A photocatalytic preparation method for low molecular weight polyphenylene ether
Low molecular weight polyphenylene ether was successfully prepared at room temperature using photocatalysis with organic peroxides and highly active amine catalysts, combined with g-C3N4 nanosheet suspension and copper tetraacetonitrile hexafluorophosphate. This method solved the problems of high molecular weight and high by-product content caused by high temperature and long reaction time in traditional methods, and improved dielectric properties and thermal stability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- TIANJIN POLYTECHNIC UNIV
- Filing Date
- 2026-05-11
- Publication Date
- 2026-06-30
AI Technical Summary
Existing technologies for preparing low molecular weight polyphenylene ethers suffer from problems such as high molecular weight, high by-product content, poor dielectric properties and thermal stability due to high-temperature and long-term reactions. Furthermore, the high copper residue in traditional methods affects dielectric properties.
Using photocatalysis, low molecular weight polyphenylene ether is prepared at room temperature by combining organic peroxide (benzoyl peroxide) with a highly active amine catalyst. The catalytic system uses g-C3N4 nanosheet suspension and copper tetraacetonitrile hexafluorophosphate as the catalyst system, replacing traditional oxygen and copper halide catalysts.
The efficient preparation of low molecular weight polyphenylene ether was achieved with a yield of up to 95.4%, a by-product content of less than 0.025%, a dielectric constant of 2.52, a dielectric loss of 1.97×10-3, and a glass transition temperature as low as 154.7℃, which improved the processing performance and dielectric properties of the material.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of polymer controllable synthesis technology, specifically relating to a photocatalytic preparation method for low molecular weight polyphenylene ether. Background Technology
[0002] Polyphenylene oxide (PPO) is an engineering plastic possessing excellent heat resistance, mechanical properties, dimensional stability, and flame retardancy. Due to its superior overall performance, PPO and its modified materials are widely used in the electronics, automotive, communications, and membrane materials industries. Therefore, exploring simple and efficient synthetic routes has become a valuable research topic. Traditional synthetic methods typically require long reaction times (24 hours) at high temperatures (80℃), resulting in products with high molecular weights (>2×10⁻⁶). 4 Its glass transition temperature (Tg) is as high as 210℃, resulting in high melt viscosity and difficulty in plasticization, which is detrimental to subsequent product processing. In addition, the excessively high molecular weight can also cause internal stress and micro-defects in the material, thereby destroying dielectric uniformity. At the same time, the long-term high-temperature reaction makes the monomers more prone to CC coupling, resulting in a high content (greater than 5%) of byproducts (3,3',5,5'-tetramethyl-4,4'-biphenylquinone, DPQ) in the resulting polyphenylene ether, which reduces dielectric properties and thermal stability.
[0003] Currently, there are two main methods for preparing low molecular weight polyphenylene oxide (PPO): monomer copolymerization and high molecular weight PPO redistribution. Monomer copolymerization uses phenolic compounds such as 2,6-dimethylphenol (DMP) and tetramethylbisphenol A (TMBPA) as raw materials. In a toluene / methanol mixed solvent, phase transfer catalytic oxidative copolymerization is employed to obtain PPO with a number average molecular weight of 1 × 10⁻⁶. 3 ~5×10 3 PPO within a certain range. For example, Chinese invention patent CN116813900 A uses a toluene-methanol mixed solvent as a solvent and a copper amine catalyst to catalyze the reaction of DMP and 2,2',3,3',5,5'-hexamethyl-4,4'-dihydroxybiphenyl to obtain low molecular weight PPO with dual-terminated hydroxyl groups. However, the residual copper content in the PPO synthesized by this method is too high (50~200ppm), requiring repeated precipitation and washing with large amounts of solvent. Even so, residual copper (1~10ppm) is still present in the final product after washing. The residual copper forms an interface with PPO, leading to charge accumulation under the action of an electric field, resulting in interfacial polarization, which in turn increases the dielectric constant and dielectric loss.
[0004] The redistribution principle for high molecular weight PPO typically uses a number-average molecular weight higher than 2 × 10⁻⁶. 4Using high molecular weight PPO as raw material, tetramethylbisphenol A (TMBPA) and other bisphenols as comonomers, and adding free radical initiators such as 3,3',5,5'-tetramethyl-4,4'-biphenylquinone (DPQ) or benzoyl peroxide (BPO) as catalysts, low molecular weight PPO (generally considered to have a number average molecular weight below 5 × 10⁻⁶) is prepared. 3 (For low molecular weight). For example, Chinese invention patent CN101389691 A uses a high molecular weight PPO redistribution method to combine free radical initiators, phenolic compounds, and a number-average molecular weight of 1×10⁻⁶. 4 The above PPO reacts in a solvent to obtain a product with a number average molecular weight of less than 4 × 10⁻⁶. 3 The method yields low molecular weight PPO. However, it still has some drawbacks: the redistribution reaction product still contains high molecular weight PPO, which needs to be separated by precipitation using a chloroform / methanol mixed solvent to remove the high molecular weight PPO, resulting in a low yield (<40%); at the same time, the gel chromatography test results of the obtained product show a bidispersive molecular weight distribution, which affects the processing performance of PPO.
[0005] Therefore, developing novel methods for preparing low molecular weight PPO to improve upon the shortcomings of traditional processes is of significant research value and application importance. Summary of the Invention
[0006] To address the shortcomings of existing technologies, the present invention aims to provide a photocatalytic preparation method for low molecular weight polyphenylene ether (PPO). This photocatalytic preparation method uses organic peroxide (BPO) instead of traditional oxygen, combining photocatalysis technology with the catalytic effect of highly active amines to achieve efficient preparation of low molecular weight PPO.
[0007] The objective of this invention is achieved through the following technical solutions.
[0008] A photocatalytic preparation method for low molecular weight polyphenylene ether includes the following steps:
[0009] Step 1: 2,6-Dimethylphenol (DMP), benzoyl peroxide (BPO), tetramethylbisphenol A (TMBPA), copper tetraacetonitrile hexafluorophosphate (CuPF6), an amine catalyst, and methanol are mixed evenly to obtain a mixture. Then, a suspension of g-C3N4 nanosheets is added to the mixture to obtain a PPO precursor solution. The amine catalyst is N,N-dimethylbutylamine (DBA) or 2,2'-bipyridine (BPy). The 2,6-dimethylphenol, benzoyl peroxide, and other components are present in the specified amounts (by molar percentage). The ratio of tetramethylbisphenol A, copper tetraacetonitrile hexafluorophosphate, and amine catalyst is (10~50):(10~20):(1~50):(1~5):(20~50); the g-C3N4 nanosheet suspension includes g-C3N4 and water, and the ratio of the molar amount of benzoyl peroxide to the mass amount of g-C3N4 in the g-C3N4 nanosheet suspension is (10~20):(0.005~0.015), where the molar amount is in mmol and the mass amount is in g;
[0010] In step 1, the concentration of g-C3N4 in the g-C3N4 nanosheet suspension is 0.5~1.5 g / L.
[0011] In step 1, the ratio of the molar amount of benzoyl peroxide to the volume amount of methanol is (10~20):(15~30), where the molar amount is in mmol and the volume amount is in mL.
[0012] In step 1, the preparation method of g-C3N4 nanosheet suspension includes: mixing g-C3N4 and water, ultrasonically dispersing, and centrifuging at 2000~4000 rpm for 1~3 min to obtain g-C3N4 nanosheet suspension.
[0013] In the above technical solution, the frequency of ultrasound is 25~50Hz and the duration of ultrasound is 30~50min.
[0014] In the above technical solution, the method for preparing g-C3N4 includes: mixing urea and melamine evenly, and heating at 2~5℃ for min. -1 The temperature is increased to 300~500℃ at a rate of 1, and held at 300~500℃ for 2~4 hours to obtain g-C3N4, wherein the ratio of urea to melamine by mass is 1:(1~4).
[0015] In step 1, the method for obtaining copper hexafluorophosphate tetraacetonitrile (CuPF6) includes: uniformly dispersing cuprous oxide in acetonitrile, adding hexafluorophosphate and performing an exothermic reaction for 5-15 min, filtering, allowing to stand for 10-30 min to precipitate crystals, filtering to obtain a solid, and freeze-drying the solid at -30 to -50 °C for 6-8 h to obtain copper hexafluorophosphate tetraacetonitrile (CuPF6), wherein the ratio of the mass fraction of cuprous oxide, the volume fraction of acetonitrile, and the volume fraction of hexafluorophosphate is (2-4):(50-90):(5-10), with the mass fraction in g and the volume fraction in mL.
[0016] Step 2: At room temperature, react the PPO precursor solution under a light source of 300-500W for 30-120 minutes to obtain the reaction solution. Centrifuge, wash, and dry to obtain low molecular weight polyphenylene ether (low molecular weight PPO).
[0017] In step 2, the illumination is ultraviolet light.
[0018] In step 2, the room temperature is 24~26℃.
[0019] In step 2, the centrifugation time is 2-5 minutes and the centrifugation speed is 2000-4000 rpm.
[0020] In step 2, the drying temperature is 60~100℃ and the drying time is 8~12h.
[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0022] 1. The photocatalytic preparation method of this invention employs photocatalysis technology, using an organic peroxide (benzoyl peroxide) instead of oxygen at room temperature, and synergistically with the catalytic action of a highly active amine (N,N-dimethylbutylamine) to successfully prepare low molecular weight PPO. Furthermore, this photocatalytic preparation method can suppress the DPQ content to below 0.025% while ensuring a high yield (95.4%). The process of this invention is simple, energy-efficient, and effectively improves upon the drawbacks of harsh conditions and long time requirements in traditional PPO synthesis methods.
[0023] 2. The low molecular weight polyphenylene ether of the present invention has good dielectric properties and thermal stability, with a dielectric constant of 2.52 and a dielectric loss of 1.97 × 10⁻⁶. -3 The glass transition temperature (Tg) is as low as 154.7℃, which is beneficial for subsequent product processing. Attached Figure Description
[0024] Figure 1 (a) Fourier transform infrared spectrum and (b) nuclear magnetic resonance (NMR) spectrum of the low molecular weight polyphenylene ether obtained in Example 1;
[0025] Figure 2 The TGA curve of the low molecular weight polyphenylene ether obtained in Example 1;
[0026] Figure 3 The DSC curve of the low molecular weight polyphenylene ether obtained in Example 1;
[0027] Figure 4 The graphs show the dielectric properties of the low molecular weight polyphenylene ether obtained in Example 1 at 1MHz~1GHz, where (a) is the dielectric constant curve (D). k (b) is the dielectric loss curve (D) f curve). Detailed Implementation
[0028] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.
[0029] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.
[0030] Example 1
[0031] A photocatalytic preparation method for low molecular weight polyphenylene ether (low molecular weight PPO) includes the following steps:
[0032] Step 1: Weigh 2,6-dimethylphenol (DMP), benzoyl peroxide (BPO, 10 mmol), tetramethylbisphenol A (TMBPA), copper tetraacetonitrile hexafluorophosphate (CuPF6), and an amine catalyst. Add these to methanol and stir until homogeneous to obtain a mixture. Then, add g-C3N4 nanosheet suspension to the mixture to obtain the PPO precursor solution. The amine catalyst is N,N-dimethylbutylamine (DBA, purchased from Kaimate (Tianjin) Chemical Technology Co., Ltd., CAS No.: 927-62-8). By molar amount, 2,6-dimethylphenol, benzoyl peroxide, tetramethylbisphenol A, and copper tetraacetonitrile hexafluorophosphate (CuPF6) are added to methanol and stirred until homogeneous to obtain a mixture. The ratio of copper tetrafluorophosphate acetonitrile to amine catalyst is 10:10:2.5:1:50; the g-C3N4 nanosheet suspension is a mixture of g-C3N4 and deionized water, with a g-C3N4 concentration of 1 g / L; the molar ratio of benzoyl peroxide to the mass fraction of g-C3N4 in the g-C3N4 nanosheet suspension is 10:0.01, with molar ratios in mmol and mass fractions in g; the molar ratio of benzoyl peroxide to the volume fraction of methanol is 10:20, with molar ratios in mmol and volume fractions in mL.
[0033] The preparation method of g-C3N4 nanosheet suspension includes: adding g-C3N4 to deionized water, sonicating (the frequency of sonication is 50Hz) for 30min to uniformly disperse g-C3N4 in deionized water, centrifuging at 4000rpm for 2min, and taking the supernatant to obtain g-C3N4 nanosheet suspension (the supernatant is g-C3N4 nanosheet suspension).
[0034] The method for preparing g-C3N4 includes: mixing urea and melamine and grinding them thoroughly to ensure uniform mixing; placing the mixture in a ceramic crucible; wrapping the ceramic crucible with tin foil; and transferring it to a muffle furnace; and heating at 5°C for 1 minute. -1 The temperature was increased to 500℃ at a certain rate and held at 500℃ for 2 hours, then naturally cooled to room temperature to obtain g-C3N4 (block), in which the ratio of urea to melamine by mass parts was 1:2.
[0035] The method for obtaining copper hexafluorophosphate tetraacetonitrile (CuPF6) includes: dissolving cuprous oxide (4g) in acetonitrile, stirring to fully dissolve the cuprous oxide, then slowly adding hexafluorophosphate (HPF6) dropwise and maintaining the exothermic reaction for 10min (the exothermic reaction includes the dropwise addition process), filtering while hot to remove brown impurities, allowing to stand for 15min to cool to room temperature and precipitate white crystals, filtering to obtain a solid, and freeze-drying the solid at -40℃ for 8h to obtain copper hexafluorophosphate tetraacetonitrile (CuPF6), wherein the mass fraction of cuprous oxide, the volume fraction of acetonitrile, and the volume fraction of hexafluorophosphate are 4:80:10, the unit of mass fraction is g, and the unit of volume fraction is mL.
[0036] Step 2: At room temperature (25℃), the PPO precursor solution was placed in a quartz tube, and the quartz tube was placed in a photoreactor (XPA-7 type, purchased from Nanjing Xujiang Electromechanical Factory). The reaction was carried out under 500W light (ultraviolet light, peak at 365nm) for 60 minutes to obtain the reaction solution. The reaction solution was centrifuged at 4000rpm for 2 minutes, washed with deionized water, and dried at 80℃ for 12 hours to obtain low molecular weight polyphenylene ether (low molecular weight PPO).
[0037] The yield of low molecular weight polyphenylene ether (low molecular weight PPO) obtained in Example 1 was 95.4%.
[0038] To further calculate the content of 3,3',5,5'-tetramethyl-4,4'-biphenylquinone (DPQ, a byproduct) in the photocatalytic preparation method, 8 mg of the low molecular weight PPO obtained in Example 1 was weighed and dissolved in 4 mL of toluene to obtain the test solution. The absorbance (A) of the test solution at a wavelength of 421 nm was measured using a UV spectrophotometer, and the concentration (c) of DPQ was calculated using the formula: c = A / εl
[0039] Where A is the absorbance of DPQ at a wavelength of 421 nm, c is the concentration of DPQ (mol / L), l is the thickness of the corresponding cuvette on the UV spectrophotometer (1 cm), and ε is the molar absorptivity of DPQ (54000 L mol / L). −1 cm −1 ).
[0040] The mass of DPQ is calculated from its concentration. The DPQ content (%) is calculated as the mass of DPQ divided by the mass of 2,6-dimethylphenol (DMP), i.e., the DPQ content (%) = m DPQ / m DMP Therefore, it can be seen that the content of 3,3',5,5'-tetramethyl-4,4'-biphenylquinone (byproduct) in the photocatalytic preparation method of Example 1 is 0.025%.
[0041] The number-average molecular weight and polydispersity index of the low molecular weight polyphenylene ether obtained in Example 1 were determined by gel permeation chromatography (Alliance E2695, purchased from WATERS, Singapore). The number-average molecular weight of the low molecular weight polyphenylene ether obtained in Example 1 was only 2.02 × 10⁻⁶. 3 Far lower than 2×10 4 Its polydispersity index was 1.343, and its GPC spectrum showed monodispersity. This indicates that a low molecular weight polyphenylene ether with monodispersity was successfully prepared by photocatalysis.
[0042] Fourier transform infrared spectroscopy was performed on the low molecular weight polyphenylene ether obtained in Example 1, and the results are as follows: Figure 1 As shown in a. From Figure 1 As can be seen from a, in the infrared spectrum of the low molecular weight PPO obtained in Example 1 prepared by photocatalysis, at 3460 cm⁻¹... -1 There is a relatively wide stretching vibration band at this point, indicating that it contains hydroxyl groups; at 2925 cm -1 and 2856cm -1 Stretching vibrations of the CH bond of the methyl group on the benzene ring were detected at 1604 cm⁻¹. -1 and 1475cm -1 The characteristic peak at 1307 cm⁻¹ is attributed to the stretching vibration of the C / C=C bonds in the backbone of the low molecular weight PPO obtained in Example 1; -1 1020cm -1 and 1188cm -1 The characteristic peak at 858 cm⁻¹ is related to the stretching vibration of the COC bond (ether bond); -1 The characteristic peak at [location] indicates the stretching vibration of the CH bond in the benzene ring structure. This proves that the low molecular weight polyphenylene ether obtained in Example 1 is PPO.
[0043] The low molecular weight polyphenylene ether obtained in Example 1 was subjected to NMR spectroscopy.1 H NMR data such as Figure 1 As shown in b. (By) Figure 1 As shown in b, in the NMR 1H spectrum of the low molecular weight polyphenylene ether obtained in Example 1, the characteristic peak a at 1.70 ppm corresponds to the hydrogen on the methyl group in the isopropylidene structure of TMBPA; the characteristic peak c at 6.37 ppm corresponds to the hydrogen on the hydroxyl group of the benzene ring; and the characteristic peak b at 6.97 ppm belongs to the characteristic peak of the hydrogen on the benzene ring of TMBPA. This further proves that the low molecular weight polyphenylene ether obtained in Example 1 is PPO.
[0044] The thermal properties of the low molecular weight polyphenylene ether obtained in Example 1 were tested, and the results are as follows: Figure 2 and Figure 3 As shown, where, Figure 2 For TGA curves, Figure 3 The figure shows the DSC curve. As can be seen from the graph, the mass loss of the low molecular weight polyphenylene ether obtained in Example 1 reached 5% (T). d5% The temperature at which the polyphenylene ether was synthesized was 397.8℃, higher than the 380℃ of polyphenylene ether synthesized by conventional methods in the prior art. Furthermore, its glass transition temperature (Tg) was only 154.7℃ (Tg value is positively correlated with number-average molecular weight), indicating that the number-average molecular weight of the polyphenylene ether synthesized by the photocatalytic method of this invention is much lower than that of polyphenylene ether synthesized by conventional methods (Tg=210℃). This shows that the low molecular weight polyphenylene ether obtained in Example 1 has good thermal stability and is more conducive to subsequent commercial processing (the lower the Tg, the more favorable it is for subsequent commercial processing).
[0045] The dielectric properties of the low molecular weight polyphenylene ether obtained in Example 1 were tested using an E4991B impedance analyzer (purchased from Keysight Technologies (China) Co., Ltd.). Its dielectric constant curve (D) was obtained from 1 MHz to 1 GHz. k (curve) such as Figure 4 As shown in Figure a, the dielectric loss curve (D) f (curve) such as Figure 4 As shown in b. (By) Figure 4 It can be seen that the dielectric constant (D0) of the low molecular weight polyphenylene ether obtained in Example 1 at 1 GHz is... k The dielectric loss (D) is 2.52. f The value is 1.97 × 10 -3 This indicates that the low molecular weight polyphenylene ether obtained in Example 1 has low loss during information transmission.
[0046] Example 2
[0047] A photocatalytic preparation method for low molecular weight polyphenylene ether is basically the same as the "photocatalytic preparation method for low molecular weight polyphenylene ether" in Example 1, except that the type of amine catalyst is 2,2'-bipyridine (BPy).
[0048] The yield of low molecular weight polyphenylene ether obtained in Example 2 was 89.5%, and the content of 3,3',5,5'-tetramethyl-4,4'-biphenylquinone (byproduct) in the photocatalytic preparation method of Example 2 was 2.58%.
[0049] The number-average molecular weight and polydispersity index of the low molecular weight polyphenylene ether obtained in Example 2 were determined by gel permeation chromatography to be 2.31 × 10⁻⁶. 3 And 1.44. This indicates that low molecular weight polyphenylene ether was successfully prepared by photocatalysis.
[0050] The thermal properties of the low molecular weight polyphenylene ether obtained in Example 2 were tested, and the T value of the low molecular weight polyphenylene ether obtained in Example 2 was obtained. d5% The temperature range (Tg) is 370.8℃, and the temperature coefficient of thermal expansion (Tg) is 170.8℃. Its Tg value is significantly lower than that of PPO synthesized by the traditional method (210℃), indicating that it has better processing performance.
[0051] The dielectric properties of the low molecular weight polyphenylene ether obtained in Example 2 were tested using an E4991B impedance analyzer. Its dielectric constant at 1 GHz was 2.88, and its dielectric loss (D0) was [not specified]. f The value is 2.67 × 10 -3 This indicates that the low molecular weight polyphenylene ether obtained in Example 2 has low loss during information transmission.
[0052] Comparative Examples 1-6
[0053] A photocatalytic preparation method for low molecular weight polyphenylene ether is basically the same as the "photocatalytic preparation method for low molecular weight polyphenylene ether" in Example 1, except that the type of amine catalyst is different. The amine catalysts used in different comparative proportions are shown in Table 1.
[0054] The yields of PPO in the photocatalytic preparation methods of Comparative Examples 1 to 6 are shown in Table 1.
[0055] Table 1
[0056]
[0057] This invention utilizes photocatalysis to successfully prepare low molecular weight poly(p-PO) at room temperature by replacing oxygen with benzoyl peroxide in combination with a highly active amine catalyst. Using N,N-dimethylbutylamine as the amine catalyst, the low molecular weight PPO can achieve a high yield (95.4%) while suppressing the content of byproducts to below 0.025%. The process of this invention is simple, energy-efficient, and effectively overcomes the drawbacks of harsh conditions and long reaction times in traditional PPO synthesis processes. Furthermore, in the photocatalytic preparation method of this invention, water-soluble CuPF6 is used instead of traditional copper halides for PPO synthesis, significantly reducing the residual copper content in the product.
[0058] The present invention has been described above by way of example. It should be noted that any simple modifications, alterations or other equivalent substitutions that can be made by those skilled in the art without creative effort without departing from the core of the present invention fall within the protection scope of the present invention.
Claims
1. A photocatalytic preparation method for low molecular weight polyphenylene ether, characterized in that, Includes the following steps: Step 1: 2,6-Dimethylphenol, benzoyl peroxide, tetramethylbisphenol A, copper tetraacetonitrile hexafluorophosphate, amine catalyst, and methanol are mixed evenly to obtain a mixture. Then, a suspension of g-C3N4 nanosheets is added to the mixture to obtain a PPO precursor solution. The amine catalyst is N,N-dimethylbutylamine or 2,2'-bipyridine. The amounts of 2,6-dimethylphenol, benzoyl peroxide, tetramethylbisphenol A, copper tetraacetonitrile hexafluorophosphate, and... (The text abruptly ends here, so the translation stops as well.) The ratio of amine catalyst is (10~50):(10~20):(1~50):(1~5):(20~50); the g-C3N4 nanosheet suspension includes g-C3N4 and water, and the ratio of the molar amount of benzoyl peroxide to the mass amount of g-C3N4 in the g-C3N4 nanosheet suspension is (10~20):(0.005~0.015), where the molar amount is in mmol and the mass amount is in g; Step 2: At room temperature, react the PPO precursor solution under a light source of 300-500W for 30-120 minutes to obtain the reaction solution. Centrifuge, wash, and dry to obtain low molecular weight polyphenylene ether.
2. The photocatalytic preparation method according to claim 1, characterized in that, In step 1, the concentration of g-C3N4 in the g-C3N4 nanosheet suspension is 0.5~1.5 g / L.
3. The photocatalytic preparation method according to claim 1, characterized in that, In step 1, the ratio of the molar amount of benzoyl peroxide to the volume amount of methanol is (10~20):(15~30), where the molar amount is in mmol and the volume amount is in mL.
4. The photocatalytic preparation method according to claim 1, characterized in that, In step 1, the preparation method of g-C3N4 nanosheet suspension includes: mixing g-C3N4 and water, ultrasonically dispersing, and centrifuging at 2000~4000 rpm for 1~3 min to obtain g-C3N4 nanosheet suspension.
5. The photocatalytic preparation method according to claim 4, characterized in that, The frequency of the ultrasound is 25~50Hz, and the duration of the ultrasound is 30~50min.
6. The photocatalytic preparation method according to any one of claims 1 to 5, characterized in that, A method for preparing g-C3N4 includes: mixing urea and melamine evenly, and heating at 2-5°C for [time missing] min. -1 The temperature is increased to 300~500℃ at a rate of 1, and held at 300~500℃ for 2~4 hours to obtain g-C3N4, wherein the ratio of urea to melamine by mass is 1:(1~4).
7. The photocatalytic preparation method according to claim 1, characterized in that, In step 1, the method for obtaining copper hexafluorophosphate tetraacetonitrile includes: uniformly dispersing cuprous oxide in acetonitrile, adding hexafluorophosphate and performing an exothermic reaction for 5-15 minutes, hot filtering, allowing it to stand for 10-30 minutes to precipitate crystals, filtering to obtain a solid, and freeze-drying the solid at -30 to -50°C for 6-8 hours to obtain copper hexafluorophosphate tetraacetonitrile, wherein the ratio of the mass fraction of cuprous oxide, the volume fraction of acetonitrile, and the volume fraction of hexafluorophosphate is (2-4):(50-90):(5-10), with the mass fraction in g and the volume fraction in mL.
8. The photocatalytic preparation method according to claim 1, characterized in that, In step 2, the room temperature is 24~26℃.
9. The photocatalytic preparation method according to claim 1, characterized in that, In step 2, the centrifugation time is 2-5 minutes and the centrifugation speed is 2000-4000 rpm.
10. The photocatalytic preparation method according to claim 1, characterized in that, In step 2, the drying temperature is 60~100℃ and the drying time is 8~12h.