Monatomic catalyst and application thereof in photocatalytic oxidation reaction of methyl phenyl sulfide

Abstract

The invention discloses a monatomic catalyst and application of the monatomic catalyst in photocatalytic oxidation of methyl phenyl sulfide. The molecular formula of the monatomic catalyst is M-TPP, M is Au, Ag, Cu or Pt, and TPP is tetra-p-tolyl porphyrin. The synthesis method of the monatomic copper catalyst is simple, the catalytic yield of the monatomic copper catalyst in the reaction for preparing methyl phenyl sulfoxide through photo-catalytic oxidation of methyl phenyl sulfide reaches 99%, the catalytic condition is mild, the catalyst is easy to recycle, and multiple catalytic cycle experiments can be carried out.

Description

Technical Field

[0001] The invention belongs to the field of chemical synthesis, and in particular relates to a single-atom catalyst and application thereof in a photocatalytic oxidation reaction of methyl phenyl sulfide. Background Art

[0002] Sulfoxides are valuable synthetic reagents for the production of a variety of important chemical and biological molecules. Oxidation of thioethers is a common method for the preparation of the corresponding series of sulfoxides. This process is widely used in the pharmaceutical industry, pre-combustion desulfurization of fuels, simple treatment of wastewater, and production of chemical reagents. Traditionally, this reaction can be achieved by thermal oxidation processes using a variety of oxidants such as trifluoroperacetic acid, hydrogen peroxide, tert-butyl hydroperoxide, and iodophenyl diacetate. In recent years, organic synthesis achieved with photocatalysts under light-driven catalytic cycles has attracted great interest due to its advantages such as simple operation and environmental friendliness. Jiang's group described three new hydrazone-linked two-dimensional porphyrin COFs, named MPor-Dha (M = Co, Ni, and Cu). In the photocatalytic oxidation of methyl phenyl sulfide, CoPor-Dha showed low catalytic activity with a yield of only 7%; NiPor-Dha had a moderate yield of 15%; CuPor-Dha had the highest catalytic activity with a yield of 82%, but the catalyst could not be recycled (10.1016 / j.cej.2023.146623). Therefore, the development of efficient, stable, and recyclable photocatalysts for organic synthesis is crucial to transform traditional thermal organic chemistry into green and sustainable organic chemistry. Summary of the invention

[0003] Based on the problems existing in the above-mentioned prior art, the present invention provides a single-atom catalyst and its application in the photocatalytic oxidation reaction of methyl phenyl sulfide. Studies have found that under the catalysis of the single-atom copper catalyst, the conversion rate of the reactants and the selectivity of the products are the highest, the catalyst has high stability, can be recycled, the operation method is simple and controllable, and has good application prospects.

[0004] The single-atom catalyst of the invention has a molecular formula of M-TPP, wherein M is Au, Ag, Cu or Pt, and TPP is tetra-p-tolylporphyrin.

[0005] The single-atom catalyst of the present invention is synthesized by a one-pot method, comprising the following steps: The metal source was added into a 100 mL round-bottom flask containing 15 mL ethanol and 35 mL acetonitrile. After stirring at room temperature for five minutes, tetra-p-tolylporphyrin dissolved in 10 mL chloroform was added, and trifluoroacetic acid was added at the same time. Stirring was continued for 30 min. The obtained reaction solution was filtered, subjected to rotary evaporation, and dried in an oven at 50 ° C for 5 h to obtain a solid product M-TPP.

[0006] The metal source is selected from chloroauric acid, silver nitrate, copper nitrate or platinum chloride, preferably copper nitrate.

[0007] The molar ratio of the metal source to tetra-p-tolylporphyrin is 20:1.

[0008] The invention discloses an application of the single-atom catalyst in the photocatalytic oxidation reaction of methyl phenyl sulfide.

[0009] Specifically, acetonitrile and methanol are used as a mixed solvent, oxygen is used as an oxidant, and in the presence of the single-atom catalyst, methyl phenyl sulfide is photocatalyzed to prepare methyl phenyl sulfoxide at room temperature; the synthesis route is as follows: .

[0010] In the mixed solvent, the volume ratio of acetonitrile to methanol is 2:1.

[0011] The light source used for the photocatalytic reaction was a 425 nm LED lamp.

[0012] The beneficial effects of the present invention are embodied in: 1. The present invention synthesizes a series of single-atom catalysts, among which the single-atom copper catalyst exhibits high catalytic activity in the photocatalytic oxidation of methyl phenyl sulfide, with a yield of up to 99% and excellent selectivity without over-oxidation to sulfone.

[0013] 2. The experimental process of the present invention is simple and easy to implement, has low cost, and has strong popularization potential.

[0014] 3. The catalytic conditions of the present invention are mild, the catalyst can be recycled, and the photocatalytic reaction can be carried out more than 5 times, and the excellent yield of more than 95% is maintained, which has high economic and environmental benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is the ultraviolet absorption diagram of the single-atom copper catalyst of the present invention.

[0016] Figure 2 This is a mass spectrometry characterization diagram of the single-atom copper catalyst of the present invention.

[0017] Figure 3 This is a single crystal structure diagram of the single-atom copper catalyst of the present invention.

[0018] Figure 4 This is a gas phase yield diagram of methyl phenyl sulfoxide prepared by photocatalytic oxidation of methyl phenyl sulfide using the single-atom copper catalyst prepared in the present invention. DETAILED DESCRIPTION

[0019] The technical solution of the present invention is further explained below in conjunction with specific embodiments. Example 1: Preparation of single-atom gold catalyst Au-TPP

[0020] At room temperature, chloroauric acid (8.9 mg, 0.025 mmol) was added to a mixed solvent of 15 mL of ethanol and 35 mL of acetonitrile. After stirring for five minutes, tetra-p-tolylporphyrin (1 mg) dissolved in 10 mL of chloroform was added, and trifluoroacetic acid (500 µL) was added at the same time. Stirring continued for 10 min. The obtained reaction solution was then filtered, subjected to rotary evaporation, and dried in an oven at 50 °C for 5 hours to obtain a solid product, Au-TPP. Example 2: Preparation of single-atom silver catalyst Ag-TPP

[0021] At room temperature, silver nitrate (5.5 mg, 0.025 mmol) was added to a mixed solvent of 15 mL of ethanol and 35 mL of acetonitrile. After stirring for five minutes, tetra-p-tolylporphyrin (1 mg) dissolved in 10 mL of chloroform was added, and trifluoroacetic acid (500 µL) was added at the same time. Stirring continued for 10 min. The obtained reaction solution was then filtered, subjected to rotary evaporation, and dried in an oven at 50°C for 5 hours to obtain a solid product, Ag-TPP. Example 3: Preparation of single-atom copper catalyst Cu-TPP

[0022] Under room temperature conditions, copper nitrate (4.7 mg, 0.025 mmol) was added to a mixed solvent of 15 mL of ethanol and 35 mL of acetonitrile. After stirring for five minutes, tetra-p-tolylporphyrin (1 mg) dissolved in 10 mL of chloroform was added, and trifluoroacetic acid (500 µL) was added at the same time. Stirring continued for 10 min; the obtained reaction solution was then filtered, subjected to rotary evaporation, and dried in an oven at 50°C for 5 hours to obtain a solid product Cu-TPP. Example 4: Preparation of single-atom platinum catalyst Pt-TPP

[0023] At room temperature, platinum chloride (6.6 mg, 0.025 mmol) was added to a mixed solvent of 15 mL of ethanol and 35 mL of acetonitrile. After stirring for five minutes, tetra-p-tolylporphyrin (1 mg) dissolved in 10 mL of chloroform was added, and trifluoroacetic acid (500 µL) was added at the same time. Stirring continued for 10 min. The obtained reaction solution was then filtered, subjected to rotary evaporation, and dried in an oven at 50°C for 5 hours to obtain a solid product, Pt-TPP. Example 5: Photocatalytic oxidation of methyl phenyl sulfide to methyl phenyl sulfoxide using single-atom copper catalyst Cu-TPP

[0024] A 10 mL Schlenk tube was selected, and a mixed solvent of 3 mL of acetonitrile and methanol (acetonitrile: methanol = 2:1) was added, followed by methyl phenyl sulfide (0.1 mmol, 12 µL) and 1 mg of catalyst Cu-TPP. The Schlenk tube was sealed with a rubber stopper and vacuumed side by side, and an oxygen balloon was tied to it. The reaction was stirred for 3 hours under a 425 nm LED light. At the end of the reaction, the balloon was removed and 23 µL of n-dodecane was added as an internal standard (the gas phase peak area ratio of the equimolar product methyl phenyl sulfoxide and the internal standard dodecane was 1.68). The catalyst was removed by centrifugation to obtain the organic matter, and the yield was analyzed by gas chromatography (GC), which was 99%. Example 6: Photocatalytic oxidation of methyl phenyl sulfide to methyl phenyl sulfoxide using single-atom silver catalyst Ag-TPP

[0025] A 10 mL Schlenk tube was selected, and a mixed solvent of 3 mL of acetonitrile and methanol (acetonitrile: methanol = 2:1) was added, followed by the addition of methyl phenyl sulfide (0.1 mmol, 12 µL) and 1 mg of catalyst Ag-TPP. The Schlenk tube was sealed with a rubber stopper and vacuumed side by side, and an oxygen balloon was tied to it. The reaction was stirred for 3 hours under a 425 nm LED light. At the end of the reaction, the balloon was removed and 23 µL of n-dodecane was added as an internal standard (the gas phase peak area ratio of the equimolar product methyl phenyl sulfoxide and the internal standard dodecane was 1.68). The catalyst was removed by centrifugation to obtain the organic matter, and the yield was analyzed by gas chromatography (GC), which was 45%. Example 7: Photocatalytic oxidation of methyl phenyl sulfide to methyl phenyl sulfoxide using single-atom platinum catalyst Pt-TPP (pure acetonitrile solvent)

[0026] A 10 mL Schlenk tube was selected, and a mixed solvent of 3 mL of acetonitrile and methanol (acetonitrile: methanol = 2:1) was added, followed by methyl phenyl sulfide (0.1 mmol, 12 µL) and 1 mg of catalyst Pt-TPP. The Schlenk tube was sealed with a rubber stopper and vacuumed side by side, and an oxygen balloon was tied to it. The reaction was stirred for 3 hours under a 425 nm LED light. At the end of the reaction, the balloon was removed and 23 µL of n-dodecane was added as an internal standard (the gas phase peak area ratio of the equimolar product methyl phenyl sulfoxide and the internal standard dodecane was 1.68). The catalyst was removed by centrifugation to obtain the organic matter, and the yield was analyzed by gas chromatography (GC), which was 34%. Example 8: Photocatalytic oxidation of methyl phenyl sulfide to methyl phenyl sulfoxide using single-atom copper catalyst Cu-TPP (pure acetonitrile solvent)

[0027] Select a 10mL Schlenk tube, add 3 mL of acetonitrile, then add methyl phenyl sulfide (0.1 mmol, 12 µL) and 1 mg of catalyst Cu-TPP, seal the Schlenk tube with a rubber stopper, evacuate side by side, tie an oxygen balloon, and stir the reaction under a 425 nm LED light for 3 hours; at the end of the reaction, remove the balloon and add 23 µL of n-dodecane as an internal standard (the gas phase peak area ratio of the equimolar product methyl phenyl sulfoxide and the internal standard dodecane is 1.68), remove the catalyst by centrifugation to obtain the organic matter, and analyze the yield by gas chromatography (GC), which is 0%. Example 9: Photocatalytic oxidation of methyl phenyl sulfide to methyl phenyl sulfoxide using single-atom copper catalyst Cu-TPP (without single-atom catalyst)

[0028] Select a 10mL Schlenk tube, add 3 mL of a mixed solvent of acetonitrile and methanol (acetonitrile: methanol = 1:2), then add methyl phenyl sulfide (0.1 mmol, 12 µL), seal the Schlenk tube with a rubber stopper, evacuate side by side, tie an oxygen balloon, and stir the reaction under a 425 nm LED light for 1 hour; at the end of the reaction, remove the balloon and add 23 µL of n-dodecane as an internal standard (the gas phase peak area ratio of the equimolar product methyl phenyl sulfoxide and the internal standard dodecane is 1.68), remove the catalyst by centrifugation to obtain the organic matter, and analyze the yield by gas chromatography (GC), which is 0%. Example 10: Cyclic test, recycling of single-atom copper catalyst Cu-TPP to photocatalytically oxidize methyl phenyl sulfide to synthesize methyl phenyl sulfoxide

[0029] 1. After completing the fresh experiment of synthesizing styrene carbonate, the centrifuged Cu-TPP was washed with dichloromethane three times and vacuum dried at 60°C for 8 hours. A 10 mL Schlenk tube was selected, and a mixed solvent of 3 mL of acetonitrile and methanol (acetonitrile: methanol = 2:1) was added, followed by methyl phenyl sulfide (0.1 mmol, 12 µL) and 1 mg of the recovered catalyst Cu-TPP. The Schlenk tube was sealed with a rubber stopper and vacuumed side by side, and an oxygen balloon was tied to it. The reaction was stirred for 3 hours under a LED light with a wavelength of 425 nm. At the end of the reaction, the balloon was removed and 23 µL of n-dodecane was added as an internal standard (the gas phase peak area ratio of the equimolar product methyl phenyl sulfoxide and the internal standard dodecane was 1.68). The catalyst was removed by centrifugation to obtain the organic matter, and the yield was analyzed by gas chromatography (GC), which was 99%.

[0030] 2. The recovered catalyst was subjected to repeated experiments under the above reaction conditions until the fifth cycle of the experiment. After the catalyst was removed by centrifugation (10,000 rpm), the target product, methyl phenyl sulfoxide, was obtained. The yield was determined by gas chromatography (GC) to be 95%.

Claims

1. A single atom catalyst, characterized in that: The molecular formula of the single-atom catalyst is M-TPP, wherein M is Au, Ag, Cu or Pt, and TPP is tetra-p-tolylporphyrin.

2. The method for preparing the single atom catalyst according to claim 1, characterized in that The steps include: The metal source was added into a reactor containing ethanol and acetonitrile, and after stirring at room temperature for five minutes, tetra-p-tolylporphyrin dissolved in chloroform was added, and trifluoroacetic acid was added at the same time, and stirring was continued for 30 minutes; the obtained reaction solution was filtered, dried after rotary evaporation, and a solid product M-TPP was obtained.

3. The preparation method according to claim 2, characterized in that The metal source is selected from chloroauric acid, silver nitrate, copper nitrate or platinum chloride.

4. The preparation method according to claim 3, characterized in that The metal source is copper nitrate.

5. The preparation method according to claim 2 or 3, characterized in that The molar ratio of the metal source to tetra-p-tolylporphyrin is 20:

1.

6. The preparation method according to claim 2, characterized in that The volume ratio of ethanol to acetonitrile was 3:

7.

7. Use of the single-atom catalyst according to claim 1 in the photocatalytic oxidation reaction of methyl phenyl sulfide.

8. The use according to claim 7, characterized in that: Acetonitrile and methanol are used as a mixed solvent, oxygen is used as an oxidant, and in the presence of the single-atom catalyst, methyl phenyl sulfide is photocatalyzed to prepare methyl phenyl sulfoxide at room temperature; the synthesis route is as follows: 。 9. The use according to claim 8, characterized in that: In the mixed solvent, the volume ratio of acetonitrile to methanol is 2:

1.

10. The use according to claim 8, characterized in that: The light source used for the photocatalytic reaction was a 425 nm LED lamp.

Images