A MIL-68@MIL-101 metal organic framework with core-satellite structure, preparation method and application thereof

Abstract

The application relates to a MIL-68@MIL-101 metal organic framework with a core-satellite structure and a preparation method and application thereof, and belongs to the technical field of crystalline materials. A metal organic framework MIL-101 is dispersed into an organic solvent to obtain a uniformly dispersed suspension, then indium nitrate hydrate and terephthalic acid are added, stirring and ultrasonic treatment are continuously carried out, finally, the mixture is transferred into a Teflon-lined hydrothermal high-pressure kettle, reaction is carried out at 70-130 DEG C for 5-9 hours, after cooling, centrifugal separation, washing and drying, the MIL-68@MIL-101 metal organic framework with the core-satellite structure is obtained. The MIL-68@MIL-101 metal organic framework with the core-satellite structure disclosed by the application has the advantages of simple synthesis method, low cost of required raw materials, better CO2 adsorption capacity, suitability for CO2 / N2 gas separation, strong universality, simple preparation method, fast operation, high use value and wide industrial application prospect.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of crystalline materials, and relates to a MIL-68@MIL-101 metal organic framework with a core-satellite structure and a preparation method and application thereof BACKGROUND

[0002] With the rapid growth of global population, energy consumption is also significantly increasing. Fossil fuels are one of the main sources of world energy, and are currently causing widespread concern and demand as an energy source. So far, since more than 85% of global energy demand is provided by fossil fuel combustion, a large amount of carbon dioxide is emitted into the atmosphere, triggering a global energy crisis and greenhouse effect. Therefore, it is imminent to control the CO2 concentration in the atmosphere, and it is of far-reaching significance to research a new material capable of efficiently adsorbing CO2.

[0003] Compared with traditional adsorption materials, metal organic frameworks have the advantages of large surface area, high porosity, adjustable morphology, etc., and have been studied and used in catalysis, ion exchange and adsorption, biological medicine, molecular recognition and sensing, etc. fields, especially in the field of gas adsorption and separation. In recent years, MOFs composed of two or more MOFs have unique structural characteristics such as high specific surface area, diverse porous structure, rich metal center and ligand, which have attracted the attention of researchers. The difficulty lies in how to prepare a multi-layer structure of the material to simultaneously improve the gas adsorption capacity and selectivity. A stable double MOF composite material should be derived from a strong coordination bond to resist the attack of guest molecules, and there is a stronger interaction between the common organic linkers in the double MOF, so the double MOF is considered to be a new adsorbent for gas adsorption and separation. Most of the existing technologies are to synthesize a core MOF first, and then grow a shell MOF or load a substance on the surface of the core. The present application is just the opposite. SUMMARY

[0004] The purpose of the present application is to provide a MIL-68@MIL-101 metal organic framework with a core-satellite structure and a preparation method and application thereof, which has better gas adsorption capacity and selectivity, and can solve the problem of separation of CO2 / N2 in flue gas of power plants.

[0005] The first aspect of the purpose of the present application is to provide a preparation method of a MIL-68@MIL-101 metal organic framework with a core-satellite structure, which comprises the following steps:

[0006] (1) dispersing the metal-organic framework MIL-101 into an organic solvent, stirring and ultrasonicating to obtain a uniformly dispersed suspension;

[0007] (2) then adding the precursor of MIL-68 into the suspension, continuing stirring and ultrasonic, and finally transferring the mixture into a Teflon-lined autoclave to react at 70-130 DEG C for 5-9 h, and after cooling, centrifuging, washing and drying, a MIL-68@MIL-101 metal organic framework with core-satellite structure is obtained.

[0008] The preparation method of the metal organic framework MIL-101 in step (1) comprises the following steps: mixing chromium nitrate nonahydrate, terephthalic acid, hydrofluoric acid and water, heating, cooling, centrifuging, washing and vacuum drying to obtain the metal organic framework MIL-101.

[0009] The organic solvent in step (1) is N,N-dimethylformamide.

[0010] In step (2), the precursor of MIL-68 comprises indium nitrate hydrate and terephthalic acid, and the mass ratio of indium nitrate hydrate to terephthalic acid is 90-100:100-110.

[0011] In step (2), the mass ratio of MIL-101 to terephthalic acid is 1:0.8-1.4.

[0012] According to the second aspect of the present application, the MOF@MOF metal organic framework with core-satellite structure prepared by the above preparation method is provided.

[0013] According to the third aspect of the present application, the application of the MIL-68@MIL-101 metal organic framework in carbon dioxide adsorption and separation is provided.

[0014] In the preparation method, terephthalic acid is used as a ligand and a structure directing agent, and is coordinated with metal ions respectively to in-situ synthesize core MIL-68 and induce satellite structure of MIL-101 to in-situ grow on the surface of MIL-68, so that the MIL-68@MIL-101 metal organic framework with core-satellite structure is finally formed.

[0015] Compared with the prior art, the present application can at least achieve one of the following beneficial effects:

[0016] 1、The application adopts an in-situ growth method to prepare MIL-68@MIL-101 metal organic framework, and the core-satellite MOF prepared by the method, i.e. MIL-68 as the core with dispersed MIL-101 growing in-situ on the surface of the core, is actually a plurality of octahedral structure MIL-101 growing outward to form a structure in which a plurality of MIL-101 surrounds MIL-68, and compared with the core-satellite MOF prepared by adding polyvinylpyrrolidone (PVP), has the advantages of adjustable loading capacity and particle size, and has more potential in gas adsorption and separation.

[0017] 2、The MIL-68@MIL-101 metal organic framework prepared by the application has more excellent CO2 adsorption performance, and the adsorption amount of carbon dioxide can reach 38.6 cm 3 / g, which is increased by 17.3% compared with the core MIL-68, and the MIL-68@MIL-101 metal organic framework has larger adsorption capacity and strong application.

[0018] 3、The preparation method of the application is simple, the raw materials are cheap and easy to implement, is suitable for CO2 / N2 gas separation, and has strong universality. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 XRD patterns of the materials obtained in Example 1, Comparative Example 1 and Comparative Example 2;

[0020] Figure 2 SEM patterns of the materials obtained in Example 1, Comparative Example 1 and Comparative Example 2;

[0021] Figure 3 77K nitrogen adsorption isotherm patterns of the materials obtained in Example 1, Comparative Example 1 and Comparative Example 2;

[0022] Figure 4 CO2 adsorption isotherm patterns of the materials obtained in Example 1 and Comparative Example 1 at 298K;

[0023] Figure 5 N2 adsorption isotherm pattern of the material obtained in Example 1 at 298K. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the application will be described clearly and completely below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the application.

[0025] Comparative Example 1:

[0026] Chromium nitrate nonahydrate (400 mg), terephthalic acid (166 mg), hydrofluoric acid (0.02 ml), and water (4.8 ml) were added to a Teflon-lined hydrothermal autoclave. After sonication for 10 min, the autoclave was placed in an oven and heated to 220 °C at a heating rate of 2 °C / min, held at that temperature for 8 h, and then slowly cooled to room temperature for 5 h. The product in the autoclave was separated by centrifugation, washed three times with hot DMF (150 °C), and once each with hot methanol (70 °C) and ethanol (90 °C). The final solid was dried in a vacuum oven (120 °C) for 5 h to obtain the metal-organic framework MIL-101 (uniform octahedral structure). The morphology of the sample was characterized using scanning electron microscopy.

[0027] Example 1:

[0028] MIL-101 (100 mg) was weighed and dispersed in DMF solution (130 ml). Then, indium nitrate hydrate (90 mg) and terephthalic acid (110 mg) were added and magnetically stirred for 30 min to obtain a uniform suspension. The suspension was then placed in a Teflon-lined thermostatic autoclave and kept at 130 °C for 5 h. The suspension was then cooled to room temperature within 5 h. The product in the autoclave was separated by centrifugation, washed three times with hot DMF (150 °C), and once each with hot methanol (70 °C) and ethanol (90 °C). The solid obtained was then dried in a vacuum oven (80 °C) for 5 h to obtain the MIL-68@MIL-101 metal-organic framework. The morphology of the sample was characterized by scanning electron microscopy.

[0029] Comparative Example 2:

[0030] Indium nitrate hydrate (0.18 g) and terephthalic acid (0.18 g) were weighed and added to 120 mL of N,N'-dimethylformamide in a 200 mL beaker. The mixture was ultrasonically dispersed for 10 minutes. Then, it was placed in a Teflon-lined thermostatic autoclave and kept at 120 °C for 6 hours. After cooling, the product was centrifuged to remove the supernatant (10,000 rpm, 10 minutes). The product was washed three times with N,N'-dimethylformamide (DMF) and methanol, respectively. Finally, it was vacuum dried at 80 °C for 12 hours to obtain the metal-organic framework MIL-68 (uniform hexagonal prism structure). The morphology of the sample was characterized by scanning electron microscopy.

[0031] The following are the structural characterization and performance tests:

[0032] 1. XRD powder diffraction test results show that the XRD powder diffraction results obtained in Example 1, Comparative Example 1, and Comparative Example 2 are as follows: Figure 1 As shown, by Figure 1 The results show that the diffraction peak results of Example 1 are consistent with those of Comparative Examples 1 and 2, indicating that MIL-101 was successfully loaded onto MIL-68.

[0033] 2. SEM test results are as follows Figure 2 As shown in the results, Comparative Example 1 ( Figure 2 (a) Morphological image of MIL-101, Comparative Example 2 ( Figure 2 (b) MIL-68 morphology diagram, and Example 1 ( Figure 2 (c) shows the topographical diagram of MIL-68@MIL-101, which indicates that MIL-101 is loaded onto MIL-68.

[0034] 3. The nitrogen adsorption isotherm at 77K is shown below. Figure 3 As shown, the adsorption isotherm of Example 1 lies between Comparative Example 1 and Comparative Example 2, indicating that MIL-101 was successfully loaded onto MIL-68.

[0035] 4. The carbon dioxide adsorption performance of the materials obtained in Example 1 and Comparative Example 2 was tested at 298 K and 1 atmosphere. The experimental results are as follows: Figure 4 As shown, the CO2 adsorption capacity of Example 1 is 38.6 cm⁻¹. 3 / g, the CO2 adsorption capacity of Comparative Example 2 was 32.9cm³. 3 / g, Example 1 underwent nitrogen adsorption performance testing under the same conditions, and the experimental results are as follows: Figure 5 As shown, the N2 adsorption capacity of Example 1 is 3.5 cm³. 3 / g, exhibiting better CO2 adsorption capacity and selective adsorption and separation of CO2 / N2 properties than Example 1.

Claims

1. A method for preparing MIL-68@MIL-101 metal-organic framework with core-satellite structure, characterized in that, The method comprises the following steps: (1) dispersing metal-organic framework MIL-101 into an organic solvent, stirring and ultrasonicating to obtain a uniformly dispersed suspension; (2) subsequently adding a precursor of MIL-68 into the suspension, continuing to stir and ultrasonicate, and finally transferring the mixture into a Teflon-lined hydrothermal high-pressure kettle to react at 70-130℃ for 5-9h, after cooling, centrifuging, washing and drying, a MIL-68@MIL-101 metal-organic framework with core-satellite structure is obtained; The precursor of MIL-68 comprises indium nitrate hydrate and terephthalic acid.

2. The method for preparing a MIL-68@MIL-101 metal-organic framework with a core-satellite structure according to claim 1, characterized in that, The ratio of indium nitrate hydrate to terephthalic acid in the precursor of MIL-68 is 90-100mg:100-110mg.

3. Process for the preparation of MIL-68@MIL-101 metal-organic frameworks with core-satellite structure according to claim 2, characterized in that, In step (2), the mass ratio of MIL-101 to terephthalic acid is 1:0.8-1.

4.

4. The method of claim 1, wherein the MIL-68@MIL-101 metal-organic framework having a core-satellite structure is prepared by, The organic solvent in step (1) is N,N-dimethylformamide.

5. A MIL-68@MIL-101 metal-organic framework with core-satellite structure prepared by the method according to any one of claims 1-4.

6. Use of a MIL-68@MIL-101 metal-organic framework with core-satellite structure prepared by the method according to any one of claims 1-4 in carbon dioxide adsorption and separation.

7. Use according to claim 6 for CO2 / N2 gas separation.

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