Breaking the catalysis-quenching dilemma in covalent organic frameworks with metal single-atom sites for enhanced electrochemiluminescence.

Precise incorporation of metal single-atom (SA) active sites into covalent organic frameworks (COFs) offers a powerful approach to enhance electrochemiluminescence (ECL) by facilitating co-reactant activation and charge transport. However, metal coordination usually triggers intramolecular electron-transfer quenching that degrades the ECL efficiency of COFs. Herein, we construct a pyrene-phenanthroline COF with coordinated Ag SA (AgSA/PP-COF) that breaks the catalysis-quenching dilemma of metals, achieving enhanced ECL performance. Density functional theory calculations reveal that, among the screened metal catalysts, the d10-configurated Ag (I) center exhibits the weakest electron coupling with the nitrogen atoms of PP-COF's phenanthroline units. This minimal perturbation ensures that the framework's intrinsic luminescence is largely retained. Specifically, AgSA serves as highly efficient active sites, facilitating co-reactant adsorption and activation while accelerating interfacial electron transfer kinetics. Remarkably, the resultant AgSA/PP-COF exhibits a 4.5-fold enhancement in ECL intensity. Moreover, AgSA/PP-COF enables the construction of a highly sensitive ECL enzymatic biosensor for organophosphorus pesticide detection. This work provides a universal strategy for the design of high-performance solid-state ECL emitters.