Polybenzimidazole based polymeric ionic liquids (PILs): Effects of controlled degree of N-quaternization on physical and gas permeation properties

New Pyridinium Type Poly(Ionic Liquids) as Membranes for CO₂ Separation

New pyridinium based PILs have been prepared by modification of their precursors based on high molecular weight aromatic polyethers bearing main chain pyridine units. The proposed methodology involves the conversion of the precursors to their ionic analogues via N-methylation reaction, followed by anion exchange methathesis reaction to result in PILs with the desirable anions (tetrafluoroborate and bis(trifluoromethylsulfonyl)imide). These PILs show excellent thermal stability, excellent mechanical properties, and most importantly can form very thin, free standing films with minimum thickness of 3 μm. As expected, the PIL containing the TFSI⁻ anion showed improved CO₂ and CH₄ permeabilities compared to its analogue containing the BF₄⁻. PIL-IL composites membranes have also been prepared using the same PIL and different percentages of pyridinium based IL where it was shown that the membrane with the highest IL weight percentage (45 wt %) showed the highest CO₂ permeability (11.8 Barrer) and a high CO₂/CH₄ ideal selectivity of 35 at room temperature.

Ionic liquid-based materials: a platform to design engineered CO2 separation membranes

This review provides a judicious assessment of the CO₂ separation efficiency of membranes using ionic liquid-based materials and highlights breakthroughs and key challenges in this field.