Preparation method and application of covalent organic framework photocatalyst with gold nanoclusters and magnetism

Abstract

The application discloses a preparation method of a covalent organic framework photocatalyst with gold nanoclusters and magnetism and application thereof, and belongs to the technical field of analysis and photocatalytic degradation and removal of chlorobenzene pollutants in water. The application solves the problems of the existing catalysts, such as difficulty in detecting and degrading chlorobenzene compounds in water, low visible light utilization rate, low catalytic efficiency, and difficulty in separating solid and liquid. The application prepares a gold nanocluster embedded magnetic covalent organic framework photocatalyst material which can be used for analysis and degradation and removal of chlorobenzene pollutants in water. The magnetic solid phase extraction method using the material is combined with gas chromatography tandem mass spectrometry technology to qualitatively and quantitatively analyze the content of chlorobenzene compounds in water. In addition, under the action of visible light, the chlorobenzene compounds in water can be rapidly degraded and removed.

Description

Technical Field

[0001] This invention relates to a method for preparing a covalent organic framework photocatalyst that combines gold nanoclusters and magnetism, and its application, belonging to the field of analysis and photocatalytic degradation and removal technology of chlorobenzene pollutants in water. Background Technology

[0002] Chlorobenzenes are important raw materials for the production of pesticides and chemical materials. They are persistent and bioaccumulative in the environment, causing damage to human skin, mucous membranes, central nervous system, and internal organs, and are listed as priority pollutants. Chlorobenzenes are highly toxic and have low biodegradability, and conventional wastewater treatment technologies have limited removal capabilities. Therefore, there is an urgent need for materials and technologies to achieve the analysis and removal of chlorobenzenes from water.

[0003] In recent years, two-dimensional covalent organic frameworks have attracted widespread attention as excellent visible light photocatalysts due to their high incident light trapping ability and fast carrier mobility. They possess delocalized planar conjugated π-π stacked structures and vertically ordered porous arrays, enabling efficient adsorption of benzene compounds and precise design of the material's band gap positions. Loading noble metal plasmon nanoparticles onto the surface of photocatalysts is an effective strategy to improve photocatalytic efficiency. Noble metals not only act as cocatalysts to capture photogenerated electrons from the photocatalyst to accelerate charge separation but also serve as light-collecting antennas to expand the light absorption region. In recent years, gold nanoclusters (1-3 nm) composed of gold atoms and ligands have attracted considerable attention as catalytic centers in photocatalytic redox systems due to their unique physical and chemical properties. However, the high surface free energy makes gold nanoclusters thermodynamically unstable, inevitably leading to aggregation of gold nanoparticles and loss of photocatalytic activity. Furthermore, nanomaterials in water are difficult to collect, often requiring long-term centrifugation in high-speed centrifuges for solid-liquid separation. This method is time-consuming and labor-intensive, hindering material recovery and reuse.

[0004] Therefore, researching and developing novel multifunctional materials with high magnetism, high specific surface area, high visible light utilization, and low photogenerated electron and hole recombination rate is a key issue for the rapid extraction and removal of chlorobenzene pollutants from water. Summary of the Invention

[0005] To address the problems of existing catalysts being difficult to detect and degrade chlorobenzene compounds in water, as well as having low visible light utilization, low catalytic efficiency, and difficulty in solid-liquid separation, this invention provides a method for preparing a covalent organic framework photocatalyst that combines gold nanoclusters and magnetism, and its application.

[0006] The technical solution of the present invention:

[0007] One objective of this invention is to provide a method for preparing a covalent organic framework photocatalyst that combines gold nanoclusters and magnetism, the method comprising the following steps:

[0008] (1) Preparation of magnetic nuclei: Anhydrous ferric chloride (FeCl3) was used as raw material, diethylene glycol (DEG) as solvent and polyacrylic acid (PAA) as surfactant. The reaction was carried out by high temperature hydrolysis under reflux with argon in the protection of inert gas. After the reaction solution became transparent, alkali solution was added to continue the reaction. After the reaction was completed, the magnetic nuclei were obtained by washing with ethanol and centrifugation.

[0009] (2) Preparation of aminated magnetic core silicon shell: Using the magnetic core aqueous solution obtained in step (1) as raw material and tetraethyl orthosilicate / ethanol solution as silicon source, a magnetic core silicon shell is prepared; then, using silane coupling agent as a bridge, amino groups are introduced on the surface of the silicon shell to obtain an aminated magnetic core silicon shell.

[0010] Specifically: Mix the magnetic core aqueous solution and ethanol, add ammonia water after mixing evenly, add tetraethyl orthosilicate / ethanol solution under water bath conditions and stir to react. After the reaction is completed, a magnetic core silicon shell is obtained. Then add the magnetic core silicon shell to an aminopropyltriethoxysilane-isopropanol solution, stir to react at room temperature for a period of time, and then heat to reflux to react. After the reaction is completed, an aminated magnetic core silicon shell is obtained.

[0011] (3) Preparation of magnetic covalent organic framework: using aminated magnetic core-silicon shell, 2,5-divinyl terephthalaldehyde and 4,4',4”-(1,3,5-triazine-1,3,5-triyl)triphenylamine as raw materials, 1,2-dichlorobenzene and butanol as solvents and acetic acid as catalyst, magnetic covalent organic framework was obtained by Schiff reaction and solvothermal method;

[0012] Specifically: Aminated magnetic core-silicon shell, 2,5-divinyl terephthalaldehyde, and 4,4',4”-(1,3,5-triazine-1,3,5-triyl)triphenylamine were mixed evenly, and then 1,2-dichlorobenzene, butanol, and acetic acid were added. After stirring evenly, the mixture was placed in liquid nitrogen and frozen, then vacuum treated, and finally thawed at room temperature. The freezing, vacuum treatment, and thawing process was repeated three times. Finally, the mixture was placed in a sealed container and heated. After the treatment was completed, it was cooled to room temperature, and the solid precipitate was collected using an external magnet. After washing, a magnetic covalent organic framework was obtained.

[0013] (4) Magnetic covalent organic framework with gold nanoclusters embedded: The N=N functional group on the magnetic covalent organic framework obtained in step (3) is reacted with 1,2-ethylenedithiol to prepare a covalent organic framework with thiol groups; then, using tetrachloroauric acid as raw material and L-glutathione as ligand, gold nanoclusters are connected to the covalent organic framework using thiol to obtain a covalent organic framework photocatalyst that combines gold nanoclusters and magnetism.

[0014] Specifically: A magnetic covalent organic framework was mixed with azobisisobutyronitrile (AIBN), and 1,2-ethylenedithiol was added under inert gas protection. The mixture was heated and stirred. After the reaction was completed, the mixture was washed and dried to obtain a magnetic covalent organic framework containing thiol. The magnetic covalent organic framework containing thiol was dispersed in ultrapure water, and then tetrachloroauric acid was added. The mixture was stirred at room temperature for 2 hours, followed by the addition of L-glutathione and stirring for another 2 hours. The mixture was then heated to react. After the reaction was completed, the solid precipitate was collected using an external magnet. The precipitate was washed and dried to obtain a covalent organic framework photocatalyst that combines gold nanoclusters and magnetism.

[0015] Further specifying, the mass-volume ratio of FeCl3, DEG and PAA in (1) is 1.5g:0.34g:89mL.

[0016] Further specifying, (1) the alkaline solution is a sodium hydroxide / diethylene glycol solution with a concentration of 0.1 g / mL, and the volume of the alkaline solution added is 10 mL.

[0017] Further specified, the heating reflux reaction temperature in (1) is 220℃.

[0018] Further specify that (1) after adding alkaline solution, the reaction continues for 1 hour.

[0019] Further specified, in (2) the concentration of the magnetic core aqueous solution is 33.5 mg / mL, the volume ratio of the magnetic core aqueous solution, ethanol, ammonia and tetraethyl orthosilicate / ethanol solution is 3:100:4:2; the volume concentration of the tetraethyl orthosilicate / ethanol solution is 25%; the mass-volume ratio of the magnetic core silicon shell and the aminopropyltriethoxysilane / isopropanol solution is 0.5 g:30 mL, and the volume concentration of the aminopropyltriethoxysilane-isopropanol solution is 13.3%.

[0020] Further specified, (2) the water bath temperature is 45℃, the reflux reaction temperature is 85℃, and the reflux reaction time is 5h.

[0021] Further specifying, in (2) after the water bath reaction for 5 min, tetraethyl orthosilicate / ethanol solution is added, and the reaction is continued for 50 min to obtain a magnetic core silicon shell.

[0022] Further specifying, the stirring reaction time at room temperature in (2) is 10h.

[0023] Further specified, (3) contains an aminated magnetic core and silicon shell, 2,5-divinyl terephthalaldehyde, 4,4',4”-(1,3,5-triazine-1,3,5-triyl)triphenylamine, 1,2-dichlorobenzene, butanol and acetic acid (in a mass-to-volume ratio of 90 mg: 55 mg: 55 mg: 1.5 mL: 1.5 mL: 0.3 mL; and the concentration of acetic acid is 6 mol / L.

[0024] Further specified, (3) is placed in a sealed container and heated to 120°C for 3 days.

[0025] Further specifying, the mass-to-volume ratio of the magnetic covalent organic framework, azobisisobutyronitrile, 1,2-ethylenedithiol, ultrapure water, tetrachloroauric acid and L-glutathione in (4) is 100mg:5mg:25mL:25mL:10mg:10mg.

[0026] Further, in (4), the heating and stirring reaction temperature is 70℃ and the time is 72h; the heating reaction temperature is 80℃ and the time is 48h.

[0027] The second objective of this invention is to provide an application of the covalent organic framework photocatalyst prepared by the above method, which combines gold nanoclusters and magnetism, specifically for analyzing the content of chlorobenzene pollutants in water samples.

[0028] Further defining the process for analyzing the content of chlorobenzene pollutants in water samples using a covalent organic framework photocatalyst that combines gold nanoclusters and magnetism, the procedure is as follows: The covalent organic framework photocatalyst that combines gold nanoclusters and magnetism is added to a water sample containing chlorobenzene pollutants. Under dark conditions, the reaction is carried out with magnetic stirring. After the reaction is completed, the covalent organic framework photocatalyst that combines gold nanoclusters and magnetism is collected using an external magnet. The chlorobenzene compounds adsorbed on its surface are then washed, eluted, and concentrated to obtain the sample solution to be tested. The sample solution to be tested is analyzed and detected using GC-MS / MS, and the actual content of chlorobenzene compounds in the environmental water sample is calculated.

[0029] To further specify, chlorobenzene contaminants include pentachlorobenzene and hexachlorobenzene.

[0030] Further specified, the magnetic stirring reaction speed is 100 rpm and the time is 30 min.

[0031] Further specifying, the volume ratio of the covalent organic framework photocatalyst, which combines gold nanoclusters and magnetism, to the water sample is 70 mg: 100 mL.

[0032] Further specified, the rinsing agent in the rinsing treatment is ethanol, and the volume ratio of the covalent organic framework photocatalyst with both gold nanoclusters and magnetism to ethanol is 70 mg: 2 mL.

[0033] Further specifying, the eluent in the elution process is acetonitrile, and the volume ratio of the covalent organic framework photocatalyst with both gold nanoclusters and magnetism to acetonitrile is 70 mg: 3 mL.

[0034] Further specifying the concentration process, the process is as follows: the combined eluent is dried with nitrogen at 45°C, and then reconstituted with 1 mL of n-hexane to obtain the sample solution to be tested.

[0035] The third objective of this invention is to provide an application of the covalent organic framework photocatalyst prepared by the above method, which combines gold nanoclusters and magnetism, specifically for the removal of chlorobenzene compounds from water samples.

[0036] Further defining the process of removing chlorobenzene compounds from water samples using a covalent organic framework photocatalyst combining gold nanoclusters and magnetism, the steps are as follows: The covalent organic framework photocatalyst, combining gold nanoclusters and magnetism, is added to an environmental water sample containing chlorobenzene pollutants. The mixture is stirred in the dark, and after uniform dispersion, it is allowed to stand for a period of time to achieve adsorption equilibrium. Subsequently, the suspension is irradiated with visible light for 150 minutes. After irradiation, the covalent organic framework photocatalyst, combining gold nanoclusters and magnetism, is collected using an external magnet. Undegraded chlorobenzene adsorbed on its surface is then eluted. The residual chlorobenzene compounds in the solution are enriched using liquid-liquid extraction. The eluent and extract are analyzed using GC-MS / MS, and the results are summed to obtain the concentration of undegraded chlorobenzene. The removal capacity of the covalent organic framework photocatalyst combining gold nanoclusters and magnetism for chlorobenzene pollutants is then calculated.

[0037] To further specify, chlorobenzene compounds include pentachlorobenzene and hexachlorobenzene.

[0038] Further specified, the magnetic stirring reaction speed is 100 rpm and the time is 30 min.

[0039] Further specifying, the volume ratio of the covalent organic framework photocatalyst, which combines gold nanoclusters and magnetism, to the water sample is 50 mg: 70 mL.

[0040] Further specifying, the visible light source is a 300W xenon lamp.

[0041] Further specified, the rinsing agent in the rinsing treatment is ethanol, and the volume ratio of the covalent organic framework photocatalyst with both gold nanoclusters and magnetism to ethanol is 50 mg: 2 mL.

[0042] Further specifying, the eluent in the elution process is acetonitrile, and the volume ratio of the covalent organic framework photocatalyst with both gold nanoclusters and magnetism to acetonitrile is 50 mg: 3 mL.

[0043] Further defining the process for enriching residual chlorobenzene compounds in the solution is as follows: Acetonitrile is first added to the aqueous phase from which the covalent organic framework photocatalyst with both gold nanoclusters and magnetism is separated, and the mixture is homogenized and shaken for 2 min. Sodium chloride is then added, and after shaking to dissolve and reach equilibrium, the mixture is allowed to stand and separate into layers. The acetonitrile organic phase is then removed, and the extraction is repeated once. The organic phases are combined, and the combined eluent is dried at 45°C by nitrogen blowing or rotary evaporation. 1 mL of n-hexane is added for redissolution to obtain the aqueous phase extract concentrate.

[0044] Furthermore, the mass-to-volume ratio of sodium chloride in the aqueous phase is 5g:30mL.

[0045] Furthermore, the volume ratio of the acetonitrile added initially to the water phase is 1:1.

[0046] Furthermore, the volume ratio of acetonitrile added to the aqueous phase during the repeated extraction process is 1:2.

[0047] Beneficial effects:

[0048] This invention prepares a magnetic covalent organic framework photocatalyst material based on gold nanoclusters for the analysis and degradation of chlorobenzene pollutants in water. Using this material, magnetic solid-phase extraction combined with gas chromatography-tandem mass spectrometry (GC-MS / MS) can qualitatively and quantitatively analyze the content of chlorobenzene compounds in water. Furthermore, under visible light, it can achieve rapid degradation and removal of chlorobenzene compounds from water. Compared with existing technologies, this invention also has the following advantages:

[0049] (1) The present invention utilizes the covalent bond between thiol and gold to fix gold nanoclusters in the pores of a covalent organic framework, and utilizes the pore size in the organic framework to limit the aggregation and growth of gold nanoclusters, thereby effectively enhancing the photoconductivity and separation of photogenerated carriers, and further improving the photocatalytic activity of the material.

[0050] (2) The magnetic covalent organic framework photocatalyst material based on gold nanocluster embedding provided by the present invention has both mesopores and gold nanoclusters, which is beneficial to the reflection and diffraction of incident light inside the material, improving the light collection of the photocatalyst, while increasing the specific surface area of ​​the material, providing a large number of adsorption sites and catalytic active sites for pollutants.

[0051] (3) The main framework of the magnetic covalent organic framework photocatalyst material based on gold nanocluster embedding provided by the present invention contains abundant benzene ring structure, and utilizes π-π conjugation to adsorb chlorobenzene compounds.

[0052] (4) The magnetic covalent organic framework photocatalyst material based on gold nanocluster embedding provided by the present invention has strong magnetism, can be quickly separated from solution, and is stable and reusable. Attached Figure Description

[0053] Figure 1 SEM image of the covalent organic framework photocatalyst with both gold nanoclusters and magnetism prepared in Example 1;

[0054] Figure 2 The image shows the pore size distribution of the covalent organic framework photocatalyst with both gold nanoclusters and magnetism prepared in Example 1.

[0055] Figure 3Selected ion spectra for GC-MS / MS of chlorobenzene compounds;

[0056] Figure 4 This is the hysteresis curve of the material under an applied magnetic field. Detailed Implementation

[0057] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0058] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0059] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0060] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.

[0061] Example 1:

[0062] Step 1: Preparation of magnetic nuclei:

[0063] Polyacrylic acid (1.5 g), anhydrous ferric chloride (0.34 g), and diethylene glycol (89 mL) were added to a reaction vessel. Under nitrogen protection and stirring, the mixture was heated from room temperature to 220 °C and refluxed at this temperature. When the reaction solution turned transparent light yellow, 10 mL of diethylene glycol alkaline solution containing 1 g of sodium hydroxide was added, and the reaction was continued for 1 h to obtain a black turbid solution. The solution was diluted and washed with 300 mL of ethanol, and the magnetic core was obtained after centrifugation.

[0064] Step 2: Preparation of Aminated Magnetic Core Silicon Shell:

[0065] Add 3 mL of the magnetic core aqueous solution (33.5 mg / mL) prepared in step one to 100 mL of ethanol, sonicate for 15 min, then add 4 mL of ammonia water. Stir mechanically for 5 min in a 45°C water bath, then add 2 mL of tetraethyl orthosilicate ethanol solution (25% v / v) dropwise. React for 50 min to obtain the magnetic core and silicon shell. Add 0.5 g of the magnetic core and silicon shell to 30 mL of aminopropyltriethoxysilane-isopropanol solution (13.3% v / v), stir at room temperature for 10 h, then heat to 85°C and reflux for 5 h to obtain the aminated magnetic core and silicon shell.

[0066] Step 3: Preparation of a magnetic covalent organic framework:

[0067] The mixture of the aminated magnetic core-silicon shell obtained in step two (90 mg), 2,5-divinyl terephthalaldehyde (55 mg), and 4,4',4”-(1,3,5-triazine-1,3,5-triyl)triphenylamine (55 mg) was added to a high-temperature resistant glass tube (outer diameter 9.8 mm, inner diameter 6 mm), followed by the addition of 1,2-dichlorobenzene (1.5 mL), butanol (1.5 mL), and acetic acid (0.3 mL, 6 mol L⁻¹). After stirring and ultrasonic dispersion for 20 min, the tube was frozen in liquid nitrogen, evacuated for 2 min, and thawed at room temperature. The freezing-vacuum-thawing process was repeated three times. Finally, the heat-resistant glass tube was sealed with a flame at 1300 °C and stored in an oven at 120 °C for 3 days. After cooling to room temperature, the solid precipitate was collected using an external magnet and washed several times with anhydrous N,N-dimethylacetamide and tetrahydrofuran until the supernatant became colorless, yielding the magnetic covalent organic framework.

[0068] Step 4: Preparation of a magnetic covalent organic framework with embedded gold nanoclusters:

[0069] The mixture of the magnetic covalent organic framework (100 mg) and azobisisobutyronitrile (5 mg) prepared in step 3 was added to a round-bottom flask (100 mL). Then, under argon protection, 1,2-ethylenedithiol (25 mL) was added to the flask. After magnetic stirring at 70 °C for 72 h, a magnetic covalent organic framework with thiol was obtained and repeatedly washed with acetone. The dried magnetic covalent organic framework with thiol was added to 25 mL of ultrapure water. After ultrasonic dispersion, tetrachloroauric acid (10 mg) was added and stirred at room temperature for 2 h. Subsequently, L-glutathione (10 mg) was added, stirred for 2 h, and heated to 80 °C. After reacting for 48 h, the solid precipitate was collected using an external magnet and washed several times with anhydrous ethanol. The product was dried under vacuum to obtain a covalent organic framework photocatalyst that combines gold nanoclusters and magnetism.

[0070] The covalent organic framework photocatalyst with both gold nanoclusters and magnetism prepared in this embodiment was characterized by its microstructure. A schematic diagram of the scanning electron microscopy characterization is shown below. Figure 1 As shown. By Figure 1 It can be seen that the synthesized material has a clear morphology, is spherical, and has a diameter of about 170-200 nm.

[0071] The internal pore size distribution of the magnetic covalent organic framework prepared in this embodiment was characterized. The results of the internal pore size distribution of the thiol-based magnetic covalent organic framework obtained based on nitrogen adsorption-desorption curves and DFT method are as follows: Figure 2 As shown, by Figure 2 It can be seen that the main pore size distribution is in the range of 2.3-2.4 nm, and this pore size can effectively limit the growth of gold nanoclusters (1.8-2.0 nm).

[0072] The magnetic properties of the covalent organic framework photocatalyst prepared in this embodiment, which combines gold nanoclusters and magnetism, were characterized, and the results are as follows: Figure 4 As shown, the material exhibits a distinct hysteresis curve, with a saturation magnetization of 35.8 emu g. -1 .

[0073] Example 2:

[0074] The adsorption performance of the covalent organic framework photocatalyst material with both gold nanoclusters and magnetism prepared in Example 1 on chlorobenzene compounds in water was investigated. The specific process is as follows:

[0075] (1) Preparation of the sample solution to be tested

[0076] a. Extraction: 100 mL of surface water was added to an Erlenmeyer flask, along with 70 mg of a covalent organic framework photocatalyst material possessing both gold nanoclusters and magnetic properties. The flask was placed on a magnetic stirrer and stirred at 100 rpm for 30 min for extraction. After extraction, chlorobenzene in the water was adsorbed onto the covalent organic framework material.

[0077] b. Washing: The covalent organic framework photocatalyst material, which combines gold nanoclusters and magnetism, is separated from the liquid using an external magnet, and the waste liquid is discarded; then 2 mL of ethanol is added as a washing agent, and the mixture is shaken for 30 s to remove the environmental matrix adsorbed on the surface of the photocatalyst material. The material is then separated from the liquid again using an external magnetic field, and the waste liquid is discarded.

[0078] c. Elution: Add 3 mL of acetonitrile as eluent to the conical flask containing the photocatalyst material, sonicate for 2 min to elute the chlorobenzene adsorbed on it, use an external magnetic field to separate the material from the liquid, repeat the elution twice, and combine the eluents;

[0079] d. Concentration: The collected eluent was dried under nitrogen at 45°C, and 1 mL of n-hexane was added to reconstitute it to obtain the sample solution to be tested.

[0080] (2) The sample solution was analyzed and detected using GC-MS / MS.

[0081] The sample solution obtained in (1) was subjected to gas chromatography separation and mass spectrometry detection: an Agilent 7890A-7000B system was used, equipped with an autosampler and other components. The chromatographic column was an Agilent HP-5ms capillary column (30m long × 0.25mm, 0.25μm). High-purity nitrogen was used as the carrier gas, with a flow rate of 1.0mL / min. The initial temperature of the column oven was 40℃ and held for 3min, then the temperature was increased to 300℃ at a rate of 10℃ / min and held for 5min. The injection port temperature was 260℃; the injection was performed in splitless mode; the injection volume was 1μL. The scanning mode was multiple reaction monitoring (MRM) mode, with retention time and two pairs of molecular ion / fragment ion pairs used for qualitative analysis (relevant parameters are shown in Table 1), and the peak area of ​​the molecular ion / fragment ion pair with the strongest response signal used for quantitative analysis. The selected ion spectrum of the chlorobenzene compounds obtained by the test is shown in the figure below. Figure 3 As shown in Table 1, the specific qualitative analysis parameters of chlorobenzene compounds by GC-MS / MS are as follows.

[0082] Table 1 Qualitative analysis parameters of chlorobenzene compounds by GC-MS / MS

[0083]

[0084] Quantitative analysis of fragment ions

[0085] Depend on Figure 3 As shown in Table 1, the test sample solution contained a large amount of chlorobenzene compounds. Experimental results indicate that the gold nanocluster-embedded magnetic covalent organic framework material prepared in this invention has good adsorption capacity for chlorobenzene compounds in water.

[0086] Example 3:

[0087] The covalent organic framework photocatalyst material with both gold nanoclusters and magnetism, prepared in Example 1, was used to remove chlorobenzene compounds from water. The specific process is as follows:

[0088] (1) Photocatalytic degradation

[0089] Take 70 mL of environmental water containing chlorobenzene pollutants, and spike the water at a concentration of 1 mg / L. -1 The sample was added to a quartz reactor, along with 50 mg of a covalent organic framework photocatalyst material that combines gold nanoclusters and magnetism. The mixture was stirred at 100 rpm for 30 minutes in the dark to achieve adsorption equilibrium. The resulting suspension was then placed under 300W visible light for 150 minutes.

[0090] (2) Undegraded chlorobenzene compounds in the enrichment system

[0091] The photocatalyst material was separated from the aqueous phase using an external magnetic field. 2 mL of ethanol was added as an eluent, and the mixture was shaken for 30 seconds to remove the adsorbed environmental matrix from the material surface. The material was then separated from the liquid using the same external magnetic field. The waste liquid was discarded, and 3 mL of acetonitrile was added as an eluent. The mixture was sonicated for 2 minutes to elute the chlorobenzene compounds adsorbed on the material surface. This eluent process was repeated twice, and the eluents were combined. The combined eluent was dried under nitrogen at 45°C, and 1 mL of n-hexane was added for reconstitution to obtain the sample solution. The chlorobenzene compounds in the sample solution were analyzed and quantified using GC-MS / MS in multiple reaction monitoring mode.

[0092] In the aqueous phase from which the covalent organic framework material was separated, 70 mL of acetonitrile was added, and the mixture was homogenized and shaken for 2 min. Then, 12 g of sodium chloride was added, and the mixture was shaken until dissolved and equilibrated. The mixture was allowed to stand and separate into layers. The acetonitrile organic phase was then removed. Another 35 mL of acetonitrile was added, and the extraction was repeated once. The organic phases were combined, and the combined eluent was dried at 45 °C using nitrogen blowing or rotary evaporation. 1 mL of n-hexane was added for resolution, yielding the aqueous extract concentrate. The chlorobenzene compounds in the aqueous extract concentrate were analyzed and quantified using GC-MS / MS in multiple reaction monitoring mode.

[0093] (3) Calculate the degradation efficiency of the material for chlorobenzene compounds.

[0094] The chlorobenzene content in the sample solution and the aqueous extract concentrate was summed and then divided by the initial chlorobenzene content in the water to calculate the photocatalytic efficiency of the gold nanocluster-embedded magnetic covalent organic framework material for chlorobenzene in water. Experimental results showed that the photocatalytic degradation rates of pentachlorobenzene and hexachlorobenzene were 89% and 82%, respectively. The gold nanocluster-embedded magnetic covalent organic framework material prepared in this invention exhibits good degradation ability for chlorobenzene compounds in water.

[0095] Example 4:

[0096] The cycling performance of the covalent organic framework photocatalyst material prepared in Step 1, which combines gold nanoclusters and magnetism, was investigated. The specific process is as follows:

[0097] The covalent organic framework photocatalyst material combining gold nanoclusters and magnetism, used in Example 3, was added to 10 mL of ethanol and sonicated for 20 min to separate the solid and liquid phases. After vacuum drying, it was used again to remove chlorobenzene compounds from water, repeating the process of Example 3. After four cycles, the covalent organic framework photocatalyst material combining gold nanoclusters and magnetism experienced a 7% mass loss, and its photocatalytic degradation performance for pentachlorobenzene and hexachlorobenzene decreased by 9% and 12%, respectively. The experimental results show that the covalent organic framework photocatalyst material combining gold nanoclusters and magnetism can be recycled without significant reduction in photocatalytic performance.

[0098] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the claims.

Claims

1. An application of a covalent organic framework photocatalyst combining gold nanoclusters and magnetism, characterized in that, Methods for preparing covalent organic framework photocatalysts that combine gold nanoclusters and magnetic properties for the removal of chlorobenzene compounds from water samples include: (1) Preparation of magnetic nuclei: FeCl3, diethylene glycol and polyacrylic acid are mixed and heated under reflux under inert gas protection. After the reaction solution becomes transparent, alkali solution is added to continue the reaction. After the reaction is completed, the magnetic nuclei are obtained by washing with ethanol and centrifugation. (2) Preparation of aminated magnetic core silicon shell: Mix the magnetic core aqueous solution and ethanol, add ammonia water after mixing evenly, add tetraethyl orthosilicate ethanol solution under water bath conditions and stir to react. After the reaction is completed, the magnetic core silicon shell is obtained; then add the magnetic core silicon shell to aminopropyltriethoxysilane-isopropanol solution, stir to react at room temperature for a period of time, and then heat to reflux to react. After the reaction is completed, the aminated magnetic core silicon shell is obtained. (3) Preparation of magnetic covalent organic framework: Aminated magnetic core and shell, 2,5-divinyl terephthalaldehyde and 4,4',4''-(1,3,5-triazine-2,4,6-triyl)triphenylamine were mixed evenly, and then 1,2-dichlorobenzene, butanol and acetic acid were added. After stirring evenly, the mixture was placed in liquid nitrogen and frozen, then vacuum treated, and finally thawed at room temperature. The freezing, vacuum treatment and thawing process was repeated three times. Finally, the mixture was placed in a sealed container and heated. After the treatment was completed, it was cooled to room temperature. The solid precipitate was collected using an external magnet, washed, and the magnetic covalent organic framework was obtained. (4) Magnetic covalent organic framework with gold nanoclusters embedded: The magnetic covalent organic framework was mixed with azobisisobutyronitrile, and 1,2-ethylenedithiol was added under inert gas protection. The mixture was heated and stirred. After the reaction was completed, the mixture was washed and dried to obtain a magnetic covalent organic framework with thiol. The magnetic covalent organic framework with thiol was dispersed in ultrapure water, and then tetrachloroauric acid was added. The mixture was stirred at room temperature for 2 h, and then L-glutathione was added. The mixture was stirred for another 2 h and then heated to react. After the reaction was completed, the solid precipitate was collected with an external magnet. The precipitate was washed and dried to obtain a photocatalyst with both gold nanoclusters and magnetic properties. In step (1), the reflux reaction temperature is 220℃; In step (2), the water bath temperature is 45℃, the reflux reaction temperature is 85℃, and the reflux reaction time is 5h. In step (3), the mass-to-volume ratio of the aminated magnetic core-silicon shell, 2,5-divinyl terephthalaldehyde, 4,4',4''-(1,3,5-triazine-2,4,6-triyl)triphenylamine, 1,2-dichlorobenzene, butanol, and acetic acid is 90 mg: 55 mg: 55 mg: 1.5 mL: 1.5 mL: 0.3 mL; In step (4), the heating and stirring reaction temperature is 70℃ and the time is 72 h; the heating reaction temperature is 80℃ and the time is 48 h.

2. The application according to claim 1, characterized in that, (1) The mass-volume ratio of FeCl3, diethylene glycol and polypropylene is 0.34 g: 89 mL: 1.5 g; the alkali solution is a sodium hydroxide / diethylene glycol solution with a concentration of 0.1 g / mL, and the volume of alkali solution added is 10 mL.

3. The application according to claim 1, characterized in that, (2) The concentration of the magnetic core aqueous solution is 33.5 mg / mL, and the volume ratio of the magnetic core aqueous solution, ethanol, ammonia and tetraethyl orthosilicate ethanol solution is 3:100:4:2; the volume concentration of the tetraethyl orthosilicate ethanol solution is 25%; the mass-volume ratio of the magnetic core silicon shell and the aminopropyltriethoxysilane-isopropanol solution is 0.5 g:30 mL, and the volume concentration of the aminopropyltriethoxysilane-isopropanol solution is 13.3%.

4. The application according to claim 1, characterized in that, (3) The concentration of acetic acid is 6 mol / L.

5. The application according to claim 1, characterized in that, (4) The mass-to-volume ratio of the magnetic covalent organic framework, azobisisobutyronitrile, 1,2-ethylenedithiol, ultrapure water, tetrachloroauric acid and L-glutathione is 100 mg: 5 mg: 25 mL: 25 mL: 10 mg: 10 mg.

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