Coumarin hydrazide condensate modified ruthenium complex photosensitizer for photocatalytic hydrogen production and preparation method thereof

Abstract

The invention belongs to the technical field of photosensitizers, and particularly relates to a coumarin hydrazide condensate modified ruthenium complex photosensitizer for photocatalytic hydrogen production and a preparation method of the ruthenium complex photosensitizer. The preparation method sequentially comprises the following steps: a step of synthesizing 7-diethylamino coumarin-3-carboxylic acid ethyl ester, a step of synthesizing 7-diethylamino coumarin-3-hydrazide, a step of preparing a coumarin hydrazide condensation compound, a step of chemically modifying a ruthenium complex by the coumarin hydrazide condensation compound, and a step of applying a photosensitizer to photocatalytic hydrogen production. Compared with an existing traditional tris (2, 2 '-bipyridine) ruthenium (II) photosensitizer, the coumarin hydrazide condensate modified ruthenium complex photosensitizer has the advantages of being simple in synthesis method, high in purity, economical and environmentally friendly in preparation process, good in light absorption performance, stable and lasting in photocatalysis and the like, the cost can be saved, and the photocatalytic hydrogen production performance can be greatly improved.

Description

Technical Field

[0001] The invention belongs to the technical field of photosensitizers, and particularly relates to a ruthenium complex photosensitizer modified by a coumarin hydrazide condensate for photocatalytic hydrogen production and a preparation method thereof. Background Art

[0002] In 1979, French scholar Lehn first reported the tris(2,2'-bipyridine)ruthenium(II) photosensitizer, thus opening a new chapter in the research of complex-based photosensitizers. In the subsequent research process, tris(2,2'-bipyridine)ruthenium(II) and its derivatives quickly emerged and became classic model compounds for evaluating the performance of complex photocatalytic hydrogen production materials. Many researchers have carried out a large number of experimental and theoretical explorations around it, deeply analyzed its mechanism of action in the process of photocatalytic hydrogen production, and tried to explore its potential from various angles.

[0003] However, it cannot be ignored that tris(2,2'-bipyridine)ruthenium(II) itself has some significant defects. Tris(2,2'-bipyridine)ruthenium(II) has poor photostability. Under light conditions, its molecular structure is easily disturbed by external factors and changes, making it difficult to maintain a stable photoactive state for a long time. At the same time, the excited state lifetime of tris(2,2'-bipyridine)ruthenium(II) is also extremely short, which means that after light excitation, the time window in which it can effectively participate in the photocatalytic reaction is very narrow, greatly limiting its full utilization of light energy and the improvement of photocatalytic hydrogen production performance. These shortcomings are like barriers that hinder the development of photocatalytic hydrogen production technology towards a more efficient and stable direction, and researchers are in urgent need of seeking effective improvement strategies.

[0004] Photosensitizers play a pivotal role in the entire photocatalytic system. They are like a key bridge, taking on the important mission of electron transfer between sacrificial electron donors and photocatalysts. When light irradiates the photosensitizer, the photosensitizer molecules absorb photon energy and transition from the ground state to the excited state. The photosensitizer in the excited state has strong oxidizing properties and can quickly seize electrons from the sacrificial electron donor and be reduced itself. Subsequently, the reduced photosensitizer transfers electrons to the photocatalyst, thereby initiating a series of photocatalytic reactions. Moreover, the photosensitizer is also the main body of light capture, and its light absorption capacity and range directly affect the amount of light energy that can be utilized by the entire photocatalytic system. Therefore, improving the performance of tri(2,2'-bipyridine)ruthenium(II) and its derivatives has far-reaching significance for enhancing the photocatalytic hydrogen production performance and promoting the practical application of photocatalytic technology. Summary of the invention

[0005] The object of the present invention is to solve the above problems, overcome the significant defects existing when tris(2,2'-bipyridine)ruthenium(II) and its derivatives are used as photosensitizers, utilize the excellent photophysical properties of coumarin and its derivatives and the antenna effect of absorbing visible light, design and stepwise prepare a coumarin hydrazide condensate, and then chemically modify Ru(bpy)2Cl2·2H2O to obtain a ruthenium complex photosensitizer modified with coumarin hydrazide condensate for photocatalytic hydrogen production, and its chemical structural formula is as Figure 1 shown. The ruthenium complex photosensitizer modified with coumarin hydrazide condensate of the present invention has the advantages of simple synthesis method, environmentally friendly and economical preparation process, high purity, good light absorption performance, stable and persistent photocatalysis, etc., realizes a significant improvement in photocatalytic hydrogen production performance, and has good market application prospects.

[0006] The preparation technical route of the photosensitizer of the present invention is as Figure 2 shown. Ethyl 7-diethylaminocoumarin-3-carboxylate is synthesized from 4-diethylamino-2-hydroxybenzaldehyde and diethyl malonate, then reacted with hydrazine hydrate to obtain 7-diethylaminocoumarin-3-hydrazide, and then reacted with 4'-methyl-2,2'-bipyridine-4-carboxaldehyde to obtain coumarin hydrazide condensate cmrbpy, and finally reacted with Ru(bpy)2Cl2·2H2O to obtain a ruthenium complex photosensitizer modified with coumarin hydrazide condensate.

[0007] The technical solution of the present invention is realized according to the following steps:

[0008] A preparation method of a ruthenium complex photosensitizer modified with coumarin hydrazide condensate for photocatalytic hydrogen production, characterized by comprising the following steps:

[0009] (1) Synthesize ethyl 7-diethylaminocoumarin-3-carboxylate: Dissolve 4-diethylamino-2-hydroxybenzaldehyde and diethyl malonate in a solvent, heat under reflux, and remove the solvent to obtain ethyl 7-diethylaminocoumarin-3-carboxylate;

[0010] (2) Synthesize 7-diethylaminocoumarin-3-hydrazide: Dissolve the ethyl 7-diethylaminocoumarin-3-carboxylate obtained in step (1) and hydrazine hydrate in a solvent, react and then cool, filter and separate to obtain 7-diethylaminocoumarin-3-hydrazide;

[0011] (3) Prepare coumarin hydrazide condensate: Dissolve the 7-diethylaminocoumarin-3-hydrazide obtained in step (2) and 4'-methyl-2,2'-bipyridine-4-carboxaldehyde in a solvent, heat under reflux, cool and filter to obtain a condensate of 4'-methyl-2,2'-bipyridine-4-carboxaldehyde and 7-diethylaminocoumarin-3-hydrazide, and this coumarin hydrazide condensate is abbreviated as cmrbpy;

[0012] (4) Preparation of a ruthenium complex photosensitizer modified with a coumarin hydrazide condensate: Use cmrbpy in step (3) to modify the ruthenium complex to obtain a ruthenium complex photosensitizer modified with a coumarin hydrazide condensate;

[0013] (5) Use the ruthenium complex photosensitizer modified with a coumarin hydrazide condensate in step (4) for photocatalytic hydrogen production.

[0014] The specific method for synthesizing ethyl 7-diethylaminocoumarin-3-carboxylate in step (1) is as follows: 2.0 - 7.0 g of 4-diethylamino-2-hydroxybenzaldehyde and 3.0 - 13.0 g of diethyl malonate are dissolved in 50 - 500 mL of absolute ethanol, then 1.0 - 5.0 mL of piperidine is added, and the mixture is heated in a water bath to 85 - 95 °C and refluxed for 5 - 12 h; after cooling to room temperature, the solvent absolute ethanol is removed by rotary evaporation at 50 - 55 °C to obtain a yellow oil, ethyl 7-diethylaminocoumarin-3-carboxylate, which is directly used in the next synthesis reaction without purification.

[0015] The specific method for synthesizing 7-diethylaminocoumarin-3-hydrazide in step (2) is as follows: 2.0 - 8.0 g of ethyl 4-diethylaminocoumarin-3-carboxylate and 2.0 - 8.0 mL of hydrazine hydrate are dissolved in 25 - 250 mL of absolute ethanol, and the mixture is magnetically stirred at 300 - 600 rpm at room temperature for 10 - 20 min, then cooled in an ice bath for 10 - 30 min until an orange solid is completely formed, and the crude product is obtained by filtration at atmospheric pressure and separated by column chromatography to obtain 7-diethylaminocoumarin-3-hydrazide. Preferably, the eluent used in the column chromatography separation is petroleum ether / ethyl acetate at a ratio of 2:1.

[0016] The specific synthesis method of cmrbpy in step (3) is as follows: 0.2 - 2.0 g of 7-diethylaminocoumarin-3-hydrazide and 0.1 - 1.0 g of 4'-methyl-2,2'-bipyridine-4-carboxaldehyde are dissolved in 50 - 500 mL of a solvent, and the solvent can be any one of absolute ethanol, absolute methanol, and dichloromethane; 1 - 5 drops of glacial acetic acid are added as a catalyst, and the mixture is heated in a water bath to 45 - 85 °C and refluxed for 8 - 20 h; after naturally cooling to room temperature, until a yellow solid completely precipitates, filtration is carried out at atmospheric pressure to obtain a yellow powdery condensate cmrbpy.

[0017] The specific method for preparing the ruthenium complex photosensitizer modified with coumarin hydrazide condensate in step (4) is as follows: 0.2 - 2.0 g of cmrbpy and 0.2 - 2.0 g of Ru(bpy)2Cl2·2H2O are dissolved in 50 - 500 mL of absolute ethanol, heated in a water bath to 85 - 95 °C under a nitrogen atmosphere, and refluxed for 5 - 16 h; naturally cooled to room temperature and filtered under normal pressure; at room temperature, 10 - 20 mL of 10 - 15% aqueous NH4PF6 solution is added dropwise to the filtrate at a rate of 60 - 100 drops / min with magnetic stirring at 300 - 600 rpm for 10 - 20 min until the formation of red solid is complete, and then filtered under reduced pressure using a Buchner funnel to obtain the crude photosensitizer; the crude photosensitizer is dissolved in 0.5 - 1.5 mL of acetonitrile, transferred to a cylindrical glass bottle with a volume of 5 mL, the bottle mouth is sealed with a polyethylene film, and 1 small hole is punctured on the film with a fine needle; then the glass bottle is placed in a wide-mouth bottle, 5 - 10 mL of ether is added to the bottom of the wide-mouth bottle, the bottle mouth of the wide-mouth bottle is sealed with a glass stopper, and needle-shaped crystals are obtained by the ether vapor diffusion method at a low temperature of -5 - -10 °C; the needle-shaped crystals are dissolved in 0.5 - 1.5 mL of N,N-dimethylformamide, transferred to a cylindrical glass bottle with a volume of 5 mL, the bottle mouth is sealed with a polyethylene film with 1 small hole punctured; then the glass bottle is placed in a wide-mouth bottle, 5 - 10 mL of ether is added to the bottom of the wide-mouth bottle, the bottle mouth of the wide-mouth bottle is sealed with a glass stopper, and block-shaped crystals [Ru(bpy)2(cmrbpy)] are obtained by the ether vapor diffusion method again at a low temperature of -5 - -10 °C 2+ , [Ru(bpy)2(cmrbpy)] 2+ is the ruthenium complex photosensitizer modified with coumarin hydrazide condensate.

[0018] The steps of using the ruthenium complex photosensitizer modified with coumarin hydrazide condensate for photocatalytic hydrogen production in step (5) include: adding the photosensitizer [Ru(bpy)2(cmrbpy)] to a quartz glass reactor 2+, photocatalyst [Co(dmgH)2pyCl] and electron sacrificial reductant N,N-dimethyl-p-toluidine, with the solvent being acetonitrile or an acetonitrile / water mixture; nitrogen is charged and discharged in the reactor to ensure the reaction proceeds in an inert atmosphere; then a xenon lamp is used to simulate sunlight to irradiate the reaction system. A 400 nm cut-off filter is equipped on the xenon light source to remove ultraviolet light; an airtight syringe is used to extract the gas at the head of the reactor and inject it into an Agilent 7890A gas chromatograph for off-line detection of the hydrogen content. According to the peak position and peak integration area, hydrogen can be separated and detected, as well as its content. High-purity nitrogen is introduced into the gas chromatograph as the carrier gas. The chromatographic column is a PORAPAK Q column with a length of 3 m, an inner diameter of 2 mm, and the column packing is stainless steel with a mesh size of 80-100. The detector is a TCD thermal conductivity detector. The hydrogen production amount is measured every 60 minutes, and each round of testing lasts for more than 600 minutes; before detecting hydrogen, high-purity hydrogen is first used to detect on the chromatographic column to make a standard curve to quantify the hydrogen production amount in subsequent photocatalytic experiments; a linear fit is performed on the standard curve, and the regression equation obtained is y = 140352x - 504.53, with a standard deviation of 99.979%. The optimized hydrogen production scheme obtained is: [Ru(bpy)2(cmrbpy)] 2+ The concentration of -4 is 1.00×10 -1 mol·L - 3 , the concentration of [Co(dmgH)2pyCl] is 1.00×10 -1 , and the concentration of N,N-dimethyl-p-toluidine is 5.00×10 -2 mol·L -1 , and the solvent is a 1:1 acetonitrile / water mixture.

[0019] A ruthenium complex photosensitizer modified with coumarin hydrazone condensate for photocatalytic hydrogen production. It has strong absorption in the visible light region, exhibits good photocatalytic water splitting hydrogen production performance under visible light, has good hydrogen production activity, and still maintains good catalytic efficiency in long-term stability tests.

[0020] The present invention has the following beneficial effects: The present invention provides a preparation method of a ruthenium complex photosensitizer modified with a coumarin hydrazide condensate for photocatalytic hydrogen production. By utilizing the excellent photophysical properties and antenna effect of visible light absorption of coumarin and its derivatives, a coumarin hydrazide condensate is prepared, and then Ru(bpy)2Cl2·2H2O is chemically modified to obtain a ruthenium complex photosensitizer modified with a coumarin hydrazide condensate for photocatalytic hydrogen production. The ruthenium complex photosensitizer modified with a coumarin hydrazide condensate of the present invention has the advantages of high purity, good light absorption performance, stable and persistent photocatalysis, etc., realizing a significant improvement in photocatalytic hydrogen production performance, so it can solve the technical bottlenecks of poor light stability, extremely short excited state lifetime, short participation time and low efficiency in photocatalytic reactions of existing tris(2,2'-bipyridine) ruthenium(II) photosensitizers. In addition, the synthesis method of the present invention is simple, the energy consumption of the preparation process is low, it is green and environmentally friendly and relatively easy, thereby improving the productivity and further reducing the production cost, and has good market application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0022] Figure 1 It is a schematic structural diagram of a ruthenium complex photosensitizer modified with a coumarin hydrazide condensate.

[0023] Figure 2 It is a preparation route diagram of a ruthenium complex photosensitizer modified with a coumarin hydrazide condensate.

[0024] Figure 3 It is the 1H NMR spectrum of the coumarin hydrazide condensate cmrbpy.

[0025] Figure 4 It is the 13C NMR spectrum of the coumarin hydrazide condensate cmrbpy.

[0026] Figure 5 It is a single crystal structure diagram of a ruthenium complex photosensitizer modified with a coumarin hydrazide condensate.

[0027] Figure 6 It is an ultraviolet-visible absorption spectrum diagram of a ruthenium complex photosensitizer modified with a coumarin hydrazide condensate. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] Next, in combination with the embodiments of the present invention, the technical solutions of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0029] Embodiment 1

[0030] A preparation method of a ruthenium complex photosensitizer modified with a coumarin hydrazide condensate for photocatalytic hydrogen production, characterized by comprising the following steps:

[0031] (1) Synthesize ethyl 7-diethylaminocoumarin-3-carboxylate: Dissolve 4-diethylamino-2-hydroxybenzaldehyde and diethyl malonate in a solvent, heat under reflux, and remove the solvent to obtain ethyl 7-diethylaminocoumarin-3-carboxylate;

[0032] (2) Synthesize 7-diethylaminocoumarin-3-hydrazide: Dissolve the ethyl 7-diethylaminocoumarin-3-carboxylate obtained in step (1) and hydrazine hydrate in a solvent, react and then cool, filter and separate to obtain 7-diethylaminocoumarin-3-hydrazide;

[0033] (3) Prepare a coumarin hydrazide condensate: Dissolve the 7-diethylaminocoumarin-3-hydrazide obtained in step (2) and 4'-methyl-2,2'-bipyridine-4-carbaldehyde in a solvent, heat under reflux, and after cooling and filtering, obtain a condensate of 4'-methyl-2,2'-bipyridine-4-carbaldehyde and 7-diethylaminocoumarin-3-hydrazide, which is abbreviated as cmrbpy;

[0034] (4) Prepare a ruthenium complex photosensitizer modified with a coumarin hydrazide condensate: Use the cmrbpy in step (3) to modify the ruthenium complex to obtain a ruthenium complex photosensitizer modified with a coumarin hydrazide condensate;

[0035] (5) Use the ruthenium complex photosensitizer modified with a coumarin hydrazide condensate in step (4) for photocatalytic hydrogen production.

[0036] The specific method for synthesizing ethyl 7-diethylaminocoumarin-3-carboxylate in step (1) is to dissolve 2.0 g of 4-diethylamino-2-hydroxybenzaldehyde and 3.0 g of diethyl malonate in 50 mL of absolute ethanol, then add 1.0 mL of piperidine, heat in a water bath to 85 °C, and reflux for 5 h; after cooling to room temperature, rotary evaporate to remove the solvent absolute ethanol at 50 °C to obtain a yellow oil, ethyl 7-diethylaminocoumarin-3-carboxylate, which is directly used for the next synthesis reaction without purification.

[0037] The specific method for synthesizing 7-diethylaminocoumarin-3-carbohydrazide in step (2) is as follows: 2.0 g of ethyl 4-diethylaminocoumarin-3-carboxylate and 2.0 mL of hydrazine hydrate are dissolved in 25 mL of absolute ethanol. At room temperature, the reaction is magnetically stirred at 300 rpm for 10 min, and then cooled in an ice bath for 10 min until an orange solid is completely formed. The crude product is obtained by normal pressure filtration using a glass funnel and filter paper, and 7-diethylaminocoumarin-3-carbohydrazide is obtained by column chromatography. The eluent used in column chromatography is petroleum ether / ethyl acetate at a ratio of 2:1.

[0038] The specific synthesis method of cmrbpy in step (3) is as follows: 0.2 g of 7-diethylaminocoumarin-3-carbohydrazide and 0.1 g of 4'-methyl-2,2'-bipyridine-4-carbaldehyde are dissolved in 50 mL of absolute ethanol; 1 drop of glacial acetic acid is added as a catalyst, and the mixture is heated in a water bath to 85 °C and refluxed for 8 h; after natural cooling to room temperature, until a yellow solid is completely precipitated, normal pressure filtration is carried out using a glass funnel and filter paper to obtain a yellow powdery condensate cmrbpy. The 1H NMR and 13C NMR spectra of cmrbpy are as Figure 3 、 Figure 4 shown. In the 1H NMR spectrum, the triplet with a chemical shift of 1.30 is attributed to 6 hydrogen atoms of the methyl group in the diethylamino group, the quartet with a chemical shift of 3.49 is attributed to 4 hydrogen atoms of the methylene group in the diethylamino group, the singlet with a chemical shift of 2.48 is attributed to 3 hydrogen atoms of the methyl group on the bipyridine ring, the singlet with a chemical shift of 12.11 is attributed to 1 hydrogen atom on the carbohydrazide bond, the singlet with a chemical shift of 8.59 is attributed to 1 hydrogen atom on the imine bond, the peak signals with chemical shifts of 6.55, 6.70 and 7.51 are respectively attributed to 3 hydrogen atoms on the benzene ring of coumarin, the singlet signal with a chemical shift of 8.32 is attributed to 1 hydrogen atom on the lactone ring of coumarin, and the peak signals with chemical shifts of 8.88, 8.75, 8.62, 8.26, 7.92 and 7.18 are attributed to 6 hydrogen atoms on the bipyridine ring, indicating the successful preparation of the coumarin carbohydrazide condensate.

[0039] The specific method for preparing the coumarin hydrazide condensate-modified ruthenium complex photosensitizer in step (4) is as follows: 0.2 g of cmrbpy and 0.2 g of Ru(bpy)2Cl2·2H2O are dissolved in 50 mL of absolute ethanol. Under a nitrogen atmosphere, the mixture is heated in a water bath to 85 °C and refluxed for 5 h. It is then naturally cooled to room temperature and filtered under normal pressure. At room temperature, 10 mL of 10% NH4PF6 aqueous solution is added dropwise to the filtrate at a rate of 60 drops / min using a burette, and the mixture is magnetically stirred at 300 rpm for 10 min until the formation of red solid is complete. Vacuum filtration is carried out using a Buchner funnel to obtain the crude photosensitizer. The crude photosensitizer is dissolved in 1 mL of acetonitrile, transferred to a cylindrical glass bottle with a volume of 5 mL, and the bottle mouth is sealed with a polyethylene film. A small hole is pricked in the film with a fine needle. Then the glass bottle is placed in a wide-mouth bottle, 5 mL of ether is added to the bottom of the wide-mouth bottle, and the mouth of the wide-mouth bottle is sealed with a glass stopper. Needle-shaped crystals are obtained by the ether vapor diffusion method at a low temperature of -5 °C. The needle-shaped crystals are dissolved in 1 mL of N,N-dimethylformamide, transferred to a cylindrical glass bottle with a volume of 5 mL, and the bottle mouth is sealed with a polyethylene film with a small hole pricked in it. Then the glass bottle is placed in a wide-mouth bottle, 5 mL of ether is added to the bottom of the wide-mouth bottle, and the mouth of the wide-mouth bottle is sealed with a glass stopper. Block-shaped crystals [Ru(bpy)2(cmrbpy)] are obtained again by the ether vapor diffusion method at a low temperature of -5 °C. 2+ , [Ru(bpy)2(cmrbpy)] 2+ is the coumarin hydrazide condensate-modified ruthenium complex photosensitizer. It is confirmed by X-ray diffraction experiment that the block-shaped crystals [Ru(bpy)2(cmrbpy)] 2+ are single crystals. The crystal structure is as Figure 5 shown. The photosensitizer crystallizes in the C2 / c space group. One ether solvent molecule, one water molecule and two hexafluorophosphate ions in the asymmetric unit are omitted. The ruthenium ion has a distorted octahedral coordination environment and coordinates with six nitrogen atoms from two 2,2'-bipyridines and the organic precursor molecule.

[0040] The steps of using the coumarin hydrazide condensate-modified ruthenium complex photosensitizer for photocatalytic hydrogen production in step (5) include: adding three components for photocatalysis, namely the photosensitizer [Ru(bpy)2(cmrbpy)] 2+ , the photocatalyst [Co(dmgH)2pyCl] and the electron sacrificial reducing agent N,N-dimethyl-p-toluidine, to a 300 mL quartz glass reactor. Then, a 1:1 acetonitrile / water mixture is added as the solvent, so that the concentrations of the three components are 1.00×10 -4 mol·L -1 , 1.00×10 -3 mol·L -1 and 5.00×10 -2 mol·L-1 ; Before the reaction, N2 was charged into the reactor to remove the influence of oxygen, so that the reaction proceeded in an inert atmosphere. A 300W xenon lamp was used to simulate sunlight to irradiate the reaction system, and a 400nm cut-off filter was equipped on the xenon light source to remove ultraviolet light. An airtight needle was used to extract the gas at the head of the reactor and injected into an Agilent 7890A gas chromatograph to detect the hydrogen content in an off-line manner. The activity and efficiency of the photosensitizer prepared in this scheme in the photocatalytic hydrogen production experiment were obtained according to the peak position, peak integration area and standard curve. On the premise of the self-decomposition of the photocatalyst [Co(dmgH)2pyCl], the photosensitizer prepared in this scheme can still maintain the hydrogen production activity for 7.5 hours. In the 7.5-hour hydrogen production experiment, the turnover number TON and turnover frequency TOF of hydrogen production obtained were 347 mol·mol PS -1 and 0.77 mol·mol PS -1 ·min -1 ; Under the same conditions, in the hydrogen production control experiment of tris(2,2'-bipyridine)ruthenium(II), the TON and TOF were 60 mol·mol PS -1 and 0.50 mol·mol PS -1 ·min -1 , and its photo-stability could only be maintained for 2 hours.

[0041] A ruthenium complex photosensitizer modified with coumarin hydrazide condensate for photocatalytic hydrogen production, which has strong absorption in the visible light region, exhibits good photocatalytic water splitting hydrogen production performance under visible light, has good hydrogen production activity, and still maintains good catalytic efficiency in long-term stability tests.

[0042] Example 2

[0043] A preparation method of a ruthenium complex photosensitizer modified with coumarin hydrazide condensate for photocatalytic hydrogen production, which is characterized by including the following steps:

[0044] (1) Synthesize ethyl 7-diethylaminocoumarin-3-carboxylate: Dissolve 4-diethylamino-2-hydroxybenzaldehyde and diethyl malonate in a solvent, heat under reflux, and remove the solvent to obtain ethyl 7-diethylaminocoumarin-3-carboxylate;

[0045] (2) Synthesize 7-diethylaminocoumarin-3-hydrazide: Dissolve the ethyl 7-diethylaminocoumarin-3-carboxylate obtained in step (1) and hydrazine hydrate in a solvent, react and then cool, filter and separate to obtain 7-diethylaminocoumarin-3-hydrazide;

[0046] (3) Preparation of coumarin hydrazide condensate: Dissolve 7 - diethylaminocoumarin - 3 - hydrazide from step (2) and 4'-methyl - 2,2'-bipyridine - 4 - carbaldehyde in a solvent, heat under reflux, and after cooling and filtration, obtain the condensate of 4'-methyl - 2,2'-bipyridine - 4 - carbaldehyde and 7 - diethylaminocoumarin - 3 - hydrazide. This coumarin hydrazide condensate is abbreviated as cmrbpy;

[0047] (4) Preparation of ruthenium complex photosensitizer modified with coumarin hydrazide condensate: Use cmrbpy from step (3) to modify the ruthenium complex to obtain a ruthenium complex photosensitizer modified with coumarin hydrazide condensate;

[0048] (5) Use the ruthenium complex photosensitizer modified with coumarin hydrazide condensate from step (4) for photocatalytic hydrogen production.

[0049] The specific method for synthesizing ethyl 7 - diethylaminocoumarin - 3 - carboxylate in step (1) is as follows: Dissolve 3.9 g of 4 - diethylamino - 2 - hydroxybenzaldehyde and 6.4 g of diethyl malonate in 100 mL of absolute ethanol, then add 2.0 mL of piperidine, heat in a water bath to 90 °C, and reflux for 6 h; after cooling to room temperature, rotary evaporate the solvent absolute ethanol at 55 °C to obtain a yellow oil, ethyl 7 - diethylaminocoumarin - 3 - carboxylate, which is directly used for the next synthesis reaction without purification.

[0050] The specific method for synthesizing 7 - diethylaminocoumarin - 3 - hydrazide in step (2) is as follows: Dissolve 4.3 g of ethyl 4 - diethylaminocoumarin - 3 - carboxylate and 3.6 mL of hydrazine hydrate in 50 mL of absolute ethanol, stir magnetically at 500 rpm at room temperature for 20 min, then cool in an ice bath for 15 min until an orange - yellow solid is completely formed, filter under atmospheric pressure using a glass funnel and filter paper to obtain a crude product, and separate 7 - diethylaminocoumarin - 3 - hydrazide by column chromatography. The eluent preferably used for column chromatography is 2:1 petroleum ether / ethyl acetate.

[0051] The specific synthesis method of cmrbpy in step (3) is as follows: Dissolve 0.5 g of 7 - diethylaminocoumarin - 3 - hydrazide and 0.3 g of 4'-methyl - 2,2'-bipyridine - 4 - carbaldehyde in 100 mL of absolute ethanol; add 2 drops of glacial acetic acid as a catalyst, heat in a water bath to 85 °C, and reflux for 12 h; after natural cooling to room temperature, until a yellow solid completely precipitates, filter under atmospheric pressure using a glass funnel and filter paper to obtain a yellow powdery condensate cmrbpy.

[0052] The specific method for preparing the coumarin hydrazide condensate-modified ruthenium complex photosensitizer in step (4) is as follows: 0.5 g of cmrbpy and 0.6 g of Ru(bpy)2Cl2·2H2O are dissolved in 100 mL of absolute ethanol. Under a nitrogen atmosphere, the solution is heated in a water bath to 92 °C and refluxed for 8 h. It is then naturally cooled to room temperature and filtered under normal pressure. At room temperature, 16 mL of a 13% aqueous NH4PF6 solution is added dropwise to the filtrate at a rate of 60 - 100 drops / min using a burette, and the mixture is stirred magnetically at 500 rpm for 20 min until the formation of red solid is complete. The crude photosensitizer is obtained by vacuum filtration using a Buchner funnel. The crude photosensitizer is dissolved in 0.5 mL of acetonitrile, transferred to a cylindrical glass bottle with a volume of 5 mL, and the bottle mouth is sealed with a polyethylene film. A small hole is pricked in the film with a fine needle. Then the glass bottle is placed in a wide-mouth bottle, 6 mL of ether is added to the bottom of the wide-mouth bottle, and the mouth of the wide-mouth bottle is sealed with a glass stopper. Needle-shaped crystals are obtained by the ether vapor diffusion method at a low temperature of -10 °C. The needle-shaped crystals are dissolved in 1 mL of N,N-dimethylformamide, transferred to a cylindrical glass bottle with a volume of 5 mL, and the bottle mouth is sealed with a polyethylene film with a small hole pricked in it. Then the glass bottle is placed in a wide-mouth bottle, 8 mL of ether is added to the bottom of the wide-mouth bottle, and the mouth of the wide-mouth bottle is sealed with a glass stopper. Block-shaped crystals [Ru(bpy)2(cmrbpy)] are obtained again by the ether vapor diffusion method at a low temperature of -8 °C 2+ , [Ru(bpy)2(cmrbpy)] 2+ is the coumarin hydrazide condensate-modified ruthenium complex photosensitizer. It is confirmed by X-ray diffraction experiments that the block-shaped crystals [Ru(bpy)2(cmrbpy)] 2+ are single crystals

[0053] The steps for using the coumarin hydrazide condensate-modified ruthenium complex photosensitizer in photocatalytic hydrogen production in step (5) include: adding three components for photocatalysis to a 300 mL quartz glass reactor: the photosensitizer [Ru(bpy)2(cmrbpy)] 2+ , the photocatalyst [Co(dmgH)2pyCl], and the electron sacrificial reducing agent N,N-dimethyl-p-toluidine. Then, a 1:1 acetonitrile / water mixture is added as a solvent, so that the concentrations of the three components are 1.00×10 -4 mol·L -1 , 1.00×10 -3 mol·L -1 and 5.00×10 -2 mol·L -1; Before the reaction, N2 was charged into the reactor to remove the influence of oxygen, so that the reaction was carried out in an inert atmosphere; A 300W xenon lamp was used to simulate sunlight to irradiate the reaction system, and a 400nm cut-off filter was equipped on the xenon light source to remove ultraviolet light. An airtight needle was used to extract the gas at the head of the reactor and injected into an Agilent 7890A gas chromatograph to detect the hydrogen content in an offline manner. The activity and efficiency of the photosensitizer prepared by this scheme in the photocatalytic hydrogen production experiment were obtained according to the peak position, peak integration area and standard curve. On the premise of the self-decomposition of the photocatalyst [Co(dmgH)2pyCl], the photosensitizer prepared by this scheme can still maintain the hydrogen production activity for 8 hours. In the 8-hour hydrogen production experiment, the turnover number TON and turnover frequency TOF of hydrogen production obtained were 390 mol·mol PS -1 and 0.80 mol·mol PS -1 ·min -1 ; Under the same conditions, in the hydrogen production control experiment of tris(2,2'-bipyridine)ruthenium(II), the TON and TOF were 60 mol·mol PS -1 and 0.50 mol·mol PS -1 ·min -1 , and its photostability could only be maintained for 2 hours.

[0054] A ruthenium complex photosensitizer modified with coumarin hydrazide condensate for photocatalytic hydrogen production has strong absorption in the visible light region. As Figure 6 shown, the molar extinction coefficient ε at 450nm is 50000 L·mol -1 ·cm -1 , which is 3 times higher than that of the model complex tris(2,2'-bipyridine)ruthenium(II); It shows good photocatalytic water splitting hydrogen production performance under visible light, has good hydrogen production activity, and still maintains good catalytic efficiency in long-term stability tests.

[0055] Example 3

[0056] A preparation method of a ruthenium complex photosensitizer modified with coumarin hydrazide condensate for photocatalytic hydrogen production, which is characterized by including the following steps:

[0057] (1) Synthesize ethyl 7-diethylaminocoumarin-3-carboxylate: Dissolve 4-diethylamino-2-hydroxybenzaldehyde and diethyl malonate in a solvent, heat under reflux, and remove the solvent to obtain ethyl 7-diethylaminocoumarin-3-carboxylate;

[0058] (2) Synthesis of 7 - diethylaminocoumarin - 3 - hydrazide: Dissolve ethyl 7 - diethylaminocoumarin - 3 - carboxylate from step (1) and hydrazine hydrate in a solvent, cool the reaction mixture after reaction, and filter and separate to obtain 7 - diethylaminocoumarin - 3 - hydrazide;

[0059] (3) Preparation of coumarin hydrazide condensate: Dissolve 7 - diethylaminocoumarin - 3 - hydrazide from step (2) and 4’ - methyl - 2,2’ - bipyridine - 4 - carbaldehyde in a solvent, heat under reflux, cool and filter to obtain the condensate of 4’ - methyl - 2,2’ - bipyridine - 4 - carbaldehyde and 7 - diethylaminocoumarin - 3 - hydrazide, and this coumarin hydrazide condensate is abbreviated as cmrbpy;

[0060] (4) Preparation of ruthenium complex photosensitizer modified by coumarin hydrazide condensate: Use cmrbpy from step (3) to modify the ruthenium complex to obtain the ruthenium complex photosensitizer modified by coumarin hydrazide condensate;

[0061] (5) Use the ruthenium complex photosensitizer modified by coumarin hydrazide condensate in step (4) for photocatalytic hydrogen production.

[0062] The specific method for synthesizing ethyl 7 - diethylaminocoumarin - 3 - carboxylate in step (1) is as follows: Dissolve 7.0 g of 4 - diethylamino - 2 - hydroxybenzaldehyde and 13.0 g of diethyl malonate in 500 mL of absolute ethanol, add 5.0 mL of piperidine, heat in a water bath to 95 °C, and reflux for 12 h; after cooling to room temperature, rotary evaporate the solvent absolute ethanol at 55 °C to obtain a yellow oily substance, ethyl 7 - diethylaminocoumarin - 3 - carboxylate, which is directly used for the next - step synthesis reaction without purification.

[0063] The specific method for synthesizing 7 - diethylaminocoumarin - 3 - hydrazide in step (2) is as follows: Dissolve 8.0 g of ethyl 4 - diethylaminocoumarin - 3 - carboxylate and 8.0 mL of hydrazine hydrate in 250 mL of absolute ethanol, stir magnetically at 600 rpm at room temperature for 20 min, then cool in an ice bath for 30 min until an orange - yellow solid is completely formed, filter under atmospheric pressure using a glass funnel and filter paper to obtain the crude product, and separate by column chromatography to obtain 7 - diethylaminocoumarin - 3 - hydrazide. The eluent used during column chromatography separation is petroleum ether / ethyl acetate at a ratio of 2:1.

[0064] The specific synthesis method of cmrbpy in step (3) is as follows: Dissolve 2.0 g of 7 - diethylaminocoumarin - 3 - hydrazide and 1.0 g of 4’ - methyl - 2,2’ - bipyridine - 4 - carbaldehyde in 500 mL of absolute methanol; add 5 drops of glacial acetic acid as a catalyst, heat in a water bath to 75 °C, and reflux for 20 h; after naturally cooling to room temperature until a yellow solid completely precipitates, filter under atmospheric pressure using a glass funnel and filter paper to obtain the yellow powdery condensate cmrbpy.

[0065] The specific method for preparing the coumarin hydrazide condensate-modified ruthenium complex photosensitizer in step (4) is as follows: 2.0 g of cmrbpy and 2.0 g of Ru(bpy)2Cl2·2H2O are dissolved in 500 mL of absolute ethanol, and the mixture is heated under reflux at 95 °C in a nitrogen atmosphere for 16 h; it is naturally cooled to room temperature and filtered under normal pressure; at room temperature, 20 mL of 15% aqueous NH4PF6 solution is added dropwise to the filtrate at a rate of 100 drops / min with a burette, and the mixture is magnetically stirred at 600 rpm for 20 min until the formation of a red solid is complete. Then, suction filtration is carried out using a Buchner funnel to obtain the crude photosensitizer; the crude photosensitizer is dissolved in 1.5 mL of acetonitrile, transferred to a cylindrical glass bottle with a volume of 5 mL, and the bottle mouth is sealed with a polyethylene film, and 1 small hole is pricked in the film with a fine needle; then the glass bottle is placed in a wide-mouth bottle, 10 mL of ether is added to the bottom of the wide-mouth bottle, and the bottle mouth of the wide-mouth bottle is sealed with a glass stopper. Needle-shaped crystals are obtained by the ether vapor diffusion method at a low temperature of -8 °C; the needle-shaped crystals are dissolved in 1.5 mL of N,N-dimethylformamide, transferred to a cylindrical glass bottle with a volume of 5 mL, and the bottle mouth is sealed with a polyethylene film with 1 small hole pricked; then the glass bottle is placed in a wide-mouth bottle, 10 mL of ether is added to the bottom of the wide-mouth bottle, and the bottle mouth of the wide-mouth bottle is sealed with a glass stopper. Block-shaped crystals [Ru(bpy)2(cmrbpy)] are obtained again by the ether vapor diffusion method at a low temperature of -10 °C 2+ , [Ru(bpy)2(cmrbpy)] 2+ is the coumarin hydrazide condensate-modified ruthenium complex photosensitizer. It is confirmed by X-ray diffraction experiments that the block-shaped crystals [Ru(bpy)2(cmrbpy)] 2+ are single crystals.

[0066] The steps for using the coumarin hydrazide condensate-modified ruthenium complex photosensitizer in photocatalytic hydrogen production in step (5) include: adding three components for photocatalysis to a 300 mL quartz glass reactor: the photosensitizer [Ru(bpy)2(cmrbpy)] 2+ , the photocatalyst [Co(dmgH)2pyCl], and the electron sacrificial reductant N,N-dimethyl-p-toluidine. Then, a 1:1 acetonitrile / water mixture is added as a solvent to make the concentrations of the three components 1.00×10 -4 mol·L -1 , 1.00×10 -3 mol·L -1 and 5.00×10 -2 mol·L -1; Before the reaction, N2 was charged into the reactor to remove the influence of oxygen, so that the reaction proceeded in an inert atmosphere; a 300W xenon lamp was used to simulate sunlight to irradiate the reaction system, and a 400nm cut-off filter was equipped on the xenon light source to remove ultraviolet light. An airtight needle was used to extract the gas at the head of the reactor and injected into an Agilent 7890A gas chromatograph to detect the hydrogen content in an off-line manner. The activity and efficiency of the photosensitizer prepared by this scheme in the photocatalytic hydrogen production experiment were obtained according to the peak position, peak integration area and standard curve. On the premise that the photocatalyst [Co(dmgH)2pyCl] decomposed itself, the photosensitizer prepared by this scheme could still maintain the hydrogen production activity for 7.8 hours. In the 7.8-hour hydrogen production experiment, the turnover number TON and turnover frequency TOF of hydrogen production obtained were 380 mol·mol PS -1 and 0.81 mol·mol PS -1 ·min -1 ; Under the same conditions, in the hydrogen production control experiment of tris(2,2'-bipyridine)ruthenium(II), TON and TOF were 60 mol·mol PS -1 and 0.50 mol·mol PS -1 ·min -1 , and its photo-stability could only be maintained for 2 hours.

[0067] A ruthenium complex photosensitizer modified with coumarin hydrazide condensate for photocatalytic hydrogen production, which has strong absorption in the visible light region, exhibits good photocatalytic water splitting hydrogen production performance under visible light, has good hydrogen production activity, and still maintains good catalytic efficiency in long-term stability tests.

[0068] The embodiments of the present invention described above and shown in the accompanying drawings should not be construed as limiting the technical idea of the present invention. The protection scope of the present invention is only limited by the content recorded in the claims, and those skilled in the art can change and modify the technical idea of the present invention in various forms. Therefore, it is obvious to those skilled in the art that such improvements and modifications will fall within the protection scope of the present invention.

[0069] Example 4

[0070] A preparation method of a ruthenium complex photosensitizer modified with coumarin hydrazide condensate for photocatalytic hydrogen production, characterized by comprising the following steps:

[0071] (1) Synthesize ethyl 7-diethylaminocoumarin-3-carboxylate: Dissolve 4-diethylamino-2-hydroxybenzaldehyde and diethyl malonate in a solvent, heat under reflux, and remove the solvent to obtain ethyl 7-diethylaminocoumarin-3-carboxylate;

[0072] (2) Synthesis of 7 - diethylaminocoumarin - 3 - hydrazide: Ethyl 7 - diethylaminocoumarin - 3 - carboxylate from step (1) and hydrazine hydrate are dissolved in a solvent. After the reaction, it is cooled, filtered, and separated to obtain 7 - diethylaminocoumarin - 3 - hydrazide;

[0073] (3) Preparation of coumarin hydrazide condensate: 7 - diethylaminocoumarin - 3 - hydrazide from step (2) and 4’ - methyl - 2,2’ - bipyridine - 4 - carbaldehyde are dissolved in a solvent, heated under reflux. After cooling and filtration, a condensate of 4’ - methyl - 2,2’ - bipyridine - 4 - carbaldehyde and 7 - diethylaminocoumarin - 3 - hydrazide is obtained. This coumarin hydrazide condensate is abbreviated as cmrbpy;

[0074] (4) Preparation of ruthenium complex photosensitizer modified with coumarin hydrazide condensate: Use cmrbpy from step (3) to modify the ruthenium complex to obtain a ruthenium complex photosensitizer modified with coumarin hydrazide condensate;

[0075] (5) Use the ruthenium complex photosensitizer modified with coumarin hydrazide condensate in step (4) for photocatalytic hydrogen production.

[0076] The specific method for synthesizing ethyl 7 - diethylaminocoumarin - 3 - carboxylate in step (1) is as follows: 5.0 g of 4 - diethylamino - 2 - hydroxybenzaldehyde and 8.0 g of diethyl malonate are dissolved in 200 mL of absolute ethanol, then 3.0 mL of piperidine is added, and the mixture is heated in a water bath to 90 °C and refluxed for 10 h; after cooling to room temperature, the solvent absolute ethanol is removed by rotary evaporation at 53 °C to obtain a yellow oily substance, ethyl 7 - diethylaminocoumarin - 3 - carboxylate, which is directly used for the next synthesis reaction without purification.

[0077] The specific method for synthesizing 7 - diethylaminocoumarin - 3 - hydrazide in step (2) is as follows: 5.8 g of ethyl 4 - diethylaminocoumarin - 3 - carboxylate and 5.0 mL of hydrazine hydrate are dissolved in 150 mL of absolute ethanol. At room temperature, the mixture is magnetically stirred at 500 rpm for 15 min, and then cooled in an ice bath for 20 min until an orange - yellow solid is completely formed. The crude product is obtained by normal pressure filtration using a glass funnel and filter paper, and 7 - diethylaminocoumarin - 3 - hydrazide is obtained by column chromatography separation. The eluent used for column chromatography separation is petroleum ether / ethyl acetate at a ratio of 2:1.

[0078] The specific synthesis method of cmrbpy in step (3) is as follows: 1.5 g of 7 - diethylaminocoumarin - 3 - hydrazide and 0.7 g of 4’ - methyl - 2,2’ - bipyridine - 4 - carbaldehyde are dissolved in 200 mL of dichloromethane; 2 drops of glacial acetic acid are added as a catalyst, and the mixture is heated in a water bath to 45 °C and refluxed for 10 h; after naturally cooling to room temperature until a yellow solid is completely precipitated, the yellow powdery condensate cmrbpy is obtained by normal pressure filtration using a glass funnel and filter paper.

[0079] The specific method for preparing the ruthenium complex photosensitizer modified with coumarin hydrazide condensate in step (4) is as follows: 0.8 g of cmrbpy and 1.0 g of Ru(bpy)2Cl2·2H2O are dissolved in 200 mL of absolute ethanol. Under a nitrogen atmosphere, the mixture is heated in a water bath to 90 °C and refluxed for 12 h. It is naturally cooled to room temperature and filtered under normal pressure. At room temperature, 15 mL of 12% NH4PF6 aqueous solution is added dropwise to the filtrate at a rate of 80 drops / min using a burette, and the mixture is magnetically stirred at 400 rpm for 15 min until the formation of a red solid is complete. Vacuum filtration is carried out using a Buchner funnel to obtain the crude photosensitizer. The crude photosensitizer is dissolved in 1 mL of acetonitrile, transferred to a cylindrical glass bottle with a volume of 5 mL, and the bottle mouth is sealed with a polyethylene film. A small hole is punctured in the film with a fine needle. Then the glass bottle is placed in a wide-mouth bottle, 10 mL of ether is added to the bottom of the wide-mouth bottle, and the bottle mouth of the wide-mouth bottle is sealed with a glass stopper. Needle-shaped crystals are obtained by the ether vapor diffusion method at a low temperature of -10 °C. The needle-shaped crystals are dissolved in 1.5 mL of N,N-dimethylformamide, transferred to a cylindrical glass bottle with a volume of 5 mL, and the bottle mouth is sealed with a polyethylene film punctured with a small hole. Then the glass bottle is placed in a wide-mouth bottle, 10 mL of ether is added to the bottom of the wide-mouth bottle, and the bottle mouth of the wide-mouth bottle is sealed with a glass stopper. Block-shaped crystals [Ru(bpy)2(cmrbpy)] are obtained by the ether vapor diffusion method again at a low temperature of -10 °C 2+ , [Ru(bpy)2(cmrbpy)] 2+ is a ruthenium complex photosensitizer modified with coumarin hydrazide condensate. It is confirmed by X-ray diffraction experiments that the block-shaped crystals [Ru(bpy)2(cmrbpy)] 2+ are single crystals

[0080] The steps of using the ruthenium complex photosensitizer modified with coumarin hydrazide condensate for photocatalytic hydrogen production in step (5) include: adding three components for photocatalysis, namely the photosensitizer [Ru(bpy)2(cmrbpy)] 2+ , the photocatalyst [Co(dmgH)2pyCl], and the electron sacrificial reducing agent N,N-dimethyl-p-toluidine, to a 300 mL quartz glass reactor. Then, a 1:1 acetonitrile / water mixture is added as a solvent, so that the concentrations of the three components are 1.00×10 -4 mol·L -1 , 1.00×10 -3 mol·L -1 and 5.00×10 -2 mol·L -1; Before the reaction, N2 was charged into the reactor to remove the influence of oxygen and make the reaction proceed in an inert atmosphere. A 300W xenon lamp was used to simulate sunlight to irradiate the reaction system, and a 400nm cut-off filter was equipped on the xenon light source to remove ultraviolet light. An airtight syringe was used to extract the gas at the head of the reactor and injected into an Agilent 7890A gas chromatograph to detect the hydrogen content in an off-line manner. The activity and efficiency of the photosensitizer prepared by this scheme in the photocatalytic hydrogen production experiment were obtained according to the peak position, peak integration area and standard curve. On the premise of the self-decomposition of the photocatalyst [Co(dmgH)2pyCl], the photosensitizer prepared by this scheme could still maintain the hydrogen production activity for 8.2 hours. In the 8.2-hour hydrogen production experiment, the turnover number TON and turnover frequency TOF of hydrogen production obtained were 410 mol·mol PS -1 and 0.83 mol·mol PS -1 ·min -1 ; Under the same conditions, in the hydrogen production control experiment of tris(2,2'-bipyridine)ruthenium(II), the TON and TOF were 60 mol·mol PS -1 and 0.50 mol·mol PS -1 ·min -1 , and its photostability could only be maintained for 2 hours.

[0081] A ruthenium complex photosensitizer modified with coumarin hydrazide condensate for photocatalytic hydrogen production, which has strong absorption in the visible light region, shows good photocatalytic water splitting hydrogen production performance under visible light, has good hydrogen production activity, and still maintains good catalytic efficiency in long-term stability tests.

Claims

1. A preparation method of a ruthenium complex photosensitizer modified by a coumarin hydrazide condensate for photocatalytic hydrogen production, characterized in that, It includes the following steps: (1) Synthesize ethyl 7 - diethylaminocoumarin - 3 - carboxylate: Dissolve 4 - diethylamino - 2 - hydroxybenzaldehyde and diethyl malonate in a solvent, heat under reflux, and after removing the solvent, obtain ethyl 7 - diethylaminocoumarin - 3 - carboxylate; (2) Synthesize 7 - diethylaminocoumarin - 3 - hydrazide: Dissolve the ethyl 7 - diethylaminocoumarin - 3 - carboxylate from step (1) and hydrazine hydrate in a solvent, react and then cool, filter and separate to obtain 7 - diethylaminocoumarin - 3 - hydrazide; (3) Prepare the coumarin hydrazide condensate: Dissolve the 7 - diethylaminocoumarin - 3 - hydrazide from step (2) and 4’ - methyl - 2,2’ - bipyridine - 4 - carbaldehyde in a solvent, heat under reflux, cool and filter to obtain the condensate of 4’ - methyl - 2,2’ - bipyridine - 4 - carbaldehyde and 7 - diethylaminocoumarin - 3 - hydrazide, and this coumarin hydrazide condensate is abbreviated as cmrbpy; (4) Prepare the ruthenium complex photosensitizer modified by the coumarin hydrazide condensate: Use cmrbpy in step (3) to modify the ruthenium complex to obtain the ruthenium complex photosensitizer modified by the coumarin hydrazide condensate; (5) Use the ruthenium complex photosensitizer modified by the coumarin hydrazide condensate in step (4) for photocatalytic hydrogen production.

2. The preparation method of a ruthenium complex photosensitizer modified by coumarin hydrazide condensate for photocatalytic hydrogen production according to claim 1, characterized in that: The specific method for synthesizing ethyl 7 - diethylaminocoumarin - 3 - carboxylate in step (1) is to dissolve 2.0 - 7.0 g of 4 - diethylamino - 2 - hydroxybenzaldehyde and 3.0 - 13.0 g of diethyl malonate in 50 - 500 mL of absolute ethanol, then add 1.0 - 5.0 mL of piperidine, heat in a water bath to 85 - 95 °C, reflux for 5 - 12 h; after cooling to room temperature, rotary evaporate to remove the solvent absolute ethanol at 50 - 55 °C to obtain a yellow oily substance, ethyl 7 - diethylaminocoumarin - 3 - carboxylate, which is directly used for the next synthesis reaction without purification.

3. The preparation method of a ruthenium complex photosensitizer modified by coumarin hydrazide condensate for photocatalytic hydrogen production according to claim 1, characterized in that: The specific method for synthesizing 7 - diethylaminocoumarin - 3 - hydrazide in step (2) is to dissolve 2.0 - 8.0 g of ethyl 4 - diethylaminocoumarin - 3 - carboxylate and 2.0 - 8.0 mL of hydrazine hydrate in 25 - 250 mL of absolute ethanol, stir magnetically at 300 - 600 rpm at room temperature for 10 - 20 min, then cool in an ice bath for 10 - 30 min until an orange - yellow solid is completely formed, filter under atmospheric pressure to obtain the crude product, and separate by column chromatography to obtain 7 - diethylaminocoumarin - 3 - hydrazide.

4. The preparation method of a ruthenium complex photosensitizer modified by coumarin hydrazide condensate for photocatalytic hydrogen production according to claim 1, characterized in that: The specific synthesis method of cmrbpy in step (3) is to dissolve 0.2 - 2.0 g of 7 - diethylaminocoumarin - 3 - hydrazide and 0.1 - 1.0 g of 4’ - methyl - 2,2’ - bipyridine - 4 - carbaldehyde in 50 - 500 mL of a solvent, and this solvent can be any one of absolute ethanol, absolute methanol and dichloromethane; add 1 - 5 drops of glacial acetic acid as a catalyst, heat in a water bath to 45 - 85 °C, reflux for 8 - 20 h; after naturally cooling to room temperature, until a yellow solid completely precipitates, filter under atmospheric pressure to obtain the yellow powdery condensate cmrbpy.

5. The preparation method of a ruthenium complex photosensitizer modified by coumarin hydrazide condensate for photocatalytic hydrogen production according to claim 1, characterized in that: The specific method for preparing the coumarin hydrazide condensate-modified ruthenium complex photosensitizer in step (4) is as follows: 0.2 - 2.0 g of cmrbpy and 0.2 - 2.0 g of Ru(bpy)2Cl2·2H2O are dissolved in 50 - 500 mL of absolute ethanol. Under a nitrogen atmosphere, the mixture is heated in a water bath to 85 - 95 °C and refluxed for 5 - 16 h; it is naturally cooled to room temperature and filtered under normal pressure; at room temperature, 10 - 20 mL of 10 - 15% NH4PF6 aqueous solution is added dropwise to the filtrate, and the mixture is magnetically stirred at 300 - 600 rpm for 10 - 20 min until the formation of the red solid is complete. Vacuum filtration is carried out using a Buchner funnel to obtain the crude photosensitizer; the crude photosensitizer is dissolved in acetonitrile, transferred to a glass bottle, and the bottle mouth is sealed with a film, and small holes are pricked in the film; then the glass bottle is placed in a wide-mouth bottle, ether is added to the bottom of the wide-mouth bottle, and the bottle mouth of the wide-mouth bottle is sealed with a glass stopper. Needle-like crystals are obtained by the ether vapor diffusion method at low temperature; the needle-like crystals are dissolved in N,N-dimethylformamide, transferred to a glass bottle, and the bottle mouth is sealed with a polyethylene film with small holes pricked. Then the glass bottle is placed in a wide-mouth bottle, ether is added to the bottom of the wide-mouth bottle, and the bottle mouth of the wide-mouth bottle is sealed with a glass stopper. Block crystals [Ru(bpy)2(cmrbpy)] are obtained again by the ether vapor diffusion method at low temperature 2+ , [Ru(bpy)2(cmrbpy)] 2+ is a coumarin hydrazide condensate-modified ruthenium complex photosensitizer.

6. The preparation method of a ruthenium complex photosensitizer modified by coumarin hydrazide condensate for photocatalytic hydrogen production according to claim 1, characterized in that: The steps of using the ruthenium complex photosensitizer modified with coumarin hydrazide condensate for photocatalytic hydrogen production in step (5) include: adding the photosensitizer [Ru(bpy)2(cmrbpy)] into a quartz glass reactor 2+ , a photocatalyst [Co(dmgH)2pyCl] and an electron sacrificial reducing agent N,N-dimethyl-p-toluidine, and the solvent is acetonitrile or an acetonitrile / water mixture; the reactor is filled and discharged with N2 to ensure that the reaction is carried out in an inert atmosphere; then a xenon lamp is used to simulate sunlight to irradiate the reaction system.

7. The preparation method of a ruthenium complex photosensitizer modified by coumarin hydrazide condensate for photocatalytic hydrogen production according to claim 3, characterized in that: The eluent used during the column chromatography separation is petroleum ether / ethyl acetate at 2:

1.

8. The preparation method of a ruthenium complex photosensitizer modified by coumarin hydrazide condensate for photocatalytic hydrogen production according to claim 5, characterized in that: The block crystal [Ru(bpy)2(cmrbpy)] 2+ was confirmed to be a single crystal by X-ray diffraction.

9. The preparation method of a ruthenium complex photosensitizer modified by coumarin hydrazide condensate for photocatalytic hydrogen production according to claim 6, characterized in that: The optimized scheme for photocatalytic hydrogen production is [Ru(bpy)2(cmrbpy)] 2+ The concentration of the single crystal is 1.00×10 -4 mol·L -1 , the concentration of [Co(dmgH)2pyCl] is 1.00×10 -3 mol·L -1 , the concentration of N,N-dimethyl-p-toluidine is 5.00×10 -2 mol·L -1 , and the solvent is a 1:1 acetonitrile / water mixture.

10. A coumarin hydrazide condensate-modified ruthenium complex photosensitizer for photocatalytic hydrogen production prepared by the preparation method according to any one of claims 1 to 9, characterized in that: The ruthenium complex photosensitizer modified with coumarin hydrazide condensate has strong absorption in the visible light region, exhibits good photocatalytic water splitting hydrogen production performance under visible light, has good hydrogen production activity, and still maintains good catalytic efficiency in long-term stability tests.

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