A polyethyleneimine-loaded polyheptazineimide composite material and its preparation method and application

Abstract

The present invention relates to a polyethyleneimine-loaded polyheptazine imide composite material and a preparation method and application thereof, and belongs to the technical field of organic polymer composite materials. The preparation method of the composite material comprises: mixing a molten salt mixture with a polyheptazine imide material precursor, heating and calcining under an inert atmosphere to obtain a solid powder; mixing the solid powder with a branched polyethyleneimine solution to obtain a mixed solution; and heating the obtained mixed solution to obtain the polyethyleneimine-loaded polyheptazine imide composite material. Compared with the prior art, the present invention improves the performance of molecular oxygen activation and conversion into hydrogen peroxide through weak interactions such as hydrogen bonds and van der Waals between polyheptazine imide and polyethyleneimine, and has the advantages of simple and efficient preparation process.

Description

Technical Field

[0001] The invention relates to the technical field of green synthesis of hydrogen peroxide, and in particular to a polyethyleneimine-loaded polyheptazineimide composite material and a preparation method and application thereof. Background Art

[0002] Hydrogen peroxide is an important chemical reagent and industrial product with a wide range of uses. It is widely used in many fields. Hydrogen peroxide has strong oxidizing and weak acidic characteristics and is often used in bleaching, chemical synthesis, disinfection, and water treatment. Especially in wastewater treatment and pollution control, hydrogen peroxide, as a highly efficient oxidant, can effectively decompose organic pollutants in water bodies, and its only by-product is water, so it is considered to be an environmentally friendly choice. With the development of environmentally friendly technologies, the increasing demand for cleaning and disinfection, and the increasing application in industries such as electronic manufacturing, papermaking, and water treatment, the global demand for hydrogen peroxide has shown a steady upward trend.

[0003] At present, more than 95% of hydrogen peroxide in the world is prepared by the anthraquinone method. This method uses anthraquinone molecules as a circulating carrier to produce hydrogen peroxide through catalytic hydrogenation and oxidation reactions. Anthraquinone molecules show excellent stability in the reaction, can be recycled repeatedly, and the chemical selectivity of the reaction is high. The produced hydrogen peroxide has high purity and can be widely used in various industrial needs. However, this method also has significant shortcomings, including high energy consumption, expensive equipment investment and complex process. The process involves the use of hydrogen, which further increases the complexity of operation and the difficulty of safety management. During the entire reaction process, the control accuracy of the process conditions is required to be high, including temperature, pressure and catalyst activity and other key factors, which makes the technical threshold of this method high and difficult to achieve popularization or wider application. With the continued global attention to climate warming and energy shortages, traditional high-energy consumption and high-cost production methods are facing major challenges. Therefore, it is particularly important to develop a green, economical and efficient hydrogen peroxide preparation process.

[0004] The technology based on photocatalytic hydrogen peroxide generation has attracted widespread attention due to its zero secondary pollution, safety and low energy consumption. Among them, sunlight is the only energy source, and the photocatalytic reaction of oxygen in the air and readily available water to generate hydrogen peroxide based on photocatalysts is an attractive approach to carbon neutrality. At present, the catalysts for photocatalytic generation of hydrogen peroxide are mainly divided into inorganic semiconductor photocatalysts and organic semiconductor photocatalysts; among them, polyheptazine imide, as a highly crystalline organic conjugated polymer photocatalyst, has good light absorption performance and photogenerated carrier migration ability, and is a suitable candidate catalyst for photocatalytic generation of hydrogen peroxide. Although polyheptazine imide can effectively activate molecular oxygen to generate superoxide radicals, an intermediate of hydrogen peroxide, the protonation process of superoxide radicals on its surface is often restricted, which reduces the selectivity of hydrogen peroxide generation and hinders the generation of efficient hydrogen peroxide.

[0005] Based on the above background, how to design and develop a highly efficient semiconductor catalyst material based on polyheptazine imide, which has active sites for highly efficient activation of molecular oxygen and can promote the protonation process of superoxide radicals, is the key to achieving efficient photocatalytic hydrogen peroxide generation. The design and development of the synthesis method of this catalyst material will have significant energy and environmental significance, and also have great commercial prospects. Summary of the invention

[0006] In order to solve the above technical problems, the present invention provides a polyethyleneimine-loaded polyheptazineimide composite material and a preparation method and application thereof.

[0007] The first object of the present invention is to provide a polyethyleneimine-loaded polyheptazineimide composite material, comprising a polyheptazineimide carrier and a branched polyethyleneimine polymer loaded on the surface of the polyheptazineimide carrier; the branched polyethyleneimine polymer is combined with the surface of the polyheptazineimide carrier through hydrogen bonds and van der Waals interactions.

[0008] In some embodiments of the present invention, the loading amount of the branched polyethyleneimine polymer is 10.0 wt.% ~25.0 wt.%.

[0009] The second object of the present invention is to provide a method for preparing a polyethyleneimine-loaded polyheptazine imide composite material, comprising the following steps:

[0010] The molten salt mixture is mixed with a polyheptazine imide material precursor, and heated and calcined under an inert atmosphere to obtain a solid powder;

[0011] mixing the solid powder with the branched polyethyleneimine solution to obtain a mixed solution;

[0012] The obtained mixed solution is subjected to heating treatment to obtain the polyethyleneimine-loaded polyheptazineimide composite material.

[0013] In some embodiments of the present invention, the molten salt mixture is selected from two or three of LiCl, NaCl and KCl.

[0014] In some embodiments of the present invention, the polyheptazine imide material precursor is selected from 5-amino-4-triazole monohydrate and / or 3-amino-5-mercapto-1,2,4-triazole.

[0015] In some embodiments of the present invention, the mass ratio of the polyheptazine imide material precursor to the molten salt mixture is (0.1 ~ 0.2):1.

[0016] In some embodiments of the present invention, the inert gas atmosphere contains inert substances selected from nitrogen and / or helium;

[0017] The heating and calcining conditions are: 500-600°C for 4-8 h, and a heating rate of 1.5-5.0°C / min. For example, it can be 1.5°C / min, 2°C / min, 2.5°C / min, 3°C / min, 3.5°C / min, 4°C / min, 4.5°C / min, 5°C / min, etc., or any interval value between any two values.

[0018] In some embodiments of the present invention, the weight average molecular weight of the branched polyethyleneimine is 600 to 25,000, and illustratively, it can be 600, 1,800, 2,000, 6,000, 10,000, 15,000, 20,000, 25,000, etc., or any interval value between any two values;

[0019] The concentration of the branched polyethyleneimine solution is 1.0 to 10.0 g / L, and illustratively, can be 1 g / L, 2 g / L, 3 g / L, 4 g / L, 5 g / L, 6 g / L, 7 g / L, 8 g / L, 9 g / L, 10 g / L, etc., or any interval value between any two values;

[0020] The dosage of the solid powder in the branched polyethyleneimine solution is 4.0 to 10.0 g / L, and illustratively, it can be 4 g / L, 5 g / L, 6 g / L, 7 g / L, 8 g / L, 9 g / L, 10 g / L, etc., or any interval value between any two values;

[0021] The heating temperature in the heat treatment is 160 ~ 200 ° C, and illustratively can be 160, 170, 18, 190, 200, etc., or any interval value between any two values; the heating time is 16 ~ 24 h, and illustratively can be 16h, 17h, 18h, 19h, 20h, 21h, 22h, 23h, 24h, etc., or any interval value between any two values.

[0022] The third object of the present invention is to provide the application of the polyethyleneimine-loaded polyheptazineimide composite material in the photocatalytic activation and conversion of molecular oxygen.

[0023] In some embodiments of the present invention, the product of the activation and conversion of molecular oxygen is hydrogen peroxide.

[0024] In the present invention, polyethyleneimine and polyheptazineimide in the polyethyleneimine-loaded polyheptazineimide composite material are compounded through hydrogen bonding and van der Waals force interactions; wherein polyheptazineimide, as an organic conjugated photocatalyst, has good light response performance and excellent carrier migration ability, and has good crystallinity, which is beneficial for photogenerated electrons to migrate to active sites and promote the molecular oxygen activation process; polyethyleneimine has abundant amino functional groups and plays an important role in the molecular oxygen activation; polyethyleneimine based on hydrogen bonding and van der Waals forces can assist the protonation process of hydrogen peroxide intermediates, which is beneficial for the generation of hydrogen peroxide.

[0025] The equation for the activation and conversion of molecular oxygen in the present invention is:

[0026] O2 + 2H2O = 2H2O2.

[0027] The above technical solution of the present invention has the following advantages compared with the prior art:

[0028] (1) The photocatalytic hydrogen peroxide generation process based on organic conjugated polymers has the advantages of being green, sustainable and low-cost. Compared with the traditional anthraquinone method, the high-efficiency system does not require high process equipment investment and strict operating procedures. In the present invention, a high-efficiency organic conjugated polymer photocatalyst is combined with a polyethyleneimine polymer to form a composite catalyst, which only uses sunlight as energy input, and oxygen and water as raw materials to catalyze the generation of hydrogen peroxide. The process is green and environmentally friendly, and the raw materials are widely available, realizing the preparation of hydrogen peroxide at room temperature and pressure.

[0029] (2) The polyethyleneimine-loaded polyheptazinimide composite material of the present invention is composed of a polyheptazinimide material with high crystallinity as a carrier and a polyethyleneimine polymer rich in amino groups; wherein the polyheptazinimide with high crystallinity has good light response ability and carrier separation efficiency, and the high crystallinity structure provides good stability, and the polyheptazinimide carrier can adsorb and activate molecular oxygen to generate superoxide free radicals as hydrogen peroxide intermediates; at the same time, polyethyleneimine assists the protonation of superoxide free radicals based on the hydrogen bond and van der Waals interaction between it and the superoxide free radicals, thereby promoting the generation of hydrogen peroxide. The system does not involve transition metals, inhibits the in-situ activation of hydrogen peroxide, and further improves the yield of hydrogen peroxide.

[0030] (3) The weak interactions such as hydrogen bonds and van der Waals based on polyethyleneimine in the polyethyleneimine-supported polyheptazinimide composite material of the present invention can inhibit the breakage of the OO bond during the activation and conversion of molecular oxygen, so that the composite catalyst material has a higher selectivity for hydrogen peroxide generation, which helps to increase the hydrogen peroxide yield. At the same time, the system is not limited by the site and can be generated and utilized in situ at the desired hydrogen peroxide production site. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below according to specific embodiments of the present invention in conjunction with the accompanying drawings, wherein:

[0032] Figure 1 HAADF-STEM images of the polyethyleneimine-loaded polyheptazineimide composite material prepared in Example 1 of the present invention and the polyheptazineimide material in Comparative Example 1; wherein a is the polyethyleneimine-loaded polyheptazineimide composite material prepared in Example 1, and b is the polyheptazineimide material in Comparative Example 2;

[0033] Figure 2 XRD diagrams of the polyethyleneimine-loaded polyheptazine imide composite material prepared in Example 1 of the present invention and the polyheptazine imide material in Comparative Example 1;

[0034] Figure 3 The thermogravimetric analysis curves of the polyethyleneimine-loaded polyheptazinimide composite material prepared in Example 1 of the present invention and the polyheptazinimide prepared in Comparative Example 1; wherein a is the polyethyleneimine-loaded polyheptazinimide composite material, and b is polyheptazinimide; the temperature range of 300 to 600° C. is the temperature range for polyethyleneimine degradation, indicating that the polyethyleneimine content in the polyethyleneimine-loaded polyheptazinimide composite material is 23.5 wt.%;

[0035] Figure 4 The performance of different catalyst materials in the present invention for photocatalytic activation and conversion of molecular oxygen to generate hydrogen peroxide;

[0036] Figure 5 The charge distribution of the polyethyleneimine-loaded polyheptazineimide composite material during the molecular oxygen activation conversion process is obtained by the first principle calculation (DFT) of the present invention; from the results, it can be seen that the polyethyleneimine-loaded polyheptazineimide composite material transfers electrons to molecular oxygen, indicating that the material can effectively transfer electrons to molecular oxygen and promote the activation conversion process of molecular oxygen. DETAILED DESCRIPTION

[0037] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0038] Example 1

[0039] This embodiment provides a polyethyleneimine-loaded polyheptazineimide composite material and a preparation method and application thereof.

[0040] (I) Preparation method of polyethyleneimine loaded polyheptazine imide composite material

[0041] 1. Prepare a polyheptazine imide material to obtain a first powder: fully grind and mix a molten salt mixture of LiCl (4.5 g) and KCl (5.5 g) and 3-amino-5-mercapto-1,2,4-triazole (2.0 g) in a mortar; transfer the obtained solid powder of the mixture to a porcelain boat and heat and calcine in a nitrogen atmosphere under the heating conditions of 550°C for 4 h and a heating rate of 2.0°C / min; wait until the temperature drops to room temperature to obtain the first powder.

[0042] 2. Dissolve 1.2 g of branched polyethyleneimine (MW=10000) in 50 mL of N,N-dimethylformamide solution to obtain polyethyleneimine solution.

[0043] 3. Add 200 mg of the first powder into the obtained polyethyleneimine solution, stir and mix thoroughly to obtain a mixed solution.

[0044] 4. The mixed solution was transferred to a high-pressure reactor lined with polytetrafluoroethylene. The reaction conditions were as follows: the reaction temperature was 180°C and the reaction time was 24 h. The polyethyleneimine-loaded polyheptazineimide composite material was obtained. The structure of the material was characterized. Figure 1 , Figure 2 and Figure 3 .

[0045] The HAADF-STEM image of the polyethyleneimine loaded polyheptazineimide composite material obtained in this example is shown in Figure 1 The XRD characterization results of the obtained materials are shown in Figure 2As shown in the figure, it can be seen that polyethyleneimine is successfully loaded on the surface of polyheptazine imide, and the loading of polyethyleneimine has no significant effect on the crystal structure of the polyheptazine imide carrier.

[0046] 2. Photocatalytic molecular oxygen activation and conversion reaction experiment

[0047] The photocatalytic molecular oxygen activation conversion performance of the polyethyleneimine-loaded polyheptazine imide composite material obtained in this example was evaluated in a PCX-50C Discver multi-channel photocatalytic reaction device (Beijing Perfect Light Technology Co., Ltd., China), which was equipped with an LED light source with a wavelength of 380 nm to 760 nm, and could accurately output the AM 1.5G solar spectrum within this range to conduct a photocatalytic molecular oxygen activation conversion experiment. The evaluation results were taken as the average of 3 tests.

[0048] Specific steps: 1.0 g / L of the polyethyleneimine-loaded polyheptazineimide composite catalyst obtained in this example is added to 50.0 mL of deionized water, and stirred for reaction for 1.0 h under the illumination of the photocatalytic reaction device. Subsequently, 2.0 mL of the reaction suspension is taken out from the reaction container and filtered with a 0.22 μm water filter membrane, and the resulting solution is measured for hydrogen peroxide concentration by DPD-POD colorimetric method.

[0049] The photocatalytic hydrogen peroxide generation efficiency of the polyethyleneimine-loaded polyheptazineimide composite material of this embodiment is as follows: Figure 4 As shown, it is shown that the composite material of polyethyleneimine and polyheptazineimide can effectively activate molecular oxygen and convert it into hydrogen peroxide under light excitation.

[0050] Example 2

[0051] The preparation method is the same as that of Example 1, except that 1.2 g of branched polyethyleneimine (MW = 600) is dissolved in 50 mL of N,N-dimethylformamide solution;

[0052] 2. Photocatalytic molecular oxygen activation and conversion reaction experiment

[0053] The method for evaluating the photocatalytic molecular oxygen activation and conversion performance of the polyethyleneimine-supported polyheptazine imide composite material obtained in this example is the same as that in Example 1. The efficiency of the catalyst for the activation and conversion of molecular oxygen to hydrogen peroxide is shown in FIG. Figure 4 shown.

[0054] Example 3

[0055] The preparation method is the same as that of Example 1, except that 0.2 g of branched polyethyleneimine (MW = 10000) is dissolved in 50 mL of N,N-dimethylformamide solution;

[0056] 2. Photocatalytic molecular oxygen activation and conversion reaction experiment

[0057] The method for evaluating the photocatalytic molecular oxygen activation and conversion performance of the polyethyleneimine-supported polyheptazine imide composite material obtained in this example is the same as that in Example 1. The efficiency of the catalyst for the activation and conversion of molecular oxygen to hydrogen peroxide is shown in FIG. Figure 4 shown.

[0058] Comparative Example 1

[0059] This comparative example uses polyheptazine imide material as a control.

[0060] (I) Preparation method of polyheptazine imide material

[0061] A polyheptazine imide material is prepared to obtain a first powder: a molten salt mixture of LiCl (4.5 g) and KCl (5.5 g) and 3-amino-5-mercapto-1,2,4-triazole (2.0 g) are fully ground and mixed in a mortar; the obtained solid powder of the mixture is transferred to a porcelain boat and heated and calcined in a nitrogen atmosphere under the heating conditions of 550°C for 4 h and a heating rate of 2.0°C / min; the polyheptazine imide material is obtained when the temperature drops to room temperature;

[0062] The HAADF-STEM image of the polyheptazine imide material obtained in this comparative example is as follows Figure 1 The XRD characterization results of the obtained materials are shown in Figure 2 shown.

[0063] 2. Photocatalytic molecular oxygen activation and conversion reaction experiment

[0064] The method for evaluating the photocatalytic molecular oxygen activation conversion performance of the polyheptazine imide material in this comparative example is the same as that in Example 1. The efficiency of the catalyst for the activation conversion of molecular oxygen to generate hydrogen peroxide is as follows: Figure 4 shown.

[0065] Comparative Example 2

[0066] This comparative example uses a linear polyethyleneimine-loaded polyheptazineimide composite material as a control.

[0067] (I) Preparation method of linear polyethyleneimine loaded polyheptazine imide composite material

[0068] 1. Prepare a polyheptazine imide material to obtain a first powder: fully grind and mix a molten salt mixture of LiCl (4.5 g) and KCl (5.5 g) and 3-amino-5-mercapto-1,2,4-triazole (2.0 g) in a mortar; transfer the obtained solid powder of the mixture to a porcelain boat and heat and calcine in a nitrogen atmosphere under the heating conditions of 550°C for 4 h and a heating rate of 2.0°C / min; wait until the temperature drops to room temperature to obtain the first powder.

[0069] 2. Dissolve 1.2 g of linear polyethyleneimine (MW=25000) in 50 mL of N,N-dimethylformamide solution to obtain polyethyleneimine solution.

[0070] 3. Add 200 mg of the first powder into the obtained polyethyleneimine solution, stir and mix thoroughly to obtain a mixed solution.

[0071] 4. The mixed solution was transferred to a high-pressure reactor lined with polytetrafluoroethylene, and the reaction conditions were: reaction temperature was 180° C., and reaction time was 24 h. The linear polyethyleneimine-loaded polyheptazineimide composite material was obtained.

[0072] 2. Photocatalytic molecular oxygen activation and conversion reaction experiment

[0073] The method for evaluating the photocatalytic molecular oxygen activation and conversion performance of the linear polyethyleneimine-supported polyheptazinamide composite material in this comparative example is the same as that in Example 1. The efficiency of the catalyst for the activation and conversion of molecular oxygen to hydrogen peroxide is shown in FIG. Figure 4 shown.

[0074] Comparative Example 3

[0075] This comparative example uses the polyethyleneimine-loaded polyheptazineimide composite material after calcination as a control.

[0076] (I) Preparation method of calcined polyethyleneimine-loaded polyheptazineimide composite material

[0077] 1. Prepare a polyheptazine imide material to obtain a first powder: fully grind and mix a molten salt mixture of LiCl (4.5 g) and KCl (5.5 g) and 3-amino-5-mercapto-1,2,4-triazole (2.0 g) in a mortar; transfer the obtained solid powder of the mixture to a porcelain boat and heat and calcine in a nitrogen atmosphere under the heating conditions of 550°C for 4 h and a heating rate of 2.0°C / min; wait until the temperature drops to room temperature to obtain the first powder.

[0078] 2. Dissolve 1.2 g of branched polyethyleneimine (MW=10000) in 50 mL of N,N-dimethylformamide solution to obtain polyethyleneimine solution.

[0079] 3. Add 200 mg of the first powder into the obtained polyethyleneimine solution, stir and mix thoroughly to obtain a mixed solution.

[0080] 4. The mixed solution was transferred to a high-pressure reactor lined with polytetrafluoroethylene, and the reaction conditions were: reaction temperature was 180°C, and reaction time was 24 h. The polyethyleneimine-loaded polyheptazineimide composite material was obtained;

[0081] 5. The composite material obtained above was transferred to a porcelain boat and heated and calcined in an argon atmosphere. The heating conditions were as follows: the heating temperature was 500°C, the heating time was 4 h, and the heating rate was 2°C / min; the calcined polyethyleneimine-loaded polyheptazineimide composite material was obtained.

[0082] 2. Photocatalytic molecular oxygen activation and conversion reaction experiment

[0083] The method for evaluating the photocatalytic molecular oxygen activation conversion performance of the calcined polyethyleneimine-supported polyheptazinamide composite material obtained in this comparative example is the same as that in Example 1. The efficiency of the catalyst for the activation conversion of molecular oxygen to generate hydrogen peroxide is shown in FIG. Figure 4 shown.

[0084] from Figure 2 It can be seen that compared with Comparative Example 1, the characteristic peak of polyheptazine imide still appears in the catalyst material in Example 1, indicating that the loading of polyethylene imine does not change the crystal structure of the polyheptazine imide carrier.

[0085] from Figure 3 It can be seen that compared with Comparative Example 1, the thermogravimetric curve of Example 1 has a mass reduction of 23.5% in the range of 300 to 600°C, indicating that the content of polyethyleneimine in the polyethyleneimine-loaded polyheptazineimide composite material in Example 1 is about 23.5 wt.%.

[0086] from Figure 4It can be seen that, compared with the comparative examples, the polyethyleneimine-supported polyheptazine imide composite materials prepared by different methods in Examples 1-3 all exhibited the activity of molecular oxygen activation and conversion into hydrogen peroxide, while Comparative Examples 1-3 all exhibited lower molecular oxygen activation and conversion into hydrogen peroxide activity, indicating that the appropriate interaction between polyethyleneimine and the polyheptazine imide carrier is the key to the efficient generation of hydrogen peroxide; compared with the linear polyethyleneimine-supported polyheptazine imide composite material in Comparative Example 2, the branched polyethyleneimine-supported polyheptazine imide composite material in Example 1 exhibited higher hydrogen peroxide activity, indicating that the interaction between branched polyethyleneimine and polyheptazine imide is beneficial to the activation and conversion of molecular oxygen into hydrogen peroxide; at the same time, the polyethyleneimine-supported polyheptazine imide composite material after calcination in Comparative Example 3 exhibited lower hydrogen peroxide generation activity, and polyethyleneimine was inactivated after calcination, indicating that the interaction between polyethyleneimine and polyheptazine imide determined the efficient hydrogen peroxide generation.

[0087] Obviously, the above embodiments are merely examples for clear explanation and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the protection scope of the invention.

Claims

1. A polyethyleneimine-loaded polyheptazineimide composite material, characterized in that: The invention comprises a polyheptazine imide carrier and a branched polyethylene imine polymer loaded on the surface of the polyheptazine imide carrier; the branched polyethylene imine polymer is combined with the surface of the polyheptazine imide carrier through hydrogen bonds and van der Waals effects; and the loading amount of the branched polyethylene imine polymer is 10.0 wt.% to 25.0 wt.%.

2. A method for preparing the polyethyleneimine-loaded polyheptazineimide composite material according to claim 1, characterized in that: The following steps are involved: The molten salt mixture is mixed with a polyheptazine imide material precursor, and heated and calcined under an inert atmosphere to obtain a solid powder; mixing the solid powder with the branched polyethyleneimine solution to obtain a mixed solution; The obtained mixed solution is subjected to heating treatment to obtain the polyethyleneimine-loaded polyheptazineimide composite material.

3. The preparation method according to claim 2, characterized in that: The molten salt mixture is selected from two or three of LiCl, NaCl and KCl.

4. The preparation method according to claim 2, characterized in that: The polyheptazine imide material precursor is selected from 5-amino-4-triazole monohydrate and / or 3-amino-5-mercapto-1,2,4-triazole.

5. The preparation method according to claim 2, characterized in that: The mass ratio of the polyheptazine imide material precursor to the molten salt mixture is (0.1-0.2):

1.

6. The preparation method according to claim 2, characterized in that: The inert atmosphere contains inert substances selected from nitrogen and / or helium; The heating and calcining conditions are: 500-600°C for 4-8 hours, and a heating rate of 1.5-5.0°C / min.

7. The preparation method according to claim 2, characterized in that: The weight average molecular weight of branched polyethyleneimine is 600~25000; The concentration of the branched polyethyleneimine solution is 1.0 ~ 10.0 g / L; The solid powder is added in an amount of 4.0 to 10.0 g / L in the branched polyethyleneimine solution; During the heating treatment, the heating temperature is 160 ~ 200 ° C, and the heating time is 16 ~ 24 h.

8. Use of the polyethyleneimine-supported polyheptazineimide composite material according to claim 1 in photocatalytic activation and conversion of molecular oxygen.

9. The use according to claim 8, characterized in that: The product of the molecular oxygen activation conversion is hydrogen peroxide.

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