Field Of Metal-organic Frameworks Research Articles

Construction and application of base-stable MOFs: a critical review.

Metal-organic frameworks (MOFs) are a new class of porous crystalline materials constructed from organic ligands and metal ions/clusters. Owing to their unique advantages, they have attracted more and more attention in recent years and numerous studies have revealed their great potential in various applications. Many important applications of MOFs inevitably involve harsh alkaline operational environments. To achieve high performance and long cycling life in these applications, high stability of MOFs against bases is necessary. Therefore, the construction of base-stable MOFs has become a critical research direction in the MOF field. This review gives a historic summary of the development of base-stable MOFs in the last few years. The key factors that can determine the robustness of MOFs under basic conditions are analyzed. We also demonstrate the exciting achievements that have been made by utilizing base-stable MOFs in different applications. In the end, we discuss major challenges for the further development of base-stable MOFs. Some possible methods to address these problems are presented.

Solvothermal Synthesis of a Novel Calcium Metal-Organic Framework: High Temperature and Electrochemical Behaviour.

The rapid growth in the field of metal-organic frameworks (MOFs) over recent years has highlighted their high potential in a variety of applications. For biological and environmental applications MOFs with low toxicity are vitally important to avoid any harmful effects. For this reason, Ca-based MOFs are highly desirable owing to their low cost and high biocompatibility. Useful Ca MOFs are still rare owing to the ionic character and large size of the Ca2+ ion tending to produce dense phases. Presented here is a novel Ca-based MOF containing 2,3-dihyrdoxyterephthalate (2,3-dhtp) linkers Ca(2,3-dhtp)(H2O) (SIMOF-4). The material undergoes a phase transformation on heating, which can be followed by variable temperature powder X-ray diffraction. The structure of the high temperature form was obtained using single-crystal X-ray diffraction. The electrochemical properties of SIMOF-4 were also investigated for use in a Na ion battery.

Combustion characteristics of EMOFs/oxygenated salts novel thermite for green energetic applications

Metal-based thermites, especially those based on aluminum, have been recently included in materials for energetic applications such as pyrotechnics, propellants, and explosives. In parallel, several advances in the field of Metal-Organic Frameworks (MOFs) and Coordination Polymers (CPs) have as well paved the road for their use in developing novel energetic materials. In this context, we are introducing new thermites compositions with low ignition temperature, stable propulsive force, and high reactivity. These thermites are based on the [Cu4Na(Mtta)5(CH3CN)]n (Mtta = 5-Methyl-1H-tetrazole) energetic metal-organic framework (EMOF-1) as a fuel instead of pure metals. We first report the synthesis of an energetic MOF via the microwave-assisted technique as a more rapid and greener method. The efficiency of composites based on EMOF-1 and Al together with various oxygenated salts were investigated. Multiple instruments are involved to characterize the morphology and the structure of EMOF-1 and the developed systems, such as SEM-EDX, FTIR, and XRD. The combustion behavior of the novel composites was evaluated by TGA/DSC, bomb calorimetry and laser ignition. Additionally, the apparent kinetic parameters (activation energy & frequency factor) were calculated by the Kissinger and Ozawa approaches. The results revealed that the new thermite mixtures exhibit superior combustion characteristics of one and half to two-folds the average heat of combustion compared to aluminum-based ones, at almost half the ignition temperature. In this sense, the combustion reaction proceeds faster, easier (reduced activation energy), the ignition temperatures are noticeably lowered, and the heat released has considerably improved. In addition, they exhibited stable force with longer burning time. Among them, EMOF-1/KIO4 thermite exhibits the highest heat release (4.7 kJ/g), while EMOF-1/NH4NO3 thermite shows the lowest onset reaction temperature (224 ᵒC). EMOF-1/KClO4 yields the highest average force (8.4 N), calculated pressure (1365 kPa), pressurization rate (0.32 kPa/μs) and the longest burning time assigned to EMOF-1/K2S2O8 (40 ms).

Redox-active ligands: Recent advances towards their incorporation into coordination polymers and metal-organic frameworks

• Developments in coordination polymers (CPs) and metal–organic frameworks (MOFs). • Electroactive CPs and MOFs possess unique redox-state dependent properties. • An exploration of key redox-active ligands investigated in the past eight years. • Emerging redox-active ligands inspired by organic photovoltaic devices (OPVs). • CP and MOFs with applications in solar cells, photo switches and photoelectrocatalysis. Over the past three decades, the field of coordination polymers (CPs) and metal–organic frameworks (MOFs) has developed rapidly due to the potential applications of these materials in gas storage, separations, catalysis and switching. Introducing redox properties into CPs and MOFs to electrochemically modulate their properties for the development of solid state electronic devices has been an interesting strategy applied in recent years. Notably, a challenge within this area is the engineering of framework materials with desired redox properties targeted at a specific function. This review explores some of the key redox-active ligands that have been investigated within the previous eight years as redox-active components of solid state materials and examines a number of key strategies for their integration into CPs and MOFs. This review further highlights emergent redox-active ligands in the literature, which take inspiration from the rich field of organic electronics. While these ligands remain largely unexplored in the field of MOFs and CPs, they offer new opportunities for the improvement of solar cells, light induced photo switches, efficient photoelectrocatalysts and long range, rapid charge transfer in MOF materials.

Building Block Symmetry Relegation Induces Mesopore and Abundant Open-Metal Sites in Metal–Organic Frameworks for Cancer Therapy

Building Block Symmetry Relegation Induces Mesopore and Abundant Open-Metal Sites in Metal–Organic Frameworks for Cancer Therapy

Mixed hierarchical local structure in a disordered metal\u2013organic framework

Amorphous metal–organic frameworks (MOFs) are an emerging class of materials. However, their structural characterisation represents a significant challenge. Fe-BTC, and the commercial equivalent Basolite® F300, are MOFs with incredibly diverse catalytic ability, yet their disordered structures remain poorly understood. Here, we use advanced electron microscopy to identify a nanocomposite structure of Fe-BTC where nanocrystalline domains are embedded within an amorphous matrix, whilst synchrotron total scattering measurements reveal the extent of local atomic order within Fe-BTC. We use a polymerisation-based algorithm to generate an atomistic structure for Fe-BTC, the first example of this methodology applied to the amorphous MOF field outside the well-studied zeolitic imidazolate framework family. This demonstrates the applicability of this computational approach towards the modelling of other amorphous MOF systems with potential generality towards all MOF chemistries and connectivities. We find that the structures of Fe-BTC and Basolite® F300 can be represented by models containing a mixture of short- and medium-range order with a greater proportion of medium-range order in Basolite® F300 than in Fe-BTC. We conclude by discussing how our approach may allow for high-throughput computational discovery of functional, amorphous MOFs.

Metal–Organic Frameworks in Italy: From synthesis and advanced characterization to theoretical modeling and applications

• This review summarizes the work of the Italian groups working in the field of MOFs • The document is a celebration of ICCC 2022 that will take place in Italy (Rimini) • This review will strengthen the scientific relationship among these Italian groups. As a celebration of the 44th International Conference on Coordination Chemistry (ICCC2022) that will take place in Italy, the Italian groups working in the research field of Metal–Organic Frameworks (MOFs) have decided to gather together and collect the results they have obtained in this area over the past 15 years. A survey that starts from the synthesis of novel heterocyclic linkers and the related MOFs and moves through advanced characterization techniques, theoretical investigations and assorted applications in the fields of gas storage and separation, heterogeneous catalysis, magnetism and sensing.

Three-Dimensional Electron Diffraction for Structural Analysis of Beam-Sensitive Metal-Organic Frameworks

Electrons interact strongly with matter, which makes it possible to obtain high-resolution electron diffraction data from nano- and submicron-sized crystals. Using electron beam as a radiation source in a transmission electron microscope (TEM), ab initio structure determination can be conducted from crystals that are 6–7 orders of magnitude smaller than using X-rays. The rapid development of three-dimensional electron diffraction (3DED) techniques has attracted increasing interests in the field of metal-organic frameworks (MOFs), where it is often difficult to obtain large and high-quality crystals for single-crystal X-ray diffraction. Nowadays, a 3DED dataset can be acquired in 15–250 s by applying continuous crystal rotation, and the required electron dose rate can be very low (<0.1 e s−1 Å−2). In this review, we describe the evolution of 3DED data collection techniques and how the recent development of continuous rotation electron diffraction techniques improves data quality. We further describe the structure elucidation of MOFs using 3DED techniques, showing examples of using both low- and high-resolution 3DED data. With an improved data quality, 3DED can achieve a high accuracy, and reveal more structural details of MOFs. Because the physical and chemical properties of MOFs are closely associated with their crystal structures, we believe 3DED will only increase its importance in developing MOF materials.

Simultaneous quantitative recognition of all purines including N6-methyladenine via the host-guest interactions on a Mn-MOF

Simultaneous quantitative recognition of all purines including N6-methyladenine via the host-guest interactions on a Mn-MOF

Metal–organic frameworks (MOFs) beyond crystallinity: amorphous MOFs, MOF liquids and MOF glasses

The field of MOFs has been incorrectly believed to be purely crystalline. Herein, non-crystalline MOFs (amorphous MOFs, MOF liquids, and MOF glasses) are reviewed. Future research directions are also discussed.

The combustion and pyrolysis process of flame-retardant polystyrene/cobalt-based metal organic frameworks (MOF) nanocomposite

Considerable toxic gases and high temperature smoke will be generated during the combustion of polystyrene (PS), which restricts its application. Here, a cobalt-based MOF-71-NH 2 (hereinafter referred to as MOF-NH 2 ) has been synthesized and further modified with phosphonitrilic chloride trimer (PCT) by a post-synthesis modification (PSM) strategy, named as PCT@MOF-NH 2 , which was used to enhance the flame retardancy of PS. Desirable results were obtained as expected: the fire safety and tensile strength of PS were prominently improved after adding PCT@MOF-NH 2 . Compared with pure PS, there were more than 40% and 31% decreases in the value of pHRR and THR with 3.0 wt% content of PCT@MOF-NH 2 . From the analysis of gaseous and condensed products after combustion, the possible flame retardancy mechanism of PS nanocomposites can be attributed to the barrier effect of PCT@MOF-NH 2 , which provides a promising application field of MOFs to improve flame retardation of polymer materials.

Automatic Deposition of Oriented Copper Hydroxide Nanobelt Films for the Heteroepitaxial Growth of Metal-Organic Frameworks

One of the key challenges that the field of metal-organic frameworks (MOFs) faces today is the possibility of processing these materials as thin films to enable their integration into existing technologies [1-4]. This is particularly important for devices that exploit anisotropic properties obtained from highly oriented materials. Based on a previously described procedure to obtain centimetre-scale oriented MOF films [5], we hereby report the optimization and extension of this procedure into an automated, operator-independent method that affords higher yields without compromising the long-range orientation. The procedure is based on the deposition of crystalline copper hydroxide nanobelts that can be aligned to obtain substrates with preferential orientation. The influence of different deposition parameters on the coverage and orientation of the films was studied and tuned in order to obtain reproducible samples with higher yields. With applications in fields such as gas storage, catalysis and light harvesting, among others, these oriented ceramic substrates can be converted on demand to different MOFs by exploiting a rapid heteroepitaxial growth [6]. This automatic method introduces the attractive prospect of the potential implementation of MOFs in large-scale thin-film processing. Figure 1: Comparison between manual and automated procedures for the deposition of oriented copper hydroxide films on silicon substrates. Left: Azimuthal angle dependence of intensity profiles of the (020) reflection of Cu(OH)2 at a diffraction angle of 23.8°corresponding to a typical sample obtained by each method, showing the superior alignment of the automatic procedure. Right: Optical images showing the surface coverage and long range (centimetre-scale, top) and micro alignment of the substrate (by polarized-light optical microscopy, bottom).

Zeolitic imidazolate frameworks for use in electrochemical and optical chemical sensing and biosensing: a review.

This review (with 145 refs.) summarizes the progress that has been made in the use of zeolitic imidazolate frameworks in chemical sensing and biosensing. Zeolitic imidazolate frameworks (ZIFs) are a type of porous material with zeolite topological structure that combine the advantages of zeolite and traditional metal-organic frameworks. Owing to the structural flexibility of ZIFs, their pore sizes and surface functionalization can be reasonably designed. Following an introduction into the field of metal-organic frameworks and the zeolitic imidazolate framework (ZIF) subclass, a first large section covers the various kinds and properties of ZIFs. The next large section covers electrochemical sensors and assays (with subsections on methods for gases, electrochemiluminescence, electrochemical biomolecules). This is followed by main sections on ZIF-based colorimetric and luminescent sensors, with subsections on sensors for metal ions and anions, for gases, and for organic biomolecules. The last section covers SERS-based assays. Several tables are presented that give an overview on the wealth of methods and materials. A concluding section summarizes the current status, addresses current challenges, and gives an outlook on potential future trends. Graphical abstract In recent years, ZIFs and their composites have been widely used as probes in chemical sensing, and these probes have shown great advantages over other materials. This review describes the current progress on ZIFs toward electrochemical, luminescence, colorimetric, and SERS-based sensing applications, highlighting the different strategies for designing ZIFs and their composites and potential challenges in this field.

Functionalized metal-organic frameworks for photocatalytic degradation of organic pollutants in environment.

Currently, many kinds of organic pollutants in air and water have a negative impact on humans and the environment. Notably, as a type of new functional materials, metal-organic frameworks (MOFs) with well-ordered porous structures and numerous active sites have been proven to be ideal photocatalysts for the degradation of organic pollutants. In the past few years, many encouraging achievements have been made in the research field of MOFs for photocatalysis. And a large number of functionalized MOFs have been constructed to improve photocatalytic activity. In this review, recent progress in the photocatalytic degradation of organic pollutants in both air and water using functionalized MOFs are summarized in detail. The focus is on photocatalytic mechanisms and some strategies employed to achieve higher degradation efficiency. Furthermore, the challenges and outlooks in this promising filed are also discussed. We hope this review would be useful for designing more functionalized MOFs with greater photocatalytic performance for the degradation of organic pollutants in the environment.

Crystallographic Visualization of Postsynthetic Nickel Clusters into Metal-Organic Framework.

Postsynthetic metalation (PSM) has been employed as a robust method for the postsynthetic modification of metal-organic frameworks (MOFs). However, the lack of relevant information that can be obtained for the postsynthetically introduced metallic ions has hindered the development of PSM applications. Thanks to the advancement in single-crystal X-ray diffraction (SCXRD) technology, there have been a few recent examples in which successful postsynthetic introduction of single metal ions into MOFs occurred at the defined chelating sites. These works have provided useful explanations about the complicated host-guest chemistry involved in PSMs. On the other hand, there are only limited examples with crystallographic snapshots of the postsynthetic installation of metal clusters into the pores of MOFs using an ordinary SCXRD due to the loss of crystallinity of parent matrix during the PSM process. Herein, by the careful selection of starting materials and controlling the reaction conditions, we report the first crystallographic visualization of metal clusters inserted into Zr-based MOFs via PSM. The structural advantages of the parent Zr-MOF, which are inherited from the stable Zr6 cluster and triazole-containing dicarboxylate ligand, ensure both the preservation of high crystallinity and the presence of flexible coordination sites for PSM. Furthermore, PSM of metal clusters in a MOF pore space enhances stability of the final samples while also imparting the functionality of a successful catalyst toward ethylene dimerization reaction. The related construction ideas and structural information detailed in this work can help lay the foundation for further advancements using the postmodification of MOFs as well as open new doors for the utilization of SCXRD technology in the field of MOFs.

Synthetic Strategies and Structural Arrangements of Isoreticular Mixed-Component Metal-Organic Frameworks.

In recent years, the synthesis of mixed-metal and mixed-linker metal-organic frameworks with multiple metals and/or linker molecules combined in one framework has become a growing field of interest. These mixed-component or multivariate metal-organic framework materials provide the possibility to introduce multiple functionalities inside one framework. The interaction of guest molecules with different functionalities in the same material is a promising approach in the fields of gas storage, separation, catalysis and drug delivery. Furthermore, the combination of different components may lead to synergistic effects that cannot be achieved otherwise. These mixed-component approaches open up new pathways to an even larger range of possible customizations in the field of metal-organic frameworks.

Mechanical properties of metal-organic frameworks.

As the field of metal-organic frameworks (MOFs) continues to grow, the physical stability and mechanical properties of these porous materials has become a topic of great interest. While strategies for synthesizing MOFs with desirable chemical functionalities or pore sizes have been established over the past twenty years, design principles to modulate the response of MOFs to mechanical stress are still underdeveloped. The inherent porosity of these frameworks results in many interesting and sometimes unexpected phenomena upon exposure to elevated pressures and other physical stimuli. Beyond its fundamental importance, an understanding of mechanical properties (e.g. bulk modulus, shear modulus, Young's modulus, linear compressibility, and Poisson's ratio) plays an essential role in the post-synthetic processing of MOFs, which has implications in the successful transition of these materials from academic interest to industrial relevance. This perspective provides a concise overview of the efforts to understand the mechanical properties of MOFs through experimental and computational methods. Additionally, current limitations and possible future directions for the field are also discussed briefly.

What’s new?

I’m proud to announce that on Feb. 28, C&EN launched a new podcast, which is aptly called Stereo Chemistry. It will feature C&EN reporters as well as the chemists making the news. We invite you to enjoy it from your desktop, any kind of smart mobile device, or even your Amazon Alexa or other voice assistant. To make sure you don’t miss an episode, subscribe now on iTunes, Google Play, or TuneIn. You can also find episodes on cen.acs.org. Although moving forward Stereo Chemistry’s frequency will be monthly, we’re publishing some special bonus episodes to celebrate the launch. The first one was released the last day of February, and it highlights the work of many chemists working in the field of metal-organic frameworks who agreed to sit down with C&EN’s Matt Davenport to tell us why these materials are so hot right now. One such chemist is Omar Yaghi, who

Supercritical fluid processing for metal–organic frameworks, porous coordination polymers, and covalent organic frameworks

The synthesis and processing of porous materials is a particularly fertile area for supercritical fluid (SCF) technology. Well-designed metal–organic hybrid porous materials such as metal–organic frameworks (MOFs) and porous coordination polymers (PCPs), which are constructed from metal-containing nodes and organic linkers, have recently been recognized as an intriguing class of crystalline nanoporous materials with a wide variety of potential applications in areas including gas storage, compound separation, biomedicine, chemical sensing, and catalysis. Furthermore, covalent organic frameworks (COFs) constructed from light elements have been developed. Recent research in the rapidly expanding field of MOFs, PCPs and COFs has demonstrated that SCF technologies, such as drying, impregnation, and synthesis, are effective approaches for processing and improving MOFs, PCPs and COFs. This short review describes the processing of MOFs, PCPs and COFs using supercritical CO2 and its mixtures. Selected examples are presented, and current achievements and challenges are summarized.

Multifaceted Modularity: A Key for Stepwise Building of Hierarchical Complexity in Actinide Metal-Organic Frameworks.

Growing necessity for efficient nuclear waste management is a driving force for development of alternative architectures toward fundamental understanding of mechanisms involved in actinide (An) integration inside extended structures. In this manuscript, metal-organic frameworks (MOFs) were investigated as a model system for engineering radionuclide containing materials through utilization of unprecedented MOF modularity, which cannot be replicated in any other type of materials. Through the implementation of recent synthetic advances in the MOF field, hierarchical complexity of An-materials was built stepwise, which was only feasible due to preparation of the first examples of actinide-based frameworks with "unsaturated" metal nodes. The first successful attempts of solid-state metathesis and metal node extension in An-MOFs are reported, and the results of the former approach revealed drastic differences in chemical behavior of extended structures versus molecular species. Successful utilization of MOF modularity also allowed us to structurally characterize the first example of bimetallic An-An nodes. To the best of our knowledge, through combination of solid-state metathesis, guest incorporation, and capping linker installation, we were able to achieve the highest Th wt % in mono- and biactinide frameworks with minimal structural density. Overall, the combination of a multistep synthetic approach with homogeneous actinide distribution and moderate solvothermal conditions could make MOFs an exceptionally powerful tool to address fundamental questions responsible for chemical behavior of An-based extended structures and, therefore, shed light on possible optimization of nuclear waste administration.