Insight into the aminosilane functionalized-montmorillonite/Pebax mixed matrix membranes with selectively fast gas transport channels for CO2 permeation

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Mixed matrix membranes (MMMs) hold a great prospect for CO2 separation and capture. To further improve the separation efficiency, surface modification of fillers with organosilanes is an effective way to establish a link between polymers and fillers with respect to optimizing the interfacial morphology. In this study, MMMs were prepared using polyether-block-polyamide (Pebax) as a continuous matrix phase and aminosilane functionalized-montmorillonite (K-MMT) as dispersive fillers. K-MMT plays multiple roles for modifying the structure and improving the performance of resultant MMMs. The introduction of K-MMT disrupts the hydrogen bonding between the hard segments and decreases the crystallinity of MMMs. Furthermore, the inner channels of K-MMT could provide high-speed facilitated gas transport passages, of which the structural metal cations further offer transport carriers so as to substantially increase the CO2 permeability. Moreover, K-MMT can positively capture CO2 in gas mixture on the dependence of the mobility of long-chain amino groups and the reversible reaction between CO2 and amine groups. Additionally, the introduction of 3-aminopropyl triethoxysilane tends to enlarge the structural interlayer spacings of MMT, resulting into the facilitated penetration of CO2 through resultant MMMs. In brief, the MMMs doped with 4 % K-MMT show the optimal gas separation, i.e., CO2 permeability of 196.4 Barrer and CO2/N2 ideal selectivity of 162.4, which is far beyond the proposed 2019 upper bound for CO2/N2 system.