Proton conductive covalent organic framework solid material as well as preparation method and application thereof

Abstract

The invention provides a proton conductive covalent organic framework solid material as well as a preparation method and application thereof, and particularly relates to the technical field of covalent organic framework solid materials. The preparation method of the proton conductive covalent organic framework solid material provided by the invention comprises the following steps: mixing and grinding an aromatic diamine compound, an aromatic trialdehyde compound, an organic acid catalyst and water, and carrying out Schiff base reaction to obtain a primary polymer; performing hydrothermal reaction on the primary polymer to obtain the proton conductive covalent organic framework solid material, the molar ratio of the aromatic diamine compound to the organic acid is 1: (5-130). According to the invention, a Schiff base reaction is utilized to form a carbon-nitrogen double bond so as to obtain a proton conduction active site; the obtained solid material has a pore structure, can absorb water molecules, is beneficial to construction of a hydrogen bond network, and improves the proton conductivity; the organic acid catalyst provides water absorption performance for the material and provides active protons, so that the proton conductivity is further improved.

Description

Technical Field

[0001] The invention belongs to the technical field of covalent organic framework solid materials, and in particular relates to a proton conductive covalent organic framework solid material and a preparation method and application thereof. Background Art

[0002] Proton exchange membrane fuel cells (PEMFC) have shown excellent performance in terms of efficiency, power density, operating temperature, etc. They are environmentally friendly and start quickly, so they are regarded as one of the energy devices with the broadest development prospects. Proton exchange membrane (PEM) is the core component of PEMFC, which has the functions of conducting protons, separating the cathode and anode, and preventing the conduction of electrons inside the battery.

[0003] Currently, the most widely used proton exchange membrane is the perfluorosulfonic acid polymer (Nafion) developed by DuPont in the United States. However, Nafion is highly dependent on water and requires a complex water management system (95-100% RH) when used. It cannot operate in a low humidity environment (<80% RH) and is expensive, which increases the cost of fuel cells. Summary of the invention

[0004] In view of this, the purpose of the present invention is to provide a proton conductive covalent organic framework solid material and its preparation method and application. The proton conductive covalent organic framework solid material prepared by the present invention has good proton conductivity in a low humidity environment and low preparation cost, and is expected to replace commercial Nafion.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0006] The present invention provides a method for preparing a proton conductive covalent organic framework solid material, comprising the following steps:

[0007] The aromatic diamine compound, the aromatic trialdehyde compound, the organic acid catalyst and water are mixed and ground to produce a Schiff base reaction to obtain a primary polymer;

[0008] subjecting the primary polymer to a hydrothermal reaction to obtain the proton conductive covalent organic framework solid material;

[0009] The molar ratio of the aromatic diamine compound to the organic acid catalyst is 1:5-130.

[0010] Preferably, the aromatic diamine compound includes one of 3,5-diamino-1,2,4-triazole, m-phenylenediamine, 2,6-diaminopyridine, 2-fluoro-[1,1'-biphenyl]-4,4'-diamine, 3,3"-diamino-m-terphenyl, 4,4'-(benzo[c][1,2,5]thiadiazole-4,7-diyl)diphenylamine and 2,6-diaminobenzo[1,2-D:4,5-D']dithiazole.

[0011] Preferably, the aromatic trialdehyde compound includes one of 1,3,5-triformylphloroglucinol, 1,3,5-tribromo-2,4,6-benzaldehyde, 2,4-dihydroxy-1,3,5-pyromellitic trimesicaldehyde, 2,4,6-tris(4-formylphenyl)-1,3,5-triazine and 1,3,5-tris(p-formylphenyl)benzene.

[0012] Preferably, the molar ratio of the aromatic diamine compound to the aromatic trialdehyde compound is 1:0.5-1.

[0013] Preferably, the organic acid catalyst comprises ammonium acetate and / or p-toluenesulfonic acid.

[0014] Preferably, the temperature of the hydrothermal reaction is 90-150° C., and the time is 12-18 hours.

[0015] Preferably, the ratio of the mass of the aromatic diamine compound to the volume of water is 1 g: 0.5-10 mL.

[0016] Preferably, the primary polymer is pressed before the hydrothermal reaction.

[0017] The present invention also provides a proton conductive covalent organic framework solid material prepared by the preparation method described in the above technical solution.

[0018] The present invention also provides the use of the proton conductive covalent organic framework solid material described in the above technical solution in a proton conductor or a proton exchange membrane of a fuel cell.

[0019] The invention provides a method for preparing a proton conductive covalent organic framework solid material, comprising the following steps: mixing and grinding an aromatic diamine compound, an aromatic trialdehyde compound, an organic acid catalyst and water to generate a Schiff base reaction to obtain a primary polymer; subjecting the primary polymer to a hydrothermal reaction to obtain the proton conductive covalent organic framework solid material; the molar ratio of the aromatic diamine compound to the organic acid catalyst is 1:5-130. The present invention utilizes diamine in aromatic diamine compounds and trialdehyde in aromatic trialdehyde compounds to undergo Schiff base reaction to form carbon-nitrogen double bonds, wherein nitrogen in the carbon-nitrogen double bonds contains lone pairs of electrons and can be used as proton conduction active sites to accept protons; the prepared proton conductive covalent organic framework solid material has a porous structure, can absorb water molecules, is conducive to building a hydrogen bond network, and improves proton conductivity; the presence of an organic acid catalyst is conducive to reducing the reaction activation energy, controlling the material to form a macroscopic block solid, forming a self-supporting material, and is conducive to pressing and molding, and the organic acid catalyst can provide the material with certain water absorption performance, further improving the proton conductivity; through mechanical grinding and hydrothermal reaction, the Schiff base reaction occurs in stages, so that the raw materials are evenly mixed and the reaction occurs fully, the prepared proton conductive covalent organic framework solid material is easy to be pressed and molded, and a self-supporting COF material is obtained. The data from the examples show that the proton conductive covalent organic framework solid material provided by the present invention has good proton conductivity of 0.02-0.2 S / cm in a low humidity environment (80° C., 76% RH), good thermal stability, and a weight retention of 25-30% at 800° C. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0021] Figure 1 The SEM images of the proton conductive covalent organic framework solid materials prepared in Examples 1 to 3;

[0022] Figure 2 XRD patterns of the proton conductive covalent organic framework solid materials prepared in Examples 1 to 3;

[0023] Figure 3 BET diagrams of proton conductive covalent organic framework solid materials prepared in Example 3 and Comparative Example 1;

[0024] Figure 4 Impedance diagrams of proton conductive covalent organic framework solid materials prepared in Example 3 and Comparative Example 1;

[0025] Figure 5 Thermogravimetric diagrams of the proton conductive covalent organic framework solid materials prepared in Examples 1, 3 and Comparative Example 1. DETAILED DESCRIPTION

[0026] The present invention provides a method for preparing a proton conductive covalent organic framework solid material, comprising the following steps:

[0027] The aromatic diamine compound, the aromatic trialdehyde compound, the organic acid catalyst and water are mixed and ground to produce a Schiff base reaction to obtain a primary polymer;

[0028] subjecting the primary polymer to a hydrothermal reaction to obtain the proton conductive covalent organic framework solid material;

[0029] The molar ratio of the aromatic diamine compound to the organic acid is 1:5-130.

[0030] In the present invention, unless otherwise specified, the raw materials and equipment used are commercially available products well known in the art.

[0031] The invention mixes and grinds aromatic diamine compounds, aromatic trialdehyde compounds, organic acid catalysts and water to generate Schiff base reaction and obtain primary polymers.

[0032] In the present invention, the mixing and grinding of the aromatic diamine compound, the aromatic trialdehyde compound, the organic acid catalyst and water preferably comprises: mixing the aromatic diamine compound and the aromatic trialdehyde compound for a first grinding, and then adding the organic acid catalyst and water for a second grinding.

[0033] The invention grinds twice so that the materials are mixed more evenly, the reaction is more thorough, and a preliminary Schiff base reaction occurs.

[0034] In the present invention, the aromatic diamine compound preferably includes one of 3,5-diamino-1,2,4-triazole, m-phenylenediamine, 2,6-diaminopyridine, 2-fluoro-[1,1'-biphenyl]-4,4'-diamine, 3,3"-diamino-m-terphenyl, 4,4'-(benzo[c][1,2,5]thiadiazole-4,7-diyl)diphenylamine and 2,6-diaminobenzo[1,2-D:4,5-D']dithiazole. In a specific embodiment of the present invention, the aromatic diamine compound is preferably 3,5-diamino-1,2,4-triazole. One of the nitrogens in the triazole structure of 3,5-diamino-1,2,4-triazole carries an active proton, which will interact with the nitrogen containing a lone pair of electrons in the carbon-nitrogen double bond generated after the Schiff base reaction to form a proton conduction process, thereby improving the proton conductivity of the material.

[0035] In the present invention, the aromatic trialdehyde compound preferably includes one of 1,3,5-triformylphloroglucinol, 1,3,5-tribromo-2,4,6-benzaldehyde, 2,4-dihydroxy-1,3,5-pyromellitic trimesicaldehyde, 2,4,6-tris(4-formylphenyl)-1,3,5-triazine and 1,3,5-tris(p-formylphenyl)benzene.

[0036] In the present invention, the molar ratio of the aromatic diamine compound to the aromatic trialdehyde compound is preferably 1:0.5-1. In a specific embodiment, the molar ratio of the aromatic diamine compound to the aromatic trialdehyde compound can be 1:0.5, 1:0.6, 1:0.7, 1:0.75, 1:0.8, 1:0.9 or 1:1.

[0037] In the present invention, the first grinding time is preferably 8 to 15 minutes. In a specific embodiment, the first grinding time can be 8 minutes, 10 minutes, 12 minutes or 15 minutes.

[0038] In the present invention, the organic acid catalyst preferably includes ammonium acetate and / or p-toluenesulfonic acid. In a specific embodiment of the present invention, the organic acid catalyst is preferably ammonium acetate. The presence of active protons in ammonium acetate is beneficial to improving the proton conductivity of the material; at the same time, the presence of ammonium acetate can improve the water adsorption capacity of the proton conductive covalent organic framework solid material.

[0039] In the present invention, the molar ratio of the aromatic diamine compound to the organic acid catalyst is 1:5 to 130. In a specific embodiment, the molar ratio of the aromatic diamine compound to the organic acid catalyst can be 1:5, 1:10, 1:20, 1:30, 1:50, 1:80, 1:100, 1:120 or 1:130. Under the action of the organic acid catalyst, the diamine in the aromatic diamine compound and the trialdehyde in the aromatic trialdehyde compound are promoted to undergo a preliminary Schiff base reaction to obtain a primary polymer. The present invention controls the morphology and water adsorption capacity of the solid material by controlling the amount of ammonium acetate, thereby improving the proton conductivity of the material, and avoiding excessive use of ammonium acetate, which causes the prepared COF material to be dispersed due to excessive water absorption and cannot be formed.

[0040] In the present invention, the ratio of the mass of the aromatic diamine compound to the volume of water is preferably 1g:0.5-10mL. In a specific embodiment, the ratio of the mass of the aromatic diamine compound to the volume of water can be 1g:0.5mL, 1g:1mL, 1g:3mL, 1g:5mL, 1g:8mL or 1g:10mL.

[0041] In the present invention, the second grinding time is preferably 1 to 5 minutes. In a specific embodiment, the second grinding time can be 1 minute, 2 minutes, 3 minutes, 4 minutes or 5 minutes.

[0042] The primary polymer is obtained, and the present invention subjects the primary polymer to a hydrothermal reaction to obtain the proton conductive covalent organic framework solid material.

[0043] In the present invention, the hydrothermal reaction is preferably preceded by pressing. In the present invention, the pressing pressure is preferably 0.5-5MPa. In a specific embodiment, the pressing pressure may be 0.5MPa, 1MPa, 2MPa, 3MPa, 4MPa or 5MPa; the pressing time is preferably 10-60s. In a specific embodiment, the pressing time may be 10s, 20s, 30s, 40s, 50s or 60s. After the primary polymer is pressed, a self-supporting COF material of a certain morphology is obtained through a hydrothermal reaction, and the corresponding electrochemical test can be directly performed to simplify the post-processing process.

[0044] In the present invention, the temperature of the hydrothermal reaction is preferably 90-150°C. In a specific embodiment, the temperature of the hydrothermal reaction can be 90°C, 100°C, 120°C or 150°C. The time of the hydrothermal reaction is preferably 12-18h. In a specific embodiment, the time of the hydrothermal reaction can be 12h, 14h, 16h or 18h. Through the hydrothermal reaction, the diamine in the aromatic diamine compound and the trialdehyde in the aromatic trialdehyde compound undergo Schiff base reaction again, and further polymerize, so that the diamine and the trialdehyde react fully.

[0045] The present invention also provides a proton conductive covalent organic framework solid material prepared by the preparation method described in the above technical solution.

[0046] In the present invention, the specific surface area of ​​the proton conductive covalent organic framework solid material is preferably 60 to 70 m 2 / g.

[0047] In the present invention, the proton conductivity of the proton conductive covalent organic framework solid material is preferably 0.02 to 0.2 S / cm.

[0048] The present invention also provides the use of the proton-conductive covalent organic framework solid material described in the above technical solution in a proton conductor or a proton exchange membrane of a fuel cell.

[0049] The present invention has no special requirements on the method and technique of the application, and the commonly used technical means in the art may be adopted.

[0050] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution of the present invention will be clearly and completely described in conjunction with specific embodiments below. The described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Any modification, equivalent replacement, improvement, etc. made to the implementation methods of the present invention based on the technical essence and general principles of the present invention without creative work should be within the scope of protection of the present invention.

[0051] Example 1

[0052] 0.021g 3,5-diamino-1,2,4-triazole (DAT) and 0.024g 1,3,5-triformyl phloroglucinol (Tp) were mixed and ground for 10 minutes to obtain a mixed powder, 0.08g ammonium acetate was added to the mixed powder, and after grinding for 2 minutes, 20μL distilled water was added and ground to obtain a primary polymer. The primary polymer was pressed at 2MPa for 10s and placed in a reactor at 90°C for 12h to obtain a COF material, which was recorded as TpDTA-1.

[0053] Example 2

[0054] 0.16 g of ammonium acetate was added to the mixed powder, and other conditions were the same as in Example 1 to obtain a COF material, which was recorded as TpDTA-2.

[0055] Example 3

[0056] 1.5 g of ammonium acetate was added to the mixed powder, and the mixture was reacted in a reactor at 150° C. for 12 h. Other conditions were the same as those in Example 1 to obtain a COF material, which was recorded as TpDTA-3. The specific surface area of ​​TpDTA-3 was 65.02 m 2 / g, BET diagram Figure 3 As shown in (a).

[0057] The proton conductive covalent organic framework solid materials prepared in Examples 1 to 3 were scanned by electron microscope to obtain Figure 1 . Figure 1 a), b) and c) correspond to the proton conductive covalent organic framework solid materials prepared in Examples 1 to 3, respectively. Figure 1 It can be seen that when the amount of ammonium acetate increases, the morphology of the obtained solid material changes from irregular blocks to pebble-like particles.

[0058] The proton conductive covalent organic framework solid materials prepared in Examples 1 to 3 were subjected to XRD test to obtain Figure 2 . Figure 2 a), b) and c) correspond to the proton conductive covalent organic framework solid materials prepared in Examples 1 to 3, respectively. Figure 2It can be seen that with the increase in the amount of ammonium acetate, an obvious peak appears (the peak represents ammonium acetate), and the more the content, the larger the peak area, and at the same time a broad peak representing an amorphous COF material is obtained.

[0059] Comparative Example 1

[0060] 0.021g 3,5-diamino-1,2,4-triazole (DAT) and 0.024g 1,3,5-triformyl phloroglucinol (Tp) were mixed and ground for 10 minutes to obtain a mixed powder, and 20μL distilled water was added and ground for 2 minutes to obtain a primary polymer. The primary polymer was pressed at 2MPa for 30s and placed in a reactor at 60℃ for 12h to obtain a COF material, which was recorded as TpDTA-0. The specific surface area of ​​TpDTA-0 is 10.71m 2 / g, such as Figure 3 As shown in b).

[0061] Comparative Example 2

[0062] 3 g of ammonium acetate was added to the mixed powder, and other conditions were the same as in Example 1 to obtain a COF material.

[0063] Due to the increase in ammonium acetate content, the water absorption performance of the material increased significantly. During the test, the material dispersed due to water absorption and the proton conductivity could not be obtained.

[0064] The proton conductive covalent organic framework solid materials prepared in Examples 1 to 3 and Comparative Example 1 and the commercially available perfluorosulfonic acid polymer were placed in a humidity measuring device at 76% RH, connected to the electrodes of an electrochemical workstation, and set the bias voltage to 0.2 V at 80° C. and the frequency to 1 to 1,000,000 Hz to obtain Figure 4 , Figure 4 a) and b) represent the proton conductive covalent organic framework solid materials prepared in Example 3 and Comparative Example 1, respectively. After obtaining the resistance value, the conductivity is calculated according to the calculation formula:

[0065] σ=L / RS Formula 1,

[0066] Where σ is the conductivity (S / cm), S and L represent the cross-sectional area of ​​the sample (cm 2 ) and thickness (cm); R is the resistance value (Ω). The calculated values ​​are shown in Table 1.

[0067] Table 1 Electrical conductivity of proton conductive covalent organic framework solid materials and perfluorosulfonic acid polymers prepared in Examples 1 to 3 and Comparative Example 1

[0068] Example 1 Example 2 Example 3 Comparative Example 1 Perfluorosulfonic acid polymer Conductivity / S / cm 0.022 0.091 0.12 0.0092 <0.01

[0069] As can be seen from Table 1, the conductivity of the proton conductive covalent organic framework solid material prepared by the present invention is 0.02-0.2 S / cm at 80° C. and 76% RH, which is better than the conductivity of the perfluorosulfonic acid polymer.

[0070] The proton conductive covalent organic framework solid materials prepared in Examples 1, 3 and Comparative Example 1 were subjected to thermogravimetric analysis to obtain Figure 5 .from Figure 5 It can be seen that when the temperature is increased from 100°C to 800°C, the weight of the proton conductive covalent organic framework solid materials prepared in Examples 1 and 3 is retained by 25-30%, while the proton conductive covalent organic framework solid material prepared in Comparative Example 1 has almost no material residue at 800°C. This indicates that the proton conductive covalent organic framework solid material prepared by the present invention has good thermal stability.

[0071] From the above test results, it can be seen that the present invention successfully obtains a self-supporting proton conductive covalent organic framework solid material by controlling the amount of organic acid catalyst and performing Schiff base reaction in stages. The material has good electrical conductivity and good thermal stability at low humidity.

[0072] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a proton conductive covalent organic framework solid material, characterized in that: The following steps are involved: The aromatic diamine compound, the aromatic trialdehyde compound, the organic acid catalyst and water are mixed and ground to produce a Schiff base reaction to obtain a primary polymer; subjecting the primary polymer to a hydrothermal reaction to obtain the proton conductive covalent organic framework solid material; The molar ratio of the aromatic diamine compound to the organic acid catalyst is 1:5-130.

2. The preparation method according to claim 1, characterized in that: The aromatic diamine compound includes one of 3,5-diamino-1,2,4-triazole, m-phenylenediamine, 2,6-diaminopyridine, 2-fluoro-[1,1'-biphenyl]-4,4'-diamine, 3,3"-diamino-m-terphenyl, 4,4'-(benzo[c][1,2,5]thiadiazole-4,7-diyl)diphenylamine and 2,6-diaminobenzo[1,2-D:4,5-D']dithiazole.

3. The preparation method according to claim 1, characterized in that: The aromatic trialdehyde compound includes one of 1,3,5-triformylphloroglucinol, 1,3,5-tribromo-2,4,6-benzaldehyde, 2,4-dihydroxy-1,3,5-pyromellitic trimesicaldehyde, 2,4,6-tris(4-formylphenyl)-1,3,5-triazine and 1,3,5-tris(p-formylphenyl)benzene.

4. The preparation method according to claim 1, 2 or 3, characterized in that: The molar ratio of the aromatic diamine compound to the aromatic trialdehyde compound is 1:0.5-1.

5. The preparation method according to claim 1, characterized in that: The organic acid catalyst includes ammonium acetate and / or p-toluenesulfonic acid.

6. The preparation method according to claim 1, characterized in that: The temperature of the hydrothermal reaction is 90-150° C. and the time is 12-18 hours.

7. The preparation method according to claim 1 or 2, characterized in that: The ratio of the mass of the aromatic diamine compound to the volume of water is 1g:0.5-10mL.

8. The preparation method according to claim 1 or 6, characterized in that: The method further comprises pressing the primary polymer before the hydrothermal reaction.

9. The proton conductive covalent organic framework solid material prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the proton conductive covalent organic framework solid material according to claim 9 in a proton conductor or a proton exchange membrane of a fuel cell.

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