Intrareticular charge transfer regulated electrochemiluminescence of donor\u2013acceptor covalent organic frameworks

Rengan Luo,Jianping Lei,Haifeng Lv,Kai Xi,Huangxian Ju,Jiarui Yang,Xiaojun Wu,Yang Li,Qiaobo Liao,Ningning Wang

doi:10.1038/s41467-021-27127-5

Rengan Luo, Jianping Lei + Show 8 more

Open Access

https://doi.org/10.1038/s41467-021-27127-5

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Abstract

The control of charge transfer between radical anions and cations is a promising way for decoding the emission mechanism in electrochemiluminescence (ECL) systems. Herein, a type of donor-acceptor (D-A) covalent organic framework (COF) with triphenylamine and triazine units is designed as a highly efficient ECL emitter with tunable intrareticular charge transfer (IRCT). The D-A COF demonstrates 123 folds enhancement in ECL intensity compared with its benzene-based COF with small D-A contrast. Further, the COF’s crystallinity- and protonation-modulated ECL behaviors confirm ECL dependence on intrareticular charge transfer between donor and acceptor units, which is rationalized by density functional theory. Significantly, dual-peaked ECL patterns of COFs are achieved through an IRCT mediated competitive oxidation mechanism: the coreactant-mediated oxidation at lower potential and the direct oxidation at higher potential. This work provides a new fundamental and approach to improve the ECL efficiency for designing next-generation ECL devices.

Highlights

The control of charge transfer between radical anions and cations is a promising way for decoding the emission mechanism in electrochemiluminescence (ECL) systems
We delicately designed a series of tris(4-formylphenyl)amine (TFPA)-based covalent organic framework (COF) that are synthesized with 2,4,6-tris(4-aminophenyl)-1,3,5-triazine (TAPT), 1,3,5-tris(4-aminophenyl)benzene (TAPB), and tris(4-aminophenyl) amine (TAPA) counterparts, denoting as t-COF, b-COF, and a-COF, respectively[29]
Highresolution transmission electron microscopy further confirmed the formation of honeycomb-like porous structures with periodicities of 1.7 ± 0.2 nm for t-COF (Fig. 1g and Supplementary Fig. 5) and 1.7 ± 0.2 nm for b-COF (Supplementary Fig. 6), and layered morphology of a-COF (Supplementary Fig. 7)

Summary

Introduction

The control of charge transfer between radical anions and cations is a promising way for decoding the emission mechanism in electrochemiluminescence (ECL) systems. A type of donor-acceptor (D-A) covalent organic framework (COF) with triphenylamine and triazine units is designed as a highly efficient ECL emitter with tunable intrareticular charge transfer (IRCT). A stepwise-oxidation induced intrareticular electron transfer based on 1,4-diazabicyclo[2.2.2]octane coordinated metal-organic framework was established for ECL enhancement[12] These works improved ECL performance by shortening the distance between emitter and coreactant, an efficient charge transfer between the emitter and coreactant was realized. D–A COFs have the ordered frameworks to stabilize electrons/holes obtained from electrode and coreactants[28], enabling the generation of excited states for ECL transduction through the IRCT process. Taking advantages of D–A pairs, a luminescent COF was designed as an ECL emitter by integrating triazine and triphenylamine as donor and acceptor units in the reticular structure, respectively (Fig. 1a). The D–A COFs provide a delicate approach to design efficient ECL emitters and enrich the fundamentals of ECL signal transduction in optoelectronic devices

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