Covalent organic framework material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of crystalline porous materials, in particular to a covalent organic framework material and a preparation method and application thereof.The preparation method includes the steps that a tridentate organic ligand monomer, a bidentate organic ligand monomer and a solid acid catalyst are evenly mixed to obtain a mixture, the rotating speed of a double-screw extruder is set to be 5-35 r / min, the temperature is set to be 80-140 DEG C, and the mixture is extruded to obtain a covalent organic framework material; and adding the mixture into a double-screw extruder, heating, kneading, mixing, washing and drying to obtain the COF material. Shear force and heat are provided through a double-screw extruder, a molten reaction monomer is used as a reaction medium, a toxic solvent is not needed, the preparation method is simple, rapid, green and environmentally friendly, the obtained COFs material is high in crystallinity, the COF material is expected to be further processed and formed through a specific extrusion head, continuous large-scale production is achieved, and the method is suitable for industrial production. And the COFs material synthesized by the method disclosed by the invention has good flame retardant property.

Description

Technical Field

[0001] The present invention relates to the technical field of crystalline porous materials, and particularly relates to a covalent organic framework material, a preparation method thereof and an application thereof. Background Art

[0002] Covalent organic frameworks (COFs) are a class of crystalline and periodic porous materials composed of organic monomers connected by reversible covalent bonds. According to different linking units, COF materials can be divided into boron-containing COFs, imine-based COFs, triazine-based COFs, etc. Triazine-based COFs are COF materials containing triazine rings. Such materials contain abundant nitrogen elements, have characteristics such as large specific surface area, high porosity, and stable chemical properties, and have extensive applications in the fields of catalysis, energy storage, flame retardancy, gas storage and separation, etc. However, most reported triazine-based COFs are obtained by cyanide polycondensation, and their crystallinity is low or amorphous, which greatly affects their performance. At present, some scholars use Schiff base condensation reactions to directly couple triazine derivatives to other monomers to form COFs connected by imine bonds with triazine as the core, and their crystallinity is significantly improved. The solvothermal method is a classic method for synthesizing COFs by Schiff base reactions. This method usually requires the use of special reaction devices (such as sealed tubes or pressurized reactors) and harsh reaction conditions (organic solvents, inert gases, high temperatures, long reaction times). Therefore, developing a method for green and efficient preparation of triazine-based COFs by Schiff base reactions is an urgent problem to be solved at present.

[0003] At present, a large number of scholars have explored the rapid and green synthesis of COFs by Schiff base reactions, mainly including exploring new energy heating methods and new reaction media. The traditional solvothermal method requires a long reaction time and continuous high-energy input to drive the reaction equilibrium to obtain thermodynamically stable crystalline products. Some scholars have assisted in the synthesis of COFs by new energy sources such as microwave, sonochemistry, photochemistry, electron beam irradiation, and plasma, shortening the reaction time, simplifying the experimental operation, and providing a certain possibility for preparing COFs with new morphologies. However, it has high requirements for instrument equipment and poor universality.

[0004] The preparation of COFs using new reaction media mainly includes water-mediated synthesis, ionic liquid-mediated synthesis, and low eutectic solvent-mediated synthesis. Water is the most abundant and environmentally friendly solvent in nature, and it is of great significance to use it as a reaction medium for the preparation of COFs. However, most COFs monomers contain benzene rings, which have poor solubility in water, which is not conducive to the preparation of COFs. Therefore, the universality of water as a reaction medium for the preparation of COFs remains to be studied. The ionic liquid and low eutectic solvent methods are simple to operate and environmentally friendly, but the high viscosity may limit the reaction, the synthesis time is long, and it is difficult to obtain COFs with regular morphology. The solvent-free synthesis method can reduce the dependence on organic solvents to a certain extent, and the preparation method is simple, fast, and environmentally friendly. However, the current solvent-free synthesis method has the following shortcomings: (1) The synthesis time is long, which makes it difficult to produce continuously on a large scale; (2) There is currently little research on the synthesis of triazine COFs materials. Summary of the invention

[0005] In view of this, the purpose of the present invention is to provide a covalent organic framework material and a preparation method and application thereof, so as to at least solve the problems existing in the prior art of reliance on organic solvents, long synthesis time, and difficulty in continuous large-scale production.

[0006] The present invention solves the above technical problems by the following technical means:

[0007] A first aspect of an embodiment of the present invention provides a method for preparing a covalent organic framework material, comprising the following steps:

[0008] The tridentate organic ligand monomer, the bidentate organic ligand monomer and the solid acid catalyst are uniformly mixed to obtain a mixture, the speed of the twin-screw extruder is set to 5-35r / min, the temperature is set to 80-140°C, the mixture is added to the twin-screw extruder, heated, kneaded and mixed, washed and dried to obtain a COF material.

[0009] In combination with the first aspect, in some embodiments, the molar ratio of the tridentate organic ligand monomer, the bidentate organic ligand monomer, and the solid acid catalyst is 2:(1.5-3):(12-20).

[0010] In combination with the first aspect, in some embodiments, the tridentate organic ligand is melamine or 4,4',4"-(1,3,5-triazine-2,4,6-triyl)triphenylamine.

[0011] In combination with the first aspect, in some embodiments, the bidentate organic ligand monomer is selected from one of terephthalaldehyde, 1,4-dihydroxyterephthalaldehyde, and 1,4-dichloroterephthalaldehyde.

[0012] In combination with the first aspect, in some embodiments, the solid acid catalyst is benzoic acid or p-toluenesulfonic acid.

[0013] In combination with the first aspect, in some embodiments, the washing is carried out by thoroughly washing with at least two of acetone, dichloromethane and tetrahydrofuran for use in washing.

[0014] In combination with the first aspect, in some embodiments, the drying conditions are drying at 60 - 75 °C for 10 - 12 h.

[0015] The second aspect of the embodiments of the present invention provides a covalent organic framework material prepared by the preparation method described in the above first aspect.

[0016] The third aspect of the embodiments of the present invention provides the application of the covalent organic framework material described in the above second aspect in flame retardant materials.

[0017] The present invention provides shear force and heat through a twin-screw extruder, uses molten reactive monomers as a reaction medium, does not require the use of toxic solvents, has a simple, rapid, green and environmentally friendly preparation method, and the obtained COFs material has strong crystallinity. The present invention is expected to further process and form the COF material through a specific extrusion head to achieve continuous large-scale production, and the COFs material synthesized by the present invention has good flame retardant performance. Description of the Drawings

[0018] Figure 1 is a schematic diagram of the production process of the preparation method of the covalent organic framework material of the present invention;

[0019] Figure 2 is the X-ray diffraction pattern of the COF-TATP material prepared in Example 1;

[0020] Figure 3 is the infrared spectrum of the COF-TATP material prepared in Example 1;

[0021] Figure 4 is the structural formula of the COF-TATP material prepared in Example 1;

[0022] Figure 5 is the X-ray diffraction pattern of the COF-TATP-OH material prepared in Example 2;

[0023] Figure 6 is the infrared spectrum of the COF-TATP-OH material prepared in Example 2;

[0024] Figure 7 is the structural formula of the COF-TATP-OH material prepared in Example 2;

[0025] Figure 8 is the X-ray diffraction pattern of the COF-SNW-1 material prepared in Example 3;

[0026] Figure 9 is the infrared spectrum of the COF-SNW-1 material prepared in Example 3;

[0027] Figure 10 is the structural formula of the COF-SNW-1 material prepared in Example 3;

[0028] Figure 11 is the heat release rate graph of the flame retardant materials prepared in Examples 6-8;

[0029] Figure 12 is the total heat release graph of the flame retardant materials prepared in Examples 6-8;

[0030] Figure 13 is the heat release rate graph of the flame retardant material prepared in Example 9;

[0031] Figure 14 is the total heat release graph of the flame retardant material prepared in Example 9. Detailed implementation manners

[0032] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the following will clearly and completely describe the technical solutions in the embodiments of this application with reference to the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are some, but not all, of the embodiments of this application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in this application without creative efforts shall fall within the scope of protection of this application.

[0033] In the embodiments of this application, words such as "exemplary" or "for example" are used to indicate examples, illustrations, or explanations. Any embodiment or design solution described as "exemplary" or "for example" in the embodiments of this application should not be construed as being more preferred or having more advantages than other embodiments or design solutions. Rather, the use of words such as "exemplary" or "for example" is intended to present relevant concepts in a specific manner.

[0034] Aiming at the problems of the current solvent-free method for preparing COFs, such as long synthesis time, difficulty in continuous large-scale production, and few studies on the preparation of triazine-based COFs materials, the present invention realizes a method for solvent-free and continuous large-scale preparation of triazine-based covalent organic framework materials. Please refer to Figure 1 , by providing shear force and heat through a twin-screw extruder, using molten reaction monomers as the reaction medium, without the use of toxic solvents, the preparation method is simple, fast, green and environmentally friendly. The obtained COFs materials have strong crystallinity, and it is expected to further process and form the COFs materials through a specific extrusion head to achieve continuous large-scale production; moreover, the COFs materials synthesized by the present invention have good flame retardant properties.

[0035] A preparation method of a covalent organic framework material of the present invention comprises the following steps:

[0036] Mix a tridentate organic ligand monomer, a bidentate organic ligand monomer, and a solid acid catalyst evenly to obtain a mixture. Set the rotation speed of the twin-screw extruder to 5 - 35 r / min and the temperature to 80 - 140 °C. Add the mixture into the twin-screw extruder for heating, kneading, mixing, washing, and drying to obtain the COF material.

[0037] Among them, the molar ratio of the tridentate organic ligand monomer, the bidentate organic ligand monomer, and the solid acid catalyst is 2:(1.5 - 3):(12 - 20); the tridentate organic ligand is melamine or 4,4',4''-(1,3,5-triazine-2,4,6-triyl)triphenylamine; the bidentate organic ligand monomer is selected from one of terephthalaldehyde, 1,4-dihydroxyterephthalaldehyde, and 1,4-dichloroterephthalaldehyde; the solid acid catalyst is benzoic acid or p-toluenesulfonic acid; washing is carried out with at least two of acetone, dichloromethane, and tetrahydrofuran; the drying condition is drying at 60 - 75 °C for 10 - 12 h.

[0038] To better understand the above technical solution, the above technical solution will be described in detail below in conjunction with the specification drawings and specific implementation manners.

[0039] Example 1

[0040] The preparation method of the covalent organic framework material in this example is as follows:

[0041] Weigh 2 mmol (0.7 g) of 4,4',4''-(1,3,5-triazine-2,4,6-triyl)triphenylamine and 40 mmol (4.8 g) of benzoic acid and put them into a mortar for mixing and grinding for 3 min. Then add 3 mmol (0.46 g) of terephthalaldehyde and 0.6 ml of deionized water and further grind and mix for 2 min. Add the mixture into the twin-screw extruder. The seven-section heating temperature of the twin-screw extruder is set to 70 °C, 115 °C, 115 °C, 115 °C, 115 °C, 115 °C, and 70 °C respectively, and the rotation speed is 35 r / min. The obtained extruded product is baked at 170 °C for 3 minutes, washed thoroughly with absolute ethanol and tetrahydrofuran, and dried in a 60 °C vacuum drying oven for 12 hours to obtain the COFs material, denoted as COF-TATP material.

[0042] Example 2

[0043] The preparation method of the covalent organic framework material in this example is as follows:

[0044] Weigh 2 mmol (0.7 g) of 4,4',4”-(1,3,5-triazine-2,4,6-triyl)triphenylamine and 40 mmol (4.8 g) of benzoic acid, put them into a mortar and mix and grind for 3 min. Then add 3 mmol (0.5 g) of 1,4-dihydroxyterephthalaldehyde and further grind and mix for 2 min. Add the mixture into a twin-screw extruder. The seven-section heating temperatures of the twin-screw extruder are set at 60 °C, 120 °C, 120 °C, 120 °C, 120 °C, 120 °C, and 70 °C respectively, and the rotation speed is 15 r / min. The obtained extruded product is washed thoroughly with absolute ethanol and tetrahydrofuran, and dried in a vacuum drying oven at 60 °C for 12 hours to obtain a COFs material, denoted as COF-TATP-OH material.

[0045] Example 3

[0046] The preparation method of the covalent organic framework material in this example is as follows:

[0047] Mix terephthalaldehyde, melamine, and p-toluenesulfonic acid with a molar ratio of 1.5:1:12 and grind them for 3 min. Add them into a twin-screw extruder. The seven-section heating temperatures of the twin-screw extruder are set at 70 °C, 100 °C, 105 °C, 105 °C, 105 °C, 105 °C, and 70 °C respectively, and the rotation speed is 20 r / min. The obtained extruded product is washed thoroughly with acetone, dichloromethane, and tetrahydrofuran, and dried in a vacuum drying oven at 60 °C for 12 hours to obtain a COFs material, denoted as COF-SNW-1 material.

[0048] Example 4

[0049] The preparation method of the covalent organic framework material in this example is as follows:

[0050] Weigh 2 mmol (0.7 g) of 4,4',4”-(1,3,5-triazine-2,4,6-triyl)triphenylamine and 40 mmol (4.8 g) of benzoic acid, put them into a mortar and mix and grind for 3 min. Then add 3 mmol (0.5 g) of 1,4-dihydroxyterephthalaldehyde and further grind and mix for 2 min. Add the mixture into a twin-screw extruder. The seven-section heating temperatures of the twin-screw extruder are set at 80 °C, 120 °C, 140 °C, 140 °C, 140 °C, 120 °C, and 80 °C respectively, and the rotation speed is 25 r / min. The obtained extruded product is washed thoroughly with absolute ethanol and tetrahydrofuran, and dried in a vacuum drying oven at 75 °C for 10 hours to obtain a COFs material, denoted as COF-TATP-OH-1 material.

[0051] Example 5

[0052] The preparation method of the covalent organic framework material in this example is as follows:

[0053] p - phthalaldehyde, melamine, and p - toluenesulfonic acid with a molar ratio of 1.5:2:20 were mixed and ground for 3 min, then added into a twin - screw extruder. The seven - zone heating temperatures of the twin - screw extruder were set at 70 °C, 100 °C, 105 °C, 105 °C, 105 °C, 105 °C, and 70 °C respectively, and the rotation speed was 5 r / min. The obtained extrusion product was thoroughly washed with acetone, dichloromethane, and tetrahydrofuran, and then dried in a vacuum drying oven at 60 °C for 12 hours to obtain the COFs material, denoted as COF - SNW - 1 - 1 material.

[0054] Example 6

[0055] This example describes a flame - retardant composite material, which contains 1 wt% of the COF - TATP - OH material prepared in Example 2. The preparation method is as follows:

[0056] The COF - TATP - OH synthesized in Example 2 was added to epoxy resin at 1 wt%. The specific operation method was as follows: Weigh 50 g of epoxy resin, add 21.7 wt% of diaminodiphenylmethane, heat and stir in an oil bath at 60 °C for 1 hour, add the corresponding mass of COF - TATP - OH, stir for 20 minutes, then pre - cure the sample in an oven at 100 °C for 2 hours, and then post - cure in an oven at 150 °C for 2 hours to obtain the flame - retardant composite material, denoted as 1% COF(TPTA + TAPT)+EP.

[0057] Example 7

[0058] This example describes a flame - retardant composite material, which contains 3 wt% of the COF - TATP - OH material prepared in Example 2. The preparation method is as follows:

[0059] The COF - TATP - OH synthesized in Example 2 was added to epoxy resin at 3 wt%. The specific operation method was as follows: Weigh 50 g of epoxy resin, add 21.7 wt% of diaminodiphenylmethane, heat and stir in an oil bath at 60 °C for 1 hour, add the corresponding mass of COF - TATP - OH, stir for 20 minutes, then pre - cure the sample in an oven at 100 °C for 2 hours, and then post - cure in an oven at 150 °C for 2 hours to obtain the flame - retardant composite material, denoted as 3% COF(TPTA + TAPT)+EP.

[0060] Example 8

[0061] This example describes a flame - retardant composite material, which contains 5 wt% of the COF - TATP - OH material prepared in Example 2. The preparation method is as follows:

[0062] The COF-TATP-OH synthesized in Example 2 was added to epoxy resin at 5 wt%, and the specific operation method was as follows: Weigh 50 g of epoxy resin, add 21.7 wt% of diaminodiphenylmethane, heat and stir in an oil bath at 60 °C for 1 hour, add the corresponding mass of COF-TATP-OH, stir for 20 minutes, then pre-cure the sample in an oven at 100 °C for 2 hours, and then post-cure in an oven at 150 °C for 2 hours to obtain a flame-retardant composite material, denoted as 5% COF(TPTA+TAPT)+EP.

[0063] Example 9

[0064] This example also describes a flame-retardant composite material, which contains 3 wt% of the COF-SNW-1 material prepared in Example 3, and its preparation method is as follows:

[0065] The COF-SNW-1 prepared in Example 3 was added to polylactic acid (PLA) at 3 wt%, and the specific operation method was as follows: Weigh 50 g of polylactic acid and 1.5 g of COF-SNW-1, mix them evenly, add them to a twin-screw extruder, set the temperature of the twin-screw extruder to 80 °C, 160 °C, 170 °C, 170 °C, 170 °C, 160 °C, 80 °C, and set the rotation speed to 55 r / min. The obtained product is the 3 wt% COF-SNW-1 / polylactic acid composite material, denoted as 3% SNW-1+PLA.

[0066] Performance test:

[0067] (1) The covalent organic framework materials prepared in Examples 1-3 were respectively subjected to X-ray diffraction test and infrared spectroscopy test. By analyzing the X-ray diffraction pattern, information such as the phase, unit cell parameters, interplanar spacing, and grain size of the material can be obtained. By analyzing the position and intensity of the absorption peaks in the infrared spectrum, its chemical groups and the content of chemical groups can be determined.

[0068] The X-ray diffraction pattern of the COF-TATP material prepared in Example 1 is as Figure 2 shown, and the infrared spectrum is as Figure 3 shown. For its structural formula, please refer to Figure 4 .

[0069] The X-ray diffraction pattern of the COF-TATP-OH material prepared in Example 2 is as Figure 5 shown, and the infrared spectrum is as Figure 6 shown. For its structural formula, please refer to Figure 7 .

[0070] The X-ray diffraction pattern of the COF-SNW-1 material prepared in Example 3 is as Figure 8As shown, the infrared spectrogram is as Figure 9 shown. For the structural formula, please refer to Figure 10 .

[0071] (2) Cone calorimeter experiments were carried out on the flame retardant materials prepared in Examples 6 - 9. The cone calorimeter is the most ideal test instrument for characterizing the combustion performance of materials at present. Its test environment is close to the real combustion environment of fire materials, and the test data obtained can evaluate the combustion behavior of materials in a fire.

[0072] For the heat release rate of the flame retardant materials prepared in Examples 6 - 8, please refer to Figure 11 , and for the total heat release of the flame retardant materials prepared in Examples 6 - 8, please refer to Figure 12 .

[0073] For the heat release rate of the flame retardant material prepared in Example 9, please refer to Figure 13 , and for the total heat release of the flame retardant material prepared in Example 9, please refer to Figure 14 .

[0074] As Figure 2 shown, the positions of the peaks in the X-ray diffraction pattern of the synthesized COF-TATP material match the simulated data, indicating the successful synthesis of COF-TATP. From the infrared spectrogram of the synthesized COF-TATP ( Figure 3 ), it can be seen that compared with the two monomers, a C=N peak appears in the synthesized COF-TATP at 1568 cm -1 , the NH2 peak in the monomer TAPT disappears, and the C=O peak in the monomer terephthalaldehyde shifts, proving the successful synthesis of COF-TATP through imine condensation reaction.

[0075] As Figure 5 shown, the positions of the peaks in the X-ray diffraction pattern of the synthesized COF-TATP-OH material match the simulated data, indicating the successful synthesis of COF-TATP-OH. From the infrared spectrogram ( Figure 6 ), it can be seen that the absorption peak of the benzene ring skeleton vibration of COF-TATP-OH is at 1580 cm -1 , the stretching vibration absorption peak of the C=N double bond is at 1515 cm -1 , the stretching vibration absorption peak of C-N is at 1368 cm -1 , the stretching vibration absorption peak of C-O is at 1144 cm -1 , the in-plane bending vibration absorption peak of C-H is at 1012 cm -1 , and the absorption peak of the out-of-plane bending vibration of C-H is at 812 cm -1This is the out-of-plane bending vibration absorption peak of C-H, which proves the successful synthesis of COF-TATP-OH. The flame-retardant material prepared from the COF-TATP-OH material synthesized in Example 2 and epoxy resin has good flame-retardant properties. For example, Figure 11 and Figure 12 show that when 3 wt% of COF-TATP-OH is added, the heat release rate of epoxy resin decreases by 31.6%, and the total heat release decreases by 6.7%; when 5 wt% of COF-TATP-OH is added, the heat release rate of epoxy resin decreases by 46.3%, and the total heat release decreases by 11.9%.

[0076] For example, Figure 8 shows that the positions of the peaks in the X-ray diffraction pattern of the COF-SNW-1 material match the simulated data, indicating the successful synthesis of COF-SNW-1. It can be seen from the infrared spectrum ( Figure 9 ) that compared with the two monomers, the synthesized COF-SNW-1 shows a C=N peak at 1650 cm -1 , the NH2 peak in the monomer melamine disappears, and the C=O peak in the monomer terephthalaldehyde shifts, proving the successful synthesis of COF-SNW-1 through imine condensation reaction. The flame-retardant material prepared from the COF-SNW-1 material synthesized in Example 3 and polylactic acid has good flame-retardant properties. For example, Figure 13 , Figure 14 show that when 3 wt% of COF-SNW-1 is added, the heat release rate of polylactic acid decreases by 9.86%, and the total heat release decreases by 10.5%.

[0077] In summary, the covalent organic framework material synthesized by the solvent-free method using the twin-screw extruder of the present invention has good flame-retardant properties and can be used to prepare flame-retardant materials.

[0078] The above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the purpose and scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention. The technologies, shapes, and structures not described in detail in the present invention are all well-known technologies.

Claims

1. A method for preparing a covalent organic framework material, characterized in that: The following steps are involved: The tridentate organic ligand monomer, the bidentate organic ligand monomer and the solid acid catalyst are uniformly mixed to obtain a mixture, the speed of the twin-screw extruder is set to 5-35r / min, the temperature is set to 80-140°C, the mixture is added to the twin-screw extruder, heated, kneaded and mixed, washed and dried to obtain a COF material.

2. The method for preparing a covalent organic framework material according to claim 1, characterized in that: The molar ratio of the tridentate organic ligand monomer, the bidentate organic ligand monomer and the solid acid catalyst is 2:(1.5-3):(12-20).

3. The method for preparing a covalent organic framework material according to claim 1 or 2, characterized in that: The tridentate organic ligand is melamine or 4,4',4"-(1,3,5-triazine-2,4,6-triyl)triphenylamine.

4. The method for preparing a covalent organic framework material according to claim 1 or 2, characterized in that: The bidentate organic ligand monomer is selected from one of terephthalaldehyde, 1,4-dihydroxyterephthalaldehyde and 1,4-dichloroterephthalaldehyde.

5. The method for preparing a covalent organic framework material according to claim 1 or 2, characterized in that: The solid acid catalyst is benzoic acid or p-toluenesulfonic acid.

6. The method for preparing a covalent organic framework material according to claim 1, characterized in that: The washing is performed with at least two of acetone, dichloromethane and tetrahydrofuran.

7. The method for preparing a covalent organic framework material according to claim 1, characterized in that: The drying condition is 60-75° C. for 10-12 hours.

8. The covalent organic framework material prepared according to the preparation method according to any one of claims 1 to 7.

9. Application of the covalent organic framework material prepared according to the preparation method of claim 8 in flame retardant materials.

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