An Electrochemical Sensor Employing Β-Cyclodextrin Chiral Cross-Linked Metal Organic Framework and Graphene Oxide for Chiral Enantiomer Recognition

Abstract

Chirality is a universal feature of nature, and the effective differentiation of chiral molecules is still a challenge. Here we propose a method for recognizing chiral molecules based on an electrochemical platform. We use β-cyclodextrin as an organic ligand and coordinate it with K ions to form a metal-organic framework (MOF), then we use diphenyl carbonate to connect MOFs to obtain chiral Cross-Linked MOF (CLMOF). This CLMOF is different from the cyclodextrin MOFs reported in previous literature in that it can maintain a stable structure in the aqueous environment. CLMOF and graphene oxide (GO) are jointly modified on the glassy carbon electrode (GCE) surface to build a GO-CLMOF/GCE electrochemical sensor which is used for the chiral recognition of the enantiomers of mandelic acid (MA). The DL enantiomers of MA exhibit different electrochemical behaviors on the GO-CLMOF/GCE sensor. Their peak current ratio (I L /I D ) reaches 1.8, and the peak potential difference ΔE (E D -E L ) is 96 mV. It shows good linearity in the range of 0.5-30mM. The detection limits of D-MA and L-MA are 0.15mM and 0.09mM, respectively. The method was successfully applied to the detection of MA racemic mixture of unknown concentration in urine. The recognition of DL enantiomers on the electrode surface is possible because DL-MA forms diastereomers with CLMOF. The electrochemical sensor made of CLMOF and GO is simple to prepare and has excellent selectivity for DL enantiomers of MA, and provides a possible idea for the identification and quantification of chiral isomers.

Keywords: β-cyclodextrin, Cross-Linked MOFs, Graphene oxide, Electrochemical sensor, chiral recognition, mandelic acid