Application of biomass-based copper monatomic material in synthesis of aromatic azo compound

Abstract

The invention discloses application of a biomass-based copper monatomic material in synthesis of an aromatic azo compound, and belongs to the technical field of catalytic organic synthesis.The biomass-based copper monatomic material, an aniline compound, alkali and a solvent react in the air atmosphere at the temperature of 75-85 DEG C, and the aromatic azo compound is obtained. The waste biomass material is used as the carrier to prepare the copper monatomic material, the preparation cost is low, the reaction condition is mild, the obtained catalyst is high in catalytic activity, other oxidizing agents and other reaction auxiliaries do not need to be added when the catalyst is applied to aromatic amine catalytic synthesis of aromatic azo compounds, only oxygen in air is used as the oxidizing agent, and the cost is low. The excellent catalytic effect can be realized. The biomass-based copper monatomic material adopted by the method is good in applicability to different substrates and high in yield, and compared with the prior art, the method has higher practical application value.

Description

Technical Field

[0001] The invention relates to the technical field of catalytic organic synthesis, and in particular to the application of biomass-based copper single-atom materials in the synthesis of aromatic azo compounds. Background Art

[0002] Aromatic azo compounds are very important functional compounds, which are widely used in the fields of pharmaceuticals, biological products, agricultural chemicals, dyes, etc. They are essential intermediates in certain chemical transformation processes. Aromatic azo compounds have a unique -N=N- structure, so they can undergo trans-to-cis isomerization under ultraviolet light and cis-to-trans reciprocating changes under visible light. Therefore, they are widely used in photoresponsive materials, such as smart polymers, liquid crystals, etc. They also play an important role as drug coating materials in medical applications.

[0003] Aromatic amine coupling is a traditional method for preparing aromatic azo compounds, but this method often requires the use of stoichiometric mercury salts, lead salts, manganese salts, ferrates, diazonium salts, peracetic acid and environmentally unfriendly oxidants to catalyze the oxidation reaction. Although it has a high yield, it is contrary to the development concept of green chemistry. Studies have shown that the catalysts Au / TiO2 and Ag / C supported on metal nanoparticles can efficiently catalyze aniline to form azobenzene, which shows that transition metals have the potential to efficiently catalyze this reaction, but the use of precious metals greatly limits their subsequent applications. Lu W et al. and Zhang C et al. have successively tried to use inexpensive and readily available divalent copper salts to replace precious metals to catalyze this reaction, but found that the catalytic effect of divalent copper salts was not good. Therefore, there are certain technical bottlenecks in the research on the efficient catalysis of divalent copper salts to form azobenzene from aniline. Summary of the invention

[0004] The present invention provides an application of a biomass-based copper single-atom material in the synthesis of aromatic azo compounds, which effectively solves the technical problems that the existing immobilized metal nanoparticles catalyze the generation of azobenzene from aniline, but the subsequent application is limited due to the use of noble metal catalysis; and the use of low-priced divalent copper salts to replace noble metals has a poor catalytic effect. The present invention loads divalent copper ions on the surface of a biomass material in an atomic form to obtain a biomass-based copper single-atom material, and the biomass-based copper single-atom material is applied to the reaction of catalyzing the generation of aromatic azo compounds from aromatic amines to achieve an excellent catalytic effect.

[0005] The purpose of the present invention is to provide an application of a biomass-based copper single atom material in the synthesis of an aromatic azo compound, specifically: using the biomass-based copper single atom material as a catalyst, using an aniline compound and a solvent as raw materials, a catalytic oxidation reaction is carried out under alkaline conditions and an air atmosphere at 75°C to 85°C to obtain an aromatic azo compound.

[0006] The preparation method of the biomass-based copper single-atom material comprises the following steps:

[0007] The silane coupling agent is added to the alcohol solution of 2-aminobenzaldehyde, a nucleophilic addition reaction occurs at 70° C. to 100° C., and dehydration is performed to obtain an alcohol solution of Schiff base.

[0008] Cu 2+ The alcohol solution of Cu is added to the alcohol solution of Schiff base to undergo coordination chelation reaction at 25°C to 80°C to obtain Cu 2+ Imprint alcoholic solutions of the pre-complexed compounds.

[0009] Adding Cu to pretreated biomass 2+ The imprinted pre-coordinated compound is placed in an alcohol solution at 65°C to 100°C. 2+ The ethoxy group in the imprinted pre-coordination compound undergoes alcoholysis reaction with the hydroxyl group on the surface of the pretreated biomass material to form an -O-Si- bond, thereby obtaining a biomass-based copper single atom material.

[0010] As a preferred embodiment, the biomass-based copper single atom material, aniline compounds, base and solvent are mixed and catalytic oxidation reaction is carried out at 75° C. to 85° C. in an air atmosphere to obtain an aromatic azo compound.

[0011] As a preferred embodiment, the usage ratio of the biomass-based copper single atom material, the aniline compound and the solvent is 0.2-0.5 mmol:1 mmol:2-3 mL, and the molar amount of the base is 15-25% of the aniline compound.

[0012] As a preferred embodiment, the catalytic oxidation reaction time is 15h to 20h.

[0013] As a preferred embodiment, thin layer chromatography is used to track the reaction progress. After the reaction is completed, the filtrate is obtained by filtration. The filter cake is rinsed with ethyl acetate, combined, dried with anhydrous Na2SO4, filtered and concentrated, and the combined liquid is separated by column chromatography to obtain an aromatic azo compound.

[0014] As a preferred embodiment, the solvent is acetonitrile, dimethyl sulfoxide, N,N-dimethylformamide, methanol, toluene, tetrahydrofuran or 1,4-dioxane.

[0015] As a preferred embodiment, the base is pyridine, triethylamine, triethylenediamine, 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), sodium hydroxide or potassium carbonate.

[0016] As a preferred embodiment, the Cu 2+ The molar ratio of the Schiff base is 1:1 to 2.

[0017] As a preferred embodiment, based on the mass of the biomass-based copper single atom material, the loading amount of copper single atoms is 7.14wt% to 7.48wt%.

[0018] As a preferred embodiment, the method for preparing the pretreated biomass material comprises the following steps:

[0019] Dissolve hexadecyl ammonium bromide in water, add ammonia water to obtain a treatment solution; add biomass material powder to the treatment solution, adjust the pH to 10-12, and perform hydrothermal reaction at 100-120° C. for 24-48 hours to obtain a pretreated biomass material.

[0020] As a preferred embodiment, the mass concentration of the ammonia water is 25% to 28%, and the usage ratio of the biomass material powder, hexadecyl ammonium bromide, water and ammonia water is 0.75g:0.4-0.6g:20-30mL:15-18mL.

[0021] As a preferred embodiment, the biomass material includes rice husks, straws, bagasse, tobacco stalks, corn cobs or peanut shells.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention provides for the first time the application of biomass-based copper single-atom materials in the synthesis of aromatic azo compounds. The biomass-based copper single-atom materials, aniline compounds, bases and solvents are reacted at 75°C to 85°C in an air atmosphere to obtain aromatic azo compounds with a high yield. The present invention uses waste biomass materials as carriers to prepare copper single-atom materials, has low preparation costs, mild reaction conditions, and the obtained catalyst has high catalytic activity. When used in the catalytic synthesis of aromatic azo compounds by aromatic amines, no other oxidants or other reaction aids need to be added, and only oxygen in the air is needed as an oxidant to achieve excellent catalytic effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 These are scanning electron microscope (SEM) images of the rice husk prepared in Example 1 of the present invention before and after pretreatment, wherein Figures a and b are original rice husks before pretreatment, and Figures c and d are rice husks after pretreatment.

[0025] Figure 2 These are scanning electron microscope (SEM) images of the biomass-based copper single-atom material prepared in Example 1 of the present invention. Figures a and b are both biomass-based copper single-atom materials prepared using pretreated rice husks.

[0026] Figure 3This is a transmission electron microscope (TEM) image of the biomass-based copper single-atom material prepared in Example 1 of the present invention, Figures a and b are TEM images of the biomass-based copper single-atom material, and Figures c to h are X-ray energy dispersion spectra (EDS) of the biomass-based copper single-atom material. DETAILED DESCRIPTION

[0027] In order to enable those skilled in the art to better understand the technical solution of the present invention and implement it, the present invention is further described below in conjunction with specific embodiments and drawings, but the embodiments are not intended to limit the present invention. The following test methods and detection methods, unless otherwise specified, are conventional methods; the reagents and raw materials, unless otherwise specified, are commercially available.

[0028] Regarding the issues mentioned in the background technology of the present invention: First, the traditional method for preparing aromatic azo compounds involves the use of mercury salts, lead salts, manganese salts, ferrates, diazonium salts, peracetic acid and environmentally unfriendly oxidants to catalyze the oxidation reaction. Although it has a higher yield, it is contrary to the development concept of green chemistry. Second, the catalysts Au / TiO2 and Ag / C supported on metal nanoparticles can efficiently catalyze aniline to produce azobenzene, but the use of precious metals greatly limits their subsequent applications. Third, inexpensive and readily available divalent copper salts are used to replace precious metals to catalyze this reaction, but the catalytic effect is not good, and the yield is below 60%. Based on the above technical problems, the present invention provides the application of biomass-based copper single-atom materials in the synthesis of aromatic azo compounds.

[0029] The technical contents of the present invention are analyzed and explained in detail below.

[0030] The present invention first provides an application of a biomass-based copper single atom material in the synthesis of an aromatic azo compound, specifically: using the biomass-based copper single atom material as a catalyst, using an aniline compound and a solvent as raw materials, a catalytic oxidation reaction is carried out at 75°C to 85°C under alkaline conditions and an air atmosphere to obtain an aromatic azo compound. Specifically: the biomass-based copper single atom material, an aniline compound, a base and a solvent are mixed, and a catalytic oxidation reaction is carried out at 75°C to 85°C in an air atmosphere to obtain an aromatic azo compound.

[0031] It should be noted that thin layer chromatography was used to track the progress of the reaction. After the reaction was completed, the filtrate was obtained by filtration. The filter cake was rinsed with ethyl acetate (3*2 mL), combined, dried over anhydrous Na2SO4, filtered, concentrated, and the combined solution was separated by column chromatography to obtain an aromatic azo compound.

[0032] In the above technical scheme, a biomass-based copper single-atom material with high catalytic activity is prepared using waste biomass materials as carriers. When it is used to catalyze the synthesis of aromatic azo compounds from aromatic amines, there is no need to add other oxidants or other reaction aids. Only oxygen in the air is needed as an oxidant to achieve excellent catalytic effects.

[0033] It should be noted that if the catalytic reaction temperature is lower than 75°C, the energy required for the reaction will be insufficient, and the yield is found to be low during the actual reaction. A higher yield can also be obtained when the temperature is higher than 85°C, but in order to reduce the waste of resources, it is best to control the temperature between 75°C and 85°C. The yield of the catalytic reaction increases with the increase of reaction time, and a good yield can be obtained in 15h. In order to ensure that the system can achieve the maximum catalytic benefit, we set the time parameter to 15h~20h.

[0034] In order to achieve a better catalytic effect, the dosage ratio of the biomass-based copper single atom material, the aniline compound and the solvent is 0.02-0.05mmol:1mmol:2-3mL, and the molar amount of the base is 15%-25% of the aniline compound. In the actual experimental process, our initial biomass-based copper single atom material dosage is 20mg. If calculated in this way, the molar mass of the single-atom copper involved in the reaction is 0.023mmol. Considering that there is a certain error in the experimental process, the minimum value is set to 0.02mmol. By increasing the dosage of the biomass-based copper single atom material by gradient, we found that when the dosage of the biomass-based copper single atom material reaches 40mg, a good catalytic effect can be achieved. If the yield is increased, it remains the same. If calculated in this way, the molar mass of the single-atom copper involved in the reaction is 0.046mmol. Considering that there is a certain error in the experimental process, the maximum value is set to 0.05mmol.

[0035] In the present invention, the solvent is acetonitrile, dimethyl sulfoxide, N,N-dimethylformamide, methanol, toluene, tetrahydrofuran or 1,4-dioxane; the base is pyridine, triethylamine, triethylenediamine, 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), sodium hydroxide or potassium carbonate.

[0036] In the above application, the method for preparing the biomass-based copper single-atom material comprises the following steps:

[0037] The silane coupling agent is added to the alcohol solution of 2-aminobenzaldehyde, a nucleophilic addition reaction occurs at 70° C. to 100° C., and dehydration is performed to obtain an alcohol solution of Schiff base.

[0038] It should be noted that since the Schiff base contains an ethoxy group that is easily hydrolyzed, it is not conducive to storage, so it is best to use it immediately after preparation. In this process, a nucleophilic addition reaction occurs, and the silane coupling agent KH-550 (APTES) acts as a nucleophilic reagent to attack the carbonyl group of 2-aminobenzaldehyde, completing the nucleophilic addition to form an intermediate α-hydroxyamine compound, which is then further dehydrated to form a Schiff base.

[0039] Cu 2+ The alcohol solution of copper is added to the alcohol solution of the Schiff base, and a coordination chelation reaction occurs at 25-80° C. Since the outer electron configuration of copper is 3d(10)4s(1), when it loses two electrons to form copper ions, its outer electron configuration is 3d(9). Since the energy of one d orbital, one s orbital and two p orbitals are similar, hybridization can be performed to form unequal dsp2 hybrid orbitals. One hybrid orbital can accommodate four lone electrons of nitrogen atoms in two Schiff bases, and chelation is performed in the form of a copper ion and two Schiff bases in a two-coordinated manner to obtain Cu 2+ Imprint alcoholic solutions of the pre-complexed compounds.

[0040] Pre-treated biomass materials (rice husk, straw, bagasse, tobacco stalk, corn cob or peanut shell) were added to Cu 2+ The imprinted pre-coordinated compound is placed in an alcohol solution at 65°C to 100°C. 2+ The ethoxy group in the imprinted pre-coordination compound undergoes alcoholysis reaction with the hydroxyl group on the surface of the pretreated biomass material to form an -O-Si- bond, thereby obtaining a biomass-based copper single atom material.

[0041] In the above technical scheme, copper ions are added to the alcohol solution of Schiff base to form a pre-coordinated compound by a one-pot method, and then pre-treated waste biomass materials are added thereto to obtain biomass-based copper single-atom materials. The preparation of single-atom materials using waste biomass materials as carriers has low preparation costs and mild reaction conditions, and the obtained biomass-based copper single-atom materials have high catalytic activity.

[0042] In order to ensure better catalytic activity, the Cu 2+ The molar ratio of the copper to the Schiff base is 1:1 to 2. If the ratio is lower than 1:1, the copper loading in the subsequently prepared biomass-based copper single-atom material will be too low, which will lead to a decrease in the active sites of the biomass-based copper single-atom material and a decrease in the catalytic effect. If the ratio is higher than 1:2, the surface energy of the biomass-based copper single-atom material will increase, which will lead to agglomeration of individual coppers, thereby reducing the activity of the biomass-based copper single-atom material.

[0043] In order to further ensure the activity of the biomass-based copper single atom material, the loading amount of copper single atoms is 7.14wt% to 7.48wt% based on the mass of the biomass-based copper single atom material. 7.35wt% is the optimal value. If it is lower than 7.14wt%, the mass of the biomass-based copper single atom material required in the subsequent catalytic reaction will increase, and the yield will be reduced in the actual catalytic reaction. The reason is analyzed as follows: due to the increase in the amount of biomass-based copper single atom material, part of the products in the catalytic system are adsorbed on the surface of the excess biomass and cannot be better separated. If it is higher than 7.48wt%, the surface energy of the biomass-based copper single atom material increases, causing agglomeration between individual coppers, thereby reducing the activity of the biomass-based copper single atom material.

[0044] In order to improve the loading effect of copper single atoms on biomass-based materials, the preparation method of the pretreated biomass material includes the following steps: dissolving hexadecyl ammonium bromide in water, adding ammonia water, and obtaining a treatment liquid; adding biomass material powder to the treatment liquid, adjusting the pH to 10-12, and hydrothermally reacting at 100°C-120°C for 24h-48h to obtain the pretreated biomass material.

[0045] In order to provide a catalyst carrier with better performance, the pH value plays a key role in the successful preparation of biomass materials. If the pH value is less than 10 or greater than 12, it will affect the thermal stability of the biomass material, thereby affecting the subsequent grafting. The hydrothermal reaction first destroys the original structure of the material and then reorganizes it into the structure we need. If the temperature is lower than 100°C, the original structure of the material cannot be destroyed. If the temperature is higher than 120°C, it will affect the reorganized structure of the material. The reorganization of the material is a relatively slow process, so the overall preparation time cannot be less than 24 hours. If it is less than 24 hours, the material structure will be incomplete, thus affecting the subsequent grafting. If the preparation time is higher than 48 hours, the effect on the material structure is relatively small, but it will cause a waste of resources. In order to better prepare the biomass material, it is best to control the time within 24 hours to 48 hours.

[0046] In the present invention, the mass concentration of the ammonia water is 25% to 28%, and the usage ratio of the biomass material powder, hexadecyl ammonium bromide, water and ammonia water is 0.75g: 0.4 to 0.6g: 20 to 30mL: 15 to 18mL.

[0047] The technical effects of the present invention are described in detail below through specific embodiments and comparative examples.

[0048] Example 1

[0049] A method for preparing a biomass-based copper single-atom material comprises the following steps:

[0050] 1.105 g of APTES (silane coupling agent) was dropped into an ethanol solution of 0.726 g of 2-aminobenzaldehyde, and the temperature was raised to 80° C. for reflux reaction, and stirred for 24 h. After the reaction was completed by TLC monitoring, a Schiff base ethanol solution was obtained.

[0051] According to Cu 2+ The molar ratio of CuCl2 to Schiff base is 1:1.5, and the ethanol solution of CuCl2 is added to the ethanol solution of the Schiff base to undergo coordination chelation reaction at 25°C to obtain Cu 2+ Imprint alcoholic solutions of the pre-complexed compounds.

[0052] According to the dosage ratio of biomass material powder, hexadecyl ammonium bromide, water and ammonia water 0.75g:0.51g:25mL:16.34mL, hexadecyl ammonium bromide is dissolved in water, and ammonia water with a mass concentration of 26% is added to obtain a treatment liquid; rice husk powder is added to the treatment liquid, the pH is adjusted to 10, and a hydrothermal reaction is carried out at 120°C for 48 hours to obtain a pretreated rice husk material.

[0053] Pre-treated rice husk material was added with Cu 2+ The alcohol solution of the imprinted pre-coordinated compound was heated to 80°C for reflux reaction, stirred for 48 hours, filtered and washed three times with anhydrous ethanol, and dried at 80°C to obtain a biomass-based copper single atom material with a copper single atom loading of 7.35wt%.

[0054] Example 2

[0055] A method for preparing a biomass-based copper single-atom material comprises the following steps:

[0056] 1.105 g of APTES (silane coupling agent) was dropped into an ethanol solution of 0.726 g of 2-aminobenzaldehyde, and the temperature was raised to 80° C. for reflux reaction, and stirred for 24 h. After the reaction was completed by TLC monitoring, a Schiff base ethanol solution was obtained.

[0057] According to Cu 2+ The molar ratio of CuCl2 to Schiff base is 1:2, and the ethanol solution of CuCl2 is added to the ethanol solution of the Schiff base to undergo coordination chelation reaction at 80°C to obtain Cu 2+ Imprint alcoholic solutions of the pre-complexed compounds.

[0058] According to the dosage ratio of biomass material powder, hexadecyl ammonium bromide, water and ammonia water 0.75g:0.4g:20mL:15mL, hexadecyl ammonium bromide is dissolved in water, and ammonia water with a mass concentration of 25% is added to obtain a treatment liquid; rice husk powder is added to the treatment liquid, the pH is adjusted to 12, and a hydrothermal reaction is carried out at 100°C for 24 hours to obtain a pretreated rice husk material.

[0059] Pre-treated rice husk material was added with Cu2+ The alcohol solution of the imprinted pre-coordinated compound was heated to 65°C for reflux reaction, stirred for 48 hours, filtered and washed with anhydrous ethanol for 5 times, and dried at 80°C to obtain a biomass-based copper single atom material with a copper single atom loading of 7.14wt%.

[0060] Example 3

[0061] A method for preparing a biomass-based copper single-atom material comprises the following steps:

[0062] 1.105 g of APTES (silane coupling agent) was dropped into an ethanol solution of 0.726 g of 2-aminobenzaldehyde, and the temperature was raised to 80° C. for reflux reaction, and stirred for 24 h. After the reaction was completed by TLC monitoring, a Schiff base ethanol solution was obtained.

[0063] According to Cu 2+ The molar ratio of CuCl2 to Schiff base is 1:1, and the ethanol solution of CuCl2 is added to the ethanol solution of the Schiff base to undergo coordination chelation reaction at 60°C to obtain Cu 2+ Imprint alcoholic solutions of the pre-complexed compounds.

[0064] According to the dosage ratio of biomass material powder, hexadecyl ammonium bromide, water and ammonia water 0.75g:0.6g:30mL:18mL, hexadecyl ammonium bromide is dissolved in water, and ammonia water with a mass concentration of 28% is added to obtain a treatment liquid; rice husk powder is added to the treatment liquid, the pH is adjusted to 10, and a hydrothermal reaction is carried out at 110°C for 36 hours to obtain a pretreated rice husk material.

[0065] Pre-treated rice husk material was added with Cu 2+ The alcohol solution of the imprinted pre-coordinated compound was heated to 100°C for reflux reaction, stirred for 48 hours, filtered and washed three times with anhydrous ethanol, and dried at 80°C to obtain a biomass-based copper single atom material with a copper single atom loading of 7.48wt%.

[0066] The morphology of the biomass-based copper single-atom materials prepared in Examples 1 to 3 was characterized. Taking Example 1 as an example, the scanning electron microscope (SEM) images of the untreated rice husk and the pretreated rice husk were compared and analyzed. Figure 1 As shown in Figures a and b in the figure, the original rice husk has different inner and outer surfaces. Some regular nodules can be observed on the outer surface of the rice husk, while the inner surface is very smooth. Figure 1 It can be observed from Figures c and d that the surface of the rice husk becomes obviously rough after pretreatment. At a higher magnification, it can be clearly observed that many new worm-like particle structures are deposited on the surface of the rice husk, indicating that due to the intervention of CTAB, a mesoporous structure is successfully formed on the surface of the rice husk, thereby greatly increasing the specific surface area of ​​the material.

[0067] The SEM image of the rice husk-based copper single-atom material prepared in Example 1 ( Figure 2 ), TEM images (such as Figure 3 ) were analyzed. From the SEM image, it can be seen that after surface modification, the surface of the rice husk after pretreatment becomes rougher, and some mesh-like pores are formed on the surface of the material, indicating that the silanization modification group has been successfully grafted on the surface of the rice husk. From the TEM image, it can be clearly observed that high-density single bright spots (marked with circles) are evenly distributed on the surface of the material, which proves that there are a large number of single-atom dispersed copper on the surface of the rice husk-based copper single-atom material, such as Figure 3 In addition, the X-ray energy dispersive spectroscopy (EDS) mapping of the rice husk-based copper single atom material shows that C, N, O, Si and Cu elements are evenly distributed on the surface of the rice husk-based copper single atom material, such as Figure 3 Figures c to h in Figure 3. From the above description, it can be seen that copper ions are uniformly dispersed on the surface of rice husk-based copper single-atom materials in an atomic form without agglomeration, which further indicates that we have successfully synthesized rice husk-based copper single-atom materials with rice husk as the carrier.

[0068] Application Examples

[0069] After testing, the catalytic performance of the biomass-based copper single-atom materials prepared in Examples 1 to 3 of the present invention is similar. Taking the biomass-based copper single-atom material prepared in Example 1 as an example, its application effect in the catalytic synthesis of aromatic azo compounds is explored.

[0070] Application Example 1

[0071] 40 mg of rice husk-based copper single atom material, 1.0 mmol of aniline, 0.2 mmol of DBU and 2 ml of toluene were added to a reaction bottle in sequence, and the reaction was carried out at 80° C. and 1 atm of air for 15 h. The reaction progress was tracked by thin layer chromatography. After the reaction was completed, the filtrate was obtained by filtration. The filter cake was rinsed with ethyl acetate (3*2 ml), combined, dried over anhydrous Na2SO4, filtered, concentrated, and the combined solution was separated by column chromatography to obtain the target product azobenzene with a yield of 98%. The product was purified by 1 H NMR and 13 C NMR was used for identification.

[0072] 1 H NMR (400MHz, DMSO-d6) δ (ppm): 7.91-7.89 (m, 4H), 7.62-7.57 (m, 6H).

[0073] 13C NMR (101MHz, DMSO-d6) δ (ppm): 152.42, 131.96, 129.91, 122.99.

[0074] Application Example 2

[0075] 40 mg of rice husk-based copper single atom material, 1.0 mmol of 4-methylaniline, 0.2 mmol of DBU and 2 ml of toluene were added to a reaction bottle in sequence, and the reaction was carried out at 80° C. and 1 atm of air for 15 h. The reaction progress was tracked by thin layer chromatography. After the reaction was completed, the filtrate was filtered to obtain the filtrate. The filter cake was rinsed with ethyl acetate (3*2 ml), combined, dried over anhydrous Na2SO4, filtered, concentrated, and the combined solution was separated by column chromatography to obtain the target product azobenzene with a yield of 96%. The product was purified by 1 H NMR and 13 C NMR was used for identification.

[0076] 1 H NMR (400MHz, DMSO-d6) δ (ppm): 7.78 (d, J = 8.1 Hz, 4H), 7.39 (d, J = 8.0 Hz, 4H), 2.40 (s, 6H).

[0077] 13 C NMR (101MHz, DMSO-d6) δ (ppm): 150.59, 141.85, 130.36, 122.88, 21.45.

[0078] Application Example 3

[0079] 40 mg of rice husk-based copper single atom material, 1.0 mmol of 3-methylaniline, 0.2 mmol of DBU and 2 ml of toluene were added to a reaction bottle in sequence, and the reaction was carried out at 80° C. and 1 atm of air for 15 h. The reaction progress was tracked by thin layer chromatography. After the reaction was completed, the filtrate was filtered to obtain the filtrate. The filter cake was rinsed with ethyl acetate (3*2 ml), combined, dried over anhydrous Na2SO4, filtered, concentrated, and the combined solution was separated by column chromatography to obtain the target product azobenzene with a yield of 95%. The product was purified by 1 H NMR and 13 C NMR was used for identification.

[0080] 1 H NMR (400MHz, Chloroform-d) δ (ppm): 7.75 (d, J = 5.4 Hz, 4H), 7.42 (t, J = 8.0 Hz, 2H), 7.30 (d, J = 7.5 Hz, 2H), 2.47 (s, 6H).

[0081] 13C NMR (101MHz, Chloroform-d) δ (ppm): 152.87, 138.94, 131.64, 128.87, 122.91, 120.42, 21.33.

[0082] Application Example 4

[0083] 40 mg of rice husk-based copper single atom material, 1.0 mmol of 2-methylaniline, 0.2 mmol of DBU and 2 ml of toluene were added to a reaction bottle in sequence, and the reaction was carried out at 80° C. and 1 atm of air for 15 h. The reaction progress was tracked by thin layer chromatography. After the reaction was completed, the filtrate was filtered to obtain the filtrate. The filter cake was rinsed with ethyl acetate (3*2 ml), combined, dried over anhydrous Na2SO4, filtered, concentrated, and the combined solution was separated by column chromatography to obtain the target product azobenzene with a yield of 76%. The product was purified by 1 H NMR and 13 C NMR was used for identification.

[0084] 1 H NMR (400MHz, Chloroform-d) δ (ppm): 7.67 (d, J = 7.9Hz, 2H), 7.41-7.28 (m, 6H), 2.78 (s, 6H).

[0085] 13 C NMR (101MHz, Chloroform-d) δ (ppm): 151.12, 138.04, 131.29, 130.71, 126.39, 115.88, 17.66.

[0086] Application Example 5

[0087] 40 mg of rice husk-based copper single atom material, 1.0 mmol of 4-ethylaniline, 0.2 mmol of DBU and 2 ml of toluene were added to a reaction bottle in sequence, and the reaction was carried out at 80° C. and 1 atm of air for 15 h. The reaction progress was tracked by thin layer chromatography. After the reaction was completed, the filtrate was obtained by filtration. The filter cake was rinsed with ethyl acetate (3*2 ml), combined, dried over anhydrous Na2SO4, filtered, concentrated, and the combined solution was separated by column chromatography to obtain the target product azobenzene with a yield of 79%. The product was purified by 1 H NMR and 13 C NMR was used for identification.

[0088] 1H NMR (400MHz, DMSO-d6) δ (ppm): 7.80 (d, J = 8.3Hz, 2H), 7.41 (d, J = 8.3Hz, 2H), 2.70 (q, J = 7.6Hz, 2H), 1.23 (t, J = 7.6Hz, 3H).

[0089] 13 C NMR (101MHz, DMSO-d6) δ (ppm): 150.75, 148.01, 129.18, 122.99, 28.51, 15.75.

[0090] Application Example 6

[0091] 40 mg of rice husk-based copper single atom material, 1.0 mmol of 2,4,6-trimethylaniline, 0.2 mmol of DB U and 2 ml of toluene were added to a reaction bottle in sequence, and the reaction was carried out at 80°C and 1 atm of air for 15 h. The reaction process was tracked by thin layer chromatography. After the reaction was completed, the filtrate was filtered to obtain the filtrate. The filter cake was rinsed with ethyl acetate (3*2 ml), combined, dried over anhydrous Na2SO4, filtered, concentrated, and the combined solution was separated by column chromatography to obtain the target product azobenzene with a yield of 73%. The product was purified by 1 H NMR and 13 CNMR was used for identification.

[0092] 1 H NMR (400MHz, DMSO-d6) δ (ppm): 7.00 (s, 4H), 2.32 (d, J = 19.5Hz, 18H).

[0093] 13 C NMR (101MHz, DMSO-d6) δ (ppm): 149.09, 138.67, 131.37, 130.47, 21.07, 20.12.

[0094] Application Example 7

[0095] 40 mg of rice husk-based copper single atom material, 1.0 mmol of 2,6-diisopropylaniline, 0.2 mmol of DB U and 2 ml of toluene were added to a reaction bottle in sequence, and the reaction was carried out at 80°C and 1 atm of air for 15 h. The reaction progress was tracked by thin layer chromatography. After the reaction was completed, the filtrate was filtered to obtain the filtrate. The filter cake was rinsed with ethyl acetate (3*2 ml), combined, dried with anhydrous Na2SO4, filtered, concentrated, and the combined solution was separated by column chromatography to obtain the target product azobenzene with a yield of 71%. The product was purified by 1 H NMR and 13 CNMR was used for identification.

[0096] 1 H NMR (400MHz, Chloroform-d) δ (ppm): 7.36-7.30 (m, 6H), 3.27 (hept, J = 6.8Hz, 4H), 1.21 (d, J = 6.9Hz, 24H).

[0097] 13 C NMR (101MHz, Chloroform-d) δ (ppm): 149.69, 140.91, 128.50, 123.75, 27.53, 24.18.

[0098] Application Example 8

[0099] 40 mg of rice husk-based copper single atom material, 1.0 mmol of 4-isopropylaniline, 0.2 mmol of DBU and 2 ml of toluene were added to a reaction bottle in sequence, and the reaction was carried out at 80° C. and 1 atm of air for 15 h. The reaction progress was tracked by thin layer chromatography. After the reaction was completed, the filtrate was obtained by filtration. The filter cake was rinsed with ethyl acetate (3*2 ml), combined, dried with anhydrous Na2SO4, filtered, concentrated, and the combined solution was separated by column chromatography to obtain the target product azobenzene with a yield of 88%. The product was purified by 1 H NMR and 13 C NMR was used for identification.

[0100] 1 H NMR (400MHz, Chloroform-d) δ (ppm): 7.85 (d, J = 8.3 Hz, 4H), 7.37 (d, J = 8.3 Hz, 4H), 3.00 (hept, J = 6.8 Hz, 2H), 1.31 (d, J = 6.9 Hz, 12H).

[0101] 13 C NMR (101MHz, Chloroform-d) δ (ppm): 151.97, 151.23, 127.02, 122.77, 34.12, 23.83.

[0102] Application Example 9

[0103] 40 mg of rice husk-based copper single atom material, 1.0 mmol of 4-tert-butylaniline, 0.2 mmol of DBU and 2 ml of toluene were added to a reaction bottle in sequence, and the reaction was carried out at 80° C. and 1 atm of air for 15 h. The reaction progress was tracked by thin layer chromatography. After the reaction was completed, the filtrate was filtered to obtain the filtrate. The filter cake was rinsed with ethyl acetate (3*2 ml), combined, dried over anhydrous Na2SO4, filtered, concentrated, and the combined solution was separated by column chromatography to obtain the target product azobenzene with a yield of 85%. The product was purified by 1H NMR and 13 C NMR was used for identification.

[0104] 1 H NMR (400MHz, Chloroform-d) δ (ppm): 7.85 (d, J = 8.2 Hz, 4H), 7.54 (d, J = 8.2 Hz, 4H), 1.38 (s, 18H).

[0105] 13 C NMR (101MHz, Chloroform-d) δ (ppm): 154.20, 150.81, 125.93, 122.43, 34.97, 31.28.

[0106] Application Example 10

[0107] 40 mg of rice husk-based copper single atom material, 1.0 mmol of 4-chloroaniline, 0.2 mmol of DBU and 2 ml of toluene were added to a reaction bottle in sequence, and the reaction was carried out at 80° C. and 1 atm of air for 15 h. The reaction progress was tracked by thin layer chromatography. After the reaction was completed, the filtrate was filtered to obtain the filtrate. The filter cake was rinsed with ethyl acetate (3*2 ml), combined, dried over anhydrous Na2SO4, filtered, concentrated, and the combined solution was separated by column chromatography to obtain the target product azobenzene with a yield of 93%. The product was purified by 1 H NMR and 13 C NMR was used for identification.

[0108] 1 H NMR (400MHz, DMSO-d6) δ (ppm): 7.92 (d, J = 8.6 Hz, 4H), 7.68 (d, J = 8.6 Hz, 4H).

[0109] 13 C NMR (101MHz, DMSO-d6) δ (ppm): 150.90, 136.82, 130.12, 124.79.

[0110] Application Example 11

[0111] 40 mg of rice husk-based copper single atom material, 1.0 mmol of 3-chloroaniline, 0.2 mmol of DBU and 2 ml of toluene were added to a reaction bottle in sequence, and the reaction was carried out at 80° C. and 1 atm of air for 15 h. The reaction progress was tracked by thin layer chromatography. After the reaction was completed, the filtrate was filtered to obtain the filtrate. The filter cake was rinsed with ethyl acetate (3*2 ml), combined, dried over anhydrous Na2SO4, filtered, concentrated, and the combined solution was separated by column chromatography to obtain the target product azobenzene with a yield of 90%. The product was purified by 1 H NMR and 13C NMR was used for identification.

[0112] 1 H NMR (400MHz, DMSO-d6) δ (ppm): 7.92-7.90 (m, 4H), 7.67-7.64 (m, 4H).

[0113] 13 C NMR (101MHz, DMSO-d6) δ (ppm): 153.16, 134.70, 131.98, 131.77, 123.13, 121.70.

[0114] Application Example 12

[0115] 40 mg of rice husk-based copper single atom material, 1.0 mmol of 4-bromoaniline, 0.2 mmol of DBU and 2 ml of toluene were added to a reaction bottle in sequence, and the reaction was carried out at 80° C. and 1 atm of air for 15 h. The reaction progress was tracked by thin layer chromatography. After the reaction was completed, the filtrate was obtained by filtration. The filter cake was rinsed with ethyl acetate (3*2 ml), combined, dried over anhydrous Na2SO4, filtered, concentrated, and the combined solution was separated by column chromatography to obtain the target product azobenzene with a yield of 91%. The product was purified by 1 H NMR and 13 C NMR was used for identification.

[0116] 1 H NMR (400MHz, Chloroform-d) δ (ppm): 7.80 (d, J = 8.6 Hz, 4H), 7.65 (d, J = 8.6 Hz, 4H).

[0117] 13 C NMR (101MHz, Chloroform-d) δ (ppm): 151.19, 132.38, 125.73, 124.39.

[0118] Application Example 13

[0119] 40 mg of rice husk-based copper single atom material, 1.0 mmol of 4-fluoroaniline, 0.2 mmol of DBU and 2 ml of toluene were added to a reaction bottle in sequence, and the reaction was carried out at 80° C. and 1 atm of air for 15 h. The reaction progress was tracked by thin layer chromatography. After the reaction was completed, the filtrate was obtained by filtration. The filter cake was rinsed with ethyl acetate (3*2 ml), combined, dried over anhydrous Na2SO4, filtered, concentrated, and the combined solution was separated by column chromatography to obtain the target product azobenzene with a yield of 89%. The product was purified by 1 H NMR and 13 C NMR was used for identification.

[0120] 1 H NMR (400MHz, DMSO-d6) δ (ppm): 7.97-7.93 (m, 4H), 7.43 (t, J = 8.7Hz, 4H).

[0121] 13 C NMR (101MHz, DMSO-d6) δ (ppm): 165.54, 163.05, 149.03, 125.37, 125.28, 117.00, 116.77.

[0122] Application Example 14

[0123] 40 mg of rice husk-based copper single atom material, 1.0 mmol of 4-nitroaniline, 0.2 mmol of DBU and 2 ml of toluene were added to a reaction bottle in sequence, and the reaction was carried out at 80° C. and 1 atm of air for 15 h. The reaction progress was tracked by thin layer chromatography. After the reaction was completed, the filtrate was filtered to obtain the filtrate. The filter cake was rinsed with ethyl acetate (3*2 ml), combined, dried with anhydrous Na2SO4, filtered, concentrated, and the combined solution was separated by column chromatography to obtain the target product azobenzene with a yield of 88%. The product was purified by 1 H NMR and 13 C NMR was used for identification.

[0124] 1 H NMR (400MHz, Chloroform-d) δ (ppm): 8.43 (d, J = 8.8 Hz, 4H), 8.11 (d, J = 8.8 Hz, 4H).

[0125] 13 C NMR (101MHz, Chloroform-d) δ (ppm): 155.15, 149.55, 124.83, 123.94.

[0126] Application Example 15

[0127] 40 mg of rice husk-based copper single atom material, 1.0 mmol of 3-nitroaniline, 0.2 mmol of DBU and 2 ml of toluene were added to a reaction bottle in sequence, and the reaction was carried out at 80° C. and 1 atm of air for 15 h. The reaction progress was tracked by thin layer chromatography. After the reaction was completed, the filtrate was obtained by filtration. The filter cake was rinsed with ethyl acetate (3*2 ml), combined, dried over anhydrous Na2SO4, filtered, concentrated, and the combined solution was separated by column chromatography to obtain the target product azobenzene with a yield of 86%. The product was purified by 1 H NMR and 13 C NMR was used for identification.

[0128] 1 H NMR (400MHz, Chloroform-d) δ (ppm): 8.80 (s, 2H), 8.41 (d, J = 8.2Hz, 2H), 8.34 (d, J = 7.8Hz, 2H), 7.77 (t, J = 8.0Hz, 2H).

[0129] 13 C NMR (101MHz, Chloroform-d) δ (ppm): 152.45, 149.16, 130.22, 129.62, 125.91, 117.24.

[0130] Application Example 16

[0131] 40 mg of rice husk-based copper single atom material, 1.0 mmol of 4-methoxyaniline, 0.2 mmol of DBU and 2 ml of toluene were added to a reaction bottle in sequence, and the reaction was carried out at 80° C. and 1 atm of air for 15 h. The reaction progress was tracked by thin layer chromatography. After the reaction was completed, the filtrate was filtered to obtain the filtrate. The filter cake was rinsed with ethyl acetate (3*2 ml), combined, dried over anhydrous Na2SO4, filtered, concentrated, and the combined solution was separated by column chromatography to obtain the target product azobenzene with a yield of 95%. The product was purified by 1 H NMR and 13 C NMR was used for identification.

[0132] 1 H NMR (400MHz, DMSO-d6) δ (ppm): 7.84 (d, J = 8.2 Hz, 4H), 7.11 (d, J = 8.3 Hz, 4H), 3.85 (s, 6H).

[0133] 13 C NMR (101MHz, DMSO-d6) δ (ppm): 161.92, 146.68, 124.58, 114.99, 56.06.

[0134] Application Example 17

[0135] 40 mg of rice husk-based copper single atom material, 1.0 mmol of 4-aminoacetophenone, 0.2 mmol of DBU and 2 ml of toluene were added to a reaction bottle in sequence, and the reaction was carried out at 80° C. and 1 atm of air for 15 h. The reaction progress was tracked by thin layer chromatography. After the reaction was completed, the filtrate was filtered to obtain the filtrate. The filter cake was rinsed with ethyl acetate (3*2 ml), combined, dried over anhydrous Na2SO4, filtered, concentrated, and the combined solution was separated by column chromatography to obtain the target product azobenzene with a yield of 90%. The product was purified by 1 H NMR and 13 C NMR was used for identification.

[0136] 1 H NMR (400MHz, Chloroform-d) δ (ppm): 8.13 (d, J = 8.3 Hz, 4H), 8.01 (d, J = 8.2 Hz, 4H), 2.68 (s, 6H).

[0137] 13 C NMR (101MHz, Chloroform-d) δ (ppm): 197.20, 154.87, 138.99, 129.36, 123.16, 26.78.

[0138] Application Example 18

[0139] 40 mg of rice husk-based copper single atom material, 1.0 mmol of ethyl 4-aminobenzoate, 0.2 mmol of DB U and 2 ml of toluene were added to a reaction bottle in sequence, and the reaction was carried out at 80° C. and 1 atm of air for 15 h. The reaction progress was tracked by thin layer chromatography. After the reaction was completed, the filtrate was obtained by filtration. The filter cake was rinsed with ethyl acetate (3*2 ml), combined, dried with anhydrous Na2SO4, filtered, concentrated, and the combined solution was separated by column chromatography to obtain the target product azobenzene with a yield of 88%. The product was purified by 1 H NMR and 13 CNMR was used for identification.

[0140] 1 H NMR (400MHz, Chloroform-d) δ (ppm): 8.21 (d, J = 8.5Hz, 4H), 7.98 (d, J = 8.5Hz, 4H), 4.43 (q, J = 7.1Hz, 4H), 1.43 (t, J = 7.1Hz, 6H).

[0141] 13 C NMR (101MHz, DMSO-d6) δ (ppm): 165.88, 154.94, 132.82, 130.58, 122.82, 61.28, 14.28.

[0142] In order to further illustrate the technical effect of the present invention, the present invention also sets an application comparison example, which is as follows:

[0143] Application Comparative Example 1

[0144] 40 mg of rice husk-based copper single atom material, 1.0 mmol of aniline, 0.2 mmol of DBU and 2 ml of acetonitrile were added to a reaction bottle in sequence, and the reaction was carried out at 80° C. and 1 atm of air for 15 h. The reaction progress was tracked by thin layer chromatography. After the reaction was completed, the filtrate was obtained by filtration. The filter cake was rinsed with ethyl acetate (3*2 ml), combined, dried over anhydrous Na2SO4, filtered, concentrated, and the combined liquid was separated by column chromatography to obtain the target product azobenzene with a yield of 68%.

[0145] Application Comparative Example 2

[0146] 40 mg of rice husk-based copper single atom material, 1.0 mmol of aniline, 0.2 mmol of DBU and 2 ml of dimethyl sulfoxide were added to the reaction bottle in sequence, and the reaction was carried out at 80° C. and 1 atm of air for 15 h. The reaction progress was tracked by thin layer chromatography. After the reaction was completed, the filtrate was obtained by filtration. The filter cake was rinsed with ethyl acetate (3*2 ml), combined, dried over anhydrous Na2SO4, filtered and concentrated, and the combined liquid was separated by column chromatography to obtain the target product azobenzene with a yield of 21%.

[0147] Application Comparative Example 3

[0148] 40 mg of rice husk-based copper single atom material, 1.0 mmol of aniline, 0.2 mmol of DBU and 2 ml of N,N-dimethylformamide were added into the reaction bottle in sequence, and the reaction was carried out at 80°C and 1 atm of air for 15 h. The reaction progress was tracked by thin layer chromatography. After the reaction was completed, the filtrate was obtained by filtration. The filter cake was rinsed with ethyl acetate (3*2 ml), combined, dried over anhydrous Na2SO4, filtered and concentrated, and the combined liquid was separated by column chromatography to obtain the target product azobenzene with a yield of 17%.

[0149] Application Comparative Example 4

[0150] 40 mg of rice husk-based copper single atom material, 1.0 mmol of aniline, 0.2 mmol of DBU and 2 ml of methanol were added to the reaction bottle in sequence, and the reaction was carried out at 80° C. and 1 atm of air for 15 h. The reaction progress was tracked by thin layer chromatography. After the reaction was completed, the filtrate was obtained by filtration. The filter cake was rinsed with ethyl acetate (3*2 ml), combined, dried over anhydrous Na2SO4, filtered, concentrated, and the combined liquid was separated by column chromatography to obtain the target product azobenzene with a yield of 10%.

[0151] Application Comparative Example 5

[0152] 40 mg of rice husk-based copper single atom material, 1.0 mmol of aniline, 0.2 mmol of DBU and 2 ml of tetrahydrofuran were added to the reaction bottle in sequence, and the reaction was carried out at 80° C. and 1 atm of air for 15 h. The reaction progress was tracked by thin layer chromatography. After the reaction was completed, the filtrate was obtained by filtration. The filter cake was rinsed with ethyl acetate (3*2 ml), combined, dried over anhydrous Na2SO4, filtered and concentrated, and the combined liquid was separated by column chromatography to obtain the target product azobenzene with a yield of 41%.

[0153] Application Comparative Example 6

[0154] 40 mg of rice husk-based copper single atom material, 1.0 mmol of aniline, 0.2 mmol of DBU and 2 ml of 1,4-dioxane were added to the reaction bottle in sequence, and the reaction was carried out at 80° C. and 1 atm of air for 15 h. The reaction progress was tracked by thin layer chromatography. After the reaction was completed, the filtrate was obtained by filtration. The filter cake was rinsed with ethyl acetate (3*2 ml), combined, dried over anhydrous Na2SO4, filtered and concentrated, and the combined liquid was separated by column chromatography to obtain the target product azobenzene with a yield of 36%.

[0155] Application Comparative Example 7

[0156] 40 mg of rice husk-based copper single atom material, 1.0 mmol of aniline, 0.2 mmol of pyridine and 2 ml of toluene were added to a reaction bottle in sequence, and the reaction was carried out at 80° C. and 1 atm of air for 15 h. The reaction progress was tracked by thin layer chromatography. After the reaction was completed, the filtrate was obtained by filtration. The filter cake was rinsed with ethyl acetate (3*2 ml), combined, dried over anhydrous Na2SO4, filtered, concentrated, and the combined liquid was separated by column chromatography to obtain the target product azobenzene with a yield of 59%.

[0157] Application Comparative Example 8

[0158] 40 mg of rice husk-based copper single atom material, 1.0 mmol of aniline, 0.2 mmol of triethylamine and 2 ml of toluene were added to a reaction bottle in sequence, and the reaction was carried out at 80° C. and 1 atm of air for 15 h. The reaction progress was tracked by thin layer chromatography. After the reaction was completed, the filtrate was obtained by filtration. The filter cake was rinsed with ethyl acetate (3*2 ml), combined, dried over anhydrous Na2SO4, filtered, concentrated, and the combined liquid was separated by column chromatography to obtain the target product azobenzene with a yield of 14%.

[0159] Application Comparative Example 9

[0160] 40 mg of rice husk-based copper single atom material, 1.0 mmol of aniline, 0.2 mmol of triethylenediamine and 2 ml of toluene were added to a reaction bottle in sequence, and the reaction was carried out at 80° C. and 1 atm of air for 15 h. The reaction progress was tracked by thin layer chromatography. After the reaction was completed, the filtrate was obtained by filtration. The filter cake was rinsed with ethyl acetate (3*2 ml), combined, dried over anhydrous Na2SO4, filtered, concentrated, and the combined liquid was separated by column chromatography to obtain the target product azobenzene with a yield of 26%.

[0161] Application Comparative Example 10

[0162] 40 mg of rice husk-based copper single atom material, 1.0 mmol of aniline, 1 mmol of sodium hydroxide and 2 ml of toluene were added into the reaction bottle in sequence, and the reaction was carried out at 80°C and 1 atm of air for 15 h. The reaction progress was tracked by thin layer chromatography. After the reaction was completed, the filtrate was obtained by filtration. The filter cake was rinsed with ethyl acetate (3*2 ml), combined, dried over anhydrous Na2SO4, filtered and concentrated, and the combined solution was separated by column chromatography, but the target product azobenzene could not be obtained.

[0163] Application Comparative Example 11

[0164] 40 mg of rice husk-based copper single atom material, 1.0 mmol of aniline, 1 mmol of potassium carbonate and 2 ml of toluene were added into the reaction bottle in sequence, and the reaction was carried out at 80°C and 1 atm of air for 15 h. The reaction progress was tracked by thin layer chromatography. After the reaction was completed, the filtrate was obtained by filtration. The filter cake was rinsed with ethyl acetate (3*2 ml), combined, dried over anhydrous Na2SO4, filtered and concentrated, and the combined solution was separated by column chromatography, but the target product azobenzene could not be obtained.

[0165] Application Comparative Example 12

[0166] 40 mg of rice husk-based copper single atom material, 1.0 mmol of aniline and 2 ml of toluene were added into the reaction bottle in sequence, and the reaction was carried out at 80°C and 1 atm of air for 15 h. The reaction progress was tracked by thin layer chromatography. After the reaction was completed, the filtrate was obtained by filtration. The filter cake was rinsed with ethyl acetate (3*2 ml), combined, dried over anhydrous Na2SO4, filtered and concentrated, and the combined solution was separated by column chromatography, but the target product azobenzene could not be obtained.

[0167] The present invention uses aniline as a template substrate, and by screening the types of solvents, toluene is the best solvent with a yield of 98% (Application Example 1). By analyzing the experimental results, it can be found that when there is no base involved, the reaction cannot be carried out (Application Comparative Example 11). Further analysis shows that when an organic base is involved, although the yield is different, there is a certain degree of yield (Application Comparative Examples 1 to 9). When an inorganic base is involved, the reaction cannot be carried out (Application Comparative Examples 10 to 11), because the addition of the inorganic base destroys the atomically dispersed copper on the surface of the rice husk-based copper single-atom material, causing it to agglomerate, thereby causing the rice husk-based copper single-atom material to be inactivated.

[0168] On the basis of optimizing the reaction conditions, the present invention expands the substrate range of aniline. The results show that aromatic amines with different substituents at the para position of the aromatic ring, including electron-donating groups such as alkyl (Application Comparative Example 12, Application Example 4, Application Example 7), alkoxy (Application Example 16), electron-withdrawing groups such as halogen (Application Examples 10-13), nitro (Application Examples 14-15), carbonyl (Application Example 17), ester (Application Example 18), react well. Aromatic amines with different substituents at the meta position of the aromatic ring, including electron-donating groups such as alkyl (Application Example 2), electron-withdrawing groups such as halogen (Application Example 10), nitro (Application Example 14), react well. Aromatic amines with alkyl groups at the ortho position of the aromatic ring (Application Example 3) have a slightly lower reaction effect than the meta and para positions. It is worth noting that the tert-butyl group with large steric hindrance on the aromatic ring can also adapt to this reaction condition. Therefore, it can be inferred from these results that the electronic properties of the substituents have little effect on the reaction efficiency.

[0169] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. Application of biomass-based copper single-atom materials in the synthesis of aromatic azo compounds, characterized in that: Using biomass-based copper single-atom materials as catalysts, aniline compounds and solvents as raw materials, catalytic oxidation reactions occur under alkaline conditions and air atmosphere to obtain aromatic azo compounds; The preparation method of the biomass-based copper single-atom material comprises the following steps: Cu 2+ The alcohol solution of the Schiff base is added to the alcohol solution, and a coordination chelation reaction occurs at 25℃~80℃ to obtain Cu 2+ Imprinting alcoholic solution of pre-complexed compound; Adding Cu to pretreated biomass 2+ The imprinted pre-coordinated compound is placed in an alcohol solution at 65°C to 100°C. 2+ The ethoxy group in the imprinted pre-coordination compound undergoes alcoholysis reaction with the hydroxyl group on the surface of the pretreated biomass material to form an -O-Si- bond, thereby obtaining a biomass-based copper single atom material.

2. The use according to claim 1, characterized in that: The biomass-based copper single atom material, aniline compounds, alkali and solvent are mixed, and a catalytic oxidation reaction is carried out at 75° C. to 85° C. in an air atmosphere to obtain an aromatic azo compound.

3. The use according to claim 2, characterized in that: The usage ratio of the biomass-based copper single atom material, the aniline compound and the solvent is 0.2-0.5 mmol:1 mmol:2-3 mL, and the molar amount of the base is 15%-25% of the aniline compound.

4. The use according to claim 1, characterized in that: The catalytic oxidation reaction time is 15h to 20h.

5. The use according to claim 1, characterized in that: The reaction progress was tracked by thin layer chromatography. After the reaction was completed, the filtrate was obtained by filtration. The filter cake was rinsed with ethyl acetate, combined, dried with anhydrous Na2SO4, filtered, concentrated, and the combined solution was separated by column chromatography to obtain an aromatic azo compound.

6. The use according to claim 1, characterized in that: The solvent is acetonitrile, dimethyl sulfoxide, N,N-dimethylformamide, methanol, toluene, tetrahydrofuran or 1,4-dioxane; the base is pyridine, triethylamine, triethylenediamine, 1,8-diazabicyclo[5.4.0]undec-7-ene, sodium hydroxide or potassium carbonate.

7. The use according to claim 1, characterized in that: The Cu 2+ The molar ratio of copper to Schiff base is 1:1-2; based on the mass of the biomass-based copper single atom material, the loading amount of copper single atoms is 7.14wt%-7.48wt%.

8. The use according to claim 1, characterized in that: The preparation method of the pretreated biomass material comprises the following steps: Dissolve hexadecyl ammonium bromide in water, add ammonia water to obtain a treatment solution; add biomass material powder to the treatment solution, adjust the pH to 10-12, and perform hydrothermal reaction at 100-120° C. for 24-48 hours to obtain a pretreated biomass material.

9. The use according to claim 8, characterized in that: The mass concentration of the ammonia water is 25% to 28%, and the dosage ratio of the biomass material powder, hexadecyl ammonium bromide, water and ammonia water is 0.75g: 0.4 to 0.6g: 20 to 30mL: 15 to 18mL.

10. The use according to claim 1, characterized in that: The biomass material includes rice husk, straw, bagasse, tobacco stalk, corn cob or peanut shell.

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