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Cardo-type porous organic nanospheres: Tailoring interfacial compatibility in thermally rearranged mixed matrix membranes for improved hydrogen purification

Dong, Liangliang, Zhang, Wenhai, Qu, Zheng, Wan, Chao, Yao, Zheng, Xu, Jibin, Kang, Xueting, Bai, Yunxiang, Zhang, Chunfang
Journal of membrane science 2020 v.612 pp. 118414
artificial membranes, carbon dioxide, condensation reactions, crosslinking, fluorenes, hydrogen, hydrogen bonding, models, nanospheres, permeability, polymers
Mixed-matrix membrane (MMM) is an effective way to overcome trade-off limitations of conventional polymeric membranes. However, the existence of defect voids at the polymer/filler interface often limits their performance improvement. Similar issues are also present in thermally rearranged polybenzoxazole (TR-PBO)-derived MMMs. To address this challenge, the selection of fillers is of great importance. Herein, a novel organic porous nanosphere (TC-cPSB), which is prepared by the polycondensation of 9,9-bis(4-aminophenyl) fluorene (BAFL) and terephthalaldehyde (TPAL) followed by thermal crosslinking, is chosen to engineer the polymer/filler interface. Benefiting from strong intermolecular interaction (π-π stacking and hydrogen bonding), the TC-cPSB nanosphere can well disperse in TR-PBO matrix with a defect-free interface. With an increase in TC-cPSB loading, well-designed MMMs exhibit a significant “anti-trade-off” phenomenon whereby gas permeability and selectivity increase simultaneously, following the trend predicted by the Maxwell model. Compared with TR-PBO membrane, the MMM containing 15 wt% of nanosphere shows an increase of 282% and 217.6% in H₂/CO₂ selectivity and H₂ permeability, respectively, which is far beyond 2008 Robeson upper bound.