Method for cyclizing imine bond of Schiff base COFs
Quinoline COFs were prepared by cyclizing Schiff base COFs with pyruvate in the presence of air. This method solved the problems of poor stability of Schiff base COFs under harsh conditions and insufficient conjugation ability of imine bonds, and realized an efficient and universal cyclization method that preserved the original crystallinity and porosity.
Patent Information
- Application Number
- CN202410958833.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-07-17
- Publication Date
- 2026-01-20
AI Technical Summary
Existing Schiff base COFs exhibit poor stability under harsh conditions and have limited imine bond conjugation ability. Existing cyclization methods suffer from low conversion rates, complexity, and lack of universality, leading to losses in crystallinity and porosity.
Schiff base COFs were reacted with pyruvate in air as a dehydrogenating agent, stirred at 15-120°C for 15 min-24 h, and then washed and dried after reaction using mesitylene and/or o-dichlorobenzene as solvents to obtain quinoline COFs.
This method achieves efficient and universal imine bond cyclization, preserves the crystallinity and porosity of Schiff base COFs, and simplifies the reaction process.
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Figure CN121362325A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the field of materials, in particular to a method for ring-closing imine bond of Schiff base COFs. BACKGROUND
[0002] Covalent organic framework (COFs) is a kind of crystalline, porous polymer material, which has been widely concerned due to its high specific surface area, unique photoelectric properties, low density, structure design and many other advantages. At present, Schiff base COFs are applied in various fields such as catalysis, energy storage, gas separation, etc. due to the characteristics of rich monomer types and good reaction reversibility. However, due to the good reaction reversibility, Schiff base COFs have poor stability under harsh conditions, which is difficult to meet the demand of practical application. In addition, the limited conjugation of imine bond also limits its application in the field of photoelectricity. So far, there are some strategies for the conversion of imine bond to stable COFs, such as enol tautomerization, ring-closing of imine bond, oxidation or reduction of imine bond, etc. Among these methods, ring-closing of imine bond not only increases the conjugation ability, but also improves the stability. However, there are still some problems in these methods: (1) the reaction conversion rate is relatively low; (2) the reaction process is complex, and some metals, acids or oxidants need to be added; (3) lack of universality; (4) the crystallinity and porosity of the ring-closed product are lost a lot. Therefore, it is crucial to develop a simple, efficient and universal ring-closing method while retaining the original crystallinity and porosity for practical application. SUMMARY
[0003] The purpose of the present application is to provide a method for ring-closing imine bond of Schiff base COFs, which is simple and efficient. The method can be used to prepare quinoline COFs with different topological structures, and the obtained quinoline COFs retain the crystallinity and porosity of the Schiff base COF precursor.
[0004] The present application first provides a method for converting Schiff base COFs into quinoline COFs, comprising the following steps: The Schiff base COFs, pyruvic acid and solvent are mixed, and air is used as a dehydrogenation reagent to carry out the reaction, so as to obtain the quinoline COFs.
[0005] In the above method, the Schiff base COFs are at least one of Py-TPA-COF, TtaTfa-COF, Py-BPTA-COF, TPB-TP-COF and TPB-DMPT-COF.
[0006] In the above method, the equivalent of the pyruvic acid is 0.5-4 times the molar number of the imine bond in the Schiff base COFs; preferably 2 times.
[0007] In the method, the solvent is mesitylene and / or o-dichlorobenzene.
[0008] In the method, the reaction temperature is 15-120℃; preferably 100-120℃, more preferably 100℃. The reaction time is 15 min-24 h; preferably 6 h.
[0009] In the method, the reaction is carried out under stirring.
[0010] In the method, the reaction is followed by washing, soxhlet extraction and drying or the reaction is followed by washing and drying. Specifically, the washing is carried out with anhydrous ethanol and tetrahydrofuran in sequence or with tetrahydrofuran. The solvent used in the soxhlet extraction is tetrahydrofuran. The drying is vacuum drying at room temperature to 120℃ or air drying at room temperature.
[0011] The room temperature in the application is well known to those skilled in the art, generally 15-35℃.
[0012] The application further provides the imine COFs prepared by the above method.
[0013] The method for converting the Schiff base COFs into quinoline COFs comprises the following steps: mixing the Schiff base COFs, pyruvic acid and a solvent, using air as a dehydrogenation reagent, stirring at 15-120℃ for 15 min-24 h, to obtain the quinoline COFs.
[0014] The application has the following advantages: (1) The method is simple and has a high conversion rate; (2) The method has very good universality; (3) The obtained quinoline COFs retains the crystallinity and porosity of the Schiff base COF precursor. BRIEF DESCRIPTION OF DRAWINGS
[0015] Figure 1 The figure is a structural schematic diagram of the Schiff base COF before and after cyclization in Example 1.
[0016] Figure 2 The figure is a powder X-ray diffraction pattern (PXRD) of the Schiff base COF before and after cyclization in Example 1.
[0017] Figure 3 The figure is an infrared spectrogram (FT-IR) of the Schiff base COF before and after cyclization in Example 1.
[0018] Figure 4Carbon spectrum (13C NMR) of the Schiff base COF before and after cyclization in Example 1.
[0019] Figure 5 X-ray photoelectron spectrum (XPS) of the Schiff base COF before and after cyclization in Example 1.
[0020] Figure 6 Specific surface area test (BET) of the Schiff base COF before and after cyclization in Example 1.
[0021] Figure 7 Structure schematic diagram of the Schiff base COF before and after cyclization in Example 2.
[0022] Figure 8 PXRD of the Schiff base COF before and after cyclization in Example 2.
[0023] Figure 9 Infrared spectrum (FT-IR) of the Schiff base COF before and after cyclization in Example 2.
[0024] Figure 10 BET of the Schiff base COF before and after cyclization in Example 2.
[0025] Figure 11 XPS of the Schiff base COF before and after cyclization in Example 2.
[0026] Figure 12 Structure schematic diagram of the Schiff base COF before and after cyclization in Example 3.
[0027] Figure 13 PXRD of the Schiff base COF before and after cyclization in Example 3.
[0028] Figure 14 Infrared spectrum (FT-IR) of the Schiff base COF before and after cyclization in Example 3.
[0029] Figure 15 BET of the Schiff base COF before and after cyclization in Example 3.
[0030] Figure 16 XPS of the Schiff base COF before and after cyclization in Example 3.
[0031] Figure 17 Structure schematic diagram of the Schiff base COF before and after cyclization in this Example 4.
[0032] Figure 18 PXRD of the Schiff base COF before and after cyclization in Example 4.
[0033] Figure 19FT-IR spectra of the Schiff base COF before and after cyclization in Example 4.
[0034] Figure 20 XPS spectra of the Schiff base COF before and after cyclization in Example 4.
[0035] Figure 21 Structural schematic of the Schiff base COF before and after cyclization in Example 5.
[0036] Figure 22 PXRD of the Schiff base COF before and after cyclization in Example 5.
[0037] Figure 23 FT-IR spectra of the Schiff base COF before and after cyclization in Example 5.
[0038] Figure 24 XPS spectra of the Schiff base COF before and after cyclization in Example 5.
[0039] Figure 25 Effect of pyruvic acid equivalent on the crystallinity of Py-TPA-COF.
[0040] Figure 26 Effect of pyruvic acid equivalent on the cyclization degree of Py-TPA-COF.
[0041] Figure 27 Effect of reaction time on the crystallinity of Py-TPA-COF.
[0042] Figure 28 Effect of reaction time on the cyclization degree of Py-TPA-COF.
[0043] Figure 29 Effect of reaction solvent on the crystallinity of Py-TPA-COF.
[0044] Figure 30 Effect of reaction solvent on the cyclization degree of Py-TPA-COF. DETAILED DESCRIPTION
[0045] The application will be further described in conjunction with the specific embodiments, and the examples given are only to illustrate the application, and are not intended to limit the scope of the application.
[0046] The experimental methods in the following examples are all conventional methods, unless otherwise specified.
[0047] The materials, reagents, etc. used in the following examples can be obtained from commercial channels, unless otherwise specified.
[0048] Py-TPA-COF powder used in the following examples was prepared according to reference F. Auras, et al. Synchronized Offset Stacking: A Concept for Growing Large-Domain and Highly Crystalline 2D Covalent Organic Frameworks. Journal of the American Chemical Society. 138, 16703-16710 (2016); TtaTfa-COF powder was prepared according to reference J. Yang, et al. Protonated Imine-Linked Covalent Organic Frameworks for Photocatalytic Hydrogen Evolution. Angewandte Chemie International Edition. 60, 19797-19803 (2021); Py-BPTA-COF powder was prepared according to reference D. Zhu, et al. Understanding fragility and engineering activation stability in two-dimensional covalent organic frameworks. Chemical Science. 13, 9655-9667 (2022); TPB-TP-COF powder was prepared according to reference Y. Yang, et al. Constructing chemical stable 4-carboxyl-quinoline linked covalent organic frameworks via Doebner reaction for nanofiltration. Nature communications. 13, 2615 (2022); TPB-DMPT-COF powder Reference H. Xu, J. Gao & D. Jiang. Stable, crystalline, porous, covalent organic frameworks as a platform for chiral organocatalysts. Nature Chemistry. 7, 905-912 (2015) preparation.
[0049] Example 1, synthesis of QL-1-COF Take 30 mg Py-TPA-COF powder dispersed in a sample bottle containing 2 mL mesitylene (4 mL), stir for 5 min, add pyruvic acid (its equivalent is twice the number of moles of imine bonds in the added Py-TPA-COF), cover the lid, and heat to 100°C for 6 h. After the reaction is completed, the obtained powder is washed with anhydrous ethanol, tetrahydrofuran, and then extracted with tetrahydrofuran, and finally dried in a vacuum drying oven at 90°C to obtain a brownish red quinoline COF (QL-1-COF).
[0050] Figure 1 The structure of the Schiff base COF before and after cyclization in this example is shown in the structure.
[0051] Figure 2 The PXRD change graph of the Schiff base COF before and after cyclization in this example is shown in the structure. Compared with the XRD of the Schiff base COF, the XRD of QL-1-COF basically did not change in peak position, indicating the retention of the framework structure of the Schiff base precursor. The relative intensity of the 220 peak is weaker, which is mainly due to the introduction of carboxyl group.
[0052] Figure 3 The infrared spectra of the Schiff base COF before and after cyclization in this example are shown in the structure. We can clearly see that after cyclization, the imine bond at 1620 cm -1 disappears, and two new peaks appear at 1607 cm -1 and 1760 cm -1 , corresponding to the C=N bond in quinoline and the C=O peak in carboxyl group, respectively, proving the successful reaction of pyruvic acid with the Schiff base COF.
[0053] Figure 4 The carbon spectra of the Schiff base COF before and after cyclization in this example are shown in the structure. After cyclization, 148 and 155 ppm correspond to the peaks of the generated quinoline structure, and in addition, 170 ppm corresponds to the peak of the carboxyl carbon, also proving the successful reaction.
[0054] Figure 5This is the XPS plot of the Schiff base before and after COF cyclization in this example. 398.9 eV corresponds to the peak position of the imine bond. Figure 5 a), after cyclization ( Figure 5 b) A new peak appears at 399.7 eV, proving the successful cyclization of the imine bond, with a conversion rate of 79%.
[0055] Figure 6 The image shows the BET plots of Schiff base COF before and after cyclization in this embodiment. Red corresponds to Py-TPA-COF, and blue corresponds to QL-1-COF. We can see that there is no significant loss in specific surface area before and after cyclization.
[0056] Example 2: Synthesis of QL-2-COF 30 mg of TtaTfa-COF powder was dispersed in a sample vial containing 2 mL of trimethylbenzene (4 mL). The mixture was stirred for 5 min, and pyruvic acid (equivalent to twice the molar number of imine bonds in the added TtaTfa-COF) was added. The vial was then capped, and the mixture was heated to 100 °C and stirred for 6 h. After the reaction was completed, the resulting powder was washed successively with anhydrous ethanol and tetrahydrofuran, extracted with tetrahydrofuran, and finally dried in a vacuum drying oven at 90 °C to obtain a brownish-red quinoline COF (i.e., QL-2-COF).
[0057] Figure 7 This is a schematic diagram of the Schiff base before and after COF cyclization in this embodiment.
[0058] Figure 8 The PXRD values for the Schiff base covalent organic framework before and after cyclization in this embodiment are shown. Similarly, the peak positions did not change significantly before and after cyclization, indicating that the framework structure of the Schiff base COF precursor was retained. The relative intensity of the corresponding 110 peak weakened, which can be mainly attributed to the introduction of the carboxyl group.
[0059] Figure 9 The images shown are FT-IR spectra of the Schiff base covalent organic framework before and after cyclization in this embodiment. After cyclization, the imine bond of TtaTfa-COF disappears, and the image appears at 1606 cm⁻¹. -1 and 1762 cm -1 The appearance of a new peak at the point corresponds to the C=N peak in quinoline and the C=O peak in the carboxyl group, proving the successful conduct of the cyclization reaction.
[0060] Figure 10 The figures represent BET values before and after cyclization of the Schiff base covalent organic framework in this embodiment. Black corresponds to TtaTfa-COF, and red corresponds to QL-2-COF. The specific surface area did not decrease significantly before and after cyclization. The partial decrease is mainly attributed to the increase in relative mass caused by the introduction of pyruvate.
[0061] Figure 11For the XPS of the Schiff base COF before and after cyclization in this example, the peak shape changed obviously before and after cyclization, 398.5 eV is mainly the peak position of the imine bond and C=N bond in triazine, 399.7 eV is mainly the peak of Ph-N in triphenylamine, and 400.0 eV corresponds to the peak of C=N bond in quinoline.
[0062] Example 3, synthesis of QL-3-COF Take 30 mg of Py-BPTA-COF powder and disperse it in a sample bottle containing 2 mL of mesitylene (4 mL), stir for 5 min, add pyruvic acid (its equivalent is twice the number of moles of imine bonds in the added Py-BPTA-COF), and cover the lid, and heat to 100°C for 6 h. After the reaction is completed, the obtained powder is washed with anhydrous ethanol, tetrahydrofuran in turn, and is eluted with tetrahydrofuran, and finally dried in a vacuum drying oven at 90°C to obtain a brownish red quinoline COF (QL-3-COF).
[0063] Figure 12 For the structure diagram of the Schiff base COF before and after cyclization in this example.
[0064] Figure 13 For the PXRD of the Schiff base COF before and after cyclization in this example, the results are similar to those of Example 1, except that the crystallinity becomes better after cyclization.
[0065] Figure 14 For the FT-IR diagram of the Schiff base COF before and after cyclization in this example, the imine bond of Py-BPTA-COF disappears after cyclization, and new peaks appear at 1602 cm -1 and 1760 cm -1 , corresponding to the C=N peak in quinoline and the C=O peak in carboxyl group, proving the successful cyclization reaction.
[0066] Figure 15 For the BET of the Schiff base COF before and after cyclization in this example, black corresponds to Py-BPTA-COF, and red corresponds to QL-3-COF. The increase in specific surface area before and after cyclization is mainly due to the improvement of crystallinity.
[0067] Figure 16 For the XPS diagram of the Schiff base COF before and after cyclization in this example, 398.9 eV corresponds to the peak position of the imine bond (a in Figure 16 ), and a new peak appears at 399.7 eV after cyclization (b in Figure 16 ), proving the successful cyclization of the imine bond, with a conversion rate of 76%.
[0068] Example 4, synthesis of QL-4-COF Take 30 mg TPB-TP-COF powder and disperse it in a sample bottle containing 2 mL mesitylene (4 mL), stir for 5 min, add pyruvic acid (its equivalent is twice the number of moles of imine bonds in the added TPB-TP-COF), and cover the lid, and heat to 100°C and stir for 6 h. After the reaction is completed, the obtained powder is washed with tetrahydrofuran, and dried at room temperature to obtain quinoline COF (QL-4-COF).
[0069] Figure 17 The structure of the Schiff base COF before and after cyclization in this example is shown in the schematic diagram.
[0070] Figure 18 The PXRD of the Schiff base covalent organic framework before and after cyclization in this example is shown, and the crystallinity can be maintained after cyclization.
[0071] Figure 19 The FT-IR graph of the Schiff base covalent organic framework before and after cyclization in this example is shown, and the imine bond of TPB-TP-COF disappears after cyclization, and new peaks appear at 1606 cm -1 and 1760 cm -1 , corresponding to the C=N peak in quinoline and the C=O peak in the carboxyl group, proving the successful cyclization reaction.
[0072] Figure 20 The XPS graph of the Schiff base COF before and after cyclization in this example is shown, and the peak position of the imine bond is 399.0 eV (a in Figure 20 ), and a new peak appears at 400.0 eV after cyclization (b in Figure 20 ), proving the successful cyclization of the imine bond, with a conversion rate of 85%.
[0073] Example 5, synthesis of QL-5-COF Take 30 mg TPB-DMPT-COF powder and disperse it in a sample bottle containing 2 mL mesitylene (4 mL), stir for 5 min, add pyruvic acid (its equivalent is twice the number of moles of imine bonds in the added COF), and cover the lid, and heat to 100°C and stir for 6 h. After the reaction is completed, the obtained powder is sequentially washed with anhydrous ethanol, tetrahydrofuran, and is eluted with tetrahydrofuran, and finally dried in a vacuum drying oven at 90°C, to obtain quinoline COF (QL-5-COF).
[0074] Figure 21 The structure of the Schiff base COF before and after cyclization in this example is shown in the schematic diagram.
[0075] Figure 22 The PXRD of the Schiff base covalent organic framework before and after cyclization in this example is shown, and the crystallinity is maintained after cyclization.
[0076] Figure 23FT-IR spectra of the Schiff base COF before and after cyclization in this example, the imine bond of TPB-DMPT-COF disappeared after cyclization, a new peak appeared at 1606 cm -1 and 1760 cm -1 , corresponding to the C=N peak in quinoline and the C=O peak in carboxyl group, proving the successful cyclization reaction.
[0077] Figure 24 XPS spectra of the Schiff base COF before and after cyclization in this example, the peak position of 399.2 eV corresponding to the imine bond (a in Figure 24 ), a new peak appeared at 399.7 eV after cyclization (b in Figure 24 ), proving the successful cyclization of the imine bond, with a conversion rate of 100%.
[0078] Example 6, Effect of reaction conditions on crystallization and cyclization degree (1) Effect of pyruvic acid equivalent Take 30 mg of Py-TPA-COF powder and disperse it in a sample bottle containing mesitylene (4 mL). Stir for 5 min, add pyruvic acid of different equivalents, and cover the lid. Heat to 100°C and stir for 6 h. After the reaction is completed, wash the obtained powder with anhydrous ethanol and tetrahydrofuran, and then elute it with tetrahydrofuran. Finally, dry it in a vacuum drying oven at 90°C to obtain brown-red quinoline COF. The results are shown in Figure 25 , which shows the effect of pyruvic acid equivalent on the crystallinity of Py-TPA-COF; from Figure 25 , it can be seen that when the equivalent of pyruvic acid is twice that of the imine, the crystallinity is well preserved. Figure 26 , which shows the effect of pyruvic acid equivalent on the cyclization degree of Py-TPA-COF; it can be seen that when the equivalent of pyruvic acid is twice or more than that of the imine, the cyclization degree is relatively sufficient.
[0079] (2) Effect of reaction time Take 30 mg of Py-TPA-COF powder and disperse it in a sample bottle containing mesitylene (4 mL). Stir for 5 min, add pyruvic acid (its equivalent is twice the number of moles of imine in the added Py-TPA-COF), and cover the lid. Heat to 100°C and stir for different times. After the reaction is completed, wash the obtained powder with anhydrous ethanol and tetrahydrofuran, and then elute it with tetrahydrofuran. Finally, dry it in a vacuum drying oven at 90°C to obtain brown-red quinoline COF.
[0080] Figure 27 Effect of reaction time on the crystallinity of Py-TPA-COF, from Figure 27 , it can be seen that too long reaction time is not conducive to crystallization, and 1 to 6 h is the best.
[0081] Figure 28 The effect of reaction time on the cyclization degree of Py-TPA-COF was studied, and the results are shown in FIG. 6. Figure 28 It can be seen that the conversion is complete when the reaction time is 6 hours or more, and the conversion is not complete when the reaction time is too short.
[0082] (3) Effect of solvent Take 20 mg of Py-TPA-COF powder and disperse it in a sample bottle containing 2 mL of o-dichlorobenzene or n-butanol or 1,4-dioxane (4 mL), stir for 5 min, add pyruvic acid (its equivalent is twice the number of moles of imine bonds of the added Py-TPA-COF), cover the lid, and heat to 100°C and stir for 6 h. After the reaction is completed, the obtained powder is washed with anhydrous ethanol, tetrahydrofuran, and then extracted with tetrahydrofuran, and finally dried in a vacuum drying oven at 90°C.
[0083] Figure 29 The effect of reaction solvent on the crystallinity of Py-TPA-COF was studied, and the results are shown in FIG. 7. Figure 29 It can be seen that the PXRD obtained by n-butanol and dioxane solvents is the same as that of Py-TPA-COF, and the PXRD obtained by o-dichlorobenzene is basically the same as that obtained by mesitylene.
[0084] Figure 30 The effect of reaction solvent on the cyclization degree of Py-TPA-COF was studied, and the results are shown in FIG. 8. Figure 30 It can be seen that the imine bond peak of the COF prepared by o-dichlorobenzene moves to 1607 cm -1 , and the COFs prepared by n-butanol and 1,4-dioxane still retain the imine bond, indicating that the Schiff base COFs corresponding to the two solvents have not been converted into quinoline COFs.
Claims
1. A method for converting Schiff base COFs into quinoline COFs, comprising the following steps: mixing the Schiff base COFs, pyruvic acid and a solvent, and performing a reaction with air as a dehydrogenation reagent to obtain the quinoline COFs.
2. The method of claim 1, wherein: The Schiff base COFs are at least one of Py-TPA-COF, TtaTfa-COF, Py-BPTA-COF, TPB-TP-COF and TPB-DMPT-COF.
3. The method according to claim 1 or 2, characterized in that: The equivalent of the pyruvic acid is 0.5-4 times the number of moles of imine bonds in the Schiff base COFs.
4. The method of claim 3, wherein: The equivalent of the pyruvic acid is 2 times the number of moles of imine bonds in the Schiff base COFs.
5. The method according to any one of claims 1-4, characterized by: The solvent is mesitylene and / or o-dichlorobenzene.
6. The method according to any one of claims 1-5, characterized by: The temperature of the reaction is 15-120℃, and the time of the reaction is 15 min-24 h.
7. The method of claim 6, wherein: The temperature of the reaction is 100℃, and the time of the reaction is 6 h.
8. The method of any one of claims 1-7, wherein: The reaction is performed under stirring.
9. The method of any one of claims 1-8, wherein: The reaction is followed by washing, soxhlet extraction and drying, or the reaction is followed by washing and drying. 10.The quinoline COFs prepared by the method of any one of claims 1-9.