Aerogel composite material with novel structure as well as preparation method and application of aerogel composite material

Abstract

The invention belongs to the field of chemical materials, and particularly relates to an aerogel composite material with a novel structure as well as a preparation method and application of the aerogel composite material. The aerogel composite material is prepared by taking a magnetic covalent organic framework as a substrate, performing chelation on chitosan and polyethyleneimine to form an aerogel composite material, and performing polydopamine molecular imprinting functionalization on the surfaces of aerogel pores. The aerogel provided by the invention belongs to a three-dimensional porous network polymer structure, and compared with the traditional aerogel, the surface imprinting effect greatly improves the high-specificity adsorption of aflatoxin; the large aperture and large specific surface area inside the magnetic covalent organic framework-based aerogel solve the problems of leakage and low adsorption capacity of a traditional two-dimensional material imprinting template, and meanwhile, the composite aerogel material can quickly reach adsorption equilibrium within one minute, so that the separation efficiency is greatly improved.

Description

Technical Field

[0001] This invention belongs to the field of chemical materials, specifically relating to a novel aerogel composite material with a specific structure, its preparation method, and its application. Background Technology

[0002] Fungal toxins pose a serious threat to human health. Among them, aflatoxins (AFTs) are a significant group of naturally occurring mycotoxins produced by Aspergillus flavus and Aspergillus parasiticus under suitable temperature and humidity conditions. These mycotoxins are considered highly toxic substances that easily contaminate foods such as grains and dairy products. They enter the food chain through direct ingestion or consumption of contaminated animal-derived products and readily accumulate in animal milk, liver, kidneys, and muscle tissue, leading to severe health damage such as gastrointestinal pain, edema, acute liver injury, and even death.

[0003] Because the content of AFTs in food matrices is very low and interference from complex matrices is severe, and the high specificity of target compounds is crucial for trace detection, materials used for the purification and extraction of AFTs require further research. Currently, two-dimensional nanomaterials such as carbon-based nanomaterials, covalent organic frameworks (COFs), metal-organic frameworks, and inorganic nanomaterials have been developed and utilized, but these materials all suffer from low adsorption efficiency and poor selectivity. For example, Non-Patent Literature 1 describes a method for the specific adsorption and enrichment of aflatoxin B in edible oils based on polydopamine magnetically imprinted two-dimensional powder materials. While the results show that the two-dimensional molecularly imprinted materials have high selectivity, their adsorption capacity is small and template leakage is prone to cause false positives.

[0004] Furthermore, three-dimensional adsorbent materials possess the inherent advantages of media barrier and rapid siphoning. Therefore, the synthesis of composite three-dimensional porous polymer materials is proposed to address the problems of poor processability, low adsorption capacity, and low adsorption rate of two-dimensional powder materials. For example, Non-Patent Literature 2 describes the preparation of magnetic iron tetroxide (Fe3O4) nanoparticles using a co-precipitation method, the preparation of polyethyleneimine-modified magnetic chitosan microspheres using glutaraldehyde as a crosslinking agent, and their application in the efficient adsorption and removal of chromium (Cr) from water. The results show that the mechanical properties of the three-dimensional gel composite material are conducive to the rapid diffusion of target molecules into the nanoporous structure inside the polymer, but it is a non-specific adsorbent material.

[0005] Therefore, the development of novel aerogel composite materials to achieve highly specific adsorption / precise detection of trace AFTs in complex food matrices, while eliminating interference from non-target macromolecules and structurally similar substances in complex matrices, and further enhancing the specific adsorption capacity of molecular imprints, has become the focus and challenge of current work. Existing technology

[0006] Non-patent literature

[0007] Non-patent literature 1: Journal of Food Safety and Quality Testing, 2022, 13(19):6391-6398;

[0008] Non-patent literature 2: Journal of Southwest University (Natural Science Edition), 2019, 41(07): 125-130. Summary of the Invention

[0009] In view of this, in order to solve the problems existing in the prior art, the present invention provides a novel aerogel composite material, its preparation method and application. The inventors have discovered that the aerogel composite material of the present invention belongs to a three-dimensional porous network polymer structure. Compared with traditional aerogels, the surface imprinting effect greatly improves the high specificity of adsorption of AFTs. At the same time, the composite aerogel material can also adsorb quickly, which greatly improves the separation efficiency. In addition, the preparation method of the aerogel composite material of the present invention does not require any special equipment. The obtained three-dimensional porous network structure material is conducive to eliminating the interference of non-target macromolecules in complex matrices, while overcoming the problem of poor processability of two-dimensional COF powder in the prior art. The large porosity of COF-based aerogel also overcomes the narrow and blocked micropores of traditional aerogels, enhancing the separation efficiency of the composite material. At the same time, the molecularly imprinted film on the surface of COF-based aerogel highly specifically enriches AFTs, greatly improving the accuracy of quantitative trace AFTs.

[0010] The technical solution adopted in this invention includes:

[0011] The first aspect of this invention discloses a novel aerogel composite material, characterized in that the aerogel composite material comprises the following structure:

[0012] Covalent organic framework powder (COF powder) with a core-shell structure magnetic covalent organic framework formed on the surface of Fe3O4; magnetic COF aerogel material with a porous surface formed by cross-linking and coupling reactions with COF powder; and a hydrophilic molecularly imprinted film formed on the surface of the pores of the aerogel material, thus becoming a magnetic COF aerogel composite material (generally denoted as Fe3O4@COF@MIP-AG).

[0013] The magnetic covalent organic framework (COF) powder has the following structure: the amino group of the C3 compound with the following structure and the aldehyde or ketone group of the C1 compound with the following structure are wrapped with carbon-nitrogen double bonds on the surface of Fe3O4 through the Mannich reaction to form a core-shell structure magnetic COF. This core-shell structure is symmetrical and rigid, and the framework has a large porosity hexagonal 2D macroring. Of course, because it has a symmetrical and rigid lattice structure, it has excellent chemical stability.

[0014] The C3 compound is selected from one or more combinations of compounds containing three aniline structures, such as C3-I, C3-II (where X is C or N), C3-III (where X is C or N), wherein C3-I is preferred.

[0015]

[0016] The C1 compound is selected from one or more combinations of the following 1, 3, 5-aryl groups containing substituted or unsubstituted aldehyde or ketone groups, such as C1-I, C1-II, C1-III, C1-IV, C1-V, C1-VI, wherein C1-I is preferred.

[0017]

[0018] The magnetic COF aerogel material has the following structure: through the chelation of magnetic COF powder by the free hydroxyl groups on the L1 compound and the free amino groups on the side chains of the L2 compound, the L1 compound and the L2 compound undergo cross-linking polymerization under the action of a cross-linking agent, forming a network polymer---spherical gel M1 in the curing agent sodium hydroxide solution; then, by using the carboxyl groups of the reducing agent to couple with the amino groups on the surface of the spherical gel, a spherical gel material M2 rich in phenolic hydroxyl groups is formed.

[0019] The L1 mentioned above is a natural biological chain-like high molecular weight chitosan as shown below, with a unit molecular weight of 161.2; where n1 is an integer from 50 to 75, and the relative molecular mass is 8000 to 12000; preferably n1 is 62, and more preferably the relative molecular mass is 10000.

[0020]

[0021] The L2 mentioned above is a branched polymer, polyethyleneimine, with a unit molecular weight of 260; n2 is an integer from 30 to 50; and a relative molecular mass of 8000 to 12000; preferably, n2 is 39 and the relative molecular mass is 10000.

[0022]

[0023] The crosslinking agent is selected from one of glyoxal, formaldehyde, glutaraldehyde, epichlorohydrin, ethylene glycol diglycidyl ether, and isocyanate; glutaraldehyde is preferred.

[0024] The reducing agent is a phenolic acid polyphenol organic compound, such as one selected from p-hydroxybenzoic acid, gallic acid, vanillic acid, protocatechuic acid, ellagic acid, and ginkgolic acid; gallic acid is preferred.

[0025] The Fe3O4@COF@MIP-AG has the following structure: a coumarin-like substance with similar structural characteristics to AFTs is selected as a virtual template, such as one selected from 7-coumarin (e.g., 7-hydroxycoumarin), 5,7-dimethoxycoumarin, 7-acetoxy-4-methylcoumarin, and naringenin, with 7-hydroxycoumarin being preferred. The virtual template is then used to form a hydrophilic molecularly imprinted film on the surface of the pores of the magnetic COF aerogel material using self-polymerizing macromolecules, thereby becoming the magnetic COF aerogel composite material. The aerogel composite material formed in this way has pores and binding sites similar in size and structure to the virtual template, and this structure is conducive to the binding of AFTs to it.

[0026] The self-polymerizing macromolecule is a catecholamine, such as one selected from norepinephrine, epinephrine, and dopamine (preferably dopamine). Since catecholamines are compounds containing a large number of phenolic hydroxyl and amino functional groups, they can undergo self-polymerization reactions, and a large number of hydrophilic phenolic hydroxyl groups remain in the surface structure after the reaction.

[0027] Furthermore, preferably, the Fe3O4@COF@MIP-AG has a three-dimensional porous network polymer structure: the bulk density of the Fe3O4@COF@MIP-AG is 1.0~1.5 g / mL; the hardness is 10.2~18.2 HV 0.1 (this hardness is measured at a pressure of 0.1 kgf); the average pore size of the Fe3O4@COF@MIP-AG is 44~234 nm; and the pore volume is 0.041~0.163 cm³. 3 / g; specific surface area is 50~1415 m² 2 / g.

[0028] A second aspect of the present invention provides a method for preparing the aforementioned novel aerogel composite material, characterized by comprising the following steps (see appendix). Figure 1 (Flowchart)

[0029] S1. Preparation of magnetic covalent organic framework (COF) powder: Fe3O4 particles, C3 compound and C1 compound were added to tetrahydrofuran in sequence by solvothermal reaction and mixed and stirred to obtain magnetic core-shell precipitate, i.e. magnetic covalent organic framework (COF) powder.

[0030] S2. Preparation of magnetic COF aerogel material: Using a room temperature method, the COF powder obtained in S1 above is mixed and stirred with compound L1 and compound L2 to obtain a colloidal liquid. Then, a crosslinking agent and a curing agent are added to continue the reaction to obtain spherical gel M1. Subsequently, a coupling agent and a reducing agent are added to it, and a reducing spherical gel M2 is formed on the surface of the spherical gel by a coupling reaction, thus obtaining the magnetic COF aerogel material.

[0031] S3. Preparation of magnetic COF aerogel composite material with surface molecular imprinted film: A one-step method was adopted. Under weakly alkaline conditions, self-polymerizing macromolecules were added, and spherical gel M2 obtained in S2 above and virtual template were added sequentially. The mixture was then stirred. After self-polymerization reaction of M2 on the surface of spherical gel, a hydrophilic molecular imprinted film was formed, which has pores and binding sites similar in size and structure to the virtual template. Thus, a magnetic COF aerogel composite material with surface molecular imprinted film was obtained, that is, an aerogel composite material with a novel structure was obtained.

[0032] The C3, C1, L1, L2, crosslinking agent, reducing agent, curing agent, coupling agent, self-polymerizing macromolecule, and virtual template are all the same as those mentioned above.

[0033] The magnetic COF aerogel composite material with surface molecular imprinted film obtained above is beneficial for AFTs to be adsorbed on the surface of the molecular imprinted material through strong covalent bonding and electrostatic interaction, thereby achieving the purpose of separation from impurities.

[0034] Wherein, (1) the magnetic shell-core COF powder in S1 is obtained by reacting and precipitating Fe3O4 particles, C3 compound and C1 compound dissolved in tetrahydrofuran, and the mass ratio of the three is (1~1.5):(0.8~1.3):(0.5~0.7) based on Fe3O4 particles.

[0035] Furthermore, the solvent in S1 can also be a mixed solvent, for example, under tetrahydrofuran-acetic acid solution conditions, with the volume ratio of acetic acid solution to tetrahydrofuran solution being (0.5~1):(30~60) (based on the volume of tetrahydrofuran).

[0036] The mass ratio of magnetic COF powder, L1 compound and L2 compound in S2 is 1:(3~5):(1~3);

[0037] The mass ratio of the crosslinking agent, curing agent, and reducing agent in S2 is 1:(1~10):(0.5~1).

[0038] The coupling agent in S2 is 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide and N-hydroxysuccinimide, with a mass ratio of (1.5~2):(0.5~1). At this time, the reducing agent and aerogel M1 are connected by chemical bonds through coupling, which requires the addition of a coupling agent.

[0039] In S3, the mass ratio of the magnetic COF aerogel material to the virtual template and the self-polymerizing macromolecule is (2~3):(1.5~2):(2~3).

[0040] The reaction in S3 was carried out in a 10 mM Tris buffer solution (pH 8.5) to synthesize molecularly imprinted aerogel materials; the volume ratio of the virtual template detergent acetic acid-water-methanol solution was (5~10):(20~50):(50~80).

[0041] (2) The stirring time in S1 is 100~150 minutes and the stirring temperature is 70~80℃;

[0042] The colloidal solution in S2 is obtained by stirring in a 5-10% (w / w) acetic acid aqueous solution system, wherein the crosslinking reaction soaking time is 120-160 minutes, the stirring time is 30-60 minutes, the coupling reaction time is 120-300 minutes, and the stirring temperature is room temperature;

[0043] The stirring in S3 is carried out in a 10 mM Tris buffer solution (pH 8.5) for 60-120 minutes at room temperature.

[0044] A third aspect of the present invention provides an application of the aforementioned novel Fe3O4@COF@MIP-AG structure, wherein the Fe3O4@COF@MIP-AG performs highly specific enrichment, purification, and adsorption of AFTs in food.

[0045] The AFTs are aflatoxin B1 (AFB1), aflatoxin B2 (AFB2), aflatoxin M1 (AFM1), aflatoxin M2 (AFM2), aflatoxin G1 (AFG1), and aflatoxin G2 (AFG2) with the oxanaphthol structure.

[0046] At this point, the novel Fe3O4@COF@MIP-AG structure of the present invention has the ability to highly specifically enrich and purify AFTs and eliminate interference from structurally similar molecules, and plays a role in media blocking and pore penetration against competing macromolecules and small molecules.

[0047] The structurally similar interfering agents include: zearalenone (ZEN), zearalenone (ZAN), trachomatisin (ST), ochratoxin A (OTA), ochratoxin C (OTC), ergotamine (AG), penicillin (PA), ergotamine (EG), mycophenolic acid (MA), tremor fungal toxin (VE), and albedoline (AL).

[0048] The competing macromolecules include carbohydrates, lipids, and proteins; the competing small molecules include minerals, vitamins, and alkaloids.

[0049] The beneficial effects of this invention are:

[0050] (1) The Fe3O4@COF@MIP-AG of the present invention is obtained by cross-linking two-dimensional COF powder as a base, chitosan and polyethyleneimine to form a three-dimensional porous network aerogel material and molecular imprinting on the pore surface. It is rarely interfered with by adsorption and expansion by external organic or inorganic solvents, and also overcomes the problems of poor processability of two-dimensional materials and false positives of template detachment in the prior art.

[0051] (2) The Fe3O4@COF@MIP-AG of the present invention has strong specific adsorption capacity, high adsorption efficiency and short adsorption equilibrium time. As can be seen in the following embodiments of the present invention, it can quickly reach adsorption equilibrium within 1 minute, which greatly improves the separation efficiency, helps to shorten the sample pretreatment time, achieve the purpose of rapid detection, supports its application in solid phase extraction, and highlights the high specific enrichment and purification of trace AFTs by Fe3O4@COF@MIP-AG in food safety applications.

[0052] (3) The Fe3O4@COF@MIP-AG of this invention has large pores, stable binding sites, and a unique media blocking effect, resulting in strong adsorption capacity for AFTs present in complex samples, with an adsorption efficiency of over 99%. In terms of eliminating competitive interference, Fe3O4@COF@MIP-AG has an adsorption efficiency of less than 2% for structurally similar substances. Therefore, the aerogel composite material of this invention has high adsorption efficiency and the ability to eliminate competitive interference, making it a promising candidate for application in the food industry.

[0053] (4) The preparation method of the present invention has mild synthesis conditions, is chemically green, simple to operate, requires no special equipment, and has low synthesis cost. Compared with traditional aerogels, imprinting separation improves the high specificity of adsorption for AFTs, while the large pore size and large specific surface area of ​​COF aerogel also solve the problem of narrow and blocked micropores in traditional aerogels, thus enhancing the separation efficiency of the composite material. Attached Figure Description

[0054] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other embodiments can be obtained based on these drawings without creative effort.

[0055] Figure 1 This is a flowchart illustrating the preparation and adsorption process of Fe3O4@COF@MIP-AG according to the present invention;

[0056] Figure 2This is a scanning electron microscope (SEM) schematic diagram of Fe3O4@COF@MIP-AG (A: surface; B: cross-section) and Fe3O4@MIP-AG (C: surface; D: cross-section) in Embodiment 1 of the present invention.

[0057] Figure 3A The XRD diffraction patterns of Fe3O4@COF, Fe3O4@COF-AG, Fe3O4@COF@MIP-AG obtained in the preparation process of Example 1 of the present invention and Fe3O4@COF@NIP-AG prepared in the comparative example (in order from bottom to top);

[0058] Figure 3B The XRD diffraction patterns of Fe3O4, Fe3O4-AG, Fe3O4@MIP-AG in Example 1 of the present invention and Fe3O4@NIP-AG in the comparative example (in order from bottom to top) are shown.

[0059] Figure 4A The infrared spectra of Fe3O4@COF, Fe3O4@COF-AG, Fe3O4@COF@MIP-AG obtained in the preparation process of Example 1 of the present invention and Fe3O4@COF@NIP-AG in the comparative example (in order from bottom to top);

[0060] Figure 4B The infrared spectra of Fe3O4, Fe3O4-AG, Fe3O4@MIP-AG in Example 1 of the present invention and Fe3O4@NIP-AG in the comparative example (in order from bottom to top);

[0061] Figure 5A The nitrogen isothermal adsorption-desorption curve and pore size distribution diagram of Fe3O4@COF@MIP-AG in Example 1 of this invention;

[0062] Figure 5B These are the nitrogen isothermal adsorption-desorption curves and pore size distribution diagrams of Fe3O4@MIP-AG in Example 1 of this invention;

[0063] Figure 6A The hysteresis loop test diagrams of Fe3O4@COF@MIP-AG and Fe3O4@MIP-AG, Fe3O4@COF in Embodiment 1 of the present invention are shown.

[0064] Figure 6B The hysteresis loop test diagrams of Fe3O4@MIP-AG, Fe3O4-AG, and Fe3O4 in Embodiment 1 of the present invention are shown.

[0065] Figure 7 The contact angle surface tension measurement diagrams are for Fe3O4@COF@MIP-AG (A) and Fe3O4@MIP-AG (B) in Embodiment 1 of the present invention;

[0066] Figure 8 Thermogravimetric analysis (TGA) results of Fe3O4@COF@MIP-AG in some embodiments 1 of this invention;

[0067] Figure 9 This is a Zeta potential analysis diagram of Fe3O4@COF@MIP-AG in some embodiments 1 of the present invention;

[0068] Figure 10A The static adsorption curves of Fe3O4@COF@MIP-AG for six AFTs in Example 1 of this invention are shown.

[0069] Figure 10B The image shows the dynamic adsorption curves of six AFTs by Fe3O4@COF@MIP-AG in Example 1 of this invention.

[0070] Figure 11 The adsorption mechanism of Fe3O4@COF@MIP-AG in Example 1 of this invention;

[0071] Figure 12A This is a schematic diagram illustrating the differences in adsorption efficiency between Fe3O4@COF, Fe3O4@COF-AG, Fe3O4@COF@MIP-AG in Example 1 of the present invention and Fe3O4@COF@NIP-AG prepared in the comparative example.

[0072] Figure 12B This is a schematic diagram illustrating the differences in adsorption efficiency between Fe3O4, Fe3O4-AG, Fe3O4@MIP-AG in Example 1 of the present invention and Fe3O4@NIP-AG in the comparative example;

[0073] Figure 13 This is a schematic diagram of the Fe3O4@COF@MIP-AG packed solid-phase extraction (SPE) column used for milk sample purification in Example 1 of this invention. Detailed Implementation

[0074] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to specific examples and the accompanying drawings.

[0075] In this invention, the term "two-dimensional material" refers to materials whose scale is nanoscale in one, two, or three dimensions, and whose shape is nanoparticles or powder.

[0076] The term "three-dimensional porous polymer" in this invention refers to a polymer network material consisting of many smaller components (called "knots" and "chains") linked together by covalent or supramolecular interactions. It has multiple hierarchical pore structures and combines the inherent properties of porous structures and three-dimensional polymers, with advantages such as ease of processing, controllable structure, and tunable surface functions.

[0077] The term "Mannich reaction" in this invention refers to the organic chemical reaction in which a compound containing active hydrogen (usually a carbonyl compound) condenses with formaldehyde and an amine to produce a β-amino (carbonyl) compound.

[0078] The term "magnetic core-shell structure" in this invention typically consists of two parts: a core part is a magnetic material, while the shell part is a non-magnetic material (such as an organic framework, polymer, etc.). This structure endows the material with unique physicochemical properties and recyclability.

[0079] In this invention, the term "COF" refers to a porous hexagonal covalent organic framework crystal material linked by imine.

[0080] In this invention, the term "aerogel" refers to a low-density three-dimensional porous solid material in which polymer molecules aggregate to form a micro-nano porous network structure and the pores are filled with a gaseous dispersion medium.

[0081] The term "molecular imprinting" in this invention refers to the preparation of covalent complexes between functional monomers and template molecules to achieve molecular recognition performance, mainly focusing on the structure and performance of molecular imprinted cavities.

[0082] The term "oxanaphthyl ketone structure" used in this invention, also known as the difuran ring class, refers to polycyclic aromatic ketone compounds characterized by the presence of oxygen atoms.

[0083] In this invention, the term "complex sample" refers to food.

[0084] The present invention will be explained below with reference to embodiments. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in the art (e.g., refer to J. Sambrook et al., *Molecular Cloning: A Laboratory Manual*, 3rd edition, Science Press, translated by Huang Peitang et al.) or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0085] Example 1: Preparation of a novel aerogel composite material (Fe3O4@COF@MIP-AG)1

[0086] S1. Preparation of magnetic covalent organic framework material Fe3O4@COF

[0087] A simple solvothermal method was used for synthesis. 0.1 g of Fe3O4 nanoparticles and 0.3 mmol of tris(4-aminophenyl)amine (TAPA) were sonicated for 30 min in a three-necked round-bottom flask to ensure uniform dispersion in 22 mL of tetrahydrofuran. The reaction system was then transferred to a water bath and heated to 70 °C with mechanical stirring at 450 rpm for 30 min. Subsequently, 0.3 mmol of 2,4,6-trialdehyde phloroglucinol (Tp) dissolved in 8 mL of tetrahydrofuran and 0.5 mL of acetic acid were added dropwise to the reaction system, immediately forming a wine-red precipitate. To ensure complete reaction, the system was stirred for 2 h. Finally, the product was separated using an external magnet, washed with acetonitrile and ethanol until the supernatant was clear, and dried overnight in a vacuum oven at 50 °C to obtain the magnetic covalent organic framework material Fe3O4@COF.

[0088] The Fe3O4@COF material is described in detail below: The stability of COF and the size of its crystal diameter play a crucial role in the porosity and dielectric barrier properties of the synthesized COF aerogel. The selected COF monomers all contain π-electron clouds, which is beneficial to the planar stability of the synthesized crystal. The triangular structure of C3 and the linear structure of C1 can form hexagonal COF crystals with a diameter of approximately 2 nm. The symmetrical rigid lattice structure exhibits excellent chemical stability. Simultaneously, C1 needs to have a porous network topology to form the hexagonal monopores, thus requiring linking active groups. Therefore, C3 is TAPA and C1 is Tp. A magnetic COF shell-core structure is formed by the Mannich reaction of the amino group of TAPA with the aldehyde and ketone groups of Tp to generate carbon-nitrogen double bonds that encapsulate the Fe3O4. Furthermore, to facilitate COF recovery, magnetic Fe3O4 is chosen as the core substrate for synthesizing the magnetic COF shell-core structure. The magnetic COF shell-core structure synthesized using the hot solvent method possesses a hexagonal 2D macrocyclic framework and a symmetrical rigid lattice structure, exhibiting excellent chemical stability.

[0089] S2. Preparation of magnetic COF aerogel materials

[0090] Aerogel composites were prepared using a room-temperature method. 0.7 g of chitosan (CS) (n = 62, molecular weight = 10000) was dissolved in 25 mL of 5% glacial acetic acid solution. 0.2 g of magnetic COF powder was added and ultrasonically dispersed until homogeneous. Then, 0.5 g of polyethyleneimine (PEI) (n = 39, molecular weight = 10000) was added and stirred at 450 rpm to obtain a mixed colloidal solution. This mixed colloidal solution was added dropwise to 100 mL of 2.5 mol / L sodium hydroxide solution and soaked for 30 min. The solution was then separated, washed several times with deionized water, and then crosslinked in 100 mL of 1% glutaraldehyde solution for 2 h to obtain spherical gel M1. Spherical gel M1 was immersed in 100 mL of deionized water, and the pH of the spherical gel M1 / water mixture was adjusted to 5–6 using 1 mol / L acetic acid.

[0091] 0.78 g of gallic acid was weighed and dissolved in 20 mL of deionized water. After complete dissolution, 1.7 g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide and 1.0 g of N-hydroxysuccinimide were added and the mixture was magnetically stirred for 1 h. The above mixed solution was added to a spherical gel M1 / water mixture and magnetically stirred for 3 h. After washing several times with deionized water, a spherical gel material M2 grafted with gallic acid was obtained. The spherical gel material M2 was freeze-dried at -50 °C under vacuum (<12 Pa) to obtain Fe3O4@COF-AG aerogel material.

[0092] Using the above method, the control material Fe3O4-AG aerogel composite material was synthesized by replacing the magnetic COF powder with Fe3O4 powder.

[0093] The Fe3O4@COF-AG material is specifically described as follows: The Fe3O4@COF-AG composite material is synthesized by CS with a relative molecular mass of 10000 and PEI with a relative molecular mass of 10000, which are chelated with COF powder in situ and precipitated as a colloidal solution at room temperature through the polyhydroxy and polyamino groups in the structure. Then, glutaraldehyde as a crosslinking agent and sodium hydroxide solution as a curing agent are used to form a 3*3*3 mm spherical gel M1. The specific crosslinking agent and curing agent system selected ensures the formation and stability of the aerogel network, while the precisely controlled stirring conditions ensure the uniform dispersion of the reactants and the uniform formation of the gel. Then, the carboxyl group of the reducing agent gallic acid is coupled with the amino group on the surface of the spherical gel M1 through the coupling of 1-ethyl-3-dimethylaminopropylcarbodiimide and N-hydroxysuccinimide to form a spherical gel material M2 rich in phenolic hydroxyl groups. The large-pore gel facilitates the passage of solvent through the gel layer, reduces the flow resistance between the narrow gel layers, and its reducing properties are beneficial to the stable synthesis of subsequent surface molecular imprinted films.

[0094] S3. Preparation of magnetic COF aerogel composites with surface molecularly imprinted films

[0095] A one-step method was used to prepare molecularly imprinted aerogel composites. 0.2 g of Fe3O4@COF-AG aerogel composite (or Fe3O4-AG aerogel composite) was weighed into a three-necked round-bottom flask. 25 mL of 10 mM Tris buffer solution (10 mmol / L, pH 8.5) was added, followed by dropwise addition of 25 mL of a methanol solution containing 1.0 mmol of 7-hydroxycoumarin (virtual template). The mixture was mechanically stirred at 450 rpm at room temperature until homogeneous. Then, 0.2 g of dopamine hydrochloride was added, and the reaction was continued for 2 h to form a molecularly imprinted polymer (i.e., a hydrophilic molecularly imprinted membrane). The reacted molecularly imprinted polymer was washed several times with 6% acetic acid-60% methanol until the template molecules were no longer detectable. It was then washed three times with ultrapure water. Finally, the Fe3O4@COF@MIP-AG aerogel composite (or Fe3O4@MIP-AG aerogel composite) was freeze-dried at -50 °C under vacuum (<12 Pa). The novel aerogel composite material (Fe3O4@COF@MIP-AG) of the present invention was obtained.

[0096] The obtained novel aerogel composite material 1 has a bulk density of 1.054 g / mL, a hardness of 15 HV0.1, an average pore size of 102.49 nm, and a pore volume of 0.129 cm³. 3 / g, with a specific surface area of ​​462.4 m². 2 / g.

[0097] The Fe3O4@COF@MIP-AG aerogel composite material is described as follows: The synthesis of the Fe3O4@COF@MIP-AG aerogel composite material involves using 7-hydroxycoumarin, which has similar structural characteristics to AFTs, as a virtual template. Dopamine hydrochloride is used in a weakly alkaline 10mM Tris buffer solution to undergo a one-step oxidative self-polymerization on the pore surface of the aerogel material, resulting in a hydrophilic polydopamine molecularly imprinted membrane. After the template molecules are eluted, pores and binding sites with similar size and structure to the virtual template are formed on the material surface, achieving separation from impurities. AFTs are adsorbed onto the surface of the molecularly imprinted material through strong covalent bonds and electrostatic interactions. Structurally similar substances are not adsorbed and exit the gel through π-π repulsion. Therefore, it is suitable for the highly specific enrichment and purification of AFTs in complex matrices such as food. Furthermore, it acts as a medium barrier and pore permeability for competing macromolecules and small molecules in complex matrices, greatly improving the rapid adsorption, enrichment, and accurate detection of trace AFTs in complex samples.

[0098] In addition, as a comparative example, Fe3O4@COF@NIP-AG and Fe3O4@NIP-AG aerogel composites were prepared under the same conditions without the participation of template molecules; also, Fe3O4@MIP-AG, a molecularly imprinted magnetic aerogel without the addition of COF, was synthesized as a comparative material. The aerogel composites of the present invention prepared above are explained by analyzing the adsorption, mechanical, and selectivity properties of each material.

[0099] Example 2 Preparation of a novel aerogel composite material (Fe3O4@COF@MIP-AG)2

[0100] S1: Preparation of magnetic covalent organic framework material Fe3O4@COF

[0101] A simple solvothermal method was used for synthesis. 0.1 g of Fe3O4 nanoparticles and 0.3 mmol of 1,3,5-tris(4-aminophenyl)benzene were sonicated for 30 min in a three-necked round-bottom flask to ensure uniform dispersion in 22 mL of tetrahydrofuran. The reaction system was then transferred to a water bath and heated to 70 °C with mechanical stirring at 450 rpm for 30 min. Subsequently, 0.3 mmol of 1,3,5-triacetylbenzene dissolved in 8 mL of tetrahydrofuran and 0.5 mL of acetic acid were added dropwise to the reaction system, immediately forming a wine-red precipitate. To ensure complete reaction, the system was stirred for another 2 h. Finally, the product was separated using an external magnet, washed with acetonitrile and ethanol until the supernatant was clear, and dried overnight in a vacuum oven at 50 °C to obtain the magnetic covalent organic framework material Fe3O4@COF.

[0102] The Fe3O4@COF material is described in detail as follows: the selected COF monomers all contain π electron clouds, which is beneficial to the planar stability of the synthesized crystal; by selecting the triangular structure of C3 and the linear structure of C1, a hexagonal COF crystal with a diameter of about 2nm can be formed, and the symmetrical lattice rigid structure has excellent chemical stability.

[0103] S2. Preparation of magnetic COF aerogel materials

[0104] Aerogel materials were prepared using a room-temperature method. 0.7 g of chitosan (CS) (n=50, molecular weight 8000) was dissolved in 25 mL of 5% glacial acetic acid solution. 0.2 g of magnetic COF powder was added and ultrasonically dispersed until homogeneous. Then, 0.5 g of polyethyleneimine (PEI) (n=31, molecular weight 8000) was added and stirred at 450 rpm to obtain a mixed colloidal solution. This mixed colloidal solution was added dropwise to 100 mL of 2.5 mol / L sodium hydroxide solution and soaked for 30 min. The solution was then separated, washed several times with deionized water, and added to 100 mL of 1% glyoxal solution for crosslinking for 2 h to obtain spherical gel M1. Spherical gel M1 was immersed in 100 mL of deionized water, and the pH of the spherical gel M1 / water mixture was adjusted to 5-6 using 1 mol / L acetic acid.

[0105] 0.78 g of vanillic acid was dissolved in 20 mL of deionized water. After complete dissolution, 1.7 g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide and 1.0 g of N-hydroxysuccinimide were added and the mixture was magnetically stirred for 1 h. The above mixed solution was added to a spherical gel M1 / water mixture and magnetically stirred for 3 h. After washing several times with deionized water, a spherical gel material M2 grafted with gallic acid was obtained. The spherical gel material M2 was freeze-dried at -50 °C under vacuum (<12 Pa) to obtain Fe3O4@COF-AG aerogel material.

[0106] The Fe3O4@COF-AG material is specifically described as follows: The Fe3O4@COF-AG aerogel material is synthesized by CS with a relative molecular mass of 8000 and PEI with a relative molecular mass of 8000, which are chelated with COF powder in situ and precipitated as a colloidal solution under room temperature conditions through the polyhydroxy and polyamino groups in the structure. Then, glyoxal and sodium hydroxide solution are used as crosslinking agents to form 3*3*3 mm spherical gels M1. Then, the carboxyl groups of vanillic acid, a reducing agent, are coupled with the amino groups on the surface of spherical gel M1 through the coupling of 1-ethyl-3-dimethylaminopropylcarbodiimide and N-hydroxysuccinimide to form spherical gel material M2 rich in phenolic hydroxyl groups. Its reducing properties are beneficial to the stable synthesis of subsequent surface molecular imprinted films.

[0107] S3. Preparation of magnetic COF aerogel composites with surface molecularly imprinted films

[0108] A one-step method was used to prepare molecularly imprinted aerogel composites. 0.2 g of Fe3O4@COF-AG aerogel material (or Fe3O4-AG aerogel material) was weighed into a three-necked round-bottom flask. 25 mL of 10 mM Tris buffer solution (10 mmol / L, pH 8.5) was added, followed by dropwise addition of 25 mL of a methanol solution of 1.0 mmol 5,7-dimethoxycoumarin (virtual template). The mixture was mechanically stirred at 450 rpm at room temperature until homogeneous. Then, 0.2 g of norepinephrine was added, and the reaction was continued for 2 h to form a molecularly imprinted polymer (i.e., a hydrophilic molecularly imprinted membrane). The reacted molecularly imprinted polymer was washed several times with 6% acetic acid-60% methanol until the template molecules were no longer detectable, followed by three washes with ultrapure water. Finally, the Fe3O4@COF@MIP-AG aerogel composite was freeze-dried at -50 °C under vacuum (<12 Pa). The novel aerogel composite material (Fe3O4@COF@MIP-AG)2 of the present invention was obtained.

[0109] The obtained novel aerogel composite material 2 has a bulk density of 1.25 g / mL, a hardness of 10.2 HV0.1, an average pore size of 44.17 nm, and a pore volume of 0.041 cm³. 3 / g, specific surface area is 50.4 m² 2 / g.

[0110] Example 3 Preparation of a novel aerogel composite material (Fe3O4@COF@MIP-AG)3

[0111] S1: Preparation of magnetic covalent organic framework material Fe3O4@COF

[0112] A simple solvothermal method was used for synthesis. 0.1 g of Fe3O4 nanoparticles and 0.3 mmol of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine were sonicated for 30 min in a three-necked round-bottom flask to ensure uniform dispersion in 22 mL of tetrahydrofuran. The reaction system was then transferred to a water bath and heated to 70 °C with mechanical stirring at 450 rpm for 30 min. Subsequently, 0.3 mmol of 1,3,5-benzenetriformaldehyde dissolved in 8 mL of tetrahydrofuran and 0.5 mL of acetic acid were added dropwise to the reaction system, immediately forming a wine-red precipitate. To ensure complete reaction, the system was stirred for another 2 h. Finally, the product was separated using an external magnet, washed with acetonitrile and ethanol until the supernatant was clear, and dried overnight in a vacuum oven at 50 °C to obtain the magnetic covalent organic framework material Fe3O4@COF.

[0113] The Fe3O4@COF material is described in detail as follows: the selected COF monomers all contain π electron clouds, which is beneficial to the planar stability of the synthesized crystal; the magnetic COF core-shell structure synthesized by hot solvent method with C3 triangular structure and C1 linear structure has a hexagonal 2D macrocyclic framework and symmetrical lattice rigid structure, and has excellent chemical stability.

[0114] S2. Preparation of magnetic COF aerogel materials

[0115] Aerogel materials were prepared using a room-temperature method. 0.7 g of chitosan (CS) (n = 75, molecular weight = 12000) was dissolved in 25 mL of 5% glacial acetic acid solution. 0.2 g of magnetic COF powder was added and ultrasonically dispersed until homogeneous. Then, 0.5 g of polyethyleneimine (PEI) (n = 47, molecular weight = 12000) was added and stirred at 450 rpm to obtain a mixed colloidal solution. This mixed colloidal solution was added dropwise to 100 mL of 2.5 mol / L sodium hydroxide solution and soaked for 30 min. The solution was then separated, washed several times with deionized water, and crosslinked in 100 mL of 1% ethylene glycol diglycidyl ether solution for 2 h to obtain spherical gel M1. Spherical gel M1 was immersed in 100 mL of deionized water, and the pH of the spherical gel M1 / water mixture was adjusted to 5–6 using 1 mol / L acetic acid.

[0116] 0.78 g of protocatechuic acid was dissolved in 20 mL of deionized water. After complete dissolution, 1.7 g of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide and 1.0 g of N-hydroxysuccinimide were added and the mixture was magnetically stirred for 1 h. The above mixed solution was added to a spherical gel M1 / water mixture and magnetically stirred for 3 h. After washing several times with deionized water, a spherical gel material M2 grafted with gallic acid was obtained. The spherical gel material M2 was freeze-dried at -50 °C under vacuum (<12 Pa) to obtain Fe3O4@COF-AG aerogel material.

[0117] The Fe3O4@COF-AG material is specifically described as follows: The Fe3O4@COF-AG material is synthesized by CS with a relative molecular mass of 12000 and PEI with a relative molecular mass of 12000, which are chelated with COF powder in situ and precipitated as a colloidal solution at room temperature through the polyhydroxy and polyamino groups in the structure. Then, ethylene glycol diglycidyl ether, a crosslinking agent, and sodium hydroxide solution, a curing agent, are used to form a 3*3*3 mm spherical gel M1. Then, the carboxyl group of the reducing agent protocatechuic acid is coupled with the amino group on the surface of the spherical gel M1 through the coupling of 1-ethyl-3-dimethylaminopropylcarbodiimide and N-hydroxysuccinimide to form a spherical gel material M2 rich in phenolic hydroxyl groups. Its reducing properties are beneficial to the stable synthesis of subsequent surface molecular imprinted films.

[0118] S3. Preparation of magnetic COF aerogel composites with surface molecularly imprinted films

[0119] A one-step method was used to prepare molecularly imprinted aerogel composites. 0.2 g of Fe3O4@COF-AG aerogel material (or Fe3O4-AG aerogel material) was weighed into a three-necked round-bottom flask. 25 mL of 10 mM Tris buffer solution (10 mmol / L, pH 8.5) was added, followed by dropwise addition of 25 mL of a methanol solution containing 1.0 mmol naringenin (virtual template). The mixture was mechanically stirred at 450 rpm at room temperature until homogeneous. Then, 0.2 g of adrenaline was added, and the reaction was continued for 2 h to form a molecularly imprinted polymer (i.e., a hydrophilic molecularly imprinted membrane). The reacted molecularly imprinted polymer was washed several times with 6% acetic acid-60% methanol until the template molecules were no longer detectable. It was then washed three times with ultrapure water. Finally, the Fe3O4@COF@MIP-AG aerogel composite was freeze-dried at -50°C under vacuum (<12 Pa). The novel aerogel composite material of this invention (Fe3O4@COF@MIP-AG)3 was obtained.

[0120] The obtained novel aerogel composite material 3 has a bulk density of 1.5 g / mL, a hardness of 18.2 HV0.1, an average pore size of 233.91 nm, and a pore volume of 0.163 cm³. 3 / g, with a specific surface area of ​​1414.9 m². 2 / g.

[0121] Example 4 Characterization of Fe3O4@COF@MIP-AG

[0122] Detailed characterization experiments were performed on the Fe3O4@COF@MIP-AG prepared in Example 1. The material morphology tests showed a bulk density of 1.054 g / mL, a hardness of 15 HV0.1, an average pore size of 102.49 nm, and a pore volume of 0.129 cm³. 3 / g, with a specific surface area of ​​462.4 m². 2 / g.

[0123] Therefore, the Fe3O4@COF@MIP-AG material is a robust and durable low-density three-dimensional solid aerogel composite material. Its excellent physicochemical properties are then characterized as follows:

[0124] (1) SEM characterization

[0125] Scanning electron microscopy analysis was performed on Fe3O4@COF@MIP-AG and Fe3O4@MIP-AG prepared in Example 1, and the results are as follows: Figure 2 As shown. Figure 2A is a scanning electron microscope image of the spherical surface of Fe3O4@COF@MIP-AG. The SEM images at 1 μm, 400 nm, and 200 nm show that the surface of the spheres has many fine pores, which are channels through which target molecules can penetrate the pores of the aerogel composite material and enter the interior for adsorption. Figure 2 B is a scanning electron microscope image of the cross-section of Fe3O4@COF@MIP-AG spheres. The SEM images at 1 μm, 400 nm, and 200 nm show that the cross-section of the spheres has a large-pore, irregular pore structure. This structure facilitates the synthesis of a specific binding membrane by molecular imprinting in the pores of the aerogel composite material. Figure 2 The C is a scanning electron microscope image of the surface of Fe3O4@MIP-AG spheres. From the SEM images of 1 μm, 400 nm and 200 nm, it can be seen that the surface of the spheres has no pores before the formation of aerogel composite material, but has multiple crystalline particles protruding from the surface. It does not have the penetrating pores of aerogel composite material. Figure 2 Image D is a scanning electron microscope (SEM) image of the cross-section of Fe3O4@MIP-AG spheres. The SEM images at 1 μm, 400 nm, and 200 nm show that the cross-section of the spheres consists of tightly packed, regularly spaced narrow pores. Compared to the large-pore structure in image B, these narrow pores are not conducive to molecular imprinting and film synthesis within the spheres, resulting in a smaller adsorption capacity. These results indicate that, compared to Fe3O4@MIP-AG, the large-pore internal structure of Fe3O4@COF@MIP-AG facilitates direct solvent penetration through the gel layer, reducing flow resistance between narrow gel gaps and thus improving adsorption capacity.

[0126] (2) XRD diffraction characterization

[0127] The crystal structures of Fe3O4@COF@MIP-AG and Fe3O4@MIP-AG prepared in Example 1 were analyzed by XRD diffraction experiments, and the results are shown in Figure 3. Figure 3A From bottom to top, it can be seen that in the XRD patterns of Fe3O4@COF, Fe3O4@COF-AG, Fe3O4@COF@MIP-AG, and the comparative example Fe3O4@COF@NIP-AG, diffraction peaks are observed at 2θ at 30.2°, 35.6°, 43.3°, 57.2°, and 62.8°. However, judging from the height of the corresponding diffraction peaks, the relative strength of the synthesized Fe3O4@COF-AG, Fe3O4@COF@MIP-AG, and Fe3O4@COF@NIP-AG composites is nearly half that of Fe3O4@COF powder, and they cannot maintain the original crystal structure of the nanoparticles, indicating the successful synthesis of macromolecular polymer aerogels. Figure 3BFrom bottom to top, it can be seen that diffraction peaks are observed at 2θ at 30.3°, 35.7°, 43.3°, 53.7°, 57.2° and 62.8° in the XRD patterns of Fe3O4, Fe3O4-AG, Fe3O4@MIP-AG and Fe3O4@NIP-AG. Among them, the diffraction peak at 53.7° is unique to Fe3O4 powder and is different from the crystal diffraction peak of Fe3O4@COF powder. However, after synthesis, the baselines of Fe3O4-AG, Fe3O4@MIP-AG and Fe3O4@NIP-AG are not flat and the data spikes are obvious, and they cannot maintain the original crystal structure of the nanopowder. In other words, compared with ordinary nanopowders, the peak intensity of polymer macromolecules in XRD is significantly reduced, the baseline is uneven, and some diffraction peaks of nanopowders are even submerged. This can also be clearly seen from the results of the two figures above. Therefore, Fe3O4@COF-AG, Fe3O4@COF@MIP-AG, Fe3O4@COF@NIP-AG, Fe3O4-AG, Fe3O4@MIP-AG, and Fe3O4@NIP-AG all belong to gel macromolecular polymer materials.

[0128] (3) FTIR characterization

[0129] The surface functional groups and chemical stability of Fe3O4@COF@MIP-AG and Fe3O4@MIP-AG prepared in Example 1 were analyzed by Fourier transform infrared spectroscopy, and the results are as follows: Figure 4A and 4B As shown. Figure 4A As can be clearly seen above, in the infrared spectra of Fe3O4@COF, Fe3O4@COF-AG, Fe3O4@COF@MIP-AG, and the comparative example Fe3O4@COF@NIP-AG, the four materials show similar infrared values ​​at 1495 cm⁻¹. –1 Characteristic absorption peaks were observed at all locations, which are vibrational absorption peaks of C=N, representing the linked covalent groups of the COF monomer, indicating the successful synthesis of Fe3O4@COF powder; at 1070 cm⁻¹... −1 The absorption peaks appearing at and 3380 cm⁻¹ −1 The absorption peaks appearing at this point can be attributed to the COC and NH vibration absorptions, which are specific covalent bonds between the molecularly imprinted membrane and the template molecule. This demonstrates the successful synthesis of Fe3O4@COF@MIP-AG and the successful assembly of the molecularly imprinted membrane on the aerogel surface. Figure 4B Infrared spectra of Fe3O4, Fe3O4-AG, Fe3O4@MIP-AG, and Fe3O4@NIP-AG in the comparative example; the four materials at 576 cm⁻¹. −1The absorption peaks appearing at 1069 cm⁻¹ can be attributed to the Fe-O vibrational absorption peaks and the absorption peaks at 1069 cm⁻¹. −1 and 3379 cm −1 The absorption peaks appearing at the point can be attributed to the COC and NH vibrational absorptions, which indicates the successful synthesis of Fe3O4@MIP-AG and the successful assembly of molecular imprints on the surface of the spherical aerogel.

[0130] (4) BET and porosity characterization

[0131] The specific surface area and porosity of Fe3O4@COF@MIP-AG and Fe3O4@MIP-AG prepared in Example 1 were analyzed using N2 adsorption-desorption isotherms, and the results are shown in Figure 5. Figure 5A It can be seen that the N2 adsorption-desorption isotherms of Fe3O4@COF@MIP-AG intersect, indicating the presence of special functional groups and chemical properties on the material surface, which have a strong effect on the adsorbate, leading to a certain degree of non-closure in the adsorption-desorption process. Furthermore, the shape of the mesoporous hysteresis loops indicates that the internal pore structure of Fe3O4@COF@MIP-AG is large-pore, consistent with the experimentally obtained average pore size of 102.49 nm and pore volume of 0.129 cm³. 3 / g, with a specific surface area of ​​462.4 m². 2 / g. Comparison Figure 5B The N2 desorption isotherm of Fe3O4@MIP-AG is significantly higher than that of adsorption isotherm, indicating that the material has no strong interaction with the adsorbate, allowing adsorbed gas molecules to completely detach from the pores. The shape of the mesoporous hysteresis loops indicates that the pore structure of Fe3O4@MIP-AG is mesopore-sized. This is consistent with the experimentally obtained average pore size of Fe3O4@MIP-AG, which is 78.71 nm, and the pore volume is 0.028 cm³. 3 / g, specific surface area is 128.8 m² (measured). 2 / g. Therefore, it can be shown that the introduction of Fe3O4@COF has an effect on the structural properties of aerogel composites by increasing the specific surface area and pore size of the aerogel, thereby overcoming the blockage of micropores by the three-dimensional stacking of the aerogel and enhancing the underwater stability of the material (i.e., the aerogel is hydrophilic, see the subsequent contact angle test results).

[0132] (5) VSM analysis

[0133] The magnetic properties of Fe3O4@COF@MIP-AG and Fe3O4@MIP-AG prepared in Example 1 were analyzed using hysteresis loop testing. The results are as follows: Figure 6A , 6B As shown. From Figure 6AIt can be seen that Fe3O4@COF powder is magnetic, with a saturation magnetization of 27.67 emu / g. After synthesizing Fe3O4@COF-AG, the saturation magnetization decreased to 5.73 emu / g, because the chelation of Fe3O4@COF by the gel affected the magnetization. However, after synthesizing Fe3O4@COF@MIP-AG, the saturation magnetization increased to 14.11 emu / g, because the molecularly imprinted film possesses electrostatic forces, thus greatly increasing the saturation magnetization of Fe3O4@COF@MIP-AG. Furthermore, from... Figure 6B It can be seen that Fe3O4 powder contains 77.48 emu / g of strong paramagnetism; after synthesizing Fe3O4-AG, the saturation magnetization drops sharply to 2.22 emu / g, which is half the saturation magnetization of Fe3O4@COF-AG. This indicates that the gel has a greater effect on the chelation of pure Fe3O4 powder than Fe3O4@COF. However, after synthesizing Fe3O4@MIP-AG, the saturation magnetization still increases to 11.05 emu / g, which is similar to the saturation magnetization of Fe3O4@COF@MIP-AG. Therefore, the results of this experiment show that the electrostatic force of the molecularly imprinted film is an important adsorption force in the specific adsorption mechanism.

[0134] (6) CA analysis

[0135] The Fe3O4@COF@MIP-AG and Fe3O4@MIP-AG prepared in Example 1 were analyzed using the contact angle surface tension test. The test method was the seated drop method. The results are as follows: Figure 7 As shown in (A), the average contact angle of Fe3O4@COF@MIP-AG is 35.6°. Figure 7 In (B), the average contact angle of Fe3O4@MIP-AG is 50.8°, and the θ value is less than 90°. It is evident that both aerogels are hydrophilic materials and can be well dispersed in liquid sample solutions, showing great potential for enriching target analytes in liquid samples. However, the introduction of large pores in Fe3O4@COF is beneficial for increasing the water permeability of the gel material, making Fe3O4@COF@MIP-AG more hydrophilic.

[0136] (7) TG analysis

[0137] Thermogravimetric analysis was performed on the Fe3O4@COF@MIP-AG prepared in Example 1. The results are as follows: Figure 8As shown, with the temperature increasing from 30℃ to 179.7℃, the material weight decreased by 11.1%, which is related to the destruction of the molecularly imprinted film on the material surface. Then, with the temperature increasing from 179.7℃ to 352.4℃, the material weight decreased by another 33.8%, which can be attributed to the increased decrease in weight due to the destruction of the gel skeleton structure. Finally, with the temperature increasing from 352.4℃ to 800℃, the material weight decreased by another 18%, which can be attributed to the destruction of the internal Fe3O4@COF covalent organic structure. The data and trends in the figure show that Fe3O4@COF@MIP-AG only begins to decompose at 179.7℃, exhibiting thermal stability. This high-temperature resistance confirms the high-efficiency thermal insulation performance of the aerogel composite material.

[0138] (8) Zeta analysis

[0139] The Fe3O4@COF@MIP-AG prepared in Example 1 was analyzed using nanoparticle size and Zeta potential analysis. The results are as follows: Figure 9 As shown, with water as the dispersant, the average zeta potential of Fe3O4@COF@MIP-AG at pH 7 is 1.04 mV, indicating that there is a net positive charge on the surface of Fe3O4@COF@MIP-AG. This means that in neutral solutions, the spherical aerogels tend to attract each other, making them more prone to aggregation and thus destabilizing the entire system, which also affects the adsorption capacity of the spherical aerogels. The average zeta potential is 21.5 mV at pH 4 and -24.06 mV at pH 10, indicating that the attractive force is lower than the repulsive force under weak acid and alkaline conditions. This shows that the Fe3O4@COF@MIP-AG system remains stable in weak alkaline solutions, and also provides a better test range for the adsorption and desorption conditions of aerogel composites.

[0140] Example 5: Feasibility Study of Adsorption of AFTs by Fe3O4@COF@MIP-AG

[0141] The feasibility of adsorbing AFB1, AFB2, AFM1, AFM2, AFG1, and AFG2 using Fe3O4@COF@MIP-AG prepared in Example 1 was investigated, as detailed below:

[0142] The adsorption performance of Fe3O4@COF@MIP-AG for six AFTs was studied by static and dynamic adsorption experiments. For the static adsorption experiment, a series of standard solutions containing the above target substances with concentrations of 10 μg / L, 20 μg / L, 50 μg / L, 100 μg / L, 200 μg / L, 500 μg / L, 1000 μg / L, 2000 μg / L, 3000 μg / L and 4000 μg / L were prepared in 1 mL. 10.0 mg of Fe3O4@COF@MIP-AG was added to each solution and the mixture was shaken for 60 minutes for adsorption. The maximum adsorption capacity of Fe3O4@COF@MIP-AG for the six AFTs was calculated using the following formula (1).

[0143] (1)

[0144] Among them, Q e C0 represents the maximum adsorption capacity (μg / g), C0 represents the initial concentration of the adsorption solution (μg / L), and C... e To achieve the target concentration (μg / L) at adsorption equilibrium, m is the mass (g) of Fe3O4@COF@MIP-AG, and V is the volume (L) of the adsorption solution.

[0145] For the dynamic adsorption experiment, 10.0 mg of Fe3O4@COF@MIP-AG was added to 1 mL of a mixed solution (100 μg / L) of 6 AFTs, and the mixture was shaken for different adsorption times (0.5 min, 1 min, 2 min, 5 min, 10 min, 20 min, 30 min, 40 min, 50 min, and 60 min). The results of this example were still calculated using formula (1) to determine the maximum adsorption capacity of Fe3O4@COF@MIP-AG for the 6 AFTs.

[0146] Furthermore, the adsorption capacity of Fe3O4@COF@MIP-AG as an adsorbent for six AFTs was investigated through static equilibrium experiments at different initial concentrations. Figure 10A As can be seen, even under low concentration conditions of the target analyte (below 200 μg / L), its adsorption capacity increases rapidly, thus proving that the composite material of the present invention has a high adsorption efficiency for trace amounts of AFTs. Furthermore, the dynamic adsorption curves of Fe3O4@COF@MIP-AG for six AFTs at different adsorption times are shown below. Figure 10B As shown, the adsorption of six AFTs by Fe3O4@COF@MIP-AG is a rapid adsorption process, reaching adsorption equilibrium within 1 minute. This indicates that the aerogel composite material of the present invention has the characteristic of rapid adsorption and separation of materials.

[0147] Example 6 Static adsorption study of AFTs by Fe3O4@COF@MIP-AG

[0148] Based on Example 5, the adsorption mechanism of six AFTs by Fe3O4@COF@MIP-AG prepared in Example 1 was further investigated using the Langmuir and Freundlich models. Langmuir is based on the assumption that the target analyte has a monolayer covering on the outer surface of the adsorbent. The linear expression of Langmuir is:

[0149] (2)

[0150] In equation (2), C e (µg / L) is the equilibrium concentration, Q e (µg / g) is the equilibrium adsorption capacity, Q s (µg / g) is the theoretical saturated adsorption capacity. (L / µg) is the Langmuir constant.

[0151] Freundlich is a multilayer adsorption based on a non-homogeneous surface. The linear form of the Freundlich equation is:

[0152] (3)

[0153] In equation (3), K f and n are the Freundlich constant and the affinity constant for the adsorption of six AFTs by Fe3O4@COF@MIP-AG, respectively.

[0154] According to formula (2), the Langmuir constant values ​​of AFB1, AFB2, AFG1, AFG2, AFM1, and AFM2 are... They were calculated to be 5.41E respectively. -4 4.95 E -4 5.12 E -4 3.96 E -4 5.45 E -4 and 5.25 E -4 Q e The values ​​were calculated to be 358.97 µg / g, 374.21 µg / g, 374.62 µg / g, 428.82 µg / g, 359.14 µg / g, and 370.85 µg / g, respectively; R 2 >0.9510. According to formula (3), the Freundlich constant K of AFB1, AFB2, AFG1, AFG2, AFM1 and AFM2 fThe values ​​were calculated as 1.8769, 1.6891, 1.7804, 1.2969, 1.8965, and 1.8281, respectively; the values ​​of n were calculated as 0.5938, 0.6077, 0.6030, 0.6456, 0.5929, and 0.5995, respectively; R 2 >0.9928. The results indicate that the Freundlich model has a better linear fitting coefficient than the Langmuir model, thus the Freundlich model is more suitable for describing this adsorption process. This suggests that the adsorption process is mainly accomplished by multiple interactions between heterogeneous binding sites. In other words, the specific adsorption process is accomplished by multiple interactions between different binding sites. Besides the strong covalent bond specific recognition force provided by molecular imprinting, electrostatic forces are also an important adsorption force in specific adsorption. Simultaneously, π-π repulsion acts as a unique force to exclude interference from structurally similar substances. Therefore, the specific adsorption performance of the aerogel composite material of this invention is the result of the synergistic effect of multiple forces.

[0155] Example 7: Dynamic adsorption study of AFTs by Fe3O4@COF@MIP-AG

[0156] Building upon Example 5, the adsorption behavior of Fe3O4@COF@MIP-AG prepared in Example 1 for six AFTs was further investigated using two conventional pseudo-first-order and pseudo-second-order models. The pseudo-first-order model assumes that adsorption is controlled by a diffusion step, i.e., physisorption behavior. The linear expression of the pseudo-first-order model is:

[0157] (4)

[0158] The pseudo-second-order model assumes that the adsorption rate is determined by the square of the number of unoccupied adsorption vacancies on the adsorbent, and that the adsorption process is controlled by the chemisorption mechanism, i.e., chemisorption behavior, which involves electron sharing or electron transfer between the adsorbent and the adsorbate.

[0159] (5)

[0160] In equations (4) and (5), q e (µg / g) and q t (µg / g) represents the adsorption capacity at equilibrium and at time t, respectively, and k1 and k2 are the adsorption rate constants for pseudo-first-order and pseudo-second-order kinetics, respectively.

[0161] According to formula (4), the pseudo-first-order constant k1 values ​​of AFB1, AFB2, AFG1, AFG2, AFM1, and AFM2 are calculated to be 6.9839, 7.8644, 6.6805, 6.8316, 7.8605, and 6.7929, respectively; R 2>0.9988. According to formula (5), the pseudo-second-order constant k2 values ​​of AFB1, AFB2, AFG1, AFG2, AFM1 and AFM2 are calculated to be 0.7445, 1.2224, 0.7803, 0.7143, 1.0803 and 0.7821, respectively; R 2 >0.9994. The pseudo-second-order model has a higher coefficient of determination than the pseudo-first-order model, indicating that chemisorption is the main rate-determining step in the interaction between Fe3O4@COF@MIP-AG and the six AFTs. This rapid adsorption kinetics is attributed to the structural advantages of the multifunctional adsorption sites, such as... Figure 11 As shown in the detailed adsorption mechanism diagram, firstly, Fe3O4@COF@MIP-AG itself possesses a certain range of large pore sizes to achieve an adsorption gradient, thus overcoming the competitive interference from complex matrices by blocking large molecules and penetrating small molecules. Secondly, the surface-specific molecularly imprinted film specifically adsorbs the target analytes AFTs through strong covalent bonds and electrostatic interactions. Finally, for structurally similar interfering substances with molecular weights close to AFTs, the interaction forces overlap with the π-π electron clouds formed by the large π array of Fe3O4@COF and the π electron clouds of the coupled reducing agent gallic acid. When the two aromatic rings are perfectly aligned face-to-face, the overlapping of π electron clouds leads to a strong electrostatic repulsion. When AFTs are specifically adsorbed by the molecularly imprinted membrane, coexisting structural analogs with similar molecular weights to the AFTs are repelled from the aerogel interior due to their energy disadvantage as benzene ring-containing structural analogs. This achieves the ability to eliminate interference from structural analogs. Thus, the above synergistic effect enables Fe3O4@COF@MIP-AG to bind to the target analyte more quickly and efficiently eliminate competing molecules and structural analogs, achieving high accuracy in the rapid detection of the target analyte.

[0162] Example 8: Study on the adsorption capacity of Fe3O4@COF@MIP-AG

[0163] Specific adsorption studies were conducted on Fe3O4@COF@MIP-AG prepared in Example 1, and Fe3O4@MIP-AG prepared in Example 1 was used for comparison. The specific details are as follows: six target compounds include: AFB1, AFB2, AFM1, AFM2, AFG1 and AFG2; eleven structurally similar interfering compounds include: ZEN, ZAN, ST, OTA, OTC, AG, PA, EG, MA, VE and AL.

[0164] 10.0 mg of Fe3O4@COF@MIP-AG and Fe3O4@MIP-AG prepared in Example 1 were dispersed in 1 mL of a blank sample solution (mixed standard concentration: 100 µg / L) containing 6 target compounds and 11 structurally similar interfering compounds. The mixture was shaken for adsorption, the supernatant was discarded, and the target compounds adsorbed on Fe3O4@COF@MIP-AG were eluted with five times the volume of desorption reagent (acetonitrile solution containing 0.01 Mol ammonia and 0.5 mmol potassium chloride). The mixture was then subjected to nitrogen blowing, reconstituted, filtered through a membrane, and analyzed by an instrument. The above experimental steps were repeated twice, and the average adsorption recovery rate was calculated.

[0165] The results are as follows Figure 12A As shown, the adsorption recoveries of Fe3O4@COF@MIP-AG for six AFTs ranged from 99.9% to 99.99%, while the adsorption recoveries for 11 structurally similar interfering substances were only OTA (2.98%), MA (0.25%), and AL. (0.37%) was detected, indicating that Fe3O4@COF@MIP-AG possesses high specificity and the ability to exclude interference from structurally similar substances; the adsorption recoveries of Fe3O4@COF@NIP-AG for 6 AFTs ranged from 5.06% to 15.09%, and the adsorption recoveries for 11 structurally similar interfering substances ranged from 22.81% to 50.81%, indicating that Fe3O4@COF@NIP-AG adsorbs both AFTs and these structurally similar substances; the adsorption recoveries of Fe3O4@COF-AG for 6 AFTs ranged from 24.27% to 28.17%, and the adsorption recoveries for 11 structurally similar interfering substances ranged from 10.51% to 64.24%, indicating that Fe3O4@COF-AG adsorbs both AFTs and these structurally similar substances, and the recoveries are significantly higher than those of Fe3O4@COF@NIP-AG; the adsorption recoveries of Fe3O4@COF powder for 6 AFTs were only AFM1. Fe3O4@COF powder was detected in 90.76% and AFM2 in 84.63%. The adsorption recoveries of 11 structurally similar interfering substances ranged from 0% to 77.1%, indicating that Fe3O4@COF powder does not specifically adsorb AFTs and such structurally similar substances.

[0166] like Figure 12BAs shown, Fe3O4@MIP-AG exhibited adsorption recoveries of 99.74%–99.99% for six AFTs and 2.54%–89.91% for 11 structurally similar interfering substances, indicating that Fe3O4@MIP-AG possesses high specificity but lacks anti-interference adsorption ability. Fe3O4@NIP-AG showed 0% adsorption recovery for the six AFTs and 0%–68.74% adsorption recovery for the 11 structurally similar interfering substances, indicating that Fe3O4@NIP-AG did not adsorb AFTs but did adsorb some structurally similar substances. This polydopa... Amine molecularly imprinted membranes effectively adsorb AFTs; Fe3O4-AG showed adsorption recoveries of 29.91%–65.23% for 6 AFTs and 13.32%–50.98% for 11 structurally similar interfering substances, indicating that Fe3O4-AG adsorbs both AFTs and their structurally similar counterparts; Fe3O4 powder showed adsorption recoveries of 0%–99.95% for 6 AFTs and 0%–75.7% for 11 structurally similar interfering substances, indicating that Fe3O4 powder does not specifically adsorb AFTs and their structurally similar counterparts.

[0167] The Fe3O4@COF@MIP-AG prepared in Example 1 was further packed into solid-phase extraction columns to process complex food matrices such as milk. The adsorption gradient capacity of the spherical gel was studied, as follows:

[0168] Take a clean, empty SPE column, place a PTFE gasket at the bottom, add 0.1 g of Fe3O4@COF@MIP-AG, ensuring uniform distribution within the column, and then place another PTFE gasket to fix the SPE column. Before loading the sample, activate the solid-phase extraction column with 1.0 mL of methanol, then add 2 mL of homogenized liquid sample and pass it through the column. Elute the adsorbed AFTs with five volumes of acetonitrile solution containing 0.01 mol ammonia and 0.5 mmol potassium chloride. Collect the eluent, purge with nitrogen, reconstitute, filter through a membrane, and analyze using an instrument.

[0169] The results are as follows Figure 13 As shown, milk homogenate samples can be directly purified by Fe3O4@COF@MIP-AG-filled SPE columns, demonstrating that the unique adsorption gradient of Fe3O4@COF@MIP-AG is conducive to the removal of non-target macromolecules such as sugars, lipids, and proteins, while promoting the rapid diffusion of target small molecules and other competing small molecules, including minerals, vitamins, and alkaloids, into the pore structure inside the three-dimensional gel to achieve rapid siphoning. In this process, the target substances are specifically adsorbed, while interfering substances are filtered out of the aerogel spheres.

[0170] Furthermore, the aerogel composite material Fe3O4@COF@MIP-AG obtained in Examples 2 and 3 also has the structure and properties shown above, which will not be elaborated here.

[0171] In summary, the aerogel composite material Fe3O4@COF@MIP-AG of this invention exhibits superior high specificity for AFTs, with improved overall adsorption capacity and increased separation efficiency. It reaches adsorption equilibrium rapidly within 1 minute and can be used as an adsorbent packing material for specific and rapid separation solid-phase extraction (SPE) columns.

[0172] Therefore, based on the above embodiments and experimental data, the specific adsorption of Fe3O4@COF@MIP-AG is mainly related to the molecularly imprinted membrane, and the adsorption forces are strong covalent bonds and electrostatic forces. It also has the ability to eliminate interference from non-target large / small molecules and structurally similar substances. In addition, the main forces are the pore penetration of the aerogel, the medium barrier, and the internal π-π mutual repulsion forces. Therefore, Fe3O4@COF@MIP-AG has mechanical properties and rapid adsorption capacity, and can be prepared as a solid-phase extraction SPF column adsorbent packing material for specific separation.

[0173] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0174] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A novel aerogel composite material, characterized in that, The aerogel composite material includes the following structure: COF powder with a core-shell structure of magnetic covalent organic framework is formed on the surface of iron oxide; and magnetic COF aerogel material with porous structure is formed by cross-linking and coupling reactions with COF powder. And a hydrophilic molecularly imprinted film is formed on the surface of the pores of the magnetic COF aerogel material, thereby forming a three-dimensional porous magnetic COF aerogel composite material. The magnetic covalent organic framework COF powder has the following structure: the amino group of the C3 compound with the structure below and the aldehyde and ketone group of the C1 compound with the structure below are wrapped on the surface of iron oxide to form a core-shell structure magnetic COF. The core-shell structure is symmetrical, the lattice is rigid, and the framework has a large porosity hexagonal 2D macrocycle. The magnetic COF aerogel material has the following structure: through the chelation of magnetic COF powder by the free hydroxyl groups on the L1 compound and the free amino groups on the side chains of the L2 compound, the L1 compound and the L2 compound undergo cross-linking polymerization under the action of a cross-linking agent, forming a network polymer---spherical gel M1 in the curing agent sodium hydroxide solution; then, by using the carboxyl groups of the reducing agent to couple with the amino groups on the surface of the spherical gel, a spherical gel material M2 rich in phenolic hydroxyl groups is formed. The aerogel composite material has the following composition: a coumarin-like substance with structural characteristics similar to aflatoxin is selected as a virtual template, and the virtual template is used to form a hydrophilic molecularly imprinted film on the surface of the pores of the magnetic COF aerogel material by utilizing self-polymerizing macromolecules, thereby becoming the magnetic COF aerogel composite material. The C3 compound is selected from one or more combinations of the following compounds containing three aniline structures: C3-I, C3-II, C3-III, wherein X in the following compounds is C or N; The C1 compound is selected from one or more combinations of the following 1,3,5-alkyl or alkyl groups containing substituted or unsubstituted aldehydes or ketones: C1-I, C1-II, C1-III, C1-IV, C1-V, C1-VI; The L1 above is the natural biological chain-like high molecular weight chitosan shown below, with a unit molecular weight of 161.2; where n1 is an integer from 50 to 75 and a relative molecular mass of 8000 to 12000; The L2 mentioned above is a branched polymer, polyethyleneimine, with a unit molecular weight of 260; n2 is an integer from 30 to 50; and a relative molecular mass of 8000 to 12000. The crosslinking agent is selected from one of glyoxal, formaldehyde, glutaraldehyde, epichlorohydrin, ethylene glycol diglycidyl ether, and isocyanate; The reducing agent is selected from one of p-hydroxybenzoic acid, gallic acid, vanillic acid, protocatechuic acid, ellagic acid, and ginkgolic acid; The self-polymerizing macromolecule is selected from one of norepinephrine, epinephrine, and dopamine. The virtual template is 7-coumarin, 5,7-dimethoxycoumarin, 7-acetoxy-4-methylcoumarin, or naringenin.

2. The novel aerogel composite material according to claim 1, characterized in that: The C3 is the aforementioned C3-I compound; The C1 is the aforementioned C1-I compound.

3. The novel aerogel composite material according to claim 1, characterized in that, In the magnetic COF aerogel composite material L1 is chitosan, with a relative molecular mass of 10,000 and n1 of 62; L2 is polyethyleneimine, with a relative molecular mass of 10,000 and n2 of 39. The crosslinking agent is specifically glutaraldehyde; The reducing agent is specifically gallic acid; The virtual template is 7-hydroxycoumarin.

4. The novel aerogel composite material according to claim 1, characterized in that, The aerogel composite material has a low-density three-dimensional porous solid network structure. Its bulk density is 1.0~1.5 g / mL; its hardness is 10.2~18.2 HV 0.

1. The average pore size ranges from 44.17 to 233.91 nm, and the pore volume ranges from 0.041 to 0.163 cm³. 3 / g, with a specific surface area of ​​50.4~1414.9 m². 2 / g.

5. A method for preparing a novel aerogel composite material with any one of claims 1 to 4, characterized in that, include: S1. Preparation of magnetic covalent organic framework (COF) powder: Using a solvothermal reaction, iron oxide particles, C3 compound and C1 compound were sequentially added to tetrahydrofuran and mixed and stirred to obtain a magnetic core-shell precipitate, i.e., magnetic covalent organic framework (COF) powder. S2. Preparation of magnetic COF aerogel material: Using a room temperature method, the COF powder obtained in S1 above is mixed and stirred with compound L1 and compound L2 to obtain a colloidal liquid. Then, a crosslinking agent and a curing agent are added to continue the reaction to obtain spherical gel M1. Subsequently, a coupling agent and a reducing agent are added to it, and a reducing spherical gel M2 is formed on the surface of the spherical gel by a coupling reaction, thus obtaining the magnetic COF aerogel material. S3. Preparation of magnetic COF aerogel composite material with surface molecular imprinted film: A one-step method was used. Under weakly alkaline conditions, self-polymerizing macromolecules were added, and spherical gel M2 obtained in S2 above and a virtual template were added sequentially. The mixture was then stirred. After a self-polymerization reaction on the surface of spherical gel M2, a hydrophilic molecular imprinted film was formed, which has pores and binding sites similar in size and structure to the virtual template. Thus, a magnetic COF aerogel composite material with surface molecular imprinted film was obtained, that is, an aerogel composite material with a novel structure. The C3 compound, C1 compound, L1 compound, L2 compound, crosslinking agent, reducing agent and curing agent, coupling agent, self-polymerizing macromolecule, and virtual template are all the same as those mentioned above.

6. The preparation method according to claim 5, characterized in that: The magnetic shell-core COF powder in S1 is obtained by reacting and precipitating iron oxide particles, C3 compound, and C1 compound dissolved in tetrahydrofuran, with the mass ratio of the three components being (1~1.5):(0.8~1.3):(0.5~0.7), based on the iron oxide particles. The process S1 is carried out under tetrahydrofuran-acetic acid solution conditions, with the volume ratio of acetic acid solution to tetrahydrofuran solution being (0.5~1):(30~60).

7. The preparation method according to claim 5, characterized in that: The mass ratio of magnetic COF powder, L1 compound and L2 compound in S2 is 1:(3~5):(1~3); The mass ratio of the crosslinking agent, curing agent, and reducing agent in S2 is 1:(1~10):(0.5~1). The coupling agent in S2 is 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide and N-hydroxysuccinimide, with a mass ratio of (1.5~2):(0.5~1).

8. The preparation method according to claim 5, characterized in that: The mass ratio of the magnetic COF aerogel material to the virtual template and the self-polymerizing macromolecules in S3 is (2~3):(1.5~2):(2~3); The reaction in S3 was carried out in 10mM Tris buffer solution to synthesize molecularly imprinted aerogel materials; the volume ratio of the virtual template detergent acetic acid-water-methanol solution was (5~10):(20~50):(50~80).

9. The preparation method according to any one of claims 6 to 8, characterized in that: The stirring time in S1 is 100-150 minutes, and the stirring temperature is 70-80℃; The colloidal solution in S2 is obtained by stirring in a 5-10% (w / w) acetic acid aqueous solution system, wherein the crosslinking reaction soaking time is 120-160 minutes, the stirring time is 30-60 minutes, the coupling reaction time is 120-300 minutes, and the stirring temperature is room temperature; The stirring in S3 is carried out in a 10mM Tris buffer solution for 60-120 minutes at room temperature.

10. The application of the aerogel composite material according to any one of claims 1 to 4 and the aerogel composite material prepared according to any one of claims 5 to 9, characterized in that, The aerogel composite material described above is used to specifically enrich, purify, and adsorb aflatoxins in food. The aflatoxins are aflatoxin B1, aflatoxin B2, aflatoxin M1, aflatoxin M2, aflatoxin G1, and aflatoxin G2 with an oxanaphthol structure.

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