Ionic covalent organic framework composite membrane for energy conversion as well as preparation method and application of ionic covalent organic framework composite membrane

Abstract

The invention provides an ionic conduction type covalent organic framework composite membrane for energy conversion and a preparation method and application thereof, and relates to the technical field of membrane materials. Comprising the following steps: synthesizing an ionic covalent organic framework material by a hydrothermal method; stripping the ionic covalent organic framework with acid; and carrying out suction filtration on the ionic covalent organic framework nanosheet to the PAN substrate film. The ionic organic framework material is deposited on the PAN film through vacuum filtration after being subjected to acid stripping treatment, the excellent energy conversion effect is achieved, effective conversion and extraction of energy in the water evaporation process can be achieved in cooperation with the photothermal conversion process, and the application prospect is good.

Description

Technical Field

[0001] This invention relates to the field of membrane materials technology, and in particular to a method for preparing ionic covalent organic framework composite membranes and their applications. Background Technology

[0002] With the depletion of fossil fuels and the escalation of environmental problems, the world is urgently seeking cleaner and more sustainable renewable energy solutions. Water covers approximately 71% of the Earth's surface, with a total volume of 1.5 billion cubic kilometers. It continuously absorbs nearly 35% of the solar energy radiating to the Earth's surface, storing the absorbed energy as thermal or kinetic energy, and converting the stored energy into various forms of energy, such as mechanical energy, through condensation, rainfall, or evaporation. Therefore, hydropower resources exhibit significant advantages such as abundant reserves, wide distribution, green and clean operation, and recyclability, possessing immense development and utilization value and broad application prospects. Currently, mature hydropower resources mainly include river energy, ocean current energy, wave energy, and tidal energy. Typically, facilities such as dams and generator units are used to convert the kinetic energy of natural water flow into mechanical energy, and then into electrical energy.

[0003] With the rapid development of nanoscience and technology, a variety of new forms of hydropower resource conversion are emerging explosively. Research indicates that functional materials with nanoscale dimensions possess unique surface and quantum effects, enabling them to couple with various liquids to generate electricity. Utilizing the solid-liquid interface interaction between functional materials and water molecules, and through the ubiquitous water evaporation phenomenon in natural processes, low-grade heat energy from the environment can be absorbed and converted into electrical energy. Furthermore, it is possible to significantly increase power generation by leveraging other natural resources such as solar and wind power.

[0004] As an emerging porous organic crystalline material, carbonaceous air (COF) possesses a high specific surface area and abundant pore structure, allowing for functional applications through precise control of building blocks and design of framework active sites. By synthesizing thin-layer COF with photothermal conversion properties and controlling the heat exchange process and ion transport channels, evaporation-induced power generation can be achieved, providing a new platform for the novel utilization of water energy. Furthermore, the regular pore distribution of COF provides an ideal model for in-depth research into the mechanism of evaporation-induced power generation. Summary of the Invention

[0005] In view of this, the present invention provides an ion-conducting covalent organic framework composite membrane for energy conversion, its preparation method and application.

[0006] The technical solution of this invention is implemented as follows: A method for preparing an ionic covalent organic framework composite membrane includes the following steps: S1. Hydrothermal synthesis of ionic covalent organic framework materials A hydrothermal synthesis method was used, in which the monomers saffron T and 1,3,5-tricarboxymethylphloroglucinol were placed in an acetic acid solution, heated to react, and then the reaction product was removed by vacuum filtration and dried. S2, acid-exfoliated ionic covalent organic framework materials The synthesized ionic covalent organic framework was placed in a mixed solution of acetonitrile, tetrahydrofuran, and trifluoroacetic acid. The enamine bonds in the ionic covalent organic framework were protonated to increase the interlayer repulsion and achieve the exfoliation effect. The process was continuously stirred. S3, Filtering ionic covalent organic framework nanosheets to PAN substrate membrane By using vacuum filtration, ionic covalent organic framework nanosheets are loaded onto a PAN membrane through vacuum-assisted self-assembly. As the acid stripping solution is removed, the interlayer repulsion of the nanosheets gradually decreases. After being reassembled in an ordered manner under vacuum filtration, an ionic covalent organic framework composite membrane can be obtained.

[0007] Furthermore, in the method for preparing the ionic covalent organic framework composite membrane described in step S1, the solid-liquid ratio of the monomer saffron T to acetic acid is 140-160:24-30 mg / mL; The heating reaction is carried out at 70-75°C for 72-96 hours; After filtration, the drying conditions are heating at 50-60℃ for 2-3 hours.

[0008] The hydrothermal synthesis route for ionic covalent organic framework materials of this invention is as follows:

[0009] Furthermore, in step S2, the acid stripping mixture has a volume ratio of acetonitrile:tetrahydrofuran:trifluoroacetic acid = 7:3:2. Furthermore, in step S2, the solid-liquid ratio of the ionic covalent organic framework material to the acid-exfoliating mixed solution is 0.1:22-25 g / mL; the acid exfoliation treatment is performed at a speed of 700-800 rpm for 72-96 h.

[0010] Furthermore, in the filtration process described in step S3, the filter membrane used is of the Lanjing brand, with a filtration accuracy of 50000; the filter membrane diameter is 5cm, and the volume of the solution used for filtration is 4-6mL.

[0011] The second aspect of this application also provides the application of the above-mentioned ionic covalent organic framework composite membrane in the field of hydroelectric power generation.

[0012] Compared with existing technologies, this application has the following advantages: This application transforms photothermal ionic covalent organic framework materials from particles into thin nanosheets via acid exfoliation, thereby increasing the surface potential and improving the material's processability. Simultaneously, the ionic sites of the ionic covalent organic framework can lower the exciton dissociation energy by providing strong polarization and suppressing nonradiative relaxation, thus improving photothermal conversion efficiency. In solar-driven water evaporation, this allows for the coupling of low-grade thermal energy harvesting, achieving highly efficient energy conversion during ion flow. Attached Figure Description

[0013] To more clearly illustrate the technical solutions in this application or the prior art, the drawings used in the description of this application or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0014] Figure 1 This is a scanning electron microscope image of the ionic covalent organic framework particles synthesized by hydrothermal method in Example 1; Figure 2 The image shown is an atomic force microscope image of the ionic covalent organic framework nanosheets formed by acid exfoliation in Example 1, demonstrating their thickness. Figure 3 The X-ray diffraction patterns of the ionic covalent organic framework before and after acid exfoliation treatment in Example 1 are shown. Figure 4 This is a scanning electron microscope cross-sectional image of the ion-type covalent organic framework composite membrane formed after filtration in Example 1; Figure 5 This is a comparison diagram of the zeta potentials before and after acid stripping treatment of the ionic covalent organic framework in Example 1; Figure 6 The image shows an infrared thermograph and a temperature rise curve of the ionic covalent organic framework composite membrane in Example 1. Figure 7 This is a contact angle test diagram of the ionic covalent organic framework composite membrane in Example 1; Figure 8 This is a test image of the power generation of the ionotropic covalent organic framework composite membrane under dark conditions in Example 1; Figure 9 This is a comparison chart of current tests conducted on the ionic covalent organic framework composite membrane in Example 1 under dark and light conditions; Figure 10 This is a power comparison chart showing the power generation of the ionic covalent organic framework composite membrane in Example 1 using 200µL deionized water or 1M NaCl solution under dark and light conditions. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0016] Unless otherwise specified, the experimental methods used in the embodiments of this application are all conventional methods.

[0017] Unless otherwise specified, all materials and reagents used in the embodiments of this invention are commercially available.

[0018] The layer-by-layer filtration method of this invention uses the filter membrane brand Lanjing, with a filtration accuracy of 50,000 and a filter membrane diameter of 5 cm. Example

[0019] The preparation method of the ionic covalent organic framework material composite film in this embodiment includes the following steps: S1. Hydrothermal synthesis of ionic covalent organic framework materials 58 mg of 1,3,5-tricarboxymethyl phloroglucinol and 140 mg of saffron T were added to 24 mL of acetic acid and stirred until homogeneous. The mixture was then transferred to an oven and heated at 70 °C for 72 h. The resulting ionic covalent organic framework particles were obtained by filtration and then dried in an oven at 50 °C for 2 h. S2, acid-exfoliated ionic covalent organic framework materials Prepare 24 mL of a mixed solution of acetonitrile:tetrahydrofuran:trifluoroacetic acid = 7:3:2 (volume ratio). Weigh 100 mg of the dried ionic covalent organic framework particles from S1 and add them to the mixed solution. Stir for 72 h. S3. Take 4 mL of acid stripping solution from S3, select a 5 cm diameter Blueview PAN filter membrane with a filtration accuracy of 50,000, and perform vacuum-assisted self-assembly to obtain an ion-type covalent organic framework composite membrane.

[0020] Test case See Figure 1 The scanning electron microscope images of the synthesized ionic covalent organic framework particles in the examples show that the ionic covalent organic frameworks synthesized by the hydrothermal method are in the micrometer range and exhibit large particle size. See Figure 2 The atomic force microscopy images of the acid-exfoliated ionic covalent organic framework material in the embodiments show that its size has decreased from the micrometer level to the nanometer level compared to the original particulate form, demonstrating the effectiveness of the acid exfoliation method.

[0021] See Figure 3 The X-ray diffraction patterns of the ionic covalent organic framework particles before and after acid exfoliation in the examples show that the ionic covalent organic framework synthesized by hydrothermal method has good crystallinity, and the acid exfoliation method does not destroy its own crystal structure.

[0022] See Figure 4 The cross-sectional scanning electron microscope image of the ion-covalent organic framework composite film in the embodiment shows that the nanosheets are stacked relatively tightly under vacuum-assisted self-assembly conditions, which creates a good channel for ion flow transport.

[0023] See Figure 5 The comparison diagram of zeta potential of ionic covalent organic framework particles before and after acid exfoliation in the embodiment shows that the surface potential was significantly improved after acid exfoliation, indicating that the nanosheets formed after exfoliation exposed more ionic sites and increased the surface charge density.

[0024] See Figure 6 In the embodiments, the heating rate test diagram and infrared thermal imaging of the ionic covalent organic framework composite film under light irradiation show that, due to the good photothermal conversion performance of the ionic covalent organic framework, it can be heated from room temperature to above 65°C in a short time under light irradiation.

[0025] See Figure 7 The contact angle test images of the ionic covalent organic framework composite membrane in the embodiments show that the ionic covalent organic framework composite membrane has good hydrophilicity and can achieve relatively good water transport.

[0026] See Figure 8 The power generation test diagram of the ion-type covalent organic framework composite membrane in the embodiment shows that after the membrane is cut into a 2cm×1cm rectangle, clamped at both ends of the membrane with flat electrode clips, and connected to an electrochemical workstation, 300µL of 1M NaCl solution is dropped onto one end of the membrane. Driven by natural evaporation, as the solution flows in the composite membrane, a microampere-level ion current can be generated, and this current can be sustained for more than 1 hour, indicating that the composite membrane has good energy conversion capability.

[0027] See Figure 9The power generation test diagram of the ion-type covalent organic framework composite membrane under periodic illumination in the embodiments is shown. The membrane was cut into a rectangle of 2cm × 1cm, and 200μL of 1M NaCl solution was dropped onto one end of the membrane. It was first left to stand in the dark for 300 seconds. Then, periodic illumination was applied, i.e., 60 seconds of illumination followed by 60 seconds of light exposure constituted one cycle, which was repeated several times. Under these conditions, it can be seen that the membrane's excellent photothermal conversion capability accelerated the movement rate of the ion current under illumination, resulting in a corresponding increase in the generated current, exhibiting a periodic response under periodic illumination.

[0028] See Figure 10 The power generation test diagram of the ion-type covalent organic framework composite membrane in the embodiment shows that the membrane was cut into a 2cm × 1cm rectangle, and 200µL of 1M NaCl solution or 200µL of deionized water was dropped at one end of the membrane. The membrane was then connected to a load, and its output power was measured. It can be seen that light exposure effectively increases the output power, and the output power increases with increasing ion concentration. This demonstrates the effectiveness of this membrane as a hydroelectric generator.

[0029] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a composite film of an ionic covalent organic framework material, characterized by, The method comprises the following steps: S1, synthesizing an ionic covalent organic framework material by a hydrothermal method Monomers safranin T and 1, 3, 5-triformylphloroglucinol are placed in an acetic acid solution and subjected to a heating reaction; the reaction product is taken out by suction filtration and dried; S2, acid stripping of the ionic covalent organic framework material The ionic covalent organic framework synthesized in S1 is placed in a mixed solution of acetonitrile, tetrahydrofuran and trifluoroacetic acid and subjected to acid stripping treatment for 72 hours; S3, suction filtration of ionic covalent organic framework nanosheets to a PAN base film The ionic covalent organic framework nanosheets are loaded on a PAN film by vacuum-assisted self-assembly by suction filtration, thereby obtaining an ionic covalent organic framework material composite film.

2. The method for preparing an ionic covalent organic framework composite membrane according to claim 1, characterized in that, In step S1, the specific monomer mass and conditions of the hydrothermal synthesis method are as follows: the mass ratio of monomers safranin T and 1, 3, 5-triformylphloroglucinol is 140-160:58-65; The solid-liquid ratio of monomers safranin T and acetic acid is 140-160:24-30 mg / mL; The heating reaction is carried out at 70-75℃ for 72-96h; The drying conditions are heating at 50-60℃ for 2-3h.

3. The method for preparing an ionic covalent organic framework composite membrane according to claim 1, characterized in that, In step S2, the acid stripping mixed solution has a volume ratio of acetonitrile: tetrahydrofuran: trifluoroacetic acid = 7:3:

2.

4. The solid-liquid ratio of the ionic covalent organic framework material and the mixed solution is 0.1:22-25 g / mL; The acid stripping treatment is carried out at a speed of 700-800 rpm for 72-96h.

5. The method for preparing an ionic covalent organic framework composite membrane according to claim 1, characterized in that, In step S3, during the suction filtration process, the filter membrane brand used is blue sky, the filtration precision is 50000, the filter membrane diameter is 5 cm, and the solution volume used for suction filtration is 4-6 mL.

6. A composite film of an ionic covalent organic framework material, characterized in that, The preparation method of any one of claims 1-4 is used.

7. The application of the ionic covalent organic framework material composite film of claim 5 or the ionic covalent organic framework composite film prepared by the preparation method of any one of claims 1-4 in the field of water-powered generation.

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