Method for continuously preparing graphite phase carbon nitride with different morphologies and application thereof

Abstract

The invention relates to a method for continuously preparing graphite-phase carbon nitride with different morphologies and application of the graphite-phase carbon nitride, and belongs to the technical field of preparation of inorganic photocatalytic materials and environmental pollution treatment. Graphite-phase carbon nitride g-C3N4 with different morphologies is prepared and comprises a body shape, a porous shape and a porous sheet shape, compared with traditional g-C3N4, a body material is obtained through heat treatment, then a porous structure is constructed through oxidation etching of concentrated sulfuric acid and concentrated nitric acid, finally, the porous sheet-shaped morphology is formed through ammonia water hydrothermal reaction stripping, and the graphite-phase carbon nitride g-C3N4 is obtained. The specific surface area and porosity of the material are remarkably increased, more reaction active sites are exposed, meanwhile, the light absorption capacity is improved, compounding of photon-generated carriers is inhibited, and the photocatalytic efficiency is improved; the prepared porous and porous sheet-shaped g-C3N4 shows higher catalytic activity, higher degradation rate and better stability on methyl orange under the irradiation of visible light.

Description

Technical Field

[0001] This invention relates to a method for the continuous preparation of graphitic carbon nitride with different morphologies and its application, belonging to the technical field of inorganic photocatalytic material preparation and environmental pollution control. Background Technology

[0002] With rapid industrial development, water pollution has become an increasingly prominent environmental challenge. Dye wastewater, particularly azo dye wastewater from the textile, printing and dyeing, and food industries, poses a serious threat to human health. Azo dyes, such as methyl orange (MO), exhibit high stability and water solubility, making them difficult to degrade. Traditional physical, chemical, and biological methods have shown some degradation effects in treating dye wastewater, but they also suffer from drawbacks such as lengthy processes, complex equipment, high investment, high operating costs, and low degradation efficiency.

[0003] Current methods for treating methyl orange dye wastewater mainly include physical adsorption, membrane separation, microbial methods, and photocatalysis. Among these, photocatalytic degradation has gained widespread attention from researchers due to its advantages of simple operation and high catalytic activity. Therefore, designing and developing highly active inorganic photocatalysts is of significant practical importance for the photocatalytic degradation of methyl orange in dyeing and printing wastewater.

[0004] Graphitic carbon nitride (g-C3N4) has attracted increasing attention in the field of photocatalysis due to its tunable electronic structure, suitable band gap, and significant chemical stability. However, bulk g-C3N4 suffers from drawbacks such as small specific surface area, low visible light absorption, and rapid recombination of photogenerated carriers. To overcome these shortcomings, methods such as heteroatom doping (Sep. Purif. Technol., 2025, 359, 130676), defect engineering (Nano Res., 2025, 18, 94907125), heterostructure construction (J. Environ. Chem. Eng., 2024, 12, 111956), and morphology control (Adv. Funct. Mater., 2025, 2500415) have been employed. Morphology control is a relatively simple method that can be used to increase specific surface area, improve stability and durability, increase reactive sites, optimize the photocatalytic reaction process, and improve photocatalytic efficiency. Currently, g-C3N4 with various morphologies, including nanowires, nanosheets, nanotubes, nanorods, mesoporous structures, and core-shell structures, has been used for photocatalytic degradation of dyes. However, these specific morphologies require template-based preparation, which is relatively complex. Summary of the Invention

[0005] To solve the above-mentioned problems, the present invention provides a method for continuously preparing graphitic carbon nitride with different morphologies.

[0006] The technical solution to the problem solved by this invention is as follows:

[0007] A method for continuously preparing graphitic carbon nitride with different morphologies includes the following steps:

[0008] S1. Preparation of bulk graphitic carbon nitride (BCN)

[0009] Melamine was placed in a quartz crucible, heated in a muffle furnace, and heat-treated using a set program to obtain bulk graphitic carbon nitride (BCN).

[0010] S2, Preparation of porous graphitic carbon nitride (PCN)

[0011] Weigh 0.5-2 parts by mass of the bulk graphitic carbon nitride BCN, then add 10-50 parts by volume of concentrated sulfuric acid and 10-50 parts by volume of concentrated nitric acid, react under continuous stirring at room temperature, then dilute with deionized water and wash until neutral; filter and dry to obtain porous graphitic carbon nitride PCN.

[0012] S3, Preparation of porous graphitic carbon nitride (FCN)

[0013] The porous graphitic carbon nitride (PCN) is hydrothermally reacted in an ammonia solution to exfoliate it into porous sheet-like graphitic carbon nitride (FCN).

[0014] As a preferred embodiment of the above technical solution, the setting program in step S1 refers to heating to 500-600℃ at a heating rate of 2-5℃ / min and maintaining the temperature for 1-3 hours.

[0015] As a preferred embodiment of the above technical solution, in step S2, the concentration of the concentrated sulfuric acid is 95-98 wt%, the concentration of the concentrated nitric acid is 65-68 wt%, and the mass-to-volume ratio of the bulk graphitic carbon nitride (BCN) to the concentrated sulfuric acid and concentrated nitric acid is BCN:concentrated sulfuric acid:concentrated nitric acid = 1 g:(15-25) mL:(15-25) mL

[0016] As a preferred embodiment of the above technical solution, in step S2, the stirring time at room temperature is 1 to 3 hours, and the stirring speed is 500 to 1000 rpm.

[0017] As a preferred embodiment of the above technical solution, in step S3, the concentration of ammonia water is 25~28wt%, the hydrothermal reaction temperature is 150~200℃, and the reaction time is 10~14 hours.

[0018] Secondly, the present invention provides an application.

[0019] The technical solution is as follows:

[0020] Application of graphitic carbon nitride prepared according to the above method in photocatalytic degradation of organic pollutants.

[0021] As a preferred embodiment of the above technical solution, the graphitic carbon nitride is at least one of porous graphitic carbon nitride (PCN) and flake-like graphitic carbon nitride (FCN).

[0022] As a preferred embodiment of the above technical solution, the organic pollutant is an azo dye.

[0023] As a preferred embodiment of the above technical solution, the azo dye is methyl orange.

[0024] In summary, the present invention has the following beneficial effects:

[0025] 1. This invention prepares graphitic carbon nitride (g-C3N4) with different morphologies through a continuous process of simple calcination, oxidation etching and ammonia hydrothermal treatment, including bulk g-C3N4 (BCN), porous g-C3N4 (PCN) and sheet-like g-C3N4 (FCN), and achieves effective control over its specific surface area, surface active sites, light absorption performance and band structure, thereby significantly optimizing its photocatalytic degradation performance of organic pollutants, especially the azo dye methyl orange;

[0026] 2. Compared with traditional bulk g-C3N4, this invention obtains the bulk material through heat treatment, then constructs a porous structure through oxidation etching with concentrated sulfuric acid and concentrated nitric acid, and finally uses ammonia water hydrothermal reaction to peel off the porous sheet morphology, which significantly increases the specific surface area and porosity of the material, exposes more reactive sites, improves light absorption capacity, inhibits recombination of photogenerated carriers, and enhances photocatalytic reaction efficiency; the prepared porous g-C3N4 (PCN) and porous sheet g-C3N4 (FCN) exhibit higher catalytic activity, faster degradation rate and better stability for methyl orange under visible light irradiation;

[0027] 3. The g-C3N4 photocatalyst for the photocatalytic degradation of methyl orange provided by this invention has the advantages of simple operation, high catalytic efficiency, and mild reaction conditions. The prepared catalyst can be directly stored in the atmospheric environment without special storage conditions, making it convenient to use and easy to promote. In addition, the synthesis method of g-C3N4 in this invention is simple and the reaction conditions are controllable. The continuous preparation of products with different morphologies can be achieved through simple raw material ratio and program control, making it suitable for large-scale production and practical application.

[0028] 4. In summary, this invention has achieved a significant improvement in the photocatalytic performance of g-C3N4 through morphology regulation strategy, and has good application prospects and promotion value in the fields of photocatalytic degradation of organic dyes, environmental purification and green catalysis technology. Attached Figure Description

[0029] Figure 1TEM images of the three graphitic carbon nitride phases in Example 1;

[0030] Figure 2 The XRD patterns of the three graphitic carbon nitride phases in Example 1 are shown.

[0031] Figure 3 This is a nitrogen desorption diagram of the three graphitic carbon nitride phases in Example 1;

[0032] Figure 4 The ultraviolet diffuse reflectance spectra of the three graphitic carbon nitride phases in Example 1 are shown below.

[0033] Figure 5 The image shows the UV-Vis spectra of methyl orange degraded by three graphitic carbon nitride phases in Example 1. Detailed Implementation

[0034] The present invention will be further explained and described below with reference to the accompanying drawings.

[0035] This specific embodiment is merely an explanation of the present invention and is not intended to limit it. Any modifications made by those skilled in the art after reading this specification, as long as they fall within the scope of the claims, will be protected by patent law.

[0036] Example 1

[0037] A method for continuously preparing graphitic carbon nitride with different morphologies includes the following steps:

[0038] S1. Preparation of bulk graphitic carbon nitride (BCN):

[0039] 5 g of melamine was placed in a porcelain crucible, covered, and then placed in a muffle furnace for heating. The temperature was set to rise to 520°C at a rate of 4°C / min. After holding at 520°C for 2 hours, the temperature was cooled to room temperature to obtain a light yellow powder (BCN).

[0040] S2. Preparation of porous graphitic carbon nitride (PCN):

[0041] Take 1 g of the prepared BCN powder and add it to a 100 ml beaker. Then add 20 ml of concentrated sulfuric acid (98 wt%) and 20 ml of concentrated nitric acid (68 wt%). React for 2 h under continuous stirring at room temperature. Then dilute with deionized water and wash several times until neutral. PCN is obtained by filtration and drying.

[0042] S3. Preparation of porous, sheet-like graphitic carbon nitride (FCN):

[0043] The obtained PCN powder was hydrothermally reacted in an ammonia solution (25wt%) at 180℃ for 12 h to exfoliate it into FCN.

[0044] The three types of graphitic carbon nitride prepared in this embodiment were characterized, and the results are as follows: Figures 1-4 As shown.

[0045] Figure 1 These are TEM images of the three graphitic carbon nitride phases in this embodiment; from Figure 1 As can be seen, the bulk g-C3N4 (BCN) exhibits a blocky structure with tightly stacked layers and no obvious pores or sheet-like structures. Compared to BCN, porous g-C3N4 (PCN) shows a rougher surface, with localized pores or edge damage, indicating that strong acid etching caused structural defects or pore formation. Porous sheet-like g-C3N4 (FCN) displays a thinner, more dispersed sheet structure, even exhibiting curled or peeled nanosheet morphologies, proving that hydrothermal treatment with ammonia achieved interlayer exfoliation, forming a two-dimensional sheet-like structure. TEM images visually demonstrate the actual effect of morphology control: from bulk → porous → sheet, verifying that the "calcination-acid etching-hydrothermal exfoliation" process achieved the expected structural evolution. The sheet-like structure of FCN is beneficial for light absorption, shortens the carrier transport path, and increases the exposure of active sites, which is closely related to its high photocatalytic activity. The porous structure of PCN also shows certain corrosion traces or pores observed through TEM, indicating that acid treatment effectively introduced defects and pore structures.

[0046] Figure 2 Here are the XRD patterns of the three graphitic carbon nitride phases in this embodiment; from Figure 2 It can be seen that all samples exhibit characteristic diffraction peaks of g-C3N4 in the range of ~25° and ~30°: these are characteristic of the interlayer stacked aromatic ring structure, similar to the interlayer peaks of graphite. The peak intensity, shape, and position vary among samples with different morphologies: BCN: peaks are generally broad and flat, indicating relatively regular interlayer stacking and high crystallinity, but with thicker lamellae; PCN: peaks are generally strong and sharp, indicating that acid etching may lead to increased crystallinity and enhanced peak intensity, suggesting that strong acid etching caused structural defects or porosity formation; FCN: peaks are further enhanced, indicating increased interlayer spacing or thinner lamellae, further improving crystallinity, but also facilitating the migration of photogenerated carriers. XRD confirms that all three samples maintained the basic structure of g-C3N4, indicating that oxidation etching and hydrothermal treatment did not destroy its main framework, but rather achieved controllable surface and structural modification.

[0047] Figure 3 This is a nitrogen desorption isotherm diagram for the three graphitic carbon nitride phases in Example 1, more specifically, the "N2 adsorption-desorption isotherm." This diagram provides crucial evidence regarding the material's specific surface area and pore structure characteristics, parameters that directly influence its performance in catalytic, adsorption, and other applications. Figure 3It can be seen that the isotherm type isotherm is type IV (characteristic of mesoporous materials), accompanied by an H3-type hysteresis loop, indicating that the material is mainly composed of plate-like particles stacked to form slit-like mesoporous or macroporous structures. Type IV isotherms are the most typical characteristic of mesoporous materials. Their shape: In the low to medium relative pressure region (P / P0 < 0.8), the adsorption amount increases slowly, and the curve is convex, corresponding to a monolayer-to-multilayer adsorption process. In the high relative pressure region (P / P0 > 0.8~1.0), the adsorption amount increases sharply, and the curve has a steep "tailed" shape, corresponding to capillary condensation, i.e., nitrogen liquefies in the mesoporous channels. Simultaneously, from... Figure 3 It can be seen that the isothermal adsorption capacities of PCN and FCN are improved to some extent, and the hysteresis loop is more obvious, indicating that acid etching introduces a large number of mesopores or micropores, resulting in a more porous structure. FCN maintains a high specific surface area, but its structure tends towards two-dimensional sheet-like stacking, indicating that hydrothermal stripping forms more exposed edges and thin-layer structures. The increase in specific surface area directly leads to more active sites and pollutant adsorption capacity, which is one of the key factors for improving photocatalytic performance. The formation of mesoporous / pore structures is beneficial for reactant diffusion, photogenerated carrier migration, and dye molecule adsorption and enrichment. Figure 3 Quantitatively, it was demonstrated that morphology control (especially acid etching and hydrothermal stripping) significantly improved the specific surface area and porosity of g-C3N4, directly echoing the technical effect of "improving active sites and optimizing the reaction process".

[0048] Figure 4 The images show the UV diffuse reflectance spectra of the three graphitic carbon nitride phases in Example 1; from Figure 4 As can be seen, the curve starts relatively high (around ~300 nm), indicating strong absorption in the ultraviolet region. For semiconductor materials (graphitic carbon nitride g-C3N4), this corresponds to intrinsic absorption, i.e., electrons transitioning from the valence band to the conduction band. The curve then drops sharply after its initial rise (around ~400 nm): this sharp drop in inflection point is called the "absorption edge," which is the most crucial characteristic. A subsequent gradual decline follows: after the absorption edge, the material's ability to absorb light weakens, entering the visible light region, and the curve becomes flatter. Figure 4This indicates that: 1. A very obvious absorption edge exists in the figure, which is the "identity card" of semiconductor materials. Only semiconductors exhibit a dramatic absorption transition at a specific wavelength (energy); 2. The absorption edge is located around ~400 nm, meaning its optical band gap is approximately 3.1 eV (preliminarily estimated using the formula Eg(eV) = 1240 / λ(nm)). This band gap value means it can be efficiently excited by ultraviolet light. More importantly, it can also be weakly excited by lower-energy but more abundant visible light (wavelength >400 nm). This directly determines its application potential in visible light photocatalysis (such as water splitting for hydrogen production and pollutant degradation). Therefore, Figure 4 This provides direct experimental evidence that it can serve as a "photoactive material".

[0049] Figure 4 The second part is the standard "Tauc Plot," also known as the "bandgap calculation plot" or "Tauc diagram." The horizontal axis represents photon energy, measured in electron volts (eV). This is the core horizontal axis of the Tauc Plot, designed to convert wavelength information into energy information so that it can be directly mapped to the material's band structure. The vertical axis represents Ahν. 2 The unit is eV 2 This is the ordinate of the graph after the Tauc formula transformation for direct bandgap semiconductors. The purpose of this transformation is to linearize the curve near the absorption edge, so that the bandgap value can be accurately obtained by extrapolation.

[0050] Right now, Figure 4 The upper part is the original data plot, and the lower part is an analytical plot based on the original data plot used to calculate the band gap. This curve is a very typical Tauc Plot curve for semiconductors with indirect band gaps or severe band tail effects. This curve does not have a clear linear region starting from zero. The "slow climb" in the low energy region (hν < 2.6 eV) represents the Urbach tail, which is caused by defects, disordered structures, or impurities in the material introducing continuous energy states in the band gap, giving electrons a certain transition probability before the formal intrinsic absorption begins.

[0051] The curve begins to rise rapidly at ~2.6 eV, marking the true beginning of the intrinsic absorption edge. Bandgap calculation: Extend the rapidly rising straight section outwards (extrapolate) until it intersects the horizontal axis (hν axis). The hν value corresponding to the intersection point is the optical bandgap Eg of the material. According to the graph, this intersection point is approximately 2.5 eV. This indicates that the bandgap of FCN material is approximately 2.3 eV, the bandgap of PCN material is approximately 2.45 eV, and the bandgap of BCN material is approximately 2.55 eV. Further indications:

[0052] The material BCN may exhibit high degradation efficiency under pure ultraviolet light or light sources whose main component is blue-violet light. However, its activity is worst under simulated sunlight (AM 1.5G) or white light. This is because only about 40% of the energy in the solar spectrum is below 486nm, and most of the visible light cannot be absorbed by it, resulting in low light energy utilization.

[0053] The PCN material has a moderate band gap. Its intrinsic absorption edge is approximately λ ≈ 1240 / 2.45 ≈ 506 nm, meaning its absorption range extends into the cyan / green light region. It can utilize a higher proportion of the solar spectrum than BCN. Its valence band position is slightly more negative than BCN, indicating a slightly weaker oxidizing ability, but it is still very strong, sufficient to oxidize most organic compounds (such as dyes and phenols). Its reducing ability also remains good.

[0054] The FCN material has the narrowest bandgap. Its intrinsic absorption edge is approximately λ ≈ 1240 / 2.3 ≈ 539 nm, meaning its absorption range covers a broad region from ultraviolet to green and even yellow light. It can utilize the highest proportion of the solar spectrum. However, it has the weakest oxidizing ability among the three. Its valence band position is the most negative, and the oxidation potential of holes is low, which may prevent it from directly oxidizing certain recalcitrant pollutants or efficiently generating ·OH radicals. This is the main trade-off of its narrow bandgap. However, under simulated sunlight or white light, its activity is likely the highest because it can maximize the utilization of various visible light sources to generate electron-hole pairs, resulting in the highest light energy utilization rate.

[0055] This embodiment also includes experiments on the performance of the obtained graphitic carbon nitride photocatalyst and its photocatalytic degradation of methyl orange. The specific experimental procedure is as follows:

[0056] (1) 0.01 g of carbon nitride of three different morphologies were added to 20 mL of three methyl orange solutions of 15 mg / L respectively, and allowed to stand in the dark for 30 minutes to reach adsorption equilibrium;

[0057] (2) Using xenon lamps to simulate sunlight (100 mW / cm²) 2 Irradiate the solution and take samples every 10 minutes to test the ultraviolet-visible spectrum in the wavelength range of 300~600nm.

[0058] The results are as follows Figure 5 As shown, Figure 5This is the UV-Vis spectrum of methyl orange degradation by three graphitic carbon nitride methods in this embodiment. The horizontal axis (time, min) represents the process of the photocatalytic degradation reaction. -30 min to 0 min typically represents the dark adsorption stage, i.e., the process where the catalyst reaches equilibrium with the adsorption of pollutants without the light on. The photocatalytic reaction officially begins at 0 min when the light is turned on. The vertical axis (degradation rate η, %): a smaller value indicates a higher concentration of remaining pollutants and a worse degradation effect; a larger value indicates a better degradation effect. Curve trend: All curves begin to decline near (0,0), meaning that methyl orange begins to degrade after the light is turned on, its concentration decreases, and the degradation rate η increases. The faster and steeper the decline of the curve, the faster the degradation rate. The higher the plateau reached by the curve, the lower the final degradation rate.

[0059] Therefore, from Figure 5 It can be seen that:

[0060] The FCN material exhibits the best performance: the fastest and steepest degradation, with the lowest final position (~95%). This indicates that the material reaches a degradation rate of approximately 95% within a very short time (30 minutes) after the onset of illumination. This demonstrates its extremely high photocatalytic activity, enabling it to generate photogenerated carriers very rapidly for use in the degradation reaction.

[0061] The PCN material exhibits superior performance: its descent rate, steepness, and final position are all between the other two (135 minutes, ~80%). This indicates that the material has good photocatalytic activity, achieving an 80% degradation rate within 135 minutes, whereas a longer reaction time would be required.

[0062] The BCN material exhibited the worst performance: the slowest degradation and the highest final position (only ~60%) after 230 minutes. This indicates that the material has the lowest photocatalytic activity, a slow degradation rate, and even after a long reaction time, the final degradation rate is not ideal (only 60%), potentially indicating severe electron-hole recombination or other problems.

[0063] Example 2

[0064] A method for continuously preparing graphitic carbon nitride with different morphologies includes the following steps:

[0065] S1. Preparation of bulk graphitic carbon nitride (BCN):

[0066] 5 g of melamine was placed in a porcelain crucible, covered, and then placed in a muffle furnace for heating. The temperature was raised to 560°C at a rate of 5°C / min, held at 580°C for 1 h, and then cooled to room temperature to obtain a light yellow powder (BCN).

[0067] S2. Preparation of porous graphitic carbon nitride (PCN):

[0068] Take 1 g of the prepared BCN powder and add it to a 100 ml beaker. Then add 25 ml of concentrated sulfuric acid (98 wt%) and 25 ml of concentrated nitric acid (68 wt%). React for 1 h under continuous stirring at room temperature. Then dilute with deionized water and wash several times until neutral. Obtain PCN by filtration and drying.

[0069] S3. Preparation of porous, sheet-like graphitic carbon nitride (FCN):

[0070] The obtained PCN powder was hydrothermally reacted in an ammonia solution (25wt%) at 200℃ for 10 h to exfoliate it into FCN.

[0071] Example 3

[0072] A method for continuously preparing graphitic carbon nitride with different morphologies includes the following steps:

[0073] S1. Preparation of bulk graphitic carbon nitride (BCN):

[0074] 5 g of melamine was placed in a porcelain crucible, covered, and then placed in a muffle furnace for heating. The temperature was set to rise to 500°C at a rate of 2°C / min. After holding at 500°C for 3 hours, the temperature was cooled to room temperature to obtain a light yellow powder (BCN).

[0075] S2. Preparation of porous graphitic carbon nitride (PCN):

[0076] Take 0.5 g of the prepared BCN powder and add it to a 100 ml beaker. Then add 10 ml of concentrated sulfuric acid (95 wt%) and 10 ml of concentrated nitric acid (25 wt%). React at room temperature with continuous stirring for 2 h. Then dilute with deionized water and wash several times until neutral. Obtain PCN by filtration and drying.

[0077] S3. Preparation of porous, sheet-like graphitic carbon nitride (FCN):

[0078] The obtained PCN powder was hydrothermally reacted in an ammonia solution (25wt%) at 150℃ for 14 h to exfoliate it into FCN.

[0079] Example 4

[0080] A method for continuously preparing graphitic carbon nitride with different morphologies includes the following steps:

[0081] S1. Preparation of bulk graphitic carbon nitride (BCN):

[0082] 5 g of melamine was placed in a porcelain crucible, covered, and then placed in a muffle furnace for heating. The temperature was set to rise to 520°C at a rate of 4°C / min. After holding at 520°C for 2 hours, the temperature was cooled to room temperature to obtain a light yellow powder (BCN).

[0083] S2. Preparation of porous graphitic carbon nitride (PCN):

[0084] Take 1 g of the prepared BCN powder and add it to a 100 ml beaker. Then add 20 ml of concentrated sulfuric acid (98 wt%) and 20 ml of concentrated nitric acid (65 wt%). React at room temperature with continuous stirring for 2 h. Then dilute with deionized water and wash several times until neutral. Obtain PCN by filtration and drying.

[0085] S3. Preparation of porous, sheet-like graphitic carbon nitride (FCN):

[0086] The obtained PCN powder was hydrothermally reacted in an ammonia solution (28wt%) at 150℃ for 12 h to exfoliate it into FCN.

[0087] Example 5

[0088] A method for continuously preparing graphitic carbon nitride with different morphologies includes the following steps:

[0089] S1. Preparation of bulk graphitic carbon nitride (BCN):

[0090] 5 g of melamine was placed in a porcelain crucible, covered, and then placed in a muffle furnace for heating. The temperature was set to rise to 520°C at a rate of 4°C / min. After holding at 520°C for 2 hours, the temperature was cooled to room temperature to obtain a light yellow powder (BCN).

[0091] S2. Preparation of porous graphitic carbon nitride (PCN):

[0092] Take 1 g of the prepared BCN powder and add it to a 100 ml beaker, then add 20 ml of concentrated sulfuric acid and 20 ml of concentrated nitric acid. React for 2 h with continuous stirring at room temperature, then dilute with deionized water and wash several times until neutral. Obtain PCN by filtration and drying.

[0093] S3. Preparation of porous, sheet-like graphitic carbon nitride (FCN):

[0094] The obtained PCN powder was hydrothermally reacted in an ammonia solution at 180°C for 12 h to exfoliate it into FCN.

Claims

1. A method for continuously preparing graphitic carbon nitride with different morphologies, comprising the following steps: S1, preparation of bulk graphitic carbon nitride BCN Melamine is placed in a quartz crucible and heated in a muffle furnace, and a programmed heat treatment is performed to obtain bulk graphitic carbon nitride BCN. S2, preparation of porous graphitic carbon nitride PCN 0.5-2 parts by mass of the bulk graphitic carbon nitride BCN is weighed, and 10-50 parts by volume of concentrated sulfuric acid and 10-50 parts by volume of concentrated nitric acid are added, and the mixture is continuously stirred at room temperature to react, and then diluted with deionized water and washed to neutral; filtration, drying, and porous graphitic carbon nitride PCN. S3, preparation of hole sheet graphitic carbon nitride FCN The porous graphitic carbon nitride PCN is hydrothermally reacted in an ammonia solution to exfoliate into hole sheet graphitic carbon nitride FCN.

2. The method of claim 1, wherein: In step S1, the programmed heat treatment is performed at a temperature increasing rate of 2-5 ℃ / min to 500-600 ℃, and then heated at a constant temperature for 1-3 h.

3. The method of claim 1, wherein: In step S2, the concentration of the concentrated sulfuric acid is 95-98 wt%, the concentration of the concentrated nitric acid is 65-68 wt%, and the mass / volume ratio of the bulk graphitic carbon nitride BCN, the concentrated sulfuric acid, and the concentrated nitric acid is BCN∶concentrated sulfuric acid∶concentrated nitric acid = 1 g∶(15-25) mL∶(15-25) mL.

4. The method of claim 1, wherein: In step S2, the stirring time at room temperature is 1-3 h, and the stirring speed is 500-1000 rpm.

5. The method of claim 1, wherein: In step S3, the concentration of the ammonia solution is 25-28 wt%, the hydrothermal reaction temperature is 150-200 ℃, and the reaction time is 10-14 h. 6.The application of the graphitic carbon nitride prepared by the method of any one of claims 1-5 in photocatalytic degradation of organic pollutants.

7. Use according to claim 6, characterized in that: The graphitic carbon nitride is at least one of porous graphitic carbon nitride PCN and hole sheet graphitic carbon nitride FCN.

8. Use according to claim 6, characterized in that: The organic pollutants are azo dyes.

9. Use according to claim 8, characterized in that: The azo dyes are methyl orange.

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