De Novo Design of Liquid‐Free, Solid‐State Ionogel Membranes Based on Polymerizable Deep Eutectic Solvent for Highly‐Selective CO 2 Separation

Abstract Ionic liquids (ILs)‐based separation membranes have been recognized as appealing platforms to achieve preferential CO 2 capture. Despite remarkable achievements, these ILs‐based membranes are largely restricted by the inferior perm‐selectivity of CO 2 and the use of high‐cost, difficult‐to‐scale ILs. Here, a new kind of liquid‐free, solid‐state ionogel membranes (IGMs) is presented by virtue of green, low‐cost, and mass‐producible polymerizable deep eutectic solvent consisting of acrylic acid and choline chloride. Leveraging Janus membranes as confined reactor, polymerizable deep eutectic solvent can be well confined within the wettability‐compatible layer of Janus membranes and be rapidly polymerized into thickness‐tunable liquid‐free, solid‐state ionogel as CO 2 ‐philic selective network. It is shown that the selective layer thickness of IGMs can be decreased by 10 folds over counterpart meanwhile possessing an enhanced breakthrough pressure, enabling a high and stable CO 2 permeance even under repeated mechanical friction and bending. Moreover, these IGMs take advantage of their liquid‐free, solid‐state dense CO 2 ‐philic network to give an extraordinary CO 2 /N 2 selectivity as high as 150, transcending most of ILs‐based membranes (< 60). The material building block and toolkit developed in this work can unleash the potential of polymerizable deep eutectic solvent and beyond in the field of gas separation membranes.