Phosphonium ionic liquid-polyacrylate copolymer membranes for improved CO2 separations

Developing new materials for the separation of gas mixtures is a key subject in setting up a circular economy. In this work, we report the synthesis and application of novel polymeric membranes, based on polymerized ionic liquids (PILs), to be used for CO2 separation from different gas pairs. Phosphonium-based PILs have been copolymerized within an original acrylate formulation that allowed the development of dense membranes able to overcome some of the main limitations related to ionic liquid membranes. Thereby, a collection of phosphonium ionic liquids has been investigated by evaluating the influence of the alkyl chain length and anion type on membrane structure and properties by employing a series of different chemo-physical characterization techniques. The membranes showed a marked preference toward CO2 permeation in the wet state, which simulates the conditions occurring with many CO2-containing gas streams, with two of the studied membranes exceeding the Robeson upper bound for the CO2/H2 gas pair.