Preparation method and application of high-coordination sulfur-doped monatomic catalyst

Abstract

This invention discloses a method for preparing a highly coordinated sulfur-doped single-atom catalyst and its application, comprising the following steps: S1, mixing and stirring zinc nitrate hexahydrate, dimethylimidazole, hexadecyltrimethylammonium bromide, a metal source, and deionized water to obtain metal-doped ZIF-8; S2, heating the metal-doped ZIF-8 under an argon atmosphere to obtain an undoped metal single-atom catalyst; S3, preparing the undoped metal single-atom catalyst into a highly coordinated sulfur-doped metal single-atom catalyst; S4, adding the highly coordinated sulfur-doped single-atom catalyst to antibiotic wastewater for treatment; This invention avoids coordination in the first shell of the metal atom by mixing the single-atom catalyst and thiourea and performing a second pyrolysis, thereby forming a sulfur-doped highly coordinated single-atom catalyst.

Description

Technical Field

[0001] This invention relates to the field of water pollution control technology, specifically to a method for preparing a highly coordinated sulfur-doped single-atom catalyst and its application. Background Technology

[0002] Access to clean water remains a key objective of the UN Sustainable Development Agenda. However, the presence of emerging pollutants in water bodies poses a significant challenge to achieving this goal. These pollutants typically exist in trace amounts within complex organic-inorganic mixtures, making them difficult to remove effectively using traditional wastewater treatment processes. Therefore, employing highly efficient purification technologies has become an essential choice for controlling the risks of emerging pollutants and ensuring water supply security.

[0003] Compared to other advanced oxidation technologies, persulfate (PS)-based advanced oxidation technologies (AOPs) can generate a variety of reactive oxygen species, including free radicals (such as hydroxyl radicals, sulfate radicals, and superoxide radicals) and non-free radical species (such as singlet oxygen, high-valence metal oxygen species, and electron transfer processes). However, the free radical-based degradation pathway is susceptible to interference from anions and organic matter in water, which not only significantly reduces the utilization rate of persulfate (PMS) but also generates harmful byproducts.

[0004] Electron transfer processes mediated by metastable intermediates formed through catalyst-PMS coupling exhibit significant advantages in water remediation due to their long half-life, high steady-state concentration, and high selectivity for pollutants. Therefore, developing catalysts that can efficiently activate PMS and selectively remove pollutants through electron transfer pathways is crucial for promoting the practical application of PMS-AOPs. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a highly coordinated sulfur-doped single-atom catalyst and its application. This method can achieve selective removal of pollutants via a highly selective electron transfer pathway, and has high efficiency, stability, and strong anti-interference performance against impurities in water.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing a highly coordinated sulfur-doped single-atom catalyst, the method comprising the following steps: S1. Zinc nitrate hexahydrate, dimethylimidazole, hexadecyltrimethylammonium bromide, metal source and deionized water are mixed and stirred. After the reaction is completed, the precipitate is collected by centrifugation. The precipitate is washed three times with methanol to obtain metal-doped ZIF-8. The molar ratio of zinc nitrate hexahydrate, dimethylimidazole, hexadecyltrimethylammonium bromide, metal source, and deionized water is 1:(6.0~7.0):(0.075~0.125):(0.04~0.05):(3000~3600). S2. The metal-doped ZIF-8 was heated under an argon atmosphere and then cooled to room temperature to obtain a black solid product. The black solid product was then ground into powder to obtain an undoped metal single-atom catalyst. S3. The undoped metal single-atom catalyst and thiourea are mixed at a mass ratio of 1:10. After grinding, the mixture powder is obtained. The mixture is heated under an argon atmosphere and then cooled to room temperature to obtain a black solid product. The black solid product is ground into powder to obtain a highly coordinated sulfur-doped metal single-atom catalyst.

[0007] Preferably, in S1, the metal source is cobalt nitrate hexahydrate or ferric nitrate nonahydrate.

[0008] Note: Cobalt and iron metal sources can chelate with carbon supports to form highly active single-atom sites, which are suitable for persulfate-activated electron transfer catalytic pathways.

[0009] Preferably, in S1, the mixing and stirring are carried out at 25~30℃ and 500~800rpm for 30~60min, followed by standing and aging at room temperature in the dark for 12~24h, and then centrifugation is performed. The centrifugation speed for collecting the precipitate was 8000~10000 rpm, and the centrifugation time was 5~10 min. The precipitate after being washed with methanol was then vacuum dried at 60℃ for 5~8 h.

[0010] Note: This parameter range ensures the regular growth of ZIF-8 crystals, forming a stable porous framework and providing sufficient anchoring points for uniform encapsulation of metal ions.

[0011] Preferably, in S2, the temperature is maintained at 950~1050℃ during the heating process, and the reaction time is 2.5~3.5h.

[0012] Preferably, in S2, the heating process adopts a segmented heating process. First, the temperature is raised from room temperature to 200-300°C at a heating rate of 2-3°C / min, and held for 1-2 hours to remove solvent and residual organic ligands. Then, the temperature is raised to 950-1050°C at a heating rate of 3-5°C / min, and held for 2.5-3.5 hours. After the holding period, the temperature is lowered to 300°C at a rate of 5°C / min, and then naturally cooled to room temperature.

[0013] Note: Segmented heating can fully remove organic components, simultaneously complete the graphitization of carbon carriers and the anchoring of metal single atoms, and effectively avoid metal agglomeration.

[0014] Preferably, in S3, the temperature is maintained at 550~650℃ during the heating process, and the reaction time is 1.8~2.2h.

[0015] Note: This process enables high-coordination doping of sulfur in the second shell of a metal, precisely controlling the electronic structure of the metal center and avoiding coordination interference in the first shell.

[0016] This invention also provides an application of a highly coordinated sulfur-doped single-atom catalyst prepared by the above method, which is used to degrade antibiotics in wastewater.

[0017] Preferably, the antibiotics include sulfadiazine, carbamazepine, bisphenol A, acetaminophen, and norfloxacin.

[0018] Note: Using sulfadiazine at this concentration and volume as the target pollutant, the catalytic performance of the catalyst for antibiotic degradation can be accurately and stably evaluated.

[0019] Preferably, the application method is as follows: S1. Adjust the pH of the antibiotic wastewater to 3-11 using H2SO4 or NaOH. Then, add 15-20 mg of highly coordinated sulfur-doped single-atom catalyst to the antibiotic wastewater at a dosage of 10-15 min for the first treatment. S2. Add potassium persulfate to the antibiotic wastewater at a dosage of 30-35 mg per 100 mg of wastewater and stir to react. Under the action of a highly coordinated sulfur-doped single-atom catalyst, the potassium persulfate is activated. The activated potassium persulfate is used to decompose and remove the antibiotics in the wastewater. The stirring speed is 380-420 rpm and the treatment time is 10-15 minutes to complete the treatment of the antibiotic-containing wastewater.

[0020] Note: This application method is applicable to a wide pH range and can be adapted to actual wastewater with different acidity and alkalinity. It eliminates the need for precise acid-base adjustment, reducing the operating cost of wastewater treatment. This rotation speed ensures sufficient contact between the catalyst, oxidant, and pollutants, enhances mass transfer efficiency, and guarantees uniform and efficient degradation reaction.

[0021] Preferably, the concentrations of both H2SO4 and NaOH are 1M.

[0022] Compared with the prior art, the beneficial effects of the present invention are reflected in the following aspects: 1. This invention uses ZIF-8 as the carbon and nitrogen source of the catalyst. During the synthesis process, metal ions are encapsulated inside the catalyst cavity and then pyrolyzed to obtain a graphite carbon support with a high specific surface area. The metal ions encapsulated inside the cavity can chelate with the carbon support to form single-atom catalysts with different metal doping. 2. This invention avoids coordination in the first shell of metal atoms by mixing a single-atom catalyst and thiourea and then performing a second pyrolysis, thereby forming a sulfur-doped highly coordinated single-atom catalyst. 3. The sulfur-doped high-coordination single-atom catalyst of the present invention has high utilization of metal active sites, specific surface area and catalytic activity. Under optimal conditions, the catalyst can remove more than 95% of sulfadiazine within 10 minutes. 4. In the catalyst of this invention, the metal atoms act as catalytic active centers. Through the electronic regulation of the metal atoms by highly coordinated sulfur, the electron transfer pathway becomes the main active substance in the activation of persulfate. In particular, the contribution of the electron transfer pathway in the degradation of sulfadiazine by sulfur-doped highly coordinated iron single atoms is as high as 94.9%. 5. The catalyst of the present invention is not only applicable to a variety of water quality environments, but also shows excellent removal efficiency for a variety of organic pollutants (such as acetaminophen, norfloxacin, carbamazepine, bisphenol A, etc.) in other wastewater. 6. The method provided by this invention has a simple catalyst synthesis process, the raw materials are easy to obtain and do not pollute the environment, the operation is safe and the equipment requirements are low, and it is suitable for the field of wastewater treatment. Attached Figure Description

[0023] Figure 1 This is a scanning electron microscope (SEM) image of the precursor of the sulfur-doped high-coordination single-atom catalyst in Example 1 of this invention, obtained using an ESEM Quanta FEG 250 environmental scanning electron microscope. Figure 2 These are scanning electron microscope (SEM) and transmission electron microscope (TEM) images of the sulfur-doped high-coordinated iron single-atom catalyst of Example 1 of this invention. Figure 3 This is a dark-field transmission electron microscope image and elemental distribution diagram of the sulfur-doped high-coordinated iron single-atom catalyst of Example 1 of the present invention. Figure 4 This is a diagram showing the formation energy and structure of the sulfur-doped high-coordinate iron single-atom catalyst of Example 1 of the present invention at different doping sites; Figure 5 This is the fine structure X-ray absorption spectrum of the sulfur-doped high-coordinated iron single-atom catalyst of Example 1 of the present invention; Figure 6 These are scanning electron microscope (SEM) and transmission electron microscope (TEM) images of the sulfur-doped, highly coordinated cobalt single-atom catalyst prepared in Example 2 of this invention. Figure 7 This is a dark-field transmission electron microscope image and elemental distribution diagram of the sulfur-doped high-coordinated cobalt single-atom catalyst prepared in Example 2 of this invention. Figure 8 This is a diagram showing the formation energy and structure of the sulfur-doped high-coordinate cobalt single-atom catalyst prepared in Example 2 of this invention at different doping sites. Figure 9 This is the fine X-ray absorption structure spectrum of the sulfur-doped highly coordinated cobalt single-atom catalyst prepared in Example 2 of this invention; Figure 10 This is a comparison chart showing the degradation effects of the catalysts prepared in Example 1, Comparative Example 1, and Comparative Example 2 of this invention and activated potassium persulfate on sulfadiazine. Figure 11 This is a comparison chart showing the degradation effects of the catalysts prepared in Example 2, Comparative Example 1, and Comparative Example 3 of the present invention and activated potassium persulfate on sulfadiazine. Figure 12 This is a graph showing the performance of the catalysts prepared in Examples 1 and 2 of this invention in removing carbamazepine, bisphenol A, acetaminophen, and norfloxacin antibiotic pollutants from water. Figure 13 This is a comparison of the degradation effects of the catalysts prepared in Examples 1 and 2 of this invention on sulfadiazine under different quenchers when potassium persulfate is activated; Figure 14 These are the electron paramagnetic resonance spectra of activated potassium persulfate in Examples 1, 2, 2, and 3 of this invention. Figure 15 This is a schematic diagram showing the steady-state concentrations of different active substances during the activation of potassium persulfate in Examples 1, 2, 2, and 3 of the present invention. Figure 16 These are open-circuit potential variation diagrams for Embodiment 1, Embodiment 2, Comparative Example 1, and Comparative Example 2 of the present invention; Figure 17 This represents the contribution of different active substances to the degradation effect of sulfadiazine during the activation of potassium persulfate in Examples 1 and 2 of this invention. Detailed Implementation

[0024] The following is combined Figures 1-17 The present invention will be described in detail below. For ease of description, the orientations mentioned below are defined as follows: The directions of up, down, left, right, front, and back mentioned below are consistent with the directions of up, down, left, right, front, and back in the projection relationship of the respective main view or structural schematic diagram.

[0025] Example 1: A method for preparing a highly coordinated sulfur-doped single-atom catalyst, comprising the following steps: S1. Dissolve zinc nitrate hexahydrate and dimethylimidazole in 5 mL and 120 mL of deionized water respectively in a molar ratio of 1:6.2 to form solution A and solution B, wherein the amount of zinc nitrate hexahydrate added is 61 mL / mmol. Add 0.18 mmol of hexadecyltrimethylammonium bromide to solution B, and add ferric nitrate nonahydrate and zinc salt to solution A at a molar ratio of 1:20. Zn(NO3)2·6H2O+2Hmim→ZIF-8+2HNO3+6H2O; The above solutions A and B were mixed and stirred, the precipitate was collected by centrifugation, and washed three times with methanol to obtain iron-doped ZIF-8 for later use. S2. The above-mentioned iron-doped ZIF-8 was heated to 1000℃ in an argon atmosphere at a heating rate of 3℃ / min, and reacted at this temperature for 3h. After the heating was completed and the mixture was allowed to cool naturally, a sulfur-free iron single-atom catalyst was obtained for later use. S3. The above-mentioned sulfur-free doped iron single-atom catalyst and thiourea are mixed in a mass ratio of 1:10, heated to 600°C at a heating rate of 3°C / min under an argon atmosphere, and reacted at this temperature for 2 hours. After the heating is completed and the mixture is allowed to cool naturally, a highly coordinated sulfur-doped iron single-atom catalyst is obtained.

[0026] The scanning electron microscope (SEM) images of the sulfur-doped highly coordinated single-atom catalyst prepared in this embodiment, obtained using an ESEM Quanta FEG 250 environmental scanning electron microscope, are shown below. Figure 1 , Figure 2 As shown in the figure, sulfur doping still maintains the original cubic shape, indicating that sulfur doping does not destroy the original structure of the catalyst. like Figure 3 The image shown is a dark-field transmission electron microscope image of the highly coordinated sulfur-doped iron single-atom catalyst prepared in this embodiment, as well as the surface distribution characterization results of the core elements Fe, N, S, and C, verifying the uniform dispersion state of iron single atoms and sulfur elements on the carbon support. like Figure 4 The figure shows the theoretically calculated formation energy and atomic structure model of the highly coordinated sulfur-doped iron single-atom catalyst prepared in this embodiment at different sulfur doping sites, which verifies the thermodynamic stability of sulfur highly coordinated doping in the second shell of iron metal. like Figure 5 The images show the fine X-ray absorption spectra of the highly coordinated sulfur-doped iron single-atom catalyst, the sulfur-free iron single-atom catalyst, and the iron foil, FeO, and Fe2O3 control samples prepared in this embodiment. These spectra are used to analyze the coordination environment, valence state, and atomic dispersion state of the iron center, and to verify the regulatory effect of sulfur doping on the electronic structure and coordination structure of the metal center.

[0027] Example 2: The difference from Example 1 is that the metal source is cobalt nitrate hexahydrate. S1 corresponds to cobalt-doped ZIF-8, S2 corresponds to sulfur-free cobalt-doped single-atom catalyst, and S3 corresponds to highly coordinated sulfur-doped cobalt-doped single-atom catalyst.

[0028] like Figure 6 , 7As shown, sulfur doping did not disrupt the original morphology and structure, and sulfur and cobalt were uniformly distributed on the catalyst. Meanwhile, aberration electron microscopy results showed that cobalt was in an atomically dispersed state on the catalyst surface, indicating that a highly coordinated sulfur-doped cobalt single-atom catalyst was successfully prepared. like Figure 8 The figure shows the theoretically calculated formation energy and atomic structure model of the highly coordinated sulfur-doped cobalt single-atom catalyst prepared in this embodiment at different sulfur doping sites, which verifies the thermodynamic stability of sulfur highly coordinated doping in the second shell of cobalt metal. like Figure 9 The images show the X-ray absorption fine structure spectra of the highly coordinated sulfur-doped cobalt single-atom catalyst, the sulfur-free cobalt single-atom catalyst, and the control samples of cobalt foil, CoO, and Co3O4 prepared in this embodiment. These spectra are used to analyze the coordination environment, valence state, and atomic dispersion state of the cobalt center, and to verify the regulatory effect of sulfur doping on the electronic structure and coordination structure of the cobalt metal center.

[0029] Comparative Example 1: The catalyst obtained by removing the metal source from Example 1 is used as Comparative Example 1.

[0030] Comparative Example 2: The sulfur-free doped iron single-atom catalyst obtained in S2 of Example 1 was used as Comparative Example 2.

[0031] Comparative Example 3: Cobalt-doped ZIF-8 prepared in S1 of Example 2 was used as Comparative Example 3.

[0032] Example 3: The difference from Example 1 is that in S1, the mixing and stirring are carried out at 25°C and 500 rpm for 30 min, followed by aging at room temperature in the dark for 12 h, and then centrifugation is performed. The centrifugation speed for collecting the precipitate was 8000 rpm and the centrifugation time was 5 min. The precipitate after being washed with methanol was then vacuum dried at 60℃ for 5~8 h.

[0033] Example 4: The difference from Example 3 is that in S1, the mixing and stirring are carried out at 30°C and 800 rpm for 60 min, followed by aging at room temperature in the dark for 24 h, and then centrifugation is performed. The centrifugation speed for collecting the precipitate was 10,000 rpm and the centrifugation time was 10 min. The precipitate after being washed with methanol was then vacuum dried at 60℃ for 8 h.

[0034] Example 5: The difference from Example 1 is that in S2, the temperature is maintained at 1050°C during the heating process, and the reaction time is 2.5h.

[0035] Example 6: The difference from Example 5 is that in S2, the temperature is maintained at 950°C during the heating process, and the reaction time is 3.5h.

[0036] Example 7: The difference from Example 1 is that in S2, the heating process adopts a segmented heating process. First, the temperature is raised from room temperature to 200°C at a heating rate of 2°C / min, and held for 2 hours to remove solvent and residual organic ligands. Then, the temperature is raised to 950°C at a heating rate of 3°C / min and held for 3.5 hours. After the holding period, the temperature is lowered to 300°C at a rate of 5°C / min, and then naturally cooled to room temperature.

[0037] Example 8: The difference from Example 7 is that in S2, the heating process adopts a segmented heating process. First, the temperature is raised from room temperature to 300°C at a heating rate of 3°C / min, and held for 1 hour to remove the solvent and residual organic ligands. Then, the temperature is raised to 1050°C at a heating rate of 5°C / min and held for 2.5 hours. After the holding period, the temperature is lowered to 300°C at a rate of 5°C / min, and then naturally cooled to room temperature.

[0038] Example 9: The difference from Example 1 is that in S3, the temperature is maintained at 550°C during the heating process, and the reaction time is 2.2h.

[0039] Example 10: The difference from Example 9 is that in S3, the temperature is maintained at 650°C during the heating process, and the reaction time is 1.8h.

[0040] Example 11: This example describes the application of the catalyst from Example 1 to the degradation of antibiotics in wastewater.

[0041] The antibiotic is: sulfadiazine; The degradation method is as follows: S1. Adjust the pH of the antibiotic wastewater to 3-11 using H2SO4 or NaOH, and then add 15-20 mg of highly coordinated sulfur-doped single-atom catalyst to the antibiotic wastewater at a dosage of 15-20 mg per 100 mg of wastewater for the first treatment, with a treatment time of 10 min. 2OH - +H₂SO₄→SO₄ 2- +2H2O; 2H + +2NaOH→2Na + +2H2O; S2. Add potassium persulfate to the antibiotic wastewater at a dosage of 30-35 mg per 100 mg of wastewater and stir to react. Under the action of a highly coordinated sulfur-doped single-atom catalyst, the potassium persulfate is activated. The activated potassium persulfate is used to decompose and remove the antibiotics in the wastewater. The stirring speed is 380-420 rpm and the treatment time is 10 minutes to complete the treatment of the antibiotic-containing wastewater.

[0042] C 12 H 14N4O2S+H3K5O 18 S4 + O2 → CO2 + H2O + K2SO4 + H2SO4 + other intermediate products; The reaction between pollutants and potassium persulfate is not a single reaction that can be accurately described by a simple chemical equation, but a complex free radical oxidation process.

[0043] Example 12: The difference from Example 11 is that the antibiotic used is carbamazepine, and the treatment time is 12 minutes.

[0044] Example 13: The difference from Example 11 is that the antibiotic is bisphenol A and the treatment time is 13 min.

[0045] Example 14: The difference from Example 11 is that the antibiotic is acetaminophen, and the treatment time is 15 minutes.

[0046] Example 15: The difference from Example 11 is that the antibiotic used is norfloxacin, and the treatment time is 15 minutes.

[0047] The degradation effects of each catalyst in Examples 1-2 and Comparative Examples 1-3 on sulfadiazine wastewater were tested.

[0048] Test method: 100 ml of 10 mg / L sulfadiazine aqueous solution was added to a light-protected catalytic reactor. The pH was adjusted to the predetermined value using 1 M H2SO4 or NaOH. Then, a heterogeneous reaction was initiated by adding 0.15 g / L of each catalyst and 1 mM potassium persulfate. Samples were extracted and tested at 1, 3, 5, 10 and 15 min respectively. Test results as follows Figure 10 and Figure 11 As shown, the test results indicate that the removal effect of potassium persulfate alone on sulfadiazine is negligible. The removal effect is improved after adding Comparative Example 1 (without metal catalyst), but it still remains low. In contrast, the removal effect of the catalyst containing metal (Comparative Example 2 and Comparative Example 3) is significantly improved. After high-coordination sulfur doping (Examples 1 and 2), the removal effect of pollutants is better, indicating that sulfur doping helps to improve the activity of the catalyst and is beneficial to improving the removal efficiency of pollutants.

[0049] The catalysts prepared in Examples 1 and 2 showed the following effects: Figure 12 As shown, the catalysts prepared in Examples 1 and 2 have good removal effects on a variety of pollutants, including carbamazepine, bisphenol A, acetaminophen and norfloxacin.

[0050] like Figure 13 , Figure 14 , Figure 15 , Figure 17 This indicates that during the degradation of pollutants by potassium persulfate activated by the catalyst, the contribution of the electron transfer pathway in the sulfur-doped metal single-atom catalyst system is higher than that in the undoped metal single-atom catalyst system. In Example 1, the contribution of the electron transfer pathway is as high as 94.9%, and in Example 2, the contribution of the electron transfer pathway is 76.6%.

[0051] Open circuit potential experiment: The purpose is to prove that electron transfer occurs in the catalyst during the activation of potassium persulfate.

[0052] The open-circuit potential experiment was conducted as follows: 5 mg of catalyst was uniformly dispersed in 0.8 mL of ethanol, 0.2 mL of deionized water, and 50 μL of 5% Nafion solution, and sonicated for 30 min to prepare a mixture. This mixture was coated onto a glassy carbon electrode as the working electrode, with a platinum sheet and a silver / silver chloride electrode serving as the counter electrode and reference electrode, respectively. In the open-circuit potential experiment, 100 mM sodium sulfate solution was used as the electrolyte. After stabilization for 30 minutes, potassium peroxymonosulfate solution was added to the electrolyte, and stabilization was continued for another 60 minutes. Then, sulfadiazine solution was added, and stabilization was maintained for another 30 minutes. The catalysts were derived from the products of Examples 1, 2, 2, and 3, respectively. Figure 16 As shown, the experimental results indicate that the prepared sulfur-doped high-coordinated iron single-atom catalyst has the highest recombination potential, indicating that a stronger electron transfer process occurs in this system. In addition, the recombination potential of the sulfur-doped catalyst system is higher than that of the undoped catalyst system, indicating that sulfur doping is more conducive to the occurrence of electron transfer and to the decomposition and removal of pollutants.

Claims

1. A method for preparing a high-coordination sulfur-doped monatomic catalyst, characterized in that, The preparation method includes the following steps: S1. Zinc nitrate hexahydrate, dimethylimidazole, hexadecyltrimethylammonium bromide, metal source and deionized water are mixed and stirred. After the reaction is completed, the precipitate is collected by centrifugation. The precipitate is washed three times with methanol to obtain metal-doped ZIF-8. The molar ratio of zinc nitrate hexahydrate, dimethylimidazole, hexadecyltrimethylammonium bromide, metal source, and deionized water is 1:(6.0~7.0):(0.075~0.125):(0.04~0.05):(3000~3600). S2. The metal-doped ZIF-8 is heated under an argon atmosphere and then cooled to room temperature to obtain a black solid product. The black solid product is then ground into powder to obtain an undoped metal single-atom catalyst. S3. The undoped metal single-atom catalyst and thiourea are mixed at a mass ratio of 1:

10. After grinding, the mixture powder is obtained. The mixture is heated under an argon atmosphere and then cooled to room temperature to obtain a black solid product. The black solid product is ground into powder to obtain a highly coordinated sulfur-doped metal single-atom catalyst.

2. The method according to claim 1, characterized in that, In S1, the metal source is cobalt nitrate hexahydrate or ferric nitrate nonahydrate.

3. The method according to claim 1, characterized in that, In S1, the mixture is stirred at 500-800 rpm for 30-60 minutes at 25-30℃, then aged at room temperature in the dark for 12-24 hours, and then centrifuged. The centrifugation speed for collecting the precipitate was 8000~10000 rpm, and the centrifugation time was 5~10 min. The precipitate after being washed with methanol was then vacuum dried at 60℃ for 5~8 h.

4. The method according to claim 1, characterized in that, In S2, the temperature is maintained at 950~1050℃ during the heating process, and the reaction time is 2.5~3.5h.

5. The method according to claim 1, characterized in that, In S2, the heating process adopts a segmented heating process. First, the temperature is raised from room temperature to 200-300℃ at a heating rate of 2-3℃ / min, and held for 1-2 hours to remove solvent and residual organic ligands. Then, the temperature is raised to 950-1050℃ at a heating rate of 3-5℃ / min, and held for 2.5-3.5 hours. After the holding period, the temperature is lowered to 300℃ at a rate of 5℃ / min, and then naturally cooled to room temperature.

6. The method according to claim 1, characterized in that, In S3, the temperature is maintained at 550~650℃ during the heating process, and the reaction time is 1.8~2.2h.

7. The application of a highly coordinated sulfur-doped single-atom catalyst prepared by the method according to any one of claims 1 to 6, characterized in that, The catalyst is used to degrade antibiotics in wastewater.

8. The application according to claim 7, characterized in that, The antibiotics include sulfadiazine, carbamazepine, bisphenol A, acetaminophen, and norfloxacin.

9. The application according to claim 7, characterized in that, The application method is as follows: S1. Adjust the pH of the antibiotic wastewater to 3-11 using H2SO4 or NaOH, and then add the highly coordinated sulfur-doped single-atom catalyst to the antibiotic wastewater at a dosage of 15-20 mg per 100 mg of wastewater for the first treatment, with a treatment time of 10-15 min. S2. Add potassium persulfate to the antibiotic wastewater at a dosage of 30-35 mg per 100 mg of wastewater and stir to react. Under the action of a highly coordinated sulfur-doped single-atom catalyst, the potassium persulfate is activated. The activated potassium persulfate is used to decompose and remove the antibiotics in the wastewater. The stirring speed is 380-420 rpm and the treatment time is 10-15 min, thus completing the treatment of the antibiotic-containing wastewater.

10. The application according to claim 9, characterized in that, The concentrations of H2SO4 and NaOH are both 1M.

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