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

Abstract

The present invention provides a cobalt-based metal organic framework material and its preparation method and application, which relates to the field of porous adsorption materials. The chemical composition of the cobalt-based metal organic framework material provided by the present invention is [Co3(OH)(FINA)4(Solvent)2(EtOH)] + X ‑a 1 / a , wherein FINA is 3-fluoropyridine-4-carboxylate, Solvent is a methylamide-containing solvent, and X ‑a is an acid radical ion or a halide ion, and a is 1 or 2. The fluorine atoms in the cobalt-based metal-organic framework material provided by the present invention can polarize ethane. Methylamide solvents and ethanol can shield Co(II) sites. The material also contains a large number of methyl groups, providing numerous ethane adsorption sites and exhibiting excellent selective ethane adsorption performance. Methyl groups are hydrophobic groups that can mitigate the effects of water vapor on ethane-ethylene separation, demonstrating promising application prospects in the selective adsorption of ethane, particularly in the separation of ethane-ethylene mixed gases.

Description

Technical Field

[0001] The present invention relates to the field of porous adsorption materials, and in particular to a cobalt-based metal organic framework material and a preparation method and application thereof. Background Art

[0002] Ethylene is a very important chemical raw material, and its main downstream product is polyethylene. The main sources of ethylene in industry are naphtha cracking, methanol-to-olefins, and coal-to-olefins. A certain amount of ethane is inevitably produced in these industrial production processes, and the physical properties of ethane are very similar to those of ethylene, making the separation of ethane and ethylene very difficult. Low-temperature and high-pressure distillation technology is commonly used in industry to separate ethane and ethylene, but this separation method is very energy-intensive. The direct separation of ethane and ethylene using physical adsorbents at room temperature and low pressure consumes less energy. The physical adsorbents used are adsorbents that preferentially adsorb ethane to achieve ethylene purification.

[0003] Metal-organic frameworks (MOFs) offer advantages such as large surface area, adjustable pore size, and the ability to functionalize the pore surface, making them ideally suited for ethane-ethylene separation. Most MOFs possess metal sites that preferentially adsorb ethylene molecules due to electrostatic interactions. However, existing MOFs require multiple adsorption and desorption cycles to collect polymer-grade ethylene. Therefore, developing MOFs that selectively adsorb ethane is crucial.

[0004] It is not difficult to find in the reported metal-organic framework materials that the inert inner surface of the pores is an important indicator for preferentially adsorbing ethane and then purifying ethylene. Secondly, the size of the pores cannot be too large and should be close to the kinetic diameter of ethane. In addition, the pore surface can be modified with some less polar functional groups to enhance the dispersion force between the ethane molecules. For example, materials modified with methyl and amino groups can improve the ethane adsorption capacity. However, the functionalization of the ligands will inevitably increase the synthesis cost of the organic ligands. Therefore, it is very important to develop a low-cost, highly selective metal-organic framework material for separating ethane and ethylene mixtures.

[0005] Wang et al. (Wang 1-x(TMBDC) x (DABCO) 0.5 (x=0, 0.2, 0.45, 0.71, 1), the metal organic framework material has excellent ethane ethylene separation ability, and the organic ligand used in its material preparation is 2,3,5,6-tetramethylterephthalic acid, which is expensive. If it is homemade, its synthesis requires multi-step reaction, and its cost is too high and not suitable for batch production. Huajun Yang et al. (Yang H, Wang Y, Krishna R, et al. Pore-Space-Partition-Enabled Exceptional Ethane Uptake and Ethane-Selective Ethane-Ethylene Separation [J]. Journal of the American Chemical Society, 2020, 142, 2222-2227.) reported Co2V-bdc-tpt. Although the metal organic framework material has a high adsorption capacity for ethane, its selectivity coefficient for ethane is only 1.5, and its selectivity for ethane is low. In 2022, Wang et al. (see Wang GD, Krishna R, Li YZ, et al. Boosting Ethane / Ethylene Separation by MOFs through the Amino-Functionalization of Pores [J]. Angewandte Chemie International Edition, 2022. e202213015) reported that the Tb-MOF76 (NH2) material can retain water molecules on the metal clusters by controlling the temperature, resulting in the inertness of the pore surface and achieving the ability to preferentially adsorb ethane. However, the selectivity coefficient of this metal-organic framework material for ethane is only 2.1, and the selectivity for ethane is low. Summary of the Invention

[0006] In view of this, the object of the present invention is to provide a cobalt-based metal-organic framework material, a preparation method and application thereof. The cobalt-based metal-organic framework material provided by the present invention has excellent ethane selective adsorption performance, and has a high selectivity coefficient for ethane when used for ethane-ethylene separation and low cost.

[0007] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0008] The present invention provides a cobalt-based metal organic framework material, the chemical composition of which is [Co3(OH)(FINA)4(Solvent)2(EtOH)] + X -a1 / a , wherein FINA is 3-fluoropyridine-4-carboxylate, Solvent is a methylamide-containing solvent, X -a is an acid radical ion or a halogen ion, and a is 1 or 2.

[0009] Preferably, the X -a Including NO3 - 、CH3COO - 、SO4 2- 、CO3 2- 、F - 、Cl - Br - or I - .

[0010] Preferably, the methylamide-containing solvent includes N-methylacetamide, N,N-dimethylacetamide, N,N-dimethylformamide, N,N-diethylformamide or N-methylformamide.

[0011] The present invention provides a method for preparing the cobalt-based metal organic framework material described in the above technical solution, comprising the following steps:

[0012] A hydrated monometallic cobalt salt, 3-fluoropyridine-4-carboxylic acid and a methylamide-containing solvent are mixed and subjected to a solvent thermal reaction to obtain a cobalt-based metal organic framework material precursor; the anion in the hydrated monometallic cobalt salt is X -a , the X -a It is an acid ion or a halide ion;

[0013] The cobalt-based metal organic framework material precursor is sequentially subjected to anhydrous ethanol replacement and degassing to obtain a cobalt-based metal organic framework material.

[0014] Preferably, the molar ratio of the 3-fluoropyridine-4-carboxylic acid to the hydrated monometallic cobalt salt is 1:1.5-3.

[0015] Preferably, the molar ratio of the hydrated monometallic cobalt salt to the methylamide-containing solvent is 1:10-300.

[0016] Preferably, the temperature of the solvent thermal reaction is 110-140° C., and the time is 18-48 hours.

[0017] Preferably, the total time for the anhydrous ethanol replacement is 48 to 72 hours, and the anhydrous ethanol is replaced every 6 to 18 hours.

[0018] Preferably, the degassing temperature is 60-80° C. and the degassing time is 8-10 h.

[0019] The present invention provides the use of the cobalt-based metal organic framework material described in the above technical solution or the cobalt-based metal organic framework material prepared by the preparation method described in the above technical solution in the selective adsorption of ethane.

[0020] The present invention provides a cobalt-based metal organic framework material, the chemical composition of which is [Co3(OH)(FINA)4(Solvent)2(EtOH)] + X -a 1 / a , wherein FINA is 3-fluoropyridine-4-carboxylate, Solvent is a methylamide-containing solvent, X -a is an acid radical ion or a halogen ion, and a is 1 or 2. The cobalt-based metal organic framework material provided by the present invention shields the metal site, thereby eliminating the charge interaction between ethylene and the metal site, thereby reducing its ability to adsorb ethylene. The interior of the cobalt-based metal organic framework material is filled with fluorine atom groups and a large number of methyl functional groups. Since the polarizability of ethane is slightly greater than that of ethylene, fluorine atoms are more capable of polarizing ethane molecules, and a large number of methyl functional groups can enhance the polarization with ethane molecules, ultimately leading to preferential adsorption of ethane molecules. In addition to the improvement in selectivity, the presence of fluorine atoms can also produce intramolecular hydrogen bonds inside the skeleton, greatly improving the thermal stability of the material. And the methyl functional group is a hydrophobic group, which can greatly reduce the influence of water vapor on the separation effect of ethane and ethylene. In addition, the cobalt-based metal organic framework material provided by the present invention is an ultra-microporous material with a three-dimensional small pore size and a suitable specific surface area, which further improves the selective adsorption performance of ethane.

[0021] The present invention provides a method for preparing the cobalt-based metal-organic framework material described in the above technical solution. Compared with traditional methods of introducing methyl groups, the present invention utilizes methylamide-containing solvents to introduce methyl groups, while simultaneously protecting the Co(II) metal sites. This improves the selective adsorption performance of the cobalt-based metal-organic framework material for ethane while significantly reducing the cost of the cobalt-based metal-organic framework material. Furthermore, the preparation method provided by the present invention is simple to operate, has a wide range of raw material sources, is low-cost, is environmentally friendly, and is suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is an SEM image of the cobalt-based metal-organic framework material precursor prepared in Example 1;

[0023] Figure 2 Schematic diagram of the structure of CoFINA prepared in Example 1;

[0024] Figure 3 77K nitrogen adsorption isotherm of CoFINA prepared in Example 1;

[0025] Figure 4The adsorption isotherms of CoFINA prepared in Example 1 for ethane and ethylene at 298K;

[0026] Figure 5 The IAST separation coefficient curve of ethane / ethylene at 298K for CoFINA prepared in Example 1;

[0027] Figure 6 1 is the adsorption isotherm curve of CoINA prepared in Comparative Example 1 for ethane and ethylene at 298K;

[0028] Figure 7 This is the IAST separation coefficient curve of ethane / ethylene of CoINA prepared in Comparative Example 1 at 298K. DETAILED DESCRIPTION

[0029] The present invention provides a cobalt-based metal organic framework material, the chemical composition of which is [Co3(OH)(FINA)4(Solvent)2(EtOH)] + X -a 1 / a , wherein FINA is 3-fluoropyridine-4-carboxylate, Solvent is a methylamide-containing solvent ligand, and X -a is an acid radical ion or a halogen ion, and a is 1 or 2.

[0030] In the present invention, the methylamide-containing solvent preferably includes N-methylacetamide (NMA), N,N-dimethylacetamide (DMA), N,N-dimethylformamide (DMF), N,N-diethylformamide (DEF) or N-methylformamide (NMF), more preferably DMA.

[0031] In the present invention, the X -a Preferably including NO3 - 、CH3COO - 、SO4 2- 、CO3 2- 、F - 、Cl - Br - or I - .

[0032] In the present invention, the chemical composition of the cobalt-based metal organic framework material is preferably [Co3(OH)(FINA)4(DMA)2(EtOH)] + NO3 - (denoted as CoFINA), the CoFINA has a cage structure, the size of the cage structure is preferably The window size of the cage structure is CoFINA has excellent performance in capturing ethane at room temperature and pressure.

[0033] The present invention provides a method for preparing the cobalt-based metal organic framework material described in the above technical solution, comprising the following steps:

[0034] A hydrated monometallic cobalt salt, 3-fluoropyridine-4-carboxylic acid and a methylamide-containing solvent are mixed and subjected to a solvent thermal reaction to obtain a cobalt-based metal organic framework material precursor; the anion in the hydrated monometallic cobalt salt is X -a , the X -a It is an acid ion or a halide ion;

[0035] The cobalt-based metal organic framework material precursor is sequentially subjected to anhydrous ethanol replacement and degassing to obtain a cobalt-based metal organic framework material.

[0036] Unless otherwise specified, the raw materials used in the present invention are all commercially available products.

[0037] The invention mixes hydrated monometallic cobalt salt, 3-fluoropyridine-4-carboxylic acid (HFINA) and a methylamide-containing solvent, and performs a solvent thermal reaction to obtain a cobalt-based metal organic framework material precursor.

[0038] In the present invention, the anion in the hydrated monometallic cobalt salt is X -a , the X -a The acid radical ion or the halogen ion includes hydrated cobalt salt or hydrated cobalt halide; the cobalt ion in the hydrated single metal cobalt salt is Co 2+ The hydrated monometallic cobalt salt preferably includes cobalt nitrate hexahydrate, cobalt acetate tetrahydrate, cobalt sulfate heptahydrate, cobalt carbonate hydrate, cobalt chloride hexahydrate, cobalt bromide hexahydrate, cobalt iodide hexahydrate or cobalt fluoride hexahydrate.

[0039] In the present invention, the molar ratio of 3-fluoropyridine-4-carboxylic acid (FINA) to the hydrated monometallic cobalt salt is preferably 1:1.5-3, more preferably 1:2-2.5.

[0040] In the present invention, the molar ratio of the hydrated monometallic cobalt salt to the methylamide-containing solvent is preferably 1:10-300, more preferably 1:20-100, and further preferably 1:30-50; in a specific embodiment of the present invention, the ratio of the amount of the hydrated monometallic cobalt salt to the volume of the methylamide-containing solvent is preferably 0.28 mmol:1 mL.

[0041] In the present invention, the mixing is preferably ultrasonic mixing, and the time of the ultrasonic mixing is preferably 3 to 15 minutes, more preferably 5 to 10 minutes. The purpose of the ultrasonic mixing is to dissolve 3-fluoropyridine-4-carboxylic acid and hydrated monometallic cobalt salt in a methylamide-containing solvent.

[0042] In the present invention, the temperature of the solvothermal reaction is preferably 110-140°C, more preferably 115-130°C; the time of the solvothermal reaction is preferably 18-48 hours, more preferably 20-25 hours; and the solvothermal reaction is preferably carried out under sealed conditions. In the present invention, the chemical composition of the cobalt-based metal-organic framework material precursor is [Co3(OH)(FINA)4(Solvent)2(H2O)] + X -a 1 / a , among which FINA, Solvent, X -a and a and the chemical composition of the aforementioned cobalt-based metal organic framework material FINA, Solvent, X -a Same as a, no further details will be given here.

[0043] After the solvent thermal reaction, the present invention preferably further comprises cooling the obtained solvent thermal reaction liquid to room temperature and then performing solid-liquid separation, washing the obtained solid component, and obtaining a cobalt-based metal organic framework material precursor. The present invention has no special limitation on the cooling, and a cooling method well known to those skilled in the art can be adopted, such as natural cooling. The present invention has no special limitation on the solid-liquid separation, and a solid-liquid separation method well known to those skilled in the art can be adopted, such as centrifugation, filtration or suction filtration. In the present invention, the washing solvent preferably comprises a methylamide-containing solvent; the methylamide-containing solvent for washing is of the same type as the aforementioned methylamide-containing solvent, and will not be repeated here; the number of washings is preferably 2 to 5 times, more preferably 3 to 4 times; and the washing is preferably flushing.

[0044] After obtaining the cobalt-based metal organic framework material precursor, the present invention sequentially performs anhydrous ethanol replacement and degassing on the cobalt-based metal organic framework material precursor to obtain the cobalt-based metal organic framework material.

[0045] In the present invention, the total time for the anhydrous ethanol replacement is preferably 48 to 72 hours, preferably 60 to 72 hours; the anhydrous ethanol replacement process is preferably performed every 6 to 18 hours, more preferably every 6 to 8 hours; and the purity of the anhydrous ethanol is ≥ 99.7%. In the present invention, ethanol activation replaces water molecules in the cobalt-based metal-organic framework precursor with ethanol molecules while preserving the methylamide-containing solvent unaffected, thereby significantly improving the selective adsorption performance of the cobalt-based metal-organic framework for ethane.

[0046] In the present invention, the degassing temperature is preferably 60-80°C, more preferably 70-80°C; the degassing time is preferably 8-10 hours, more preferably 8-9 hours; the degassing is preferably carried out in a vacuum drying environment, more preferably vacuum degassing; the purpose of the degassing is to remove free organic solvent molecules (ethanol) in the pores and improve the selective adsorption performance of the cobalt-based metal-organic framework material for ethane.

[0047] The present invention provides the application of the cobalt-based metal organic framework material described in the above technical solution or the cobalt-based metal organic framework material obtained by the preparation method described in the above technical solution in the selective adsorption of ethane, and the application is preferably the separation of ethane and ethylene mixed gas. In the cobalt-based metal organic framework material provided by the present invention, the presence of fluorine atoms in 3-fluoropyridine-4-carboxylic acid allows hydrogen bonding to exist within the cobalt-based metal organic framework material, significantly improving the thermal stability of the material; moreover, the fluorine atoms themselves, as strong polar functional groups, can polarize ethane molecules and improve the selective adsorption performance of the material for ethane. Methylamide-containing solvent molecules and ethanol (EtOH) molecules can shield Co (II) metal sites as ligands. At the same time, methylamide-containing solvents and ethanol contain a large number of methyl groups, which point to the interior of the pores of the material, providing a large number of ethane adsorption sites (mainly due to the effect of dispersion forces), and have excellent selective adsorption performance for ethane. Moreover, methyl is a hydrophobic group, which can greatly reduce the influence of water vapor on the separation effect of ethane and ethylene, and has good application prospects in the selective adsorption of ethane, especially the separation of ethane and ethylene mixed gases.

[0048] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0049] In the following examples and comparative examples, the nitrogen adsorption curves of the prepared cobalt-based metal-organic framework materials at 77 K were measured using a Micromeritics ASAP 2420 adsorption instrument. Anhydrous ethanol was analytical grade ethanol.

[0050] Example 1

[0051] 0.28 mmol of cobalt nitrate hexahydrate, 0.14 mmol of 3-fluoropyridine-4-carboxylic acid, and 1 mL of N,N-dimethylacetamide were placed in a 10 mL glass vial with a press-on cap and ultrasonically mixed for 10 minutes. The mixture was sealed and placed in a 120°C constant temperature oven for 24 hours. The mixture was then cooled to room temperature, filtered, and the resulting solid product, N,N-dimethylacetamide, was rinsed three times to obtain a cobalt-based metal-organic framework precursor. The cobalt-based metal-organic framework precursor was then immersed in anhydrous ethanol at room temperature for 3 days, with the anhydrous ethanol replaced every 6 hours. The metal-organic framework material (named CoFINA) was then vacuum-degassed at 80°C for 10 hours to obtain the metal-organic framework material.

[0052] Figure 1 This is the SEM image of the cobalt-based metal organic framework material precursor. Figure 1 It can be seen that the cobalt-based metal-organic framework material precursor is a red block crystal.

[0053] Figure 2 Schematic diagram of the structure of CoFINA.

[0054] Figure 3 is the nitrogen adsorption isotherm of CoFINA at 77K, Figure 3 It can be seen that the BET specific surface area of ​​CoFINA is 452m 2 ·g -1 .

[0055] Figure 4 is the adsorption isotherm of CoFINA for ethane and ethylene at 298K. Figure 4 It can be seen that CoFINA adsorbs ethane at 50 cm2 at 298 K and 1 atm. 3 / g, adsorption of ethylene 26cm 3 / g. From the adsorption results, the adsorption amount of ethane is much greater than that of ethylene, which proves that CoFINA has the ability to selectively adsorb ethane.

[0056] Figure 5 is the IAST separation coefficient curve of ethane / ethylene of CoFINA at 298K, Figure 5 It can be seen that the ideal adsorption solution theory (IAST, C2H4 / C2H6 volume ratio = 1 / 1) predicts that the ethane selectivity coefficient at 101 kPa is 7.7 under room temperature conditions.

[0057] Example 2

[0058] 0.28mmol of cobalt nitrate hexahydrate, 0.14mmol of 3-fluoropyridine-4-carboxylic acid and 1mL of N,N-dimethylacetamide were placed in a 10mL small glass bottle with a pressure cap and ultrasonically mixed for 10min. After sealing, the mixture was placed in a constant temperature oven at 130°C for 24h, cooled to room temperature, filtered, and the obtained solid product N,N-dimethylacetamide was rinsed three times to obtain a cobalt-based metal organic framework material precursor. The cobalt-based metal organic framework material precursor was placed in anhydrous ethanol and soaked at room temperature for 3d, and the anhydrous ethanol was replaced every 6h, and then vacuum degassed at 80°C for 10h to obtain a metal organic framework material. The metal organic framework material prepared in this example has a selectivity coefficient for ethane that is basically the same as that of CoFINA.

[0059] Example 3

[0060] 0.28mmol of cobalt nitrate hexahydrate, 0.14mmol of 3-fluoropyridine-4-carboxylic acid and 1mL of N, N-dimethylacetamide were placed in a 10mL small glass bottle with a pressure cap and ultrasonically mixed for 10min. After sealing, it was placed in a constant temperature oven at 115°C for 24h, cooled to room temperature, filtered, and the resulting solid product N, N-dimethylacetamide was rinsed three times to obtain a cobalt-based metal organic framework material precursor. The cobalt-based metal organic framework material precursor was placed in anhydrous ethanol and soaked at room temperature for 3d, and the anhydrous ethanol was replaced every 6h, and then vacuum degassed at 80°C for 10h to obtain a metal organic framework material (named CoFINA). The metal organic framework material prepared in this embodiment has a selectivity coefficient for ethane that is substantially the same as that of CoFINA.

[0061] Example 4

[0062] 0.28mmol of cobalt nitrate hexahydrate, 0.14mmol of 3-fluoropyridine-4-carboxylic acid and 1mL of N, N-dimethylacetamide were placed in a 10mL small glass bottle with a pressure cap and ultrasonically mixed for 10min. After sealing, it was placed in a constant temperature oven at 130°C for 24h, cooled to room temperature, filtered, and the resulting solid product N, N-dimethylacetamide was rinsed three times to obtain a cobalt-based metal organic framework material precursor. The cobalt-based metal organic framework material precursor was placed in anhydrous ethanol and soaked at room temperature for 3d, and the anhydrous ethanol was replaced every 6h, and then vacuum degassed at 80°C for 10h to obtain a metal organic framework material (named CoFINA). The metal organic framework material prepared in this embodiment has a selectivity coefficient for ethane that is substantially the same as that of CoFINA.

[0063] Example 5

[0064] 0.28mmol of cobalt nitrate hexahydrate, 0.14mmol of 3-fluoropyridine-4-carboxylic acid and 1mL of N, N-dimethylacetamide were placed in a 10mL small glass bottle with a pressure cap and ultrasonically mixed for 10min. After sealing, the mixture was placed in a constant temperature oven at 140°C for 18h, cooled to room temperature, filtered, and the solid product N, N-dimethylacetamide was rinsed three times to obtain a cobalt-based metal organic framework material precursor. The cobalt-based metal organic framework material precursor was placed in anhydrous ethanol and soaked at room temperature for 3d, and the anhydrous ethanol was replaced every 6h, and then vacuum degassed at 80°C for 10h to obtain a metal organic framework material (named CoFINA). The metal organic framework material prepared in this embodiment has a selectivity coefficient for ethane that is substantially the same as that of CoFINA.

[0065] Comparative Example 1

[0066] A cobalt-based metal organic framework material was prepared according to the method of Example 1, the only difference from Example 1 being that 3-fluoropyridine-4-carboxylic acid was replaced with isonicotinic acid to obtain a cobalt-based metal organic framework material (named CoINA).

[0067] Figure 6 is the ethane and ethylene adsorption curve of CoINA at 298K, Figure 6 It can be seen that although the structure of CoINA is the same as that of CoFINA, CoINA does not have the ability to selectively adsorb ethane. This is because the Co metal site is exposed, resulting in CoINA preferentially adsorbing ethylene molecules.

[0068] Figure 7 IAST (C2H4 / C2H6 volume ratio = 1 / 1) for CoINA at room temperature predicted an ethylene selectivity coefficient of 3.4 at 101 kPa.

[0069] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A cobalt-based metal-organic framework material, characterized in that The chemical composition is [Co3(OH)(FINA)4(Solvent)2(EtOH)] + X -a 1 / a , wherein FINA is 3-fluoropyridine-4-carboxylate, Solvent is a methylamide solvent, X- a is an acid radical ion or a halogen ion, and a is 1 or 2.

2. The cobalt-based metal-organic framework material according to claim 1, characterized in that The X- a Including NO3 - 、CH3COO - 、SO4 2- 、CO3 2- 、F - 、Cl - Br - or I - .

3. The cobalt-based metal-organic framework material according to claim 1, characterized in that The methylamide-containing solvent includes N-methylacetamide, N,N-dimethylacetamide, N,N-dimethylformamide, N,N-diethylformamide or N-methylformamide.

4. The method for preparing the cobalt-based metal organic framework material according to any one of claims 1 to 3, characterized in that: The following steps are involved: A hydrated monometallic cobalt salt, 3-fluoropyridine-4-carboxylic acid and a methylamide-containing solvent are mixed and subjected to a solvent thermal reaction to obtain a cobalt-based metal organic framework material precursor; the anion in the hydrated monometallic cobalt salt is X -a , the X -a It is an acid ion or a halide ion; The cobalt-based metal organic framework material precursor is sequentially subjected to anhydrous ethanol replacement and degassing to obtain a cobalt-based metal organic framework material.

5. The preparation method according to claim 4, characterized in that The molar ratio of the 3-fluoropyridine-4-carboxylic acid to the hydrated monometallic cobalt salt is 1:1.5-3.

6. The preparation method according to claim 4, characterized in that The molar ratio of the hydrated monometallic cobalt salt to the methylamide-containing solvent is 1:10-300.

7. The preparation method according to claim 4, 5 or 6, characterized in that: The temperature of the solvent thermal reaction is 110-140° C., and the time is 18-48 hours.

8. The preparation method according to claim 4, characterized in that The total time for the anhydrous ethanol replacement is 48 to 72 hours, and the anhydrous ethanol is replaced every 6 to 18 hours.

9. The preparation method according to claim 4, characterized in that The degassing temperature is 60-80° C. and the degassing time is 8-10 hours.

10. Use of the cobalt-based metal organic framework material according to any one of claims 1 to 3 or the cobalt-based metal organic framework material prepared by the preparation method according to any one of claims 4 to 9 in the selective adsorption of ethane.

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