Sulfur-containing macrocyclic binuclear nickel complex as well as preparation method and application thereof

Abstract

The invention discloses a sulfur-containing macrocyclic binuclear nickel complex as well as a preparation method and application thereof. The crystal form of the sulfur-containing macrocyclic binuclear nickel complex belongs to a monoclinic crystal system and a C2 / c space group, and the preparation method of the sulfur-containing macrocyclic binuclear nickel complex comprises the following steps: putting 2, 6-diformyl-4-methoxy-N, N-dimethyl carbamoyl thiophenol into an organic solvent, carrying out a reflux reaction in an alkaline environment, adding nickel perchlorate hexahydrate and diamine into the obtained reflux solution, and carrying out a reaction under the alkaline environment to obtain the sulfur-containing macrocyclic binuclear nickel complex. And filtering the material liquid obtained by the reaction to obtain powder, and dissolving and crystallizing the powder in a mixed solvent composed of acetonitrile and diethyl ether. When the crystal form of the complex is used as a photocatalyst, CO2 can be converted into HCOOH, and high catalytic activity and selectivity are shown.

Description

Technical Field

[0001] The invention relates to a metal complex, and in particular to a sulfur-containing macrocyclic binuclear nickel complex and a preparation method and application thereof. Background Art

[0002] With the rapid development of industrialization, human demand for fossil fuels and their exploitation have increased dramatically, and energy and environmental crises have become increasingly serious. The burning of fossil fuels produces a large amount of CO2 gas, which is the culprit of the greenhouse effect. According to the survey report, the greenhouse effect has caused records in surface temperature, ocean heat and acidification, sea level rise, Antarctic sea ice sheet and glacier retreat to be broken again, and the corresponding changes are accelerating. The catalytic conversion of CO2 into valuable carbon-containing chemicals or fuels is an effective solution to reduce the concentration of CO2 in the atmosphere and alleviate the energy crisis.

[0003] As we all know, the main way to consume CO2 in nature is through photosynthesis of plants. Based on this, scientists have developed artificial simulated photosynthesis, which converts CO2 into high value-added carbon-containing chemical raw materials through photocatalysis, and replaces various functional components of photosynthesis with light sources, photosensitizers, catalysts, sacrificial agents and solvents, and converts CO2 into energy and chemical raw materials such as HCOOH, CO, CH3OH and CH4 through photocatalysis. This technology can not only effectively catalyze and convert CO2, but also further protect the ecological environment and alleviate the energy crisis, allowing people to live in harmony with nature.

[0004] The development of efficient catalysts is an important research topic in the construction of photocatalytic CO2 reduction systems. Traditional homogeneous catalysts mostly use expensive precious metal complexes, which are not conducive to large-scale production and application. In recent years, the development of efficient and low-cost non-precious metal complex catalysts has become a current research hotspot. Therefore, the design and development of non-precious metal complex catalysts has important research significance and value. For example, the invention patent with publication number CN109705168A discloses a binuclear nickel coordination compound Specifically, 4,4'-dimethyl-2,2'-bipyridine and nickel ions form a binuclear molecular structure through a chlorine bridge bond, and the binuclear nickel ligand compound is used as a photocatalyst to convert greenhouse gas CO2 into methane gas and CO. After searching, there is no related report on the conversion of CO2 into HCOOH by a sulfur-containing binuclear nickel complex formed by connecting nickel ions and N / S as a photocatalyst. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a sulfur-containing macrocyclic binuclear nickel complex and its preparation method and application. The two nickel ions in the complex are coordinated with four N atoms and two S atoms to form a planar tetragonal binuclear structure. It can be used as a photocatalyst to convert CO2 into HCOOH and exhibits high catalytic activity and selectivity.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] A sulfur-containing macrocyclic binuclear nickel complex having the chemical formula C 28 H 32 Cl2N6Ni2O 10 S2, the structure is shown in the following formula (I):

[0008]

[0009] The crystal form of the sulfur-containing macrocyclic binuclear nickel complex belongs to the monoclinic system, C2 / c space group, and its unit cell parameters are: α=90°,β=116.773(3)°,γ=90°. The crystal form is a red block crystal, the nickel ion at the metal center is divalent, and the two nickel ions are coordinated with the four N atoms and two S atoms in the dianionic ligand obtained by condensation of 1,3-diaminopropane and 2,6-diformyl-4-methoxydiphenol, forming a planar tetragonal binuclear structure.

[0010] The method for preparing the crystalline form of the sulfur-containing macrocyclic binuclear nickel complex of the present invention comprises: placing a compound represented by the following formula (C) in an organic solvent, performing a reflux reaction in an alkaline environment, adding nickel perchlorate hexahydrate and 1,3-propylenediamine to the obtained reflux solution, performing a reflux reaction again, filtering the obtained reaction solution, collecting the filter cake, and dissolving and crystallizing the filter cake in a mixed solvent composed of acetonitrile and ether;

[0011]

[0012] In the above preparation method, the organic solvent can be isopropanol and / or N,N-dimethylformamide. The amount used is preferably such that it can dissolve the raw materials participating in the reaction. Usually, based on 1 mmol of the compound represented by formula (C), the total amount of organic solvent used for all raw materials is controlled to be 50-150 mL.

[0013] In the above preparation method, the alkaline environment is a weak alkaline environment, preferably a weak alkaline environment with a pH of 8.0 to 10.0. The alkaline environment is provided by adding an alkaline substance to the reaction system. The alkaline substance is a conventional choice in the prior art, preferably one or a combination of two or more selected from sodium hydroxide, potassium hydroxide, sodium carbonate, cesium carbonate and triethylamine. Under weak alkaline and heating conditions, the N,N-dimethylformyl group connected to S in the compound shown in formula (C) falls off to form S - ions. The S - The ions are then coordinated and condensed with nickel perchlorate hexahydrate and diamine to obtain the target product.

[0014] In the above preparation method, the reaction is preferably carried out under the protection of an inert gas (such as nitrogen, argon or helium).

[0015] In the above preparation method, in the mixed solvent composed of acetonitrile and diethyl ether, the proportion of acetonitrile is 10 to 45 v / v%, preferably 20 to 35 v / v%.

[0016] The compound represented by formula (C) involved in the above preparation method is 2,6-diformyl-4-methoxy-N,N-dimethylcarbamoylthiophenol, which can be synthesized with reference to existing literature (such as invention patent application with publication number CN117466806A, or J. Chem. SOC. D,alton Trans., 1996, Pages 3031-3037.), which will not be described in detail here.

[0017] The present invention also includes the use of the above-mentioned sulfur-containing macrocyclic binuclear nickel complex or its crystal form as a catalyst in photocatalytic carbon dioxide reduction. In a specific application, the photocatalytic system includes a photosensitizer, a catalyst, a sacrificial agent and a solvent, wherein the catalyst is the above-mentioned sulfur-containing macrocyclic binuclear nickel complex or its crystal form, and the selection of the photosensitizer, the sacrificial agent and the solvent is the same as the prior art. Specifically, the photosensitizer can be [Ru(phen)3](PF6)2, [Ru(phen)3]Cl2 or [Ru(bpy)3]Cl2, preferably [Ru(phen)3](PF6)2; the sacrificial agent is preferably triethanolamine (TEOA) and / or triethylamine (TEA); the solvent is preferably a mixed solution containing water and acetonitrile, wherein the volume ratio of water to acetonitrile is preferably 1:4. In the photocatalytic system, the concentration of the photosensitizer is preferably 400-500 μM, the concentration of the catalyst is preferably 0.05-1 μM, and the concentration of the sacrificial agent is preferably 0.30-0.35M.

[0018] The present invention also provides a catalyst, which contains the sulfur-containing macrocyclic binuclear nickel complex or its crystal form.

[0019] Compared with the prior art, the present invention synthesizes a novel N4S2-type ligand binuclear nickel complex by an in-situ method. The complex can selectively generate formic acid during photocatalytic CO2 reduction as a homogeneous molecular catalyst, showing high catalytic activity, selectivity and stability. The applicant's test results show that when the concentration of the complex is 0.1 μM as a catalyst, photocatalytic CO2 reduction generates 1.70 μmol formic acid, the turnover number TON value of selective formic acid generation reaches 3400, and the selectivity for formic acid reaches 94%. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is the infrared spectrum of the sulfur-containing macrocyclic binuclear nickel complex prepared in Example 1 of the present invention.

[0021] Figure 2 This is the mass spectrum of the sulfur-containing macrocyclic binuclear nickel complex prepared in Example 1 of the present invention.

[0022] Figure 3 The mass spectrum fitting diagram of the single crystal sample and single crystal simulation of the sulfur-containing macrocyclic binuclear nickel complex prepared in Example 1 of the present invention.

[0023] Figure 4 This is a crystal structure diagram of the sulfur-containing macrocyclic binuclear nickel complex prepared in Example 1 of the present invention.

[0024] Figure 5 Response diagram of adding fresh photosensitizer (a) and sacrificial agent (b) to the solution after photocatalytic CO2 reduction of the sulfur-containing macrocyclic binuclear nickel complex prepared in Example 1 of the present invention for 12 hours. DETAILED DESCRIPTION

[0025] In order to better explain the technical solution of the present invention, the present invention is further described in detail below in conjunction with embodiments, but the embodiments of the present invention are not limited thereto.

[0026] The compounds represented by formula (C) involved in the following examples were prepared according to the following method:

[0027]

[0028] 1) Preparation of the compound represented by formula (B):

[0029] Under an inert atmosphere, the compound shown in formula (A) (2,6-diformyl-4-methoxyphenol, 696 mg, 3.87 mmol) was dissolved in dry DMF (N,N-dimethylformamide, 25 mL), 1,4-diazabicyclo[2.2.2]octane (DABCO, 867 mg, 7.74 mmol) was added, the solution turned orange, and then dimethylthiocarbamoyl chloride (715.5 mg, 5.8 mmol) was added, and the reaction was stirred for 18 hours. After the reaction was completed, 100 mL of water was added, cooled to 0 ° C, filtered, and a reddish brown beige powder was obtained. The obtained reddish brown beige powder was dissolved in CHCl3 and dried over anhydrous Na2SO4 to obtain a reddish brown solid product (B) (820 mg, 84%). 1 H NMR (400MHz, Chloroform-d) δ10.05 (s, 1H), 7.63 (s, 1H), 3.91 (s, 2H), 3.49 (d, J = 2.1Hz, 3H).

[0030] 2) Preparation of the compound represented by formula (C):

[0031] Under an inert atmosphere, the compound represented by formula (B) (910 mg, 3.41 mmol) was dissolved in 20 mL of 1,2-dichloroethane, and BF3.Et2O (500 μL, 4.05 mmol) was added under stirring, and the temperature was raised to 80°C for reaction for 3 hours. After the reaction was completed, it was cooled to 0°C, and then 20 mL of water was added thereto, the two-phase mixture was decanted, the aqueous layer was extracted with CH2Cl2 (3×30 mL), the organic layer was collected, the organic layer was dried over anhydrous Na2SO4, and the solvent was evaporated under reduced pressure to obtain a brown solid (C) (803 mg, 93%). 1 H NMR (400MHz, Chloroform-d) δ10.05 (s, 2H), 7.63 (s, 2H), 3.91 (s, 3H), 3.49 (d, J = 2.6Hz, 6H).

[0032] Example 1

[0033] The compound represented by formula (C) (2,6-diformyl-4-methoxy-N,N-dimethylcarbamoylthiophenol, 510 mg, 2.03 mmol) was dissolved in isopropanol (150 mL), and NaOH (80 mg, 2.0 mmol) was added thereto, and the color of the solution changed from yellow to dark red. The temperature was raised to 80°C and refluxed for 5 hours, and then Ni(ClO4)2·6H2O (742 mg, 2.03 mmol) and H2N(CH2)3NH2 (0.17 mL, 2.03 mmol) were added to the reflux solution. The mixture was heated to 80°C and refluxed for 4 hours, and filtered while hot to obtain a red solid, which was placed in a mixed solvent consisting of MeCN and Et2O in a volume ratio of 1:3 for recrystallization to obtain red block crystals (212 mg, yield 41%).

[0034] The product obtained in this example was characterized:

[0035] (1) Infrared spectrum, its spectrum is as follows Figure 1 shown.

[0036] IR(KBr,cm -1 ): 3436w, 3327w, 3165w, 2919m, 1647s, 1548m, 1401m, 1337m, 1283w, 1238m, 1189w, 1110m, 992w, 927w, 809m, 765w, 602w, 529w.

[0037] (2) Mass spectrometry analysis:

[0038] When performing mass spectrometry analysis, the mass spectrometer is set to positive ion mode, which only detects and analyzes cations, excluding anions and solvent molecules.

[0039] The mass spectrum of the single crystal obtained in this embodiment is as follows Figure 2 As shown, ESI-MS (CH3CN): m / z [Ni2L] 2+ , calculated value: 291.02, actual value: 291.01, L represents the divalent anion of the product obtained by condensing the product (2,6-diformyl-4-methoxythiophenol) after the compound represented by formula (C) is hydrolyzed with NaOH and 1,3-propylenediamine.

[0040] Figure 3 The mass spectrum fitting diagram of the single crystal sample prepared in this example and the single crystal simulation is shown in Figure 1. The figure proves that the diffraction peaks of the synthesized single crystal sample and the simulated powder diffraction are consistent, indicating that the synthesized sample has high purity and is the target product.

[0041] (3) Crystal structure analysis:

[0042] A red crystal of appropriate size was selected and placed on a Bruker SMART CCD diffractometer using graphite monochromatized Cu-K α The initial crystal structures of the products obtained in this example were solved by the SHELXS-97 direct method, and the geometric hydrogenation, non-hydrogen atomic coordinates and anisotropic thermal parameters were refined by the full matrix least squares method using SHELXL-97. The obtained crystallographic and structural refinement data are shown in Table 1 below, and some bond length and bond angle data are shown in Tables 2 and 3 below, respectively. The crystal structure of the obtained red crystal is shown in Figure 4 shown.

[0043] Table 1 Crystallographic data of the nickel complex of the present invention

[0044]

[0045] Table 2 Partial bond length data of nickel complexes described in the present invention

[0046]

[0047] Table 3 Partial bond angle data of the nickel complex of the present invention (°)

[0048]

[0049] Therefore, it is determined that the red crystals obtained in this example are the target product of the present invention.

[0050] Example 2

[0051] Example 1 was repeated, except that the mixed solvent used in the recrystallization consisted of MeCN and Et2O in a volume ratio of 1:5.

[0052] As a result, red block crystals (200 mg, yield 39%) were obtained.

[0053] Experimental Example 1: The sulfur-containing macrocyclic binuclear nickel complex of the present invention was used as a homogeneous molecular catalyst to test its photocatalytic CO2 reduction performance in an aqueous solvent system.

[0054] (1) Materials used:

[0055] Photosensitizer: [Ru(phen)3](PF6)2, catalyst: sulfur-containing macrocyclic binuclear nickel complex prepared according to the method described in Example 1 of the present invention (hereinafter referred to as complex 1), sacrificial agent TEA, LED light source (wavelength 450nm, light intensity 100mW·cm -2 , the irradiation area is 0.8cm 2), a 15 mL quartz reactor, CO2 gas, rubber tubing, analytical balance, stirrer and gas chromatograph.

[0056] (2) Experimental steps:

[0057] Weigh 2 mg of photosensitizer [Ru(phen)3](PF6)2, transfer 200 μL of sacrificial agent TEA and complex 1 (1 μM) into a quartz glass tube, add 4 mL of ultra-dry acetonitrile and 1 mL of water, seal tightly with a rubber tube, and introduce CO2 gas for 10 to 20 minutes. -2 , irradiation area is 0.8cm 2 The mixture was irradiated for 12 h under an LED light with stirring. After the above operation, a gas sample was injected into a gas chromatograph to detect the gas phase product of CO2 reduction. The liquid product was tested by ion chromatography. The results showed that when the complex 1 was 1 μM, it catalyzed CO2 reduction to produce 2.25 μmol of HCOOH and 0.19 μmol of H2 as a byproduct. The catalytic conversion number was TON. HCOOH The value is 450, and the selectivity for HCOOH is as high as 93%.

[0058] The above method was subjected to parallel experiments at different concentrations, and the results are shown in the following Table 4. As can be seen from Table 4, under different catalytic system conditions, the catalytic effect of the photocatalytic CO2 reduction of the complex of the present invention is significantly higher than that of other catalytic systems.

[0059] Table 4 Experimental data of photocatalytic CO2 reduction using the nickel complex of the present invention as a catalyst

[0060]

[0061] Reaction conditions: At 25°C, LED light (450nm, 100mW·cm -2 , illumination time 12h, illumination area 0.8cm 2 ) was irradiated with 5 mL of catalyst, photosensitizer [Ru(phen)3](PF6)2 (0.4 mM), and sacrificial agent TEA (0.3 M). No. 1: complex 1 (1 μM); No. 2: complex 1 (0.1 μM); No. 3: complex 1 (0.05 μM); No. 4: blank control group without catalyst.

[0062] From the above photocatalytic results, it can be seen that the complex of the present invention has a good visible light catalytic CO2 reduction effect as a homogeneous catalyst in an aqueous system. In the photocatalytic system constructed by the present invention, when the concentration of the catalyst complex 1 is 0.1 μM, the catalytic conversion number TON HCOOHThe value is 3400. When the catalyst concentration is reduced to 0.05 μM, the catalytic conversion number TON HCOOH The value was increased to 3600, and the selectivity for HCOOH was 93%, which was better than most of the reported metal complex catalysts. However, when there was no catalyst complex 1 in the system, no HCOOH was generated in the reaction system, indicating that the HCOOH produced in this reaction did come from the photocatalytic CO2 reduction of complex 1.

[0063] (3) Study on the stability of the catalytic system

[0064] As the illumination time increases, the photosensitizer that can play a role gradually decreases. In order to verify whether the cessation of the catalytic reaction is caused by the degradation and inactivation of the photosensitizer, the applicant added a fresh photosensitizer to the catalytic system after 12 hours of reaction. The experimental results are as follows Figure 5 As shown in (a), after 12 h of reaction with 0.4 mM catalyst, 2 μmol of HCOOH was produced and the catalytic reaction stopped. After adding a fresh photosensitizer [Ru(phen)3](PF6)2 (0.4 mM), the catalytic system could carry out the photocatalytic reaction normally, indicating that the cessation of the photocatalytic reaction may be caused by the deactivation of the photosensitizer.

[0065] The second reason may be the consumption of the sacrificial agent. The sacrificial agent is gradually consumed after providing electrons during the catalytic reaction. Therefore, the reason for the cessation of the catalytic reaction may also be that the sacrificial agent is completely consumed. To verify this, the applicant used the same method to add a fresh sacrificial agent (0.3M) to the reaction system where the catalysis stopped after 12 hours of light exposure. The experimental results are as follows Figure 5 As shown in (b), the catalytic system did not recover after the addition of the sacrificial agent, indicating that the consumption of the sacrificial agent was not the reason for the cessation of the catalytic system, which means that the sacrificial agent was excessive and there was enough sacrificial agent to support the reaction.

[0066] In summary, the consumption of the photosensitizer is the main reason for the cessation of the catalytic system, which indicates that the sulfur-containing macrocyclic binuclear nickel complex prepared by the present invention is a stable molecular catalyst.

Claims

1. A sulfur-containing macrocyclic binuclear nickel complex having the chemical formula C 28 H 32 Cl2N6Ni2O 10 S2, the structure is shown in the following formula (I):

2. A crystal form of the sulfur-containing macrocyclic binuclear nickel complex according to claim 1, which belongs to the monoclinic system, C2 / c space group, and its unit cell parameters are: α=90°, β=116.773(3)°, γ=90°.

3. The method for preparing the crystalline form of the sulfur-containing macrocyclic binuclear nickel complex according to claim 2, characterized in that: The compound represented by the following formula (C) is placed in an organic solvent, and refluxed under an alkaline environment, nickel perchlorate hexahydrate and 1,3-propylenediamine are added to the obtained reflux solution, and refluxed again, the obtained feed liquid is filtered, the filter cake is collected, and the filter cake is placed in a mixed solvent composed of acetonitrile and diethyl ether to dissolve and crystallize to obtain; 4. The preparation method according to claim 3, characterized in that: The organic solvent is isopropanol and / or N,N-dimethylformamide.

5. The preparation method according to claim 3, characterized in that: The alkaline environment is pH = 8.0 ~ 10.

0.

6. The preparation method according to claim 3, characterized in that: An alkaline substance is added to the reaction system to provide an alkaline environment.

7. The preparation method according to claim 6, characterized in that: The alkaline substance is one or a combination of two or more of sodium hydroxide, potassium hydroxide, sodium carbonate, cesium carbonate and triethylamine.

8. The preparation method according to claim 3, characterized in that: In the mixed solvent composed of acetonitrile and diethyl ether, the proportion of acetonitrile is 10 to 45 v / v%.

9. Use of the sulfur-containing macrocyclic binuclear nickel complex according to claim 1 or the crystal form according to claim 2 as a catalyst in photocatalytic carbon dioxide reduction.

10. A photocatalyst comprising the sulfur-containing macrocyclic binuclear nickel complex according to claim 1 or the crystal form according to claim 2.

Images