Preparation method and application of o-trifluoromethyl benzoic acid modified Ni-Mg-MOF-74

Abstract

The invention discloses a metal organic framework (MOF) with an efficient adsorption effect and a preparation method and application thereof, and belongs to the field of gas adsorption separation. According to the preparation method disclosed by the invention, solvent synthesis defects of the MOF material are utilized, a polar tube energy group is introduced to replace a defect group, and an adsorption dead zone is eliminated, so that the o-trifluoromethyl benzoic acid modified Ni-Mg-MOF-74 material capable of efficiently adsorbing is obtained. The MOF material prepared by the invention has excellent CO2 adsorption capacity and high CO2 / N2 selectivity.

Description

Technical Field

[0001] This invention belongs to the field of gas adsorption and separation, specifically relating to the preparation method of o-trifluoromethylbenzoic acid modified Ni-Mg-MOF-74 and its application in CO2 adsorption. Background Technology

[0002] With industrial development, humanity has had an unprecedented impact on the environment. The process of industrialization has led to the emission of greenhouse gases. Large amounts of CO2 emissions have had a significant impact on the environment, such as ocean acidification and global warming. Therefore, carbon reduction is an urgent task. Most of the emitted CO2 comes from the flue gas of power plants that burn fossil fuels; therefore, reducing CO2 emissions from point sources can be achieved through carbon capture and storage (CCS) technology.

[0003] Various physical adsorption materials have been reported for carbon dioxide adsorption, but they face problems such as high energy consumption and equipment corrosion. Compared with traditional adsorbents, metal-organic frameworks (MOFs) have advantages such as high specific surface area and easily adjustable pore size, and are widely used in gas adsorption and separation. MOF-74 greatly improves CO2 adsorption capacity due to its high density of open metal sites, but this also makes it highly susceptible to water adsorption, causing structural collapse. Therefore, it is necessary to improve the water stability and high adsorption capacity of the framework. Summary of the Invention

[0004] This invention addresses the problems of poor material structural stability and low CO2 / N2 selectivity by introducing polar tube groups to address the shortcomings of solvent synthesis. It provides a method for preparing o-trifluoromethylbenzoic acid-modified Ni-Mg-MOF-74 and its application in CO2 adsorption. The Ni-Mg-MOF-74-TBA of this invention enhances material stability and increases CO2 adsorption capacity.

[0005] The preparation method of Ni-Mg-MOF-74-TBA material of the present invention includes the following steps: Dry Ni-Mg-MOF-74 and a certain mass of o-trifluoromethylbenzoic acid are dispersed or dissolved in 20 mL of DMF, and stirred evenly respectively; the two solutions are mixed and stirred for 2 hours, then reacted in an oil bath at 70°C for 24 hours; after the reaction, the product is washed successively with 30 mL of diethyl ether and 50 mL of acetone; finally, it is vacuum dried at 60°C for 24 hours to obtain the Ni-Mg-MOF-74-TBA material.

[0006] Furthermore, the synthesis method of the Ni-Mg-MOF-74 precursor includes: dissolving H4dobdc, magnesium salt, and nickel salt in a mixed solvent composed of DMF, ethanol, and water, with a total volume of 25 mL, and placing the solution in a 50 mL reaction flask and sonicating it until fully dissolved; after stirring for 1 hour, transferring the mixed solution to a 100 mL reaction vessel liner and continuing to stir for 2 hours; sealing the reaction vessel and reacting at 135°C for 24 hours; after the reaction, washing twice with DMF and four times with methanol; collecting the solid product and vacuum drying at 60°C for 24 hours to obtain the Ni-Mg-MOF-74 precursor, which is then activated under vacuum conditions for later use.

[0007] Furthermore, in the preparation method of the Ni-Mg-MOF-74-TBA material of the present invention, the mass ratio of Ni-Mg-MOF-74 to o-trifluoromethylbenzoic acid is 20:19.

[0008] Furthermore, in the preparation method of Ni-Mg-MOF-74 material of the present invention, the nickel salt and magnesium salt are NiCl2 and MgCl2, and the molar mass ratio of NiCl2 and MgCl2 is: 0.76:0.24, 0.54:0.46, 0.32:0.68, 1:0.

[0009] Furthermore, in the preparation method of Ni-Mg-MOF-74 material of the present invention, the volume ratio of DMF / ethanol / water is 15:1:1.

[0010] Furthermore, in the preparation method of the MOF material Ni-Mg-MOF-74-TBA of the present invention, the conditions for the vacuum activation step are: activation at 255°C for 12 hours.

[0011] The MOF material Ni-Mg-MOF-74-TBA of the present invention exhibits excellent CO2 adsorption performance and CO2 / N2 selectivity.

[0012] (1) At 298K and 1 atm, Ni 0.32 Mg 0.68 The saturated CO2 adsorption capacity of -MOF-74-TBA is 214 cm⁻¹. 3 / g.

[0013] (2) Specific CO2 capture applications exhibit excellent adsorption capacity. Under a pressure of 112 mmHg (post-combustion carbon dioxide capture-PC), Ni-Mg-MOF-74-TBA demonstrates excellent adsorption performance, with CO2 adsorption capacity reaching 114-149 cm⁻¹. 3 / g.

[0014] (3) Ni 0.32 Mg 0.68-MOF-74-TBA exhibits a CO2 / N2 adsorption selectivity of 550. Compared to previous benchmark materials, Ni-Mg-MOF-74-TBA demonstrates superior CO2 adsorption capacity and high CO2 / N2 adsorption selectivity. Attached Figure Description

[0015] Figure 1 The powder X-ray diffraction pattern of the Ni-Mg-MOF-74 precursor in Examples 1-4 is shown.

[0016] Figure 2 The powder X-ray diffraction patterns of Ni-Mg-MOF-74-TBA in Examples 1-4 are shown.

[0017] Figure 3 The Fourier transform infrared spectrum of the Ni-Mg-MOF-74 precursor in Example 1-4 is shown.

[0018] Figure 4 The Fourier transform infrared spectrum of the Ni-Mg-MOF-74-TBA precursor in Example 1-4 is shown.

[0019] Figure 5 The image shows the SEM image of the Ni-Mg-MOF-74 precursor in Example 3.

[0020] Figure 6 The image shows the SEM image of Example 3, Ni-Mg-MOF-74-TBA.

[0021] Figure 7 The CO2 adsorption curve of the Ni-Mg-MOF-74 precursor in Example 5 is shown.

[0022] Figure 8 The N2 adsorption curve of the Ni-Mg-MOF-74 precursor in Example 6 is shown.

[0023] Figure 9 The CO2 adsorption curve is shown for Ni-Mg-MOF-74-TBA in Example 7.

[0024] Figure 10 The N2 adsorption curve is shown for Example 8, Ni-Mg-MOF-74-TBA.

[0025] Figure 11 The CO2 / N2 adsorption selectivity of the Ni-Mg-MOF-74 precursor in Example 9.

[0026] Figure 12 The CO2 / N2 adsorption selectivity of Example 10 Ni-Mg-MOF-74-TBA. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings.

[0028] Example 1: 1.Ni 0.76 Mg 0.24 The synthesis method of the MOF-74 precursor includes: dissolving 0.1661 g H4dobdc, 0.3936 g nickel chloride hexahydrate, and 0.1063 g magnesium chloride hexahydrate in a mixed solvent composed of DMF, ethanol, and water, with a total volume of 25 mL. The solution is placed in a 50 mL reaction flask and sonicated to ensure complete dissolution. After stirring for 1 hour, the solution is transferred to a 100 mL reaction vessel liner and stirred for another 2 hours. The reaction vessel is sealed and reacted at 135 °C for 24 hours. After the reaction, the product is washed twice with DMF and four times with methanol. The solid product is collected and vacuum dried at 60 °C for 24 hours to obtain Ni. 0.76 Mg 0.24 -MOF-74 precursor, activated under vacuum conditions for later use.

[0029] 2. After drying, 200 mg of Ni 0.76 Mg 0.24 The MOF-74 precursor and 120 mg of o-trifluoromethylbenzoic acid were separately dispersed or dissolved in 20 mL of DMF and stirred thoroughly. The two solutions were then mixed and stirred for 2 hours, followed by reaction in a 70°C oil bath for 24 hours. After the reaction, the product was washed successively with 30 mL of diethyl ether and 50 mL of acetone. Finally, the product was vacuum dried at 60°C for 24 hours to obtain Ni. 0.76 Mg 0.24 -MOF-74-TBA material.

[0030] Example 2: 1.Ni 0.54 Mg 0.46 The synthesis method of the MOF-74 precursor includes: dissolving 0.1661 g H4dobdc, 0.2797 g nickel chloride hexahydrate, and 0.2038 g magnesium chloride hexahydrate in a mixed solvent composed of DMF, ethanol, and water, with a total volume of 25 mL. The solution is placed in a 50 mL reaction flask and sonicated to ensure complete dissolution. After stirring for 1 hour, the solution is transferred to a 100 mL reaction vessel liner and stirred for another 2 hours. The reaction vessel is sealed and reacted at 135 °C for 24 hours. After the reaction, the product is washed twice with DMF and four times with methanol. The solid product is collected and vacuum dried at 60 °C for 24 hours to obtain Ni. 0.54 Mg 0.46-MOF-74 precursor, activated under vacuum conditions for later use.

[0031] 2. After drying, 200mg of Ni 0.54 Mg 0.46 The MOF-74 precursor and 120 mg of o-trifluoromethylbenzoic acid were separately dispersed or dissolved in 20 mL of DMF and stirred thoroughly. The two solutions were then mixed and stirred for 2 hours, followed by reaction in a 70°C oil bath for 24 hours. After the reaction, the product was washed successively with 30 mL of diethyl ether and 50 mL of acetone. Finally, the product was vacuum dried at 60°C for 24 hours to obtain Ni. 0.54 Mg 0.46 -MOF-74-TBA material.

[0032] Example 3: 1.Ni 0.32 Mg 0.68 The synthesis method of the MOF-74 precursor includes: dissolving 0.1661 g H4dobdc, 0.1657 g nickel chloride hexahydrate, and 0.3012 g magnesium chloride hexahydrate in a mixed solvent composed of DMF, ethanol, and water, with a total volume of 25 mL. The solution is placed in a 50 mL reaction flask and sonicated to ensure complete dissolution. After stirring for 1 hour, the solution is transferred to a 100 mL reaction vessel liner and stirred for another 2 hours. The reaction vessel is sealed and reacted at 135 °C for 24 hours. After the reaction, the product is washed twice with DMF and four times with methanol. The solid product is collected and vacuum dried at 60 °C for 24 hours to obtain Ni. 0.32 Mg 0.68 -MOF-74 precursor, activated under vacuum conditions for later use.

[0033] 2. After drying, 200 mg of Ni 0.32 Mg 0.68 The MOF-74 precursor and 120 mg of o-trifluoromethylbenzoic acid were separately dispersed or dissolved in 20 mL of DMF and stirred thoroughly. The two solutions were then mixed and stirred for 2 hours, followed by reaction in a 70°C oil bath for 24 hours. After the reaction, the product was washed successively with 30 mL of diethyl ether and 50 mL of acetone. Finally, the product was vacuum dried at 60°C for 24 hours to obtain Ni. 0.32 Mg 0.68 -MOF-74-TBA material.

[0034] Example 4: 1. The synthesis method of Ni-MOF-74 precursor includes: dissolving 0.1661 g H4dobdc and 0.5179 g nickel chloride hexahydrate in a mixed solvent composed of DMF, ethanol and water, with a total volume of 25 mL. The solution is placed in a 50 mL reaction flask and sonicated to ensure complete dissolution. After stirring for 1 hour, the mixed solution is transferred to a 100 mL reaction vessel liner and stirred for another 2 hours. The reaction vessel is sealed and reacted at 135 °C for 24 hours. After the reaction, the product is washed twice with DMF and four times with methanol. The solid product is collected and vacuum dried at 60 °C for 24 hours to obtain Ni-MOF-74 precursor, which is then activated under vacuum for later use.

[0035] 2. 200 mg of dried Ni-MOF-74 precursor and 120 mg of o-trifluoromethylbenzoic acid were dispersed or dissolved in 20 mL of DMF and stirred evenly. The two solutions were mixed and stirred for 2 hours, and then reacted in an oil bath at 70 °C for 24 hours. After the reaction was completed, the product was washed with 30 mL of diethyl ether and 50 mL of acetone in sequence. Finally, the product was vacuum dried at 60 °C for 24 hours to obtain Ni-MOF-74-TBA material.

[0036] Example 5: CO2 adsorption performance test of Ni-Mg-MOF-74 precursor Weigh a clean glass tube and record it as m1. Weigh approximately 100 mg of the Ni-Mg-MOF-74 precursor and place it in the glass tube. Record the total mass of the glass tube and sample as m2. Then, install the glass tube in the pretreatment station of the adsorption instrument and set the pretreatment temperature and time to 255℃ for 10 hours. After treatment, weigh the glass tube and sample and record the total mass as m3. The net mass of the sample is m3 - m1. Then, place the glass tube containing the sample in the analysis station of the adsorption instrument, set the processing parameters, and test the CO2 adsorption curve at 298K. The results are as follows: Figure 6 .

[0037] Example 6: N2 adsorption performance test of Ni-Mg-MOF-74 precursor Weigh a clean glass tube and record it as m1. Weigh approximately 100 mg of the Ni-Mg-MOF-74 precursor and place it in the glass tube. Record the total mass of the glass tube and sample as m2. Then, install the glass tube in the pretreatment station of the adsorption instrument and set the pretreatment temperature and time to 255℃ for 10 hours. After treatment, weigh the glass tube and sample and record the total mass as m3. The net mass of the sample is m3 - m1. Then, place the glass tube containing the sample in the analysis station of the adsorption instrument, set the treatment parameters, and test the N2 adsorption curve at 298 K. The results are as follows: Figure 7 .

[0038] Example 7: CO2 adsorption performance test of Ni-Mg-MOF-74-TBA Weigh a clean glass tube and record it as m1. Weigh approximately 100 mg of Ni-Mg-MOF-74-TBA and place it in the glass tube. Record the total mass of the glass tube and sample as m2. Then, install the glass tube in the pretreatment station of the adsorption instrument and set the pretreatment temperature and time to 255℃ for 10 hours. After treatment, weigh the glass tube and sample and record the total mass as m3. The net mass of the sample is m3 - m1. Then, place the glass tube containing the sample in the analysis station of the adsorption instrument, set the processing parameters, and test the CO2 adsorption curve at 298K. The results are as follows: Figure 6 .

[0039] Example 8: N2 adsorption performance test of Ni-Mg-MOF-74-TBA Weigh a clean glass tube and record it as m1. Weigh approximately 100 mg of Ni-Mg-MOF-74-TBA and place it in the glass tube. Record the total mass of the glass tube and sample as m2. Then, install the glass tube in the pretreatment station of the adsorption instrument and set the pretreatment temperature and time to 255℃ for 10 hours. After treatment, weigh the glass tube and sample and record the total mass as m3. The net mass of the sample is m3 - m1. Then, place the glass tube containing the sample in the analysis station of the adsorption instrument, set the treatment parameters, and test the N2 adsorption curve at 298 K. The results are as follows: Figure 7 .

[0040] Example 9: The adsorption selectivity of the mixed gas was calculated using the ideal adsorption solution theory (IAST) based on the CO2 and N2 adsorption curves obtained in Examples 5 and 6.

[0041] Example 10: The adsorption selectivity of the mixed gas was calculated using the ideal adsorption solution theory (IAST) based on the CO2 and N2 adsorption curves obtained in Examples 7 and 8.

[0042] Comparative Example 1: Changing the reaction temperature of Example 1 to 110 and 120 °C, while keeping other steps and conditions unchanged, ultimately failed to obtain the target product Ni-Mg-MOF-74 with crystallinity.

[0043] Comparative Example 2: In Example 5, the pretreatment temperature and time were set to 255℃ and 10 hours. If the pretreatment temperature or the pretreatment time was reduced, the CO2 saturated adsorption capacity would decrease.

Claims

1. The application of a Ni-Mg-MOF-74 material modified with o-trifluoromethylbenzoic acid in CO2 separation, characterized in that, By utilizing the inherent defects of the in-situ formate in the material, o-trifluoromethylbenzoic acid was introduced through post-synthesis modification to partially replace the formate, thus obtaining a MOF material with polar functional groups, denoted as Ni-Mg-MOF-74-TBA.

2. The application according to claim 1, characterized in that, The preparation method of the Ni-Mg-MOF-74-TBA material includes the following steps: Dry Ni-Mg-MOF-74 and a certain mass of o-trifluoromethylbenzoic acid are separately dispersed in 20 mL of DMF and stirred evenly; the two solutions are mixed and stirred for 2 hours, then reacted in an oil bath at 70°C for 24 hours; after the reaction, the product is washed with 100 mL of acetone; finally, it is vacuum dried at 60°C for 24 hours to obtain the Ni-Mg-MOF-74-TBA material.

3. The preparation method of the MOF material Ni-Mg-MOF-74-TBA according to claim 2, characterized in that, The synthesis method of the Ni-Mg-MOF-74 precursor includes: dissolving H4dobdc, magnesium salt, and nickel salt in a mixed solvent composed of DMF, ethanol, and water, with a total volume of 25 mL, and placing the solution in a 50 mL reaction flask and sonicating it until fully dissolved; stirring for 1 hour, transferring the mixed solution to a 100 mL reaction vessel liner, and continuing stirring for 2 hours; sealing the reaction vessel and reacting at 135°C for 24 hours; after the reaction, washing twice with DMF (3 hours apart each time) and four times with methanol (12 hours apart each time); collecting the solid product, vacuum drying at 60°C for 24 hours to obtain the Ni-Mg-MOF-74 precursor, and activating it under vacuum conditions for later use.

4. The preparation method of the MOF material Ni-Mg-MOF-74-TBA according to claim 2, characterized in that, The mass ratio of Ni-Mg-MOF-74 to o-trifluoromethylbenzoic acid is 20:

19.

5. The preparation method of the MOF material Ni-Mg-MOF-74-TBA according to claim 3, characterized in that, The nickel and magnesium salts are NiCl2 and MgCl2, respectively, with the following molar mass ratios: 0.76:0.24, 0.54:0.46, 0.32:0.68, and 1:

0.

6. The preparation method of the MOF material Ni-Mg-MOF-74-TBA according to claim 3, characterized in that, The volume ratio of DMF / ethanol / water is 15:1:

1.

7. The method for preparing the MOF material Ni-Mg-MOF-74-TBA according to claim 3, characterized in that, The conditions for the vacuum activation step are: activation at 255°C for 12 hours.

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