Host-guest interaction induced ion channels for accelerated OH− transport in anion exchange membranes

Abstract

Anion exchange membranes (AEMs) with fast ion transport capability are highly desired in numerous industries. Improving the ion conductivity of AEMs through rational molecular structure design is of great importance. Inspired by the biological ion channels formed by the supramolecular assembly of protein chains, we herein develop a strategy for preparing high-performance AEMs by constructing ion conduction channels via crown ether-based supramolecular host-guest interaction. In relatively apolar solvent media, one dibenzo[24]crown-8 (DB24C8) ring tethers one dibenzylammonium salt (DBAS) guest molecule to form stable supramolecular assembly. Hence, by grafting DB24C8 rings and DBAS moieties onto the cationic side chains, the resulting host-guest interaction actuates cationic groups to assembly into connected ion conducting channels in AEM, as proved by small angle X-ray scattering and transmission electron microscopy analyses. The host-guest interaction induced ion channels boost the OH− conduction in AEM, thus the conductivity of the resultant AEM is twice that of the control membrane (without host-guest interaction) in spite of the same ion exchange capacity. Besides, a demonstration of the H2/O2 AEMFC using the host-guest interacted AEM offers almost two times higher peak power density than the control membrane. This design of supramolecular host-guest interaction induced ion channels provides a roadmap for developing AEMs with satisfactory ion conductivity.