A composite photocatalyst based on a pyrene-heptaazine cycloelectron donor-acceptor structure, its preparation method and application

Abstract

This invention provides a composite photocatalyst based on a pyrene-heptaazine ring electron donor-acceptor structure, its preparation method, and its application, belonging to the field of catalyst technology. The preparation method of the composite photocatalyst involves uniformly mixing a pyrene precursor and urea, followed by calcination to obtain the composite photocatalyst; the mass ratio of the pyrene precursor to urea is 0.001–0.005:1. This invention innovatively employs a molecular modification strategy, grafting pyrene (Py) units with strong electron-donating properties to the edge of the heptaazine ring group. By precisely controlling the molecular orbital energy level matching, an electronic D-A structure with a strong built-in electric field is constructed. This significantly enhances the light absorption range and carrier separation efficiency, exhibiting excellent degradation performance of organic pesticide pollutants. The process of this invention is simple and low-cost, and the resulting photocatalyst has good stability and high reproducibility.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, and in particular to a composite photocatalyst based on a pyrene-heptaazine ring electron donor-acceptor structure, its preparation method, and its application. Background Technology

[0002] Photocatalysis technology has attracted much research attention in recent years due to its environmentally friendly and efficient characteristics. Photocatalysis technology mainly involves adding a photocatalyst to photodegradation to promote the rapid generation of large amounts of reactive oxygen species (·OH, ·OH) in water under light irradiation. 1 O2、·O2 - etc.), photogenerated charge (e - ) and holes (h + Photocatalysts, such as polycarbon nitride (PCN), participate in the degradation of pollutants. Active substances primarily attack specific sites on pollutant molecules, disrupting their molecular structure and rendering them non-toxic. Photocatalysts play a crucial role in the photocatalytic degradation process; therefore, targeted selection of photocatalysts is essential for rapid and complete degradation. From a practical application perspective, photocatalysts should possess characteristics such as structural stability, strong photoresponsiveness, and safety and environmental friendliness to ensure the stable and efficient photocatalytic degradation of pollutants in water. Therefore, polycarbon nitride with a stable framework has attracted considerable research interest. However, the localization of excitons, incomplete conversion to charge-separated states, and carrier recombination limit the photocatalytic performance of single-component PCN. Summary of the Invention

[0003] To address the issues of high charge recombination rate and narrow photoresponse range in traditional PCN photocatalysts, this invention aims to provide a composite photocatalyst based on a pyrene-heptaazine ring electron donor-acceptor structure, along with its preparation method and applications. This invention innovatively employs a molecular modification strategy, grafting pyrene (Py) units with strong electron-donating properties to the edge of the heptaazine ring group. By precisely controlling the molecular orbital energy level matching, an electronic DA structure with a strong built-in electric field is constructed. This significantly enhances the light absorption range and carrier separation efficiency, exhibiting excellent degradation performance of organic pesticide pollutants. The process of this invention is simple and low-cost, and the resulting photocatalyst exhibits good stability and high reproducibility.

[0004] To achieve the above objectives, the present invention provides the following technical solution:

[0005] One of the technical solutions of the present invention is a method for preparing a composite photocatalyst based on a pyrene-heptaazine ring electron donor-acceptor structure, wherein a pyrene precursor and urea are mixed evenly and then calcined to obtain the composite photocatalyst;

[0006] The mass ratio of the pyrene precursor to urea is 0.001 to 0.005:1.

[0007] The second technical solution of the present invention is a composite photocatalyst based on a pyrene-heptaazine ring electron donor-acceptor structure prepared by the above preparation method.

[0008] The third technical solution of the present invention is the application of the above-mentioned composite photocatalyst based on the pyrene-heptaazine ring electron donor-acceptor structure in the photocatalytic degradation of organic pollutants.

[0009] The fourth technical solution of the present invention is a method for degrading pesticide-containing wastewater, wherein the above-mentioned composite photocatalyst is mixed with pesticide-containing wastewater for pesticide adsorption, and then the reaction system is subjected to catalytic reaction under visible light conditions.

[0010] The present invention discloses the following technical effects:

[0011] (1) The preparation method of the composite photocatalyst provided by the present invention can achieve the purpose by fully grinding and mixing and one-step high-temperature thermal polycondensation, and the preparation method is simple.

[0012] (2) This invention successfully modifies the heptaazine unit of pure PCN at the molecular level, forming an intramolecular electronic DA structure. The covalent grafting strategy effectively suppresses phase separation and enhances structural stability. The DA pair of the pyrene (Py) and heptaazine groups forms a strong built-in electric field within the photocatalyst, constructing a rapid intermolecular electron transfer pathway and achieving directional intramolecular charge transfer. Furthermore, the addition of Py significantly alters the nanosheet morphology of the original PCN, resulting in a highly efficient photoresponse system. Under the synergistic effect of the components, e- and h+ rapidly separate during the PyCN photoreaction and aggregate in the A and D units, respectively, forming highly reactive sites that participate in the reaction. This has significant application value in fields such as solar energy conversion and environmental remediation.

[0013] (3) The photocatalyst prepared by the present invention has good stability and high reproducibility, and exhibits a rod-shaped edge curled morphology that is different from that of the original polymerized carbon nitride.

[0014] (4) The pesticide-containing wastewater treatment method provided by this invention only requires the addition of the photocatalyst prepared by this invention to the reaction system. Without adding any other substances, it can rapidly and efficiently degrade pollutants in agricultural wastewater under visible light. The method is simple, easy to operate, and low in cost. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 The images show a partial scanning electron microscope (SEM) image (a) and a high-resolution transmission electron microscope (HRTEM) image (b) of the PyCN-30 obtained in Example 1, and a partial scanning electron microscope (SEM) image (c) of the PCN obtained in Comparative Example 1.

[0017] Figure 2 X-ray diffraction analysis patterns of PyCN-30 obtained in Example 1 and PCN obtained in Comparative Example 1 are shown.

[0018] Figure 3 The UV-Vis diffuse reflectance spectra of PyCN-30 obtained in Example 1 and PCN obtained in Comparative Example 1 are shown.

[0019] Figure 4 This is a schematic diagram showing the relationship between the concentration of PyCN-30 obtained in Example 1 and PCN obtained in Comparative Example 1 and the concentration of imidacloprid degraded under visible light and the change over time.

[0020] Figure 5 The diagram shows the cyclic effect of PyCN-30 on the degradation of imidacloprid obtained in Example 1;

[0021] Figure 6 The images show the photodegradation effect of DA-type polymeric photocatalyst (PyCN) formed by 1-PBA and urea in different mass ratios and the PCN obtained in Comparative Example 1 on imidacloprid.

[0022] Figure 7 The graph shows the degradation effect of PyCN-30 on imidacloprid under different imidacloprid concentrations obtained in Example 1.

[0023] Figure 8 The graph shows the degradation effect of PyCN-30 obtained in Example 1 on imidacloprid under different pH conditions. Detailed Implementation

[0024] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0025] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0026] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0027] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0028] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0029] The pyrene group (Py) possesses the ability to absorb and transfer laser radiation energy, and can act as a derivatizing agent to interact with neighboring functional groups under mild conditions to form covalent adducts. Furthermore, Py in organic polymer structures exhibits high ultraviolet laser quantum absorption and extremely strong electron-withdrawing capabilities. Py can react with distal ·OH groups to promote photocatalytic reactions. Small-molecule Py with a π-conjugated molten ring structure is considered a typical ladder-conjugated small molecule group. Ladder-conjugated polymers, due to the rigid planar structure and strong conjugation of their π-π ring units (which are linked by sharing at least two atoms), are considered a class of organic polymers with good thermal, chemical, and mechanical stability. Simultaneously, because conjugated ladder polymers have a greater degree of conjugation than other organic polymers, their intramolecular charge transfer rate and fluorescence quantum efficiency are also higher.

[0030] To overcome the limitations of exciton localization, incomplete conversion to charge-separated states, and carrier recombination in polymeric carbon nitride (PCN), this invention attempts to modify PCN at the molecular structure level by introducing specific functional molecular groups. Utilizing the stability of PCN, it serves as a substrate to support the modification of most functional molecules, thereby enhancing the photocatalytic performance of the original PCN. When the electronegativity of the introduced small molecular groups differs significantly from that of the heptaazine ring group in pure PCN, the resulting molecular pairs exhibit pronounced electron donor-acceptor (DA) characteristics under light irradiation. This electronic DA structure effectively promotes exciton pair dissociation and intramolecular charge transfer during the photoreaction, overcoming the limitations of pure PCN performance.

[0031] This invention utilizes a molecular modification strategy to graft pyrene (Py) units with strong electron-donating properties onto the edge of heptaazine ring groups. By precisely controlling the matching of molecular orbital energy levels, a DA structure with a strong built-in electric field is constructed. The covalent grafting strategy effectively suppresses phase separation and enhances structural stability. The DA pair of pyrene (Py) and heptaazine groups forms a strong built-in electric field within the photocatalyst, constructing a rapid intermolecular electron transfer pathway and achieving directional intramolecular charge transfer. This successfully solves the problems of high charge recombination rate and narrow photoresponse range in the original polymeric carbon nitride (PCN) materials. The study demonstrates that the electric field of the electronic DA structure has a very positive impact on exciton dissociation, highly suppressing electron recombination inactivation and stimulating ultra-high reactivity of the reaction system. Furthermore, the addition of Py also leads to a significant change in the nanosheet morphology of the original PCN, and the entire reaction system exhibits excellent photoresponse capability. Under the synergistic effect of the components, e- and h+ rapidly separate during the PyCN photoreaction and aggregate in A and D units, respectively, forming highly reactive sites to participate in the reaction. It has important application value in fields such as solar energy conversion and environmental remediation.

[0032] The first aspect of this invention provides a method for preparing a composite photocatalyst based on a pyrene-heptaazine ring electron donor-acceptor structure, wherein a pyrene precursor and urea are mixed evenly and then calcined to obtain the composite photocatalyst;

[0033] The mass ratio of the pyrene precursor to urea is 0.001 to 0.005:1.

[0034] In a preferred embodiment of the present invention, the mass ratio of the pyrene precursor to urea is 0.001:1, 0.002:1, 0.003:1, 0.004:1 or 0.005:1.

[0035] In a preferred embodiment of the present invention, the pyrene precursor is 1-pyreneboronic acid.

[0036] In a preferred embodiment of the present invention, the method of achieving uniform mixing is grinding. The present invention does not impose specific limitations on the grinding parameters; conventional parameters well-known to those skilled in the art can be selected. This application achieves thorough mixing and refinement of ordinary urea and 1-pyreneboronic acid through grinding, thereby improving the efficiency of subsequent calcination and facilitating the formation of the composite photocatalyst structure.

[0037] In a preferred embodiment of the present invention, the calcination temperature is 500–600°C, specifically 500°C, 520°C, 540°C, 560°C, 580°C, 600°C, or any value between the two aforementioned values; the time is 3–5 h, specifically 3 h, 3.5 h, 4 h, 4.5 h, 5 h, or any value between the two aforementioned values; the heating rate is 3–5°C / min, specifically 3°C / min, 4°C / min, 5°C / min, or any value between the two aforementioned values.

[0038] A second aspect of this invention provides a composite photocatalyst based on a pyrene-heptaazine ring electron donor-acceptor structure prepared by the above-described method. The composite catalyst provided by this invention, due to the pyrene group grafted onto the edge of the heptaazine ring group, results in a strong built-in electric field within the catalyst, simultaneously improving the activity and migration rate of key charges in the photocatalytic reaction. Its morphology differs from that of the original polymerized carbon nitride, exhibiting a porous, rod-like shape with rolled edges.

[0039] The third aspect of this invention provides the application of the above-mentioned composite photocatalyst based on the pyrene-heptaazine ring electron donor-acceptor structure in the photocatalytic degradation of organic pollutants.

[0040] In a preferred embodiment of the present invention, the organic pollutant is imidacloprid. Furthermore, experimental verification has shown that the present invention also exhibits strong degradation performance against pollutants such as antibiotics (e.g., ciprofloxacin), pesticides (e.g., atrazine), and antibacterial drugs (e.g., sulfadiazine).

[0041] The fourth aspect of the present invention provides a method for degrading pesticide-containing wastewater, wherein the above-mentioned composite photocatalyst is mixed with pesticide-containing wastewater for pesticide adsorption, and then the reaction system is subjected to catalytic reaction under visible light conditions.

[0042] In a preferred embodiment of the present invention, the pesticide-containing wastewater is imidacloprid-containing wastewater, ciprofloxacin-containing wastewater, atrazine-containing wastewater, or sulfadiazine-containing wastewater; the visible light wavelength is λ>420nm; the pH value of the reaction system is 3-11, specifically 3, 5, 7, 9, 11, or any value between the two aforementioned values; the temperature of the catalytic reaction is 10-35℃, specifically 10℃, 15℃, 20℃, 25℃, 30℃, 35℃, or any value between the two aforementioned values; the time is 1-2h, specifically 1h, 1.5h, 2h, or any value between the two aforementioned values.

[0043] In a preferred embodiment of the present invention, the concentration of pesticide in the pesticide-containing wastewater is 1-10 mg / L; the mass-to-volume ratio of the composite photocatalyst to the pesticide-containing wastewater is 20 mg: 50 mL; the adsorption time is 10-20 min, specifically 10 min, 15 min, 20 min, 25 min, or any value between the two aforementioned values.

[0044] Unless otherwise specified, the technical solutions described in this invention are all conventional solutions in the field.

[0045] In the following examples, the concentration of imidacloprid was determined using high-performance liquid chromatography (HPLC). Unless otherwise specified, all raw materials and instruments used were commercially available. Urea and 1-pyreneboronic acid were purchased from Shanghai Maclean Biochemical Technology Co., Ltd. The pesticide wastewater used was a self-prepared imidacloprid solution, and imidacloprid was purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0046] In the following examples, unless otherwise specified, the data obtained are the average values ​​of three or more repeated experiments, with the room temperature being 30±10℃.

[0047] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0048] Example 1

[0049] PyCN was prepared via a one-step thermopolymerization method using urea and 1-pyreneboronic acid as precursors.

[0050] First, weigh 10g of urea and 30mg of 1-pyreneboric acid, grind and mix thoroughly, and place in a 100mL ceramic crucible. Cover with aluminum foil and then put on the lid. Place in a muffle furnace and heat to 550℃ at a rate of 5℃ / min, maintaining the temperature for 3 hours. After cooling, grind the synthesized blocky solid into powder and place in centrifuge tubes labeled PyCN-30. (In this example, the mass ratio of 1-pyreneboric acid to urea is 0.003:1)

[0051] Example 2

[0052] PyCN was prepared via a one-step thermopolymerization method using urea and 1-pyreneboronic acid as precursors.

[0053] First, weigh 10g of urea and 10mg of 1-pyreneboric acid, grind and mix thoroughly, and place in a 100mL ceramic crucible. Cover with aluminum foil and then put on the lid. Place in a muffle furnace and heat to 550℃ at a rate of 5℃ / min, maintaining the temperature for 3 hours. After cooling, grind the synthesized blocky solid into powder and place in a centrifuge tube labeled PyCN-10. (That is, the difference from Example 1 is that the mass ratio of 1-pyreneboric acid to urea is 0.001:1.)

[0054] Example 3

[0055] PyCN was prepared via a one-step thermopolymerization method using urea and 1-pyreneboronic acid as precursors.

[0056] First, weigh 10g of urea and 20mg of 1-pyreneboric acid, grind and mix thoroughly, and place in a 100mL ceramic crucible. Cover with aluminum foil and then put on the lid. Place in a muffle furnace and heat to 550℃ at a rate of 5℃ / min, maintaining the temperature for 3 hours. After cooling, grind the synthesized blocky solid into powder and place in a centrifuge tube labeled PyCN-20. (That is, the difference from Example 1 is that the mass ratio of 1-pyreneboric acid to urea is 0.002:1.)

[0057] Example 4

[0058] PyCN was prepared via a one-step thermopolymerization method using urea and 1-pyreneboronic acid as precursors.

[0059] First, weigh 10g of urea and 50mg of 1-pyreneboric acid, grind and mix thoroughly, and place in a 100mL ceramic crucible. Cover with aluminum foil and then put on the lid. Place in a muffle furnace and heat to 550℃ at a rate of 5℃ / min, maintaining the temperature for 3 hours. After cooling, grind the synthesized blocky solid into powder and place in a centrifuge tube labeled PyCN-50. (That is, the difference from Example 1 is that the mass ratio of 1-pyreneboric acid to urea is 0.005:1.)

[0060] Comparative Example 1

[0061] Weigh 10g of urea, grind and mix thoroughly, and place in a 100mL ceramic crucible. Cover with aluminum foil and then put on the lid. Place in a muffle furnace and heat to 550℃ at a heating rate of 5℃ / min, and hold for 3 hours. After cooling, ordinary polycarbon nitride (PCN) is obtained.

[0062] Effect verification

[0063] Test Example 1

[0064] The PyCN-30 obtained in Example 1 and the PCN obtained in Comparative Example 1 were compared using scanning electron microscopy (SEM), and PyCN-30 was analyzed using transmission electron microscopy (TEM). The results are as follows: Figure 1As shown, (a) is a SEM image of PyCN-30, (b) is a TEM image of PyCN-30, and (c) is a SEM image of PCN. Ordinary PCN exhibits a nanosheet-like structure, while PyCN transforms into a porous rod-like structure. Furthermore, PyCN nanolayers show more pronounced and denser pores and edge curling compared to the nanosheet-like structure of PCN. This indicates that the morphology of the catalyst changes after pyrene grafting modification, and a novel DA-polymerized carbon nitride photocatalyst has been successfully prepared.

[0065] XRD analysis was performed on PyCN-30 obtained in Example 1 and PCN obtained in Comparative Example 1, respectively. The results are as follows: Figure 2 As shown in the figure (PyCN represents PyCN-30 obtained in Example 1), both modified PyCN and PCN exhibited typical diffraction peaks (001) of the carbon nitride heptaazine ring group and interlayer stacking peaks (002). It is also evident that the peak intensity at 12.7° shifted significantly to the left after the introduction of the small molecule pyrene group. This indicates that the small molecule group was successfully grafted onto the edge of the heptaazine group to form an electronic DA structure, leading to active intermolecular electron migration and causing the shift. The weakened peak intensity indicates a reduction in interlayer stacking along the (002) direction and a more pronounced amorphous characteristic, which is related to the increase in aromatic conjugated structures in the material due to the introduction of the pyrene group. This also provides favorable interlayer conditions for the photodegradation reaction process.

[0066] The PyCN-30 obtained in Example 1 and the PCN obtained in Comparative Example 1 were subjected to UV-Vis diffuse reflectance analysis, and the results are as follows: Figure 3 As shown in the figure (PyCN in the figure represents PyCN-30 obtained in Example 1), both PyCN and PCN exhibit significant photoresponse characteristics. The addition of the pyrene group significantly increases the light absorption intensity, which is attributed to the strong ultraviolet light absorption capability of Py itself. PyCN shows significant π-π* electron delocalization in the 236.2-395.8 nm wavelength region and significant n-π* electron transitions in the 428.1-545.2 nm wavelength region, fully demonstrating the positive influence of the intermolecular DA structure on the internal photogenerated charge transfer of the material.

[0067] Test Example 2

[0068] (1) Under light-protected conditions, 20 mg of PyCN-30 obtained in Example 1 and 20 mg of PCN obtained in Comparative Example 1 were weighed and mixed with 50 mL of imidacloprid solution with an initial concentration of 10 mg / L. The mixture was adsorbed for 20 min to obtain a mixed solution. During this period, about 2 mL of sample solution was taken every 10 min and filtered through a 0.22 μm aqueous filter membrane into 2 mL sampling bottles, which were labeled as 1 and 2 respectively. The original solution was labeled as 0.

[0069] (2) After adsorption equilibrium, the mixed solution was placed on a magnetic stirrer and stirred at 600 rpm while the photoreaction was carried out. A 300W xenon lamp (PLS-SXE 300D, Beijing Perfectlight, China) was used as the light source, and the filter was λ>420nm. Starting from the time of placement under the xenon lamp, approximately 2 mL of sample solution was taken at 20 min, 40 min, and 60 min, respectively, filtered through a 0.22 μm aqueous filter membrane, and placed into 2 mL sample bottles labeled as 3, 4, and 5. Finally, the concentration of imidacloprid was determined by high performance liquid chromatography (HPLC) at a detection wavelength of 270 nm, with a mobile phase of 55% methanol and 45% ultrapure water, and a flow rate of 1 mL / min. According to the formula (concentration ratio = C / C0 × 100%, where C0 is the initial concentration of imidacloprid), the residual amount of imidacloprid in the reaction solution was calculated, which represents the degradation effect of imidacloprid. The results are as follows. Figure 4 As shown in the figure (PyCN in the figure represents PyCN-30 obtained in Example 1), the degradation rate D of imidacloprid is calculated according to the formula (D=(C0-C) / C0×100%, where C0 is the initial concentration of imidacloprid).

[0070] from Figure 4 As can be seen, PyCN-30 obtained in Example 1 exhibits outstanding imidacloprid degradation performance, with a degradation efficiency of up to 70% after 60 minutes of light irradiation, and a reaction rate constant (k) of 18.97 × 10⁻⁶. -3 min -1 This is 3.18 times that of PCN (D = 22%) obtained in Comparative Example 1. This is due to the strong trapezoidal conjugation properties of the Py group, which enhances the overall conjugated structure of the PyCN reaction system and further strengthens the DA electric field. Furthermore, PyCN possesses denser, larger pores and curled edges compared to other samples, providing more active sites for the reaction.

[0071] Test Example 3

[0072] (1) Under light-protected conditions, 20 mg of PyCN-30 obtained in Example 1 was weighed and mixed with 50 mL of imidacloprid solution with an initial concentration of 10 mg / L. The mixture was adsorbed for 20 min to obtain a mixed solution. During this period, about 2 mL of sample solution was taken every 10 min and filtered through a 0.22 μm aqueous filter membrane into 2 mL sampling bottles, which were labeled as 1 and 2 respectively. The original solution was labeled as 0.

[0073] (2) After adsorption equilibrium was reached, the mixed solution was placed on a magnetic stirrer and stirred at 600 rpm while the photoreaction was carried out. A 300W xenon lamp (PLS-SXE 300D, Beijing Perfectlight, China) was used as the light source, with a filter for λ>420nm. Starting from the time of placement under the xenon lamp, approximately 2 mL of sample solution was taken at 20 min, 40 min, and 60 min, respectively, filtered through a 0.22 μm aqueous filter membrane, and placed into 2 mL sample bottles, labeled as 3, 4, and 5.

[0074] (3) The reaction solution obtained in step (2) was vacuum filtered to collect the PyCN-30 catalyst powder, and washed with a large amount of ultrapure water and anhydrous ethanol. Then it was placed in a 60°C oven and dried for 12 hours to obtain the regenerated DA type polymeric carbon nitride material.

[0075] (4) Repeat steps (1) to (3) four times with the regenerated DA-type polymeric carbon nitride material. Take the reaction solution sample obtained each time, filter it with a 0.22 μm filter membrane, and detect the concentration C of imidacloprid in the sample solution. Calculate the removal rate D of imidacloprid according to the formula (D=(C0-C) / C0×100%, where C0 is the initial concentration of imidacloprid) to obtain the cyclic degradation effect. The results are as follows: Figure 5 As shown.

[0076] Depend on Figure 5 It can be seen that after four cycles of use, the DA-type polymeric carbon nitride material obtained in Example 1 still achieved a removal rate of up to 65% for imidacloprid within 1 hour, which indicates that the DA-type polymeric carbon nitride material provided by the present invention has good stability and reusability.

[0077] Test Example 4

[0078] Following the method in Test Example 2, experiments simulating the photodegradation of imidacloprid in agricultural wastewater were conducted using PyCN-30 obtained in Example 1 and PCN obtained in Comparative Example 1. The degradation performance of PyCN (Examples 1-4) with different mass ratios of 1-pyreneboronic acid and urea was also compared under the same reaction conditions. Figure 6 As shown, when the mass ratio of 1-pyreneboronic acid to urea is 0.001:1, 0.002:1, 0.003:1, and 0.005:1, the degradation rates (D) of imidacloprid are 57%, 60%, 70%, and 50%, respectively, while the imidacloprid removal rate of PCN is only 25%. Clearly, the strong trapezoidal conjugation property of the Py group enhances the overall conjugated structure of the PyCN reaction system, further strengthening the DA electric field, thus giving the PyCN reaction system excellent photocatalytic degradation performance of imidacloprid.

[0079] Test Example 5

[0080] (1) Under light-protected conditions, 20 mg of PyCN-30 obtained in Example 1 was weighed and mixed with 50 mL of imidacloprid solutions with initial concentrations of 0.2, 0.4, 0.6, and 0.8 mg / L. The mixture was allowed to adsorb for 20 min to obtain a mixed solution. During this period, approximately 2 mL of sample solution was taken every 10 min and filtered through a 0.22 μm aqueous filter membrane into 2 mL sampling bottles, which were labeled as 1 and 2, respectively. The original solution was labeled as 0.

[0081] (2) After adsorption equilibrium, the mixed solution was placed on a magnetic stirrer and stirred at 600 rpm while the photoreaction was carried out. A 300W xenon lamp (PLS-SXE 300D, Beijing Perfectlight, China) was used as the light source, with a filter of λ>420nm. Starting from the time of placement under the xenon lamp, approximately 2 mL of sample solution was taken at 20 min, 40 min, and 60 min, respectively, filtered through a 0.22 μm aqueous filter membrane, and placed into 2 mL sample bottles labeled 3, 4, and 5. The concentration C of imidacloprid in the sample solution was measured. The remaining concentration of imidacloprid in the reaction solution was calculated according to the formula (concentration ratio = C / C0 × 100%, where C0 is the initial concentration of imidacloprid). The removal effect of the reaction was shown in the figure. Figure 7 .

[0082] Figure 7 It can be seen that PyCN-30 exhibits excellent degradation performance for imidacloprid solutions of different concentrations. In particular, when the concentration of imidacloprid in the solution is low, PyCN-30 can achieve a degradation rate of up to 100% within 60 minutes of photocatalytic reaction. This demonstrates the promising application prospects of the PyCN photocatalytic reaction system in the photodegradation of imidacloprid in agricultural wastewater.

[0083] Test Example 6

[0084] (1) Under light-protected conditions, 20 mg of PyCN-30 obtained in Example 1 was weighed and mixed with 50 mL of imidacloprid solution with an initial concentration of 10 mg / L. The pH values ​​of the imidacloprid solution were 3, 5, 7, 9, and 11, respectively. The mixture was adsorbed for 20 min to obtain a mixed solution. During this period, about 2 mL of sample solution was taken every 10 min and filtered through a 0.22 μm aqueous filter membrane into 2 mL sampling bottles, which were labeled as 1 and 2, respectively. The original solution was labeled as 0.

[0085] (2) After adsorption equilibrium, the mixed solution was placed on a magnetic stirrer and stirred at 600 rpm while the photoreaction was carried out. A 300W xenon lamp (PLS-SXE 300D, Beijing Perfectlight, China) was used as the light source, with a filter of λ>420nm. Starting from the time of placement under the xenon lamp, approximately 2 mL of sample solution was taken at 20 min, 40 min, and 60 min, respectively, and filtered through a 0.22 μm aqueous filter membrane into 2 mL sampling bottles, labeled as 3, 4, and 5. The concentration C of imidacloprid in the sample solution was measured, and the removal effect of the reaction imidacloprid was calculated according to the formula (concentration ratio = C / C0 × 100%, where C0 is the initial concentration of imidacloprid).

[0086] The results are as follows Figure 8 As shown, the pH of the 10 mg / L imidacloprid stock solution was approximately 7.5, significantly higher than the imidacloprid degradation rate and k-value at pH 7.0. The PyCN reaction system exhibits a wide pH adaptability range; excessively acidic or alkaline environments inhibit the reaction. However, the study found that at approximately pH 9, the imidacloprid degradation rate reached 72% after 60 minutes, with an optimal k-value of 19.8 × 10⁻⁶. -3 min -1 A weakly alkaline environment promotes the reaction, which is related to the fact that the PyCN reaction system has a strong oxidizing ability due to the full utilization of electrons in the DA structure under weakly alkaline conditions. This demonstrates the excellent environmental adaptability of the PyCN reaction system.

[0087] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. The application of a composite photocatalyst based on a pyrene-heptaazine ring electron donor-acceptor structure in the photocatalytic degradation of organic pollutants, characterized in that, The organic pollutant is imidacloprid; The preparation method of the composite photocatalyst based on the pyrene-heptaazine ring electron donor-acceptor structure is as follows: the pyrene precursor and urea are mixed evenly and then calcined to obtain the composite photocatalyst; The mass ratio of the pyrene precursor to urea is 0.001 to 0.004:1; The pyrene precursor is 1-pyreneboronic acid; The calcination temperature is 500–600℃, the time is 3–5 h, and the heating rate is 3–5℃ / min.

2. The application of the composite photocatalyst based on the pyrene-heptaazine ring electron donor-acceptor structure according to claim 1 in the photocatalytic degradation of organic pollutants, characterized in that, The method for achieving uniform mixing is grinding.

3. A method for degrading pesticide-containing wastewater, characterized in that, The composite photocatalyst prepared in claim 1 is mixed with pesticide-containing wastewater for pesticide adsorption, and then the reaction system is subjected to catalytic reaction under visible light conditions; the pesticide-containing wastewater is imidacloprid-containing wastewater.

4. The method for degrading pesticide-containing wastewater according to claim 3, characterized in that, The visible light wavelength is λ>420nm; the pH value of the reaction system is 3-11; the temperature of the catalytic reaction is 10-35℃, and the time is 1-2h.

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