An alkyne-modified acylhydrazone covalent organic framework material, a preparation method thereof and application thereof in fuel cells

Abstract

The application relates to an acetylenyl-modified acyl covalent organic framework (COF) material and its application, and relates to the preparation of a crystalline porous material and a fuel cell. The material is a covalent organic framework material synthesized by a solvothermal reaction under specific conditions with 1,3,5-triformylphloroglucinol and 2,5-bis(2-propynoxy)terephthalic dihydrazide as raw materials, and has high crystallinity. The material has good proton conductivity, and the highest proton conductivity can reach 6.16163*10 ‑4 S / cm. The mechanical performance is also enhanced due to the introduction of the acetylenyl group. The acetylenyl group is a kind of active functional group, can be derived into various chemical reactions, and greatly improves the potential application value of the material.

Description

Technical Field

[0001] This invention relates to a method for preparing an alkynyl-modified acylhydrazone covalent organic framework material, which has excellent mechanical properties and chemical tunability and is suitable for fuel cell technology. Background Technology

[0002] In recent years, fuel cells have become a key component in electrochemical devices. The proton exchange membrane (PEM) within the cell acts as an anode and cathode separator, while also being responsible for proton conduction and participating in the charge balance process during electrochemical reactions. Therefore, the performance and quality of the PEM significantly impact the cell's output power, efficiency, lifespan, and stability. Currently, various materials, such as multiple MOFs and porous organic polymers, are widely used in fuel cells.

[0003] Covalent organic frameworks (COFs) are a new type of crystalline porous material, consisting of ordered porous network structures formed by organic monomers through covalent bonds. Due to their high porosity, large specific surface area, and tunable pore size and porosity, COFs show promising applications in optoelectronic fields such as photocatalysis, proton conduction, gas storage, and energy storage.

[0004] Current COF materials, due to their highly ordered pore structure and rigid covalent bonds, are prone to fracture under external forces, lacking sufficient toughness and elasticity. Furthermore, under certain conditions, the mechanical stability of COF materials may decrease, leading to structural damage or performance degradation. Moreover, COF materials prepared in the laboratory are usually in powder form; processing them into films or other forms may reduce their mechanical strength, limiting their application in some fields. In addition, regarding chemical tunability, although the synthesis routes of COFs allow for a certain degree of pre-design and functionalization, introducing new functional groups or further modifying existing functional groups after material synthesis remains challenging. Therefore, for applications requiring highly selective chemical modification, existing COF systems may be insufficient. This invention utilizes an inexpensive and readily available monomer, 1,3,5-tricarboxymethyl phloroglucinol, and 2,5-bis(2-propynoxy)terephthalohydrazide to self-assemble under solvothermal conditions to form an alkynyl-modified acylhydrazone-based COF material. This COF crystal structure exhibits high porosity, and the introduction of alkynyl groups reduces the overall rigidity of the material, resulting in better elasticity and plasticity. Furthermore, alkynyl groups are reactive functional groups that can be further derivatized through various reactions. This modifiability allows for the introduction of new functional groups, thereby altering the physicochemical properties of the material. Summary of the Invention

[0005] This invention relates to a method for preparing an alkynyl-modified acylhydrazone covalent organic framework material and its application in fuel cells. The material is prepared from 1,3,5-tricarboxymethyl phloroglucinol and 2,5-bis(2-propynoxy)terephthaloyl hydrazine via a solvothermal reaction to obtain a highly crystalline covalent organic framework material. This material exhibits good proton conductivity. Furthermore, the presence of an alkynyl group in the material structure enhances its mechanical properties to some extent. As a reactive functional group, the alkynyl group can be further derivatized through various reactions to introduce new functional groups, altering the physicochemical properties of the material and thus improving the conductivity of the proton exchange membrane in fuel cells.

[0006] One object of the present invention is to provide an alkynyl-modified acylhydrazone covalent organic framework material, with the following structural formula:

[0007]

[0008] The thin film material has alkoxyalkynyl branches in its structural formula; the thin film material also has acylhydrazone bonds -C=O(NH-NH2).

[0009] The organic framework material exhibits characteristic diffraction peaks near 2θ angles of approximately 3°, 7°, and 27°. The organic framework material also exhibits diffraction peaks at approximately 3305 cm⁻¹. -1 2125cm -1 and 1643cm -1 The location shows a characteristic infrared absorption peak.

[0010] The method for preparing the alkynyl-modified acylhydrazone covalent organic framework material includes the following steps:

[0011] After mixing 2,5-bis(2-propynoxy)terephthalohydrazide and 1,3,5-tricarboxymethylphloroglucinol in a reaction flask, an organic solvent was added, and the mixture was ultrasonically dispersed. Then, an acid solution was added as a catalyst.

[0012] The mixture was then rapidly frozen, vacuum-sealed, and heated in an oil bath after sealing the bottle. After the oil bath reaction was complete, the resulting solid product was washed with solvent, extracted for a certain period, filtered, and dried to obtain the alkynyl-modified acylhydrazone covalent organic framework material. The specific reaction formula is as follows:

[0013]

[0014] The molar ratio of 2,5-bis(2-propynoxy)terephthalohydrazide to 1,3,5-tricarboxymethyl phloroglucinol is 1-3:1-3; preferably, the ratio of 2,5-bis(2-propynoxy)terephthalohydrazide to 1,3,5-tricarboxymethyl phloroglucinol is 2-2.5:1.5-2.0.

[0015] The organic solvent is one or more combinations of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, mesitylene, 1,4-dioxane, o-dihydrobenzene, n-butanol and benzyl alcohol; the preferred solvents are mesitylene, 1,4-dioxane and n-butanol.

[0016] In some embodiments, the organic solvent is a mixed solvent, and is mixed in a certain ratio of 1-3:1-4; the preferred solvent ratio is 4-5:1-2 between mesitylene and 1,4-dioxane.

[0017] The acid solution is an aqueous solution of acetic acid or hydrochloric acid; the concentration of the acid solution is 3M-12M; preferably, the concentration of the acid solution is 3-6M.

[0018] The reaction temperature range in the oil bath is 100-150℃; the preferred reaction temperature is 100-120℃; the reaction time in the oil bath is 12-144h; the preferred reaction time is 36-48h.

[0019] In some embodiments, the solvent used for washing the solid product with a solvent is one of acetone, ethyl acetate, dichloromethane, methanol, ethanol, 1,4-dioxane, N,N-dimethylformamide, tetrahydrofuran, ammonia, and deionized water; the solvent used for washing is preferably acetone, 1,4-dioxane, tetrahydrofuran, deionized water, or ethanol.

[0020] The solvent selected for extraction is one of acetone, ethyl acetate, dichloromethane, methanol, ethanol, 1,4-dioxane, and tetrahydrofuran; the solvent selected for extraction is preferably tetrahydrofuran and acetone; the extraction time is 12-72 hours; the extraction time is preferably 48 hours.

[0021] A proton conductor for a fuel cell includes the alkyne-modified acylhydrazone covalent organic framework material, or the alkyne-modified acylhydrazone covalent organic framework material prepared by the method.

[0022] The obtained sample was activated by soaking in methanol for a period of time, dried at a certain temperature, collected, ground, vibrated, and then pressed into a pellet. It was then fixed with 5-50 μm gold wire and coated with conductive silver paste on both sides. After drying, the sample was placed in an environment with constant humidity and temperature. A preliminary EIS impedance analyzer was used to test and fit the corresponding fitted internal resistance of the sample at that humidity and temperature. Then, different temperatures and humidity levels were adjusted, and the fitted internal resistance of the sample at different humidity and temperature levels was tested and fitted using an EIS impedance analyzer. The conductivity and activation energy were then calculated.

[0023] The pressure of the tablet is 100-400 kg / cm². 2 The tableting time is 0.5-5 minutes, and the thickness is 0.50-3.50 mm; preferably 250 kg / cm². 2 The tablet holding time is 0.5-5 min, preferably 1 min, and the thickness is 0.50-3.50 mm, preferably 3 mm.

[0024] In the above steps, after the conductive silver paste is applied, the drying temperature is 30-70℃, preferably 50℃, the drying time is 10-50min, preferably 15min, and the humidity is 90-98%.

[0025] During the stability test, the sample obtained was placed in a closed environment. The humidity was set to 90-98% through the program settings. The temperature was first increased from 30℃ to 90℃, and then decreased from 90℃ to 30℃. After several consecutive heating and cooling cycles, operation (3) was repeated to analyze whether the proton conductivity changed. In the stability test, the humidity was 50-98%, the temperature before the increase was 20-35℃, the temperature after the increase was 85-95℃, and the number of cycles was greater than or equal to 2.

[0026] The specific beneficial effects of this material are as follows:

[0027] 1. Cost-effectiveness and structural advantages: 1,3,5-tricarboxymethyl phloroglucinol, as an organic monomer, provides an economical and efficient solution for material synthesis due to its simple structure and relatively low price;

[0028] 2. Enhanced ionic conductivity: Its hydroxyl group coordination modes are abundant, which not only form stable coordination with the host material, but also significantly improve the conductivity of hydrogen ions and optimize the ionic conductivity of the material;

[0029] 3. Excellent stability: The CTGU-COF material remains stable even in harsh environments such as acids, alkalis and boiling water, demonstrating its excellent weather resistance and durability;

[0030] 4. Improved processing performance: The introduction of acetylene groups reduces the rigidity of the material, giving it good elasticity and plasticity, making it easier to process and shape, and broadening its application range;

[0031] 5. Flexible functionalization capability: As an active functional group, the alkynyl group can be easily introduced into new functional groups through chemical reactions, providing unlimited possibilities for the control of the physicochemical properties of materials;

[0032] 6. Potential optical properties: The unique optical properties that may result from the participation of alkyne groups in the conjugated system indicate the great potential of this material in optoelectronic devices and sensors; Attached Figure Description

[0033] Figure 1 This is a structural diagram of CTGU-COF prepared in Example 1 of this invention.

[0034] Figure 2 The image shows the IR spectrum of CTGU-COF prepared in Example 1 of this invention.

[0035] Figure 3 The images show the XRD patterns of CTGU-COF prepared in Example 1 of this invention and its XRD patterns after immersion in different acid and alkaline media.

[0036] Figure 4 The 2,5-bis(2-propynoxy)terephthalohydrazide in this invention 1 H NMR spectrum.

[0037] Figure 5 The 2,5-bis(2-propynoxy)terephthalohydrazide in this invention 13 C10 NMR spectrum.

[0038] Figure 6 This is the EIS diagram of the CTGU-COF material in this invention.

[0039] Figure 7 This is a conductivity diagram of the CTGU-COF material in this invention.

[0040] Figure 8 This is the Arrhenius diagram of the CTGU-COF material in this invention. Detailed Implementation

[0041] The present invention will be further described below with reference to the embodiments, but the present invention is not limited to the following embodiments.

[0042] Example 1

[0043] Add 2,5-bis(2-propynoxy)terephthalohydrazide (69.0 mg, 2.2 mmol) and 1,3,5-tricarboxymethyl phloroglucinol (31.5 mg, 1.5 mmol) to an ampoule, then add 1.8 mL of anhydrous 1,4-dioxane and 7.2 mL of mesitylene. After sonicating for 30 min, add 0.9 mL of acetic acid aqueous solution (6 mol·L⁻¹). -1 The ampoule was quickly frozen in liquid nitrogen. After it was completely frozen, a vacuum was drawn and the ampoule was sealed with a flame torch. The ampoule containing the reactants was placed in an oil bath and heated at 120°C for 72 hours. Finally, the resulting reddish-brown solid was washed with DMF and THF in sequence, dried and filtered under vacuum at 100°C to obtain dry CTGU-COF powder.

[0044] Figure 1The structure in the figure shows that the CTGU-COF mainly forms an acylhydrazone-type organic covalent bond through the amino-aldehyde condensation of the acylhydrazine bond and the aldehyde group. The figure shows the basic building unit of the CTGU-COF.

[0045] Figure 2 The IR spectrum shows that C≡C, C=O, C=O(NH) and other bonds of the raw material 2,5-bis(2-propynoxy)-terephthalohydrazide all appear in the COF; and the primary amine peak in the raw material 2,5-bis(2-propynoxy)-terephthalohydrazide disappears, and a new C=N bond appears in the COF, indicating that the COF was successfully prepared.

[0046] Figure 3 The images show the XRD patterns of CTGU-COF in this invention and its XRD patterns after immersion in different acid and alkaline media. The structure of COF did not change after immersion in boiling water, 12M NaOH, and 12M HCl solutions for 12 hours.

[0047] Figure 4 2,5-bis(2-propynoxy)-terephthalohydrazide 1 The H NMR spectrum showed the chemical shifts of various H atoms in 2,5-bis(2-propynoxy)-terephthalohydrazide, further confirming the accuracy of the raw material's structure. 1 H NMR (500MHz, DMSO-d6) δ9.34(d,J=3.7Hz,2H),7.49(s,2H),4.91(d,J=2.4Hz,4H),4.59(d,J=3.9Hz,4H),3.65(t,J=2.4Hz,2H).

[0048] Figure 5 2,5-bis(2-propynoxy)-terephthalohydrazide 13 The C10 NMR spectrum showed the chemical shifts of various C atoms in 2,5-bis(2-propynoxy)terephthalohydrazide, further confirming the accuracy of the raw material's structure.

[0049] 13 C NMR (126MHz, DMSO-d6) δ163.9,149.2,126.0,115.8,79.5,79.3,57.2.

[0050] The above results demonstrate the successful synthesis of alkynyl-modified acylhydrazone CTGU-COF materials. Their unique alkynyl structure endows the materials with superior mechanical properties and enhances their chemical tunability, providing a valuable approach for improving the proton conductivity of similar CTGU-COF materials in the future and promoting the application of this type of material in the fields of hydrocarbon functional groups and electrochemistry.

[0051] Example 1-1

[0052] The other operating steps are the same as in Example 1, except that the volume ratio of anhydrous 1,4-dioxane to mesitylene is 1:3, the volume of anhydrous 1,4-dioxane is 0.6 mL, and the volume of mesitylene is 1.8 mL. CTGU-COF with good crystallinity can also be successfully prepared.

[0053] Examples 1-2

[0054] Other operating steps are the same as in Example 1. Placing the ampoule containing the reactants in an oil bath and heating at 130°C for 48 hours can also successfully prepare CTGU-COF with good crystallinity.

[0055] Examples 1-3

[0056] The other operating steps are the same as in Example 1, followed by the addition of 0.5 mL of acetic acid aqueous solution (12 mol·L⁻¹). -1 It can also successfully prepare CTGU-COF with better crystallinity.

[0057] Example 2

[0058] The steps for testing the proton conduction performance of COF are as follows:

[0059] First, the sample was activated with methanol for 3 days. After activation, the sample was dried in a vacuum drying oven at 80℃ for 12 hours and then collected. The preparation procedure for the sheet-like sample for impedance testing is as follows: First, the sample was ground in a mortar for 2 minutes. After grinding, an appropriate amount of powdered sample was added to a tablet press, vibrated evenly, and then pressurized to 250 kg / cm². 2 The sample was pressurized and held under pressure for 60 seconds. Then, the sheet sample was removed and its diameter and thickness were measured; the diameter was 4.00 mm and the thickness was 3.00 mm. Finally, the sheet sample was fixed with 50 μm diameter gold wire and conductive silver paste was applied to both sides. It was then dried at 50°C for 15 minutes. The constant temperature and humidity instrument was then programmed, with the humidity set to 98% and the temperature to 30°C. To ensure the sample met the required humidity and temperature conditions, it was first stabilized for 24 hours in the specified environment before testing. Then, an EIS impedance analyzer was used to test and fit the internal resistance of the CTGU-COF at different temperatures under 98% RH, and the conductivity and activation energy were calculated.

[0060] Figure 6 The EIS of the CTGU-COF material shows that, under 98% RH conditions, the resistance of the CTGU-COF material continuously decreases with increasing temperature, indicating that its conductivity continuously improves.

[0061] Figure 7The conductivity diagram of the CTGU-COF material shows that it has good proton conductivity, with a maximum proton conductivity of 6.16163 × 10⁻⁶. -4 Its conductivity (S / cm) gradually increases with increasing temperature.

[0062] Figure 8 The Arrhenius diagram of the CTGU-COF material shows that the CTGU-COF material transports H + The required activation energy is less than 0.4 eV, which belongs to the proton skipping mechanism and is consistent with the design idea of ​​building a hydrogen bond network through the framework.

[0063] Example 2-1

[0064] The testing procedure for the proton conduction performance of COF is the same as in Example 2:

[0065] Add an appropriate amount of powder sample to the tablet press, vibrate to mix, and then pressurize to 350 kg / cm². 2 The pressure was maintained for 30 seconds; then, the sheet sample was removed and its diameter and thickness were measured. The diameter was found to be 4.00 mm, and its thickness still met the requirements for proton conduction performance testing; and the performance remained stable.

[0066] Example 2-2

[0067] The COF proton conductivity test followed the same procedure as in Example 2: conductive silver paste was applied to both sides of the sheet sample, and the sample was dried at 40°C for 35 minutes. The sample still met the requirements for proton conductivity testing, and the performance remained stable.

[0068] Example 3

[0069] The steps for testing the cyclic stability of COF are as follows:

[0070] By setting the humidity to 98%RH through the program, the temperature was first increased from 30℃ to 90℃, and then decreased from 90℃ to 30℃. After two consecutive heating and cooling cycles, the test results showed that the proton conductivity of the material did not change significantly, proving the excellent cycle stability of the material.

[0071] The above description is merely a preferred embodiment of the present invention and does not limit the scope of the invention. Therefore, any equivalent or modified versions made without departing from the spirit disclosed in the present invention are within the protection scope of the present invention.

Claims

1. A proton conductor for a fuel cell, characterized in that, This includes alkynyl-modified acylhydrazone covalent organic framework materials. The structural formulas of the alkynyl-modified acylhydrazone covalent organic framework materials are as follows: 。 2. The proton conductor for a fuel cell according to claim 1, characterized in that, The organic framework material includes characteristic diffraction peaks that appear around 2θ angles of approximately 3°, 7°, and 27°.

3. The proton conductor for a fuel cell according to claim 1, characterized in that, The organic framework material is contained in approximately 3305 cm -1 2125 cm -1 and 1643 cm -1 The location shows a characteristic infrared absorption peak.

4. The proton conductor for a fuel cell according to any one of claims 1-3, characterized in that, The preparation method of alkynyl-modified acylhydrazone covalent organic framework materials includes the following steps: After mixing 2,5-bis(2-propynoxy)terephthalohydrazide and 1,3,5-tricarboxymethylphloroglucinol in a reaction flask, an organic solvent was added, and the mixture was ultrasonically dispersed. Then, an acid solution was added as a catalyst. The product was then rapidly frozen, evacuated, and heated in an oil bath after being sealed. After the oil bath reaction was completed, the resulting solid product was washed with solvent and extracted for a certain period of time before being filtered and dried to obtain an alkynyl-modified acylhydrazone covalent organic framework material.

5. The proton conductor for a fuel cell according to claim 4, characterized in that, The molar ratio of 2,5-bis(2-propynoxy)terephthalohydrazide to 1,3,5-tricarboxymethylphloroglucinol is 1 - 3: 1 - 3.

6. The proton conductor for a fuel cell according to claim 4, characterized in that, The organic solvent is one or a combination of N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, mesitylene, 1,4-dioxane, o-dihydrobenzene, n-butanol and benzyl alcohol.

7. The proton conductor for a fuel cell according to claim 4, characterized in that, The acid solution is an aqueous solution of acetic acid or hydrochloric acid; the concentration of the acid solution is 3 M-12 M.

8. The proton conductor for a fuel cell according to claim 4, characterized in that, The reaction temperature range of the oil bath heating is 100-150℃; the reaction time of the oil bath heating is 12-144 h.

9. The proton conductor for a fuel cell according to claim 8, characterized in that, The reaction temperature range of the oil bath heating is 100-120 ℃; the reaction time of the oil bath heating is 36-48 h.

10. The proton conductor for a fuel cell according to claim 4, characterized in that, The solvent selected for extraction is one of acetone, ethyl acetate, dichloromethane, methanol, ethanol, 1,4-dioxane, and tetrahydrofuran; the extraction time is 12-72 h.

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