A two-dimensional ultrathin graphene nanosheet and preparation method thereof

Abstract

The present invention relates to the technical field of inorganic non-metallic materials, and specifically to a two-dimensional ultra-thin graphene nanosheet and a preparation method thereof. The two-dimensional ultra-thin graphene nanosheet is prepared based on a zinc-based metal organic framework material. In the preparation method, based on the zinc-based metal organic framework material, the preparation from bulk MOF material to two-dimensional ultra-thin graphene nanosheet is completed in one step. The preparation steps are simple, the operation is simple, the purity of the obtained product is high, and no tedious post-processing is required, thereby improving the production efficiency of the product. The obtained two-dimensional ultra-thin graphene nanosheet material has a stable framework, an ultra-thin structure, and rich pores. It can be used as a solid carrier to provide a large number of exposed sites for loading catalytically active substances. It has excellent performance in various catalytic reactions and is easy to promote and use.

Description

Technical Field

[0001] The present invention relates to the technical field of inorganic non-metallic materials, and in particular to a two-dimensional ultra-thin graphene nanosheet and a preparation method thereof. Background Art

[0002] Low-dimensional nanomaterials have been widely studied in the fields of optics, catalysis, energy storage, etc. Among them, two-dimensional ultra-thin graphene nanosheets constructed from a few layers of atoms not only have the unique advantages of graphene, but also exhibit the anisotropic characteristics of one-dimensional nanostructures, showing excellent physical and chemical properties. In recent years, the synthesis of graphene nanosheets has generally adopted methods such as mechanical or chemical exfoliation, electrodeposition, or bottom-up organic synthesis. However, in the actual application process of these traditional methods, it has been found that not only are the operations complicated, time-consuming and labor-intensive, but the morphology and composition of the resulting products are also difficult to adjust. In particular, when used to construct catalytic materials, there are great difficulties in effectively controlling the pores on the surface of the material and the precise introduction of active species.

[0003] Metal-organic framework (MOF) materials possess ordered crystal structures and porosity, with flexible frameworks and precisely controllable active sites, making them promising for the synthesis of materials with specific structures. However, the preparation of two-dimensional carbon materials based on MOFs still requires the pre-design of the two-dimensional MOF and the control of morphology preservation during heat treatment. While sonochemical treatment and activation of MOF-derived carbon nanorods can yield two-dimensional graphene nanosheets, this involves multiple processing steps, resulting in poor operability and low product purity. Further post-processing requires cumbersome steps, resulting in low production efficiency.

[0004] Therefore, designing a simple and efficient method to complete the preparation of two-dimensional ultrathin graphene nanosheets from bulk MOF materials in one step without tedious post-processing has great application value. This can open up new avenues for the development of low-dimensional nanomaterials, but it is also a major challenge. Summary of the Invention

[0005] To address the shortcomings of the existing technology, the present invention provides two-dimensional ultrathin graphene nanosheets based on zinc-based metal-organic frameworks and methods for their preparation. A MOF material with a one-dimensional channel structure was synthesized and successfully prepared into two-dimensional ultrathin graphene nanosheets through a one-step heat treatment. The resulting two-dimensional ultrathin graphene nanosheets have a stable framework, an ultrathin structure, and abundant pores. They can serve as a robust support, providing numerous exposed sites for loading catalytically active substances. They exhibit excellent performance in a variety of catalytic reactions and are readily applicable.

[0006] The technical solution of the present invention is:

[0007] A two-dimensional ultrathin graphene nanosheet is prepared based on a zinc-based metal organic framework material.

[0008] Preferably, the method for preparing the above-mentioned two-dimensional ultrathin graphene nanosheets comprises the following steps:

[0009] S1. Dissolve zinc metal salt and 2,5-dihydroxyterephthalic acid organic monomer in organic solvents respectively, add the two solutions into a reactor to obtain a mixture, disperse the above mixture evenly by ultrasound, and then seal and heat it. After the reaction is completed and cooled to room temperature, filter or centrifuge to separate the solid, wash it with an organic solvent, and then dry it to obtain a zinc-based metal organic framework material.

[0010] S2. The zinc-based metal organic framework material obtained in S1 is subjected to heat treatment, and after pyrolysis and cooling in an atmosphere, a two-dimensional ultrathin graphene nanosheet material is obtained.

[0011] Preferably, the mass ratio of the zinc metal salt and the 2,5-dihydroxyterephthalic acid organic monomer in S1 is (1-3):(1-4).

[0012] Preferably, the mass ratio of the zinc metal salt and the 2,5-dihydroxyterephthalic acid organic monomer in S1 is 1:1.

[0013] Preferably, the zinc metal salt in S1 is zinc acetate, zinc nitrate or zinc chloride.

[0014] Preferably, the reaction solvent is one or more of methanol, ethanol, n-butanol, n-hexane, and N,N-dimethylformamide.

[0015] Preferably, the reaction solvent is methanol and ethanol.

[0016] Preferably, the ultrasonic treatment time in S1 is 1 to 30 minutes.

[0017] Preferably, the ultrasonic treatment time in S1 is 5 min.

[0018] Preferably, the heating temperature of the reactor in S1 is 130-180° C., and the heating time is 6-24 hours.

[0019] Preferably, the heating temperature of the reactor in S1 is 150° C. and the heating time is 18 h.

[0020] Preferably, the washing solvent in S1 is methanol or ethanol, and the washing times are 3 to 6 times.

[0021] Preferably, the number of washing times in S1 is 3 times.

[0022] Preferably, in S1, a non-zinc metal salt is added to the zinc metal salt to obtain an organic framework material loaded with the corresponding metal.

[0023] Preferably, iron is loaded into the finished graphene nanosheets by adding ferric chloride to the zinc metal salt solution.

[0024] Preferably, after obtaining the zinc-based metal organic framework material, a non-zinc metal loaded organic framework material is obtained by post-processing.

[0025] Preferably, the post-treatment method is a two-solvent method.

[0026] Preferably, the heat treatment temperature of the zinc-based metal organic framework material in S2 is 900-1100° C., and the treatment time is 0.5-4 h.

[0027] Preferably, the heat treatment temperature of the zinc-based metal organic framework material in S2 is 1000° C. and the treatment time is 2 h.

[0028] Preferably, the atmosphere is an inert atmosphere or an atmosphere required for element doping.

[0029] Preferably, the atmosphere required for element doping is ammonia. The ammonia is generated by simultaneously heat-treating the zinc-based metal organic framework material in S2 with a substance that generates ammonia.

[0030] The beneficial effects achieved by the present invention are:

[0031] 1. The present invention is based on zinc-based metal organic framework materials and completes the preparation from bulk MOF materials to two-dimensional ultrathin graphene nanosheets in one step. The preparation steps are simple and the operation is simple. The obtained product has high purity and does not require tedious post-processing, thereby improving the production efficiency of the product.

[0032] 2. The two-dimensional ultra-thin graphene nanosheet material obtained by the present invention has a stable framework, ultra-thin structure, and rich pores. It can be used as a solid carrier to provide a large number of exposed sites for loading catalytic active substances. It has excellent performance in various catalytic reactions and is easy to promote and use. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a flow chart of the present invention for preparing two-dimensional ultrathin graphene nanosheet materials.

[0034] Figure 2 This is the preparation process of the two-dimensional ultrathin graphene nanosheet material obtained in Examples 1 to 7 of the present invention and the one-dimensional carbon nanorod material obtained in Comparative Examples 1 to 2.

[0035] Figure 3It is the X-ray diffraction (PXRD) diagram of the metal organic framework material involved in the embodiments and comparative examples of the present invention.

[0036] Figure 4 It is the X-ray diffraction (PXRD) diagram of the two-dimensional ultrathin graphene nanosheet material obtained in the embodiment of the present invention and the one-dimensional carbon nanorod material obtained in the comparative example.

[0037] Figure 5 A is a scanning electron microscope (SEM) image of MOF-130T-(1:1) in an embodiment of the present invention.

[0038] Figure 5 B is a scanning electron microscope image of MOF-150T-(1:1) in an embodiment of the present invention.

[0039] Figure 5 C is a scanning electron microscope image of MOF-180T-(1:1) in an embodiment of the present invention.

[0040] Figure 5 D is a scanning electron microscope image of MOF-150T-(2:1) in an embodiment of the present invention.

[0041] Figure 5 E is a scanning electron microscope image of Fe@MOF-150T-(1:1) in an embodiment of the present invention.

[0042] Figure 5 F is a scanning electron micrograph of Fe-MOF-150T-(1:1) in an embodiment of the present invention.

[0043] Figure 5 G is a scanning electron microscope image of Fe-MOF-150T-(3:1) in an embodiment of the present invention.

[0044] Figure 5 H is a scanning electron micrograph of Fe-MOF-150T-(4:1) in an embodiment of the present invention.

[0045] Figure 6 A is a scanning electron microscope image of GNS-130T-(1:1) in an embodiment of the present invention.

[0046] Figure 6 B is a scanning electron microscope image of GNS-150T-(1:1) in an embodiment of the present invention.

[0047] Figure 6C is a scanning electron microscope image of GNS-180T-(1:1) in an embodiment of the present invention.

[0048] Figure 6 D is a scanning electron microscope image of GNS-150T-(2:1) in an embodiment of the present invention.

[0049] Figure 6 E is a scanning electron microscope image of Fe@NGNS-150T-(1:1) in an embodiment of the present invention.

[0050] Figure 6 F is a scanning electron microscope image of Fe-NGNS-150T-(1:1) in an embodiment of the present invention.

[0051] Figure 6 G is a scanning electron microscope image of CNR-150T-(3:1) in an embodiment of the present invention.

[0052] Figure 6 H is a scanning electron microscope image of CNR-150T-(4:1) in an embodiment of the present invention.

[0053] Figure 7 This is an atomic force microscope (AFM) image of the two-dimensional ultrathin graphene nanosheet material obtained in Example 2 of the present invention.

[0054] Figure 8 This is a scanning transmission electron microscopy (STEM) image of the two-dimensional ultrathin graphene nanosheet material obtained in Example 2 of the present invention;

[0055] Figure 9 This is the nitrogen adsorption isotherm of the two-dimensional ultrathin graphene nanosheet material obtained in Example 2 of the present invention.

[0056] Figure 10 This is a pore size distribution diagram of the two-dimensional ultrathin graphene nanosheet material obtained in Example 2 of the present invention.

[0057] Figure 11 This is a performance diagram of the application of the nitrogen-doped iron-loaded two-dimensional ultrathin graphene nanosheet material obtained in Example 6 of the present invention in the oxygen reduction reaction.

[0058] Figure 12 This is a performance diagram of the application of the nitrogen-doped iron-loaded two-dimensional ultrathin graphene nanosheet material obtained in Example 6 of the present invention in the carbon dioxide reduction reaction. DETAILED DESCRIPTION

[0059] To facilitate understanding of the present invention by those skilled in the art, specific embodiments of the present invention are described below with reference to the accompanying drawings. The experimental methods described in the examples are conventional methods unless otherwise specified. The reagents and materials described are commercially available unless otherwise specified.

[0060] It should be noted that in the following examples and comparative examples, for ease of reference, the MOF precursor materials are named MOF-XT-(Y), where X is the MOF synthesis temperature and Y is the ratio of zinc salt to organic ligand. Correspondingly, graphene nanosheets are named GNS-XT-(Y), and carbon nanorods are named CNR-XT-(Y).

[0061] Example 1

[0062] S1. Dissolve 0.2g of zinc acetate and 0.2g of 2,5-dihydroxyterephthalic acid in 8mL of methanol and 60mL of ethanol, respectively. Then mix the two solutions in a solvent thermal reactor to obtain a suspension. The suspension is ultrasonicated for 5min to ensure that the mixed solution is evenly dispersed. Subsequently, the reactor is sealed and heated at 130°C for 24h. After cooling, the solid is centrifuged and washed three times with excess methanol. After drying, a brown-yellow metal-organic framework material, MOF-130T-(1:1), is obtained.

[0063] S2. The metal organic framework MOF-130T-(1:1) obtained in S1 was placed in a tubular furnace, heated to 1000°C at a heating rate of 5°C / min under an Ar atmosphere and kept warm for 2 hours. After cooling to room temperature, a two-dimensional ultrathin graphene nanosheet material based on the metal organic framework MOF-130T-(1:1) was obtained (denoted as GNS-130T-(1:1)).

[0064] Example 2

[0065] S1. Dissolve 0.2g of zinc acetate and 0.2g of 2,5-dihydroxyterephthalic acid in 8mL of methanol and 60mL of ethanol, respectively. Then mix the two solutions in a solvent thermal reactor to obtain a suspension. The suspension is ultrasonicated for 5min to ensure that the mixed solution is evenly dispersed. Subsequently, the reactor is sealed and heated at 150°C for 18h. After cooling, the solid is centrifuged and washed three times with excess methanol. After drying, a brown-yellow metal-organic framework material, MOF-150T-(1:1), is obtained.

[0066] S2. The metal organic framework MOF-150T-(1:1) obtained in S1 was placed in a tubular furnace, heated to 1000°C at a heating rate of 5°C / min under an Ar atmosphere and kept warm for 2 hours. After cooling to room temperature, a two-dimensional ultrathin graphene nanosheet material based on the metal organic framework MOF-150T-(1:1) was obtained (denoted as GNS-150T-(1:1)).

[0067] Example 3

[0068] S1. Dissolve 0.2g of zinc acetate and 0.2g of 2,5-dihydroxyterephthalic acid in 8mL of methanol and 60mL of ethanol, respectively. Then, mix the two solutions in a solvent thermal reactor to obtain a suspension. The suspension is ultrasonicated for 5min to ensure that the mixed solution is evenly dispersed. Subsequently, the reactor is sealed and heated at 180°C for 6h. After cooling, the solid is centrifuged and washed three times with excess methanol. After drying, a brown-yellow metal-organic framework material, MOF-180T-(1:1), is obtained.

[0069] S2. The metal organic framework MOF-180T obtained in S1 was placed in a tubular furnace, heated to 1000°C at a heating rate of 5°C / min under an Ar atmosphere and kept warm for 2 h. After cooling to room temperature, a two-dimensional ultrathin graphene nanosheet material based on the metal organic framework MOF-180T (denoted as GNS-180T-(1:1)) was obtained.

[0070] Example 4

[0071] S1. Dissolve 0.4 g of zinc acetate and 0.2 g of 2,5-dihydroxyterephthalic acid in 8 mL of methanol and 60 mL of ethanol, respectively. Then, mix the two solutions in a solvent thermal reactor to obtain a suspension. The suspension is ultrasonicated for 5 minutes to ensure that the mixed solution is evenly dispersed. Subsequently, the reactor is sealed and heated at 150 ° C for 18 hours. After cooling, the solid is centrifuged and washed three times with excess methanol. After drying, a brown-yellow metal-organic framework material, MOF-150T-(2:1), is obtained.

[0072] S2. The metal organic framework MOF-150T-(2:1) obtained in S1 was placed in a tubular furnace, heated to 1000°C at a heating rate of 5°C / min under an Ar atmosphere and kept warm for 2 hours. After cooling to room temperature, a two-dimensional ultrathin graphene nanosheet material based on the metal organic framework MOF-150T-(2:1) (denoted as GNS-150T-(2:1)) was obtained.

[0073] Example 5

[0074] S1. Dissolve 0.2g of zinc acetate and 0.2g of 2,5-dihydroxyterephthalic acid in 8mL of methanol and 60mL of ethanol, respectively. Then mix the two solutions in a solvent thermal reactor to obtain a suspension. The suspension is ultrasonicated for 5min to ensure that the mixed solution is evenly dispersed. Subsequently, the reactor is sealed and heated at 150°C for 18h. After cooling, the solid is centrifuged and washed three times with excess methanol. After drying, a brown-yellow metal-organic framework material, MOF-150T-(1:1), is obtained.

[0075] S2. Place 1g MOF-150T-(1:1) obtained in S1 and 2g melamine in a tubular furnace, with melamine and the metal-organic framework material at the upstream and downstream respectively. Heat to 1000°C at a heating rate of 5°C / min under Ar atmosphere and keep warm for 2h. After cooling to room temperature, obtain nitrogen-doped two-dimensional ultrathin graphene nanosheet material based on the metal-organic framework MOF-150T-(1:1) (denoted as NGNS-150T).

[0076] Example 6

[0077] S1. Dissolve 0.2g of zinc acetate and 0.2g of 2,5-dihydroxyterephthalic acid in 8mL of methanol and 60mL of ethanol, respectively. The two solutions are then mixed in a solvothermal reactor to obtain a suspension. The suspension is then sonicated for 5 minutes to ensure uniform dispersion of the mixed solution. The reactor is then sealed and heated at 150°C for 18 hours. After cooling, the solid is centrifuged and washed three times with excess methanol. After drying, a brown-yellow metal-organic framework material, MOF-150T-(1:1), is obtained. 1g of MOF-150T-(1:1) is ultrasonically suspended in n-hexane, and an aqueous solution of ferric acetate is added dropwise. After complete absorption of the solution, the solid is centrifuged and dried to obtain a brown-yellow metal-organic framework material with ferric acetate adsorbed internally, namely [Fe]@MOF-150T-(1:1).

[0078] S2. Place 1g [Fe]@MOF-150T, a metal organic framework with iron acetate adsorbed inside, and 2g melamine obtained in S1 in a tubular furnace, with melamine and the metal organic framework material located upstream and downstream, respectively. Heat to 1000°C at a heating rate of 5°C / min under Ar atmosphere and keep warm for 2h. After cooling to room temperature, obtain a nitrogen-doped iron-loaded two-dimensional ultrathin graphene nanosheet material based on the metal organic framework MOF-150T-(1:1) (denoted as Fe / NGNS-150T-(1:1)).

[0079] Example 7

[0080] S1. Dissolve 0.2g of zinc acetate and 0.2g of 2,5-dihydroxyterephthalic acid in 8mL of methanol and 60mL of ethanol, respectively. Then mix the two solutions in a solvent thermal reactor to obtain a suspension. Add a methanol solution of ferric chloride to the suspension, and sonicate the suspension for 5 minutes to ensure that the mixed solution is evenly dispersed. Subsequently, seal the reactor and heat at 150°C for 18 hours. After cooling, centrifuge the solid and wash it three times with excess methanol. After drying, a brown-green metal-organic framework material, Fe-MOF-150T-(1:1), is obtained.

[0081] S2. Place 1 g Fe-MOF-150T-(1:1) metal organic framework obtained in S1 and 2 g melamine in a tubular furnace, with melamine and the metal organic framework material at the upstream and downstream respectively. Heat to 1000 °C at a heating rate of 5 °C / min under Ar atmosphere and keep warm for 2 h. After cooling to room temperature, obtain nitrogen-doped iron-loaded two-dimensional ultrathin graphene nanosheet material based on the metal organic framework MOF-150T-(1:1) (denoted as Fe-NGNS-150T-(1:1)).

[0082] Comparative Example 1

[0083] Compared with Example 1, the main difference is that the mass ratio of zinc metal salt to 2,5-dihydroxyterephthalic acid organic monomer is adjusted from 1:1 to 3:1.

[0084] S1. Dissolve 0.6 g of zinc acetate and 0.2 g of 2,5-dihydroxyterephthalic acid in 8 mL of methanol and 60 mL of ethanol, respectively. Then mix the two solutions in a solvent thermal reactor to obtain a suspension, and sonicate the suspension for 5 minutes to ensure that the mixed solution is evenly dispersed. Subsequently, seal the reactor and heat at 150 ° C for 18 hours. After cooling, centrifuge the solid and wash it three times with excess methanol. After drying, a brown-yellow metal-organic framework material, MOF-150T-(3:1), is obtained.

[0085] S2. The metal organic framework MOF-150T-(3:1) obtained in S1 was placed in a tubular furnace, heated to 1000°C at a heating rate of 5°C / min under an Ar atmosphere and kept warm for 2 hours. After cooling to room temperature, a one-dimensional carbon nanorod material based on the metal organic framework MOF-150T-(3:1) (denoted as CNR-150T-(3:1)) was obtained.

[0086] Comparative Example 2

[0087] Compared with Example 1, the main difference is that the mass ratio of zinc metal salt to 2,5-dihydroxyterephthalic acid organic monomer is adjusted from 1:1 to 4:1.

[0088] S1. Dissolve 0.8g of zinc acetate and 0.2g of 2,5-dihydroxyterephthalic acid in 8mL of methanol and 60mL of ethanol, respectively. Then mix the two solutions in a solvent thermal reactor to obtain a suspension, and sonicate the suspension for 5min to ensure that the mixed solution is evenly dispersed. Subsequently, seal the reactor and heat at 150°C for 18h. After cooling, centrifuge the solid and wash it three times with excess methanol. After drying, a brown-yellow metal-organic framework material, MOF-150T-(4:1), is obtained.

[0089] S2. The metal organic framework L-MOF-1 obtained in S1 was placed in a tubular furnace, heated to 1000°C at a heating rate of 5°C / min under an Ar atmosphere and kept warm for 2 hours. After cooling to room temperature, a one-dimensional carbon nanorod material based on the metal organic framework MOF-150T-(4:1) (denoted as CNR-150T-(4:1)) was obtained.

[0090] Figure 1 This is a flow chart of the present invention for preparing two-dimensional ultrathin graphene nanosheet materials.

[0091] Figure 2 The following is a flow chart of the preparation of Examples 1-7 and Comparative Examples 1-2 of the present invention, demonstrating that despite differences in the composition of the metal-organic framework, the material morphology and structure remain unchanged, and both yield two-dimensional ultrathin graphene nanosheets. However, changes in the synthetic raw material ratios lead to differences in the material morphology, and the altered morphology and structure make it impossible to obtain two-dimensional ultrathin graphene nanosheets.

[0092] Figure 3 is the X-ray diffraction of the MOF precursors involved in the examples and comparative examples of the present invention, Figure 4 The following are X-ray diffraction patterns of the two-dimensional ultrathin graphene nanosheets obtained in the examples of the present invention and the one-dimensional carbon nanorods obtained in the comparative examples. In the derived carbon material patterns, only two broad peaks appear at approximately 24° and 44°, corresponding to the (002) and (101) crystal planes of the graphene phase, respectively. This indicates a high degree of carbonization and no residual zinc metal.

[0093] Figure 5 A-5H is a scanning electron micrograph of the MOF precursor material MOF-XT-Y (X=130, 150, 180; Y=(1:1), (2:1)) obtained in an embodiment of the present invention; Figure 6 A-6F is a scanning electron micrograph of the two-dimensional ultrathin graphene nanosheet material GNS-XT-Y (X=130, 150, 180; Y=(1:1), (2:1)) obtained in an embodiment of the present invention; Figure 5G-5H is a scanning electron microscope image of the MOF precursor material MOF-150T-Y (Y=(3:1), (4:1)) obtained in the comparative example of the present invention; Figure 6 G-6H is a scanning electron micrograph of the one-dimensional carbon nanorod material CNR-150T-Y (Y = (3:1), (4:1)) obtained in a comparative example of the present invention. The product obtained in the example exhibits a distinct graphene nanosheet structure with an extremely high exposed area. In contrast, the product obtained in the comparative example exhibits a one-dimensional carbon nanorod structure with a smaller exposed area.

[0094] Figure 7 This is an atomic force microscope image of the two-dimensional ultrathin graphene nanosheet material obtained in Example 2 of the present invention, showing that the thickness of the graphene nanosheet is about 5 nm.

[0095] Figure 8 This is a scanning transmission electron microscope image of the two-dimensional ultrathin graphene nanosheet material obtained in Example 2 of the present invention, in which the ultrathin structure of the graphene nanosheet can be clearly observed.

[0096] Figure 9 This is a nitrogen adsorption isotherm diagram of the two-dimensional ultrathin graphene nanosheet material obtained in Example 2 of the present invention. Figure 10 The pore size distribution diagram of the two-dimensional ultrathin graphene nanosheet material obtained in Example 2 of the present invention shows a typical type II adsorption isotherm, indicating that the material presents a non-porous or macroporous structure. This is because the material presents an ultrathin (~5nm) nanosheet structure; the isotherm is processed using the BET (Brunauer-Emmet-Teller) formula, and its specific surface area is 225m 2 / g, which is beneficial to the contact between the surface sites of the material and the surrounding environment and the transmission of substances.

[0097] Figure 11 This is a performance diagram of the application of the nitrogen-doped iron-loaded two-dimensional ultrathin graphene nanosheet material obtained in Example 6 of the present invention in the oxygen reduction reaction.

[0098] Figure 12 This is a performance diagram of the application of the nitrogen-doped iron-loaded two-dimensional ultrathin graphene nanosheet material obtained in Example 6 of the present invention in the carbon dioxide reduction reaction.

[0099] In summary, the two-dimensional ultrathin graphene nanosheet material prepared by the present invention has a stable framework, ultrathin structure and rich porosity, so it can be used as a strong carrier to provide a large number of exposed sites for loading catalytic active substances, and is easy to promote and use.

[0100] The above-described embodiments of the present invention do not limit the scope of protection of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the claims of the present invention.

Claims

1. A method for preparing two-dimensional ultrathin graphene nanosheets, characterized in that: The steps include: S1. Dissolve a zinc metal salt and a 2,5-dihydroxyterephthalic acid organic monomer in an organic solvent, add the two solutions to a reactor to obtain a mixture, disperse the mixture evenly by ultrasonication, and then seal and heat. After the reaction is completed and cooled to room temperature, filter or centrifuge to separate the solid, wash it with an organic solvent, and then dry it to obtain a zinc-based metal organic framework material; the ultrasonic treatment time is 5 minutes; S2, heat-treating the zinc-based metal organic framework material obtained in S1, pyrolyzing it in an atmosphere, and cooling it to obtain a two-dimensional ultrathin graphene nanosheet material; The mass ratio of the zinc metal salt and the 2,5-dihydroxyterephthalic acid organic monomer in S1 is 1:1; The heating temperature of the reactor in S1 is 130-180°C, and the heating time is 6-24h; The heat treatment temperature of the zinc-based metal organic framework material in S2 is 900-1100° C. and the treatment time is 0.5-4 h; The organic solvent in S1 is methanol or ethanol.

2. The method for preparing a two-dimensional ultrathin graphene nanosheet according to claim 1, wherein: The zinc metal salt in S1 is zinc acetate, zinc nitrate or zinc chloride.

3. The method for preparing a two-dimensional ultrathin graphene nanosheet according to claim 1, wherein: The washing solvent in S1 is methanol or ethanol, and the washing times are 3-6 times.

4. The method for preparing a two-dimensional ultrathin graphene nanosheet according to claim 1, wherein: In S1, a non-zinc metal salt is added to a zinc metal salt to obtain an organic framework material loaded with the corresponding metal; or an organic framework material loaded with a non-zinc metal is obtained by post-processing after obtaining a zinc-based metal organic framework material.

5. The method for preparing a two-dimensional ultrathin graphene nanosheet according to claim 1, wherein: The atmosphere is an inert atmosphere or an atmosphere required for element doping.

Images