Carboxyl-functionalized magnetic covalent organic framework material, and preparation method and application thereof

Abstract

The application discloses a carboxyl functionalized magnetic covalent organic framework material and a preparation method and application thereof. The carboxyl functionalized magnetic covalent organic framework material is prepared from 2,5-di(4'-formylphenyl) terephthalic acid and 1,3,5-tri(4-aminophenyl) benzene as monomers, and Fe3O4@SiO2-NH2 nanoparticles as a carrier, and is synthesized by a top-down one-step method to obtain the carboxyl functionalized magnetic covalent organic framework material Fe3O4@SiO2@COFs. The carboxyl functionalized magnetic covalent organic framework material prepared by the application not only has the mechanical strength of silica gel filler, but also increases the action sites of the material. The carboxyl functionalized magnetic covalent organic framework material has multiple interactions such as complexation, hydrogen bonding, pi-pi interaction and anion exchange with analytes, is suitable for the enrichment of aniline stimulants and organophosphorus pesticide residues, and provides a new enrichment and extraction material for the judicial identification of drugs and the organic phosphorus pollution of river water and other water bodies.

Description

Technical Field

[0001] This invention relates to the field of analytical testing, and in particular to a carboxyl-functionalized magnetic covalent organic framework material, a method for preparing the carboxyl-functionalized magnetic covalent organic framework material, and the application of the carboxyl-functionalized magnetic covalent organic framework material. Background Technology

[0002] Covalent organic frameworks (COFs) are a novel type of ordered crystalline porous polymer formed by strong covalent bonds between light elements (H, O, C, N, B, Si) and organic monomers. COFs possess advantages such as low crystal density, large specific surface area, tunable pore size, and excellent thermal stability. These advantages have led to their widespread application in chemical sensors, catalysis, gas storage, gas adsorption, optoelectronic devices, and chromatographic separation. COFs are composed of organic building blocks with different structural features, and can be mainly classified into: boric anhydride-formed, borate ester-formed, nitrile ring trimer-formed, hydrazine-formed, and imine-formed COFs.

[0003] Magnetic covalent organic framework MCOFs Magnetic covalent organic frameworks (COFs) are magnetized COFs. Currently, the main methods for magnetizing COFs include monomer polymerization, coating, or in-situ synthesis. Among these, the coating method involves directly coating COFs onto magnetic nanoparticles. It offers advantages such as simple synthesis, adjustable outer layer thickness, and easy control over adsorption area and sites, making it a frequently used preparation method. The most commonly used magnetic nanoparticles for magnetic covalent organic frameworks are Fe3O4 and Fe3O4@SiO2. In recent years, magnetic microsphere-modified materials have been widely used in analytical chemistry, especially in sample pretreatment techniques, for enriching and separating target analytes in complex media. Magnetic covalent organic framework materials have potential applications in sample pretreatment and separation. For example, CN201810143237.3 discloses a magnetic sulfonic acid-functionalized COF material for enriching biphenyl compounds in samples, and CN202211086882.9 discloses a magnetic squaric acid-functionalized COF material for extracting phenylpyrazole pesticides. However, there are currently no reports on the use of magnetic covalent organic framework materials for sample pretreatment of various polar analytes such as drugs and organophosphates.

[0004] In summary, the development of magnetic COFs materials with high selectivity, enrichment, versatility, and ease of operation is of great significance for the analysis and detection of polar analytes such as drugs and organophosphates. Summary of the Invention

[0005] In view of this, the first objective of the present invention is to provide a carboxyl-functionalized magnetic covalent organic framework material. The second objective of the present invention is to provide a method for preparing a carboxyl-functionalized magnetic covalent organic framework material. The third objective of the present invention is to provide applications of the carboxyl-functionalized magnetic covalent organic framework material.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] The carboxyl-functionalized magnetic covalent organic framework material of this invention is synthesized in one step using a top-down strategy with 2,5-bis(4'-formylphenyl)terephthalic acid and 1,3,5-tris(4-aminophenyl)benzene as monomers and Fe3O4@SiO2-NH2 nanoparticles as a carrier. The structural formula of COFs in Fe3O4@SiO2@COFs is as follows:

[0008] .

[0009] The beneficial effects are that this invention employs a top-down strategy to synthesize carboxyl-functionalized magnetic covalent organic framework materials containing carboxylic acid groups in a single step, achieving direct modification of the carboxylic acid groups without requiring post-modification of COFs. Furthermore, the Fe3O4@SiO2@COFs directly modified with carboxylic acid groups obtained by this invention possess multiple interaction sites, including complexation, hydrogen bonding, π-π interactions, and anion exchange, enabling specific recognition of substances with different polarities (such as aniline stimulants and organophosphorus pesticide residues). It can enrich a wide variety of analytes, which is of great significance for forensic identification of drugs and detection of organophosphorus pesticide residues in water bodies.

[0010] This invention also provides a method for preparing carboxyl-functionalized magnetic covalent organic framework materials (i.e., Fe3O4@SiO2@COFs), the preparation method comprising the following steps:

[0011] S1, Fe3O4 nanoparticles were synthesized using a solvothermal method;

[0012] S2, silicon dioxide is bonded to the surface of Fe3O4 nanoparticles to obtain nano Fe3O4@SiO2;

[0013] S3, silanize nano-Fe3O4@SiO2 to obtain Fe3O4@SiO2-NH2 nanoparticles;

[0014] S4. Fe3O4@SiO2-NH2 nanoparticles were reacted with 2,5-bis(4'-formylphenyl)terephthalic acid and 1,3,5-tris(4-aminophenyl)benzene at room temperature to obtain carboxyl-functionalized magnetic covalent organic framework material Fe3O4@SiO2@COFs.

[0015] The beneficial effects are that this invention employs a top-down strategy to synthesize COFs with carboxylic acid groups on the surface of Fe3O4@SiO2-NH2 nanoparticles in one step. The reaction can be completed at room temperature, with mild reaction conditions, facilitating mass production. Compared to post-modified functional materials, this invention simplifies the synthesis steps of existing carboxyl-functionalized magnetic covalent organic framework materials, and the mild reaction conditions further reduce material costs.

[0016] This invention employs a top-down strategy to synthesize carboxylic acid-modified Fe3O4@SiO2@COFs in one step. The core-shell structure is stable, exhibiting excellent dispersibility and reusability. It possesses advantages such as stability and reusability, enabling the specific identification of substances with different polarities (such as aniline stimulants and organophosphorus pesticide residues). This is of great significance for the forensic identification of drugs and the detection of organophosphorus pesticide residues in water bodies.

[0017] In this invention, the Schiff base reaction in S4 uses o-dichlorobenzene and / or n-butanol as solvents and glacial acetic acid as a catalyst. Specifically, it includes the following steps: adding 2,5-bis(4'-formylphenyl)terephthalic acid and 1,3,5-tris(4-aminophenyl)benzene to Fe3O4@SiO2-NH2 nanoparticles, then adding o-dichlorobenzene and / or n-butanol and glacial acetic acid, mixing thoroughly, and reacting at room temperature; after the reaction is completed, centrifuging or filtering to obtain a precipitate, washing, and drying to obtain the carboxyl-functionalized magnetic covalent organic framework material Fe3O4@SiO2@COFs.

[0018] More preferably, the volume ratio of o-dichlorobenzene, n-butanol and glacial acetic acid in S4 is 12-36:8-24:0.2-0.6.

[0019] More preferably, in S4, the weight ratio of Fe3O4@SiO2-NH2 nanoparticles, 2,5-bis(4'-formylphenyl)terephthalic acid and 1,3,5-tris(4-aminophenyl)benzene is (8-22):(35-80):(10-24).

[0020] This invention also provides the application of carboxyl-functionalized magnetic covalent organic framework materials as solid-phase extraction materials in the enrichment of aniline stimulants and organophosphorus pesticide residues. These include methamphetamine, phenethylamine, amphetamine, 3,4-methylenedioxyamphetamine, 3,4-methylenedioxymethylamphetamine, and / or N-methyldiethanolamine.

[0021] The organophosphorus pesticide residues include dichlorvos, acephate, dimethoate, methyl parathion, chlorpyrifos, fenthion, triazophos and / or phosmet.

[0022] In the application of this invention, the analytes in the extracted sample are first enriched using the carboxyl-functionalized magnetic covalent organic framework material of this invention (i.e., carboxyl-rich Fe3O4@SiO2@COFs), then eluted with acetone and / or methanol, and finally qualitatively and quantitatively analyzed by GC-MS / MS; wherein,

[0023] For samples containing aniline stimulants, the chromatographic conditions were as follows: helium was used as the carrier gas at a flow rate of 3.0 mL / min; the column was an Rtx-5MS flexible quartz capillary column; the injection port temperature and detector temperature were set to 270℃ and 330℃, respectively; split injection mode was used; the injection volume was 1 μL; the column oven temperature program was as follows: initial temperature 90℃, heating rate 15℃ / min, reaching 150℃, and holding for 2 min; the mass spectrometry conditions were as follows: EI ion source was selected, electron energy was set to 0.3 kV, ion source temperature was set to 230℃, ion detection (SIM) scanning was selected, interface temperature was set to 150℃, and mass scan was performed in the range of 30–382 m / z.

[0024] For organophosphorus pesticide residue samples, the gas chromatography conditions were as follows: Rtx-5MS flexible quartz capillary column (30m × 0.25mm, 0.25µm), injection port temperature 250℃, splitless injection, helium as carrier gas, pressure control mode at 100kPa, initial column temperature 70℃, held for 2 min, then ramped to 140℃ at a rate of 20℃ / min, then to 165℃ at a rate of 10℃ / min and held for 2.5 min, then to 190℃ at a rate of 3℃ / min, then to 220℃ at a rate of 5℃ / min, and finally to 280℃ at a rate of 10℃ / min and held for 9 min. The mass spectrometry conditions were as follows: SIM acquisition mode, interface temperature 280℃, ion source temperature 230℃, solvent delay time 2 min.

[0025] Compared with existing technologies, this invention uses 5-bis(4'-formylphenyl)terephthalic acid and 1,3,5-tris(4-aminophenyl)benzene as monomers, and polymerizes them to form COFs that coat the surface of core-shell Fe3O4@SiO2-NH2 nanoparticles. This results in a carboxyl-functionalized magnetic covalent organic framework material that combines the mechanical strength of silica gel fillers with increased interaction sites. It exhibits various interactions with the analytes, including complexation, hydrogen bonding, π-π interactions, and anion exchange, resulting in excellent extraction and enrichment capabilities.

[0026] Furthermore, this invention employs a "top-down" strategy to obtain Fe3O4@SiO2@COFs in one step. The preparation method is simple, and the reaction conditions between the monomer and the magnetic nanoparticles Fe3O4@SiO2-NH2 are mild, achieving pre-modification of the carboxylic acid groups. This results in low cost, and the prepared Fe3O4@SiO2@COFs are not only reusable but also have excellent dispersibility, which is of great significance for the detection and separation of polar substances.

[0027] The Fe3O4@SiO2@COFs prepared in this invention exhibits high recovery rate and precision, making it suitable not only for the extraction of aniline stimulants from samples but also for the extraction of low-content organophosphorus pesticide residues in river water, reservoirs, and other water bodies, with high extraction efficiency. This provides a new extraction material for forensic identification of narcotics and for addressing organophosphorus pollution in river water and other water bodies. Experiments have shown that the GC-MS / MS quantitative detection method for stimulants and organophosphorus pesticide residues based on Fe3O4@SiO2@COFs established in this invention not only has a wide linear range but also low limits of detection and quantitation, exhibiting high sensitivity. It can achieve quantitative detection of trace amounts of stimulants and organophosphorus pesticide residues, possessing significant guiding significance and promotional value. Attached Figure Description

[0028] Figure 1 This is a synthetic route diagram for the carboxyl-functionalized magnetic covalent organic framework material described in this invention.

[0029] Figure 2 This is the infrared spectrum of the carboxyl-functionalized magnetic covalent organic framework material and monomer of the present invention.

[0030] Figure 2 In the image, (a) represents Fe3O4@SiO2; (b) represents COFs; and (c) represents Fe3O4@SiO2@COFs.

[0031] Figure 3 This is a hysteresis loop diagram of the carboxyl-functionalized magnetic covalent organic framework material of the present invention.

[0032] Figure 4 This is a SEM image of Fe3O4@SiO2@COFs described in this invention.

[0033] Figure 5 This is the TEM image and elemental distribution map of Fe3O4@SiO2@COFs described in this invention.

[0034] Figure 6 This is the XRD pattern of Fe3O4@SiO2@COFs and COFs described in this invention.

[0035] Figure 7 These are the chromatograms of the blank hair sample and the spiked sample in Example 2 of this invention.

[0036] Figure 7 In the spectrum, Blank represents the blank hair sample; Low represents the low-concentration spiked hair sample; Medium represents the medium-concentration spiked hair sample; High represents the high-concentration spiked hair sample; and 1-6 in the spectrum represent amphetamine, phenethylamine, methamphetamine, MDA, MDMA, and MDEA, respectively.

[0037] Figure 8 This is a chromatographic separation diagram of low-concentration, medium-concentration, and high-concentration spiked samples after enrichment and extraction using the carboxyl-functionalized magnetic covalent organic framework material of this invention.

[0038] Figure 8 In the figure, Blank represents the blank sample; Low, Medium, and High represent low, medium, and high concentration labeled samples, respectively. In addition, (1)-(8) in the figure represent Dichlorvos, Acephate, Dimethoate, Parathion-Methyl, Chlorpyrifos, Fenthion, Triazophos, and Phosmet, respectively. Detailed Implementation

[0039] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. These embodiments are implemented based on the technical solution of the present invention, and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments. Furthermore, it should be noted that, unless otherwise specified, the reagents used in the present invention are all commercially available reagents, and the equipment used is all standard laboratory equipment.

[0040] Example 1: The carboxyl-functionalized magnetic covalent organic framework material of the present invention

[0041] I. Preparation method of the carboxyl-functionalized magnetic covalent organic framework material of the present invention

[0042] The carboxyl-functionalized magnetic covalent organic framework material of this invention is a COFs polymerized from 2,5-bis(4'-formylphenyl) terephthalic acid (i.e., 3P-COOH) and 12.6 mg of 1,3,5-tris(4-aminophenyl)benzene (i.e., TAPB) bonded to the surface of Fe3O4@SiO2-NH2 nanoparticles. The preparation route is as follows: Figure 1 The content includes:

[0043] S1, Fe3O4 nanoparticles were synthesized using a solvothermal method.

[0044] Add 80 mL of ethylene glycol to 2.7 g of FeCl3 in a 100 mL reactor liner, and sonicate to dissolve ferric chloride. Then, slowly add 7.2 g of anhydrous sodium acetate and 2.0 g of polyethylene glycol with a degree of polymerization of 1000, and sonicate for 15 min until it becomes silky. Fix the reactor liner in the reactor and slowly heat to 200 °C under nitrogen protection. React at 200 °C for 12 h. After the reaction is completed, cool to room temperature and wash the black product four times alternately with anhydrous ethanol and water (using a magnet to assist in the washing process) to obtain Fe3O4 magnetic nanoparticles. Store the prepared Fe3O4 magnetic nanoparticles in anhydrous ethanol for later use.

[0045] S2, by bonding silicon dioxide to the surface of Fe3O4 nanoparticles, nano Fe3O4@SiO2 is prepared;

[0046] 200 mL of 0.1 mol / L citric acid solution was added to 2 g of Fe3O4 nanoparticles, and the mixture was ultrasonically mixed and stirred at 40°C for 12 h. After the reaction, the nanoparticles were separated by a magnet and the solution was discarded. Then, the nanoparticles were washed three times with ultrapure water and ethanol under the assistance of a magnet. After washing, 160 mL of ethanol / water (v / v = 4:1) was added and the mixture was ultrasonicated for 10 min. Then, 4 mL of ammonia solution was added and the mixture was ultrasonicated for 20 min. 2 mL of tetraethyl silicate was slowly added dropwise and the mixture was stirred at 45°C for 12 h. After the reaction, the nanoparticles were separated by a magnet and the solution was discarded. The separated product was washed three times with acetone, ultrapure water and anhydrous ethanol, and then dried under vacuum at 50°C for 12 h to obtain Fe3O4@SiO2 nanoparticles.

[0047] S3, silanize nano-Fe3O4@SiO2 to obtain Fe3O4@SiO2-NH2 nanoparticles;

[0048] 60 mL of freshly distilled anhydrous toluene was added to 1.0 g of Fe3O4@SiO2 nanoparticles. After ultrasonic mixing, 2 mL of 3-aminopropyltriethoxysilane was added under stirring. The reaction temperature was raised to 120°C and the stirring speed was increased. The reaction was carried out under nitrogen protection for 8 h. After the reaction was completed, the solid product was separated by a magnet and washed three times with toluene, acetone, ultrapure water and ethanol respectively. Finally, the product was vacuum dried at 40 °C for 12 h to obtain Fe3O4@SiO2-NH2 nanoparticles.

[0049] S4, COFs with carboxylic acid groups coated on the surface of Fe3O4@SiO2-NH2 nanoparticles.

[0050] 40.5 mg of 2,5-bis(4'-formylphenyl) terephthalic acid (3P-COOH) and 12.6 mg of 1,3,5-tris(4-aminophenyl)benzene (TAPB) were added to 11.1 mg of Fe3O4@SiO2-NH2 nanoparticles. Then, 18 ml of o-dichlorobenzene, 12 ml of n-butanol, and 0.3 ml of glacial acetic acid were added sequentially. After sonication for 10 min, the mixture was reacted at room temperature for 48 h. After the reaction was completed, the solution was separated and discarded using a magnet. The solid product was washed with DMF, methanol, acetone, and ethanol alternately to completely remove excess reactants. Finally, the product was freeze-dried for 12 h to obtain the carboxyl-functionalized magnetic covalent organic framework material Fe3O4@SiO2@COFs.

[0051] The structural formula of COFs modified on the surface of core-shell Fe3O4@SiO2-NH2 nanoparticles is as follows:

[0052] .

[0053] II. Characterization of the Carboxyl-functionalized Magnetic Covalent Organic Framework Material of the Present Invention

[0054] 1. The prepared double-shell magnetic organic covalent framework material (Fe3O4@SiO2@COFs) and its corresponding monomers were characterized by Fourier transform infrared spectroscopy. The results are shown in the figure. Figure 2 .Depend on Figure 2 It can be seen that Fe3O4@SiO2@COFs at 1620 cm⁻¹ -1 An absorption peak for the C=N stretching vibration was observed at the [location missing], while Fe3O4@SiO2@COFs did not exhibit the characteristic stretching peaks corresponding to the C=O bond of 3P-COOH and the NH bond of TAPB. The results indicate that the 3P-COOH monomer and TAPB monomer were successfully cross-linked with Fe3O4@SiO2-NH2, and the carboxyl-functionalized covalent organic framework material COFs was successfully modified onto the surface of magnetic silica nanoparticles.

[0055] 2. Hysteresis loop characterization was performed on Fe3O4, Fe3O4@SiO2, and Fe3O4@SiO2@COFs. The saturation magnetization of unmodified Fe3O4 was 83 emu g. -1 The saturation magnetization after coating Fe3O4 with silicon dioxide is 35 emu g. -1 The saturation magnetization of Fe3O4@SiO2@COFs decreased to 19 emu g. -1 See details Figure 3 Although the saturation magnetization of Fe3O4@SiO2@COFs is reduced, it still has a high saturation magnetization and paramagnetism, and can be attracted by a magnet.

[0056] 3. The prepared carboxyl-functionalized magnetic covalent organic framework material Fe3O4@SiO2@COFs was observed using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and elemental analysis (EDS). The SEM results are shown in the figure. Figure 4 .Depend on Figure 4 It can be seen that Fe3O4@SiO2@COFs are spherical particles with a lamellar and wrinkled surface and uniform particle size.

[0057] TEM-EDS characterization results of Fe3O4@SiO2@COFs are shown in [reference needed]. Figure 5 .Depend on Figure 5 It can be seen that the Fe3O4@SiO2@COFs prepared by this invention has a distinct core-shell structure; elemental analysis shows that the core of the carboxyl-functionalized magnetic covalent organic framework material is Fe, and the shell is composed of light elements such as C, H, and O.

[0058] The results show that carboxyl-functionalized covalent organic framework materials (COFs) were successfully modified onto the Fe3O4@SiO2-NH2 surface.

[0059] 4. The Fe3O4@SiO2@COFs of the present invention were characterized by XRD, and the results are shown in the figure. Figure 6 .Depend on Figure 6 It can be seen that the peaks of Fe3O4@SiO2@COFs at 2θ = 30.1, 35.3, 42.9, 53.2, 57.1, and 62.7 correspond to 220, 311, 400, 422, 511, and 440, respectively, which are characteristic peaks of iron(III) oxide. Furthermore, the XRD patterns of the COFs and the composite material are identical, indicating that the magnetic composite material was successfully prepared.

[0060] Example 2: Application of the Fe3O4@SiO2@COFs described in this invention as a solid-phase extraction material in the enrichment and extraction of methamphetamine.

[0061] 1. Spiking test for methamphetamine-type stimulants

[0062] The first step is sample pretreatment.

[0063] Hair samples (from normal individuals who have not inhaled aniline stimulants) were shredded, and 20 mg of the shredded hair was weighed into a centrifuge tube. The samples were washed successively with acetone, pure water, and ethanol. Then, 1 mL of 10% NaOH solution was added, and the mixture was heated at 80°C in a metal bath for 10 min to obtain the hair extract.

[0064] Add 3 mL of 10% NaOH solution to 7 mL of urine sample (from a normal person who has not inhaled aniline stimulants) and adjust the pH to above 13; then add NaCl (solid particles) to the sample until saturation, vortex for 2 min, centrifuge, and take the supernatant to obtain the extract of the urine sample.

[0065] Take 1 mL of blood sample (from a normal person who has not inhaled aniline stimulants) into a centrifuge tube, add 1 mL of 10% NaOH solution, vortex for 2 min, and obtain the blood sample extract;

[0066] Six stimulants—methamphetamine (MATM), phenethylamine (PEA), amphetamine (AMP), 3,4-methylenedioxyamphetamine (MDA), 3,4-methylenedioxymethamphetamine (MDMA), and N-methyldiethanolamine (MDEA)—were added to the above extracts to prepare three different concentrations of spiked samples: high, medium, and low. In the high-concentration spiked sample, the concentration of each stimulant was 20 ng / mL; in the low-concentration spiked sample, the concentration of each stimulant was 100 ng / mL; and in the medium-concentration spiked sample, the concentration of each stimulant was 200 ng / mL.

[0067] The second step is enrichment extraction and elution.

[0068] Add 10 mg of Fe3O4@SiO2@COFs to 50 mL of spiked sample, vortex for 25 min, use a magnet to assist separation and discard the aqueous solution, place the magnetic adsorbent in 1 mL of acetone and sonicate for 1 min, dry the eluent at 40 °C under nitrogen; finally, add 0.5 mL of methanol to redissolve, filter through a 0.22 µm filter membrane to obtain the test solution enriched with the target analyte;

[0069] The third step is the quantitative analysis of the eluent by GC-MS / MS.

[0070] Gas chromatography-mass spectrometry (GC-MS / MS) was used to detect the enriched and eluted samples. Chromatographic conditions included: helium as the carrier gas at a flow rate of 3.0 mL / min; an Rtx-5MS flexible quartz capillary column; injection port and detector temperatures set to 270℃ and 330℃, respectively; split injection mode with an injection volume of 1 μL; and a column oven temperature program of: initial temperature 90℃, ramp rate 15℃ / min, ramp to 150℃, and hold for 2 min. Mass spectrometry conditions included: an EI ion source with an electron energy of 0.3 kV and an ion source temperature of 230℃; SIM scanning with an interface temperature of 150℃; and mass scanning within the range of 30–382 m / z. The standard recoveries and RSDs of each drug in the spiked samples are shown in Table 1. Chromatograms of the analytes in the blank samples and the high, medium, and low spiked samples are shown in [Table 1]. Figure 7 .

[0071] Table 1. Standard recoveries and RSDs of aniline stimulants

[0072]

[0073] From the above table 1 and Figure 7 It is known that the Fe3O4@SiO2@COFs of this invention can be used to enrich and extract six amine stimulants from the solution. The Fe3O4@SiO2@COFs exhibits good recovery rate and high precision for each stimulant, indicating that the Fe3O4@SiO2@COFs prepared by this invention has a good enrichment ability for amphetamine, PEA, MAM, MDA, MDMA and MDEA. This provides a new enrichment and extraction material for the forensic identification of various anilines, and has important research significance and promotion value.

[0074] 2. Linear range, limit of quantitation, and limit of detection of methamphetamine-type stimulants.

[0075] Standard solutions of methamphetamine stimulants at different concentrations (≤1000 ng / mL) were prepared. 50 mL of the standard solution was added to 10 mg of Fe3O4@SiO2@COFs, and the mixture was vortexed for 25 min. The aqueous solution was discarded after separation using a magnet. The magnetic adsorbent was placed in 1 mL of acetone and ultrasonically eluted for 1 min. The eluent was dried at 40℃ under nitrogen. Finally, 0.5 mL of methanol was added to redissolve the eluent, which was then filtered through a 0.22 µm filter membrane to obtain the eluent enriched with the target analyte. The eluent was quantitatively analyzed using the detection method and conditions described in step 3 of section 1 of this embodiment. The results are shown in Table 2.

[0076] Table 2. Standard curves, limits of quantitation, and limits of detection for aniline stimulants.

[0077]

[0078] As shown in Table 2, the linear range of each AMINE in this embodiment is 25-1000 ng / mL, and the linear correlation coefficient is ≥0.9974, indicating a very high correlation and good linearity. In addition, the GC-MS / MS detection method of AMINE based on Fe3O4@SiO2@COFs established in this invention also has a low limit of detection (as low as 0.22 ng / mL) and limit of quantitation (in the range of 0.66-1.11 ng / mL), indicating that the method has high detection sensitivity.

[0079] In summary, the GC-MS / MS detection method of AMINE based on Fe3O4@SiO2@COFs of this invention not only has a wide linear range, high detection sensitivity and reliability, but is also applicable to the quantitative detection of trace (or even ultra-trace) doping agents in samples. Furthermore, it can achieve the simultaneous detection of at least six AMINEs, providing a new approach for the forensic identification of doping agents and has significant guiding significance and promotional value.

[0080] Example 3: Application of the Fe3O4@SiO2@COFs described in this invention as a solid-phase extraction material in the enrichment of trace organophosphorus compounds in water.

[0081] 1. This invention utilizes Fe3O4@SiO2@COFs materials and combines GC-MS / MS technology to reliably detect trace organophosphorus pesticide residues in water.

[0082] The first step involved preparing spiked samples containing eight organophosphorus pesticide residues at high, medium, and low concentrations. The high-concentration spiked sample contained 200 ng / mL of each organophosphorus pesticide residue; the medium-concentration spiked sample contained 100 ng / mL of each organophosphorus pesticide residue; and the low-concentration spiked sample contained 20 ng / mL of each organophosphorus pesticide residue. The eight organophosphorus pesticide residues included dichlorvos, acephate, dimethoate, parathion-methyl, chlorpyrifos, fenthion, triazophos, and phosmet.

[0083] The second step involves taking 50 mL of spiked sample and adding 20 mg of solid-phase extraction material (i.e., Fe3O4@SiO2@COFs prepared in Example 1) to each spiked sample, and vortexing for 20 min.

[0084] The aqueous solution was discarded by magnetic separation using a magnet. The solid-phase extraction material was placed in 4 mL of methanol at pH = 10 and ultrasonically eluted for 2 min. The eluent was dried under nitrogen at 40 °C, and then 0.5 mL of methanol was added to redissolve it. The solution was then filtered through a 0.22 µm filter membrane.

[0085] The third step involved analyzing the enriched samples obtained from the extraction using gas chromatography-mass spectrometry (GC-MS / MS). The GC conditions were as follows: Rtx-5MS flexible quartz capillary column (30m × 0.25mm, 0.25µm), injection port temperature 250℃, splitless injection, helium as carrier gas, pressure control mode at 100kPa, initial column temperature of 70℃ for 2 min, followed by a temperature ramp to 140℃ at 20℃ / min, then to 165℃ at 10℃ / min and a hold for 2.5 min, then to 190℃ at 3℃ / min, then to 220℃ at 5℃ / min, and finally to 280℃ at 10℃ / min and a hold for 9 min. The mass spectrometry conditions were as follows: SIM acquisition mode, interface temperature 280℃, ion source temperature 230℃, and solvent delay time 2 min.

[0086] The standard recoveries and RSDs of the eight organophosphorus pesticide residues were tested and are shown in Table 3. Chromatograms of the eight organophosphorus pesticide residues in the blank sample and the high, medium, and low spiked samples are shown in Table 3. Figure 4 .

[0087] Table 3 Standard recoveries and RSDs of eight organophosphorus pesticide residues

[0088]

[0089] Combined with Table 3 and Figure 8 It is known that the standard recoveries of Fe3O4@SiO2@COFs as a solid-phase extraction material for eight organophosphorus pesticides in this invention range from 87% to 110%, with standard deviations ranging from 2.3% to 6.7%. This indicates that Fe3O4@SiO2@COFs as a solid-phase extraction material has good precision in the standard recoveries of eight organophosphorus pesticides and can be used for the enrichment of trace organophosphorus pesticides in water samples such as river water and lake water. This demonstrates that the GC-MS / MS detection method for organophosphorus pesticide residues in water based on Fe3O4@SiO2@COFs established in this invention has certain feasibility.

[0090] 2. The Fe3O4@SiO2@COFs prepared in Example 1 were used as a solid-phase extraction material for the enrichment of organophosphorus pesticide residues in actual river water samples.

[0091] First, draw the standard curve for each organophosphorus pesticide residue.

[0092] Add 20 mg of solid-phase extraction material (i.e., Fe3O4@SiO2@COFs prepared in Example 1) to standard solutions of organophosphorus pesticide residues of different concentrations, and vortex for 20 min; discard the aqueous solution by magnetic separation using a magnet, place the solid-phase extraction material in 4 mL of methanol at pH = 10 (pH was adjusted to 10 with 10% sodium hydroxide) and sonicate for 2 min, dry the eluent at 40 °C under nitrogen, then add 0.5 mL of methanol to redissolve it, and filter it through a 0.22 µm filter membrane;

[0093] The eluent after elution was subjected to gas chromatography-mass spectrometry analysis using the detection conditions in the spiked test (i.e., item 1 of this embodiment). The standard curves, limits of quantitation, and limits of detection for the eight organophosphorus pesticide residues are shown in Table 4.

[0094]

[0095] Table 4 shows the correlation coefficients of the standard curves for the eight organophosphorus pesticide residues. R 2 All values ​​were greater than 0.99, indicating good linearity and a wide linear range. The limits of quantification for organophosphorus pesticide residues ranged from 0.24 to 3.19 ng / mL, and the limits of detection for eight organophosphorus pesticide residues were ≤0.96 ng / mL, even as low as 0.053 ng / mL. These results demonstrate that this invention exhibits high sensitivity and a wide linear range for organophosphorus pesticides.

[0096] Secondly, extraction and quantitative detection of organophosphorus pesticide residues in actual river water samples.

[0097] Sixteen river water samples were obtained (collected from rivers in various cities in Henan Province). 50 mL of each river water sample was taken (each river water sample was in triplicate). 20 mg of solid phase extraction material (i.e., Fe3O4@SiO2@COFs prepared in Example 1) was added to each river water sample and vortexed for 20 min.

[0098] The aqueous solution was discarded by magnetic separation using a magnet. The solid-phase extraction material was placed in 4 mL of methanol at pH = 10 (pH was adjusted to 10 with 10% sodium hydroxide) and ultrasonically eluted for 2 min. The eluent was dried at 40 °C under nitrogen, and then 0.5 mL of methanol was added to redissolve it. The mixture was filtered through a 0.22 µm filter membrane to extract the sample containing organophosphorus pesticide residues.

[0099] Quantitative analysis of actual drinking water samples was performed using the same detection conditions as the organophosphorus spiked test (i.e., the chromatographic and mass spectrometric conditions of GC-MS / MS in item 1 of this embodiment). The contents of eight organophosphorus pesticide residues in the 16 river water samples are shown in Table 5.

[0100] Table 5. Organic phosphorus content in 16 river water samples (unit: ng / mL)

[0101]

[0102] In Table 5: — indicates not detected.

[0103] As shown in Table 5, the Fe3O4@SiO2@COFs of the present invention, as a solid-phase extraction material, can enrich eight organophosphorus pesticide residues in river water, namely Dichlorvos, Acephate, Dimethoate, Parathion-Methyl, Chlorpyrifos, Fenthion, Triazophos, and Phosmet, thereby achieving effective enrichment of organophosphorus pesticide residues in river water, which is of great significance for the detection of organophosphorus pesticide residue pollution in river water.

[0104] Furthermore, as can be seen from the table above, the Fe3O4@SiO2@COFs of the present invention exhibits excellent extraction and enrichment capabilities for organophosphorus pesticide residues, enabling the detection of trace organophosphorus pesticide residues in river water. For example, the concentration of Triazophos in a river in Kaifeng was 0.2341 ng / mL, the concentration of Triazophos in a river in Luoyang was 0.4205 ng / mL, and the concentration of Dichlorvos in a river in Puyang was 0.4661 ng / mL.

Claims

1. A method for preparing a carboxyl-functionalized magnetic covalent organic framework material, characterized in that: The preparation method uses 2,5-bis(4'-formylphenyl)terephthalic acid and 1,3,5-tris(4-aminophenyl)benzene as monomers, and Fe3O4@SiO2-NH2 nanoparticles as a carrier to synthesize carboxyl-functionalized magnetic covalent organic framework material Fe3O4@SiO2@COFs in one step using a top-down strategy. The specific steps include: S1, Fe3O4 nanoparticles were synthesized using a solvothermal method; S2, silicon dioxide is bonded to the surface of Fe3O4 nanoparticles to obtain nano Fe3O4@SiO2; S3, silanize nano-Fe3O4@SiO2 to obtain Fe3O4@SiO2-NH2 nanoparticles; S4. Fe3O4@SiO2-NH2 nanoparticles were reacted with 2,5-bis(4'-formylphenyl)terephthalic acid and 1,3,5-tris(4-aminophenyl)benzene at room temperature to obtain carboxyl-functionalized magnetic covalent organic framework material Fe3O4@SiO2@COFs; wherein the weight ratio of Fe3O4@SiO2-NH2 nanoparticles, 2,5-bis(4'-formylphenyl)terephthalic acid and 1,3,5-tris(4-aminophenyl)benzene was (8-22):(35-80):(10-24).

2. The method for preparing the carboxyl-functionalized magnetic covalent organic framework material according to claim 1, characterized in that, The Schiff base reaction in S4 uses o-dichlorobenzene and n-butanol as solvents and glacial acetic acid as a catalyst. Specifically, it includes the following steps: adding 2,5-bis(4'-formylphenyl)terephthalic acid and 1,3,5-tris(4-aminophenyl)benzene to Fe3O4@SiO2-NH2 nanoparticles, followed by the addition of o-dichlorobenzene, n-butanol, and glacial acetic acid. After mixing thoroughly, the mixture is reacted at room temperature. After the reaction is complete, the precipitate is obtained by centrifugation or filtration, washed, and dried to obtain the carboxyl-functionalized magnetic covalent organic framework material Fe3O4@SiO2@COFs.

3. The method for preparing the carboxyl-functionalized magnetic covalent organic framework material according to claim 2, characterized in that: In step S4, the volume ratio of o-dichlorobenzene, n-butanol, and glacial acetic acid is (12-36): (8-24): (0.2-0.6).

4. The method for preparing the carboxyl-functionalized magnetic covalent organic framework material according to claim 2, characterized in that: The washing in S4 is performed by alternating washing with DMF, methanol, acetone and ethanol.

5. A carboxyl-functionalized magnetic covalent organic framework material, characterized in that: It is prepared by the method for preparing carboxyl-functionalized magnetic covalent organic framework materials according to any one of claims 1-4.

6. The application of the carboxyl-functionalized magnetic covalent organic framework material prepared according to any one of claims 1-4 as a solid-phase extraction material in the detection of aniline stimulants, N-methyldiethanolamine and organophosphorus pesticide residues.

7. The application according to claim 6, characterized in that: The aniline stimulants are methamphetamine, phenethylamine, amphetamine, 3,4-methylenedioxymethamphetamine, or 3,4-methylenedioxymethamphetamine; the organophosphorus pesticide residues are dichlorvos, acephate, dimethoate, methyl parathion, chlorpyrifos, fenthion, triazophos, or imidacloprid.

8. The application according to claim 6, characterized in that: When detecting aniline stimulants, N-methyldiethanolamine, and organophosphorus pesticide residues, the samples were first enriched and extracted using carboxyl-functionalized magnetic covalent organic framework materials, and then the enriched and eluted samples were qualitatively and quantitatively analyzed by GC-MS / MS.

Images