Photocatalyst loaded with palladium clusters, and preparation method and application thereof

Abstract

The present application relates to the technical field of photocatalyst materials, and is a kind of supported palladium cluster photocatalyst and its preparation method and application, the supported palladium cluster photocatalyst, on the one hand, break through the limitation of traditional noble metal simple physical loading, in situ introduction of palladium acetate in suzuki coupling reaction stage, make palladium with oxidation state Pd (II) anchor in polymer precursor, then reduced to highly dispersed zero-valent palladium Pd (0) cluster, this unique synthesis and combination mode makes the supported palladium cluster photocatalyst have excellent photocatalytic performance.On the other hand, the supported palladium cluster photocatalyst of the present application is applied in photocatalytic methane reaction, which is combined with microfluidic reactor and ultrasonic environment, improves and promotes the mass transfer process of multiphase interface, so that the photocatalytic methane reaction time is greatly shortened, and the reaction efficiency and methane conversion rate of photocatalytic methane reaction can be significantly improved.

Description

Technical Field

[0001] This invention relates to the field of photocatalyst material preparation technology, specifically a photocatalyst supported on palladium clusters, its preparation method, and its application. Background Technology

[0002] Currently, the direct on-site oxidation of methane from associated gas in oil fields into easily stored and transportable liquid chemicals (methanol, formic acid, etc.) is an ideal way to achieve "negative emissions" and high-value utilization of methane. However, traditional methane conversion mainly relies on high-temperature (approximately 800 °C) and steam reforming to generate syngas, followed by Fischer-Tropsch synthesis to prepare liquid hydrocarbons. This route suffers from technical problems such as complex product separation. In contrast, the direct photocatalytic oxidation of methane to produce liquid products such as methanol and formic acid at ambient temperature and pressure has attracted much attention due to its advantages of safety, energy saving, and environmental protection. However, this technology faces two major challenges: first, the inherent chemical inertness of methane molecules makes it difficult to activate carbon-hydrogen bonds, resulting in low conversion rates; second, the products are prone to deep oxidation in complex reaction networks, leading to poor selectivity of liquid products. Existing research indicates that effectively enhancing mass transfer at multiphase interfaces is key to overcoming the above technical bottlenecks, but existing photocatalysts still struggle to achieve both high conversion rates and high selectivity in terms of reaction design and mass transfer enhancement.

[0003] Chinese patent document CN117654621B discloses a method for preparing and applying a metal-free photocatalyst TCP / g-C3N4. It uses tribromotriptene as a raw material, and through multiple nitro, amino, and bromine substitution reactions, tribromotriptene monomer is obtained. Subsequently, g-C3N4 is added, and a Suzuki coupling reaction is used to synthesize a porous tribromotriptene polymer in situ. However, this prior art has significant drawbacks: First, the synthesis of the monomeric tribromotriptene requires multiple substitution reactions, making the preparation process cumbersome and the raw material cost of tribromotriptene extremely high, severely restricting its large-scale application. Second, the Suzuki coupling reaction typically relies on palladium species catalysis, and it is difficult to completely remove residual palladium from the catalyst system after the reaction. More importantly, zero-valent palladium has extremely high activity for the photocatalytic hydrogen evolution reaction, and residual Pd species can act as hidden active centers, severely interfering with the catalytic reaction pathway and product distribution. This patent does not mention or assess the adverse effects of residual metals.

[0004] Chinese patent document CN117443408B discloses a method for preparing a PtCu-TCP composite photocatalyst and its application. This method involves reacting chloroplatinic acid hexahydrate, copper nitrate trihydrate, and a triptene porous polymer in ethylene glycol at 170-180°C. The reducing properties of ethylene glycol are used to reduce and disperse the high-valence metal on the polymer surface. However, this technology also faces several problems: firstly, it heavily relies on noble metals (chloroplatinic acid) and expensive triptene as core raw materials, resulting in high catalyst preparation costs; secondly, this method of simply depositing metals onto the polymer surface using a reducing agent only provides free metal active centers, lacking strong chemical interactions between the metal particles and the support surface, thus failing to form a stable coordination environment. This unstable structure leads to metal agglomeration or detachment after repeated use, causing rapid catalyst deactivation and affecting the catalytic performance of the composite photocatalyst.

[0005] The existing photocatalysts mentioned above have complex synthesis processes. At the same time, the existing photocatalysts are difficult to effectively enhance mass transfer at multiphase interfaces and cannot overcome the problems of low methane reaction efficiency and low conversion rate caused by the chemical inertness of methane. Summary of the Invention

[0006] This invention provides a photocatalyst supported on palladium clusters, its preparation method, and its application, overcoming the shortcomings of the prior art. It can effectively solve the problems of low methane reaction efficiency and low conversion rate of existing photocatalysts in the photocatalytic methane reaction.

[0007] One of the technical solutions of the present invention is achieved through the following measures: a photocatalyst supported on palladium clusters, comprising a boric acid organic compound, 2,5-dibromo-3,6-dihydroxy-p-benzoquinone, potassium carbonate, and palladium acetate in a mass ratio of (150 to 250):(200 to 250):(150 to 200):(5 to 15), potassium carbonate, and palladium acetate, wherein the boric acid organic compound is one of triphenylamine-4,4',4"-triboronic acid, 1,3,5-tris[(4-phenylboronic acid)]benzene, and [(1,3,5-triazine-2,4,6-triyl)tri(benzene-4,1-diyl)]triboronic acid, preferably, the boric acid organic compound is [(1,3,5-triazine-2,4,6-triyl)tri(benzene-4,1-diyl)]triboronic acid.

[0008] The following are further optimizations and / or improvements to one of the above-mentioned technical solutions: The above-mentioned photocatalyst supported on palladium clusters was obtained by the following method: In the first step, under an inert gas atmosphere, the required amounts of boric acid organic compounds, 2,5-dibromo-3,6-dihydroxy-p-benzoquinone, potassium carbonate and palladium acetate are dispersed in N,N-dimethylformamide, heated and reacted to obtain the reaction product; The second step involves cooling and filtering the reaction product, collecting the precipitate, washing the precipitate, stirring and washing it in sulfuric acid solution, then stirring and washing it in methanol solution, and finally extracting the precipitate with dichloromethane to obtain a solid product. The third step involves dispersing the solid product in deionized water to obtain a suspension. Sodium borohydride aqueous solution is then added to the suspension and stirred to react. After drying, a photocatalyst with supported palladium clusters is obtained.

[0009] In the first step above, the inert gas is argon.

[0010] In the first step above, the temperature is heated to 150°C and the reaction time is 1.0 h to 1.5 h.

[0011] In the second step above, during washing, first wash with N,N-dimethylformamide 2 to 3 times, and then wash with water 2 to 3 times.

[0012] In the second step above, the precipitate is placed in a sulfuric acid solution with a molar concentration of 1.5 mol / L to 2.5 mol / L and stirred and washed at 80°C to 85°C for 2.0 h to 2.5 h, and then placed in a methanol solution with a volume concentration of 50% to 55% and stirred and washed overnight at room temperature.

[0013] In the second step above, the extraction temperature is 50℃ to 55℃ and the extraction time is 48h to 50h.

[0014] In the third step above, a sodium borohydride aqueous solution with a molar concentration of 0.10 mol / L to 0.60 mol / L and a temperature of 5°C to 10°C is injected into the suspension and stirred for 2.0 h to 2.5 h. The volume ratio of the suspension to the sodium borohydride aqueous solution is (20 to 30):10.

[0015] In the third step above, the drying is carried out at 80°C to 85°C for 8.0 to 8.5 hours. Preferably, a sodium borohydride aqueous solution with a molar concentration of 0.20 mol / L and a temperature of 5°C is injected into the suspension and stirred for 2.0 hours. The volume ratio of the suspension to the sodium borohydride aqueous solution is 25:10.

[0016] The second technical solution of the present invention is achieved by the following measures: a method for preparing a photocatalyst supported on palladium clusters, which is carried out according to the following method: First, under an inert gas atmosphere, the required amount of boric acid organic compound, 2,5-dibromo-3,6-dihydroxy-p-benzoquinone, potassium carbonate and palladium acetate are dispersed in N,N-dimethylformamide, heated and reacted to obtain the reaction product; The second step involves cooling and filtering the reaction product, collecting the precipitate, washing the precipitate, stirring and washing it in sulfuric acid solution, then stirring and washing it in methanol solution, and finally extracting the precipitate with dichloromethane to obtain a solid product. The third step involves dispersing the solid product in deionized water to obtain a suspension. Sodium borohydride aqueous solution is then added to the suspension and stirred to react. After drying, a photocatalyst with supported palladium clusters is obtained.

[0017] The third technical solution of the present invention is achieved through the following measures: the application of a photocatalyst supported on palladium clusters in the photocatalytic methane reaction, wherein the photocatalytic methane reaction includes a batch reaction and a plug flow reaction, wherein the plug flow reaction is carried out using a microfluidic reactor, the microfluidic reactor includes an upper fixed plate and a lower fixed plate, at least two longitudinal grooves are provided on the upper side of the lower fixed plate at left and right intervals, at least two transverse grooves are provided on the upper side of the lower fixed plate at front and back intervals, the intersection of the longitudinal grooves and the transverse grooves are connected, and flexible tubes are sequentially wound in the longitudinal grooves and the transverse grooves, and the upper fixed plate and the lower fixed plate are detachably connected together.

[0018] This invention overcomes the limitations of traditional simple physical loading of precious metals by introducing palladium acetate in situ during the Suzuki coupling reaction stage. This anchors palladium in the polymer precursor as oxidized Pd(II), followed by reduction to obtain highly dispersed zero-valent palladium Pd(0) clusters. This unique synthesis and bonding method gives the palladium-supported photocatalyst excellent photocatalytic performance. Furthermore, applying this palladium-supported photocatalyst to the photocatalytic methane reaction, combined with a microfluidic reactor and ultrasonic environment, enhances and promotes the multiphase interface mass transfer process, significantly shortening the photocatalytic methane reaction time and substantially improving the reaction efficiency and methane conversion rate. Attached Figure Description

[0019] Figure 1 This is a process flow diagram for preparing the photocatalyst supported on palladium clusters according to the present invention.

[0020] Figure 2 The photocatalyst supported on palladium clusters of this invention 13 C NMR spectrum.

[0021] Figure 3 This is the FT-IR spectrum of the photocatalyst supported on palladium clusters according to the present invention.

[0022] Figure 4 The image shows the XRD pattern of the palladium-supported photocatalyst of this invention.

[0023] Figure 5 This is a scanning electron microscope image of the photocatalyst supported on palladium clusters according to the present invention.

[0024] Figure 6 This is the X-ray photoelectron spectrum of the photocatalyst supported on palladium clusters according to the present invention.

[0025] Figure 7 This is the UV / Vis diffuse reflectance spectrum of the photocatalyst supported on palladium clusters according to the present invention.

[0026] Figure 8 The photocurrent response curve of the palladium cluster-supported photocatalyst of this invention is shown.

[0027] Figure 9 This is the electrochemical impedance spectroscopy of the photocatalyst supported on palladium clusters according to the present invention.

[0028] Figure 10 The fluorescence spectrum of the photocatalyst supported on palladium clusters in this invention is shown.

[0029] Figure 11 This refers to the fluorescence lifetime of the photocatalyst supported on palladium clusters in this invention.

[0030] Figure 12 This is a graph showing the change in formic acid (liquid phase product) concentration over time in the batch reaction of the palladium cluster-supported photocatalyst of this invention.

[0031] Figure 13 This is a graph showing the change in formic acid (liquid phase product) concentration over time in a plug flow reaction of the photocatalyst supported on palladium clusters according to the present invention.

[0032] Figure 14 This is a graph showing the change of the velocity field over time at the methane gas boundary for the photocatalyst supported on palladium clusters according to the present invention.

[0033] Figure 15 This is a schematic diagram of the microfluidic reactor used in the photocatalyst application of the palladium cluster supported by this invention.

[0034] Appendix Figure 15 In the diagram, 1 is the upper fixing plate, 2 is the first longitudinal groove, 3 is the second longitudinal groove, 4 is the third longitudinal groove, 5 is the fourth longitudinal groove, 6 is the fifth longitudinal groove, 7 is the sixth longitudinal groove, 8 is the first transverse groove, 9 is the second transverse groove, 10 is the third transverse groove, 11 is the fourth transverse groove, 12 is the fifth transverse groove, 13 is the sixth transverse groove, and 14 is the flexible hose. Detailed Implementation

[0035] This invention is not limited to the following embodiments, and specific implementation methods can be determined according to the technical solutions and actual conditions of this invention. Unless otherwise specified, all chemical reagents and chemicals mentioned in this invention are well-known and commonly used chemical reagents and chemicals in the prior art; unless otherwise specified, all percentages in this invention are mass percentages; unless otherwise specified, all solutions in this invention are aqueous solutions with water as the solvent, for example, hydrochloric acid solution is an aqueous solution of hydrochloric acid; room temperature in this invention generally refers to a temperature between 15°C and 25°C, generally defined as 25°C.

[0036] The present invention will be further described below with reference to embodiments: Example 1: The photocatalyst supported on palladium clusters comprises a boric acid organic compound, 2,5-dibromo-3,6-dihydroxy-p-benzoquinone, potassium carbonate, and palladium acetate in a mass ratio of (150 to 250):(200 to 250):(150 to 200):(5 to 15), potassium carbonate, and palladium acetate. The boric acid organic compound is one of triphenylamine-4,4',4"-triboronic acid, 1,3,5-tris[(4-phenylboronic acid)]benzene, and [(1,3,5-triazine-2,4,6-triyl)tri(benzene-4,1-diyl)]triboronic acid. Preferably, the boric acid organic compound is [(1,3,5-triazine-2,4,6-triyl)tri(benzene-4,1-diyl)]triboronic acid.

[0037] Example 2: As an optimization of the above examples, a photocatalyst supported on palladium clusters was obtained by the following method: In the first step, under an inert gas atmosphere, the required amounts of boric acid organic compounds, 2,5-dibromo-3,6-dihydroxy-p-benzoquinone, potassium carbonate and palladium acetate are dispersed in N,N-dimethylformamide, heated and reacted to obtain the reaction product; The second step involves cooling and filtering the reaction product, collecting the precipitate, washing the precipitate, stirring and washing it in sulfuric acid solution, then stirring and washing it in methanol solution, and finally extracting the precipitate with dichloromethane to obtain a solid product. The third step involves dispersing the solid product in deionized water to obtain a suspension. Sodium borohydride aqueous solution is then added to the suspension and stirred to react. After drying, a photocatalyst with supported palladium clusters is obtained.

[0038] Example 3: As an optimization of the above example, in the first step, the inert gas is argon.

[0039] Example 4: As an optimization of the above example, in the first step, the temperature is heated to 150°C and the reaction time is 1.0h to 1.5h.

[0040] Example 5: As an optimization of the above example, in the second step, during washing, N,N-dimethylformamide is first used to wash 2 to 3 times, and then water is used to wash 2 to 3 times.

[0041] Example 6: As an optimization of the above example, in the second step, the precipitate is placed in a sulfuric acid solution with a molar concentration of 1.5 mol / L to 2.5 mol / L and stirred and washed at 80°C to 85°C for 2.0 h to 2.5 h, and then placed in a methanol solution with a volume concentration of 50% to 55% and stirred and washed overnight at room temperature.

[0042] Example 7: As an optimization of the above example, in the second step, the extraction temperature is 50°C to 55°C and the extraction time is 48h to 50h.

[0043] Example 8: As an optimization of the above embodiment, in the third step, an aqueous solution of sodium borohydride with a molar concentration of 0.10 mol / L to 0.60 mol / L and a temperature of 5°C to 10°C is injected into the suspension and stirred for 2.0 h to 2.5 h. The volume ratio of the suspension to the aqueous solution of sodium borohydride is (20 to 30):10. Preferably, an aqueous solution of sodium borohydride with a molar concentration of 0.20 mol / L and a temperature of 5°C is injected into the suspension and stirred for 2.0 h. The volume ratio of the suspension to the aqueous solution of sodium borohydride is 25:10.

[0044] Example 9: As an optimization of the above example, in the third step, the drying is carried out at 80°C to 85°C for 8.0h to 8.5h.

[0045] Compared with the prior art, the beneficial effects of the present invention are as follows: First, the preparation process of the photocatalyst supported on palladium clusters in this invention (e.g.) Figure 1 (As shown) Specifically: First, boric acid organic compounds and 2,5-dibromo-3,6-dihydroxy-p-benzoquinone were coupled via a Suzuki reaction in an acidic environment provided by potassium carbonate and with the catalyst palladium acetate to obtain the reaction product, which is a polymer precursor containing oxidized palladium (Pd(II)). In the polymer precursor containing oxidized palladium (Pd(II)), the oxidized palladium (Pd(II)) is a catalytic residue, which is mainly physically encapsulated in the polymer precursor and maintains its oxidized state by weak coordination / interaction with acetate or hydroxyl groups. The reaction product was then filtered to obtain a precipitate. The precipitate was washed with N,N-dimethylformamide and water, mainly to remove unreacted reactants (monomers and potassium carbonate). It was then washed with sulfuric acid solution and methanol solution and extracted with dichloromethane to remove residual palladium acetate from the precipitate (the washing step cannot completely remove palladium acetate, but can only remove the easily soluble part and retain the most stable part as a new active site). After that, a solid product was obtained. Finally, the solid product was dispersed in water to obtain a suspension. A reducing agent (sodium borohydride aqueous solution) was injected into the suspension. The reducing agent (sodium borohydride aqueous solution) was used to reduce the oxidized divalent palladium (Pd(II)) in the suspension to the reduced zero-valent palladium (Pd(0)), that is, the reduced zero-valent palladium (Pd(0)) was formed on the surface of the material. The zero-valent palladium (Pd(0)) was stabilized on the surface of the material by hydrogen bonding with hydroxyl groups, and a photocatalyst with palladium clusters was obtained.

[0046] Therefore, the preparation process of this invention is not simply loading noble metals, but rather, in the Suzuki coupling reaction of boric acid organic compounds and 2,5-dibromo-3,6-dihydroxy-p-benzoquinone, palladium acetate is used as a catalyst to obtain a polymer precursor containing oxidized divalent palladium (Pd(II)). Then, a reducing agent (sodium borohydride aqueous solution) is used to reduce the oxidized divalent palladium (Pd(II)) to the reduced zero-valent palladium (Pd(0)), resulting in a photocatalyst loaded with palladium clusters, which has excellent photocatalytic performance.

[0047] Secondly, the palladium-supported photocatalyst of this invention, when used in the photocatalytic methane reaction, includes both batch and flow-based reactions. In the batch reaction, the concentration of the liquid product reaches its maximum of 76.8 μmol during a reaction time of 3.5 to 4.5 hours (based on 10 mL of methane), indicating a high conversion rate. In the flow-based reaction, since the interfacial mass transfer between methane, catalyst, and water in the photocatalytic methane reaction is essentially a coupled process of substrate diffusion, adsorption, reaction, and product diffusion, this invention combines the palladium-supported photocatalyst with a microfluidic reactor and an ultrasonic microfluidic reaction environment (i.e., in an ultrasonic environment) to efficiently promote the methane mass transfer process. This significantly shortens the photocatalytic methane reaction time and increases the reaction efficiency. The concentration of the liquid product (formic acid) reaches its maximum of 87.8 μmol within 20 to 25 minutes. This is because the use of microfluidic reactors and the constructed ultrasonic microfluidic reaction environment has several advantages. First, the microfluidic reactor can utilize cavitation and acoustic flow effects to generate intense turbulence and vortices in the relatively static interface region within the microscale channel, significantly reducing diffusion resistance and accelerating the transport of reactants to the interface while carrying away liquid products. Second, the periodic oscillation of microbubbles generated by ultrasound not only inhibits catalyst particle aggregation and removes the passivation layer on their surface, continuously exposing active sites, but also increases the effective contact area between phases. Most importantly, the local extreme high temperature and pressure generated by ultrasound can both promote CH4 dissolution and break down water molecules to generate hydroxyl radicals (•OH), increasing the oxidation rate and depth.

[0048] Therefore, applying the palladium cluster-supported photocatalyst of this invention to the photocatalytic methane reaction, combined with a microfluidic reactor and an ultrasonic microfluidic reaction environment, can effectively improve the reaction efficiency and conversion rate of the photocatalytic methane reaction.

[0049] Example 10: The photocatalyst supported on palladium clusters has the following reaction mechanism diagram: Figure 1 As shown, it is obtained as follows: In the first step, boric acid organic compounds (triphenylamine-4,4',4"-triboronic acid, 188.4 mg, 0.50 mmol), 2,5-dibromo-3,6-dihydroxy-p-benzoquinone (223.4 mg, 0.75 mmol), potassium carbonate (172.8 mg), and palladium acetate (10.0 mg) were sequentially added to a dried round-bottom flask. The round-bottom flask was then evacuated and purged three times with argon gas (pre-dehydrated). 40 mL of N,N-dimethylformamide (pre-saturated with argon gas to remove air) was added to the round-bottom flask. The mixture was heated to 150 °C in a microwave reactor (MCR-3, Yuhua, China) for 1 h to obtain the reaction product. In the second step, the reaction product was cooled to room temperature, filtered, and the precipitate was collected. The precipitate was washed 2 to 3 times with N,N-dimethylformamide, and then washed 2 to 3 times with water. Next, it was placed in a 2 mol / L sulfuric acid solution and stirred at 80°C for 2.0 h, and then placed in a 50% methanol solution and stirred overnight at room temperature. Subsequently, the precipitate was placed in a Soxhlet extractor containing dichloromethane and extracted at 50°C for 48 hours to obtain a solid product (labeled as Pd-CBAP). The third step involves dispersing the solid product in 25 mL of deionized water to obtain a suspension. 10 mL of sodium borohydride aqueous solution (molar concentration of 0.20 mol / L, temperature of 5 °C, injection time of 20 min) is injected into the suspension at a rate of 0.5 mL / min and stirred for 2.0 h. After drying in an oven at 80 °C for 8 h, a photocatalyst with supported palladium clusters is obtained, labeled as Pd-CBAP-X (263.6 mg, yield of 64%, X=0.33, where 0.33 represents the proportion of zero-valent palladium (Pd(0)) in the total palladium in Pd-CBAP-X, i.e., Pd-CBAP-0.33).

[0050] Example 11: The fabrication process flow diagram for this palladium-supported photocatalyst is shown below. Figure 1 As shown, it is obtained as follows: In the first step, boric acid organic compounds (1,3,5-tris[(4-phenylboronic acid)]benzene, 218.9 mg, 0.50 mmol), 2,5-dibromo-3,6-dihydroxy-p-benzoquinone (223.4 mg, 0.75 mmol), potassium carbonate (172.8 mg), and palladium acetate (10.0 mg) were sequentially added to a dried round-bottom flask. Then, the round-bottom flask was evacuated and purged three times with argon gas (pre-dehydrated). 40 mL of N,N-dimethylformamide (pre-saturated with argon gas to remove air) was added to the round-bottom flask. The mixture was heated to 150 °C in a microwave reactor (MCR-3, Yuhua, China) for 1 h to obtain the reaction product. In the second step, the reaction product was cooled to room temperature, filtered, and the precipitate was collected. The precipitate was washed 2 to 3 times with N,N-dimethylformamide, and then washed 2 to 3 times with water. Next, it was placed in a 2 mol / L sulfuric acid solution and stirred at 80°C for 2.0 h. Then, it was placed in a 50% methanol solution and stirred overnight at room temperature. Subsequently, the precipitate was placed in a Soxhlet extractor containing dichloromethane and extracted at 55°C for 48 hours to obtain a solid product (labeled as Pd-CBBP). The third step involves dispersing the solid product in 25 mL of deionized water to obtain a suspension. 10 mL of sodium borohydride aqueous solution (molar concentration of 0.20 mol / L, temperature of 5 °C, injection time of 20 min) is then injected into the suspension at a rate of 0.5 mL / min. The mixture is stirred for 2.0 h and dried in an oven at 80 °C for 8 h to obtain a photocatalyst with supported palladium clusters, labeled as Pd-CBBP-X (247.7 mg, yield 56%, X=0.33, where 0.33 represents the proportion of zero-valent palladium (Pd(0)) in the total palladium in Pd-CBBP-X, i.e., Pd-CBBP-0.33).

[0051] Example 12: The fabrication process flow diagram for this palladium-supported photocatalyst is shown below. Figure 1 As shown, it is obtained as follows: In the first step, boric acid organic compounds ([(1,3,5-triazine-2,4,6-triyl)tris(benzene-4,1-diyl)]triboronic acid, 220.4 mg, 0.50 mmol), 2,5-dibromo-3,6-dihydroxy-p-benzoquinone (223.4 mg, 0.75 mmol), potassium carbonate (172.8 mg), and palladium acetate (10.0 mg) were sequentially added to a dried round-bottom flask. Then, the round-bottom flask was evacuated and purged three times with argon gas (pre-dehydrated). 40 mL of N,N-dimethylformamide (pre-saturated with argon gas to remove air) was added to the round-bottom flask. The mixture was heated to 150 °C in a microwave reactor (MCR-3, Yuhua, China) for 1 h to obtain the reaction product. In the second step, the reaction product was cooled to room temperature, filtered, and the precipitate was collected. The precipitate was washed 2 to 3 times with N,N-dimethylformamide, and then washed 2 to 3 times with water. Next, it was placed in a 2 mol / L sulfuric acid solution and stirred at 80°C for 2.0 h. Then, it was placed in a 50% methanol solution and stirred overnight at room temperature. Subsequently, the precipitate was placed in a Soxhlet extractor containing dichloromethane and extracted at 52°C for 48 hours to obtain a solid product (labeled as Pd-CBTP). The third step involves dispersing the solid product in 25 mL of deionized water to obtain a suspension. 10 mL of sodium borohydride aqueous solution (molar concentration of 0.10 mol / L, temperature of 5℃, injection time of 20 min) is injected into the suspension at a rate of 0.5 mL / min and stirred for 2.0 h. After drying in an oven at 80℃ for 8 h, a photocatalyst with supported palladium clusters is obtained, labeled as Pd-CBTP-X (288.5 mg, yield 65%, X = 0.15, where 0.15 represents the proportion of zero-valent palladium (Pd(0)) in the total palladium in Pd-CBTP-X, i.e., Pd-CBTP-0.15).

[0052] Example 13: The fabrication process flow diagram for this palladium-supported photocatalyst is shown below. Figure 1 As shown, it is obtained as follows: In the first step, boric acid organic compounds ([(1,3,5-triazine-2,4,6-triyl)tris(benzene-4,1-diyl)]triboronic acid, 220.4 mg, 0.50 mmol), 2,5-dibromo-3,6-dihydroxy-p-benzoquinone (223.4 mg, 0.75 mmol), potassium carbonate (172.8 mg), and palladium acetate (10.0 mg) were sequentially added to a dried round-bottom flask. Then, the round-bottom flask was evacuated and purged three times with argon gas (pre-dehydrated). 40 mL of N,N-dimethylformamide (pre-saturated with argon gas to remove air) was added to the round-bottom flask. The mixture was heated to 150 °C in a microwave reactor (MCR-3, Yuhua, China) for 1 h to obtain the reaction product. In the second step, the reaction product was cooled to room temperature, filtered, and the precipitate was collected. The precipitate was washed 2 to 3 times with N,N-dimethylformamide, and then washed 2 to 3 times with water. Next, it was placed in a 2 mol / L sulfuric acid solution and stirred at 80°C for 2.0 h. Then, it was placed in a 50% methanol solution and stirred overnight at room temperature. Subsequently, the precipitate was placed in a Soxhlet extractor containing dichloromethane and extracted at 52°C for 48 hours to obtain a solid product (labeled as Pd-CBTP). The third step involves dispersing the solid product in 25 mL of deionized water to obtain a suspension. 10 mL of sodium borohydride aqueous solution (molar concentration of 0.20 mol / L, temperature of 5 °C, injection time of 20 min) is then injected into the suspension at a rate of 0.5 mL / min. The mixture is stirred for 2.0 h and dried in an oven at 80 °C for 8 h to obtain a photocatalyst with supported palladium clusters, labeled as Pd-CBTP-X (270.7 mg, yield 61%, X=0.33, where 0.33 represents the proportion of zero-valent palladium (Pd(0)) in the total palladium in Pd-CBTP-X, i.e., Pd-CBTP-0.33).

[0053] Example 14: The fabrication process flow diagram for this palladium-supported photocatalyst is shown below. Figure 1 As shown, it is obtained as follows: In the first step, boric acid organic compounds ([(1,3,5-triazine-2,4,6-triyl)tris(benzene-4,1-diyl)]triboronic acid, 220.4 mg, 0.50 mmol), 2,5-dibromo-3,6-dihydroxy-p-benzoquinone (223.4 mg, 0.75 mmol), potassium carbonate (172.8 mg), and palladium acetate (10.0 mg) were sequentially added to a dried round-bottom flask. Then, the round-bottom flask was evacuated and purged three times with argon gas (pre-dehydrated). 40 mL of N,N-dimethylformamide (pre-saturated with argon gas to remove air) was added to the round-bottom flask. The mixture was heated to 150 °C in a microwave reactor (MCR-3, Yuhua, China) for 1 h to obtain the reaction product. In the second step, the reaction product was cooled to room temperature, filtered, and the precipitate was collected. The precipitate was washed 2 to 3 times with N,N-dimethylformamide, and then washed 2 to 3 times with water. Next, it was placed in a 2 mol / L sulfuric acid solution and stirred at 80°C for 2.0 h. Then, it was placed in a 50% methanol solution and stirred overnight at room temperature. Subsequently, the precipitate was placed in a Soxhlet extractor containing dichloromethane and extracted at 52°C for 48 hours to obtain a solid product (labeled as Pd-CBTP). The third step involves dispersing the solid product in 25 mL of deionized water to obtain a suspension. 10 mL of sodium borohydride aqueous solution (molar concentration of 0.60 mol / L, temperature of 5 °C, injection time of 20 min) is injected into the suspension at a rate of 0.5 mL / min and stirred for 2.0 h. After drying in an oven at 80 °C for 8 h, a photocatalyst with supported palladium clusters is obtained, labeled as Pd-CBTP-X (266.3 mg, yield 60%, X = 0.77, where 0.77 represents the proportion of zero-valent palladium (Pd(0)) in the total palladium in Pd-CBTP-X, i.e., Pd-CBTP-0.77).

[0054] Experimental Example 1: The structure of the palladium cluster-supported photocatalyst of the present invention was characterized.

[0055] Experimental methods: The structures of Pd-CBAP-0.33 prepared in Example 10, Pd-CBBP-0.33 prepared in Example 11, and Pd-CBTP-0.33 prepared in Example 13 were characterized by nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, and X-ray diffraction, respectively.

[0056] Experimental results: Pd-CBAP-0.33, Pd-CBBP-0.33, Pd-CBTP-0.33 13 The C NMR spectrum is as follows Figure 2As shown, the C-Br bond signal in the boric acid-based organic compound is around 105 ppm, while the C-Br bond signal in the 2,5-dibromo-3,6-dihydroxy-p-benzoquinone is around 110 ppm. Neither of these signals were detected in the product spectrum, indicating that the monomer polymerization reaction was complete and there was virtually no monomer residue.

[0057] In the Suzuki coupling reaction, the C-B bond in the boric acid organic compound and the C-Br bond in 2,5-dibromo-3,6-dihydroxy-p-benzoquinone both break, and then -C bonds are linked together to form new CC bonds. The simultaneous appearance of signals near 132 ppm and 125 ppm indicates the formation of new CC bonds, suggesting that the polymer was successfully synthesized.

[0058] from Figure 2 As can be seen from the Pd-CBBP NMR carbon spectrum, position 1 corresponds to C in C=O (171 ppm), position 2 corresponds to C in CO (168 ppm), position 3 corresponds to C in the benzene ring connected to other units (144 ppm), position 4 corresponds to C in the benzene ring connected to other units (143 ppm), position 5 corresponds to C in the benzene ring connected to quinone units (130 ppm), position 6 corresponds to C in C=C in the benzene ring (128 ppm), position 7 corresponds to C in C=C in the benzene ring (125 ppm), and position 8 corresponds to C in C=C in the quinone unit (125 ppm).

[0059] In the Pd-CBTP carbon NMR spectrum, position 1 corresponds to C in C=O (172 ppm), position 2 corresponds to C in the triazine ring (170 ppm), position 3 corresponds to C in CO (168 ppm; because the peak positions are very close, they cannot be separated, so a broad peak is formed), position 4 corresponds to C in the benzene ring connected to the triazine ring (135 ppm), position 5 corresponds to C in the benzene ring connected to the quinone unit (133 ppm), position 6 corresponds to C in C=C in the benzene ring (127 ppm), and position 7 corresponds to C in C=C in the quinone unit (125 ppm).

[0060] In the Pd-CBAP carbon NMR spectrum, position 1 corresponds to C in C=O (172 ppm), position 2 corresponds to C in CO (168 ppm), position 3 corresponds to C in the benzene ring connected to the N ring (138 ppm), position 4 corresponds to C in the benzene ring connected to the quinone unit (133 ppm), position 5 corresponds to C in the C=C in the benzene ring (125 ppm), and position 6 corresponds to C in the C=C in the quinone unit (125 ppm).

[0061] The FT-IR spectra of Pd-CBAP-0.33, Pd-CBBP-0.33, and Pd-CBTP-0.33 are as follows: Figure 3As shown, from Figure 3 It can be seen that 1604cm -1 and 815cm -1 The absorption peaks at 1670 cm⁻¹ are attributed to the stretching vibrations of C=N and CN, respectively, while the absorption peaks at 1670 cm⁻¹ are attributed to the stretching vibrations of C=N and CN, respectively. -1 1100cm -1 and 3427cm -1 The peaks at these locations are attributed to the stretching vibrations of C=O, CO, and OH, respectively.

[0062] The XRD patterns of Pd-CBAP-0.33, Pd-CBBP-0.33, and Pd-CBTP-0.33 are as follows: Figure 4 As shown, from Figure 4 It can be seen that all three materials exhibit a distinct broad peak, which is a typical characteristic of amorphous structures.

[0063] therefore, 13 The C NMR spectrum, FT-IR spectrum, and XRD pattern collectively demonstrate that the monomers successfully underwent a polymerization reaction, and the photocatalyst supported on palladium clusters of this invention has been successfully prepared.

[0064] Experimental Example 2: The content of zero-valent palladium (Pd(0)) in the photocatalyst supported on palladium clusters of the present invention was analyzed.

[0065] Experimental method: The content of zero-valent palladium (Pd(0)) in Pd-CBTP-0.15 prepared in Example 12, Pd-CBTP-0.33 prepared in Example 13, and Pd-CBTP-0.77 prepared in Example 14 was analyzed by X-ray photoelectron spectroscopy.

[0066] Experimental results: The scanning electron microscope image of Pd-CBTP-0.33 is as follows. Figure 5 As shown, from Figure 5 It can be seen that many irregular Pd clusters (about 3 nm) are dispersed on the polymer surface.

[0067] X-ray photoelectron spectra of Pd-CBTP-0.15, Pd-CBTP-0.33, and Pd-CBTP-0.77, as shown below. Figure 6 As shown, from Figure 6 It can be seen that as the concentration of sodium borohydride aqueous solution (NaBH4) increases (0.1mol / L, 0.2mol / L, 0.6mol / L), the content of zero-valent palladium (Pd(0)) also increases.

[0068] The elemental contents (C, N, O, Pd) in the second step of Pd-CBTP preparation in Example 13 of this invention were analyzed, and the results are shown in Table 1. Table 1 shows that the total palladium content in the solid product is 0.85%, and Pd-CBTP contains only divalent palladium (Pd(II)). After selective reduction with sodium borohydride aqueous solution, the total palladium content remains unchanged. With the increase of sodium borohydride aqueous solution (NaBH4) concentration (0.1 mol / L, 0.2 mol / L, 0.6 mol / L), the content of zero-valent palladium (Pd(0)) in Pd-CBTP continuously increases (X = 0.15, 0.33, 0.77). This indicates that by using sodium borohydride aqueous solution for selective reduction, this invention can increase the content of zero-valent palladium (Pd(0)) on the surface of Pd-CBTP, thereby improving the overall catalytic activation performance.

[0069] Experimental Example 3: The photocatalytic activity of the palladium cluster-supported photocatalyst of this invention was investigated.

[0070] Experimental objective: To evaluate the photocatalytic activity of Pd-CBAP prepared in the second step of Example 10, Pd-CBBP prepared in the second step of Example 11, Pd-CBTP prepared in the second step of Example 12, and Pd-CBTP-0.15, Pd-CBTP-0.33, and Pd-CBTP-0.77 prepared in Examples 12 to 14, using these materials in this experiment, through photophysical and photoelectric property studies.

[0071] Experimental methods and results: (1) The optical band gap (OG) and conduction band (CB) positions of each material were determined by ultraviolet-visible diffuse reflectance spectroscopy. The two can be used to determine the band structure of each material. The ultraviolet / visible diffuse reflectance spectra of each material are as follows: Figure 7 As shown. From Figure 7 Data from Pd-CBTP, Pd-CBTP-0.15, Pd-CBTP-0.33, and Pd-CBTP-0.77 show that the conduction band (CB) value gradually decreases with increasing zero-valent palladium (Pd(0)) content in Pd-CBTP. This indicates that the introduction of zero-valent palladium (Pd(0)) is beneficial to improving the reducibility of the material. For Pd-CBTP-0.33, its conduction band (CB) value is -0.99V, which is lower than O2 / •O2. − The standard reduction potential (-0.33 V vs NHE) and the standard reduction potential of O2 / H2O2 (0.68 V vs NHE) demonstrate the great potential to reduce O2 to H2O2.

[0072] When the proportion of zero-valent palladium (Pd(0)) increases from 0 to 0.33, the optical band gap (OG) increases, the photocurrent is enhanced, the radius of the electrochemical impedance curve decreases, the fluorescence emission peak intensity weakens, and the average fluorescence lifetime continues to shorten. When the proportion of zero-valent palladium (Pd(0)) is further increased to 0.77, the photocurrent and fluorescence peak intensity show a significant decrease, the impedance radius does not change much, and the optical band gap (OG) and average lifetime increase slightly. These results indicate that modifying the Pd-CBTP surface with an appropriate amount of zero-valent palladium (Pd(0)) at a proportion of 0.33 can enable the excited-state material to possess a higher photogenerated carrier concentration, stronger photoelectron migration capability, and better photoexcited electron-hole separation efficiency.

[0073] (2) The photogenerated carrier concentration of each material was evaluated by measuring the photoelectric response curve. The photocurrent response curves of each material are shown below. Figure 8 As shown, from Figure 8 It can be seen that compared with Pd-CBAP and Pd-CBBP, Pd-CBTP has a higher photocurrent, and the photocurrent reaches its maximum when the proportion of zero-valent palladium (Pd(0)) increases from 0 to 0.33, indicating that the Pd-CBTP-0.33 surface has the highest concentration of photogenerated carriers.

[0074] (3) Electrochemical impedance spectroscopy was measured to evaluate the photoelectron mobility of each material. The electrochemical impedance spectra of each material are as follows: Figure 9 As shown, from Figure 9 It can be seen that compared with Pd-CBAP and Pd-CBBP, Pd-CBTP has a smaller radius of electrochemical impedance curve, and the curve radius is the smallest when the proportion of zero-valent palladium (Pd(0)) increases from 0 to 0.33, indicating that the Pd-CBTP-0.33 surface has the strongest photoelectron migration ability.

[0075] (4) Fluorescence spectra and fluorescence lifetimes were measured to evaluate the photogenerated electron-hole separation efficiency of each material surface. The fluorescence spectra of each material are shown below. Figure 10 As shown, the fluorescence lifetimes of each material are as follows: Figure 11 As shown, from Figure 10 and Figure 11 It can be seen that compared with Pd-CBAP and Pd-CBBP, Pd-CBTP has a lower fluorescence emission peak intensity and a shorter average fluorescence lifetime. Furthermore, when the proportion of zero-valent palladium (Pd(0)) increases from 0 to 0.33, the fluorescence emission peak intensity is the weakest and the average fluorescence lifetime is the shortest, indicating that the Pd-CBTP-0.33 surface has the highest photoexcitation electron-hole separation efficiency.

[0076] In summary, Pd-CBAP, Pd-CBBP, and Pd-CBTP exhibit good photogenerated carrier concentration, strong photoelectron mobility, and good photoexcited electron-hole separation efficiency. Compared with Pd-CBAP and Pd-CBBP, Pd-CBTP has superior photogenerated carrier concentration, photoelectron mobility, and photoexcited electron-hole separation efficiency. Preferably, Pd-CBTP-0.33 shows particularly outstanding performance in photogenerated carrier concentration, photoelectron mobility, and photoexcited electron-hole separation efficiency, i.e., higher photogenerated carrier concentration, stronger photoelectron mobility, and better photoexcited electron-hole separation efficiency.

[0077] Experiment Example 4: The present invention relates to the application of a palladium-supported photocatalyst in the photocatalytic reaction of methane.

[0078] Experimental Objective: To investigate the photocatalytic performance of Pd-CBTP-0.15, Pd-CBTP-0.33, and Pd-CBTP-0.77 prepared in Examples 12 to 14 of this invention in the photocatalytic methane reaction. The photocatalytic methane reaction includes batch reaction and plug flow reaction. The plug flow reaction is carried out using a microfluidic reactor. The schematic diagram of the microfluidic reactor is shown below. Figure 15 As shown, it includes an upper fixing plate 1 and a lower fixing plate. The upper side of the lower fixing plate is provided with at least two longitudinal grooves spaced apart from left to right, and the upper side of the lower fixing plate is provided with at least two transverse grooves spaced apart from front to back. The intersection of the longitudinal grooves and the transverse grooves is connected. The longitudinal grooves and the transverse grooves are sequentially coiled in the longitudinal grooves and the transverse grooves. The upper fixing plate 1 and the lower fixing plate are detachably connected together.

[0079] Depending on the requirements, the specific winding method of the hose 14 (e.g.) Figure 15 As shown, the lower fixing plate has six longitudinal grooves spaced apart on the upper side, including a first longitudinal groove 2, a second longitudinal groove 3, a third longitudinal groove 4, a fourth longitudinal groove 5, a fifth longitudinal groove 6 and a sixth longitudinal groove 7 arranged sequentially from left to right. The lower fixing plate has six transverse grooves spaced apart on the upper side, including a first transverse groove 8, a second transverse groove 9, a third transverse groove 10, a fourth transverse groove 11, a fifth transverse groove 12 and a sixth transverse groove 13 arranged sequentially from front to back. The hose 14 enters from the sixth longitudinal groove 7 and then passes through the fourth longitudinal groove 5, the second longitudinal groove 3, the fifth longitudinal groove 6, the first longitudinal groove 2, the third longitudinal groove 4, the first transverse groove 8, the third transverse groove 10, the fifth transverse groove 12, the second transverse groove 9 and the sixth transverse groove 13, and exits from the fourth transverse groove 11.

[0080] Experimental methods: (1) Specific process of batch reaction: First, 20.0 mg of Pd-CBTP-0.15, Pd-CBTP-0.33, and Pd-CBTP-0.77 were uniformly dispersed in vials containing 4.0 mL of sulfuric acid solution (pH = 4) to obtain suspensions. O2 was bubbled into the suspensions for 15 minutes, followed by stirring in the dark for 30 minutes to reach adsorption-desorption equilibrium. Then, 10 mL of methane was injected into the vial and the suspensions were irradiated with a 300 W xenon lamp. After a period of reaction, the type and content of the gaseous products were determined by gas chromatography, and the composition and concentration of the liquid products were analyzed by gas chromatography or liquid chromatography.

[0081] (2) Specific process of plug flow reaction: First, 600.0 mg of Pd-CBTP-0.15, Pd-CBTP-0.33, and Pd-CBTP-0.77 were dispersed in 100 mL of sulfuric acid solution (pH=4) to obtain a suspension. O2 was bubbled into the suspension for 30 min, and then stirred in the dark for 30 min to reach adsorption-desorption equilibrium. Then, two transparent polytetrafluoroethylene tubing 14 (Φ3.6×0.8 mm) were used to transport methane and the suspension respectively, and the flow rate ratio of the two was maintained at 2:1 by a syringe pump. The two fluids were mixed through a Y-connector. Finally, they entered the microfluidic reactor in a continuous and regular plug flow form. After a period of UV irradiation and ultrasonic treatment at room temperature and pressure, the type and content of gaseous products were determined by gas chromatography, and the composition and concentration of liquid products were analyzed by gas chromatography or liquid chromatography.

[0082] Experimental Setup: The experimental setup for the plug flow reaction includes a microfluidic reactor, a mercury lamp, a mass flow meter, a syringe pump, and a plate-type ultrasonic generator. These components—the microfluidic reactor, mercury lamp, mass flow meter, syringe pump, and plate-type ultrasonic generator—create a plug flow reaction environment, i.e., an ultrasonic microfluidic reaction environment. Details are as follows: The microfluidic reactor consists of two colorless and transparent acrylic plates of different thicknesses (upper fixed plate 1 and lower fixed plate) (10×10×0.5cm and 10×10×0.7cm respectively). A milling machine is used to carve longitudinal and transverse grooves on the thicker plate (lower fixed plate) and arrange them in a crisscross pattern. The flexible tube 14 (Refer, Tygon 2475, 1m, Φ3.6×0.8mm, acid resistant, colorless and transparent) is arranged in a coiled manner in the longitudinal and transverse grooves, so that the microfluidic reactor receives relatively concentrated light and the residence time is adjustable within a wide range.

[0083] Using a mercury lamp light source (Zhongjiao Jinyuan Company, model CEL-M500, 500W ~ 5000W / m) 2 Increase light intensity to increase system energy input.

[0084] The gas flow rate was controlled using a mass flow meter (Seven Star Huachuang Company, model D07-15, ~5 SCCM, 3MPa).

[0085] The syringe pump (Refer, model TYD02-02, ~150mL / min, ~150mL) controls the liquid flow rate and adjusts the ratio of the two to ensure that the bubbles are stably and uniformly distributed in the liquid phase.

[0086] A plate-type ultrasonic generator (Jiemeng Company, model JP-10061, ~300W, 300×200×100mm, dual vibrators) is used to amplify the fluctuations in the flow field at the gas boundary, thereby increasing the vibration frequency of the bubbles and the stability of their structure during the flow process.

[0087] The changes in the velocity field at the bubble boundary were observed and recorded in real time using a fluorescence microscope (Nikon, ECLIPSE Si) and a high-definition camera (Nikon, DS-Fi3, 2880×2048 resolution).

[0088] The concentrations of each component were accurately determined using gas chromatography (Tianmei, SCION 456C, TCD and FID detectors, capillary column KB-624 and packed column TDX-01, methane conversion furnace, headspace sampler) and liquid chromatography (Shimadzu, LC-2030 Plus, SH1011 column).

[0089] Experimental results: The graph shows the change in formic acid (liquid phase product) concentration over time for each material in a batch reaction. Figure 12 As shown, from Figure 12 It can be seen that after 4 hours of photocatalytic methane reaction using Pd-CBTP-0.33, the HCOOH concentration reached a maximum of 76.8 μmol (3.84 mmol / g * 20 mg * 1000), which is 1.8 times that of Pd-CBTP-0.15 and 1.4 times that of Pd-CBTP-0.77. This indicates that the introduction of zero-valent palladium (Pd(0)) onto the surface of the material can promote CH4 oxidation, and adjusting the content of zero-valent palladium (Pd(0)) can control the CH4 reaction process. Therefore, the photocatalytic methane reaction of Pd-CBTP-0.33 yielded the highest concentration of formic acid (liquid phase product), indicating the optimal conversion rate.

[0090] The graph shows the change in formic acid (liquid phase product) concentration over time for each material in a plug flow reaction. Figure 13 As shown, from Figure 13It can be seen that, compared with the batch reaction, the reaction time of the plug-flow reaction in the microfluidic reactor and ultrasonic microfluidic reaction environment is significantly shortened. When the photocatalytic methane reaction time is 20 minutes, the formic acid concentration obtained by Pd-CBTP-0.33 in the plug-flow reaction reaches 87.8 μmol / L, indicating that ultrasound (ultrasound-assisted) in the microfluidic reaction environment can promote the methane mass transfer process. After four cycles of experiments, the concentration of formic acid (liquid phase product) did not decrease significantly, showing that the materials have good stability in the ultrasonic microfluidic reaction environment.

[0091] The changes in the boundary flow field of methane gas in an ultrasonic microfluidic reaction environment were analyzed using particle image velocimetry (PIV). The changes in the methane gas boundary velocity field over time are shown in the figure below. Figure 14 As shown, from Figure 14 It can be seen that the velocity field distribution around the bubble at the initial moment is regular, indicating that the fluid moves in a plug flow manner. After the application of ultrasound (ultrasound-assisted), the acoustic flow and cavitation effect generate microscale turbulence and convection, which breaks the laminar flow characteristics and produces a small number of vortices, causing changes in the velocity field distribution. As the ultrasound process continues, the number of vortices increases, the radius becomes larger, and the rotation direction varies, intensifying the turbulence of the velocity field and enhancing the disturbance to the entire flow field around the bubble. This not only increases the contact area between methane, materials (catalyst), and solution, but also changes their contact mode and dynamic behavior, effectively enhancing the mass transfer process.

[0092] Therefore, applying the palladium cluster-supported photocatalyst of this invention to the photocatalytic methane reaction, combined with a microfluidic reactor and an ultrasonic microfluidic reaction environment, can effectively improve the reaction efficiency and conversion rate of the photocatalytic methane reaction.

[0093] In summary, this invention overcomes the limitations of traditional simple physical loading of precious metals by introducing palladium acetate in situ during the Suzuki coupling reaction stage. This anchors palladium in the polymer precursor as oxidized Pd(II), followed by reduction to obtain highly dispersed zero-valent palladium Pd(0) clusters. This unique synthesis and bonding method gives the palladium-supported photocatalyst excellent photocatalytic performance. Furthermore, applying this palladium-supported photocatalyst to the photocatalytic methane reaction, combined with a microfluidic reactor and ultrasonic environment, enhances and promotes the multiphase interface mass transfer process, significantly shortening the photocatalytic methane reaction time and substantially improving the reaction efficiency and methane conversion rate.

[0094] The above technical features constitute the embodiments of the present invention, which have strong adaptability and implementation effect. Unnecessary technical features can be added or removed according to actual needs to meet the needs of different situations.

[0095] Table 1 。

Claims

1. A photocatalyst supported on palladium clusters, characterized in that... The raw materials include a boric acid organic compound, 2,5-dibromo-3,6-dihydroxy-p-benzoquinone, potassium carbonate, and palladium acetate in a mass ratio of 150 to 250:200 to 250:150 to 200:5 to 15, wherein the boric acid organic compound is one of triphenylamine-4,4',4"-triboronic acid, 1,3,5-tris[(4-phenylboronic acid)]benzene, and [(1,3,5-triazine-2,4,6-triyl)tri(phenyl-4,1-diyl)]triboronic acid.

2. The photocatalyst supported on palladium clusters according to claim 1, characterized in that... Obtained using the following method: In the first step, under an inert gas atmosphere, the required amounts of boric acid organic compounds, 2,5-dibromo-3,6-dihydroxy-p-benzoquinone, potassium carbonate and palladium acetate are dispersed in N,N-dimethylformamide, heated and reacted to obtain the reaction product; The second step involves cooling and filtering the reaction product, collecting the precipitate, washing the precipitate, stirring and washing it in sulfuric acid solution, then stirring and washing it in methanol solution, and finally extracting the precipitate with dichloromethane to obtain a solid product. The third step involves dispersing the solid product in deionized water to obtain a suspension. Sodium borohydride aqueous solution is then added to the suspension and stirred to react. After drying, a photocatalyst with supported palladium clusters is obtained.

3. The photocatalyst supported on palladium clusters according to claim 2, characterized in that... In the first step, the inert gas is argon; and / or, in the first step, the temperature is raised to 150°C and the reaction time is 1.0 h to 1.5 h.

4. The photocatalyst with supported palladium clusters according to claim 2 or 3, characterized in that... In the second step, during washing, first wash with N,N-dimethylformamide 2 to 3 times, and then wash with water 2 to 3 times.

5. The photocatalyst supported on palladium clusters according to claim 4, characterized in that... In the second step, the precipitate is placed in a sulfuric acid solution with a molar concentration of 1.5 mol / L to 2.5 mol / L and stirred and washed at 80°C to 85°C for 2.0 h to 2.5 h, and then placed in a methanol solution with a volume concentration of 50% to 55% and stirred and washed overnight at room temperature.

6. The photocatalyst with supported palladium clusters according to claim 2, 3, or 5, characterized in that... In the second step, the extraction temperature is 50℃ to 55℃, and the extraction time is 48h to 50h.

7. The photocatalyst with supported palladium clusters according to claim 6, characterized in that... In the third step, an aqueous solution of sodium borohydride with a molar concentration of 0.10 mol / L to 0.60 mol / L and a temperature of 5°C to 10°C is injected into the suspension and stirred for 2.0 h to 2.5 h. The volume ratio of the suspension to the aqueous solution of sodium borohydride is 20 to 30:

10.

8. The photocatalyst with supported palladium clusters according to claim 2, 3, 5, or 7, characterized in that... In the third step, drying is carried out at 80℃ to 85℃ for 8.0h to 8.5h.

9. A method for preparing a photocatalyst with supported palladium clusters according to any one of claims 1, 3 to 8, characterized in that... Perform it as follows: In the first step, under an inert gas atmosphere, the required amounts of boric acid organic compounds, 2,5-dibromo-3,6-dihydroxy-p-benzoquinone, potassium carbonate and palladium acetate are dispersed in N,N-dimethylformamide, heated and reacted to obtain the reaction product; The second step involves cooling and filtering the reaction product, collecting the precipitate, washing the precipitate, stirring and washing it in sulfuric acid solution, then stirring and washing it in methanol solution, and finally extracting the precipitate with dichloromethane to obtain a solid product. The third step involves dispersing the solid product in deionized water to obtain a suspension. Sodium borohydride aqueous solution is then added to the suspension and stirred to react. After drying, a photocatalyst with supported palladium clusters is obtained.

10. The application of a photocatalyst with supported palladium clusters according to any one of claims 1 to 8 in the photocatalytic reaction of methane, characterized in that, Photocatalytic methane reaction includes batch reaction and plug flow reaction. The plug flow reaction is carried out using a microfluidic reactor, which includes an upper fixed plate and a lower fixed plate. The upper side of the lower fixed plate is provided with at least two longitudinal grooves spaced from left to right, and the upper side of the lower fixed plate is provided with at least two transverse grooves spaced from front to back. The intersection of the longitudinal grooves and the transverse grooves is connected. The longitudinal grooves and the transverse grooves are sequentially wound with flexible tubes. The upper fixed plate and the lower fixed plate are detachably connected together.

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