Task-Specific Ionic Liquids Tuning ZIF-67/PIM-1 Mixed Matrix Membranes for Efficient CO2 Separation

Ionic liquids (ILs) have become attractive in membranes for CO2 separation because of the designable structure, high CO2 affinity, and good compatibility and stability. Modification of metal-organic frameworks with ILs is an effective strategy to improve the gas separation performance of mixed matrix membranes (MMMs). In this work, task-specific ionic liquids (TSILs) were incorporated to prepare TSIL@ZIF-67/PIM-1 MMMs and improve CO2 separation performance because of the high CO2 solubility and great compatibility toward ZIF-67 and PIM-1. The TSILs (TMGHIM and TMGHPhO) selectively and reversibly interact with CO2 and improve the interfacial compatibility between ZIF-67 and PIM-1, leading to higher CO2/CH4 and CO2/N-2 selectivities than that of the ZIF-67/PIM-1 MMM and the directly blended membrane (TSIL/ZIF-67/PIM-1). The 10 wt % TMGHIM@ZIF-67/PIM-1 MMM shows enhanced CO2/N-2 and CO2/CH4 selectivities of 13.7 and 10.5, respectively; meanwhile, the CO2 permeability reaches 12,848.5 Barrer and is 2.5 times that of the pure PIM-1 membrane. The TSIL@ZIF-67/PIM-1 MMMs also show good stability against physical aging.