A magnetic calix[4]arene covalent organic framework as well as a preparation method and application thereof

Abstract

The application discloses a kind of magnetic calix [4] areal covalent organic framework and its preparation method and application, it is related to organic compound technical field.The magnetic calix [4] areal covalent organic framework of the application has core-shell structure, with magnetic nano particle as core;With aldehyde group calix [4] areal connection and 4,4'-diamino azobenzene covalent organic framework formed as shell.The magnetic calix [4] areal covalent organic framework of the application has excellent adsorption performance, strong enrichment capacity, also has the characteristics of high saturation magnetization, can satisfy magnetic separation demand, and good thermal stability, can be repeatedly used.The magnetic calix [4] areal covalent organic framework can be used for fusarium toxin detection, also has practical application value in food analysis and environmental analysis.

Description

Technical Field

[0001] This invention relates to the field of organic compound technology, and in particular to a magnetic cup[4] aromatic covalent organic framework, its preparation method and application. Background Technology

[0002] The inherent cavity of calixarenes endows them with host-guest recognition capabilities. They contain abundant hydroxyl and aromatic groups, providing numerous adsorption sites through hydrogen bonding and π-π interactions. Furthermore, calixarenes are easily functionalized, allowing for the modification of different functional groups as needed, and have been used to construct macrocyclic covalent organic polymers. Among these, macrocyclic covalent organic frameworks, possessing both the inherent cavity of macrocyclic molecules and the porosity and structural order of covalent organic frameworks, show great potential for application in adsorption separation.

[0003] However, calixarenes are nonplanar, making their introduction into ordered framework materials challenging. Furthermore, as the cavity size increases, their conformation becomes more flexible, further complicating the formation of covalent organic frameworks and limiting their applications in adsorption media. In addition, covalent organic frameworks typically require relatively harsh reaction conditions for synthesis, which also significantly restricts their practical applications. Summary of the Invention

[0004] The present invention aims to at least solve one of the above-mentioned technical problems existing in the prior art. To this end, the purpose of the present invention is to provide a magnetic cup[4] aromatic covalent organic framework that retains the cavity of the macrocyclic main molecule and also has the advantages of a covalent organic framework, with excellent enrichment and adsorption effects, and can be used as an adsorption medium.

[0005] A second aspect of the present invention is to provide a method for preparing a magnetic cup[4] aromatic covalent organic framework.

[0006] A third aspect of the present invention is to provide an adsorption medium.

[0007] A fourth aspect of the present invention is to provide an application of a magnetic cup[4] aromatic covalent organic framework or adsorption medium.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] The first aspect of the present invention provides a magnetic calix [4] aromatic covalent organic framework, wherein the magnetic calix [4] aromatic covalent organic framework has a core-shell structure, wherein the inner shell is a magnetic nanoparticle, and the outer shell is a covalent organic framework formed by linking aldehyde-modified calix [4] aromatic hydrocarbon and 4,4'-diaminoazobenzene.

[0010] The magnetic calix[4]arene covalent organic framework of the present invention uses magnetic nanoparticles as the magnetic core, and aldehyde-modified calix[4]arene and 4,4'-diaminoazobenzene are connected by reversible covalent bonds to form an ordered network structure. The resulting covalent organic framework is coated on the surface of the magnetic nanoparticles as a shell. This magnetic calix[4]arene covalent organic framework has the unique cavity structure of calix[4]arene and the porosity and orderliness of covalent organic frameworks, which can provide unique host-guest recognition function and rich recognition sites. It has a strong binding ability for a variety of compounds and a strong adsorption and enrichment ability. At the same time, the magnetic nanoparticle core makes the magnetic calix[4]arene covalent organic framework have a high saturation magnetization intensity, which can meet the requirements of magnetic separation. This also makes the magnetic calix[4]arene covalent organic framework easy to recover and reuse after application.

[0011] In some embodiments of the present invention, the mass ratio of the magnetic nanoparticles to the aldehyde-modified calix[4]arene is 1:(0.5-2).

[0012] In some embodiments of the present invention, the mass ratio of the magnetic nanoparticles to the aldehyde-modified calix[4]arene is 1:(0.5-1).

[0013] In some specific embodiments of the present invention, the mass ratio of the magnetic nanoparticles to the aldehyde-modified calix[4]arene is 1:(0.6-0.7).

[0014] In some embodiments of the present invention, the mass ratio of the aldehyde-modified calix[4] aryl hydrocarbon to 4,4'-diaminoazobenzene is 1:(0.6-1).

[0015] In some embodiments of the present invention, the mass ratio of the aldehyde-modified calix[4] aromatic hydrocarbon to 4,4'-diaminoazobenzene is 1:(0.8-1).

[0016] In some embodiments of the present invention, the magnetic nanoparticles include at least one of NiFe2O4 and Fe3O4.

[0017] In some embodiments of the present invention, the magnetic nanoparticles have a particle size of 50–200 nm.

[0018] In some embodiments of the present invention, the magnetic nanoparticles have a particle size of 70–100 nm.

[0019] In some embodiments of the present invention, the magnetic cup[4] aromatic covalent organic framework has a microporous structure.

[0020] In some embodiments of the present invention, the specific surface area of ​​the magnetic cup [4] aromatic covalent organic framework is 35-55 m². 2 / g.

[0021] In some embodiments of the present invention, the specific surface area of ​​the magnetic cup [4] aromatic covalent organic framework is 40-50 m². 2 / g.

[0022] In some specific embodiments of the present invention, the specific surface area of ​​the magnetic cup [4] aromatic covalent organic framework is 40-45 m². 2 / g.

[0023] In some embodiments of the present invention, the saturation magnetization of the magnetic cup [4] aromatic covalent organic framework is 24 to 37 emu / g.

[0024] In some embodiments of the present invention, the saturation magnetization of the magnetic cup [4] aromatic covalent organic framework is 25-35 emu / g.

[0025] In some specific embodiments of the present invention, the saturation magnetization of the magnetic cup [4] aromatic covalent organic framework is 28-32 emu / g.

[0026] In some embodiments of the present invention, the magnetic cup[4] aromatic covalent organic framework has a rounded square morphology.

[0027] The magnetic cup[4] of the present invention has good crystallinity and its overall morphology is a rounded square.

[0028] A second aspect of the present invention provides a method for preparing the magnetic cup [4] aromatic covalent organic framework described in the first aspect of the present invention, comprising the following steps:

[0029] The magnetic nanoparticles, the 4,4'-diaminoazobenzene, and the aldehyde-modified calix[4] aromatic hydrocarbon are mixed in 1,3,5-trimethylbenzene and reacted to obtain the final product.

[0030] The magnetic cup[4] aromatic covalent organic framework of the present invention is prepared under mild conditions. By using mild reaction conditions, calixarene is introduced into the covalent organic framework material, thereby realizing the simple preparation of calixarene-based covalent organic framework.

[0031] Reaction in 1,3,5-trimethylbenzene facilitates the formation of a covalent organic framework.

[0032] The preparation method provided by this invention has the advantages of being mild, simple, and efficient.

[0033] In some embodiments of the present invention, the reaction is carried out at room temperature.

[0034] In some embodiments of the present invention, the magnetic nanoparticles and the 4,4'-diaminoazobenzene are mixed and dispersed in 1,3,5-trimethylbenzene, and then the aldehyde-modified calix[4] aromatic hydrocarbon is added.

[0035] In some embodiments of the present invention, after adding the aldehyde-modified calix[4] aromatic hydrocarbon, an aqueous solution of acetic acid is added, and the mixture is then mixed and dispersed.

[0036] In some embodiments of the present invention, the concentration of the aqueous acetic acid solution is 6 to 9 mol / L.

[0037] In some embodiments of the present invention, the molar ratio of the aldehyde-modified calix[4]arene, 1,3,5-trimethylbenzene to acetic acid is 1:(760-770):(125-200).

[0038] In some embodiments of the present invention, the reaction is carried out under stirring conditions.

[0039] In some embodiments of the present invention, the stirring time is 20 to 48 hours.

[0040] In some specific embodiments of the present invention, the stirring time is 20 to 30 hours.

[0041] In some examples of the present invention, the stirring time is 23 to 26 hours.

[0042] In some embodiments of the present invention, after the reaction is completed, the following steps are further included: collecting the reaction products using a magnet, washing and drying them.

[0043] In some embodiments of the present invention, the washing solvent includes tetrahydrofuran and / or methanol.

[0044] In some embodiments of the present invention, the drying temperature is 40–80°C; the drying time is 20–48 h.

[0045] In some specific embodiments of the present invention, the drying temperature is 50-70°C; the drying time is 20-30 hours.

[0046] In some examples of the present invention, the drying temperature is 55-65°C; the drying time is 23-16 hours.

[0047] In some embodiments of the present invention, the preparation method of the aldehyde-modified calix[4]arene includes the following steps:

[0048] Calico[4] aromatics and hexamethylenetetramine were added to trifluoroacetic acid, heated, and refluxed. Inorganic acid and dichloromethane were added, mixed, allowed to stand and separate into layers, and the organic phase was extracted, which was aldehyde-modified calix[4] aromatics.

[0049] Trifluoroacetic acid is used as a solvent, and dichloromethane is used as an extractant.

[0050] In some embodiments of the present invention, the extraction process includes taking an organic phase, washing, and rotary evaporation.

[0051] In some embodiments of the present invention, the mass ratio of the calixarene to hexamethylenetetramine is 1:(10-14).

[0052] In some embodiments of the present invention, the temperature of the reflux reaction is 80–100°C.

[0053] In some embodiments of the present invention, the reflux reaction time is 23 to 25 hours.

[0054] In some embodiments of the present invention, the inorganic acid is dilute hydrochloric acid; the concentration of the dilute hydrochloric acid is 0.5 to 1.5 mol / L.

[0055] In some embodiments of the present invention, the magnetic nanoparticles are NiFe2O4.

[0056] In some embodiments of the present invention, the preparation method of the magnetic NiFe2O4 includes the following steps:

[0057] The soluble iron salt, urea, and soluble nickel salt are mixed and dissolved in water, and then subjected to a solvothermal reaction to obtain the product.

[0058] In some embodiments of the present invention, the mass ratio of the soluble iron salt, urea and soluble nickel salt is 1:(1-2):(0.3-0.5).

[0059] In some embodiments of the present invention, the soluble iron salt and the soluble nickel salt are both chloride salts.

[0060] In some embodiments of the present invention, the temperature of the solvothermal reaction is 160–200°C.

[0061] In some embodiments of the present invention, the solvothermal reaction time is 8 to 12 hours.

[0062] In some embodiments of the present invention, the solvothermal reaction is followed by washing and drying steps.

[0063] A third aspect of the present invention provides an adsorption medium comprising the magnetic cup [4] aromatic covalent organic framework described in the first aspect of the present invention.

[0064] In some embodiments of the present invention, the adsorption medium is used for sample pretreatment.

[0065] In some embodiments of the present invention, the adsorption medium is a solid-phase extraction adsorption medium.

[0066] In some embodiments of the present invention, the solid-phase extraction is magnetic solid-phase extraction.

[0067] The fourth aspect of the present invention provides an application of the magnetic cup[4] aromatic covalent organic framework described in the first aspect of the present invention or the adsorption medium described in the third aspect of the present invention in the detection of Fusarium toxins, food analysis or environmental analysis.

[0068] Compared with the prior art, the beneficial effects of the present invention are:

[0069] (1) The magnetic cup of the present invention [4] has a rich number of recognition sites with host-guest recognition function, excellent adsorption performance, strong binding ability for a variety of compounds, strong enrichment ability, and high saturation magnetization intensity, which can meet the magnetic separation requirements. It also has good thermal stability and can be reused multiple times.

[0070] (2) The preparation method of the magnetic cup [4] aromatic covalent organic framework of the present invention is simple and the reaction conditions are mild, which overcomes the shortcomings of existing covalent organic frameworks that usually require relatively harsh reaction conditions for synthesis and are limited in practical applications.

[0071] (3) The magnetic cup [4] aromatic covalent organic framework of the present invention has a strong binding ability for a variety of compounds, excellent adsorption performance, and good enrichment performance. It can be used as an adsorption medium, especially a solid phase extraction adsorption medium. It can be combined with high performance liquid chromatography-tandem mass spectrometry for the enrichment and detection of Fusarium toxins. Therefore, the magnetic cup [4] aromatic covalent organic framework or an adsorption medium containing the magnetic cup [4] aromatic covalent organic framework can be used for Fusarium toxin detection and has practical application value in food analysis and environmental analysis. Attached Figure Description

[0072] Figure 1 This is a schematic diagram of the structure of the magnetic cup[4] aromatic covalent organic framework of Embodiment 1 of the present invention.

[0073] Figure 2 The X-ray powder diffraction pattern of the magnetic cup [4] aromatic covalent organic framework of Example 1 of the present invention is shown.

[0074] Figure 3 This is a scanning electron microscope image of the magnetic cup[4] aromatic covalent organic framework of Example 1 of the present invention.

[0075] Figure 4 This is a transmission electron microscope image of the magnetic cup[4] aromatic covalent organic framework of Example 1 of the present invention.

[0076] Figure 5The nitrogen adsorption-desorption isotherm of the magnetic cup [4] of the present invention in Example 1 is shown.

[0077] Figure 6 The infrared spectrum of the magnetic cup[4] aromatic covalent organic skeleton of Example 1 of the present invention is shown.

[0078] Figure 7 The X-ray photoelectron spectrum of the magnetic cup[4] aromatic covalent organic framework of Example 1 of the present invention is shown.

[0079] Figure 8 The magnetic hysteresis loop diagram of the magnetic cup[4] aromatic covalent organic framework of the present invention in Example 1 is shown.

[0080] Figure 9 Thermogravimetric curve of the magnetic cup[4] aromatic covalent organic skeleton of Example 1 of the present invention.

[0081] Figure 10 The adsorption efficiency of the magnetic cup [4] aromatic covalent organic framework of the present invention for eight Fusarium toxins is shown in Example 1 of the present invention.

[0082] Figure 11 The graph shows the repeatable extraction performance of the magnetic cup [4] aromatic covalent organic framework of Example 1 of the present invention on 8 kinds of Fusarium toxins.

[0083] Figure 12 The chromatogram obtained by using the magnetic cup [4] aromatic covalent organic framework of the present invention as the adsorption medium to enrich and detect DON, 15-DON and ZEN in wheat in Example 1 of the present invention; wherein, Figure 12 A, Figure 12 B. Figure 12 C represents the chromatograms of DON, 15-DON, and ZEN, respectively. Detailed Implementation

[0084] The present invention will be further described in detail below through specific embodiments. Unless otherwise specified, the raw materials, reagents, or apparatus used in the embodiments and comparative examples are all available from conventional commercial sources or can be obtained by existing technical methods. Unless otherwise specified, the test or experimental methods are conventional methods in the art.

[0085] Example 1

[0086] This embodiment provides a magnetic calix[4] aromatic covalent organic framework with a core-shell structure, using magnetic NiFe2O4 as the core and a covalent organic framework formed by linking aldehyde-modified calix[4] aromatics and 4,4'-diaminoazobenzene as the shell. Its structural schematic diagram is shown below. Figure 1 As shown.

[0087] In this magnetic calix[4] aromatic covalent organic framework, the mass ratio of magnetic NiFe2O4 to aldehyde-modified calix[4] aromatic is 1:0.67; the mass ratio of aldehyde-modified calix[4] aromatic to 4,4'-diaminoazobenzene is 1:0.8.

[0088] The preparation method of the magnetic cup [4] aromatic covalent organic framework in this embodiment can refer to the following steps:

[0089] In the organic solvent 1,3,5-trimethylbenzene, using magnetic NiFe2O4 as a support, aldehyde-modified calix[4]arene was reacted with 4,4'-diaminoazo at room temperature to prepare a magnetic calix[4]arene covalent organic framework. The specific steps are as follows:

[0090] 80 mg of 4,4'-diaminoazobenzene and 150 mg of NiFe2O4 were added to 50 mL of mesitylene and ultrasonically dispersed for 30 min. Then 100 mg of aldehyde-modified calix[4]arene was added, and 10 mL of 9 mol / L acetic acid aqueous solution was added under ultrasonic conditions. The mixture was stirred at room temperature for 24 h. The resulting solid precipitate was collected with a magnet, washed three times with tetrahydrofuran and methanol, and vacuum dried at 60 °C for 24 h to obtain the magnetic calix[4]arene covalent organic framework.

[0091] The preparation method of aldehyde-modified calix[4] aromatic hydrocarbons includes the following steps:

[0092] 1.0 g of calix[4] aromatic hydrocarbon and 12.0 g of hexamethylenetetramine were added to 80 mL of trifluoroacetic acid and heated and stirred under reflux at 90 °C for 24 h. After the reaction, 100 mL of 1 mol / L dilute hydrochloric acid and 80 mL of dichloromethane were added and stirred for 24 h. The resulting mixed liquid was allowed to stand and separate into layers. The organic phase was washed with 200 mL of water and evaporated by rotary evaporation to obtain a pale yellow aldehyde-modified calix[4] aromatic hydrocarbon.

[0093] The preparation method of magnetic NiFe2O4 includes the following steps:

[0094] 0.541 g FeCl3·H2O, 0.8 g urea, and 0.238 g NiCl2·6H2O were dissolved in 50 mL of deionized water and stirred for 20 min. The resulting mixture was transferred to a polytetrafluoroethylene-lined reactor and reacted at 180 °C for 10 h, then naturally cooled to room temperature. The product was collected using an external magnet and washed three times with ultrapure water and ethanol. Finally, NiFe2O4 was vacuum dried at 60 °C for 24 h to obtain magnetic NiFe2O4 particles with a particle size of 70–100 nm.

[0095] The following describes in detail the structure, morphology, and properties of the magnetic cup[4] aromatic covalent organic framework of Example 1, using test examples and application examples.

[0096] Test case

[0097] (1) Structural morphology

[0098] The magnetic cup[4] aromatic covalent organic framework of Example 1 was characterized by X-ray powder diffraction, and its X-ray powder diffraction pattern is shown below. Figure 2 As shown, the magnetic cup[4] aromatic covalent organic framework has typical NiFe2O4 diffraction peaks, and there is a diffraction peak at a small angle of 4.76°, which can be attributed to the diffraction of the covalent organic framework. This indicates that the covalent organic framework has been successfully grown on magnetic NiFe2O4 and has good crystallinity.

[0099] The magnetic cup [4] aromatic covalent organic framework of Example 1 was characterized by scanning electron microscopy. Figure 3 The scanning electron microscope image shows that the magnetic cup[4] aromatic covalent organic framework exhibits a regular rounded square shape. Further characterization by transmission electron microscopy yielded the following results: Figure 4 As shown, it can be seen that the magnetic cup[4] aromatic covalent organic framework contains square NiFe2O4 inside and a layer of covalent organic framework material on the outer surface, indicating that the covalent organic framework formed by aldehyde-modified cup[4] aromatic and 4,4'-diaminoazobenzene is successfully coated on the surface of NiFe2O4.

[0100] The magnetic cup [4] aromatic covalent organic framework of Example 1 was characterized using a fully automated rapid specific surface area and porosity analyzer, such as... Figure 5 As shown, the magnetic cup[4] aromatic covalent organic framework exhibits a type I adsorption isotherm, indicating that the material has a microporous structure, and the BET specific surface area is calculated to be 44.6 m². 2 / g.

[0101] Figure 6 The infrared spectrum of the magnetic cup [4] aromatic covalent organic framework of Example 1 of this invention shows that the infrared spectrum of the magnetic cup [4] aromatic covalent organic framework contains C=N (1647cm). -1 The peak of ) indicates that a covalent organic framework shell was successfully grown on the surface of NiFe2O4.

[0102] The magnetic cup [4] aromatic covalent organic framework of Example 1 was characterized by X-ray photoelectron spectroscopy, and the results are as follows: Figure 7 As shown in the X-ray photoelectron spectrum, the magnetic cup[4]arene covalent organic framework has five peaks: C1s, N1s, O 1s, Fe 2p, and Ni 2p. This indicates that the magnetic cup[4]arene covalent organic framework was successfully synthesized, and that the magnetic NiFe2O4 core is coated with a covalent organic framework shell formed by aldehyde-modified cup[4]arene and 4,4'-diaminoazobenzene.

[0103] (2) Saturation magnetization

[0104] The magnetic cup[4] aromatic covalent organic framework of Example 1 was characterized using a vibrating sample magnetometer. Figure 8 The hysteresis loop shows that the saturation magnetization of the magnetic cup[4] aromatic covalent organic framework is 30.8 emu / g, which is superparamagnetic and can meet the requirements of magnetic separation.

[0105] (3) Thermal stability

[0106] The magnetic cup [4] aromatic covalent organic framework prepared above was characterized by thermogravimetric analysis. Figure 9 The thermogravimetric curve shows that the weight of the adsorbent medium remains basically unchanged between 30 and 368 °C, indicating that the covalent organic framework has good thermal stability. After 368 °C, the weight begins to drop sharply, which is the reason for the thermal decomposition of the covalent organic framework at high temperature. This also shows that the aldehyde-modified calix[4]arene and 4,4'-diaminoazobenzene successfully formed a covalent organic framework and coated the surface of NiFe2O4.

[0107] (4) Adsorption performance

[0108] Two mg of the magnetic cup [4] aromatic covalent organic framework from Example 1 was immersed in 1 mg / L of eight fusarium toxins. The eight fusarium toxins were serpentin (DAS), zearalenone (ZEN), T2-toxin (T2), fumonisin B2 (FB2), fumonisin (FB1), 15-acetyldeoxynivalenol (15-DON), 3-acetyldeoxynivalenol (3-DON), and deoxynivalenol (DON). The content of fusarium toxins in the solution before and after immersion was tested, and the adsorption efficiency of the magnetic cup [4] aromatic covalent organic framework for the eight fusarium toxins was calculated. The results are as follows. Figure 10 As shown. From Figure 10 It can be seen that the magnetic calix[4] aromatic covalent organic framework has a high adsorption capacity for eight Fusarium toxins, with an adsorption efficiency between 86.0% and 98.7%, which is mainly attributed to the host-guest recognition of calix aromatics and the abundant binding sites on the covalent organic framework.

[0109] Application examples

[0110] Using the magnetic cup [4] aromatic covalent organic framework of the present invention in Example 1 above as the magnetic solid phase extraction adsorption medium, combined with high performance liquid chromatography-tandem mass spectrometry, it was applied to the separation, enrichment and detection of Fusarium toxins in wheat. The specific method is as follows:

[0111] Chromatographic conditions: Mobile phase A was 0.5% formic acid-2 mmol / L ammonium acetate aqueous solution, mobile phase B was acetonitrile, and the flow rate was 0.3 mL / min; gradient elution was performed: 0–5 min, mobile phase B 80→100%; the chromatographic column was a Dikma Endeavorsil C18 column (150×2.1 mm, 1.8 μm), and the column temperature was 40℃;

[0112] Magnetic solid phase extraction conditions: 10 mg of 10 μg / L of 8 Fusarium toxins (DAS, ZEN, T2, FB2, FB1, 15-DON, 3-DON, DON), 10 mg of adsorption medium, water as the extraction solvent, and 5 min of extraction time.

[0113] Elution conditions: The elution solvent was methanol:water:formic acid = 90:9:1 (volume ratio), the elution time was 5 min, and the elution volume was 2 mL;

[0114] The magnetic cup[4] aromatic covalent organic framework is used as a solid phase extraction adsorption medium to adsorb and enrich Fusarium toxin in wheat through solid phase extraction, and then the toxin is determined by high phase liquid chromatography-tandem mass spectrometry after elution.

[0115] The results are as follows Figure 11 As shown.

[0116] Figure 11 The graph shows the reproducible extraction performance of the magnetic cup [4] aromatic covalent organic framework of Example 1 of this invention for eight Fusarium toxins. Figure 11 As shown, Fusarium toxins DON, 3-DON, 15-DON, DAS, T2, FB1, FB2, and ZEN were used as research objects. Magnetic cup [4] aromatic covalent organic framework was used as the adsorption medium, and the determination was carried out by high-performance liquid chromatography-tandem mass spectrometry to evaluate the reusability of the adsorption medium. After 7 enrichment extractions and repeated use, the adsorption performance of the magnetic cup [4] aromatic covalent organic framework for the 8 Fusarium toxins did not decrease significantly, indicating that the magnetic cup [4] aromatic covalent organic framework as an adsorption medium has good reusability and regeneration performance, and has certain practical significance.

[0117] Before performing the above-mentioned magnetic cup[4] aromatic covalent organic framework as adsorption medium and combined with high phase liquid chromatography tandem mass spectrometry for determination, the sample was pretreated and spiked. The specific steps are as follows: Wheat was ground finely with a grinder, and 5.0g of unspiked sample and spiked sample were placed in 50mL centrifuge tubes, and 20mL of extraction solution (acetonitrile:water:glacial acetic acid = 80:19:1 (volume ratio)) was added. The mixture was vigorously shaken for 2min and ultrasonically extracted for 20min. The resulting mixture was then centrifuged at 8600×g for 10min, and the clear supernatant was collected and transferred to a centrifuge tube containing 4g MgSO4 and 2g NaCl. The mixture was immediately vortexed for 2min and centrifuged at 8600×g for 10min to remove impurities. 10mL of supernatant was transferred to a 10mL test tube and evaporated to dryness under nitrogen flow. The supernatant was then redissolved in 10mL of water and used in the above magnetic solid phase extraction procedure.

[0118] Figure 12 The chromatograms of DON, 15-DON and ZEN in wheat were obtained by using the magnetic cup [4] aromatic covalent organic framework as an adsorption medium in Example 1 of this invention. The lower part of the figure is the chromatogram before spiking, and the upper part is the chromatogram after spiking. The results show that the contents of DON, 15-DON and ZEN in wheat were 4.6 μg / kg, 7.8 μg / kg and 0.26 μg / kg, respectively, indicating that the magnetic cup [4] aromatic covalent organic framework of this invention has an enrichment effect and is beneficial for the enrichment and detection of Fusarium toxins.

[0119] In summary, the magnetic cup [4] aromatic covalent organic framework of the present invention has excellent adsorption performance, strong enrichment capacity, and high saturation magnetization, which can meet the requirements of magnetic separation. It also has good thermal stability and can be reused multiple times. Therefore, the magnetic cup [4] aromatic covalent organic framework can be used for Fusarium toxin detection and has practical application value in food analysis and environmental analysis.

[0120] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A magnetic cup [4] aromatic covalent organic framework, characterized in that, The magnetic calix[4] aromatic covalent organic framework has a core-shell structure, wherein the core is a magnetic nanoparticle and the shell is a covalent organic framework formed by linking aldehyde-modified calix[4] aromatic hydrocarbon and 4,4'-diaminoazobenzene; The mass ratio of the magnetic nanoparticles to the aldehyde-modified calix[4] aromatic hydrocarbon is 1:(0.5~2); the mass ratio of the aldehyde-modified calix[4] aromatic hydrocarbon to 4,4'-diaminoazobenzene is 1:(0.6~1). The preparation method of the magnetic cup [4] aromatic covalent organic framework includes the following steps: The magnetic nanoparticles, the 4,4'-diaminoazobenzene, and the aldehyde-modified calix[4] aromatic hydrocarbon are mixed in 1,3,5-trimethylbenzene and reacted to obtain the product; the magnetic nanoparticles and the 4,4'-diaminoazobenzene are mixed and dispersed in 1,3,5-trimethylbenzene, and then the aldehyde-modified calix[4] aromatic hydrocarbon is added; after adding the aldehyde-modified calix[4] aromatic hydrocarbon, an aqueous solution of acetic acid is added, and the mixture is mixed and dispersed.

2. The magnetic cup [4] aromatic covalent organic framework according to claim 1, characterized in that, The magnetic nanoparticles include at least one of NiFe2O4 and Fe3O4.

3. The magnetic cup [4] aromatic covalent organic framework according to claim 1, characterized in that, The magnetic cup [4] aromatic covalent organic framework has a microporous structure; And / or, the specific surface area of ​​the magnetic cup [4] aromatic covalent organic framework is 35~55m². 2 / g.

4. The magnetic cup [4] aromatic covalent organic framework according to claim 1, characterized in that, The saturation magnetization of the magnetic cup[4] aromatic covalent organic framework is 24~37 emu / g.

5. A method for preparing the magnetic cup [4] aromatic covalent organic framework according to any one of claims 1 to 4, characterized in that, Includes the following steps: The magnetic nanoparticles, the 4,4'-diaminoazobenzene, and the aldehyde-modified calix[4] aromatic hydrocarbon are mixed in 1,3,5-trimethylbenzene and reacted to obtain the product; the magnetic nanoparticles and the 4,4'-diaminoazobenzene are mixed and dispersed in 1,3,5-trimethylbenzene, and then the aldehyde-modified calix[4] aromatic hydrocarbon is added; after adding the aldehyde-modified calix[4] aromatic hydrocarbon, an aqueous solution of acetic acid is added, and the mixture is mixed and dispersed.

6. The preparation method according to claim 5, characterized in that, The reaction is carried out at room temperature.

7. The preparation method according to claim 6, characterized in that, The molar ratio of the aldehyde-modified calix[4] aromatic hydrocarbon, 1,3,5-trimethylbenzene and acetic acid is 1:(760~770):(125~200).

8. An adsorption medium, characterized in that, The adsorption medium includes the magnetic cup [4] aromatic covalent organic framework as described in any one of claims 1 to 4.

9. The application of the magnetic cup[4] aromatic covalent organic framework according to any one of claims 1 to 4, or the adsorption medium according to claim 8, in the detection of Fusarium toxins, food analysis, or environmental analysis.

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