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

Abstract

The invention relates to a fluorine-based three-dimensional covalent organic framework material as well as a preparation method and application thereof, and belongs to the technical field of covalent organic framework materials. Under the action of a catalyst, a first monomer (the first monomer is selected from a regular tetrahedron-containing amino monomer or a regular tetrahedron-containing aldehyde group monomer) and a second monomer (the second monomer is selected from a fluorine-containing aldehyde group monomer or a fluorine-containing amino monomer) are subjected to a condensation reaction in an organic solvent to obtain the fluorine-based three-dimensional covalent organic framework material. The method comprises the following steps of: preparing a solid-phase microextraction probe by taking the perfluorinated compound as an adsorbent through in-situ growth on the surface of a probe matrix, and then combining the solid-phase microextraction probe with an open-type mass spectrum to detect trace perfluorinated compounds in a complex matrix. The fluorine-based three-dimensional covalent organic framework material disclosed by the invention is good in chemical stability and high in hydrophobicity, has a good adsorption effect on perfluorinated compounds, and is high in repeated utilization rate.

Description

Technical Field

[0001] The present invention belongs to the technical field of covalent organic framework materials, and in particular relates to a fluorine-based three-dimensional covalent organic framework material and a preparation method and application thereof. Background Art

[0002] Per- and polyfluoroalkyl substances (PFASs) are a large class of synthetic fluorinated organic chemicals that have shown great applicability in industrial and household scenarios. However, due to the high dissociation energy of the CF bond, PFASs have extremely high stability, persistence, and long-range mobility in the environment, which increases their bioaccumulation and potential ecological and health risks. According to the Stockholm Convention, some PFASs have been listed as persistent organic pollutants and are subject to strict regulation by the United States Environmental Protection Agency (USEPA), including maximum concentration limits. However, since PFSAs usually appear in complex environmental matrices at trace or ultra-trace levels, rapid and sensitive removal and detection of PFSAs remains a difficulty. At present, adsorption method is one of the most important control methods for removing PFSAs from complex environmental matrices, but traditional adsorbents have low adsorption capacity and slow kinetics, poor chemical stability, and short lifespan, and the effect is always unsatisfactory in application.

[0003] Covalent organic frameworks (COFs), as a new type of crystalline material composed of molecular building blocks connected by covalent bonds, can provide opportunities to adjust the structure, pore size and surface chemical properties, thereby compensating for the shortcomings of traditional adsorbents to improve the adsorption effect of target molecules. Currently, 2D COFs have been widely used in the adsorption of PFASs. However, since 2D COFs exhibit a layered stacking structure and their single one-dimensional pores easily make the adsorption process inflexible and reduce the mass transfer efficiency. In contrast, when 3D COFs extend in three-dimensional space, they tend to form larger cage-like cavities with more complex interconnected porous networks, which will facilitate the multi-party diffusion and mass transfer of the target. However, the skeletons of existing 3D COFs are mostly non-polar and easily produce hydrophobic interactions with highly hydrophobic PFSAs. Therefore, it will be of great significance to develop a functionalized covalent organic framework that can extract PFSAs. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a fluorine-based three-dimensional covalent organic framework material and its preparation method and application. A fluorine-containing three-dimensional covalent organic framework is prepared by a solvent thermal synthesis method, and further used as an adsorbent, in situ grown on the surface of a probe substrate to prepare a solid phase microextraction probe, which is then combined with an open mass spectrometer to detect trace perfluorinated compounds in complex matrices. The fluorine-based three-dimensional covalent organic framework material of the present invention has good chemical stability, high hydrophobicity, good adsorption effect on perfluorinated compounds, and high reuse rate.

[0005] The first object of the present 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-containing monomer or a tetrahedral aldehyde-containing monomer; the second monomer is selected from a fluorine-containing aldehyde-containing monomer or a fluorine-containing amino-containing monomer;

[0006] When the first monomer is a monomer containing a tetrahedral amino group, the second monomer is a monomer containing a fluorine aldehyde group;

[0007] When the first monomer is a monomer containing a regular tetrahedral aldehyde group, the second monomer is a monomer containing a fluorine amino group.

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

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

[0010] The fluorine-containing aldehyde monomer is selected from one or more of 2,3,5,6-tetrafluorobenzaldehyde, 2,5-difluoroterephthalaldehyde, 2,3-difluoroterephthalaldehyde, 2-fluoroterephthalaldehyde and 2,2',3,3',5,5',6,6'-octafluoro-[1,1'-biphenyl]-4,4'-dicarboxaldehyde;

[0011] The fluorine-containing 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-biphenylenediamine and 2-(trifluoromethyl)-1,4-phenylenediamine.

[0012] In one embodiment of the present invention, the fluorine-containing 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-biphenyl diamine and 2-(trifluoromethyl)-1,4-phenylenediamine.

[0013] In one embodiment of the present invention, the molar ratio of the first monomer to 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 the 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 condensation reaction is carried out at a temperature of 30°C-120°C and for a time of 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 steps of washing, centrifugation and drying are further included; the washing solvent is one or more of tetrahydrofuran, ethanol and ultrapure water; and the unreacted monomers are washed away by washing.

[0019] The second object of the present invention is to provide a fluorine-based three-dimensional covalent organic framework material prepared by the method.

[0020] The third object of the present invention is to provide an application of the fluorine-based three-dimensional covalent organic framework material in detecting perfluorinated compounds.

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

[0022] S1, preparing a fluorine-based three-dimensional covalent organic framework material on the surface of a probe substrate to obtain a solid phase microextraction probe;

[0023] S2, contacting the solid phase microextraction probe with the target;

[0024] S3, connecting the solid phase microextraction probe after contacting the target object to a voltage source;

[0025] S4. Use it in conjunction with an open mass spectrometer online to analyze and detect perfluorinated compounds in the mass spectrometer.

[0026] In one embodiment of the present invention, the probe substrate is selected from a stainless steel needle, a stainless steel sheet, a paper sheet or a toothpick.

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

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

[0029] (2) The fluorine-based three-dimensional covalent organic framework material described in the present invention is formed by complete covalent bonds, has better chemical stability, and has greater advantages in enrichment. It is loaded on the surface of the probe substrate by in-situ growth, which improves the reproducibility and recycling rate of the probe. When detecting perfluorinated compounds, the solid phase microextraction method is used to treat the sample, which does not require too much operation and shortens the sample processing time. No chromatographic separation is required, the operation is simple, and the solvent loss is small, which reduces the matrix effect in the analysis process and improves the accuracy and sensitivity of the analysis of trace perfluorinated compounds in the matrix. The detection limit is 0.05ng / L-0.86ng / L, and the linear relationship is good; at the same time, after repeated use for 150 times, the extraction effect has no obvious change. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below according to specific embodiments of the present invention in conjunction with the accompanying drawings, wherein:

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

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

[0033] Figure 3 Characterization diagram of 3D COF TFPM-Pa-CF3 in Test Example 2 of the present invention; wherein a is an X-ray diffraction pattern (PXRD), b is an X-ray diffraction pattern (PXRD) after treatment with different solvents, c is an infrared spectrum (FT-IR), and d is an X-ray photoelectron spectrum;

[0034] Figure 4The scanning electron microscope image and contact angle image of 3D COF TFPM-Pa-CF3 in Test Example 2 of the present invention; wherein a is a scanning electron microscope image, and b is a contact angle image;

[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; wherein 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 kinetics diagram;

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

[0037] Figure 7 3D COF TFPM-Pa-CF3-SS in Test Example 4 of the present invention is a PXRD pattern;

[0038] Figure 8 The photographs and scanning electron microscope images of 3D COF TFPM-Pa-CF3-SS in Test Example 4 of the present invention; wherein, a is a photograph of 3D COF TFPM-Pa-CF3-SS, b is a scanning electron microscope image of a bare needle, c is a scanning electron microscope image of 3D COF TFPM-Pa-CF3-SS, and d is a scanning electron microscope image of a cross section of 3D COF TFPM-Pa-CF3-SS;

[0039] Fig. 9 This is the optimization diagram of solid phase microextraction in Test Example 5 of the present invention;

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

[0041] Fig.11 This is the calibration curve for detecting PFASs by 3D COF TFPM-Pa-CF3-SS in Test Example 5 of the present invention; wherein a is PFBS, b is PFHxS, c is PFOS, d is 6:2FTS, and e is OBS;

[0042] Fig.12 This is a PXRD comparison diagram of 3D COF TFPM-Pa-CF3 before and after extraction in Test Example 5 of the present invention;

[0043] Fig.13 This is a comparison chart of 3D COF TFPM-Pa-CF3 before and after extraction 150 times in Test Example 5 of the present invention. DETAILED DESCRIPTION

[0044] The present invention is further described below in conjunction with specific embodiments so that those skilled in the art can better understand the present invention and implement it. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. 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 the present invention, unless otherwise defined, technical and scientific terms used in the present invention have the same meanings as commonly understood by those skilled in the art to which the present invention belongs.

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

[0047] In the present invention, unless otherwise stated, the experimental methods used in the embodiments of the present invention are conventional methods unless otherwise stated, and the materials, reagents, etc. used are all commercially available unless otherwise stated.

[0048] Example 1

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

[0050] S1. Weigh tetrakis(4-formylphenyl)methane TFPM (0.05mmol, 21.6mg) and 2-(trifluoromethyl)-1,4-phenylenediamine Pa-CF3 (0.1mmol, 17.6mg) into a 35mL Pyrex tube, add 1mL acetonitrile at the same time, and ultrasonically treat for 5min to make the two monomers evenly dispersed in the solution.

[0051] S2. Under ultrasound, 6 mol / L acetic acid (0.1 mL) was slowly added dropwise to the mixed solution. After waiting for 10 min of ultrasound, the mixture was degassed using 3 freeze-pump-thaw cycles. The mixture was condensed at 90° C. for 3 days to obtain a yellow precipitate.

[0052] S3, collect the yellow precipitate by centrifugation, wash it 3 times with tetrahydrofuran to remove the unreacted monomer, and then repeat the washing 3 times with ethanol. Finally, the precipitate is dried overnight at 60°C under vacuum for 24 hours to obtain a yellow powder with a yield of 87.3%, i.e., a fluorine-based three-dimensional covalent organic framework material (3D COF TFPM-Pa-CF3).

[0053] Example 2

[0054] Basically the same as Example 1, except that 2-(trifluoromethyl)-1,4-phenylenediamine is replaced with 1,4-diamino-2,5-difluorobenzene, and the characterization results of the prepared fluorine-based three-dimensional covalent organic framework material are similar to those of Example 1.

[0055] Example 3

[0056] Basically the same as Example 1, except that tetrakis(4-formylphenyl)methane is replaced by 1,3,5,7-tetrakis(4-aminophenyl)-adamantane, and 2-(trifluoromethyl)-1,4-phenylenediamine is replaced by 2,3,5,6-tetrafluorobenzaldehyde. The characterization results of the prepared fluorine-based three-dimensional covalent organic framework material are similar to those in Example 1.

[0057] Example 4

[0058] Basically the same as Example 1, except that tetrakis(4-formylphenyl)methane is replaced by tetrakis(4-formylphenyl)silane, and the characterization results of the prepared fluorine-based three-dimensional covalent organic framework material are similar to those of Example 1.

[0059] Example 5

[0060] Basically the same as Example 1, except that tetrakis(4-formylphenyl)methane is replaced by 1,3,5,7-tetraaminoadamantane, and 2-(trifluoromethyl)-1,4-phenylenediamine is replaced by 2,2',3,3',5,5',6,6'-octafluoro-[1,1'-biphenyl]-4,4'-dicarbaldehyde. The characterization results of the obtained fluorine-based three-dimensional covalent organic framework material are similar to those in Example 1.

[0061] Example 6

[0062] Basically the same as Example 1, except that 2-(trifluoromethyl)-1,4-phenylenediamine is replaced with 3,3-bistrifluoromethyl-4,4-biphenylenediamine, and the characterization results of the prepared fluorine-based three-dimensional covalent organic framework material are similar to those of Example 1.

[0063] Comparative Example 1

[0064] Tp (0.05 mmol, 10.5 mg) and Pa-CF3 (0.075 mmol, 13.2 mg) were weighed and added to 35 mL of Pyrex, and 1.5 mL of mesitylene and 1,4-dioxane (1:1, v:v) were added. Ultrasonic dispersion was performed, and 6 mol / L acetic acid (100 μL) was added. Degassing was performed by three freeze-pump-thaw cycles. The reaction was maintained at 120 °C for 2 days, washed with tetrahydrofuran (THF), and the brown-red precipitate was collected by centrifugation, namely 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°C, 60°C, 90°C, 120°C), different concentrations of catalysts (3 mol / L, 6 mol / L, 9 mol / L, 12 mol / L), and different condensation reaction times (1 day, 2 days, 3 days, 4 days) on the fluorine-based three-dimensional covalent organic framework material 3D COF TFPM-Pa-CF3 crystal form were investigated. The PXRD diffraction patterns of TFPM-Pa-CF3 prepared under different conditions are shown in Figure 1. Figure 2 The solvent system is one of the important factors in the synthesis of COF. It affects the formation of COF imine bonds through its own solvent heat. Figure 2 It can be seen from a that when the reaction solvent is acetonitrile, the material has obvious characteristic peaks, while in other systems the peaks are incomplete or amorphous polymers; the reaction temperature is an important condition to ensure the reversibility of the reaction. If the temperature is too low, the reaction rate will be slow, while if the temperature is too high, it will affect the polymerization of the two monomers. Figure 2 b It can be seen that the PXRD diffraction peak is the highest at 90°C; Figure 2 c It can be seen that a lower catalyst concentration is not conducive to the formation of the material crystal form, while a too high catalyst concentration is prone to cause the collapse of the structure. Therefore, it is necessary to synthesize at an appropriate concentration. The crystal form of this material is best under the condition of 9 mol / L. Figure 2 d It can be seen that in a short time, the material forms an amorphous crystalline polymer, and then continuously self-repairs at the right time to finally form 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, scanning electron microscopy, etc. The results are as follows Figure 3-Figure 4 As shown. Figure 3 a It can be seen that 3D COF TFPM-Pa-CF3 shows main PXRD characteristic peaks at 8.58°, 17.08°, 19.76° and 21.38°, indicating that 3D COF TFPM-Pa-CF3 was successfully synthesized. Figure 3 b It can be seen that the PXRD spectra after treatment with different organic solvents have no obvious changes, which proves that it has high chemical stability and lays the foundation for subsequent applications. Figure 3 c It can be seen that the 3D COF TFPM-Pa-CF3 in the infrared spectrum is at 1625cm -1The characteristic imine band appeared at the same time, and the characteristic peak of TFPM aldehyde group (1700cm -1 ) obviously decayed, which again indicated that TFPM and Pa-CF3 were successfully condensed through Schiff base reaction. -1 The strong stretching peak at shows the characteristic peak of -CF3. Figure 3 As can be seen from d, the obvious F1s peak in the XPS scanning 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 produce fluorine-fluorine interaction with PFASs. Figure 4 a It can be seen that the 3D COF TFPM-Pa-CF3 has a spherical morphology. Figure 4 b It can be seen that 3D COF TFPM-Pa-CF3 has high hydrophobicity and can form hydrophobic interactions with PFASs.

[0069] Test Example 3

[0070] In view of the rich fluorine affinity, high chemical stability and super hydrophobicity of 3D COF TFPM-Pa-CF3, a series of PFSAs adsorption experiments were carried out using 6:2FTS with a concentration of 200ppm as a model and 2D COF TpPa-CF3 of Example 1 as a comparative material. First, the adsorption pH values ​​of the two materials were optimized. Figure 5 a- Figure 5 As shown in b, the 3D COF TFPM-Pa-CF3 reached a maximum adsorption capacity of 182.98 mg / L at pH 5, and the 2D COF TpPa-CF3 reached a maximum adsorption capacity of 105.4 mg / L at pH 3. In subsequent experiments, the two were compared under their optimal pH conditions.

[0071] The adsorption behavior was studied by kinetic experiments. Figure 5 As shown in Figure c, it takes less time for 6:2FTS to reach adsorption equilibrium on the 3D COF TFPM-Pa-CF3, only 5 minutes, but it takes 10 minutes on the equivalent 2D COF TpPa-CF3. This reveals that the complex pore structure in the 3D COF is conducive to promoting the diffusion and transport of molecules, while the abundant active sites on the surface provide a huge role for adsorption. Pseudo-first-order and pseudo-second-order models are 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 chemical adsorption of 6:2FTS on COFs is mainly related to the fluorine-fluorine interaction between the trifluoromethyl group and the target.

[0072] Test Example 4 Preparation of solid phase microextraction probe

[0073] Reference Figure 6 As shown, the probe substrate stainless steel wire (0.25 mm × 40 mm) was first soaked in aqua regia for 10 min to produce 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) and stirred for 12 h, and dried in an oven at 80 ° C for 12 h. Then, the dried probe was immersed in a mixture containing 1 mL of ethanol and Pa-CF3 monomer for 4 h at 90 ° C to graft -NH2 on the probe. Finally, the probe was inserted into a mixed solution of TFPM (21.6 mg), Pa-CF3 (17.6 mg), 1 mL acetonitrile and acetic acid (6 M, 0.1 mL), and after ultrasonic treatment for 10 min, it was degassed by three freeze-pump-thaw cycles and placed at 90 ° C for 3 days to allow TFPM and Pa-CF3 to fully react, thereby obtaining a solid phase microextraction probe 3D COF TFPM-Pa-CF3-SS coated with 3DCOF TFPM-Pa-CF3. The probe was rinsed with tetrahydrofuran to remove the unreacted ligand, and then rinsed with ethanol and dried at room temperature.

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

[0075] The photos and SEM images of 3D COF TFPM-Pa-CF3-SS are shown in Figure 8 As shown. Figure 8 The actual picture of the solid phase microextraction probe in a shows that there is a clear yellow 3D COF TFPM-Pa-CF3 coating at the end of the probe. Figure 8 b- Figure 8 c SEM image of solid phase microextraction probe. It is obvious that compared with the bare needle, after grafting 3D COF TFPM-Pa-CF3, uniform and dense spherical particles are formed on the probe surface, which once again verifies the successful bonding of 3D COF TFPM-Pa-CF3. Figure 8 The cross-sectional SEM image in (d) shows that the thickness of the 3D COF TFPM-Pa-CF3 coating is about 12 μm.

[0076] Test Example 5

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

[0078] S2. Condition optimization: 3D COF TFPM-Pa-CF3-SS was immersed in 1.5mL 5ppb sample of the above five PFASs for extraction. The enrichment and elution conditions were optimized by 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 shown in Figure 2. Fig. 9 As shown, the rotation speed is preferably 800 rpm, the extraction time is preferably 2 min, the solution pH is preferably 5, the ion concentration is preferably 0, the elution solvent is preferably methanol, the voltage source is preferably 3200 V, and the eluent flow rate is preferably 20 μL / min.

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

[0080] Table 1

[0081] Analytes Linear range (ng / L) Correlation coefficient Detection limit (ng / L) Limit of quantitation (ng / L) PFBS 5-10000 0.9994 0.55 1.83 PFh 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 scraped from the solid phase microextraction probe for characterization and comparison. Fig.12 As shown in the figure, there is no obvious change in PXRD before and after extraction, which proves the high stability of 3D COF TFPM-Pa-CF3. After 150 extractions with 3D COF TFPM-Pa-CF3-SS, the performance before and after extraction is compared. Fig.13 As shown in Figure 2, 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. In addition, the I analytes / I IS The relative standard deviation (RSD) of PFASs using three different TFPM-Pa-CF3-SS was 2.5%-6.7%. analytes / I IS The RSDs were 3.6%-13.7%, indicating that the probe had good reproducibility.

[0083] Obviously, the above embodiments are merely examples for clear explanation and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the protection scope of the invention.

Claims

1. A method for preparing a fluorine-based three-dimensional covalent organic framework material, characterized in that: The method comprises 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 monomer containing a regular tetrahedral amino group or a monomer containing a regular tetrahedral aldehyde group; the second monomer is selected from a monomer containing a fluorine aldehyde group or a monomer containing a fluorine amino group; When the first monomer is a monomer containing a tetrahedral amino group, the second monomer is a monomer containing a fluorine aldehyde group; When the first monomer is a monomer containing a regular tetrahedral aldehyde group, the second monomer is a monomer containing a fluorine amino group.

2. The method for preparing a fluorine-based three-dimensional covalent organic framework material according to claim 1, characterized in that: The tetrahedral amino group-containing monomer is selected from one or more of tetrakis(4-aminophenyl)methane, 1,3,5,7-tetrakis(4-aminophenyl)-adamantane, 1,3,5,7-tetraaminoadamantane and tetrakis(4-aminophenyl)silane; The tetrahedral aldehyde group-containing monomer is selected from one or more of tetrakis(4-formylphenyl)methane, tetrakis(4-formylphenyl)silane, 1,3,5,7-tetrakis(4-benzaldehyde)-adamantane and 1,3,5,7-tetraaldehyde-adamantane; The fluorine-containing aldehyde monomer is selected from one or more of 2,3,5,6-tetrafluorobenzaldehyde, 2,5-difluoroterephthalaldehyde, 2,3-difluoroterephthalaldehyde, 2-fluoroterephthalaldehyde and 2,2',3,3',5,5',6,6'-octafluoro-[1,1'-biphenyl]-4,4'-dicarboxaldehyde; The fluorine-containing 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-biphenylenediamine and 2-(trifluoromethyl)-1,4-phenylenediamine.

3. The method for preparing a 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).

4. The method for preparing a 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.

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

6. The method for preparing a fluorine-based three-dimensional covalent organic framework material according to claim 1, characterized in that: The condensation reaction temperature is 30° C.-120° C., and the reaction time is 1 day-5 days.

7. The method for preparing a 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.

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

9. Use of the fluorine-based three-dimensional covalent organic framework material as claimed in claim 8 in detecting perfluorinated compounds.

10. The use according to claim 9, characterized in that: The method of application comprises the following steps: S1, preparing a fluorine-based three-dimensional covalent organic framework material on the surface of a probe substrate to obtain a solid phase microextraction probe; S2, contacting the solid phase microextraction probe with the target; S3, connecting the solid phase microextraction probe after contacting the target object to a voltage source; S4. Use it online with an open mass spectrometer to analyze and detect perfluorinated compounds in the mass spectrometer.

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