Intrareticular electron coupling pathway driven electrochemiluminescence in hydrogen-bonded organic frameworks

Abstract

The annihilation reaction between anionic and cationic radicals of the emitters is a key step to produce electrochemiluminescence (ECL). However, the charge transfer process in the annihilation reaction has not been fully studied in nanostructures. Herein, benefiting from the densely stacked structure, hydrogen-bonded organic frameworks (HOFs) as efficient ECL emitters are designed to amplify the ECL signal through the intrareticular electron coupling (IREC) pathway. Due to the electron accumulation between the adjacent interlayer benzenes, 1,3,6,8-tetra(4-carboxylphenyl)pyrene-based HOF-101 exhibited a strong IREC effect with 3.61 cm² V⁻¹ s⁻¹ electron mobility. Significantly, the expanded aromatic HOF-101 demonstrates a 440-fold enhancement in ECL intensity compared with 1,3,6,8-tetracarboxypyrene-based HOF-100 due to the high electron coupling energy and ultrafast excited carrier dynamics, which is rationalized by the Hall effect and density functional theory. Furthermore, the reduced ECL efficiency of Mg-based organic frameworks with antiparallel stacked morphology confirms that the IREC process is a determining step for the generation of ECL. HOFs as ideal ECL emitters provide a tunable intrareticular charge transfer pathway to decode the fundamentals of ECL.