Enhancing interfacial compatibility of porous organic polymer-filled mixed-matrix membranes using covalent grafted PIM-1 network

The trade-off limitation between permeability and selectivity has hindered the widespread applications of polymer membranes. The integration of solid fillers into polymer membranes, namely the development of mixedmatrix membranes (MMMs), can overcome the trade-off effect, serving as an effective method to fabricate highperformance membranes. Porous organic polymer of PP, made from dichloro-p-xylene via Friedel-Crafts alkylation reaction, is excellent candidate for MMMs fabrication. However, tailoring PP for membrane CO2 separation with desirable performance is still a challenge. Herein, we report the development of a functionalized PP, namely PP@oPIM-1, which is achieved by covalently grafting PIM-1 oligomers (oPIM-1) on the surface of PP. This functionalized product is used as a filler material to construct MMMs. Compared to PP-loaded MMMs, the MMMs containing PP@oPIM-1 filler demonstrate improved interfacial adhesion. Thanks to the excellent interfacial compatibility, the tensile strength of 10 wt% PP@oPIM-1/Matrimid is 59.29 MPa, which is higher than 30.24 MPa and 54.06 MPa for 10 wt% PP/Matrimid and pure Matrimid membrane, respectively. Meanwhile, the interweaving structures between oPIM-1 network on the surface of PP@oPIM-1 and polymer chains of matrix lead to the formation of highly interconnected paths between two phases, which is beneficial to fully demonstrating the advantages of filler in selective permeation of gas molecules. As such, the 10 wt% PP@oPIM-1/ Matrimid membrane displays a CO2 permeability of 17.4 Barrer and CO2/N2 selectivity of 46.7, which are increased by 104.7 % and 51.1 % compared to the bare Matrimid membrane. Additionally, the broad applicability of PP@oPIM-1 in various polymer matrices, such as 6FDA-DAM polyimide and PIM-1, has also been explored.