High CO2 Permeability Research Articles

Biodegradable bio-film based on Rhizopus oryzae and metal–organic frameworks for fruit preservation and pesticide degradation

The spoilage of post-harvest fruits caused by physiological metabolic activities can affect people’s consumption. Therefore, the development of effective packaging material for fruits is beneficial in ensuring the quality of fruits and avoiding wastage. In this study, we developed a multifunctional and biodegradable fruit packaging material using Rhizopus oryzae for the first time. Ag@PCN-222 (Zn) was introduced into the mycelium to endow the bio-film with antibacterial properties and pesticide degradability. The bio-film had nearly 100% biodegradability only after one week. The bio-film exhibited excellent antioxidant properties, as well as effective antibacterial activity. The prepared bio-film maintained high CO2 permeability and low O2 permeability, which was beneficial for shelf-life extension of fruits. The result of pesticide degradation experiments showed that the Bio-Ag@Zn film could effectively degrade the organophosphorus pesticide methyl parathion and improve the safety of fruits. At the same time, experiments on fruit preservation demonstrated that composite biofilms effectively inhibit fruit decay and prolong shelf life. The experimental results indicated that the Bio-Ag@Zn film was expected to be a green and multifunctional fruit packaging material.

Novel polyethylene glycol methyl ether substituted polysiloxane membrane materials with high CO2 permeability and selectivity

Membrane gas separation is a promising technology for CO2 capture. However, one of the key challenges is the development of stable-in-time and highly permeable materials with increased CO2 permselectivity. In this study, two series of novel polysiloxanes with linear (methyl oligoethyleneglycol allyl ether (PEG8)) and branched (vinyl-bis- [methyltriethyleneglycol] (B-PEG4)) oxygen-containing side substituents were synthesized. By crosslinking PEG-substituted polymethylsiloxanes with polydimethylsiloxane (PDMS), a series of CO2-highly selective membrane materials with a PDMS content of 6.5–50 wt% was obtained for the first time. The effect of the side chain geometry on the sorption and transport properties of these membranes for different gases (N2, O2, CO2, CH4, C2H6) was evaluated. The specific interactions between the PEG substituents and CO2 that contribute to the enhanced selectivity of these materials were identified. The introduction of both linear and branched PEG substituents leads to in an increase in the selectivity of diffusion, solubility, and CO2/gas permeability, compared to PDMS.The CO2/N2 and CO2/CH4 permselectivities and diffusion selectivities are increases, as well as the permeability coefficients of the membrane materials for all gases are decreases, as the PDMS content reduces from 50 % to 6.5 % wt. Within the PDMS concentrations range between 6.5 and 12.5 % wt., there was a sharp increase in diffusion and permeability coefficients of membrane materials. For this polysiloxanes with linear PEG substituents, an unexpectedly high diffusion selectivity for CO2 was observed. Such value determined the maximum CO2 permselectivity among the polysiloxanes studied. The most promising membrane material from these series was identified as PEG8-substituted polysiloxane with 12.5 wt% PDMS. It has a CO2 permeability coefficient of 1300 Barrer, CO2/N2 selectivity of 37 and CO2/CH4 selectivity of 10.

Building ternary mixed matrix membranes with ionic liquid-functional COF fillers for efficient CO2 separation

Developing novel mixed matrix membranes (MMMs) with high CO2 permeability and selectivity, while overcoming the limitations of traditional MMMs, presents a significant challenge. Herein, we reported a simple and straightforward method to develop ternary mixed matrix membranes (TMMMs) featuring excellent matrix-filler compatibility for CO2 separation through the modification of the covalent organic framework (COF) using ionic liquid (IL) additives. A novel IL ([Bmim][Tf2N]) encapsulated COF filler (IL@TpTta-COF) was facilely prepared, and incorporated into the PIM-1 matrix to develop a series of TMMMs.The incorporation of ILs with high affinity towards CO2 within the TpTta-COF improves the molecular sieving effect of the functional filler, and helps to enhance polymer-filler interfacial compatibility, and mitigates particle agglomeration during the preparation of TMMMs. Notably, the resultant TMMMs demonstrate remarkable stability, and achieve an impressive CO2 permeability of 10,035 Barrer and an excellent selectivity of 30.2 for CO2/N2 mixtures, exceeding the Robeson upper bound in 2019. This research underscores the potential of integrating functional additives to produce novel COF-based MMMs with enhanced CO2 separation efficiency for industrial applications.

Thin Film Composite Mixed-Matrix Membranes Based on Matrimid and Zeolitic Imidazolate Frameworks for CO2/N2 Separation Performance.

Membrane-based gas separation processes are a technology in continuous evolution. Various types of polymer membranes have been developed, many exhibiting high CO2 permeability and selective properties over competing gases such as N2 and CH4. In order to be competitive, membranes must be less-expensive, more stable, and more efficient, and their production must be scalable. One solution is to develop thin-film composites with mixed-matrix membranes (TFC_MMM) that have the potential to boost productivity while maintaining low costs. In this work, TFC_MMMs containing Matrimid mixed with 12 wt % ZIF-94 were prepared by kiss coating on a porous support. The SEM analysis showed that defect-free membranes with a 3 μm selective layer have been obtained. At 1 bar, the addition of ZIF resulted in improved the separation performance for the CO2/N2 pair, with CO2 permeance of 4 GPU and CO2/N2 selectivity of 40, surpassing neat TFC-Matrimid (CO2 permeance ≈ 3 GPU, CO2/N2 selectivity ≈ 29). The use of ZIF-94 also had a stabilizing effect on the membranes against CO2 plasticization at high pressure.

PIM-1 based mixed matrix membranes with MOF-808(Ce) for CO2 separations

Metal-organic frameworks (MOFs) have shown potential as nanofillers for the selective capture of specific gases in mixed matrix membranes (MMMs). This study introduces an efficient method, utilizing a mild (100 °C) reaction condition and a short reaction time (20 min), for the synthesis of MOF-808(Ce) nanocrystals. The MOF-808(Ce) that is obtained exhibits porous characteristics, a notable affinity for CO2, and robust intermolecular interactions with PIM-1. Furthermore, this study pioneers the incorporation of MOF-808(Ce) as a filler into PIM-1, with varying loadings, to create PIM/MOF-808 MMMs for the purpose of CO2 separation. Consequently, the MMMs containing 2 wt% MOF-808(Ce) demonstrate high CO2 permeability of 6854 Barrer and CO2/N2 selectivity of 23.2, which is far surpasses 2008 upper bound from Robeson and approaches the refined 2019 upper bound from MeKenow. A comparative analysis demonstrates the efficacy of MOF-808(Ce) as a filler in PIM-1 for the purpose of CO2 separation.

CO2-selective membrane reactor process for water-gas-shift reaction with CO2 capture in a coal-based IGCC power plant

Integrated gasification combined cycle (IGCC) power plants enable pre-combustion carbon capture to reduce CO2 emissions. Membrane water-gas-shift (WGS) reactors can intensify these processes by converting raw syngas to H2 with simultaneous CO2 capture in one unit. This paper reports process design and techno-economic analysis (TEA) for a membrane reactor (MR) process with a CO2 selective ceramic-carbonate dual-phase (CCDP) membrane for WGS reaction with CO2 capture for a IGCC power plant. The target performance includes CO conversion > 95 %, hydrogen purity > 90 %, CO2 purity > 95 %, and carbon capture > 90 %. Using a commercial catalyst and a CCDP membrane, the MR can achieve the performance target at 750 °C and space velocity of 250 h−1. The outcome of the process design and TEA shows that the CCDP MR has an operating cost of $24 M/year, significantly lower than that for the conventional processes (40 M$/year). However, the MR process has a higher capital cost ($1007 M) than the conventional process ($527 M) because of the higher cost of the CCDP MRs. Modeling analysis shows a MR with higher CO2 permeance can deliver the target at a higher space velocity and lower membrane surface area to catalyst volume ratio, leading to a significantly reduced MR capital costs.

Investigation of mixed matrix membranes of graphene and acid‐treated graphene fillers in cellulose acetate and polyetherimide polymers for CO2 separation from biogas

AbstractGas separation membranes are crucial for upgrading biogas by separating carbon dioxide (CO2) from biogas, thereby enhancing its calorific value and reducing greenhouse gas emissions. This study aims to improve CO2/CH4 separation using mixed‐matrix membranes (MMMs) by incorporating graphene (Gr) and acid‐treated graphene (AGr) fillers in a cellulose acetate (CA) polymer matrix. Similarly, polyetherimide (PEI) MMMs were also prepared with Gr and AGr fillers to draw a comparison. Various characterization techniques, including Fourier transform infrared spectroscopy, differential scanning calorimetry, field emission scanning electron microscopy, Raman spectroscopy, and X‐ray diffraction, were employed to investigate the structural and morphological properties of the membranes and fillers. Gas permeation tests using a model biogas mixture (40% CO2 and 60% CH4) revealed that the 0.1%AGr/CA membrane achieved the highest CO2 permeability of 43 Barrers, which is approximately 307% more than that of the pure CA membrane, and showed a CO2/CH4 selectivity of 14.80. The 0.5%Gr/PEI membrane demonstrated the best performance among PEI‐based MMMs, with a CO2 permeability of 17.48 Barrers and a CO2/CH4 selectivity of 8.96. These results indicate that the incorporation of Gr and AGr significantly enhances the gas separation performance over pure CA and PEI membranes.Highlights Graphene (G) and acid‐treated Gr‐based cellulose acetate (CA) and polyetherimide (PEI) mixed‐matrix membranes (MMMs) were fabricated. Model biogas was used for testing CO2 and CH4 gas permeation. The 0.1% AGr/CA MMM showed 307% higher CO2 permeability than pure CA. The 0.5% Gr/PEI MMM showed 435% higher CO2 permeabilit than pure PEI. Structural properties were confirmed by Fourier transform infrared spectroscopy, differential scanning calorimetry, field emission scanning electron microscopy, Raman, and X‐ray diffraction.

Heterostructure ZIF-8@MXene with sieving effect in mixed matrix membranes for CO2 separation

At the present time, the realm of gas separation membranes is predominantly centered on the development of membrane materials that simultaneously exhibit exceptional gas permeability and selectivity. Mixed Matrix Membranes (MMMs) hold significant promise in addressing the long-standing challenge of balancing membrane selectivity with permeability. By incorporating a molecular sieving mechanism, an enhanced gas separation process is achieved. In this research endeavor, single-layer MXene nanosheets serve as an ideal substrate for the direct growth of ZIF-8 nanoparticles, yielding heterogeneously structured nanofillers, coined ZIF-8@MXene. The composite filler, ZIF-8@MXene, maintains a two-dimensional lamellar structure reminiscent of MXene, while also integrating ZIF-8 nanoparticles with their optimal pore size of 3.4 Å. This optimal pore size efficiently facilitates the unimpeded passage of CO2 molecules through the channels, creating a preferential pathway. Conversely, N2 molecules encounter greater difficulty traversing these channels, effectively coupling the solubility-diffusion mechanism with the molecular sieving mechanism to enhance selectivity in gas separation processes. Consequently, the mixed matrix membrane exhibits a remarkable enhancement in gas selectivity. Particularly, under sub-ambient conditions (−20 °C), the PEO/ZIF-8@MXene-0.3 % membrane achieves an exceptional CO2/N2 selectivity of 294.1, accompanied by a high CO2 permeability of 115.58 Barrer. This outstanding performance surpasses the 2019 upper bound, underscoring the significant potential of heterostructured nanofillers to be harnessed in advancing various mixed matrix membranes (MMMs) towards high-performance gas separation capabilities.

A facilitated transport membrane composed of amine-containing ionic liquid confined in a GO/CNT network for highly efficient carbon capture

Carbon capture is a key approach to manage carbon dioxide (CO2) emissions and promote net removal of CO2 from the atmosphere. Post combustion flue gas emissions from power plants contribute a significant fraction of CO2 released into the atmosphere. Membrane-based separation strategies offer environmentally sustainable and economically viable solutions for efficient CO2 capture from power plants. Facilitated transport membranes, although showing strong capability for CO2 capture at low concentrations and under humid conditions, suffer from the loss of facilitators, such as amines, leading to decline in performance over long-term operation. Ionic liquids (ILs) are chemically and thermally stable and have low vapor pressure, which is ideal to prevent aforementioned losses. However, making a thin network for effective IL confinement is still a challenge. In this work, we developed a stable high performing IL based CO2 selective membrane that can operate at temperatures as high as 80 °C under humid conditions. An amino acid-based IL (containing facilitated carriers), 1-ethyl-3-methylimidazolium glycinate, [EMIM][GLY], was used as the separating agent. In order to selectively load and confine the IL in a thin selective layer, we designed and fabricated a network composed of stacked graphene oxide (GO) nanosheets intercalated by carbon nanotubes (CNT). While CNT acts as a nanowedge that helps in increasing the nanochannels to facilitate low-resistance gas transport, GO nanosheets act as anchoring sites due to presence of various functional groups resulting in electrostatic interaction between GO and cation of IL. Due to the aforementioned reason, distribution of GO in the network plays a critical role in forming a thin, uniform selective IL layer. The GO distribution was optimized by adjusting the pH of the coating solution; after optimizing IL coating, this results in a thin, defect free selective layer, providing a membrane with high CO2 permeance of ∼1600 GPU and CO2/N2 selectivity of 400, superior to most of the reported IL membranes. This network composed of GO/CNT network not only facilitates fabrication of a stable, ultrathin, high permeance and high selectivity supported IL membrane but also provides a platform for preparation of other IL-based membranes for desired separations.

Fabrication of a high-performance MOF-COP-based porous hollow fiber membrane for carbon dioxide separation

A thin-film nanocomposite (TFNC) hollow fiber membrane with high CO2 permeability and selectivity was synthesized for the separation of carbon dioxide, a major greenhouse gas. A highly porous polyethersulfone (PES) hollow fiber membrane support with a porous structure was first fabricated using heat and pressure treatments, and a thin film was prepared via interfacial polymerization by reacting polyethylenimine (PEI) with 1,3,5-benzenetricarbonyl trichloride (TMC) on the surface of the PES support. A metal–organic framework (MOF)-covalent organic polymer (COP) complex, obtained via polycondensation between an UiO-66-NH2 based MOF and a piperazine- and cyanuric chloride-based COP, was then added to the TFNC to prepare the mixed matrix membrane. The complex contributed to reducing defects between the porous support and the coating layer and additionally led to high CO2 permselectivity by providing a CO2 permeation pathway within the support. The newly prepared TFNC hollow fiber membrane contributed to its excellent separation performance, as evidenced by a CO2 permeability of 352 GPU and a CO2/N2 ideal selectivity of 75 after optimization of the MOF-COP content.

Bimetallic MOF-74-based mixed matrix membrane for efficient CO2 separation

The bimetallic Ni(Zn)-MOF-74 nanoparticles were fabricated by the metal substitution method and doped into a polyether-polyamide block copolymer (Pebax 1657) matrix to obtain mixed matrix membrane (MMM) for CO2/CH4 separation. The pore structure and chemical properties of Ni(Zn)-MOF-74 nanoparticles were controlled by changing the molar ratio of Ni/Zn, and the effect of heterometallic on the gas separation performance of MMMs was studied. In particular, when the molar ratio of Ni/Zn was 2:1, the Pebax/Ni(Zn)-MOF-74-21 MMMs has the optimal CO2 separation performance. The main reason was that Ni(Zn)-MOF-74-21 has the smallest pore size (0.68 nm) and abundant CO2 adsorption sites, which could effectively prevent the entry of CH4 molecules after preferentially adsorbing one or two CO2 molecules, and improve the selectivity of CO2/CH4 molecules. Furthermore, the unreplaced pore size of 1.48 nm and the increased polymer chain spacing in Ni(Zn)-MOF-74-21 nanoparticles could provide a fast transport channel for CO2 and improve the permeability of MMMs. The developed Pebax/Ni(Zn)-MOF-74-21 MMMs loaded with 2 wt% filler displayed a CO2/CH4 selectivity of 33.7 and a high CO2 permeability of 719.9 barrer, exceeding the gas separation performance of many previously reported MOF-74-based MMMs. The results showed that the development and design of bimetallic organic framework was an important way to obtain high performance MOF-74-based MMM.

Enhancement of CO2/N2 separation in MMMs by the regulation of nanofiller microenvironment

Mixed-matrix membranes (MMMs) incorporating Metal-Organic Frameworks (MOFs) represent a promising approach for gas separation, which can combine the advantages of selective adsorbents and processable polymers, and display great potential in the gas separation process. However, the further application of MMMs is severely impeded owing to the non-ideal interface between fillers and polymer matrix. In this work, a series of MIL-101(Cr) nanofillers, equipped with different kinds of counter anions were introduced to regulate the chemical microenvironment of the MMMs and improve the interfacial relationship between inorganic filler and polymer. The filler of MIL-101-HNO3 exhibits improved dispersibility in solvents and heightened interface relationship with the polymer matrix (PIM-1) due to its optimal particle size and distinctive exposure of crystallographic planes. Moreover, gas sorption isotherms reveal that the MIL-101-HNO3 MOF show reduced N2 adsorption capacity. Therefore, the MOF filler of MMMs were optimized rationally by microenvironment regulate strategy, leading to the MIL-101-HNO3/PIM-1 MMMs achieve high CO2 permeability and exceptional CO2/N2 ideal selectivity (CO2 = 14879 barrer, CO2/N2 = 24.3), surpassing the latest 2019 upper bound. That makes MIL-101-HNO3/PIM-1 a potential candidate for the selective removal of CO2 from stack gas and provides new insights into the regulation of the MMMs nanofiller microenvironment.

Constructing bio-inspired anion channels by dual-ligand MOF in membranes for efficient CO2 separation

One of the biggest challenges of Pebax-based membranes is how to simultaneously achieve high CO2 permeability and selectivity. Hence, three-dimensional L-histidine@zeolitic imidazole framework-8 (His@ZIF-8 (X)) was synthesized as dual-ligand metal-organic framework (MOF), and it was incorporated into the Pebax 1657 matrix to fabricate mixed matrix membranes (MMMs) for efficient CO2 separation. The three-dimensional His@ZIF-8 (X) with abundant His mimicked anion transport protein, and it constructed bio-inspired anion transport channels. His@ZIF-8 (X) played important functions when it was incorporated into the MMMs: the bio-inspired active sites of His@ZIF-8 with the Zn2+ bonded to three Hmim and one water molecule had similar function with the active sites in carbonic anhydrase (CA), which can catalyze CO2 into water-soluble bicarbonate (HCO3−). Subsequently, the bio-inspired anion transport channels allowed HCO3− to rapidly transport, because they had His residues that can form anion-dipole interactions with HCO3− in His@ZIF-8 (X). Therefore, Pebax 1657/His@ZIF-8 (X) MMMs were endowed with the excellent separation performance due to the bio-inspired anion transport channels constructed by His@ZIF-8 (X). In particularly, MMM contained 4 wt% His@ZIF-8 (12.5) achieved the optimal separation performance with a CO2 permeability of 541 ± 9 Barrer and CO2/CH4 selectivity of 35 ± 0.6. The work implies that the construction of the bio-inspired anion transport channels within MMMs was a potential strategy for efficient CO2 separation.

Preparation of UiO-66 membrane through heterogeneous nucleation assisted growth strategy for efficient CO2 capture under humid conditions

Metal-organic frameworks (MOFs) have driven the development of polycrystalline membranes in the field of gas separation owing to the strong adsorption-desorption behavior and stable framework structure. However, the poor heterogeneous bonding ability between crystals and the substrate leads to the unsatisfactory gas separation as well as low stability of MOF membranes, especially in the humid environment. Herein, we prepared a thin and defect-free UiO-66 membrane by a crystal heterogeneous nucleation assisted growth strategy for efficient CO2/N2 separation. The addition of small amount of water in the precursor solution promoted the crystal nucleation process on the substrate surface. Meanwhile, the smooth PDMS interlayer guaranteed the heterogeneous well-intergrown of crystals into thin UiO-66 membranes, and provided a hydrophobic environment. Therefore, the dense UiO-66 membrane with a small thickness exhibited a high CO2 permeance (177.4 × 10−9 mol·m−2·s−1·Pa−1) with moderate CO2/N2 selectivity (24.3) under humid conditions. Furthermore, the prepared membrane demonstrated excellent renewable performance after dehumidification at high temperature, and maintained good hydrothermal stability during long-term operation under the humid environment. This work provides a new insight for the design of high-quality MOF membranes and promotes the development of MOF membranes in practical gas separation process.

Laser Patterning of Porous Support Membranes to Enhance the Effective Surface Area of Thin-Film Composite-Facilitated Transport Membranes for CO2 Separation.

Although thin-film composite membranes have achieved great success in CO2 separation, further improvements in the CO2 permeance are required to reduce the size and cost of the CO2 separation process. Herein, we report the fabrication of composite membranes with high CO2 permeability using a laser-patterned porous membrane as the support membrane. High-aspect-ratio micropatterns with well-defined micropores on their surface were carved on microporous polymer supports by a direct laser writing process using a short-pulsed laser. By using a Galvano scanner and optimizing the laser conditions and target materials, in-plane micropatterns, such as microhole arrays, microline grating, microlattices, and out-of-plane hierarchical micropatterns, were created on porous membranes. An aqueous suspension of hydrogel microparticles doped with an amine-based mobile carrier was sprayed onto the patterned surface to form a defect-free thin separation layer. The surface area of the separation layer on the patterned support is up to 80% larger than that of flat pristine membranes, resulting in a 52% higher CO2 permeance (1106 GPU) with a CO2/N2 selectivity of 172. The laser-patterned porous membranes allow the development of inexpensive and high-performance functional membranes not only for CO2 separation but also for other applications, such as water treatment, cell culture, micro-TAS, and membrane reactors.

Removing mesopores from metal-organic framework MIL-100(Cr) membranes for superior CO2 separation

Membranes with high CO2 permeance and satisfactory CO2/N2 selectivity have been in demand for industrial applications, especially for the first stage of two-stage membrane-based process. MOF membranes with abundant pores have the potential to achieve high CO2 permeance, but most current MOF membranes fall short of the requirements (CO2 permeance >3000 GPU). Research on novel MOF membranes is urgently needed. Here, a new kind of non-crystalline (NC) MIL-100(Cr) membrane removed mesopores is fabricated by a non-fine assembly process. NC-MIL-100(Cr) possesses similar bonding structure and surface properties to crystalline MIL-100(Cr), but delivers more suitable pore size and high processibility for membrane formation. NC-MIL-100(Cr) membranes are prepared under different Cr3+ concentrations in reaction solution and secondary growth durations, among which NC-MIL-100(Cr) membranes prepared with Cr3+ concentration of 2 mmol/mol DMF and secondary growth duration of 36 h display CO2 permeance of about 4638 GPU and CO2/N2 selectivity of about 35 for mixed CO2/N2 (15/85, v/v) separation, as well as CO2 permeance of about 8670 GPU for single CO2 permeation.

High gas permeance in CO2-selective thin film composite membranes from bis(phenyl)fluorene-containing blends with PIM-1

A novel approach to improve the initial performance as well as to prevent physical aging of superglassy high free volume polymer PIM-1 is reported. Bis(phenyl)fluorene-based polymer of intrinsic microporosity (Cardo-PIM-1) was used at different loadings in PIM-1 to fabricate thin film composite (TFC) membranes and freestanding membranes. The gas performances of both TFCs and thick freestanding membranes exhibited similar trends; higher CO2 permeance and higher CO2/CH4 selectivity at relatively low loadings (≤5 wt %). TFCs containing 5 wt % Cardo-PIM-1 achieved a CO2 permeance of (12600 ± 866 GPU), which corresponds to about a threefold increase as compared to the pristine TFC-PIM-1 membranes (2850 ± 254 GPU) and higher CO2/CH4 selectivity (14.6 ± 1.3) as compared to pure PIM-1 (10 ± 3). With regards to physical aging, PIM-1 TFC membranes experienced a 96 % reduction in CO2 permeance after 1 year. However, for the TFCs containing 5 wt % cardo the reduction was considerably lower (59%) and all took place at an initial stage of up to 37 days, remaining at a good and stable CO2 permeance of c.a. 5000 GPU for the remaining testing period of up to one year.

Amine‐Rich Molecular Nodule‐Assembled Membrane Having 5 Angstrom Channels for CO2/N2 Separation

AbstractPorous organic cages (POCs) with abundant porosity and interconnected cavities have garnered significant research attention as a distinct class of porous materials due to their potential applications in gas sorption and separation. However, the ordered arrangement of POCs to eliminate inter‐cage defects remains challenging in the assembly of molecular‐selective membranes, which greatly hinders the effectiveness of pore sieving. Here, amine‐rich molecular nodules (AMNs) are created by reduction of the porous organic cage CC2, in which the spatial structure incurs a vertex collapse into the interior of the original tetrahedral structure, which eliminates the large window of CC2. By an interfacial reaction with terephthaloyl chloride, the AMNs assemble into a cross‐linked topological network having angstrom‐scale channels for selective CO2/N2 separation. The AMN‐assembled membrane displays a high CO2 permeance of 752 GPU, a CO2/N2 selectivity of 67 at 1 bar, as well as high‐pressure resistance, operational stability, and scalable manufacture potential, which provides a cost‐effective and practical solution for developing membranes for capturing CO2 from industrial flue gas.

Ultrathin PEI-functionalized carboxyl covalent organic framework membranes for efficient CO2/N2 separation

Covalent organic frameworks (COF) are deemed as disruptive membrane materials owing to their versatile functionalities, high stability and ordered nanochannels. However, the size mismatch between the COF intrinsic pore and gas molecules becomes a grand challenge when using COF membrane for carbon capture. Herein, we propose a new type of polymer-functionalized COF laminar membranes through grafting CO2-phlic polyethyleneimine (PEI) polymer onto carboxylic acid COF (cCOF) laminar membranes. The cCOF nanosheets with high density of carboxyl groups are prepared via modified single phase solution method and then assembled to fabricate membranes. Further, the cCOF membranes are functionalized with PEI using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide/N-Hydroxysuccinimide (EDC/NHS) coupling chemistry. The introduction of abundant amino groups from PEI afford the affinity of membranes toward CO2. Meanwhile, the graft of the PEI polymers reduces the defects or pinholes on the membrane surface. As a result, the PEI functionalized cCOF membranes exhibit a high CO2 permeance of 1004 GPU and a CO2/N2 selectivity of 33.7, which reach the carbon capture target performance and show great prospect for treating real flue gas. Our approach of functionalizing cCOF membranes with tailored functionalities may inspire the design of molecule-selective COF membranes.

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.