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

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, Cu^II ₂(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.