Inorganic/organic double-network ion gel membrane with a high ionic liquid content for CO2 separation

To examine the potential of ion gels as materials for CO2 separation membranes, inorganic/organic double-network ion gel (DN ion gel) membranes with different ionic liquid (IL) contents were fabricated. The composition of the inorganic and organic networks was optimized to maximize the mechanical strength of the DN ion gel. The DN ion gel with an inorganic/organic network composition of 0.35 mol/mol showed the maximum mechanical strength because the inorganic and organic networks sufficiently acted as sacrificial bonds and hidden lengths, respectively. Using DN ion gel membranes with different IL contents prepared with the optimized precursor solution, the relationship between the CO2 permeability and IL content of the DN ion gel membranes was examined. The DN ion gel membrane with 95.2 wt% IL had a CO2 permeability of 1380 barrer, which was ~67% of the theoretical maximum predicted for the pure IL membrane. The CO2 permeability of the DN ion gel membrane exponentially increased with increasing IL content and approached the theoretical maximum. DN ion gels with high strength can be used to develop maximum-performance IL-based CO2 separation membranes by giving the membrane the maximum IL potential.