A magnetic metal-organic framework composite based on interface molecule regulation and a preparation method and application thereof

Abstract

The application discloses a kind of magnetic metal organic framework composite based on interface molecule regulation and its preparation method and application, by sequentially constructing silanization interface layer, PAMAM molecular regulation layer and MOF-5-NH2 functional layer on the surface of Fe3O4 Magnetic core, obtain the magnetic metal organic framework composite with hierarchical composite structure;Silanization interface layer is used to improve the surface stability of Fe3O4 Magnetic core and provide subsequent functionalization reaction site;PAMAM molecular regulation layer is used as the interface anchoring site for the in-situ growth of MOF-5-NH2 to improve the number of material surface functional sites;MOF-5-NH2 functional layer is used to enhance the enrichment capacity of the material to alkylphenol compounds;Magnetic metal organic framework composite has magnetic response, interface stability and target adsorption affinity, and can be used for magnetic solid-phase extraction pretreatment of alkylphenol compounds in actual water sample.

Description

Technical Field

[0001] This invention belongs to the field of environmental sample pretreatment and magnetic solid-phase extraction materials technology, specifically relating to a magnetic metal-organic framework composite material based on interface molecular regulation, its preparation method and application. Background Technology

[0002] Alkylphenols are widely used as dispersants, detergents, wetting agents, emulsifiers, and stabilizers in pesticide production, food container manufacturing, and daily necessities production. They have attracted considerable attention due to their endocrine-disrupting activity and potential toxicity to the reproductive, nervous, and immune systems. However, the detection of alkylphenols in real-world samples remains challenging due to their low concentrations, similar structures, and frequent coexistence with matrix interfering agents. Therefore, developing efficient enrichment materials and analytical methods for alkylphenols is crucial for environmental monitoring and public health efforts.

[0003] Magnetic solid-phase extraction (MSPE) technology, with its advantages of short extraction equilibrium time and rapid magnetic separation of adsorbent and sample solution, has become an important sample pretreatment technique for the enrichment analysis of organic pollutants in environmental water samples. The core of MSPE lies in the rational design of magnetic adsorbents, enabling them to possess suitable surface chemistry, structure, and adsorption affinity for target analytes. Metal-organic frameworks (MOFs) and their composites, with their tunable structure and multifunctionality, are gradually becoming functional adsorbent carriers for the selective enrichment of active components. However, single MOF materials may suffer from difficulties in dispersion and recovery, insufficient structural stability, or limited utilization efficiency of adsorption sites in aqueous environments. Combining MOF materials with magnetic nanoparticles can improve their separation performance, but how to construct a stable and regulated interface layer between the magnetic core and the functional layers of the MOF material remains a key issue in improving the material's adsorption performance and cycling stability.

[0004] The prior art patent document CN202410290321.3 discloses a metal-organic framework-derived carbon magnetic solid-phase extraction material, its preparation method and application. It uses metal-organic framework-derived carbon Fc-MOF@NC as an adsorbent in magnetic solid-phase extraction technology to enrich trace PPDs and PPD-Qs in environmental water. Combined with liquid chromatography-tandem mass spectrometry, it establishes a detection method for PPDs and PPD-Qs in environmental water, thereby providing a simple, rapid and efficient analysis of PPDs and PPD-Qs in environmental water. Patent document CN202610241725.2 discloses a magnetic molecularly imprinted polymer and its preparation method and application. Fe3O4 nanoparticles are used as magnetic cores. SiO2 is coated by sol-gel method to obtain Fe3O4@SiO2. After grafting PAMAM, it is combined with a deep eutectic solvent and Schisandra lignan template molecules. Fe3O4@SiO2@PAMAM magnetic molecularly imprinted polymer is obtained by prepolymerization and polymerization. It has high adsorption capacity and selectivity for Schisandra lignans. When used as a magnetic solid phase extraction adsorbent combined with HPLC, it has excellent linearity and low detection limit, and can efficiently separate and enrich lignans in Schisandra chinensis. Patent document CN202311489647.0 discloses a magnetic metal-organic framework material, its preparation method and application. The metal-organic framework material is prepared by composite of Fe3O4 magnetic particles, MOF-545 and AMSA. As a magnetic solid phase extraction material, it can rapidly separate and adsorb heterocyclic amines under the action of an external magnetic field. It has a good adsorption effect on heterocyclic amines in pollutants, can be recycled and reused, and has good stability and anti-interference properties. Patent document CN202210543026.5 discloses a Mg / Zn-MOF-74@Fe3O4 magnetic composite material and its application in the enrichment of aflatoxin. The method involves preparing Fe3O4 magnetic nanoparticles with uniform particle size and strong magnetic responsiveness using a hydrothermal method. Subsequently, a hollow organic framework material Mg / Zn-MOF-74, a mixture of Mg and Zn metals, is synthesized using an ion exchange method. The amino groups on the Fe3O4 surface are then combined with the Mg / Zn metals of the metal framework material through a layer-by-layer assembly method. Under microwave assistance, the Mg / Zn-MOF-74@Fe3O4 magnetic composite material is rapidly synthesized. Applying this material to magnetic solid-phase extraction can achieve highly efficient adsorption of aflatoxin B1 in food.Patent document CN202411293487.7 discloses a graft-modified magnetic MOF adsorbent, its preparation method, and its application in cannabinoid detection. This adsorbent utilizes the ring-opening reaction between the amino group of 1-(3-aminopropyl)imidazole and epoxy to modify a large number of imidazole functional groups on the surface of Fe3O4@poly(GMA / DVB) microspheres. Then, the adsorbent is prepared by the self-assembly reaction of the amino-imidazolium group on the surface of the microspheres with zinc salt and 2-methylimidazolium. It is used as a magnetic solid-phase extraction adsorbent for the extraction and purification of four cannabinoids, namely tetrahydrocannabinol, cannabidiol, cannabinol, and tetrahydrocannabinic acid, in urine or saliva, and exhibits excellent selectivity and adsorption performance. However, the technical solutions in the aforementioned patent documents do not involve the preparation of MNPs@G2.5@MOF-5-NH2 magnetic MOF composite materials based on the interfacial molecule PAMAM, nor do they involve the application of this magnetic MOF composite material as a magnetic solid-phase extraction adsorbent in the enrichment, separation, and detection pretreatment of alkylphenol compounds in environmental water samples. Furthermore, there is no technical inspiration regarding how to construct a stable and regulatory interfacial layer between the magnetic core and the functional layer of the MOF material to improve the material's adsorption performance and cycle stability. Summary of the Invention

[0005] To address the technical problems of insufficient utilization of functional sites, limited stability of the binding between the functional layer of the MOF material and the magnetic substrate, and the need to improve the recycling performance of magnetic MOF adsorbent materials in water sample pretreatment, this invention provides a magnetic metal-organic framework composite material based on interface molecular regulation and its preparation method. This magnetic metal-organic framework composite material can be used as a magnetic solid-phase extraction adsorbent for the enrichment, separation, and detection of alkylphenol compounds in water samples.

[0006] This invention obtains a magnetic metal-organic framework composite material with a hierarchical composite structure by sequentially constructing a silanized interface layer, a PAMAM molecular regulation layer, and a MOF-5-NH2 functional layer on the surface of an Fe3O4 magnetic core. The silanized interface layer enhances the surface stability of the Fe3O4 magnetic core and provides sites for subsequent functionalization reactions. The PAMAM molecular regulation layer, rich in nitrogen-containing functional groups, serves as an interface anchoring point for the in-situ growth of MOF-5-NH2, while also increasing the number of functional sites on the material surface. The MOF-5-NH2 functional layer provides Zn-O clusters, amino groups, and aromatic ligands, which enhance the material's enrichment capacity for alkylphenol compounds. Therefore, the prepared magnetic metal-organic framework composite material possesses magnetic responsiveness, interfacial stability, and target analyte adsorption affinity, making it suitable for pretreatment of alkylphenol compounds in actual water samples using magnetic solid-phase extraction.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: a method for preparing a magnetic metal-organic framework composite material based on interface molecular regulation, the specific preparation steps of which are as follows:

[0008] Step S1, Preparation of Fe3O4 magnetic nanoparticles: Dissolve ferric salt and ferrous salt in water to obtain a mixed solution of iron salts. Add an alkaline precipitant to the mixed solution of iron salts under stirring and heat the reaction. After the reaction is completed, obtain Fe3O4 magnetic nanoparticles by magnetic separation, washing and drying.

[0009] Step S2, Preparation of silanized MNPs: The Fe3O4 magnetic nanoparticles obtained in step S1 are dispersed in an alcohol solvent, and then an aminosilane coupling agent is added to cause the aminosilane coupling agent to undergo a hydrolysis and condensation reaction on the surface of the Fe3O4 magnetic nanoparticles. After the reaction is completed, the silanized MNPs are obtained by washing and drying.

[0010] Step S3, Preparation of MNPs@G0.5 semi-generation product: The silanized MNPs obtained in step S2 are dispersed in an alcohol solvent, and then acrylate monomers are added to allow the acrylate monomers to undergo a Michael addition reaction with the amino groups on the surface of the silanized MNPs. After the reaction is completed, the MNPs@G0.5 semi-generation product is obtained by magnetic separation, washing and drying.

[0011] Step S4, Preparation of MNPs@G2.5: The half-generation product of MNPs@G0.5 obtained in step S3 is dispersed in an alcohol solvent, and then a diamine monomer is added to carry out an amidation reaction to obtain the full-generation product of MNPs@G1.0; the Michael addition reaction of acrylate monomers and the amidation reaction of diamine monomers are repeated alternately to obtain MNPs@G2.5;

[0012] Step S5, Preparation of MNPs@G2.5@MOF-5-NH2: The MNPs@G2.5 obtained in step S4 and 2-aminoterephthalic acid are dispersed in an organic solvent to carry out an interfacial anchoring reaction to obtain an intermediate product loaded with amino organic ligands. Then, the intermediate product is combined with zinc salt in an organic solvent to carry out a coordination assembly reaction so that the MOF-5-NH2 functional layer is grown in situ on the surface of MNPs@G2.5. After the reaction, the material is obtained by magnetic separation, washing and drying to obtain the MNPs@G2.5@MOF-5-NH2 magnetic MOF composite adsorbent material.

[0013] Further, in step S1, the trivalent ferric salt is FeCl3·6H2O, the divalent ferric salt is FeSO4·7H2O, and the alkaline precipitant is an ammonia solution; the feeding ratio of FeCl3·6H2O, FeSO4·7H2O, water, and ammonia solution is 2.5~3g:1.2~1.5g:40~60mL:8~10mL, and the mass concentration of the ammonia solution is 25%~28%; the heating reaction temperature is 70~90℃, and the heating reaction time is 20~60min.

[0014] Further, in step S2, the alcohol solvent is ethanol, the aminosilane coupling agent is 3-aminopropyltriethoxysilane, the feeding ratio of Fe3O4 magnetic nanoparticles, ethanol and 3-aminopropyltriethoxysilane is 1g:80~120mL:5~9mL, the hydrolysis condensation reaction temperature is 50~70℃, and the hydrolysis condensation reaction time is 5~9h.

[0015] Further, in step S3, the alcohol solvent is methanol, the acrylate monomer is methyl acrylate, the feeding ratio of silanized MNPs, methanol and methyl acrylate is 2g:40~60mL:15~25mL, the Michael addition reaction temperature is room temperature, and the Michael addition reaction time is 5~10h.

[0016] Further, in step S4, the alcohol solvent is methanol, the diamine monomer is ethylenediamine, the half-generation product of MNPs@G0.5 is dispersed in methanol, and after ultrasonic treatment and mechanical stirring, ethylenediamine is added, and the amidation reaction is carried out at room temperature for 6-10 hours to obtain the full-generation product of MNPs@G1.0; the Michael addition reaction of methyl acrylate and the amidation reaction of ethylenediamine are repeated alternately until MNPs@G2.5 is obtained.

[0017] Further, in step S5, the organic solvent is N,N-dimethylformamide, and the zinc salt is zinc nitrate hexahydrate; the mass ratio of MNPs@G2.5 to 2-aminoterephthalic acid is 1:0.5~2, the interface anchoring reaction temperature is 60~80℃, and the interface anchoring reaction time is 8~16h; the coordination assembly reaction temperature is 60~80℃, and the coordination assembly reaction time is 8~16h.

[0018] This invention also provides a magnetic metal-organic framework composite material based on interface molecular regulation prepared by the above method. The magnetic metal-organic framework composite material has a hierarchical composite structure with an Fe3O4 magnetic core and a silanized interface layer, a PAMAM molecular regulation layer and an amino-functionalized MOF-5-NH2 functional layer loaded on the surface of the Fe3O4 magnetic core. The magnetic metal-organic framework composite material has magnetic responsiveness, interface stability, abundant surface functional sites and MOF porous structure, which is beneficial to improve its enrichment ability of alkylphenol compounds. By introducing the silanized interface layer and the PAMAM molecular regulation layer, the surface stability and dispersibility of Fe3O4 magnetic nanoparticles are improved, and interface anchoring points are provided for the in-situ growth of MOF-5-NH2, thereby enhancing the bonding stability between the MOF-5-NH2 functional layer and the magnetic substrate.

[0019] This invention also provides the application of the aforementioned interface-molecule-regulated magnetic metal-organic framework composite material as a magnetic solid-phase extraction adsorbent in the pretreatment of alkylphenol compounds for magnetic solid-phase extraction, enrichment, separation, or detection in actual water samples, wherein the interface-molecule-regulated magnetic metal-organic framework composite material is available in the range of 0.1~300 μg·L⁻¹. -1 It exhibits good linear response within the concentration range, with a detection limit of 0.046–0.063 μg·L⁻¹. -1 The enrichment factor is 210~248, the actual water sample spiked recovery rate is 92%~118%, and the relative standard deviation is 0.7%~2.0%; after 8 cycles, it still maintains more than 95% of the initial extraction performance.

[0020] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0021] 1. This invention employs a hierarchical construction strategy of Fe3O4 magnetic core, silanized interface layer, PAMAM molecular regulation layer and MOF-5-NH2 functional layer to prepare MNPs@G2.5@MOF-5-NH2 magnetic MOF composite adsorbent material. The resulting material combines magnetic responsiveness, interface stability, abundant surface functional sites and MOF porous structure, which is beneficial to improving its enrichment capacity for alkylphenol compounds.

[0022] 2. This invention improves the surface stability and dispersibility of Fe3O4 magnetic nanoparticles by introducing a silanized interface layer and a PAMAM molecular regulation layer, and provides interface anchoring points for the in-situ growth of MOF-5-NH2, thereby enhancing the bonding stability between the MOF-5-NH2 functional layer and the magnetic substrate.

[0023] 3. The MNPs@G2.5@MOF-5-NH2 magnetic MOF composite adsorbent obtained in this invention can be rapidly separated from the water sample system under the action of an external magnetic field, which facilitates magnetic solid phase extraction operation and is suitable for the enrichment, separation and detection pretreatment of alkylphenol compounds in actual water samples.

[0024] 4. The MNPs@G2.5@MOF-5-NH2 magnetic MOF composite adsorbent obtained in this invention exhibits excellent performance in the detection of alkylphenol compounds and good stability during recycling. Experimental results show that the linear range of the alkylphenol compound detection method established based on this material is 0.1~300 μg·L⁻¹. -1 The detection limit is 0.046~0.063 μg·L⁻¹. -1 The enrichment factor is 210~248, the actual water sample spiked recovery rate is 92%~118%, and the relative standard deviation is 0.7%~2.0%; after 8 cycles, it still maintains more than 95% of the initial extraction performance. Attached Figure Description

[0025] Figure 1 The diagram illustrates the reaction principle for preparing the MNPs@G2.5@MOF-5-NH2 magnetic MOF composite adsorbent material according to this invention.

[0026] Figure 2 The image shows a SEM image of the MNPs@G2.5@MOF-5-NH2 magnetic MOF composite adsorbent material prepared in Example 1.

[0027] Figure 3 The image shows a TEM image of the MNPs@G2.5@MOF-5-NH2 magnetic MOF composite adsorbent material prepared in Example 1.

[0028] Figure 4 The XRD comparison diagrams show the MNPs@G2.5@MOF-5-NH2 magnetic MOF composite adsorbent material prepared in Example 1 and the MNPs@G2.5 magnetic composite material prepared in Comparative Example 3.

[0029] Figure 5 The image shows a comparison of FTIR values ​​between the MNPs@G2.5@MOF-5-NH2 magnetic MOF composite adsorbent material prepared in Example 1 and the MNPs@G2.5 magnetic composite material prepared in Comparative Example 3.

[0030] Figure 6 XPS image of the MNPs@G2.5@MOF-5-NH2 magnetic MOF composite adsorbent material prepared in Example 1.

[0031] Figure 7The VSM curves are for the MNPs@G2.5@MOF-5-NH2 magnetic MOF composite adsorbent prepared in Example 1 and the MNPs@G2.5 magnetic composite material prepared in Comparative Example 3.

[0032] Figure 8 A comparison chart showing the adsorption / recovery effects of different materials.

[0033] Figure 9 Chromatogram of an actual water sample spiked with chromatograms.

[0034] Figure 10 The graph shows a comparison of the cyclic stability of the MNPs@G2.5@MOF-5-NH2 magnetic MOF composite adsorbent material prepared in Example 1. Detailed Implementation

[0035] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments, but this should not be construed as limiting the invention. Unless otherwise specified, the technical means used in the following embodiments are conventional means well known to those skilled in the art, and the materials, reagents, etc. used in the following embodiments are commercially available unless otherwise specified.

[0036] Example 1

[0037] Preparation of MNPs@G2.5@MOF-5-NH2 magnetic MOF composite adsorbent materials:

[0038] (1) Preparation of Fe3O4 magnetic nanoparticles

[0039] 5.4 g of ferric chloride hexahydrate (FeCl3·6H2O) and 2.78 g of ferrous sulfate heptahydrate (FeSO4·7H2O) were weighed and dissolved in 100 mL of deionized water to obtain a mixed iron salt solution. Then, under stirring, 18 mL of ammonia solution with a mass concentration of 25%–28% was added dropwise to the iron salt solution, and the reaction system was heated to 80 °C and stirred continuously for 30 min. After the reaction was completed, the product was collected under an external magnetic field, washed repeatedly with ultrapure water, and then dried overnight in a vacuum drying oven at 50 °C to obtain Fe3O4 magnetic nanoparticles.

[0040] (2) Preparation of silanized Fe3O4 magnetic nanoparticles

[0041] 2.0 g of the Fe3O4 magnetic nanoparticles obtained in step (1) were ultrasonically dispersed in 200 mL of ethanol. Then, 14 mL of 3-aminopropyltriethoxysilane (APTES) was added dropwise to the dispersion, and the reaction system was heated to 60 °C and stirred for 7 h. After the reaction was complete, the product was washed five times with methanol and dried overnight in a vacuum drying oven at 50 °C to obtain silanized Fe3O4 magnetic nanoparticles, abbreviated as MNPs.

[0042] (3) Preparation of the half-generation product of MNPs@G0.5

[0043] 2.0 g of the MNPs obtained in step (2) was weighed and dispersed in 50 mL of methanol. After sonication for 15 min, the mixture was mechanically stirred for 30 min. Then, 20 mL of methyl acrylate (MA) was added dropwise to the reaction system, and stirring was continued to mix the reaction system evenly. The reaction was then stirred at room temperature for 7 h. After the reaction was completed, the product was collected by applying an external magnetic field, washed three times with methanol, and dried overnight under vacuum at 60 °C to obtain the MNPs@G0.5 semi-generation product.

[0044] (4) Preparation of MNPs@G2.5

[0045] The MNPs@G0.5 semi-generation product obtained in step (3) was dispersed in 50 mL of methanol, sonicated for 15 min, and then mechanically stirred for 30 min. Subsequently, 20 mL of ethylenediamine (EDA) was added dropwise, and the reaction was carried out at room temperature for 8 h. After the reaction was completed, the product was collected under an external magnetic field, washed five times with methanol, and dried overnight under vacuum at 60 °C to obtain MNPs@G1.0. The Michael addition reaction of methyl acrylate and the amidation reaction of ethylenediamine were carried out alternately until MNPs@G2.5 was obtained.

[0046] (5) Preparation of MNPs@G2.5@MOF-5-NH2

[0047] Weigh 0.2 g of MNPs@G2.5 obtained in step (4) and 0.2 g of 2-aminoterephthalic acid and add them to 60 mL of N,N-dimethylformamide (DMF). After sonicating the mixture for 20 min, transfer it to a three-necked flask and stir mechanically for 30 min. Then, continue stirring at 70 °C for 12 h. After the reaction is complete, collect the product using an external magnetic field and wash it three times with DMF and methanol, respectively. Then, dry it overnight under vacuum at 60 °C to obtain the intermediate product loaded with the amino organic ligand.

[0048] The intermediate product was ground and dispersed in 60 mL of DMF. 0.6 g of zinc nitrate hexahydrate was added, and the mixture was sonicated for 20 min and mechanically stirred for 30 min. The reaction system was then stirred at 70 °C for 12 h. After the reaction was complete, the product was collected using an external magnetic field and washed three times with DMF and methanol, respectively. The washed product was then dried in a vacuum drying oven at 60 °C to obtain the MNPs@G2.5@MOF-5-NH2 magnetic MOF composite adsorbent material.

[0049] Comparative Example 1

[0050] Preparation of MNPs@G0.5@MOF-5-NH2 magnetic MOF composite materials:

[0051] The preparation method of Example 1 is different in that the PAMAM modification generation is G0.5 instead of G2.5. That is, after synthesizing MNPs@G0.5, the MOF-5-NH2 functional layer is directly grown in situ to obtain the MNPs@G0.5@MOF-5-NH2 magnetic MOF composite material.

[0052] Comparative Example 2

[0053] Preparation of MNPs@G1.5@MOF-5-NH2 magnetic MOF composite materials:

[0054] The preparation method of Example 1 is different in that the PAMAM modification generation is G1.5 instead of G2.5. That is, the MNPs@G1.5 functional layer is grown in situ after the Michael addition reaction of methyl acrylate and the amidation reaction of ethylenediamine are carried out alternately to MNPs@G1.5, so as to obtain the MNPs@G1.5@MOF-5-NH2 magnetic MOF composite material.

[0055] Comparative Example 3

[0056] Preparation of MNPs@G2.5 magnetic composite materials:

[0057] The preparation method of Example 1 is different in that only MNPs@G2.5 is prepared, and the in-situ growth of the MOF-5-NH2 functional layer is not performed, so as to obtain the MNPs@G2.5 magnetic composite material.

[0058] Structural characterization of magnetic MOF composite adsorbent materials:

[0059] The MNPs@G2.5@MOF-5-NH2 magnetic MOF composite adsorbent material and related intermediates prepared in Example 1 were characterized by SEM, TEM, XRD, FTIR, XPS and VSM to verify the successful construction of the Fe3O4 magnetic core, silanized interface layer, PAMAM molecular regulation layer and MOF-5-NH2 functional layer.

[0060] Figure 2 The image shows a SEM image of the MNPs@G2.5@MOF-5-NH2 magnetic MOF composite adsorbent material prepared in Example 1. As can be seen from the image, the prepared material has a granular or agglomerated granular morphology and a relatively rough surface.

[0061] Figure 3The image shows a TEM image of the MNPs@G2.5@MOF-5-NH2 magnetic MOF composite adsorbent material prepared in Example 1. As can be seen from the image, the prepared material has a dark magnetic core and a lighter outer modification layer structure, exhibiting an irregular shell-core structure. HRTEM clearly shows that the Fe3O4 lattice fringes were not destroyed by multiple surface modifications, indicating that the magnetic core crystal structure remains intact.

[0062] Figure 4 The XRD patterns of the MNPs@G2.5@MOF-5-NH2 magnetic MOF composite adsorbent prepared in Example 1 and the MNPs@G2.5 magnetic composite material prepared in Comparative Example 3 are shown in the figure. As shown, both the MNPs@G2.5 magnetic composite material and the MNPs@G2.5@MOF-5-NH2 magnetic MOF composite adsorbent retain the characteristic diffraction peaks of Fe3O4, indicating that the crystal structure of the magnetic core was not destroyed after multi-step surface modification. Compared with the MNPs@G2.5 magnetic composite material, the MNPs@G2.5@MOF-5-NH2 magnetic MOF composite adsorbent shows low-angle diffraction peaks related to MOF-5-NH2, indicating that the MOF-5-NH2 crystal structure has been introduced into the composite adsorbent.

[0063] Figure 5 The figure shows a comparison of the FTIR spectra of the MNPs@G2.5@MOF-5-NH2 magnetic MOF composite adsorbent prepared in Example 1 and the MNPs@G2.5 magnetic composite material prepared in Comparative Example 3. As shown, absorption peaks related to Fe-O, Si-O / Si-O-Si, C=O / CN, and carboxylate coordination are observed in the MNPs@G2.5@MOF-5-NH2 magnetic MOF composite adsorbent. Compared with the MNPs@G2.5 magnetic composite material, the MNPs@G2.5@MOF-5-NH2 magnetic MOF composite adsorbent exhibits characteristic absorption peaks related to the coordination of MOF-5-NH2 organic ligands and carboxylates, indicating that the MOF-5-NH2 functional layer has been successfully introduced.

[0064] Figure 6 XPS images of the MNPs@G2.5@MOF-5-NH2 magnetic MOF composite adsorbent material prepared in Example 1 are shown. As shown, elements such as C, N, O, Fe, Si, and Zn were detected on the surface of the MNPs@G2.5@MOF-5-NH2 magnetic MOF composite adsorbent material. Among them, N is associated with PAMAM and amino functional groups, Zn is associated with the zinc coordination structure in MOF-5-NH2, and Si originates from the APTES silanized interface layer. These results further demonstrate that the PAMAM molecular regulation layer and the MOF-5-NH2 functional layer have been introduced into the surface of the magnetic composite material.

[0065] Figure 7 The VSM curves of the MNPs@G2.5@MOF-5-NH2 magnetic MOF composite adsorbent prepared in Example 1 and the MNPs@G2.5 magnetic composite material prepared in Comparative Example 3 are shown. As shown in the figure, the MNPs@G2.5@MOF-5-NH2 magnetic MOF composite adsorbent prepared in Example 1 still exhibits obvious magnetic response characteristics. Compared with the MNPs@G2.5 magnetic composite material, the magnetization of the material is reduced after the introduction of the MOF-5-NH2 functional layer, but rapid separation can still be achieved under the action of an external magnetic field, indicating that this material is suitable for rapid recovery in magnetic solid-phase extraction processes.

[0066] Example 2

[0067] Comparison of enrichment properties of different magnetic composite materials for alkylphenol compounds:

[0068] The composite materials prepared in Example 1 and Comparative Examples 1-3 were used as magnetic solid-phase extraction adsorbents to enrich and detect water samples containing 4-hexylphenol (4-PP), 4-pentylphenol (4-HepP), 4-tert-octylphenol (4-t-OP), and 4-heptylphenol (4-HP) under the same conditions. The effects of different PAMAM modification generations and MOF-5-NH2 functional layers on the enrichment performance of multiple targets were compared.

[0069] As shown in Examples 1 and Comparative Examples 1-3, the generation of PAMAM modification and the introduction of the MOF-5-NH2 functional layer affect the enrichment performance of magnetic composite materials for alkylphenol compounds. Comparative Example 1 used PAMAM (G0.5) as the interface layer, which has relatively few nitrogen-containing functional groups and interface anchoring sites, hindering the full construction of the MOF-5-NH2 functional layer. The resulting material showed weak recovery of various alkylphenol compounds. Comparative Example 2 used PAMAM (G1.5) as the interface layer. The resulting material exhibited high recovery rates for some alkylphenol targets, but relatively weak recovery rates for others, demonstrating some target selectivity. Example 1 used PAMAM (G2.5) as the interface layer. Although its recovery rate for a single target may not always be the highest, it showed a more balanced enrichment effect for various alkylphenol compounds, making it suitable for pretreatment for simultaneous multi-target detection. Furthermore, Comparative Example 3 lacked the MOF-5-NH2 functional layer, thus lacking the metal coordination sites, amino and aromatic ligand structures provided by MOF-5-NH2, resulting in a weaker overall adsorption and enrichment capacity for alkylphenol compounds. This demonstrates that regulating the generation of PAMAM modification and introducing the MOF-5-NH2 functional layer play a crucial role in enhancing the material's overall applicability in enriching multiple target alkylphenols.

[0070] Figure 8The results of comparing the spiked recoveries of four alkylphenol compounds using different magnetic composite materials are used to further verify the differences in enrichment performance mentioned above.

[0071] Example 3

[0072] Establishment and performance evaluation of MSPE-HPLC-VWD method based on MNPs@G2.5@MOF-5-NH2 magnetic MOF composite adsorbent:

[0073] Using the MNPs@G2.5@MOF-5-NH2 magnetic composite adsorbent prepared in Example 1 as a magnetic solid-phase extraction adsorbent, combined with high performance liquid chromatography-variable wavelength detector (HPLC-VWD), an analytical method for alkylphenol compounds was established, and the method performance was evaluated.

[0074] Under optimized magnetic solid-phase extraction (MSE) conditions, a certain concentration of alkylphenol standard solution was added to the water sample, along with 80 mg of magnetic composite adsorbent. Extraction was carried out by shaking at 25°C for 60 min. After extraction, the adsorbent was rapidly separated under an external magnetic field and eluted with acetonitrile. The eluent was concentrated by nitrogen blowing and then redissolved in chromatographic-grade methanol for HPLC-VWD analysis.

[0075] As shown in Table 1, the target alkylphenol compounds ranged from 0.1 to 300 μg·L⁻¹. -1 It exhibits a good linear relationship within the concentration range, R 2 The range of values ​​was 0.9905–0.9983, indicating that the method has good quantitative analytical capabilities; the detection limit of the method was 0.046–0.063 μg·L⁻¹. -1 This indicates that the method is suitable for the analysis of trace alkylphenol compounds; the enrichment factor is 210~248, indicating that the magnetic composite adsorbent material prepared in this invention has a strong enrichment ability for the target analyte.

[0076] Table 1 shows the analytical performance parameters of the established MSPE-HPLC-VWD method for determining alkylphenols (APs).

[0077] 4-PP y = 0.1224x + 3.7919 0.1-300 0.9924 1.8 0.063 210 4-t-OP y = 0.1903x + 6.0225 0.1-300 0.9905 1.6 0.051 225 4-HepP y = 0.2432x + 6.6293 0.1-300 0.9983 1.7 0.046 234 4-HP y = 0.4670x + 5.2402 0.1-300 0.9976 1.8 0.058 248

[0078] Example 4

[0079] Application of MNPs@G2.5@MOF-5-NH2 magnetic MOF composite adsorbent material in magnetic solid-phase extraction and detection of alkylphenol compounds in actual water samples:

[0080] The MNPs@G2.5@MOF-5-NH2 magnetic MOF composite adsorbent prepared in Example 1 was used as a magnetic solid-phase extraction adsorbent to enrich, elute, concentrate, and detect alkylphenol compounds in actual water samples using high-performance liquid chromatography. The applicability of this material in the pretreatment of actual water samples was verified by spiked recovery experiments.

[0081] Actual water samples included commercial bottled purified water, chemical plant water samples, pharmaceutical plant water samples, and hospital water samples. The actual water samples were filtered through a 0.22 μm aqueous phase filter membrane before use. 60 mL of each filtered water sample was taken to prepare a 0 μg·L⁻¹ spiking solution. -1 0.5 μg·L -1 5 μg·L -1 and 20 μg·L -1 The spiked water sample system.

[0082] 80 mg of the MNPs@G2.5@MOF-5-NH2 magnetic MOF composite adsorbent prepared in Example 1 was added to each spiked water sample, and the sample was extracted by shaking in a 25°C constant temperature water bath for 60 min. After extraction, the adsorbent was separated by applying an external magnetic field. 3 mL of acetonitrile was added to the separated adsorbent for elution, and the elution time was 3 min, repeated three times. The eluents were combined, dried by nitrogen blowing at 40°C, and redissolved in 200 μL of chromatographic grade methanol. The eluents were then detected and analyzed by high performance liquid chromatography with a variable wavelength detector.

[0083] The results showed that when using the MNPs@G2.5@MOF-5-NH2 magnetic MOF composite adsorbent prepared in this invention for magnetic solid-phase extraction, the recoveries of four alkylphenol compounds in actual water samples were 92%–118%, with relative standard deviations of 0.7%–2.0%. These results indicate that the MSPE-HPLC-VWD method established in this invention is suitable for the enrichment and pretreatment of alkylphenol compounds in actual water samples.

[0084] Figure 9 The figure shows the chromatogram of a spiked water sample. As shown, after processing the actual water sample using the MSPE-HPLC-VWD method described in this invention, four alkylphenol compounds were effectively separated and detected. Combined with the spiked recovery results, it can be concluded that the magnetic MOF composite adsorbent material described in this invention is suitable for pretreatment of alkylphenol compounds in actual water samples.

[0085] Example 5

[0086] Validation of the recyclability of MNPs@G2.5@MOF-5-NH2 magnetic MOF composite adsorbent:

[0087] The magnetic MOF composite adsorbent material prepared in Example 1 was repeatedly used for magnetic solid-phase extraction of alkylphenol compounds according to the method in Example 4, and the retention of its extraction performance after multiple cycles was investigated. Figure 10 The graph shows the recycling performance of Embodiment 5 of the present invention. As can be seen from the graph, when the device is reused 8 times, the recycling rate can still maintain more than 95% of the initial performance.

[0088] The foregoing has shown and described the basic principles, main features and advantages of the present invention. Various changes and modifications can be made to the present invention without departing from the spirit and scope thereof, and all such changes and modifications fall within the scope of the present invention as claimed.

Claims

1. A method for preparing a magnetic metal-organic framework composite material based on interfacial molecular regulation, characterized in that: A magnetic metal-organic framework composite material with a hierarchical composite structure was obtained by sequentially constructing a silanized interface layer, a PAMAM molecular regulation layer, and a MOF-5-NH2 functional layer on the surface of an Fe3O4 magnetic core. The silanized interface layer enhances the surface stability of the Fe3O4 magnetic core and provides sites for subsequent functionalization reactions. The PAMAM molecular regulation layer, rich in nitrogen-containing functional groups, serves as an interface anchoring point for the in-situ growth of MOF-5-NH2, increasing the number of functional sites on the material surface. The MOF-5-NH2 functional layer provides Zn-O clusters, amino groups, and aromatic ligands to enhance the material's enrichment capacity for alkylphenol compounds. The resulting magnetic metal-organic framework composite material exhibits magnetic responsiveness, interfacial stability, and target adsorption affinity, making it suitable for pretreatment of alkylphenol compounds in actual water samples using magnetic solid-phase extraction.

2. The method for preparing magnetic metal-organic framework composite materials based on interface molecular regulation according to claim 1, characterized in that... The specific preparation steps are as follows: Step S1, Preparation of Fe3O4 magnetic nanoparticles: Dissolve ferric salt and ferrous salt in water to obtain a mixed solution of iron salts. Add an alkaline precipitant to the mixed solution of iron salts under stirring and heat the reaction. After the reaction is completed, obtain Fe3O4 magnetic nanoparticles by magnetic separation, washing and drying. Step S2, Preparation of silanized MNPs: The Fe3O4 magnetic nanoparticles obtained in step S1 are dispersed in an alcohol solvent, and then an aminosilane coupling agent is added to cause the aminosilane coupling agent to undergo a hydrolysis and condensation reaction on the surface of the Fe3O4 magnetic nanoparticles. After the reaction is completed, the silanized MNPs are obtained by washing and drying. Step S3, Preparation of MNPs@G0.5 semi-generation product: The silanized MNPs obtained in step S2 are dispersed in an alcohol solvent, and then acrylate monomers are added to allow the acrylate monomers to undergo a Michael addition reaction with the amino groups on the surface of the silanized MNPs. After the reaction is completed, the MNPs@G0.5 semi-generation product is obtained by magnetic separation, washing and drying. Step S4, Preparation of MNPs@G2.5: The half-generation product of MNPs@G0.5 obtained in step S3 is dispersed in an alcohol solvent, and then a diamine monomer is added to carry out an amidation reaction to obtain the full-generation product of MNPs@G1.0; the Michael addition reaction of acrylate monomers and the amidation reaction of diamine monomers are repeated alternately to obtain MNPs@G2.5; Step S5, Preparation of MNPs@G2.5@MOF-5-NH2: The MNPs@G2.5 obtained in step S4 and 2-aminoterephthalic acid are dispersed in an organic solvent to carry out an interfacial anchoring reaction to obtain an intermediate product loaded with amino organic ligands. Then, the intermediate product is combined with zinc salt in an organic solvent to carry out a coordination assembly reaction so that the MOF-5-NH2 functional layer is grown in situ on the surface of MNPs@G2.

5. After the reaction, the material is obtained by magnetic separation, washing and drying to obtain the MNPs@G2.5@MOF-5-NH2 magnetic MOF composite adsorbent material.

3. The method for preparing magnetic metal-organic framework composite materials based on interface molecular regulation according to claim 2, characterized in that: In step S1, the trivalent ferric salt is FeCl3·6H2O, the divalent ferric salt is FeSO4·7H2O, and the alkaline precipitant is an ammonia solution. The feeding ratio of FeCl3·6H2O, FeSO4·7H2O, water, and ammonia solution is 2.5~3g:1.2~1.5g:40~60mL:8~10mL, and the mass concentration of the ammonia solution is 25%~28%. The heating reaction temperature is 70~90℃, and the heating reaction time is 20~60min.

4. The method for preparing magnetic metal-organic framework composite materials based on interface molecular regulation according to claim 2, characterized in that: The alcohol solvent in step S2 is ethanol, the aminosilane coupling agent is 3-aminopropyltriethoxysilane, the feeding ratio of Fe3O4 magnetic nanoparticles, ethanol and 3-aminopropyltriethoxysilane is 1g:80~120mL:5~9mL, the hydrolysis condensation reaction temperature is 50~70℃, and the hydrolysis condensation reaction time is 5~9h.

5. The method for preparing magnetic metal-organic framework composite materials based on interface molecular regulation according to claim 2, characterized in that: In step S3, the alcohol solvent is methanol, the acrylate monomer is methyl acrylate, the feeding ratio of silanized MNPs, methanol and methyl acrylate is 2g:40~60mL:15~25mL, the Michael addition reaction temperature is room temperature, and the Michael addition reaction time is 5~10h.

6. The method for preparing magnetic metal-organic framework composite materials based on interface molecular regulation according to claim 2, characterized in that: In step S4, the alcohol solvent is methanol, the diamine monomer is ethylenediamine, the half-generation product of MNPs@G0.5 is dispersed in methanol, and after ultrasonic treatment and mechanical stirring, ethylenediamine is added. The amidation reaction is carried out at room temperature for 6-10 hours to obtain the full-generation product of MNPs@G1.

0. The Michael addition reaction of methyl acrylate and the amidation reaction of ethylenediamine are repeated alternately until MNPs@G2.5 is obtained.

7. The method for preparing magnetic metal-organic framework composite materials based on interface molecular regulation according to claim 2, characterized in that: The organic solvent in step S5 is N,N-dimethylformamide, and the zinc salt is zinc nitrate hexahydrate; the mass ratio of MNPs@G2.5 to 2-aminoterephthalic acid is 1:0.5~2, the interface anchoring reaction temperature is 60~80℃, and the interface anchoring reaction time is 8~16h; the coordination assembly reaction temperature is 60~80℃, and the coordination assembly reaction time is 8~16h.

8. The magnetic metal-organic framework composite material based on interfacial molecular regulation prepared by the method according to any one of claims 1 to 7, characterized in that: The magnetic metal-organic framework composite material has a hierarchical composite structure with an Fe3O4 magnetic core and a silanized interface layer, a PAMAM molecular regulation layer, and an amino-functionalized MOF-5-NH2 functional layer loaded on the surface of the Fe3O4 magnetic core. The magnetic metal-organic framework composite material has magnetic responsiveness, interface stability, abundant surface functional sites, and MOF porous structure, which is beneficial to improving its enrichment ability of alkylphenol compounds. By introducing the silanized interface layer and the PAMAM molecular regulation layer, the surface stability and dispersibility of Fe3O4 magnetic nanoparticles are improved, and interface anchoring points are provided for the in-situ growth of MOF-5-NH2, thereby enhancing the bonding stability between the MOF-5-NH2 functional layer and the magnetic substrate.

9. The application of the magnetic metal-organic framework composite material based on interface molecular regulation prepared by the method according to any one of claims 1 to 7 as a magnetic solid-phase extraction adsorbent in the pretreatment of alkylphenol compounds for magnetic solid-phase extraction, enrichment, separation or detection in actual water samples.

10. The application according to claim 9, characterized in that: The magnetic metal-organic framework composite material based on interface molecular regulation is available in the range of 0.1~300 μg·L⁻¹. -1 It exhibits good linear response within the concentration range, with a detection limit of 0.046–0.063 μg·L⁻¹. -1 The enrichment factor is 210~248, the actual water sample spiked recovery rate is 92%~118%, and the relative standard deviation is 0.7%~2.0%; after 8 cycles, it still maintains more than 95% of the initial extraction performance.

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