Ionic\nCovalent–Organic Frameworks Composed\nof Anthryl-Extended Viologen as a Kind of Electrochemiluminescence\nLuminophore

Nowadays,\ncovalent–organic frameworks (COFs) integrated\nwith the electrochemiluminescence (ECL) behavior are highly desired\nowing to the significant advantages including multifunctionality,\nhigh sensitivity, and low background noise. Here, two ionic COFs (iCOFs)\nconsisting of the anthryl-extended viologen as the backbone were designed\nand synthesized via the Zincke reaction. It is found for the first\ntime that the as-prepared iCOFs accompanied by potassium persulfate\nas the coreactant can provide a clear ECL response in a water-bearing\nmedium. The maximum ECL emissions of the iCOFs were in agreement with\nthe photoluminescence spectra. Besides, cyclic voltammetry and electron\nparamagnetic resonance measurements reveal that the pyridinium unit\nwas electrochemically reduced to afford the free radical. Then, it\nreacted with SO<sub>4</sub><sup>·–</sup> to generate the\nexcited-state [iCOF]*. Finally, [iCOF]* quickly returned to its ground\nstate coupled with a clear ECL emission, yielding a maximum ECL quantum\nefficiency of 23.4% compared with tris(2,2′-bipyridyl) ruthenium(II)\nas the benchmark. In brief, the current study opens a way to develop\na kind of ECL emitter that holds great potential in sensing, imaging,\nand light-emitting devices.