Tuning fluorocarbon chain length in fluorine-amine co-functionalized mesocellular silica foam for efficient PFAS adsorption from water

A chain-length-tunable fluorine–amine co-functionalized adsorbent platform was developed. • Moderate perfluoroalkyl chain length (F9) strikes the optimal affinity for PFAS. • MCF@PEI-F9 exhibits robustness for PFAS (>C6) adsorption under real environmental conditions. • Synergistic electrostatic and fluorophilic interactions were elucidated by DFT calculations and spectroscopic analysis. Per - and polyfluoroalkyl substances (PFAS) persist at trace levels in water and resist conventional treatment, posing a challenge for both detection and remediation. Fluorinated adsorbents offer specific fluorophilic affinity for PFAS, yet suffer from limited capacity and a poorly understood structure-property relationship. To address this, we synthesized a series of fluorine-amine co-functionalized adsorbents (MCF@PEI-F x , x  = 3, 9, 13, 17) by grafting fluorocarbon chains of varying lengths onto a PEI-modified mesocellular silica foam (MCF) platform. This design enabled systematic investigation of the chain-length-dependent adsorption performance and its underlying mechanism. Among the series, MCF@PEI-F9 exhibited the highest adsorption capacity (863 mg g −1 ), the fastest adsorption kinetics (equilibrium within 5 min), and exceptional selectivity (>99% adsorption) under pH 3–9 and coexisting components. Notably, MCF@PEI-F9 maintained >99% adsorption over five regeneration cycles and removed >95% of long-chain PFAS in real Yangtze River water. Density functional theory calculations confirmed that MCF@PEI-F9 struck an optimal balance between strong electrostatic and abundant fluorophilic interactions, with the most favorable binding affinity towards PFOA (adsorption energy: −0.376 eV). These results provide a rational design strategy for next-generation fluorinated adsorbents for PFAS enrichment and remediation, via tuning chain lengths of surface functional groups. Download: Download high-res image (208KB) Download: Download full-size image