Preparation method of novel green high-specific-surface-area COF-TpPa-H film

Abstract

The invention discloses a preparation method of a novel green high-specific-surface-area COF-TpPa-H film, and relates to the technical field of green materials and sensing. The preparation method comprises the following steps: uniformly grinding p-phenylenediamine, 2, 4, 6-trihydroxy-1, 3, 5-benzenetricarboxaldehyde, p-toluenesulfonic acid monohydrate and deionized water, blade-coating a glass sheet with an obtained colloidal precursor to form a thin film, then putting the glass sheet carrying the thin film into a reaction kettle, heating the reaction kettle, then putting the reaction kettle into water, and enabling the thin film to fall off from a glass sheet carrier, so as to obtain the composite material. The self-supporting COF-TpPa-H membrane is soaked and heated, and the novel green COF-TpPa-H membrane with the high specific surface area is obtained. The novel green high-specific-surface-area COF-TpPa-H film prepared by the method provided by the invention has excellent adsorption performance and structural stability, and the problems that an existing COFs film has strong dependence on a substrate, the mechanical strength of the film is poor, a large-area film material is difficult to obtain and the environment is polluted are effectively solved.

Description

Technical Field

[0001] The present invention relates to the fields of green materials and sensing technologies, and particularly to a preparation method of a novel green high specific surface area COF-TpPa-H film. Background Art

[0002] Since the first COF material was successfully synthesized in 2005, COF has become a hot research topic at the forefront of current science and technology. Covalent organic framework (COF) films are highly ordered, porous three-dimensional or two-dimensional structures formed by covalently bonding organic monomers. Common synthesis methods of COF films include solvothermal method, solvent evaporation method, electrochemical method, Langmuir-Blodgett (LB) interfacial polymerization, solid-liquid interfacial polymerization, liquid-gas interfacial polymerization, and solid-phase polymerization, etc.

[0003] However, these several methods for preparing COFs films have certain disadvantages: for example, they have a strong dependence on the substrate, the mechanical strength of the film is poor, or it is difficult to obtain large-area film materials. However, the advantages of high specific surface area materials are mainly reflected in improving the reactivity, adsorption and sensitivity of the materials. Especially in the fields of gas storage, catalysis, sensors, separation, and energy storage, high specific surface area materials can significantly improve their performance and expand the application range. Therefore, the reasonable design and optimization of the specific surface area of materials have become an important direction in material research and development and applications. In addition, although the performance of COF films is excellent, the current synthesis process is complex, and the required raw materials may be relatively expensive, which limits their large-scale production and applications. And toxic organic solvents are used in the production process, causing environmental pollution. Summary of the Invention

[0004] In view of the above deficiencies in the prior art, the present invention provides a preparation method of a novel green high specific surface area COF-TpPa-H film. The COF-TpPa-H film prepared by the method provided by the present invention has excellent adsorption performance and structural stability, effectively solving the problems of strong dependence of existing COFs films on the substrate, poor mechanical strength of the film, difficulty in obtaining large-area film materials, and environmental pollution.

[0005] To achieve the above object, the technical solution adopted by the present invention to solve its technical problems is: providing a preparation method of a novel green high specific surface area COF-TpPa-H film, including the following steps:

[0006] S1. Grind p-phenylenediamine, 2,4,6-trihydroxy-1,3,5-benzenetricarboxaldehyde, p-toluenesulfonic acid monohydrate and deionized water evenly to obtain a colloidal precursor;

[0007] S2. Coat the colloidal precursor obtained in step S1 on a glass sheet by scraping on a fiber mesh to form a uniform film;

[0008] S3. Fabricate an iron mesh at the center of the inner lining of the reaction kettle, place the glass sheet carrying the thin film on the iron mesh, introduce nitrogen gas, then put the reaction kettle into a vacuum drying oven for heating. After cooling, place the glass sheet carrying the thin film into water, and the thin film naturally detaches from the glass sheet carrier to obtain a self-supported COF-TpPa-H film;

[0009] S4. Immerse the self-supported COF-TpPa-H film obtained in step S3, and then heat it to obtain a novel green high specific surface area COF-TpPa-H film.

[0010] Furthermore, in step S1, the molar volume ratio of p-phenylenediamine, 2,4,6-trihydroxy-1,3,5-benzenetricarbaldehyde, p-toluenesulfonic acid monohydrate, and deionized water is 0.2 - 0.4 mmol: 0.1 - 0.3 mmol: 1 - 3 mmol: 40 - 60 μL.

[0011] Furthermore, in step S1, the molar volume ratio of p-phenylenediamine, 2,4,6-trihydroxy-1,3,5-benzenetricarbaldehyde, p-toluenesulfonic acid monohydrate, and deionized water is 0.3 mmol: 0.2 mmol: 2 mmol: 50 μL.

[0012] Furthermore, in step S2, at 20 - 30 °C and a humidity of 34 - 46%, use a rubber spatula to scrape the colloidal precursor on the fiber mesh onto the glass sheet.

[0013] Furthermore, in step S2, at 25 °C and a humidity of 40%, use a rubber spatula to scrape the colloidal precursor on the fiber mesh onto the glass sheet.

[0014] Furthermore, the fiber mesh is a 100-mesh fiber mesh.

[0015] Furthermore, in step S3, introduce nitrogen gas for 2 - 4 min.

[0016] Furthermore, in step S3, introduce nitrogen gas for 3 min.

[0017] Furthermore, in step S3, first heat at 45 - 55 °C for 5.5 - 6.5 h, then heat at 85 - 95 °C for 5.5 - 6.5 h, and then heat at 115 - 125 °C for 5.5 - 6.5 h.

[0018] Furthermore, in step S3, first heat at 50 °C for 6 h, then heat at 90 °C for 6 h, and then heat at 120 °C for 6 h.

[0019] Furthermore, in step S3, naturally cool at room temperature.

[0020] Furthermore, in step S4, soak successively with water, tetrahydrofuran, and absolute ethanol, repeat 3 - 4 times, and each time for 12 - 13 h.

[0021] Further, in step S4, soak it successively with water, tetrahydrofuran and absolute ethanol for 3 times, 12 hours each time.

[0022] Further, in step S4, heat it in a vacuum drying oven at 55 - 65 °C for 23 - 25 hours.

[0023] Further, in step S4, heat it in a vacuum drying oven at 60 °C for 24 hours.

[0024] The novel green high specific surface area COF-TpPa-H membrane prepared by the above preparation method of the novel green high specific surface area COF-TpPa-H membrane.

[0025] The present invention has the following beneficial effects:

[0026] 1. The preparation method provided by the present invention has a simple process and a short polymerization time. Compared with traditional complex preparation processes such as the solvothermal method, it can significantly improve production efficiency, save time and energy. Different from the traditional COF membrane preparation method that relies on organic solvents, the present invention uses ultrapure water as a solvent, completely avoiding the use of organic solvents, thus reducing the environmental pollution and human harm of toxic solvents, conforming to the concept of green chemistry, and promoting the development of environmental protection materials. The ultrapure water replacing organic solvents not only reduces the risk of chemical pollution but also can effectively reduce the emission of harmful gases or wastes that may be generated during the preparation process, reducing the environmental burden.

[0027] 2. The COF-TpPa-H membrane prepared by the present invention has a relatively high specific surface area (reaching 2795.9 m 2 / g), which is much higher than that of the COF-TpPa-H membrane obtained by traditional methods. The COF-TpPa-H membrane with a high specific surface area can provide more active sites, improving its effects and performance in applications such as gas adsorption and catalysis.

[0028] 3. In the present invention, the Schiff base condensation reaction of 1,3,5-trihydroxybenzene and p-phenylenediamine. The aldehyde group (-CHO) in 1,3,5-trihydroxybenzene reacts with the amino group (-NH 2 ) in p-phenylenediamine to form an imine (C=N) bond, thereby constructing a two-dimensional covalent network with a highly ordered structure. Inside the unit cell, 1,3,5-trihydroxybenzene serves as the central unit, forming stable imine (C=N) bonds through its aldehyde group and the amino group of Pa. Each unit cell has a hexagonal symmetric structure with uniform pores, and the pore diameter is usually in the range of 1 - 2 nanometers. The repeating units within a single unit cell form a highly ordered network, and this orderliness endows the COF-TpPa-H membrane with excellent specific surface area, stability, and high adsorption performance, making it suitable for the fields of catalysis, gas storage, and sensing. Description of the Drawings

[0029] Figure 1 is the flow chart of the present invention;

[0030] Figure 2 is the molecular structure composition diagram of the COF-TpPa-H film;

[0031] Figure 3 is a single unit cell of the COF-TpPa-H film;

[0032] Figure 4 is the scanning electron microscope image of the COF-TpPa-H film;

[0033] Figure 5 is the elemental analysis result;

[0034] Figure 6 is the XRD image of the COF-TpPa-H film;

[0035] Figure 7 is the nitrogen adsorption-desorption isotherm diagram of the COF-TpPa-H film;

[0036] Figure 8 is the pore size distribution diagram of the COF-TpPa-H film;

[0037] Figure 9 is the BET image of the COF-TpPa-H film;

[0038] Figure 10 is the BET image of the COF-TpPa material prepared in Comparative Example 1. Detailed implementation manners

[0039] The principles and features of the present invention are described below. The examples given are only used to explain the present invention and are not intended to limit the scope of the present invention. For those not specified in the examples, conventional conditions or conditions recommended by the manufacturer are used. For reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0040] Example 1

[0041] A novel green high specific surface area COF-TpPa-H film, and its preparation method includes the following steps:

[0042] S1. Grind 0.3 mmol of p-phenylenediamine, 0.2 mmol of 2,4,6-trihydroxy-1,3,5-benzenetricarboxaldehyde, 2 mmol of p-toluenesulfonic acid monohydrate and 50 μL of deionized water evenly to obtain a colloidal precursor;

[0043] S2. At 25 °C and a humidity of 40%, use a rubber spatula to scrape the colloidal precursor obtained in step S1 on a 100-mesh fiber net onto a glass slide to form a uniform film;

[0044] S3. Make an iron mesh in the center of the inner lining of the reaction kettle, place the glass sheet carrying the film on the iron mesh, introduce nitrogen for 3 min, then put the reaction kettle into a vacuum drying oven, first heat at 50 °C for 6 h, then heat at 90 °C for 6 h, and then heat at 120 °C for 6 h. After natural cooling at room temperature, put the glass sheet carrying the film into water, and the film naturally falls off from the glass sheet carrier to obtain a self-supporting COF-TpPa-H film;

[0045] S4. Immerse the self-supporting COF-TpPa film obtained in step S3 in water, tetrahydrofuran and absolute ethanol in sequence, repeat 3 times, 12 h each time, and then heat to obtain a novel green high specific surface area COF-TpPa-H film.

[0046] The flow chart of the present invention is as Figure 1 shown. The molecular structure composition diagram of the COF-TpPa-H film is as Figure 2 shown. The single unit cell of the COF-TpPa-H film is as Figure 3 shown.

[0047] Example 2

[0048] A novel green high specific surface area COF-TpPa-H film, and its preparation method includes the following steps:

[0049] S1. Grind 0.2 mmol of p-phenylenediamine, 0.1 mmol of 2,4,6-trihydroxy-1,3,5-benzenetricarboxaldehyde, 1 mmol of p-toluenesulfonic acid monohydrate and 40 μL of deionized water evenly to obtain a colloidal precursor;

[0050] S2. At 20 °C and a humidity of 34%, use a rubber spatula to scrape the colloidal precursor obtained in step S1 on a 100-mesh fiber mesh onto a glass sheet to form a uniform film;

[0051] S3. Make an iron mesh in the center of the inner lining of the reaction kettle, place the glass sheet carrying the film on the iron mesh, introduce nitrogen for 2 min, then put the reaction kettle into a vacuum drying oven, first heat at 45 °C for 5.5 h, then heat at 85 °C for 5.5 h, and then heat at 115 °C for 5.5 h. After natural cooling at room temperature, put the glass sheet carrying the film into water, and the film naturally falls off from the glass sheet carrier to obtain a self-supporting COF-TpPa-H film;

[0052] S4. Immerse the self-supporting COF-TpPa-H film obtained in step S3 in water, tetrahydrofuran and absolute ethanol in sequence, repeat 3 times, 12 h each time, and then heat to obtain a novel green high specific surface area COF-TpPa-H film.

[0053] Example 3

[0054] A novel green COF-TpPa-H membrane with a high specific surface area, and its preparation method comprises the following steps:

[0055] S1. Grind 0.4 mmol of p-phenylenediamine, 0.3 mmol of 2,4,6-trihydroxy-1,3,5-benzenetricarboxaldehyde, 3 mmol of p-toluenesulfonic acid monohydrate and 60 μL of deionized water evenly to obtain a colloidal precursor;

[0056] S2. At 30 °C and a humidity of 46%, use a rubber spatula to scrape the colloidal precursor obtained in step S1 onto a glass slide on a 100-mesh fiber mesh to form a uniform thin film;

[0057] S3. Make an iron mesh in the center of the inner liner of the reaction kettle, place the glass slide carrying the thin film on the iron mesh, introduce nitrogen for 4 min, then put the reaction kettle into a vacuum drying oven, first heat at 55 °C for 6.5 h, then heat at 95 °C for 6.5 h, and then heat at 125 °C for 6.5 h. After natural cooling at room temperature, put the glass slide carrying the thin film into water, and the thin film naturally peels off from the glass slide carrier to obtain a self-supporting COF-TpPa-H membrane;

[0058] S4. Immerse the self-supporting COF-TpPa-H membrane obtained in step S3 in water, tetrahydrofuran and absolute ethanol in sequence, repeat 4 times, 13 h each time, and then heat to obtain the novel green COF-TpPa-H membrane with a high specific surface area.

[0059] Comparative Example 1

[0060] A preparation method of a COF-TpPa material, comprising the following steps:

[0061] S1. Dissolve terephthalic acid and p-phenylenediamine in a molar ratio of 1:1 in dimethylacetamide to obtain a uniform solution;

[0062] S2. Transfer the uniform solution obtained in step S1 to a sealed reaction kettle, carry out a solvothermal reaction at 120-200 °C for 24-72 h, then cool to room temperature, and wash the product with ethanol to obtain the COF-TpPa material.

[0063] Test Example 1

[0064] The SEM image of the novel green COF-TpPa-H membrane prepared in Example 1 is as Figure 4 shown.

[0065] As Figure 4 can be seen, the novel green COF-TpPa-H membrane prepared by the present invention has dense small holes and good uniformity.

[0066] Test Example 2

[0067] The novel green high specific surface area COF-TpPa-H film prepared in Example 1 was subjected to elemental analysis testing using a carbon, nitrogen, and oxygen elemental analyzer, and the results are as Figure 5 shown. Figure 5 Among them, the images of carbon, nitrogen, and oxygen from left to right, and the statistical results of atomic percentages are shown in Table 1.

[0068] Table 1 Statistical results of atomic percentages

[0069] Element Signal type Atomic percentage (%) Carbon EDS 72.37 Nitrogen EDS 12.92 Oxygen EDS 14.96

[0070] From Figure 5 and Table 1, it can be seen that by selecting five spectra, the elemental ratios of the COF-TpPa-H film can be calculated. Among them, the atomic percentage of the C element is 72.37%, the atomic percentage of the N element is 12.92%, and the atomic percentage of the O element is 14.96%. It is found that the elemental content of the novel green high specific surface area COF-TpPa-H film prepared in Example 1 is consistent with its theoretical elemental content.

[0071] Test Example 3

[0072] The X-ray diffraction (XRD) patterns of the novel green high specific surface area COF-TpPa-H film prepared by combining screen printing technology and a reaction kettle in Example 1 and the COF-TpPa material prepared in Comparative Example 1 are as Figure 6 shown.

[0073] From Figure 6 it can be seen that compared with the COF-TpPa material synthesized by the traditional solvothermal method and solvent evaporation method in Comparative Example 1, the X-ray diffraction (XRD) patterns of the novel green high specific surface area COF-TpPa-H film prepared by combining screen printing technology and a reaction kettle in Example 1 are highly consistent, indicating that the COF-TpPa-H film prepared by screen printing technology has similar crystallinity and structural orderliness to the traditional method. The screen printing technology can accurately deposit the precursor solution onto the substrate and complete the polymerization reaction in the reaction kettle, which can not only improve the synthesis efficiency, but also enable large-area preparation, and retain the excellent properties of COF-TpPa, such as high specific surface area and stable pore structure. This proves the feasibility and effectiveness of the screen printing method in the preparation of COF membranes.

[0074] Test Example 4

[0075] The nitrogen adsorption-desorption isotherm of the novel green high specific surface area COF-TpPa-H film prepared in the test example was tested, and the results are as Figure 7 shown.

[0076] From Figure 7It can be seen that in the low-pressure region (P / P0 < 0.1), the amount of nitrogen adsorbed by this material rapidly reaches saturation, presenting a typical type I adsorption curve. This curve shape indicates that the COF-TpPa-H membrane mainly relies on micropores for adsorption, and its pore diameter is less than 2 nm. The type I adsorption curve is a common characteristic of microporous adsorption materials, meaning that this material shows significant nitrogen adsorption capacity at low pressures, and the adsorption amount rapidly reaches saturation, further confirming its excellent microporous structure.

[0077] Test Example 5

[0078] By characterizing the pore diameter of the novel green high specific surface area COF-TpPa-H membrane prepared in Example 1, the results are as Figure 8 shown.

[0079] It can be seen from Figure 8 that the main pore diameter of the COF-TpPa-H membrane is distributed between 0.43 nm and 1.15 nm. This pore diameter range enables it to effectively adsorb small molecule gases and quickly reach adsorption saturation at low pressures. In fields such as gas separation, catalysis, and sensing, this microporous structure is particularly important because it can provide a large number of surface sites and microscopic pores, facilitating molecular-level selective adsorption.

[0080] Test Example 6

[0081] The specific surface area is one of the important indicators for describing the properties of porous materials (such as COF membranes). Generally, a high specific surface area means that the material has more surface active sites, thus showing more excellent performance in applications such as adsorption, catalysis, and energy storage.

[0082] The specific surface areas of the novel green high specific surface area COF-TpPa-H membrane prepared in Example 1 and the COF-TpPa material prepared in Comparative Example 1 were respectively tested, and the results are as Figure 9 and Figure 10 shown.

[0083] It can be seen from Figure 9 and Figure 10 that the specific surface area of the COF-TpPa material obtained by the traditional preparation method in Comparative Example 1 is approximately 900 m 2 / g. However, when preparing the COF-TpPa-H membrane by the method combining the novel screen printing technology and the reaction kettle in Example 1, its specific surface area can be significantly increased, reaching 2795.9 m 2 / g. This value is much higher than the materials prepared by the traditional method and belongs to the category of high specific surface area COF membranes. The specific surface area of the COF-TpPa-H membrane reaches 2795.9 m 2 / g, indicating that it can provide more pores and active sites when adsorbing gases (such as nitrogen), and has excellent adsorption capacity.

[0084] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a novel green high specific surface area COF-TpPa-H membrane, characterized in that: The following steps are involved: S1, grinding p-phenylenediamine, 2,4,6-trihydroxy-1,3,5-benzenetricarboxaldehyde, p-toluenesulfonic acid monohydrate and deionized water to obtain a colloidal precursor; S2, applying the colloidal precursor obtained in step S1 on the fiber web onto the glass sheet to form a uniform film; S3, make an iron mesh in the center of the inner lining of the reactor, put the glass sheet carrying the film on the iron mesh, introduce nitrogen, and then put the reactor into a vacuum drying oven for heating. After cooling, put the glass sheet carrying the film into water, and the film naturally falls off from the glass sheet carrier to obtain a self-supporting COF-TpPa-H film; S4. Soak the self-supporting COF-TpPa-H membrane obtained in step S3, and then heat it to obtain a new green COF-TpPa-H membrane with a high specific surface area.

2. The method for preparing the novel green high specific surface area COF-TpPa-H membrane according to claim 1, characterized in that: In step S1, the molar volume ratio of p-phenylenediamine, 2,4,6-trihydroxy-1,3,5-benzenetricarboxaldehyde, p-toluenesulfonic acid monohydrate and deionized water is 0.2-0.4 mmol: 0.1-0.3 mmol: 1-3 mmol: 40-60 μL.

3. The method for preparing the novel green high specific surface area COF-TpPa-H membrane according to claim 1, characterized in that: In step S2, at 20-30°C and a humidity of 34-46%, a rubber scraper is used to scrape the colloidal precursor from the fiber web onto a glass sheet.

4. The method for preparing the novel green high specific surface area COF-TpPa-H membrane according to claim 1 or 3, characterized in that: In step S2, the fiber web is a 100-mesh fiber web.

5. The method for preparing the novel green high specific surface area COF-TpPa-H membrane according to claim 1, characterized in that: In step S3, nitrogen is introduced for 2-4 min.

6. The method for preparing the novel green high specific surface area COF-TpPa-H membrane according to claim 1, characterized in that: In step S3, the mixture is first heated at 45-55° C. for 5.5-6.5 h, then heated at 85-95° C. for 5.5-6.5 h, and then heated at 115-125° C. for 5.5-6.5 h.

7. The method for preparing the novel green high specific surface area COF-TpPa-H membrane according to claim 1, characterized in that: In step S3, the mixture is naturally cooled at room temperature.

8. The method for preparing the novel green high specific surface area COF-TpPa-H membrane according to claim 1, characterized in that: In step S4, Soak in water, tetrahydrofuran and anhydrous ethanol in turn, soak for 12-13 hours each time, and repeat 3-4 times.

9. The method for preparing the novel green high specific surface area COF-TpPa-H membrane according to claim 1, characterized in that: In step S4, the mixture is heated in a vacuum drying oven at 55-65° C. for 23-25 ​​h.

10. A novel green COF-TpPa-H membrane with high specific surface area obtained by the method for preparing a novel green COF-TpPa-H membrane with high specific surface area according to any one of claims 1 to 9.

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