A dual-ligand metal-organic framework material, preparation method and application thereof

Abstract

The present invention provides a method for preparing a dual-ligand metal-organic framework material, comprising the following steps: S1) mixing an acidic organic ligand and a basic organic ligand in water to obtain a ligand precursor; S2) mixing the ligand precursor, an alkaline auxiliary, and a metal source to obtain a mixed solution; and S3) crystallizing the mixed solution at high temperature to obtain the dual-ligand metal-organic framework material. Compared to the prior art, the present invention produces a dual-ligand metal-organic framework material by mixing two organic ligands of different acidity and alkalinity with a metal source and then performing coordination with the aid of an alkaline auxiliary. The dual-ligand metal-organic framework material has a large specific surface area, a rich pore structure, and a large number of unsaturated metal sites. Furthermore, it exhibits advantages such as high catalytic activity, good selectivity, and strong stability. When used as a catalyst in the cycloaddition reaction of epoxides and carbon dioxide in an uncatalyst-free system, it exhibits excellent catalytic effects.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalysts, and in particular relates to a dual-ligand metal organic framework material, a preparation method and an application thereof. Background Art

[0002] Efficiently capturing and chemically converting excess carbon dioxide (CO2) generated by human activities into high-value fuels and chemicals is a very important strategy to mitigate global warming and environmental problems. However, due to the chemical stability of CO2 molecules, it still requires efficient catalysts and harsh reaction conditions to promote this process. The direct conversion of CO2 into high-value fuels and chemicals, such as methane, methanol, ethanol, and formic acid, has been intensively studied, but its low efficiency and poor selectivity hinder its industrial application.

[0003] In this regard, the non-redox cyclization of CO2 with epoxides has emerged as an effective and promising strategy due to its high efficiency and 100% atom economy. Meanwhile, the resulting cyclic carbonates are widely used as monomers for the production of chemical intermediates such as polar solvents, electrolytes, fuel additives, and pharmaceuticals. To this end, various catalysts, including homogeneous organometallic compounds, ionic liquids, heterogeneous metal-organic frameworks (MOFs), and covalent organic frameworks (COFs), have been developed for the production of cyclic carbonates via the CO2 cyclization route. However, promoting the cycloaddition of CO2 with epoxides usually requires cocatalysts such as tetrabutylammonium bromide (TBAB), which limits their practical application due to the high cost of separation and purification processes. Therefore, the development of simple, economical, and efficient heterogeneous catalysts for the non-oxidative cyclization of CO2 under mild conditions without cocatalysts is highly desirable.

[0004] At present, researchers have developed a variety of homogeneous and heterogeneous catalysts. Considering the cost of separation and recovery, heterogeneous catalysts are gradually receiving more and more attention. Among them, the metal organic framework catalytic material system based on non-precious metals has become a strong competitor for cycloaddition reactions due to its stable structure, low cost, simple synthesis method, and easy separation and recovery of products. Although metal organic catalytic materials have large specific surface area, rich pore structure, adjustable surface chemical environment, and easy modification of acid and base sites, they still cannot meet the requirements of efficient cycloaddition reactions in an uncatalyst-free system due to their saturated coordination and single ligand. Therefore, the design of dual-ligand metal organic catalytic materials with unsaturated coordination is crucial for the efficient utilization of carbon dioxide, and also provides some new ideas for the development and application of such catalysts. Summary of the Invention

[0005] In view of this, the technical problem to be solved by the present invention is to provide a dual-ligand metal-organic framework material with high catalytic activity, selectivity and stability, and a preparation method and application thereof.

[0006] The present invention provides a method for preparing a dual-ligand metal-organic framework material, comprising the following steps:

[0007] S1) mixing an acidic organic ligand and a basic organic ligand in water to obtain a ligand precursor;

[0008] S2) mixing the ligand precursor, the alkaline auxiliary agent and the metal source to obtain a mixed solution;

[0009] S3) crystallizing the mixed solution at high temperature to obtain a biligand metal organic framework material.

[0010] Preferably, the molar ratio of the acidic organic ligand to the basic organic ligand is 1:(0.5-1.5);

[0011] The molar ratio of the total molar number of the acidic organic ligand and the basic organic ligand to the metal source is (1-2):1;

[0012] The molar ratio of the alkaline auxiliary agent to the acidic organic ligand is 2:(0.5-1).

[0013] Preferably, the total molar concentration of the acidic organic ligand and the basic organic ligand in the mixed solution is 0.04 to 0.25 mol / L.

[0014] Preferably, the acidic organic ligand is selected from one or more of terephthalic acid, 2-aminoterephthalic acid, 2,5-dihydroxyterephthalic acid, 2,5′-thiophenedicarboxylic acid, and 2,5′-furandicarboxylic acid;

[0015] The basic organic ligand is selected from pyridine ligands;

[0016] The alkaline auxiliary agent is selected from one or more of sodium hydroxide, potassium hydroxide and triethylamine;

[0017] The metal source is selected from one or more of zinc salts, aluminum salts, copper salts and nickel salts.

[0018] Preferably, the mixing time in step S2) is 15 to 60 minutes;

[0019] The temperature of the high-temperature crystallization is 120° C. to 160° C.; and the time of the high-temperature crystallization is 24 to 72 hours.

[0020] Preferably, in step S3), the high-temperature crystallization is followed by centrifugal washing and drying to obtain a biligand metal-organic framework material; the centrifugal washing is performed using water and ethanol.

[0021] The present invention also provides a dual-ligand metal organic framework material, which is formed by coordination between organic ligands and metal ions; the organic ligands include acidic organic ligands and basic organic ligands.

[0022] Preferably, the dual-ligand metal-organic framework material has a porous two-dimensional layered structure.

[0023] The present invention also provides the use of the above-mentioned dual-ligand metal organic framework material in catalyzing the cycloaddition reaction of epoxy compounds and carbon dioxide.

[0024] Preferably, the biligand metal-organic framework material catalyzes the cycloaddition reaction of epoxy compounds and carbon dioxide in the absence of a co-catalyst.

[0025] The present invention provides a method for preparing a dual-ligand metal-organic framework material, comprising the following steps: S1) mixing an acidic organic ligand and a basic organic ligand in water to obtain a ligand precursor; S2) mixing the ligand precursor, a basic auxiliary agent, and a metal source to obtain a mixed solution; and S3) crystallizing the mixed solution at high temperature to obtain the dual-ligand metal-organic framework material. Compared with the prior art, the present invention prepares the dual-ligand metal-organic framework material by mixing two organic ligands of different acidity and basicity with a metal source and then performing coordination with the aid of a basic auxiliary agent. The dual-ligand metal-organic framework material has a large specific surface area, a rich pore structure, and a large number of unsaturated metal sites. Furthermore, it has the advantages of high catalytic activity, good selectivity, and strong stability. Therefore, the unsaturated-coordinated dual-ligand metal-organic framework material is not only simple to prepare and low in cost, but also exhibits excellent catalytic performance when used as a catalyst in the cycloaddition reaction of epoxides and carbon dioxide in an uncatalyst-free system.

[0026] The experimental results show that the dual-ligand metal-organic framework material prepared by the present invention catalyzes the cycloaddition reaction of epoxide and carbon dioxide in an uncatalyst-free system. Under the optimal conditions, the conversion rate and selectivity are both over 95%, and there is no decrease in activity after multiple cycles. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is the X-ray diffraction pattern of the dual-ligand metal-organic framework material obtained in Example 1 of the present invention;

[0028] Figure 2 This is a scanning electron microscope photograph of the dual-ligand metal-organic framework material obtained in Example 1 of the present invention;

[0029] Figure 3 This is a gas chromatogram of the biligand metal organic framework material obtained in Example 1 of the present invention after being used as a carbon dioxide cycloaddition reaction in an uncatalyst-free system;

[0030] Figure 4This is a mass spectrum of propylene oxide, the reactant, after the biligand metal organic framework material obtained in Example 1 of the present invention is used as a carbon dioxide cycloaddition reaction in an uncatalyst-free system;

[0031] Figure 5 This is a mass spectrum of propylene carbonate, the product of the carbon dioxide cycloaddition reaction using the biligand metal-organic framework material obtained in Example 1 of the present invention in an uncatalyst-free system;

[0032] Figure 6 This is a catalytic performance diagram of the biligand metal organic framework material obtained in Example 1 of the present invention used as a catalyst for carbon dioxide cycloaddition reaction in an uncatalyst-free system;

[0033] Figure 7 This is a catalytic performance diagram of the cyclic stability of the dual-ligand metal-organic framework material obtained in Example 1 of the present invention when used as a catalyst for the carbon dioxide cycloaddition reaction in an uncatalyst-free system. DETAILED DESCRIPTION

[0034] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0035] The present invention provides a preparation method of a dual-ligand metal-organic framework material, comprising the following steps: S1) mixing an acidic organic ligand and a basic organic ligand in water to obtain a ligand precursor; S2) mixing the ligand precursor, an alkaline auxiliary agent and a metal source to obtain a mixed solution; S3) crystallizing the mixed solution at high temperature to obtain the dual-ligand metal-organic framework material.

[0036] The present invention has no particular limitation on the sources of all raw materials, and any commercially available raw materials may be used.

[0037] An acidic organic ligand and a basic organic ligand are mixed in water to obtain a ligand precursor; the acidic organic ligand is preferably a carboxylic acid organic ligand, more preferably one or more of terephthalic acid, 2-aminoterephthalic acid, 2,5-dihydroxyterephthalic acid, 2,5′-thiophenedicarboxylic acid, and 2,5′-furandicarboxylic acid; the basic organic ligand is preferably a pyridine ligand, more preferably bipyridine, and even more preferably 4,4′-bipyridine; the molar ratio of the acidic organic ligand to the basic organic ligand is preferably 1:(0.5-1.5), more preferably 1:(0.6-1); in the embodiments provided by the present invention, the molar ratio of the acidic organic ligand to the basic organic ligand is specifically 1:1 or 1.5:1; the water is preferably deionized water; the mixing method is a method well known to those skilled in the art and is not particularly limited. In the present invention, ultrasonic mixing and uniform dispersion are preferred.

[0038] A ligand precursor, an alkaline auxiliary agent and a metal source are mixed to obtain a mixed solution; the total molar concentration of the acidic organic ligand and the alkaline organic ligand in the mixed solution is preferably 0.04-0.25 mol / L, more preferably 0.04-0.1 mol / L, and even more preferably 0.04-0.05 mol / L; the alkaline auxiliary agent is preferably an alkali metal hydroxide and / or an organic amine compound, more preferably one or more of sodium hydroxide, potassium hydroxide and triethylamine; the molar ratio of the alkaline auxiliary agent to the acidic organic ligand is preferably 2:(0.5-1), more preferably 2:(0.8-1); in the embodiment provided by the present invention, the molar ratio of the alkaline auxiliary agent to the acidic organic ligand is specifically 2:1; The metal source is any metal source well known to those skilled in the art and is not particularly limited. In the present invention, it is preferably one or more of zinc salts, aluminum salts, copper salts and nickel salts; the anions in the metal source are preferably one or more of nitrate ions, chloride ions, acetate ions and sulfate ions; the molar ratio of the total molar number of the acidic organic ligand and the basic organic ligand to the metal source is preferably (1-2):1, more preferably (1.5-2):1, and even more preferably (1.6-2):1; in the present invention, in this step, the alkaline auxiliary agent is preferably first added to the ligand precursor, and then the metal source is quickly added and mixed to obtain a mixed solution; the mixing time is preferably 15-60 min; and preliminary coordination is achieved by mixing.

[0039] The mixed solution is subjected to high-temperature crystallization; the high-temperature crystallization is preferably carried out in a hydrothermal reactor; the temperature of the high-temperature crystallization is preferably 120°C to 160°C, more preferably 130°C to 150°C, and even more preferably 140°C; the time of the high-temperature crystallization is preferably 24 to 72 hours; in the embodiments provided in the present invention, the time of the high-temperature crystallization is specifically 24 hours, 48 ​​hours or 72 hours.

[0040] After high temperature crystallization, the material is preferably centrifugally washed and dried to obtain a bi-ligand metal organic framework material; the centrifugal washing is preferably performed using water and ethanol; the number of centrifugal washings is preferably 3 to 5 times.

[0041] The present invention prepares a dual-ligand metal-organic framework material by mixing two organic ligands with different acidity and alkalinity with a metal source and then performing alkaline auxiliary coordination. The dual-ligand metal-organic framework material has a large specific surface area, a rich pore structure and a large number of unsaturated metal sites, and has the advantages of high catalytic activity, good selectivity and strong stability. Therefore, the unsaturated coordinated dual-ligand metal-organic framework material is not only simple to prepare and low in cost, but also has an excellent catalytic effect when used as a catalyst for the cycloaddition reaction of epoxide and carbon dioxide in an uncatalyst-free system.

[0042] The present invention also provides a dual-ligand metal-organic framework material prepared by the above method; the dual-ligand metal-organic framework material is formed by coordination between organic ligands and metal ions; the organic ligands include acidic organic ligands and basic organic ligands.

[0043] The acidic organic ligand is preferably a carboxylic acid organic ligand, more preferably one or more of terephthalic acid, 2-aminoterephthalic acid, 2,5-dihydroxyterephthalic acid, 2,5′-thiophenedicarboxylic acid, and 2,5′-furandicarboxylic acid; the basic organic ligand is preferably a pyridine ligand, more preferably bipyridine, and even more preferably 4,4′-bipyridine; the molar ratio of the acidic organic ligand to the basic organic ligand is preferably 1:(0.5-1.5), more preferably 1:(0.6-1).

[0044] The metal ions are preferably one or more of zinc ions, aluminum ions, copper ions and nickel ions.

[0045] The organic ligand and the metal ion are preferably coordinated in the presence of an alkaline auxiliary agent; the alkaline auxiliary agent is preferably an alkali metal hydroxide and / or an organic amine compound, more preferably one or more of sodium hydroxide, potassium hydroxide and triethylamine.

[0046] The dual-ligand metal-organic framework material preferably has a porous two-dimensional layered structure.

[0047] The present invention also provides an application of a biligand metal-organic framework material in catalyzing the cycloaddition reaction of an epoxy compound and carbon dioxide. Preferably, the biligand metal-organic framework material catalyzes the cycloaddition reaction of an epoxy compound and carbon dioxide in the absence of a co-catalyst.

[0048] The biligand metal-organic framework (MOF) materials with unsaturated coordination provided by the present invention possess a large surface area, a rich pore structure, numerous unsaturated metal sites, and a unique biligand structure. They also exhibit advantages such as high activity, good selectivity, and strong stability. In the addition reaction of epoxy compounds with carbon dioxide, the biligand MOF materials provided by the present invention exhibit very high catalytic performance and can promote cycloaddition reactions without a co-catalyst, far surpassing other catalysts.

[0049] To further illustrate the present invention, the following describes in detail a dual-ligand metal-organic framework material, a preparation method thereof, and applications thereof in conjunction with embodiments.

[0050] The reagents used in the following examples are all commercially available.

[0051] Example 1

[0052] 1.1 Add 1.5 mmol 2-aminoterephthalic acid and 1.5 mmol 4,4'-bipyridine to 100 mL polytetrafluoroethylene liner, add 60 mL deionized water, mix well and disperse by ultrasonic.

[0053] 1.2 Add 3.0 mmol of sodium hydroxide to the mixture and stir evenly. Then quickly add 1.5 mmol of zinc nitrate hexahydrate to the mixture and stir evenly. Stir for 15 minutes to obtain a uniform colloidal suspension, which is then placed in a reactor for a high-temperature hydrothermal reaction at 140°C for 72 hours.

[0054] 1.3 Take out the obtained product, wash it with water and ethanol respectively, and centrifuge it for 3 to 5 times, and then dry it in a vacuum drying oven overnight to obtain an unsaturated coordinated biligand metal-organic framework material.

[0055] The bi-ligand metal organic framework material obtained in Example 1 was characterized by X-ray diffraction, and the following Figure 1 The X-ray diffraction pattern shown. Figure 1 It can be seen that the material prepared in Example 1 is an unsaturated coordinated bi-ligand metal-organic framework material.

[0056] The dual-ligand metal organic framework material obtained in Example 1 was observed using a scanning electron microscope to obtain the following Figure 2 The scanning electron microscope photo shown. Figure 2 It can be seen that the material prepared in Example 1 is a two-dimensional layered structure.

[0057] The biligand metal organic framework material obtained in Example 1 was used as a catalyst for the carbon dioxide cycloaddition reaction under an uncatalyst system and its performance was tested. The specific process is as follows: 10 mg of the biligand metal organic framework material obtained in Example 1, 0.50 mmol of propylene oxide, and 0.25 mL of DMF solvent were added to a closed reactor (the internal volume of the reactor is 10 mL and the maximum pressure that can be applied is 20 MPa), and 2 MPa of high-purity carbon dioxide was introduced into the reactor. The system was initially heated to 120 ° C at a heating rate of 4 ° C / min and reacted for 30 hours. After the reaction was completed, it was cooled in an ice water bath, and the liquid phase product was extracted and detected in a gas chromatography-mass spectrometry (helium was used as the carrier gas, 1 μL was manually injected, the injection port temperature was 250 ° C, and the detection method was to stabilize at 40 ° C for 2 minutes, then heat it to 100 ° C at 10 ° C / min, stabilize it for 2 minutes, then heat it to 220 ° C at 20 ° C / min, and then stabilize it for 2 minutes). The gas chromatogram after the reaction was obtained as shown below. Figure 3 As shown, the mass spectrum of raw material propylene oxide is as follows Figure 4 The mass spectrum of the product propylene carbonate is shown in Figure 5 The product was propylene carbonate with a yield of 95.0%. During the reaction, the liquid phase product was sampled and extracted and tested by gas chromatography-mass spectrometry to obtain a curve of conversion rate over time. Figure 6 shown.

[0058] The bi-ligand metal organic framework material after catalyzing the carbon dioxide cycloaddition reaction was washed with water and ethanol and centrifuged 3 to 5 times, then dried in a vacuum drying oven overnight, and then used as a catalyst for the carbon dioxide cycloaddition reaction under the uncatalyst system under the above conditions and the performance was tested. The results were repeated many times to obtain the cyclic stability catalytic performance diagram as shown in the figure. Figure 7 shown.

[0059] Example 2

[0060] The specific material preparation process is the same as that of Example 1, except that 1.5 mmol of terephthalic acid is used as the ligand. The reaction performance test is the same as that of Example 1, and the yield of the carbon dioxide-propylene oxide cycloaddition reaction without a co-catalyst system is 96.3%.

[0061] Example 3

[0062] The specific material preparation process is the same as that of Example 1, except that 1.5 mmol of 2,5-furandicarboxylic acid is used as the ligand. The reaction performance test is the same as that of Example 1, and the yield of the carbon dioxide-propylene oxide cycloaddition reaction without a co-catalyst system is 94.1%.

[0063] Example 4

[0064] The specific material preparation process is the same as that of Example 1, except that the amount of 4,4'-bipyridine used is 1 mmol. The reaction performance test is the same as that of Example 1, and the yield of the carbon dioxide-propylene oxide cycloaddition reaction without a co-catalyst system is 94.5%.

[0065] Example 5

[0066] The specific material preparation process is the same as that of Example 1, except that 1.5 mmol zinc chloride is used as the metal salt. The reaction performance test is the same as that of Example 1, and the yield of the carbon dioxide-propylene oxide cycloaddition reaction without a co-catalyst system is 95.4%.

[0067] Example 6

[0068] The specific material preparation process is the same as that of Example 1, except that 1.5 mmol zinc acetate is used as the metal salt. The reaction performance test is the same as that of Example 1, and the yield of the carbon dioxide-propylene oxide cycloaddition reaction without a co-catalyst system is 96.1%.

[0069] Example 7

[0070] The specific material preparation process is the same as that of Example 1, except that 3.0 mmol potassium hydroxide is used as the alkaline auxiliary agent. The reaction performance test is the same as that of Example 1, and the yield of the carbon dioxide-propylene oxide cycloaddition reaction without a catalyst system is 93.9%.

[0071] Example 8

[0072] The specific material preparation process is the same as that of Example 1, except that the alkaline auxiliary agent and metal salt are added and stirred for 30 minutes. The reaction performance test is the same as that of Example 1. The yield of the carbon dioxide-propylene oxide cycloaddition reaction without a catalyst system is 96.5%.

[0073] Example 9

[0074] The specific material preparation process is the same as that of Example 1, except that the mixture is mixed and stirred and then subjected to high temperature hydrothermal reaction for 24 hours. The reaction performance test is the same as that of Example 1, and the yield of the carbon dioxide-propylene oxide cycloaddition reaction without a co-catalyst system is 92.5%.

[0075] Example 10

[0076] The specific material preparation process is the same as that of Example 1, except that the mixture is stirred and then subjected to high temperature hydrothermal reaction for 48 hours. The reaction performance test is the same as that of Example 1, and the yield of the carbon dioxide-propylene oxide cycloaddition reaction without a co-catalyst system is 93.6%.

[0077] In summary, the embodiments of the present invention not only have high activity, high selectivity and high stability, but also have a simple preparation method and low preparation cost, and can exhibit very high catalytic performance in the cycloaddition reaction of epoxides and carbon dioxide under uncatalyst conditions.

[0078] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing a dual-ligand metal-organic framework material, characterized in that: The following steps are involved: S1) mixing an acidic organic ligand and a basic organic ligand in water to obtain a ligand precursor; S2) mixing the ligand precursor, the alkaline auxiliary agent and the metal source to obtain a mixed solution; S3) crystallizing the mixed solution at high temperature to obtain a biligand metal-organic framework material; The molar ratio of the acidic organic ligand to the basic organic ligand is 1:(0.5-1.5); The molar ratio of the total molar number of the acidic organic ligand and the basic organic ligand to the metal source is (1-2):1; The molar ratio of the alkaline auxiliary agent to the acidic organic ligand is 2: (0.5-1); The acidic organic ligand is selected from one or more of terephthalic acid, 2-aminoterephthalic acid, 2,5-dihydroxyterephthalic acid, 2,5′-thiophenedicarboxylic acid, and 2,5′-furandicarboxylic acid; The basic organic ligand is selected from pyridine ligands; The alkaline auxiliary agent is selected from one or more of sodium hydroxide, potassium hydroxide and triethylamine; The metal source is selected from one or more of zinc salts, aluminum salts, copper salts and nickel salts.

2. The preparation method according to claim 1, characterized in that The total molar concentration of the acidic organic ligand and the basic organic ligand in the mixed solution is 0.04-0.25 mol / L.

3. The preparation method according to claim 1, characterized in that The mixing time in step S2) is 15 to 60 minutes; The temperature of the high-temperature crystallization is 120° C. to 160° C.; and the time of the high-temperature crystallization is 24 to 72 hours.

4. The preparation method according to claim 1, characterized in that In the step S3), high temperature crystallization is followed by centrifugal washing and drying to obtain a bi-ligand metal organic framework material; the centrifugal washing is performed using water and ethanol.

5. A dual-ligand metal-organic framework material prepared by the preparation method according to any one of claims 1 to 4, characterized in that: It is formed by coordination between organic ligands and metal ions; the organic ligands include acidic organic ligands and basic organic ligands.

6. The dual-ligand metal-organic framework material according to claim 5, characterized in that The dual-ligand metal-organic framework material has a porous two-dimensional layered structure.

7. Use of the biligand metal organic framework material prepared by the preparation method according to any one of claims 1 to 4 in catalyzing the cycloaddition reaction of epoxy compounds and carbon dioxide.

8. The use according to claim 7, characterized in that The dual-ligand metal organic framework material catalyzes the cycloaddition reaction of epoxy compounds and carbon dioxide in the absence of a co-catalyst.

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