Mixed matrix membrane development progress and prospect of using 2D nanosheet filler for CO2 separation and capture

Molecular simulation of [P8883][Tf2N] ionic liquid decorated silica in 6FDA-ODA based mixed matrix membrane for enhanced CO2/CH4 separation

Mixed-matrix membranes (MMMs) have been reported to have considerable scope in gas separation applications because of their merged inherent strength of a durable polymer matrix and the exceptional performance capabilities of inorganic fillers. The selection of comparatively suitable polymers with fillers that can match each other and boost interfacial compatibility while ensuring uniform dispersion of filler within the polymer is still intensively demanding and is challenging at the experimental scale. Ionic liquids (ILs) are effective in promoting better dispersion and compatibility, leading to improved separation performance. A computational molecular simulation approach is employed in current work to design a hybrid membrane having Trioctapropyl phosphonium bis(trifluoromethylsulfonyl)imide [P8883][Tf2N] IL decorated silica as a filler and 4,4'-(hexafluoroisopropylidene)diphthalic anhydride-4,4'-oxydianiline (6FDA-ODA) polymer for carbon dioxide (CO2) separation from methane (CH4). Thermophysical and gas transport properties under pure and mixed gas condition (30, 50, and 70% CO2/CH4) within the MMMs with varying filler loadings (5, 10, and 15 wt% IL-silica) are examined via Grand Canonical Monte Carlo (GCMC) and Molecular Dynamics (MD) simulations. Membrane characteristics like glass transition temperature (T g), Fractional Free Volume (v f), X-Ray Diffraction (XRD), solubility, diffusivity, permeability, and selectivity for neat and IL-silica filled 6FDA-ODA are computed. The results show that the T g of the composite membrane with 5 wt% IL-silica is found to be considerably higher (with 305 °C) than that of the pure 6FDA-ODA polymer having 298 °C. A higher T g value highlights the effective dispersion and higher adhesion between the filler and polymer membrane. Additionally, CO2 permeability for 5 wt% IL-silica/6FDA-ODA MMM is significantly improved, measuring 319.0 barrer while maintaining a CO2/CH4 selectivity of 16.2. These values are 89% and 56% respectively, greater than the corresponding values of neat 6FDA-ODA membrane. Published data from the literature review is used to validate the findings and guarantee their reliability. The obtained results exhibited an error in the range of 0.7-9%. Hence, it is concluded from the study that molecular simulation can be used to design IL decorated silica incorporated within 6FDA-ODA matrix, which is able to boost the interfacial compatibility, with elevated CO2/CH4 selectivity and CO2 permeability.

High CO2 permeation using a new Ce0.85Gd0.15O2-δ-LaNiO3 composite ceramic-carbonate dual-phase membrane

This work shows the synthesis, characterization and evaluation of dense-ceramic membranes made of Ce0.85Gd0.15O2-δ-LaNiO3 (CG-LN) composites, where the fluorite-perovskite ratio (CG:LN) was varied as follows: 75:25, 80:20 and 85:15 wt.%. Supports were initially characterized by XRD, SEM and electrical conductivity (using vacuum and oxygen atmospheres), to determine the composition, microstructural and ionic-electronic conductivity properties. Later, supports were infiltrated with an eutectic carbonates mixture, producing the corresponding dense dual-phase membranes, in which CO2 permeation tests were conducted. Here, CO2 permeation experiments were performed from 900 to 700°C, in the presence and absence of oxygen (flowed in the sweep membrane side). Results showed that these composites possess high CO2 permeation properties, where the O2 addition significantly improves the ionic conduction on the sweep membrane side. Specifically, the GC80-LN20 composition presented the best results due to the following physicochemical characteristics: high electronic and ionic conductivity, appropriate porosity, interconnected porous channels, as well as thermal and chemical stabilities between the composite support and carbonate phases.

New generation mixed matrix membrane for CO2 separation: Transition from binary to quaternary mixed matrix membrane

Contemporary advances in material development associated with membrane gas separation refer to the cost-effective fabrication of high-performance, defect-free mixed matrix membranes (MMMs). For clean energy production, natural gas purification, and CO2 capture from flue gas systems, constituting a functional integration of polymer matrix and inorganic filler materials find huge applications. The broad domain of research and development of MMMs focused on the selection of appropriate materials, inexpensive membrane fabrication, and comparative study with other gas separation membranes for real-world applications. This study addressed a comprehensive review of the advanced MMMs wrapping various facets of membrane material selection; polymer and filler particle morphology and compatibility between the phases and the relevance of several fillers in the assembly of MMMs are analyzed. Further, the research on binary MMMs, their problems, and solutions to overcome these challenges have also been discussed. Finally, the future directions and scope of work on quaternary MMM are scrutinized in the article.

CO2-Philic Nanocomposite Polymer Matrix Incorporated with MXene Nanosheets for Ultraefficient CO2 Capture

The incorporation of two-dimensional (2D) functional nanosheets in polymeric membranes is a promising material strategy to overcome their inherent performance trade-off behavior. Herein, we report a novel nanocomposite membrane design by incorporating MXene, a 2D sheet-like nanoarchitecture known for its advantageous lamellar morphology and surface functionalities, into a cross-linked polyether block amide (Pebax)/poly(ethylene glycol) methyl ether acrylate (PEGMEA) blend matrix, which delivered exceptional CO2/N2 and CO2/H2 separation performances that are critical to industrial CO2 capture applications. The finely dispersed Ti3C2Tx nanosheets in the blend polymer matrix led to an expansion of the free volume within the resultant mixed matrix membrane (MMM), giving rise to a substantially enhanced CO2 permeability of up to 1264.6 barrer, which is 102% higher than that of the pristine polymer. Moreover, these MXene-incorporated MMMs exhibited preferential sorption for CO2 over light gases, which contributed to an exceptional CO2/N2 and CO2/H2 selectivity (64.3 and 19.2, respectively) even at a small loading of only 1 wt %, allowing the overall performance to not only surpass the latest upper bounds but also exceed many previously reported high-performance nanosheet-based nanocomposite membranes. Long-term performance tests have also demonstrated the good stability of these membranes. This composite membrane design strategy reveals the remarkable potential of combining a blend copolymer matrix with ultrathin MXene nanosheets to achieve superior gas separation performance for environmentally important gas separations.

Graphene-Oxide-Modified Metal-Organic Frameworks Embedded in Mixed-Matrix Membranes for Highly Efficient CO2/N2 Separation

MOF-74 (metal-organic framework) is utilized as a filler in mixed-matrix membranes (MMMs) to improve gas selectivity due to its unique one-dimensional hexagonal channels and high-density open metal sites (OMSs), which exhibit a strong affinity for CO2 molecules. Reducing the agglomeration of nanoparticles and improving the compatibility with the matrix can effectively avoid the existence of non-selective voids to improve the gas separation efficiency. We propose a novel, layer-by-layer modification strategy for MOF-74 with graphene oxide. Two-dimensional graphene oxide nanosheets as a supporting skeleton creatively improve the dispersion uniformity of MOFs in MMMs, enhance their interfacial compatibility, and thus optimize the selective gas permeability. Additionally, they extended the gas diffusion paths, thereby augmenting the dissolution selectivity. Compared with doping with a single component, the use of a GO skeleton to disperse MOF-74 into Pebax®1657 (Polyether Block Amide) achieved a significant improvement in terms of the gas separation effect. The CO2/N2 selectivity of Pebax®1657-MOF-74 (Ni)@GO membrane with a filler concentration of 10 wt% was 76.96, 197.2% higher than the pristine commercial membrane Pebax®1657. Our results highlight an effective way to improve the selective gas separation performance of MMMs by functionalizing the MOF supported by layered GO. As an efficient strategy for developing porous MOF-based gas separation membranes, this method holds particular promise for manufacturing advanced carbon dioxide separation membranes and also concentrates on improving CO2 capture with new membrane technologies, a key step in reducing greenhouse gas emissions through carbon capture and storage.

Heteroepitaxial growth of ZIF-67 nanoparticles on the ZIF-L(Zn) nanosheets for fabrication of Pebax mixed matrix membranes with highly efficient CO2 separation

ZIF-67 nanoparticles were grown on ZIF-L(Zn) nanosheets by in-situ heteroepitaxial method, resulting in ZIF-67@ZIF-L(Zn) as a charming two-dimensional (2D) nanocomposite for incorporation into the Pebax-1657 and improving its CO2/N2 separation performance. The fabricated nanofillers and membranes were analyzed by characterization tests (FTIR, XRD, FESEM, and EDAX-mapping) and gas separation experiments (effect of filler loading, filler type, feed pressure, and long-term stability). It was observed that the nanosheets were well dispersed in the matrix, and they had formed a proper interaction by creating hydrogen bonds at the interface; in addition, due to their crystalline nature, they increased the crystallinity of the MMMs. The results of the gas permeability test showed that these nanofillers, with their composite structure, had a synergistic effect on the gas solubility and screening and caused a significant improvement in the separation performance of MMMs. So that the best performance achieved with a CO2 permeability of 72.9 Barrer and a CO2/N2 selectivity of 102.9 at 10 bar for the MMM containing 2 wt% of ZIF-L(Zn)@ZIF-67, also exceeding Robeson's upper bound. Moreover, Mindex as a criterion for evaluation of the gas separation performance of MMMs in simultaneous improvement of the permeability and selectivity was proposed in this work. The Mindex values in the range of 0.5-1.5 were calculated for the MMM containing 2 wt% of ZIF-L(Zn)@ZIF-67 nanosheet which indicating a good quality for the gas separation performance. Furthermore, at equal filler loading (2 wt%), this membrane outperformed all MMMs containing other nanofillers (ZIF-67, ZIF-8, ZIF-L(Co), or ZIF-L(Zn)).

Polydimethylsiloxane/Magnesium Oxide Nanosheet Mixed Matrix Membrane for CO2 Separation Application

Carbon dioxide (CO₂) concentration is now 50% higher than in the preindustrial period and efforts to reduce CO₂ emission through carbon capture and utilization (CCU) are blooming. Membranes are one of the attractive alternatives for such application. In this study, a rubbery polymer polydimethylsiloxane (PDMS) membrane is incorporated with magnesium oxide (MgO) with a hierarchically two-dimensional (2D) nanosheet shape for CO₂ separation. The average thickness of the synthesized MgO nanosheet in this study is 35.3 ± 1.5 nm. Based on the pure gas separation performance, the optimal loading obtained is at 1 wt.% where there is no observable significant agglomeration. CO₂ permeability was reduced from 2382 Barrer to 1929 Barrer while CO₂/N₂ selectivity increased from only 11.4 to 12.7, and CO₂/CH₄ remained relatively constant when the MMM was operated at 2 bar and 25 °C. Sedimentation of the filler was observed when the loading was further increased to 5 wt.%, forming interfacial defects on the bottom side of the membrane and causing increased CO₂ gas permeability from 1929 Barrer to 2104 Barrer as compared to filler loading at 1 wt.%, whereas the CO₂/N₂ ideal selectivity increased from 12.1 to 15.0. Additionally, this study shows that there was no significant impact of pressure on separation performance. There was a linear decline of CO₂ permeability with increasing upstream pressure while there were no changes to the CO₂/N₂ and CO₂/CH₄ selectivity.