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

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 H 2 /CO 2 selectivity and H 2 permeability, respectively, which is far beyond 2008 Robeson upper bound. Image 1 • TR-PBO/TC-cPSB MMMs were prepared for H 2 purification from the H 2 /CO 2 mixture. • The MMMs simultaneously increased gas permeability and selectivity due to good interfacial compatibility between TC-cPSB and TR-PBO. • TR-PBO/TC-cPSB-15 presented separation performance with 312.5 barrer of H 2 permeability and 5.35 of H 2 /CO 2 selectivity. [ABSTRACT FROM AUTHOR]