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Among the various types of materials with intrinsic porosity, porous organic cages (POCs) are distinctive as discrete molecules that possess intrinsic cavities and extrinsic channels capable of facilitating molecular sieving. However, the fabrication of POC membranes remains highly challenging due to the weak noncovalent intermolecular interactions and most reported POCs are powders. In this study, we constructed crystalline free‐standing porous organic cage membranes by fortifying intermolecular interactions through the induction of intramolecular hydrogen bonds, which was confirmed by single‐crystal X‐ray analysis. To elucidate the driving forces behind, a series of terephthaldehyde building blocks containing different substitutions were reacted with flexible triamine under different conditions via interfacial polymerization (IP). Furthermore, density functional theory (DFT) calculations suggest that intramolecular hydrogen bonding can significantly boost the intermolecular interactions. The resulting membranes exhibited fast solvent permeance and high rejection of dyes not only in water, but also in organic solvents. In addition, the membrane demonstrated excellent performance in precise molecular sieving in organic solvents. This work opens an avenue to designing and fabricating free‐standing membranes composed of porous organic materials for efficient molecular sieving. [ABSTRACT FROM AUTHOR]

Promising advances in adsorption technology can lead to energy‐efficient solutions in industrial sectors. This work presents precise molecular sieving of xylene isomers in the polymer‐metal‐oragnic framework (polyMOF), a hybrid porous material derived from the parent isoreticular MOF‐1 (IRMOF‐1). PolyMOFs are synthesized by polymeric ligands bridged by evenly spaced alkyl chains, showing reduced pore sizes and enhanced stabilities compared to its parent material due to tethered polymer bridge within the pores while maintaining the original rigid crystal lattice. However, the exact configuration of the ligands within the crystals remain unclear, posing hurdles to predicting the adsorption performances of the polyMOFs. This work reveals that the unique pore structure of polyIRMOF‐1‐7a can discriminate xylene isomers with sub‐angstrom size differences, leading to highly selective adsorption of p‐xylene over other isomers and alkylbenzenes in complex liquid mixtures (αpX/OM = 15 and αpX/OME = 9). The structural details of the polyIRMOF‐1‐7a are elucidated through computational studies, suggesting a plausible configuration of alkyl chains within the polyMOF crystal, which enable a record‐high p‐xylene selectivity and stability in liquid hydrocarbon. With this unprecedented molecular selectivity in MOFs, "polymer‐MOF" hybridization is expected to meet rigorous requirements for high‐standard molecular sieving through precisely tunable and highly stable pores. [ABSTRACT FROM AUTHOR]

Background: Genotyping and amyloid fibril detection in tissues are generally considered the diagnostic gold standard in transthyretin-related amyloidosis. Patients carry less stable TTR homotetramers prone to dissociation into non-native monomers, which rapidly self-assemble into oligomers and, ultimately, amyloid fibrils. Thus, the initial event of the amyloid cascade produces the smallest transthyretin species: the monomers. This creates engineering opportunities for diagnosis that remain unexplored. Methods: We hypothesise that molecular sieving represents a promising method for isolating and concentrating trace TTR monomers from the tetramers present in plasma samples. Subsequently, immunodetection can be utilised to distinguish monomeric TTR from other low molecular weight proteins within the adsorbed fraction. A two-step assay was devised (ImmunoSieve assay), combining molecular sieving and immunodetection for sensing monomeric transthyretin. This assay was employed to analyse plasma microsamples from 10 individuals, including 5 pre-symptomatic carriers of TTR-V30M, the most prevalent amyloidosis-associated TTR variant worldwide, and 5 healthy controls. Results: The ImmunoSieve assay enable sensitive detection of monomeric transthyretin in plasma microsamples. Moreover, the circulating monomeric TTR levels were significantly higher in carriers of amyloidogenic TTR mutation. Conclusions: Monomeric TTR can function as a biomarker for evaluating disease progression and assessing responses to therapies targeted at stabilising native TTR. [ABSTRACT FROM AUTHOR]

Molecular sieving is an ideal separation mechanism, but controlling pore size, restricting framework flexibility, and avoiding strong adsorption are all very challenging. Here, we report a flexible adsorbent showing molecular sieving at ambient temperature and high pressure, even under high humidity. While typical guest‐induced transformations are observed, a high transition pressure of 16.6 atm is observed for C2H4 at 298 K because of very weak C2H4 adsorption (~16 kJ mol−1). Also, C2H6 is completely excluded below the pore‐opening pressure of 7.7 atm, giving single‐component selectivity of ca. 300. Quantitative high‐pressure column breakthrough experiments using 1 : 1 C2H4/C2H6 mixtures at 10 atm as input confirm molecular sieving with C2H4 adsorption of 0.73 mmol g−1 or 32 cm3(STP) cm−3 and negligible C2H6 adsorption of 0.001(2) mmol g−1, and the adsorbent can be completely regenerated by inert gas purging. Furthermore, it is highly hydrophobic with negligible water adsorption, and the C2H4/C2H6 separation performance is unaffected at high humidity. [ABSTRACT FROM AUTHOR]

n‐C4H10 and iso‐C4H10 are both important petrochemical raw materials. Considering the coexistence of the isomers in the production process, it is necessary to achieve their efficient separation through an economical way. However, to obtain high‐purity n‐C4H10 and iso‐C4H10 in one‐step separation process, developing iso‐C4H10‐exclusion adsorbents with high n‐C4H10 adsorption capacity is crucial. Herein, we report a cage‐like MOF (SIFSIX‐Cu‐TPA) with small windows and large cavities which can selectively allow smaller n‐C4H10 enter the pore and accommodate a large amount of n‐C4H10 simultaneously. Adsorption isotherms reveal that SIFSIX‐Cu‐TPA not only completely excludes iso‐C4H10 in a wide temperature range, but also exhibits a very high n‐C4H10 adsorption capacity of 94.2 cm3 g−1 at 100 kPa and 298 K, which is the highest value among iso‐C4H10‐exclusion‐type adsorbents. Breakthrough experiments show that SIFSIX‐Cu‐TPA has excellent n/iso‐C4H10 separation performance and can achieve a record‐high productivity of iso‐C4H10 (3.2 mol kg−1) with high purity (>99.95 %) as well as 3.0 mol kg−1 of n‐C4H10 (>99 %) in one separation circle. More importantly, SIFSIX‐Cu‐TPA can realize the efficient separation of butanes at different flow rates, temperatures, as well as under high humid condition, which indicates that SIFSIX‐Cu‐TPA can be deemed as an ideal platform for industrial butane isomers separation. [ABSTRACT FROM AUTHOR]

Nanofilms that can fast permeate solvents and accurately sieve molecules are of significant importance for separation. A promising strategy is to align the inner cavities of macrocycles into the channels within nanofilms, and control the channel size by selecting the macrocycles. However, the channels outside the macrocycles are ignored. Here, we prepare nanofilms with hydrophobic channels (cyclodextrin inner cavity) and hydrophilic channels (cyclodextrin outer space) through interfacial polymerization of azobenzene-4,4′-dicarbonyl dichloride and amino-functionalized β-cyclodextrin. By utilizing the significant geometric changes caused by the photoisomerization of azobenzene, nanofilms with adjustable hydrophilic channel sizes were obtained. Our nanofilms have high permeability to polar and non-polar solvents, and can distinguish molecules with almost the same molecular weight but different shapes. This work expands the development of next-generation nanofilms generated through interfacial polymerization by incorporating rational molecular design. [ABSTRACT FROM AUTHOR]

Abstract Promising advances in adsorption technology can lead to energy‐efficient solutions in industrial sectors. This work presents precise molecular sieving of xylene isomers in the polymer‐metal‐oragnic framework (polyMOF), a hybrid porous material derived from the parent isoreticular MOF‐1 (IRMOF‐1). PolyMOFs are synthesized by polymeric ligands bridged by evenly spaced alkyl chains, showing reduced pore sizes and enhanced stabilities compared to its parent material due to tethered polymer bridge within the pores while maintaining the original rigid crystal lattice. However, the exact configuration of the ligands within the crystals remain unclear, posing hurdles to predicting the adsorption performances of the polyMOFs. This work reveals that the unique pore structure of polyIRMOF‐1‐7a can discriminate xylene isomers with sub‐angstrom size differences, leading to highly selective adsorption of p‐xylene over other isomers and alkylbenzenes in complex liquid mixtures (αpX/OM = 15 and αpX/OME = 9). The structural details of the polyIRMOF‐1‐7a are elucidated through computational studies, suggesting a plausible configuration of alkyl chains within the polyMOF crystal, which enable a record‐high p‐xylene selectivity and stability in liquid hydrocarbon. With this unprecedented molecular selectivity in MOFs, “polymer‐MOF” hybridization is expected to meet rigorous requirements for high‐standard molecular sieving through precisely tunable and highly stable pores.

Lithium–oxygen (Li–O2) batteries with ultra-high theoretical specific energy (3500 Wh kg−1) have attracted significant attention, but the sluggish electrochemical processes of discharge product Li2O2 lead to poor cycling stability. Redox mediators (RMs) as soluble catalysts are widely used to assist with the electrochemical formation/decomposition of Li2O2. However, the shuttle effect of RMs causes severe deterioration of both RMs and Li metal anodes. Herein, for the first time we synthesize a lithiated zeolite-based protective layer on Li anodes to mitigate the shuttle effect of 2,2,6,6-tetramethylpiperidinyloxy (TEMPO) in Li–O2 batteries. The protective layer successfully blocks the migration of TEMPO toward the Li anode owing to the angstrom-level aperture size of lithiated zeolite. Due to the excellent redox-mediator-sieving capability of the protective layer, the cycle life of the Li−O2 batteries is significantly prolonged more than ten times at a current density of 250 mA g−1 and a limited capacity of 500 mA h g−1. This work demonstrates that the lithiated zeolite-based protective layer capable of molecular sieving is a facile and scalable way to mitigate the shuttle effect of RMs in Li–O2 batteries.

Soft porous coordination polymers (PCPs) have the remarkable ability to recognize similar molecules as a result of their structural dynamics. However, their guest‐induced gate‐opening behaviors often lead to issues with selectivity and separation efficiency, as co‐adsorption is nearly unavoidable. Herein, we report a strategy of a confined‐rotational shutter, in which the rotation of pyridyl rings within the confined nanospace of a halogen‐bonded coordination framework (NTU‐88) creates a maximum aperture of 4.4 Å, which is very close to the molecular size of propyne (C3H4: 4.4 Å), but smaller than that of propylene (C3H6: 5.4 Å). This has been evidenced by crystallographic analyses and modelling calculations. The NTU‐88o (open phase of activated NTU‐88) demonstrates dedicated C3H4 adsorption, and thereby leads to a sieving separation of C3H4/C3H6 under ambient conditions. The integrated nature of high uptake ratio, considerable capacity, scalable synthesis, and good stability make NTU‐88 a promising candidate for the feasible removal of C3H4 from C3H4/C3H6 mixtures. In principle, this strategy holds high potential for extension to soft families, making it a powerful tool for optimizing materials that can tackle challenging separations with no co‐adsorption, while retaining the crucial aspect of high capacity. [ABSTRACT FROM AUTHOR]

Adsorptive separation by porous solids provides an energy-efficient alternative for the purification of important chemical species compared to energy-intensive distillations. Particularly, the separation of linear hexane isomers from its branched counterparts is crucial to produce premium grade gasoline with high research octane number (RON). Herein, we report the synthesis of a new, flexible zinc-based metal-organic framework, [Zn5(μ3-OH)2(adtb)2(H2O)5·5 DMA] (Zn-adtb), constructed from a butterfly shaped carboxylate linker with underlying (4,8)-connected scu topology capable of separating the C6 isomers nHEX, 3MP, and 23DMB. The sorbate-sorbent interactions and separation mechanisms were investigated and analyzed through in situ FTIR, solid state NMR measurements and computational modeling. These studies reveal that Zn-adtb discriminates the nHEX/3MP isomer pair through a kinetic separation mechanism and the nHEX/23DMB isomer pair through a molecular sieving mechanism. Column breakthrough measurements further demonstrate the efficient separation of linear nHEX from the mono- and dibranched isomers.

Membrane technology offers solutions for separation of complex gas mixtures. Therefore, new efficient and durable membranes are required to produce gas permeation modules with high area/volume for CO2 removal from natural gas. This study aims to develop cost-effective zeolite DD3R alumina composite hollow fibers to achieve these process requirements. A porous hollow fiber support from low-cost alumina was prepared via phase inversion followed by thermal treatment. DD3R zeolite seeds were then implanted over the surface of the microporous hollow fibers to form a selective layer by hydrothermal synthesis. The thickness of the selective layer was controlled by the seed concentration, which also affected the crystal intergrowth and competing zeolite phase formation, Sigma-2, which influenced the membrane performance. A reduced-diameter composite DD3R-alumina hollow fiber was obtained with a selectivity of 203 and a CO2 permeance of 5.4 x 10-8 mol m−2 s−1 Pa−1 at a pressure of 2 bar.

The purification of 1,3-butadiene from C4 hydrocarbon mixtures currently relies on energy-intensive extractive distillation. In this study, we employed ZIF membranes for this challenging separation for the first time, unveiling their superior capability in isolating 1,3-butadiene from other C4 hydrocarbons with similar sizes, including 1-butene, isobutene, and n-butane. This strong sieving effect was evident from two types of ZIF-8 membranes: one with low crystallinity fabricated via the all-vapor-phase ligand-induced permselectivation (LIPS) method and another with high crystallinity synthesized through the seeded growth method. The gas permeances decreased with increasing kinetic diameters, following the order of 1,3-butadiene (4.31 Å) > 1-butene (4.46 Å) > n-butane (4.687 Å) > isobutene (4.84 Å). The LIPS-ZIF-8 membrane exhibited a high 1,3-butadiene permeance of approximately 1.43 × 10−7 mol/m2 s Pa (∼430 GPU) and ideal separation factors of 18, 56, and 134 for 1,3-butadiene over 1-butene, n-butane, and isobutene, respectively. In separating four-component C4 mixtures, these membranes could enrich 1,3-butadiene content from 50% in the feed to 96–98% in the permeate through a single separation step. This unprecedented performance is attributed to differences in C4 diffusivities that span several orders of magnitude.

Membranes with precise molecular sieving channels that break the permeability‐selectivity trade‐off are desirable for energy‐efficient gas separation. Two‐dimensional (2D) membranes sieve gas through their special interlayer channels between neighboring nanosheets. However, the regulation and precise control of the nanochannels that match well with the size of the gas molecules remains a big challenge. Herein, accurate tuning of the interlayer spacing of layered double hydroxide (LDH) membranes at sub‐nanometer level was achieved by intercalation of Cl−, Br−, I−, and NO3− ions. Such high‐precision control allows customizable gas separation by selecting specific LDH membranes with appropriate channels according to the size of the gas molecules. Two membranes were used for demonstration: Cl‐LDH membrane shows high H2 permeance of ∼1870 GPU and desirable selectivities for H2/CO2(81), H2/N2(197), H2/CH4(320), and H2/C3H8(603); while I‐LDH membrane displays CO2 permeance of ∼1780 GPU and CO2/N2, CO2/CH4 selectivities of 182 and 297, respectively. The simultaneously high permeabilities and selectivities surpass the 2008 Robeson upper bounds. Molecular dynamics simulations quantitatively support the experiment results, further confirming the significant role of interlayer anions in the regulation of gas‐sieving channels. Given the rich variability of layered spacing and interlayer microenvironment for LDH materials, this work provides a platform membrane for various molecular sieving, including gas separation, solvent purification, seawater desalination, and so on. [ABSTRACT FROM AUTHOR]

Here, we report a new class of peptidomimetic macrocycles with well‐defined three‐dimensional structures and low conformational flexibility. They are assembled from fused‐ring spiro‐ladder oligomers (spiroligomers) by modular solid‐phase synthesis. Two‐dimensional nuclear magnetic resonance confirms their shape persistency. Triangular macrocycles of tunable sizes assemble into membranes with atomically precise pores, which exhibit size and shape‐dependent molecular sieving towards a series of structurally similar compounds. The exceptional structural diversity and stability of spiroligomer‐based macrocycles will be explored for more applications. [ABSTRACT FROM AUTHOR]

The ethanol/water separation challenge highlights the adsorption capacity/selectivity trade‐off problem. We show that the target guest can serve as a gating component of the host to block the undesired guest, giving molecular sieving effect for the adsorbent possessing large pores. Two hydrophilic/water‐stable metal azolate frameworks were designed to compare the effects of gating and pore‐opening flexibility. Large amounts (up to 28.7 mmol g−1) of ethanol with fuel‐grade (99.5 %+) and even higher purities (99.9999 %+) can be produced in a single adsorption process from not only 95 : 5 but also 10 : 90 ethanol/water mixtures. More interestingly, the pore‐opening adsorbent possessing large pore apertures showed not only high water adsorption capacity but also exceptionally high water/ethanol selectivity characteristic of molecular sieving. Computational simulations demonstrated the critical role of guest‐anchoring aperture for the guest‐dominated gating process. [ABSTRACT FROM AUTHOR]

Dynamic covalent chemistry (DCC) opens up a fascinating route for the construction of well‐organized supramolecular architectures, starting from organic molecular cages to crystalline macromolecular covalent organic frameworks (COFs). Herein, for the first time, we have manifested a facile room‐temperature DCC‐directed transformation of discrete organic imine cage‐to‐COF film at the liquid–liquid interface. The unfolding of the cage leading to the generation of imine intermediates, followed by their interface‐assisted preorganization and subsequent growth of the COF film, are elucidated through detailed spectroscopic and microscopic investigations. The interfacial cage‐to‐COF transformation provides a facile route for the faster fabrication of free‐standing COF films with high porosity and crystallinity, demonstrating excellent performance towards molecular sieving and high solvent permeance. Thus, the current study opens up a new route for structural interconversion between two crystalline entities with diverse dimensionality employing DCC at the confined interface. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO) membranes have great potential for separation applications due to their low-friction water permeation combined with unique molecular sieving ability. However, the practical use of deposited GO membranes is limited by the inferior mechanical robustness of the membrane composite structure derived from conventional deposition methods. Here, we report a nanostructured GO membrane that possesses great permeability and mechanical robustness. This composite membrane consists of an ultrathin selective GO nanofilm (as low as 32 nm thick) and a postsynthesized macroporous support layer that exhibits excellent stability in water and under practical permeability testing. By utilizing thin-film lift off (T-FLO) to fabricate membranes with precise optimizations in both selective and support layers, unprecedented water permeability (47 L·m-2·hr-1·bar-1) and high retention (>98% of solutes with hydrated radii larger than 4.9 Å) were obtained.

Although many porous materials, including metal–organic frameworks (MOFs), have been reported to selectively adsorb C2H2 in C2H2/CO2 separation processes, CO2‐selective sorbents are much less common. Here, we report the remarkable performance of MFU‐4 (Zn5Cl4(bbta)3, bbta=benzo‐1,2,4,5‐bistriazolate) toward inverse CO2/C2H2 separation. The MOF facilitates kinetic separation of CO2 from C2H2, enabling the generation of high purity C2H2 (>98 %) with good productivity in dynamic breakthrough experiments. Adsorption kinetics measurements and computational studies show C2H2 is excluded from MFU‐4 by narrow pore windows formed by Zn−Cl groups. Postsynthetic F−/Cl− ligand exchange was used to synthesize an analogue (MFU‐4‐F) with expanded pore apertures, resulting in equilibrium C2H2/CO2 separation with reversed selectivity compared to MFU‐4. MFU‐4‐F also exhibits a remarkably high C2H2 adsorption capacity (6.7 mmol g−1), allowing fuel grade C2H2 (98 % purity) to be harvested from C2H2/CO2 mixtures by room temperature desorption. [ABSTRACT FROM AUTHOR]

Silver-modified LTA zeolites are validated to be one of the most efficient nanomaterials applied in adsorptive separation, which is an energy-efficient alternative to the state-of-the-art cryogenic distillation for ethylene and ethane separation. Here, three representative LTA zeolites, Ag modifications via different methods including ion-exchange, mechanical mixing, and acid leaching, are systematically explored by X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, H2 temperature-programming reduction, and ultraviolet–visible spectroscopy with the assistance of Grand Canonical Monte Carlo simulations to identify the location of various Ag species in the LTA zeolite and thus to understand the mechanism of promoted separation performance in nature. The performance of these zeolites for the separation of ethylene/ethane is validated via ideal adsorbed solution theory and breakthrough experiments under ambient conditions. It is confirmed that Ag+ can afford selective binding of ethylene via π-complexation. Ag2O nanoparticles encapsulated in the zeolitic channels narrow the pore diameters to the suitable size, excluding ethane via molecular sieving. The synergistic effect of π-complexation and molecular sieving from Ag+ and Ag2O nanoparticles in the zeolitic channels triggers highly selective adsorption of ethylene over ethane. [ABSTRACT FROM AUTHOR]

Nanofiltration (NF) membranes as high selective separators are appealing for molecular sieving, which still remains a great challenge for the mixed dyes with same charge. In this study, cellulose acetate (CA) membranes were firstly aminated by ethylene imine polymer (PEI), and then the thin film of metal organic frameworks (MOFs) were constructed onto aminated CA membrane through forward-diffusion, slow crystallization and in situ growth of FeCo-Prussian blue (FeCo-PB) crystallization layers. The designed PB@CA composite NF membrane shows an ideal rejection for Congo red (CR)/methyl orange (MO) mixture solution, with 99.7%±0.2% for CR and 33.5%±2% for MO. In addition, the composite NF membrane demonstrated good efficiency for photocatalytic degradation of organic fouling (permeability recovery ratio was up to 92%) due to the active FeCo-PB micro-cubes. Thus, this work provides a practical strategy to prepare MOFs mediated thin film composite nanofiltration membrane for precise molecular sieving and catalytic antifouling performances. [ABSTRACT FROM AUTHOR]

Ultrafast molecular-sieving graphene-based membranes with selective separation of volatile aromatic compounds (VACs) have great potential in environmental protection, reutilization of expensive materials, and industrial separation processes. However, current graphene-based absorbents suffer from slow removal speed and limited adsorption capacity for VACs. Herein, pristine and Ni2+-controlled graphene oxide membranes (GOMs) with a permeance up to ∼8.0 × 10–6 mol m–2 s–1 Pa–1, being 1–2 orders of magnitude higher than those of previously reported membranes. The GOMs selectively separate VACs from N2 is achieved on ceramic substrates via the size-exclusion effect for the first time. At a high VACs feed concentration, such GOMs show high rejection rates of 99.8, 99.4, 95.9, and 97.3% for phenol, benzaldehyde, benzoic acid, and benzylamine, respectively. X-ray diffraction (XRD) results show the two-dimensional (2D) channel size for gas transportation within the GOMs is 0.44 nm, which can reject the transportation of VACs but have no effect on N2. Interestingly, using improved Ni2+-controlled GOMs, the rejection rates of benzoic acid and benzylamine rejection rates increased from 95.9 to 98.6% and from 97.3 to 99.4%, respectively. Our finding provides a fast and efficient way to filter VACs in air and has potential applications in air purification and industrial processes. [ABSTRACT FROM AUTHOR]

Adsorbents executing molecular sieving mechanisms for the efficient separation of n‐hexane (C6) alkane isomers require delicate pore size control, but afford unsatisfactory single‐component separations according to their branch degrees. Herein, we report a novel oxygenate‐pillared microporous adsorbent, MoOFOUR‐Co‐tpb, ([Co(tpb)2MoO4], tpb = 1,2,4,5‐tetra(pyridin‐4‐yl) benzene), with three gourd‐shaped channels for dual pore‐size sieving of C6 isomers. In particular, MoOFOUR‐Co‐tpb excludes 2,2‐dimethylbutane, while 3‐methylpentane (3MP) can enter one channel showing a high uptake of 82.6 mg g−1, contrasting to the n‐hexane (nHEX) adsorption by two channels (136 mg g−1). This dual pore‐size control strategy renders a record high equilibrium–kinetic combined selectivity for nHEX/3MP (30.2). Moreover, three‐ and five‐component breakthrough experiments confirm the practical separation performances and cycling stability. Multiple theoretical simulations reveal the separation mechanism and adsorption sites. [ABSTRACT FROM AUTHOR]

Plasma-induced polymerization of liquid silsesquioxane monomer (1,2-bis-(triethoxysilyl)-ethane, BTESE) at the gas–liquid interface was achieved at room temperature by employing an atmospheric-pressure plasma jet. The polymerization of the liquid monomer under exposure to atmospheric-pressure plasma resulted in the formation of a thin polysilsesquioxane layer at the immediate surface of the porous support. The confined polymerization at the plasma-liquid interface was demonstrated to be beneficial for preparing nanocomposite membranes with a thin selective layer on top of the porous support. The BTESE-derived polysilsesquioxane membrane exhibited high selectivity for gas separation (H2/CH4 = 195) based on the molecular sieving mechanism. [ABSTRACT FROM AUTHOR]

The efficient separation of acetylene (C2H2) from carbon dioxide (CO2) and CnH4 (n = 1 and 2) to manufacture high purity C2H2 and recover other light hydrocarbons is technologically important, while posing significant challenges. Herein, we reported a new TiF62− anion (TIFSIX) pillared metal-organic framework (MOF) ZNU-5 (ZNU = Zhejiang Normal University) with ultramicropores for highly selective C2H2 capture with low adsorption heat through gate opening based molecular sieving effect. ZNU-5 takes up a large amount of C2H2 (128.6 cm3/g) at 1.0 bar and 298 K but excludes CO2, CH4, and C2H4. Such high capacity has never been realized in MOFs with molecular sieving. The breakthrough experiments further confirmed the highly selective C2H2 separation performance from multi-component gas mixtures. 3.3, 2.8, and 2.2 mmol/g of C2H2 is captured at ZNU-5 from equimolar C2H2/CO2, C2H2/CO2/CH4, and C2H2/CO2/CH4/C2H4 mixtures, respectively. Furthermore, 2.6, 2.0, and 1.5 mmol/g of > 98% purity C2H2 can be recycled from the desorption process. Combining high working capacity, low adsorption heat, as well as good recyclability, ZNU-5 is promising for C2H2 purification. [ABSTRACT FROM AUTHOR]

A high-performance MOF-based mixed matrix membrane was constructed via incorporating o-BA modified ZIF-8 nanoparticles into PIM-1 matrices. The synergistic effect of molecular sieving and adsorption inhibition of the obtained membrane offers good chance for efficient mixed O 2 /N 2 separation. [Display omitted] • High-performance MOF-based MMMs were developed for mixed O 2 /N 2 separation. • The synergistic effect of size sieving and adsorption inhibition promotes excellent separation performance. • The modification of o-CB on the outer surface of ZIF-8 contributes to the improved interfacial compatibility. • The optimal membrane exhibits a mixed O 2 /N 2 selectivity of 8.9 with O 2 permeability of 796.5 Barrer. Oxygen/nitrogen (O 2 /N 2) separation is of great importance but faces huge challenges owing to their similar molecular size and close polarity. In this work, we construct a polymer of intrinsic microporosity (PIM-1) based mixed matrix membrane (MMM) for efficient O 2 /N 2 separation by using ZIF-8 as the sieving filler along with surface modification of o-carborane (o-CB) to strengthen selective N 2 adsorption fixation as well as polymer-filler interfaces. Markedly, the o-CB on the outer surface of ZIF-8 not only affords the requisite interfacial compatibility in molecular sieving MMMs, but also increases the diffusion difference between O 2 and N 2 by the preferential adsorption with N 2 molecules. This synergistic effect of molecular sieving and adsorption inhibition achieves efficient O 2 /N 2 diffusion differential separation. As expected, the optimal membrane with o-CB-ZIF-8 loading of 35 wt% exhibits an O 2 permeability of 796.5 Barrer and a mixed O 2 /N 2 selectivity of 8.9 with O 2 /N 2 (20:80, vol.) mixtures, exceeding the latest 2015 upper bound limits. Moreover, the according membrane module with o-CB-ZIF-8 loading of 20 wt% also displays moderate O 2 permeability of 391.7 Barrer and O 2 /N 2 selectivity of 5.5 under pressure of 1 bar. This work may provide a feasible platform for designing high-performance MOF-based membranes in air separations. [ABSTRACT FROM AUTHOR]

[Display omitted] • Structure of organosilica membranes was tailored via controlling the unsaturated degree of bridges. • Membranes exhibited satisfied separation performance for the n-butanol/water mixtures. • Pervaporation performance can be predicted by the gas permeation properties. In the petroleum industry, the mixing of ethanol (EtOH), isopropanol (IPA), and n-butanol (n-BuOH) with water is a prevalent occurrence in both production and recovery phases. Obtaining the required degree of purity via dehydration poses a significant challenge that needs to be addressed. Pervaporation has emerged as a promising method for separating azeotropic mixtures due to its energy efficiency and independence from vapor-liquid equilibrium constraints. In this study, organosilica precursors, namely 1,2-bis(triethoxysilyl)ethane (BTESE), 1,2-bis(triethoxysilyl)ethylene (BTESEthy), and 1,2-bis(triethoxysilyl)acetylene (BTESA), were utilized for the fabrication of organosilica membranes using the sol–gel method. Subsequently, these membranes were employed for pervaporation dehydration of EtOH, IPA, and n-BuOH. This study investigates the effect of the degree of unsaturation of the bridged group, feed composition, and C atom count of alcohol on membrane dehydration performance. The membranes demonstrated superior separation performance for the n-butanol/water mixtures compared to other alcohol/water systems investigated. In this particular context, BTESE membrane exhibited a significant separation factor, although accompanied by a reduced permeation flux. Conversely, BTESA membrane demonstrated a decreased separation factor but an increased permeation flux. The comparison between gas permeation and pervaporation highlighted that the separation mechanism was primarily governed by molecular sieving through the organosilica membranes. [ABSTRACT FROM AUTHOR]

• A stable and cost-effective MOF was prepared for benchmark CO 2 capture. • High CO 2 capacity with record CO 2 /N 2 and CO 2 /CH 4 selectivity was achieved. • Impressive CO 2 capacity of 2.60 mmol/g in CO 2 /N 2 breakthrough experiments. • MOF beads were granulated with high MOF loading and retained separation performance. The design of porous materials for CO 2 capture from flue gas and natural gas is highly demanded. However, it is challenging to target materials that combine high CO 2 capacity and CO 2 selectivity. In this work, we report a robust metal–organic framework (MOF) Zn-ox-mtz with one dimensional channels and narrow windows for excellent CO 2 capture from CO 2 /N 2 (simulated flue gas) and CO 2 /CH 4 (simulated natural gas) with high selectivity. Zn-ox-mtz exhibits a high CO 2 capacity (58.0 STP cm3 g−1 at 15 kPa), excellent CO 2 /N 2 (15/85, S > 106) and CO 2 /CH 4 (50/50, S > 105) selectivity and good chemical stability. In addition, the practical separation performance is demonstrated by breakthrough experiments under various process conditions. A efficient separation is achieved with the impressive CO 2 capacity of 2.60 ± 0.12 mmol g−1 at 298 K. Importantly, the outstanding performance is sustained under high humidity. The molecular sieving mechanism investigated by theoretical calculations indicated that CO 2 with small molecular size is tightly trapped by multiple C = O···H-C hydrogen bonding and O = C···O forces in the cavity while CH 4 and N 2 with larger molecular size display overlarge energy barrier to cross the contract pore windows. Moreover, the granulation of Zn-ox-mtz by hydroxypropyl cellulose is realized with high MOF loading (93.8 %) and the granulated Zn-ox-mtz beads retained the excellent CO 2 /N 2 and CO 2 /CH 4 separation performance. [ABSTRACT FROM AUTHOR]

The discharge of wastewater containing dyes not only causes serious environmental pollution but also poses a severe threat to human health. The selective separation of dyes and reuse of inorganic salts are vital in the textile industry. In this work, nitrogen-doped graphene quantum dots (N-GQDs) was successfully synthesized via the "one-step solvothermal method", and the N-GQDs composite membranes were innovatively fabricated by constructing a thin selective layer top the modified multi-walled carbon nanotubes (MWCNTs) matrix membrane via interfacial polymerization process. The pore size of the N-GQDs membranes could be flexibly modulated by regulating the contents of the N-GQDs. The suitable N-GQDs membrane (M4, 0.35 wt % of N-GQDs) possessed over 96 % rejection rate for diverse charged dyes, which was higher than that of the piperazine polyamide (PA3) membrane. Notably, the rejection of the smaller molecular weight of Methylene Blue by the M4 membrane reached ∼98.93 %, which was higher than that reported in most literature, mainly owing to the relatively smaller average pore size and stronger electronegativity of the membrane. Especially compared with our previous work, the prepared M3 and M4 membranes exhibited an enhancement of ∼37.79 % and 39.48 % in rejection of Methylene Blue, ∼ 78 % and 19 % in pure water permeability, respectively. On account of the size sieving and charge effect, the N-GQDs membrane (M4) could maintain high rejection for dyes and exhibited efficient separation for dye/salt with a separation factor of 115 for the Congo Red/sodium chloride mixture after continuous cross-flow filtration for 24 h in the simulated wastewater condition. Furthermore, the N-GQDs membrane also exhibited favorable acid-base resistance and satisfactory anti-fouling performance. Importantly, the N-GQDs membranes presented excellent decolorization efficiency for the practical textile wastewater. These results revealed that the as-prepared N-GQDs membrane possessed great potential for actual textile wastewater advanced treatment and purification. This study also offers a new candidate to rationally manipulate the separation properties of nanofiltration membranes adopting new aqueous monomers. [Display omitted] • The pore size of the membrane could be flexibly regulated by N-GQDs contents. • The custom-tailored N-GQDs membrane was suitable for efficient dye separation. • N-GQDs membranes show worthy durability and selectivity even in harsh conditions. • N-GQDs membranes present superior decolorization for actual dye wastewater. [ABSTRACT FROM AUTHOR]

The realization of ideal molecular sieves has a great potential to achieve the desired gas separations by fine‐tuning pore structures to generate suitable aperture sizes, which can be exclusive to larger molecules thus performing efficient separations. Despite numerous attempts, there are few developed porous materials that implement molecular sieving for C2H2/CH4 separation. Herein, we show how fine‐tuning of pore size in a series of selected SIFSIX materials achieves ideal molecular sieving for C2H2/CH4 separation at ambient conditions. With an optimized pore size of 3.4 Å and abundant binding sites in the channels, UTSA‐200 shows complete exclusion of larger CH4 molecules, while maintaining strong affinities toward C2H2. Therefore, this material exhibits both high uptake capacity at low pressure (up to 41 cm3 g−1 at 0.01 bar and 296 K) and record C2H2/CH4 selectivity (over 1×107). Dynamic breakthrough experiments validated the ideal sieving separation performance of UTSA‐200 for C2H2/CH4 mixtures, affording an exceptionally high C2H2 capacity of 73.5 L kg−1 with high purity of 99.5 % per cycle. [ABSTRACT FROM AUTHOR]

Efficient incorporation of supramolecular hosts in polymeric membranes can impart the overall matrix with new properties for a range of cutting-edge applications. Here, we introduce a Supramolecular Interfacial Assembly (SIA) method for the fabrication of polymeric membranes featuring embedded macrocycles. Through harnessing the quasi-liquid nature of the concentrated polymer solution, SIA orchestrates the homogenous spreading of macrocycles in an aqueous layer on its surface, leading to the creation of an interface between "water/water" phases, subsequently forming a cross-linked membrane driven by supramolecular electrostatic interactions. Remarkably, compared to the traditional interfacial polymerization, SIA adheres to a "green" paradigm without the need for organic solvents. The resultant composite membrane exhibits superior performance in organic solvent nanofiltration (OSN), owing to the precise molecular sieving property provided by the macrocycles with well-defined permanent cavities. This fabrication method holds great promise for the innovative design of composite membranes, which can greatly impact the production of smart membrane materials for advanced technology applications in the future., (© 2024 Wiley‐VCH GmbH.)

In recent years, extensive research has used molecular dynamics simulations to investigate gas separation through nanoporous graphene (NPG) membranes. However, most studies have considered graphene membranes as rigid, overlooking the impact of their inherent flexibility. This study systematically quantifies the effect of graphene flexibility on gas permeation by comparing the diffusion of various gases through flexible and rigid single-layer NPG models. The results demonstrate that flexibility notably increases permeance, particularly for gases with larger molecular diameters/pore size ratios, by allowing gas molecules greater mobility within the pore. Interestingly, the effect of flexibility boils down to the expansion of the average pore size, and the detail of the membrane's vibrational dynamics is of little importance in quantifying permeance. Our work shows that accounting for flexibility in molecular models improves the alignment of simulation results with experimental data, emphasizing the importance of considering membrane flexibility in predictive models of NPG membrane performance.

Molecular sieving is an ideal separation mechanism, but controlling pore size, restricting framework flexibility, and avoiding strong adsorption are all very challenging. Here, we report a flexible adsorbent showing molecular sieving at ambient temperature and high pressure, even under high humidity. While typical guest-induced transformations are observed, a high transition pressure of 16.6 atm is observed for C 2 H 4 at 298 K because of very weak C 2 H 4 adsorption (~16 kJ mol -1 ). Also, C 2 H 6 is completely excluded below the pore-opening pressure of 7.7 atm, giving single-component selectivity of ca. 300. Quantitative high-pressure column breakthrough experiments using 1 : 1 C 2 H 4 /C 2 H 6 mixtures at 10 atm as input confirm molecular sieving with C 2 H 4 adsorption of 0.73 mmol g -1 or 32 cm 3 (STP) cm -3 and negligible C 2 H 6 adsorption of 0.001(2) mmol g -1 , and the adsorbent can be completely regenerated by inert gas purging. Furthermore, it is highly hydrophobic with negligible water adsorption, and the C 2 H 4 /C 2 H 6 separation performance is unaffected at high humidity., (© 2024 Wiley-VCH GmbH.)

The precise manipulation of the microstructure (pore size, free volume distribution, and connectivity of the free-volume elements), thickness, and mechanical characteristics of membranes holds paramount significance in facilitating the effective utilization of self-standing membranes. In this contribution, the synthesis of two innovative ester-linked covalent-organic framework (COF) membranes is first reported, which are generated through the selection of plant-derived ellagic acid and quercetin phenolic monomers in conjunction with terephthaloyl chloride as a building block. The optimization of the microstructure of these two COF membranes is systematically achieved through the application of three different interfacial electric field systems: electric neutrality, positive electricity, and negative electricity. It is observed that the positively charged system facilitates a record increase in the rate of membrane formation, resulting in a denser membrane with a uniform pore size and enhanced flexibility. In addition, a correlation is identified wherein an increase in the alkyl chain length of the surfactants leads to a more uniform pore size and a decrease in the molecular weight cutoff of the COF membrane. The resulting COF membrane exhibits an unprecedented combination of high water permeance, superior sieving capability, robust mechanical strength, chemical robustness for promising membrane-based separation science and technology., (© 2024 Wiley‐VCH GmbH.)

The outermost component of cell envelopes of most bacteria and almost all archaea comprise a protein lattice, which is termed Surface (S-)layer. The S-layer lattice constitutes a highly porous structure with regularly arranged pores in the nm-range. Some archaea thrive in extreme milieus, thus producing highly stable S-layer protein lattices that aid in protecting the organisms. In the present study, fragments of the cell envelope from the hyperthermophilic acidophilic archaeon Saccharolobus solfataricus P2 (SSO) have been isolated by two different methods and characterized. The organization of the fragments and the molecular sieving properties have been elucidated by transmission electron microscopy and by determining the retention efficiency of proteins varying in size, respectively. The porosity of the archaeal S-layer fragments was determined to be 45%. S-layer fragments of SSO showed a retention efficiency of up to 100% for proteins having a molecular mass of ≥ 66 kDa. Moreover, the extraction costs for SSO fragments have been reduced by more than 80% compared to conventional methods, which makes the use of these archaeal S-layer material economically attractive. [ABSTRACT FROM AUTHOR]

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

• Novel method for rGOA production by dithionite (DTN) driven reduction induced self-assembly. • The optimal DTN to GO ratio is 2:1 by mass based on Raman, FTIR, and nitrogen adsorption results. • Limited access of hexane isomers to pores and the surface of rGOAs dependent on the molecule kinetic diameter. • Hexane isomers can be separated in rGOAs based on molecular kinetic sieving effect. • Aromatic C6 hydrocarbon establish strong specific interactions with the rGOA surface. The ability of reduced graphene oxide aerogels (rGOAs) for challenging gas-phase separation was investigated with hexane isomers and benzene (C6 hydrocarbons) using inverse gas chromatography (IGC). For the first, rGOAs were synthesized with sodium dithionite (DTN) as a reductant. Experiments revealed that the most optimal DTN to graphene oxide mass ratio was 2:1, resulting in the highest specific surface area of 432.3 m2 g−1 and the highest degree of graphitization among analyzed samples. C6 hydrocarbon adsorption tests demonstrated the dominant role of the kinetic effect for the adsorption of branched and cyclic hexane isomers - the partition coefficient decreased as the molecule kinetic diameter increased. The contribution of thermodynamic effects was distinguished for molecules with uneven charge distribution. A comparison of the partition coefficient ratios for different pairs of hydrocarbons demonstrated the potential of rGOAs in separating various C6 hydrocarbons. The selectivity, calculated from binary-component adsorption tests of benzene (Bz)/cC6 equimolar mixture, was 13.7, 8.5 and 2.8 for DTN4, DTN2, and DTN1. The research indicates that rGOAs may have potential as adsorbents for the selective separation of hydrocarbons, however, the competitive adsorption and performance at high surface coverages of adsorbates have to be accounted for in further research to assess the applicability of rGOAs reliably. [ABSTRACT FROM AUTHOR]

Organic solvent nanofiltration (OSN) membranes with precise molecular-sieving performance have become increasingly important in chemical and pharmaceutical industries, desiring superior membranes with both high permeability and selectivity. Herein, the V-shape Tröger's base (TB) structure is incorporated in the polyamide network to engineer microporosity as well as the molecular-sieving performance of the thin-film composite (TFC) polyamide membrane for organic solvent nanofiltration (OSN). The TFC membrane containing the TB structure features a rigid and contorted chain structure, which affords high and stable methanol permeability in OSN applications. Furthermore, the H-bond interaction between the H of amide groups and N in TB reinforces the interchain interaction, endowing the membrane with a precise selectivity to organic solutes. The as-prepared TFC membrane demonstrated high methanol permeance of 16.6 L m−2 h−1 bar−1 and sieving performance to organic molecules with molecular weight cut-off (MWCO) down to 349 Da. Furthermore, the membrane demonstrates shape selectivity for organic solutes, exploiting the fine microporous structure. This study may provide insights into the molecular design of TFC membranes by finely tuning the molecular features for precise solute separations. TFC membranes prepared by interfacial polymerization using TBDA as an aqueous monomer with a V-shape structure were selected for the formation of trapped nanovoids in the polymer network. [Display omitted] • The V-shape TBDA was explored as aqueous phase to incorporate contorted polymer chains in the polymer network. • The PA-TBDA TFC membranes with a fine microporous structure exhibit both size and shape selectivity for organic solutes. • The PA-TBDA TFC membranes show excellent methanol permeance of 16.6 L m−2 h −1 bar −1 with MWCO down to 349 Da. • The PA-TBDA TFC membranes demonstrate excellent long-term stability and can be operated at 10 bar for 7 days in DMF. [ABSTRACT FROM AUTHOR]

[Display omitted] • Scale-up preparation of Cu(BF 4) 2 (4-DPDS) 2 using room temperature and green solvent. • Simultaneously achieves extremely high selectivity for binary components of C 2 H 4 /C 2 H 6 , C 3 H 6 /C 3 H 8 , and C 2 H 2 /CO 2. • Calculations verified the dynamic diffusion behavior of olefins in the flexible gourd channel. • Simultaneously capture and separation of C 2 H 4 and C 3 H 6 from seven-component cracking gases at ambient conditions. • Extraordinarily stable structure enables multiple cycles of gas separation under 75% humidity. Simultaneously capturing and separating high-purity C 2 H 4 and C 3 H 6 from cracked gas mixtures presents a significant challenge. Herein, a robust metal–organic framework (Cu(BF 4) 2 (4-DPDS) 2) was designed featuring a gourd-shaped one-dimensional channel. Its specific alkenes match structure can only adsorb alkenes while completely excluding alkanes. With a remarkable adsorption selectivity of 76,203 for equimolar C 2 H 4 /C 2 H 6 and high selectivity of 159 for equimolar C 3 H 6 /C 3 H 8 , Cu(BF 4) 2 (4-DPDS) 2 not only achieves >99 % purity separation of C 2 H 4 and C 3 H 6 from binary mixtures but also simultaneously captures and separates these compounds from seven-component cracking gases at ambient conditions. Its performance stability remains intact even under 75 % RH conditions, thanks to its robust framework. Based on the particular gourd-shaped channel, it can also achieve efficient C 2 H 2 /CO 2 separation. Ab initio Molecular Dynamics simulations demonstrate the dynamic diffusion process of gas molecules in the structure, and in situ infrared analyses reveal the framework's rich C-H•••F and S•••π binding sites with C 2 H 4 and C 3 H 6. This material's robust structure, exceptional alkene sieving capabilities, and repeatable separation performance comprehensively showcase Cu(BF 4) 2 (4-DPDS) 2 as a unique metal–organic framework for simultaneous recognition and capture of C 2 H 4 and C 3 H 6. [ABSTRACT FROM AUTHOR]

[Display omitted] • Recent advances in MOFs for C 3 H 6 - and C 3 H 8 -selective separation were reviewed. • Mechanisms for C 3 H 6 - and C 3 H 8 -selective separation by MOFs were discussed. • Parameters influencing C 3 H 6 /C 3 H 8 -selective separation by MOFs were investigated. Due to their similar physicochemical characteristics, the separation of propylene (C 3 H 6) from propane (C 3 H 8) is a challenging but essential process in the petrochemical industry. Currently, the majority of known techniques use either one-sided thermodynamic or kinetic separation. However, purification under ambient conditions is possible via adsorption-based separation using porous particles, which may have positive energy and environmental effects. Metal–organic frameworks (MOFs) are the most promising option for selectively separating C 3 H 6 and C 3 H 8 due to their ability to control pore shape and functionality. This review discusses the different separation processes, key separation variables, and benchmarked C 3 H 6 /C 3 H 8 separation variables, including the current state of C 3 H 6 /C 3 H 8 selective separation using MOFs. It also examines the primary challenges and opportunities associated with using MOFs for the effective separation of C 3 H 6 /C 3 H 8. [ABSTRACT FROM AUTHOR]

Porous single-layer graphene is believed to be an ultimate molecular sieving membrane. One of the bottlenecks in scaling up graphene membranes is the transfer process in which capillary forces as well as the mechanical tensions imposed on the graphene film generate unwanted cracks and tears. Herein, we report a single-step fishing-free transfer technique for the fabrication of a helium-sieving graphene membrane using a spin-coating-assisted approach in which no capillary forces and mechanical tensions are exerted on the graphene film. The porous polysulfone (PS), which is synthesized in this method, is applied as both the graphene protective layer and the porous reinforcing support; thus, eliminating the fishing stage in which the graphene film is scooped onto a supporting substrate. The proposed technique yields a crack-free and large-area (∼1 cm2) graphene film on the porous polymer substrate. This technique also eliminates the issue with polymer residues remaining on the graphene surface during the transfer process. A relatively high gas molecular sieving performance (gas selectivity of 25, 24, and 1.1 for He/CH4, H2/CH4, and He/H2 separation, respectively) was obtained, which demonstrates the presence of sub-nanometer intrinsic defects as well as the absence of cracks and tears in the graphene membrane. Despite the low graphene porosity of 0.002%, agreeable He and H2 permeance (up to 5.18 × 10–8 mol m–2 s–1 Pa–1) was observed, which highlights the success of the developed technique used for the fabrication of graphene membrane in the current work. [ABSTRACT FROM AUTHOR]

The problem of ever‐increasing industrial demand versus the supply shortage of helium (He) is inevitably encountered by scientists worldwide. Membrane‐based separation technology provides an economical method to alleviate the current He scarcity. In this study, using a combination of first‐principles calculations and molecular dynamics simulations, it is theoretically demonstrated that the phosphorus carbide membrane P2C3 possesses high efficiency in He separation from the natural gas (H2, N2, CO, H2O, CO2, and CH4) and other noble gas atoms (Ne and Ar). In addition, the He permeance exceeds 10–4 mol m–2 s–1 Pa–1 over a wide range of temperatures (200–500 K), which is far beyond the industrially acceptable value. Combining the zero‐point‐energy and quantum tunneling effects, the quantum analysis shows that the P2C3 membrane has great potential for 3He/4He isotope separation, thus providing a combined means for both He and 3He isotope separation. The results uncover a new solution of utilizing P2C3 nanomaterial as a novel medium for gas treatment and the findings of this study will promote experimental efforts in the future. [ABSTRACT FROM AUTHOR]

Membrane materials with excellent selectivity and high permeability are the key for high-efficiency membrane separation. New-type porous materials have developed as ideal building blocks for molecular sieving membranes due to their inherent properties, such as permanent porosity, high surface area, structural diversity and low mass transfer barriers. In actual industrial promotion and separation applications, porous materials need to be combined with substrates to prepare porous composite membranes. In order to reduce costs and increase processing flexibility, the combination of organic polymer substrates and porous materials has received more attentions. The multifunctional design strategy of the membrane material and membrane structure of porous composite membranes based on the organic subatrates is the key to realize the further improvement of mass transfer. In this review, we focus on the organic matrix porous composite membrane based on the participation of inorganicorganic hybrid materials and organic-organic composite materials, and conduct an in-depth discussion on the transport mechanism of porous composite membranes, and highlight diverse structural control strategies from the perspectives of macrostructural design and microstructural regulation of membrane structures. Finally, the applications of porous composite membrane based on organic substrate in precise molecular sieving are summarized, and the future opportunities and challenges in this field are discussed briefly. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks with programmed surface charge enable tunable permeation behaviors of water permeation of 15.5 to 34.5 L m−2 h−1 bar−1 and dye removal up to 99%. This is attributed to the modulation of wetting and solid surface energy which provide further insight into controllable molecular transport and design of nanomaterials for sieving, water treatment, and energy conversion. [Display omitted] Molecular separation is critical to mitigating the issues of water contamination and shortage and currently focuses on the use of framework materials fabricated by special building blocks. However, developing a simple and tunable synthesis methodology for materials with alternative permeation and selectivity remains challenging. Here, we fabricate a series of nanochannel membranes composed of uniform spherical covalent organic frameworks (COFs). Diversified spherical COFs have diameters ranging from ∼150 to ∼800 nm, therefore demonstrating a programmable surface charge distribution from −24 to −63 mV. COF membranes with tailor-made surface charge enable different surface energy levels and allow increasing water permeation of 15.5 to 34.5 L m−2 h−1 bar−1. Furthermore, COFs can also act as filters, achieving up to 99.7% rejection and separation of the opposite charged dyes. We expect these COFs with tunable surface charge to be applicable to variety of fields, including sieving, batteries, and water treatments. [ABSTRACT FROM AUTHOR]

Monolayer graphene growth on liquid copper (Cu) has attracted attention due to advantages of a flat/smooth catalytic growth surface, high synthesis temperature (>1080 °C) as well as the possibility of forming graphene domains that are mobile on the liquid Cu with potential to minimize grain boundary defects and self-assemble into a continuous monolayer film. However, the quality of monolayer graphene grown on liquid copper and its suitability for size-selective ionic/molecular membrane separations has not been evaluated/studied. Here, we probe the quality of monolayer graphene grown on liquid Cu (via a metallurgical process, HSMG ^® ) using Scanning Electron Microscope (SEM), High-resolution transmission electron microscope (HR-TEM), Raman spectroscopy and report on a facile approach to assess intrinsic sub-nanometer to nanometer-scale defects over centimeter-scale areas. We demonstrate high transfer yields of monolayer graphene (>93% coverage) from the growth substrate to polyimide track etched membrane (PITEM, pore diameter ∼200 nm) supports to form centimeter-scale atomically thin membranes. Next, we use pressure-driven transport of ethanol to probe defects > 60 nm and diffusion-driven transport of analytes (KCl ∼0.66 nm, L-Tryptophan ∼0.7–0.9 nm, Vitamin B12 ∼1–1.5 nm and Lysozyme ∼3.8–4 nm) to probe nanoscale and sub-nanometer scale defects. Diffusive transport confirms the presence of intrinsic sub-nanometer to nanometer scale defects in monolayer graphene grown on liquid Cu are no less than that in high-quality graphene synthesized via chemical vapor deposition (CVD) on solid Cu. Our work not only benchmarks quality of graphene grown on liquid copper for membrane applications but also provides fundamental insights into the origin of intrinsic defects in large-area graphene synthesized via bottom-up processes for membrane applications.

Molecular sieving of propylene (C 3 H 6 ) from propane (C 3 H 8 ) is highly demanded for C 3 H 6 purification. However, delicate control over aperture size to achieve both high C 3 H 6 uptake and C 3 H 6 /C 3 H 8 selectivity with low cost remains a significant challenge. Herein, a green and scalable approach is reported for preparing an isomeric CALF-20 adsorbent, termed as NCU-20, using water as the only solvent with a cost of $10 per kilogram. NCU-20 features a contracted pore size (4.2 × 4.7 Å 2 ) compared to CALF-20 (5.2 × 5.7 Å 2 ), which enables molecular sieving of C 3 H 6 (4.16 × 4.65 Å 2 ) from C 3 H 8 (4.20 × 4.80 Å 2 ). Notably, NCU-20 exhibits record-high C 3 H 6 adsorption capacity (94.41 cm 3  cm -3 ) at 298 K and 1.0 bar, outperforming all C 3 H 6 /C 3 H 8 molecular sieving adsorbents. The sieving performances of C 3 H 6 /C 3 H 8 are well maintained at elevated temperatures. Therefore, a delicate balance between C 3 H 6 adsorption capacity (91.62 cm 3  cm -3 ) and C 3 H 6 /C 3 H 8 selectivity (uptake ratio of 22.2) is obtained on NCU-20 at 298 K and 0.5 bar. Furthermore, dynamic breakthrough experiments demonstrate a high productivity of 65.39 cm 3  cm -3 for high-purity C 3 H 6 (>99.5%) from an equimolar C 3 H 6 /C 3 H 8 gas-mixture., (© 2024 Wiley‐VCH GmbH.)

Two-dimensional graphene oxide (GO) membranes exhibit great potential for environmental aqueous separation and purification. However, their viability and performance are greatly limited under cross-flow conditions due to the enlargement of interlayer spacing and peeling of stacked GO laminates in aqueous environments. Herein, inspired by natural nacre structure, we present a dual-functional and ultra-stable β-cyclodextrin (β-CD) -polyacrylic acid (PAA) -GO composite membrane, with a constant d-spacing in both wet and dry states. Nanosheets and chain polymers construct a typical "brick-mortar" structural configuration, which exhibits great anti-swelling property compared with other reported GO membranes. By rationally optimizing and tuning the membrane structures, the ultrathin GO membrane (∼50 nm) exhibits outstanding stability in cross-flow and long-term filtration. Moreover, the designed membrane shows dual functions (high-throughput enantioselectivity and excellent dyes rejection) with the increase of molecular size. This strategy boosts the ongoing research in designing robust lamellar membrane materials for practical engineering applications in aqueous environments. [Display omitted] [ABSTRACT FROM AUTHOR]

Coordination polymer (CP) glasses offer a way to tackle the fabrication challenges encountered by inorganic porous membranes and show great potentials for size‐exclusive gas separation. However, their processability and performance still cannot simultaneously meet the requirements for high‐performance membrane separation. Herein, we have developed a series of CP glasses (M‐P‐dmbIm, M=Zn, Cd, Cu, and Mn), which possess low vitrification temperature as well as low viscosity (η) and lave capability above the transition temperatures. The derived glass (agM‐P‐dmbIm) membranes show outstanding performances for H2/CO2, H2/N2, and H2/CH4 separation, which all far surpass the Robeson upper bound and even rival against the best of the state‐of‐the‐art gas separation membranes. The low viscosities not only allow us to hot‐cast or hot‐press the CP glasses into thin membranes within 5 min without sacrificing their selectivity and permeability, but also endow the resulted glass membranes with healing ability. [ABSTRACT FROM AUTHOR]