Efficient CO₂ Separation of Multi-Permselective Mixed Matrix Membranes with a Unique Interfacial Structure Regulated by Mesoporous Nanosheets

Abstract

A facile strategy to elevate gas separation performances of polymers is to introduce a versatile particle. In this study, the novel F-Ce nanosheets are synthesized, and then F-Ce is functionalized with 1-ethyl-3-methylimidazole thiocyanate (ionic liquids, ILs), obtaining multifunctional f-F-Ce nanosheets by the facile and environment-friendly methods. The multifunctional f-F-Ce nanosheets are incorporated into the Pebax (Pebax 1657) matrix to fabricate mixed matrix membranes (MMMs) for efficient CO 2 separation. The f-F-Ce nanosheets play versatile parts in elevating membrane gas separation performance. On the one hand, f-F-Ce tends to arrange horizontally and constructs a unique interfacial structure for cross-layer CO 2 transport in MMMs. On the other hand, the abundant mesopores from f-F-Ce construct high-speed CO 2 transport channels in MMMs and notably elevate the gas permeability. Moreover, the as-prepared MMMs separate CO 2 efficiently due to the comprehensive improvements of diffusivity selectivity, solubility selectivity, and reactivity selectivity. First, the high aspect ratio of f-F-Ce provides the tortuous pathways for gas transport and generates the rigid interface between the Pebax matrix and f-F-Ce nanosheets, increasing the diffusivity selectivity. Second, SCN − groups from ILs show excellent affinity to CO 2 , enhancing the solubility selectivity. Third, amine groups from ILs with abundant methylimidazole generate reversible reaction with CO 2 to elevate reactivity selectivity. Consequently, the f-F-Cedoped MMMs display excellent CO 2 permeability and CO 2 /CH 4 selectivity. In particular, the MMM incorporated with 8 wt % f-F-Ce displays a CO 2 permeability of 1823 Barrer and a CO 2 /CH 4 selectivity of 35, overcoming the Robeson upper bound line (2008).

Preparation of Polyimide/Ionic Liquid Hybrid Membrane for CO2/CH4 Separation

“…Numerous studies [17,18] have been conducted to determine that the chemical makeup of polyimides affects their gas penetration characteristics. However, the PI membrane is influenced by the "trade-off" effect between permeability and selectivity [19][20][21], and it is challenging to overcome the Robeson upper bounds [22,23]. As a consequence, there are numerous strategies by which to increase gas permeability and selectivity, including molecular design [24,25], inorganic inclusion [26,27], chemical crosslinking [28], and the blending of organic species [29][30][31][32][33], among others.…”

Light-responsive metal–organic framework sheets constructed smart membranes with tunable transport channels for efficient gas separation

“…[17][18][19] The rational design of advanced two-dimensional (2D) llers was conducted to reach predominant permeability and selectivity of MMM. [20][21][22] The 2D llers, including graphene oxide, 20,[23][24][25][26] metal-organic framework (MOF) sheets, 22,27 and MXene sheets, [28][29][30][31] were introduced into the polymer to fabricate MMMs. Among them, MOF sheets have attracted the attention of researchers due to the merits of structural characteristics, which consist of ultrathin thickness in nanoscale, porous channels in micropores, and rich interaction sites.…”

Constructing rapid water vapor transport channels within mixed matrix membranes based on two-dimensional mesoporous nanosheets

“…Compared with traditional nanoparticles, F-Ce nanosheets have the advantages of mesoporous structure, hydrophilic surfaces, high surface area, and ultrathin morphology (1–2 nm in thickness). F-Ce nanosheets and their composite with ILs have been introduced into the polymer matrix for effective CO 2 removal applications 32 , and the results show that MMMs doped with F-Ce nanosheets have good properties for CO 2 /CH 4 separation, and exceed the Robeson 2008 upper bound line.…”