Covalent organic framework material loaded with noble metal as well as preparation method and application of covalent organic framework material

Abstract

The invention relates to a covalent organic framework material loaded with noble metal as well as a preparation method and application thereof, and belongs to the technical field of tobacco detection. The preparation method of the covalent organic framework material loaded with the noble metal comprises the following steps that 2, 5-diaminobenzene sulfonic acid and trialdehyde phloroglucinol are subjected to a Schiff base reaction under the action of a catalyst, and the covalent organic framework material is obtained; and sequentially mixing the covalent organic framework material with chloroauric acid and silver nitrate in water for reaction to obtain the covalent organic framework material loaded with the noble metal. When the prepared covalent organic framework material loaded with the noble metal is used as a surface enhanced Raman spectrum detection substrate material, the covalent organic framework material loaded with the noble metal selectively adsorbs nicotine in a liquid phase, and then realizes enhancement of nicotine molecular signals through loaded nanogold and silver; and thus, sensitive detection of liquid-phase nicotine is realized.

Description

Technical Field

[0001] The invention relates to a covalent organic framework material loaded with precious metals and a preparation method and application thereof, belonging to the technical field of tobacco detection. Background Art

[0002] Nicotine is an alkaloid found in Solanaceae plants that can stimulate the release of neurotransmitters, thereby regulating emotions. When smoking or using tobacco products, nicotine quickly enters the blood circulation through the lungs and then travels to the brain, stimulating the central nervous system to produce a series of physiological and psychological effects, including refreshing, improving attention, and enhancing mood. However, due to its addictive nature, long-term use of tobacco products may lead to physical and mental health problems. Therefore, achieving trace detection of nicotine is of great significance to human health. The detection of nicotine in liquid samples such as environmental water samples, saliva, and urine is a key issue in environmental monitoring, disease diagnosis, and other fields. At present, the main detection methods for nicotine include liquid / gas chromatography, fluorescence determination, capillary electrophoresis, etc., but these technical means have complicated sample preparation processes.

[0003] Surface-enhanced Raman spectroscopy has the advantages of high detection sensitivity, strong selectivity, and easy miniaturization of equipment, and has attracted extensive attention in the fields of food safety, environmental protection, and medical testing. However, the common surface-enhanced Raman spectroscopy detection substrate materials have weak chemical affinity for nicotine in liquid samples, and the detection sensitivity is low. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing a covalent organic framework material loaded with precious metals, which can solve the problem that the current surface enhanced Raman spectroscopy detection substrate material has weak chemical affinity for nicotine in liquid samples and low detection sensitivity.

[0005] The second object of the present invention is to provide a covalent organic framework material loaded with precious metals, which can solve the problem that the current surface enhanced Raman spectroscopy detection substrate material has weak chemical affinity for nicotine in liquid samples and low detection sensitivity.

[0006] The third object of the present invention is to provide an application of a covalent organic framework material loaded with precious metals, which can solve the problem of weak chemical affinity and low detection sensitivity of the current surface enhanced Raman spectroscopy detection substrate material for nicotine in liquid samples.

[0007] In order to achieve the above objectives, the technical solution adopted by the method for preparing the covalent organic framework material loaded with precious metals of the present invention is:

[0008] A method for preparing a covalent organic framework material loaded with noble metals comprises the following steps:

[0009] (1) 2,5-diaminobenzenesulfonic acid and trialdehyde phloroglucinol are subjected to a Schiff base reaction in the presence of a catalyst to obtain a covalent organic framework material;

[0010] (2) The covalent organic framework material is sequentially mixed with chloroauric acid and silver nitrate in water under the action of a reducing agent to obtain a covalent organic framework material loaded with precious metals.

[0011] The preparation method of the covalent organic framework material loaded with precious metals of the present invention is prepared by gradually loading gold and silver nanoparticles on the covalent organic framework material by a reduction method. The covalent organic framework material loaded with precious metals obtained by the present invention has the characteristics of being porous and having a strong adsorption capacity for nicotine, wherein the sulfonic acid group covalent organic framework material can selectively adsorb nicotine, and the gold and silver nanoparticles are closely distributed, generating a large number of localized surface plasma electromagnetic field "hot spots", and having good surface enhanced Raman spectroscopy enhancement performance. When the covalent organic framework material loaded with precious metals prepared by the present invention is used as a surface enhanced Raman spectroscopy detection substrate material, the covalent organic framework material loaded with precious metals first selectively adsorbs nicotine in the liquid phase, and then enhances the nicotine molecular signal through the loaded nano-gold and silver, thereby realizing sensitive detection of liquid phase nicotine.

[0012] Preferably, the molar ratio of the 2,5-diaminobenzenesulfonic acid to trialdehyde phloroglucinol is 0.45:0.35.

[0013] Preferably, the catalyst is p-toluenesulfonic acid; the molar ratio of the 2,5-diaminobenzenesulfonic acid, trialdehyde phloroglucinol and the catalyst is 0.45:0.35:2.5.

[0014] Preferably, the temperature of the Schiff base reaction is 170° C. and the time is 10 min.

[0015] Preferably, for every 2.5 mg of the covalent organic framework material, the mass of the chloroauric acid used is 0.5 mg, and the mass of the silver nitrate is 2.1-12.8 mg.

[0016] Preferably, the method of mixing and reacting the covalent organic framework material with chloroauric acid and silver nitrate in water in sequence under the action of a reducing agent is as follows: first, adding chloroauric acid solution to the covalent organic framework material dispersion for a first mixing reaction, then adding a reducing agent and a silver nitrate solution to the system after the first mixing reaction for a second mixing reaction, solid-liquid separation, and drying to obtain a covalent organic framework material loaded with gold and silver; the mass fraction of the covalent organic framework material dispersion is 0.25%; the mass fraction of the chloroauric acid solution is 1%, the addition rate of the chloroauric acid solution is 0.2mL / min, and the time of the first mixing reaction is 30min; the concentration of the silver nitrate solution is 10mmol / L, the addition rate of the silver nitrate solution is 0.5mL / min, the temperature of the second mixing reaction is 70°C, and the time is 1h; the reducing agent is sodium citrate dihydrate.

[0017] The technical solution adopted by the covalent organic framework material loaded with precious metals of the present invention is:

[0018] A covalent organic framework material loaded with noble metals is prepared by the method for preparing a covalent organic framework material loaded with noble metals as described above.

[0019] The covalent organic framework material loaded with precious metals of the present invention comprises a sulfonic acid covalent organic framework material and loaded nano-gold and silver particles. The sulfonic acid covalent organic framework material can selectively adsorb nicotine in a liquid phase, and the loaded nano-gold and silver can enhance nicotine molecular signals.

[0020] The technical solution adopted in the application of the covalent organic framework material loaded with precious metals of the present invention is:

[0021] An application of the covalent organic framework material loaded with noble metals as described above to detecting liquid-phase nicotine in surface enhanced Raman spectroscopy.

[0022] The covalent organic framework material loaded with precious metals of the present invention has the characteristics of being porous and having a strong ability to adsorb nicotine, wherein the sulfonic acid covalent organic framework material can selectively adsorb nicotine, and the gold and silver nanoparticles are closely distributed, generating a large number of localized surface plasma electromagnetic field "hot spots", and having good surface enhanced Raman spectroscopy enhancement performance. When the covalent organic framework material loaded with precious metals prepared by the present invention is used as a surface enhanced Raman spectroscopy detection substrate material, the covalent organic framework material loaded with precious metals first selectively adsorbs nicotine in the liquid phase, and then enhances the nicotine molecular signal through the loaded nano-gold and silver, thereby realizing sensitive detection of liquid phase nicotine.

[0023] Preferably, the application comprises the following steps: using the covalent organic framework material dispersion loaded with precious metals as a surface enhanced Raman spectroscopy detection substrate material, performing Raman spectroscopy detection on nicotine in a liquid phase standard sample, and using the detection results to construct a corresponding relationship between the Raman spectroscopy signal intensity of nicotine and the nicotine concentration in the liquid phase.

[0024] Preferably, the Raman spectrum detection conditions are as follows: the laser wavelength is 785 nm, the laser intensity is 50 mW, the integration time is 1 s, and the number of integrations is 20 times. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a microstructure diagram of the covalent organic framework material loaded with precious metals prepared in Example 1;

[0026] Figure 2 A schematic diagram of the detection results of the covalent organic framework material loaded with precious metals prepared in Example 1-5 detecting a nicotine solution with a concentration of 50 mg / L;

[0027] Figure 3 A schematic diagram of the test results of the covalent organic framework material loaded with precious metals prepared in Example 1 detecting nicotine in nicotine solutions of different concentrations;

[0028] Figure 4 The wavelength is 1075cm -1 Schematic diagram of the linear relationship between the intensity of the characteristic peak at and the nicotine concentration. DETAILED DESCRIPTION

[0029] The preparation method of the covalent organic framework material loaded with precious metals of the present invention is a pioneering invention. The present invention loads gold and silver nanoparticles on the covalent organic framework material, so that a synergistic effect is generated between the covalent organic framework material and the precious metal nanoparticles. On the one hand, the covalent organic framework material exhibits high adsorption performance for nicotine, shortens the distance between nicotine and the precious metal nanoparticles, and then effectively utilizes the surface plasma resonance effect of the precious metal nanoparticles. On the other hand, the gold-silver nanoparticles with a core-shell structure can produce a bimetallic synergistic effect and improve the surface enhanced Raman spectroscopy activity.

[0030] The technical solution of the present invention is further described below in conjunction with specific implementation methods.

[0031] 1. Specific embodiments of the covalent organic framework material loaded with precious metals and the preparation method thereof of the present invention are as follows:

[0032] Example 1

[0033] The method for preparing the covalent organic framework material loaded with precious metals in this embodiment specifically comprises the following steps:

[0034] (1) Synthesis of covalent organic framework material TpPa-SO3H using grinding method

[0035] 2,5-Diaminobenzenesulfonic acid (0.45mmol, 84.7mg) and p-toluenesulfonic acid (2.5mmol, 430.5mg) were placed in a mortar and ground for 15min, then trialdehyde pyrogallol (0.35mmol, 74.2mg) and 20μL ultrapure water were added, and the grinding was continued for 15min. Then, the ground material was placed in an oven and heated at 170°C for 10min to obtain a powdered covalent organic framework material named TpPa-SO3H.

[0036] (2) Preparation of TpPa-SO3H-Au@Ag by step-by-step reduction method

[0037] 2.5 mg of the covalent organic framework material TpPa-SO3H prepared in step (1) was dispersed in 1 mL of ultrapure water and subjected to ultrasound for 5 min to obtain a covalent organic framework material dispersion. Then, a chloroauric acid solution (mass fraction of 1%, volume of 50 μL, mass of chloroauric acid in the chloroauric acid solution of 0.5 mg) was added to the covalent organic framework material dispersion at a rate of 0.2 mL / min under vigorous stirring, and the reaction was stirred for 30 min. Then, a reducing agent sodium citrate dihydrate (sodium citrate dihydrate addition amount of 25 mg) was added to the system after the stirring reaction, and then an AgNO3 solution (concentration of 10 mmol / L, volume of 0.95 mL, mass of AgNO3 in the AgNO3 solution of 2.1 mg) was added at a rate of 0.5 mL / min. The reaction was heated and stirred at 70°C for 1 h. After the reaction was completed, the mixture was filtered, washed, and dried to obtain a covalent organic framework material loaded with gold and silver, i.e., a covalent organic framework material loaded with precious metals, named TpPa-SO3H-Au@Ag.

[0038] Example 2

[0039] The method for preparing the covalent organic framework material loaded with precious metals in this embodiment specifically comprises the following steps:

[0040] (1) This step is the same as step (1) of Example 1.

[0041] (2) Preparation of TpPa-SO3H-Au@Ag by step-by-step reduction method

[0042] 2.5 mg of the covalent organic framework material TpPa-SO3H prepared in step (1) was dispersed in 1 mL of ultrapure water and subjected to ultrasound for 5 min to obtain a covalent organic framework material dispersion. Then, a chloroauric acid solution (mass fraction of 1%, volume of 50 μL, mass of chloroauric acid in the chloroauric acid solution of 0.5 mg) was added to the covalent organic framework material dispersion at a rate of 0.2 mL / min under vigorous stirring, and the reaction was stirred for 30 min. Then, a reducing agent sodium citrate dihydrate (sodium citrate dihydrate addition amount of 25 mg) was added to the system after the stirring reaction, and then an AgNO3 solution (concentration of 10 mmol / L, volume of 1.9 mL, mass of AgNO3 in the AgNO3 solution of 3.2 mg) was added at a rate of 0.5 mL / min. The reaction was heated and stirred at 70°C for 1 h. After the reaction was completed, the mixture was filtered, washed, and dried to obtain a covalent organic framework material loaded with gold and silver, i.e., a covalent organic framework material loaded with precious metals, named TpPa-SO3H-Au@Ag.

[0043] Example 3

[0044] The method for preparing the covalent organic framework material loaded with precious metals in this embodiment specifically comprises the following steps:

[0045] (1) This step is the same as step (1) of Example 1.

[0046] (2) Preparation of TpPa-SO3H-Au@Ag by step-by-step reduction method

[0047] 2.5 mg of the covalent organic framework material TpPa-SO3H prepared in step (1) was dispersed in 1 mL of ultrapure water and subjected to ultrasound for 5 min to obtain a covalent organic framework material dispersion. Then, a chloroauric acid solution (mass fraction of 1%, volume of 50 μL, mass of chloroauric acid in the chloroauric acid solution of 0.5 mg) was added to the covalent organic framework material dispersion at a rate of 0.2 mL / min under vigorous stirring, and the reaction was stirred for 30 min. Then, a reducing agent sodium citrate dihydrate (sodium citrate dihydrate addition amount of 25 mg) was added to the system after the stirring reaction, and then an AgNO3 solution (concentration of 10 mmol / L, volume of 3.81 mL, mass of AgNO3 in the AgNO3 solution of 6.4 mg) was added at a rate of 0.5 mL / min, and the reaction was heated and stirred at 70°C for 1 h. After the reaction was completed, the mixture was filtered, washed, and dried to obtain a covalent organic framework material loaded with gold and silver, i.e., a covalent organic framework material loaded with precious metals, named TpPa-SO3H-Au@Ag.

[0048] Example 4

[0049] The method for preparing the covalent organic framework material loaded with precious metals in this embodiment specifically comprises the following steps:

[0050] (1) This step is the same as step (1) of Example 1.

[0051] (2) Preparation of TpPa-SO3H-Au@Ag by step-by-step reduction method

[0052] 2.5 mg of the covalent organic framework material TpPa-SO3H prepared in step (1) was dispersed in 1 mL of ultrapure water and subjected to ultrasound for 5 min to obtain a covalent organic framework material dispersion. Then, a chloroauric acid solution (mass fraction of 1%, volume of 50 μL, mass of chloroauric acid in the chloroauric acid solution of 0.5 mg) was added to the covalent organic framework material dispersion at a rate of 0.2 mL / min under vigorous stirring, and the reaction was stirred for 30 min. Then, a reducing agent sodium citrate dihydrate (sodium citrate dihydrate addition amount of 25 mg) was added to the system after the stirring reaction, and then an AgNO3 solution (concentration of 10 mmol / L, volume of 5.72 mL, mass of AgNO3 in the AgNO3 solution of 9.6 mg) was added at a rate of 0.5 mL / min, and the reaction was heated and stirred at 70°C for 1 h. After the reaction was completed, the mixture was filtered, washed, and dried to obtain a covalent organic framework material loaded with gold and silver, i.e., a covalent organic framework material loaded with precious metals, named TpPa-SO3H-Au@Ag.

[0053] Example 5

[0054] The method for preparing the covalent organic framework material loaded with precious metals in this embodiment specifically comprises the following steps:

[0055] (1) This step is the same as step (1) of Example 1.

[0056] (2) Preparation of TpPa-SO3H-Au@Ag by step-by-step reduction method

[0057] 2.5 mg of the covalent organic framework material TpPa-SO3H prepared in step (1) was dispersed in 1 mL of ultrapure water and subjected to ultrasound for 5 min to obtain a covalent organic framework material dispersion. Then, a chloroauric acid solution (mass fraction of 1%, volume of 50 μL, mass of chloroauric acid in the chloroauric acid solution of 0.5 mg) was added to the covalent organic framework material dispersion at a rate of 0.2 mL / min under vigorous stirring, and the reaction was stirred for 30 min. Then, a reducing agent sodium citrate dihydrate (sodium citrate dihydrate addition amount of 25 mg) was added to the system after the stirring reaction, and then an AgNO3 solution (concentration of 10 mmol / L, volume of 7.62 mL, mass of AgNO3 in the AgNO3 solution of 12.8 mg) was added at a rate of 0.5 mL / min, and the reaction was heated and stirred at 70°C for 1 h. After the reaction was completed, the mixture was filtered, washed, and dried to obtain a covalent organic framework material loaded with gold and silver, i.e., a covalent organic framework material loaded with precious metals, named TpPa-SO3H-Au@Ag.

[0058] 2. Specific embodiments of the covalent organic framework material loaded with precious metals of the present invention are as follows:

[0059] The covalent organic framework material loaded with a noble metal in this embodiment is a covalent organic framework material loaded with a noble metal prepared by any method for preparing a covalent organic framework material loaded with a noble metal in any of Embodiments 1-5.

[0060] 3. Specific examples of the application of the covalent organic framework material loaded with precious metals of the present invention are as follows:

[0061] The covalent organic framework material loaded with a noble metal prepared by any of the methods for preparing a covalent organic framework material loaded with a noble metal in Examples 1-5 is used to detect liquid-phase nicotine in surface enhanced Raman spectroscopy.

[0062] Experimental Example 1

[0063] In this experimental example, a transmission electron microscope (TEM) was used to analyze the microstructure of the covalent organic framework material loaded with precious metals. The specific method is as follows: the covalent organic framework material sample loaded with precious metals was dispersed in ultrapure water, and then dripped onto a 200-mesh copper grid coated with a carbon film after ultrasonic dispersion. After drying, TEM test was performed. The microstructure of the covalent organic framework material loaded with precious metals prepared in Example 2 is shown in FIG. Figure 1 As shown by Figure 1 It can be seen that the silver nanoparticles are evenly distributed on the covalent organic framework material, and the distance between the silver nanoparticles is relatively close, which is conducive to the generation of surface enhanced Raman spectroscopy enhancement hotspots.

[0064] Experimental Example 2

[0065] In this experimental example, the covalent organic framework material loaded with precious metals prepared in Examples 1-5 was used to detect nicotine in a nicotine solution, and the concentration of the nicotine solution was 50 mg / L. The specific test method is as follows: 15 μL of the covalent organic framework material dispersion loaded with precious metals was stirred and mixed with 1 mL of nicotine solution for 10 minutes, and then the mixed liquid was dropped onto a glass slide and placed under the fiber optic Raman spectrometer probe for Raman detection. The detection conditions of the Raman spectrometer are as follows: the laser wavelength is 785 nm, the laser intensity is 50 mW, the integration time is 1 s, and the number of integrations is 20 times. Different sampling points are randomly selected for each sample, and at least 10 samples are collected. The obtained spectra are averaged to obtain the final Raman spectrum of the sample. The detection results of the covalent organic framework material loaded with precious metals prepared in Examples 1-5 for detecting a nicotine solution with a concentration of 50 mg / L are shown as follows. Figure 2 ( Figure 2 The vertical axis represents the wavelength of 1075cm -1 The molar ratios of the gold element in the chloroauric acid solution and the silver element in the AgNO3 solution in Examples 1-5 are 1:10, 1:15, 1:30, 1:45, and 1:60, respectively. Figure 2 1:10, 1:15, 1:30, 1:45, and 1:60 represent the covalent organic framework materials loaded with precious metals prepared in Examples 1-5, respectively.

[0066] Depend on Figure 2 It can be seen that as the molar ratio of gold in chloroauric acid solution to silver in AgNO3 solution increases from 1:10 to 1:60, the Raman spectrum signal of nicotine increases first and then decreases, and the best enhancement effect is obtained when the molar ratio is 1:15. + The dosage is very important for producing a better enhancement effect. When the molar ratio of gold element in chloroauric acid solution and silver element in AgNO3 solution is 1:15, the prepared covalent organic framework material loaded with precious metals has the best surface enhanced Raman enhancement performance.

[0067] Experimental Example 3

[0068] In this experimental example, the covalent organic framework material loaded with precious metals prepared in Examples 1-5 was used to detect nicotine in nicotine solutions of different concentrations, so as to obtain the detection limit of nicotine by the covalent organic framework material loaded with precious metals. The experimental method is as follows: First, a 6.0×10 -5 mol / L、3.0×10 -5 mol / L、6.0×10 -6 mol / L,3.0×10 - 6 mol / L,6.0×10 -7mol / L,6.0×10 -8 mol / L,3.0×10 -9 mol / L,6.0×10 -10 mol / L nicotine solution, and then 15μL of the covalent organic framework material dispersion loaded with precious metals was evenly stirred with 1mL of nicotine solution of different concentrations. After standing for adsorption for 5 hours, the liquid after standing for adsorption was placed on a glass slide, and then placed under the probe of a fiber optic Raman spectrometer for Raman detection. The detection conditions of the Raman spectrometer are as follows: the laser wavelength is 785nm, the laser intensity is 50mW, the integration time is 1s, and the number of integrations is 20 times. Different sampling points are randomly selected for each sample, and the samples are collected at least 10 times. The obtained spectra are averaged to obtain the final Raman spectrum of the sample. The test results of the covalent organic framework material loaded with precious metals prepared in Example 2 for detecting nicotine in nicotine solutions of different concentrations are shown as follows. Figure 3 shown.

[0069] Depend on Figure 3 It can be seen that as the nicotine concentration decreases, its characteristic Raman signal gradually decreases, and the detection limit is as low as 6.0×10 -10 mol / L. Figure 3 Based on the wavelength of 1075cm -1 The intensity of the characteristic peak at 100° was linearly related to the nicotine concentration. The results are as follows: Figure 4 ( Figure 4 The horizontal axis is the nicotine concentration, and the vertical axis on the left is the normalized signal intensity, which is calculated as follows: the wavelength is 1075cm -1 The intensity of the characteristic peak at 1380 cm-1 is divided by the wavelength. -1 The intensity of the characteristic peak at the right ordinate is the wavelength of 1075cm -1 The intensity of the characteristic peak at Figure 4 It can be seen that with a wavelength of 1075cm -1 Taking the characteristic peak intensity at as a reference, there is a good linear relationship between the Raman spectrum signal intensity of nicotine and the logarithm of the nicotine concentration, indicating that the covalent organic framework material loaded with noble metals prepared in Example 2 can be used for sensitive quantitative detection of nicotine.

Claims

1. A method for preparing a covalent organic framework material loaded with precious metals, characterized in that: The following steps are involved: (1) 2,5-diaminobenzenesulfonic acid and trialdehyde phloroglucinol are subjected to a Schiff base reaction in the presence of a catalyst to obtain a covalent organic framework material; (2) The covalent organic framework material is sequentially mixed with chloroauric acid and silver nitrate in water under the action of a reducing agent to obtain a covalent organic framework material loaded with precious metals.

2. The method for preparing a covalent organic framework material loaded with noble metals according to claim 1, characterized in that: The molar ratio of the 2,5-diaminobenzenesulfonic acid to trialdehyde phloroglucinol is 0.45:0.

35.

3. The method for preparing a covalent organic framework material loaded with noble metals according to claim 1, characterized in that: The catalyst is p-toluenesulfonic acid; the molar ratio of the 2,5-diaminobenzenesulfonic acid, trialdehyde phloroglucinol and the catalyst is 0.45:0.35:2.

5.

4. The method for preparing a covalent organic framework material loaded with noble metals according to claim 3, characterized in that: The temperature of the Schiff base reaction is 170° C. and the time is 10 min.

5. The method for preparing a covalent organic framework material loaded with noble metals according to claim 1, characterized in that: For every 2.5 mg of the covalent organic framework material, the mass of the chloroauric acid used is 0.5 mg, and the mass of the silver nitrate is 2.1 to 12.8 mg.

6. The method for preparing a covalent organic framework material loaded with a noble metal according to any one of claims 1 to 5, characterized in that: The method for mixing and reacting a covalent organic framework material with chloroauric acid and silver nitrate in water in sequence under the action of a reducing agent is as follows: first, adding a chloroauric acid solution to a covalent organic framework material dispersion for a first mixing reaction, then adding a reducing agent and a silver nitrate solution to the system after the first mixing reaction for a second mixing reaction, solid-liquid separation, and drying to obtain a covalent organic framework material loaded with gold and silver; the mass fraction of the covalent organic framework material dispersion is 0.25%; the mass fraction of the chloroauric acid solution is 1%, the addition rate of the chloroauric acid solution is 0.2 mL / min, and the time of the first mixing reaction is 30 min; the concentration of the silver nitrate solution is 10 mmol / L, the addition rate of the silver nitrate solution is 0.5 mL / min, the temperature of the second mixing reaction is 70° C., and the time is 1 h; the reducing agent is sodium citrate dihydrate. 7 . A covalent organic framework material loaded with noble metals prepared by the method for preparing a covalent organic framework material loaded with noble metals as claimed in any one of claims 1 to 6 .

8. Use of the covalent organic framework material loaded with noble metals as claimed in claim 7 for detecting liquid-phase nicotine in surface enhanced Raman spectroscopy.

9. The use according to claim 8, characterized in that The application comprises the following steps: using the covalent organic framework material dispersion loaded with precious metals as a surface enhanced Raman spectroscopy detection substrate material, performing Raman spectroscopy detection on nicotine in a liquid phase standard sample, and using the detection results to construct a corresponding relationship between the Raman spectroscopy signal intensity of nicotine and the nicotine concentration in the liquid phase.

10. The use according to claim 8, characterized in that The Raman spectrum detection conditions are as follows: laser wavelength is 785 nm, laser intensity is 50 mW, integration time is 1 s, and integration times are 20 times.

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