C3N5-x-Oy catalyst with dual defects of O doping and N vacancy as well as preparation method and application of C3N5-x-Oy catalyst

Abstract

The invention discloses a C3N5-x-Oy catalyst with O doping and N vacancy dual defects as well as a preparation method and application of the C3N5-x-Oy catalyst, and belongs to the technical field of photocatalytic oxidation. The preparation method of the C3N5-x-Oy catalyst comprises the following steps: mixing 3-amino-1, 2, 4-triazole with oxalic acid, carrying out high-temperature calcination in different atmospheres, and applying the obtained catalyst to a photocatalytic oxidation reaction of aldehydes to prepare corresponding carboxylic acid. The C3N5-x-Oy catalyst with dual defects of O doping and N vacancy is adopted, and the photocatalytic oxidation activity of the C3N5 catalyst is improved by utilizing the photocatalytic activity of C3N5 and the synergistic effect among different defect sites. The catalyst has the advantages of low cost, simple preparation method, high photocatalytic activity, long service life and stability, and can be recycled.

Description

Technical Field

[0001] The present invention belongs to the field of photocatalytic oxidation of biomass, and particularly relates to a C3N 5-x -O y catalyst with dual defects of O doping and N vacancy, and its preparation method and application. Background Art

[0002] As an important biomass-derived platform compound, 5-hydroxymethylfurfural can be selectively oxidized into various high-value-added derivatives, such as 2,5-furandicarboxaldehyde, 5-hydroxymethyl-2-furoic acid, 5-formyl-2-furoic acid, and 2,5-furandicarboxylic acid. Among them, 2,5-furandicarboxylic acid, as one of the raw materials for producing biodegradable plastics, is an ideal substitute for traditional petroleum-based monomers such as terephthalic acid, isophthalic acid, adipic acid, succinic acid, and bisphenol A in the synthesis of bio-based polymers such as polyesters, polyamides, and epoxy resins.

[0003] Currently, the selective oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid mainly relies on high temperature, high pressure, other metals, and high-cost catalysts. Homogeneous catalysts such as Co / Mn / Br, Cu(NO3)2 / VOSO4, and NaBr usually require a high temperature above 120 °C to catalyze the selective oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid (ACS Sustain. Chem. Eng. 2016, 4, 3659-3668; ChemSusChem. 2011, 4, 51-54; ChemCatChem. 2014, 6, 1195-1198.), and the catalysts are difficult to separate, further leading to an increase in by-products and inorganic waste. Heterogeneous catalysts are easily separated from the reactants and can be reused multiple times. So far, various different heterogeneous catalysts have been applied to the reaction of catalytically selective oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid, and most of them are inorganic material-supported noble metals such as Pd, Pt, Ru, Rh, and Au (ACS Catal. 2014, 4, 2175-2185; Green Chem. 2015, 17, 1610-1617; J. Catal. 2014, 315, 67-74.). For example, Au nanoparticles supported on CeO2 show excellent catalytic activity for this oxidation reaction under strong alkaline conditions and 10 bar oxygen pressure, with a yield as high as 99% (Micropor. Mesopor. Mat. 2016, 226, 466-475.). However, noble metal materials are costly and prone to agglomeration and deactivation during high-temperature reactions, making it difficult to be widely applied in industrial production.

[0004] Photocatalytic reactions have mild conditions, do not require high temperature and high-pressure oxygen conditions, and the emissions after the reaction have little pollution. Therefore, the selective conversion of 5-hydroxymethylfurfural by photocatalysis has broad development prospects. At present, a variety of heterogeneous photocatalysts have been found to be applicable to the catalytic selective oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid. For example, Au-Ag bimetallic nanoparticles supported on TiO2 have higher catalytic activity than monometallic catalysts. At normal temperature and pressure, under irradiation with a 300 W xenon lamp for 5 h, the conversion rate of 5-hydroxymethylfurfural is 42.6%, and the selectivity for 2,5-furandicarboxylic acid is 98.1% (Appl. Surf. Sci. 2023, 613, 156036). Dispersing cobalt-thiopyrrole- on g -C3N4 as a photocatalyst can also carry out this oxidation reaction in an aqueous phase system (J. Am. Chem. Soc. 2017, 139, 14775-14782.). Under irradiation with a xenon lamp at normal temperature and pressure for 14 h, the conversion rate of 5-hydroxymethylfurfural is 99.1%, and the selectivity for 2,5-furandicarboxylic acid is as high as 97.0%. However, most current reactions use a xenon lamp to provide light, and transition metals need to be used, and their costs and reaction conditions will limit the application and promotion of this reaction. Summary of the Invention

[0005] The purpose of the present invention is to solve the deficiencies of the prior art, and to provide a C3N with dual defects of O doping and N vacancies 5-x -O y catalyst and its preparation method and application.

[0006] To achieve the above purpose, the technical scheme adopted by the present invention is as follows: The present invention provides a preparation method of a C3N with dual defects of O doping and N vacancies 5-x -O y catalyst, including the following steps: Step 1: Mix 3-amino-1,2,4-triazole with oxalic acid, and calcine at high temperature in an inert gas atmosphere. After the calcination is completed, cool naturally to obtain Material I; Step 2: Calcinate the Material I obtained in Step 1 at high temperature in air. After the calcination is completed, cool naturally, wash and dry to obtain the C3N with dual defects of O doping and N vacancies 5-x -O y catalyst.

[0007] Furthermore, the molar ratio of 3-amino-1,2,4-triazole to oxalic acid in Step 1 is 2~2.7:0.8~1.2.

[0008] Further, the inert gas in Step 1 is nitrogen or argon; the high-temperature calcination is specifically as follows: heating to 500 °C at a heating rate of 5 °C / min and then maintaining the temperature for calcination for 3 h.

[0009] Further, the high-temperature calcination in Step 2 is specifically as follows: heating to 500 °C at a heating rate of 5 °C / min and then maintaining the temperature for calcination for 3 h.

[0010] The present invention also provides C3N with double defects of O doping and N vacancies as described in any one of the above. 5-x -O y The C3N with double defects of O doping and N vacancies prepared by the preparation method of the catalyst. 5-x -O y Catalyst.

[0011] The present invention also provides a C3N with double defects of O doping and N vacancies. 5-x -O y Application of the catalyst in photocatalytic oxidation of aldehyde compounds, including the following steps: Adding the aldehyde compound, the C3N 5-x -O y Catalyst, alkali and solvent into a reaction vessel, stirring and reacting for a certain time under a certain pressure, gas atmosphere and visible light irradiation, and performing post-treatment after the reaction ends.

[0012] Further, the aldehyde compound is one of aromatic aldehydes such as 5-hydroxymethylfurfural, 3-pyridinecarboxaldehyde, furfural, 5-methylfurfural, benzene-1,3,5-tricarbaldehyde, benzaldehyde, 2-chlorobenzaldehyde and p-trifluorobenzaldehyde; the alkali is one of sodium carbonate, cesium carbonate or ammonium carbonate, and the solvent is water.

[0013] Further, 10 mg of C3N5-x-Oy catalyst is required for every 0.2 mmol of aldehyde compound; the molar ratio of the aldehyde compound, alkali and solvent is 0.8 - 1.2:1.8 - 2.2:100 - 120.

[0014] Further, the reaction is carried out in an oxygen atmosphere, at a pressure of 0.1 MPa and under visible light irradiation at 413 nm.

[0015] Furthermore, the temperature during the reaction is 40 - 60 °C, and the reaction time is 16 - 20 h.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] First: The present invention adopts a mild reaction system, which can achieve efficient reactions under visible light irradiation. This system can increase the conversion rate of 5-hydroxymethylfurfural to 96%, and the yield of the target product 2,5-furandicarboxylic acid also reaches 96%. This achievement has important application value in industrial production.

[0018] Second: The present invention uses a C3N5-x-Oy catalyst with dual defects of O doping and N vacancies. By combining the photocatalytic activity of C3N5 itself and the synergistic effect between defect sites, the catalytic performance of the catalyst is significantly improved.

[0019] Third: The prepared C3N5-x-Oy catalyst does not contain metal elements, has low raw material costs and a simple preparation process, and also has excellent stability and recyclability. The introduction of dual defects of O doping and N vacancies effectively reduces the luminescence intensity of C3N5, promotes the separation of photogenerated carriers, and further enhances the catalytic efficiency. Brief Description of the Drawings

[0020] Figure 1a TEM image of the C3N 5-x -O y -1 catalyst at a size of 200 nm; Figure 1b TEM image of the C3N 5-x -O y -1 catalyst at a size of 100 nm; Figure 1c HAADF image of the C3N 5-x -O y -1 catalyst at a size of 200 nm; Figure 2a Mapping image of the C element distribution of the C3N 5-x -O y -1 catalyst; Figure 2b Mapping image of the N element distribution of the C3N 5-x -O y -1 catalyst; Figure 2c Mapping image of the O element distribution of the C3N 5-x -O y -1 catalyst; Figure 3 TEM image of the C3N 5-x -O y- XRD pattern of the catalyst - 1. In the figure, C3N5 is 3 - amino - 1,2,4 - triazole; Figure 4 is C3N prepared in Example 1 of the present invention 5-x -O y - Ultraviolet spectrum of the catalyst - 1. In the figure, C3N5 is 3 - amino - 1,2,4 - triazole; Figure 5 is the infrared spectrum of the product 2,5 - furandicarboxylic acid obtained in Example 8 of the present invention; Figure 6 is the 1H NMR spectrum of the product 2,5 - furandicarboxylic acid obtained in Example 8 of the present invention; 1 H NMR (500 MHz,DMSO - d6) δ 8.46 (s, 1H).

[0021] From Figures 1a - 1c it can be seen that C3N 5-x -O y - 1 catalyst is in the form of thin - layer flakes with a large surface area, providing a basis for excellent photocatalytic activity; From Figures 2a - 2c it can be seen that C3N 5-x -O y - 1 catalyst has a uniform distribution of three elements C, N, and O in the catalyst; From Figure 3 it can be seen that C3N 5-x -O y - 1 catalyst and C3N5 have two diffraction peaks at 13.4° and 27.5°, and C3N 5-x -O y - 1 y The obvious decrease in the intensity of the diffraction peak in the catalyst indicates that there are certain defects inside. From Figure 4 it can be seen that the absorption band generated by the electron transition of C3N 5-x -O y - 1 catalyst is significantly amplified, indicating that the defect engineering optimizes the electronic structure of the catalyst. From Figure 5 it can be seen that the infrared spectra of the crude product of the reaction product 2,5 - furandicarboxylic acid and the pure product 2,5 - furandicarboxylic acid are nearly identical. Detailed implementation mode

[0022] The present invention will be further described in detail below in conjunction with the embodiments.

[0023] Those skilled in the art will understand that the following embodiments are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. For those not specified in the embodiments regarding specific techniques or conditions, they shall be carried out according to the techniques or conditions described in the literature in this field or according to the product instructions. For the reagents or instruments not specified for the manufacturer, they are all conventional products that can be obtained by purchase.

[0024] Example 1: Catalyst C3N 5-x -O y -1 Preparation Step 1: Mix 1 g of 3-amino-1,2,4-triazole with 0.396 g of oxalic acid, and then heat it to 500 °C at a heating rate of 5 °C / min in an argon atmosphere and calcine for 3 h. After the calcination is completed, let it cool naturally to obtain Material I; Step 2: Heat the Material I obtained in Step 1 to 500 °C at a heating rate of 5 °C / min in air and calcine for 3 h. After the calcination is completed, let it cool naturally. After washing and drying, C3N with double defects of O doping and N vacancies is obtained 5-x -O y -1 catalyst.

[0025] Example 2: Catalyst C3N 5-x -O y -2 Preparation Step 1: Mix 1 g of 3-amino-1,2,4-triazole with 0.297 g of oxalic acid, and then heat it to 500 °C at a heating rate of 5 °C / min in an argon atmosphere and calcine for 3 h. After the calcination is completed, let it cool naturally to obtain Material I; Step 2: Heat the Material I obtained in Step 1 to 500 °C at a heating rate of 5 °C / min in air and calcine for 3 h. After the calcination is completed, let it cool naturally. After washing and drying, C3N with double defects of O doping and N vacancies is obtained 5-x -O y -2 catalyst.

[0026] Example 3: Preparation of Catalyst C3N5-O y -3 Preparation Step 1: Mix 1 g of 3-amino-1,2,4-triazole with 0.594 g of oxalic acid, and then heat it to 500 °C at a heating rate of 5 °C / min in an argon atmosphere and calcine for 3 h. After the calcination is completed, let it cool naturally to obtain Material I; Step 2: Heat the Material I obtained in Step 1 to 500 °C at a heating rate of 5 °C / min in air and calcine for 3 h. After the calcination is completed, let it cool naturally. After washing and drying, C3N with double defects of O doping and N vacancies is obtained 5-x -O y -3 catalyst.

[0027] Example 4: Preparation of Catalyst C3N5 Heat 1 g of 3-amino-1,2,4-triazole to 500 °C at a heating rate of 5 °C / min in an air atmosphere, calcine for 4 h, and let it cool naturally after the calcination is completed. After washing and drying, the C3N5 catalyst is obtained.

[0028] Example 5: Preparation of Catalyst C3N4 9 g of urea and 1 g of melamine were heated to 550 °C at a heating rate of 2.5 °C / min in a nitrogen atmosphere, calcined at high temperature for 4 h, cooled naturally after the calcination, stirred in water for 4 h, washed and dried to obtain the C3N4 catalyst.

[0029] Example 6: Preparation of Catalyst C3N5-O 1 g of 3-amino-1,2,4-triazole and 0.396 g of oxalic acid were mixed, then heated to 500 °C at a heating rate of 5 °C / min in a nitrogen atmosphere, calcined at high temperature for 3 h, cooled naturally after the calcination, washed and dried to obtain the C3N5-O catalyst.

[0030] Example 7: Preparation of Catalyst C3N5-S 1 g of 3-amino-1,2,4-triazole and 0.396 g of thiourea were mixed, then heated to 500 °C at a heating rate of 5 °C / min in a nitrogen atmosphere, calcined at high temperature for 3 h, cooled naturally after the calcination, washed and dried to obtain the C3N5-S catalyst.

[0031] Example 8: Photocatalytic Oxidation of 5-Hydroxymethylfurfural Conversion Reaction

[0032] 25.2 mg of 5-hydroxymethylfurfural, 2 mL of water, 10 mg of the C3N 5-x -O y -1 catalyst prepared in Example 1 and 42.4 mg of sodium carbonate were successively added to a pressure-resistant reaction tube. Under an oxygen atmosphere, at a pressure of 0.1 MPa, at room temperature and under 413 nm visible light irradiation, the mixture was stirred and reacted for 18 h (rotation speed 450 rpm); after the reaction, it was taken out, the catalyst and the aqueous phase were separated, and the aqueous phase was determined by a high-performance liquid chromatograph (using acetonitrile with a volume fraction of 55% and water with a volume fraction of 45% as the mobile phase, flow rate 0.7 mL / min; detection wavelength 254 nm; and the external standard method was used for characterization) to obtain the yield of the target product 2,5-furandicarboxylic acid was 96%. The light source used was an LED lamp with a power of 15 W.

[0033] Example 9: Photocatalytic Oxidation of 5-Hydroxymethylfurfural Conversion Reaction

[0034] 25.2 mg of 5-hydroxymethylfurfural, 2 mL of water, 10 mg of the C3N 5-x -O y-1 catalyst and 130.3 mg of cesium carbonate were successively added into a pressure-resistant reaction tube. Under an oxygen atmosphere, with a pressure of 0.1 MPa, at room temperature, and under irradiation with visible light at 413 nm, the mixture was stirred and reacted for 18 h (rotation speed 450 rpm); after the reaction ended, it was taken out, the catalyst and the aqueous phase were separated, and the aqueous phase was determined by a high-performance liquid chromatograph (using acetonitrile with a volume fraction of 55% and water with a volume fraction of 45% as the mobile phase; flow rate 0.7 mL / min; detection wavelength 254 nm; and the external standard method was used for characterization), and the yield of the target product 2,5-furandicarboxylic acid was 92%. Among them, an LED lamp with a power of 15 W was selected as the light source.

[0035] Example 10: Photocatalytic oxidation of 3-pyridinecarboxaldehyde conversion reaction

[0036] 21.4 mg of 3-pyridinecarboxaldehyde, 2 mL of water, and 10 mg of C3N prepared in Example 1 5-x -O y -1 catalyst and 42.4 mg of sodium carbonate were successively added into a pressure-resistant reaction tube. Under an oxygen atmosphere, with a pressure of 0.1 MPa, at room temperature, and under irradiation with visible light at 413 nm, the mixture was stirred and reacted for 18 h (rotation speed 450 rpm); after the reaction ended, it was taken out, the catalyst and the aqueous phase were separated, and the aqueous phase was determined by a high-performance liquid chromatograph (using acetonitrile with a volume fraction of 55% and water with a volume fraction of 45% as the mobile phase; flow rate 0.7 mL / min; detection wavelength 254 nm; and the external standard method was used for characterization), and the yield of the target product nicotinic acid was 86%. Among them, an LED lamp with a power of 15 W was selected as the light source.

[0037] Example 11: Photocatalytic oxidation of furfural conversion reaction

[0038] 19.2 mg of furfural, 2 mL of water, and 10 mg of C3N prepared in Example 1 5-x -O y -1 catalyst and 42.4 mg of sodium carbonate were successively added into a pressure-resistant reaction tube. Under an oxygen atmosphere, with a pressure of 0.1 MPa, at room temperature, and under irradiation with visible light at 413 nm, the mixture was stirred and reacted for 18 h (rotation speed 450 rpm); after the reaction ended, it was taken out, the catalyst and the aqueous phase were separated, and the aqueous phase was determined by a high-performance liquid chromatograph (using acetonitrile with a volume fraction of 55% and water with a volume fraction of 45% as the mobile phase; flow rate 0.7 mL / min; detection wavelength 254 nm; and the external standard method was used for characterization), and the yield of the target product furoic acid was 94%. Among them, an LED lamp with a power of 15 W was selected as the light source.

[0039] Example 12: Photocatalytic oxidation of 5-methylfurfural conversion reaction

[0040] 22 mg of 5-methylfurfural, 2 mL of water, 10 mg of the C3N 5-x -O y -1 catalyst prepared in Example 1 and 42.4 mg of sodium carbonate were successively added into a pressure-resistant reaction tube. Under an oxygen atmosphere, with a pressure of 0.1 MPa, at room temperature, and under irradiation with visible light at 413 nm, the mixture was stirred and reacted for 18 h (rotation speed 450 rpm). After the reaction ended, the catalyst and the aqueous phase were separated. The aqueous phase was analyzed by a high-performance liquid chromatograph (using a mobile phase of acetonitrile with a volume fraction of 55% and water with a volume fraction of 45%; flow rate 0.7 mL / min; detection wavelength 254 nm; and characterized by the external standard method), and the yield of the target product, furoic acid, was determined to be 95%. The light source used was an LED lamp with a power of 15 W.

[0041] Example 13: Photocatalytic oxidation of aromatic aldehyde conversion reaction

[0042] 0.2 mmol of the raw materials 9a - 9i, 2 mL of water, 10 mg of the C3N 5-x -O y -1 catalyst prepared in Example 1 and 42.4 mg of sodium carbonate were successively added into a pressure-resistant reaction tube. Under an oxygen atmosphere, with a pressure of 0.1 MPa, at room temperature, and under irradiation with visible light at 413 nm, the mixture was stirred and reacted for 18 h (rotation speed 450 rpm). After the reaction ended, the catalyst and the aqueous phase were separated. The aqueous phase was analyzed by a high-performance liquid chromatograph (using a mobile phase of acetonitrile with a volume fraction of 55% and water with a volume fraction of 45%; flow rate 0.7 mL / min; detection wavelength 254 nm; and characterized by the external standard method), and the yields of the target products 1a - 1i are shown as follows. The light source used was an LED lamp with a power of 15 W.

[0043]

[0044] Example 14: Repeated use of C3N 5-x -O y -1 catalyst for photocatalytic oxidation of 5-hydroxymethylfurfural conversion reaction 25.2 mg of 5-hydroxymethylfurfural, 2 mL of water, 10 mg of the C3N 5-x -O y-1 catalyst and 42.4 mg of sodium carbonate were successively added to a pressure-resistant reaction tube. Under an oxygen atmosphere, with a pressure of 0.1 MPa, at room temperature, and under irradiation with visible light at 413 nm, stirring (rotation speed 450 rpm) was carried out for 18 h; after the reaction, the catalyst was separated by centrifugation, washed three times with methanol and dried. The above process was repeated five times, and the yield of 2,5-furandicarboxylic acid in the aqueous phase was determined by high performance liquid chromatography to be 96%, 95%, 94%, 92%, and 91% respectively.

[0045] Comparative Example 1

[0046] The difference from Example 8 was only that the C3N 5-x -O y -1 catalyst used in Example 8 was changed to 10 mg of the C3N5 catalyst prepared in Example 4, and the reaction was carried out under the same reaction conditions; after the reaction, it was taken out, the catalyst and the aqueous phase were separated, and the aqueous phase was passed through a high performance liquid chromatography (using acetonitrile with a volume fraction of 55% and water with a volume fraction of 45% as the mobile phase; flow rate 0.7 mL / min; detection wavelength 254 nm; and the external standard method was used for characterization) to determine that the yield of the target product was 90%. Among them, a LED lamp with a power of 15 W was selected as the light source. Comparative Example 2

[0047] The difference from Example 8 was only that the C3N 5-x -O y -1 catalyst used in Example 8 was changed to 10 mg of the C3N4 catalyst prepared in Example 5, and the reaction was carried out under the same reaction conditions; after the reaction, it was taken out, the catalyst and the aqueous phase were separated, and the aqueous phase was passed through a high performance liquid chromatography (using acetonitrile with a volume fraction of 55% and water with a volume fraction of 45% as the mobile phase; flow rate 0.7 mL / min; detection wavelength 254 nm; and the external standard method was used for characterization) to determine that the yield of the target product was 84%. Among them, a LED lamp with a power of 15 W was selected as the light source. Comparative Example 3

[0048] The difference from Example 8 was only that the C3N 5-x -O y -1 catalyst used in Example 8 was changed to 10 mg of the C3N5-O catalyst prepared in Example 6, and the reaction was carried out under the same reaction conditions; after the reaction, it was taken out, the catalyst and the aqueous phase were separated, and the aqueous phase was passed through a high performance liquid chromatography (using acetonitrile with a volume fraction of 55% and water with a volume fraction of 45% as the mobile phase; flow rate 0.7 mL / min; detection wavelength 254 nm; and the external standard method was used for characterization) to determine that the yield of the target product was 53%. Among them, a LED lamp with a power of 15 W was selected as the light source. Comparative Example 4

[0049] The difference from Example 8 is only that the C3N 5-x -O y -1 catalyst used in Example 8 was changed to 10 mg of the C3N5-S catalyst prepared in Example 7, and the reaction was carried out under the same reaction conditions; after the reaction was completed, it was taken out, the catalyst and the aqueous phase were separated, and the yield of the target product was determined to be 24% by a high performance liquid chromatograph (using acetonitrile with a volume fraction of 55% and water with a volume fraction of 45% as the mobile phase; flow rate 0.7 mL / min; detection wavelength 254 nm; and the external standard method was used for characterization). Among them, the light source was an LED lamp with a power of 15 W.

[0050] The above embodiments have described the implementation manners of the present invention in detail, but the present invention is not limited to the above implementation manners, and various changes can be made without departing from the gist of the present invention within the scope of knowledge possessed by those of ordinary skill in the art. The above are only preferred and feasible embodiments of the present invention, and thus do not limit the scope of the rights of the present invention. Any equivalent structural changes made by using the content of the specification of the present invention are included within the scope of the rights of the present invention.

Claims

1. Preparation method of C3N with double defects of O doping and N vacancy 5-x -O y The catalyst is characterized in that It includes the following steps: Step 1: Mix 3-amino-1,2,4-triazole with oxalic acid, and conduct high-temperature calcination in an inert gas atmosphere. After the calcination is completed, let it cool naturally to obtain Material I; Step 2: Calcinate the obtained Material I in Step 1 at high temperature in air. After the calcination is completed, let it cool naturally. After washing and drying, the C3N with dual defects of O doping and N vacancies is obtained. 5-x -O y catalyst.

2. The preparation method of the C3N catalyst with dual defects of O doping and N vacancies according to claim 1, characterized in that 5-x -O y In Step 1, the molar ratio of the 3-amino-1,2,4-triazole to the oxalic acid is 2~2.7:0.8~1.

2. ​ 3. The preparation method of the C3N catalyst with double defects of O doping and N vacancies according to claim 1, characterized in that 5-x -O y In Step 1, the inert gas is nitrogen or argon; the specific high-temperature calcination is as follows: Heat it to 500 °C at a heating rate of 5 °C / min, and then conduct isothermal calcination for 3 h.

4. Preparation method of C3N catalyst with double defects of O doping and N vacancy according to claim 1, characterized in that 5-x -O y In Step 2, the specific high-temperature calcination is as follows: Heat it to 500 °C at a heating rate of 5 °C / min, and then conduct isothermal calcination for 3 h. ​ 5. C₃N with dual defects of O doping and N vacancies according to any one of claims 1 to 4 5-x -O y C₃N with dual defects of O doping and N vacancies prepared by the preparation method of the catalyst 5-x -O y catalyst 6. Application of the C3N with dual defects of O doping and N vacancies according to claim 5 5-x -O y in photocatalytic oxidation of aldehyde compounds, characterized in that It includes the following steps: Add the aldehyde compound and the C3N 5-x -O y catalyst, base and solvent into a reaction vessel, stir and react for a certain time under a certain pressure, gas atmosphere and visible light irradiation, and perform post-treatment after the reaction ends.

7. Use of the C3N 5-x 5-x -O y catalyst with dual defects of O doping and N vacancies in the photocatalytic oxidation of aldehyde compounds, characterized in that The aldehyde compound is one of aromatic aldehydes such as 5-hydroxymethylfurfural, 3-pyridinecarboxaldehyde, furfural, 5-methylfurfural, benzene-1,3,5-tricarbaldehyde, benzaldehyde, 2-chlorobenzaldehyde, and p-trifluorobenzaldehyde; the base is one of sodium carbonate, cesium carbonate, or ammonium carbonate, and the solvent is water.

8. Use of the C3N - O catalyst with dual defects of O doping and N vacancies according to claim 6 in the photocatalytic oxidation of aldehyde compounds, characterized in that, 5-x -O y For every 0.2 mmol of aldehyde compound, 10 mg of C3N 5-x -O y catalyst is required; the molar ratio of the aldehyde compound, base and solvent is 0.8~1.2:1.8~2.2:100~120. ​ 9. Use of the C3N catalyst with dual defects of O doping and N vacancies according to claim 6 5-x -O y in the photocatalytic oxidation of aldehyde compounds, characterized in that The reaction is carried out in an oxygen atmosphere, at a pressure of 0.1 MPa and under visible light irradiation at 413 nm.

10. Application of the C3N catalyst with dual defects of O doping and N vacancies according to claim 9 5-x -O y in the photocatalytic oxidation of aldehyde compounds, characterized in that The temperature during the reaction is 40~60 °C, and the reaction time is 16~20 h.

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