Tuning the microstructure of crosslinked Poly(ionic liquid) membranes and gels via a multicomponent reaction for improved CO2 capture performance

Crosslinked poly(ionic liquid) (PIL) and poly(ionic liquid)-ionic liquid (PIL-IL) based membranes with tunable micromolecular structure have been synthesized in a simple way to optimize their CO2 capture performance. Amino-terminated PILs of two molecular weights (MW) were synthesized via the Debus-Radziszewski multicomponent reaction and then reacted with two commercial glycidyl ether crosslinkers, (polyoxyethylene bis(glycidyl ether) and trimethylolpropane triglycidyl ether). The effects of the PIL MW, crosslinker type and content, and IL content on CO2/N2 permeation-separation performance were systematically investigated. For the neat PIL membranes, both the utilization of ether-containing crosslinker and an increase in the crosslinker content increased the CO2 solubility and diffusivity, with the best PILs membrane exhibiting an excellent CO2 permeability of 170 Barrer and a CO2/N2 permselectivity of 36. For the PIL-IL membranes, an increase in the IL content increased the CO2 solubility and diffusivity, but also resulted in a decrease in the diffusivity selectivity. The best permeation-selectivity performance belongs to a PIL-IL membrane that showed a CO2 permeability of 2070 Barrer and a CO2/N2 permselectivity of 24.6. Among all the PIL-IL membranes reported in literature, this PIL-IL membrane demonstrated the highest permeability and also a cost-effective permselectivity, with its separation performance approaching the 2008 Robeson upper bound.