A ketone enamine covalent organic framework film, and a preparation method and application thereof

Abstract

This application provides a ketene-enamine covalent organic framework thin film, its preparation method, and its application. The preparation method includes: mixing an aldehyde monomer with an acetic acid solution to obtain an aldehyde monomer solution; mixing an amine monomer with water to obtain an amine monomer solution; mixing the amine monomer solution and the aldehyde monomer solution and then performing a condensation reaction to obtain a first mixture containing an imine intermediate; mixing the first mixture with water to obtain a second mixture; centrifuging the second mixture to obtain a precursor solution containing the imine intermediate; and performing a film-forming treatment on the precursor solution, during which the imine intermediate reacts to form a ketene-enamine material, thereby obtaining the ketene-enamine covalent organic framework thin film. This invention can shorten the film preparation cycle and obtain ketene-enamine covalent organic framework thin films with high mechanical strength and good stability.

Description

Technical Field

[0001] This invention relates to the field of new material thin film technology, specifically to a ketene amine covalent organic framework thin film, its preparation method, and its application. Background Technology

[0002] The energy crisis, global warming, and freshwater shortage have become core challenges facing human society. Membrane technology has significant application potential in addressing energy crises, water scarcity, and environmental pollution. To fully realize the potential of membranes, developing next-generation advanced membrane materials that significantly outperform traditional polymer membrane materials in terms of processing performance and long-term service stability has become an urgent need and a research hotspot.

[0003] Compared to polymers, zeolites, and metal-organic frameworks (MOFs), covalent organic frameworks (COFs) are considered highly effective membrane materials due to their unique structure and properties. For example, COFs possess highly tunable and ordered crystalline pore structures, high porosity, and stability, making them excellent membrane materials. In terms of stability, COFs are more stable than MOFs, and in some cases even more stable than zeolites. Furthermore, due to their abundant two-dimensional structures, COFs typically exhibit better film-forming ability, making the fabrication of ultrathin films easier.

[0004] At present, there are many methods for preparing COFs thin films, such as: (1) blending the reactants into a paste, coating it into a film, and heating it to react directly to obtain a self-supporting COFs film; (2) using COFs powder as a nanofiller, blending it with an organic polymer matrix, and then forming a composite film by filtration or drying; (3) first synthesizing COFs nanocrystals, and then using physical deposition methods such as vacuum filtration to stack the nanocrystals on the substrate surface to form a film; (4) directly synthesizing COFs nanoporous membranes at the phase interface through polymerization and crystallization reactions between two phase interfaces (such as reactions at the liquid-liquid interface, gas-liquid interface, and gas-solid interface); (5) modifying the substrate surface and growing COFs in situ under solvothermal conditions to construct a dense COFs nanoporous membrane on the substrate surface.

[0005] However, existing COFs thin film preparation processes generally suffer from drawbacks such as complex process steps, long cycle time, and high toxicity of solvents and other reagents used. Furthermore, it is difficult to prepare large-area COFs films, and the prepared COFs films generally suffer from poor performance in terms of thermal stability, mechanical strength, flexibility, and surface smoothness, which urgently need to be addressed. Summary of the Invention

[0006] This invention provides a keteneamine covalent organic framework thin film, its preparation method, and its application. The process is simple, has a short cycle, uses reagents with low toxicity, and can prepare COFs films over a large area. The prepared films exhibit good thermal stability, mechanical strength, flexibility, and surface smoothness.

[0007] This invention provides a ketene-amine covalent organic framework thin film and its preparation method, comprising the following steps: mixing an aldehyde monomer with an acetic acid solution to obtain an aldehyde monomer solution; mixing an amine monomer with water to obtain an amine monomer solution; mixing the amine monomer solution and the aldehyde monomer solution and performing a condensation reaction to obtain a first mixture containing an imine intermediate; mixing the first mixture with water to obtain a second mixture; centrifuging the second mixture to obtain a precursor solution containing the imine intermediate; performing a film-forming treatment on the precursor solution, and during the film-forming treatment, reacting the imine intermediate to form a ketene-amine material to obtain the ketene-amine covalent organic framework thin film.

[0008] According to one embodiment of the present invention, the molar ratio of the amine monomer to the aldehyde monomer is 1.2 to 2.

[0009] According to one embodiment of the present invention, the aldehyde monomer comprises trialdehyde phloroglucinol.

[0010] According to one embodiment of the present invention, the amine monomer includes one or more of 5,5'-diamino-2,2'-bipyridine and 2,5-diaminopyridine.

[0011] According to one embodiment of the present invention, the concentration of the aldehyde monomer in the aldehyde monomer solution is 0.05 mol / L to 0.1 mol / L.

[0012] According to one embodiment of the present invention, the molar concentration of the amine monomer in the amine monomer solution is 0.1 mol / L to 0.15 mol / L.

[0013] According to one embodiment of the present invention, an aldehyde monomer is mixed with an acetic acid solution and then stirred at a speed of 300 rpm to 500 rpm to obtain the aldehyde monomer solution; wherein the stirring time is 0.3 h to 0.8 h and the stirring temperature is room temperature.

[0014] According to one embodiment of the present invention, an amine monomer is mixed with water and then subjected to ultrasonic treatment to obtain the amine monomer solution; wherein the ultrasonic treatment time is 0.2h to 0.5h and the ultrasonic treatment temperature is room temperature.

[0015] According to one embodiment of the present invention, the condensation reaction is carried out under stirring, the condensation reaction time is 48h~96h, and the condensation reaction temperature is 5℃~15℃.

[0016] According to one embodiment of the present invention, the process of forming a film from the precursor solution includes: injecting the precursor solution into a mold or spraying it onto a substrate, and then drying it to obtain the ketene-amine covalent organic framework film.

[0017] According to one embodiment of the present invention, the mold comprises a glass petri dish.

[0018] According to one embodiment of the present invention, the precursor solution is injected into a mold and dried to obtain the ketene-amine covalent organic framework film; wherein the drying temperature is 60°C to 100°C and the drying time is 12h to 24h.

[0019] According to one embodiment of the present invention, after the drying process, the obtained membrane precursor is washed with water to obtain the ketene-amine covalent organic framework film.

[0020] According to one embodiment of the present invention, the precursor solution is sprayed onto a substrate and dried to obtain the ketene-amine covalent organic framework film; wherein the drying time is 0.5 h to 4 h and the drying temperature is room temperature.

[0021] The present invention also provides a keteneamine covalent organic framework thin film, which is prepared by the above-described method for preparing keteneamine covalent organic framework thin films according to the present invention.

[0022] The present invention also provides an application of the aforementioned keteneamine covalent organic framework thin film in water treatment.

[0023] The present invention provides a ketene-amine covalent organic framework thin film and its preparation method. The method involves dissolving an aldehyde monomer in acetic acid solution to obtain an aldehyde monomer solution, dissolving an ammonia monomer in water to obtain an amine monomer solution, mixing the aldehyde and amine monomer solutions for a condensation reaction to form an imine intermediate, centrifuging to obtain a precursor solution containing the imine intermediate, and then reacting the imine intermediate in the precursor solution during film formation to generate a ketene-amine material, thus obtaining the ketene-amine covalent organic framework thin film. The entire preparation process uses acetic acid solution and water as solvents, making it safe and environmentally friendly. It can provide a better reaction environment for condensation reactions, which helps to improve the reaction efficiency of condensation of aldehyde monomers and amine monomers to form imine monomers. Combined with subsequent centrifugation and film formation treatment (while reacting imine intermediates to generate ketoamide materials), it can shorten the preparation cycle of ketoenamine covalent organic framework films. It also has the advantages of simple process steps and convenient operation. In particular, it can realize the preparation of large-area ketoenamine covalent organic framework films. Moreover, the prepared COFs films have good thermal stability and flexibility, as well as high mechanical strength and surface smoothness, which is of great significance for industrial applications. Attached Figure Description

[0024] Figure 1 This is an X-ray diffraction pattern of the ketene-amine covalent organic framework thin film obtained in Example 1 of the present invention;

[0025] Figure 2 This is the X-ray diffraction pattern of the ketene-amine covalent organic framework thin film obtained in Example 3 of the present invention;

[0026] Figure 3 The infrared absorption spectrum of the ketene-amine covalent organic framework thin film obtained in Example 1 of this invention;

[0027] Figure 4 Thermogravimetric analysis (TGA) results of the ketene-amine covalent organic framework thin film obtained in Example 1 of this invention are shown below.

[0028] Figure 5 The tensile strength test diagram of the ketene-amine covalent organic framework film obtained in Example 1 of this invention is shown.

[0029] Figure 6 The tensile strength test diagram of the ketene-amine covalent organic framework film obtained in Example 3 of this invention is shown.

[0030] Figure 7 The images shown are scanning electron microscope (SEM) images of the ketene-amine covalent organic framework thin film obtained in Example 1 of this invention before and after folding.

[0031] Figure 8 This is a scanning electron microscope (SEM) image of the ketene-amine covalent organic framework thin film obtained in Example 2 of the present invention before folding.

[0032] Figure 9 This is a scanning electron microscope (SEM) image of the ketene-amine covalent organic framework thin film obtained in Example 4 of the present invention before folding.

[0033] Figure 10 This is a scanning electron microscope (SEM) image of the ketene-amine covalent organic framework thin film obtained in Example 5 of the present invention before folding.

[0034] Figure 11 This is a scanning electron microscope (SEM) image of the ketene-amine covalent organic framework thin film obtained in Example 3 of the present invention before folding.

[0035] Figure 12 This is a small-angle scattering test image of the ketene-amine covalent organic framework thin film obtained in Example 1 of the present invention. Detailed Implementation

[0036] To enable those skilled in the art to better understand the solutions of this invention, the following provides a more detailed description of this application. The specific embodiments listed below are merely descriptions of the principles and features of this invention; the examples are only for explaining the invention and are not intended to limit its scope. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention.

[0037] This invention provides a ketene-amine covalent organic framework thin film and its preparation method, comprising the following steps: mixing an aldehyde monomer with an acetic acid solution to obtain an aldehyde monomer solution; mixing an amine monomer with water to obtain an amine monomer solution; performing a condensation reaction after mixing the amine monomer solution and the aldehyde monomer solution to obtain a first mixture containing an imine intermediate; mixing the first mixture with water to obtain a second mixture; centrifuging the second mixture to obtain a precursor solution containing an imine intermediate; performing a film-forming treatment on the precursor solution, and during the film-forming treatment, reacting the imine intermediate to form a ketene-amine material to obtain a ketene-amine covalent organic framework thin film.

[0038] According to the inventors' research, in the preparation process of the above-mentioned ketene-amine covalent organic framework film, the aldehyde monomer is first dissolved in acetic acid solution, and the amine monomer is dissolved in water. The resulting aldehyde monomer solution and amine monomer solution are then mixed and subjected to a condensation reaction. This process facilitates the uniform mixing of the aldehyde and amine monomers, improving the efficiency of the condensation reaction. The acetic acid solution not only serves as a solvent to dissolve the aldehyde monomer but also provides a favorable reaction environment for the condensation reaction, increasing the generation efficiency of the imine monomer. This facilitates subsequent processes such as water dilution (mixing the first mixture with water), centrifugation, and film formation, thereby improving the preparation efficiency of the ketene-amine covalent organic framework film and enhancing the thermal stability, mechanical strength, and surface smoothness of the resulting film.

[0039] Meanwhile, since acetic acid solution is used to dissolve aldehyde monomers, the overall reaction system is weakly acidic after the amine monomer and aldehyde monomer are first condensed to obtain an imine intermediate. Mixing the resulting first mixture with water helps to dilute the acidic environment of the reaction system, which facilitates the reduction of the solubility of the imine intermediate in the lower aqueous phase during subsequent centrifugation, allowing it to enter the upper precursor solution more fully. This, combined with the subsequent film-forming process, improves the conversion rate of the imine intermediate formed by the condensation of aldehyde and amine monomers into ketene amine materials. At the same time, mixing the first mixture with water before centrifugation helps to synergistically cooperate with the subsequent film-forming process, providing a good reaction environment and film-forming environment for the reaction of the imine intermediate to generate ketene amine materials, improving reaction efficiency and film quality, and producing ketene amine covalent organic framework films with good thermal stability, flexibility, high mechanical strength, and high surface smoothness.

[0040] Compared to other ketene-amine covalent organic framework (KEM) film preparation processes, such as first preparing a KEM material and then performing film formation to form a KEM film, or directly reacting two reactants to generate a KEM film, the preparation process described in this application involves first forming an imine intermediate through the condensation of an aldehyde monomer and an amine monomer. Then, the imine intermediate is used to generate a KEM material in situ during film formation, simultaneously forming a film. This in-situ formation of the KEM film from the imine intermediate helps improve the uniformity and surface smoothness of the KEM film, and enhances its chemical stability, thermal stability, mechanical strength, and bending resistance. In particular, it enables the preparation of large-area KEM films. Furthermore, the entire preparation process uses acetic acid solution and water as solvents, making it safe and environmentally friendly, and also offering advantages such as simple process steps and convenient operation.

[0041] In some implementations, the molar ratio of amine monomer to aldehyde monomer is 1.2 to 2. A molar ratio of amine monomer to aldehyde monomer of not less than 1.2 ensures that the aldehyde monomer reacts almost completely, reducing unreacted aldehyde group residues and helping to suppress side reactions such as self-condensation or degradation of aldehyde groups under acidic conditions, thus further improving film quality. A molar ratio of amine monomer to aldehyde monomer of not more than 2 avoids an increase in the viscosity of the precursor solution due to excessive amine monomer, which would affect film formation efficiency and quality. This helps to further improve the preparation efficiency of ketene-amine covalent organic framework films and the strength of the prepared ketene-amine covalent organic framework films.

[0042] In some embodiments, the aldehyde monomer includes trialdehyde phloroglucinol; trialdehyde phloroglucinol has a symmetrical trialdehyde structure, which makes it easier to undergo condensation reaction with amine monomers and generate imine intermediates with stronger structure and stability, thereby further improving the mechanical strength and stability of the prepared ketene amine covalent organic framework film.

[0043] In some embodiments, the amine monomer includes one or more of 5,5'-diamino-2,2'-bipyridine and 2,5-diaminopyridine, which helps to further improve the mechanical strength and stability of the prepared ketene-amine covalent organic framework film. The reason for this is that 5,5'-diamino-2,2'-bipyridine or 2,5-diaminopyridine are both rigid aromatic heterocycles containing two amino groups, which have strong rigidity and chemical stability, thus helping to improve the mechanical strength and stability of the prepared ketene-amine covalent organic framework film. At the same time, these amine monomers are also more suitable for the above-mentioned film-forming process of first condensing with aldehyde monomers to form an imine intermediate, and then allowing the imine intermediate to react in situ during the film-forming process to generate ketene-amine materials, which helps to improve the preparation efficiency of ketene-amine covalent organic framework films.

[0044] In a more specific embodiment, the aldehyde group of trialdehyde phloroglucinol combines with the rigid structure of 5,5'-diamino-2,2'-bipyridine or 2,5-diaminopyridine to form a ketene-amine bond that is more stable than a common imine bond, thereby improving the mechanical strength and stability of the prepared ketene-amine covalent organic framework film.

[0045] In some embodiments, the concentration of aldehyde monomer in the aldehyde monomer solution is 0.05 mol / L to 0.1 mol / L, and the molar concentration of amine monomer in the amine monomer solution is 0.1 mol / L to 0.15 mol / L. This allows the aldehyde monomer and amine monomer to react and form a uniformly sized and well-dispersed imine intermediate. This avoids excessively high concentrations that lead to a rapid reaction, increased byproducts, uneven intermediate size in the precursor solution, and turbidity. It also avoids excessively low concentrations that cause the aldehyde monomer and amine monomer to react too slowly, resulting in monomer residues and thus low crystallinity and poor stability of the ketene-amine covalent organic framework film.

[0046] Specifically, the concentration of the aldehyde monomer can be in the range of 0.05 mol / L, 0.06 mol / L, 0.07 mol / L, 0.08 mol / L, 0.09 mol / L, 0.1 mol / L, or any combination thereof; the concentration of the amine monomer can be in the range of 0.1 mol / L, 0.11 mol / L, 0.12 mol / L, 0.13 mol / L, 0.14 mol / L, 0.15 mol / L, or any combination thereof.

[0047] In some embodiments, after mixing the aldehyde monomer with the acetic acid solution, the mixture is stirred at a speed of 300 rpm to 500 rpm to obtain an aldehyde monomer solution. Stirring can accelerate the wetting, dispersion and dissolution of solid particles, prevent the aldehyde monomer from accumulating or agglomerating at the bottom of the container, and further improve the stability of ketene amine covalent organic framework films.

[0048] Specifically, the stirring speed can be 300 rpm, 350 rpm, 400 rpm, 450 rpm, 500 rpm, or any combination of two of these.

[0049] More specifically, the concentration of the acetic acid solution is 3 mol / L to 9 mol / L, for example, 3 mol / L, 6 mol / L, 9 mol / L, or any combination thereof. The protons in the acetic acid solution promote the formation of an imine from the aldehyde group and the amino group, and further promote its transformation into a more stable ketene-enamine structure. In addition, the acetic acid concentration of 3 mol / L to 9 mol / L can provide sufficient protons to ensure that the reaction can proceed smoothly and avoid the potential damage to the monomer structure by strong acid or strong base environments. At the same time, the acetic acid solution at this concentration is easy to prepare, store and handle, and is suitable for large-scale preparation.

[0050] It should be noted that the acetic acid solution in this invention is an aqueous solution of acetic acid, the solute is an acetic acid compound, and the solvent is water.

[0051] In some embodiments, the mixing and stirring time of the aldehyde monomer and the acetic acid solution is 0.3h to 0.8h, for example, 0.3h, 0.4h, 0.5h, 0.6h, 0.7h, 0.8h or any two of these ranges. This can eliminate concentration errors and uneven reactions caused by incomplete dissolution, and can also avoid side reactions of the aldehyde monomer caused by excessive stirring time, which could introduce impurities and ensure the stability of the obtained ketene-amine covalent organic framework film.

[0052] In some embodiments, the mixing and stirring temperature of the aldehyde monomer and acetic acid solution is room temperature, which is safe to operate, reduces cost and complexity, and provides a basis for large-scale production. It can avoid the reaction process being affected by the volatilization of acetic acid due to excessively high temperature, and also avoid the dissolution rate being significantly slowed down due to excessively low temperature, thereby further improving the mechanical strength of ketene amine covalent organic framework films.

[0053] In some embodiments, the amine monomer is mixed with water and then subjected to ultrasonic treatment to obtain an amine monomer solution. This can obtain a uniform and transparent amine monomer solution in a short time, prevent the amine monomer from forming and accumulating in advance, and ensure that it participates in subsequent reactions in the form of a single molecule. This is beneficial to the formation of a regular COF structure and to obtain a ketene amine covalent organic framework film with stronger stability and higher mechanical strength.

[0054] In addition, the ultrasonic time for mixing amine monomers with water is 0.2h to 0.5h, for example, 0.2h, 0.3h, 0.4h, 0.5h or any two of these ranges. This ensures the dissolution effect while maximizing efficiency, avoiding uneven dispersion of amine monomers due to excessively short ultrasonic time, which would affect the crystal quality and pore size distribution of the film. It also avoids damaging the structure of amine monomers due to excessively long ultrasonic time, thereby further improving the stability of ketene amine covalent organic framework films.

[0055] In addition, the ultrasonic mixing temperature of amine monomers and water is room temperature, which can avoid the increase in viscosity of the amine monomer solution and the decrease in dispersion effect due to excessively low temperature, and can also avoid the degradation of amine monomers due to excessively high temperature, which would prevent them from forming a complete keteneamine structure. This helps to improve the stability of keteneamine covalent organic framework films.

[0056] In some embodiments, the condensation reaction is carried out under stirring, and the condensation reaction time is 48h to 96h, for example, 48h, 60h, 72h, 84h, 96h or any two of these ranges. The crystallinity of the ketene amine covalent organic framework film can be controlled by time according to different needs, so as to obtain a ketene amine covalent organic framework film with better flexibility and surface smoothness.

[0057] In some embodiments, the temperature of the condensation reaction is 5°C to 15°C, such as 5°C, 7°C, 10°C, 15°C or any two of these ranges. This ensures that the reaction proceeds slowly and orderly, avoiding problems such as reaction stagnation due to excessively low temperature or excessively rapid reaction due to excessively high temperature, disordered crystal growth, and decreased film porosity. This improves the mechanical strength and stability of keteneamine covalent organic framework films.

[0058] Furthermore, the combination of time and temperature parameters creates a mild, dynamic, and controllable reaction environment, effectively avoiding a series of problems commonly encountered in traditional thin film synthesis, such as rapid precipitation, low crystallinity, and the need for high temperature and high pressure, thus obtaining ketene amine covalent organic framework thin films with higher mechanical strength and stability.

[0059] In some embodiments, the process of forming a film from the precursor solution includes: injecting the precursor solution into a mold or spraying it onto a substrate, and then drying it to obtain a ketene-amine covalent organic framework film. The injection molding method is suitable for preparing self-supporting films, is simple to operate, and is suitable for laboratory and small-batch production, with a film thickness of 2 μm to 20 μm. The spraying method is suitable for preparing large-area, flexible substrates or composite films, and can achieve controllable thickness and uniform coating, with a film thickness of 500 nm to 10 μm. Both methods do not require complex equipment, and the pore size of the resulting ketene-amine covalent organic framework films is 1.5 nm to 2.5 nm. Furthermore, the precursor solution has good rheological properties and is suitable for various film formation processes.

[0060] Specifically, the coating substrate is a hydrophilic polymer; the hydrophilic substrate can interact and bind tightly with the precursor solution, promoting uniform film formation and enhancing the interfacial stability of the film. More specifically, the coating base is a hydrophilic composite cellulose.

[0061] In some embodiments, the mold includes a glass culture dish, which has excellent surface smoothness and chemical inertness, does not react chemically with the reactants in the system, and can ensure that no other impurities are introduced; in addition, glass has good thermal stability, will not deform or release small organic molecules, and glass also has moderate hydrophilicity, which is conducive to the uniform spreading of the precursor solution and obtaining a ketene amine covalent organic framework film with better surface smoothness.

[0062] In some embodiments, the precursor solution is injected into a mold and dried to obtain a ketene-amine covalent organic framework film. The drying temperature is 60°C to 100°C, for example, 60°C, 70°C, 80°C, 90°C, 100°C or any two of these ranges. This removes the solvent, allowing water, acetic acid, etc., to evaporate slowly and uniformly, avoiding the formation of bubbles inside the film. At the same time, it promotes the final formation and solidification of ketene-amine bonds, forming a highly stable chemical structure and further improving the stability of the ketene-amine covalent organic framework film.

[0063] In some embodiments, the drying time of the precursor solution injected into the mold is 12h to 24h, for example, 12h, 16h, 20h, 24h or any two of these ranges, which allows solvent molecules to diffuse from the interior to the surface and evaporate, avoiding solvent residue from affecting the separation performance, thereby obtaining a more stable ketene amine covalent organic framework film.

[0064] In some embodiments, after drying, the obtained membrane precursor is washed with water to obtain a ketene-amine covalent organic framework membrane. Water washing can remove impurities, including any residual acetic acid or soluble impurity monomers, so that the membrane will not corrode equipment or affect water quality due to slow acid release during application, and ensure that the prepared ketene-amine covalent organic framework membrane can maintain long-term stability.

[0065] Furthermore, the membrane was washed three times in water at room temperature for 1 minute.

[0066] In some embodiments, a precursor solution is sprayed onto a substrate and dried to obtain a ketene-amine covalent organic framework film; wherein the drying time is 0.5 h to 4 h and the drying temperature is room temperature.

[0067] Furthermore, compared to injection molding, spray drying produces an ultra-thin composite layer attached to the substrate surface. The sprayed film is extremely thin, with a small total amount of solvent, which exists only in the ultra-thin coating, resulting in faster evaporation and curing. The advantages of spraying are: firstly, it has extremely high production efficiency, suitable for continuous and large-scale production; the spraying process itself is fast, and combined with short drying time, it greatly increases production throughput and enables industrial applications; secondly, the drying temperature is room temperature, resulting in low energy consumption and no need for external heat input, saving a significant amount of energy costs; room temperature drying also avoids damage to the substrate caused by high temperatures.

[0068] This invention also provides a ketene-amine covalent organic framework thin film, prepared according to the above-described method for preparing ketene-amine covalent organic framework thin films. The ketene-amine covalent organic framework thin film prepared according to the above-described method of this invention possesses superior properties in terms of thermal stability, mechanical strength, flexibility, and surface smoothness.

[0069] The present invention can also apply the prepared ketene-amine covalent organic framework film to water treatment and other fields. The ketene-amine covalent organic framework film of this application has good thermal stability and high mechanical strength, and can achieve efficient permeation of water molecules and selective retention of impurities, and has application potential in water treatment and other fields.

[0070] The present invention will be further described below through specific embodiments.

[0071] Example 1

[0072] S1 Aldehyde Monomer Solution: Mix 0.3 mmol of trialdehyde phloroglucinol with 4 ml of acetic acid (6 mol / L) solution and stir at 400 r / min for 0.5 h to obtain the aldehyde monomer solution.

[0073] S2 amine monomer solution: 5,5'-diamino-2,2'-bipyridine (0.45 mmol) was mixed with 4 ml of water and sonicated for 0.5 h to obtain the amine monomer solution;

[0074] S3 Mixing: The amine monomer solution and the aldehyde monomer solution are mixed and treated, and the mixing temperature is controlled at 10℃. The mixture is stirred at 400 rpm for 72 h to allow the two to undergo a condensation reaction, resulting in a first mixture containing an imine intermediate.

[0075] S4 Dilution and Centrifugation: Mix the first mixture with 40 ml of pure water to obtain the second mixture. Centrifuge the second mixture to obtain the upper precursor solution.

[0076] S5 film formation: The obtained precursor solution was introduced into a glass petri dish and dried in an oven at 60°C for 24 hours, forming a yellow film in the petri dish.

[0077] S6 Washing: The obtained film was washed three times in pure water to obtain a deep yellow ketone-enamine covalent organic framework film Tp-Bpy.

[0078] Example 2

[0079] S1 Aldehyde Monomer Solution: Mix 0.3 mmol of trialdehyde phloroglucinol with 4 ml of acetic acid (6 mol / L) solution and stir at 400 r / min for 0.5 h to obtain the aldehyde monomer solution.

[0080] S2 amine monomer solution: 5,5'-diamino-2,2'-bipyridine (0.45 mmol) was mixed with 4 ml of water and sonicated for 0.5 h to obtain the amine monomer solution;

[0081] S3 Mixing: The amine monomer solution and the aldehyde monomer solution are mixed and treated at a temperature of 10°C. The mixture is stirred at 400 rpm for 72 hours to allow the two to undergo a condensation reaction, resulting in a first mixture containing an imine intermediate.

[0082] S4 Dilution and Centrifugation: Mix the first mixture with 40 ml of pure water to obtain the second mixture. Centrifuge the second mixture to obtain the upper precursor solution.

[0083] S5 film formation: The obtained precursor solution is sprayed with hydrophilic composite cellulose as a substrate for 1 minute to form a thin film on the substrate.

[0084] S6 Drying: The film was placed at room temperature and dried for 2 hours to obtain a pale yellow ketene amine covalent organic framework film Tp-Bpy-CL.

[0085] Example 3

[0086] S1 Aldehyde Monomer Solution: Mix 0.3 mmol of trialdehyde phloroglucinol with 4 ml of acetic acid (6 mol / L), stir at 400 r / min for 0.5 h to obtain the aldehyde monomer solution;

[0087] S2 amine monomer solution: 2,5-diaminopyridine (0.45 mmol) was mixed with 4 ml of water and sonicated for 0.5 h to obtain the amine monomer solution;

[0088] S3 Mixing: The amine monomer solution and the aldehyde monomer solution were mixed at a controlled temperature of 10°C and stirred at 400 rpm for 72 hours to allow them to undergo a condensation reaction, resulting in a first mixture containing an imine intermediate.

[0089] S4 Dilution and Centrifugation: Mix the first mixture with 40 ml of pure water to obtain the second mixture. Centrifuge the second mixture to obtain the upper precursor solution.

[0090] S5 film formation: The obtained precursor solution was introduced into a glass petri dish and dried in an oven at 60°C for 24 hours, forming a yellow film in the petri dish.

[0091] S6 Washing: The obtained film was washed three times in pure water to obtain a deep yellow ketone-amino acid covalent organic framework film Tp-Dpy.

[0092] Example 4: The difference from Example 2 is that the spraying time in step S5 is 2 minutes. The remaining conditions of Example 4 are the same as those of Example 2.

[0093] Example 5: The difference from Example 2 is that the spraying time in step S5 is 4 minutes. The remaining conditions of Example 5 are the same as those of Example 2.

[0094] Furthermore, based on Examples 1 to 5, if the acetic acid in these examples is replaced with inorganic acids such as hydrochloric acid or organic acids such as formic acid, it is difficult to form a first mixture containing imine intermediates in step S3, making it difficult to perform subsequent film-forming treatment.

[0095] Meanwhile, the inventors found that in step S3, (1) without step S1, the aldehyde monomer and acetic acid solution are directly added to the amine monomer solution obtained in step S2; (2) without step S2, the amine monomer and water are directly added to the aldehyde monomer solution obtained in step S1; (3) without steps S1 and S2, the aldehyde monomer, acetic acid solution, amine monomer and water are directly mixed in one step, all of which make it difficult to form a first mixture containing imine intermediates, and difficult to carry out subsequent film formation treatment.

[0096] Test case

[0097] (1) X-ray diffraction analysis

[0098] X-ray diffraction analysis of the films prepared in Examples 1 to 5 confirmed the successful synthesis of ketene-amine covalent organic framework films, indicating that the films prepared in Examples 1 to 3 have a certain crystalline structure.

[0099] Taking Examples 1 and 3 as examples, the X-ray diffraction pattern of the thin film Tp-Bpy obtained in Example 1 is shown below. Figure 1 As shown (the horizontal axis represents the diffraction angle (2θ), and the vertical axis represents the diffraction intensity); the X-ray diffraction pattern of the thin film Tp-Dpy obtained in Example 3 is shown below. Figure 2The curve corresponding to TP-Dpy (where the horizontal axis is the diffraction angle (2θ) and the vertical axis is the diffraction intensity) is shown in the figure. Figure 1 and Figure 2 As can be seen, the distinct characteristic diffraction peaks of the Tp-Bpy and Tp-Dpy films around 3.4° demonstrate the successful synthesis of ketene-amine covalent organic framework films, which possess a certain crystalline structure.

[0100] (2) Infrared absorption analysis

[0101] Infrared absorption analysis was performed on the films prepared in Examples 1 to 5. The results showed that the films prepared in Examples 1 to 3 contained ketene-amine bonds, which provided a stable covalent backbone for the films.

[0102] Taking Example 1 as an example, the infrared absorption analysis of the Tp-Bpy film prepared in Example 1 was performed, and the infrared absorption pattern of the ketene-amine covalent organic framework film is shown below. Figure 3 The curve corresponding to the TP-Bpy-film is shown; in step S4 of Example 1, the precipitate obtained after centrifugation of the second mixture was dried to obtain ketene-amine covalent organic framework powder (TP-Bpy-powder). Infrared absorption analysis was performed on it, and the infrared absorption spectrum of the ketene-amine covalent organic framework powder is shown below. Figure 2 The curve corresponding to TP-Bpy powder is shown below. From... Figure 3 As can be seen, both the curves corresponding to TP-Bpy thin films and the curves corresponding to TP-Bpy powder exhibit C=C 1571cm. -1 and CN 1213cm -1 The characteristic absorption peak at the point corresponds to the stretching vibrations of C=C and CN, indicating that the Tp-Bpy film prepared in Example 1 has ketene-amine bonds consistent with the ketene-amine covalent organic framework powder, which can provide a stable covalent backbone for the film.

[0103] (3) Thermogravimetric test

[0104] Thermogravimetric analysis was performed on the films prepared in Examples 1 to 5. The results showed that the films prepared in Examples 1 to 3 had good thermal stability.

[0105] Taking Example 1 as an example, the thermogravimetric analysis (TGA) of the prepared Tp-Bpy thin film was performed, and the results are as follows: Figure 4 As shown, from Figure 4 As can be seen, when the temperature is increased from 100°C to 300°C at a heating rate of 10°C / min, the film Tp-Bpy still retains more than 90% of its mass, indicating that the ketene-amine covalent organic framework film prepared in Example 1 has good thermal stability.

[0106] (4) Mechanical strength test

[0107] Mechanical strength tests were conducted on the films prepared in Examples 1 to 5, and the results showed that the films prepared in Examples 1 to 3 had good mechanical strength.

[0108] Taking Example 1 as an example, the tensile strength and elongation at break of the Tp-Bpy film prepared in Example 1 were tested according to GB / T 1040.3. The sample type was dumbbell-shaped, and the tensile rate was 10 mm / min. The results are as follows: Figure 5 As shown, from Figure 5 As can be seen, the tensile strength and elongation at break of the film synthesized in Example 1 are 74.1 MPa and 2.34%, respectively, indicating that the keteneamine covalent organic framework film synthesized in Example 1 has high mechanical strength.

[0109] Taking Example 3 as an example, the tensile strength and elongation at break of the Tp-Dpy film prepared in Example 3 were tested according to GB / T 1040.3. The sample type was dumbbell-shaped, and the tensile strength was 10 mm / min. The results are as follows. Figure 6 As shown, from Figure 6 As can be seen, the tensile strength and elongation at break of the film synthesized in Example 3 are 46.8 MPa and 2.88%, respectively, indicating that the keteneamine covalent organic framework film synthesized in Example 3 has good mechanical strength.

[0110] (5) Scanning electron microscopy test

[0111] The films prepared in Examples 1 to 5 were folded, and the films before and after folding were tested by scanning electron microscopy. The results showed that the films prepared in Examples 1 to 3 had good surface flatness before folding and no surface breakage after folding, indicating that the films have good mechanical strength and flexibility.

[0112] Taking Example 1 as an example, the Tp-Bpy thin film prepared in Example 1 was subjected to scanning electron microscopy tests before and after folding, and the results are as follows: Figure 7 As shown, Figure 7 (a) is a scanning electron microscope image before folding, from Figure 7 As can be seen in (a), the film synthesized in Example 1 showed good flatness before folding. Figure 7 (b) is a scanning electron microscope image after folding, from Figure 7 As can be seen in (b), the surface of the film synthesized in Example 1 did not break after folding, indicating that the keteneamine covalent organic framework film synthesized in Example 1 has high mechanical strength and flexibility.

[0113] Taking Examples 2, 4, and 5 as examples, the Tp-Bpy-CL thin film prepared in Example 2 was subjected to scanning electron microscopy (SEM) testing before folding, and the results are as follows: Figure 8 As shown, from Figure 8 As can be seen in (a), the film surface obtained in Example 2 is smooth, from Figure 8 As shown in (b), the film thickness obtained on the substrate in Example 2 is approximately 500 nm; scanning electron microscopy (SEM) tests were performed on the films obtained in Examples 4 and 5 before folding, and the results are as follows. Figure 9 and Figure 10 As shown, from Figure 9 As can be seen, the film thickness obtained on the substrate in Example 4 is approximately 1 μm. Figure 10 As can be seen, the film thickness obtained on the substrate in Example 5 is about 2.5 μm, indicating that the film thickness can be adjusted by controlling the different spraying times.

[0114] Taking Example 3 as an example, the Tp-Dpy thin film prepared in Example 3 was subjected to scanning electron microscopy before folding, and the results are as follows: Figure 11 As shown, from Figure 11 As can be seen in (a), the surface of the film synthesized in Example 3 is smooth. Figure 11 As can be seen in (b), the thickness of the film synthesized in Example 3 is about 2 μm.

[0115] (6) Small-angle scattering test

[0116] Small-angle scattering tests were performed on the films prepared in Examples 1 to 3. The results showed that the films prepared in Examples 1 to 3 had uniform and continuous pore size, complete structure, and fibrous morphology inside.

[0117] Taking Example 1 as an example, a small-angle scattering test was performed on the Tp-Bpy thin film prepared in Example 1, and the results are as follows: Figure 12 As shown (the horizontal axis represents the scattering vector (q), and the vertical axis represents the scattering intensity), the data was fitted using the Guinier–Porod formula, and the fitted curve is... Figure 12 The curve corresponding to Fit in the test curve is... Figure 12 The curve corresponding to TP-Bpy shows that the s value is 1.21, which is between 1 and 2, and the radius of gyration is 14.26 nm, indicating that the ketene amine covalent organic framework film synthesized in Example 1 is composed of fibers with a length of about 14 nm.

[0118] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a keteneamine covalent organic framework thin film, characterized in that, Includes the following steps: (1) Mix the aldehyde monomer with acetic acid solution to obtain an aldehyde monomer solution; (2) Mix the amine monomer with water to obtain an amine monomer solution; (3) The amine monomer solution and the aldehyde monomer solution are mixed and then subjected to a condensation reaction to obtain a first mixture containing an imine intermediate; (4) Mix the first mixture with water to obtain a second mixture; The second mixture was centrifuged to obtain a precursor solution containing the imine intermediate; (5) The precursor solution is subjected to film formation treatment, and the imine intermediate is reacted to form keteneamine material during the film formation treatment to obtain the keteneamine covalent organic framework film.

2. The method for preparing keteneamine covalent organic framework thin films according to claim 1, characterized in that, The molar ratio of the amine monomer to the aldehyde monomer is 1.2 to 2; And / or, the aldehyde monomer includes trialdehyde phloroglucinol; And / or, the amine monomer includes one or more of 5,5'-diamino-2,2'-bipyridine and 2,5-diaminopyridine.

3. The method for preparing keteneamine covalent organic framework thin films according to claim 1 or 2, characterized in that, The concentration of the aldehyde monomer in the aldehyde monomer solution is 0.05 mol / L to 0.1 mol / L; And / or, the molar concentration of the amine monomer in the amine monomer solution is 0.1 mol / L to 0.15 mol / L.

4. The method for preparing keteneamine covalent organic framework thin films according to claim 1 or 2, characterized in that, The aldehyde monomer is mixed with an acetic acid solution and stirred at 300 rpm to 500 rpm to obtain the aldehyde monomer solution; wherein the stirring time is 0.3 h to 0.8 h and the stirring temperature is room temperature; And / or, the amine monomer is mixed with water and then subjected to ultrasonic treatment to obtain the amine monomer solution; wherein the ultrasonic treatment time is 0.2h~0.5h and the ultrasonic treatment temperature is room temperature.

5. The method for preparing keteneamine covalent organic framework thin films according to claim 1, characterized in that, The condensation reaction is carried out under stirring, the condensation reaction time is 48h~96h, and the condensation reaction temperature is 5℃~15℃.

6. The method for preparing keteneamine covalent organic framework thin films according to claim 1, characterized in that, The process of forming a film from the precursor solution includes: injecting the precursor solution into a mold or spraying it onto a substrate, and then drying it to obtain the ketene-amine covalent organic framework film.

7. The method for preparing keteneamine covalent organic framework thin films according to claim 6, characterized in that... The mold includes a glass petri dish; And / or, the precursor solution is injected into a mold and dried to obtain the ketene-amine covalent organic framework film; wherein the drying temperature is 60℃~100℃ and the drying time is 12h~24h; And / or, after the aforementioned drying, the obtained membrane precursor is washed with water to obtain the ketene-amine covalent organic framework film.

8. The method for preparing keteneamine covalent organic framework thin films according to claim 6, characterized in that, The precursor solution is sprayed onto a substrate and dried to obtain the ketene-amine covalent organic framework film; wherein the drying time is 0.5 h to 4 h and the drying temperature is room temperature.

9. A keteneamine covalent organic framework thin film, characterized in that, The ketene-amine covalent organic framework film is prepared according to the preparation method of the ketene-amine covalent organic framework film according to any one of claims 1 to 8.

10. The application of the keteneamine covalent organic framework thin film of claim 9 in water treatment.

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