Preparation method and application of a carbon-nitrogen-based semiconductor material with strong surface polarity

Abstract

The present invention belongs to the field of catalyst preparation technology, and specifically relates to a preparation method and application of a carbon-nitride-based semiconductor material with strong surface polarity. The material includes a porous carbon-nitride-based semiconductor substrate, and the surface of the porous carbon-nitride-based semiconductor substrate has strong polar chemical bonds; the preparation method is: using triazine compounds as raw materials to prepare a porous carbon-nitride-based semiconductor substrate by thermal polymerization, and forming strong polar chemical bonds on the surface of the carbon-nitride-based semiconductor substrate by light irradiation and in-situ self-assembly positioning framework. The carbon-nitride-based material with strong polar chemical bonds prepared by the present invention has more excellent structural characteristics and component advantages, and is a highly potential catalytic system with broad application prospects in the future fields of environmental governance, energy storage and utilization, etc.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalyst preparation, and in particular relates to a preparation method and application of a carbon-nitrogen-based semiconductor material with strong surface polarity. Background Art

[0002] The use of catalysts can alter chemical reaction pathways and adjust reaction barriers, finding applications in a wide range of fields, from new energy to traditional chemical engineering. Numerous studies have demonstrated that polar chemical bonds can effectively regulate the distribution of electrons and charge density within materials. These bonds are considered to be reactive sites on the surface of compounds, effectively enhancing catalyst performance. Although polar chemical bonds have attracted extensive attention and research in recent years, the commonly used methods for synthesizing polar chemical bonds traditionally include: high-temperature pyrolysis (HU P, XU Y, LEI Y, et al. Piezoelectric nanofoams with the interlaced ultrathin graphene confining Zn–N–C dipoles for efficient piezocatalytic H2evolution under low-frequency vibration[J]. Journal of Energy Chemistry, 2022, 69: 115-122.), one-pot synthesis (HUANG K, RONG C, ZHANG W, et al. MOF-assisted synthesis of Ni, Co, Zn, and N multidoped porous carbon as highly efficient oxygen reduction electrocatalysts in Zn–air batteries[J]. Materials Today Energy, 2021, 19: 100579.), sol-thermal method (ZHANG X, JIAO C, LI X, et al. Zn ion-modulated polyamide membrane with enhanced facilitated transport effect for CO2separation[J]. Separation and Purification Technology, 2022, 292: 121051.) and multi-step synthesis method (YUE B, LI Q, IWAI H, et al. Hydrogen production using zinc-doped carbonnitride catalyst irradiated with visible light[J]. Science and technology of advanced materials, 2011.).The synthesis methods in the existing technology are mainly carried out under high temperature or high pressure reaction conditions, and have the main problems of energy waste, complex operation and uncontrollable experimental results. These shortcomings limit the large-scale synthesis and application of polar chemical bonds.

[0003] Therefore, developing a method for preparing surface strong polar chemical bonds with mild reaction conditions, simple preparation process and controllable performance can meet the synthesis and design requirements of a series of catalysts. Summary of the Invention

[0004] To address the shortcomings of the aforementioned existing methods, the present invention aims to provide a method for preparing carbon-nitride-based semiconductor materials with strong surface polarity and their applications. This method utilizes light irradiation and an in-situ self-assembly alignment framework to form strong polar chemical bonds on the surface of a carbon-nitride-based semiconductor substrate. The method is simple, easy to operate, non-toxic, and harmless, and the resulting carbon-nitride-based semiconductor material exhibits excellent catalytic activity.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] On the one hand, the present invention provides a method for preparing a carbon-nitride-based semiconductor material with strong surface polarity. The material includes a carbon-nitride-based semiconductor substrate, and the surface of the carbon-nitride-based semiconductor substrate has strong polar chemical bonds. The preparation method comprises: using a triazine compound as a raw material to prepare a carbon-nitride-based semiconductor substrate by a thermal polymerization method, and forming strong polar chemical bonds on the surface of the nitride-based semiconductor substrate by a light irradiation method and an in-situ self-assembled positioning framework.

[0007] In the above technical solution, further, the method includes the following steps:

[0008] Step 1: heat-treating the triazine compound to obtain a carbon-nitride-based semiconductor matrix;

[0009] Step 2: dispersing the carbon-nitride-based semiconductor matrix obtained in step 1 in an inorganic metal salt solution to obtain a mixed suspension A, stirring the mixed suspension A under light irradiation conditions, centrifuging and ultrasonically washing to obtain a solid, and then drying to obtain a carbon-nitride-based semiconductor material loaded with metal ions;

[0010] Step 3: Disperse the metal ion-loaded carbon-nitride-based semiconductor material obtained in step 2 in a nitrogen-containing ligand solution, stir, centrifuge, and ultrasonically wash to obtain a solid, which is then dried to obtain a carbon-nitride-based semiconductor material with strong surface polarity.

[0011] In the above technical solution, further, the mass ratio of the triazine compound to the inorganic metal salt is (60-98):(2-40), and the molar ratio of the inorganic metal salt to the nitrogen-containing ligand is 1:(1-3).

[0012] In the above technical solution, further, in step 1, the triazine compound includes one or more of urea, melamine, thiourea, and thiocyanate. Nitrogen-containing triazine compounds can generate structural carbon-nitrogen-based semiconductors with a high degree of graphitization through heat treatment.

[0013] In the above technical solution, further, in step 1, the heat treatment is performed in one or more atmospheres of air, nitrogen, or an inert gas, or under vacuum; the heat treatment temperature is 350-550°C, the heat treatment time is 1-5 hours, and the heating rate of the heat treatment is 0.5-20°C / min. Nitrogen-containing triazine compounds have a molecular structure containing multiple stable aromatic rings and require sufficient energy to decompose. Higher temperatures and heating rates will cause their molecular structure to decompose rapidly, resulting in a reduced yield of the generated carbon-nitrogen material.

[0014] In the above technical solution, further, in step 2, the inorganic metal salt solution includes one or more of zinc nitrate, zinc chloride, zinc carbonate, cobalt nitrate, ferric chloride, and manganese chloride, the solvent of the inorganic metal salt solution includes one or more of deionized water, methanol, and ethanol, and the concentration of the inorganic metal salt solution is 1 mmol / L to 5 mol / L. The carbonitride-based semiconductor material is dispersed in the inorganic metal salt solution, and the metal ions in the metal salt solution have coordination ability and can coordinate with nitrogen on the surface of the carbonitride-based semiconductor.

[0015] In the above technical solution, further, in step 2, the light irradiation conditions are: a wavelength of 200 to 800 nm, and a distance of 1 to 15 cm from the surface of the mixed suspension A. Carbon-nitride-based semiconductors generally have a wavelength between 1.5 and 5 eV. Therefore, under irradiation with a light source with a wavelength of 200 to 800 nm, they can generate photogenerated electrons that effectively attract more metal ions in the solution.

[0016] In the above technical solution, further, in step 2, the stirring time is 2 to 24 hours, and the stirring rate is 200 to 600 rpm / min.

[0017] In the above technical solution, further, in step 2, the centrifugal speed is 6000-12000 rpm / min, and the time is 3-15 min.

[0018] In the above technical solution, further, in step 2, the solvents for ultrasonic washing are one or more of deionized water, methanol, and ethanol, and the number of washing times is 3 to 6 times.

[0019] In the above technical solution, further, in step 2, the drying temperature is 40-60°C and the drying time is 3-24 hours. The inorganic metal salt solution requires time to coordinate with the nitrogen on the surface of the carbonitride-based semiconductor. If the drying temperature is too high or the drying time is too long, the complex will easily form metal oxides, metal nitrides, or metal carbides.

[0020] In the above technical solution, further in step 3, the nitrogen-containing ligand solution includes one or more of 2-methylimidazole, N,N-dimethylformamide, and terephthalic acid, and the solvent of the nitrogen-containing ligand solution includes one or more of deionized water, methanol, and ethanol. The concentration of the nitrogen-containing ligand solution is 1 mmol / L to 5 mol / L. The nitrogen-containing ligand can coordinate with the metal on the surface of the carbonitride-based semiconductor, changing the electron cloud density around the metal and increasing the polarity of the chemical bond.

[0021] In the above technical solution, further, in step 3, the stirring time is 2 to 24 hours, and the stirring rate is 200 to 600 rpm / min;

[0022] In the above technical solution, further, in step 3, the centrifugal speed is 6000-12000 rpm / min, and the time is 3-15 min;

[0023] In the above technical solution, further, in step 3, the solvent for ultrasonic washing is one or more of deionized water, methanol, and ethanol, and the number of washing times is 3 to 6 times;

[0024] In the above technical solution, further, in step 3, the drying temperature is 40-60°C and the drying time is 3-24 hours. The inorganic metal salt solution requires time to coordinate with the nitrogen on the surface of the carbonitride-based semiconductor. If the drying temperature is too high or the drying time is too long, the complex will easily form metal oxides, metal nitrides, or metal carbides.

[0025] Another aspect of the present invention provides an application of a carbon-nitrogen-based semiconductor material with strong surface polarity obtained by the above-mentioned preparation method for photocatalytic degradation of dye-containing wastewater.

[0026] The present invention also provides an application of the carbon-nitride-based semiconductor material with strong surface polarity prepared by the above preparation method, which is used for photo / electrocatalytic redox reaction of metal ions.

[0027] Compared with the existing technology, it has the following beneficial effects:

[0028] 1) Through green, environmentally friendly, sustainable clean energy - light irradiation, nitrogen-containing ligands and carbon-nitride-based semiconductor surface metal in situ self-assembly to prepare carbon-nitride-based semiconductor materials with strong polar chemical bonds;

[0029] 2) The selected raw materials, such as triazine compounds, inorganic metal salts, nitrogen-containing ligands and other reagents, are cheap and readily available. Compared with the traditional method of preparing polar bonds, this method is simple and easy to operate, has low cost, and can be produced on a large scale.

[0030] 3) The obtained product has a large specific surface area and has strong polar chemical bonds on the surface. Therefore, the obtained material has stronger catalytic ability and more catalytic active sites. Compared with conventional carbon-nitrogen-based materials, the prepared carbon-nitrogen-based material with strong polar chemical bonds has more excellent structural characteristics and component advantages. It is a highly promising catalytic system with broad application prospects in future fields such as environmental governance and energy storage and utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 XRD spectra of the carbon-nitride-based semiconductor of Comparative Example 3, the carbon-nitride-based semiconductor material with strong polar zinc-nitrogen bonds of Example 1, and the metal compound of Comparative Example 2, wherein (a) is Comparative Example 3, (b) is Example 1, and c is Comparative Example 2;

[0032] Figure 2 This is the SEM spectrum of the carbon-nitride-based semiconductor material with strong polar zinc-nitrogen bonds of Example 1;

[0033] Figure 3 TEM spectrum of the carbon-nitride-based semiconductor material with strong polar zinc-nitrogen bonds of Example 1;

[0034] Figure 4 N1s XPS spectra of the carbonitride-based semiconductor material with strong polar zinc-nitrogen bonds of Example 1, the carbonitride-based semiconductor of Comparative Example 3, and the metal compound of Comparative Example 2, wherein (a) is Example 1, (b) is Comparative Example 3, and (c) is Comparative Example 2;

[0035] Figure 5 The Zn 2p XPS spectra of the carbonitride-based semiconductor material with a strong polar zinc-nitrogen bond of Example 1 and the metal compound of Comparative Example 2 are shown, wherein (a) is Example 1 and (b) is Comparative Example 2;

[0036] Figure 6 N2 gas adsorption / desorption curves of the carbon-nitride-based semiconductor of Comparative Example 3 and the carbon-nitride-based semiconductor material with a strong polar zinc-nitrogen bond in Example 4, wherein (a) is Comparative Example 3 and (b) is Example 4;

[0037] Figure 7 These are XRD spectra of the carbon-nitride-based semiconductor material with strong polar cobalt-nitrogen bonds of Example 5 and the carbon-nitride-based semiconductor material with strong polar iron-nitrogen bonds of Example 6, where (a) is Example 5 and (b) is Example 6. DETAILED DESCRIPTION

[0038] The present invention will be described in detail below with reference to specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those skilled in the art, several variations and improvements can be made without departing from the scope of the present invention. These all fall within the scope of protection of the present invention.

[0039] Example 1

[0040] 1) Weigh 5 g of urea and place it in a 50 ml crucible. Heat the temperature to 450°C at a rate of 20°C / min in an air atmosphere and hold at this temperature for 3 h. Then cool it naturally to room temperature. Grind the resulting yellow mass into powder to obtain a carbon-nitride-based semiconductor matrix.

[0041] 2) Weigh 4.875 g of zinc nitrate solid and add it to 100 ml of anhydrous methanol solution (AR, ≥99%), ultrasonicate for 2 minutes to mix it evenly, and obtain a colorless and transparent zinc nitrate solution; weigh 4 g of yellow carbon nitride-based semiconductor matrix powder and add it to the zinc nitrate solution at room temperature, place it on a magnetic stirrer at a speed of 300 rpm and stir for 12 hours, while placing an ultraviolet lamp with a wavelength of 365 nm at 5 cm from the upper liquid surface and continuously irradiating it for 12 hours; the suspension is centrifuged and ultrasonically washed three times with anhydrous ethanol and deionized water respectively to obtain a solid, which is then placed in a drying oven at a temperature of 60°C and dried for 12 hours to obtain a carbon nitride-based semiconductor material loaded with zinc ions;

[0042] 3) Weigh 4.010 g of 2-methylimidazole solid and add it to 100 ml of anhydrous methanol solution (AR, ≥99%), ultrasonicate for 2 min to mix it evenly, and obtain a colorless and transparent imidazole solution; disperse the zinc ion-loaded carbon-nitride-based semiconductor material in the imidazole solution at room temperature, place it on a magnetic stirrer at a speed of 300 rpm and stir for 12 h; centrifuge the suspension and ultrasonically wash it three times with anhydrous ethanol and deionized water respectively to obtain a solid, which is then placed in a drying oven at a temperature of 60°C and dried for 12 h to obtain a carbon-nitride-based semiconductor material with a strong polar zinc-nitrogen bond (Zn-N) on the surface.

[0043] Example 2

[0044] 1) Weigh 5 g of urea and place it in a 50 ml crucible. Heat the temperature to 450°C at a rate of 20°C / min in an air atmosphere and hold at this temperature for 3 h. Then cool it naturally to room temperature. Grind the resulting yellow mass into powder to obtain a carbon-nitride-based semiconductor matrix.

[0045] 2) Weigh 2.4375 g of zinc nitrate solid and add it to 100 ml of anhydrous methanol solution (AR, ≥99%). Ultrasonicate for 2 minutes to mix it evenly to obtain a colorless and transparent zinc nitrate solution. Weigh 4 g of yellow carbon-nitride-based semiconductor matrix powder and add it to the zinc nitrate solution at room temperature. Place it on a magnetic stirrer at a speed of 300 rpm and stir for 12 hours. At the same time, place an ultraviolet light source with a wavelength of 365 nm at 5 cm from the upper liquid surface and irradiate it for 12 hours. Centrifuge the suspension and ultrasonically wash it three times with anhydrous ethanol and deionized water respectively to obtain a solid. Then place it in a drying oven at a temperature of 60°C and dry it for 12 hours to obtain a carbon-nitride-based semiconductor material loaded with zinc ions.

[0046] 3) Weigh 2.005 g of 2-methylimidazole solid and add it to 100 ml of anhydrous methanol solution (AR, ≥99%), ultrasonicate for 2 min to mix it evenly, and obtain a colorless and transparent imidazole solution; disperse the zinc ion-loaded carbon-nitride-based semiconductor material in the imidazole solution at room temperature, place it on a magnetic stirrer at a speed of 300 rpm and stir for 12 h; centrifuge the suspension and ultrasonically wash it three times with anhydrous ethanol and deionized water respectively to obtain a solid, which is then placed in a drying oven at a temperature of 60°C and dried for 12 h to obtain a carbon-nitride-based semiconductor material with a strong polar zinc-nitrogen bond on the surface.

[0047] Example 3

[0048] 1) Weigh 5 g of urea and place it in a 50 ml crucible. Heat the temperature to 450°C at a rate of 20°C / min in an air atmosphere and hold at this temperature for 3 h. Then cool it naturally to room temperature. Grind the resulting yellow mass into powder to obtain a carbon-nitride-based semiconductor matrix.

[0049] 2) Weigh 7.3125 g of zinc nitrate solid and add it to 100 ml of anhydrous methanol solution (AR, ≥99%). Ultrasonicate for 2 minutes to mix evenly to obtain a colorless and transparent zinc nitrate solution. Weigh 4 g of yellow carbonitride-based semiconductor matrix powder and add it to the zinc nitrate solution at room temperature. Place it on a magnetic stirrer at a speed of 300 rpm and stir for 12 hours. At the same time, place a 365 nm ultraviolet light source 5 cm from the upper liquid surface and irradiate it for 12 hours. Centrifuge the suspension and ultrasonically wash it three times with anhydrous ethanol and deionized water respectively to obtain a solid. Then, place it in a drying oven at a temperature of 60°C and dry it for 12 hours to obtain a zinc ion-loaded carbonitride-based semiconductor material.

[0050] 3) Weigh 6.015 g of 2-methylimidazole solid and add it to 100 ml of anhydrous methanol solution (AR, ≥99%), ultrasonicate for 2 min to mix it evenly, and obtain a colorless and transparent imidazole solution; disperse the zinc ion-loaded carbon-nitride-based semiconductor material in the imidazole solution at room temperature, place it on a magnetic stirrer at a speed of 300 rpm and stir for 12 h; centrifuge the suspension and ultrasonically wash it three times with anhydrous ethanol and deionized water respectively to obtain a solid, which is then placed in a drying oven at a temperature of 60°C and dried for 12 h to obtain a carbon-nitride-based semiconductor material with a strong polar zinc-nitrogen bond on the surface.

[0051] Example 4

[0052] 1) Weigh 5 g of urea and place it in a 50 ml crucible. Heat the temperature to 450°C at a rate of 20°C / min in an air atmosphere and hold at this temperature for 3 h. Then cool it naturally to room temperature. Grind the resulting yellow mass into powder to obtain a carbon-nitride-based semiconductor matrix.

[0053] 2) Weigh 9.750 g of zinc nitrate solid and add it to 100 ml of anhydrous methanol solution (AR, ≥99%). Ultrasonicate for 2 minutes to mix evenly to obtain a colorless and transparent zinc nitrate solution. Weigh 4 g of yellow carbonitride-based semiconductor matrix powder and add it to the zinc nitrate solution at room temperature. Place it on a magnetic stirrer at a speed of 300 rpm and stir for 12 hours. At the same time, place a 365 nm ultraviolet light source 5 cm from the upper liquid surface and irradiate it for 12 hours. Centrifuge the suspension and ultrasonically wash it three times with anhydrous ethanol and deionized water respectively to obtain a solid. Then, place it in a drying oven at a temperature of 60°C and dry it for 12 hours to obtain a carbonitride-based semiconductor material loaded with zinc ions.

[0054] 3) Weigh 8.004 g of 2-methylimidazole solid and add it to 100 ml of anhydrous methanol solution (AR, ≥99%), and ultrasonicate for 2 min to mix it evenly to obtain a colorless and transparent imidazole solution; disperse the zinc ion-loaded carbon-nitride-based semiconductor material in the imidazole solution at room temperature and stir it on a magnetic stirrer at a speed of 300 rpm for 12 h; centrifuge the suspension and ultrasonically wash it three times with anhydrous ethanol and deionized water respectively to obtain a solid, which is then placed in a drying oven at a temperature of 60°C and dried for 12 h to obtain a carbon-nitride-based semiconductor material with a strong polar zinc-nitrogen bond on the surface.

[0055] Example 5

[0056] 1) Weigh 5 g of urea and place it in a 50 ml crucible. Heat the temperature to 450°C at a rate of 20°C / min in an air atmosphere and hold at this temperature for 3 h. Then cool it naturally to room temperature. Grind the resulting yellow mass into powder to obtain a carbon-nitride-based semiconductor matrix.

[0057] 2) Weigh 9.147 g of cobalt nitrate solid and add it to 100 ml of anhydrous methanol solution (AR, ≥99%). Ultrasonicate for 2 minutes to mix evenly to obtain a colorless and transparent zinc nitrate solution. Weigh 4 g of yellow carbonitride-based semiconductor matrix powder and add it to the cobalt nitrate solution at room temperature. Place it on a magnetic stirrer at a speed of 300 rpm and stir for 12 hours. At the same time, place a 365 nm ultraviolet light source 5 cm from the upper liquid surface and irradiate it for 12 hours. Centrifuge the suspension and ultrasonically wash it three times with anhydrous ethanol and deionized water respectively to obtain a solid. Then place it in a drying oven at a temperature of 60°C and dry it for 12 hours to obtain a carbonitride-based semiconductor material loaded with cobalt ions.

[0058] 3) Weigh 8.004 g of 2-methylimidazole solid and add it to 100 ml of anhydrous methanol solution (AR, ≥99%), ultrasonicate for 2 min to mix it evenly, and obtain a colorless and transparent imidazole solution; disperse the cobalt ion-loaded carbon nitride-based semiconductor material in the imidazole solution at room temperature, place it on a magnetic stirrer at a speed of 300 rpm and stir for 12 h; centrifuge the suspension and ultrasonically wash it three times with anhydrous ethanol and deionized water respectively to obtain a solid, which is then placed in a drying oven at a temperature of 60°C and dried for 12 h to obtain a carbon nitride-based semiconductor material with a strong polar cobalt-nitrogen bond on the surface.

[0059] Example 6

[0060] 1) Weigh 5 g of urea and place it in a 50 ml crucible. Heat the temperature to 450°C at a rate of 20°C / min in an air atmosphere and hold at this temperature for 3 h. Then cool it naturally to room temperature. Grind the resulting yellow mass into powder to obtain a carbon-nitride-based semiconductor matrix.

[0061] 2) Weigh 16.220 g of ferric chloride solid and add it to 100 ml of anhydrous methanol solution (AR, ≥99%), ultrasonicate for 2 minutes to mix evenly, and obtain a colorless and transparent ferric chloride solution; weigh 4 g of yellow carbon nitride-based semiconductor matrix powder and add it to the ferric chloride solution at room temperature, place it on a magnetic stirrer at a speed of 300 rpm and stir for 12 hours, while placing a 365 nm ultraviolet light source 5 cm from the upper liquid surface and continuously irradiating for 12 hours; centrifuge the suspension and ultrasonically wash it three times with anhydrous ethanol and deionized water respectively to obtain a solid, which is then placed in a drying oven at a temperature of 60°C and dried for 12 hours to obtain a carbon nitride-based semiconductor material loaded with iron ions;

[0062] 3) Weigh 8.004 g of 2-methylimidazole solid and add it to 100 ml of anhydrous methanol solution (AR, ≥99%), ultrasonicate for 2 min to mix it evenly, and obtain a colorless and transparent imidazole solution; disperse the iron ion-loaded carbon-nitride-based semiconductor material in the imidazole solution at room temperature, place it on a magnetic stirrer at a speed of 300 rpm and stir for 12 h; centrifuge the suspension and ultrasonically wash it three times with anhydrous ethanol and deionized water respectively to obtain a solid, which is then placed in a drying oven at a temperature of 60°C and dried for 12 h to obtain a carbon-nitride-based semiconductor material with a strong polar iron-nitrogen bond on the surface.

[0063] Comparative Example 1

[0064] The preparation method is similar to that of Example 1, except that in step 2, a mixed solution of carbon-nitride-based semiconductor matrix powder and zinc nitrate solution is stirred in the dark.

[0065] 1) Weigh 5 g of urea and place it in a 50 ml crucible. Heat the temperature to 450°C at a rate of 20°C / min in an air atmosphere and hold at this temperature for 3 h. Then cool it naturally to room temperature. Grind the resulting yellow mass into powder to obtain a carbon-nitride-based semiconductor matrix.

[0066] 2) Weigh 2.4375 g of zinc nitrate solid and add it to 100 ml of anhydrous methanol solution (AR, ≥99%). Ultrasonicate for 2 minutes to mix evenly to obtain a colorless and transparent zinc nitrate solution. Weigh 4 g of yellow carbonitride-based semiconductor matrix powder and add it to the zinc nitrate solution at room temperature. Stir on a magnetic stirrer at 300 rpm in the dark for 12 hours. Centrifuge the suspension and ultrasonically wash it three times with anhydrous ethanol and deionized water to obtain a solid. Then, place it in a drying oven at 60°C and dry it for 12 hours to obtain a zinc ion-loaded carbonitride-based semiconductor material.

[0067] 3) Weigh 2.005 g of 2-methylimidazole solid and add it to 100 ml of anhydrous methanol solution (AR, ≥99%), ultrasonicate for 2 min to mix it evenly, and obtain a colorless and transparent imidazole solution; disperse the zinc ion-loaded carbon-nitride-based semiconductor material in the imidazole solution at room temperature, place it on a magnetic stirrer at a speed of 300 rpm and stir for 12 h; centrifuge the suspension and ultrasonically wash it three times with anhydrous ethanol and deionized water respectively to obtain a solid, which is then placed in a drying oven at a temperature of 60°C and dried for 12 h to obtain a carbon-nitride-based semiconductor material with a strong polar zinc-nitrogen bond on the surface.

[0068] Comparative Example 2

[0069] Weigh 4.875 g of zinc nitrate solid and add it to 100 ml of anhydrous methanol solution (AR, ≥99%). Ultrasonicate for 2 min to mix evenly to obtain a colorless and transparent zinc nitrate solution.

[0070] 2) Weigh 4.010 g of 2-methylimidazole solid and add it to 100 ml of anhydrous methanol solution (AR, ≥99%). Ultrasonicate for 2 minutes to mix thoroughly to obtain a colorless, transparent imidazole solution.

[0071] 3) Dispersing the zinc nitrate solution in the imidazole solution at room temperature and stirring on a magnetic stirrer at 300 rpm for 24 hours; centrifuging the suspension and ultrasonically washing it three times with anhydrous ethanol and deionized water to obtain a solid, which was then dried in a drying oven at 60° C. for 12 hours to obtain a metal compound.

[0072] Comparative Example 3

[0073] Weigh 5 grams of urea and place it in a 50-ml crucible. Heat it to 450°C at a heating rate of 20°C / min under air atmosphere, keep it at this temperature for 3 hours, and then cool it naturally to room temperature. Grind the resulting yellow lump into powder, which is a carbon-nitride-based semiconductor.

[0074] The zinc ion-loaded carbon-nitrogen materials and the carbon-nitrogen-based semiconductor materials with strong polar zinc-nitrogen bonds prepared in the above examples were characterized by XRD, TEM, SEM, XPS and N2 gas adsorption / desorption.

[0075] Figure 1 (a)-(c) are the XRD spectra of the carbon-nitride-based semiconductor of Comparative Example 3 of the present invention, the carbon-nitride-based semiconductor material with a strong polar zinc-nitrogen bond of Example 1, and the metal compound of Comparative Example 2. The XRD pattern of the carbon-nitride-based semiconductor material has characteristic peaks of both the metal compound and the carbon-nitride-based semiconductor, indicating that the metal compound is successfully bonded to the carbon-nitride-based semiconductor.

[0076] Figure 2 This is an SEM image of the carbonitride-based semiconductor material with a strong polar zinc-nitrogen bond in Example 1 of the present invention. The carbonitride-based semiconductor exhibits a flake-like or block-like morphology with a fluffy structure. The metal compounds on the carbonitride-based semiconductor material have irregular shapes with an average size of approximately 30 nm.

[0077] Figure 3 This is the TEM spectrum of the carbon-nitride-based semiconductor material with strong polar zinc-nitrogen bonds on the surface in Example 1 of the present invention.

[0078] Figure 4(a)-(c) are the N1s XPS spectra of the carbon-nitride-based semiconductor material with strong polar zinc-nitrogen bonds in Example 1 of the present invention, the carbon-nitride-based semiconductor in Comparative Example 3, and the metal compound in Comparative Example 2. The results show that additional peaks are observed at 398.2 eV in the carbon-nitride-based semiconductor material in Example 1, which correspond to polar Zn-N bonds.

[0079] Figure 5 (a)-(b) are the Zn 2p XPS spectra of the carbonitride-based semiconductor material in Example 1 of the present invention and the metal compound in Comparative Example 2, respectively. The results show that the Zn 2p3 / 2 and Zn 2p1 / 2 peaks of the carbonitride-based semiconductor material shift to higher binding energies compared to the metal compound, indicating a lower electron density around the zinc atoms. This suggests that the zinc atoms in the carbonitride-based semiconductor material are highly electropositive and have strongly polar Zn-N bonds on their surfaces.

[0080] Figure 6 (a)-(b) N2 gas adsorption / desorption curves for the carbon-nitride semiconductor in Comparative Example 3 and the carbon-nitride semiconductor material with a strong polar zinc-nitrogen bond in Example 4, respectively. The results show that after UV irradiation and in situ self-assembly, the material's specific surface area increases by approximately 55%, effectively increasing the contact area between the reaction solution and the material, facilitating the reaction.

[0081] Figure 7 (a) and (b) are XRD spectra of carbonitride-based semiconductor materials with strong polar cobalt-nitrogen bonds and iron-nitrogen bonds according to Examples 5 and 6 of the present invention, respectively. The XRD patterns of the carbonitride-based semiconductor materials exhibit characteristic peaks of both metal compounds and carbonitride-based semiconductors, indicating that the metal compound is successfully bonded to the carbonitride-based semiconductor.

[0082] Test Example 1

[0083] Table 1 shows the statistical results of the adsorption efficiency and Zn-N bond content of methylene blue by carbon-nitride-based semiconductor materials and metal compounds with strong polar zinc-nitrogen bonds in Examples 1-4 and Comparative Examples 1-2 within 2 hours.

[0084] Table 1 Comparison of adsorption efficiency and Zn-N bond content of samples in methylene blue solution for 2h

[0085] Example No. Methylene adsorption efficiency (%) Zn-N bond content (%) Example 1 44.0％ 1.0％ Example 2 39.8％ 0.3％ Example 3 47.3％ 1.6％ Example 4 54.2％ 2.3％ Comparative Example 1 35.0％ 0.2％ Comparative Example 2 9.2％ 0％

[0086] From the results, it can be seen that the amount of methylene blue adsorbed by the sample is proportional to the content of Zn-N bonds.

[0087] Test Example 2

[0088] Table 2 compares the catalytic effects on iron and the Zn-N bond content of carbonitride-based semiconductor materials and metal compounds with strong polar zinc-nitrogen bonds in 0.2 mol / L ferrous chloride solution in Examples 1-4 and Comparative Examples 1-2.

[0089] Table 2 Comparison of the catalytic effect of samples on iron and the content of Zn-N bonds in 0.2 mol / L ferrous chloride solution

[0090]

[0091] The results show that with the increase of Zn-N bond content, the oxidation potential of iron gradually shifts negatively, the reduction potential gradually shifts positively, and the current density increases.

[0092] In summary, the present invention proposes a method for preparing a carbon-nitride-based semiconductor material with strong surface polarity, which uses light irradiation to form strong polar chemical bonds on the surface of the carbon-nitride-based semiconductor material. The material thus obtained has the characteristics of many active sites, large specific surface area, good stability and a three-dimensional composite structure. Compared with conventional carbon-nitride-based semiconductor materials, carbon-nitride-based semiconductor materials loaded with strong polar chemical bonds have more excellent structural characteristics and component advantages, and are a highly promising photoelectrocatalytic material. This method has the advantages of a simple preparation process and low pollution, and proves the possibility of regulating strong polar chemical bonds. This research provides new opportunities to have a significant impact in the fields of environmental improvement and clean energy applications.

[0093] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other manner. Any person skilled in the art may utilize the above-disclosed technical content to modify or modify the present invention into equivalent embodiments. However, any simple modifications, equivalent variations, and modifications to the above embodiments that do not depart from the technical content of the present invention and are based on the technical essence of the present invention remain within the scope of protection of the present invention.

Claims

1. A method for preparing a carbon-nitride-based semiconductor material with strong surface polarity, characterized in that: The material includes a carbon-nitride-based semiconductor matrix, and the surface of the carbon-nitride-based semiconductor matrix has strong polar chemical bonds. The preparation method comprises: preparing the carbon-nitride-based semiconductor matrix by a thermal polymerization method, and forming strong polar chemical bonds on the surface of the carbon-nitride-based semiconductor matrix by a light irradiation method and an in-situ self-assembled positioning framework; The method specifically comprises the following steps: Step 1: heat-treating the raw materials to obtain a carbon-nitride-based semiconductor matrix; Step 2: dispersing the carbon-nitride-based semiconductor matrix obtained in step 1 in an inorganic metal salt solution to obtain a mixed suspension A, stirring the mixed suspension A under light irradiation conditions, centrifuging and ultrasonically washing to obtain a solid, and then drying to obtain a carbon-nitride-based semiconductor material loaded with metal ions; Step 3: dispersing the metal ion-loaded carbon-nitride-based semiconductor material obtained in step 2 in a nitrogen-containing ligand solution, stirring, centrifuging, and ultrasonically washing to obtain a solid, which is then dried to obtain a carbon-nitride-based semiconductor material with a strong surface polarity; In step 1, the raw materials are one or more of urea, melamine, thiourea, and thiocyanuric acid, and the heat treatment is carried out in one or more atmospheres of air, nitrogen, and inert gas, or under vacuum, at a temperature of 350 to 550° C. and for a time of 1 to 5 hours; In step 2, the inorganic metal salt includes one or more of zinc nitrate, zinc chloride, zinc carbonate, cobalt nitrate, ferric chloride, and manganese chloride, and the light irradiation conditions are: the light wavelength is 200-800 nm, and the light source is 1-15 cm away from the liquid surface of the mixed suspension A; In step 3, the nitrogen-containing ligand includes one or more of 2-methylimidazole and terephthalic acid.

2. The method for preparing a carbon-nitride-based semiconductor with a strong surface polarity according to claim 1, wherein: The mass ratio of the raw material to the inorganic metal salt is (60-98): (2-40), and the molar ratio of the inorganic metal salt to the nitrogen-containing ligand is 1: (1-3).

3. The method for preparing a carbon-nitride-based semiconductor with a strong surface polarity according to claim 1, wherein: In step 1, the heating rate of the heat treatment is 0.5-20°C / min.

4. The method for preparing a carbon-nitride-based semiconductor with strong surface polarity according to claim 1, wherein: In step 2, the solvent of the inorganic metal salt solution includes one or more of deionized water, methanol, and ethanol, and the concentration of the inorganic metal salt solution is 1 to 5 mol / L.

5. The method for preparing a carbon-nitride-based semiconductor with strong surface polarity according to claim 1, wherein: In step 2, the stirring time is 2 to 24 h, and the stirring rate is 200 to 600 rpm / min; The centrifugal speed is 6000-12000 rpm / min, and the time is 3-15 min; The solvents for ultrasonic washing are one or more of deionized water, methanol, and ethanol, and the washing times are 3 to 6 times; The drying temperature is 40-60° C., and the drying time is 3-24 h.

6. The method for preparing a carbon-nitride-based semiconductor with strong surface polarity according to claim 1, wherein: In step 3, the solvent of the nitrogen-containing ligand solution includes one or more of deionized water, methanol, and ethanol, and the concentration of the nitrogen-containing ligand solution is 1 mmol / L to 5 mol / L.

7. An application of a carbon-nitride-based semiconductor material with strong surface polarity obtained by the preparation method according to any one of claims 1 to 6, characterized in that: Used for photocatalytic degradation of dye-containing wastewater.

8. An application of a carbon-nitride-based semiconductor material with a strong surface polarity obtained by the preparation method according to any one of claims 1 to 6, characterized in that: Used for electrocatalytic redox reactions of metal ions.

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