Porous copper complex, preparation method thereof and application of porous copper complex in SF6 adsorption and SF6 / n2 mixed gas separation

Abstract

The application discloses a porous copper complex, a preparation method thereof and application of the complex in SF6 adsorption and SF6 / N2 mixed gas separation. 12 (H2O)6(PTB)8(PYZ)3], wherein PTB represents 2,4,6-tri(4-carboxylphenyl)-pyrazine trivalent anion with three hydrogen atoms removed from-COOH, and PYZ represents pyrazine; the single crystal structure of the complex belongs to a cubic system, an Im-3 space group, and cell parameters are alpha=beta=gamma=90 DEG. The complex has good adsorption capacity for SF6 small molecules, and has good separation effect on SF6 / N2 mixed gas components which are difficult to separate at present, and can realize low-energy-consumption, low-cost storage, recovery and recycling of SF6 gas.

Description

Technical Field

[0001] This invention belongs to the field of small molecule gas adsorption and separation materials technology, specifically relating to a porous copper complex material constructed with 2,4,6-tris(4-carboxyphenyl)-pyrazine and pyrazine as ligands. This material has excellent selective adsorption performance for small SF6 gas molecules, and can not only be used as a material for SF6 gas storage, but also applied to the separation of SF6 / N2 mixed gases to achieve the purification of SF6 gas. Background Technology

[0002] SF6 gas, due to its non-toxicity, non-flammability, good chemical stability, and excellent arc-quenching and insulating properties, is widely used in the power, semiconductor, and cable industries as an insulating gas, plasma etching contrast agent, and thermoacoustic insulator. However, in industrial applications, SF6 is often mixed with N2 and directly emitted during use, leading not only to SF6 waste but also severe environmental damage. SF6 is an extremely potent greenhouse gas, with a greenhouse effect 23,900 times greater than that of CO2 of the same volume, and it has a very long atmospheric lifetime. Therefore, finding a porous adsorbent material that can effectively adsorb SF6 and efficiently separate SF6 / N2 mixtures to achieve SF6 gas recycling and reuse, thereby reducing its negative environmental impact, is an urgent task.

[0003] Metal-organic complexes are a novel type of porous mesh structure material formed by the self-assembly of metal ions or metal clusters and organic ligands through coordination bonds. Due to their designable structure and tunable pore surface, they show great promise for applications in gas adsorption and separation. Summary of the Invention

[0004] The purpose of this invention is to provide a porous copper complex with 2,4,6-tris(4-carboxyphenyl)-pyrazine and pyrazine as the main ligands, a method for preparing the complex, and to provide new applications for the complex.

[0005] To achieve the above objectives, the structural unit of the porous copper complex used in this invention is [Cu 12 [(H₂O)₆(PTB)₈(PYZ)₃], where PTB represents the 2,4,6-tris(4-carboxyphenyl)-pyrazine trivalent anion with three hydrogen atoms removed from the -COOH groups, and PYZ represents pyrazine; the single-crystal structure of this complex belongs to the cubic crystal system, space group Im⁻³, and the unit cell parameters are... α = β = γ = 90°.

[0006] The above-mentioned porous copper complex is prepared by adding copper nitrate, 2,4,6-tris(4-carboxyphenyl)-pyrazine, and pyrazine in a molar ratio of 1.5-2:1-1.2:2-3 to a mixture of tetrafluoroboric acid, N,N-dimethylformamide, ethanol, and water in a volume ratio of 0.1:3-5:1.5-2:0.5-1. The mixture is then sealed in a glass bottle, dissolved by ultrasonication, and allowed to stand at a constant temperature of 60-90°C for 2-6 days to obtain the porous copper complex.

[0007] This invention relates to the use of porous copper complexes in the adsorption of small gas molecules, wherein the small gas molecule is SF6. To improve the adsorption performance of the complexes for small gas molecules, the porous copper complexes are first soaked in acetonitrile for 2-3 days before use, with the acetonitrile being replaced 2-3 times daily. Then, the complexes are degassed under vacuum at 80-100°C for 10-12 hours.

[0008] This invention relates to the use of porous copper complexes in the separation of small gas molecules, wherein the small gas molecules are a mixture of SF6 and N2. To improve the separation performance of the complexes for small gas molecules, before use, the porous copper complexes are soaked in acetonitrile for 2-3 days, with the acetonitrile being replaced 2-3 times daily. Then, they are degassed under vacuum at 80-100°C for 10-12 hours before being packed into a separation column for the separation of small gas molecules.

[0009] The beneficial effects of this invention are as follows:

[0010] This invention selects 2,4,6-tris(4-carboxyphenyl)-pyrazine and pyrazine as organic ligands, and a "pedal"-like binuclear copper cluster constructed from metallic copper, water molecules and carboxylate ions as the inorganic structural unit to construct a porous copper complex. This complex not only has excellent adsorption performance for small SF6 gas molecules and can be used as a gas storage material, but also has excellent separation performance for mixed gases SF6 / N2, enabling low-energy consumption and low-cost storage, recovery and reuse of SF6 gas. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the asymmetric unit structure in the porous copper complex prepared in Example 1.

[0012] Figure 2 This is a schematic diagram of the inorganic structural unit of the "foot pedal" type binuclear metallic copper cluster in the porous copper complex prepared in Example 1.

[0013] Figure 3 This is a diagram showing the connection between ligand 2,4,6-tris(4-carboxyphenyl)-pyrazine and binuclear copper in the porous copper complex prepared in Example 1.

[0014] Figure 4 This is a three-dimensional structural diagram of the porous copper complex prepared in Example 1.

[0015] Figure 5 This is a powder X-ray diffraction pattern of the porous copper complex prepared in Example 1.

[0016] Figure 6 This is a thermogravimetric diagram of the porous copper complex prepared in Example 1.

[0017] Figure 7 This is the N2 adsorption diagram of the porous copper complex prepared in Example 1 at 77K and 1 atm.

[0018] Figure 8 This is the adsorption diagram of small molecules of SF6 and N2 gas at 273 K and 1 atm for the porous copper complex prepared in Example 1.

[0019] Figure 9 This is the adsorption diagram of small molecules of SF6 and N2 gas at 298 K and 1 atm for the porous copper complex prepared in Example 1.

[0020] Figure 10 This is the adsorption enthalpy diagram of SF6 on the porous copper complex prepared in Example 1.

[0021] Figure 11 This is the adsorption enthalpy diagram of N2 on the porous copper complex prepared in Example 1.

[0022] Figure 12 This is a breakthrough curve separation diagram of SF6 / N2 of the porous copper complex prepared in Example 1 at 298K and 1 atm. Detailed Implementation

[0023] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments, but the scope of protection of the present invention is not limited to these embodiments.

[0024] Example 1

[0025] Add 0.036 g (0.15 mmol) of copper sulfate hexahydrate, 0.033 g (0.075 mmol) of 2,4,6-tris(4-carboxyphenyl)-pyrazine, and 0.017 g (0.15 mmol) of pyrazine to a 20 mL glass bottle. Then add 5.1 mL of a mixture of tetrafluoroboric acid, N,N-dimethylformamide, ethanol, and water in a volume ratio of 0.1:3:2:1. Stir well, seal the glass bottle, and let it react at 70 °C for 3 days to obtain the structural unit [Cu]. 12 [(H2O)6(PTB)8(PYZ)3] is a porous copper complex, in which PTB represents a 2,4,6-tris(4-carboxyphenyl)-pyrazine trivalent anion with three hydrogen atoms removed from the -COOH group, and PYZ represents pyrazine.

[0026] The prepared porous copper complex has a single-crystal structure belonging to the cubic crystal system, space group Im-3, and cell parameters of [missing information]. α = β = γ = 90°. Its basic structural unit includes two copper atoms, 1 / 3 of a deprotonated 2,4,6-tris(4-carboxyphenyl)-pyrazine and 1 / 3 of a pyrazine ligand, and one water molecule. Cu1 coordinates with four oxygen atoms from the carboxyl groups of 2,4,6-tris(4-carboxyphenyl)-pyrazine and one nitrogen atom of the pyrazine to form a pentahedral coordination pattern, while Cu2 coordinates with four oxygen atoms from the four carboxyl groups of 2,4,6-tris(4-carboxyphenyl)-pyrazine and one O atom from the H2O molecule to form a pentahedral coordination pattern (see...). Figure 1 Cu1 and Cu2 are bridged by four ligand carboxyl groups, forming a "pedal" type binuclear metal cluster (see...). Figure 2 The metal cluster can connect to four 2,4,6-tris(4-carboxyphenyl)-pyrazines, and each 2,4,6-tris(4-carboxyphenyl)-pyrazine connects to three of the metal clusters (see...). Figure 3 The metal cluster extends into a three-dimensional porous structure through the connection of 2,4,6-tris(4-carboxyphenyl)-pyrazine ligands and pyrazine (see...). Figure 4 ).Depend on Figure 5 It is evident that the powder X-ray diffraction curve of the obtained complex matches the single-crystal data simulation curve, indicating that it has excellent crystallinity and purity. Figure 6 Thermogravimetric analysis also shows that its thermal stability can reach 380℃.

[0027] Example 2

[0028] The application of the porous copper complex in the adsorption of SF6 gas in Example 1 is as follows:

[0029] The porous copper complex was immersed in acetonitrile for 2 days, with the acetonitrile being replaced 3 times daily. It was then degassed under vacuum at 80°C for 12 hours. The adsorption capacities for N2 and SF6 were measured using a Micron 3Flex adsorption analyzer. The N2 adsorption temperature was 77K, primarily controlled by liquid nitrogen. The N2 test results showed that the BET and Langmuir specific surface areas of the complex were 1515 m² / s. 3 / g and 2246m 3 / g (see Figure 7 The adsorption of N2 and SF6 at different temperatures was mainly achieved through the reflux of ethanol in an externally connected temperature control device. Tests were conducted primarily at 273K and 298K. At 273K and 1 atmosphere, the adsorption capacities of N2 and SF6 reached 5.53 cm³. 3 / g, 115.28cm 3 / g (see Figure 8At 298 K and 1 atmosphere, the adsorption capacities of N2 and SF6 can reach 3.51 cm⁻¹, respectively. 3 / g, 77.60cm 3 / g (see Figure 9 ).

[0030] In summary, under conditions of 273K or 298K and one atmosphere, this complex exhibits excellent adsorption performance for small gaseous SF6 molecules, with an adsorption capacity far exceeding that for N2, making it suitable as a storage material for SF6 gas.

[0031] Adsorption enthalpy is an important parameter measuring the strength of the interaction between the adsorbent and gas molecules during the adsorption process. It determines the energy required for gas desorption and the adsorption selectivity for various gases. To gain a deeper understanding of the interaction between the complex and the gas, the isothermal adsorption heat (-Qst) is used. The virial equation is used to fit the isothermal adsorption curve of a single-component gas at 298 K to obtain the virial value, which is then used to calculate the adsorption enthalpy (-Qst). Figure 10 and 11 It can be seen that the adsorption enthalpies of this complex for SF6 and N2 at the initial pressure of 0 atmospheres are 23.97 and 15.04 kJ / mol, respectively.

[0032] Example 3

[0033] The application of the porous copper complex in Example 1 in the separation of SF6 and N2 mixed gases, and the specific separation method are as follows:

[0034] The porous copper complex was soaked in acetonitrile for 2 days, with the acetonitrile being replaced 3 times daily. It was then degassed under vacuum at 80°C for 12 hours before being packed into a separation column with an inner diameter of 4 mm. The complex loading was 1.1242 g, and the loading height was 13.5 cm. SF6 and N2 were mixed at a volume ratio of 10:90 using a separation breakthrough curve apparatus. The mixed gas was then passed through the packed separation column, which was connected to a temperature control device. The temperature was controlled by ethanol reflux. The flow rate and velocity of the mixed gas were controlled by a pressure valve and a flow meter. The test conditions were 25°C, one atmosphere, and a mixed gas flow rate of 1 mL / min. Before testing with the separation column, the entire sample bed was purged with helium at a flow rate of 20 mL / min at room temperature for 1 hour. The separation time reflects the separation capability. Figure 12 As can be seen, the separation times for SF6 and N2 at 1 mL / min are 104 min and 18 min, respectively, under the conditions of 298 K and one atmosphere. This indicates that the complex has good separation performance for the above SF6 and N2 mixed gas and can be used as a separation material for SF6 and N2 mixed gas.

Claims

1. A porous copper complex, characterized by: The single crystal structure of the complex belongs to cubic system, Im-3 space group, and the cell parameters are a=b=c=26.8 Å, α=β=γ=90°; The basic structural unit thereof comprises two copper atoms, 1 / 3 of 2,4,6-tris(4-carboxyphenyl)-triazine from which protons are removed, 1 / 3 of a pyrazine ligand, and one water molecule; Cu1 is coordinated with four oxygen atoms from the carboxyl groups in 2,4,6-tris(4-carboxyphenyl)-triazine and one nitrogen atom in the pyrazine to form a pentahedral coordination mode, and Cu2 is coordinated with four oxygen atoms from the four carboxyl groups in 2,4,6-tris(4-carboxyphenyl)-triazine and one oxygen atom in the H2O molecule to form a pentahedral coordination mode; Cu1 and Cu2 are bridged by four ligand carboxyl groups to form a "foot pedal" type binuclear metal cluster; the metal cluster can be connected to four 2,4,6-tris(4-carboxyphenyl)-triazines, and each 2,4,6-tris(4-carboxyphenyl)-triazine is connected to three metal clusters, and the metal clusters are expanded to form a three-dimensional porous structure through the connection of 2,4,6-tris(4-carboxyphenyl)-triazine ligands and pyrazines; The preparation method of the porous copper complex is as follows: copper nitrate, 2,4,6-tris(4-carboxyphenyl)-triazine, and pyrazine are added into a mixed solution of tetrafluoroboric acid and N,N-dimethylformamide, ethanol, and water in a volume ratio of 0.1:3-5:1.5-2:0.5-1, sealed in a glass bottle, ultrasonically dissolved, and then placed at a constant temperature of 60-90 ℃ for 2-6 days to obtain the porous copper complex.

2. Use of the porous copper complex of claim 1 in adsorbing SF6 gas.

3. Use of the porous copper complex according to claim 2 for adsorbing SF6 gas, characterized by: Before use, the porous copper complex is soaked in acetonitrile for 2-3 days, and the acetonitrile is replaced 2-3 times a day, and then vacuum degassed at 80-100 ℃ for 10-12 hours.

4. Use of the porous copper complex of claim 1 in separating SF6 and N2 mixed gas.

5. Use of the porous copper complex according to claim 4 for separating SF6 and N2 mixed gas, characterized by: Before use, the porous copper complex is soaked in acetonitrile for 2-3 days, and the acetonitrile is replaced 2-3 times a day, and then vacuum degassed at 80-100 ℃ for 10-12 hours, and then loaded into a separation column to separate SF6 and N2 mixed gas.

Images