A composite carbon-based catalyst of ultramicroporous carbon / carbon nanosheet containing m-x / y-c active sites and a preparation method and application thereof

Abstract

The present application provides a kind of super-microporous carbon / carbon nanosheet containing M-X / Y-C active site composite carbon-based catalyst, the composite carbon-based catalyst is composed of super-microporous carbon as substrate and carbon nanosheet containing M-X / Y-C active site loaded and anchored thereon;Wherein X / Y-C and M form carbon heteroatom covalent bond with complex structure, M is selected from at least one of Fe, Co, Ni, Cu, Zn and Mn, X and Y are different heteroatoms, X and Y are selected from any one of N, O, S, P;The catalyst has the characteristics of less metal content, multiple active sites coexist, large specific surface area and stable structure, good conductivity, etc., improves the catalytic activity, selectivity and cycle life of catalyst.The preparation process is simple and green and pollution-free, which is conducive to the application of carbon-based catalyst in photocatalytic oxidation degradation of organic pollutants in wastewater.

Description

Technical Field

[0001] This invention relates to the field of carbon-based catalyst preparation, specifically to a composite carbon-based catalyst of ultraporous carbon / carbon nanosheets containing MX / YC active sites, its preparation method, and its application. Background Technology

[0002] Multicomponent catalysts and multi-active-site catalysts with different types of active sites are becoming increasingly popular, especially in heterogeneous catalytic reaction systems with multiple reactant components, exhibiting significantly superior activity compared to single-active-site catalysts. Experimentally, various multicomponent catalysts have been designed and synthesized. For example, by reacting metallic Pt with the metal hydroxide Ni(OH)... )2 Combined preparation of Pt / Ni(OH) )2 Composite catalysts can enhance the activity of alkaline hydrogen evolution reactions. For example, Fischer-Tropsch synthesis composite catalysts composed of oxides and zeolites have been successfully applied in C1 chemistry (Diffusion Coupling Kinetics in Multisite Catalysis: A Microkinetic Framework, ACS Catalysis, 2023, 13, 5, 2937–2947). However, for heterogeneous catalytic reactions in some specialized fields, such as electrocatalysis and photocatalysis, not only is synergistic cooperation of multi-active-site catalysts required, but the catalysts also need excellent conductivity to improve electron transport during the catalytic process, thereby increasing catalytic efficiency. To this end, many researchers have prepared multi-active-site synergistic catalysts by combining various metals with organic compounds or carbon materials with conjugated structures, achieving excellent results in electrocatalysis and photocatalysis. For example, Academician Li Yadong and others from Tsinghua University prepared a multi-active-site CO2 reduction electrocatalyst by atomic substitution between PtNi nanoalloys and Zn-ZIF-8, exhibiting lower CO2 protonation and CO desorption energy barriers in the CO2 reduction reaction, significantly improving the electrocatalytic performance of the CO2 reduction reaction. (Atomic Replacement of PtNi Nanoalloys within Zn-ZIF-8 for the Fabrication of a Multisite CO2 Reduction Electrocatalyst, J.Am.Chem.Soc.2022,144,50,23223–23229)

[0003] Chinese patent CN202310256352.2 proposes a structural design for the photodegradation of organic wastewater by carbon-based catalysts. This design involves constructing different M-XmYn-C (M is a transition metal, X and Y are heteroatoms, and m and n are coordination numbers) active sites in the catalyst and then improving the structure of the catalyst through synergistic reactions between these different active sites. This provides a new approach to the structural design of metal-coordinated carbon-based catalysts. However, for conjugated organic / carbon and metal complex catalysts, improving the metal stability under reaction conditions and avoiding metal loss is crucial to the industrial application of such catalysts. In existing literature, Wang et al. reported that improving the conjugated structure of the carbon matrix can significantly improve the stability of the catalyst (Pyridinic-N-Dominated Doped Defective Graphene as a Superior Oxygen Electrocatalyst for Ultrahigh-Energy-Density Zn-Air Batteries. Acs Energy Letters, 2018, 3(5): 1183-1191.). That is, N is doped at the defects of highly conjugated three-dimensional graphene to form a pyridine structure and coordinate with the metal. This structure not only improves the catalytic performance of the catalyst, but also significantly improves the complexation stability of the coordinated metal atoms, thereby increasing the catalyst lifetime.

[0004] However, while designing defects and doping heteroatoms on the graphene surface to construct metal active centers can effectively improve the stability of coordinated metal ions, it is difficult to precisely control the heteroatomation of multiple active sites on the graphene surface, and the preparation process is also very complex. This limits the widespread application and promotion of this type of catalyst.

[0005] 0D, 1D, and 2D highly conductive carbon materials (highly conductive carbon black, carbon nanotubes, graphene) not only possess excellent conductivity but also exhibit a large exposed surface area, facilitating liquid-phase electrocatalysis / photocatalysis. Specifically, creating pores <1 nm on the surface of these highly conductive carbon materials allows for the preparation of specialized highly conductive ultraporous carbon. This not only provides excellent conductivity but also significantly increases the potential energy at the defects in the carbon materials due to the ultraporous structure, thereby significantly improving the interfacial stability of the carbon materials with other small molecules. For example, Qiu et al. reported in the existing literature that ultraporous graphene prepared by Al reduction could still stably adsorb a certain amount of anthraquinone molecules under electrochemical charge-discharge conditions, thus significantly improving the pseudocapacitance of graphene. This further verifies that ultraporous graphene, while possessing excellent conductivity and a conjugated large π structure, can stably anchor with other molecules through the defects in the ultraporous pores, and the anchoring of small molecules remains stable even under high-current charge-discharge conditions. (Dual MoleculesCooperatively Confined In-Between Edge-oxygen-rich Graphene Sheets as Ultrahigh Rate and Stable Electrodes for Super Capacitors. Small, 2023:2302316.).

[0006] It is evident that highly conductive ultraporous carbon not only possesses excellent conductivity and a conjugated structure conducive to metal stability, but also has defective active sites capable of stably binding other molecules. This provides possibilities for the design of multi-active-site catalysts, making it an excellent carbon support for photo / electrocatalysts. Currently, research in this area is scarce. Therefore, developing a simple, convenient, and efficient method to apply highly conductive ultraporous carbon to multi-active-site carbon-based catalysts, forming composite catalysts, and designing multi-active-site structures to achieve a combination of high specific surface area, multiple active sites, and large pore volume, is of great significance for improving the catalytic efficiency and stability of catalysts. Summary of the Invention

[0007] To address the problems in the prior art, this invention provides a composite carbon-based catalyst of ultraporous carbon / carbon nanosheets containing MX / YC active sites, its preparation method, and its applications. This composite carbon-based catalyst consists of highly conductive ultraporous carbon as a substrate, with carbon nanosheets containing MX / YC active sites supported and anchored thereon. This catalyst features low metal content, multiple coexisting active sites, large specific surface area, structural stability, and good conductivity, significantly improving the catalytic activity, selectivity, and cycle life of the catalyst. Its preparation process is simple, green, and pollution-free, easily scaled up for production, and beneficial for the application of carbon-based catalysts in the photocatalytic oxidation degradation of organic pollutants in wastewater.

[0008] To achieve the objectives of this invention, the following technical solution is adopted:

[0009] The first aspect of the present invention provides a composite carbon-based catalyst of ultraporous carbon / carbon nanosheets containing MX / YC active sites, wherein the composite carbon-based catalyst comprises an ultraporous carbon substrate and carbon nanosheets containing MX / YC active sites supported thereon; the carbon nanosheets containing MX / YC active sites are composed of carbon heteroatom covalent bonds with complex structures formed between M and carbon nanosheets containing X / Y heteroatoms; wherein M is a transition metal and exists in a single-atom site state, and M is selected from at least one of Fe, Co, Ni, Cu, Zn and Mn; wherein X / YC are carbon heteroatom bonds on the carbon nanosheets that can form complex structures with metal ions, and X and Y are different heteroatoms, both of which are selected from N, O, S and P.

[0010] Furthermore, the pore size of the ultraporous carbon is <1 nm.

[0011] Furthermore, the resistivity of the ultraporous carbon is <50Ω / cm.

[0012] Furthermore, the mass ratio of the ultraporous carbon, transition metal M, and carbon nanosheets containing X / Y heteroatoms is (0.01-5):0.5-(10:100).

[0013] A second aspect of the present invention provides a composite carbon-based catalyst of ultraporous carbon / carbon nanosheets containing MX / YC active sites, specifically comprising the following steps:

[0014] (1) Preparation of ultraporous carbon / precursor composite material containing X / Y heteroatoms

[0015] Ultraporous carbon was dispersed in an aqueous solution of a precursor containing X / Y heteroatoms. After stirring evenly, the mixture was subjected to hydrothermal reaction at 150–250 °C for 15–20 h. Subsequently, the mixture was evaporated to dryness in a water bath at 80 °C to obtain an ultraporous carbon / precursor composite material containing X / Y heteroatoms.

[0016] (2) Preparation of ultraporous carbon / precursor composite material containing MX / YC active sites

[0017] The above-mentioned microporous carbon / heteroatom-containing precursor composite material was dispersed in deionized water and added to a chloride or nitrate solution of transition metal M to allow the transition metal M to undergo a complexation reaction with the heteroatom-containing precursor. After reacting at 80°C for 2-6 hours, the mixture was evaporated in a water bath to obtain the microporous carbon / precursor composite material containing MX / YC active sites.

[0018] (3) Preparation of composite carbon-based catalysts of ultraporous carbon / carbon nanosheets containing MX / YC active sites

[0019] The above-mentioned microporous carbon / precursor composite material containing MX / YC active sites was placed in a tube furnace under an Ar protective atmosphere and heated to 500°C at a heating rate of 1-5°C / min, and held at that temperature for 3-5 hours. After cooling to room temperature with the furnace, the product was obtained. The product was then acid-washed and dried to obtain a composite carbon-based catalyst of microporous carbon / carbon nanosheets containing MX / YC active sites.

[0020] Furthermore, the heteroatom-containing precursor in step S1 is any combination of two or more of the following: nitrogen-containing (N) precursor, oxygen-containing (O) precursor, sulfur-containing (S) precursor, and phosphorus-containing (P) precursor.

[0021] Further, the nitrogen-containing precursor is any one of dicyandiamide, thiourea, and melamine; the oxygen-containing organic compound is any one of anthraquinone compounds and polyphenolic compounds; the anthraquinone compound is 2,6-diaminoanthraquinone or 1,5-dihydroxyanthraquinone; the polyphenolic compound is preferably tannic acid or gallic acid.

[0022] Furthermore, the sulfur-containing S precursor is thiophene or its derivative; the phosphorus-containing P precursor is any one of triphenylphosphine, phenyl phosphoric acid, diphenyl phosphoric acid, phenyl phosphate, and diphenyl phosphate.

[0023] A third aspect of the present invention provides an application of a composite carbon-based catalyst of ultraporous carbon / carbon nanosheets containing MX / YC active sites in the photocatalytic oxidation degradation of organic pollutants in wastewater.

[0024] Compared with the prior art, the beneficial effects of the present invention include:

[0025] (1) The composite carbon-based catalyst of the present invention, which is composed of microporous carbon / carbon nanosheets containing MX / YC active sites, anchors multiple MX / YC catalytic active sites together on a highly conductive microporous carbon substrate. Electrons can be rapidly transferred between different active sites, which can enable multiple active sites to play a synergistic role and synergistically activate different reactants on the same catalyst surface, thereby improving catalytic efficiency and catalytic activity and thus improving the degradation efficiency of reactants.

[0026] (2) The composite carbon-based catalyst of the present invention, which is an ultraporous carbon / carbon nanosheet containing MX / YC active sites, involves doping X / Y heteroatoms onto carbon nanosheets and forming carbon heteroatom covalent bonds with transition metal ions M to form carbon nanosheets containing MX / YC active sites. By tightly anchoring different MX / YC catalytic active sites to the surface of a hyperconjugated, highly conductive ultraporous carbon substrate with van der Waals forces at the defects of the ultraporous pores, the formed hyperconjugated structure can enhance the delocalization of metal ions, inhibit the removal and loss of metal ions during the reaction process, and improve the stability of the catalyst.

[0027] (3) The composite carbon-based catalyst of the present invention, which is composed of ultraporous carbon / carbon nanosheets containing MX / YC active sites, has the characteristics of multiple active sites, large specific surface area, low metal content, stable structure and good conductivity. With the support of the high conductivity of ultraporous carbon, it can realize spontaneous and efficient charge transfer between active sites and efficiently utilize visible light to accelerate charge transfer, thereby improving photo / electrocatalytic efficiency. Attached Figure Description

[0028] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0029] Figure 1 This is a comparison diagram of the microporous structures of ultraporous graphene and ordinary reduced graphene in Example 1 of the present invention;

[0030] Figure 2 This is a transmission electron microscope (TEM) image of the ultraporous graphene in Example 1 of the present invention.

[0031] Figure 3 This is a schematic diagram of the composite carbon-based catalyst in Example 1 of the present invention;

[0032] Figure 4 This is a transmission electron microscope image of the composite carbon-based catalyst in Example 1 of the present invention;

[0033] Figure 5 The above are XPS-C1s spectra of the composite carbon-based catalysts prepared in Example 1 and Comparative Example 3 of this invention, respectively.

[0034] Figure 6 The above are XPS-O1s spectra of the composite carbon-based catalysts prepared in Example 1 and Comparative Example 3 of this invention, respectively.

[0035] Figure 7 The types of free radicals generated by the composite carbon-based catalyst prepared in Example 1 of this invention during the photocatalytic oxidation of oxygen and / or hydrogen peroxide;

[0036] Figure 8 This is a comparison chart showing the photocatalytic oxidation degradation performance of the composite carbon-based catalyst prepared in Example 1 of the present invention on organic pollutants in wastewater under the conditions of oxygen and / or hydrogen peroxide as oxidants.

[0037] Figure 9The graph shows a comparison of the degradation performance of the composite carbon-based catalysts prepared in Example 1, Comparative Example 1, and Comparative Example 2 of this invention under the conditions of oxygen and hydrogen peroxide as oxidants, in the synergistic photocatalytic oxidation degradation of organic pollutants in wastewater.

[0038] Figure 10 The graph shows a comparison of the degradation performance of the composite carbon-based catalysts prepared in Example 1 and Comparative Example 3 of this invention in synergistic photocatalytic oxidation of organic pollutants in wastewater under the conditions of oxygen and hydrogen peroxide as oxidants.

[0039] Figure 11 The graph shows the cycle stability test results of the composite carbon-based catalyst prepared in Example 1 of the present invention under the condition of synergistic photocatalytic oxidation and degradation of organic pollutants in wastewater with oxygen and / or hydrogen peroxide as oxidants.

[0040] Figure 12 The graph shows a comparison of the cycle stability of the composite carbon-based catalysts prepared in Example 1, Comparative Example 1, and Comparative Example 2 of this invention under the conditions of synergistic photocatalytic oxidation and degradation of organic pollutants in wastewater using oxygen and hydrogen peroxide as oxidants.

[0041] Figure 13 The graph shows a comparison of the cycle stability of the composite carbon-based catalysts prepared in Example 1 and Comparative Example 3 of this invention under the conditions of synergistic photocatalytic oxidation and degradation of organic pollutants in wastewater using oxygen and hydrogen peroxide as oxidants.

[0042] Figure 14 This is a comparison chart showing the degradation efficiency of the composite carbon-based catalysts prepared in Examples 2 and 3 of the present invention in the photocatalytic synergistic oxidation degradation of organic pollutants in wastewater under the conditions of oxygen and hydrogen peroxide as oxidants.

[0043] Figure 15 This is a comparison chart showing the degradation efficiency of the composite carbon-based catalysts prepared in Examples 4 and 5 of the present invention in the photocatalytic synergistic oxidation degradation of organic pollutants in wastewater under the conditions of oxygen and hydrogen peroxide as oxidants. Detailed Implementation

[0044] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0045] Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. The term "and / or" as used in this specification includes any and all combinations of one or more of the associated listed items.

[0046] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0047] Example 1

[0048] (1) Preparation of ultraporous graphene

[0049] Graphene oxide (GO) was synthesized using a modified Hummers method.

[0050] 3.00 g of aluminum powder was added to 100 mg of GO dispersion (1.2 mg / mL), stirred for 10 min, and then 100 mL of HCl (35 wt%) was poured into the solution. After reacting for 3 min, the solution was centrifuged, the precipitate was washed and washed with deionized water until neutral, and then freeze-dried to obtain highly conductive ultraporous graphene. The surface resistivity was measured to be 1 Ω / cm using the four-probe method.

[0051] Figure 1 This is a comparison diagram of the microporous structures of ultraporous graphene and ordinary reduced graphene in this invention; from Figure 1 As can be seen, compared with ordinary reduced graphene, the microporous graphene prepared in this embodiment contains a large number of micropores with pore sizes of 0.5 nm and 0.8 nm. Figure 2 This is a transmission electron microscope (TEM) image of the ultraporous graphene in this invention. Figure 2 As can be seen, the ultraporous graphene contains a large number of ultrapores with a diameter of less than 0.8 nm.

[0052] (2) Preparation of ultraporous graphene / precursor containing N / O heteroatoms

[0053] 0.0025 g of ultraporous graphene was dispersed in 150 mL of deionized water containing 2.25 g of melamine and 0.01 g of tannic acid. The mixture was stirred in a water bath at 80 °C for 1 h. After stirring until homogeneous, the mixture was transferred to a hydrothermal reactor and placed in a constant temperature drying oven. The mixture was then hydrothermally reacted at 180 °C for 20 h. Subsequently, the mixture was evaporated to dryness in a water bath at 80 °C to obtain ultraporous graphene / precursor containing N / O heteroatoms.

[0054] (3) Preparation of ultraporous graphene / precursor containing Fe-N / OC active sites

[0055] The ultraporous graphene / precursor containing N / O heteroatoms prepared above was dissolved in 150 mL of deionized water, and 0.3 g of ferric chloride hexahydrate was added and dissolved completely. After the reaction was complete, the mixture was evaporated to dryness in a water bath at 80 °C to obtain the ultraporous graphene / precursor containing Fe-N / OC active sites.

[0056] (4) Preparation of composite carbon-based catalysts of ultraporous carbon / carbon nanosheets containing Fe-N / OC active sites

[0057] The precursor of ultraporous graphene / Fe-N / OC active sites was spread in a square corundum covered crucible and heated to 500°C at a rate of 3°C / min in a tube furnace under Ar protection, and held at that temperature for 4 hours. After cooling to room temperature in the furnace, the resulting solid was acid-washed with 2 mol / L hydrochloric acid at 20°C for 24 hours, ground and vacuum dried to obtain the composite carbon-based catalyst of ultraporous carbon / carbon nanosheets containing Fe-N / OC active sites in Example 1. The sample mass M1 was obtained by weighing.

[0058] Component content testing

[0059] A certain amount of the composite carbon-based catalyst of ultraporous carbon / carbon nanosheets containing Fe-N / OC active sites prepared in Example 1 was weighed, and the Fe percentage was determined by atomic absorption spectrometry. The final catalyst mass was calculated by subtracting the Fe mass M from the Fe mass. Fe The mass ratio of ultraporous graphene (M2) to carbon nanosheets containing N / O heteroatoms (M3) in the final catalyst is 0.22:5.3:100. The calculation formula is as follows:

[0060] M Fe =M1×Fe wt %

[0061] M3 = M1 - M Fe -M2

[0062] Please see Figure 3 , Figure 3 This is a schematic diagram of the structure of the composite carbon-based catalyst in Example 1 of the present invention; from Figure 3 As can be seen, this composite carbon-based catalyst uses ultraporous graphene as a substrate and is a layered carbon-based catalyst composed of Fe ions anchored on its surface and N, O co-doped carbon nanosheets. Please refer to [link to relevant documentation]. Figure 4 , Figure 4 This is a transmission electron microscope (TEM) image of the composite carbon-based catalyst in Example 1 of this invention; from Figure 4 It can be seen that the composite catalyst is a stacked structure formed by many carbon nanosheets anchored on ultraporous graphene.

[0063] Example 2

[0064] (1) Preparation of ultraporous graphene

[0065] Graphene oxide (GO) was synthesized using a modified Hummers method.

[0066] 3.00 g of aluminum powder was added to 100 mg of GO dispersion (1.2 mg / mL), stirred for 10 min, and then 100 mL of HCl (35 wt%) was poured into the solution. After reacting for 3 min, the solution was centrifuged, the precipitate was washed and washed with deionized water until neutral, and then freeze-dried to obtain highly conductive ultraporous graphene. The surface resistivity was measured to be 1 Ω / cm using the four-probe method.

[0067] (2) Preparation of ultraporous graphene / precursor containing N / S heteroatoms

[0068] 0.05 g of ultraporous graphene was dispersed in 150 mL of deionized water containing 2.25 g of dicyandiamide and 0.04 g of thiophene. The mixture was stirred in a water bath at 80 °C for 1 h. After stirring until homogeneous, the mixture was transferred to a hydrothermal reactor and placed in a constant temperature drying oven. The mixture was then hydrothermally reacted at 180 °C for 20 h. Finally, the mixture was evaporated to dryness in a water bath at 80 °C to obtain an ultraporous graphene precursor containing N / S heteroatoms.

[0069] (3) Preparation of ultraporous graphene / precursor containing Co-N / SC active sites

[0070] The ultraporous graphene / N / S heteroatom-containing precursor prepared above was dissolved in 150 mL of deionized water, and 0.3 g of cobalt nitrate hexahydrate was added and dissolved completely. After the reaction was complete, the mixture was evaporated to dryness in a water bath at 80 °C to obtain the ultraporous graphene / Co-N / SC active site-containing precursor.

[0071] (4) Preparation of composite carbon-based catalysts of ultraporous carbon / carbon nanosheets containing Co-N / SC active sites

[0072] The highly conductive ultraporous graphene / Co-N / SC precursor was spread in a square corundum covered crucible and heated to 500°C at a rate of 3°C / min in a tube furnace under Ar protection. The temperature was held for 4 hours and then cooled to room temperature with the furnace. The resulting solid was acid-washed with 2 mol / L hydrochloric acid at 20°C for 24 hours, ground, and vacuum dried to obtain the composite carbon-based catalyst of ultraporous carbon / carbon nanosheets containing Co-N / SC active sites as described in Example 2. The sample mass M1 was obtained by weighing.

[0073] Component content testing

[0074] A certain mass of the composite carbon-based catalyst prepared in Example 2, consisting of ultraporous carbon / carbon nanosheets containing Co-N / SC active sites, was weighed. The percentage of Co was determined by atomic absorption spectrometry. The final catalyst mass was calculated by subtracting the mass of Co from the mass of the catalyst, resulting in a mass M. Co The mass ratio of ultraporous graphene (M2) and carbon nanosheets containing N / S heteroatoms (M3) in the raw materials is 4.27:5.02:100 in the final catalyst.

[0075] M Co =M1×Co% wt

[0076] M3 = M1 - M Co -M2

[0077] Example 3

[0078] (1) Preparation of ultraporous carbon nanotubes

[0079] 3.00 g of multi-walled carbon nanotubes (Shenzhen Nanoport) were ultrasonically dispersed in 100 mL of deionized water. 0.5 g of KMO4 was added and stirred to dissolve. The mixture was then microwaved for 5 min to obtain a black precipitate of carbon nanotubes / MnO2. Then, an appropriate amount of oxalic acid was added to remove MnO2. The mixture was then filtered, washed, and washed with deionized water until neutral. After freeze-drying, ultraporous carbon nanotubes were obtained. The surface resistivity was measured to be 5 Ω / cm using the four-probe method, and the average pore size of the material was determined to be 0.5 nm using the CO2 room temperature adsorption method.

[0080] (2) Preparation of ultraporous electro-carbon nanotubes / precursors containing N / P heteroatoms

[0081] 0.003 g of ultraporous carbon nanotubes were dispersed in 150 mL of deionized water containing 2.25 g of melamine and 0.05 g of thiophene triphenylphosphine. The mixture was stirred in a water bath at 80 °C for 1 h. After stirring until homogeneous, the mixture was transferred to a hydrothermal reactor and placed in a constant temperature drying oven. The mixture was then hydrothermally reacted at 180 °C for 20 h. Subsequently, the mixture was evaporated to dryness in a water bath at 80 °C to obtain the ultraporous carbon nanotube / N / PC heteroatom-containing precursor.

[0082] (3) Preparation of ultraporous carbon nanotubes / precursors containing Ni-N / PC active sites

[0083] The ultraporous carbon nanotubes / precursor containing N / P heteroatoms prepared above were dissolved in 150 mL of deionized water, and 0.55 g of nickel nitrate hexahydrate was added and dissolved completely. After reacting for 2 h, the mixture was evaporated to dryness in a water bath at 80 °C to obtain the ultraporous carbon nanotubes / precursor containing Ni-N / PC active sites.

[0084] (4) Preparation of composite carbon-based catalysts of ultraporous carbon / carbon nanosheets containing Ni-N / PC active sites

[0085] The precursor of ultraporous carbon nanotubes / Ni-N / PC active sites was spread evenly in a square corundum covered crucible and heated to 500°C at a rate of 3°C / min in a tube furnace under Ar protection, and held at that temperature for 4 hours. After cooling to room temperature in the furnace, the resulting solid was acid-washed with 2 mol / L hydrochloric acid at 20°C for 24 hours, ground, and vacuum dried. The composite carbon-based catalyst of ultraporous carbon / carbon nanosheets containing Ni-N / PC active sites of Example 3 was obtained, and its mass after weighing was recorded as M1.

[0086] Component content testing

[0087] A certain mass of the composite carbon-based catalyst prepared in Example 3, consisting of ultraporous carbon / carbon nanosheets containing Ni-N / PC active sites, was weighed. The percentage of Ni was determined by atomic absorption spectrometry. The final catalyst mass was calculated by subtracting the mass of Ni, M. Ni The mass ratio of the catalyst components is calculated as follows: M2 is the mass of ultraporous carbon nanotubes in the raw material; M3 is the mass of carbon nanosheets containing N / P heteroatoms. The mass ratio of ultraporous carbon nanotubes:Ni:carbon nanosheets containing N / P heteroatoms is 0.26:9.63:100. The calculation formula is:

[0088] M Co =M1×Ni% wt

[0089] M3 = M1 - M Ni -M2

[0090] Example 4

[0091] (1) Preparation of ultraporous carbon nanotubes

[0092] 3.00 g of multi-walled carbon nanotubes (Shenzhen Nanoport) were ultrasonically dispersed in 100 mL of deionized water. 0.5 g of KMO4 was added and stirred to dissolve. The mixture was then microwaved for 5 min to obtain a black precipitate of carbon nanotubes / MnO2. Then, an appropriate amount of oxalic acid was added to remove MnO2. The mixture was then filtered, washed, and washed with deionized water until neutral. After freeze-drying, highly conductive ultraporous carbon nanotubes were obtained. The surface resistivity was measured to be 5 Ω / cm using the four-probe method. The average pore size of the material was determined to be 0.5 nm using the CO2 room temperature adsorption method.

[0093] (2) Preparation of ultraporous carbon nanotubes / precursors containing N / O heteroatoms

[0094] 0.003 g of ultraporous carbon nanotubes were dispersed in 150 mL of deionized water containing 2.25 g of melamine and 0.02 g of 1,5-dihydroxyanthraquinone. The mixture was stirred in a water bath at 80 °C for 1 h. After stirring until homogeneous, the mixture was transferred to a hydrothermal reactor and placed in a constant temperature drying oven. The mixture was then hydrothermally reacted at 180 °C for 20 h. Finally, the mixture was evaporated to dryness in a water bath at 80 °C to obtain the precursor of ultraporous carbon nanotubes containing N / O heteroatoms.

[0095] (3) Preparation of ultraporous carbon nanotubes / precursors containing Fe-N / OC active sites

[0096] The highly conductive ultraporous carbon nanotubes / precursors containing N / O heteroatoms prepared above were dissolved in 150 mL of deionized water. After adding 0.03 g of ferric chloride hexahydrate and dissolving it completely, the mixture was reacted for 2 h and then evaporated to dryness in a water bath at 80 °C to obtain ultraporous carbon nanotubes / precursors containing Fe-N / OC active sites.

[0097] (4) Preparation of composite carbon-based catalysts of ultraporous carbon nanotubes / carbon nanosheets containing Fe-N / OC active sites

[0098] Highly conductive ultraporous carbon nanotubes / precursors containing Fe-N / OC active sites were spread evenly in a square corundum covered crucible. The crucible was heated to 500°C at a rate of 3°C / min in a tube furnace under Ar protection and held at that temperature for 4 hours. After cooling to room temperature with the furnace, the resulting solid was acid-washed with 2 mol / L hydrochloric acid at 20°C for 24 hours, ground, and vacuum-dried. The composite carbon-based catalyst of ultraporous carbon nanotubes / carbon nanosheets containing Fe-N / OC active sites, as described in Example 4, was obtained, and its mass was denoted as M1.

[0099] Component content testing

[0100] A certain mass of the composite carbon-based catalyst prepared in Example 3, consisting of ultraporous carbon nanotubes and carbon nanosheets containing Fe-N / OC active sites, was weighed. The percentage of Fe in the catalyst was determined by atomic absorption spectrometry. The final catalyst mass was calculated by subtracting the mass of Fe from the mass of the catalyst, M. Fe The mass of the ultraporous carbon nanotubes in the raw material, M2, and the mass of the carbon nanosheets containing N / O heteroatoms, M3, are used to obtain the catalyst. The mass ratio of each component is 0.26:0.54:100 for ultraporous carbon nanotubes:Fe:carbon nanosheets containing N / O heteroatoms. The calculation formula is:

[0101] M Fe =M1×Fe% wt

[0102] M3 = M1 - M Fe -M2

[0103] Example 5

[0104] (1) Preparation of ultraporous carbon black

[0105] 3.00 g of Cabot carbon black was ultrasonically dispersed in 100 mL of deionized water. 0.5 g of KMO4 was added and stirred to dissolve. The mixture was then microwaved for 5 min to obtain a black precipitate of carbon black / MnO2. Then, an appropriate amount of oxalic acid was added to remove MnO2. The mixture was then filtered, washed, and washed with deionized water until neutral. After freeze-drying, highly conductive ultraporous carbon black was obtained. The surface resistivity was measured to be 7 Ω / cm using the four-probe method, and the average pore size of the material was determined to be 0.5 nm using the CO2 room temperature adsorption method.

[0106] (2) Preparation of ultraporous carbon black / precursor containing N / O heteroatoms

[0107] 0.003 g of highly conductive microporous carbon black was dispersed in 150 mL of deionized water containing 2.25 g of melamine and 0.02 g of gallic acid. The mixture was stirred in a water bath at 80 °C for 1 h. After stirring until homogeneous, the mixture was transferred to a hydrothermal reactor and placed in a constant temperature drying oven. The mixture was then hydrothermally reacted at 180 °C for 20 h. Finally, the mixture was evaporated to dryness in a water bath at 80 °C to obtain microporous carbon black / precursor containing N / O heteroatoms.

[0108] (3) Preparation of ultraporous carbon black / precursor containing Fe-N / OC active sites

[0109] The highly conductive microporous carbon black / N / OC precursor prepared above was dissolved in 150 mL of deionized water. After adding 0.3 g of ferric chloride hexahydrate and dissolving it completely, the mixture was reacted for 2 h and then evaporated to dryness in a water bath at 80 °C to obtain microporous carbon black / precursor containing Fe-N / OC active sites.

[0110] (4) Preparation of composite carbon-based catalysts of ultraporous carbon black / carbon nanotubes containing Fe-N / OC active sites

[0111] Microporous carbon black / precursor containing Fe-N / OC active sites

[0112] The solid was spread evenly in a square corundum crucible with a lid and heated to 500°C at a rate of 3°C / min in a tube furnace under Ar protection, and held at that temperature for 4 hours. After cooling to room temperature in the furnace, the resulting solid was acid-washed with 2 mol / L hydrochloric acid at 20°C for 24 hours, ground, and vacuum dried. The composite carbon-based catalyst of ultraporous carbon black / carbon nanotubes containing Fe-N / OC active sites, as described in Example 5, was obtained, and its mass after weighing was recorded as M1.

[0113] Component content testing

[0114] A certain mass of the composite carbon-based catalyst prepared in Example 5, consisting of ultraporous carbon black and carbon nanotubes containing Fe-N / OC active sites, was weighed. The percentage of Fe in the catalyst was determined by atomic absorption spectrometry. The final catalyst mass was calculated by subtracting the mass of Fe from the mass of the catalyst, M. Fe The mass ratio of the catalyst components is calculated as follows: M2 is the mass of ultraporous carbon black in the raw material, M3 is the mass of carbon nanosheets containing N / O heteroatoms, and the mass ratio of ultraporous carbon black:Fe:carbon nanosheets containing N / O heteroatoms is 0.26:5.46:100. The calculation formula is:

[0115] M Fe =M1×Fe% wt

[0116] M3 = M1 - M Fe -M2

[0117] Comparative Example 1

[0118] By replacing the microporous graphene with ordinary graphene oxide, and following the same preparation process as in Example 1, the RGO / Fe-N4-C / Fe-N2O2-C composite carbon-based catalyst prepared in Comparative Example 1 was obtained.

[0119] Comparative Example 2

[0120] Without adding microporous graphene, the other preparation processes were the same as in Example 1, resulting in the Fe-N4-C / Fe-N2O2-C composite carbon-based catalyst prepared in Comparative Example 2.

[0121] Comparative Example 3

[0122] Without adding ferric chloride hexahydrate, the other preparation processes were the same as in Example 1, resulting in the ultraporous graphene / N / OC composite carbon-based catalyst prepared in Comparative Example 3.

[0123] Catalyst microstructure characterization

[0124] Please refer to Figure 5 , Figure 5 The above are XPS-C1s spectra comparisons of the composite carbon-based catalysts prepared in Example 1 and Comparative Example 3 of this invention; from Figure 5 As can be seen, after the addition of iron, the half-maximum width of the triazine ring peak (binding energy of 288.50 eV) in the C3N4 generated after melamine carbonization becomes wider due to the presence of Fe, indicating the presence of Fe-N4-C coordinated with N in the triazine ring. In addition, compared with Comparative Example 3 (microporous graphene / N / OC), the iron-filled microporous graphene / Fe-N / OC has an additional cyano group absorption at a binding energy of 286.35 eV. This is due to the nitrogen-containing dangling bonds of cyano groups generated at the edge of C3N4 during the catalyst preparation process. Figure 6XPS-O1s spectra of the composite carbon-based catalysts prepared in Example 1 and Comparative Example 3 of this invention; from Figure 6 As can be seen, the phenolic hydroxyl peak (binding energy of 553.2 eV) on the carbon support is significantly enhanced after the addition of iron to the carbon-based catalyst. This is due to the iron co-coordinated with the phenolic hydroxyl groups formed after the carbonization of tannic acid. At the same time, these phenolic hydroxyl groups, together with the cyano groups and other amino groups at the edge of C3N4, coordinate with iron to form Fe-N2O2-C.

[0125] Catalyst performance testing

[0126] Catalytic efficiency tests of catalysts for oxidizing organic matter in wastewater under H2O2 and O2 conditions were conducted.

[0127] The composite carbon-based catalyst prepared in Example 1 was investigated for its application in the oxidation of organic pollutants in wastewater. The catalytic activity of the catalyst under H2O2, O2, and combinations thereof was tested. First, at the start of the reaction, O2 was replaced with N2, and the catalytic activity of the catalyst under H2O2 oxidation alone was examined, specifically its efficiency in catalyzing the generation of hydroxyl radicals from hydrogen peroxide, thereby degrading methylene blue. Subsequently, only O2 was introduced without H2O2, and the catalytic activity of the catalyst under O2 oxidation alone was examined, specifically its efficiency in catalyzing the generation of superoxide radicals from oxygen, thereby degrading methylene blue.

[0128] Characterization tests of active species during photocatalytic reactions

[0129] Electron paramagnetic resonance (ESR) characterization: Reactive oxygen species (ROSs) that may be generated in the degradation systems of Example 1, Comparative Example 1, and Comparative Example 2 in this patent were detected using an A200 electron paramagnetic resonance spectrometer (ESR) manufactured by Bruker GmbH, Germany. 5,5-Dimethyl-1-pyrrolline-N-oxide (DMPO) was used as a OH and O2 sample. 2- Spin trapping agents were used to detect the formation of spin adducts DMPO-OH and DMPO-O. 2- To determine whether hydroxyl radicals and superoxide radicals are generated in the system.

[0130] The composite carbon-based catalyst prepared in Example 1 of this invention was tested to catalyze the oxidation of oxygen and / or hydrogen peroxide to degrade organic pollutants in wastewater. In this catalytic degradation system, it was tested whether the system contained hydroxyl radicals and / or superoxide radicals.

[0131] Testing revealed that when the composite carbon-based catalyst prepared in Example 1 catalyzed the oxidation of oxygen to degrade organic pollutants in wastewater, superoxide radicals were generated in the system. When the composite carbon-based catalyst prepared in Example 1 catalyzed the oxidation of hydrogen peroxide to degrade organic pollutants in wastewater, hydroxyl radicals were generated in the system. When the composite carbon-based catalyst prepared in Example 1 catalyzed the oxidation of hydrogen peroxide to degrade organic pollutants in wastewater, both superoxide radicals and hydroxyl radicals were generated in the system. This demonstrates that the catalyst can catalyze the gain of electrons in oxygen to generate superoxide radicals and catalyze the gain of electrons in hydrogen peroxide to generate hydroxyl radicals, thereby enabling superoxide radicals and hydroxyl radicals to synergistically oxidize organic pollutants and degrade organic wastewater.

[0132] Test results are as follows Figure 7 , Figure 8 , Figure 9 , Figure 10 and Figure 11 As shown. Please refer to [the original text]. Figure 7 , Figure 7 The types of free radicals generated during the photocatalytic oxidation of the composite carbon-based catalyst prepared in Example 1 of this invention, analyzed by electron paramagnetic resonance (ESR), are determined by the following analysis: Figure 7 It can be seen that when O2 is used alone as the oxidant, the active intermediate is ·O2, meaning the catalyst can catalyze the formation of ·O2 from oxygen. When H2O2 is used alone as the oxidant, the active intermediate is ·OH radical, meaning the catalyst can catalyze the formation of ·OH from hydrogen peroxide. When hydrogen peroxide and oxygen are used simultaneously, ·O2 and ·OH can be detected simultaneously, indicating that the catalyst has dual active sites and can simultaneously catalyze the reduction of hydrogen peroxide and oxygen to generate ·OH and ·O2 respectively, thus synergistically oxidizing and degrading organic pollutants.

[0133] Please see Figure 8 , Figure 8 This is a comparison chart showing the degradation performance of the composite carbon-based catalyst prepared in Example 1 of the present invention in the oxidation of organic pollutants in wastewater using oxygen and / or hydrogen peroxide. From... Figure 8 The results show that when hydrogen peroxide and oxygen work together as oxidants, their synergistic effect can significantly improve the degradation efficiency of the organic pollutant methylene blue. Figure 9 This is a comparison chart showing the degradation performance of the composite carbon-based catalysts prepared in Example 1, Comparative Example 1, and Comparative Example 2 of the present invention, respectively, in the oxidation of organic pollutants in wastewater using oxygen and hydrogen peroxide. From... Figure 9 It can be seen that the ultraporous graphene in the composite catalyst plays an important role in the catalytic degradation of organic matter. If ordinary graphene is used instead, or if no graphene is added, the degradation efficiency of methylene blue will be significantly reduced. Figure 10 This is a comparison chart showing the degradation performance of the composite carbon-based catalysts prepared in Example 1 and Comparative Example 3 of this invention in the oxidation of organic pollutants in wastewater using oxygen and hydrogen peroxide, respectively; from Figure 10 As can be seen, the metallic iron atoms complexed with heteroatom-doped carbon play an important role in the catalyst. They are the main active sites for the catalytic generation of hydroxyl radicals and superoxide radicals from hydrogen peroxide and oxygen, respectively. Without the addition of metallic iron, the catalyst has almost no catalytic activity.

[0134] Efficiency test of photocatalytic degradation of methylene blue in wastewater

[0135] Conventional photocatalytic degradation experiment: The experiment was conducted at 25±2℃ under xenon lamp illumination simulating visible light (300W Xe lamp, CEL-HXF300, 420nm filter). 100 mL of a 200 mg / L methylene blue solution was placed in the photocatalytic reactor. The pH of the solution was adjusted to 9 with 1 mol / L NaOH solution, and the specified amount of the composite carbon-based catalyst powder prepared in Example 1 (0.25 g / L) was added. O2 was continuously introduced and the mixture was stirred continuously in the dark for 60 min to allow the system to reach adsorption-desorption equilibrium. Subsequently, 1 mL of H2O2 was added simultaneously with the light source to initiate the photocatalytic degradation reaction. Samples were taken at specific reaction times, centrifuged, and the absorbance of the supernatant at 664 nm was measured using liquid chromatography-ultraviolet (LC-UV) spectrometry. The corresponding concentration was calculated, and the degradation efficiency was calculated using the following formula.

[0136]

[0137] E: Pollutant degradation rate, %

[0138] C: Concentration of pollutants at a specific reaction time, mg / L

[0139] C0: Initial concentration of pollutant, mg / L

[0140] Catalytic cycle test

[0141] The degradation rate of organic pollutants detected by repeated experiments is an important criterion for judging the stability of the catalyst. The catalyst dosage and other reaction conditions are kept consistent in the repeated experiments. The amount of catalyst collected from multiple degradation experiments ensures that a sufficient amount of catalyst is added after each cycle. The specific experimental procedure is as follows: After the catalytic experiment, solid-liquid separation is performed by centrifugation, and the catalyst is washed multiple times with deionized water and alcohol. After vacuum drying, it is collected directly and then reused in the degradation experiment. The specific catalytic experimental steps are the degradation experimental steps described above.

[0142] Test results are as follows Figure 11 , Figure 12 , Figure 13 and Figure 14 As shown. Please refer to [the original text]. Figure 11 , Figure 11The results of methylene blue removal rate and mineralization after five cycles of recycling of the composite carbon-based catalyst prepared in Example 1 of this invention, as well as the loss of iron from the catalyst, are presented. Figure 11 As can be seen from the results, the photocatalytic performance of the catalyst prepared in Implementation 1 is very stable. After five consecutive uses, the degradation rate and mineralization of methylene blue are almost unaffected, while the iron loss rate is only 0.2%, indicating that the catalyst remains very stable under light and has strong resistance to photochemical corrosion. Figure 12 This is a comparative graph showing the cyclic stability test results of the composite carbon-based catalysts prepared in Example 1, Comparative Example 1, and Comparative Example 2 of this invention, respectively, for the degradation of organic pollutants in wastewater using oxygen and / or hydrogen peroxide. Figure 12 As can be seen from the results, compared with the results of Comparative Example 1 and Comparative Example 2, the catalyst of Example 1 not only has high catalytic activity, but also good cycle stability and stable catalyst structure. This indicates that the ultraporous graphene support plays a crucial role in the structural stability of the composite catalyst. Figure 13 This is a comparison of the cyclic stability of the composite carbon-based catalysts prepared in Example 1 and Comparative Example 3 of this invention in the oxidation and degradation of organic pollutants in wastewater using oxygen and hydrogen peroxide, respectively; from Figure 13 As can be seen, Fe is the main active component of the composite catalyst. Without iron, the catalyst not only has very low activity, but also poor cycle stability.

[0143] Figure 14 and 15 The figures show the degradation efficiency of the composite carbon-based catalysts prepared in Examples 2, 3, 4 and 5 of this invention under synergistic photocatalytic oxidation for the degradation of organic pollutants in wastewater under oxygen and hydrogen peroxide oxidation conditions. As can be seen from the figures, the composite carbon-based catalysts prepared on different highly conductive ultraporous carbon substrates all have excellent photocatalytic synergistic oxidation efficiency for organic pollutants.

[0144] Mineralization capacity test

[0145] Mineralization is one of the important indicators for judging whether a catalyst has completely degraded pollutants in water, that is, the ability of the catalyst to completely degrade pollutants in water to produce CO2 and H2O. The concentration of residual organic carbon in the reaction solution after the photocatalytic degradation experiment (specifically, after 60 minutes of photocatalysis in this invention) was measured using a total organic carbon analyzer, and the removal rate of organic carbon in water by the catalyst was calculated. The calculation process is as follows:

[0146]

[0147] In the formula, Mineralization is the degree of mineralization, in %; TOC is the concentration of organic carbon in the reaction solution at a specific reaction time, in mg / L; and TOC0 is the initial concentration of organic carbon in the reaction solution, in mg / L.

[0148] The mineralization of the composite carbon-based catalyst prepared in Example 1 of this invention was calculated, and the calculation process is shown in Equation 2, with a mineralization of 84.33%. The mineralization of the composite carbon-based catalyst prepared in Example 2 of this invention was calculated, and the calculation process is shown in Equation 2, with a mineralization of 84.12%. The mineralization of the composite carbon-based catalyst prepared in Example 3 of this invention was calculated, and the calculation process is shown in Equation 2, with a mineralization of 83.79%. The mineralization of the composite carbon-based catalyst prepared in Example 3 of this invention was calculated, and the calculation process is shown in Equation 2, with a mineralization of 83.79%. The mineralization of the composite carbon-based catalyst prepared in Example 4 of this invention was calculated, and the calculation process is shown in Equation 2, with a mineralization of 85.60%. The mineralization of the composite carbon-based catalyst prepared in Example 3 of this invention was calculated, and the calculation process is shown in Equation 2, with a mineralization of 87.12%.

[0149] The mineralization of the composite carbon-based catalyst prepared in Comparative Example 1 of this invention was calculated, and the calculation process is shown in Equation 2, with a mineralization of 73.29%. The mineralization of the composite carbon-based catalyst prepared in Comparative Example 2 of this invention was calculated, and the calculation process is shown in Equation 2, with a mineralization of 50.43%. The mineralization of the composite carbon-based catalyst prepared in Comparative Example 3 of this invention was calculated, and the calculation process is shown in Equation 2, with a mineralization of 29.56%.

[0150] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Additionally, any content not described in detail herein is prior art known to those skilled in the art.

[0151] 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 composite carbon-based catalyst of ultraporous carbon / carbon nanosheets containing MX / YC active sites, characterized in that, The composite carbon-based catalyst consists of an ultraporous carbon substrate and carbon nanosheets containing MX / YC active sites supported thereon. The carbon nanosheets containing MX / YC active sites are formed by covalent bonds between M and carbon nanosheets containing X / Y heteroatoms, which have a complex structure. M is a transition metal existing in a single-atom site state, and M is selected from at least one of Fe, Co, Ni, Cu, Zn, and Mn. X and Y are different heteroatoms, and X and Y are each selected from N, O, S, and P. The ultraporous carbon is any one of highly conductive graphene, carbon nanotubes, and carbon black with ultraporous pores on its surface. The pore size of the ultraporous carbon is <1 nm. The resistivity of the ultraporous carbon is <50 Ω / cm. The mass ratio of the ultraporous carbon, the transition metal M, and the carbon nanosheets containing X / Y heteroatoms is (0.01-5):0.5:(10:100).

2. A method for preparing a composite carbon-based catalyst of ultraporous carbon / carbon nanosheets containing MX / YC active sites as described in claim 1, characterized in that, Includes the following steps: S1 disperses ultraporous carbon in an aqueous solution of a precursor containing X / Y heteroatoms, stirs it evenly, and then performs a hydrothermal reaction at 150-250℃ for 15-20h. Subsequently, it is evaporated to dryness in a water bath at 80℃ to obtain an ultraporous carbon / precursor composite material containing X / Y heteroatoms. S2 disperses the above-mentioned microporous carbon / precursor composite material containing X / Y heteroatoms in deionized water and adds a chloride or nitrate solution of transition metal M to cause the transition metal M to undergo a complexation reaction with the precursor containing X / Y heteroatoms. After reacting at 80°C for 2-6 hours, the mixture is evaporated in a water bath to obtain the microporous carbon / precursor composite material containing MX / YC active sites. S3 The above-mentioned microporous carbon / precursor composite material containing MX / YC active sites was placed in a tube resistance furnace under Ar protective atmosphere, heated to 500°C at a heating rate of 1-5°C / min, and held at that temperature for 3-5 hours. After cooling to room temperature with the furnace, the product was obtained. The product was acid washed and dried to obtain a composite carbon-based catalyst of microporous carbon / carbon nanosheets containing MX / YC active sites.

3. The method for preparing the composite carbon-based catalyst according to claim 2, characterized in that, The precursor containing X / Y heteroatoms mentioned in step S1 is a combination of any two of the following: N-containing precursor, O-containing precursor, S-containing precursor, and P-containing precursor.

4. The method for preparing the composite carbon-based catalyst according to claim 3, characterized in that, The nitrogen-containing precursor is any one of dicyandiamide, thiourea, and melamine; the oxygen-containing precursor is any one of anthraquinone compounds and polyphenolic compounds; the anthraquinone compound is 2,6-diaminoanthraquinone or 1,5-dihydroxyanthraquinone; and the polyphenolic compound is tannic acid or gallic acid.

5. The method for preparing the composite carbon-based catalyst according to claim 4, characterized in that, The S-containing precursor is thiophene or its derivative; the P-containing precursor is any one of triphenylphosphine, phenyl phosphoric acid, diphenyl phosphoric acid, phenyl phosphate, and diphenyl phosphate.

6. The application of a composite carbon-based catalyst of ultraporous carbon / carbon nanosheets containing MX / YC active sites as described in claim 1 in the photocatalytic degradation of organic pollutants in wastewater.

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