COF polymer containing hydrogen bonds as well as preparation method and application of COF polymer

Abstract

The invention relates to the technical field of porous organic polymer materials, in particular to a hydrogen bond-containing COF polymer as well as a preparation method and application thereof. When the DHTA-BDU-COF polymer provided by the invention is used as a catalyst to catalyze a tandem deacetalization-Knoevenagel condensation reaction, the yield can reach up to 99%. Meanwhile, after 15 times of circular reaction, the DHTA-BDU-COF polymer still keeps the catalytic yield of 90% or above, no special, toxic and harmful reagent is used in the catalytic experiment process, the reaction condition is mild, meanwhile, the stability and recoverability are high, and the application value is good.

Description

Technical Field

[0001] The invention relates to the technical field of porous organic polymer materials, and in particular to a COF polymer containing hydrogen bonds and a preparation method and application thereof. Background Art

[0002] Covalent organic frameworks (COFs) are a new type of multifunctional crystalline organic catalyst constructed from organic monomers through strong covalent bonds. COFs have the advantages of periodic network structure, clear structure, regular pores, and strong designability, and are considered to be a very promising catalyst carrier. Hydrogen bond donors (HBDs) can significantly improve the yield and selectivity of the reaction by forming hydrogen bonds with the substrate in the catalytic reaction, and have structural adjustability and good stability.

[0003] The tandem deacetalization-Knoevenagel reaction is an important organic synthesis reaction that combines the two steps of deacetalization and Knoevenagel condensation to construct complex organic molecules. Currently, researchers are exploring various new catalysts. However, the synthesis of these catalysts is complex, the cost is high, and they may show poor stability and recyclability in practical applications. Although the tandem deacetalization-Knoevenagel reaction has great potential in organic synthesis, the above problems still limit its wide application. Therefore, seeking catalysts with simple and efficient reactions, low cost and high stability is still an important research direction. Summary of the invention

[0004] In order to solve the above problems, the present invention 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 a tandem deacetalization-Knoevenagel reaction, it has efficient and stable catalytic performance and can be recycled multiple times.

[0005] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0006] In the first aspect, the present invention provides a DHTA-BDU-COF polymer, wherein the structure shown in formula (I) is used as a structural repeating unit:

[0007]

[0008] In a second aspect, the present invention provides a method for preparing the above-mentioned DHTA-BDU-COF polymer, comprising the following steps:

[0009] (1) Using 1,4-phenylene diisocyanate and ammonia water as raw materials, mixing and reacting to prepare 1,4-diphenylurea;

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

[0011] In a specific embodiment of the present invention, 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 to aqueous ammonia is (1.0-1.5) g: (0.3-0.5) mol.

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

[0014] After the reaction is completed, the mixture is filtered, washed and dried, wherein the washing step is water-tetrahydrofuran washing at a volume ratio of (1-3):1;

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

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

[0017] In a specific embodiment of the present invention, in step (2), the solvent consists of o-dichlorobenzene and tert-butanol, and the volume ratio of o-dichlorobenzene to tert-butanol is 1.8 to 2.2:1, preferably 2:1.

[0018] In a specific embodiment of the present invention, in step (2), the reaction temperature is 100-120°C, preferably 110°C; the reaction time is 90-100h, preferably 92h;

[0019] After the reaction is completed, washing and drying are also carried out;

[0020] The washing is washing with dimethylformamide and tetrahydrofuran respectively;

[0021] The drying is vacuum drying.

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

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

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

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

[0026] In a specific embodiment of the present invention, the reaction temperature is 70-80° C., and the reaction time is 4-6 hours.

[0027] Furthermore, the reaction temperature is 75° C. and the reaction time is 5 h.

[0028] The beneficial effects of the present invention are:

[0029] (1) The DHTA-BDU-COF polymer prepared in the present invention has the properties of high crystallinity, large porosity, and good chemical stability, and therefore has the potential to be used as a catalyst.

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

[0031] (3) The DHTA-BDU-COF polymer provided by the present invention is used as a catalyst for catalyzing the tandem deacetalization-Knoevenagel reaction. The catalyst is low in price, high in yield, high in purity, and easy to separate. No special, toxic or harmful reagents are used during the experiment. The reaction conditions are mild. In practical applications, it shows high stability and recyclability, and has good practical value. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0033] Figure 1 This is a scanning electron microscope image of DHTA-BDU-COF prepared in Example 2 of the present invention;

[0034] Figure 2 Thermogravimetric diagram of DHTA-BDU-COF prepared in Example 2 of the present invention;

[0035] Figure 3 The experimental and simulated PXRD patterns of DHTA-BDU-COF prepared in Example 2 of the present invention;

[0036] Figure 4N is the N of DHTA-BDU-COF prepared in Example 2 of the present invention 2 Adsorption map;

[0037] Figure 5 This is the PXRD image of DHTA-BDU-COF prepared in Example 2 of the present invention after being used as a catalyst for 15 cycles. DETAILED DESCRIPTION

[0038] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0039] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in conjunction with specific embodiments.

[0040] Example 1

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

[0042] Cool 26 mL of 27.75 M ammonia solution to 0°C, and then add 3 g of 1,4-phenylene diisocyanate in batches. Stir the reaction mixture at 0°C for 5 hours, then warm it to room temperature and continue stirring for 11 hours. Collect the white solid by filtration, wash it with 150 mL of water and 150 mL of tetrahydrofuran (THF), and dry it in vacuum at room temperature to obtain white 1,4-diphenylurea (BDU). The reaction process is:

[0043]

[0044] Example 2

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

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

[0047] The reaction process is:

[0048]

[0049] The DHTA-BDU-COF polymer prepared in this example was characterized. Figure 1 is the scanning electron microscope image of DHTA-BDU-COF polymer. Figure 2 This is the thermogravimetric image of DHTA-BDU-COF polymer. The weight of COF does not decrease significantly before the temperature reaches 307°C, which proves that the synthesized COF has good thermal stability. Figure 3 Figure 2 is the PXRD pattern of DHTA-BDU-COF polymer, indicating that COF has good crystallinity. Figure 4 N is the N of DHTA-BDU-COF polymer 2 Adsorption image. The test results show that the nitrogen adsorption capacity of DHTA-BDU-COF is 90 cm at 77K. 3 / g, surface area is 31.37m 2 / g. From Figure 1 , Figure 3 and Figure 4 It can be seen from the above that the DHTA-BDU-COF polymer prepared in this example has a porous structure. Figure 2-Figure 3 It can be seen that DHTA-BDU-COF polymer is a crystalline porous material with high thermal stability.

[0050] Example 3

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

[0052] Example 4

[0053] The difference from Example 2 is that the molar ratio of DHTA to BDU is 1:1.2, and the other preparation processes are exactly the same as those in 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 invention was used as a heterogeneous catalyst to catalyze a one-pot tandem deacetalization-Knoevenagel condensation reaction. The reaction process is as follows:

[0056]

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

[0058] In the presence of DHTA-BDU-COF (6 mg, 3 mol%), 0.2 mL (2.0 mmol) of benzaldehyde dimethyl acetal and 132 mg (2.0 mmol) of malononitrile were mixed and placed in a flask, and subjected to solvent-free heating reflux 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 to finally obtain 2-benzylidene malononitrile, which was a white solid powder with a yield of up to 99%.

[0059] The reaction was tracked by TLC. After the reaction was completed, the catalyst was recovered by centrifugation and directly put into the next cycle reaction. According to the above conditions, the catalyst was used for 15 cycles. The reaction solution was separated and the yield was calculated. The catalytic effect is shown in Table 1. Figure 5 The PXRD pattern of the catalyst after 15 cycles. Figure 5 It can be seen that after 15 cycles of the catalyst, the DHTA-BDU-COF framework has not changed. As can be seen from Figure 1, the yield of the product remains basically the same, and after 15 cycles, it only shows a slight downward trend, reflecting the excellent stability of the catalyst, which can be reused more than 15 times, can significantly improve the utilization rate of the catalyst, and reduce production costs.

[0060] Table 1 Catalytic effect of multiple cyclic reactions of DHTA-BDU-COF

[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 present invention is used as a catalyst to catalyze a one-pot tandem deacetalization-Knoevenagel condensation reaction, and the yield can be as high as 99%. At the same time, after 15 cycles of reaction, the DHTA-BDU-COF polymer still maintains a catalytic yield of more than 90%, which proves that the DHTA-BDU-COF polymer provided by the present invention has efficient and stable catalytic performance and can be recycled multiple times.

[0063] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A DHTA-BDU-COF polymer, characterized in that The structure shown in formula (I) is a repeating unit:

2. A method for preparing the DHTA-BDU-COF polymer according to claim 1, characterized in that: The following steps are involved: (1) mixing 1,4-phenylene diisocyanate and aqueous ammonia to react to prepare 1,4-diphenylurea; (2) 1,4-diphenylurea, 2,4-dihydroxy-1,3,5-benzenetricarboxaldehyde and acetic acid are reacted to prepare DHTA-BDU-COF polymer.

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

4. The method for preparing the DHTA-BDU-COF polymer according to claim 2, characterized in that: In step (1), the reaction is carried out at 0-5°C for 1-3 hours, and then the temperature is raised to room temperature for 3-5 hours; After the reaction is completed, filtering, washing and drying are also performed; The drying is vacuum drying at room temperature.

5. The method for preparing the DHTA-BDU-COF polymer according to claim 2, characterized in that: In step (2), the molar ratio of 2,4-dihydroxy-1,3,5-benzenetricarboxaldehyde, 1,4-diphenylurea and acetic acid is 1:

1.

6. Use of the DHTA-BDU-COF polymer according to claim 1 in catalyzing a tandem deacetalization-Knoevenagel condensation reaction.

7. A method for catalyzing a tandem deacetalization-Knoevenagel condensation reaction, characterized in that: The DHTA-BDU-COF polymer according to claim 1 is used as a catalyst, and benzaldehyde dimethyl acetal and malononitrile are subjected to a reflux reaction to prepare 2-benzylidene malononitrile.

8. The method for catalyzing the tandem deacetalization-Knoevenagel condensation reaction as claimed in claim 6, characterized in that: The molar ratio of the DHTA-BDU-COF polymer, benzaldehyde dimethyl acetal and malononitrile is (2-4): (1-3): (1-3).

9. The method for catalyzing the tandem deacetalization-Knoevenagel condensation reaction as claimed in claim 7, characterized in that: The molar ratio of the DHTA-BDU-COF polymer, benzaldehyde dimethyl acetal and malononitrile is 3:2:

2.

10. The method for catalyzing the tandem deacetalization-Knoevenagel condensation reaction according to claim 6, characterized in that: The reaction temperature is 70-80° C., and the reaction time is 4-6 hours.

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