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.

Mixed Matrix Membranes Using Porous Organic Polymers (POPs)-Influence of Textural Properties on CO2/CH4 Separation

Mixed matrix membranes (MMMs) provide the opportunity to test new porous materials in challenging applications. A series of low-cost porous organic polymer (POPs) networks, possessing tunable porosity and high CO2 uptake, has been obtained by aromatic electrophilic substitution reactions of biphenyl, 9,10-dihydro-9,10-dimethyl-9,10-ethanoanthracene (DMDHA), triptycene and 1,3,5-triphenylbenzene (135TPB) with dimethoxymethane (DMM). These materials have been characterized by FTIR, 13C NMR, WAXD, TGA, SEM, and CO2 uptake. Finally, different loadings of these POPs have been introduced into Matrimid, Pebax, and chitosan:polyvinyl alcohol blends as polymeric matrices to prepare MMMs. The CO2/CH4 separation performance of these MMMs has been evaluated by single and mixed gas permeation experiments at 4 bar and room temperature. The effect of the porosity of the porous fillers on the membrane separation behavior and the compatibility between them and the different polymer matrices on membrane design and fabrication has been studied by Maxwell model equations as a function of the gas permeability of the pure polymers, porosity, and loading of the fillers in the MMMs. Although the gas transport properties showed an increasing deviation from ideal Maxwell equation prediction with increasing porosity of the POP fillers and increasing hydrophilicity of the polymer matrices, the behavior of biopolymer-based CS:PVA MMMs approached that of Pebax-based MMMs, giving scope to not only new filler materials but also sustainable polymer choices to find a place in membrane technology.

Ionic Liquids Functionalized MOFs for Adsorption

Metal-organic frameworks (MOFs) and ionic liquids (ILs) represent promising materials for adsorption separation. ILs incorporated into MOF materials (denoted as IL/MOF composites) have been developed, and IL/MOF composites combine the advantages of MOFs and ILs to achieve enhanced performance in the adsorption-based separation of fluid mixtures. The designed different ILs are introduced into the various MOFs to tailor their functional properties, which affect the optimal adsorptive separation performance. In this Perspective, the rational fabrication of IL/MOF composites is presented, and their functional properties are demonstrated. This paper provides a critical overview of an emergent class of materials termed IL/MOF composites as well as the recent advances in the applications of IL/MOF composites as adsorbents or membranes in fluid separation. Furthermore, the applications of IL/MOF in adsorptive gas separations (CO2 capture from flue gas, natural gas purification, separation of acetylene and ethylene, indoor pollutants removal) and liquid separations (separation of bioactive components, organic-contaminant removal, adsorptive desulfurization, radionuclide removal) are discussed. Finally, the existing challenges of IL/MOF are highlighted, and an appropriate design strategy direction for the effective exploration of new IL/MOF adsorptive materials is proposed.

Mixed Matrix Membranes for Carbon Capture and Sequestration: Challenges and Scope

Carbon dioxide (CO₂) is a major greenhouse gas responsible for the increase in global temperature, making carbon capture and sequestration (CCS) crucial for controlling global warming. Traditional CCS methods such as absorption, adsorption, and cryogenic distillation are energy-intensive and expensive. In recent years, researchers have focused on CCS using membranes, specifically solution-diffusion, glassy, and polymeric membranes, due to their favorable properties for CCS applications. However, existing polymeric membranes have limitations in terms of permeability and selectivity trade-off, despite efforts to modify their structure. Mixed matrix membranes (MMMs) offer advantages in terms of energy usage, cost, and operation for CCS, as they can overcome the limitations of polymeric membranes by incorporating inorganic fillers, such as graphene oxide, zeolite, silica, carbon nanotubes, and metal-organic frameworks. MMMs have shown superior gas separation performance compared to polymeric membranes. However, challenges with MMMs include interfacial defects between the polymeric and inorganic phases, as well as agglomeration with increasing filler content, which can decrease selectivity. Additionally, there is a need for renewable and naturally occurring polymeric materials for the industrial-scale production of MMMs for CCS applications, which poses fabrication and reproducibility challenges. Therefore, this research focuses on different methodologies for carbon capture and sequestration techniques, discusses their merits and demerits, and elaborates on the most efficient method. Factors to consider in developing MMMs for gas separation, such as matrix and filler properties, and their synergistic effect are also explained in this Review.

Merging Proline:Xylitol Eutectic Solvent in Crosslinked Chitosan Pervaporation Membranes for Enhanced Water Permeation in Dehydrating Ethanol

The scope of this research aims at merging a new deep eutectic mixture (DES) into a biopolymer-based membrane for a pervaporation application in dehydrating ethanol. Herein, an L-proline:xylitol (at 5:1) eutectic mixture was successfully synthesized and blended with chitosan (CS). A complete characterization of the hybrid membranes, in terms of morphology, solvent uptake, and hydrophilicity, has been conducted. As part of their applicability, the blended membranes were assayed for their ability to separate water from ethanolic solutions by means of pervaporation. At the highest temperature (50 °C), a water permeation of ca. 0.46 kg m^-2 h^-1 was acquired, representing a higher permeation than the pristine CS membranes (ca. 0.37 kg m^-2 h^-1). Therefore, CS membranes demonstrated an enhanced water permeation thanks to their blending with the hydrophilic L-proline:xylitol agent, making these membranes a good candidate for other separations containing polar solvents.

Biocatalytic Membranes for Carbon Capture and Utilization

Innovative carbon capture technologies that capture CO₂ from large point sources and directly from air are urgently needed to combat the climate crisis. Likewise, corresponding technologies are needed to convert this captured CO₂ into valuable chemical feedstocks and products that replace current fossil-based materials to close the loop in creating viable pathways for a renewable economy. Biocatalytic membranes that combine high reaction rates and enzyme selectivity with modularity, scalability, and membrane compactness show promise for both CO₂ capture and utilization. This review presents a systematic examination of technologies under development for CO₂ capture and utilization that employ both enzymes and membranes. CO₂ capture membranes are categorized by their mode of action as CO₂ separation membranes, including mixed matrix membranes (MMM) and liquid membranes (LM), or as CO₂ gas-liquid membrane contactors (GLMC). Because they selectively catalyze molecular reactions involving CO₂, the two main classes of enzymes used for enhancing membrane function are carbonic anhydrase (CA) and formate dehydrogenase (FDH). Small organic molecules designed to mimic CA enzyme active sites are also being developed. CO₂ conversion membranes are described according to membrane functionality, the location of enzymes relative to the membrane, which includes different immobilization strategies, and regeneration methods for cofactors. Parameters crucial for the performance of these hybrid systems are discussed with tabulated examples. Progress and challenges are discussed, and perspectives on future research directions are provided.

Synthesis and performance evaluation of copper and magnesium-based metal organic framework supported ionic liquid membrane for CO2/N2 separation

The CO₂ emission is enhancing drastically because of the continuous emission from industries and transport sector. Although the CO₂ emission had decreased in the first half of 2020 by 8.8% due to COVID-19 restrictions however, it is again on the rise and it might exceed the estimated level in 2030. The current methods used for CO₂ separation have serious operational and environmental constraints. To overcome these problems we have devised a supported ionic liquid membrane (SILM) incorporated with the blend of bimetallic metal-organic framework (MOF) of copper and magnesium ions (Cu_xMg_x) and Trihexyltetradecylphosphonium chloride [P₆₆₆₁₄] [Cl] ionic liquid (IL). Cu_xMg_x MOF were synthesized and characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction analysis (XRD), and energy dispersive X-ray analysis (EDX). Cu_xMg_x MOF with [P₆₆₆₁₄] [Cl] IL were immobilized on a flat sheet of polytetrafluoroethylene (PTFE) membrane. Single gas permeation tests of membranes loaded with 0.2/0.8 wt/wt% MOF/IL solution showed the highest CO₂ permeability of 2937 Barrer and CO₂/N₂ selectivity of 33.26. The performance of SILM was also investigated with different water loadings of (30 wt % and 50 wt %) in addition to MOF/IL solution and at different feed pressure varying from 0.5 to 2 bars. Membranes showed enhancement in CO₂ permeability to 3738 and 4628 Barrer whereas CO₂/N₂ selectivity decreased to 23.53 and 21.8 with membranes loaded with 30 and 50 wt % water, respectively, at a feed pressure of 2 bar. The gas permeation results show that the incorporation of Cu_xMg_x MOF with IL in polymeric membrane enhances the CO₂/N₂ separation under humid conditions but slightly decreases CO₂/N₂ selectivity with an increase in feed pressure. The SILM synthesized in this research is highly viable for industrial flue gases because of the incorporation of phosphonium-based ILs that have high thermal stability.

Preparation of Pebax 1657/MAF-7 Mixed Matrix Membranes with Enhanced CO2/N2 Separation by Active Site of Triazole Ligand

Fillers play a critical role in the performance of mixed matrix membranes (MMMs). Microporous metal azolate frameworks (MAFs) are a subclass material of metal-organic frameworks (MOFs). Due to the uncoordinated nitrogen of the organic ligands, MAF-7 (SOD-[Zn(mtz)₂], Hmtz = 3-methyl-1,2,4-triazole, window: d = 0.34 nm) shows excellent CO₂ adsorption performance. In this work, Pebax 1657/MAF-7 MMMs were prepared by a sample solution casting method with MAF-7 particles as fillers for the first time. By means of X-ray diffraction (XRD), scanning electron microscope (SEM), infrared radiation (IR), and thermogravimetry (TG), the compositional and structural properties of the mixed matrix membrane with different filler content were analyzed. The results show that the compatibility of MAF-7 and Pebax is good with a filler content of 5 wt.%. The pure gas testing showed that mixed matrix membrane has a high ideal CO₂/N₂ selectivity of 124.84 together with a better CO₂ permeability of 76.15 Barrer with the optimized filler content of 5 wt.%. The obtained membrane showed 323.04% enhancement in selectivity of CO₂/N₂ and 27.74% increase in the permeability of CO₂ compared to the pristine membrane at 25 °C and 3 bar. The excellent separation performance may be due to the ligands that can afford a Lewis base active site for CO₂ binding with the uniform dispersion of MAF-7 particles in Pebax and the favorable interface compatibility. The obtained membrane overcomes the Robeson's upper bound in 2008 for CO₂/N₂ separation. This work provides a new strategy by utilizing MAFs as fillers with triazole ligand to enhance the gas separation performance of mixed matrix membranes.

Use of Chitosan as Copper Binder in the Continuous Electrochemical Reduction of CO2 to Ethylene in Alkaline Medium

This work explores the potential of novel renewable materials in electrode fabrication for the electrochemical conversion of carbon dioxide (CO₂) to ethylene in alkaline media. In this regard, the use of the renewable chitosan (CS) biopolymer as ion-exchange binder of the copper (Cu) electrocatalyst nanoparticles (NPs) is compared with commercial anion-exchange binders Sustainion and Fumion on the fabrication of gas diffusion electrodes (GDEs) for the electrochemical reduction of carbon dioxide (CO₂R) in an alkaline medium. They were tested in membrane electrode assemblies (MEAs), where selectivity to ethylene (C₂H₄) increased when using the Cu:CS GDE compared to the Cu:Sustainion and Cu:Fumion GDEs, respectively, with a Faradaic efficiency (FE) of 93.7% at 10 mA cm^-2 and a cell potential of -1.9 V, with a C₂H₄ production rate of 420 µmol m^-2 s^-1 for the Cu:CS GDE. Upon increasing current density to 90 mA cm^-2, however, the production rate of the Cu:CS GDE rose to 509 µmol/m²s but the FE dropped to 69% due to increasing hydrogen evolution reaction (HER) competition. The control of mass transport limitations by tuning up the membrane overlayer properties in membrane coated electrodes (MCE) prepared by coating a CS-based membrane over the Cu:CS GDE enhanced its selectivity to C₂H₄ to a FE of 98% at 10 mA cm^-2 with negligible competing HER. The concentration of carbon monoxide was below the experimental detection limit irrespective of the current density, with no CO₂ crossover to the anodic compartment. This study suggests there may be potential in sustainable alernatives to fossil-based or perfluorinated materials in ion-exchange membrane and electrode fabrication, which constitute a step forward towards decarbonization in the circular economy perspective.

Green Recycling Methods to Treat Lithium-Ion Batteries E-Waste: A Circular Approach to Sustainability

E-waste generated from end-of-life spent lithium-ion batteries (LIBs) is increasing at a rapid rate owing to the increasing consumption of these batteries in portable electronics, electric vehicles, and renewable energy storage worldwide. On the one hand, landfilling and incinerating LIBs e-waste poses environmental and safety concerns owing to their constituent materials. On the other hand, scarcity of metal resources used in manufacturing LIBs and potential value creation through the recovery of these metal resources from spent LIBs has triggered increased interest in recycling spent LIBs from e-waste. State of the art recycling of spent LIBs involving pyrometallurgy and hydrometallurgy processes generates considerable unwanted environmental concerns. Hence, alternative innovative approaches toward the green recycling process of spent LIBs are essential to tackle large volumes of spent LIBs in an environmentally friendly way. Such evolving techniques for spent LIBs recycling based on green approaches, including bioleaching, waste for waste approach, and electrodeposition, are discussed here. Furthermore, the ways to regenerate strategic metals post leaching, efficiently reprocess extracted high-value materials, and reuse them in applications including electrode materials for new LIBs. The concept of "circular economy" is highlighted through closed-loop recycling of spent LIBs achieved through green-sustainable approaches.

Polymeric composite membranes in carbon dioxide capture process: a review

Carbon dioxide (CO₂) emission to the atmosphere is the prime cause of certain environmental issues like global warming and climate change, in the present day scenario. Capturing CO₂ from various stationary industrial emission sources is one of the initial steps to control the aforementioned problems. For this concern, a variety of resources, such as liquid absorbents, solid adsorbents, and membranes, have been utilized for CO₂ capturing from various emission sources. Focused on membrane-based CO₂ capture, polymeric membranes with composite structure (polymeric composite membrane) offer a better performance in CO₂ capturing process than other membranes, due to the composite structure it offers higher gas flux and less material usage, thus facile to use high performed expensive material for membrane fabrication and achieved good efficacy in CO₂ capture. This compressive review delivers the utilization of different polymeric composite membranes in CO₂ capturing applications. Further, the types of polymeric materials used and the different physicochemical modifications of those membrane materials and their CO₂ capturing ability are briefly discussed in the text. In conclusion, the current status and possible perspective ways to improve the CO₂ capture process in industrial CO₂ gas separation applications are described in this review.

Biopolymer-Based Mixed Matrix Membranes (MMMs) for CO2/CH4 Separation: Experimental and Modeling Evaluation

Alternative materials are needed to tackle the sustainability of membrane fabrication in light of the circular economy, so that membrane technology keeps playing a role as sustainable technology in CO2 separation processes. In this work, chitosan (CS)-based mixed matrix thin layers have been coated onto commercial polyethersulfone (PES) supports. The CS matrix was loaded by non-toxic 1-Ethyl-3-methylimidazolium acetate ionic liquid (IL) and/or laminar nanoporous AM-4 and UZAR-S3 silicates prepared without costly organic surfactants to improve CO2 permselectivity and mechanical robustness. The CO2/CH4 separation behavior of these membranes was evaluated experimentally at different feed gas composition (CO2/CH4 feed mixture from 20:80 to 70:30%), covering different separation applications associated with this separation. A cross-flow membrane cell model built using Aspen Custom Modeler was used to validate the process performance and relate the membrane properties with the target objectives of CO2 and CH4 recovery and purity in the permeate and retentate streams, respectively. The purely organic IL-CS and mixed matrix AM-4:IL-CS composite membranes showed the most promising results in terms of CO2 and CH4 purity and recovery. This is correlated with their higher hydrophilicity and CO2 adsorption and lower swelling degree, i.e., mechanical robustness, than UZAR-S3 loaded composite membranes. The purity and recovery of the 10 wt.% AM-4:IL-CS/PES composite membrane were close or even surpassed those of the hydrophobic commercial membrane used as reference. This work provides scope for membranes fabricated from renewable or biodegradable polymers and non-toxic fillers that show at least comparable CO2/CH4 separation as existing membranes, as well as the simultaneous feedback on membrane development by the simultaneous correlation of the process requirements with the membrane properties to achieve those process targets.

Application of polysaccharide-based metal organic framework membranes in separation science

Polysaccharide/MOF composite membranes have captured the interests of many researchers during decontamination of polluted environments. Their popularity can be attributed to the relatively high chemical and thermal stabilities of these composite membranes. Chitosan is among the polysaccharides extensively used during the synthesis of hybrid membranes with MOFs. The applications of chitosan/MOF composite membranes in separation science are explored in detail in this paper. Researchers have also synthesised mixed matrix membranes of MOFs with cellulose and cyclodextrin that have proved to be effective during separation of a variety of materials. The uses of cellulose/MOF and cyclodextrin/MOF membranes for the removal of environmental pollutants are discussed in this review. In addition, the challenges associated with the use of these mixed matrix membranes are explored in this current paper.

Impact of Ionic Liquid Structure and Loading on Gas Sorption and Permeation for ZIF-8-Based Composites and Mixed Matrix Membranes

Carbon dioxide (CO2) capture has become of great importance for industrial processes due to the adverse environmental effects of gas emissions. Mixed matrix membranes (MMMs) have been studied as an alternative to traditional technologies, especially due to their potential to overcome the practical limitations of conventional polymeric and inorganic membranes. In this work, the effect of using different ionic liquids (ILs) with the stable metal-organic framework (MOF) ZIF-8 was evaluated. Several IL@ZIF-8 composites and IL@ZIF-8 MMMs were prepared to improve the selective CO2 sorption and permeation over other gases such as methane (CH4) and nitrogen (N2). Different ILs and two distinct loadings were prepared to study not only the effect of IL concentration, but also the impact of the IL structure and affinity towards a specific gas mixture separation. Single gas sorption studies showed an improvement in CO2/CH4 and CO2/N2 selectivities, compared with the ones for the pristine ZIF-8, increasing with IL loading. In addition, the prepared IL@ZIF-8 MMMs showed improved CO2 selective behavior and mechanical strength with respect to ZIF-8 MMMs, with a strong dependence on the intrinsic IL CO2 selectivity. Therefore, the selection of high affinity ILs can lead to the improvement of CO2 selective separation for IL@ZIF-8 MMMs.

A review on chitosan-based membranes for sustainable CO2 separation applications: Mechanism, issues, and the way forward

Effective carbon dioxide (CO₂) separation by nominal energy utilization is the factual attempt in the present era of energy scarcity and environmental calamity. In this perspective, the membrane- based gas separation technology is a budding endeavour owing to its cost -effectiveness, ease of operational maintenance and compact modular design. Among various membrane materials, bio-based polymers are of interest as they are abundant and can be obtained from renewable resources, and can also reduce our dependency on exhaustible fossil fuel-based sources. In this review, the structure-property relationship of chitosan and some of its film-forming derivatives has been critically studied for the first time in view of the fundamental properties required for gas separation applications. Various factors affecting the gas permeation performance of chitosan-based membranes have been highlighted along with prospects and propositions for the design of a few novel bio-based membranes based on the exhaustive analyses.

Fast Track to Acetate-Based Ionic Liquids: Preparation, Properties and Application in Energy and Petrochemical Fields

Acetate-based ionic liquids (AcILs), as a kind of typical carboxylate-based ILs, display excellent structure tunability, non-volatility, good solubility to biomass, and favorable adsorption capacity, etc. These unique characteristics of AcILs make them important candidates for a range of applications in the field of energy and in the petrochemical industry. This paper intends to provide a comprehensive overview of recent advances in AcILs, including pure AcILs, AcIL-based multi-solvents, and AcIL-based composites, etc. Preparation methods, with one- and two-step synthesis, are reviewed. The relationship between properties and temperature is discussed, and some physical and thermodynamic properties of different AcILs are summarized and further calculated. The applications of AcILs in the fields of biomass processing, organic synthesis, separation, electrochemistry, and other fields are reviewed based on their prominent properties. Thereinto, the dual functions of AcILs as solvents and activators for biomass dissolution are discussed, and the roles of AcILs as catalysts and reaction mediums in clean organic synthesis are highlighted. Meanwhile, the reaction mechanisms of AcILs with acid gases are posed by means of molecular simulation and experimental characterization. Moreover, AcILs as electrolytes for zinc batteries, supercapacitors, and electrodeposition are particularly introduced. Finally, the future research challenges and prospects of AcILs are presented.

Preparation of Amino-Functional UiO-66/PIMs Mixed Matrix Membranes with [bmim][Tf2N] as Regulator for Enhanced Gas Separation

Development of mixed matrix membranes (MMMs) with excellent permeance and selectivity applied for gas separation has been the focus of world attention. However, preparation of high-quality MMMs still remains a big challenge due to the lack of enough interfacial interaction. Herein, ionic liquid (IL)-modified UiO-66-NH₂ filler was first incorporated into microporous organic polymer material (PIM-1) to prepare dense and defect-free mixed matrix membranes via a coating modification and priming technique. IL [bmim][Tf₂N] not only improves the hydrophobicity of UiO-66-NH₂ and facilitates better dispersion of UiO-66-NH₂ nanoparticles into PIM-1 matrix, but also promotes the affinity between MOFs and polymer, sharply reducing interface non-selective defects of MMMs. By using this strategy, we can not only facilely synthesize high-quality MMMs ignoring non-selective interfacial voids, but also structurally regulate MOF nanoparticles in the polymer substrate and greatly improve interface compatibility and stability of MMMs. The method also gives suitable level of generality for fabrication of versatile defect-free MMMs based on different combination of MOFs and PIMs. The prepared UiO-66-NH₂@IL/PIM-1 membrane exhibited outstanding gas separation behavior with large CO₂ permeation of 8283.4 Barrer and high CO₂/N₂ selectivity of 22.5.

Effect of Water and Organic Pollutant in CO2/CH4 Separation Using Hydrophilic and Hydrophobic Composite Membranes

Membrane technology is a simple and energy-conservative separation option that is considered to be a green alternative for CO2 capture processes. However, commercially available membranes still face challenges regarding water and chemical resistance. In this study, the effect of water and organic contaminants in the feed stream on the CO2/CH4 separation performance is evaluated as a function of the hydrophilic and permselective features of the top layer of the membrane. The membranes were a commercial hydrophobic membrane with a polydimethylsiloxane (PDMS) top layer (Sulzer Chemtech) and a hydrophilic flat composite membrane with a hydrophilic [emim][ac] ionic liquid-chitosan (IL-CS) thin layer on a commercial polyethersulfone (PES) support developed in our laboratory. Both membranes were immersed in NaOH 1M solutions and washed thoroughly before characterization. The CO2 permeance was similar for both NaOH-treated membranes in the whole range of feed concentration (up to 250 GPU). The presence of water vapor and organic impurities of the feed gas largely affects the gas permeance through the hydrophobic PDMS membrane, while the behavior of the hydrophilic IL-CS/PES membranes is scarcely affected. The effects of the interaction of the contaminants in the membrane selective layer are being further evaluated.

Molecular simulation on the stability and adsorption properties of choline-based ionic liquids/IRMOF-1 hybrid composite for selective H2S/CO2 capture

The compatibility and performance of an Isoreticular Metal-Organic Frameworks (IRMOF-1) impregnated with choline-based ionic liquids (ILs) for selective adsorption of H₂S/CO₂, were studied by molecular dynamics (MD) simulation. Cholinium alanate ([Chl][Ala]) was nominated as the suitable IL for impregnation into IRMOF-1, consistent with the low RMSD values (0.546 nm, 0.670 nm, 0.776 nm) at three IL/IRMOF-1 w/w ratios (W_IL/IRMOF-1 = 0.4, 0.8, and 1.2). The [Chl]⁺ and [Ala]^- ion pair was located preferentially around the carboxylate group within the IRMOF-1 framework, with the latter interacting strongly with the host than the [Chl]⁺. Results of radius of gyration (Rg) and root mean square displacement (RMSD) revealed that a ratio of 0.4 w/w of IL/IRMOF-1 (Rg = 1.405 nm; RMSD = 0.546 nm) gave the best conformation to afford an exceptionally stable IL/IRMOF-1 composite. It was discovered that the IL/IRMOF-1 composite was more effective in capturing H₂S and CO₂ compared to pristine IRMOF-1. The gases adsorbed in higher quantities in the IL/IRMOF-1 composite phase compared to the bulk phase, with a preferential adsorption for H₂S, as shown by the uppermost values of adsorption ( [Formula: see text] = 17.954 mol L^-1 bar^-1) and an adsorption selectivity ( [Formula: see text] = 43.159) at 35 IL loading.

Leveraging Nanocrystal HKUST-1 in Mixed-Matrix Membranes for Ethylene/Ethane Separation

The energy-intensive ethylene/ethane separation process is a key challenge to the petrochemical industry. HKUST-1, a metal–organic framework (MOF) which possesses high accessible surface area and porosity, is utilized in mixed-matrix membrane fabrication to investigate its potential for improving the performance for C₂H₄/C₂H₆ separation. Prior to membrane fabrication and gas permeation analysis, nanocrystal HKUST-1 was first synthesized. This step is critical in order to ensure that defect-free mixed-matrix membranes can be formed. Then, polyimide-based polymers, ODPA-TMPDA and 6FDA-TMPDA, were chosen as the matrices. Our findings revealed that 20 wt% loading of HKUST-1 was capable of improving C₂H₄ permeability (155% for ODPA-TMPDA and 69% for 6FDA-TMPDA) without excessively sacrificing the C₂H₄/C₂H₆ selectivity. The C₂H₄ and C₂H₆ diffusivity, as well as solubility, were also improved substantially as compared to the pure polymeric membranes. Overall, our results edge near the upper bound, confirming the effectiveness of leveraging nanocrystal HKUST-1 filler for performance enhancements in mixed-matrix membranes for C₂H₄/C₂H₆ separation.

Study of the versatility of CuBTC@IL-derived materials for heterogeneous catalysis

The versatility of CuBTC (HKUST-1) MOF materials to be functionalized to improve their catalytic activity performance was evaluated. CuBTC@IL catalysts are selective for the cycloaddition of CO₂ to epoxides, giving rise to value-added products.

Effect of Humidity on CO2/N2 and CO2/CH4 Separation Using Novel Robust Mixed Matrix Composite Hollow Fiber Membranes: Experimental and Model Evaluation

In this work, the performance of new robust mixed matrix composite hollow fiber (MMCHF) membranes with a different selective layer composition is evaluated in the absence and presence of water vapor in CO2/N2 and CO2/CH4 separation. The selective layer of these membranes is made of highly permeable hydrophobic poly(trimethyl-1-silylpropine) (PTMSP) and hydrophilic chitosan-ionic liquid (IL-CS) hybrid matrices, respectively, filled with hydrophilic zeolite 4A particles in the first case and HKUST-1 nanoparticles in the second, coated over compatible supports. The effect of water vapor in the feed or using a commercial hydrophobic PDMSXA-10 HF membrane has also been studied for comparison. Mixed gas separation experiments were performed at values of 0 and 50% relative humidity (RH) in the feed and varying CO2 concentration in N2 and CH4, respectively. The performance has been validated by a simple mathematical model considering the effect of temperature and relative humidity on membrane permeability.

Recent Innovation of Metal-Organic Frameworks for Carbon Dioxide Photocatalytic Reduction

The accumulation of carbon dioxide (CO2) pollutants in the atmosphere begets global warming, forcing us to face tangible catastrophes worldwide. Environmental affability, affordability, and efficient CO2 metamorphotic capacity are critical factors for photocatalysts; metal-organic frameworks (MOFs) are one of the best candidates. MOFs, as hybrid organic ligand and inorganic nodal metal with tailorable morphological texture and adaptable electronic structure, are contemporary artificial photocatalysts. The semiconducting nature and porous topology of MOFs, respectively, assists with photogenerated multi-exciton injection and adsorption of substrate proximate to void cavities, thereby converting CO2. The vitality of the employment of MOFs in CO2 photolytic reaction has emerged from the fact that they are not only an inherently eco-friendly weapon for pollutant extermination, but also a potential tool for alleviating foreseeable fuel crises. The excellent synergistic interaction between the central metal and organic linker allows decisive implementation for the design, integration, and application of the catalytic bundle. In this review, we presented recent MOF headway focusing on reports of the last three years, exhaustively categorized based on central metal-type, and novel discussion, from material preparation to photocatalytic, simulated performance recordings of respective as-synthesized materials. The selective CO2 reduction capacities into syngas or formate of standalone or composite MOFs with definite photocatalytic reaction conditions was considered and compared.

Graphene-Incorporated Biopolymeric Mixed-Matrix Membrane for Enhanced CO2 Separation by Regulating the Support Pore Filling

The CO₂ separation performance by a membrane is influenced essentially by film thickness, temperature, moisture, and pressure. Pore formation on the active layer and pore clogging of the membrane support are critical factors that impedes the CO₂ separation performance. This study involves the development of a novel nanocomposite membrane (CS/SF/GNP) consisting of chitosan (CS), silk fibroin (SF), and graphene nanoparticles (GNP). The CS acts as the matrix, SF contributes to the CO₂ facilitated transport by its inherent amines as carriers, and GNP helped in counteracting the support pore blockage during the gas separation test. The positive effect of GNP in the CS/SF/GNP was further apparent in the CO₂ permeance inconsequential drop of ∼7% during the initial 12 h in the presence of moisture and pressure. The detailed characterizations including FESEM, AFM, and swelling were performed for the membranes. The effect of sweep water flow rate, temperature, and feed absolute pressure on CO₂ separation performance from binary gas were performed. The CS/SF/GNP membrane exhibited CO₂ permeance of 159 GPU and CO₂/N₂ selectivity of 93 at 90 °C and a feed absolute pressure of 2 bar having a sweep side water flow rate of 0.05 mL/min. Further, when CS/SF/GNP membrane was tested to separate CO₂ from ternary gas mixture (CO₂/N₂/H₂), it displayed excellent CO₂ permeance of 126 GPU and selectivity for CO₂/N₂ and CO₂/H₂ as 104 and 52, respectively. The TGA isotherm and XPS analysis of CS/SF/GNP membrane suggested a thermal stability of the prepared membrane that establishes its suitability for the gas permeation at different temperature.

Performance of Mixed Matrix Membranes Containing Porous Two-Dimensional (2D) and Three-Dimensional (3D) Fillers for CO₂ Separation: A Review

Application of conventional polymeric membranes in CO₂ separation processes are limited by the existing trade-off between permeability and selectivity represented by the renowned upper bound. Addition of porous nanofillers in polymeric membranes is a promising approach to transcend the upper bound, owing to their superior separation capabilities. Porous nanofillers entice increased attention over nonporous counterparts due to their inherent CO₂ uptake capacities and secondary transport pathways when added to polymer matrices. Infinite possibilities of tuning the porous architecture of these nanofillers also facilitate simultaneous enhancement of permeability, selectivity and stability features of the membrane conveniently heading in the direction towards industrial realization. This review focuses on presenting a complete synopsis of inherent capacities of several porous nanofillers, like metal organic frameworks (MOFs), Zeolites, and porous organic frameworks (POFs) and the effects on their addition to polymeric membranes. Gas permeation performances of select hybrids with these three-dimensional (3D) fillers and porous nanosheets have been summarized and discussed with respect to each type. Consequently, the benefits and shortcomings of each class of materials have been outlined and future research directions concerning the hybrids with 3D fillers have been suggested.

Modeling of Gas Permeation through Mixed-Matrix Membranes Using Novel Computer Application MOT

The following article proposes a modern computer application MOT (Membrane Optimization Tool) for modeling of gas transport processes through mixed-matrix membranes (MMMs). The current version of the application is based on the Maxwell model, which can be successfully used to model gas transport through the simplest types of hybrid membranes without any defects. The application has been verified on the example of four types of hybrid membranes, consisting of various types of polymer matrix, such as: poly (vinyl acetate), 2, 2′-BAPB + BPADA, Ultem, hyperbranched polyimide (ODPA-MTA) and zeolite 4A. The average absolute relative error (AARE) and root-mean-square error (RMSE) were calculated in order to compare the theoretical MOT-predicted results with the experimental results. It was found that the AARE ranges from 29% to 36%, while the RMSE is in the range of 10% to 29%. The article presents also the comparison of MOT-predicted data obtained with Maxwell and Bruggeman models. To obtain more accurate reproduction of experimental results, further versions of the proposed application will be extended with next-generation permeation models (Lewis–Nielsen, Pal, modified Maxwell or Felske models), allowing for the description of transport in more complex systems with the possibility of taking into account possible defects.

Development and Characterization of Defect-Free Matrimid® Mixed-Matrix Membranes Containing Activated Carbon Particles for Gas Separation

In this work, mixed-matrix membranes (MMMs) for gas separation in the form of thick films were prepared via the combination of the polymer Matrimid® 5218 and activated carbons (AC). The AC particles had a mean particle size of 1.5 μm and a mean pore diameter of 1.9 nm. The films were prepared by slow solvent evaporation from casting solutions in chloroform, which had a varying polymer⁻AC ratio. It was possible to produce stable films with up to a content of 50 vol % of AC. Thorough characterization experiments were accomplished via differential scanning calorimetry and thermogravimetric analysis, while the morphology of the MMMs was also investigated via scanning electron microscopy. The gas transport properties were revealed by employing time-lag measurements for different pure gases as well as sorption balance experiments for the filler particles. It was found that defect free Matrimid® MMMs with AC were prepared and the increase of the filler content led to a higher effective permeability for different gases. The single gas selectivity αij of different gas pairs maintained stable values with the increase of AC content, regardless of the steep increase in the effective permeability of the pure gases. Estimation of the solubilities and the diffusivities of the Matrimid®, AC, and MMMs allowed for the explanation of the increasing permeabilities of the MMMs, with the increase of AC content by modelling.

Functionalized ionic liquid membranes for CO2 separation

It is imperative to develop efficient, reversible and economic technologies for separating CO₂ which mainly comes from flue gas, natural gas and syngas.