Room-Temperature Synthesis of a Multifunctional Covalent Organic Framework for Highly Efficient Extraction of Anionic Per- and Polyfluoroalkyl Substances

Efficient extraction of perfluoroalkyl and polyfluoroalkyl substances (PFAS) poses a significant challenge for water treatment and food safety. Here, we report a multifunctional covalent organic framework (COF) for the selective and efficient extraction of PFAS. A facile room-temperature imine condensation of two monomers, 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (BTFDA) and 1,3,5-triformylphloroglucinol (Tp), produced a multifunctional COF (TpBTFDA). TpBTFDA was rationally designed to synergistically integrate chemical moieties capable of leveraging both fluorophilic (via trifluoromethyl groups) and hydrogen bonding (via β-ketoenamine linkages) interactions with PFAS molecules. Batch adsorption experiments, coupled with systematic comparative studies against control COFs (lacking either the fluorophilic or hydrogen-bonding sites), revealed that this synergistic interplay is essential for the efficient capture of PFAS, demonstrating that both interaction mechanisms are indispensable. Consequently, the TpBTFDA exhibited exceptionally high adsorption capacities (379-521 mg g^-1) for eight PFAS. The fabricated TpBTFDA was applied to develop a selective solid-phase extraction method for UHPLC-MS/MS determination of PFAS. The developed method showed a wide linear range (0.01-200 μg L^-1), low detection limits (0.006-0.59 μg L^-1), good precision (RSD ≤ 5.2%), and recovery (83.0-112.3%) for the accurate determination of PFAS in real water and food samples. This study underscores the potential of rationally designed COFs for effectively enriching and detecting PFAS in practical applications.