Preparation method of ultra-microporous metal organic framework material and application of ultra-microporous metal organic framework material in adsorption of sulfur hexafluoride

Abstract

The invention discloses a preparation method of an ultra-microporous metal organic framework material, which comprises the following steps: mixing a nitric acid metal salt, a polycarboxylic acid layered ligand and a nitrogen heterocyclic columnar ligand in a solvent, carrying out ultrasonic dissolution, carrying out heating reaction at 120-150 DEG C for 24-72 hours, cooling to room temperature, carrying out solid-liquid separation, centrifugally washing the solid with the solvent, and drying to obtain the ultra-microporous metal organic framework material. Drying in vacuum at 100-150 DEG C and activating for 12-24 hours to obtain the ultra-microporous metal organic framework material. The ultra-microporous metal organic framework material prepared by the invention is used for adsorption separation of greenhouse gas SF6, and has high adsorption capacity and good IAST selectivity.

Description

TECHNICAL FIELD

[0001] The application relates to a preparation method of an ultramicroporous metal organic framework material and application of the ultramicroporous metal organic framework material in adsorption of sulfur hexafluoride gas, and belongs to the technical field of material chemical industry. BACKGROUND

[0002] Sulfur hexafluoride (SF6) plays a crucial role in the industrial field of ultra-large scale integrated circuits and ultra-high voltage power equipment due to its excellent electrical insulation and arc extinguishing performance, and is widely used as an electrical insulator in high-voltage power transmission and distribution equipment. SF6 is one of the greenhouse gases that need to be strictly controlled and discharged globally according to the Kyoto Protocol, and its global warming potential (GWP) is as high as 23900 times that of carbon dioxide, and its lifetime in the atmosphere can reach 3200 years. With the urgent demand for SF6 emission reduction globally, SF6 mixed gas replacement technology emerges as the times require, that is, by mixing SF6 with nitrogen (N2), carbon dioxide, perfluorocarbon and other gases to form binary or ternary mixed gas, so as to reduce the use of SF6 while meeting the performance requirements. However, the dilution application of SF6 does not fundamentally solve the emission reduction problem. Therefore, under the background of national "energy saving and emission reduction", efficient adsorption and separation of SF6 is imminent.

[0003] Traditional porous adsorption materials, such as carbon-based adsorbents and zeolite molecular sieves, have been applied to the adsorption and separation of SF6 due to their excellent chemical and thermal stability. However, such materials have obvious limitations in terms of precise control of pore size and regulation of pore chemical environment, resulting in a trade-off between the adsorption capacity and selectivity of SF6. In recent years, metal organic framework materials (MOFs) have been developed, which have ultra-high specific surface area, precisely controllable pore size and chemical environment, and rich surface functionalization potential, providing a promising solution for efficient capture and separation of SF6. By carefully designing ligands and metal nodes, MOFs with suitable pore window size, strong adsorption sites and specific pore chemical environment can be constructed, thereby realizing high selective recognition and adsorption of SF6 molecules. In addition, the pore size of ultramicroporous MOFs materials (pore size < 10 Å) can be adjusted to match the size of SF6 molecules (5.5 Å) in dynamic diameter, which helps to break the dilemma of trade-off between adsorption capacity and selectivity in the adsorption process of SF6. Therefore, developing new ultramicroporous MOFs adsorbents with high SF6 adsorption capacity, excellent selectivity (SF6 / N2) and good stability is of great significance for promoting the resource utilization of SF6 and greenhouse gas emission reduction. SUMMARY

[0004] In view of the problem of trade-off between adsorption capacity and selectivity in the process of adsorbing SF6 by traditional adsorbents, the application provides a preparation method of a super-microporous metal organic framework material, which comprises the following steps: mixing a metal nitrate, a polycarboxylic acid layer-type ligand and a nitrogen heterocyclic column-type ligand in a solvent, ultrasonic dissolving, transferring into a hydrothermal reaction kettle, heating at 120-150 DEG C for 24-72 h, cooling to room temperature after the reaction, solid-liquid separation, centrifugal washing of the solid with a solvent, vacuum drying at 100-150 DEG C for 12-24 h and activation, and then the columnar super-microporous metal organic framework material is obtained.

[0005] The molar ratio of the metal nitrate to the polycarboxylic acid layer-type ligand is 2-3:1-3, and the molar ratio of the metal nitrate to the nitrogen heterocyclic column-type ligand is 2-3:4.

[0006] The metal nitrate is one of nickel nitrate hexahydrate, zinc nitrate hexahydrate, cobalt nitrate hexahydrate, copper nitrate hexahydrate and manganese nitrate hexahydrate; the polycarboxylic acid layer-type ligand is one of 1,3,5-tris(4-carboxyphenyl)benzene, 2,4,6-tris(4-carboxyphenyl)-1,3,5-triazine, 1,2,4,5-benzenetetracarboxylic acid, 3,3',5,5'-diphenyltetracarboxylic acid, 1,1,2,2-tetrakis(4-carboxyphenyl)ethylene, 1,2,4,5-tetrakis(4-carboxyphenyl)benzene and 1,3,6,8-tetrakis(4-carboxyphenyl)pyrene; and the nitrogen heterocyclic column-type ligand is one of 1,4-diazabicyclo[2.2.2]octane, 1,2-bis(4-pyridyl)ethane and 1,2-bis(4-pyridyl)ethylene.

[0007] The solvent is one of methanol, ethanol, water, N,N-dimethylformamide and N,N-dimethylacetamide.

[0008] Another object of the application is to provide the super-microporous metal organic framework material prepared by the above method.

[0009] Another object of the application is to apply the super-microporous metal organic framework material to the adsorption of sulfur hexafluoride, and a 3flex physical adsorption instrument produced by American Micromeritics Company is used to measure the single-component adsorption isotherm of SF6 or N2 in the range of 0.01-100 kPa at 25 DEG C; specifically, 0.1-0.5 g of the super-microporous metal organic framework material is loaded into a sample tube of the physical adsorption instrument, the sample tube is connected to a desorption station of the physical adsorption instrument, impurities on the surface of the super-microporous metal organic framework adsorbent are removed by vacuum desorption at 120-150 DEG C for 8-12 h, after the desorption, the sample tube is connected to an adsorption station of the physical adsorption instrument, and the single-component adsorption isotherm is measured by introducing SF6 or N2 with a volume concentration of 99.999%.

[0010] After obtaining the single-component adsorption isotherms of SF6 and N2, the adsorption selectivity of the mixed-component gas (SF6 / N2) is predicted by using the ideal adsorbed solution theory (IAST), and the method in the literature J. Am. Chem. Soc. Recovery of High-Purity SF6from Humid SF6 / N2Mixture within a Co(II)-Pyrazolate Framework. 2024, 146, 19303-19309 is referred to for prediction.

[0011] Compared with the prior art, the present application has the following advantages: The method synthesizes a columnar-type ultramicroporous metal-organic framework material, and the pore size and pore surface environment are regulated by the ligand chain length and the number of π bonds, so that the material has high adsorption capacity and high selectivity in SF6 adsorption. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 is a powder X-ray diffraction (XRD) pattern of the ultramicroporous metal-organic framework material of Example 1; Figure 2 is a N2 adsorption / desorption curve (left) and a DFT pore size distribution graph (right) of Example 1; Figure 3 is a single-component adsorption isotherm of SF6 and N2 of the ultramicroporous metal-organic framework material prepared in Example 1 at 25℃; Figure 4 is an IAST selectivity curve graph of the ultramicroporous metal-organic framework material prepared in Example 1 by calculation. DETAILED DESCRIPTION

[0013] The present application will be further described in detail below by way of examples and drawings, but the protection of the present application is not limited to the content described. Example 1

[0014] (1) 0.4362 g of nickel nitrate hexahydrate, 0.3798 g of 1,2,4,5-tetrakis(4-carboxyphenyl)benzene, and 0.3366 g of 1,4-diazabicyclo[2.2.2]octane are mixed and dissolved in 60 mL of N,N-dimethylformamide, the mixture is ultrasonicated for 30 min, then transferred into the inner liner of a hydrothermal reaction kettle, placed in a forced air drying oven, heated at 135℃ for 72 h, cooled to room temperature, and then solid-liquid separation, the solid is washed by centrifugation with solvent N,N-dimethylformamide for 3 times, and then washed by centrifugation with ethanol for 3 times, and then placed in a vacuum drying oven for vacuum drying at 120℃ and activation for 24 h, to obtain an ultramicroporous metal-organic framework material (Ni-DMOF-1); The crystal structure of the super-microporous metal-organic framework material is characterized by powder X-ray diffraction (XRD) Figure 1 ), Figure 1 It can be seen that there are sharp diffraction peaks at 5-20°, which proves its high crystallinity; the low-angle region 5-10° is a layered characteristic peak, and 17-18° is a periodic peak of 1,4-diazabicyclo [2.2.2] octane; these characteristic peaks together prove the synthesis of its crystalline material; the specific surface area and pore size distribution of the super-microporous metal-organic framework material are characterized by nitrogen adsorption and desorption experiments, the BET specific surface area of the super-microporous metal-organic framework material Ni-DMOF-1 is 1625 m 2 / g, and its DFT pore size distribution range is between 0.7-0.8 nm Figure 2 ); (3) 0.1 g of super-microporous metal-organic framework material Ni-DMOF-1 is loaded into the sample tube of the physical adsorption instrument, the sample tube is connected to the desorption station of the physical adsorption instrument, and the desorption is carried out at 150°C for 12h under vacuum. After the desorption is completed, it is connected to the adsorption station of the physical adsorption instrument, and the SF6 single-component adsorption isotherm at 25°C is tested by setting the program and introducing SF6 with a volume concentration of 99.999%, and the maximum adsorption capacity at 100kPa is 5.52mmol / g. In the same way, N2 with a volume concentration of 99.999% is introduced to test the N2 single-component adsorption isotherm at 25°C, and the maximum adsorption capacity at 100kPa is 0.27mmol / g Figure 3 ); the adsorption selectivity of SF6 / N_ mixed gas (10 / 90, v / v) is predicted by IAST, which is 201 at 100kPa Figure 4 。 Example 2

[0015] (1) 0.4362g of nickel nitrate hexahydrate, 0.4642g of 1,3,6,8-tetrakis(4-carboxyphenyl)pyrene, and 0.3366g of 1,4-diazabicyclo [2.2.2] octane are mixed and dissolved in 60mL of N,N-dimethylformamide. After ultrasonic treatment for 30min, the obtained mixture is transferred into the inner liner of a hydrothermal reaction kettle, heated at 135°C for 72h, cooled to room temperature, and then solid-liquid separation. The solid is washed by centrifugation with N,N-dimethylformamide for 3 times, and then washed with ethanol for 3 times. The solid is placed in a vacuum drying box and vacuum dried at 120°C for 24h to obtain a super-microporous metal-organic framework material (Ni-DMOF-2); (2) The ultra-microporous metal-organic framework material Ni-DMOF-2 prepared in step (1) was applied to the adsorption experiment of SF6 and N2 at 25°C. The implementation method was the same as that in Example 1, and the single-component adsorption isotherms of SF6 and N2 were obtained. The adsorption amount of SF6 was 3.88 mmol / g, the adsorption amount of N2 was 0.20 mmol / g, and the IAST selectivity was 110. Example 3

[0016] (1) 0.4462 g of zinc nitrate hexahydrate, 0.4642 g of 1,1,2,2-tetrakis(4-carboxyphenyl)ethylene and 0.3458 g of 1,4-diazabicyclo[2.2.2]octane were mixed and dissolved in 60 mL of N,N-dimethylformamide. The resulting mixture was ultrasonicated for 30 min and then transferred to the inner lining of a hydrothermal reactor. The mixture was heated at 135 °C for 72 h. After cooling to room temperature, the solid-liquid separation was performed. The solid was washed three times by centrifugation with N,N-dimethylformamide solvent and then washed three times by centrifugation with ethanol. The solid was placed in a vacuum drying oven at 120 °C and activated for 24 h to obtain an ultra-microporous metal-organic framework material (Zn-DMOF-1). (2) The ultra-microporous metal-organic framework material Zn-DMOF-1 prepared in step (1) was applied to the adsorption experiment of SF6 or N2 at 25°C. The implementation method was the same as that in Example 1, and the single-component adsorption isotherms of SF6 and N2 were obtained. The adsorption amount of SF6 was 3.20 mmol / g, the adsorption amount of N2 was 0.25 mmol / g, and the IAST selectivity was 137.

Claims

1. A method for preparing an ultra-microporous metal-organic framework material, characterized by: A metal nitrate, a polycarboxylic acid layer-type ligand, and a nitrogen heterocyclic column-type ligand are mixed in a solvent, dissolved by ultrasonication, heated at 120-150°C for reaction for 24-72 hours, cooled to room temperature, and subjected to solid-liquid separation. The solid is washed by centrifugation with a solvent, vacuum-dried at 100-150°C, and activated for 12-24 hours to obtain an ultramicroporous metal-organic framework material.

2. The method for preparing an ultra-microporous metal-organic framework material according to claim 1, wherein: The molar ratio of the metal nitrate to the polycarboxylic acid layer-type ligand is 2-3:1-3, and the molar ratio of the metal nitrate to the nitrogen heterocyclic column-type ligand is 2-3:

4.

3. The method for preparing an ultra-microporous metal-organic framework material according to claim 2, wherein: The metal nitrate is one of nickel nitrate hexahydrate, zinc nitrate hexahydrate, cobalt nitrate hexahydrate, copper nitrate hexahydrate, and manganese nitrate hexahydrate.

4. The method for preparing an ultra-microporous metal-organic framework material according to claim 2, wherein: The polycarboxylic acid layer-type ligand is one of 1,3,5-tris(4-carboxyphenyl)benzene, 2,4,6-tris(4-carboxyphenyl)-1,3,5-triazine, 1,2,4,5-benzenetetracarboxylic acid, 3,3',5,5'-biphenyltetracarboxylic acid, 1,1,2,2-tetra(4-carboxyphenyl)ethylene, 1,2,4,5-tetra(4-carboxyphenyl)benzene, and 1,3,6,8-tetra(4-carboxyphenyl)pyrene.

5. The method for preparing an ultra-microporous metal-organic framework material according to claim 2, wherein: The nitrogen heterocyclic columnar ligand is one of 1,4-diazabicyclo[2.2.2]octane, 1,2-bis(4-pyridyl)ethane, 1,2-di(4-pyridyl)ethylene, and 1,4-di(p-pyridyl)benzene.

6. The method for preparing an ultra-microporous metal-organic framework material according to claim 1, wherein: The solvent is one of methanol, ethanol, water, N,N-dimethylformamide and N,N-dimethylacetamide.

7. The ultramicroporous metal-organic framework material obtained by the method for preparing the ultramicroporous metal-organic framework material according to any one of claims 1 to 6.

8. Use of the ultramicroporous metal organic framework material according to claim 7 in the adsorption of sulfur hexafluoride.

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