Deciphering a volcano-shaped relationship between radical stability and reticular electrochemiluminescence

Electrochemiluminescence (ECL) is a light-emitting process in which the stability of electrochemically generated radicals has a crucial impact on the efficiency and durability of excited state generation. Therefore, deciphering a relationship between radical stability and ECL performance is highly appealing. In this work, three sp2 carbon-conjugated covalent organic framework (COF) reticular nanoemitters compositing of same pyrene luminophores but different acrylonitrile linkers are designed with progressive electron affinities, named as CN-COF-1, 2, and 3. By precisely modulating the electron affinity of CN-COFs, a volcano relationship between ECL and radical stability is discovered with 78 folds enhancement in ECL intensity. Density functional theoretical calculations indicate that CN-COF-2 exhibits moderate radical stabilization capacity as well as efficient electron transport between the pyrene cores, facilitating ECL generation. Significantly, the appropriate radical stability of CN-COF-2 not only achieves the self-enhanced cathodic ECL but also promotes durability of the ECL intensity. The rational regulation of radical stability paves the way for developing efficient reticular nanoemitters and decoding the ECL fundamentals. Deciphering the relationship between radical stability and electrochemiluminescence performance is important since the stability of electrochemically generated radicals has an impact on the efficiency and durability of excited state generation. Here, the authors describe a volcano shaped relationship via modulating the electron affinity of three acrylonitrile-linked covalent organic frameworks.