A method for photocatalytic decarboxylation coupling of saturated chain carboxylic acids

Abstract

This invention relates to the technical field of photocatalytic carbon chain lengthening, and more particularly to a method for photocatalytic decarboxylation coupling of saturated chain carboxylic acids. Saturated chain carboxylic acids, a photocatalyst, and a solvent are added to a photocatalytic reactor. After replacing the atmosphere in the reactor with an inert gas, the reactor is sealed and stirred until homogeneous. The decarboxylation coupling reaction occurs at 10-40°C under external light irradiation for 1-10 hours. The mass ratio of saturated chain carboxylic acid to solvent is 1:1-50, and the mass ratio of saturated chain carboxylic acid to photocatalyst is 10-100:1. Compared with existing processes, this method has the advantages of low catalyst cost, low energy consumption, fast reaction rate, high selectivity, and no hydrogen consumption. This invention provides a new approach for carboxylic acid cross-coupling reactions and the production of higher alkanes from biomass fatty acids.

Description

Technical Field

[0001] This invention relates to the technical field of photocatalytic carbon chain lengthening, and more particularly to a method for photocatalytic decarboxylation coupling of saturated chain carboxylic acids. Background Technology

[0002] CC coupling reactions are central to organic synthesis and are crucial for constructing complex organic compounds and functional materials. Transition metal-catalyzed coupling reactions are an extremely powerful and versatile synthetic approach for this purpose. Traditional coupling methods typically require expensive transition metals and complex organometallic ligand compounds.

[0003] Previous research on CC coupling has mainly focused on the dehalogenation coupling of halides, such as Suzuki coupling, the Heck reaction, and Sonogashira coupling. The dehalogenation coupling of halides typically relies on noble metals such as Pd and Pt, through which the carbon-halogen (CX) bond is broken by the metal, leading to the formation of a radical intermediate. This radical intermediate is stabilized on a catalyst, thus shifting the selectivity towards CC coupling. In recent years, carboxylic acids have attracted widespread research interest because they can form aryl / alkyl radicals with similar properties by extruding CO2.

[0004] For decades, the scarcity of fossil-derived resources has been a serious problem for global energy consumption. Many researchers have attempted to identify alternative, sustainable, and clean biofuels to overcome this challenge. Saturated chain carboxylic acids are ideal feedstocks for hydrocarbon production due to their low cost and availability in large quantities from natural resources. However, traditional methods for fatty acid decarboxylation to hydrocarbon production typically involve harsh conditions, low-value byproducts, multiple steps, and expensive, toxic catalysts. Therefore, there is a strong need to find alternative methods for converting fatty acids into alkanes under environmentally friendly conditions.

[0005] Currently, the decarboxylation and hydrogenation of saturated chain carboxylic acids can be achieved by thermocatalysis (ACS Catal. 2019, 9, 3753–3763), photocatalysis (Nat. Catal. 2020, 3, 170–178), and electrocatalysis (ACS Sustain. Chem. Eng. 2021, 9, 5288–5297), but reports on the selective production of coupling products are few. Homocoupling studies after decarboxylation of saturated chain carboxylic acids mainly focus on the Kolbe reaction, which involves electrochemical decarboxylation coupling to form carbon-carbon bonds. Despite more than a century of research, the application of this reaction is limited due to its low selectivity and dependence on noble metal Pt electrodes (Science 2023, 380, 81–87). Summary of the Invention

[0006] Therefore, the purpose of this invention is to provide a photocatalytic method for the decarboxylation coupling of saturated chain carboxylic acids. This method features low-cost catalysts, low energy consumption, fast reaction rates, high selectivity, and no hydrogen consumption. This invention provides a new approach for carboxylic acid cross-coupling reactions and the production of higher alkanes from biomass fatty acids.

[0007] To solve the above-mentioned technical problems of the present invention, the present invention provides the following technical solution:

[0008] This invention provides a method for photocatalytic decarboxylation coupling of saturated chain carboxylic acids, characterized by comprising the following steps:

[0009] Saturated chain carboxylic acid, photocatalyst and solvent are added to a photocatalytic reactor. The atmosphere in the reactor is replaced with an inert gas and then sealed. The mixture is stirred and homogenized. Under the irradiation of an external light source, a decarboxylation coupling reaction occurs at 10-40℃ for 1-10 hours.

[0010] The mass ratio of saturated chain carboxylic acid to solvent is 1:1-50, and the mass ratio of saturated chain carboxylic acid to photocatalyst is 10-100:1.

[0011] Taking ruthenium as the photocatalyst metal, titanium dioxide as the semiconductor, and ultraviolet LED (wavelength: 365nm) as the external light source as an example, the reaction equation is as follows:

[0012]

[0013] Furthermore, the saturated chain carboxylic acid contains 4-12 carbon atoms.

[0014] Furthermore, the saturated chain carboxylic acid is at least one of butyric acid, valeric acid, isovaleric acid, hexanoic acid, heptanoic acid, octanoic acid, decanoic acid, lauric acid, and levulinic acid.

[0015] Furthermore, the photocatalyst is a metal-supported semiconductor catalyst;

[0016] The metal is at least one of ruthenium (Ru), platinum (Pt), rhodium (Rh), palladium (Pd), copper (Cu), silver (Ag), and gold (Au); the semiconductor is at least one of titanium dioxide, cerium dioxide, tungsten trioxide, and tantalum pentoxide; and the metal loading is 0.1%-10% of the semiconductor mass.

[0017] Preferably, the best metal is Ru or Pt; the best semiconductor is TiO2 (with a P25 phase configuration), and the best metal loading is 0.2%-5% of the semiconductor mass.

[0018] Furthermore, the solvent is one or more selected from water, ethyl acetate, acetonitrile, tetrahydrofuran, toluene, dimethyl sulfoxide, cyclohexane, and 1,4-dioxane.

[0019] Furthermore, the mass ratio of the saturated chain carboxylic acid to the solvent is 1:1-20; the mass ratio of the saturated chain carboxylic acid to the photocatalyst is 5-50:1.

[0020] Furthermore, the inert gas is one or both of nitrogen and argon.

[0021] Furthermore, the decarboxylation coupling reaction is carried out at a temperature of 15-35°C for 2-4 hours.

[0022] Furthermore, the external light source is one or both of ultraviolet LED (wavelength: 365nm, 10-60W) and xenon lamp (150-300W).

[0023] The beneficial effects of this invention are:

[0024] 1. This invention develops a photocatalytic decarboxylation coupling method for saturated chain carboxylic acids. The reaction is carried out under an inert atmosphere and does not consume hydrogen, overcoming the disadvantage of traditional decarboxylation reactions that require a large amount of hydrogen, resulting in low energy consumption.

[0025] 2. This invention utilizes a low-cost Ru / TiO2 catalyst, resulting in a short reaction time, high reaction rate, and high reaction selectivity. After the reaction, product separation is simple, the solid catalyst is easily recyclable, and the entire reaction process is green and environmentally friendly. This invention provides a new approach for carboxylic acid cross-coupling reactions and the production of higher alkanes from biomass fatty acids. Attached Figure Description

[0026] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a GC diagram of the coupling product of Embodiment 20 of the present invention;

[0028] Figure 2 This is a GC diagram of the coupling product of Embodiment 24 of the present invention. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] Unless otherwise specified, the experimental methods described in the following examples are conventional methods. The reagents or instruments involved in this invention that do not specify the manufacturer are all commercially available products that can be purchased from the market.

[0031] In the following embodiments of the present invention, the Ru / TiO2 catalyst was prepared by impregnation and calcination method. First, 500 mg of P25 powder and 10.3 mg of RuCl3 were dispersed in 20 mL of ultrapure water and stirred for 12 h. Then, the water was evaporated under vigorous stirring at 105 °C. Finally, the solution was purified by tubular furnace at a flow rate of 30 mL / min. -1 airflow at 5℃·min -1 The heating rate was 350℃ for calcination for 4 hours, at 60 mL / min. -1 In a 10 vol.% H2 (N2 is the equilibrium gas) gas stream at 5 °C·min -1 The heating rate was 400℃ for 4 hours to reduce the metal oxide.

[0032] In this invention, quantitative analysis of the yield was performed using a gas chromatograph (Agilent 7890B) with an Agilent HP-5 capillary column (30m*32μm*0.25μm). Qualitative analysis was performed using a Thermo Scientific TRACE 1310 gas chromatograph-mass spectrometer with a Thermos Scientific TG-MS capillary column (30m*32μm*0.25μm).

[0033] Example 1:

[0034] 300.0 mg of octanoic acid, 10.0 mg of Ru / TiO2 catalyst with a Ru content of 1.0 wt.%, and 1.0 mL of acetonitrile were added to a photocatalytic reactor. The reactor atmosphere was replaced by continuous vacuuming and nitrogen purging five times. The reactor was irradiated at 25 °C with a xenon lamp (300 W) for 10 h. After the decarboxylation coupling reaction was completed, the volume was adjusted with acetonitrile solvent. The product was analyzed by GC, and the molar yield of the coupling product was calculated to be 65%.

[0035] Example 2:

[0036] 14.4 mg of octanoic acid, 5.0 mg of Ru / TiO2 catalyst with a Ru content of 1.0 wt.% and 1.0 mL of acetonitrile were added to a photocatalytic reactor. The reactor atmosphere was replaced by continuous vacuuming and nitrogen purging five times. The reactor was irradiated at 25 °C with a 365 nm LED (10 W) for 2 h. After the decarboxylation coupling reaction was completed, the volume was adjusted with acetonitrile solvent. The product was analyzed by GC, and the molar yield of the coupling product was calculated to be 58%.

[0037] Example 3:

[0038] 14.4 mg of octanoic acid, 5.0 mg of Ru / TiO2 catalyst with a Ru content of 1.0 wt.% and 1.0 mL of acetonitrile were added to a photocatalytic reactor. The reactor atmosphere was replaced by continuous vacuuming and nitrogen purging five times. The reactor was irradiated at 25 °C with a 365 nm LED (10 W) for 3 h. After the decarboxylation coupling reaction was completed, the volume was adjusted with acetonitrile solvent. The product was analyzed by GC, and the molar yield of the coupling product was calculated to be 83%.

[0039] Example 4:

[0040] 14.4 mg of octanoic acid, 5.0 mg of Ru / TiO2 catalyst with a Ru content of 1.0 wt.%, and 1.0 mL of acetonitrile were added to a photocatalytic reactor. The reactor atmosphere was replaced by continuous vacuuming and nitrogen purging five times. The reactor was irradiated at 30 °C with a 365 nm LED (10 W) for 4 h. After the decarboxylation coupling reaction was completed, the volume was adjusted with acetonitrile solvent. The product was analyzed by GC, and the molar yield of the coupling product was calculated to be 83%.

[0041] Example 5:

[0042] 14.4 mg of octanoic acid, 5.0 mg of Ru / TiO2 catalyst with a Ru content of 1.0 wt.% and 1.0 mL of acetonitrile were added to a photocatalytic reactor. The reactor atmosphere was replaced by continuous vacuuming and nitrogen purging five times. The reactor was irradiated at 26 °C with a 365 nm LED (10 W) for 10 h. After the decarboxylation coupling reaction was completed, the volume was adjusted with acetonitrile solvent. The product was analyzed by GC, and the molar yield of the coupling product was calculated to be 83%.

[0043] Example 6:

[0044] 14.4 mg of octanoic acid, 5.0 mg of Ru / TiO2 catalyst with a Ru content of 0.1 wt.% and 1.0 mL of acetonitrile were added to a photocatalytic reactor. The reactor atmosphere was replaced by continuous vacuuming and nitrogen purging five times. The reactor was irradiated at 25 °C with a 365 nm LED (10 W) for 3 h. After the decarboxylation coupling reaction was completed, the volume was adjusted with acetonitrile solvent. The product was analyzed by GC, and the molar yield of the coupling product was calculated to be 62%.

[0045] Example 7:

[0046] 14.4 mg of octanoic acid, 5.0 mg of Ru / TiO2 catalyst with a Ru content of 0.2 wt.% and 1.0 mL of acetonitrile were added to a photocatalytic reactor. The reactor atmosphere was replaced by continuous vacuuming and nitrogen purging five times. The reactor was irradiated at 25 °C with a 365 nm LED (10 W) for 3 h. After the decarboxylation coupling reaction was completed, the volume was adjusted with acetonitrile solvent. The product was analyzed by GC, and the molar yield of the coupling product was calculated to be 61%.

[0047] Example 8:

[0048] 14.4 mg of octanoic acid, 5.0 mg of Ru / TiO2 catalyst with a Ru content of 0.5 wt.% and 1.0 mL of acetonitrile were added to a photocatalytic reactor. The reactor atmosphere was replaced by continuous vacuuming and nitrogen purging five times. The reactor was irradiated at 25 °C with a 365 nm LED (10 W) for 3 h. After the decarboxylation coupling reaction was completed, the volume was adjusted with acetonitrile solvent. The product was analyzed by GC, and the molar yield of the coupling product was calculated to be 71%.

[0049] Example 9:

[0050] 14.4 mg of octanoic acid, 5.0 mg of Ru / TiO2 catalyst with a Ru content of 2.0 wt.% and 1.0 mL of acetonitrile were added to a photocatalytic reactor. The reactor atmosphere was replaced by continuous vacuuming and nitrogen purging five times. The reactor was irradiated at 25 °C with a 365 nm LED (10 W) for 3 h. After the decarboxylation coupling reaction was completed, the volume was adjusted with acetonitrile solvent. The product was analyzed by GC, and the molar yield of the coupling product was calculated to be 83%.

[0051] Example 10:

[0052] 14.4 mg of octanoic acid, 5.0 mg of Ru / TiO2 catalyst with a Ru content of 5.0 wt.% and 1.0 mL of acetonitrile were added to a photocatalytic reactor. The reactor atmosphere was replaced by continuous vacuuming and nitrogen purging five times. The reactor was irradiated at 25 °C with a 365 nm LED (10 W) for 3 h. After the decarboxylation coupling reaction was completed, the volume was adjusted with acetonitrile solvent. The product was analyzed by GC, and the molar yield of the coupling product was calculated to be 83%.

[0053] Example 11:

[0054] 144.4 mg of octanoic acid, 10.0 mg of Ru / TiO2 catalyst with a Ru content of 1.0 wt.% and 1.0 mL of acetonitrile were added to a photocatalytic reactor. The reactor atmosphere was replaced by continuous vacuuming and nitrogen purging five times. The reactor was irradiated at 25 °C with a 365 nm LED (10 W) for 3 h. After the decarboxylation coupling reaction was completed, the volume was adjusted with acetonitrile solvent. The product was analyzed by GC, and the molar yield of the coupling product was calculated to be 80%.

[0055] Example 12:

[0056] 14.4 mg of octanoic acid, 5.0 mg of Ru / TiO2 catalyst with a Ru content of 1.0 wt.% and 1.0 mL of acetonitrile were added to a photocatalytic reactor. The reactor atmosphere was replaced by continuous vacuuming and purging with argon five times. The reactor was irradiated at 25 °C with a 365 nm LED (10 W) for 3 h. After the decarboxylation coupling reaction was completed, the volume was adjusted with acetonitrile solvent. The product was analyzed by GC, and the molar yield of the coupling product was calculated to be 82%.

[0057] Example 13:

[0058] 14.4 mg of octanoic acid, 5.0 mg of Ru / TiO2 catalyst with a Ru content of 1.0 wt.% and 1.0 mL of acetonitrile were added to a photocatalytic reactor. The reactor atmosphere was replaced by continuous vacuuming and hydrogen purging five times. The reactor was irradiated at 25 °C with a 365 nm LED (10 W) for 3 h. After the decarboxylation coupling reaction was completed, the volume was adjusted with acetonitrile solvent. The product was analyzed by GC, and the molar yield of the coupling product was calculated to be 78%.

[0059] Example 14:

[0060] 300.0 mg of octanoic acid, 10.0 mg of Ru / TiO2 catalyst with a Ru content of 1.0 wt.%, and 1.0 mL of acetonitrile were added to a photocatalytic reactor. The reactor atmosphere was replaced by continuous vacuuming and nitrogen purging five times. The reactor was irradiated at 25 °C with a 365 nm LED (50 W) for 10 h. After the decarboxylation coupling reaction was completed, the volume was adjusted with acetonitrile solvent. The product was analyzed by GC, and the molar yield of the coupling product was calculated to be 76%.

[0061] Example 15:

[0062] 14.4 mg of octanoic acid, 5.0 mg of Ru / TiO2 catalyst with a Ru content of 1.0 wt.% and 1.0 mL of tetrahydrofuran were added to a photocatalytic reactor. The reactor atmosphere was replaced by continuous vacuuming and nitrogen purging five times. The reactor was irradiated at 25 °C with a 365 nm LED (10 W) for 3 h. After the decarboxylation coupling reaction was completed, the volume was adjusted with tetrahydrofuran solvent. The product was analyzed by GC, and the molar yield of the coupling product was calculated to be 48%.

[0063] Example 16:

[0064] 300.0 mg of octanoic acid, 10.0 mg of Ru / TiO2 catalyst with a Ru content of 1.0 wt.%, and 1.0 mL of acetonitrile were added to a photocatalytic reactor. The reactor atmosphere was replaced by continuous vacuuming and nitrogen purging five times. The reactor was irradiated at 25 °C with a xenon lamp (150 W) for 10 h. After the decarboxylation coupling reaction was completed, the volume was adjusted with acetonitrile solvent. The product was analyzed by GC, and the molar yield of the coupling product was calculated to be 67%.

[0065] Example 17:

[0066] 14.4 mg of octanoic acid, 5.0 mg of Ru / TiO2 catalyst with a Ru content of 1.0 wt.% and 1.0 mL of cyclohexane were added to a photocatalytic reactor. The reactor atmosphere was replaced by continuous vacuuming and nitrogen purging five times. The reactor was irradiated at 25 °C with a 365 nm LED (10 W) for 3 h. After the decarboxylation coupling reaction was completed, the volume was adjusted with cyclohexane solvent. The product was analyzed by GC, and the molar yield of the coupling product was calculated to be 80%.

[0067] Example 18:

[0068] 14.4 mg of octanoic acid, 5.0 mg of Ru / TiO2 catalyst with a Ru content of 1.0 wt.% and 1.0 mL of toluene were added to a photocatalytic reactor. The reactor atmosphere was replaced by continuous vacuuming and nitrogen purging five times. The reactor was irradiated at 25 °C with a 365 nm LED (10 W) for 3 h. After the decarboxylation coupling reaction was completed, the volume was adjusted with toluene solvent. The product was analyzed by GC, and the molar yield of the coupling product was calculated to be 72%.

[0069] Example 19:

[0070] 11.6 mg of hexanoic acid, 5.0 mg of Ru / TiO2 catalyst with a Ru content of 1.0 wt.%, and 1.0 mL of acetonitrile were added to a photocatalytic reactor. The reactor atmosphere was replaced by continuous vacuuming and nitrogen purging five times. The reactor was irradiated at 25 °C with a 365 nm LED (10 W) for 3 h. After the decarboxylation coupling reaction was completed, the volume was adjusted with acetonitrile solvent. The product was analyzed by GC, and the molar yield of the coupling product was calculated to be 62%.

[0071] Example 20:

[0072] 14.4 mg of n-octanoic acid, 5.0 mg of Ru / TiO2 catalyst with a Ru content of 1.0 wt.%, and 1.0 mL of acetonitrile were added to a photocatalytic reactor. The reactor atmosphere was replaced by continuous vacuuming and nitrogen purging five times. The reactor was irradiated at 25 °C with a 365 nm LED (30 W) for 3 h. After the decarboxylation coupling reaction was completed, the volume was adjusted with acetonitrile solvent. The product was analyzed by GC, and the GC chromatogram of the coupling product is shown in [Figure missing]. Figure 1 The molar yield of the coupling product was calculated to be 90%.

[0073] Example 21:

[0074] 17.2 mg of ortho-capric acid, 5.0 mg of Ru / TiO2 catalyst with a Ru content of 1.0 wt.%, and 1.0 mL of acetonitrile were added to a photocatalytic reactor. The reactor atmosphere was replaced by continuous vacuuming and nitrogen purging five times. The reactor was irradiated at 25 °C with a 365 nm LED (10 W) for 3 h. After the decarboxylation coupling reaction was completed, the volume was adjusted with acetonitrile solvent. The product was analyzed by GC, and the molar yield of the coupling product was calculated to be 79%.

[0075] Example 22:

[0076] 20.0 mg lauric acid, 5.0 mg Ru / TiO2 catalyst with a Ru content of 1.0 wt.%, and 1.0 mL acetonitrile were added to a photocatalytic reactor. The reactor atmosphere was replaced by continuous vacuuming and nitrogen purging five times. The reactor was irradiated at 25 °C with a 365 nm LED (10 W) for 3 h. After the decarboxylation coupling reaction was completed, the volume was adjusted with acetonitrile solvent. The product was analyzed by GC, and the molar yield of the coupling product was calculated to be 65%.

[0077] Example 23:

[0078] 11.6 mg lauric acid, 5.0 mg Ru / TiO2 catalyst with a Ru content of 1.0 wt.%, and 1.0 mL acetonitrile were added to a photocatalytic reactor. The reactor atmosphere was replaced by continuous vacuuming and nitrogen purging five times. The reactor was irradiated at 25 °C with a 365 nm LED (10 W) for 3 h. After the decarboxylation coupling reaction was completed, the volume was adjusted with acetonitrile solvent. The product was analyzed by GC, and the molar yield of the coupling product was calculated to be 75%.

[0079] Example 24:

[0080] 13.0 mg of n-heptanoic acid, 5.0 mg of Ru / TiO2 catalyst with a Ru content of 1.0 wt.%, and 1.0 mL of acetonitrile were added to a photocatalytic reactor. The reactor atmosphere was replaced by continuous vacuuming and nitrogen purging five times. The reactor was irradiated at 25 °C with a 365 nm LED (10 W) for 3 h. After the decarboxylation coupling reaction was completed, the volume was adjusted with acetonitrile solvent. The product was analyzed by GC, and the GC chromatogram of the coupling product is shown in [Figure missing]. Figure 2 The molar yield of the coupling product was calculated to be 85%.

[0081] Example 25:

[0082] 14.4 mg of octanoic acid, 5.0 mg of Ru / TiO2 catalyst with a Ru content of 1.0 wt.% and 1.0 mL of acetonitrile were added to a photocatalytic reactor. The reactor atmosphere was replaced by continuous vacuuming and nitrogen purging five times. The reactor was irradiated at 25 °C with a 365 nm LED (60 W) for 3 h. After the decarboxylation coupling reaction was completed, the volume was adjusted with acetonitrile solvent. The product was analyzed by GC, and the molar yield of the coupling product was calculated to be 80%.

[0083] The preferred embodiments of this patent have been described in detail above. However, this patent is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, other variations or modifications can be made. It is neither necessary nor possible to exhaustively list all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the protection scope of the claims of this invention.

Claims

1. A method for photocatalytic decarboxylation coupling of saturated chain carboxylic acids, characterized by, Comprising the following steps: Saturated chain carboxylic acid, photocatalyst and solvent are added into a photocatalytic reactor, and the atmosphere in the reactor is replaced with inert gas and sealed after stirring, and decarboxylation coupling reaction occurs at 10-40℃ under the irradiation of an external light source, and the reaction time is 1-10 h; The mass ratio of saturated chain carboxylic acid to solvent is 1:1-50, and the mass ratio of saturated chain carboxylic acid to photocatalyst is 10-100:1; The saturated chain carboxylic acid is at least one of n-pentanoic acid, iso-valeric acid, n-hexanoic acid, n-heptanoic acid, n-octanoic acid, n-decanoic acid, lauric acid, and acetylpropionic acid; The photocatalyst is a metal-supported semiconductor catalyst; wherein the metal is ruthenium; the semiconductor is titanium dioxide; and the metal loading is 0.1%-10% of the mass of the semiconductor; The solvent is one or more of ethyl acetate, acetonitrile, tetrahydrofuran, toluene, dimethyl sulfoxide, cyclohexane, and 1,4-dioxane.

2. The method of claim 1, wherein: The mass ratio of saturated chain carboxylic acid to solvent is 1:1-20, and the mass ratio of saturated chain carboxylic acid to photocatalyst is 5-50:

1.

3. The method of claim 1, wherein: The inert gas is one or both of nitrogen and argon.

4. The method of claim 1, wherein: The reaction temperature of the decarboxylation coupling reaction is 15-35℃, and the reaction time is 2-4 h.

5. The method of claim 1, wherein: The external light source is one or both of ultraviolet LED and xenon lamp.

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