An electrochemical sensor employing β-cyclodextrin chiral cross-linked metal organic framework and graphene oxide for chiral enantiomer recognition

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 detection method. We use beta-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 (IL/ID) reaches 1.8, and the peak potential difference Delta E (ED-EL) is 96 mV. It shows good linearity in the range of 0.5-30 mM. The detection limits of D-MA and L-MA are 0.15 mM and 0.09 mM, respectively. The method was successfully applied to the detection of DL-MA enantiomer 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.