Bis(phenyl)fluorene-based polymer of intrinsic microporosity/functionalized multi-walled carbon nanotubes mixed matrix membranes for enhanced CO2 separation performance.

Polymers of intrinsic microporosity (PIM) as one of potential next generation membrane materials for gas separation has attracted great interests due to its ultra-permeable characteristics. Herein, a novel bis(phenyl)fluorene-based PIMs (Cardo-PIM-1) based on 9,9-bis(3,4-dihydroxyphenyl) fluorene (BDPF), 2,3,5,6-tetrafluoroterephthalonitrile (TFTPN) and spirocyclic 5,5′,6,6′-tetrahydroxy-3,3′,3,3′-tetramethylspirobisindane (TTSBI) were prepared vis dibenzodioxane polymerization reaction, and then the functionalized multi-walled carbon nanotubes (f-MWCNTs) were incorporated into Cardo-PIM-1 to fabricate mixed matrix membranes (MMMs) with solution mixing method for CO 2 separation. The structure analysis indicated that the MWCNTs were cut into short ropes and the amino groups were incorporated into the nanotubes surface after treated with acid mixtures followed by ethylenediamine modification. FTIR spectroscopy and nuclear magnetic resonance (NMR) measurement confirmed the formation of Cardo-PIM-1 macromolecule. BET and positron annihilation lifetime spectroscopy (PALS) analysis exhibited that Cardo-PIM-1 contained larger pore-size distribution and fractional free volume (FFV), and preferential CO 2 adsorption capacity over N 2 compared with that of PIM-1. This work investigated the structure of polymer as well as the effect of nanofillers in the gas separation performance. High CO 2 permeability of 2.9 × 104 Barrer with a desirable CO 2 /N 2 separation factor of 24.2 was achieved using the MMMs with 7.5 wt% f-MWCNTs loading, which were among the best performance for CO 2 separation. The Cardo-PIM-1/f-MWCNTs MMMs will provide a promising alternative in industrial flue gas separation and CO 2 capture process. • A novel bis(phenyl)fluorene-based PIMs (Cardo-PIM-1) with dibenzodioxin polymerization reaction was prepared. • Cardo-PIM-1/functionalized MWCNTs MMMs were fabricated by the solution mixing method. • Cardo-PIM-1 membrane exhibited excellent CO 2 /N 2 separation performance. • Functionalized MWCNTs in the MMMs further improved the CO 2 separation performance. [ABSTRACT FROM AUTHOR]