Preparation of porous organic polymer-based metal catalysts and their application in reduction of nitrobenzene

Abstract

The application discloses a kind of porous organic polymer-based metal catalyst preparation and its application in nitrobenzene reduction.The porous organic polymer-based metal catalyst has structure formula shown in formula IThe porous organic polymer-based metal catalyst of the application can effectively catalyze the chemical selective reduction of nitrobenzene compound when ammonia borane is used as hydrogen source, and shows good catalytic activity and stability.Porous organic polymer-based metal catalyst, nitrobenzene, ammonia borane, solvent are mixed, and after 10-24h reaction, nitrobenzene conversion rate can reach 100%, and aniline is the only product.Nitrobenzene conversion rate is maintained above 90% in the first 8 cycles, and the yield of aniline is 91-99%.

Description

Technical Field

[0001] This application relates to a method for preparing a porous organic polymer-based metal catalyst, and the application of the catalyst in the preparation of the chemical product aniline. Background Technology

[0002] Aniline is an important chemical intermediate with significant applications in pesticides, dyes, and other fields. Catalytic reduction of nitrobenzene compounds to produce aniline is one of the most direct and effective methods. Currently used catalytic systems for this conversion exhibit distinct characteristics in both homogeneous and heterogeneous catalysts. Homogeneous catalytic systems have clearly defined active sites, making them easier to understand and finely control at the molecular level; however, their susceptibility to large-scale industrial production is limited by catalyst regeneration issues. Heterogeneous systems, on the other hand, have diverse active sites, but the different catalytic functional centers on the support surface often exist in an isolated and disordered manner, making it difficult to synergistically regulate the chemoselectivity of the product during the reaction. Therefore, developing highly efficient heterogeneous catalytic systems capable of precisely controlling the chemoselectivity of nitrobenzene hydrogenation products remains a key challenge for the industrial production of aniline.

[0003] To address the aforementioned problems, this invention, based on the understanding of the synergistic effects between catalytic active sites in homogeneous catalysis, uses a covalent organic framework as a research platform for catalytic materials. Leveraging the high designability of its material structure, a bispyridine diimine functional site is introduced. Utilizing the pincer coordination effect of the pyridine diimine and the synergistic effect of the bispyridine diimine, the hydrogen transfer process is promoted, thereby precisely controlling the reduction of nitrobenzene. This allows for the selective reduction of only the nitrobenzene functional group while leaving the benzene ring unaffected, thus enabling the efficient and highly chemoselective preparation of aniline.

[0004] Meanwhile, the hydrogen source used for the reduction of nitrobenzene in this invention is ammonia borane, which has a hydrogen storage density of up to 19.6 wt%. It is a white solid, easy to store, non-flammable and non-explosive, and its high hydrogen storage density effectively avoids the use of dangerous hydrogen sources. Summary of the Invention

[0005] To address the problems of high cost of precious metal catalysts and difficulty in recovering homogeneous catalysts, this invention provides a method for preparing a porous organic polymer-based metal catalyst and its application in the catalytic reduction of nitrobenzene to aniline. The method uses two monomers, 2,6-pyridinedicarboxaldehyde and 2,3,6,7,10,11-hexaaminotriphenyl, to form a porous organic polymer 3 via a hot solvent method. The resulting porous organic polymer 3 is then loaded with various transition metal salts as catalysts for the reduction of nitrobenzene to aniline. The catalyst preparation method of this invention is simple to operate, does not involve the use of precious metals, and can be recycled multiple times, greatly reducing the catalyst preparation cost. Furthermore, when applied to the chemical selective reduction of nitrobenzene to aniline, the catalyst uses water as the reaction solvent and ammonia borane as the hydrogen source. The conversion rate of nitrobenzene can reach 100%, and the yield of aniline can reach over 99%. This method is environmentally friendly, simple to operate, and does not involve the use of organic solvents or hazardous hydrogen sources.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] A porous organic polymer-based metal catalyst, wherein the porous organic polymer-based metal catalyst is a compound having the structural formula shown in Formula I:

[0008]

[0009] The method for preparing the porous organic polymer-based metal catalyst of the present invention includes the following steps:

[0010] (1) Mix compound 1 and compound 2 and react them in an organic or non-aqueous solution to obtain porous organic polymer 3;

[0011] Compound 1 is selected from compounds having the structural formula II;

[0012]

[0013] Compound 2 is selected from compounds having the structural formula shown in Formula III;

[0014]

[0015] The porous organic polymer 3 is selected from compounds having the structural formula shown in Formula IV;

[0016]

[0017] (2) The porous organic polymer 3 obtained in step (1) is stirred and reacted with different types of metal salts in methanol to load the metal salts, thereby obtaining porous organic polymer-based metal catalysts loaded with different metal types.

[0018] Furthermore, the synthesis method of porous organic polymer 3 in step (1) is a solvothermal synthesis method, and the specific steps are as follows: 2,3,6,7,10,11-hexaaminotriphenyl, 2,6-pyridinedicarboxaldehyde, solvent and acid aqueous solution are added to a Pyrex tube to obtain a mixed reaction solution. The mixed reaction solution is frozen into a solid by liquid nitrogen, then vacuumed, then thawed, and nitrogen gas is introduced. The above operation is repeated three times to remove the air in the Pyrex tube. Then the Pyrex tube is sealed with a flame torch and placed in an oven at 120°C for 72 hours. A large amount of insoluble solid material will be generated in the Pyrex tube, which is the crude suspension of porous organic polymer 3. The suspension is filtered, washed, purified and dried to obtain porous organic polymer 3.

[0019] Furthermore, the solvent is at least one selected from o-dichlorobenzene, n-butanol, N-methylpyrrolidone, mesitylene, ethanol, N,N-dimethylacetamide, 1,4-dioxane, N,N-dimethylformamide, and toluene; the acid aqueous solution is an aqueous solution of acetic acid or p-toluenesulfonic acid, and the concentration of the acid aqueous solution is 3 mol / L to 12 mol / L; the molar ratio of 2,3,6,7,10,11-hexaaminotriphenyl and 2,6-pyridinedicarboxaldehyde is 1:3.

[0020] Furthermore, the washing and purification method involves filtering the crude suspension of the sintered porous organic polymer 3 through a funnel filter membrane, and then sequentially adding N,N-dimethylacetamide, tetrahydrofuran, N,N-dimethylformamide, anhydrous ethanol, and methanol solution for washing. Finally, the mixture is placed in a vacuum oven and dried for 12 hours at a temperature of 70°C.

[0021] Furthermore, the metal salt in step (2) is ferric acetate, cobalt acetate, manganese acetate, nickel acetate, copper acetate, ferric chloride, cobalt chloride, manganese chloride, nickel chloride, copper chloride, ferric nitrate, cobalt nitrate, manganese nitrate, nickel nitrate, or copper nitrate.

[0022] Furthermore, the reaction temperature of the stirred reaction loading metal salt in step (2) is 30°C, and the reaction time is 1-24h; the mass ratio of the porous organic polymer 3 to the metal salt is 5:1; and the concentration of the porous organic polymer 3 in methanol is 8mg / mL.

[0023] This invention also provides the application of porous organic polymer-based metal catalysts in the catalytic selective reduction of nitrobenzene compounds to prepare aniline compounds. The hydrogen source for reducing nitrobenzene compounds is ammonia borane. The specific steps include: adding porous organic polymer-based metal catalysts, water, and ammonia borane to a thick-walled pressure-resistant bottle, and finally adding nitrobenzene compounds. Under a closed reaction system, the reaction is heated to prepare aniline compounds. After the raw materials have reacted completely, dichloromethane is added to the reaction system as an extraction solvent, and a saturated sodium chloride aqueous solution is added as a demulsifier. After three extractions, the organic phases are combined, and then the organic phases are concentrated and separated and purified on a silica gel column to obtain the aniline product.

[0024] Furthermore, the heating reaction temperature is 80℃, and the time is 10-24h; the mass ratio of the nitrobenzene compound to the porous organic polymer-based metal catalyst is 1:1; the equivalent ratio of the nitrobenzene compound to ammonia borane is 1:(1-5); and the concentration of the nitrobenzene compound in water is 5mg / mL.

[0025] Furthermore, the nitrobenzene compounds are nitrobenzene, 2-nitro-5-chloropyridine, p-fluoronitrobenzene, p-bromonitrobenzene, p-chloronitrobenzene, p-nitroacetanilide, p-nitrobenzyl alcohol, 7-nitrotetrahydroquinoline, 4-nitroanisole, 3-nitrotoluene, 2-nitrothiophene, and 1-nitronaphthalene.

[0026] The beneficial effects of this invention: This invention discloses a method for preparing and applying a porous organic polymer-based metal catalyst, which has significant advantages over existing nitrobenzene hydrogenation reactions, specifically in the following aspects:

[0027] 1. Currently, the catalysts commonly used in the laboratory for the hydrogenation of nitrobenzene to aniline are noble metal catalysts. Noble metal catalysts such as Pt, Pd, Ru, and Au exhibit good catalytic activity for the hydrogenation of nitrobenzene, but their production costs are relatively high, significantly limiting their industrial applications. Therefore, using inexpensive metals to replace noble metals for the targeted synthesis of aniline is a promising strategy.

[0028] 2. The porous organic polymer-based metal catalyst disclosed in this invention has a bispyridine bisimine coordination structure. This unique design allows the two bischelate coordination structures to work synergistically during the catalytic reduction of nitrobenzene, precisely positioning the nitro functional group, thereby ensuring that only the nitro functional group is reduced during the reduction process, while the benzene ring remains unaffected.

[0029] 3. The porous organic polymer-based metal catalyst involved in this invention can be recycled multiple times in the catalytic reduction of nitrobenzene, and maintains a nitrobenzene conversion rate of over 90% in the first 8 cycles, while the yield of aniline can also be maintained between 91-99%.

[0030] 4. The solvent used in the method for preparing aniline by reduction of nitrobenzene involved in this invention is water, which is green and environmentally friendly and avoids the use of organic solvents.

[0031] Therefore, this invention provides a new approach for the efficient hydrogenation of nitroaromatics to produce amines. Attached Figure Description

[0032] Figure 1 The image shows the PXRD pattern of the porous organic polymer 3.

[0033] Figure 2 The 1H NMR spectrum of aniline obtained in Example 26 is shown.

[0034] Figure 3 The image shows the 1H NMR spectrum of 2-amino-5-chloropyridine obtained in Example 45.

[0035] Figure 4 The image shows the 1H NMR spectrum of 4-fluoroaniline obtained in Example 46.

[0036] Figure 5 The image shows the 1H NMR spectrum of 4-bromoaniline obtained in Example 48.

[0037] Figure 6 The image shows the 1H NMR spectrum of 4-aminoacetanilide prepared in Example 49.

[0038] Figure 7 The image shows the 1H NMR spectrum of 3-aminobenzyl alcohol obtained in Example 50.

[0039] Figure 8 The image shows the 1H NMR spectrum of p-chloroaniline obtained in Example 47.

[0040] Figure 9 The image shows the 1H NMR spectrum of p-methoxyaniline obtained in Example 51.

[0041] Figure 10 The image shows the 1H NMR spectrum of 7-aminoquinoline obtained in Example 54.

[0042] Figure 11 The image shows the 1H NMR spectrum of 2-thiophene methylamine obtained in Example 52.

[0043] Figure 12 The image shows the 1H NMR spectrum of 1-naphthylamine obtained in Example 55.

[0044] Figure 13 The image shows the 1H NMR spectrum of 3-methylaniline obtained in Example 53. Detailed Implementation

[0045] The present invention will be further described below with reference to specific embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Those skilled in the art can make some non-essential improvements and adjustments based on the above-described invention.

[0046] Example 1

[0047] The preparation method of porous organic polymer 3 in this embodiment includes the following steps:

[0048] (1) 26.9 mg of 2,3,6,7,10,11-hexaaminotriphenyl and 20.3 mg of 2,6-pyridinedicarboxaldehyde were added to a Pyrex tube in sequence, followed by the addition of 0.25 mL of o-dichlorobenzene, 0.25 mL of n-butanol and 50 μL of 6 mol / L acetic acid aqueous solution to obtain a mixed reaction solution.

[0049] (2) The resulting mixed reaction solution was frozen into a solid using liquid nitrogen, then evacuated, thawed, and then purged with nitrogen. This process was repeated three times to remove air from the system. The Pyrex tube was then sealed with a flame torch and placed in a 120°C oven for 72 hours. Subsequently, a large amount of insoluble substances were generated in the reaction system. These insoluble substances were washed, filtered, and dried using organic substances such as methanol, ethanol, tetrahydrofuran, DMF, and DMAC. This series of purifications yielded a porous organic polymer 3 with a yield of 83%.

[0050] Example 2

[0051] The preparation method of porous organic polymer 3 in this embodiment includes the following steps:

[0052] (1) 26.9 mg of 2,3,6,7,10,11-hexaaminotriphenyl and 20.3 mg of 2,6-pyridinedicarboxaldehyde were added to a Pyrex tube in sequence, followed by the addition of 0.8 mL of N-methylpyrrolidone, 0.4 mL of mesitylene and 100 μL of 3 mol / L p-toluenesulfonic acid solution to obtain a mixed reaction solution.

[0053] (2) Same as step (2) in Example 1. The yield of the porous organic polymer material product is 92%.

[0054] Example 3

[0055] The preparation method of porous organic polymer 3 in this embodiment includes the following steps:

[0056] (1) 26.9 mg of 2,3,6,7,10,11-hexaaminotriphenyl and 20.3 mg of 2,6-pyridinedicarboxaldehyde were added to a Pyrex tube in sequence, followed by 0.5 mL of N,N-dimethylacetamide, 0.5 mL of 1,4-dioxane and 50 μL of 4 mol / L acetic acid aqueous solution to obtain a mixed reaction solution.

[0057] (2) Same as step (2) in Example 1. The yield of the porous organic polymer material product is 60%.

[0058] Example 4

[0059] The preparation method of porous organic polymer 3 in this embodiment includes the following steps:

[0060] (1) 26.9 mg of 2,3,6,7,10,11-hexaaminotriphenyl and 20.3 mg of 2,6-pyridinedicarboxaldehyde were added to a Pyrex tube in sequence, followed by 1.4 mL of N,N-dimethylformamide, 0.7 mL of toluene and 50 μL of 5 mol / L acetic acid aqueous solution to obtain a mixed reaction solution.

[0061] (2) Same as step (2) in Example 1. The yield of the porous organic polymer material product is 55%.

[0062] Example 5

[0063] The preparation method of porous organic polymer 3 in this embodiment includes the following steps:

[0064] (1) 26.9 mg of 2,3,6,7,10,11-hexaaminotriphenyl and 20.3 mg of 2,6-pyridinedicarboxaldehyde were added to a Pyrex tube in sequence, followed by 1.5 mL of ethanol and 150 μL of 7 mol / L acetic acid aqueous solution to obtain a mixed reaction solution.

[0065] (2) Same as step (2) in Example 1. The yield of the porous organic polymer material product is 70%.

[0066] Example 6

[0067] The preparation method of porous organic polymer 3 in this embodiment includes the following steps:

[0068] (1) 26.9 mg of 2,3,6,7,10,11-hexaaminotriphenyl and 20.3 mg of 2,6-pyridinedicarboxaldehyde were added to a Pyrex tube in sequence, followed by 0.8 mL of N-methylpyrrolidone, 0.4 mL of mesitylene and 100 μL of 8 mol / L acetic acid aqueous solution to obtain a mixed reaction solution.

[0069] (2) Same as step (2) in Example 1. The yield of the porous organic polymer material product is 90%.

[0070] Example 7

[0071] The preparation method of porous organic polymer 3 in this embodiment includes the following steps:

[0072] (1) 26.9 mg of 2,3,6,7,10,11-hexaaminotriphenyl and 20.3 mg of 2,6-pyridinedicarboxaldehyde were added to a Pyrex tube in sequence, followed by 1.4 mL of N,N-dimethylacetamide, 0.7 mL of 1,4-dioxane and 50 μL of 9 mol / L p-toluenesulfonic acid aqueous solution to obtain a mixed reaction solution.

[0073] (2) Same as step (2) in Example 1. The yield of the porous organic polymer material product is 84%.

[0074] Example 8

[0075] The preparation method of porous organic polymer 3 in this embodiment includes the following steps:

[0076] (1) 26.9 mg of 2,3,6,7,10,11-hexaaminotriphenyl and 20.3 mg of 2,6-pyridinedicarboxaldehyde were added to a Pyrex tube in sequence, followed by 1.5 mL of N,N-dimethylformamide, 0.7 mL of toluene and 50 μL of 10 mol / L p-toluenesulfonic acid aqueous solution to obtain a mixed reaction solution.

[0077] (2) Same as step (2) in Example 1. The yield of the porous organic polymer material product is 53%.

[0078] Example 9

[0079] The preparation method of porous organic polymer 3 in this embodiment includes the following steps:

[0080] (1) 26.9 mg of 2,3,6,7,10,11-hexaaminotriphenyl and 20.3 mg of 2,6-pyridinedicarboxaldehyde were added to a Pyrex tube in sequence, followed by the addition of 1.5 mL of ethanol and 100 μL of 3 mol / L and 50 μL of 11 mol / L acetic acid aqueous solution to obtain a mixed reaction solution.

[0081] (2) Same as step (2) in Example 1. The yield of the porous organic polymer material product is 70%.

[0082] Example 10

[0083] The preparation method of porous organic polymer 3 in this embodiment includes the following steps:

[0084] (1) 26.9 mg of 2,3,6,7,10,11-hexaaminotriphenyl and 20.3 mg of 2,6-pyridinedicarboxaldehyde were added to a Pyrex tube in sequence, followed by the addition of 0.25 mL of o-dichlorobenzene, 0.25 mL of n-butanol and 50 μL of 12 mol / L p-toluenesulfonic acid aqueous solution to obtain a mixed reaction solution.

[0085] (2) Same as step (2) in Example 1. The yield of the porous organic polymer material product is 80%.

[0086] Example 11

[0087] The preparation method of the porous organic polymer-based copper acetate catalyst in this embodiment is as follows:

[0088] Take 4 mg of copper acetate metal salt, add 2.5 mL of methanol, and dissolve it thoroughly in an ultrasonic machine. Add 20 mg of the porous organic polymer 3 prepared in Example 1, and stir thoroughly for 24 h. Wash the resulting insoluble substance with methanol, filter, and dry to obtain the porous organic polymer-based copper acetate catalyst.

[0089] Example 12

[0090] Except for the metal salt being ferric acetate and the stirring time being 1 hour, the other conditions were the same as in Example 11, and a porous organic polymer-based ferric acetate catalyst was obtained.

[0091] Example 13

[0092] Except for the metal salt being cobalt acetate and the stirring time being 2 hours, the other conditions were the same as in Example 11, and a porous organic polymer-based cobalt acetate catalyst was obtained.

[0093] Example 14

[0094] Except for the metal salt being manganese acetate and the stirring time being 3 hours, the other conditions were the same as in Example 11, and a porous organic polymer-based manganese acetate catalyst was obtained.

[0095] Example 15

[0096] Except for the metal salt being nickel acetate and the stirring time being 4 hours, the other conditions were the same as in Example 11, and a porous organic polymer-based nickel acetate catalyst was obtained.

[0097] Example 16

[0098] Except for the metal salt being ferric chloride and the stirring time being 5 hours, the other conditions were the same as in Example 11, and a porous organic polymer-based ferric chloride catalyst was obtained.

[0099] Example 17

[0100] Except for the metal salt being cobalt chloride and the stirring time being 6 hours, the other conditions were the same as in Example 11, and a porous organic polymer-based cobalt chloride catalyst was obtained.

[0101] Example 18

[0102] Except for the metal salt being manganese chloride and the stirring time being 8 hours, the other conditions were the same as in Example 11, and a porous organic polymer-based manganese chloride catalyst was obtained.

[0103] Example 19

[0104] Except for the metal salt being nickel chloride and the stirring time being 10 hours, the other conditions were the same as in Example 11, and a porous organic polymer-based manganese chloride catalyst was obtained.

[0105] Example 20

[0106] Except for the metal salt being copper chloride and the stirring time being 12 hours, the other conditions were the same as in Example 11, and a porous organic polymer-based copper chloride catalyst was obtained.

[0107] Example 21

[0108] Except for the metal salt being ferric nitrate and the stirring time being 14 hours, the other conditions were the same as in Example 11, and a porous organic polymer-based ferric nitrate catalyst was obtained.

[0109] Example 22

[0110] Except for the metal salt being cobalt nitrate and the stirring time being 16 hours, the other conditions were the same as in Example 11, and a porous organic polymer-based cobalt nitrate catalyst was obtained.

[0111] Example 23

[0112] Except for the metal salt being manganese nitrate and the stirring time being 18 hours, the other conditions were the same as in Example 11, and a porous organic polymer-based manganese nitrate catalyst was obtained.

[0113] Example 24

[0114] Except for the metal salt being nickel nitrate and the stirring time being 20 hours, the other conditions were the same as in Example 11, and a porous organic polymer-based nickel nitrate catalyst was obtained.

[0115] Example 25

[0116] Except for the metal salt being copper nitrate and the stirring time being 22 hours, the other conditions were the same as in Example 11, thus obtaining a porous organic polymer-based copper nitrate catalyst.

[0117] Example 26

[0118] The reaction steps for the reduction of nitrobenzene to aniline using a supported metal porous organic polymer are as follows: 50 mg of the porous organic polymer-based copper acetate catalyst prepared in Example 11 was added to a thick-walled, pressure-resistant bottle. Three equivalents of ammonia borane were added, followed by 5 mL of water as a solvent. Finally, 25 mg of nitrobenzene was added, and the mixture was stirred at a constant temperature of 80°C for 10 h to prepare aniline. The final product was extracted, separated, and purified. The product was then analyzed by liquid chromatography (e.g., [missing information]). Figure 2 As shown, the conversion rate of nitrobenzene is 100%, and the yield of aniline is 99%.

[0119] Examples 27-41

[0120] Examples 27-41 are identical to Example 26 except for the use of porous organic polymer supported catalysts and different reaction times. The specific changes in reaction conditions and corresponding reaction effects in each example are shown in Table 1.

[0121] Table 1

[0122]

[0123]

[0124] Example 41

[0125] Except for the absence of a catalyst, the other conditions were the same as in Example 26. The product was detected by liquid chromatography, and the conversion rate of nitrobenzene was 20%, and the yield of aniline was 5%.

[0126] Example 42

[0127] Except for the addition of copper acetate metal salt as the catalyst, the other conditions were the same as in Example 26. The product was detected by liquid chromatography, and the conversion rate of nitrobenzene was 30% and the yield of aniline was 10%.

[0128] Example 43

[0129] The hydrogen source was replaced with hydrogen gas, and the specific implementation steps were as follows: 50 mg of the porous organic polymer-based copper acetate catalyst prepared in Example 11 was added to a Schlenk tube, followed by 5 mL of water as a solvent. Finally, 25 mg of nitrobenzene was added, and hydrogen gas was replaced with hydrogen gas. A hydrogen balloon was inserted into the rubber stopper of the reaction tube, and the tube was purged with air three times. The temperature was kept constant at 80°C, and the reaction was stirred for 10 hours to prepare aniline. The final product was extracted, separated, and purified. The product was detected by liquid chromatography (e.g., ...). Figure 2 As shown in the figure, the conversion rate of nitrobenzene is 10%, and the yield of aniline is 0%.

[0130] Example 44

[0131] The porous organic polymer-based copper acetate catalyst prepared in Example 11 was circulated 10 times. The reaction steps were as follows: For the first time, 50 mg of the porous organic polymer-based copper acetate catalyst prepared in Example 11 was added to a thick-walled pressure-resistant bottle, along with 3 equivalents of ammonia borane, 5 mL of water as a solvent, and finally 25 mg of nitrobenzene. The mixture was kept at a constant temperature of 80°C and stirred for 10 h to prepare aniline. The catalyst was then filtered and washed with methanol solution and dried for 2 h. It was then added back to the thick-walled pressure-resistant bottle, and the reaction steps were similar to those described above. After 10 catalytic cycles, the nitrobenzene conversion rate was 92%-99% in the first 8 cycles, all exceeding 90%, and the aniline yield was also maintained between 91% and 99%.

[0132] Examples 45-56

[0133] Examples 45-56 are examples of preparing aniline compounds from nitrobenzene compounds using the porous organic polymer-based metal catalyst prepared in Example 11. The operation steps of Examples 45-56 are the same as those of Example 26, except that the type of reaction substrate is changed, i.e., different nitrobenzene compounds are used. The specific changes in reaction conditions and corresponding reaction effects in each example are shown in Table 2.

[0134] Table 2

[0135]

[0136]

[0137] The experimental data above show that, with ammonia borane as the hydrogen source, the porous organic polymer-based metal catalyst of this invention exhibits extremely high reactivity and selectivity for the reduction of nitrobenzene compounds. Compared to the reaction without a catalyst or with only metal salt as a catalyst, the reaction conversion rate is higher and the product selectivity is better.

[0138] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by those skilled in the art within the scope of the technology disclosed in the present invention and within the spirit and principles of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A porous organic polymer-based metal catalyst, characterized in that, The porous organic polymer-based metal catalyst is a compound having the structural formula shown in Formula I: Formula I.

2. The method for preparing the porous organic polymer-based metal catalyst according to claim 1, characterized in that, Includes the following steps: (1) Compound 1 and Compound 2 were mixed and reacted in a non-aqueous solution to obtain porous organic polymer 3; Compound 1 is a compound with structural formula II; Formula II Compound 2 is selected from compounds having the structural formula shown in Formula III; Formula III The porous organic polymer 3 is selected from compounds having the structural formula shown in Formula IV; Formula IV (2) The porous organic polymer 3 obtained in step (1) is stirred and reacted with different types of metal salts in methanol to load the metal salts, thereby obtaining porous organic polymer-based metal catalysts loaded with different metal types.

3. The method for preparing the porous organic polymer-based metal catalyst according to claim 2, characterized in that, The method for synthesizing porous organic polymer 3 in step (1) is a solvothermal synthesis method. The specific steps are as follows: 2,3,6,7,10,11-hexaaminotriphenyl, 2,6-pyridinedicarboxaldehyde, solvent and acid aqueous solution are added to a Pyrex tube to obtain a mixed reaction solution. The mixed reaction solution is frozen into a solid by liquid nitrogen, then vacuumed, then thawed, and nitrogen gas is introduced. The above operation is repeated three times to remove the air in the Pyrex tube. Then the Pyrex tube is sealed with a flame torch and placed in an oven at 120°C for 72 hours. A large amount of insoluble solid material will be generated in the Pyrex tube, which is the crude suspension of porous organic polymer 3. The suspension is filtered, washed, purified and dried to obtain porous organic polymer 3.

4. The method for preparing the porous organic polymer-based metal catalyst according to claim 3, characterized in that, The solvent is at least one selected from o-dichlorobenzene, n-butanol, N-methylpyrrolidone, mesitylene, ethanol, N,N-dimethylacetamide, 1,4-dioxane, N,N-dimethylformamide, and toluene; the acid aqueous solution is an aqueous solution of acetic acid or p-toluenesulfonic acid, and the concentration of the acid aqueous solution is 3 mol / L to 12 mol / L; the molar ratio of 2,3,6,7,10,11-hexaaminotriphenyl and 2,6-pyridinedicarboxaldehyde is 1:

3.

5. The method for preparing the porous organic polymer-based metal catalyst according to claim 3, characterized in that, The washing and purification method involves filtering the crude porous organic polymer 3 suspension obtained by sintering through a funnel filter membrane, and then sequentially adding N,N-dimethylacetamide, tetrahydrofuran, N,N-dimethylformamide, anhydrous ethanol, and methanol solution for washing. Finally, the suspension is placed in a vacuum oven and dried for 12 hours at a temperature of 70°C.

6. The method for preparing the porous organic polymer-based metal catalyst according to claim 2, characterized in that, The metal salt in step (2) is cobalt acetate, manganese acetate, nickel acetate, copper acetate, cobalt chloride, manganese chloride, nickel chloride, copper chloride, cobalt nitrate, manganese nitrate, nickel nitrate, or copper nitrate.

7. The method for preparing the porous organic polymer-based metal catalyst according to claim 2, characterized in that, The reaction temperature of the metal salt in step (2) is 30°C and the reaction time is 1-24h; the mass ratio of the porous organic polymer 3 to the metal salt is 5:1; the concentration of the porous organic polymer 3 in methanol is 8mg / mL.

8. The application of the porous organic polymer-based metal catalyst according to claim 1 in the catalytic selective reduction of nitrobenzene compounds to aniline compounds, characterized in that... The process includes the following steps: a porous organic polymer-based metal catalyst, water, and ammonia borane are added to a thick-walled, pressure-resistant bottle, followed by the addition of nitrobenzene compounds. The reaction is carried out under heat in a closed system to prepare aniline compounds. After the raw materials have reacted completely, dichloromethane is added to the reaction system as an extraction solvent, and a saturated sodium chloride aqueous solution is added as a demulsifier. After three extractions, the organic phases are combined, concentrated, and then separated and purified on a silica gel column to obtain the aniline product.

9. The application according to claim 8, characterized in that: The heating reaction temperature is 80℃, and the time is 10-24h; the mass ratio of the nitrobenzene compound to the porous organic polymer-based metal catalyst is 1:1; the equivalent ratio of the nitrobenzene compound to ammonia borane is 1:(1-5); and the concentration of the nitrobenzene compound in water is 5mg / mL.

10. The application according to claim 8, characterized in that: The nitrobenzene compounds are nitrobenzene, 2-nitro-5-chloropyridine, p-fluoronitrobenzene, p-bromonitrobenzene, p-chloronitrobenzene, p-nitroacetanilide, p-nitrobenzyl alcohol, 7-nitrotetrahydroquinoline, 4-nitroanisole, 3-nitrotoluene, 2-nitrothiophene, and 1-nitronaphthalene.

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