Preparation method and application of guanidyl ionic liquid modified metal organic framework material
By synthesizing metal-organic framework materials modified with guanidine-based ionic liquids, the problems of catalyst separation and equipment corrosion in the reaction of carbon dioxide and epoxides were solved, achieving the effect of highly efficient catalysis of carbon dioxide and propylene oxide to synthesize propylene carbonate.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- FUZHOU UNIV
- Filing Date
- 2026-01-12
- Publication Date
- 2026-04-28
AI Technical Summary
Existing technologies are difficult to effectively catalyze the cycloaddition reaction of carbon dioxide and epoxides, and ionic liquid catalysts are difficult to separate from the reaction system, leading to equipment corrosion and resource waste.
A metal-organic framework (MOF) material modified with guanidine-containing ionic liquid was synthesized. The ionic liquid was loaded into the MOF material through a preparation process to form an ILs-MOF composite material, which was applied to the reaction of carbon dioxide and propylene oxide to synthesize propylene carbonate.
It achieves high specific surface area, nanoscale pores and good thermal stability, solves the problem of difficult recovery of ionic liquids, and exhibits high catalytic efficiency in catalytic reactions. It is also insoluble in the product and easy to separate.
Smart Images
Figure CN121927680A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of metal-organic framework material synthesis technology, specifically a method for preparing a metal-organic framework material modified with guanidine ionic liquid, and its application in carbon dioxide catalytic conversion. Background Technology
[0002] Current energy systems and infrastructure rely heavily on fossil fuels. The carbon dioxide produced by burning fossil fuels exceeds the capacity of plants to consume it in the natural carbon cycle. Data released by the Mauna Loa Observatory shows that the global annual atmospheric carbon dioxide concentration is rising steadily, reaching 425 ppm in 2025, far exceeding the global annual atmospheric CO2 concentration of 278 ppm before the Industrial Revolution. This has caused a series of serious harms, including global warming and ocean acidification.
[0003] As the most abundant C1 resource in nature, CO2 possesses characteristics such as non-flammability, non-toxicity, and renewability. To date, scientific research and industrial applications of CO2 resource utilization have been extensive. For example, CO2 has been used as a raw material to prepare urea, salicylic acid, methanol, formic acid, cyclic carbonates (PC), dimethyl carbonate (DMC), and polyurethane. Among these, the preparation of cyclic carbonates from carbon dioxide and epoxides via a cycloaddition reaction has the following advantages: the reaction produces almost no byproducts, has 100% atom economy, and both the raw materials and products are green reagents.
[0004] Metal-organic frameworks (MOFs) are a novel type of porous material, formed by coordination bonds between metal ions or metal clusters and organic ligands, resulting in an ordered framework structure. First, MOFs possess extremely high specific surface area and porosity, providing ample space for adsorption and reaction. Second, MOFs exhibit high designability and tunability, allowing for precise customization of pore size, structure, and chemical function by selecting different metal ions and organic ligands, thus achieving "design on demand." Furthermore, the pore structure of MOFs is highly ordered, uniform, and chemically diverse. These superior properties enable them to demonstrate far greater application potential than traditional porous materials (such as zeolites, activated carbon, and porous silicates) in fields such as gas storage and separation, catalysis, chemical sensing, and drug delivery.
[0005] Ionic liquids (ILs) are molten salts composed of organic cations and inorganic anions. Most ionic liquids are liquid at 100°C. Ionic liquids have the characteristics of low melting point, low vapor pressure, low volatility, and good thermal stability. They are environmentally friendly functional materials that meet the requirements of green chemistry. They are effective solvents or catalysts for the cycloaddition reaction of CO2 with epoxides.
[0006] In CO2 conversion reactions, CO2 has the advantages of abundant reserves, low price, and non-toxicity, but it is also limited by its thermodynamic stability and kinetic inertness (ΔH). f = -393.5 kJ·mol -1 Therefore, the key to CO2 conversion lies in establishing an efficient catalytic system to reduce the activation energy and overcome the thermodynamic and kinetic barriers to CO2 in the reaction. Ionic liquids exhibit good catalytic effects in this reaction system, but because the reaction system is homogeneous, it is difficult to separate them from the products after the reaction. Therefore, it is necessary to immobilize the ionic liquids to synthesize ILs-metal-organic frameworks.
[0007] Besides synthesizing highly efficient ILs, the selection of MOFs as supporting materials is also extremely important. Researchers have found that porous nanomaterials with nanoscale pores (micropore size = 0.35-2.0 nm, mesopore size = 2.0-50 nm) and large specific surface areas (500-5000 m²) are highly effective. 2 Lewis acid (LW) is a good adsorbent for CO2 and an excellent heterogeneous catalyst for CO2 conversion. Therefore, by synthesizing highly efficient Lewis acid (ILs) and selecting suitable Lewis metallofibrils (MOFs) and immobilizing them, bifunctional catalysts with both Lewis acid and Lewis base active centers can be synthesized. These catalysts have advantages such as being porous, having a large specific surface area, good catalytic effect, being insoluble in the product, and being easy to separate, and play a key role in the subsequent CO2 conversion. Summary of the Invention
[0008] The main objective of this invention is to synthesize a metal-organic framework modified with a guanidine ionic liquid, which can be used in the reaction of carbon dioxide and propylene oxide to synthesize propylene carbonate.
[0009] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: A method for preparing a metal-organic framework material modified with a guanidine-containing ionic liquid includes the following steps: (1) Preparation of guanidine ionic liquids: guanidine compounds and organic compounds Br-C n H 2n -X is dissolved in organic solvent A and heated in an oil bath under reflux and stirring. After the reaction is complete, organic solvent A is removed by rotary evaporator. After removal, the mixture is washed with washing solvent B. After washing, the washing solvent is removed by filtration and the mixture is dried in an oven to obtain the desired guanidine ionic liquid, named ILs.
[0010] (2) Preparation of metal-organic framework materials: Chromium nitrate nonahydrate, 2-aminoterephthalic acid and sodium hydroxide aqueous solution were added to a beaker in a certain molar ratio and magnetically stirred until the internal substances were uniformly dispersed. The mixture was then transferred to a hydrothermal synthesis vessel and compacted. It was placed in an oven and heated to the corresponding temperature T1. After the reaction was completed, the mixture was cooled to room temperature and washed with organic solvent C to obtain a green viscous substance. The mixture was then uniformly dispersed in organic solvent D and transferred to a hydrothermal synthesis vessel and compacted. It was placed in an oven and heated to the corresponding temperature T2. After the reaction was completed, the mixture was cooled to room temperature and centrifuged to remove organic solvent D to obtain the product. Finally, the product obtained by vacuum drying was a green solid metal-organic framework material, named MOFs.
[0011] (3) Preparation of ILs-supported metal-organic frameworks: The metal-organic framework material, guanidine ionic liquid, and 4-dimethylaminopyridine (DAMP) were dissolved in organic solvent E and heated in an oil bath with reflux and stirring. After the reaction was completed, the precipitate was collected and washed multiple times with washing solvent F until the filtrate was colorless. The washed product was placed in an oven for drying. The final product was a green solid metal-organic framework material modified with guanidine ionic liquid, named ILs-MOFs.
[0012] The guanidine compound mentioned in step (1) is selected from one of 1,1,3,3-tetramethylguanidine, 1,1,2,3,3-pentamethylguanidine, and 1,1,3,3-tetraethylguanidine.
[0013] The organic compound Br-C described in step (1) n H 2n The number of carbon elements n in -X is one of 1, 2, 3, or 4.
[0014] The organic compound Br-C described in step (1) n H 2n The functional group -X in -X is one of -NH2, -COOH, -OH, or -Br.
[0015] The guanidine compound and organic compound Br-C mentioned in step (1) n H 2n The molar ratio of -X is 1:1 to 1:4.
[0016] The organic solvent A mentioned in step (1) is one of ethanol, methanol, acetonitrile, ethyl acetate, and N,N-dimethylformamide, and the amount used is 30-70 mL.
[0017] The reaction in step (1) is carried out at a temperature of 60 ℃-90 ℃ for 1-2 days.
[0018] The washing solvent B mentioned in step (1) is one of ethanol, methanol, acetone, ethyl acetate, and n-heptane. It is used to wash the crude product, with a volume of 10-30 mL each time and a washing frequency of 4-7 times.
[0019] The vacuum drying temperature of the washed product in step (1) is 50-90 ℃, and the drying time is 12-20 h.
[0020] The molar ratio of chromium nitrate nonahydrate, 2-aminoterephthalic acid compound and sodium hydroxide in step (2) is 1:0.5:0.5-1:1.5:3.
[0021] The concentration of the sodium hydroxide aqueous solution in step (2) is 0.1-0.4 mol / L.
[0022] The reaction temperature T1 in step (2) is 120-220℃, and the reaction time is 5-28h.
[0023] The organic solvent C mentioned in step (2) is N,N-dimethylformamide. The crude product is washed with 10-50 mL each time, and the number of washes is 2-7.
[0024] The product is vacuum dried at a temperature of 50-90 ℃ for 12-20 h.
[0025] The reaction temperature in step (2) is 50-80 ℃ and the reaction time is 5-15 h.
[0026] The organic solvent D mentioned in step (2) is ethanol, and the amount used is 10-50 mL.
[0027] After the reaction described in step (2) is completed, the product is allowed to stand and cool, then centrifuged to obtain the product. The product is then vacuum dried at a temperature of 50-90℃ for 12-20 hours.
[0028] The molar ratio of metal-organic framework material, guanidinium ionic liquid, and DAMP in step (3) is 1:0.25:0.1-1:3:2.
[0029] The organic solvent E mentioned in step (3) is N,N-dimethylformamide.
[0030] The reaction in step (3) is carried out at a temperature of 50 ℃-120 ℃ for 1 day-3 days.
[0031] The washing solvent F mentioned in step (3) is ethanol, and the washing times are 3-7 times, with a volume of 10-30 mL each time.
[0032] The product drying temperature after washing in step (3) is 70-90 ℃, and the drying time is 12-20h.
[0033] This invention relates to a metal-organic framework material modified with a guanidine ionic liquid as a catalyst used in the synthesis of propylene carbonate from carbon dioxide and propylene oxide. The specific operation involves adding the guanidine ionic liquid-modified metal-organic framework material and propylene oxide into a high-pressure reactor, introducing CO2 at 0.5-2.5 MPa, and stirring the reaction at a temperature of 80-160°C for 0.5-5 hours to finally obtain the product propylene carbonate.
[0034] The beneficial effects of this invention are as follows: The metal-organic framework material provided by this invention is a solid powder. Ionic liquids are readily soluble in reaction systems, difficult to recycle, and prone to corroding equipment. By loading a guanidine-containing ionic liquid into a metal-organic framework material, the composite material prepared by this method is a solid powder with a high specific surface area (specific surface area = 1683 m²). 2 With advantages such as high density ( / g), nanoscale pores (most material pore sizes are 1.1-2.2 nm), strong thermal stability, and dispersed active sites, this method solves the problems of difficulty in recovering ionic liquids from the reaction system and equipment corrosion. Moreover, it can achieve good catalytic effects in the same reaction system and has high application value. Attached Figure Description
[0035] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein: Figure 1 The flowchart and molecular structure diagram of ILs-MOFs preparation are shown. Figure 2 The image shows the XRD pattern of the ILs-MOFs material in Example 1. Figure 3 The infrared spectrum of the ILs-MOFs material in Example 1 is shown below. Figure 4 TGA image of ILs-MOFs material in Example 1; Figure 5 XPS plot of ILs-MOFs material in Example 1; Figure 6 SEM measurements of MOFs and ILs-MOFs materials in Example 1; (a) MOFs material; (b) ILs-MOFs material; Figure 7 BET tests of MOFs and ILs-MOFs materials in Example 1; (a) N2 adsorption-desorption curves of MOFs; (b) N2 adsorption-desorption curves of ILs-MOFs; (c) Pore size diagram of ILs-MOFs. Detailed Implementation
[0036] The present invention will be further illustrated by the following specific embodiments. However, the scope of protection of the present invention is not limited to the following embodiments. Example 1
[0037] Reference Figure 1 As shown, a highly stable and crystalline ILs-MIL-101-NH2 material was prepared, specifically including the following steps: 1,1,3,3-Tetramethylguanidine (40 mmol) and 1,4-dibromobutane (40 mmol) were dissolved in acetonitrile (70 mL). The mixture was added to a 250 mL round-bottom flask and heated in an oil bath at 70 °C with stirring under reflux for 1 day. After the reaction was complete, the acetonitrile was removed by rotary evaporation, followed by washing with ethyl acetate. After washing, the ethyl acetate was removed by centrifugation, and the mixture was dried in an oven at 80 °C to obtain the desired ionic liquid, named ILs.
[0038] Chromium nitrate nonahydrate (4 mmol), 2-aminoterephthalic acid (4 mmol), sodium hydroxide solid (8 mmol), and 30 mL of water were added sequentially to a beaker. The mixture was magnetically stirred for 30 min until the substances were uniformly dispersed. The mixture was then transferred to a hydrothermal synthesis vessel and compacted. The vessel was placed in a 150 °C oven and heated for 10 h. After the reaction was completed, the oven was turned off, and the mixture was allowed to cool naturally to room temperature. After washing with DMF, a green viscous substance was obtained. This substance was then uniformly dispersed in ethanol, transferred to a hydrothermal synthesis vessel, and compacted. The vessel was placed in a 90 °C oven and heated for 6 h. After the reaction was completed, the mixture was cooled to room temperature, and the ethanol was removed by centrifugation to obtain the product. The washed product was then dried in a 70 °C vacuum drying oven for 12 h. The resulting product was a green solid, which was named MOFs.
[0039] Metal-organic frameworks (0.46 g), ionic liquid (0.75 mmol), and DAMP (0.1 g) were dissolved in N,N-dimethylformamide (25 mL). The mixture was added to a 100 mL round-bottom flask and heated in an oil bath at 70 °C with stirring under reflux for 3 days. After the reaction was complete, the precipitate was collected by centrifugation and washed five times with ethanol until the filtrate was colorless. The washed product was then dried in an oven at 70 °C for 12 h. The final product was a green solid, named ILs-MOFs.
[0040] Figure 1 The flowchart and molecular structure diagram of the preparation of ILs-MOFs in this implementation case are shown.
[0041] Figure 2The XRD pattern of the ILs-MOFs material in this embodiment is shown. The crystallinity of the material was characterized using powder X-ray diffraction (XRD). The scanning range was set to 2θ = 1.5°–30° with a step size of 0.02°. The material powder was placed on a glass substrate for scanning. Three distinct characteristic peaks were observed on the curve. The peak with the highest diffraction intensity was located at 2.77°, while the other diffraction peaks were located at 5.06° and 8.97°. The XRD data preliminarily confirms that the ILs-MOFs were successfully synthesized and retain good crystallinity after being loaded with ionic liquid.
[0042] Figure 3 This is the infrared spectrum of MOFs and ILs-MOFs in this implementation case. In the spectrum, at 600 cm⁻¹... -1 The absorption peak at 1259 cm⁻¹ indicates the stretching of the Cr-O bond; -1 The absorption peak at 1391 cm⁻¹ indicates the stretching of the CN bond; -1 With 1430cm -1 The absorption peak at 1496 cm⁻¹ indicates the stretching of the OCO bond; the C=C bond absorption peak appears at 1496 cm⁻¹. -1 Location; 1660cm -1 The absorption peak at 1660 cm⁻¹ corresponds to the stretching of the NH bond in the primary amine, confirming the successful synthesis of MOFs. Comparing the FT-IR spectra of ILs-MOFs and MOFs, the original peak at 1660 cm⁻¹ is observed after modification with the ionic liquid. -1 The absorption peak of the primary amine NH at 1577 cm⁻¹ disappears, and the absorption peak at 1577 cm⁻¹ disappears. -1 The secondary amine NH stretching peak can be observed at the point, indicating that the ionic liquid was successfully grafted onto MOFs.
[0043] Figure 4 The TGA image shows the ILs-MOFs material. Thermogravimetric analysis results show that ILs-MOFs decompose into ionic liquid at 165℃ under nitrogen atmosphere, and the framework is destroyed after 320℃. Thermogravimetric analysis results indicate that ILs-MOFs have good thermal stability.
[0044] Figure 5 The XPS image of the ILs-MOFs material shows that the characteristic band of Br in the XPS is 67.67 eV, which confirms the presence of bromide anions in the ILs-MOFs and indicates the successful synthesis of ionic liquids and metal-organic framework materials.
[0045] Figure 6 The images show SEM images of the synthesized MOFs and ILs-MOFs materials. Figure 6 As shown in (a), the synthesized MOF material consists of uniformly sized aggregated particles with numerous pores on its surface, and... Figure 6Comparing the crystal morphologies of the ILs-MOFs materials loaded with ionic liquid in (b), the morphologies are similar and there is no significant change, indicating that the ionic liquid modification process has little effect on the morphology of MOFs.
[0046] Figure 7 The ILs-MOF is the BET test plot of the material, from Figure 7 Both (a) and (b) show that both MOFs and ILs-MOFs materials exhibit type I adsorption isotherms, indicating that both have microporous structures. Figure 7 As shown in (c), the pore size of the ILs-MOF material is mostly 1.1-2.2 nm. Simultaneously, when the adsorption isotherm approaches the saturated vapor pressure, the curve exhibits an H2-type hysteresis loop, which is attributed to the interconnected mesoporous cage structure in MIL-101-NH2. Table 1 shows that the specific surface area of the ILs-MOF material is 1683 m². 2 / g, compared to the specific surface area of MOFs before modification (1723m²). 2 The specific surface area (S / g) decreased slightly, which is due to the ionic liquid occupying the channels of MIL-101-NH2. Compared with the specific surface area of other common porous materials (including MOFs, COFs, molecular sieves, and HCPs) loaded with ionic liquids, ILs-MOFs materials have a high specific surface area, which is conducive to CO2 adsorption, diffusion, and uniform distribution of active sites. They are good adsorbents for CO2 and excellent heterogeneous catalysts for CO2 conversion.
[0047] Table 1. Comparison of specific surface area test results of MOF materials and ILs-MOF materials with other common porous materials after loading ionic liquids.
[0048] Application Example 1 ILs-MOFs material and propylene oxide were weighed and added to a high-pressure reactor at a mass ratio of 2wt%. 2MPa CO2 was introduced, and the mixture was stirred at 140℃ for 6 hours. The reaction solution was collected into centrifuge tubes and centrifuged at 10000r for 10 minutes. The supernatant was taken for gas chromatography analysis. The PO conversion rate was 99.5%, and the PC yield was 99.5%.
[0049] Obviously, the above embodiments are merely examples for clear illustration and are not intended to limit the implementation. Any obvious variations or modifications derived therefrom are still within the protection scope of this invention.
Claims
1. A method for preparing a metal-organic framework material modified with a guanidine-based ionic liquid, characterized in that, Includes the following steps: (1) Preparation of guanidine ionic liquids: guanidine compounds and organic compounds Br-C n H 2n -X is dissolved in organic solvent A and heated in an oil bath under reflux and stirring. After the reaction is complete, organic solvent A is removed by rotary evaporator. After removal, the mixture is washed with washing solvent B. After washing, the washing solvent is removed by filtration and the mixture is dried in an oven to obtain guanidine ionic liquid. (2) Preparation of metal-organic framework material: Chromium nitrate nonahydrate, 2-aminoterephthalic acid, and sodium hydroxide aqueous solution were added to a beaker in a certain molar ratio and magnetically stirred until uniformly dispersed. The mixture was then transferred to a hydrothermal synthesis vessel and compacted. It was placed in an oven and heated to the corresponding temperature T1. After the reaction was completed, the mixture was cooled to room temperature and washed with organic solvent C to obtain a green viscous substance. The substance was then uniformly dispersed in organic solvent D and transferred to a hydrothermal synthesis vessel and compacted. It was placed in an oven and heated to the corresponding temperature T2. After the reaction was completed, the mixture was cooled to room temperature and centrifuged to remove organic solvent D to obtain the product. Finally, the product was obtained by vacuum drying. (3) Preparation of ILs-supported metal-organic frameworks: The metal-organic framework material, guanidine ionic liquid, and 4-dimethylaminopyridine DAMP are dissolved in organic solvent E and heated in an oil bath with reflux and stirring. After the reaction is completed, the precipitate is collected and washed multiple times with washing solvent F until the filtrate is colorless. The washed product is placed in an oven for drying to obtain the guanidine ionic liquid-modified metal-organic framework material.
2. The preparation method according to claim 1, characterized in that, The guanidine compound mentioned in step (1) is selected from one of 1,1,3,3-tetramethylguanidine, 1,1,2,3,3-pentamethylguanidine, and 1,1,3,3-tetraethylguanidine; The organic compound Br-C described in step (1) n H 2n The number of carbon atoms n in -X is one of 1, 2, 3, or 4; the functional group -X is one of -NH2, -COOH, -OH, or -Br. The guanidine compound and organic compound Br-C mentioned in step (1) n H 2n The molar ratio of -X is 1:1 to 1:
4.
3. The preparation method according to claim 1, characterized in that, The organic solvent A mentioned in step (1) is one of ethanol, methanol, acetonitrile, ethyl acetate, and N,N-dimethylformamide; The reaction in step (1) is carried out at a temperature of 60 ℃-90 ℃ for 1-2 days; The washing solvent B mentioned in step (1) is one of ethanol, methanol, acetone, ethyl acetate, and n-heptane. The washing is performed 4-7 times. After washing, the product is vacuum dried at a temperature of 50-90 °C for 12-20 h.
4. The preparation method according to claim 1, characterized in that, The molar ratio of chromium nitrate nonahydrate, 2-aminoterephthalic acid and sodium hydroxide in step (2) is 1:0.5:0.5-1:1.5:3; The concentration of the sodium hydroxide aqueous solution in step (2) is 0.1-0.4 mol / L.
5. The preparation method according to claim 1, characterized in that, The reaction temperature T1 in step (2) is 120-220℃, and the reaction time is 5-28h; The organic solvent C mentioned in step (2) is N,N-dimethylformamide; The organic solvent D mentioned in step (2) is ethanol.
6. The preparation method according to claim 1, characterized in that, The reaction temperature in step (2) is 50-80 ℃ and the reaction time is 5-15 h; In step (2), the vacuum drying temperature is 50-90 ℃ and the drying time is 12-20h.
7. The preparation method according to claim 1, characterized in that, The molar ratio of metal-organic framework material, guanidinium ionic liquid, and DAMP in step (3) is 1:0.25:0.1-1:3:
2. The organic solvent E mentioned in step (3) is N,N-dimethylformamide.
8. The preparation method according to claim 1, characterized in that, The reaction in step (3) is carried out at a temperature of 50 ℃-120 ℃ for 1 day to 3 days; The washing solvent F mentioned in step (3) is ethanol, and the washing is performed 3-7 times; In step (3), the drying temperature is 70-90 ℃ and the drying time is 12-20 h.
9. A guanidine-based ionic liquid-modified metal-organic framework material prepared by the method according to any one of claims 1-8.
10. The application of the guanidinium ionic liquid-modified metal-organic framework material as described in claim 9 in the catalytic reaction of carbon dioxide and propylene oxide to synthesize propylene carbonate.