Efficient Capture of Short- and Long-Chain PFAS from Water by a Metal–Organic Framework

Abstract

Per- and polyfluoroalkyl substances (PFAS), known as “forever chemicals,” present major environmental and health risks due to their extreme stability and dual hydrophobic–hydrophilic character, which complicates remediation. Conventional adsorbents such as activated carbon and ion-exchange resins show limited performance, particularly for short-chain PFAS. Metal–organic frameworks (MOFs) have emerged as promising alternatives owing to their tunable porosity, large surface area, and adjustable functionality. Here, we assess the PFAS removal potential of a robust, water-stable, biologically derived MOF, CuII2(S,S)-hismox·5H2O (denoted 1), synthesized from L-histidine. MOF 1 features medium-sized trapezoidal nanoscale channels exhibiting both hydrophobic and hydrophilic character. It achieved high capture efficiencies (80–100%) for long-chain PFAS (C₇–C₁2), including PFDA, PFUnDA, PFDoDA, PFOS, and 8:2 FTSA, and remarkable removal rates of 70% (PFBA) and 86% (PFBS) for short-chain analogues –surpassing conventional adsorbents and other reported MOFs. Excellent reusability and rapid adsorption kinetics were observed under continuous-flow solid-phase extraction with contact times under 30 seconds. The high crystallinity of MOF 1 also enabled single-crystal X-ray diffraction studies of encapsulated PFBA and PFOS (PFBA@1 and PFOS@1). These findings highlight MOF 1 as a high-performance, bio-derived platform for efficient PFAS remediation and advance the development of MOF-based water treatment technologies.