Synergistic Fe/Ni dual-metal sites induce interfacial electron redistribution for enhanced tetracycline hydrochloride adsorption in MOFs

Tetracycline hydrochloride (TCH) contamination poses significant ecological and health risks and remains difficult to remediate. Although metal-organic frameworks (MOFs) show promise as adsorbents, monometallic MOFs often suffer from limited adsorption efficiency. Herein, a bimetallic Fe/Ni metal-organic framework was rationally constructed via in situ metal modulation to achieve highly efficient adsorption of TCH from aqueous systems. Fe/Ni-MOF(5:1) exhibited superior adsorption performance due to hierarchical porous architecture, numerous metal centers, and the electronic synergistic effect of bimetallic centers, with a maximum TCH adsorption amount (476.19 mg g −1 ), outperforming pristine MIL-88B(Fe) and Ni-MOF. Density functional theory (DFT) calculations demonstrated that appropriate Ni incorporation induced pronounced interfacial charge redistribution between Fe and Ni via bridging O 2p orbitals and electrostatic polarization, which allowed the efficient adsorption of TCH. Fe/Ni-MOF(5:1) also shows the largest charge transfer from TCH to the adsorbent. Ni doping enhances the quantity of active sites and modifies the internal electronic structure, thereby accelerating electron transfer. Moreover, the hierarchically porous structure creates abundant migration channels and enhances the accessibility of tetracycline hydrochloride molecules. TCH uptake mechanism governed by pore filling, coordination, H-bonding, and π-π interactions. This study provides fundamental insights into designing high-performance bimetallic MOFs adsorbents for wastewater treatment. These results establish a composition-structure-electronic property-adsorption relationship and provide a mechanistic basis for regulating mixed-metal MOFs for antibiotic capture.