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Two novel imide/imine‐based organic cages have been prepared and studied as materials for the selective separation of CO2 from N2 and CH4 under vacuum swing adsorption conditions. Gas adsorption on the new compounds showed selectivity for CO2 over N2 and CH4. The cages were also tested as fillers in mixed‐matrix membranes for gas separation. Dense and robust membranes were obtained by loading the cages in either Matrimid® or PEEK‐WC polymers. Improved gas‐transport properties and selectivity for CO2 were achieved compared to the neat polymer membranes. [ABSTRACT FROM AUTHOR]

Membrane-based processes are taking a more and more prominent position in the search for sustainable and energy-efficient gas separation applications. It is known that the separation performance of pure polymers may significantly be improved by the dispersion of suitable filler materials in the polymer matrix, to produce so-called mixed matrix membranes. In the present work, four different organic cages were dispersed in the poly(ether ether ketone) with cardo group, PEEK-WC. The m-xylyl imine and furanyl imine-based fillers yielded mechanically robust and selective films after silicone coating. Instead, poor dispersion of p-xylyl imine and diphenyl imine cages did not allow the formation of selective films. The H2, He, O2, N2, CH4, and CO2 pure gas permeability of the neat polymer and the MMMs were measured, and the effect of filler was compared with the maximum limits expected for infinitely permeable and impermeable fillers, according to the Maxwell model. Time lag measurements allowed the calculation of the diffusion coefficient and demonstrated that 20 wt % of furanyl imine cage strongly increased the diffusion coefficient of the bulkier gases and decreased the diffusion selectivity, whereas the m-xylyl imine cage slightly increased the diffusion coefficient and improved the size-selectivity. The performance and properties of the membranes were discussed in relation to their composition and morphology. [ABSTRACT FROM AUTHOR]

Membrane-based gas separation has been recognized as one of the most promising and energy-efficient processes for CO 2 capture from industrial gas streams. Remarkably, commercial gas separation membranes typically contain conventional polymers with sub-optimal performance, necessitating the search for better-performing materials. In this work, we developed novel mixed matrix membranes (MMMs) based on the benchmark polyimide Matrimid® 9725 and a soluble poly (ether ether ketone) PEEK-WC. The addition of a zinc-based metal-organic cage (MOC) featuring two calixsalen macrocyclic units significantly improved the transport properties for various gas pairs with an up to 100 % increase in permeability and up to 10 % increase in selectivity at 30 % MOC. SEM and DSC analyses offered valuable insights into the compatibility between the polymer and MOC, revealing excellent dispersion of up to 30 % of MOC with almost complete phase separation from the matrix. The thermal properties and transport properties were successfully described using the Fox equation and the Maxwell model, respectively. Most interestingly, thin film composites (TFCs) performed much better at 3 times higher cage concentrations than the corresponding self-standing thick films because the faster solvent evaporation limited crystal growth to sub-micron size, favouring a fine homogeneous distribution of the MOC in the polymer matrix. Based on their pure and mixed gas permeation, the TFC-MMMs show promise for the future development of new-generation gas separation membranes. [Display omitted] • Metalorganic cages (MOC) as porous fillers in mixed matrix membranes for gas separation. • The soluble MOCs crystallize to sub-micron sized homogeneously dispersed crystals. • Thin film composites allow ≥3 times higher MOC loadings than thick self-standing films. • MOCs double the permeability, maintaining the good selectivity or increasing it up to 10 %. • Mixed gas separation shows promise for several industrially relevant gas pairs. [ABSTRACT FROM AUTHOR]