Acidic compounds, polyimide covalent organic frameworks, and methods of making and using the same

Abstract

This application provides acidic compounds, polyimide covalent organic frameworks, their preparation methods, and applications. The structural formula of the acidic compounds is shown in formula (I), wherein R1 is selected from substituted or unsubstituted arylene groups or substituted or unsubstituted heteroarylene groups, and X is selected from chlorine, bromine, or iodine atoms. The acidic compounds provided in this application can be used to prepare three-dimensional polyimide covalent organic frameworks. Furthermore, the polyimide covalent organic frameworks contain phosphorus-containing pivots, which provide flame retardant effects, thus facilitating the use of polyimide covalent organic frameworks.

Description

Technical Field

[0001] This application relates to the field of materials technology, and in particular to acid compounds, polyimide covalent organic frameworks, their preparation methods and applications. Background Technology

[0002] Covalent organic frameworks (COFs) are novel crystalline organic porous materials formed by dynamic covalent bonds, applicable to fields such as adsorption, storage and separation, sensing, photoelectric applications, catalysis, chromatographic separation and analysis, and drug delivery. Based on their different dimensions, COFs can be classified into two-dimensional layered structures and three-dimensional structures. Currently, most research and development focuses on two-dimensional layered COFs, with very little research and development on three-dimensional COFs, and even less on polyimide-based three-dimensional COFs. Therefore, research and development of polyimide-based three-dimensional COFs is of great significance for the application of COFs. Summary of the Invention

[0003] In view of this, this application provides an acid compound, a polyimide covalent organic framework, a method for preparing the same, and its application. The acid compound can be used to synthesize a polyimide covalent organic framework with a three-dimensional structure, which is beneficial for the use of the polyimide covalent organic framework.

[0004] In a first aspect, this application provides an acid compound, the structural formula of which is shown in formula (I).

[0005]

[0006] Wherein, R1 is selected from substituted or unsubstituted aryl or substituted or unsubstituted heteroaryl, and X is selected from chlorine, bromine or iodine atoms.

[0007] Optionally, the substituted or unsubstituted aryl group is a substituted or unsubstituted C6-C6 group. 30 Alpha-aryl compounds.

[0008] Optionally, the substituted or unsubstituted heteroaryl group is a substituted or unsubstituted C2-C3 group. 30 Hybrid aryl groups.

[0009] Optionally, the acid compound includes at least one of the compounds shown in formulas (I-1) to (I-3).

[0010]

[0011]

[0012] Secondly, this application provides a polyimide covalent organic framework, wherein the polyimide covalent organic framework comprises repeating units represented by formula (II).

[0013]

[0014] Wherein, R1 is selected from substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene, R2 is selected from substituted or unsubstituted alkylene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene, and X is selected from chlorine atom, bromine atom, or iodine atom.

[0015] Optionally, the number of repetitions of the repeating unit shown in formula (II) is 10 to 200.

[0016] Thirdly, this application provides a method for preparing an acid compound, comprising:

[0017] R3-O-R1-Mg-X1 is mixed with phosphorus trichloride, and a first reaction yields the compound shown in formula (III-1), wherein R1 is selected from substituted or unsubstituted aryl or substituted or unsubstituted heteroaryl, R3 is selected from substituted or unsubstituted alkyl or substituted or unsubstituted aryl, and X1 is selected from chlorine, bromine, or iodine atoms.

[0018]

[0019] The compound represented by formula (III-1) is mixed with a halogenated product to form a coupling reaction solution, and the coupling reaction yields the compound represented by formula (III-2), wherein X is selected from chlorine, bromine, or iodine atoms.

[0020]

[0021] The compound represented by formula (III-2) is mixed with acetic acid and hydrobromic acid, and a second reaction is carried out to obtain the compound represented by formula (III-3).

[0022]

[0023] The compound represented by formula (III-3) is mixed with 4-nitrophthalonitrile and subjected to a third reaction to give the compound represented by formula (III-4).

[0024]

[0025] The compound represented by formula (III-4) undergoes hydrolysis in an alkaline solution to yield an acid compound, the structural formula of which is shown in formula (I).

[0026]

[0027] Optionally, the molar ratio of R3-O-R1-Mg-X1 to phosphorus trichloride is (2.9-3.5):1.

[0028] Optionally, the reaction temperature of the first reaction is 0℃~80℃, and the reaction time is 10h~20h.

[0029] Optionally, the coupling reaction solution further includes a first catalyst, which comprises at least one of a palladium catalyst and a nickel catalyst. The palladium catalyst comprises at least one of bis(3,5,3',5'-dimethoxydibenzylacetone)palladium, bis(tri-tert-butyl)palladium, tribenzylacetonepalladium, palladium chloride, palladium acetate, tetra(triphenylphosphine)palladium, and bis(tri-tert-butylphosphine)palladium. The nickel catalyst comprises at least one of [1,1'-bis(diphenylphosphine)ferrocene]nickel dichloride and bis(1,5-cyclooctadiene)nickel.

[0030] Optionally, the coupling reaction is carried out at a temperature of 80°C to 120°C and for a reaction time of 8 hours to 16 hours.

[0031] Optionally, the molar ratio of the compound represented by formula (III-2), the acetic acid, and the hydrobromic acid is 1:(1.5-50):(0.75-50).

[0032] Optionally, the reaction temperature of the second reaction is 60℃~110℃, and the reaction time is 10h~15h.

[0033] Optionally, the molar ratio of the compound represented by formula (III-3) to the 4-nitrophthalonitrile is 1:(2 to 2.5).

[0034] Optionally, the reaction temperature of the third reaction is 80℃~120℃, and the reaction time is 4h~8h.

[0035] Optionally, the hydrolysis reaction is carried out at a temperature of 50℃ to 100℃ and for a time of 8h to 14h.

[0036] Fourthly, this application provides a method for preparing a polyimide covalent organic framework, comprising mixing an acidic compound as described in the first aspect or an acidic compound prepared by the method described in the third aspect with a diamine to form a mixture, and then performing a fourth reaction to obtain a polyimide covalent organic framework, wherein the polyimide covalent organic framework comprises repeating units represented by formula (II).

[0037]

[0038] Wherein, R1 is selected from substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene, R2 is selected from substituted or unsubstituted alkylene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene, and X is selected from chlorine atom, bromine atom, or iodine atom.

[0039] Optionally, the diamine has the structural formula H2N-R2-NH2.

[0040] Optionally, the molar ratio of the acid compound to the diamine is 1:(1-6).

[0041] Optionally, the mixture further includes a second catalyst, which includes at least one of piperidine, isoquinoline, pyridine, potassium hydroxide, and sodium hydroxide.

[0042] Optionally, the mixture further includes a first solvent, which includes at least one selected from mesitylene, N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, toluene, dioxane, water, benzyl alcohol, ethanol, and n-butanol.

[0043] Optionally, the reaction temperature of the fourth reaction is 120℃~240℃, and the reaction time is 24h~240h.

[0044] Optionally, the fourth reaction may further include a drying process, which may include at least one of vacuum drying and supercritical carbon dioxide drying.

[0045] Optionally, the vacuum drying includes a vacuum degree of 10. -5 Pa~10 -2 Dry at -40℃ to 160℃ for 5 to 24 hours.

[0046] Optionally, the supercritical carbon dioxide drying includes drying at 40℃~80℃, 6MPa~24MPa, and a carbon dioxide flow rate of 15mL / min~200mL / min for 1h~8h.

[0047] Fifthly, this application provides the application of polyimide covalent organic frameworks prepared by the method described in the second aspect or the fourth aspect in battery separators, insulating films, flame retardants, sound-absorbing layers or magnetic layers.

[0048] The acidic compounds provided in this application can be used to prepare three-dimensional polyimide covalent organic frameworks. Furthermore, the polyimide covalent organic frameworks prepared by these acidic compounds have phosphorus-containing pivots, which can play a flame-retardant role and are more conducive to the use of polyimide covalent organic frameworks. Detailed Implementation

[0049] The technical solutions of this application will be clearly and thoroughly described below. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0050] This application provides an acid compound with the structural formula shown in formula (I).

[0051]

[0052] Wherein, R1 is selected from substituted or unsubstituted aryl groups or substituted or unsubstituted heteroaryl groups, and X is selected from chlorine, bromine, or iodine atoms. The acidic compounds provided in this application can be used in the preparation of polyimide covalent organic frameworks, and can produce polyimide covalent organic frameworks with three-dimensional structures, which is beneficial for the use of polyimide covalent organic frameworks. Furthermore, the polyimide covalent organic frameworks prepared by these acidic compounds have phosphorus-containing pivots, which can provide flame retardant effects, further facilitating the widespread use of polyimide covalent organic frameworks.

[0053] In this application, aryl is an aromatic group, and arylene is a divalent aromatic group. Specifically, arylene may include, but is not limited to, at least one of phenylene, biphenylene, terphenylene, naphthylene, anthracene, tetraphenylene, pentaphenylene, and tetrahydronaphthylene. In one embodiment of this application, the substituted or unsubstituted arylene is a substituted or unsubstituted C6-C group. 30 The arylene group; that is, the number of carbon atoms in the arylene group can be 6 to 30. Specifically, the number of carbon atoms in the arylene group can be, but is not limited to, 6, 10, 12, 15, 17, 19, 20, 22, 25, 28, 29 or 30, etc.

[0054] In this application, a heteroaryl group is an aryl group having at least one oxygen, sulfur, or nitrogen atom, and a heteroaryl group is a divalent heteroaryl group. Specifically, a heteroaryl group may include, but is not limited to, at least one of pyridylene, furanylene, thiopheneylene, indoleylene, quinolinylene, imidazolinylene, and thiazolylene. In embodiments of this application, the substituted or unsubstituted heteroaryl group is a substituted or unsubstituted C2-C group. 30 The heteroaryl group; that is, the number of carbon atoms in the heteroaryl group is 2 to 30. Specifically, the number of carbon atoms in the heteroaryl group can be, but is not limited to, 2, 3, 5, 7, 10, 12, 15, 18, 20, 23, 25, 26, 28 or 30, etc.

[0055] In this application, the substituted group (such as arylene or heteroarylene) refers to the group substituted by the substituent. In one embodiment, the substituent includes at least one selected from halogen, nitrogen atom, oxygen atom, sulfur atom, hydroxyl, nitro, amino, mercapto, methoxy, and cyano. That is, when R1 is selected from a substituted arylene, R1 can be at least one substituent selected from halogen, nitrogen atom, oxygen atom, sulfur atom, hydroxyl, nitro, amino, mercapto, methoxy, and cyano to replace the arylene; when R1 is selected from a substituted heteroarylene, R1 can be at least one substituent selected from halogen, nitrogen atom, oxygen atom, sulfur atom, hydroxyl, nitro, amino, mercapto, methoxy, and cyano to replace the heteroarylene.

[0056] In one embodiment of this application, the acid compound includes at least one of the compounds shown in formulas (I-1) to (I-3).

[0057]

[0058] The aforementioned acid compounds are stable and easy to prepare, which is beneficial for the synthesis and use of polyimide covalent organic frameworks.

[0059] This application provides a method for preparing an acid compound, comprising: mixing R3-O-R1-Mg-X1 with phosphorus trichloride, and undergoing a first reaction to obtain the compound shown in formula (III-1); mixing the compound shown in formula (III-1) with a halogenated compound to form a coupling reaction solution, and undergoing a coupling reaction to obtain the compound shown in formula (III-2); mixing the compound shown in formula (III-2) with acetic acid and hydrobromic acid, and undergoing a second reaction to obtain the compound shown in formula (III-3); mixing the compound shown in formula (III-3) with 4-nitrophthalonitrile, and undergoing a third reaction to obtain the compound shown in formula (III-4); and hydrolyzing the compound shown in formula (III-4) in an alkaline solution to obtain an acid compound, the structural formula of which is shown in formula (I); wherein, R1 is selected from substituted or unsubstituted aryl groups or substituted or unsubstituted heteroaryl groups, R3 is selected from substituted or unsubstituted alkyl groups or substituted or unsubstituted aryl groups, X1 is selected from a chlorine atom, a bromine atom, or an iodine atom, and X is selected from a chlorine atom, a bromine atom, or an iodine atom.

[0060]

[0061] The method for preparing acid compounds provided in this application has high preparation efficiency and low process difficulty, and it can produce acid compounds with high purity, which is beneficial to the use of acid compounds.

[0062] In this application, R3 is selected from substituted or unsubstituted alkyl groups or substituted or unsubstituted aryl groups. In this application, an alkyl group is an alkane molecule with one hydrogen atom removed, and can include straight-chain alkyl groups and branched-chain alkyl groups. Specifically, alkyl groups can include, but are not limited to, at least one of methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, 2-methylbutyl, 3-methylbutyl, 4-methylbutyl, 2,2-dimethylpropyl, n-hexyl, heptyl, 2-methylhexyl, 3-methylhexyl, 4-methylpentyl, 5-methylpentyl, 2-ethylbutyl, 3-ethylbutyl, heptyl, octyl, nonyl, and decyl. In embodiments of this application, the substituted or unsubstituted alkyl group can be a substituted or unsubstituted C1-C8 alkyl group; that is, the alkyl group has 1 to 8 carbon atoms. Specifically, the alkyl group can have, but is not limited to, 1, 2, 3, 4, 5, 6, 7, or 8 carbon atoms. In one embodiment of this application, R3 is selected from substituted or unsubstituted C1-C8 alkyl groups, or substituted or unsubstituted C6-C8 alkyl groups. 30 The aryl group. The substituted groups are as described above and will not be repeated here.

[0063] In one embodiment of this application, R3-O-R1-X1 reacts with magnesium in the presence of a third catalyst to generate Grignard reagent R3-O-R1-Mg-X1 via a fifth reaction. In one embodiment of this application, the third catalyst includes at least one of iodine and 1,2-dibromoethane. In one embodiment of this application, the molar ratio of R3-O-R1-X1 to magnesium can be 1:1, which is beneficial for the preparation of R3-O-R1-Mg-X1 and can effectively avoid the occurrence of side reactions. In one embodiment of this application, the reaction temperature of the fifth reaction is 45℃~55℃, and the reaction time is 30min~60min, thereby facilitating the efficient preparation of R3-O-R1-Mg-X1. Specifically, the reaction temperature of the fifth reaction can be, but is not limited to, 45℃, 47℃, 49℃, 50℃, 53℃, or 55℃, and the reaction time can be, but is not limited to, 30min, 40min, 50min, or 60min.

[0064] In one embodiment of this application, the molar ratio of R3-O-R1-Mg-X1 to phosphorus trichloride is (2.9–3.5):1, which facilitates the efficient preparation of the compound represented by formula (III-1). Specifically, the molar ratio of R3-O-R1-X1 to phosphorus trichloride can be, but is not limited to, 2.9:1, 3:1, 3.1:1, 3.2:1, 3.3:1, 3.4:1, or 3.5:1. In one embodiment of this application, R3-O-R1-Mg-X1 and phosphorus trichloride can be mixed in an ice-water bath, which effectively avoids the volatilization of phosphorus trichloride and facilitates the subsequent reaction.

[0065] In one embodiment of this application, the reaction temperature of the first reaction is 0°C to 80°C, and the reaction time is 10h to 20h, which facilitates the preparation of the compound shown in formula (III-1) and effectively avoids the occurrence of side reactions. Specifically, the reaction temperature of the first reaction can be, but is not limited to, 0°C, 10°C, 20°C, 25°C, 40°C, 50°C, 60°C, 70°C, or 80°C, and the reaction time of the first reaction can be, but is not limited to, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, or 20h.

[0066] In one embodiment of this application, the first reaction can be quenched with a saturated NH4Cl solution. In another embodiment of this application, the first reaction can be further extracted with ethyl acetate or dichloromethane, and the organic phase can be dried with anhydrous Na2SO4 or anhydrous MgSO4 and concentrated to obtain the compound shown in formula (III-1), which is beneficial to improving the purity of the compound shown in formula (III-1).

[0067] In one embodiment of this application, the halogenated compound has the structural formula R4-X, wherein R4 is selected from substituted or unsubstituted alkyl groups, substituted or unsubstituted alkoxy groups, substituted or unsubstituted aryl groups, or substituted or unsubstituted heteroaryl groups, and X is selected from chlorine atoms, bromine atoms, or iodine atoms. In this application, the alkoxy group is composed of an alkyl group and an oxygen atom, and it can be a straight-chain structure, a branched structure, or a cyclic structure. Specifically, the alkoxy group can include, but is not limited to, at least one of methoxy, ethoxy, propoxy, butoxy, pentoxy, hexoxy, and heptoxy. In one embodiment of this application, R4 is selected from substituted or unsubstituted C1-C8 alkyl groups, substituted or unsubstituted C1-C8 alkoxy groups, substituted or unsubstituted C6-C8 alkoxy groups, or substituted or unsubstituted C6-C8 alkoxy groups. 30 aryl group, or substituted or unsubstituted C2-C 30 The heteroaryl group. The substituted groups are as described above and will not be repeated here. In one embodiment of this application, the molar ratio of the compound represented by formula (III-1) to the halide can be 1:1, which is beneficial to the coupling reaction.

[0068] In one embodiment of this application, the coupling reaction solution further includes a first catalyst, which comprises at least one of a palladium catalyst and a nickel catalyst. The palladium catalyst comprises at least one of bis(3,5,3',5'-dimethoxydibenzylacetone)palladium, bis(tri-tert-butyl)palladium, tribenzylacetonepalladium, palladium chloride, palladium acetate, tetra(triphenylphosphine)palladium, and bis(tri-tert-butylphosphine)palladium. The nickel catalyst comprises at least one of [1,1'-bis(diphenylphosphine)ferrocene]nickel dichloride and bis(1,5-cyclooctadiene)nickel. Adding the first catalyst can increase the reaction rate of the coupling reaction, which is beneficial for the preparation of the compound shown in formula (III-2).

[0069] In one embodiment of this application, the coupling reaction temperature is 80℃~120℃, and the reaction time is 8h~16h, which is beneficial for the efficient preparation of the compound shown in formula (III-2). Specifically, the coupling reaction temperature can be, but is not limited to, 80℃, 90℃, 100℃, 110℃ or 120℃, and the coupling reaction time can be, but is not limited to, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h or 16h.

[0070] In one embodiment of this application, after the coupling reaction, the mixture can be washed with a saturated Na₂SO₄ solution, then extracted with ethyl acetate or dichloromethane. The organic phase is then dried with anhydrous Na₂SO₄ or anhydrous MgSO₄ and concentrated to obtain the compound shown in formula (III-1). Washing removes impurities such as catalysts, and extraction and drying help improve the purity of the compound shown in formula (III-2).

[0071] In one embodiment of this application, the molar ratio of the compound represented by formula (III-2), acetic acid, and hydrobromic acid is 1:(1.5-50):(0.75-50), which facilitates the full reaction of the compound represented by formula (III-2) with acetic acid and hydrobromic acid, thereby improving the preparation efficiency. Specifically, the molar ratio of the compound represented by formula (III-2), acetic acid, and hydrobromic acid can be, but is not limited to, 1:(2-35):(1-45), 1:(3-30):(1.5-40), or 1:(4-20):(2-30), etc.

[0072] In one embodiment of this application, the reaction temperature of the second reaction is 60°C to 110°C, and the reaction time is 10h to 15h, which facilitates the efficient preparation of the compound represented by formula (III-3). Specifically, the reaction temperature of the second reaction can be, but is not limited to, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, or 120°C, and the reaction time of the second reaction can be, but is not limited to, 10h, 11h, 12h, 13h, 14h, or 15h.

[0073] In one embodiment of this application, after the second reaction, extraction can be performed using ethyl acetate or dichloromethane. The organic phase is then added dropwise to an alkaline solution to separate the aqueous phase. After washing the aqueous phase with ethyl acetate or dichloromethane, the aqueous phase is adjusted to acidity and filtered to obtain the compound shown in formula (III-3). The alkaline solution removes unreacted acetic acid, hydrobromic acid, etc., and adjusting the aqueous phase to acidity prevents the compound shown in formula (III-3) from dissolving in the solution, thus improving the preparation rate and purity of the compound shown in formula (III-3). Specifically, the alkaline solution can be, but is not limited to, sodium hydroxide solution, potassium hydroxide solution, etc., such as a 10 wt% sodium hydroxide solution; the pH value of the aqueous phase can be less than 5 when adjusted to acidity.

[0074] In one embodiment of this application, the molar ratio of the compound represented by formula (III-3) to 4-nitrophthalonitrile is 1:(2 to 2.5), which is beneficial for the preparation of the compound represented by formula (III-4). Specifically, the molar ratio of the compound represented by formula (III-3) to 4-nitrophthalonitrile can be, but is not limited to, 1:2, 1:2.1, 1:2.2, 1:2.3, 1:2.4, or 1:2.5. In one embodiment of this application, the compound represented by formula (III-3) and 4-nitrophthalonitrile are mixed to form a third reaction solution. The third reaction solution further includes a second solvent, which includes at least one of N,N-dimethylformamide, N,N-dimethylacetamide, and N,N-dimethylpyrrolidone, thereby facilitating the dispersion and reaction of the compound represented by formula (III-3) and 4-nitrophthalonitrile.

[0075] In one embodiment of this application, the reaction temperature of the third reaction is 80°C to 120°C, and the reaction time is 4h to 8h, which facilitates the efficient preparation of the compound represented by formula (III-4). Specifically, the reaction temperature of the third reaction can be, but is not limited to, 80°C, 90°C, 100°C, 110°C, or 120°C, and the reaction time can be, but is not limited to, 4h, 5h, 6h, 7h, or 8h. In one embodiment of this application, the compound represented by formula (III-4) can be purified by column chromatography after the third reaction to improve the purity of the obtained compound.

[0076] In one embodiment of this application, the alkaline solution may be, but is not limited to, at least one of sodium hydroxide solution and potassium hydroxide solution. In one embodiment, the alkaline solution may be 10 wt% potassium hydroxide. In one embodiment of this application, the hydrolysis reaction temperature is 50°C to 100°C, and the reaction time is 8 h to 14 h, which is beneficial for the preparation of acid compounds. Specifically, the hydrolysis reaction temperature may be, but is not limited to, 50°C, 60°C, 70°C, 80°C, 90°C, or 100°C, and the hydrolysis reaction time may be, but is not limited to, 8 h, 9 h, 10 h, 11 h, 12 h, 13 h, or 14 h. In one embodiment of this application, after the hydrolysis reaction, recrystallization with glacial acetic acid can be performed to obtain acid compounds with high purity.

[0077] This application provides a polyimide covalent organic framework comprising repeating units as shown in formula (II).

[0078]

[0079] Wherein, R1 is selected from substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene, R2 is selected from substituted or unsubstituted alkylene, substituted or unsubstituted arylene, or substituted or unsubstituted heteroarylene, and X is selected from chlorine atom, bromine atom, or iodine atom.

[0080] The polyimide covalent organic framework of this application has both a three-dimensional structure and high order, and the phosphorus-containing pivots therein can play a flame-retardant role, which is conducive to the widespread use of polyimide covalent organic framework.

[0081] In this application, alkylene is a divalent saturated group formed by removing one hydrogen atom from an alkyl group. In one embodiment of this application, the substituted or unsubstituted alkylene is a C1-C8 alkylene; that is, the alkylene has 1 to 8 carbon atoms. Specifically, the number of carbon atoms in the alkylene can be, but is not limited to, 1, 2, 3, 4, 5, 6, 7, or 8. As described above, aryl, heteroaryl, and substituted groups will not be repeated here.

[0082] In one embodiment of this application, the number of repetitions of the repeating unit shown in formula (II) in the polyimide covalent organic framework is 10 to 200, which is beneficial for the preparation and use of the polyimide covalent organic framework. Specifically, the number of repetitions of the repeating unit shown in formula (II) can be, but is not limited to, 10, 30, 40, 50, 80, 100, 120, 150, 170, 180, or 200.

[0083] In one embodiment of this application, the dielectric constant of the polyimide covalent organic framework is 1.5 to 3.4. The dielectric constant of the polyimide covalent organic framework is tested according to ASTM D150-18. The polyimide covalent organic framework provided in this application has a dielectric constant close to that of air. The polyimide covalent organic framework has a three-dimensional porous structure and excellent insulation properties, which is beneficial for its use. Specifically, the dielectric constant of the polyimide covalent organic framework can be, but is not limited to, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, or 3. In one embodiment of this application, the dielectric constant of the polyimide covalent organic framework can be 1.5 to 2.5.

[0084] In one embodiment of this application, the 5% decomposition temperature of the polyimide covalent organic framework is 450°C to 600°C. The 5% decomposition temperature is the temperature at which the mass loss of the polyimide covalent organic framework reaches 5% of its original mass. The 5% decomposition temperature of the polyimide covalent organic framework provided in this application is relatively high, meaning that the polyimide covalent organic framework has good high-temperature resistance and high structural stability, which is beneficial for its use. Specifically, the 5% decomposition temperature of the polyimide covalent organic framework can be, but is not limited to, 450°C, 480°C, 500°C, 530°C, 550°C, 580°C, or 600°C, etc.

[0085] In one embodiment of this application, the pore size of the polyimide covalent organic framework is 0.5 μm to 10 μm. Specifically, the pore size of the polyimide covalent organic framework can be, but is not limited to, 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, or 10 μm.

[0086] This application provides a method for preparing a polyimide covalent organic framework, comprising mixing an acid compound from any of the above embodiments with a diamine to form a mixture, and then performing a fourth reaction to obtain a polyimide covalent organic framework, wherein the polyimide covalent organic framework comprises a repeating unit as shown in formula (II).

[0087] In one embodiment of this application, the diamine has the structural formula H2N-R2-NH2. In the acid compound structural formula, each benzene ring is attached to two carboxyl groups. In the fourth reaction, one of these two carboxyl groups reacts with the diamine to generate an amide-containing moiety. The amide-containing moiety then reacts with the other of the two carboxyl groups to form a ring, creating an imide-containing moiety. It can be understood that the carboxyl groups in all four benzene rings of the acid compound structural formula undergo the above process, thereby obtaining a polyimide covalent organic framework.

[0088] In one embodiment of this application, the molar ratio of the acid compound to the diamine is 1:(1-6), which is beneficial for the rapid preparation of polyimide covalent organic frameworks. Specifically, the molar ratio of the acid compound to the diamine can be, but is not limited to, 1:1, 1:2, 1:3, 1:4, 1:4.5, 1:5, 1:5.5, or 1:6. In one embodiment of this application, the molar ratio of the acid compound to the diamine can be 1:4.5, which is even more beneficial for the rapid preparation of polyimide covalent organic frameworks.

[0089] In one embodiment of this application, the mixture further includes a second catalyst, which comprises at least one of piperidine, isoquinoline, pyridine, potassium hydroxide, and sodium hydroxide, facilitating the rapid progress of the fourth reaction. Specifically, the concentration of potassium hydroxide can be 3 mol / L, and the concentration of sodium hydroxide can be 3 mol / L.

[0090] In one embodiment of this application, the mixture further includes a first solvent, which includes at least one selected from mesitylene, N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, toluene, dioxane, water, benzyl alcohol, ethanol, and n-butanol, which is beneficial for the mixing and reaction of acidic compounds with diamines. In one embodiment of this application, the first solvent may be a mixture of water and n-butanol in a volume ratio of 2:1.

[0091] In one embodiment of this application, the reaction temperature of the fourth reaction is 120℃~240℃, and the reaction time is 24h~240h, which is beneficial for the preparation of polyimide covalent organic frameworks. Specifically, the reaction temperature of the fourth reaction can be, but is not limited to, 120℃, 150℃, 160℃, 170℃, 190℃, 200℃, 210℃, or 240℃, and the reaction time can be, but is not limited to, 24h, 48h, 96h, 120h, 148h, 172h, 196h, 220h, or 240h. In one embodiment of this application, the fourth reaction can be carried out in a reaction apparatus, which can be a glass-sealed tube, a hydrothermal reactor, etc. In one embodiment of this application, the mixture is placed in the reaction apparatus, degassed by cyclic freeze-thaw cycles, and then sealed. The polyimide covalent organic framework is obtained through the fourth reaction.

[0092] In one embodiment of this application, the fourth reaction is followed by washing to remove impurities. In one embodiment of this application, the product obtained from the fourth reaction is soaked in N,N-dimethylformamide, N,N-dimethylacetamide, or N,N-dimethylpyrrolidone for 5 to 8 hours (e.g., 5 hours, 6 hours, 7 hours, or 8 hours), then soaked in methanol, tetrahydrofuran, acetone, ethyl acetate, ethanol, or 1,4-dioxane for 5 to 8 hours (e.g., 5 hours, 6 hours, 7 hours, or 8 hours), and then Soxhlet extracted with tetrahydrofuran and acetone for 24 to 48 hours (e.g., 24 hours, 30 hours, 36 hours, 42 hours, or 48 hours).

[0093] In one embodiment of this application, a drying process is further included after the fourth reaction. The drying process can be performed after the fourth reaction or after washing. In one embodiment of this application, the drying process includes at least one of vacuum drying and supercritical carbon dioxide drying. In one embodiment of this application, vacuum drying includes drying at a vacuum degree of 10... -5 Pa~10 -2 Pa (e.g., 10) -5 Pa, 10 -4 Pa, 10 -3 Pa or 10 -2Drying at temperatures ranging from -40℃ to 160℃ (e.g., -40℃, -30℃, -20℃, 0℃, 10℃, 20℃, 30℃, 40℃, 50℃, 60℃, 90℃, 100℃, 110℃, 120℃, 135℃, 150℃, or 160℃, etc.) for 5h to 24h (e.g., 5h, 7h, 10h, 12h, 13h, 15h, 17h, 20h, 22h, or 24h, etc.) is suitable for drying for 5h to 24h. In one embodiment of this application, supercritical carbon dioxide drying includes drying at a carbon dioxide flow rate of 40℃~80℃ (e.g., 40℃, 50℃, 60℃, 70℃ or 80℃, etc.), 6MPa~24MPa (e.g., 6MPa, 9MPa, 10MPa, 13MPa, 15MPa, 18MPa, 20MPa, 23MPa or 24MPa, etc.) and 15mL / min~200mL / min (e.g., 15mL / min, 30mL / min, 50mL / min, 70mL / min, 90mL / min, 120mL / min, 150mL / min, 175mL / min or 200mL / min, etc.) for 1h~8h (e.g., 1h, 3h, 5h, 6h, 7h or 8h, etc.).

[0094] This application provides the application of the polyimide covalent organic framework in any of the above embodiments in battery separators, insulating films, flame retardants, sound-absorbing layers, or magnetic layers. The polyimide covalent organic framework provided in this application has a three-dimensional porous structure, which can be used in battery separators to isolate the positive and negative electrodes and prevent electrons from freely passing through while allowing ions to pass freely. The polyimide covalent organic framework provided in this application has a suitable dielectric constant and a porous structure, exhibiting excellent insulation properties, and can be used in insulating films. For example, the polyimide covalent organic framework can be used as a material for low-dielectric enameled wires. The polyimide covalent organic framework provided in this application has phosphorus-containing pivots, which can play a flame-retardant role, thus allowing its use as a flame retardant. For example, the polyimide covalent organic framework can be used as an aerogel flame retardant. The polyimide covalent organic framework provided in this application has a three-dimensional porous structure, capable of absorbing sound and electromagnetic fields, thus allowing its use in sound-absorbing layers and magnetic layers.

[0095] The technical solution of this application will be further described below through specific embodiments and comparative examples.

[0096] Example A1

[0097] A method for preparing an acid compound, comprising:

[0098] 3 mol of 4-methoxybromobenzene Grignard reagent was prepared by reacting 3 mol of magnesium powder with iodine under catalysis. 1 mol of phosphorus trichloride was added dropwise to an ice-water bath, and the reaction was carried out at 25°C for 10 h. The reaction was then quenched with saturated ammonium chloride solution, followed by extraction with ethyl acetate. The organic phase obtained from the extraction was dried with anhydrous sodium sulfate and concentrated to obtain compound A1.

[0099] Compound A1 was coupled with 4-methoxybromobenzene in the presence of tetra(triphenylphosphine)palladium catalysis (coupling reaction temperature 80℃, coupling reaction time 16 h). After the reaction, the mixture was washed with saturated sodium sulfate solution, extracted with ethyl acetate, and the organic phase was dried with anhydrous sodium sulfate and concentrated to obtain compound A2.

[0100] Compound A2 was added to excess acetic acid and 48 wt% hydrobromic acid for reaction (molar ratio of compound A2, acetic acid, and hydrobromic acid: 1:20:20; reaction temperature: 60℃; reaction time: 12 h). After the reaction was completed and cooled to room temperature, the mixture was extracted with ethyl acetate. The organic phase was then removed, and 10 wt% sodium hydroxide solution was slowly added dropwise to separate the aqueous phase. The aqueous phase was washed three times with dichloromethane, the pH was adjusted to 2 with hydrochloric acid, and the mixture was filtered to obtain compound A3.

[0101] 1 mol of compound A3 and 2 mol of 4-nitrophthalonitrile were dissolved in 20 mol of N,N-dimethylformamide, and the mixture was heated to 100 °C and reacted for 5 h. After cooling the reaction product to room temperature, compound A4 was purified by column chromatography.

[0102]

[0103] Compound A4 was dissolved in a 10 wt% potassium hydroxide solution and hydrolyzed (reaction temperature 100℃, reaction time 10 h), followed by recrystallization with glacial acetic acid to obtain an acid compound.

[0104] The 1H NMR data of the acid compounds are as follows (500 MHz, Chloroform-d): δ 7.78 (d, J = 8.4 Hz, 1H), 7.75–7.69 (m, 2H), 7.33 (d, J = 2.2 Hz, 1H), 7.07 (dd, J = 8.4, 2.4 Hz, 1H), 7.04–6.97 (m, 2H).

[0105] Example A2

[0106] A method for preparing an acid compound, comprising:

[0107] 3 mol of 4-bromo-4'-methoxybiphenyl Grignard reagent was prepared by reacting 3 mol of magnesium powder with iodine under catalysis. 1 mol of phosphorus trichloride was added dropwise to an ice-water bath, and the reaction was carried out at 0°C for 10 h. The reaction was then quenched with saturated ammonium chloride solution, followed by extraction with ethyl acetate. The organic phase obtained from the extraction was dried with anhydrous sodium sulfate and concentrated to obtain compound B1.

[0108] Compound B1 was coupled with 4-bromo-4'-methoxybiphenyl in the presence of tetra(triphenylphosphine)palladium catalysis (coupling reaction temperature: 120 °C; coupling reaction time: 16 h). After the reaction, the mixture was washed with saturated sodium sulfate solution, extracted with ethyl acetate, and the organic phase was dried with anhydrous sodium sulfate and concentrated to obtain compound B2.

[0109] Compound B2 was added to excess acetic acid and 48 wt% hydrobromic acid for reaction (molar ratio of compound B2, acetic acid, and hydrobromic acid: 1:20:20; reaction temperature: 80℃; reaction time: 12 h). After the reaction was completed and cooled to room temperature, the mixture was extracted with ethyl acetate. The organic phase was then removed, and 10 wt% sodium hydroxide solution was slowly added dropwise to separate the aqueous phase. The aqueous phase was washed three times with dichloromethane, and the pH was adjusted to less than 2 with hydrochloric acid. The mixture was then filtered to obtain compound B3.

[0110] 1 mol of compound B3 and 2 mol of 4-nitrophthalonitrile were dissolved in 10 mol of N,N-dimethylformamide, and the mixture was heated to 100 °C and reacted for 5 h. After cooling the reaction product to room temperature, compound B4 was purified by column chromatography.

[0111]

[0112] Compound B4 was dissolved in a 10 wt% potassium hydroxide solution and hydrolyzed (reaction temperature 50℃, reaction time 10 h), followed by recrystallization with glacial acetic acid to obtain an acid compound.

[0113] The 1H NMR data of the acid compounds are as follows (500 MHz, Chloroform-d): δ 7.89–7.84 (m, 2H), 7.78 (d, J = 8.4 Hz, 1H), 7.74–7.68 (m, 2H), 7.61 (td, J = 8.1, 1.5 Hz, 2H), 7.33 (d, J = 2.2 Hz, 1H), 7.20–7.14 (m, 2H), 7.07 (dd, J = 8.4, 2.4 Hz, 1H).

[0114] Example B1

[0115] A method for preparing a polyimide covalent organic framework, comprising:

[0116] In a reaction vessel, 0.2 mmol of the acid compound prepared in Example A1 and 0.4 mmol of p-phenylenediamine were added to a mixed solvent of 2 mL of water and 1 mL of n-butanol. After sonication for 5 min, a yellow turbid solution was obtained. 0.15 mL of pyridine was added to the reaction vessel as a catalyst. The reaction vessel was placed in a liquid nitrogen bath and rapidly frozen at 77 K, and degassed by a freeze-pump-thaw cycle three times, and then sealed. The reaction vessel was then placed in an oven at 180 °C for 5 days. After the reaction, the yellow solid was separated by centrifugation and washed twice with N,N-dimethylacetamide (10 mL) and then soaked and washed twice with acetone (10 mL). The precipitate was filtered and then thoroughly washed with tetrahydrofuran and acetone for 48 h by Soxhlet extraction. The washed sample was transferred to a vacuum oven and evacuated to 10 °C at 80 °C. -3 Pa, dried for 24 h, to obtain polyimide covalent organic framework.

[0117] The structure of the prepared polyimide covalent organic framework was characterized by nuclear magnetic resonance (NMR). The 1H NMR spectra were as follows: 1H NMR (500MHz, Chloroform-d) δ 7.78 (d, J = 8.4 Hz, 1H), 7.75-37.69 (m, 2H), 7.33 (d, J = 1.9 Hz, 1H), 7.07 (dd, J = 8.4, 2.1 Hz, 1H), 7.04-6.97 (m, 2H).

[0118] Example B2

[0119] A method for preparing a polyimide covalent organic framework, comprising:

[0120] In a reaction vessel, 0.2 mmol of the acid compound prepared in Example A2 and 0.6 mmol of p-phenylenediamine were added to a mixed solvent of 2 mL water and 1 mL n-butanol. After sonication for 5 min, a yellow turbid solution was obtained. 0.15 mL of pyridine was added to the reaction vessel as a catalyst. The reaction vessel was placed in a liquid nitrogen bath and rapidly frozen at 77 K, and degassed by a freeze-pump-thaw cycle three times before being sealed. The reaction vessel was then placed in an oven at 180 °C for 5 days. After the reaction, the yellow solid was separated by centrifugation and washed twice with N,N-dimethylacetamide (10 mL) and then soaked and washed twice with acetone (10 mL). The precipitate was filtered and then thoroughly washed with tetrahydrofuran and acetone for 48 h by Soxhlet extraction. The washed sample was transferred to a vacuum oven and evacuated to 10 °C. -3 Pa, dried for 24 h, to obtain polyimide covalent organic framework.

[0121] The structure of the prepared polyimide covalent organic framework was characterized by nuclear magnetic resonance (NMR). The 1H NMR spectra were as follows: 1H NMR (500MHz, Chloroform-d) δ 7.89-7.84 (m, 2H), 7.78 (d, J = 8.4 Hz, 1H), 7.74-7.68 (m, 2H), 7.61 (td, J = 8.1, 1.5 Hz, 2H), 7.33 (d, J = 1.9 Hz, 1H), 7.20-7.14 (m, 2H), 7.07 (dd, J = 8.4, 2.1 Hz, 1H).

[0122] Comparative Example 1

[0123] A method for preparing polyimide, comprising:

[0124] In a reaction vessel, 0.4 mmol of pyromellitic dianhydride and 0.4 mmol of p-phenylenediamine were added to a mixed solvent of 2 mL of water and 1 mL of n-butanol. After sonication for 5 min, a yellow turbid solution was obtained. 0.15 mL of pyridine was added to the reaction vessel as a catalyst. The reaction vessel was placed in a liquid nitrogen bath and rapidly frozen at 77 K, and degassed by a freeze-pump-thaw cycle three times before sealing. The reaction vessel was then placed in an oven at 180 °C for 5 days. After the reaction, the yellow solid was separated by centrifugation and washed twice with N,N-dimethylacetamide (10 mL) followed by two washes with acetone (10 mL). The precipitate was filtered and then thoroughly washed with tetrahydrofuran and acetone for 48 h by Soxhlet extraction. The washed sample was transferred to a vacuum oven and evacuated to 10 °C. -3 Pa, dried for 24 hours, to obtain polyimide.

[0125] Comparative Example 2

[0126] A method for preparing a polyimide covalent organic framework, comprising:

[0127] In a reaction vessel, 0.2 mmol of melamine and 0.4 mmol of terephthalaldehyde were added to a mixed solvent of 2 mL of water and 1 mL of n-butanol. After sonication for 5 min, a yellow turbid solution was obtained. 0.15 mL of pyridine was added to the reaction vessel as a catalyst. The reaction vessel was placed in a liquid nitrogen bath and rapidly frozen at 77 K, and degassed by a freeze-pump-thaw cycle three times before sealing. The reaction vessel was then placed in an oven at 180 °C for 5 days. After the reaction, the yellow solid was separated by centrifugation and washed twice with N,N-dimethylacetamide (10 mL) followed by two washes with acetone (10 mL). The precipitate was filtered and then thoroughly washed with tetrahydrofuran and acetone for 48 h by Soxhlet extraction. The washed sample was transferred to a vacuum oven and evacuated to 10 °C. -3 Pa, dried for 24 h, to obtain polyimide covalent organic framework.

[0128] Performance testing

[0129] The dielectric constant of the polyimides prepared in the examples and comparative examples was tested according to ASTM D150-18; the specific surface area of ​​the polyimides prepared in the examples and comparative examples was tested according to GB / T19587-2017 "Determination of Specific Surface Area of ​​Solid Substances by Gas Adsorption BET Method"; the limiting oxygen index of the polyimides prepared in the examples and comparative examples was tested according to GB / T2406.2-2009 using a limiting oxygen index tester; the 5% decomposition temperature (the temperature corresponding to the mass loss of the sample reaching 5% of its original mass) of the polyimides prepared in the examples and comparative examples was tested according to GB / T 13464-2008 "Thermal Analysis Test Method for Thermal Stability of Substances". The results are shown in Table 1.

[0130] Table 1 Performance Test Results

[0131]

[0132] The closer the dielectric constant is to that of air (1), the higher the air content in the material. Therefore, the dielectric constant results show that the polyimide covalent organic framework prepared in this application has a high air content, which indirectly reflects that the polyimide covalent organic framework has a three-dimensional porous structure. Furthermore, the dielectric constant is suitable, indicating that the polyimide covalent organic framework has good insulation properties. Since the polyimide prepared in Comparative Example 1 has a one-dimensional linear structure and the polyimide covalent organic framework prepared in Comparative Example 2 has a two-dimensional structure, its dielectric constant is higher. At the same time, the specific surface area results also show that the polyimide covalent organic framework prepared in this application has a high specific surface area, while the specific surface areas of Comparative Example 1 and Comparative Example 2 are low, indicating that the polyimide covalent organic framework prepared in this application has a three-dimensional porous structure. The limiting oxygen index (LOI) refers to the volume fraction of oxygen in a polymer in an oxygen-nitrogen mixture that just allows it to burn. It is an index characterizing the combustion behavior of a material; materials with a high LIO are difficult to burn, and those with an LIO of 27% or higher are generally considered flame-retardant. Therefore, the polyimide covalent organic framework prepared in the embodiments of this application has a high LIO and contains phosphorus-containing pivots, making it suitable for use in flame retardants. The 5% decomposition temperature results show that, except for Comparative Example 2, the polyimides prepared in the other examples exhibit better high-temperature resistance and stability, which is beneficial for their use. In summary, the polyimide covalent organic framework prepared in the embodiments of this application has a three-dimensional structure and a large specific surface area, excellent insulation, is difficult to burn, and has good stability, which is beneficial for its use.

[0133] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. An acid compound, characterized in that, The structural formula of the acid compound is shown in formula (I). （I）， R1 is selected from substituted or unsubstituted C6~C. 30 aryl groups, or substituted or unsubstituted C2~C 30 The heteroaryl group, X is selected from chlorine, bromine or iodine atoms, and the substituents in the substituted aryl group and the substituted heteroaryl group are independently selected from at least one of halogen, hydroxyl, nitro, amino, mercapto, methoxy and cyano.

2. The acid compound according to claim 1, characterized in that, The acid compounds include at least one of the compounds shown in formulas (I-1) to (I-3). （I-1）， （I-2）， （I-3）。 3. A polyimide covalent organic framework, characterized in that, The polyimide covalent organic framework comprises repeating units as shown in formula (II). (II), R1 is selected from substituted or unsubstituted C6~C. 30 aryl groups, or substituted or unsubstituted C2~C 30 The heteroaryl group, R2 is selected from substituted or unsubstituted C1-C8 alkylene groups, substituted or unsubstituted C6-C8 alkylene groups. 30 aryl groups, or substituted or unsubstituted C2~C 30 The heteroarylene, X is selected from chlorine, bromine or iodine atoms, and the substituents in the substituted arylene, substituted heteroarylene and substituted alkylene are independently selected from at least one of halogen, hydroxyl, nitro, amino, mercapto, methoxy and cyano.

4. The polyimide covalent organic framework as described in claim 3, characterized in that, The number of repetitions of the repeating unit shown in formula (II) is 10 to 200.

5. A method for preparing an acid compound, characterized in that, include: When mixed with phosphorus trichloride, a first reaction yields the compound shown in formula (III-1), wherein R1 is selected from substituted or unsubstituted C6~C6 groups. 30 aryl groups, or substituted or unsubstituted C2~C 30 The heteroaryl group, R3 is selected from substituted or unsubstituted C1-C8 alkyl groups, or substituted or unsubstituted C6-C8 alkyl groups. 30 The aryl group, X1 is selected from a chlorine atom, a bromine atom, or an iodine atom, and the substituents in the substituted aryl group, substituted heteroaryl group, substituted alkyl group, and substituted aryl group are independently selected from at least one of halogen, hydroxyl, nitro, amino, mercapto, methoxy, and cyano groups. (III-1); The compound represented by formula (III-1) is mixed with a halogenated product to form a coupling reaction solution, and the coupling reaction yields the compound represented by formula (III-2), wherein X is selected from chlorine, bromine, or iodine atoms. (III-2); The compound represented by formula (III-2) is mixed with acetic acid and hydrobromic acid, and a second reaction is carried out to obtain the compound represented by formula (III-3). (III-3); The compound represented by formula (III-3) is mixed with 4-nitrophthalonitrile and subjected to a third reaction to give the compound represented by formula (III-4). (III-4); The compound represented by formula (III-4) undergoes hydrolysis in an alkaline solution to yield an acid compound, the structural formula of which is shown in formula (I). （I）。 6. The preparation method according to claim 5, characterized in that, The The molar ratio of phosphorus trichloride to phosphorus trichloride is (2.9~3.5):1; and / or The reaction temperature of the first reaction is 0℃~80℃, and the reaction time is 10h~20h; and / or The coupling reaction solution further includes a first catalyst, which comprises at least one of a palladium catalyst and a nickel catalyst. The palladium catalyst is at least one of bis(3,5,3',5'-dimethoxydibenzylacetone)palladium, bis(tri-tert-butyl)palladium, tribenzylacetonepalladium, palladium chloride, palladium acetate, tetra(triphenylphosphine)palladium, and bis(tri-tert-butylphosphine)palladium. The nickel catalyst is at least one of [1,1'-bis(diphenylphosphine)ferrocene]nickel dichloride and bis(1,5-cyclooctadiene)nickel; and / or The coupling reaction is carried out at a temperature of 80℃~120℃ for a reaction time of 8h~16h; and / or The molar ratio of the compound represented by formula (III-2), the acetic acid, and the hydrobromic acid is 1:(1.5~50):(0.75~50); and / or The second reaction is carried out at a temperature of 60℃~110℃ for a time of 10h~15h; and / or The molar ratio of the compound represented by formula (III-3) to the 4-nitrophthalonitrile is 1:(2~2.5); and / or The reaction temperature of the third reaction is 80℃~120℃, and the reaction time is 4h~8h; and / or The hydrolysis reaction is carried out at a temperature of 50℃ to 100℃ for a time of 8h to 14h.

7. A method for preparing a polyimide covalent organic framework, characterized in that, The method includes mixing an acidic compound according to any one of claims 1 to 2 or an acidic compound prepared by any one of claims 5 to 6 with a diamine to form a mixture, and then subjecting the mixture to a fourth reaction to obtain a polyimide covalent organic framework, wherein the polyimide covalent organic framework comprises repeating units represented by formula (II). (II), R1 is selected from substituted or unsubstituted C6~C. 30 aryl groups, or substituted or unsubstituted C2~C 30 The heteroaryl group, R2 is selected from substituted or unsubstituted C1-C8 alkylene groups, substituted or unsubstituted C6-C8 alkylene groups. 30 aryl groups, or substituted or unsubstituted C2~C 30 The heteroarylene, X is selected from chlorine, bromine or iodine atoms, and the substituents in the substituted arylene, substituted heteroarylene and substituted alkylene are independently selected from at least one of halogen, hydroxyl, nitro, amino, mercapto, methoxy and cyano.

8. The preparation method according to claim 7, characterized in that, The structural formula of the diamine is as follows: ; The molar ratio of the acid compound to the diamine is 1:(1~6). The mixture further includes a second catalyst, which is at least one selected from piperidine, isoquinoline, pyridine, potassium hydroxide, and sodium hydroxide. The mixture further includes a first solvent, which is at least one selected from the following: mesitylene, N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, toluene, dioxane, water, benzyl alcohol, ethanol, and n-butanol; The reaction temperature of the fourth reaction is 120℃~240℃, and the reaction time is 24h~240h.

9. The preparation method according to claim 7, characterized in that, The fourth reaction is followed by a drying process, which includes at least one of vacuum drying and supercritical carbon dioxide drying. The vacuum drying process includes a vacuum degree of 10. -5 Pa~10 -2 Dry at -40℃ to 160℃ for 5 to 24 hours; The supercritical carbon dioxide drying process includes drying at 40℃~80℃, 6MPa~24MPa, and a carbon dioxide flow rate of 15mL / min~200mL / min for 1h~8h.

10. The use of the polyimide covalent organic framework as described in any one of claims 3 to 4 or the polyimide covalent organic framework prepared by the preparation method as described in any one of claims 7 to 9 in battery separators, insulating films or flame retardants.

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