A covalent organic framework aerogel and a preparation method and application thereof

Abstract

The application discloses a kind of covalent organic framework aerogel and its preparation method and application, belong to aerogel material technical field.The preparation method of the application is by graphite phase carbon nitride / graphene oxide heterojunction with 1,3,5-triformylphloroglucinol, 2,5-diaminobenzenesulfonic acid, sodium hydroxide is hydrothermal reaction, and join gold source and be modified, to prepare covalent organic framework aerogel.The covalent organic framework aerogel prepared in the application has the advantages of strong adsorption and self-cleaning capacity, and based on surface-enhanced Raman scattering spectrum (SERS) technology can be directly used as substrate to detect pollutants, and the concentration of pollutants can be evaluated.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of aerogels, and particularly relates to a covalent organic framework aerogel and a preparation method and application thereof. BACKGROUND

[0002] Due to the continuous intensification of industrialization, a large amount of organic dyes are discharged into the environment, which poses a great threat to biological populations and ecosystems. At present, a variety of adsorption materials are used for the removal of pollutants in water environment. Among various porous adsorbents, covalent organic frameworks (COFs) have become a very promising application material due to their structural diversity, low density, permanent porosity and designable pore function. However, the covalent organic frameworks produced by traditional synthesis methods are usually powders, which are difficult to process. Moreover, due to the microporous, mesoporous characteristics and highly stacked structure of most covalent organic frameworks, the pollutant molecules are limited to enter the inside of the pores, and even the phenomenon of pore blockage occurs, resulting in poor pollutant adsorption effect. In addition, the prepared aerogels cannot be directly used as a substrate for surface-enhanced Raman scattering spectroscopy (SERS) technology to detect and evaluate the concentration of pollutants.

[0003] At present, the related technology prepares covalent organic framework aerogels by compounding different types of functional materials with covalent organic framework materials to improve the adsorption performance of the covalent organic framework aerogels. For example, the prior art with the application publication number CN 115193417 A discloses a laminar covalent organic framework aerogel and a preparation method thereof. The laminar covalent organic framework aerogel is obtained by compounding a covalent organic framework material with a sol matrix. The covalent organic framework material is formed by coordination of 1,3,5-tris(4-aminophenyl)benzene, mesitylene and 2,5-dimethoxybenzene-1,4-diformaldehyde, and the sol matrix is selected from sodium alginate, chitosan, cellulose and glucomannan. The prepared covalent organic framework material is mixed with a sol matrix aqueous solution, stirred uniformly and then freeze-dried to obtain the laminar covalent organic framework aerogel.

[0004] However, the preparation method described above has the following problems in application: first, the covalent organic framework aerogel can only selectively adsorb quinolone antibiotics, and the removal effect is single and does not have broad-spectrum nature; second, the covalent organic framework aerogel only has physical adsorption performance, and after saturation of adsorption, desorption is needed for repeated use, and the covalent organic framework aerogel does not have self-cleaning performance; third, the prepared covalent organic framework aerogel cannot be directly used as a substrate for surface-enhanced Raman scattering spectroscopy (SERS) testing. SUMMARY

[0005] The application discloses a covalent organic framework aerogel and a preparation method and application thereof, and aims to solve the technical problems of the existing covalent organic framework aerogel material, such as single pollutant removal type, lack of self-cleaning performance and inability to directly serve as a substrate for SERS testing.

[0006] To achieve the above object, the technical scheme of the present application is:

[0007] The first aspect of the present application provides a preparation method of a covalent organic framework aerogel, comprising:

[0008] Preparation of a graphite phase carbon nitride / graphene oxide heterojunction;

[0009] Under the catalysis of p-toluenesulfonic acid, the graphite phase carbon nitride / graphene oxide heterojunction, 1,3,5-triformylphloroglucinol, chloroauric acid, 2,5-diaminobenzenesulfonic acid and a mixed aqueous solution of sodium hydroxide are subjected to a hydrothermal reaction to obtain a covalent organic framework hydrogel;

[0010] The covalent organic framework hydrogel is freeze-dried to obtain a covalent organic framework aerogel.

[0011] The second aspect of the present application provides a preparation method of a covalent organic framework aerogel, comprising:

[0012] Preparation of a graphite phase carbon nitride / graphene oxide heterojunction;

[0013] Under the catalysis of p-toluenesulfonic acid, the graphite phase carbon nitride / graphene oxide heterojunction, 1,3,5-triformylphloroglucinol, 2,5-diaminobenzenesulfonic acid and a mixed aqueous solution of sodium hydroxide are subjected to a hydrothermal reaction to obtain a covalent organic framework hydrogel;

[0014] The covalent organic framework hydrogel is freeze-dried and gold nanoparticles are added to obtain a covalent organic framework aerogel.

[0015] In combination with the first aspect or the second aspect, preferably, the method for preparing the graphite phase carbon nitride / graphene oxide heterojunction comprises: mixing and reacting a graphite phase carbon nitride dispersion liquid with a graphene oxide dispersion liquid to obtain a graphite phase carbon nitride / graphene oxide heterojunction.

[0016] In combination with the first aspect or the second aspect, preferably, when the graphite phase carbon nitride dispersion liquid is mixed and reacted with the graphene oxide dispersion liquid, the concentration ratio of the graphene oxide to the graphite phase carbon nitride is 1:2-1:1.

[0017] In combination with the first aspect or the second aspect, preferably, the molar ratio of 1,3,5-triformylphloroglucinol to 2,5-diaminobenzenesulfonic acid in the mixed aqueous solution is 2:3-8:11.

[0018] In combination with the second aspect, preferably, the average particle size of the gold nanoparticles in the gold nanoparticle dispersion liquid is 16 nm.

[0019] Preferably in combination with the first aspect or the second aspect, the temperature of the hydrothermal reaction is 120℃, and the time is 24-48h.

[0020] Preferably in combination with the first aspect or the second aspect, the temperature of the freeze-drying is -80~-50℃, and the time is 18-30h.

[0021] The third aspect of the present application provides a covalent organic framework aerogel prepared by the method of the first aspect or the second aspect.

[0022] The fourth aspect of the present application provides an application of the covalent organic framework aerogel of the third aspect in the field of water environment treatment and surface enhanced Raman scattering spectrum.

[0023] Compared with the prior art, the advantages or beneficial effects of the embodiments of the present application at least include:

[0024] The preparation method provided by the present application effectively solves the technical problems that the existing covalent organic framework aerogel material has a single type of pollutant removal, does not have a self-cleaning performance, and cannot be directly used as a substrate for SERS testing.

[0025] The advantages of the present application are that the preparation method introduces a graphite phase carbon nitride / oxidized graphene heterojunction into the covalent organic framework and modifies it with gold nanoparticles, which can produce a full synergistic effect of the covalent organic framework, gold nanoparticles and graphite phase carbon nitride / oxidized graphene heterojunction. On the one hand, the covalent organic framework aerogel can adsorb pollutants of different sizes, and the types of adsorbed pollutants are diverse. On the other hand, the photocatalytic performance is improved, and the adsorbed pollutants can be degraded under visible light irradiation, which has a self-cleaning ability and makes the material recyclable. Thirdly, the Raman signal is significantly enhanced, and the material has high surface enhanced Raman scattering spectrum (SERS) activity, which can be directly used as a substrate for pollutant detection and evaluation of pollutant concentration. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments described in the present application, and those skilled in the art can obtain other drawings according to these drawings without creating any creative labor.

[0027] Figure 1 SEM image of g-C3N4 prepared in advance in the preparation of COF / g-C3N4 / rGO / Au-1.

[0028] Figure 2 SEM image of g-C3N4 / GO heterojunction prepared in advance for COF / g-C3N4 / rGO / Au-1 of the present application embodiment;

[0029] Figure 3 SEM image of COF / g-C3N4 / rGO-1 provided for the present application embodiment;

[0030] Figure 4 SEM image of COF / g-C3N4 / rGO / Au-1 modified gold nanoparticles provided for the present application embodiment;

[0031] Figure 5 Actual image of COF / g-C3N4 / rGO / Au-1 provided for the present application embodiment;

[0032] Figure 6 Optical image of COF / g-C3N4 / rGO / Au-1 provided for the present application embodiment;

[0033] Figure 7 Adsorption performance image of COF / g-C3N4 / rGO / Au-1 provided for the present application embodiment;

[0034] Figure 8 Self-cleaning performance image of COF / g-C3N4 / rGO / Au-1 provided for the present application embodiment;

[0035] Figure 9 Adsorption performance image of COF / g-C3N4 / rGO / Au-1 and COF-SO3Na provided for the present application embodiment. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present application.

[0037] In the following description of the present embodiment, the terms “include”, “contain”, “have” and “comprise” and the like are all open terms, that is, they mean including but not limited to.

[0038] In the following description of the embodiments, the term "and / or" is used to describe the relationship between associated objects, indicating that there can be three relationships, for example, A and / or B, which can represent the cases of A alone, B alone, and A and B existing at the same time. Wherein A, B can be singular or plural. The character " / " generally represents that the associated objects before and after are in an "or" relationship.

[0039] In the following description of the embodiments, the term "at least one" means one or more, and "multiple" means two or more. "At least one of the following (one)" or similar expressions means any combination of these items, including any combination of single (one) or multiple items. For example, "at least one of a, b or c", or "at least one of a, b and c", can represent a, b, c, a-b (i.e. a and b), a-c, b-c, or a-b-c, where a, b, c can be single or multiple.

[0040] Those skilled in the art should understand that in the following description of the embodiments of the present application, the order of the serial numbers does not mean the order of execution, and some or all steps can be executed in parallel or in sequence, and the execution order of each process should be determined according to its function and inherent logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0041] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a" and "the" used in the embodiments of the present application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0042] It should be noted that all raw reagents in the embodiments of the present application are purchased on the market or prepared according to conventional methods well known to those skilled in the art, for example, 1,3,5-triformylphloroglucinol, 2,5-diaminobenzenesulfonic acid, graphene oxide, p-toluenesulfonic acid, etc. are obtained by market purchase.

[0043] In a first aspect, the embodiments of the present application provide a preparation method of a covalent organic framework aerogel, the method comprising:

[0044] Preparation of a graphite phase carbon nitride / graphene oxide heterojunction;

[0045] Under the catalysis of p-toluenesulfonic acid, the graphite phase carbon nitride / graphene oxide heterojunction, 1,3,5-triformylphloroglucinol, chloroauric acid, 2,5-diaminobenzenesulfonic acid and a mixed aqueous solution of sodium hydroxide are subjected to a hydrothermal reaction to obtain a covalent organic framework hydrogel;

[0046] The covalent organic framework hydrogel is freeze-dried to collect a covalent organic framework aerogel.

[0047] In a second aspect, the embodiments of the present application provide a preparation method of a covalent organic framework aerogel, the method comprising:

[0048] preparing a graphite phase carbon nitride / graphene oxide heterojunction;

[0049] under the catalysis of p-toluenesulfonic acid, performing a hydrothermal reaction on the graphite phase carbon nitride / graphene oxide heterojunction, 1,3,5-triformylphloroglucinol, a 2,5-diaminobenzenesulfonic acid and a sodium hydroxide aqueous solution to obtain a covalent organic framework hydrogel;

[0050] freeze-drying the covalent organic framework hydrogel, adding gold nanoparticles, and collecting a covalent organic framework aerogel.

[0051] It should be noted that the embodiments of the present application freeze-dry the prepared covalent organic framework hydrogel, which can maximize the physical and chemical properties of the aerogel. In the freeze-drying process, the structure of the material is not destroyed, and the integrity of the material structure is preserved.

[0052] It should be noted that after adding chloroauric acid and gold nanoparticles, the final product is a gold nanoparticle-modified covalent organic framework aerogel. The chloroauric acid is added before the hydrothermal reaction, and the reduced gold nanoparticles are uniformly and stably adsorbed into the covalent organic framework aerogel after the hydrothermal reaction. After the freeze-drying is completed, gold nanoparticles are added. Due to the presence of nitrogen and sulfur atoms in the covalent organic framework, chemical bonds can be formed with gold nanoparticles and uniformly and stably combined.

[0053] In summary, the preparation method of the present application introduces a graphite phase carbon nitride / graphene oxide heterojunction into the covalent organic framework and modifies it with gold nanoparticles. This can enable the covalent organic framework, gold nanoparticles and heterojunction to produce a full synergistic effect. On the one hand, the covalent organic framework aerogel can adsorb pollutants of different sizes, and the types of adsorbed pollutants are diverse. On the other hand, it increases its photocatalytic performance, which can degrade the adsorbed pollutants under visible light irradiation, has self-cleaning ability, and enables the material to be recycled and reused. Thirdly, it can significantly enhance the Raman signal and has high surface-enhanced Raman scattering (SERS) activity, which can be directly used as a substrate for pollutant detection and evaluation of pollutant concentration.

[0054] In specific embodiments, the method for preparing the graphite phase carbon nitride / graphene oxide heterojunction comprises: mixing a graphite phase carbon nitride dispersion liquid and a graphene oxide dispersion liquid, ultrasonically dispersing the graphite phase carbon nitride dispersion liquid in deionized water, ultrasonically dispersing the graphene oxide dispersion liquid in deionized water, and then mixing and ultrasonically stirring to obtain the graphite phase carbon nitride / graphene oxide heterojunction.

[0055] In specific embodiments, the concentration ratio of the selected graphene oxide and graphite phase carbon nitride is preferably 1:2-1:1. Among them, when the concentration ratio of graphene oxide and graphite phase carbon nitride is less than 1:2, graphene oxide and graphite phase carbon nitride fail to fully contact, and cannot form a heterojunction structure, affecting the photocatalytic performance; when the concentration ratio of graphene oxide and graphite phase carbon nitride is greater than 1:1, the concentration of graphene oxide is relatively large, resulting in that the interaction between materials is too strong, affecting the formation of heterojunction. Therefore, the concentration ratio of graphene oxide and graphite phase carbon nitride is preferably 1:2-1:1.

[0056] In specific embodiments, the molar ratio of 1,3,5-triformylphloroglucinol and 2,5-diaminobenzenesulfonic acid in the selected mixed aqueous solution is preferably 2:3-8:11. Among them, when the molar ratio of 1,3,5-triformylphloroglucinol and 2,5-diaminobenzenesulfonic acid is less than 2:3, a complete covalent organic framework material cannot be formed, resulting in a collapsed structure framework; when the molar ratio of 1,3,5-triformylphloroglucinol and 2,5-diaminobenzenesulfonic acid is greater than 8:11, 1,3,5-triformylphloroglucinol is not completely reacted, affecting the adsorption performance of the material. Therefore, the molar ratio of 1,3,5-triformylphloroglucinol and 2,5-diaminobenzenesulfonic acid is preferably 2:3-8:11.

[0057] In specific embodiments, the average particle size of the gold nanoparticles in the selected gold nanoparticle dispersion is 16 nm. Among them, when the particle size of the gold nanoparticles is too large, effective adsorption cannot be performed, resulting in a weakened Raman signal and the inability to detect pollutants; among them, when the particle size of the gold nanoparticles is too small, the gold nanoparticles finally prepared in the covalent organic framework aerogel are prone to agglomeration, greatly affecting the self-cleaning performance of the material.

[0058] In specific embodiments, the selected hydrothermal reaction temperature is 120°C, and the time is preferably 24-48h. Among them, when the reaction time is less than 24h, the reaction is not complete, and a complete covalent organic framework cannot be formed; when the reaction is greater than 48h, the stability of the generated covalent organic framework material will be destroyed, thereby reducing the yield of the reaction. Therefore, the hydrothermal reaction temperature is 120°C, and the time is preferably 24-48h.

[0059] In specific embodiments, the temperature of the freeze-drying is preferably -80 to -50°C, and the time is 18-30h. Among them, when the temperature of the freeze-drying is lower than -80°C and the freeze-drying time is less than 18h, the drying time is too long, increasing the production cost, and also causing the residual of water in the aerogel, greatly affecting the adsorption performance of the material; when the temperature of the freeze-drying is higher than -50°C and the freeze-drying time is greater than 18h, the structure and stability of the covalent organic framework aerogel will be affected. Therefore, the temperature of the freeze-drying is preferably -80 to -50°C, and the time is preferably 18-30h.

[0060] In a third aspect, the application further provides a covalent organic framework aerogel prepared by the preparation method of the first aspect or the second aspect. The preparation method of the first aspect or the second aspect can make the aerogel have a regular and stable structure. Therefore, the covalent organic framework aerogel prepared by the application has high adsorption capacity, self-cleaning ability and the performance of evaluating the concentration of pollutants.

[0061] In a fourth aspect, the application further provides an application of the covalent organic framework aerogel of the third aspect in the field of water environment treatment and surface enhanced Raman scattering spectrum. The covalent organic framework aerogel has the advantages of high adsorption capacity, self-cleaning ability and the performance of evaluating the concentration of pollutants. Therefore, after the covalent organic framework aerogel of the application is used as an adsorbent, it can adsorb and degrade pollutants, and can be directly used as a substrate to evaluate the concentration of pollutants.

[0062] The technical solutions of the application will be further described below with reference to specific embodiments.

[0063] Embodiment 1

[0064] S101: ultrasonic dispersion in deionized water for 2h to obtain a stable graphite phase carbon nitride dispersion. 18.5mL of 4.0mg·mL -1 of graphene oxide dispersion is mixed with 74mg of graphite phase carbon nitride dispersion, ultrasonic stirring for 1h to obtain graphite phase carbon nitride / graphene oxide heterojunction α1;

[0065] S102: first, 21.2mg of 2,5-diaminobenzenesulfonic acid and 4.5mg of sodium hydroxide are dissolved in water, and 119mg of p-toluenesulfonic acid is used as a catalyst. The graphite phase carbon nitride / graphene oxide heterojunction α1, 15.8mg of 1,3,5-triformylphloroglucinol and 6ml of chloroauric acid are added and mixed, and hydrothermal reaction is carried out at 120℃ for 24h to prepare a covalent organic framework hydrogel γ1;

[0066] S103: the obtained covalent organic framework hydrogel γ1 is frozen at-80℃ and dried for 18h to form a covalent organic framework aerogel COF / g-C3N4 / rGO / Au-1.

[0067] In order to verify the morphology and structure of the covalent organic framework aerogel prepared by the application, the structure of the COF / g-C3N4 / rGO / Au-1 prepared by the application is characterized, and the result is shown in Figures 1 to 6 Figure 1 Figure 2 ​​SEM image of g-C3N4 / GO heterojunction prepared in advance for COF / g-C3N4 / rGO / Au-1; Figure 3 SEM image of COF / g-C3N4 / rGO-1; Figure 4 SEM image of COF / g-C3N4 / rGO / Au-1 after modification of gold nanoparticles; Figure 5 Actual image of COF / g-C3N4 / rGO / Au-1; Figure 6 Optical image of COF / g-C3N4 / rGO / Au-1.

[0068] According to Figure 1 It can be seen that the g-C3N4 prepared by the preparation method of the embodiment of the application is a stacked nanosheet structure;

[0069] According to Figure 2 It can be seen that the g-C3N4 / GO heterojunction prepared by the preparation method of the embodiment of the application is a stacked ultrathin nanosheet structure, indicating that a heterojunction structure is formed;

[0070] According to Figure 3 It can be seen that the covalent organic framework aerogel prepared by the preparation method of the embodiment of the application is a three-dimensional porous stacked ultrathin structure;

[0071] According to Figure 4 It can be seen that after the covalent organic framework aerogel prepared by the preparation method of the embodiment of the application is modified with gold nanoparticles, the gold nanoparticles can be clearly observed to be combined to the surface of the material;

[0072] According to Figure 5 And Figure 6 It can be seen that the covalent organic framework aerogel prepared by the preparation method of the embodiment of the application has a porous structure, ultralow density, and can be placed on a leaf.

[0073] Through the above characterization analysis, it can be seen that the preparation method of the embodiment of the application can make the covalent organic framework aerogel form a stable material structure, thereby improving the adsorption and degradation performance of the aerogel.

[0074] In order to verify the adsorption performance of the covalent organic framework aerogel prepared by the embodiment of the application, the performance of COF / g-C3N4 / rGO / Au-1 prepared in Example 1 was characterized, and the results are shown in Figures 7 to 8 The results are shown in FIG. 1. Among them, Figure 7 Adsorption performance diagram of COF / g-C3N4 / rGO / Au-1; Figure 8 Self-cleaning performance diagram of COF / g-C3N4 / rGO / Au-1.

[0075] According to Figure 7It can be seen that the adsorption performance of the COF / g-C3N4 / rGO / Au-1 of the embodiment of the application is tested, 5 mg of the adsorbent is put into 15 mL of 5×10 -5 In the RhB solution of M, the absorbance at 554 nm is measured by a UV-vis spectrophotometer to monitor the concentration of rhodamine B at different times. With the passage of time, the concentration of the pollutant gradually decreases, indicating that the adsorption and removal of the positively charged dye are strong.

[0076] According to Figure 8 It can be seen that the self-cleaning performance of the COF / g-C3N4 / rGO / Au-1 of the embodiment of the application is tested. The completely absorbed aerogel is immersed in deionized water, and after irradiation by a 500W xenon lamp, the content of the residual analyte on the aerogel is detected by SERS. After the aerogel completes the self-cleaning process through the photodegradation process, it is washed several times with water and freeze-dried for the next cycle.

[0077] Example 2

[0078] S201: A stable graphite phase carbon nitride dispersion is obtained by ultrasonic dispersion in deionized water for 2h. 18.5mL of 4.0mg·mL -1 of graphene oxide dispersion is mixed with 74mg of graphite phase carbon nitride dispersion, ultrasonic stirring for 1h, to obtain graphite phase carbon nitride / graphene oxide heterojunction α2;

[0079] S202: First, 10.6mg of 2,5-diaminobenzenesulfonic acid is dissolved in water with 2.25mg of sodium hydroxide, and 59.5mg of p-toluenesulfonic acid is added as a catalyst. Graphite phase carbon nitride / graphene oxide heterojunction α2, 7.9mg of 1,3,5-triformylphloroglucinol and 6ml of chloroauric acid are mixed, and a hydrothermal reaction is carried out at 120℃ for 48h to prepare a covalent organic framework hydrogel γ2;

[0080] S203: The obtained covalent organic framework hydrogel γ2 is dried at a freezing temperature of-80℃ for 19h to form a covalent organic framework aerogel COF / g-C3N4 / rGO / Au-2.

[0081] Example 3

[0082] S301: A stable graphite phase carbon nitride dispersion is obtained by ultrasonic dispersion in deionized water for 2h. 18.5mL of 4.0mg·mL -1 of graphene oxide dispersion is mixed with 74mg of graphite phase carbon nitride dispersion, ultrasonic stirring for 1h, to obtain graphite phase carbon nitride / graphene oxide heterojunction α3;

[0083] S302: First, 56.4 mg of 2,5-diaminobenzenesulfonic acid and 9.0 mg of sodium hydroxide were dissolved in water. Under the catalysis of 238 mg of p-toluenesulfonic acid, graphite phase carbon nitride / graphene oxide heterostructure α3, 39.2 mg of 1,3,5-tricarboxymethyl phloroglucinol and 6 ml of chloroauric acid were added and mixed. The mixture was subjected to a hydrothermal reaction at 120 °C for 36 h to obtain covalent organic framework hydrogel γ3.

[0084] S303: The obtained covalent organic framework hydrogel γ3 was frozen at -70℃ and dried for 25h to form a covalent organic framework aerogel COF / g-C3N4 / rGO / Au-3.

[0085] Example 4

[0086] S401: A stable graphitic carbon nitride dispersion was obtained by ultrasonic dispersion in deionized water for 2 hours. 18.5 mL of 4.0 mg / mL solution was then used. -1 The graphene oxide dispersion was mixed with 74 mg of graphitic carbon nitride dispersion and ultrasonically stirred for 1 h to obtain graphitic carbon nitride / graphene oxide heterostructure α4.

[0087] S402: First, 63.6 mg of 2,5-diaminobenzenesulfonic acid and 13.5 mg of sodium hydroxide were dissolved in water. Under the catalysis of 357 mg of p-toluenesulfonic acid, the graphitic carbon nitride / graphene oxide heterostructure α4, 47.3 mg of 1,3,5-tricarboxymethyl phloroglucinol and 6 ml of chloroauric acid were added and mixed. The mixture was subjected to a hydrothermal reaction at 120 °C for 40 h to obtain covalent organic framework hydrogel γ4.

[0088] S403: The obtained covalent organic framework hydrogel γ4 was frozen at -60℃ and dried for 30h to form a covalent organic framework aerogel COF / g-C3N4 / rGO / Au-4.

[0089] Example 5

[0090] S501: A stable graphitic carbon nitride dispersion was obtained by ultrasonic dispersion in deionized water for 2 hours. 18.5 mL of 4.0 mg / mL solution was then used. -1 The graphene oxide dispersion was mixed with 74 mg of graphitic carbon nitride dispersion and ultrasonically stirred for 1 h to obtain graphitic carbon nitride / graphene oxide heterostructure α5.

[0091] S502: First, 21.2 mg of 2,5-diaminobenzenesulfonic acid and 4.5 mg of sodium hydroxide were dissolved in water. Under the catalysis of 119 mg of p-toluenesulfonic acid, the graphite phase carbon nitride / graphene oxide heterostructure α5 and 15.8 mg of 1,3,5-tricarboxymethyl phloroglucinol were added and mixed. The mixture was subjected to a hydrothermal reaction at 120 °C for 48 h to obtain covalent organic framework hydrogel γ5.

[0092] S503: The obtained covalent organic framework hydrogel γ5 was frozen at -50°C and dried for 30 h, 30 ml of gold nanoparticles were added to form the covalent organic framework aerogel COF / g-C3N4 / rGO / Au-5.

[0093] To verify the adsorption performance of the covalent organic framework aerogels COF / g-C3N4 / rGO / Au-1-COF / g-C3N4 / rGO / Au-5 prepared in the embodiments of the present application, the following Comparative Example 1 is provided for detailed description.

[0094] Comparative Example 1

[0095] S601: 84.7 mg of 2,5-diaminobenzenesulfonic acid was dissolved in water with 18.0 mg of sodium hydroxide, 63.0 mg of 1,3,5-triformylphloroglucinol was added under the catalysis of 475 mg of p-toluenesulfonic acid, and a hydrothermal reaction was performed to obtain a covalent organic framework hydrogel γ6.

[0096] S602: The obtained covalent organic framework hydrogel γ6 was freeze-dried to form a covalent organic framework aerogel COF-SO3Na.

[0097] To verify the performance of the covalent organic framework aerogels prepared in the comparative examples, the adsorption performance of COF-SO3Na prepared in the comparative examples was characterized, and the results are shown in Table 1. Figure 9 As shown in Table 1, the removal efficiency of COF-SO3Na is lower than that of COF / g-C3N4 / rGO / Au-1. Figure 9 As shown in Table 1, the removal efficiency of COF-SO3Na is lower than that of COF / g-C3N4 / rGO / Au-1.

[0098] According to the results shown in Table 1, it can be seen that the adsorption performance of COF-SO3Na prepared in the comparative examples of the present application is gradually removed with time, although the adsorption performance of the aerogel COF / g-C3N4 / rGO / Au-1 is slightly worse than that of COF-SO3Na in the early stage, but with the increase of time, the COF / g-C3N4 / rGO / Au-1 still maintains a strong adsorption capacity for RhB, while the adsorption performance of COF-SO3Na becomes weak, and after 90 min, the removal rate of COF / g-C3N4 / rGO / Au-1 for RhB exceeds that of COF-SO3Na, and still reaches 95% for RhB at 200 min. Figure 9 To verify the adsorption capacity of the aerogels in the embodiments and comparative examples for rhodamine B, the removal efficiency of the prepared aerogels was tested within 200 min.

[0099] Table 1 Removal efficiency of the aerogels prepared in the embodiments and comparative examples

[0100] As shown in Table 1, the removal efficiency of COF-SO3Na is lower than that of COF / g-C3N4 / rGO / Au-1.

[0101]

[0102] It is found by comparing the test results of the comparative examples and the examples that, by adding the graphite-phase carbon nitride / graphene oxide heterojunction and gold nanoparticles into the pure COF-SO3Na material, the adsorption performance of the aerogel is improved, the decomposition ability of the aerogel to pollutants is increased, and the aerogel can be directly used as a substrate to evaluate the concentration of pollutants. The synergistic advantages of the structural advantages of the sodium sulfonate functionalized covalent organic framework, the functional site advantages of the gold nanoparticles and the decomposition ability of the graphite-phase carbon nitride / graphene oxide heterojunction make the prepared material have strong adsorption performance and self-cleaning ability, and also have excellent SERS activity, so that the material can be directly used as a substrate to detect pollutants and evaluate the concentration of pollutants.

[0103] The various embodiments in the specification are described in a progressive manner, and the same or similar parts between the various embodiments can be mutually referred to. Each embodiment focuses on the difference from other embodiments.

[0104] The above examples are only used to illustrate the technical solutions of the present application, and are not limited to the present application. Although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions recorded in the foregoing examples can still be modified, or some or all of the technical features can be replaced by equivalents. The modification or replacement does not make the essence of the corresponding technical solution deviate from the scope of the technical solutions of the present application.

Claims

1. A method for preparing a covalent organic framework aerogel, characterized in that, The method includes: Preparation of graphitic carbon nitride / graphene oxide heterostructures; Under the catalysis of p-toluenesulfonic acid, a mixed aqueous solution containing the graphitic carbon nitride / graphene oxide heterostructure, 1,3,5-tricarboxymethyl phloroglucinol, chloroauric acid, 2,5-diaminobenzenesulfonic acid and sodium hydroxide was subjected to a hydrothermal reaction to obtain a covalent organic framework hydrogel. The covalent organic framework hydrogel was freeze-dried to obtain a covalent organic framework aerogel.

2. A method for preparing a covalent organic framework aerogel, characterized in that, The method includes: Preparation of graphitic carbon nitride / graphene oxide heterostructures; Under the catalysis of p-toluenesulfonic acid, a mixed aqueous solution containing the graphitic carbon nitride / graphene oxide heterostructure, 1,3,5-tricarboxymethyl phloroglucinol, 2,5-diaminobenzenesulfonic acid and sodium hydroxide was subjected to a hydrothermal reaction to obtain a covalent organic framework hydrogel. After freeze-drying the covalent organic framework hydrogel, a gold nanoparticle dispersion was added to react and obtain a covalent organic framework aerogel.

3. The preparation method according to claim 1 or 2, characterized in that, The method for preparing graphitic carbon nitride / graphene oxide heterostructures includes: A graphitic carbon nitride dispersion and a graphene oxide dispersion were mixed and reacted to obtain a graphitic carbon nitride / graphene oxide heterojunction.

4. The preparation method according to claim 3, characterized in that, When the graphitic carbon nitride dispersion and the graphene oxide dispersion are mixed and reacted, the concentration ratio of the graphene oxide to the graphitic carbon nitride is 1:2 to 1:

1.

5. The preparation method according to claim 1 or 2, characterized in that, The molar ratio of 1,3,5-tricarboxymethyl phloroglucinol to 2,5-diaminobenzenesulfonic acid in the mixed aqueous solution is 2:3 to 8:

11.

6. The preparation method according to claim 2, characterized in that, The average particle size of the gold nanoparticles in the gold nanoparticle dispersion is 16 nm.

7. The preparation method according to claim 1 or 2, characterized in that, The hydrothermal reaction was carried out at a temperature of 120°C for 24-48 hours.

8. The preparation method according to claim 1 or 2, characterized in that, The freeze-drying temperature is -80 to -50°C, and the time is 18-30 hours.

9. Covalent organic framework aerogels prepared by any one of the preparation methods according to claims 1-8.

10. The application of covalent organic framework aerogels prepared according to any one of claims 1-8 in the field of water environment remediation and surface-enhanced Raman scattering spectroscopy.

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