Polymer-carbon nitride composite powder material and preparation method thereof
By forming conjugated polymer-carbon nitride composite powder materials through electrostatic self-assembly, the problems of small surface area and severe carrier recombination in pure carbon nitride photocatalytic materials are solved, achieving high-efficiency photocatalytic performance and expanding its application in the fields of photocatalysis and energy.
Patent Information
- Application Number
- CN202311082072.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-08-26
- Publication Date
- 2025-11-25
- Estimated Expiration
- 2043-08-26
AI Technical Summary
Pure carbon nitride photocatalytic materials suffer from small surface area and severe carrier recombination. Furthermore, the aromatic conjugated structure of carbon nitride restricts photoexcited carriers to be confined within its aromatic ring. Existing heterostructure construction mainly focuses on inorganic semiconductors, lacking research on heterostructures composed of organic semiconductors and carbon nitride.
Two-dimensional/two-dimensional van der Waals S-type heterojunctions were formed by electrostatic self-assembly of conjugated polymer nanosheets and carbon nitride nanosheets. Polymer-carbon nitride composite powder materials were prepared by utilizing intermolecular π-π interactions. The conjugated polymer powder was TPAPy, which was obtained through the Suzuki reaction. The band gaps of the nanosheet carbon nitride and the conjugated polymer powder were matched to enhance the photocatalytic performance.
High-performance photocatalytic materials have been developed, exhibiting excellent photocatalytic carbon dioxide reduction activity. This avoids the drawbacks of using metal catalysts, is low in cost, has a simple process, and is environmentally friendly and pollution-free, making it suitable for photocatalysis, energy, and environmental fields.
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Figure CN117101722B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of photocatalyst preparation technology, specifically, it relates to a polymer-carbon nitride composite powder material and its preparation method. Background Technology
[0002] The depletion of fossil fuels has led to increasingly severe energy demands and environmental problems. This has become increasingly apparent over the past few decades. Simultaneously, rapid industrialization and population growth will further increase energy demand. Currently, the world's energy needs rely primarily on fossil fuels such as oil, coal, and natural gas, but these energy sources are rapidly depleting. Among various renewable energy sources, utilizing inexhaustible and clean solar energy is a theoretically feasible technological approach to address these issues. Therefore, semiconductor-based photocatalysis, which directly converts solar energy into fuels and chemical energy, has long been considered one of the most effective ways to solve future energy problems and environmental crises.
[0003] Therefore, photocatalytic powder materials have been extensively studied. Among various semiconductor photocatalytic powder materials, carbon nitride is a widely recognized one due to its visible light activity, suitable band gap, high chemical stability, ease of preparation, low cost, and non-toxicity. However, pure carbon nitride suffers from problems such as small surface area and severe carrier recombination. Furthermore, the aromatic conjugated structure of carbon nitride limits photoexcited carriers to within its aromatic rings. To improve the photocatalytic performance of carbon nitride, current main strategies include nanostructure design, elemental doping, and the construction of heterostructures. Constructing heterostructures is considered an effective strategy for improving the photocatalytic performance of carbon nitride. While heterostructure construction generally focuses on inorganic semiconductors, research on heterostructures composed of organic semiconductors and carbon nitride is relatively limited. Summary of the Invention
[0004] The technical problem to be solved by the present invention is to provide a polymer-carbon nitride composite powder material and its preparation method that utilizes organic semiconductors and carbon nitride to form a heterojunction structure to improve its photocatalytic performance.
[0005] The technical solution of the present invention to solve the above-mentioned technical problems is as follows:
[0006] A polymer-carbon nitride composite powder material is composed of 95-99% carbon nitride powder and 1-5% conjugated polymer powder by mass ratio, which are combined by electrostatic self-assembly through intermolecular π-π interactions to form heterojunctions. The carbon nitride powder and the conjugated polymer powder are both in nanosheet form. The conjugated polymer powder is TPAPy, which is obtained by the Suzuki reaction of 4,4',4' tribromotriphenylamine and 2,7 pyrene diborate.
[0007] Specifically, the nanosheet-shaped carbon nitride powder has a size of 500 nm to 2 μm, a thickness of 2 to 20 nm, and a band gap of 2.8 to 2.9 eV; the nanosheet-shaped conjugated polymer powder has a thickness of 1 to 10 nm and a band gap of 2.5 to 2.6 eV.
[0008] Specifically, the heterojunction is a two-dimensional / two-dimensional van der Waals S-type heterojunction.
[0009] Another technical solution of the present invention to solve the above-mentioned technical problem is:
[0010] A method for preparing a polymer-carbon nitride composite powder material includes the following steps:
[0011] To prepare carbon nitride powder, a precursor containing carbon and nitrogen compounds was placed in a muffle furnace for two-stage calcination. After calcination, the temperature was lowered to room temperature. During the calcination interval, the product was ground into a light yellow powder. After two-stage calcination, carbon nitride powder was obtained.
[0012] To prepare conjugated polymer powder, 4,4',4' tribromotriphenylamine and 2,7 pyrene diborate were polymerized via the Suzuki reaction to obtain a yellow-green precipitate, which was then centrifuged, washed and dried to obtain the conjugated polymer powder.
[0013] Nanosheet formation: Carbon nitride powder and conjugated polymer powder are added to chloroform solvent and ultrasonically dispersed to obtain corresponding nanosheet carbon nitride suspension and nanosheet conjugated polymer suspension.
[0014] To prepare the composite powder, a nanosheet-shaped conjugated polymer suspension was dropwise added to a nanosheet-shaped carbon nitride suspension and ultrasonically dispersed. After dispersion, the mixture was magnetically stirred. The resulting product was then separated to obtain a semi-finished product. The semi-finished product was washed and dried to obtain a polymer-carbon nitride composite powder material.
[0015] Specifically, the step of preparing carbon nitride powder includes the following steps:
[0016] The precursor was placed in a crucible, the crucible was covered and then placed in a muffle furnace for calcination. After calcination, a light yellow solid was obtained.
[0017] Grinding: The pale yellow powder is fixed in a grinder and ground to obtain powder A;
[0018] In the second stage of calcination, powder A is placed back into the crucible, covered, and then placed in a muffle furnace for calcination. After calcination, carbon nitride powder is obtained.
[0019] Preferably, in the first calcination step, the calcination temperature is 550℃ and the calcination time is 2~6h; in the second calcination step, a stepped calcination is adopted, firstly, the temperature is raised to 400~500℃ at a heating rate of 2~10℃ / min and calcined for 1~5h, and then the temperature is further raised to 500~650℃ at a heating rate of 1~15℃ / min and calcined for 2~6h to complete the calcination.
[0020] Specifically, in the step of preparing the conjugated polymer powder, the Suzuki reaction is as follows:
[0021] 4,4',4' tribromotriphenylamine was completely dissolved in N,N-dimethylformamide and introduced into a three-necked flask, followed by the introduction of nitrogen gas into the three-necked flask;
[0022] After completely dissolving 2,7-pyrene diboronic acid ester in N,N-dimethylformamide, it was added to a three-necked flask;
[0023] Transfer the three-necked flask to an oil bath, add the catalyst to the three-necked flask, and connect the reflux condenser.
[0024] Heat the oil bath to 120~200℃ and reflux the three-necked flask for 24~72 hours to obtain a yellow-green precipitate;
[0025] The molar ratio of 4,4',4' tribromotriphenylamine and 2,7 pyrene diborate dissolved in N,N-dimethylformamide is 1:1 to 5; the catalyst is tetratriphenylphosphine palladium, a zero-valent palladium compound.
[0026] Specifically, in both the nanosheet generation step and the nanosheet generation step, the ultrasonic time is 1 to 6 hours.
[0027] Specifically, in the step of preparing composite powder, the stirring time of magnetic stirring is 1-6 hours, the washing is performed by washing with deionized water and anhydrous ethanol in sequence, and the number of washings is 3 times each. The drying temperature is 50-100℃ and the drying time is 6-24 hours.
[0028] Preferably, the precursor includes one of acrylonitrile, cyanuric acid, cyanuric chloride, thiourea, urea, dicyandiamine, and melamine.
[0029] The present invention has the following beneficial effects:
[0030] (1) Carbon nitride powder was prepared by using carbon-nitrogen precursors through two-stage calcination thermal polymerization and exfoliation, and then ultrasonically processed into nanosheets. At the same time, conjugated polymers were prepared by Suzuki reaction polymerization and ultrasonically processed into nanosheets as raw materials. The nanosheets of the conjugated polymers were loaded onto the nanosheets of carbon nitride through a simple electrostatic self-assembly method, thus realizing the preparation of high-performance two-dimensional / two-dimensional conjugated polymer-carbon nitride composite powder materials.
[0031] (2) The preparation method provided by the present invention has simple procedures, is easy to operate, does not require complex equipment, has low synthesis cost, mild reaction conditions, and is easy to store. It has the characteristics of being simple, environmentally friendly and pollution-free. It is a green and mild preparation method, and the powder obtained has good thermal and chemical stability.
[0032] (3) Thanks to the strong intermolecular π-π interaction, a two-dimensional / two-dimensional conjugated van der Waals S-type heterojunction with large contact area, good adhesion and stability is formed through electrostatic self-assembly. The obtained polymer-carbon nitride composite powder material has low cost and good catalytic ability, and has excellent photocatalytic carbon dioxide reduction activity, thus avoiding the disadvantages of using metal catalysts or heavy metal catalysts.
[0033] (4) The polymer-carbon nitride composite powder material obtained has uniformly dispersed conjugated polymer nanosheets, which have broad application prospects in photocatalysis, energy and environment. Attached Figure Description
[0034] Figure 1 This is a scanning electron microscope image of Embodiment 1 of the present invention.
[0035] Figure 2 The graph shows a comparison of the carbon dioxide reduction rates in the photocatalytic carbon dioxide reduction experiments of Examples 1-2 and Comparative Examples 1-2 of the present invention, where a is Comparative Example 1, b is Comparative Example 2, c is Example 1, and d is Example 2.
[0036] Figure 3 The images show the XRD diffraction peak patterns of Examples 1-2 and Comparative Examples 1-2 of the present invention, where a is Comparative Example 1, b is Comparative Example 2, c is Example 1, and d is Example 2. Implementation
[0037] The present invention will now be described in detail with reference to the embodiments.
[0038] A polymer-carbon nitride composite powder material is composed of 95-99% carbon nitride powder and 1-5% conjugated polymer powder by mass ratio, which are combined by electrostatic self-assembly through intermolecular π-π interactions to form a heterojunction. Specifically, the heterojunction is a two-dimensional / two-dimensional van der Waals S-type heterojunction. Both the carbon nitride powder and the conjugated polymer powder are in the form of nanosheets. The conjugated polymer powder is TPAPy, which is obtained by the Suzuki reaction of 4,4',4' tribromotriphenylamine and 2,7 pyrene diborate.
[0039] Specifically, the nanosheet-shaped carbon nitride powder has a size of 500 nm to 2 μm, a thickness of 2 to 20 nm, and a band gap of 2.8 to 2.9 eV; the nanosheet-shaped conjugated polymer powder has a thickness of 1 to 10 nm and a band gap of 2.5 to 2.6 eV.
[0040] By introducing two-dimensional conjugated polymer nanosheets to construct S-shaped heterojunctions, photocatalytic activity can be enhanced. Two-dimensional conjugated polymers possess π-conjugated structures and two-dimensional properties similar to carbon nitride, which can enhance the overlap of π electron clouds, thereby strengthening the built-in electric field. Therefore, two-dimensional conjugated polymer nanosheets are suitable as semiconductors for constructing two-dimensional / two-dimensional van der Waals S-shaped heterojunctions. These S-shaped heterojunctions facilitate the separation of photogenerated carriers. Due to their two-dimensional and conjugated structures and different electron donor-acceptor characteristics, their carrier transfer mechanism follows an S-shaped transfer route. Simultaneously, they can suppress the recombination of photogenerated electrons and holes, thus preserving the maximum redox capacity of photogenerated electrons and holes. This achieves the effect of enhancing photocatalytic performance using van der Waals S-shaped heterojunctions. This two-dimensional / two-dimensional conjugated polymer / carbon nitride van der Waals S-shaped heterojunction composite powder material has broad application prospects in photocatalysis, energy, and environmental fields.
[0041] A method for preparing a polymer-carbon nitride composite powder material according to Example 1 of the present invention includes the following steps:
[0042] In the first calcination step, 5g of a carbon-nitrogen compound precursor was placed in a crucible, the crucible was covered and placed in a muffle furnace for calcination at 550°C for 2 hours. After calcination, a pale yellow solid was obtained. In this embodiment, urea was used as the precursor, but other carbon-nitrogen compounds such as ammonia, cyanuric acid, cyanuric chloride, thiourea, dicyandiamide, melamine, or other carbon-nitrogen compounds can also be used as precursors.
[0043] Grinding: Place the pale yellow powder into a grinder and grind it until it becomes a fine powder to obtain powder A.
[0044] For the second stage of calcination, 0.5g of powder A was placed back into the crucible, covered, and then placed in a muffle furnace. Step calcination was carried out. First, the temperature was raised to 430℃ at a heating rate of 5℃ / min and calcined for 3 hours. Then, the temperature was raised to 600℃ at a heating rate of 10℃ / min and calcined for 3 hours. After calcination, the mixture was allowed to cool naturally to room temperature to obtain carbon nitride powder.
[0045] To prepare conjugated polymer powder, 4,4',4'' tribromotriphenylamine and 2,7-pyrene diborate were polymerized in a molar ratio of 1:3 via the Suzuki reaction to obtain a yellow-green precipitate. Specifically, 4,4',4'' tribromotriphenylamine was completely dissolved in N,N-dimethylformamide and introduced into a three-necked flask, followed by the introduction of nitrogen gas into the flask. 2,7-pyrene diborate was completely dissolved in N,N-dimethylformamide and added to the three-necked flask. The flask was then transferred to an oil bath, and tetrakis(triphenylphosphine)palladium catalyst was added. A reflux condenser was connected. The oil bath was heated to 160°C, and the flask was refluxed for 72 hours to obtain a yellow-green precipitate. The precipitate was then separated using a centrifuge, washed with deionized water and anhydrous ethanol, and subsequently dried in air at 80°C to obtain the conjugated polymer powder.
[0046] Nanosheet formation: 97% carbon nitride powder and 3% conjugated polymer powder were added to an appropriate amount of chloroform solvent according to the mass ratio, and ultrasonically dispersed for 3 hours to obtain the corresponding nanosheet carbon nitride suspension and nanosheet conjugated polymer suspension.
[0047] To prepare the composite powder, a suspension of nanosheet-shaped conjugated polymer was dropwise added to a suspension of nanosheet-shaped carbon nitride, and ultrasonically dispersed for 6 hours. After dispersion, the mixture was magnetically stirred for 6 hours. The resulting product was then separated by centrifugation to obtain a precipitated semi-finished product. This semi-finished product was washed three times each with deionized water and anhydrous ethanol, and then dried at 80°C for 6–24 hours to obtain the polymer-carbon nitride composite powder material. In this example, the content of the conjugated polymer in the product was 3%.
[0048] The product of this embodiment was examined by scanning electron microscopy, and the results were as follows: Figure 1 The scanned esports image, by Figure 1 It is evident that the carbon nitride powder has a sheet-like structure. According to the scale in the figure, the carbon nitride nanosheets are approximately 500 nanometers to 2 micrometers in size, with a thickness of about 2 to 20 nm; the conjugated polymer powder has a thickness of about 1 to 10 nm.
[0049] A method for preparing a polymer-carbon nitride composite powder material according to Example 2 of the present invention includes the following steps:
[0050] In the first calcination step, 5g of a carbon-nitrogen compound precursor was placed in a crucible, the crucible was covered and placed in a muffle furnace for calcination at 550°C for 5 hours. After calcination, a pale yellow solid was obtained. In this embodiment, urea was used as the precursor.
[0051] Grinding: Place the pale yellow powder into a grinder and grind it until it becomes a fine powder to obtain powder A.
[0052] For the second stage of calcination, 0.5g of powder A was placed back into the crucible, covered, and then placed in a muffle furnace. Step calcination was carried out. First, the temperature was raised to 500℃ at a heating rate of 10℃ / min and calcined for 4 hours. Then, the temperature was raised to 650℃ at a heating rate of 15℃ / min and calcined for 5 hours. After calcination, the mixture was allowed to cool naturally to room temperature to obtain carbon nitride powder.
[0053] To prepare conjugated polymer powder, 4,4',4'-tribromotriphenylamine and 2,7-pyrene diborate were polymerized in a molar ratio of 1:5 via the Suzuki reaction to obtain a yellow-green precipitate. Specifically, 4,4',4'-tribromotriphenylamine was completely dissolved in N,N-dimethylformamide and introduced into a three-necked flask, followed by the introduction of nitrogen gas into the flask. 2,7-pyrene diborate was completely dissolved in N,N-dimethylformamide and added to the three-necked flask. The flask was then transferred to an oil bath, and tetrakis(triphenylphosphine)palladium catalyst was added. A reflux condenser was connected. The oil bath was heated to 200°C, and the flask was refluxed for 36 hours to obtain a yellow-green precipitate. The precipitate was then separated using a centrifuge, washed with deionized water and anhydrous ethanol, and subsequently dried in air at 70°C to obtain the conjugated polymer powder.
[0054] Nanosheet formation: 95% carbon nitride powder and 5% conjugated polymer powder were added to an appropriate amount of chloroform solvent according to the mass ratio, and ultrasonically dispersed for 4 hours to obtain the corresponding nanosheet carbon nitride suspension and nanosheet conjugated polymer suspension.
[0055] To prepare the composite powder, a suspension of nanosheet-shaped conjugated polymer was dropwise added to a suspension of nanosheet-shaped carbon nitride, and ultrasonically dispersed for 6 hours. After dispersion, the mixture was magnetically stirred for 6 hours. The resulting product was then separated by centrifugation to obtain a precipitated semi-finished product. This semi-finished product was washed sequentially with deionized water and anhydrous ethanol, three times each. It was then dried at 80°C for 6–24 hours to obtain the polymer-carbon nitride composite powder material. In this example, the content of the conjugated polymer in the product was 5%.
[0056] The preparation process of carbon nitride nanosheet powder according to Comparative Example 1 of this invention is as follows: A certain amount of urea is placed in a crucible, covered, and placed in a muffle furnace. The temperature is increased to 550 °C at a heating rate of 2 °C / min and held at this temperature for 2 h. After the temperature drops to room temperature, the resulting yellow solid powder is ground. Then, 0.5 g of the powder obtained above is placed in a muffle furnace for a second stage of programmed heating and calcination. The temperature is increased to 430 °C at a heating rate of 5 °C / min and held at this temperature for 3 h. Then, the temperature is increased to 600 °C at a heating rate of 10 °C / min and held at this temperature for 3 h. After the temperature drops to room temperature, the resulting light yellow powder is the carbon nitride nanosheet powder.
[0057] The preparation process of a conjugated polymer powder according to Comparative Example 2 of the present invention is as follows: the precursor of 4,4',4'-tribromotriphenylamine is dissolved in N,N-dimethylformamide and added to a three-necked flask. Nitrogen gas is introduced, and the precursor of 2,7-pyrene diborate is dissolved in N,N-dimethylformamide and added to the above solution. The mixture is placed in an oil bath, and a tetra-triphenylphosphine palladium catalyst is added. A reflux condenser is added, and the mixture is refluxed at 160°C for 72 h. The resulting yellow-green precipitate is centrifuged and washed, and the resulting yellow-green powder is the conjugated polymer powder.
[0058] To investigate the superior photocatalytic carbon dioxide reduction performance of the polymer-carbon nitride composite powder material prepared in this invention, photocatalytic carbon dioxide reduction experiments were conducted using the products of Comparative Examples 1-2 and Examples 1-2, respectively. The specific experimental procedure was carried out in a 200 mL self-made double-necked quartz bottle, with a groove on one side of the bottle neck for placing the corresponding product as a photocatalyst. The experiment was conducted at room temperature and atmospheric pressure. A 300 W xenon lamp (Zhongjiao Jinyuan, China) was used as the irradiation source and placed approximately 10 cm above the reaction apparatus. The testing procedure was as follows: First, the photocatalyst was uniformly dispersed in water by ultrasonic treatment to form a suspension. Then, it was completely dried in an oven at 80°C, resulting in a uniformly distributed film at the bottom of the bottle, with an area approximately equal to the bottom surface area. Next, 0.084 g of sodium bicarbonate was added to the groove in the bottle neck as a carbon dioxide source, and the bottle mouth was sealed with a piston. Before irradiation, nitrogen gas was purged through the reactor for 30 min to remove air and ensure an oxygen-free environment for the reaction system. 0.8 mL of 2 mol / L dilute sulfuric acid solution was injected into the groove using a syringe to react with sodium bicarbonate and generate gaseous carbon dioxide. The double-necked flask was then irradiated under a xenon lamp for 1 hour. Every hour, 0.4 mL of gas was extracted from the reactor, and the product content was analyzed using a gas chromatograph (GC-2014C, Shimadzu, Japan) equipped with a methane converter / flame ionization detector (FID). High-purity nitrogen was used as the carrier gas in the GC-2014C instrument. The concentration of the gas components was calculated using the external standard method based on peak area, and the retention time values were calibrated using a mixture of standard gases to determine the products of photocatalytic carbon dioxide reduction. The final detection results are as follows: Figure 2 As shown, from Figure 2 As can be seen, the photocatalytic efficiency of the products obtained in Examples 1 and 2 of this invention is significantly higher than that of the single materials in Comparative Examples 1 and 2, and their photocatalytic carbon dioxide reduction performance is significantly improved. Furthermore, XRD image analysis of the products from Comparative Examples 1-2 and Examples 1-2 shows... Figure 3 As shown in the figure, the characteristic diffraction peaks of carbon nitride are clearly visible. Due to the poor crystallinity of the two-dimensional conjugated polymer, it exhibits a broad diffraction peak, corresponding to the π-π stacking peak.
[0059] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the inventive concept, and all such modifications and substitutions should be considered within the scope of protection of the present invention.
Claims
1. A method for preparing a polymer-carbon nitride composite powder material, characterized in that: The polymer-carbon nitride composite powder material is composed of 95-99% carbon nitride powder and 1-5% conjugated polymer powder by mass ratio, which are combined through electrostatic self-assembly using intermolecular π-π interactions to form heterojunctions. Both the carbon nitride powder and the conjugated polymer powder are in nanosheet form. The conjugated polymer powder is TPAPy, obtained by the Suzuki reaction of 4,4',4' tribromotriphenylamine and 2,7-pyrene diborate, including the following steps: To prepare carbon nitride powder, a precursor containing carbon and nitrogen compounds was placed in a muffle furnace for two-stage calcination. After calcination, the temperature was lowered to room temperature. During the calcination interval, the product was ground into a light yellow powder. After two-stage calcination, carbon nitride powder was obtained. To prepare conjugated polymer powder, 4,4',4' tribromotriphenylamine and 2,7 pyrene diborate were polymerized via the Suzuki reaction to obtain a yellow-green precipitate, which was then centrifuged, washed and dried to obtain the conjugated polymer powder. Nanosheet formation: Carbon nitride powder and conjugated polymer powder are added to chloroform solvent and ultrasonically dispersed to obtain corresponding nanosheet carbon nitride suspension and nanosheet conjugated polymer suspension. To prepare the composite powder, a nanosheet conjugated polymer suspension was dropped into a nanosheet carbon nitride suspension and ultrasonically dispersed. After dispersion, the mixture was magnetically stirred. The resulting product was then separated to obtain a semi-finished product. The semi-finished product was washed and dried to obtain a polymer-carbon nitride composite powder material. The Suzuki reaction is as follows: 4,4',4' tribromotriphenylamine was completely dissolved in N,N-dimethylformamide and introduced into a three-necked flask, followed by the introduction of nitrogen gas into the three-necked flask; After completely dissolving 2,7-pyrene diboronic acid ester in N,N-dimethylformamide, it was added to a three-necked flask; Transfer the three-necked flask to an oil bath, add the catalyst to the three-necked flask, and connect the reflux condenser. Heat the oil bath to 120~200℃ and reflux the three-necked flask for 24~72 hours to obtain a yellow-green precipitate; The molar ratio of 4,4',4' tribromotriphenylamine and 2,7 pyrene diborate dissolved in N,N-dimethylformamide is 1:1 to 5; the catalyst is tetratetraphenylphosphine palladium, a zero-valent palladium compound.
2. The method for preparing the polymer-carbon nitride composite powder material according to claim 1, characterized in that: The carbon nitride powder in nanosheet form has a size of 500 nm to 2 μm, a thickness of 2 to 20 nm, and a band gap of 2.8 to 2.9 eV; the conjugated polymer powder in nanosheet form has a thickness of 1 to 10 nm and a band gap of 2.5 to 2.6 eV.
3. The method for preparing the polymer-carbon nitride composite powder material according to claim 1 or 2, characterized in that: The heterojunction is a two-dimensional / two-dimensional van der Waals S-type heterojunction.
4. The method for preparing the polymer-carbon nitride composite powder material according to claim 1, characterized in that, The step of preparing carbon nitride powder includes the following steps: The precursor was placed in a crucible, the crucible was covered and then placed in a muffle furnace for calcination. After calcination, a light yellow solid was obtained. Grinding: The pale yellow powder is fixed in a grinder and ground to obtain powder A; In the second stage of calcination, powder A is placed back into the crucible, covered, and then placed in a muffle furnace for calcination. After calcination, carbon nitride powder is obtained.
5. The method for preparing the polymer-carbon nitride composite powder material according to claim 4, characterized in that: In the first calcination step, the calcination temperature is 550℃ and the calcination time is 2~6h; in the second calcination step, a stepped calcination is adopted. First, the temperature is raised to 400~500℃ at a heating rate of 2~10℃ / min and calcined for 1~5h. Then, the temperature is raised to 500~650℃ at a heating rate of 1~15℃ / min and calcined for 2~6h to complete the calcination.
6. The method for preparing the polymer-carbon nitride composite powder material according to claim 4, characterized in that: In the nanosheet generation step, the ultrasonic time is 1~6h.
7. The method for preparing the polymer-carbon nitride composite powder material according to claim 4, characterized in that: In the step of preparing the composite powder, the stirring time of the magnetic stirring is 1-6 hours, the washing is performed by washing with deionized water and anhydrous ethanol in sequence, and the number of washings is 3 times each. The drying temperature is 50-100℃ and the drying time is 6-24 hours.
8. The method for preparing the polymer-carbon nitride composite powder material according to claim 2, characterized in that: The precursor includes one of the following: acrylonitrile, cyanuric acid, cyanuric chloride, thiourea, urea, dicyandiamide, and melamine.