Decoding host–guest interactions: tuning pore functionality in MOFs for efficient capture of short- and long-chain PFAS

Abstract

Per- and polyfluoroalkyl substances (PFAS) are persistent environmental pollutants of growing concern due to their widespread occurrence, chemical stability, and adverse health effects. In this study, we explore the impact of pore-surface functionality in a series of bio-derived metal–organic frameworks (MOFs), including multivariate MOFs (MTV-MOFs), as a strategy for designing next-generation adsorbents for the efficient removal of both long- and short-chain PFAS from aqueous solutions. Building on a previously reported MOF featuring thioether-functionalized channels (MOF 1), we synthesized and evaluated four structural analogues (MOFs 2–5), systematically tuning pore chemistry through amino acid side-chain substitutions (L-serine and L-leucine). Adsorption studies reveal that increasing the hydrophobicity of the pore environment significantly enhances PFAS uptake, particularly for short-chain compounds. MOF 5, incorporating L-leucine-based hydrophobic side chains, demonstrated superior performance across all tested PFAS, along with excellent reusability and high sorption capacity. Single-crystal X-ray diffraction provided molecular-level insight into host–guest interactions, confirming both metal coordination and key supramolecular interactions. Complementary theoretical calculations based on the resolved crystal structure of MOF 5 with embedded PFOA molecules (PFOA@5′) further confirm the dominant role of rationally introduced hydrophobic functionalities in driving efficient PFAS capture. These findings underscore the central role of pore functionality in enabling efficient, tuneable MOF platforms for water remediation.