Constructing a dual transport pathway within mixed matrix membranes for efficient CO2/CH4 separation

A dual transport channels network constructed within mixed matrix membranes (MMMs) has revealed the potential to enhance separation performance. In this study, Cu-TCPP(BA) nanosheets with unsaturated copper sites were synthesized as suitable fillers. Subsequently, Cu-TCPP(BA) nanosheets were incorporated into Pebax® MH 1657 (Pebax) to fabricate MMMs for CO 2 separation. Cu-TCPP(BA) nanosheets significantly enhance CO 2 /CH 4 separation performance by constructing dual transport pathways within the mixed matrix membrane. This mechanism centers on the dual pathways: on one hand, gas molecules can diffuse through the intrinsic microporous channels of the nanosheets; on the other hand, they can also be transported via the interlayer channels formed by the stacking of nanosheets. The synergistic effect of these two pathways collectively enhances the efficient permeation and selective sieving of CO 2 . Furthermore, the regularly aligned unsaturated copper sites on the nanosheet surface act as strong Lewis's acid active centers, preferentially adsorbing CO 2 molecules through quadrupole moment interactions, which provides the chemical basis for high separation selectivity. The adsorbed CO 2 then rapidly diffuses along the dual pathways, forming an “adsorption-diffusion” synergistic transport network. In comparison to pure Pebax membranes, the mixed matrix membranes (MMMs) infused with 3 wt% Cu-TCPP(BA) demonstrated excellent CO 2 separation performance, exhibiting a 77% enhancement in CO 2 permeability and a 44% improvement in CO 2 /CH 4 selectivity. The use of 2D fillers to create a dual transport channels network is an efficiency approach for enhancing CO 2 separation in MMMs.