A two-dimensional hexagonal nanoskeleton constructed by replacing triazine ring with trace Pt atoms and a preparation method and application thereof

Abstract

This invention discloses a two-dimensional hexagonal nanoframework constructed using trace amounts of Pt atoms to replace triazine rings, its preparation method, and its applications. Specifically, a defective two-dimensional hexagonal nanoframework is used as a substrate, with trace amounts of Pt single atoms anchored at the missing triazine rings. In this material, the Pt single atoms act as high-energy photocatalytic active sites, exhibiting ultra-high photocatalytic reduction yield of CO2 and specific selectivity for the reduction product CO. Based on these properties, this two-dimensional hexagonal nanoframework material constructed using trace amounts of Pt atoms to replace triazine rings is synthesized using an environmentally friendly method, possesses ultra-high catalytic performance, and is easily recyclable, making it suitable for applications in carbon treatment, environmental remediation, and chemical industries.

Description

Technical Field

[0001] This invention belongs to the field of materials preparation, specifically relating to a two-dimensional hexagonal nanoframework constructed using trace amounts of Pt atoms to replace triazine rings, its preparation method, and its application. Technical Background

[0002] With the increasing energy crisis and the growing pollution caused by fossil fuel consumption, the exploration of new and efficient energy conversion technologies is urgently needed, most of which involve catalysis. Designing highly efficient catalysts with excellent activity and selectivity is of great significance in catalytic reactions and the chemical industry. For supported metal catalysts, high specific surface area and volume ratio are key to improving catalytic performance. To achieve this, a simple and common approach is to reduce the particle size of the metal to the nanoscale. Therefore, atomically dispersed metal catalysts have attracted great interest in the field of catalysis due to their unique properties. Isolated single or a few metal atoms can be fixed on a substrate through chemical bonds or spatial confinement, thereby maximizing atomic utilization efficiency. However, due to the high surface energy of single atoms, how to disperse individual metal atoms on a suitable support and prevent them from agglomerating into clusters or nanoparticles remains a challenge. Therefore, precisely controlling the geometry and electronic structure of the active metal center, thus significantly affecting the performance of the catalyst, is key to solving this problem. Among many semiconductor photocatalysts, two-dimensional hexagonal nanoframeworks possess unique inherent properties, such as a wide light absorption range, an extended π-π conjugated structure, and efficient charge transfer. More importantly, the tunable structural units and rich coordination modes provide a foundation for modulating the electronic states of metals. Therefore, it is crucial to achieve efficient photocatalysis of two-dimensional hexagonal nanoframework materials through trace metal anchoring. Summary of the Invention

[0003] To address the aforementioned problems, this invention provides a two-dimensional hexagonal nanoframework constructed using trace amounts of Pt atoms to replace triazine rings, along with its preparation method and applications. This reduces waste when using precious metals and ensures the metal's stable presence within the two-dimensional hexagonal nanoframework.

[0004] To effectively control Pt atom clusters, this invention employs a novel approach: by changing the type of precursor, triazine ring defects are naturally formed through self-assembly, avoiding external intervention. Due to the instability of the defect sites, they readily bond with Pt atoms, firmly anchoring the Pt atoms at the defect sites.

[0005] The two-dimensional hexagonal nanoframework constructed by replacing triazine rings with trace amounts of Pt atoms uses the defective two-dimensional hexagonal nanoframework as a substrate, with Pt atoms anchored at the defect sites.

[0006] Specifically, this is achieved through the following technical solutions:

[0007] A method for preparing a two-dimensional hexagonal nanoframework using trace amounts of Pt atoms to replace triazine rings includes the following steps: constructing a defective two-dimensional hexagonal nanoframework; anchoring Pt single atoms on the defective two-dimensional hexagonal nanoframework to obtain trace amounts of Pt atoms to replace triazine rings and construct the two-dimensional hexagonal nanoframework, wherein the defective two-dimensional hexagonal nanoframework is prepared by using 1,4-dicyanobenzene and 4-cyanopyridine.

[0008] Furthermore, a method for preparing a two-dimensional hexagonal nanoframework using trace amounts of Pt atoms to replace triazine rings includes the following steps:

[0009] (1) Dissolve 1,4-dicyanobenzene and 4-cyanopyridine in trifluoromethanesulfonic acid, stir vigorously in an ice-water bath at -8 to 2°C for 60-120 min, and then quickly place them in an electric heating constant temperature drying oven at 100°C to form a yellow transparent solid.

[0010] (2) After crushing and grinding the yellow transparent solid, wash it with deionized water and ethanol alternately and centrifuge it several times to remove residual monomers and acidic substances. Place the thoroughly washed solid in a vacuum drying oven at 60°C and dry it for 12-36 hours. Then grind it into fine powder to obtain a defective two-dimensional hexagonal nanoframework.

[0011] (3) Disperse the defective two-dimensional hexagonal nanoframework in an alcohol solution, mix at room temperature for 20-60 min, transfer to an electric thermostatic drying oven, react at a constant temperature, and after natural cooling, obtain a yellow solid substance. Wash with ethanol and water alternately to remove unreacted residues and obtain hydroxylated defective two-dimensional hexagonal nanoframework.

[0012] (4) Disperse the hydroxylated defective two-dimensional hexagonal nanoframework obtained in step (3) in deionized water, add chloroplatinic acid solution dropwise under continuous stirring and mix thoroughly, irradiate under ultraviolet light for 20-40 min, then wash with deionized water and dry in a vacuum drying oven for 12-36 h to obtain yellow powder.

[0013] (5) The yellow powder obtained in step (4) is heated by a program and kept at a constant temperature to finally obtain a two-dimensional hexagonal nanoframework constructed by replacing the triazine ring with trace amounts of Pt atoms.

[0014] Furthermore, in step (1), the molar ratio of 1,4-dicyanobenzene and 4-cyanopyridine is 2 to 20:1.

[0015] Furthermore, in step (3), the solid-liquid ratio of the defective two-dimensional hexagonal nanoframework to the alcohol solution is 10-20 mg / mL, preferably 100 mg: 6 mL.

[0016] Furthermore, in step (3), the alcohol solution is methanol, ethanol, ethylene glycol, glycerol, preferably ethylene glycol.

[0017] Furthermore, in step (3), the temperature of the electric heating constant temperature drying oven is 100-180℃, preferably 150℃; the time is 3-6h, preferably 4h.

[0018] Furthermore, in step (4), the ratio of chloroplatinic acid to deionized water is 5-10 μL / mL, preferably 6 μL / mL; the Pt content in chloroplatinic acid is 1-3 g / L, preferably 1.883 g / L.

[0019] Furthermore, in step (5), the temperature rise rate is 3-6℃ / min, preferably 3℃ / min; the temperature is raised to 120-200℃, preferably 180℃; and the holding time is 1-3h, preferably 2h.

[0020] A two-dimensional hexagonal nanoframework constructed by replacing triazine rings with trace amounts of Pt atoms using the above-mentioned preparation method is characterized in that the framework is based on a defective two-dimensional hexagonal nanoframework, with Pt atoms anchored at the defect sites.

[0021] Applications of a two-dimensional hexagonal nanoframework constructed by replacing triazine rings with trace amounts of Pt atoms in the field of photocatalysis, including but not limited to CO2 reduction, H2O2 production, or H2 reduction.

[0022] The beneficial effects of this invention are as follows:

[0023] This invention provides a method for anchoring trace amounts of Pt atoms at defect sites in triazine rings as a highly active photocatalytic material. In practical application, this material offers the following advantages: Compared to traditional composite materials, the Pt atom anchoring method involves bonding with the substrate, effectively making it a complete non-composite material, allowing Pt atoms to stably exist at the defect sites; moreover, it avoids the waste of previously used high-value precious metals, and experiments have demonstrated stable cycling performance; simultaneously, a single Pt atom, as a highly active photocatalytic site, can accelerate the effective separation of photogenerated electrons and holes, enhancing photocatalytic performance. Because this method of using trace amounts of Pt atoms to replace triazine rings to construct a two-dimensional hexagonal nanoframework in metal-based catalysts possesses significant energy-saving and environmentally friendly advantages, it has potential economic value. Attached Figure Description

[0024] Figure 1 Transmission electron microscope image of the material prepared in Example 1;

[0025] Figure 2 Transmission electron microscope image of the material obtained in Example 2;

[0026] Figure 3 Transmission electron microscope image of the material prepared in Example 3;

[0027] Figure 4 Transmission electron microscope image of the material prepared in Example 4;

[0028] Figure 5 This is a spherical aberration electron microscope image of the material prepared in Example 4. Detailed Implementation

[0029] The present invention will be further described below with reference to the accompanying drawings and embodiments, so that those skilled in the art can better understand the essence of the invention. Unless otherwise specified, all reagents or materials used in this invention are commercially available products.

[0030] Example 1

[0031] In this embodiment, the specific steps for preparing the original two-dimensional hexagonal nanoframework are as follows:

[0032] (1) Dissolve 5.5 mmol of 1,4-dicyanobenzene solid in 3 mL of trifluoromethanesulfonic acid, stir vigorously in an ice-water bath at 0 °C for 90 min, and then quickly place it in an electric thermostatic drying oven at 100 °C for 20 min to form a yellow transparent solid.

[0033] (2) After crushing and grinding the yellow transparent solid, centrifuge it in a centrifuge at 10,000 rpm for 5 min with deionized water and ethanol alternately. Wash and centrifuge several times to remove residual monomers and acidic substances. Place the thoroughly washed solid in a vacuum drying oven at 60°C and dry it for 24 h. Then grind it into fine powder to obtain the original two-dimensional hexagonal nanoframework.

[0034] Example 2

[0035] In this embodiment, the specific steps for preparing the defective two-dimensional hexagonal nanoskeleton are as follows:

[0036] (1) Dissolve 5.2 mmol of 1,4-dicyanobenzene and 0.3 mmol of 4-cyanopyridine in 3 mL of trifluoromethanesulfonic acid. After stirring vigorously in an ice-water bath at 0 °C for 90 min, quickly place the mixture in an electric thermostatic drying oven at 100 °C for 20 min to form a yellow transparent solid.

[0037] (2) After crushing and grinding the yellow transparent solid, centrifuge it in a centrifuge at 10,000 rpm for 5 min with deionized water and ethanol alternately. Wash and centrifuge several times to remove residual monomers and acidic substances. Place the thoroughly washed solid in a vacuum drying oven at 60°C and dry it for 24 h. Then grind it into fine powder to obtain a defective two-dimensional hexagonal nanoframework.

[0038] Example 3

[0039] In this embodiment, the specific steps for preparing the two-dimensional hexagonal nanoframework supported by Pt nanoparticles are as follows:

[0040] (1) 100 mg of the original two-dimensional hexagonal nanoframework obtained in Example 1 was dispersed in 6 mL of ethylene glycol solution and mixed at room temperature of 25°C for 30 min. The resulting solid-liquid mixture was carefully transferred to a 20 mL polytetrafluoroethylene-lined autoclave and then the sealed autoclave was placed in an electric thermostatic drying oven at 150°C for 4 h and allowed to cool naturally to room temperature.

[0041] (2) The white solid after cooling to room temperature in step (1) was washed and centrifuged alternately with deionized water and ethanol. The centrifuge was kept at 10,000 rpm for 5 min. Then the washed solid was placed in a vacuum drying oven at 60°C for 24 h to obtain the hydroxylated original two-dimensional hexagonal nanoframework.

[0042] (3) Disperse 100 mg of the hydroxylated original two-dimensional hexagonal nanoframework obtained in step (2) in 10 mL of deionized water, add 60 μL of chloroplatinic acid (Pt: 1.883 g / L) dropwise under continuous stirring, mix, irradiate under ultraviolet light for 30 min, then wash with deionized water and centrifuge at 10000 rpm for 5 min, and dry in a vacuum drying oven at 60 °C for 24 h to obtain a yellow powder.

[0043] (4) The yellow powder obtained in step (3) is heated to 180°C at a program of 3°C / min and held for 2 hours to finally obtain a two-dimensional hexagonal nanoframework supported by Pt nanoparticles.

[0044] Example 4

[0045] In this embodiment, the specific steps for preparing a single-atom Pt dispersed two-dimensional hexagonal nanoframework are as follows:

[0046] (1) 100 mg of the defective two-dimensional hexagonal nanoframework obtained in Example 2 was dispersed in 6 mL of ethylene glycol solution and mixed at room temperature of 25°C for 30 min. The resulting solid-liquid mixture was carefully transferred to a 20 mL polytetrafluoroethylene-lined autoclave. The sealed autoclave was then placed in an electric thermostatic drying oven at 150°C for 4 h and allowed to cool naturally to room temperature.

[0047] (2) The white solid cooled to room temperature in step (1) was washed and centrifuged alternately with deionized water and ethanol. The centrifuge was kept at 10,000 rpm for 5 min. Then the washed solid was placed in a vacuum drying oven at 60°C for 24 h to obtain hydroxylated defective two-dimensional hexagonal nanoframeworks.

[0048] (3) Disperse 100 mg of the hydroxylated defective two-dimensional hexagonal nanoframework obtained in step (2) in 10 mL of deionized water. Add 60 μL of chloroplatinic acid (Pt: 1.883 g / L) dropwise under continuous stirring and mix. Irradiate under UV light for 30 min, then wash with deionized water and centrifuge at 10,000 rpm for 5 min. Place in a vacuum drying oven at 60 °C and dry for 24 h to obtain a yellow powder.

[0049] (4) The yellow powder obtained in step (3) is heated to 180°C at a program of 3°C / min and held for 2 hours to finally obtain a two-dimensional hexagonal nanoframework with single-atom Pt dispersion.

[0050] Transmission electron microscopy (TEM) was performed on the two-dimensional hexagonal nanoskeletons obtained in Examples 1, 2, 3, and 4, and the results are as follows: Figure 1 , Figure 2 , Figure 3 , Figure 4 As shown in the transmission electron microscope (TEM) image, the two-dimensional hexagonal nanoframework is entirely composed of sheet-like two-dimensional structures. Figure 3 The two-dimensional hexagonal nanoframework supported by Pt nanoparticles clearly shows Pt clusters forming nanoparticles, while Figure 4 The presence of Pt nanoparticles is completely invisible, indicating the absence of Pt nanoparticles. Further aberration-corrected electron microscopy (SEM) analysis of the two-dimensional hexagonal nanoframework dispersed as single-atom Pt showed... Figure 5 As shown, dispersed bright spots are clearly visible, indicating that Pt exists as single atoms within the two-dimensional hexagonal nanoframework. This demonstrates that the defect structure plays a crucial role in the dispersion of metal atoms.

[0051] Application Example 1

[0052] The two-dimensional hexagonal nanoframework catalysts obtained in Examples 1-4 were used to conduct photocatalytic reduction experiments on CO2 under visible light irradiation.

[0053] The experimental conditions were as follows: 20 mg of the two-dimensional hexagonal nanoframework catalyst prepared in Examples 1-4 was dispersed in a reactor containing 10 mL of deionized water, 20 mL of acetonitrile, and 5 mL of triethanolamine, and stirred thoroughly for 30 min. Subsequently, after purging the reactor and introducing sufficient CO2, the CO2 photocatalytic reduction performance was tested in a closed gas system. A 300 W xenon lamp was used as the light source (intensity: 100 mW / cm²). 2 The reaction temperature was maintained at 20℃. Every 30 minutes, a gas sample (1 mL) was taken out from the reactor and qualitatively analyzed by gas chromatography. Gases such as CO and H2 were detected by thermal conductivity detector (TCD). The results are shown in Table 1.

[0054] Table 1. Photocatalytic CO2 reduction yield (mmol / (g·h)) and selectivity (%) of different materials

[0055]

[0056] As shown in Table 1, the two-dimensional hexagonal nanoframework constructed by substituting trace amounts of Pt atoms for triazine rings in this invention exhibits the best yield and selectivity for the photocatalytic reduction of CO2 to CO. In Pt materials synthesized using the original two-dimensional hexagonal nanoframework as a substrate, metallic Pt atoms aggregate to form nanoparticles. These clustered Pt atoms are equivalent to bulk Pt, resulting in a lower reduction efficiency compared to single-atom Pt. In contrast, the two-dimensional hexagonal nanoframework material with single-atom Pt dispersed and anchored at defect sites is prepared by anchoring Pt materials to a defective two-dimensional hexagonal nanoframework substrate, where metallic Pt atoms are independently dispersed at the defect sites. This independent dispersion of photocatalytic sites accelerates the separation and transfer of photogenerated electrons and holes, thereby enhancing the photocatalytic reduction effect.

[0057] It can be seen that the photocatalytic reduction efficiency of the two-dimensional hexagonal nanoframework constructed by replacing the triazine ring with trace amounts of Pt atoms is extremely high. After several rounds of cyclic experiments, the two-dimensional hexagonal nanoframework constructed by replacing the triazine ring with trace amounts of Pt atoms still has high catalytic activity.

[0058] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the invention. For example, although the raw materials used in the preparation process in the above embodiments are 1,4-dicyanobenzene and 4-cyanopyridine, it does not mean that they must all be used. As long as polymerization can produce a covalent backbone and triazine deficiency, the effects of the present invention can be achieved. For example, the above embodiments only selected Pt atoms for anchoring, but this does not mean that only Pt atoms can be selected for anchoring. Other methods that can achieve similar effects to Pt atoms, such as anchoring metal single atoms with nickel chloride, cobalt nitrate, zinc chloride, and palladium chloride, can also achieve the technical effects of the present invention. As another example, the above embodiments only listed the case where the mass fraction of Pt atoms is 0.1 wt%, but through experiments, adjustments can be made before and after this value, such as a mass fraction of Pt atoms of 0.05 wt%, 0.5 wt%, or even more than 1 wt%, which can also achieve the technical effects of the present invention.

[0059] Therefore, those skilled in the art can make various changes and modifications without departing from the spirit and scope of this invention. Thus, all technical solutions obtained through equivalent substitution or transformation fall within the protection scope of this invention.

Claims

1. A method for preparing a two-dimensional hexagonal nanoskeleton constructed using micro-amounts of Pt atoms instead of a triazine ring, characterized by, The method comprises the following steps: constructing a defective two-dimensional hexagonal nanoskeleton; and anchoring Pt single atoms on the defective two-dimensional hexagonal nanoskeleton to obtain a two-dimensional hexagonal nanoskeleton in which a trace amount of Pt atoms replace triazine rings, wherein the defective two-dimensional hexagonal nanoskeleton is prepared from 1,4-dicyanobenzene and 4-cyanopyridine.

2. The production method according to claim 1, wherein The method comprises the following steps: (1) dissolving 1,4-dicyanobenzene and 4-cyanopyridine in trifluoromethanesulfonic acid, stirring vigorously in an ice water bath at -8 to 2 ℃ for 60 to 120 min, and then quickly placing in a 100 ℃ electric heating constant temperature drying oven to form a yellow transparent solid; (2) crushing and grinding the yellow transparent solid, washing and centrifuging several times with deionized water and ethanol alternately to eliminate residual monomers and acidic substances, and then placing the washed solid in a 60 ℃ vacuum drying oven to dry for 12 to 36 h, and then grinding into fine powder to obtain the defective two-dimensional hexagonal nanoskeleton; (3) dispersing the defective two-dimensional hexagonal nanoskeleton in an alcohol solution, mixing at room temperature for 20 to 60 min, and then transferring to an electric heating constant temperature drying oven for constant temperature reaction, and then naturally cooling to obtain a yellow solid substance, washing with ethanol and water alternately to remove unreacted residues, and then obtaining a hydroxylated defective two-dimensional hexagonal nanoskeleton; (4) dispersing the hydroxylated defective two-dimensional hexagonal nanoskeleton obtained in step (3) in deionized water, adding chloroplatinic acid solution drop by drop under continuous stirring, mixing thoroughly, and then irradiating under a UV lamp for 20 to 40 min, and then washing with deionized water and placing in a vacuum drying oven to dry for 12 to 36 h to obtain a yellow powder; (5) performing programmed temperature rising on the yellow powder obtained in step (4) and keeping constant temperature to finally obtain a two-dimensional hexagonal nanoskeleton in which a trace amount of Pt atoms replace triazine rings.

3. The production method according to claim 2, wherein In step (1), the molar ratio of 1,4-dicyanobenzene to 4-cyanopyridine is 2 to 20:

1.

4. The production method according to claim 2, wherein In step (3), the solid-liquid ratio of the defective two-dimensional hexagonal nanoskeleton to the alcohol solution is 10 to 20 mg / mL.

5. The production method according to claim 2 or 4, characterized by, In step (3), the alcohol solution is methanol, ethanol, ethylene glycol or glycerol.

6. The production method according to claim 2, characterized by, In step (3), the temperature of the electric heating constant temperature drying oven is 100 to 180 ℃, and the time is 3 to 6 h.

7. The production method according to claim 2, characterized by, In step (4), the ratio of chloroplatinic acid to deionized water is 5 to 10 μL / mL, and the Pt content in the chloroplatinic acid is 1 to 3 g / L.

8. The production method according to claim 2, wherein In step (5), the temperature rising rate of the programmed temperature rising is 3 to 6 ℃ / min, the temperature rising is 120 to 200 ℃, and the holding time is 1 to 3 h.

9. The production method according to claim 4, wherein In step (3), the solid-liquid ratio of the defective two-dimensional hexagonal nanoskeleton to the alcohol solution is 100 mg:6 mL.

10. The production method according to claim 5, wherein In step (3), the alcohol solution is ethylene glycol.

11. The production method according to claim 6, characterized by, In step (3), the temperature of the electric heating constant temperature drying oven is 150 ℃, and the time is 4 h.

12. The production method according to claim 7, wherein In step (4), the ratio of chloroplatinic acid to deionized water is 6 μL / mL, and the Pt content in the chloroplatinic acid is 1.883 g / L.

13. The production method according to claim 8, wherein In step (5), the temperature rising rate of the programmed temperature rising is 3 ℃ / min, the temperature rising is 180 ℃, and the holding time is 2 h.

14. A two-dimensional hexagonal nanoskeleton constructed by replacing triazine ring with micro-amount of Pt atoms, prepared by the method of any one of claims 1-8. The nanoskeleton takes the defective two-dimensional hexagonal nanoskeleton as a substrate, and Pt atoms are anchored at the defect sites.

15. The use of the two-dimensional hexagonal nanoskeleton constructed by replacing triazine ring with micro Pt atoms according to claim 14 in the field of photocatalysis.

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