MOF-in-COF molecular sieving membrane for selective hydrogen separation

Harnessing S-scheme BiOCl/COF heterojunctions for sustainable and efficient photocatalytic hydrogen peroxide synthesis under visible light

Photocatalytic hydrogen peroxide production offers a greener alternative, but its efficiency is limited by high carrier recombination. Covalent organic frameworks, with their highly ordered structures and tunable properties, are promising photocatalysts. However, their application in H2O2 production has been constrained by the lack of effective strategies to enhance catalytic activity. In this study, BiOCl/COF (TFPB-BPY) S-scheme heterojunctions were prepared via a simple in-situ growth method. The heterojunction exploits the nitrogen-rich architecture and charge transport of the COF, combined with the broad light absorption and internal electric field of BiOCl. This synergy enables superior visible light absorption, efficient charge separation, and suppressed recombination. Mechanistic studies confirmed the S-scheme mechanism as the key to its enhanced performance. This work provides a scalable and eco-friendly strategy for improving COF-based photocatalysts through S-scheme heterojunctions, offering a pathway for sustainable H2O2 production and advancing the rational design of photocatalysts for green energy applications.

Synthesis and characterization of a delivery system by combining cobalt (II) with soluble dietary fiber from Cyperus esculentus L. to regulate gut-derived neuroactive metabolite biosynthesis

Cobalt (Co) deficiency significantly impacts vegetarians and individuals with malabsorption disorders. To enhance loading efficiency, safety, and bioavailability of Co, a novel organic delivery system, CESDF-Co (II), was constructed using soluble dietary fiber from Cyperus esculentus L. (CESDF) as an organic ligand, synthesized using a microwave-assisted solid-phase method. Comprehensive analyses were conducted to determine the structural characteristics of CESDF-Co (II) and evaluate its stability, targeted release efficiency, and potential to regulate the biosynthesis of gut-derived neuroactive metabolites. Results revealed the formation of a three-dimensional cross-linked network within the CESDF-Co (II) due to Co (II) coordination bridging, with a cobalt loading of 78.14 mg/g. This structure enhanced its thermal stability and surface hydrophobicity while retaining the intrinsic resistance of CESDF to gastrointestinal digestion, facilitating colon-targeted delivery of CESDF-Co (II). In vitro fermentation demonstrated that CESDF-Co (II) significantly increased neuroactive-related amino acid precursors (tryptophan, tyrosine, glutamic acid, and methionine by 2.04-, 2.92-, 2.33-, and 2.58-fold, respectively) and neurotransmitters (serotonin, γ-aminobutyric acid, dopamine, and acetylcholine by 3.28-, 4.93-, 1.73-, and 1.54-fold, respectively). This enhancement positively correlated with increased production of total short-chain fatty acids (1.57-fold) and cobalt-dominated vitamin B12 synthesis (16.25-fold). These findings offer valuable insights for constructing secure colon-targeted, microbiota-triggered release delivery systems.

Superior Hydrogen Separation in Nanofluidic Membranes by Synergistic Effect of Pore Tailoring and Host-Guest Interaction

High-purity H2 production accompanied by precise decarbonization paves the way for a carbon-neutral society. Hydrogen-bonded organic frameworks (HOFs) are promising materials for advanced gas separation membranes, but their broad nanoscale pores limit selective separation. High-quality carboxylic acid-based HOF membranes (HOF-S, HOF-M, HOF-L) with pore sizes of 6.2, 16, and 24 Å were synthesized using an innovative pore-tailoring strategy. Under optimized conditions, H2 can pass through while CO2 is blocked by the size-exclusion principle. Abundant carboxylic acid groups in pores hinder the mobility of CO2 via electrostatic interaction, integrating adsorption and molecular sieving to enable excellent H2 transport and separation. The HOF-S membrane combines size exclusion and HOF-CO2 interactions, exhibiting excellent selectivity for H2/CO2 (164) and a ternary gas mixture (H2/CO2 selectivity: 154; H2/CH4 selectivity: 201). It also displays long-term stability under both dry and wet conditions. This strategy opens new possibilities for customizing nanofluidic membranes for advanced gas separation technologies.

Reducing the excition binding energy of covalent-organic frameworks via spatial-confined NiCo-NC as internal nanoreactors for photocatalytic hydrogen evolution

COFs (covalent-organic frameworks) are regarded as ideal photocatalyst for hydrogen-evolution, due to their structural controllability, but they possess poor electrical conductivity and high exciton binding energy, which limits their photocatalytic activity. Here, the NiCo-ZIF-67 derived NiCo-nitrogen-doped carbon (NiCo-NC) with superior conductivity and high light-absorption capacity was spatially confined in the channels of TP-BD COF (TP: 2, 4, 6-triformylphloroglucino; BD: 4, 4'-biphenylenediamin) by constructing hydrogen bonds to form NiCo-NC@TP-BD COF core@shell heterojunctions and NiCo-NC acts as internal highly active nanoreactor, which could accelerate the photocatalytic efficiency. Specifically, the optimal catalyst NiCo-NC@TP-BD-0.6 (NT-0.6) exhibits the maximum H2 evolution rate of 78.97mmol g-1 h-1 without Pt cocatalyst, which is approximately 395 times higher than that of bare TP-BD COF. Systematic investigations imply that the NiCo-NC as a high active nanoreactor was stably encapsulated in the pore of TP-BD by hydrogen bonds and formed a close interfacial contact, which is revealed by Fourier-transform infrared spectroscopy (FT-IR) and proton nuclear magnetic resonance (1H NMR). Meanwhile, the charge transfer and Hydrogen Evolution Reaction (HER) are revealed by the density functional theory (DFT) calculation. This work offers a promising strategy to reduce the high excitation binding energy of COFs-based catalysts in photocatalytic H2 evolution.

Shielding CO2-Philic Sites in Trimmed Covalent Organic Framework Pores by Atomic Layer Deposition

Strong adsorptive sites toward unwanted gas molecules in porous framework materials often lead to reversed sorption selectivity, creating tremendous challenges for enhancing the diffusion-driven membrane separations targeted at the weakly adsorbed species in the gas pair. While post-synthetic modification methods have been reported to downsize the pores in covalent organic frameworks (COFs), effective approaches to shield the highly adsorptive sites within the pores are rarely explored. Here, a solvent-less pore modification strategy is developed using atomic layer deposition (ALD). it is shown that controlled amounts of ZnO can be uniformly deposited into the COF pores, offering the ability to fine-tune the pore dimensions. Moreover, the Zn─O moieties grown into the COF pore are found to interact with the CO2-philic ketoenamine groups, and substantially reduce the CO2 solubility by 72.4% in the COF membrane. Accordingly, the simultaneously increased diffusion selectivity and sorption selectivity for H2/CO2 lead to a 330% improvement of the permselectivity in membrane separation, demonstrating the efficacy of the strategy for pore engineering in COFs.

Converging the Complementary Traits of Metal-Organic Frameworks and Covalent Organic Frameworks

Since their discovery, metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) featuring permanent nanopores have transformed the landscape of porous materials, excelling as platforms for catalysis, gas separation, and sensing thanks to their exceptional surface areas, adjustable pore sizes, and modular functionality. However, MOFs, while versatile, face stability challenges due to their coordination bonds, whereas COFs, although robust, lack metal sites, limiting their catalytic activity, redox functionality, and other metal-specific applications. To bridge these gaps, innovative porous materials, such as MCOFs, which incorporate metal ions into COF lattices; covalent cluster frameworks, formed by assembling metal clusters into covalent networks; and MOF-COF composites, which integrate the strengths of both systems, have emerged. This review explores the synthesis and design principles of these advanced materials, showcasing their applications and the unique advantages conferred by their composite nature. It provides insights into future directions and their potential to address key challenges in materials science and beyond.

Lithium complexing strategy based on host-guest recognition for efficient Mg2+/Li+ separation

Ion selective membranes with precise Mg2+/Li+ separation have attracted extensive interest in lithium extraction to circumvent the lithium supply shortage. However, realizing this target remains a significant challenge mainly due to a high concentration ratio of Mg2+/Li+ as well as the relatively close ionic hydration radius and chemical. Herein, inspired by the host-guest recognition between alkali-metal ions and crown ether (CE), a novel approach was proposed to regulate the membrane internal structure by introducing CE to strengthen the complexation between Li+ and CE. The CE modified membranes achieved the unique outcome of "Li+ rejection-Mg2+ permeation" deriving from enhanced solubility (KS) and retarded diffusivity (DS) of Li+ compared to that of Mg2+. The Mg2+/Li+ separation factors for MgSO4/Li2SO4 and MgCl2/LiCl of modified membranes (i.e., 20.1 and 17.7) are about 21.9 and 19.9 time higher than that of pristine membranes, respectively. The results from density function theory (DFT) indicated that the stronger host-guest interaction between CE and Li+ combined them closely, thereby increasing solubility and reducing diffusivity of Li+. Our findings develop a new efficient membrane-based strategy enabling the production of high-purity lithium salts from simulated brine.

Covalently Bound MOF/COF Aerogels as Robust Catalytic Filters for Rapid Nerve Agent Decomposition

Metal-organic frameworks (MOFs) show promising results in various fields, such as gas separation and catalysis, but they face limitations due to problems associated with their low processability. This study addresses these challenges by utilizing postsynthetic modification (PSM) of NH2-UiO-66 and NH2-MOF-808 with 1,3,5-benzene tricarbaldehyde (BTCA) to form hybrid aerogels consisting of MOF-loaded covalent organic framework (COF). BTCA-modified MOF nanoparticles via imine bond formation were confirmed by 1H NMR, FTIR, and solid-state 13C NMR spectroscopies. MOF/COF composites were analyzed via TGA, PXRD, BET, and solid-state 13C NMR, showing retained crystallinity and increased porosity in comparison to the sum of the individual components. Moreover, improved aerogel mechanical properties and increased MOF loading of up to 75 wt % were achieved for covalently bound aerogels. Hybrid aerogel composites were successfully utilized as catalytic filters for the decomposition of nerve agent simulant and pesticide dimethyl-4-nitrophenylphosphate (DMNP), avoiding secondary pollution associated with MOF powder catalysis.

Harnessing Pore Size in COF Membranes: A Concentration Gradient-Driven Molecular Dynamics Study on Enhanced H2/CH4 Separation

This work presents a novel approach for accurately predicting the gas transport properties of covalent organic framework (COF) membranes using a nonequilibrium molecular dynamics (NEMD) methodology called concentration gradient-driven molecular dynamics (CGD-MD). We first simulated the flux of hydrogen (H2) and methane (CH4) across two distinct COF membranes, COF-300 and COF-320, for which experimental data are available in the literature. Our CGD-MD simulation results aligned closely with the experimentally measured gas permeability and selectivity of these COF membranes. Leveraging the same methodology, we discovered promising COF candidates for H2/CH4 separation, including NPN-1, NPN-2, NPN-3, TPE-COF-I, COF-303, DMTA-TPB2, 3D-Por-COF, COF-921, COF-IM AA, TfpBDH, and PCOF-2. We then compared our findings with simulations utilizing the well-known approach that merges grand canonical Monte Carlo (GCMC) and equilibrium molecular dynamics (EMD) to predict gas adsorption and diffusion parameters in COFs. Our results showed that when the pore sizes of COF membranes are below 10 Å, the choice of the method plays a significant role in determining the performance of the membranes. The GCMC+EMD approach suggested that COFs tend to exhibit CH4 selectivity when their pore limiting diameters are below 10 Å, whereas the CGD-MD results reveal a preference for H2. Density functional theory calculations indicate that H2 has a lower affinity for three promising COFs, NPN-1, NPN-2, and NPN-3, compared to CH4, which results in H2 remaining unbound, while CH4 occupies all of the adsorption sites, thereby facilitating the selective recovery of H2 at the end of the separation process. We proposed a relationship between adsorption time and diffusion time, highlighting the critical role of selecting an appropriate simulation method. This relationship underscores how adsorption and diffusion processes interplay, impacting material performance. Overall, these insights not only improve the accuracy of predictive models but also guide the development of more efficient COF-based membrane applications for future research and industrial applications.

Palladium Membrane Applications in Hydrogen Energy and Hydrogen-Related Processes

In recent years, increased attention has been paid to environmental issues and, in connection with this, to the development of hydrogen energy. In turn, this requires the large-scale production of ultra pure hydrogen. Currently, most hydrogen is obtained by converting natural gas and coal. In this regard, the issue of the deep purification of hydrogen for use in fuel cells is very relevant. The deep purification of hydrogen is also necessary for some other areas, including microelectronics. Only palladium membranes can provide the required degree of purification. In addition, the use of membrane catalysis is very relevant for the widely demanded processes of hydrogenation and dehydrogenation, for which reactors with palladium membranes are used. This process is also successfully used for the single-stage production of high-purity hydrogen. Polymeric palladium-containing membranes are also used to purify hydrogen and to remove various pollutants from water, including organochlorine products, nitrates, and a number of other substances.

Integrating Humidity-Resistant and Colorimetric COF-on-MOF Sensors with Artificial Intelligence Assisted Data Analysis for Visualization of Volatile Organic Compounds Sensing

Direct visualization and monitoring of volatile organic compounds (VOCs) sensing processes via portable colorimetric sensors are highly desired but challenging targets. The key challenge resides in the development of efficient sensing systems with high sensitivity, selectivity, humidity resistance, and profuse color change. Herein, a strategy is reported for the direct visualization of VOCs sensing by mimicking human olfactory function and integrating colorimetric COF-on-MOF sensors with artificial intelligence (AI)-assisted data analysis techniques. The Dye@Zeolitic Imidazolate Framework@Covalent Organic Framework (Dye@ZIF-8@COF) sensor takes advantage of the highly porous structure of MOF core and hydrophobic nature of the COF shell, enabling highly sensitive colorimetric sensing of trace number of VOCs. The Dye@ZIF-8@COF sensor exhibits exceptional sensitivity to VOCs at sub-parts per million levels and demonstrates excellent humidity resistance (under 20-90% relative humidity), showing great promise for practical applications. Importantly, AI-assisted information fusion and perceptual analysis greatly promote the accuracy of the VOCs sensing processes, enabling direct visualization and classification of seven stages of matcha drying processes with a superior accuracy of 95.74%. This work paves the way for the direct visualization of sensing processes of VOCs via the integration of advanced humidity-resistant sensing materials and AI-assisted data analyzing techniques.

Oriented PolyMOFs Enabled by Bridging Coligand for CO2 Separation

Despite enormous research efforts in recent years, polymer-metal-organic framework (polyMOF) development still faces several drawbacks, such as the substantial decrease in surface area, poor crystallinity, and monophyletic chemical structure of polyMOFs. Herein, we overcome the constraints of the coordination mode of conventional polyMOFs and report a bridging coligand strategy to prepare new types of polyMOFs, where the MOFs featuring accessible CuII sites are compelled to orientally regrow within the confined channels of semirigid PIM-1 in dimethyl sulfoxide. Coordination-substitution characteristics and solvent-modulated synthesis enable the Cu centers in MOFs to coordinate with the N atoms from PIM-1 by bridging coligand mode. The reduced particle size, enhanced ultramicroporosity, preferential orientation, and superior filler-matrix compatibility endow the polyMOF-based mixed matrix membrane with excellent CO2 separation performance, with a CO2 permeability of 4669 Barrer, and with a CO2/N2 selectivity of ∼30. This polyMOF design concept exploits a viable avenue for developing more inorganic-organic hybrid materials.

Vacuum-Assisted Confined Growth of MOF@COF Composite Membranes with Enhanced Hydrogen Permselectivity

With ordered and periodic network structures, adjustable pore sizes and high chemical stability, covalent organic frameworks (COFs) have drawn much attention for the fabrication of superior separation membranes. However, it is challenging to prepare COF membranes with a molecular sieving property for gas separation due to their relatively large pore size. In this work, we develop the MOF-in-COF concept for vacuum-assisted synthesis of metal-organic framework (MOF) ZIF-8 inside the pores of TB-COF formed from trihydroxy-benzene-tricarbaldehyde (T) and diamino-biphenyl-disulfonic acid (B), thus constructing a novel ZIF-8@TB-COF membrane. Attributing to the formation of a well-defined one-dimensional (1D) nanoscale transport channel, the ZIF-8@TB-COF membrane displays a high hydrogen permselectivity. At 100 °C and 200 kPa, the mixture separation factors of H2/CO2, H2/CH4 and H2/C3H8 are 21.9, 63.1 and 134.4, respectively, which are much higher than those of the pristine TB-COF membrane due to the precise size sieving channels brought about by the incorporated MOF. The synthesis of ZIF-67@TB-COF membrane demonstrates the versatility of the synthesis strategy.

MOF-derived Carbon-Based Materials for Energy-Related Applications

New carbon-based materials (CMs) are recommended as attractively active materials due to their diverse nanostructures and unique electron transport pathways, demonstrating great potential for highly efficient energy storage applications, electrocatalysis, and beyond. Among these newly reported CMs, metal-organic framework (MOF)-derived CMs have achieved impressive development momentum based on their high specific surface areas, tunable porosity, and flexible structural-functional integration. However, obstacles regarding the integrity of porous structures, the complexity of preparation processes, and the precise control of active components hinder the regulation of precise interface engineering in CMs. In this context, this review systematically summarizes the latest advances in tailored types, processing strategies, and energy-related applications of MOF-derived CMs and focuses on the structure-activity relationship of metal-free carbon, metal-doped carbon, and metallide-doped carbon. Particularly, the intrinsic correlation and evolutionary behavior between the synergistic interaction of micro/nanostructures and active species with electrochemical performances are emphasized. Finally, unique insights and perspectives on the latest relevant research are presented, and the future development prospects and challenges of MOF-derived CMs are discussed, providing valuable guidance to boost high-performance electrochemical electrodes for a broader range of application fields.

Self-Organized Protonic Conductive Nanochannel Arrays for Ultra-High-Density Data Storage

While the highest-performing memristors currently available offer superior storage density and energy efficiency, their large-scale integration is hindered by the random distribution of filaments and nonuniform resistive switching in memory cells. Here, we demonstrate the self-organized synthesis of a type of two-dimensional protonic coordination polymers with high crystallinity and porosity. Hydrogen-bond networks containing proton carriers along its nanochannels enable uniform resistive switching down to the subnanoscale range. Leveraging such nanochannel arrays, we achieve logic operations of graphical gate circuits with negligible leakage and sneak path currents over areas ranging from 0.5 μm × 0.5 μm to 20 nm × 20 nm, providing the smallest building blocks to date for large-scale integration. The nonvolatile resistive switching exhibits high mobility (∼0.309 cm2 V-1 s-1), a large on/off ratio (∼103), and ultrahigh-density data storage (∼645 Tbit/in2), even within a trilayer (∼4.01 nm). An ultrahigh-precision artificial retina with integrated convolutional neural network calculations is demonstrated, enabling facial and color recognition capabilities.

Non-selective Defect Minimization towards Highly Efficient Metal-Organic Framework Membranes for Gas Separation

The persistence of defects in polycrystalline membranes poses a substantial obstacle to reaching the theoretical molecular sieving separation and scaling up production. The low membrane selectivity in most reported literature is largely due to the unavoidable non-selective defects during synthesis, leading to a mismatch between the well-defined pore structure of polycrystalline molecular sieve materials. This paper presents a novel approach for minimizing non-selective defects in metal-organic framework (MOF) membranes by a constricted crystal growth strategy in a confined environment. The in situ ZIF formation using the densely packed seeding array between the substrate and the pre-grown top ZIF layer yields a confined membrane interlayer, which is highly uniform with a tightly packed crystalline structure. Unlike uncontrolled crystal growth, we purposely regulate the interlayer membrane growth in the direction parallel to the substrate. A notable 99 % decrease in defects in the confined interlayer was achieved compared to the random-grown top layer, leading to a ~353 % increment in H2/N2 selectivity over the non-confined reference MOF membrane. The performance of this new membrane sits in the optimal range above the Robeson upper bound. The membrane boasts a balanced high H2 permeability (>5000 Barrer) and selectivity (>50), significantly surpassing peer ZIF membranes.

Effect of Plasma Treatment on Coating Adhesion and Tensile Strength in Uncoated and Coated Rubber Under Aging

The degradation of rubber materials under environmental and mechanical stress presents a significant challenge, particularly due to UV (ultraviolet light) exposure, which severely impacts the material's physical properties. This study aims to enhance the UV stability and longevity of rubber by evaluating the performance of modified polyurethane and silicone coatings as protective stabilizers. Natural rubber-styrene-butadiene rubber (NR-SBR), known for its exceptional mechanical properties, was selected as the base material. To ensure strong adhesion, cold atmospheric plasma treatment was applied, increasing the surface energy by 250%, primarily through an enhancement of the polar component. After treatment, supplier-recommended coatings were applied and tested for adhesion using the pull-out method. Aging tests under UV exposure, water immersion, and high temperatures were conducted to assess durability, with tensile tests used to monitor changes over time. Coatings exhibiting cracking after UV exposure were excluded from further analysis. A silicone coating demonstrating superior moisture resistance and durability under extreme conditions was identified as a promising candidate for future UV stabilization applications. These findings provide a foundation for developing advanced coatings to significantly extend the service life of rubber materials in demanding environments.

Steering diffusion selectivity of chemical isomers within aligned nanochannels of metal-organic framework thin film

The movement of molecules (i.e. diffusion) within angstrom-scale pores of porous materials such as metal-organic frameworks (MOFs) and zeolites is influenced by multiple complex factors that can be challenging to assess and manipulate. Nevertheless, understanding and controlling this diffusion phenomenon is crucial for advancing energy-economic membrane-based chemical separation technologies, as well as for heterogeneous catalysis and sensing applications. Through precise assessment of the factors influencing diffusion within a porous metal-organic framework (MOF) thin film, we have developed a chemical strategy to manipulate and reverse chemical isomer diffusion selectivity. In the process of cognizing the molecular diffusion within oriented, angstrom-scale channels of MOF thin film, we have unveiled a dynamic chemical interaction between the adsorbate (chemical isomers) and the MOF using a combination of kinetic mass uptake experiments and molecular simulation. Leveraging the dynamic chemical interactions, we have reversed the haloalkane (positional) isomer diffusion selectivity, forging a chemical pathway to elevate the overall efficacy of membrane-based chemical separation and selective catalytic reactions.

Superselective Hydrogen Separation through a Mixed Conducting Graphene Oxide Membrane

A cost-effective H2 separation method is required for the purification of gaseous mixtures containing H2. Thus, in this study, we investigate the H2 separation properties of Ce ion-doped partially reduced graphene oxide (prGO) membranes. Pt/C-catalyst-coated, dense, micrometer-thick membranes are fabricated by stacking Ce-prGO nanosheets, followed by thermal annealing. They are permeable to only H2 at room temperature. H2 permeation occurs based on mixed conduction; the H2 initially dissociates into protons and electrons at the feed side. Thereafter, they diffuse into the membrane and recombine to produce H2 at the permeate side. However, the diffusion of other molecules, such as He and CO2, is inhibited, resulting in superselective separation. The developed carbon-based mixed proton/electron conduction (MPEC) membrane can be employed for H2 capture, deuterium gas production from D2O, and organic molecule deuteration.

Topology Control of Covalent Organic Frameworks with Interlaced Unsaturated 2D and Saturated 3D Units for Boosting Electrocatalytic Hydrogen Peroxide Production

Modulating the electronic state of multicomponent covalent organic framework (COF) electrocatalysts is crucial for enhancing catalytic activity. However, the effect of dimensionality on their physicochemical functionalities is still lacking. Herein, we report an interlaced unsaturated 2D and saturated 3D strategy to develop multicomponent-regulated COFs with tunable gradient dimensionality for high selectivity and activity electrocatalysis. Compared with the two-component 2D and 3D model COFs, the 2D/3D framework interlaced COFs with locally irregular dimensions and electronic structures are more practical in optimizing the intrinsic electrode surface reaction and mass transfer. Remarkably, the unsaturated 2D-inserted 3D TAE-COF regulates the adsorption mode of OOH* species to supply a favorable dynamic pathway for the H2O2 process, thereby achieving an excellent production rate of 8.50 mol gcat -1 h-1. Moreover, utilizing theoretical calculation and in situ ATR-FTIR experiment, we found that the central carbon atom of the tetraphenyl-based unit (site-1 and site-6) are potential active sites. This strategy of operating the adsorption ability of reactants with dimensionality-interconnected building blocks provides an idea for designing durable and efficient electrocatalysts.

Covalent Organic Framework Membranes with Regulated Orientation for Monovalent Cation Sieving

Continuous covalent organic framework (COF) thin membranes have garnered broad concern over the past few years due to their merits of low energy requirements, operational simplicity, ecofriendliness, and high separation efficiency in the application process. This study marks the first instance of fabricating two distinct, self-supporting COF membranes from identical building blocks through solvent modulation. Notably, the precision of the COF membrane's separation capabilities is substantially enhanced by altering the pore alignment from a random to a vertical orientation. Within these confined channels, the membrane with vertically aligned pores and micron-scale stacking thickness demonstrates rapid and selective transportation of Li+ ions over Na+ and K+ ions, achieving Li+/K+ and Li+/Na+ selectivity ratios of 38.7 and 7.2, respectively. This research not only reveals regulated orientation and layer stacking in COF membranes via strategic solvent selection but also offers a potent approach for developing membranes specialized in Li+ ion separation.

Wrinkled metal-organic framework thin films with tunable Turing patterns for pliable integration

Flexible integration spurs diverse applications in metal-organic frameworks (MOFs). However, current configurations suffer from the trade-off between MOF loadings and mechanical compliance. We report a wrinkled configuration of MOF thin films. We established an interfacial synthesis confined and controlled by a polymer topcoat and achieved multiple Turing motifs in the wrinkled thin films. These films have complete MOF surface coverage and exhibit strain tolerance up to 53.2%. The enhanced mechanical properties allow film transfer onto various substrates. We obtained membranes with large H2/CO2 selectivity (41.2) and high H2 permeance (8.46 × 103 gas permeation units), showcasing negligible defects after transfer. We also achieved soft humidity sensors on delicate electrodes by avoiding exposure to harsh MOF synthesis conditions. These results highlight the potential of wrinkled MOF thin films for plug-and-play integration.

Functionalized 2D membranes for separations at the 1-nm scale

The ongoing evolution of two-dimensional (2D) material-based membranes has prompted the realization of mass separations at the 1-nm scale due to their well-defined selective nano- and subnanochannels. Strategic membrane functionalization is further found to be key to augmenting channel accuracy and efficiency in distinguishing ions, gases and molecules within this range and is thus trending as a research focus in energy-, resource-, environment- and pharmaceutical-related applications. In this review, we present the fundamentals underpinning functionalized 2D membranes in various separations, elucidating the critical "method-interaction-property" relationship. Starting with an introduction to various functionalization strategies, we focus our discussion on functionalization-induced channel-species interactions and reveal how they shape the transport- and operation-related features of the membrane in different scenarios. We also highlight the limitations and challenges of current functionalized 2D membranes and outline the necessary breakthroughs needed to apply them as reliable and high-performance separation units across industries in the future.

New Advances in Covalent Network Polymers via Dynamic Covalent Chemistry

Covalent network polymers, as materials composed of atoms interconnected by covalent bonds in a continuous network, are known for their thermal and chemical stability. Over the past two decades, these materials have undergone significant transformations, gaining properties such as malleability, environmental responsiveness, recyclability, crystallinity, and customizable porosity, enabled by the development and integration of dynamic covalent chemistry (DCvC). In this review, we explore the innovative realm of covalent network polymers by focusing on the recent advances achieved through the application of DCvC. We start by examining the history and fundamental principles of DCvC, detailing its inception and core concepts and noting its key role in reversible covalent bond formation. Then the reprocessability of covalent network polymers enabled by DCvC is thoroughly discussed, starting from the significant milestones that marked the evolution of these polymers and progressing to their current trends and applications. The influence of DCvC on the crystallinity of covalent network polymers is then reviewed, covering their bond diversity, synthesis techniques, and functionalities. In the concluding section, we address the current challenges faced in the field of covalent network polymers and speculates on potential future directions.

Ultrathin and Self-Supporting MOF/COF-Based Composite Membranes for Hydrogen Separation and Purification from Coke Oven Gas

Coke oven gas (COG) is considered to be one of the most likely raw materials for large-scale H2 production in the near or medium term, with membrane separation technologies standing out from traditional technologies due to their less energy-intensive structures as well as simple operation and occupation. Based on the "MOF-in/on-COF" pore modification strategy, the COF membrane (named the PBD membrane) and ZIF-67 were used as assembly elements to design advanced molecular sieving membranes for hydrogen separation. The composition and microstructure of membranes before and after ZIF-67 loading as well as ZIF-67-in-PBD membranes under different preparation conditions (metal ion concentration, metal-ligand ratio, and reaction time) were investigated by various characterizations to reveal the synthesis regularity and microstructure regulation. Furthermore, H2/CH4 separation performances and separation mechanisms were also analyzed and compared. Finally, a dense, continuous, ultrathin, and self-supporting ZIF-67-in-PBD membrane with a Co2+ concentration of 0.02 mol/L, a metal-ligand ratio of 1:4, and a reaction time of 6 h exhibited the largest specific surface area, micropore proportion, and the best H2/CH4 separation selectivity (α = 33.48), which was significantly higher than the Robeson upper limit and was in a leading position among reported MOF membranes. The separation mechanism was mainly size screening, and adsorption selectivity also contributed a little.

On-Water Surface Synthesis of Vinylene-Linked Cationic Two-Dimensional Polymer Films as the Anion-Selective Electrode Coating

Vinylene-linked two-dimensional polymers (V-2DPs) and their layer-stacked covalent organic frameworks (V-2D COFs) featuring high in-plane π-conjugation and robust frameworks have emerged as promising candidates for energy-related applications. However, current synthetic approaches are restricted to producing V-2D COF powders that lack processability, impeding their integration into devices, particularly within membrane technologies reliant upon thin films. Herein, we report the novel on-water surface synthesis of vinylene-linked cationic 2DPs films (V-C2DP-1 and V-C2DP-2) via Knoevenagel polycondensation, which serve as the anion-selective electrode coating for highly-reversible and durable zinc-based dual-ion batteries (ZDIBs). Model reactions and theoretical modeling revealed the enhanced reactivity and reversibility of the Knoevenagel reaction on the water surface. On this basis, we demonstrated the on-water surface 2D polycondensation towards V-C2DPs films that show large lateral size, tunable thickness, and high chemical stability. Representatively, V-C2DP-1 presents as a fully crystalline and face-on oriented film with in-plane lattice parameters of a=b≈43.3 Å. Profiting from its well-defined cationic sites, oriented 1D channels, and stable frameworks, V-C2DP-1 film possesses superior bis(trifluoromethanesulfonyl)imide anion (TFSI-)-transport selectivity (transference, t_=0.85) for graphite cathode in high-voltage ZDIBs, thus triggering additional TFSI--intercalation stage and promoting its specific capacity (from ~83 to 124 mAh g-1) and cycling life (>1000 cycles, 95 % capacity retention).

Confined-Coordination Induced Intergrowth of Metal-Organic Frameworks into Precise Molecular Sieving Membranes

Metal-organic framework (MOF) membranes with rich functionality and tunable pore system are promising for precise molecular separation; however, it remains a challenge to develop defect-free high-connectivity MOF membrane with high water stability owing to uncontrollable nucleation and growth rate during fabrication process. Herein, we report on a confined-coordination induced intergrowth strategy to fabricate lattice-defect-free Zr-MOF membrane towards precise molecular separation. The confined-coordination space properties (size and shape) and environment (water or DMF) were regulated to slow down the coordination reaction rate via controlling the counter-diffusion of MOF precursors (metal cluster and ligand), thereby inter-growing MOF crystals into integrated membrane. The resulting Zr-MOF membrane with angstrom-sized lattice apertures exhibits excellent separation performance both for gas separation and water desalination process. It was achieved H2 permeance of ~1200 GPU and H2/CO2 selectivity of ~67; water permeance of ~8 L ⋅ m-2 ⋅ h-1 ⋅ bar-1 and MgCl2 rejection of ~95 %, which are one to two orders of magnitude higher than those of state-of-the-art membranes. The molecular transport mechanism related to size-sieving effect and transition energy barrier differential of molecules and ions was revealed by density functional theory calculations. Our work provides a facile approach and fundamental insights towards developing precise molecular sieving membranes.

Mechanically stable polymer molecular sieve membranes with switchable functionality designed for high CO2 separation performance

The development of high-performance membranes selective for carbon dioxide is critically important for advancing energy-efficient carbon dioxide capture technologies. Although molecular sieves have long been attractive membrane materials, turning them into practical membrane applications has been challenging. Here, we introduce an innovative approach for crafting a polymeric molecular sieve membrane to achieve outstanding carbon dioxide separation performance while upholding the mechanical stability. First, a polymer molecular sieve membrane having high gas permeability and mechanical stability was fabricated from a judiciously designed polymer that is solution-processable, hyper-cross-linkable, and functionalizable. Then, the carbon dioxide selectivity was fine-tuned by the subsequent introduction of various amine-based carriers. Among the diverse amines, polyethyleneimine stands out by functionalizing the larger pore region while preserving ultramicropores, leading to improved carbon dioxide/dinitrogen separation performance. The optimized membrane demonstrates exceptional carbon dioxide/dinitrogen separation performance, outperforming other reported polymer molecular sieve membranes and even competing favorably with most carbon molecular sieve membranes reported to date.

Regulating the Layered Stacking of a Covalent Triazine Framework Membrane for Aromatic/Aliphatic Separation

Membrane separation of aromatics and aliphatics is a crucial requirement in chemical and petroleum industries. However, this task presents a significant challenge due to the lack of membrane materials that can endure harsh solvents, exhibit molecular specificity, and facilitate easy processing. Herein, we present a novel approach to fabricate a covalent triazine framework (CTF) membrane by employing a mix-monomer strategy. By incorporating a spatial monomer alongside a planar monomer, we were able to subtly modulate both the pore aperture and membrane affinity, enabling preferential permeation of aromatics over aliphatics with molecular weight below 200 Dalton (Da). Consequently, we achieved successful all-liquid phase separation of aromatic/aliphatic mixtures. Our investigation revealed that the synergistic effects of size sieving and the affinity between the permeating molecules and the membrane played a pivotal role in separating these closely resembling species. Furthermore, the membrane exhibited remarkable robustness under practical operating conditions, including prolonged operation time, various feed compositions, different applied pressure, and multiple feed components. This versatile strategy offers a feasible approach to fabricate membranes with molecule selectivity toward aromatic/aliphatic mixtures, taking a significant step forward in addressing the grand challenge of separating small organic molecules through membrane technology.

Bio-Inspired Subnanofluidics: Advanced Fabrication and Functionalization

Biological ion channels can realize high-speed and high-selective ion transport through the protein filter with the sub-1-nanometer channel. Inspired by biological ion channels, various kinds of artificial subnanopores, subnanochannels, and subnanoslits with improved ion selectivity and permeability are recently developed for efficient separation, energy conversion, and biosensing. This review article discusses the advanced fabrication and functionalization methods for constructing subnanofluidic pores, channels, tubes, and slits, which have shown great potential for various applications. Novel fabrication methods for producing subnanofluidics, including top-down techniques such as electron beam etching, ion irradiation, and electrochemical etching, as well as bottom-up approaches starting from advanced microporous frameworks, microporous polymers, lipid bilayer embedded subnanochannels, and stacked 2D materials are well summarized. Meanwhile, the functionalization methods of subnanochannels are discussed based on the introduction of functional groups, which are classified into direct synthesis, covalent bond modifications, and functional molecule fillings. These methods have enabled the construction of subnanochannels with precise control of structure, size, and functionality. The current progress, challenges, and future directions in the field of subnanofluidic are also discussed.

Porous organic framework membranes based on interface-induced polymerisation: design, synthesis and applications

Porous organic frameworks (POFs) are novel porous materials that have attracted much attention due to their extraordinary properties, such as high specific surface area, tunable pore size, high stability and ease of functionalisation. However, conventional synthesised POFs are mostly large-sized particles or insoluble powders, which are difficult to recycle and have low mass transfer efficiencies, limiting the development of their cutting-edge applications. Therefore, processing POF materials into membrane structures is of great significance. In recent years, interface engineering strategies have proved to be efficient methods for the formation of POF membranes. In this perspective, recent advances in the use of interfaces to prepare POF membranes are reviewed. The challenges of this strategy and the potential applications of the formed POF membranes are discussed.

Hybrid organic frameworks: Synthesis strategies and applications in photocatalytic wastewater treatment - A review

Hybrid organic framework materials are a class of hierarchical porous crystalline materials that have emerged in recent years, composed of three types of porous crystal materials, namely metal-organic frameworks (MOFs), covalent organic frameworks (COFs), and hydrogen-bonded organic frameworks (HOFs). The combination of various organic framework properties in hybrid organic frameworks generates synergistic effects, which has attracted widespread attention from researchers. The synthesis methods of hybrid organic frameworks are also an intriguing topic, enabling the formation of core-shell heterostructures through epitaxial growth, template conversion, medium growth, or direct combination. These hybrid organic framework materials have demonstrated remarkable performance in the application of photocatalytic wastewater purification and have developed various forms of applications. This article reviews the preparation principles and methods of various hybrid organic frameworks and provides a detailed overview of the research progress of photocatalytic water purification hybrid organic frameworks. Finally, the challenges and development prospects of hybrid organic framework synthesis and their application in water purification are briefly discussed.

Multifunctional In-MOF and Its S-Scheme Heterojunction toward Pollutant Decontamination via Fluorescence Detection, Physical Adsorption, and Photocatalytic REDOX

A novel doubly interpenetrated indium-organic framework of 1 has been assembled by In3+ ions and highly conjugated biquinoline carboxylate-based bitopic connectors (H2L). The isolated 1 exhibits an anionic framework possessing channel-type apertures repleted with exposed quinoline N atoms and carboxyl O atoms. Owing to the unique architecture, 1 displays a durable photoluminescence effect and fluorescence quenching sensing toward CrO42-, Cr2O72-, and Cu2+ ions with reliable selectivity and anti-interference properties, fairly high detection sensitivity, and rather low detection limits. Ligand-to-ligand charge transition (LLCT) was identified as the essential cause of luminescence by modeling the ground state and excited states of 1 using DFT and TD-DFT. In addition, the negatively charged framework has the ability to rapidly capture single cationic MB, BR14, or BY24 and their mixture, including the talent to trap MB from the (MB + MO) system with high selectivity. Moreover, intrinsic light absorption capacity and band structure feature endow 1 with effective photocatalytic decomposition ability toward reactive dyes RR2 and RB13 under ultraviolet light. Notably, after further polishing the band structure state of 1 by constructing the S-scheme heterojunction of In2S3/1, highly efficient photocatalytic detoxification of Cr(VI) and degradation of reactive dyes have been fully achieved under visible light. This finding may open a new avenue for designing novel multifunctional MOF-based platforms to address some intractable environmental issues, i.e., detection of heavy metal ions, physical capture of pony-sized dyes, and photochemical decontamination of ultrastubborn reactive dyes and highly toxic Cr(VI) ions from water.

Sub-micro porous thin polymer membranes for discriminating H2 and CO2

Polymeric membranes with high permeance and remarkable selectivity for simultaneous H2 purification and CO2 capture under industry-relevant conditions are absent. Herein, sub-micro pores with precise molecular sieving capability are created in ultra-thin (13-30 nm) polymer membranes via controllable transformation of amine-linked polymer (ALP) films into benzimidazole-and-amine-linked polymer (BIALP) layers. The BIALP membranes exhibit stable unprecedented H2/CO2 selectivity of 120 with a H2 permeance of 315 GPU. Furthermore, high pressure (up to 11 bar) and thermal (up to 300 °C) resistance is delivered. This work provides a concept on designing porous polymeric membranes for precise molecular discrimination.

Recent advances of pure/independent covalent organic framework membrane materials: preparation, properties and separation applications

Covalent organic frameworks (COF) are porous crystalline polymers connected by covalent bonds. Due to their inherent high specific surface area, tunable pore size, and good stability, they have attracted extensive attention from researchers. In recent years, COF membrane materials developed rapidly, and a large amount of research work has been presented on the preparation methods, properties, and applications of COF membranes. This review focuses on the research on independent/pure continuous COF membranes. First, based on the membrane formation mechanism, COF membrane preparation methods are categorized into two main groups: bottom-up and top-down. Four methods are presented, namely, solvothermal, interfacial polymerization, steam-assisted conversion, and layer by layer. Then, the aperture, hydrophilicity/hydrophobicity and surface charge properties of COF membranes are summarized and outlined. According to the application directions of gas separation, water treatment, organic solvent nanofiltration, pervaporation and energy, the latest research results of COF membranes are presented. Finally, the challenges and future directions of COF membranes are summarized and an outlook provided. It is hoped that this work will inspire and motivate researchers in related fields.

Recent Progress in 2D Metal-Organic Framework-Related Materials

2D metal-organic frameworks-based (2D MOF-related) materials benefit from variable topological structures, plentiful open active sites, and high specific surface areas, demonstrating promising applications in gas storage, adsorption and separation, energy conversion, and other domains. In recent years, researchers have innovatively designed multiple strategies to avoid the adverse effects of conventional methods on the synthesis of high-quality 2D MOFs. This review focuses on the latest advances in creative synthesis techniques for 2D MOF-related materials from both the top-down and bottom-up perspectives. Subsequently, the strategies are categorized and summarized for synthesizing 2D MOF-related composites and their derivatives. Finally, the current challenges are highlighted faced by 2D MOF-related materials and some targeted recommendations are put forward to inspire researchers to investigate more effective synthesis methods.

Continuous Covalent Organic Frameworks Membranes: From Preparation Strategies to Applications

Covalent organic frameworks (COFs) are porous crystalline polymeric materials formed by the covalent bonding of organic units. The abundant organic units library gives the COFs species diversity, easily tuned pore channels, and pore sizes. In addition, the periodic arrangement of organic units endows COFs regular and highly connected pore channels, which has led to the rapid development of COFs in membrane separations. Continuous defect-free and high crystallinity of COF membranes is the key to their application in separations, which is the most important issue to be addressed in the research. This review article describes the linkage types of covalent bonds, synthesis methods, and pore size regulation strategies of COFs materials. Further, the preparation strategies of continuous COFs membranes are highlighted, including layer-by-layer (LBL) stacking, in situ growth, interfacial polymerization (IP), and solvent casting. The applications in separation fields of continuous COFs membranes are also discussed, including gas separation, water treatment, organic solvent nanofiltration, ion conduction, and energy battery membranes. Finally, the research results are summarized and the future prospect for the development of COFs membranes are outlined. More attention may be paid to the large-scale preparation of COFs membranes and the development of conductive COFs membranes in future research.

Fabrication of a magnetic metal-organic framework/covalent organic framework composite for simultaneous magnetic solid-phase extraction of seventeen trace quinolones residues in meats

Effective capture of quinolones (QNs) in animal-derived food is a vital procedure for food safety monitoring. However, the lack of adsorption specificity and difficult to recycle in complex substrate conditions have been major problems for most of the adsorbents. In this work, a magnetic Fe3O4/MOF/COF composite (named Fe3O4@NH2-MIL-125@TpPa-SO3H) was successfully synthesized with good magnetic responsiveness and conspicuous affinity towards QNs. The Fe3O4/MOF/COF composite was used as a magnetic solid-phase extraction (MSPE) adsorbent for pretreatment and determination of QNs in meat samples. Under optimal MSPE conditions in combination with high performance liquid chromatography-quadrupole orbitrap high resolution mass spectrometer (HPLC-Q-Orbitrap HRMS), the proposed method had good linearity (R2 ≥ 0.9978) from 0.01 to 100ng g-1, low limits of detection (0.0016 to 0.0940ng g-1), good precision with relative standard deviations lower than 5.8%. This method was effectively applied to the detection of 17 QNs in the spiked pork, chicken and beef samples with satisfactory recoveries from 83.9 to 106.2%. The separation selectivity mainly due to the π-π interaction, hydrogen bonding, and electrostatic attraction between QNs and the sulfonic acid and amino functional groups of the composite. After verification, the stability and reusability of the composite meet the requirements of complex matrix sample pretreatment. The developed MSPE method based on the magnetic Fe3O4/MOF/COF composite provided an ideal sample pretreatment alternative for determining trace QNs in complex matrixes with selectivity, simplicity, rapidity, and efficiency.

Gradient Channel Segmentation in Covalent Organic Framework Membranes with Highly Oriented Nanochannels

Covalent organic frameworks (COFs) offer an exceptional platform for constructing membrane nanochannels with tunable pore sizes and tailored functionalities, making them promising candidates for separation, catalysis, and sensing applications. However, the synthesis of COF membranes with highly oriented nanochannels remains challenging, and there is a lack of systematic studies on the influence of postsynthetic modification reactions on functionality distribution along the nanochannels. Herein, we introduced a "prenucleation and slow growth" approach to synthesize a COF membrane featuring highly oriented mesoporous channels and a high Brunauer-Emmett-Teller surface area of 2230 m2 g-1. Functional moieties were anchored to the pore walls via "click" reactions and coordinated with Cu ions to serve as segmentation functions. This led to a remarkable H2/CO2 separation performance that surpassed the Robeson upper bound. Moreover, we found that the functionalities distributed along the nanochannels could be influenced by functionality flexibility and postsynthetic reaction rate. This strategy paved the way for the accurate design and construction of COF-based artificial solid-state nanochannels with high orientation and precisely controlled channel environments.

A stable core-shell metal-organic framework@covalent organic framework composite as solid-phase extraction adsorbent for selective enrichment and determination of flavonoids

Hydrophobization and stability is crucial for the practical application of most metal-organic frameworks (MOFs) in extraction technique. In this study, a stable core-shell MOF@COF composite (NH2-MIL-101(Fe)@TAPB-FPBA-COF) was successfully prepared by Schiff base reaction and applied to solid-phase extraction (SPE) of hydrophobic flavonoids. Notably, the TAPB-FPBA-COF shell acts as a hydrophobic "shield", which not only improves the hydrophobicity and stability of hydrophilic NH2-MIL-101(Fe), but also makes the extraction efficiency of flavonoids from MOF@COF composite significantly higher than that of pure NH2-MIL-101(Fe) and TAPB-FPBA-COF. In addition, a sensitive analytical method with excellent linearities (0.1-500 ng mL-1, R2 ≥ 0.9967), low limits of detection (0.02-0.04 ng mL-1 for water; 0.04-0.07 ng mL-1 for grape juice; 0.06-0.08 ng mL-1 for honey), good repeatability (intra-day/inter-day precision are 1.86-5.37%/1.82-7.79%, respectively) and only 5 mg of adsorbent per cartridge was established by optimizing the SPE process combined with high performance liquid chromatography with ultraviolet-visible detector (HPLC-UV). Meanwhile, selectivity study and comparative experiments with the commercial C18 adsorbent showed that the MOF@COF adsorbent exhibited satisfactory extraction efficiency for flavonoids due to multiple interactions such as hydrogen bonding, hydrophobic, and π-π interactions. Finally, the good recoveries in grape juice (84.5-102.5%) and honey (87.5-104.6%) samples further validated the applicability of the proposed method in complex samples.

Recent Advances in Multifunctional Reticular Framework Nanoparticles: A Paradigm Shift in Materials Science Road to a Structured Future

Porous organic frameworks (POFs) have become a highly sought-after research domain that offers a promising avenue for developing cutting-edge nanostructured materials, both in their pristine state and when subjected to various chemical and structural modifications. Metal-organic frameworks, covalent organic frameworks, and hydrogen-bonded organic frameworks are examples of these emerging materials that have gained significant attention due to their unique properties, such as high crystallinity, intrinsic porosity, unique structural regularity, diverse functionality, design flexibility, and outstanding stability. This review provides an overview of the state-of-the-art research on base-stable POFs, emphasizing the distinct pros and cons of reticular framework nanoparticles compared to other types of nanocluster materials. Thereafter, the review highlights the unique opportunity to produce multifunctional tailoring nanoparticles to meet specific application requirements. It is recommended that this potential for creating customized nanoparticles should be the driving force behind future synthesis efforts to tap the full potential of this multifaceted material category.

Solid-solvent processing of ultrathin, highly loaded mixed-matrix membrane for gas separation

Mixed-matrix membranes (MMMs) that combine processable polymer with more permeable and selective filler have potential for molecular separation, but it remains difficult to control their interfacial compatibility and achieve ultrathin selective layers during processing, particularly at high filler loading. We present a solid-solvent processing strategy to fabricate an ultrathin MMM (thickness less than 100 nanometers) with filler loading up to 80 volume %. We used polymer as a solid solvent to dissolve metal salts to form an ultrathin precursor layer, which immobilizes the metal salt and regulates its conversion to a metal-organic framework (MOF) and provides adhesion to the MOF in the matrix. The resultant membrane exhibits fast gas-sieving properties, with hydrogen permeance and/or hydrogen-carbon dioxide selectivity one to two orders of magnitude higher than that of state-of-the-art membranes.

Interfacial chemistries in metal-organic framework (MOF)/covalent-organic framework (COF) hybrids

Metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) have been attracting tremendous attention in various applications due to their unique structural properties. Recent interest has been focused on their combination as hybrids to enable the engineering of new classes of frameworks with complementary properties. This review gives a comprehensive summary on the interfacial chemistries in MOF/COF hybrids, which play critical roles in their hybridization. The challenges and perspectives in the field of MOF/COF hybrids are also provided to inspire more efforts in diversifying this hybrid family and their cross-disciplinary applications.

Graphene oxide-fullerene nanocomposite laminates for efficient hydrogen purification

Graphene oxide (GO) with its unique two-dimensional structure offers an emerging platform for designing advanced gas separation membranes that allow for highly selective transport of hydrogen molecules. Nevertheless, further tuning of the interlayer spacing of GO laminates and its effect on membrane separation efficiency remains to be explored. Here, positively charged fullerene C60 derivatives are electrostatically bonded to the surface of GO sheets in order to manipulate the interlayer spacing between GO nanolaminates. The as-prepared GO-C60 membranes have a high H2 permeance of 3370 GPU (gas permeance units) and an H2/CO2 selectivity of 59. The gas separation selectivity is almost twice that of flat GO membranes because of the role of fullerene.

Nanofiltration Performance of Poly(p-xylylene) Nanofilms with Imidazole Side Chains

Herein, we report the nanofiltration performance of poly(p-xylylene) thin films with imidazole side chains that were deposited onto commercial polyethersulfone ultrafiltration membranes using a chemical vapor deposition process. The resulting thin films with a few tens of nanometers exhibited water permeation under a pressure difference of 0.5 MPa and selectively rejected water-soluble organic dyes based on their molecular sizes. Additionally, thin flaky ZIF-L crystals (Zn(mim)2·(Hmim)1/2·(H2O)3/2) (Hmim = 2-methylimidazole) formed on the surface of imidazole-containing poly(p-xylylene) films, and the composite films demonstrated the ability to adsorb methylene blue molecules within the cavities of ZIF-L.

Principles of Design and Synthesis of Metal Derivatives from MOFs

Materials derived from metal-organic frameworks (MOFs) have demonstrated exceptional structural variety and complexity and can be synthesized using low-cost scalable methods. Although the inherent instability and low electrical conductivity of MOFs are largely responsible for their low uptake for catalysis and energy storage, a superior alternative is MOF-derived metal-based derivatives (MDs) as these can retain the complex nanostructures of MOFs while exhibiting stability and electrical conductivities of several orders of magnitude higher. The present work comprehensively reviews MDs in terms of synthesis and their nanostructural design, including oxides, sulfides, phosphides, nitrides, carbides, transition metals, and other minor species. The focal point of the approach is the identification and rationalization of the design parameters that lead to the generation of optimal compositions, structures, nanostructures, and resultant performance parameters. The aim of this approach is to provide an inclusive platform for the strategies to design and process these materials for specific applications. This work is complemented by detailed figures that both summarize the design and processing approaches that have been reported and indicate potential trajectories for development. The work is also supported by comprehensive and up-to-date tabular coverage of the reported studies.

Composite materials based on covalent organic frameworks for multiple advanced applications

Covalent organic frameworks (COFs) stand for a class of emerging crystalline porous organic materials, which are ingeniously constructed with organic units through strong covalent bonds. Their excellent design capabilities, and uniform and tunable pore structure make them potential materials for various applications. With the continuous development of synthesis technique and nanoscience, COFs have been successfully combined with a variety of functional materials to form COFs-based composites with superior performance than individual components. This paper offers an overview of the development of different types of COFs-based composites reported so far, with particular focus on the applications of COFs-based composites. Moreover, the challenges and future development prospects of COFs-based composites are presented. We anticipate that the review will provide some inspiration for the further development of COFs-based composites.

Asymmetric membranes for gas separation: interfacial insights and manufacturing

State-of-the-art gas separation membrane technologies combine the properties of polymers and other materials, such as metal-organic frameworks to yield mixed matrix membranes (MMM). Although, these membranes display an enhanced gas separation performance, when compared to pure polymer membranes; major challenges remain in their structure including, surface defects, uneven filler dispersion and incompatibility of constituting materials. Therefore, to avoid these structural issues posed by today's membrane manufacturing methodologies, we employed electrohydrodynamic emission and solution casting as a hybrid membrane manufacturing method, to produce ZIF-67/cellulose acetate asymmetric membranes with improved gas permeability and selectivity for CO2/N2, CO2/CH4, and O2/N2. Rigorous molecular simulations were used to reveal the key ZIF-67/cellulose acetate interfacial phenomena (e.g., higher density, chain rigidity, etc.) that must be considered when engineering optimum composite membranes. In particular, we demonstrated that the asymmetric configuration effectively leverages these interfacial features to generate membranes superior to MMM. These insights coupled with the proposed manufacturing technique can accelerate the deployment of membranes in sustainable processes such as carbon capture, hydrogen production, and natural gas upgrading.

Pore-in-Pore Engineering in a Covalent Organic Framework Membrane for Gas Separation

Covalent organic framework (COF) membranes have emerged as a promising candidate for energy-efficient separations, but the angstrom-precision control of the channel size in the subnanometer region remains a challenge that has so far restricted their potential for gas separation. Herein, we report an ultramicropore-in-nanopore concept of engineering matreshka-like pore-channels inside a COF membrane. In this concept, α-cyclodextrin (α-CD) is in situ encapsulated during the interfacial polymerization which presumably results in a linear assembly (LA) of α-CDs in the 1D nanochannels of COF. The LA-α-CD-in-TpPa-1 membrane shows a high H₂ permeance (∼3000 GPU) together with an enhanced selectivity (>30) of H₂ over CO₂ and CH₄ due to the formation of fast and selective H₂-transport pathways. The overall performance for H₂/CO₂ and H₂/CH₄ separation transcends the Robeson upper bounds and ranks among the most powerful H₂-selective membranes. The versatility of this strategy is demonstrated by synthesizing different types of LA-α-CD-in-COF membranes.

Microkinetic insights into the role of catalyst and water activity on the nucleation, growth, and dissolution during COF-5 synthesis

The chemical pathway for synthesizing covalent organic frameworks (COFs) involves a complex medley of reaction sequences over a rippling energy landscape that cannot be adequately described using existing theories. Even with the development of state-of-the-art experimental and computational tools, identifying primary mechanisms of nucleation and growth of COFs remains elusive. Other than empirically, little is known about how the catalyst composition and water activity affect the kinetics of the reaction pathway. Here, for the first time, we employ time-resolved in situ Fourier transform infrared spectroscopy (FT-IR) coupled with a six-parameter microkinetic model consisting of ∼10 million reactions and over 20 000 species. The integrated approach elucidates previously unrecognized roles of catalyst pK_a on COF yield and water on growth rate and size distribution. COF crystalline yield increases with decreasing pK_a of the catalysts, whereas the effect of water is to reduce the growth rate of COF and broaden the size distribution. The microkinetic model reproduces the experimental data and quantitatively predicts the role of synthesis conditions such as temperature, catalyst, and precursor concentration on the nucleation and growth rates. Furthermore, the model also validates the second-order reaction mechanism of COF-5 and predicts the activation barriers for classical and non-classical growth of COF-5 crystals. The microkinetic model developed here is generalizable to different COFs and other multicomponent systems.