New Class Of Crystalline Materials Research Articles

3D Covalent Organic Frameworks from Design, Synthesis to Applications in Optoelectronics.

Covalent organic frameworks (COFs), a new class of crystalline materials connected by covalent bonds, have been developed rapidly in the past decades. However, the research on COFs is mainly focused on two-dimensional (2D) COFs, and the research on three-dimensional (3D) COFs is still in the initial stage. In 2D COFs, the covalent bonds exist only in the 2D flakes and can form 1D channels, which hinder the charge transport to some extent. In contrast, 3D COFs have a more complex pore structure and thus exhibit higher specific surface area and richer active sites, which greatly enhance the 3D charge carrier transport. Therefore, compared to 2D COFs, 3D COFs have stronger applicability in energy storage and conversion, sensing, and optoelectronics. In this review, it is first introduced the design principles for 3D COFs, and in particular summarize the development of conjugated building blocks in 3D COFs, with a special focus on their application in optoelectronics. Subsequently, the preparation of 3D COF powders and thin films and methods to improve the stability and functionalization of 3D COFs are summarized. Moreover, the applications of 3D COFs in electronics are outlined. Finally, conclusions and future research directions for 3D COFs are presented.

Post-synthetic Covalent Organic Framework to Improve the Performance of Solid-State Li+ Electrolytes.

As a new class of crystalline materials, covalent organic frameworks (COFs) have long-range ordered channels and feasibility to functionalize. The well-arranged pores make it possible to contain and transport ions. Here, we designed a novel functionalized anionic COF-SS-Li by a post-synthetic method utilizing the Povarov reaction of BDTA-COF, anchoring -SO3- groups to the COF backbone and converting the imine linkage to a more stable quinoline unit. The grafted -SO3- groups and directional channels can promote the lithium-ion transport through a hopping mechanism. As a solid-state lithium-ion electrolyte, COF-SS-Li exhibits the conductivities of 9.63 × 10-5 S cm-1 at 20 °C and 1.28 × 10-4 S cm-1 at 40 °C and a wide electrochemical window of 4.85 V. The assembled Li|COF-SS-Li|Li symmetric cell can cycle stably for 600 h at 0.1 mA cm-2. Also, the Li|COF-SS-Li|LiFePO4 cell delivers an initial capacity of 117 mAh g-1 at 0.1 A g-1 and retains a capacity rate of 56.7% after 500 cycles. The research enriches the solid-state electrolytes for lithium-ion batteries.

Metal-Organic Frameworks in Modern Physics: Highlights and Perspectives.

Owing to the synergistic combination of a hybrid organic–inorganic nature and a chemically active porous structure, metal–organic frameworks have emerged as a new class of crystalline materials. The current trend in the chemical industry is to utilize such crystals as flexible hosting elements for applications as diverse as gas and energy storage, filtration, catalysis, and sensing. From the physical point of view, metal–organic frameworks are considered molecular crystals with hierarchical structures providing the structure‐related physical properties crucial for future applications of energy transfer, data processing and storage, high‐energy physics, and light manipulation. Here, the perspectives of metal–organic frameworks as a new family of functional materials in modern physics are discussed: from porous metals and superconductors, topological insulators, and classical and quantum memory elements, to optical superstructures, materials for particle physics, and even molecular scale mechanical metamaterials. Based on complementary properties of crystallinity, softness, organic–inorganic nature, and complex hierarchy, a description of how such artificial materials have extended their impact on applied physics to become the mainstream in material science is offered.

Metalo Hydrogen-Bonded Organic Frameworks (MHOFs) as New Class of Crystalline Materials for Protonic Conduction.

Recently, proton conduction has been a thread of high potential owing to its wide applications in fuel-cell technology. In the search for a new class of crystalline materials for protonic conductors, three metalo hydrogen-bonded organic frameworks (MHOFs) based on [Ni(Imdz)6 ]2+ and arene disulfonates (MHOF1 and MHOF2) or dicarboxylate (MHOF3) have been reported (Imdz=imidazole). The presence of an ionic backbone with charge-assisted H-bonds, coupled with amphiprotic imidazoles made these MHOFs protonic conductors, exhibiting conduction values of 0.75×10-3 , 3.5×10-4 and 0.97×10-3 S cm-1 , respectively, at 80 °C and 98 % relative humidity, which are comparable to other crystalline metal-organic framework, coordination polymer, polyoxometalate, covalent organic framework, and hydrogen-bonded organic framework materials. This report initiates the usage of MHOF materials as a new class of solid-state proton conductors.

Supramolecular Metal-Coordination Polymers, Nets, and Frameworks from Synthetic Coiled-Coil Peptides.

Metal coordination and peptide-directed self-assembly are two proven methods for creating defined supramolecular architectures. Here, we report a new class of crystalline materials based on coiled-coil peptides bearing unnatural metal-chelating terpyridine moieties. High-resolution structural characterization of lattices formed in the presence of Cu2+ reveals a general assembly mechanism. Subtle sequence variation in the modular synthetic ligand dictates assembly morphology.

Unusual Regenerable Porous Metal-Organic Framework Based on a New Triple Helical Molecular Necklace for Separating Organosulfur Compounds

Desulfurization of fuels is receiving more and more attention all over the world due to the increase of stringent environmental regulations and fuel specifications. The metal-organic framework (MOF) is a new class of crystalline materials, and high porosity, one of the most important properties of MOFs, plays a central role in the functional properties. However, the investigation of MOFs, being employed as sorbents for adsorptive desulfurization, is still scarce. In this regard, we have constructed a new 3D porous compound 1 by using rigidly designed carboxylate ligands, which, for the first time, exhibit an unusual triple molecular necklace-like helix. The N(2) sorption isotherms of 1 show that it has a large Brunauer-Emmett-Teller (BET) surface area and pore volume. With the stable pore structure and appropriate pore sizes, compound 1 has been used as a sorbent for adsorptive desulfurization. The results indicate that compound 1 shows an excellent adsorption property and, more importantly, displays excellent stability, repeatability, and regenerability. Thus, the design and synthesis of targeted MOFs with appropriate pore size and increased interactions between organosulfur compounds and ligands/metals from MOFs is crucial for adsorptive desulfurization, which might be an effective guide to find an efficient and green adsorbent for desulfurization.

Molecular Capsules in Modular Frameworks

In a rare example of crystal engineering through empirical design, the metric and symmetry complementarity between the four sulfonates appended to the upper rim of tetrasulfonated calix[4]arenes and the sulfonate nodes of the guanidinium-sulfonate hydrogen-bonded sheet permits the formation of single crystals comprising antiparallel interdigitated arrays of calixarene capsules embedded in discrete bilayers wherein each calixarene is suspended from a single guanidinium-sulfonate sheet through four sulfonate attachments. A hydrate of the parent compound tetraguanidinium calix[4]arenetetrasulfonate, in which water occupies the calixarene as well as positions in the hydrogen-bonded sheet, undergoes a single crystal-single crystal phase transition with loss of all water molecules, but with remarkable retention of crystallinity. These compounds suggest a path to a new class of crystalline materials with molecular capsules that can be tailored for selective guest inclusion for separations and regulation of solid-state properties through the encapsulation of functional guests.

POROUS CRYSTALLINE ORGANIC FRAMEWORKS

THE RECIPE is exceedingly simple: Add one or two organic building blocks to a solvent mixture, heat at 85 °G inside a sealed tube for several days, and—voila—you have created a new class of crystalline materials with remarkable properties. The new materials are three-dimensional covalent organic frameworks (COFs)— that is, porous networks constructed entirely of strong covalent bonds between light elements such as carbon, boron, and oxygen. They are stable to temnera- tures above 450 °G, and their surface areas (as high as 4,210 m2/g) are among the highest known for any materials. Most strikingly, these materials have extremely low densities. In fact, one member of this family, designated COF-108, boasts a density of just 0.17 g/cm3—the lowest-density crystal known. A diamond, by comparison, has a density of 3.5 g/cm3. We believe these porous materials are going to have a large impact on gas separation and storage technology, says Adrien ...

Hydrogen storage in metal–organic frameworks

Metal–organic frameworks (MOFs) are a new class of crystalline materials consisting of metal ions linked together by organic ligands, resulting in a highly microporous network. Owing to their high specific surface area and tailored pore dimensions, MOFs are ideal materials for hydrogen storage based on physisorption. This review gives an overview on the progress achieved in the field of hydrogen adsorption in MOFs. Advantages over other classes of porous materials as well as limits of MOFs are also discussed.