A method for the preparation of dense self-supporting imine bond linked covalent organic framework thin films by force-driven- gradient method and uses thereof

Abstract

The application discloses a method for preparing a dense self-supporting imine bond connected covalent organic framework film by force driving-gradient method and application. The method comprises the following steps: placing a substrate in a centrifuge tube, keeping the substrate in a vertical state during centrifugation; adding a reaction solution into the centrifuge tube; in-situ gradient growth under the action of continuous centrifugal force; after centrifugation is completed, standing, separating the obtained film from the substrate, and purifying and drying to obtain a dense self-supporting imine bond connected covalent organic framework film. The method is simple, has wide applicability, and has a wide thickness control range. The obtained film has excellent crystallinity, no obvious structural defects, and a dense stacking morphology. In the prepared series of samples, TMix-COF prepared by the reaction of mixed aldehyde components of terephthaldehyde and 2,3,5,6-tetrafluoroterephthaldehyde with 2,4,6-tris(4-aminophenyl)-1,3,5-triazine has the highest mechanical strength, the Young's modulus is as high as 7.5 Gpa, and good mechanical properties are exhibited; the obtained lithium battery solid-state electrolyte has excellent electrochemical performance.

Description

Technical Field

[0001] This invention belongs to the field of functional materials preparation, and relates to a method and application of preparing dense self-supporting imine bond-linked covalent organic framework thin films by a force-driven gradient method. Background Technology

[0002] Two-dimensional covalent organic frameworks (COFs), due to their one-dimensional channels formed by the close packing of framework molecules, are considered ideal pathways for the transport of molecules, ions, and protons. However, in practical engineering applications, the uniform and ordered pore structure and function of COF materials at the nanoscale are difficult to effectively extend to the macroscale, especially in fields such as electrolytes, seawater desalination, and molecular sieving, where transmembrane transport of substances typically requires functional channels to extend throughout the entire membrane material. Currently, common methods for preparing COF thin films mainly include: solvothermal synthesis, assisted evaporation conversion, continuous flow synthesis, ultra-high vacuum deposition, and chemical vapor deposition based on in-situ growth strategies; liquid-liquid and gas-liquid interface methods based on interface-assisted synthesis; and molding and nanosheet assembly methods. However, these methods generally suffer from slow reaction rates, significant interpore defects in the prepared films, and difficulty in controlling the overall thickness. Therefore, developing a high-quality, dense covalent organic framework membrane with macroscale, defect-free structure and pore orientation aligned with the material transport direction has become an ideal research goal. Developing an efficient, thickness-tunable, dense, and self-supporting method for preparing COF thin films is particularly important. Summary of the Invention

[0003] The purpose of this invention is to address the shortcomings of existing technologies by providing a method and application for preparing dense self-supporting imine-linked covalent organic framework thin films using a force-driven gradient method. This method can prepare dense self-supporting COFs thin films simply, quickly, and with adjustable thickness, and can also produce high-performance solid electrolyte thin films.

[0004] According to some embodiments of the present invention, the technical solution of the present invention is as follows:

[0005] A force-driven gradient method for preparing dense, self-supporting imine-linked covalent organic framework films is disclosed. This method is a general approach for obtaining dense and self-supporting imine-linked covalent organic framework films, and includes the following steps:

[0006] The substrate is placed in a centrifuge tube, the structure of which can compensate for its tilt angle in the centrifuge, so that the substrate remains vertical during centrifugation.

[0007] The aldehyde monomers, amine monomers, and catalyst used to form the imine-bonded covalent organic framework film are dissolved in a solvent to form a reaction solution, which is then added to the centrifuge tube.

[0008] Start the centrifuge and perform in-situ gradient growth under continuous centrifugal force;

[0009] After centrifugation, the membrane is allowed to stand to form an imine-bonded covalent organic framework film on the substrate. The film is then separated from the substrate, purified by Soxhlet extraction, and dried to obtain a dense, self-supporting imine-bonded covalent organic framework film.

[0010] In the above technical solution, furthermore, the bottom surface inside the centrifuge tube is provided with an inclined surface. The angle between this inclined surface and the horizontal direction is equal to the angle between the centrifuge tube and the horizontal direction after the centrifuge tube is placed in the centrifuge. This ensures that the substrate remains vertical during centrifugation, which is beneficial for the directional sedimentation and orderly assembly of the product under the coupled action of gravity and centrifugal force. A three-dimensional model of the centrifuge tube can be constructed using computer-aided modeling, and this special centrifuge tube with angle compensation function can be prepared using photopolymerization 3D printing technology.

[0011] Furthermore, the centrifugal force is 2000 g - 12000 g.

[0012] Furthermore, the in-situ gradient growth is carried out at a temperature of 0-60℃ for a time of 10 min-6 h.

[0013] Furthermore, the aldehyde monomers are terephthalaldehyde, 2,3,5,6-tetrafluoroterephthalaldehyde, 2,5-thiophene dicarboxaldehyde, 2,5,2''-trialdehyde-3,3':4',3''-terthiophene, 2,5-divinylterephthalaldehyde, 2,5-bis(prop-2-yn-1-yloxy)terephthalaldehyde, 2,6-dihydroxynaphthalene-1,5-dicarboxaldehyde, 3,4-bis(octyloxy)thieno[3,2-b]thiophene-2,5-dicarboxaldehyde, tetra(4-formylphenyl)ethylene, tetra(4-formylphenyl)dithieno[3,2-b:2',3'-d]thiophene, tetra(4-formylphenyl)-[1,1'-biphenyl]-4,4'- Diamine, 2,2',5,5'-tetraaldehyde biphenyl, trans-2,5-dihydroxy-1,4-bis(formylvinyl)benzene, 4,4'-dialdehyde biphenyl, 5,5'-dialdehyde-2,2'-bipyridine, 1,4-bis(4-formylphenyl)acetylene, benzimidazole onium salt derivatives, 4,4''-dialdehyde-p-terphenyl, N,N'-bis(4-formylphenyl)-4,4'-bipyridine onium disalt, 2,5-bis(4-formylphenylethynyl)benzo[c][1,2,5]thiadiazole, 2,5-bis(4-formylphenylethynyl)-3,4-dimethoxybenzene, N,N'-biindole-4,4',7,7'-tetracarboxaldehyde, 1,3,6,8 One or more of tetra(4-formylphenyl)perylene and tetra(4-formylphenyl)benzene;

[0014] The amine monomers are 1,3,5-tris(4-aminophenyl)-benzene, 2,4,6-tris(4-aminophenyl)-1,3,5-triazine, hydrazine, ethylenediamine, 2,6-diaminopyridine, p-phenylenediamine and its derivatives, 2,3,5,6-tetrafluoro-p-phenylenediamine, 2,5-disubstituted-1,4-phenylenediamine, 9,10-dihydroanthracene-2,7-diamine, N,N'-diamino-1,4,5,8-anthracene tetracarboxylic acid diimide, N,N'-diamino-1,4,5,8-anthracene tetracarboxylic acid diimide, 5,5'-diamino-2,2'-bipyridine, 3,3''-disubstituted-4,4''-diamino-p-terphenyl, 6,13-diaminopentaphenyl, 2-amino- One of 9,10-anthraquinone, N-ethyl-4,4'-diaminostilbene pyridinium salt, 4,4'-diaminostilbene, 4,4'-diaminoazobenzene, 4,4'-diaminodiphenylacetylene, 4,4''-diamino-p-terphenyl, tetra(4-aminophenyl)ethylene, and 1,3,6,8-tetra(4-aminophenyl)pyrene;

[0015] The catalyst is scandium trifluoromethanesulfonate.

[0016] Furthermore, when the amine monomer is 2,4,6-tris(4-aminophenyl)-1,3,5-triazine, the aldehyde monomer is a mixture of terephthalaldehyde and 2,3,5,6-tetrafluoroterephthalaldehyde in a molar ratio of (0.25:1) to (4:1) to obtain a thin film with better crystallinity and denser structure.

[0017] Furthermore, after centrifugation, the film is allowed to stand for 6-24 hours. This standing period provides the system with a static reaction time free from external interference, allowing unreacted precursor monomers / oligomers on the substrate to continue covalent polymerization, completing the ordered arrangement of unit cells and the cross-linking of the framework. This further enhances the crystallinity and structural rigidity of the COFs film, while alleviating the shear stress and interfacial tension accumulated inside the film during centrifugation, reducing structural incompleteness such as microcracks and grain boundary defects, and improving the mechanical stability and continuity of the COFs film.

[0018] Furthermore, the film is separated from the substrate by the following method: the sample obtained after standing is immersed in 0.1 mol / L NaOH solution for 5-10 minutes to allow the film to detach from the substrate surface.

[0019] Furthermore, the reaction solution also contains a bis(trifluoromethanesulfonyl)imine salt; the bis(trifluoromethanesulfonyl)imine salt includes, but is not limited to, one of LiTFSI, NaTFSI, KTFSI, Mg(TFSI)2, Zn(TFSI)2 and Ca(TFSI)2; its concentration is 0.1 mol / L – 2.0 mol / L.

[0020] A dense, self-supporting imine-linked covalent organic framework thin film is prepared by the method described in any of the preceding methods.

[0021] A method for preparing a solid electrolyte thin film includes the following steps:

[0022] The covalent organic framework (COF) film, as described above, is immersed in the electrolyte precursor solution;

[0023] The system is subjected to vacuum treatment to ensure that the electrolyte precursor solution is fully immersed in the nanopores of the COFs film;

[0024] After the film is removed, heating initiates an in-situ polymerization reaction, forming a cross-linked ionic conductive network within the pores to obtain a self-supporting COFs-based solid composite electrolyte film.

[0025] A solid-state lithium battery includes a positive electrode, a negative electrode, and a solid electrolyte layer disposed between the two; the solid electrolyte layer is composed of a COFs-based solid composite electrolyte film prepared by the above method, and is used to conduct lithium ions and prevent short circuits between the electrodes.

[0026] The beneficial effects of this invention are:

[0027] This invention provides a novel method for preparing COFs thin films. The reaction system is transferred to a centrifuge, and a dense, self-supporting COFs thin film is synthesized via a force-driven gradient method. The force-driven gradient method refers to the differential sedimentation behavior of COFs precursor particles with different sizes under centrifugal force. Larger particles preferentially migrate and deposit towards the bottom of the system, while smaller particles, due to their superior dispersion stability, have a much lower sedimentation rate and can remain suspended in the upper region of the system for extended periods. Based on this particle size-dependent sedimentation difference, a gradient distribution of particle size and concentration spontaneously forms in the vertical direction, thereby achieving layer-by-layer growth of the COFs thin film. This method exhibits excellent thickness adjustability; the film thickness can be flexibly controlled within the range of 100 nm to 100 μm by adjusting the solution volume and reaction time. It is applicable to various imine-bonded COFs, demonstrating good versatility. This method applies centrifugal force in situ during COF growth, promoting close packing of crystalline regions within the film and constructing a dense microstructure without significant porosity defects, thus endowing the material with excellent flexibility. Among the prepared series of samples, TMix-COF (prepared by reacting a mixed aldehyde component of terephthalaldehyde and 2,3,5,6-tetrafluoroterephthalaldehyde with 2,4,6-tris(4-aminophenyl)-1,3,5-triazine) exhibits the highest mechanical strength, with a Young's modulus reaching 7.5 GPa, demonstrating excellent mechanical properties. Furthermore, this method can introduce bis(trifluoromethanesulfonyl)imine salts into the monomer solution. Without affecting crystallinity, the addition of this salt promotes the polymerization reaction of the covalent organic framework, thereby forming a film with even better density. By filling the nanopores of this film with polymer electrolytes, a high-performance solid electrolyte film was successfully constructed. This electrolyte film exhibits outstanding performance in electrochemical stability, lithium-ion transference number, and cycle stability: it achieves an electrochemical window of 5.1 V, a lithium-ion transference number of 0.78, and maintains stable cycling for over 2000 hours in lithium / lithium symmetric batteries. Full-cell testing further validates its excellent cycle stability, providing crucial support for the development of next-generation lithium batteries. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the force-driven gradient method for preparing COF thin films.

[0029] Figure 2 X-ray diffraction patterns of COFs thin films (PD-COF) synthesized under different centrifugal forces in Example 1.

[0030] Figure 3 This is a schematic diagram of COF films (PD-COF) of different thicknesses in Example 1.

[0031] Figure 4The images show a comparison of X-ray diffraction patterns, SEM images, and optical photographs of the COFs films obtained by centrifugation and those not obtained by centrifugation in Example 1.

[0032] Figure 5 The images show a comparison of COFs films in Example 1 that were peeled off after being soaked in NaOH solution and those that were not.

[0033] Figure 6 This is an optical photograph of the COF self-supporting thin film (PD-COF) in Example 1.

[0034] Figure 7 The structural formulas of the five COFs in Examples 1-5 are shown.

[0035] Figure 8 The images show the X-ray diffraction patterns of the five COFs thin films in Examples 1-5.

[0036] Figure 9 It is a monomer used in the synthesis of various commonly used imine-linked COFs.

[0037] Figure 10 X-ray diffraction patterns of COFs thin films prepared by introducing various bis(trifluoromethanesulfonyl)imine salts.

[0038] Figure 11 SEM comparison images of lithium bis(trifluoromethanesulfonyl)imine with and without bis(trifluoromethanesulfonyl)imine.

[0039] Figure 12 The images show scanning electron microscope (SEM) images of the lower surfaces of the four COFs films in Examples 1-4.

[0040] Figure 13 Example 1: Lithium / lithium symmetric battery at 0.1 mA cm -2 Constant current charge-discharge curves at current density.

[0041] Figure 14 The full battery of Example 1 has a cyclic charge-discharge capacity retention curve at 0.1C. Detailed Implementation

[0042] The technical solution of the present invention will be further described below with reference to the embodiments, but it is not limited to the following embodiments. Any modifications or equivalent substitutions to the technical solution of the present invention without departing from the scope of the technical solution of the present invention shall fall within the scope of protection of the present invention.

[0043] According to some embodiments of the present invention, a method for preparing a dense, self-supporting imine-bonded COFs thin film involves placing the entire reaction system in a centrifuge and growing it in situ under centrifugal force. A centrifuge tube with angle compensation is designed, and the bottom surface of the centrifuge tube has an inclined surface (the centrifuge tube can be fabricated by 3D printing or other methods). The angle between this inclined surface and the horizontal direction is equal to the angle between the centrifuge tube and the horizontal direction after it is placed in the centrifuge. This ensures that the product is deposited on a vertically positioned substrate surface during centrifugation, thereby achieving in-situ growth under horizontal centrifugal force to form a tightly packed COFs thin film. Subsequently, the film is separated from the substrate, washed using Soxhlet extraction, and finally dried with supercritical carbon dioxide to obtain the dense, self-supporting imine-bonded COFs thin film.

[0044] Example 1:

[0045] (1) Preparation of the monomer solution:

[0046] Weigh 1,3,5-tris(4-aminophenyl)benzene (149 mg, 0.424 mmol) and scandium trifluoromethanesulfonate (100 mg, 0.203 mmol), dissolve them in 50 mL of acetonitrile, and sonicate for 60 seconds to ensure complete dissolution of the monomers, forming reaction monomer solution A. Then weigh terephthalaldehyde (85 mg, 0.634 mmol) and add it to 50 mL of acetonitrile, sonicate for 60 seconds to ensure complete dissolution of the monomers, forming reaction monomer solution B.

[0047] (2) Preparation of dense self-supporting COF thin films - PD-COF:

[0048] Equal volumes of solution A and solution B were added to an angle-compensated centrifuge tube, shaken well, and quickly placed in a centrifuge. The centrifuge was started (at room temperature), and the reaction was carried out for 60 minutes under centrifugal force. After centrifugation, the centrifuge tube was removed, and the mixture was allowed to stand for 6 hours. The sample was then immersed in 0.1 mol / L NaOH solution for 10 minutes to allow the film to detach from the substrate surface. The prepared PD-COF film was washed with tetrahydrofuran in a Soxhlet extractor for 24 hours. Finally, it was dried using supercritical carbon dioxide.

[0049] Figure 1 This is a schematic diagram of the synthesis of COFs thin films by centrifugal force. Figure 2 These are X-ray diffraction patterns of COFs films under different centrifugal forces, indicating that the synthesis can be controlled by adjusting the magnitude of the centrifugal force. Figure 3 These are schematic diagrams of COFs films of different thicknesses.

[0050] Corresponding to Example 1, a COF membrane not obtained based on the force-driven gradient method was also prepared. The specific preparation method was as follows: 1,3,5-tris(4-aminophenyl)benzene (149 mg, 0.424 mmol) and scandium trifluoromethanesulfonate (100 mg, 0.203 mmol) were weighed and dissolved in 50 mL of acetonitrile. The solution was sonicated for 60 seconds to ensure complete dissolution of the monomers, forming reaction monomer solution A. Then, terephthalaldehyde (85 mg, 0.634 mmol) was weighed and added to 50 mL of acetonitrile. The solution was sonicated for 60 seconds to ensure complete dissolution of the monomers, forming reaction monomer solution B. Equal volumes of solutions A and B were added to a regular centrifuge tube, shaken well, and allowed to stand for 6 hours. After standing, the reaction solution was separated by vacuum filtration, and the resulting solid product was collected. The prepared PD-COF particles were washed with tetrahydrofuran in a Soxhlet extractor for 24 h. Then, supercritical carbon dioxide drying was performed. The dried PD-COF particles were loaded into a stainless steel tableting mold, and a pressure of 5 MPa was applied at room temperature using a manual hydraulic tablet press. The pressure was held for 2 minutes to obtain a self-supporting circular film. Figure 4 The morphology and structure of COF membranes obtained by the two processes were compared. When COF particles without centrifugation were physically pressed to form a film, numerous pores, poor crystallinity, and insufficient density were observed. In contrast, the COF membrane obtained by Example 1, which was formed directly under centrifugal force using the force-driven gradient method, had a smooth and dense surface with significantly reduced pores. XRD and SEM analyses confirmed that its crystallinity and density were significantly superior to the former.

[0051] In addition, after growing the COF film on the substrate, the COF film can be directly peeled off the substrate, but it is more preferable to immerse the obtained sample in a 0.1 mol / L NaOH solution for 5-10 minutes. This treatment allows the film to detach from the substrate surface on its own, which is more conducive to obtaining a large-area, undamaged film. Figure 5 The effects of the two separation methods were compared: Figure a shows that the COF membrane without soaking in NaOH solution can only be partially peeled off and is prone to cracking; in contrast, Figure b shows that after soaking in NaOH, the COF membrane can be completely peeled off over a large area without damage.

[0052] The method of this invention is a general preparation method for dense and self-supporting imine-bonded covalent organic framework films. The feasibility of this method has been demonstrated by using it to prepare imine-bonded COF films formed from different aldehyde monomers and amine monomers. Figure 7 The diagram shows the structural formulas of five COF thin films. Figure 8 The X-ray diffraction patterns of five COF thin films demonstrate the versatility of this synthesis method. Figure 9 These are monomers involved in the synthesis of COFs linked by various commonly used imine bonds.

[0053] Furthermore, the compactness of the obtained COFs membrane can be further improved by directly adding bis(trifluoromethanesulfonyl)imine salt to the reaction solution; the bis(trifluoromethanesulfonyl)imine salt includes, but is not limited to, one of LiTFSI, NaTFSI, KTFSI, Mg(TFSI)2, Zn(TFSI)2 and Ca(TFSI)2, and its concentration in the reaction solution is preferably 0.1 mol / L – 2.0 mol / L. Figure 10 The introduction of bis(trifluoromethanesulfonyl)imine salt to synthesize COFs membranes (the only difference from Example 1 is the addition of 3.64 g and 12.68 mmol of LiTFSI to the monomer solution B) indicates that the introduction of bis(trifluoromethanesulfonyl)imine salt does not affect the crystallinity of COFs. Figure 11 For lithium salts without the introduction of bis(trifluoromethanesulfonyl)imine ( Figure 11 a) and the introduction of lithium bis(trifluoromethanesulfonyl)imine ( Figure 11 As can be seen from the comparison in b), the introduction of lithium bis(trifluoromethanesulfonyl)imine can yield COFs membranes with better density. Figure 12 The images show scanning electron microscope (SEM) images of the lower surfaces of four COF films, indicating that the COF films synthesized by the force-driven gradient method have a dense structure.

[0054] (3) Preparation of PD-COF electrolyte:

[0055] Ethylene ethylene carbonate (VEC) and polyethylene glycol diacrylate (PEGDA) were mixed at a volume ratio of 6:1 (corresponding monomer ratio of 20:1). Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) was then dissolved in this solution to obtain a 1 mol / L solution. Next, 0.5 wt% of AIBN monomer was added to the solution, and the mixture was stirred for 5 minutes to obtain an electrolyte precursor solution. The COFs film was then immersed in the electrolyte precursor solution, and a vacuum was applied for 30 minutes to ensure that the electrolyte precursor solution fully wetted the nanopores. The COFs film filled with the electrolyte precursor solution was then removed and treated at 70°C for 20 hours to complete the polymerization reaction.

[0056] The obtained PD-COF solid electrolyte and lithium sheet were assembled into a lithium / lithium symmetric battery in a glove box, and charge-discharge tests were performed after standing for 12 hours. In addition, lithium iron phosphate was selected as the positive electrode and assembled into a full battery with lithium sheet in a glove box.

[0057] Figure 13 For lithium / lithium symmetric batteries at 0.1 mA cm -2 The constant current charge-discharge curves at current density show that the battery using PD-COF electrolyte can stably cycle for up to 2000 hours. Figure 14The full cell has a cyclic charge-discharge capacity retention curve at 0.1C. After 400 cycles, its capacity retention rate and coulombic efficiency are 82% and 98.17%, respectively.

[0058] Example 2:

[0059] The monomer precursor solution was prepared according to the method described in Example 1 above. 1,3,5-Tris(4-aminophenyl)benzene (149 mg, 0.424 mmol) and scandium trifluoromethanesulfonate (100 mg, 0.203 mmol) were weighed and dissolved in 50 mL of acetonitrile. The solution was sonicated for 60 seconds to ensure complete dissolution of the monomer, forming precursor solution A. Then, 2,3,5,6-tetrafluoroterephthalaldehyde (131 mg, 0.634 mmol) was weighed and added to 50 mL of acetonitrile. The solution was sonicated for 60 seconds to ensure complete dissolution of the monomer, forming precursor solution B. Equal volumes of solutions A and B were added to an angle-compensated centrifuge tube, shaken well, and quickly placed in a centrifuge. The centrifuge was started, and the mixture was allowed to react for 60 minutes under centrifugal force. After centrifugation, the centrifuge tube was removed, and the mixture was allowed to stand for 6 hours. The sample was then immersed in 0.1 mol / L NaOH solution for 10 minutes to allow the film to detach from the substrate surface. The prepared PF-COF film was washed with tetrahydrofuran in a Soxhlet extractor for 24 h. Then, it was dried with supercritical carbon dioxide to obtain a dense, self-supporting covalent organic framework film material.

[0060] Example 3:

[0061] The monomer precursor solution was prepared using the method described in Example 1 above. 2,4,6-tris(4-aminophenyl)-1,3,5-triazine (150 mg, 0.424 mmol) and scandium trifluoromethanesulfonate (100 mg, 0.203 mmol) were weighed and dissolved in 50 mL of acetonitrile. The solution was sonicated for 60 seconds to ensure complete dissolution, forming precursor solution A. Then, terephthalaldehyde (85 mg, 0.634 mmol) was weighed and added to 50 mL of acetonitrile. The solution was sonicated for 60 seconds to ensure complete dissolution, forming precursor solution B. Equal volumes of solutions A and B were added to an angle-compensated centrifuge tube, shaken well, and quickly placed in a centrifuge. The centrifuge was started, and the mixture was allowed to react for 60 minutes under centrifugal force. After centrifugation, the centrifuge tube was removed, and the mixture was allowed to stand for 6 hours. The sample was then immersed in 0.1 mol / L NaOH solution for 10 minutes to allow the film to detach from the substrate surface. The prepared TD-COF film was washed with tetrahydrofuran in a Soxhlet extractor for 24 hours. Then, it was dried with supercritical carbon dioxide to obtain a dense, self-supporting covalent organic framework film material.

[0062] Example 4:

[0063] The monomer precursor solution was prepared using the method described in Example 1 above. 2,4,6-tris(4-aminophenyl)-1,3,5-triazine (150 mg, 0.424 mmol) and scandium trifluoromethanesulfonate (100 mg, 0.203 mmol) were weighed and dissolved in 50 mL of acetonitrile. The solution was sonicated for 60 seconds to ensure complete dissolution, forming precursor solution A. Then, 2,3,5,6-tetrafluoroterephthalaldehyde (131 mg, 0.634 mmol) was weighed and added to 50 mL of acetonitrile. The solution was sonicated for 60 seconds to ensure complete dissolution, forming precursor solution B. Equal volumes of solutions A and B were added to an angle-compensated centrifuge tube, shaken well, and quickly placed in a centrifuge. The centrifuge was started, and the mixture was allowed to react for 60 minutes under centrifugal force. After centrifugation, the centrifuge tube was removed, and the mixture was allowed to stand for 6 hours. The sample was then immersed in 0.1 mol / L NaOH solution for 10 minutes to allow the film to detach from the substrate surface. The prepared TF-COF film was washed with tetrahydrofuran in a Soxhlet extractor for 24 hours. Then, it was dried with supercritical carbon dioxide to obtain a dense, self-supporting covalent organic framework film material.

[0064] Example 5:

[0065] The monomer precursor solution was prepared using the method described in Example 1 above. 2,4,6-tris(4-aminophenyl)-1,3,5-triazine (150 mg, 0.424 mmol) and scandium trifluoromethanesulfonate (100 mg, 0.203 mmol) were weighed and dissolved in 50 mL of acetonitrile. The solution was sonicated for 60 seconds to ensure complete dissolution of the monomer, forming precursor solution A. Then, terephthalaldehyde (28 mg, 0.209 mmol) and 2,3,5,6-tetrafluoroterephthalaldehyde (87 mg, 0.422 mmol) were weighed and added to 50 mL of acetonitrile. The solution was sonicated for 60 seconds to ensure complete dissolution of the monomer, forming precursor solution B. Equal volumes of solutions A and B were added to an angle-compensated centrifuge tube, shaken well, and quickly placed in a centrifuge. The centrifuge was started, and the mixture was allowed to react for 60 minutes under centrifugal force. After centrifugation, the centrifuge tube was removed, and the mixture was allowed to stand for 6 hours. The sample was then immersed in 0.1 mol / L NaOH solution for 10 minutes to allow the film to detach from the substrate surface. The prepared TMix-COF film was washed with tetrahydrofuran in a Soxhlet extractor for 24 hours. Supercritical carbon dioxide drying was then performed to obtain a dense, self-supporting covalent organic framework thin film material. Figure 8 , Figure 12 It can be seen that, compared with using only one aldehyde monomer in Examples 3 and 4, the use of two aldehyde monomers in this embodiment can produce a film with superior performance, which is denser and has significantly higher crystallinity.

[0066] The embodiments described above are merely some preferred embodiments of the present invention, and are not intended to limit the invention. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the invention. Therefore, all technical solutions obtained by equivalent substitution or equivalent transformation fall within the protection scope of the present invention.

Claims

1. A method for preparing dense, self-supporting imine-bonded covalent organic framework thin films using a force-driven gradient method, characterized in that, This method is a general approach to obtaining dense and self-supporting imine-linked covalent organic framework thin films, and includes the following steps: The substrate is placed in a centrifuge tube, the structure of which can compensate for its tilt angle in the centrifuge, so that the substrate remains vertical during centrifugation. The aldehyde monomers, amine monomers, and catalyst used to form the imine-bonded covalent organic framework film are dissolved in a solvent to form a reaction solution, which is then added to the centrifuge tube. Start the centrifuge and perform in-situ gradient growth under continuous centrifugal force; After centrifugation, the film is allowed to stand to form an imine-bonded covalent organic framework film on the substrate. The film is then separated from the substrate, purified by Soxhlet extraction, and dried to obtain a dense, self-supporting imine-bonded covalent organic framework film. The aldehyde monomers are one or more selected from the following: terephthalaldehyde, 2,3,5,6-tetrafluoroterephthalaldehyde, 2,5-thiophene dicarboxaldehyde, 2,5-divinylterephthalaldehyde, 2,5-bis(prop-2-yn-1-yloxy)terephthalaldehyde, tetra(4-formylphenyl)ethylene, 2,2',5,5'-tetraaldehyde biphenyl, 4,4'-dialdehyde biphenyl, 5,5'-dialdehyde-2,2'-bipyridine, 1,4-bis(4-formylphenyl)acetylene, 4,4''-dialdehyde-p-terphenyl, 1,3,6,8-tetra(4-formylphenyl)perylene, and tetra(4-formylphenyl)benzene. The amine monomers are 1,3,5-tris(4-aminophenyl)-benzene, 2,4,6-tris(4-aminophenyl)-1,3,5-triazine, hydrazine, 2,6-diaminopyridine, p-phenylenediamine, 2,3,5,6-tetrafluoro-p-phenylenediamine, 2,5-disubstituted-1,4-phenylenediamine, 9,10-dihydroanthracene-2,7-diamine, N,N'-diamino-1,4,5,8-anthracene tetracarboxylic acid diimide, N,N'-diamino-1,4,5,8-anthracene tetracarboxylic acid diimide, 5,5'-diamino-2,2'-bipyridine, 3,3''-disubstituted- One of 4,4''-diamino-p-terphenyl, 6,13-diaminopentaphenyl, 4,4'-diaminostilbene, 4,4'-diaminoazobenzene, 4,4'-diaminodiphenylacetylene, 4,4''-diamino-p-terphenyl, tetra(4-aminophenyl)ethylene, and 1,3,6,8-tetra(4-aminophenyl)pyrene.

2. The method for preparing dense, self-supporting imine-bonded covalent organic framework thin films using the force-driven gradient method according to claim 1, characterized in that, The centrifuge tube has an inclined surface on its inner bottom surface. The angle between the inclined surface and the horizontal direction is equal to the angle between the centrifuge tube and the horizontal direction after the centrifuge tube is placed in the centrifuge, so as to ensure that the base remains vertical during the centrifugation process.

3. The method for preparing dense, self-supporting imine-bonded covalent organic framework thin films using the force-driven gradient method according to claim 1, characterized in that, The centrifugal force is 2000 g - 12000 g.

4. The method for preparing dense, self-supporting imine-bonded covalent organic framework thin films using the force-driven gradient method according to claim 1, characterized in that, The in-situ gradient growth is carried out at a temperature of 0-60℃ for 10 min–6 h.

5. The method for preparing dense, self-supporting imine-bonded covalent organic framework thin films using the force-driven gradient method according to claim 1, characterized in that, The catalyst is scandium trifluoromethanesulfonate.

6. The method for preparing dense, self-supporting imine-bonded covalent organic framework thin films using the force-driven gradient method according to claim 1, characterized in that, When the amine monomer is 2,4,6-tris(4-aminophenyl)-1,3,5-triazine, the aldehyde monomer is a mixture of terephthalaldehyde and 2,3,5,6-tetrafluoroterephthalaldehyde in a molar ratio of (0.25:1) to (4:1) to obtain a thin film with better crystallinity and denser structure.

7. The method for preparing dense, self-supporting imine-bonded covalent organic framework thin films using the force-driven gradient method according to claim 1, characterized in that, The thin film was separated from the substrate by immersing the sample obtained after standing in a 0.1 mol / L NaOH solution for 5-10 minutes to allow the thin film to detach from the substrate surface.

8. The method for preparing dense, self-supporting imine-bonded covalent organic framework thin films using the force-driven gradient method according to claim 1, characterized in that, The reaction solution also contains a bis(trifluoromethanesulfonyl)imine salt; the bis(trifluoromethanesulfonyl)imine salt is one of LiTFSI, NaTFSI, KTFSI, Mg(TFSI)2, Zn(TFSI)2 and Ca(TFSI)2; its concentration is 0.1 mol / L – 2.0 mol / L.

9. A dense, self-supporting imine-bonded covalent organic framework thin film, characterized in that, It is prepared by the method as described in any one of claims 1 to 8.

10. A method for preparing a solid electrolyte thin film, characterized in that, Includes the following steps: The covalent organic framework (COFs) film as described in claim 9 is immersed in the electrolyte precursor solution; The system is subjected to vacuum treatment to ensure that the electrolyte precursor solution is fully immersed in the nanopores of the COFs film; After the film is removed, heating initiates an in-situ polymerization reaction, forming a cross-linked ionic conductive network within the pores to obtain a self-supporting COFs-based solid composite electrolyte film.

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