Acid compound, polyimide covalent organic framework and preparation method and application thereof

Abstract

The invention provides an acid compound, a polyimide covalent organic framework and a preparation method and application thereof. The structural formula of the acid compound is as shown in formula (I) # imgabs0 #, R1 is selected from substituted or unsubstituted arylene or substituted or unsubstituted heteroarylene, and X is selected from chlorine atoms, bromine atoms or iodine atoms. The acid compound provided by the invention can be used for preparing a polyimide covalent organic framework with a three-dimensional structure, and meanwhile, the polyimide covalent organic framework has a phosphorus-containing fulcrum, so that a flame-retardant effect can be achieved, and the use of the polyimide covalent organic framework is facilitated.

Description

Technical Field

[0001] The present application relates to the field of material technology, and in particular to acid compounds, polyimide covalent organic frameworks, and preparation methods and applications thereof. Background Art

[0002] Covalent Organic Frameworks (COFs) are a new type of crystalline organic porous material formed by dynamic covalent bonds. They can be used in the fields of material adsorption, storage and separation, sensing, optoelectronics, catalysis, chromatographic separation analysis, drug delivery, etc. According to the different dimensions of COFs, they can be divided into two-dimensional layered structures and three-dimensional structures. At present, most of the research and development is aimed at two-dimensional layered COFs, and there is very little research and development on three-dimensional COFs, and even less research and development on three-dimensional COFs of polyimides. Therefore, the research and development of three-dimensional COFs of polyimides is of great significance to the application of COFs. Summary of the invention

[0003] In view of this, the present application provides an acid compound, a polyimide covalent organic framework, and a preparation method and application thereof. The acid compound can synthesize a polyimide covalent organic framework with a three-dimensional structure, which is beneficial to the use of the polyimide covalent organic framework.

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

[0005]

[0006] Wherein, R1 is selected from a substituted or unsubstituted arylene group or a substituted or unsubstituted heteroarylene group, and X is selected from a chlorine atom, a bromine atom or an iodine atom.

[0007] Optionally, the substituted or unsubstituted arylene group is a substituted or unsubstituted C6~C 30 arylene group.

[0008] Optionally, the substituted or unsubstituted heteroarylene group is a substituted or unsubstituted C2-C 30 The heteroarylene group.

[0009] Optionally, the acid compound includes at least one of the compounds represented by formula (I-1) to formula (I-3),

[0010]

[0011]

[0012] In a second aspect, the present application provides a polyimide covalent organic framework, wherein the polyimide covalent organic framework comprises a repeating unit 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, bromine or iodine atoms.

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

[0016] In a third aspect, the present application provides a method for preparing an acid compound, comprising:

[0017] R3-O-R1-Mg-X1 is mixed with phosphorus trichloride, and subjected to a first reaction to obtain a compound represented by formula (III-1), wherein R1 is selected from a substituted or unsubstituted arylene group, or a substituted or unsubstituted heteroarylene group, R3 is selected from a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group, and X1 is selected from a chlorine atom, a bromine atom, or an iodine atom,

[0018]

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

[0020]

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

[0022]

[0023] The compound represented by formula (III-3) is mixed with 4-nitrophthalonitrile, and a compound represented by formula (III-4) is obtained by a third reaction.

[0024]

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

[0026]

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

[0028] Optionally, the reaction temperature of the first reaction is 0°C to 80°C, and the reaction time is 10h to 20h.

[0029] Optionally, the coupling reaction liquid also includes a first catalyst, which includes at least one of a palladium catalyst and a nickel catalyst, the palladium catalyst includes at least one of bis(3,5,3',5'-dimethoxydibenzylideneacetone)palladium, di(tri-tert-butyl)palladium, tridibenzylideneacetonepalladium, palladium chloride, palladium acetate, tetrakis(triphenylphosphine)palladium and di(tri-tert-butylphosphine)palladium, and the nickel catalyst includes at least one of [1,1'-bis(diphenylphosphino)ferrocene]dichloronickel and bis(1,5-cyclooctadiene)nickel.

[0030] Optionally, the reaction temperature of the coupling reaction is 80°C to 120°C, and the reaction time is 8h to 16h.

[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°C to 110°C, and the reaction time is 10h to 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°C to 120°C, and the reaction time is 4h to 8h.

[0035] Optionally, the reaction temperature of the hydrolysis reaction is 50°C to 100°C, and the reaction time is 8h to 14h.

[0036] In a fourth aspect, the present application provides a method for preparing a polyimide covalent organic framework, comprising mixing the acid compound described in the first aspect or the acid compound obtained by the preparation method described in the third aspect with a diamine to form a mixed solution, and performing a fourth reaction to obtain a polyimide covalent organic framework, wherein the polyimide covalent organic framework comprises a repeating unit 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, bromine or iodine atoms.

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

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

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

[0042] Optionally, the mixed liquid further includes a first solvent, and the first solvent includes at least one of 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°C to 240°C, and the reaction time is 24h to 240h.

[0044] Optionally, the fourth reaction further includes a drying treatment, and the drying treatment includes at least one of vacuum drying and supercritical carbon dioxide drying.

[0045] Optionally, the vacuum drying comprises drying at a vacuum degree of 10 -5 Pa~10 -2 Pa, dry at -40℃~160℃ for 5h~24h.

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

[0047] In a fifth aspect, the present application provides the use of the polyimide covalent organic framework as described in the second aspect or the polyimide covalent organic framework prepared by the preparation method described in the fourth aspect in battery separators, insulating films, flame retardants, sound absorbing layers or magnetic absorbing layers.

[0048] The acid compounds provided in the present application can be used to prepare a three-dimensional polyimide covalent organic framework. At the same time, the polyimide covalent organic framework prepared by the acid compounds has phosphorus-containing fulcrums, which can have a flame retardant effect and is more conducive to the use of the polyimide covalent organic framework. DETAILED DESCRIPTION

[0049] The technical solution of the present application will be described clearly and in detail below. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present application.

[0050] The present application provides an acid compound, the structural formula of the acid compound is shown in formula (I),

[0051]

[0052] Wherein, R1 is selected from substituted or unsubstituted arylene or substituted or unsubstituted heteroarylene, and X is selected from chlorine atom, bromine atom or iodine atom. The acid compound provided in the present application can be used in the preparation of polyimide covalent organic framework, and can prepare polyimide covalent organic framework with three-dimensional structure, which is beneficial to the use of polyimide covalent organic framework, and the polyimide covalent organic framework prepared by the acid compound has phosphorus-containing fulcrum, which can play a flame retardant effect, which is more conducive to the widespread use of polyimide covalent organic framework.

[0053] In the present 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, pentphenylene and tetrahydronaphthylene. In one embodiment of the present application, the substituted or unsubstituted arylene is a substituted or unsubstituted C6~C 30 that is, the number of carbon atoms in the arylene group may be 6 to 30. Specifically, the number of carbon atoms in the arylene group may be, but is not limited to, 6, 10, 12, 15, 17, 19, 20, 22, 25, 28, 29 or 30, etc.

[0054] In the present application, a heteroaryl group is an aryl group having at least one oxygen, sulfur or nitrogen, and a heteroarylene group is a divalent heteroaryl group. Specifically, the heteroarylene group may include, but is not limited to, at least one of a pyridylene group, a furylene group, a thienylene group, an indolylene group, a quinolylene group, an imidazolinylene group and a thiazolylene group. In the embodiments of the present application, a substituted or unsubstituted heteroarylene group is a substituted or unsubstituted C2 to C 30 that is, the number of carbon atoms in the heteroarylene group is 2 to 30. Specifically, the number of carbon atoms in the heteroarylene 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 the present application, a substituted group (such as an arylene group, a heteroarylene group) refers to a group substituted by a substituent. In one embodiment, the substituent includes at least one of a halogen, a nitrogen atom, an oxygen atom, a sulfur atom, a hydroxyl, a nitro group, an amine group, a thiol group, a methoxy group, and a cyano group. That is, when R1 is selected from a substituted arylene group, R1 can be substituted by at least one of a halogen, a nitrogen atom, an oxygen atom, a sulfur atom, a hydroxyl, a nitro group, an amine group, a thiol group, a methoxy group, and a cyano group; when R1 is selected from a substituted heteroarylene group, R1 can be substituted by at least one of a halogen, a nitrogen atom, an oxygen atom, a sulfur atom, a hydroxyl, a nitro group, an amine group, a thiol group, a methoxy group, and a cyano group.

[0056] In one embodiment of the present application, the acid compound includes at least one of the compounds represented by formula (I-1) to formula (I-3),

[0057]

[0058] The acid compounds are stable in nature and simple to prepare, which is beneficial to the synthesis and use of the polyimide covalent organic framework.

[0059] The present application provides a method for preparing an acid compound, comprising: mixing R3-O-R1-Mg-X1 with phosphorus trichloride, and obtaining a compound of formula (III-1) through a first reaction; mixing the compound of formula (III-1) with a halogenated substance to form a coupling reaction liquid, and obtaining a compound of formula (III-2) through a coupling reaction; mixing the compound of formula (III-2) with acetic acid and hydrobromic acid, and obtaining a compound of formula (III-3) through a second reaction; mixing the compound of formula (III-3) with 4-nitrophthalonitrile, and obtaining a compound of formula (III-4) through a third reaction; and hydrolyzing the compound of formula (III-4) in an alkaline solution to obtain an acid compound, wherein the acid compound has a structural formula as shown in formula (I); wherein R1 is selected from a substituted or unsubstituted arylene group, or a substituted or unsubstituted heteroarylene group, R3 is selected from a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group, 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 the acid compounds provided in the present application has high preparation efficiency and low process difficulty, and can prepare acid compounds with high purity, which is conducive to the use of the acid compounds.

[0062] In the present application, R3 is selected from substituted or unsubstituted alkyl, or substituted or unsubstituted aryl. In the present application, alkyl is an alkane molecule with one hydrogen atom removed, and may include straight-chain alkyl and branched alkyl. Specifically, the alkyl may include, but is not limited to, 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 an embodiment of the present application, the substituted or unsubstituted alkyl may be a substituted or unsubstituted C1 to C8 alkyl; that is, the number of carbon atoms of the alkyl is 1 to 8. Specifically, the number of carbon atoms of the alkyl may be, but is not limited to, 1, 2, 3, 4, 5, 6, 7 or 8. In one embodiment of the present application, R3 is selected from substituted or unsubstituted C1-C8 alkyl, or substituted or unsubstituted C6-C 30 The substituted groups are as described above and will not be described in detail here.

[0063] In one embodiment of the present application, R3-O-R1-X1 and magnesium are reacted under the action of a third catalyst to generate a Grignard reagent R3-O-R1-Mg-X1 through a fifth reaction. In one embodiment of the present application, the third catalyst includes at least one of iodine and 1,2-dibromoethane. In one embodiment of the present application, the molar ratio of R3-O-R1-X1 to magnesium can be 1:1, which is conducive to the preparation of R3-O-R1-Mg-X1 and can effectively avoid the occurrence of side reactions. In one embodiment of the present application, the reaction temperature of the fifth reaction is 45°C to 55°C, and the reaction time is 30min to 60min, which is conducive to the efficient preparation of R3-O-R1-Mg-X1. Specifically, the reaction temperature of the fifth reaction can be, but not limited to, 45°C, 47°C, 49°C, 50°C, 53°C or 55°C, and the reaction time of the fifth reaction can be, but not limited to, 30min, 40min, 50min or 60min, etc.

[0064] In one embodiment of the present application, the molar ratio of R3-O-R1-Mg-X1 to phosphorus trichloride is (2.9-3.5):1, which is conducive to 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, etc. In one embodiment of the present application, R3-O-R1-Mg-X1 and phosphorus trichloride can be mixed in an ice water bath, so as to effectively avoid the volatilization of phosphorus trichloride, which is conducive to the subsequent reaction.

[0065] In one embodiment of the present application, the reaction temperature of the first reaction is 0°C to 80°C, and the reaction time is 10h to 20h, which is beneficial to 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 may 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 may be, but is not limited to, 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h or 20h, etc.

[0066] In one embodiment of the present application, saturated NH4Cl solution can be used for quenching after the first reaction. In one embodiment of the present application, ethyl acetate or dichloromethane can be used for extraction after the first reaction, and the organic phase can be dried with anhydrous Na2SO4 or anhydrous MgSO4 and then concentrated to obtain the compound represented by formula (III-1), which is beneficial to improve the purity of the compound represented by formula (III-1).

[0067] In one embodiment of the present application, the structural formula of the halide is R4-X, wherein R4 is selected from substituted or unsubstituted alkyl, substituted or unsubstituted alkoxy, substituted or unsubstituted aryl, or substituted or unsubstituted heteroaryl, and X is selected from chlorine atom, bromine atom or iodine atom. In the present application, the alkoxy group is composed of an alkyl group and an oxygen atom, which can be a linear structure, a branched structure or a ring structure. Specifically, the alkoxy group can include but is not limited to at least one of methoxy, ethoxy, propoxy, butoxy, pentyloxy, hexyloxy, and heptyloxy. In one embodiment of the present application, R4 is selected from substituted or unsubstituted C1~C8 alkyl, substituted or unsubstituted C1~C8 alkoxy, substituted or unsubstituted C6~C 30 aryl, or substituted or unsubstituted C2~C 30 The substituted groups are as described above and will not be described again. In one embodiment of the present application, the molar ratio of the compound represented by formula (III-1) and the halide when mixed can be 1:1, which is conducive to the coupling reaction.

[0068] In one embodiment of the present application, the coupling reaction liquid further includes a first catalyst, the first catalyst includes at least one of a palladium catalyst and a nickel catalyst, the palladium catalyst includes at least one of bis(3,5,3',5'-dimethoxydibenzylideneacetone)palladium, di(tri-tert-butyl)palladium, tridibenzylideneacetone palladium, palladium chloride, palladium acetate, tetrakis(triphenylphosphine)palladium and di(tri-tert-butylphosphine)palladium, and the nickel catalyst includes at least one of [1,1'-bis(diphenylphosphino)ferrocene]dichloronickel and bis(1,5-cyclooctadiene)nickel. By adding the first catalyst, the reaction rate of the coupling reaction can be increased, which is beneficial to the preparation of the compound shown in formula (III-2).

[0069] In one embodiment of the present application, the reaction temperature of the coupling reaction is 80°C to 120°C, and the reaction time is 8h to 16h, which is conducive to the efficient preparation of the compound represented by formula (III-2). Specifically, the reaction temperature of the coupling reaction can be, but is not limited to, 80°C, 90°C, 100°C, 110°C or 120°C, and the reaction time of the coupling reaction can be, but is not limited to, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h or 16h, etc.

[0070] In one embodiment of the present application, after the coupling reaction, a saturated Na2SO4 solution can be used for washing, and then ethyl acetate or dichloromethane can be used for extraction, and the organic phase can be dried with anhydrous Na2SO4 or anhydrous MgSO4 and then concentrated to obtain the compound shown in formula (III-1). Impurities such as catalysts can be removed by washing, and extraction and drying are beneficial to improve the purity of the compound shown in formula (III-2).

[0071] In one embodiment of the present 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 is conducive to 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 the present application, the reaction temperature of the second reaction is 60°C to 110°C, and the reaction time is 10h to 15h, which is conducive to 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, etc.

[0073] In one embodiment of the present application, after the second reaction, ethyl acetate or dichloromethane can be used for extraction, the organic phase can be dripped into an alkaline solution, the aqueous phase can be separated, the aqueous phase can be washed with ethyl acetate or dichloromethane, the aqueous phase can be adjusted to acidic, and the compound shown in formula (III-3) can be obtained by filtering. Unreacted acetic acid, hydrobromic acid, etc. can be removed by alkaline solution, and the compound shown in formula (III-3) can be prevented from dissolving in the solution by adjusting the aqueous phase to acidic, which is beneficial to improve 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 10wt% sodium hydroxide solution; when the aqueous phase is adjusted to acidic, the pH value can be less than 5.

[0074] In one embodiment of the present application, the molar ratio of the compound shown in formula (III-3) to 4-nitrophthalonitrile is 1: (2 to 2.5), which is conducive to the preparation of the compound shown in formula (III-4). Specifically, the molar ratio of the compound shown in 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, etc. In one embodiment of the present application, the compound shown in formula (III-3) and 4-nitrophthalonitrile are mixed to form a third reaction solution, and the third reaction solution also includes a second solvent, and the second solvent includes at least one of N, N-dimethylformamide, N, N-dimethylacetamide and N, N-dimethylpyrrolidone, so as to facilitate the dispersion and reaction of the compound shown in formula (III-3) and 4-nitrophthalonitrile.

[0075] In one embodiment of the present application, the reaction temperature of the third reaction is 80°C to 120°C, and the reaction time is 4h to 8h, which is conducive to the efficient preparation of the compound shown in formula (III-4). Specifically, the reaction temperature of the third reaction may be, but is not limited to, 80°C, 90°C, 100°C, 110°C or 120°C, and the reaction time of the third reaction may be, but is not limited to, 4h, 5h, 6h, 7h or 8h, etc. In one embodiment of the present application, column chromatography may be used for purification after the third reaction to improve the purity of the compound shown in formula (III-4) obtained.

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

[0077] The present application provides a polyimide covalent organic framework, wherein the polyimide covalent organic framework comprises a repeating unit represented by 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, bromine or iodine atoms.

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

[0081] In the present application, an alkylene group is a divalent saturated group formed by removing a hydrogen atom from an alkyl group. In one embodiment of the present application, a substituted or unsubstituted alkylene group is a substituted or unsubstituted C1 to C8 alkylene group; that is, the number of carbon atoms of the alkylene group is 1 to 8. Specifically, the number of carbon atoms of the alkylene group may be, but is not limited to, 1, 2, 3, 4, 5, 6, 7 or 8. The arylene group, heteroarylene group, and substituted group are as described above and will not be described in detail here.

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

[0083] In one embodiment of the present application, the dielectric constant of the polyimide covalent organic framework is 1.5 to 3.4. Among them, the dielectric constant of the polyimide covalent organic framework is detected according to ASTM D150-18. The polyimide covalent organic framework provided in the present application is closer to the dielectric constant of air. The polyimide covalent organic framework has a three-dimensional pore structure and good insulation performance, which is conducive to 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 the present application, the dielectric constant of the polyimide covalent organic framework can be 1.5 to 2.5.

[0084] In one embodiment of the present application, the 5% decomposition temperature of the polyimide covalent organic framework is 450°C to 600°C. Among them, the 5% decomposition temperature is the temperature corresponding to when 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 the present application is relatively high, that is, the polyimide covalent organic framework has good high temperature resistance and high structural stability, which is conducive to 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 the present 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, etc.

[0086] The present application provides a method for preparing a polyimide covalent organic framework, comprising mixing an acid compound in any of the above embodiments with a diamine to form a mixed solution, and obtaining a polyimide covalent organic framework through a fourth reaction, wherein the polyimide covalent organic framework comprises a repeating unit represented by formula (II).

[0087] In one embodiment of the present application, the structural formula of the diamine is H2N-R2-NH2. Two carboxyl groups are connected to each benzene ring in the acid compound structural formula. In the fourth reaction, one of the two carboxyl groups reacts with the diamine to form an amide group-containing portion, and the amide group-containing portion reacts with the other of the two carboxyl groups to form a ring to form an imide group-containing portion; it can be understood that the carboxyl groups in the four benzene rings in the acid compound structural formula are subjected to the above process to obtain a polyimide covalent organic framework.

[0088] In one embodiment of the present application, the molar ratio of the acid compound to the diamine is 1: (1 to 6), which is conducive to the rapid preparation of the polyimide covalent organic framework. 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, etc. In one embodiment of the present application, the molar ratio of the acid compound to the diamine can be 1: 4.5, which is more conducive to the rapid preparation of the polyimide covalent organic framework.

[0089] In one embodiment of the present application, the mixed solution further includes a second catalyst, and the second catalyst includes at least one of piperidine, isoquinoline, pyridine, potassium hydroxide and sodium hydroxide, which is conducive to 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 the present application, the mixed solution further includes a first solvent, and the first solvent includes at least one of mesitylene, N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, toluene, dioxane, water, benzyl alcohol, ethanol and n-butanol, which is conducive to the mixing and reaction of the acid compound and the diamine. In one embodiment of the present application, the first solvent can be a mixed solvent of water and n-butanol in a volume ratio of 2:1.

[0091] In one embodiment of the present application, the reaction temperature of the fourth reaction is 120°C to 240°C, and the reaction time is 24h to 240h, which is conducive to the preparation of the polyimide covalent organic framework. Specifically, the reaction temperature of the fourth reaction may be, but is not limited to, 120°C, 150°C, 160°C, 170°C, 190°C, 200°C, 210°C or 240°C, and the reaction time of the fourth reaction may be, but is not limited to, 24h, 48h, 96h, 120h, 148h, 172h, 196h, 220h or 240h, etc. In one embodiment of the present application, the fourth reaction may be carried out in a reaction device, and the reaction device may be a glass sealed tube, a hydrothermal reactor, etc. In one embodiment of the present application, the mixed solution is placed in a reaction device, and the mixture is sealed after freeze-thaw degassing, and the polyimide covalent organic framework is obtained by the fourth reaction.

[0092] In one embodiment of the present application, washing is further performed after the fourth reaction to remove impurities. In one embodiment of the present application, the product obtained by the fourth reaction is soaked in N,N-dimethylformamide, N,N-dimethylacetamide or N,N-dimethylpyrrolidone for 5h to 8h (such as 5h, 6h, 7h or 8h, etc.), and then soaked in methanol, tetrahydrofuran, acetone, ethyl acetate, ethanol or 1,4-dioxane for 5h to 8h (such as 5h, 6h, 7h or 8h, etc.), and then Soxhlet extraction is performed with tetrahydrofuran and acetone for 24h to 48h (such as 24h, 30h, 36h, 42h or 48h, etc.).

[0093] In one embodiment of the present application, the fourth reaction further includes a drying process. The drying process can be performed after the fourth reaction or after washing. In one embodiment of the present application, the drying process includes at least one of vacuum drying and supercritical carbon dioxide drying. In one embodiment of the present application, the vacuum drying includes drying the mixture at a vacuum degree of 10 -5 Pa~10 -2 Pa (such as 10 -5 Pa, 10 -4 Pa, 10 -3 Pa or 10 -2The method comprises the following steps: drying the mixture at -40°C to 160°C (such as -40°C, -30°C, -20°C, 0°C, 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, 90°C, 100°C, 110°C, 120°C, 135°C, 150°C or 160°C, etc.) for 5h to 24h (such as 5h, 7h, 10h, 12h, 13h, 15h, 17h, 20h, 22h or 24h, etc.). In one embodiment of the present application, supercritical carbon dioxide drying includes drying for 1h to 8h (such as 1h, 3h, 5h, 6h, 7h or 8h, etc.) at a carbon dioxide flow rate of 40°C to 80°C (such as 40°C, 50°C, 60°C, 70°C or 80°C, etc.), 6MPa to 24MPa (such as 6MPa, 9MPa, 10MPa, 13MPa, 15MPa, 18MPa, 20MPa, 23MPa or 24MPa, etc.) and 15mL / min to 200mL / min (such as 15mL / min, 30mL / min, 50mL / min, 70mL / min, 90mL / min, 120mL / min, 150mL / min, 175mL / min or 200mL / min, etc.).

[0094] The present application provides the use of the polyimide covalent organic framework in any of the above embodiments in a battery separator, an insulating film, a flame retardant, a sound absorbing layer or a magnetic absorption layer. The polyimide covalent organic framework provided in the present application is a three-dimensional porous structure, which can be used in a battery separator, and plays a role in isolating the positive electrode and the negative electrode and preventing the electrons in the battery from passing freely while the ions can pass freely. The dielectric constant of the polyimide covalent organic framework provided in the present application is suitable and is a porous structure, and has good insulation performance, and can be used in an insulating film. For example, the polyimide covalent organic framework can be used as a material for low-dielectric enameled wire, etc. The polyimide covalent organic framework provided in the present application has a phosphorus-containing fulcrum, which can play a flame retardant role, and thus can be used 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 the present application is a three-dimensional porous structure, which can absorb sound and electromagnetics, and is thus used in a sound absorbing layer and a magnetic absorption layer.

[0095] The technical solution of the present application is further illustrated below through specific embodiments and comparative examples.

[0096] Example A1

[0097] A method for preparing an acid compound comprises:

[0098] 3 mol of 4-methoxybromobenzene It reacts with 3 mol of magnesium powder under the initiation of a catalytic amount of iodine to produce a Grignard reagent. 1 mol of phosphorus trichloride was added dropwise in an ice water bath, reacted at 25°C for 10 h, quenched with a saturated ammonium chloride solution, extracted with ethyl acetate, and the organic phase obtained by extraction was dried over anhydrous sodium sulfate and concentrated to obtain compound A1

[0099] Compound A1 was subjected to coupling reaction with 4-methoxybromobenzene under the catalysis of tetrakis(triphenylphosphine)palladium (coupling reaction temperature was 80°C and coupling reaction time was 16h). After the reaction, the mixture was washed with saturated sodium sulfate solution and extracted with ethyl acetate. 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 (the molar ratio of compound A2, acetic acid and hydrobromic acid was 1:20:20, the reaction temperature was 60°C, and the reaction time was 12 h). After the reaction was completed, the mixture was cooled to room temperature and extracted with ethyl acetate. After the organic phase was taken out, a 10 wt% sodium hydroxide solution was slowly added dropwise to separate the aqueous phase. The aqueous phase was washed with dichloromethane 3 times, and then hydrochloric acid was added to adjust the pH to 2, 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, heated to 100°C for 5 h, and the reaction product was cooled to room temperature and purified by column chromatography to obtain compound A4.

[0102]

[0103] Compound A4 was dissolved in a 10 wt% potassium hydroxide solution for hydrolysis (reaction temperature was 100°C, reaction time was 10 h), and then recrystallized with glacial acetic acid to obtain an acid compound.

[0104] The hydrogen nuclear magnetic resonance spectrum data of the acid compounds are 1H NMR (500 MHz, Chloroform-d) δ7.78 (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 comprises:

[0107] 3 mol of 4-bromo-4'-methoxybiphenyl It reacts with 3 mol of magnesium powder under the initiation of a catalytic amount of iodine to produce a Grignard reagent. 1 mol of phosphorus trichloride was added dropwise in an ice water bath, reacted at 0°C for 10 h, quenched with saturated ammonium chloride solution, extracted with ethyl acetate, and the organic phase obtained by extraction was dried with anhydrous sodium sulfate and concentrated to obtain compound B1

[0108] Compound B1 was subjected to coupling reaction with 4-bromo-4'-methoxybiphenyl under the catalysis of tetrakis(triphenylphosphine)palladium (coupling reaction temperature was 120°C and coupling reaction time was 16h). After the reaction, the mixture was washed with saturated sodium sulfate solution and extracted with ethyl acetate. 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 (the molar ratio of compound B2, acetic acid and hydrobromic acid was 1:20:20, the reaction temperature was 80°C, and the reaction time was 12 h). After the reaction was completed and the temperature was cooled to room temperature, the mixture was extracted with ethyl acetate. After the organic phase was taken out, a 10 wt% sodium hydroxide solution was slowly added dropwise to separate the aqueous phase. The aqueous phase was washed with dichloromethane 3 times, and hydrochloric acid was added to adjust the pH to less than 2, and the mixture was 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, heated to 100°C for 5 h, and the reaction product was cooled to room temperature and purified by column chromatography to obtain compound B4.

[0111]

[0112] Compound B4 was dissolved in 10 wt% potassium hydroxide solution for hydrolysis (reaction temperature was 50°C, reaction time was 10 h), and then recrystallized with glacial acetic acid to obtain an acid compound.

[0113] The hydrogen nuclear magnetic resonance spectrum data of the acid compounds are 1H NMR (500 MHz, Chloroform-d) δ7.89-7.84 (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 comprises:

[0116] In a reactor, 0.2 mmol of the acid compound obtained 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 ultrasonication for 5 minutes, a yellow turbid solution was obtained. 0.15 mL of pyridine was added to the reactor as a catalyst. The reactor was placed in a liquid nitrogen bath and quickly frozen at 77K, and degassed by freeze-pump-thaw, cycled three times, and then sealed. The reactor 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 resulting precipitate was filtered and then thoroughly washed with tetrahydrofuran and acetone by Soxhlet extraction for 48 hours. The washed sample was transferred to a vacuum oven and evacuated to 10 at 80°C. -3 Pa, dried for 24 h, and a polyimide covalent organic framework was obtained.

[0117] The structure of the prepared polyimide covalent organic framework was characterized by nuclear magnetic resonance, and the obtained nuclear magnetic resonance hydrogen spectrum results were: 1H NMR (500 MHz, Chloroform-d) δ7.78 (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 comprises:

[0120] In a reactor, 0.2 mmol of the acid compound obtained in Example A2 and 0.6 mmol of p-phenylenediamine were added to a mixed solvent of 2 mL of water and 1 mL of n-butanol. After ultrasonication for 5 minutes, a yellow turbid solution was obtained. 0.15 mL of pyridine was added to the reactor as a catalyst. The reactor was placed in a liquid nitrogen bath and quickly frozen at 77K, and degassed by freeze-pump-thaw, cycled three times, and then sealed. The reactor 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 resulting precipitate was filtered and then thoroughly washed with tetrahydrofuran and acetone by Soxhlet extraction for 48 hours. The washed sample was transferred to a vacuum oven and evacuated to 10 at 80°C. -3 Pa, dried for 24 h, and a polyimide covalent organic framework was obtained.

[0121] The structure of the prepared polyimide covalent organic framework was characterized by nuclear magnetic resonance, and the obtained nuclear magnetic resonance hydrogen spectrum results were: 1H NMR (500MHz, Chloroform-d) δ7.89-7.84 (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 a polyimide, comprising:

[0124] In a reactor, 0.4 mmol of pyromellitic anhydride 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 ultrasonication for 5 minutes, a yellow turbid solution was obtained. 0.15 mL of pyridine was added to the reactor as a catalyst. The reactor was placed in a liquid nitrogen bath and quickly frozen at 77K, and degassed by freeze-pump-thaw, cycled three times, and then sealed. The reactor 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 resulting precipitate was filtered and then thoroughly washed with tetrahydrofuran and acetone by Soxhlet extraction for 48 hours. The washed sample was transferred to a vacuum oven and evacuated to 10 at 80°C. -3 Pa, dried for 24 hours to obtain polyimide.

[0125] Comparative Example 2

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

[0127] In a reactor, 0.2mmol melamine and 0.4mmol terephthalaldehyde were added to a mixed solvent of 2mL water and 1mL n-butanol. After ultrasonication for 5min, a yellow turbid solution was obtained. 0.15mL pyridine was added to the reactor as a catalyst. The reactor was placed in a liquid nitrogen bath and quickly frozen at 77K, and degassed by freeze-pump-thaw, cycled three times, and then sealed. The reactor 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 (10mL) and then soaked and washed twice with acetone (10mL). The resulting precipitate was filtered and then thoroughly washed with tetrahydrofuran and acetone by Soxhlet extraction for 48h. The washed sample was transferred to a vacuum oven and evacuated to 10 at 80°C. -3 Pa, dried for 24 h, and a polyimide covalent organic framework was obtained.

[0128] Performance Testing

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

[0130] Table 1 Performance test results

[0131]

[0132] The closer the dielectric constant is to the dielectric constant of air (1), the more air content there is in the material. Therefore, from the dielectric constant results, it can be seen that the polyimide covalent organic framework prepared in the embodiment of the present application has a large air content, which indirectly reflects that the polyimide covalent organic framework has a three-dimensional pore structure, and the dielectric constant is suitable, and the polyimide covalent organic framework has good insulation. Since the polyimide prepared in Comparative Example 1 is a one-dimensional linear structure, the polyimide covalent organic framework prepared in Comparative Example 2 is a two-dimensional structure, and its dielectric constant is relatively high. At the same time, it can also be seen from the specific surface area results that the polyimide covalent organic framework prepared in the embodiment of the present application has a high specific surface area, while the specific surface areas of Comparative Examples 1 and Comparative Examples 2 are low, indicating that the polyimide covalent organic framework prepared in the embodiment of the present application is a three-dimensional porous structure. The limiting oxygen index refers to the volume fraction concentration of oxygen in a polymer in a mixture of oxygen and nitrogen when it can just support its combustion. It is an index that characterizes the combustion behavior of the material. Materials with a large limiting oxygen index are difficult to burn, and those above 27% are generally considered to be difficult to burn; therefore, the polyimide covalent organic framework prepared in the embodiment of the present application has a high limiting oxygen index, and it has a phosphorus-containing fulcrum and can be used in flame retardants. It can be seen from the 5% decomposition temperature results that, except for Comparative Example 2, the polyimides prepared in other examples have good high temperature resistance and better stability, which is beneficial to their use. In summary, the polyimide covalent organic framework prepared in the embodiment of the present application has a three-dimensional structure and a large specific surface area, good insulation, is difficult to burn, and has good stability, which is beneficial to its use.

[0133] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. An acid compound, characterized in that The structural formula of the acid compound is shown in formula (I), Wherein, R1 is selected from a substituted or unsubstituted arylene group or a substituted or unsubstituted heteroarylene group, and X is selected from a chlorine atom, a bromine atom or an iodine atom.

2. The acid compound according to claim 1, characterized in that The substituted or unsubstituted arylene group is a substituted or unsubstituted C6~C 30 arylene; The substituted or unsubstituted heteroarylene group is a substituted or unsubstituted C2 to C 30 The heteroarylene group.

3. The acid compound according to claim 1, characterized in that The acid compound includes at least one of the compounds represented by formula (I-1) to formula (I-3), 4. A polyimide covalent organic framework, characterized in that: The polyimide covalent organic framework comprises a repeating unit represented by formula (II), 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, bromine or iodine atoms.

5. The polyimide covalent organic framework according to claim 4, characterized in that The number of repetitions of the repeating unit represented by the formula (II) is 10 to 200.

6. A method for preparing an acid compound, characterized in that: include: R3-O-R1-Mg-X1 is mixed with phosphorus trichloride, and subjected to a first reaction to obtain a compound represented by formula (III-1), wherein R1 is selected from a substituted or unsubstituted arylene group, or a substituted or unsubstituted heteroarylene group, R3 is selected from a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group, and X1 is selected from a chlorine atom, a bromine atom, or an iodine atom, The compound represented by formula (III-1) is mixed with a halogenated compound to form a coupling reaction solution, and a coupling reaction is performed to obtain a compound represented by formula (III-2), wherein X is selected from a chlorine atom, a bromine atom or an iodine atom. The compound represented by formula (III-2) is mixed with acetic acid and hydrobromic acid, and subjected to a second reaction to obtain a compound represented by formula (III-3). The compound represented by formula (III-3) is mixed with 4-nitrophthalonitrile, and a compound represented by formula (III-4) is obtained by a third reaction. The compound represented by formula (III-4) is subjected to a hydrolysis reaction in an alkaline solution to obtain an acid compound, the structural formula of which is shown in formula (I).

7. The preparation method according to claim 6, characterized in that: The molar ratio of the R3-O-R1-Mg-X1 to the phosphorus trichloride is (2.9-3.5):1; and / or The reaction temperature of the first reaction is 0°C to 80°C, and the reaction time is 10h to 20h; and / or The coupling reaction solution further includes a first catalyst, the first catalyst includes at least one of a palladium catalyst and a nickel catalyst, the palladium catalyst includes at least one of bis(3,5,3',5'-dimethoxydibenzylideneacetone)palladium, di(tri-tert-butyl)palladium, tridibenzylideneacetonepalladium, palladium chloride, palladium acetate, tetrakis(triphenylphosphine)palladium and di(tri-tert-butylphosphine)palladium, and the nickel catalyst includes at least one of [1,1'-bis(diphenylphosphino)ferrocene]nickel dichloride and bis(1,5-cyclooctadiene)nickel; and / or The reaction temperature of the coupling reaction is 80°C to 120°C, and the reaction time is 8h to 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 reaction temperature of the second reaction is 60°C to 110°C, and the reaction time is 10h to 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°C to 120°C, and the reaction time is 4h to 8h; and / or The reaction temperature of the hydrolysis reaction is 50° C. to 100° C., and the reaction time is 8 h to 14 h.

8. A method for preparing a polyimide covalent organic framework, characterized in that: The method comprises mixing the acid compound according to any one of claims 1 to 3 or the acid compound obtained by the preparation method according to any one of claims 6 to 7 with a diamine to form a mixed solution, and performing a fourth reaction to obtain a polyimide covalent organic framework, wherein the polyimide covalent organic framework comprises a repeating unit represented by formula (II), 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, bromine or iodine atoms.

9. The preparation method according to claim 8, characterized in that: The structural formula of the diamine is H2N-R2-NH2; The molar ratio of the acid compound to the diamine is 1:(1-6); The mixed solution further includes a second catalyst, wherein the second catalyst includes at least one of piperidine, isoquinoline, pyridine, potassium hydroxide and sodium hydroxide; The mixed liquid further includes a first solvent, wherein the first solvent includes at least one of 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° C. to 240° C., and the reaction time is 24 h to 240 h.

10. The preparation method according to claim 8, characterized in that: The fourth reaction further includes a drying process, wherein the drying process includes at least one of vacuum drying and supercritical carbon dioxide drying; The vacuum drying comprises a vacuum degree of 10 -5 Pa~10 -2 Pa, dry at -40℃~160℃ for 5h~24h; The supercritical carbon dioxide drying includes drying for 1 hour to 8 hours at 40° C. to 80° C., 6 MPa to 24 MPa, and a carbon dioxide flow rate of 15 mL / min to 200 mL / min.

11. Use of the polyimide covalent organic framework according to any one of claims 4 to 5 or the polyimide covalent organic framework prepared by the preparation method according to any one of claims 8 to 10 in battery separators, insulating films, flame retardants, sound absorbing layers or magnetic absorbing layers.

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