(738e) Thermodynamic Implications of Size, Hydrophilicity, and Fluorine Content on Perfluoroalkyl Adsorption in NU-1000

The molecular mechanisms of adsorption are central to engineering new adsorbents to capture environmental contaminants, such as per- and polyfluoroalkyl substances (PFAS). Metal-organic frameworks (MOFs) have been shown to adsorb some PFAS classes, yet a fundamental understanding of how PFAS identity in the presence of water affects their adsorption capacity is not known. We performed grand canonical Monte Carlo simulations and molecular dynamics of perfluoroalkanoic acids (PFAAs) adsorption in MOF NU-1000 under aqueous conditions with varying carbon chain length to interrogate how PFAS chemical structure affects adsorption capacity. We found that larger PFAAs adsorb more favorably into NU-1000 than smaller chain PFAAs due to the formation of aggregates in the mesopores that stabilize anionic adsorption to the node. Due to their size and hydrophilicity, smaller chains tend to limit interactions with the adsorbent. We characterized aggregate formation based on the strength of node and linker interactions. These insights offer directions to develop novel materials to promote aggregate formation to capture and retain a wider set of PFAS from aqueous solutions. We then describe post-synthetic strategies to promote aggregate formation where nonpolar interactions may improve short chain perfluoroalkane adsorption.