Chlorine-functionalized covalent organic framework / graphene aerogel materials, methods of making and applications thereof

Abstract

The application provides a chlorine-functionalized covalent organic framework / graphene aerogel material, a preparation method and application thereof. The chlorine-functionalized covalent organic framework / graphene aerogel material is prepared by the following method: using an amino-containing silane reagent to modify graphene oxide under low-temperature conditions, then reducing the modified graphene oxide at high temperature, and freeze-drying to obtain amino-functionalized graphene aerogel; placing the amino-functionalized graphene aerogel in a solvent, sequentially adding chlorine-functionalized aldehyde ligands and amino ligands of a covalent organic framework, and through Schiff base reaction under catalysis of an acetic acid aqueous solution, a chlorine-functionalized covalent organic framework / graphene aerogel material is prepared. The chlorine-functionalized covalent organic framework / graphene aerogel material can be used to prepare a solid-phase microextraction fiber coating, and the obtained solid-phase microextraction fiber coating can be applied to efficient enrichment and sensitive detection of halogenated aromatic pollutants such as polychlorinated naphthalenes in environmental samples.

Description

Technical Field

[0001] This invention relates to the field of solid-phase microextraction, specifically to a chlorine-functionalized covalent organic framework / graphene aerogel material, its preparation method, and its applications. Background Technology

[0002] In recent years, environmental water pollution caused by polychlorinated naphthalenes (PCNs) has attracted continuous attention. Due to their bioaccumulation and biomagnification properties, long-term exposure to contaminated water or consumption of contaminated aquatic products can lead to their accumulation in the human body, thus threatening public health. Although the production of PCNs is currently prohibited, they can still be unintentionally generated during waste incineration and non-ferrous metal smelting, and enter environmental waters through various pathways such as atmospheric deposition and terrestrial runoff. Therefore, developing accurate and sensitive detection methods for monitoring PCNs in environmental water is crucial. However, the environmental water matrix is ​​complex, and PCNs are present at trace levels (pg / mL), requiring sample pretreatment before detection. Accelerated solvent extraction and liquid-liquid extraction techniques have been developed, but these techniques struggle to achieve efficient enrichment and sensitive detection of trace PCNs in environmental water, thus limiting their application.

[0003] Solid-phase microextraction (SPME) is widely used in the analysis of trace environmental pollutants due to its solvent-free operation, simplicity, and high enrichment rates. The coating is the core of SPME, and improving its extraction performance has always been a problem that analytical chemists have sought to solve. This invention proposes a chlorinated functionalized covalent organic framework / graphene aerogel (COF-GA) material that can be used to extract trace amounts of polychlorinated naphthalene from environmental water samples. Summary of the Invention

[0004] The purpose of this invention is to provide a chlorinated functionalized covalent organic framework / graphene aerogel material, its preparation method and application. This chlorinated functionalized covalent organic framework / graphene aerogel material is made into a solid-phase microextraction fiber coating, which can be applied to the efficient enrichment and sensitive detection of halogenated aromatic pollutants such as polychlorinated naphthalene in environmental samples.

[0005] This invention is implemented as follows:

[0006] A chlorinated functionalized covalent organic framework / graphene aerogel material is prepared by a Schiff base reaction of amino-functionalized graphene aerogel, chlorinated functionalized aldehyde ligands of the covalent organic framework, and amino ligands of the covalent organic framework under the catalysis of aqueous acetic acid.

[0007] The preparation method of the above-mentioned chlorine-functionalized covalent organic framework / graphene aerogel material specifically includes the following steps:

[0008] a. Graphene oxide is ultrasonically dispersed in ultrapure water to obtain a graphene oxide dispersion.

[0009] b. In the system of the graphene oxide dispersion obtained in step a, the graphene oxide is modified with an amino functionalization agent, then reduced at high temperature, followed by solid-liquid separation and washing of the product, and freeze-drying to obtain amino-functionalized graphene aerogel.

[0010] c. Disperse the amino-functionalized graphene aerogel obtained in step b in a solvent, add the chlorinated functionalized aldehyde ligand of the covalent organic framework, let stand for 4-8 h, then add the amino ligand of the covalent organic framework, and maintain at 60-80 °C for 24-36 h under the catalysis of acetic acid aqueous solution. After solid-liquid separation, wash the product with tetrahydrofuran, anhydrous ethanol and ultrapure water in sequence, and freeze-dry to obtain the chlorinated functionalized covalent organic framework / graphene aerogel material.

[0011] Preferably, the concentration of the graphene oxide dispersion in step a is 1 mg / mL.

[0012] Preferably, the modifying agent in step b is 3-aminopropyltrimethoxysilane or 3-aminopropyltriethoxysilane.

[0013] Preferably, in step c, the solvent is acetonitrile or N,N-dimethylformamide.

[0014] Preferably, in step c, the chlorofunctionalized aldehyde ligand is 2,5-dichloroterephthalaldehyde, and the amino ligand is tetra-(4-aminophenyl)ethylene; the molar ratio of the chlorofunctionalized aldehyde ligand to the amino ligand is 2:1 to 3:1; and the molar concentration of the amino ligand is 4 to 8 μmol / mL.

[0015] Preferably, in step c, the mass concentration of the amino-functionalized graphene aerogel is 1–2 mg / mL.

[0016] The chlorinated functionalized covalent organic framework / graphene aerogel material prepared according to the above method is used to prepare a solid-phase microextraction fiber coating. The specific preparation method of the solid-phase microextraction fiber coating is as follows:

[0017] a. Stainless steel fibers are etched with aqua regia, followed by ultrasonic cleaning and drying to obtain bare fibers;

[0018] b. Apply glue to the bare fiber filaments, then coat the bare fiber filaments with chlorinated functionalized covalent organic framework / graphene aerogel material, and then place them in a forced-air drying oven for curing to obtain a preliminary solid-phase microextraction fiber coating.

[0019] c. Apply glue to the obtained preliminary solid-phase microextraction fiber coating, then coat it with chlorine-functionalized covalent organic framework / graphene aerogel material, and then place it in a forced-air drying oven for curing;

[0020] d. After several coatings, drying and curing, a solid-phase microextraction fiber coating is obtained.

[0021] Preferably, in step a, stainless steel fibers are etched with aqua regia for 15-20 minutes, and then the etched parts of the stainless steel fibers are washed with methanol, ultrapure water, carbon tetrachloride and acetone in sequence, and then dried in a forced-air drying oven.

[0022] Preferably, in step b, the preparation process of the adhesive is as follows: a certain amount of silicone sealant is dissolved in a solvent to obtain an adhesive with a concentration of 0.5 to 1 mg / mL.

[0023] The solid-phase microextraction fiber coating prepared according to the above method is applied to the extraction of polychlorinated naphthalenes from environmental water samples to solve the problem of the difficulty in detecting trace PCNs in complex environmental water samples.

[0024] This invention prepares a chlorinated functionalized covalent organic framework / graphene aerogel material, which has the advantages of high porosity, fast mass transfer rate and good thermal stability. When used as a solid phase microextraction coating and combined with GC-MS / MS, it can be used for efficient enrichment and sensitive detection of halogenated aromatic pollutants such as polychlorinated naphthalene in environmental water, and has broad application prospects. Attached Figure Description

[0025] Figure 1 This is a scanning electron microscope image of COF-GA1 prepared in Example 1 of the present invention.

[0026] Figure 2 Thermogravimetric analysis (TGA) diagram of COF-GA1 prepared in Example 1 of this invention.

[0027] Figure 3 The infrared spectra of COF-GA1 prepared in Example 1 and GA prepared in Comparative Example 1 are shown.

[0028] Figure 4 This is a scanning electron microscope image of COF-GA2 prepared in Example 2 of the present invention.

[0029] Figure 5 This is a scanning electron microscope image of COF-GA3 prepared in Example 3 of the present invention.

[0030] Figure 6 Scanning electron microscope (SEM) images of the COF-GA1 solid-phase microextraction fiber coating (A) and bare fiber filaments (B) prepared in Example 4 of this invention.

[0031] Figure 7This invention establishes a COF-GA1 solid-phase microextraction fiber coating-solid-phase microextraction-gas chromatography-mass spectrometry method for detecting the total ion chromatogram of four PCNs in environmental water. Detailed Implementation

[0032] The present invention will be further illustrated below with reference to the embodiments. These embodiments are for illustrative purposes only and do not limit the scope of protection of the present invention in any way. All reagents used in the embodiments are analytical grade or chemically pure and are commercially available. The following embodiments all achieve the objectives of the present invention.

[0033] Example 1: Preparation of a chlorinated functionalized covalent organic framework / graphene aerogel material

[0034] 64 mg of graphene oxide powder was ultrasonically dispersed in 64 mL of ultrapure water for 4 h. 16 mL of 3-aminopropyltriethoxysilane was slowly added dropwise, and the mixture was stirred for 10 min. The mixture was then transferred to a high-pressure reactor and dried in a 60 °C oven for 6 h, followed by heating to 200 °C and holding for 24 h. The resulting product was washed sequentially with anhydrous ethanol and ultrapure water, and then freeze-dried to obtain amino-functionalized graphene aerogel. 10 mg of amino-functionalized graphene aerogel was added to 5 mL of acetonitrile containing 0.08 mmol of 2,5-dichloroterephthalaldehyde and allowed to stand for 4 h. Then, 5 mL of acetonitrile containing 0.04 mmol of tetra-(4-aminophenyl)ethylene was added, and the mixture was transferred to a reactor. The temperature was raised to 80 °C, and 1.2 mL of 6M acetic acid aqueous solution was added. The mixture was then maintained at 80 °C for 24 h. The obtained product was separated into solid and liquid phases using filter paper, and then washed sequentially with tetrahydrofuran, anhydrous ethanol, and ultrapure water. After freeze-drying, chlorine-functionalized covalent organic framework / graphene aerogel material (COF-GA1) was obtained.

[0035] Comparative Example 1: Preparation of an amino-functionalized graphene aerogel material

[0036] 64 mg of graphene oxide powder was ultrasonically dispersed in 64 mL of ultrapure water for 4 h. 16 mL of 3-aminopropyltriethoxysilane was slowly added dropwise, and the mixture was stirred for 10 min. The mixture was then transferred to a high-pressure reactor and dried in a 60 °C oven for 6 h, followed by heating to 200 °C and holding for 24 h. The resulting product was washed sequentially with anhydrous ethanol and ultrapure water, and then freeze-dried to obtain amino-functionalized graphene aerogel (GA).

[0037] The COF-GA1 obtained in Example 1 was characterized by scanning electron microscopy and thermogravimetric analysis, and the results are as follows: Figure 1 and Figure 2 As shown.

[0038] from Figure 1It can be seen that the chlorinated functionalized covalent organic framework is attached to the surface of the graphene aerogel, and the growth of the covalent organic framework does not destroy the aerogel state, and the material exhibits a porous structure.

[0039] Figure 2 The thermogravimetric analysis (TGA) diagram of the chlorine-functionalized covalent organic framework / graphene aerogel material shows that the material underwent two weight loss stages. The weight loss at 100℃ is attributed to the evaporation of adsorbed water. Furthermore, the weight loss below 400℃ is slow, demonstrating the material's good thermal stability and suitability for use as a solid-phase microextraction coating.

[0040] The COF-GA1 obtained in Example 1 and the GA material obtained in Comparative Example 1 were characterized by infrared spectroscopy, and the results are as follows: Figure 3 As shown, the appearance of the CN bond characteristic peak indicates the successful preparation of the material.

[0041] Example 2: Preparation of a chlorinated functionalized covalent organic framework / graphene aerogel material

[0042] 64 mg of graphene oxide powder was ultrasonically dispersed in 64 mL of ultrapure water for 4 h. 16 mL of 3-aminopropyltriethoxysilane was slowly added dropwise, and the mixture was stirred for 10 min. The mixture was then transferred to a high-pressure reactor and dried in a 60 °C oven for 6 h, followed by heating to 200 °C and holding for 24 h. The resulting product was washed sequentially with anhydrous ethanol and ultrapure water, and then freeze-dried to obtain amino-functionalized graphene aerogel. 20 mg of amino-functionalized graphene aerogel was added to 5 mL of acetonitrile containing 0.08 mmol of 2,5-dichloroterephthalaldehyde and allowed to stand for 4 h. Then, 5 mL of acetonitrile containing 0.04 mmol of tetra-(4-aminophenyl)ethylene was added, and the mixture was transferred to a reactor. The temperature was raised to 80 °C, and 1.2 mL of 6M acetic acid aqueous solution was added. The mixture was then maintained at 80 °C for 24 h. The obtained product was separated into solid and liquid phases using filter paper, and then washed sequentially with tetrahydrofuran, anhydrous ethanol, and ultrapure water. After freeze-drying, chlorine-functionalized covalent organic framework / graphene aerogel material (COF-GA2) was obtained.

[0043] The COF-GA2 obtained in Example 2 was characterized by scanning electron microscopy, and the results are as follows: Figure 4 As shown in the figure, chlorinated functionalized covalent organic frames are attached to the surface of graphene aerogel.

[0044] Example 3: Preparation of a chlorinated functionalized covalent organic framework / graphene aerogel material

[0045] 64 mg of graphene oxide powder was ultrasonically dispersed in 64 mL of ultrapure water for 4 h. 16 mL of 3-aminopropyltriethoxysilane was slowly added dropwise, and the mixture was stirred for 10 min. The mixture was then transferred to a high-pressure reactor and dried in a 60 °C oven for 6 h, followed by heating to 200 °C and holding for 24 h. The resulting product was washed sequentially with anhydrous ethanol and ultrapure water, and then freeze-dried to obtain amino-functionalized graphene aerogel. 10 mg of amino-functionalized graphene aerogel was added to 4 mL of acetonitrile containing 0.08 mmol of 2,5-dichloroterephthalaldehyde and allowed to stand for 4 h. Then, 4 mL of acetonitrile containing 0.04 mmol of tetra-(4-aminophenyl)ethylene was added, and the mixture was transferred to a reactor. The temperature was raised to 80 °C, and 1.2 mL of 6M acetic acid aqueous solution was added. The mixture was then maintained at 80 °C for 24 h. The obtained product was separated into solid and liquid phases using filter paper, and then washed sequentially with tetrahydrofuran, anhydrous ethanol, and ultrapure water. After freeze-drying, chlorine-functionalized covalent organic framework / graphene aerogel material (COF-GA3) was obtained.

[0046] The COF-GA3 obtained in Example 3 was characterized by scanning electron microscopy, and the results are as follows: Figure 5 As shown, chlorinated functionalized covalent organic frameworks are also attached to the surface of graphene aerogel.

[0047] Example 4: Preparation of a chlorine-functionalized covalent organic framework / graphene aerogel solid-phase microextraction fiber coating

[0048] (1) Immerse the end 2cm of a 23cm long and 0.36mm diameter stainless steel fiber into aqua regia for 20min. Then, put the stainless steel fiber into a 5μL microsyringe to assemble the SPME extraction device. Wash the etched part of the stainless steel fiber with methanol, ultrapure water and acetone respectively. Dry the SPME extraction device in a 70℃ oven.

[0049] (2) The etched portion of the stainless steel fiber was pushed out and placed into the adhesive (0.5 g / mL neutral silicone sealant toluene solution). After removal, it was quickly rotated on weighing paper to distribute the adhesive evenly on the etched portion of the stainless steel fiber. Then, the etched portion of the stainless steel fiber, coated with adhesive, was quickly inserted into the chlorinated functionalized covalent organic framework / graphene aerogel material COF-GA1 prepared in Example 1, rotated 10 times, and finally placed in a 70°C forced-air drying oven for 1 hour to cure. The above process was repeated 3 times to obtain the chlorinated functionalized covalent organic framework / graphene aerogel solid-phase microextraction fiber coating.

[0050] The COF-GA1 solid-phase microextraction fiber coating (A) and bare fiber filaments (B) obtained in Example 4 were characterized by scanning electron microscopy, and the results are as follows: Figure 6 As shown, by Figure 6It can be seen that the thickness of the fiber coating is about 60μm, and COF-GA1 is uniformly coated on the surface of the fiber filaments.

[0051] Example 5:

[0052] The chlorine-functionalized covalent organic framework / graphene aerogel solid-phase microextraction fiber coating from Example 4 was applied to determine the residues of PCNs in environmental water samples. The specific process is as follows:

[0053] After natural sedimentation, 10 mL of the clear portion of the environmental water sample was placed in a 30 mL headspace vial. After optimizing the extraction parameters, 0.5 g of sodium chloride was added, and the COF-GA1 solid-phase microextraction fiber coating was exposed above the water sample. Extraction was performed in a water bath at 80 °C and 700 rpm for 30 min. Subsequently, the COF-GA1 solid-phase microextraction fiber coating was returned to the SPME device, and the SPME device was quickly inserted into the gas chromatograph inlet at 290 °C. The fiber coating was then removed, and after thermal desorption for 5 min, the GC-MS / MS detection program was run.

[0054] Through the above operations, the established method was validated methodologically. The total ion chromatogram of the method established in this invention for four PCNs (CN-2, CN-5, CN-13, and CN-27) in environmental water is shown below. Figure 7 As shown. Figure 7 The intensity of CN-2 and CN-5 is relatively high, while that of CN-13 and CN-27 is relatively weak. This is mainly due to the different response values ​​of the instrument to different substances.

[0055] The methodological parameters and spiked recoveries for the detection of four PCNs in environmental water established in this invention are shown in Tables 1 and 2 below.

[0056] Table 1. Methodological parameters for the detection of four PCNs in environmental water using chlorinated functionalized covalent organic frameworks / graphene aerogel solid-phase microextraction fiber coating combined with GC-MS / MS.

[0057]

[0058]

[0059] Table 2. Spiking recoveries of four PCNs in ambient water by chlorinated functionalized covalent organic frameworks / graphene aerogel solid-phase microextraction fiber coating combined with GC-MS / MS

[0060]

[0061] As shown in Tables 1 and 2, the detection limit of the method of this invention is as low as 0.001–0.018 pg / mL; the linear relationship is good (r ≥ 0.9995), and the relative standard deviation is ≤ 9.1%; the enrichment factor for the four PCNs is as high as 4557–7877, and the spiked recovery rate for the four PCNs is 83.8–119.9%. In summary, the chlorinated functionalized covalent organic framework / graphene aerogel material of this invention has been successfully applied to the detection of trace PCNs residues in environmental water, and the application effect is good.

[0062] The data results above show that the COF-GA1 solid-phase microextraction fiber coating combined with gas chromatography-tandem mass spectrometry of the present invention has good sensitivity, accuracy and precision for the extraction and detection of PCNs in environmental water.

Claims

1. An application of a solid-phase microextraction fiber coating for the detection of trace PCNs in environmental water samples, characterized in that, The solid-phase microextraction fiber coating is made of chlorinated functionalized covalent organic framework / graphene aerogel material; the chlorinated functionalized covalent organic framework / graphene aerogel material is prepared by a Schiff base reaction under the catalysis of acetic acid aqueous solution, consisting of amino-functionalized graphene aerogel, chlorinated functionalized aldehyde ligands of covalent organic framework and amino ligands of covalent organic framework. The preparation method of the chlorinated functionalized covalent organic framework / graphene aerogel material includes the following steps: a. Graphene oxide is ultrasonically dispersed in ultrapure water to obtain a graphene oxide dispersion. b. In the system of the graphene oxide dispersion obtained in step a, the graphene oxide is modified with an amino functionalization agent, then reduced at high temperature, followed by solid-liquid separation and washing of the product, and freeze-drying to obtain amino-functionalized graphene aerogel. c. Disperse the amino-functionalized graphene aerogel obtained in step b in a solvent, add the chlorinated functionalized aldehyde ligand of the covalent organic framework, let stand for 4-8 h, then add the amino ligand of the covalent organic framework, and keep at 60-80 °C for 24-36 h under the catalysis of acetic acid aqueous solution. After solid-liquid separation, wash the product with tetrahydrofuran, anhydrous ethanol and ultrapure water in sequence, and freeze-dry to obtain the chlorinated functionalized covalent organic framework / graphene aerogel material. In step c, the chlorinated functionalized aldehyde ligand is 2,5-dichloroterephthalaldehyde, and the amino ligand is tetra-(4-aminophenyl)ethylene.

2. The application according to claim 1, characterized in that, The modifying agent mentioned in step b is 3-aminopropyltrimethoxysilane or 3-aminopropyltriethoxysilane.

3. The application according to claim 1, characterized in that, In step c, the molar ratio of chlorofunctionalized aldehyde ligand to amino ligand is 2:1 to 3:

1.

4. The application according to claim 1, characterized in that, In step c, the solvent is acetonitrile or N,N-dimethylformamide.

5. The application according to claim 1, characterized in that, In step c, the mass concentration of the amino-functionalized graphene aerogel is 1~2 mg / mL.

6. The application according to claim 1, characterized in that, The preparation method of the solid-phase microextraction fiber coating is as follows: a. Stainless steel fibers are etched with aqua regia, followed by ultrasonic cleaning and drying to obtain bare fibers; b. Apply glue to the bare fiber filaments, then coat the bare fiber filaments with chlorinated functionalized covalent organic framework / graphene aerogel material, and then place them in a forced-air drying oven for curing to obtain a preliminary solid-phase microextraction fiber coating. c. Apply glue to the obtained preliminary solid-phase microextraction fiber coating, then coat it with chlorine-functionalized covalent organic framework / graphene aerogel material, and then place it in a forced-air drying oven for curing; d. After several coatings, drying and curing, a solid-phase microextraction fiber coating is obtained.

Images