CN117551280B - Fluorinated metal-organic framework materials for purification of fluorine-containing electronic special gases and preparation methods thereof - Google Patents

Abstract

The invention relates to the technical field of gas adsorption separation, in particular to a fluorinated metal organic framework material for purifying fluorine-containing electron-specific gas and a preparation method thereof, wherein the chemical molecular formula of the fluorinated metal organic framework material is Zn ₄ (bzc‑CF ₃ ) ₃ Coordination polymers formed by the organic ligand 5- (trifluoromethyl) -1H-pyrazole-4-carboxylic acid and the metal salt zinc nitrate hexahydrate; the Zn is ₄ (bzc‑CF ₃ ) ₃ Contains tetrahedrally-formed metal clusters { Zn } in the framework ₄ (µ ₄ -O) said metal cluster { Zn } ₄ (µ ₄ -O) } six sides of the tetrahedron are bridged by the ligand 5- (trifluoromethyl) -1H-pyrazole-4-carboxylic acid, which extends spatially indefinitely by the above-described connection, forming a three-dimensional cage-like skeleton. The Zn is ₄ (bzc‑CF ₃ ) ₃ Has high chemical stability and thermal stability to C ₃ F ₈ And C ₃ F ₆ The separation has infinite selectivity, and can be regenerated and repeatedly used after adsorption.

Description

Fluorinated metal-organic framework materials for purification of fluorine-containing electronic special gases and their preparation method

Technical field

The invention relates to the technical field of gas adsorption and separation, and in particular to a fluorinated metal organic framework material used for the purification of fluorine-containing electronic special gases and a preparation method thereof.

Background technique

Electronic specialty gases are special gases widely used in electronic industries such as integrated circuits, semiconductors, solar cells, and 5G communications. They are key basic materials required for the production of the electronic industry. Among them, integrated circuits are considered the "foundation" of the information society, and high-purity fluorine-containing electronic special gases, as necessary cleaning gases and plasma etching gases for the extremely large-scale integrated circuit industry, are called the "blood" of the integrated circuit industry. It ensures the generation of extremely large-scale integrated circuits during the chip manufacturing process and ensures that the circuits can function effectively.

Octafluoropropane (C ₃ F ₈ ) and hexafluoroethane (C ₂ F ₆ ) are commonly used fluorine-containing electronic special gases, which are chemically stable and non-flammable. Compared with traditional industrial gases, the field of integrated circuits has higher requirements for the purity of electronic special gases. This is because its purity directly determines the performance, integration and yield rate of the product. In fact, every order of magnitude increase in the purity of electron gas can promote a qualitative leap in semiconductor devices. However, industrially C ₃ F ₈ and C ₂ F ₆ are usually prepared by thermal decomposition of polytetrafluoroethylene or perfluoroolefin and fluorine addition, which is inevitably accompanied by the presence of hexafluoropropylene (C ₃ F ₆ ) impurity.

Achieving efficient separation of C ₃ F ₆ /C ₃ F ₈ is the key to preparing high-purity C ₃ F ₈ electron special gas. In addition, the recovered C ₃ F ₆ is also an important raw material for the preparation of fluoropolymers. Since the physical and chemical properties of C ₃ F ₆ /C ₃ F ₈ are very similar, the size difference is small, and azeotropes are easily formed during low-temperature distillation, the current industry is mainly separated by thermally driven extractive distillation methods. . Since it involves multiple phase changes, it requires large equipment investment, high energy consumption, and low separation factor. Therefore, it is of great significance to develop efficient and low energy consumption C ₃ F ₆ /C ₃ F ₈ separation technology. The non-thermally driven adsorption separation method operates at room temperature, has simple equipment, low investment, and low energy consumption, and has good application prospects in gas separation. In addition, the adsorption separation method is particularly suitable for the deep removal of low-concentration impurities, which is very important. Suitable for the refining of ultra-high purity electronic specialty gases.

As a new type of porous material, metal-organic framework (MOF) materials are crystalline porous materials with regular pore structures formed by the coordination self-assembly of organic bridging ligands and metal ions or metal clusters. Compared with traditional porous materials, MOF materials have high crystallinity, large specific surface area, and various types. In particular, their pore structure and chemical composition can be easily controlled at the molecular scale.

Since product purity is highly dependent on separation efficiency, there is an urgent need to develop advanced adsorbents suitable for molecular sieving separation of C ₃ F ₆ /C ₃ F ₈ mixtures to meet the special purity of C ₃ F ₈ electronic special gases in the electronic semiconductor and integrated circuit manufacturing industries. Require. However, considering that the molecular sizes of _C3F6 and _C3F8 are very similar, it remains a challenge to tune the pore size of MOFs on _the sub _- angstrom scale to achieve molecular _screening separation of _C3F6 and _{C3F8 .} In _addition to _{C3F8 -} specific size, the ideal _C3F6 / _C3F8 separation adsorbent should also have high affinity for _{C3F6 adsorption} and have _a sturdy structure to achieve cycle regeneration.

Contents of the invention

In view of the technical problems existing in the prior art, one of the purposes of the present invention is to provide a fluorinated metal-organic framework material, which has high stability and high resistance to C ₃ F ₆ Adsorption capacity, excellent C ₃ F ₈ separation selectivity and good regeneration.

The object of the present invention is achieved through the following technical solutions:

A fluorinated metal-organic framework material has a chemical molecular formula of Zn ₄ (bzc-CF ₃ ) ₃ and is named Zn-bzc-CF _3. The fluorinated metal-organic framework material Zn-bzc-CF ₃ is formed by organic compounding. A coordination polymer formed from 5-(trifluoromethyl)-1H-pyrazole-4-carboxylic acid and the metal salt zinc nitrate hexahydrate; the fluorinated metal organic framework material Zn-bzc-CF ₃ The skeleton is cage-shaped.

On the basis of the above scheme, further, the framework of the fluorinated metal organic framework material Zn-bzc-CF ₃ contains tetrahedral metal clusters {Zn ₄ (µ ₄ -O)}, and the metal clusters { The six edges of the Zn ₄ (µ ₄ -O)} tetrahedron are bridged by the organic ligands 5-(trifluoromethyl)-1H-pyrazole-4-carboxylic acid, each 5-(trifluoromethyl)- 1H-pyrazole-4-carboxylic acid connects two {Zn ₄ (µ ₄ -O)} clusters, which extend infinitely in space through the above-mentioned connection method, forming a three-dimensional cage-like skeleton.

On the basis of the above scheme, further, from the perspective of frame connection construction, Zn-bzc-CF ₃ belongs to a three-dimensional metal-organic framework crystal material. Its crystal structure belongs to the cubic crystal system, the space group is FM/3M, and the unit cell edges The length a=b=c=20.2100Å.

Based on the above solution, further, the fluorinated metal-organic framework material has a small pore size and a large pore volume, and the size of the pore size is 5.13Å×4.84Å.

The second object of the present invention is to provide a preparation method of fluorinated metal organic framework material Zn-bzc-CF ₃ , which includes the following steps: from the organic monomer 5-(trifluoromethyl)-1H-pyrazole-4 -Carboxylic acid and zinc nitrate hexahydrate are reacted thermally in N,N-diethylformamide (DEF) solution to obtain a caged fluorinated metal organic framework material, and then washed with DEF and methanol to obtain a fluorinated caged metal. Organic skeleton.

Based on the above scheme, preferably, the reaction conditions of the thermal reaction are that the reaction temperature is 140-160°C and the reaction time is 36-60 h.

Based on the above scheme, preferably, the molar ratio of the organic monomer 5-(trifluoromethyl)-1H-pyrazole-4-carboxylic acid to zinc nitrate hexahydrate is 1:2.

The third object of the present invention is to provide an application of a fluorinated metal organic framework material in the selective separation of C ₃ F ₆ /C ₃ F ₈ .

Beneficial technical effects of the present invention:

1. The preparation steps of the metal organic framework material Zn-bzc-CF ₃ are simple and do not require expensive catalysts and organic solvents.

2. The metal organic framework material Zn-bzc-CF ₃ has high chemical stability and thermal stability, and has excellent C ₃ F ₈ separation performance.

3. The metal framework material Zn-bzc-CF ₃ has infinite selectivity for the separation of C ₃ F ₈ and C ₃ F ₆ .

4. The metal framework material Zn-bzc-CF ₃ can be regenerated very well after adsorption and can be used repeatedly.

Description of the drawings

Figure 1 is a schematic diagram of the synthesis of fluorinated metal organic framework materials;

Figure 2 is a powder X-ray diffraction (PXRD) pattern of fluorinated metal organic framework materials;

Figure 3 shows the N ₂ adsorption and desorption isotherms of fluorinated metal-organic framework materials;

Figure 4 is a scanning electron microscope (SEM) image of fluorinated metal-organic framework materials;

Figure 5 is a thermogravimetric analysis curve of fluorinated metal-organic framework materials;

Figure 6 shows the temperature-variable X-ray diffraction pattern of fluorinated metal-organic framework materials;

Figure 7 shows the adsorption isotherm of C ₃ F ₈ and C ₃ F ₆ by fluorinated metal organic framework materials at 273K;

Figure 8 shows the adsorption isotherm of C ₃ F ₈ and C ₃ F ₆ by fluorinated metal organic framework materials at 298K;

Figure 9 shows the adsorption isotherm of C ₃ F ₈ and C ₃ F ₆ by fluorinated metal organic framework materials at 323K;

Figure 10 is a breakthrough column separation diagram of C ₃ F ₈ and C ₃ F ₆ using fluorinated metal organic framework materials;

Figure 11 is a cycle diagram of the C ₃ F ₆ adsorption isotherm of fluorinated metal organic framework materials at 298K;

Figure 12 is a breakthrough column separation cycle diagram of C ₃ F ₈ /C ₃ F ₆ by fluorinated metal organic framework materials;

Figure 13 shows the XRD comparison chart of fluorinated metal organic framework materials after soaking in different pH solutions for 24 hours;

Figure 14 shows the adsorption isotherms of C ₃ F ₆ after fluorinated metal-organic framework materials were soaked in different pH solutions for 24 hours;

Figure 15 is the XRD comparison chart of the fluorinated metal organic framework material after the C ₃ F ₈ adsorption isotherm cycle diagram at 298K;

Figure 16 is an XRD comparison chart after breaking through the column separation cycle chart of C ₃ F ₈ /C ₃ F ₆ using fluorinated metal organic framework materials;

Figure 17 is the adsorption isotherm of C ₃ F ₆ after the fluorinated metal organic framework material breaks through the column separation cycle diagram of C ₃ F ₈ /C ₃ F ₆ .

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings and examples.

The experimental methods described in the following examples are all conventional methods unless otherwise specified; the reagents and materials described can be obtained from commercial sources unless otherwise specified.

Example 1

A preparation method of fluorinated metal organic framework material Zn-bzc- _CF3 , including the following steps:

Dissolve 2 mol of zinc nitrate hexahydrate and 1 mol of 5-(trifluoromethyl)-1H-pyrazole-4-carboxylic acid in 30 ml of DEF solvent, place it in a 75 ml reactor bottle, and place it in the reactor bottle. The solution was heated to 140°C, and the reaction time was 60 h. After the reaction was completed, it was cooled, centrifuged to collect the solid, washed with DEF, then with methanol, and dried at 60°C to obtain the target product.

Example 2

A preparation method of fluorinated metal organic framework material Zn-bzc- _CF3 , including the following steps:

Dissolve 2 mol of zinc nitrate hexahydrate and 1 mol of 5-(trifluoromethyl)-1H-pyrazole-4-carboxylic acid in 30 ml of DEF solvent, place it in a 75 ml reactor bottle, and place it in the reactor bottle. The solution was heated to 160°C, and the reaction time was 36 h. After the reaction was completed, it was cooled, centrifuged to collect the solid, washed with DEF, then with methanol, and dried at 60°C to obtain the target product.

Example 3

A preparation method of fluorinated metal organic framework material Zn-bzc- _CF3 , including the following steps:

Dissolve 2 mol of zinc nitrate hexahydrate and 1 mol of 5-(trifluoromethyl)-1H-pyrazole-4-carboxylic acid in 30 ml of DEF solvent, place it in a 75 ml reactor bottle, and place it in the reactor bottle. The solution was heated to 150°C, and the reaction time was 48 h. After the reaction was completed, it was cooled, centrifuged to collect the solid, washed with DEF, then with methanol, and dried at 60°C to obtain the target product.

The schematic diagram of the synthesis of the fluorinated metal organic framework materials described in Examples 1-3 is shown in Figure 1.

Characterize the metal organic framework material Zn-bzc-CF ₃ prepared in Examples 1-3:

(1) Powder X-ray diffraction characterization

Take a certain amount of the fluorinated metal organic framework material Zn-bzc-CF ₃ synthesized in Examples 1-3 and conduct a powder X-ray diffraction test; the test results are shown in Figure 2. In the figure, the abscissa 2Theta is the incident x-ray Twice the angle, the ordinate is the intensity of the diffraction peak. It can be seen that the XRD of the synthesized Zn-bzc-CF ₃ corresponds to each peak of the XRD of the simulated Zn-bzc-CF ₃ , indicating that Zn-bzc-CF ₃ Successfully synthesized.

(2) Nitrogen adsorption

Weigh a certain amount of dry sample and place it in a test tube for vacuum degassing. After degassing is completed, the nitrogen adsorption at 77K is tested. Figure 3 shows the N ₂ adsorption and desorption diagram of Zn-bzc-CF ₃ under 77K conditions. The abscissa is the relative pressure P / P ₀ , P ₀ represents the saturated vapor pressure of the gas at the adsorption temperature, and P represents the adsorption equilibrium. gas phase pressure. The material shows reversible typical type I _N2 adsorption isotherms with closed adsorption and desorption branches without hysteresis, indicating its inherent microporosity properties.

(3) Scanning electron microscope (SEM) image

Figure 4 is a scanning electron microscope (SEM) image of the fluorinated metal organic framework material Zn-bzc-CF _3. It can be seen from the figure that Zn-bzc-CF ₃ exhibits a regular cubic morphology and has high crystallinity.

(4) Thermogravimetric analysis

Figures 5 and 6 show the thermogravimetric analysis curves and variable temperature X-ray diffraction patterns of fluorinated metal organic framework materials. It can be seen from the figures that Zn-bzc-CF ₃ does not begin to collapse until 470°C, and has good thermal stability. sex.

Example 4

C ₃ F ₈ /C ₃ F ₆ adsorption separation test on fluorinated metal organic framework material Zn-bzc-CF ₃

Take a certain amount of the metal-organic framework material Zn-bzc-CF ₃ synthesized in Example 1-3 and place it in a test tube for vacuum degassing. After the degassing is completed, the C ₃ F ₈ and C ₃ F ₆ adsorption.

Figure 7, Figure 8 and Figure 9 show the adsorption isotherms of C ₃ F ₈ and C ₃ F ₆ of Zn-bzc-CF ₃ at 273K, 298K and 323K respectively. At 273K and 100KPa, C ₃ F ₈ and C The adsorption capacities of ₃ F ₆ are 1.6cm ³ /g and 55cm ³ /g respectively. At 298K and 100KPa, the adsorption capacities of C ₃ F ₈ and C ₃ F ₆ are 1.5cm ³ /g and 47cm ³ /g respectively. At 323K and 100KPa, the adsorption amounts of C ₃ F ₈ and C ₃ F ₆ are 1.5cm ³ /g and 43cm ³ /g respectively.

Breakthrough experiments were conducted using a multi-component adsorption breakthrough curve analyzer (BSD-MAB). About 0.8g of fluorinated metal-organic framework material sample was placed in a cylindrical quartz tube (φ6mm × 60mm). The space at both ends of the tube is filled tightly with quartz wool. To separate the C ₃ F ₆ /C ₃ F ₈ gas mixture, the mixture system was flowed through the sample bed at 298 K, and the concentration at the outlet was analyzed by mass spectrometry. Before each test, the samples were regenerated by flowing through a metal-organic framework material-loaded bed at a constant flow rate for 2 h at 140 °C. Figure 10 is the breakthrough column separation diagram of C ₃ F ₈ and C ₃ F ₆ by fluorinated metal organic framework materials. The ordinate is the relative concentration C / C ₀ , C is the outlet concentration, and C ₀ is the inlet concentration; Figure 10 As shown, Zn-bzc-CF ₃ has excellent separation ability. _C3F8 elutes at the beginning of _the process, which is consistent with the size adsorption _{of C3F8} expected. In contrast, C ₃ F ₆ continues to be adsorbed in the column for 27 minutes, and high-purity C ₃ F ₈ (>99.9%) can be directly produced.

The recycling of adsorbents is of great significance in practical industrial applications. The adsorption isotherms of Zn-bzc- _CF were tested with 5 cycles. As shown in Figure 11, after the cycle test, the adsorption capacity of C ₃ F ₆ remains basically unchanged, and it has good cycle regeneration ability. In order to demonstrate the recyclability of _C3F8 / _C3F6 separation in Zn-bzc- _CF3 , the fixed-bed _{adsorption of C3F8/C3F6 separation was performed} continuously for 5 _{times .} After each test, Zn-bzc- _CF3 was regenerated by vacuum desorption for 2 h. As shown _in Figure 12, the adsorption layer of Zn-bzc- _CF3 adsorbent has almost the same retention time for _C3F6 , indicating that Zn-bzc- _CF3 has good cycle performance and regeneration ability.

In order to prove the high stability of Zn-bzc-CF ₃ , we soaked Zn-bzc-CF ₃ in solutions of different pH for 24h, and then conducted X-ray diffraction tests. Figure 13 shows the fluorinated metal organic framework materials in different pH solutions. XRD comparison chart after immersed in solution for 24 hours, in which the abscissa 2Theta is twice the incident angle of x-rays, and the ordinate is the intensity of the diffraction peak, as shown in Figure 13, Zn-bzc-CF ₃ after immersion in solutions of different pH Its XRD is consistent with the original XRD and the adsorption amount of C ₃ F ₆ has not changed, proving that Zn-bzc-CF ₃ has high stability. In addition, Zn-bzc-CF ₃ was tested after 5 static adsorption cycles and 5 The XRD and C ₃ F ₆ adsorption isotherms after sub-fixed bed adsorption are shown in Figure 14, Figure 15, Figure 16 and Figure 17. Among them, Figure 15 shows the adsorption of C ₃ F ₈ by fluorinated metal organic framework materials at 298K. The XRD comparison diagram after the isotherm cycle diagram; Figure 16 is the XRD comparison diagram after the breakthrough column separation cycle diagram of C ₃ F ₈ /C ₃ F ₆ by fluorinated metal organic framework materials; in the XRD diagram, the abscissa 2Theta is twice the incident angle _of stability.

Separation mechanism research

In order to further understand the molecular screening mechanism on the metal-organic framework material Zn-bzc- _CF3 channel, the interaction of _{the C3F6} / _C3F8 separation process was carried out using first-principles density functional theory ₍ DFT) calculations. Can scan. The minimum energy path (MEP) associated with _{the C3F6} and _C3F8 diffusion programs on Zn- _bzc - _CF3 as a function of the distance through one cage to the other. The diffusion path length is approximately 7.5Å, and the interaction potential energy of the gas molecules relative to the relative position of the pore pocket. The calculated MEP spectrum shows that for fluorinated Zn-bzc-CF ₃ , the diffusion energy barrier when C ₃ F ₆ passes through the pore is from 17.1kJ/mol increased to 63.3kJ/mol, while the kinetic energy barrier of C ₃ F ₈ increased significantly from 28.6kJ/mol to 250kJ/mol. This suggests that transport of _C3F8 molecules is kinetically prohibited due to the narrow pore size, suggesting that the ideal molecular screening effect is modeled by the fluorination window size of _the caged MOF with trifluoromethyl groups for _{C3F8 6} /C ₃ F ₈ separation.

Claims (7)

1. A fluorinated metal-organic framework material, characterized in that the chemical formula of the fluorinated metal-organic framework material is Zn ₄ (bzc-CF ₃ ) ₃ and is named Zn-bzc-CF ₃ ; The fluorinated metal organic framework material Zn-bzc-CF ₃ is a porous compound formed by the organic ligand 5-(trifluoromethyl)-1H-pyrazole-4-carboxylic acid and the metal salt zinc nitrate hexahydrate. bit polymer; The skeleton of Zn ₄ (bzc-CF ₃ ) ₃ is cage-shaped; The skeleton of the fluorinated metal organic framework material Zn ₄ (bzc-CF ₃ ) ₃ contains metal clusters {Zn ₄ (µ ₄ -O)} in the form of tetrahedrons, and the metal clusters {Zn ₄ (µ ₄ -O) )} The six edges of the tetrahedron are bridged by the organic ligand 5-(trifluoromethyl)-1H-pyrazole-4-carboxylic acid, each 5-(trifluoromethyl)-1H-pyrazole-4- Carboxylic acid connects two {Zn ₄ (µ ₄ -O)} clusters, which extend infinitely in space through the above-mentioned connection method to form a three-dimensional cage-like skeleton. 2. The fluorinated metal-organic framework material according to claim 1, characterized in that, from the perspective of frame connection construction, Zn-bzc-CF ₃ belongs to a three-dimensional metal-organic framework crystal material, and its crystal structure belongs to the cubic crystal system, The space group is FM/3M, and the unit cell side length is a=b=c=20.2100Å. 3. The fluorinated metal-organic framework material according to claim 1, characterized in that the fluorinated metal-organic framework material has a small pore diameter and a large pore volume, and the size of the small pore diameter is 5.13Å×4.84Å. 4. A method for preparing the fluorinated metal organic framework material according to any one of claims 1 to 3, characterized in that it includes the following steps: from the organic ligand 5-(trifluoromethyl)-1H- Pyrazole-4-carboxylic acid and zinc nitrate hexahydrate are reacted thermally in N, N-diethylformamide (DEF) solution to obtain cage-like fluorinated metal-organic framework materials, and then washed with DEF and methanol to obtain fluorine Caged metal-organic frameworks. 5. The preparation method of fluorinated metal organic framework materials according to claim 4, characterized in that the reaction conditions of the thermal reaction are that the reaction temperature is 140-160°C and the reaction time is 36-60 h. 6. The preparation method of fluorinated metal organic framework materials according to claim 4, characterized in that the organic ligand 5-(trifluoromethyl)-1H-pyrazole-4-carboxylic acid and nitric acid hexahydrate The molar ratio of zinc is 1:2. 7. Application of the fluorinated metal organic framework material according to any one of claims 1 to 3 in the selective separation of C ₃ F ₆ /C ₃ F ₈ .