Porous framework material, preparation method thereof and application of porous framework material in separation and purification of hexafluoroethane

Abstract

The invention discloses a porous framework material, a preparation method thereof and hexafluoroethane separation and purification application. The porous framework material is obtained by reacting and coordinating raw materials including Al < 3 + > and m-carborane dicarboxylic acid; in the porous framework material, Al < 3 + > is coordinated with hydroxyl OH and carboxyl O to form a cis-[Al (OH) (COO) 2] aluminum oxygen cluster structure. The preparation method comprises the following steps: carrying out a sealed reaction on a salt containing Al < 3 + > and m-carborane dicarboxylic acid in a solvent at 50-100 DEG C, placing the obtained solid product in methanol, carrying out one or more times of solvent exchange to remove solvent molecules, and then carrying out vacuumizing, degassing and activating to remove methanol molecules in pore channels to obtain the porous framework material. The pore size of the porous framework material is matched with the dynamic diameter of hexafluoroethane, weak adsorption sites are densely distributed on the surface of the porous framework material by introducing carborane, and high-capacity hexafluoroethane is realized while good selectivity and deep removal are shown.

Description

Technical Field

[0001] The present invention relates to the technical field of the synthesis of porous materials and gas adsorption, and particularly relates to a porous framework material based on a three-dimensional (3D) ligand, a preparation method thereof, and an application thereof. Background Art

[0002] Hexafluoroethane (C2F6), as an important fluorine-containing electronic special gas, is an important raw material in the etching and cleaning processes of chips. However, the ionization rate of C2F6 during the etching process is less than 50%, and the remaining is discharged into the atmosphere after hydrogenation combustion. The traditional hydrogenation combustion treatment method widely used in the industry at present not only has high energy consumption but also causes a large amount of waste of precious C2F6 resources. Compared with this method, the adsorption separation technology using adsorbents is more energy-saving and environmentally friendly.

[0003] Metal-organic framework materials (MOFs) are a class of porous materials formed by the self-assembly of metal ions and organic ligands through coordination bonds. It has the advantages of a large specific surface area, adjustable pore size and pore channel properties, and has potential application prospects in gas adsorption and separation.

[0004] Therefore, it is of great significance to develop a method for separating and purifying hexafluoroethane using a shaped adsorbent.

[0005] The existing technologies for hexafluoroethane adsorption materials are as follows:

[0006] The patent specification with the publication number CN118045459A discloses a metal-organic framework material synthesized from an aluminum salt that can capture hexafluoroethane from etching tail gas. Adsorbent preparation method: (1) Add 1,4-naphthalenedicarboxylic acid (0.108 g, 0.5 mmol), AlCl3·6H2O (0.241 g, 1 mmol), and 10 mL of H2O to a reaction kettle, and react at 120 °C for 24 h. (2) Cool to room temperature, filter, and wash with distilled water to obtain a light yellow powder. (3) Immerse the above product in anhydrous methanol and replace anhydrous methanol every six hours for more than 5 times to remove solvent molecules in the pores of the material. Obtain the inexpensive porous material Al(OH)(1,4-NDC). The selectivity of C2F6 in the C2F6 / N2 mixed gas can reach more than 200 (C2F6 / N2 volume ratio = 10 / 90). However, the dynamic capture amount of hexafluoroethane by this material is small and the capture efficiency is low.

[0007] The patent specification with the publication number CN117244354A discloses a metal-organic framework material with a hydrophobic material attached to its surface that can adsorb hexafluoroethane in industrial tail gas. Al 3+The ions form coordination bonds with the oxygen atoms of the unsaturated dicarboxylic acid ligands and self-assemble to form metal-organic framework materials. All of the above porous framework materials are based on bidentate ligands, with limited pore interaction sites formed, lacking efficient recognition of hexafluoroethane and resulting in low separation selectivity.

[0008] The present invention uses 3D aromatic ligand m-carborane dicarboxylic acid as a linker to construct a rigid framework material with dense B-H interaction sites on the pore surface, which can form a large number of interactions with hexafluoroethane, thereby achieving high-selectivity adsorption of hexafluoroethane. So far, porous framework materials for the separation of hexafluoroethane based on the neutral carborane (C2B 10 H 12 ) framework have never been reported. Summary of the Invention

[0009] The present invention provides a porous framework material based on a 3D carborane skeleton for selectively adsorbing hexafluoroethane from a mixed gas of hexafluoroethane and nitrogen, and its preparation method and application. The porous framework material provided by the present invention can capture hexafluoroethane from etching tail gas, etc. with high capacity and high selectivity, has a high removal depth, is easy to regenerate the adsorbent, and has good hydrothermal stability.

[0010] The specific technical solutions are as follows:

[0011] [1] A porous framework material based on a 3D carborane skeleton for selectively adsorbing hexafluoroethane from a mixed gas of hexafluoroethane and nitrogen, which is obtained by the coordination reaction of raw materials including Al 3+ and m-carborane dicarboxylic acid;

[0012] The m-carborane dicarboxylic acid, with the expression of m-C2B 10 H 10 (COOH)2, has the following structure:

[0013]

[0014] In the porous framework material, Al 3+ coordinates with the hydroxyl group OH and the carboxyl group O to form a cis-[Al(OH)(COO)2] aluminum-oxygen cluster structure.

[0015] [1] The porous framework material has a three-dimensional network structure with one-dimensional channels formed by the coordination of aluminum-oxygen chains and m-carborane dicarboxylic acid.

[0016] [1] The pore diameter of the porous framework material is

[0017] [1] The porous framework material has the following single-crystal structure data:

[0018]

[0019] [2] The preparation method of the porous framework material according to [1] includes: reacting a salt containing Al 3+ and metacarborane dicarboxylic acid in a solvent at 50-100°C in a sealed manner, placing the obtained solid product in methanol for one or more solvent exchanges to remove solvent molecules, and then performing vacuum degassing activation to remove methanol molecules in the pores to obtain the porous framework material.

[0020] The aluminum-oxygen cluster structure described in the present invention is cis-[Al(OH)(COO)2], and on average each Al 3+ ion binds two carboxylate ions COO - , and the metacarborane dicarboxylic acid ligand has two carboxyl groups. In order to achieve charge balance, in the preparation method described in [2], it is preferred to add the salt containing Al 3+ and metacarborane dicarboxylic acid in a molar ratio of 1:1. 3+ and metacarborane dicarboxylic acid.

[0021] In the preparation method described in [2], the salt containing Al 3+ may include at least one of nitrates, chlorides, sulfates, etc. It can be understood that the nitrates, chlorides, sulfates, etc. described in the present invention may or may not contain water of crystallization.

[0022] In the preparation method described in [2], the solvent may include at least one of N,N-dimethylformamide (DMF), water, and N,N-dimethylacetamide (DMA), and preferably includes DMF and water. Further, the volume ratio of DMF to water in the solvent may be 1:4.

[0023] In the preparation method described in [2], the time for the sealed reaction may be 12-18 h.

[0024] In the preparation method described in [2], the time for each solvent exchange may be 5-8 h.

[0025] In the preparation method described in [2], the vacuum pressure for the vacuum degassing activation treatment may be -0.01 to -0.1 MPa, the activation temperature may be 50-120°C, such as 75°C, 80°C, 90°C, 100°C, etc., and the activation time may be 10-20 h.

[0026] [3] The application of the porous framework material according to [1] or the porous framework material prepared by the preparation method according to [2] for adsorbing hexafluoroethane.

[0027] [4] Use of the porous framework material described in [1] or the porous framework material prepared by the preparation method described in [2] in the field of selective adsorption and separation of gases. Further, the porous framework material can be used to selectively adsorb hexafluoroethane from a mixed gas containing hexafluoroethane and nitrogen, so as to separate hexafluoroethane and nitrogen.

[0028] [5] A method for adsorbing hexafluoroethane, comprising: using the porous framework material described in [1] and / or the porous framework material prepared by the preparation method described in [2] to adsorb hexafluoroethane.

[0029] [6] A method for selectively adsorbing hexafluoroethane from a mixed gas containing hexafluoroethane and nitrogen, comprising: contacting the porous framework material described in [1] and / or the porous framework material prepared by the preparation method described in [2] with the mixed gas, so that the porous framework material selectively adsorbs hexafluoroethane from the mixed gas containing hexafluoroethane and nitrogen, and separates hexafluoroethane and nitrogen.

[0030] [3], [4] The applications described above and [5], [6] the methods described above. The porous framework material can be vacuum-activated before being used to adsorb hexafluoroethane. Further, the vacuum pressure of the vacuum activation treatment can be -0.01 to -0.1 MPa, the activation temperature can be 50 to 120 °C, such as 75 °C, 80 °C, 90 °C, 100 °C, etc., and the activation time can be 3 to 20 h, such as 10 h, 12 h, etc.

[0031] [3], [4] The applications described above and [5], [6] the methods described above. The adsorption temperature can be independently -20 to 60 °C, such as 5 °C, 25 °C, 35 °C, etc.

[0032] [3], [4] The applications described above and [5], [6] the methods described above. The adsorption pressure can be independently 0.5 to 10 bar, such as 1 bar, etc.

[0033] [4] The application described above and [6] the method described above. The volume ratio of hexafluoroethane to nitrogen in the mixed gas can be (99:1) to (1:99).

[0034] [5] or [6] The method described above may further include: desorbing and recovering hexafluoroethane from the porous framework material adsorbed with hexafluoroethane under the conditions of 50 to 120 °C (such as 75 °C, 80 °C, 90 °C, 100 °C, etc.) and 0 to 1 atm, and regenerating the porous framework material.

[0035] [5] or [6] The method described above can independently adopt one or a combination of several of fixed-bed adsorption, fluidized-bed adsorption, moving-bed adsorption, etc.

[0036] The porous framework material of the present invention is particularly suitable for selectively adsorbing hexafluoroethane from a mixed system containing hexafluoroethane and nitrogen, thereby realizing the separation of hexafluoroethane and nitrogen.

[0037] One of the sources of hexafluoroethane is the industrial exhaust gas containing hexafluoroethane discharged after the high-precision fine line etching stage and surface cleaning stage of semiconductors using hexafluoroethane as a plasma etchant in the semiconductor manufacturing process. Its composition is relatively complex and also includes nitrogen, oxygen, water vapor, etc. This requires that the adsorbent must have a strong selective adsorption ability for hexafluoroethane and can effectively exclude other gas components, especially nitrogen with the largest proportion.

[0038] The porous framework material of the present invention can be used for selectively adsorbing, separating, and purifying hexafluoroethane, and specifically can be used for adsorbing and separating hexafluoroethane in a mixed gas containing hexafluoroethane and nitrogen.

[0039] In the present invention, the volume ratio of hexafluoroethane to nitrogen in the mixed gas containing hexafluoroethane and nitrogen can be (99:1) to (1:99). The hexafluoroethane adsorbed by the porous framework material can be desorbed to obtain hexafluoroethane with a very low nitrogen content, and the purity can reach the 5N level (purity > 99.999%), which can meet the requirements of most semiconductor manufacturing processes for the purity of hexafluoroethane.

[0040] The porous framework material developed in the present invention can effectively adsorb the greenhouse gas hexafluoroethane (C2F6) in the etching exhaust gas. In view of the low actual utilization rate of hexafluoroethane in the etching process, its exhaust gas still contains a large amount of unreacted gas components. If this greenhouse gas is directly discharged into the atmosphere, it will significantly exacerbate the greenhouse effect. It should be noted that hexafluoroethane itself has important industrial application value in the fields of semiconductor manufacturing, plasma etching, etc. The porous framework material provided by the present invention not only can achieve the goal of environmentally friendly exhaust gas treatment through selective adsorption technology, but also can purify and regenerate the hexafluoroethane gas through the adsorption-desorption process, provide a high-purity hexafluoroethane gas source for industrial production, realize recycling and reuse, and further reduce costs.

[0041] The porous framework material of the present invention can capture hexafluoroethane from etching exhaust gas, etc. with high capacity and high selectivity, has a high removal depth, is easy to regenerate the adsorbent, and has good hydrothermal stability.

[0042] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0043] 1) The porous framework material designed and synthesized based on the 3D meta-carborane skeleton in the present invention has unique structural characteristics. Using meta-carborane as the skeleton improves the inherent planarity of the previous phenyl ring, thereby improving the limitations of organic linkers in terms of composition and application.

[0044] 2) Replacing the benzene ring with neutral carborane (C2B10 H 12 ) Changing the electrostatic potential in the pores enables strong single-molecule cage adsorption of hexafluoroethane.

[0045] 3) The present invention uses cage-like polyhedral carborane as the framework, which exhibits stronger thermal stability and chemical stability due to the delocalization of its charges and hydrophobicity.

[0046] 4) The pore size of the porous framework material designed and synthesized based on the 3D meta-carborane framework in the present invention is about matched with the kinetic diameter of hexafluoroethane. Introducing carborane makes the surface of the porous framework material densely covered with weak adsorption sites, achieving high-capacity hexafluoroethane while showing good selectivity and deep removal. Description of the Drawings

[0047] Figure 1 It is the thermogravimetric curve of CB-100 in Example 2.

[0048] Figure 2 It is the single-component adsorption isotherm diagrams of hexafluoroethane and nitrogen on CB-100 at 278K, 298K, and 308K in Example 3.

[0049] Figure 3 It is the comparison diagram of the single-component adsorption isotherms of hexafluoroethane on CB-100 before and after soaking in water in Example 4.

[0050] Figure 4 It is the breakthrough curve diagram of the N2 / C2F6 (volume ratio v:v = 90:10) mixed gas on CB-100 in Example 5.

[0051] Figure 5 It is the summary diagram of the cycle results of the single-component adsorption isotherm of hexafluoroethane on CB-100 at 298K in Example 6, where the columns correspond to the adsorption amount of hexafluoroethane and the dotted lines correspond to the pressure. Detailed Embodiments

[0052] The present invention will be further described below in conjunction with the drawings and specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention.

[0053] For the operating methods without specific conditions noted in the following embodiments, they are usually in accordance with conventional conditions or in accordance with the conditions recommended by the manufacturer.

[0054] Example 1:

[0055] 1 mmol of meta-carboranedicarboxylic acid m-C2B 10 H 10(COOH)2 (0.232 g), 0.5 mmol of Al2(SO4)3·18H2O (0.333 g) were added to a 100 mL reaction kettle, 40 mL of deionized water and 10 mL of DMF were added, and the mixture was stirred for 30 min. The reaction kettle was sealed and placed in an oven at 100 °C for reaction for 12 hours. After the reaction was completed, it was cooled to room temperature, filtered and washed with deionized water 3 times to obtain colorless microcrystals. The obtained product was soaked in anhydrous methanol for 8 h for solvent exchange, and fresh methanol was changed every 8 h for a total of 3 times for 24 h. It was dried under vacuum at 80 °C for 20 hours to obtain the target porous framework material, denoted as CB-100.

[0056] The single crystal structure data such as the unit cell parameters of CB-100 are listed in Table 1.

[0057] Table 1

[0058]

[0059] Example 2:

[0060] The porous framework material CB-100 obtained according to Example 1 was subjected to thermogravimetric testing. As Figure 1 shown, a decrease in mass fraction was only observed above 400 °C, indicating that the structure of CB-100 collapsed at this time, proving that the porous framework material of the present invention has very good thermal stability.

[0061] Example 3:

[0062] The porous framework material CB-100 obtained according to Example 1 was placed under dynamic vacuum pressure and activated at 100 °C for 10 hours. The activated porous framework material CB-100 was loaded into a gas adsorption instrument, and the single-component adsorption isotherms of hexafluoroethane (C2F6) and nitrogen (N2) were measured at 278 K, 298 K, and 308 K respectively. The hexafluoroethane and nitrogen adsorption isotherms are as Figure 2 shown. Based on the ideal adsorbed solution theory (IAST) and adsorption data fitting calculation, the separation selectivity of the C2F6 / N2 mixed gas (volume ratio 10 / 90) was as high as over 500, indicating that the porous framework material has excellent adsorption selectivity for hexafluoroethane.

[0063] Example 4:

[0064] The porous framework material CB-100 obtained according to Example 1 was soaked in water for 1 week, then filtered and placed under dynamic vacuum pressure and activated at 90 °C for 10 hours. The activated porous framework material was loaded into a gas adsorption instrument, and the single-component adsorption isotherm of hexafluoroethane (C2F6) was measured at 298 K and compared with the originally synthesized porous framework material. It was found that the hexafluoroethane adsorption isotherm at 298 K was almost the same, as Figure 3As shown, it shows that the material has excellent water stability.

[0065] Example 5:

[0066] The porous framework material CB-100 obtained according to Example 1 was loaded into a fixed-bed adsorption column with an inner diameter of 10 mm and a packing height of 100 mm. At room temperature (25 °C), a C2F6 / N2 (volume ratio 10 / 90) mixed gas was passed through the adsorption column at a flow rate of 5 mL / min. The concentration of C2F6 in the outlet gas was monitored in real time by a gas chromatograph. Within the first 108 minutes, the concentration of C2F6 in the outlet gas was extremely low, indicating that the porous framework material has high dynamic capture ability for hexafluoroethane. The dynamic capture amount is as Figure 4 shown.

[0067] Example 6:

[0068] The sample that completed the 298K adsorption test process in Example 3 was vacuum-activated at 50 °C for 3 hours, and then 20 cycles of tests under the same conditions were repeated. The activation conditions between the cycle tests were all vacuum-activation at 50 °C for 3 hours. As Figure 5 shown, the almost identical results of the cyclic adsorption curves indicate that CB-100 can be regenerated under mild conditions and has good cycle stability.

[0069] In addition, it should be understood that after reading the above description of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

Claims

1. A porous framework material based on a 3D carborane skeleton that can selectively adsorb hexafluoroethane from a mixed gas of hexafluoroethane and nitrogen, characterized in that, Reacted and coordinated from raw materials including Al 3+ and meta-carborane dicarboxylic acid; The meta-carborane dicarboxylic acid, with the expression of m-C2B 10 H 10 (COOH)2, has the structure shown below: In the porous framework material, Al 3+ coordinates with hydroxyl OH and carboxyl O to form a cis-[Al(OH)(COO)2] aluminum-oxygen cluster structure.

2. The porous framework material according to claim 1, wherein The porous framework material has a three-dimensional network structure with one-dimensional channels formed by the coordination of aluminum-oxygen chains and closo-carborane dicarboxylic acid; The pore size of the porous framework material is The porous framework material has the following single crystal structure data:

3. The preparation method of the porous framework material according to claim 1 or 2, characterized in that, Including: A salt containing Al 3+ and metacarborane dicarboxylic acid are sealed and reacted in a solvent at 50-100 °C. The obtained solid product is placed in methanol for one or more solvent exchanges to remove solvent molecules, and then vacuum degassed and activated to remove methanol molecules in the pores, thereby obtaining the porous framework material.

4. The preparation method according to claim 3, characterized in that, Add according to Al 3+ Add the salt containing Al 3+ and meta-carborane dicarboxylic acid in a molar ratio of 1:1; The salt containing Al 3+ includes at least one of nitrate, chloride, and sulfate; The solvent includes at least one of DMF, water, and DMA, preferably including DMF and water; The time for the sealed reaction is 12 to 18 h; The time for each solvent exchange is 5 to 8 h; The vacuum pressure for the vacuum degassing activation treatment is -0.01 to -0.1 MPa, the activation temperature is 50 to 120 °C, and the activation time is 10 to 20 h.

5. Use of the porous framework material according to claim 1 or 2 or the porous framework material prepared by the preparation method according to claim 3 or 4 for adsorbing hexafluoroethane.

6. Use of the porous framework material according to claim 1 or 2 or the porous framework material prepared by the preparation method according to claim 3 or 4 in the field of selective adsorption and separation of gases.

7. The application according to claim 6, characterized in that, The porous framework material is used for selectively adsorbing hexafluoroethane from a gas mixture containing hexafluoroethane and nitrogen to achieve the separation of hexafluoroethane and nitrogen.

8. A method for adsorbing hexafluoroethane, characterized in that, Including: Adsorbing hexafluoroethane using the porous framework material according to claim 1 or 2 and / or the porous framework material prepared by the preparation method according to claim 3 or 4.

9. A method for selectively adsorbing hexafluoroethane from a mixed gas containing hexafluoroethane and nitrogen, characterized in that, Including: Contacting the porous framework material according to claim 1 or 2 and / or the porous framework material prepared by the preparation method according to claim 3 or 4 with the gas mixture, so that the porous framework material selectively adsorbs hexafluoroethane from the gas mixture containing hexafluoroethane and nitrogen to achieve the separation of hexafluoroethane and nitrogen.

10. The method according to claim 8 or 9, characterized in that The temperature of the adsorption is -20 to 60 °C, and the pressure of the adsorption is 0.5 to 10 bar; The method further includes: desorbing and recovering hexafluoroethane from the porous framework material adsorbed with hexafluoroethane under the conditions of 50 to 120 °C and 0 to 1 atm to regenerate the porous framework material; The method adopts one or a combination of fixed bed adsorption, fluidized bed adsorption, and moving bed adsorption.

Images