Ionic Liquid-Functionalized Defective MOFs for Membrane-Based CO2 Separation: A Dual Optimization Approach for Interface and Transport

Defective MOFs have been identified as promising candidates for efficient membrane-based separation applications. However, the utilization of defective MOFs in membrane gas separation is still in its infancy due primarily to the inefficient molecular differentiation induced by structural defects. Herein, we report a strategic combination of ionic liquid (IL) and defective UiO-66-NH2 MOF to ameliorate the CO2/N2 selectivity within the highly permeable PIM-1 polymer. Characterizations and analysis have shown that postmodification of defective UiO-66-NH2 with IL greatly improved its dispersion and compatibility within PIM-1. Meanwhile, the CO2-philic nature of IL facilitated increased adsorption of CO2 molecules, enabling them to pass rapidly through the transport channels in defective MOF. As a result, the optimal membranes demonstrated a concurrent enhancement in both the CO2 permeability and the CO2/N2 ideal selectivity, which were 197.1% and 24.9% greater than those of PIM-1, respectively. Additionally, the complex Lewis acid/base and hydrogen bonding interactions among IL/defective MOF/PIM-1 have ensured that the resulting membranes possess long-term operational durability and significant antiaging behavior. This deliberate matching between IL and defective MOFs has well circumvented the potential limitation of defective MOFs for carbon capture, with potential applications in other areas.