Synergistic Vacancy-Mediated Adsorption-Activation Strategy and Spatial Confinement Effect for Enhanced Electrochemiluminescence Sensing of Isocarbophos

Abstract Exploring advanced strategies to overcome the sluggish activation kinetics of co-reactants and insufficient radical generation is pivotal for boosting electrochemiluminescence (ECL) sensing performance. Herein, an active radical-enriched ECL sensing platform for the ultrasensitive detection of isocarbophos (ICP) was fabricated by utilizing a synergistic vacancy-mediated adsorption-activation strategy coupled with a spatial confinement effect. Specifically, an oxygen-deficient titanium metal−organic framework (D-Ti MOF) was integrated as a robust co-reaction accelerator to trigger the emission of a pyrene-based hydrogen-bonded organic framework (PSA-HOF). Mechanistic studies revealed that abundant oxygen vacancies in D-Ti MOF served as catalytic sites, lowering the activation barrier of peroxydisulfate (K2S2O8) and promoting targeted adsorption and O−O bond cleavage to generate a high flux of sulfate radicals (SO4•−). Meanwhile, the porous MOF architecture imposed nanoscale spatial confinement, enriching reactive intermediates at the electrode interface and reducing diffusional loss. Such a confinement-enabled interfacial microenvironment was further substantiated by kinetic analyses, which revealed that D-Ti MOF promoted S2O82− reduction and redirected the process from predominantly diffusion-controlled behavior toward an adsorption- and confinement-coupled pathway, thereby increasing the local availability and productive utilization of reactive intermediates. Leveraging an isocarbophos-specific split aptamer recognition strategy, the proposed ECL biosensor exhibited a broad linear range (10 fM to 0.1 μM), an ultralow detection limit (8.38 fM), excellent stability, remarkable selectivity and reproducibility, making it highly applicable for practical sample monitoring. This work offers a new perspective for advancing co-reactant-based ECL biosensors and proposes a novel design strategy for ultrasensitive ECL sensing platforms.