Magnetically separable CoFe 2 O 4 @UiO-66-NH 2 composite for efficient U(VI) remediation: Synthesis, adsorption performance, and mechanistic insights

A magnetically responsive metal-organic framework (MOF) composite, CoFe 2 O 4 @UiO-66-NH 2 , was synthesized via a solvothermal strategy and applied for efficient adsorption of U(VI) from aqueous solutions. The integration of CoFe 2 O 4 nanoparticles within the UiO-66-NH 2 framework enabled rapid magnetic separation while preserving the material’s high surface area and active functional groups. The composite exhibited a maximum U(VI) adsorption capacity of 193.99 mg·g -1 and followed pseudo-second-order kinetics and Langmuir adsorption behavior, with performance reproducible across replicates. The thermodynamic parameters confirmed the process to be spontaneous and endothermic. Mechanistic insights were obtained through X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations. Binding energy analyses revealed that uranyl ions interact primarily with amino and oxygen-containing groups, especially at Zr-O-C and -NH 2 sites. DFT simulations further confirmed the favorable coordination via strong inner-sphere complexation. This work demonstrates a rational approach to designing magnetically separable MOF-based adsorbents with defined molecular-level binding mechanisms, offering promising potential for practical uranium remediation.