A copper-based metal-organic framework material, its preparation method and application

Abstract

This invention discloses a copper-based metal-organic framework material, its preparation method, and its applications. The chemical formula of the material is [Cu2(6-Qc)4]. n 6-Qc is 6-quinoline carboxylic acid; the central metal of the material is five-coordinate Cu. 2+ Two Cu 2+ The components are linked by four carboxyl groups to form a paddlewheel-shaped binuclear structural unit; the 6-Qc ligand connects adjacent binuclear structural units together through the nitrogen atom and carboxyl group on the quinoline ring, and finally stacks to form a three-dimensional porous framework; preparation method: cuprous salt, 6-quinoline carboxylic acid and triethylenediamine are added to DMF to dissolve, and then heated to react. During the reaction, solids precipitate from the clear solution. After cooling and filtration, the product is obtained; this copper-based metal-organic framework material has a dynamic gate opening effect. Under the same temperature conditions, it exhibits different gate opening pressures for ethane and ethylene, and the gate opening pressure of ethane is significantly lower than that of ethylene, thus enabling efficient separation of ethane and ethylene.

Description

Technical Field

[0001] This invention relates to a metal-organic framework material and its preparation method, and particularly to a copper-based metal-organic framework material, its preparation method, and its applications. Background Technology

[0002] Ethylene is a core product of the petrochemical industry and a fundamental raw material for the synthesis of polyethylene and other high-value-added organic chemicals. Ethylene production technology and capacity are indicators of a nation's petrochemical industry development level. Petroleum hydrocarbon cracking (including ethane steam cracking) is the most important method for industrial ethylene production. The product obtained from this process typically contains small amounts of ethane and other impurities. The presence of these impurities can cause catalyst poisoning during the further processing of ethylene and even lead to explosions. Therefore, obtaining high-purity ethylene is crucial. To obtain polymer-grade ethylene (ethylene content not less than 99.95%), industrial processes typically employ methods such as cryogenic distillation to remove impurities such as ethane. However, because ethane and ethylene are extremely similar in molecular size, kinetic diameter, and relative volatility, to achieve high selectivity and reflux ratio, the number of trays in the distillation column needs to exceed 100, making this separation process extremely energy-intensive.

[0003] In contrast, adsorption separation based on solid porous materials has become one of the most promising technologies to replace cryogenic distillation due to its advantages of low cost and low energy consumption. Utilizing differences in molecular geometry and physical properties, porous materials can exhibit different adsorption capacities for various components in a mixture. However, apart from a few chemisorbents, traditional porous materials exhibit poor adsorption selectivity for hydrocarbon mixtures due to the lack of recognition mechanisms. Metal-organic frameworks (MOFs) are a new type of crystalline porous material composed of a metal center and organic ligands linked by coordination bonds. Compared to traditional porous materials, MOFs offer greater tunability in terms of composition, pore shape and size, and surface chemical environment. These characteristics make them show great application potential in the field of gas storage and separation.

[0004] To date, research on the adsorption and separation of ethane and ethylene using MOF materials has been reported. However, it is worth noting that the ethane / ethylene adsorption-separation ratio of most materials in existing studies remains relatively low. Furthermore, due to their fixed pore size, the adsorption-separation ratio typically decreases further with increasing operating temperature. Therefore, designing and constructing MOF materials that can maintain high ethane / ethylene adsorption-separation capabilities over a wide temperature range (especially above room temperature) has significant academic value and practical implications. Summary of the Invention

[0005] Objectives of this invention: The objective of this invention is to provide a copper-based metal-organic framework material that exhibits dynamic gate-opening behavior during the adsorption of single-component ethane and ethylene, enabling efficient purification of ethylene; the second objective of this invention is to provide a method for preparing the copper-based metal-organic framework material; and the third objective of this invention is to provide the application of the copper-based metal-organic framework material in the adsorption and separation of ethane and ethylene.

[0006] Technical solution: The copper-based metal-organic framework material of this invention has the chemical formula [Cu2(6-Qc)4]. n 6-Qc is 6-quinolinecarboxylic acid; the central metal of the material is five-coordinate Cu. 2+ Two Cu 2+ The two are linked by four carboxyl groups to form a paddlewheel-shaped binary structural unit (structure as shown in the image). Figure 1 (As shown); the 6-Qc ligand connects adjacent binuclear structural units together through the nitrogen atom and carboxyl group on the quinoline ring, ultimately stacking to form a three-dimensional porous framework (structure as shown). Figure 2 (As shown).

[0007] The structural formula of the 6-quinolinecarboxylic acid is as follows:

[0008] The copper-based metal-organic framework material is a green crystal.

[0009] The unit cell parameters of the crystal are: α=90°, β=96.48°, γ=90°.

[0010] The thermal decomposition temperature of the copper-based metal-organic framework material is 270℃.

[0011] The preparation method of the copper-based metal-organic framework material of the present invention includes the following steps: adding cuprous salt, 6-quinoline carboxylic acid (6-Qc) and triethylenediamine to N,N-dimethylformamide, dissolving them, and then heating to react. During the reaction, solids precipitate out of the clear solution. After cooling and filtration, green crystals are obtained, which are the copper-based metal-organic framework material.

[0012] Preferably, the heating reaction temperature is 90–120°C, and the reaction time is 24–48 hours.

[0013] Preferably, the molar ratio of CuI, 6-Qc and TEDA is 1:4:1 to 4.

[0014] Preferably, the cuprous salt is CuI, CuBr, or CuCl.

[0015] The application of the copper-based metal-organic framework material described in this invention in the adsorption and separation of ethane and ethylene.

[0016] The copper-based metal-organic framework material exhibits opening pressure differences of 16 kPa, 17.5 kPa, and 20 kPa for ethane and ethylene at 303 K, 308 K, and 313 K, respectively.

[0017] Mechanism of Invention: In the copper-based metal-organic framework (MOF) material of this invention, 6-Qc is a short organic ligand with relatively concentrated coordination sites. Utilizing this type of molecule to assemble with the central metal maximizes the preservation of the microporous characteristics of the resulting MOF material. Furthermore, the uncoordinated quinoline rings at the square windows provide the structural basis for the material's dynamic gate-opening behavior. More importantly, these quinoline rings with abundant π electrons can form more and stronger CH···π interactions with ethane. Therefore, in a binary gas mixture, ethane can open the pores of the copper-based MOF material first at a lower pressure, while the opening pressure for ethylene is relatively higher. This means that the material can effectively separate ethane and ethylene, ensuring a good adsorption-to-separation ratio. Moreover, as the temperature increases, the interaction force between the gas and the window gradually weakens, making window opening more difficult. Due to differences in affinity, heating has a greater impact on ethylene. Theoretically, this inevitably leads to a higher ethane / ethylene separation ratio and better separation effect within a certain range at higher temperatures.

[0018] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: (1) The copper-based metal-organic framework material uses 6-Qc as the organic ligand and the central metal Cu 2+ The assembly exhibits a dynamic opening effect, showing different opening pressures for ethane and ethylene under the same temperature conditions, with the opening pressure of ethane being significantly lower than that of ethylene, thus enabling efficient separation of ethane and ethylene; (2) This copper-based metal-organic framework material can maintain a high ethane / ethylene adsorption separation ratio over a wide temperature range; (3) This copper-based metal-organic framework material has high thermal stability; (4) The preparation method is simple and can achieve large-scale production; (5) When this copper-based metal-organic framework material is used for the adsorption separation of ethane and ethylene, the opening pressure difference between ethane and ethylene at 303K, 308K, and 313K is 16kPa, 17.5kPa, and 20kPa, respectively. Attached Figure Description

[0019] Figure 1 This is a coordination environment diagram of the copper-based metal-organic framework material of the present invention;

[0020] Figure 2 This is a three-dimensional packing diagram of the copper-based metal-organic framework material of the present invention;

[0021] Figure 3 A diagram of the green bulk crystalline copper-based metal-organic framework material prepared in Example 1;

[0022] Figure 4 Thermogravimetric (TG) curve of the copper-based metal-organic framework material prepared in Example 1;

[0023] Figure 5 The single-component ethane adsorption curves of the copper-based metal-organic framework material prepared in Example 1 at 303K, 308K, and 313K are shown.

[0024] Figure 6 The image shows the ethylene single-component adsorption curves of the copper-based metal-organic framework material prepared in Example 1 at 303K, 308K, and 313K.

[0025] Figure 7 The image shows the breakthrough curve of the ethane / ethylene mixture in the copper-based metal-organic framework material prepared in Example 1. Detailed Implementation

[0026] The technical solution of the present invention will be further described below with reference to the embodiments.

[0027] Example 1

[0028] The copper-based metal-organic framework material [Cu2(6-Qc)4] of the present invention n Its preparation method includes the following steps:

[0029] Accurately weigh 0.1 mmol of CuI, 0.4 mmol of 6-Qc, and 0.1 mmol of TEDA into a glass bottle, then add 6 mL of DMF. Sonicate until the solution becomes clear, seal the bottle, and place it in a constant temperature drying oven. React at 100°C for 48 hours. After cooling to room temperature, filter to obtain a green, blocky copper-based metal-organic framework material (e.g., Figure 3 As shown in the figure, the yield was 76%.

[0030] Example 2

[0031] The copper-based metal-organic framework material [Cu2(6-Qc)4] of the present invention n Its preparation method includes the following steps:

[0032] Accurately weigh 0.1 mmol of CuI, 0.4 mmol of 6-Qc, and 0.3 mmol of TEDA and add them to a glass bottle. Then add 6 mL of DMF and sonicate until the solution becomes clear. Seal the glass bottle and place it in a constant temperature drying oven. React at 100°C for 48 h. After cooling to room temperature, filter to obtain the same copper-based metal-organic framework material as in Example 1, with a yield of 60%.

[0033] Example 3

[0034] The copper-based metal-organic framework material [Cu2(6-Qc)4] of the present invention nIts preparation method includes the following steps:

[0035] Accurately weigh 0.1 mmol of CuI, 0.4 mmol of 6-Qc, and 0.4 mmol of TEDA and add them to a glass bottle. Then add 6 mL of DMF and sonicate until the solution becomes clear. Seal the glass bottle and place it in a constant temperature drying oven. React at 100°C for 48 h. After cooling to room temperature, filter to obtain the same copper-based metal-organic framework material as in Example 1, with a yield of 53%.

[0036] Example 4

[0037] The copper-based metal-organic framework material [Cu2(6-Qc)4] of the present invention n Its preparation method includes the following steps:

[0038] Accurately weigh 0.1 mmol of CuBr, 0.4 mmol of 6-Qc, and 0.1 mmol of TEDA and add them to a glass bottle. Then add 6 mL of DMF and sonicate until the solution becomes clear. Seal the glass bottle and place it in a constant temperature drying oven. React at 90°C for 48 h. After cooling to room temperature, filter to obtain the same copper-based metal-organic framework material as in Example 1, with a yield of 40%.

[0039] Example 5

[0040] The copper-based metal-organic framework material [Cu2(6-Qc)4] of the present invention n Its preparation method includes the following steps:

[0041] Accurately weigh 0.1 mmol of CuCl, 0.4 mmol of 6-Qc, and 0.1 mmol of TEDA and add them to a glass bottle. Then add 6 mL of DMF and sonicate until the solution becomes clear. Seal the glass bottle and place it in a constant temperature drying oven. React at 120°C for 24 hours. After cooling to room temperature, filter to obtain the same copper-based metal-organic framework material as in Example 1, with a yield of 45%.

[0042] Comparative Example 1

[0043] Based on Example 1, without adding TEDA, all other conditions remain unchanged.

[0044] During the reaction, the same product as in Example 1 was not obtained; only a small amount of green amorphous precipitate of unknown composition was obtained.

[0045] Material characterization

[0046] (1) Crystal structure characterization

[0047] Diffraction data of the copper-based metal-organic framework material prepared in Example 1 were collected using a Bruker Smart Apex II X-ray single-crystal diffractometer and analyzed using OLEX. 2 The software performs structural analysis and refinement. Its unit cell parameters are: α = 90°, β = 96.48°, γ = 90°. The relevant parameters during the refinement process are shown in Table 1 below.

[0048] Table 1 Crystal parameters

[0049]

[0050]

[0051] (2) Thermal stability test

[0052] Thermogravimetric (TG) analysis of the metal-organic framework material prepared in Example 1 was performed, and the results are as follows: Figure 4 As shown.

[0053] Depend on Figure 4 It can be seen that the metal-organic framework material can be stabilized up to 270℃. After 270℃, the structure begins to collapse and decompose, so the material has good thermal stability.

[0054] Material property testing

[0055] (1) The metal-organic framework material of the present invention performs single-component adsorption of ethane and ethylene.

[0056] [Cu2(6-Qc)4] needs to be removed before the adsorption test. n The solvent molecules in the solution were removed. The resulting green blocky crystals were immersed in dichloromethane (DCM) for one week, with fresh DCM replaced every other day. Under vacuum conditions, the solvent-exchanged sample was heated to 100°C for 24 hours to obtain the activated sample a-[Cu2(6-Qc)4]. n .

[0057] 300 mg of activated sample material was used, and the single-component adsorption-desorption isotherms of ethane and ethylene at different temperatures were measured using a Bel-Sorp MAX instrument. The test temperature was controlled by a constant temperature bath. The test results are as follows: Figure 5 and Figure 6 As shown.

[0058] like Figure 5 As shown, the metal-organic framework material does not adsorb ethane at low pressure (<50 kPa), but when the pressure reaches 52-54 kPa, the adsorption capacity of ethane suddenly increases to 45 cm⁻¹. 3 / g, after which the adsorption capacity increases more gradually, stabilizing at approximately 48cm³. 3 / g.

[0059] Similarly, such as Figure 6 As shown, under low pressure conditions (<70 kPa), this material does not adsorb ethylene at all; however, when the pressure reaches 70 kPa, the amount of ethylene adsorbed increases sharply to 38 cm⁻¹. 3 / g, after which the adsorption rate leveled off, stabilizing at approximately 42cm³. 3 / g.

[0060] Both ethane and ethylene exhibit S-shaped single-component isothermal adsorption curves, indicating that the material possesses typical dynamic gate-opening behavior. Under the same temperature conditions, the gate-opening pressure of ethane is significantly lower than that of ethylene, suggesting that the material has the ability to preferentially adsorb ethane in an ethane-ethylene mixture.

[0061] Furthermore, comparing the difference in opening pressure between ethane and ethylene at the same temperature reveals that the differences are 16 kPa, 17.5 kPa, and 20 kPa at 303 K, 308 K, and 313 K, respectively, indicating that the difference in opening pressure between ethane and ethylene increases with increasing temperature (from 303 K to 313 K).

[0062] (2) Penetration test of the metal-organic framework material of the present invention through a mixture of ethane and ethylene gas.

[0063] A breakthrough experiment was conducted using the activated sample material to test its separation effect on an ethane-ethylene mixture. Test method: Approximately 1 g of the activated sample was packed into a 50 x 4.6 mm stainless steel packed column. An ethane / ethylene mixture with a volume ratio of 1:1 was passed through the column at a constant flow rate. The gas components exiting the column were monitored in real time by gas chromatography. The test results are as follows: Figure 7 As shown.

[0064] like Figure 7 As shown, when the ethane / ethylene mixing ratio is 1:1, ethylene elutes from the column in approximately 15 minutes, while ethane is only detected after 27 minutes, indicating that the two gases are effectively separated. Gas chromatography did not detect ethane gas in the first elute ethylene, meaning that high-purity ethylene can be obtained directly in a single breakthrough operation.

Claims

1. A copper-based metal-organic framework material, characterized in that, Its chemical formula is [Cu2(6-Qc)4] n Qc is 6-quinoline carboxylic acid; the central metal of the material is five-coordinate Cu. 2+ Two Cu 2+ The two binuclear structural units are connected by four carboxyl groups to form a paddlewheel-shaped binuclear structural unit; the 6-Qc ligand connects the adjacent binuclear structural units together through the nitrogen atom and carboxyl group on the quinoline ring, and finally stacks to form a three-dimensional porous framework.

2. The copper-based metal-organic framework material according to claim 1, characterized in that, The copper-based metal-organic framework material is a green crystal.

3. The copper-based metal-organic framework material according to claim 2, characterized in that, The unit cell parameters of the crystal are: a = 9.854 Å, b = 16.47 Å, c = 13.25 Å, α = 90°, β = 96.48°, γ = 90°.

4. The copper-based metal-organic framework material according to claim 1, characterized in that, The thermal decomposition temperature of the copper-based metal-organic framework material is 270℃.

5. A method for preparing a copper-based metal-organic framework material according to any one of claims 1 to 4, characterized in that, The process includes the following steps: adding cuprous salt, 6-quinoline carboxylic acid and triethylenediamine to N,N-dimethylformamide, dissolving them, and then heating the solution to react. During the reaction, solids precipitate out of the clear solution. After cooling and filtration, green crystals are obtained, which are the copper-based metal-organic framework material.

6. The method for preparing the copper-based metal-organic framework material according to claim 5, characterized in that, The reaction temperature of the heating reaction is 90~120℃.

7. The method for preparing the copper-based metal-organic framework material according to claim 5, characterized in that, The molar ratio of cuprous salt, 6-quinoline carboxylic acid and TEDA is 1:4:1~4.

8. The method for preparing the copper-based metal-organic framework material according to claim 5, characterized in that, The cuprous salt is CuI, CuBr, or CuCl.

9. The application of a copper-based metal-organic framework material according to any one of claims 1 to 4 in the adsorption and separation of ethane and ethylene.

10. In the application according to claim 9, the copper-based metal-organic framework material exhibits opening pressure differences of 16 kPa, 17.5 kPa, and 20 kPa for ethane and ethylene at 303 K, 308 K, and 313 K, respectively.

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