A method for homogeneous electrocatalytic reduction of co2 to co by electron-donating group modified fe porphyrin molecules

Abstract

The application discloses a method for reducing CO2 to CO by homogeneous electrocatalysis of electron-donating group modified Fe porphyrin molecules, and relates to the technical field of CO2 reduction, and comprises the following steps: (1) preparing an electrolyte: dissolving 0.5mmmol / L of an electron-donating group modified Fe porphyrin catalyst in an N,N dimethylformamide solution; (2) inert atmosphere pretreatment: introducing argon into the electrolyte for 30min to remove dissolved oxygen. The method for reducing CO2 to CO by homogeneous electrocatalysis of electron-donating group modified Fe porphyrin molecules has good water solubility of the synthesized FeTSPP, so that the FeTSPP can be uniformly dispersed in a reaction system and fully contact with reactants, and the reaction efficiency is improved; and under the condition of the CO2 reduction reaction, the structure of the FeTSPP is relatively stable, the existence of the sulfonic acid group of the FeTSPP increases the spatial steric hindrance of the molecule and the uniformity of the electron cloud density distribution, so that the FeTSPP is not prone to structural change or degradation in the reaction process, can maintain catalytic activity, and realizes sustained and stable CO2 reduction catalysis.

Description

Technical Field

[0001] This invention relates to the field of CO2 reduction technology, specifically to a method for homogeneous electrocatalytic reduction of CO2 to CO using Fe porphyrin molecules modified with electron-donating groups. Background Technology

[0002] Converting CO2 into high-value-added chemicals (such as CO, HCOOH, etc.) is an important way to mitigate the greenhouse effect and realize the carbon cycle. Metal porphyrins (such as Fe porphyrins) have become a research hotspot for homogeneous electrocatalytic reduction of CO2 due to their planar conjugated macrocyclic structure and tunable central metal. Their catalytic process usually involves the redox cycle of the metal center, realizing the activation and conversion of CO2 through a single electron transfer step. By introducing different functional groups (such as electron-donating groups and electron-withdrawing groups) onto the porphyrin ring, the electron density of the Fe center can be controlled through conjugation effect or inductive effect. Substituents on the porphyrin ring can significantly affect the overpotential and selectivity of CO2 reduction.

[0003] Although Fe porphyrins have certain potential as CO2 reduction catalysts, they still have the following problems: First, the catalytic activity and selectivity need to be further improved; second, the overpotential is relatively high, resulting in low energy efficiency; third, the catalyst has insufficient stability and is prone to degradation. Therefore, this invention optimizes the redox potential by rationally designing the functional groups on the porphyrin ring, regulating the electronic structure of the Fe center, and thereby reducing the CO2 reduction overpotential and improving the catalytic activity and selectivity. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a method for homogeneous electrocatalytic reduction of CO2 to CO using Fe porphyrin molecules modified with electron-donating groups, thus solving the problems mentioned in the background section.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for homogeneous electrocatalytic reduction of CO2 to CO using Fe porphyrin molecules modified with electron-donating groups, comprising the following steps:

[0006] (1) Preparation of electrolyte: Dissolve the Fe porphyrin catalyst modified with electron-donating groups in N,N dimethylformamide solution;

[0007] (2) Inert atmosphere pretreatment: Argon gas is introduced into the electrolyte to remove dissolved oxygen;

[0008] (3) First cyclic voltammetry test: Cyclic voltammetry test was performed on the pretreated electrolyte under an argon atmosphere;

[0009] (4) CO2 saturation treatment: Carbon dioxide is introduced into the electrolyte to saturate it;

[0010] (5) Second cyclic voltammetry test: Cyclic voltammetry test was performed again under carbon dioxide saturation conditions to realize the homogeneous electrocatalytic reduction of CO2 to CO.

[0011] Preferably, in (1), the N,N dimethylformamide solution contains tetrabutylammonium hexafluorophosphate.

[0012] Preferably, in (1), the Fe porphyrin catalyst modified with electron-donating groups is prepared by the following steps:

[0013] S1. After dissolving pyrrole and its corresponding precursor in dichloromethane, argon gas is introduced under light-protected conditions.

[0014] S2, add boron trifluoride diethyl ether, and react at room temperature;

[0015] S3, 2,3-dichloro-5,6-dicyanobenzoquinone was added, and the reaction was carried out by heating;

[0016] S4. After the reaction is complete, the reaction product is subjected to vacuum distillation, purification and recrystallization in sequence to obtain porphyrin;

[0017] S5. Porphyrin and ferrous chloride tetrahydrate are dissolved in N,N-dimethylformamide and reacted under argon protection by heating.

[0018] S6. Continue the reaction by exposing it to air, and after cooling to room temperature, add deionized water to precipitate the product.

[0019] S7. Centrifuge to collect the precipitate, wash it, and obtain the Fe porphyrin catalyst modified with electron-donating groups.

[0020] Preferably, in S1, the corresponding precursor is a benzaldehyde derivative containing an electron-donating group.

[0021] Preferably, the benzaldehyde derivative containing an electron-donating group is specifically selected from either 4-(10H-phenthiazin-10-yl)benzaldehyde or 4-(10H-phenoxazin-10-yl)benzaldehyde.

[0022] Preferably, when the benzaldehyde derivative containing the electron-donating group is 4-(10H-phenthiazin-10-yl)benzaldehyde, the structural formula of the Fe porphyrin catalyst is:

[0023] .

[0024] Preferably, when the benzaldehyde derivative containing the electron-donating group is 4-(10H-phenoxazine-10-yl)benzaldehyde, the structural formula of the Fe porphyrin catalyst is:

[0025] .

[0026] Preferably, in step S1, the light-protection condition is achieved by wrapping the reaction vessel with tin foil.

[0027] Preferably, in step S4, purification is performed using an eluent; recrystallization is performed using a mixed solution of methanol and dichloromethane, with a volume ratio of methanol to dichloromethane of 10:1.

[0028] Preferably, the eluent is selected from a mixture of pure dichloromethane, ethyl acetate and petroleum ether; wherein the volume ratio of ethyl acetate to petroleum ether is 1:1.

[0029] Beneficial effects

[0030] This invention provides a method for homogeneous electrocatalytic reduction of CO2 to CO using Fe porphyrin molecules modified with electron-donating groups. Compared with existing technologies, it has the following advantages:

[0031] (1) The method of modifying Fe porphyrin molecules with electron-donating groups for homogeneous electrocatalytic reduction of CO2 to CO. The synthesized FeTSPP has good water solubility, which allows it to be uniformly dispersed in the reaction system and fully contact the reactants, thereby improving the reaction efficiency. Moreover, under the conditions of carbon dioxide reduction reaction, the structure of FeTSPP is relatively stable. The presence of its sulfonic acid group increases the steric hindrance of the molecule and the uniformity of the electron cloud density distribution, making it less prone to structural changes or degradation during the reaction process. It can maintain catalytic activity and achieve continuous and stable carbon dioxide reduction catalysis.

[0032] (2) The method of modifying Fe porphyrin molecules with electron-donating groups for homogeneous electrocatalytic reduction of CO2 to CO, in the photocatalytic carbon dioxide reduction reaction, the phenothiazine group conjugated structure in the synthesized FeTOPP gives it good light absorption performance, can effectively absorb visible light, generate photogenerated charge carriers, and provide the energy and electrons required for the carbon dioxide reduction reaction; at the same time, the electron delocalization of the phenothiazine group helps to separate photogenerated electrons and holes, reduce the recombination probability, improve photocatalytic efficiency, and can make fuller use of solar energy to drive the carbon dioxide reduction reaction. Attached Figure Description

[0033] Figure 1 A synthetic route diagram of Feporphyrin provided by the present invention;

[0034] Figure 2 Mass spectrometry data of Fe porphyrin provided for this invention;

[0035] Figure 3 The CV diagram of Feporphyrin provided by this invention. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] Example 1

[0038] The Fe porphyrin catalyst modified with electron-donating groups was prepared by the following steps:

[0039] S1. Dissolve 0.72 mol of freshly distilled pyrrole and 0.72 mol of 4-(10H-phenthiazin-10-yl)benzaldehyde in 500 mL of dichloromethane, cover with tin foil to protect from light, and then introduce argon gas.

[0040] S2, add 0.24 mmol of boron trifluoride diethyl ether, and react at room temperature for 2 h;

[0041] S3, add 0.66 mol of 2,3-dichloro-5,6-dicyanobenzoquinone, and heat to 40℃ for 30 min;

[0042] S4. After the reaction is complete, the reaction product is subjected to vacuum distillation and purified using the eluent. Then, it is recrystallized using a mixed solution of methanol and dichloromethane (v%:v%=10:1) to obtain porphyrin.

[0043] S5. Dissolve 0.1 mol porphyrin and 0.3 mmol ferrous chloride tetrahydrate in N,N dimethylformamide and react at 140 °C for 5 h under argon protection.

[0044] S6. Expose to air and continue the reaction for 2 hours. After cooling to room temperature, add deionized water to precipitate the product.

[0045] After centrifugation at 8000 r / min for 3 min, the precipitate was collected and washed five times with ultrapure water to obtain the Fe porphyrin catalyst modified with electron-donating groups. The structural formula is as follows:

[0046] .

[0047] Example 2

[0048] In Example 1, 4-(10H-phenthiazin-10-yl)benzaldehyde was replaced with 4-(10H-phenoxazin-10-yl)benzaldehyde; all other parameters remained unchanged. The resulting Fe porphyrin catalyst with electron-donating group modification has the following structural formula:

[0049]

[0050] Comparative Example 1

[0051] In Example 1, 4-(10H-phenthiazin-10-yl)benzaldehyde was replaced with benzaldehyde; all other parameters remained unchanged. The resulting Fe porphyrin catalyst with electron-donating group modification has the following structural formula:

[0052] .

[0053] Comparative Example 2

[0054] In Example 1, 4-(10H-phenthiazin-10-yl)benzaldehyde was replaced with 4-(diphenylamino)benzaldehyde; all other parameters remained unchanged. The resulting Fe porphyrin catalyst with electron-donating group modification has the following structural formula:

[0055] .

[0056] Comparative Example 3

[0057] In Example 1, 4-(10H-phenthiazin-10-yl)benzaldehyde was replaced with 4-(9H-carbazole-9-yl)benzaldehyde; all other parameters remained unchanged. The resulting Fe porphyrin catalyst with electron-donating group modification has the following structural formula:

[0058] .

[0059] A method for homogeneous electrocatalytic reduction of CO2 to CO using Fe porphyrin molecules modified with electron-donating groups, comprising the following steps:

[0060] (1) Preparation of electrolyte: Dissolve 0.5 mmol / L of electron-donating group-modified Fe porphyrin catalyst in a dimethylformamide solution containing 0.1 mol / L tetrabutylammonium hexafluorophosphate N,N;

[0061] (2) Inert atmosphere pretreatment: Argon gas is introduced into the electrolyte for 30 min to remove dissolved oxygen;

[0062] (3) First cyclic voltammetry test: Cyclic voltammetry test was performed on the pretreated electrolyte under an argon atmosphere;

[0063] (4) CO2 saturation treatment: Carbon dioxide is introduced into the electrolyte for 30 minutes to saturate it;

[0064] (5) Second cyclic voltammetry test: Cyclic voltammetry test was performed again under carbon dioxide saturation conditions to realize the homogeneous electrocatalytic reduction of CO2 to CO.

[0065] Physical characterization:

[0066] Feporphyrin was physically characterized by time-of-flight mass spectrometry (TOF-MS / MS), and the test results showed that... Figure 2Taking FeTDPP (M=C92H64FeN8Cl) as an example, two distinct peaks were observed at M / Z of 1370.98 and 1335.92, corresponding to [M]+=1371.43 and [M-Cl]+=1336.46, respectively. The measured values ​​are consistent with the theoretical values, indicating that FeTDPP was successfully synthesized. The measured values ​​of the other four Fe porphyrins are also consistent with the theoretical values.

[0067] Homogeneous electrocatalysis test conditions: 0.5 mmol / L Fe porphyrin catalyst was weighed and dissolved in a DMF solution containing 0.1 mol / L tetrabutylammonium hexafluorophosphate. Argon gas (Ar) was passed through the solution for 30 min, followed by cyclic voltammetry (CV). CO2 was then passed through the solution for 30 min, and CV was performed again. The test results are shown below. Figure 3 As shown in the figure, under Ar conditions, Fe porphyrins exhibit three distinct redox peaks, which are due to the three single-electron redox reactions of Fe. These three redox peaks, from left to right, correspond to FeI / FeO, FeII / FeI, and FeIII / FeII, respectively. Comparing the changes in current density under CO2 and Ar conditions reveals a significant change in the current density of FeI / FeO, while FeII / FeI and FeIII / FeII show no significant change. Therefore, FeI / FeO (R3) is the primary catalytic center. Further comparison reveals a significant change in the positions of the Fe redox peaks after functional group modification. Compared to FeTPP, FeTCPP, FeTOPP, and FeTSPP all show a substantial positive shift in E1 / 2 (R3), with FeTOPP and FeTSPP shifting by approximately 120 mV, while FeTDPP's E1 / 2 (R3) only shifts positively by 10 mV. This may be attributed to the stronger conjugation effect of FeTCPP, FeTOPP, and FeTSPP.

[0068] Furthermore, any content not described in detail in this specification is existing technology known to those skilled in the art.

[0069] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0070] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for homogeneous electrocatalytic reduction of CO2 to CO using Fe porphyrin molecules modified with electron-donating groups, characterized in that, Includes the following steps: (1) Preparation of electrolyte: Dissolve the Fe porphyrin catalyst modified with electron-donating groups in N,N dimethylformamide solution; (2) Inert atmosphere pretreatment: Argon gas is introduced into the electrolyte to remove dissolved oxygen; (3) First cyclic voltammetry test: Cyclic voltammetry test was performed on the pretreated electrolyte under an argon atmosphere; (4) CO2 saturation treatment: Carbon dioxide is introduced into the electrolyte to saturate it; (5) Second cyclic voltammetry test: Cyclic voltammetry test was performed again under carbon dioxide saturation conditions to realize the homogeneous electrocatalytic reduction of CO2 to CO.

2. The method for homogeneous electrocatalytic reduction of CO2 to CO by modifying Fe porphyrin molecules with electron-donating groups according to claim 1, characterized in that: In (1), the N,N dimethylformamide solution contains tetrabutylammonium hexafluorophosphate.

3. The method for homogeneous electrocatalytic reduction of CO2 to CO by modifying Fe porphyrin molecules with electron-donating groups according to claim 1, characterized in that: In (1), the Fe porphyrin catalyst modified with electron-donating groups is prepared by the following steps: S1. After dissolving pyrrole and its corresponding precursor in dichloromethane, argon gas is introduced under light-protected conditions. S2, add boron trifluoride diethyl ether, and react at room temperature; S3, 2,3-dichloro-5,6-dicyanobenzoquinone was added, and the reaction was carried out by heating; S4. After the reaction is complete, the reaction product is subjected to vacuum distillation, purification and recrystallization in sequence to obtain porphyrin; S5. Porphyrin and ferrous chloride tetrahydrate are dissolved in N,N-dimethylformamide and reacted under argon protection by heating. S6. Continue the reaction by exposing it to air, and after cooling to room temperature, add deionized water to precipitate the product. S7. Centrifuge to collect the precipitate, wash it, and obtain the Fe porphyrin catalyst modified with electron-donating groups.

4. The method for homogeneous electrocatalytic reduction of CO2 to CO by modifying Fe porphyrin molecules with electron-donating groups according to claim 3, characterized in that: In S1, the corresponding precursor is a benzaldehyde derivative containing an electron-donating group.

5. The method for homogeneous electrocatalytic reduction of CO2 to CO by modifying Fe porphyrin molecules with electron-donating groups according to claim 4, characterized in that: The benzaldehyde derivative containing an electron-donating group is specifically selected from either 4-(10H-phenothiazin-10-yl)benzaldehyde or 4-(10H-phenothiazin-10-yl)benzaldehyde.

6. The method for homogeneous electrocatalytic reduction of CO2 to CO by modifying Fe porphyrin molecules with electron-donating groups according to claim 5, characterized in that: When the benzaldehyde derivative containing the electron-donating group is 4-(10H-phenthiazin-10-yl)benzaldehyde, the structural formula of the Fe porphyrin catalyst is: 。 7. The method for homogeneous electrocatalytic reduction of CO2 to CO by modifying Fe porphyrin molecules with electron-donating groups according to claim 5, characterized in that: When the benzaldehyde derivative containing the electron-donating group is 4-(10H-phenoxazine-10-yl)benzaldehyde, the structural formula of the Fe porphyrin catalyst is: 。 8. The method for homogeneous electrocatalytic reduction of CO2 to CO by modifying Fe porphyrin molecules with electron-donating groups according to claim 3, characterized in that: In S1, the light-protection condition is achieved by wrapping the reaction vessel with tin foil.

9. The method for homogeneous electrocatalytic reduction of CO2 to CO by modifying Fe porphyrin molecules with electron-donating groups according to claim 3, characterized in that: In step S4, purification is performed using an eluent; recrystallization is performed using a mixed solution of methanol and dichloromethane, with a volume ratio of methanol to dichloromethane of 10:

1.

10. The method for homogeneous electrocatalytic reduction of CO2 to CO by modifying Fe porphyrin molecules with electron-donating groups according to claim 7, characterized in that: The eluent is selected from a mixture of pure dichloromethane, ethyl acetate and petroleum ether; wherein the volume ratio of ethyl acetate to petroleum ether is 1:1.

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