Shaping of Metal-Organic Frameworks: From Fluid to Shaped Bodies and Robust Foams

Pickering emulsions stabilized by metal-organic framework nanoparticles

Pickering emulsions are attractive formulations due to their simplicity, similar to traditional surfactant-based emulsions, and their potential to create functional materials. Recently, Pickering emulsions stabilized by metal-organic framework (MOF) nanoparticles have garnered significant interest. This Review aims to systematize our knowledge of how MOF nanoparticles stabilize Pickering emulsions, providing fundamental insights for advancing this field. We thoroughly examine the emulsification process of Pickering emulsions stabilized by MOF nanoparticles. Additionally, we detail the superstructures derived from these emulsions, including colloidosomes, hydrogel droplets, 3D honeycomb network structures, molecularly imprinted polymers, monoliths, and micromotors. Finally, we discuss challenges and future research opportunities related to this type of emulsion.

In Situ ZIF-8-Coated Copper Laminate System for Fluid-Phase Adsorptive Separation

The use of structured adsorbents is emerging as a promising approach for adsorptive separation processes, and several ex situ structuring routes like extrusion, three-dimensional (3D) printing, and coating over substrates have been extensively investigated. However, in situ growth of adsorbents such as metal-organic frameworks (MOFs) on metal laminates remains underexplored. This study introduces a novel laminate system, where aluminum pieces, inspired by the "LEGO" concept, were designed through CNC milling and used to fabricate embossed/dented copper laminates. These laminates were then coated with ZIF-8 crystals (ZIF-8@Cu) via a direct in situ coating method at room temperature, resulting in a 100 μm coating. The system was assembled, packed in a custom-designed column, and evaluated for alcohol recovery from methanol/water and n-butanol/water mixtures. The ZIF-8@Cu laminates exhibited high adsorption capacities: 0.19 gMeOH/gZIF-8, 0.26 gn-BuOH/gZIF-8, and excellent selectivity toward alcohols (αMeOH/H2O = 8.5; αn-BuOH/H2O = 68). Vapor-phase experiments showed dispersive effects in the elution curve, attributed to the intrinsic properties of ZIF-8 (S-shaped equilibrium isotherm) and mass transfer limitation caused by channel nonuniformities and inlet flow maldistribution. For both separation mixtures, the laminate system was regenerated within 2 h via thermal swing adsorption (TSA), thereby exhibiting the combined benefits of microporosity, low-pressure drop, mechanical stability, and efficient heat transfer. The adsorptive properties were further highlighted in liquid-phase separation, where the laminates selectively captured n-butanol from 2.0 wt % aqueous solution and were successfully regenerated via TSA. This study provides proof of concept for the application of MOF-coated metal laminates in multiple adsorption-desorption cycles, thus highlighting their potential for process intensification.

The structuring of porous reticular materials for energy applications at industrial scales

Reticular synthesis constructs crystalline architectures by linking molecular building blocks with robust bonds. This process gave rise to reticular chemistry and permanently porous solids. Such precise control over pore shape, size and surface chemistry makes reticular materials versatile for gas storage, separation, catalysis, sensing, and healthcare applications. Despite their potential, the transition from laboratory to industrial applications remains largely limited. Among various factors contributing to this translational gap, the challenges associated with their formulation through structuring and densification for industrial compatibility are significant yet underexplored areas. Here, we focus on the shaping strategies for porous reticular materials, particularly metal-organic frameworks (MOFs) and covalent organic frameworks (COFs), to facilitate their industrial application. We explore techniques that preserve functionality and ensure durability under rigorous industrial conditions. The discussion highlights various configurations - granules, monoliths, pellets, thin films, gels, foams, and glasses - structured to maintain the materials' intrinsic microscopic properties at a macroscopic level. We examine the foundational theory and principles behind these shapes and structures, employing both in situ and post-synthetic methods. Through case studies, we demonstrate the performance of these materials in real-world settings, offering a structuring blueprint to inform the selection of techniques and shapes for diverse applications. Ultimately, we argue that advancing structuring strategies for porous reticular materials is key to closing the gap between laboratory research and industrial utilization.

Experimental and Theoretical Study of Two 3D Difunctional Electrocatalytic Hybrid Vanadate-Containing Metal-Organic Motifs

Two novel 3D inorganic-organic hybrids based on [V6O18]6-/[V3O9]3- clusters, [Cu18(bbpy)18(V6O18)6]·3H2O (1) and [Cu4Ag4(pty)4(V3O9)4]·H2O (2) (bbpy = 3,5-bis(1-benzimidazole) pyridine, pty = 4'-(4″-pyridyl)-2,2':6',2″-terpyridine), were isolated in the same POV/Cu/N-heterocycle ligand reaction systems. Hybrids 1 and 2 possess novel three-dimensional bimetallic frameworks derived from [V6O18]6-/[V3O9]3- clusters and Cu-organic complexes. In 1, bbpy ligands are grafted by Cu2+ to a grid ribbon 2D sheet, which are connected with benzene-like [V6O18]6- to yield a 3D framework. In 2, helical {O-V-O-V-}n chains are bridged by Cu(II) ions into a 2D layer including eight-membered rings {V6Cu2} and six-membered rings {V4Cu2}, and the adjoining sheets are joined by Ag-N coordination bonds to form a framework structure. Moreover, hybrid 1 has superior electrocatalytic properties for nitrite reduction and oxidation of ascorbic acid with electrocatalytic efficiencies of 397.2 and 96%, respectively. Hybrid 2 displays coordinated electrocatalytic performance toward oxidation reaction through V and Cu centers. Meanwhile, the corresponding theoretical studies were conducted to evaluate electrocatalytic active sites and charge distribution.

Utilizing MOFs Melt-Foaming to Design Functionalized Carbon Foams for 100% Deep-Discharge and Ultrahigh Capacity Sodium Metal Anodes

Meltable metal-organic frameworks (MOFs) offer significant accessibility to chemistry and moldability for developing carbon-based materials. However, the scarcity of low melting point MOFs poses challenges for related design. Here, we propose a MOFs melt-foaming strategy toward Ni single atoms/quantum dots-functionalized carbon foams (NiSA/QD@CFs). Melt-foaming highly depends on two factors: flexible metal-phosphorus bonds with cage-like ligands bridged in a zipper configuration via hydrogen bonds, facilitating MOFs conformational melting below 200 °C, and high annealing rates that lead to MOFs foaming by reducing the energy barrier and enhancing the pyrolysis enthalpy. When used as hosts for sodium metal anodes, foam structure regulates metallic Na to preferentially deposit inside the pores, while Ni SA and QD synergistically enhance Na absorption. Consequently, NiSA/QD@CF electrodes exhibit stable cyclic performance for 1000 h in symmetrical cells, with a low hysteresis voltage of 98 mV at 100 mA/cm2, 100 mAh/cm2, and 100% depth of discharge. Moreover, both full cells and anode-free ones exhibit excellent rate and cyclic performances. This strategy enriches the liquid MOFs family and their applications in mild-processing CFs for electrochemical energy storage.

Solution-Processable Metal-Organic Framework Featuring Highly Tunable Dynamic Aggregation States

The limited processability of metal-organic frameworks (MOFs) is hindered flexibility in the manipulation of their aggregation state and applications. Therefore, achieving highly processable MOFs is of great significance but a challenging goal. Herein, a facile strategy is presented for achieving the construction of solution-processable Mg-based MOF, NKU-Mg-1, allowing for dynamic control of the aggregation state through dynamic self-assembly (DySA) process and reversible circularly polarized luminescence (CPL) switcher modulation. Notably, micron-sized crystals of NKU-Mg-1 can be readily dispersed in water to form nano-sized colloids, triggered by the dynamic COO-Mg coordination bonding interruption by the competitive H2O-Mg bonding. Accordingly, the aggregation state of the colloid MOF can be readily tuned from 50-80 nm up to 1000 nm, in turn enabling control of aggregation-dependent emission. Specially, the solid-phase aggregation can be controlled via structural transitions between 3D NKU-Mg-1-rec-1 and 2D NKU-Mg-1-rec-2 nano-crystals, as confirmed by 3D electron diffraction. Furthermore, benefiting from its highly dynamic tunable aggregation nature, the rational incorporation of the chiral module confers significant CPL activity (glum up to 0.01). Importantly, controllable dynamic aggregation enables reversible switching of the CPL activity by precisely regulating the aggregation states. The solution-processable and dynamic aggregation-tunable features endow it highly promising for applications.

Recent development towards the novel applications and future prospects for cellulose-metal organic framework hybrid materials: a review

The hybrid material created by combining cellulose and MOF is highly promising and possesses a wide range of useful properties. Cellulose-based metal-organic frameworks (CelloMOFs) combine the inherent biocompatibility and sustainability of cellulose with the tunable porosity and diverse metal coordination chemistry of MOFs. Cellulose-MOF hybrids have countless applications in various fields, such as energy storage, water treatment, air filtration, gas adsorption, catalysis, and biomedicine. They are particularly remarkable as adsorbents that can eliminate pollutants from wastewater, including metals, oils, dyes, antibiotics, and drugs, and act as catalysts for oxidation and reduction reactions. Furthermore, they are highly efficient air filters, able to remove carbon dioxide, particulate matter, and volatile organic compounds. When it comes to energy storage, these hybrids have demonstrated exceptional results. They are also highly versatile in the realm of biomedicine, with applications such as antibacterial and drug delivery. This article provides an in-depth look at the fabrication methods, advanced applications of cellulose-MOF hybrids, and existing and future challenges.

Nanocomposites Based on Magnetic Nanoparticles and Metal-Organic Frameworks for Therapy, Diagnosis, and Theragnostics

In the last two decades, metal-organic frameworks (MOFs) with highly tunable structure and porosity, have emerged as drug nanocarriers in the biomedical field. In particular, nanoscaled MOFs (nanoMOFs) have been widely investigated because of their potential biocompatibility, high drug loadings, and progressive release. To enhance their properties, MOFs have been combined with magnetic nanoparticles (MNPs) to form magnetic nanocomposites (MNP@MOF) with additional functionalities. Due to the magnetic properties of the MNPs, their presence in the nanosystems enables potential combinatorial magnetic targeted therapy and diagnosis. In this Review, we analyze the four main synthetic strategies currently employed for the fabrication of MNP@MOF nanocomposites, namely, mixing, in situ formation of MNPs in presynthesized MOF, in situ formation of MOFs in the presence of MNPs, and layer-by-layer methods. Additionally, we discuss the current progress in bioapplications, focusing on drug delivery systems (DDSs), magnetic resonance imaging (MRI), magnetic hyperthermia (MHT), and theragnostic systems. Overall, we provide a comprehensive overview of the recent advances in the development and bioapplications of MNP@MOF nanocomposites, highlighting their potential for future biomedical applications with a critical analysis of the challenges and limitations of these nanocomposites in terms of their synthesis, characterization, biocompatibility, and applicability.

Hierarchically porous amino-functionalized nanoMOF network anchored phosphomolybdic acid for oxidative desulfurization and shaping application

The applications of hierarchically porous metal-organic frameworks (HP-MOFs) against traditional microporous counterparts for oxidative desulfurization (ODS) have triggered wide research interests due to their highly exposed accessible active sites and fast mass transfer of substrate molecules, particularly for the large-sized refractory sulfur compounds. Herein, a series of hierarchically porous amino-functionalized Zr-MOFs (HP-UiO-66-NH2-X) network with controllable mesopore sizes (3.5-9.2 nm) were firstly prepared through a template-free method, which were further utilized as anchoring support to bind the active phosphomolybdic acid (PMA) via the strong host-guest interaction to catalyze the ODS reaction. Benefitting from the hierarchically porous structure, accessible active sites and the strong host-guest interaction, the resultant PMA/HP-UiO-66-NH2-X exhibited excellent ODS performance, of which, the PMA/HP-UiO-66-NH2-9 with an appropriate mesopore size (4.0 nm) showed the highest catalytic activity, achieving a 99.9% removal of dibenzothiophene (DBT) within 60 min at 50 °C, far exceeding the microporous sample and PMA/HP-UiO-66. Furthermore, the scavenger experiments confirmed that •OH radical was the main reactive species and the density functional theory (DFT) calculations revealed that electron transfer (from amino group to PMA) made PMA react more easily with oxidant, thereby generating more •OH radical to promote the ODS reaction. Finally, from the industrial point of view, the powdered MOF nanoparticles (NPs) were in situ grown on the carboxymethyl cellulose (CMC) substrates and shaped into monolithic MOF-based catalysts, which still exhibited satisfying ODS performance in the case of model real fuel with good reusability, indicating its potential industrial application prospect.

Fast Gas-Adsorption Kinetics in Supraparticle-Based MOF Packings with Hierarchical Porosity

Metal-organic frameworks (MOFs) are microporous adsorbents for high-throughput gas separation. Such materials exhibit distinct adsorption characteristics owing to the flexibility of the crystal framework in a nanoparticle, which can be different from its bulk crystal. However, for practical applications, such particles need to be compacted into macroscopic pellets, creating mass-transport limitations. In this work, this problem is addressed by forming materials with structural hierarchy, using a supraparticle-based approach. Spherical supraparticles composed of nanosized MOF particles are fabricated by emulsion templating and they are used as the structural component forming a macroscopic material. Zeolitic imidazolate framework-8 (ZIF-8) particles are used as a model system and the gas-adsorption kinetics of the hierarchical material are compared with conventional pellets without structural hierarchy. It is demonstrated that a pellet packed with supraparticles exhibits a 30 times faster adsorption rate compared to an unstructured ZIF-8 powder pellet. These results underline the importance of controlling structural hierarchy to maximize the performance of existing materials. In the hierarchical MOFs, large macropores between the supraparticles, smaller macropores between individual ZIF-8 primary particles, and micropores inherent to the ZIF-8 framework collude to combine large surface area, defined adsorption sites, and efficient mass transport to enhance performance.

Nanoarchitectonics of Bimetallic MOF@Lab-Grade Flexible Filter Papers: An Approach Towards Real-Time Water Decontamination and Circular Economy

This study presents a novel approach to decontaminate ferrocyanide-contaminated wastewater. The work effectively demonstrates the use of bimetallic Mo/Zr-UiO-66 as a super-adsorbent for rapid sequestration of Prussian blue, a frequently found iron complex in cyanide-contaminated soils/groundwater. The exceptional performance of Mo/Zr-UiO-66 is attributed to the insertion of secondary metallic sites, which deliver synergistic effects, benefiting the inherent qualities of the framework. Moreover, to extend the industrial applications of metal-organic frameworks (MOFs) in real-world scenarios, an approach is delivered to structure the nanocrystalline powders into MOF-based macrostructures. The work demonstrates an interfacial process to develop continuous MOF nanostructures on ordinary laboratory-grade filter papers. The novelty of the work lies in the development of robust free-standing filtration materials to purify PB dye-contaminated water. Additionally, the work embraces a circular economy concept to address problems related to resource scarcity, excessive waste production, and maintenance of economic benefits. Consequently, the PB dye-loaded adsorbent waste is re-employed for the adsorption of heavy metals (Pb2+ and Cd2+ ). Simultaneously, the study aims to address the problems related to the real-time handling of powdered adsorbents, and the generation of ecologically harmful secondary waste, thereby, progressing toward a more sustainable system.

Microscopic insight into the shaping of MOFs and its impact on CO2 capture performance

The traditional synthesis method produces microcrystalline powdered MOFs, which prevents direct implementation in real-world applications which demand strict control of shape, morphology and physical properties. Therefore, shaping of MOFs via the use of binders is of paramount interest for their practical use in gas adsorption/separation, catalysis, sensors, etc. However, so far, the binders have been mostly selected by trial-and-error without anticipating the adhesion between the MOF and binder components to ensure the processability of homogeneous and mechanically stable shaped MOFs and the impact of the shaping on the intrinsic properties of the MOFs has been overlooked. Herein, we deliver a first systematic multiscale computational exploration of MOF/binder composites by selecting CALF-20, a prototypical MOF for real application in the field of CO2 capture, and a series of binders that cover a rather broad spectrum of properties in terms of rigidity/flexibility, porosity, and chemical functionality. The adhesion between the two components and hence the effectiveness of the shaping as well as the impact of the overall porosity of the CALF-20/binder on the CO2/N2 selectivity, CO2 sorption capacity and kinetics was analyzed. Shaping of CALF-20 by carboxymethyl cellulose was predicted to enable a fair compromise between excellent adhesion between the two components, whilst maintaining high CO2/N2 selectivity, large CO2 uptake and CO2 transport as fast as in the CALF-20. This multiscale computational tool paves the way towards the selection of an appropriate binder to achieve an optimum shaping of a given MOF in terms of processability whilst maintaining its high level of performance.

Gel transformation as a general strategy for fabrication of highly porous multiscale MOF architectures

The structure and chemistry of metal-organic frameworks or MOFs dictate their properties and functionalities. However, their architecture and form are essential for facilitating the transport of molecules, the flow of electrons, the conduction of heat, the transmission of light, and the propagation of force, which are vital in many applications. This work explores the transformation of inorganic gels into MOFs as a general strategy to construct complex porous MOF architectures at nano, micro, and millimeter length scales. MOFs can be induced to form along three different pathways governed by gel dissolution, MOF nucleation, and crystallization kinetics. Slow gel dissolution, rapid nucleation, and moderate crystal growth result in a pseudomorphic transformation (pathway 1) that preserves the original network structure and pores, while a comparably faster crystallization displays significant localized structural changes but still preserves network interconnectivity (pathway 2). MOF exfoliates from the gel surface during rapid dissolution, thus inducing nucleation in the pore liquid leading to a dense assembly of percolated MOF particles (pathway 3). Thus, the prepared MOF 3D objects and architectures can be fabricated with superb mechanical strength (>98.7 MPa), excellent permeability (>3.4 × 10^-10 m²), and large surface area (1100 m² g^-1) and mesopore volumes (1.1 cm³ g^-1).

One-Pot Synthesis Method of MIL-96 Monolith and Its CO2 Adsorption Performance

A novel preparation method was proposed for a metal-organic framework (MOF) monolith using a simple one-pot synthesis method. A MOF tubular monolith was successfully prepared by the hydrothermal treatment for an α-Al₂O₃ monolith in an aqueous solution of 1,3,5-benzenetricarboxylic acid and nitric acid without the addition of a metal source. The effects of temperature and the HNO₃ concentration in the synthesis solution on the crystallization behavior of MIL-96 were studied. HNO₃ enhanced the dissolution of the α-Al₂O₃ monolith and the growth of MIL-96. The growth rate of MIL-96 was also influenced by the synthesis temperature; a synthesis temperature of over 453 K was required for crystallization. The CO₂ adsorption capacity of the prepared MIL-96 monoliths was evaluated and found to be comparable to that of the well-grown MIL-96 powdery crystal. Furthermore, the MIL-96 monoliths demonstrated good stability as their adsorption properties were retained even after 2 months of storage under atmospheric conditions.

Enhanced performance of ZIF-8 nanocrystals hybrid monolithic composites via an in-situ growth strategy for efficient capillary microextraction of perfluoroalkyl phosphonic acids

Enrichment of perfluoroalkyl phosphonic acids (PFPAs) is of great significance and challenging for environmental monitoring, due to their toxic and persistent nature, highly fluorinated character as well as low concentration. Herein, novel metal-organic frameworks (MOFs) hybrid monolithic composites were prepared via metal oxide-mediated in situ growth strategy and utilized for capillary microextraction (CME) of PFPAs. A porous pristine monolith was initially obtained by copolymerization of the zinc oxide nanoparticles (ZnO-NPs)-dispersed methacrylic acid (MAA) with ethylenedimethacrylate (EDMA) and dodecafluoroheptyl acrylate (DFA). Afterwards, nanoscale-facilitated transformation of ZnO nanocrystals into the zeolitic imidazolate framework-8 (ZIF-8) nanocrystals was successfully realized via the dissolution-precipitation of the embedded ZnO-NPs in the precursor monolith in the presence of 2-methylimidazole. Experimental and spectroscopic results (SEM, N₂ adsorption-desorption, FT-IR, XPS) revealed that the coating of ZIF-8 nanocrystals significantly increased the surface area of the obtained ZIF-8 hybrid monolith and endowed the material abundant surface-localized unsaturated zinc sites. The proposed adsorbent showed highly enhanced extraction performance for PFPAs in CME, which was mainly ascribed to the strong fluorine affinity, Lewis acid/base complexing, anion-exchange, and weakly π-CF interaction. The coupling of CME with LC-MS enables effective and sensitive analysis of ultra-trace PFPAs in environment water and human serum. The coupling method demonstrated low detection limits (2.16-4.12 ng L^-1) with satisfactory recoveries (82.0-108.0%) and precision (RSDs ≤6.2%). This work offered a versatile route to design and fabricate selective materials for emerging contaminant enrichment in complicated matrices.

Direct synthesis of amorphous coordination polymers and metal–organic frameworks

Coordination polymers (CPs) and their subset, metal-organic frameworks (MOFs), can have porous structures and hybrid physicochemical properties that are useful for diverse applications. Although crystalline CPs and MOFs have received the most attention to date, their amorphous states are of growing interest as they can be directly synthesized under mild conditions. Directly synthesized amorphous CPs (aCPs) can be constructed from a wider range of metals and ligands than their crystalline and crystal-derived counterparts and demonstrate numerous unique material properties, such as higher mechanical robustness, increased stability and greater processability. This Review examines methods for the direct synthesis of aCPs and amorphous MOFs, as well as their properties and characterization routes, and offers a perspective on the opportunities for the widespread adoption of directly synthesized aCPs.

Saiz P, Reizabal A, Wuttke S, Celaya-Azcoaga L, Valverde A, Fernández de Luis R. A State-of-the-Art of Metal-Organic Frameworks for Chromium Photoreduction vs. Photocatalytic Water Remediation

Hexavalent chromium (Cr(VI)) is a highly mobile cancerogenic and teratogenic heavy metal ion. Among the varied technologies applied today to address chromium water pollution, photocatalysis offers a rapid reduction of Cr(VI) to the less toxic Cr(III). In contrast to classic photocatalysts, Metal-Organic frameworks (MOFs) are porous semiconductors that can couple the Cr(VI) to Cr(III) photoreduction to the chromium species immobilization. In this minireview, we wish to discuss and analyze the state-of-the-art of MOFs for Cr(VI) detoxification and contextualizing it to the most recent advances and strategies of MOFs for photocatalysis purposes. The minireview has been structured in three sections: (i) a detailed discussion of the specific experimental techniques employed to characterize MOF photocatalysts, (ii) a description and identification of the key characteristics of MOFs for Cr(VI) photoreduction, and (iii) an outlook and perspective section in order to identify future trends.

Metal-porphyrinic framework nanotechnologies in modern agricultural management

Metal-porphyrinic frameworks are an important subclass of metal-organic frameworks (MOFs). These porous materials exhibit a large number of applications for sustainable development and related environmental considerations. Their attractive features include (1) as a free base or metalated with zinc(II) or iron(II or III), they are environmentally benign, and (2) they absorb visible light and are emissive and semi-conducting, making them convenient tools for sensing agrochemicals. But the key feature that makes these nano-sized pristine materials or their composites in many ways superior to most MOFs is their ability to photo-generate reactive oxygen species with visible light, including singlet oxygen. This review describes important issues related to agriculture, including controlled delivery of pesticides and agrochemicals, detection of pesticides and pathogenic metals, elimination of pesticides and toxic metals, and photodynamic antimicrobial activity, and has an important implication for food safety. This comprehensive review presents the progress of the rather rapid developments of these functional and increasingly nano-sized materials and composites in the area of sustainable agriculture.

Self-healing mixed matrix membranes containing metal-organic frameworks

Mixed-matrix membranes (MMMs) provide a means to formulate metal-organic frameworks (MOFs) into processable films that can help to advance their use in various applications. Conventional MMMs are inherently susceptible to craze or tear upon exposure to impact, cutting, bending, or stretching, which can limit their intended service life and usage. Herein, a simple, efficient, and scalable in situ fabrication approach was used to prepare self-healing MMMs containing Zr(iv)-based MOFs. The ability of these MMMs to self-heal at room temperature is based on the reversible hydrolysis of boronic-ester conjugates. Thiol-ene 'photo-click' polymerization yielded robust MMMs with ∼30 wt% MOF loading and mechanical strength that varied based on the size of MOF particles. The MMMs could undergo repeated self-healing with good retention of mechanical strength. In addition, the MMMs were catalytically active toward the degradation of the chemical warfare agent (CWA) simulant dimethyl-4-nitrophenyl phosphate (DMNP) with no change in activity after two damage-healing cycles.

Structure of Industrial Sacrificial Fragile Cementitious Foams

Sacrificial fragile cementitious foams (SFCFs) act as a core material of the engineered material arresting system (EMAS) installed in airports to enhance the safe take-offs and landings of aircrafts. The foam structures and foaming mechanisms that greatly impact the collapse strength, specific energy, and arresting efficiency of SFCFs, however, have not been fully addressed. Herein, the engineering properties, chemical characteristics, and pore-skeleton structures of three batches of industrial SFCFs were experimentally investigated. Penetration tests showed significant differences in collapse strength and specific energy among the SFCFs with a similar density. Three-dimensional (3D) pore-skeleton structures were resolved by microfocused X-ray computed tomography. The pore-skeleton anisotropy was investigated to uncover the stages of differences in the SFCFs' engineering properties. The results demonstrate that the pore anisotropy rather than the porosity dominates the collapse of cementitious foams. Viscosity-associated nucleation and growth mechanisms were proposed to account for the featured pore-skeleton structures of the SFCFs. The findings would contribute to better pore structure controls of SFCFs toward the improved quality of EMAS.

Wettability tunable metal organic framework functionalized high internal phase emulsion porous monoliths for fast solid-phase extraction and sensitive analysis of hydrophilic heterocyclic amines

Surface wettability greatly influences the adsorptive, catalytic, and diffuse performances of a porous material. To realize the improved adsorption performance to hydrophilic heterocyclic amines (HAs), polymeric high internal phase emulsions (polyHIPEs) that can be tuned from hydrophobic to hydrophilic is synthesized by facilely regulating the amount of metal organic frameworks (MOFs). The water contact angle of the MOFs and polyHIPEs hybrids (MOFs@polyHIPEs) decreases from 133° to 0° as the amount of amide-modified MOFs increases from 0% to 10%. The hydrophilization of divinybenzene (DVB) based polyHIPEs by MOFs hybridization significantly enhances their adsorption performance and enables them to be suitable for the solid phase extraction (SPE) of hydrophilic HAs. Under the optimized conditions, the MOFs@polyHIPEs achieve adsorption capacities ranging from 42.89 to 86.71 µg/g for HAs through the π-π interaction and hydrogen bonding. The adsorption follows the pseudo-second-order kinetic model, and the nitrogen atoms in/on the imidazole ring are identified as the active adsorption sites for hydrogen bonding. This SPE method, along with HPLC-MS detection, provides detection limits of HAs as low as 0.00020-0.00040 ng/mL. This work offers a feasible strategy in tuning the surface wettability of polyHIPEs without post-modification to achieve high-efficiency enrichment and analysis of HAs.

Environmentally Benign Biosynthesis of Hierarchical MOF/Bacterial Cellulose Composite Sponge for Nerve Agent Protection

The fabrication of MOF polymer composite materials enables the practical applications of MOF-based technology, in particular for protective suits and masks. However, traditional production methods typically require organic solvent for processing which leads to environmental pollution, low-loading efficiency, poor accessibility, and loss of functionality due to poor solvent resistance properties. For the first time, we have developed a microbial synthesis strategy to prepare a MOF/bacterial cellulose nanofiber composite sponge. The prepared sponge exhibited a hierarchically porous structure, high MOF loading (up to ≈90 %), good solvent resistance, and high catalytic activity for the liquid- and solid-state hydrolysis of nerve agent simulants. Moreover, the MOF/ bacterial cellulose composite sponge reported here showed a nearly 8-fold enhancement in the protection against an ultra-toxic nerve agent (GD) in permeability studies as compared to a commercialized adsorptive carbon cloth. The results shown here present an essential step toward the practical application of MOF-based protective gear against nerve agents.

ZrBDC-Based Functional Adsorbents for Small-Scale Methane Storage Systems

Metal-organic frameworks (MOF), potentially porous coordination structures, are envisioned for adsorption-based natural gas (ANG) storage, including mobile applications. The factors affecting the performance of the ANG system with a zirconium-based MOF with benzene dicarboxylic acid as a linker (ZrBDC) as an adsorbent were considered: textural properties of the adsorbent and thermal effect arising upon adsorption. The high-density ZrBDC-based pellets were prepared by mechanical compaction of the as-synthesized MOF powder at different pressures from 30 to 240 MPa at 298 K without a binder and mixed with polymer binders: polyvinyl alcohol (PVA) and carboxyl methylcellulose (CMC). The structural investigations revealed that the compaction of ZrBDC with PVA under 30 MPa was optimal to produce the ZrBDC-PVA adsorbent with more than a twofold increase in the packing density and the lowest degradation of the porous structure. The specific total and deliverable volumetric methane storage capacities of the ZrBDC-based adsorbents were evaluated from the experimental data on methane adsorption measured up to 10 MPa and within a temperature range from 253 to 333 K. It was measured experimentally that at 253 K, an 100 mL adsorption tank loaded with the ZrBDC-PVA pellets exhibited the deliverable methane storage capacity of 172 m3(NTP)/m3 when the pressure dropped from 10 to 0.1 MPa. The methane adsorption data for the ZrBDC powder and ZrBDC-PVA pellets were used to calculate the important thermodynamic characteristic of the ZrBDC/CH4 adsorption system—the differential molar isosteric heat of adsorption, which was used to evaluate the state thermodynamic functions: entropy, enthalpy, and heat capacity. The initial heats of methane adsorption in powdered ZrBDC evaluated from the experimental adsorption isosteres were found to be ~19.3 kJ/mol, and then these values in the ZrBDC/CH4 system decreased at different rates during adsorption. In contrast, the heat of methane adsorption onto the ZrBDC-PVA pellets increased from 19.4 kJ/mol to a maximum with a magnitude, width, and position depended on temperature, and then it fell. The behaviors of the thermodynamic state functions of the ZrBDC/CH4 adsorption system were interpreted as a variation in the state of adsorbed molecules determined by a ratio of CH4-CH4 and CH4-ZrBDC interactions. The heat of adsorption was used to calculate the temperature changes of the ANG systems loaded with ZrBDC powder and ZrBDC pellets during methane adsorption under adiabatic conditions; the maximum integrated heat of adsorption was found at 273 K. The maximum temperature changes of the ANG system with the ZrBDC materials during the adsorption (charging) process did not exceed 14 K that are much lower than those reported for the systems loaded with activated carbons. The results obtained are of direct relevance for designing the adsorption-based methane storage systems for the automotive industry, developing new gas-power robotics systems and uncrewed aerial vehicles.

Understanding the Effects of Binders in Gas Sorption and Acidity of Aluminium Fumarate Extrudates

Understanding the impact of shaping processes on solid adsorbents is critical for the implementation of MOFs in industrial separation processes or as catalytic materials. Production of MOF-containing shaped particles is typically associated with loss of porosity and modification of acid sites, two phenomena that affect their performance. Herein, we report a detailed study on how extrusion affects the crystallinity, porosity, and acidity of the aluminium fumarate MOF with clays or SiO2 gel binders. Thorough characterization showed that the clay binders confer the extrudates a good mechanical robustness at the expense of porosity, while silica gel shows an opposite trend. The CO2 selectivity towards CH4 , of interest for natural gas separation processes, is maintained upon the extrusion process. Moreover, probe FTIR spectroscopy revealed no major changes in the types of acid sites. This study highlights that these abundant and inexpensive clay materials may be used for scaling MOFs as active adsorbents.

Hierarchical porous metal–organic gels and derived materials: from fundamentals to potential applications

This review summarizes recent progress in the development and applications of metal–organic gels (MOGs) and their hybrids and derivatives dividing them into subclasses and discussing their synthesis, design and structure–property relationship.

Templating Synthesis of Metal-Organic Framework Nanofiber Aerogels and Their Derived Hollow Porous Carbon Nanofibers for Energy Storage and Conversion

A kind of metal-organic framework (MOF) aerogels are synthesized by the self-assembly of uniform and monodisperse MOF nanofibers. Such MOF nanofiber aerogels as carbon precursors can effectively avoid the aggregation of nanofibers during calcination, resulting in the formation of well-dispersed hollow porous carbon nanofibers (HPCNs). Moreover, HPCNs with well-dispersion are investigated as sulfur host materials for Li-S batteries and electrocatalysts for cathode oxygen reduction reaction (ORR). On the one hand, HPCNs act as hosts for the encapsulation of sulfur into their hierarchical micro- and mesopores as well as hollow nanostructures. The obtained sulfur cathode exhibits excellent electrochemical features, good cycling stability and high coulombic efficiency. On the other hand, HPCNs exhibit better electrocatalytic activity than aggregated counterparts for ORR. Furthermore, a highly active single atom electrocatalyst can be prepared by the carbonization of bimetallic MOF nanofiber aerogels. The results indicate that well-dispersed HPCNs show enhanced electrochemical properties in contrast to their aggregated counterparts, suggesting that the dispersion situation of nanomaterials significantly influence their final performance. The present concept of employing MOF nanofiber aerogels as precursors will provide a new strategy to the design of MOF-derived nanomaterials with well-dispersion for their applications in energy storage and conversion.

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.

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.

Concentration gradient induced in situ formation of MOF tubes

The concentration gradient arising from the migration of metal ions and organic ligands could transform alginate fibres into MOF tubes in an aqueous environment. The tubes (10-20 μm thick) formed by alginate and ZIF-67 particles (∼500 nm and ∼1.5 μm) show high performance in contaminant removal. The facile preparation of tubular MOF composites would facilitate the application of MOFs.

Chitin/Metal-Organic Framework Composites as Wide-Range Adsorbent

Composites based on chitin (CH) biopolymer and metal-organic framework (MOF) microporous nanoparticles have been developed as broad-scope pollutant absorbent. Detailed characterization of the CH/MOF composites revealed that the MOF nanoparticles interacted through electrostatic forces with the CH matrix, inducing compartmentalization of the CH macropores that led to an overall surface area increase in the composites. This created a micro-, meso-, and macroporous structure that efficiently retained pollutants with a broad spectrum of different chemical natures, charges, and sizes. The unique prospect of this approach is the combination of the chemical diversity of MOFs with the simple processability and biocompatibility of CH that opens application fields beyond water remediation.

Facile One-Step Metal-Organic Framework Surface Polymerization Method

A simple one-step approach that only uses commercially available small-molecule reagents was developed for the construction of metal-organic framework (MOF)@polymer core-shell composite particles. Here, the MOF particles were incorporated into a typical reversible addition-fragmentation chain-transfer (RAFT) polymerization solution containing a solvent, a chain-transfer agent, an initiator, and a monomer mixture with at least one hydrogen-bond-donating monomer such as 2-hydroxyethyl methacrylate or acrylic acid. The elongation of polymer chains during polymerization gradually increases MOF/polymer interfacial interaction and eventually results in the adsorption of a random copolymer onto the MOF surface through hydrogen-bond cross-linking and MOF/polymer interfacial interaction. The continuous growth of the polymer leads to a uniform polymer coating on the MOF. Benefiting from the tacky polymer surface, these well-defined MOF@polymer composite particles can be further assembled into highly ordered monolayer composite thin films either alone or with an additional polymer matrix through the Langmuir-Blodgett technique.

Composite Materials Manufactured by Photopolymer 3D Printing with Metal-Organic Frameworks

Abstract

New composite materials containing metal-organic framework (MOF-5) particles were manufactured by 3D printing. The optimal composition of the photopolymer formulation and printing conditions ensuring the highest quality of printing were selected. Retention of the metal-organic framework (MOF) structure in the resulting composite objects was demonstrated by powder X-ray diffraction. The distribution of MOF-5 particles over the whole bulk of the 3D product was studied by X-ray computed tomography. In the future, composite materials of this type containing catalytically active MOFs, with their structure and properties being controllable at the micro and macro levels, could find application as catalysts of various chemical processes.