Application of SiC QDs catalyst in photocatalytic benzylamine oxidative coupling reaction

Abstract

The invention discloses an application of a SiC QDs catalyst in a photocatalytic benzylamine oxidative coupling reaction. The catalyst takes SiC as a raw material. The preparation method specifically comprises the following steps: dispersing SiC in a hydrofluoric acid-nitric acid mixed aqueous solution, heating to 100 DEG C in a hydrothermal kettle, maintaining for 1-6 hours, taking out, cooling to room temperature, diluting with deionized water, carrying out ultrasonic oscillation, carrying out centrifugal acid removal to obtain neutral large particles, dispersing into deionized water, carrying out ultrasonic treatment, centrifuging, taking supernatant, and carrying out freeze drying treatment to obtain the SiC-based composite material. The SiC QDs catalyst is obtained. By applying the SiC QDs catalyst, the benzylamine can be efficiently subjected to photocatalytic oxidative coupling in an air atmosphere. Compared with the traditional metal photocatalyst, the metal-free nano photocatalyst prepared by the method has the advantage that the catalyst cost is greatly reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of photocatalysts, and particularly relates to the application of SiC QDs catalysts in the photocatalytic oxidative coupling reaction of benzylamine. Background Art

[0002] With the increasing global attention to green chemistry and sustainable development, the development of efficient and environmentally friendly catalytic systems has become one of the important directions in modern chemical research. Photocatalytic technology, which can drive chemical reactions using solar energy and has advantages such as low energy consumption and environmental friendliness, is considered one of the key technologies to solve energy crisis and environmental pollution problems. In the field of organic synthesis, photocatalytic technology has been widely applied to various reaction types, such as oxidation reactions, reduction reactions, coupling reactions, etc. The oxidative coupling reaction of benzylamine, as an important transformation process, can generate imine compounds, which are important intermediates for drugs, pesticides, dyes, and functional materials. However, traditional methods usually rely on dangerous oxidants or harsh reaction conditions, which not only increase production costs but also bring serious environmental problems. Therefore, it is of great significance to develop an efficient and green photocatalytic system for the oxidative coupling reaction of benzylamine.

[0003] In contrast, photocatalytic technology can achieve the selective oxidative coupling of benzylamine under mild conditions, avoiding the use of dangerous reagents and conforming to the concept of green chemistry. In recent years, researchers have developed various photocatalysts for this reaction, such as metal oxides, metal sulfides, and covalent organic framework materials (COFs). However, these catalysts generally have problems such as narrow light absorption range, high charge recombination rate, or poor stability, making it difficult to meet the actual application requirements.

[0004] Silicon carbide is an indirect bandgap semiconductor with excellent physical and chemical properties and good biocompatibility, and its bulk material has extremely low luminescence efficiency. Due to the quantum confinement effect, when the size of silicon carbide is reduced to the quantum dot size (less than about ten nanometers), it will have strong continuously tunable wavelength luminescence, a larger bandgap width, and it is easier to generate electron-hole pairs, which is beneficial to the occurrence of photoinduced redox reactions, making silicon carbide nanomaterials have good application prospects. Silicon carbide quantum dots (SiC QDs), as an emerging metal-free nanomaterial, possess the excellent electrical conductivity, thermal conductivity, and good thermal stability of SiC. At the same time, its surface is rich in a large number of groups such as hydroxyl and carboxyl groups, which is very conducive to catalytic oxidation reactions and can be used as an ideal catalyst in oxidation reactions. Compared with traditional photocatalysts (such as TiO2, ZnO, etc.), SiC QDs have higher light absorption efficiency, a wider light response range, and stronger charge separation ability.

[0005] Therefore, it is highly necessary to provide a SiC QDs catalyst and use it as a catalyst for the photocatalytic oxidative coupling reaction of benzylamine. Summary of the Invention

[0006] The object of the present invention is to prepare a metal-free photocatalyst at the quantum dot level for improving the yield of the oxidative coupling reaction of benzylamine under mild conditions. The catalyst obtained by the method provided by the present invention has good stability and a simple preparation method, and at the same time has excellent performance for the oxidative coupling reaction of benzylamine.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] The present invention provides a preparation method of a SiC QDs catalyst, using SiC as a raw material and preparing the SiC QDs catalyst by a chemical etching method; wherein, the SiC includes one or two of α-SiC and β-SiC.

[0009] Further, the preparation method specifically includes: (1) dispersing SiC in a hydrofluoric acid-nitric acid mixed aqueous solution, heating to 100 °C and maintaining for 1-6 h, taking it out and cooling to room temperature to obtain a reaction solution; (2) diluting the reaction solution with deionized water and centrifuging multiple times until neutral, taking the lower-layer powder solid and drying it in an oven for 5 h to obtain a reactant; (3) adding the reactant to deionized water for dispersion, ultrasonic oscillation, removing large particles by centrifugation, taking the supernatant, and freeze-drying to obtain the SiC QDs catalyst.

[0010] Further, in step (1), the volume ratio of hydrofluoric acid to nitric acid in the hydrofluoric acid-nitric acid mixed aqueous solution is 0.5-3:1.

[0011] Further, in step (3), the added deionized water is 10-50 mL, the ultrasonic duration is 30-120 min; optionally, the rotation speed for removing large particles by centrifugation is 8000-12000 rpm, and the time is 5-15 min; optionally, the freeze-drying temperature is -60 °C, and the freeze-drying time is 1-24 h.

[0012] The present invention also provides a SiC QDs catalyst prepared by the preparation method of the SiC QDs catalyst as described above.

[0013] The present invention also provides the application of the SiC QDs catalyst as described above in the photocatalytic oxidative coupling reaction of benzylamine.

[0014] Further, the application method includes: placing the SiC QDs catalyst, benzylamine and a reaction solvent in a reactor, and starting stirring and heating.

[0015] Furthermore, the dosage of the SiC QDs catalyst is 10% - 30% of the mass of benzylamine.

[0016] Furthermore, the reaction solvent is one of acetonitrile, toluene, trifluorotoluene, and dimethyl sulfoxide; the reaction temperature is 30 - 150 °C, the stirring rate is 100 - 800 rpm, and the reaction time is 0.1 - 8 h. Preferably, the reaction light source is a xenon lamp, and the light intensity is 0 - 5 W.

[0017] Furthermore, in the photocatalytic oxidative coupling reaction of benzylamine, the conversion rate of benzylamine is 60% - 100%, and the selectivity of imine is 60% - 99%.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] The present invention uses SiC QDs as a catalyst for the photocatalytic oxidation reaction of benzylamine. This catalyst belongs to a metal-free nanophotocatalyst. Metal-free photocatalysts have the characteristics of green chemistry, being pollution-free, environmentally friendly, having good stability, and being reusable. Moreover, this SiC QDs catalyst has the characteristics of being resistant to acid and alkali corrosion, high temperature resistance, good thermal and electrical conductivity, quantum effect, large band gap, and strong photoluminescence ability. It has a good response ability to visible light. At the same time, its surface is rich in a large number of groups such as hydroxyl and carboxyl groups, which is very helpful for the photocatalytic oxidative coupling of benzylamine to prepare imine. In addition, this metal-free nanophotocatalyst produces no harmful gases during the reaction process, is green and environmentally friendly, has mild reaction conditions, a short time period, simple operation, and at the same time, the product yield is high and the cost is low. It is an efficient and stable catalyst and catalytic reaction. Specific Embodiments

[0020] The present invention will be described in detail below in conjunction with specific embodiments.

[0021] The present invention provides a preparation method of a SiC QDs catalyst, which specifically includes:

[0022] (1) Disperse SiC in a mixed aqueous solution of hydrofluoric acid - nitric acid, heat to 100 °C and maintain for 1 - 6 h, take it out and cool to room temperature to obtain a reaction solution;

[0023] (2) Dilute the reaction solution with deionized water and centrifuge it multiple times until it is neutral. Take the lower-layer powdered solid and dry it in an oven for 5 h to obtain a reactant;

[0024] (3) Add the reactant to deionized water for dispersion, ultrasonically vibrate, remove large particles by centrifugation, take the supernatant, and obtain the SiC QDs catalyst after freeze-drying;

[0025] Among them, the SiC includes one or both of α-SiC and β-SiC.

[0026] In step (1), the ratio of the hydrofluoric acid-nitric acid mixed aqueous solution is 0.5-3:1.

[0027] In step (3), the deionized water added is 10-50 mL, and the ultrasonic time is 30-120 min; optionally, the rotation speed for centrifugally removing large particles is 8000-12000 rpm, and the time is 5-15 min; optionally, the freeze-drying temperature is -60 °C, and the freeze-drying time is 1-24 h.

[0028] Example 1

[0029] Disperse β-SiC in a hydrofluoric acid-nitric acid mixed aqueous solution (volume ratio 3:1), heat to 100 °C and maintain for 3 h, take out and cool to room temperature to obtain a reaction solution. Dilute the reaction solution with deionized water and centrifuge multiple times until neutral, take the lower-layer powder solid, dry it in an oven for 5 h to obtain a reactant. Add the reactant to 50 ml of deionized water for dispersion, ultrasonically vibrate for 30 min, centrifuge at 12000 rpm for 15 min by a centrifuge to remove large particles, take the supernatant, and obtain the SiC QDs catalyst after freeze-drying for 24 h.

[0030] Place the above SiC QDs catalyst in a stainless-steel high-pressure reactor with a quartz window, add 5 mL of acetonitrile and 0.1 mmol of benzylamine, seal the photocatalytic reactor, ultrasonically vibrate the reactor in an ultrasonic machine for 2 min and then transfer it to a constant-temperature water bath. While irradiating with a xenon lamp source with an intensity of 2.4 W / cm 2 magnetically stir at a rotation speed of 600 rpm and heat the temperature of the reactor to 50 °C, stir and react at a constant temperature for 3 h. After the reaction, the conversion rate of benzylamine is detected to be 93.5%, and the selectivity of imine is 99.9%.

[0031] Example 2

[0032] Disperse α-SiC in a hydrofluoric acid-nitric acid mixed aqueous solution (volume ratio 3:1), heat to 100 °C and maintain for 3 h, take out and cool to room temperature to obtain a reaction solution. Dilute the reaction solution with deionized water and centrifuge multiple times until neutral, take the lower-layer powder solid, dry it in an oven for 5 h to obtain a reactant. Add the reactant to 50 ml of deionized water for dispersion, ultrasonically vibrate for 30 min, centrifuge at 12000 rpm for 15 min by a centrifuge to remove large particles, take the supernatant, and obtain the SiC QDs catalyst after freeze-drying for 24 h.

[0033] Place the above-mentioned SiC QDs catalyst into a stainless-steel high-pressure reactor equipped with a quartz window, add 5 mL of acetonitrile and 0.1 mmol of benzylamine, seal the photocatalytic reactor, place the reactor in an ultrasonic machine for ultrasonic treatment for 2 min, and then transfer it to a constant-temperature water bath. While irradiating with a xenon lamp source with an intensity of 2.4 W / cm 2 , magnetically stir at a speed of 600 rpm and heat the temperature of the reactor to 50 °C. Keep stirring at a constant temperature for 3 h. After the reaction is completed, the conversion rate of benzylamine is detected to be 80.5%, and the selectivity of imine is 99.9%.

[0034] Example 3

[0035] Disperse β-SiC in a hydrofluoric acid-nitric acid mixed aqueous solution (volume ratio of 0.5), heat it to 100 °C and maintain for 3 h. After taking it out and cooling to room temperature, a reaction solution is obtained. Dilute the reaction solution with deionized water and centrifuge it several times until it is neutral. Take the lower-layer powder solid, dry it in an oven for 5 h to obtain a reactant. Add the reactant to 50 ml of deionized water for dispersion, ultrasonically vibrate for 30 min, centrifuge at 12,000 rpm for 15 min to remove large particles, take the supernatant, and freeze-dry it for 24 h to obtain the SiC QDs catalyst.

[0036] Place the above-mentioned SiC QDs catalyst into a stainless-steel high-pressure reactor equipped with a quartz window, add 5 mL of acetonitrile and 0.1 mmol of benzylamine, seal the photocatalytic reactor, place the reactor in an ultrasonic machine for ultrasonic treatment for 2 min, and then transfer it to a constant-temperature water bath. While irradiating with a xenon lamp source with an intensity of 2.4 W / cm 2 , magnetically stir at a speed of 600 rpm and heat the temperature of the reactor to 50 °C. Keep stirring at a constant temperature for 3 h. After the reaction is completed, the conversion rate of benzylamine is detected to be 56.8%, and the selectivity of imine is 99.9%.

[0037] Example 4

[0038] Disperse β-SiC in a hydrofluoric acid-nitric acid mixed aqueous solution (volume ratio of 1:1), heat it to 100 °C and maintain for 3 h. After taking it out and cooling to room temperature, a reaction solution is obtained. Dilute the reaction solution with deionized water and centrifuge it several times until it is neutral. Take the lower-layer powder solid, dry it in an oven for 5 h to obtain a reactant. Add the reactant to 50 ml of deionized water for dispersion, ultrasonically vibrate for 30 min, centrifuge at 12,000 rpm for 15 min to remove large particles, take the supernatant, and freeze-dry it for 24 h to obtain the SiC QDs catalyst.

[0039] Place the above-mentioned SiC QDs catalyst in a stainless-steel high-pressure reactor with a quartz window, add 5 mL of acetonitrile and 0.1 mmol of benzylamine, seal the photocatalytic reactor, place the reactor in an ultrasonic machine and ultrasonicate for 2 min, and then transfer it to a constant-temperature water bath. While irradiating with a xenon lamp source with an intensity of 2.4 W / cm 2 magnetically stir at a speed of 600 rpm and heat the temperature of the reactor to 50 °C, and keep stirring at a constant temperature for 3 h. After the reaction is completed, the conversion rate of benzylamine is detected to be 68.7%, and the selectivity of imine is 99.9%.

[0040] Example 5

[0041] Disperse β-SiC in a hydrofluoric acid-nitric acid mixed aqueous solution (volume ratio 3:1), heat to 100 °C and maintain for 1 h, take it out and cool to room temperature to obtain a reaction solution. Dilute the reaction solution with deionized water and centrifuge it several times until neutral, take the lower-layer powdered solid, dry it in an oven for 5 h to obtain a reactant. Add the reactant to 50 ml of deionized water for dispersion, ultrasonically vibrate for 30 min, centrifuge at 12,000 rpm for 15 min to remove large particles, take the supernatant, and freeze-dry for 24 h to obtain the SiC QDs catalyst.

[0042] Place the above-mentioned SiC QDs catalyst in a stainless-steel high-pressure reactor with a quartz window, add 5 mL of acetonitrile and 0.1 mmol of benzylamine, seal the photocatalytic reactor, place the reactor in an ultrasonic machine and ultrasonicate for 2 min, and then transfer it to a constant-temperature water bath. While irradiating with a xenon lamp source with an intensity of 2.4 W / cm 2 magnetically stir at a speed of 600 rpm and heat the temperature of the reactor to 50 °C, and keep stirring at a constant temperature for 3 h. After the reaction is completed, the conversion rate of benzylamine is detected to be 45.2%, and the selectivity of imine is 99.9%.

[0043] Example 6

[0044] Disperse β-SiC in a hydrofluoric acid-nitric acid mixed aqueous solution (volume ratio 3:1), heat to 100 °C and maintain for 5 h, take it out and cool to room temperature to obtain a reaction solution. Dilute the reaction solution with deionized water and centrifuge it several times until neutral, take the lower-layer powdered solid, dry it in an oven for 5 h to obtain a reactant. Add the reactant to 50 ml of deionized water for dispersion, ultrasonically vibrate for 30 min, centrifuge at 12,000 rpm for 15 min to remove large particles, take the supernatant, and freeze-dry for 24 h to obtain the SiC QDs catalyst.

[0045] Place the above-mentioned SiC QDs catalyst in a stainless-steel high-pressure reactor with a quartz window, add 5 mL of acetonitrile and 0.1 mmol of benzylamine, seal the photocatalytic reactor, place the reactor in an ultrasonic machine and ultrasonicate for 2 min, and then transfer it to a constant-temperature water bath. While irradiating with a xenon lamp source with an intensity of 2.4 W / cm 2 and magnetically stirring at a speed of 600 rpm, heat the temperature of the reactor to 50 °C, stir and react at a constant temperature for 3 h. After the reaction is completed, the conversion rate of benzylamine is detected to be 33.7%, and the selectivity of imine is 99.9%.

[0046] Example 7

[0047] Disperse β-SiC in a mixed aqueous solution of hydrofluoric acid and nitric acid (volume ratio 3:1), heat to 100 °C and maintain for 3 h, take it out and cool to room temperature to obtain a reaction solution. Dilute the reaction solution with deionized water and centrifuge it several times until neutral, take the lower-layer powdered solid, dry it in an oven for 5 h to obtain a reactant. Add the reactant to 10 ml of deionized water for dispersion, ultrasonically vibrate for 30 min, centrifuge at 12000 rpm for 15 min to remove large particles, take the supernatant, and freeze-dry for 24 h to obtain the SiC QDs catalyst.

[0048] Place the above-mentioned SiC QDs catalyst in a stainless-steel high-pressure reactor with a quartz window, add 5 mL of acetonitrile and 0.1 mmol of benzylamine, seal the photocatalytic reactor, place the reactor in an ultrasonic machine and ultrasonicate for 2 min, and then transfer it to a constant-temperature water bath. While irradiating with a xenon lamp source with an intensity of 2.4 W / cm 2 and magnetically stirring at a speed of 600 rpm, heat the temperature of the reactor to 50 °C, stir and react at a constant temperature for 3 h. After the reaction is completed, the conversion rate of benzylamine is detected to be 87.5%, and the selectivity of imine is 99.9%.

[0049] Example 8

[0050] Disperse β-SiC in a mixed aqueous solution of hydrofluoric acid and nitric acid (volume ratio 3:1), heat to 100 °C and maintain for 3 h, take it out and cool to room temperature to obtain a reaction solution. Dilute the reaction solution with deionized water and centrifuge it several times until neutral, take the lower-layer powdered solid, dry it in an oven for 5 h to obtain a reactant. Add the reactant to 50 ml of deionized water for dispersion, ultrasonically vibrate for 30 min, centrifuge at 8000 rpm for 15 min to remove large particles, take the supernatant, and freeze-dry for 24 h to obtain the SiC QDs catalyst.

[0051] Place the above-mentioned SiC QDs catalyst in a stainless-steel high-pressure reactor with a quartz window, add 5 mL of acetonitrile and 0.1 mmol of benzylamine, seal the photocatalytic reactor, place the reactor in an ultrasonic machine and ultrasonicate for 2 min, and then transfer it to a constant-temperature water bath. While irradiating with a xenon lamp source with an intensity of 2.4 W / cm 2 and magnetically stirring at a rotation speed of 600 rpm, heat the temperature of the reactor to 50 °C, stir and react at a constant temperature for 3 h. After the reaction is completed, the conversion rate of benzylamine is detected to be 79.5%, and the selectivity of imine is 99.9%.

[0052] Example 9

[0053] Disperse β-SiC in a mixed aqueous solution of hydrofluoric acid and nitric acid (volume ratio 3:1), heat to 100 °C and maintain for 3 h, take it out and cool to room temperature to obtain a reaction solution. Dilute the reaction solution with deionized water and centrifuge it several times until it is neutral. Take the lower-layer powder solid, dry it in an oven for 5 h to obtain a reactant. Add the reactant to 50 ml of deionized water for dispersion, ultrasonically vibrate for 30 min, centrifuge at 12,000 rpm for 5 min by a centrifuge to remove large particles, take the supernatant, and freeze-dry it for 24 h to obtain the SiC QDs catalyst mentioned above.

[0054] Place the above-mentioned SiC QDs catalyst in a stainless-steel high-pressure reactor with a quartz window, add 5 mL of acetonitrile and 0.1 mmol of benzylamine, seal the photocatalytic reactor, place the reactor in an ultrasonic machine and ultrasonicate for 2 min, and then transfer it to a constant-temperature water bath. While irradiating with a xenon lamp source with an intensity of 2.4 W / cm 2 and magnetically stirring at a rotation speed of 600 rpm, heat the temperature of the reactor to 50 °C, stir and react at a constant temperature for 3 h. After the reaction is completed, the conversion rate of benzylamine is detected to be 82.7%, and the selectivity of imine is 99.9%.

[0055] Application Example 1

[0056] Place 3 mg of the SiC QDs prepared in Example 1 in a stainless-steel high-pressure reactor with a quartz window, add 5 mL of acetonitrile and 0.1 mmol of benzylamine, seal the photocatalytic reactor, place the reactor in an ultrasonic machine and ultrasonicate for 2 min, and then transfer it to a constant-temperature water bath. While irradiating with a xenon lamp source with an intensity of 2.4 W / cm 2 and magnetically stirring at a rotation speed of 600 rpm, heat the temperature of the reactor to 50 °C, stir and react at a constant temperature for 3 h. After the reaction is completed, the conversion rate of benzylamine is detected to be 93.5%, and the selectivity of imine is 99.9%.

[0057] Application Example 2

[0058] 3 mg of the SiC QDs prepared in Example 1 were placed in a stainless-steel high-pressure reactor equipped with a quartz window. 5 mL of acetonitrile and 0.1 mmol of benzylamine were added. The photocatalytic reactor was sealed, sonicated in an ultrasonic machine for 2 min, and then transferred to a constant-temperature water bath. While magnetically stirring at a speed of 600 rpm, the temperature of the reactor was heated to 50 °C and the reaction was stirred at a constant temperature for 3 h. After the reaction ended, the conversion rate of benzylamine was detected to be 6.0% and the selectivity for imine was 99.9%.

[0059] Application Example 3

[0060] 3 mg of the SiC QDs prepared in Example 1 were placed in a stainless-steel high-pressure reactor equipped with a quartz window. 5 mL of acetonitrile and 0.1 mmol of benzylamine were added. The photocatalytic reactor was sealed, sonicated in an ultrasonic machine for 2 min, and then transferred to a constant-temperature water bath. Under irradiation with a xenon lamp source with an intensity of 3.4 W / cm 2 while magnetically stirring at a speed of 600 rpm, the temperature of the reactor was heated to 40 °C and the reaction was stirred at a constant temperature for 3 h. After the reaction ended, the conversion rate of benzylamine was detected to be 100% and the selectivity for imine was 99.9%.

[0061] Application Example 4

[0062] 3 mg of the SiC QDs prepared in Example 1 were placed in a stainless-steel high-pressure reactor equipped with a quartz window. 5 mL of toluene and 0.1 mmol of benzylamine were added. The photocatalytic reactor was sealed, sonicated in an ultrasonic machine for 2 min, and then transferred to a constant-temperature water bath. Under irradiation with a xenon lamp source with an intensity of 2.4 W / cm 2 while magnetically stirring at a speed of 600 rpm, the temperature of the reactor was heated to 50 °C and the reaction was stirred at a constant temperature for 3 h. After the reaction ended, the conversion rate of benzylamine was detected to be 55.4% and the selectivity for imine was 99.9%.

[0063] Application Example 5

[0064] 3 mg of the SiC QDs prepared in Example 1 were placed in a stainless-steel high-pressure reactor equipped with a quartz window. 5 mL of benzotrifluoride and 0.1 mmol of benzylamine were added. The photocatalytic reactor was sealed, sonicated in an ultrasonic machine for 2 min, and then transferred to a constant-temperature water bath. Under irradiation with a xenon lamp source with an intensity of 2.4 W / cm 2 while magnetically stirring at a speed of 600 rpm, the temperature of the reactor was heated to 50 °C and the reaction was stirred at a constant temperature for 3 h. After the reaction ended, the conversion rate of benzylamine was detected to be 34.7% and the selectivity for imine was 99.9%.

[0065] Application Example 6

[0066] Place 3 mg of the SiC QDs prepared in Example 1 into a stainless-steel high-pressure reactor with a quartz window, add 5 mL of dimethyl sulfoxide and 0.1 mmol of benzylamine, seal the photocatalytic reactor, place the reactor in an ultrasonic machine for ultrasonic treatment for 2 min, and then transfer it to a constant-temperature water bath. While irradiating with a xenon light source with an intensity of 2.4 W / cm 2 magnetically stir at a speed of 600 rpm and heat the temperature of the reactor to 50 °C. After continuously stirring the reaction at a constant temperature for 3 h, after the reaction ends, the conversion rate of benzylamine is detected to be 46.8%, and the selectivity for imine is 99.9%.

[0067] Application Example 7

[0068] Place 3 mg of the SiC QDs prepared in Example 1 into a stainless-steel high-pressure reactor with a quartz window, add 5 mL of acetonitrile and 0.1 mmol of benzylamine, seal the photocatalytic reactor, place the reactor in an ultrasonic machine for ultrasonic treatment for 2 min, and then transfer it to a constant-temperature water bath. While irradiating with a xenon light source with an intensity of 2.4 W / cm 2 magnetically stir at a speed of 600 rpm and heat the temperature of the reactor to 60 °C. After continuously stirring the reaction at a constant temperature for 3 h, after the reaction ends, the conversion rate of benzylamine is detected to be 100%, and the selectivity for imine is 99.9%.

[0069] Application Example 8

[0070] Place 3 mg of the SiC QDs prepared in Example 1 into a stainless-steel high-pressure reactor with a quartz window, add 5 mL of acetonitrile and 0.1 mmol of benzylamine, seal the photocatalytic reactor, place the reactor in an ultrasonic machine for ultrasonic treatment for 2 min, and then transfer it to a constant-temperature water bath. While irradiating with a xenon light source with an intensity of 2.4 W / cm 2 magnetically stir at a speed of 600 rpm and heat the temperature of the reactor to 40 °C. After continuously stirring the reaction at a constant temperature for 3 h, after the reaction ends, the conversion rate of benzylamine is detected to be 88.8%, and the selectivity for imine is 99.9%.

[0071] Application Example 9

[0072] Place 3 mg of the SiC QDs prepared in Example 1 into a stainless-steel high-pressure reactor with a quartz window, add 5 mL of acetonitrile and 0.1 mmol of benzylamine, seal the photocatalytic reactor, place the reactor in an ultrasonic machine for ultrasonic treatment for 2 min, and then transfer it to a constant-temperature water bath. While irradiating with a xenon light source with an intensity of 2.4 W / cm 2 magnetically stir at a speed of 600 rpm and heat the temperature of the reactor to 30 °C. After continuously stirring the reaction at a constant temperature for 3 h, after the reaction ends, the conversion rate of benzylamine is detected to be 82.3%, and the selectivity for imine is 99.9%.

[0073] Application Example 10

[0074] Place 3 mg of the SiC QDs prepared in Example 1 into a stainless-steel high-pressure reactor with a quartz window, add 5 mL of acetonitrile and 0.1 mmol of benzylamine, seal the photocatalytic reactor, place the reactor in an ultrasonic machine for ultrasonic treatment for 2 min, and then transfer it to a constant-temperature water bath. While irradiating with a xenon light source with an intensity of 2.4 W / cm 2 , heat the temperature of the reactor to 50 °C with magnetic stirring at a speed of 600 rpm, stir and react at a constant temperature for 2 h. After the reaction is completed, the conversion rate of benzylamine is detected to be 87.8%, and the selectivity for imine is 99.9%.

[0075] Application Example 11

[0076] Place 3 mg of the SiC QDs prepared in Example 1 into a stainless-steel high-pressure reactor with a quartz window, add 5 mL of acetonitrile and 0.1 mmol of benzylamine, seal the photocatalytic reactor, place the reactor in an ultrasonic machine for ultrasonic treatment for 2 min, and then transfer it to a constant-temperature water bath. While irradiating with a xenon light source with an intensity of 2.4 W / cm 2 , heat the temperature of the reactor to 50 °C with magnetic stirring at a speed of 600 rpm, stir and react at a constant temperature for 1 h. After the reaction is completed, the conversion rate of benzylamine is detected to be 70.2%, and the selectivity for imine is 99.9%.

[0077] Application Example 12

[0078] Place 3 mg of the SiC QDs prepared in Example 1 into a stainless-steel high-pressure reactor with a quartz window, add 5 mL of acetonitrile and 0.1 mmol of benzylamine, seal the photocatalytic reactor, place the reactor in an ultrasonic machine for ultrasonic treatment for 2 min, and then transfer it to a constant-temperature water bath. While irradiating with a xenon light source with an intensity of 2 W / cm 2 , heat the temperature of the reactor to 50 °C with magnetic stirring at a speed of 600 rpm, stir and react at a constant temperature for 3 h. After the reaction is completed, the conversion rate of benzylamine is detected to be 77.4%, and the selectivity for imine is 99.9%.

[0079] Application Example 13

[0080] Place 3 mg of the SiC QDs prepared in Example 1 into a stainless-steel high-pressure reactor with a quartz window, add 5 mL of acetonitrile and 0.1 mmol of benzylamine, seal the photocatalytic reactor, place the reactor in an ultrasonic machine for ultrasonic treatment for 2 min, and then transfer it to a constant-temperature water bath. While irradiating with a xenon light source with an intensity of 1.5 W / cm 2 , heat the temperature of the reactor to 50 °C with magnetic stirring at a speed of 600 rpm, stir and react at a constant temperature for 3 h. After the reaction is completed, the conversion rate of benzylamine is detected to be 59.3%, and the selectivity for imine is 99.9%.

[0081] Application Example 14

[0082] Place 3 mg of the SiC QDs prepared in Example 1 into a stainless-steel high-pressure reactor with a quartz window, add 5 mL of acetonitrile and 0.1 mmol of benzylamine, seal the photocatalytic reactor, place the reactor in an ultrasonic machine for ultrasonic treatment for 2 min, and then transfer it to a constant-temperature water bath. While irradiating with a xenon lamp source with an intensity of 1 W / cm 2 magnetically stir at a speed of 600 rpm and heat the temperature of the reactor to 50 °C, and stir and react at a constant temperature for 3 h. After the reaction is completed, the conversion rate of benzylamine is detected to be 38.7%, and the selectivity of imine is 99.9%.

[0083] Application Example 15

[0084] Place 3 mg of the SiC QDs prepared in Example 1 into a stainless-steel high-pressure reactor with a quartz window, add 5 mL of acetonitrile and 0.1 mmol of benzylamine, seal the photocatalytic reactor, place the reactor in an ultrasonic machine for ultrasonic treatment for 2 min, and then transfer it to a constant-temperature water bath. While irradiating with a xenon lamp source with an intensity of 2.4 W / cm 2 magnetically stir at a speed of 300 rpm and heat the temperature of the reactor to 50 °C, and stir and react at a constant temperature for 3 h. After the reaction is completed, the conversion rate of benzylamine is detected to be 85.4%, and the selectivity of imine is 99.9%.

[0085] It can be seen that the conversion rate of the benzylamine oxidative coupling reaction using the SiC QDs catalyst prepared in Example 1 can reach 60% - 100%, and the selectivity can reach 60% - 99%.

[0086] Those of ordinary skill in the art can understand that the above embodiments are specific examples for implementing the present invention. In actual applications, various changes can be made in form and details without departing from the spirit and scope of the present invention. Any person skilled in the art can make their own changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be determined by the scope defined in the claims.

Claims

1. A preparation method of a SiC QDs catalyst, characterized in that, The SiC QDs catalyst is prepared by a chemical etching method using SiC as a raw material; wherein, the SiC includes one or both of α-SiC and β-SiC.

2. The preparation method of the SiC QDs catalyst according to claim 1, characterized in that, The preparation method specifically includes: (1) Disperse SiC in a hydrofluoric acid-nitric acid mixed aqueous solution, heat to 100 °C and maintain for 1-6 h, take out and cool to room temperature to obtain a reaction solution; (2) Dilute the reaction solution with deionized water and centrifuge it multiple times until neutral, take the lower-layer powder solid, and dry it in an oven for 5 h to obtain a reactant; (3) Add the reactant to deionized water for dispersion, ultrasonically vibrate, remove large particles by centrifugation, take the supernatant, and obtain the SiC QDs catalyst after freeze-drying.

3. The preparation method of the SiC QDs catalyst according to claim 2, characterized in that, In step (1), the volume ratio of hydrofluoric acid to nitric acid in the hydrofluoric acid-nitric acid mixed aqueous solution is 0.5-3:

1.

4. The preparation method of the SiC QDs catalyst according to claim 2, characterized in that, In step (3), the added deionized water is 10-50 mL, and the ultrasonic time is 30-120 min; Optionally, the rotation speed for centrifuging to remove large particles is 8000-12000 rpm, and the time is 5-15 min; Optionally, the freeze-drying temperature is -60 °C, and the freeze-drying time is 1-24 h.

5. The SiC QDs catalyst prepared by the preparation method of the SiC QDs catalyst according to any one of claims 1 to 4.

6. The application of the SiC QDs catalyst according to claim 5 in the photocatalytic oxidative coupling reaction of benzylamine.

7. The application according to claim 6, wherein The application method includes: placing the SiC QDs catalyst, benzylamine, and a reaction solvent in a reactor, and starting stirring and heating.

8. The application according to claim 7, wherein The dosage of the SiC QDs catalyst is 10%-30% of the mass of benzylamine.

9. The application according to claim 7, characterized in that The reaction solvent is one of acetonitrile, toluene, trifluorotoluene, and dimethyl sulfoxide; the reaction temperature is 30-150 °C, the stirring rate is 100-800 rpm, and the reaction time is 0.1-8 h.

10. The application according to claim 7, wherein In the photocatalytic oxidative coupling reaction of benzylamine, the conversion rate of benzylamine is 60%-100%, and the selectivity of imine is 60%-99%.