Atomically Precise Engineering of Synergistic Binding Sites in a Zirconium Metal-Organic Framework for the Capture of Perfluorooctanoic Acid.

The persistent contamination of water sources by perfluorooctanoic acid (PFOA) poses a major environmental and public health challenge. PFOA is a representative member of per- and polyfluoroalkyl substances (PFAS), a class of compounds characterized by high chemical stability, bioaccumulation potential, and toxicity. Conventional water treatment processes are not fully effective in removing PFOA, underscoring the urgent need for advanced remediation strategies. Here, we report the development of Fe-MOF-808, a novel porous material obtained by incorporating binuclear iron species into the Zr6O8 nodes of the MOF-808 framework. Comprehensive structural characterization was performed, including ex/in situ synchrotron-based techniques combined with computational modeling. The results confirm successful iron integration without compromising the structural integrity and accessibility of the porous network. Moreover, the presence of multiple, spatially accessible binding sites enables Fe-MOF-808 to capture PFAS through a combination of electrostatic, hydrophobic and coordinative interactions. This resulted in high removal efficiencies across various water matrices and for a wide range of PFAS pollutants and concentrations. Fe-MOF-808 notably achieves complete PFOA removal within minutes and demonstrates excellent recyclability over multiple adsorption cycles. The material also reaches experimental uptake and a maximum Langmuir adsorption capacity of 2081 and 3120 mg PFOA g-1, respectively, vastly outperforming the pristine MOF-808 and other state-of-the-art MOF materials. Overall, mechanistic insights gained from this study highlight the critical role of designing specific chemical environments within MOFs to maximize pollutant-sorbent interactions.