A chiral metal-organic framework/cyclodextrin sensing interface for the chiral discrimination of tryptophan enantiomers

A chiral metal-organic framework (CMOF) was synthesized by introducing l-histidine (l-His) to zeolitic imidazolate framework-8 (ZIF-8) and then grafting with carboxymethyl-beta-cyclodextrin (CM-beta-CD). Compared with l-His-ZIF-8, the CM-beta-CD-functionalized l-His-ZIF-8 (l-His-ZIF-8-CD) showed significantly enhanced discrimination ability for the tryptophan (Trp) enantiomers owing to the inherent chirality of CM-beta-CD. The specificity of the chiral interface was also studied, and the results indicated that the discrimination ability for Trp enantiomers is significantly stronger than that for the enantiomers of cysteine (Cys) and tyrosine (Tyr), which might be due to the better matching between the indole ring of Trp and the chiral cavity of CM-beta-CD. A CMOF is synthesized by the grafting of carboxymethyl-beta-CD to l-histidine-functionalized ZIF-8, which is used for the discrimination of tryptophan enantiomers.