Beta-Cyclodextrin-Modified\nCovalent Organic Framework\nNanochannel for Electrochemical Chiral Recognition of Amino Acids

The chiral recognition and separation of enantiomers\nare of great\nimportance for biological research and the pharmaceutical industry.\nPreparing homochiral materials with adjustable size and chiral binding\nsites is beneficial for achieving an efficient chiral recognition\nperformance. Here, a homochiral covalent organic framework membrane\nmodified with β-cyclodextrin (CD-COF) was constructed, which\nwas subsequently utilized as an electrochemical sensor for the enantioselective\nsensing of tryptophan (Trp) molecules. The preferential adsorption\nof l-Trp over d-Trp at the β-CD sites can\nenhance the surface charge density and hydrophilicity of the CD-COF\nmembrane, resulting in an increased transmembrane ionic current. Trp\nenantiomers with concentrations down to 0.28 nM can be effectively\ndiscriminated. The l-/d-Trp recognition selectivity\nincreases with the Trp concentration and reaches a value of 19.2 at\n1 mM. The selective adsorption of l-Trp to the CD-COF membrane\nwill also hinder its transport, resulting in a l-/d-Trp permeation selectivity of 15.3. This study offers a new strategy\nto construct homochiral porous membranes and achieve efficient chiral\nsensing and separation.