Fluorinated amino covalent organic frameworks for efficient adsorption of per- and polyfluoroalkyl substances in water

Per- and polyfluoroalkyl substances (PFAS) have been classified as emerging pollutants requiring global control, and the development of highly efficient adsorbents is a key technological challenge hindering the effective treatment of PFAS. In this study, we prepared a novel fluorinated amino covalent organic framework (COF-FS-NH₂) via multimonomer hybrid synthesis and post-synthesis modification. The kinetic data of PFAS adsorption on COF-FS-NH₂ were well fitted using the pseudo-second-order model. Using the Langmuir model, the maximum adsorption capacities of COF-FS-NH₂ for perfluorooctanoic acid (PFOA), perfluoro-2,5-dimethyl-3,6-dioxanonanoic acid (HFPO-TA), perfluoro-2,5-dimethyl-3,6-dioxaheptanoic acid (C7 HFPO-TA), and perfluoro(2-methyl-3-oxahexanoic) acid (GenX) were found to be 0.331, 0.289, 0.319, and 0.210 mmol/g, respectively. PFAS adsorption mainly relied on the electrostatic interaction between the amino group of COF-FS-NH₂ and the anionic group of PFAS as well as the van der Waals forces. Compared with the conventional activated carbon and resin materials, COF-FS-NH₂ exhibited high selectivity and adsorption capacity for PFAS, with high removal percentage (>80%) for the four PFAS at environmental concentration (10 μg/L). This study demonstrates that COF-FS-NH₂ has great potential for the efficient removal of PFAS from water, providing a new material strategy for practical water remediation.