Carborane hybridized cobalt cluster-based metal organic framework as well as preparation method and application thereof
By designing the carborane hybrid cobalt cluster-based metal-organic framework ZNU-21, the problem of separating C2HF5 and C2F6 was solved, achieving efficient and stable gas separation, which is suitable for C2F6 purification in semiconductor manufacturing.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-11
- Publication Date
- 2026-04-03
AI Technical Summary
Existing technologies struggle to efficiently separate mixtures of C2HF5 and C2F6. Traditional methods present environmental and safety issues, and existing MOF materials exhibit poor water stability, failing to meet industrial requirements.
A carborane hybrid cobalt cluster-based metal-organic framework, ZNU-21, was designed. By modifying it with cobalt binuclear clusters and electronegative chlorine atoms, appropriate pore size and pore surface chemistry were formed, achieving highly selective adsorption of C2HF5 and repulsion of C2F6.
It achieves efficient and stable C2HF5/C2F6 separation, exhibits excellent thermal and water stability, is suitable for various environmental conditions, and is ideal for C2F6 purification in semiconductor manufacturing.
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Abstract
Description
Technical Field
[0001] This invention relates to the fields of porous material synthesis and gas adsorption and separation technology, specifically to a carborane hybrid cobalt cluster-based metal-organic framework, its preparation method, and its application in the purification of hexafluoroethane (C2F6). Background Technology
[0002] C2F6 is a key material for etching nanoscale chips in the semiconductor industry. Currently, the main industrial methods for producing C2F6 include electrochemical fluorination of hydrogen fluoride, fluorination of cobalt trifluoride, and direct fluorination of fluorine. These methods typically produce pentafluoroethane (C2HF5) as a byproduct, and these impurities must be effectively removed to obtain high-purity C2F6. However, their boiling points are close to those of C2F6 (195.2 K) and C2HF5 (224.9 K), and they readily form azeotropes. This makes traditional cryogenic distillation extremely challenging. Current HCl-based industrial azeotropic distillation methods are unsustainable and plagued by environmental and safety concerns. Therefore, replacing it with efficient and energy-saving purification technologies has become an urgent priority for advancing semiconductor manufacturing.
[0003] Metal-organic frameworks (MOFs) have emerged as a novel type of crystalline porous material with tunable pore size and environment, demonstrating great potential in various gas separation applications. Among various adsorbents, MOFs, as crystalline porous materials formed by the self-assembly of organic ligands and metals, exhibit excellent performance in the separation of light hydrocarbons, such as C2H2 / C2H4 [Adv. Mater. 2023, 35, 2204553], C2H2 / CO2 [Angew. Chem. Int. Ed. 2025, 64, e202506055], and C2H4 / C2H6 [J. Am. Chem. Soc. 2021, 143, 1485-1492.]. In contrast, the separation of C2HF5 / C2F6 mixtures remains particularly challenging due to their kinetic diameter (4.4 Å vs 5.1 Å) and polarizability (4.36 × 10⁻⁶). 24 cm -3 vs 6.82 × 10 24 cm -3 Similar to C₂HF₅, it lacks functional groups that promote selective binding (e.g., C≡C, C=C, etc.). To date, there are few reports on adsorbents for the efficient separation of C₂HF₅ / C₂F₆. Among them, SIFSIX-1-Cu stands out as a benchmark material, exhibiting high C₂HF₅ adsorption and selectivity. However, its poor water stability hinders practical application under various environmental conditions. Therefore, the development of hydrolysis-resistant MOFs for this separation remains an urgent need. Summary of the Invention
[0004] Considering the molecular size and polarizability of C2HF5 and C2F6, this invention envisions appropriately reducing the pore size and increasing the electronegativity of the pores to enhance the synergistic interaction between the framework and C2HF5, thereby promoting the adsorption of C2HF5 and repelling C2F6. Furthermore, if we can further modify the electronegative sites to recognize the H atoms of C2HF5, we can achieve highly precise selective adsorption of C2HF5.
[0005] This invention uses Co 2+ By forming cobalt binuclear clusters and introducing electronegative chlorine atoms to alter the pore size and pore surface chemistry of porous materials, C2F6 is purified from C2HF5 and C2F6 in one step. This is based on para-carborane. p -C2B 10 H 12 Porous materials that serve as a framework for C2HF5 / C2F6 separation have never been reported to date.
[0006] Here, we propose a carborane-based MOF for the reaction of carborane-1,12-dicarboxylic acid and N 1 N 1 N 3 N 3 N 5 N 5 -Hexa(pyridin-4-yl)phenyl-1,3,5-triamine as the organic ligand, with Co 2+ A carborane-hybridized cobalt cluster-based metal-organic framework (referred to as ZNU-21) was constructed using a metal source and designed for the selective capture of C2HF5. The cobalt binuclear cluster enables N... 1 N 1 N 3 N 3 N 5 N 5 The full coordination of hexa(pyridin-4-yl)phenyl-1,3,5-triamine with metal nodes not only improves the material's stability but also gives it a partitioned double-cage structure, unlike the single one-dimensional channels found in typical MOF materials. This structural evolution leads to a significant improvement in gas separation performance. Both static adsorption and dynamic breakthrough experiments demonstrate the excellent adsorption and separation performance of C2HF5 / C2F6.
[0007] The specific technical solution is as follows: In a first aspect, the present invention provides a carborane hybrid cobalt cluster-based metal-organic framework capable of selectively adsorbing C2HF5 from a mixture containing C2HF5 and C2F6, comprising p-carborane dicarboxylate ions and metal ions Co. 2+ Chloride ions and organic nitrogen-containing ligands N 1 N 1 N3 N 3 N 5 N 5 It is composed of hexa(pyridin-4-yl)phenyl-1,3,5-triamine, in which two Co 2+ It is bridged with the four oxygen atoms and a μ-Cl of two p-borane dicarboxylate ions to form a cobalt binuclear cluster. The cobalt binuclear cluster is interconnected with organic nitrogen-containing ligands to form a three-dimensional framework with a double cage structure.
[0008] Furthermore, the double-cage structure consists of a large cage with a size of 5.8 Å and a small cage with a size of 3.8 Å.
[0009] The expression for carborane dicarboxylic acid is: p -C2B 10 H 10 (COOH)₂ has the structure shown in formula (I): (I).
[0010] When the two carboxyl hydrogens of p-borane dicarboxylic acid leave, the p-borane dicarboxylic acid ion is formed.
[0011] N 1 N 1 N 3 N 3 N 5 N 5 The chemical structure of -hexa(pyridin-4-yl)phenyl-1,3,5-triamine is shown below: .
[0012] In a second aspect, the present invention provides a method for preparing the carborane hybrid cobalt cluster-based metal-organic framework described in the first aspect, comprising the steps of: (1) CoCl2, N 1 N 1 N 3 N 3 N 5 N 5 -Hexa(pyridin-4-yl)phenyl-1,3,5-triamine and p-carborane dicarboxylic acid react in acidic solution at 50-80°C to give a solid product; (2) The solid product is placed in methanol for one or more solvent exchanges to remove solvent molecules, and then vacuum degassing and activation are performed to remove methanol molecules in the channels to obtain the carborane hybrid cobalt cluster-based metal-organic framework.
[0013] In step (1), CoCl2 and N 1 N 1 N3 N 3 N 5 N 5 The molar ratio of hexa(pyridin-4-yl)benzene-1,3,5-triamine to p-carborane dicarboxylic acid is preferably 1:1 to 3:1 to 3, more preferably 1:1:1, to allow p-carborane dicarboxylic acid to react fully.
[0014] In step (1), the acid in the acidic solution is preferably at least one of tetrafluoroboric acid, hydrochloric acid, and nitric acid.
[0015] In step (1), the solvent in the acidic solution is preferably at least one of methanol, DMF (N,N-dimethylformamide), water, DMA (N,N-dimethylacetamide), ethanol, acetone, and acetonitrile.
[0016] In step (1), the reaction time is preferably 5 to 48 hours, such as 24 hours.
[0017] In step (2), the preferred time for each solvent exchange is 5 to 8 hours.
[0018] In step (2), the preferred temperature for vacuum degassing activation is room temperature to 120°C, and the preferred time is 10 to 24 hours.
[0019] Thirdly, the present invention provides the application of the carborane hybrid cobalt cluster-based metal-organic framework described in the first aspect for adsorbing gases. Further, the gas is C2HF5 or C2F6.
[0020] Fourthly, the present invention provides the application of the carborane hybrid cobalt cluster-based metal-organic framework described in the first aspect for the separation of C2HF5 and C2F6. Further, the carborane hybrid cobalt cluster-based metal-organic framework is used to selectively adsorb C2HF5 from a mixture containing C2HF5 and C2F6 to achieve the separation of C2HF5 and C2F6.
[0021] Fifthly, the present invention provides a method for adsorption separation of C2HF5 and C2F6, comprising: selectively adsorbing C2HF5 from a mixture containing C2HF5 and C2F6 using the carborane hybrid cobalt cluster-based metal-organic framework described in the first aspect to achieve separation of C2HF5 and C2F6.
[0022] In the application described in the fourth aspect and the method described in the fifth aspect, the volume ratio of C2HF5 to C2F6 in the mixture containing C2HF5 and C2F6 is (50:50) to (1:99).
[0023] In the application described in the fourth aspect and the method described in the fifth aspect, the carborane hybrid cobalt cluster-based metal-organic framework is used to selectively adsorb C2HF5 from a mixture containing C2HF5 and C2F6 at a pressure of 1~10 bar and a temperature of 298~343 K.
[0024] Compared with the prior art, the beneficial effects of this invention are as follows: 1) This invention designs and synthesizes a novel carborane hybrid cobalt cluster-based metal-organic framework, ZNU-21. The ZNU-21 framework features a suitably sized double-cage structure with appropriate pore size and negatively charged chlorine atoms, significantly enhancing its ability to accurately recognize C2HF5 molecules. The complete coordination of ligands within the framework and the binuclear cluster structure give ZNU-21 excellent thermal and water stability.
[0025] 2) ZNU-21 achieves highly selective adsorption and separation of C2HF5 / C2F6, and is currently the only carborane hybrid porous material that can efficiently and accurately identify C2HF5 and repel C2F6 impurities.
[0026] 3) This invention uses cage-like polyhedral carborane as a framework, which exhibits stronger thermal stability, water stability and hydrophobicity, and is expected to be applied to more gas separation applications.
[0027] 4) The porous framework material based on the carborane skeleton designed and synthesized in this invention has high separation selectivity for C2HF5 / C2F6 and preferential adsorption selectivity for C2HF5. Attached Figure Description
[0028] Figure 1 This is a schematic diagram of the crystal structure of ZNU-21, a porous framework material based on a carborane skeleton, in Example 1.
[0029] Figure 2 This is a density functional theory (DFT) calculation diagram of ZNU-21 that adsorbed C2HF5 or C2F6 molecules in Example 2.
[0030] Figure 3 This is the 77 K nitrogen adsorption curve of ZNU-21 in Example 3.
[0031] Figure 4 This is a single-component adsorption curve of C2HF5 and C2F6 of ZNU-21 measured at 298 K in Example 3.
[0032] Figure 5 This is the IAST selectivity diagram for the separation of mixed gases C2HF5 and C2F6, calculated by ZNU-21 based on isotherms in Example 4.
[0033] Figure 6This is the adsorption heat curve of C2HF5 and C2F6 of ZNU-21 calculated based on the isotherm in Example 4.
[0034] Figure 7 This is a dynamic penetration curve of ZNU-21 used for C2HF5 and C2F6 separation in Example 5.
[0035] Figure 8 The graph shows the stability test results of ZNU-21 in Example 6.
[0036] Figure 9 The thermogravimetric curve of ZNU-21 in Example 6 is shown. Detailed Implementation
[0037] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.
[0038] Example 1: In a 10 mL vial, 5.9 mg CoCl₂·6H₂O (0.025 mmol), 5.8 mg p-carboxyborane (0.025 mmol), and 14.6 mg N₂ were added. 1 N 1 N 3 N 3 N 5 N 5 Hexa(pyridin-4-yl)phenyl-1,3,5-triamine (0.025 mmol) was dissolved in a mixed solution of DMF / MeOH / H2O (2 / 1 / 0.5 mL), followed by the addition of 10 μL of nitric acid solution. After sonication for 5 minutes, the solution was sealed and reacted at 80 °C for 24 hours to obtain pink crystals of ZNU-21. The pink crystals were collected by filtration and washed with methanol (5 mL × 3). After exchanging the solvent three times with anhydrous methanol (3 × 8 h), the crystals were stored by immersion in anhydrous methanol. Before gas adsorption testing, the synthesized ZNU-21 was activated under vacuum at room temperature for 2 h, followed by activation at 100 °C for 10 h to completely remove methanol molecules.
[0039] Figure 1 This is a schematic diagram of the crystal structure of ZNU-21. Co 2+ Cl 1- The oxygen atom and N atom on the carborane dicarboxylic acid ligand 1 N 1 N 3 N 3 N 5 N 5 The nitrogen atoms of hexa(pyridin-4-yl)phenyl-1,3,5-triamine form a cobalt binuclear cluster bridged by μ-Cl. Figure 1a- Figure 1 c). Cobalt binuclear clusters and ligands extend and connect with each other through self-assembly, forming a three-dimensional framework with a double-cage structure. Figure 1 e), divided into large cage (5.8Å) and small cage (3.8Å) Figure 1 d、 Figure 1 f), which exhibits an excellent pore structure. This gas-size-fits-all double-cage structure facilitates the selective separation of C2HF5 and C2F6.
[0040] Table 1 shows the crystal data for ZNU-21.
[0041] Table 1 Example 2: To further explore guest-skeletal interactions, density functional theory calculations were used to determine the predominant adsorption sites of C2HF5 and C2F6 on ZNU-21. In ZNU-21, C2HF5 occupies two distinct sites. The first is located at the window of the large cage (…). Figure 2 a) This involves eight CF···HC (2.52–3.53 Å) and one CH···π (2.84 Å) interactions, with a binding energy of -68.21 kJ·mol⁻¹. -1 This indicates a favorable mating position. The second position is located inside the small cage (…). Figure 2 b) The interaction consists of 7 CF···HC (2.57–3.17 Å) and 1 BH···HC (2.91 Å), with a binding energy of -67.47 kJ·mol⁻¹. -1 Conversely, C2F6 only appears in the center of the large cage ( Figure 2 c) Interacting through 6 CF···HC forces, with a strength of -53.79 kJ·mol⁻¹. -1 This indicates that its interaction with the framework is weaker than that of C2HF5. The significant difference in binding energy highlights the key influence of the pore size and gas molecule size adaptation, and the double-cage structure of ZNU-21 provides multiple interaction sites to enhance the binding energy of C2HF5.
[0042] Example 3: N2 adsorption at 77 K confirmed the permanent porosity of ZNU-21 ( Figure 3 The results showed that, at a P / P0 ratio of 0.99, ZNU-21 adsorbed 188.7 cm⁻¹ N₂. 3 g -1 Subsequently, gas adsorption isotherms of C2HF5 and C2F6 were collected by ZNU-21 at 298 K. Figure 4ZNU-21 exhibits a significantly higher adsorption capacity for C2HF5 than for C2F6. At 298 K and 1 bar, the C2HF5 adsorption capacity of ZNU-21 is 63.8 cm⁻¹. 3 g -1 It far exceeds its 14.9 cm. 3 g -1 The adsorption capacity of C2F6 was measured. Under low pressure, the adsorption difference between C2HF5 and C2F6 was more pronounced. At 1 kPa, the adsorption capacity of C2HF5 was 31.3 cm⁻¹. 3 g -1 It exceeds the adsorption capacity of C2F6 by more than 157 times (0.21 cm⁻¹). 3 g -1 ).
[0043] Example 4: The adsorption selectivity was evaluated using the Ideal Adsorption Solution Selectivity Theory (IAST). Figure 5 At 100 kPa pressure and 298 K, the ZNU-21 exhibits a high C2HF5 / C2F6 selectivity of 412.5, demonstrating its excellent performance in separating C2HF5 and C2F6. This was achieved using the Clausius-Clapeyron equation (…). Figure 6 Calculate the adsorption enthalpy (Q) of C2HF5 and C2F6. st ZNU-21 C2HF5 Q st It is 48.7 kJ mol -1 C2F6 Q st It is 31.3 kJ mol -1 This indicates that the bonding force of C2HF5 in the pores is much stronger than that of C2F6. The Q values of C2HF5 and C2F6... st The differences further illustrate the significant variations in adsorption affinity.
[0044] Example 5: To further verify the actual separation performance of C2HF5 / C2F6 by ZNU-21, dynamic breakthrough experiments of C2HF5 / C2F6 (C2HF5:C2F6 volume ratio = 50 / 50-5 / 95) were conducted at 298-313 K. Under the conditions of 298 K and a C2HF5:C2F6 volume ratio of 5 / 95, as... Figure 7As shown, C2F6 eluted very quickly (3.6 min), while C2HF5 adsorption was maintained until 651.1 min before eluting from the column. The C2HF5 / C2F6 separation time interval of ZNU-21 was as high as 647.5 min. Furthermore, it also exhibited excellent separation performance under other conditions, with separation intervals of 36 min (298 K, C2HF5:C2F6 volume ratio = 50 / 50), 55 min (298 K, C2HF5:C2F6 volume ratio = 40 / 60), 52 min (308 K, C2HF5:C2F6 volume ratio = 40 / 60), 48 min (313 K, C2HF5:C2F6 volume ratio = 40 / 60), 76 min (298 K, C2HF5:C2F6 volume ratio = 30 / 70), 123 min (298 K, C2HF5:C2F6 volume ratio = 20 / 80), and 275 min (298 K, C2HF5:C2F6 volume ratio = 10 / 90). The calculated C2F6 yield was 56.4 mol / kg (298 K, C2HF5:C2F6 volume ratio = 5 / 95).
[0045] Therefore, ZNU-21 can produce pure C2F6 in a one-step separation process of C2HF5 and C2F6 over a considerable period of time.
[0046] Example 6: Figure 8 Powder X-ray diffraction (PXRD) patterns show that ZNU-21 exhibits excellent structural stability after being immersed in water and organic solvents (dichloromethane DCM, methanol MeOH, acetone) for 24 hours or after long-term exposure to air for two weeks.
[0047] Furthermore, thermogravimetric analysis results show that ZNU-21 crystals exhibit good thermal stability at 260℃. Figure 9 ).
[0048] The above experimental results further confirm the good stability of ZNU-21.
[0049] Furthermore, it should be understood that after reading the above description of the present invention, those skilled in the art can make various alterations or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims.
Claims
1. A carborane hybrid cobalt cluster-based metal-organic framework capable of selectively adsorbing C2HF5 from a mixture containing C2HF5 and C2F6, characterized in that, Composed of carborane dicarboxylate ions and metal ions Co 2+ Chloride ions and organic nitrogen-containing ligands N 1 N 1 N 3 N 3 N 5 N 5 It is composed of hexa(pyridin-4-yl)phenyl-1,3,5-triamine, in which two Co 2+ It is bridged with the four oxygen atoms and a μ-Cl of two p-borane dicarboxylate ions to form a cobalt binuclear cluster. The cobalt binuclear cluster is interconnected with organic nitrogen-containing ligands to form a three-dimensional framework with a double cage structure.
2. The method for preparing a carborane hybrid cobalt cluster-based metal-organic framework according to claim 1, characterized in that, Including the following steps: (1) CoCl2, N 1 N 1 N 3 N 3 N 5 N 5 -Hexa(pyridin-4-yl)phenyl-1,3,5-triamine and p-carborane dicarboxylic acid react in acidic solution at 50-80°C to give a solid product; (2) The solid product is placed in methanol for one or more solvent exchanges to remove solvent molecules, and then vacuum degassing and activation are performed to remove methanol molecules in the channels to obtain the carborane hybrid cobalt cluster-based metal-organic framework.
3. The preparation method according to claim 2, characterized in that, In step (1), CoCl2 and N 1 N 1 N 3 N 3 N 5 N 5 The molar ratio of hexa(pyridin-4-yl)phenyl-1,3,5-triamine to p-carborane dicarboxylic acid is 1:1~3:1~3.
4. The preparation method according to claim 2, characterized in that, In step (1): The acid in the acidic solution is selected from at least one of tetrafluoroboric acid, hydrochloric acid, and nitric acid; The solvent in the acidic solution is selected from at least one of methanol, DMF, water, DMA, ethanol, acetone, and acetonitrile.
5. The preparation method according to claim 2, characterized in that, In step (1), the reaction time is 5 to 48 hours.
6. The preparation method according to claim 2, characterized in that, In step (2); Each solvent exchange takes 5-8 hours; The vacuum degassing activation temperature is room temperature to 120℃, and the time is 10 to 24 hours.
7. The application of the carborane hybrid cobalt cluster-based metal-organic framework according to claim 1 for gas adsorption.
8. The application according to claim 7, characterized in that, The gas is C2HF5 or C2F6.
9. The application of the carborane hybrid cobalt cluster-based metal-organic framework according to claim 1 for the separation of C2HF5 and C2F6, characterized in that, The carborane hybrid cobalt cluster-based metal-organic framework is used to selectively adsorb C2HF5 from a mixture containing C2HF5 and C2F6 to achieve the separation of C2HF5 and C2F6.
10. A method for adsorption separation of C2HF5 and C2F6, characterized in that, include: The carborane hybrid cobalt cluster-based metal-organic framework of claim 1 is used to selectively adsorb C2HF5 from a mixture containing C2HF5 and C2F6 to achieve the separation of C2HF5 and C2F6.