Mixed Matrix Composite Membranes Research Articles

Intensifying the CO2/N2 separation performance of PVAm membrane by amine-functionalized porous montmorillonite

Multilayered montmorillonite (MMT) exhibits the building block stacking in polymer matrix, which has tortuous transport passageways and a few CO2 affinity sites, thus mixed matrix membranes incorporated with MMT have low molecular recognition ability for CO2. Herein, the porous MMT (p-MMT) was initially prepared through the solid-phase desilication reaction, and then amine-functionalized p-MMT (P3.2@p-MMT) was synthesized by the electrostatic interaction between positively charged polyethyleneimine (PEI) and negatively charged p-MMT, in which PEI was confined within the pore. Subsequently, mixed matrix composite membranes (MMCMs) were developed by the dispersion of polyvinylamine (PVAm) and P3.2@p-MMT, as well as hydrophilic-modified polysulfone as a support. It was observed that P3.2@p-MMT was uniformly dispersed in polymer matrix, and two phases had good interfacial compatibility due to hydrogen bonding. As a result, the gas separation performance of as-prepared MMCMs achieved a CO2 permeance of 217 GPU with a CO2/N2 selectivity of 112.3, which were 2.97 and 2.45 times that of the pristine PVAm membrane, and 1.57 and 2.49 times that of MMCMs incorporated with p-MMT respectively. The excellent gas separation performance is attributed to the relatively straight transport passageways, which originates from P3.2@p-MMT. Moreover, the amine groups within the pore of P3.2@p-MMT facilitate CO2 transport in the MMCMs. In addition, as-prepared MMCMs had high stability during over 360 h-testing, which displayed an average CO2 permeance of 238 GPU with the CO2/N2 selectivity of 124.1 utilized a gas mixture as the feed gas.

Amidation-Reaction Strategy Constructs Versatile Mixed Matrix Composite Membranes towards Efficient Volatile Organic Compounds Adsorption and CO2 Separation.

Mixed matrix composite membranes (MMCMs) have shown advantages in reducing VOCs and CO2 emissions. Suitable composite layer, substrate, and good compatibility between the filler and the matrix in the composite layer are critical issues in designing MMCMs. This work develops a high-performance UiO-66-NA@PDMS/MCE for VOCs adsorption and CO2 permea-selectivity, based on a simple and facile fabrication of composite layer using amidation-reaction approach on the substrate. The composite layer shows a continuous morphological appearance without interface voids. This outstanding compatibility interaction between UiO-66-NH2 and PDMS is confirmed by molecular simulations. The Si─O functional group and UiO-66-NH2 in the layer leads to improved VOCs adsorption via active sites, skeleton interaction, electrostatic interaction, and van der Waals force. The layer and ─CONH─ also facilitate CO2 transport. The MMCMs show strong four VOCs adsorption and high CO2 permeance of 276.5 GPU with a selectivity of 36.2. The existence of VOCs in UiO-66-NA@PDMS/MCE increases the polarity and fine-tunes the pore size of UiO-66-NH2, improving the affinity towards CO2 and thus promoting the permea-selectivity for CO2, which is further verified by GCMC and EMD methods. This work is expected to offer a facile composite layer manufacturing method for MMCMs with high VOC adsorption and CO2 permea-selectivity.

Mixed matrix composite membranes based on Pebax and nano-amorphous MIP-202 for CO2 separation

Membrane-based separation technology for carbon capture has received increasing attention in the world due to low energy consumption, investment and operating cost. However, the simultaneous improvement in selectivity and permeance has faced large challenge for mixed matrix membranes owing to limited affinity sites and transport channels. Herein, the nano-scale MIP-202 (SM-202) was first prepared by inhibited Ostwald ripening strategy during crystal growth, and then nano-scale amorphous MIP-202 (ASM-202) was prepared by thermal chemical reaction. Subsequently, mixed matrix composite membranes (MMCMs) were developed by using ASM-202 as a filler and polyether-block-amide (Pebax) as a polymer matrix, and the hydrophilicity-modified polysulfone ultrafiltration membrane (mPSf) was utilized as a porous support. It is observed that ASM-202 possessed good miscibility with Pebax polymer chains as a result of hydrogen bonds between two phases. Thus, the as-obtained MMCMs showed outstanding CO2 separation performance (CO2 permeance: 936 GPU; CO2/N2 selectivity: 52), which were enhanced by 138 % and 108 % over that of the pristine Pebax membrane, as well as 15.3 % and 13.0 % over that of MMCMs incorporating with SM-202, respectively. The improvement in gas separation performance can be explained by the reason that the nano-scale ASM-202 with large specific surface area afforded more unsaturated metal sites and nitrogen-doped structure, thus improving the CO2 affinity in membranes. Moreover, the loose amorphous structure of ASM-202 provides more transport passageways, which enhanced the diffusion rate of gas molecules through the membranes. Besides, resultant MMCMs maintained great stability for over 360 h using the CO2/N2 mixed gas as feed gas, whose average CO2 permeance and CO2/N2 selectivity fluctuated at 880 GPU and 47.

Pore-optimized MOF-808 made through a facile method using for fabrication of high-performance mixed matrix composite CO2 capture membranes

Mixed matrix composite membranes (MMCMs) are considered as one of the potential directions for the development of CO2 capture membranes. Nevertheless, the high cost and the challenging nature of improving separation performance are significant obstacles that prevent MMCMs from being widely applied in practice. In this study, we developed a cost-effective modified pore-optimized MOF-808 (MOF-808@PVAm) and utilized it to fabricate high-performance CO2 capture MMCMs. Specifically, MOF-808 and polyvinylamine (PVAm) were cross-linked by γ-(2,3-epoxypropoxy) propytrimethoxysilane (KH-560), which improved the pore structure characteristics of MOF-808 and led to high-performance MMCMs. For 2 bar feed gas (CO2/N2, 15/85), the MMCM with 33.33 wt.% MOF-808@PVAm loading displayed remarkable CO2 permeance of 2753 GPU and selectivity of 181. The prepared MMCM demonstrated good operational stability in simulated flue gas and exhibited potential for application in various gas purification fields (CO2/CH4, CO2/H2) through gas permeation tests.

Separating 2-phenylethanol from aqueous solution by mixed matrix composite membranes based on beta-cyclodextrin metal organic frameworks

Natural 2-phenylethanol (2-PE) is a spice with the rose-like fragrance and non-toxicity to human, whose classical separation technique from the plants has faced great challenge owing to high energy consumption, chemical engineering safety and environmental pollution issue. Herein, the mixed matrix composite membranes (MMCMs) for 2-PE pervaporation separation from aqueous solution were engineered by incorporating beta-cyclodextrin metal organic frameworks (β-CD-MOFs) with a large amount of hydroxyl groups and hydrophobic cavities into the polydimethylsiloxane (PDMS) matrix. The as-prepared MMCMs exhibited excellent 2-PE pervaporation separation performance with the permeation total flux, separation factor, and pervaporation separation index of 1186 g m−2 h−1, 21.3 and 24076 g m−2 h−1, respectively, which increased by 25.8 %, 129.0 % and 208.6 % compared with that of the pristine one, outperforming MMCMs embedding with other fillers, when 2-PE concentration in aqueous solution is 6000 ppm. This can be explained by the fact that the hydrogen bonding and hydrophobic interaction between β-CD-MOFs and 2-PE improves 2-PE dissolution in the membrane, thus enhancing the 2-PE solubility selectivity in MMCMs. Thus, MMCMs had specific recognition for 2-PE over a spice maltol, whose 2-PE flux and the 2-PE/water separation factor only reduced by 15.0 % and 37.6 % respectively, when maltol concentration increased to 2000 ppm in 6000 ppm of 2-PE aqueous solution. Besides, resultant MMCMs showed long-term stability for over 140 h with the average permeation total flux of 1317 g m−2 h−1 and the separation factor of 21.8.

Chitosan-based mixed matrix composite membranes for CO2/CH4 mixed gas separation. Experimental characterization and performance validation

Membrane technology is acknowledged as one of the most efficient for biogas upgrading, separating simultaneously CH4 and CO2 in the retentate and permeate streams, respectively. The sustainability would still be improved by using renewable and environmentally friendly materials for membrane fabrication. Specifically, this study is focused on laboratory-scale mixed gas separation tests of composite membranes prepared from chitosan (CS), a hydrophilic, biodegradable and biocompatible polymer from abundant natural resources, with good adhesive and film forming properties and high affinity for CO2 due to the primary amine and hydroxyl groups functionalities in CS. To improve mechanical resistance and CO2/CH4 separation, CS was hybridized by a 5 wt% loading of non-toxic ionic [emim][acetate] liquid (IL), and variable loadings of compatible inorganic fillers, such as 3D zeolite 4A and NaETS-10, and layered AM-4 titanosilicate. The CS-based mixed matrix layer was coated on porous polyether sulfone (PES) support. The CO2 permeance and CO2/CH4 separation were measured at different feed concentrations to evaluate the membranes performance in the treatment of different streams. This separation behavior was explained by the wet thickness, water uptake, morphology and ionic resistance of the composite membrane. As such, the 5 wt% Zeolite 4A and NaETS-10-filled ILCS/PES membranes provided a good dispersion in the ILCS matrix and the mixed matrix layer a good adhesion with the porous PES support, leading to high CO2 permeances and separation factors up to 30, whereas the more hydrophilic lamellar AM-4 titanosilicate-filled ILCS layer showed cluster agglomeration in the matrix and a faster detachment of the coated layer from the PES substrate. With increasing filler loading, an increase of the permeance of both CO2 and CH4 gas components was, although selectivity decreased upon increasing AM-4 filler loading. The CO2/CH4 mixed gas separation performance was validated by a custom-built model for a wide range of feed composition, to cover such processes as natural gas sweetening, biogas upgrading and enhanced oil recovery with acceptable relative error below 10% (absolute value), except for the AM-4 titanosilicate-filled ILCS membranes, showing morphological fabrication defects.

Boosting membranes for CO2 capture toward industrial decarbonization

Membrane technology for carbon capture is becoming increasingly attractive to combat the excessive greenhouse gas emitted into the atmosphere, which involves the benefits of cost-effectiveness, environmental-friendly, easy scalability, high energy efficiency, simplicity in design, etc. However, most state-of-the-art membrane materials suffer from either low CO2 permeability, low selectivity towards CO2 separation, poor resistance to plasticization, or inadequate long-term stability, rendering it still challenging to be upscaled to an industrial level. Therefore, the development of advanced membrane materials as well as a reasonable design of the membrane separation process is crucial and urgent for its real-life application in the future. This account reviews the details of some recent research progress in our group on carbon capture from different scenarios including post-combustion carbon capture, biogas upgrading and natural gas sweetening and hydrogen purification. Notably, considerable efforts have been invested in the development of some novel membrane materials in our group, such as facilitated transport membranes, carbon molecular sieving membranes, mixed matrix membranes, composite membranes, and poly(ionic liquids)-based membranes. Meanwhile, some studies focusing on the techno-economic feasibility analysis of membrane technology have also demonstrated its promising application on practical carbon capture.

Mixed-matrix ZIF-loaded membranes for effective separation of bio-butanol from fermentation broth

Mixed matrix composite membranes offer superior performance for separation of alcohols from fermentation broth. In this study bio-butanol (Butanol) is recovered from Acetone: Butanol: Ethanol (ABE) fermentation broth using ZIF-71 -PDMS-PVDF membranes. The significance of this work is the supported PVDF layer that was prepared using a dual coagulation bath to increase the surface roughness and contact angle. The addition of hydrophobic ZIF-71 particles into the matrix increases their thermal stability, hydrophobicity, and strength of the membrane. The synthesized membranes exhibited higher hydrophobic characteristic with a contact angle of around 120°. The Pervaporation efficiency of these membranes was analyzed by various experimental parameters such as ZIF loading, permeate pressure, feed temperature, and stirring speed. The membrane interaction parameters were calculated using Flory Huggins and Flory-Rehner equations. The membrane performance was also assessed by Maxwell-Stefan model fitting along with the evaluation of the friction coefficient. The butanol flux (50 g/m2h) was estimated using mathematical modeling and compared with the experimental results (120 g/m2h). The studies inferred that the models are well-fitted for butanol extraction which implies the penetrant-penetrant interaction is lower than penetrant-membrane interactions. A comparison of the present study with literature is well-defined to scale-up the process at an industrial level.

Improving CO2 separation performance of PVAm membrane by the addition of polyethylenimine-functionalized halloysite nanotubes

Mixed matrix composite membranes (MMCMs) integrate the merits of inorganic and organic materials, but the tortuous transport passageways bring about large transfer mass resistance for gas transport. Herein, we prepared polyethylenimine-functionalized halloysite nanotubes (PEI-HNTs) by the electrostatic self-assembly of positively charged polyethylenimine and negatively charged halloysite nanotubes. Blending as-obtained PEI-HNTs with polyvinylamine (PVAm), MMCMs were prepared by casting above mixed solution on the top of ultrafiltration polysulfone (PSf) support. PEI-HNTs had good miscibility with PVAm due to hydrogen bonding. MMCMs (1 wt% PEI-HNTs loading) exhibited exceptional separation performance (CO2 permeance: 179 GPU; CO2/N2 selectivity: 127.9), respectively, which were 1.4 and 2.3 times that of MMCMs embedding with 1 wt% HNTs. Noticeably, its value was beyond those of MMCMs incorporating with reported hollow tubular filler as well as other shape filler. This is due to the fact that PEI on the surfaces of HNTs provides a lot of amine carriers, which facilitate CO2 transport. More importantly, the transport passageways are continuous, thus presumably reducing the CO2 transfer resistance compared to other shape inorganic material filled-MMMs. Besides, resultant MMCMs revealed desirable stability for over 360 h, with a CO2/N2 mixture as feed gas. Remarkably, it maintained superior gas separation performance (CO2 permeance of 126 GPU; CO2/N2 selectivity of 88.6) under the acidic conditions.

Mixed matrix composite membranes with MOF-protruding structure for efficient CO2 separation

Mixed matrix composite membranes (MMCMs) hold great potential to realize efficient CO2 removal from natural gas. However, the reduction of separation performance arising from the interfacial defects, significant plasticization and aging effect in the thin films severely limit their application. Herein, we fabricated a series of polyimide MMCMs with MOF-protruding structure wherein amino-functionalized ZIF-8 nanocrystals nearly penetrate the thin selective layer. Through engineering the interfacial interactions, e.g., covalent or hydrogen bondings, we successfully fabricated defect-free MMCMs with the thickness ranging from 140 to 280 nm. The stronger interfacial interactions eliminate the interfacial defects and restrict the mobility of polymer chains under high pressure. Accordingly, the MMCM displays a high CO2 permeance of 778 GPU and a CO2/CH4 selectivity of 34 with significantly improved resistance to plasticization and aging. Considering the superior performance, we anticipate our work could provide guidelines on designing advanced MMMs to tackle critical separations.

Aminosilane-Functionalized Zeolite Y in Pebax Mixed Matrix Hollow Fiber Membranes for CO2/CH4 Separation

Due to their interfacial defects between inorganic fillers and polymer matrices, research into mixed matrix membranes (MMMs) is challenging. In the application of CO2 separation, these defects can potentially jeopardize the performance of membranes. In this study, aminosilane functionalization is employed to improve the nano-sized zeolite Y (ZeY) particle dispersion and adhesion in polyether block amide (Pebax). The performance of CO2/CH4 separation of Pebax mixed matrix composite hollow fiber membranes, incorporated with ZeY and aminosilane-modified zeolite Y (Mo-ZeY), is investigated. The addition of the zeolite filler at a small loading at 5 wt.% has a positive impact on both gas permeability and separation factor. Due to the CO2-facilitated transport effect, the performance of MMMs is further improved by the amino-functional groups modified on the ZeY. When 5 wt.% of Mo-ZeY is incorporated, the gas permeability and CO2/CH4 separation factor of the Pebax membrane are enhanced by over 100% and 35%, respectively.

Mixed matrix composite PEM with super proton conductivity developed from ionic liquid modified silica nanoparticle and polybenzimidazole

Phosphoric acid (PA) leaching, low proton conductivity and weak mechanical strength of the polybenzimidazole (PBI) membrane need to be improved considerably for the development of proton exchange membrane (PEM). We have addressed these issues by preparing a mixed matrix composite (MMC) membrane comprising of oxy-polybenzimidazole (OPBI) and imidazole ionic liquid modified silica (ImILSi). Imidazolium based ionic liquid was synthesized and grafted to the surface of the silica nanoparticles (SiNP) to obtain ImILSi which further blended with OPBI to obtain OPBI@ImILSi. The uniform dispersion nature of the ImILSi in the OPBI matrix and the strong H-bonded interfacial interactions between nanofillers and polymers are found to be primary reason for significant improvement of various physical properties of the MMC. TGA, DMA and stress-strain studies exhibited significant enhancement in the thermal and mechanical properties of the MMC membranes. Most importantly, due to the loading of hydrophilic ImILSi, the MMC membranes resulted higher PA loading (∼3-fold increase) which enabled the formation of facial proton transport nanochannels for their superior proton conduction under anhydrous environment and elevated temperature. For example, the OPBI@ImILSi-3% membrane showed proton conductivity value of 0.219 S cm−1 at 160 °C which is a ∼4-fold increase compared to OPBI membrane.

Relationship between wet coating thickness and nanoparticle loadings based on the performance of mixed matrix composite membranes

Wet coating thickness and nanoparticle loadings are two important parameters that greatly impact the performance of mixed matrix composite membranes (MMCMs). In this work, two kinds of MMCMs, with Pebax as the continuous phase polymer and MIL-101(Cr) and UiO-66(Zr) as the dispersed phase porous materials respectively, were fabricated to explore the internal relationship between the two parameters. The change of membrane performance via adjusting wet coating thickness and nanoparticle loadings is discussed through pure gas and mixed gas tests and shown by contour data analysis. Generally, the wet coating thickness is significant to keep the membrane densification and nanoparticle loadings to increase the permselectivity to some degree. In addition, the nanoparticle size shows great impact on membrane performance due to the small-size nanoparticles with huge surface energy. At last, this work verifies that reinforcing the interaction between nanoparticles and polymer matrix is beneficial to improve the membrane performance.

ZIF-8@NENP-NH2 embedded mixed matrix composite membranes utilized as CO2 capture

Mixed matrix composite membranes (MMCMs) for CO2 capture have great potential in carbon neutral goal. However, simultaneous enhancement in permeance and selectivity is very difficult, since mismatching pore and chemical structures of filler with polymer matrix are the stumbling block. Herein, novel core–shell MOFs@COFs hybrids were prepared by growing hierarchical pore covalent organic frameworks (COFs, nitrogen-enriched nanoporous polytriazine (NENP)) on the surface of metal organic framework (MOFs, zeolite imidazolate framework-8 (ZIF-8)), where ethylenediamine were impregnated into NENP pore to adjust the chemistry environment of the shell. Subsequently, a porous polysulfone (PSf) membrane-supported MMCMs were developed by a coating method using a mixed dispersion of ZIF-8@NENP-NH2 and polyvinylamine (PVAm), which was used to efficiently separate CO2 from N2. The rough COFs layer (NENP-NH2) was closely wrapped on the smooth surface of ZIF-8 as identified by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and N2 adsorption. Even-distributed ZIF-8@NENP-NH2 had well miscibility with the PVAm matrix from hydrogen bonding as evidenced by SEM, attenuated total reflectance-FTIR and differential scanning calorimetry. The CO2 permeance as high as 301 GPU accompanied with a selectivity of 91 was obtained for MMCMs loaded with 7 wt% ZIF-8@NENP-NH2, which were enhanced by 296.1% and 89.6%, respectively, when compared with the pristine PVAm membrane, transcending 2019 upper bound. We assume that the surface chemistry environment in hierarchical pore of the shell and molecular sieving pore in the core in the short-range order facilitate CO2 permeation. Furthermore, this membrane maintained an average CO2 permeance of 369 GPU and a CO2/N2 selectivity of 97.3 for over 360 h using CO2/N2 mixed gas as feed gas.

The influence of intermediate layer and graphene oxide modification on the CO2 capture efficiency of Pebax-GO/PDMS/PSf mixed matrix composite membranes

Background: Greenhouse gasses are still a global concern where minimization of or controlling its emission should be prioritized. This could be efficiently resolved through membrane separation technology.Methods: Herein, a mixed matrix composite membrane made from poly(dimethylsiloxane) (PDMS), Pebax® MH1657 (Pebax), and 3-(Aminopropyl)triethoxysilane (APTES)-modified graphene oxide on a polysulfone (PSf) substrate was prepared. The hydrophilicity of PDMS intermediate layer was improved by UV/O3 treatment. While the concentrations of Pebax and APTES-GO loading were varied to observe the combined effects of active and intermediate layers on CO2 capture.Significant findings: The membrane with 1 wt% GO loading had the optimal gas separation performance with a CO2 permeability of 54.5 GPU and a CO2/N2 selectivity of 36.9 at 35 °C and 0.1 MPa. The separation was further improved with APTES-functionalized GO (aGO). The mixed matrix composite membrane with 1 wt% aGO loading augmented the CO2 permeance to 208.9 GPU with a CO2/N2 selectivity of 40 at 35 °C and 0.7 MPa. The amine groups augmented the CO2 adsorption and selectivity and provided enhanced membrane stability that can also be operated at higher pressure. This study provides an understanding on the function of each layer on a gas separation mixed matrix composite membrane.

Enhanced n‐butanol permselective vapor permeation by incorporating ZIF‐8 into a polydimethylsiloxane composite membrane: Effect of filler loading contents

AbstractFabricating high‐performance mixed matrix composite membranes (MMMs) based on the integration of metal‐organic frameworks (MOFs) and hydrophobic polymer matrix are highly sought for the industrial development of vapor permeation (VP) technology. In this work, ZIF‐8@polydimethylsiloxane/polyvinylidene fluoride (ZIF‐8@PDMS/PVDF) MMMs with various ZIF‐8 nanofiller loading contents were prepared via a simple “prime” blending method. The dispersion and agglomeration of ZIF‐8 nanoparticles on both surface and cross‐section of these membranes were characterized by scanning electron microscopy (SEM) and energy‐dispersive X‐ray spectroscopy (EDS), respectively. The hydrophobicity of as‐obtained MMMs was investigated by water contact angle and swelling degree tests. Furthermore, VP experiments were carried out to evaluate the perm‐selection performance of the ZIF‐8@PDMS/PVDF MMMs for the butanol/water mixture separation. Compared to the conventional PDMS membrane, the separation factor and total flux of MMM with ZIF‐8 loading content of 20 wt% increased by 70 % and 23 %, respectively. The mechanism of mass transfer of butanol and water molecules inside the MMMs was also discussed.

Ultrathin, Highly Permeable Graphene Oxide/Zeolitic Imidazole Framework Polymeric Mixed-Matrix Composite Membranes: Engineering the CO2-Philic Pathway

High-performance, thin-film mixed-matrix membranes (MMMs) on a porous support have been developed, using zeolitic imidazole framework (ZIF) decorated graphene oxide (GO) as a filler, dispersed in a...

Improving gas permeation performance of PDMS by incorporating hollow polyimide nanoparticles with microporous shells and preparing defect-free composite membranes for gas separation

Recently, various types of hollow materials have been added into polymer matrices to improve the gas permeation and separation performance of polymer materials. In this study, hollow polyimide (PI) nanoparticles with microporous shells were synthesized by interfacial polymerization between 4,4-(9-fluorenylidene)-dianiline and 1,2,4,5-benzenetetracarbonyl tetrachloride in the microemulsion. Free-standing polydimethylsiloxane (PDMS)/hollow PI nanoparticles mixed matrix membranes were prepared and the gas permeation-separation performance was investigated. The hollow and porous structure of the nanoparticles was well-preserved in membranes, which reduced the mass transport resistance. The permeability firstly increased and then decreased as the nanoparticle loading increased without sacrificing the permselectivity. Compared to the neat PMDS membranes with O2 and CO2 permeability of 786 and 3484 Barrer, respectively, the mixed matrix membranes with 3 wt% hollow PI nanoparticles achieved a O2 permeability up to 1664 Barrer accompanied with an O2/N2 permselectivity of 2.3 and a CO2 permeability up to 6639 Barrer accompanied with a CO2/N2 permselectivity of 9.1 at 35 °C and 0.2 MPa. Mixed-matrix composite membranes were fabricated by dip-coating the porous polyetherimide substrate into a PDMS solution with 3 wt% nanoparticles. The resultant defect-free mixed-matrix composite membrane showed excellent O2 and CO2 permeances of up to 1677 and 6502 GPU, respectively. The air separation measurement showed that the composite membranes could produce oxygen-enriched permeate stream enriched to ca. 30 vol%.

Polyvinylamine/ZIF-8-decorated metakaolin composite membranes for CO2/N2 separation

• ZIF-8-d-MK hybrid with the interlayer spaces was developed by coordinating ZIF-8 particles to amorphous MK sheets. • PVAm/ZIF-8-d-MK MMCMs for CO 2 /N 2 separation were successfully fabricated. • The interlayer spaces of ZIF-8-d-MK in the MMCMs function as CO 2 transport pathways. • The ZIF-8-d-MK hybrid was homogenously dispersed in PVAm matrix due to amorphous structure of MK sheets. Mixed-matrix composite membranes (MMCMs) have great potential in chemical separation process due to high performance, but the dispersibility of the filler is an enormous challenge we face. In this study, a ZIF-8-decorated metakaolin (ZIF-8-d-MK) hybrid was prepared by the AlO 4 tetrahedron oxygens in amorphous MK coordinating with the zinc ions of ZIF-8. MMCMs by coating polysulfone (PSf) ultrafiltration membranes with a mixture of hybrid and polyvinylamine (PVAm) were obtained, which can efficiently separate CO 2 from N 2 . SEM and TEM results indicated that ZIF-8 particles were present between the amorphous MK sheets, and the coordination between the two phases was validated by FTIR. ZIF-8-d-MK, with a partially amorphous structure, exhibited homogeneous distribution in the PVAm matrix, as verified by SEM and XRD, and ZIF-8-d-MK had a strong interaction with the polymer matrix as certified by attenuated total reflectance-FTIR. A highest CO 2 permeance of 169 GPU with CO 2 /N 2 selectivity of 86.7 were acquired for MMCMs, loaded with 3 wt% ZIF-8-d-MK under pure gas conditions, which were much higher than those of MMCMs loaded with MK, ZIF-8, or a mixture of MK and ZIF-8. The improved values were primarily ascribed to the well-dispersed ZIF-8-d-MK serving as CO 2 transport pathways because of its molecular sieving effect for CO 2 /N 2 . Importantly, under mixed gas feed conditions, the stability measurement demonstrated that the MMCMs adding 3 wt% ZIF-8-d-MK did long-term operation for over 360 h, and maintained great CO 2 separation performance.

Mixed matrix composite membranes based on amination of reduced graphene oxide for CO2 separation: Effects of heating time and nanofiller loading

The CO2 gas separation performance of aminated reduced graphene oxide (A-rGO) incorporated PEBAX mixed matrix composite membranes, by means of amination heating time and A-rGO loading, is reported. The 5 h of heating time resulted in an essential molecular sieving property for CO2 separation, thus used in membrane fabrication. The selective PEBAX/A-rGO5 layers were fabricated on top of the polysulfone supporting layer by a dip-coating method. The A-rGO was well-dispersed, the selective and support layers were seamlessly attached. The CO2 permeability and CO2/N2 selectivity of the PEBAX/A-rGO5 was greater than that of pristine PEBAX. 3 wt% of A-rGO5 loading resulted as the optimum since the gas selectivity decreased at higher loading. The PEBAX/A-rGO5 performance, which was slightly above the Robeson 2008 upper bound of permeability-selectivity relation for CO2/N2 gas separation, shows a promising application for industrial CO2 gas separation process.