Multi-affinity electrochemical perfluorooctanoic acid sensing enabled by a microenvironment-engineered MOF synergy.

The accumulation of perfluorooctanoic acid (PFOA) in environmental waters poses substantial environmental and health risks, even at trace levels, owing to its environmental persistence. Here we developed an electrochemical sensor integrating molecularly imprinted polymers with functionalized metal-organic frameworks (MOFs) for the ultrasensitive detection of PFOA. Strategic incorporation of electron-donating and electron-withdrawing groups (-H, -NH2, -NO2, -F4) enabled precise modulation of the surface and pore chemistry of the MOFs. Among the resulting composites, MIP-Zr(F) exhibited the best sensing performance owing to its ligand-modulated microenvironment and abundant active sites. Combined characterization experiments and density functional theory calculations revealed a multi-affinity synergistic recognition mechanism: the imprinted cavities provide shape selectivity and hydrogen bonding interactions, while the ligand-modulated Zr(F) substrate enables Lewis acid-base interactions, hydrophobic attraction, and F-F interactions. The sensor achieved a limit of detection of 28.2 pg mL-1 over a linear concentration range of 0.2-2000 ng mL-1 and exhibited high selectivity against interfering per- and polyfluoroalkyl substances (PFAS) and common coexisting interferents. Successful validation in tap water, river water, seawater, and groundwater demonstrated its practical utility for environmental water analysis, with the results showing strong agreement with those obtained by LC-MS/MS.