Grand Challenges and Future Opportunities for Metal–Organic Frameworks

Abstract

Metal–organic frameworks (MOFs) allow compositional and structural diversity beyond conventional solid-state materials. Continued interest in the field is justified by potential applications of exceptional breadth, ranging from gas storage and separation, which takes advantage of the inherent pores and their volume, to electronic applications, which requires precise control of electronic structure. In this Outlook we present some of the pertinent challenges that MOFs face in their conventional implementations, as well as opportunities in less traditional areas. Here the aim is to discuss select design concepts and future research goals that emphasize nuances relevant to this class of materials as a whole. Particular emphasis is placed on synthetic aspects, as they influence the potential for MOFs in gas separation, electrical conductivity, and catalytic applications.

Synthesis and Electric Properties of a Two‐Dimensional Metal‐Organic Framework Based on Phthalocyanine

“…Metal‐organic frameworks (MOFs) are crystalline porous materials composed of metal ions and multidentate organic ligands. Many kinds of coordination frameworks and porous structures have been prepared with a variety of metal‐ligand combinations, which showed diverse applications including storage, separation, sensing, catalysts, and ion transport . In particular, two‐dimensional (2D) MOFs with good electrical conductivity have attracted much attention, where multidentate ligands having bidentate moieties such as o ‐semiquinone and dithiolene are bridged with metal ions in a square‐planar geometry .…”

Anisotropic Thermal and Guest‐Induced Responses of an Ultramicroporous Framework with Rigid Linkers

“…Microporous framework solids have shown promising performance in the realm of gas sorption, in which selective and efficient uptake is highly desirable for achieving a wide range of industrial gas separations . Metal–organic frameworks (MOFs) have attracted particular attention in this area due to the exceptional tunability of their pore shape, size, and chemistry, which can be used to improve separation performance by targeting differences in the physical (size, shape) or chemical (polarity, polarizability) characteristics of competing guests . Host–guest interactions in porous systems must be well understood for such tuning to be accomplished effectively, because the steric and chemical interactions of the guest molecules can significantly perturb the host framework structure and dynamics.…”

Switching in Metal–Organic Frameworks

“…This, along with the presence of various interactions, including hydrogen bonding, van der Waals interactions, π–π stacking, and metal coordination, have made MOFs promising functional compounds. In particular, the uniquely tunable structural properties of MOFs have seen potential applications proposed for them in areas as diverse as gas storage and separation, sensing, and catalysis …”

“…Compared to porous polymers, MOF crystallinity, periodicity, and permanent porosity makes characterization by X‐ray diffraction techniques more amenable. Finally, while covalent organic frameworks (COFs) are often lighter and have larger pore structures that are more stable than in MOF counterparts, MOFs boast more diverse synthetic conditions and the additional tunability provided by the metal structural building unit (SBU) can permit facile incorporation of photochemical properties, catalytic centers, and gas sorption sites …”