Enhancing Interfacial Compatibility of PIM-1-Based Mixed-Matrix Membranes through In Situ-Formed cPIM-1 Networked Fillers

Efficient CO2 capture, demonstrating significant potential in reducing excessive carbon emissions and advancing carbon neutrality, is crucial for advancing carbon capture, utilization, and storage (CCUS) technology. Membrane technology is environmentally friendly and energy-saving for CO2 capture. Mixed matrix membranes (MMMs) consisting of polymers of intrinsic microporosity (PIMs)-grafted composite fillers and PIM matrices are promising for gas separation. However, conventional two-phase MMMs often face a fundamental challenge: the trade-off between permeability and selectivity, coupled with nonselective interfacial defects arising from poor compatibility between the polymer matrix and fillers. Moreover, the synthesis of composite fillers is usually complex and highly dependent on the reasonable matching of fillers and grafted polymers, restraining the wide application of this material system. To fundamentally address this issue of interfacial compatibility, we focused on designing a distinct third phase at the interface. Herein, we report a concept of polymer–filler–polymer ternary-phase MMMs (TMMMs) for efficient CO2 separation. The key point is that the membrane system consists of a PIM matrix, filler, and a functionalized PIM-type third component. As the functionalized PIMs selected can form strong interactions with both fillers and PIM matrices, they can work as a molecular bridge between two phases, diminishing the generation of nonselective interfacial defects. Meanwhile, the functionalized PIMs’ incorporation can increase the quantity of CO2 adsorption sites as well as facilitate the formation of a porous network structure between filler and matrix phases, making the performance improvement of the resultant membranes foreseeable. Particularly, the representative ternary membrane made from 3D-COF (filler, 5 wt %), PIM-1 (matrix), and carboxylated PIM-1 (cPIM-1, third component, 1 wt %) exhibits significantly improved CO2 permeability of 9560 Barrer, CO2/N2 selectivity of 22.7, and antiaging performance in comparison to the pure PIM-1 membrane and PIM-1/3D-COF binary membrane. We believe that this concept proposed here offers an alternative way to produce defect-free and high-performing PIM-based MMMs for CO2 capture and other separations.