Mixed-matrix membranes composed of dopamine modified covalent organic framework and PIM-1 for efficient CO2/N2 separation

Due to the good compatibility and adjustable porous structure, covalent organic frameworks (COFs) gradually become one favorable filler to fabricate mixed matrix membranes (MMMs) used for efficient CO2 separation. In this study, TPB-TMDP-COF (TD-COF) with high porosity and long-range ordered structure was chosen to improve the CO2/N2 separation performance of the PIM-1 membrane. Meanwhile, the dopamine modified TD-COF was facilely prepared and incorporated into PIM-1 to fabricate MMMs considering the aperture adjustment and CO2-philic channel decoration. The MMMs composed of 3 wt% TD-COF shows a CO2 permeability of 8427.1 Barrer and a CO2/N2 ideal selectivity of 16.9 among three tested compositions. In comparison, the PIM-1 based MMMs that contains 3 wt% PDA@TD-COF exhibits a maximum CO2 permeability of 9750.6 Barrer and a CO2/N2 ideal selectivity of 26.4 at 1 bar and 30 oC, which are 82.0% and 54.3% higher than the pure PIM-1 membrane, respectively, far exceeding the known upper bound reported for CO2/N2 separation. Furthermore, the significant improvement of MMMs performance can be ascribed to the intensified gas diffusion due to long-range ordered channels of TD-COFs and the improved CO2 dissolution caused by more CO2 affinity sites of dopamine. In addition, the PDA@TD-COF/PIM-1 MMMs displayed decent plasticization resistance and long-term operational stability, indicating the great potential in industrial application.