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Guanghui Zhu1 Christopher Jones1 Ryan Lively1

1, Georgia Institute of Technology, Atlanta, Georgia, United States

Porous organic cages (POCs) are individual molecules that are porous and soluble in certain common solvents. Compared to their extended framework counterparts, such as zeolites and metal-organic frameworks (MOFs), POCs offer the advantage of solution processability. Moreover, when fabricated into mixed matrix membranes, the soluble POC molecules have the potential to exhibit molecular-level intimate mixing with matrix polymer. The incorporation of POCs into mixed matrix membrane is still in its infancy and lacks demonstration of comprehensive improvement of membrane performance. In this work, we utilized vertex functionalized amorphous scrambled porous organic cages (ASPOCs) in mixed matrix membranes to study a series of key questions in this field. The dispersion of ASPOCs possessing different crystallization tendencies within a polymer matrix are probed using Raman imaging and Energy Dispersive X-Ray (EDX) mapping. Gas permeation experiments of N2, CO2, CH4 and SF6 were carried out as a function of ASPOC loading and crystallization tendency. A 4-8 fold of permeability increase was observed for N2, CO2 and CH4 compared to pure polymer membrane. Moreover, a clear molecular sieving effect was observed for SF6, resulting in 2-4 fold of increase of N2/SF6 selectivity compared to the pure polymer membrane. The membranes were further examined in organic solvent nanofiltration experiments using a cross-flow permeation approach. The Molecular Weight Cut Off (MWCO) of the membranes were calculated based on the polystyrene permeation tests. Overall, these membranes demonstrated homogeneous mixing between the POC molecules and the polymer matrix, and showed potential to be used in molecular separation processes.

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