A hydrogen-bonded cof polymer and a preparation method and application thereof

Abstract

The present application relates to the technical field of porous organic polymer materials, in particular to a hydrogen bond-containing COF polymer and a preparation method and application thereof.The DHTA-BDU-COF polymer provided by the present application has a yield of up to 99% when used as a catalyst to catalyze a tandem de-aldol-Knoevenagel condensation reaction.Meanwhile, the DHTA-BDU-COF polymer still maintains a catalytic yield of more than 90% after 15 cycles of reaction, no special, toxic and harmful reagents are used in the catalytic experiment, the reaction conditions are mild, and the DHTA-BDU-COF polymer shows high stability and recyclability, and has good application value.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of porous organic polymer materials, and particularly relates to a hydrogen-bond-containing COF polymer and a preparation method and application thereof. BACKGROUND

[0002] Covalent organic framework material (COF) is a new type of multifunctional crystalline organic catalyst constructed by organic monomers through strong covalent bonds. COFs have periodic network structure, clear structure, regular pore, strong designability and other advantages, and are considered as a very promising catalyst carrier. Hydrogen bond donor (HBD) can significantly improve the yield and selectivity of the reaction by forming hydrogen bonds with the substrate in the catalytic reaction, and has structural adjustability and good stability.

[0003] The tandem deoxo-Knoevenagel reaction is an important organic synthesis reaction that combines deoxo and Knoevenagel condensation steps to construct complex organic molecules. Currently, researchers are exploring various new catalysts, however, the synthesis of these catalysts is complex, costly, and may exhibit poor stability and recyclability in practical applications. Despite the great potential of the tandem deoxo-Knoevenagel reaction in organic synthesis, the above problems still limit its widespread application. Therefore, seeking a simple and efficient, low-cost, and highly stable catalyst is still an important research direction. SUMMARY

[0004] In order to solve the above problems, the present application provides a hydrogen-bond-containing COF polymer and a preparation method and application thereof. When the hydrogen-bond-containing COF polymer is used as a catalyst to catalyze the tandem deoxo-Knoevenagel reaction, it has high and stable catalytic performance and can be recycled multiple times.

[0005] To achieve the above technical purposes, the present application adopts the following technical solutions:

[0006] In a first aspect, the present application provides a DHTA-BDU-COF polymer, which takes the structure represented by formula (I) as a structural repeat unit:

[0007]

[0008] In a second aspect, the present application provides a preparation method of the above-mentioned DHTA-BDU-COF polymer, which comprises the following steps:

[0009] (1) 1,4-phenylene diisocyanate and ammonia water are used as raw materials to prepare 1,4-diphenyl urea by mixing reaction;

[0010] (2) DHTA-BDU-COF polymer is prepared by reacting 1,4-diphenylurea with 2,4-dihydroxy-1,3,5-benzene tricarboxaldehyde and acetic acid.

[0011] In the specific embodiment of the present application, in step (1), the concentration of the ammonia water is 25-30 mol·L -1 ;

[0012] The mixing ratio of the 1,4-phenylene diisocyanate and the ammonia water is (1.0-1.5) g:(0.3-0.5) mol.

[0013] In the specific embodiment of the present application, in step (1), the reaction is carried out at 0-5℃ for 1-3h, and then the temperature is raised to room temperature for 3-6h.

[0014] After the reaction is completed, filtration, washing and drying treatment are further carried out, and the washing is carried out with water-tetrahydrofuran with a volume ratio of (1-3):1.

[0015] The drying is vacuum drying at room temperature.

[0016] In the specific embodiment of the present application, in step (2), the molar ratio of the 2,4-dihydroxy-1,3,5-benzene tricarboxaldehyde, 1,4-diphenylurea and acetic acid is 1:1.

[0017] In the specific embodiment of the present application, in step (2), the solvent is composed of o-dichlorobenzene and tert-butyl alcohol, and the volume ratio of the o-dichlorobenzene and the tert-butyl alcohol is 1.8-2.2:1, preferably 2:1.

[0018] In the specific embodiment of the present application, in step (2), the reaction is carried out at a temperature of 100-120℃, preferably 110℃, and the reaction time is 90-100h, preferably 92h.

[0019] After the reaction is completed, washing and drying treatment are further carried out.

[0020] The washing is carried out with dimethylformamide and tetrahydrofuran respectively.

[0021] The drying is vacuum drying.

[0022] In a third aspect, the present application provides application of the above-mentioned DHTA-BDU-COF polymer in catalyzing a tandem deacetalization-Knoevenagel reaction.

[0023] In a fourth aspect, the present application provides a method for catalyzing a tandem deacetalization-Knoevenagel reaction, which adopts the above-mentioned DHTA-BDU-COF polymer as a catalyst, and carries out reflux reaction of benzaldehyde dimethyl acetal and malononitrile to prepare 2-benzylidene malononitrile.

[0024] In the detailed description of the present application, the molar ratio of the DHTA-BDU-COF polymer, benzaldehyde dimethyl acetal and malononitrile is (2-4):(1-3):(1-3).

[0025] Further, the molar ratio of the DHTA-BDU-COF polymer, benzaldehyde dimethyl acetal and malononitrile is 3:2:2.

[0026] In the detailed description of the present application, the reaction temperature is 70-80℃, and the reaction time is 4-6h.

[0027] Further, the reaction temperature is 75℃, and the reaction time is 5h.

[0028] The present application has the following beneficial effects:

[0029] (1) The DHTA-BDU-COF polymer prepared by the present application has high crystallinity, large porosity and good chemical stability, and thus has the potential as a catalyst.

[0030] (2) When the DHTA-BDU-COF polymer provided by the present application is used as a catalyst for catalyzing the tandem deacetalization-Knoevenagel reaction, the yield can be as high as 99%.

[0031] (3) The DHTA-BDU-COF polymer provided by the present application is used as a catalyst for catalyzing the tandem deacetalization-Knoevenagel reaction, and has the advantages of low price, high yield, high purity, easy separation, no use of special, toxic and harmful reagents in the experimental process, mild reaction conditions, high stability and recyclability in practical application, and good practical value. BRIEF DESCRIPTION OF DRAWINGS

[0032] The drawings constituting a part of the specification of the present application are used to provide further understanding of the present application, and the schematic embodiments of the present application and the description thereof are used to explain the present application, and do not constitute an improper limitation on the present application.

[0033] Figure 1 The scanning electron microscope image of the DHTA-BDU-COF prepared for Example 2 of the present application;

[0034] Figure 2 The thermogravimetric diagram of the DHTA-BDU-COF prepared for Example 2 of the present application;

[0035] Figure 3 The experimental and simulated PXRD diagram of the DHTA-BDU-COF prepared for Example 2 of the present application;

[0036] Figure 4N2adsorption plot of DHTA-BDU-COF prepared for Example 2 of the present invention;

[0037] Figure 5 PXRD pattern of DHTA-BDU-COF prepared for Example 2 of the present invention after 15 cycles as a catalyst. DETAILED DESCRIPTION

[0038] It should be noted that the following detailed description is exemplary in nature and is intended to provide further description of the application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0039] In order to enable persons skilled in the art to more clearly understand the technical solutions of the present application, the technical solutions of the present application will be described in detail below in combination with specific examples.

[0040] Example 1

[0041] Preparation of ligand 1,4-diphenylurea (BDU):

[0042] A 26 mL, 27.75 M solution of ammonia was cooled to 0 °C, and 3 g of 1,4-phenylene diisocyanate was added portionwise. The reaction mixture was stirred at 0 °C for 5 h, then warmed to room temperature and stirred for an additional 11 h. The white solid was collected by filtration, washed with 150 mL of water and 150 mL of tetrahydrofuran (THF), and dried under vacuum at room temperature to yield white 1,4-diphenylurea (BDU). The reaction process is as follows:

[0043]

[0044] Example 2

[0045] Preparation of DHTA-BDU-COF polymer:

[0046] The ligand 1,4-diphenylurea (BDU) (0.02 mmol, 3.88 mg) and 2,4-dihydroxy-1,3,5-benzene tricarboxaldehyde (0.02 mmol, 3.56 mg) prepared in Example 1 were placed in a pressure-resistant glass tube, a mixture of o-dichlorobenzene and tert-butyl alcohol (5 mL:2 mL) was used as the reaction solvent, and 400 ul of 6M acetic acid solution was added. The mixture was ultrasonically treated to mix uniformly, then degassed by freeze-pump-thaw cycle, and vacuum sealed for reaction at 110 °C for 4 days. After the glass tube was cooled, the product was collected by filtration, washed with DMF and THF three times respectively, and dried under vacuum to obtain red-brown crystalline powder DHTA-BDU-COF.

[0047] The reaction process is as follows:

[0048] The reaction process is as follows:

[0049] The DHTA-BDU-COF polymer prepared in the embodiment was characterized. Figure 1 The scanning electron microscope image of the DHTA-BDU-COF polymer, Figure 2 The thermogravimetric image of the DHTA-BDU-COF polymer shows that the weight of the COF does not decrease significantly before the temperature reaches 307°C, proving that the synthesized COF has good thermal stability. Figure 3 The PXRD image of the DHTA-BDU-COF polymer shows that the COF has good crystallinity. Figure 4 The N2 adsorption image of the DHTA-BDU-COF polymer. The test results show that the nitrogen adsorption amount of the DHTA-BDU-COF is 90 cm 3 / g, and the surface area is 31.37 m 2 / g at 77K. As can be seen from Figure 1 , Figure 3 and Figure 4 , the DHTA-BDU-COF polymer prepared in the embodiment has a porous structure. As can be seen from Figures 2-3 , the DHTA-BDU-COF polymer is a crystalline porous material with high thermal stability.

[0050] Example 3

[0051] Different from Example 2, the molar ratio of DHTA to BDU is 1:0.8, and other preparation processes are exactly the same as those of Example 2, but the DHTA-BDU-COF polymer cannot be synthesized.

[0052] Example 4

[0053] Different from Example 2, the molar ratio of DHTA to BDU is 1:1.2, and other preparation processes are exactly the same as those of Example 2, but the DHTA-BDU-COF polymer cannot be synthesized.

[0054] Catalytic performance

[0055] The DHTA-BDU-COF polymer prepared in Example 2 of the present application was used as a heterogeneous catalyst to catalyze a one-pot tandem de-aldol-Knoevenagel condensation reaction. The reaction process is as follows:

[0056]

[0057] The specific experimental steps of the DHTA-BDU-COF catalyzed tandem de-aldol-Knoevenagel reaction are as follows:

[0058] In the presence of DHTA-BDU-COF (6 mg, 3 mol%), 0.2 mL (2.0 mmol) benzaldehyde dimethyl acetal was mixed with 132 mg (2.0 mmol) malononitrile in a flask and subjected to solvent-free heating reflux operation at 75°C for 5 hours. After the reaction, the yield was determined by GC-MS, and column chromatography (petroleum ether: ethyl acetate = 5:1) was used for purification, and finally 2-benzylidene malononitrile was obtained in the form of white solid powder with a yield of 99%.

[0059] The reaction was tracked by TLC, and after the reaction, the catalyst was recovered by centrifugation and directly used in the next cycle. According to the above conditions, the catalyst was used for 15 cycles, and the reaction liquid was separated to calculate the yield, and the catalytic effect is shown in Table 1. Figure 5 PXRD image of the catalyst after 15 cycles, from Figure 5 It can be seen that after 15 cycles of the catalyst, the DHTA-BDU-COF framework does not change. As can be seen from Table 1, the yield of the product remains basically unchanged, and after 15 cycles, only a slight downward trend is shown, which reflects the excellent stability of the catalyst, which can be reused for more than 15 times, can significantly improve the utilization rate of the catalyst, and reduce the production cost.

[0060] Table 1 Catalytic effect of DHTA-BDU-COF in multiple cycles

[0061] Number of reactions Reaction time (h) Yield (%) 1 5 99 2 5 99 3 5 98 4 5 98 5 5 96 6 5 96 7 5 96 8 5 95 9 5 95 10 5 94 11 5 93 12 5 92 13 5 92 14 5 91 15 5 90

[0062] The DHTA-BDU-COF polymer provided by the application can be used as a catalyst to catalyze one-pot tandem deacetalization-Knoevenagel condensation reaction, and the yield can be as high as 99%. At the same time, after 15 cycles of the DHTA-BDU-COF polymer, the catalytic yield is still more than 90%, so it can be proved that the DHTA-BDU-COF polymer provided by the application has high and stable catalytic performance and can be recycled for multiple times.

[0063] The above only describes the preferred embodiments of the application and is not intended to limit the application. Those skilled in the art can make various modifications and changes to the application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the application shall be included in the protection scope of the application.

Claims

1. Application of a DHTA-BDU-COF polymer in catalyzing a tandem deacetalization-Knoevenagel condensation reaction, wherein the DHTA-BDU-COF polymer has a structure represented by formula (I) as a repeating unit: Formula (I).

2. The use according to claim 1, characterized in that The preparation method of the DHTA-BDU-COF polymer comprises the following steps: (1) Prepared by mixing 1,4-phenylene diisocyanate and ammonia water ; (2) DHTA-BDU-COF polymer was prepared by reacting 2,4-dihydroxy-1,3,5-benzenetricarboxaldehyde with acetic acid.

3. The use according to claim 2, characterized in that In step (1), the concentration of the ammonia water is 25-30 mol·L -1 ; The mixing ratio of the 1,4-phenylene diisocyanate and aqueous ammonia is (1.0-1.5) g: (0.3-0.5) mol.

4. The use according to claim 2, characterized in that In step (1), the reaction is carried out at 0-5°C for 1-3 h, and then the temperature is raised to room temperature and the reaction is carried out for 3-5 h; After the reaction is completed, filtration, washing and drying are also carried out; The drying is vacuum drying at room temperature.

5. The use according to claim 2, characterized in that In step (2), 2, 4-dihydroxy-1, 3, 5-benzenetricarboxaldehyde, The molar ratio is 1:

1.

6. The use according to claim 1, wherein 2-Benzalmalononitrile was prepared by reflux reaction of benzaldehyde dimethyl acetal and malononitrile using DHTA-BDU-COF polymer as catalyst.

7. The use according to claim 6, characterized in that The molar ratio of DHTA-BDU-COF polymer, benzaldehyde dimethyl acetal and malononitrile is (2~4):(1~3):(1~3).

8. The use according to claim 7, characterized in that The molar ratio of DHTA-BDU-COF polymer, benzaldehyde dimethyl acetal and malononitrile is 3:2:

2.

9. The use according to claim 6, characterized in that The reflux reaction temperature is 70-80° C., and the reaction time is 4-6 h.

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