Preparation and application of ionic ethylene metal covalent organic framework material

Abstract

The application discloses a preparation and application of an ionic ethylene metal covalent organic framework material, and belongs to the technical field of organic synthesis. The preparation is that a metal cluster containing an aldehyde group and an ionic monomer containing a methyl group are added into a reaction tube, and under the catalysis of piperidine, the metal covalent organic framework material linked by crystalline ionic carbon-carbon bonds is generated in an organic solvent. 2 The carbon-carbon bond linkage improves the stability of the material, and the method uniformly distributes the metal and ion sites in the framework material. In the material, the metal and the ion are introduced into the monomer by in-situ synthesis, the uniform distribution of the functional sites is realized, the problems of uneven distribution of the metal and difficulty in quantification caused by the introduction of the metal by the post-modification method are solved, and the method has important value for improving the performance of the COFs material.

Description

Technical Field

[0001] This invention belongs to the field of porous organic materials technology, and relates to a covalently coordinated polymer material, and more particularly to a method for preparing and applying a vinyl-linked ionic metal covalent organic framework material. Background Technology

[0002] Covalent organic frameworks (COFs) are a class of crystalline porous materials prepared through reversible condensation reactions of organic "building blocks" composed of lightweight elements such as C, H, O, N, and B. The organic building blocks are integrated into primary or higher-order structures with well-defined structures. The development of COFs has provided insights into the design of periodically ordered polymer materials. By utilizing stepwise growth polymerization, the chains grow in two-dimensional or three-dimensional structures; therefore, the rigid framework of COFs exhibits long-range order in its topological structure. As an emerging class of organic porous materials, the COF library has rapidly expanded since 2005 due to researcher interest. Subsequently, boron-oxygen bonds, hydrazone bonds, enone bonds, imide bonds, and imine bonds formed through reversible condensation reactions have been reported. Further development has led to the formation of more stable, less reversible triazine bonds and vinyl-linked carbon-carbon double bonds. COFs not only possess the low density and high specific surface area characteristics of conventional porous materials, but their organic crystalline structure also endows them with unique advantages: compared to inorganic porous materials such as zeolites and molecular sieves, COFs have advantages such as variable topology, tunable nanopore size, and ease of functionalization; compared to MOFs, COFs exhibit higher chemical stability in aqueous solutions, and even in strong acid and strong alkali solutions. Furthermore, compared to amorphous porous organic materials, such as conjugated microporous polymers (CMPs), crystalline COFs possess a regular, ordered, and uniform pore structure. COFs are mainly functionalized through post-modification methods, such as loading metals and ionic liquids, to form composite materials with MOFs. Benefiting from these advantages, COFs have been widely used in recent years in fields such as gas adsorption, heterogeneous catalysis, energy storage and conversion, and sensing.

[0003] Vinyl-linked COFs (sp 2 c-COFs have attracted widespread attention from researchers since their first report in 2016 due to their advantages such as poor bond reversibility, acid-base stability, and strong conjugation. Currently, vinyl-linked sps are mainly prepared through Knoevenagel condensation, Aldol condensation, and HWE reaction. 2 c-COFs. However, the types of monomers involving carbon-carbon double bonds are currently limited, and their synthesis is relatively complex. Currently, sp... 2 Reports on c-COFs are scarce. Therefore, the preparation of sp... 2 c-COFs are necessary.

[0004] In recent years, covalent organic frameworks (COFs) have shown increasing advantages in CO2 cycloaddition reactions due to their high specific surface area and modifiability. Introducing Lewis acids and nucleophilic ion sites into COFs can synergistically catalyze CO2 cycloaddition reactions. Currently, most reported COFs used for catalyzing this reaction are linked by imine bonds, and functional groups are introduced into the COF framework through a multi-step post-modification method. This method is relatively cumbersome, and the amount of functional groups introduced cannot be precisely determined. Therefore, it is essential to develop new methods to synthesize functionalized COFs with high stability. Summary of the Invention

[0005] To address the issues of cumbersome multi-step synthesis of functionalized COFs and the poor stability of imine-linked COFs, this invention discloses a method for preparing functionalized ionic vinyl metal covalent organic framework materials. This method involves in-situ introduction of metals and ionic sites onto aldehyde and methyl monomers. Through a Knoevenagel condensation reaction, a certain catalyst is added via a solvothermal method to induce the Knoevenagel condensation of the aldehyde and methyl groups. The metal centers, acting as active sites, can catalyze various reactions, and the introduction of ionic sites improves the microenvironment of the material's pores, significantly enhancing the catalytic performance of the COFs.

[0006] The ionic vinyl metal covalent organic framework material of the present invention has the structure shown in formula (I) or (II) as follows: The preparation method is as follows: a cyclic trinuclear copper metal cluster containing an aldehyde group and an ionic monomer containing a methyl group are co-dissolved in an organic solvent. Under the catalysis of piperidine, the mixture is heated to 170~190℃ under vacuum for 72~96h. After that, it is cooled to room temperature, centrifuged, washed, and vacuum dried to obtain the ionic vinyl metal covalent organic framework material.

[0007] The reaction route is as follows: .

[0008] The aldehyde-containing cyclic trinuclear copper metal cluster is C 12 H9Cu3N6O3 (Cu3L3); the methyl-containing ionic monomer is one of 1,2,4,6-tetramethylpyridine iodide (TMPI-I) or 1,2,4,6-tetramethylpyridine-1-tetrafluoroborate ammonium (TMPI-BF4); the molar ratio of the aldehyde-containing cyclic trinuclear copper metal cluster to the methyl-containing ionic monomer is 1:4 to 4:1. The organic solvent is N,N-dimethylformamide (DMF) or o-dichlorobenzene (…). o At least one of DCB or mesitylene (mes).

[0009] The 1,2,4,6-tetramethylpyridine iodide is prepared by co-dissolving 2,4,6-trimethylpyridine and iodomethane in dichloromethane, stirring the reaction at room temperature for 20-25 hours, and then filtering, washing, and drying; wherein the molar ratio of 2,4,6-trimethylpyridine to iodomethane is 1:3 to 3:1.

[0010] The 1,2,4,6-tetramethylpyridine-1-tetrafluoroboric acid is prepared from 2,4,6-trimethylpyridine and tetrafluoroboric acid. The mixture is heated at 140-160°C and microwaved at 80-120W for 10-20 minutes using trimethyl orthoformate as a methylating agent. After cooling to room temperature, the mixture is filtered, washed, and dried. The molar ratio of 2,4,6-trimethylpyridine to tetrafluoroboric acid is 1:2 to 2:1, and the molar ratio of tetrafluoroboric acid to trimethyl orthoformate is 1:3 to 3:1.

[0011] Compared with existing technologies, the method for preparing ionic vinyl metal covalent organic framework materials of this invention involves the condensation of pyrazolium metal clusters with pyridine methyl organic monomers to prepare highly crystalline ionic metal covalent organic framework materials with carbon-carbon double bonds. This is achieved through a bottom-up strategy to generate sp... 2 c-COFs, with their carbon-carbon bonds enhancing material stability, and this method uniformly distributes metal and ionic sites within the framework material. In this material, in-situ synthesis introduces metals and ions into the monomer, achieving a uniform distribution of functional sites. This solves the problems of uneven metal distribution and difficulty in quantification caused by current post-modification methods, and is of significant value for improving the performance of COFs materials. The ionic vinyl metal covalent organic framework material prepared using the method of this invention has advantages such as high specific surface area and high stability, and can be applied in catalysis, adsorption sensing, and other fields. Furthermore, the ionic metal covalent organic framework prepared using the method of this invention also exhibits excellent CO2 cycloaddition reaction performance. Attached Figure Description

[0012] Figure 1 This is a refined XRD pattern of the ionic vinyl metal covalent organic framework material prepared in Example 1.

[0013] Figure 2 This is a refined XRD pattern of the ionic vinyl metal covalent organic framework material prepared in Example 2.

[0014] Figure 3 The N2 physisorption diagram (a) and pore size distribution diagram (b) of the ionic vinyl metal covalent organic framework material prepared in Example 1 are shown.

[0015] Figure 4 This is a CO2 physisorption diagram of the ionic vinyl metal covalent organic framework material prepared in Example 1.

[0016] Figure 5 This is a schematic diagram of the CO2 cycloaddition cycle performance of the ionic vinyl metal covalent organic framework material prepared in Example 1.

[0017] Figure 6 This is a generalization diagram of CO2 cycloaddition substrates for the ionic vinyl metal covalent organic framework material prepared in Example 1. Detailed Implementation

[0018] The present invention will be further explained and described below with reference to specific embodiments.

[0019] Example 1: (1) Preparation of Cu3L3 200 mg of copper nitrate trihydrate (0.83 mmol) and 96 mg of 1H-pyrazole-4-carboxaldehyde (1.0 mmol) were weighed into a 25 mL sample vial. 6.7 mL of N,N-dimethylformamide (DMF), 5 mL of H₂O, and 6.7 mL of ethanol were added. The vial was sealed and placed in an oven at 100 °C for 12 h. After the reaction was complete, pale yellow needle-like crystals were obtained. The solid was filtered and soaked in water for 3 days, with the water changed every 8 h. Finally, the crystals were washed three times with acetone (30 mL × 3) and dried under vacuum at 120 °C for 24 h, yielding 65%.

[0020] (2) Preparation of TMPI-I 2,4,6-Trimethylpyridine (2 mL, 15 mmol) and iodomethane (2.85 mL, 45 mmol) were dissolved in 10 mL of CH₂Cl₂ and stirred overnight at room temperature. The mixture was filtered to obtain a white solid. The solid was then recrystallized from methanol, filtered to obtain the target product, and dried under vacuum at 60 °C for 6 h.

[0021] (3) Preparation of ionic vinyl covalent organic framework material TMPI-Cu-MCOF-I Weigh Cu3L3 (23.9 mg, 0.05 mmol) and TMPI-I (13.2 mg, 0.05 mmol) into a reaction tube, add 2 mL of DMF and o-DCB (volume ratio 3:1), with 100 μL piperidine as a catalyst, was sonicated for 5 min. The reaction tube was then frozen in liquid nitrogen, and after three cycles of N2 purging and vacuum evacuation, it was sealed and heated at 180 °C for 4 days. After the reaction, it was cooled to room temperature and washed 2-3 times sequentially with DMF, methanol, and CH2Cl2 to remove oligomers or monomers. The product was then dried in a 100 °C vacuum drying oven for 12 h. The solid was collected by filtration, yielding a reddish-brown metal cluster-based crystalline porous material TMPI-Cu-MCOF-I. The structural formula of this material is: .

[0022] The yield of the above materials was 91%. Powder X-ray diffraction was performed on the prepared ionic vinyl metal covalent organic framework material, and its refined XRD pattern is shown below. Figure 1 As shown, the material exhibits good crystallinity. Through structural simulation using MaterialsStudio, the structure can be identified as an AA packing model.

[0023] Example 2 (1) Preparation of Cu3L3 Same as Example 1.

[0024] (2) Preparation of TMPI-BF4 2,4,6-Trimethylpyridine (2.5 mmol) and tetrafluoroboric acid (2.5 mmol) were mixed in an ice-water bath, and the temperature was then raised to room temperature and maintained for 1 h. After the reaction was complete, the solvent in the resulting mixture was evaporated under reduced pressure and dried under vacuum. Trimethyl orthoformate (7.5 mmol) was added to the solid obtained above, and the mixture was kept in a microwave reactor (150 °C, 100 W) for 10 min. After cooling to room temperature, the resulting solid was filtered, washed with ethanol, and dried under vacuum to obtain the product (TMPI-BF4).

[0025] (3) Preparation of ionic vinyl covalent organic framework material TMPI-Cu-MCOF-BF4 Weigh 23.9 mg (0.05 mmol) Cu3L3 and 9.2 mg (0.05 mmol) TMPI-BF4 into a reaction tube, add 2 mL of DMF and mes (volume ratio 3:1), then add piperidine as a catalyst, sonicate for 5 min, freeze the reaction tube in liquid nitrogen, and seal the reaction tube after three cycles of N2 purging and vacuum evacuation, and heat at 180 °C for 4 days. After the reaction is complete, cool to room temperature and wash 2-3 times sequentially with DMF, methanol, dichloromethane and ethanol to remove oligomers or monomers. Then dry the product in a vacuum drying oven at 100 °C for 12 h, filter and collect the solid to obtain the wine-red ionic vinyl metal covalent organic framework material TMPI-Cu-MCOF-BF4. The structural formula of this material is as follows: .

[0026] The prepared ionic vinyl metal covalent organic framework material was subjected to powder X-ray diffraction, and its refined XRD pattern is shown below. Figure 2 As shown, the material exhibits good crystallinity. Through structural simulation with Materials Studio, the structure can be identified as an AA packing model.

[0027] Product performance evaluation and application research To properly characterize the porosity of the ionic vinyl metal covalent organic framework material, nitrogen adsorption at 77K was tested after the material was degassed at 120℃ for 12h.

[0028] Figure 3 a represents the N2 physical adsorption and desorption isotherm of the ionic vinyl metal covalent organic framework material prepared in Example 1. Figure 3 b is the pore size distribution curve of Example 1, which shows that the specific surface area of ​​the material is 361 m². 2 The pore size distribution is 1.2 nm, which indicates that the material has a microporous framework structure.

[0029] Figure 4 This is a physisorption diagram of CO2 on the ionic vinyl metal covalent organic framework material prepared in Example 1. (From...) Figure 4 It can be seen that the material prepared in Example 1 has an adsorption capacity of 1.95 mmol / g of CO2 at 273 K and 1.4 mmol / g of CO2 at 298 K, indicating that the material prepared in Example 1 can effectively adsorb CO2 and can be used as a catalyst for CO2 cycloaddition reaction.

[0030] CO2 cycloaddition performance testing of ionic vinyl metal covalent organic framework materials The ionic vinyl metal covalent organic framework material prepared in Example 1 was dried under vacuum at 120°C for 12 h. Then, different equivalents (1 mmol%, 2 mmol%, 3 mmol%, 4 mmol%, 5 mmol%, 6 mmol%, 7 mmol%, 8 mmol%, 9 mmol%, 10 mmol%, 11 mmol%) of the dried material were added to a reactor as a catalyst. 10 mmol of epichlorohydrin was added, and the reactor was purged three times with CO2 gas to remove the air. Finally, 2 MPa of CO2 was introduced, and the reaction was carried out at 120°C for 48 h. The changes in the reaction with reaction time, reaction temperature, and CO2 pressure were then investigated. Simultaneously, the same equivalent amount of the ionic vinyl metal covalent organic framework material prepared in Example 2 was dried under vacuum at 120°C for 12 hours, and then added to a reaction vessel as a catalyst. 10 mmol of epichlorohydrin was added as a reactant, and CO2 was introduced into the vessel at a certain pressure to purge the air. This operation was repeated three times. Afterward, 2 MPa CO2 was introduced, and the reaction was carried out at 120°C for 48 hours. After the reaction was completed and cooled to room temperature, a deuterated reagent and an internal standard were added. 1 The yield of the product was determined by ¹H NMR. It is evident that using TMPI-Cu-MCOF-I as a catalyst yielded a 95% cyclic carbonate yield, while the yield of the comparative sample TMPI-Cu-MCOF-BF4 was lower (78%) under the same conditions. This is presumably due to the stronger nucleophilicity of iodide ions. The data are listed in Table 1.

[0031] Table 1. CO2 cycloaddition properties of ionic vinyl metal covalent framework materials prepared in Examples 1 and 2 .

[0032] Catalytic cycling test of CO2 cycloaddition reaction of ionic vinyl metal covalent organic framework materials The ionic vinyl metal covalent organic framework material prepared in Example 1 was dried under vacuum at 120°C for 12 h. Then, 8 mmol% of the dried material was placed in a reaction vessel, 10 mmol of epichlorohydrin was added, and CO2 was introduced into the vessel at a certain pressure. The air in the reaction vessel was then purged. This process was repeated three times. Finally, 2 MPa of CO2 was introduced, and the reaction was carried out at 120°C for 48 h. After the reaction was completed and the temperature was allowed to return to room temperature, the vessel was cooled with an ice-water bath, and the remaining CO2 was slowly released by opening the exhaust valve. The reaction vessel was opened, and the internal standard 1,1,2,2-tetrachloroethane was added. The inner wall of the reaction vessel was cleaned with a small amount of CDCl3-d6. The washing liquid was collected in the reaction vessel and sonicated until the generated reaction solution was completely and uniformly dispersed. The catalyst was separated by centrifugation, and 0.5 mL of the supernatant was added to an NMR tube and analyzed by 1H NMR (1H NMR spectroscopy). 1Quantitative analysis by ¹H NMR was performed to calculate the yield. The catalyst was washed with DMF, CH₃OH, and CH₃CH₂OH, and further purified by Soxhlet extraction. It was then vacuum-dried at 120 °C for future use. The catalyst performance after 6 cycles was as follows: Figure 5 As shown, the yield of cyclic carbonate did not decrease significantly, indicating that the material prepared in Example 1 has good cycle stability.

[0033] Study on the universality of CO2 cycloaddition substrates of ionic vinyl metal covalent organic frameworks After obtaining the optimal reaction conditions using epichlorohydrin as a model reaction, the substrate applicability of the material prepared in Example 1 was further explored. An attempt was made to achieve cycloaddition reactions between CO2 and several epoxy compounds to prepare various cyclic carbonates. For example... Figure 6 As shown, 1a-1f represent epoxy compounds with different substituents, namely epichlorohydrin, epibromopropane, 4-((allyloxy)methyl)-1,3-dioxolane-2-one, 4-(butoxymethyl)-1,3-dioxolane-2-one, 1,4-butanediol diglycidyl ether, and styrene oxide, respectively. 2a-2f represent the corresponding cyclic carbonate products. The ionic vinyl metal covalent organic framework material prepared in Example 1 was dried under vacuum at 120°C for 12 hours. Then, 8 mmol% of the activated material was placed in a reactor as a catalyst, 10 mmol of epichlorohydrin was added, and CO2 was introduced into the reactor at a certain pressure to purge the air. This operation was repeated three times. Finally, 2 MPa of CO2 was introduced, and the reaction was carried out at 120°C for 48 hours. After the reaction was completed and the temperature was allowed to return to room temperature, the reactor was cooled in an ice-water bath, and the remaining CO2 was slowly released by opening the exhaust valve. Open the reactor, add the internal standard 1,1,2,2-tetrachloroethane, and wash the inner wall of the reactor with a small amount of CDCl3-d6. Collect the washings in the reactor and sonicate until the generated reaction solution is completely and uniformly dispersed. Centrifuge to separate the catalyst, and take 0.5 mL of the supernatant into an NMR tube. Spectroscopy using 1H NMR (1-H NMR) is performed. 1 Quantitative analysis by ¹H NMR was performed to calculate the yield. The results showed that the cycloaddition of 1a-1e with CO2 without the addition of any additives yielded the desired cyclic carbonates. Surprisingly, the cycloaddition of 1,4-butanediol diglycidyl ether with CO2 yielded an 89% product, indicating that the material prepared in Example 1 has good substrate universality. Due to the large molecular size of styrene oxide (1f) (reaction time 72 hours), which is unfavorable for substrate adsorption and product conversion and desorption at the catalyst active site, the reaction activity was poor. It is speculated that the poor nucleophilic activity of the β-carbon may also be a reason for the low yield.

Claims

1. An ionic vinyl metal covalent organic framework material for catalyzing CO2 cycloaddition reactions, characterized in that, The ionic vinyl metal covalent organic framework has the structure shown in the following formula: ， Wherein, the dashed lines represent the bond connection positions; R is selected from any of the following structures: or .

2. A method for preparing the ionic vinyl metal covalent organic framework material as described in claim 1, characterized in that, A trinuclear copper metal cluster containing an aldehyde group and an ionic monomer containing a methyl group were co-dissolved in an organic solvent. Under piperidine catalysis, the mixture was heated to 170-190°C under vacuum for 72-96 hours. After cooling to room temperature, the mixture was centrifuged, washed, and vacuum dried to obtain the ionic vinyl metal covalent organic framework material.

3. The method for preparing an ionic vinyl metal covalent organic framework material as described in claim 2, characterized in that: The aldehyde-containing cyclic trinuclear copper metal cluster is C 12 H9Cu3N6O3; the methyl-containing ionic monomer is one of 1,2,4,6-tetramethylpyridine iodide or 1,2,4,6-tetramethylpyridine-1-tetrafluoroborate ammonium; the molar ratio of the aldehyde-containing cyclic trinuclear copper metal cluster to the methyl-containing ionic monomer is 1:4 to 4:

1.

4. The method for preparing an ionic vinyl metal covalent organic framework material as described in claim 3, characterized in that, The 1,2,4,6-tetramethylpyridine iodide is prepared by co-dissolving 2,4,6-trimethylpyridine and iodomethane in dichloromethane, stirring at room temperature for 20-25 hours, and then filtering, washing, and drying. The 1,2,4,6-tetramethylpyridine-1-tetrafluoroboric acid is prepared by using 2,4,6-trimethylpyridine and tetrafluoroboric acid as raw materials, and by using trimethyl orthoformate as a methylating agent, maintaining the mixture at 140-160℃ and 80-120W microwave power for 10-20 minutes, cooling to room temperature, filtering, washing, and drying.

5. The method for preparing an ionic vinyl metal covalent organic framework material as described in claim 4, characterized in that, The molar ratio of 2,4,6-trimethylpyridine to iodomethane is 1:3 to 3:1; the molar ratio of 2,4,6-trimethylpyridine to tetrafluoroboric acid is 1:2 to 2:1; and the molar ratio of tetrafluoroboric acid to trimethyl orthoformate is 1:3 to 3:

1.

6. The method for preparing the ionic vinyl metal covalent organic framework material as described in claim 2, characterized in that, The organic solvent is at least one of N,N-dimethylformamide, o-dichlorobenzene, or mesitylene.

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