Microenvironment-regulated UiO-67-based metal-organic frameworks for efficient removal of perfluorohexanoic acid from...

Short-chain perfluoroalkyl carboxylic acid (PFCAs) have been widely detected in aquatic systems, posing adverse threats to human health and the environment. However, the effective remediation of short-chain PFCAs in contaminated groundwater remains a major challenge. In this study, Zr-based metal-organic framework UiO-67-featuring tetrahedral cages (12 Å) and octahedral cages (14 Å)-was employed as a platform for precise pore microenvironment regulation. A new modulation strategy using glycine hydrochloride enabled the introduction of linker defects, thereby enhancing the surface positive charge and electrostatic interactions. By incorporating amine and fluorophilic CF₃ functional groups into the organic ligands, three UiO-67 series MOFs, UiO-67-X (X = H, NH₂, 2CF₃), were synthesized for efficient removal of perfluorohexanoic acid (PFHxA) from aqueous solution. Among them, UiO-67-2CF₃, with a hierarchical pore structure (0.89 nm, 1.14 nm), exhibited exceptional PFHxA adsorption capacity (1386 mg/g), rapid adsorption kinetics (4 min), and excellent selectivity and recyclability. Continuous column breakthrough experiments further demonstrated that UiO-67-2CF₃ effectively reduced PFHxA concentrations from 1 μg/L to below 10 ng/L. In addition, experimental characterizations and DFT theoretical calculations revealed that the adsorption mechanism involves electrostatic interaction, F···F interactions, Lewis acid-base interactions, anion-π interactions, CF₃-π interactions and hydrogen bonding. These excellent adsorption performances highlight UiO-67-2CF₃ as a promising material for the remediation of short-chain PFCA-contaminated water. This study also provides new insights into the rational design of advanced adsorbents for short-chain PFCAs removal.