Photocatalytic synthesis of trifluoromethanesulfonic acid

Abstract

This invention belongs to the field of fluorochemical technology, specifically relating to a method for the photocatalytic synthesis of trifluoromethanesulfonic acid. The method for photocatalytic synthesis of trifluoromethanesulfonic acid described in this invention involves: firstly, dissolving 4-fluorothiophenol, a trifluoromethyl source, and a photocatalyst in a solvent, and catalyzing the reaction under visible light at room temperature. The reaction solution is then treated to obtain the intermediate 4-fluorotrifluoromethylthiobenzene. Next, the intermediate 4-fluorotrifluoromethylthiobenzene is mixed with formic acid and hydrogen peroxide, and oxidized at 40°C. After quenching, extraction, and purification, solid 4-fluorotrifluoromethyl sulfone is obtained. Finally, 4-fluorotrifluoromethyl sulfone is mixed with concentrated sulfuric acid for hydrolysis. The resulting reaction solution is quenched and then treated to obtain trifluoromethanesulfonic acid. The photocatalytic synthesis method for trifluoromethanesulfonic acid provided by this invention uses safe raw materials, operates under mild reaction conditions, has simple steps, and is environmentally friendly.

Description

Technical Field

[0001] This invention belongs to the field of fluorochemical technology, specifically relating to a method for photocatalytic synthesis of trifluoromethanesulfonic acid. Background Technology

[0002] Trifluoromethanesulfonic acid (CF3SO3H) is an important super-strong organic acid with an acidity close to that of 100% sulfuric acid. It also possesses high thermal stability, relatively low corrosiveness, and its anion (trifluoromethanesulfonate, CF3SO3H) is present. - Its weak nucleophilicity and high stability make it irreplaceable in many high-tech fields: in the pharmaceutical industry, it is both a highly efficient and mild acidic catalyst for the synthesis of various complex drug molecules and an important building block for introducing the key pharmacophore trifluoromethanesulfonyl group; in materials science, it can be used to prepare high-performance special engineering plastics, ion exchange membranes (such as proton exchange membranes for fuel cells), and functional ionic liquids; in the electronic chemicals industry, it is an important component of lithium-ion battery electrolytes and a special chemical for etching and cleaning processes in semiconductor manufacturing; in addition, it is also used to synthesize highly efficient, low-residue fluorinated pesticides and herbicides.

[0003] Currently, the industrial production of trifluoromethanesulfonic acid mainly relies on two traditional process routes. The first is the trifluorobromomethane-sulfur trioxide route, the core of which lies in the stepwise molecular construction: firstly, under strictly anhydrous and oxygen-free conditions, an active metal (such as zinc powder) reacts with highly toxic trifluorobromomethane (CF3Br) to generate a highly reactive trifluoromethylzinc reagent. This reagent then reacts with highly corrosive and easily polymerizable sulfur trioxide (SO3), followed by neutralization, acidification, and distillation to obtain the product. This method has harsh process conditions, involves multiple highly hazardous raw materials, has extremely high requirements for equipment materials and operational safety, and is lengthy. The second mainstream method is the electrolytic fluorination method, which typically uses methanesulfonyl chloride / fluorine as raw materials, dissolved in excess anhydrous hydrogen fluoride (HF), and electrolyzes to produce the perfluorinated intermediate trifluoromethanesulfonyl fluoride (CF3SO2F), which is then obtained through alkali absorption and acidification. While this method avoids some highly toxic raw materials, the electrolysis process generates a large amount of hydrogen, resulting in low concentrations of the target intermediate, making separation and purification difficult, and incurring high equipment investment and operating costs. Furthermore, it also requires the handling of highly corrosive anhydrous hydrogen fluoride.

[0004] Existing published patents CN102911087A and CN115894308A both provide production processes for trifluoromethanesulfonic acid, but they still have the following problems: they all heavily rely on highly hazardous, toxic, or corrosive raw materials such as trifluoromethane, sulfur trioxide, and anhydrous hydrogen fluoride, resulting in significant production safety risks and environmental pressures; the process flow is complex and the conditions are harsh (such as strict anhydrous and oxygen-free control and intense exothermic management), leading to inconvenient operation, low automation, high energy consumption, and significant challenges in the treatment of waste. These shortcomings collectively restrict the further development and application expansion of trifluoromethanesulfonic acid production technology. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the above-mentioned defects of the prior art and provide a method for photocatalytic synthesis of trifluoromethanesulfonic acid, which has safe raw materials, mild reaction conditions, simple steps and environmental friendliness.

[0006] The method for photocatalytic synthesis of trifluoromethanesulfonic acid according to the present invention is as follows: First, 4-fluorothiophenol, trifluoromethyl source and photocatalyst are dissolved in a solvent, and the reaction is carried out by irradiation with visible light at room temperature. The wavelength of visible light is 450~455nm. The reaction solution is treated to obtain the intermediate 4-fluorotrifluoromethylthiobenzene. Then, the intermediate 4-fluorotrifluoromethylthiobenzene, formic acid and hydrogen peroxide are mixed and oxidized at 30~50℃. After quenching, extraction and purification, solid 4-fluorotrifluoromethyl sulfone is obtained. Finally, 4-fluorotrifluoromethyl sulfone is mixed with concentrated sulfuric acid to carry out a hydrolysis reaction. The resulting reaction solution is quenched and treated to obtain trifluoromethanesulfonic acid.

[0007] The catalytic reaction time is 12-16 hours with stirring, and the oxidation reaction time is 6-8 hours.

[0008] The hydrolysis reaction temperature is 120℃~150℃, and the reaction time is 24h~48h.

[0009] After the catalytic reaction is completed, the reaction solution is extracted, washed, dried and concentrated, and then purified by silica gel column chromatography.

[0010] After the hydrolysis reaction is completed, the mixture is cooled to room temperature, then quenched below 0°C, and then extracted with diethyl ether. The aqueous phase is then concentrated under low temperature and reduced pressure, and the fraction at 160-164°C is collected by vacuum distillation.

[0011] The trifluoromethyl source is sodium trifluoromethyl sulfinate.

[0012] The photocatalyst is ferrous trifluoromethanesulfonate or an organic photocatalyst. Ferrous trifluoromethanesulfonate or an organic photocatalyst (such as 4CzIPN) is preferred.

[0013] The solvent is anhydrous acetonitrile, N,N-dimethylformamide, or acetone, and the water content is required to be less than 50 ppm to ensure the smooth progress of the free radical reaction.

[0014] The molar ratio of 4-fluorothiophenol to trifluoromethyl source is 1:1.05~1.5, the amount of photocatalyst is 0.5~5.0 mol% of 4-fluorothiophenol, and the molar ratio of 4-fluorotrifluoromethylthiobenzene to hydrogen peroxide is 1:2~6.

[0015] The molar ratio of 4-fluorotrifluoromethyl sulfone to concentrated sulfuric acid is 1:20~85.

[0016] Specifically, the method for photocatalytic synthesis of trifluoromethanesulfonic acid includes the following steps:

[0017] (1) Dissolve 4-fluorothiophenol, trifluoromethyl source and photocatalyst in solvent, place in a strictly degassed reaction tube, irradiate with visible light at room temperature with a wavelength of 450~455nm, stir for 12~16h, extract, wash, dry and concentrate the reaction solution, and then purify by silica gel column chromatography to obtain the intermediate 4-fluorotrifluoromethylthiobenzene;

[0018] (2) The intermediate 4-fluorotrifluoromethylthiobenzene was mixed with formic acid and hydrogen peroxide and reacted at 40°C for 6-8 hours. After quenching, extraction and purification, solid 4-fluorotrifluoromethyl sulfone was obtained.

[0019] (3) 4-fluorotrifluoromethyl sulfone and concentrated sulfuric acid were placed in a pressure-resistant reactor and sealed at 130°C for 36 hours. After the reaction solution was completely cooled, it was slowly added dropwise to crushed ice for safe quenching. Then, the aromatic byproducts were removed by extraction with diethyl ether. The final aqueous phase was concentrated under low temperature and reduced pressure, and the fraction at 160~164°C was collected by vacuum distillation to obtain the trifluoromethanesulfonic acid product.

[0020] This invention does not directly use hazardous gases or highly corrosive reagents to construct or modify CF3SO3H molecules, but instead breaks down their synthesis into two modular steps that can be carried out efficiently under mild conditions:

[0021] Step 1 (Photocatalytic construction): Using mature and green visible light catalytic trifluoromethylation technology, a key sulfur-containing intermediate with a well-defined structure is synthesized with high selectivity and high yield by reacting a stable solid trifluoromethyl source with readily available sulfur-containing raw materials.

[0022] The second step (oxidation-hydrolysis): The intermediate is subjected to controlled deep oxidation, followed by selective CS bond cleavage (hydrolysis) under specific conditions, thereby releasing pure trifluoromethanesulfonic acid.

[0023] The above shifts the risk of synthesis from "using high-risk raw materials" to "controlling known organic reactions".

[0024] This invention uses sodium trifluoromethyl sulfinate as the trifluoromethyl source, completely replacing gaseous, highly toxic trifluorobromomethane. Its characteristic is that it can be oxidized with a single electron under photocatalytic conditions, efficiently generating trifluoromethyl radicals. Furthermore, 4-fluorothiophenol is used as a sulfur-containing raw material, with the fluorine atom on the benzene ring acting as a directing and activating group. This not only adjusts the electron cloud density, making subsequent oxidation steps easier, but also facilitates its removal as hydrogen fluoride under strong acid hydrolysis conditions, avoiding complex aromatic ring byproducts.

[0025] This invention begins with the preparation of 4-fluorotrifluoromethylthiobenzene, specifically a photocatalytic radical coupling step. Under inert gas protection, 4-fluorothiophenol, sodium trifluoromethylsulfinate, and the photocatalyst ferrous trifluoromethanesulfonate are dissolved in anhydrous acetonitrile and placed in a strictly degassed reaction tube. After irradiation with visible light at a wavelength of 453 nm at room temperature and stirring for 12–16 h, the reaction solution is extracted, washed, dried, and concentrated, then purified by silica gel column chromatography to obtain the intermediate 4-fluorotrifluoromethylthiobenzene. Next is the preparation of trifluoromethanesulfonic acid, which involves two steps: oxidation and hydrolysis. In the oxidation stage, the intermediate obtained in the previous step is mixed with formic acid and hydrogen peroxide and reacted at 40 °C for 6–8 h. After quenching, extraction, and purification, solid 4-fluorotrifluoromethyl sulfone is obtained. The subsequent hydrolysis stage involves placing the sulfone intermediate and concentrated sulfuric acid in a pressure-resistant reactor and reacting at 130 °C in a sealed container for 36 h. After the reaction solution has completely cooled, it must be slowly added dropwise to crushed ice for safe quenching, followed by extraction with diethyl ether to remove aromatic byproducts. The final aqueous phase is concentrated under low temperature and reduced pressure, and the fraction collected at 160-164℃ is obtained by vacuum distillation to yield pure trifluoromethanesulfonic acid.

[0026] The working principle of this invention lies in employing an innovative strategy of "modular construction and mild transformation" to avoid the dependence on high-risk reagents and harsh conditions inherent in traditional methods. Its core is the design of the synthesis of trifluoromethanesulfonic acid as two chemical stages carried out under mild and controllable conditions. The first stage utilizes visible light catalysis to drive a safe and stable trifluoromethyl source to generate trifluoromethyl radicals, which then undergo a highly efficient radical addition-oxidative coupling reaction with arylthiophenols, thereby constructing the crucial carbon-sulfur-trifluoromethyl skeleton at room temperature and atmospheric pressure. The second stage achieves molecular tailoring and final assembly through stepwise chemical transformations: firstly, the thioether unit is selectively converted to sulfone through peroxyacid oxidation; subsequently, under the combined action of strong acid and high temperature, the sulfone intermediate undergoes acid-catalyzed electrophilic cleavage, specifically breaking the carbon-sulfur bond, ultimately releasing the target product, trifluoromethanesulfonic acid, while the aromatic ring portion departs as a simple byproduct. This entire route design shifts the synthetic risk from the handling of uncontrollable high-risk materials to the control of a series of well-defined steps and mechanisms of classical organic reactions, achieving a fundamental innovation in safety and controllability in principle.

[0027] Compared with the prior art, the beneficial effects of the present invention are:

[0028] (1) This invention brings about a leap forward in inherent safety. The highly hazardous raw materials that traditional processes rely on, such as the highly toxic trifluoromethane gas, liquid sulfur trioxide, and anhydrous hydrogen fluoride, are completely eliminated. They are replaced by solid sodium trifluoromethanesulfinate, which is stable at room temperature and pressure and is easy to store and transport safely, as well as conventional organic solvents and oxidants. This fundamental change in the raw material system completely eliminates the extremely high risks of leakage, poisoning, corrosion, and explosion inherent in traditional production.

[0029] (2) This invention achieves significantly milder reaction conditions and greater energy-saving potential. The most critical trifluoromethylation step can be carried out efficiently under visible light irradiation at room temperature and atmospheric pressure, replacing the continuous high-power consumption process required by traditional electrolytic fluorination, and avoiding the precise control requirements of a strictly anhydrous and oxygen-free environment and violent exothermic reactions in the trifluorobromomethane method. Although the final acidolysis step still requires heating, the overall energy consumption, especially the energy input form of the preceding reaction, becomes cleaner and lower-carbon. According to publicly available industry energy consumption data, the unit product comprehensive energy consumption of traditional electrolytic fluorination processes is extremely high, while this method provides a clear path to achieve significant energy saving and consumption reduction in principle.

[0030] (3) Since this invention no longer uses chlorine-containing raw materials, it eliminates the generation of chlorine-containing organic waste and difficult-to-treat chlorine-containing waste salts at the source. The entire reaction route has higher atom economy, and the byproducts are clear and relatively simple (such as water, carbon dioxide, recyclable aromatics, etc.). Compared with the complex composition and high treatment cost of fluorine- and chlorine-containing wastewater and waste gas generated by traditional methods, the burden of subsequent waste treatment is significantly reduced, which is more in line with the development direction of modern green chemistry.

[0031] (4) This invention offers the dual advantages of simplified operation and optimized cost. The modular three-step process of "photo-oxidation-hydrolysis" involves classic organic reactions at each step, with separable and precisely monitored intermediates. The process is flexible and easily scaled up to production scale. This avoids reliance on complex electrolytic cells and gas handling systems constructed with special corrosion-resistant materials (such as all-Monel alloys for hydrofluoric acid), and is expected to significantly reduce initial equipment investment and long-term maintenance costs. At the same time, the use of solid raw materials simplifies the material conveying and metering system, further reducing operational complexity and safety management costs. Attached Figure Description

[0032] Figure 1 The gas chromatogram of trifluoromethanesulfonic acid, the product prepared in Example 1.

[0033] Figure 2 The product trifluoromethanesulfonic acid prepared in Example 1 13C10 NMR spectrum. Detailed Implementation

[0034] The present invention will be further described below with reference to specific embodiments.

[0035] 4-Fluorothiophenol: Aladdin, purity ≥98%. 4CzIPN: Aladdin, purity ≥99%. Ferrous trifluoromethanesulfonate: Anaiji, purity ≥98%. Sodium trifluoromethylsulfinate: Aladdin, purity ≥98%.

[0036] Example 1

[0037] The method for photocatalytic synthesis of trifluoromethanesulfonic acid includes the following steps:

[0038] 4-Fluorothiophenol (126 mg, 1.0 mmol), sodium trifluoromethyl sulfinate (180 mg, 1.15 mmol), and ferrous trifluoromethanesulfonate (7.2 mg, 0.02 mmol) were dissolved in anhydrous acetonitrile (5 mL) and placed in a strictly degassed reaction tube. The mixture was irradiated with visible light at a wavelength of 453 nm at room temperature and stirred for 14 h. The reaction solution was then extracted, washed, dried, and concentrated, followed by purification by silica gel column chromatography to obtain 187 mg of the intermediate 4-fluorotrifluoromethyl thiobenzene. 4-Fluorotrifluoromethyl thiobenzene (187 mg, 0.95 mmol) was mixed with formic acid (5 mL) and hydrogen peroxide (0.39 mL, 3.8 mmol) and reacted at 40 °C for 7 h. After quenching, extraction, and purification, 205 mg of solid 4-fluorotrifluoromethyl sulfone was obtained. 205 mg (0.90 mmol) of 4-fluorotrifluoromethyl sulfone and 2.0 mL (37 mmol) of 98% concentrated sulfuric acid were placed in a pressure-resistant reactor and reacted at 130 °C for 36 h. After the reaction solution was completely cooled, it was slowly added dropwise to crushed ice to quench the reaction. Aromatic byproducts were then removed by extraction with diethyl ether. The final aqueous phase was concentrated under reduced pressure in a 35 °C water bath, and the fraction collected at 160–164 °C was obtained by vacuum distillation to yield 118 mg of trifluoromethanesulfonic acid. Its structure was determined as follows. Figure 2 As shown, gas chromatography analysis revealed a purity of 99.8%. Figure 1 As shown, its yield was calculated to be 78.6%.

[0039] Example 2

[0040] The method for photocatalytic synthesis of trifluoromethanesulfonic acid includes the following steps:

[0041] 4-Fluorothiophenol (126 mg, 1.0 mmol), sodium trifluoromethyl sulfinate (165 mg, 1.05 mmol), and 4CzIPN (3.94 mg, 0.005 mmol) were dissolved in N,N-dimethylformamide (5 mL) and placed in a strictly degassed reaction tube. The mixture was irradiated with visible light at a wavelength of 450 nm at room temperature and stirred for 12 h. The reaction solution was then extracted, washed, dried, and concentrated, followed by purification by silica gel column chromatography to obtain 180 mg of the intermediate 4-fluorotrifluoromethylthiobenzene. 4-Fluorotrifluoromethylthiobenzene (180 mg, 0.92 mmol) was mixed with formic acid (5 mL) and hydrogen peroxide (0.18 mL, 1.8 mmol) and reacted at 30 °C for 6 h. After quenching, extraction, and purification, 199 mg of solid 4-fluorotrifluoromethyl sulfone was obtained. 4-Fluorotrifluoromethyl sulfone (199 mg, 0.87 mmol) and 98% concentrated sulfuric acid (0.95 mL, 17.4 mmol) were placed in a pressure-resistant reactor and reacted at 120 °C for 24 h. After the reaction solution was completely cooled, it was slowly added dropwise to crushed ice to quench the reaction. Aromatic byproducts were then removed by extraction with diethyl ether. The final aqueous phase was concentrated under reduced pressure in a 35 °C water bath, and the fraction from 160 to 164 °C was collected by vacuum distillation to obtain 109 mg of trifluoromethanesulfonic acid with a purity of 99.5%. The yield was calculated to be 72.6%.

[0042] Example 3

[0043] The method for photocatalytic synthesis of trifluoromethanesulfonic acid includes the following steps:

[0044] 4-Fluorothiophenol (126 mg, 1.0 mmol), sodium trifluoromethylsulfinate (234 mg, 1.5 mmol), and ferrous trifluoromethanesulfonate (18.1 mg, 0.05 mmol) were dissolved in acetone (5 mL) and placed in a strictly degassed reaction tube. The mixture was irradiated with visible light at a wavelength of 455 nm at room temperature and stirred for 16 h. The reaction solution was then extracted, washed, dried, and concentrated, followed by purification by silica gel column chromatography to obtain 185 mg of the intermediate 4-fluorotrifluoromethylthiobenzene. 4-Fluorotrifluoromethylthiobenzene (185 mg, 0.943 mmol) was mixed with formic acid (5 mL) and hydrogen peroxide (0.58 mL, 5.7 mmol) and reacted at 50 °C for 8 h. After quenching, extraction, and purification, 203 mg of solid 4-fluorotrifluoromethyl sulfone was obtained. 203 mg (0.89 mmol) of 4-fluorotrifluoromethyl sulfone and 4.1 mL (75.7 mmol) of 98% concentrated sulfuric acid were placed in a pressure-resistant reactor and reacted at 150 °C for 48 h. After the reaction solution was completely cooled, it was slowly added dropwise to crushed ice to quench the reaction. Aromatic byproducts were removed by extraction with diethyl ether. The final aqueous phase was concentrated under reduced pressure in a water bath at 35 °C. The fraction from 160 to 164 °C was collected by vacuum distillation to obtain 111 mg of trifluoromethanesulfonic acid with a purity of 99.6%. The yield was calculated to be 73.9%.

[0045] Comparative Example 1

[0046] 4-Fluorothiophenol (126 mg, 1.0 mmol), sodium trifluoromethyl sulfinate (180 mg, 1.15 mmol), and ferrous trifluoromethanesulfonate (7.2 mg, 0.02 mmol) were dissolved in anhydrous acetonitrile (5 mL) and placed in a strictly degassed reaction tube. The mixture was irradiated with visible light at a wavelength of 430 nm at room temperature and stirred for 14 h. The reaction solution was then extracted, washed, dried, and concentrated, followed by purification by silica gel column chromatography to obtain 19 mg of the intermediate 4-fluorotrifluoromethyl thiobenzene. 4-Fluorotrifluoromethyl thiobenzene (19 mg, 0.09 mmol) was mixed with formic acid (5 mL) and hydrogen peroxide (0.04 mL, 0.39 mmol) and reacted at 40 °C for 7 h. After quenching, extraction, and purification, 21 mg of solid 4-fluorotrifluoromethyl sulfone was obtained. 4-Fluorotrifluoromethyl sulfone (21 mg, 0.09 mmol) and 98% concentrated sulfuric acid (0.2 mL, approximately 3.7 mmol) were placed in a pressure-resistant reactor and reacted at 130 °C for 36 h. After the reaction solution was completely cooled, it was slowly added dropwise to crushed ice to quench the reaction. Aromatic byproducts were then removed by extraction with diethyl ether. The final aqueous phase was concentrated under reduced pressure in a 35 °C water bath, and the fraction from 160–164 °C was collected by vacuum distillation to obtain 11.4 mg of trifluoromethanesulfonic acid with a purity of 99.7%, and the yield was calculated to be 7.6%.

[0047] Comparative Example 2

[0048] 4-Fluorothiophenol (126 mg, 1.0 mmol), trifluoromethanesulfonyl chloride (173 mg, 1.15 mmol), and ferrous trifluoromethanesulfonate (7.2 mg, 0.02 mmol) were dissolved in anhydrous acetonitrile (5 mL) and placed in a strictly degassed reaction tube. The mixture was irradiated with visible light at a wavelength of 453 nm at room temperature and stirred for 14 h. The reaction solution was then extracted, washed, dried, and concentrated, followed by purification by silica gel column chromatography to obtain 63 mg of the intermediate 4-fluorotrifluoromethylthiobenzene. 4-Fluorotrifluoromethylthiobenzene (63 mg, 0.32 mmol) was mixed with formic acid (5 mL) and hydrogen peroxide (0.13 mL, 1.28 mmol) and reacted at 40 °C for 7 h. After quenching, extraction, and purification, 67.5 mg of solid 4-fluorotrifluoromethyl sulfone was obtained. 4-Fluorotrifluoromethyl sulfone (67.5 mg, 0.29 mmol) and 98% concentrated sulfuric acid (0.63 mL, approximately 11.6 mmol) were placed in a pressure-resistant reactor and reacted at 130 °C for 36 h. After the reaction solution was completely cooled, it was slowly added dropwise to crushed ice to quench the reaction. Aromatic byproducts were then removed by extraction with diethyl ether. The final aqueous phase was concentrated under reduced pressure in a 35 °C water bath, and the fraction from 160–164 °C was collected by vacuum distillation to obtain 35.7 mg of trifluoromethanesulfonic acid with a purity of 98.5%, and the yield was calculated to be 23.8%.

Claims

1. A method for photocatalytic synthesis of trifluoromethanesulfonic acid, characterized in that: First, 4-fluorothiophenol, a trifluoromethyl source, and a photocatalyst are dissolved in solvent A, and a catalytic reaction is carried out by irradiation with visible light at room temperature (wavelength 450-455 nm). The reaction solution is treated to obtain the intermediate 4-fluorotrifluoromethylthiobenzene. Then, the intermediate 4-fluorotrifluoromethylthiobenzene is mixed with solvent B and hydrogen peroxide, and oxidized at 30-50°C. After quenching, extraction, and purification, solid 4-fluorotrifluoromethyl sulfone is obtained. Finally, 4-fluorotrifluoromethyl sulfone is mixed with concentrated sulfuric acid for hydrolysis. The resulting reaction solution is quenched and treated to obtain trifluoromethanesulfonic acid. The trifluoromethyl source is sodium trifluoromethylsulfinate, and the catalyst is ferrous trifluoromethanesulfonate or 4CzIPN. The hydrolysis reaction temperature is 120℃~150℃, and the reaction time is 24h~48h; The molar ratio of 4-fluorotrifluoromethyl sulfone to concentrated sulfuric acid is 1:20~85.

2. The method for photocatalytic synthesis of trifluoromethanesulfonic acid according to claim 1, characterized in that: The catalytic reaction time is 12-16 hours with stirring, and the oxidation reaction time is 6-8 hours.

3. The method for photocatalytic synthesis of trifluoromethanesulfonic acid according to claim 1, characterized in that: After the catalytic reaction is completed, the reaction solution is extracted, washed, dried and concentrated, and then purified by silica gel column chromatography.

4. The method for photocatalytic synthesis of trifluoromethanesulfonic acid according to claim 1, characterized in that: After the hydrolysis reaction is completed, the mixture is cooled to room temperature, then quenched below 0°C, and then extracted with diethyl ether. The aqueous phase is then concentrated under low temperature and reduced pressure, and the fraction at 160-164°C is collected by vacuum distillation.

5. The method for photocatalytic synthesis of trifluoromethanesulfonic acid according to claim 1, characterized in that: Solvent A is anhydrous acetonitrile, N,N-dimethylformamide, or acetone; solvent B is formic acid.

6. The method for photocatalytic synthesis of trifluoromethanesulfonic acid according to claim 1, characterized in that: The molar ratio of 4-fluorothiophenol to trifluoromethyl source is 1:1.05~1.5, the amount of photocatalyst is 0.5~5.0 mol% of 4-fluorothiophenol, and the molar ratio of 4-fluorotrifluoromethylthiobenzene to hydrogen peroxide is 1:2~6.

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