Extrinsically conducting MOFs: guest-promoted enhancement of electrical conductivity, thin film fabrication and applications

Conductive metal-organic frameworks are of current interest in chemical science because of their applications in chemiresistive sensing, electrochemical energy storage, electrocatalysis, etc. Different strategies have been employed to design conductive frameworks. In this review, we discuss the influence of different types of guest species incorporated within the pores or channels of metal-organic frameworks (MOFs) and porous coordination polymers (PCPs) to generate charge transfer pathways and modulate their electrical conductivity. We have classified dopants or guest species into three different categories: (i) metal-based dopants, (ii) molecule and molecular entities and (iii) organic conducting polymers. Different types of metal ions, metal nano-clusters and metal oxides have been used to enhance electrical conductivity in MOFs. Metal ions and metal nano-clusters depend on the hopping process for efficient charge transfer whereas metal-oxides show charge transport through the metal-oxygen pathway. Several types of molecules or molecular entities ranging from neutral TCNQ, I2, and fullerene to ionic methyl viologen, organometallic like nickelcarborane, etc. have been used. In these cases, the charge transfer process varies with the guest species. When organic conducting polymers are the guest, the charge transport occurs through the polymer chains, mostly based on extended π-conjugation. Here we provide a comprehensive and critical review of these strategies to add electrical conductivity to the, in most cases, otherwise insulating MOFs and PCPs. We point out the guest encapsulation process, the geometry and structure of the resulting host-guest complex, the host-guest interactions and the charge transport mechanism for each case. We also present the methods for thin film fabrication of conducting MOFs (both, liquid-phase and gas-phase based methods) and their most relevant applications like electrocatalysis, sensing, charge storage, photoconductivity, photocatalysis,… We end this review with the main obstacles and challenges to be faced and the appealing perspectives of these 21st century materials.

Brain gliomas: Diagnostic and therapeutic issues and the prospects of drug-targeted nano-delivery technology

Glioma is the most common intracranial malignant tumor, with severe difficulty in treatment and a low patient survival rate. Due to the heterogeneity and invasiveness of tumors, lack of personalized clinical treatment design, and physiological barriers, it is often difficult to accurately distinguish gliomas, which dramatically affects the subsequent diagnosis, imaging treatment, and prognosis. Fortunately, nano-delivery systems have demonstrated unprecedented capabilities in diagnosing and treating gliomas in recent years. They have been modified and surface modified to efficiently traverse BBB/BBTB, target lesion sites, and intelligently release therapeutic or contrast agents, thereby achieving precise imaging and treatment. In this review, we focus on nano-delivery systems. Firstly, we provide an overview of the standard and emerging diagnostic and treatment technologies for glioma in clinical practice. After induction and analysis, we focus on summarizing the delivery methods of drug delivery systems, the design of nanoparticles, and their new advances in glioma imaging and treatment in recent years. Finally, we discussed the prospects and potential challenges of drug-delivery systems in diagnosing and treating glioma.

Recent Progress in MOF-Aerogel Fabrication and Applications

Recent advancements in metal-organic frameworks (MOFs) underscore their significant potential in chemical and materials research, owing to their remarkable properties and diverse structures. Despite challenges like intrinsic brittleness, powdered crystalline nature, and limited stability impeding direct applications, MOF-based aerogels have shown superior performance in various areas, particularly in water treatment and contaminant removal. This review highlights the latest progress in MOF-based aerogels, with a focus on hybrid systems incorporating materials like graphene, carbon nanotube, silica, and cellulose in MOF aerogels, which enhance their functional properties. The manifold advantages of MOF-based aerogels in energy storage, adsorption, and catalysis are discussed, with an emphasizing on their improved stability, processability, and ease of handling. This review aims to unlock the potential of MOF-based aerogels and their real-world applications. Aerogels are expected to reshape the technological landscape of MOFs through enhanced stability, adaptability, and efficiency.

Scalable multifunctional MOFs-textiles via diazonium chemistry

Cellulose fiber-based textiles are ubiquitous in daily life for their processability, biodegradability, and outstanding flexibility. Integrating cellulose textiles with functional coating materials can unlock their potential functionalities to engage diverse applications. Metal-organic frameworks (MOFs) are ideal candidate materials for such integration, thanks to their unique merits, such as large specific surface area, tunable pore size, and species diversity. However, achieving scalable fabrication of MOFs-textiles with high mechanical durability remains challenging. Here, we report a facile and scalable strategy for direct MOF growth on cotton fibers grafted via the diazonium chemistry. The as-prepared ZIF-67-Cotton textile (ZIF-67-CT) exhibits excellent ultraviolet (UV) resistance and organic contamination degradation via the peroxymonosulfate activation. The ZIF-67-CT is also used to encapsulate essential oils such as carvacrol to enable antibacterial activity against E. coli and S. aureus. Additionally, by directly tethering a hydrophobic molecular layer onto the MOF-coated surface, superhydrophobic ZIF-67-CT is achieved with excellent self-cleaning, antifouling, and oil-water separation performances. More importantly, the reported strategy is generic and applicable to other MOFs and cellulose fiber-based materials, and various large-scale multi-functional MOFs-textiles can be successfully manufactured, resulting in vast applications in wastewater purification, fragrance industry, and outdoor gears.

Measuring Mass Transfer of n-Hexane and 2-Chloroethyl Ethyl Sulfide in Sorbent/Polymer Fiber Composites Using a Volumetric Adsorption Apparatus

The integration of metal-organic frameworks (MOFs) into composite systems serves as an effective strategy to increase the processability of these materials. Notably, MOF/fiber composites have shown much promise as protective equipment for the capture and remediation of chemical warfare agents. However, the practical application of these composites requires an understanding of their mass transport properties, as both mass transfer resistance at the surface and diffusion within the materials can impact the efficacy of these materials. In this work, we synthesized composite fibers of MOF-808 and amidoxime-functionalized polymers of intrinsic microporosity (PIM-1-AX) and measured the adsorption and mass transport behavior of n-hexane and 2-chloroethyl ethyl sulfide (CEES), a sulfur mustard simulant. We developed a new Fickian diffusion model for cylindrical shapes to fit the dynamic adsorption data obtained from a commercial volumetric adsorption apparatus and found that mass transport behavior in composite fibers closely resembled that in the pure PIM fibers, regardless of MOF loading. Moreover, we found that n-hexane adsorption mirrors that of CEES, indicating that it could be used as a structural mimic for future adsorption studies of the sulfur mustard simulant. These preliminary insights and the new model introduced in this work lay the groundwork for the design of next-generation composite materials for practical applications.

A Natural Casein-Based Separator with Brick-and-Mortar Structure for Stable, High-Rate Proton Batteries

Rechargeable aqueous proton batteries with small organic molecule anodes are currently considered promising candidates for large-scale energy storage due to their low cost, stable safety, and environmental friendliness. However, the practical application is limited by the poor cycling stability caused by the shuttling of soluble organic molecules between electrodes. Herein, a cell separator is modified by a GO-casein-Cu2+ layer with a brick-and-mortar structure to inhibit the shuttling of small organic molecules. Experimental and calculation results indicate that, attributed to the synergistic effect of physical blocking of casein molecular chains and electrostatic and coordination interactions of Cu2+, bulk dissolution and shuttling of multiple small molecules can be inhibited simultaneously, while H+ transfer across the separators is not almost affected. With the protection of the GO-casein-Cu2+ separator, soluble small molecules, such as diquinoxalino[2,3-a:2',3'-c]phenazine,2,3,8,9,14,15-hexacyano (6CN-DQPZ) exhibit a high reversible capacity of 262.6 mA h g-1 and amazing stability (capacity retention of 92.9% after 1000 cycles at 1 A g-1). In addition, this strategy is also proved available to other active conjugated small molecules, such as indanthrone (IDT), providing a general green sustainable strategy for advancing the use of small organic molecule electrodes in proton cells.

Designing a MOF-functionalized Nanofibrous Aerogel via Vapor-Phase Synthesis

Designing 3D mechanically robust and high-surface-area substrates for uniform and high-density deposition of metal-organic frameworks (MOFs) provide a promising strategy to enhance surface accessibility and application of these highly functional materials. Nanofibrous aerogel (NFA) with its highly porous self-supported structure composed of interconnected nanofibrous network offers an ideal platform in this regard. Herein, a facile one-pot strategy is introduced, which utilizes direct deposition of MOF on the nanofibrous surface of the NFAs. NFAs are synthesized using electrospun polyacrylonitrile/polyvinylpyrrolidone (PAN/PVP) polymer nanofibers containing zinc acetate (Zn(Ac)2), which are subjected to freeze drying and thermal treatment. The latter converts Zn(Ac)2 to zinc oxide (ZnO), providing the sites for MOF growth while also adding mechanical integrity to the NFAs through cyclization of the PAN. Exposure of the NFA to the vapor-phase of organic ligand, 2-methylimidazole (2-MeIm) enables in situ growth of zeolitic imidazolate framework-8 (ZIF-8) MOF on the NFA. ZIF-8 loading on the NFAs is further improved by more than tenfold by synthesizing ZnO nanorods/protrusions on the nanofibers, which enables more sites for MOF growth. These findings underscore a significant advancement in designing MOF-based hybrid aerogels, offering a streamlined approach for their use in diverse applications, from catalysis to sensing and water purification.

Novel multifunctional environmentally friendly degradable zeolitic imidazolate frameworks@poly (γ-glutamic acid) hydrogel with efficient dye adsorption function

Recently, metal-organic frameworks (MOFs) have been widely developed due to the rich porosity, excellent framework structure and multifunctional nature. Meanwhile, a series of MOFs crystals and MOF-based composites have been emerged. However, the widespread applications of MOFs are hindered by challenges such as rigidity, fragility, solution instability, and processing difficulties. In this study, we addressed these limitations by employing an in-situ green growth approach to prepare a zeolitic imidazolate frameworks-8@poly (γ-glutamic acid) hydrogel (ZIF-8@γ-PGA) with hierarchical structures. This innovative method effectively resolves the inherent issues associated with MOFs. Furthermore, the ZIF-8@γ-PGA hydrogel is utilized for dye adsorption, demonstrating an impressive maximum adsorption capacity of 1130 ± 1 mg/g for methylene blue (MB). The adsorption behavior exhibits an excellent agreement with both the kinetic model and isotherm. Meanwhile, because the adsorbent raw materials are all green non-toxic materials, multiple applications of materials can also be realized. Significantly, the results of antibacterial experiments showed that the ZIF-8@γ-PGA hydrogel after in-situ growth of ZIF-8 had better antibacterial properties. Thus, the ZIF-8@γ-PGA hydrogel has great potential for development in wound dressings, sustained drug owing to its biocompatibility and antibacterial activity.

Metal-Organic-Framework-Based Nanoarrays for Oxygen Evolution Electrocatalysis

The development of highly active and stable electrode materials for the oxygen evolution reaction (OER) is essential for the widespread application of electrochemical energy conversion systems. In recent years, various metal-organic frameworks (MOFs) with self-supporting array structures have been extensively studied because of their high porosity, abundant metal sites, and flexible and adjustable structures. This review provides an overview of the recent progress in the design, preparation, and applications of MOF-based nanoarrays for the OER, beginning with the introduction of the architectural advantages of the nanoarrays and the characteristics of MOFs. Subsequently, the design principles of robust and efficient MOF-based nanoarrays as OER electrodes are highlighted. Furthermore, detailed discussions focus on the composition, structure, and performance of pristine MOF nanoarrays (MOFNAs) and MOF-based composite nanoarrays. On the one hand, the effects of the two components of MOFs and several modification methods are discussed in detail for MOFNAs. On the other hand, the review emphasizes the use of MOF-based composite nanoarrays composed of MOFs and other nanomaterials, such as oxides, hydroxides, oxyhydroxides, chalcogenides, MOFs, and metal nanoparticles, to guide the rational design of efficient OER electrodes. Finally, perspectives on current challenges, opportunities, and future directions in this research field are provided.

Fiber Integrated Metal-Organic Frameworks as Functional Components in Smart Textiles

Owing to high modularity and synthetic tunability, metal-organic frameworks (MOFs) on textiles are poised to contribute to the development of state-of-the-art wearable systems with multifunctional performance. While these composite materials have demonstrated promising functions in sensing, filtration, detoxification, and biomedicine, their applicability in multifunctional systems is only beginning to materialize. This review highlights the multifunctionality and versatility of MOF-integrated textile systems. It summarizes the operational goals of MOF@textile composites, encompassing sensing, filtration, detoxification, drug delivery, UV protection, and photocatalysis. Building upon these recent advances, this review concludes with an outlook on emerging opportunities for the diverse applications of MOF@textile systems in the realm of smart wearables.

Ultrafast and Scalable Fabrication of Coordination Polymer Films on Network Substrates via Thermal Current-Induced Dewetting

Coordination polymers are among the most favored active materials by researchers due to their broad application prospects. However, most of them are usually difficult to directly process into applicable devices because of their unsatisfied processability. One process of great concern for researchers is the in situ preparation of the coordination polymer on the applicable substrate, especially for the favored network substrates with good mechanical properties and 3D porous structure, which could provide obvious convenience and facilitation in the application process. Herein, we present an ultrafast and scalable thermal current-induced dewetting strategy to obtain uniform coordination polymer film in situ on network substrates, which could enable unprecedented convenience to obtain directly usable coordination polymer composites such as practical catalytic electrodes with excellent electrocatalytic performance. The proposed thermal current-induced dewetting method provides a highly adaptable and efficient practical production approach to integrate coordination polymer materials with network substrates and also provides new inspiration for understanding and applying the dewetting process on complex 3D network substrates.

A new strategy to prepare high-performance copper azide film for micro-initiator

Copper azide (CA) has gradually become the chosen priming agent for microexplosive devices as a lead-free green priming agent. However, charge loading is challenging due to its high electrostatic sensitivity, severely limiting its practical application. In this study, copper hydroxide particles were evenly coated on the surface of carbon fiber using electrospinning and quick hot-pressing, and CA-based composites with uniform load were created using thein situazide technique while keeping good film characteristics. The produced CA-HP film has an electroostatic sensitivity of 3.8 mJ, which is much higher than the raw material of 0.05 mJ. The flame sensitivity has also been increased from 45 to 51 cm, and the use safety has been considerably enhanced. Furthermore, hot-pressed CA-HP films can improve the film's qualities, such as easy cutting and processing into the required shape, compatibility with MEMS processes, and the ability to successfully detonate secondary explosives with only 1 mg. This novel coupling technology expands the possibilities for developing high-safety primers for micro-initiator.

Sub-second ultrafast yet programmable wet-chemical synthesis

Wet-chemical synthesis via heating bulk solution is powerful to obtain nanomaterials. However, it still suffers from limited reaction rate, controllability, and massive consumption of energy/reactants, particularly for the synthesis on specific substrates. Herein, we present an innovative wet-interfacial Joule heating (WIJH) approach to synthesize various nanomaterials in a sub-second ultrafast, programmable, and energy/reactant-saving manner. In the WIJH, Joule heat generated by the graphene film (GF) is confined at the substrate-solution interface. Accompanied by instantaneous evaporation of the solvent, the temperature is steeply improved and the precursors are concentrated, thereby synergistically accelerating and controlling the nucleation and growth of nanomaterials on the substrate. WIJH leads to a record high crystallization rate of HKUST-1 (~1.97 μm s-1), an ultralow energy cost (9.55 × 10-6 kWh cm-2) and low precursor concentrations, which are up to 5 orders of magnitude faster, -6 and -2 orders of magnitude lower than traditional methods, respectively. Moreover, WIJH could handily customize the products' amount, size, and morphology via programming the electrified procedures. The as-prepared HKUST-1/GF enables the Joule-heating-controllable and low-energy-required capture and liberation towards CO2. This study opens up a new methodology towards the superefficient synthesis of nanomaterials and solvent-involved Joule heating.

Free-Standing Metal-Organic Framework Membranes Made by Solvent-Free Space-Confined Conversion for Efficient H2/CO2 Separation

Metal-organic frameworks (MOFs) are promising candidates for the advanced membrane materials based on their diverse structures, modifiable pore environment, precise pore sizes, etc. Nevertheless, the use of supports and large amounts of solvents in traditional solvothermal synthesis of MOF membranes is considered inefficient, costly, and environmentally problematic, coupled with challenges in their scalable manufacturing. In this work, we report a solvent-free space-confined conversion (SFSC) approach for the fabrication of a series of free-standing MOF (ZIF-8, Zn(EtIm)₂, and Zn₂(BIm)₄) membranes. This approach excludes the employment of solvents and supports that require tedious pretreatment and, thus, makes the process more environment-friendly and highly efficient. The free-standing membranes feature a robust and unique architecture, which comprise dense surface layers and highly porous interlayer with large amounts of irregular-shaped micron-scale pore cavities, inducing satisfactory H₂/CO₂ selectivities and exceptional H₂ permeances. The ZIF-8 membrane affords a considerable H₂ permeance of 2653.7 GPU with a competitive H₂/CO₂ selectivity of 17.1, and the Zn(EtIm)₂ membrane exhibits a high H₂/CO₂ selectivity of 22.1 with an excellent H₂ permeance (6268.7 GPU). The SFSC approach potentially provides a new pathway for preparing free-standing MOF membranes under solvent-free conditions, rendering it feasible for scale-up production of membrane materials for gas separation.

Fabrication of Cellulose Filters Incorporating Metal-Organic Frameworks for Efficient Nicotine Adsorption from Cigarette Smoke

To prevent negative effects of smoking, there is constant research on the development of various types of sustainable filter materials, capable of removing toxic compounds present in cigarette smoke. Because of the extraordinary porosity and adsorption properties, metal-organic frameworks (MOFs) represent promising adsorbents for volatile toxic molecules such as nicotine. This study reports new hybrid materials wherein six types of common MOFs of different porosity and particle size are incorporated into sustainable cellulose fiber from bamboo pulp, resulting in a series of cellulose filter samples abbreviated as MOF@CF. The obtained hybrid cellulose filters were fully characterized and investigated in nicotine adsorption from cigarette smoke, using a specially designed experimental setup. The results revealed that the UiO-66@CF material features the best mechanical performance, facile recyclability, and excellent nicotine adsorption efficiency that attains 90% with relative standard deviations lower than 8.80%. This phenomenon may be caused by the large pore size, open metal sites, and high loading of UiO-66 in cellulose filters. Additionally, the high adsorption capacity showed almost 85% removal of nicotine after the third adsorption cycle. The DFT calculation methods allowed further investigation of the nicotine adsorption mechanism, showing that the energy difference between HOMO and LUMO for UiO-66 was the closest to that of nicotine, which further proves the adsorption ability of nicotine by this material. Owing to the flexibility, recyclability, and excellent adsorption performance, the prepared hybrid MOF@CF materials may find prospective applications in nicotine adsorption from cigarette smoke.

Solvothermal In-Situ Synthesis of MIL-53(Fe)@Carbon Felt Photocatalytic Membrane for Rhodamine B Degradation

In this study, MIL-53(Fe) was innovatively incorporated into carbon felt (CF) by growing in-situ using the solvothermal method. MIL-53(Fe)@carbon felt (MIL-53(Fe)@CF) was prepared and used for the degradation of rhodamine B (RhB). As a new photocatalytic membrane, MIL-53(Fe)@CF photocatalytic membrane has the characteristics of high degradation efficiency and recyclability. Influence of various parameters including MIL-53(Fe)@CF loading, light, electron trapper type, and starting pH on RhB degradation were investigated. The morphology, structure, and degradation properties of MIL-53(Fe)@CF photocatalytic membrane were characterized. Corresponding reaction mechanisms were explored. The results indicated that pH at 4.5 and 1 mmol/L H₂O₂, 150 mg MIL-53(Fe)@CF could photocatalytically degrade 1 mg/L RhB by 98.8% within 120 min, and the reaction rate constant (k) could reach 0.03635 min^-1. The clearance rate of RhB decreased by only 2.8% after three operations. MIL-53(Fe)@CF photocatalytic membrane was found to be stable.

Toxin-Blocking Textiles: Rapid, Benign, Roll-to-Roll Production of Robust MOF-Fabric Composites for Organophosphate Separation and Hydrolysis

Current approaches to create zirconium-based metal-organic framework (MOF) fabric composites for catalysis, water purification, wound healing, gas sorption, and other applications often rely on toxic solvents, long reaction/post processing times, and batch methods hindering process scalability. Here, a novel mechanism was reported for rapid UiO-66-NH₂ synthesis in common low-boiling-point solvents (water, ethanol, and acetic acid) and revealed acid-base chemistry promoting full linker dissolution and vapor-based crystallization. The mechanism enabled scalable roll-to-roll production of mechanically resilient UiO-66-NH₂ fabrics with superior chemical protective capability. Solvent choice and segregated spray delivery of organic linker and metal salt MOF precursor solutions allowed for rapid MOF nucleation on the fiber surface and decreased the energy and time needed for post-processing, producing an activated composite in less than 165 min, far outpacing conventional MOF-fabric synthesis approaches. The MOF-fabric hydrolyzed and blocked permeation of the chemical warfare agent soman, outperforming the protection-standard activated carbon cloth. This work presents both chemical insights into Zr-MOF powder and fabric composite formation by a rapid, industrially relevant approach and demonstrates its practicality and affordability for high-performing personal protective equipment.

A Visible Light-Induced and ROS-Dependent Method for the Rapid Formation of a MOF Composite Membrane with Antibacterial Properties

The diverse application potential of metal-organic framework (MOF) materials are currently limited by their challenging and complicated preparation processes. In this study, we successfully developed a novel strategy for the rapid synthesis of a sustainable MOF composite membrane under neutral conditions with improved physicochemical and antibacterial properties. Our reaction pipeline comprised visible light that induced the production of reactive oxygen species (ROS) from ZIF-8 particles, which facilitated the rapid oxidative polymerization of dopamine to polydopamine. The physicochemical properties of the composite membrane were assessed using imaging methods, including scanning and transmission electron microscopy, X-ray photoelectron spectrometry, and nitrogen adsorption/desorption; its antibacterial effects against Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa were measured using optical densitometry. The bactericidal potency of the synthesized membrane was >99% against all tested strains under the conditions of simulated sunlight. Moreover, the composite membrane retained its structural integrity and antibacterial effect after multiple cycles of use and recovery, showcasing remarkable stability. Overall, this study displays a ROS-mediated method for the rapid preparation of sustainable MOF composite membranes under neutral conditions with optimal physicochemical characteristics, antibacterial properties, and performance. Our study provides insights into the use of membrane materials as design platforms for a range of diverse practical applications.

Towards attaining SDG 6: The opportunities available for capacitive deionization technology to provide clean water to the African population

The unavailability of clean water caused by population growth, increased industrial activities, and global climate change is a major challenge in many communities. A number of desalination technologies including distillation, reverse osmosis and electrodialysis, have been used to supplement the available water resources. However, these technologies are energy intensive and demand a significant financial commitment. Capacitive deionization (CDI) is an emerging desalination technology which is promising to provide water at a reasonable cost, especially in societies with limited incomes such as those in Africa. The opportunities for CDI to provide clean water to the African population are discussed in this paper. These opportunities include electrosorption at low potential, low energy consumption, large quantities of agricultural wastes for the production of electrode materials, high sunshine irradiation throughout the year, suitability for disinfection and defluoridation and its applications in the removal of heavy metals and emerging pollutants. Due to the existence of numerous enabling conditions, the analysis from this paper demonstrates that CDI can be a dependable method to provide clean water in Africa.

Decorating metal organic framework on nickel foam for efficient Cu2+ removal based on adsorption and electrochemistry

The removal of heavy metal ions in wastewater has a great significance to human health and environment protection. Metal organic framework possesses high surface area, rich porosity, tunable pore size and abundant active sites. However, the intrinsic aggregation and fragility of MOF nanoparticles make its poor adsorption and undesirable reusage. Herein, a facile and unique hot-pressing method is adopted to decorate the MOF nanoparticles on nickel foam (ZIF-8/NF), which simultaneously serves as self-supporting substrate of ZIF-8 nanoparticles and electrode of a self-powered multifunctional purification system. In adsorption, the ZIF-8/NF composite presents high Cu²⁺ removal rate of 49.5% with the concentration of 10 mg/100 ml. More importantly, integrating with electrochemistry, the Cu²⁺ removal rate of the ZIF-8/NF composite reaches 54.7% in 5 min. The superior performance is attributed to the comprehensive effects of ion exchange, chemical bonding and physical adsorption. Moreover, the low-cost, fast and scalable preparation contributes to commercially fabricate MOF nanoparticles on self-supported substrate to treat wastewater with high efficiency and good recyclability.

Analysis of Mn2+ and Zn2+ Ions in Macroalgae with Heteroelement-Doped Carbon-Based Fluorescent Probe

Kelp and laver are large economic macroalgae in China, which are rich in nutrients, especially Mn and Zn. Excessive intake of Mn and Zn can be harmful to the human body. Therefore, it is necessary to develop a convenient and efficient method to detect the contents of Mn and Zn in macroalgae. In this experiment, red carbon dots (R-CDs) doped with N and S elements were prepared by the thermal solvent method. The obtained R-CDs displayed excitation wavelength-independent fluorescent emission in the red spectral region. The R-CDs were used to construct a fluorescent probe for specific recognition of Mn²⁺ and Zn²⁺, achieving high-sensitivity detection of Mn²⁺ and Zn²⁺. The detection results showed a good linear relationship between fluorescence intensity and Mn²⁺ concentration, and the calculated detection limit was 0.23 nmol/L. For the detection of Zn²⁺, the detection limit was estimated as 19.1 nmol/L. At the same time, the content distribution of Mn and Zn elements in macroalgae produced in Fujian was investigated by the constructed fluorescence probe. It was found that kelp, laver, and their products are rich in Mn and Zn elements, and the content of Mn and Zn elements in laver is higher than that in kelp, which can be used as the optimal food supplement for Mn and Zn elements.

Reactive Extrusion Printing for Simultaneous Crystallization-Deposition of Metal-Organic Framework Films

Reactive extrusion printing (REP) is demonstrated as an approach to simultaneously crystallize and deposit films of the metal-organic framework (MOF) Cu3 btc2 (btc=1,3,5-benzenetricarboxylate), also known as HKUST-1. The technique co-delivers inks of the copper(II) acetate and H3 btc starting materials directly on-surface and on-location for rapid nucleation into films at room temperature. The films were analyzed using PXRD, profilometry, SEM and thermal analysis techniques and confirmed high-quality Cu3 btc2 films are produced in low-dispersity interconnected nanoparticulate form. The porosity was examined using gas adsorption which showed REP gives Cu3 btc2 films with open interconnected pore structures, demonstrating the method bestows features that traditional synthesis does not. REP is a technique that opens the field to time-efficient large-scale fabrication of MOF interfaces and should find use in a wide variety of coating application settings.

Emerging advances and current applications of nanoMOF-based membranes for water treatment

Metal-organic frameworks (MOFs) are significantly tunable materials that can be exploited in a wide range of applications. In recent years, a large number of studies have been focused on synthesizing nano-scale MOFs (nanoMOFs), thus taking advantage of these unique materials in various applications, especially those that are only possible at nano-scale. One of the technologies where nanoMOF materials occupy a central role is the membrane technology as one of the most efficient separation techniques. Therefore, numerous reports can be found on the enhancement of the physicochemical properties of polymeric membranes by using nanoMOFs, leading to remarkably improved performance. One of the most considerable applications of these nanoMOF-based membranes is in water treatment systems, because freshwater scarcity is now an undeniable crisis facing humanity. In this in-depth review, the most prominent synthesis and post-synthesis methods for the fabrication of nanoMOFs are initially discussed. Afterwards, different nanoMOF-based composite membranes such as thin-film nanocomposites (TFN) and mixed-matrix membranes (MMM) and their various fabrication methods are reviewed and compared. Then, the impacts of using MOFs-based membranes for water purification through growing metal-organic frameworks crystals on the support materials and utilization of metal-organic frameworks as fillers in mixed matrix membrane (MMM) are highlighted. Finally, a summary of pros and cons of using nanoMOFs in membrane technology for water treatment purposes and clear future prospects and research potentials are presented.

Binder-free mechanochemical metal-organic framework nanocrystal coatings

The practical applications of metal-organic frameworks (MOFs) usually require their assembly into mechanically robust structures, usually achieved via coating onto various types of substrates. This paper describes a simple, scalable, and versatile mechanochemical technique for producing MOF nanocrystal coatings on various non-prefunctionalised substrates, including ZrO₂, carbon cloth, porous polymer, nickel foam, titanium foil and fluorine-doped tin oxide glass. We revealed the detailed mechanisms that ensure the coating's stability, and identified the coating can facilitate the interfacial energy transfer, which allowed the electrocatalysis application of the MOF coating on conductive substrates. We further demonstrated that coatings can be directly generated in a one-pot fashion by ball milling MOF precursors with substrates.

Phytic Acid Doped Polyaniline as a Binding Coating Promoting Growth of Prussian Blue on Cotton Fibers for Adsorption of Copper Ions

In recent years, the elimination of heavy metals from wastewater has become an important topic due to rapid industrialization, and it is of considerable interest to develop renewable and degradable materials for this purpose. In this work, a novel Prussian blue/polyaniline@cotton fibers (PB/PANI@CFs) composite was fabricated by a two-step process. Phytic acid doped PANI as a binding coating greatly promoted both the growth of PB and the adsorption of Cu2+. The deposition ratio of PB was as high as 24.68%. Scanning electron microscopy (SEM) displayed that PB nanoparticles were grown more uniformly in the composite and formed a perfect nanocube structure compared with PB@CFs. The successful deposition of both PB and PANI on CFs was demonstrated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FITR), and X-ray photoelectron spectroscopy (XPS). The effect of adsorption time, adsorbent dose, initial pH value, and initial copper sulphate concentration on the adsorption of PB/PANI@CFs composite for Cu2+ was studied by static adsorption and was compared with those of PANI@CFs and PB@CFs. The results showed that the maximum removal efficiency of Cu2+ by PB/PANI@CFs can reach 93.4% within 5 h, and the maximum adsorption capacity of Cu2+ can reach 31.93 mg·g−1. The adsorption of Cu2+ on PB/PANI@CFs followed the pseudo-second order kinetic model and conformed to the Freundlich adsorption isothermal model. The PB-functionalized CFs provided new insights into the design of efficient and low-cost absorbents for heavy metal remediation. The proposed process solves two problems simultaneously, i.e., the utilization of environmentally friendly and biodegradable biomass resources and the adsorption of heavy metal ions, and is a good approach to achieve high-quality and sustainable development.

Robust Al3+ MOF with Selective As(V) Sorption and Efficient Luminescence Sensing Properties toward Cr(VI)

Herein, we report the synthesis and characterization of a new robust Al³⁺ metal-organic framework MOF, [Al(OH)(PATP)]·solvent (Al-MOF-1, with PATP^2- = 2-((pyridin-2-ylmethyl)amino)terephthalate). Al-MOF-1 exhibits excellent stability from highly acidic (pH = 2) to basic (pH = 12) aqueous solutions or in the presence of oxoanionic species [As(V) and Cr(VI)]. On the contrary, the related MIL-53(Al) MOF (Al(OH) (BDC), with BDC^2- = terephthalate) shows a partial structure collapse under these conditions, signifying the superior chemical robustness of Al-MOF-1. Al-MOF-1 was proved to be an effective sorbent toward As(V) with efficient sorption capacity (71.9 ± 3.8 mg As/g), rapid sorption kinetics (equilibrium time ≤1 min), and high selectivity in the presence of various competing anions. Furthermore, Al-MOF-1 revealed high sorption capacities for Cr(VI) species in both neutral (124.5 ± 8.6 mg Cr/g) and acidic (63 ± 2 mg Cr/g) aqueous media, combining fast kinetics and relatively good selectivity. The limited porosity (BET = 38 m²/g) and small pores (2-3 Å) of the material indicate that the sorption process occurs exclusively on the external surface of Al-MOF-1 particles. The driving force for the capture of oxoanions by Al-MOF-1 is the strong electrostatic interactions between the oxoanionic species and the positively charged surface of MOF particles. Aiming at a practical wastewater treatment, we have also immobilized Al-MOF-1 on a cotton substrate, coated with polydopamine. The fabric sorbent exhibited highly effective removal of the toxic oxoanionic species from aqueous media under either batch or dynamic (continuous flow) conditions. In addition, Al-MOF-1 was found to be a promising luminescence sensor for detecting trace amounts of Cr(VI) in real water samples, with Cr(VI) being successfully detected at concentrations well below the acceptable limits (<50 ppb). Moreover, Al-MOF-1 was demonstrated to be a sufficient water sensor in organic solvents (LOD ≤0.25% v/v). All the above indicate that Al-MOF-1 represents a multifunctional material with a multitude of potential applications, such as environmental remediation, industrial wastewater treatment, chemical analysis, and water determination in biofuels.

Vapor-Phase Processing of Metal-Organic Frameworks

ConspectusPorous metal-organic frameworks (MOFs), formed from organic linkers and metal nodes, have attracted intense research attention. Because of their high specific surface areas, uniform and adjustable pore sizes, and versatile physicochemical properties, MOFs have shown disruptive potential in adsorption, catalysis, separation, etc. For many of these applications, MOFs are synthesized solvothermally as bulk powders and subsequently shaped as pellets or extrudates. Other applications, such as membrane separations and (opto)electronics, require the implementation of MOFs as (patterned) thin films. Most thin-film formation methods are adapted from liquid-phase synthesis protocols. Precursor transport and nucleation are difficult to control in these cases, often leading to particle formation in solution. Moreover, the use of solvents gives rise to environmental and safety challenges, incompatibility issues with some substrates, and corrosion issues in the case of dissolved metal salts. In contrast, vapor-phase processing methods have the merits of environmental friendliness, control over thickness and conformality, scalability in production, and high compatibility with other workflows.In this Account, we outline some of our efforts and related studies in the development and application of vapor-phase processing of crystalline MOF materials (MOF-VPP). We first highlight the advances and mechanisms in the vapor-phase deposition of MOFs (MOF-VPD), mainly focusing on the reactions between a linker vapor and a metal-containing precursor layer. The characteristics of the obtained MOFs (thickness, porosity, crystallographic phase, orientation, etc.) and the correlation of these properties with the deposition parameters (precursors, temperatures, humidity, post-treatments, etc.) are discussed. Some in situ characterization methods that contributed to a fundamental understanding of the involved mechanisms are included in the discussion. Second, four vapor-phase postsynthetic functionalization (PSF) methods are summarized: linker exchange, guest loading, linker grafting, and metalation. These approaches eliminate potential solubility issues and enable fast diffusion of reactants and guests as well as a high loading or degree of exchange. Vapor-phase PSF provides a platform to modify the MOF porosity or even introduce new functionalities (e.g., luminescence photoswitching and catalytic activity). Third, since vapor-phase processing methods enable the integration of MOF film deposition into a (micro)fabrication workflow, they facilitate a range of applications with improved performance (low-k dielectrics, sensors, membrane separations, etc.). Finally, we provide a discussion on the limitations, challenges, and further opportunities for MOF-VPP. Through the discussion and analysis of the vapor-phase processing strategies as well as the underlying mechanisms in this Account, we hope to contribute to the development of the controllable synthesis, functionalization, and application of MOFs and related materials.

Green Synthesis of Zeolitic Imidazolate Frameworks: A Review of Their Characterization and Industrial and Medical Applications

Metal organic frameworks (MOF) are a class of hybrid networks of supramolecular solid materials comprising a large number of inorganic and organic linkers, all bound to metal ions in a well-organized fashion. Zeolitic imidazolate frameworks (ZIFs) are a sub-group of MOFs with imidazole as an organic linker to metals; it is rich in carbon, nitrogen, and transition metals. ZIFs combine the classical zeolite characteristics of thermal and chemical stability with pore-size tunability and the rich topological diversity of MOFs. Due to the energy crisis and the existence of organic solvents that lead to environmental hazards, considerable research efforts have been devoted to devising clean and sustainable synthesis routes for ZIFs to reduce the environmental impact of their preparation. Green chemistry is the key to sustainable development, as it will lead to new solutions to existing problems. Moreover, it will present opportunities for new processes and products and, at its heart, is scientific and technological innovation. The green chemistry approach seeks to redesign the materials that make up the basis of our society and our economy, including the materials that generate, store, and transport our energy, in ways that are benign for humans and the environment and that possess intrinsic sustainability. This study covers the principles of green chemistry as used in designing strategies for synthesizing greener, less toxic ZIFs the consume less energy to produce. First, the necessity of green methods in today's society, their replacement of the usual non-green methods and their benefits are discussed; then, various methods for the green synthesis of ZIF compounds, such as hydrothermally, ionothermally, and by the electrospray technique, are considered. These methods use the least harmful and toxic substances, especially concerning organic solvents, and are also more economical. When a compound is synthesized by a green method, a question arises as to whether these compounds can replace the same compounds as synthesized by non-green methods. For example, is the thermal stability of these compounds (which is one of the most important features of ZIFs) preserved? Therefore, after studying the methods of identifying these compounds, in the last part, there is an in-depth discussion on the various applications of these green-synthesized compounds.

Homogeneous and Fast Li-Ion Transport Enabled by a Novel Metal-Organic-Framework-Based Succinonitrile Electrolyte for Dendrite-Free Li Deposition

Lithium (Li) metal has emerged as a promising electrode material for high-energy-density batteries. However, serious Li dendrite issues during cycling have plagued the safety and cyclability of the batteries, thus limiting the practical application of Li metal batteries. Herein, we prepare a novel metal-organic-framework-based (MOF-based) succinonitrile electrolyte, which enables homogeneous and fast Li-ion (Li+) transport for dendrite-free Li deposition. Given the appropriate aperture size of the MOF skeleton, the targeted electrolyte can allow only small-size Li+ to pass through its pores, which effectively guides uniform Li+ transport. Specially, Li ions are coordinated by the C═N of the MOF framework and the C≡N of succinonitrile, which could accelerate Li+ migration jointly. These characteristics afford an excellent quasi-solid-state electrolyte with a high ionic conductivity of 7.04 × 10-4 S cm-1 at room temperature and a superior Li+ transference number of 0.68. The Li/LiFePO4 battery with the MOF-based succinonitrile electrolyte exhibits dendrite-free Li deposition during the charge process, accompanied by a high capacity retention of 98.9% after 100 cycles at 0.1C.

Janus Metal-Organic Frameworks/Wood Aerogel Composites for Boosting Catalytic Performance by Le Châtelier's Principle

Elaborate design of metal-organic frameworks (MOFs) composites with enhanced properties is of fundamental interest and practical importance in the fields of catalysis. Typical strategies are usually focused on how to increase MOFs contents while lacking architecture design for performance improvements. Herein, we first report MOFs composites with Janus structures to boost catalytic performance by Le Châtelier's principle when using wood aerogel as a versatile platform. Janus structures mean that one part of the composite is still wood aerogel while the other part is decorated with MOFs. The underoil hydrophilicity of the wood aerogels endows the Janus composites with dehydration capacity for promoting the equilibrium movement so as to boost the catalytic performance. The catalytic performance of Janus composites for the Knoevenagel reaction increases more than 40% compared with those symmetric composites. Moreover, both the final conversion and the reaction rate are much better for the Janus composites than other state-of-the-art heterogeneous ZIF-8-based catalysts. Our design is general and paves the way to exploit composites with special architecture.

Mechanochemically Synthesised Flexible Electrodes Based on Bimetallic Metal-Organic Framework Glasses for the Oxygen Evolution Reaction

The melting behaviour of metal-organic frameworks (MOFs) has aroused significant research interest in the areas of materials science, condensed matter physics and chemical engineering. This work first introduces a novel method to fabricate a bimetallic MOF glass, through melt-quenching of the cobalt-based zeolitic imidazolate framework (ZIF) [ZIF-62(Co)] with an adsorbed ferric coordination complex. The high-temperature chemically reactive ZIF-62(Co) liquid facilitates the formation of coordinative bonds between Fe and imidazolate ligands, incorporating Fe nodes into the framework after quenching. The resultant Co-Fe bimetallic MOF glass therefore shows a significantly enhanced oxygen evolution reaction performance. The novel bimetallic MOF glass, when combined with the facile and scalable mechanochemical synthesis technique for both discrete powders and surface coatings on flexible substrates, enables significant opportunities for catalytic device assembly.

Hydrolytically stable foamed HKUST-1@CMC composites realize high-efficient separation of U(VI)

HKUST-1@CMC (HK@CMC) composites that show good acid and alkali resistance and radiation resistance were successfully synthesized by introducing carboxymethyl cellulose (CMC) onto the surface of HKUST-1 using a foaming strategy. For the first time, the composites were explored as efficient adsorbents for U(VI) trapping from aqueous solution, with encouraging results of large adsorption capacity, fast adsorption kinetics, and desirable selectivity toward U(VI) over a series of competing ions. More importantly, a hybrid derivative film was successfully prepared for the dynamic adsorption of U(VI). The results show that ∼90% U(VI) can be removed when 45 mg L-1 U(VI) was passed through the film one time, and the removal percentage is still more than 80% even after four adsorption-desorption cycles, ranking one of the most practical U(VI) scavengers. This work offers new clues for application of the Metal-organic-framework-based materials in the separation of radionuclides from wastewater.

Coordination Polymer Glasses with Lava and Healing Ability for High-Performance Gas Sieving

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 (a_g M-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.

Metal-organic frameworks functionalized smart textiles for adsorptive removal of hazardous aromatic pollutants from ambient air

Organic pollutants, with their increasing concentrations in the ambient air, are posing a severe threat to human health. Metal-organic frameworks (MOFs), due to their active functionalities and porous nature, have emerged as potential materials for the capture of organic pollutants and cleaning of the environment/air. In this work, the functionalization of cotton fabric is reported by the in-situ growth of zeolitic imidazolate framework (ZIF-8 and ZIF-67) MOFs on carboxymethylated cotton (CM Cotton) by employing a rapid and eco-friendly approach. The physicochemical characterization of the MOF functionalized fabrics (ZIF-8@CM Cotton and ZIF-67@CM Cotton) revealed uniform and wash durable attachment of porous ZIF nanocrystals on the surface of the fabric. These ZIF functionalized fabrics possessed high surface area and have been observed to adsorb significantly high concentrations of organic pollutants such as aniline, benzene, and styrene from ambient air. Interestingly these fabrics could be regenerated and reused repeatedly without any deterioration in their adsorption capacity. The negative and low binding energies calculated by DFT confirmed the physisorption of the aromatic pollutants on the surface of MOF functionalized fabrics. Such fabrics have a huge potential as protective textiles, anti-odor clothing, air purification filters, and related products.

MOF based engineered materials in water remediation: Recent trends

The significant upsurge in the demand for freshwater has prompted various developments towards water sustainability. In this context, several materials have gained remarkable interest for the removal of emerging contaminants from various freshwater sources. Among the currently investigated materials for water treatment, metal organic frameworks (MOFs), a developing class of porous materials, have provided excellent platforms for the separation of several pollutants from water. The structural modularity and the striking chemical/physical properties of MOFs have provided more room for target-specific environmental applications. However, MOFs limit their practical applications in water treatment due to poor processability issues of the intrinsically fragile and powdered crystalline forms. Nevertheless, growing efforts are recognized to impart macroscopic shapability to render easy handling shapes for real-time industrial applications. Furthermore, efforts have been devoted to improve the stabilities of MOFs that are subjected to fragile collapse in aqueous environments expanding their use in water treatment. Advances made in MOF based material design have headed towards the use of MOF based aerogels/hydrogels, MOF derived carbons (MDCs), hydrophobic MOFs and magnetic framework composites (MFCs) to remediate water from contaminants and for the separation of oils from water. This review is intended to highlight some of the recent trends followed in MOF based material engineering towards effective water regeneration.

Fiber-Based Gas Filter Assembled via In Situ Synthesis of ZIF-8 Metal Organic Frameworks for an Optimal Adsorption of SO2: Experimental and Theoretical Approaches

For environmental protection from exposure to airborne toxic gases, metal organic frameworks (MOFs) have drawn great attention as gas adsorbent options, with their advantages in chemical tailorability and large porosity. To develop a fiber-based gas filter that is effective against SO₂ gas, zeolite imidazole framework-8 (ZIF-8) was applied to polypropylene nonwoven by various methods. Among the tested methods, the sol-gel impregnation method showed the highest ZIF-8 loading efficiency. There existed an optimal loading of ZIF-8 for the maximum adsorption efficiency, and it was associated with the accessibility of gas molecules to the ZIF-8 pores and active sites. Dominant adsorption processes and mechanisms were investigated by fitting the theoretical sorption models to experimental data. The results demonstrate that the increased ZIF-8 loading to fibers, beyond a certain level, may hinder the diffusivity and increase the barrier effect, eventually decreasing the adsorption efficiency. This study is novel and significant in that a multifaceted approach, including experimental analysis, theoretical investigation, and computational modeling, was made for scrutinizing the intricate phenomena occurring in the gas sorption process. The results of this study provide the fundamental yet practical information on the manufacturing considerations for the optimal design of MOF-loaded fibrous adsorbents.

Scalable crystalline porous membranes: current state and perspectives

Crystalline porous materials (CPMs) with uniform and regular pore systems show great potential for separation applications using membrane technology. Along with the research on the synthesis of precisely engineered porous structures, significant attention has been paid to the practical application of these materials for preparation of crystalline porous membranes (CPMBs). In this review, the progress made in the preparation of thin, large area and defect-free CPMBs using classical and novel porous materials and processing is presented. The current state-of-the-art of scalable CPMBs with different nodes (inorganic, organic and hybrid) and various linking bonds (covalent, coordination, and hydrogen bonds) is revealed. The advances made in the scalable production of high-performance crystalline porous membranes are categorized according to the strategies adapted from polymer membranes (interfacial assembly, solution-casting, melt extrusion and polymerization of CPMs) and tailored based on CPM properties (seeding-secondary growth, conversion of precursors, electrodeposition and chemical vapor deposition). The strategies are compared and ranked based on their scalability and cost. The potential applications of CPMBs have been concisely summarized. Finally, the performance and challenges in the preparation of scalable CPMBs with emphasis on their sustainability are presented.