Incorporation of a pyrrolidinium-based ionic liquid/MIL-101(Cr) composite into Pebax sets a new benchmark for CO2/N2 selectivity

Mixed matrix membranes (MMMs) offer a broad potential for energy efficient removal of CO2 from flue gas and natural gas. In this study, we synthesized a novel ionic liquid (IL)/metal organic framework (MOF) composite, [MPPyr][DCA]/MIL-101(Cr), where [MPPyr][DCA] is 1-methyl-1-propyl pyrrolidinium dicyanamide, and incorporated it as a filler into Pebax to fabricate IL/MOF/polymer MMMs. The superior solubility of CO2 in the [MPPyr][DCA] and the strong interactions between IL and CO2 molecules boost the CO2 selectivity of the membrane over N2 and CH4. The results showed that CO2 permeability of the MMM having 15 wt.% [MPPyr][DCA]/MIL-101(Cr) composite as the filler (148 Barrer) was similar to that of pure Pebax membrane (134 Barrer), while the ideal CO2/N2 selectivity (1347) and ideal CO2/CH4 selectivity (1 2 2) of the MMM were 45- and 10-times higher compared to the selectivities of pure Pebax membrane, respectively. To the best of our knowledge, the remarkable enhancement in the CO2/N2 selectivity of the MMM sets a new benchmark value for the IL/MOF/polymer MMMs in the literature. These results demonstrate the great potential of using [MPPyr][DCA]/MIL-101(Cr) composite as a filler for the fabrication of highly selective IL/MOF/polymer MMMs for CO2/N2 and CO2/CH4 separations.