Unveiling the Differential Intensity of Fluorous Active Sites Toward Selective Polyfluoroalkyl Substance Removal: Insights into Adsorption and Desorption Trade-Offs

The design of selective sorption sites for per- and polyfluoroalkyl substance (PFAS) removal, integrated with efficient regenerative strategies, remains a critical yet underexplored challenge. While existing technologies prioritize adsorption capacity over regenerative sustainability, we engineered a fluorinated hydrogel with tailored fluorous binding sites to target PFAS via their hydrophobic C-F termini. This design achieved over 90% PFAS removal efficiency in real water matrices (e.g., tap and lake water), at environmentally relevant concentrations (1 μg L-1), with robust resistance to competing background ions and natural organic matter. Selectivity correlated strongly with PFAS chain length (F9 > F12 > F6), driven by stable adsorption configurations (C-F···F-C vs C-H···F-C) and a favorable adsorption energy of -29.06 kcal mol-1. Leveraging controlled noncovalent F···F interactions, the hydrogel enabled efficient desorption (60-80% efficiency using 1% NaCl, 1% NH4Cl, or 0.5% NH4OH-NH4Cl) without structural degradation. Full regeneration (>92% recovery) was achieved with 50% methanol, supporting five reuse cycles with minimal performance decline. In continuous operation, using 1% NaCl achieved a 10-fold PFAS enrichment, while 50% methanol enabled a significantly higher 51-fold enrichment. Both approaches reduced eluent consumption by 20-50% compared to conventional activated carbon and resins. Overall, balancing PFAS adsorption and desorption trade-offs significantly reduces environmental footprint and operational costs, providing a sustainable strategy for PFAS remediation.