Development of an ion gel-based CO₂ separation membrane composed of Pebax 1657 and a CO₂-philic ionic liquid

A tough ion gel membrane containing a CO₂-philic ionic liquid, 1-ethyl-3-methylimidazolium tricyanomethanide ([Emim][C(CN)₃]), was developed, and its CO₂ permeation properties were evaluated under humid conditions at elevated temperatures. Pebax 1657, which is a diblock copolymer composed of a polyamide block and a polyethylene oxide block, was used as the gel network of the ion gel membrane to prepare a tough ion gel with good ionic liquid-holding properties. The polyamide block formed a semicrystalline structure in [Emim][C(CN)₃] to toughen the ion gel membrane via an energy dissipation mechanism. The polyethylene oxide block exhibited good compatibility with [Emim][C(CN)₃] and contributed to the retention of the ionic liquid in the ion gel. The developed ion gel membrane showed a good CO₂ separation performance of 1677 barrer CO₂ permeability and 37 CO₂/N₂ permselectivity under humid conditions of 75% relative humidity at an elevated temperature of 50 °C, which corresponds to an exhaust gas from a coal-fired power plant.