Polynuclear cobalt formate complexes, methods of making and using the same

Abstract

The present application relates to the technical field of metal coordination compound functional materials, and discloses a polynuclear cobalt formate complex, a preparation method and application thereof.The polynuclear cobalt formate complex is novel and stable in structure, has good thermal stability, and has certain photocatalytic effect, and can be used as a catalyst in a photocatalytic system to convert methane into methanol, has potential application value in photocatalysis, and has the advantages of simple preparation method, high product purity, easy preparation of the polynuclear cobalt formate complex, and favorable application and promotion.

Description

Technical Field

[0001] This invention relates to the field of functional materials technology of metal coordination compounds, and more specifically, to cobalt polynucleoformate complexes, their preparation methods and applications. Background Technology

[0002] With the increasing scarcity of oil resources, people are paying more and more attention to the development and utilization of natural gas. Methane, as the main component of natural gas, has considerable reserves worldwide, exceeding those of oil according to some studies. Compared to coal and oil, methane has a higher hydrogen-to-carbon ratio and is considered a clean energy source. Besides being used directly as fuel, methane can also be converted into methanol or other high-value-added products through catalytic technology, thus achieving more efficient utilization. Because photocatalysis technology has advantages such as simple operation, low energy consumption, no secondary pollution, and high efficiency, its application in methane conversion has significant academic and industrial application value.

[0003] Photocatalytic reactions generate high-energy electrons and holes through light excitation, which participate in the activation of the CH bond in methane and the formation of free radicals, thereby compensating for the increase in the Gibbs free energy of the reaction. Furthermore, photocatalytic reactions typically occur under relatively mild conditions, providing a new pathway for low-temperature methane conversion. In recent years, the direct conversion of methane to oxygen-containing products such as methanol by oxidants has attracted considerable attention. Following the development and utilization of light energy, research on photocatalytic methane conversion has also deepened. In the system of photocatalytic methane to methanol conversion, the catalyst plays a crucial role. Although catalysts containing noble metals such as Rh and Pt have good photocatalytic performance, their limited reserves and high prices result in high catalytic costs, hindering their application in large-scale production. Therefore, developing inexpensive non-noble metal catalysts for the photocatalytic conversion of methane to methanol is of great significance. Summary of the Invention

[0004] The purpose of this invention is to overcome at least one of the shortcomings of the prior art and to provide a novel and inexpensive polynucleoformate cobalt complex to solve the problem of high production costs caused by the use of precious metal-containing materials as catalysts in the reaction of methane to methanol.

[0005] The technical solution adopted in this invention is to provide a polynuclear cobalt formate complex, wherein the polynuclear cobalt formate complex has cobalt ions as the central ion, formate ions as ligands, and water molecules as auxiliary ligands.

[0006] Another object of the present invention is to provide a method for preparing the above-mentioned polynuclear cobalt formate complex, specifically synthesized by formic acid, sodium bicarbonate and bis(triphenylphosphine)cobalt(II) chloride through a volatile solvent.

[0007] Another object of the present invention is to provide the application of the above-mentioned cobalt polynuclear formate complex in the field of photocatalysis, specifically in the reaction of converting methane into methanol.

[0008] Compared with existing technologies, the advantages of this invention are as follows: First, this invention utilizes the bidentate coordination characteristic of formic acid to stably coordinate divalent cobalt ions, resulting in a novel polynuclear cobalt formate complex. Second, this invention uses inexpensive cobalt salts as raw materials, reducing the preparation cost of the catalyst. Third, the preparation method provided by this invention is simple, the product has high purity, and the polynuclear cobalt formate complex is easily produced. Finally, the polynuclear cobalt formate complex of this invention exhibits good thermal stability and photocatalytic activity, making it suitable for use in the reaction of methane to methanol conversion, and showing promising application prospects in the field of photocatalytic methane-to-methanol conversion. Attached Figure Description

[0009] Figure 1 This is a schematic diagram of the crystal structure unit of the polynuclear cobalt formate complex of the present invention.

[0010] Figure 2 This is a gas chromatographic detection diagram of the polynuclear cobalt formate complex of the present invention used as a photocatalyst to reduce methane to methanol.

[0011] Figure 3 This is a thermogravimetric diagram of the polynucleoformate cobalt complex of the present invention. Detailed Implementation

[0012] This invention provides a polynuclear cobalt formate complex, wherein the polynuclear cobalt formate complex has cobalt ions as the central ion, formate ions as ligands, and water molecules as auxiliary ligands.

[0013] The molecular formula of the above-mentioned cobalt polynucleoformate complex is C2H8CoO6.

[0014] The crystal of the above-mentioned cobalt polynucleate complex is a solid crystal. The crystal belongs to the monoclinic crystal system, space group P21 / c (no. 14), and the cell parameters are: a = 8.6781(17) Å, b = 7.1693(14) Å, c = 9.2870(19) Å, α = 90°, β = 97.45(3)°, γ = 90°, V = 572.9(2) Å3.

[0015] The aforementioned cobalt polyformate complex begins to lose water molecules at 151.4℃, i.e., the decomposition temperature is 151.4℃; the structure begins to collapse at 281.2℃, and the structure completely collapses at 998.4℃.

[0016] The present invention also provides a method for preparing the above-mentioned polynuclear cobalt formate complex, specifically synthesized by formic acid, sodium bicarbonate and bis(triphenylphosphine)cobalt(II) chloride through a volatile solvent.

[0017] Among them, the chemical formula of bis(triphenylphosphine)cobalt(II) chloride is C 36 H 30 Cl2CoP2.

[0018] The above preparation method specifically includes the following steps:

[0019] S1. Dissolve sodium bicarbonate in DMF and dissolve cobalt(II) bis(triphenylphosphine) chloride in acetonitrile, mix them, and obtain a mixed solution;

[0020] S2. Add a mixed acid containing formic acid to the mixture obtained in step S1, evaporate the solvent, and precipitate pink blocky crystals;

[0021] S3. Wash the pink blocky crystals obtained in step S2, and dry them to obtain a single crystal sample of the polynucleoformate cobalt complex.

[0022] Further, in step S2, according to the method for preparing cobalt polynucleoformate complex according to claim 4, the ratio of sodium bicarbonate to bis(triphenylphosphine)cobalt(II) chloride in step S1 is 20 mmol: 3 mmol.

[0023] Further, in step S2, the mixed acid is a mixed solution of acetic acid and formic acid in a volume ratio of 3:7.

[0024] According to the method for preparing cobalt polyformate complexes according to claim 5, the ratio of the mixed acid to sodium bicarbonate in step S2 is 10 mL: 1 mmol.

[0025] Furthermore, in step S2, the volatile solvent is subjected to evaporation at room temperature for 60 to 120 days, preferably 70 to 90 days.

[0026] In step S3, the pink blocky crystals obtained in step S2 are preferably washed with acetonitrile or DMF. After washing, they are dried using a vacuum drying oven or other drying equipment to obtain a single crystal sample of the polynuclear cobalt formate complex.

[0027] The above preparation method is simple and easy to obtain the polynucleoformate cobalt complex.

[0028] The present invention also provides the application of the above-mentioned polynuclear cobalt formate complex as a photocatalyst, specifically, the photocatalyst is used in the reaction of converting methane into methanol.

[0029] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims of the present invention.

[0030] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0031] The present invention will now be further illustrated with specific examples. The following embodiments are only for explaining the present invention and do not constitute a limitation thereof. The test samples and test procedures used in the following embodiments include the following (if the specific experimental conditions are not specified in the embodiments, they are usually performed according to conventional conditions or the conditions recommended by the reagent company; the reagents, consumables, etc. used in the following embodiments can be obtained commercially unless otherwise specified).

[0032] Example 1

[0033] 196.2 mg (0.3 mmol) of bis(triphenylphosphine)cobalt(II) chloride and 168.0 mg (2.0 mmol) of sodium bicarbonate were dissolved in acetonitrile (10 mL) and DMF (10 mL), respectively. The two solutions were then mixed to obtain a mixed solution. A mixture of acetic acid and formic acid in a volume ratio of 3:7 (20 mL) was added to the resulting mixed solution. The solvent was allowed to evaporate at room temperature. After 120 days, pink crystals were obtained. These crystals were washed with acetonitrile and dried in a vacuum drying oven to obtain a single crystal sample of the polynuclear cobalt formate complex.

[0034] Example 2

[0035] 98.1 mg (0.15 mmol) of bis(triphenylphosphine)cobalt(II) chloride and 84.0 mg (1.0 mmol) of sodium bicarbonate were dissolved separately in acetonitrile (5 mL) and DMF (5 mL), respectively. The two solutions were then mixed to obtain a mixed solution. A mixture of acetic acid and formic acid in a volume ratio of 3:7 (10 mL) was then added to the resulting mixed solution. The solvent was allowed to evaporate at room temperature. After 70 days, pink crystals were obtained. These crystals were washed with DMF and dried in a vacuum drying oven to obtain a single crystal sample of the polynuclear cobalt formate complex.

[0036] Example 3

[0037] 65.4 mg (0.1 mmol) of bis(triphenylphosphine)cobalt(II) chloride and 56.0 mg (0.67 mmol) of sodium bicarbonate were dissolved separately in acetonitrile (5 mL) and DMF (5 mL), respectively. The two solutions were then mixed to obtain a mixed solution. A mixture of acetic acid and formic acid in a volume ratio of 3:7 (6.7 mL) was then added to the resulting mixed solution. The solvent was allowed to evaporate at room temperature. After 80 days, pink crystals were obtained. These crystals were washed with acetonitrile and dried in a vacuum drying oven to obtain a single crystal sample of the polynuclear cobalt formate complex.

[0038] Example 4

[0039] 130.8 mg (0.2 mol) of bis(triphenylphosphine)cobalt(II) chloride and 109.2 mg (1.3 mmol) of sodium bicarbonate were dissolved separately in acetonitrile (5 mL) and DMF (5 mL), respectively. The two solutions were then mixed to obtain a mixed solution. A mixture of acetic acid and formic acid in a volume ratio of 3:7 (13 mL) was then added to the mixed solution. The solvent was allowed to evaporate at room temperature. After 60 days, pink crystals were obtained. These crystals were washed with DMF and dried in a vacuum drying oven to obtain a single crystal sample of the polynuclear cobalt formate complex.

[0040] Example 5

[0041] 163.5 mg (0.25 mmol) of bis(triphenylphosphine)cobalt(II) chloride and 142.8 mg (1.7 mmol) of sodium bicarbonate were dissolved in acetonitrile (7 mL) and DMF (7 mL), respectively. The two solutions were then mixed to obtain a mixed solution. A mixture of acetic acid and formic acid in a volume ratio of 3:7 (17 mL) was added to the resulting mixed solution. The solvent was allowed to evaporate at room temperature. After 90 days, pink crystals were obtained. These crystals were washed with acetonitrile and dried in a vacuum drying oven to obtain a single crystal sample of the polynuclear cobalt formate complex.

[0042] Test methods

[0043] I. Single Crystal Diffraction Test

[0044] Diffraction tests were performed on the single-crystal samples obtained in Examples 1-5 using a Rigaku R-AXIS SPIDER diffractometer. The results are as follows: Figure 1 As shown in the figure. The test results indicate that the synthesized product is a novel polynucleoformate cobalt complex.

[0045] II. Gas Chromatography Detection

[0046] When the prepared cobalt polynucleoformate complex was used as a photocatalyst for methane conversion, the gas-phase test results of the liquid product at GC-2014C were as follows: Figure 2 As shown in the figure. The solvent used in the photocatalytic system is PC (propylene carbonate), and the relevant gas phase detection parameters are: split ratio 50:1, FID column, and N2 as carrier gas. The test results show that the liquid product obtained after reduction contains a methanol peak, indicating that when using cobalt polynuclear formate complexes as photocatalysts, methane can be reduced to methanol.

[0047] III. Thermogravimetric Test

[0048] The prepared cobalt polynucleate complex was subjected to thermogravimetric analysis using a STA2500 thermogravimetric analyzer in the United States. The test results are as follows: Figure 3 As shown in the figure. The test results show that the cobalt polynucleoformate complex begins to lose water molecules at 151.4℃, the structure begins to collapse at 281.2℃, and the structure completely collapses at 998.4℃, exhibiting good thermal stability.

[0049] IV. Test Conclusion

[0050] In summary, the polynucleoformate cobalt complex synthesized in this invention not only has a novel structure and good thermal stability, but also exhibits certain photocatalytic effects. It can be used as a catalyst in photocatalytic systems to convert methane into methanol, demonstrating potential application value in photocatalysis. Furthermore, its preparation method is simple, the product has high purity, and the preparation of polynucleoformate cobalt complexes is easy, which is conducive to its application and promotion.

[0051] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a polynuclear cobalt formate complex, the polynuclear cobalt formate complex having a cobalt ion as a central ion, a formate ion as a ligand, and a water molecule as an auxiliary ligand, characterized by, The preparation method is to synthesize a polynuclear formic acid cobalt complex from formic acid, sodium bicarbonate and bis(triphenylphosphine) cobalt (II) chloride by volatilizing a solvent, and specifically comprises the following steps: S1. Dissolve sodium bicarbonate in DMF, dissolve bis(triphenylphosphine) cobalt (II) chloride in acetonitrile, and mix the two solutions to obtain a new mixed solution; S2. Add a mixed acid containing formic acid to the mixed solution obtained in step S1, volatilize the solvent, and precipitate pink block-shaped crystals; the mixed acid is a mixed solution of acetic acid and formic acid with a volume ratio of 3:7; S3. Wash the pink block-shaped crystals obtained in step S2, dry, and obtain a single crystal sample of the polynuclear formic acid cobalt complex.

2. The method for preparing cobalt polynucleoformate complexes according to claim 1, characterized in that, In step S1, the amount ratio of sodium bicarbonate to bis(triphenylphosphine) cobalt (II) chloride is 20 mmol:3 mmol.

3. The method for preparing cobalt polynucleoformate complexes according to claim 2, characterized in that, In step S2, the ratio of the mixed acid to sodium bicarbonate is 10 mL:1 mmol.

4. The process according to any one of claims 1 to 3, characterized in that, In step S2, the volatilization of the solvent is carried out at room temperature for 60-120 days.

5. The method for preparing cobalt polynucleoformate complexes according to claim 4, characterized in that, The volatilization of the solvent is carried out for 70-90 days.

6. The process according to any one of claims 1 to 2, wherein the process is carried out in the presence of a base. In step S3, the pink block-shaped crystals are washed with acetonitrile or DMF. In step S1, the amount ratio of sodium bicarbonate to bis(triphenylphosphine) cobalt (II) chloride is 20 mmol:3 mmol. In step S2, the ratio of the mixed acid to sodium bicarbonate is 10 mL:1 mmol. In step S2, the volatilization of the solvent is carried out at room temperature for 60-120 days. The volatilization of the solvent is carried out for 70-90 days. In step S3, the pink block-shaped crystals are washed with acetonitrile or DMF.

7. The process according to any one of claims 1 to 3, wherein the process is carried out in the presence of a base. The crystal of the polynuclear cobalt formate complex is monoclinic, space group P21 / c (no. 14), with cell parameters of a = 8.6781(17) Å, b = 7.1693(14) Å, c = 9.2870(19) Å, α = 90°, β = 97.45(3)°, γ = 90°, V = 572.9(2) Å 3 ; and the polynuclear cobalt formate complex has a decomposition temperature of 151.4 °C.

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