Strong\nElectrochemiluminescence Response Derived from\nIonic Chiral Covalent Organic Frameworks for Enantioselective Discrimination\nof Amino Acid Enantiomers via an Electrostatic Attraction Effect

Porous chiral materials accompanied\nby electrochemiluminescence\n(ECL) activity are rarely reported for enantioselective discrimination\nbecause of the big challenges to integrate the stereogenic center\nand ECL-active unit in the backbone. In the present study, ionic chiral\ncovalent organic frameworks (iCCOFs) consisting of the pyridinium\nunit as the ECL-active species were prepared by a facile strategy.\nWe were amazed that such iCCOFs could display strong cathodic ECL\nresponses. Meanwhile, the as-prepared ECL-active iCCOFs performed\nenantioselective ECL quenching toward amino acid enantiomers, attributed\nto the enhanced photoinduced electron transfer process derived from\nthe formed complex between the iCCOFs and amino acids via an electrostatic\nattraction effect. The iCCOF with an (<i>S</i>)-configuration\nwas prone to interact with l-amino acids, producing a lower\nECL intensity. The maximum intensity ratio between the d-\nand l-enantiomers was 33.0. Finally, the enantiomeric compositions\nof the measured amino acids presented a good linear relation with\nthe obtained ECL intensity, which was fit for the determination of\n samples with unknown enantiomeric purity. In brief, the obtained\nresults convince us that this study advances a new generation of ECL-active\niCCOFs and displays great potential in enantioselective sensing.