Chemically Tailored Metal-Organic Frameworks for Enhanced Capture of Short- and Long-Chain Per- and Polyfluoroalkyl Substances from Water

Per- and polyfluoroalkyl substances (PFAS) are emerging as bioaccumulative and toxic water pollutants, posing a large threat to human and aquatic organisms. This threat is aggravated by their extreme persistence to common degradation methods. Adsorption is regarded as the most conventional method to treat these contaminants, however, existing sorbents present considerable limitations on performance. The development of more efficient PFAS adsorbents is therefore of urgent need. The class of metal-organic frameworks (MOFs) can hold great promise for these purposes, featuring porous materials with high tailoring potential. Herein, a series of functionalized Zr-MOFs have been designed with boosted capacities for the adsorption of short- and long-chain perfluorinated carboxylic acids of environmental interest. The approach relies on chemistry-based concepts to introduce targeted post-synthetic modifications that promote PFAS···MOF interactions, specifically through coordinative bonding and hydrophobic effects. In particular, the framework TFA-MOF-808 (TFA = trifluoroacetic acid) displays the highest capture capacities reported for MOF materials in this pollutant class. Mechanistic studies, assisted by advanced synchrotron characterization techniques and theoretical calculations, support a ligand exchange process occurring during the adsorption phenomena. The results demonstrate the potential of this design approach in developing advanced PFAS sorbents with optimal performance.