CN109225339B

CN109225339B - Hierarchical assembly method and application of high-activity synergistic MOF catalyst

Info

Publication number: CN109225339B
Application number: CN201811139067.8A
Authority: CN
Inventors: 朱成峰; 汤海同; 胡圆圆; 杨可可; 李昌达; 李德; 吴祥; 李有桂; 罗云飞
Original assignee: Hefei University of Technology
Current assignee: Hefei University of Technology
Priority date: 2018-09-28
Filing date: 2018-09-28
Publication date: 2021-05-25
Anticipated expiration: 2038-09-28
Also published as: CN109225339A

Abstract

The invention discloses a hierarchical assembly method and application of a high-activity synergistic MOF catalyst, wherein ONO tridentate Schiff base is selected as a framework, an ONO tridentate Schiff base bridged ligand containing terminal carboxyl is designed and synthesized at first, and then a porous two-dimensional MOF catalyst 2 is synthesized by utilizing a hierarchical assembly method; secondly, the catalyst is used for immobilizing a molecular catalyst with a unique coordination environment and a spatial configuration in a pore channel structure of the MOF through the immobilization and domain-limiting effects of the MOF structure; and thirdly, the similar copper ions in the MOF catalyst can simultaneously activate two reaction substrates in the F-C reaction or the Henry reaction, so that the catalytic reaction is more efficient and easier to carry out, the catalytic activity of the catalyst is obviously improved compared with that of a mononuclear copper complex catalyst only containing one active catalytic site, and the MOF catalyst can still keep the catalytic activity unchanged after being recycled for 5 times as a heterogeneous catalyst.

Description

Hierarchical assembly method and application of high-activity synergistic MOF catalyst

Technical Field

The invention belongs to the technical field of organic chemistry and material chemistry, and particularly relates to a hierarchical assembly method and application of a high-activity synergistic MOF catalyst.

Background

Enzyme catalysis is a major process in nature because it has excellent conversion, specificity, efficiency and conversion range, which usually requires coordination between a metal center and a protein residue to activate a substrate. Therefore, in the past decades, efforts have been made to synthesize mononuclear metal-centered or multinuclear metal-centered biomimetic catalysts. Many homogeneous enzyme-mimetic co-catalysts, especially catalysts containing bimetallic catalytic centers, have been extensively studied due to their ease of design and synthesis, but they are limited in terms of stability and recyclability. In order to overcome the disadvantages of homogeneous catalysis, the method of supporting molecular catalyst on inorganic or organic carrier and further designing and synthesizing heterogeneous cooperative catalyst has been focused on by chemists. For example, li can and co-workers have recently developed a series of high performance heterogeneous solid catalysts with multiple active sites by using inorganic microporous/mesoporous materials or porous organic frameworks as supports to achieve efficient asymmetric concerted catalysis. Even with some progress in the research of such heterogeneous concerted catalysts, the structure of the active centres of these solid catalysts remains mysterious. It is known that the configuration and spatial distance of active sites greatly affect the efficiency of the catalyst, so that the rational design and synthesis of the solid-phase catalyst with precise structure and coordinated catalytic performance still face certain challenges and are also receiving more and more attention.

Metal-organic frameworks (MOFs) as a class of crystalline materials have great potential for application in heterogeneous catalysis due to their high porosity, high stability, compositional tunability, and well-defined reaction microenvironment. Particularly, the structural engineering and the modulation synthesis method of the MOF make considerable progress in recent years, and the control of the space configuration of a catalytic active center can be realized, so that the MOF becomes an ideal platform for designing a high-performance synergistic catalyst. For example, treyon topic group recently reported a series of MOF catalysts containing metal salen, which can achieve high efficiency and selectivity for catalyzing asymmetric cyanation of aldehydes and kinetic resolution of epoxides by utilizing the bimetallic concerted catalytic effect. The forest study group loads a cobalt (III) porphyrin molecular catalyst in MOFs with interpenetrating structures, thereby realizing efficient hydration reaction for catalyzing terminal alkynes. Despite the impressive progress of these studies, the reports of MOF-based co-catalysts are still very rare, and thus it is a current research focus to design new co-catalysts with high efficiency in organic catalytic reactions.

In order to obtain MOF-based synergistic catalysts with dual or multiple active metal centers, it is first of all necessary to judiciously select a suitable organic functionalized ligand as framework and a metal ion with a specific coordination configuration and catalytic properties as catalytic center and metal node, respectively. The ONO tridentate Schiff base is taken as a framework, and the ONO tridentate sites can be firmly bonded with metal ions through coordination and can form complexes with various metal centers, so that the catalyst has potential catalytic performance; and a terminal carboxyl group is introduced through modification of the tridentate Schiff base, so that the Schiff base metal complex can be further integrated into the MOF structure due to the fact that the ONO chelating center and the carboxyl group show different binding capacities to metals, and the MOF catalyst with a specific structure and function is obtained.

Disclosure of Invention

Aiming at the technical difficulty in the preparation of the MOF catalyst with the bimetallic synergistic activation performance at present, the MOF catalyst with the bimetallic synergistic catalytic performance is successfully constructed by a bottom-up hierarchical assembly method. According to the invention, a Schiff base bridged ligand simultaneously having a terminal carboxyl group and an ONO tridentate chelating site is prepared through organic synthesis reaction, a Schiff base mononuclear copper complex (1) is prepared through a solvothermal method and metal copper ions, and the mononuclear copper complex (1) is connected with cadmium-oxygen clusters with 2-connection and 4-connection effects through the solvothermal method, so that the porous two-dimensional MOF (2) is assembled. Different from the mononuclear copper complex 1, the MOF 2 has a binuclear copper metal center connected by a bridging oxygen atom, and the unique metal coordination environment and molecular space configuration thereof enable the binuclear metal center to show a synergistic catalytic effect in the Friedel-Crafts reaction between catalytic indole and nitrostyrene and the Henry reaction between aromatic aldehyde and nitromethane, so that the MOF catalyst shows ultrahigh catalytic activity compared with the mononuclear copper complex catalyst 1. To our knowledge, MOF catalyst 2 is currently the first example of a heterogeneous MOF catalyst based on a tridentate schiff base ligand framework and possessing a binuclear copper concerted catalytic center.

In order to achieve the above object, the present invention provides the following technical solutions:

a high-activity synergistic MOF catalyst comprises a compound 1 of a homogeneous catalyst with a mononuclear copper catalytic center and a compound 2 of an MOF catalyst with a bimetallic synergistic catalytic reaction effect, and has the following chemical structures:

the structures of the

compounds

1 and 2 are shown in figure 1.

The synthesis method of the compound 1 comprises the following steps:

(1) dissolving a mixture containing (1S, 2R) - (-) -1-amino-2-indanol and 3' -tert-butyl-5 ' -formyl-4 ' -hydroxybiphenyl-4-carboxylic acid in a methanol solvent, reacting at 60 ℃ for 12 hours, removing the organic solvent in vacuum, and washing with methanol to obtain the tridentate Schiff base ligand H containing the ONO electron donor₃L；

(2) Will contain Cu (OAc)₂·H₂O and ligand H₃The mixture of L was put into a mixed solvent containing DMF, MeOH and water, sealed, and heated at 60 ℃ for 24 hours to give compound 1 as blue needle crystals, which was washed with methanol and dried at room temperature.

The synthesis method of the compound 2 comprises the following steps:

will contain CdBr₂And Compound 1 in DMF, MeOH and water, sealed in a colorless glass bottle, and at 80 ℃ for a sustained heating reaction for 36 hours, after cooling and filtering, compound 2 blue bulk crystal, methanol washing, room temperature drying.

The structures of compound 1 and compound 2 were confirmed by single crystal X-ray diffraction, infrared spectroscopy and TGA. It is noteworthy that both

compounds

1 and 2 are very stable in air, with compound 2 being insoluble in water and common organic solvents.

Single crystal X-ray diffraction analysis showed Compound 1 crystallized in P2₁The space group comprises two crystal phase independent copper ions, two HL molecules, two coordination methanol molecules and a free methanol molecule. In the structure of 1, ligand H₃L acts as a tridentate chelating center through the ONO electron donor provided by the imine group and the two hydroxyl groups. As shown in FIG. 2, each metallic copper center is associated with 1 ligand H₃L of ONO electron donor coordinated with one MeOH molecule, Cu²⁺The ions adopt a distorted planar quadrilateral coordination configuration in which the Cu-O bond length ranges from 1.884(3) to

The Cu-N bond lengths range from 1.905(3) to

Notably, the carboxyl group in Compound 1 is protonated at 1700cm^-1At protonation COOH has a vC ═ O stretching vibration, which is consistent with ligand H before complex formation₃The characteristic peaks of L remain consistent. Thus, compound 1 of the present invention can be used as a secondary building block to make porous MOF materials.

Mixing the mononuclear copper complex 1 and Cd²⁺Carrying out solvothermal reaction on the ions to obtain a single crystal of the compound 2, wherein the single crystal X-ray diffraction shows that the compound 2 is a porous two-dimensional MOF structure and is crystallized in an orthogonal space groupP2 ₁2₁2. The CuL structural unit in the compound 2 has a similar quadrilateral coordination mode with the copper ions in the Cu (HL) structural unit in the compound 1, wherein the Cu-O bond length range is

The Cu-N bond length ranges respectively from

Unlike compound 1, the CuL as a molecular building block in compound 2 is bridged with two bridging oxygen atoms to form a cis-structured dimer (CuL)₂(as shown in fig. 3). Compound 2 contains two crystallographically independent Cd²⁺Ion, the center of Cd1 coordinates with 8 oxygen atoms from carboxylic acid groups at the ends of four ligands to form a distorted double-cap triangular prism coordination configuration with a Cd-O bond length in the range of

Cd2 is coordinated with 1 DMF molecule, two water molecules and 4 oxygen atoms of two ligand terminal carboxylic acid groups to form a twisted pentagonal bipyramid coordination configuration, and the Cd-O bond length range is

As shown in FIG. 4, in the present invention, dimeric (CuL)₂The units can be 2-linked organic building blocks, each with 4-linked Cd₁O₈Cluster and 2-linked Cd₂O₇The clusters are connected to form a two-dimensional network frame structure which respectively has about a axis

And the combination

And about along the c-axis

Open channel (fig. 5). Calculations using PLATON software showed that the porosity in compound 2 was 41.8% and was available to accommodate guest molecules. Thermogravimetric analysis showed that the guest molecules, such as methanol, water and DMF molecules, in the framework of compound 2 could be removed at a temperature range of 25-220 ℃ and the thermal stability of the framework of compound was as high as-315 ℃ (figure 6). The results of the powder X-ray diffraction experiments show that the framework structure and crystallinity of compound 2 remain intact after removal of the guest molecule (fig. 7).

The invention also provides an application of the

compounds

1 and 2 as catalysts in Friedel-Crafts catalytic reaction:

wherein R is selected from optionally substituted phenyl, 4-methylphenyl, 4-trifluoromethylphenyl, 3-methoxyphenyl, 4-chlorophenyl, 4-nitrophenyl; r¹Selected from H, methyl; r²Selected from H, phenyl, methyl; r³Selected from H, 5-methyl, 5-methoxy, 5-chloro, 6-methyl.

The catalytic reaction comprises the following steps:

(1) activation of the catalyst

The

compounds

1 and 2 as catalysts are firstly subjected to guest molecule exchange with an anhydrous ultra-dry solvent, then activated at 100 ℃, and the completion of the activation is verified through thermogravimetric analysis;

(2) catalytic Friedel-Crafts reaction

1.0mol% equivalent of the activated catalyst was added to a solution of 10mmol of β -nitroolefin derivative and 12mmol of indole in methylene chloride, the mixture was stirred at room temperature for 12 hours, then the mixture was centrifuged at 14000rpm for 10 minutes, and the supernatant was concentrated in vacuo,¹HNMR monitors reaction results and yields.

(3) Catalytic contrast reaction

Controlling the ratio of the catalyst and the nitrostyrene or the 4-methylnitrostyrene from 1: 100 to 1:1000 and 1: 10000, keeping the amount of nitrostyrene or 4-methylnitrostyrene at 10mmol and the amount of indole at 12mmol, stirring the mixture at room temperature for 12 hours, centrifuging at 14000rpm for 10 minutes, and concentrating the supernatant in vacuum,¹HNMR monitors reaction results and yields.

The results show that: under the same F-C reaction conditions, the mononuclear copper compound 1 only shows very general catalytic activity, and the MOF catalyst 2 with binuclear metallic copper catalytic center shows ultrahigh catalytic activity. And this difference in catalytic activity becomes more pronounced at very low catalyst to reaction substrate ratios.

The invention also provides an application of the

compounds

1 and 2 as catalysts in Henry catalytic reaction:

the catalytic reaction comprises the following steps:

(1) activation of the catalyst

The

compounds

(2) catalytic Henry reaction

1.0mol% equivalent of the activated catalyst was added to a methanol solution of 10mmol of the benzaldehyde derivative and 100mmol of nitromethane, the reaction mixture was stirred at 60 ℃ for 12 hours, then the mixture was centrifuged at 14000rpm for 10 minutes, the supernatant was concentrated in vacuo,¹HNMR monitors reaction results and yields.

(3) Catalytic contrast reaction

Controlling the ratio of the catalyst to the p-nitrobenzaldehyde from 1: 100 to 1: 1000 and 1: 10000, keeping p-nitrobenzaldehyde at 10mmol and nitromethane at 100mmol, stirring the mixture at 60 ℃ for 12 hours, then centrifuging the mixture at 14000rpm for 10 minutes, and concentrating the supernatant in vacuum,¹HNMR monitors reaction results and yields.

The results show that: under the same Henry reaction conditions, the catalytic activity of the MOF catalyst 2 with a bimetallic copper catalytic center is obviously increased compared with that of the compound 1 with mononuclear copper, and the difference of the catalytic activity becomes more obvious at a very low ratio of the catalyst to the reaction substrate.

The invention has the advantages that:

the method selects ONO tridentate Schiff base as a framework, firstly designs and synthesizes ONO tridentate Schiff base bridged ligand containing terminal carboxyl, and then synthesizes a porous two-dimensional MOF catalyst 2 by utilizing a hierarchical assembly method; secondly, the catalyst is used for immobilizing a molecular catalyst with a unique coordination environment and a spatial configuration in a pore channel structure of the MOF through the immobilization and domain-limiting effects of the MOF structure; and thirdly, the similar copper ions in the MOF catalyst can simultaneously activate two reaction substrates in the F-C reaction or the Henry reaction, so that the catalytic reaction is more efficient and easier to carry out, the catalytic activity of the catalyst is obviously improved compared with that of a mononuclear copper complex catalyst only containing one active catalytic site, and the MOF catalyst can still keep the catalytic activity unchanged after being recycled for 5 times as a heterogeneous catalyst.

Drawings

Fig. 1 shows the structures of compound 1 of a homogeneous catalyst with a mononuclear copper catalytic center and compound 2 of an MOF catalyst with a bimetallic concerted catalytic reaction effect.

FIG. 2 shows a molecular structure diagram of Compound 1.

FIG. 3 shows the connection pattern of the binuclear (CuL)2 unit with two cadmium-oxygen clusters in Compound 2.

FIG. 4 shows a stacking diagram of the framework structure of Compound 2 along the a-axis.

FIG. 5 shows a stacking diagram of the framework structure of Compound 2 along the c-axis.

Figure 6 shows the TGA profile of

compounds

1 and 2.

FIG. 7 shows a PXRD pattern of Compound 2.

Detailed Description

The foregoing and other aspects of the present invention are achieved by the following detailed description, which should not be construed to limit the claimed subject matter in any way. All technical solutions realized based on the above contents of the present invention belong to the scope of the present invention. The present invention has been described generally and/or specifically with respect to materials used in testing and testing methods.

Example 1

Compound H₃Preparation of L

Dissolving a mixture containing (1S, 2R) - (-) -1-amino-2-indanol and 3' -tert-butyl-5 ' -formyl-4 ' -hydroxybiphenyl-4-carboxylic acid in a methanol solvent, reacting at 60 ℃ for 12 hours, removing the organic solvent in vacuum, and washing with methanol to obtain the tridentate Schiff base ligand H containing the ONO electron donor₃L, yield 92%. FT-IR data (KBr pellet, cm)^-1)：3480(w)，2952(s)，2910(s)，2867(m)，1700(w)，1670(w)，1630(s)，1605(s)，1533(s)，1480(m)，1460(m)，1440(m)，1386(s)，1268(m)，1251(m)，1224(w)，1169(m)，1095(w)，1052(w)，1016(w)，993(w)，952(w)，888(w)，860(m)，790(m)，775(w)，750(s)，712(w)，651(w)，634(w)，620(w)，564(w)，527(m)，500(w)，449(w)。

Example 2

Preparation of Compound 1

Will contain Cu (OAc)₂·H₂O (10mmol) and ligand H₃A mixture of L (10mmol) was placed in a glass bottle containing a mixed solvent of DMF, MeOH and water. The bottle was sealed and heated at 60 ℃ for 24 hours. Compound 1 was collected as blue needle crystals, washed with methanol and dried at room temperature. Based on H₃The yield of L was about 75.0%. FT-IR data (KBr pellet, cm)^-1)：3480(s)，2950(s)，2910(s)，2870(m)，2360(w)，1700(w)，1620(s)，1604(s)，1533(s)，1478(w)，1458(w)，1420(m)，1386(s)，1328(m)，1275(s)，1258(m)，1228(m)，1166(s)，1107(s)，1072(m)，1053(w)，1013(w)，980(w)，950(w)，895(w)，857(m)，805(w)，788(m)，774(m)，751(m)，731(w)，711(w)，680(w)，640(w)，605(w)，548(w)，521(m)，491(w)，448(w)。

Example 3

Preparation of Compound 2

Will contain CdBr₂(0.2mmol) and Compound 1(0.2mmol) were placed in a glass vial containing a mixed solvent of DMF, MeOH and water. The bottle was sealed and heated at 80 ℃ for 36 hours to give blue blocky crystals 2, which were washed with methanol and dried at room temperature. Based on Cdbr₂The yield of (a) was about 60.0%. FT-IR data (KBr pellet, cm)^-1)：3450(s)，2951(s)，2908(s)，1660(s)，1620(s)，1603(s)，1529(s)，1478(w)，1457(m)，1393(s)，1324(m)，1277(s)，1257(s)，1230(m)，1199(w)，1163(s)，1099(m)，1010(w)，892(w)，860(s)，806(w)，788(s)，776(s)，752(s)，712(m)，662(m)，607(m)，544(m)，519(w)，464(m)。

The catalytic activity of two

catalyst compounds

1 and 2 designed and synthesized according to the present invention was examined below.

1. Catalytic Performance of different catalysts in the Frededl-Crafts reaction

1.0mol% of the catalyst was added to a solution of β -nitrostyrene derivative (10mmol) and indole (12mmol) in dichloromethane, and the mixture was stirred at room temperature for 12 hours. The mixture was then centrifuged at 14000rpm for 10 minutes, and the supernatant was concentrated in vacuo,¹yield by HNMR was determined as follows:

the results show that: under the optimum catalytic reaction conditions of the present invention, catalyst 2 effectively catalyzes the F-C reaction of indole with β -nitrostyrene, 4-methyl- β -nitrostyrene and 4-trifluoromethyl- β -nitrostyrene, wherein only 1.0mol% of the equivalent of catalyst can achieve 95%, 92% and 95% yields, respectively, in 12 hours (entries 1, 3, 5). In contrast, when the mononuclear copper complex 1 was used as the catalyst (same loading as the CuL unit in 2), the reaction yield was significantly reduced to only 39%, 31% and 42%, respectively (entries 2, 4, 6). This result indicates that compound 1 as a control shows only a very general catalytic activity. It can be seen that the unique bimetallic copper center contained in the structure of compound 2 of the present invention plays an important role in the catalytic activity of the F-C reaction.

2. Catalytic Activity of Compound 2 on different substrates

1.0mol% of a catalyst was added to a solution of a β -nitrostyrene derivative (10mmol) and an indole derivative (12mmol) in methylene chloride, and the mixture was stirred at room temperature for 12 hours. The mixture was then centrifuged at 14000rpm for 10 minutes, and the supernatant was concentrated in vacuo,¹yield by HNMR was determined as follows:

the substrate tolerance of compound 2 of the present invention was examined by the F-C reaction between various β -nitroolefin derivatives and indole derivatives. As a result, it was found that Compound 2 has a broad substrate tolerance to both indole and β -nitroolefin derivatives.

In the presence of the catalyst 2 of the present invention, it was found that various trans- β -nitrostyrene derivatives having different electron donating or electron withdrawing substituents can effectively react with indole to give the corresponding products in yields of 89-96% (entries 1, 3, 5, 6-9). In addition, the F-C reaction between trans- β -nitrostyrene and various indole derivatives (including mono-or di-substituted groups) under the action of catalyst 2 also gives the corresponding products in yields varying from 89 to 97% (entries 10-17). These results again indicate that 2, containing a bimetallic active center, can be used as a highly efficient catalyst in the F-C reaction with a wide substrate tolerance.

3. Synergistic activity of compound 2 in catalyzing F-C reaction

On the basis of the preliminary research on the reaction activity of the catalyst 2, the invention further researches the cooperativity of the compound 2 in the process of catalyzing the F-C reaction.

The uniform catalytic reaction conditions are maintained, but the ratio of the catalyst to the reaction substrate, namely the nitrostyrene or the 4-methylnitrostyrene, is controlled from 1: 100 to 1: 1000 and 1: 10000. the mixture was stirred at room temperature for 12 hours. The mixture was then centrifuged at 14000rpm for 10 minutes, and the supernatant was concentrated in vacuo,¹yield by HNMR was determined as follows:

to confirm that the binuclear metallic copper centers immobilized within the channels of MOF catalyst 2 were able to synergistically activate the reaction substrates indole and nitrostyrene, the catalytic activity of

catalysts

1 and 2 was further examined at very low C/S ratio (molar ratio of catalyst to nitrostyrene). The experimental results show that as the C/S ratio is varied from 1: 100 to 1: 1000 and 1: 10000, the catalytic activity of 1 is sharply reduced from 39% to 14% and 0% in the F-C reaction of indole and beta-nitrostyrene, compared with catalyst 1, the catalyst has a C/S ratio of 1: 1000 and 1: 10000 MOF catalyst 2 was still able to catalyze the reaction and higher yields of 52% and 17% were obtained. Similar observations were also made when 4-methyl- β -nitrostyrene was used as substrate under the same reaction conditions. These results indicate that the homogeneous mononuclear copper catalyst 1 has a lower reactivity at lower C/S ratios, probably due to the longer distance between the two culs, which hinders the synergistic effect of the CuL units in the catalytic process.MOF Structure immobilized binuclear copper (CuL) contrary to the low reactivity of 1₂The unit can simultaneously activate indole and nitrostyrene, and the synergistic catalytic process enables the catalyst 2 of the invention to show obviously enhanced catalytic activity compared with a mononuclear copper catalyst.

4. Stability and recoverability of Compound 2

On the basis of the research on the reaction activity of the catalyst 2, the invention further researches the stability and the cyclic usability of the compound 2 in the process of catalyzing the F-C reaction between nitrostyrene and indole.

1.0mol% of a catalyst was added to a solution of a β -nitrostyrene derivative (10mmol) and an indole derivative (12mmol) in methylene chloride, and the mixture was stirred at room temperature for 12 hours. The mixture was then centrifuged at 14000rpm for 10 minutes, and catalyst 2 was easily recovered quantitatively from the reaction mixture by centrifugation, and after washing with fresh solvent, catalyst 2 was reused. The catalyst is recycled for 5 times, the reaction yield is respectively 97, 95, 94, 93 and 93 percent, and the catalytic activity is hardly lost; in addition PXRD characterization of catalyst 2 after 5 cycles showed that the catalyst remained highly crystalline despite slight structural distortion (figure 7). Furthermore, it is noteworthy that if the catalyst is removed by centrifugation, the reaction will stop immediately. It is thus believed that compound 2 of the present invention is indeed a highly efficient and stable catalyst for the F-C reaction.

5. Catalytic performance of different catalysts in Henry reaction

Compounds

1 and 2 as catalysts exchanged guest molecules with anhydrous ultra-dry solvent, respectively, and then activated at 100 deg.C, 1.0mol% equivalent of the activated catalyst was added to a methanol solution of benzaldehyde derivative (10mmol) and nitromethane (100mmol), the mixture was stirred at 60 deg.C for 12 hours and then centrifuged at 14000rpm for 10 minutes, the supernatant was vacuum-concentrated,¹HNMR monitors the reaction results and yields as follows:

the results show that: under the optimal reaction conditions, the catalyst 2 of the present invention can efficiently catalyze the Henry reaction between benzaldehyde and its derivatives and nitromethane, wherein a catalyst loading of only 1.0mol% can provide reaction yields of 86-97% within 12 hours, respectively (entries 1, 3, 5-7). In the case of benzaldehyde and 4-nitrobenzaldehyde, when the mononuclear copper compound 1 was used as the catalyst (same loading as the CuL unit of 2), the reaction yield was significantly reduced to 48% and 53%, respectively (entries 2, 4). This result indicates that: the catalyst 2 of the present invention can also be used as a high-efficiency catalyst for the Henry reaction, while the catalyst 1 of the present invention as a control shows only a very general catalytic activity. It can be seen that the unique bimetallic copper center contained in the structure of compound 2 of the present invention also plays an important role in the catalytic activity of the Henry reaction.

6. Synergism of Compound 2 during catalytic Henry reaction

On the basis of the research on the activity of the compound 2 for catalyzing the Henry reaction, the invention also verifies that the compound 2 has the same cooperativity in the process of catalyzing the Henry reaction.

The consistent catalytic reaction condition is maintained, but the ratio of the catalyst to the reaction substrate p-nitrobenzaldehyde is controlled, and the reaction temperature is controlled from 1: 100 to 1: 1000 and 1: 10000. after stirring the mixture at 60 ℃ for 12 hours, the mixture was centrifuged at 14000rpm for 10 minutes, the supernatant was concentrated in vacuo,¹yield by HNMR was determined as follows:

the experimental results show that as the ratio of C/S is varied from 1: 100 to 1: 1000 and 1: 10000, the catalytic activity of the comparative compound 1 of the present invention sharply decreases from 53% to 20% and 3% in the Henry reaction between p-nitrobenzaldehyde and nitromethane, and the ratio of C/S is 1: 1000 and 1: 10000 f, MOF catalyst 2 of the present invention still allowed this reaction and achieved higher yields of 68% and 33%. Considering that the aldehyde compound carbonyl and the nitro group in nitromethane can be activated by Lewis acid catalyst, and combining the results of this comparative experiment, it is shown that under the same Henry reaction conditions, the higher catalytic performance exhibited by MOF catalyst 2 having bimetallic copper center can be attributed to the synergistic catalytic process of the reaction, i.e., the aldehyde and nitromethane are both immobilized on the bimetallic (CuL) on the channel walls of the MOF 2₂The units are activated synergistically. However, for the homogeneous catalyst 1 system, especially at low concentrations of CuL catalyst, the mode of concerted catalysis is unlikely to occur because the probability of activated nucleophile and electrophile collisions is very low. Also, this invention better illustrates that the preparation of a synergistic bimetallic catalyst can be conveniently achieved by the loading of the MOF structure. Thus, it is believed that the MOF catalyst 2 of the present invention, which is obtained by a bottom-up method through hierarchical assembly using a tridentate schiff base framework as a platform, is indeed a stable and efficient catalyst for a synergistic reaction.

Claims

1. A high-activity synergistic MOF catalyst, comprising a homogeneous catalyst compound 1 as a mononuclear copper complex and a MOF catalyst compound 2 as a MOF catalyst having a bimetallic copper synergistic catalytic effect;

the synthesis method of the compound 1 comprises the following steps:

(2) Will contain Cu (OAc)₂·H₂O and ligand H₃Placing the mixture of L into a mixed solvent containing DMF, MeOH and water, sealing, heating at 60 deg.C for 24 hr to obtain blue needle crystal compound 1, washing with methanol, and drying at room temperature;

the synthesis method of the compound 2 comprises the following steps:

2. The high activity synergistic MOF catalyst according to claim 1, characterized by the use of Friedel-Crafts catalytic reaction:

wherein R is selected from optionally substituted phenyl; r¹Selected from H, methyl; r²Selected from H, phenyl, methyl; r³Selected from H, 5-methyl, 5-methoxy, 5-chloro, 6-methyl.

3. The high activity synergistic MOF catalyst according to claim 2, wherein R is selected from optionally substituted 4-methylphenyl, 4-trifluoromethylphenyl, 3-methoxyphenyl, 4-chlorophenyl, 4-nitrophenyl.

4. Use of a high activity synergistic MOF catalyst according to claim 2 in Friedel-Crafts catalysed reactions, characterized in that the catalysed reaction comprises the steps of:

(1) activation of the catalyst

The compounds 1 and 2 as catalysts are firstly subjected to guest molecule exchange with an anhydrous ultra-dry solvent, then activated at 100 ℃, and the completion of the activation is verified through thermogravimetric analysis;

(2) catalytic Friedel-Crafts reaction

1.0mol% equivalent of the activated catalyst was added to a solution of 10mmol of β -nitroolefin derivative and 12mmol of indole in dichloromethane, the mixture was stirred at room temperature for 12 hours, then the mixture was centrifuged at 14000rpm for 10 minutes, and the supernatant was concentrated in vacuo.

5. The high activity synergistic MOF catalyst according to claim 1, characterized by the application in Henry's catalytic reaction:

。

6. use of the high activity synergistic MOF catalyst according to claim 5 in Henry catalytic reactions, characterized in that the catalytic reaction comprises the following steps:

(1) activation of the catalyst

(2) catalytic Henry reaction

1.0mol% equivalent of the activated catalyst was added to a methanol solution of 10mmol of benzaldehyde derivative and 100mmol of nitromethane, the reaction mixture was stirred at 60 ℃ for 12 hours, then the mixture was centrifuged at 14000rpm for 10 minutes, and the supernatant was concentrated in vacuo.

7. The high activity synergistic MOF catalyst according to claim 1, wherein compound 1 is the application of catalyst 2 as a control in Friedel-Crafts and Henry reactions.