Gas Separation Performance Research Articles

Ordered 2D RUB‐15 nanosheets with high loading in mixed matrix membranes for H2/CO2 separation

AbstractMixed matrix membranes (MMMs) combining functional fillers with polymer matrices hold promise for high‐efficiency separation. However, it remains a great challenge to enhance the loading to fully harness the capabilities of the fillers. Herein, we introduced RUB‐15 nanosheets as fillers for MMMs to approach parallel alignment of nanosheets within the matrix, thus achieving a high‐loading rate of up to 55 wt% and constructing fast and continuous mass transfer channels. The parallel orientation reduced the occurrence of defects, which played a critical role in enhancing separation. An optimized membrane with a 50 wt% loading rate exhibited exceptional H2/CO2 gas separation performance with H2 permeability of 1934 Barrer and selectivity of 44.5, maintaining a separation factor of 16.7 at 125°C. This study maximizes the performance of porous functional fillers within the membrane by enhancing gas separation capabilities through the ordered alignment of nanosheets and provides valuable insights for future membrane development.

Diffusion-Regulated Interfacial Polymerization of Hierarchically Microporous Polyamide Membranes for Permselective Gas Separations.

Interfacial polymerization has emerged as a robust method for fabricating task-specific polyamide (PA) membranes. However, the limited microporosity of highly cross-linked PA membranes constrains their effectiveness in gas separation applications. Herein, we introduce an ionic liquid (IL)-regulated interfacial polymerization process to fabricate polyamide nanofilms incorporating kinked tetrakis (4-aminophenyl) methane monomers. In situ ultraviolet-visible spectroscopy demonstrates that the diffusion of 1,3,5-benzenetricarbonyl trichloride (TMC) toward the interface increases with the IL/H2O ratio, leading to the formation of a more compact membrane with a higher cross-linking degree. The PA-TAM7/3-60 min membrane exhibits a CO2 permeance of 29.8 GPU and a CO2/CH4 selectivity of 109, exceeding the 2008 Robeson upper bond. Additionally, the highly cross-linked structure imparts the membranes with notable plasticization resistance. Mixed-gas tests (CO2/CH4 = 50/50, v/v) reveal that the PA-TAM7/3-60 min membrane experiences only a 2% reduction in CO2 permeance and a 10% decrease in CO2/CH4 selectivity at a CO2 partial pressure of 300 PSIG, compared to its performance at 30 PSIG. The ease of tuning membrane structure and gas separation performance, along with its excellent plasticization resistance, underscores the potential of these PA membranes for task-specific gas separations.

Preparation of Pebax based ternary mixed matrix membranes for enhancing CO2 transport and separation

As a type of material for membrane separation in carbon capture technology, mixed matrix membranes (MMMs) have the advantages of simple processing and excellent gas separation performance and have great research prospects. However, the affinity between organic matrix and inorganic fillers is usually poor, and microphase separation occurs at the interface. At the same time, as the filler content increases, the filler particles will aggregate, leading to non-selective defects in the homogeneous membrane and reducing the gas separation performance of MMMs. Herein, the strategy of adding a third component was adopted. Small molecule polyethylene glycol dimethyl ether (PEGDME) was introduced into the Pebax/NH2-MIL-101 membrane to prepare a ternary mixed matrix membrane Pebax/PEGDME/NH2-MIL-101. Adding small molecules as the third component optimized the membrane structure by utilizing the interaction between the third component, inorganic fillers, and polymer matrix, effectively improving the physical microenvironment of gas separation. At the same time, NH2-MIL-101 was modified to PEI-MIL-101, further improving the performance of the mixed matrix membrane. The CO2 permeability of the Pebax/PEGDME/NH2-MIL-101 ternary mixed matrix membrane reached 313 Barrer, and the CO2/N2 selectivity reached 47.7. The CO2 permeability coefficient of Pebax/PEGDME/PEI-MIL-101 membrane reached 286 Barrer, and the CO2/N2 selectivity coefficient reached 54.2. This work provides new ideas for optimizing the gas separation performance of mixed matrix membranes.

Unveiling the Mystery: How TR precursors lead to exceptional gas separation performance in CMSMs

One of the main issues with membrane-based gas separation lies in the unexplored relationship between the precursors and their derived carbon molecular sieve membranes (CMSMs). Herein, we designed a series of TR polymers with gradient PBO content as precursors to investigate the carbonization mechanisms of PBO structure. The process of transforming the polymer precursor into carbon structure throughout pyrolysis involves utilizing an array of characterization techniques along with pyrolysis simulation. Results indicated that a higher PBO content leads to stronger molecular sieving effect of the resulting CMSM. The TR-CMS-50 membrane demonstrated exceptional gas separation performance with high permeability (PH2 = 3154 and PCO2 = 1495 Barrer) as well as ultra-high H2/CH4 (384) and CO2/CH4 (166) selectivity, which far exceeded the newest Upper bound line, showing significant potential for practical applications. This may can be attributed to “delayed effect” of the PBO structure which requires pyrolysis at higher temperatures, leading to more intense pyrolysis and the release of nitrogen-containing substances. Meanwhile, PBO has a cyclic system with a strong aromatic structure that closely resembles a carbon strand, which probably facilitates aromatization and enables it to more easily integrate into CMS structure, resulting in a more orderly arrangement in the Langmuir phase and generating higher concentration of pyrrolic-N (58.7 % vs. 44.1 %) as well as graphitic-N (31.6 % vs. 17.2 %). Thus, increasing the PBO content makes the derived CMS denser and significantly enhances its molecular sieving capacity. This study offers new insights into the development of precursor structures that creates high-performance CMSMs.

Theoretical perspectives on CO2 separation by ionic liquids: Addressing crucial questions

The global population explosion necessitates more natural resources for energy, making it a major factor in climate change. CO2 is a leading actor in the greenhouse gas effect, and advancements in CO2 capture processes have attracted researchers in recent years. Numerous technologies are practiced for CO2 separation. Nevertheless, due to the intricate nature of gases and different process conditions, most of them continue to face challenges. To overcome these challenges, researchers focus on finding or designing innovative materials compatible with various processes. From the discovery of high CO2 solubility of ionic liquids (ILs), these unique compounds have rapidly gained popularity for different applications like gas separation. Molecular simulations play a crucial role in supporting researchers in understanding the connection between the properties and chemical structure of newly developed materials as ILs in a time-efficient manner. Despite the growing number of molecular simulation studies, there is a gap in the review papers that effectively highlight the benefits and feasibility of the theoretical approach. Up to date, mostly experimental studies mainly focusing on gas transport mechanisms and the relationship between chemical composition and properties were summarized. Herein, we concentrated on molecular simulation studies investigating the adsorption- and membrane-based CO2 separation performance of confined ILs. We systematically addressed prominent questions posed by researchers in each simulation study, demonstrating how to examine confined ILs and interpret the resulting data in relation to gas separation performance. The most pertinent inquiries encompass the influence of ion type (cation or anion) on gas adsorption at the gas–liquid interface and through the confined IL phase, the significance of the confined form of cation or anion in gas transport, the impact of IL thickness on gas separation, and the discernible effects of the material in which ILs are confined. Therefore, we hope to guide researchers in developing innovative membranes or adsorbents by leveraging insights obtained from the answers to these questions derived from molecular simulations of confined ILs.

Low-crystallinity ZIF-8/dcIm membranes for CO2 sieving

Metal-organic framework membranes have shown great potential for efficient separation applications. However, unavoidable grain boundary defects and the inconstant pore size due to framework flexibility hinder the application of MOF membranes for gas separation. Herein, low-crystallinity ZIF-8/dcIm-x membranes are synthesized via fast current-driven synthesis. The competitive coordination of 4,5-dichloroimidazole (dcIm) linker leads to the formation of a low-crystallinity MOF with reduced grain boundary defects for better gas separation performance. Meanwhile, the in-situ substitution of the mIm linker by dcIm narrows the pore size and transforms the ZIF-8 structure in the stiffened Cm polymorph, allowing precise CO2 sieving. Consequently, the low-crystallinity ZIF-8/dcIm-14 membrane exhibits a promising CO2/CH4 selectivity of 32.4 with a CO2 permeance of 1.73 × 10−8 mol m−2 s−1 Pa−1, which surpasses other membranes. Furthermore, the membrane presents a remarkable pressure resistance up to 3 bar and stable temperature-swing operation between room temperature and 125 °C over 120 h.

Composite organic ionic plastic crystal membranes: The effect of ether-functionalized cations on light-gas separation performance

In light of increasing concerns about climate change, there is a growing need for innovative solutions to address CO2 emissions. Addressing this urgency, this work presents a unique approach to CO2 separation utilizing composite membranes of organic ionic plastic crystals (OIPCs) with ether-functionalized cations and poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP). Here we report the gas separation performance of OIPC-based membranes of 3,3-dimethyloxazolidinium [C1moxa]+, 4-ethyl-4-methylmorpholinium [C2mmor]+ and 4-isopropyl-4-methylmorpholinium [Ci3mmor]+ cations paired with the bis(fluorosulfonyl)imide [FSI]- anion. These composites demonstrated very good gas separation properties, especially [C1moxa][FSI] which produced a permeability of 63 barrer for CO2 and an overall selectivity (CO2/N2) of 205, which is the highest amongst all the OIPCs reported so far. Additionally, a large change in separation performance was observed for the [Ci3mmor][FSI] membrane upon heating above the solid-solid phase transition (II - I) at 48 °C; the CO2 permeability increased from 7 to 163 barrer and an approximately 3-fold increase in selectivity was observed. These findings advance the design of composite membranes based on OIPCs towards increased selectivity and sustained effectiveness in the separation of light gases.

High-Performance Carbon Molecular Sieve Membranes Derived from a PPA-Cross-linked Polyimide Precursor for Gas Separation.

Carbon molecular sieve (CMS) membranes have emerged as attractive gas membranes due to their tunable pore structure and consequently high gas separation performances. In particular, polyimides (PIs) have been considered as promising CMS precursors because of their tunable structure, superior gas separation performance, and excellent thermal and mechanical strength. In the present work, polyphosphoric acid (PPA) was employed as both cross-linker and porogen, it created pores within the PI polymeric matrix, while it also effectively acting as a cross-linker to regulate the ultramicropores of the CMS membranes, thus simultaneously improving both permeability and selectivity of the CMS membranes. By employing PI/PPA hybrid with PPA content of 5 wt % as a precursor, the obtained CMS membrane exhibited a CO2 and He permeability of 1378.3 Barrer and 1431.4 Barrer, respectively, which was an approximately 10-fold increase compared to the precursor membrane. Under optimized conditions, the CO2/CH4 and He/CH4 selectivity of the obtained CMS membrane reached 81.5 and 89.9, respectively, which was 278% and 307% higher than that of the pristine PI membrane. In addition, the membrane exhibited good long-term stability during a one-week continuous test. This study clearly denoted PPA can be used for precisely tailoring the ultramicroporosity of CMS membranes.

Huge improved gas separation performance of carbon molecular sieve membrane by forming a double crosslinked polyimide precursor

A vital issue in searching for advanced gas separation membranes is understanding the precursor structure-gas separation properties of carbon molecular sieve (CMS) membranes. Here, we reported two crosslinked polyimides and used as CMS precursors, in which, the DCPI-4 is a double cross-linkable polyimide with 4 % triptycene triamine as a crosslinker (Type I) and COOH group that can be crosslinked at 350 °C by decarboxylation (Type II), whereas the DCPI-0 with COOH (Type II). After pyrolysis at 550 °C, the DCPI-4-CMS showed a higher SBET (812 vs 713 m2g-1), larger ultra-microporosity ratio (26.6 % vs 17.8 %), larger d-spacing (4.08 vs 3.94 Å), less graphitization (sp3/sp2 of 0.156 vs 0.118), 5.5 times higher CO2 permeability (7573 vs 1391 Barrer) and same CO2/CH4 selectivity (∼62) than DCPI-0-CMS. We consider this is due to the type I crosslinking enhances the rigidity of the polyimide backbone, and inhibits the collapse of micropores during the carbonization, which causes improved ultra-microporosity and ultra-micropore ratio that both enhances the gas diffusion and solubility coefficient as well activation energy difference of gas pairs. Conclusively, this double crosslinking method provides a good perspective for achieving CMS membranes with excellent gas separation performance.

Theoretical study on the luminescence mechanism of AIEgens based HOFs adsorbing small molecules

The diversity and reversibility of non-covalent interactions give hydrogen-bonded organic frameworks (HOFs) excellent gas adsorption and separation performance. Here we designed and synthesized HOFs based on aggregation-induced emission luminogens (AIEgens) to visualize the adsorption process of HOFs. We focused on the SQ system and its solvated SQ frameworks by different solvent conditions, employing the thermal vibration correlation function rate formalism coupled hybrid quantum mechanics/molecular mechanics protocol, to elucidate the relation between crystal structure and luminescent properties, as well as the specific adsorption ability of porous SQ HOF crystals on acetylene gas. It is found that compare to SQ crystal, the SQ symmetry in cocrystals are improved, and SQ-DCM cocrystal has the best symmetry. The absorption spectra of five SQ-based crystals are close to each other, and their emission spectra blueshifted from 540 nm of SQ, to 509 nm, 508 nm, 507 nm of SQ-EA, SQ-ACN, SQ-DCM, and then to 495 nm of SQ-TOL, consistent with experimental results. The kic of solvated cocrystals are about 1∼2 orders of magnitude smaller than that of non-solvated crystal SQ, resulting in significantly higher Φexp of solvated cocrystals than that of un-solvated one. DCM with small volume and C2v point group is more suitable for SQ crystal channel, indicating that small free region and shape matching are the key factors affecting the reversibility of crystallization of porous frames during solvent transport. Finally, the volume of the adsorbed gas C2H2 which is close to DCM, is more easily adsorbed by SQ framework. Our study offers theoretical insights into the design of porous crystals for gas adsorption and separation applications.

Performance tuning of surface modified ceria based mixed matrix membrane for effective CO2 separation

AbstractMixed matrix membranes (MMMs) with enhanced selectivity and permeability are investigated by incorporating deep eutectic solvents (DES) functionalized CeO2 as fillers. DES is well known owing to the intrinsic benefits of low cost, environmentally friendly, biodegradable, and CO2 philic nature. Characterization confirms the collaboration of polymer and functional CeO2 fillers. Experiments of gas separation show that the introduction of DES‐modified CeO2 fillers (2%–15%) significantly improves CO2 penetrability from 27 to 48 Barrer. The ideal separation factor of CO2/CH4 and CO2/N2 also increases from 46 to 62 and 60 to 86, respectively, with increasing filler percentage. MMMs correspond to the superior gas separation performance compared with DES liquid membranes. The collaboration between DES‐treated CeO2 and CO2 contributes to the improved results. The fabricated MMM films are tested under operating parameters, confirming the potential of ceria modified fillers for CO2 capture applications. This research reveals the advancements achieved by incorporating DES‐functionalized CeO2 fillers in MMMs, enhancing selectivity and permeability for CO2 capture. These findings correspond to the development of effective and viable membrane technologies for various industrial applications.

Mixed-Matrix Organo-Silica-Hydrotalcite Membrane for CO2 Separation Part 1: Synthesis and Analytical Description.

Hydrotalcite exhibits the capability to adsorb CO2 at elevated temperatures. High surface area and favorable coating properties are essential to harness its potential for practical applications. Stable alcohol-based dispersions are needed for thin film applications of mixed membranes containing hydrotalcite. Currently, producing such dispersions without the need for delamination and dispersing agents is a challenging task. This work introduces, for the first time, a manufacturing approach to overcoming the drawbacks mentioned above. It includes a synthesis of hydrotalcite nanoparticles, followed by agent-free delamination of their layers and final dispersion into alcohol without dispersing agents. Further, the hydrotalcite-derived sorption agent is dispersed in a matrix based on organo-silica gels derived from 1,2-bis(triethoxysilyl)ethane (BTESE). The analytical results indicate that the interconnection between hydrotalcite and BTESE-derived gel occurs via forming a strong hydrogen bonding system between the interlayer species (OH groups, CO32-) of hydrotalcite and oxygen and silanol active gel centers. These findings lay the foundation for applications involving incorporating hydrotalcite-like compounds into silica matrices, ultimately enabling the development of materials with exceptional mass transfer properties. In part 2 of this study, the gas separation performance of the organo-silica and the hydrotalcite-like materials and their combined form will be investigated.

Oriented growth of large-area metal-organic framework ZIF-8 membrane for hydrogen separation

Optimal orientation is the key factor to optimize the gas separation performance of metal-organic framework (MOF) membranes. However, it is still greatly challenging to prepare large-area oriented MOF membranes for industrial applications. Herein, we prepared compact and (100) oriented zeolitic-imidazolate framework-8 (ZIF-8) membranes with membrane area up to 500 cm2 on the graphite substrate via support-induced strategy within 2 h. With membrane thickness of only 620 nm, the (100) oriented ZIF-8 membranes exhibit high gas separation performances due to the reduction of inter-crystalline defects and permeation resistance. At 100 °C and 1 bar, the separation factors of H2/CO2, H2/CH4 and H2/C3H8 are 18.5, 58.2 and 101.6, respectively, with H2 permeance of about 160 x 10−9 mol m−2 s−1·Pa−1. The different positions of the 500 cm2 ZIF-8 membrane show complete consistency in orientation and separation performance, recommending this membrane suitable for future industrial applications. Further, also oriented ZIF-67 and MOF-303 membranes can be consistently prepared by this strategy, confirming its versatility for the preparation of large-area MOF membranes.

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.

Crystalline Metal-Organic Framework Coatings Engineered via Metal-Phenolic Network Interfaces.

Crystalline metal-organic frameworks (MOFs) have garnered extensive attention owing to their highly ordered porous structure and physicochemical properties. However, their practical application often requires their integration with various substrates, which is challenging because of their weakly adhesive nature and the diversity of substrates that exhibit different properties. Herein, we report the use of amorphous metal-phenolic network coatings to facilitate the growth of crystalline MOF coatings on various particle and planar substrates. Crystalline MOFs with different metal ions and morphologies were successfully deposited on substrates (13 types) of varying sizes, shapes, and surface chemistries. Furthermore, the physicochemical properties of the coated crystalline MOFs (e.g., composition, thickness) could be tuned using different synthesis conditions. The engineered MOF-coated membranes demonstrated excellent liquid and gas separation performance, exhibiting a high H2 permeance of 63200 GPU and a H2/CH4 selectivity of 10.19, likely attributable to the thin nature of the coating (~180 nm). Considering the vast array of MOFs available (>90,000) and the diversity of substrates, this work is expected to pave the way for creating a wide range of MOF composites and coatings with potential applications in diverse fields.

Crystalline Metal–Organic Framework Coatings Engineered via Metal–Phenolic Network Interfaces

AbstractCrystalline metal–organic frameworks (MOFs) have garnered extensive attention owing to their highly ordered porous structure and physicochemical properties. However, their practical application often requires their integration with various substrates, which is challenging because of their weakly adhesive nature and the diversity of substrates that exhibit different properties. Herein, we report the use of amorphous metal–phenolic network coatings to facilitate the growth of crystalline MOF coatings on various particle and planar substrates. Crystalline MOFs with different metal ions and morphologies were successfully deposited on substrates (13 types) of varying sizes, shapes, and surface chemistries. Furthermore, the physicochemical properties of the coated crystalline MOFs (e.g., composition, thickness) could be tuned using different synthesis conditions. The engineered MOF‐coated membranes demonstrated excellent liquid and gas separation performance, exhibiting a high H2 permeance of 63200 GPU and a H2/CH4 selectivity of 10.19, likely attributable to the thin nature of the coating (~180 nm). Considering the vast array of MOFs available (>90,000) and the diversity of substrates, this work is expected to pave the way for creating a wide range of MOF composites and coatings with potential applications in diverse fields.

High-vacuum-calcined multi-MOF mixed-matrix membrane for CH4/N2 separation

Methane/nitrogen (CH4/N2) separation remains a persistent challenge owing to the similar polarities, kinetic diameters, and boiling points of CH4 and N2. Herein, a novel method is proposed for enhancing the separation performance of CH4/N2 via vacuum resistance calcination, which uses surface-carbonized and hardened ZIF-8 (SCH-Z), MOF-74-Ni (SCH-M), and UiO-66-NH2 (SCH–U). The nanoparticles treated by vacuum resistance calcination remain the microporous characteristics of MOF, while introducing additional mesoporous structure and unsaturated metal sites. Such multistage pore structure and rich metal sites display a significant improvement in the CH4 adsorption over N2. In addition, the separation performance of multiple metal–organic frameworks (MOFs) mixed matrix membranes (MMMs) fabricated by homogeneously mixing the alkaline polymer polyvinylamine (PVAm) with SCH-M/SCH-Z and SCH-M/SCH–U was investigated, respectively. When the measured pressure was 0.1 MPa and the binary filler loading was 48 %, the PVAm/(SCH-M)0.7(SCH-Z)0.3/MPSf MMM exhibited outstanding CH4/N2 separation performance (CH4 permeance of 2888.48 GPU and selectivity of 4.38). Furthermore, when the loading of the binary filler was 45 %, the ideal CH4/N2 selectivity and CH4 permeance of PVAm/(SCH-M)0.67(SCH–U)0.33/MPSf MMM are 5.57 and 2263.94 GPU, respectively. This study provides a novel idea that introducing multi-MOF nanoparticles into MMMs for optimizing gas separation performance.

Molecular Dynamics Simulations of Gas Transport Properties in Cross-Linked Polyamide Membranes: Tracing the Morphology and Addition of Silicate Nanotubes.

This study employs molecular dynamics (MD) simulations to fundamentally provide insight into the role of cross-link density in the CO2 separation properties of interfacially polymerized polyamide (PA) membranes. For this purpose, two atomistic models of pure polyamide membranes with different cross-link densities are constructed by MD simulations to conceptually determine how the fractional free volume of polyamide affects the gas separation performance of the membrane. The PA membrane with a lower cross-link density (LCPA) shows a higher gas diffusion coefficient, a lower gas solubility coefficient, and a higher gas permeability than the PA membrane with a higher cross-link density (HCPA). Moreover, the pristine and modified silicate nanotubes (SNTs) as the fast gas transport channels are incorporated into the polyamide membranes to assess the effect of the SNT/PA interface chemistry on the CO2 separation properties of the membranes. SNTs are systematically modified by three modifying agents with different CO2-philic groups and different interfacial interaction energies with the polyamide matrix. The results of MD simulations demonstrate that the incorporation of silicate nanotubes into the PA matrix increases the gas diffusivity and permeability and decreases the CO2/gas selectivity. Moreover, the membranes containing modified SNTs possessing high CO2-philicity and high SNTs/PA interfacial interactions show a high CO2 separation performance.

Preparation of KH560‐UiO‐66‐NH2/Pebax mixed matrix membranes and CO2 separation

AbstractMetal–organic frame UiO‐66‐NH2 was modified by 3‐glycidyl ether oxypropyl trimethoxysilane (KH560), and KH560‐UiO‐66‐NH2 was synthetized and added to Pebax to prepare KH560‐UiO‐66‐NH2/Pebax mixed matrix membranes (MMMs). The epoxy group of KH560 had an amine‐epoxidation reaction with the NH2 in UiO‐66‐NH2, which prevented UiO‐66‐NH2 from agglutinating in the MMMs. In addition, the NH bond and OH bond of KH560‐UiO‐66‐NH2 could theoretically form hydrogen bonds with CO and NH bonds in the main chain of polymerization, respectively, so as to improve the interfacial compatibility between fillers and polymers. The structure and properties of the filler particles and MMMs were evaluated by Fourier transform infrared spectrometer, x‐ray diffraction, scanning electron microscopy, and thermogravimetric analyzer. The results showed that the filler particles were successfully synthesized, and had good crystallinity, uniform size distribution, and good thermal stability. The inorganic and organic interfaces of MMMs had no obvious interface defects. The obtained KH560‐UiO‐66‐NH2/Pebax MMMs showed CO2 permeability of 111.52 Barre and CO2/N2 selectivity of 92.16, which were 85.65% and 88.73% higher than that of pristine membranes, respectively. The gas separation performance of MMMs was significantly improved, exceeding the upper bound of 2008 Robeson.

Fluorine Incorporation for Enhanced Gas Separation Performance in Porous Organic Polymers: Investigating Reaction Pathways and Pore Structure Control.

The precise control of pore structures in porous organic polymer (POP) materials is of paramount importance in addressing a wide range of challenges associated with gas separation processes. In this study, we present a novel approach to optimize the gas separation performance of POPs through the introduction of fluorine groups and figure out an important factor of reaction decision that whether the AlCl3-catalyzed polymerization is Scholl reaction or Friedel-Crafts alkylation. In the chloroform system, the steric hindrance of function groups could make direct coupling between the benzene rings difficult, which would lead to part solvent knitting (Friedel-Crafts alkylation) instead. The fluorinated polymers show enhanced surface area and pore size characteristics. Notably, the fluorinated polymers exhibited significantly improved adsorption and separation performance for SF6, as evidenced by an ideal adsorbed solution theory selectivity (SF6/N2, v: v = 50:50, 273 K) increase of 75.0, 668.8, and 502.8% compared to the nonfluorinated POPs. These findings highlight the potential of fluorination as a strategy for tailoring the properties of POP materials for advanced gas separation applications.