Molecular insights into the selective separation of perfluoroalkyl substances: The construction and application of capsule adsorbents

Perfluoroalkyl substances (PFAS) pollution has been a worldwide environmental challenge. Inspired by the semipermeable function of cell membranes, we constructed a millimeter-sized capsule adsorbent with specific molecular recognition capability to capture a broad spectrum of PFAS. This novel capsule consists of a core with a regulated nanoscale amine-rich network powder (ANP) and a porous polyvinylidene fluoride (PVDF) shell. Adsorption experiments and molecular simulations revealed that the PVDF shell acted as a semipermeable membrane, allowing only PFAS to pass through while repelling the coexisting environmental matrices, whereas the ANP core could provide the driving force for PFAS to enter the interior of the capsule adsorbent. Moreover, by regulating the hydrophilic functional structure of ANP, the driving force for short-chain PFAS to enter the capsule interior was enhanced, enabling the efficient capture of a wide range of PFAS (C-F number: 3-9). Further mechanistic studies demonstrated that the dual driving forces based on fluorophilicity and hydrogen bonding were key to capturing broad-spectrum PFAS. The fixed-bed experiments further demonstrated that the aminated organic fluorine capsule (AFC) column could treat approximately 18,000 bed volumes of effluent from synthetic PFOA-polluted water, with the effluent PFOA concentration remaining below 40 ng/L from an initial influent concentration of 1 μg/L (compared with the World Health Organization's drinking-water standard of 100 ng/L). Overall, this work not only provides a promising approach to treat PFAS-containing water but also sheds light on the design of functional remediation materials based on molecular properties and confined structures.