Rapid enantioselective fluorescence recognition and chiral separation of free amino acids

Enantioselective recognition and chiral separation of amino acids hold significant importance in chemistry, materials science, and life science. Here, we report a water-soluble chiral fluorescent probe that enables visual chiral recognition and separation by incorporating a morpholinium quaternary cation into the 1,1'-bi-2-naphthol frameworks. Upon binding with free amino acid enantiomers, the probe achieves rapid chiral discrimination within 100 s, accompanied by distinct changes in luminescence color or intensity. The underlying mechanism of this chiral recognition involves imine formation and electrostatic interactions, accompanied by aggregation-induced emission. These processes collectively promote selective aggregation and precipitation between the probe and specific enantiomers of amino acids. Furthermore, the enantiomers can be efficiently separated from D-/L- amino acid mixtures through a simple filtration process. Comparative analyses using a fluorescence visualization and chiral high performance liquid chromatography further validate the probe's efficacy in achieving efficient chiral separation. This study provides a practical approach for the precise detection and separation of amino acid enantiomers.