An interlayer confined heteroatom-doped carbon material, a preparation method therefor and applications thereof

Abstract

This invention discloses an interlayer confined heteroatom-doped carbon material, its preparation method, and its applications. Utilizing the tunable size of LDH crystals, the interlayer confined nanoscale of the carbon material can be precisely controlled by adjusting the synthesis pH. The controllable structure directly enhances reaction kinetics, making the reduction efficiency of Fe³⁺ by the CNS material more than 2.5 times that of traditional carbon materials, while simultaneously significantly improving antibiotic degradation capabilities. The interlayer confined space functions as both a rapid mass transfer channel and a nano-enrichment device, greatly increasing the reactant transport rate and local concentration. Combined with heteroatom doping, it significantly enhances the adsorption and electron transfer capabilities for Fe³⁺, effectively suppressing iron ion hydrolysis and iron sludge formation, simultaneously addressing the three major drawbacks of traditional Fenton processes and bulk carbon-based materials: low utilization of active sites, slow mass transfer, and low iron recycling efficiency. The process is simple and controllable, uses economical raw materials, and the resulting solid material is easy to recycle, making it suitable for the efficient treatment of recalcitrant organic pollutants in rural sewage, industrial wastewater, and other scenarios, demonstrating strong practicality.

Description

Technical Field

[0001] This invention relates to the field of advanced oxidation novel water treatment environmental materials technology, specifically to an interlayer confined heteroatom-doped carbon material, its preparation method and application. Background Technology

[0002] In rural areas, with the development of animal husbandry and increased drug use after the pandemic, domestic sewage often contains antibiotics and other recalcitrant organic pollutants, posing a potential threat to the local water environment and human health. The Fenton process, as the most widely used water treatment technology in environmental engineering, can achieve efficient degradation of pollutants in the deep treatment of rural domestic sewage. However, in practical applications for rural domestic sewage treatment, the Fenton process faces problems such as slow Fe2+ / Fe3+ cycling and the formation of large amounts of iron sludge. Especially in rural environments with large fluctuations in water quality and limited operational capabilities, the kinetics of Fe3+ to Fe2+ conversion are slow, leading to the continuous accumulation of Fe3+ in the reaction system. Simultaneously, as the reaction pH continuously rises, a large amount of iron sludge is easily formed, which not only reduces reaction efficiency but may also cause secondary pollution, increasing the difficulty and cost of subsequent sludge disposal. Therefore, developing a Fenton co-catalyst material that can effectively promote Fe3+ / Fe2+ cycling, inhibit iron sludge formation, and is suitable for the characteristics of rural domestic sewage treatment is of great significance for improving the effectiveness of rural sewage treatment and promoting the application of green and low-carbon treatment technologies.

[0003] Carbon-based materials, with their abundant micro / mesoporous structures and surface functional groups, hold promise for alleviating the limitations of the Fenton process. The rich micro / mesoporous structure can adsorb organic pollutants in water and enrich deactivated Fe3+, preventing its hydrolysis and loss. The abundant functional groups and heteroatoms (S, P, B, etc.) on the carbon surface can also act as excellent electron donors, promoting the Fe3+ / Fe2+ cycle. Furthermore, these functional groups and heteroatoms can capture Fe3+ through chemical coordination, preventing its hydrolysis and thus mitigating some of the Fenton process's shortcomings. However, in practical applications, the co-catalytic effect of carbon-based materials is quite limited. Although carbon-based materials have abundant pore structures, bulk carbon nanoparticles lack open structures, resulting in insufficient utilization of internal active sites due to the isolation between the material's interior and the external environment. Influenced by pore size, mass transfer of pollutants / Fe3+ at the carbon material interface is slow due to steric hindrance, thereby reducing the Fenton reaction rate. In addition, the electronic structure of carbon-based materials is affected by functional groups, but the regulation of electronic structure activity by a single functional group or heteroatom is limited, resulting in insufficient reduction ability of Fe3+.

[0004] As disclosed in the prior art, patent CN120790193A presents a technical application method for enhancing the oxidation performance of Fenton reactions using a defect-rich carbon-based co-catalyst. This technology uses a metal-organic framework ZIF-8 as a precursor, removing zinc through high-temperature pyrolysis and acid washing to obtain a porous carbon material rich in nitrogen-doped defects (especially pyridine nitrogen). This material utilizes the defect sites on its surface to adsorb Fe³⁺, and promotes its reduction through a dynamic coordination field effect, thereby improving the oxidation performance of the Fenton system and broadening its pH applicability range. This technology represents the current mainstream approach of enhancing the intrinsic reduction activity of carbon materials by constructing atomic-level defects.

[0005] However, such "defect-rich carbon" strategies based on pyrolysis porous precursors, such as MOFs and biomass, essentially consist of a three-dimensional random porous network composed of an interconnected carbon skeleton. While this structure provides a high specific surface area and abundant defects, it still has the following inherent limitations that restrict further improvement in its co-catalytic efficiency: First, the diffusion resistance of reactants (Fe³⁺, H₂O₂, organic pollutants) within the tortuous, disordered, and non-uniformly sized random channels is high, resulting in slow mass transfer and the inability to fully utilize the active sites within the material, thus limiting the overall reaction rate to the mass transfer steps. Second, a large number of active defect sites are located in the deep pores within the material. Due to potential blockage of the pore inlets or excessively long mass transfer paths, these sites are difficult to access and function in actual reactions, leading to low utilization of active sites. Third, the pore structure and defect distribution generated by high-temperature pyrolysis are random, making precise control difficult, hindering the establishment of structure-property relationships, and affecting the stability and reproducibility of material performance.

[0006] In summary, although existing technologies have recognized the potential of carbon-based materials as Fenton cocatalysts and have enhanced their electron-donating capabilities by introducing defects, the fundamental contradiction of slow reactant mass transfer and low utilization of internal active sites caused by the disordered and tortuous microstructure of the materials themselves has not yet been effectively resolved. Therefore, developing a novel carbon-based cocatalyst structure that combines efficient mass transfer channels with a high density of usable active surfaces is of urgent practical necessity and significant theoretical value for fully realizing the cocatalytic potential of carbon materials in Fenton reactions, especially in rural decentralized wastewater treatment scenarios requiring rapid response and efficient treatment. Summary of the Invention

[0007] Based on the above-mentioned technical problems, the purpose of this invention is to provide an interlayer confined heteroatom-doped carbon material, its preparation method, and its application. The aim is to greatly shorten the diffusion path of reactants and enhance the local concentration of reactants near the active sites by constructing a directional, open, and uniformly sized nanoscale confined space, thereby simultaneously improving electron transfer efficiency and interfacial reaction kinetics. Ultimately, this will achieve a significant breakthrough in the Fe³⁺ / Fe²⁺ cycle rate and pollutant degradation efficiency in the Fenton reaction, and better meet the treatment needs of complex water qualities such as rural domestic sewage.

[0008] This invention protects a method for preparing interlayer confined heteroatom-doped carbon materials, specifically comprising the following steps: Step 1, Preparation of two-dimensional layered template: Weigh ZnCl2:AlCl3·6H2O in the ratio of 2~4:1~2, dissolve it completely in deionized water, stir vigorously until completely transparent, and obtain a mixed salt solution for later use; Add five times the amount of ZnCl2 to the mixed salt solution as an interlayer anion source Na2CO3, then adjust the pH of the solution to 8.0-12.0 with NaOH, and continue stirring at room temperature for 8-12 hours. The product is centrifuged, washed with deionized water, pre-frozen, sublimated, dried, and ground to obtain a white carbonate-type zinc-aluminum layered double hydroxide ZnAl-CO3LDH two-dimensional layered template powder; denoted as LDH-pHx, where x is the synthesis pH value. Step 2: The carbon precursor and heteroatom source recombine on the template: Polyvinyl alcohol (PVA) was dissolved in deionized water at a material-to-liquid ratio of 1~2:40. The solution was stirred in a water bath at 65~95℃ until fully dissolved to obtain a transparent PVA solution for later use. Take the ZnAl-CO3-LDH two-dimensional layered template powder prepared in step 1 at a material-to-liquid ratio of 1~5:100 and dissolve it in deionized water. Continuously sonicate it to disperse it evenly until a uniform, stable, milky white LDH-containing suspension without obvious precipitation is formed and set aside for later use. After cooling the transparent PVA solution to room temperature, a suspension containing LDH was added to it under continuous medium-speed stirring to form a PVA / LDH composite suspension. Twice the amount of polyvinyl alcohol, thiourea or urea was added to the PVA / LDH composite suspension to obtain a mixed system. The mixed system was stirred overnight at room temperature and then freeze-dried to remove all solvents to obtain a lightweight, porous PVA-heteroatom-LDH composite aerogel with a certain strength. Step 3, carbonization and template removal: The obtained composite aerogel was placed in a tube furnace and heated to 350℃ for 30 min at a nitrogen atmosphere, then heated to 800℃ for 2 h at a rate of 5-10℃ / min. After natural cooling, a carbon / metal composite intermediate was obtained. The intermediate powder was mixed with a 2 mol / L HCl solution and refluxed at 85℃ for 6-12 h to completely dissolve the LDH template. After the reaction was completed, the solid was separated by centrifugation and repeatedly washed with deionized water until the filtrate was neutral and no chloride ions were detected. Finally, the carbon powder was freeze-dried to obtain interlayer confined heteroatom-doped carbon powder material.

[0009] Furthermore, in step 1, ZnCl2 and AlCl3·6H2O are fully dissolved in 50~100mL of deionized water.

[0010] Further, in step 1, the concentration of NaOH is 2 mol / L; it is dissolved in deionized water, and the product is centrifuged at 6000 rpm for 5-10 min, the supernatant is discarded, and it is washed with deionized water 3-5 times until no Cl⁻ or white precipitate is detected in the supernatant using AgNO₃ solution. The LDH wet filter cake is dispersed in a small amount of water to form a slurry, which is placed in an ultra-low temperature freezer and rapidly deep-frozen at -80℃ for 6 h for pre-freezing. Subsequently, the pre-frozen sample is freeze-dried in a freeze dryer under the conditions of cold trap temperature -80℃ and vacuum degree below 10 Pa for 36 h, ground, and passed through a 200-mesh sieve.

[0011] Furthermore, in the LDH-pHx, x represents the synthesis pH values ​​of 8, 10, and 12.

[0012] Furthermore, in step 2, during the preparation of the PVA solution, magnetic stirring is used for water bath stirring; the ZnAl-CO3-LDH two-dimensional layered template powder is dissolved in deionized water and continuously sonicated using an ultrasonic cell disruptor to ensure uniform dispersion. Continuous sonication aims to fully exfoliate the LDH layers, reduce stacking, increase its specific surface area and reactive sites, which is beneficial for subsequent intercalation; the mixed system is continuously stirred at 300~500 rpm for 10~12 h at room temperature using a magnetic stirrer. The long-term gentle stirring is to allow sufficient time for thiourea / urea molecules and PVA segments to diffuse and insert into the interlayer domains of LDH, achieving uniform mixing and pre-assembly at the molecular level.

[0013] Furthermore, in step 2, freeze drying is performed in a freeze dryer at a temperature below -50°C and a vacuum degree below 10Pa for 24 to 48 hours until all solvents are completely removed. Rapid deep freezing forms small ice crystals, which, after sublimation, leave fine pores, which is beneficial for the escape of gases and the formation of carbon skeletons during subsequent pyrolysis.

[0014] Further, in step 3, under a nitrogen atmosphere, the temperature is first raised to 350℃ at 3℃ / min and held for 30min, then raised to 800℃ at 5℃ / min and held for 2h, and after natural cooling, a carbon / metal composite intermediate is obtained; the intermediate powder is mixed with 2mol / L HCl solution at a solid-liquid ratio of 1:80, and refluxed and stirred at 85℃ for 8h.

[0015] This invention also protects the interlayer confined heteroatom-doped carbon material CNS-pHx obtained by the above method, where x is the synthesis pH value of 8, 10 and 12.

[0016] This invention also protects the application of the above-mentioned interlayer confined heteroatom-doped carbon material, which is used in the co-catalytic Fenton reaction.

[0017] Furthermore, the application is suitable for the efficient and advanced treatment of antibiotic organic pollutants in rural domestic sewage, and the specific application method is as follows: Prepare 50 mL of sulfamethoxazole (SIZ) solution with a concentration of 10–50 μmol / L and place it in a 100 mL beaker. Adjust the pH to 2.0–5.0 with sulfuric acid and NaOH solution. Add 0.005–0.015 g of CNS material and sonicate for 15 s to ensure uniform dispersion in the solution. Add 0.1–1.0 mL of 10 mmol / L Fe(NO3)3 solution and 0.1–1.0 mL of 100 mmol / L H2O2 solution, respectively, and start the reaction immediately. Four experimental groups were set up: CNS, CNS-8, CNS-10, and CNS-12, with CNS serving as a control group without added template. The beaker was placed on a magnetic stirrer at 500 rpm for the reaction. Samples were taken at 0, 2, 5, 10, 20, 40, and 60 min, with 1.0 g taken each time. The sample was filtered through a 0.22 μm filter and the reaction was stopped with 0.5 mL of methanol. The sample was then quantitatively detected by a high-performance liquid chromatograph equipped with a diode array detector and a C18 liquid chromatographic column. The mobile phase was 70% 0.1% formic acid aqueous solution and 30% acetonitrile, and the detection wavelength was 270 nm.

[0018] Compared with existing technologies, the present invention has the following beneficial effects: 1. This invention utilizes the tunability of LDH crystal size to prepare a series of LDH templates of different thicknesses by simply adjusting the synthesis pH, thereby achieving precise control of the interlayer confinement nanoscale of the final carbon material.

[0019] 2. This controllable structure provides an ideal platform for exploring and optimizing the nanoconfining effect. The reduction efficiency of CNS-10 material for Fe³⁺ is more than 2.5 times that of traditional template-free carbon materials, and its ability to degrade antibiotics is also significantly improved. This directly confirms the decisive strengthening effect of the interlayer confinement structure on reaction kinetics.

[0020] 3. The unique interlayer confined space combines the functions of a rapid mass transfer channel and a nano-enrichment device, significantly improving the transport rate and local concentration of reactants such as Fe³⁺ / Fe²⁺, H₂O₂, and pollutants. Combined with heteroatom doping, this structure significantly enhances the adsorption, enrichment, and electron transfer capabilities of carbon materials for Fe³⁺, effectively suppressing the hydrolysis and loss of iron ions and the formation of iron sludge. This simultaneously solves the three core defects of traditional Fenton processes and bulk carbon-based cocatalysts: low utilization of active sites, slow mass transfer, and low iron recycling efficiency.

[0021] 4. The preparation process is simple and controllable, the raw materials are economical, and the resulting solid material is easy to use and recycle. It is particularly suitable for the efficient and in-depth treatment of recalcitrant organic pollutants in rural sewage, industrial wastewater and other scenarios, and has strong engineering applicability. Attached Figure Description

[0022] Figure 1 XRD patterns of LDH-8, LDH-10, and LDH-12 prepared according to the present invention; Figure 2 SEM image (8.0 mm) of LDH-8 prepared for this invention; Figure 3 SEM image (7.9 mm) of CNS-8 prepared for this invention; Figure 4 TEM and EDS surface scan images of CNS-8 prepared for this invention; Figure 5 A comparison chart showing the ability of CNS to reduce Fe3+ prepared in this invention; Figure 6 A comparison chart showing the performance of CNS-co-catalyzed Fenton reaction for SIZ degradation prepared in this invention. Detailed Implementation

[0023] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0024] Example 1 A method for preparing interlayer confined heteroatom-doped carbon materials specifically includes the following steps: 1. Preparation of two-dimensional layered templates Weigh 1.37g of ZnCl2 and 0.80g of AlCl3·6H2O, dissolve them completely in 60mL of deionized water, and stir vigorously until completely transparent to obtain a mixed salt solution for later use. Add 0.2 g of interlayer anion source Na2CO3 to the mixed salt solution, then adjust the pH of the solution to 8.0, 10.0, and 12.0 with NaOH, and continue stirring at room temperature for 8-12 h. Centrifuge the product at 6000 rpm for 5 min, discard the supernatant, and wash with deionized water 3-5 times until no Cl⁻ or white precipitate is detected in the supernatant using AgNO3 solution. Disperse the wet LDH filter cake in a small amount of water to form a slurry, place it in an ultra-low temperature freezer, and rapidly freeze it at -80℃ for 6 h for pre-freezing. Then freeze-dry the pre-frozen sample in a freeze dryer at a cold trap temperature of -80℃ and a vacuum degree of less than 10 Pa for 36 h, grind it, and pass it through a 200-mesh sieve to obtain a white carbonate-type zinc-aluminum layered double hydroxide ZnAl-CO3LDH two-dimensional layered template powder; denoted as LDH-pHx, where x is the synthesis pH value, and x represents the synthesis pH values ​​of 8, 10, and 12.

[0025] The XRD patterns of the obtained LDH series are detailed in the appendix. Figure 1 For detailed SEM images of LDH-8, please refer to the appendix. Figure 2 The calculated LDH grain size results are shown in Table 1.

[0026] Table 1 Grain Size of LDH The results showed that the crystal size increased significantly with the increase of the synthesis pH, indicating that the synthesis of LDH crystal size by pH adjustment was successful. SEM images showed that LDH-8 exhibited a layered / plate-like structure, which was in line with expectations.

[0027] 2. Recombination of carbon precursor and heteroatom source on template: Dissolve 1.0g of polyvinyl alcohol (PVA) in 20mL of deionized water and stir magnetically in an 80℃ water bath until fully dissolved to obtain a transparent PVA solution for later use. Dissolve 0.5g of ZnAl-CO3-LDH two-dimensional layered template powder in 10mL of deionized water, and use an ultrasonic cell disruptor to continuously sonicate it to disperse it evenly until a uniform, stable, milky white LDH-containing suspension without obvious precipitation is formed for later use. After cooling the transparent PVA solution to room temperature, an LDH-containing suspension was added to it under continuous medium-speed stirring to form a PVA / LDH composite suspension. 2.0 g of thiourea or 1.5 g of urea was added to the PVA / LDH composite suspension to obtain a mixed system. The mixed system was continuously stirred at 300 rpm for 12 h at room temperature using a magnetic stirrer. The system was then dried in a freeze dryer at a temperature below -50℃ and a vacuum degree below 10 Pa for 48 h until all solvents were completely removed, resulting in a lightweight, porous PVA-heteroatom-LDH composite aerogel with a certain strength.

[0028] 3. Carbonization and template removal The obtained composite aerogel was placed in a tube furnace and heated to 350℃ for 30 min at a nitrogen atmosphere, then heated to 800℃ for 2 h at a rate of 5℃ / min. After natural cooling, a carbon / metal composite intermediate was obtained. The intermediate powder was mixed with a 2 mol / L HCl solution at a solid-liquid ratio of 1:80 and refluxed at 85℃ with stirring and acid washing for 8 h to completely dissolve the LDH template. After the reaction was completed, the solid was separated by centrifugation and repeatedly washed with deionized water until the filtrate was neutral and no chloride ions were detected. Finally, the solid was freeze-dried to obtain interlayer confined heteroatom-doped carbon powder materials, CNS-8, CNS-10, and CNS-12.

[0029] The same method was used, but without the addition of an LDH template, to prepare heteroatom-doped carbon CNS without interlayer confinement, which served as a comparative example for the application in Example 2.

[0030] The SEM images of the obtained CNS-8 are detailed in the appendix. Figure 3 For detailed TEM and corresponding EDS energy spectrum scans, please refer to the appendix. Figure 4 .

[0031] Example 2 The reduction and adsorption capabilities of interlayer confined heteroatom-doped carbon (CNS) for Fe3+ were investigated, including the following steps: The reducing power of CNS for Fe3+ was investigated as follows: 50 mL of a 0.1 mmol / L Fe(NO3)3 solution was prepared and placed in a 100 mL beaker. The pH was adjusted to 3.0 ± 0.1 using sulfuric acid and sodium hydroxide solution. 0.01 g of CNS material and 0.5 mL of a 30 mmol / L o-phenanthroline solution were added, and the reaction was initiated. Four experimental groups (CNS, CNS-8, CNS-10, and CNS-12) were set up. The beakers were placed on a magnetic stirrer at 500 rpm for reaction. Samples were taken at 0, 2, 5, 10, 20, 40, and 60 min, with 1.0 mL taken each time. 4 mL of deionized water was added to dilute the sample to 5 mL. The samples were quantitatively detected by UV-Vis spectrophotometer at a wavelength of 510 nm. The results are shown in the attached figure. Figure 5 As shown.

[0032] The results show that CNS-10 prepared using LDH-10 as a template has the strongest ability to reduce Fe3+, which is 2.5 times that of CNS prepared without a template. This indicates that the confinement effect can significantly enhance the reduction ability of CNS to Fe3+, and the confinement effect is most obvious at this interlayer scale.

[0033] Example 3 This invention prepares interlayer confined heteroatom-doped carbon materials for the degradation of sulfamethoxazole (SIZ), a typical antibiotic in water, comprising the following steps: Prepare 50 mL of SIZ solution with a concentration of 50 μmol / L and place it in a 100 mL beaker. Adjust the pH to 3.0 ± 0.1 with sulfuric acid and sodium hydroxide solution. Add 0.01 g of CNS material and sonicate for 15 s to disperse it evenly in the solution. After adding 0.5 mL of 10 mmol / L Fe(NO3)3 solution and 0.5 mL of 100 mmol / L H2O2 solution, the reaction begins immediately. Four experimental groups were set up (CNS, CNS-8, CNS-10, and CNS-12). The beakers were placed on a magnetic stirrer at 500 rpm for reaction. Samples were taken at 0, 2, 5, 10, 20, 40, and 60 minutes, with 1.0 mL taken each time. The samples were filtered through a 0.22 μm filter, and the reaction was stopped with 0.5 mL of methanol. The samples were quantitatively analyzed by high-performance liquid chromatography (HPLC), equipped with a diode array detector and a C18 HPLC column. The mobile phase was 70% 0.1% formic acid aqueous solution and 30% acetonitrile, and the detection wavelength was 270 nm. Results are attached. Figure 6 As shown.

[0034] The results showed that CNS-10 with LDH-10 as a template had the strongest catalytic degradation ability for SIZ, which was consistent with the Fe3+ reduction ability, indicating that the confinement effect can significantly enhance the catalytic degradation ability of CNS.

[0035] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing interlayer confined heteroatom-doped carbon materials, characterized in that, Specifically, the steps include the following: Step 1, Preparation of two-dimensional layered template: Weigh ZnCl2:AlCl3·6H2O in the ratio of 2~4:1~2, dissolve it completely in deionized water, stir vigorously until completely transparent, and obtain a mixed salt solution for later use; Add five times the amount of ZnCl2 to the mixed salt solution as an interlayer anion source Na2CO3, then adjust the pH of the solution to 8.0-12.0 with NaOH, and continue stirring at room temperature for 8-12 hours. The product is centrifuged, washed with deionized water, pre-frozen and sublimated, dried, and ground to obtain a white carbonate-type zinc-aluminum layered double hydroxide ZnAl-CO3LDH two-dimensional layered template powder; denoted as LDH-pHx, where x is the synthesis pH value. Step 2: The carbon precursor and heteroatom source recombine on the template: Polyvinyl alcohol (PVA) was dissolved in deionized water at a material-to-liquid ratio of 1-2:

40. The solution was stirred in a water bath at 65-95°C until fully dissolved to obtain a transparent PVA solution for later use. Take the ZnAl-CO3-LDH two-dimensional layered template powder prepared in step 1 at a material-to-liquid ratio of 1~5:100 and dissolve it in deionized water. Continuously sonicate it to disperse it evenly until a uniform, stable, milky white LDH-containing suspension without obvious precipitation is formed and set aside for later use. After cooling the transparent PVA solution to room temperature, a suspension containing LDH was added to it under continuous medium-speed stirring to form a PVA / LDH composite suspension. Twice the amount of polyvinyl alcohol, thiourea or urea was added to the PVA / LDH composite suspension to obtain a mixed system. The mixed system was stirred overnight at room temperature and then freeze-dried to remove all solvents to obtain a lightweight, porous PVA-heteroatom-LDH composite aerogel with a certain strength. Step 3, carbonization and template removal: The obtained composite aerogel was placed in a tube furnace and heated to 350℃ for 30 min at a nitrogen atmosphere, then heated to 800℃ for 2 h at a rate of 5-10℃ / min. After natural cooling, a carbon / metal composite intermediate was obtained. The intermediate powder was mixed with a 2 mol / L HCl solution and refluxed at 85℃ for 6-12 h to completely dissolve the LDH template. After the reaction was completed, the solid was separated by centrifugation and repeatedly washed with deionized water until the filtrate was neutral and no chloride ions were detected. Finally, the carbon powder was freeze-dried to obtain interlayer confined heteroatom-doped carbon powder material.

2. The preparation method according to claim 1, characterized in that, In step 1, ZnCl2 and AlCl3·6H2O are fully dissolved in 50~100mL of deionized water.

3. The preparation method according to claim 2, characterized in that, In step 1, the concentration of NaOH is 2 mol / L; it is dissolved in deionized water, and the product is centrifuged at 6000 rpm for 5-10 min. The supernatant is discarded, and the product is washed with deionized water 3-5 times until no Cl⁻ or white precipitate is detected in the supernatant using AgNO₃ solution. The wet LDH filter cake is dispersed in a small amount of water to form a slurry, which is placed in an ultra-low temperature freezer and rapidly deep-frozen at -80℃ for 6 h for pre-freezing. Subsequently, the pre-frozen sample is freeze-dried in a freeze dryer at a cold trap temperature of -80℃ and a vacuum degree of less than 10 Pa for 36 h, ground, and passed through a 200-mesh sieve.

4. The preparation method according to claim 1, characterized in that, The LDH-pHx, where x represents the synthesis pH values ​​of 8, 10, and 12.

5. The preparation method according to claim 1, characterized in that, In step 2, during the preparation of the PVA solution, magnetic stirring was used for water bath stirring; ZnAl-CO3-LDH two-dimensional layered template powder was dissolved in deionized water and continuously ultrasonicated to ensure uniform dispersion using an ultrasonic cell disruptor; the mixed system was continuously stirred at 300-500 rpm for 10-12 hours at room temperature using a magnetic stirrer.

6. The preparation method according to claim 1, characterized in that, In step 2, freeze drying is performed in a freeze dryer at a temperature below -50°C and a vacuum degree below 10Pa for 24 to 48 hours until all solvents are completely removed.

7. The preparation method according to claim 1, characterized in that, In step 3, under a nitrogen atmosphere, the temperature is first increased to 350℃ at 3℃ / min and held for 30 min, then increased to 800℃ at 5℃ / min and held for 2 h. After natural cooling, a carbon / metal composite intermediate is obtained. The intermediate powder is mixed with a 2 mol / L HCl solution at a solid-liquid ratio of 1:80 and refluxed and stirred at 85℃ for 8 h for acid washing.

8. A carbon-doped material with interlayer confined heteroatoms, characterized in that, The material is prepared by the method according to claims 1-7, wherein the interlayer confined heteroatom doped carbon material CNS-pHx, where x is the synthesis pH value of 8, 10 and 12.

9. The application of the interlayer confined heteroatom-doped carbon material according to claim 8, characterized in that, The material is used in the co-catalytic Fenton reaction.

10. The application of the interlayer confined heteroatom-doped carbon material according to claim 9, characterized in that, The application is suitable for the efficient and advanced treatment of antibiotic organic pollutants in rural domestic sewage. The specific application method is as follows: Prepare 50 mL of sulfamethoxazole SIZ solution with a concentration of 10–50 μmol / L and place it in a 100 mL beaker. Adjust the pH to 2.0–5.0 with sulfuric acid and NaOH solution. Add 0.005–0.015 g of CNS material and sonicate for 15 seconds to ensure uniform dispersion in the solution. Add 0.1–1.0 mL of 10 mmol / L Fe(NO3)3 solution and 0.1–1.0 mL of 100 mmol / L H2O2 solution, respectively, and start the reaction immediately. Four experimental groups were set up: CNS, CNS-8, CNS-10, and CNS-12, with CNS serving as a control group without added template. The beaker was placed on a magnetic stirrer at 500 rpm for the reaction. Samples were taken at 0, 2, 5, 10, 20, 40, and 60 minutes, with 1.0 g taken each time. The sample was filtered through a 0.22 μm filter and the reaction was stopped with 0.5 mL of methanol. The sample was then quantitatively detected by a high-performance liquid chromatograph equipped with a diode array detector and a C18 liquid chromatographic column. The mobile phase was 70% 0.1% formic acid aqueous solution and 30% acetonitrile, and the detection wavelength was 270 nm.

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