Postsynthetic Modification Strategy for Constructing Electrochemiluminescence-Active Chiral Covalent Organic Frameworks Performing Efficient Enantioselective Sensing

Electrochemiluminescence (ECL), integrating the characteristics of electrochemistry and fluorescence, has the advantages of high sensitivity and low background. However, only a few studies have been reported for enantioselective sensing based on the ECL-active platform because of the huge challenges in constructing tunable chiral ECL luminophores. Here, we developed a facile strategy to design and prepare ECL-active chiral covalent organic frameworks (COFs) Ph-triPy⁺-(R)-Ru(II) for enantioselective sensing. In such an artificial structure, the ionic skeleton of COFs was beneficial to the electron transfer on the working electrode surface and the chiral Ru-ligand was used as the chiral ECL-active luminophore. It was found that Ph-triPy⁺-(R)-Ru(II) coupled with sodium persulfate (Na₂S₂O₈) as the coreactant exhibited obvious ECL signals. More importantly, a clear difference toward l- and d-enantiomers was observed in the response of the ECL intensity, resulting in a uniform recognition law. That is, for amino alcohols, d-enantiomers (1 mM) measured by Ph-triPy⁺-(R)-Ru(II) showed a higher ECL intensity compared with l-enantiomers. Differently, amino acids (1 mM) gave an inverse recognition phenomenon. The ECL intensity ratios between l- and d-enantiomers (1 mM) are in the range of 1.25–1.94 for serine, aspartic acid, glutamic acid, valine, leucine, leucinol, and valinol. What is more interesting is that the ECL intensity was closely related to the concentration of l-amino alcohols and d-amino acids, whereas their inverse configurations remained unchanged. In a word, the present concept demonstrates a feasible direction toward chiral ECL-active COFs and their potential for efficient enantioselective sensing.