Lewis Acid-Mediated Interfacial Microenvironment Engineering for Enhanced Cathodic Electrochemiluminescence Aptasensing of Perfluorooctanoic Acid Based on Ligand Defect-Modulated MIL-88B(Fe) MOF

Efficient interfacial activation of co-reactants to generate sufficient radical intermediates is fundamental to constructing high-performance co-reactant-type electrochemiluminescence (ECL) biosensing platforms. This work reported a microenvironment-engineered cathodic ECL strategy by integrating PSA-HOF as the luminophore with defect-engineered MIL-88B(Fe) as the co-reactant activation modulator for the sensitive detection of perfluorooctanoic acid (PFOA). Specifically, pyrrole-2-carboxylic acid-regulated Pca-MIL-88B(Fe), as a defect-engineered material, generated coordinatively unsaturated, electron-deficient Fe centers with exceptional Lewis acidity. These defect-derived sites established an optimal interfacial microenvironment for persulfate activation by critically enhancing K2S2O8 enrichment, optimizing adsorption configuration, facilitating electron redistribution, and promoting O–O bond polarization. This collective action significantly lowered the cathodic driving force required for K2S2O8 reduction and accelerated SO4•– generation through a Lewis acid-mediated pathway, ultimately leading to a marked enhancement in cathodic ECL efficiency. As a result, the PSA-HOF/Pca-MIL-88B(Fe) composite exhibited an approximately threefold increase in ECL intensity compared with pristine PSA-HOF. Leveraging this efficient signal amplification mechanism, the developed aptasensor exhibited superior analytical performance with the assistance of PFOA aptamer, featuring a wide linear response range spanning from 10 fM to 1 μM and an ultralow detection limit of 9.8 fM, while also exhibiting outstanding stability, selectivity, and reproducibility. This work provided a robust physicochemical insight into defect-mediated co-reactant activation and paved the way for designing high-efficiency ECL emitters for environmental monitoring.