Boosting CO2 transport of poly (ethylene oxide) membranes by hollow Rubik-like "expressway" channels with anion pillared hybrid ultramicroporous materials.

• Three ultramicroporous materials were incorporated into Pebax/PEGDME to fabricate MMM. • DFT calculation reveal effect of GEFSIX-2-Cu-i to CO 2 via C···F and O···H interaction. • The ultramicroporous material create unique Rubik's tube-like channels for CO 2. • 1-GEF-M exhibits optimal CO 2 permeability of 460 Barrers and CO 2 /N 2 of 57. In order to overcome "trade-off" Robeson upper bound 2008 and simultaneously increase the CO 2 permeability and selectivity of traditional poly (ethylene oxide) polymer membrane, three anion pillared hybrid ultramicroporous materials (SIFSIX-2-Cu-i, TIFSIX-2-Cu-i and GEFSIX-2-Cu-i) were incorporated into Pebax/PEGDME polymer to fabricate mixed matrix membranes (MMMs). DFT-D2 calculation revealed that the C···F distance (2.62 Å) between CO 2 molecule and pillared anion (GeF 6 2-) in GEFSIX-2-Cu-i was lower than SIFSIX-2-Cu-i and TIFSIX-2-Cu-i. The synergistic effects of C···F van der Waals (vdW) interactions and O···H hydrogen bonding interactions in GEFSIX-2-Cu-i gave a higher CO 2 binding energy (34.5 kJ/mol) than SIFSIX-2-Cu-i and TIFSIX-2-Cu-i. It was verified that GEFSIX-2-Cu-i with higher CO 2 binding energy and specific surface area exhibited higher CO 2 adsorption capacity of 5.02 mmol/g than SIFSIX-2-Cu-i and TIFSIX-2-Cu-i. These anion-pillared hybrid ultramicroporous materials with suitable porosity and surface chemistry, enabling multiple host–guest interactions, created unique Rubik's tube-like "expressway" channels for CO 2 molecule passage through the membrane. Results showed that the MMMs with 1 wt% GEFSIX-2-Cu-i nanoparticles exhibited optimal CO 2 separation performance in terms of CO 2 permeability (460 Barrers) and CO 2 /H 2 (17, an increase of 12.2%), CO 2 /CH 4 (18, an increase of 24.1%), and CO 2 /N 2 (57, an increase of 9.6%) selectivities, as compared with the pure Pebax/PEGDME membrane. As GEFSIX-2-Cu-i loading increase from 1 to 10 wt%, the overall CO 2 separation performance decrease due to the aggregation of these nanoparticles. Positron annihilation lifetime spectroscopy (PALS) experiments revealed that the fractional free volume of MMMs with 1 wt% GEFSIX-2-Cu-i nanofillers (FFV = 3.63%) was higher than those of MMMs incorporated with a higher loading (2.5–10 wt%) of GEFSIX-2-Cu-i. [ABSTRACT FROM AUTHOR]