Epichlorohydrin-Bridged β-CD-PIM Membranes: Microporous Structure Regulation for Enhanced CO2 Separation

The fine regulating of micropores distribution in polymer of intrinsic microporosity (PIM) is necessary to improve membrane-based CO2 separation. Here, epichlorohydrin (ECH) was proposed to bridge adjacent polymer chain of β-CD-modified PIM through the cross-linking of its epoxy rings with the hydroxyl groups of β-cyclodextrin (β-CD). Regulating the cross-linking process could not only adjust chain spacing of PIM to regulate its micropore distribution for molecular sieving, but could also form CO2-philic ether bonds to increase the affinity of CO2 for the membrane. Additionally, the hollow cavity of β-CD could further facilitate the fast permeation of CO2. Consequently, this ECH-bridged β-CD-PIM membrane could possess both high CO2 permeability and high CO2 selectivity. The CO2/N2 and CO2/CH4 separation performances of the prepared 1.0%-β-CD-P4̅ membrane approached the McKeown upper bound in 2019. This simple and universal cross-linking strategy shows great potentials in polymer membranes-based CO2 separation.