Preparation and application of cerium-based solid hindered Lewis acid-base pair catalytic material

Abstract

The invention discloses preparation and application of a cerium-based solid hindered Lewis pair catalytic material, and belongs to the field of advanced nano composite catalytic materials. The preparation method comprises the following steps: inducing abundant defect structures in an MOF-808 (Ce) framework in situ, and further constructing a series of solid hindered Lewis acid-base pair catalysts containing Ce-OH (used as Lewis base sites) and coordinated unsaturated cerium active sites (Ce-CUS, used as Lewis acid sites). Stable existence of the hindered Lewis acid-base pair is guaranteed through the space limiting effect of a metal organic framework (MOFs), and a functional group can be regarded as a remote microenvironment for adjusting the electronic characteristics of the hindered Lewis acid-base pair. The groups with electron donating characteristics improve the polarization capability of hindered Lewis acid-base para-sites by adjusting the spatial redistribution of local electron density. The catalyst prepared by the invention has the advantages of simple synthesis process, controllable parameters and short period, and is suitable for large-scale production.

Description

Technical Field

[0001] The present invention relates to the field of cerium-containing compound catalysts and the catalytic hydrogenation of unsaturated organic compounds, and particularly to a metal-organic framework (MOF) hydrogenation catalyst, a preparation method thereof, and an application thereof. Background Art

[0002] The catalytic hydrogenation of unsaturated organic compounds is a powerful tool in synthetic chemistry and chemical production, and is of great significance for promoting industrial upgrading. Developing green catalytic technologies is the only way to achieve sustainable chemistry. Replacing precious metals, which currently dominate the field of hydrogenation catalysts, with abundant, environmentally friendly, and cost-effective inexpensive metals has become one of the primary goals in the development of new hydrogenation catalysts. This transformation not only helps reduce production costs but also promotes a win-win situation for the widespread application of catalysts and environmentally friendly production. Currently, most of the reported inexpensive metal catalysts have limited catalytic activity, which greatly restricts the popularization and application of inexpensive metal catalysts. In view of this, the scientific research community is actively committed to exploring a class of catalytic sites with simple preparation, excellent stability, and highly adjustable structures, aiming to break through the existing bottlenecks, promote the efficient catalytic application of inexpensive metals in hydrogenation reactions, and thus open up new, greener, and more economical chemical transformation pathways. Stephan first proposed the new concept of frustrated Lewis pairs, deeply elaborating on the unique synergistic mechanism between Lewis acid and Lewis base sites to promote the efficient heterolytic cleavage of hydrogen molecules, and emphasizing the indispensability of both. Given that neutralization reactions easily occur between Lewis acids and bases, leading to a significant reduction in catalytic activity, precisely designing the spatial configurations of Lewis acids and Lewis bases to ensure their efficient synergistic action with reaction substrates is crucial for maintaining the excellent performance of the catalyst.

[0003] Early frustrated Lewis pair catalysts were mainly based on main group element molecules in homogeneous systems, such as frustrated Lewis pair catalysts composed of compounds of boron and phosphorus, which could effectively activate hydrogen and exhibit excellent hydrogenation activity for unsaturated organic compounds under mild conditions. Nevertheless, these frustrated Lewis pair catalysts also have obvious limitations. For example, borane-tetrahydrofuran adduct (BH 3 ·THF) and PPh 3The hindered Lewis acid-base pair catalysts show high activity in hydrogenation reactions, but their stability is insufficient and they are easily decomposed during the reaction, causing the activity of the catalyst to decrease over time. In addition, such catalysts are often difficult to separate and recover from the reaction mixture after the reaction. For example, the phosphine ligands may be oxidized after the reaction, making the recycling of the catalyst complicated and costly. In view of this, the researchers introduced the hindered Lewis acid-base pair catalyst into a porous material system to achieve its heterogeneous transformation. This heterogeneous hindered Lewis acid-base pair catalyst can not only improve stability and reusability, but also enhance catalytic efficiency and selectivity, providing new ideas for the development of green chemistry and sustainable catalytic processes.

[0004] The invention patent (CN116328835B) uses chromium-based MIL-101, gold compound solution and Lewis base solution to prepare a fully fixed hindered Lewis acid-base pair material (Au@MIL-101-LB). This method has problems such as expensive raw materials for catalyst preparation and complex catalyst preparation process.

[0005] The invention patent (CN117399069A) uses piperazine to react with chloromethylated polyphenylene sulfide fiber, and introduces 3-bromopropylene and HB (C 6 F 5 ) 2 A polyphenylene sulfide fiber-supported hindered Lewis acid-base catalyst is prepared. The method has the problems of complex preparation and high catalyst price. Summary of the invention

[0006] In view of the above problems, the technical problem to be solved by the present invention is to improve the atom economy of hindered Lewis acid-base catalysts and improve the conversion rate of unsaturated organic compounds. By changing the composition and catalytic mechanism of the catalyst active sites and optimizing the synthesis conditions of MOFs, a method for preparing a low-cost cerium-based solid hindered Lewis acid-base catalyst material with simple process, mild conditions and controllable parameters is developed for application in the hydrogenation reaction of unsaturated organic compounds.

[0007] The technical solution adopted by the present invention is as follows:

[0008] A method for preparing a cerium-based solid hindered Lewis acid-base pair catalytic material, specifically comprising the following steps:

[0009] a. The 1,3,5-benzenetricarboxylic acid, the monocarboxylic acid functional group ligand and N, N-dimethylformamide were mixed to obtain a solution 1;

[0010] b. The ammonium cerium nitrate and deionized water were mixed to obtain a solution 2;

[0011] c. Solution 1 and solution 2 were mixed and placed in an oil bath for reaction. After the reaction was completed, the mixture was cooled, centrifuged and washed to obtain a solid precipitate.

[0012] d. The solid precipitate obtained in c is dried and then activated to obtain the cerium-based solid hindered Lewis acid-base catalytic material MOF-808 (Ce) -X.

[0013] Furthermore, the mass ratio of 1,3,5-benzenetricarboxylic acid, monocarboxylic acid functional group ligand and N, N-dimethylformamide described in a is 1: 0.05~0.20: 30~80.

[0014] Further, the monocarboxylic acid functional group ligand described in a is one of 4-aminobenzoic acid, 4-hydroxybenzoic acid, 4-mercaptobenzoic acid, 3-aminobenzoic acid, and 3-hydroxybenzoic acid;

[0015] Furthermore, the solution 1 and solution 2 described in c are mixed, wherein the mass ratio of ammonium cerium nitrate to 1,3,5-benzenetricarboxylic acid is 6~10:1.

[0016] Furthermore, the reaction described in c is carried out at a stirring speed of 300 to 800 rpm / min, a reaction temperature of 80 to 120°C, and a reaction time of 15 to 30 min.

[0017] Furthermore, the washing liquid used for washing described in c is N, N-dimethylformamide and one or two of methanol, ethanol or acetone, and the washing times are 3 to 6 times.

[0018] Furthermore, the drying temperature described in d is 80°C, and the activation is vacuum activation at a temperature of 150-200°C for 3-5 hours.

[0019] The cerium-based solid hindered Lewis acid-base catalytic material obtained by the preparation method is applied to the hydrogenation reaction of unsaturated organic compounds.

[0020] Furthermore, the application includes the following steps: contacting an unsaturated organic compound with a cerium-based solid hindered Lewis acid-base pair catalytic material in a fixed bed reactor in the presence of a solvent, fully sealing the high-pressure reactor, introducing nitrogen for replacement 2 to 5 times, then filling with hydrogen, and raising the temperature for hydrogenation reaction, wherein the pressure of the hydrogenation reaction is 2 to 3 MPa, the reaction temperature is 100 to 120°C, and the reaction time is 10 to 12 h; the mass ratio of the cerium-based solid hindered Lewis acid-base pair catalytic material to the unsaturated organic compound is 0.3 to 2: 2 to 5.

[0021] Furthermore, the unsaturated organic compound is one of dicyclopentadiene, styrene, phenylacetylene and 1-hexene.

[0022] The present invention uses hydrogen as a hydrogen source and dicyclopentadiene as a substrate, utilizes an addition reaction to hydrogenate dicyclopentadiene to dihydrodicyclopentadiene, uses a cerium-based solid hindered Lewis acid-base pair catalytic material as the catalyst, and utilizes cerium ammonium nitrate, 1,3,5-benzenetricarboxylic acid and a monocarboxylic acid functionalized ligand to in-situ synthesize defective MOF-808 (Ce) -X.

[0023] Through the above technical solution, the present invention has the following beneficial effects:

[0024] The present invention adopts a simple functionalized monocarboxylic acid ligand competitive coordination strategy, and directly uses the cerium-based solid hindered Lewis acid-base pair catalytic material for the hydrogenation of unsaturated organic compounds, obtaining a >99% conversion rate of dicyclopentadiene and a ~80% conversion rate of styrene. The competitive coordination of the monocarboxylic acid ligand with an electron-donating functional group in the present invention induces the formation of defects, thereby constructing a series of solid hindered Lewis acid-base pair catalytic materials containing Ce-OH (as a Lewis base site) and coordinated unsaturated cerium active sites (Ce-CUS, as Lewis acid sites), and the Ce-CUS and Ce-OH sites are respectively connected to the σ and σ of HH. Orbital action and "push-pull" synergy promote the heterolytic cleavage of HH bonds. Functional groups, as remote microenvironments, improve the polarization ability of hindered Lewis acid-base sites by adjusting the spatial redistribution of local electron density, thereby promoting their reaction activation and showing excellent hydrogenation activity. At the same time, compared with traditional homogeneous hindered Lewis acid-base catalysts, the preparation process of this solid heterogeneous hindered Lewis acid-base catalyst is simple, the parameters are controllable, the cost is lower, and it is suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The MOF-808(Ce), MOF-808(Ce)-NH obtained in Comparative Example 1 and Examples 1 and 2 of the present invention 2 and SEM images of MOF-808(Ce)-OH.

[0026] Figure 2 The MOF-808(Ce), MOF-808(Ce)-NH obtained in Comparative Example 1 and Examples 1 and 2 of the present invention 2 and pore size distribution of MOF-808(Ce)-OH.

[0027] Figure 3 The MOF-808(Ce) and MOF-808(Ce)-NH obtained in Comparative Example 1 and Example 1 of the present invention are 2 Diffuse reflectance infrared image.

[0028] Figure 4The MOF-808(Ce) and MOF-808(Ce)-NH obtained in Comparative Example 1 and Example 1 of the present invention are 2 Electron paramagnetic resonance image. DETAILED DESCRIPTION

[0029] The present invention is further described below in conjunction with specific examples, which are only a part of the present invention, rather than all of the examples. Unless otherwise specified, the various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0030] Example 1

[0031] a. Mix 210 mg (1 mmol) of 1,3,5-benzenetricarboxylic acid, 27.4 mg (0.2 mmol) of 4-aminobenzoic acid and 12 mL of N, N-dimethylformamide, and ultrasonicate for 5 min to obtain a clear mixed solution 1;

[0032] b. 1753 mg (3.2 mmol) of ammonium cerium nitrate and 6 mL of deionized water were mixed evenly and ultrasonicated for 5 min to obtain a clear mixed solution 2;

[0033] c. Mix the mixed solution 1 and the mixed solution 2 evenly and place them in an oil bath, react at 600 rpm / min and 100°C for 15 min. After the reaction is completed, cool to room temperature, centrifuge the mixed solution at 10,000 rpm to separate the solid precipitate, and wash it with N, N-dimethylformamide and methanol three times respectively;

[0034] d. The solid precipitate obtained in c was dried in a vacuum oven at 80 °C for 12 h and activated at 150 °C for 3 h to obtain MOF-808 (Ce) -NH 2 ;

[0035] e. The prepared MOF-808 (Ce)-NH 2 For the hydrogenation reaction test, 20 mg of the activated MOF-808 (Ce) -X catalyst was weighed and placed in a high-pressure reactor. 200 μL of dicyclopentadiene and 5 mL of methanol were added. The high-pressure reactor was fully sealed, nitrogen was introduced for replacement three times, and then hydrogen was filled in. The temperature was raised to 100 °C and the reaction was carried out for 10 h.

[0036] f. Cool the reactor to room temperature, take out the reaction solution, centrifuge and take the supernatant, dilute it 10 times with methanol, and analyze and detect it with gas chromatography. The detection instrument is GC-MS Agilent 7890 analyzer. The components to be tested are qualitatively analyzed according to the retention time of the chromatographic peaks, and quantitatively analyzed by area normalization method to obtain the conversion rate of unsaturated organic compounds. The test procedure is: the temperatures of the injector and the detector are set to 250 ℃ and 280 ℃ respectively, and the column is heated from 50 ℃ to 100 ℃ at a rate of 20 ℃ / min and maintained for 2 min, and then heated to 120 ℃ at a rate of 5 ℃ / min and maintained for 2 min. The test results are shown in the table.

[0037] Example 2

[0038] The 4-aminobenzoic acid in Example 1 was replaced by 4-hydroxybenzoic acid, and the rest was the same as Example 1 to obtain the catalytic material MOF-808(Ce)-OH.

[0039] Example 3

[0040] The 4-aminobenzoic acid in Example 1 was replaced by 4-mercaptobenzoic acid, and the rest was the same as Example 1 to obtain the catalytic material MOF-808(Ce)-SH.

[0041] Example 4

[0042] The 4-aminobenzoic acid in Example 1 was replaced by 3-aminobenzoic acid, and the rest was the same as Example 1 to obtain the catalytic material MOF-808 (Ce) -NH 2 -1.

[0043] Example 5

[0044] The 1753 mg (3.2 mmol) of ammonium cerium nitrate and 210 mg (1 mmol) of 1,3,5-benzenetricarboxylic acid in Example 1 were replaced by 1370 mg (2.5 mmol) of ammonium cerium nitrate and 210 mg (1 mmol) of 1,3,5-benzenetricarboxylic acid, and the rest was the same as in Example 1 to obtain the catalytic material MOF-808 (Ce) -NH 2 -2.

[0045] Example 6

[0046] The 27.4 mg (0.2 mmol) 4-aminobenzoic acid in Example 1 was replaced by 20.5 mg (0.15 mmol) 4-aminobenzoic acid, and the rest was the same as in Example 1 to obtain the catalytic material MOF-808 (Ce) -NH 2 -3.

[0047] Example 7

[0048] The N, N-dimethylformamide and methanol in step c of Example 1 were replaced by N, N-dimethylformamide and acetone, and the rest was the same as in Example 1 to obtain the catalytic material MOF-808 (Ce) -NH 2 -4.

[0049] Comparative Example 1

[0050] The rest is the same as Example 1, except that: no 4-aminobenzoic acid (monocarboxylic acid functional group ligand) is added, and the catalytic material MOF-808 (Ce) is obtained.

[0051] The hydrogenation reaction results of Examples 1 to 7 and Comparative Example 1 are shown in the following table:

[0052]

[0053] As can be seen from the above table, the hydrogenation activity of dicyclopentadiene and styrene of the cerium-based solid hindered Lewis acid-base pair catalytic material MOF-808-X is much higher than that of MOF-808, indicating that the cerium-based solid hindered Lewis acid-base pair catalytic material prepared by the monocarboxylic acid ligand competitive coordination and electron-donating functional group remote control strategy adopted in the present invention can significantly improve the catalytic activity of the hydrogenation reaction of unsaturated organic compounds such as dicyclopentadiene / styrene.

[0054] MOF-808-NH obtained in Examples 1 and 2 2 The scanning electron microscope images and pore size distribution diagram of MOF-808-OH catalyst are shown in Figure 1 and Figure 2 Compared with MOF-808 synthesized without adding monocarboxylic acid functional group ligand, MOF-808-NH 2 The increase in the number of mesopores and the average pore size of MOF-808-OH indicate that the competitive coordination of the monocarboxylic acid ligands induces the formation of defects while maintaining the MOF framework structure. The increase in mesopores helps to improve the diffusion and adsorption efficiency of the substrate, providing a favorable prerequisite for achieving excellent hydrogenation performance.

[0055] Figure 3 and Figure 4 MOF-808-NH 2 In situ diffuse reflectance infrared images and electron paramagnetic resonance images of MOF-808. 2 It contains the most Ce-CUS (Lewis acid) and Ce-OH (Lewis base) sites, which indicates that it has more hindered Lewis acid-base pair sites and thus exhibits higher hydrogenation activity.

[0056] The above description is only a preferred embodiment of the present invention, but the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements and improvements based on the technical solutions and inventive concepts of the present invention within the technical scope disclosed by the present invention, and all of these should be covered by the protection scope of the present invention.

Claims

1. A method for preparing a cerium-based solid hindered Lewis acid-base catalytic material, characterized in that: The following steps are involved: a. The 1,3,5-benzenetricarboxylic acid, the monocarboxylic acid functional group ligand and N, N-dimethylformamide were mixed to obtain a solution 1; b. The ammonium cerium nitrate and deionized water were mixed to obtain a solution 2; c. Solution 1 and solution 2 were mixed and placed in an oil bath for reaction. After the reaction was completed, the mixture was cooled, centrifuged and washed to obtain a solid precipitate. d. The solid precipitate obtained in c is dried and then activated to obtain the cerium-based solid hindered Lewis acid-base pair catalytic material MOF-808 (Ce) -X.

2. The preparation method according to claim 1, characterized in that: The mass ratio of 1,3,5-benzenetricarboxylic acid, monocarboxylic acid functional group ligand and N, N-dimethylformamide described in step a is 1: 0.05~0.20: 30~80.

3. The preparation method according to claim 1, characterized in that: The monocarboxylic acid functional group ligand described in step a is one of 4-aminobenzoic acid, 4-hydroxybenzoic acid, 4-mercaptobenzoic acid, 3-aminobenzoic acid and 3-hydroxybenzoic acid.

4. The preparation method according to claim 1, characterized in that: The solution 1 and solution 2 described in step c are mixed, wherein the mass ratio of ammonium cerium nitrate to 1,3,5-benzenetricarboxylic acid is 6-10:

1.

5. The preparation method according to claim 1, characterized in that: The reaction in step c is carried out at a stirring speed of 300 to 800 rpm / min, a reaction temperature of 80 to 120°C, and a reaction time of 15 to 30 min.

6. The preparation method according to claim 1, characterized in that: The washing liquid used for washing in step c is N, N-dimethylformamide and one or two of methanol, ethanol or acetone, and the washing times are 3 to 6 times.

7. The preparation method according to claim 1, characterized in that: The drying temperature in step d is 80°C, and the activation is vacuum activation at 150-200°C for 3-5 hours.

8. The cerium-based solid hindered Lewis acid-base catalytic material obtained by the preparation method according to any one of claims 1 to 7 is used in the hydrogenation reaction of unsaturated organic compounds.

9. The use of the cerium-based solid hindered Lewis acid-base catalytic material according to claim 8, characterized in that The unsaturated organic compound is contacted with a cerium-based solid hindered Lewis acid-base catalytic material in the presence of a solvent in a fixed bed reactor, the high-pressure reactor is fully sealed, nitrogen is introduced for replacement 2 to 5 times, hydrogen is then introduced, and the temperature is increased for hydrogenation reaction, the pressure of the hydrogenation reaction is 2 to 3 MPa, the reaction temperature is 100 to 120 ° C, and the reaction time is 10 to 12 h; the mass ratio of the cerium-based solid hindered Lewis acid-base catalytic material to the unsaturated organic compound is 0.3 to 2: 2 to 5.

10. Use of the cerium-based solid hindered Lewis acid-base pair catalytic material according to claim 8 or 9, characterized in that: The unsaturated organic compound is one of dicyclopentadiene, styrene, phenylacetylene and 1-hexene.

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