Fluorine-functionalized MOF modified GCE for highly sensitive electrochemical detection of persistent pollutant perfluorooctanoic acid

Perfluorooctanoic acid (PFOA) is one of typical per- and polyfluoroalkyl substances (PFASs) in water environments, which attracts global concern due to its high persistence, bioaccumulation, and toxicity. Electrochemical detection provides a feasible, cost-effective, in-situ, and real-time detection approach for PFOA. And the fluorine-functionalized metal-organic frameworks (MOFs) have shown great adsorbing affinity towards PFOA with their fluorophilic interaction, electrostatic interaction, anion-π stacking, large specific area and porous structure. In this work, fluorine-functionalized Ce-UiO-66 (Ce-UiO-66-F) modified glass carbon electrode (GCE) was utilized to effectively and sensitively detect PFOA with redox probe strategy. The adsorption of PFOA occupied cavities of MOFs and blocked the active sites on Ce-UiO-66-F/GCE interface, leading to a decreasing probe current with PFOA concentration increasing. The quantitative detection mechanism was investigated with Langmuir isotherm model and Freundlich-Langmuir isotherm model, transducing the decreasing probe signal into PFOA concentration information. A detection range of 0.40-450 nM was obtained, and the limit of detection (LOD) was estimated to be 0.048 nM, which satisfied the domestic water requirements of Untied State Environmental Protection Agency (USEPA). This work provides a rapid and convenient electrochemical approach to detect PFOA and extends the applicability of MOFs as deployable modifiers for PFAS sensors.