Development of Fe-Zr hybrid MOFs for high-efficiency arsenic removal in aqueous systems

• Acetic acid isntroduced defects, increasing arsenic adsorption sites. • Iron filled defects, strengthening arsenic binding interactions. • Fe-UiO-66 achieved 178 mg/g across wide pH range. • Freundlich and pseudo-second-order models indicated multilayer chemisorption. Arsenic pollution in water poses significant environmental concerns and human health hazards. While pristine UiO-66 can remove arsenic effectively, its adsorption performance can be further enhanced. In this study, acetic acid was employed as a modulating agent during the synthesis process to promote missing-linker defects, generating additional active sites. Fe doping was then introduced to occupy these defect sites and further improve arsenic capture. The resulting Fe-UiO-66 exhibits a defect-rich structure with enhanced surface properties, enabling efficient uptake. The adsorption experiments revealed a notable adsorption capacity of 178 mg/g over a broad pH range. The process conformed to the Freundlich isotherm and was described by a pseudo-second order kinetic model, suggesting multilayer chemisorption occurring on heterogeneous surface sites. Characterization by FTIR, XRD, SEM, EDS, and XPS confirmed successful Fe incorporation and interactions of Fe/Zr–OH groups with arsenic. Overall, Fe-UiO-66 offers a highly efficient approach for arsenic removal, combining defect engineering and metal doping to optimize MOF-based adsorbents.