Incorporation of benzimidazole linked polymers into Matrimid to yield mixed matrix membranes with enhanced CO2/N2 selectivity

Two different highly cross-linked benzimidazole linked polymers (BILPs) displaying high surface area were successfully incorporated into Matrimid polymer to form a series of new mixed matrix membranes (MMMs). The surface functionality of the BILPs, BILP-4 and BILP-101, were exploited to assure the interaction with the Matrimid matrix and produce robust MMMs, which displayed significantly improved CO2 gas permeability. The ideal selectivities for CO2/N2 were calculated with enhancements as high as 34% at 15 wt% BILP loading. While BILP-4 and BILP-101 have similar structures and functionality, the two materials have notably different surface areas and CO2 adsorption capacity. Despite the differences in their gas adsorption properties, MMMs composed of Matrimid/BILP-4 and Matrimid/BILP-101 had very similar gas transport properties. These results suggest that the functional groups of the filler particle and the resulting interaction with the polymer matrix may have had more influence on the gas separation properties of the mixed matrix membrane than the adsorption properties of the fillers.