Ferrocobalt bimetal organic framework material as well as preparation method and application thereof

Abstract

The invention provides a ferrocobalt bimetal organic framework material as well as a preparation method and application thereof, and belongs to the technical field of hydrogen evolution catalysts. The organic amine alkaline regulator is added, so that carboxylic acid organic ligands are effectively coordinated with cobalt ions and iron ions; through the cavitation effect of ultrasonic treatment, the coordination reaction between cobalt ions and iron ions and carboxylic acid organic ligands can be accelerated, efficient mixing and homogenization can be achieved, cluster or gel is prevented from being formed under the effect of an organic amine alkaline regulator, and a more uniform precursor complexing system is formed; in addition, a large number of tiny and uniform crystal nucleuses can be induced to be formed through ultrasonic treatment, the formed crystal nucleus structure is closer to the final MOF crystal structure, good thermodynamic stability is achieved, the crystal nucleus can serve as seeds for follow-up crystal growth, crystal activation energy is reduced, and high crystallinity is achieved at the low hydrothermal reaction temperature.

Description

Technical Field

[0001] This invention belongs to the field of hydrogen evolution catalyst technology, specifically relating to a cobalt-iron bimetallic organic framework material, its preparation method, and its application. Background Technology

[0002] Hydrogen is a new type of energy with high calorific value and no carbon emissions. Electrolysis of water to produce hydrogen is a highly efficient hydrogen production technology that is widely used in hydrogen production.

[0003] Electrolysis of water to produce hydrogen generally requires the addition of a catalyst to reduce overpotential and increase the reaction rate. Commonly used catalysts are divided into noble metal catalysts and non-noble metal catalysts. Noble metal catalysts, such as Pt, are expensive and difficult to use on a large scale. Non-noble metal catalysts, such as MoS2 and transition metal compounds, reduce the cost of the catalyst, but have insufficient catalytic activity and high overpotential.

[0004] Transition metal-organic frameworks (MOFs) have attracted widespread attention in the electrocatalytic hydrogen evolution reaction (HER) due to their unique structural tunability, high specific surface area, and well-defined active sites, enabling them to overcome the limitations of traditional catalysts. However, single-metal MOFs suffer from poor conductivity and limited catalytic activity. Therefore, researchers have proposed introducing different transition metals to form bimetallic MOFs to regulate electronic structure, enhance synergistic effects, and improve catalytic activity and stability. However, current methods for preparing bimetallic MOFs generally suffer from harsh reaction conditions and poor crystallinity, resulting in unsatisfactory catalytic HER effects and hindering the development of hydrogen production through water electrolysis. Summary of the Invention

[0005] The purpose of this invention is to provide a cobalt-iron bimetallic organic framework material, its preparation method, and its applications. The preparation method provided by this invention uses mild conditions, and the resulting cobalt-iron bimetallic organic framework material exhibits high crystallinity and good catalytic hydrogen evolution effect.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] This invention provides a method for preparing a cobalt-iron bimetallic organic framework material, comprising the following steps:

[0008] A mixture is prepared by mixing a carboxylic acid organic ligand, an iron salt, a cobalt salt, an organic amine basic regulator, and an aqueous mixed solvent. The molar ratio of iron ions to cobalt ions in the mixture is 1:(1-3). The molar ratio of the carboxylic acid organic ligand to the total molar ratio of iron ions and cobalt ions is (0.5-0.8):0.75.

[0009] The mixture is ultrasonicated and then subjected to a hydrothermal reaction to obtain a cobalt-iron bimetallic organic framework material; the ultrasonication time is 5-7 hours; the hydrothermal reaction temperature is 100-150°C and the hydrothermal reaction time is 10-15 hours.

[0010] Preferably, the frequency of the ultrasound is 50-100 kHz and the power is 50-150 W.

[0011] Preferably, the carboxylic acid organic ligand is pyromellitic acid, 1,3,5-phenyltricarboxylic acid, or terephthalic acid.

[0012] Preferably, the concentration of carboxylic acid organic ligands in the mixture is 0.01 to 0.025 mol / L.

[0013] Preferably, the organic amine alkalinity regulator is triethylamine or tri-n-propylamine.

[0014] Preferably, the volume concentration of the organic amine alkaline regulator in the mixture is 1.5% to 2.5%.

[0015] Preferably, the aqueous mixed solvent is a mixture of N,N-dimethylformamide, ethanol, and water.

[0016] Preferably, the volume ratio of N,N-dimethylformamide, ethanol and water in the aqueous mixed solvent is (30-32):2:2.

[0017] The present invention also provides a cobalt-iron bimetallic organic framework material prepared by the preparation method described in the above technical solution.

[0018] This invention also provides the application of the cobalt-iron bimetallic organic framework material prepared by the above-described preparation method as a hydrogen evolution catalyst.

[0019] This invention provides a method for preparing a cobalt-iron bimetallic organic framework material, comprising the following steps: mixing a carboxylic acid organic ligand, an iron salt, a cobalt salt, an organic amine basic regulator, and an aqueous mixed solvent to obtain a mixed solution; the molar ratio of iron ions to cobalt ions in the mixed solution is 1:(1-3); the molar ratio of the carboxylic acid organic ligand to the total molar ratio of iron ions and cobalt ions is (0.5-0.8):0.75; subjecting the mixed solution to a hydrothermal reaction after ultrasonication to obtain the cobalt-iron bimetallic organic framework material; the ultrasonication time is 5-7 hours; the hydrothermal reaction temperature is 100-150°C, and the hydrothermal reaction time is 10-15 hours. This invention enables the effective coordination of carboxylic acid organic ligands with cobalt and iron ions by adding an organic amine-based alkaline regulator. By limiting the molar ratio of cobalt and iron ions, a heterostructure with electronic regulation can be formed, effectively adjusting the electronic structure of the MOF framework, promoting charge transfer, and improving catalytic performance. By limiting the molar ratio of organic ligands to metal ions, the MOF structure can be controlled, exposing more active sites and improving catalytic activity. The cavitation effect of ultrasonic treatment can accelerate the coordination reaction between cobalt and iron ions and carboxylic acid organic ligands, achieving efficient mixing and homogenization, avoiding the formation of clusters or gels under the action of the organic amine-based alkaline regulator, and forming a more uniform precursor complex system. Moreover, ultrasonic treatment can induce the formation of a large number of small, uniform crystal nuclei. The resulting crystal nuclei structure is closer to the final MOF crystal structure and has good thermodynamic stability. They can serve as seeds for subsequent crystal growth, reducing the crystal activation energy and achieving high crystallinity at a lower hydrothermal reaction temperature. The results of the examples show that the cobalt-iron bimetallic organic framework material prepared by the preparation method provided by the present invention has a highly ordered crystal structure, an overpotential between 0.21 and 0.269 V, and good hydrogen evolution catalytic activity. Attached Figure Description

[0020] Figure 1 The images show the XRD patterns of the CoFe-MOF materials prepared in Example 1 and Comparative Examples 1-3 of this invention.

[0021] Figure 2 The voltammetric curves are those of the CoFe-MOF materials prepared in Examples 1, 10, and 11 of this invention.

[0022] Figure 3 The voltammetric curves are those of the CoFe-MOF materials prepared in Examples 2-5 of this invention.

[0023] Figure 4 The voltammetric curves of the CoFe-MOF materials prepared in Examples 6-7 of this invention are shown.

[0024] Figure 5The voltammetric curves of the CoFe-MOF materials prepared in Examples 8-9 of this invention are shown.

[0025] Figure 6 The voltammetric curves are those of the CoFe-MOF materials prepared in Examples 2, 6, and 8 of this invention.

[0026] Figure 7 The voltammetric curves of the CoFe-MOF materials prepared in Embodiment 8 and Comparative Example 4 of this invention are shown. Detailed Implementation

[0027] All raw materials used in this invention are not particularly limited in their source; they can be purchased from the market or prepared using conventional methods known to those skilled in the art.

[0028] There are no particular restrictions on the purity of any of the raw materials used in this invention, but analytical grade raw materials are preferred.

[0029] This invention provides a method for preparing a cobalt-iron bimetallic organic framework material, comprising the following steps:

[0030] A mixture is prepared by mixing a carboxylic acid organic ligand, an iron salt, a cobalt salt, an organic amine basic regulator, and an aqueous mixed solvent. The molar ratio of iron ions to cobalt ions in the mixture is 1:(1-3). The molar ratio of the carboxylic acid organic ligand to the total molar ratio of iron ions and cobalt ions is (0.5-0.8):0.75.

[0031] The mixture is ultrasonicated and then subjected to a hydrothermal reaction to obtain a cobalt-iron bimetallic organic framework material; the ultrasonication time is 5-7 hours; the hydrothermal reaction temperature is 100-150°C and the hydrothermal reaction time is 10-15 hours.

[0032] This invention involves mixing carboxylic acid organic ligands, iron salts, cobalt salts, organic amine basic regulators, and an aqueous mixed solvent to obtain a mixed solution.

[0033] In this invention, the carboxylic acid organic ligand is preferably pyromellitic acid, 1,3,5-phenyltricarboxylic acid, or terephthalic acid, more preferably terephthalic acid. The aforementioned carboxylic acid organic ligands are beneficial for obtaining MOF materials with multiple active sites, further improving the catalytic activity of the materials.

[0034] In this invention, the concentration of carboxylic acid organic ligands in the mixture is preferably 0.01–0.025 mol / L, more preferably 0.015–0.02 mol / L. As one embodiment of this invention, the concentration of carboxylic acid organic ligands in the mixture can be 0.01 mol / L, 0.013 mol / L, 0.016 mol / L, 0.02 mol / L, or 0.022 mol / L. A concentration of carboxylic acid organic ligands in the mixture within the above range is beneficial for obtaining MOF materials with more active sites, further improving the catalytic activity of the material.

[0035] In one embodiment of the present invention, the iron salt may be ferric chloride hexahydrate; the cobalt salt may be cobalt chloride hexahydrate.

[0036] In this invention, the molar ratio of iron ions to cobalt ions in the mixture is 1:(1-3), preferably 1:2. When the molar ratio of iron ions to cobalt ions is within the above range, a heterostructure with electronic regulation can be formed, effectively adjusting the electronic structure of the MOF framework, promoting the charge transfer process, and improving the catalytic effect.

[0037] In this invention, the molar ratio of the carboxylic acid organic ligand to the total molar ratio of iron ions and cobalt ions is (0.5–0.8):0.75, preferably (0.6–0.7):0.75. As one embodiment of this invention, the molar ratio of the carboxylic acid organic ligand to the total molar ratio of iron ions and cobalt ions can be 0.5:0.75, 0.6:0.75, 0.7:0.75, 0.75:0.75, or 0.8:0.75. Maintaining the molar ratio of the carboxylic acid organic ligand to the metal ions within the above range can regulate the MOF structure, expose more active sites, and improve the catalytic activity of the material.

[0038] In this invention, the organic amine basicity modifier is preferably triethylamine or tri-n-propylamine, more preferably triethylamine. Organic amine basicity modifiers are weakly basic, and while regulating the MOF structure, they can prevent metal ion precipitation. These organic amine basicity modifiers are beneficial for further improving the catalytic activity of the material.

[0039] In this invention, the volume concentration of the organic amine basic regulator in the mixture is preferably 1.5–2.5%; more preferably 1.8–2.2%. As one embodiment of this invention, the volume concentration of the organic amine basic regulator in the mixture can be 1.64%, 1.75%, 1.9%, 2.0%, 2.18%, or 2.30%. Using organic amine basic regulators within the above ranges is beneficial for obtaining MOF materials with more active sites, further improving the catalytic activity of the materials.

[0040] In this invention, the aqueous mixed solvent is preferably a mixture of N,N-dimethylformamide, ethanol, and water, and the volume ratio of N,N-dimethylformamide, ethanol, and water in the aqueous mixed solvent is preferably (30-32):2:2, more preferably 32:2:2. Using the above-mentioned mixed solvent facilitates the dissolution of the raw materials, promotes the formation of specific crystal phases, and further improves the catalytic activity of the material.

[0041] As one embodiment of the present invention, the mixing method can be as follows: under stirring conditions, iron salt, cobalt salt and carboxylic acid organic ligands are first dissolved in an aqueous mixed solvent, then an organic amine alkaline regulator is added dropwise, and stirring is continued for 5 minutes until the mixture is uniform; the stirring speed can be 1000 rpm.

[0042] After obtaining the mixture, the present invention performs a hydrothermal reaction on the mixture after sonication to obtain a cobalt-iron bimetallic organic framework material.

[0043] In this invention, the frequency of the ultrasound is preferably 50–100 kHz, more preferably 60–90 kHz; as one embodiment of this invention, the frequency of the ultrasound can be 60 kHz, 70 kHz, 80 kHz, or 90 kHz. Ultrasound frequencies within the above ranges are beneficial for further improving the crystallinity of the material.

[0044] In this invention, the ultrasonic power is preferably 50-150W, more preferably 60-140W; as one embodiment of this invention, the ultrasonic power can be 60W, 80W, 100W, 120W, or 140W. Ultrasonic power within the above range is beneficial for further improving the crystallinity of the material.

[0045] In this invention, the ultrasound duration is 5–7 hours, preferably 6 hours. Ultrasound duration within this range allows for the formation of MOF crystal nuclei, thereby increasing the crystallinity of the material.

[0046] In this invention, the hydrothermal reaction temperature is 100–150°C, preferably 110–130°C; as one embodiment of this invention, the hydrothermal reaction temperature can be 100°C, 110°C, 120°C, 130°C, 140°C, or 150°C. Within the above temperature range, highly crystalline MOF materials can be formed, improving the structural order and stability, and enhancing the catalytic activity of the material.

[0047] In this invention, the hydrothermal reaction time is 10–15 h, preferably 12–13 h; as one embodiment of this invention, the hydrothermal reaction time can be 10 h, 11 h, 12 h, 13 h, 14 h, or 15 h. Within the above range, a highly crystalline MOF material can be formed, improving the structural order and stability, and enhancing the catalytic activity of the material.

[0048] In one embodiment of the present invention, the hydrothermal reaction can be carried out in a high-pressure reactor.

[0049] After the hydrothermal reaction is completed, the present invention preferably cools the product of the hydrothermal reaction and performs solid-liquid separation. The obtained solid is washed and dried to obtain a cobalt-iron bimetallic organic framework material (CoFe-MOF).

[0050] In one embodiment of the present invention, after the hydrothermal reaction is completed, the product is naturally cooled to room temperature, and a solid product is obtained by centrifugation. The product is washed three times with anhydrous ethanol to remove residual impurities, and then dried under vacuum at 60°C for 12 hours to obtain a cobalt-iron bimetallic organic framework material (CoFe-MOF).

[0051] This invention enables the effective coordination of carboxylic acid organic ligands with cobalt and iron ions by adding an organic amine-based alkaline regulator. By limiting the molar ratio of cobalt and iron ions, a heterostructure with electronic regulation can be formed, effectively adjusting the electronic structure of the MOF framework, promoting charge transfer, and improving catalytic performance. By limiting the molar ratio of organic ligands to metal ions, the MOF structure can be controlled, exposing more active sites and improving catalytic activity. The cavitation effect of ultrasonic treatment can accelerate the coordination reaction between cobalt and iron ions and carboxylic acid organic ligands, achieving efficient mixing and homogenization, avoiding the formation of clusters or gels under the action of the organic amine-based alkaline regulator, and forming a more uniform precursor complex system. Moreover, ultrasonic treatment can induce the formation of a large number of small, uniform crystal nuclei. The resulting crystal nuclei structure is closer to the final MOF crystal structure and has good thermodynamic stability. They can serve as seeds for subsequent crystal growth, reducing the crystal activation energy and achieving high crystallinity at a lower hydrothermal reaction temperature.

[0052] This invention also provides a cobalt-iron bimetallic organic framework material prepared by the method described above. The CoFe-MOF provided by this invention is a powdered solid, insoluble in water and ketone solvents.

[0053] This invention also provides the application of the cobalt-iron bimetallic organic framework material prepared by the above-described preparation method as a hydrogen evolution catalyst.

[0054] As one embodiment of the present invention, the CoFe-MOF can be used directly as an electrocatalyst or loaded onto the surface of a conductive substrate.

[0055] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0056] Example 1

[0057] A method for preparing a cobalt-iron bimetallic organic framework material, comprising the following specific steps:

[0058] Weigh out 0.75 mmol of carboxylic acid organic ligands: 1,3,5-benzenetricarboxylic acid (H3BTC); and 0.5 mmol of metal salts: cobalt chloride hexahydrate (CoCl2·6H2O) and ferric chloride hexahydrate (FeCl3·6H2O). Dissolve them in an aqueous mixed solvent at 1000 rpm. The aqueous mixed solvent is a mixture of 32 mL of N,N-dimethylformamide (DMF), 2 mL of ethanol, and 2 mL of deionized water. Add 0.8 mL of triethylamine dropwise to the above solution and continue stirring for 5 min to homogenize the solution, thus obtaining a mixed solution.

[0059] The mixture was sonicated at room temperature for 6 hours (100 kHz, 150 W). The solution was then transferred to a high-pressure reactor and reacted at 120 °C for 12 hours. After the reaction, the mixture was allowed to cool naturally to room temperature. The solid product was obtained by centrifugation and washed three times with anhydrous ethanol to remove residual impurities. The product was then vacuum dried at 60 °C for 12 hours to obtain the target CoFe-MOF material, denoted as Co2Fe1-MOF, which was sonicated for 6 hours.

[0060] Comparative Example 1

[0061] A method for preparing a cobalt-iron bimetallic organic framework material, the raw materials and process are the same as in Example 1, the difference being that the ultrasonic time is 8 hours, and the product is denoted as Co2Fe1-MOF ultrasonicated for 8 hours.

[0062] Comparative Example 2

[0063] A method for preparing a cobalt-iron bimetallic organic framework material, the raw materials and process are the same as in Example 1, the difference being that the ultrasonic time is 4 hours, and the product is denoted as Co2Fe1-MOF ultrasonicated for 4 hours.

[0064] Comparative Example 3

[0065] A method for preparing a cobalt-iron bimetallic organic framework material, the raw materials and process are the same as in Example 1, the difference being that the ultrasonic time is 2h, and the product is denoted as Co2Fe1-MOF ultrasonicated for 2h.

[0066] Example 2

[0067] A method for preparing a cobalt-iron bimetallic organic framework material, using the same raw materials and process as in Example 1, except that the amount of H3BTC added is 0.5 mmol.

[0068] Example 3

[0069] A method for preparing a cobalt-iron bimetallic organic framework material, using the same raw materials and process as in Example 1, except that the amount of H3BTC added is 0.6 mmol.

[0070] Example 4

[0071] A method for preparing a cobalt-iron bimetallic organic framework material, using the same raw materials and process as in Example 1, except that the amount of H3BTC added is 0.7 mmol.

[0072] Example 5

[0073] A method for preparing a cobalt-iron bimetallic organic framework material, using the same raw materials and process as in Example 1, except that the amount of H3BTC added is 0.8 mmol.

[0074] Example 6

[0075] A method for preparing a cobalt-iron bimetallic organic framework material, using the same raw materials and process as in Example 1, except that the carboxylic acid organic ligand is 0.5 mmol of pyromellitic acid.

[0076] Example 7

[0077] A method for preparing a cobalt-iron bimetallic organic framework material, using the same raw materials and process as in Example 1, except that the carboxylic acid organic ligand is 0.6 mmol of pyromellitic acid.

[0078] Example 8

[0079] A method for preparing a cobalt-iron bimetallic organic framework material, using the same raw materials and process as in Example 1, except that the carboxylic acid organic ligand is 0.5 mmol of terephthalic acid.

[0080] Example 9

[0081] A method for preparing a cobalt-iron bimetallic organic framework material, using the same raw materials and process as in Example 1, except that the carboxylic acid organic ligand is 0.6 mmol of terephthalic acid.

[0082] Example 10

[0083] A method for preparing a cobalt-iron bimetallic organic framework material, using the same raw materials and process as in Example 1, except that the molar ratio of CoCl2·6H2O to FeCl3·6H2O is 1:1, the total amount of substance is 0.75 mmol, and the product is designated as Co1Fe1-MOF.

[0084] Example 11

[0085] A method for preparing a cobalt-iron bimetallic organic framework material, using the same raw materials and process as in Example 1, except that the molar ratio of CoCl2·6H2O to FeCl3·6H2O is 3:1, the total amount of substance is 0.75 mmol, and the product is designated as Co3Fe1-MOF.

[0086] Comparative Example 4

[0087] A method for preparing a cobalt-iron bimetallic organic framework material, using the same raw materials and process as in Example 1, except that a hydrothermal reaction is not performed.

[0088] Test Example 1

[0089] The CoFe-MOF materials of Example 1 and Comparative Examples 1-3 were analyzed using X-ray diffraction, and XRD patterns were obtained, as shown below. Figure 1 As shown. From Figure 1 It can be seen that the crystallinity of the sample changes significantly with the extension of ultrasonic time: when the ultrasonic time is 2h and 4h, only weak and wide diffraction peaks appear in the low-angle region of the XRD pattern, indicating that the MOF crystal nuclei have not been fully formed and the material is in a poor crystallization state, indicating that the structure is not yet stable; when the ultrasonic time is extended to 6h, multiple clear and sharp diffraction peaks appear in the XRD pattern of the sample, located at 6.63°, 9.51° and 11.5° respectively. According to the literature and reference standard card (based on HKUST-1 topological comparison), these diffraction peaks correspond to the (200), (220) and (222) crystal planes respectively, indicating that the crystallinity of the sample synthesized at this ultrasonic time is the best, the MOF structure is fully formed, and the surface is smooth and uniform; when the ultrasonic time is further extended to 8h, some diffraction peaks in the XRD pattern are weakened and the peak shape begins to become blunt. This is because excessive ultrasonication causes local dissolution or agglomeration of the crystal, thereby affecting the long-range order of the crystal.

[0090] At a sonication time of 6 hours, sharp and high-intensity main diffraction peaks (approximately 5.5° and 9.8°) appeared in the 5°–10° range, indicating that the material had formed a highly ordered crystalline structure. Comparing with other curves: sonication for 2 hours / 4 hours: the main peak broadened and had lower intensity → incomplete crystallization (high proportion of amorphous / microcrystalline); sonication for 8 hours: the main peak intensity was slightly lower than at 6 hours → excessive sonication may damage the stability of the crystal nuclei. Conclusion: Sonication for 6 hours is the optimal condition for crystallinity, laying the foundation for subsequent hydrothermal reactions. Low-angle region (<15°): 5.5°: corresponds to the (110) crystal plane of MOF, reflecting the periodic arrangement of channels, which is a sign of MOF framework formation; 9.8°: belongs to the (200) crystal plane, confirming the long-range order of layered or cubic crystal systems; Medium-angle region (20°~40°): 26.5°: is the (222) crystal plane of the bimetallic cluster Co-O-Fe, reflecting heterometallic cooperative coordination; 35.2°: corresponds to the (331) crystal plane, characteristically verifying the stable connection between BTC ligands and metal nodes; High-angle region (>40°): weak broad peak, a small amount of amorphous impurities (such as unreacted metal salts).

[0091] Test Example 2

[0092] Electrodes were fabricated using the CoFe-MOF materials prepared in Examples 1-11 and Comparative Example 4, respectively, and their electrocatalytic performance was then tested. Electrode preparation method: A working electrode (platinum electrode clip), a reference electrode (mercury / mercuric oxide), and a counter electrode (carbon rod) were prepared. The working electrode was cleaned with alcohol and ultrapure water, and the electrode surface was dried with a clean paper towel. A dispersion was then prepared by dispersing 5 mg of CoFe-MOF material in a mixture of 450 μL anhydrous ethanol, 450 μL deionized water, and 50 μL Nafion solution, followed by ultrasonic treatment for 1 h. An electrocatalytic slurry was prepared by uniformly dropping 40 μL of the slurry onto pretreated nickel foam and allowing it to air dry at room temperature. The working electrode was then connected to an electrochemical workstation, and the parameters were set. The electrochemical performance was tested using linear voltammetry, and the voltammetric curves were obtained as shown below. Figures 2-7 As shown. According to Figures 2-7 The overpotentials of each sample were obtained from the voltammetric curves, as shown in Table 1.

[0093] Table 1. Overpotential Records of Materials in Examples 1-11 and Comparative Example 4

[0094] / Key variables <![CDATA[Current density (mA / cm 2 )]]> Overpotential (V) Example 1 Co:Fe = 2:1 -10 -0.243 Example 10 Co:Fe = 1:1 -10 -0.269 Example 11 Co:Fe = 3:1 -10 -0.25 Example 2 <![CDATA[0.5mmolH3BTC]]> -10 -0.236 Example 3 <![CDATA[0.6mmolH3BTC]]> -10 -0.241 Example 4 <![CDATA[0.7mmolH3BTC]]> -10 -0.245 Example 5 <![CDATA[0.8mmolH3BTC]]> -10 -0.266 Example 6 0.5 mmol pyromellitic acid -10 -0.222 Example 7 0.6 mmol pyromellitic acid -10 -0.225 Example 8 0.5 mmol terephthalic acid -10 -0.196 Example 9 0.6 mmol terephthalic acid -10 -0.22 Comparative Example 4 No hydrothermal reaction -10 -0.278

[0095] From Table 1 and Figure 2 It can be seen that the material prepared with a molar ratio of cobalt ions to iron ions of 2:1 has the best catalytic activity.

[0096] From Table 1 and Figure 3 , Figure 4 , Figure 5It can be seen that when the amount of carboxylic acid organic ligand is 0.5 mmol, the molar ratio of carboxylic acid organic ligand to metal salt is 0.5:0.75, and the prepared material has the best catalytic activity.

[0097] From Table 1 and Figure 6 It can be seen that the material prepared with terephthalic acid as the carboxylic acid organic ligand has the best catalytic activity.

[0098] From Table 1 and Figure 7 It can be seen that hydrothermal reaction can improve the catalytic activity of materials.

[0099] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a cobalt-iron bimetallic organic framework material, comprising the following steps: A mixture is prepared by mixing a carboxylic acid organic ligand, an iron salt, a cobalt salt, an organic amine basic regulator, and an aqueous mixed solvent. The molar ratio of iron ions to cobalt ions in the mixture is 1:(1-3). The molar ratio of the carboxylic acid organic ligand to the total molar ratio of iron ions and cobalt ions is (0.5-0.8):0.

75. The mixture is ultrasonicated and then subjected to a hydrothermal reaction to obtain a cobalt-iron bimetallic organic framework material; the ultrasonication time is 5-7 hours; the hydrothermal reaction temperature is 100-150°C and the hydrothermal reaction time is 10-15 hours.

2. The preparation method according to claim 1, characterized in that, The frequency of the ultrasound is 50–100 kHz, and the power is 50–150 W.

3. The preparation method according to claim 1, characterized in that, The carboxylic acid organic ligands are pyromellitic acid, 1,3,5-benzenetricacid, or terephthalic acid.

4. The preparation method according to claim 1 or 3, characterized in that, The concentration of carboxylic acid organic ligands in the mixture is 0.01–0.025 mol / L.

5. The preparation method according to claim 1, characterized in that, The organic amine alkaline regulator is triethylamine or tri-n-propylamine.

6. The preparation method according to claim 1 or 5, characterized in that, The volume concentration of the organic amine alkaline regulator in the mixture is 1.5% to 2.5%.

7. The preparation method according to claim 1, characterized in that, The aqueous mixed solvent is a mixture of N,N-dimethylformamide, ethanol, and water.

8. The preparation method according to claim 7, characterized in that, The volume ratio of N,N-dimethylformamide, ethanol and water in the aqueous mixed solvent is (30-32):2:

2.

9. The cobalt-iron bimetallic organic framework material prepared by the preparation method according to any one of claims 1 to 8.

10. The application of the cobalt-iron bimetallic organic framework material of claim 9 as a hydrogen evolution catalyst.

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