Method for preparing metal organic framework type oxide catalyst

Abstract

The invention provides a method for preparing a metal organic framework type oxide catalyst. The method comprises the following steps: pretreating carbon paper; a metal source solution and an organic ligand solution are prepared, the metal source solution comprises nitrate, and the organic ligand solution comprises imidazole organic matter; growing a metal organic framework on the surface of the carbon paper in situ, wherein the metal organic framework is generated by reaction of a metal source solution and an organic ligand solution; and carrying out annealing treatment on the metal organic framework to form the metal organic framework type oxide catalyst. Therefore, the metal organic framework type oxide catalyst obtained by the preparation method disclosed by the invention has a pore structure and excellent stability, and the problem of structure collapse of the metal organic framework type oxide catalyst is effectively solved.

Description

Technical Field

[0001] The present invention relates to the field of electrocatalytic oxygen evolution, and in particular to a method for preparing a metal organic framework type oxide catalyst on carbon paper. Background Art

[0002] With the increasing environmental pollution caused by fossil fuels, the exploration of new energy sources and their technological advancements require rigorous research. As a reliable alternative to fossil fuels, hydrogen has been widely used in recent years in new energy vehicles, green chemicals, and even aerospace research. However, in early hydrogen production processes, only 5% of hydrogen was generated through green chemical water electrolysis, while 95% came from fossil fuel extraction and processing. This has failed to effectively mitigate the environmental damage caused by fossil fuels. It has been reported that green chemical water electrolysis can produce hydrogen under a certain potential, and the unique two-electron transfer process of the hydrogen production reaction results in a relatively low reaction energy barrier. However, the half-reaction at the anode is an oxygen evolution reaction with a four-electron transfer process. This reaction produces multiple adsorbed intermediates and has high reaction barriers at each stage, resulting in a very slow reaction rate, making it the limiting step in the overall water splitting hydrogen production reaction. To optimize the water splitting reaction, researchers are considering developing catalytic materials with reduced reaction free energy.

[0003] Metal-organic frameworks (MOFs) have been applied as powdered catalytic materials in the energy and environmental fields due to their unique morphology, abundant surface porosity, and mild preparation conditions. However, existing reports on the stability of water splitting catalysis have reported cases of MOF components collapsing or even decomposing. This is particularly true during the oxygen evolution reaction at the anode, where the metal elements that comprise the MOF may transition to their highest valence state during the oxidation reaction, a process accompanied by decomposition and a decrease in porosity. Furthermore, the catalytic behavior of single metal sites within the MOF is difficult to optimize.

[0004] Therefore, it is necessary to develop a catalytic substrate with a mild preparation environment, excellent performance and easy doping and modification, so that it has the unique pore structure of the metal-organic framework and overcomes the poor stability caused by structural collapse. Summary of the Invention

[0005] The present invention aims to, to a certain extent, address at least one of the technical problems existing in the prior art. To this end, the present invention provides a method for preparing a metal-organic framework-based oxide catalyst. The metal-organic framework-based oxide catalyst of the present invention possesses a porous structure and excellent stability, effectively overcoming the structural collapse problem of metal-organic framework catalysts.

[0006] Therefore, in the first aspect of the present invention, a method for preparing a metal-organic framework-type oxide catalyst is proposed, comprising the following steps: preparing a metal source solution and an organic ligand solution, wherein the metal source solution includes nitrates and the organic ligand solution includes imidazole organic matter; in situ growing a metal-organic framework on the surface of carbon paper, wherein the metal-organic framework is generated by the reaction of the metal source solution and the organic ligand solution; and annealing the metal-organic framework to form a metal-organic framework-type oxide catalyst.

[0007] Therefore, the metal organic framework oxide catalyst obtained by the preparation method of the present invention has a porous structure and excellent stability, which effectively overcomes the structural collapse problem of the metal organic framework catalyst.

[0008] In some embodiments, the nitrate includes any one of cobalt nitrate hexahydrate, zinc nitrate, copper nitrate, and iron nitrate, and the concentration of the metal source solution is 0.3 to 0.5 mol / L.

[0009] In some embodiments, the imidazole organic compound includes any one of dimethylimidazole, 4-methylimidazole, and 1,2-dimethylimidazole, and the concentration of the organic ligand solution is 49.2 to 196.8 g / L.

[0010] In some embodiments, the step of in situ growing a metal organic framework on the surface of carbon paper includes: placing the carbon paper in a metal source solution; then placing the carbon paper in an organic ligand solution; adding the metal source solution to the organic ligand solution to grow the metal organic framework on the surface of the carbon paper.

[0011] In some embodiments, the carbon paper is placed in the metal source solution for 9 to 11 hours.

[0012] In some embodiments, in the step of adding the metal source solution to the organic ligand solution, the amount of the metal source solution added is 900-1100 μL.

[0013] In some embodiments, before the step of in situ growth of a metal organic framework on the carbon paper surface, the carbon paper is also pretreated. The carbon paper pretreatment step includes: treating the carbon paper with an alkaline solution and an acidic solution in sequence; the alkaline solution includes a sodium hydroxide solution, and the acidic solution includes an aqua regia solution.

[0014] In some embodiments, during the annealing process, the control parameters meet the following requirements: a heating rate of 1.5 to 2.5° C. / min, a heating temperature of 300 to 400° C., and a heating time of 30 to 120 min.

[0015] In some embodiments, the step of annealing the metal organic framework further includes: cleaning and drying. The drying temperature is 55-65° C. and the drying time is 15-25 minutes.

[0016] In the second aspect of the present invention, the present invention provides a metal organic framework type oxide catalyst, including the metal organic framework type oxide catalyst obtained by the preparation method of the first aspect.

[0017] Therefore, the metal organic framework oxide catalyst obtained by the preparation method of the present invention will have a porous structure and excellent stability.

[0018] Compared with the prior art, the present invention has the following beneficial technical effects:

[0019] 1. This invention in situ grows a metal-organic framework-type oxide catalyst on carbon paper. The carbon paper, composed of a collection of carbon nanowires, is both tough and provides numerous nucleation sites, enabling the large-scale growth of the metal-organic framework. Furthermore, the carbon paper's good conductivity allows it to serve as a self-supporting electrode material in electrochemical processes, supplying electrons to the catalytic layer on its surface.

[0020] 2. The present invention, through thermal annealing at an appropriate temperature, can not only maintain the unique pore structure of the metal-organic framework, but also demonstrate the excellent corrosion resistance and physical and chemical stability of the metal oxide. It has the potential to add other metal sources to form bimetallic organic framework materials and bimetallic oxides, which can provide a reliable modification template for other subsequent work.

[0021] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments with reference to the following drawings, in which:

[0023] Figure 1 This is a flow chart of preparing a metal organic framework oxide catalyst on carbon paper in Example 1 of the present invention;

[0024] Figure 2 This is a SEM image of Co-MOF-1 constructed in Example 1 of the present invention;

[0025] Figure 3 This is a SEM image of Co-MOF-2 constructed in Comparative Example 1 of the present invention;

[0026] Figure 4 This is a SEM image of Co-MOF-3 constructed in Example 2 of the present invention;

[0027] Figure 5 This is a SEM image of Co-MOF-4 constructed in Comparative Example 2 of the present invention;

[0028] Figure 6 This is a SEM image of Co-MOF-5 constructed in Comparative Example 3 of the present invention;

[0029] Figure 7 XRD patterns of Co-MOF-1 to Co-MOF-5 constructed in Examples 1 to 2 and Comparative Examples 1 to 3 of the present invention;

[0030] Figure 8 Raman graphs of Co-MOF-1 to Co-MOF-5 constructed in Examples 1 to 2 and Comparative Examples 1 to 3 of the present invention;

[0031] Figure 9 1 is a SEM image of the metal organic framework oxide catalyst formed under different annealing parameters in Example 1 of the present invention;

[0032] Figure 10 1 is an XRD pattern of the metal organic framework oxide catalyst formed under different annealing parameters in Example 1 of the present invention;

[0033] Figure 11 1 is a Raman graph of the metal organic framework oxide catalyst formed under different annealing parameters in Example 1 of the present invention;

[0034] Figure 12 : SEM images of the metal organic framework oxide catalyst formed under different annealing parameters in Example 2 of the present invention;

[0035] Figure 13 1 is an XRD pattern of the metal organic framework oxide catalyst formed under different annealing parameters in Example 2 of the present invention;

[0036] Figure 14 1 is a Raman graph of the metal organic framework oxide catalyst formed under different annealing parameters in Example 2 of the present invention;

[0037] Figure 15 CV graphs of Co-MOF-1 at different scan rates in Example 1 of the present invention;

[0038] Figure 16 CV graphs of Co-MOF-1 at different scan rates after annealing at 300°C for 30 min in Example 1 of the present invention;

[0039] Figure 17 ECSA diagram of Co-MOF-1 before and after annealing at 300°C for 30 minutes in Example 1 of the present invention;

[0040] Figure 18 CV polarization curves of Co-MOF-1 before and after annealing at 300°C for 30 min in Example 1 of the present invention;

[0041] Figure 19 LSV curves of Co-MOF-1 before and after annealing at 300°C for 30 minutes in Example 1 of the present invention;

[0042] Figure 20 The Tafel diagram of Co-MOF-1 before and after annealing at 300°C for 30 minutes in Example 1 of the present invention;

[0043] Figure 21 1 is the EIS spectrum of Co-MOF-1 before and after annealing at 300°C for 30 minutes in Example 1 of the present invention. DETAILED DESCRIPTION

[0044] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be understood as limiting the present invention.

[0045] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, features defined as "first" or "second" may explicitly or implicitly include one or more of such features. Furthermore, in the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0046] The endpoints of the ranges and any values disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0047] In this document, the terms “include” or “comprising” are open expressions, that is, including the contents specified in the present invention, but not excluding other contents.

[0048] In the first aspect of the present invention, a method for preparing a metal-organic framework-type oxide catalyst is proposed, comprising the following steps: preparing a metal source solution and an organic ligand solution, wherein the metal source solution includes nitrates and the organic ligand solution includes imidazole organic matter; in situ growing a metal-organic framework on the surface of carbon paper, wherein the metal-organic framework is generated by the reaction of the metal source solution and the organic ligand solution; and annealing the metal-organic framework to form a metal-organic framework-type oxide catalyst.

[0049] In the preparation method provided by the embodiment of the present invention, the inventor grows the metal organic framework type oxide catalyst in situ on the surface of carbon paper. The carbon paper of the present invention is composed of a collection of carbon nanowires, which has both toughness and a large number of nucleation sites, and can supply large-scale growth of metal organic frameworks. Secondly, the conductivity of carbon paper is good, and it can be used as a self-supporting electrode material to supply electrons to the catalytic layer on its surface during the electrochemical process. In the present invention, the carbon paper is first pretreated to remove organic and inorganic impurities on the surface of the carbon paper and to enhance its hydrophilicity. The hydrophilic carbon paper can make its nucleation sites more uniform during the growth of the metal organic framework, avoiding the formation of local clusters. In addition, since the hydrophilic groups on the carbonaceous surface are negatively charged and the metal ions are positively charged, when the metal organic framework grows, the metal ions will preferentially form temporary coordination bonds with the hydrophilic groups on the surface of the carbon paper, becoming anchor points for subsequent organic ligand connection. The pretreated carbon paper surface often has micrometer or nanometer roughness (such as etched grooves), and the metal organic framework can be mechanically embedded in the concave-convex structure, so that the metal organic framework is adsorbed and grown on the carbon paper surface. A metal source solution and an organic ligand solution are then prepared to react chemically to form a metal-organic framework with a three-dimensional network structure. The material is formed by the coordination of nitrogen atoms in the imidazole organic compound with metal ions in the nitrate, forming a tetrahedral coordination configuration (such as CoN4). The 145° bond angle of the imidazole ligand is similar to the bond angle of Si-O-Si in zeolite (approximately 145°), so the metal-organic framework can form a tetrahedral topology similar to zeolite. These tetrahedra are expanded into a three-dimensional network by sharing the imidazole ligand, generating nanoscale cage-like pores and microporous windows, giving the metal-organic framework a porous structure. At the same time, the introduction of a methyl group on the imidazole ring increases the steric hindrance of the ligand. However, the precise coordination geometry stabilizes the above-mentioned channel structure, so the metal-organic framework generated by the present invention has a unique pore structure. Finally, the resulting metal-organic framework is annealed to form a metal oxide. The metal-oxygen coordination structure has relatively high bonding strength. By using the preparation method of the present invention, a porous metal-organic framework is first constructed, and then annealed to form an oxide, thereby producing a catalyst that possesses both a porous structure and excellent stability. Thus, the metal-organic framework-type oxide catalyst obtained by the preparation method of the present invention possesses a porous structure and excellent stability, effectively overcoming the structural collapse problem of metal-organic framework catalysts.

[0050] In some embodiments of the present invention, the nitrate includes any one of cobalt nitrate hexahydrate, zinc nitrate, copper nitrate, and iron nitrate, and the concentration of the metal source solution is 0.3-0.5 mol / L.

[0051] The nitrate provided in the embodiment of the present invention easily reacts with the organic ligand solution to form a metal-organic framework-type oxide catalyst with a three-dimensional network structure. Therefore, the preparation method of the present invention can obtain a metal-organic framework-type oxide catalyst with excellent performance.

[0052] As an example, the solution concentration is 0.3 mol / L, 0.35 mol / L, 0.4 mol / L, 0.45 mol / L, 0.5 mol / L, etc.

[0053] In some embodiments of the present invention, the imidazole organic compound includes any one of dimethylimidazole, 4-methylimidazole, and 1,2-dimethylimidazole, and the concentration of the organic ligand solution is 49.2 to 196.8 g / L.

[0054] The imidazole organic compound provided in the embodiment of the present invention is mainly used as an organic ligand to construct a framework structure. The two nitrogen atoms (N) on the imidazole ring have lone pairs of electrons and can react with metal ions (such as Co 2+ ) form coordination bonds, forming tetrahedral structural units. Simultaneously, the rigid structure and coordination mode of imidazole create a microporous structure, giving the metal-organic framework-based oxide catalyst a porous structure. Furthermore, the inventors discovered that by varying the concentration of the organic ligand solution, the catalyst morphology can be controlled, thereby obtaining a metal-organic framework-based oxide catalyst with diverse morphologies and excellent performance.

[0055] As examples, the solution concentrations are 49.2 g / L, 73.8 g / L, 98.4 g / L, 147.6 g / L, 196.8 g / L, etc.

[0056] In some embodiments of the present invention, the step of in situ growing a metal-organic framework on the surface of carbon paper includes: placing the carbon paper in a metal source solution; then placing the carbon paper obliquely in an organic ligand solution; adding the metal source solution to all the organic ligand solutions to grow the metal-organic framework on the surface of the carbon paper.

[0057] In the present invention, carbon paper is placed in a metal source solution and soaked. Through soaking, metal ions can be physically adsorbed or weakly coordinated with oxygen-containing functional groups (such as -OH, -COOH, from carbon paper pretreatment) on the surface of the carbon paper to form active sites, thereby enhancing the adsorption of metal ions on the surface of the carbon paper. When immersed in an organic ligand solution, the imidazole ligand quickly coordinates with the adsorbed metal ions, inducing the in-situ growth of metal-organic framework crystals. The metal source solution is then added to the organic ligand solution in order to allow the metal-organic framework to grow more and denser on the surface of the carbon paper. Thus, the metal-organic framework-type oxide catalyst obtained by the preparation method of the present invention will have a porous structure and excellent stability.

[0058] In some embodiments of the present invention, the carbon paper is placed in the metal source solution for 9 to 11 hours.

[0059] The time provided by the embodiment of the present invention is conducive to fully soaking the carbon paper, thereby enhancing the adsorption of metal ions on the surface of the carbon paper, thereby further enhancing the performance of the metal organic framework oxide catalyst.

[0060] As an example, the times are 9h, 9.5h, 10h, 10.5h, 11h, etc.

[0061] In some embodiments of the present invention, in the step of adding the metal source solution to the organic ligand solution, the amount of the metal source solution added is 900 to 1100 μL. Thus, a metal-organic framework-type oxide catalyst with excellent performance can be obtained.

[0062] As an example, the added amount is 900 μL, 950 μL, 1000 μL, 1050 μL, 1100 μL, etc.

[0063] In some embodiments of the present invention, before the step of in situ growth of a metal organic framework on the carbon paper surface, the carbon paper is also pretreated. The paper pretreatment step includes: treating the carbon paper with an alkaline solution and an acidic solution in sequence; the alkaline solution includes a sodium hydroxide solution, and the acidic solution includes an aqua regia solution.

[0064] In the present invention, the alkaline solution is used to remove dust and impurities on the surface of the carbon paper, and the acidic solution is used to provide hydrophilic groups on the surface of the carbon paper to enhance the hydrophilicity of the carbon paper and make the subsequent growth of the metal organic framework more uniform.

[0065] In some embodiments of the present invention, the aqua regia solution is prepared by mixing a hydrochloric acid solution and a nitric acid solution in a volume ratio of 1:1.

[0066] In some embodiments of the present invention, during the annealing process, the control parameters meet the following requirements: a heating rate of 1.5 to 2.5° C. / min, a heating temperature of 300 to 400° C., and a heating time of 30 to 120 min.

[0067] In the present invention, annealing treatment can promote atomic rearrangement of the metal organic framework catalyst, repair lattice defects, enhance the mechanical / thermal stability of the framework, and maintain its porous structure. The metal organic framework oxide catalyst finally obtained, the substrate can provide larger active sites and flexible modification methods for subsequent catalytic material design. Therefore, by thermal annealing at a suitable temperature, the unique pore structure of the metal organic framework can be guaranteed, and the excellent corrosion resistance and physicochemical stability of the metal oxide can be demonstrated. It has the potential to add other metal sources to form bimetallic organic framework materials and bimetallic oxides, which can provide a reliable modification template for other subsequent work.

[0068] As an example, the heating rate is 1.5℃ / min, 1.8℃ / min, 2.0℃ / min, 2.2℃ / min, 2.4℃ / min, 2.5℃ / min, etc.; the heating temperature is 300℃, 320℃, 340℃, 360℃, 380℃, 400℃, etc.; the heating time is 30min, 50min, 70min, 90min, 110min, 120min, etc.

[0069] In some embodiments of the present invention, the step of annealing the metal organic framework further comprises: cleaning and drying. The drying temperature is 55-65° C. and the drying time is 15-25 minutes.

[0070] As an example, the temperature of the drying process is 55°C, 57°C, 60°C, 62°C, 64°C, 65°C, etc.; the time is 15 min, 17 min, 19 min, 20 min, 22 min, 24 min, 25 min, etc.

[0071] In a second aspect, the present invention provides a metal-organic framework-based oxide catalyst, comprising the metal-organic framework-based oxide catalyst prepared by the preparation method of the first aspect. Thus, the metal-organic framework-based oxide catalyst prepared by the preparation method of the present invention possesses a porous structure and excellent stability.

[0072] Below, the scheme of the present invention will be explained in conjunction with embodiment.It will be understood by those skilled in the art that the following examples are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention.In the embodiment, if specific technology or conditions are not indicated, the technology or conditions described in the literature in this area or the product instructions are used.The reagents or instruments used are not indicated by the manufacturer, and are all conventional products that can be obtained by commercial purchase.

[0073] Example 1:

[0074] 1. Preparation of Metal-Organic Framework Catalysts:

[0075] (1) Cut commercial 060 model hydrophilic carbon paper into a size of 2*4cm and place it in a Teflon reactor. Use granular sodium hydroxide with a mass fraction of 95% to prepare a 1mol / L sodium hydroxide aqueous solution. After fully dissolving, pour it into the Teflon reactor in an appropriate volume to encapsulate and provide an alkaline pressure environment of 80℃ and 5h. After the reactor cools to room temperature, take out the carbon paper and rinse it with deionized water for 3min. Add the above cleaned carbon paper to an aqua regia solution prepared with hydrochloric acid and nitric acid in a volume ratio of 1:1. Use a glass container to press the carbon paper floating on the surface of the aqua regia to the bottom of the container and soak it for 24h to obtain clean carbon paper with strong hydrophilicity.

[0076] (2) Prepare a metal source solution by weighing 4 mmol of cobalt nitrate hexahydrate and dissolving it in 10 ml of deionized water. Ultrasonicate the resulting solution for 15 minutes to obtain a dark pink, clear solution. Prepare an organic ligand solution by weighing 0.492 g of dimethylimidazole and ultrasonically dissolving it in 10 ml of deionized water. Ultrasonicate and shake for 15 minutes to obtain a transparent, clear solution.

[0077] (3) In order to remove the strong acidity generated on the surface of the hydrophilic carbon paper due to soaking in aqua regia, the carbon paper is washed with deionized water for 10 minutes to obtain neutral carbon paper with better hydrophilicity. In addition, the above carbon paper is placed in the metal source solution and soaked for 10 hours. After the carbon paper is fully etched in the metal source solution, it can be taken out and immediately placed in a dimethylimidazole aqueous solution at an angle of 60 degrees relative to the bottom of the cup. When obvious bright blue substance adsorption is observed on the surface of the carbon paper, 1000μl of the metal source solution is quickly injected into it using a pipette, and a large amount of bright blue substance is immediately observed. Subsequently, the glass container with the carbon paper placed at an angle is sealed and the precipitated substance therein is evenly dispersed. The carbon paper needs to be allowed to stand in the solution and soaked at room temperature for 24 hours. The metal-valent catalyst Co-MOF-1 (cobalt-based metal-organic framework-1) is obtained through the above steps.

[0078] (IV) The carbon paper loaded with a large amount of attachments is taken out from the reaction solution and the physically adsorbed metal organic framework is washed with deionized water. Subsequently, it is dried on a heating table at 60°C for 20 minutes. It is placed on a ceramic boat in a quartz tube and placed in the center of the heating zone of the tubular furnace. Subsequently, the heating rate, heating temperature, and working time of the tubular furnace are set, and the materials are divided into four groups for annealing treatment respectively. The parameter settings are as follows: (1) 2°C / min, 300°C, 30min; (2) 2°C / min, 300°C, 1h; (3) 2°C / min, 300°C, 2h; (4) 2°C / min, 400°C, 2h. When the furnace temperature drops to room temperature, the Co-MOF-1 series oxide substrate is obtained in situ on the carbon paper. The substrate can provide larger active sites and flexible modification means for the subsequent catalytic material design. The preparation process of the metal organic framework type oxide catalyst of Example 1 is as follows: Figure 1 shown.

[0079] 2. Testing of Metal-Organic Framework Catalysts:

[0080] (1) Use a scanning electron microscope to take the Co-MOF-1 and Co-MOF-1 series oxide substrates in Example 1 to obtain their SEM images, as shown in FIG. Figure 2 As shown in Figure 2, Co-MOF-1 has a uniform starfish-like morphology. The morphology of the annealed Co-MOF-1 series oxides is shown in Figure 2. Figure 9As shown. Within the aforementioned annealing temperature and time ranges, changes in annealing temperature and time have relatively little effect on the uniformity of the metal-organic framework-type oxide, resulting in good uniformity and good thermal stability. Within the annealing parameter range of the present invention, as the annealing temperature and / or annealing time increase, the metal-organic framework-type oxide exhibits deconstruction, and the surface thermal stability tends to decrease.

[0081] (2) The Co-MOF-1 and Co-MOF-1 series oxide substrates obtained in Example 1 were tested using an X-ray diffractometer to obtain their XRD patterns, as shown in FIG. Figure 7 and Figure 10 The characteristic peaks of the above two types of materials are shown in the XRD results, which confirms the successful preparation of the materials. Figure 10 In the annealing experiments, the main characteristic peak intensity and half-height width in XRD decreased with the increase of annealing time and temperature, indicating that higher annealing temperature and / or annealing time would affect the structural stability of Co-MOF.

[0082] (3) The Co-MOF-1 and Co-MOF-1 series oxide substrates obtained in Example 1 were tested using a confocal Raman spectrometer to obtain their Raman spectra, such as Figure 8 and Figure 11 As shown, the characteristic peaks of the above two materials are both shown in the Raman results, which confirms the successful preparation of the catalytic substrate.

[0083] (IV) Using the sample obtained in Example 1 (taking the sample annealed at 300°C for 30 min and the original sample (Co-MOF-1) as an example), HgHgO, and Pt wire as the working electrode, reference electrode, and counter electrode, respectively, the Co-MOF-1 and Co-MOF-1 series oxide substrates obtained in Example 1 were subjected to non-Faraday interval CV, ECSA, Faraday interval CV, LSV, Tafel, and EIS calculations and characterizations using a CHI760e (Shanghai Chenhua) electrochemical workstation, as shown in FIG. Figures 15 to 21 It can be clearly seen that the electrochemical active area, performance, reaction kinetics, and impedance of the metal-organic framework oxide catalyst did not change significantly before and after annealing, indicating that the calcination treatment during the formation of the Co-MOF-1 oxide substrate did not cause significant deconstruction of the metal-organic framework oxide catalyst. This demonstrates that the metal-organic framework oxide catalyst of the present invention possesses a porous structure and excellent stability, effectively overcoming the structural collapse problem of metal-organic framework catalysts.

[0084] Example 2:

[0085] 1. Preparation of Metal-Organic Framework Catalysts:

[0086] (1) Cut commercial 060 model hydrophilic carbon paper into a size of 2*4cm and place it in a Teflon reactor. Use granular sodium hydroxide with a mass fraction of 95% to prepare a 1mol / L sodium hydroxide aqueous solution. After fully dissolving, pour it into a Teflon reactor in an appropriate volume to encapsulate and provide an alkaline pressure environment of 80℃ and 5h. After the reactor cools to room temperature, take out the carbon paper and rinse it with deionized water for 3min. Add the above-mentioned cleaned carbon paper to an aqua regia solution prepared with hydrochloric acid and nitric acid in a volume ratio of 1:1. Use a glass container to press the carbon paper floating on the surface of the aqua regia to the bottom of the container and soak it for 24h to obtain clean carbon paper with strong hydrophilicity.

[0087] (2) Prepare a metal source solution by weighing 4 mmol of cobalt nitrate hexahydrate and dissolving it in 10 ml of deionized water. Ultrasonicate the resulting solution for 15 minutes to obtain a dark pink, clear solution. Prepare an organic ligand solution by weighing 0.984 g of dimethylimidazole and ultrasonically dissolving it in 10 ml of deionized water. Ultrasonicate and shake for 15 minutes to obtain a transparent, clear solution.

[0088] (3) In order to remove the strong acidity generated on the surface of the hydrophilic carbon paper due to soaking in aqua regia, the carbon paper was washed with deionized water for 10 minutes to obtain neutral carbon paper with better hydrophilicity. In addition, the above carbon paper was placed in a metal source solution and soaked for 10 hours. After the carbon paper was fully etched in the metal source solution, it was taken out and immediately placed in a dimethylimidazole aqueous solution at an angle of 60 degrees relative to the bottom of the cup. When obvious bright blue substance adsorption was observed on the surface of the carbon paper, 1100μl of the metal source solution was quickly injected into it using a pipette, and a large amount of bright blue substance was immediately observed. Subsequently, the glass container with the carbon paper placed obliquely was sealed and the precipitated substance therein was evenly dispersed. The carbon paper was allowed to stand in the solution and soaked at room temperature for 24 hours. The metal-organic framework Co-MOF-3 was obtained through the above steps.

[0089] (IV) The carbon paper loaded with a large amount of attachments was removed from the reaction solution and the physically adsorbed metal organic framework was washed with deionized water. Subsequently, it was dried on a heating table at 60°C for 20 minutes. It was placed on a ceramic boat in a quartz tube and placed in the center of the heating zone of a tube furnace. Subsequently, the heating rate, heating temperature, and working time of the tube furnace were set, and the materials were divided into four groups for annealing treatment. The parameters were as follows: (1) 2°C / min, 300°C, 30 minutes; (2) 2°C / min, 300°C, 1 hour; (3) 2°C / min, 300°C, 2 hours; (4) 2°C / min, 400°C, 2 hours. When the furnace temperature dropped to room temperature, the Co-MOF-3 series oxide substrate was obtained in situ on the carbon paper. This substrate can provide larger active sites and flexible modification methods for the subsequent catalytic material design.

[0090] 2. Testing of Metal-Organic Framework Catalysts:

[0091] (1) Using a scanning electron microscope, the Co-MOF-3 and Co-MOF-3 series oxide substrates obtained in Example 2 were photographed to obtain their SEM images, as shown in FIG. Figure 4 As shown in Figure 2, Co-MOF-3 forms a uniform nano-magic square morphology. The morphology of the Co-MOF-3 series oxides after annealing is shown in Figure 2. Figure 12 As shown in the figure, the uniformity of the material does not change with the increase of temperature and annealing time, and the material has good uniformity and good thermal stability.

[0092] (2) The Co-MOF-3 and Co-MOF-3 series oxide substrates obtained in Example 2 were tested using an X-ray diffractometer to obtain their XRD patterns, as shown in FIG. Figure 7 and Figure 13 The characteristic peaks of the above two materials are shown in the XRD results, which confirms the successful preparation of the materials.

[0093] (3) The Co-MOF-3 and Co-MOF-3 series oxide substrates obtained in Example 2 were tested using a confocal Raman spectrometer to obtain their Raman spectra, such as Figure 8 and Figure 14 The characteristic peaks of the two materials mentioned above are shown in the Raman results, which confirms the successful preparation of the catalytic substrate.

[0094] This indicates that the metal organic framework oxide catalyst of the present invention has a porous structure and excellent stability, and effectively overcomes the structural collapse problem of the metal organic framework catalyst.

[0095] Comparative Example 1:

[0096] 1. Preparation of Metal-Organic Framework Catalysts:

[0097] (1) Cut commercial 060 model hydrophilic carbon paper into a size of 2*4cm and place it in a Teflon reactor. Use granular sodium hydroxide with a mass fraction of 95% to prepare a 1mol / L sodium hydroxide aqueous solution. After fully dissolving, pour it into a Teflon reactor in an appropriate volume to encapsulate and provide an alkaline pressure environment of 80℃ and 5h. After the reactor cools to room temperature, take out the carbon paper and rinse it with deionized water for 3min. Add the above-mentioned cleaned carbon paper to an aqua regia solution prepared with hydrochloric acid and nitric acid in a volume ratio of 1:1. Use a glass container to press the carbon paper floating on the surface of the aqua regia to the bottom of the container and soak it for 24h to obtain clean carbon paper with strong hydrophilicity.

[0098] (2) Prepare a metal source solution by weighing 4 mmol of cobalt nitrate hexahydrate and dissolving it in 10 ml of deionized water. Ultrasonicate the resulting solution for 15 minutes to obtain a dark pink, clear solution. Prepare an organic ligand solution by weighing 0.738 g of dimethylimidazole and ultrasonically dissolving it in 10 ml of deionized water. Ultrasonicate and shake for 15 minutes to obtain a transparent, clear solution.

[0099] (3) In order to remove the strong acidity generated on the surface of the hydrophilic carbon paper due to soaking in aqua regia, the carbon paper was washed with deionized water for 10 minutes to obtain neutral carbon paper with better hydrophilicity. In addition, the above carbon paper was placed in a metal source solution and soaked for 10 hours. After the carbon paper was fully etched in the metal source solution, it was taken out and immediately placed at an angle of 60° relative to the bottom of the cup in dimethylimidazole aqueous solutions of different concentrations. It was observed that there was obvious adsorption of bright blue substance on the surface of the carbon paper. 900μl of metal source solution was quickly injected into it using a pipette, and a large amount of bright blue substance was immediately observed. Subsequently, the glass container with the carbon paper placed at an angle was sealed and the precipitated substance therein was evenly dispersed. The carbon paper needs to be allowed to stand in the solution and soaked at room temperature for 24 hours. The metal-organic framework catalyst Co-MOF-2 was obtained through the above steps.

[0100] 2. Testing of Metal-Organic Framework Catalysts:

[0101] (1) Using a scanning electron microscope, the Co-MOF-2 obtained in Comparative Example 1 was photographed to obtain its SEM image, as shown in FIG. Figure 3 As shown in Figure 2, Co-MOF-2 forms a uniform starfish polyhedron morphology. Compared with Co-MOF-1 with a starfish morphology, the vertical angle at the center of the starfish is being filled, thus forming a starfish polyhedron morphology. At this time, the sample morphology is in a transitional state.

[0102] (2) The Co-MOF-2 obtained in Comparative Example 1 was tested using an X-ray diffractometer to obtain its XRD pattern, as shown in FIG. Figure 7 The characteristic peaks of Co-MOF are shown in the XRD results, which confirms the successful preparation of the material.

[0103] (3) The Co-MOF-2 obtained in Comparative Example 1 was tested using a confocal Raman spectrometer to obtain its Raman spectrum, such as Figure 8 As shown, the characteristic peaks are all displayed in the Raman results, which confirms the successful preparation of the catalytic substrate.

[0104] (IV) Using the sample obtained in Comparative Example 1, HgHgO, and Pt wire as the working electrode, reference electrode, and counter electrode, respectively, a CHI760e (Shanghai Chenhua) electrochemical workstation was used to perform Faradaic CV, ECSA, Faradaic CV, LSV, Tafel, and EIS calculations and characterization of the Co-MOF-2 obtained in Comparative Example 1. The test results indicate that due to the lack of annealing treatment in the sample of Comparative Example 1, the electrochemical active area, performance, reaction kinetics, and impedance of the metal-organic framework oxide catalyst were all poor.

[0105] The test results show that the Co-MOF-2 catalytic substrate that has not undergone annealing treatment has a structural collapse problem and its performance is unstable.

[0106] Comparative Example 2:

[0107] 1. Preparation of Metal-Organic Framework Catalysts:

[0108] (1) Cut commercial 060 model hydrophilic carbon paper into a size of 2*4cm and place it in a Teflon reactor. Use granular sodium hydroxide with a mass fraction of 95% to prepare a 1mol / L sodium hydroxide aqueous solution. After fully dissolving, pour it into a Teflon reactor in an appropriate volume to encapsulate and provide an alkaline pressure environment of 80℃ and 5h. After the reactor cools to room temperature, take out the carbon paper and rinse it with deionized water for 3min. Add the above-mentioned cleaned carbon paper to an aqua regia solution prepared with hydrochloric acid and nitric acid in a volume ratio of 1:1. Use a glass container to press the carbon paper floating on the surface of the aqua regia to the bottom of the container and soak it for 24h to obtain clean carbon paper with strong hydrophilicity.

[0109] (2) Prepare a metal source solution: Weigh 4 mmol of cobalt nitrate hexahydrate and dissolve it in 10 ml of deionized water. Ultrasonicate the resulting solution for 15 minutes to obtain a dark pink, clear solution. Weigh 1.476 g of dimethylimidazole, a common organic ligand used in the synthesis of metal-organic framework catalysts, and ultrasonically dissolve it in 10 ml of deionized water. Ultrasonicate and shake for 15 minutes to obtain a clear, transparent solution.

[0110] (3) In order to remove the strong acidity generated on the surface of the hydrophilic carbon paper due to soaking in aqua regia, the carbon paper was washed with deionized water for 10 minutes to obtain neutral carbon paper with better hydrophilicity. In addition, the above-mentioned carbon paper was placed in a metal source solution and soaked for 10 hours. After the carbon paper was fully etched in the metal source solution, it was taken out and immediately placed in a dimethylimidazole aqueous solution at an angle of 60 degrees relative to the bottom of the cup. When obvious bright blue substance adsorption was observed on the surface of the carbon paper, 1000μl of the metal source solution was quickly injected into it using a pipette, and a large amount of bright blue substance was immediately observed. Subsequently, the glass container with the carbon paper placed at an angle was sealed and the precipitated substance therein was evenly dispersed. The carbon paper was allowed to stand in the solution and soaked at room temperature for 24 hours. The metal-organic framework Co-MOF-4 was obtained through the above steps.

[0111] 2. Testing of Metal-Organic Framework Catalysts:

[0112] (1) Using a scanning electron microscope, the Co-MOF-4 obtained in Comparative Example 2 was photographed to obtain its SEM image, as shown in FIG. Figure 5 As shown, Co-MOF-4 has spherical and rounded tetrahedral morphologies of varying sizes.

[0113] (2) The Co-MOF-4 obtained in Comparative Example 2 was tested using an X-ray diffractometer to obtain its XRD pattern, as shown in FIG. Figure 7 The characteristic peaks of Co-MOF are shown in the XRD results, which confirms the successful preparation of the material.

[0114] (3) The Co-MOF-4 obtained in Comparative Example 2 was tested using a confocal Raman spectrometer to obtain its Raman spectrum, as shown in FIG. Figure 8 As shown, the characteristic peaks are all displayed in the Raman results, which confirms the successful preparation of the catalytic substrate.

[0115] (IV) Using the sample obtained in Comparative Example 2, HgHgO, and Pt wire as the working electrode, reference electrode, and counter electrode, respectively, a CHI760e (Shanghai Chenhua) electrochemical workstation was used to perform Faradaic CV, ECSA, Faradaic CV, LSV, Tafel, and EIS calculations and characterization of the Co-MOF-4 obtained in Comparative Example 2. The test results indicate that due to the lack of annealing treatment in the sample of Comparative Example 2, the electrochemical active area, performance, reaction kinetics, and impedance of the metal-organic framework oxide catalyst were all poor.

[0116] The test results show that the Co-MOF-2 catalytic substrate that has not undergone annealing treatment has a structural collapse problem and its performance is unstable.

[0117] Comparative Example 3:

[0118] 1. Preparation of Metal-Organic Framework Catalysts:

[0119] (1) Cut commercial 060 model hydrophilic carbon paper into a size of 2*4cm and place it in a Teflon reactor. Use granular sodium hydroxide with a mass fraction of 95% to prepare a 1mol / L sodium hydroxide aqueous solution. After fully dissolving, pour it into a Teflon reactor in an appropriate volume to encapsulate and provide an alkaline pressure environment of 80℃ and 5h. After the reactor cools to room temperature, take out the carbon paper and rinse it with deionized water for 3min. Add the above-mentioned cleaned carbon paper to an aqua regia solution prepared with hydrochloric acid and nitric acid in a volume ratio of 1:1. Use a glass container to press the carbon paper floating on the surface of the aqua regia to the bottom of the container and soak it for 24h to obtain clean carbon paper with strong hydrophilicity.

[0120] (2) Prepare a metal source solution by weighing 4 mmol of cobalt nitrate hexahydrate and dissolving it in 10 ml of deionized water. Ultrasonicate the resulting solution for 15 minutes to obtain a dark pink, clear solution. Prepare an organic ligand solution by weighing 2.5 g of dimethylimidazole and ultrasonically dissolving it in 10 ml of deionized water. Ultrasonicate and shake for 15 minutes to obtain a transparent, clear solution.

[0121] (3) In order to remove the strong acidity generated on the surface of the hydrophilic carbon paper due to soaking in aqua regia, the carbon paper was washed with deionized water for 10 minutes to obtain neutral carbon paper with better hydrophilicity. In addition, the above carbon paper was placed in a metal source solution and soaked for 10 hours. After the carbon paper was fully etched in the metal source solution, it was taken out and immediately placed in a dimethylimidazole aqueous solution at an angle of 60 degrees relative to the bottom of the cup. When obvious bright blue substance adsorption was observed on the surface of the carbon paper, 1000μl of the metal source solution was quickly injected into it using a pipette, and a large amount of bright blue substance was immediately observed. Subsequently, the glass container with the carbon paper placed at an angle was sealed and the precipitated substance therein was evenly dispersed. The carbon paper was allowed to stand in the solution and soaked at room temperature for 24 hours. The metal-organic framework Co-MOF-5 was obtained through the above steps.

[0122] 2. Testing of Metal-Organic Framework Catalysts:

[0123] (1) Using a scanning electron microscope, the Co-MOF-5 obtained in Comparative Example 3 was photographed to obtain its SEM image, as shown in FIG. Figure 6 As shown, Co-MOF-5 has a spherical morphology of varying sizes, and the growth of the sample is inhibited by excess organic ligands, and cannot grow into an obvious metal-organic framework catalyst.

[0124] (2) The Co-MOF-5 obtained in Comparative Example 3 was tested using an X-ray diffractometer to obtain its XRD pattern, as shown in FIG. Figure 7 The characteristic peaks of Co-MOF are shown in the XRD results, indicating the preparation of the material.

[0125] (3) The Co-MOF-5 obtained in Comparative Example 3 was tested using a confocal Raman spectrometer to obtain its Raman spectrum, as shown in FIG. Figure 8 As shown, the characteristic peaks are all displayed in the Raman results, indicating the preparation of the catalytic substrate.

[0126] The test results show that although the metal-organic framework catalyst was prepared, when the amount of organic ligand used exceeds the range of the present invention, it will have an adverse effect on the morphology formation of the metal-organic framework catalyst, and may further affect its function.

[0127] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0128] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A method for preparing a metal organic framework oxide catalyst, characterized in that: The following steps are involved: preparing a metal source solution and an organic ligand solution, wherein the metal source solution includes nitrate and the organic ligand solution includes imidazole organic matter; In-situ growing a metal organic framework on the surface of the carbon paper, wherein the metal organic framework is generated by reacting the metal source solution and the organic ligand solution; The metal organic framework is annealed to form a metal organic framework type oxide catalyst.

2. The method according to claim 1, characterized in that The nitrate includes any one of cobalt nitrate hexahydrate, zinc nitrate, copper nitrate, and iron nitrate, and the concentration of the metal source solution is 0.3-0.5 mol / L.

3. The method according to claim 1 or 2, characterized in that The imidazole organic compound includes any one of dimethylimidazole, 4-methylimidazole, and 1,2-dimethylimidazole, and the concentration of the organic ligand solution is 49.2 to 196.8 g / L.

4. The method according to claim 1 or 2, characterized in that The step of in-situ growing a metal organic framework on the carbon paper surface comprises: placing the carbon paper in the metal source solution; Then placing the carbon paper in the organic ligand solution; The metal source solution is added to the organic ligand solution to grow a metal organic framework on the surface of the carbon paper.

5. The method according to claim 4, characterized in that The carbon paper is placed in the metal source solution for 9 to 11 hours.

6. The method according to any one of claim 4, characterized in that In the step of adding the metal source solution to the organic ligand solution, the amount of the metal source solution added is 900-1100 μL.

7. The method according to any one of claims 1 to 6, characterized in that Before the step of in-situ growing the metal organic framework on the carbon paper surface, the carbon paper is also pretreated, and the carbon paper pretreatment step includes: The carbon paper is treated with an alkaline solution and an acidic solution in sequence; the alkaline solution includes a sodium hydroxide solution, and the acidic solution includes a water regia solution.

8. The method according to any one of claims 1 to 7, characterized in that During the annealing treatment, the control parameters are as follows: a heating rate of 1.5 to 2.5° C. / min, a heating temperature of 300 to 400° C., and a heating time of 30 to 120 min.

9. The method according to any one of claims 1 to 8, characterized in that Before the step of annealing the metal organic framework, the method further comprises: cleaning and drying. The drying temperature is 55 to 65° C. and the drying time is 15 to 25 minutes.

10. A metal organic framework oxide catalyst, characterized in that: A metal organic framework oxide catalyst obtained by the method according to any one of claims 1 to 9.

Images