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[Display omitted] • PEI and APTES modified MfMCNs are prepared by pre-assembly experiment. • MfMCNs contains hydroxyl and amino groups to enhance the adsorption of CO 2. • The pore size of MfMCNs decreased to 0.53–0.55 nm, which enhanced screening of CO 2. • By adding MfMCNs, the phase interface defect is improved and the separation performance of MMMs is enhanced. Traditional two-dimensional (2D) membrane fillers are prone to interfacial defects such as agglomeration and phase separation in the membrane, limiting the separation performance of membrane. In this paper, microporous carbon nanoplates (MCNs) with controllable microporous structures were functionalized with two different amine carriers of low molecular weight polyethyleneimine (PEI) and 3-aminopropyl triethoxysilane (APTES) to prepare multi-functionalized microporous carbon nanoplates (MfMCNs). It is worth noting that with the success of composite functionalization, the filling content of mixed matrix membranes is also high to a certain extent. To a certain extent, it has been demonstrated that interfacial compatibility between the polymer and the fillers has been improved. It was confirmed by characterization technology that the morphology of the fillers had not been changed, but the pore size of MfMCNs was declined to 0.53–0.55 nm because part of the amino carrier was immersed in the pore structure of MfMCNs. The gas permeability tests under dry gas and wet gas conditions show that the improvement of phase interface by MfMCNs is significant. Under the condition of a dry gas test, the CO 2 /N 2 selectivity of MfMCNs/Pebax-1.0 wt% MMMs is 76.3, which is 27 % higher than that of MCNs/Pebax-1.0 wt% MMMs. Under the moisture condition, the permeability and selectivity of MfMCNs/Pebax-1.0 wt% MMMs CO 2 are 287.72 Barrer and 79.1 separately. Compared with Pebax membrane, the permeability of CO 2 (176.6 Barrer) was rose by 62.9 %, and the selectivity of CO 2 (59.1) was rose by 33.84 %. Significantly, the best MMMs separation performance exceeds upper limit of Robeson. This provides a powerful strategy to strengthen the compatibility between inorganic materials and polymers and strengthen the performance of MMMs in CO 2 gas capture. [ABSTRACT FROM AUTHOR]

Conventional two-dimensional (2D) fillers in membranes have undesirable gas transport resistance owing to their interfacial barriers. In this work, 2D microporous carbon nanoplates (MCNs) were proposed to construct low-resistance and high-selectivity gas transport channels in mixed-matrix membranes (MMMs) to enhance the CO 2 separation performance. MCNs were synthesized using a phase-transition material as a removable template and incorporated with Pebax-1657 to prepare MMMs. Micropores measuring 0.58 nm in the MCNs provided low-resistance CO 2 diffusion channels that significantly improved CO 2 permeability, as confirmed by the diffusion coefficient calculated through molecular simulation. Meanwhile, the random and effective stacking of the MCNs in the MMMs created highly selective gas transport channels that dramatically enhanced CO 2 /N 2 selectivity. The MMMs with 0.5 wt% MCNs showed the best separation performance. In the mixed-gas test, the CO 2 permeability reached 160.69 Barrer, and the CO 2 /N 2 selectivity reached 61.2. In the pure-gas test, the CO 2 permeability and CO 2 /N 2 selectivity were 123 Barrer and 76, exhibiting distinct increases of 53.0% and 28.8% compared to those of the pristine Pebax membrane. Notably, the best CO 2 separation performance of the prepared MMMs exceeded Robeson's upper bound. The proposed template-removal 2D MCNs with low-resistance and high-selectivity transport multi-channels facilitate a new process for molecularly selective and energy-efficient CO 2 separation. Image 1 • Low-resistance and high-selectivity multi-channels were constructed by introducing MCNs in MMMs. • The structural and transport properties of MCNs/Pebax MMMs were simulated. • CO 2 /N 2 separation performance has exceeded Robeson's upper bound. [ABSTRACT FROM AUTHOR]

[Display omitted] • MMMs based on Pebax-1657 and microporous CNs were successfully prepared. • CO 2 permeability and CO 2 /N 2 selectivity were improved with CNs addition. • Microporous CNs with accessible inner channels provided low-resistance transport channels for CO 2. • The CNs-600(0.5 wt%)/Pebax MMMs showed the best CO 2 permeability and selectivity. We investigated the use of microporous carbon nanospheres (CNs) as fillers to prepare mixed matrix membranes (MMMs) for permeable and selective CO 2 separation. CNs with a uniform size of 650 nm and unique amorphous structure were characterized by SEM and XRD. The N content of CNs with different carbonization temperatures was determined by XPS. The surface area and micropore size of the samples could be easily adjusted by varying the carbonization temperature; in particular, increasing the carbonization temperature improved both parameters. At 600 °C, the particles (CNs-600) exhibited a higher N content and narrower micropores, which ensured higher affinity and enhanced capture of CO 2 molecules. Thus, CNs-600/Pebax MMMs exhibited superior CO 2 separation performances compared to other CNs-based MMMs. Furthermore, when the loading of CNs-600 was 0.5 wt%, the MMMs exhibited the best CO 2 /N 2 separation properties, with a 39.51% improvement compared to pristine Pebax membranes. These outstanding performances are attributed to the fact that microporous CNs with accessible inner channels can provide a low-resistance transport pathway to gas molecules. Moreover, the strong interaction between CO 2 and the pore walls, along with the high N content, enabled an effective separation of CO 2 from other gas molecules. Importantly, the CNs-600/Pebax MMMs displayed superior CO 2 /N 2 selectivity compared to previously reported Pebax-based MMMs with other fillers. The proposed CNs, with microporous structure and high N content, may represent a promising alternative for the fillers of MMMs. [ABSTRACT FROM AUTHOR]

Cage-type MOFs based Mixed-matrix membranes (MMMs) hardly exhibit screening effect of gas molecules due to the flexible aperture. Regulation of nanocages of MOFs by Ionic Liquid (IL) has been proved to be effective. Therefore, in this work, an IL adsorption/infiltration two-step strategy is proposed to confine IL into the nanocages of MOFs, achieving fine tuning of effective cage size for screening gas pair with similar size. [Bmim][PF 6 are first adsorbed on the outer-surface of ZIF-8, then through heat treatment, the aperture of ZIF-8 is dilated, and the bigger [Bmim][PF 6 molecules infiltrate through the dilated aperture into the nanocage driven by thermodynamics and differential concentration. When the temperature is down to room temperature, the aperture is narrowed to 3.4 Å, thus [Bmim][PF6] are confined into nanocages, which are confirmed by PXRD, TGA and FT-IR characteristics. By controlling IL content in the cage, the effective cage size of ZIF-8 is tuned to specific slope among dynamic diameters of CO 2 over N 2 , which is perfectly reflected in the CO 2 /N 2 separation. Compared with ZIF-8/Pebax MMMs, the IL@ZIF-8/Pebax MMMs exhibit improved CO 2 /N 2 selectivity but decreased CO 2 permeability, demonstrating effectiveness of cage size adjustment. Furthermore, with the IL molecules inside ZIF-8 cage increasing, the CO 2 /N 2 selectivity of the MMMs continues to rise, indicating cage size screening effect of ZIF-8 by IL infiltration. Especially, the IL 8 @ZIF-8/Pebax MMMs exhibit the best gas separation performances with CO 2 permeability of 117 Barrer and CO 2 /N 2 selectivity of 84.5, beyond the 2008 Robinson upper bound. The proposed strategy provides an effective but facile way to confine IL into the cages of MOFs to precisely screen gas pairs with similar size and can be easily expanded to other IL and MOFs system. Image 1 • Cage Size of MOFs was finely tuned by Ionic Liquid adsorption/infiltration. • IL@MOFs based MMMs present precise gas screening effect over CO 2 and N 2. • Highly selective and permeable CO 2 transport membranes. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO) materials have been widely attempted as functional fillers in mixed matrix membranes (MMMs). In virtue of their high-aspect-ratio sheet structure, they are very effective to tune gas diffusion pathway and enhance selectivity. However, the frequently-used GO sheets are often stacking and folding like barriers in MMMs, and accordingly impair gas permeation ability seriously. In order to make GO fillers stretched and dispersed to decrease mass transfer barriers in MMMs, the modification strategy with continuous ZIF-8 cover layer forming on the surface of GO sheets was proposed. In this composite structure, the rigid ZIF-8 layer, acting like an armor suit, would unfold the GO sheets nicely. Afterwards, the MMMs with ZIF-8@GO flake-like fillers in PEBAx are fabricated by solution casting. SEM images revealed that the specified ZIF-8@GO fillers have been synthesized in accordance with the concept; moreover, the stretched and orderly dispersed structure could be retained well in the MMMs. Gas permeation tests demonstrated that both permeability P CO2 and ideal selectivity α CO2/N2 are enhanced obviously by dredging the pathways for mass transfer. The MMMs containing 20 wt% stretched ZIF-8@GO achieve the best performance, with P CO2 up to 136.2 Barrer and α CO2/N2 up to 77.9 increased 66.0% and 60.0% respectively in comparison with pristine PEBAx membrane. Compare with the MMMs containing equivalent pure GO, this permeability is 74.8% higher, while the ideal selectivity is almost the same. On the whole, the composite flake-like fillers, in which GO sheets were stretched and dispersed perfectly by the ZIF-8 armor, could greatly reduce mass transfer barriers in MMMs and consequently enhance CO 2 separation performance. Image 1 • Pre-Zn(II)-doping method was succeeded in fabricating ZIF-8@GO flake-like fillers. • GO sheets were stretched and unfolded nicely by the armor-like ZIF-8 cover layer. • ZIF-8 armor is the shortcut to bypass GO barriers and reduce permeation resistance. • GO and ZIF-8 are synergistic in ZIF-8@GO composites to enhance CO 2 /N 2 separation. • ZIF-8@GO/PEBAx membranes are excellent with α CO2/N2 = 77.9 and P CO2 = 136.2 Barrer. [ABSTRACT FROM AUTHOR]