Ionic Liquid‐Enhanced Functionalization of MOFs: A Novel Approach for Effective Diclofenac Removal

ABSTRACT

This study presents a green and efficient strategy for enhancing the adsorption performance of metal–organic frameworks (MOFs) toward diclofenac (DCF), an emerging pharmaceutical contaminant frequently detected in aquatic environments. Zinc‐ and nickel‐based phosphonate MOFs using phenylphosphonic acid (PP), forming Zn and Ni phosphonate metal organic frameworks (ZnPP and NiPP), were synthesized under environmentally benign conditions and functionalized with quaternary ammonium‐ or phosphonium‐based ionic liquids to improve their affinity regarding anionic pollutants. Comprehensive physicochemical characterization confirmed successful functionalization without compromising the structural integrity of the frameworks. Ionic‐liquid modification using methyl trialkyl ammonium chloride (AmIL), trihexyl(tetradecyl)phosphonium chloride (PhIL) significantly enhanced DCF removal, with ZnPP–AmIL showing the highest adsorption capacity (q _max = 170 mg/g) due to combined electrostatic attraction, hydrogen bonding, π–π interactions, and anion‐exchange effects. Kinetic studies revealed rapid adsorption with pseudo‐second‐order behavior, while equilibrium data were best described by the Langmuir isotherm, indicating monolayer adsorption and strong adsorbent–adsorbate interactions. The materials exhibited good reusability after multiple adsorption–desorption cycles and maintained high removal efficiencies in real groundwater matrices, demonstrating minimal interference from coexisting ions. This work underscores the critical role of functionalization in optimizing adsorptive properties, showcasing the potential of ionic liquid‐functionalized MOFs as innovative materials for the efficient removal of pharmaceutical pollutants, thereby contributing to improved environmental sustainability and water quality management.