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

Abstract

The annihilation reaction between anionic and cationic radicals of the emitters is the determining step to produce electrochemiluminescence (ECL). However, the charge transfer process in the annihilation reaction has not been fully studied. Herein, benefiting from the densely-stacked structure, the hydrogen-bonded organic frameworks (HOFs) as efficient ECL emitters are designed to amplify the ECL signal through interlayer electron coupling (ILEC) pathway. Due to the electron accumulations between the adjacent interlayer benzenes, the 1,3,6,8-tetra(4-carboxylphenyl)pyrene-based HOF-101 exhibited the strong ILEC 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 ultrafast excited carrier dynamics and high ILEC energy, which is rationalized by density functional theory and the Hall effect. Furthermore, the reduced ECL efficiency of Mg-based organic frameworks with antiparallel stacked morphology confirms that the ILEC process is a determining step during the generation of ECL. In addition, the unique properties of HOFs enable in situ self-repairing ECL capability. HOFs as ideal ECL emitters provide a tunable interlayer charge transfer pathway to decode the fundamentals of ECL.