ZIF-8 material grown on Cu substrate as well as preparation method and application of ZIF-8 material

Abstract

The invention discloses a Cu substrate growing ZIF-8 material and a preparation method and application thereof.The preparation method includes the steps that the material is synthesized at the mild room temperature, a high-added-value chemical is obtained at a cathode, p-nitrobenzoic acid can be electrically reduced into p-aminobenzoic acid at the low potential, the Faraday efficiency reaches up to 996% or above, and the material can be recycled for 6 times or above; the stability is good, and large-scale preparation and the yield of gram level or above can be realized. The catalyst material disclosed by the invention is simple and feasible in preparation process, economical, environment-friendly and easy to treat, and has a wide market application prospect in the fields of industrial electro-catalytic organic synthesis and new energy.

Description

Technical Field

[0001] This invention relates to the field of organic synthesis, specifically to a method for growing ZIF-8 material on a Cu substrate, its preparation, and its applications. Background Technology

[0002] PABA (para-aminobenzoic acid) is an important substrate for the synthesis of various biological scaffolds. Its pharmacological significance is evident in drugs such as folic acid and benzocaine, used to treat certain biological diseases. Although not a vitamin, it is still considered a member of the vitamin B group. PABA deficiency can lead to several conditions, such as unstable white patches on the skin, gray hair, fatigue, depression, and irritability. Besides its important medicinal value, PABA is also used to synthesize various biologically active heterocyclic nuclei, such as benzimidazoles, azidinones, thiazolidinones, and pyrazolines, highlighting its importance as a multifunctional substrate. Para-nitrobenzoic acid (PNBA), as a nitroaromatic pollutant, has adverse effects on the natural environment and human health; therefore, the hydrogenation reduction of PNBA to high-value-added PABA is of extraordinary significance. Electrocatalytic hydrogenation is an economical and sustainable method for preparing high-purity para-aminobenzoic acid (PABA), exhibiting high selectivity, high yield, and Faraday efficiency. However, existing electrocatalysts lack sufficient research, and the low Faradaic efficiency caused by the uncontrollable competitive hydrogen evolution reaction at high overpotentials, coupled with the inherent cycling stability of the materials, hinders their realization. Therefore, utilizing electrocatalytic reduction technology to convert these materials into high-value-added molecules will promote the application of electrocatalytic synthesis technology in industrial production. Summary of the Invention

[0003] The purpose of this section is to summarize some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the abstract and title of this application to avoid obscuring the purpose of this section, the abstract and the title of the invention, and such simplifications or omissions should not be used to limit the scope of the present invention.

[0004] In view of the problems existing in the above and / or prior art, the present invention is proposed.

[0005] Therefore, the purpose of this invention is to overcome the shortcomings of the prior art and provide a method for growing ZIF-8 material on a Cu substrate, as well as its preparation and application.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a method for preparing ZIF-8 material based on Cu substrate growth, characterized in that it includes,

[0007] The copper foam substrate was oxidized to obtain a copper hydroxide precursor.

[0008] After drying, it is first mixed with zinc nitrate hexahydrate methanol solution, and then dimethylimidazolium methanol solution is added to obtain a mixture. After stirring evenly, the reaction is allowed to end at room temperature. The mixture is then washed with anhydrous ethanol and deionized water, ultrasonicated, and vacuum dried to obtain a ZIF-8 material-based heterojunction material grown on a Cu substrate.

[0009] In a preferred embodiment of the preparation method described in this invention, the concentration of zinc nitrate hexahydrate in the mixture is 0.01 mol / L to 0.1 mol / L, and the concentration of dimethylimidazole is 0.05 mol / L to 0.35 mol / L.

[0010] As a preferred embodiment of the preparation method described in this invention, the copper hydroxide precursor is obtained by immersing a conductive substrate electrode in a mixed aqueous solution of alkaline and strong oxidizing salts, followed by ultrasonic treatment in water and anhydrous ethanol, and vacuum drying.

[0011] In a preferred embodiment of the preparation method described in this invention, the conductive substrate electrode material is copper foam; the alkaline solution is either sodium hydroxide solution or potassium hydroxide solution; the strong oxidizing salt liquid includes one or more of ammonium persulfate and sodium persulfate; and the mass ratio of the alkaline solution to the strong oxidizing salt is 2-3:0.5-3.

[0012] As a preferred embodiment of the preparation method of the present invention, the copper hydroxide precursor, after drying, is first mixed with zinc nitrate hexahydrate methanol solution and stirred for 1 hour at a reaction temperature of 20-25°C; the addition of dimethylimidazolium methanol solution is stirred for 1 hour at a reaction temperature of 20-25°C.

[0013] In a preferred embodiment of the preparation method described in this invention, the vacuum drying temperature is 60°C and the time is 5 hours.

[0014] Another objective of this invention is to overcome the shortcomings of the prior art and provide a method for preparing Cu-based ZIF-8 materials.

[0015] Another objective of this invention is to overcome the shortcomings of the prior art and provide a method for preparing ZIF-8 material grown on a Cu substrate, and to apply the product obtained from this method to the electrosynthesis of gram-level p-aminobenzoic acid.

[0016] As a preferred embodiment of the application described in this invention, the application includes electrocatalytic treatment of nitrate-containing wastewater, soil remediation, coatings, anti-counterfeiting, printing, textiles, environmental engineering for toxic gas adsorption, synthesis of pharmaceutical intermediates, and electrocatalytic reduction of organic nitrobenzene and its derivatives to amines.

[0017] As a preferred embodiment of the application described in this invention, the application in the field of electrocatalytic reduction of organic nitrobenzene and its derivatives to amines includes: using the heterojunction material as a cathode catalyst to reduce nitrobenzene and its derivatives to aromatic amines as high-value-added chemicals through electrocatalytic reduction.

[0018] In a preferred embodiment of the application described in this invention, the Cu substrate-grown ZIF-8 material is used as an electrocatalytic reducing agent for electrocatalytic hydrogenation. A stone-ground rod / platinum sheet is used as the counter electrode, a calomel electrode is used as the reference electrode, a neutral PBS solution is used as the electrolyte solution with a pH of around 7, an electrolysis voltage of -0.4V to -0.8V, and a constant voltage reaction time of more than 0.5h.

[0019] Beneficial effects of this invention:

[0020] (1) This invention provides a synthesis scheme for growing ZIF-8 on a rod-shaped structure by oxidizing copper hydroxide on the surface of copper foam, thereby forming negative ZIF-8 particles. This scheme achieves the synthesis of MOFs from a simple precursor at room temperature, optimizing the surface morphology and thus improving the catalytic activity of the material. The synthesis process is simple, can be mass-produced, is environmentally friendly and economical, and has low raw material costs, meeting the requirements of industrial applications. This material exhibits excellent performance in the electrocatalytic reduction of p-nitrobenzoic acid to p-aminobenzoic acid.

[0021] (2) This invention provides a method for preparing the above-mentioned electrode material, which is obtained in two steps: room temperature oxidation and room temperature solvent immersion. Copper foam is immersed in a mixed aqueous solution of alkaline and strong oxidizing salts and allowed to react at 20-30°C for 20 minutes to obtain copper hydroxide (denoted as Cu(OH)2 / CF) grown on the surface of the copper foam. The copper hydroxide substrate solution grown on the surface of the copper foam is then transferred to a zinc nitrate hexahydrate methanol solution and stirred for 1 hour at a reaction temperature of 20-25°C. The sample is washed more than three times with anhydrous ethanol and deionized water, and then vacuum dried at 60°C for 10 hours to obtain the prepared electrode material. This synthesis method is simple and convenient, and the mild conditions are conducive to large-scale industrial production.

[0022] (3) This invention provides a mixed electrode material for growing ZIF-8 on a Cu substrate. Its unique advantage of large-scale preparation makes it widely applicable in the field of electrocatalytic oxidation of small biomass molecules, especially in the electrocatalytic reduction of p-nitrobenzoic acid to p-aminobenzoic acid, exhibiting excellent conversion rate, high selectivity, high Faradaic efficiency, and good stability. The entire reaction process is simple, thus possessing broad market application prospects. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0024] The electrode material is simply referred to as ZIF-8 / Cu(OH)2 / CF.

[0025] Figure 1 The powder X-ray diffraction patterns of the typical ZIF-8 / Cu(OH)2 / CF electrode material and the precursor Cu(OH)2 / CF described in Example 1 are shown.

[0026] Figure 2 The image shows the EDX spectrum of the ZIF-8 / Cu(OH)2 / CF electrode.

[0027] Figure 3 The image shown is a scanning electron microscope (SEM) image of the typical ZIF-8 / Cu(OH)2 / CF electrode material described in Example 1. Figure 3 (ab) is Cu(OH)2 / CF. Figure 3 (cd) is ZIF-8 / Cu(OH)2 / CF.

[0028] Figure 4 The image shows the XPS spectrum of the ZIF-8 / Cu(OH)2 / CF electrode material in Example 1.

[0029] Figure 5 The ZIF-8 / Cu(OH)2 / CF electrode material described in Example 1 is used at 5mVs -1 The polarization curve of the scan rate.

[0030] Figure 6 This is a distribution diagram of the raw materials and products obtained from the ZIF-8 / Cu(OH)2 / CF electrode material described in Example 1.

[0031] Figure 7 The image shows the Faraday efficiency of the ZIF-8 / Cu(OH)2 / CF electrode material in Example 1, representing the cycle stability.

[0032] Figure 8 The polarization curves of the ZIF-8 / Cu(OH)2 / CF electrode material described in Example 1 and the comparative examples 1(1)(2)(3) are shown.

[0033] Figure 9 The images show physical pictures of the ZIF-8 / Cu(OH)2 / CF electrode material described in Example 1 and the materials in Comparative Examples 1 (1)(2)(3).

[0034] Figure 10 The Faraday efficiency and selectivity of the ZIF-8 / Cu(OH)2 / CF electrode materials with different masses of zinc nitrate hexahydrate and dimethylimidazole as described in Examples 4-8 are presented. Detailed Implementation

[0035] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0036] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0037] Secondly, the term "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive of other embodiments.

[0038] Unless otherwise specified, all raw materials used in the examples are commercially available.

[0039] Example 1

[0040] This invention provides a method for large-scale preparation of ZIF-8 material grown on a Cu substrate:

[0041] (1) The copper foam was ultrasonically cleaned in hydrochloric acid, ethanol and aqueous solution for 20 min respectively to obtain a clean copper foam substrate (denoted as CF).

[0042] (2) Dissolve 10g of sodium hydroxide in water and stir well. Then add 5g of ammonium persulfate to this solution and stir well. (The last part, "2×2cm", appears to be a typo and should be left as is.) 2 The copper foam substrate was immersed in the solution and allowed to stand for 20 minutes. It was then washed three times or more with anhydrous ethanol and deionized water, and finally dried in a vacuum drying oven at 60°C for 6 hours to obtain the copper hydroxide precursor (denoted as Cu(OH)₂ / CF).

[0043] (3) Add 1.5g of zinc nitrate hexahydrate to 100mL of methanol solution and stir well. Then, add 2×2cm... 2The Cu(OH)2 / CF precursor was added to the solution and stirred slowly for 1 hour. Then, a methanol solution containing 1.5 g of 2-methylimidazolium was added and stirred for 1 hour. The sample was washed more than 3 times with anhydrous ethanol and deionized water. The prepared sample was then vacuum dried at 60°C for 6 hours to obtain the prepared electrode material (ZIF-8 / Cu(OH)2 / CF).

[0044] Example 2

[0045] The difference from Example 1 is that in step (2), the methanol solution is replaced with an ethanol solution.

[0046] Example 3

[0047] The difference from Example 1 is that the zinc source in step (3) is zinc sulfate.

[0048] Example 4

[0049] The difference from Example 1 is that in step (3), the concentration of zinc nitrate hexahydrate added is 0.0168 mol / L and the concentration of dimethylimidazole is 0.052 mol / L.

[0050] Example 5

[0051] The difference from Example 1 is that in step (3), the concentration of zinc nitrate hexahydrate added is 0.0336 mol / L and the concentration of dimethylimidazole is 0.01 mol / L.

[0052] Example 6

[0053] The difference from Example 1 is that in step (3), the concentration of zinc nitrate hexahydrate added is 0.067 mol / L and the concentration of dimethylimidazole is 0.21 mol / L.

[0054] Example 7

[0055] The difference from Example 1 is that in step (3), the concentration of zinc nitrate hexahydrate added is 0.084 mol / L and the concentration of dimethylimidazole is 0.26 mol / L.

[0056] Example 8

[0057] The difference from Example 1 is that in step (3), the concentration of zinc nitrate hexahydrate added is 0.01 mol / L and the concentration of dimethylimidazole is 0.31 mol / L.

[0058] Additional information on testing standards, procedures, and instruments used for Faraday efficiency and selectivity:

[0059] The experiment was conducted on a Shanghai Chenhua 760E electrochemical workstation at a voltage of 5 mV·s. -1The polarization curve of the LSV was tested at a rate of 5 mV / s. Before the linear sweep voltammetry (LSV) test, a steady state was achieved by scanning 20 times at 100 mV / s, followed by testing at a scan rate of 5 mV / s. The potential value was calculated according to the equation E vs RHE = E vs SCE + 0.2412 + 0.0591pH, where EvsRHE is the relative reversible hydrogen electrode potential (V) and E vs SCE is the relative saturated calomel electrode potential (V).

[0060] High performance liquid chromatography was used to detect the raw materials and products. Under the conditions of this invention, PNBA is converted into para-aminobenzoic acid (PABA). Therefore, 6 electrons are transferred in the whole process, and 1 mol of PABA can be obtained for every 1 mol of PNBA converted.

[0061] The selectivity, yield, and Faraday efficiency (FE) of PABA are calculated using the following formula, where F is the Faraday constant (96485.34).

[0062] Selectivity = (molar mass of generated PABA) / (molar mass of consumed PABA) × 100% (Equation (1));

[0063] Yield = (molar mass of generated PABA) / (molar mass of initial PABA) × 100% (Equation 2);

[0064] Faraday efficiency FE = molar mass of generated PABA n / total charge of reaction Q × 100% Equation (3).

[0065] The results are shown in Table 1.

[0066] Table 1

[0067] Faraday efficiency (%) Selectivity (%) Example 1 95 98 Example 2 92 90 Example 3 91 90 Example 8 92 95

[0068] As shown in Table 1, a good PABA conversion rate and Faraday efficiency can also be achieved using different solvents and different zinc sources. Figure 10 As shown, by comparing different ZIF-8 concentrations, it can be concluded that adding 1.5g of zinc nitrate and dimethylimidazole can achieve the best PNBA conversion rate and PABA selectivity.

[0069] The crystal structure of the ZIF-8 / Cu(OH)2 / CF material prepared in Example 1 was analyzed:

[0070] Powder X-ray diffraction was performed on a Bruker D8 X-ray powder diffractometer (Germany), under the following conditions: fixed target, monochromatic light source Cu-Kα, and wavelength... The scanning range is 5-60°, and the scanning step size is 0.02°. Sample 1# is a typical electrode material prepared in Example 1.

[0071] like Figure 1 As shown. The fitted X-ray diffraction pattern is consistent with... Figure 1 By comparing the X-ray diffraction pattern obtained from the powder scraped off sample #1, it can be seen that the prepared material contains Cu(OH)2 (PDF#35-0505) and Cu (PDF#04-0836). This indicates that under these mild and environmentally friendly conditions, the surface of the foamed copper can be easily oxidized to copper hydroxide, and then ZIF-8 particles can be grown on the copper hydroxide at room temperature to obtain the ZIF-8 / Cu(OH)2 / CF material.

[0072] In addition, from Figure 2 EDX spectroscopy revealed that the main components of the material are N, C, O, Cu, and Zn, further confirming that the obtained material is ZIF-8 / Cu(OH)2 / CF.

[0073] The CoNi-Al based heterojunction material prepared in Example 1 was characterized and tested:

[0074] The morphology of the prepared Example 1 was characterized by SEM. The prepared precursor material generally exhibited a rod-like structure with a relatively uniform morphology, such as... Figure 3 As shown in (ab); after introducing ZIF-8, ZIF-8 particles are grown on the original rod-shaped structure, as follows. Figure 3 As shown in (cd), this increases the contact surface between the catalyst and the reaction substrate, exposing more reactive sites, thereby improving the catalytic activity of the catalyst.

[0075] Figure 4 The XPS spectrum of the ZIF-8 / Cu(OH)2 / CF electrode material described in Example 1 confirms the presence of N, C, Cu, O, and Zn on the electrocatalyst surface using X-ray photoelectron spectroscopy (XPS), consistent with EDS results. Further investigation was conducted into the chemical composition and chemical state of these products. Cu is represented by two significant peaks at 952.17 eV and 934.38 eV, indicating the presence of Cu. 2+ The oxidation state, with values ​​of 532.4 eV and 952.1 eV, indicates that Cu has Cu oxidation state. 0 and Cu + The Zn plot shows two peaks with binding energies of 11044.81 eV and 1021.75 eV, indicating the presence of Zn. 2+In the O spectrum, three main peaks can be clearly identified: Zn-OC / HO bond (531 eV), Cu-O bond (529.4 eV), and CO / C=O (531.6 eV).

[0076] Polarization curves of the ZIF-8 / Cu(OH)2 / CF material prepared in Example 1:

[0077] ZIF-8 / Cu(OH)2 / CF heterojunction electrode material was used as the working electrode, and a calomel electrode and a Pt sheet were used as the reference and counter electrodes, respectively. 1M PBS neutral solution and 50mM p-nitrobenzoic acid (PNBA) were used as the electrolyte and electrolyte solution, respectively. Electrochemical tests were conducted on a Shanghai Chenhua 760E electrochemical workstation at a rate of 5mV·s. -1 The polarization curves of the LSV were tested at a rate of 5 mV / s. Before the linear sweep voltammetry (LSV) test, a steady-state state was achieved by scanning 20 times at 100 mV / s, followed by testing at a scan rate of 5 mV / s. The potential value was calculated according to the equation E vs RHE = E vs SCE + 0.2412 + 0.0591pH, where E vs RHE is the relative reversible hydrogen electrode potential (V) and E vs SCE is the relative saturated calomel electrode potential (V). The polarization curves are shown below. Figure 5 As shown in the figure, the ZIF-8 / Cu(OH)2 / CF heterojunction electrode material exhibits excellent performance in PNBA reduction, with a current density exceeding -200 mA / cm² at -0.45V (vs RHE). 2 It meets the industrial current density requirements and can be used in industrial production applications.

[0078] The catalytic reaction pathway, after detection of the intermediate products, shows that PNBA is converted into para-aminobenzoic acid (PABA) under the conditions of this invention. Therefore, 6 electrons are transferred in the whole process, and 1 mol of PABA can be obtained for every 1 mol of PNBA converted.

[0079] Distribution of products and substrates at different coulomb numbers during charging of the ZIF-8 / Cu(OH)2 / CF-based heterojunction material prepared in Example 1:

[0080] The products obtained by the ZIF-8 / Cu(OH)2 / CF electrocatalysis with a neutral solution of 0.1M PBS containing 50mM PNBA at different reaction times were characterized by liquid chromatography. Figure 6 The diagram shows the distribution of products and substrates in solutions with different Coulomb numbers during charging.

[0081] The yield, Faraday efficiency, and cycle stability of p-aminobenzoic acid in the ZIF-8 / Cu(OH)2 / CF-based heterojunction material prepared in Example 1 were evaluated as follows:

[0082] The ZIF-8 / Cu(OH)2 / CF electrode was placed in an H-type electrolytic cell as the working electrode, the calomel electrode as the reference electrode, the Pt sheet as the counter electrode, the Nafion proton exchange membrane as the diaphragm, and the electrolyte being a 1M PBS neutral solution containing 50mM PNBA. Figure 7 As shown, the bar represents the Faraday efficiency, and the horizontal axis represents the number of cycles. Under the same voltage, the high Faraday efficiency is observed even after multiple cycles, indicating that the prepared electrode material has the characteristics of high yield and high catalytic stability for the electrocatalytic reduction of PNBA.

[0083] The cyclic performance of the ZIF-8 / Cu(OH)2 / CF electrode material was tested in 1M PBS neutral solution at -0.345V vs RHE voltage. Figure 7 As shown, after 6 cycles, the catalyst still maintains excellent PNBA reduction conversion efficiency (≥98%) and high selectivity (≥98%). This demonstrates the stability and cyclic applicability of the prepared catalyst, which is beneficial for industrial application and promotion. Furthermore, this technology has certain guiding significance for the electrocatalytic synthesis of small biomass molecules.

[0084] Comparative Example 1

[0085] The copper foam was ultrasonically cleaned in hydrochloric acid, ethanol, and aqueous solution for 20 minutes each to obtain a clean copper foam substrate (denoted as CF).

[0086] Comparative Example 2

[0087] Dissolve 10g of sodium hydroxide in water and stir well. Then, add 5g of ammonium persulfate to the solution and stir well. Add the copper foam substrate to the solution and let it stand for 20 minutes. Wash it three times or more with anhydrous ethanol and deionized water. Place it in a vacuum drying oven at 60℃ for 6 hours to obtain the copper hydroxide precursor (denoted as Cu(OH)2 / CF).

[0088] Commercially available copper foam electrode material was used as the working electrode, and a saturated calomel electrode and a stone-ground rod were used as the reference and counter electrodes, respectively. Electrochemical catalytic reactions were carried out in 50 mL aqueous solutions containing 1 M PBS and 1 M PBS plus 50 mM PNBA. The results are as follows: Figure 8 As shown in the figure, the LSV curve indicates that the applied voltage is reduced after the addition of PNBA, but it is still higher than that of the electrode material prepared in this invention. Figure 9 The images show physical pictures of the CF electrode material described in Comparative Example 1, the Cu(OH)2 / CF electrode material described in Comparative Example 2, and the ZIF-8 / Cu(OH)2 / CF electrode material described in Example 1.

[0089] Comparative Example 3

[0090] The preparation method in the literature Xu G, Dong JS, Liu JH, et al. Constructing Lewis Acid-Base Pairs to Boost Electrocatalytic Hydrogenation of p-Nitrobenzoic Acid to Valuable p-Aminobenzoic Acid Using Water as the Hydrogen Source. [J]. Small (Weinheim ander Bergstrasse, Germany), 2024, 21(5):e2409455. is as follows:

[0091] First, Co5(OH)8(NO3)2 (hereinafter referred to as CNH) was successfully synthesized on Ni Foam (NF) using the molten salt method: precursor NF (2×2 cm⁻¹) 2 Soak in 3M HCl for 30 minutes, then wash with ethanol and water at least three times. During synthesis, add 5g Co(NO3)2·6H2O to a 50mL PTFE-substrate reactor, and heat to 90℃ at a rate of 2℃·min. -1 Heating for half an hour. The prepared NF was immersed in the above reactor and kept at 90℃ for 5 hours. Finally, Co5(OH)8(NO3)2 was uniformly distributed on the NF, denoted as CNH / NF (loading amount of 13 mg / cm³). -2 ).

[0092] Using CNH / NF derived from its molten salt as a raw material, without the addition of an additional Co source, the ZIF-67 precursor was successfully synthesized at room temperature: 5 g of dimethylimidazole was dissolved in 200 mL of deionized water to form a homogeneous solution, and then CNH / NF (2 × 2 cm⁻¹) was added. 2 The precursor was immersed in solution at room temperature for 15 min, then removed, washed repeatedly, and dried at 60 °C to obtain CNH-ZIF / NF (mass loading of 18 mg / cm³). -2 ).

[0093] A one-step hydrothermal method was used to synthesize Co1-xNix(OH)(CO3) / Al(OH)3 / NF: 0.5g urea, 0.5g Al(NO)3·9H2O and above, yielding CNH-ZIF / NF (2×2cm). 2 The mixture was added to 80 mL of deionized water and transferred to a 100 mL PTFE-substrate reactor. The mixture was heated to 140 °C at 1 °C·min⁻¹ for 10 h, and then further heated at 0.5 °C·min⁻¹. -1Cool to room temperature, wash and dry overnight at 60°C. Prepare Co1-xNix(OH)(CO3) / Al(OH)3 (CoNiCH / Al(OH)3) (mass loading 4 mg / cm³). -2 Different amounts of Al(NO)3·9H2O (0.25g, 0.5g, 0.75g, 1.0g) and the same CNH-ZIF / NF (2×2cm) were added to the reaction system. 2 The resulting products were recorded as CoNiCH / Al(OH)3-0.25, CoNiCH / Al(OH)3-0.5, CoNiCH / Al(OH)3-0.75, and CoNiCH / Al(OH)3-1, respectively. The synthesis of CoNiCH / Co(OH)2 was the same as the above scheme, except that Al(NO)3·9H2O was not added.

[0094] Compared to previously published articles, Faraday efficiency was improved by 3.16%, and selectivity by 3.06%.

[0095] Therefore, it can be seen that the heterojunction material prepared by this invention has significant performance advantages over existing commercial electrode materials.

[0096] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the present invention.

Claims

1. A method for preparing ZIF-8 material based on Cu substrate growth, characterized in that: include, The copper foam substrate was oxidized to obtain a copper hydroxide precursor. After drying, it is first mixed with zinc nitrate hexahydrate methanol solution, and then dimethylimidazolium methanol solution is added to obtain a mixture. After stirring evenly, the reaction is allowed to end at room temperature. The mixture is then washed with anhydrous ethanol and deionized water, ultrasonicated, and vacuum dried to obtain a ZIF-8 material-based heterojunction material grown on a Cu substrate.

2. The preparation method according to claim 1, characterized in that: The concentration of zinc nitrate hexahydrate in the mixture is 0.01 mol / L to 0.1 mol / L, and the concentration of dimethylimidazole is 0.05 mol / L to 0.35 mol / L.

3. The preparation method according to claim 1, characterized in that: The copper hydroxide precursor was obtained by immersing a conductive substrate electrode in a mixed aqueous solution of alkaline and strong oxidizing salts, followed by ultrasonic treatment in water and anhydrous ethanol, and vacuum drying.

4. The preparation method according to claim 3, characterized in that: The conductive substrate electrode material is copper foam; the alkaline solution is either sodium hydroxide solution or potassium hydroxide solution; the strong oxidizing salt liquid includes one or more of ammonium persulfate and sodium persulfate. The mass ratio of the alkaline solution to the strong oxidizing salt is 2-3:0.5-3.

5. The preparation method according to claim 1, characterized in that: The copper hydroxide precursor, after drying, is first mixed with zinc nitrate hexahydrate methanol solution and stirred for 1 hour at a reaction temperature of 20–25°C; the addition of dimethylimidazolium methanol solution is then stirred for 1 hour at a reaction temperature of 20–25°C.

6. The preparation method according to claim 1, characterized in that: The vacuum drying temperature is 60℃ and the time is 5 hours.

7. ZIF-8 material grown on a Cu substrate by the preparation method according to any one of claims 1 to 6.

8. The application of the Cu substrate for growing ZIF-8 material according to claim 7, characterized in that: The applications include electrocatalytic treatment of nitrate-containing wastewater, soil remediation, coatings, anti-counterfeiting, printing, textiles, environmental engineering for toxic gas adsorption, synthesis of pharmaceutical intermediates, and electrocatalytic reduction of organic nitrobenzenes and their derivatives to amines.

9. The application as described in claim 8, characterized in that: The application in the field of electrocatalytic reduction of organic nitrobenzene and its derivatives to amines includes: using the heterojunction material as a cathode catalyst to reduce nitrobenzene and its derivatives to aromatic amines as high-value-added chemicals through electrocatalytic reduction.

10. The application as described in claim 8, characterized in that: The Cu substrate-grown ZIF-8 material is used as an electrocatalytic reducing agent for electrocatalytic hydrogenation. A stone-ground rod / platinum sheet is used as the counter electrode, a calomel electrode is used as the reference electrode, a neutral PBS solution is used as the electrolyte solution with a pH of around 7, an electrolysis voltage of -0.4V to -0.8V, and a constant voltage reaction time of more than 0.5h.

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