Melamine covalent organic framework supported graphene material, preparation method and application thereof

Abstract

The present application relates to melamine covalent organic framework load graphene material and preparation method and application, belong to the technical field of energy storage material preparation.The technical problem solved by the present application is to provide a simple method for preparing a covalent organic framework load graphene material.The method mixes melamine, acid material and graphene oxide with water, then adds dialdehyde material, reacts at 120-180 DEG C for 70-75 hours, takes the solid, purifies and dries to obtain a covalent organic framework load graphene material.The present application uses melamine as a COF block, which is low in cost, high in nitrogen content, rich in porosity, has an ordered pore structure, a high specific surface area and excellent thermal stability, is synthesized by a hydrothermal method, is non-toxic and non-polluting, has a simple synthesis method and is easy to mass-produce.Furthermore, the in-situ growth of COF and the synchronous reduction of graphene oxide material greatly improve the electrical conductivity of the material, so that the material has good electrochemical energy storage performance.

Description

Technical Field

[0001] This invention relates to melamine covalent organic framework supported graphene materials, their preparation methods, and applications, belonging to the field of energy storage material preparation technology. Background Technology

[0002] Compared to traditional capacitors, supercapacitors possess ultra-high specific capacitance, high energy density, and excellent cycle performance, making them ideal energy storage devices. Supercapacitors not only exhibit the rapid charge-discharge performance of traditional capacitors but also possess the energy storage characteristics of secondary batteries, making them an ideal new type of energy storage device. Supercapacitors mainly consist of electrodes, electrolyte, separator, and current collector. The electrode materials and electrolyte have a significant impact on their electrochemical performance. The separator primarily serves to isolate the positive and negative electrodes, preventing short circuits, and provides ion transport channels during charge and discharge. The current collector mainly acts as a conductive carrier for the electrodes; it is often selected from metallic materials that are stable in the electrolyte, do not react with the electrodes, and have good conductivity, in order to reduce the internal resistance of the capacitor.

[0003] Covalent organic frameworks (COFs) are a novel type of crystalline organic porous material, first synthesized in 2005. Their designable structures, unique chemistry, regular pore structures, and novel structures and applications are increasingly expanding. Currently, COF materials show great promise in adsorption, energy storage, catalysis, optoelectronics, and sensing. However, single COF materials often exhibit low electrical conductivity, which hinders their performance in practical electrode applications.

[0004] Chinese invention patent application number 201810972176.1 discloses a graphene-like composite electrode material and its preparation method and application. This electrode material is prepared by combining graphene-like material (made from walnut shells) with a covalent organic framework. The composite method involves directly ultrasonically dispersing the graphene-like material in deionized water for 1-2 hours, adding the covalent organic framework, stirring for 8-12 hours, centrifuging, and vacuum drying. This method is a physical blending process, which cannot effectively improve electrochemical performance. Furthermore, the covalent organic framework is prepared using a solvothermal method, employing high-boiling-point organic solvents such as dimethylacetamide and o-dichlorobenzene, which is complex and costly.

[0005] Chinese invention patent application number 201810860222.9 discloses a method for preparing a covalent organic framework / graphene composite material and its electrical properties. This material is produced at room temperature using reduced graphene oxide uniformly dispersed in the bulk phase as a template, and a covalent organic framework structure is grown in situ based on Schiff base polymerization. The covalent organic framework uses 1,3,5-pyromellitic methyl ether and 3,8-diamino-6-phenylphenanthridine as precursor molecules, with 6M acetic acid providing acidic conditions. The Schiff base polymerization reaction uniformly distributes pyridine nitrogen atoms within the covalent organic framework, providing uniform active sites. While this method can composite covalent organic frameworks and graphene, improving their electrochemical performance, it requires dioxane as a solvent, making the process complex and costly.

[0006] In summary, existing graphene-covalent organic framework composites all employ organic solvent systems, which are complex to operate, costly, and difficult to apply on a large scale. Summary of the Invention

[0007] To address the above deficiencies, the first technical problem solved by this invention is to provide a simple method for preparing graphene materials supported by a melamine covalent organic framework.

[0008] The present invention discloses a method for preparing graphene materials supported on melamine covalent organic frameworks, comprising the following steps:

[0009] Melamine, acid materials, graphene oxide, and water were mixed, and then dialdehyde materials were added. The mixture was reacted at 120–180 °C for 70–75 h. The solid was purified and dried to obtain covalent organic framework-supported graphene materials.

[0010] By weight, melamine 14-130 parts, acid materials 20-2100 parts, dialdehyde materials 28-250 parts, and graphene oxide 100-150 parts.

[0011] In one specific embodiment, the acid material is at least one selected from acetic acid, p-toluenesulfonic acid, hydrochloric acid, and sulfuric acid.

[0012] In one specific embodiment, the dialdehyde material is at least one of piperazine dicarboxaldehyde, terephthalaldehyde, 2,5-dihydroxyterephthalaldehyde, and dialdehyde pyridine.

[0013] In one embodiment of the present invention, the mixing is performed by ultrasonication and stirring dispersion for a time of 0.5 to 1 hour.

[0014] In one specific implementation, the reaction is carried out at 120–150°C for 72 hours.

[0015] In one specific embodiment of the present invention, the weight ratio of melamine to graphene oxide is 1:1 to 10. In another specific embodiment, the weight ratio of melamine to graphene oxide is 1:2.9 to 6.

[0016] The purification of the present invention can be carried out using conventional methods. In one specific embodiment of the present invention, the purification is carried out by Soxhlet extraction of the solid material with ethanol, acetone and water for 8-12 hours respectively.

[0017] In one specific embodiment of the present invention, the extraction time is 10 hours.

[0018] The present invention also provides a melamine covalent organic framework supported graphene material prepared by the method of the present invention.

[0019] This invention relates to a melamine covalent organic framework-supported graphene material, composed of a covalent organic framework and graphene oxide, wherein the covalent organic framework is grown in situ on the graphene oxide, and the graphene oxide is reduced during the synthesis process. This material exhibits high electrical conductivity and good electrochemical energy storage performance.

[0020] In one specific embodiment of the present invention, the specific surface area of ​​the melamine covalent organic framework-supported graphene material is 230–410 m². 2 / g.

[0021] This invention also provides the application of the melamine covalent organic framework-supported graphene material described herein in supercapacitor electrode materials.

[0022] The melamine covalent organic framework-supported graphene material of this invention can be used as an electrode material in supercapacitors.

[0023] In one specific embodiment, the supercapacitor electrode is prepared by the following method: melamine covalent organic framework-supported graphene material, conductive carbon black and PVDF are milled and dispersed with N-methylpyrrolidone, uniformly coated onto the current collector surface, and dried to obtain the electrode.

[0024] In one specific embodiment, the weight ratio of melamine covalent organic framework-supported graphene material, conductive carbon black, and PVDF is 5–10:0.5–2:1. In one embodiment of the present invention, the weight ratio of melamine covalent organic framework-supported graphene material, conductive carbon black, and PVDF is 8:1:1.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. This invention uses melamine as COF building blocks, which are low in cost, high in nitrogen content, porous, have an ordered pore structure, high specific surface area, and excellent thermal stability.

[0027] 2. This invention uses a hydrothermal method for synthesis, which is non-toxic and pollution-free. The synthesis method is simple and easy to mass-produce.

[0028] 3. This invention utilizes the in-situ growth of COF and the simultaneous reduction of graphene oxide material to greatly improve the electrical conductivity of COF material. Compared with existing COF materials, the melamine-based covalent organic supported graphene material of this invention has better electrochemical energy storage performance. Attached Figure Description

[0029] Figure 1 This is a scanning electron microscope image of the melamine covalent organic framework-supported graphene material prepared in Example 1.

[0030] Figure 2 This is a scanning electron microscope image of the melamine covalent organic framework-supported graphene material prepared in Example 2.

[0031] Figure 3 This is a scanning electron microscope image of the melamine covalent organic framework-supported graphene material prepared in Example 3.

[0032] Figure 4 This is a scanning electron microscope image of the melamine covalent organic framework-supported graphene material prepared in Example 4.

[0033] Figure 5 This is a scanning electron microscope image of the melamine covalent organic framework-supported graphene material prepared in Example 5.

[0034] Figure 6 Scanning electron microscope image of the organic framework material prepared for Comparative Example 1.

[0035] Figure 7 Thermogravimetric curves of the organic framework material prepared in Comparative Example 1 and the melamine covalent organic framework-supported graphene material prepared in Example 4. Detailed Implementation

[0036] The present invention discloses a method for preparing graphene materials supported on melamine covalent organic frameworks, comprising the following steps:

[0037] Melamine, acidic materials, graphene oxide, and water were mixed, and then dialdehyde materials were added. The mixture was reacted at 120–180 °C for 70–75 h. The solid was purified and dried to obtain melamine covalent organic framework supported graphene material.

[0038] By weight, melamine 14-130 parts, acid materials 20-2100 parts, dialdehyde materials 28-250 parts, and graphene oxide 100-150 parts.

[0039] This invention utilizes water as the reaction medium, resulting in low cost and high performance. Covalent organic framework materials are grown in situ on graphene oxide, while the graphene oxide is reduced during the synthesis process. The resulting melamine-covalent organic framework-supported graphene material exhibits improved conductivity and specific capacitance.

[0040] Commonly used acid materials are all suitable for this invention. In one specific embodiment, the acid material is at least one selected from acetic acid, p-toluenesulfonic acid, hydrochloric acid, and sulfuric acid. In one specific embodiment, the acid material is p-toluenesulfonic acid.

[0041] Commonly used dialdehyde materials are applicable to this invention. In one specific embodiment, the dialdehyde material is at least one of piperazine dicarboxaldehyde, terephthalaldehyde, 2,5-dihydroxyterephthalaldehyde, and dialdehyde pyridine.

[0042] The mixing method can employ conventional methods in the art, such as stirring, shaking, and ultrasonication. In one embodiment of the present invention, the mixing is ultrasonication followed by stirring and dispersion for 0.5 to 1 hour.

[0043] In one specific embodiment of the present invention, melamine, acidic materials, graphene oxide, and water are mixed using the following method: after the melamine and acidic materials are homogenized, they are added to an aqueous solution of graphene oxide.

[0044] In one specific embodiment of the present invention, the weight ratio of melamine to graphene oxide is 1:1 to 10. In another specific embodiment, the weight ratio of melamine to graphene oxide is 1:2.9 to 6.

[0045] In one specific implementation, the reaction is carried out at 120–150°C for 72 hours.

[0046] The purification of the present invention can be carried out using conventional methods. In one specific embodiment of the present invention, the purification is carried out by Soxhlet extraction of the solid material with ethanol, acetone and water for 8-12 hours respectively.

[0047] The extraction time of 8–12 h refers to the extraction time for each extraction, which means first extracting the solid with ethanol for 8–12 h, then extracting the solid with acetone for 8–12 h, and finally extracting the solid with water for 8–12 h.

[0048] In one specific embodiment of the present invention, the extraction time is 10 hours.

[0049] After purification, the product is dried. Commonly used drying methods in the field are applicable to this invention, such as baking and freeze drying.

[0050] The present invention also provides a melamine covalent organic framework supported graphene material prepared by the method of the present invention.

[0051] This invention relates to a melamine covalent organic framework-supported graphene material, composed of a covalent organic framework and graphene oxide, wherein the covalent organic framework is grown in situ on the graphene oxide, and the graphene oxide is reduced during the synthesis process. This material exhibits high electrical conductivity and good electrochemical energy storage performance.

[0052] In one specific embodiment of the present invention, the specific surface area of ​​the melamine covalent organic framework-supported graphene material is 230–410 m². 2 / g.

[0053] This invention also provides the application of the melamine covalent organic framework-supported graphene material described herein in supercapacitor electrode materials.

[0054] The melamine covalent organic framework-supported graphene material of this invention can be used as an electrode material in supercapacitors.

[0055] In one specific embodiment, the supercapacitor electrode is prepared by the following method: melamine covalent organic framework-supported graphene material, conductive carbon black and PVDF are milled and dispersed with N-methylpyrrolidone, uniformly coated onto the current collector surface, and dried to obtain the electrode.

[0056] In one specific embodiment, the weight ratio of melamine covalent organic framework-supported graphene material, conductive carbon black, and PVDF is 5–10:0.5–2:1. In one embodiment of the present invention, the weight ratio of melamine covalent organic framework-supported graphene material, conductive carbon black, and PVDF is 8:1:1.

[0057] The specific embodiments of the present invention will be further described below with reference to examples, but the present invention is not limited to the scope of the embodiments described herein.

[0058] Example 1

[0059] The following method was used to prepare melamine covalent organic framework-supported graphene materials:

[0060] 128 mg of melamine and 2025 mg of p-toluenesulfonic acid were ground evenly and then added to an aqueous solution containing 130 mg of graphene oxide. The mixture was ultrasonically dispersed and stirred for 1 hour. 249 mg of 2,5-dihydroxyterephthalaldehyde was then added and homogenized. The system was then sealed in a hydrothermal reactor and reacted at 150 °C for 72 hours. After the reaction was completed, the solid material was extracted with ethanol, acetone, and water, respectively, using a Soxhlet extractor for 10 hours. Finally, the solid was freeze-dried to obtain melamine covalent organic framework-supported graphene material.

[0061] The scanning electron microscope image of the melamine covalent organic framework-supported graphene material is shown below. Figure 1 Independent rod-shaped COF crystals were observed under field emission scanning electron microscopy, and BET characterization showed that the specific surface area of ​​this material was 405 m². 2 / g.

[0062] Example 2

[0063] The following method was used to prepare melamine covalent organic framework-supported graphene materials:

[0064] 85 mg of melamine and 1350 mg of p-toluenesulfonic acid were ground evenly and then added to an aqueous solution containing 130 mg of graphene oxide. The mixture was ultrasonically dispersed and stirred for 1 hour. 166 mg of dialdehyde pyridine was then added and homogenized. The system was then sealed in a hydrothermal reactor and reacted at 120 °C for 72 hours. After the reaction was completed, the solid material was extracted with ethanol, acetone, and water, respectively, using a Soxhlet extractor for 10 hours. Finally, the solid was freeze-dried to obtain melamine covalent organic framework-supported graphene material.

[0065] The scanning electron microscope image of the melamine covalent organic framework-supported graphene material is shown below. Figure 2 Uniformly grown COF on the graphene surface was observed using field emission scanning electron microscopy, and BET characterization showed that the specific surface area of ​​this material was 366 m². 2 / g.

[0066] Example 3

[0067] The following method was used to prepare melamine covalent organic framework-supported graphene materials:

[0068] 43 mg of melamine and 340 mg of 6 mol / L glacial acetic acid were mixed evenly and then added to an aqueous solution containing 130 mg of graphene oxide. The mixture was ultrasonically dispersed by stirring for 1 hour, followed by the addition of 166 mg of terephthalaldehyde and homogenization. The system was then sealed in a hydrothermal reactor and reacted at 120 °C for 72 hours. After the reaction was complete, the solid material was extracted with ethanol, acetone, and water, respectively, using a Soxhlet extractor for 10 hours. Finally, the solid was freeze-dried to obtain melamine covalent organic framework-supported graphene material.

[0069] The scanning electron microscope image of the melamine covalent organic framework-supported graphene material is shown below. Figure 3 Uniformly grown COF on the graphene surface was observed using field emission scanning electron microscopy, with no independent COF crystals found. BET characterization determined the specific surface area of ​​this material to be 320 m². 2 / g.

[0070] Example 4

[0071] The following method was used to prepare melamine covalent organic framework-supported graphene materials:

[0072] After mixing 22 mg of melamine and 138 mg of 1 mol / L hydrochloric acid, the mixture was added to an aqueous solution containing 130 mg of graphene oxide. The mixture was ultrasonically dispersed and stirred for 1 hour. Then, 42 mg of terephthalaldehyde was added and homogenized. The system was then sealed in a hydrothermal reactor and reacted at 150 °C for 72 hours. After the reaction was completed, the solid material was extracted with ethanol, acetone, and water, respectively, using a Soxhlet extractor for 10 hours. Finally, the solid was freeze-dried to obtain melamine covalent organic framework-supported graphene material.

[0073] The scanning electron microscope image of the melamine covalent organic framework-supported graphene material is shown below. Figure 4 Uniformly grown COF on the graphene surface was observed using field emission scanning electron microscopy, with no independent COF crystals found. BET characterization determined the specific surface area of ​​this material to be 230 m² / s. 2 / g.

[0074] Example 5

[0075] The following method was used to prepare melamine covalent organic framework-supported graphene materials:

[0076] After mixing 14 mg of melamine and 85 mg of 1 mol / L hydrochloric acid, the mixture was added to an aqueous solution containing 130 mg of graphene oxide. The mixture was ultrasonically dispersed and stirred for 1 hour. Then, 28 mg of piperazine dicarboxylate was added and homogenized. The system was then sealed in a hydrothermal reactor and reacted at 150 °C for 72 hours. After the reaction was completed, the solid material was extracted with ethanol, acetone, and water, respectively, using a Soxhlet extractor for 10 hours. Finally, the solid was freeze-dried to obtain covalent organic framework-supported graphene material.

[0077] The scanning electron microscope image of the melamine covalent organic framework-supported graphene material is shown below. Figure 5 Uniformly grown COF on the graphene surface was observed using field emission scanning electron microscopy; no independent COF crystals were found. BET characterization determined the specific surface area of ​​this material to be 100 m². 2 / g.

[0078] Example 6

[0079] Melamine covalent organic framework-supported graphene material, conductive carbon black, and PVDF were dispersed in an 8:1:1 mass ratio using N-methylpyrrolidone and then uniformly coated onto the surface of the current collector. After drying at 80°C for 24 hours, the desired electrode was obtained. The specific capacitance of the motor material was measured using a three-electrode 0.5M sulfuric acid solution. The melamine covalent organic framework-supported graphene material used was prepared according to Examples 1-5, and the measurement results are shown in Table 1.

[0080] Table 1

[0081] Example 1 201 Example 2 210 Example 3 330 Example 4 390 Example 5 280

[0082] Comparative Example 1

[0083] Organic framework materials were prepared using the following method:

[0084] After mixing 22 mg of melamine and 138 mg of 1 mol / L hydrochloric acid evenly, 42 mg of terephthalaldehyde was added and homogenized. The system was then sealed in a hydrothermal reactor and reacted at 150 °C for 72 h. After the reaction was completed, the solid material was extracted with ethanol, acetone, and water respectively by Soxhlet extraction for 10 h. Finally, the solid was freeze-dried to obtain the organic framework material.

[0085] The scanning electron microscope image of the organic framework material is shown below. Figure 6 Rod-shaped COF crystals were observed using field emission scanning electron microscopy, and BET characterization showed that the specific surface area of ​​this material was 450 m². 2 / g.

[0086] The thermogravimetric curves of the materials in Comparative Example 1 and Example 4 are shown below. Figure 7 As can be seen from the figure, the material of this invention has good thermal stability.

[0087] The organic framework material, conductive carbon black, and PVDF were dispersed in an 8:1:1 mass ratio using N-methylpyrrolidone, then uniformly coated onto the current collector surface. After drying at 80°C for 24 hours, the desired electrode was obtained. The specific capacitance of this electrode material in a 0.5M sulfuric acid solution with three electrodes was 0.5 F / g. The low electrochemical energy storage of this material can be attributed to the fact that the pure COF material is an insulator, unable to effectively transport ions, and also makes it difficult for the redox active groups inside the COF to participate in the reaction.

[0088] Comparative Example 2

[0089] The covalent organic framework blended graphene material was prepared using the following method:

[0090] (1) After mixing 43 mg of melamine and 340 mg of 6 mol / L glacial acetic acid evenly, 166 mg of terephthalaldehyde material was added and homogenized. The system was then sealed in a hydrothermal reactor and reacted at 120 °C for 72 h. After the reaction was completed, the solid material was extracted with ethanol, acetone and water respectively by Soxhlet extraction for 10 h. Finally, the solid was freeze-dried to obtain the organic framework material.

[0091] (2) 130 mg of graphene oxide aqueous solution was sealed in a hydrothermal reactor and reacted at 120 °C for 72 h. After the reaction was completed, the solid material was extracted by Soxhlet extraction with ethanol, acetone and water for 10 h respectively. Finally, the solid was freeze-dried to obtain reduced graphene oxide material.

[0092] (3) The above-mentioned organic framework material and reduced graphene oxide are blended to obtain covalent organic framework blended graphene material.

[0093] The covalent organic framework (COF) blended with graphene, conductive carbon black, and PVDF was dispersed in an 8:1:1 mass ratio using N-methylpyrrolidone and then uniformly coated onto the current collector surface. After drying at 80°C for 24 hours, the desired electrode was obtained. The specific capacitance of this electrode material in a 0.5M sulfuric acid solution with three electrodes was 60 F / g. The capacitance performance of this material is far inferior to that of Example 3. This is because the COF was not grown in situ on the graphene surface, which failed to effectively improve the conductivity of the COF, thus preventing it from fully realizing its electrochemical performance.

[0094] Comparative Example 3

[0095] Reduced graphene oxide material was prepared using the following method:

[0096] 130 mg of graphene oxide was dissolved in an aqueous solution and sealed in a hydrothermal reactor. The reaction was carried out at 120 °C for 72 h. After the reaction was completed, the solid material was extracted with ethanol, acetone, and water respectively using a Soxhlet extractor for 10 h each. Finally, the solid was freeze-dried to obtain reduced graphene oxide material. Smooth graphene sheets could be observed under a field emission scanning electron microscope. BET characterization showed that the specific surface area of ​​this material was 80 m². 2 / g.

[0097] The reduced graphene oxide blend, conductive carbon black, and PVDF were dispersed in an 8:1:1 mass ratio using N-methylpyrrolidone and then uniformly coated onto the current collector surface. After drying at 80°C for 24 hours, the desired electrode was obtained. The specific capacitance of this electrode material in a 0.5M sulfuric acid solution with three electrodes was 80 F / g. The capacitance performance of this material is far inferior to that of the embodiments of this invention because the porous structure of the reduced graphene oxide only provides double-layer capacitance characteristics.

Claims

1. A method for preparing graphene materials supported on melamine covalent organic frameworks, characterized in that, Includes the following steps: Melamine, acidic materials, graphene oxide, and water were mixed, and then dialdehyde materials were added. The mixture was subjected to a hydrothermal reaction at 120–180°C for 70–75 hours. The solid was purified and dried to obtain melamine covalent organic framework-supported graphene material. The mixing was performed by ultrasonication and stirring for 0.5–1 hour. By weight, the composition includes 14-130 parts melamine, 20-2100 parts acidic materials, 28-250 parts dialdehyde materials, and 100-150 parts graphene oxide; the weight ratio of melamine to graphene oxide is 1:2.9-6.

2. The method for preparing melamine covalent organic framework-supported graphene material according to claim 1, characterized in that: The acid material is at least one of acetic acid, p-toluenesulfonic acid, hydrochloric acid, and sulfuric acid; the dialdehyde material is at least one of piperazine dicarboxaldehyde, terephthalaldehyde, 2,5-dihydroxyterephthalaldehyde, and dialdehyde pyridine.

3. The method for preparing melamine covalent organic framework-supported graphene material according to claim 1, characterized in that: Hydrothermal reaction at 120–150℃ for 72 hours.

4. The method for preparing melamine covalent organic framework-supported graphene material according to claim 1, characterized in that: The purification process involved Soxhlet extraction of the solid with ethanol, acetone, and water for 8–12 hours, respectively.

5. The method for preparing melamine covalent organic framework-supported graphene material according to claim 4, characterized in that: The purification process involved Soxhlet extraction of the solid with ethanol, acetone, and water for 10 hours each.

6. The melamine covalent organic framework-supported graphene material prepared by the method according to any one of claims 1 to 5.

7. The application of the melamine covalent organic framework-supported graphene material according to claim 6 in supercapacitor electrode materials.

8. The application of the melamine covalent organic framework-supported graphene material according to claim 7 in supercapacitor electrode materials, characterized in that, The supercapacitor electrode was prepared by the following method: melamine covalent organic framework-supported graphene material, conductive carbon black and PVDF were dispersed by grinding with N-methylpyrrolidone, uniformly coated onto the surface of the current collector, and dried to obtain the electrode.

9. The application of the melamine covalent organic framework-supported graphene material according to claim 8 in supercapacitor electrode materials, characterized in that: The weight ratio of melamine covalent organic framework-supported graphene material, conductive carbon black and PVDF is 5-10:0.5-2:

1.

10. The application of the melamine covalent organic framework-supported graphene material according to claim 9 in supercapacitor electrode materials, characterized in that: The weight ratio of melamine covalent organic framework-supported graphene material, conductive carbon black, and PVDF is 8:1:1.

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