Fabrication of mixed-matrix membrane containing metal–organic framework composite with task-specific ionic liquid for efficient CO2 separation

Mixed-matrix membranes (MMMs) have exhibited advantages in membrane-based gas separation in recent years, however, there is still intensive demand for the development of a proper method to design effective fillers to further enhance the gas separation performance of MMMs. In this work, a nanoporous material to selectively facilitate CO2 transport was proposed through the loading of a task-specific ionic liquid (TSIL) into a metal–organic framework (MOF). [C3NH2bim][Tf2N] and NH2-MIL-101(Cr) were selected as a demonstrative TSIL and MOF, respectively. The amine-containing TSIL worked as a selective CO2 transport carrier, which can be beneficial for the improvement of CO2 permeability and CO2/N2 selectivity. Simultaneously, NH2-MIL-101(Cr) is an appropriate porous host material that can control the good dispersion of TSIL and can effectively expose more active adsorption sites of the TSIL. Meanwhile, the amine-containing porous MOF is helpful for rapid CO2 transport and further increases the CO2 permeability. We further incorporated the porous composite into PIM-1 to fabricate MMMs with different loadings. The prepared TSIL@NH2-MIL-101(Cr)/PIM-1 membrane exhibits largely improved gas permeability and selectivity for CO2/N2 separation, with CO2 permeation values of 2979 Barrer and a CO2/N2 separation selectivity of 37 at 5 wt% loading. Compared with NH2-MIL-101(Cr)/PIM-1 and PIM-1 membranes, the CO2/N2 separation selectivity was increased by 116% and 119%, respectively, at the same loading.