Preparation method of nitrogen-containing micropore-mesoporous carbon with oversized mesopores

Abstract

The preparation method comprises the following steps: by taking starch, glucose or cellulose as a carbon source, imidazole or phenanthroline as a nitrogen source and mixed inorganic salt as a pore-foaming agent, carrying out ball-milling mixing, pre-carbonization, carbonization, washing and drying to prepare a nitrogen-containing micropore-mesoporous carbon material with super-large mesopores; the material contains a cross-linked microporous / mesoporous carbon structure, the mesoporous aperture is 3.7-28.3 nanometers, and the micropore aperture is 0.53-0.56 nanometers. The micropore-mesopore coexistence structure is beneficial to adsorption of phenol molecules and desorption of products; nitrogen, carbon and oxygen elements are uniformly distributed, the nitrogen element exists in forms of pyridine nitrogen, graphite nitrogen and pyrrole nitrogen and can efficiently catalyze potassium peroxydisulfate to generate hydroxyl free radicals, singlet oxygen and sulfate anion free radicals, and phenol is efficiently degraded. According to the method, no mesoporous silicon template agent is used, the steps are few, and the preparation cost is low; and the nitrogen content, the specific surface area, the mesoporous volume and the mesoporous aperture can be regulated and controlled.

Description

Technical Field

[0001] This invention relates to the field of microporous-mesoporous carbon material preparation technology, specifically to a method for preparing nitrogen-containing microporous-mesoporous carbon with ultra-large mesoporous structures. Background Technology

[0002] Porous carbon materials doped with nitrogen have a large specific surface area, micropore volume, and mesopore volume. The introduction of nitrogen can change the inert electronic structure of carbon atoms, forming a large number of defect sites, which can effectively improve the adsorption capacity of materials for organic compounds. Furthermore, the introduction of nitrogen atoms in different forms, such as pyrrole nitrogen, pyridine nitrogen, and graphitic nitrogen, can efficiently catalyze potassium persulfate or potassium monopersulfate to produce active species such as hydroxyl groups and singlet oxygen. This can catalyze the oxidation of highly toxic and recalcitrant organic pollutants such as phenols, converting them into small molecule organic products with benzene ring cleavage, dicarboxylic acids, or CO2, thus facilitating the further degradation treatment of wastewater using the activated sludge process.

[0003] The prior art, disclosed in CN100999317A, describes a method for synthesizing nitrogen-containing ordered mesoporous carbon. This method uses soluble resin and a nitrogen-containing precursor as raw materials, and polyethylene oxide-propylene oxide as a soft template agent. The carbon is prepared through polymerization and calcination, resulting in mesoporous carbon with pore sizes of 2-6 nanometers. However, this method uses expensive ethylene oxide-propylene oxide (P123), involves numerous steps, has high synthesis costs, and is difficult to scale up. CN114735673B discloses a method for preparing nitrogen-doped ordered mesoporous carbon materials using SBA-15 or SBA-3 as a hard template agent, yielding nitrogen-doped ordered mesoporous carbon with pore sizes of 2.8-5.0 nanometers. However, the preparation process for SBA-15 or SBA-3 precursors is complex and expensive, preventing large-scale industrial production. Furthermore, the precursors require removal with 10% hydrofluoric acid in post-processing, a hazardous and environmentally polluting step. Fluorine-containing wastewater is difficult to treat and has high production costs. Therefore, establishing a green, inexpensive, simple, and feasible method to prepare nitrogen-containing microporous-mesoporous carbon with ultra-large mesoporous pore sizes has significant application value. Summary of the Invention

[0004] 1. The technical problem to be solved: To address the aforementioned technical problems, this invention provides a method for preparing nitrogen-containing microporous-mesoporous carbon with ultra-large mesoporous structures. This method overcomes the shortcomings of existing preparation techniques, such as expensive precursors, numerous steps, and low yields.

[0005] 2. Technical Solution: A method for preparing ultra-large mesoporous nitrogen-containing microporous-mesoporous carbon is characterized by: using a polyhydroxy carbon-containing compound of glucose, starch, or cellulose as a carbon source, an imidazole or o-phenanthroline nitrogen-containing heterocyclic compound as a nitrogen source, and a mixture of potassium- and sodium-containing inorganic salts as a porogen; the prepared nitrogen-containing microporous-mesoporous carbon material has a mesoporous pore size that can be adjusted by regulating the total amount of porogen, the composition of the inorganic salts of the porogen, and the carbonization temperature; the adjusted material contains cross-linked micropores and mesoporous carbon structures, has a large specific surface area and pore volume, with a mesoporous pore size of 3.7~28.3 nm and a micropore size of 0.53~0.56 nm; The preparation method specifically includes the following steps: Step 1: Weigh out the polyhydroxy carbon-containing compound, nitrogen-containing heterocyclic compound, potassium-containing inorganic salt, and zinc-containing inorganic salt in a mass ratio of 50:6:(25~75):(25~75), mix them, and add them to a mortar for grinding; transfer the obtained powder to the jar of a planetary ball mill for grinding at a public speed of 100-200 rpm and a private speed of 400-600 rpm for 30-60 minutes to obtain a precursor mixture; the ratio of potassium-containing inorganic salt to zinc-containing inorganic salt is 1:1; Step 2: Add the precursor mixture obtained in Step 1 into a tube furnace, introduce nitrogen gas at a flow rate of 100-200 ml per minute, heat to 240°C at a rate of 1-5°C per minute, and perform pre-carbonization for 120 minutes; to obtain the pre-carbonized product. Step 3: The pre-carbide is heated to 600-900℃ at a rate of 1-5℃ per minute and then carbonized for 120-240 minutes to obtain a black nitrogen-containing carbon powder. Step 4: Soak the black nitrogen-containing carbon powder in 1-5% sulfuric acid, and stir at 200-500 rpm for 20 minutes at room temperature; filter the obtained sample, wash the solid obtained by filtration with distilled water 3 times, and dry the black powder in an oven to obtain nitrogen-containing microporous-mesoporous carbon material.

[0006] Furthermore, the potassium-containing inorganic salt is either potassium nitrate or potassium chloride.

[0007] Furthermore, the zinc-containing inorganic salt is either zinc nitrate or zinc chloride.

[0008] Furthermore, the drying temperature in step four is 80~120 ℃, and the drying time is 120 minutes.

[0009] 3. Beneficial effects: (1) This method provides a method for preparing ultra-large mesoporous nitrogen-containing microporous-mesoporous carbon. Potassium chloride, potassium nitrate, zinc chloride, or zinc nitrate are used in a pre-carbonization process at 240 °C to form a vaporizable melt. As the melt vaporizes, a mesoporous structure is formed. By adjusting the type and amount of inorganic salts, carbon materials with different specific surface areas, mesopore diameters, and mesopore volumes can be prepared. During carbonization at 600-900 °C, starch or glucose undergoes dehydration carbonization to form a microporous carbon structure. Hydroxyl groups undergo dehydration to form carbonyl oxygen. Imidazole or o-phenanthroline forms pyridine nitrogen, pyrrole nitrogen, or graphitic nitrogen species containing carbon-nitrogen bonds at high temperatures. This method does not require the use of mesoporous silica hard template agents such as SBA-15 or SBA-3, significantly reducing preparation costs, reducing steps, and increasing reliability.

[0010] (2) This method provides a method for preparing nitrogen-containing microporous-mesoporous carbon with ultra-large mesoporous structure. The physical properties of the prepared nitrogen-containing microporous-mesoporous carbon material can be controlled, such as nitrogen content, mesoporous volume and mesoporous pore size. The larger mesoporous structure is beneficial to increasing the adsorption amount of phenol on nitrogen-containing microporous-mesoporous carbon and to the dissociation of degradation products from the pore structure of the material, thereby increasing the degradation rate of phenol.

[0011] (3) This method provides a method for preparing nitrogen-containing microporous-mesoporous carbon with ultra-large mesoporous structure. The prepared nitrogen-containing microporous-mesoporous carbon material has a large specific surface area, uniform distribution of micropore and mesopore size, and mesopore size greater than 20 nanometers. The nitrogen element is uniformly distributed, and pyridine nitrogen, pyrrole nitrogen or graphitic nitrogen species can efficiently catalyze the activation of potassium persulfate to generate hydroxyl radicals, singlet oxygen and sulfate anion radicals, which can effectively degrade phenolic organic pollutants in wastewater. Attached Figure Description

[0012] Figure 1 XRD 1(a) and Raman spectrum of the material generated in Example 3 Figure 1 (b); Figure 2 The attached diagram shows the nitrogen adsorption-desorption process of the material generated in Example 3. Figure 3 The following are pore size distribution diagrams of the materials generated in the examples: (a) is the mesopore size distribution diagram of Example 1; (b) is the mesopore size distribution diagram of Example 2; (c) is the mesopore size distribution diagram of Example 7; and (d) is the mesopore size distribution diagram of Example 5. Figure 4 SEM and elemental mapping images of the material generated in Example 5; Figure 5 XPS plot of the material generated in Example 5; Figure 6The electron spin resonance spectrum of the material generated in Example 3 is shown below; (a) is 5,5-dimethyl-1-pyrrolline-N-oxide (DMPO) as a free radical scavenger; (b) is 2,2,6,6-tetramethylpiperidine N-oxide (TEMP) as a free radical scavenger. Detailed Implementation

[0013] The present invention will now be described in detail with reference to the embodiments.

[0014] A method for preparing ultra-large mesoporous nitrogen-containing microporous-mesoporous carbon is characterized by: using a polyhydroxy carbon-containing compound of glucose, starch, or cellulose as a carbon source, an imidazole or o-phenanthroline nitrogen-containing heterocyclic compound as a nitrogen source, and a mixture of potassium- and sodium-containing inorganic salts as a porogen; the prepared nitrogen-containing microporous-mesoporous carbon material has a mesoporous pore size that can be adjusted by regulating the total amount of porogen, the composition of the inorganic salts of the porogen, and the carbonization temperature; the adjusted material contains cross-linked micropores and mesoporous carbon structures, has a large specific surface area and pore volume, with a mesoporous pore size of 3.7~28.3 nm and a micropore size of 0.53~0.56 nm; The preparation method specifically includes the following steps: Step 1: Weigh out the polyhydroxy carbon-containing compound, nitrogen-containing heterocyclic compound, potassium-containing inorganic salt, and zinc-containing inorganic salt in a mass ratio of 50:6:(25~75):(25~75), mix them, and add them to a mortar for grinding; transfer the obtained powder to the jar of a planetary ball mill for grinding at a public speed of 100-200 rpm and a private speed of 400-600 rpm for 30-60 minutes to obtain a precursor mixture; the ratio of potassium-containing inorganic salt to zinc-containing inorganic salt is 1:1; Step 2: Add the precursor mixture obtained in Step 1 into a tube furnace, introduce nitrogen gas at a flow rate of 100-200 ml per minute, heat to 240°C at a rate of 1-5°C per minute, and perform pre-carbonization for 120 minutes; to obtain the pre-carbonized product. Step 3: The pre-carbide is heated to 600-900℃ at a rate of 1-5℃ per minute and then carbonized for 120-240 minutes to obtain a black nitrogen-containing carbon powder. Step 4: Soak the black nitrogen-containing carbon powder in 1-5% sulfuric acid, and stir at 200-500 rpm for 20 minutes at room temperature; filter the obtained sample, wash the solid obtained by filtration with distilled water 3 times, and dry the black powder in an oven to obtain nitrogen-containing microporous-mesoporous carbon material.

[0015] Furthermore, the potassium-containing inorganic salt is either potassium nitrate or potassium chloride.

[0016] Furthermore, the zinc-containing inorganic salt is either zinc nitrate or zinc chloride.

[0017] Furthermore, the drying temperature in step four is 80~120 ℃, and the drying time is 120 minutes.

[0018] I. The physical properties of the material generated in this application and the corresponding catalytic degradation rate of phenol are described. Example 1: (1) Weigh 5.0 g starch, 0.6 g imidazole, 2.5 g potassium chloride and 2.5 g zinc chloride, grind them in a mortar for 10 minutes, transfer them to the jar of a planetary ball mill, grind them at a speed of 200 rpm and a speed of 400 rpm for 30 minutes to obtain a precursor mixture.

[0019] (2) Add the precursor mixture to the tube furnace, introduce nitrogen gas, maintain the nitrogen gas flow rate at 200 ml per minute, increase the temperature to 240 °C at 3 °C per minute, and maintain the temperature at 240 °C for 120 minutes to carry out pre-carbonization.

[0020] (3) Heat the furnace at 1℃ per minute to 600℃ and carbonize it at 600℃ for 120 minutes. Then cool the furnace to room temperature to obtain black nitrogen-containing carbon powder.

[0021] (4) Add black nitrogen-containing carbon powder to 100 ml of 1% sulfuric acid, stir at 20°C and 200 rpm for 20 minutes. Wash three times with 100 ml of distilled water, filter, and dry in an oven at 80°C for 120 minutes to remove moisture, thus obtaining nitrogen-containing microporous-mesoporous carbon.

[0022] Example 2: (1) Weigh 5.0 g of glucose, 0.6 g of imidazole, 5.0 g of potassium chloride and 5.0 g of zinc chloride using an analytical balance, grind them in a mortar for 10 minutes, transfer them to the jar of a planetary ball mill, grind them at a speed of 100 rpm and a speed of 400 rpm for 50 minutes to obtain a precursor mixture.

[0023] (2) Add the precursor mixture to the tube furnace, introduce nitrogen gas, maintain the nitrogen gas flow rate at 200 ml per minute, increase the temperature to 240 °C at 1 °C per minute, and maintain the temperature at 240 °C for 120 minutes to carry out pre-carbonization.

[0024] (3) Heat the furnace at 5°C per minute to 700°C and carbonize it at 700°C for 140 minutes. Then cool the furnace to room temperature to obtain black nitrogen-containing carbon powder.

[0025] (4) Add black nitrogen-containing carbon powder to 100 ml of 5% sulfuric acid, stir at 20°C and 200 rpm for 20 minutes. Wash three times with 100 ml of distilled water, filter, and dry in an oven at 120°C for 120 minutes to remove moisture, and obtain nitrogen-containing microporous-mesoporous carbon.

[0026] Example 3: (1) Weigh 5.0 g of starch, 0.6 g of imidazole, 7.5 g of potassium nitrate and 7.5 g of zinc chloride using an analytical balance, grind them in a mortar for 10 minutes, transfer them to the jar of a planetary ball mill, grind them at a speed of 200 rpm and a speed of 400 rpm for 60 minutes to obtain a precursor mixture.

[0027] (2) Add the precursor mixture to the tube furnace, introduce nitrogen gas, maintain the nitrogen gas flow rate at 200 ml per minute, increase the temperature to 240 °C at 5 °C per minute, and maintain the temperature at 240 °C for 120 minutes to carry out pre-carbonization.

[0028] (3) Heat the furnace at 2°C per minute to 800°C and carbonize it at 800°C for 240 minutes. Then cool the furnace to room temperature to obtain black nitrogen-containing carbon powder.

[0029] (4) Add black nitrogen-containing carbon powder to 100 ml of 2% sulfuric acid, stir at 20°C and 200 rpm for 20 minutes. Wash three times with 100 ml of distilled water, filter, and dry in an oven at 90°C for 120 minutes to remove moisture, thus obtaining nitrogen-containing microporous-mesoporous carbon.

[0030] Example 4: (1) Weigh 5.0 g of starch, 0.6 g of o-phenanthroline, 7.5 g of potassium chloride, and 7.5 g of zinc nitrate using an analytical balance. Mix them and add them to a mortar. Grind for 10 minutes to obtain a white powder. Transfer the white powder to the jar of a planetary ball mill. Grind at a speed of 200 rpm for the main rotation and 600 rpm for the neutral rotation for 30 minutes to obtain a precursor mixture.

[0031] (2) Add the precursor mixture to the tube furnace, introduce nitrogen gas, maintain the nitrogen gas flow rate at 200 ml per minute, increase the temperature to 240 °C at 2 °C per minute, and maintain the temperature at 240 °C for 120 minutes to carry out pre-carbonization.

[0032] (3) Heat the furnace at 4°C per minute to 800°C, hold at 800°C for 210 minutes to carbonize, cool the furnace to room temperature, and obtain black nitrogen-containing carbon powder.

[0033] (4) Add 100 ml of 1% sulfuric acid to black nitrogen-containing carbon powder and stir at 200 rpm at 20 ℃. Wash three times with 100 ml of distilled water, filter, and dry the black powder in an oven at 100 ℃ to obtain nitrogen-containing microporous-mesoporous carbon.

[0034] Example 5: (1) Weigh 5.0 g of glucose, 0.6 g of imidazole, 7.5 g of potassium chloride, and 7.5 g of zinc chloride using an analytical balance. Mix them and add them to a mortar. Grind for 10 minutes to obtain a white powder. Transfer the white powder to the jar of a planetary ball mill. Grind at a speed of 200 rpm for the general rotation and 400 rpm for the free rotation for 30 minutes to obtain a precursor mixture.

[0035] (2) Add the precursor mixture to the tube furnace, introduce nitrogen gas, maintain the nitrogen gas flow rate at 200 ml per minute, increase the temperature to 240 °C at 4 °C per minute, and maintain the temperature at 240 °C for 120 minutes to carry out pre-carbonization.

[0036] (3) Heat the furnace at 4°C per minute to 900°C, hold at 900°C for 120 minutes to carbonize, cool the furnace to room temperature, and obtain black nitrogen-containing carbon powder.

[0037] (4) Add 100 ml of 4% sulfuric acid to black nitrogen-containing carbon powder and stir at 200 rpm at 20 ℃. Wash three times with 100 ml of distilled water, filter, and dry the black powder in an oven at 120 ℃ to obtain nitrogen-containing microporous-mesoporous carbon.

[0038] Example 6: (1) Weigh 5.0 g of cellulose, 0.6 g of o-phenanthroline, 7.5 g of potassium chloride, and 7.5 g of zinc chloride using an analytical balance. Mix them and add them to a mortar. Grind for 10 minutes to obtain a white powder. Transfer the white powder to the jar of a planetary ball mill. Keep the jar in the planetary ball mill at a rotational speed of 200 rpm and a rotational speed of 500 rpm for 40 minutes to obtain a precursor mixture.

[0039] (2) Add the precursor mixture to the tube furnace, introduce nitrogen gas, maintain the nitrogen gas flow rate at 200 ml per minute, increase the temperature to 240 °C at 3 °C per minute, and maintain the temperature at 240 °C for 120 minutes to carry out pre-carbonization.

[0040] (3) The temperature is increased to 800 °C at a rate of 3 °C per minute, and held at 800 °C for 120 minutes for carbonization. The temperature is then reduced with the furnace to room temperature. Black nitrogen-containing carbon powder is obtained.

[0041] (4) Add 100 ml of 1% sulfuric acid to black nitrogen-containing carbon powder and stir at 200 rpm at 20 ℃. Wash three times with 100 ml of distilled water, filter, and dry the black powder in an oven at 80 ℃ for 100 minutes to obtain nitrogen-containing microporous-mesoporous carbon.

[0042] Example 7: (1) Weigh 5.0 g of cellulose, 0.6 g of imidazole, 5.0 g of potassium nitrate and 5.0 g of zinc chloride using an analytical balance. Place them in the jar of a planetary ball mill at a rotational speed of 200 rpm and a rotational speed of 400 rpm for 60 minutes to obtain a precursor mixture.

[0043] (2) Add the precursor mixture to the tube furnace, introduce nitrogen gas, maintain the nitrogen gas flow rate at 200 ml per minute, increase the temperature to 240 °C at 3 °C per minute, and maintain the temperature at 240 °C for 120 minutes to carry out pre-carbonization.

[0044] (3) The temperature is increased to 800 °C at a rate of 5 °C per minute, and held at 800 °C for 120 minutes for carbonization. The temperature is then reduced with the furnace to room temperature. Black nitrogen-containing carbon powder is obtained.

[0045] (4) Add 100 ml of 1% sulfuric acid to black nitrogen-containing carbon powder and stir at 200 rpm at 20 ℃. Wash three times with 100 ml of distilled water, filter, and dry the black powder in an oven at 100 ℃ to obtain nitrogen-containing microporous-mesoporous carbon.

[0046] Comparative Example 1: No inorganic salt porogen added.

[0047] (1) Weigh 5.0 g of cellulose, 0.6 g of imidazole, 0 g of potassium chloride, and 0 g of zinc nitrate using an analytical balance. Place them in the jar of a planetary ball mill at a rotational speed of 200 rpm and a rotational speed of 400 rpm for 60 minutes to obtain a precursor mixture.

[0048] (2) Add the precursor mixture to the tube furnace, introduce nitrogen gas, maintain the nitrogen gas flow rate at 200 ml per minute, increase the temperature to 240 °C at 3 °C per minute, and maintain the temperature at 240 °C for 120 minutes to carry out pre-carbonization.

[0049] (3) The temperature is increased to 800 °C at a rate of 5 °C per minute, and held at 800 °C for 120 minutes for carbonization. The temperature is then reduced with the furnace to room temperature. Black nitrogen-containing carbon powder is obtained.

[0050] (4) Add 100 ml of 1% sulfuric acid to black nitrogen-containing carbon powder and stir at 200 rpm at 20 ℃. Wash three times with 100 ml of distilled water, filter, and dry the black powder in an oven at 100 ℃ to obtain nitrogen-containing microporous-mesoporous carbon.

[0051] Comparative Example 2: Adsorption of phenol using commercial activated carbon.

[0052] Table 1. Physical property parameters of nitrogen-containing microporous-mesoporous carbon materials prepared in each embodiment.

[0053] Table 2. Catalytic phenol degradation data for each embodiment and example.

[0054] As can be seen from the above examples, the material prepared by this method has a relatively large specific surface area and total pore volume, with mesopore diameters ranging from 3.74 to 28.3 nanometers, and the maximum and minimum values ​​being approximately nine times apart. The type and amount of porogen, different carbonization temperatures, or different nitrogen sources can adjust the mesopore diameter; in practice, different preparation experimental conditions can be selected to adjust the mesopore diameter. Furthermore, the examples above show that the nitrogen-containing microporous mesoporous carbon catalyst prepared in Example 5 exhibits the best degradation rate of phenol.

[0055] II. Using this method, different nitrogen-containing microporous and mesoporous carbons were prepared, and their phenol removal rates were compared. In Examples 8-10 below, the carbonization temperature was 700℃, the nitrogen source was 0.24g of o-phenanthroline, and the starch mass was 2.0g; the preparation method followed the steps of this method; other conditions were as follows: Example 8: Prepared using a mixed salt of 2.0 g potassium nitrate and 2.0 g zinc chloride as a pore-forming agent, with a mass ratio of pore-forming agent to starch of 2:1.

[0056] Example 9: Prepared using a mixed salt of 1.0 g potassium nitrate and 1.0 g zinc chloride as a pore-forming agent, with a mass ratio of pore-forming agent to starch of 1:1.

[0057] Example 10: Prepared using a mixed salt of 3.0 g potassium nitrate and 3.0 g zinc chloride as a pore-forming agent, with a mass ratio of pore-forming agent to starch of 3:1.

[0058] Table 3: Catalytic degradation performance of phenol by the products prepared in Examples 8-10 Reaction time (minutes) 10 20 30 40 50 60 Example 8 Catalytic phenol degradation rate (%) 38.5 49.3 58.9 70.2 80.4 76.1 Phenol degradation rate (%) in Example 9 29.2 31.8 32.6 33.1 34.2 35.4 Phenol degradation rate (%) in Example 10 51.6 64.5 73.3 81.2 89.5 84.7 Conclusion: When the ratio of porogen to starch is 3:1, the phenol degradation rate reaches 84.7% after 30 minutes of reaction; while it is 76.1% at 2:1 and 35.4% at 1:1. Therefore, the 3:1 ratio of porogen to starch is superior to 2:1 and 1:1. Thus, the catalytic degradation performance of phenol can be optimized by adjusting different ratios.

[0059] First, the physical properties of the material generated in real-time Example 5 are verified. Figure 1(a) is the X-ray diffraction pattern of the nitrogen-containing microporous-mesoporous carbon material with ultra-large mesoporous structure generated in this embodiment; as can be seen from the figure, the two broad diffraction peaks at 23.2 and 43.7 degrees are (002) and (100) of the carbon material, indicating that the nitrogen-containing microporous-mesoporous carbon material with ultra-large mesoporous structure has a graphite microcrystalline structure.

[0060] Figure 1 (b) Raman spectrum of the ultra-large mesoporous nitrogen-containing microporous-mesoporous carbon material prepared in Example 5, 1330 cm⁻¹ -1 The absorption peak is attributed to the D peak, indicating the presence of defect sites in the ultra-large mesoporous nitrogen-containing microporous-mesoporous carbon material; 1589 cm⁻¹ -1 The absorption peak is attributed to the G peak, indicating the presence of SP in the ultra-large mesoporous nitrogen-containing microporous-mesoporous carbon material. 2 Hybridized graphite structure. The intensity ratio of the D peak to the G peak is 1.04, indicating that the nitrogen-containing microporous-mesoporous carbon material with ultra-large mesoporous structure contains a large number of defect sites and is a highly irregular carbon material.

[0061] Figure 2 The attached figure shows the nitrogen adsorption-desorption curve of the ultra-large mesoporous nitrogen-containing microporous-mesoporous carbon material prepared in Example 5. The curve belongs to type IV, and it is in the low-pressure region (10) of the relative pressure. -6 -10 -2 The nitrogen adsorption volume increased sharply, attributed to the adsorption of nitrogen by the microporous structure, proving that the ultra-mesoporous nitrogen-containing microporous-mesoporous carbon material contains abundant microporous structures. A significant hysteresis loop exists between relative pressures of 0.5 and 0.8, indicating the presence of mesoporous structures in the ultra-mesoporous nitrogen-containing microporous-mesoporous carbon material. The nitrogen adsorption-desorption diagram further demonstrates that the ultra-mesoporous nitrogen-containing microporous-mesoporous carbon material contains both micropores and mesopores, representing a hierarchical porous carbon material.

[0062] Figure 3 (a)-(d) are mesopore distribution diagrams of nitrogen-containing microporous-mesoporous carbon materials with ultra-large mesopores in Examples 1, 2, 7 and 5, respectively. It can be shown that there are a large number of mesopores in the nitrogen-containing microporous-mesoporous carbon materials with ultra-large mesopores, and the pore size of the mesopores can be adjusted between 3.7-28.3 nanometers.

[0063] Figure 4 (a) is a SEM image of the ultra-large mesoporous nitrogen-containing microporous-mesoporous carbon material prepared in Example 5. It can be seen that the ultra-large mesoporous nitrogen-containing microporous-mesoporous carbon material is an irregularly shaped block. The dimensions are 59 micrometers in length and 93 micrometers in width. Figure 4 (b)-4(d) are elemental mapping diagrams of C, O and N in the ultra-large mesoporous nitrogen-containing microporous-mesoporous carbon material prepared in Example 5, which can prove that C, O and N are uniformly distributed in C, O and N.

[0064] Figure 5 (a) is the O2p diagram of the ultra-large mesoporous nitrogen-containing microporous-mesoporous carbon material of Example 5, which contains C(O)OH, C=O and C-OH species, wherein the atomic ratio of C=O is 58.8%. Figure 5 (b) is the N1s plot of the nitrogen-containing microporous-mesoporous carbon material with ultra-large mesoporous structure from Example 5. 398.5 eV, 400.2 eV, 401.2 eV, and 404.6 eV are attributed to pyridine nitrogen, pyrrole nitrogen, graphitic nitrogen, and pyrrole nitrogen-oxide, respectively. Among these, graphitic nitrogen has an atomic ratio of 38.9%. Graphitic nitrogen can effectively and efficiently catalyze the generation of hydroxyl radicals, singlet oxygen, and sulfate anion radicals from potassium persulfate, thereby efficiently degrading phenol.

[0065] Figure 6 The electron spin resonance spectrum of the ultra-large mesoporous nitrogen-containing microporous-mesoporous carbon material prepared in Example 5, catalyzing the oxidation of phenol by potassium persulfate. Figure 6 (a) Using 5,5-dimethyl-1-pyrrolline-N-oxide (DMPO) as a radical scavenger, it was demonstrated that highly active and strongly oxidizing hydroxyl radicals and sulfate radicals were generated in the system. Figure 6 (b) Using 2,2,6,6-tetramethylpiperidine N-oxide (TEMP) as a radical scavenger, it was demonstrated that singlet oxygen reactive species also exist in the system. The high specific surface area and large mesoporous pore size of the ultra-mesoporous nitrogen-containing microporous-mesoporous carbon material improve the adsorption capacity of phenol and facilitate the desorption of degradation products from the catalyst surface. Graphite nitrogen species can catalyze the generation of hydroxyl radicals, sulfate radicals, and singlet oxygen from potassium persulfate, thereby catalyzing the degradation of phenol.

[0066] In summary, the ultra-large mesoporous nitrogen-containing microporous-mesoporous carbon material prepared by this invention possesses a large specific surface area and pore volume, exhibits a graphitic microcrystalline structure, and contains abundant defect sites. It contains cross-linked microporous and mesoporous carbon structures, with mesoporous pore sizes ranging from 3.7 to 28.3 nm and microporous pore sizes ranging from 0.53 to 0.56 nm. Carbon, oxygen, and nitrogen elements are uniformly distributed, with nitrogen existing in pyridine nitrogen, graphitic nitrogen, and pyrrole nitrogen forms, and oxygen atoms mainly existing as carbonyl oxygen species. The coexistence of micropores and mesopores in the ultra-large mesoporous nitrogen-containing microporous-mesoporous carbon material is beneficial for the adsorption of phenol molecules and the desorption of products. It can efficiently catalyze the generation of hydroxyl radicals, singlet oxygen, and sulfate anion radicals from potassium persulfate, thereby efficiently degrading phenol.

[0067] Although the present invention has been disclosed above with reference to preferred embodiments, these are not intended to limit the invention. Any person skilled in the art can make various changes or modifications without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention should be defined by the scope of the claims of this application.

Claims

1. A method for preparing ultra-large mesoporous nitrogen-containing microporous-mesoporous carbon, characterized in that: Using polyhydroxy carbon compounds of glucose, starch, or cellulose as carbon sources, imidazole or o-phenanthroline nitrogen-containing heterocyclic compounds as nitrogen sources, and a mixture of potassium- and sodium-containing inorganic salts as porogens, nitrogen-containing microporous-mesoporous carbon materials were prepared. The mesopore size of the prepared materials could be modulated by adjusting the total amount of porogen, the composition of the inorganic salts in the porogen, and the carbonization temperature. The modulated materials contained cross-linked microporous and mesoporous carbon structures, with a large specific surface area and pore volume. The mesopore size was 3.7~28.3 nm, and the micropore size was 0.53~0.56 nm. The preparation method specifically includes the following steps: Step 1: Weigh out the polyhydroxy carbon-containing compound, nitrogen-containing heterocyclic compound, potassium-containing inorganic salt, and zinc-containing inorganic salt in a mass ratio of 50:6:(25~75):(25~75), mix them, and add them to a mortar for grinding; transfer the obtained powder to the jar of a planetary ball mill for grinding at a public speed of 100-200 rpm and a private speed of 400-600 rpm for 30-60 minutes to obtain a precursor mixture; the ratio of potassium-containing inorganic salt to zinc-containing inorganic salt is 1:1; Step 2: Add the precursor mixture obtained in Step 1 into a tube furnace, introduce nitrogen gas at a flow rate of 100-200 ml per minute, heat to 240°C at a rate of 1-5°C per minute, and perform pre-carbonization for 120 minutes; to obtain the pre-carbonized product. Step 3: The pre-carbide is heated to 600-900℃ at a rate of 1-5℃ per minute and then carbonized for 120-240 minutes to obtain a black nitrogen-containing carbon powder. Step 4: Soak the black nitrogen-containing carbon powder in 1-5% sulfuric acid, and stir at 200-500 rpm for 20 minutes at room temperature; filter the obtained sample, wash the solid obtained by filtration with distilled water 3 times, and dry the black powder in an oven to obtain nitrogen-containing microporous-mesoporous carbon material.

2. The method for preparing ultra-large mesoporous nitrogen-containing microporous-mesoporous carbon according to claim 1, characterized in that: The potassium-containing inorganic salt is either potassium nitrate or potassium chloride.

3. The method for preparing ultra-large mesoporous nitrogen-containing microporous-mesoporous carbon according to claim 1, characterized in that: The zinc-containing inorganic salt is either zinc nitrate or zinc chloride.

4. The method for preparing ultra-large mesoporous nitrogen-containing microporous-mesoporous carbon according to claim 1, characterized in that: The drying temperature in step four is 80~120 ℃, and the drying time is 120 minutes.

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