Magnetic amide functionalized covalent organic framework material as well as preparation method and application thereof

Abstract

The invention discloses a magnetic amide functionalized covalent organic framework material and a preparation method and application thereof, the preparation method comprises the following steps: S1, uniformly dispersing Fe3O4 nanoparticles and ammonia water, adding tetraethyl orthosilicate, and reacting; s2, a product obtained in the step S1 and 3-aminopropyltriethoxysilane are uniformly dispersed and subjected to a reaction, and aminated magnetic nanoparticles Fe3O4 (at) SiO2-NH2 are obtained; and S3, uniformly dispersing the Fe3O4 (at) SiO2-NH2 and trialdehyde phloroglucinol in a mixed solution of o-dichlorobenzene and N, N-dimethylformamide, adding 4, 4 '-diaminobenzanilide, uniformly mixing, then adding an acetic acid solution, and reacting at the temperature of 100-120 DEG C for 3-5 days to obtain the magnetic covalent organic framework Fe3O4 (at) Am-COFs material. The Fe3O4atAm-COFs prepared by the preparation method disclosed by the invention has a large specific surface area, rapid magnetic separation capability and abundant active sites, so that the adsorption performance of the material on a target object is effectively improved.

Description

Technical Field

[0001] This invention relates to magnetic covalent framework materials, specifically to a magnetic amide-functionalized covalent organic framework material, its preparation method, and its applications. Background Technology

[0002] Hyoscyamine is a coumarin compound naturally found in various plants, exhibiting significant biological activities such as anticancer, antioxidant, and anti-inflammatory effects, and toxicity assessments indicate that it is non-toxic. Given its abundant pharmacological activities, the determination of hyoscyamine content has become an indicator for quality evaluation of many traditional Chinese medicinal materials. However, its low abundance in complex plant matrices hinders its widespread research and potential utilization. Therefore, developing a reliable and sensitive analytical method for the selective enrichment and detection of hyoscyamine in natural plants is of great significance.

[0003] Sample pretreatment techniques are an important component of detection technology, as they can both improve detection sensitivity by concentrating target analytes and reduce interference from other components in complex matrices. Commonly used methods include solid-phase extraction (SPE), microsolid-phase extraction (MSPE), dispersed phase extraction (SPIE), and magnetic solid-phase extraction (MSPE). Among these, MSPE is the most commonly used extraction method in sample pretreatment. This method utilizes an external magnetic field to achieve rapid recovery of the adsorbent, greatly improving analytical efficiency. It is characterized by its simplicity, high efficiency, good repeatability, and wide applicability. Notably, the adsorbent plays a crucial role in MSPE, directly affecting extraction efficiency and analytical sensitivity. In recent years, various advanced materials such as cross-linked polymers, metal-organic frameworks (MOFs), and porous carbon have been developed as adsorbents for the enrichment of various harmful pollutants and active molecules. However, these materials generally suffer from low adsorption efficiency and insufficient water stability, severely limiting their application in hydrophilic environments. In contrast, covalent organic frameworks (COFs) exhibit outstanding adsorption performance advantages due to their unique high specific surface area, tunable pore structure, and excellent chemical stability. Studies have found that the adsorption mechanism of existing COFs materials mainly relies on π-π stacking and hydrophobic interactions, resulting in poor performance in the adsorption of polar organic molecules. Summary of the Invention

[0004] To address the problem of poor adsorption performance of COFs materials in polar molecules, this invention provides a magnetic amide-functionalized covalent organic framework material, its preparation method, and its application. This COF uses an amino monomer containing an amide group as a building monomer, which can introduce abundant and uniformly distributed active sites into the COF. Through the formation of hydrogen bonds with the target molecule, it can effectively improve its adsorption performance for hyoscyamine.

[0005] To achieve the above objectives, the present invention provides a method for preparing magnetic amide-functionalized covalent organic frameworks, characterized by comprising the following steps: S1. Disperse Fe3O4 nanoparticles and ammonia water evenly, add coupling agent to react, wherein the mass ratio of Fe3O4, ammonia water and coupling agent is (4~5):(45~48):3; S2. The product of step S1 is dispersed evenly with an aminosilane reagent and reacted to obtain aminomagnetic nanoparticles Fe3O4@SiO2-NH2. S3. Fe3O4@SiO2-NH2 and trialdehyde phloroglucinol are evenly dispersed in a mixed solution of o-dichlorobenzene and N,N-dimethylformamide. 4,4'-diaminobenzoyl aniline is added and mixed. Acetic acid solution is then added and reacted at 100~120 °C for 3~5 days to obtain magnetic covalent organic framework Fe3O4@Am-COFs material. The mass ratio of Fe3O4@SiO2-NH2, trialdehyde phloroglucinol and 4,4'-diaminobenzoyl aniline is 15:(7~8):(10~11).

[0006] In the above technical solution, aminated magnetic spheres were first prepared. Then, 4,4'-diaminobenzoylaniline and trialdehyde phloroglucinol containing amide groups were used as building blocks to grow COFs in situ on the surface of magnetic nanoparticles via a one-step solvothermal method. The prepared magnetic COF framework contains abundant and uniformly distributed amide groups, which provides abundant hydrogen bonding sites for the adsorption of the target analyte. Simultaneously, the conjugated structure of the benzene ring of the target molecule and the COFs also facilitates the generation of π-π stacking interactions between them, thereby effectively improving the adsorption performance of the material for the target analyte. Compared with previously reported adsorbent materials, this material also has the following advantages: (1) Functionalized magnetic COFs materials are synthesized by a one-step solvothermal method. The synthesis process is simple. The high specific surface area, ordered pore structure and functional groups uniformly distributed in the framework of COFs can achieve rapid capture of target materials.

[0007] (2) When COFs are combined with magnetic nanoparticles, the magnetic separation capability can be used to achieve rapid recovery of the adsorbent, which greatly improves the detection efficiency of the entire analytical method.

[0008] (3) The conjugated structure and the abundant amide groups in the framework of COFs help to generate various interactions with target molecules, such as hydrogen bonding, π-π stacking, and hydrophobic interactions, thereby improving the adsorption performance and selectivity of magnetic COFs for target substances.

[0009] Specifically, in step S1, the Fe3O4 nanoparticles are prepared by dissolving the iron salt, mixing sodium citrate and sodium acetate evenly, and reacting at 200~220 °C for 8~10 hours to obtain Fe3O4 nanoparticles; wherein the mass ratio of iron salt, sodium citrate and sodium acetate is (27~30):4:(30~32).

[0010] In step S1, the silane reagent is tetraethyl orthosilicate, tetramethyl orthosilicate, methyl orthosilicate, or methyltriethoxysilane; the silane reagent is used to protect the magnetic beads and to connect the aminosilanizing reagent. The amino-modified silane reagent is 3-aminopropyltriethoxysilane, γ-aminopropylmethyldiethoxysilane, or 3-aminopropyltrimethoxysilane.

[0011] Preferably, in step S3, Fe3O4@SiO2-NH2 is first dispersed in an organic solvent, and then mixed and dispersed with other substances. The organic solvent is isopropanol, ethanol, or toluene.

[0012] The second aspect of the present invention provides magnetic amide functionalized covalent organic frameworks Fe3O4@Am-COFs prepared by the above-described preparation method.

[0013] A third aspect of this invention provides the application of the above-mentioned magnetic amide-functionalized covalent organic framework Fe3O4@Am-COFs in the extraction of hyoscyamine.

[0014] Specifically, the extraction conditions were as follows: Fe3O4@Am-COFs dosage 20~30 mg, hyoscyamine solution pH 3~7, extraction time 20~40 min, and acetonitrile as eluent, with a dosage of 1.5~2 mL.

[0015] The detection limit for Fe3O4@Am-COFs was 0.1 ng / mL. -1 .

[0016] Under optimal solid-phase extraction conditions combined with high-performance liquid chromatography, an analytical method based on this material was established, exhibiting a wide linear range (0.25-300 ng / mL). -1 ) and a low limit of detection (0.1 ng / mL) -1 This provides a reliable and efficient analytical method for the extraction and detection of hyoscyamine in natural plants.

[0017] Through the above technical solution, the present invention achieves the following beneficial effects: This invention uses o-dichlorobenzene and N,N-dimethylacetamide as reaction solvents. Two monomers, aminoamide benzene and trialdehyde phloroglucinol, are mixed in the presence of Fe3O4. After adding an aqueous acetic acid solution, the mixture is reacted at high temperature for several days to prepare magnetic amidated covalent organic frameworks (Fe3O4@Am-COFs). Then, Fe3O4@Am-COFs are used as magnetic solid-phase extraction adsorbents, combined with high-performance liquid chromatography (HPLC), to establish an analytical method based on Fe3O4@Am-COFs for the extraction and detection of hyoscyamine in natural plants. The prepared magnetic COFs framework contains abundant and uniformly distributed amide groups, which provide abundant hydrogen bonding sites for the adsorption of the target molecule. Simultaneously, the conjugated structure of the benzene ring of the target molecule and the COFs facilitates the generation of π-π stacking interactions between them, thereby effectively improving the adsorption performance of the material for the target molecule. In the extraction and detection of hyoscyamine in natural plants, a wide linear range (0.25-300 ng / mL) is observed. -1 ) and a low limit of detection (0.1 ng / mL) -1 ). Attached Figure Description

[0018] Figure 1 This is a flowchart of the preparation process of Fe3O4@Am-COFs and the magnetic solid-phase extraction process; Figure 2 The images show the FT-IR (a) and XRD patterns (b) of Am-COFs and Fe3O4@Am-COFs, and the nitrogen adsorption-desorption curve (c) of Fe3O4@Am-COFs. The inset shows the pore size distribution. 2- Hysteresis loops (d) of NH2 and Fe3O4@Am-COFs; Figure 3 The effects of different COFs (a), adsorption dosage (b), extraction time (c), sample pH (d), eluent type (e), and eluent dosage (f) on the recovery rate of hyoscyamine extraction were investigated. Figure 4 These are chromatograms of mulberry bark (a) and artemisia annua (b) before and after magnetic solid-phase extraction. Detailed Implementation

[0019] The specific embodiments of the present invention will be described in detail below with reference to examples. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0020] Example 1: Preparation of Fe3O4@Am-COFs (1) Synthesis of Fe3O4 nanoparticles by solvothermal method FeCl3·6H2O (1.62 g) was dissolved in ethylene glycol, and sodium citrate (0.24 g) was added and ultrasonically mixed until homogeneous. Sodium acetate (1.8 g) was then added under magnetic stirring, and stirring continued for 0.5 hours. The mixture was then transferred to a reaction vessel and placed at 200°C for 10 hours. After cooling to room temperature, the precipitate was washed several times with ethanol and water, and then vacuum dried overnight at 45°C to obtain Fe3O4 nano-ions.

[0021] (2) Amide modification of magnetic nanoparticles ① Weigh 150 mg of Fe3O4 nanoparticles and place them in a three-necked flask. Add 25 mL of water, 100 mL of ethanol and 1.5 mL of ammonia. After sonicating for half an hour, slowly add 5 mL of tetraethyl orthosilicate (0.1 mL) in ethanol dispersion under mechanical stirring. Continue stirring for 12 hours. Wash the product several times with ethanol and water.

[0022] ② The above product was dispersed in 120 mL of isopropanol, and 0.3 mL of 3-aminopropyltriethoxysilane was added under mechanical stirring. Stirring was continued for 12 hours. The product was washed several times with ethanol and water and vacuum dried overnight to obtain aminated magnetic nanoparticles (Fe3O4@SiO2-NH2).

[0023] (3) Preparation of Fe3O4@Am-COFs materials Weigh 30 mg of Fe3O4@SiO2-NH2 and 14 mg of trialdehyde phloroglucinol, add them to 3.75 mL of o-dichlorobenzene and 1.25 mL of N,N-dimethylformamide, and sonicate to disperse evenly. Then add 22 mg of 4,4'-diaminobenzoyl aniline to the mixture and sonicate to mix evenly. Finally, add 0.3 mL of acetic acid aqueous solution (6 mol L⁻¹). -1 The mixture was placed in a reaction vessel and heated at 120°C for 3 days. After the reaction, the precipitate was obtained by magnetic separation, washed sequentially with N,N-dimethylformamide, tetrahydrofuran, and acetone, and then vacuum dried to obtain the Fe3O4@Am-COFs material. Figure 1 ).

[0024] The prepared materials were characterized using Fourier transform infrared spectroscopy and X-ray diffraction. Figure 2 As shown in a, it is located at 1293 cm. -1 and 1514 cm -1The characteristic peaks at these locations correspond to the stretching vibrations of C=C and CN, respectively, confirming the successful condensation reaction between the amino group in 4,4'-diaminobenzoylaniline and the aldehyde group in trialdehyde phloroglucinol, and also indicating the enol-ketone tautomerism in the COFs. The XRD patterns of the Am-COFs show obvious diffraction peaks at 3.12° and 5.4°, confirming the high crystallinity of the prepared COFs material. Furthermore, in the Fe3O4@Am-COFs pattern, the peaks at 30.2°, 35.6°, and 43.2° correspond to the (220), (311), and (400) crystal planes of Fe3O4, respectively. Figure 2 b).

[0025] To analyze the specific surface area and porosity of COFs materials, we performed nitrogen adsorption-desorption tests. Figure 2 c), the results showed that the BET surface area of ​​Fe3O4@Am-COFs was 149.61 m². 2 g -1 The pore volume is 0.17 cm. 3 g -1 With a pore size of 2.3 nm, the prepared magnetic COFs material shows promise as an ideal adsorbent. Furthermore, hysteresis curves reveal that the saturation magnetic susceptibility of Fe3O4@SiO2-NH2 and Fe3O4@Am-COFs are 63 and 28 emu g, respectively. -1 ( Figure 2 d), which indicates that the prepared composite material exhibits superparamagnetic behavior, enabling rapid recovery through magnetic separation during magnetic solid-phase extraction.

[0026] Example 2 (1) Synthesis of Fe3O4 nanoparticles by solvothermal method FeCl3·6H2O (1.8 g) was dissolved in ethylene glycol, and sodium citrate (0.24 g) was added and ultrasonically mixed until homogeneous. Sodium acetate (1.92 g) was then added under magnetic stirring, and stirring continued for 0.5 hours. The mixture was then transferred to a reaction vessel and placed at 220°C for 8 hours. After cooling to room temperature, the precipitate was washed several times with ethanol and water, and then vacuum dried overnight at 45°C to obtain Fe3O4 nano-ions.

[0027] (2) Amide modification of magnetic nanoparticles ① Weigh 120 mg of Fe3O4 nanoparticles and place them in a three-necked flask. Add 25 mL of water, 100 mL of ethanol and 1.78 mL of ammonia. After sonicating for half an hour, slowly add 5 mL of tetraethyl orthosilicate (0.1 mL) in ethanol dispersion under mechanical stirring. Continue stirring for 12 hours. The product is washed several times with ethanol and water.

[0028] ② The above product was dispersed in 120 mL of isopropanol, and 0.3 mL of γ-aminopropylmethyldiethoxysilane was added under mechanical stirring. The stirring was continued for 12 hours. The product was washed several times with ethanol and water and vacuum dried overnight to obtain aminated magnetic nanoparticles (Fe3O4@SiO2-NH2).

[0029] (3) Preparation of Fe3O4@Am-COFs materials Weigh 30 mg of Fe3O4@SiO2-NH2 and 16 mg of trialdehyde phloroglucinol, add them to 3.75 mL of o-dichlorobenzene and 1.25 mL of N,N-dimethylformamide, and sonicate to disperse evenly. Then add 20 mg of 4,4'-diaminobenzoyl aniline to the mixture and sonicate to mix evenly. Finally, add 0.3 mL of acetic acid aqueous solution (6 mol / L). -1 The mixture was placed in a reactor and heated at 120 °C for 3 days. After the reaction, the precipitate was obtained by magnetic separation, washed sequentially with N,N-dimethylformamide, tetrahydrofuran, and acetone, and then vacuum dried to obtain the Fe3O4@Am-COFs material.

[0030] Example 3 (1) Synthesis of Fe3O4 nanoparticles by solvothermal method FeCl3·6H2O (1.75 g) was dissolved in ethylene glycol, and sodium citrate (0.24 g) was added and ultrasonically mixed until homogeneous. Sodium acetate (1.90 g) was then added under magnetic stirring, and stirring continued for 0.5 hours. The mixture was then transferred to a reaction vessel and placed at 210 °C for 9 hours. After cooling to room temperature, the precipitate was washed several times with ethanol and water, and then vacuum dried overnight at 45 °C to obtain Fe3O4 nano-ions.

[0031] (2) Amide modification of magnetic nanoparticles ① Weigh 135 mg of Fe3O4 nanoparticles and place them in a three-necked flask. Add 25 mL of water, 100 mL of ethanol and 1.70 mL of ammonia. After sonicating for half an hour, slowly add 5 mL of tetraethyl orthosilicate (0.1 mL) in ethanol dispersion under mechanical stirring. Continue stirring for 12 hours. Wash the product several times with ethanol and water.

[0032] ② The above product was dispersed in 120 mL of isopropanol, and 0.3 mL of 3-aminopropyltrimethoxysilane was added under mechanical stirring. Stirring was continued for 12 hours. The product was washed several times with ethanol and water and vacuum dried overnight to obtain aminated magnetic nanoparticles (Fe3O4@SiO2-NH2).

[0033] (3) Preparation of Fe3O4@Am-COFs materials Weigh 30 mg of Fe3O4@SiO2-NH2 and 15 mg of trialdehyde phloroglucinol, add them to 3.75 mL of o-dichlorobenzene and 1.25 mL of N,N-dimethylformamide, and sonicate to disperse evenly. Then add 21 mg of 4,4'-diaminobenzoyl aniline to the mixture and sonicate to mix evenly. Finally, add 0.3 mL of acetic acid aqueous solution (6 mol L⁻¹). -1 The mixture was placed in a reactor and heated at 120 °C for 3 days. After the reaction, the precipitate was obtained by magnetic separation, washed sequentially with N,N-dimethylformamide, tetrahydrofuran, and acetone, and then vacuum dried to obtain the Fe3O4@Am-COFs material.

[0034] Comparative Example 1 The other conditions are the same as in Example 1, except that 4,4'-diaminobenzoyl aniline is replaced with benzidine to obtain Fe3O4@COF-TpBD.

[0035] Comparative Example 2 The other conditions are the same as in Example 1, except that 4,4'-diaminobenzoyl aniline is replaced with p-diaminoazobenzene to obtain Fe3O4@COF-Azo.

[0036] Performance testing of magnetic solid phase extraction of hyoscyamine Liquid chromatography was performed on a Waters e2695 chromatograph equipped with a 2998 PDA detector. A C18 column (250 mm × 4.6 mm, 5 μm) was used for analyte separation. The mobile phase was acetonitrile and 0.01% formic acid aqueous solution at a ratio of 30:70 (v / v), and the flow rate was 1 mL / min. -1 The detection wavelength was set to 344 nm.

[0037] (1) Optimization of magnetic solid phase extraction conditions: adsorption dosage, extraction time, sample pH and type and amount of eluent.

[0038] Optimization of adsorption dosage: 10, 15, 20, 25, and 30 mg of Fe3O4@Am-COFs from Example 1 were dispersed in 40 mL and 50 ng mL solutions, respectively. -1 After shaking for 30 min in an aqueous solution, the supernatant was discarded by magnetic separation. 0.5 mL of acetonitrile was added for elution, and the eluent was collected by magnetic separation. This process was repeated four times. The combined eluent was then subjected to nitrogen purging and brought to a final volume of 0.2 mL in a 40 °C water bath for liquid chromatography analysis.

[0039] Optimization of extraction time: 25 mg of the adsorbent from Example 1 was dispersed in an aqueous solution of hyoscyamine at pH 5 and shaken for 5, 10, 20, 30 and 40 minutes respectively. The supernatant was discarded by magnetic separation, and 0.5 mL of acetonitrile was added for elution. The eluent was collected by magnetic separation and repeated four times. The combined supernatant was then subjected to nitrogen blowing and brought to a final volume of 0.2 mL in a 40 °C water bath for liquid chromatography analysis.

[0040] Optimization of sample pH: The pH of the water sample was adjusted to 3, 5, 7, 9, and 11 using hydrochloric acid or sodium hydroxide solution. 25 mg of the adsorbent from Example 1 was dispersed in hyoscyamine aqueous solutions at different pH values ​​and shaken for 30 minutes. The supernatant was discarded by magnetic separation, and 0.5 mL of acetonitrile was added for elution. The eluent was collected by magnetic separation and repeated four times (0.5 mL × 4). The combined supernatant was then subjected to nitrogen blowing and brought to a final volume of 0.2 mL in a 40 °C water bath for liquid chromatography analysis.

[0041] Optimization of eluent type: 25 mg of the adsorbent from Example 1 was dispersed in an aqueous solution of hyoscyamine at pH 5 and shaken for 30 minutes. The supernatant was discarded by magnetic separation. Acetonitrile, methanol and acetone (0.5 mL × 4) were added for elution, and the eluent was collected by magnetic separation. The combined supernatant was then subjected to nitrogen blowing and brought to a final volume of 0.2 mL in a 40 °C water bath for liquid chromatography analysis.

[0042] Optimization of elution dosage: 25 mg of the adsorbent from Example 1 was dispersed in an aqueous solution of hyoscyamine at pH 5 and shaken for 30 minutes. After magnetic separation, the supernatant was discarded. Acetonitrile was added in amounts of 0.5 mL, 0.5 mL × 2, 0.5 mL × 3, and 0.5 mL × 4, respectively, for elution. The eluent was collected by magnetic separation. The supernatant was then subjected to nitrogen blowing and brought to a final volume of 0.2 mL in a 40 °C water bath for liquid chromatography analysis.

[0043] The results showed that 25 mg of Fe3O4@Am-COFs had the best extraction recovery rate for hyoscyamine. Figure 3 b); When shaken for 30 minutes during extraction, the adsorbent showed better adsorption performance for hyoscyamine. Figure 3 c); The recovery rate of hyoscyamine was highest at pH 5, therefore the pH of the sample was adjusted to 5 with hydrochloric acid solution before subsequent magnetic solid-phase extraction. Figure 3 d). Elution with 2 mL of acetonitrile yields the highest extraction recovery ( Figure 3 e, 3f).

[0044] (2) Validation of the analytical method: The analytical method for carbamate pesticides was validated under optimal solid-phase extraction conditions by investigating several parameters. A series of solutions ranging from 0.05 to 500 ng / mL were prepared. -1The hyoscyamine solution was subjected to magnetic solid-phase extraction, and quantitative analysis was performed by HPLC-UV. A working curve was obtained by linear regression of peak area with corresponding concentration, and the correlation coefficient (R²) was calculated. 2 This is used to evaluate the linearity of the working curve. The limit of detection (LOD) and limit of quantitation (LOQ) are determined by concentrations with signal-to-noise ratios (S / N) of 3 and 10, respectively.

[0045] Under optimal magnetic solid-phase extraction conditions, a series of hyoscyamine solutions of different concentrations (0.05-500 ng / mL) were tested. -1 Magnetic solid-phase extraction was performed, and the eluent was concentrated before liquid chromatography analysis. A working curve was plotted using peak area versus corresponding concentration. Data analysis showed that the linear range of this analytical method is 0.25–300 ng / mL. -1 (R) 2 =0.995), and the limit of detection (LOD) was 0.1 ng / mL. -1 Subsequently, we applied the established analytical method to the extraction and detection of hyoscyamine in actual samples of mulberry bark and artemisia annua. From Figure 4 It is evident that, compared to the untreated samples, the chromatograms of mulberry bark and artemisia annua show significantly enhanced peak intensities after treatment, indicating that the established method is reliable and applicable for the detection of hyoscyamine in actual samples.

[0046] (3) The effect of amide groups on the properties of adsorbent materials during the extraction process 25 mg of the adsorbent from Example 1, Comparative Example 1, and Comparative Example 2 was dispersed in 40 mL of a solution with a pH of 5 and a concentration of 50 ng / mL. -1 After shaking in the hyoscyamine aqueous solution for 30 minutes, the supernatant was discarded by magnetic separation. Acetonitrile (0.5 mL × 4) was added for elution, and the eluent was collected by magnetic separation. The combined supernatant was then subjected to nitrogen blowing and brought to a final volume of 0.2 mL in a 40 °C water bath for liquid chromatography analysis.

[0047] The results showed that Fe3O4@Am-COFs had a significantly better extraction recovery rate for hyoscyamine than the other two materials, confirming that the amide groups in the framework help enhance the adsorption performance of the COFs material. Figure 3 a).

[0048] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0049] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0050] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A method for preparing a magnetic amide-functionalized covalent organic framework, characterized in that, Includes the following steps: S1. Disperse Fe3O4 nanoparticles and ammonia water evenly, add coupling agent to react, wherein the mass ratio of Fe3O4, ammonia water and coupling agent is (4~5):(45~48):3; S2. The product of step S1 is dispersed evenly with an aminosilane reagent and reacted to obtain aminomagnetic nanoparticles Fe3O4@SiO2-NH2. S3. Fe3O4@SiO2-NH2 and trialdehyde phloroglucinol are evenly dispersed in a mixed solution of o-dichlorobenzene and N,N-dimethylformamide. 4,4'-diaminobenzoyl aniline is added and mixed. Acetic acid solution is then added and reacted at 100~120 °C for 3~5 days to obtain magnetic covalent organic framework Fe3O4@Am-COFs material. The mass ratio of Fe3O4@SiO2-NH2, trialdehyde phloroglucinol and 4,4'-diaminobenzoyl aniline is 15:(7~8):(10~11).

2. The preparation method according to claim 1, characterized in that, In step S1, the Fe3O4 nanoparticles are prepared by dissolving the iron salt, mixing sodium citrate and sodium acetate evenly, and reacting at 200~220 °C for 8~10 hours to obtain Fe3O4 nanoparticles; wherein the ratio of iron salt, sodium citrate and sodium acetate is (27~30):4:(30~32).

3. The preparation method according to claim 1, characterized in that, In step S1, the coupling agent is tetraethyl orthosilicate, tetramethyl orthosilicate, methyl orthosilicate, or methyltriethoxysilane. The amino-modified silane reagent is 3-aminopropyltriethoxysilane, γ-aminopropylmethyldiethoxysilane, or 3-aminopropyltrimethoxysilane.

4. The preparation method according to claim 1, characterized in that, In step S3, Fe3O4@SiO2-NH2 is first dispersed in an organic solvent, and then mixed and dispersed with other substances.

5. The magnetic amide functionalized covalent organic framework Fe3O4@Am-COFs prepared by the preparation method according to any one of claims 1 to 4.

6. The application of the magnetic amide-functionalized covalent organic framework Fe3O4@Am-COFs as described in claim 5 in the extraction of hyoscyamine.

7. The application according to claim 6, characterized in that, The extraction conditions were as follows: Fe3O4@Am-COFs dosage 20~30mg, hyoscyamine solution pH 3~7, extraction time 20~40 min, and acetonitrile as eluent, with a dosage of 1.5~2 mL.

8. The application according to claim 6, characterized in that, The detection limit for Fe3O4@Am-COFs was 0.1 ng / mL.

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