Hydrogenation degradation method for polyimide

Abstract

The invention discloses a hydrogenation degradation method for polyimide. The polyimide hydrogenation degradation method comprises the following steps: in a hydrogen atmosphere, heating polyimide, a pincerlike manganese catalyst and an alkaline substance in a selected solvent to react, so as to realize degradation of the polyimide, the pincerlike manganese catalyst comprises a tridentate pincerlike manganese complex, and the tridentate pincerlike manganese complex has the following structure: R1 is selected from C1-C20 alkyl groups or aryl groups, and R2, R3 and R4 are selected from H and C1-C20 alkyl groups or aryl groups. Compared with a traditional method, the hydrogenation degradation method for polyimide provided by the invention has the advantages of high reaction activity, mild reaction conditions, good selectivity, high substrate universality, small environmental pollution, simplicity in operation, easiness in industrialization and the like, and has a wide market application prospect.

Description

TECHNICAL FIELD

[0001] The application relates to a polyimide hydrogenation degradation method, in particular to a polyimide hydrogenation degradation method catalyzed by a tridentate pincer-shaped manganese complex, and belongs to the technical field of organic chemistry and polymer material recycling. BACKGROUND

[0002] Polyimide (PI) is a kind of high-performance polymer with imide ring structure in the main chain, which is widely used in aerospace, microelectronic packaging, flexible display substrate and high-temperature filtration membrane fields due to its excellent thermal stability, excellent mechanical strength, chemical corrosion resistance and dielectric properties. According to statistics, the global polyimide annual output has exceeded 100,000 tons, and with the rapid development of emerging industries such as 5G communication and new energy vehicles, its demand is still showing a rapid growth trend. However, the highly cross-linked structure and chemical inertness of polyimide make it difficult to degrade in the natural environment, and after being discarded, it is mostly treated by landfill or incineration, which not only causes resource waste, but also releases toxic gases (such as nitrogen oxides and carbon monoxide), aggravating environmental pollution and carbon emission problems.

[0003] At present, the degradation methods for polyimide mainly include thermal cracking method, strong acid / strong base chemical decomposition method and biological enzymatic hydrolysis method. The thermal cracking method needs to be carried out at a high temperature of 400 DEG C or above, which has high energy consumption and complex products (such as coke and small molecule gas), and it is difficult to recover high-value monomers; the chemical decomposition method often uses corrosive reagents such as concentrated sulfuric acid and sodium hydroxide, which has harsh reaction conditions and produces a large amount of waste liquid, and has significant environmental burden; the biological enzymatic hydrolysis method has mild conditions, but the enzyme activity is easily affected by environmental factors, the degradation efficiency is very low (the period is as long as several months), and it is almost ineffective for highly cross-linked polyimide. Therefore, it is urgent to develop an efficient, green and low-cost polyimide degradation technology. SUMMARY

[0004] The main purpose of the present application is to provide a new method for polyimide hydrogenation degradation catalyzed by a tridentate pincer-shaped manganese complex, so as to fill the gap of the current technology.

[0005] In order to achieve the above-mentioned purpose of the application, the technical scheme adopted by the present application comprises:

[0006] The polyimide hydrogenation degradation method provided by the present application comprises:

[0007] In a hydrogen atmosphere, polyimide, pincer-shaped manganese catalyst and alkaline substance are heated and reacted in a selected solvent, so as to realize the degradation of polyimide;

[0008] The pincer-shaped manganese catalyst comprises a tridentate pincer-shaped manganese complex, and the tridentate pincer-shaped manganese complex has a structure as shown in formula (I):

[0009]

[0010] wherein R 1 is selected from C1-C 20 alkyl or aryl, R 2 , R 3 and R 4 are selected from H, C1-C 20 alkyl or aryl.

[0011] In some embodiments, the polyimide has a structural formula as shown in Formula (II) or Formula (III):

[0012]

[0013] wherein R, R' are selected from any one or more combinations of C1-C 40 aliphatic groups, C6-C 60 aryl groups, and oxygen atoms, and n is 1-500.

[0014] Compared with the prior art, the present application has at least the following advantages:

[0015] 1) The polyimide hydrogenation degradation method provided by the present application fills the gap in the current polyimide hydrogenation degradation method, and improves the shortcomings of other degradation methods such as low efficiency and harsh reaction conditions, and can efficiently degrade polyimide under relatively mild conditions.

[0016] 2) The polyimide hydrogenation degradation method provided by the present application has the advantages of high reaction activity, mild reaction conditions, good selectivity, high substrate universality, small environmental pollution, simple operation, high selectivity and yield, and easy industrialization, and has a broad market application prospect. DETAILED DESCRIPTION

[0017] In recent years, hydrogenation degradation has attracted widespread attention. Hydrogen, as a clean reducing agent, has only water as a byproduct, which meets the principles of green chemistry. However, so far, it has not been possible to achieve efficient degradation of polyimides by hydrogenolysis. Considering that the selection of metal catalysts is crucial for catalytic hydrogenolysis and can directly affect the activity and selectivity of the reaction, it is of great significance to develop a new type of pincer metal catalyst for efficient hydrogenolysis of polyimides. Not only does it open up a new way for the recycling of waste polyimides, but it also provides important theoretical and technical support for solving the problem of high-performance polymer pollution.

[0018] In view of the defects of the prior art, the present inventors have, through long-term research and a large number of practices, come up with the technical solution of the present application, which is mainly to use a synthesized tridentate pincer manganese catalyst with a PNN type quinaldine skeleton for the hydrogenation degradation reaction of polyimide in a hydrogen atmosphere. The technical solution, its implementation process and principles will be further explained as follows.

[0019] As one aspect of the technical solution of the present application, it relates to the application of a class of tridentate pincer manganese complexes as metal catalysts in the hydrogenation degradation of polyimide (i.e. the preparation of polyols and diamines through the hydrogenation reaction of polyimide), wherein the tridentate pincer manganese complexes have a structure as shown in formula (I):

[0020]

[0021] wherein R 1 is selected from any one or combination of C1-C 20 alkyl or aryl groups, R 2 , R 3 and R 4 are selected from any one or combination of H, C1-C 20 alkyl or aryl groups.

[0022] As another aspect of the technical solution of the present application, the preparation method of the tridentate pincer manganese complexes comprises:

[0023] firstly preparing a tridentate pincer ligand having a structure as shown in formula (1);

[0024]

[0025] wherein R 1 is selected from any one or combination of C1-C 20 alkyl or aryl groups, R 2 , R 3 and R 4 are selected from any one or combination of H, C1-C 20 alkyl or aryl groups;

[0026] reacting the tridentate pincer ligand with a metal manganese catalyst precursor to obtain the tridentate pincer manganese complex as shown in formula (I).

[0027]

[0028] wherein R 1 is selected from any one or combination of C1-C 20 alkyl or aryl groups, R 2 , R 3 and R 4 are selected from any one or combination of H, C1-C 20a combination of any one or more of alkyl or aryl groups.

[0029] In some preferred embodiments, the metal manganese catalyst precursor comprises Mn(CO)5Br.

[0030] In some preferred embodiments, the method for preparing the tridentate pincer ligand of the structure shown in formula (1) mainly comprises: in a protective atmosphere, using 8-fluoroquinaldine as a starting material, a series of tridentate pincer ligands with PNN type quinaldine novel skeleton are synthesized through 4-6 steps.

[0031] The ligand structure provided by the application is a PNN type tridentate pincer skeleton based on quinoline skeleton and a corresponding manganese catalyst, and a unique spatial and electronic effect distribution is formed by connecting Csp 2 sites through P atoms and connecting Csp 3 sites through N atoms in the quinoline skeleton, which significantly improves the selectivity of the metal catalyst.

[0032] In some embodiments, a method for preparing a novel tridentate pincer ligand comprises:

[0033] In a protective atmosphere, 8-fluoroquinaldine is reacted with selenium dioxide to obtain substituted 8-fluoroquinoline-2-carboxaldehyde having a structure shown in formula (2);

[0034] After the substituted 8-fluoroquinoline-2-carboxaldehyde is mixed with a primary amine R 3 NH2, a reducing agent is added, then the reaction is quenched, and then Boc2O is added for reaction to obtain a product shown in formula (3);

[0035] The phosphine lithium reagent R 1 R 1 PLi is reacted with the product shown in formula (3) to obtain a product shown in formula (4); and then acid treatment is performed to prepare a tridentate pincer ligand shown in formula (5).

[0036]

[0037] R 1 is selected from C1-C 20 alkyl or aryl groups, R 3 is selected from H or C1-C 20 alkyl or aryl groups.

[0038] In some other embodiments, a method for preparing a tridentate pincer ligand comprises:

[0039] In a protective atmosphere, 8-fluoroquinaldine is reacted with selenium dioxide to obtain substituted 8-fluoroquinoline-2-carboxaldehyde having a structure shown in formula (2);

[0040] reacting the substituted 8-fluoroquinoline-2-carboxaldehyde with a Grignard reagent R 2 MgBr to give an alcohol as shown in formula (6), followed by reaction with a first base to give a chlorine-containing compound as shown in formula (7);

[0041] reacting the chlorine-containing compound as shown in formula (7) with an aminating reagent R 3 R 4 NH, a second base, and an iodine-containing additive to give a product as shown in formula (8);

[0042] reacting a phosphine lithium reagent R 1 R 1 PLi with the product as shown in formula (8) to give a tridentate pincer ligand as shown in formula (1);

[0043]

[0044] wherein R 1 is selected from C1-C 20 alkyl or aryl, R 2 , R 3 , and R 4 are selected from H or C1-C 20 alkyl or aryl, or a combination of any one or more thereof.

[0045] In some preferred embodiments, the above preparation method, the preparation method of the substituted 8-fluoroquinoline-2-carboxaldehyde specifically comprises: heating a mixed reaction system comprising 8-fluoroquinaldine, selenium dioxide, and a first solvent to 50-150°C in a protective atmosphere for 1-24h to obtain the substituted 8-fluoroquinoline-2-carboxaldehyde.

[0046] In some preferred embodiments, the molar ratio of the 8-fluoroquinaldine to the selenium dioxide is 1:0.5-1:10.

[0047] Further, the first solvent can include N,N-dimethylformamide, dichloromethane, methanol, ethanol, isopropanol, acetonitrile, 1,4-dioxane, acetone, tetrahydrofuran, and toluene, or a combination of two or more thereof, but is not limited thereto.

[0048] In some preferred embodiments, the above preparation method specifically comprises: mixing the substituted 8-fluoroquinoline-2-carboxaldehyde with a second solvent, adding a primary amine R 3 NH2, and stirring at room temperature for 12-24h, adding a third solvent and a reducing agent after concentrating the solvent, continuing to stir, quenching the reaction, and then adding Boc2O and reacting at 0-150°C for 1-24h to obtain a product as shown in formula (3).

[0049] In some preferred embodiments, the molar ratio of the substituted 8-fluoroquinoline-2-carboxaldehyde, the primary amine, and the reducing agent is 1:1:1 to 1:5:10.

[0050] Further, the reducing agent can include any one or a combination of two or more of sodium borohydride, sodium cyanoborohydride, sodium acetyl borohydride, lithium borohydride, lithium aluminum hydride, borane, and red aluminum, but is not limited thereto.

[0051] Further, the second solvent can include any one or a combination of two or more of diethyl ether, dichloromethane, N,N-dimethylformamide, methanol, ethanol, isopropanol, acetonitrile, 1,4-dioxane, tetrahydrofuran, and toluene, but is not limited thereto.

[0052] Further, the third solvent can include any one or a combination of two or more of methanol, ethanol, isopropanol, 1,4-dioxane, and tetrahydrofuran, but is not limited thereto.

[0053] In some preferred embodiments, the preparation method specifically includes: mixing the substituted 8-fluoroquinoline-2-carboxaldehyde with a phosphine lithium reagent R 1 R 1 reacting the PLi with a product represented by formula (3) in a fourth solvent at -78 to 150°C for 6 to 48 hours to obtain a product represented by formula (4).

[0054] In some preferred embodiments, the product represented by formula (3) and the phosphine lithium reagent R 1 R 1 The molar ratio of the product represented by formula (3), the phosphine lithium reagent R

[0055] Further, the fourth solvent can include any one or a combination of two or more of diethyl ether, 1,4-dioxane, tetrahydrofuran, but is not limited thereto.

[0056] In some preferred embodiments, the preparation method specifically includes: subjecting the product represented by formula (4) to acid treatment with an N-deprotection reagent to obtain a tridentate pincer ligand represented by formula (5).

[0057] In some preferred embodiments, the molar ratio of the product represented by formula (4), the tridentate pincer ligand represented by formula (5), and the N-deprotection reagent is 1:1:1 to 1:5:10.

[0058] In some preferred embodiments, the preparation method specifically includes: mixing the substituted 8-fluoroquinoline-2-carboxaldehyde with a fifth solvent and then adding a Grignard reagent R 2 MgBr to react to obtain an alcohol represented by formula (6).

[0059] In some preferred embodiments, the molar ratio of the substituted 8-fluoroquinoline-2-carboxaldehyde to the Grignard reagent is 1:0.5-1:10.

[0060] Further, the fifth solvent can include any one or a combination of two or more of diethyl ether, 1,4-dioxane, tetrahydrofuran, etc., but is not limited thereto.

[0061] In some preferred embodiments, the preparation method specifically includes: reacting an alcohol represented by formula (6), thionyl chloride, and a first base to obtain a chlorine-containing compound represented by formula (7), wherein the reaction temperature is 25-150°C, and the reaction time is 1-24 h.

[0062] In some preferred embodiments, the molar ratio of the alcohol represented by formula (6), thionyl chloride, and the first base is 1:1:0.01-1:10:5.

[0063] Further, the first base can include any one or a combination of two or more of triethylamine, triethylene diamine (DABCO), 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 4-dimethylaminopyridine (DMAP), pyridine, potassium tert-butoxide, potassium methoxide, sodium methoxide, potassium ethoxide, sodium ethoxide, etc., but is not limited thereto.

[0064] In some preferred embodiments, the preparation method specifically includes: reacting a chlorine-containing compound represented by formula (7), an aminating reagent R 3 R 4 NH, a second base, and an iodine-containing additive at 0-150°C for 12-24 h to obtain a product represented by formula (8).

[0065] In some preferred embodiments, the molar ratio of the chlorine-containing compound represented by formula (7), the aminating reagent R 3 R 4 NH, the second base, and the iodine-containing additive is 1:1:1:0.01-1:5:10:5.

[0066] Further, the second base can include any one or a combination of two or more of sodium hydroxide, sodium tert-butoxide, potassium tert-butoxide, potassium methoxide, sodium methoxide, potassium ethoxide, sodium ethoxide, sodium carbonate, potassium hydroxide, potassium carbonate, sodium hydride, potassium hydride, and potassium phosphate, etc., but is not limited thereto.

[0067] In some preferred embodiments, the preparation method specifically includes: reacting a phosphorus lithium reagent R 1 R 1 PLi with a product represented by formula (8) in a fourth solvent at -78-150°C for 6-48 h to obtain a tridentate pincer ligand represented by formula (1).

[0068] In some preferred embodiments, the molar ratio of the product represented by formula (8) to the lithium phosphine reagent is 1:0.5 to 1:10.

[0069] In some more specific embodiments, the method for preparing a tridentate pincer ligand having a structure as shown in formula (5) comprises:

[0070] In a protective atmosphere, heating a mixed reaction system comprising 8-fluoroquinaldine, selenium dioxide, and the first solvent to 50-150° C. for 1-24 hours to obtain a substituted 8-fluoroquinoline-2-carboxaldehyde;

[0071] The substituted 8-fluoroquinoline-2-carboxaldehyde is mixed with a second solvent, and a primary amine R is added. 3 NH2 and stirred at room temperature for 12 to 24 hours. After concentrating the solvent, add the third solvent and the reducing agent, continue stirring and quench the reaction. After post-treatment, the crude secondary amine product is obtained. Boc2O is added and reacted at 0 to 150 ° C for 1 to 24 hours to obtain the product shown in formula (3). 1 R 1 PLi reacts with the product of formula (3) in a fourth solvent at -78 to 150°C for 6 to 48 hours to obtain a product of formula (4). After acid treatment and deprotection, a novel tridentate pincer ligand of formula (5) is obtained.

[0072]

[0073] Among them, R 1 Selected from C1-C 20 Alkyl or aryl, R 3 Selected from H or C1-C 20 any one or more combinations of alkyl or aryl groups.

[0074] In some more specific embodiments, the method for preparing a tridentate pincer ligand having a structure as shown in formula (1) comprises:

[0075] In a protective atmosphere, heating a mixed reaction system comprising 8-fluoroquinaldine, selenium dioxide, and the first solvent to 50-150° C. for 1-24 hours to obtain a substituted 8-fluoroquinoline-2-carboxaldehyde;

[0076] The 8-fluoroquinoline-2-carboxaldehyde is mixed with the fifth solvent and then the Grignard reagent R is added at -78 to 50°C. 2 MgBr, to obtain the corresponding alcohol shown in formula (6); then the alcohol is reacted with dichlorothionyl and the first base to obtain the chlorine-containing compound shown in formula (7). 3 R 4NH, a second base, an iodine-containing additive at 0-150°C for 12-24 hours to obtain a product shown as formula (8). A phosphine lithium reagent R 1 R 1 PLi and the product shown as formula (8) are reacted in a fourth solvent at -78-150°C for 6-48 hours to obtain a novel tridentate pincer ligand shown as formula (1).

[0077]

[0078] wherein, R 1 is selected from C1-C 20 alkyl or aryl, R 2 , R 3 and R 4 are selected from any one or more combinations of H or C1-C 20 alkyl or aryl.

[0079] Specifically, the synthesis method of the tridentate pincer ligand shown as formula (1) or formula (5) comprises the following steps:

[0080]

[0081] Further, R 1 is selected from phenyl, R 2 and R 4 are hydrogen, R 3 is benzyl, the structural formula of the ligand is:

[0082]

[0083] And its nuclear magnetic and high-resolution characterization data are: 1 H NMR (400 MHz, CDCl3) δ 8.08 (d, J = 8.4 Hz, 1H), 7.78 (d, J = 8.4 Hz, 1H), 7.40-7.19 (m, 17H), 7.10-7.07 (m, 1H), 3.92 (s, 2H), 3.56 (s, 2H), 2.45 (br, 1H); 13 C NMR (151 MHz, CDCl3) δ 159.1, 148.7 (d, J = 15.9 Hz), 140.3, 138.6 (d, J = 12.1 Hz), 137.7 (d, J = 10.0 Hz), 136.6, 134.4 (d, J = 20.7 Hz), 133.9, 128.7, 128.6 (d, J = 7.2 Hz), 128.4 (d, J = 5.1 Hz), 126.9 (d, J = 2.4 Hz), 126.2, 121.1, 54.1, 53.0; 31P NMR (243 MHz, CDCI3) δ -13.2; HRMS (ESI) calcd for C 29 H 26 N2P[M+H]: 433.1834, found: 433.1819.

[0084] Further, R 1 is selected from phenyl, R 2 and R 4 is hydrogen, R 3 is cyclohexyl, the structure of the ligand is:

[0085]

[0086] and its NMR and high resolution characterization data are: 1 H NMR (400 MHz, CDCI3) δ 8.12 (d, J = 8.0 Hz, 1H), 7.80 (d, J = 8.0 Hz, 1H), 7.41 - 7.29 (m, 12H), 7.09 - 7.06 (m, 1H), 4.08 (s, 2H), 2.44 - 2.39 (m, 1H), 1.76 - 1.53 (m, 5H), 1.15 - 0.96 (m, 5H); 13 C NMR (151 MHz, CDCI3) δ 148.5 (d, J = 15.9 Hz), 138.2 (d, J = 12.4 Hz), 137.5 (d, J = 10.6 Hz), 137.1, 134.4 (d, J = 20.4 Hz), 128.8, 128.6 (d, J = 7.4 Hz), 128.5, 127.0, 126.5, 120.8, 57.0, 51.4, 32.6, 25.9, 25.0; 31 P NMR (162 MHz, CDCI3) δ -13.7; HRMS (ESI) calcd for C 28 H 30 N2P[M+H]: 425.2147, found: 425.2139.

[0087] Further, R 1 is selected from phenyl, R 2 is methyl, R 3 is cyclohexyl, R 4 is hydrogen, the structure of the ligand is:

[0088]

[0089] and its NMR characterization data are: 1H NMR (400 MHz, CDC13) δ 8.09 (d, J = 8.4 Hz, 1H), 7.78 (d, J = 8.0 Hz, 1H), 7.38-7.30 (m, 12H), 7.08-7.05 (m, 1H), 4.02 (q, J = 6.8 Hz, 1H), 2.11-2.05 (m, 1H), 1.80-1.76 (m, 1H), 1.62-1.42 (m, 4H), 1.16 (d, J = 6.4 Hz, 3H), 1.04-0.86 (m, 5H); 13 CNMR (151 MHz, CDC13) δ 148.6, 148.4, 138.6, 138.5, 138.0, 137.8, 137.7, 136.4, 134.4, 134.3, 134.2, 134.1, 133.7, 128.4, 128.4, 128.3, 128.2, 126.7, 125.9, 120.1, 55.7, 54.4, 33.9, 33.0, 26.1, 25.2, 25.0, 23.4; 31 PNMR (162 MHz, CDC13) δ -13.2; HRMS (ESI) calcd. for C 28 H 30 N2P[M+H]: 439.2303, found: 439.2284.

[0090] In some more preferred embodiments, the tridentate pincer ligand having the structure of formula (5) comprises the following specific reaction steps:

[0091] The 8-fluoroquinaldine, selenium dioxide and a first solvent are added to a reaction flask under nitrogen protection, and the reaction is carried out at 50-150°C for 1-24 hours. After cooling, filtration is performed, and column chromatography is used to separate to obtain the substituted 8-fluoroquinoline-2-carboxaldehyde shown in formula (2). Subsequently, the substituted 8-fluoroquinoline-2-carboxaldehyde, the primary amine R 3 NH2and a second solvent are added to the reaction flask, and stirring is performed at room temperature for 12-24 hours. After concentration of the solvent, a third solvent and a reducing agent are added, and stirring is continued, and then the reaction is quenched. After work-up, the secondary amine crude product is obtained, Boc20 is added, and the reaction is carried out at 0-150°C for 1-24 hours to obtain the product shown in formula III. The in-situ prepared phosphine lithium reagent R 1 R 1 The PLi is reacted with the product shown in formula (3) in a fourth solvent at -78-150°C for 6-48 hours to obtain the product shown in formula (4). After treatment with trifluoromethanesulfonic acid, deprotection is performed to obtain the novel tridentate pincer ligand shown in formula (5).

[0092] In some more preferred embodiments, the tridentate pincer ligand having the structure of formula (1) comprises the following specific reaction steps:

[0093] Under nitrogen protection, 8-fluoroquinaldine, selenium dioxide and a first solvent are added to a reaction bottle, and the reaction is carried out at 50-150°C for 1-24 hours. After cooling, filtration is performed, and column chromatography is used to separate to obtain a substituted 8-fluoroquinoline-2-carboxaldehyde shown in formula (2). Under nitrogen protection, the substituted 8-fluoroquinoline-2-carboxaldehyde is mixed with a fifth solvent, and Grignard reagent R 2 MgBr is added at -78-50°C to obtain the corresponding alcohol shown in formula (6). Then, the alcohol is reacted with dichlorosulfoxide and a first base to obtain a chlorine-containing compound shown in formula (7). The chlorine-containing compound is reacted with an aminating agent R 3 R 4 NH, a second base, and an iodine-containing additive at 0-150°C for 12-24 hours to obtain a product shown in formula (8). A lithium phosphide reagent R 1 R 1 PLi is reacted with the product shown in formula (8) in a fourth solvent at -78-150°C for 6-48 hours to obtain a novel tridentate pincer ligand shown in formula (1).

[0094] In some preferred embodiments, the preparation method specifically comprises: mixing the tridentate pincer ligand and a metal manganese catalyst precursor in a sixth solvent, and heating to react to obtain a novel tridentate pincer manganese complex. Specifically, the reaction process is as follows:

[0095]

[0096] In some preferred embodiments, the molar ratio of the tridentate pincer ligand to the metal manganese catalyst precursor is 1:2-10:1, preferably 1:1-3:1.

[0097] Further, the sixth solvent can include any one or a combination of two or more of tetrahydrofuran, toluene, benzene, dichloromethane, methanol, ethanol, isopropanol, diethyl ether, n-hexane, and 1,4-dioxane, but is not limited thereto.

[0098] In some preferred embodiments, the reaction temperature is 25-150°C, preferably 50-110°C, and the reaction time is 6-36 hours.

[0099] In some more preferred embodiments, the preparation method comprises the following specific reaction steps: under a nitrogen atmosphere, a tridentate pincer ligand shown in formula (1), a metal manganese catalyst precursor, and a sixth solvent are added to a reaction bottle, and heated to react for 6-36 hours. After returning to room temperature, concentration, washing, centrifugation, concentration, and other steps are performed to obtain a target tridentate pincer manganese complex shown in formula (I).

[0100] As a preferred technical solution, the preparation method comprises: adding a trident pincer-shaped ligand and a metal manganese catalyst precursor Mn(CO) 5 Br into a reaction bottle, and heating to 25-150 DEG C for 6-36 hours. After the reaction is completed, the temperature is lowered to room temperature, the solvent is pumped dry, the reaction bottle is transferred into a glove box and a solvent is added for washing, centrifuged, and concentrated to obtain an orange solid, i.e. a trident pincer-shaped manganese complex having a structure as shown in formula (I).

[0101] In summary, the trident pincer-shaped manganese complex prepared by the present application has a brand-new skeleton structure, and has shown excellent catalytic activity in a polyimide hydrogenation degradation reaction through preliminary testing. The preparation method is mild in conditions, simple in operation, and easy to industrialize, and the obtained pincer-shaped manganese catalyst will have a broad application prospect in the future. Further, the preparation route of the metal pincer-shaped manganese catalyst used by the present application is clear, which improves the operability of the present application to some extent.

[0102] As another aspect of the technical solution of the present application, a polyimide hydrogenation degradation method comprises:

[0103] In a hydrogen atmosphere at a certain pressure, polyimide, pincer-shaped manganese catalyst and basic substance are heated to react in a selected solvent, so as to realize degradation of the polyimide;

[0104] The pincer-shaped manganese catalyst comprises a trident pincer-shaped manganese complex having a structure as shown in formula (I):

[0105]

[0106] wherein, R 1 is selected from C1-C 20 alkyl or aryl, R 2 , R 3 and R 4 are selected from H, C1-C 20 alkyl or aryl.

[0107] In some embodiments, the polyimide has a structural formula as shown below:

[0108]

[0109] wherein, R, R' are selected from any one or a combination of C1-C 40 aliphatic groups, C6-C 60 aryl groups and oxygen atoms, and n has a value of 1-500.

[0110] In some preferred embodiments, the polyimide hydrogenolysis method specifically comprises: heating and reacting polyimide, pincer manganese catalyst and alkaline substance in a selected solvent in a hydrogen atmosphere, so as to realize the degradation of polyimide and prepare polyol compounds and diamine compounds;

[0111] The structural formula of the polyol compound is The structural formula of the diamine compound is

[0112] wherein R and R' are independently selected from any one or a combination of C1-C 40 aliphatic groups, C6-C 60 aromatic groups, and oxygen atoms.

[0113] The aforementioned pincer manganese catalyst can efficiently catalyze the degradation of polyimide represented by the following formula. The polyimide hydrogenolysis reaction formula is as follows:

[0114]

[0115] The catalytic mechanism of the hydrogenolysis reaction of the present application is that, unlike polyester hydrogenolysis which mainly targets the cleavage of ester bonds (C-O bonds) to generate alcohol and carboxylic acid derivatives, polyimide hydrogenolysis faces the problem of selective cleavage of more complex chemical bonds, and needs to precisely control the cleavage process of C-N bonds and C=O bonds in the imide ring. More importantly, the polyol and diamine in the polyimide hydrogenolysis product will tightly bind to the active center of the metal catalyst through chelation, resulting in catalyst deactivation. However, the pincer manganese catalyst of the present application can avoid this problem, which is an important technical difficulty that needs to be overcome in the present application.

[0116] In some preferred embodiments, the reaction step of the polyimide hydrogenolysis method is specifically:

[0117] In a glove box, the aforementioned pincer manganese catalyst, alkaline substance and selected solvent are added to a reaction bottle, stirred, and then polyimide is added. The reaction bottle is placed in a high-pressure reaction kettle and removed from the glove box. Hydrogen gas with a certain pressure is added to the high-pressure kettle, and stirred at a certain temperature for 1-120 hours. After the reaction is completed, the target product polyol and diamine are obtained by column chromatography.

[0118] In some preferred embodiments, the molar ratio of polyimide, pincer manganese catalyst and alkaline substance is 1:0.0001:0.0001-1:0.1:0.3.

[0119] In some preferred embodiments, the heating reaction temperature is 25-200°C, preferably 30-150°C, and the reaction time is 1-120h.

[0120] In some preferred embodiments, the pressure of the hydrogen atmosphere is 1-100 bar.

[0121] In some preferred embodiments, the basic substance includes any one or a combination of two or more of potassium tert-butoxide, sodium tert-butoxide, sodium ethoxide, sodium methoxide, sodium hydride, potassium hydride, potassium ethoxide, potassium methoxide, potassium phosphate, potassium bis(trimethylsilyl)amide, sodium bis(trimethylsilyl)amide, lithium bis(trimethylsilyl)amide, etc., but is not limited thereto.

[0122] In some preferred embodiments, the selected solvent includes any one or a combination of two or more of methanol, ethanol, isopropanol, tetrahydrofuran, toluene, n-hexane, benzene, n-propanol, 1,4-dioxane, dimethyl sulfoxide, dimethylbenzene, anisole, ethylene glycol dimethyl ether, mesitylene, etc., but is not limited thereto.

[0123] Further, the yield of the polyol compound is 50% or more, and the yield of the diamine compound is 50% or more.

[0124] In summary, the polyimide degradation method provided by the present application has the advantages of high catalytic activity, mild reaction conditions, high yield, small environmental pollution, simple operation, easy industrialization, etc., fills the blank of the previous polyimide hydrogenation degradation, and will have a broad market application prospect in the future.

[0125] The technical solutions of the present application will be further explained and described below in combination with several preferred embodiments. Those skilled in the art can easily understand that the embodiments are only to help understand the present application and should not be regarded as specific limitations on the present application.

[0126] In the following examples, the experimental materials used are commercially available from conventional biochemical reagent companies, unless otherwise specified.

[0127] The synthesis of the tridentate pincer manganese complex [Mn]-1 (i.e., manganese catalyst-1) used in the following Examples 1-15 is as follows:

[0128]

[0129] The specific steps are as follows:

[0130] Under nitrogen protection, 8-fluoroquinaldine (5.3 g, 33.0 mmol), selenium dioxide (7.3 g, 66.0 mmol) and 1,4-dioxane (60 mL) were added to a reaction bottle, and the reaction was carried out at 80°C for 4 hours. After cooling, filtration and concentration, column chromatography was performed to obtain S-2 (4.7 g, yield 81%).

[0131] S-2 (4.9 g, 28.0 mmol), cyclohexylamine (3.1 g, 30.8 mmol) and toluene (25 mL) were added to a reaction flask under nitrogen protection and stirred at room temperature for 12 hours. The solvent was removed by concentration to obtain the crude product which was dissolved in methanol (60 mL). After the addition of NaBH4(1.3 g, 33.6 mmol) in portions, it was stirred for 4 hours. Then the reaction was quenched with saturated ammonium chloride solution. The solvent was removed by concentration and the product was extracted with ethyl acetate. The organic phase was combined, dried over anhydrous sodium sulfate and concentrated to obtain the crude product. Then it was dissolved in dichloromethane (30 mL), DMAP (341.6 mg, 2.8 mmol) and Boc20 (9.2 g, 42.0 mmol) were added and reacted at room temperature for 12 hours. Then the reaction was quenched with saturated ammonium chloride, concentrated and column chromatographed to obtain S-3 (8.6 g, yield 86%).

[0132] Ph2PH (4.0 g, 21.5 mmol) and tetrahydrofuran (40 mL) were added to a reaction flask under nitrogen protection and cooled to -78 °C. Then n-butyllithium (8.6 mL, 21.5 mmol) was added, followed by stirring at room temperature for 1 hour, cooling to -78 °C again and adding the THF (10 mL) solution of S-3 described above, followed by warming to 60 °C and reacting for 12 hours. After the reaction was completed, the solvent was concentrated and column chromatographed to obtain S-4 (8.0 g, yield 71%) as a white solid.

[0133] S-4 (315 mg, 0.6 mmol) and dichloromethane (5 mL) were added to a reaction flask under nitrogen protection, followed by the addition of trifluoroacetic acid (1 mL) and reaction at room temperature for 4 hours. The solvent was removed by concentration and the excess acid was removed with NaOH (aq. 2M solution). Then it was extracted with dichloromethane, the organic phase was combined, dried over anhydrous sodium sulfate and concentrated to obtain the crude product which was directly used in the next step.

[0134] The crude product of the previous step was dissolved in THF (5 mL) and transferred into a reaction flask under nitrogen protection. Then Mn(CO)5Br (138 mg, 0.5 mmol) was added as a catalyst precursor of metallic manganese and heated to 70 °C for 12 hours. After the reaction was completed, the temperature was lowered to room temperature, the solvent was removed by suction and the reaction flask was transferred into a glove box. Then ether was added for washing, centrifuged, concentrated and orange-red solid [Mn]-1 (295.3 mg, yield 96%) was obtained, which was a novel tridentate pincer manganese complex.

[0135] The inventors of the present case also characterized the orange-red solid [Mn]-1 by nuclear magnetic resonance, high resolution and the like, and the data are as follows: 1H NMR (400 MHz, CDC13) δ 8.26 (s, 1H), 8.13-8.05 (m, 4H), 7.76 (s, 1H), 7.49 (br, 1H), 7.40 (s, 3H), 7.27 (br, 3H), 7.20-7.16 (m, 2H), 4.39 (s, 2H), 4.21 (br, 1H), 2.91-2.86 (m, 1H), 2.26-2.23 (m, 1H), 2.19-2.16 (m, 1H), 1.92-1.80 (m, 4H), 1.72-1.68 (m, 1H), 1.39-1.27 (m, 3H); 13 C NMR (151 MHz, CDC13 / CD30D) δ 231.7, 230.4, 165.9, 161.8, 152.4 (d, J = 22.2 Hz), 137.6 (d, J = 27.3 Hz), 136.9, 134.8 (d, J = 23.6 Hz), 134.8 (d, J = 9.8 Hz), 133.2, 132.9, 132.5, 131.2 (d, J = 10.3 Hz), 130.9, 130.0 (d, J = 2.4 Hz), 129.1, 128.6, 128.1 (d, J = 9.1 Hz), 127.9 (d, J = 9.7 Hz), 127.5 (d, J = 4.8 Hz), 120.2, 119.0, 62.8 (m), 59.4, 57.8, 32.2 (d, J = 45.9 Hz), 25.5 (m); 31 P NMR (162 MHz, CDC13) δ 85.5. HRMS (ESI) calcd. for MnC 30 H 29 N2O2P[M-Br]: 535.1347, found: 535.1337. IR (vco) = 1906.6, 1824.4 cm -1 .

[0136] The synthesis method of the manganese catalyst-2 ([Mn]-2) used in Example 16 is as follows:

[0137] Compared with the synthesis method of the product [Mn]-1, the preparation of [Mn]-2 is different in that cyclohexylamine is replaced by benzylamine. The structure of the obtained product [Mn]-2 is as follows:

[0138]

[0139] The present inventors also carried out nuclear magnetic, high resolution and other characterizations on the product, and the data are as follows: 1H NMR (400 MHz, CDC13) δ 8.20 (d, J = 2.8 Hz, 1H), 8.10 - 8.01 (m, 4H), 7.74 (s, 1H), 7.44 - 7.35 (m, 8H), 7.31 - 7.29 (m, 4H), 7.25 - 7.20 (m, 2H), 4.90 (d, J = 13.6 Hz, 1H), 4.44 (s, 1H), 4.23 - 4.19 (m, 1H), 4.11 - 3.98 (m, 2H); 13 C NMR (101 MHz, CDC13) δ 231.2, 229.5 (d, J = 17.8 Hz), 161.7 (d, J = 3.6 Hz), 152.5 (d, J = 22.2 Hz), 138.3, 138.0, 137.3, 137.1 (d, J = 3.9 Hz), 136.8, 134.9 (d, J = 10.1 Hz), 133.4, 133.2, 131.5 (d, J = 10.7 Hz), 130.9, 130.2 (d, J = 2.3 Hz), 129.3, 129.2, 128.9, 128.5, 128.3 (d, J = 9.7 Hz), 128.1 (d, J = 9.8 Hz), 127.7 (d, J = 4.5 Hz), 118.8, 61.4, 59.2; 31 P NMR (162 MHz, CDC13) δ 83.7. HRMS (ESI) calcd. for MnC 31 H 25 N2O2P[M-Br]: 543.1034, found: 543.1018. IR (vco) = 1923, 1843 cm-1.

[0140] The synthesis method of manganese catalyst-3 ([Mn]-3) used in Example 17 is as follows:

[0141] Compared with the synthesis method of product [Mn]-1, the preparation of [Mn]-3 is different in that cyclohexylamine is replaced by isopropylamine, and the final product tridentate pincer manganese complex [Mn]-3 has the following structural formula:

[0142]

[0143] The structure of manganese catalyst-4 ([Mn]-4) used in Example 18 is as follows:

[0144]

[0145] The structure of manganese catalyst-5 ([Mn]-5) used in Example 19 is as follows:

[0146]

[0147] The structure of the manganese catalyst-6 ([Mn]-6) employed in Example 20 is:

[0148]

[0149] Example 1

[0150] The tridentate pincer manganese complex [Mn]-1 (i.e. manganese catalyst-1) was used for the hydrodegradation of polyimide, the reaction process was as follows:

[0151]

[0152] In the glove box, manganese catalyst-1 (3.0 mol%), potassium tert-butoxide (9.0 mol%), methanol (1.0 mL) and toluene (0.5 mL) were added to the reaction bottle, after stirring for 10 minutes, polyimide-1 (0.2 mmol) was added. The reaction bottle was placed in an autoclave, and the autoclave was removed from the glove box. 50 bar of hydrogen was added to the autoclave, and the reaction was carried out at 100°C for 48 hours. After the reaction was completed, column chromatography was carried out to obtain the product polyol 1 with a yield of 93% and diamine 2 with a yield of 95%.

[0153] The nuclear magnetic resonance and high resolution characterization of the product polyol 1 were tested as follows: 1 H NMR (400 MHz, DMSO-d6) δ 7.50-7.48 (m, 4H), 7.19 (d, J = 8.4 Hz, 2H), 5.26-5.22 (m, 4H), 4.56 (d, J = 5.6 Hz, 8H); 13 C NMR (101 MHz, DMSO-d6) δ 140.3, 130.8, 127.8, 127.0, 126.5, 59.8 (d, J = 12.6 Hz), 48.6; 19 F NMR (377 MHz, DMSO-d6) δ -62.8. HRMS (ESI) calcd. for C 19 H 18 F6O4Na: 447.1007, found: 447.0984.

[0154] Example 2

[0155] The tridentate pincer manganese complex [Mn]-1 (i.e. manganese catalyst-1) was used for the hydrodegradation of polyimide, the reaction process was as follows:

[0156]

[0157] In a glove box, manganese catalyst-1 (1.0 mol%), potassium tert-butoxide (3.0 mol%), methanol (1.0 mL) and toluene (0.5 mL) were added to a reaction vial and stirred for 10 min before adding polyimide-1 (0.2 mmol). The reaction vial was placed in a high pressure vessel and the high pressure vessel was removed from the glove box. Hydrogen gas was added to the high pressure vessel at 50 bar and the reaction was carried out at 100 °C for 48 h. After the reaction was completed, the product polyol 1 was obtained in 92% yield and diamine 2 was obtained in 93% yield after column chromatography.

[0158] Example 3

[0159] The tridentate pincer manganese complex [Mn]-1 (i.e. manganese catalyst-1) was used for the hydrodegradation of polyimides with the following reaction procedure:

[0160]

[0161] In a glove box, manganese catalyst-1 (3.0 mol%), potassium tert-butoxide (9.0 mol%), methanol (1.0 mL) and toluene (0.5 mL) were added to a reaction vial and stirred for 10 min before adding polyimide-2 (0.2 mmol). The reaction vial was placed in a high pressure vessel and the high pressure vessel was removed from the glove box. Hydrogen gas was added to the high pressure vessel at 50 bar and the reaction was carried out at 100 °C for 48 h. After the reaction was completed, the product polyol 1 was obtained in 90% yield and diamine 3 was obtained in 94% yield after column chromatography.

[0162] Example 4

[0163] The tridentate pincer manganese complex [Mn]-1 (i.e. manganese catalyst-1) was used for the hydrodegradation of polyimides with the following reaction procedure:

[0164]

[0165] In a glove box, manganese catalyst-1 (3.0 mol%), potassium tert-butoxide (9.0 mol%), methanol (1.0 mL) and toluene (0.5 mL) were added to a reaction vial and stirred for 10 min before adding polyimide-3 (0.2 mmol). The reaction vial was placed in a high pressure vessel and the high pressure vessel was removed from the glove box. Hydrogen gas was added to the high pressure vessel at 50 bar and the reaction was carried out at 100 °C for 48 h. After the reaction was completed, the product polyol 1 was obtained in 82% yield and diamine 4 was obtained in 82% yield after column chromatography.

[0166] Example 5

[0167] The tridentate pincer manganese complex [Mn]-1 (i.e. manganese catalyst-1) was used for the hydrodegradation of polyimides with the following reaction procedure:

[0168]

[0169] In a glove box, manganese catalyst-1 (3.0 mol%), potassium tert-butoxide (9.0 mol%), methanol (1.0 mL) and toluene (0.5 mL) were added to a reaction vial and stirred for 10 min before adding polyimide-4 (0.2 mmol). The reaction vial was placed in a high pressure vessel and the high pressure vessel was removed from the glove box. Hydrogen gas was added to the high pressure vessel at 50 bar and the reaction was carried out at 100 °C for 48 h. After the reaction was completed, the product polyol 1 was obtained in 82% yield and diamine 5 was obtained in 80% yield after column chromatography.

[0170] Example 6

[0171] The tridentate pincer manganese complex [Mn]-1 (i.e. manganese catalyst-1) was used for the hydrodegradation of polyimide, the reaction process was as follows:

[0172]

[0173] In a glove box, manganese catalyst-1 (3.0 mol%), potassium tert-butoxide (9.0 mol%), methanol (1.0 mL) and toluene (0.5 mL) were added to a reaction vial and stirred for 10 min before adding polyimide-5 (0.2 mmol). The reaction vial was placed in a high pressure vessel and the high pressure vessel was removed from the glove box. Hydrogen gas was added to the high pressure vessel at 50 bar and the reaction was carried out at 100 °C for 48 h. After the reaction was completed, the product polyol 1 was obtained in 83% yield and diamine 6 was obtained in 82% yield after column chromatography.

[0174] Example 7

[0175] The tridentate pincer manganese complex [Mn]-1 (i.e. manganese catalyst-1) was used for the hydrodegradation of polyimide, the reaction process was as follows:

[0176]

[0177] In a glove box, manganese catalyst-1 (3.0 mol%), potassium tert-butoxide (9.0 mol%), methanol (1.0 mL) and toluene (0.5 mL) were added to a reaction vial and stirred for 10 min before adding polyimide-1 (0.2 mmol). The reaction vial was placed in a high pressure vessel and the high pressure vessel was removed from the glove box. Hydrogen gas was added to the high pressure vessel at 50 bar and the reaction was carried out at 100 °C for 48 h. After the reaction was completed, the product polyol 1 was obtained in 82% yield and diamine 5 was obtained in 80% yield after column chromatography.

[0178] Example 8

[0179] The tridentate pincer manganese complex [Mn]-1 (i.e. manganese catalyst-1) was used for the hydrodegradation of polyimide, the reaction process was as follows:

[0180]

[0181] In a glove box, manganese catalyst-1 (3.0 mol%), potassium tert-butoxide (9.0 mol%), methanol (1.0 mL) and toluene (0.5 mL) were added to a reaction vial, after stirring for 10 minutes, polyimide-1 (0.2 mmol) was added. The reaction vial was placed in an autoclave, the autoclave was removed from the glove box. 50 bar of hydrogen was added to the autoclave, and reacted at 150 °C for 48 hours. After the reaction was completed, column chromatography was performed to obtain the product polyol 1 with a yield of 95%, and diamine 2 with a yield of 96%.

[0182] Example 9

[0183] The tridentate pincer manganese complex [Mn]-1 (i.e. manganese catalyst-1) was used for the hydrodegradation of polyimide, the reaction process was as follows:

[0184]

[0185] In a glove box, manganese catalyst-1 (3.0 mol%), potassium tert-butoxide (9.0 mol%), methanol (1.0 mL) and toluene (0.5 mL) were added to a reaction vial, after stirring for 10 minutes, polyimide-1 (0.2 mmol) was added. The reaction vial was placed in an autoclave, the autoclave was removed from the glove box. 50 bar of hydrogen was added to the autoclave, and reacted at 150 °C for 48 hours. After the reaction was completed, column chromatography was performed to obtain the product polyol 1 with a yield of 95%, and diamine 2 with a yield of 96%.

[0186] Example 10

[0187] The tridentate pincer manganese complex [Mn]-1 (i.e. manganese catalyst-1) was used for the hydrodegradation of polyimide, the reaction process was as follows:

[0188]

[0189] In a glove box, manganese catalyst-1 (3.0 mol%), potassium tert-butoxide (9.0 mol%), methanol (1.0 mL) and toluene (0.5 mL) were added to a reaction vial, after stirring for 10 minutes, polyimide-1 (0.2 mmol) was added. The reaction vial was placed in an autoclave, the autoclave was removed from the glove box. 50 bar of hydrogen was added to the autoclave, and reacted at 150 °C for 48 hours. After the reaction was completed, column chromatography was performed to obtain the product polyol 1 with a yield of 95%, and diamine 2 with a yield of 96%.

[0190] The product polyol 7 was tested, and the nuclear magnetic resonance and high resolution characterization were as follows: 1H NMR (400 MHz, DMSO-d6) δ 7.37 (d, J = 8.0 Hz, 2H), 7.07 (d, J = 2.8 Hz, 2H), 6.87 (dd, Ji = 2.4 Hz, J2= 8.4 Hz, 2H), 5.18-5.15 (m, 2H), 5.08-5.06 (m, 2H), 4.56 (d, J = 5.2 Hz, 4H), 5.00 (d, J = 5.2 Hz, 4H); 13 C NMR (101 MHz, DMSO-d6) δ 156.0, 142.0, 133.9, 128.7, 116.6, 116.4, 60.1, 59.9; HRMS (ESI) calcd. for C 16 H 18 O5Na: 313.1052, found: 313.1049.

[0191] Example 11

[0192] The tridentate pincer manganese complex [Mn]-1 (i.e. manganese catalyst-1) was used for the hydrodegradation of polyimide, the reaction procedure was as follows:

[0193]

[0194] In the glove box, manganese catalyst-1 (3.0 mol%), potassium tert-butoxide (9.0 mol%), methanol (1.0 mL) and toluene (0.5 mL) were added to the reaction vial, after stirring for 10 min, polyimide-7 (0.2 mmol) was added. The reaction vial was put into the autoclave, the autoclave was removed from the glove box. 50 bar of hydrogen was added to the autoclave, and reacted at 100 °C for 48 h. After the reaction was completed, column chromatography was carried out to obtain the product polyol 8 in a yield of 86% and diamine 9 in a yield of 84%.

[0195] The product polyol 8 was tested, and the nuclear magnetic resonance and high resolution characterization were as follows: 1 H NMR (400 MHz, DMSO-d6) δ 7.38-7.36 (m, 2H), 7.25-7.22 (m, 4H), 7.11-7.10 (m, 2H), 6.92-6.85 (m, 6H), 5.19-5.16 (m, 2H), 5.10-5.07 (m, 2H), 4.57 (d, J = 5.6 Hz, 4H), 4.51 (d, J = 5.6 Hz, 4H), 1.64 (s, 6H); 13C NMR (101 MHz, DMSO-d6) δ 155.5, 154.9, 145.0, 142.0, 134.2, 128.7, 128.0, 117.8, 116.8, 116.5, 60.1, 59.9, 41.6, 30.7; HRMS (ESI) calcd for C 31 H 32 O6Na: 523.2097, found: 523.2051.

[0196] The NMR and high resolution of the product diamine 9 are as follows: 1 H NMR (400 MHz, DMSO-d6) δ 7.91 (d, J = 8.8 Hz, 4H), 7.11 - 7.03 (m, 6H), 6.45 (d, J = 8.0 Hz, 2H), 6.26 - 6.25 (m, 2H), 6.21 - 6.19 (m, 2H), 5.33 (s, 4H); 13 C NMR (101 MHz, DMSO-d6) δ 161.6, 155.4, 150.8, 134.8, 130.414, 129.7, 117.8, 110.7, 106.8, 104.9; HRMS (ESI) calcd for C 24 H 21 N2O4S: 433.1222, found: 433.1227.

[0197] Example 12

[0198] The tridentate pincer manganese complex [Mn]-1 (i.e. manganese catalyst-1) was used for the hydrodegradation of polyimide, the reaction process was as follows:

[0199]

[0200] In the glove box, manganese catalyst-1 (3.0 mol%), potassium tert-butoxide (9.0 mol%), methanol (1.0 mL) and toluene (0.5 mL) were added into the reaction bottle, after stirring for 10 minutes, polyimide-4 (0.2 mmol) was added. The reaction bottle was put into the autoclave, the autoclave was taken out of the glove box. 50 bar of hydrogen was added into the autoclave, and reacted at 100 °C for 48 hours. After the reaction was completed, column chromatography was carried out, the yield of product polyol 10 was 86%, and the yield of diamine 11 was 84%.

[0201] In addition, the present inventors also selected R, R' from C1 aliphatic group, C4 aliphatic group, R 10 aliphatic group, C 40 aliphatic group, C6-containing aryl group, C 20aryl group, C 60 The same experiment was performed with aryl groups containing C

[0202] Example 13

[0203] The tridentate pincer manganese complex [Mn]-1 (i.e. manganese catalyst-1) was used for the hydrodeoxygenation of polyimide, the reaction process was as follows:

[0204] In the glove box, manganese catalyst-1 (0.01 mol%), sodium ethoxide (0.01 mol%) and tetrahydrofuran (1.5 mL) were added into the reaction vial, after stirring for 10 minutes, polyimide-1 (0.2 mmol) was added. The reaction vial was put into the autoclave, the autoclave was removed from the glove box. 100 bar of hydrogen was added into the autoclave, and reacted at 25 °C for 4 days. After the reaction was completed, column chromatography was performed to obtain the target product polyol 1 with a yield of 82% and diamine 2 with a yield of 83%.

[0205] Example 14

[0206] The tridentate pincer manganese complex [Mn]-1 (i.e. manganese catalyst-1) was used for the hydrodeoxygenation of polyimide, the reaction process was as follows:

[0207] In the glove box, manganese catalyst-1 (0.01 mol%), sodium ethoxide (0.01 mol%) and tetrahydrofuran (1.5 mL) were added into the reaction vial, after stirring for 10 minutes, polyimide-1 (0.2 mmol) was added. The reaction vial was put into the autoclave, the autoclave was removed from the glove box. 100 bar of hydrogen was added into the autoclave, and reacted at 25 °C for 4 days. After the reaction was completed, column chromatography was performed to obtain the target product polyol 1 with a yield of 82% and diamine 2 with a yield of 83%.

[0208] Example 15

[0209] The tridentate pincer manganese complex [Mn]-1 (i.e. manganese catalyst-1) was used for the hydrodeoxygenation of polyimide, the reaction process was as follows:

[0210] In the glove box, manganese catalyst-1 (10 mol%), potassium phosphate (30 mol%) and 1,4-dioxane (1.5 mL) were added into the reaction vial, after stirring for 10 minutes, polyimide-1 (0.2 mmol) was added. The reaction vial was put into the autoclave, the autoclave was removed from the glove box. 1 bar of hydrogen was added into the autoclave, and reacted at 200 °C for 1 h. After the reaction was completed, column chromatography was performed to obtain the target product polyol 1 with a yield of 75% and diamine 2 with a yield of 73%.

[0211] Example 16

[0212] Tridentate pincer manganese complex [Mn]-2 (i.e. manganese catalyst-2) was used for the hydrodegradation of polyimide, the reaction process was as follows:

[0213] In the glove box, manganese catalyst-2 (1.0 mol%), potassium tert-butoxide (6.0 mol%) and toluene (1.5 mL) were added into the reaction vial, after stirring for 10 minutes, polyimide-1 (0.2 mmol) was added. The reaction vial was put into the autoclave, the autoclave was removed from the glove box. 50 bar of hydrogen was added into the autoclave, and reacted at 80 °C for 4 days. After the reaction was completed, column chromatography was carried out, the yield of the target product polyol 1 was 75% and the yield of diamine 2 was 76%.

[0214] Example 17

[0215] Tridentate pincer manganese complex [Mn]-3 (i.e. manganese catalyst-3) was used for the hydrodegradation of polyimide, the reaction process was as follows:

[0216] In the glove box, manganese catalyst-3 (1.0 mol%), potassium tert-butoxide (6.0 mol%) and toluene (1.5 mL) were added into the reaction vial, after stirring for 10 minutes, polyimide-1 (0.2 mmol) was added. The reaction vial was put into the autoclave, the autoclave was removed from the glove box. 50 bar of hydrogen was added into the autoclave, and reacted at 80 °C for 4 days. After the reaction was completed, column chromatography was carried out, the yield of the target product polyol 1 was 65% and the yield of diamine 2 was 63%.

[0217] Example 18

[0218] Tridentate pincer manganese complex [Mn]-4 (i.e. manganese catalyst-4) was used for the hydrodegradation of polyimide, the reaction process was as follows:

[0219] In the glove box, manganese catalyst-4 (1.0 mol%), sodium hydride (6.0 mol%) and anisole (1.5 mL) were added into the reaction vial, after stirring for 10 minutes, polyimide-1 (0.2 mmol) was added. The reaction vial was put into the autoclave, the autoclave was removed from the glove box. 50 bar of hydrogen was added into the autoclave, and reacted at 80 °C for 4 days. After the reaction was completed, column chromatography was carried out, the yield of the target product polyol 1 was 81% and the yield of diamine 2 was 85%.

[0220] Example 19

[0221] Tridentate pincer manganese complex [Mn]-5 (i.e. manganese catalyst-5) was used for the hydrodegradation of polyimide, the reaction process was as follows:

[0222] In the glove box, manganese catalyst-5 (1.0 mol%), sodium hydride (6.0 mol%) and anisole (1.5 mL) were added into the reaction bottle, and after stirring for 10 minutes, polyimide-1 (0.2 mmol) was added. The reaction bottle was placed in the autoclave, and the autoclave was removed from the glove box. 50 bar of hydrogen was added to the autoclave, and the reaction was carried out at 80°C for 4 days. After the reaction was completed, column chromatography was carried out to obtain the target product polyol 1 with a yield of 64% and diamine 2 with a yield of 68%.

[0223] Example 20

[0224] The tridentate pincer manganese complex [Mn]-6 (i.e. manganese catalyst-6) was used for the hydrogenolysis of polyimide, and the reaction process was as follows:

[0225] In the glove box, manganese catalyst-6 (1.0 mol%), sodium hydride (6.0 mol%) and anisole (1.5 mL) were added into the reaction bottle, and after stirring for 10 minutes, polyimide-1 (0.2 mmol) was added. The reaction bottle was placed in the autoclave, and the autoclave was removed from the glove box. 50 bar of hydrogen was added to the autoclave, and the reaction was carried out at 80°C for 4 days. After the reaction was completed, column chromatography was carried out to obtain the target product polyol 1 with a yield of 75% and diamine 2 with a yield of 72%.

[0226] In addition, the present inventors also carried out hydrogenolysis reaction of polyimide with the remaining pincer manganese catalyst, and the results were similar to the above examples.

[0227] From the above examples, it can be found that the tridentate pincer manganese complex as a catalyst can realize the hydrogenolysis of polyimide, and the reaction is efficient, which has good application prospect.

[0228] It should be understood that the above examples are only for illustrating the technical concept and characteristics of the present application, and the purpose is to enable those skilled in the art to understand the content of the present application and to implement it, and it cannot limit the protection scope of the present application. Any equivalent changes or modifications made in accordance with the spirit and essence of the present application should be covered within the protection scope of the present application.

Claims

1. A polyimide hydrogenation degradation method, characterized in that: include: In a hydrogen atmosphere, polyimide, a pincer manganese catalyst, and an alkaline substance are heated and reacted in a selected solvent, thereby achieving degradation of the polyimide; The pincer manganese catalyst includes a tridentate pincer manganese complex, and the tridentate pincer manganese complex has a structure as shown in formula (I): Among them, R 1 Selected from C1~C 20 Alkyl or aryl, R 2 、R 3 and R 4 Selected from H, C1~C 20 alkyl or aryl.

2. The polyimide hydrogenation degradation method according to claim 1, characterized in that: The structural formula of the polyimide is shown in formula (II) or formula (III): Wherein, R and R' are selected from C1-C 40 Fatty groups containing C6-C 60 Any one or more combinations of aryl groups and oxygen atoms, wherein n is 1 to 500.

3. The polyimide hydrogenation degradation method according to claim 1, wherein: The molar ratio of the polyimide, the pincer manganese catalyst and the alkaline substance is 1:0.0001:0.0001 to 1:0.1:0.

3.

4. The polyimide hydrogenation degradation method according to claim 1, wherein: The temperature of the heating reaction is 25 to 200° C., and the reaction time is 1 to 120 hours.

5. The polyimide hydrogenation degradation method according to claim 1, wherein: The pressure of the hydrogen atmosphere is 1 to 100 bar.

6. The polyimide hydrogenation degradation method according to claim 1, wherein: The alkaline substance includes any one or a combination of two or more of potassium tert-butoxide, sodium tert-butoxide, sodium ethoxide, sodium methoxide, sodium hydride, potassium hydride, potassium ethoxide, potassium methoxide, potassium phosphate, potassium bis(trimethylsilyl)amide, sodium bis(trimethylsilyl)amide, and lithium bis(trimethylsilyl)amide.

7. The polyimide hydrogenation degradation method according to claim 1, wherein: The selected solvent includes any one or a combination of two or more of methanol, ethanol, isopropanol, tetrahydrofuran, toluene, n-hexane, benzene, n-propanol, 1,4-dioxane, dimethyl sulfoxide, xylene, anisole, ethylene glycol dimethyl ether, and mesitylene.

8. The polyimide hydrogenation degradation method according to claim 2, characterized in that: include: In a hydrogen atmosphere, polyimide, a pincer manganese catalyst, and an alkaline substance are heated and reacted in a selected solvent, thereby achieving degradation of the polyimide to produce polyol compounds and diamine compounds; The structural formula of the polyol compound is The structural formula of the diamine compound is Wherein, R and R' are selected from C1-C 40 Fatty groups containing C6-C 60 any one or more combinations of aromatic groups and oxygen atoms.

9. The polyimide hydrogenation degradation method according to claim 8, characterized in that: The temperature of the heating reaction is 30-150°C.

10. The polyimide hydrogenation degradation method according to claim 8, characterized in that: The yield of the polyol compound is above 50%, and the yield of the diamine compound is above 50%.

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