Graphitic carbon nitride with pyridine N content regulated by magnetic field, preparation method and application thereof

Abstract

The present invention discloses a graphite carbon nitride (GCN) with a pyridinic N content regulated by a magnetic field, as well as a preparation method and application thereof. The preparation method specifically uses formamide as a raw material and applies a magnetic field to conduct a solvothermal reaction. Beneficial effects: Formamide used in the present invention is a cheap and readily available chemical material. Graphite carbon nitride with a higher pyridinic N content and lower defects is constructed through a simple chemical reaction, effectively achieving high-value utilization of biomass resources. The resulting graphite carbon nitride with a higher pyridinic N content and lower defects exhibits enhanced chemical kinetics and tumor treatment effects.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon nanomaterials, and in particular to graphite carbon nitride in which the pyridine N content is regulated by a magnetic field, and a preparation method and application thereof. Background Art

[0002] Research progress in metal-free carbon-based nanomaterials lies in finding suitable methods to enhance their catalytic performance. Currently, heteroatom doping, replacing certain carbon atoms in the crystal lattice, can improve the surface electronic structure of carbon-based nanozymes to enhance catalytic activity, including increasing carrier density, electrical conductivity, or thermal conductivity. Magnetic fields, like temperature and pressure, can alter chemical reaction pathways. To date, magnetic fields have primarily been used to modulate the composition or crystal growth of metals, but the application of magnetic fields to non-metals has only been reported for aligning carbon nanotubes or regulating oxygen vacancies in graphene quantum dots. High magnetic fields have made it possible to observe magnetic effects in non-magnetic materials such as carbon nanotubes, but the use of high magnetic fields is more desirable because they can enhance reaction activity and produce more fixed components, such as pyridinic nitrogen. To address these issues, using magnetic fields to modulate nitrogen content and explore its actual catalytic capabilities appears to be a viable approach.

[0003] Cancer is one of the most serious diseases that threatens human health. Currently, chemotherapy, which utilizes chemotherapeutic drugs to kill cancer cells, is the mainstay of treatment for all types of cancer. However, the use and systemic delivery of chemotherapeutic drugs results in the killing of both cancer and normal cells through apoptosis or necrosis. Tumor microenvironment (TME)-responsive chemodynamic therapy (CDT) is an important approach for cancer treatment due to its low side effects, ease of use, and the absence of anticancer drugs and external stimuli. CDT can be achieved in situ at the tumor site, where the pathological microenvironment exhibits specific physicochemical properties, such as acidic pH and elevated H₂O₂ concentrations. This is due to the reduced ability of cancer cells to metabolize H₂O₂ compared to normal cells. Due to their multivalency and high spin properties, metals are highly efficient in converting H₂O₂ to ·OH. However, some metal-based nanozymes lack specificity, and drawbacks such as low stability under certain pH and temperature conditions, aggregation in aqueous phases, and potential biosafety issues have limited their clinical application. Consequently, carbon-based nanomaterials have attracted increasing attention.

[0004] A major obstacle to the widespread application of carbon-based nanozymes is the regulation of their performance. Currently, the chemical kinetics of carbon-based nanozymes are far inferior to those of metal nanozymes because the active sites at play are not well understood. Most studies have shown that nitrogen is easily co-doped into the graphite lattice, as the electronegativity and comparable radii between nitrogen and carbon influence the electronic structure of adjacent carbon atoms, resulting in different catalytic properties. However, suppressing or enhancing certain doping types of nitrogen species in carbon-based catalysts remains a challenge. Therefore, it is particularly important to study how to determine and regulate the active sites of carbon-based nanomaterials (pyridinic nitrogen, graphitic nitrogen, etc.) through external conditions such as magnetic fields.

[0005] The Chinese patent application document with publication number CN105752953A discloses a method for preparing graphite-phase carbon nitride. The preparation process includes: using nitrogen-rich organic matter as raw material and graphite or silicon carbide as microwave absorber, uniformly mixing the nitrogen-rich organic matter and microwave absorber, controlling the pressure to 5-35kPa, the microwave irradiation power to 2-10kW, and the heating rate to 50-500℃ / min in the electromagnetic field of microwave irradiation, and keeping the reaction at 450-700℃ for 5-30min to obtain graphite-phase carbon nitride. This method is based on a high-energy microwave irradiation treatment method and can quickly and efficiently obtain graphite-phase carbon nitride with a layered structure. The method has the advantages of being simple, efficient, low-cost, and does not use various expensive or environmentally harmful reagents such as catalysts, organic solvents, and protective gases. It is environmentally friendly and does not require pretreatment of the raw materials. However, the patent does not involve the use of a magnetic field to control the content of pyridine nitrogen. Summary of the Invention

[0006] The technical problem to be solved by the present invention is how to regulate the content of pyridine N in carbon-based nanomaterials so as to have a stronger chemokinetic therapeutic effect.

[0007] The present invention solves the above technical problems through the following technical means:

[0008] A method for preparing graphite carbon nitride by regulating the pyridine N content through a magnetic field comprises the following steps: using formamide as a raw material and performing a solvent thermal reaction under a magnetic field environment to obtain the graphite carbon nitride.

[0009] Beneficial effects: In the present invention, formamide is used as a raw material to react in a magnetic field environment to obtain graphitic carbon nitride, which has a small tube diameter, a higher pyridinic N content, lower defects (the higher the pyridinic N content, the lower the vacancies, that is, the lower the defects), good hydrophilicity and chemical dynamic tumor treatment performance.

[0010] Preferably, the volume of the formamide is 15 mL≤20 mL.

[0011] Preferably, the magnetic field is 3T≤9T.

[0012] Preferably, the temperature of the solvent thermal reaction is 180-200° C., and the time is ≥15 h.

[0013] Preferably, the method further comprises dialyzing, drying and centrifuging the product after the solvent thermal reaction.

[0014] Preferably, the method comprises the following steps: placing 20 mL of formamide in a hydrothermal reactor, reacting at 200 ° C. for 20 h in a 9T water-cooled magnet, cooling to room temperature after the reaction, aspirating the product into a dialysis bag with a molecular weight cutoff of 100 kD, dialyzing in water, collecting the dialyzed solution, vacuum drying until about 100 mL of water remains, centrifuging at 12000 rpm for 3 minutes, pouring off the supernatant and washing with ethanol and water three times respectively, collecting the precipitate and vacuum drying until the water completely disappears to obtain the graphite carbon nitride.

[0015] The present invention also provides graphite carbon nitride prepared by the above preparation method.

[0016] The present invention also proposes the use of graphite carbon nitride prepared by the above preparation method in tumor treatment.

[0017] The advantages of the present invention are:

[0018] (1) In the present invention, formamide is used as a raw material to react in a magnetic field environment to obtain graphitic carbon nitride, which has a small tube diameter, a higher pyridinic N content, lower defects, good hydrophilicity and chemical dynamic tumor treatment performance;

[0019] (2) The present invention generates graphitic carbon nitride with fewer defects, which can be applied to photocatalysis, electrocatalysis, biomedicine and other aspects;

[0020] (3) Compared with other inventions, the present invention uses low-cost raw materials, has a short synthesis time, simpler steps, and can regulate the content of pyridine N. It has great prospects for future application in biomedicine to improve catalytic efficiency;

[0021] (4) The formamide used in the present invention is a cheap and readily available chemical material. Through a simple chemical reaction, graphite carbon nitride with a higher pyridinic N content and lower defects is constructed, effectively realizing the high-value utilization of biomass resources. The obtained graphite carbon nitride with a higher pyridinic N content and lower defects has a higher chemical kinetic effect and tumor treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the synthesis steps of graphite carbon nitride prepared in Example 1 of the present invention;

[0023] Figure 2 Scanning electron microscopy characterization of the graphite carbon nitride prepared in Example 1 of the present invention;

[0024] Figure 3 Transmission electron microscopy characterization of graphite carbon nitride prepared in Example 1 of the present invention;

[0025] Figure 4 This is a high-resolution image of graphite carbon nitride prepared in Example 1 of the present invention;

[0026] Figure 5 X-ray diffraction characterization of the graphite carbon nitride prepared in Example 1 of the present invention;

[0027] Figure 6 Raman characterization of graphite carbon nitride prepared in Example 1 of the present invention;

[0028] Figure 7 is the electron paramagnetic resonance spectrum of graphite carbon nitride prepared in Example 1 of the present invention;

[0029] Figure 8 This is the infrared characterization of the graphite carbon nitride prepared in Example 1 of the present invention;

[0030] Figure 9 is the X-ray photoelectron spectrum of the graphite carbon nitride prepared in Example 1 of the present invention;

[0031] Figure 10 is the X-ray photoelectron spectroscopy N1s spectrum of the graphite carbon nitride prepared in Example 1 of the present invention;

[0032] Figure 11 is the near-edge absorption spectrum of synchrotron radiation N of the graphite carbon nitride prepared in Example 1 of the present invention;

[0033] Figure 12 This is the electron paramagnetic resonance spectrum of OH produced by graphitic carbon nitride prepared in Example 1 of the present invention;

[0034] Figure 13 is the Michaelis-Menten equation curve of the graphite carbon nitride prepared in Example 1 of the present invention (hydrogen peroxide is the substrate);

[0035] Figure 14 This is a double reciprocal plot of graphite carbon nitride prepared in Example 1 of the present invention (hydrogen peroxide is the substrate);

[0036] Figure 15 The cell viability of 4T1 cells on graphitic carbon nitride prepared in Example 1 of the present invention (pH = 7.4, 6.2 and 5.0);

[0037] Figure 16These are digital photos of ex vivo tumors with various treatment procedures during the in vivo anti-tumor test of graphitic carbon nitride prepared in Example 1 of the present invention;

[0038] Figure 17 is the relative tumor volume of mice treated with different graphite carbon nitrides prepared in Example 1 of the present invention;

[0039] Figure 18 The in vitro tumor masses of mice treated with different amounts of graphite carbon nitride prepared in Example 1 of the present invention;

[0040] Figure 19 X-ray diffraction characterization of the graphite carbon nitride prepared in Example 2 of the present invention;

[0041] Figure 20 is the electron paramagnetic resonance spectrum of graphite carbon nitride prepared in Example 2 of the present invention;

[0042] Figure 21 is the relative tumor volume of the graphite carbon nitride prepared in Example 2 of the present invention in the in vivo anti-tumor test;

[0043] Figure 22 X-ray diffraction characterization of the graphite carbon nitride prepared in Example 3 of the present invention;

[0044] Figure 23 X-ray diffraction characterization of the graphite carbon nitride prepared in Example 4 of the present invention;

[0045] Figure 24 This is the electron paramagnetic resonance spectrum of the graphite carbon nitride prepared in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0046] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0047] Unless otherwise specified, the test materials and reagents used in the following examples can be obtained from commercial sources.

[0048] If no specific techniques or conditions are specified in the examples, they can be carried out according to the techniques or conditions described in the literature in the field or according to the product instructions.

[0049] Example 1:

[0050] A preparation method for controlling defects in graphite carbon nitride by using a magnetic field comprises the following steps: placing 20 mL of formamide solution in a 25 mL hydrothermal reactor, placing the reactor in a 9 T water-cooled magnet, heating the reactor to 200° C. for reaction for 20 hours, cooling the reactor to room temperature after the reaction, aspirating the solution into a dialysis bag with a molecular weight cutoff of 100 kD, and dialyzing the solution in water; during the dialysis process, collecting the solution outside the dialysis bag at regular intervals and adding new water; vacuum drying the collected solution until 100 mL of water remains, centrifuging the solution at 12,000 rpm for 3 minutes, discarding the supernatant, washing the solution with ethanol and water three times respectively, collecting the precipitate, and vacuum drying the precipitate until the water completely disappears, thereby obtaining the prepared graphite carbon nitride.

[0051] Figure 1 This is a schematic diagram of the synthesis of this example. Formamide is used as the solvent. The optimal reaction conditions are a 25 ml reactor at 200°C for 20 hours in a 9T water-cooled magnet. After 20 hours, the reaction is placed in a dialysis bag to remove large particles, followed by vacuum drying and centrifugation. It can be applied to various tumor treatment systems.

[0052] Figure 2 The scanning electron microscope characterization of the graphite carbon nitride prepared in Example 1 of the present invention is shown in FIG. Figure 3 Transmission electron microscopy characterization of the graphite carbon nitride prepared in Example 1 of the present invention, Figure 2 and Figure 3 Many graphite carbon nitride nanofibers with a diameter of about 29 nm can be clearly seen; Figure 4 This is a high-resolution image of the graphite carbon nitride prepared in Example 1 of the present invention, wherein the lattice fringe of 0.31 nm belongs to the (002) plane of the graphite carbon nitride; Figure 5 The X-ray diffraction characterization of the graphitic carbon nitride-9T prepared in Example 1 of the present invention can prove that the characteristic peak at 27.3° is attributed to the (002) crystal plane of the graphitic carbon nitride-9T; Figure 6 This is the Raman characterization of the graphite carbon nitride-9T prepared in Example 1 of the present invention. The D peak and G peak belonging to the carbon material can be clearly seen; these characteristics can prove that the prepared material is graphite carbon nitride with a tube diameter of 29 nm.

[0053] Figure 7 This is the electron spin resonance (ESR) spectrum of the graphite carbon nitride prepared in Example 1 of the present invention. The single Lorentzian line at g=2.003 comes from the unpaired electrons on the aromatic ring carbon atoms, and has a lower defect content compared with the subsequent Comparative Example 1. Figure 8 This is the infrared characterization of the graphite carbon nitride prepared in Example 1 of the present invention, which can reveal the various bond positions contained in the graphite carbon nitride, 3420cm -1The characteristic peak at 1400-1730cm corresponds to NH or OH stretching vibration, indicating that the N element in the raw material formamide has been successfully converted into the amino group in the product and has good hydrophilic properties; -1 The appearance of the peak corresponds to the CN heterocycle; 650 cm -1 The absorption peak at belongs to the heptane repeating unit. Figure 9 This is the X-ray photoelectron spectrum of the graphite carbon nitride prepared in Example 1 of the present invention. The C content in the graphite carbon nitride is 56.15%, the N content is 37.42%, and the O content is 6.43%; Figure 10 This is the X-ray photoelectron spectrum N1s spectrum of the graphite carbon nitride prepared in Example 1 of the present invention. The high-resolution N1s spectrum shows three peaks of C=NC, N-(C)3 and N-Hx at 398.8 eV, 399.9 eV and 400.7 eV, respectively.

[0054] Figure 11 The near-edge absorption spectrum of synchrotron radiation N of the graphite carbon nitride prepared in Example 1 of the present invention is divided into three peaks, which are the nitrogen atoms (N1, π * C–N–C , 398.8 eV), in a tri-triazine unit (N2, π * N-（C）3 , 400.4eV), the bridging nitrogen atom, three tri-triazine heterocycles (N3, σ * C–N , 401.8eV), compared with Comparative Example 1, it is found that Example 1 has a higher N1 content, which means it has a higher pyridine N content and lower defects;

[0055] Electron paramagnetic resonance (ESR) technology showed that the graphite carbon nitride prepared in Example 1 catalyzed the production of OH under acidic conditions, indicating that the tumor specificity of graphite carbon nitride ( Figure 12 ). Subsequently, we used acidic PBS (pH = 5.0) with immobilized TMB and immobilized graphitic carbon nitride to precisely identify the POD-like mechanism. Specifically, the POD-mimicking performance of graphitic carbon nitride was monitored by colorimetric determination using a UV-vis-NIR spectrometer at room temperature. Briefly, various volumes of H2O2 (commercially available, 30% wt / vol) were injected into a mixed buffer (pH = 5.0, 2 mL) containing graphitic carbon nitride (1 mg / mL) and TMB (10 mg / mL, 200 μL). The absorbance of the oxidation product ox-TMB at 652 nm was then immediately recorded. Quantification of the ·OH generation rate by varying the H2O2 concentration showed a good agreement with the typical Michaelis-Menten equation curve, with a maximum rate = 0.549×10 -8 M / s, indicating the tumor specificity of graphitic carbon nitride-9T ( Figure 13-14 ).

[0056] 4T1 cells were seeded in 96-well plates and incubated in cell culture medium at pH 5.0, 6.2 and 7.4, respectively, and then treated with graphite carbon nitride (0, 12.5, 25, 50 and 100 μg / mL) prepared in Example 1 for 24 hours. Cell viability was then assessed using the MTT method. The survival rate of 4T1 cells treated with PBS was defined as 100%. The in vitro anti-proliferative effect of graphite carbon nitride as a CDT agent was verified using 4T1 as a cell model. The results showed that tumor cell survival rate was inversely proportional to the dose or pH of graphite carbon nitride ( Figure 15 ).

[0057] In vivo anti-tumor test: 4-week-old female nude mice (Beijing Weitonglihua Laboratory Animal Technology Co., Ltd., China) were used as test subjects. 4T1 cells suspended in matrigel were subcutaneously injected into the right flank of nude mice to establish a tumor model. When the tumor grew to 60 mm on the 5th day, the tumor was 3 Nude mice bearing 4T1 tumors were treated with different procedures. Animal experiments were performed according to protocols approved by the Institutional Animal Care and Use. 4T1 nude mice were randomly divided into three groups: 1: treated with 200 μL PBS buffer (direct tail vein injection), 2: treated with 200 μL graphitic carbon nitride prepared in Example 1 (1 mg / mL, tail vein injection i.v.), repeated every two days for the first six days of the treatment cycle. Tumor size and mouse weight were measured every other day for 14 days. Ex vivo tumors could be obtained on day 14 for further analysis.

[0058] During the 14-day treatment period, the inhibitory effect of graphite carbon nitride on tumor growth was more significant than that of the PBS treatment group, and it had a stronger therapeutic effect than that of Comparative Example 1. The in vitro tumor and tumor growth curves were consistent, which once again proved that graphite carbon nitride with lower defects at higher magnetic fields had a stronger and more significant anti-tumor effect ( Figure 16-18 The above results confirm that graphitic carbon nitride can act as a POD mimetic enzyme to catalyze the in situ generation of ·OH in tumor tissues to inhibit tumor growth.

[0059] Example 2:

[0060] A preparation method for controlling defects in graphite carbon nitride by using a magnetic field comprises the following steps: placing 20 mL of formamide solution in a 25 mL hydrothermal reactor, placing the reactor in a 6 T water-cooled magnet, heating the reactor to 200° C. for reaction for 20 hours, cooling the reactor to room temperature after the reaction, aspirating the solution into a dialysis bag with a molecular weight cutoff of 100 kD, and dialyzing the solution in water; during the dialysis process, collecting the solution outside the dialysis bag at regular intervals and adding new water; vacuum drying the collected solution until 100 mL of water remains, centrifuging the solution at 12,000 rpm for 3 minutes, discarding the supernatant, and washing the solution with ethanol and water three times respectively; collecting the precipitate, and vacuum drying the precipitate until the water completely disappears, thereby obtaining the prepared graphite carbon nitride.

[0061] Figure 19 The X-ray diffraction characterization in Example 2 of the present invention can prove that the material is graphite carbon nitride. Figure 20 The electron spin resonance (ESR) spectrum of Example 2 of the present invention is compared with the subsequent Comparative Example 1, which proves that it has a lower defect content. Figure 21 This is the tumor treatment growth curve in Example 2 of the present invention, which has a stronger treatment effect than that in Comparative Example 1. Figure 19-21 It is demonstrated that the graphite carbon nitride prepared in Example 2 is similar to the graphite carbon nitride prepared in Example 1, both having lower N defects and good tumor treatment effects.

[0062] Example 3:

[0063] A preparation method for controlling defects in graphite carbon nitride by using a magnetic field comprises the following steps: placing 15 mL of formamide solution in a 25 mL hydrothermal reactor, placing the reactor in a 9 T water-cooled magnet, heating the reactor to 200° C. for reaction for 20 hours, cooling the reactor to room temperature after the reaction, aspirating the solution into a dialysis bag with a molecular weight cutoff of 100 kD, and dialyzing the solution in water; during the dialysis process, collecting the solution outside the dialysis bag at regular intervals and adding new water; vacuum drying the collected solution until 100 mL of water remains, centrifuging the solution at 12,000 rpm for 3 minutes, discarding the supernatant, and washing the solution with ethanol and water three times respectively; collecting the precipitate, and vacuum drying the precipitate until the water completely disappears, thereby obtaining the prepared graphite carbon nitride.

[0064] Figure 22 This is the X-ray diffraction characterization of the graphite carbon nitride prepared in Example 3 of the present invention, which is similar to the graphite carbon nitride prepared in Example 1.

[0065] Example 4:

[0066] A preparation method for controlling defects in graphite carbon nitride by using a magnetic field comprises the following steps: placing 20 mL of formamide solution in a 25 mL hydrothermal reactor, placing the reactor in a 9 T water-cooled magnet, heating the reactor to 200° C. for reaction for 16 hours, cooling the reactor to room temperature after the reaction, aspirating the solution into a dialysis bag with a molecular weight cutoff of 100 kD, and dialyzing the solution in water; during the dialysis process, collecting the solution outside the dialysis bag at regular intervals and adding new water; vacuum drying the collected solution until 100 mL of water remains, centrifuging the solution at 12,000 rpm for 3 minutes, discarding the supernatant, washing the solution with ethanol and water three times respectively, collecting the precipitate, and vacuum drying the precipitate until the water completely disappears, thereby obtaining the prepared graphite carbon nitride.

[0067] Figure 23 This is the X-ray diffraction characterization of the graphite carbon nitride prepared in Example 4 of the present invention, which is similar to the graphite carbon nitride prepared in Example 1.

[0068] Example 5:

[0069] The difference between this embodiment and embodiment 1 is that the “9T water-cooled magnet” is replaced by a “3T water-cooled magnet”, and the other steps are the same as those in embodiment 1.

[0070] Comparative Example 1:

[0071] 20 mL of formamide solution was placed in a 25 mL hydrothermal reactor, placed in a vacuum oven, heated to 200° C. and reacted for 20 hours. After the reaction, it was cooled to room temperature, and the solution inside was aspirated into a dialysis bag with a molecular weight cutoff of 100 kD, and dialyzed in water. During the dialysis process, the solution outside the dialysis bag was collected and new water was added at regular intervals. The collected solution was vacuum dried until 100 mL of water remained, centrifuged at 12,000 rpm for 3 minutes, the supernatant was poured out, and the solution was washed with ethanol and water three times respectively. The precipitate was collected and vacuum dried until the water completely disappeared to obtain the prepared graphite carbon nitride.

[0072] The difference between Comparative Example 1 and Example 1 is that the 9T water-cooled magnet environment is missing, that is, 0T.

[0073] Figure 24 The material prepared in Comparative Example 1 of the present invention has higher N defects than Examples 1 and 2, proving that the magnetic field can indeed effectively reduce the generation of defects.

[0074] Comparative Example 2:

[0075] 20 mL of formamide solution was placed in a 25 mL hydrothermal reactor, placed in a vacuum oven, heated to 100 °C and reacted for 20 h. After the reaction was completed, it was cooled to room temperature.

[0076] By comparing the prepared material with the raw material, it was found that the color of the solution did not change, proving that there was no reaction, and that formamide would not react if the temperature was not high enough.

[0077] Comparative Example 3:

[0078] 20 mL of tert-octylamine solution was placed in a 25 mL hydrothermal reactor, placed in a vacuum oven, heated to 100 °C and reacted for 20 h. After the reaction was completed, it was cooled to room temperature.

[0079] By comparing the prepared material with the raw material, it was found that the color of the solution did not change, proving that there was no reaction and that only formamide could react to produce graphite carbon nitride.

[0080] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for preparing graphite carbon nitride by regulating the pyridine N content by magnetic field, characterized in that: The following steps are involved: The solvent thermal reaction is carried out with formamide as a raw material in a magnetic field environment to obtain the product; the intensity of the magnetic field is 3-9T; and the temperature of the solvent thermal reaction is 180-200°C.

2. The preparation method according to claim 1, characterized in that The volume of the formamide is 15-20 mL.

3. The preparation method according to claim 1, characterized in that The intensity of the magnetic field is 6T.

4. The preparation method according to claim 1, characterized in that The intensity of the magnetic field is 9T.

5. The preparation method according to claim 1, characterized in that The temperature of the solvothermal reaction is 200°C.

6. The preparation method according to claim 1, characterized in that The solvent thermal reaction time is ≥15h.

7. The preparation method according to claim 1, characterized in that The method also includes dialyzing the product after the solvent thermal reaction with water, drying, and centrifuging.

8. The preparation method according to claim 1, characterized in that The following steps are involved: 20 mL of formamide solution was placed in a 25 mL hydrothermal reactor, placed in a 9T water-cooled magnet, heated to 200°C for reaction for 20 hours, cooled to room temperature after the reaction, and the solution inside was aspirated into a dialysis bag with a molecular weight cutoff of 100 kD, and dialyzed in water; during the dialysis process, the solution outside the dialysis bag was collected at regular intervals and new water was added; the collected solution was vacuum dried until 100 mL of water remained, centrifuged at 12000 rpm for 3 minutes, the supernatant was poured out, and the solution was washed with ethanol and water three times respectively, and the precipitate was collected and vacuum dried until the water completely disappeared to obtain the prepared graphite carbon nitride.

9. Graphitic carbon nitride prepared by the preparation method according to any one of claims 1 to 8.

10. Use of graphite carbon nitride prepared by the preparation method according to any one of claims 1 to 8 in preparing drugs for treating tumors.

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