Postsynthetic Polymerization of UiO-66-NH ₂ for the Fabrication of Nylon/MOF Hybrid Membranes with Enhanced PFOS and PFOA Uptake

This study presents an approach for fabricating Nylon/MOF hybrid membranes via the postsynthetic modification of UiO-66-NH2 to introduce polymerizable moieties, followed by in situ polymerization with Nylon. Comprehensive characterization (FTIR, XPS, TGA, powder X-ray diffraction, SEM/EDS, TEM, and LC-MS) confirms the retention of MOF crystallinity, homogeneous dispersion within the Nylon (PA) matrix, and effective capture of per- and polyfluoroalkyl substances (PFAS). The resulting composites exhibit markedly enhanced adsorption capacities from water: for perfluorooctanesulfonic acid (PFOS), PA membranes show Qmax = 94 mg g–1 while PA–MOF achieves 102 mg g–1; for perfluorooctanoic acid (PFOA), PA membranes show Qmax = 18 mg g–1 while PA–MOF reaches 31 mg g–1, corresponding to increases of 9 and 72%, respectively. Although the hybrid membranes display lower Qmax values than the pure MOF (160 to >2000 mg g–1), they exhibit significantly higher affinity constants. From the best-fit models, the affinity constants were: PFOS─PA (Double-Langmuir) KL,1 = 0.22, KL,2 = 11.02; PA–MOF (Double-Langmuir) KL,1 = 0.36, KL,2 = 25.96; and PFOA─PA (Sips) KS = 0.90 (n = 0.68), PA–MOF (Sips) KS = 0.36 (n = 1.32). These results indicate stronger interactions and superior uptake efficiency at low PFAS concentrations─an essential feature for real water treatment applications─and, in the case of PA–MOF, a cooperative intrapore mechanism for PFOA adsorption (n > 1). Adsorption modeling reveals dual-site interactions best described by the Double-Langmuir and Sips isotherms, consistent with heterogeneous binding arising from polar amide functionalities in Nylon and the intrinsically high surface area of the MOF. Overall, this work demonstrates a robust and scalable route to hybrid membranes for advanced water purification and environmental remediation.