A MOF-type molecular sieve adsorbent, its preparation method, and its application.

Abstract

This invention discloses a MOF-type molecular sieve adsorbent, its preparation method, and its applications, belonging to the field of adsorbent material technology. The raw materials used in the synthesis of the MOF-type molecular sieve adsorbent prepared by this invention are relatively inexpensive, and the trifluoromethyl functional group can act as a constituent unit to regulate the pore size of the MOF material. The channel size in the crystal structure of the MOF-type molecular sieve adsorbent lies between the molecular dynamics sizes of perfluoropropylene and perfluoropropane, providing a structural basis for the adsorption and separation process of sieving perfluoropropylene from perfluoropropane. Furthermore, the presence of hydrogen bonding sites within the channels and the restriction of the pore size by the trifluoromethyl functional group facilitates the entry of perfluoropropylene molecules with smaller dynamic sizes, and strengthens the interaction between perfluoropropylene gas molecules and the framework. This achieves preferential adsorption of perfluoropropylene gas from the perfluoropropylene / perfluoropropane mixture, purifying the perfluoropropane component in the mixture and reducing the energy consumption of the separation process.

Description

Technical Field

[0001] This invention relates to the field of adsorbent materials technology, and more specifically, to a MOF-type molecular sieve adsorbent, its preparation method, and its application. Background Technology

[0002] Perfluoropropane (C3F8) is an extremely important perfluorocarbon compound widely used in the semiconductor industry, liquid crystal display panel manufacturing, and photovoltaic industry. It is primarily used as a highly efficient plasma etching gas and cleaning gas for the microfabrication of silicon wafers and the cleaning of deposition chambers. In addition, perfluoropropane also has special applications in cryogenic refrigerants and medical ultrasound contrast agents. As integrated circuit manufacturing processes continue to miniaturize (e.g., 7 nm, 5 nm and below nodes), the purity requirements for electronic specialty gases are becoming increasingly stringent. Typically, perfluoropropane purity must reach 5N (99.999%) or even 6N (99.9999%) levels. Any trace of impurities can lead to etching defects, short circuits, or degraded device performance.

[0003] In the industrial synthesis of perfluoropropane (usually via hydrofluorination, direct fluorination, or electrolytic fluorination of hexafluoropropylene), the byproduct perfluoropropylene (C3F6) is inevitably produced. Perfluoropropylene has a similar molecular structure to perfluoropropane and similar boiling points (C3F8 boiling point is approximately -36.7 °C, C3F6 boiling point is approximately -29.4 °C). Under certain conditions, they easily form a near-azeotropic system, making separation extremely difficult. As an olefin, perfluoropropylene is chemically more reactive than perfluoropropane and possesses a certain degree of toxicity. If it remains in the final product, it will not only affect the uniformity of the etching rate but may also cause unintended polymerization reactions under certain process conditions, contaminating the reaction chamber.

[0004] Currently, the main industrial methods for separating perfluoropropylene impurities from perfluoropropane include cryogenic distillation, chemical reaction, and traditional adsorption. However, these methods all have significant drawbacks: 1. Cryogenic Distillation: Due to the relatively low volatility of both perfluoropropane and perfluoropropylene, extremely high reflux ratios and a large number of theoretical plates are required to achieve high electronic-grade purity. This results in large distillation column equipment, extremely high energy consumption, and low production efficiency, making it difficult to economically remove trace amounts (ppm level) of olefin impurities. 2. Chemical Reaction / Oxidation: This method uses oxidants such as potassium permanganate or reacts with perfluoropropylene under the action of a catalyst to remove it. This type of method has a long process flow, generates a large amount of waste liquid and solid waste, and has poor environmental friendliness. Furthermore, the introduced chemical reagents may cause secondary pollution, and complex dehydration and impurity removal steps are required afterward. 3. Traditional Adsorption Separation: This method uses traditional adsorbents such as activated carbon and zeolite molecular sieves (e.g., 13X, 5A). Traditional adsorbents are mainly based on pore size sieving or polarity differences. However, the molecular dynamic diameter differences between perfluoropropane and perfluoropropylene are extremely small, making it difficult for adsorbents to accurately identify them. Often, while adsorbing impurities, a large amount of product gas is also adsorbed, resulting in a decrease in yield. Traditional adsorbents also exhibit weak surface interactions with perfluorocarbons, leading to limited adsorption capacity and high costs associated with frequent regeneration.

[0005] Metal-organic frameworks (MOFs) are a novel class of porous materials assembled from metal nodes and organic ligands. Compared with traditional molecular sieves, MOFs have the following significant advantages: Tunable structure: The pore size and shape can be precisely controlled by selecting specific metal centers and organic ligands. Surface functionalization: Specific functional sites (such as open metal sites (OMS), Lewis acid sites, etc.) can be introduced into the pores. For the separation of perfluoropropylene (olefins) and perfluoropropane (alkanes), theoretically, efficient separation can be achieved by utilizing the π-complexation between the π bonds in the olefins and the metal sites in the MOF material, or by utilizing the molecular sieving effect generated by the slight differences in pore shape. However, research on the separation of perfluoropropylene from perfluoropropane using MOF materials is still in its early stages. Many existing MOF materials suffer from poor stability under fluorination environments, insufficient selectivity for perfluoroolefins, or excessively high preparation costs, limiting their practical industrial applications. Therefore, developing a MOF-type molecular sieve with high selectivity, high adsorption capacity and stable structure for the deep purification of perfluoropropane is a technical challenge that urgently needs to be solved in the field of electronic specialty gas purification. Summary of the Invention

[0006] In view of this, and in order to solve one of the above-mentioned technical problems, the present invention provides a MOF-type molecular sieve adsorbent, its preparation method, and its application, the specific technical solution of which is as follows:

[0007] A method for preparing a MOF-type molecular sieve adsorbent, the method comprising the following steps: S1. Dissolve zinc nitrate hexahydrate in alcohol to obtain solution A; S2. Dissolve 5-trifluoromethyl-1H-pyrazole-4-carboxylic acid in amide to obtain solution B; S3. Mix solution A and solution B thoroughly, then sonicate for 0.5-1.5 hours to obtain a mixed solution; S4. Transfer the mixed solution to a closed reaction vessel, heat at 80-120°C for 24-72 hours, allow it to cool naturally to room temperature, and collect the product; S5. Wash the product alternately with amide and alcohol until the washing solution is clear; then perform solvent exchange in methanol, replacing the methanol with fresh methanol every 12-24 hours for 3-7 days. After drying, obtain MOF molecular sieve adsorbent.

[0008] Furthermore, the molar ratio of zinc nitrate hexahydrate to 5-trifluoromethyl-1H-pyrazole-4-carboxylic acid is 1:(0.5-2.0).

[0009] Furthermore, the volume ratio of the alcohol to the amide is (1-3):(1-3).

[0010] Further, in step S1, the concentration of zinc nitrate hexahydrate in solution A is 0.1-0.5 mol / L.

[0011] Furthermore, in step S1, the pure substance is at least one of methanol and ethanol.

[0012] Further, in step S2, the concentration of 5-trifluoromethyl-1H-pyrazole-4-carboxylic acid in solution B is 0.1-0.6 mol / L.

[0013] Further, in step S2, the amide is at least one selected from N,N-dimethylformamide, N,N-dimethylacetamide, and N,N-diethylformamide.

[0014] Furthermore, in step S5, the drying process is vacuum drying at 80-150°C for 15-30 hours.

[0015] In addition, the present invention also provides a MOF-type molecular sieve adsorbent, which is prepared by the preparation method described above.

[0016] In addition, the present invention also provides an application of MOF-type molecular sieve adsorbent, wherein the application is the adsorption and separation of impurities in perfluoropropane by the MOF-type molecular sieve adsorbent.

[0017] Compared with the prior art, the present invention has the following beneficial effects: (1) The organic ligand 5-trifluoromethyl-1H-pyrazole-4-carboxylic acid used in the synthesis of the MOF molecular sieve adsorbent of the present invention has a simple structure and relatively low price, and the trifluoromethyl functional group can be used as a constituent unit to regulate the pore size of the MOF material.

[0018] (2) The crystal structure of the MOF molecular sieve adsorbent prepared in this invention contains a unique one-dimensional channel with a channel size between the molecular dynamics size of perfluoropropylene and perfluoropropane, which provides a structural basis for the adsorption and separation process of sieving perfluoropropylene from perfluoropropane.

[0019] (3) The MOF molecular sieve adsorbent of the present invention has hydrogen bond interaction sites in the pores and the pore size is restricted by the trifluoromethyl functional group, which is conducive to the entry of perfluoropropylene molecules with smaller kinetic size and strengthens the interaction force between perfluoropropylene gas molecules and the framework. This enables the preferential adsorption of perfluoropropylene gas from the perfluoropropylene / perfluoropropane mixture, thereby purifying the perfluoropropane component in the mixture and reducing the energy consumption of the above separation process. Attached Figure Description

[0020] The invention will be further understood from the following description taken in conjunction with the accompanying drawings. The components in the drawings are not necessarily drawn to scale, but rather the emphasis is on illustrating the principles of the embodiments. In different views, the same reference numerals designate corresponding parts.

[0021] Figure 1 This is a comparison of the powder X-ray diffraction (PXRD) patterns of Zn-MOF-1 (including vacuum degassed state and solvent exchange state) prepared in Example 1 and Zn-MOF-2 prepared in Example 2 with the single-crystal simulated patterns. Figure 2 This is a thermogravimetric analysis (TGA) curve of Zn-MOF-1 prepared in Example 1 of this invention under a nitrogen atmosphere; Figure 3 This is a comparison chart of the PXRD stability test results of Zn-MOF-1 prepared in Example 1 of this invention after treatment under different environmental conditions (water immersion, air exposure, heating); Figure 4 This is a single-component adsorption isotherm diagram of Zn-MOF-1 prepared in Example 1 of the present invention for perfluoropropylene (C3F6) and perfluoropropane (C3F8) at different temperatures (298 K, 288 K, 308 K); Figure 5 This is a breakthrough curve of Zn-MOF-1 prepared in Example 1 of the present invention against a perfluoropropylene / perfluoropropane (10 / 90, v / v) mixture. Figure 6 This is a comparison diagram of the breakthrough experiment of Zn-MOF-1 prepared in Example 1 of the present invention on a perfluoropropylene / perfluoropropane mixed gas after three adsorption-desorption cycles. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to its embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the scope of protection of the invention.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0024] A method for preparing a MOF-type molecular sieve adsorbent according to one embodiment of the present invention includes the following steps: S1. Dissolve zinc nitrate hexahydrate in alcohol to obtain solution A; S2. Dissolve 5-trifluoromethyl-1H-pyrazole-4-carboxylic acid in amide to obtain solution B; S3. Mix solution A and solution B thoroughly, then sonicate for 0.5-1.5 hours to obtain a mixed solution; S4. Transfer the mixed solution to a closed reaction vessel, heat at 80-120°C for 24-72 hours, allow it to cool naturally to room temperature, and collect the product; S5. Wash the product alternately with amide and alcohol until the washing solution is clear; then perform solvent exchange in methanol, replacing the methanol with fresh methanol every 12-24 hours for 3-7 days. After drying, obtain MOF molecular sieve adsorbent.

[0025] In one embodiment, the molar ratio of zinc nitrate hexahydrate to 5-trifluoromethyl-1H-pyrazole-4-carboxylic acid is 1:(0.5-2.0).

[0026] In one embodiment, the volume ratio of the alcohol to the amide is (1-3):(1-3).

[0027] In one embodiment, in step S1, the concentration of zinc nitrate hexahydrate in solution A is 0.1-0.5 mol / L.

[0028] In one embodiment, in step S1, the pure substance is at least one of methanol and ethanol.

[0029] In one embodiment, in step S2, the concentration of 5-trifluoromethyl-1H-pyrazole-4-carboxylic acid in solution B is 0.1-0.6 mol / L.

[0030] In one embodiment, in step S2, the amide is at least one selected from N,N-dimethylformamide, N,N-dimethylacetamide, and N,N-diethylformamide.

[0031] In one embodiment, in step S4, the sealed reaction vessel is a pressure-resistant glass bottle or a high-pressure hydrothermal reactor with a polytetrafluoroethylene liner.

[0032] In one embodiment, in step S5, the drying process is vacuum drying at 80-150°C for 15-30 hours.

[0033] In one embodiment, the present invention also provides a MOF-type molecular sieve adsorbent, which is prepared by the preparation method described above.

[0034] In one embodiment, the present invention also provides an application of a MOF-type molecular sieve adsorbent, wherein the MOF-type molecular sieve adsorbent is used to adsorb and separate impurities in perfluoropropane.

[0035] The implementation schemes of the present invention will now be described in detail with reference to specific embodiments.

[0036] Example 1: A method for preparing a MOF-type molecular sieve adsorbent includes the following steps: (1) Weigh the raw materials in a molar ratio of 4:3: Weigh zinc nitrate hexahydrate (6.0 mmol) and dissolve it in 15 mL methanol (MeOH) to obtain solution A; Weigh 5-trifluoromethyl-1H-pyrazole-4-carboxylic acid (4.5 mmol) and dissolve it in 15 mL N,N-dimethylformamide (DMF) to obtain solution B; (2) Mix the solution A with the solution B (at this time the volume ratio of alcohol to amide is 1:1), and sonicate for 0.5 h to obtain a homogeneous mixed solution; (3) Transfer the mixed solution to a 50 mL pressure-resistant glass bottle, seal it and place it in an oven. Heat it at 100°C for 40 h. After the reaction is complete, allow it to cool naturally to room temperature and collect the product. (4) The product was washed with DMF and methanol alternately to remove unreacted ligands. Then the product was soaked in 50 mL of anhydrous methanol for solvent exchange. Fresh methanol was replaced every 6 h for 5 days to replace the DMF solvent molecules in the pores. Finally, the product was placed at 150 °C for vacuum drying and activation for 12 h to obtain MOF molecular sieve adsorbent (denoted as Zn-MOF-1).

[0037] Example 2: A method for preparing a MOF-type molecular sieve adsorbent includes the following steps: (1) Weigh the raw materials in a molar ratio of 4:3: Weigh zinc nitrate hexahydrate (12.0 mmol) and dissolve it in 30 mL methanol (MeOH) to obtain solvent A; Weigh 5-trifluoromethyl-1H-pyrazole-4-carboxylic acid (9.0 mmol) and dissolve it in 30 mL N,N-dimethylformamide (DMF) to obtain solvent B; (2) Mix the solution A with the solution B (at this time the volume ratio of alcohol to amide is 1:1), and sonicate for 1.0 h to obtain a homogeneous mixed solution; (3) Transfer the mixed solution to a 100 mL high-pressure reactor with a polytetrafluoroethylene liner, seal it and place it in an oven, heat it at 110°C for 72 h, and after the reaction is completed, allow it to cool naturally to room temperature and collect the product. (4) The product was washed with DMF and methanol alternately to remove unreacted ligands. Then the product was soaked in 100 mL of anhydrous methanol for solvent exchange. Fresh methanol was replaced every 6 hours for 7 days to replace the DMF solvent molecules in the pores. Finally, the product was placed at 150 °C for vacuum drying and activation for 24 hours to obtain MOF molecular sieve adsorbent (denoted as Zn-MOF-2).

[0038] Experimental Example: Performance Testing of MOF-type Molecular Sieve Adsorbents To verify the performance of the materials prepared in this invention, the Zn-MOF-1 sample prepared in Example 1 was subjected to structural characterization and adsorption separation performance testing.

[0039] 1. Crystal structure and stability characterization (1) XRD characterization: Powder X-ray diffraction (PXRD) was performed on the sample. For example... Figure 1 As shown, the characteristic diffraction peak positions of Zn-MOF-1 are highly consistent with the single-crystal simulation pattern, and the peaks are sharp, indicating that a target phase with high purity and high crystallinity has been prepared.

[0040] (2) Thermal stability (TGA): Thermogravimetric analysis (TGA) curve under nitrogen atmosphere ( Figure 2The results showed that the material did not exhibit significant skeletal weight loss before 470℃, indicating that it could withstand activation and regeneration temperatures of 150℃.

[0041] (3) Environmental stability: The PXRD patterns of the samples were tested after treatment with water immersion, air exposure (7 days), and heating. The results showed that the intensity and position of the diffraction peaks of the treated samples did not change significantly (see [reference]). Figure 3 This demonstrates that the material possesses excellent water and chemical stability.

[0042] 2. Adsorption performance test of perfluoropropane / perfluoropropylene Single-component adsorption isotherms of Zn-MOF-1 for perfluoropropylene (C3F6) and perfluoropropane (C3F8) were determined at 288, 298, and 308 K. Figure 4 The test results show that in the low-pressure region (0~0.1 bar), the adsorption capacity of the material for C3F6 is significantly higher than that for C3F8 (specific values ​​are: C3F6 adsorption capacity is about 56.8 cm3 / g, and C3F8 adsorption capacity is about 1.2 cm3 / g), exhibiting extremely high thermodynamic selectivity. The calculated adsorption ratio of C3F6 / C3F8 is 47.3.

[0043] 3. Gas-mixed breakthrough experiment (actual separation simulation) Dynamic breakthrough experiments were conducted using a perfluoropropylene / perfluoropropane mixture with a volume ratio of 10 / 90. For example... Figure 5 As shown, at the outlet of the adsorption column, high-purity perfluoropropane (C3F8) was detected first, and its concentration rapidly reached the feed level. Perfluoropropylene (C3F6), as an impurity, was effectively retained by the adsorbent, and its breakthrough time was significantly delayed compared to perfluoropropane (approximately 200 min / g). This result directly demonstrates that Zn-MOF-1 can efficiently remove perfluoropropylene impurities from a mixture rich in perfluoropropane.

[0044] 4. Recycling performance After adsorption saturation, the adsorption column is regenerated by simple heating and vacuum regeneration, and then adsorption tests are performed again. For example... Figure 6 As shown, after three consecutive adsorption-desorption cycles, the adsorption capacity and breakthrough time of the material for perfluoropropylene did not show significant decrease, indicating that the adsorbent has excellent reusability.

[0045] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0046] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing a MOF-type molecular sieve adsorbent, characterized in that, The preparation method includes the following steps: S1. Dissolve zinc nitrate hexahydrate in alcohol to obtain solution A; S2. Dissolve 5-trifluoromethyl-1H-pyrazole-4-carboxylic acid in amide to obtain solution B; S3. Mix solution A and solution B thoroughly, then sonicate for 0.5-1.5 hours to obtain a mixed solution; S4. Transfer the mixed solution to a closed reaction vessel, heat at 80-120°C for 24-72 hours, allow it to cool naturally to room temperature, and collect the product; S5. Wash the product alternately with amide and alcohol until the washing solution is clear; then perform solvent exchange in methanol, replacing the methanol with fresh methanol every 12-24 hours for 3-7 days. After drying, obtain MOF molecular sieve adsorbent.

2. The preparation method according to claim 1, characterized in that, The molar ratio of zinc nitrate hexahydrate to 5-trifluoromethyl-1H-pyrazole-4-carboxylic acid is 1:(0.5-2.0).

3. The preparation method according to claim 1, characterized in that, The volume ratio of the alcohol to the amide is (1-3):(1-3).

4. The preparation method according to claim 1, characterized in that, In step S1, the concentration of zinc nitrate hexahydrate in solution A is 0.1-0.5 mol / L.

5. The preparation method according to claim 1, characterized in that, In step S1, the pure substance is at least one of methanol and ethanol.

6. The preparation method according to claim 1, characterized in that, In step S2, the concentration of 5-trifluoromethyl-1H-pyrazole-4-carboxylic acid in solution B is 0.1-0.6 mol / L.

7. The preparation method according to claim 1, characterized in that, In step S2, the amide is at least one of N,N-dimethylformamide, N,N-dimethylacetamide, and N,N-diethylformamide.

8. The preparation method according to claim 1, characterized in that, In step S5, the drying process is vacuum drying at 80-150℃ for 15-30 hours.

9. A MOF-type molecular sieve adsorbent, characterized in that, The MOF-type molecular sieve adsorbent is prepared by the preparation method described in any one of claims 1 to 8.

10. An application of a MOF-type molecular sieve adsorbent, characterized in that, The application is the use of the MOF molecular sieve adsorbent according to any one of claims 1 to 8 in the adsorption and separation of impurities in perfluoropropane.

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