Preparation method and application of a COF material containing phenylboronic acid functional groups

Abstract

The application discloses a preparation method of BrCOF-PBA containing a phenylboronic acid functional group and application of the BrCOF-PBA as a solid-phase extraction agent, and belongs to the technical field of covalent organic framework material preparation. The BrCOF-PBA containing a phenylboronic acid functional group is obtained by modifying a COF containing a bromine functional group through Suzuki coupling, and then a flavonoid drug quercetin containing a cis-ortho diol structure is selectively and efficiently adsorbed through the COF containing the phenylboronic acid functional group. The novel functionalized covalent organic framework containing the phenylboronic acid functional group has good adsorption performance on quercetin (QUE) based on multi-mode interactions such as pi-pi* interaction, hydrogen bond and reversible covalent bond; meanwhile, the BrCOF-PBA can realize efficient adsorption on the QUE due to the advantages such as a large specific surface area, stable crystal structure, good selectivity on the QUE, fast adsorption rate and large adsorption capacity.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of covalent organic framework material preparation, and particularly relates to a preparation method of a COF material containing a phenylboronic acid functional group and application of the COF material as a solid-phase extraction agent. BACKGROUND

[0002] Flavonoids are a class of natural products with polyphenol structure, and due to their excellent antioxidant activity, they can be used for treating various diseases such as autoimmune diseases, neurodegenerative diseases, cardiovascular and cerebrovascular diseases, liver diseases, inflammation and cancer. Quercetin is a representative of important flavonoids, has similar pharmacological activities, and is used as a food antioxidant and a nutritional fortifier. Quercetin is often present in natural plants, and is also rich in many common vegetables and fruits in life, such as onions, tomatoes, broccoli, kale, etc.; at present, many traditional Chinese medicines also contain quercetin, such as purple hu, mulberry leaves, sophora fruit and hawthorn, etc., and these drug ingredients often appear in our daily diet, so its extraction and separation are of great significance.

[0003] Covalent organic frameworks (COF) are a new type of macromolecular organic polymer connected by covalent bonds. Due to its unique network structure, stacking form and strong conjugation effect, it has a series of special physical and chemical properties, such as controllable porosity and pore size, low density, high specific surface area, stable chemical properties, etc., which make COF have a wide application prospect. At present, it plays a prominent role in gas separation and collection, solid separation and collection, photoelectric catalysis, energy conversion, chemical sensing, etc. Cis-diol-containing biomolecules are an important class of compounds, including glycoproteins, carbohydrates, nucleosides and nucleotides, etc., which play an important role in biological systems. Boric acid can reversibly bind to cis-diol, and usually, when the surrounding pH is equal to or greater than the pKa value of boric acid, it can adduct with the hydroxyl group to form a tetrahedral boronate anion (sp 3 ), so as to react with cis-diol to form a five- or six-membered ring ester. When the surrounding pH is much lower than the pKa value of boric acid, the boric acid-cis-diol complex dissociates because the boric acid completely restores to the trigonal configuration (sp 2 ). Therefore, boric acid complex materials have attracted more and more attention in recent years.

[0004] Currently, quercetin is mostly obtained from natural plants with complex components by a method with severe conditions, which is not conducive to its separation and subsequent analysis; solid phase extraction is a relatively reliable and convenient method, however, the existing adsorbents for quercetin or its analogs still have the problem of low adsorption capacity, and since flavonoids have the same parent nucleus, ordinary adsorbents are difficult to selectively adsorb flavonoids with similar structures, which is not conducive to the purification of quercetin and subsequent use. Now there are many kinds of nanomaterials used as solid phase extractants to extract quercetin, such as molecularly imprinted polymers, metal-organic frameworks, mesoporous silica nanoparticles, nanogels, liquid capsules, etc. However, in terms of adsorption of quercetin, these materials still have defects such as low adsorption capacity, long adsorption equilibrium time and weak adsorption specificity. SUMMARY

[0005] The purpose of the present application is to provide a preparation method of a COF material containing a phenylboronic acid functional group and its application as a solid phase extraction agent, the present application can enable the COF containing a phenylboronic acid functional group to selectively and efficiently adsorb the flavonoid drug quercetin containing a cis-ortho diol structure by modifying the COF containing a bromine functional group through Suzuki coupling to obtain BrCOF-PBA containing a phenylboronic acid functional group.

[0006] The purpose of the present application is achieved by the following technical solutions:

[0007] A preparation method of a COF material containing a phenylboronic acid functional group, comprising the following steps:

[0008] (1) Synthesis of BrCOF: 2,5-dibromophthaldehyde, 1,3,5-tris(4-aminophenyl)benzene and o-dichlorobenzene are loaded into a Schlenk flask, degassed with high-purity N2 gas; then the Schlenk flask is sealed, and the mixture is reacted at 120℃ for 72h; after filtration and collection, the precipitate is washed with THF and purified by Soxhlet extraction overnight; vacuum drying to obtain yellow powder BrCOF;

[0009] (2) Synthesis of BrCOF-PBA: the above-synthesized BrCOF and 1,4-p-phenylenediboronic acid, THF are loaded into a Schlenk flask, degassed with high-purity Ar gas; then cesium carbonate aqueous solution, deionized water and tetrakis(triphenylphosphine)palladium are added to the Schlenk flask, which is sealed; the above mixture is kept at room temperature overnight, and then reacted at 90℃ for 48h; after filtration and collection, the precipitate is washed with deionized water at least five times, and extracted with excess deionized H2O and THF; finally, vacuum drying overnight to obtain modified BrCOF-PBA.

[0010] Further, in step (1), the molar ratio of 2,5-dibromophthalaldehyde and 1,3,5-tris(4-aminophenyl)benzene added is 0.80:0.54.

[0011] Further, in step (2), the mass ratio of BrCOF and 1,4-p-benzenediboronic acid is 30.8:124.3-207.2.

[0012] Further, in step (2), the mass ratio of cesium carbonate, tetrakis(triphenylphosphine)palladium and deionized water added is 97.7:7:0.48.

[0013] In another aspect, the application provides a use of the COF containing phenylboronic acid functional groups prepared by the above method as a solid phase extraction agent for separating and extracting flavonoids.

[0014] Further, the flavonoids are quercetin.

[0015] The application has the following beneficial effects:

[0016] 1. The application successfully synthesizes modified BrCOF-PBA by modifying phenylboronic acid functional groups on COF through Suzuki-Miyaura coupling reaction, and the new functionalized covalent organic framework containing phenylboronic acid functional groups has good adsorption performance on quercetin (QUE) based on multi-mode interactions such as π-π* interaction, hydrogen bonding and reversible covalent binding.

[0017] 2. The synthesized BrCOF-PBA has the advantages of large specific surface area, stable crystal structure, good selectivity to QUE, fast adsorption rate, large adsorption capacity and the like, and can realize efficient adsorption of QUE; and by adjusting the pH value, the adsorbed QUE can be released, and the desorbed BrCOF-PBA can still be repeatedly adsorbed and desorbed.

[0018] 3. The application provides a new synthesis method for phenylboronic acid functionalized COFs, realizes efficient and selective adsorption of QUE, and opens up a development direction for future drug extraction and administration. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 It is a synthesis route diagram of the target material BrCOF-PBA of the application;

[0020] Figure 2 It is a comparison of FT-IR spectra and PXRD patterns of BrCOF and BrCOF-PBA in the embodiments of the application: (a) comparison of FT-IR spectra between BrCOF and BrCOF-PBA; (b) comparison of PXRD patterns;

[0021] Figure 3 SEM images of BrCOF and BrCOF-PBA in embodiments of the present application: wherein (a) SEM image of BrCOF, (b) SEM image of BrCOF-PBA; 13 C CP-MAS NMR spectra comparison: wherein (a) solid state CP-MAS NMR spectra of BrCOF, (b) solid state CP-MAS NMR spectra of BrCOF-PBA; 13 C CP-MAS NMR spectra, (b) solid state CP-MAS NMR spectra of BrCOF-PBA; 13 C CP-MAS NMR spectra;

[0022] Figure 4 TEM images of BrCOF and BrCOF-PBA in embodiments of the present application: wherein (a) TEM image of BrCOF, (b) TEM image of BrCOF-PBA;

[0023] Figure 5 TGA images of BrCOF and BrCOF-PBA in embodiments of the present application: wherein (a) TGA curve of BrCOF, (b) TGA curve of BrCOF-PBA;

[0024] Figure 6 Analytical pretreatment and analytical test process illustration for embodiments of the present application;

[0025] Figure 7 Analytical pretreatment and analytical test process illustration for embodiments of the present application;

[0026] Figure 8 Adsorption kinetics experimental results for embodiments of the present application: wherein (a) adsorption kinetics plot of BrCOF-PBA at pH = 9; (b) adsorption kinetics simulation curve of BrCOF-PBA at pH = 9; (c) linear fitting of the curve using pseudo-first-order kinetics model of QUE / BrCOF-PBA; (d) linear fitting of the curve using pseudo-second-order kinetics model of QUE / BrCOF-PBA;

[0027] Figure 9 Adsorption isotherm of QUE / BrCOF-PBA in embodiments of the present application;

[0028] Figure 10 Adsorption capacity of BrCOF-PBA synthesized in embodiments of the present application for three flavonoid substances;

[0029] Figure 11 Reusability test of BrCOF-PBA synthesized in embodiments of the present application. DETAILED DESCRIPTION

[0030] For those skilled in the relevant art to better understand the content of the present patent, the following detailed description of the embodiments of the present application is given, which are implemented on the premise of the technical solutions of the present application, and detailed implementation modes and specific operation processes are given, but the content of the present application is not limited to the examples described below.

[0031] In the present application, BrCOF is synthesized by solvothermal condensation of 2,5-dibromo benzaldehyde (DBTA) and 1,3,5-tris(4-aminophenyl)benzene (TAPB); then, the phenylboronic acid functional group is combined by post-modification of BrCOF with 1,4-para-benzene diboronic acid, Figure 1 The synthesis route of the target material BrCOF-PBA is shown in the figure.

[0032] Example 1

[0033] The specific preparation scheme of BrCOF-PBA is as follows:

[0034] (1) Synthesis of BrCOF

[0035] 232.9 mg (0.80 mmol) of 2,5-dibromo benzaldehyde (i.e. DBTA), 189.5 mg (0.54 mmol) of 1,3,5-tris(4-aminophenyl)benzene (i.e. TAPB) and 2 mL of o-dichlorobenzene were charged into a Schlenk flask, then degassed with high-purity N2 gas three times; the Schlenk flask was sealed and the mixture was allowed to react at 120°C for 3 days; after being collected by filtration, the precipitate was washed with tetrahydrofuran (THF) at least five times, and purified by Soxhlet extraction with THF overnight; finally, the solid was placed in a vacuum oven to obtain BrCOF in the form of yellow powder (yield: 91.5%).

[0036] (2) Synthesis of BrCOF-PBA

[0037] 61.6 mg of BrCOF, 1.5 mmol of 1,4-phenyldiboronic acid and 2.25 mL of THF were charged into a Schlenk flask, then degassed with high-purity Ar gas three times; then 0.5 mL of the above mixture was added to a 0.3M Cs2CO3 aqueous solution, 0.48 mL of deionized water and 7.0 mg of Pd(PPh3)4, and then sealed; the above mixture was kept at room temperature overnight, and then reacted at 90°C for 48 h; after being collected by filtration, the precipitate was washed with deionized water at least 5 times, and extracted with excess deionized water and THF; finally, the solid was dried at 120°C under vacuum overnight to obtain modified BrCOF-PBA (yield: 88.9%).

[0038] Example 2

[0039] The synthesis of BrCOF in this example is the same as Example 1;

[0040] Synthesis of BrCOF-PBA: A Schlenk flask was charged with 61.6 mg of BrCOF, 2 mmol of 1,4-benzenediboronic acid and 2.25 mL of THF, then degassed with high-purity Ar gas for 3 times. Then 0.5 mL of 0.3M Cs2CO3 aqueous solution, 0.48 mL of deionized water and 7.0 mg of Pd(PPh3)4 were added, and then sealed. The above mixture was kept at room temperature overnight, and then reacted at 90°C for 48 h. After filtration collection, the precipitate was washed with deionized water for at least 5 times, and extracted with excess deionized water and THF. Finally, the solid was dried under vacuum at 120°C overnight to obtain modified BrCOF-PBA.

[0041] Example 3: Characterization of the reaction mechanism of BrCOF-PBA

[0042] As Figure 1 The synthesis route of the target material BrCOF-PBA is shown in the figure, in order to prove the successful combination of 1,4-p-benzenediboronic acid and BrCOF, this example compares the Fourier transform infrared (FT-IR) spectra of BrCOF and BrCOF-PBA synthesized based on Example 1. The experimental results are shown in Figure 2 According to the experimental results, it can be observed that the C=N characteristic peak at 1616 cm -1 is well preserved on BrCOF and BrCOF-PBA, which proves that the original Schiff base structure of BrCOF is not destroyed by the Suzuki-Miyaura cross coupling. At the same time, three new characteristic peaks appear at 1361 cm -1 , 1055 cm -1 and 767 cm -1 . Compared with previous reports, they may be caused by B-O stretching vibration, C-B stretching vibration and -OH out-of-plane bending vibration. The above data prove the success of the later modification. Powder X-ray diffraction (PXRD) analysis shows that for BrCOF, the simulated PXRD pattern of the overlapping (AA) stacking mode matches the experimental results better than the interlaced (AB) stacking mode, proving their actual AA stacking structure; in addition, Pawley refinement is used to define the final unit of BrCOF, which gives a good agreement factor (BrCOF Rwp=5.43%). The H and N contents of BrCOF determined by elemental analysis are in good agreement with the theoretical values of the infinite two-dimensional structure, indicating the effectiveness of the proposed topology. The PXRD pattern of BrCOF-PBA does not decrease significantly compared with the above. The above verifies the high crystallinity of BrCOF and BrCOF PBA.

[0043] AsFigure 3 As shown, by solid-state 13 The CP-MAS NMR spectra better confirmed the existence of each chemical bond of BrCOF and BrCOF-PBA. Obviously, compared with BrCOF, BrCOF-PBA added new characteristic peaks such as C-B bond due to the successful addition of phenylboronic acid functional groups.

[0044] SEM images showed that BrCOF and BrCOF-PBA were vermicular, and the results were shown in Figure 4 TEM images as Figure 5 indicated that BrCOF and BrCOF-PBA had two-dimensional layered mesoporous structures. As can be seen from the figure, after modification, the morphology of BrCOF-PBA remained roughly the same as that of BrCOF and did not change greatly.

[0045] TGA tests as Figure 6 shown indicated that BrCOF remained good thermal stability before 435℃, and although the thermal stability of BrCOF-PBA decreased slightly, it could still maintain good structural integrity within 395℃.

[0046] Example 4: Adsorption kinetics analysis

[0047] After the sample (QUE) was dissolved into a methanol solution, the pH was adjusted to 9.0 with a Na2HPO4 / NaH2PO4 buffer solution. 10 mg of the adsorbent (BrCOF-PBA) prepared according to Example 1 above was added to 20 mL of the above mixture. The solution was ultrasonically treated for 5 minutes to ensure that the material was fully mixed, and then it was placed in a constant temperature vibrator and shaken at room temperature. At 20, 30, 45, 60, 90, 120, 150, and 180 minutes, the solution was filtered with an MCE syringe filter (0.22 μm) to obtain the supernatant to quantify the residue. Finally, the content of QUE in the supernatant was determined by high performance liquid chromatography. The adsorption capacity Q t (mg g -1 ) of the adsorbate (QUE, MOR, and KAE) by BrCOF-PBA at time t (min) and the equilibrium adsorption capacity Q e (mgg -1 ) were calculated by the following formulae:

[0048]

[0049]

[0050] In the formula, C0, C t , and C eThese are the initial concentration, the concentration at time t, and the equilibrium concentration of the adsorbate (mg / L). -1 V represents the volume of the adsorbate solution (L); m is the mass of the adsorbent (g).

[0051] The adsorption kinetics process was analyzed using pseudo-first-order and pseudo-second-order kinetic models, which are expressed by the following formulas:

[0052] ln(Q e -Q t )=ln(Q e )-k1t

[0053]

[0054] In the formula, Q e and Q t These are the equilibrium adsorption capacities (mg g) -1 ) and adsorption capacity at time t (mg g) -1 k1 represents the rate constant (mg g) of pseudo-first-order kinetics. -1 min -1 k2 represents the rate constant (g mg) of the pseudo-second-order kinetics. -1 min -1 ).

[0055] Experimental results show that QUE is rapidly adsorbed by BrCOF-PBA in the first 90 minutes, then the adsorption gradually slows down until no adsorption occurs after 120 minutes. The maximum adsorption capacity of BrCOF-PBA for QUE is as follows: Figure 8 As shown in a, the result is 204.81 mg g. -1 This indicates that BrCOF-PBA exhibits good adsorption of QUE. Furthermore, pseudo-first-order and pseudo-second-order kinetic models were applied to study the adsorption process. Figure 8 c and 8d). The correlation coefficient R of the fitting results 2 It was confirmed that the adsorption process of QEU on BrCOF-PBA conforms to the pseudo-second-order kinetic model, as shown in Table 1 below, with a correlation coefficient of approximately 0.994, indicating that BrCOF-PBA plays a dominant role in the adsorption process.

[0056] Table 1. Pseudo-second-order kinetic model parameters for quercetin adsorption on BrCOF-PBA.

[0057]

[0058]

[0059] Add 2 mg of adsorbent (BrCOF-PBA) to 4 mL of solution with a concentration range of 50-300 mg / L. -1The QUE sample was added into the BrCOF-PBA sample. After ultrasonic mixing for 5 min, the mixture was placed in a constant temperature shaker and shaken for 2 h at room temperature. The QUE content in the supernatant was measured using the same method as in the kinetics experiment. The adsorption mechanism of BrCOF-PBA was evaluated using the Langmuir and Freundlich models. The empirical linear equations of the Langmuir and Freundlich models are as follows:

[0060]

[0061] ln(Q e ) = nln(C e ) + ln(K F )

[0062] where Q m (mg g -1 ) is the saturated adsorption capacity of the adsorbent, K L (L mg -1 ) is the Langmuir adsorption equilibrium constant, K F ((mg g -1 )(mg L -1 ) n ) is the Freundlich adsorption equilibrium constant. n is the adsorbent heterogeneity index, which indicates good adsorption when 0 < n < 1, and indicates synergistic adsorption when n is greater than 1.

[0063] Figure 9 The results show that after adding BrCOF-PBA prepared according to Example 2 above to quercetin solutions with different initial concentrations for 120 min of adsorption, the corresponding adsorption isotherms were obtained by fitting the Langmuir model and the Freundlich model. The Langmuir model assumes that the solid surface is uniform, each adsorption site has the same affinity for gas molecules, and only one gas molecule can be adsorbed on one adsorption site to form a monolayer of adsorption. The Freundlich model describes the adsorption conditions on a non-uniform surface. The calculated parameters are shown in Table 2, R1 2 >R2 2 indicates that the Langmuir model is more suitable for explaining the adsorption of BrCOF-PBA on Que. The calculated maximum adsorption capacity Q m is 213.96 mg g -1 , which is consistent with the calculation result in the kinetics experiment. At the same time, n calculated according to the Freundlich model is between 0 and 1, indicating good adsorption.

[0064] Table 2 Parameter values of Freundlich and Langmuir models

[0065]

[0066] Specificity test

[0067] After dissolving the samples (QUE, MOR and KAE) in methanol solution, the pH was adjusted to 9.0 with Na2HPO4 / NaH2PO4buffer solution. 10 mg of adsorbent (BrCOF-PBA) prepared based on Example 1 above was added to 20 mL of the above mixture. The solution was sonicated for 5 minutes to ensure proper mixing of the material, which was then placed in a thermostatic shaker and shaken at room temperature. At 20, 30, 45, 60, 90, 120, 150, 180 minutes, the solution was filtered with a MCE syringe filter (0.22 pm) to obtain the supernatant to quantify the residue. Finally, the content of QUE in the supernatant was determined by high performance liquid chromatography. The adsorption capacity Q t (mg g -1 ) of the adsorbate (QUE, MOR and KAE) by BrCOF-PBA at time t (min) and the equilibrium adsorption capacity Q e (mg g -1 ) were calculated by the following equations, respectively:

[0068]

[0069]

[0070] wherein C0, C t and C e are the initial concentration, the concentration at time t and the equilibrium concentration of the adsorbate (mg L -1 ), respectively; V represents the volume of the adsorbate solution (L); m is the mass of the adsorbent (g).

[0071] The adsorption kinetics process was analyzed using the pseudo-first order kinetic model and the pseudo-second order kinetic model, represented by the following equations, respectively:

[0072] ln(Q e -Q t ) = ln(Q e ) - k1t

[0073]

[0074] wherein Q e and Q t are the equilibrium adsorption capacity (mg g -1 ) and the adsorption capacity at time t (mg g -1 ), respectively; k1 represents the rate constant of the pseudo-first order kinetics (mg g -1 min -1k2 represents the rate constant (g mg) of the pseudo-second-order kinetics. -1 min -1 ).

[0075] In the adsorption specificity test, QUE reached adsorption equilibrium after 90 minutes, while morin and kaempferol showed almost no adsorption on BrCOF-PBA. The maximum adsorption capacity of BrCOF-PBA for the three flavonoids (quercetin, morin, and kaempferol) is as follows: Figure 10 As shown, the values ​​are 204.81 mg g. -1 27.62 mg g -1 and 21.76 mg g -1 This indicates that BrCOF-PBA exhibits good selectivity for QUE. This significant QUE-selective capture can be attributed to the borate affinity and the chemical interaction between the organic molecule and BrCOF-PBA, which is the dominant binding in the adsorption process compared to hydrophobic interactions.

[0076] Recycling Experiment

[0077] The QUE / BrCOF-PBA was immersed in a NaH2PO4 / H3PO4 (pH=3.0) buffer solution for 1 h until the QUE / BrCOF-PBA was completely dissociated. Then, the adsorbent BrCOF-PBA was recovered according to the method described in the kinetic adsorption experiment and recycled for the next run using the same concentration of QUE solution.

[0078] To determine the reusability of BrCOF-PBA, multiple adsorption and desorption cycles were performed. The results are as follows: Figure 11 As shown, the composite material retains more than 70% of its adsorption capacity after five repeated uses compared to the initial use. This is likely due to the stability of the COF structure and the flexible covalent adsorption function of the phenylboronic acid functional groups under pH regulation.

[0079] The above description is only a preferred embodiment of the present invention and is not limited to the above implementation method. Any equivalent modifications, substitutions and improvements made by those skilled in the art based on the content disclosed in the present invention should be included in the protection scope of the claims.

Claims

1. The application of COF containing phenylboronic acid functional groups as a solid-phase extractant for the separation and extraction of flavonoids, characterized in that, The preparation method of COF materials containing phenylboronic acid functional groups includes the following steps: (1) Synthesis of BrCOF: 2,5-dibromo-terephthalaldehyde, 1,3,5-tris(4-aminophenyl)benzene and o-dichlorobenzene were placed in a Schlenk flask and degassed with high-purity N2 gas; then the Schlenk flask was sealed and the mixture was allowed to react at 120 °C for 72 h; after filtration and collection, the precipitate was washed with THF and purified by Soxhlet extraction overnight; vacuum drying was performed to obtain yellow powder BrCOF; (2) Synthesis of BrCOF-PBA: The synthesized BrCOF, 1,4-terephthaloboric acid, and THF were placed in a Schlenk flask and degassed with high-purity Ar gas. Then, cesium carbonate aqueous solution, deionized water, and tetra(triphenylphosphine)palladium were added to the Schlenk flask and sealed. The mixture was kept at room temperature overnight and then allowed to react at 90 °C for 48 hours. After filtration and collection, the precipitate was washed with deionized water at least five times and extracted with excess deionized H2O and THF. Finally, it was vacuum dried overnight to obtain modified BrCOF-PBA.

2. The application of the COF containing phenylboronic acid functional groups as a solid-phase extractant according to claim 1 in the separation and extraction of flavonoids, characterized in that, In step (1), the molar ratio of 2,5-dibromo-terephthalaldehyde and 1,3,5-tris(4-aminophenyl)benzene is 0.80:0.

54.

3. The application of the COF containing phenylboronic acid functional groups as a solid-phase extractant according to claim 1 in the separation and extraction of flavonoids, characterized in that, In step (2), the mass ratio of BrCOF to 1,4-terephthalic acid is 30.8:124.3~207.

2.

4. The application of the COF containing phenylboronic acid functional groups as a solid-phase extractant according to claim 3 in the separation and extraction of flavonoids, characterized in that, In step (2), the mass ratio of cesium carbonate, tetra(triphenylphosphine)palladium and deionized water is 97.7:7:0.

48.

5. The application of the COF containing phenylboronic acid functional groups according to claim 1 as a solid-phase extractant for the separation and extraction of flavonoids, characterized in that, The flavonoid compound is quercetin.

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