Membranes For Separation Applications Research Articles

Preparation and properties of asymmetric inverse opal-like microfiltration membranes

Most types of commercially available MF membranes suffer limited separation performances due to huge deviations in pore size and low porosity. In view of this, a new and facile assembly strategy was proposed to prepare an asymmetric inverse opal (IO) like microfiltration (MF) membrane with ordered pore structure, high porosity and large water flux, which is a composite of a disordered layer with three-dimensional pore structures made by dissolved N, N-dimethylformamide (DMF) and an ordered layer with uniform pore size by using a sacrificial template method. The effects of SiO2 microsphere size and DMF treatment on the structure and properties have been investigated. Different DMF treatment times can significantly change the asymmetric structure distribution of MF membrane and further affect the permeability. The water flux of the asymmetric membrane increases with the DMF infiltration time. Based on the SiO2 microsphere template size of 494 nm and the DMF treatment time of 90 s, the porosity and pure water flux can reach 78 % and 1810 L/m2h, respectively. The membrane retains the IO-like structure layer with uniform pore size, and features excellent retention (almost 100 %) for SiO2 microspheres, indicating the great potential of asymmetric IO-like MF membranes for membrane separation applications.

How to transform microporous organic polymers for membrane-based separation: A review

Microporous organic polymers (MOPs) are ideal candidates for designing highly efficient and precise molecular sieving separation membranes due to their exceptional porosity, rigid pore structure, pore size designability, and ease of functionalization. These materials encompass COFs, POCs, PAFs, PIMs, CMPs, and HCPs. However, the path to utilizing MOPs as separation membrane applications has encountered obstacles. Several studies have been conducted to fully exploit the exceptional properties of these polymers. The better application of MOPs materials should be considered in terms of material design and synthesis, membrane formation, and membrane task-specific applications. This review objectively reclassifies MOPs materials based on the latest research and material ordering and provides a systematic summary of MOPs material synthesis and design, MOPs-based membrane fabrication difficulties, and current novel MOPs-based membrane design. Additionally, it introduces in detail the preparation of different types of MOPs-based membranes. The applications of MOPs-based membranes in separation applications are also thoroughly summarized. Finally, this review summarizes the challenges of current MOPs-based membrane development, proposes future opportunities and potential applications in the separation and purification field.

La0·8Mn0·2FeO3 impregnated ceramic membrane for membrane fouling elimination via peroxymonosulfate activation

To endow SiC ceramic membranes a catalytic self-cleaning capability, a pore-functionalized SiC ceramic membrane with impregnated a perovskite-type catalyst La0·8Mn0·2FeO3 was fabricated by a urea-assisted one-step combustion method. Diffraction of X-ray (XRD), canning electronic microscopy (SEM) with an energy dispersion X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) were employed to investigate the effects of the impregnating of La0·8Mn0·2FeO3 on SiC membrane pore-structure (La0·8Mn0·2FeO3-CM). The catalytic self-cleaning performance of the as-prepared membranes was assessed through peroxymonosulfate (PMS) activation under a cross-flow filtration mode. Results indicate that La0·8Mn0·2FeO3 has been successfully impregnated into the macropores of SiC membranes without pore blocking, and 92.4 % of the flux recovery rate (FRR) was achieved when the PMS concentration was 70 mM and catalytic flushing time was 45 min. Therefore, the La0·8Mn0·2FeO3 impregnated SiC membrane exhibited excellent catalytic self-cleaning property, which can effectively avoid the environmental pollution and the deterioration of membrane materials caused by chemical cleaning for membrane fouling. In addition, the radical quenching experiment and electron spin resonance (EPR) tests were conducted in the catalytic self-cleaning process, and the results suggested that the hydroxyl radical (⋅OH) and sulfate radical (SO4•‾) are simultaneously captured and ⋅OH is the dominant active species. This study embarks on a novel and environmental friendly membrane cleaning approach for irreversible fouling eliminates in diverse membrane separation applications.

Unifying the Conversation: Membrane Separation Performance in Energy, Water, and Industrial Applications.

Dense polymer membranes enable a diverse range of separations and clean energy technologies, including gas separation, water treatment, and renewable fuel production or conversion. The transport of small molecular and ionic solutes in the majority of these membranes is described by the same solution-diffusion mechanism, yet a comparison of membrane separation performance across applications is rare. A better understanding of how structure-property relationships and driving forces compare among applications would drive innovation in membrane development by identifying opportunities for cross-disciplinary knowledge transfer. Here, we aim to inspire such cross-pollination by evaluating the selectivity and electrochemical driving forces for 29 separations across nine different applications using a common framework grounded in the physicochemical characteristics of the permeating and rejected solutes. Our analysis shows that highly selective membranes usually exhibit high solute rejection, rather than fast solute permeation, and often exploit contrasts in the size and charge of solutes rather than a nonelectrostatic chemical property, polarizability. We also highlight the power of selective driving forces (e.g., the fact that applied electric potential acts on charged solutes but not on neutral ones) to enable effective separation processes, even when the membrane itself has poor selectivity. We conclude by proposing several research opportunities that are likely to impact multiple areas of membrane science. The high-level perspective of membrane separation across fields presented herein aims to promote cross-pollination and innovation by enabling comparisons of solute transport and driving forces among membrane separation applications.

Hydrogen-bonded organic frameworks for membrane separation.

Hydrogen-bonded organic frameworks (HOFs) are a new class of crystalline porous materials that are formed through the interconnection of organic or metal-organic building units via intermolecular hydrogen bonds. The remarkable flexibility and reversibility of hydrogen bonds, coupled with the customizable nature of organic units, endow HOFs with mild synthesis conditions, high crystallinity, solvent processability, and facile self-healing and regeneration properties. Consequently, these features have garnered significant attention across various fields, particularly in the realm of membrane separation. Herein, we present an overview of the recent advances in HOF-based membranes, including their advanced fabrication strategies and fascinating applications in membrane separation. To attain the desired HOF-based membranes, careful consideration is dedicated to crucial factors such as pore size, stability, hydrophilicity/hydrophobicity, and surface charge of the HOFs. Additionally, diverse preparation methods for HOF-based membranes, including blending, in situ growth, solution-processing, and electrophoretic deposition, have been analyzed. Furthermore, applications of HOF-based membranes in gas separation, water treatment, fuel cells, and other emerging application areas are presented. Finally, the challenges and prospects of HOF-based membranes are critically pointed out.

Integrated Approach: Characterization, Application of Alumina Kaolin Membrane for Glycerol Separation in Biodiesel Production, and Flux Recovery Strategies

The transesterification process used for biodiesel production yields glycerol as a prominent byproduct. Given glycerol's adverse effects on engine performance and longevity, regulatory standards, such as those set by SNI and international authorities, restrict free glycerol content in biodiesel to below 0.02 wt.% or 200 ppm. Consequently, the removal of glycerol has become a critical step in biodiesel production. Traditional purification methods are energy-intensive and generate substantial wastewater, prompting the exploration of alternative solutions like membrane separation technology. Ceramic microfiltration membranes, renowned for their exceptional thermal, chemical, and mechanical durability, have emerged as a prominent choice. The development and application of a cost-effective Alumina-Kaolin ceramic microfiltration membrane for glycerol removal in biodiesel signify a promising advancement in water purification processes. The current study was conducted to evaluate the microfiltration performance of the Alumina-Kaolin ceramic membrane, investigate the impact of the membrane’s microstructure on separation performance, and explore cleaning strategies aimed at enhancing flux recovery ratio (FRR). The microstructure analysis through SEM and BET demonstrated pores in the membrane, featuring a 3.375 m2/g surface area, 30.367 % porosity, and 0.18 μm pore size. Several tests employed using different glycerol and water concentration in the feed of 1000 ppm, 5000 ppm and 10000 ppm. The evaluation gave high glycerol rejection rates of 92.07%, 98.52% and 98.94% for the respective feed concentrations with the permeate flux of 65.42 [l/(m2h)], 61.09 [l/(m2h)] and 52.91 [l/(m2h)] respectively. The microstructure of alumina-kaolin membrane could separate the larger particles of glycerol-water droplets and gave high separation performance. As the flux decline ratio increased (from 2.13% to 20.86%) due to rising glycerol concentration (1,000 to 10,000 ppm), cleaning became crucial for flux recovery. Employing various agents, benzalkonium chloride notably enhanced alumina-kaolin flux recovery ratio (FRR) to 98.17%.

Unidirectional Freezing of Polymer Solution Droplets.

Ice templating provides a means of generating textures with a well-defined topography. Recent applications involve the freezing of water droplets, with or without colloids, on flat or textured surfaces. An interesting feature of water droplets freezing on a substrate is the formation of a pointy tip at a constant angle, regardless of the substrate temperature, surface energy, or droplet volume. Here, by adding the polymer to water, we demonstrate how to manipulate and even prevent the formation of such an icy tip. We find that the sharpness of the tip decreases with increasing polymer concentration until completely disappearing above the overlap concentration, while the total freezing time increases concomitantly. Building on these observations, we combined simple geometrical arguments with heat flux measurements to model and connect the spatial and temporal evolution of polymer droplets under unidirectional freezing. Together our results provide new ways to control the shape of frozen droplets for ice templating or microstructure fabrication, with applications in tissue engineering, separation membranes, and soft robotics.

Environmental sustainability of FO membrane separation applications – Bibliometric analysis and state-of-the-art review

Water treatment, product concentration, and resource recovery are few examples of the many areas where the economic promise of osmotic driven membrane separation remains unrealized. The most futuristic and sustainable, osmotic driven membrane separation process which works with-out any external hydraulic energy is forward osmosis (FO) process. This study comprises two parts first is of bibliometric analysis which helps to identify and analyze the current research trend in osmotic membrane filtration technique, and are represented along with nodal network visualization. Desalination and wastewater treatment seem to be the major application of FO technology followed by fertigation, algal dewatering, pharmaceutical and textile industries. The second part is the literature review on major applications of forward osmotic technique shortlisted from bibliometric analysis, which includes recent developments in FO research. An application based critical analysis on thin film nano composite membrane, draw solutes, nano particles for membrane modifications and hybrid FO units were performed. Analysing literatures from 2005 to 2022, this study pinpoints potential applications, future prospects and existing challenges in Forward Osmosis (FO), for the successful implementation of scale-up.

2D MOFs and Zeolites for Composite Membrane and Gas Separation Applications: A Brief Review.

Commercial membranes have predominantly been fabricated from polymers due to their economic viability and processability. This choice offers significant advantages in energy efficiency, cost-effectiveness, and operational simplicity compared to conventional separation techniques like distillation. However, polymeric membranes inherently exhibit a trade-off between their permeability and selectivity, which is summarized in the Robeson upper bound. To potentially surpass these limitations, mixed-matrix membranes (MMMs) can be an alternative solution, which can be constructed by combining polymers with inorganic additives such as metal-organic frameworks (MOFs) and zeolites. Incorporating high-aspect-ratio fillers like MOF nanosheets and zeolite nanosheets is of significant importance. This incorporation not only enhances the efficiency of separation processes but also reinforces the mechanical robustness of the membranes. We outline synthesis techniques for producing two-dimensional (2D) crystals (including nanocrystals with high aspect ratio) and provide examples of their integration into membranes to customize separation performances. Moreover, we propose a potential trajectory for research in the area of high-aspect-ratio materials-based MMMs, supported by a mathematical-model-based performance prediction.

Understanding the performance of RHO type zeolite membrane for CH4/N2 separation based on molecular dynamics and deep neural network methods

This study shows a molecular dynamics (MD) simulation study on the performance of the RHO zeolite membrane for separating nitrogen from methane/nitrogen gas mixtures. The contamination of natural gas, predominantly composed of methane, with nitrogen diminishes its value. Zeolite membranes offer promising prospects for gas separation due to their stability, rigid pore structure, and molecular sieving properties. The study investigates the impact of pressure difference (up to 30 MPa), feed composition, and membrane thickness on the separation rate at a system temperature of 298 K. Results demonstrate that the RHO zeolite membrane exhibits high permeability and selectivity for N2 separation, surpassing the upper limit defined by Robson with a maximum permeability of 2.14 × 105 GPU (Gas Permeation Units). Exceptional selectivity of N2 over CH4 molecules is observed. Additionally, altering the feed composition and membrane thickness positively influences the membrane's separation performance, thereby enhancing its efficiency. The findings contribute to the advancement of separation technologies, providing valuable insights into the potential application of zeolite membranes for efficient N2 separation from CH4/N2 gas mixtures in natural gas processing. Furthermore, the study explores the use of Deep Neural Network (DNN) models to predict the membrane's performance under diverse operating conditions. The DNN models, trained using simulation data from MD simulations, exhibit high accuracy with a coefficient of determination (R2) exceeding 0.9, ensuring reliable predictions. The integration of DNN models facilitates the optimization of zeolite membrane-based gas separation systems, improving their design and operation.

Self-cleaning MOF integrated membrane embedded with piezocatalytic Bi2WO6 nanocrystals for synergistic wastewater purification and dyes removal

The widespread application of high-performance separation membranes in sewage purification is limited by their permeability and membrane fouling. Herein, we report a method for growing CAU-17 MOF on the flexible polymer substrate and embedding piezoelectric Bi2WO6 (BWO) nanocrystals based on Bi ion sites. The integrated membrane inherits the hydrophilicity and adsorption characteristics of MOF, showing a high flux and separation coefficient of 90.3% for rhodamine B (RhB) solution. In addition, this strategy optimizes the piezoelectric field of CAU-17 into the entire surface through surface modification of BWO nanocrystals. The piezocatalytic degradation rate constant of RhB reaches 0.040 min1. The flexibility and abundant mesoporous of polyvinylidene fluoride (PVDF) substrate provide the piezoelectric response to weak forces and more reactive active sites, enabling the integrated membrane to achieve dye degradation under low-frequency water flow. The BWO@CAU-17 evolved from MOF matrix enables self-cleaning of membranes. The synergistic function of multiple effects drives the rapid separation and complete degradation of pollutants, which greatly promotes the practical application of integrated membranes.

Application of polypropylene microfiltration membranes for separation of wastewater from car wash

In the final stage of washing the car is waxed and rinsed with demineralized water, however, at an initial stage reusing treated effluents as process water is possible. In the current work, the application of microfiltration (MF) polypropylene (PP) membranes for treatment of carwash wastewater was investigated. To compare the transport properties, more hydrophobic PTFE capillary membranes were also used. The examined process is restricted by the fouling phenomenon, which has been thoroughly studied by filtering both the synthetic and real wastewaters. The use of different types of foaming agents and hydrowaxes, allowed to found that the membranes fouling was caused not only by the impurities removed from the car, but also by the mixtures of commercial washing agents. As a result, the permeate flux was quickly reduced, to a level of 100–200 LHM for PP membrane and to 50–150 LHM for PTFE membrane (TMP = 0.05 MPa). Regardless of the degree of feed contamination, the clean permeate with turbidity of 0.2–0.8 NTU was obtained. In the case PTFE membrane, the permeate turbidity was at a level of 2–3 NTU. The tested wastewaters (5–100 NTU) contained the particles with the size in the range of 0.1–400 μm. The removal of larger particles by prefiltration was found to increase the membranes fouling. It has been noted that rinsing the modules with water was not effective. Nevertheless, the membranes were cleaned using alkaline solutions (pH = 11.5–12.0) used at the car wash station to remove insects and to wash the wheel. This procedure was less effective for PTFE membranes, which experienced significantly greater irreversible fouling. It has been shown that the PP membranes used, in addition to removing turbidity, ensured the retention of Escherichia coli in almost 100%.

Innovative integration of porous materials and membranes: Achieving optimized pore orientation for enhanced performance

Incorporating inorganic porous materials into polymer membranes presents a promising strategy to rectify their inherent imperfections. Nonetheless, achieving peak efficiency necessitates pores oriented perpendicular to the membrane surface, a feat that remains challenging due to orientation control complexities. In this study, a novel synthesis approach for two-dimensional (2D) mesoporous silica nanoparticles (MSN) featuring high aspect ratios and vertical pore channels is presented. These channels, oriented perpendicular to the membrane surface, optimize water permeability. This unique orientation is meticulously achieved via cetyltrimethylammonium bromide (CTAB) acting as a surfactant at the nexus of polar and non-polar fluids, guaranteeing interface evenness. Intriguingly, the resultant mesoporous compound harbors both micro and mesopores—a phenomenon attributed to surfactant non-polar segment expansion within non-polar solvents or the distinct U-shaped interface upon contact with hydrophilic mesoporous entities. After depositing a tannic acid (TA) coating on a polyvinylidene fluoride (PVDF) base membrane, 2D MSN was fixed on the membrane surface using polyethyleneimine (PEI) as a linker through strong hydrogen bonding. Thanks to the asymmetric structure of the mesoporous separation layer combining micro and mesopores, the perpendicular pore channels with superhydrophilic features, water can permeate through the separation membrane with the shortest distance and lowest resistance, achieving an ultra-high pure water permeation volume of 394.5 L−1h−1bar−1. The uniform pore channels of 2D MSN show a rejection rate of over 97% for large molecular dyes such as Evans blue (EB), Congo red (CR), and Rose Bengal sodium (RB). This work not only advances the synthesis of two-dimensional materials with vertical pore channels but also underscores their potential in membrane separation applications.

Fabrication of hydrophobic PI nanofibrous membrane with controllable pore structures

Polyimide (PI) has garnered increasing attention in the field of membrane technology owing to its excellent comprehensive performance. In this work, PI nanofibrous membranes with a controllable pore structure were fabricated by the thermal imidization of electrospun polyamide acid (PAA) nanofibrous membranes. Polytetrafluoroethylene (PTFE) and poly(tetrafluoroethylene-hexafluoropropylene) (FEP) particles were introduced into the PAA nanofibrous membrane with the aim of enhancing the membrane's hydrophobicity and regulating its pore structure by electrospraying the PTFE/FEP mixed aqueous dispersion. During the thermal imidization process, melt casting of FEP particles occurred, leading to the adhesion of PI nanofibrous membranes and subsequent regulation of the membrane's pore structure. Meanwhile, due to the imidization temperature being lower than PTFE’s melting temperature, the unmelted PTFE particles would further enhance the membrane’s hydrophobicity. We have successfully provided a novel method for fabricating PI nanofibrous membranes with controllable pore structures and excellent hydrophobicity to expand their applications in membrane separation. Owing to the hydrophobicity and lipophilicity, the obtained PI nanofibrous membranes were applied to oil-water (kerosene/water) separation to characterize the separation performance. The results showed that, following the regulation of the pore structure, the PI nanofibrous membranes exhibited a high oil flux (203.83 L/m2·h) and separation efficiency (＞99.00%) without external pressure.

Hydrogen Exchange and Diffusion Kinetics at Elevated Temperatures in Proton-Conducting Solid Oxide Materials

Storage of purified hydrogen is one of the central challenges in addressing climate change and reducing our reliance on fossil fuels for energy conversion and storage, and therefore there is a global surge in research and development concerning hydrogen purification and storage. In this regard, we are studying proton conduction in solid oxide materials at elevated temperatures for applications in hydrogen separation and compression membranes. Hydrogen compression is the most recommended method to store hydrogen for automotive applications as it allows an increase in the hydrogen volumetric energy density.Traditionally the protonic conductivity in these materials is measured by indirect methods. For example, conductivity measurements in mixed gas atmospheres, comparing for example dry N2 with humidified N2, thereby allowing the contribution of protons to be evaluated. In this study, we for the first time report the evaluation of protonic conductivity in BaZr1-xCexY0.2O3−δ, BaZr0.1Ce0.7Y0.2–xYbxO3–δ and Ba7Nb4MoO20 by direct measurements afforded by the Isotope Exchange Depth Profiling technique with deuterium labelling. We also report the kinetics of H/D transport through the bulk materials and across metal-ceramic interfaces with a particular interest in the behaviour of the interface between the key Pd/Pd alloy catalyst component and the hydrogen-transporting oxide ceramic material. The transport and interface behaviour information will be of significance in designing hydrogen separation and compression membranes. Figure 1

Surface modification of polymers by ion irradiation: Reactivity principle and application

Modifying polymers through ion irradiation is an advantageous method for controlling polymer with desirable properties. The surface modification mechanism and application of polymers by ion irradiation are under exploration. This review systematically analyzes the recent progress on the surface modification of common polymers by ion irradiation. The fundamentals of irradiation principle and chemical interaction, the irradiation effect of microstructure, macroproperties, and related characterization methods are introduced for the innovated applications. The effect of ion beam conditions (heavy or light ions, high or low energy/fluences) on different polymers is systematically analyzed for the different irradiation effect to achieve surface modification, in which the coupling mechanism between nuclear and electronic stopping power is provided. To meet the requirement of various application, the relationship between micro representation and macro performance is thoroughly discussed and established combined with the concerns regarding ion irradiation induced regulation mechanism. For the practical/potential application prospects, the frontier research on membrane separation, electrical, and biomedical applications are discussed. This review offers valuable insights into the modified microstructures versus the necessary surface properties of polymer by ion irradiation.

Can MXene be the Effective Nanomaterial Family for the Membrane and Adsorption Technologies to Reach a Sustainable Green World?

Environmental pollution has intensified and accelerated due to a steady increase in the number of industries, and exploring methods to remove hazardous contaminants, which can be typically divided into inorganic and organic compounds, have become inevitable. Therefore, the development of efficacious technology for the separation processes is of paramount importance to ensure the environmental remediation. Membrane and adsorption technologies garnered attention, especially with the use of novel and high performing nanomaterials, which provide a target-specific solution. Specifically, widespread use of MXene nanomaterials in membrane and adsorption technologies has emerged due to their intriguing characteristics, combined with outstanding separation performance. In this review, we demonstrated the intrinsic properties of the MXene family for several separation applications, namely, gas separation, solvent dehydration, dye removal, separation of oil-in-water emulsions, heavy metal ion removal, removal of radionuclides, desalination, and other prominent separation applications. We highlighted the recent advancements used to tune separation potential of the MXene family such as the manipulation of surface chemistry, delamination or intercalation methods, and fabrication of composite or nanocomposite materials. Moreover, we focused on the aspects of stability, fouling, regenerability, and swelling, which deserve special attention when the MXene family is implemented in membrane and adsorption-based separation applications.

Facile physical modification of ultrathin polyethylene by trace poly(vinyl alcohol)

Poly (vinyl alcohol) (PVA) modification to nonpolar polymers has been intensively investigated due to the performance improvement in membrane separation, tissue engineering, and other applications. Slightly deviated from the conventional route, no covalent bonding by crosslinking or hydrogen bonding is needed to anchor PVA onto the target matrix. This work harnessed van der Waals interaction only to achieve the modification. Owing to the high surface energy and aspect ratio of ultra-high molecular weight polyethylene (UHMWPE) ultrathin membranes, the physical binding between PVA and PE was found stable and easy to establish. This interaction is initiated by the entropy-driven hydrophobic effect at the liquid-solid interface to reduce surface energy. By encapsulation of PVA on the fibrils, the PE hydrophilicity could be overturned (from 134.6° to 48.4°) with micro-structures remaining almost intact at the low loading of modification (0.001% conc. solution dip-coating). The resultant hydrophilic ultrathin PVA-PE membranes showed high transparency, high mechanical strength (380 MPa in tensile max. stress), and high porosity with only 200 nm thickness in a freestanding state. This work provides a facile approach to switch the hydrophilicity of nonpolar polymer ultrathin membranes by establishing vdW physical bonding only. By trace-adsorption, this method could also be helpful in fine-tuning nanostructures of the target polymer matrix by a resolution of nanometer level.

Studies on application of Petcoke-based graphene membranes for CO2 separation

ABSTRACT Graphene-based separation membranes exhibit high separation potential to separate ions and molecules by the interlayer spacing with high surface area, porosity and tunable nanosized channels. The large-scale manufacturing of graphene-based membranes for gas separation is limited and challenging. Deposition of uniform, and selective ultrathin films as membrane is a big challenge for scalable separation with existing methods. In present study, solvent-ink-jet printing technique is applied for dispersing and uniform coating of graphene layers onto the membrane support. Preparation of graphene-based ink is the core objective of the operation for evaluating stability, coating and followed by separation studies. As prepared, graphene ink is filled in the cartridge of HP Desk-Jet-1110 series, which is available and slightly modified for the printing on the RO-membrane as support. The prepared membranes are characterized and analyzed for gas separation performance study. The decrease in gas composition of CO2 in permeate is observed and around 93% ± 0.5 of CO2 is separated from the gaseous mixtures.

Mixed-linker strategy for suppressing structural flexibility of metal-organic framework membranes for gas separation

Structural flexibility is a critical issue that limits the application of metal-organic framework (MOF) membranes for gas separation. Herein we propose a mixed-linker approach to suppress the structural flexibility of the CAU-10-based (CAU = Christian-Albrechts-University) membranes. Specifically, pure CAU-10-PDC membranes display high separation performance but at the same time are highly unstable for the separation of CO2/CH4. A partial substitution (30 mol.%) of the linker PDC with BDC significantly improves its stability. Such an approach also allows for decreasing the aperture size of MOFs. The optimized CAU-10-PDC-H (70/30) membrane possesses a high separation performance for CO2/CH4 (separation factor of 74.2 and CO2 permeability of 1,111.1 Barrer under 2 bar of feed pressure at 35°C). A combination of in situ characterization with X-ray diffraction (XRD) and diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, as well as periodic density functional theory (DFT) calculations, unveils the origin of the mixed-linker approach to enhancing the structural stability of the mixed-linker CAU-10-based membranes during the gas permeation tests.