Ionic liquid cobalt complex as O2 carrier in the PIM-1 membrane for O2/N2 separation

Ionic liquids (ILs) are attractive and prospective materials used in membranes due to the nonvolatility, structure tunability, and the ability to tune the interface compatibility. The cobalt IL Bmim 2 Co(NCS) 4 possesses the porphyrin-like N4-coordinated cobalt center which could selectively and reversibly interact with O 2 . Herein the Bmim 2 Co(NCS) 4 as liquid-phase oxygen carrier was used to fabricate thin-film composite (TFC) membrane with the polymer of intrinsic microporosity (PIM-1). The microstructures, properties and gas separation performance of the membrane were compared with the TFC membrane which takes cobalt porphyrin (T(4-Cl)PPCo) as a carrier. We found that the addition of a small amount of T(4-Cl)PPCo can enlarge the d -spacing of packed chains of PIM-1 and significantly increase the fractional free volume (FFV) and the gas permeability of the membrane, but the selectivity is unsatisfactory. It is worth noting that adding Bmim 2 Co(NCS) 4 into the polymer can increase greatly the O 2 /N 2 selectivity which is higher than that of the membrane with T(4-Cl)PPCo. Although the addition of Bmim 2 Co(NCS) 4 decreases the d -spacing of packed chains of PIM-1, resulting in the slight decline of FFV and gas permeability of the membrane, the Bmim 2 Co(NCS) 4 /PIM-1 TFC membranes exhibit better O 2 /N 2 separation performance than the T(4-Cl)PPCo/PIM-1 TFC membranes in consideration of the Robeson upper bound.