Introduction
Nitro COFs linkers refer to compounds containing nitro functional groups that can be used in the construction of COFs. Nitro compounds are a very important class of nitrogen derivatives and valuable building blocks because of their convenient transformation into a wide variety of important compounds such as amines, carboxylic acids, aldehydes, and nitriles. However, as a COFs linker, its status is not so prominent, and only a few COFs have been built from it. But that doesn‘t mean that nitro COFs linkers aren’t important or deserve to be taken seriously. In fact, nitro-based linkers are gradually being used to develop novel COFs structures with new linkages, which greatly increases the structural diversity of COFs. Here's the thing to know is that the development of COFs mainly focuses on the development of new structures and new applications since the first COF was reported in 2005. Therefore, it is believed that nitro COFs linkers will play an increasingly important role in the field of COFs.
Applications
Nitro-based linkers are mainly used to synthesize viologen-linked COFs. In addition, there are also a small number of reports demonstrating that nitro-based linkers can be used to build other COFs. The details are as follows.
- Synthesis of viologen-linked COFs: By reaction of 2,4-dinitro-chlorobenzene with a primary amine (also known as Zincke reaction) can be used in synthesis of viologen-linked COFs. The first viologen-linked COF (GOGF) was reported in 2017 and synthesized via the Zincke reaction between 1,1' -bis(2,4-dinitrophenyl)-[4,4′-bipyridine]-1,1'-diium dichloride (BDB) and 1,3,5-tris(4-aminophenyl)benzene (TAPB) under both solvothermal and microwave conditions. Later, two porphyrin-based viologen-linked COFs, Zn-PV-COF and Red-PV-COF, were synthesized under microwave conditions by using 1,1'-bis(2,4-dinitrophenyl)-[4,4'-bipyridine]-1,1'-diium dichloride and 5,10,15,20-Tetrakis(4-aminophenyl)porphyrin [1]. Viologen-based linkages contain charged 4,40-bipyridinium moieties. These linkages exhibit three redox states, which can be accessed electrochemically and also vary from hydrophilic to hydrophobic in nature. Due to this feature, these COFs materials are promising candidates to adsorb multiple dyes with different polarities [2].
Fig. 1. Synthetic route to Zn-PV-COF and Red-PV-COF through the Zincke reaction by nitro-based linker.
- Synthesis of phthalocyanine-based COFs: By coupling reaction with phthalocyanine containing nitro and a primary amine can be used to synthesize phthalocyanine-based COFs which may be used in the field of battery material. For example, three phthalocyanine-based COF materials (NA-NiPc, PPDA-NiPc and DAB-NiPc) were prepared by the reaction of 4-nitro-nickel phthalocyanine (NiPc(N02)4) with 4-amino-nickel phthalocyanine (NiPc(NH2)4), p-phenylenediamine, benzidine, respectively. The three COFs are typical two-dimensional layered quadrilateral AA stacked structures. And the average pore size of NA-NiPc, PPDA-NiPc and DAB-NiPc is ~1.5 nm, ~2.2 nm, ~2.8 nm, respectively, through the simulation calculation, and the layer spacing is about 0.33 nm. The two-dimensional arrangement of the uniform layer stacking structure greatly facilitates the transport of carriers and the layered storage of lithium/sodium ions, and makes these COFs well used as electrode materials for lithium/sodium ion batteries.
Fig. 2. Synthetic route of NA-NiPc, PPDA-NiPc and DAB-NiPc through the coupling reaction by nitro-based linker.
Alfa Chemistry offers a series of nitro-based COFs linkers, which have been widely used to construct viologen-based COFs and many other COFs. You can click on our product list for a detailed view. At the same time, we also offer product customization according to customer's detailed requirements. If you are interested in our products or have any questions or needs, please feel free to contact us. We will be happy to provide you with support and services.
References:
- Skorjanc T, Shetty D, Gándara F, et al. Remarkably efficient removal of toxic bromate from drinking water with a porphyrin–viologen covalent organic framework[J]. Chemical Science, 2020, 11(3): 845-850.
- Bhambri H., et al. Nitrogen-rich covalent organic frameworks: a promising class of sensory materials[J]. Materials Advances, 2022, 3(1): 19-124.
