Terpyridyl ferrous catalyst derived from terthiophenes and application of terpyridyl ferrous catalyst in photocatalysis of CO2

Abstract

The invention discloses a terpyridyl ferrous catalyst derived from terthiophenes and application of the terpyridyl ferrous catalyst in photocatalysis of CO2. The catalyst has a structure as shown in a formula I. According to the catalyst, a light capture unit terthiophene is integrated to a terpyridyl ferrous catalytic center through molecular design to form an integrated structure with a self-sensitization function, and the preparation method comprises the following steps: condensing 2, 2 ': 5', 2 ''-trithiophene-5-formaldehyde and 2-acetylpyridine under an alkaline condition to obtain a ligand; and coordinating with ferrous chloride to obtain the target catalyst. According to the present invention, in the photocatalytic CO2 reduction reaction, the efficient catalysis can be achieved without the addition of the noble metal photosensitizer, the CO conversion number is up to 642, the selectivity exceeds 98%, and the low-cost and high-activity new scheme is provided for solving the dependence on the noble metal in the prior art.

Description

Technical Field

[0001] This invention relates to a terthiophene-derived terpyridine ferrous catalyst and its application in photocatalytic CO2, belonging to the field of chemical technology. Background Technology

[0002] With the rapid increase in atmospheric carbon dioxide concentration due to modern industrial activities and the extensive use of fossil fuels, consequences such as global warming, glacial melting, and rising sea levels have emerged. Humans have proposed many methods to reduce atmospheric carbon dioxide concentration, including physical capture, mineralization, electrochemical conversion, and photocatalytic conversion. Photocatalytic carbon dioxide conversion has attracted considerable interest from scientists because it can utilize abundant solar energy resources without requiring additional energy input, and the process is relatively mild.

[0003] Photocatalytic reduction of carbon dioxide to useful chemicals is an ideal pathway for utilizing solar energy and fixing carbon dioxide. Among these processes, homogeneous photocatalytic carbon dioxide reduction has attracted considerable attention due to its well-defined molecular structure, good reproducibility, and high conversion number. A typical homogeneous carbon dioxide photocatalytic reaction usually involves a photosensitizer, a photocatalyst, and a sacrificial agent. The photosensitizer absorbs light energy, acquires electrons from the sacrificial agent, and transfers these electrons to the photocatalyst, which ultimately combines with carbon dioxide to generate the product. In homogeneous photocatalytic carbon dioxide reduction reactions, noble metal complexes are the most commonly used photosensitizers due to their large visible light molar extinction coefficient, long triplet fluorescence lifetime, and suitable reduction potential. Therefore, developing environmentally friendly, photosensitizer-free, non-noble metal carbon dioxide photocatalysts is of great significance in reducing the use of noble metal photosensitizers.

[0004] Ferrous terpyridine photocatalysts have been widely used in CO2 photocatalysis. Using ferrous terpyridine and photosensitizers such as CZIPN can achieve conversion numbers exceeding 6000 and CO selectivity of 99% (Wang, Y.; Liu, T.; Chen, L.; Chao, D.). Inorg. Chem. 2021, 60 (8), 5590–5597.). This invention introduces a terthiophene photosensitizer into a terpyridine catalyst, achieving a CO conversion number of 642 and a selectivity of 98%, providing a new approach to reduce the use of precious metal photosensitizers. Summary of the Invention

[0005] The purpose of this invention is to provide a terthiophene-derived terpyridine ferrous catalyst and its application in photocatalysis of CO2. By introducing the terthiophene motif into the terpyridine ferrous coordination center, an integrated structure with self-sensitization function is constructed, aiming to solve the dependence of existing technologies on noble metal photosensitizers and provide a highly active and selective CO2 photoreduction solution.

[0006] The structural formula of the terthiophene-derived terpyridineferrous iron provided by this invention is shown in Formula I;

[0007] The present invention also provides a method for preparing the terthiophene-derived terpyridine ferrous iron, comprising the following steps: S1. Under the presence of alkali and concentrated ammonia, 2,2':5',2''-trithiophene-5-carboxaldehyde and 2-acetylpyridine undergo a condensation reaction to obtain the ligand shown in Formula II.

[0008] S2. The ligand shown in Formula II is mixed with ferrous chloride and refluxed, and then excess ammonium hexafluorophosphate is added. After anion exchange reaction, the terpyridine ferrous derivative of terthiophene as described in claim 1 is obtained.

[0009] In step S1, the molar ratio of 2,2':5',2''-trithiophene-5-carboxaldehyde, 2-acetylpyridine, and the base is 1:1-5:1-5, preferably 1:2:2; The alkali may be potassium hydroxide, sodium hydroxide, or potassium carbonate, etc. The concentration of the concentrated ammonia solution is 15%-30%, and the dosage is 2-5 mL / mmol.

[0010] In step S1, the condensation reaction is carried out in solvents such as ethanol and methanol; The condensation reaction was carried out under reflux at a temperature of 50℃-90℃ for 12 h-72 h.

[0011] In step S2, the molar ratio of the ligand shown in Formula II to the ferrous chloride is 1:1 to 1:2; The reflux temperature is 50℃-90℃, and the time is 12 h-72 h.

[0012] The terpyridine ferrous derivative of terthiophene of this invention can be used as a photocatalyst to catalyze the conversion of CO2 to CO.

[0013] Specifically, the present invention further provides a method for photocatalytic conversion of CO2 to CO, comprising the following steps: adding a proton source and a sacrificial agent to the solution of the terthiophene-derived terpyridine ferrous oxide, saturating it with carbon dioxide, and then irradiating it with LED light to achieve the conversion of carbon dioxide.

[0014] Preferably, the solution of the terthiophene-derived terpyridinium ferrous sulfate is prepared using acetonitrile, dimethylformamide and / or dimethylacetamide; The concentration of the solution is 2-100 μmol / L, preferably 4-50 μmol / L, and more preferably 5-20 μmol / L.

[0015] Preferably, the proton source is trifluoroethanol, and the concentration of the proton source in the solution is 0.05-0.5 mol / L; Preferably, the sacrificial agent is 1,3-dimethyl-2-phenylbenzimidazoline, and the concentration of the sacrificial agent in the solution is 0.01-0.1 mol / L.

[0016] Preferably, the wavelength of the LED light is 365-600 nm.

[0017] The present invention has the following beneficial technical effects: The Fe(3T-tpy)2 catalyst prepared by this invention can achieve a maximum conversion number (TON) of 642 within 48 hours in the photocatalytic CO2 reduction reaction without the need for any added precious metal photosensitizer, while maintaining a selectivity of over 98% for the target product CO, thus achieving a balance between high efficiency and high selectivity.

[0018] This invention successfully constructs a molecular structure that integrates light absorption and catalytic functions by directly bonding the terthiophene light-harvesting unit to the terpyridine iron catalytic center. This "self-sensitization" design fundamentally eliminates the dependence on traditional expensive precious metal photosensitizers, significantly reduces material costs, and provides a new path for developing economical photocatalysts.

[0019] This invention conducted parallel experiments using a control catalyst Fe(Ph-tpy)2 that did not contain terthiophene. The results showed that the catalyst was completely inactive, which contrasted sharply with the catalyst of this invention. This demonstrates that the terthiophene moiety is the decisive structural factor for achieving photocatalytic function, highlighting the rationality and necessity of the molecular design of this invention. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the synthesis process of the photocatalyst Fe(3T-tpy)2; Figure 2 This is a schematic diagram of the synthesis process of the photocatalyst Fe(Ph-tpy)2; Figure 3 The hydrogen nuclear magnetic resonance spectrum of the ligand 3T-tpy prepared in this invention; Figure 4 The hydrogen NMR spectrum of the ligand Ph-tpy; Figure 5 Here is the high-resolution mass spectrum of the photocatalyst Fe(3T-tpy)2 prepared in this invention via electrospray ionization: Figure 6 The high-resolution mass spectrum of the photocatalyst Fe(Ph-tpy)2 prepared in this invention is obtained by electrospray ionization. Figure 7The following diagram illustrates the catalytic results of the photocatalyst Fe(3T-tpy)2 prepared in this invention applied to the photocatalytic conversion of CO2 to CO (photocatalyst concentration is 5 μmol / L): Figure 8 The image shows the catalytic results of the photocatalyst Fe(3T-tpy)2 prepared in this invention applied to the photocatalytic conversion of CO2 to CO (photocatalyst concentration is 10 μmol / L). Figure 9 The image shows the catalytic results of the photocatalyst Fe(3T-tpy)2 prepared in this invention applied to the photocatalysis of CO2 to CO (photocatalyst concentration is 20 μmol / L). Detailed Implementation

[0021] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0022] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0023] This invention relates to the field of photocatalytic materials technology, specifically providing a terthiophene-derived terpyridine ferrous catalyst, its preparation method, and its application in photocatalytic carbon dioxide reduction.

[0024] The catalyst provided by this invention has an integrated molecular structure as shown in Formula I, characterized by the covalent integration of a terthiophene moiety with excellent light-harvesting capabilities with a terpyridine ferrous catalytic center. This design enables the catalyst to possess both light absorption and catalytic activity, achieving intramolecular self-sensitization, thus eliminating the need for any external noble metal photosensitizers during the catalytic process.

[0025] The catalyst of this invention is prepared by using 2,2':5',2''-trithiophene-5-carboxaldehyde and 2-acetylpyridine as starting materials. The terthiophene-terpyridine ligand is generated by a condensation reaction under alkaline catalysis, and then coordinated with ferrous chloride and subjected to anion exchange to finally obtain the target catalyst.

[0026] In terms of application, this catalyst exhibits extremely high catalytic efficiency and selectivity when used in the photocatalytic CO2 reduction reaction. Experimental results show that it can achieve a CO conversion number as high as 642 without the addition of a photosensitizer, and the selectivity for CO exceeds 98%. Compared with the control catalyst without the terthiophene structure, its activity is significantly improved by orders of magnitude, fully demonstrating the rationality and superiority of the molecular structure design of this invention.

[0027] This invention provides a novel, highly active, low-cost, and environmentally friendly solution to address the dependence of existing CO2 photoreduction technologies on precious metals.

[0028] Example 1: Preparation of photocatalyst Fe(3T-tpy)2 The reaction equation is as follows Figure 1 As shown.

[0029] A mixture of 2,2':5',2''-trithiophene-5-carboxaldehyde (276 mg, 1.0 mmol), 2-acetylpyridine (242 mg, 2.0 mmol), potassium hydroxide (112 mg, 2.0 mmol), ammonia solution (30%, 3 mL), and ethanol (20 mL) was refluxed for 48 hours. After cooling to room temperature, the product 3T-tpy was filtered, washed with water and ethanol, and finally dried in an oven overnight. The yield was 58%. The obtained ligand was dissolved in deuterated chloroform for proton NMR spectroscopy.

[0030] Figure 3 The 1H NMR spectrum of 3T-tpy is shown, and it can be seen that the obtained ligand is consistent with the previously reported structure, and the photosensitizing ligand 3T-tpy was successfully synthesized.

[0031] The product 3T-tpy (144 mg, 0.3 mmol) was added to dichloromethane (10 mL), followed by the addition of a methanol solution of FeCl2·4H2O (30 mg, 0.15 mmol) with stirring, and refluxed for 12 hours. The mixture was filtered to remove unreacted 3T-tpy, and excess NH4PF6 was added to the filtrate with stirring to precipitate it. The product was filtered, washed several times with methanol, and finally dried in an oven overnight. The yield was 41%.

[0032] Figure 5 The high-resolution mass spectrum of the photocatalyst Fe(3T-tpy)2 by electrospray ionization is shown. It can be seen that the charge ratio of the obtained complex is consistent with the expected result, and the photocatalyst Fe(3T-tpy)2 was successfully synthesized.

[0033] Example 2: Photocatalyst Fe(3T-tpy)2 for photocatalytic conversion of CO2 to CO A 2 mL acetonitrile solution of Fe(3T-tpy)₂ was diluted to 5 μmol / L. 60 μL of trifluoroethanol was added to achieve a trifluoroethanol concentration of 0.4 mol / L. 11.2 mg of 1,3-dimethyl-2-phenylbenzimidazoline was added to achieve a 1,3-dimethyl-2-phenylbenzimidazoline concentration of 0.025 mol / L. After carbon dioxide was introduced to saturate the gas, it was irradiated with a 405 nm LED for 6, 12, 18, 24, 30, 36, 42, and 48 hours. 500 μL of the gas was injected into a gas chromatograph equipped with a TCD detector to detect the CO and H₂ content.

[0034] Figure 7The conversion number and yield of gas-phase products of 5 μmol / L photocatalyst Fe(3T-tpy)2 at different times are shown. It can be seen that the highest conversion number is 642 at 48 h and the CO selectivity is 98.6%.

[0035] Comparative Example 1: Preparation and Application of Photocatalyst Fe(Ph-tpy)2 The reaction equation is as follows Figure 2 As shown.

[0036] A mixture of benzaldehyde (1.06 g, 10 mmol), 2-acetylpyridine (2.42 g, 20 mmol), potassium hydroxide (1.54 g, 27.5 mmol), ammonia solution (30%, 35 mL), and ethanol (75 mL) was refluxed for 24 hours. After cooling to room temperature, the product Ph-tpy was filtered, washed with water and ethanol, and finally dried in an oven overnight. The yield was 42%. The obtained ligand was dissolved in deuterated chloroform for proton NMR spectroscopy.

[0037] Figure 4 The proton NMR spectrum of Ph-tpy is shown, and it can be seen that the obtained ligand is consistent with the previously reported results, indicating that Ph-tpy was successfully obtained.

[0038] The product Ph-tpy (144 mg, 0.3 mmol) was added to 10 mL of dichloromethane, followed by the addition of 10 mL of a methanol solution of FeCl2·4H2O (30 mg, 0.15 mmol) under stirring. The mixture was refluxed for 12 hours. After cooling to room temperature, excess NH4PF6 was added to precipitate the product. The product was filtered, washed several times with methanol, and finally dried overnight in an oven. The yield was 74%.

[0039] Figure 6 The high-resolution mass spectrum of the photocatalyst Fe(Ph-tpy)2 by electrospray ionization is shown. It can be seen that the charge ratio of the obtained complex is consistent with the expected result, and the photocatalyst Fe(Ph-tpy)2 was successfully synthesized.

[0040] Photocatalytic effect of Fe(Ph-tpy)2: Following the steps of Example 2, except that the photocatalyst was changed to Fe(Ph-tpy)2, no gaseous products were detected.

[0041] Example 3 The operation steps are the same as in Example 2, except that the concentration of the photocatalyst Fe(3T-tpy)2 is changed to 10 μmol / L.

[0042] Figure 8The gas-phase product conversion number and yield of 10 μmol / L photocatalyst Fe(3T-tpy)2 at different times are shown. It can be seen that the highest conversion number is 479 at 48 h, with a CO selectivity of 98.9%.

[0043] Example 4 The operation steps are the same as in Example 2, except that the concentration of the photocatalyst Fe(3T-tpy)2 is changed to 20 μmol / L.

[0044] Figure 9 The gas-phase product conversion number and yield of the 20 μmol / L photocatalyst Fe(3T-tpy)2 at different times are shown. It can be seen that the highest conversion number is 362 at 48 h, with a CO selectivity of 99.8%.

Claims

1. The terpyridinium ferrous derivative of terthiophene shown in Formula I; 。 2. The method for preparing the terthiophene-derived terpyridinium ferrous oxide according to claim 1, comprising the following steps: S1. Under the presence of alkali and concentrated ammonia, 2,2':5',2''-trithiophene-5-carboxaldehyde and 2-acetylpyridine undergo a condensation reaction to obtain the ligand shown in Formula II. S2. The ligand shown in Formula II is mixed with ferrous chloride and refluxed, and then excess ammonium hexafluorophosphate is added. After anion exchange reaction, the terpyridine ferrous derivative of terthiophene as described in claim 1 is obtained.

3. The preparation method according to claim 2, characterized in that: In step S1, the molar ratio of 2,2':5',2''-trithiophene-5-carboxaldehyde, 2-acetylpyridine, and the base is 1:1-5:1-5; The concentration of the concentrated ammonia solution is 15%-30%, and the dosage is 2-5 mL / mmol.

4. The preparation method according to claim 2 or 3, characterized in that: In step S1, the condensation should be carried out in ethanol or methanol; The condensation reaction was carried out under reflux at a temperature of 50℃-90℃ for 12 h-72 h.

5. The preparation method according to any one of claims 2-4, characterized in that: In step S2, the molar ratio of the ligand shown in Formula II to the ferrous chloride is 1:1 to 1:2; The reflux temperature is 50℃-90℃, and the time is 12 h-72 h.

6. The application of the terthiophene-derived terpyridinium ferrous oxide as described in claim 1 as a photocatalyst for the conversion of CO2 to CO.

7. A method for photocatalytic conversion of CO2 to CO, comprising the following steps: adding a proton source and a sacrificial agent to a solution of terpyridine ferrous derivative derived from terthiophene as described in claim 1, saturating the solution with carbon dioxide, and then irradiating it with an LED light to achieve the conversion of carbon dioxide.

8. The method according to claim 7, characterized in that: A solution of the terthiophene-derived terpyridinium ferrous sulfate was prepared using acetonitrile, dimethylformamide and / or dimethylacetamide; The concentration of the solution is 2-100 μmol / L.

9. The method according to claim 7 or 8, characterized in that: The proton source is trifluoroethanol, and the concentration of the proton source in the solution is 0.05-0.5 mol / L; The sacrificial agent is 1,3-dimethyl-2-phenylbenzimidazol, and the concentration of the sacrificial agent in the solution is 0.01-0.1 mol / L.

10. The method according to any one of claims 7-9, characterized in that: The wavelength of the LED light is 365-600 nm.

Images