Multi-core iron-based complex containing oxygen bridge as well as preparation method and application of multi-core iron-based complex

Abstract

The invention discloses a polynuclear iron-based complex containing an oxygen bridge as well as a preparation method and application of the polynuclear iron-based complex. The structure of the multi-core iron-based complex is shown as a formula I or a formula II. According to the multi-core iron-based complex provided by the invention, through the multi-charge storage capacity of a multi-core structure and the synergistic effect among metals, the stability and activity of a catalyst are effectively improved, and a homogeneous catalytic water oxidation process is realized under chemical driving force, optical driving force or electric driving force; and electrons and protons are provided for the processes of preparing hydrogen by decomposing water, carrying out dioxide reduction and the like. The invention further provides a method for preparing the multi-core iron-based complex, the method is easy to operate, and the multi-core iron-based complex is high in yield and good in repeatability. # imgabs0 #

Description

Technical Field

[0001] The present invention relates to the technical field of water oxidation catalysis, and more specifically to a polynuclear iron-based complex containing an oxygen bridge, and a preparation method and application thereof. Background Art

[0002] Using solar energy to decompose water to generate hydrogen as a clean energy source and oxygen for breathing is one of the most promising strategies to solve energy and environmental problems. As a half-reaction of water decomposition, water oxidation reaction requires a relatively high energy of about 113.5 kcal / mol (E θ =1.23V vs. NHE at pH=0), the reaction involves the transfer of 4 protons and 4 electrons and the formation of OO bonds, which is considered to be the bottleneck of the water decomposition process. The development of efficient, stable and inexpensive water oxidation catalysts is of great significance. In nature, water oxidation reactions are catalyzed by the Mn4CaO5 cluster of the oxygen evolution complex (OEC). Due to the advantages of transition metal complexes such as clear structure and easy and precise regulation, the research on molecular water oxidation catalysts based on transition metals has received widespread attention in the past forty years. The first molecular catalyst for water oxidation was the "Blue Dimer" reported by Meyer et al. in 1982, in which the oxygen bridge is considered to be the key structure of the molecular water oxidation.

[0003] As the transition metal element with the largest reserves in the earth's crust, iron is cheap, easy to obtain, environmentally friendly and has rich oxidation states. In 2010, the Collins research group reported the first iron-based molecular water oxidation molecular catalyst Fe-TAML (J.Am.Chem.Soc.2010,132,10990-10991). Subsequently, water oxidation catalytic systems based on transition metal iron were reported one after another, but most of the iron-based molecular water oxidation catalysts have poor antioxidant properties and are prone to oxidative degradation of ligands under strong oxidation conditions to generate nanoparticles. Although iron is one of the most potential central metal elements for building water oxidation catalysts, the molecular structure of the catalyst often cannot be maintained in the catalytic cycle.

[0004] Based on this, there is an urgent need to develop a new iron-based molecular water oxidation catalyst with good stability and high catalytic activity. Summary of the invention

[0005] Based on the above research background, the first object of the present invention is to provide a polynuclear iron-based complex containing oxygen bridges. The polynuclear iron-based complex effectively improves the stability of its molecular structure and catalytic activity through the multi-charge storage capacity of the polynuclear structure and the synergistic effect between metals.

[0006] The second object of the present invention is to provide a method for preparing a polynuclear iron-based complex containing an oxygen bridge as described in Formula I. The method is simple to operate, has a high final product yield, and has good reproducibility.

[0007] The third object of the present invention is to provide a method for preparing a polynuclear iron-based complex containing an oxygen bridge as described in Formula II. The method is simple to operate, has a high final product yield, and has good reproducibility.

[0008] The fourth object of the present invention is to provide a use of the multi-nuclear iron-based complex as described above in catalyzing water oxidation reactions.

[0009] In order to achieve the above first object, the present invention adopts the following technical scheme:

[0010] The present invention discloses a polynuclear iron-based complex containing an oxygen bridge, wherein the structure of the polynuclear iron-based complex is as shown in Formula I or Formula II:

[0011]

[0012] wherein X represents any one of F, Cl, Br, I, OAc and NO2;

[0013] R1 and R2 are each independently selected from any one of H, N(CH3)2, COOH, F, Cl, Br, I and an alkyl group having a carbon number of C1-C5;

[0014] Ring A is selected from any one of a phenyl group, a naphthyl group and a pyridyl group.

[0015] The present invention discloses the above two types of oxygen-bridge-containing polynuclear iron-based complex structures. These two types of oxygen-bridge-containing polynuclear iron-based complexes can be used as catalysts in water oxidation systems. The catalyst utilizes the multi-charge storage capacity of the polynuclear structure and the synergistic effect between metals to avoid charge accumulation, improve the stability and activity of the catalyst, and realize an efficient homogeneous catalytic water oxidation process.

[0016] Further, the multi-nuclear iron-based complex is selected from one of the following structures:

[0017]

[0018] In order to achieve the above second purpose, the present invention adopts the following technical solutions:

[0019] The present invention discloses a method for preparing a multi-nuclear iron-based complex (structure of formula I), comprising the following steps:

[0020] 1) Compound I-1 was dissolved in trifluoroacetic acid, and then an excess of H2O2 solution was added dropwise, and stirred at room temperature for 8-12 hours; after the reaction was completed, dichloromethane was added for extraction, and the liquids were separated, and the organic phase was collected, washed, dried over anhydrous sodium sulfate, and the solvent was removed by rotary evaporation to obtain compound I-2;

[0021]

[0022] 2) Under an inert atmosphere, compound I-2 and trimethylsilyl cyanide are dissolved in dichloromethane, then placed in an ice-water bath, benzoyl chloride is added dropwise, and after the addition is complete, the mixture is transferred to room temperature for reaction for 3-5 days; after the reaction is completed, the mixture is transferred to an ice-water bath again, sodium carbonate solution is added, the liquids are separated, the aqueous phase is extracted with dichloromethane, the organic phases are combined, dried over anhydrous sodium sulfate, the solvent is removed by rotary evaporation, and separation and purification are performed by column chromatography to obtain compound I-3;

[0023]

[0024] 3) Under an inert atmosphere, compound I-3 is dissolved in toluene, then placed in an ice-water bath, methylmagnesium bromide solution is added dropwise, and after the addition is complete, the mixture is refluxed for reaction for 8-12 hours; after the reaction is complete, the reaction is quenched with a saturated ammonium chloride solution, concentrated hydrochloric acid is added, the liquids are separated, the aqueous phase is collected, the pH of the aqueous phase is adjusted to alkaline with sodium hydroxide, dichloromethane is added for extraction, the liquids are separated, the organic phase is collected, dried over anhydrous sodium sulfate, the solvent is removed by rotary evaporation, and separation and purification is performed by column chromatography to obtain compound I-4;

[0025]

[0026] 4) Under an inert atmosphere, compound I-4 is dissolved in acetonitrile to obtain solution A; iron salt is dissolved in acetonitrile to obtain solution B; solution A or B is dripped into the other solution (solution A can be dripped into solution B, or solution B can be dripped into solution A), and the reaction is carried out at room temperature for 8-12 hours; after the reaction is completed, it is transferred to the air and stirred for 20-30 minutes to produce a large amount of precipitate, which is filtered and washed to obtain the compound of formula I.

[0027]

[0028] Furthermore, when washing is performed in step 1), a NaOH solution is first used for washing once, and then a saturated sodium chloride solution is used for washing twice.

[0029] Furthermore, in step 2), the molar ratio of compound I-2, trimethylsilyl cyanide and benzoyl chloride is 1:7-10:1.2-1.5; preferably 1:7:1.3.

[0030] Furthermore, in step 2), the eluents used in column chromatography are ethyl acetate and petroleum ether.

[0031] Furthermore, in step 3), the molar ratio of compound I-3 to methylmagnesium bromide is 3.0-4.0:1.

[0032] Furthermore, in step 3), the eluents used in column chromatography are dichloromethane and methanol.

[0033] Furthermore, in step 4), the molar ratio of compound I-4 to iron salt is 1:1.0-1.2.

[0034] Furthermore, the dichloromethane, toluene and acetonitrile used in steps 2-4 are ultra-dry solvents.

[0035] Furthermore, the iron salt is selected from any one of FeCl2, FeCl3, FeBr3, FeI3, Fe(OAc)2, Fe(OAc)3 and Fe(NO2)3.

[0036] In order to achieve the third object, the present invention adopts the following technical solutions:

[0037] The present invention discloses a method for preparing a multi-nuclear iron-based complex (structure of formula II), wherein steps 1 to 3 are the same as the preparation process for preparing the compound of formula I, and specifically comprise the following steps:

[0038] 1) Compound I-1 was dissolved in trifluoroacetic acid, and then an excess of H2O2 solution was added dropwise, and the reaction was stirred at room temperature for 8-12 hours; after the reaction was completed, dichloromethane was added for extraction, and the liquids were separated, and the organic phase was collected, washed, dried over anhydrous sodium sulfate, and the solvent was removed by rotary evaporation to obtain compound I-2;

[0039]

[0040] 2) Under an inert atmosphere, compound I-2 and trimethylsilyl cyanide are dissolved in dichloromethane, then placed in an ice-water bath, benzoyl chloride is added dropwise, and after the addition is complete, the mixture is transferred to room temperature for reaction for 3-5 days; after the reaction is completed, the mixture is transferred to an ice-water bath again, sodium carbonate solution is added, the liquids are separated, the aqueous phase is extracted with dichloromethane, the organic phases are combined, dried over anhydrous sodium sulfate, the solvent is removed by rotary evaporation, and separation and purification are performed by column chromatography to obtain compound I-3;

[0041]

[0042] 3) Under an inert atmosphere, compound I-3 is dissolved in toluene, then placed in an ice-water bath, methylmagnesium bromide solution is added dropwise, and after the addition is complete, the mixture is refluxed for reaction for 8-12 hours; after the reaction is complete, the reaction is quenched with a saturated ammonium chloride solution, hydrochloric acid is added, the liquids are separated, the aqueous phase is collected, the pH of the aqueous phase is adjusted to alkaline with sodium hydroxide, dichloromethane is added for extraction, the liquids are separated, the organic phase is collected, dried over anhydrous sodium sulfate, the solvent is removed by rotary evaporation, and separation and purification is performed by column chromatography to obtain compound I-4;

[0043]

[0044] 4) Under an inert atmosphere, compound I-4 was dissolved in N,N-dimethylformamide to obtain solution C; compound II-1 was dissolved in DMF to obtain solution D; solution C or D was added dropwise to the other solution, and then solid K2CO3 was added, and the mixture was reacted at room temperature for one day. After the reaction was completed, the mixture was quenched with water, extracted with dichloromethane, and the organic phase was collected, washed, dried over anhydrous sodium sulfate, and the solvent was removed by rotary evaporation. The mixture was separated and purified by column chromatography to obtain compound II-2;

[0045]

[0046] 5) Under an inert atmosphere, compound II-2 is dissolved in methanol to obtain solution E; iron salt is dissolved in methanol to obtain solution F; solution E or F is added dropwise to the other solution (solution E can be added dropwise to solution F, or solution F can be added dropwise to solution E), and the reaction is carried out at room temperature for 8-12 hours; after the reaction is completed, the mixture is stirred in the air for 20-30 minutes, and a large amount of precipitate is precipitated, which is filtered and washed to obtain a compound of formula II.

[0047]

[0048] Furthermore, when washing is performed in step 1), a NaOH solution is first used for washing once, and then a saturated sodium chloride solution is used for washing twice.

[0049] Furthermore, in step 2), the molar ratio of compound I-2, trimethylsilyl cyanide and benzoyl chloride is 1:7-10:1.2-1.5; preferably 1:7:1.3.

[0050] Furthermore, in step 2), the eluents used in column chromatography are ethyl acetate and petroleum ether.

[0051] Furthermore, in step 3), the molar ratio of compound I-3 to methylmagnesium bromide is 3.0-4.0:1.

[0052] Furthermore, in step 3), the eluents used in column chromatography are dichloromethane and methanol.

[0053] Further, in step 4), the molar ratio of compound I-4, compound II-1 and K2CO3 is 2-2.2:1:1.

[0054] Furthermore, in step 4), the eluents used in column chromatography are dichloromethane and methanol.

[0055] Furthermore, in step 5), the molar ratio of compound II-2 to iron salt is 1:2-2.2.

[0056] Furthermore, the iron salt is selected from any one of FeF3, FeCl2, FeCl3, FeBr3, FeI3, Fe(OAc)2, Fe(OAc)3 and Fe(NO2)3.

[0057] Furthermore, the dichloromethane, toluene, N,N-dimethylformamide and methanol used in steps 2-5 are ultra-dry solvents.

[0058] In order to achieve the fourth objective, the present invention adopts the following technical solutions:

[0059] The present invention discloses an application of the multi-nuclear iron-based complex as described above or the multi-nuclear iron-based complex prepared by the method as described above in catalyzing water oxidation reaction.

[0060] Furthermore, in the application, the multi-nuclear iron-based complex catalyzes a homogeneous water oxidation reaction under the action of chemical driving force, light driving force or electrical driving force; at the same time, the homogeneous molecular process facilitates the in-depth study of the water oxidation mechanism.

[0061] The beneficial effects of the present invention are as follows:

[0062] The present invention discloses a multi-nuclear iron-based complex containing oxygen bridges and a preparation method and application thereof. Compared with the prior art, the present invention has the following advantages:

[0063] 1. The structure of the multi-core iron-based complex contains an oxygen bridge structure and a multi-core structure, wherein the oxygen bridge is conducive to enhancing the synergistic effect between metals, while the multi-core structure has multiple charge storage capabilities and synergistic effects between metals, avoiding charge accumulation, and can effectively improve the stability and activity of the catalyst to achieve homogeneous water oxidation reaction.

[0064] 2. The polynuclear iron-based complex containing oxygen bridges provided by the present invention can realize homogeneous catalytic water oxidation process under the action of chemical driving force, light driving force and electric driving force, and provides an effective half-reaction for decomposing water to produce hydrogen, carbon dioxide reduction and other processes, and at the same time provides the possibility for studying the mechanism of homogeneous catalytic water oxidation process.

[0065] 4. The preparation method of the oxygen-bridged multi-nuclear iron-based complex provided by the present invention is simple to operate, has a high yield of the multi-nuclear iron-based complex, and has good repeatability.

[0066] 5. The polynuclear iron-based complex containing oxygen bridges of the present invention has good solubility and is easily soluble in water and can be dissolved in organic solvents such as acetonitrile and acetone. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] The specific implementation modes of the present invention will be further described in detail below in conjunction with the accompanying drawings.

[0068] Figure 1The crystal structure diagram of the multi-nuclear iron-based complex prepared in Preparation Example 1 is shown.

[0069] Figure 2 The crystal structure diagram of the multi-nuclear iron-based complex prepared in Preparation Example 2 is shown.

[0070] Figure 3 A curve showing the change in oxygen concentration over time in Test Example 1 is shown.

[0071] Figure 4 A curve showing the change of oxygen concentration over time at different catalyst concentrations in Test Example 2 is shown.

[0072] Figure 5 The constant-pressure electrolysis spectrum and gas spectrum in Test Example 3 are shown;

[0073] in, Figure 5 a in the figure is the constant voltage electrolysis spectrum. Figure 5 Middle b is the gas spectrum. DETAILED DESCRIPTION

[0074] In order to more clearly illustrate the present invention, the present invention is further described below in conjunction with preferred embodiments and accompanying drawings. Similar components in the accompanying drawings are represented by the same reference numerals. It should be understood by those skilled in the art that the content specifically described below is illustrative rather than restrictive, and should not be used to limit the scope of protection of the present invention.

[0075] In addition, unless otherwise specified, the raw materials used in the present invention can be obtained commercially, and any range recorded in the present invention includes the end value and any numerical value between the end values ​​and any sub-range formed by the end value or any numerical value between the end values.

[0076] Preparation Example

[0077] Preparation Example 1

[0078] This preparation example provides a method for preparing a polynuclear iron-based complex containing an oxygen bridge, comprising the following steps:

[0079] 1) Place 10.0 g of 2,2'-bipyridine in a 250 mL round-bottom flask and dissolve it in 50 mL of trifluoroacetic acid at 10°C to obtain a mixed solution; add 10 mL of a 30 wt% H2O2 aqueous solution to the mixed solution. Stir for 10 hours at room temperature. After the reaction is completed, add 80 mL of dichloromethane for extraction, separate the liquids, collect the organic phase, wash the organic phase with a 3M NaOH solution and a saturated sodium chloride solution in turn, dry it with anhydrous sodium sulfate, and spin dry to obtain 2,2'-bipyridine-nitrogen-oxide; the reaction equation is as follows:

[0080]

[0081] 2) Under the protection of inert gas, 15.26g of 2,2'-bipyridine-nitrogen-oxide and 50mL of trimethylsilyl cyanide were dissolved in 250mL of dichloromethane to obtain a mixed solution; the mixed solution was placed in an ice-water bath, 20.4mL of benzoyl chloride was slowly added under stirring, and stirred at room temperature for 4 days. After the reaction was completed, the mixed solution was placed in an ice-water bath again, 200mL of 10% sodium carbonate solution was slowly added under stirring, and the liquid was separated, the aqueous phase was extracted with dichloromethane, the organic phases were combined, dried over anhydrous sodium sulfate, and spin-dried to obtain a crude product, which was separated and purified by column chromatography (eluents were ethyl acetate and petroleum ether) to obtain 6-cyano-2,2'-bipyridine, and the reaction formula is shown in the figure below:

[0082]

[0083] 3) Under the protection of inert gas, 1.35 g of 6-nitrile-2,2'-bipyridine was dissolved in 80 mL of ultra-dry toluene to obtain a mixed solution; the mixed solution was placed in an ice-water bath, and 3 equivalents of methylmagnesium bromide solution were slowly added dropwise under stirring, and refluxed for 10 hours after the addition was completed. After the reaction was completed, the solution was cooled to room temperature, 30 mL of saturated ammonium chloride solution was added to quench the reaction, and 10 mL of concentrated hydrochloric acid was added. At this time, the crude product was in the aqueous phase. After separation, the aqueous phase was obtained, and the pH value of the aqueous phase was adjusted to alkaline with sodium hydroxide solution. Dichloromethane was added to extract the aqueous phase product, and the organic phase was collected, dried over anhydrous sodium sulfate, and spin-dried to obtain a crude product. The crude product was separated and purified by column chromatography (eluents were dichloromethane and methanol) to obtain the target ligand 1 2-([2,2'-bipyridine]-6-yl)propan-2-amine, and the reaction formula was shown in the following figure:

[0084]

[0085] 1 H NMR (400MHz, CDCl3) δ8.50(d,J=4.1Hz,1H),8.35(d,J=8.0Hz,1H),8.13(d,J=7.8Hz,1H),7.5 9(dt,J=15.1,7.6Hz,2H),7.27(d,J=7.8Hz,1H),7.13–7.01(m,1H),1.98(s,2H),1.40(s,6H).

[0086] 13 C NMR (101MHz, CDCl3) δ167.31,156.29,154.50,148.90,137.22,136.55,123.44,120.91,118.29,54.05,31.14.

[0087] Mass Spectrometry ESI-MS: [M+H] + : m / z=214.1339; Calcd: 214.1329.

[0088] 4) Under the protection of inert gas, 370.5 mg of 2-([2,2'-bipyridine]-6-yl)propan-2-amine was dissolved in 5 mL of acetonitrile to obtain solution A; 220.18 mg of ferrous chloride was dissolved in 5 mL of acetonitrile to obtain solution B; solution B was slowly added dropwise to solution A, and solution B immediately turned purple. After the addition was completed, it was stirred overnight at room temperature. After the reaction was completed, it was stirred in the air for half an hour, and the color of the solution turned brown, accompanied by a large amount of solid precipitation. It was filtered and washed with n-hexane to obtain a multi-nuclear iron-based complex containing oxygen bridges, with a yield of 50%. The single crystal structure is as follows Figure 1 The reaction equation is shown below:

[0089]

[0090] Elemental analysis: C 26 H 30 Cl4Fe2N6O·2H2O (732.0870): C, 42.66; H, 4.68; N, 11.48. Found: C, 42.68; H, 4.62; N, 11.34.

[0091] Mass Spectrometry ESI-MS: [M-Cl] + : m / z=659.0238; Calcd: 659.0240; [M-Cl] 2+ : m / z=312.0273; Calcd: 312.0273.

[0092] Preparation Example 2

[0093] This preparation example provides a preparation method of a polynuclear iron-based complex containing an oxygen bridge. The preparation method is based on the target ligand 1 2-([2,2'-bipyridine]-6-yl)propan-2-amine obtained in Preparation Example 1, and further ligand modification is performed to obtain a new ligand target ligand 2, which is then compounded with an Fe salt to prepare a new polynuclear iron-based complex. The steps are as follows:

[0094] 1) Under the protection of inert gas, 100 mg of 1,4-di(bromomethyl)benzene was dissolved in 3 mL of N,N-dimethylformamide to obtain solution C; 2.1 equivalents of 2-([2,2'-bipyridyl]-6-yl)propan-2-amine was dissolved in 3 mL of DMF to obtain solution D; after the two solutions were mixed, 1 equivalent of K2CO3 solid was added under the protection of inert gas, and stirred at room temperature for 1 day. After the reaction was completed, quenched with 10 mL of water, extracted three times with 20 mL of dichloromethane, the organic phases were combined, washed twice with 15 mL of concentrated brine, dried over anhydrous sodium sulfate, and the solvent was removed by rotary evaporation. The target ligand 2 was separated and purified by column chromatography (the eluents were dichloromethane and methanol), and the reaction formula was shown in the figure below:

[0095]

[0096] 1 H NMR (400MHz, DMSO-d6) δ8.67(dt,J=5.3,1.1Hz,2H),8.44(d,J=8.0Hz,2H),8.23(d,J=7.7Hz,2H),7.94–7.87(m,4 H),7.71–7.66(m,2H),7.42(ddd,J=7.5,4.8,1.2Hz,2H),7.17(dd,J=5.9,4.2Hz,4H),3.39(s,4H),1.51(s,12H).

[0097] Mass Spectrometry ESI-MS: [M+H] + : m / z=529.3088; Calcd: 529.3074.

[0098] 2) Under the protection of inert gas, 400 mg of the target ligand 2 was dissolved in 5 mL of methanol to obtain solution E; 2 equivalents of ferrous chloride were dissolved in 5 mL of methanol to obtain solution F; solution F was slowly added dropwise to solution E and stirred overnight at room temperature. After the reaction was completed, the mixture was stirred in air for half an hour. A large amount of solid precipitated, which was filtered and washed with n-hexane to obtain a multi-nuclear iron-based complex containing an oxygen bridge. The single crystal structure is shown in FIG. Figure 2 The reaction equation is shown below:

[0099]

[0100] Test Case

[0101] Test Example 1

[0102] This test case is used to test the catalytic water oxidation process of polynuclear iron-based complexes containing oxygen bridges under chemical driving force, as follows:

[0103] A homogeneous thermal catalytic water oxidation system based on a polynuclear iron-based complex containing an oxygen bridge comprises: the polynuclear iron-based complex containing an oxygen bridge obtained in Preparation Example 1 and a terminal oxidant.

[0104] The terminal oxidant is oxone with a concentration of 0.1 mol / L.

[0105] The concentration of the polynuclear iron-based complex containing oxygen bridges in the homogeneous thermal catalytic water oxidation system is 1 mmol / L;

[0106] Take 2mL of 0.1mol / L oxone aqueous solution and place it in the reaction chamber of the Clark oxygen electrode. Pass inert gas into the solution to remove the oxygen in the solution. Add the multi-nuclear iron-based complex containing oxygen bridges to make its concentration 1mmol / L. The Clark oxygen electrode can monitor the changes in oxygen concentration in the system in real time. Figure 3 As shown, it is demonstrated that polynuclear iron-based complexes containing oxygen bridges can catalyze water oxidation processes under chemical driving force conditions.

[0107] Test Example 2

[0108] This test example is used to test the catalytic water oxidation process of polynuclear iron-based complexes containing oxygen bridges under light-driven force, as follows:

[0109] A homogeneous photocatalytic water oxidation system based on a polynuclear iron-based complex containing an oxygen bridge comprises: the polynuclear iron-based complex containing an oxygen bridge obtained in Preparation Example 1, terpyridine ruthenium (II), an electron sacrificial agent and an aqueous solvent.

[0110] The concentration of the polynuclear iron-based complex containing oxygen bridges in the homogeneous photocatalytic water oxidation system is 0.1 μmol / L;

[0111] The concentration of the terpyridine ruthenium (II) is 0.1 mmol / L;

[0112] The electron sacrificial agent includes but is not limited to cobalt reagent, sodium persulfate, potassium persulfate, methyl viologen, etc. In this test example, sodium persulfate is selected with a concentration of 10 mmol / L;

[0113] The aqueous solvent is a mixture of water and acetonitrile;

[0114] Take 2mL of homogeneous photocatalytic water oxidation system solution and place it in the reaction chamber of the Clark oxygen electrode. Inert gas is introduced into the solution to remove the oxygen in the solution. After sealing, illuminate it with LED light with a wavelength of 450nm. The real-time oxygen concentration in the system can be read through the Clark oxygen electrode. Figure 4 As shown in the figure, it is shown that the oxygen-bridged multi-nuclear iron-based complex can catalyze the water oxidation process under the condition of light-driven force. The average oxygen conversion number calculated based on the catalyst molecule is 4063, and the maximum conversion efficiency is 0.76s-1 .

[0115] Test Example 3

[0116] This test case is used to test the catalytic water oxidation process of multi-nuclear iron-based complexes containing oxygen bridges under electrical driving force, as follows:

[0117] A homogeneous electrocatalytic water oxidation system based on a polynuclear iron-based complex containing oxygen bridges comprises: the polynuclear iron-based complex containing oxygen bridges obtained in Preparation Example 1 and an electrolyte solution.

[0118] The concentration of the polynuclear iron-based complex containing oxygen bridges in the homogeneous electrocatalytic water oxidation system is 1 mmol / L;

[0119] The electrolyte solution includes, but is not limited to, one or more of an acetate buffer solution, a nitric acid aqueous solution, a carbonate buffer solution, a boric acid buffer solution, and a phosphate buffer solution; the boric acid buffer solution used in this preparation example has a concentration of 0.2 mol / L.

[0120] The electrolytic cell is a 40mL H-type double-chamber electrolytic cell separated by an anion exchange membrane. The working electrode is FTO conductive glass; the counter electrode is a platinum sheet; and the reference electrode is an Ag / AgCl electrode. The generated oxygen is monitored by an Ocean Optics fiber optic oxygen content sensor HIOXY.

[0121] The working electrode needs to be pretreated, that is, the FTO conductive glass is cut into a size of 12*7mm, and is thoroughly cleaned with ultrasound in ultrapure water and anhydrous ethanol until the surface is clean, and then dried for later use.

[0122] The Ocean Optics fiber optic oxygen sensor HIOXY requires a two-point calibration in oxygen-free water and oxygen-saturated water.

[0123] Take 20mL of homogeneous photocatalytic water oxidation system solution in the electrolytic cell, seal it and introduce inert gas into the electrolytic cell to remove oxygen in the solution and gas phase. Place the HIOXY optical fiber next to the conductive surface of the FTO conductive glass to read the real-time oxygen concentration changes in the system, such as Figure 5 As shown, the multi-core iron-based complex containing oxygen bridges can catalyze water oxidation under the condition of electric driving force, with an overpotential as low as 390 mV and a TOF as high as 360 s. -1 .

[0124] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the protection scope of the present invention.

Claims

1. A polynuclear iron-based complex containing oxygen bridges, characterized in that: The structure of the multi-nuclear iron-based complex is shown in Formula I or Formula II: wherein X represents any one of F, Cl, Br, I, OAc and NO2; R1 and R2 are each independently selected from any one of H, N(CH3)2, COOH, F, Cl, Br, I and an alkyl group having a carbon number of C1-C5; Ring A is selected from any one of a phenyl group, a naphthyl group and a pyridyl group.

2. The multi-nuclear iron-based complex according to claim 1, characterized in that The multi-nuclear iron-based complex is selected from one of the following structures:

3. The method for preparing a multi-nuclear iron-based complex according to any one of claims 1 or 2, characterized in that: When preparing the compound of formula I, the following steps are included: 1) Compound I-1 was dissolved in trifluoroacetic acid, and then H2O2 solution was added dropwise, and stirred at room temperature for 8-12 hours; after the reaction was completed, dichloromethane was added for extraction, and the liquids were separated, and the organic phase was collected, washed, dried over anhydrous sodium sulfate, and the solvent was removed by rotary evaporation to obtain compound I-2; 2) Under an inert atmosphere, compound I-2 and trimethylsilyl cyanide are dissolved in dichloromethane, then placed in an ice-water bath, benzoyl chloride is added dropwise, and after the addition is complete, the mixture is transferred to room temperature for reaction for 3-5 days; after the reaction is completed, the mixture is transferred to an ice-water bath again, sodium carbonate solution is added, the liquids are separated, the aqueous phase is extracted with dichloromethane, the organic phases are combined, dried over anhydrous sodium sulfate, the solvent is removed by rotary evaporation, and separation and purification are performed by column chromatography to obtain compound I-3; 3) Under an inert atmosphere, compound I-3 is dissolved in toluene, then placed in an ice-water bath, methylmagnesium bromide solution is added dropwise, and after the addition is complete, the mixture is refluxed for reaction for 8-12 hours; after the reaction is complete, the reaction is quenched with a saturated ammonium chloride solution, concentrated hydrochloric acid is added, the liquids are separated, the aqueous phase is collected, the pH of the aqueous phase is adjusted to alkaline with sodium hydroxide, dichloromethane is added for extraction, the liquids are separated, the organic phase is collected, dried over anhydrous sodium sulfate, the solvent is removed by rotary evaporation, and separation and purification is performed by column chromatography to obtain compound I-4; 4) Under an inert atmosphere, compound I-4 is dissolved in acetonitrile to obtain solution A; iron salt is dissolved in acetonitrile to obtain solution B; solution A or B is added dropwise to the other solution, and the mixture is reacted at room temperature for 8-12 hours; after the reaction is completed, the mixture is stirred in the air for 20-30 minutes to produce a large amount of precipitate, which is filtered and washed to obtain a compound of formula I.

4. The preparation method according to claim 3, characterized in that: In step 2), the molar ratio of compound I-2, trimethylsilyl cyanide and benzoyl chloride is 1:7-10:1.2-1.

5.

5. The preparation method according to claim 3, characterized in that: In step 3), the molar ratio of compound I-3 to methylmagnesium bromide is 3.0-4.0:

1.

6. The preparation method according to claim 3, characterized in that: In step 4), the molar ratio of compound I-4 to iron salt is 1:1.0-1.2; Preferably, the iron salt is selected from any one of FeCl2, FeCl3, FeBr3, FeI3, Fe(OAc)2, Fe(OAc)3 and Fe(NO2)3.

7. The method for preparing a multi-nuclear iron-based complex according to any one of claims 1 or 2, characterized in that: When preparing the compound of formula II, the following steps are included: 1) Compound I-1 was dissolved in trifluoroacetic acid, and then H2O2 solution was added dropwise, and the reaction was stirred at room temperature for 8-12 hours; after the reaction was completed, dichloromethane was added for extraction, and the liquids were separated, and the organic phase was collected, washed, dried over anhydrous sodium sulfate, and the solvent was removed by rotary evaporation to obtain compound I-2; 2) Under an inert atmosphere, compound I-2 and trimethylsilyl cyanide are dissolved in dichloromethane, then placed in an ice-water bath, benzoyl chloride is added dropwise, and after the addition is complete, the mixture is transferred to room temperature for reaction for 3-5 days; after the reaction is completed, the mixture is transferred to an ice-water bath again, sodium carbonate solution is added, the liquids are separated, the aqueous phase is extracted with dichloromethane, the organic phases are combined, dried over anhydrous sodium sulfate, the solvent is removed by rotary evaporation, and separation and purification are performed by column chromatography to obtain compound I-3; 3) Under an inert atmosphere, compound I-3 is dissolved in toluene, then placed in an ice-water bath, methylmagnesium bromide solution is added dropwise, and after the addition is complete, the mixture is refluxed for reaction for 8-12 hours; after the reaction is complete, the reaction is quenched with a saturated ammonium chloride solution, concentrated hydrochloric acid is added, the liquids are separated, the aqueous phase is collected, the pH of the aqueous phase is adjusted to alkaline with sodium hydroxide, dichloromethane is added for extraction, the liquids are separated, the organic phase is collected, dried over anhydrous sodium sulfate, the solvent is removed by rotary evaporation, and separation and purification is performed by column chromatography to obtain compound I-4; 4) Under an inert atmosphere, compound I-4 was dissolved in N,N-dimethylformamide to obtain solution C; compound II-1 was dissolved in DMF to obtain solution D; solution C or D was added dropwise to the other solution, and then solid K2CO3 was added, and the mixture was reacted at room temperature for one day. After the reaction was completed, the mixture was quenched with water, extracted with dichloromethane, and the organic phase was collected, washed, dried over anhydrous sodium sulfate, and the solvent was removed by rotary evaporation. The mixture was separated and purified by column chromatography to obtain compound II-2; 5) Under an inert atmosphere, compound II-2 is dissolved in methanol to obtain solution E; iron salt is dissolved in methanol to obtain solution F; solution E or F is added dropwise to the other solution and reacted at room temperature for 8-12 hours; after the reaction is completed, it is transferred to the air and stirred for 20-30 minutes. A large amount of precipitate is precipitated, which is filtered and washed to obtain the compound of formula II.

8. The method according to claim 7, characterized in that In step 4), the molar ratio of compound I-4, compound II-1 and K2CO3 is 2-2.2:1:

1.

9. The method according to claim 7, characterized in that: In step 5), the molar ratio of compound II-2 to iron salt is 1:2-2.

2.

10. Use of the multi-nuclear iron-based complex according to claim 1 or 2 in catalyzing water oxidation reactions; Preferably, in the application, the multi-nuclear iron-based complex catalyzes water oxidation reaction under the action of chemical driving force, light driving force or electrical driving force.

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