A magnetic covalent organic framework nanomaterial, its preparation method and application

Abstract

This invention discloses a method for preparing magnetic covalent organic framework nanomaterials, comprising the following steps: preparing magnetic Fe3O4 nanoparticles; preparing modified magnetic Fe3O4 nanoparticles based on the magnetic Fe3O4 nanoparticles; preparing a reaction system by reacting ethanol, water, ammonia, and ethyl silicate at a temperature of 20-40°C, then adding the prepared modified magnetic Fe3O4 nanoparticles to the reaction system for further reaction, and after the reaction is completed, washing and drying to obtain Fe3O4@SiO2 nanoparticles; using the obtained Fe3O4@SiO2 nanoparticles as a basis to prepare magnetic covalent organic framework nanomaterials Fe3O4@SiO2@COFs; compared with the prior art, the Fe3O4@SiO2@COFs prepared by this invention can still achieve a removal efficiency of over 92% for ethyl carbamate after being reused 10 times.

Description

Technical Field

[0001] This invention relates to the field of extractant preparation, specifically to a magnetic covalent organic framework nanomaterial, its preparation method, and its application. Background Technology

[0002] Various sample pretreatment methods, such as liquid-liquid extraction, solid-phase extraction, and ultrasound-assisted microextraction, have been reported for the enrichment of target analytes in complex sample matrices. However, magnetic solid-phase extraction (MSPE) is an important branch of solid-phase extraction. MSPE has attracted widespread attention due to its advantages such as fast adsorption-separation rate, low adsorbent dosage, and simple operation. Therefore, developing magnetic solid-phase extraction (MSPE) adsorbents that adsorb ethyl carbamate is crucial for improving adsorption performance.

[0003] Imino-based COFs, obtained by the dehydration condensation of aldehydes and amino groups, exhibit significantly better chemical stability compared to other COFs, thus leading to a wider range of applications. They are used as novel sensors, photocatalysts, adsorption separation materials, and electrochemical energy storage and conversion materials. Among these, the porous imino-based COFs possess a large specific surface area, hydrophobicity, mesoporous microenvironment, and excellent adsorption properties. Combining them with magnetic nanoparticles further promotes the practical application of COFs for the efficient and selective adsorption and separation of target pollutants.

[0004] In recent years, people have paid increasing attention to food safety issues. Ethyl carbamate (EC) is a toxic byproduct of metabolism and side reactions that inevitably occur during the fermentation and storage of alcoholic beverages. It is carcinogenic and teratogenic, posing a potential risk to human health. Therefore, the issue of EC in alcoholic beverages has attracted industry attention and become a new challenge for the industry. In 2006, the Joint FAO / WHO Expert Committee on Food Additives (JECFA) estimated that the lowest baseline dose (BMDL) of EC was 0.3 mg / kg body weight per day, and the average daily dietary intake (ADI) of EC from food was approximately 15 ng / kg body weight per day. Therefore, it is essential to develop simple, rapid, green, and practical methods for detecting and removing EC from various samples.

[0005] To address the aforementioned problems, patent application CN202210068436.9 discloses a method for preparing magnetic covalent organic framework nanomaterials, characterized by the following steps:

[0006] Step 1: Prepare magnetic Fe3O4 nanoparticles;

[0007] Step 2: Magnetic Fe3O4 nanoparticles are dispersed in ethanol to obtain a Fe3O4 dispersion. 2,5-Dihydroxyterephthalaldehyde is dissolved in ethanol. The Fe3O4 dispersion is mixed with the ethanol solution of 2,5-dihydroxyterephthalaldehyde, with a mass ratio of magnetic Fe3O4 nanoparticles to 2,5-dihydroxyterephthalaldehyde of 0.1–1:0.03–0.12. The resulting mixture is stirred at 30–65°C for 1–3 hours. After cooling, the reaction solution is magnetically separated to obtain the first-modified Fe3O4 nanoparticles.

[0008] Step 3: The first-modified Fe3O4 nanoparticles, 1,3,5-tris(4-aminophenyl)benzene, and 2,5-dihydroxyterephthalaldehyde were dispersed in ethanol, with the mass ratio of the first-modified Fe3O4, 1,3,5-tris(4-aminophenyl)benzene, and 2,5-dihydroxyterephthalaldehyde being 0.05–0.4:0.01–0.2:0.01–0.1. The three solutions were mixed and acetic acid solution was added. The mixture was stirred and reacted at room temperature. After the reaction was completed, magnetic separation was performed, and the nanoparticles were washed and dried to obtain the magnetic covalent organic framework nanomaterial Fe3O4@COFs.

[0009] When the magnetic covalent organic framework nanomaterial Fe3O4@COFs prepared above was applied to remove ethyl carbamate from wine, the removal efficiency of ethyl carbamate was still 88% after being reused 6 times, which is relatively low. Summary of the Invention

[0010] To address the shortcomings of existing technologies, the present invention aims to provide a magnetic covalent organic framework nanomaterial, its preparation method, and its application, thereby solving the problem that the existing Fe3O4@COFs, when applied to remove ethyl carbamate from alcohol, still achieves a relatively low removal efficiency of 88% after six repeated uses.

[0011] To achieve the above objectives, the first aspect of this invention adopts the following technical solution: a method for preparing magnetic covalent organic framework nanomaterials, comprising the following steps:

[0012] Preparation of magnetic Fe3O4 nanoparticles;

[0013] Modified magnetic Fe3O4 nanoparticles were prepared based on magnetic Fe3O4 nanoparticles.

[0014] The reaction system was prepared by reacting ethanol, water, ammonia and ethyl silicate at a temperature of 20-40℃. The prepared modified magnetic Fe3O4 nanoparticles were then added to the reaction system to continue the reaction. After the reaction was completed, Fe3O4@SiO2 nanoparticles were obtained by washing and drying.

[0015] The obtained Fe3O4@SiO2 nanoparticles were used as the basis to prepare magnetic covalent organic framework nanomaterials Fe3O4@SiO2@COFs.

[0016] The optimized preparation of the magnetic covalent organic framework nanomaterial Fe3O4@SiO2@COFs includes the following steps:

[0017] The obtained Fe3O4@SiO2 nanoparticles were mixed with fused-ring aromatic amine and 2,4,6-trihydroxypyridine trialdehyde in a solvent, and then anhydrous acetic acid was added and stirred at room temperature.

[0018] After the reaction is complete, the product is obtained by washing and drying.

[0019] The optimized molecular structure of the fused-ring aromatic amine is as follows:

[0020]

[0021] The optimized composition is that the mass ratio of Fe3O4@SiO2 nanoparticles, fused-ring aromatic amine, and 2,4,6-trihydroxybenzenetrialdehyde is 1-4:0.5-3:0.2-1.5, and the amount of anhydrous acetic acid added to each gram of Fe3O4@SiO2 nanoparticles is 10-50 mL.

[0022] The optimized preparation of the magnetic Fe3O4 nanoparticles includes the following steps:

[0023] Under an inert gas environment, FeCl3·6H2O and FeCl2·4H2O are dissolved and then ammonia water is added and the reaction is carried out at 40-60℃.

[0024] After the reaction is complete, the product is obtained through separation and washing.

[0025] The optimized concentration of FeCl3·6H2O is 0.05–0.1 mol / L, the molar ratio of FeCl3·6H2O to FeCl2·4H2O is 1.8–2.2:1, the mass percentage of solute in ammonia water is 25–28%, and the amount of ammonia water added to each millimole of FeCl3·6H2O is 1.2–1.8 mL.

[0026] The optimized preparation of the modified magnetic Fe3O4 nanoparticles includes the following steps:

[0027] Magnetic Fe3O4 nanoparticles were ultrasonically mixed with a silane coupling agent solution and then reacted at a temperature of 75–85 °C.

[0028] After the reaction is complete, the temperature is lowered to 20-40°C, then a surfactant is added and ultrasonically emulsified and dispersed, followed by centrifugation to obtain the final product.

[0029] Optimized, the silane coupling agent is at least one of KH550, KH560 and KH570.

[0030] The second aspect of the present invention adopts the following technical solution: a magnetic covalent organic framework nanomaterial, which is prepared by the preparation method of the magnetic covalent organic framework nanomaterial.

[0031] The third aspect of this invention adopts the following technical solution: the application of a magnetic covalent organic framework nanomaterial, wherein the magnetic covalent organic framework nanomaterial is used as an extractant to remove ethyl carbamate from wine.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1. The Fe3O4@SiO2@COFs prepared in this invention have SiO2 coated on the surface of magnetic Fe3O4, and then covalent organic frameworks (COFs) with mesoporous structures are further prepared on the surface. This method helps to improve the monodispersity and chemical stability of the material and broaden the application fields of the material.

[0034] 2. The Fe3O4@SiO2@COFs prepared by this invention have abundant hydroxyl and amine groups on their surface, resulting in a large number of negative charges on the material surface. Meanwhile, the target compound urethane is weakly alkaline in solution and has a positive charge on its surface, thus exhibiting good adsorption properties.

[0035] 3. This invention utilizes the abundant amine and hydroxyl groups of COFs material monomer molecules, which provide a large number of reaction sites. This results in the prepared Fe3O4@SiO2@COFs having a large specific surface area, rich spatial structure, and abundant adsorption sites, thus achieving efficient adsorption and separation while maintaining high adsorption capacity.

[0036] 4. After the Fe3O4@SiO2@COFs prepared in this invention are reused 10 times, the removal efficiency of ethyl carbamate can still reach more than 92%. Detailed Implementation

[0037] The present invention will be further described in detail below through specific embodiments:

[0038] A method for preparing magnetic covalent organic framework nanomaterials includes the following steps:

[0039] Preparation of magnetic Fe3O4 nanoparticles;

[0040] Modified magnetic Fe3O4 nanoparticles were prepared based on magnetic Fe3O4 nanoparticles.

[0041] The reaction system was prepared by reacting ethanol, water, ammonia and ethyl silicate at a temperature of 20-40℃. The prepared modified magnetic Fe3O4 nanoparticles were then added to the reaction system to continue the reaction. After the reaction was completed, Fe3O4@SiO2 nanoparticles were obtained by washing and drying.

[0042] The obtained Fe3O4@SiO2 nanoparticles were used as the basis to prepare magnetic covalent organic framework nanomaterials Fe3O4@SiO2@COFs.

[0043] The optimized preparation of the magnetic covalent organic framework nanomaterial Fe3O4@SiO2@COFs includes the following steps:

[0044] The obtained Fe3O4@SiO2 nanoparticles were mixed with fused-ring aromatic amine and 2,4,6-trihydroxypyridine trialdehyde in a solvent, and then anhydrous acetic acid was added and stirred at room temperature.

[0045] After the reaction is complete, the product is obtained by washing and drying.

[0046] The optimized molecular structure of the fused-ring aromatic amine is as follows:

[0047]

[0048] Fused ring aromatic amines contain a large number of amino groups, which can react with the hydroxyl groups in 2,4,6-trihydroxybenzenetrialdehyde to form a more stable network structure to coat the outer side of Fe3O4@SiO2 nanoparticles.

[0049] Optimally, the mass ratio of Fe3O4@SiO2 nanoparticles, fused-ring aromatic amine, and 2,4,6-trihydroxypyromellitic aldehyde is 1–4:0.5–3:0.2–1.5, and the amount of anhydrous acetic acid added per gram of Fe3O4@SiO2 nanoparticles is 10–50 mL. Specifically, the mass ratio of Fe3O4@SiO2 nanoparticles, fused-ring aromatic amine, and 2,4,6-trihydroxypyromellitic aldehyde can be 1:0.5:0.2, 2:3:1.5, 1:3:0.2, or 4:0.5:1.5, etc., and the amount of anhydrous acetic acid added per gram of Fe3O4@SiO2 nanoparticles can be 10 mL, 20 mL, 30 mL, 40 mL, or 50 mL.

[0050] The optimized preparation of the magnetic Fe3O4 nanoparticles includes the following steps:

[0051] Under an inert gas environment, FeCl3·6H2O and FeCl2·4H2O are dissolved and then ammonia water is added and the reaction is carried out at 40-60℃.

[0052] After the reaction is complete, the product is obtained through separation and washing.

[0053] Optimized, the concentration of FeCl3·6H2O is 0.05–0.1 mol / L, the molar ratio of FeCl3·6H2O to FeCl2·4H2O is 1.8–2.2:1, the mass percentage of solute in the ammonia solution is 25–28%, and the amount of ammonia solution added per millimole of FeCl3·6H2O is 1.2–1.8 mL. Specifically, the concentration of FeCl3·6H2O is 0.05 mol / L, 0.08 mol / L, or 0.1 mol / L, etc., and the molar ratio of FeCl3·6H2O to FeCl2·4H2O is 1.8:1, 2:1, or 2.2:1, etc.; the ammonia solution is commercially available, and the amount of ammonia solution added per millimole of FeCl3·6H2O is 1.2 mL, 1.4 mL, 1.5 mL, 1.7 mL, or 1.8 mL, etc.

[0054] The optimized preparation of the modified magnetic Fe3O4 nanoparticles includes the following steps:

[0055] Magnetic Fe3O4 nanoparticles were ultrasonically mixed with a silane coupling agent solution and then reacted at a temperature of 75–85 °C.

[0056] After the reaction is complete, the temperature is lowered to 20-40°C, then a surfactant is added and ultrasonically emulsified and dispersed, followed by centrifugation to obtain the final product.

[0057] Optimally, the silane coupling agent is at least one of KH550, KH560, and KH570. Specifically, the silane coupling agent can be a combination of KH550, KH560, KH570, a combination of KH550 and KH560, or a combination of KH560 and KH570, etc.

[0058] Optimized, the surfactant can be SDS, and the concentration of SDS is 1-3 g / L, specifically 1 g / L, 2 g / L or 3 g / L, etc.

[0059] The magnetic covalent organic framework nanomaterial disclosed in this invention has a spherical particle structure, wherein the spherical particles are composed of SiO2-coated magnetic Fe3O4 nanoparticles and a covalent organic framework with a mesoporous structure attached to the surface of the nanoparticles; and the particle size range of the Fe3O4@SiO2@COFs magnetic covalent organic framework nanomaterial is 100-400 nm, and the pore size of the mesoporous covalent organic framework is 2-30 nm.

[0060] This invention also discloses a method for using Fe3O4@SiO2@COFs magnetic covalent organic framework nanomaterials prepared by the method of this invention as an extractant to remove ethyl carbamate from wine, combined with gas chromatography detection.

[0061] Specifically:

[0062] (1) Preparation of standard solution: Accurately weigh 100 mg EC into a 100 mL volumetric flask, dissolve and dilute to volume with methanol to obtain a 1.0 mg / mL stock solution, and store at 4 °C for later use. The working concentrations of the standard curve are 2 μg / mL, 1.5 μg / mL, 1.2 μg / mL, 0.8 μg / mL, 0.5 μg / mL, 0.1 μg / mL, and 0.05 μg / mL.

[0063] (2) Pretreatment of the wine samples to be tested: Baijiu samples of different aroma types were diluted with ultrapure water at a ratio of 1:6 to reduce matrix interference before the extraction process.

[0064] (3) Magnetic solid-phase adsorption: Fe3O4@SiO2@COFs magnetic covalent organic framework nanomaterials were mixed with wine samples, wherein the volume ratio of wine sample to Fe3O4@SiO2@COFs material was 1 ml: 2 mg; after adsorption and standing for 20 min, the mixture was eluted with n-hexane, the eluent was discarded, and then eluted with 25 mL of 5% ethyl acetate-ether solution (referring to a 5% solution prepared with ethyl acetate as solute and ether as solvent). The eluent was collected and blown with nitrogen until nearly dry.

[0065] The extraction process of this invention does not require the use of large amounts of organic solvents, and the operation is simple and convenient; it solves the problems of using large amounts of organic solvents and time consumption in traditional extraction and separation methods.

[0066] This invention is not limited to baijiu (Chinese white liquor), but is also applicable to huangjiu (yellow wine), wine, etc.

[0067] Example 1:

[0068] Step 1: Dissolve 0.01 mol of FeCl3·6H2O and 0.0055 mol of FeCl2·4H2O in 200 mL of ultrapure water, and purge with nitrogen gas. Then add 18 mL of ammonia water. React at 40 °C for 60 min. Separate the reaction products with a magnet and then wash with ultrapure water to remove unreacted ammonia water to obtain magnetic Fe3O4 nanoparticles.

[0069] Step 2: Take 0.5g of the magnetic Fe3O4 nanoparticles obtained in Step 1 and 100mL of 1% KH550 solution, mix them by sonication for 5min, and then react them at 80℃ for 8 hours; then cool down to 40℃, add 0.3g of SDS, and sonicate and disperse for 20min; then centrifuge to obtain surface-modified magnetic Fe3O4 nanoparticles.

[0070] Step 3: Mix 50 mL of ethanol, 1 mL of ultrapure water, 1.5 mL of ammonia and 0.3 mL of tetraethyl orthosilicate (TEOS), and stir at 40 °C for 20 min. Then, add 0.2 g of the surface-modified magnetic Fe3O4 nanoparticles obtained in Step 2 to the reaction system and continue stirring at 40 °C for 5 h. Finally, wash the obtained nanoparticles thoroughly with water and ethanol, and dry them with nitrogen to obtain Fe3O4@SiO2 nanoparticles.

[0071] Step 4: Take 0.1g of Fe3O4@SiO2 nanoparticles obtained in Step 3, 0.08g of fused-ring aromatic amine, and 0.04g of 2,4,6-trihydroxypyromellitic aldehyde and mix them in 50mL of ethanol. Then add 5mL of anhydrous acetic acid and stir the mixture at room temperature for 48h. After the reaction is completed, perform magnetic separation, wash and dry to obtain the magnetic covalent organic framework nanomaterial Fe3O4@SiO2@COFs.

[0072] The prepared Fe3O4@SiO2@COFs have a particle size range of 140 nm, and the pore size of the mesoporous covalent organic framework is 3 nm.

[0073] The prepared Fe3O4@SiO2@COFs were used as an extractant to remove ethyl carbamate from wine. In this embodiment, the detection equipment was a two-dimensional gas chromatography-quadrupole time-of-flight high-resolution mass spectrometer. Specifically:

[0074] (1) Preparation of standard solution: Accurately weigh 100 mg EC into a 100 mL volumetric flask, dissolve and dilute to volume with methanol to obtain a 1.0 mg / mL stock solution, and store at 4 °C for later use. The working concentrations of the standard curve are 2 μg / mL, 1.5 μg / mL, 1.2 μg / mL, 0.8 μg / mL, 0.5 μg / mL, 0.1 μg / mL, and 0.05 μg / mL.

[0075] (2) Pretreatment of the wine samples to be tested: Different wine samples were diluted with ultrapure water at a ratio of 1:6 to reduce matrix interference before the extraction process.

[0076] (3) Magnetic solid phase adsorption: Fe3O4@SiO2@COFs was mixed with wine sample, wherein the volume of wine sample was 1 ml and Fe3O4@SiO2@COFs was 2 mg; after adsorption and standing for 20 min, it was eluted with n-hexane, the eluent was discarded, and then eluted with 25 mL of 5% ethyl acetate-ether solution. The eluent was collected and blown with nitrogen until nearly dry.

[0077] The Fe3O4@SiO2@COFs prepared in this embodiment removes ethyl carbamate (concentration of 1.0 μg / mL, 1 mL standard sample) with a removal efficiency of 95.6%. After 10 cycles of use, the removal efficiency of ethyl carbamate (concentration of 1.0 μg / mL, 1 mL standard sample) reaches over 93%.

[0078] Take 1 mL of each of the five different baijiu samples after treatment, and then add 1 μg / mL of urethane. After magnetic solid-phase adsorption, the removal efficiency of urethane reached over 92%.

[0079] Example 2:

[0080] Step 1: Dissolve 0.015 mol of FeCl3·6H2O and 0.008 mol of FeCl2·4H2O in 200 mL of ultrapure water, and purge with nitrogen gas. Then add 12 mL of ammonia water. React at 60 °C for 30 min. Separate the reaction products with a magnet and then wash with ultrapure water to remove unreacted ammonia water to obtain magnetic Fe3O4 nanoparticles.

[0081] Step 2: Take 0.5g of the magnetic Fe3O4 nanoparticles obtained in Step 1 and 100mL of KH560 solution with a mass fraction of 0.75%, mix ultrasonically for 5min, and then react at 80℃ for 6 hours; then cool down to 30℃, add 0.2g of SDS, and ultrasonically emulsify and disperse for 30min; then centrifuge to obtain surface-modified magnetic Fe3O4 nanoparticles.

[0082] Step 3: Mix 50 mL of ethanol, 1 mL of ultrapure water, 1.5 mL of ammonia and 0.3 mL of tetraethyl orthosilicate (TEOS), and stir at 30 °C for 40 min. Then, add 0.2 g of the surface-modified magnetic Fe3O4 nanoparticles obtained in Step 2 to the reaction system and continue stirring at 30 °C for 4 h. Finally, wash the obtained nanoparticles thoroughly with water and ethanol, and dry them with nitrogen to obtain Fe3O4@SiO2 nanoparticles.

[0083] Step 4: Take 0.1g of Fe3O4@SiO2 nanoparticles obtained in Step 3, 0.3g of fused-ring aromatic amine, and 0.1g of 2,4,6-trihydroxybenzenetrialdehyde and mix them in 50mL of ethanol. Then add 5mL of anhydrous acetic acid and stir the mixture at room temperature for 36h. After the reaction is completed, perform magnetic separation, wash and dry to obtain the magnetic covalent organic framework nanomaterial Fe3O4@SiO2@COFs.

[0084] The prepared Fe3O4@SiO2@COFs have a particle size range of 280 nm and a pore size of 4 nm for the mesoporous covalent organic framework.

[0085] The prepared Fe3O4@SiO2@COFs were used as an extractant to remove ethyl carbamate from wine, and the specific implementation steps and methods were the same as in Example 1.

[0086] The Fe3O4@SiO2@COFs prepared in this embodiment removes ethyl carbamate (concentration of 1.0 μg / mL, 1 mL standard sample), achieving a removal efficiency of 96.7%. After 10 cycles of use, the removal efficiency of ethyl carbamate (concentration of 1.0 μg / mL, 1 mL standard sample) reaches over 94.5%.

[0087] Take 1 mL of each of the five different baijiu samples after treatment, and then add 1 μg / mL of urethane. After magnetic solid-phase adsorption, the removal efficiency of urethane reached over 94%.

[0088] Example 3:

[0089] Step 1: Dissolve 0.02 mol of FeCl3·6H2O and 0.0091 mol of FeCl2·4H2O in 200 mL of ultrapure water, and purge with nitrogen gas. Then add 15 mL of ammonia water. React at 60 °C for 30 min. Separate the reaction products with a magnet and then wash with ultrapure water to remove unreacted ammonia water to obtain magnetic Fe3O4 nanoparticles.

[0090] Step 2: Take 0.5g of the magnetic Fe3O4 nanoparticles obtained in Step 1 and 100mL of KH570 solution with a mass fraction of 1%, mix ultrasonically for 5min, and then react at 80℃ for 4h; then cool down to 20℃, add 0.1g of SDS, and ultrasonically emulsify and disperse for 40min; then centrifuge to obtain surface-modified magnetic Fe3O4 nanoparticles.

[0091] Step 3: Mix 50 mL of ethanol, 1 mL of ultrapure water, 1.5 mL of ammonia and 0.3 mL of tetraethyl orthosilicate (TEOS), and stir at 30 °C for 40 min. Then, add 0.2 g of the surface-modified magnetic Fe3O4 nanoparticles obtained in Step 2 to the reaction system and continue stirring at 40 °C for 2 h. Then, wash the obtained nanoparticles thoroughly with water and ethanol, and dry them with nitrogen to obtain Fe3O4@SiO2 nanoparticles.

[0092] Step 4: Take 0.1g of Fe3O4@SiO2 nanoparticles obtained in Step 3, 0.2g of fused-ring aromatic amine, and 0.09g of 2,4,6-trihydroxypyromellitic aldehyde and mix them in 50mL of ethanol. Then add 4mL of anhydrous acetic acid and stir the mixture at room temperature for 24h. After the reaction is completed, perform magnetic separation, wash and dry to obtain the magnetic covalent organic framework nanomaterial Fe3O4@SiO2@COFs.

[0093] The prepared Fe3O4@SiO2@COFs have a particle size range of 230 nm and a pore size of 4 nm for the mesoporous covalent organic framework.

[0094] The prepared Fe3O4@SiO2@COFs were used as an extractant to remove ethyl carbamate from wine, and the specific implementation steps and methods were the same as in Example 1.

[0095] The Fe3O4@SiO2@COFs prepared in this embodiment removes ethyl carbamate (concentration of 1.0 μg / mL, 1 mL standard sample), achieving a removal efficiency of 94.8%. After 10 cycles of use, the removal efficiency of ethyl carbamate (concentration of 1.0 μg / mL, 1 mL standard sample) reaches over 92.6%.

[0096] Take 1 mL of each of the five different baijiu samples after treatment, and then add 1 μg / mL of urethane. After magnetic solid-phase adsorption, the removal efficiency of urethane reached over 92%.

[0097] Comparative Example 1

[0098] The only difference from Example 1 is that step 3 is not performed and the Fe3O4@SiO2 nanoparticles added in step 4 are replaced with an equal amount of surface-modified magnetic Fe3O4 nanoparticles obtained in step 3, so that Fe3O4@COFs magnetic covalent organic framework nanomaterials are finally obtained.

[0099] The prepared Fe3O4@COFs magnetic covalent organic framework nanomaterials have a particle size range of 280 nm, and the pore size of the mesoporous covalent organic framework is 6 nm.

[0100] The prepared Fe3O4@COFs magnetic covalent organic framework nanomaterial was used as an extractant to remove ethyl carbamate from wine. The specific implementation steps and methods are the same as in Example 1.

[0101] The Fe3O4@COFs magnetic covalent organic framework nanomaterials prepared in this embodiment were used to remove ethyl carbamate (concentration of 1.0 μg / mL, 1 mL standard sample). The removal efficiency of ethyl carbamate reached 90%. After 10 cycles of use, the removal efficiency of ethyl carbamate (concentration of 1.0 μg / mL, 1 mL standard sample) reached more than 89%.

[0102] Take 1 mL of each of the five different baijiu samples after treatment, and then add 1 μg / mL of urethane. After magnetic solid-phase adsorption, the removal efficiency of urethane reached over 87.6%.

[0103] Comparative Example 2

[0104] The only difference from Example 2 is that step 3 is not performed and the Fe3O4@SiO2 nanoparticles added in step 4 are replaced with an equal amount of surface-modified magnetic Fe3O4 nanoparticles obtained in step 3, so that Fe3O4@COFs magnetic covalent organic framework nanomaterials are finally obtained.

[0105] The prepared Fe3O4@COFs magnetic covalent organic framework nanomaterials have a particle size range of 280 nm, and the pore size of the mesoporous covalent organic framework is 4 nm.

[0106] The prepared Fe3O4@COFs magnetic covalent organic framework nanomaterial was used as an extractant to remove ethyl carbamate from wine. The specific implementation steps and methods are the same as in Example 1.

[0107] The Fe3O4@COFs magnetic covalent organic framework nanomaterials prepared in this embodiment achieved a urethane removal efficiency of 89.5% (concentration of 1.0 μg / mL and 1 mL standard sample). After 10 cycles of use, the urethane removal efficiency reached over 86.3%.

[0108] Take 1 mL of each of the five different baijiu samples after treatment, and then add 1 μg / mL of urethane. After magnetic solid-phase adsorption, the removal efficiency of urethane reached over 88.2%.

[0109] Comparative Example 3

[0110] The only difference from Example 1 is that in step 4, 2,4,6-trihydroxypyromellitic aldehyde is replaced with 2,5-dihydroxyterephthalaldehyde.

[0111] The Fe3O4@SiO2@COFs prepared in this comparative example achieved a urethane removal efficiency of 88.5% (concentration of 1.0 μg / mL and 1 mL standard sample). After 10 cycles of use, the urethane removal efficiency reached over 82.3%.

[0112] Take 1 mL of each of the five different baijiu samples after treatment, and then add ethyl carbamate at a concentration of 1 μg / mL. After magnetic solid-phase adsorption, the removal efficiency of ethyl carbamate reached over 81.5%.

[0113] Comparative Example 4

[0114] The only difference from Example 1 is that in step 4, the fused-ring aromatic amine is replaced with 1,3,5-tris(4-aminophenyl)benzene.

[0115] The Fe3O4@SiO2@COFs prepared in this comparative example achieved a urethane removal efficiency of 87.2% (concentration of 1.0 μg / mL and 1 mL standard sample). After 10 cycles of use, the urethane removal efficiency reached over 80.4%.

[0116] Take 1 mL of each of the five different baijiu samples after treatment, and then add 1 μg / mL of urethane. After magnetic solid-phase adsorption, the removal efficiency of urethane reached over 80.1%.

[0117] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing magnetic covalent organic framework nanomaterials for removing urethane from wine, characterized in that, Includes the following steps: Preparation of magnetic Fe3O4 nanoparticles; Modified magnetic Fe3O4 nanoparticles were prepared based on magnetic Fe3O4 nanoparticles. The reaction system was prepared by reacting ethanol, water, ammonia and ethyl silicate at a temperature of 20-40℃. The prepared modified magnetic Fe3O4 nanoparticles were then added to the reaction system to continue the reaction. After the reaction was completed, Fe3O4@SiO2 nanoparticles were obtained by washing and drying. The obtained Fe3O4@SiO2 nanoparticles were used as the basis to prepare magnetic covalent organic framework nanomaterials Fe3O4@SiO2@COFs; The preparation of the modified magnetic Fe3O4 nanoparticles includes the following steps: Magnetic Fe3O4 nanoparticles were ultrasonically mixed with a silane coupling agent solution and then reacted at a temperature of 75-85℃. After the reaction is complete, the temperature is lowered to 20~40℃, then a surfactant is added and ultrasonically emulsified and dispersed, followed by centrifugation to obtain the final product. The preparation of the magnetic covalent organic framework nanomaterial Fe3O4@SiO2@COFs includes the following steps: The obtained Fe3O4@SiO2 nanoparticles were mixed with fused-ring aromatic amine and 2,4,6-trihydroxypyridine trialdehyde in a solvent, and then anhydrous acetic acid was added and stirred at room temperature. After the reaction is complete, the product is obtained by washing and drying. The molecular structure of the fused-ring aromatic amine is as follows:

2. The method for preparing magnetic covalent organic framework nanomaterials according to claim 1, characterized in that: The mass ratio of Fe3O4@SiO2 nanoparticles, fused-ring aromatic amine, and 2,4,6-trihydroxybenzyltrialdehyde is 1~4:0.5~3:0.2~1.5, and the amount of anhydrous acetic acid added to each gram of Fe3O4@SiO2 nanoparticles is 10~50 mL.

3. The method for preparing magnetic covalent organic framework nanomaterials according to claim 1, characterized in that: Preparation of the magnetic Fe3O4 nanoparticles Includes the following steps: Under an inert gas environment, FeCl3·6H2O and FeCl2·4H2O are dissolved and then ammonia water is added and the reaction is carried out at 40~60℃. After the reaction is complete, the product is obtained through separation and washing.

4. The method for preparing magnetic covalent organic framework nanomaterials according to claim 3, characterized in that: The concentration of FeCl3·6H2O is 0.05~0.1mol / L, the molar ratio of FeCl3·6H2O to FeCl2·4H2O is 1.8~2.2:1, the mass percentage of solute in ammonia water is 25-28%, and the amount of ammonia water added to each millimole of FeCl3·6H2O is 1.2~1.8mL.

5. The method for preparing magnetic covalent organic framework nanomaterials according to claim 1, characterized in that, The silane coupling agent is at least one of KH550, KH560 and KH570.

6. A magnetic covalent organic framework nanomaterial, characterized in that, The magnetic covalent organic framework nanomaterials are prepared by any one of claims 1-5.

7. An application of the magnetic covalent organic framework nanomaterial as described in claim 6, characterized in that, The application involves using magnetic covalent organic framework nanomaterials as extractants to remove ethyl carbamate from wine.

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