MOF-decorated track-etched membranes for the U(VI) ions sorption removal

This study presents the development of metal-organic framework functionalized track-etched membranes (MOF@TeMs) as efficient adsorbents for uranium(VI) removal from water. Poly(N-vinylformamide) was grafted onto PET membranes by UV-induced RAFT polymerization, hydrolyzed to poly(vinylamine), and further modified with terminal alkyne groups. Chromium-based MIL-101 MOFs were post-synthetically functionalized with azide groups and covalently immobilized onto the membrane surface through copper-catalyzed azide-alkyne cycloaddition. This covalent click-immobilization strategy provided a stable integration of MOFs onto polymer track-etched membranes, which has not been demonstrated previously for uranium(VI) sorption. Comprehensive characterization, including FTIR, XPS, SEM/EDX, BET, and contact angle, confirmed each modification step and successful MOF integration. The resulting composites displayed a uranium adsorption capacity of 418 mg g^-1 at pH 6.3, with kinetics following a pseudo-second-order model and isotherm fitting best to the Freundlich equation, indicating heterogeneous sorption sites. The Dubinin-Radushkevich model yielded an adsorption energy of 14.4 kJ·mol^-1, consistent with coordination-driven interactions. Despite the relatively long equilibrium time (96 h), the membranes retained 70% of their capacity after five regeneration cycles and showed strong selectivity for U(VI) over competing cations (Co²⁺, Cr²⁺, Pb²⁺, Zr²⁺, Zn²⁺). The membrane architecture offers mechanical stability, reusability, and ease of handling, highlighting the potential of MOF-immobilized TeMs as practical sorbents for uranium remediation.