A graphite-phase carbon nitride composite material covalently modified by a polymethyl methacrylate polymer containing a porphyrin group at the end group and a preparation method thereof

Abstract

A graphite-phase carbon nitride composite material covalently modified with a polymethyl methacrylate polymer containing a porphyrin group at its end, and a preparation method thereof, belong to the technical field of nonlinear optical materials. The composite material is characterized by being formed by covalently modifying graphite-phase carbon nitride with polymethyl methacrylate containing a porphyrin group at its end. The preparation method comprises first preparing polymethyl methacrylate containing a porphyrin group at its end by atom transfer radical polymerization, and then covalently linking the polymethyl methacrylate with a graphite-phase carbon nitride covalently modified with benzyl alcohol to prepare a graphite-phase carbon nitride composite material covalently modified with polymethyl methacrylate containing a porphyrin group at its end. The composite material is a nonlinear optical material. This method can produce a composite material with excellent nonlinear optical properties, and the nonlinear optical properties of the composite material can be controlled by varying the polymer of the porphyrin polymer.

Description

Technical Field

[0001] The invention discloses a graphite phase carbon nitride composite material covalently modified by a polymethyl methacrylate polymer containing a porphyrin group at the end group and a preparation method thereof, belonging to the technical field of nonlinear optical materials. Technical Background

[0002] Graphitic carbon nitride (g-C3N4), a metal-free two-dimensional conjugated semiconductor, boasts a tunable electronic structure, a moderate band gap, excellent visible-light response, high chemical stability, low cost, and ease of processing. It holds broad application prospects in optical and optoelectronic fields, including photocatalysis, sensing, and solar cells, and has attracted widespread attention. In recent years, g-C3N4 has exhibited stronger saturation absorption in the visible than in the near-infrared, making it a promising candidate for optical limiting. However, drawbacks such as a high recombination rate of photogenerated electron-hole pairs, a narrow visible-light absorption edge, and poor dispersibility in organic solvents have hindered its application in nonlinear optical devices. Current research on g-C3N4 modification focuses primarily on fundamental structural studies, including structural modification, element doping, nanocomposites, and covalent functionalization. While some progress has been made, practical applications remain a long way off. Therefore, designing and developing g-C3N4 materials with controllable structure, ideal nonlinear optical properties, and practical application in nonlinear optical devices is still very challenging and is a long-term task for scientific researchers.

[0003] Porphyrins are a class of organic heterocyclic compounds based on porphyrin with peripheral substituents. Their structure is characterized by a highly conjugated, large π system with 18 π electrons, making them excellent third-order nonlinear optical materials. Exploiting the readily tailorable and modifiable nature of porphyrins, polymers can be synthesized to manipulate their chemical and physical properties, improving their solubility and aggregation in media and enhancing their nonlinear optical performance. Therefore, covalently bonding porphyrin to g-C3N4 in a polymeric manner to prepare a porphyrin-polymer-g-C3N4 covalent complex not only combines the advantages of both porphyrin and g-C3N4, but also effectively improves the shortcomings of g-C3N4, enhancing its nonlinear optical properties and potentially resolving the challenges that have hindered its practical application as a nonlinear optical device. Currently, few reports exist on the synthesis, photophysical properties, and nonlinear optical properties of porphyrin-polymer covalent complexes with g-C3N4. It is a very meaningful research work to study the photophysical and nonlinear optical properties of the complex, reveal the structure-activity relationship between the material structure and nonlinear optical performance, and provide new strategies for the study of polymerized g-C3N4-based complexes in the field of nonlinear optics. Summary of the Invention

[0004] The present invention relates to a graphite-phase carbon nitride composite material covalently modified with a polymethyl methacrylate polymer containing a porphyrin group at its end group and a preparation method thereof. The prepared composite material exhibits good nonlinear optical properties and has good dispersibility in solid organic reagents. It can be used to prepare optical plastics and has good application prospects in the field of nonlinear optics. Its structural formula is shown below:

[0005]

[0006] The molecular weight of the polymethyl methacrylate polymer containing a porphyrin group at the end group is in the range of 11500-34300.

[0007] The present invention discloses a graphite-phase carbon nitride composite material covalently modified by a polymethyl methacrylate polymer containing a porphyrin group at the end group and a preparation method thereof, which belongs to the technical field of nonlinear optical materials. The composite material is characterized in that the composite material is a composite material formed by covalently modifying a graphite-phase carbon nitride with polymethyl methacrylate containing a porphyrin group at the end group, wherein the polymer part of the material is a polymethyl methacrylate polymer with a porphyrin as the end group, and the preparation method comprises firstly using the Alder method to prepare a 5-(4-hydroxyphenyl)-1-nitropropene having an asymmetric structure. The researchers used a hydroxyl group of 5-(4-2-bromoisobutyric acid methoxyphenyl)-10,15,20-triphenylporphyrin to prepare 5-(4-2-bromoisobutyric acid methoxyphenyl)-10,15,20-triphenylporphyrin. The hydroxyl group was then acylated to prepare 5-(4-2-bromoisobutyric acid methoxyphenyl)-10,15,20-triphenylporphyrin. Finally, poly(methyl methacrylate) containing a porphyrin end group was prepared by atom transfer radical polymerization. This was then covalently linked to graphite-phase carbon nitride covalently modified with benzyl alcohol to prepare a poly(methyl methacrylate) covalently modified graphite-phase carbon nitride composite material containing a porphyrin end group. This composite material is a nonlinear optical material. This method can produce a composite material with excellent nonlinear optical properties, and the nonlinear optical properties of the composite material can be controlled by changing the polymer of the porphyrin polymer.

[0008] The technical effect of the present invention is that a graphite-phase carbon nitride composite material covalently modified by a polymethyl methacrylate polymer containing a porphyrin group at the end group has good dispersibility in solid polymethyl methacrylate and good anti-saturation absorption characteristics, which can be authenticated by an open-hole Z-scan test. DETAILED DESCRIPTION

[0009] A graphite phase carbon nitride composite material covalently modified by a polymethyl methacrylate polymer containing a porphyrin group at the end group and a preparation method thereof (since the structures of the polymethyl methacrylate polymers containing a porphyrin group at the end group of this series are similar, only the molecular weight is different. Therefore, a polymethyl methacrylate polymer containing a porphyrin group at the end group (Por-PMMA) with a degree of polymerization of 100 is used as the starting material for the preparation of the graphite phase carbon nitride composite material. 100) as an example to explain it), the specific implementation method is as follows:

[0010] Por-OH was synthesized using the Adler method, as shown in the following reaction formula: p-Hydroxybenzaldehyde (2.20 g, 18 mmol) and benzaldehyde (4.75 mL, 54 mmol) were added sequentially to a 100 mL two-necked flask containing 30 mL of propionic acid. After dissolution and mixing, the reaction solution was then refluxed. Pyrrole (5 mL, 72 mmol) dissolved in 20 mL of propionic acid was then added dropwise via a constant pressure dropping funnel. After complete addition, the mixture was stirred at reflux for 2 hours. After completion of the reaction, 60 mL of ethanol was added at 60°C and stirred for 15 minutes. The mixture was then allowed to stand for 12 hours and filtered under reduced pressure for solid-liquid separation. The filter cake was washed with ethanol until the filtrate was colorless, collected, and dried in a vacuum drying oven overnight. The dried solid was purified by column chromatography using dichloromethane as the eluent. The second color band product was collected and the solvent removed by vacuum distillation to yield 0.730 g of a bright purple solid powder in a 7% yield. FT-IR(KBr pellet)ν:3510, 3317, 3024, 1596, 1514, 1473, 966, 800cm -1 ; 1 H NMR (500MHz, CDCl3), δppm: 8.87 (m, 8H), 8.24 (m, 6H), 8.12 (m, 2H), 7.62 (m, 9H), 7.20 (m, 2H), 5.19 (s, 1H), -2.74 (s, 2H).

[0011] The reaction formula is:

[0012]

[0013] 5-(4-2-bromoisobutyric acid methoxyphenyl)-10,15,20-triphenylporphyrin was prepared by esterification of hydroxyl groups. Its chemical formula is Por-Br. The reaction formula is as follows: Por-OH (0.2 g, 0.27 mmol), 30 mL of anhydrous dichloromethane and triethylamine (0.027 g, 0.27 mmol) were added to a 100 mL two-necked flask. After stirring at 0 ° C for 30 min, α-bromoisobutyryl bromide (0.028 g, 0.27 mmol) dissolved in anhydrous dichloromethane (10 mL) was added to the mixed solution through a constant pressure dropping funnel, and the reaction was continued at 0 ° C for 12 h. After the reaction was completed, the mixed solution was respectively treated with 0.1 mol L -1The product was washed with a dilute hydrochloric acid solution, a saturated sodium bicarbonate solution, and a saturated NaCl solution, dried over anhydrous NaSO, filtered, and the dichloromethane solvent removed by vacuum distillation. The crude product was purified by column chromatography using dichloromethane and petroleum ether (v:v, 1:1) as the eluent. The first color band was collected to obtain 0.185 g of a bright purple solid powder with a yield of 86%. FT-IR (KBr pellet) ν: 3028, 1750, 1600, 1516, 1475, 1294, 965, 800 cm -1 ; 1 HNMR (500MHz, CDCl3): δppm: 8.80 (m, 8H), 8.25 (m, 8H), 7.78 (m, 9H), 7.56 (d, 2H), 2.21 (m, 6H), -2.76 (s, 2H).

[0014] The reaction formula is:

[0015]

[0016] Por-PMMA was prepared by ATRP 100 The reaction formula is as follows: Under nitrogen protection, cuprous bromide (1.4 mg, 0.01 mmol), N,N,N′,N″,N″-pentamethyldiethylenetriamine (PMEDTA, 20 μL, 0.01 mmol) and DMF (1 mL) were placed on one side of an H-type reaction tube and stirred at room temperature for 30 min. DMF (1 mL), Por-Br (7.78 mg, 0.01 mmol) and MMA (106 μL, 1 mmol) were placed on the other side of the H-type reaction tube and stirred thoroughly for 30 min. The mixtures on both sides of the H-type reaction tube were mixed at 45°C, reacted for 12 h, and then exposed to air to terminate the reaction. The reaction solution was diluted with THF, the residual copper complex in the reaction system was removed with neutral alumina, and the solution was purified by precipitation in cold methanol. The insoluble matter was collected by filtration and dried under vacuum to obtain 45.6 mg of dark red solid powder with a yield of 42.3%. M n,GPC , 1.1×10 4 g mol -1 ;M n , MALS , 1.2×10 4 g mol -1 ;M w / M n (GPC) = 1.05.

[0017] The reaction formula is:

[0018]

[0019] g-C3N4 was prepared using a high-temperature, high-pressure synthesis method. The experimental route was as follows: thiourea (5.0 g, 0.066 mol) and ammonium chloride (5.0 g, 0.093 mol) were added to a corundum crucible, mixed thoroughly, and heated to 550°C for 4 hours. After the reaction was complete, the resulting solid powder was cooled to 500°C at a rate of 2°C / min and then held for 4 hours to complete the reaction, yielding g-C3N4 as a pale yellow solid powder.

[0020] The reaction formula is:

[0021]

[0022] g-C3N4-BO was prepared using the diazonium salt coupling method, as shown in the following reaction scheme. First, NaOH (0.28 g, 7 mmol), 4-aminophenol (0.76 g, 7 mmol), and deionized water (80 mL) were added to a 250 mL single-necked round-bottom flask. After thorough mixing, NaNO2 (0.526 g, 7 mmol) was added portionwise to the reaction system at 0°C and stirred for 30 minutes. Next, 20% hydrochloric acid solution was slowly added dropwise to the solution until an orange insoluble substance appeared, and the mixture was stirred for 45 minutes. Finally, g-C3N4 (100 mg) was added to the diazonium salt solution, and stirring was continued at 0°C for 4 hours. After the reaction, the mixture was filtered under reduced pressure, and the filter cake was collected, washed with distilled water, ethanol, and DMF, and dried in a vacuum oven at 60°C overnight to obtain g-C3N4-BO as an orange solid powder.

[0023] The reaction formula is:

[0024]

[0025] Preparation of Por-PMMA by Williamson ether synthesis reaction 100 -g-C3N4, the reaction formula is as follows, the specific preparation process is as follows: first, acetonitrile (10mL, 0.19mmol) was added to a two-necked flask, and an excess of anhydrous potassium carbonate was added thereto. After stirring at room temperature for 30min, g-C3N4-BO (5mg) was added to the above solution and continued to stir for 30min. Finally, Por-PMMA was added to the reaction system. 100 (3 mg, 0.3 μmol), stirred at 80 ° C for 24 h, and the crude product was separated by centrifugation. The crude product was washed with dichloromethane, ethanol and deionized water to obtain Por-PMMA 100 -g-C3N4 brown solid powder.

[0026] The reaction formula is:

[0027]

[0028] An optical resin sheet containing Por-PMMA-g-C3N4 was prepared by casting. First, a certain amount of azobisisobutyronitrile was dissolved in an appropriate amount of methyl methacrylate. The solution was prepolymerized at 65°C with stirring until a certain viscosity was reached. Next, a DMF solution containing a nonlinear optical sample was added to the prepolymerized solution and stirred to disperse uniformly. Finally, the mixture was poured into a mold coated with a release agent and placed in an oven. The mold was heated at 70°C for 3 hours, 80°C for 2 hours, and 90°C for 1 hour. After heating, the sheet was naturally cooled to room temperature. After demolding, a 2 mm thick solid optical plastic resin sheet containing the nonlinear optical sample was obtained.

[0029] Por-PMMA 100 The FT-IR spectrum of Figure 1 As shown, compared with Por-Br, most of the characteristic peaks are retained, and Por-Br is located at 645cm -1 The characteristic peaks at 2922 and 2850 cm -1 A new characteristic vibration peak appears, which is attributed to the stretching vibration peak of the continuous methylene in the PMMA main chain, at 1750cm -1 The characteristic peak at 1242 cm is attributed to the C=O stretching vibration peak of the ester group in PMMA. -1 The characteristic peaks at 986 and 800 cm-1 are attributed to the CO stretching vibration peaks in the ester group of PMMA. -1 The characteristic vibration peak at is attributed to the characteristic vibration peak of the porphyrin ring skeleton.

[0030] Figure 2 Por-PMMA 100 of 1 H NMR spectrum, δ = 8.23 ​​ppm corresponds to the chemical shift of the hydrogen proton peak on the benzene ring in porphyrin; δ = 8.87 ppm corresponds to the chemical shift of the hydrogen proton peak on the pyrrole ring; δ = 3.51 ppm corresponds to the chemical shift of the hydrogen proton peak on the methoxy group in MMA; δ = 1.79 ppm corresponds to the chemical shift of the hydrogen proton peak on the continuous methylene group in the main chain of MMA; δ = -2.72 ppm corresponds to the chemical shift of the hydrogen proton peak on the -NH- of the pyrrole ring. Based on the integrated area calculation of the hydrogen proton peak on the methoxy group in MMA and the hydrogen proton peak on the -NH- of the pyrrole ring, it is known that the three polymers are Por-PMMA. n The number of units in the molecular chains are 100, 218 and 323 respectively.

[0031] Figure 3 For three polymers Por-PMMA nThe SEC curves of the three polymers Por-PMMA were unimodal and narrow. With the increase of polymerization degree, the elution time decreased and the SEC curve shifted to the left, indicating that the molecular weight of the polymer can be regulated by controlling the ratio of monomer to initiator. During the whole polymerization process, the molecular weight distribution of the polymer was relatively uniform, all less than 1.1, and the whole polymerization process showed good controllability. The number average molecular weight (M) of the three polymers Por-PMMA was determined by GPC and SLS. n ), weight average molecular weight (M w ) and molecular weight distribution, the results are shown in Table 3-2, which are consistent with the theoretical values, reflecting the controllable activity of ATRP polymerization. n，MALS With M n，GPC The consistency further demonstrates that the porphyrin groups are bonded to the ends of the polymer chains. The steric effect of the polymer chains effectively inhibits aggregation of porphyrin molecules, effectively enhancing the nonlinear optical properties of the porphyrins. Overall, the above data confirm the successful synthesis of Por-PMMA.

[0032] Figure 4 Por-PMMA 100 , Por-PMMA 100 -XRD spectra of g-C3N4 and g-C3N4-BO, g-C3N4-BO shows obvious characteristic diffraction peaks of g-C3N4. 100 No obvious characteristic diffraction peaks were observed, proving its amorphous structure. 100 After covalent bonding with g-C3N4-BO, the characteristic diffraction peak of g-C3N4 was not observed. This may be due to the destruction of the structure of g-C3N4-BO caused by covalent bonding, which proves that Por-PMMA 100 and g-C3N4-BO.

[0033] Figure 5 Por-PMMA 100 , g-C3N4-BO, Por-PMMA 100 -g-C3N4,Por-PMMA 218 -g-C3N4 and Por-PMMA 323 - The N1s high-resolution XPS spectrum of g-C3N4 shows three characteristic peaks at 398.25, 399.45 and 400.55 eV, corresponding to CN=C, N-(C)3 and N in C-NH2 in g-C3N4-BO, respectively. 100 There are two N1s characteristic peaks at 398.6 and 400.0 eV, corresponding to NH on pyrrole and N in C=N, respectively.100 In the N1s spectrum of -g-C3N4, we can observe the 100 The characteristic peaks of NH on pyrrole and N in C=N can also be observed from the characteristic peaks of CN=C, N-(C)3 and N in C-NH2 in g-C3N4-BO, which are similar to those of g-C3N4-BO and Por-PMMA. 100 Compared with Por-PMMA 100 The binding energies of CN=C, C-NH2 and N-(C)3 in -g-C3N4 have changed, which may be due to the 100 The electron interaction between the Por-PMMA and g-C3N4 groups is caused by the electron interaction between the Por-PMMA and g-C3N4 groups. In addition, in the N1s spectrum, with the increase of the number of MMA units in Por-PMMA-g-C3N4, the peak area ratio of C=N in Por-PMMA and CN=N in g-C3N4 decreases, indicating that the porphyrin content in the composite decreases with the increase of the molecular weight of the terminal porphyrin-based polymethyl methacrylate. This can be attributed to the combined effect of the following two factors: first, with the increase of the molecular weight of the terminal porphyrin-based polymethyl methacrylate, the content of porphyrin in the polymer decreases; second, the increase of the molecular weight of the terminal porphyrin-based polymethyl methacrylate causes the steric hindrance effect of the porphyrin-based polymer to increase, resulting in a decrease in the binding amount of the terminal porphyrin-based polymethyl methacrylate polymer when reacting with an appropriate amount of g-C3N4-BO.

[0034] Figure 6 Por-PMMA 100 -Z-scan curves of g-C3N4 in DMF solvent, compared with g-C3N4-BO and Por-PMMA 100 Compared with the transmittance, it shows a significant "V" shape, indicating that Por-PMMA 100 -g-C3N4 has strong nonlinear absorption properties. Por-PMMA 100 The β value of -g-C3N4 is 4.5×10 -9 m / W, significantly higher than that of Por-PMMA 100 The improvement of the nonlinear optical performance of g-C3N4-BO is attributed to the accumulation of the following two effects: one is the accumulation of the inherent nonlinear optical properties of porphyrin and g-C3N4-BO itself. It is worth noting that the β and Im[χ (3)] is a negative value, and the specific reasons may be as follows: for g-C3N4, due to its graphene-like structure, according to the Pauli exclusion principle, the interband light absorption of g-C3N4 is easily saturated under strong excitation, resulting in an upward absorption peak; secondly, there is a light-induced electron or energy transfer between the porphyrin group and the g-C3N4 group. This transfer effect can produce a charge-separated excited state, thereby generating a larger nonlinear absorption, further improving the nonlinear optical performance.

[0035] In order to improve practicality, Por-PMMA 100 -g-C3N4,Por-PMMA 100 and g-C3N4-BO were incorporated into PMMA matrix at different concentrations to prepare optical plastics. Figure 7 Here are photos of optical plastics with different doping concentrations. Figure 7 It can be seen that although the appearance of the prepared optical plastics shows different colors due to different doping concentrations, the color distribution is uniform and transparent, indicating that the modification of g-C3N4 by covalent bonding with porphyrin after polymerization can effectively improve the dispersibility of g-C3N4 and porphyrin in organic media, and has good compatibility and processability. 100 -g-C3N4 / PMMA, g-C3N4-BO / PMMA, Por-PMMA 100 The nonlinear optical performance parameters of Por-PMMA optical plastics are shown in Table 1. 100 -g-C3N4 / PMMA optical plastic, along with Por-PMMA 100 - With the increase of g-C3N4 doping concentration, the β value increases and the linear transmittance decreases. By optimizing the doping concentration, the β and T λ Compare the Por-PMMA with the same doping concentration (0.05g / L) in Table 1. 100 -g-C3N4 / PMMA, g-C3N4-BO / PMMA and Por-PMMA 100 / PMMAThe nonlinear optical properties of three optical plastics were studied, and Por-PMMA was found 100 -g-C3N4 / PMMA(β=4.7×10 -9 m / W) has significantly higher nonlinear optical performance than Por-PMMA 100 / PMMA(β=1.5×10 -9 m / W) and g-C3N4-BO / PMMA (β=-2.1×10 -9 m / W), which is attributed to the accumulation of the amount of porphyrin groups in the optical plastic and the strength of the photoinduced electron or energy transfer effect between the g-C3N4 group and the porphyrin group.

[0036] Table 1 Por-PMMA 100 / PMMA, Por-PMMA 100 Nonlinear optical properties of g-C3N4 / PMMA and g-C3N4-BO / PMMA optical plastics

[0037]

[0038] a A laser with a pulse width of 7 ns, a frequency of 10 Hz, and an output wavelength of 532 nm is used as the light source. During the measurement process, 5 μJ of energy is output to irradiate the sample. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 FT-IR spectra of Por-Br, PMMA, and Por-PMMA100

[0040] Figure 2 Por-PMMA 100 In CDCl3 1 HNMR spectrum

[0041] Figure 3 SEC curves of three polymers Por-PMMA

[0042] Figure 4 Por-PMMA 100 、g-C3N4-BO,Por-PMMA 100 -XRD spectrum of g-C3N4

[0043] Figure 5 Por-PMMA 100 、g-C3N4-BO、Por-PMMA 100 -g-C3N4、Por-PMMA 218 -g-C3N4 and Por-PMMA 323 -N1s high-resolution spectrum of g-C3N4

[0044] Figure 6 Por-PMMA 100 , g-C3N4-BO and Por-PMMA 100 -Opening Z-scan curve of g-C3N4 in DMF (0.05 g / L)

[0045] Figure 7 Photo of optical plastic (A) Por-PMMA 100 -g-C3N4 / PMMA(0.03g / L); (B)Por-PMMA 100 -g-C3N4 / PMMA(0.05g / L); (C)Por-PMMA100 -g-C3N4 / PMMA(0.07g / L);(D)Por-PMMA 100 / PMMA(0.05g / L);(E)g-C3N4-BO / PMMA(0.05g / L)。

Claims

1. A graphite-phase carbon nitride composite material covalently modified with a polymethyl methacrylate polymer containing a porphyrin group at the end group, characterized in that The composite material is a composite material formed by covalent bonding of polymethyl methacrylate groups with porphyrin as the end group and graphite phase carbon nitride modified with benzyl alcohol. Its chemical formula is Por-PMMA. n -g-C3N4, where n is the degree of polymerization of PMMA, which is in the range of 100≤n≤300. The structural formula of the graphite phase carbon nitride composite material covalently modified by a polymethyl methacrylate polymer containing a porphyrin group at the end group is as follows: .

2. The method for preparing a graphite-phase carbon nitride composite material covalently modified with a polymethyl methacrylate polymer having a porphyrin group at the end according to claim 1, characterized in that The preparation method of the composite material is carried out according to the following steps: Step 1: Prepare benzyl alcohol-modified graphite carbon nitride by diazonium salt coupling method. First, add sodium hydroxide, 4-aminophenol and deionized water to a 250 mL single-necked round-bottom flask. After thorough mixing, add sodium nitrite to the reaction system and continue stirring. Secondly, slowly add hydrochloric acid solution to the solution until orange insoluble matter appears. Finally, add graphite carbon nitride to the above diazonium salt solution and continue stirring at 0°C. After the reaction is completed, the mixture is filtered under reduced pressure, and the filter cake is collected. It is washed with distilled water, ethanol, and DMF in sequence and dried in a vacuum drying oven at 60°C overnight to obtain benzyl alcohol-modified graphite carbon nitride as an orange solid powder with a chemical formula of g-C3N4-BO. Step 2: A polymethyl methacrylate polymer containing a porphyrin group at the end was prepared by the ATRP method. The specific method is as follows: under nitrogen protection, cuprous bromide, N,N,N′,N″,N″-pentamethyldiethylenetriamine and N,N-dimethylformamide were placed on one side of an H-type reaction tube and stirred at room temperature. N,N-dimethylformamide, an atom transfer radical polymerization initiator containing a porphyrin group, and methyl methacrylate were placed on the other side of the H-type reaction tube and stirred thoroughly. Subsequently, the mixtures on both sides of the H-type reaction tube were mixed. After the reaction was completed, the mixture was exposed to air to terminate the reaction. The reaction solution was diluted with THF, neutral alumina was used to remove the residual copper complex in the reaction system, and the solution was purified by precipitation in cold methanol. The insoluble matter was collected by filtration and dried under vacuum to obtain a dark red solid powder of a polymethyl methacrylate polymer containing a porphyrin group at the end. Its chemical formula is Por-PMMA. 100 ; Step 3: Por-PMMA-g-C3N4 was prepared by Williamson ether synthesis reaction. The specific preparation process is as follows: first, acetonitrile was added to a two-necked flask, and an excess of anhydrous potassium carbonate was added thereto. The mixture was stirred at room temperature. g-C3N4-BO was added to the above solution and continued to stir. Finally, Por-PMMA was added to the reaction system. 100 The mixture was stirred at 80 ° C for 24 hours, and the crude product was separated by centrifugation. The crude product was washed with dichloromethane, ethanol and deionized water respectively to obtain a brown solid powder of a graphite phase carbon nitride composite material covalently modified with a polymethyl methacrylate polymer containing a porphyrin group at the end group. Its chemical formula is Por-PMMA 100 -g-C3N4.

3. The method for preparing a graphite-phase carbon nitride composite material covalently modified with a polymethyl methacrylate polymer having a porphyrin group at its end group according to claim 2, wherein in step 1, the molar ratio of sodium hydroxide to 4-aminophenol is 1:

1.

4. The method for preparing a graphite-phase carbon nitride composite material covalently modified with a polymethyl methacrylate polymer having a porphyrin group at its end according to claim 2, wherein in step 1, the graphite-phase carbon nitride is added to the diazonium salt and stirred for 4-8 hours.

5. The method for preparing a graphite-phase carbon nitride composite material covalently modified with a polymethyl methacrylate polymer containing a porphyrin group at its end group according to claim 2, wherein in step 2, the molar ratio of cuprous bromide, N,N,N′,N″,N″-pentamethyldiethylenetriamine and the atom transfer radical polymerization initiator containing a porphyrin group is 1:1:

1.

6. The method for preparing a graphite-phase carbon nitride composite material covalently modified with a polymethyl methacrylate polymer containing a porphyrin group at its end group according to claim 2, wherein in step 2, before the reaction is terminated, all reaction steps are performed under anhydrous and oxygen-free conditions.

Images