Preparation method and application of a magnetic multi-level pore iron-nitrogen-carbon catalyst

Abstract

The application provides a preparation method of a magnetic multi-level hole iron-nitrogen-carbon catalyst and belongs to the field of new advanced oxidation catalyst materials. The preparation method is as follows: (1) dissolving iron nitrate nonahydrate in N,N-dimethylformamide, dissolving 2-amino terephthalic acid in N,N-dimethylformamide, and then mixing the two liquids; (2) transferring the mixed liquid into a closed reaction container and heating into a gel in a blast drying oven; (3) washing with N,N-dimethylformamide and ethanol, drying in a fume hood at room temperature to obtain a multi-level hole metal organic framework gel FeBDC-NH2; (4) transferring into a porcelain boat and placing into a tube furnace to react at high temperature under an anaerobic atmosphere, so that the magnetic multi-level hole iron-nitrogen-carbon catalyst is obtained. The catalyst prepared by the method has rich defects and excellent electron transfer capacity, the multi-level hole structure of the material accelerates the mass transfer efficiency of the catalytic reaction, the material magnetism facilitates recycling, and the material can directionally catalyze the degradation of amoxicillin by a non-free radical path through persulfate.

Description

Technical Field

[0001] The present invention relates to the field of new materials for advanced oxidation catalysts, and in particular to a magnetic multi-level porous iron-nitrogen-carbon composite material catalyst for catalyzing the efficient degradation of amoxicillin with persulfate, and a preparation and use method thereof. Background Art

[0002] Persulfate oxidation technology has become one of the most popular advanced oxidation technologies because of its ability to non-selectively degrade organic pollutants. Usually, the active oxidizing species produced during persulfate oxidation are mainly SO4 - · and ·OH. In recent years, studies have reported that persulfate catalytic systems can produce 1 Pollutants are degraded through methods such as O2, electron transfer, and high-valent metals.

[0003] Compared with active free radicals, non-radical active oxidizing substances 1 O2 has a longer life, higher selectivity and stronger anti-interference ability. Common anions and other natural substances in nature have 1 The impact of O2 oxidation process is also smaller. 1 The electrophilicity of O2 itself determines that it is more effective in removing electron-rich organic matter such as antibiotics and endocrine disruptors. 1 Persulfate oxidation technology with O2 as the main active oxidant is of great significance for achieving antibiotic degradation.

[0004] Nitrogen-doped carbon materials effectively catalyze persulfate production 1 The potential for O2 synthesis has been demonstrated. Combining metal catalysts with nitrogen-doped carbon materials not only improves the electronic structure of carbon-based catalysts but also reduces metal ion leakage and facilitates catalyst recovery. Metal-organic frameworks (MOFs), composed of metal ions and organic ligands, are excellent templates for creating metal-on-carbon materials, providing a platform for achieving the complementary advantages of these two catalyst types.

[0005] However, the predominantly microporous pore structure of metal-organic framework compounds limits the mass transfer efficiency of the catalytic reaction, and the macroscopic powder also poses a challenge to cyclic stability and recycling. CN112774634A provides a method for preparing an easily regenerated adsorbent material, which involves dispersing ferric nitrate nonahydrate and a metal-organic framework material in anhydrous ethanol to produce a powdered material of an iron-ion-loaded metal-organic framework. This method uses a composite material as a template, and the composite material synthesis steps sequentially involve metal-organic framework compound synthesis, iron ion loading, and polymer material compounding. This requires numerous synthetic raw materials and complex synthesis steps.

[0006] CN109847803A provides a defective MOF catalyst, its preparation method, and application. This method uses a five-membered heterocyclic monocarboxylic acid to in situ modify MOFs (Fe) to construct a new defective iron MOF material. The disadvantage of this method is that the pore structure of the synthesized product is still mainly microporous (accounting for 80% to 96%), which limits the mass transfer efficiency of the catalytic reaction, and the product is a powder material that is not conducive to recycling.

[0007] The present invention is proposed to construct an efficient activated persulfate non-radical pathway catalyst to achieve amoxicillin degradation, while improving the defects of MOFs materials such as single microporous structure, recycling, and water instability in the application of antibiotic degradation as advanced oxidation catalysts, and promote their practical application. Summary of the Invention

[0008] To address the aforementioned issues in the prior art, the present invention provides a method for preparing a magnetic multi-level porous iron-nitrogen-carbon catalyst and its application. The catalyst prepared by the present invention exhibits abundant defects and excellent electron transfer capabilities. Its multi-level porous structure accelerates mass transfer efficiency in the catalytic reaction, while its magnetic properties facilitate recycling. It can also catalyze the non-radical degradation of amoxicillin by persulfate.

[0009] The technical solutions of the present invention are as follows:

[0010] A method for preparing a magnetic multi-level porous iron-nitrogen-carbon catalyst comprises the following steps:

[0011] (1) dissolving ferric nitrate nonahydrate in N,N-dimethylformamide to obtain solution A, and dissolving 2-aminoterephthalic acid in N,N-dimethylformamide to obtain solution B, and then mixing solution A and solution B uniformly;

[0012] (2) transferring the mixed solution obtained in step (1) into a sealed reaction vessel and heating it in a forced air drying oven, and then gelling it to obtain a jelly-like substance;

[0013] (3) washing the colloidal substance obtained in step (2) with N,N-dimethylformamide and ethanol, and then drying the product at room temperature in a fume hood to obtain a hierarchical metal-organic framework gel FeBDC-NH2;

[0014] (4) The multi-level porous metal organic framework gel FeBDC-NH2 obtained in step (3) is transferred to a porcelain boat and placed in a tube furnace, and reacted at 400-800°C for 1-5 hours in an oxygen-free atmosphere to obtain the magnetic multi-level porous iron nitrogen carbon catalyst.

[0015] Preferably, the molar ratio of the ferric nitrate nonahydrate to 2-aminoterephthalic acid in step (1) is 1:0.8-1.2.

[0016] More preferably, in step (1), 8-13 mL of N,N-dimethylformamide is used per 1 mmol of ferric nitrate nonahydrate in solution A.

[0017] More preferably, in step (1), 8-13 mL of N,N-dimethylformamide is used per 1 mmol of 2-aminoterephthalic acid in solution B.

[0018] Preferably, the sealed reaction vessel in step (2) is a sealed glass reaction bottle with a polytetrafluoroethylene gasket, or a polytetrafluoroethylene-lined reactor.

[0019] More preferably, the heating temperature of the blast drying oven in step (2) is 75-90° C., and the heating time is 12-36 hours.

[0020] Preferably, the anaerobic atmosphere in step (4) is a nitrogen atmosphere or an argon atmosphere.

[0021] More preferably, the heating rate during the reaction in step (4) is 2-10°C / min.

[0022] The present invention also provides an application of the magnetic multi-level porous iron-nitrogen-carbon catalyst obtained by the preparation method, that is, the catalyst is used to catalyze the degradation of amoxicillin by a non-radical pathway of persulfate.

[0023] Furthermore, when the catalyst is used to catalyze the degradation of amoxicillin in water, the dosage of the catalyst is 50-200 mg / L, the dosage of the persulfate is 50-200 mg / L, and the concentration of amoxicillin is 0.5-5 mg / L.

[0024] The beneficial technical effects of the present invention are:

[0025] 1. The specific surface area of ​​the magnetic multi-level porous iron-nitrogen-carbon composite catalyst prepared by the present invention is 6-127m 2 / g, the average pore size calculated by BJH method is 4.02-16.93nm, with a micropore-mesopore-macropore ternary pore structure, in which V 微孔 :V 介孔 :V 大孔 =1:3.14-123.34:1.02-88.25.

[0026] The resulting hierarchical micropore-mesopore-macroporous structure is more conducive to mass transfer during catalytic degradation reactions, and the bulk morphology resists agglomeration, ensuring cyclic stability. Because the template contains iron, the calcined product exhibits magnetic properties and is easily recyclable. The abundant defects in the structure impart excellent electron transfer capabilities, making it an ideal advanced oxidation catalyst.

[0027] 2. The catalyst obtained by the present invention is obtained by calcining a gel-like FeBDC-NH2. The synthesis of a metal-organic framework gel template with a hierarchical pore structure is key to the multi-level pore structure of the iron-nitrogen-carbon composite catalyst. The MOF gel template obtained by the present invention has multi-level pores (micropores, mesopores, and macropores), and calcination further promotes the formation of multi-level pores in the product. In addition, the choice of ligand in the metal-organic framework gel determines the formation of nitrogen doping in the material after pyrolysis. At the same time, the coordination defects in the metal-organic framework gel itself are also important for the formation of defects in the subsequent material.

[0028] 3. The FeBDC-NH2 gel itself suffers from insufficient coordination, resulting in more structural defects after calcination, which promotes the generation of singlet oxygen. Furthermore, as a metal-organic framework compound with a macroscopic bulk morphology and a hierarchical porous structure, the carbonized material not only retains the original hierarchical porous framework but also maintains the bulk morphology, preventing agglomeration and deactivation of the powdered catalyst. The MOF gel template of the present invention is macroscopically shaped, and the calcined product is also macroscopically shaped.

[0029] 4. Compared to traditional powdered MOFs carbonization catalysts, the hierarchical pore structure of the catalyst of this invention not only provides abundant reactive sites but also promotes mass transfer efficiency in the catalytic reaction. Its macroscopic bulk structure effectively prevents the aggregation and deactivation of active sites during the catalytic process, maintaining cyclic stability. Its magnetic properties facilitate material recycling. The material's abundant defects and nitrogen-doped structure enable targeted activation of persulfate to produce reactive oxides, primarily non-radicals, for efficient degradation of amoxicillin.

[0030] 5. This invention focuses on the synthesis of FeBDC-NH2 gel. The synthesis of FeBDC-NH2 gel is first regulated. The preferred reaction conditions are N,N-dimethylformamide as the solvent, ferric nitrate as the metal salt, and a raw material concentration of 0.8-1.2M. The resulting precursor FeBDC-NH2 gel exhibits a hierarchical pore structure and a macroscopic bulk morphology. If the solvent is methanol, ethanol, or acetone, the resulting gel is a heterogeneous phase.

[0031] The type of metal salt was also optimized; using other iron salts failed to form a gel product. A raw material concentration of 0.8-1.2M was also optimized; at concentrations too low, the product remained liquid and failed to form a solid gel. Therefore, by optimizing N,N-dimethylformamide as the solvent, ferric nitrate as the metal salt, and a raw material concentration of 0.8-1.2M, the synthesized FeBDC-NH2 gel exhibited a multi-level pore structure and a macroscopic block morphology, resulting in a uniform structure that further enhanced catalyst activity.

[0032] The present invention controls the product from liquid to gel during the reaction process by adjusting the reactant concentration in the precursor to form a network gel structure with macropores and mesopores, and simultaneously controls the template calcination temperature to control the carbonization process of the pore structure and promote the formation of multi-level pores.

[0033] 6. The magnetic multi-level porous iron-nitrogen-carbon composite catalyst of the present invention can catalyze the degradation of amoxicillin by persulfate in a non-radical pathway. The amount of catalyst and persulfate used in the catalytic degradation system is relatively small, and the catalytic degradation effect (degradation rate of 97.6% in half an hour) is better than that of commercially available nano-ferrosoferric oxide (degradation rate of 45.1% in half an hour) and template metal-organic framework gel (degradation rate of 39.3% in half an hour). It has strong anti-interference ability and high cyclic stability, and can effectively achieve high-efficiency degradation of low-concentration amoxicillin, which has potential value for the practical application of this technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present invention and the solutions of the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. The drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0035] Figure 1 This is a high-resolution transmission electron microscopy image of the magnetic multi-level porous iron-nitrogen-carbon catalyst obtained in Example 1;

[0036] Figure 2 This is the nitrogen adsorption-desorption isotherm of the magnetic multi-level porous iron-nitrogen-carbon catalyst obtained in Example 1;

[0037] Figure 3 This is the pore size distribution diagram of the magnetic multi-level porous iron-nitrogen-carbon catalyst obtained in Example 1;

[0038] Figure 4 This is a magnetometer curve of the vibrating sample of the magnetic multi-level porous iron-nitrogen-carbon catalyst obtained in Example 1;

[0039] Figure 5 This is the Raman spectrum of the magnetic multi-level porous iron-nitrogen-carbon catalyst obtained in Example 1;

[0040] Figure 6 The catalytic degradation of amoxicillin by the magnetic multi-level porous iron-nitrogen-carbon obtained in Example 1 was compared with that by the metal organic framework gel template and commercially available nano-ferrosoferric oxide;

[0041] Figure 7 Magnetic hierarchical porous iron-nitrogen-carbon catalyzed persulfate degradation of amoxicillin 1 O2 capture electron spin resonance spectrum. DETAILED DESCRIPTION

[0042] The present invention is described in detail below with reference to the accompanying drawings and embodiments. It is apparent that the embodiments described are only a portion of the embodiments of the present invention, rather than all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are intended to fall within the scope of protection of the present invention.

[0043] Example 1:

[0044] (1) Dissolve 1 mmol of ferric nitrate nonahydrate in 5 mL of N,N-dimethylformamide to obtain solution A. Dissolve 1 mmol of 2-aminoterephthalic acid in another 5 mL of N,N-dimethylformamide to obtain solution B. Then, mix the two solutions evenly.

[0045] (2) Transfer the mixed solution into a sealed pressure-resistant reaction vessel. Place the sealed pressure-resistant reaction vessel in an 80°C forced air drying oven for 24 hours to obtain the product;

[0046] (3) The product was washed three times with N,N-dimethylformamide and ethanol respectively, and then dried at room temperature in a fume hood to obtain the hierarchical metal-organic framework gel FeBDC-NH2;

[0047] (4) The dried product was placed in a tubular furnace with a target temperature of 800°C and calcined. The calcination and cooling processes were carried out in an argon atmosphere. The heating rate was 5°C / min. The product was calcined at the target temperature for 3 hours and then naturally cooled to room temperature to obtain a magnetic multi-level porous iron-nitrogen-carbon composite material catalyst.

[0048] The high-resolution transmission electron microscopy image of the prepared magnetic multi-level porous iron-nitrogen-carbon composite catalyst is shown in the figure below: Figure 1 As shown, there are zero-valent iron, ferroferric oxide, FeN 0.0499 ; Nitrogen adsorption-desorption isotherms such as Figure 2 As shown, the N2 adsorption-desorption curve presents a type IV adsorption isotherm. The increase in low-pressure adsorption capacity indicates the presence of micropores in the structure, and the presence of a hysteresis loop in the high-pressure section indicates the presence of mesopores in the product structure.

[0049] The pore size distribution diagram calculated according to the BJH method is as follows Figure 3 As shown, there are micropores, mesopores and macropores in the structure, V 微孔 :V 介孔 :V 大孔 =1:123.34:88.25. The magnetometer curve of the vibrating sample of this material is as follows Figure 4 The material has the characteristics of a typical soft magnetic material, with a coercive force of 255G and a saturation magnetization of 37.8emu·g -1 , with good magnetic properties.

[0050] The Raman spectrum of this material is Figure 5, material at 1350cm -1 and 1590cm -1 There is a main peak at , where D peak represents disordered carbon and G peak represents graphite carbon. The ratio of the two peak intensities is D / I G Commonly used to characterize the defects and graphitization level of carbon-based materials, Material I D / I G The value is 0.924, indicating a high degree of defects in the material structure.

[0051] Application Example 1:

[0052] The magnetic multi-level porous iron-nitrogen-carbon composite catalyst obtained in Example 1 was compared with the commercially available nano-ferroferric oxide and template metal organic framework gel in catalyzing the degradation of amoxicillin by persulfate. The manufacturer model of the commercially available nano-ferroferric oxide is McLean I861679, and the preparation method of the template iron-based metal organic framework gel catalyst is based on the paper "Porousorganic-inorganic hybrid aerogels based on Cr 3+ / Fe 3+ and rigid bridgingcarboxylates" (Journal of Materials Chemistry, 2012, Vol. 22:1862~1867).

[0053] The experimental process of degrading amoxicillin is as follows:

[0054] Experimental water was prepared with an amoxicillin concentration of 5 mg / L, and the pH was adjusted to 7.0 with HCl and NaOH. 7.5 mg of the iron-nitrogen-carbon composite catalyst prepared in Example 1, commercially available nano-ferroferric oxide, and the template iron-based metal-organic framework gel catalyst were each added to 100 mL of experimental water. Subsequently, 5 mg of potassium persulfate was added to initiate the catalytic degradation reaction.

[0055] During the reaction, the solution was stirred at 400 r / min with a magnetic stirrer for 30 min at a temperature of 298 K. 1 mL of water was sampled with a syringe at reaction times of 0, 2.5, 5, 10, 15, 20, 30, 45, and 60 min. The water sample was filtered with a 0.22 μm aqueous filter. 10 μL of 100 mM L-histidine was then added to the water sample to quench the reaction, and the amoxicillin concentration in the sample was determined by liquid chromatography.

[0056] The results are as follows Figure 6 As shown in the figure, the degradation rate and efficiency of the magnetic multi-level porous iron-nitrogen-carbon composite catalyst are better than those of the commercially available nano-ferroferric oxide and template metal organic framework gel. 1O2 captured electron spin resonance spectrum such as Figure 7 shown.

[0057] Example 2:

[0058] (1) Dissolve 0.8 mmol of ferric nitrate nonahydrate in 5 mL of N,N-dimethylformamide to obtain solution A. Dissolve 0.8 mmol of 2-aminoterephthalic acid in another 5 mL of N,N-dimethylformamide to obtain solution B. Then, mix the two solutions evenly.

[0059] (2) transferring the mixed solution into a sealed pressure-resistant reaction vessel, placing the sealed pressure-resistant reaction vessel in a 90° C. forced air drying oven for 18 h to obtain the product;

[0060] (3) The product was washed three times with N,N-dimethylformamide and ethanol, respectively, and then dried at room temperature in a fume hood;

[0061] (4) The dried product was placed in a tubular furnace with a target temperature of 600°C and calcined. The calcination and cooling processes were carried out in an argon atmosphere. The heating rate was 10°C / min. The product was calcined at the target temperature for 4 hours and then naturally cooled to room temperature to obtain a magnetic multi-level porous iron-nitrogen-carbon composite material catalyst.

[0062] The prepared magnetic multi-level porous iron-nitrogen-carbon composite catalyst is 127m 2 / g, the average pore diameter calculated by BJH method is 4.02nm, with a multi-level pore structure, V 微孔 :V 介孔 :V 大孔 =1:3.14:1.02.

[0063] Example 3:

[0064] (1) Dissolve 0.9 mmol of ferric nitrate nonahydrate in 5 mL of N,N-dimethylformamide to obtain solution A. Dissolve 1.1 mmol of 2-aminoterephthalic acid in another 5 mL of N,N-dimethylformamide to obtain solution B. Then, mix the two solutions evenly.

[0065] (2) transferring the mixed solution into a sealed pressure-resistant reaction vessel, placing the sealed pressure-resistant reaction vessel in a 75° C. forced air drying oven for 36 hours to obtain the product;

[0066] (3) The product was washed three times with N,N-dimethylformamide and ethanol, respectively, and then dried at room temperature in a fume hood;

[0067] (4) The dried product was placed in a tubular furnace with a target temperature of 400°C and calcined. The calcination and cooling processes were carried out in an argon atmosphere. The heating rate was 2°C / min. The product was calcined at the target temperature for 1 hour and then naturally cooled to room temperature to obtain a magnetic multi-level porous iron-nitrogen-carbon composite material catalyst.

[0068] The prepared magnetic multi-level porous iron-nitrogen-carbon composite catalyst is 6m 2 / g, the average pore size calculated by BJH method is 15.41nm, with a multi-level pore structure, V 微孔 :V 介孔 :V 大孔 =1:11.41:4.77.

[0069] Comparative Example 1: Effect of Changing Synthesis Solvent on Product

[0070] Based on Example 1, the solvent N,N-dimethylformamide was replaced with methanol, ethanol and acetone. Since the solubility of the ligand 2-aminoterephthalic acid in the above solutions was low, the obtained gel product was not uniform.

[0071] Comparative Example 2: Effect of Changing the Type of Metal Salt on the Product

[0072] Based on Example 1, the ferric nitrate nonahydrate was replaced by ferrous sulfate heptahydrate, ferric chloride, and ferric acetylacetonate, respectively. The obtained product was a turbid liquid, not a gel.

[0073] Comparative Example 3: Effect of Changing Metal Salt Concentration on the Product

[0074] Based on Example 1, the concentrations of the metal salt and the ligand were diluted 2.5 times, and the obtained product was a turbid liquid, not a gel.

[0075] Based on Example 1, the concentrations of the metal salt and the ligand were diluted 5 times, and the obtained product was a turbid liquid, not a gel.

[0076] Based on Example 1, the concentrations of the metal salt and the ligand were diluted 10 times, and the obtained product was a turbid liquid, not a gel.

[0077] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the description and implementation methods. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, for those of ordinary skill in the art, various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to specific details.

Claims

1. A method for preparing a magnetic multi-level porous iron-nitrogen-carbon catalyst, characterized in that: The preparation of the catalyst comprises the following steps: (1) Dissolve ferric nitrate nonahydrate in N,N-dimethylformamide to obtain solution A, and dissolve 2-aminoterephthalic acid in N,N-dimethylformamide to obtain solution B, and then mix solution A and solution B evenly; (2) transferring the mixed solution obtained in step (1) into a sealed reaction vessel and heating it in a forced air drying oven, and then gelling it to obtain a colloid-like substance; (3) washing the colloidal substance obtained in step (2) with N,N-dimethylformamide and ethanol, and then drying the product at room temperature in a fume hood to obtain a hierarchical metal-organic framework gel FeBDC-NH2; (4) transferring the hierarchical porous metal organic framework gel FeBDC-NH2 obtained in step (3) to a porcelain boat and placing it in a tube furnace, reacting it at 400-800 °C for 1-5 hours in an oxygen-free atmosphere to obtain the magnetic hierarchical porous iron nitrogen carbon catalyst; The molar ratio of the ferric nitrate nonahydrate to 2-aminoterephthalic acid in step (1) is 1:0.8-1.2; In step (1), 1 mmol of ferric nitrate nonahydrate is dissolved in every 5 mL of N,N-dimethylformamide in solution A, and 1 mmol of 2-aminoterephthalic acid is dissolved in every 5 mL of N,N-dimethylformamide in solution B; Or in step (1), 0.8 mmol of ferric nitrate nonahydrate is dissolved in every 5 mL of N,N-dimethylformamide in solution A, and 0.8 mmol of 2-aminoterephthalic acid is dissolved in every 5 mL of N,N-dimethylformamide in solution B; Alternatively, in step (1), 0.9 mmol of ferric nitrate nonahydrate is dissolved in every 5 mL of N,N-dimethylformamide in solution A, and 1.1 mmol of 2-aminoterephthalic acid is dissolved in every 5 mL of N,N-dimethylformamide in solution B.

2. The preparation method according to claim 1, characterized in that The sealed reaction vessel in step (2) is a sealed glass reaction bottle with a polytetrafluoroethylene gasket, or a polytetrafluoroethylene-lined reactor.

3. The preparation method according to claim 1, characterized in that The heating temperature of the blast drying oven in step (2) is 75-90°C, and the heating time is 12-36 h.

4. The preparation method according to claim 1, characterized in that The oxygen-free atmosphere in step (4) is a nitrogen atmosphere or an argon atmosphere.

5. The preparation method according to claim 1, characterized in that The heating rate during the reaction of step (4) is 2-10°C / min.

6. Use of the magnetic multi-level porous iron-nitrogen-carbon catalyst obtained by the preparation method according to any one of claims 1 to 5, characterized in that: The catalyst is used for catalyzing the degradation of amoxicillin by a persulfate non-radical pathway.

7. The use according to claim 6, characterized in that When the catalyst is used to catalyze the degradation of amoxicillin in water, the dosage of the catalyst is 50-200 mg / L, the dosage of the persulfate is 50-200 mg / L, and the concentration of amoxicillin is 0.5-5 mg / L.

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