Metal-organic framework (MOFs) materials are skeleton compounds with periodic network structures self-assembled by ligands and metal ions. Since most MOFs materials have regular pore structures and large specific surface areas, they have great application value in gas adsorption and separation, dye degradation, drug carriers and heterogeneous catalysis. As a newly emerging material, MOFs materials can select appropriate metal ions and their ligands to make the most suitable MOFs materials for different applications due to the variability of composition and structure. Because of this characteristic of MOFs, people's related research on it has emerged like a fountain. With the development of structure determination technology, various MOFs materials have been synthesized, and MOFs materials have become increasingly abundant, so there are many classification methods. According to the changes in the central metal ions, they can be divided into transition metal organic framework materials, rare earth metal organic framework materials, alkali metal organic framework materials, alkaline earth metal organic framework materials and mixed metal organic framework materials; according to the skeleton structure, they can be divided into one-dimensional chain, two-dimensional layered and three-dimensional framework organic framework materials. However, in the production process of MOFs materials, ligands play a greater role than metal ions, and different ligands correspond to MOFs products with different structures and functions.
Figure 1. MOF (metal-organic framework) hybrid preparation methods. (Joshua D. Sosa, et al.; 2018)
Therefore, we classify MOFs materials according to the types of organic ligands. MOFs materials can be roughly divided into three categories according to the types of organic ligands: 1. MOFs materials constructed with organic carboxylic acid ligands Organic carboxylic acid ligands can obtain MOFs materials with diverse structures due to their relatively good solubility, strong coordination ability, high thermal stability of the generated skeleton structure, and variable coordination modes of carboxyl groups. Common organic carboxylic acid ligands include 1,4-benzenedicarboxylic acid, 2,6,10-triphenyltricarboxylic acid, 1,3,5-benzenetricarboxylic acid, isophthalic acid and benzenetetracarboxylic acid. Among them, representative MOFs materials constructed with organic carboxylic acid ligands include IRMOF (Isoreticular MOF) series materials, MILs (Materialsof Institute Lavoisier) series materials, etc. 2. MOFs products constructed with nitrogen-containing heterocyclic ligands Since there are many types of nitrogen-containing heterocyclic ligands such as imidazoles, pyridines and their derivatives, which can generally combine with metal ions to form bonds that are not easy to break, this ligand is of great value in the design of MOFs materials. Common nitrogen-containing heterocyclic ligands include 4,4'-bipyridine, 2,2'-bipyridine, 1,10-phenanthroline, imidazole, 2-methylimidazole, etc. Among them, the most representative MOFs material constructed with nitrogen-containing heterocyclic ligands is ZIF (Zelitic Imidazolate framework). 3. MOFs materials constructed with nitrogen-containing and oxygen-containing mixed ligands This series of MOFs materials can be synthesized by reacting a single nitrogen-heterocyclic carboxylic acid ligand with a metal, such as pyridine carboxylic acid, pyrazine carboxylic acid, pyrazole carboxylic acid, etc. In nitrogen-heterocyclic carboxylic acid ligands, both the carboxyl group and the nitrogen atom can react with metal ions, thus showing the diversity of coordination. In addition, this series of MOFs materials can also be obtained by reacting nitrogen-containing ligands or carboxylic acid ligands with metal ions.
As a widely used organic ligand, multidentate cluster acid compounds have been increasingly used as connectors in the synthesis of metal-organic frameworks (MOPS), such as benzene derivatives containing multiple carboxylic acid groups. Triphenylamine tricarboxylate (H3TCA) is used as the main ligand to construct metal-organic frameworks not only because it has a large conjugated group that can effectively transfer the absorbed energy to the metal ions, but also because it contains three carboxylic acid groups, has a variety of coordination modes, and can obtain novel topological structures. In addition, the three carboxylic acid groups extend in different directions, and the coordination size is larger, making it easier to construct metal-organic frameworks with larger holes.
Alternate Names:
Triphenylene-2,6,10-tricarboxylic acid
2,6,10-Triphenylene tricarboxylic acid
2,6,10-Tri(carboxyphenyl)triphenylene
Triphenylene-2,6,10-tricarboxylate
2,6,10-Tris(carboxyphenyl)triphenylene
Tris(carboxyphenyl)triphenylene
References:
1. Joshua D. Sosa, et al.; Metal–Organic Framework Hybrid Materials and Their Applications. Crystals. 2018, 8(8):325.
2. Wu MX, Yang YW. Metal-Organic Framework (MOF)-Based Drug/Cargo Delivery and Cancer Therapy. Adv Mater. 2017, 29(23).
Metal-Organic Frameworks (MOFs) for Cancer Therapy
Materials (Basel).
Authors: Saeb MR, Rabiee N, Mozafari M, Verpoort F, Voskressensky LG, Luque R.
Abstract
MOFs exhibit inherent extraordinary features for diverse applications ranging from catalysis, storage, and optics to chemosensory and biomedical science and technology. Several procedures including solvothermal, hydrothermal, mechanochemical, electrochemical, and ultrasound techniques have been used to synthesize MOFs with tailored features. A continued attempt has also been directed towards functionalizing MOFs via "post-synthetic modification" mainly by changing linkers (by altering the type, length, functionality, and charge of the linkers) or node components within the MOF framework. Additionally, efforts are aimed towards manipulating the size and morphology of crystallite domains in the MOFs, which are aimed at enlarging their applications window. Today's knowledge of artificial intelligence and machine learning has opened new pathways to elaborate multiple nanoporous complex MOFs and nano-MOFs (NMOFs) for advanced theranostic, clinical, imaging, and diagnostic purposes. Successful accumulation of a photosensitizer in cancerous cells was a significant step in cancer therapy. The application of MOFs as advanced materials and systems for cancer therapy is the main scope beyond this perspective. Some challenging aspects and promising features in MOF-based cancer diagnosis and cancer therapy have also been discussed.
Substituted 1,3,5-Triazine Hexacarboxylates as Potential Linkers for MOFs
Molecules.
Authors: Klinkebiel A, Beyer O, Lüning U.
Abstract
Hexacarboxylates are promising linkers for MOFs such as NU-109 or NU-110, which possess large values for surfaces and pore volumina. Starting from 2,4,6-tris(bromoaryl)-1,3,5-triazines, palladium-catalyzed cross coupling reactions (Suzuki-Miyaura, Sonogashira-Hagihara) form elongated hexacarboxylate linkers. Eight new 2,4,6-tris(biphenyl) and 2,4,6-tris(phenylethynylphenyl) 1,3,5-triazines have been prepared in quantities ranging from 40 mg to 1.1 g. In five cases, one of the arms of the linker carries an additional functionality (NO2 or OMe).
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