A functional group modified two-dimensional imidazole-based covalent organic framework material, a preparation method and applications thereof

Abstract

The application belongs to the technical field of covalent organic framework materials, and particularly relates to a functional group modified two-dimensional imidazole-based covalent organic framework material, a preparation method and application thereof. The two-dimensional imidazole-based covalent organic framework material synthesized by the application introduces a strong electron-withdrawing group through design, increases an electrochemical active site, adjusts the charge density of the COF, and improves the electrocatalytic performance thereof. Meanwhile, the unique high specific surface area and uniformly distributed pores of the OH-COF provide an electron and ion transmission channel, so that the OH-COF has excellent electrocatalytic oxygen reduction reaction (ORR) performance and can be practically applied in the field of metal-air batteries.

Description

Technical Field

[0001] This invention belongs to the field of covalent organic framework materials technology, specifically relating to a two-dimensional imidazole-based covalent organic framework material modified with functional groups, its preparation method, and its application. Background Technology

[0002] The oxygen reduction reaction (ORR) is a crucial half-reaction in next-generation energy storage and conversion systems such as fuel cells and metal-air batteries. Metal-free carbon-based catalysts, with their advantages of inexpensive and abundant sources, high activity, stability, and large specific surface area, have attracted considerable attention in ORR catalysis and are considered the most promising alternative to Pt-based catalysts. Current methods for improving the catalytic performance of metal-free carbon-based materials mainly include defect engineering, heteroatom doping, and surface modification. However, the active sites of carbon-based materials cannot be precisely controlled, and determining the location and number of their catalytic active sites remains a significant challenge. Therefore, developing metal-free catalysts with well-defined and abundant active sites is of great importance for ORR. Summary of the Invention

[0003] The purpose of this invention is to provide a functionally modified two-dimensional imidazole-based covalent organic framework material, its preparation method, and its application, for electrocatalysis of 4e... - ORR's 2D COFs material offers a new design approach.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0005] A two-dimensional imidazole-based covalent organic framework material modified with functional groups, the structural formula of which is as follows:

[0006]

[0007] This invention further provides a method for preparing the covalent organic framework material, using 2,7-di-tert-butylpyrene-4,5,9,10-tetraone, ammonium acetate, and substance A as raw materials, and preparing the covalent organic framework material OH-COF via a one-pot three-component Debus-Radziszewski condensation reaction using a solvothermal method; substance A is 5'-(4-formyl-3-hydroxyphenyl)-3,3”-dihydroxy-[1,1':3',1”-terphenyl]-4,4”-dicarboxaldehyde, with the following structural formula:

[0008]

[0009] Further, 2,7-di-tert-butylpyrene-4,5,9,10-tetraone, ammonium acetate, and substance A were placed in a reaction vessel, and mesitylene and dioxane were added. After thorough mixing, the air was removed and the reaction was sealed. The reaction mixture was purified to obtain the covalent organic framework material.

[0010] Furthermore, the molar ratio of 2,7-di-tert-butylpyrene-4,5,9,10-tetraone, ammonium acetate, and substance A is 3:18:2.

[0011] The volume ratio of mesitylene to dioxane is 1:1. There are no special requirements for the amount added, as long as it can dissolve the raw materials.

[0012] Furthermore, the reaction of the present invention is carried out in a Pyrex tube. After adding mesitylene and dioxane, the mixture is ultrasonically mixed for about 1 minute. Then, the air in the Pyrex tube is removed by three freeze-pump-thaw cycles.

[0013] The sealing reaction involves sealing the tube neck with a flame, cooling it to room temperature, and then placing it in an oven for reaction, preferably at 150°C for 5 days.

[0014] The sealing process uses butane gas as fuel.

[0015] The reactants were purified by washing multiple times with anhydrous ethanol and tetrahydrofuran after the reaction, extracting with tetrahydrofuran for 48 hours, and drying in a vacuum at 80°C for 12 hours.

[0016] The covalent organic framework material described above can be well applied in electrocatalytic oxygen reduction reactions.

[0017] Furthermore, the covalent organic framework material is ground and uniformly dispersed in a mixed solution of Nafion, isopropanol and anhydrous ethanol, and the solution is added dropwise to the working electrode during use.

[0018] Specifically, Nafion, isopropanol, and anhydrous ethanol can be ultrasonically dispersed and thoroughly mixed at room temperature.

[0019] The preferred volume ratio of Nafion, isopropanol, and anhydrous ethanol is 2:3:95.

[0020] Covalent organic frameworks (COFs) are a new class of organic crystalline materials with periodic topologies formed by the thermodynamically reversible polymerization of small organic monomers. Due to their advantages such as designable structure, functional diversity, high specific surface area, uniform pore distribution, and good stability, they are widely used in gas storage and separation, catalysis, biomedicine, and chemical sensing. Furthermore, the excellent charge transport capabilities and predictable active sites of COFs make them suitable for use as ORR electrocatalysts.

[0021] This invention designs a COF structure by rationally selecting monomers with strong electron-withdrawing groups (-OH). Based on the Debus-Radziszewski condensation reaction, it not only introduces new electrochemical active sites but also modulates the band structure of the COF framework and the electronic environment of the original active site (imidazolium ring). Simultaneously, the high specific surface area and uniformly distributed pores unique to OH-COF provide electron and ion transport channels, giving it excellent electrocatalytic oxygen reduction reaction (ORR) performance. Furthermore, a zinc-air battery assembled from OH-COF can light up an LED panel, demonstrating that OH-COF can be practically applied in the field of metal-air batteries. Moreover, this catalytic material is metal-free and environmentally friendly.

[0022] Compared with the prior art, the advantages of the present invention are as follows:

[0023] The two-dimensional imidazole-based covalent organic framework material synthesized in this invention increases the electrochemical active sites by introducing strong electron-withdrawing groups and improves the electrocatalytic performance by adjusting the charge density of COFs. At the same time, the high specific surface area and uniformly distributed pores of OH-COF provide electron and ion transport channels, giving it excellent electrocatalytic oxygen reduction reaction energy and making it practically applicable in the field of metal-air batteries. Attached Figure Description

[0024] Figure 1 This is a schematic diagram illustrating the synthesis process of the functionally modified two-dimensional imidazole covalent organic framework material (OH-COF) of the present invention and the comparative sample H-COF;

[0025] Figure 2 The powder X-ray diffraction (PXRD) patterns of OH-COF synthesized in Example 1 of this invention and the comparative sample H-COF are shown.

[0026] Figure 3 The Fourier transform infrared spectra of the synthesized OH-COF, the comparative sample H-COF, and the raw material monomers in Example 1 of this invention are shown below.

[0027] Figure 4 The N2 adsorption-desorption isotherms of OH-COF synthesized in Example 1 of this invention and the comparative sample H-COF are shown.

[0028] Figure 5 The pore size distribution diagrams are shown for the OH-COF synthesized in Example 1 of this invention and the comparative sample H-COF.

[0029] Figure 6 The solid-state nuclear magnetic resonance spectra of OH-COF synthesized in Example 1 of this invention and the comparative sample H-COF are shown below.

[0030] Figure 7The contact angles of OH-COF synthesized in Example 1 of this invention and the comparative sample H-COF are shown.

[0031] Figure 8 The LSV curves of the electrocatalytic ORR process of OH-COF synthesized in Example 1 of this invention and the comparative sample H-COF are shown.

[0032] Figure 9 The Tafel slopes of the electrocatalytic ORR process of OH-COF synthesized in Example 1 of this invention and the comparative sample H-COF are shown.

[0033] Figure 10 The above are ECSA diagrams of the electrocatalytic ORR process of OH-COF synthesized in Example 1 of this invention and the comparative sample H-COF.

[0034] Figure 11 The graph shows the number of electrons transferred and the H2O2 yield during the electrocatalytic ORR process of OH-COF synthesized in Example 1 of this invention and the comparative sample H-COF.

[0035] Figure 12 EIS diagrams of the electrocatalytic ORR process of OH-COF synthesized in Example 1 of this invention and the comparative sample H-COF;

[0036] Figure 13 The LED panel is illuminated by the zinc-air battery assembled from the OH-COF synthesized in Example 1 of this invention. Detailed Implementation

[0037] The technical solution of the present invention is illustrated below with specific embodiments, but the scope of protection of the present invention is not limited thereto:

[0038] Example 1

[0039] A functionalized two-dimensional imidazole-based covalent organic framework was synthesized using 2,7-di-tert-butylpyrene-4,5,9,10-tetraone, ammonium acetate, and 5'-(4-formyl-3-hydroxyphenyl)-3,3”-dihydroxy-[1,1':3',1”-terphenyl]-4,4”-dicarboxaldehyde as raw materials via a one-pot three-component Debus-Radziszewski condensation reaction via a solvothermal method. The specific reaction process is as follows: Figure 1 As shown.

[0040] The specific steps are as follows:

[0041] 2,7-Di-tert-butylpyrene-4,5,9,10-tetraone (18 mg, 0.048 mmol), ammonium acetate (22 mg, 0.288 mmol), and 5'-(4-formyl-3-hydroxyphenyl)-3,3”-dihydroxy-[1,1':3',1”-terphenyl]-4,4”-dicarboxaldehyde (14 mg, 0.032 mmol) were added to a Pyrex tube. Trimethylbenzene (0.5 mL) and dioxane (0.5 mL) were added to the tube, and the mixture was sonicated for 1 min to remove air. The tube neck was sealed with a flame and cooled to room temperature. The tube was then placed in a 150°C oven for 5 days. After the reaction was completed, the tube was washed several times with anhydrous ethanol and tetrahydrofuran, and extracted with tetrahydrofuran for 48 hours. The tube was then dried in a vacuum oven at 80°C for 12 hours to obtain an orange-yellow powder, namely OH-COF.

[0042] Example 2-Example 12

[0043] For the parameters in the variation embodiment, please refer to the table below. Other parameters are the same as in Embodiment 1.

[0044] Example solvent catalyst Temperature (°C) Time and Atmosphere Crystallinity 2 Dioxane ammonium acetate 150 5 days, vacuum amorphous 3 n-Butanol: o-Dichlorobenzene = 1:1 ammonium acetate 150 5 days, vacuum amorphous 4 Dioxane: Trimethylbenzene = 1:1 ammonium acetate 150 5 days, vacuum High crystallinity 5 Dioxane: Trimethylbenzene = 1:1 ammonium acetate 150 3 days, vacuum amorphous 6 Dioxane: Ethanol = 1:1 ammonium acetate 150 5 days, vacuum Medium crystallization 7 Dioxane: Trimethylbenzene = 3:2 ammonium acetate 150 5 days, vacuum Low crystallinity 8 Dioxane: Trimethylbenzene = 4:1 ammonium acetate 150 5 days, vacuum Low crystallinity 9 Dioxane: Trimethylbenzene = 9:1 ammonium acetate 150 5 days, vacuum amorphous 10 Dioxane: Trimethylbenzene = 2:3 ammonium acetate 150 5 days, vacuum Low crystallinity 11 Dioxane: Trimethylbenzene = 1:4 ammonium acetate 150 5 days, vacuum amorphous 12 n-Butanol:Dioxane:o-dichlorobenzene = 9:4:1 ammonium acetate 150 5 days, vacuum amorphous

[0045] Preparation of control sample:

[0046] The 5'-(4-formyl-3-hydroxyphenyl)-3,3”-dihydroxy-[1,1':3',1”-terphenyl]-4,4”-dicarboxaldehyde was replaced with 1,3,5-tris(p-formylphenyl)benzene (structural formula below).

[0047]

[0048] The specific steps are as follows:

[0049] 2,7-Di-tert-butylpyrene-4,5,9,10-tetraone (17 mg, 0.045 mmol), ammonium acetate (21 mg, 0.27 mmol), and 1,3,5-tris(p-formylphenyl)benzene (12 mg, 0.030 mmol) were added to a Pyrex tube, along with 0.8 mL of mesitylene and 0.2 mL of dioxane. The mixture was sonicated for 1 min to ensure homogeneity. The air in the Pyrex tube was removed by three freeze-pump-thaw cycles. The tube neck was then sealed with a flame. After cooling to room temperature, the tube was placed in a 150°C oven and reacted for 5 days. After the reaction was complete, the tube was washed multiple times with anhydrous ethanol and tetrahydrofuran, and extracted with tetrahydrofuran for 48 hours. The tube was then dried in a vacuum oven at 80°C for 12 hours to obtain a yellow-green powder, namely H-COF.

[0050] For detailed characterization of the obtained OH-COF (product of Example 1) and H-COF (comparative sample), please refer to [link to relevant documentation]. Figure 2-7 .

[0051] Figure 2 The figure shows the powder X-ray diffraction patterns of OH-COF and H-COF. As shown in the figure, there are obvious diffraction peaks at 2θ of 3.3° and 3.2°, which correspond to the diffraction peaks of OH-COF and H-COF, respectively, proving the successful synthesis of crystalline OH-COF and H-COF.

[0052] Figure 3 The figures show the Fourier transform infrared (FTIR) spectra of OH-COF, H-COF, and their corresponding raw material monomers. The figures show that at 1620 cm⁻¹... -1 and 3450cm -1 There are obvious stretching vibration peaks nearby, corresponding to the C=N and NH bonds of the imidazole ring in the COF structure, respectively; in addition, at 3210 cm⁻¹... -1 There is a broad absorption peak nearby, corresponding to the stretching vibration peak of the intermolecular hydrogen bonds in OH-COF, which indicates the successful construction of OH-COF and H-COF materials.

[0053] Figure 4 The N2 adsorption-desorption isotherms for OH-COF and H-COF are given. Based on the Brunauer-Emmett-Teller theory, the specific surface areas of OH-COF and H-COF are calculated to be 664.57 m². 2 / g and 538.36m 2 / g.

[0054] Figure 5 The diagram shows the pore size distribution of OH-COF and H-COF. Calculations using local density functional theory show that the main pore size of OH-COF and H-COF is 1.57 nm, indicating that the synthesized OH-COF and H-COF materials have a microporous structure.

[0055] Figure 6 The figures show the solid-state NMR spectra of OH-COF and H-COF. The figures reveal typical carbon atom resonance signals of the imidazole ring at chemical shifts of 157, 127, and 119 ppm, confirming the presence of the imidazole moiety in the COF structure.

[0056] Figure 7 The figures show the contact angles of OH-COF and H-COF. As can be seen from the figure, the contact angles of OH-COF and H-COF are 100° and 119°, respectively, indicating that OH-COF and H-COF materials are hydrophobic. Meanwhile, the intermolecular hydrogen bonds present in OH-COF are hydrophilic, which reduces the contact angle of OH-COF.

[0057] application:

[0058] Add 5 mg OH-COF and 5 mg CNT to a mixture of 950 μL anhydrous ethanol, 30 μL isopropanol, and 20 μL Nafion solution. Disperse the mixture ultrasonically at 25°C for 60 minutes. Take 5 μL of the mixture and evenly coat it onto a 0.19625 cm⁻¹ plate. -2 The catalyst was naturally air-dried on the working electrode, and this process was repeated three times to obtain a glassy carbon electrode with the catalyst uniformly covered.

[0059] Electrochemical tests were conducted at room temperature (25±1℃) using a three-electrode cell with a rotating disk electrode (RDE) system on an electrochemical workstation (Shanghai Chenhua CHI660) to evaluate the ORR performance. A 0.1 mol L⁻¹ solution was used. -1 KOH solution was used as the electrolyte, and a glassy carbon electrode (GC, 0.19625 cm⁻¹) was selected. 2 Platinum wire and silver / silver chloride electrodes were used as working electrodes, counter electrodes, and reference electrodes, respectively, and the potentials used were all converted to reversible hydrogen electrode (RHE).

[0060] Figure 8 Linear sweep voltammetry (LSV) curves of the electrocatalytic ORR process for OH-COF and the control sample H-COF are shown. The LSV curves were obtained at a rotation speed of 1600 rpm and a scan rate of 10 mV / s. -1 0.1 mol L of oxygen saturated -1 It was obtained from KOH solution. As shown in the figure, the initial potential (E) of OH-COF... on ), half-wave potential (E) 1 / 2 ) and current density (J k The values ​​were 0.89V vs. RHE, 0.80V vs. RHE, and 4.87mA cm, respectively. -2 All are higher than H-COF(E) on =0.79V vs. RHE, E 1 / 2 =0.63V vs. RHE, J k =2.5mA cm -2 This indicates that OH-COF with functional groups has higher catalytic performance.

[0061] Figure 9 The figures show the Tafel slopes of the electrocatalytic ORR process for OH-COF and the control sample H-COF. The Tafel slope is calculated based on the LSV curve using the Tafel formula: η = a + b * log|j| (where η is the overpotential, j is the current density, and b is the Tafel slope). As shown in the figure, the slope of the fitted curve for OH-COF is 53.7 mF / cm². -2 It is far lower than the 107.5 mF cm of H-COF. -2This indicates that OH-COF has faster reaction kinetics.

[0062] Figure 10 ECSA chromatograms of the electrocatalytic ORR process for OH-COF and the control sample H-COF are shown. The scan rates (10, 20, 30, 40, and 50 mV s) were varied. -1 ), to obtain at 0.1 mol L -1 The CV curves were tested in KOH solution to obtain the effective electrode surface area (ECSA) of the COF material. The scan rates were varied (10, 20, 30, 40, and 50 mV s). -1 The obtained CV curves were plotted using the double-layer current against the scan rate. The slope of the resulting straight line represents the double-layer capacitance, which is proportional to the electrochemically active area of ​​the ORR catalyst. In the figure, the double-layer capacitance of OH-COF is 5.65 mF cm⁻¹. -2 The double-layer capacitance of H-COF is greater than 0.074 mF cm. -2 This indicates that OH-COF has a larger active surface area and catalytic active sites.

[0063] Figure 11 The graph shows the number of electrons transferred and the H2O2 yield in the electrocatalytic ORR process for OH-COF and the control sample H-COF. Within the range of 0.2–0.6 V vs. RHE, the number of electrons transferred for H-COF is 2.86–3.28, and the selectivity for H2O2 is 36.16%–56.80%, close to 2e. - In the ORR process, OH-COF has a higher number of transferred electrons, ranging from 3.61 to 3.7, while the selectivity of H2O2 is 14.56% to 17.90%, close to 4e. - ORR procedure.

[0064] This invention employs rotating ring-disk electrode (RRDE) testing to explore the yield of the intermediate product H2O2 and the ORR electron transfer mechanism. The number of electrons transferred and the yield of H2O2 are calculated using the following formula:

[0065]

[0066] In the formula, I d It is the disk current, I r N is the ring current, and N is the current collection efficiency of the ring electrode (N = 37%).

[0067] Figure 12 The image shows the EIS spectra of the electrocatalytic ORR process for OH-COF and the control sample H-COF. Electrochemical impedance spectroscopy (EIS) was performed at a constant potential (10 mA cm⁻¹). -2The results were obtained under test conditions from 100kHz to 0.1Hz with an applied voltage of 5mV. The figure shows that OH-COF has a smaller semi-circle diameter, i.e., charge transfer resistance, further illustrating that OH-COF can effectively promote charge transfer, resulting in lower resistance and better conductivity.

[0068] The zinc-air battery assembled using the OH-COF synthesized in Example 1 of this invention can light up the "ZZU" LED panel, see details. Figure 13 .

[0069] The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, and these simple modifications all fall within the protection scope of the present invention. In addition, the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately. Furthermore, various different embodiments of the present invention can also be arbitrarily combined, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A functional group-modified two-dimensional imidazol-based covalent organic framework material, characterized in that, The structural formula of the covalent organic framework material is as follows:

2. The method of claim 1, wherein the covalent organic framework material is prepared by, The covalent organic framework material OH-COF is prepared by using 2,7-di-tert-butylpyrene-4,5,9,10-tetraone, ammonium acetate and substance A as raw materials, and using a solvent thermal method through a one-pot three-component Debus-Radziszewski condensation reaction; the substance A is 5'-(4-formyl-3-hydroxyphenyl)-3,3"-dihydroxy-[1,1':3',1"-terphenyl]-4,4"-diformaldehyde, and the structural formula is as follows:

3. The method for preparing the covalent organic framework material as described in claim 2, characterized in that, 2,7-di-tert-butylpyrene-4,5,9,10-tetraone, ammonium acetate and substance A are placed in a reaction container, mesitylene and dioxane are added, and after being mixed uniformly, the air in the reaction container is removed and the reaction container is sealed, and the covalent organic framework material is obtained after the reactants are purified.

4. The method for preparing the covalent organic framework material as described in claim 3, characterized in that, The molar ratio of 2,7-di-tert-butylpyrene-4,5,9,10-tetraone, ammonium acetate and substance A is 3:18:

2.

5. The method for preparing the covalent organic framework material as described in claim 3, characterized in that, The volume ratio of mesitylene and dioxane is 1:

1.

6. The method for preparing the covalent organic framework material as described in claim 3, characterized in that, The sealed reaction is that the neck of the tube is flame-sealed, and after being cooled to room temperature, it is placed in a 150℃ oven for reaction for 4-6 days.

7. The covalent organic framework material of claim 1 is used in electrocatalytic oxygen reduction reaction.

8. Use according to claim 7, wherein the compound is ###0002### The covalent organic framework material is ground and uniformly dispersed in a mixed solution of Nafion, isopropanol and anhydrous ethanol, and the mixed solution is added dropwise on the working electrode when used.

9. Use according to claim 8, wherein the compound is ###0002### The volume ratio of the Nafion, isopropanol and anhydrous ethanol is 2:3:95.

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