A metal-organic framework material, a preparation method thereof, and application thereof in separating and adsorbing sulfur hexafluoride from nitrogen

Abstract

The present invention discloses a metal-organic framework material, a preparation method thereof, and an application thereof in separating and adsorbing sulfur hexafluoride from nitrogen. The metal-organic framework material of the present invention has a two-dimensional structure, and is composed of an organic ligand 4,4'-(1,10-phenanthroline-2,9-diyl)bis[benzoic acid] through carboxylate ions and Sc 3+ This metal-organic framework material is novel in structure, relatively stable, and easy to synthesize. It can selectively adsorb and separate sulfur hexafluoride from nitrogen, with high adsorption capacity and selectivity.

Description

Technical Field

[0001] The present invention relates to the technical field of porous materials, and in particular to a metal-organic framework material, a preparation method thereof, and an application thereof in separating and adsorbing sulfur hexafluoride from nitrogen. Background Art

[0002] Sulfur hexafluoride (SF6) is a man-made inert gas that is colorless, odorless, non-toxic, and non-flammable at room temperature and pressure. The molecular structure of sulfur hexafluoride is octahedral, with a small bonding distance and high bonding energy, so it is very stable. When the temperature does not exceed 180°C, its compatibility with electrical structural materials is similar to that of nitrogen.

[0003] SF6 is a highly electronegative gas. Its molecules readily absorb free electrons to form massive negative ions, weakening the collision ionization process within the gas. This results in a high electrical insulation strength. Due to its excellent arc-extinguishing and insulating properties, as well as its good chemical stability, SF6 has been used as an arc-extinguishing medium in high-voltage circuit breakers since the late 1950s. In ultra-high and ultra-high voltage circuit breakers, SF6 has replaced oil and, to a large extent, compressed air as an arc-extinguishing medium.

[0004] At the same time, sulfur hexafluoride is an asphyxiant. At high concentrations, it can cause breathing difficulties, wheezing, blue skin and mucous membranes, and whole-body convulsions. After inhaling a mixture of 80 vol% sulfur hexafluoride and 20 vol% oxygen for a few minutes, the human body will experience numbness in the limbs and may even suffocate to death. my country stipulates that the allowable concentration of sulfur hexafluoride gas in the air of the operating room shall not exceed 6g / m 3 Or the oxygen content in the air should be greater than 18 vol%; for short-term exposure, the allowable concentration of sulfur hexafluoride gas in the air should not exceed 7.5 g / m 3 Sulfur hexafluoride is a pharmacologically inert gas with low toxicity, but it can be asphyxiating to humans. During daily life or use, it decomposes some trace amounts of toxic sulfur low-fluorine compounds and fluorine oxides. Therefore, it is necessary to develop a method for separating sulfur hexafluoride by adsorption. This will not only reduce accidents caused by sulfur hexafluoride leaks, but also recover sulfur hexafluoride and improve economic benefits. However, the difficulty in recovering sulfur hexafluoride from the air lies in separating nitrogen and sulfur hexafluoride, which have the same properties.

[0005] Metal-organic frameworks (MOFs) are a new class of porous materials. Their high surface area and well-developed pore distribution offer unique advantages in gas adsorption and separation. Numerous patent applications have been filed for their applications in the separation and adsorption of mixed gases. Due to their excellent stability, MOFs can be recycled multiple times while maintaining high adsorption and selectivity.

[0006] Patent publication number CN110465272A discloses the use of a two-dimensional metal-organic framework (Cu-MOF-OMe) for SF6 / N2 separation. This material contains CH-type ligands and unsaturated metal sites for sulfur hexafluoride, forming a strong affinity (multi-point van der Waals interaction) with it. However, its affinity for nitrogen is relatively weak, thus effectively separating SF6 / N2.

[0007] Patent specification with publication number CN116586037A discloses a molded ultra-microporous metal-organic framework material, its preparation method, and its application in selective adsorption of sulfur hexafluoride. The ultra-microporous metal-organic framework material is prepared by a coordination reaction of a mixture of a soluble metal salt, an organic ligand, an alkali, and water; the metal ion in the soluble metal salt is Cr 3+ 、Al 3+ 、V 3+ and Fe 3+ The organic ligand is fumaric acid or a fumaric acid derivative. The ultra-microporous metal-organic framework material prepared by this patented technology has a high SF6 adsorption capacity and good selectivity, and can achieve effective separation of SF6 / N2 or SF6 / CF4. Summary of the Invention

[0008] In a first aspect, the present invention provides a metal-organic framework material having microporous and ultramicroporous structures, novel structure, relative stability, and convenient synthesis.

[0009] Specifically, the metal-organic framework material has a two-dimensional structure, which is composed of an organic ligand 4,4'-(1,10-phenanthroline-2,9-diyl)bis[benzoic acid] through carboxylate ions and Sc 3+ The structure of the metal-organic framework material is shown in the figure below. Figure 1 shown.

[0010] The 4,4'-(1,10-phenanthroline-2,9-diyl)bis[benzoic acid] has the chemical structure shown below:

[0011]

[0012] The crystal structure of the metal-organic framework material of the present invention can be accurately analyzed by single crystal cultivation and single crystal X-ray diffraction.

[0013] The organic ligand 4,4'-(1,10-phenanthroline-2,9-diyl)bis[benzoic acid] described in the present invention is prior art and can be obtained by methods disclosed in prior art, for example, by referring to the patent specification with publication number US5998594A (published on December 7, 1999).

[0014] In one embodiment, the specific surface area of ​​the metal-organic framework material is 500-700 m 2 / g, and the pore size distribution is between 0.4 and 0.6 nm.

[0015] In a second aspect, the present invention provides a method for preparing the metal-organic framework material described in the first aspect, wherein ScCl3·6H2O and the organic ligand 4,4'-(1,10-phenanthroline-2,9-diyl)bis[benzoic acid] are dispersed in DMF (N,N-dimethylformamide), and acetic acid is added for acidification. The resulting mixture is subjected to a solvothermal reaction to obtain the metal-organic framework material.

[0016] In the preparation method described in the second aspect, in one embodiment, the mass ratio of ScCl 3 ·6H 2 O to the organic ligand 4,4′-(1,10-phenanthroline-2,9-diyl)bis[benzoic acid] is not less than 2:1.

[0017] In the preparation method described in the second aspect, in one embodiment, the ratio of ScCl3·6H2O to DMF is 10 mg: 1-5 mL.

[0018] In the preparation method described in the second aspect, acetic acid is used as a regulator. If other acids are used to replace acetic acid, the metal-organic framework material with the target structure cannot be obtained.

[0019] In the preparation method described in the second aspect, in one embodiment, the volume ratio of DMF to acetic acid is 20:0.5-1.5.

[0020] In the preparation method described in the second aspect, in one embodiment, the temperature of the solvent thermal reaction is 110-130° C., and the time is 1-3 days.

[0021] In the preparation method described in the second aspect, in one embodiment, the preparation method further comprises washing the solid product of the solvothermal reaction after the solvothermal reaction to obtain the metal-organic framework material. Furthermore, the washing solvent used in the washing can be at least one of DMF and ethanol.

[0022] In a third aspect, the present invention provides use of the metal-organic framework material described in the first aspect for separating and adsorbing sulfur hexafluoride from nitrogen.

[0023] In a fourth aspect, the present invention provides a method for selectively adsorbing and separating sulfur hexafluoride from a mixture containing nitrogen and sulfur hexafluoride, wherein the metal-organic framework material described in the first aspect is used as an adsorbent, the adsorbent is contacted with the mixture containing nitrogen and sulfur hexafluoride, and the adsorbent selectively adsorbs sulfur hexafluoride, thereby achieving separation of sulfur hexafluoride from the mixture containing nitrogen and sulfur hexafluoride.

[0024] In the third and fourth aspects, in one embodiment, the metal-organic framework material is activated before use, specifically comprising: soaking the metal-organic framework material in acetone to purify its pores, then taking out the metal-organic framework material and blowing away the residual acetone with nitrogen, and finally completing the activation by vacuum drying at room temperature.

[0025] In the third and fourth aspects, after the metal-organic framework material adsorbs sulfur hexafluoride, the metal-organic framework material can be regenerated by desorbing sulfur hexafluoride by vacuuming. The regenerated metal-organic framework material can be directly used for the next adsorption of sulfur hexafluoride, thereby realizing the recycling of the metal-organic framework material and can also be preserved for a long time in a nitrogen atmosphere.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The present invention provides a novel structure, relatively stable and conveniently synthesized metal-organic framework material, which is composed of an organic ligand 4,4'-(1,10-phenanthroline-2,9-diyl)bis[benzoic acid] through carboxylate ions and Sc 3+ It is formed by ion coordination connection and has a two-dimensional structure as well as microporous and ultramicroporous structure. It can selectively adsorb and separate sulfur hexafluoride from nitrogen and has a high adsorption capacity and adsorption selectivity for sulfur hexafluoride. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0029] Figure 1 Schematic diagram of the structure of the metal-organic framework material of the present invention.

[0030] Figure 2 This is the metal-organic framework material prepared in Example 1 and its X-ray powder diffraction pattern after BET testing.

[0031] Figure 3 This is a scanning electron microscope photograph of the metal-organic framework material prepared in Example 1.

[0032] Figure 4 This is the thermogravimetric curve of the metal-organic framework material prepared in Example 1.

[0033] Figure 5This is an infrared spectrum of the metal-organic framework material prepared in Example 1 and the organic ligand 4,4'-(1,10-phenanthroline-2,9-diyl)bis[benzoic acid] (PHDC).

[0034] Figure 6 This is a nitrogen adsorption-desorption isotherm graph of the metal-organic framework material prepared in Example 1 before and after adsorption of sulfur hexafluoride.

[0035] Figure 7 This is the sulfur hexafluoride adsorption-desorption isotherm curve of the metal-organic framework material prepared in Example 1.

[0036] Figure 8 This is a graph showing the sulfur hexafluoride / nitrogen selectivity of the metal-organic framework material prepared in Example 1. DETAILED DESCRIPTION

[0037] The present invention will be further described below with reference to the accompanying drawings and specific examples. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention.

[0038] In the following examples, the operating methods without specifying specific conditions are generally carried out under conventional conditions or conditions recommended by the manufacturer.

[0039] Example 1

[0040] Scandium trichloride hexahydrate (ScCl3·6H2O, 10 mg) and 4,4'-(1,10-phenanthroline-2,9-diyl)bis[benzoic acid] (5 mg) were added to a 15 mL glass vial. N,N-dimethylformamide (2 mL) was added and ultrasonically dispersed. After homogenization, 0.1 mL of acetic acid was added. The vial was sealed and placed in a 120°C forced air drying oven for two days. The mixture was then removed and cooled to room temperature. The supernatant was removed and washed with 12 mL of N,N-dimethylformamide and then 12 mL of ethanol to obtain a colorless crystalline solid, which is the metal-organic framework material of the present invention, designated Sc-cage-MOFs.

[0041] The structure and properties of the obtained colorless crystalline solid were characterized:

[0042] The ball-and-stick model structure is as follows Figure 1 As shown;

[0043] The X-ray powder diffraction results are as follows Figure 2 As shown, the powder diffraction results obtained are consistent with the diffraction results simulated by the crystal structure, proving that the powder still has a crystal structure;

[0044] Scanning electron microscopy results Figure 3 As shown, the obtained nanoparticles are regular cuboid shapes;

[0045] Thermogravimetric test results are as follows Figure 4 As shown, the obtained powder loses solvent after heating, which is related to the possible residual solvent in the pores;

[0046] The infrared spectrum results are as follows Figure 5 As shown, the main infrared absorption peak of the obtained powder is similar to the infrared absorption of the organic ligand phdc, indicating that the organic ligand phdc is indeed present in the metal-organic framework material of the present invention.

[0047] Example 2

[0048] The gas adsorption performance of the metal-organic framework material obtained in Example 1 was tested.

[0049] The specific steps include:

[0050] (a) The metal-organic framework synthesized in Example 1 was washed with 10 mL of acetone and then immersed in 5 mL of acetone for three days, with the acetone exchanged every 12 hours. The colorless solid containing acetone was then removed and placed in an adsorption tube. The acetone was gradually dried with nitrogen gas, and then dried under vacuum at room temperature for 6 hours to obtain an activated sample.

[0051] (b) The activated sample was transferred to the adsorption instrument, and the adsorption-desorption curves of sulfur hexafluoride were measured at 278K, 288K, and 298K; the adsorption-desorption curves of nitrogen were measured at 77K, 278K, 288K, and 298K.

[0052] The nitrogen adsorption and desorption curve results are as follows Figure 6 As shown. Figure 6 The Sc-cage-MOFs curve in Figure 2 shows that the maximum adsorption capacity of metal-organic framework material Sc-cage-MOFs for nitrogen at 77K is 230cm 3 g -1 (relative pressure p / p0=0.9), specific surface area (BET) reaches 600m 2 g -1 After the above BET test, the samples were subjected to X-ray powder diffraction characterization test. The results are shown in Figure 2 In the Sc-cage-MOFs-BET sample, the material maintained basic crystallinity, proving that the material is relatively stable.

[0053] After the metal-organic framework material obtained in Example 1 was used to adsorb SF6 at room temperature (298K), it was subjected to the above-mentioned nitrogen adsorption and desorption process. The sample maintained its initial specific surface area. The results showed that the sample still maintained its porosity after adsorbing sulfur hexafluoride at room temperature, which indirectly illustrates its stability.

[0054] The results of the sulfur hexafluoride adsorption and desorption curve are as follows Figure 7As shown. Figure 7 It can be seen that the maximum adsorption capacity of SF6 by the metal-organic framework material Sc-cage-MOFs at room temperature (298K) is 34 cm 3 g -1 .

[0055] The above results indicate that the metal-organic framework material has certain stability and porosity, and has application potential in adsorbing SF6 gas.

[0056] Example 3

[0057] See attached Figure 8 The ideal solution adsorption theory (IAST) was used to calculate the SF6 and N2 gas adsorption data of Sc-cage-MOFs at 278K, 288K, and 298K. The results showed that at 278K and vacuum 0kPa, the adsorption selectivity of Sc-cage-MOFs for SF6 in a binary SF6 / N2 (50:50, v / v) gas mixture was 312; at 278K and 100kPa, the adsorption selectivity of Sc-cage-MOFs for SF6 in a binary SF6 / N2 (50:50, v / v) gas mixture was 20.

[0058] In addition, it should be understood that after reading the above description of the present invention, those skilled in the art may make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims attached to this application.

Claims

1. A metal-organic framework material, characterized in that The metal-organic framework material has a two-dimensional structure, which is composed of an organic ligand 4,4'-(1,10-phenanthroline-2,9-diyl)bis[benzoic acid] through carboxylate ions and Sc 3+ Ionic coordination bond formation; The 4,4'-(1,10-phenanthroline-2,9-diyl)bis[benzoic acid] has the chemical structure shown below:

2. The metal-organic framework material according to claim 1, characterized in that The specific surface area of ​​the metal-organic framework material is 500 to 700 m 2 / g, and the pore size distribution is between 0.4 and 0.6 nm.

3. The method for preparing a metal-organic framework material according to claim 1 or 2, characterized in that: ScCl3·6H2O and an organic ligand 4,4'-(1,10-phenanthroline-2,9-diyl)bis[benzoic acid] are dispersed in DMF, and acetic acid is added for acidification. The obtained mixture is subjected to a solvothermal reaction to obtain the metal-organic framework material.

4. The preparation method according to claim 3, characterized in that The mass ratio of ScCl3·6H2O to the organic ligand 4,4'-(1,10-phenanthroline-2,9-diyl)bis[benzoic acid] is not less than 2:

1.

5. The preparation method according to claim 3, characterized in that The usage ratio of ScCl3·6H2O and DMF is 10 mg:1~5 mL.

6. The preparation method according to claim 3, characterized in that The volume ratio of DMF to acetic acid is 20:0.5-1.

5.

7. The preparation method according to claim 3, characterized in that The temperature of the solvent thermal reaction is 110-130° C., and the time is 1-3 days.

8. The preparation method according to claim 3, characterized in that The preparation method further comprises washing the solid product of the solvent thermal reaction after the solvent thermal reaction is completed to obtain the metal-organic framework material; The washing solvent used in the washing is at least one of DMF and ethanol.

9. Use of the metal-organic framework material according to claim 1 or 2 for separating and adsorbing sulfur hexafluoride in nitrogen.

10. A method for selectively adsorbing and separating sulfur hexafluoride from a mixture containing nitrogen and sulfur hexafluoride, characterized in that: The metal-organic framework material according to claim 1 or 2 is used as an adsorbent, and the adsorbent is contacted with a mixture containing nitrogen and sulfur hexafluoride. The adsorbent selectively adsorbs sulfur hexafluoride, thereby separating sulfur hexafluoride from the mixture containing nitrogen and sulfur hexafluoride.

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