Preparation method and application of a bi-hof catalyst

Abstract

The application discloses a preparation method and application of a Bi-HOF catalyst. The synthesis method of the catalyst comprises the following steps: dissolving 1,3,5-benzene tricarboxylic acid and melamine respectively, mixing, stirring, transferring to a reaction kettle for a solvothermal reaction, centrifugal washing and drying to obtain a HOF precursor; dispersing the obtained HOF in deionized water, adding a bismuth nitrate pentahydrate solution, stirring, transferring to a reaction kettle for a solvothermal reaction, centrifugal washing and drying to obtain the Bi-HOF catalyst. The synthesized Bi-HOF catalyst is applied to the preparation of formic acid by reduction of carbon dioxide, the special hollow tubular structure exposes rich active sites, the one-dimensional tubular channel significantly improves the mass transfer efficiency of reactants / products, and the Bi-HOF catalyst has the advantages of high current density, high Faraday efficiency and good stability. Meanwhile, the synthesis method has the advantages of small solvent consumption, small pollution and large yield, and provides a new idea for the method for preparing formic acid by reduction of carbon dioxide.

Description

Technical Field

[0001] This invention relates to the field of catalyst preparation, specifically to a method for preparing and applying a Bi-HOF catalyst. Background Technology

[0002] The catalytic reduction of carbon dioxide to formic acid (HCOOH) has attracted much attention due to the ease of storage and transportation of the products and their high economic value. Currently, although noble metal catalysts (such as Au and Ag) exhibit high catalytic activity for carbon dioxide reduction, their high cost limits their large-scale industrial application.

[0003] Metal-organic frameworks (MOFs) and hydrogen-bonded organic frameworks (HOFs) have shown great potential in the CO2RR field due to their tunable pore structures and abundant active sites. However, traditional MOFs / HOFs materials suffer from the following key problems: 1) high cost, requiring large amounts of organic solvents for synthesis; 2) a gap between small-scale laboratory synthesis and industrial production, making it difficult to guarantee yield, purity, and consistency; and 3) poor electronic conductivity affecting catalytic efficiency. Especially for HOFs, although they offer advantages such as mild synthesis conditions and strong structural designability, conventional preparation methods struggle to achieve precise morphology control, resulting in catalytic performance that fails to meet industrial requirements.

[0004] This invention innovatively develops a hollow tubular Bi-HOF catalyst, achieving multiple advantages through unique morphology design:

[0005] (1) The hollow tubular structure exposes abundant active sites;

[0006] (2) One-dimensional tubular channels significantly improve the mass transfer efficiency of reactants / products;

[0007] (3) The bismuth metal center in the structure works synergistically with the organic ligands to optimize the carbon dioxide activation energy barrier and the formic acid generation pathway.

[0008] The catalyst was prepared by precisely controlling the self-assembly process of 1,3,5-benzenetricarboxylic acid and melamine, combined with the coordination effect of bismuth metal, successfully constructing a Bi-HOF material with a regular hollow tubular structure. Experiments show that this unique structural design enables the catalyst to exhibit excellent catalytic activity and stability in the catalytic reduction of carbon dioxide to formic acid, providing an innovative solution to the key problems currently faced by CO2RR catalysts. Summary of the Invention

[0009] The purpose of this invention is to synthesize a Bi-HOF catalyst with a hollow tubular morphology, which has a good supporting structure and can optimize the electron transport path, ultimately achieving efficient catalytic reduction of carbon dioxide to formic acid, thus meeting the industrial needs of energy recycling.

[0010] The present invention solves the problem through the following technical solution:

[0011] A method for synthesizing a Bi-HOF catalyst includes the following steps:

[0012] Step 1: Dissolve 1,3,5-benzenetricarboxylic acid and melamine in anhydrous methanol and deionized water, respectively;

[0013] Step 2: Mix the two solutions obtained in Step 1 and stir thoroughly;

[0014] Step 3: The solution obtained in Step 2 is subjected to a solvothermal reaction to obtain the HOF template, which is then centrifuged, washed, and dried.

[0015] Step 4: Disperse the HOF obtained in Step 3 in deionized water and mix it thoroughly with bismuth nitrate pentahydrate solution.

[0016] Step 5: After thorough stirring, the solution is subjected to a solvothermal reaction, followed by centrifugation, washing, and drying to obtain the Bi-HOF catalyst.

[0017] The above preparation method yields a Bi-HOF catalyst material. This material will be used to catalyze the reduction of carbon dioxide to formic acid.

[0018] Compared with the prior art, the present invention has the following significant advantages: (1) less solvent is used, less pollution, and larger output; (2) the hollow tubular structure provides multiple active sites for exposure and optimizes the electron transport path; (3) it has good stability and formic acid selectivity. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the synthesis route for the Bi-HOF catalyst.

[0020] Figure 2 This is a field emission scanning electron microscope (SEM) image of the HOF precursor in Example 1.

[0021] Figure 3 These are field emission transmission electron microscope (TEM) images of Bi-HOF in Example 1, as well as elemental distribution diagrams of bismuth, carbon, oxygen, and nitrogen.

[0022] Figure 4 These are the X-ray diffraction (XRD) patterns of Example 1, Comparative Examples 1, 2, and 3.

[0023] Figure 5 This is a field emission scanning electron microscope (SEM) image of Comparative Example 1.

[0024] Figure 6 This is a field emission scanning electron microscope (SEM) image of Comparative Example 2.

[0025] Figure 7 This is a field emission scanning electron microscope (SEM) image of Comparative Example 3. Detailed Implementation

[0026] The present invention will be further described in conjunction with the accompanying drawings and embodiments:

[0027] The present invention will now be described in detail through specific embodiments, examples of which are illustrated in the accompanying drawings. It should be noted that the same or similar reference numerals in the drawings always correspond to the same or similar technical features, or components having the same or similar functions. These embodiments described with reference to the accompanying drawings are only used to explain the technical solutions of the present invention, and are not intended to limit the scope of protection of the present invention.

[0028] It should be understood in the description of this invention that the terms "load" and "assembly" should be interpreted broadly in this invention, including but not limited to material composite methods such as chemical bonding, physical adsorption, and in-situ growth.

[0029] In the description of this invention, it should be understood that "hollow tubular structure" specifically refers to a micromorphology with an axially continuous channel (as shown in the attached figure). Figure 3 (As shown). The terms "inner" and "outer" refer to the inner and outer walls of the hollow channel, respectively, when describing tubular structures.

[0030] To enable those skilled in the art to better understand the technical solutions of the present invention, the implementation technical solutions of the present invention will be further described below with reference to the accompanying drawings and through specific embodiments and comparative examples.

[0031] Combination Figure 1 This invention provides a method for preparing a Bi-HOF carbon dioxide reduction catalyst, comprising the following steps:

[0032] Step 1: Dissolve 1,3,5-benzenetricarboxylic acid and melamine in anhydrous methanol and deionized water, respectively;

[0033] Step 2: Mix the two solutions obtained in Step 1 and stir thoroughly;

[0034] Step 3: The solution obtained in Step 2 is subjected to a solvothermal reaction to obtain the HOF template, which is then centrifuged, washed, and dried.

[0035] Step 4: Disperse the HOF obtained in Step 3 in deionized water and mix it thoroughly with bismuth nitrate pentahydrate solution.

[0036] Step 5: After thorough stirring, the solution is subjected to a solvothermal reaction, followed by centrifugation, washing, and drying to obtain the Bi-HOF catalyst.

[0037] Based on the above technical solution, in step one, the molar ratio of 1,3,5-benzenetricarboxylic acid and melamine is (1-2):1, and the volume ratio of anhydrous methanol and deionized water is (1-2):1. Preferably, the molar ratio of 1,3,5-benzenetricarboxylic acid and melamine is 1:1, and the volume ratio of anhydrous methanol and deionized water is 1:1.

[0038] Based on the above technical solution, the stirring time in step two is 30-60 minutes. Preferably, the stirring time is 30 minutes.

[0039] Based on the above technical solution, in step three, the solvothermal reaction involves a heating rate of 5–10 °C / min, heating to 120–150 °C, and holding at that temperature for 10–14 h. The stock solution is centrifuged once at 5000–10000 rpm for 5–10 minutes, washed 3–6 times with deionized water, methanol, or ethanol, and dried at 50–70 °C for 12–24 h. Preferably, the heating rate is 5 °C / min, heating to 150 °C, and holding at that temperature for 12 h; the centrifugation speed is 10000 rpm for 5 minutes, the solution is washed twice with deionized water and once with methanol, and dried at 60 °C for 12 h.

[0040] Based on the above technical solution, in step four, the mass ratio of HOF and bismuth nitrate pentahydrate is (1-2):1; HOF is dispersed in 20-40 mL of deionized water; and the ratio of DMF to deionized water in the DMF solution is 1:(4-8). Preferably, the mass ratio of HOF and bismuth nitrate pentahydrate is 1:1; HOF is dispersed in 20 mL of deionized water; and the ratio of DMF to deionized water in the DMF solution is 1:4.

[0041] Based on the above technical solution, the solvothermal reaction in step five has a heating rate of 5–10 °C / min, reaching 100–120 °C, and holding at that temperature for 2–24 h. Preferably, the heating rate is 5 °C / min, reaching 100 °C, and holding at that temperature for 24 h. The centrifugal drying and washing procedures are the same as described in step three.

[0042] Example 1

[0043] Step 1: Dissolve 2.4 mmol of 1,3,5-benzenetriacrylic acid and 2.4 mmol of melamine in 35 mL of methanol and deionized water, respectively.

[0044] Step 2: Mix the two solutions formed in Step 1 and stir at room temperature for 30 minutes.

[0045] Step 3: Transfer the mixed solution formed in Step 2 to a 100 mL reaction vessel and heat it to 150 °C at a heating rate of 5 °C / min. Hold at this temperature for 12 h.

[0046] Step four: Centrifuge the HOF precursor obtained in step three once, wash twice with deionized water, and finally wash once with methanol. Centrifuge at 10,000 rpm for 5 minutes. Transfer the product to a 60°C vacuum oven and dry for 12 hours before recovering the powder.

[0047] Step 5: Weigh 300 mg of bismuth nitrate pentahydrate and dissolve it in 10 mL of DMF solution and 40 mL of deionized water; weigh 300 mg of HOF obtained in step 4 and disperse it in 20 mL of deionized water.

[0048] Step six: Mix the two liquids obtained in step five and stir at room temperature for 30 minutes. Then transfer them to a reaction vessel and heat to 100°C at a rate of 5°C / min, and maintain the temperature for 24 hours.

[0049] Step 7: Centrifuge, wash and dry the product obtained in Step 6, following the same procedure as described in Step 4.

[0050] Comparative Example 1

[0051] Step 1: Dissolve 2.4 mmol of 1,3,5-benzenetriacrylic acid and 2.4 mmol of melamine in 35 mL of methanol and deionized water, respectively.

[0052] Step 2: Mix the two solutions formed in Step 1 and stir at room temperature for 30 minutes.

[0053] Step 3: Transfer the mixed solution formed in Step 2 to a 100 mL reaction vessel and heat it to 150 °C at a heating rate of 5 °C / min. Hold at this temperature for 12 h.

[0054] Step four: Centrifuge the HOF precursor obtained in step three once, wash twice with deionized water, and finally wash once with methanol. Centrifuge at 10,000 rpm for 5 minutes. Transfer the product to a 60°C vacuum oven and dry for 12 hours before recovering the powder.

[0055] Step 5: Weigh 300 mg of bismuth nitrate pentahydrate and dissolve it in 10 mL of DMF solution and 40 mL of deionized water; weigh 300 mg of HOF obtained in step 4 and disperse it in 20 mL of deionized water.

[0056] Step six: Mix the two liquids obtained in step five and stir at room temperature for 30 minutes. Then transfer them to a reaction vessel and heat to 100°C at a rate of 5°C / min, and hold at that temperature for 2 hours.

[0057] Step 7: Centrifuge, wash and dry the product obtained in Step 6, following the same procedure as described in Step 4.

[0058] Comparative Example 2

[0059] Step 1: Dissolve 2.4 mmol of 1,3,5-benzenetriacrylic acid and 2.4 mmol of melamine in 35 mL of methanol and deionized water, respectively.

[0060] Step 2: Mix the two solutions formed in Step 1 and stir at room temperature for 30 minutes.

[0061] Step 3: Transfer the mixed solution formed in Step 2 to a 100 mL reaction vessel and heat it to 150 °C at a heating rate of 5 °C / min. Hold at this temperature for 12 h.

[0062] Step four: Centrifuge the HOF precursor obtained in step three once, wash twice with deionized water, and finally wash once with methanol. Centrifuge at 10,000 rpm for 5 minutes. Transfer the product to a 60°C vacuum oven and dry for 12 hours before recovering the powder.

[0063] Step 5: Weigh 300 mg of bismuth nitrate pentahydrate and dissolve it in 10 mL of DMF solution and 40 mL of deionized water; weigh 300 mg of HOF obtained in step 4 and disperse it in 20 mL of deionized water.

[0064] Step 6: Mix the two liquids obtained in Step 5 and stir at room temperature for 30 minutes. Then transfer them to a reaction vessel and heat to 100°C at a rate of 5°C / min, and hold at that temperature for 6 hours.

[0065] Step 7: Centrifuge, wash and dry the product obtained in Step 6, following the same procedure as described in Step 4.

[0066] Comparative Example 3

[0067] Step 1: Dissolve 2.4 mmol of 1,3,5-benzenetriacrylic acid and 2.4 mmol of melamine in 35 mL of methanol and deionized water, respectively.

[0068] Step 2: Mix the two solutions formed in Step 1 and stir at room temperature for 30 minutes.

[0069] Step 3: Transfer the mixed solution formed in Step 2 to a 100 mL reaction vessel and heat it to 150 °C at a heating rate of 5 °C / min. Hold at this temperature for 12 h.

[0070] Step four: Centrifuge the HOF precursor obtained in step three once, wash twice with deionized water, and finally wash once with methanol. Centrifuge at 10,000 rpm for 5 minutes. Transfer the product to a 60°C vacuum oven and dry for 12 hours before recovering the powder.

[0071] Step 5: Weigh 300 mg of bismuth nitrate pentahydrate and dissolve it in 10 mL of DMF solution and 40 mL of deionized water; weigh 300 mg of HOF obtained in step 4 and disperse it in 20 mL of deionized water.

[0072] Step six: Mix the two liquids obtained in step five and stir at room temperature for 30 minutes. Then transfer them to a reaction vessel and heat to 100°C at a rate of 5°C / min, and hold at that temperature for 12 hours.

[0073] Step 7: Centrifuge, wash and dry the product obtained in Step 6, following the same procedure as described in Step 4.

[0074] Both the examples and comparative examples were tested in an H-type electrolytic cell. The electroreduction performance of carbon dioxide was tested using a three-electrode system, with Bi-HOF-loaded carbon paper as the working electrode, a Pt electrode as the counter electrode, and a saturated Ag / AgCl electrode as the reference electrode. A 0.5 mol·L⁻¹ electrode was used. -1 The KHCO3 solution was used as the electrolyte. The electroreduction performance of CO2 was tested using a chronoamperometry method, with a test potential range of -0.7 to -1.2 V (vs. RHE) for 30 min, and a constant CO2 flow rate of 20 mL / min. -1 The liquid products after the reaction were detected by 1H NMR spectroscopy, and the gaseous products were detected by gas chromatography. The Faraday efficiency was calculated.

[0075] The results of the Faraday efficiency test are shown in Table 1.

[0076] Table 1. Results of formic acid selectivity in Example 1 and Comparative Examples 1, 2, and 3

[0077] Group FE(HCOOH) other Example 1 96.1％ 3.9％ Comparative Example 1 89.7％ 10.3％ Comparative Example 2 91.2％ 8.8％ Comparative Example 3 93.4％ 6.6％

[0078] Table 1 shows that different solvothermal reaction times have a significant impact on the formic acid selectivity of Bi-HOF. As the solvothermal reaction time increases, the formic acid selectivity of Bi-HOF gradually increases, with Example 1 exhibiting the highest Faraday efficiency of 96.1%. This is because, with longer solvothermal time, the structure of the hollow nanotubes tends to stabilize, the bismuth element is more uniformly distributed, and the resulting coordination environment is more suitable for the formation of formic acid products.

[0079] Figure 1 This is a schematic diagram of the synthesis route for the Bi-HOF catalyst.

[0080] Figure 2 This is a field emission scanning electron microscope (SEM) image of the HOF precursor in Example 1. The image shows that the HOF precursor exhibits a rod-like structure.

[0081] Figure 3This is a field emission transmission electron microscope (TEM) image of Bi-HOF-24h from Example 1, along with elemental distribution diagrams of bismuth, carbon, oxygen, and nitrogen. The image shows the hollow tubular structure of Bi-HOF-24h and the distribution of different elements; it can be seen from the image that Bi is uniformly distributed within the tube wall.

[0082] Figure 4 These are the X-ray diffraction (XRD) patterns of Example 1, and Comparative Examples 1, 2, and 3. The figures show the XRD patterns of the precursor HOF and Bi-HOF with different solvothermal reaction times. It can be seen from the figures that the precursor HOF has good crystallinity and can still retain some HOF characteristics after adding Bi and undergoing a solvothermal reaction.

[0083] Figure 5 , 6 Figures 7 and 8 show the field emission scanning electron microscope (SEM) images of Comparative Examples 1, 2, and 3. The figures show that as the solvothermal time increases, the original rod-like structure of HOF is maintained, combined with... Figure 3 It can be inferred that as the solvothermal time increases, the Bi-HOF material gradually changes from a solid rod-shaped structure to a hollow tubular structure.

Claims

1. A method for preparing a Bi-HOF catalyst, characterized in that, Includes the following steps: Step 1: Dissolve 1,3,5-benzenetricarboxylic acid and melamine in anhydrous methanol and deionized water, respectively; Step 2: Mix the two solutions obtained in Step 1 and stir thoroughly; Step 3: The solution obtained in Step 2 is subjected to a solvothermal reaction. The solvothermal reaction is carried out at a heating rate of 5-10 °C / min to 120-150 °C, and the temperature is maintained for 10-14 h to obtain the HOF template. The template is then centrifuged, washed, and dried. Step 4: Disperse the HOF obtained in Step 3 in 20-40 mL of deionized water and mix it thoroughly with the DMF solution of bismuth nitrate pentahydrate. The mass ratio of bismuth nitrate pentahydrate to HOF is 1:(1-2), and the volume ratio of deionized water to DMF in the DMF solution is 4-8:

1. The stirring time is 30-60 min. Step 5: The solution after thorough stirring in Step 4 is subjected to a solvothermal reaction. The solvothermal reaction is carried out by heating at a rate of 5-10 °C / min to 100-120 °C and holding at that temperature for 12-24 h. After the reaction is completed, the solution is centrifuged, washed, and dried to obtain a Bi-HOF catalyst with a hollow tubular morphology.

2. The method for preparing the Bi-HOF catalyst according to claim 1, characterized in that, In step one, the molar ratio of 1,3,5-benzenetricarboxylic acid to melamine is (1-2):1, and the volume ratio of anhydrous methanol to deionized water is (1-2):

1.

3. The method for preparing the Bi-HOF catalyst according to claim 1, characterized in that, The stirring time for step two is 30 to 60 minutes.

4. The method for preparing the Bi-HOF catalyst according to claim 1, characterized in that, In step three, the centrifugation speed is 5000-10000 rpm, the centrifugation time is 5-10 min, the washing solvent is deionized water, methanol or ethanol solution, the number of washings is 3-5, the drying temperature is 50-70 ℃, and the time is 12-24 h.

5. A Bi-HOF catalyst, characterized in that, The Bi-HOF catalyst is prepared by the method described in any one of claims 1 to 4.

6. The application of the Bi-HOF catalyst as described in claim 5 in the reduction of carbon dioxide to formic acid.

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