Boric acid-functionalized covalent organic framework microcapsule adsorbent, its preparation method and application

Abstract

The present invention discloses a boric acid-functionalized covalent organic framework microcapsule adsorbent and its preparation method and application. First, TAPB-BTCA-BPTA COFs are synthesized, and Pickering water-in-oil single emulsions are obtained by using TAPB-BTCA-BPTA COFs as stabilizing particles. Using the Pickering water-in-oil emulsion droplets as carriers, a COF shell layer is formed by an autonomous growth method at the emulsion droplet interface for subsequent introduction of azidoboric acid. Finally, the boric acid-functionalized covalent organic framework microcapsule BA-TAPB-BTCA-BPTA MC is prepared by grafting azidoboric acid N3-PBA through the "azide-alkyne" click reaction. It has excellent mechanical strength and stability and is used for the specific adsorption and separation research of active ingredients.

Description

Technical Field

[0001] The present invention belongs to the technical field of the preparation of environmental functional materials, and relates to a preparation method and application of a boric acid-functionalized covalent organic framework microcapsule adsorbent. Background Art

[0002] Industrial wastewater has a huge impact on the environment. Especially various industrial wastewaters generated during industrial production processes contain a large amount of harmful and useful substances. If not properly treated, it will not only pollute the environment but also affect the water use safety and life health of surrounding residents. Therefore, it is necessary to strengthen the optimized treatment of wastewater, actively implement the requirements of environmental protection construction, and promote the sustainable development of industry. During the process of treating wastewater, energy-saving optimization control is carried out to reduce pollution emissions, separate useful substances, and also reduce energy consumption, laying a good foundation for the healthy development of industry.

[0003] China is a major producer of pomelos. However, only a very small part of pomelo peels is used for the extraction of essence and spices, and most of them are directly discarded, which not only causes waste of resources but also pollutes the environment. Pomelo peels contain rich active substance naringin, which is a natural flavonoid compound with an ortho-cis-dihydroxy structure and has various pharmacological activities, such as antioxidant, anti-inflammatory, anti-aging, anti-cancer, antiviral, and prevention and treatment of cardiovascular diseases. At present, there are already methods such as solvent extraction, ultrasonic-assisted extraction, microwave-assisted extraction, and liquid-liquid extraction to separate and purify naringin in pomelo sacs. Although these methods have their own advantages, they often require the combination of multiple methods and lack selectivity, and the use cost is high. Therefore, establishing and improving a new strategy for selectively recognizing and separating and purifying naringin in pomelo peel extract, so as to increase the yield and obtain a naringin product with a higher purity at the same time, has attracted great attention. Boric acid-based adsorbents are based on the boron affinity mechanism and are used for selectively recognizing and reversibly adsorbing and releasing vicinal dihydroxy compounds. Microcapsules are a kind of hollow microparticles composed of a solid shell surrounding a core that can permanently or temporarily trap substances to form a space. Due to their unique properties such as large specific surface area and surface permeability, they are used in drug release, biomedicine, protecting sensitive molecules in the environment, and adsorption and separation fields, etc. Therefore, constructing a boric acid-functionalized covalent organic framework microcapsule adsorbent is expected to realize the selective separation and purification of naringin.

[0004] The Pickering emulsion templating method is one of the important types of soft templating methods. Its prominent feature is the use of solid micro- and nano-particles with suitable surface wettability to replace surfactants to construct emulsion templates. The obtained emulsions have good stability and high controllability of droplet size, and have broad application prospects. According to the emulsion morphology classification, the emulsion templating method can be divided into Pickering single emulsion templating method, Pickering double emulsion templating method, and Pickering high internal phase emulsion templating method, etc. Among them, the use of functionalized covalent organic frameworks to stabilize Pickering single emulsions for constructing boronic acid-functionalized covalent organic framework microcapsule adsorbents has become a research hotspot. Summary of the Invention

[0005] The present invention uses the emulsion templating method and the "azide-alkyne" click reaction to construct a boronic acid-functionalized covalent organic framework microcapsule adsorbent, and finally specifically recognizes and separates and enriches the target naringin molecule; specifically: Select TAPB, BTCA, and alkyne-capped BPTA as three typical functional monomers for constructing covalent organic frameworks (COFs) to synthesize nano-sized alkynylated TAPB-BTCA-BPTA COFs, and increase their dispersibility in mesitylene by adding competitive substances benzaldehyde and aniline. Then, use mesitylene dispersing TAPB-BTCA-BPTA COF particles as the oil phase, and deionized water dissolved with the catalyst Sc(OTf) 3 as the water phase and drop it into the oil phase to obtain a Pickering W / O emulsion under high-speed stirring. Using the above emulsion droplets as soft templates, by adding TAPB, BTCA, BPTA, and a small amount of catalyst Sc(OTf) present in the water phase 3 to carry out secondary emulsion interfacial polymerization to construct TAPB-BTCA-BPTA microcapsules, and a continuous shell layer with good mechanical stability is easily formed on its surface. Azidoboronic acid N 3 -PBA is introduced into the TAPB-BTCA-BPTA microcapsules coated with an alkynylated COF layer through the azide-alkyne click reaction to obtain a boronic acid-functionalized covalent organic framework microcapsule adsorbent (BA-TAPB-BTCA-BPTA MC), and it is used for the selective separation and enrichment of NRG molecules.

[0006] The technical solution adopted by the present invention is:

[0007] (1) Preparation of TAPB-BTCA-BPTA COF particles

[0008] First, a certain amount of 1,3,5-tris(4-aminophenyl)benzene (TAPB), benzene-1,3,5-tricarbaldehyde (BTCA), and 2,5-bis(prop-2-yn-1-yloxy)terephthalaldehyde (BPTA) were dissolved in solvent A. Then, the competitors benzaldehyde and aniline were added. Subsequently, a solution of a certain amount of the catalyst scandium trifluoromethanesulfonate (Sc(OTf)) 3 in solvent B was added. After mixing the above solutions, the reaction was carried out at room temperature for 24 h. Subsequently, the mixture was washed with acetonitrile to remove excess impurities. The yellow powder obtained after centrifugation was vacuum-dried at 60 ºC overnight to obtain the final product, TAPB-BTCA-BPTA COFs particles;

[0009] In step (1), the 1,3,5-tris(4-aminophenyl)benzene (TAPB), benzene-1,3,5-tricarbaldehyde (BTCA), 2,5-bis(prop-2-yn

[0010] -1-yloxy)terephthalaldehyde (BPTA), solution A, benzaldehyde, aniline, and scandium trifluoromethanesulfonate (Sc(OTf)) 3 were added in the ratio of (15.6 - 18.6) mg : (7.1 - 9.1) mg : (0.9 - 1.1) mg : (38 - 40) mL : (59.8 - 61.8) mL : (53.4 - 55.4) mL : (10.8 - 12.8) mg : (0.9 - 1.1) mL; Solvents A and B were both acetonitrile.

[0011] (2) Preparation of TAPB-BTCA-BPTA microcapsules

[0012] The TAPB-BTCA-BPTA microcapsules were prepared by the method of emulsion interfacial polymerization:

[0013] A certain amount of the catalyst scandium trifluoromethanesulfonate (Sc(OTf)) 3 was dissolved in deionized water to form the aqueous phase;

[0014] The oil phase was composed of a certain amount of mesitylene and TAPB-BTCA-BPTA COFs particles. A certain amount of the above-prepared aqueous phase was added dropwise, and then homogenously stirred at a speed of 15000 rpm for 3 s to form a water-in-oil single emulsion. Then, the emulsion was transferred into a centrifuge tube. Subsequently, a certain amount of mesitylene was added. Then, a chloroform solution containing 1,3,5-tris(4-aminophenyl)benzene (TAPB), benzene-1,3,5-tricarbaldehyde (BTCA), 2,5-bis(prop-2-yn-1-yloxy)terephthalaldehyde (BPTA), and the competitors benzaldehyde and aniline was added. At the same time, the density of the added solvents was adjusted to approximately 1 g / cm 3Polymerize at room temperature for 24 h, and finally obtain the product TAPB-BTCA-BPTA microcapsules after washing with mesitylene;

[0015] In step (2),

[0016] In the aqueous phase, scandium trifluoromethanesulfonate Sc(OTf) 3 , and the dosage ratio of deionized water is (7.1 - 7.4) mg: (1.1 - 1.2) mL;

[0017] In the oil phase, the addition ratio of mesitylene and TAPB-BTCA-BPTA COFs particles is (3.9 - 4.1) mL: (1.6 - 1.8) mg;

[0018] The dosage ratio of the aqueous phase to the oil phase is (99 - 101) mL: (1.9 - 2.1) mL;

[0019] The dosage ratio of mesitylene, 1,3,5-tris(4-aminophenyl)benzene TAPB, benzene-1,3,5-tricarbaldehyde BTCA, 2,5-bis(prop-2-yn-1-yloxy)terephthalaldehyde BPTA, benzaldehyde, aniline, and chloroform is (3.9 - 4.1) mL: (3.4 - 3.6)mg: (1.5 - 1.7) mg: (0.1 - 0.3) mg: (11.1 - 13.1) mL: (9.8 - 11.8) mL: (1.9 - 2.1) mL.

[0020] (3)Preparation of azidophenylboronic acid N 3 -PBA

[0021] Azidophenylbenzeneboronic acid N 3 -PBA is prepared according to the Sandmeyer reaction:

[0022] First, dissolve a certain amount of 4-aminophenylboronic acid 4-APBA in hydrochloric acid and stir. Then, add a certain amount of aqueous sodium nitrite solution and sodium azide NaN 3 React for 0.5 h. Mix and stir the above solution for 1 h, and then extract with ethyl acetate and dry with anhydrous magnesium sulfate MgSO 4 Dry, and obtain the final product N 3 -PBA through rotary evaporation and vacuum drying.

[0023] In step (3), the 4-aminophenylboronic acid 4-APBA, hydrochloric acid solution, aqueous sodium nitrite solution, and sodium azide NaN 3The added ratio is (0.4 - 0.6) g : (9 - 11) mL : (1.5 - 3.5) mL : (185 - 205) mg; the concentration of the hydrochloric acid solution is 6 mol / L, and the concentration of the sodium nitrite aqueous solution is 1.2 mol / L.

[0024] (4)Preparation of BA-TAPB-BTCA-BPTA microcapsules

[0025] The BA-TAPB-BTCA-BPTA microcapsules are prepared by azide-alkyne click reaction:

[0026] First, disperse the synthesized TAPB-BTCA-BPTA microcapsules in DMSO / H 2 O (5 / 1, V / V) mixed solution;

[0027] Subsequently, add a certain amount of azidophenylboronic acid N 3 -PBA, and then immediately add sodium ascorbate and copper sulfate pentahydrate;

[0028] Mix the above solution and react at room temperature for 24 h, then wash with dimethyl sulfoxide DMSO and ethanol respectively, and finally obtain the product BA-TAPB-BTCA-BPTA microcapsules after vacuum drying at 50 ºC overnight.

[0029] In step (4), the added ratio of the TAPB-BTCA-BPTA microcapsules, DMSO / H 2 O mixed solution, azidophenylboronic acid N 3 -PBA, sodium ascorbate, and copper sulfate pentahydrate is (1.9 - 2.1) mg : (4.9 - 5.1) mL : (1.9 - 2.1)mg : (9 - 11) mg : (11.5 - 13.5) mg;

[0030] Use of the boronic acid-functionalized covalent organic framework microcapsule adsorbent prepared by the present invention for the selective separation of flavonoid compounds.

[0031] Use the boronic acid-functionalized covalent organic framework microcapsule adsorbent prepared by the present invention for the selective separation of o-dihydroxy compounds.

[0032] Technical advantages of the present invention:

[0033] The boronic acid-functionalized covalent organic framework microcapsule adsorbent prepared by the present invention constructs hydrophobic TAPB-BPTA-BTCA COFs particles using TAPB, BPTA, and BTCA as functional monomers, and uses them as solid particles to stabilize W / O Pickering emulsions. Using the emulsion droplets as a platform, TAPB, BPTA, and BTCA are added to self-assemble a dense COF shell layer on their surface to form TAPB-BPTA-BTCA microcapsules. Using it as an anchoring group, azidoboronic acid N 3 -PBA is introduced through the "azide-alkyne" click reaction to construct a boronic acid-functionalized covalent organic framework microcapsule adsorbent. The material has a hollow structure, excellent chemical properties and mass transfer kinetic properties. In addition, the material exhibits excellent mechanical properties, is easy to recycle, and has a pH-responsive function, which can simplify the adsorption and desorption operations. Description of the Drawings

[0034] Figure 1 Scanning electron microscopy images, EDS spectra (a 1 ) and scanning elemental analysis images (d) of the boronic acid-functionalized covalent organic framework microcapsule adsorbent (BA-TAPB-BTCA-BPTA MC) (c-c 1 ) and covalent organic framework microcapsule adsorbents (TAPB-BTCA MC) (a-a 1 ), (TAPB-BTCA-BPTA MC) (b-b 2 -c 2 ) prepared in Example 1;

[0035] Figure 2 Optical microscopy images of emulsions stabilized by TAPB-BTCA COFs (a 1 , a 2 ) and TAPB-BTCA-BPTA COFs (b 1 ,b 2 ) prepared in Example 1, LSCM images of emulsion droplets after negative staining of the aqueous phase with rhodamine B (a 3 , b 3 ), emulsion droplet size distribution and corresponding physical photos (c, d);

[0036] Figure 3 Contact angle results of TAPB-BTCA MC (a), TAPB-BTCA-BPTA MC (b) and BA-TAPB-BTCA-BPTA MC (c) prepared in Example 1 and LSCM images of BA-TAPB-BTCA-BPTA MC after acid washing and alkali washing after negative staining with alizarin red S;

[0037] Figure 4 Nitrogen adsorption - desorption isotherm curve of the covalent organic framework microcapsule adsorbent (BA - TAPB - BTCA - BPTA MC) prepared in Example 1;

[0038] Figure 5 Adsorption kinetic curve of the boric acid - functionalized covalent organic framework microcapsule in Test Example 1;

[0039] Figure 6 Adsorption isotherm curve of the boric acid - functionalized covalent organic framework microcapsule in Test Example 2;

[0040] Figure 7 Competitive adsorption bar chart of the boric acid - functionalized covalent organic framework microcapsule in Test Example 3. Embodiment

[0041] In the specific embodiment of the present invention, the recognition performance evaluation is carried out according to the following method: completed by static adsorption experiment. Add 5 mL of a certain concentration of NRG solution into a centrifuge tube, add a certain amount of boric acid - functionalized covalent organic framework microcapsule adsorbent and place it in a constant temperature water bath at 25 o °C for several hours of static placement. After adsorption, the content of NRG is measured by an ultraviolet - visible spectrophotometer, and the adsorption capacity is calculated according to the results; after saturated adsorption, the boric acid - functionalized covalent organic framework microcapsule adsorbent is collected by centrifugation, and several hydroxy - containing compounds with similar structures and properties are selected as competitive adsorbates to participate in the study of the recognition performance of the polymer.

[0042] The present invention will be further described below in conjunction with the attached drawings of the specific embodiments. Example

[0043] (1) Preparation of TAPB - BTCA - BPTA COFs particles

[0044] First, dissolve 16.6 mg of 1,3,5 - tris(4 - aminophenyl)benzene TAPB, 7.1 mg of benzene - 1,3,5 - tricarbaldehyde BTCA, and 0.9 mg of 2,5 - bis(prop - 2 - ynyloxy)terephthalaldehyde BPTA in 38 mL of acetonitrile. Then, add 59.8 mL of benzaldehyde and 53.4 mL of aniline. Next, add 0.9 mL of an acetonitrile solution containing 10.8 mg of the catalyst scandium trifluoromethanesulfonate Sc(OTf) 3 to the above - mentioned solution. After mixing the above - mentioned solution, react at room temperature for 24 h. Subsequently, wash with acetonitrile to remove excess impurities. The yellow powder obtained after centrifugation is vacuum - dried at 60 °C overnight to obtain the final product TAPB - BTCA - BPTA COFs particles.

[0045] (2) Preparation of TAPB-BTCA-BPTA Microcapsules

[0046] The preparation of TAPB-BTCA-BPTA microcapsules adopts the method of emulsion interfacial polymerization:

[0047] Dissolve 7.2 mg of the catalyst scandium trifluoromethanesulfonate Sc(OTf) 3 in 0.9 mL of deionized water to form an aqueous phase;

[0048] The oil phase is composed of 3.9 mL of mesitylene and 1.6 mg of TAPB-BTCA-BPTA COFs particles. Add it dropwise to 199 mL of the above-prepared aqueous phase, and then homogenize and stir at a speed of 14000 - 15000 rpm for 3 s to form a water-in-oil single emulsion. Then transfer 1.9 mL of the emulsion into a centrifuge tube, then add 3.9 mL of mesitylene, and then add 1.9 mL of a chloroform solution containing 3.4 mg of 1,3,5-tris(4-aminophenyl)benzene TAPB, 1.5 mg of benzene-1,3,5-tricarbaldehyde BTCA, 0.1 mg of 2,5-bis(prop-2-yn-1-yloxy)terephthalaldehyde BPTA, 11.1 mL of benzaldehyde and 9.8 mL of aniline. At the same time, adjust the density of the added solvent to about 1 g / cm 3 by adding mesitylene and chloroform. Then polymerize at room temperature for 24 h, and finally wash with mesitylene to obtain the product TAPB-BTCA-BPTA microcapsules.

[0049] (3)Preparation of Azidophenylboronic Acid N 3 -PBA

[0050] Azidophenylbenzeneboronic acid N 3 -PBA is prepared according to the Sandmeyer reaction:

[0051] First, dissolve 0.5 g of 4-aminophenylboronic acid 4-APBA in 10 mL of 6M hydrochloric acid and stir. Then, add 2.5 mL of an aqueous sodium nitrite solution and 195 mg of sodium azide NaN 3 and react for 0.5 h. Mix and stir the above solution for 1 h, and then extract with ethyl acetate and dry with anhydrous magnesium sulfate MgSO 4 to obtain the final product N3-PBA through rotary evaporation and vacuum drying.

[0052] (4)Preparation of BA-TAPB-BTCA-BPTA MC Microcapsules

[0053] BA-TAPB-BTCA-BPTA microcapsules are prepared by azide-alkyne click reaction:

[0054] First, disperse 1.9 mg of the above-synthesized TAPB-BTCA-BPTA MC microcapsules in 4.9 mL of a DMSO / H 2 O (5 / 1, V / V) mixture;

[0055] Subsequently, add 2 mg of azidophenylboronic acid N 3 -PBA, and then immediately add 9 mg of sodium ascorbate and 11.5 mg of copper sulfate pentahydrate;

[0056] Mix the above solution and react at room temperature for 24 h. Then wash it with dimethyl sulfoxide DMSO and ethanol respectively. Finally, obtain the product BA-TAPB-BTCA-BPTA microcapsules after vacuum drying at 50 ºC overnight.

[0057] It can be seen from Figure 1 that TAPB-BTCA MC, TAPB-BTCA-BPTA MC, and BA-TAPB-BTCA-BPTA MC have continuous shell layers, and many COFs particles are distributed on their outer surfaces and have a hollow structure. From Figure c 2 and Figure d, it can be seen that BA-TAPB-BTCA-BPTA MC has abundant boric acid recognition sites, which can improve the recognition efficiency and accelerate the mass transfer rate.

[0058] It can be seen from Figure 2 that the deionized water is negatively stained with rhodamine B and used as the aqueous phase to form an emulsion. The emulsion droplets are observed by a fluorescence microscope to determine their type. Compared with the blank in Figure 2a 2 and 2b 2 , it can be observed from Figure 2a 3 and 2b 3 that for the emulsions stabilized by either TAPB-BTCA-BPTA COFs or TAPB-BTCA COFs, their inner phases show bright red under the fluorescence microscope. This is mainly due to the hydrophobic property of the COF particles, thus forming Pickering W / O emulsions. At the same time, the droplet size of the emulsion stabilized by TAPB-BTCA COFs is 35 - 80 mm (Figure 2c), which is similar to the droplet size of the emulsion stabilized by TAPB-BTCA-BPTA COFs (Figure 2d). It can be found from Figure 2a 1 and 2b 1 that COFs can exist in the form of a black contour around the emulsion droplets as an emulsifier, which further proves the good emulsifying performance of the COF particles and provides a platform for the formation of the microcapsule shell layer.

[0059] It is composed ofFigure 3 As shown, the contact angles of TAPB-BTCA MC and TAPB-BTCA-BPTA MC are 133.37 ° and 122.12 ° respectively, which proves that the microcapsules are successfully prepared by interfacial polymerization of hydrophobic stabilizing particles (TAPB-BTCA-BPTA COFs and TAPB-BTCA COFs) emulsion. In addition, the contact angle of BA-TAPB-BTCA-BPTA MC at the oil / water interface is 115.20 °, and the decreasing trend can be attributed to the successful introduction of N 3 -PBA. As can be seen from Figure 3, BA-TAPB-BTCA-BPTA MC is dispersed in 80 mL of 0.02 mM ARS solution (100 mM PBS, pH = 8.0), and green fluorescence appears around it, which means that ARS forms a five-membered lactone with N 3 -PBA. On the contrary, almost no fluorescence can be observed in an acidic environment (100 mM PBS, pH = 4.0) (Figure 3). Therefore, BA-TAPB-BTCA-BPTA MC has been successfully modified by azidoboric acid N 3 -PBA through click reaction and has good pH-responsive performance.

[0060] As shown by Figure 4 the specific surface area spectrum of BA-TAPB-BTCA-BPTA MC, its average pore diameter is detected to be 4.63 nm and it has a high specific surface area (133.15 m 2 / g), which can prove that the Pickering emulsion template method successfully constructs hollow boronic acid affinity microcapsules, which can load more phenylboronic acid recognition sites. Example

[0061] (1) Preparation of TAPB-BTCA-BPTA COF particles

[0062] First, dissolve 17.6 mg of 1,3,5-tris(4-aminophenyl)benzene TAPB, 8.1 mg of benzene-1,3,5-tricarbaldehyde BTCA, and 1.0 mg of 2,5-bis(prop-2-yn-1-yloxy)terephthalaldehyde BPTA in 39 mL of acetonitrile. Then, add 60.8 mL of benzaldehyde and 54.4 mL of aniline. Then, add 1 mL of an acetonitrile solution containing 11.8 mg of the catalyst scandium trifluoromethanesulfonate Sc(OTf) 3 . After mixing the above solutions, react at room temperature for 24 h. Subsequently, wash with acetonitrile to remove excess impurities. The yellow powder obtained by centrifugation is vacuum dried at 60 ºC overnight to obtain the final product TAPB-BTCA-BPTA COF particles.

[0063] (2) Preparation of TAPB-BTCA-BPTA Microcapsules

[0064] The TAPB-BTCA-BPTA microcapsules were prepared by the method of emulsion interfacial polymerization:

[0065] Dissolve 7.3 mg of the catalyst scandium trifluoromethanesulfonate Sc(OTf) 3 in 1 mL of deionized water to form an aqueous phase;

[0066] The oil phase was composed of 4 mL of mesitylene and 1.7 mg of TAPB-BTCA-BPTA COF particles. It was added dropwise to 200 mL of the above-prepared aqueous phase, and then homogenized and stirred at a speed of 15000 rpm for 3 s to form a water-in-oil single emulsion. Then, 2 mL of the emulsion was transferred into a centrifuge tube, followed by the addition of 4 mL of mesitylene. Subsequently, 2 mL of a chloroform solution containing 3.5 mg of 1,3,5-tris(4-aminophenyl)benzene TAPB, 1.6 mg of benzene-1,3,5-tricarbaldehyde BTCA, 0.2 mg of 2,5-bis(prop-2-yn-1-yloxy)terephthalaldehyde BPTA, 12.1 mL of benzaldehyde, and 10.8 mL of aniline was added. At the same time, the density of the added solvent was adjusted to about 1 g / cm 3 by adding mesitylene and chloroform. Then, it was polymerized at room temperature for 24 h, and finally, the product TAPB-BTCA-BPTA microcapsules were obtained after washing with mesitylene.

[0067] (3) Preparation of Azidophenylboronic Acid N 3 -PBA

[0068] Azidophenylbenzeneboronic acid N 3 -PBA was prepared according to the Sandmeyer reaction:

[0069] First, 0.4 g of 4-aminophenylboronic acid 4-APBA was dissolved in 9 mL of 6M hydrochloric acid and stirred. Then, 1.5 mL of an aqueous sodium nitrite solution and 185 mg of sodium azide NaN 3 were added and reacted for 0.5 h. The above solutions were mixed and stirred for 1 h, and then extracted with ethyl acetate and dried over anhydrous magnesium sulfate MgSO 4 Finally, the final product N3-PBA was obtained by rotary evaporation and vacuum drying.

[0070] (4) Preparation of BA-TAPB-BTCA-BPTA Microcapsules

[0071] BA-TAPB-BTCA-BPTA microcapsules were prepared by azide-alkyne click reaction:

[0072] First, disperse 2 mg of the synthesized TAPB-BTCA-BPTA microcapsules in 5 mL of a DMSO / H 2 O (5 / 1, V / V) mixture;

[0073] Subsequently, add 2 mg of azidophenylboronic acid N 3 -PBA, and then immediately add 10 mg of sodium ascorbate and 12.5 mg of copper sulfate pentahydrate;

[0074] Mix the above solution and react at room temperature for 24 h. Then, wash it with dimethyl sulfoxide DMSO and ethanol respectively. Finally, obtain the product BA-TAPB-BTCA-BPTA MC microcapsules after vacuum drying at 50 ºC overnight. Example

[0075] (1) Preparation of TAPB-BTCA-BPTA COF particles

[0076] First, dissolve 18.6 mg of 1,3,5-tris(4-aminophenyl)benzene TAPB, 9.1 mg of benzene-1,3,5-tricarbaldehyde BTCA, and 1.1 mg of 2,5-bis(prop-2-yn-1-yloxy)terephthalaldehyde BPTA in 40 mL of acetonitrile. Then, add 61.8 mL of benzaldehyde and 55.4 mL of aniline. Next, add 1.1 mL of an acetonitrile solution containing 12.8 mg of the catalyst scandium trifluoromethanesulfonate Sc(OTf) 3 . After mixing the above solution, react at room temperature for 24 h. Then, wash it with acetonitrile to remove excess impurities. The yellow powder obtained by centrifugation is vacuum dried at 60 ºC overnight to obtain the final product TAPB-BTCA-BPTA COF particles.

[0077] (2) Preparation of TAPB-BTCA-BPTA microcapsules

[0078] The preparation of TAPB-BTCA-BPTA microcapsules adopts the method of emulsion interfacial polymerization:

[0079] Dissolve 7.4 mg of the catalyst scandium trifluoromethanesulfonate Sc(OTf) 3 in 1.1 mL of deionized water to form an aqueous phase;

[0080] The oil phase is composed of 4.1 mL of mesitylene and 1.8 mg of TAPB-BTCA-BPTA COF particles. It is added dropwise to 201 mL of the above-prepared aqueous phase, and then homogenously stirred at a speed of 14000 - 15000 rpm for 3 s to form a water-in-oil single emulsion. Then, 2.1 mL of the emulsion is transferred into a centrifuge tube, followed by adding 4.1 mL of mesitylene. Subsequently, 2.1 mL of a chloroform solution containing 3.6 mg of 1,3,5-tris(4-aminophenyl)benzene TAPB, 1.7 mg of benzene-1,3,5-tricarbaldehyde BTCA, 0.3 mg of 2,5-bis(prop-2-yn-1-yloxy)terephthalaldehyde BPTA, 13.1 mL of benzaldehyde, and 11.8 mL of aniline is added. At the same time, the density of the added solvent is adjusted to approximately 1 g / cm by adding mesitylene and chloroform. 3 It is then polymerized at room temperature for 24 h, and finally the product TAPB-BTCA-BPTA microcapsules are obtained after washing with mesitylene.

[0081] (3)Preparation of azidophenylboronic acid N 3 -PBA

[0082] Azidophenylbenzeneboronic acid N 3 -PBA is prepared according to the Sandmeyer reaction:

[0083] First, 0.6 g of 4-aminophenylboronic acid 4-APBA is dissolved in 11 mL of 6M hydrochloric acid and stirred. Then, 3.5 mL of an aqueous sodium nitrite solution and 205 mg of sodium azide NaN 3 are added and reacted for 0.5 h. The above solutions are mixed and stirred for 1 h, and then extracted with ethyl acetate and dried over anhydrous magnesium sulfate MgSO 4 Finally, the final product N3-PBA is obtained by rotary evaporation and vacuum drying.

[0084] (4)Preparation of BA-TAPB-BTCA-BPTA microcapsules

[0085] BA-TAPB-BTCA-BPTA microcapsules are prepared by azide-alkyne click reaction:

[0086] First, the above-synthesized 2.1 mg of TAPB-BTCA-BPTA microcapsules are dispersed in 5.1 mL of a DMSO / H 2 O (5 / 1, V / V) mixture;

[0087] Subsequently, 2.1 mg of azidophenylboronic acid N 3 -PBA is added, followed immediately by adding 11 mg of sodium ascorbate and 13.5 mg of copper(II) sulfate pentahydrate;

[0088] Mix the above solutions and react at room temperature for 24 h. Then wash with dimethyl sulfoxide (DMSO) and ethanol respectively. Finally, obtain the product BA-TAPB-BTCA-BPTA microcapsules after vacuum drying at 50 ºC overnight.

[0089] Test Example 1:

[0090] Take 5.0 mL of naringin (NRG) solution with an initial concentration of 35 mg / L and add it to a centrifuge tube. Add 5 mg of the boric acid-functionalized covalent organic framework microcapsule adsorbent (BA-TAPB-BTCA-BPTA MC) in Example 2 respectively. Place the test solution in a water bath oscillator at 25 °C and take it out at 15 min, 30 min, 60 min, 90 min, 120 min, 180 min, and 270 min respectively. Separate the boric acid-functionalized covalent organic framework microcapsule adsorbent (BA-TAPB-BTCA-BPTA MC), the covalent organic framework microcapsule adsorbent (TAPB-BTCA-BPTA MC), and the naringin (NRG) solution with tweezers, and then filter the solution through a microporous nitrocellulose membrane with a pore size of 0.45 mm to remove suspended particles. The concentration of NRG in the filtrate is measured by a UV-visible spectrophotometer at a wavelength of 283 nm, and the adsorption capacity is calculated according to the results. Figure 5 From the results, it can be seen that the adsorption process of the boric acid-functionalized covalent organic framework microcapsule adsorbent (BA-TAPB-BTCA-BPTA MC) can be divided into a rapid stage (the first 120 min) and a slow stage. The adsorption capacity in the rapid stage reaches 88.7% of the equilibrium capacity and then slowly increases until equilibrium, demonstrating that the boric acid-functionalized covalent organic framework microcapsule adsorbent (BA-TAPB-BTCA-BPTA MC) has rapid adsorption kinetics, and the hollow structure and abundant boric acid recognition sites on the surface are conducive to the rapid separation and enrichment of naringin molecules.

[0091] Test Example 2:

[0092] Take 5 mg of the boric acid-functionalized covalent organic framework microcapsule adsorbent (BA-TAPB-BTCA-BPTA MC) and add it to 5.0 mL of NRG solutions with initial concentrations of 10, 15, 25, 35, and 50 mg / L (pH = 8.0). Static adsorption is carried out for 6.0 h in a water bath oscillation, and the test solution is at 25 °C. After the adsorption is completed, separate the boric acid-functionalized covalent organic framework microcapsule adsorbent (BA-TAPB-BTCA-BPTA MC) with tweezers and take the supernatant. The concentration of NRG in the supernatant is detected by UV-vis, and the maximum absorption wavelength is 283 nm, and the adsorption capacity is calculated according to the results. Figure 6The results can be obtained. When the initial concentration is 35 mg / L, the adsorption of the boric acid-functionalized covalent organic framework microcapsule adsorbent (BA-TAPB-BTCA-BPTA MC) tends to reach equilibrium.

[0093] Test Example 3:

[0094] Luteolin, hydroquinone, and o-nitrophenol were selected as the hydroxyl compounds for competitive adsorption. Aqueous solutions of the above four hydroxyl compounds were prepared respectively, and the concentration of each competitive adsorbent was 35 mg / L. 5 mL of the prepared solution was taken and added to a centrifuge tube. 5 mg of the boric acid-functionalized covalent organic framework microcapsule adsorbent (BA-TAPB-BTCA-BPTA MC) and the covalent organic framework microcapsule adsorbent (TAPB-BTCA-BPTA MC) in Example 2 were added respectively and separated. The test solution was placed in a water bath at 25 °C and shaken for 6.0 h. After the standing time was completed, the boric acid-functionalized covalent organic framework microcapsule adsorbent (BA-TAPB-BTCA-BPTA MC) and the covalent organic framework microcapsule adsorbent (TAPB-BTCA-BPTA MC) were separated by tweezers, and the supernatant was taken. The concentrations of the unadsorbed competitive adsorption hydroxyl compounds were measured by ultraviolet. From Figure 7 the results can be obtained that the adsorption capacities of BA-TAPB-BTCA-BPTA MC for naringin, luteolin, hydroquinone, and o-nitrophenol are 20.36, 11.92, 7.06, and 6.52 μmol / g respectively. It shows that BA-TAPB-BTCA-BPTA MC has significant specific recognition for NRG, and the adsorption capacity is much higher than that of other competitive molecules.

Claims

1. A preparation method of a boric acid-functionalized covalent organic framework microcapsule adsorbent, characterized in that, it includes the following steps: (1) Prepare TAPB-BTCA-BPTA COFs particles for later use; (2) Prepare TAPB-BTCA-BPTA MC microcapsules for later use; The TAPB-BTCA-BPTA MC microcapsules are prepared by the method of emulsion interfacial polymerization: Dissolve a certain amount of the catalyst scandium trifluoromethanesulfonate Sc(OTf) 3 in deionized water to form an aqueous phase; The oil phase is composed of a certain amount of mesitylene and TAPB-BTCA-BPTA COF particles, and a certain amount of the above-prepared aqueous phase is added dropwise. Immediately, homogenizing stirring is carried out at a certain speed to form a water-in-oil single emulsion. Then the emulsion is transferred into a centrifuge tube. Next, a certain amount of mesitylene is added, and then a chloroform solution dissolved with 1,3,5-tris(4-aminophenyl)benzene (TAPB), benzene-1,3,5-tricarbaldehyde (BTCA), 2,5-bis(prop-2-yn-1-yloxy)terephthalaldehyde (BPTA) and competitors benzaldehyde and aniline is added. At the same time, the density of the added solvent is adjusted to about 1 g / cm 3 Post-polymerization is carried out until the reaction ends, and finally the product TAPB-BTCA-BPTA MC microcapsules are obtained after washing with mesitylene; (3) Prepare azidophenylboronic acid N 3 -PBA for standby; Azidophenylboronic acid N 3 -PBA was prepared according to the Sandmeyer reaction: First, dissolve a certain amount of 4-aminophenylboronic acid (4-APBA) in hydrochloric acid and stir; Subsequently, a certain amount of sodium nitrite solution and sodium azide NaN 3 were reacted for 0.5 h; Mix the above solution and stir for 1 h, then extract with ethyl acetate and dry with anhydrous magnesium sulfate MgSO 4 to obtain the final product N 3 -PBA by rotary evaporation and vacuum drying; (4) Prepare BA-TAPB-BTCA-BPTA MC microcapsules; The BA-TAPB-BTCA-BPTA MC microcapsules are prepared by azide-alkyne click reaction: First, disperse the above-synthesized TAPB-BTCA-BPTA MC microcapsules in a DMSO / H 2 O (5 / 1, V / V) mixed solution; Subsequently, a certain amount of azidophenylboronic acid N 3 -PBA was added, and then sodium ascorbate and copper sulfate pentahydrate were added immediately; Mix the above solutions and react at room temperature for 24 h, then wash with dimethyl sulfoxide (DMSO) and ethanol respectively, and finally obtain the product BA-TAPB-BTCA-BPTA MC microcapsules through vacuum drying.

2. The preparation method of the boric acid-functionalized covalent organic framework microcapsule adsorbent according to claim 1, characterized in that, In step (1), the steps for preparing TAPB-BTCA-BPTA COFs particles are as follows: dissolve a certain amount of 1,3,5-tris(4-aminophenyl)benzene (TAPB), benzene-1,3,5-tricarbaldehyde (BTCA), and 2,5-bis(prop-2-yn-1-yloxy)terephthalaldehyde (BPTA) in solvent A; then, add the competitors benzaldehyde and aniline, and then add solvent B containing a certain amount of the catalyst scandium trifluoromethanesulfonate (Sc(OTf)). 3 Mix the above solutions and react at room temperature for 24 h. Subsequently, wash with acetonitrile to remove excess impurities. The yellow powder obtained after centrifugation is the final product, TAPB-BTCA-BPTA COFs particles, after vacuum drying. Among them, the 1,3,5-tris(4-aminophenyl)benzene TAPB, benzene-1,3,5-tricarbaldehyde BTCA, 2,5-bis(prop-2-yn-1-yloxy)terephthalaldehyde BPTA, solvent A, benzaldehyde, aniline, scandium(III) trifluoromethanesulfonate Sc(OTf) 3 , the addition ratio of solvent B is (15.6 - 18.6) mg: (7.1 - 9.1) mg: (0.9 - 1.1) mg: (38 - 40) mL: (59.8 - 61.8) mL: (53.4 - 55.4) mL: (10.8 - 12.8) mg: (0.9 - 1.1) mL; both solvents A and B are acetonitrile; the vacuum drying condition is overnight at 60 °C.

3. The preparation method of the boric acid-functionalized covalent organic framework microcapsule adsorbent according to claim 1, characterized in that, In step (2), In the aqueous phase, scandium trifluoromethanesulfonate Sc(OTf) 3 , the dosage ratio of deionized water is (7.2 - 7.4) mg: (0.9 - 1.1) mL; In the oil phase, the addition ratio of mesitylene and TAPB-BTCA-BPTA COFs particles is (3.9 - 4.1) mL : (1.6 - 1.8) mg; In the water phase, the usage ratio of the oil phase is (199 - 201) mL : (3.9 - 4.1) mL; For the emulsion, the usage ratio of mesitylene, 1,3,5-tris(4-aminophenyl)benzene (TAPB), benzene-1,3,5-tricarbaldehyde (BTCA), 2,5-bis(prop-2-yn-1-yloxy)terephthalaldehyde (BPTA), benzaldehyde, aniline, and chloroform is (1.9 - 2.1) mL : (3.9 - 4.1) mL : (3.4 - 3.6) mg : (1.5 - 1.7) mg : (0.1 - 0.3) mg : (11.1 - 13.1) mL : (9.8 - 11.8) mL : (1.9 - 2.1) mL.

4. The preparation method of the boric acid-functionalized covalent organic framework microcapsule adsorbent according to claim 1, characterized in that, In step (2), the speed of homogenizing and stirring is 14000 - 15000 rpm per minute, and the time is 3 s; the temperature of the polymerization reaction is 20 - 30 °C, and the time is 23 - 25 h.

5. The preparation method of the boric acid-functionalized covalent organic framework microcapsule adsorbent according to claim 1, characterized in that, In step (3), the 4-aminophenylboronic acid 4-APBA, hydrochloric acid solution, sodium nitrite solution, and sodium azide NaN 3 are added in a ratio of (0.4 - 0.6) g : (9 - 11) mL : (1.5 - 3.5) mL : (185 - 205) mg; the concentration of the hydrochloric acid solution is 6 mol / L, and the concentration of the sodium nitrite solution is 1.2 mol / L.

6. The preparation method of the boric acid-functionalized covalent organic framework microcapsule adsorbent according to claim 1, characterized in that, In step (4), for the TAPB-BTCA-BPTA MC microcapsules, the DMSO / H 2 O mixed solution, azidophenylboronic acid N 3 -PBA, sodium ascorbate, and copper sulfate pentahydrate are added in a ratio of (1.9 - 2.1) mg : (4.9 - 5.1) mL : (1.9 - 2.1) mg : (9 - 11) mg : (11.5 - 13.5) mg; the vacuum drying condition is overnight at 50 ºC.

7. A boric acid-functionalized covalent organic framework microcapsule adsorbent, characterized in that, it is prepared by the preparation method described in any one of claims 1 to 6.

8. An application of the boric acid-functionalized covalent organic framework microcapsule adsorbent described in claim 7 in the selective separation and purification of flavonoids.

9. The application according to claim 8, characterized in that, the boric acid-functionalized covalent organic framework microcapsule adsorbent is used for the selective separation and purification of o-dihydroxy compounds.

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