Preparation method and application of metal organic framework material

Abstract

The present invention relates to a preparation method and application of a metal organic framework material, the method comprising the steps of: dissolving an iron salt and a nickel salt in N,N-dimethylacetamide and stirring evenly to form a first solution; dissolving terephthalic acid containing a halogen substituent in N,N-dimethylacetamide and stirring evenly to form a second solution; mixing the first solution and the second solution and stirring evenly to form a third solution; heating the third solution to a preset temperature and maintaining it for a preset time, and then cooling, washing, centrifuging and drying to obtain a metal organic framework material. The preparation method and application of the metal organic framework material of the present invention adopts terephthalic acid containing a halogen substituent as an organic ligand to react with metal ions, thereby adjusting the properties of the metal organic framework material, and greatly improving its oxygen production activity when applied to water electrolysis.

Description

Technical Field

[0001] The present invention relates to the technical field of metal organic framework materials, and more specifically to a preparation method and application of a metal organic framework material. Background Art

[0002] Metal organic frameworks (MOFs) are a type of coordination polymer that has developed rapidly in recent years. They have a three-dimensional pore structure and are widely used in many fields such as water electrolysis.

[0003] In the prior art, MOFs are mainly optimized by regulating metal sites, such as changing the composition, proportion or coordination saturation of metal sites. However, there are fewer ways to regulate ligands, which are generally modified by amino or carboxyl groups to simply adjust the surface properties of MOFs.

[0004] However, existing metal-organic framework materials have poor oxygen production performance when applied to water electrolysis. Summary of the invention

[0005] The purpose of the present invention is to provide a preparation method and application of a metal organic framework material, using halogen-modified ligands to optimize the metal organic framework material so that its oxygen production performance can be significantly improved compared with existing metal framework materials.

[0006] Based on the above purpose, the present invention provides a method for preparing a metal organic framework material, comprising the following steps:

[0007] Dissolving iron salt and nickel salt in N,N-dimethylacetamide and stirring evenly to form a first solution;

[0008] Dissolving an organic ligand in N,N-dimethylacetamide and stirring evenly to form a second solution, wherein the organic ligand is terephthalic acid containing a halogen substituent;

[0009] Mixing the first solution and the second solution and stirring them uniformly to form a third solution;

[0010] The third solution is heated to a preset temperature and maintained for a preset time, so that the iron ions, nickel ions and organic ligands are self-assembled, and then the metal organic framework material is obtained after cooling, washing, centrifugation and drying.

[0011] Furthermore, the iron salt is ferric chloride hexahydrate or ferric nitrate nonahydrate, and the nickel salt is nickel chloride hexahydrate or nickel nitrate hexahydrate.

[0012] Furthermore, in the first solution, the molar ratio of iron ions to nickel ions is 1:1 to 5:1.

[0013] Furthermore, the terephthalic acid containing a halogen substituent is 2-fluoroterephthalic acid, 2-chloroterephthalic acid or 2-bromoterephthalic acid.

[0014] Further, when the terephthalic acid containing a halogen substituent is 2-fluoroterephthalic acid, the preset temperature is 140-160° C.;

[0015] When the terephthalic acid containing a halogen substituent is 2-chloroterephthalic acid or 2-bromoterephthalic acid, the preset temperature is 170-185°C.

[0016] Furthermore, the preset time is 12-24 hours.

[0017] Further, the metal organic framework material is obtained after cooling, washing, centrifuging and drying, which specifically includes:

[0018] The solid is naturally cooled to room temperature and washed with ethanol and deionized water for multiple times, and then centrifuged to obtain a solid. The solid is transferred to an oven and dried at a temperature of 26-60° C. for 8-24 hours to obtain a metal organic framework material.

[0019] Another aspect of the present invention provides an application of a metal organic framework material prepared by the method for preparing the metal organic framework material as described above, wherein the metal organic framework material is coated on a working electrode as an anode catalyst for electrolyzing water.

[0020] Furthermore, the working electrode is a glassy carbon electrode.

[0021] Furthermore, the metal organic framework material is mixed with carbon powder and dissolved in a mixed solution containing deionized water, isopropanol and naphthalene, and then rolled; and then coated on a glassy carbon electrode to be used as a working electrode.

[0022] Furthermore, the metal active centers in the metal organic framework material are adjusted by the halogen in the organic ligand to promote the adsorption of oxygen-containing intermediate species.

[0023] Furthermore, the metal active center is nickel.

[0024] The preparation method and application of the metal organic framework material of the present invention adopts terephthalic acid containing halogen substituents as an organic ligand to react with metal ions, thereby adjusting the properties of the metal organic framework material. After modification with halogens with relatively large electronegativity, the Bader charge of nickel, an active center in the metal organic framework material, is greatly improved, and the center of the Ni-3d band is closer to the Fermi level, thereby promoting the adsorption of oxygen-containing species in the reaction by the metal organic framework material, and greatly improving its oxygen production activity when applied to water electrolysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A flow chart of a method for preparing a metal organic framework material according to the present invention;

[0026] Figure 2 The current density-potential diagram of the metal organic framework materials of the control group and the experimental group 1 according to the present invention during the water electrolysis test;

[0027] Figure 3 The current density-potential diagram of the metal organic framework materials of the control group and the experimental group 2 according to the present invention during the water electrolysis test;

[0028] Figure 4 1 is a current density-potential diagram of the metal organic framework materials of the control group and the experimental group 3 according to the present invention during the water electrolysis test. DETAILED DESCRIPTION

[0029] The preferred embodiments of the present invention are given below in conjunction with the accompanying drawings and described in detail.

[0030] like Figure 1 As shown, the present invention provides a method for preparing a metal organic framework material, which comprises the following steps:

[0031] S100: dissolving iron salt and nickel salt in N,N-dimethylacetamide and stirring evenly to form a first solution.

[0032] The iron salt and the nickel salt are used to provide iron ions and nickel ions, respectively, so as to self-assemble with the organic ligands in a fixed ratio through coordination bonds to form a nanocrystalline structure in the subsequent step, thereby obtaining the desired metal organic framework material. For example, the iron salt can be ferric chloride hexahydrate (FeCl3·6H2O) or ferric nitrate nonahydrate (Fe(NO3)3·9H2O), and the nickel salt can be nickel chloride hexahydrate (NiCl2·6H2O) or nickel nitrate hexahydrate (Ni(NO3)2·6H2O).

[0033] S200: dissolving terephthalic acid containing a halogen substituent in N,N-dimethylacetamide and stirring the solution to form a second solution.

[0034] Wherein, the organic ligand is terephthalic acid containing halogen substituents. The terephthalic acid containing halogen substituents is one of 2-fluoroterephthalic acid, 2-chloroterephthalic acid and 2-bromoterephthalic acid. Iron ions, nickel ions and organic ligands need to be self-assembled under certain proportions and concentration conditions, wherein the amount ratio of terephthalic acid containing halogen substituents to the sum of metal ions (i.e., the sum of iron ions and nickel ions) is 1:1. Under the premise of ensuring the above ratio, the ratio between iron ions and nickel ions can be regulated as needed, for example, the amount ratio of iron ions and nickel ions can be (1 to 5): 1, preferably 3: 1. In an exemplary embodiment, the iron salt is ferric chloride hexahydrate, the nickel salt is nickel nitrate hexahydrate, and the amount ratio of terephthalic acid containing halogen substituents, ferric chloride hexahydrate, and nickel nitrate hexahydrate is 4: 3: 1.

[0035] S300: mixing the first solution and the second solution and stirring them uniformly to form a third solution;

[0036] S400: The third solution is heated to a preset temperature and maintained for a preset time, and then cooled, washed, centrifuged and dried to obtain a metal organic framework material.

[0037] At a preset temperature, iron ions, nickel ions and organic ligands will react. After the preset reaction time, they are naturally cooled to room temperature, and then repeatedly washed and centrifuged to obtain a solid. The solid can be dried to obtain an iron-nickel based metal organic framework material. For example, it can be dried in an oven at a temperature of 26-60°C (preferably 40°C) for 8-24 hours (preferably 12 hours).

[0038] The following will take 2-fluoroterephthalic acid, 2-chloroterephthalic acid and 2-bromoterephthalic acid as examples to specifically illustrate the preparation methods of the metal organic framework materials according to different embodiments of the present invention.

[0039] In the first embodiment of the present invention, the terephthalic acid containing a halogen substituent is 2-fluoroterephthalic acid, and the preparation method of the corresponding metal organic framework material comprises the following steps:

[0040] S11: Weigh 0.15 mmol of ferric chloride hexahydrate and 0.05 mmol of nickel nitrate hexahydrate respectively, then dissolve them in 1 ml of N,N-dimethylacetamide, and stir them evenly with a magnetic force to form a first solution;

[0041] S12: Weigh 0.2 mmol of 2-fluoroterephthalic acid and dissolve it in 2 ml of N,N-dimethylacetamide, and stir it evenly with a magnetic force to form a second solution;

[0042] S13: mixing the first solution and the second solution and stirring them uniformly to form a third solution;

[0043] S14: The third solution is transferred to a high-pressure reactor, heated to a preset temperature of 150°C, and then maintained at this temperature for a preset time of 15 hours, so that the iron ions, nickel ions and organic ligands can fully react; after the reaction is completed, it is naturally cooled to room temperature, and then the reactants are repeatedly washed with ethanol and deionized water for multiple times, and then a solid is obtained by centrifugation, and the solid is transferred to an oven at 40°C for drying for 12 hours to obtain a metal organic framework material F-FeNi-MOF.

[0044] The preset temperature may also be any temperature between 140° C. and 160° C., and the preset time may also be any time between 12 hours and 24 hours.

[0045] In a second embodiment of the present invention, the terephthalic acid containing a halogen substituent is 2-chloroterephthalic acid, and the preparation method of the corresponding metal organic framework material comprises the following steps:

[0046] S21: Weigh 0.075 mmol of ferric chloride hexahydrate and 0.025 mmol of nickel nitrate hexahydrate respectively, then dissolve them in 1 ml of N,N-dimethylacetamide, and stir them evenly with a magnetic force to form a first solution;

[0047] S22: Weigh 0.1 mmol of 2-chloroterephthalic acid and dissolve it in 2 ml of N,N-dimethylacetamide, and stir it evenly with a magnetic force to form a second solution;

[0048] S23: mixing the first solution and the second solution and stirring them uniformly to form a third solution;

[0049] S24: The third solution is transferred to a high-pressure reactor, heated to a preset temperature of 180°C, and then maintained at this temperature for a preset time of 15 hours, so that the iron ions, nickel ions and organic ligands can fully react; after the reaction is completed, it is naturally cooled to room temperature, and then the reactants are repeatedly washed with ethanol and deionized water for multiple times, and then a solid is obtained by centrifugation, and the solid is transferred to an oven at 40°C and dried for 12 hours to obtain a metal organic framework material Cl-FeNi-MOF.

[0050] The preset temperature may also be any temperature between 170° C. and 185° C., and the preset time may also be any time between 12 hours and 24 hours.

[0051] In a third embodiment of the present invention, the terephthalic acid containing a halogen substituent is 2-bromoterephthalic acid, and the preparation method of the corresponding metal organic framework material comprises the following steps:

[0052] S31: Weigh 0.075 mmol of ferric chloride hexahydrate and 0.025 mml of nickel nitrate hexahydrate respectively, then dissolve them in 1 ml of N,N-dimethylacetamide, and stir them evenly with a magnetic force to form a first solution;

[0053] S32: Weigh 0.1 mmol of 2-bromoterephthalic acid and dissolve it in 2 ml of N,N-dimethylacetamide, and stir it evenly with a magnetic force to form a second solution;

[0054] S33: mixing the first solution and the second solution and stirring them uniformly to form a third solution;

[0055] S34: The third solution is transferred to a high-pressure reactor, heated to a preset temperature of 185°C, and then maintained at this temperature for a preset time of 15 hours, so that the iron ions, nickel ions and organic ligands can fully react; after the reaction is completed, it is naturally cooled to room temperature, and then the reactants are repeatedly washed with ethanol and deionized water for multiple times, and then a solid is obtained by centrifugation, and the solid is transferred to an oven at 40°C and dried for 12 hours to obtain a metal organic framework material Br-FeNi-MOF.

[0056] The preset temperature may also be any temperature between 170° C. and 185° C., and the preset time may also be any time between 12 hours and 24 hours.

[0057] The present invention also provides an application of the metal organic framework material prepared by the method. When applied, the metal organic framework material is coated on a working electrode and used as an anode catalyst to electrolyze water.

[0058] In order to verify the effect of the metal organic framework material prepared by the preparation method of the present invention in the electrolysis of water, the electrolysis of water using the metal organic framework material without halogen was used as the control group, and the electrolysis of water using the metal organic framework material prepared by the methods of the first, second and third embodiments of the present invention were used as experimental groups 1-3 respectively, and the control group and experimental groups 1-3 were compared.

[0059] The halogen-free metal organic framework material uses terephthalic acid as an organic ligand, and the preparation method thereof comprises the following steps:

[0060] S41: Weigh 0.0375 mmol of ferric chloride hexahydrate and 0.0125 mmol of nickel nitrate hexahydrate respectively, dissolve them in 1 mL of N,N-dimethylacetamide, and stir them evenly with a magnetic stirrer to form a first solution;

[0061] S42: Weigh 0.05 mmol of terephthalic acid and dissolve it in 2 ml of N,N-dimethylacetamide, and stir the mixture magnetically to form a second solution;

[0062] S43: mixing the first solution and the second solution and stirring them uniformly to form a third solution;

[0063] S44: The third solution is transferred to a high-pressure reactor, heated to a preset temperature of 140-160°C, and then maintained at this temperature for a preset time of 12-24 hours, so that the iron ions, nickel ions and organic ligands can fully react; after the reaction is completed, it is naturally cooled to room temperature, and then the reactants are repeatedly washed with ethanol and deionized water for multiple times, and then a solid is obtained by centrifugation, and the solid is transferred to an oven at 40°C for drying for 12 hours to obtain a halogen-free metal organic framework material FeNi-MOF.

[0064] In the control group, 5 mg of the metal organic framework material FeNi-MOF was weighed and mixed with 5 mg of carbon powder and dissolved in a mixed solution containing 750 μl of deionized water, 250 μl of isopropanol and 40 μl of naphthalene, and rolled for 12 hours; 8 μl of the above solution was evenly coated on the polished glassy carbon electrode as the working electrode to be tested.

[0065] In experimental group 1, 5 mg of F-FeNi-MOF and 5 mg of carbon powder were weighed and mixed and dissolved in a mixed solution containing 750 μl of deionized water, 250 μl of isopropanol and 40 μl of naphthalene, and rolled for 12 h; 8 μl of the above solution was evenly coated on the polished glassy carbon electrode as the working electrode to be tested.

[0066] In experimental group 2, 5 mg of Cl-FeNi-MOF and 5 mg of carbon powder were weighed and mixed and dissolved in a mixed solution containing 750 μl of deionized water, 250 μl of isopropanol and 40 μl of naphthalene, and rolled for 12 h; 8 μl of the above solution was evenly coated on the polished glassy carbon electrode as the working electrode to be tested.

[0067] In experimental group 3, 5 mg of Br-FeNi-MOF and 5 mg of carbon powder were weighed and mixed and dissolved in a mixed solution containing 750 μl of deionized water, 250 μl of isopropanol and 40 μl of naphthalene, and rolled for 12 h; 8 μl of the above solution was evenly coated on the polished glassy carbon electrode as the working electrode to be tested.

[0068] To ensure the comparison effect, the dosage of metal organic framework in the control group and experimental groups 1-3 was the same, which was 0.196 mg / cm 2 .

[0069] The electrolyzed water test results of the control group and experimental groups 1-3 were collected respectively, and the following results were obtained: Figure 2 , Figure 3 and Figure 4 The current density-potential diagram shown. Figure 2It can be seen that F-FeNi-MOF at 10 mA cm -2 The overpotential at is reduced by 32mV; Figure 3 It can be seen that Cl-FeNi-MOF has a -2 The overpotential at the Figure 4 It can be seen that Br-FeNi-MOF has a -2 The overpotential at the electrode was reduced by 14 mV. That is to say, in the method of the present invention, the metal active sites are more likely to reach a higher oxidation state at the same potential, which is more conducive to the activity of anode water electrolysis, and its oxygen production activity is significantly improved.

[0070] The preparation method and application of the metal-organic framework material of the embodiment of the present invention adopts terephthalic acid containing halogen substituents as an organic ligand to react with metal ions, thereby adjusting the properties of the metal-organic framework material. After modification with halogens with high electronegativity, the Bader charge of the active center nickel in the metal-organic framework material is greatly improved, and the center of the Ni-3d band is closer to the Fermi level, thereby promoting the adsorption of oxygen-containing species in the reaction by the metal-organic framework material, greatly improving its oxygen production activity when applied to water electrolysis.

[0071] The above is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. The above embodiment of the present invention can also be modified in various ways. That is, all simple, equivalent changes and modifications made according to the claims and the description of the present invention fall within the scope of protection of the claims of the present invention. The contents not described in detail in the present invention are all conventional technical contents.

Claims

1. A method for preparing a metal organic framework material, characterized in that: The following steps are involved: Dissolving iron salt and nickel salt in N,N-dimethylacetamide and stirring evenly to form a first solution; In the first solution, the molar ratio of iron ions to nickel ions is 1:1 to 5:1; Dissolving an organic ligand in N,N-dimethylacetamide and stirring evenly to form a second solution, wherein the organic ligand is terephthalic acid containing a halogen substituent; the molar ratio of the terephthalic acid containing a halogen substituent to the sum of iron ions and nickel ions is 1:1; Mixing the first solution and the second solution and stirring them uniformly to form a third solution; The third solution is heated to a preset temperature and maintained for a preset time, so that the iron ions, nickel ions and organic ligands are self-assembled, and then the metal organic framework material is obtained after cooling, washing, centrifugation and drying; the preset time is 12-24 hours; The terephthalic acid containing a halogen substituent is 2-fluoroterephthalic acid, 2-chloroterephthalic acid or 2-bromoterephthalic acid; when the terephthalic acid containing a halogen substituent is 2-fluoroterephthalic acid, the preset temperature is 140-160°C; when the terephthalic acid containing a halogen substituent is 2-chloroterephthalic acid or 2-bromoterephthalic acid, the preset temperature is 170-185°C.

2. The method for preparing a metal organic framework material according to claim 1, characterized in that: The iron salt is ferric chloride hexahydrate or ferric nitrate nonahydrate, and the nickel salt is nickel chloride hexahydrate or nickel nitrate hexahydrate.

3. The method for preparing a metal organic framework material according to claim 1, characterized in that: Then, after cooling, washing, centrifugation and drying, the metal organic framework material is obtained, which specifically includes: The solid is naturally cooled to room temperature and washed with ethanol and deionized water for multiple times, and then centrifuged to obtain a solid. The solid is transferred to an oven and dried at a temperature of 26-60° C. for 8-24 hours to obtain a metal organic framework material.

4. An application of a metal organic framework material prepared by the method for preparing a metal organic framework material according to any one of claims 1 to 3, characterized in that: The metal organic framework material is coated on a working electrode to serve as an anode catalyst for electrolyzing water.

5. The use of the metal organic framework material according to claim 4, characterized in that: The working electrode is a glassy carbon electrode.

6. The use of the metal organic framework material according to claim 5, characterized in that: The metal organic framework material is mixed with carbon powder and dissolved in a mixed solution containing deionized water, isopropanol and naphthalene, and then rolled; and then coated on a glassy carbon electrode to serve as a working electrode.

7. The use of the metal organic framework material according to claim 4, characterized in that: The metal active centers in the metal organic framework material are tuned by the halogen in the organic ligand to promote the adsorption of oxygen-containing intermediate species.

8. The use of the metal organic framework material according to claim 7, characterized in that: The metal active center is nickel.

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