Covalent triazine structure and method for producing the same

Abstract

To provide a production method capable of synthesizing a covalent triazine structure in a milder condition than a conventional one and in mass production in view of the fact that conventionally, synthesis of a covalent triazine structure is performed in a closed state at a high temperature, and mass production is difficult and a productivity is low.SOLUTION: A production method of a covalent triazine structure includes subjecting a dicyano-aryl compound and / or a tricyano-aryl compound to a liquid phase reaction without using a metallic compound under normal pressure. A solvent and / or a catalyst is used for the liquid phase reaction so that a reaction temperature can be in a range of 100-300°C.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a covalent triazine structure and a method for producing the same. More specifically, the present invention relates to a covalent triazine structure that can be produced in a liquid phase and without using a metal, and a method for producing the same.

Background Art

[0002] Carbon materials containing many nitrogen atoms (such as carbon alloys, g-C3N4, etc.) have been widely studied as catalyst supports, electrode catalysts, photocatalysts, etc. Among them, a covalent triazine structure (CTF), which is a type of covalent organic framework (COF), has attracted attention. Conventional CTF synthesis has been carried out by heating an aromatic compound having two or more cyanos together with a metal salt such as zinc chloride in an ampoule under sealed conditions (Patent Document 1, Non-Patent Document 1). In addition, reactions using zinc chloride in an organic solvent have been studied (Non-Patent Document 2).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Non-Patent Documents

[0004]

Non-Patent Document 1

Non-Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] Conventionally, CTF synthesis has been carried out under high-temperature, sealed conditions, making mass production difficult and resulting in low productivity. Furthermore, the use of metal components posed a problem, as residual metal components could become fatal impurities when the resulting CTF was used in various applications. In view of the above circumstances, the present invention aims to provide a manufacturing method for CTF that enables mass production under milder reaction conditions and without metals compared to conventional methods. [Means for solving the problem]

[0006] The inventors of this invention conducted various studies to achieve the above objectives and arrived at the present invention. In other words, the present invention provides a method for producing a covalent triazine structure (CTF) characterized by reacting a dicyanoaryl compound and / or a tricyanoaryl compound in a liquid phase under normal pressure without using a metal compound. [Effects of the Invention]

[0007] The present invention's method for producing CTF involves carrying out the reaction at atmospheric pressure and in a liquid phase without using metal compounds. This reduces constraints on the material and capacity of the reaction vessel, and its liquid state makes it easy to handle. Therefore, the present invention's method for producing CTF is well-suited to industrial production methods and enables mass production. [Brief explanation of the drawing]

[0008] [Figure 1] This is the Raman spectrum of the covalent triazine structure obtained in Example 1. [Figure 2] This is the XRD spectrum of the covalent triazine structure obtained in Example 1. [Figure 3] This is an SEM image of the covalent triazine structure obtained in Example 1. [Figure 4] This is the XPS survey scan spectrum of the covalent triazine structure obtained in Example 1. [Figure 5]These are the XPS·C1s and N1s vectors of the covalent triazine structure obtained in Example 1. [Modes for carrying out the invention]

[0009] The present invention will be described in detail below. Furthermore, combinations of two or more of the individual preferred embodiments of the present invention described below are also preferred embodiments of the present invention.

[0010] [Method for producing covalently bonded triazine structures (CTFs)] The present invention relates to a method for producing covalent triazine compounds, characterized by a liquid-phase reaction of a dicyanoaryl compound and / or a tricyanoaryl compound under atmospheric pressure without the use of a metal compound. Methods for carrying out a liquid-phase reaction under atmospheric pressure include raising the temperature of the dicyanoaryl compound or tricyanoaryl compound above its melting point and carrying out the reaction, or raising the temperature in the presence of a solvent and / or a catalyst and carrying out the reaction. Under atmospheric pressure means not only not actively pressurizing or depressurizing, but also not sealing the reaction vessel to prevent the contents from volatilizing.

[0011] The reaction temperature for the liquid-phase reaction of the present invention is preferably as high as possible from the viewpoint of promoting the reaction and dissolving in the solvent. Specifically, it is preferably 100°C to 300°C. More preferably 120°C or higher, and even more preferably 150°C or higher. As an upper limit for the reaction temperature, it is more preferably 280°C or lower, and even more preferably 250°C or lower. Furthermore, when the reaction is carried out in the presence of a solvent and / or a catalyst, it is preferably below the boiling point of the solvent and catalyst used.

[0012] As the solvent used in the present invention, a solvent having a boiling point of 120 °C or higher under normal pressure is preferable, more preferably 120 °C or higher, and even more preferably 150 °C or higher. Specifically, glyme solvents such as diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, dipropylene glycol dimethyl ether, aromatic solvents such as mesitylene, chlorobenzene, diphenyl ether, etc. may be mentioned.

[0013] The catalyst used in the present invention is not particularly limited as long as it promotes the cyclization of the cyano group to form a triazine ring, but preferably a liquid at normal temperature and pressure. Examples include strong acidic catalysts such as sulfuric acid, methanesulfonic acid, trifluoromethanesulfonic acid, and strong basic catalysts such as diazabicycloundecene (DBU) and diazabicyclononene (DBN). With such a liquid catalyst, the catalyst itself can serve both as a catalyst and as a solvent. Particularly, methanesulfonic acid and trifluoromethanesulfonic acid are more preferable. By reacting under such strong acid and strong base conditions, the reactivity can be enhanced, and the generated covalent triazine structure can be dissolved well, thereby maintaining the reaction system uniformly and promoting the formation of the covalent triazine structure.

[0014] In the production method of the present invention, a covalent triazine structure can be formed under conditions where water is present. However, in order to form a higher-quality covalent triazine structure, it is preferable to reduce the amount of water in the solvent and the catalyst. Specifically, the amount of water in the reaction solution is 5% or less, more preferably 3% or less, and most preferably 1% or less. It is also preferable to include a drying step for the solvent and the catalyst before the reaction step.

[0015] In the production method of the present invention, a covalent triazine structure can be formed under various atmospheric conditions. However, in order to form a higher-quality covalent triazine structure, production in an inert gas is desirable. Preferred atmospheres are an inert gas atmosphere such as nitrogen or argon, or a dry air atmosphere.

[0016] In the production method of the present invention, a covalently bonded triazine structure can be formed without using a metal salt as a reaction catalyst.

[0017] The dicyanoaryl compound or tricyanoaryl compound of the present invention may be any compound in which two or three cyano groups are substituted on an aromatic ring. Specifically, phthalonitrile, isophthalonitrile, terephthalonitrile; 1,4-dicyanonaphthalene, 2,3-dicyanonaphthalene, 1,8-dicyanonaphthalene; 2,3-dicyanopyridine, 3,4-dicyanopyridine, 2,4-dicyanopyridine; 2,5-dicyanofuran, 3,4-dicyanothiophene; 4,5-dicyanoimidazole; 1,3,5-tricyanobenzene; 2,4,6-tricyano-1,3,5-triazine, 2,4,6-tris(4-cyanophenyl)-1,3,5-triazine, etc. can be mentioned, and terephthalonitrile, 1,3,5-tricyanobenzene, 2,4,6-tricyano-1,3,5-triazine are preferable. Most preferably, it is 2,4,6-tricyano-1,3,5-triazine.

[0018] [Covalently bonded triazine structure] The CTF obtained by the production method of the present invention is a structure having a structure in which the cyano groups of a dicyanoaryl compound or a tricyanoaryl compound are condensed to continuously form a 1,3,5-triazine ring. It is a carbon material containing a large amount of nitrogen atoms. Also, its shape is a laminated structure (layered structure) and is flaky.

[0019] The confirmation of the formation of the covalently bonded triazine structure can be confirmed by Raman analysis by the presence of peaks around 1600 cm -1 and 1350 cm -1 附近のピークの存在により確認できる。

[0020] When the most preferred 2,4,6-tricyano-1,3,5-triazine is used, the elemental ratio of carbon to nitrogen (C / N), determined by elemental analysis, is 1. Specifically, a C / N ratio of 0.9-1.1 is preferred. Within this range, the covalent triazine structure can best exhibit its function. More preferably, the C / N ratio is 0.95-1.05, and most preferably 0.98-1.02. Furthermore, the elemental ratio of hydrogen to oxygen (H / O), determined by elemental analysis, is around 2. A ratio around 2 suggests that the hydrogen and oxygen originate from water, indicating that hydrogen and oxygen are not covalently bonded to the covalent triazine structure, but rather that water is adsorbed or added to it. Conversely, if this ratio deviates from 2, it suggests that hydrogen and oxygen are covalently bonded to the covalent triazine structure, which is far from the ideal structure of a covalent triazine structure. Specifically, an H / O ratio of 1.8-2.2 is preferred. Within this range, the covalent triazine structure can best exhibit its function. More preferably, the H / O ratio is 1.9-2.1, and most preferably 1.95-2.05.

[0021] When the most preferred 2,4,6-tricyano-1,3,5-triazine is used, the ideal structure is only the triazine ring structure, and therefore the C1s and N1s binding states obtained from XPS are only one state. In other words, the area ratio of the peaks {C1s (286.5-287.5 eV), N1s (398.4-399.2 eV)} derived from the triazine structure to all binding states is 100%. If this ratio deviates from 100%, it can be said that it is far from the ideal structure of the covalent triazine structure. Specifically, it is preferable that it be 80% or more. Within this range, the covalent triazine structure can best exhibit its function. More preferably it is 85% or more, and most preferably it is 90% or more.

[0022] It is preferable that the covalent triazine structure obtained by the manufacturing method of the present invention can be confirmed to have a layered structure by SEM or X-ray diffraction analysis. If the reaction proceeds ideally, the covalent triazine structure will take on a layered structure in which sheet-like covalent triazine structures are stacked on top of each other. Specifically, it is preferable that the layered structure can be confirmed by SEM observation, and that peaks originating from the layered structure can be confirmed by X-ray diffraction analysis. Particularly preferable is that the peak is at 25-30°.

[0023] The CTF of the present invention is preferably one in which halogens and transition metals are not detected by XPS survey scan. By not using metal salts as catalysts, contamination by metal ions is suppressed, and when used in electrodes or reaction catalysts, longer lifespan and suppression of side reactions can be expected.

[0024] The covalent triazine structure obtained by the manufacturing method of the present invention is expected to have applications as a catalyst support, sensor, semiconductor, electrode material, photocatalyst, and reaction catalyst. [Examples]

[0025] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, "parts" means "parts by mass" and "%" means "percent mass".

[0026] [Raman spectroscopy measurement] Raman spectroscopy was performed using the following equipment and conditions. Measurement device: Micro-Raman (JASCO NRS-3100) Measurement conditions: 532nm laser used, 20x objective lens, CCD acquisition time 1 second, 64 integrations (resolution = 4cm) -1 )

[0027] [X-ray diffraction measurement] XRD measurements were performed using a fully automated horizontal X-ray diffractometer (Rigaku Corporation, SMART LAB) under the following conditions. CuKα1 line: 0.15406nm Scanning range: 10°-90° X-ray output settings: 45kV-200mA Step size: 0.020° Scan speed: 0.5°min -1 -4°min -1

[0028] [XPS analysis] XPS measurements were performed using a photoelectron spectrometer (JPS-9000MX, manufactured by JEOL Ltd.). Since hydrogen was not detected, the total amount of elements other than hydrogen was calculated as 100%.

[0029] [SEM] SEM measurements were performed using a JEOL FE-SEM, JSM7600F, with an acceleration voltage of 1kV and in gentle beam mode.

[0030] [Example 1] Synthesis of CTF 250 mg of 2,4,6-tricyano-1,3,5-triazine (manufactured by Tokyo Chemical Industry Co., Ltd.) was placed in a 30 ml reactor, and 5 g of trifluoromethylsulfonic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) was added and dissolved. The reaction was carried out in an oil bath at 170°C for 7 hours under a nitrogen atmosphere with a water content of 1% or less. After the reaction, excess water was poured into the reaction mixture, and the precipitated solid was filtered. The obtained solid was washed with water and a 1% aqueous ammonia solution, and then vacuum-dried at room temperature to obtain 250 mg of a blackish-purple solid.

[0031] Raman analysis confirmed the formation of a covalent triazine structure. Furthermore, no metallic or halogen components were detected from the XPS analysis, and the bonding ratio derived from the triazine structure was 94.9% from C1s and 91.1% from N1s. SEM analysis revealed that the formation of covalent triazine structures leads to the creation of flaky and layered structures. X-ray diffraction results revealed a 28° peak originating from the layered structure. The elemental analysis results of the obtained solid are as follows: the elemental ratio of carbon to nitrogen (C / N) is 0.99, which is very close to the ideal ratio of 1. Also, the H / O ratio is 2.02, which is very close to the ideal ratio of 2. Elemental analysis (%): C:32.38, H:3.43, N:37.05, O:27.15.

[0032] [Example 2] Synthesis of CTF 250 mg of 2,4,6-tricyano-1,3,5-triazine (manufactured by Tokyo Chemical Industry Co., Ltd.) was added to a 30 ml reactor, and 20 g of tetraethylene glycol dimethyl ether (manufactured by Tokyo Chemical Industry Co., Ltd.) and 1 g of trifluoromethylsulfonic acid (manufactured by Tokyo Chemical Industry Co., Ltd.) were added and dissolved. The reaction was carried out in an oil bath at 170°C for 7 hours under a nitrogen atmosphere with a water content of 1% or less. After the reaction, excess water was added to the reaction mixture, and the precipitated solid was filtered. The obtained solid was washed with water and 1% aqueous ammonia solution, and then vacuum-dried at room temperature to obtain 190 mg of a blackish-purple solid. Raman analysis confirmed the formation of a covalent triazine structure. Furthermore, no metal or halogen components were detected by XPS analysis. Elemental analysis (%): C: 41.94, H: 47.87, N: 3.34, O: 6.86.

[0033] [Comparative Example] 250 mg of 2,4,6-tricyano-1,3,5-triazine (manufactured by Tokyo Chemical Industry Co., Ltd.) was placed in a 100 ml three-necked flask, and 20 g of tetraethylene glycol dimethyl ether (manufactured by Tokyo Chemical Industry Co., Ltd.) and 1 g of zinc chloride (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were added and dissolved. The reaction was carried out in an oil bath at 160°C under a nitrogen atmosphere for 7 hours. After the reaction, excess water was poured into the reaction mixture, and the precipitated solid was filtered. After washing the obtained solid with water and then with a 1% aqueous ammonia solution, the obtained solid dissolved. It was found that the reaction did not proceed well when zinc chloride was used, and a covalent triazine structure could not be obtained.

Claims

1. A method for producing a covalently bonded triazine structure, characterized by reacting 2,4,6-tricyano-1,3,5-triazine in a liquid phase under normal pressure, using trifluoromethanesulfonic acid as a catalyst, without using a metal compound.

2. The manufacturing method according to claim 1, characterized in that the reaction temperature of the liquid-phase reaction is 100°C or higher and 300°C or lower, and below the boiling point of the solvent and / or catalyst.

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