High-performance Composite Membranes Research Articles

Flexible Piezoelectric Sensor Based on Two-Dimensional Topological Network of PVDF/DA Composite Nanofiber Membrane

AbstractOwing to the robust scalability, ease of control and substantial industrial applications, the utilization of electrospinning technology to produce piezoelectric nanofiber materials demonstrates a significant potential in the development of wearable products including flexible wearable sensors. However, it is unfortunate that the attainment of high-performance piezoelectric materials through this method remains a challenging task. Herein, a high-performance composite nanofiber membrane with a coherent and uniformly dispersed two-dimensional network topology composed of polyvinylidene fluoride (PVDF)/dopamine (DA) nanofiber membranes and ultrafine PVDF/DA nanofibers was successfully fabricated by the electrospinning technique. Based on the evidence obtained from simulations, experimental and theoretical results, it was confirmed that the unique structure of the nanofiber membrane significantly enhances the piezoelectric performance. The present PVDF/DA composite nanofibers demonstrated a remarkable piezoelectric performance such as a wide response range (1.5–40 N), high sensitivity to weak forces (0–4 N, 7.29 V N−1), and outstanding operational durability. Furthermore, the potential application of the present PVDF/DA membrane as a flexible wearable sensor for monitoring human motion and subtle physiological signals has also been validated. This work not only introduces a novel strategy for the application of electrospun nanofibers in sensors but also provides new insights into high-performance piezoelectric materials. Graphical Abstract

Construction of TiO2-ZrO2 composite nanofiltration membranes for efficient selective separation of dyes and salts

The ceramic nanofiltration (NF) membrane exhibits excellent potential for textile wastewater treatment due to its efficient selective separation of dyes and salts. In this study, a high-performance TiO2-ZrO2 composite nanofiltration membrane was fabricated via a sol–gel method. Stable sols with an average particle size of approximately 2 nm were obtained. The addition of TiO2 effectively inhibits the phase transformation of ZrO2 during heat treatment, thus improving the integrity and ensuring separation accuracy of the membrane. Moreover, an optimal balance between membrane integrity and thickness was achieved, promoting efficient selectivity towards dyes and salts. The optimized NF membrane exhibited a MWCO of 1 kDa, a membrane thickness of 100 nm, and pure water permeance of 44 L∙m−2∙h−1∙bar−1. Additionally, the NF membrane demonstrated exceptional performance in dye/salt separation as evidenced by rejection rates exceeding 97.71 % for Reactive Blue 19 while maintaining rejections below 5 % for NaCl/Na2SO4 solutions. A stable permeance of 21.65 L∙m−2∙h−1∙bar−1 was achieved during the separation process. In conclusion, this study presents a high-performance ceramic NF membrane which exhibits significant potential for treating dye/salt containing wastewater.

Construction of PDMS@ZIF-8 composite membrane on PVDF hollow fiber inner surface for ultrafast ethanol/water separation

Construction of ultra-thin and defect-free separation membrane on inner surface of hollow fiber supports is significant but challenging for molecular separation. In this study, the highly permeable PDMS@ZIF-8/PVDF composite membranes were successfully fabricated upon the inner-surface of polyvinylidene fluoride (PVDF) hollow fiber membrane for pervaporation (PV) ethanol/water separation. The efficient preparation of hierarchical PDMS@ZIF-8/PVDF composite membranes benefited from the precise regulation of ZIF-8 layer through interfacial synthesis and sequential coating of PDMS matrix. The thickness of the PDMS layer was only 16±2 nm, which admirably eliminated the non-selective defects in ZIF-8 layer. Owning to the optimal combination of MOF layer and ultra-thin polymer layer, the as-prepared membrane exhibited the excellent ethanol flux of 1.34 kg m-2 h-1 with an ethanol concentration in permeate of 31.3 wt.% for separating 5 wt.% ethanol aqueous solution at 40°C. The separation performance of the resultant membrane was superior to that of the other ethanol selective PV membranes. These findings herein provided a new way for preparing high-performance hollow fiber composite membranes for PV separation.

High-performance SPEEK composite membrane with ultrahigh selectivity enabled by sulfonated PANI for vanadium flow battery

The sulfonated poly(ether ether ketone) (SPEEK) composite membranes (S/SPANI) are prepared by blending sulfonated polyaniline (SPANI), which was synthesized through a post-sulfonation method. With the SPANI contents varying from 1 to 4 wt%, the S/SPANI membranes exhibit excellent physicochemical properties and cell performance, and at loading 3 wt% SPANI, S/SPANI-3 presents a higher proton conductivity (43.3 mS cm−1) and superior ion selectivity (49 × 103 S min cm−3) against SPEEK and Nafion 212. Moreover, its outstanding coulombic efficiency (95.9–98.4%) and energy efficiency (EE: 80.4–70.2%) at the current density of 100–200 mA cm−2 demonstrate an optimized tradeoff of proton conductivity and vanadium ion permeability. The performance optimization guarantees enhanced durability for 600 cycles and stable EE (76%) at 150 mA cm−2, which originated from the acid-base interaction, synergistic proton network, and interconnected chain structure. So, this provides a facile method to develop high-performance membranes by introducing desirable controllable topological molecular chains to construct synergistic proton transportation networks.

Construction of a high-performance hollow fiber composite NF membrane via the simultaneous modification of substrate and selective layer

Hollow fiber composite (HFC) nanofiltration (NF) membrane demonstrates significant commercial potential profiting from its self-supporting characteristic, high packing density and strong fouling resistance. In this work, a high-performance HFC NF membrane was successfully developed through simultaneous modification of the substrate via alkaline hydrolysis and incorporation of iopamidol (IPD) into the selective layer. Alkaline hydrolysis enhanced the hydrophilicity of the polyacrylonitrile (PAN) substrate by converting –CN groups into –COOH, thereby sharply improving the success rate of HFC NF membrane fabrication. The addition of IPD into piperazine (PIP) solution effectively increased the water permeability of the HFC NF membrane without compromising its salt rejection. Specifically, the optimized membrane sample denoted as NF-0.15P + 0.5I with 0.5 w/v% IPD added demonstrated a 44 % increase in PWP from 21.8 L·m−2·h−1·bar−1 to 31.5 L·m−2·h−1·bar−1, while maintaining a Na2SO4 rejection over 96.8 %. This improvement can be attributed to the decreased selective layer thickness and reduced MWCO. Furthermore, the membrane exhibited exceptional dye/salt separation performance. This work represents a novel approach leading to the development of a HFC NF membrane suitable for dye/salt separation.

Synergistic Effect of Ti3C2Tx MXene Nanosheets and Tannic Acid-Fe3+ Network in Constructing High-Performance Hydrogel Composite Membrane for Photothermal Membrane Distillation.

Photothermal membrane distillation (PMD) has emerged as a promising and sustainable approach for seawater desalination and wastewater purification. However, the wide application of the technique is severely impeded by low freshwater production and membrane fouling/wetting issues. Herein, we developed an advanced hydrogel-engineered membrane with simultaneously enhanced photothermal conversion capacity and desired fouling and wetting resistance for PMD. By the synergies of photothermal Ti3C2Tx MXene nanosheets and the tannic acid-Fe3+ network in the hydrogel, the membrane was endowed with excellent surface self-heating ability, yielding the highest freshwater production rate (1.71 kg m-2 h-1) and photothermal efficiency among the fabricated hydrogel composite membranes under 1 sun irradiation. Meanwhile, the PMD membrane could robustly resist oil-induced fouling and surfactant-induced wetting, significantly extending the membrane lifespan in treating contaminated saline water. Furthermore, when desalinating real seawater, the membrane exhibited superior durability with a stable vapor flux and excellent ion rejection (e.g., 99.24% for boron) for 100 h.

LEGO® brick-inspired ultra-stable and rapid transport 2D membrane for fast water purification

Inspired by the modular homogenization and interlocking structure concepts of LEGO® bricks, we developed high-performance graphene oxide composite nanofiltration membranes using the subject–object recognition effect.

A nanocrystal garnet skeleton-derived high-performance composite solid-state electrolyte membrane

Composite solid-state electrolytes (SSEs) can improve the flexibility of the oxide SSEs to decrease the interfacial resistance between the electrolytes and the electrodes. However, the ceramic nanofillers within the composite SSEs suffer from the agglomeration at high concentrations, decreasing the ion conductivities. In this study, a continuous nanocrystal Li6.5La3Zr1.5Ta0.5O12 (LLZTO) skeleton is prepared by the ultrafast high-temperature sintering (UHS) together with tape-casting. Due to the short sintering time of ∼5 s from precursors, the LLZTO grains are restrained to ∼300 nm with limited Li loss. Even with trace solvent (3 wt%), the composite SSE membrane exhibits an ion conductivity of 5 × 10−4 S⋅cm−1, ∼50 times higher than the DOL electrolyte (1 × 10−5 S⋅cm−1, 8 wt% solvent), which further proves the high Li-ion conductivity of the nanocrystal LLZTO skeleton. The composite SSE membrane exhibits a critical current density of 3.4 mA⋅cm−2, among the highest reported values for ceramic-polymer SSEs. The Li/composite SSEs/Li symmetric cells can cycle ∼ 120 h at the current density from 0.2 to 0.4 mA⋅cm−2. The LiFePO4/LLZTO-PEGDA composite SSEs/Li full cell exhibits a high specific discharge capacity of ∼150 mAh⋅g−1 for ∼50 cycles with a Coulombic efficiency of ∼97%. To explore the processability of the membrane with large size, we also demonstrate a pouch cell (2 cm × 5 cm) with a high specific capacity of ∼150 mAh⋅g−1 for ∼25 cycles and a capacity retention of ∼94.5%. This work paves a new way to manufacture the nanocrystal ceramic SSE skeleton for high energy density all-solid-state batteries.

Dual 2D nanosheets with tunable interlayer spacing enable high-performance self-cleaning thin-film composite membrane

Interlayered thin-film composite (TFC) membranes are promising in overcoming the permeability-selectivity tradeoff of conventional membranes. However, fabricating high-performance TFC membranes with tunable interlayer spacing and antifouling properties remains challenging. Here we develop a high-performance self-cleaning TFC graphene oxide (GO) membrane by employing multifunctional bismuthyl bromide (BiOBr) nanosheets to construct a unique photocatalytic GO@BiOBr interlayer. BiOBr has multiple functions, including regulating the GO nanosheet spacing (i.e., the channel size), mediating the surface properties of the interlayer to enable a desirable selective layer during interfacial polymerization, and imparting photocatalytic properties to the TFC membrane. Because of the dimensional difference between GO and BiOBr nanosheets, the spacing of the dual 2D nanosheets (GO and BiOBr) can be finely tailored by adjusting BiOBr loading. Coupling of the 2D nanosheets enables tunable interlayer properties and a highly thin and selective rejection layer, leading to significantly enhanced separation performance of the TFC membrane. The GO@BiOBr interlayered TFC membrane shows a water permeability of 29.9 L·m−2·h−1·bar−1, which is six times higher than the TFC membrane without an interlayer. The GO@BiOBr interlayered TFC membrane displays 100% rejections to various small molecules (e.g., Rhodamine B, Basic Blue 26 and Ofloxacin). The rise of BiOBr loading in the GO@BiOBr composite increases the interlayer spacing of the dual 2D nanosheets, likely leading to more monomer diffusion and eruptive interfacial polymerization. As a result, thicker and rougher polyamide layers are formed, resulting in decreased water permeability of the TFC membrane. This study presents a viable approach for engineering the next generation of high-performance self-cleaning TFC membranes for reverse osmosis, forward osmosis and nanofiltration within the realm of water treatment.

Flexible UiO-67(Zr)@cyclodextrin-based nanofiber membrane for efficient removal of ibuprofen

The efficient removal of pharmaceutical pollutants in groundwater has become an urgent issue in sewage treatment. β-cyclodextrin (β-CD), a polysaccharide and rich in raw materials, has broad applications in adsorption and separation due to its host–guest interaction with many molecules. In this paper, a flexible and water-insoluble UiO-67(Zr)-modified cyclodextrin-based nanofiber membrane (UiO-67@β-CD-NP) was synthesized via a combination of electrospinning and solvothermal methods. By virtue of the synergetic adsorption effect of cyclodextrin and MOFs, the UiO-67@β-CD-NP shows excellent performance for ibuprofen (IBP) removal. The adsorption of IBP onto UiO-67@β-CD-NP was well-fitted with the pseudo-second-order kinetic model and Freundlich isothermal model, yielding an adsorption capacity of 226.24 mg/g. Furthermore, the UiO-67@β-CD-NP nanofibers demonstrate a high removal rate of 100 % and exhibit good regenerability in dynamic adsorption experiments. After the filtration of UiO-67@β-CD-NP, the chemical oxygen demand (COD) concentration of IBP has evidently reduced below the discharge standard of pharmaceutical sewage. This study provides a simple and novel strategy for preparing low-cost and high-performance composite nanofiber membrane incorporating cyclodextrin and MOFs. This membrane holds great potential as a candidate for adsorption applications in practical pharmaceutical sewage treatment.

Large-scale preparation of UV photo-crosslinked composite membrane with high pervaporation desalination properties and excellent fouling resistance

In this study, we developed a high-performance composite membrane with rapid cross-linking and large-scale technology for PV desalination. Some strategies were adopted to achieve this purpose. First, photo cross-linking was used to shorten the cross-linking time of PVA within 60 s. Second, a PTFE microfiltration membrane was utilized as the substrate that mitigated the transport resistance of the supporting layer. Third, an large-scale spray-coating device was built-up which completed the amplification preparation of composite PV membrane. Finally, ZIF-8 nano-particle was introduced into the PVA layer that increased the free volume and amorphous region of PVA, enhancing the water flux of membrane. When desalted a 3.5 wt% NaCl solution at 80 °C, a water flux of 307.58 ± 15.09 kg/m2·h was achieved for the PVA/ZIF-8/PTFE composite membrane. To better reflect the membrane performance, the permeance of PVA/ZIF-8/PTFE membrane was also calculated, which was reached to 674.37 kg/m2 h bar, exceeding 18.4% than the highest reported property of PVA/PAN nanofiber membrane (569.55 kg/m2 h bar). In addition, the composite membrane showed stable water flux and salt rejection when treating highly concentrated brine solution containing organic pollutant. When desalinated a 10 wt% NaCl solution with 1 wt% HA at 80 °C, the PVA/ZIF-8/PTFE membrane produced water with low conductivity of 15.78 μs/cm and a high water flux of 129.95 kg/m2·h in a period of 180 min.

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.

A super liquid-repellent hierarchical porous membrane for enhanced membrane distillation

Membrane distillation (MD) is an emerging desalination technology that exploits phase change to separate water vapor from saline based on low-grade energy. As MD membranes come into contact with saline for days or weeks during desalination, membrane pores have to be sufficiently small (typically <0.2 µm) to avoid saline wetting into the membrane. However, in order to achieve high distillation flux, the pore size should be large enough to maximize transmembrane vapor transfer. These conflicting requirements of pore geometry pose a challenge to membrane design and currently hinder broader applications of MD. To address this fundamental challenge, we developed a super liquid-repellent membrane with hierarchical porous structures by coating a polysiloxane nanofilament network on a commercial micro-porous polyethersulfone membrane matrix. The fluorine-free nanofilament coating effectively prevents membrane wetting under high hydrostatic pressure (>11.5 bar) without compromising vapor transport. With large inner micro-porous structures, the nanofilament-coated membrane improves the distillation flux by up to 60% over the widely used commercially available membranes, while showing excellent salt rejection and operating stability. Our approach will allow the fabrication of high-performance composite membranes with multi-scale porous structures that have wide-ranging applications beyond desalination, such as in cleaning wastewater.

Hollow fiber PSF fine porous supports with ultrahigh permeance for composite membrane fabrication: Novel inert bore liquid (IBL) spinning technique

The development of high-performance thin-film composite (TFC) hollow fiber membranes coated on top of porous supports is a hot topic both in industry and in science. However, it has been documented in recent literature that a porous support can hinder mass transfer through a composite membrane. Taking this into account, ultra-high permeable polysulfone (PSF) hollow fiber supports with an outer porous skin layer suitable for the fabrication of composite membranes were developed in this work. To address this ambitious challenge, the concept of spinning with an inert bore liquid (IBL) using wet air gap conditions was developed and successfully implemented. While the external non-solvent (water) ensures the formation of a thin porous skin layer, the inert bore liquid makes it possible to implement two important conditions for the formation of macropores on the lumen side of the hollow fiber: i) the coagulant enters only from the outer side of the dope solution layer, ii) there is no noticeable transport of the dope solution components into the inert bore liquid and vice versa. The following alkanes were studied as the IBL: pentane, hexane, heptane, and iso-octane. For example, using hexane and heptane as the bore liquids, PSF hollow fiber supports with high values of CO2 gas permeance, namely 20400 and 36700 GPU, respectively, were achieved. These values are an order of magnitude larger than the permeance of similar PSF supports reported in the literature. The presence of macropores on the lumen side of these hollow fibers was demonstrated by scanning electron microscopy. Composite membranes with a selective layer of polydecylmethylsiloxane (PDecMS) were coated and the separation of an eight-component mixture of C1-C4 hydrocarbons in a hollow fiber module was studied. Using a modified resistance model, it was shown that the absence of a skin layer on the lumen side of the hollow fiber reduced the support resistance and increased the contribution of the PDecMS selective layer to the total resistance of the composite membrane (for N2 and CO2: from 11.3% to 21.2 % and from 13 % to 20.5 %, respectively).

Advanced composite membranes based on multifunctional fillers constructed by covalently linking phosphotungstic acid with mesoporous carbon nitride for high-performance and durable fuel cell under low humidity

Two-dimensional (2D) nanosheets possessing large specific surface area and high aspect ratio can serve as proton-conduction accelerators owing to their continuous proton transport feature. Herein, phosphotungstic acid (HPW) is chemically grafted to mesoporous carbon nitride nanosheets (CN) via a hydrothermal process to produce water-insoluble HPW/CN (PCN) nanofillers, and subsequently embedded into sulfonated poly(arylene ether sulfone) (SPAES) to develop a long-range proton transport channels for high-performance composite membranes. The loading of hydrophilic HPW enhances the dispersivity and compatibility with the SPAES polymer and improves the mechanical-dimensional-chemical stability of the composite membranes. The formed hydrogen-bonding networks and acid-base interactions between fillers and polymers could endow the SPAES/PCN membranes with favorable water-absorption ability and proton-conducting performance. Besides, the excellent interfacial interactions working as a “bridge” facilitates the formation of well-defined phase-separation structure and constructs long-range ionic/water channels at the SPAES-PCN interface. Moreover, the strong acidic HPW on surface and mesoporous structure of CN enhance effectively water-retention ability of the composite membranes, which is specially contribute to rapid proton transport at low humidity. The proton conductivity of the SPAES/PCN-7.5 membrane reaches up to 250 mS cm−1 at 90 °C, hydrous condition, and 46 mS cm−1 at 80 °C, 50 % RH, which are 42 % and 84 % higher than those of the control SPAES membrane, respectively. The SPAES/PCN-7.5 membrane achieves highest maximum power density of 404–824 mW cm−2 at 80 °C and 50%–100 % RH, exceeding that of the SPAES membrane (207–546 mW cm−2) and Nafion® 112 (359–723 mW cm−2). It still remains stable cell performance, as well as undergoes lower voltages loss and hydrogen permeation after the durability test (144 h, 80 °C/60 % RH). In addition, molecular dynamics simulation analysis is performed to offer new insight into elucidating the structure-property relationships of the composite membrane. These results indicate that the SPAES/PCN composite system is an advanced membrane for the practical applications of fuel cells.

Bioinspired MOF-Glucose-PDA composite membrane with high performance and antifouling ability based on three-dimensional modification for molecular separation

Membrane separation technology has been increasingly applied owing to its high efficiency and low energy consumption during resource treatment. However, the development of eco-friendly membranes with high performance and long-term sustainability remains a challenge. To address this issue, we designed a three-dimensional (3D)-modified biopolymer-based membrane using renewable glucose and a zirconium-based metal–organic framework (Zr-MOF) for molecules/ions separation. The Zr-MOF and basal membrane were polymerized at the interface using natural glucose molecules and dopamine as bridging agents to form a 3D-integrated Zr-MOF–Glucose–Polydopamine (Zr-MOF–GP) composite membrane, serving as a “green” separation layer. The developed separation layer emerged additional molecular transport channels, rapid adsorption, ultrafast penetration of the solution on the surface and inside the Zr-MOF–GP composite membrane, and high molecular retention while achieving ultrahigh permeability. Moreover, the Zr-MOF–GP composite membrane exhibited excellent structural and long-term application stability in complex systems owing to the new chemical bonds formed between glucose and Zr-MOF and polydopamine substrate (synergistic effect). The experimental results demonstrated that the designed membrane exhibits superior desalination properties (99.8% Na2SO4 retention while the water flux is 31.6 L/ m2∙h∙bar), good removal of heavy metal ions (69.4% for 2000 ppm Pb2+), and considerable organic solvent resistance (98.8% Rose Bengal retention while the N,N-dimethylformamide permeance is 15.6 L/ m2∙h∙bar), and excellent antifouling performance. This high-performance and environment-friendly biopolymer-based composite membrane will inspire the further the development of sustainable membrane-separation technologies.

Construction of high-performance thin-film composite membrane for CO2 separation via interface engineering

High-efficiency CO2 capture has become increasingly vital for alleviating the ongoing global temperature which leads to severe impacts on virtually every aspect of human life. Thin-film composite membranes (TFCM) have attracted growing attention for conducting CO2 capture, owning to their energy-efficient and environment-friendly merits. However, the nonideal interface between the gutter layer and the separation layer hampers the fabrication of defect-free and thin separation layer, which renders low separation performance. In this work, we developed a strategy, i.e., coupling the oxygen-plasma modification with spin-coating, for engineering the interface between the gutter layer and separation layer of TFCM. Leveraging this idea, the TFC membrane, consisting polydimethylsiloxane (PDMS) served as the gutter layer and poly (ether-block-amide) (PEBA) as the thin separation layer, was manufactured by conveniently spin-coating PEBA solution on the oxygen-plasma-treated PDMS layer. The optimized PEBA-based TFCM membrane realized superior separation performance, e.g., a CO2 permeance of 2011 GPU, a CO2/N2 selectivity of 24, and 100-hour stably running, which outperformed most of the reported PEBA-based TFCM. Thus, the interface engineering strategy proposed in this study opens a new door for rational fabrication of high-performance TFCM.

PPy-NTs/C/TiO2/poly(ether sulfone) porous composite membrane: Efficient ultrafiltration of Evans blue dye from industrial wastewater

Developing a high-performance composite membrane with excellent flexibility in dye filtration remains a big challenge. Polypyrrole nanotubes (PPy-NTs), polypyrrole nanotubes/C (PPy-NTs/C), and polypyrrole nanotubes/C/TiO2(PPy-NTs/C/TiO2) modified porous poly(ether sulfone), assigned as (PPy-NTs/PES; PPy-NTs/C/PES; PPy-NTs/C/TiO2/PES) membranes, are prepared and employed in ultrafiltration of Evans blue anionic dye (EB) from industrial and municipal wastewater. X-ray diffraction, Fourier transform infrared-attenuated total reflectance, and field emission scanning electron microscope were used to characterize the composite membranes. In the adsorption investigations, experiments were conducted under different factors, including temperature (25–45 °C), stirring time, solution pH (2–12), adsorbent dosage (1–5 g/L), and initial dye concentrations (10–50 mg/L), to establish the ideal conditions. According to the experiments, at pH = 7 and 25 °C, the elimination percentage of Evans blue (EB) anionic dye might reach up to 99 %. Additionally, many isotherm models, including Freundlich and Langmuir, were used. Based on the correlation coefficients, the Freundlish isotherm model was the most suitable model (R2 = 0.9974).

Appealing sheath-core spun high-performance composite carbon molecular sieve membranes.

Carbon molecular sieve (CMS) membranes are attractive candidates to meet requirements for challenging gas separations. The added ability to maintain such intrinsic properties in an asymmetric morphology with a structure that we term a "Pseudo Wheel+Hub & Spoke" asymmetric form offers new opportunities. For CMS membrane, specifically, the structure provides both selective layer support and low flow resistance even for high feed pressures and fluxes in CO2 removal from natural gas. This capability is unavailable to even rigid glassy polymers due to the much higher modulus of CMS materials. Combining precursor asymmetric hollow fiber formation and optimized pyrolysis creates a defect free CMS proof-of-concept membrane for this application. Facile formation of the sheath-core spun precursor with a 6FDA-DAM sheath and Matrimid® core also avoids the need to seal defects before or after the carbonization of the precursors. The composite CMS membrane shows CO2 /CH4 (50 : 50) mixed gas feed with an attractive CO2 /CH4 selectivity of 64.3 and CO2 permeance of 232 GPU at 35 °C. A key additional benefit of the approach is reduction in use of the more costly high performance 6FDA-DAM in a composite sheath-core CMS membrane with the "Pseudo Wheel+Hub & Spoke" structure.

Polymer-Infiltrated Metal–Organic Frameworks for Thin-Film Composite Mixed-Matrix Membranes with High Gas Separation Properties

Thin-film composite mixed-matrix membranes (TFC-MMMs) have potential applications in practical gas separation processes because of their high permeance (gas flux) and gas selectivity. In this study, we fabricated a high-performance TFC-MMM based on a rubbery comb copolymer, i.e., poly(2-[3-(2H-benzotriazol-2-yl)-4-hydroxyphenyl] ethyl methacrylate)-co-poly(oxyethylene methacrylate) (PBE), and metal-organic framework MOF-808 nanoparticles. The rubbery copolymer penetrates through the pores of MOF-808, thereby tuning the pore size. In addition, the rubbery copolymer forms a defect-free interfacial morphology with polymer-infiltrated MOF-808 nanoparticles. Consequently, TFC-MMMs (thickness = 350 nm) can be successfully prepared even with a high loading of MOF-808. As polymer-infiltrated MOF is incorporated into the polymer matrix, the PBE/MOF-808 membrane exhibits a significantly higher CO2 permeance (1069 GPU) and CO2/N2 selectivity (52.7) than that of the pristine PBE membrane (CO2 permeance = 431 GPU and CO2/N2 selectivity = 36.2). Therefore, the approach considered in this study is suitable for fabricating high-performance thin-film composite membranes via polymer infiltration into MOF pores.