Fluorine-based three-dimensional covalent organic framework material and preparation method and application thereof

Abstract

The present application relates to a kind of fluorine-based three-dimensional covalent organic framework material and its preparation method and application, belong to covalent organic framework material technical field.The present application under the action of catalyst, first monomer (first monomer is selected from containing normal tetrahedron amino monomer or containing normal tetrahedron aldehyde group monomer) and second monomer (second monomer is selected from containing fluorine aldehyde group monomer or containing fluorine amino monomer) carry out condensation reaction in organic solvent, obtain fluorine-based three-dimensional covalent organic framework material, and further as adsorbent, in-situ growth on probe substrate surface preparation solid phase microextraction probe, then with open mass spectrometry, for detecting trace perfluorinated compound in complex matrix.The fluorine-based three-dimensional covalent organic framework material of the present application has good chemical stability, high hydrophobicity, good adsorption effect on perfluorinated compound, and high reusability.

Description

Technical Field

[0001] This invention belongs to the field of covalent organic framework materials technology, and particularly relates to a fluorine-based three-dimensional covalent organic framework material, its preparation method and application. Background Technology

[0002] Per- and polyfluoroalkyl substances (PFASs) are a large class of synthetic fluorinated organic chemicals with wide applicability in industrial and household settings. However, due to the high dissociation energy of the CF bond, PFASs exhibit extremely high stability, persistence, and long-distance migration in the environment, increasing their bioaccumulation and potential ecological and health risks. Under the Stockholm Convention, some PFASs have been classified as persistent organic pollutants and are subject to strict regulation by the U.S. Environmental Protection Agency (USEPA), including maximum concentration limits. However, since PFASs typically occur at trace or ultra-trace levels in complex environmental matrices, rapid and sensitive removal and detection of PFASs remains a challenge. Currently, adsorption methods are one of the primary control methods for removing PFASs from complex environmental matrices, but traditional adsorbents have low adsorption capacity, slow kinetics, poor chemical stability, and short lifespans, resulting in consistently unsatisfactory performance in applications.

[0003] Covalent organic frameworks (COFs), as novel crystalline materials composed of molecular structural units linked by covalent bonds, offer opportunities to adjust their structure, pore size, and surface chemistry, thereby overcoming the shortcomings of traditional adsorbents and improving the adsorption efficiency for target molecules. Currently, 2D COFs are widely used for the adsorption of PFASs. However, the layered, stacked structure of 2D COFs and their single-dimensional channels can lead to inflexible adsorption processes and reduced mass transfer efficiency. In contrast, 3D COFs, when extended in three-dimensional space, easily form larger cage-like cavities and possess a more complex interconnected porous network, which is beneficial for the multidirectional diffusion and mass transfer of target molecule. However, the existing 3D COF frameworks are mostly nonpolar, easily exhibiting hydrophobic interactions with highly hydrophobic PFASs. Therefore, developing a functionalized covalent organic framework capable of extracting PFASs is of great significance. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a fluorine-based three-dimensional covalent organic framework material, its preparation method, and its applications. A fluorine-containing three-dimensional covalent organic framework is prepared via solvothermal synthesis and further used as an adsorbent to prepare a solid-phase microextraction probe by in-situ growth on a probe substrate. This probe is then coupled with open-cell mass spectrometry for the detection of trace perfluorinated compounds in complex matrices. The fluorine-based three-dimensional covalent organic framework material of this invention exhibits good chemical stability, high hydrophobicity, excellent adsorption performance for perfluorinated compounds, and high reusability.

[0005] The first objective of this invention is to provide a method for preparing a fluorine-based three-dimensional covalent organic framework material, comprising the following steps: under the action of a catalyst, a first monomer and a second monomer undergo a condensation reaction in an organic solvent to obtain the fluorine-based three-dimensional covalent organic framework material; the first monomer is selected from a tetrahedral amino monomer or a tetrahedral aldehyde monomer; the second monomer is selected from a fluorinated aldehyde monomer or a fluorinated amino monomer.

[0006] When the first monomer is a tetrahedral amino monomer and the second monomer is a fluorinated aldehyde monomer;

[0007] When the first monomer is a tetrahedral aldehyde monomer and the second monomer is a fluorinated amino monomer.

[0008] In one embodiment of the present invention, the tetrahedral amino monomer is selected from one or more of tetra(4-aminophenyl)methane, 1,3,5,7-tetra(4-aminophenyl)adamantane, 1,3,5,7-tetraaminoadamantane and tetra(4-aminophenyl)silane;

[0009] The tetrahedral aldehyde monomer is selected from one or more of tetra(4-formylphenyl)methane, tetra(4-formylphenyl)silane, 1,3,5,7-tetra(4-benzaldehyde)-adamantane and 1,3,5,7-tetraaldehyde-adamantane;

[0010] The fluorinated aldehyde monomer is selected from one or more of 2,3,5,6-tetrafluoro-p-diphenylaldehyde, 2,5-difluoro-p-phenylaldehyde, 2,3-difluoro-p-phenylaldehyde, 2-fluoro-p-phenylaldehyde and 2,2',3,3',5,5',6,6'-octafluoro-[1,1'-biphenyl]-4,4'-dicarboxaldehyde;

[0011] The fluorinated amino monomer is selected from one or more of 1,4-diamino-2,5-difluorobenzene, 4,4'-diaminooctafluorobiphenyl, 4,4-diamino-3,3-difluorobiphenyl, 2,2',5,5'-tetrafluoro-[1,1'-biphenyl]-4,4'-diamine, 3,3-bistrifluoromethyl-4,4-biphenyldiamine, and 2-(trifluoromethyl)-1,4-phenylene diamine.

[0012] In one embodiment of the present invention, the fluorinated amino monomer is selected from one or more of 1,4-diamino-2,5-difluorobenzene, 4,4'-diaminooctafluorobiphenyl, 4,4-diamino-3,3-difluorobiphenyl, 2,2',5,5'-tetrafluoro-[1,1'-biphenyl]-4,4'-diamine, 3,3-bistrifluoromethyl-4,4-biphenyldiamine, and 2-(trifluoromethyl)-1,4-phenylene diamine.

[0013] In one embodiment of the present invention, the molar ratio of the first monomer and the second monomer is 1:(1-5).

[0014] In one embodiment of the present invention, the catalyst is selected from acetic acid and / or scandium trifluoromethanesulfonate.

[0015] In one embodiment of the present invention, the amount of catalyst used is 5%-20% of the total molar amount of the first monomer and the second monomer.

[0016] In one embodiment of the present invention, the temperature of the condensation reaction is 30°C-120°C and the time is 1 day-5 days.

[0017] In one embodiment of the present invention, the organic solvent is selected from one or more of acetonitrile, dimethyl sulfoxide, dichloromethane, mesitylene, dioxane, o-dichlorobenzene, n-butanol and chloroform.

[0018] In one embodiment of the present invention, after the condensation reaction, the process further includes washing, centrifugation, and drying; the washing solvent is one or more of tetrahydrofuran, ethanol, and ultrapure water; and unreacted monomers are washed away.

[0019] A second objective of this invention is to provide a fluorine-based three-dimensional covalent organic framework material prepared by the method described above.

[0020] A third objective of this invention is to provide an application of the aforementioned fluorine-based three-dimensional covalent organic framework material in the detection of perfluorinated compounds.

[0021] In one embodiment of the present invention, the method of application includes the following steps:

[0022] S1. Fluorine-based three-dimensional covalent organic framework material is prepared onto the surface of the probe matrix to obtain a solid-phase microextraction probe.

[0023] S2. Contact the solid-phase microextraction probe with the target analyte;

[0024] S3. Connect the solid-phase microextraction probe, after contact with the target, to a voltage source;

[0025] S4. Coupled with an open-type mass spectrometer online, it can be used to analyze and detect perfluorinated compounds in a mass spectrometer.

[0026] In one embodiment of the present invention, the probe substrate is selected from stainless steel needles, stainless steel sheets, paper, or toothpicks.

[0027] The technical solution of the present invention has the following advantages compared with the prior art:

[0028] (1) The fluorine-based three-dimensional covalent organic framework material of the present invention has a high surface area and a rich and complex interconnected porous network. Compared with the single one-dimensional channels formed by the stacking of 2D COFs, it is more conducive to the multidirectional diffusion and mass transfer of PFASs, thus improving the mass transfer efficiency. At the same time, the framework of 3D COFs is nonpolar, which easily generates hydrophobic interactions with highly hydrophobic PFASs, thereby improving the adsorption effect. In addition, since most PFASs contain at least one fully fluorinated methyl group (or methylene group), introducing fluorine into the COFs framework can enhance the fluorine affinity with PFASs and precisely generate intermolecular interactions with PFASs, such as fluorine-fluorine interactions, hydrogen bonds, and π-π interactions, thereby further improving the adsorption efficiency.

[0029] (2) The fluorine-based three-dimensional covalent organic framework material described in this invention is formed by complete covalent bonds, exhibiting better chemical stability and greater advantages in enrichment. It is loaded onto the probe matrix surface using an in-situ growth method, improving probe reproducibility and recyclability. When detecting perfluorinated compounds, solid-phase microextraction is used to process the sample, requiring minimal manipulation and shortening sample processing time. No chromatographic separation is needed, making the operation simple and reducing solvent consumption. This reduces matrix effects during analysis, improving the accuracy and sensitivity of analyzing trace perfluorinated compounds in the matrix. The detection limit is 0.05 ng / L-0.86 ng / L, with good linearity; furthermore, after 150 cycles of repeated use, the extraction effect shows no significant change. Attached Figure Description

[0030] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein:

[0031] Figure 1 This is a schematic diagram of the synthesis of 3D COF TFPM-Pa-CF3 in Example 1 of the present invention;

[0032] Figure 2 PXRD diffraction patterns of 3D COF TFPM-Pa-CF3 prepared under different conditions in Test Example 1 of the present invention; where a represents different organic solvents, b represents the temperature of the condensation reaction, c represents the concentration of catalyst, and d represents the time of different condensation reactions.

[0033] Figure 3 The image shows the characterization of 3D COF TFPM-Pa-CF3 in Test Example 2 of this invention; where a is the X-ray diffraction pattern (PXRD), b is the X-ray diffraction pattern (PXRD) after treatment with different solvents, c is the Fourier transform infrared spectrum (FT-IR), and d is the X-ray photoelectron spectrum.

[0034] Figure 4The images shown are scanning electron microscope (SEM) images and contact angle diagrams of 3D COF TFPM-Pa-CF3 in Test Example 2 of this invention; where a is the SEM image and b is the contact angle diagram.

[0035] Figure 5 The adsorption performance test results of 3D COF TFPM-Pa-CF3 and 2D COF TpPa-CF3 in Test Example 3 of the present invention are shown; where a is the pH optimization diagram of 3D COF TFPM-Pa-CF3, b is the pH optimization diagram of 2D COF TpPa-CF3, and c is the adsorption kinetic diagram.

[0036] Figure 6 This is a process diagram of the online coupling of solid-phase microextraction probe and open mass spectrometry in Test Example 4 of the present invention;

[0037] Figure 7 The PXRD pattern of 3D COF TFPM-Pa-CF3-SS in Test Example 4 of this invention;

[0038] Figure 8 The images and scanning electron microscope (SEM) images of the 3D COF TFPM-Pa-CF3-SS in Test Example 4 of this invention are shown below; where a is an image of the 3D COF TFPM-Pa-CF3-SS, b is an SEM image of the bare needle, c is an SEM image of the 3D COF TFPM-Pa-CF3-SS, and d is an SEM image of the cross-section of the 3D COF TFPM-Pa-CF3-SS.

[0039] Figure 9 This is an optimized diagram of solid-phase microextraction in Test Example 5 of the present invention;

[0040] Figure 10 This is the elution curve of 3D COF TFPM-Pa-CF3-SS in Test Example 5 of this invention;

[0041] Figure 11 The calibration curves for detecting PFASs using 3D COF TFPM-Pa-CF3-SS in Test Example 5 of this invention are shown; where a is PFBS, b is PFHxS, c is PFOS, d is 6:2FTS, and e is OBS.

[0042] Figure 12 This is a comparison of PXRD patterns before and after 3D COF TFPM-Pa-CF3 extraction in Test Example 5 of this invention;

[0043] Figure 13 This is a comparison image of 3D COF TFPM-Pa-CF3 before and after 150 extractions in Test Example 5 of this invention. Detailed Implementation

[0044] The present invention will be further described below with reference to specific embodiments, so that those skilled in the art can better understand and implement the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. It should be understood that the specific embodiments are only used to explain the present invention, but the embodiments are not intended to limit the present invention.

[0045] In this invention, unless otherwise stated, the technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0046] In this invention, unless otherwise stated, the term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0047] In this invention, unless otherwise specified, the experimental methods used in the embodiments of this invention are conventional methods, and the materials and reagents used are commercially available unless otherwise specified.

[0048] Example 1

[0049] Reference Figure 1 As shown, the fluorine-based three-dimensional covalent organic framework material (TFPM-Pa-CF3) and its preparation method in this embodiment specifically include the following steps:

[0050] S1. Weigh tetra(4-formylbenzene)methane TFPM (0.05 mmol, 21.6 mg) and 2-(trifluoromethyl)-1,4-phenylene diamine Pa-CF3 (0.1 mmol, 17.6 mg) into a 35 mL Plyrex tube, add 1 mL of acetonitrile, and sonicate for 5 min to ensure that the two monomers are evenly dispersed in the solution.

[0051] S2. Under ultrasound, slowly add 6 mol / L acetic acid (0.1 mL) dropwise to the mixed solution. After waiting for 10 min of ultrasound, degas the solution using a freeze pump-thaw cycle three times. Then, condense the solution at 90℃ for 3 days to obtain a yellow precipitate.

[0052] S3. The yellow precipitate was collected by centrifugation, washed three times with tetrahydrofuran to remove unreacted monomers, and then washed three times with ethanol. Finally, the precipitate was dried overnight at 60°C under vacuum for 24 hours to obtain a yellow powder with a yield of 87.3%, namely the fluorine-based three-dimensional covalent organic framework material (3D COF TFPM-Pa-CF3).

[0053] Example 2

[0054] The results were basically the same as in Example 1, except that 2-(trifluoromethyl)-1,4-phenylene diamine was replaced with 1,4-diamino-2,5-difluorobenzene. The characterization results of the fluorine-based three-dimensional covalent organic framework material were similar to those in Example 1.

[0055] Example 3

[0056] The results were basically the same as in Example 1, except that tetra(4-formylbenzene)methane was replaced with 1,3,5,7-tetra(4-aminophenyl)-adamantane and 2-(trifluoromethyl)-1,4-phenylene diamine was replaced with 2,3,5,6-tetrafluoro-p-dibenzaldehyde. The characterization results of the fluorine-based three-dimensional covalent organic framework material were similar to those in Example 1.

[0057] Example 4

[0058] The results were basically the same as in Example 1, except that tetra(4-formylphenyl)methane was replaced with tetra(4-formylphenyl)silane. The characterization results of the fluorine-based three-dimensional covalent organic framework material were similar to those in Example 1.

[0059] Example 5

[0060] The process was basically the same as in Example 1, except that tetra(4-formylbenzene)methane was replaced with 1,3,5,7-tetraaminoadamantane and 2-(trifluoromethyl)-1,4-phenylene diamine was replaced with 2,2',3,3',5,5',6,6'-octafluoro-[1,1'-biphenyl]-4,4'-dicarboxaldehyde. The characterization results of the fluorine-based three-dimensional covalent organic framework material were similar to those in Example 1.

[0061] Example 6

[0062] The results were basically the same as in Example 1, except that 2-(trifluoromethyl)-1,4-phenylene diamine was replaced with 3,3-bistrifluoromethyl-4,4-biphenyldiamine. The characterization results of the fluorine-based three-dimensional covalent organic framework material were similar to those in Example 1.

[0063] Comparative Example 1

[0064] Weigh out Tp (0.05 mmol, 10.5 mg) and Pa-CF3 (0.075 mmol, 13.2 mg) and add them to 35 mL of Pyrex. Add 1.5 mL of trimethylbenzene and 1,4-dioxane (1:1, v:v), disperse by sonication, and add 6 mol / L acetic acid (100 μL). Degas the mixture by three freeze-thaw cycles. Maintain the reaction at 120 °C for 2 days. Wash with tetrahydrofuran (THF), and collect the brownish-red precipitate by centrifugation. This is the fluorine-based two-dimensional covalent organic framework material (2D COF TpPa-CF3).

[0065] Test Example 1

[0066] Based on Example 1, the effects of different organic solvents (acetonitrile ACN, dimethyl sulfoxide DMSO, dichloromethane DCM, mesitylene, o-dichlorobenzene 1,2-DCB, chloroform TCM), different condensation reaction temperatures (40℃, 60℃, 90℃, 120℃), different catalyst concentrations (3mol / L, 6mol / L, 9mol / L, 12mol / L), and different condensation reaction times (1 day, 2 days, 3 days, 4 days) on the crystal form of the fluorine-based three-dimensional covalent organic framework material 3D COF TFPM-Pa-CF3 were investigated. The PXRD diffraction patterns of TFPM-Pa-CF3 prepared under different conditions are shown below. Figure 2 As shown. The solvent system is one of the important factors in the synthesis of COF, as it affects the formation of imine bonds in COF through its own solvothermal effect. Figure 2 As can be seen from a, when the reaction solvent is acetonitrile, the material exhibits distinct characteristic peaks, while in other systems, the peaks are incomplete or represent amorphous polymers. Reaction temperature is a crucial condition for ensuring the reversibility of the reaction; too low a temperature results in a slow reaction rate, while too high a temperature will affect the polymerization of the two monomers. Figure 2 As can be seen from b, the PXRD diffraction peak is highest at 90℃; from Figure 2 As can be seen from c, lower catalyst concentrations are not conducive to the formation of the material's crystal form, while excessively high catalyst concentrations can easily lead to structural collapse. Therefore, synthesis needs to be carried out at a suitable concentration. This material exhibits the best crystal form under the condition of 9 mol / L. From Figure 2 As can be seen from d, in a short period of time, the material forms an amorphous crystalline polymer, and then continuously self-repairs at the appropriate time, eventually forming a crystalline polymer with an ordered structure, which is optimal at 3 days.

[0067] Test Example 2

[0068] The fluorine-based three-dimensional covalent organic framework material 3D COF TFPM-Pa-CF3 prepared in Example 1 was characterized by X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy. The results are as follows: Figures 3-4 As shown. From Figure 3 As can be seen from the results, 3D COF TFPM-Pa-CF3 exhibits the main PXRD characteristic peaks at 8.58°, 17.08°, 19.76°, and 21.38°, indicating the successful synthesis of 3D COF TFPM-Pa-CF3. From... Figure 3 As can be seen from b, the PXRD spectra after treatment with different organic solvents did not change significantly, demonstrating its high chemical stability and laying the foundation for subsequent applications. From Figure 3 c shows that 3D COF TFPM-Pa-CF3 in the infrared spectrum is at 1625 cm⁻¹ -1The characteristic imine band appeared at [location], and the characteristic peak of the aldehyde group of TFPM (1700 cm⁻¹) was also observed. -1 The significant attenuation further indicates that TFPM and Pa-CF3 successfully condensed via a Schiff base reaction at 1139 cm⁻¹. -1 The strong stretching peak at that location indicates the characteristic peak of -CF3. From Figure 3 As can be seen from d, the obvious F1s peak in the XPS scan spectrum also proves that 3D COF TFPM-Pa-CF3 is rich in fluorine, confirming that 3D COF TFPM-Pa-CF3 can provide fluorine affinity and generate fluorine-fluorine interactions with PFASs. From Figure 4 As can be seen from this, 3D COF TFPM-Pa-CF3 exhibits a spherical morphology. From Figure 4 b shows that 3D COF TFPM-Pa-CF3 has high hydrophobicity and can form hydrophobic interactions with PFASs.

[0069] Test Example 3

[0070] Given the abundant fluorine affinity, high chemical stability, and superhydrophobicity of 3D COF TFPM-Pa-CF3, a series of PFSA adsorption experiments were conducted using 200 ppm 6:2 FTS as a model and 2D COF TpPa-CF3 as a control material. First, the adsorption pH of both materials was optimized. The results... Figure 5 a- Figure 5 As shown in b, 3D COF TFPM-Pa-CF3 achieved a maximum adsorption capacity of 182.98 mg / L at pH 5, while 2D COF TpPa-CF3 achieved a maximum adsorption capacity of 105.4 mg / L at pH 3. Subsequent experiments compared the two under their optimal pH conditions.

[0071] The adsorption behavior was studied using kinetic experiments, and the results are as follows: Figure 5 As shown in Figure c, 6:2FTS reaches adsorption equilibrium on 3D COF TFPM-Pa-CF3 in a shorter time, requiring only 5 minutes, but on an equal amount of 2D COF TpPa-CF3, it requires 10 minutes. This reveals that the complex pore structure of 3D COF facilitates molecular diffusion and transport, while the abundant active sites on the surface play a significant role in adsorption. Pseudo-first-order and pseudo-second-order models were used to further evaluate the kinetic mechanism. In both materials, the pseudo-second-order model showed a higher correlation coefficient than the pseudo-first-order model, indicating that the chemisorption of 6:2FTS on COFs is mainly related to the fluorine-fluorine interaction between the trifluoromethyl group and the target analyte.

[0072] Test Example 4: Preparation of Solid-Phase Microextraction Probe

[0073] Reference Figure 6 As shown, the probe substrate stainless steel wire (0.25mm × 40mm) was first immersed in aqua regia for 10 minutes to create a rough substrate, washed with ultrapure water, and dried in an oven. Subsequently, the probe was immersed in a dopamine solution (pH 8.5, 2 mg / mL) with stirring for 12 hours and dried in an oven at 80°C for 12 hours. Then, the dried probe was immersed in a mixture containing 1 mL of ethanol and Pa-CF3 monomer for 4 hours at 90°C to graft -NH2 onto the probe. Finally, the probe was inserted into a mixed solution of TFPM (21.6 mg), Pa-CF3 (17.6 mg), 1 mL of acetonitrile, and 0.1 mL of acetic acid (6 M). After sonication for 10 min, the probe was degassed by three freeze-thaw cycles and placed at 90 °C for 3 days to allow TFPM and Pa-CF3 to react fully, thus obtaining a solid-phase microextraction probe 3D COF TFPM-Pa-CF3-SS coated with 3DCOF TFPM-Pa-CF3. The probe was washed with tetrahydrofuran to remove unreacted ligands, then rinsed with ethanol, and finally dried at room temperature.

[0074] 3D COF TFPM-Pa-CF3-SS was scraped from the solid-phase microextraction probe 3D COF TFPM-Pa-CF3-SS for characterization. The PXRD pattern is shown below. Figure 7 As shown. From Figure 7 It can be seen that the PXRD pattern of 3D COF TFPM-Pa-CF3 scraped from the probe shows obvious diffraction peaks at 8.58°, which are consistent with the peak positions of powder 3D COF TFPM-Pa-CF3, confirming the successful bonding of 3D COF TFPM-Pa-CF3.

[0075] Photographs and scanning electron microscope images of 3D COF TFPM-Pa-CF3-SS are as follows: Figure 8 As shown. From Figure 8 The physical image of solid-phase microextraction probe a shows a distinct yellow 3D COF TFPM-Pa-CF3 coating at the probe tail. (Comparison) Figure 8 b- Figure 8 The SEM image of the solid-phase microextraction probe clearly shows that, compared to the bare probe, the probe surface formed uniform and dense spherical particles after grafting with 3D COF TFPM-Pa-CF3, further verifying the successful bonding of 3D COF TFPM-Pa-CF3. From Figure 8 The cross-sectional SEM image of d shows that the thickness of the 3D COF TFPM-Pa-CF3 coating is approximately 12 μm.

[0076] Test Example 5

[0077] S1. Preparation of mixed working solutions: A series of PFASs (0.5 ng / L-10000 ng / L) were prepared using pure water, among which... 13 The concentration of the C4-PFOS internal standard compound (IS) was 100 ng / L. The five PFAS were perfluorobutane sulfonate (PFBS), perfluorohexane sulfonate (PFHxS), perfluorooctane sulfonate (PFOS), perfluorohexyl ethyl sulfonate (6:2FTS), and sodium perfluorononane sulfonate (OBS).

[0078] S2. Condition Optimization: 3D COF TFPM-Pa-CF3-SS was immersed in 1.5 mL of 5 ppb samples of the above five PFASs for extraction. The enrichment and elution conditions were optimized using open mass spectrometry, including extraction speed, extraction time, solution pH, ion concentration, elution solvent, mass spectrometry voltage source, and eluent flow rate. The results are as follows: Figure 9 As shown, the preferred rotation speed is 800 rpm, the preferred extraction time is 2 min, the preferred solution pH is 5, the preferred ion concentration is 0, the preferred elution solvent is methanol, the preferred voltage source is 3200V, and the preferred eluent flow rate is 20 μL / min.

[0079] S3. Quantitative determination: Based on elution time Figure 10 It can be seen that elution can be completed within 1 minute, and the standard curve obtained by mass spectrometry analysis is as follows. Figure 11 As shown in Table 1:

[0080] Table 1

[0081] Analytes Linear range (ng / L) Correlation coefficient Limit of detection (ng / L) Limit of quantitation (ng / L) PFBS 5-10000 0.9994 0.55 1.83 PFHxS 5-10000 0.9955 0.86 2.88 PFOS 1-10000 0.9989 0.18 0.60 6:2FTS 1-10000 0.9994 0.09 0.30 OBS 1-10000 0.9996 0.05 0.18

[0082] (4) Reusability experiment: The 3D COF TFPM-Pa-CF3 before and after extraction was characterized and compared by scraping samples from the solid-phase microextraction probe, such as... Figure 12 As shown, there was no significant change in PXRD before and after extraction, demonstrating the high stability of 3D COF TFPM-Pa-CF3. After 150 extractions using 3D COF TFPM-Pa-CF3-SS, the performance before and after extraction was compared as follows: Figure 13 As shown, the peak height ratio of 5000 ng / LPFASs to the internal standard did not change significantly, indicating that the prepared TFPM-Pa-CF3-SS probe can be reused for a long time. Furthermore, the I-value of PFAS extracted three times was... analytes / I IS The relative standard deviation (RSD) was 2.5%–6.7%. IF was obtained using three different TFPM-Pa-CF3-SS PFASs. analytes / I IS The RSD was 3.6%-13.7%, indicating that the probe reproducibility was good.

[0083] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing a fluorine-based three-dimensional covalent organic framework material, characterized in that, The process includes the following steps: Under the action of a catalyst, a first monomer and a second monomer undergo a condensation reaction in an organic solvent to obtain the fluorine-based three-dimensional covalent organic framework material; the first monomer is a tetrahedral aldehyde monomer; the second monomer is a fluorine-containing amino monomer; The tetrahedral aldehyde monomer is selected from one or more of tetra(4-formylphenyl)methane, tetra(4-formylphenyl)silane, 1,3,5,7-tetra(4-benzaldehyde)-adamantane and 1,3,5,7-tetraaldehyde-adamantane; The fluorinated amino monomer is selected from one or more of 1,4-diamino-2,5-difluorobenzene, 4,4'-diaminooctafluorobiphenyl, 4,4-diamino-3,3-difluorobiphenyl, 2,2',5,5'-tetrafluoro-[1,1'-biphenyl]-4,4'-diamine, 3,3-bistrifluoromethyl-4,4-biphenyldiamine, and 2-(trifluoromethyl)-1,4-phenylene diamine.

2. The method for preparing the fluorine-based three-dimensional covalent organic framework material according to claim 1, characterized in that, The molar ratio of the first monomer to the second monomer is 1:(1-5).

3. The method for preparing the fluorine-based three-dimensional covalent organic framework material according to claim 1, characterized in that, The catalyst is selected from acetic acid and / or scandium trifluoromethanesulfonate.

4. The method for preparing the fluorine-based three-dimensional covalent organic framework material according to claim 1, characterized in that, The amount of catalyst used is 5%-20% of the total molar amount of the first and second monomers.

5. The method for preparing the fluorine-based three-dimensional covalent organic framework material according to claim 1, characterized in that, The condensation reaction is carried out at a temperature of 30℃-120℃ for 1-5 days.

6. The method for preparing the fluorine-based three-dimensional covalent organic framework material according to claim 1, characterized in that, The organic solvent is selected from one or more of acetonitrile, dimethyl sulfoxide, dichloromethane, mesitylene, dioxane, o-dichlorobenzene, n-butanol, and chloroform.

7. A fluorine-based three-dimensional covalent organic framework material prepared by the method according to any one of claims 1-6.

8. The application of the fluorine-based three-dimensional covalent organic framework material as described in claim 7 in the detection of perfluorinated compounds.

9. The application according to claim 8, characterized in that, The method of application includes the following steps: S1. Fluorine-based three-dimensional covalent organic framework material is prepared onto the surface of the probe matrix to obtain a solid-phase microextraction probe. S2. Contact the solid-phase microextraction probe with the target analyte; S3. Connect the solid-phase microextraction probe, after contact with the target, to a voltage source; S4. Coupled with an open-type mass spectrometer online, it can be used to analyze and detect perfluorinated compounds in a mass spectrometer.

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