Metal-organic framework crystal-glass composites

Mechanochemical Synthesis Enables Melting, Glass Formation and Glass-Ceramic Conversion in a Cadmium-Based Zeolitic Imidazolate Framework

Metal-organic frameworks (MOFs) are versatile materials with tunable properties and broad applications. Here, we report the first cadmium-based zeolitic imidazolate framework (ZIF) glass, prepared by melt-quenching sub-micrometer-sized Cd(im)2 particles (im- = imidazolate) obtained via mechanochemical synthesis. This route increases defect density and reduces crystallite domain size, lowering the melting temperature from 461 °C (for larger solution-synthesized microcrystals) to 455 °C, thereby mitigating thermal decomposition during melting. Crystalline Cd(im)2 adopts a two-fold interpenetrated diamondoid (dia-c) topology, assembled from tetrahedral Cd2+ centers and im- linkers. Rapid cooling of the Cd(im)2 melt yields a monolithic glass with a glass transition temperature (Tg) of 175 °C. Structural analysis confirms that short-range connectivity within individual networks is maintained, whereas interactions between the interpenetrated networks are disrupted in the glass. Upon reheating, partial recrystallization produces a single-component glass-ceramic with enhanced mechanical properties, an unprecedented behavior in melt-quenched ZIF glasses. Investigations of thermal parameters (cooling rates) and partial linker substitution reveal strategies for tuning the phase behavior of both glass and glass-ceramic. These findings extend ZIF glass systems to second-row transition metal ions and underscore mechanochemical synthesis as a tool for tailoring the thermal properties of MOFs. This dual-phase functionality, combining glassy and crystalline domains of identical composition within a single material, offers potential for applications in thermal energy storage, phase change memory, and optics.

Solvent-free approach for the synthesis of heterometallic Fe-Zn-ZIF glass via a melt-quenched process

We report the solvent-free synthesis of a crystalline heterometallic imidazolate derivative with formula [Fe1Zn2(im)6(Him)2], designated MUV-25, incorporating both iron and zinc. The structure imposes strict positional constraints on the metal centres due to the lattice containing distinct geometric coordination sites, tetrahedral and octahedral. As a consequence, each metal is exclusively directed to its specific coordination site, ensuring precise spatial organization within the lattice. Atom locations were meticulously monitored utilizing X-ray diffraction (single crystal and total scattering) and XAS techniques, demonstrating that the tetrahedral sites are occupied exclusively by zinc, and the octahedral sites are occupied by iron. This combination of metal centres results, upon heating, in a structural phase transformation to the zni topology at a very low temperature. Further heating causes the melting of the solid, yielding a heterometallic MOF-derived glass. The methodology lays the groundwork for tailoring crystalline structures to advance the development of novel materials capable of melting and forming glasses upon cooling.

Deep Blue Emitting Lead Halide Perovskite and Metal-Organic Framework Glass Composites Through Mechanochemistry

Mixed-halide perovskites are promising materials for optoelectronic applications due to their tunable bandgaps and high photoluminescence quantum yields. However, these materials face challenges such as phase segregation under excitation and instability when exposed to polar solvents, especially in blue-emitting regions. In this study, a facile mechanochemical synthesis method is developed to produce CsPb(BrxCl1-x)3  - MOF (Metal-organic framework) glass composites. By precisely controlling the halide composition and optimizing milling conditions, glass composites containing quantum-confined perovskite particles with significantly improved phase stability, photoluminescence (PL), and solvent resistance are achieved. Notably, the composite can maintain up to 77% PL efficiency after soaking in water for a year. Structural and optical analyses revealed that the mechanochemical process fosters interfacial bonding between the perovskite and MOF glass, effectively regulating perovskite particle size and passivating surface defects. To demonstrate practical applications, violet and blue light-emitting diode (LED) devices are fabricated, achieving CIE color coordinates of (0.152, 0.031) and (0.134, 0.045), respectively. This work offers a scalable, eco-friendly approach to synthesizing stable, high-performance blue-emitting perovskites, paving the way for their integration into next-generation optoelectronic devices.

Advanced Microporous Framework Membranes for Sustainable Separation

Advancements in membrane-based separation hinge on the design of materials that transcend conventional limitations. Microporous materials, including metal-organic frameworks (MOFs), covalent-organic frameworks (COFs), macrocycles, and porous organic cages (POCs) offer unprecedented control over pore architecture, chemical functionality, and transport properties, making them promising candidates for next-generation membrane technologies. The well-defined and tunable micropores provide a pathway to directly address the permeability-selectivity trade-off inherent in conventional polymer membranes. Here, this review explores the latest advancements in these four representative microporous membranes, emphasizing their breakthroughs in hydrocarbon separation, liquid-phase molecular sieving, and ion-selective transport, particularly focusing on their structure-performance relationships. While their tailored structures enable exceptional performance, practical adoption requires overcoming hurdles in scalability, durability, and compatibility with industrial processes. By offering insights into membrane structure optimization and innovative design strategies, this review provides a roadmap for advancing microporous membranes from laboratory innovation to real-world implementation, ultimately supporting global sustainability goals through energy-efficient separation processes.

Upgrading Electron Transfer with High Conductivity MOF Composites for Supercapacitors

Supercapacitors (SCs) have emerged as promising energy storage devices, offering flexibility and smart functionalities to meet the growing demands of modern applications. However, challenges such as limited conductivity and stability continue to hinder their performance. Herein, a conductive composite was designed by forming one-dimension rod-like conductive MOFs (Ni-HHTP) on the hierarchical nickel oxalate (Ni-OA). The extended conjugated system between Ni2+ and HHTP establishes a robust electron delocalization network, significantly enhancing the conductivity and stability of the MOFs. Simultaneously, the incorporation of Ni-HHTP with Ni-OA effectively reduces internal electron transfer impedance, improving charge transport within the delocalized electronic networks. The synthesized Ni-OA@Ni-HHTP-6//AC achieves a remarkable energy density of 24.78 Wh kg-1 at a power density of 113.03 W kg-1, with a peak power density of 2924.58 W kg-1 at an energy density of 19.68 Wh kg-1. This work provides valuable insights into the design of oxalate@conductive-MOF composites, paving the way for energy storage devices.

Design and Development of a Self-Supporting ZIF-62 Glass MOF Membrane with Enhanced Molecular Sieving for High H2 Separation Efficiency

The purpose of this study was to design and develop a self-supporting glass MOF membrane (GMM) including its design, fabrication under different heat treatment temperatures, analysis of its physical-chemical properties, and assessment of its separation performance. Glass MOFs preserve metal-ligand bonding structures similar to their crystalline counterparts, providing intrinsic gas separation properties alongside the benefits of amorphous materials, including reduced grain boundaries and ease of processing. In this work, ZIF-62 was melted and then cooled to fabricate GMMs using vitrification to enhance molecular sieving. This study systematically examines the impact of varying thermal treatment temperatures (400-475 °C) on the physical and chemical transformations of GMMs, revealing their effects on the porosity, defect formation, and molecular sieving performance through advanced characterization techniques (e.g., solid-state nuclear magnetic resonance (13C NMR), X-ray photoelectron spectroscopy (XPS), He pycnometry, and positron annihilation lifetime spectroscopy (PALS)). The optimal GMM exhibits an impressive separation performance, particularly for H2 separation. The GMM at 4 bar and 25 °C exhibited He, H2, CO2, N2, and CH4 gas permeations of 576.37, 509.23, 146.07, 3.45, and 2.28 barrer, respectively. The ideal selectivities of H2/CH4, CO2/N2, CO2/CH4, H2/N2, and H2/CO2 gas pairs were 223.47, 42.37, 64.10, 147.71, and 3.49, respectively, which significantly exceed earlier reported values for ZIF-62 membranes, demonstrating the significant potential for GMMs as high-performance molecular sieve membranes, particularly for H2 separation. This work by optimizing the vitrification process through systematic temperature control highlights GMM's ability to achieve high selectivity and permeability, positioning it as a promising candidate for industrial gas separation applications.

Highly porous metal-organic framework glass design and application for gas separation membranes

Crystalline metal-organic frameworks (MOFs) exhibit enormous potential application in gas separation, thanks to their highly porous structures and precise pore size distributions. Nevertheless, the inherent limitations in mechanical stability of crystalline MOFs cause challenges in processing MOF powders into bulky structures, particularly for membrane filtrations. Melt-quenched MOF glasses boast excellent processability due to liquid-like properties. However, the melting process diminishes the inherent porosity, leading to reduced gas adsorption capacities and lower gas diffusion coefficients. In this work, we demonstrated that enhancing the porosity of MOF glasses is achievable through topological engineering on the crystalline precursors. Crystalline zeolitic imidazolate frameworks (ZIFs) with large 12-membered rings pores, including AFI and CAN topology, were synthesized by using both structure-directing agents and mixed organic ligands. The large pores are partially preserved in the melt-quenched glass as evidenced by high-pressure CO2 absorption at 3000 kPa. The agAFI-[Zn(Im)1.68(bIm)0.32] glass was then fabricated into self-supported membranes, which shows high gas separation performance, for example, CO2 permeance of 3.7 × 104 GPU with a CO2/N2 selectivity of 14.8.

Directly Gel-Thermal Processing of Linker-Mixed Crystal-Glass Composite Membranes for Sorption-Preferential Gas Separation

Membrane processes are promising for energy-saving industrial applications. However, efficient separation for some valuable gas mixtures with similar characteristics, such as CH4/N2 and O2/N2, remains extremely challenging. Metal-organic framework (MOF) membranes have been attracting intensive attention for gas sieving, but it is difficult to manufacture MOF membranes in scalability and precisely tune their transport property. In this study, Gel-thermal processing of linker-mixed MOF crystal-glass composite membranes is reported directly, with the mechanism of adjusting metal-linker bond strengths and angles to disrupt long-range periodicity of MOFs and promote glass phase formation, for sharply sorption-preferential gas separation. This strategy can be realized by using a simple, solvent/precursor-less, and cost-effective gel-thermal approach with two steps of gel coating and thermal conversion, thereby constructing crystal-glass composite membranes in a controllable, processable, versatile, and environmentally friendly route. Moreover, the mixed linkers enable preferential gas affinities and the ultramicroporous glasses can eliminate any membrane defects. The membranes exhibit outstanding gas separation performance for the challenging systems of CH4/N2 and O2/N2, with mixture selectivities up to 9.3 and 9.6, respectively, far exceeding those of polymer, MOF, and mixed-matrix membranes. The study provides an available route for architecting high-performance membranes for gas separations.

Intermarrying MOF Glass and Lead Halide Perovskites for Artificial Photosynthesis

The development of efficient artificial photosynthesis systems is crucial for sustainable chemical production, as they mimic natural processes to convert solar energy into chemical products, thereby addressing both energy and environmental challenges. The main bottlenecks in current research include fabricating highly selective, stable, and scalable catalysts, as well as effectively harnessing the full spectrum of light, particularly the low-energy, long-wavelength portion. Herein, we report a novel composite photocatalyst system based on lead halide perovskites embedded in functionalized MOF glass. The construction of a well-defined interface between the light-harvesting perovskite and stable Rh single-atom-containing MOF glass mimics the functions of photosystem I (PS I). This facilitates efficient photoinduced electron generation under visible light and subsequent electron transfer for coenzyme (NADH) regeneration with high selectivity. The regenerated NADH can then be consumed by immobilized enzymes for CO2 reduction, realizing the artificial photosynthesis process for formic acid generation. This work also elucidates the interactions and optoelectronic responses between MOF glass and perovskites, offering insights into the design and fabrication of nanocomposite photocatalysts for other advanced chemical syntheses.

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.

Atomistic Structure Investigation of Eu-Doped ZnO Nanosponges

Zinc oxide (ZnO) is a semiconductor with a wide range of applications, and often the properties are modified by metal-ion doping. The distribution of dopant atoms within the ZnO crystal strongly affects the optical and magnetic properties, making it crucial to comprehend the structure down to the atomic level. Our study reveals the dopant structure and its contents in Eu-doped ZnO nanosponges with up to 20% Eu-O clusters. Eu was distributed over the ZnO:Eu crystals, with an additional amorphous intercrystalline phase observed, especially in the 20% Eu sample. The electron pair distribution function revealed the presence of nonperiodic Eu3+-oxide clusters and proved highly effective for analyzing the coordination environment of Eu-O, ranging from 2.0 to 2.8 Å. It uncovered three-, four-, and five-coordinate Eu-O configurations in the 20% Eu sample, and there were significant changes in Eu coordination between the samples, which is ascribed due to the intercrystalline phase. The proposed method offers a potential characterization routine for a detailed investigation of complex doped materials.

Solution Processable Metal-Organic Frameworks: Synthesis Strategy and Applications

Metal-organic frameworks (MOFs), constructed by inorganic secondary building units with organic linkers via reticular chemistry, inherently suffer from poor solution processability due to their insoluble nature, resulting from their extensive crystalline networks and structural rigidity. The ubiquitous occurrence of precipitation and agglomeration of MOFs upon formation poses a significant obstacle to the scale-up production of MOF-based monolith, aerogels, membranes, and electronic devices, thus restricting their practical applications in various scenarios. To address the previously mentioned challenge, significant strides have been achieved over the past decade in the development of various strategies aimed at preparing solution-processable MOF systems. In this review, the latest advance in the synthetic strategies for the construction of solution-processable MOFs, including direct dispersion in ionic liquids, surface modification, controllable calcination, and bottom-up synthesis, is comprehensively summarized. The respective advantages and disadvantages of each method are discussed. Additionally, the intriguing applications of solution-processable MOF systems in the fields of liquid adsorbent, molecular capture, sensing, and separation are systematically discussed. Finally, the challenges and opportunities about the continued advancement of solution-processable MOFs and their potential applications are outlooked.

Exploring porous structures without crystals: advancements with pair distribution function in metal- and covalent organic frameworks

The pair distribution function (PDF) is a versatile characterisation tool in materials science, capable of retrieving atom-atom distances on a continuous scale (from a few angstroms to nanometres), without being restricted to crystalline samples. Typically, total scattering experiments are performed using high-energy synchrotron X-rays, neutrons or electrons to achieve a high atomic resolution in a short time. Recently, PDF analysis provides a powerful approach to target current characterisation challenges in the field of metal- and covalent organic frameworks. By identifying molecular interactions on the pore surfaces, tracking complex structural transformations involving disorder states, and elucidating nucleation and growth mechanisms, structural analysis using PDF has provided invaluable insights into these materials. This review article highlights the significance of PDF analysis in advancing our understanding of MOFs and COFs, paving the way for innovative applications and discoveries in porous materials research.

The Key to MOF Membrane Fabrication and Application: the Trade-off between Crystallization and Film Formation

Metal-organic frameworks (MOFs), owing the merits of ordered and tailored channel structures in the burgeoning crystalline porous materials, have demonstrated significant promise in construction of high-performance separation membranes. However, precisely because this crystal structure with strong molecular interaction in their lattice provides robust structural integrity and resistance to chemical and thermal degradation, crystalline MOFs typically exhibit insolubility, infusibility, stiffness and brittleness, and therefore their membrane-processing properties are far inferior to the flexible amorphous polymers and hinder their subsequent storage, transportation, and utilization. Hence, focusing on film-formation and crystallization is the foundation for exploring the fabrication and application of MOF membranes. In this review, the film-forming properties of crystalline MOFs are fundamentally analyzed from their inherent characteristics and compared with those of amorphous polymers, influencing factors of polycrystalline MOF membrane formation are summarized, the trade-off relationship between crystallization and membrane formation is discussed, and the strategy solving the film formation of crystalline MOFs in recent years are systematically reviewed, in anticipation of realizing the goal of preparing crystalline membranes with optimized processability and excellent performance.

Transparent and high-porosity aluminum alkoxide network-forming glasses

Metal-organic network-forming glasses are an emerging type of material capable of combining the modular design and high porosity of metal-organic frameworks and the high processability and optical transparency of glasses. However, a generalizable strategy for achieving both high porosity and high glass-forming ability in modularly designed metal-organic networks has yet to be developed. Herein, we develop a series of aluminum alkoxide glasses and monoliths by linking aluminum-oxo clusters with alcohol linkers. A bulky monodentate alcohol modulator is introduced during synthesis and act as both network plasticizer and pore template, which can be removed by the subsequent solvent exchange to give gas accessible pores. Glasses synthesized with the modulator template exhibit well-defined glass transitions in their as-synthesized form and high surface areas up to 500 m2/g after activation, making them among the most porous glassy materials. The aluminum alkoxide glasses also have optical transparency and fluorescent properties, and their structures are elucidated by pair-distribution functions, spectroscopic and compositional analysis. These findings could significantly expand the library of microporous metal-organic network-forming glasses and enable their future applications.

Loading and thermal behaviour of ZIF-8 metal-organic framework-inorganic glass composites

Here we describe the synthesis of a compositional series of metal-organic framework crystalline-inorganic glass composites (MOF-CIGCs) containing ZIF-8 and an inorganic phosphate glass, 20Na2O-10NaCl-70P2O5, to expand the library of host matrices for metal-organic frameworks. By careful selection of the inorganic glass component, a relatively high loading of ZIF-8 (70 wt%) was achieved, which is the active component of the composite. A Zn⋯O-P interfacial bond, previously identified in similar composites/hybrid blends, was suggested by analysis of the total scattering pair distribution function data. Additionally, CO2 and N2 sorption and variable-temperature PXRD experiments were performed to assess the composites' properties.

Hierarchical porous amorphous metal-organic frameworks constructed from ZnO/MOF glass composites

For the first time, hierarchical porous amorphous metal-organic frameworks (HP-aMOFs) containing ultramicropores, micropores, and mesopores were synthesized by etching a composite of MOF glass (agZIF-76) and ZnO using ammonia. These materials show potential applications in the adsorption of C2 hydrocarbons.

Recent Advances in Metal-Organic Framework (MOF)-Based Composites for Organic Effluent Remediation

Environmental pollution caused by organic effluents emitted by industry has become a worldwide issue and poses a serious threat to the public and the ecosystem. Metal-organic frameworks (MOFs), comprising metal-containing clusters and organic bridging ligands, are porous and crystalline materials, possessing fascinating shape and size-dependent properties such as high surface area, abundant active sites, well-defined crystal morphologies, and huge potential for surface functionalization. To date, numerous well designated MOFs have emerged as critical functional materials to solve the growing challenges associated with water environmental issues. Here we present the recent progress of MOF-based materials and their applications in the treatment of organic effluents. Firstly, several traditional and emerging synthesis strategies for MOF composites are introduced. Then, the structural and functional regulations of MOF composites are presented and analyzed. Finally, typical applications of MOF-based materials in treating organic effluents, including chemical, pharmaceutical, textile, and agricultural wastewaters are summarized. Overall, this review is anticipated to tailor design and regulation of MOF-based functional materials for boosting the performance of organic effluent remediation.

Improved ACOM pattern matching in 4D-STEM through adaptive sub-pixel peak detection and image reconstruction

The technique known as 4D-STEM has recently emerged as a powerful tool for the local characterization of crystalline structures in materials, such as cathode materials for Li-ion batteries or perovskite materials for photovoltaics. However, the use of new detectors optimized for electron diffraction patterns and other advanced techniques requires constant adaptation of methodologies to address the challenges associated with crystalline materials. In this study, we present a novel image-processing method to improve pattern matching in the determination of crystalline orientations and phases. Our approach uses sub-pixel adaptive image processing to register and reconstruct electron diffraction signals in large 4D-STEM datasets. By using adaptive prominence and linear filters, we can improve the quality of the diffraction pattern registration. The resulting data compression rate of 103 is well-suited for the era of big data and provides a significant enhancement in the performance of the entire ACOM data processing method. Our approach is evaluated using dedicated metrics, which demonstrate a high improvement in phase recognition. Several features are extracted from the registered data to map properties such as the spot count, and various virtual dark fields, which are used to enhance the handling of the results maps. Our results demonstrate that this data preparation method not only enhances the quality of the resulting image but also boosts the confidence level in the analysis of the outcomes related to determining crystal orientation and phase. Additionally, it mitigates the impact of user bias that may occur during the application of the method through the manipulation of parameters.

Highly porous metal-organic framework liquids and glasses via a solvent-assisted linker exchange strategy of ZIF-8

By combining the porosity of crystalline metal-organic frameworks (MOFs) with the unique processability of the liquid state, melt-quenched MOF glasses offer exciting opportunities for molecular separation. However, progress in this field is limited by two factors. Firstly, only very few MOFs melt at elevated temperatures and transform into stable glasses upon cooling the corresponding MOF liquid. Secondly, the MOF glasses obtained thus far feature only very small porosities and very small pore sizes. Here, we demonstrate solvent-assisted linker exchange (SALE) as a versatile method to prepare highly porous melt-quenched MOF glasses from the canonical ZIF-8. Two additional organic linkers are incorporated into the non-meltable ZIF-8, yielding high-entropy, linker-exchanged ZIF-8 derivatives undergoing crystal-to-liquid-to-glass phase transitions by thermal treatment. The ZIF-8 glasses demonstrate specific pore volumes of about 0.2 cm3g-1, adsorb large amounts of technologically relevant C3 and C4 hydrocarbons, and feature high kinetic sorption selectivities for the separation of propylene from propane.

Recent advances in the interfacial engineering of MOF-based mixed matrix membranes for gas separation

The membrane process stands as a promising and transformative technology for efficient gas separation due to its high energy efficiency, operational simplicity, low environmental impact, and easy up-and-down scaling. Metal-organic framework (MOF)-polymer mixed matrix membranes (MMMs) combine MOFs' superior gas-separation performance with polymers' processing versatility, offering the opportunity to address the limitations of pure polymer or inorganic membranes for large-scale integration. However, the incompatibility between the rigid MOFs and flexible polymer chains poses a challenge in MOF MMM fabrication, which can cause issues such as MOF agglomeration, sedimentation, and interfacial defects, substantially weakening membrane separation efficiency and mechanical properties, particularly gas separation. This review focuses on engineering MMMs' interfaces, detailing recent strategies for reducing interfacial defects, improving MOF dispersion, and enhancing MOF loading. Advanced characterisation techniques for understanding membrane properties, specifically the MOF-polymer interface, are outlined. Lastly, it explores the remaining challenges in MMM research and outlines potential future research directions.

A Short Review of Advances in MOF Glass Membranes for Gas Adsorption and Separation

The phenomenon of melting in metal-organic frameworks (MOFs) has recently garnered attention. Crystalline MOF materials can be transformed into an amorphous glassy state through melt-quenching treatment. The resulting MOF glass structure eliminates grain boundaries and retains short-range order while exhibiting long-range disorder. Based on these properties, it emerges as a promising candidate for high-performance separation membranes. MOF glass membranes exhibit permanent and accessible porosity, allowing for selective adsorption of different gas species. This review summarizes the melting mechanism of MOFs and explores the impact of ligands and metal ions on glassy MOFs. Additionally, it presents an analysis of the diverse classes of MOF glass composites, outlining their structures and properties, which are conducive to gas adsorption and separation. The absence of inter-crystalline defects in the structures, coupled with their distinctive mechanical properties, renders them highly promising for industrial gas separation applications. Furthermore, this review provides a summary of recent research on MOF glass composite membranes for gas adsorption and separation. It also addresses the challenges associated with membrane production and suggests future research directions.

Water Promotes Melting of a Metal-Organic Framework

Water is one of the most reactive and abundant molecules on Earth, and it is thus crucial to understand its reactivity with various material families. One of the big unknown questions is how water in liquid and vapor forms impact the fast-emerging class of metal-organic frameworks (MOFs). Here, we discover that high-pressure water vapor drastically modifies the structure and hence the dynamic, thermodynamic, and mechanical properties of MOF glasses. In detail, we find that an archetypical MOF (ZIF-62) is extremely sensitive to heat treatments performed at 460 °C and water vapor pressures up to ∼110 bar. Both the melting and glass transition temperatures decrease remarkably (by >100 °C), and simultaneously, hardness and Young's modulus increase by up to 100% under very mild treatment conditions (<20 bar of hydrothermal pressure). Structural analyses suggest water to partially coordinate to Zn in the form of a hydroxide ion by replacing a bridging imidazolate-based linker. The work provides insight into the role of hot-compressed water in influencing the structure and properties of MOF glasses and opens a new route for systematically changing the thermodynamics and kinetics of MOF liquids and thus altering the thermal and mechanical properties of the resulting MOF glasses.

Melt-quenched carboxylate metal-organic framework glasses

Although carboxylate-based frameworks are commonly used architectures in metal-organic frameworks (MOFs), liquid/glass MOFs have thus far mainly been obtained from azole- or weakly coordinating ligand-based frameworks. This is because strong coordination bonds of carboxylate ligands to metals block the thermal vitrification pathways of carboxylate-based MOFs. In this study, we present the example of carboxylate-based melt-quenched MOF glasses comprising Mg2+ or Mn2+ with an aliphatic carboxylate ligand, adipate. These MOFs have a low melting temperature (Tm) of 284 °C and 238 °C, respectively, compared to zeolitic-imidazolate framework (ZIF) glasses, and superior mechanical properties in terms of hardness and elastic modulus. The low Tm may be attributed to the flexibility and low symmetry of the aliphatic carboxylate ligand, which raises the entropy of fusion (ΔSfus), and the lack of crystal field stabilization energy on metal ions, reducing enthalpy of fusion (ΔHfus). This research will serve as a cornerstone for the integration of numerous carboxylate-based MOFs into MOF glasses.

In situ recrystallization of zero-dimensional hybrid metal halide glass-ceramics toward improved scintillation performance

Zero-dimensional (0D) hybrid metal halide (HMH) glasses are emerging luminescent materials and have gained attention due to their transparent character and ease of processing. However, the weakening of photoluminescence quantum efficiency from crystal to glass phases poses limitations for photonics applications. Here we develop high-performance glass-ceramic (G-C) scintillators via in situ recrystallization from 0D HMH glass counterparts composed of distinct organic cations and inorganic anions. The G-C scintillators maintain excellent transparency and exhibit nearly 10-fold higher light yields and lower detection limits than those of glassy phases. The general in situ recrystallization within the glass component by a facile heat treatment is analyzed via combined experimental elaboration and structural/spectral characterization. Our results on the development of G-Cs can initiate more exploration on the phase transformation engineering in 0D HMHs, and therefore make them highly promising for large-area scintillation screen applications.

Interfacial Bonding between a Crystalline Metal-Organic Framework and an Inorganic Glass

The interface within a composite is critically important for the chemical and physical properties of these materials. However, experimental structural studies of the interfacial regions within metal-organic framework (MOF) composites are extremely challenging. Here, we provide the first example of a new MOF composite family, i.e., using an inorganic glass matrix host in place of the commonly used organic polymers. Crucially, we also decipher atom-atom interactions at the interface. In particular, we dispersed a zeolitic imidazolate framework (ZIF-8) within a phosphate glass matrix and identified interactions at the interface using several different analysis methods of pair distribution function and multinuclear multidimensional magic angle spinning nuclear magnetic resonance spectroscopy. These demonstrated glass-ZIF atom-atom correlations. Additionally, carbon dioxide uptake and stability tests were also performed to check the increment of the surface area and the stability and durability of the material in different media. This opens up possibilities for creating new composites that include the intrinsic chemical properties of the constituent MOFs and inorganic glasses.

Order-Disorder Transition of Two-Dimensional Molecular Networks through a Stoichiometric Design

Materials with disordered structures may exhibit interesting properties. Metal-organic frameworks (MOFs) are a class of hybrid materials composed of metal nodes and coordinating organic linkers. Recently, there has been growing interest in MOFs with structural disorder and the investigations of amorphous structures on surfaces. Herein, we demonstrate a bottom-up method to construct disordered molecular networks on metal surfaces by selecting two organic molecule linkers with the same symmetry but different sizes for preparing two-component samples with different stoichiometric ratios. The amorphous networks are directly imaged by scanning tunneling microscopy under ultrahigh vacuum with a submolecular resolution, allowing us to quantify its degree of disorder and other structural properties. Furthermore, we resort to molecular dynamics simulations to understand the formation of the amorphous metal-organic networks. The results may advance our understanding of the mechanism of formation of monolayer molecular networks with structural disorders, facilitating the design and exploration of amorphous MOF materials with intriguing properties.

Effective Suppressing Phase Segregation of Mixed-Halide Perovskite by Glassy Metal-Organic Frameworks

Lead mixed-halide perovskites offer tunable bandgaps for optoelectronic applications, but illumination-induced phase segregation can quickly lead to changes in their crystal structure, bandgaps, and optoelectronic properties, especially for the Br-I mixed system because CsPbI3 tends to form a non-perovskite phase under ambient conditions. These behaviors can impact their performance in practical applications. By embedding such mixed-halide perovskites in a glassy metal-organic framework, a family of stable nanocomposites with tunable emission is created. Combining cathodoluminescence with elemental mapping under a transmission electron microscope, this research identifies a direct relationship between the halide composition and emission energy at the nanoscale. The composite effectively inhibits halide ion migration, and consequently, phase segregation even under high-energy illumination. The detailed mechanism, studied using a combination of spectroscopic characterizations and theoretical modeling, shows that the interfacial binding, instead of the nanoconfinement effect, is the main contributor to the inhibition of phase segregation. These findings pave the way to suppress the phase segregation in mixed-halide perovskites toward stable and high-performance optoelectronics.

Tetrahedral Imidazolate Frameworks with Auxiliary Ligands (TIF-Ax): Synthetic Strategies and Applications

Zeolitic imidazolate frameworks (ZIFs) are an important subclass of metal-organic frameworks (MOFs). Recently, we reported a new kind of MOF, namely tetrahedral imidazolate frameworks with auxiliary ligands (TIF-Ax), by adding linear ligands (Hint) into the zinc-imidazolate system. Introducing linear ligands into the M2+-imidazolate system overcomes the limitation of imidazole derivatives. Thanks to the synergistic effect of two different types of ligands, a series of new TIF-Ax with interesting topologies and a special pore environment has been reported, and they have attracted extensive attention in gas adsorption, separation, catalysis, heavy metal ion capture, and so on. In this review, we give a comprehensive overview of TIF-Ax, including their synthesis methods, structural diversity, and multi-field applications. Finally, we also discuss the challenges and perspectives of the rational design and syntheses of new TIF-Ax from the aspects of their composition, solvent, and template. This review provides deep insight into TIF-Ax and a reference for scholars with backgrounds of porous materials, gas separation, and catalysis.

Metal-organic framework glass composites

The melting phenomenon in metal-organic frameworks (MOFs) has been recognised as one of the fourth generation MOF paradigm behaviours. Molten MOFs have high processibility for producing mechanically robust glassy MOF macrostructures, and they also offer highly tunable interfacial characteristics when combined with other types of functional materials, such as crystalline MOFs, inorganic glass and metal halide perovskites. As a result, MOF glass composites have emerged as a family of functional materials with dynamic properties and hierarchical structural control. These nanocomposites allow for sophisticated materials science studies as well as the fabrication of next-generation separation, catalysis, optical, and biomedical devices. Here, we review the approaches for designing, fabricating, and characterising MOF glass composites. We determine the key application opportunities enabled by these composites and explore the remaining hurdles, such as improving thermal and chemical compatibility, regulating interfacial properties, and scalability.

Functions and applications of emerging metal-organic-framework liquids and glasses

Traditional metal-organic-frameworks (MOFs) have been extensively studied and applied in various fields across chemistry, biology and engineering in the past decades. Recently, a family of emerging MOF liquids and glasses have gained ever-growing research interests owing to their fascinating phase transitions and unique functions. To date, a growing number of MOF crystals have been found to be capable of transforming into liquid and glassy states under external stimuli, which overcomes the limitations of MOF crystals by introducing functional disorder in a controlled manner and offering some desirable properties. This review is dedicated to compiling recent advances in the fundamental understanding of the phase and structure evolution during crystal melting and glass formation in order to give insights into the underlying conversion mechanism. Benefiting from the disordered metal-ligand arrangement and free grain boundaries, various functional properties of liquid and glassy MOFs including porosity, ionic conductivity, and optical/mechanical properties are summarized and evaluated in detail, accompanied by the structure-property correlation. At the same time, their potential applications are further assessed from a developmental perspective according to their unique functions. Finally, we summarize the current progress in the development of liquid/glassy MOFs and point out the serious challenges as well as the potential solutions. This work provides perspectives on the functional applications of liquid/glassy MOFs and highlights the future research directions for the advancement of MOF liquids and glasses.

Mapping nanocrystalline disorder within an amorphous metal-organic framework

Intentionally disordered metal-organic frameworks (MOFs) display rich functional behaviour. However, the characterisation of their atomic structures remains incredibly challenging. X-ray pair distribution function techniques have been pivotal in determining their average local structure but are largely insensitive to spatial variations in the structure. Fe-BTC (BTC = 1,3,5-benzenetricarboxylate) is a nanocomposite MOF, known for its catalytic properties, comprising crystalline nanoparticles and an amorphous matrix. Here, we use scanning electron diffraction to first map the crystalline and amorphous components to evaluate domain size and then to carry out electron pair distribution function analysis to probe the spatially separated atomic structure of the amorphous matrix. Further Bragg scattering analysis reveals systematic orientational disorder within Fe-BTC's nanocrystallites, showing over 10° of continuous lattice rotation across single particles. Finally, we identify candidate unit cells for the crystalline component. These independent structural analyses quantify disorder in Fe-BTC at the critical length scale for engineering composite MOF materials.

Brittle-to-ductile transition and theoretical strength in a metal-organic framework glass

Metal-organic framework (MOF) glasses, a new type of melt-quenched glass, show great promise to deal with the alleviation of greenhouse effects, energy storage and conversion. However, the mechanical behavior of MOF glasses, which is of critical importance given the need for long-term stability, is not well understood. Using both micro- and nanoscale loadings, we find that pillars of a zeolitic imidazolate framework (ZIF) glass have a compressive strength falling within the theoretical strength limit of ≥E/10, a value which is thought to be unreachable in amorphous materials. Pillars with a diameter larger than 500 nm exhibited brittle failure with deformation mechanisms including shear bands and nearly vertical cracks, while pillars with a diameter below 500 nm could carry large plastic strains of ≥20% in a ductile manner with enhanced strength. We report this room-temperature brittle-to-ductile transition in ZIF-62 glass for the first time and demonstrate that theoretical strength and large ductility can be simultaneously achieved in ZIF-62 glass at the nanoscale. Large-scale molecular dynamics simulations have identified that microstructural densification and atomistic rearrangement, i.e., breaking and reconnection of inter-atomistic bonds, were responsible for the exceptional ductility. The insights gained from this study provide a way to manufacture ultra-strong and ductile MOF glasses and may facilitate their processing toward real-world applications.

Composite with a Glassy Nonporous Coordination Polymer Enhances Gas Adsorption Selectivity

A glass-crystal composite (g-NCP/PCP), comprising a glassy nonporous coordination polymer (g-NCP) and a crystalline porous coordination polymer (PCP)/metal-organic framework, was synthesized by using a melt-quenched method. Compared to that of the PCP itself, g-NCP/PCP has an enhanced gas adsorption selectivity. The results should stimulate further studies of the chemistry of g-NCP/PCP glass-crystal composites.

Metal Organic Framework Glasses: a New Platform for Electrocatalysis?

Metal organic framework (MOF) glasses are a coordination network of metal nodes and organic ligands as an undercooled frozen-in liquid, and have therefore broadened the potential of MOF materials in the fundamental research and application scenarios. On the road to deploying MOF glasses as electrocatalysts, it remains several basic scientific hurdles although MOF glasses not only inherit the structural merits of MOFs but also endow with active catalytic features including concentrated defects, metal centers and disorder structure etc. The research on the ionic conductivity, catalytic stability and reactivity of MOF glasses has yielded scientific insights towards its electrocatalytic applications. Here, we first comb the history, definition and basic properties of MOF glasses. Then, we identify the main synthetic methods and characterization techniques. Finally, we advance the potentials and challenges of MOF glasses as electrocatalysts in furthering the understanding of these themes.

Direct Sintering Behavior of Metal Organic Frameworks/Coordination Polymers

In this study, we investigate the sintering behavior and mechanisms of metal-organic frameworks/coordination polymers (CPs) through physical and microstructural characterization of [Zn(HPO₄)(H₂PO₄)₂]·2H₂Im (ZPI; a melting CP, Im = imidazole) and ZIF-8 (a non-melting CP). By performing simple compaction and subsequent sintering, a bulk body of CPs was obtained without losing the macroscopic crystallinity. The sintering behavior was found to be dependent on the temperature, heating rate, and physical properties of the CPs and, in particular, their meltability. During sintering, shrinkage occurred in both the CPs, but the observed shrinkage rate of the ZPI was in the 10-20% range, whereas that of the ZIF-8 was less than 1%. Additionally, the sintering mechanisms of the ZPI and ZIF-8 varied between low and high temperatures, and in the case of ZPI, localized melting between the primary particles was the dominant mechanism on the high-temperature side. However, substantial shrinkage did not correspond to an increase in density; on the contrary, a decrease in the apparent density of ZPI was observed as the sintering temperature was increased. The sintering technique is well established and commercially available; thus, the results obtained in this study can be utilized for optimizing the manufacturing conditions of melting CPs.

Eutectic CsHSO4-Coordination Polymer Glasses with Superprotonic Conductivity

Superprotonic phase transition in CsHSO₄ allows fast protonic conduction, but only at temperatures above the transition temperature of 141 °C (T_c). Here, we preserve the superprotonic conductivity of CsHSO₄ by forming a binary CsHSO₄-coordination polymer glass system, showing eutectic melting. Their anhydrous proton conductivities below T_c are at least 3 orders of magnitude higher than CsHSO₄ without compromising conductivity at higher temperatures or the need for humidification, reaching 6.3 mS cm^-1 at 180 °C. The glass also introduces processability to the conductor, as its viscosity below 10³ Pa·s can be achieved at 65 °C. Solid-state NMR and X-ray pair distribution functions reveal the oxyanion exchanges and the origin of the preserved conductivity. Finally, we demonstrate the preparation of a micrometer-scale thin-film proton conductor showing low resistivity with high transparency (transmittance >85% between 380-800 nm).

A hybrid ZIF-8/ZIF-62 glass membrane for gas separation

Metal-organic framework (MOF) glasses have demonstrated great potential for high-performance separation. Herein a uniform hybrid MOF glass membrane was fabricated by using the liquid state of ZIF-62 to facilitate the melting of ZIF-8. The doping of ZIF-8 enhanced both the adsorption capacity as well as the ideal C₃H₆/C₃H₈ selectivity of ZIF-62 glass. As expected, the hybrid glass membrane exhibited good C₃H₆/C₃H₈ separation performance while preserving the CO₂ performance of the sole ZIF-62 membrane.

Materials Formed by Combining Inorganic Glasses and Metal‐Organic Frameworks

Here, we propose the combination of glassy or crystalline metal‐organic frameworks (MOFs) with inorganic glasses to create novel hybrid composites and blends.The motivation behind this new composite approach is to improve the processability issues and mechanical performance of MOFs, whilst maintaining their ubiquitous properties. Herein, the precepts of successful composite formation and pairing of MOF and glass MOFs with inorganic glasses are presented. Focus is also given to the synthetic routes to such materials and the challenges anticipated in both their production and characterisation. Depending on their chemical nature, materials are classified as crystalline MOF‐glass composites and blends. Additionally, the potential properties and applications of these two classes of materials are considered, the key aim being the retention of beneficial properties of both components, whilst circumventing their respective drawbacks.

Tailored Inorganic-Organic Architectures via Metalloligands

This article discusses the design principles and strategies and the structural outcome of various supramolecular architectures constructed by utilizing well-defined coordination complexes as the metalloligands. We have included selected examples of metalloligands, offering either pyridyl or arylcarboxylic acid groups as the appended functional groups, for illustrating the construction of their supramolecular architectures. Both geometrical position and the number of the appended functional groups emerging from a metalloligand were found to critically regulate the structural aspects and dimensionality of the resultant material. The article concludes by delineating the structure-directing lessions as well as the potential applications of the metalloligand-based supramolecular architectures for the generation of next-level materials.

The deformation of short-range order leading to rearrangement of topological network structure in zeolitic imidazolate framework glasses

In recent years, the study of the glassy structure of zeolitic imidazolate frameworks (ZIFs) has been a key breakthrough in glass science. Yet the theoretical understanding of the structure of these complex materials is still in its infancy, especially the short-range structure. The short-structural disorder of two ZIFs and their corresponding molten structure, namely, ZIF-4 and ZIF-62 are studied, using ab initio simulations. Changes in short-range order are investigated, particularly the changes in bond length, bond angle, and tetrahedral unit volume. Furthermore, the asymmetric distribution of organic groups caused by the benzimidazole functional group leads to the difference in short-range disorder between ZIF-4 and ZIF-62 glasses, which contribute to the glass-forming ability difference.

Unraveling timescale-dependent Fe-MOFs crystal evolution for catalytic ozonation reactivity modulation

Iron-based metal-organic frameworks (Fe-MOFs) have been considered competitive catalyst candidates for the effective degradation of organic pollutants via advanced oxidation processes (AOPs) due to their unique porous architecture and tunable active site structure. However, little is known about the role of synergetic relationship between porous architecture and active site exposure of Fe-MOFs on catalysis for AOPs yet. Here, we demonstrated an overlooked compromise over these two features on modulating the catalytic ozonation reactivity of MIL-53(Fe) through a timescale-dependent crystal evolution. Enabled by intramolecular hydrogen bonds, the MIL-53(Fe) was subjected to six evolution steps in terms of crystal morphology, leading to a volcano plot of catalytic ozonation reactivity for Rhodamine B (RhB) degradation versus the crystallization time. Evidence suggested that the surface area of MIL-53(Fe) decreased dramatically, while the density of accessible active site increased when prolonging crystallization time, allowing for the facile modulation of catalytic ozonation reactivity of MIL-53(Fe). Electron paramagnetic resonance and fluorescence quantification tests verified that the screened MIL-53(Fe)s had a much better capacity for ∙OH generation than benchmark ozonation catalyst α-MnO₂ and α-FeOOH. Moreover, the MIL-53(Fe) with the highest reactivity (i.e., MIL-53(Fe)-18H) could effectively destruct a broad spectrum of emerging and refractory organic pollutants and allow the thorough purification of secondary effluents discharged from textile dyeing & finishing industry for in situ reuse. Therefore, our study advances the understanding of the compromise effect between porous architecture and active site on catalysis reactivity of Fe-MOFs and promotes the rational design of more effective Fe-MOFs as well as their derivatives for environmental applications.

From Operando Raman Mechanochemistry to "NMR Crystallography": Understanding the Structures and Interconversion of Zn-Terephthalate Networks Using Selective 17O-Labeling

The description of the formation, structure, and reactivity of coordination networks and metal-organic frameworks (MOFs) remains a real challenge in a number of cases. This is notably true for compounds composed of Zn2+ ions and terephthalate ligands (benzene-1,4-dicarboxylate, BDC) because of the difficulties in isolating them as pure phases and/or because of the presence of structural defects. Here, using mechanochemistry in combination with operando Raman spectroscopy, the observation of the formation of various zinc terephthalate compounds was rendered possible, allowing the distinction and isolation of three intermediates during the ball-milling synthesis of Zn3(OH)4(BDC). An "NMR crystallography" approach was then used, combining solid-state NMR (1H, 13C, and 17O) and density functional theory (DFT) calculations to refine the poorly described crystallographic structures of these phases. Particularly noteworthy are the high-resolution 17O NMR analyses, which were made possible in a highly efficient and cost-effective way, thanks to the selective 17O-enrichment of either hydroxyl or terephthalate groups by ball-milling. This allowed the presence of defect sites to be identified for the first time in one of the phases, and the nature of the H-bonding network of the hydroxyls to be established in another. Lastly, the possibility of using deuterated precursors (e.g., D2O and d 4-BDC) during ball-milling is also introduced as a means for observing specific transformations during operando Raman spectroscopy studies, which would not have been possible with hydrogenated equivalents. Overall, the synthetic and spectroscopic approaches developed herein are expected to push forward the understanding of the structure and reactivity of other complex coordination networks and MOFs.

Effect of process parameters over carbon-based ZIF-62 nano-rooted membrane for environmental pollutants separation

The paper evaluates the routes towards the evaluation of membranes using ZIF-62 metal organic framework (MOF) nano-hybrid dots for environmental remediation. Optimization of interaction of operating parameters over the rooted membrane is challenging issue. Subsequently, the interaction of operating parameters including temperature, pressure and CO₂ gas concentration over the resultant rooted membranes are evaluated and optimized using response surface methodology for environmental remediation. In addition, the stability and effect of hydrocarbons on the performance of the resulting membrane during the gas mixture separation are evaluated at optimum conditions to meet the industrial requirements. The characterization results verified the fabrication of the ZIF-62 MOF rooted composite membrane. The permeation results demonstrated that the CO₂ permeability and CO₂/CH₄ selectivity of the composite membrane was increased from 15.8 to 84.8 Barrer and 12.2 to 35.3 upon integration of ZIF-62 nano-glass into cellulose acetate (CA) polymer. Subsequently, the optimum conditions have been found at a temperature of 30 °C, the pressure of 12.6 bar and CO₂ feed concentration of 53.3 vol%. These optimum conditions revealed the highest CO₂ permeability, CH₄ permeability and CO₂/CH₄ separation factor of 47.9 Barrer, 0.2 Barrer and 26.8. The presence of hydrocarbons in gas mixture dropped the CO₂ permeability of 56.5% and separation factor of 46.4% during 206 h of testing. The separation performance of the composite membrane remained stable without the presence of hydrocarbons for 206 h.