Preparation of M2070-UiO-66-OH@[BMim][PF6]/Pebax mixed matrix membranes and CO2 separation

Abstract

A novel porous liquid, M2070-UiO-66-OH@[BMim][PF₆], has been synthesized using zirconium-based metal–organic framework (UiO-66-OH), 1-butyl-3-methylimidazolium hexafluorophosphate ([BMim][PF₆]) and polyetheramine M2070. To enhance the CO₂ separation performance, M2070-UiO-66-OH@[BMim][PF₆] was incorporated as a filler into a mixed matrix membrane (MMM) using polyether block amide (Pebax-1657) as the membrane matrix. The properties of the synthesized M2070-UiO-66-OH@[BMim][PF₆] and the resulting MMMs have been characterized through FTIR, TGA, DSC, and SEM analyses. The results of porous liquid stability revealed that grafting polyetheramine M2070 onto the surface of UiO-66-OH@[BMim][PF₆] significantly increased the steric hindrance, thereby preventing agglomeration within the membrane. Additionally, the functional groups (amino and ether) present in M2070-UiO-66-OH@[BMim][PF₆] contributed to an increased number of active sites for CO₂ adsorption, facilitating enhanced CO₂ transport through the membrane. Compared to the Pebax membrane, the MMM containing 3% M2070-UiO-66-OH@[BMim][PF₆] exhibited significantly improved CO₂ permeability of 104.07 Barrer (an increase of 73.22%) and CO₂/N₂ selectivity of 92.37 (an increase of 148.95%) at 30 °C and 0.3 MPa, surpassing the 2008 Robeson upper bound. These findings suggest that M2070-UiO-66-OH@[BMim][PF₆] is a highly promising additive for the fabrication of mixed matrix membranes with superior CO₂ separation performance.

Graphical abstract

A porous liquid, (M2070-UiO-66-OH@[BMim][PF₆]) has been prepared using UiO-66-OH@[BMim][PF₆] as the core and polyetheramine M2070 as the canopy. Afterwards, M2070-UiO-66-OH@[BMim][PF₆] has been added to the Pebax matrix to prepare M2070-UiO-66-OH@[BMim][PF₆]/Pebax mixed matrix membranes, which have been subjected to gas separation studies.