Induction of chiral polymers from metal-organic framework for stereoselective recognition

Abstract

So far, the fabrication of chiral metal-organic framework (CMOF) is difficult to predict and the chiral functionality mainly comes from the building blocks that is a part of the frameworks. The induction effect in the chiral nanochannels of the metal-organic framework (MOF) makes achiral polymers have chiral properties, which has not been well explored. Therefore, CMOFs with chiral nanochannels or chiral pores appear to have special functions. Herein, CMOFs (D-his-ZIF-8) with chiral micropores or chiral nanochannels are prepared through a simple 2-methyl imidazolate in-situ substitution by d-histidine. The unmodified polyaniline with chirality (c-PANI) was synthesized in chiral nanochannels and pores of CMOF, which brought about chiral induction from the chiral nanochannels and pores of CMOF to c-PANI chains. The circular dichroism shows that the c-PANI chains released from the chiral nanochannel still maintains the chiral properties even leaves the chiral nanochannel. It can be seen from the electrochemical results that c-PANI has excellent conductivity, and the conductivity of CMOF is very poor. Electrochemical recognition showed that both CMOF and c-PANI have certain chiral recognition effects for L-Trp and D-Trp, from which the optimal recognition effect was obtained from c-PANI chains. This shows that the excellent conductivity of c-PANI not only expands the electrochemical signal, but also the helical structure of the c-PANI chains accelerates the distinction of chiral molecules. This study provides a novel perspective to induce chiral polymer chains with better conductivity in the nanochannels of CMOF.