Preparation method of MIL-101 (Fe) composite core-shell S-shaped heterojunction modified by double rare earth ions as well as product and application of MIL-101 (Fe) composite core-shell S-shaped heterojunction

Abstract

The invention relates to a preparation method of a double-rare earth ion modified MIL-101 (Fe) composite core-shell S-shaped heterojunction as well as a product and application of the double-rare earth ion modified MIL-101 (Fe) composite core-shell S-shaped heterojunction, generation of ligand defects is induced by utilizing acid etching, a large number of metal sites with unsaturated coordination are constructed, and the anchoring adsorption capacity of a metal precursor is improved. Furthermore, the core-shell heterojunction is constructed through the coordination of double rare earth metals, so that the formation of a directional built-in electric field is effectively promoted, and the defects of low interface carrier separation and transfer efficiency, poor surface reaction activity and the like of the traditional heterojunction are overcome. Besides, the catalyst effectively reduces dissolution of metal in the heterojunction catalyst by utilizing a synergistic effect among metal ions, has relatively good stability, promotes cyclic utilization of the catalyst, and has a relatively great application prospect.

Description

Technical Field

[0001] This invention relates to a method for preparing a dual rare earth ion modified MIL-101(Fe) composite core-shell S-type heterojunction, its products, and applications. The dual rare earth ions promote the construction of the built-in electric field of defect-type MIL-101(Fe), effectively enhancing charge transfer and promoting visible light catalysis, and can be used in the field of photocatalysis. Background Technology

[0002] Persistent organic pollutants (POPs) have a lasting impact on humans due to their environmental persistence, bioaccumulation, long-distance migration, and high toxicity. Currently, the main methods for treating POPs include physical, chemical, and bioremediation methods. Among these, photocatalytic oxidation is one of the more effective methods for treating POPs, offering advantages such as operation at room temperature and pressure, non-selectivity, complete degradation of organic matter, no secondary pollution, and low operating costs. The development of highly efficient photocatalysts has become a focus of attention for researchers.

[0003] Traditional semiconductor photocatalysts (such as TiO2) suffer from low quantum efficiency due to the rapid recombination of photogenerated electron-hole pairs, significantly limiting their applications in photocatalysis. Metal-organic frameworks (MOFs), with their superior advantages of high specific surface area, large pore volume, and tunable structural composition, are widely used in artificial photosynthesis, CO2 reduction, and organic pollutant degradation. By optimizing the structure of MOFs before synthesis or modifying them after synthesis, their structural performance can be regulated and optimized, thereby expanding their application areas.

[0004] Studies have shown that S-type heterojunctions of MOFs can expand the light absorption range, enhance photogenerated carrier separation, and reduce charge transfer resistance, thus achieving efficient degradation of organic wastewater. However, research on the application of MIL-101(Fe)-based S-type heterojunctions for visible light photocatalytic degradation remains limited. Furthermore, a key challenge in constructing high-performance heterojunctions lies in the randomness of band arrangement in traditional heterojunctions, making it difficult to accurately predict and control the strength and direction of their built-in electric field.

[0005] Based on this, this patent application employs acid etching to introduce ligand defects and construct coordinate-unsaturated metal sites. Simultaneously, the introduction of multifunctional dual rare-earth metal elements to construct a synergistic redox cycle is expected to enable band structure modulation to alter the built-in electric field strength, thereby improving the efficiency of visible light photocatalytic degradation of organic matter and further enhancing the stability of the catalytic material through its core-shell structure. Summary of the Invention

[0006] To address the issues of low photocatalytic efficiency and stability of traditional photocatalysts, this invention aims to provide a method for preparing a dual rare earth ion modified MIL-101(Fe) composite core-shell S-type heterojunction. This method employs ion doping and heterojunction construction to achieve efficient degradation of organic matter under visible light, and enhances the stability of the catalyst through the core-shell structure.

[0007] Another objective of this invention is to provide a dual rare earth ion modified MIL-101(Fe) composite core-shell S-type heterojunction product prepared by the above method.

[0008] Another object of the present invention is to provide an application of the above-mentioned product.

[0009] The objective of this invention is achieved through the following scheme: a method for preparing a dual rare earth ion modified MIL-101(Fe) composite core-shell S-type heterojunction, which utilizes acid etching to induce ligand defects, and uses dual rare earth metal oxides to coat MIL-101(Fe) with ligand defects to form a heterojunction. By constructing a built-in electric field, the method effectively accelerates the migration of photogenerated carriers and improves the photocatalytic efficiency of the composite catalyst for recalcitrant pollutants. The specific steps include: (1) First, under magnetic stirring, terephthalic acid and acid etchant are mixed and dispersed in DMF at a certain molar ratio and stirred for 30 min; (2) Add Fe(NO3)3·6H2O to (1) according to a certain molar ratio of nFe(NO3)3·6H2O:nterephthalic acid. After ultrasonic dispersion, transfer the resulting mixed solution to a hydrothermal reactor and control the hydrothermal temperature and time. (3) After the reaction is complete, the product is naturally cooled to room temperature. The product is washed and filtered with DMF and anhydrous ethanol, then dried and placed in a vacuum drying oven to obtain defect type MIL-101(Fe). (4) Dissolve two different rare earth nitrates in deionized water according to a certain molar ratio, stir vigorously for 4-8 hours, wash with ethanol and deionized water 2-3 times, and dry in a vacuum drying oven at 60℃. (5) Place the product obtained in (4) in a muffle furnace and calcine it at a certain temperature with a heating rate of 5℃ / min to obtain the dual rare earth ion modified MIL-101(Fe) composite core-shell S-type heterojunction.

[0010] The molar ratio of terephthalic acid to acid etchant is 1:(1~5), and the acid etchant is any one of glacial acetic acid or ferrocene dicarboxylic acid; The ratio of nFe(NO3)3·6H2O:nterephthalic acid is 1:(1~2); the hydrothermal reaction temperature and time are 120~150℃ and 24~48h, respectively. The rare earth nitrates mentioned are any two of Ni(NO3)2·6H2O, Ce(NO3)3•6H2O, Eu(NO3)3·6H2O, and Tb(NO3)3·6H2O, and the molar ratio of the rare earth nitrates is (0.5~10):1; The calcination temperature and time are 270~450 ℃ and 2~6 h, respectively.

[0011] This invention provides a dual rare earth ion modified MIL-101(Fe) composite core-shell S-type heterojunction, which is prepared according to any of the methods described above.

[0012] This invention provides an application of a dual rare earth ion modified MIL-101(Fe) composite core-shell S-type heterojunction photocatalyst for the degradation of tetracycline.

[0013] The photocatalytic degradation experiment of the dual rare earth ion modified MIL-101(Fe) composite core-shell S-type heterojunction was carried out in a photocatalytic reactor. 10 mg of photocatalyst powder was added to a 40 mg / L tetracycline solution. After dark treatment for 1 h, a 300 W xenon lamp was turned on for illumination. The TOC value was measured using a total organic carbon analyzer, and the mineralization rate of the tetracycline wastewater was calculated.

[0014] Beneficial effects The present invention has the following advantages: (1) The present invention proposes a dual rare earth ion modified MIL-101(Fe) composite core-shell S-type heterojunction, which utilizes organic or inorganic acid etching to induce ligand defects, effectively increases the number of coordination unsaturated metal sites, enhances the anchoring adsorption capacity of metal precursors, and regulates the built-in electric field strength.

[0015] (2) By constructing a core-shell heterojunction through the synergistic use of two rare earth metals, the formation of a directional built-in electric field is effectively promoted, overcoming the shortcomings of traditional heterojunctions such as low carrier separation and transfer efficiency and poor surface reactivity. A core-shell heterojunction is constructed by coating ligand-deficient MIL-101(Fe) with two rare earth metal oxides, which effectively enhances the carrier separation efficiency and maintains the strong redox ability of the components. This structure is also conducive to improving the catalytic stability of the catalyst and avoiding secondary pollution caused by metal leaching.

[0016] Furthermore, this catalyst utilizes the synergistic effect between metal ions to effectively reduce the dissolution of metals in heterojunction catalysts, exhibits good stability, promotes catalyst recycling, and has great application prospects.

[0017] (3) The visible light-driven dual rare earth ion modified MIL-101(Fe) composite core-shell S-type heterojunction proposed in this invention can utilize MIL-101(Fe) and dual rare earth metal oxides to form a gradient energy level structure, providing a directional migration path for photogenerated electrons and reducing the probability of bulk recombination; while the lattice defects and exposed metal sites introduced by doping enhance the adsorption capacity of the material for O2 and H2O, accelerate the generation cycle of active oxygen species, and effectively solve the problems of low photocatalytic efficiency and stability of traditional heterojunctions. Detailed Implementation

[0018] The present invention will be further illustrated by the examples.

[0019] Example 1: A dual-rare-earth ion modified MIL-101(Fe) composite core-shell S-type heterojunction is prepared by acid etching to induce ligand defects, and by coating the ligand-defective MIL-101(Fe) with dual rare-earth metal oxides to form a heterojunction. An internal electric field is built in to accelerate the migration of photogenerated carriers and improve the photocatalytic efficiency of the composite catalyst for recalcitrant pollutants. The preparation is carried out according to the following steps: (1) Terephthalic acid and glacial acetic acid are mixed and dispersed in DMF under magnetic stirring, wherein the molar ratio of terephthalic acid to glacial acetic acid is 1:5, and the mixture is stirred for 30 min; wherein glacial acetic acid can be replaced by ferrocene dicarboxylic acid. (2) Add Fe(NO3)3·6H2O to (1), the molar ratio of nFe(NO3)3·6H2O:nterephthalic acid is 1:2; after ultrasonic dispersion, transfer the resulting mixed solution to a hydrothermal reactor and carry out hydrothermal reaction at 150℃ for 24h; (3) After the reaction is complete, the product is naturally cooled to room temperature, washed and filtered with DMF and anhydrous ethanol, dried, and then placed in a vacuum drying oven to dry, thus obtaining defect type MIL-101(Fe); (4) Dissolve Ni(NO3)2·6H2O and Ce(NO3)3•6H2O in deionized water according to the molar ratio of Ni(NO3)2·6H2O:Ce(NO3)3•6H2O of 1:1. Stir vigorously for 4~8h, wash with ethanol and deionized water 2~3 times, and dry in a vacuum drying oven at 60℃. (5) The product obtained in (4) was placed in a muffle furnace and calcined at 270°C for 6 h at a heating rate of 5°C / min to obtain a dual rare earth ion modified MIL-101(Fe) composite core-shell S-type heterojunction.

[0020] The prepared photocatalyst achieved a tetracycline mineralization rate of 80.5%.

[0021] Example 2: A dual rare earth ion modified MIL-101(Fe) composite core-shell S-type heterojunction was prepared according to the following steps: (1) Terephthalic acid and glacial acetic acid were mixed and dispersed in DMF under magnetic stirring, with a molar ratio of 1:4 for terephthalic acid and glacial acetic acid, and stirred for 30 min. (2) Add Fe(NO3)3·6H2O to (1), the molar ratio of nFe(NO3)3·6H2O:nterephthalic acid is 1:2, after ultrasonic dispersion, transfer the resulting mixed solution to a hydrothermal reactor, and react hydrothermally at 110℃ for 24h; (3) After the reaction is complete, the product is naturally cooled to room temperature, washed and filtered with DMF and anhydrous ethanol, dried, and then placed in a vacuum drying oven to dry, thus obtaining defect type MIL-101(Fe); (4) According to the molar ratio of Ni(NO3)2·6H2O:Eu((NO3)3·6H2O) is 1:5, Ni(NO3)2·6H2O and Eu((NO3)3·6H2O) are dissolved in deionized water, stirred vigorously for 4~8h, washed 2~3 times with ethanol and deionized water, and dried in a vacuum drying oven at 60℃. (5) The product obtained in (4) was placed in a muffle furnace and calcined at 350°C for 5 h at a heating rate of 5°C / min to obtain a dual rare earth ion modified MIL-101(Fe) composite core-shell S-type heterojunction.

[0022] The prepared photocatalyst achieved a tetracycline mineralization rate of 72.4%.

[0023] Example 3: A dual rare earth ion modified MIL-101(Fe) composite core-shell S-type heterojunction was prepared according to the following steps: (1) Terephthalic acid and glacial acetic acid were mixed and dispersed in DMF under magnetic stirring, with a molar ratio of 1:2. The mixture was stirred for 30 min. (2) Add Fe(NO3)3·6H2O to (1) so that the molar ratio of nFe(NO3)3·6H2O:nterephthalic acid is 1:1. After ultrasonic dispersion, transfer the resulting mixed solution to a hydrothermal reactor and react it at 110℃ for 48h. (3) After the reaction is complete, the product is naturally cooled to room temperature, washed and filtered with DMF and anhydrous ethanol, dried, and then placed in a vacuum drying oven to dry, thus obtaining defect type MIL-101(Fe); (4) According to the molar ratio of Ce(NO3)3•6H2O:Tb(NO3)3·6H2O of 1:10, Ce(NO3)3•6H2O and Tb(NO3)3·6H2O are dissolved in deionized water, stirred vigorously for 4~8h, washed 2~3 times with ethanol and deionized water, and dried in a vacuum drying oven at 60℃; (5) Place the product obtained in (4) in a muffle furnace and calcine it at 400°C for 3 hours at a heating rate of 5°C / min to obtain the dual rare earth ion modified MIL-101(Fe) composite core-shell S-type heterojunction.

[0024] The prepared photocatalyst achieved a tetracycline mineralization rate of 59.2%.

[0025] Example 4: A dual rare earth ion modified MIL-101(Fe) composite core-shell S-type heterojunction was prepared according to the following steps: (1) Terephthalic acid and glacial acetic acid were mixed and dispersed in DMF under magnetic stirring, with a molar ratio of terephthalic acid to glacial acetic acid of 1:5, and stirred for 30 min. (2) Add Fe(NO3)3·6H2O to (1), the molar ratio of nFe(NO3)3·6H2O:nterephthalic acid is 1:1, after ultrasonic dispersion, transfer the resulting mixed solution to a hydrothermal reactor and react at 150℃ for 48h. (3) After the reaction is complete, the product is naturally cooled to room temperature, washed and filtered with DMF and anhydrous ethanol, dried, and then placed in a vacuum drying oven to dry, thus obtaining defect type MIL-101(Fe); (4) According to the molar ratio of Ce(NO3)3•6H2O:Ni(NO3)2·6H2O of 1:0.5, Ce(NO3)3•6H2O and Ni(NO3)2·6H2O are dissolved in deionized water, stirred vigorously for 4~8h, washed 2~3 times with ethanol and deionized water, and dried in a vacuum drying oven at 60℃. (5) Place the product obtained in (4) in a muffle furnace and calcine it at 450°C for 2 hours at a heating rate of 5°C / min to obtain the dual rare earth ion modified MIL-101(Fe) composite core-shell S-type heterojunction.

[0026] The prepared photocatalyst achieved a tetracycline mineralization rate of 64.4%.

Claims

1. A method for preparing a dual rare earth ion modified MIL-101(Fe) composite core-shell S-type heterojunction, characterized in that, The process involves utilizing acid etching to induce ligand defects, forming a heterojunction by coating MIL-101(Fe) with ligand defects using dual rare-earth metal oxides, and accelerating photogenerated carrier migration through a built-in electric field to improve the photocatalytic efficiency of the composite catalyst for recalcitrant pollutants. The steps include: (1) Terephthalic acid and acid etchant are mixed and dispersed in DMF under magnetic stirring, wherein the molar ratio of terephthalic acid to acid etchant is 1: (1~5), and the mixture is stirred for 30 min; (2) Add Fe(NO3)3·6H2O to (1), nFe(NO3)3·6H2O:nterephthalic acid = 1: (1~2); after ultrasonic dispersion, transfer the resulting mixed solution to a hydrothermal reactor and carry out hydrothermal reaction at 120~150℃; (3) After the reaction is complete, the product is naturally cooled to room temperature, washed and filtered with DMF and anhydrous ethanol, dried, and then placed in a vacuum drying oven to dry, thus obtaining defect type MIL-101(Fe); (4) Dissolve two different rare earth nitrates in deionized water, stir vigorously for 4-8 hours, wash with ethanol and deionized water 2-3 times, and dry in a vacuum drying oven at 60℃. The rare earth nitrates are any two of Ni(NO3)2·6H2O, Ce(NO3)3•6H2O, Eu(NO3)3·6H2O, and Tb(NO3)3·6H2O, and the molar ratio of the rare earth nitrates is (0.5-10):

1. (5) The product obtained in (4) is placed in a muffle furnace and calcined at 270~450 ℃ for 2~6 h at a heating rate of 5℃ / min to obtain a dual rare earth ion modified MIL-101(Fe) composite core-shell S-type heterojunction.

2. The method for preparing a dual rare earth ion modified MIL-101(Fe) composite core-shell S-type heterojunction according to claim 1, characterized in that, The acid etching agent is either glacial acetic acid or ferrocene dicarboxylic acid.

3. The method for preparing a dual rare earth ion modified MIL-101(Fe) composite core-shell S-type heterojunction according to claim 1, characterized in that... In step (2), the hydrothermal reaction time is 24~48h.

4. The method for preparing a dual rare earth ion modified MIL-101(Fe) composite core-shell S-type heterojunction according to claim 1, characterized in that, Prepare according to the following steps: (1) Terephthalic acid and glacial acetic acid were mixed and dispersed in DMF under magnetic stirring, wherein the molar ratio of terephthalic acid to glacial acetic acid was 1:5, and the mixture was stirred for 30 min. (2) Add Fe(NO3)3·6H2O to (1), the molar ratio of nFe(NO3)3·6H2O:nterephthalic acid is 1:2; after ultrasonic dispersion, transfer the resulting mixed solution to a hydrothermal reactor and carry out hydrothermal reaction at 150℃ for 24h; (3) After the reaction is complete, the product is naturally cooled to room temperature, washed and filtered with DMF and anhydrous ethanol, dried, and then placed in a vacuum drying oven to dry, thus obtaining defect type MIL-101(Fe); (4) Dissolve Ni(NO3)2·6H2O and Ce(NO3)3•6H2O in deionized water according to the molar ratio of Ni(NO3)2·6H2O:Ce(NO3)3•6H2O of 1:

1. Stir vigorously for 4~8h, wash with ethanol and deionized water 2~3 times, and dry in a vacuum drying oven at 60℃. (5) The product obtained in (4) was placed in a muffle furnace and calcined at 270°C for 6 hours at a heating rate of 5°C / min to obtain a dual rare earth ion modified MIL-101(Fe) composite core-shell S-type heterojunction.

5. The method for preparing a dual rare earth ion modified MIL-101(Fe) composite core-shell S-type heterojunction according to claim 1, characterized in that, Prepare according to the following steps: (1) Terephthalic acid and glacial acetic acid were mixed and dispersed in DMF under magnetic stirring, with a molar ratio of 1:4 for terephthalic acid and glacial acetic acid, and stirred for 30 min. (2) Add Fe(NO3)3·6H2O to (1), the molar ratio of nFe(NO3)3·6H2O:nterephthalic acid is 1:2, after ultrasonic dispersion, transfer the resulting mixed solution to a hydrothermal reactor, and react hydrothermally at 110℃ for 24h; (3) After the reaction is complete, the product is naturally cooled to room temperature, washed and filtered with DMF and anhydrous ethanol, dried, and then placed in a vacuum drying oven to dry, thus obtaining defect type MIL-101(Fe); (4) According to the molar ratio of Ni(NO3)2·6H2O:Eu((NO3)3·6H2O) is 1:5, Ni(NO3)2·6H2O and Eu((NO3)3·6H2O) are dissolved in deionized water, stirred vigorously for 4~8h, washed 2~3 times with ethanol and deionized water, and dried in a vacuum drying oven at 60℃. (5) The product obtained in (4) was placed in a muffle furnace and calcined at 350°C for 5 h at a heating rate of 5°C / min to obtain a dual rare earth ion modified MIL-101(Fe) composite core-shell S-type heterojunction.

6. The method for preparing a dual rare earth ion modified MIL-101(Fe) composite core-shell S-type heterojunction according to claim 1, characterized in that, Prepare according to the following steps: (1) Terephthalic acid and glacial acetic acid were mixed and dispersed in DMF under magnetic stirring, with a molar ratio of 1:

2. The mixture was stirred for 30 min. (2) Add Fe(NO3)3·6H2O to (1) so that the molar ratio of nFe(NO3)3·6H2O:nterephthalic acid is 1:

1. After ultrasonic dispersion, transfer the resulting mixed solution to a hydrothermal reactor and react it at 110℃ for 48h. (3) After the reaction is complete, the product is naturally cooled to room temperature, washed and filtered with DMF and anhydrous ethanol, dried, and then placed in a vacuum drying oven to dry, thus obtaining defect type MIL-101(Fe); (4) According to the molar ratio of Ce(NO3)3•6H2O:Tb(NO3)3·6H2O of 1:10, Ce(NO3)3•6H2O and Tb(NO3)3·6H2O are dissolved in deionized water, stirred vigorously for 4~8h, washed 2~3 times with ethanol and deionized water, and dried in a vacuum drying oven at 60℃; (5) Place the product obtained in (4) in a muffle furnace and calcine it at 400°C for 3 hours at a heating rate of 5°C / min to obtain the dual rare earth ion modified MIL-101(Fe) composite core-shell S-type heterojunction.

7. The method for preparing a dual rare earth ion modified MIL-101(Fe) composite core-shell S-type heterojunction according to claim 1, characterized in that, Prepare according to the following steps: A dual rare earth ion modified MIL-101(Fe) composite core-shell S-type heterojunction was prepared according to the following steps: (1) Terephthalic acid and glacial acetic acid were mixed and dispersed in DMF under magnetic stirring, with a molar ratio of terephthalic acid to glacial acetic acid of 1:5, and stirred for 30 min. (2) Add Fe(NO3)3·6H2O to (1), the molar ratio of nFe(NO3)3·6H2O:nterephthalic acid is 1:1, after ultrasonic dispersion, transfer the resulting mixed solution to a hydrothermal reactor and react at 150℃ for 48h. (3) After the reaction is complete, the product is naturally cooled to room temperature, washed and filtered with DMF and anhydrous ethanol, dried, and then placed in a vacuum drying oven to dry, thus obtaining defect type MIL-101(Fe); (4) According to the molar ratio of Ce(NO3)3•6H2O:Ni(NO3)2·6H2O of 1:0.5, Ce(NO3)3•6H2O and Ni(NO3)2·6H2O are dissolved in deionized water, stirred vigorously for 4~8h, washed 2~3 times with ethanol and deionized water, and dried in a vacuum drying oven at 60℃. (5) Place the product obtained in (4) in a muffle furnace and calcine it at 450°C for 2 hours at a heating rate of 5°C / min to obtain the dual rare earth ion modified MIL-101(Fe) composite core-shell S-type heterojunction.

8. A dual rare earth ion modified MIL-101(Fe) composite core-shell S-type heterojunction, characterized in that... Prepared according to any one of claims 1-7.

9. The application of a dual rare earth ion modified MIL-101(Fe) composite core-shell S-type heterojunction photocatalyst according to claim 8 in the degradation of tetracycline.