A self-photocatalytic platinum (II) complex material and its preparation method and application

Abstract

The present invention discloses a self-photocatalytic platinum (II) complex material, its preparation method, and application. The self-photocatalytic platinum (II) complex material introduces a triphenylamine macroconjugated group and an electron-donating thiophene group to optimize the ligand structure, resulting in a platinum complex exhibiting enhanced light absorption and overall structural stability. One side of the main ligand is structurally stable and does not decompose, while the ligand on the other side is freed and dropped during the reaction, exposing the Pt center with catalytic activity for CO2. This catalytically reduces CO2 to products such as CO, resulting in a highly efficient self-photocatalytic catalyst with both "photosensitive and catalytic" properties. When used with [Co(TPA)ClO4]ClO4 as a co-catalyst, the TON can reach 1962. The self-photocatalytic platinum (II) complex material can be prepared at relatively low temperatures under inert gas, eliminating the need for harsh reaction conditions.

Description

Technical Field

[0001] The invention belongs to the technical field of photocatalytic materials and relates to a self-photosensitive catalytic platinum (II) complex material and a preparation method and application thereof. Background Art

[0002] Due to modern industrialization, humans have emitted large amounts of carbon dioxide into the atmosphere, exacerbating global climate change. Increased carbon dioxide emissions have exacerbated the greenhouse effect, leading to rising temperatures across the globe and severely impacting global biodiversity, agricultural production, and human health. Furthermore, rising temperatures have accelerated sea level rise, posing a significant threat to coastal communities and ecosystems. Therefore, reducing and controlling carbon dioxide emissions is an urgent task for protecting the Earth and humanity's future. Artificially constructing photocatalytic carbon dioxide reduction systems to convert carbon dioxide into high-value substances such as carbon monoxide and formic acid is of great significance for alleviating environmental challenges, resolving the energy crisis, and achieving the goals of "carbon peak" and "carbon neutrality."

[0003] At present, various types of complexes have been developed in the field of metal complex applications, and have achieved certain results in the catalytic reduction of carbon dioxide. For example, complexes based on metals such as cobalt, iron, copper, nickel, rhenium, ruthenium, iridium, and palladium have all demonstrated certain catalytic ability or photosensitivity in the photocatalytic reduction of carbon dioxide. Platinum metal is a widely used catalyst; however, there are few reports on the application of its complexes in homogeneous photocatalytic reduction of carbon dioxide systems. In addition, traditional platinum (II) complexes have a simple structure and are prone to rapid deactivation during the catalytic reduction reaction. The absorption range and absorption intensity in the visible light absorption spectrum are relatively poor. Therefore, when such platinum (II) complexes are used in fields involving light energy conversion such as photocatalytic reactions, the results are often not ideal. Summary of the Invention

[0004] In order to overcome the shortcomings of the existing technology, the first object of the present invention is to provide a self-photosensitive catalytic platinum (II) complex material, which has stronger light absorption ability under visible light and enhanced overall structural stability. The structure of one side of the main ligand is stable and does not decompose, while the ligand on the other side of the structure is free and falls off during the reaction, exposing the Pt center. The Pt center catalytically reduces CO2 to products such as CO, making it a highly efficient self-photosensitive catalyst with "photosensitive + catalytic" dual properties.

[0005] The second object of the present invention is to provide a method for preparing the above-mentioned self-photocatalytic platinum (II) complex material.

[0006] The third object of the present invention is to provide an application of the above-mentioned self-photocatalytic platinum (II) complex material.

[0007] The first object of the present invention can be achieved by adopting the following technical solutions:

[0008] A self-photocatalytic platinum (II) complex material having a structure shown in Formula I:

[0009]

[0010] The second object of the present invention can be achieved by adopting the following technical solutions:

[0011] A method for preparing a self-photocatalytic platinum (II) complex material comprises the following steps:

[0012] Step S1, reacting a ligand of the structure shown in Formula II with chloroplatinate to prepare a platinum (II) dimer of the structure shown in Formula III;

[0013] Step S2, depolymerizing the platinum (II) dimer prepared in step S1 in a DMSO solution to obtain the self-photocatalytic platinum (II) complex material;

[0014] The structure shown in formula II is:

[0015]

[0016] The structure shown in formula III is:

[0017]

[0018] Furthermore, step S1 is carried out in a solvent, wherein the solvent is a mixed solvent of ethylene glycol ethyl ether and water, and the volume ratio of ethylene glycol ethyl ether to water is (1-5):1.

[0019] Furthermore, the molar ratio of the ligand to the chloroplatinate is (1-1.2):1.

[0020] Furthermore, the reaction conditions are: 70-90° C. for 3-48 hours under an inert gas atmosphere.

[0021] Furthermore, in step S2, the reaction conditions are: reflux reaction under an inert gas atmosphere for 1-5 hours.

[0022] Furthermore, in step S1, after the reaction is completed, a solid-liquid separation and purification process is performed: the reaction liquid is cooled to room temperature, water is added, and filtered to obtain a crude product platinum (II) dimer; and the crude product platinum (II) dimer is washed with one or more of dichloromethane, ether, n-hexane and ethanol in sequence.

[0023] Furthermore, in step S2, after the reaction is completed, a solid-liquid separation and purification process is performed: the reaction liquid is cooled to room temperature, water is added, and filtered to obtain a crude product, which is dissolved in dichloromethane and recrystallized with n-hexane to obtain the self-photocatalytic platinum (II) complex material.

[0024] Furthermore, the chloroplatinate is sodium chloroplatinate or potassium chloroplatinate and hydrates thereof.

[0025] Furthermore, the ligand of the structure shown in Formula II is prepared via the following preparation route:

[0026]

[0027] Furthermore, the compound of the structure shown in Formula IV is prepared via the following preparation route:

[0028]

[0029] The third object of the present invention can be achieved by adopting the following technical solutions:

[0030] The self-photosensitive platinum (II) complex material is used as a self-photosensitive photocatalytic reaction catalyst, and the self-photosensitive photocatalytic reaction catalyst is used for photocatalytic reduction of carbon dioxide.

[0031] Furthermore, the self-photosensitive photocatalytic reaction catalyst and the synergistic catalyst are used together for photocatalytic reduction of carbon dioxide; the synergistic catalyst is [Co(TPA)ClO4]ClO4.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1. The present invention provides a self-photosensitive catalytic platinum (II) complex material, which is obtained by a cyclometallation reaction between a ligand containing 2-(2-thienyl)pyridine and 4,4′-dimethyltriphenylamine groups and a divalent platinum ion; the introduction of a large conjugated group and an electron-donating group for structural optimization makes the platinum complex have stronger light absorption ability under visible light and enhances its overall structural stability, so that the structure of one side of the main ligand is stable and does not decompose; the ligand on the other side of the structure is freed and dropped during the reaction, exposing the Pt center and having catalytic activity. Therefore, it is a highly promising high-efficiency self-photosensitive catalyst with dual properties of "photosensitivity + catalysis".

[0034] 2. The present invention provides a method for preparing a self-photocatalytic platinum (II) complex material. A ligand containing a 2-(2-thienyl)pyridine group undergoes a cyclometalation reaction with a divalent platinum ion to produce a dimer, which is then depolymerized in a solvent to produce the platinum (II) complex. The reaction occurs at relatively low temperatures under an inert atmosphere, eliminating the need for harsh reaction conditions.

[0035] 3. The application of a self-photosensitive catalytic platinum (II) complex material of the present invention can absorb more blue light in the photocatalytic reduction reaction of carbon dioxide under 460nm light irradiation, and has a high efficiency in converting photon energy into chemical reaction energy, and has better photosensitivity than traditional platinum (II) complexes. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 is the H NMR spectrum of the self-photocatalytic platinum (II) complex material (I) of the present invention;

[0037] Figure 2 This is an infrared spectrum of the self-photocatalytic platinum (II) complex material (I) of the present invention;

[0038] Figure 3 is an absorption spectrum of the self-photocatalytic platinum (II) complex material (I) of the present invention;

[0039] Figure 4 1 is a single crystal structure diagram of the self-photocatalytic platinum (II) complex material (I) of the present invention;

[0040] Figure 5 The molecular structure diagram of the self-photocatalytic platinum (II) complex material (I) of the present invention. DETAILED DESCRIPTION

[0041] The technical solutions of the present invention will be described clearly and completely below with reference to specific embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are also within the scope of protection of the present invention.

[0042] Existing platinum (II) complexes, such as Pt-ppy-Cl-DMSO platinum (II) complex using the traditional organic ligand 2-phenylpyridine (ppy);

[0043]

[0044] The absorption range and intensity of these platinum(II) complexes in the visible light absorption spectrum are relatively poor. Therefore, when these platinum(II) complexes are used in applications involving light energy conversion, such as photocatalytic reactions, they often have suboptimal results. Furthermore, due to their simple structure, they tend to deactivate rapidly during catalytic reduction reactions, hindering the efficient operation of the system.

[0045] Therefore, the present invention provides a self-photocatalytic platinum (II) complex material having a structure shown in Formula I, such as Figure 5 As shown:

[0046]

[0047] A self-photosensitive catalytic platinum (II) complex material of the present invention has a structure shown in Formula I, wherein the ligand is a 2-(2-thienyl)pyridine group with a 4,4′-dimethyltriphenylamine group attached to the 2-position. The thiophene group replaces the benzene ring on the ppy ligand, and the 4,4′-dimethyltriphenylamine ligand is then attached to the thiophene group. The nitrogen atom on the pyridine and a carbon atom on the thiophene form a five-membered ring with the platinum. By introducing a large conjugated group and an electron-donating group to optimize the structure, it exhibits stronger light absorption under visible light and enhances its overall structural stability. The main ligand on one side is structurally stable and does not decompose, while the Pt material itself has catalytic activity for carbon dioxide. During the reaction, the ligand on the other side of the structure is freed and dropped, exposing the Pt center. The Pt center catalytically reduces CO2 to products such as CO, making it a highly promising, high-efficiency, self-photosensitive catalyst with dual properties of "photosensitivity + catalysis."

[0048] A method for preparing a self-photocatalytic platinum (II) complex material comprises the following steps:

[0049] Step S1, reacting a ligand of the structure shown in Formula II with chloroplatinate to prepare a platinum (II) dimer of the structure shown in Formula III;

[0050] Step S2, depolymerizing the platinum (II) dimer prepared in step S1 in a DMSO solution to obtain the self-photocatalytic platinum (II) complex material;

[0051] The structure shown in formula II is:

[0052]

[0053] The structure shown in formula III is:

[0054]

[0055] The ligand of formula II undergoes a cyclometallation reaction with the divalent platinum ion of chloroplatinate to obtain a platinum dimer of formula III, which is then depolymerized in an organic solvent to obtain the self-photocatalytic platinum (II) complex material. The cyclometallation reaction of the ligand of formula II with the divalent platinum ion of chloroplatinate occurs at the carbon atom at the fourth position of the thiophene ring and the nitrogen atom of the pyridine ring, forming a five-membered ring after cyclometallation with platinum.

[0056] In one embodiment, step S1 is performed in a solvent, wherein the solvent is a mixed solvent of ethylene glycol ethyl ether and water, wherein the volume ratio of ethylene glycol ethyl ether to water is (1-5):1; preferably, the volume ratio of ethylene glycol ethyl ether to water is 3:1. The water is preferably deionized water.

[0057] In one embodiment, the molar ratio of the ligand to the chloroplatinate is (1-1.2):1. A slight excess of the ligand allows sufficient formation of platinum dimers, facilitating subsequent separation and purification. Preferably, the molar ratio of the ligand to the chloroplatinate is 1.05:1.

[0058] In one embodiment, the reaction conditions are: 70-90° C. for 3-48 hours under an inert gas atmosphere. The inert gas atmosphere can be nitrogen or argon. A reaction temperature of 70-90° C. can ensure efficient reaction.

[0059] As one embodiment, in step S2, the reaction conditions are: reflux reaction for 1-5 hours under an inert gas atmosphere. Step S2 is a depolymerization process of platinum dimer.

[0060] In one embodiment, in step S1, after the reaction is completed, a solid-liquid separation and purification process is performed: the reaction liquid is cooled to room temperature, water is added, and filtration is performed to obtain a crude platinum (II) dimer product; the crude platinum (II) dimer product is then washed sequentially with one or more of dichloromethane, ether, n-hexane, and ethanol. Washing with an organic reagent can remove unreacted ligands.

[0061] As one embodiment, in step S2, after the reaction is completed, a solid-liquid separation and purification process is performed: the reaction liquid is cooled to room temperature, water is added, and filtered to obtain a crude product, which is dissolved in dichloromethane and recrystallized with n-hexane to obtain the self-photocatalytic platinum (II) complex material.

[0062] In one embodiment, the chloroplatinate is sodium chloroplatinate or potassium chloroplatinate and hydrates thereof. Sodium chloroplatinate or potassium chloroplatinate has good solubility, and the sodium chloride or potassium chloride obtained after the reaction has good water solubility and is easily dissolved in water for removal.

[0063] As one embodiment, the ligand of the structure shown in Formula II is prepared via the following preparation route:

[0064]

[0065] 2-(2-thienyl)pyridine is used as a starting material. A halogen atom, especially a bromine atom, is connected to the 5 position of the thiophene ring to replace the benzene ring on the ppy ligand. Pinacolato borate is connected to the para position of one benzene ring of the ligand 4,4′-dimethyltriphenylamine as a reactive group. The bromine atom on the thiophene group is replaced by a coupling reaction to obtain a ligand with a structure shown in formula II. Thiphene pyridine undergoes a cyclometalation reaction with a divalent platinum ion.

[0066] In one embodiment, 2-bromothiophene pyridine is dissolved in an organic solvent, and NBS is slowly added thereto for reaction; after the reaction is completed, 5-bromo-2-thiophene pyridine is obtained after purification.

[0067] In this embodiment, the molar ratio of 2-bromothiophenepyridine to NBS is 1 (1-1.2); the organic solvent is preferably chloroform; the reaction is performed in the dark for 3-12 hours; purification is performed by silica gel column chromatography using n-hexane as the eluent; and the reaction yield is greater than 72%.

[0068] As one embodiment, 4-boronic acid pinacol ester-4′,4″-dimethyltriphenylamine reacts with 5-bromo-2-thienylpyridine in a solvent under a zero-valent palladium catalyst system to obtain a ligand with a structure shown in Formula II.

[0069] In this embodiment, the molar ratio of 4-boronic acid pinacol ester-4',4"-dimethyltriphenylamine to 5-bromo-2-thienylpyridine is 1:(1-1.2); the zero-valent palladium catalytic system is a mixture of tetrakistriphenylphosphine palladium and potassium carbonate; the molar ratio of triphenylphosphine palladium and potassium carbonate is 0.05:(1.5-3); the amount of tetrakistriphenylphosphine palladium added is 0.02-0.1 equivalents of 4-boronic acid pinacol ester-4',4"-dimethyltriphenylamine; and the solvent is a mixed solvent of toluene / ethanol / water, wherein the volume ratio of toluene / ethanol / water is 7:1:2.

[0070] The reaction conditions are 80-100° C. for 3-24 h under an inert gas atmosphere.

[0071] The separation and purification steps after the reaction are as follows: after the reaction is stopped, the solvent is removed, and the organic layer is extracted and dried with ethyl acetate and saturated brine, and the organic layer is concentrated and purified by column chromatography. The eluent ratio is petroleum ether / ethyl acetate / dichloromethane (20 / 1 / 1, v / v / v).

[0072] As one embodiment, the compound of the structure shown in Formula IV is prepared via the following preparation route:

[0073]

[0074] 4-Bromo-4′,4″-dimethyltriphenylamine reacts with bis-pinacolatodiboron, potassium acetate, and [1,1′-bis(diphenylphosphino)ferrocene]palladium(II) dichloride in a solvent to obtain a compound with a structure represented by formula IV, 4-boronic acid pinacolato ester-4′,4″-dimethyltriphenylamine.

[0075] In this embodiment, the molar ratio of 4-bromo-4′,4″-dimethyltriphenylamine, bis-pinacolatodiboron, potassium acetate, and [1,1′-bis(diphenylphosphino)ferrocene]palladium(II) dichloride is 1:(2-3):(1-6):(0.01-0.1); and the solvent is 1,4-dioxane.

[0076] The reaction conditions are 80-110° C. for 3-24 h under an inert gas atmosphere.

[0077] The separation and purification steps of the reaction are as follows: the reaction solution is extracted and dried with dichloromethane and water to obtain an organic layer, which is then purified by column chromatography using n-hexane / ethyl acetate (20 / 1, v / v) as the eluent.

[0078] The self-photosensitive platinum (II) complex material of the present invention is used as a self-photosensitive photocatalytic reaction catalyst, and the self-photosensitive photocatalytic reaction catalyst is used for photocatalytic reduction of carbon dioxide.

[0079] As one embodiment, the self-photosensitive photocatalytic reaction catalyst and a synergistic catalyst are used together for photocatalytic reduction of carbon dioxide; the synergistic catalyst is [Co(TPA)ClO4]ClO4.

[0080] The following is a further description with reference to specific embodiments.

[0081] Example 1

[0082] 1) Synthesis of 4-boronic acid pinacol ester-4′,4″-dimethyltriphenylamine (IV): 4-Bromo-4′,4″-dimethyltriphenylamine (0.3522 g, 1 mmol), bis-pinacol diboron (0.6355 g, 2.5 mmol), potassium acetate (0.2944 g, 3 mmol), and [1,1′-bis(diphenylphosphino)ferrocene] dichloropalladium(II) (0.0424 g, 0.058 mmol) were added to a 100 mL single-necked flask. 50 mL of 1,4-dioxane was added, and the mixture was reacted at 100°C under nitrogen for 16 h. The reaction solution was extracted with dichloromethane and water to obtain an organic layer, which was then purified by column chromatography using n-hexane / ethyl acetate (20 / 1, v / v) as the eluent to obtain 4-boronic acid pinacol ester-4′,4″-dimethyltriphenylamine in a yield of 35%.

[0083] 2) Synthesis of 5-bromo-2-thiophenepyridine (V): 2-Bromo-2-thiophenepyridine (0.1630 g, 1 mmol) was dissolved in 50 mL of chloroform. NBS (0.1869 g, 1.05 mmol) was slowly added and the reaction was allowed to proceed overnight in the dark. After the reaction, the solution was concentrated and an appropriate amount of silica gel was added. The sample was then dry-applied using n-hexane as the eluent. After purification, 5-bromo-2-thiophenepyridine was obtained in a yield of 72%.

[0084] 3) Synthesis of Ligand (II): 4-boronic acid pinacol ester-4′,4″-dimethyltriphenylamine (0.1198 g, 0.3 mmol), 5-bromo-2-thienylpyridine (0.0792 g, 0.33 mmol), tetrakistriphenylphosphine palladium (0.0173 g, 0.015 mmol), and potassium carbonate (0.0829 g, 0.6 mmol) were weighed into a 100 mL single-necked flask. 30 mL of a solvent of toluene / ethanol / deionized water (7 / 1 / 2, v / v / v) was added. The mixture was reacted at 100°C under nitrogen overnight. After the reaction ceased, the solvent was removed by swirl, and the organic layer was extracted with ethyl acetate and saturated brine to dryness. The concentrated organic layer was purified by column chromatography with a elution ratio of petroleum ether / ethyl acetate / dichloromethane (20 / 1 / 1, v / v / v) to obtain Ligand II in a yield of 67%.

[0085] 4) Synthesis of self-photocatalytic platinum (II) complex material (I): Ligand II (0.0865 g, 0.2 mmol), potassium tetrachloroplatinate (0.0789 g, 0.19 mmol), and 12 mL of ethylene glycol ether / deionized water (3 / 1, v / v) were weighed and placed in a 50 mL single-necked flask. The mixture was reacted at 80°C under nitrogen for 10 h. The reaction solution was cooled to room temperature, 30 mL of deionized water was added, and the crude product, platinum (II) dimer, was filtered to obtain the crude product. The impurities in the crude product were then washed with small amounts of dichloromethane, ether, n-hexane, and ethanol to obtain product III in a yield of 90%.

[0086] Weigh III, dissolve it in 3 mL of dimethyl sulfoxide (DMSO), and reflux under nitrogen for 2 h. After the reaction solution is cooled to room temperature, deionized water is added to precipitate and filtered to obtain a crude product, which is then dissolved in dichloromethane and collected. Most of the dichloromethane is removed using a rotary evaporator, and n-hexane is added for recrystallization multiple times to obtain a self-photocatalytic platinum (II) complex material (I), named Pt-Dmtpa-thiopy-Cl-DMSO, with a yield of 45%.

[0087] Compound characterization:

[0088] (1) The NMR data of Pt-Dmtpa-thiopy-Cl-DMSO are: 1 H NMR(400MHz,Chloroform-d)δ9.27(d,J=6.1Hz,1H),7.82-7.63(m,2H),7.48(d,J= 8.6Hz,2H),7.32(d,J=8.0Hz,1H),7.11-6.93(m,10H),3.62(s,6H),2.32(s,6H), see Figure 1 .

[0089] (2) The infrared spectrum of Pt-Dmtpa-thiopy-Cl-DMSO is shown in Figure 2. Figure 2 shown.

[0090] from Figure 2 As can be seen, 3021.66cm -1 The absorption peak at 3087.74 cm is the unsaturated CH stretching vibration in the benzene ring. -1 The peak at 2917.22 cm corresponds to the CH stretching vibration of the methyl group. -1 The peak at 1600-1467.85 cm should be attributed to the CH stretching vibration of the benzene ring. -1 The peak between is the skeleton vibration peak of the benzene ring, 1322.91cm -1 The CN stretching vibration is 1600-1401.77cm -1 It should be attributed to the C=C symmetric stretching vibration and C=C asymmetric stretching vibration on the thiophene ring, 1288.8 cm -1 The peak at 1154.42 cm corresponds to the in-plane bending vibration of CH on the thiophene ring. -1 The peak at 819.89 cm should be attributed to the stretching vibration of the SO bond. -1 The peak at 762.95 cm is probably caused by the out-of-plane bending vibration of CH on the thiophene ring. -1 The peak at is the out-of-plane deformation vibration of CH on the aromatic ring.

[0091] (3) The absorption spectra of Pt-Dmtpa-thiopy-Cl-DMSO and Pt-ppy-Cl-DMSO platinum (II) complexes are shown in Figure 2. Figure 3 As shown;

[0092] In the study of photocatalytic reduction of carbon dioxide, researchers generally use blue light from 400nm to 460nm as the light source. When the traditional platinum (II) complex Pt-ppy-Cl-DMSO is used as a photosensitizer, its visible light absorption capacity is insufficient, especially in the range of 400nm to 460nm, it has almost no absorption capacity. Figure 3 As shown in the figure, the absorption intensity of the UV-visible absorption spectrum of Pt-ppy-Cl-DMSO is very small between 400nm and 460nm, and the absorption peak is mainly distributed between 200-400nm. At the same concentration (10 -5mol / L), the absorption intensity of the Pt-Dmtpa-thiopy-Cl-DMSO of the present application between 400nm and 460nm is as high as 0.0989 (at 456nm) and as low as 0.0531 (at 407nm). The light absorption capacity of Pt-Dmtpa-thiopy-Cl-DMSO is much stronger than that of Pt-ppy-Cl-DMSO. Therefore, in the photocatalytic reduction of carbon dioxide reaction under 400 to 460nm blue light irradiation, Pt-Dmtpa-thiopy-Cl-DMSO has better light absorption efficiency.

[0093] (4) The single crystal structure of Pt-Dmtpa-thiopy-Cl-DMSO is shown in the figure below. Figure 4 The single crystal data are shown in Table 1; the bond lengths and bond angles of the characteristic bonds are shown in Table 2.

[0094] Table 1 X-ray crystal data of Pt-Dmtpa-thiopy-Cl-DMSO

[0095]

[0096] a R1=Σ||Fo|-|Fc|| / Σ|Fo|.wR2={Σ[w(Fo 2 -Fc 2 ) 2 ] / Σ[w(Fo 2 ) 2 ]} 1 / 2 .

[0097] b GoF=[(Σw|Fo|-|Fc|) 2 / (Nobs-Nparam)] 1 / 2 .

[0098] Table 2. Bond lengths and angles of characteristic bonds of Pt-Dmtpa-thiopy-Cl-DMSO.

[0099]

[0100] Photocatalytic performance test

[0101] 1) Prepare stock solutions of Pt-Dmtpa-thiopy-Cl-DMSO in DMA (N,N′-dimethylacetamide) as the photosensitizer and 1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzimidazole (BIH) as the electron sacrificial agent in the reaction system. A 10 mL ground-edge thick-walled round-bottom test tube was used as the reaction vessel, and the total reaction volume for the photocatalytic experiment was 2 mL.

[0102] (2) Place a stirring magnet in the test tube and add a photosensitizer, an electron sacrificial agent, and a solvent. The concentration of Pt-Dmtpa-thiopy-Cl-DMSO in the system is 0.4 mM, BIH is 0.1 M, and DMA (N,N′-dimethylacetamide) is used as the solvent. Plug the tube with a rubber stopper and seal the bottleneck with parafilm. Use a long needle to pass carbon dioxide into the solution in the test tube for 50 minutes to ensure that the solution is saturated with carbon dioxide. Then seal the rubber stopper with electrical tape.

[0103] (3) Finally, the vented test tube was stirred under a magnetic stirrer and irradiated with a 460nm visible blue LED lamp at a reaction temperature of 25°C. After each 24h of illumination, the carbon monoxide content in the test tube was detected by gas chromatography, and the formic acid content in the test tube was detected by ion chromatography until the reaction was completed. The total reaction time was 120h. The conversion data were obtained according to the standard curve equation for quantitative detection of the product established by the analytical instrument used, as shown in Table 3. Table 3 Application of Pt-Dmtpa-thiopy-Cl-DMSO as a self-photosensitive catalyst in the homogeneous photocatalytic reduction of carbon dioxide

[0104]

[0105] As can be seen from Table 3, in the presence of 0.4 mM Pt-Dmtpa-thiopy-Cl-DMSO of the present application, the total light reaction time was 120 h, and the CO production reached 29.3 μmol, with a selectivity of up to 94% and a TON of 37. In contrast, in the control group 2 without the addition of 0.4 mM Pt-Dmtpa-thiopy-Cl-DMSO of the present application, the light reaction was also carried out for 120 h, but no CO was produced, indicating that carbon dioxide was not reduced to CO.

[0106] (4) The mature catalyst was added to the system to co-catalyze with Pt-Dmtpa-thiopy-Cl-DMSO. 0.0125 mM [Co(TPA)ClO4]ClO4 was added, and the reaction was irradiated with a 460 nm visible blue LED light at a temperature of 25°C. The product of the reaction system was detected after every 24 h of illumination until the reaction was completed. The total reaction time was 120 h. The results are shown in Table 4:

[0107] Table 4 Pt-Dmtpa-thiopy-Cl-DMSO as a self-photosensitized catalyst synergistically applied in homogeneous photocatalytic reduction of carbon dioxide with [Co(TPA)ClO4]ClO4 catalyst

[0108]

[0109] From the data in Table 3, it can be seen that when 0.0125 mM [Co(TPA)ClO4]ClO4 is added to the reaction system as a co-catalyst, the CO content reaches 49.1 umol, which is almost twice that when [Co(TPA)ClO4]ClO4 is not added. The selectivity still reaches 93%, but the TON has reached 1962, which is much higher than the effect when [Co(TPA)ClO4]ClO4 is not added.

[0110] When the control group 4 only contained [Co(TPA)ClO4]ClO4, no CO was produced, indicating that simply containing [Co(TPA)ClO4]ClO4 could not convert carbon dioxide into CO; this also means that [Co(TPA)ClO4]ClO4 was used in conjunction with the Pt-Dmtpa-thiopy-Cl-DMSO of the present application, and the synergistic and efficient catalysis significantly improved the efficiency of the reaction system.

[0111] In summary, the self-photosensitive catalytic platinum (II) complex material (I) of the present application, based on the ligand 2-(5-bromo-2-thienyl) pyridine, uses a thiophene group connected to a bromine atom to replace the benzene ring, and then uses the ligand 4,4′-dimethyltriphenylamine to replace the bromine atom on the thiophene group to form a new ligand, which undergoes a cyclometallation reaction with divalent platinum ions to obtain a self-photosensitive catalytic platinum (II) complex material (I); the introduction of large conjugated groups and electron-donating groups for structural optimization shows stronger light absorption ability under visible light, and enhances its overall structural stability, so that the structure of one side of the main ligand is stable and does not decompose; the ligand on the other side of the structure is free and falls off during the reaction, exposing the Pt center, and utilizing the catalytic activity of the Pt material itself for carbon dioxide, the Pt center catalytically reduces CO2 to products such as CO, becoming a highly promising "photosensitive + catalytic" dual-property high-efficiency self-photosensitive catalyst.

[0112] The above embodiments are only preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and replacements made by technicians in this field on the basis of the present invention fall within the scope of protection required by the present invention.

Claims

1. A self-photocatalytic platinum (II) complex material, characterized in that: Having the structure shown in formula I:

2. The method for preparing a self-photocatalytic platinum (II) complex material according to claim 1, characterized in that: The following steps are involved: Step S1, reacting a ligand of the structure shown in Formula II with chloroplatinate to prepare a platinum (II) dimer of the structure shown in Formula III; Step S2, depolymerizing the platinum (II) dimer prepared in step S1 in a DMSO solution to obtain the self-photocatalytic platinum (II) complex material; The structure shown in formula II is: The structure shown in formula III is:

3. The method for preparing the self-photocatalytic platinum (II) complex material according to claim 2, characterized in that: Step S1 is carried out in a solvent, wherein the solvent is a mixed solvent of ethylene glycol ethyl ether and water, and the volume ratio of ethylene glycol ethyl ether to water is (1-5):1; The molar ratio of the ligand to chloroplatinate is (1-1.2):1; The reaction conditions are: 70-90° C. for 3-48 h under an inert gas atmosphere.

4. The method for preparing the self-photocatalytic platinum (II) complex material according to claim 2, characterized in that: In step S2, the reaction conditions are: reflux reaction under an inert gas atmosphere for 1-5 hours.

5. The method for preparing the self-photocatalytic platinum (II) complex material according to claim 2, characterized in that: In step S1, after the reaction is completed, a solid-liquid separation and purification process is performed: the reaction liquid is cooled to room temperature, water is added, and filtration is performed to obtain a crude product of platinum (II) dimer; the crude product of platinum (II) dimer is then washed with one or more of dichloromethane, ether, n-hexane, and ethanol in sequence; In step S2, after the reaction is completed, a solid-liquid separation and purification process is performed: the reaction solution is cooled to room temperature, water is added, and filtered to obtain a crude product, which is dissolved in dichloromethane and recrystallized with n-hexane to obtain the self-photocatalytic platinum (II) complex material.

6. The method for preparing the self-photocatalytic platinum (II) complex material according to claim 2, characterized in that: The chloroplatinate is sodium chloroplatinate or potassium chloroplatinate and hydrates thereof.

7. The method for preparing the self-photocatalytic platinum (II) complex material according to claim 2, characterized in that: The ligand of the structure shown in formula II is prepared via the following preparation route:

8. The method for preparing the self-photocatalytic platinum (II) complex material according to claim 7, characterized in that: The compound of formula IV is prepared by the following preparation method:

9. Use of the self-photosensitive platinum (II) complex material according to claim 1 as a self-photosensitive photocatalytic catalyst, characterized in that: The self-photosensitive photocatalytic reaction catalyst is used for photocatalytic reduction of carbon dioxide.

10. The use according to claim 9, characterized in that The self-photosensitive photocatalytic reaction catalyst and the synergistic catalyst are used together for photocatalytic reduction of carbon dioxide; the synergistic catalyst is [Co(TPA)ClO4]ClO4.

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