3-Dimensionally disordered mesoporous silica (DMS)-containing mixed matrix membranes for CO₂and non-CO₂ greenhouse gas separations

The effect of 3-dimensionally disordered mesoporous silica (DMS) was investigated on the transport of two different glassy polymer matrices, 6FDA-DAM:DABA (3:2) and polysulfone (PSf). More specifically, single gas (i.e. N₂, CO₂, CH₄ and NF₃) permeabilities of the mixed matrix membranes (MMMs) were characterized as a function of DMS volume fractions. Our permeation results demonstrated that both 6FDA-DAM:DABA (3:2)- and PSf-based MMMs with a nominal DMS weight fraction of 0.2 substantially improved all the single gas permeabilities mainly due to the diffusivity improvement. Such a significant increase in diffusivity is attributed to the 3-dimensionally interconnected pore structures of DMS particles. NF₃, a missing greenhouse gas, exhibited the permeability improvement mechanism different from other gases. Besides, at the relatively lower DMS loading, difference in the extent of increase in permeability was observed for two different polymer cases. It was explained presumably by the effect of a high resistance zone-of-influence, or the rigidification of matrix polymer chains around inorganic particles. Our study suggests that 3-dimensional DMS particle-containing MMMs can provide a useful material platform for separating N₂/NF₃, CO₂/CH₄, and CO₂/N₂, by substantially increasing permeability, thereby cutting down the capital cost of membrane units.