Metal-Organic Framework

The opportunity to generate functional solids with defned properties by deliberate design has not been materialized in traditional solid-state chemistry over many decades. The emergence of metal–organic frameworks (MOFs), permanently porous, crystalline solids with defned metrics, has allowed for studying design, synthesis, and properties, which then translated into new applications. Aggregates of metal ions stitched together by multidentate functional groups form such metal oxide clusters and represent the nodes of MOFs. These clusters, termed secondary building units (SBUs), are decorated with organic moieties that provide directionality and can be linked through geometric principles into extended nets using organic molecules (spacers). This concept of reticular chemistry has aforded permanently porous MOFs, and has resulted in over 20,000 structures over the past 20 years. However, there are still only a limited number of symmetric, discrete SBUs commonly used to design and synthesize MOFs. We herein introduce the most important SBUs that have emerged over time together with prototypal MOF structures and their fundamental applications. Both the discovery and the scientifc impact will be highlighted alongside advantages and/or drawbacks. In addition, an outlook will be given on how the combination of multiple SBUs can lead to heterogeneous but ordered materials with higher complexity and functionality.

Given the unique properties of metal–organic frameworks (MOFs) including adjustable porosity, high surface area, and easy modifcation, they have attracted great attention as excellent solid supports for the incorporation of biomolecules. The formed biomolecules–MOFs composites show promising prospects in various felds such as biocatalysis, drug delivery, and biosensing. This review focuses on the stateof-the-art of biomolecules-incorporation using MOFs. Moreover, the relationship between properties of MOFs and biomolecules-incorporation is also discussed and highlighted. We hope this work will inspire the innovation in this emerging feld for highly efcient synthesis of biomolecules–MOFs composites with various properties and advanced applications.

Interpenetration in metal–organic frameworks (MOFs) can have signifcant impacts on the structure, porous nature, and functional applications of MOFs. Considered to be disadvantageous in the initial phases leading to a decrease in surface area, interpenetration has proved to be highly useful for modulation of pore size and selective separation of gases. The importance of interpenetration has been realized over the last decade, and numerous approaches to graft interpenetration and utilize it for improved functions and applications have been achieved. Several factors such astemperature, solvent system, time duration and steric aspects of the ligands have been utilized to regulate the degree of interpenetration (DOI). In this review, we summarize recent advances in regulating the DOI in MOFs and its impact on the resulting properties.

Over the past two decades, metal–organic frameworks (MOFs) with fexible structures or dynamic behavior have shown great potential as functional materials in many felds. This paper presents a review of these dynamic and functional MOFs, which can undergo controllable and reversible transformation, with regard to their application as smart switches. Trigger conditions, which include physical/chemical stimuli (e.g., guest molecules, light, temperature, pressure), are also discussed. Research methods for investigating the dynamic processes and mechanisms involving experimental characterization and computational modeling are briefy mentioned as well. The emphasis is on the aspects of the design and functionalization of dynamic MOFs. The pre-design of metal nodes, organic linkers, and topology, as well as post-modifcation of components, increases the possibility of obtaining functionalized dynamic materials. Recent advances with regard to potential applications for dynamic frameworks as smart switches for adsorption and sensing are also reviewed.

Petroleum is an essential source of energy for our daily life. However, crude oil contains various kinds of sulfur-containing compounds that will form sulfur oxides upon combustion and cause severe environmental problems. To reduce the environmental impact of petroleum energy, the desulfurization of fuels is necessary. Metal– organic frameworks (MOFs), an emerging class of porous materials, have shown great potential in a variety of applications. In this review, we summarize the use of MOFs in the desulfurization of fuels. The scope of this review includes MOFs and MOF-derived materials that have been applied in oxidative desulfurization and adsorptive desulfurization processes. We aim to provide an overview of the progress of MOFs in fuel desulfurization as well as shed light on the development of superior MOF-based materials in the feld of desulfurization.

Metal–organic frameworks (MOFs) are an emerging class of porous crystalline materials attracting attention for their vast array of topologies as well as potential applications in gas storage, heterogeneous catalysis, and molecular sensing. In most cases, organocarboxylates (or corresponding carboxylic acids) are the most common building block, achieving well-defined metal-carboxylate coordination motifs in MOF structures. However, organosulfonates (or corresponding sulfonic acids) have been less well studied in MOF chemistry, probably owing to the weak coordination tendency of the sulfonate oxygens toward metal centers. This review summarizes the research on organosulfonate-based porous crystalline MOFs in recent years. The construction of most porous organosulfonate MOFs relies on using either a second N-donor ligand or carboxylate–sulfonate bifunctional ligands. Despite occupying more confined porosity than the carboxylate counterpart, the permanent porosity in organosulfonate MOFs is often highly polar and hydrophilic. Thus, organosulfonate MOFs often exhibit improved proton/Li+ conductivity as well as CO2 affinity compared with their carboxylate-based counterparts. In addition, the application of organosulfonate MOFs in molecular sensing, molecular sieving, catalysis, and anion exchange are discussed in this review as well.

Classical molecular simulations can provide significant insights into the gas adsorption mechanisms and binding sites in various metal–organic frameworks (MOFs). These simulations involve assessing the interactions between the MOF and an adsorbate molecule by calculating the potential energy of the MOF–adsorbate system using a functional form that generally includes nonbonded interaction terms, such as the repulsion/dispersion and permanent electrostatic energies. Grand canonical Monte Carlo (GCMC) is the most widely used classical method that is carried out to simulate gas adsorption and separation in MOFs and identify the favorable adsorbate binding sites. In this review, we provide an overview of the GCMC methods that are normally utilized to perform these simulations. We also describe how a typical force field is developed for the MOF, which is required to compute the classical potential energy of the system. Furthermore, we highlight some of the common analysis techniques that have been used to determine the locations of the preferential binding sites in these materials. We also review some of the early classical molecular simulation studies that have contributed to our working understanding of the gas adsorption mechanisms in MOFs. Finally, we show that the implementation of classical polarization for simulations in MOFs can be necessary for the accurate modeling of an adsorbate in these materials, particularly those that contain open-metal sites. In general, molecular simulations can provide a great complement to experimental studies by helping to rationalize the favorable MOF–adsorbate interactions and the mechanism of gas adsorption.

Two-dimensional (2D) metal–organic frameworks (MOFs) belong to a subgroup of MOFs reminiscent of graphite and covalent organic frameworks (COFs). In the past decade, conductive 2D MOFs have received increasing attention due to their relatively high charge carrier mobility and low resistivity that originate from in-plane charge delocalization and extended π conjugation within the layers. This review comprises the current state-of-the-art of the representative progress in theoretical exploration and electronic applications of conductive 2D MOFs. Special emphasis is placed on the intrinsic relations between the structural factors and the electronic properties of conductive 2D MOFs. This review will provide guidance for researchers to design and synthesize conductive 2D MOFs for advanced applications.

Separation of hydrocarbon mixtures into single components is a very important industrial process because all represent very important energy resources/raw chemicals in the petrochemical industry. The well-established industrial separation technology highly relies on the energy-intensive cryogenic distillation processes. The discovery of new materials capable of separating hydrocarbon mixtures by adsorbent- based separation technologies has the potential to provide more energy-efficient industrial processes with remarkable energy savings. Porous metal–organic frameworks (MOFs), also known as porous coordination polymers, represent a new class of porous materials that offer tremendous promise for hydrocarbon separations because of their easy tunability, designability, and functionality. A number of MOFs have been designed and synthesized to show excellent separation performance on various hydrocarbon separations. Here, we summarize and highlight some recent significant advances in the development of microporous MOFs for hydrocarbon separation applications.

Metal–organic frameworks (MOFs) have gathered tremendous interest among researchers for their potential applications such as in storage and separation. While some progress has been made towards shaping of MOFs to realize industrial applications, the mechanical properties of MOFs remain more or less unexplored. Over the last decade, this area has witnessed a steady growth in terms of understanding the mechanical stability of MOFs and its consequence on their performance. In this review, the mechanical properties of the reported macroscopic shaped MOF structures (mainly granules, pellets, tablets, monoliths, and gels) are discussed. Conclusions are then drawn to determine which shapes and shaping techniques promise to meet industrial requirements on the basis of mechanical stability. Finally, future research directions are proposed to improve our understanding, and possibly enhance stability, by correlating the properties from microscopic single-crystalline level to the industrially relevant macroscopic polycrystalline scale.

The dramatic increase in atmospheric carbon dioxide ( CO2) concentrations has attracted human attention and many strategies about converting CO2 into high-value chemicals have been put forward. Metal–organic frameworks (MOFs), as a class of versatile materials, have been widely used in CO2 capture and chemical conversion, due to their unique porosity, multiple active centers and good stability and recyclability. Herein, we focused on the processes of chemical conversion of CO2 by MOFs-based catalysts, including the coupling reactions of epoxides, aziridines or alkyne molecules, CO2 hydrogenation, and other CO2 conversion reactions. The synthesized methods and high catalytic activity of MOFs-based materials were also analyzed systematically. Finally, a brief perspective on feasible strategies is presented to improve the catalytic activity of novel MOFs-based materials and explore the new CO2 conversion reactions.