Sulfonated Microporous Polymer Membranes with Fast and Selective Ion Transport for Electrochemical Energy Conversion and Storage

Abstract Membranes which allow fast and selective transport of protons and cations are required for a wide range of electrochemical energy conversion and storage devices, such as proton‐exchange membrane (PEM) fuel cells (PEMFCs) and redox flow batteries (RFBs). Herein we report a new approach to designing solution‐processable ion‐selective polymer membranes with both intrinsic microporosity and ion‐conductive functionality. Polymers are synthesized with rigid and contorted backbones, which incorporate hydrophobic fluorinated and hydrophilic sulfonic acid functional groups, to produce membranes with negatively charged subnanometer‐sized confined ionic channels. The ready transport of protons and cations through these membranes, and the high selectivity towards nanometer‐sized redox‐active molecules, enable efficient and stable operation of an aqueous alkaline quinone redox flow battery and a hydrogen PEM fuel cell.