Photocatalyst as well as preparation method and application thereof

Abstract

The invention discloses a photocatalyst as well as a preparation method and application thereof, and relates to the field of catalysts. The photocatalyst is prepared by adopting a hydrothermal-calcining-photodeposition method and comprises nanoflowers formed by indium zinc sulfide ultrathin nanosheets and iridium metal atoms loaded on the surfaces of the nanoflowers. The catalyst can be applied to a free radical type photocatalytic alkylation reaction, especially an indole C-2 alkylation reaction, and the yield and selectivity of the reaction are greatly improved. The photocatalyst also has the advantages of small addition amount of noble metal, high stability and capability of catalyzing reaction under visible light, and has a wide application prospect in the field of organic synthesis.

Description

Technical Field

[0001] The present invention relates to the field of catalysts, and in particular to a photocatalyst and a preparation method and application thereof. Background Art

[0002] In the field of fine chemical synthesis, alkylation reactions are used to prepare intermediates and final products such as various medicines, pesticides, fragrances, dyes, etc. By precisely controlling the alkylation reaction, compounds with specific structures and functionalities can be synthesized to meet specific application requirements. The development of alkylation technology not only helps to improve the efficiency of chemical production, but also helps to reduce environmental impact. Alkylation processes with good selectivity and few by-products can reduce the generation of waste and promote the effective utilization and recycling of resources.

[0003] Traditional alkylation reactions require extremely high reaction temperatures, consume a lot of energy, and are not very selective for alkyl substitution sites. Photocatalytic alkylation reactions can be carried out at room temperature, are clean and energy-efficient, have high atomic utilization, and can have good substitution site selectivity depending on the choice of catalyst. Due to its mild conditions, it can also be compatible with a variety of substitution-directing functional groups.

[0004] The main types of existing alkylation photocatalysts include metal oxides, composite metal oxides and metal complexes. Among them, metal oxides such as TiO2, ZnO and SiO2 have good chemical stability and catalytic performance, but their band gap is narrow, usually only absorb ultraviolet light, and have low light energy efficiency; composite metal oxides such as TiO2 and Nb2O5 can broaden the light response range and enhance the catalytic activity under visible light by adjusting the composite ratio, but the composite process is complicated and the cost is relatively high; metal complexes such as Ru, Pd, Rh and other metal complexes have high catalytic activity and good selectivity under visible light, but the price is generally more expensive and the stability is insufficient, which limits their large-scale application.

[0005] Nanomaterials have a large specific surface area and special light absorption properties, making them very suitable as catalysts in photochemical reactions. The Chinese invention patent with publication number CN113145152A discloses a visible light catalytic one-pot multi-directional chemical selective N-alkylation method, in which the photocatalyst used is a MXene (transition metal carbon / nitride two-dimensional nanosheet) material dispersed with 3% metal nanoparticles, and the metal nanoparticles can be platinum, iridium, etc. The catalyst to which this invention belongs shows excellent catalytic activity and selectivity in the presence of alkaline additives, but the catalyst material has more precious metals added and is more complicated to prepare. Alkaline conditions are required in specific applications, and it only solves the N-alkylation problem, which is not very helpful for the selective alkylation problem on aromatic carbon. Summary of the invention

[0006] In view of the shortcomings of the prior art, the present invention provides a photocatalyst and a preparation method and application thereof. The photocatalyst comprises indium zinc sulfide nanoflowers and iridium metal atoms loaded on their surfaces, which have high stability, good catalytic performance, a wide light response range, and a low content of precious metals, and can effectively improve the yield and selectivity of free radical photocatalytic alkylation reactions on some unsaturated carbons.

[0007] One of the purposes of the present invention is to provide a photocatalyst, comprising nanoflowers composed of ultra-thin nanosheets of indium zinc sulfide (ZnIn2S4) and iridium metal atoms loaded on the surface thereof.

[0008] Another object of the present invention is to provide a method for preparing the above-mentioned photocatalyst, comprising the following steps:

[0009] (1) weighing a zinc salt, an indium salt and a sulfur source, stirring them in a solvent until they are completely dissolved, then performing a hydrothermal reaction, cooling and filtering, washing and drying the filter residue to obtain a catalyst carrier;

[0010] (2) The catalyst carrier is calcined under an inert atmosphere;

[0011] (3) The calcined catalyst carrier and the iridium ion reagent are mixed uniformly in water, degassed, and subjected to photodeposition reduction, centrifuged, and the obtained precipitate is dried to obtain the photocatalyst.

[0012] The last object of the present invention is to provide the use of the above-mentioned photocatalyst in a free radical type photocatalytic alkylation reaction.

[0013] The technical solution of the present invention has the following beneficial effects:

[0014] 1. The photocatalyst of the present invention uses nanoflowers to support iridium metal atoms, which requires a small amount of precious metal, has a large contact area and a good catalytic effect. It only needs to add 0.05-0.1 mol% of a catalyst with an iridium metal atom loading of 0.3-0.7wt%, and the yield of the target reaction can reach a maximum of more than 90%. The amount of transition metal atoms added is 1-3 orders of magnitude lower than that of the prior art, and the cost is low and the efficiency is high.

[0015] 2. The photocatalyst of the present invention uses nanoflowers to support iridium metal atoms, which improves the dispersibility of iridium atoms, shifts the maximum absorption wavelength into the visible light region, improves the light response range, and reduces the energy consumption of the photocatalytic reaction.

[0016] 3. In the preparation method of the photocatalyst of the present invention, the catalyst carrier is calcined at a high temperature of 200 to 300°C, which makes the prepared photocatalyst highly stable, does not produce harmful substances when used in exothermic reactions, and is environmentally friendly and durable.

[0017] 4. The photocatalyst of the present invention is applied to the photocatalytic alkylation reaction of indole compounds, which can effectively solve the problem of C-2 selectivity and reduce the generation of C-3 alkylation products in the absence of a guiding group at the N-1 site; the C-2 alkylation yield can reach up to 92%. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a scanning electron microscope image of the alkylated photocatalyst particles described in Example 1 of the present invention.

[0019] Figure 2 This is a transmission electron microscope image of the alkylated photocatalyst particles described in Example 1 of the present invention, wherein the red circle represents iridium metal atoms.

[0020] Figure 3 It is the X-ray diffraction pattern of the catalyst carrier and alkylated photocatalyst particles described in Example 1 of the present invention, as well as the standard diffraction data of ZnIn2S4.

[0021] Figure 4 This is a test diagram of the alkylation photocatalytic cycle of Example 3 of the present invention, wherein each cycle is 8 hours. DETAILED DESCRIPTION

[0022] In order to make the technical means, creative features, objectives and effects of the present invention easy to understand, the present invention is further described below in conjunction with embodiments and drawings. Obviously, the described embodiments are only part of the implementation methods of the present invention, and are an explanation of the technical solution of the present invention rather than a limitation.

[0023] The invention provides a photocatalyst, comprising nanoflowers composed of ultra-thin nanosheets of indium zinc sulfide (ZnIn2S4) and iridium metal atoms loaded on the surface thereof.

[0024] Furthermore, the diameter of the nanoflower is 7 to 10 μm.

[0025] Furthermore, the loading amount of the iridium metal atoms is 0.3-0.7 wt %. Preferably, the loading amount of the iridium metal atoms is 0.5 wt %.

[0026] The present invention also provides a method for preparing the above-mentioned photocatalyst, comprising the following steps:

[0027] (1) weighing a zinc salt, an indium salt and a sulfur source, stirring them in a solvent until they are completely dissolved, then performing a hydrothermal reaction, cooling and filtering, washing and drying the filter residue to obtain a catalyst carrier;

[0028] (2) The catalyst carrier is calcined under an inert atmosphere;

[0029] (3) The calcined catalyst carrier and the iridium ion reagent are mixed uniformly in water, degassed, and subjected to photodeposition reduction, centrifuged, and the obtained precipitate is dried to obtain the photocatalyst.

[0030] Furthermore, based on zinc, indium and sulfur elements, the molar ratio of the zinc salt, indium salt and sulfur source is 1:1.5 to 2:4 to 5. Preferably, the molar ratio of the zinc salt, indium salt and sulfur source is 1:2:4.5.

[0031] Thioacetamide is one of the commonly used sulfurizing agents in the laboratory. It has moderate reactivity and is milder than strong sulfurizing agents such as Na2S. It is easy to control the reaction rate and obtain nanostructures of suitable size. The ratio of the substrate is based on the molar ratio of indium zinc sulfide (ZnIn2S4), that is, 1:2:4. On this basis, a slightly excessive amount of sulfur is used to ensure complete reaction of the metal element; optionally, the amount of indium used can be slightly reduced to save costs without destroying the overall morphology of the catalyst carrier.

[0032] Furthermore, the zinc salt is preferably zinc chloride, the indium salt is preferably indium chloride tetrahydrate, the sulfur source is preferably thioacetamide, and the solvent is ethylene glycol and / or water.

[0033] Furthermore, the hydrothermal reaction is carried out at 120-160°C for 10-12h; the filter residue is washed and dried with deionized water and anhydrous ethanol, and then dried at 60°C for 8-12h. Preferably, the hydrothermal reaction is carried out in a polytetrafluoroethylene-lined container.

[0034] Furthermore, the calcination treatment condition is calcination at 200-300° C. for 6-8 hours; and the inert atmosphere is a nitrogen atmosphere.

[0035] Alkylation is generally an exothermic reaction, and its reaction heat release is generally 100-150 kJ / mol. The catalyst used cannot produce toxic and harmful substances at higher temperatures. For this reason, the catalyst carrier needs to be calcined to remove decomposable impurities and harmful substances, and to improve the mechanical properties and adsorption activity of the catalyst carrier. Since sulfides are easily oxidized at high temperatures, atmospheric pressure nitrogen needs to be used as a protective gas to avoid damage to the structure of the catalyst carrier nanoflowers.

[0036] Furthermore, the iridium ion reagent is iridium chloride or sodium hexachloroiridate; the photodeposition reduction is carried out for 1 to 3 hours. Specifically, the iridium chloride is iridium trichloride and its hydrate, and the sodium hexachloroiridate is sodium hexachloroiridate (III) and its hydrate.

[0037] The iridium ion reagent selects a trivalent iridium compound with weaker oxidizing property among relatively stable trivalent and tetravalent iridium compounds, which is conducive to its photo-deposition reduction and has less effect on the sulfide catalyst carrier with certain reducing property.

[0038] The photoreduction is to reduce the high-valent iridium in the iridium ion reagent into iridium atoms and deposit them evenly on the nanoflowers. To this end, it is necessary to remove oxidizing gases such as oxygen in the reaction system. The degassing method can be: freeze the solution into a solid with liquid nitrogen, evacuate the container for a period of time, then introduce an inert gas, and finally heat the solid to melt into a solution.

[0039] Finally, the present invention provides the use of the above-mentioned photocatalyst in a free radical photocatalytic alkylation reaction, wherein the added amount of the photocatalyst is 0.05-0.1 mol%; preferably, the added amount of the photocatalyst is 0.08 mol%.

[0040] Specifically, the present invention provides the use of the above-mentioned photocatalyst in the photocatalytic alkylation reaction of indole compounds, especially in the selective alkylation reaction of indole C-2:

[0041]

[0042] Wherein R1 is selected from hydrogen or methyl, R2 is selected from hydrogen, alkyl or alkoxy, R3 is selected from hydrogen, ester group or diethoxyphosphonyl group, and R4 is selected from methyl, ethyl or phenyl. The conditions for making the C-2 alkylation yield higher are: the substituent of the diazo compound is hydrogen or an electron-withdrawing group, and the substituted alkyl on the indole benzene ring is hydrogen or an electron-donating group at the 4th position.

[0043] Due to the strong nucleophilicity of the C-3 position of indole, the general electrophilic substitution alkylation method has a high selectivity for C-3 alkylation products; in order to obtain C-2 alkylation products, it is necessary to pre-install guiding groups at the N-1 and C-3 positions. The free radical substitution method can selectively carry out C-2 alkylation of indole without a guiding group, because the benzylic free radical intermediate formed during the C-2 substitution process has higher stability.

[0044] The present invention is described in detail below with reference to the examples. The experimental methods are conventional methods unless otherwise specified; the reagents and materials are commercially available unless otherwise specified.

[0045] Preparation Example 1

[0046] (1) Weigh 4 mmol of zinc chloride, 8 mmol of indium chloride tetrahydrate and 18 mmol of thioacetamide, add them to a mixed solution of 120 mL of ethylene glycol and 120 mL of deionized water, stir for 20 min, transfer to a reactor lined with polytetrafluoroethylene, and perform hydrothermal reaction at 140° C. for 10 h. After the reaction solution is cooled to room temperature, filter and collect the precipitate therein, rinse with deionized water 3 times, rinse with anhydrous ethanol 3 times, and then dry the precipitate at 60° C. for 8 h to obtain a catalyst carrier.

[0047] (4) placing the catalyst support in a calcination chamber, continuously introducing nitrogen and maintaining the pressure in the chamber consistent with the external atmospheric pressure, and calcining the catalyst support at 300° C. for 6 h;

[0048] (5) The calcined catalyst carrier (4 mmol) was dispersed in deionized water in a quartz photoreactor, and 22.1 mg of sodium hexachloroiridate (III) hydrate (Na3IrCl6·H2O) was added and stirred to dissolve. After degassing, photoreduction was performed for 2 h, and centrifuged. The resulting precipitate was naturally dried in an oven to obtain photocatalyst 1, in which the iridium nanoparticle loading was 0.5 wt%.

[0049] The photocatalyst (0.5 wt % Ir-ZnIn2S4) obtained in Example 1 was analyzed using a scanning electron microscope (SEM) to obtain a scanning electron microscope photograph, as shown in FIG. Figure 1 As shown, the indium zinc sulfide ultrathin nanosheet structure and the spherical nanoflowers formed by its stacking can be seen.

[0050] The photocatalyst (0.5 wt% Ir-ZnIn2S4) obtained in Example 1 was analyzed using a transmission electron microscope (TEM) to obtain a transmission electron microscope photograph, as shown in FIG. Figure 2 As shown, at a higher magnification than the SEM photo, evenly dispersed iridium metal atoms can be seen on the indium zinc sulfide ultra-thin nanosheet in the lower left part.

[0051] The catalyst carrier and alkylated photocatalyst particles obtained in Example 1 were subjected to X-ray powder diffraction test, and the results are as follows: Figure 3 As shown. It can be seen that the catalyst carrier and the alkylation catalyst particles both show the main diffraction peaks of indium zinc sulfide (ZnIn2S4), while 0.5% trace iridium has no significant effect on the crystal structure, indicating that the catalyst carrier maintains its structural properties after loading iridium metal atoms.

[0052] Preparation Example 2

[0053] The only difference between the preparation method of the photocatalyst in this example and that in Example 1 is that the raw material dosage of the catalyst carrier is 4 mmol of zinc chloride, 6 mmol of indium chloride tetrahydrate, and 16 mmol of thioacetamide, and photocatalyst 2 is prepared.

[0054] Preparation Example 3

[0055] The only difference between the preparation method of the photocatalyst in this embodiment and that in the preparation embodiment 1 is that the hydrothermal reaction conditions are 120° C. for 12 h to prepare the photocatalyst 3.

[0056] Preparation Example 4

[0057] The only difference between the preparation method of the photocatalyst in this embodiment and that in the preparation embodiment 1 is that the hydrothermal reaction conditions are 160° C. for 10 h to prepare the photocatalyst 4.

[0058] Preparation Example 5

[0059] The only difference between the preparation method of the photocatalyst in this embodiment and that in the preparation embodiment 1 is that the calcination condition is calcination at 200° C. for 8 h to prepare the photocatalyst 5.

[0060] Preparation Example 6

[0061] The only difference between the preparation method of the photocatalyst in this example and that in Example 1 is that the amount of sodium hexachloroiridate (III) hydrate added is 31.0 mg, and photocatalyst 6 is prepared, in which the iridium metal atom loading is 0.7 wt%.

[0062] Preparation Example 7

[0063] The only difference between the preparation method of the photocatalyst in this example and that in Example 1 is that the amount of sodium hexachloroiridate (III) hydrate added is 13.3 mg, and photocatalyst 7 is prepared, in which the iridium metal atom loading is 0.3 wt%.

[0064] The alkylation photocatalyst particles obtained in this example were subjected to an alkylation photocatalytic cycle test, and four cycles were tested with one cycle of 8 hours. The results are as follows: Figure 4 It can be seen that at the minimum catalyst addition amount within the scope of the present invention, the catalyst particles can still maintain their high catalytic activity in continuous catalytic experiments, indicating that the alkylation photocatalyst particles of the present invention have strong stability and are easy to recycle.

[0065] The photocatalysts obtained in the preparation examples of the present invention are used below to implement their application in the photocatalytic indole C-2 selective alkylation reaction.

[0066] Application Example 1

[0067] This example uses the photocatalyst 1 obtained in Preparation Example 1 and applies it to the following indole C-2 alkylation reaction:

[0068]

[0069] The reaction was carried out in a specially constructed photoreactor consisting of a cooling block and LED board connected to a constant current (0.7A) power supply. The experimental procedure was as follows:

[0070] 4mmol (4equiv) N-methylindole, 1mmol (1equiv) ethyl diazoacetate and 0.8μmol (0.08mol%, based on 1equiv reaction, the same below) of the photocatalyst 1 obtained in Example 1 were dispersed in a mixed solvent of 10mL methanol and 1mL water (volume ratio 10:1), stirred continuously and uniformly, and after degassing for 30min, a photocatalytic alkylation reaction was carried out under a 3W visible light LED lamp. During the reaction, the reaction temperature was controlled at 28°C by a cooling block. The product was analyzed by gas chromatography (GC) using argon as the carrier gas, and the target molecule yield was calculated to be 92%.

[0071] Application Example 2

[0072] The only difference between this embodiment and Application Example 1 is that the added amount of the photocatalyst 1 is 1.0 μmol (0.1 mol%), and the target molecule yield is 89%.

[0073] Application Example 3

[0074] The only difference between this embodiment and Application Example 1 is that the added amount of the photocatalyst 1 is 0.5 μmol (0.05 mol%), and the target molecule yield is 79%.

[0075] Application Example 4

[0076] The only difference between this embodiment and Application Example 1 is that the amounts of methanol and water used are 10.0 mL and 0.2 mL respectively (volume ratio 50:1), and the yield of the target molecule is 75%.

[0077] Application Example 5

[0078] The only difference between this embodiment and Application Example 1 is that the amounts of methanol and water used are 7.0 mL and 3.5 mL respectively (volume ratio 2:1), and the yield of the target molecule is 77%.

[0079] Application Example 6

[0080] The only difference between this embodiment and Application Example 1 is that the photocatalyst 2 obtained in Preparation Example 2 is used for the reaction, and the yield of the target molecule is 90%.

[0081] Application Example 7

[0082] The only difference between this embodiment and Application Example 1 is that the photocatalyst 3 obtained in Preparation Example 3 is used for the reaction, and the yield of the target molecule is 87%.

[0083] Application Example 8

[0084] The only difference between this embodiment and Application Example 1 is that the photocatalyst 4 obtained in Preparation Example 4 is used for the reaction, and the yield of the target molecule is 85%.

[0085] Application Example 9

[0086] The only difference between this embodiment and Application Example 1 is that the photocatalyst 5 obtained in Preparation Example 5 is used for the reaction, and the yield of the target molecule is 81%.

[0087] Application Example 10

[0088] The only difference between this embodiment and Application Example 1 is that the photocatalyst 6 obtained in Preparation Example 6 is used for the reaction, and the yield of the target molecule is 82%.

[0089] Application Example 11

[0090] The only difference between this embodiment and Application Example 1 is that the photocatalyst 7 obtained in Preparation Example 7 is used for the reaction, and the yield of the target molecule is 73%.

[0091] Application Example 12

[0092] The only difference between this embodiment and Application Example 1 is that the photocatalyst 1 used is calcined at 150° C. for 20 min before feeding, and the yield of the target molecule is 91%.

[0093] Application Example 13

[0094] The only difference between this example and Application Example 1 is that the reaction used is as follows, and the yield of the target molecule is 93%.

[0095]

[0096] Application Example 14

[0097] The only difference between this example and Application Example 1 is that the reaction used is as follows, and the yield of the target molecule is 74%.

[0098]

[0099] Application Comparative Example 1

[0100] The only difference between this embodiment and Application Example 1 is that no photocatalyst is added and the yield of the target molecule is 0.

[0101] Application Comparative Example 2

[0102] The only difference between this embodiment and Application Example 1 is that no LED illumination is performed and the yield of the target molecule is 0.

[0103] Application Comparative Example 3

[0104] The only difference between this embodiment and Application Example 1 is that the photocatalyst 1 is replaced by the catalyst carrier obtained in Preparation Example 1 with the same mass but without iridium metal atoms loaded thereon, and the target molecule yield is 0.

[0105] Table 1 Effect of alkylation conditions on the yield of target molecules in reaction 1:

[0106]

[0107] It can be seen from the experimental results summarized in Table 1 that catalyst and light are essential for the alkylation reaction to occur; under the conditions of the embodiments, the yield of the target molecule (3-substituted product) is above 75%, among which Application Example 1 is the best, with a target molecule yield of up to 92%.

[0108] Table 2 Effect of catalyst preparation method on target molecule yield of reaction 1:

[0109]

[0110] It can be seen from the experimental results summarized in Table 2 that the photocatalyst preparation conditions described in Preparation Example 1 are the optimal preparation conditions within the scope of the present invention. Prolonging the hydrothermal reaction time in the preparation process can improve the crystallinity and particle size of the material, which is conducive to the formation of a uniform microstructure, but too long a time may lead to agglomeration and affect the dispersibility; increasing the hydrothermal reaction temperature, accelerating the reaction rate, promoting morphology evolution, and facilitating the formation of nanostructures, but too high a temperature can easily cause grain coarsening and damage performance; suitable preparation conditions are conducive to the formation of highly active sites and achieve a balance between photocatalyst performance and stability.

[0111] The iridium nanoparticles in the photocatalyst of the present invention contribute greatly to the selectivity and yield of the indole C-2 alkylation reaction. W. Ciszewski et al. pointed out in their research that when the same reaction as in Application Example 1 was carried out under the same conditions using a rubidium complex catalyst, the yield of the target molecule was 68-76%, which is much lower than the optimal embodiment of the present invention.

[0112] Obviously, the above embodiments are merely examples for clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description, and the obvious changes or modifications derived therefrom should still be considered as the protection scope of the present invention.

Claims

1. A photocatalyst, characterized in that: It includes nanoflowers composed of ultra-thin indium zinc sulfide nanosheets and iridium metal atoms loaded on their surface.

2. The photocatalyst according to claim 1, characterized in that The diameter of the nanoflower is 7-10 μm.

3. The photocatalyst according to claim 1, characterized in that The loading amount of the iridium metal atoms on the surface of the nanoflower is 0.3-0.7 wt %; preferably, the loading amount of the iridium metal atoms on the surface of the nanoflower is 0.5 wt %.

4. A method for preparing a photocatalyst according to any one of claims 1 to 3, characterized in that: The steps include: Weighing zinc salt, indium salt and sulfur source, stirring in a solvent until completely dissolved, then performing a hydrothermal reaction, cooling and filtering, washing and drying the filter residue to obtain a catalyst carrier; The catalyst carrier is calcined in an inert atmosphere; The calcined catalyst carrier and the iridium ion reagent are mixed uniformly in water, degassed, and subjected to photodeposition reduction, centrifuged, and the obtained precipitate is dried to obtain the photocatalyst.

5. The method for preparing a photocatalyst according to claim 4, characterized in that: Calculated on the basis of zinc, indium and sulfur elements, the molar ratio of the zinc salt, indium salt and sulfur source is 1:1.5 to 2:4 to 5; preferably, the molar ratio of the zinc salt, indium salt and sulfur source is 1:2:4.

5.

6. The method for preparing a photocatalyst according to claim 5, characterized in that: The zinc salt is zinc chloride; the indium salt is indium chloride tetrahydrate; the sulfur source is thioacetamide; and the solvent is ethylene glycol and / or water.

7. The method for preparing a photocatalyst according to claim 4, characterized in that: The conditions of the hydrothermal reaction are to react at 120-160° C. for 10-12 hours; the filter residue is washed and dried with deionized water and anhydrous ethanol, and then dried at 60° C. for 8-12 hours; preferably, the hydrothermal reaction is carried out in a container lined with polytetrafluoroethylene.

8. The method for preparing a photocatalyst according to claim 4, characterized in that: The calcination treatment conditions are calcination at 200-300° C. for 6-8 hours; the inert atmosphere is a nitrogen atmosphere.

9. The method for preparing a photocatalyst according to claim 4, characterized in that: The iridium ion reagent is iridium chloride or sodium hexachloroiridate; the photodeposition reduction is carried out for 1 to 3 hours.

10. Use of the photocatalyst according to any one of claims 1 to 3 in a photocatalytic alkylation reaction, characterized in that: The added amount of the photocatalyst is 0.05-0.1 mol%; preferably, the added amount of the photocatalyst is 0.08 mol%.

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