A melamine-cyanuric acid supramolecular material and its preparation method

Abstract

This invention relates to melamine-cyanuric acid supramolecular nanosheets and their preparation method. The process of this invention is simple. The melamine-cyanuric acid supramolecular sheets prepared under the control of a capping agent have extremely small nanoscale dimensions and good crystallinity. Using these as a precursor, nanoscale graphitic carbon nitride can be directly pyrolyzed to obtain nanoscale graphitic carbon nitride. The resulting product has increased specific surface area, reduced structural defects, and increased yield. The final nanoscale graphitic carbon nitride can be widely used in wastewater purification and hydrogen production.

Description

Technical Field

[0001] This invention belongs to the field of supramolecular material preparation technology, specifically relating to a melamine-cyanuric acid supramolecular material and its preparation method. Background Technology

[0002] The information disclosed in the background section of this invention is intended only to enhance the understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Graphitic carbon nitride is an important and effective photocatalyst. Extensive research has been conducted both domestically and internationally to utilize its photocatalytic activity to split water and produce hydrogen, in order to solve the problem of over-reliance on fossil fuels. In addition, graphitic carbon nitride does not contain metal elements and can be directly generated by the simple pyrolysis of nitrogen-rich small molecules, which is undoubtedly very beneficial for its large-scale promotion in the future.

[0004] In current research, the small molecules used to synthesize graphitic carbon nitride mainly include urea, dicyandiamide, and melamine. Different precursors have different reaction pathways, but all suffer from low yields and numerous structural defects in the resulting graphitic carbon nitride. One solution is to use melamine and cyanuric acid as precursors. The two can spontaneously assemble into a supramolecular network structure in a solvent. After pyrolysis, graphitic carbon nitride with fewer structural defects can be directly generated. Moreover, the yield is improved by avoiding problems such as the sublimation of the precursors. Currently, melamine-cyanuric acid supramolecular materials of various shapes, such as rods and spheres, have been prepared by changing the solvent. However, the size of the supramolecular materials obtained by this continuous self-assembly is generally above the micrometer level. The size of the graphitic carbon nitride prepared by pyrolysis is also at the micrometer level. The relatively large size is not conducive to sufficient contact between the carbon nitride and the reaction substrate as a photocatalyst, nor is it conducive to its loading on the nanoscale pores of the support. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention proposes a melamine-cyanuric acid supramolecular material and its preparation method. This invention achieves control over the supramolecular structure of melamine-cyanuric acid by introducing aniline small molecules as end-capping agents. The amino groups in the end-capping agent can compete with the amino groups in melamine for binding sites with cyanuric acid. After the end-capping agent binds to the supramolecular structure, it stops the continued binding of nearby cyanuric acid or melamine. Therefore, the size of the final supramolecular sheet is limited to the nanoscale. The graphitic carbon nitride prepared by pyrolysis using this as a precursor also has a correspondingly small size.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] In a first aspect, the present invention provides a method for preparing a melamine-cyanuric acid supramolecular material, comprising the following steps:

[0008] (1) Weigh out melamine, cyanuric acid and capping agent respectively;

[0009] (2) Dissolve each of the above raw materials in a hot solvent;

[0010] (3) Mix the hot solvents that have dissolved the three raw materials separately, and keep stirring for 30-180 minutes. Ultrasonic treatment can be used during this period.

[0011] (4) After the reaction is complete, the precipitate in the solution is filtered out, washed with water and dried to obtain melamine-cyanuric acid supramolecular material.

[0012] The terminator uses aniline-based small molecules as terminators to control its structure and shape. These terminators are various types of molecular structures obtained by connecting one or more benzene rings to one or more amino groups, such as aniline, o-phenylenediamine, naphthylamine, anthraceneamine, etc.

[0013] In the preparation method of this invention, melamine, cyanuric acid, and the capping agent can be synthesized in solvents such as water, ethanol, dimethyl sulfoxide, and dimethylformamide. Melamine, cyanuric acid, and the capping agent are dissolved and mixed separately within a temperature range of 50°C to no more than the boiling point of the solvent used. Stirring is maintained for 30-180 minutes to obtain the supramolecular nanomaterials. In the raw material formulation, the amounts of "melamine + capping agent" and "cyanuric acid" should be approximately the same. The preparation process can be supplemented with ultrasonic treatment to further reduce the size of the melamine-cyanuric acid supramolecular nanosheets. Preferably, the molar ratio of melamine and the capping agent to the amount of cyanuric acid is (1-1.1):(1-1.1); and the molar ratio of melamine to the capping agent is (0-1):(0-1). In some specific embodiments, the molar ratio of melamine, capping agent, and cyanuric acid can be 1 / 3:2 / 3:1, 1 / 2:1 / 2:1, or 2 / 3:1 / 3:1.

[0014] In a second aspect, the present invention provides a melamine-cyanuric acid supramolecular material prepared by the above preparation method.

[0015] The melamine-cyanuric acid supramolecular nanomaterials prepared by this invention are light brown particles in appearance. The brown color gradually deepens with the increase of the capping agent content, and the microstructure of the particles is a nanoscale sheet structure.

[0016] The melamine-cyanuric acid supramolecular nanomaterials prepared by this invention are in the form of sheets with a sheet particle size between 1-1000 nanometers and a thickness between 1-500 nanometers. The nanosheets as a whole have very good crystallinity.

[0017] A third aspect of the present invention provides the application of the above-mentioned melamine-cyanuric acid supramolecular material in the preparation of nanoscale graphitic carbon nitride.

[0018] The melamine-cyanuric acid supramolecular nanomaterials prepared by this invention can be used as precursors to directly generate graphitic carbon nitride at 500-600℃. The resulting product retains the layered structure of the precursor melamine-cyanuric acid supramolecular nanomaterials, with increased specific surface area, reduced structural defects, and increased yield. The final nanoscale graphitic carbon nitride can be widely used in wastewater purification and hydrogen production.

[0019] The melamine-cyanuric acid supramolecular nanomaterials were applied to the pyrolysis preparation of nanoscale graphitic carbon nitride. The specific preparation steps are as follows:

[0020] Melamine-cyanuric acid supramolecular nanomaterials were placed in a crucible; the crucible containing the sample was placed in a tube furnace and heated to 500-600℃ at a heating rate of 1-10℃ / min, held at that temperature for 1-5h, and then cooled to room temperature at a cooling rate of 1-10℃ / min; the product in the crucible was collected and ground into powder to obtain well-crystallized graphitic carbon nitride.

[0021] Compared with the prior art, the present invention has achieved the following beneficial effects:

[0022] In this invention, aniline-based substances are used as end-capping agents to prepare nanoscale melamine-cyanuric acid supramolecular materials. The amino groups in the aniline-based substances compete with the amino groups in melamine for binding sites with cyanuric acid. The aniline-based end-capping agent, after binding with cyanuric acid, restricts the further growth and expansion of the nearby supramolecular network, ultimately reducing the size of the melamine-cyanuric acid supramolecular nanomaterials from the micrometer scale to the nanometer scale. Using this as a precursor, graphitic carbon nitride nanosheets can be prepared through a simple pyrolysis process. The nanoscale size of the supramolecular material extends into the final carbon nitride product, which is beneficial for increasing the specific surface area of ​​the final product and fully leveraging its photocatalytic activity. Attached Figure Description

[0023] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0024] Figure 1 This is a SEM image of a melamine-cyanuric acid supramolecular material without end-capping agents.

[0025] Figure 2 This is a SEM image of a melamine-cyanuric acid supramolecular material containing a capping agent.

[0026] Figure 3The image shows the XRD pattern of the melamine-cyanuric acid supramolecular material. Detailed Implementation

[0027] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0028] Example 1

[0029] 0.5 g of m-phenylenediamine, 1.0 g of melamine, and 1.6 g of cyanuric acid were dissolved in 100 mL of deionized water at 60 °C. The mixture was thoroughly stirred mechanically, with ultrasonic treatment added during the reaction. After 2 hours of reaction, the reactants were filtered to obtain a precipitate. The precipitate was washed with deionized water, dried at 60 °C for 4 hours, and then ground into powder to obtain the final melamine-cyanuric acid supramolecular nanomaterials. Its SEM and XRD patterns are shown below. Figure 2 , 3 As shown.

[0030] Weigh 1g of the above supramolecular nanomaterial powder and place it in a crucible. Heat the temperature to 500℃ at a rate of 2℃ / min and keep it at that temperature for 4h. After the product cools to room temperature, grind it into powder to obtain the final nanoscale graphitic carbon nitride material.

[0031] Comparative Example 1

[0032] 1.0 g of melamine and 1.0 g of cyanuric acid were dissolved separately in 100 mL of deionized water at 60 °C. The mixture was thoroughly stirred mechanically and subjected to ultrasonic treatment. After reacting for 2 hours, the reactants were filtered to obtain a precipitate. The precipitate was washed with deionized water, dried at 60 °C for 4 hours, and then ground into powder to obtain the final melamine-cyanuric acid supramolecular nanomaterials. Its SEM and XRD patterns are shown below. Figure 1 , 3 As shown.

[0033] according to Figure 1-3 It can be seen that without the addition of a capping agent, the supramolecular product obtained by the self-assembly of melamine and cyanuric acid is in the shape of a long rod with a size of 1-5 micrometers. However, after the introduction of the capping agent, the supramolecular product changes from a rod shape to a sheet shape, and the size is reduced to about 500 nanometers.

[0034] Example 2

[0035] 1.0 g of m-phenylenediamine, 1.1 g of melamine, and 2.2 g of cyanuric acid were dissolved in 100 mL of deionized water at 80 °C. The three were thoroughly mixed under mechanical stirring. After reacting for 1 h, the reactants were filtered to obtain the product precipitate. The product was washed with deionized water, dried at 60 °C for 4 h, and ground into powder to obtain the final melamine-cyanuric acid supramolecular nanomaterial.

[0036] Weigh 1g of the above supramolecular nanomaterial powder and place it in a crucible. Heat the temperature to 550℃ at a rate of 3℃ / min and keep it at that temperature for 4 hours. After the product cools to room temperature, grind it into powder to obtain the final nanoscale graphitic carbon nitride material.

[0037] Example 3

[0038] 1.0 g of m-phenylenediamine, 0.5 g of melamine, and 1.6 g of cyanuric acid were dissolved in 100 mL of deionized water at 70 °C. The three were thoroughly mixed under mechanical stirring, with ultrasonic treatment during the process. After reacting for 2 h, the reactants were filtered to obtain the product precipitate. The product was washed with deionized water, dried at 60 °C for 4 h, and ground into powder to obtain the final melamine-cyanuric acid supramolecular nanomaterial.

[0039] Weigh 1g of the above supramolecular nanomaterial powder and place it in a crucible. Heat the temperature to 600℃ at a rate of 3℃ / min and keep it at that temperature for 3h. After the product cools to room temperature, grind it into powder to obtain the final nanoscale graphitic carbon nitride material.

[0040] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a melamine-cyanuric acid supramolecular material, characterized in that, Includes the following steps: (1) Weigh out melamine, cyanuric acid and capping agent respectively; (2) Dissolve each of the above raw materials in a hot solvent; (3) Mix the hot solvents that dissolve the three raw materials separately, and keep stirring for 30-180 minutes, during which time ultrasonic treatment is also performed; (4) After the reaction is complete, the precipitate in the solution is filtered out, washed with water and dried to obtain melamine-cyanuric acid supramolecular material; The capping agent is an aniline-based small molecule.

2. The preparation method according to claim 1, characterized in that, The capping agent is one or more of aniline, o-phenylenediamine, naphthylamine, and anthracene.

3. The preparation method according to claim 1, characterized in that, The hot solvent is selected from one or more of water, ethanol, dimethyl sulfoxide, and dimethylformamide.

4. The preparation method according to claim 1, characterized in that, In step (2), the temperature during dissolution is within the range of 50°C to no more than the boiling point of the solvent used; in step (3), the drying temperature is 40-70°C.

5. The preparation method according to claim 1, characterized in that, The molar ratio of melamine and capping agent to cyanuric acid is (1-1.1):(1-1.1); and the molar ratio of melamine to capping agent is (0-1):(0-1). The molar ratio of melamine to the capping agent is not 0.

6. The melamine-cyanuric acid supramolecular material prepared according to the preparation method of any one of the preceding claims.

7. The melamine-cyanuric acid supramolecular material according to claim 6, characterized in that, The sheet particle size is between 1-1000 nanometers, and the thickness is between 1-500 nanometers.

8. The application of the melamine-cyanuric acid supramolecular material according to claim 6 or 7 in the preparation of nanoscale graphitic carbon nitride.

9. The application according to claim 8, characterized in that, The specific preparation steps are as follows: Melamine-cyanuric acid supramolecular nanomaterials were placed in a crucible; the crucible containing the sample was placed in a tube furnace and heated to 500-600℃ at a heating rate of 1-10℃ / min, held at that temperature for 1-5h, and then cooled to room temperature at a cooling rate of 1-10℃ / min; the product in the crucible was collected and ground into powder to obtain well-crystallized graphitic carbon nitride.

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