Superhigh CO2-Permeable Mixed Matrix Membranes Composed of a Polymer of Intrinsic Microporosity (PIM-1) and Surface-Modified Silica Nanoparticles

Polymer gas separation membranes, especially the mixed matrix membranes (MMMs) that consist of polymer matrix and additives, find important applications in carbon dioxide (CO2) separation or capture. Here we show the CO2 permeation properties of MMMs composed of a polymer of intrinsic microporosity (PIM-1) and nonporous silica nanoparticles modified with various organic moieties including terephthalic acid (TPA), 3,5-diaminobenzoic acid (DABA), and 3,5-dimethylbenzoic acid (DMBA). The MMM with a loading of 25 wt % DMBA-modified nanoparticles indicated outstanding CO2 permeability (7930 Barrer), which was more than 6 times higher than the original PIM-1 membrane (1250 Barrer), with only a 15% decrease in CO2/N-2 selectivity (19.8 for PIM-1 membrane and 16.8 for the MMM). Physical aging in the PIM-1 membrane is well-known to reduce CO2 permeability in the short term significantly and limits the application to CO2 separation or capture; however, it was clear that the MMMs containing the DMBA-modified nanoparticles maintained the enhanced CO2 permeability without a decline in CO2/N-2 selectivity after storing under ambient conditions for 60 days.