field strength, forming a highly active mixed-valence system. Under microwave irradiation, Fe-BDC/SA1.2 achieved 96.80% TC degradation within 6 min, exhibiting a 4.5-fold enhancement over the unmodified control (Fe-BDC/SA0). The superior performance arises from the “grape-like” hierarchical nanostructure, which enhances the localized electric field and mass transfer, while dielectric polarization and electron delocalization synergistically promote the generation of reactive radicals (·O2–/·OH). This work provides a insight into designing microwave-responsive catalysts through ligand-induced valence regulation and the establishment of multiple synergistic mechanisms for microwave nonthermal effects.