Postmodification of UiO-66-NH₂ Enhances the Interfacial Interaction of Mixed Matrix Membranes for Efficient CO₂/N₂ Separation

MOFs-filled mixed matrix membranes (MMMs) have great potential to break the trade-off effects of traditional gas separation membranes. However, achieving good interfacial compatibility and adequate dispersion of the MOF is not straightforward. In this study, a continuous postmodification was developed for advanced CO2/N2 MMMs. UiO-66-NH2 was easily modified with trimesoyl chloride (UiO-66-TMC) and polyethylene glycol (UiO-66-PEG) sequentially, which was utilized as fillers to construct polyimide (PI) mixed matrix membranes (MMMs). Rich interactions between modified UiO-66-NH2 and the PI polymer contribute to efficient CO2 and N2 separation. At 25 °C and 0.1 MPa, UiO-66-TMC/PI MMMs showed a CO2/N2 selectivity of 55.3, and a CO2 permeability of 616.17 Barrer, and those are 56.7 and 686 Barrer for UiO-66-PEG200/PI MMMs. Both of their CO2/N2 separation performances exceed the 2008 Robeson upper bound. The ether bonds in PEG exhibit strong interactions with the CO2 molecules and improve the CO2 dissolution selectivity. Meanwhile, the introduction of organic ingredients realized good dispersion and interfacial compatibility within the PI matrix. This work lays the groundwork for the further fabrication of highly selective CO2 separation materials with specific microscopic interface structures and properties.