Functionalized carbon nanotube immobilized cobalt molecular complex complex and preparation method and application thereof

Abstract

The invention discloses a preparation method of a functionalized carbon nanotube immobilized cobalt molecule complex and research on electrocatalytic CO2 reduction of the functionalized carbon nanotube immobilized cobalt molecule complex. The invention provides a dual combination strategy, specifically, a composite catalyst is prepared through an in-situ mixing process by taking a functionalized multi-walled carbon nanotube (MWCNT) as a conductive carrier and taking a peripheral modified cobalt tetrabipyridine molecular complex (Coqpy) as a catalytic active component. A carbon nanotube functional group is used as a first coordination ball to realize axial coordination bonding with a Co center, so that more electrochemical active cobalt complexes are allowed to be loaded, and interface electron transfer is accelerated. The pi-pi coupling effect of the peripheral conjugated group of Coqpy and MWCNT further strengthens the interaction and stability of electrons in the complex, and the CO Faraday efficiency and conversion frequency are respectively as high as 97.5% and 79s <-1 >. According to the composite electrode designed by the invention, the catalytic activity and stability of the catalyst are greatly improved, the process is simple, the method is novel, and the method is expected to become a universal and convenient method for preparing the heterogeneous molecular electrocatalyst.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of electrocatalysis, and particularly relates to a functionalized carbon nanotube supported cobalt molecular complex composite as well as a preparation method and application thereof. BACKGROUND

[0002] Under the background of the current era of "carbon peak" and "carbon neutralization", the electrochemical reduction of carbon dioxide (CO2RR) for producing high value-added chemicals using renewable electricity has attracted much attention. However, there are still many challenges in designing CO2RR electrocatalysts with high activity, high selectivity and stability. Metal molecular complexes are excellent systems for exploring the mechanism of CO2RR due to their high efficiency and high selectivity in the process of catalyzing CO2 conversion, as well as highly adjustable structural characteristics. However, their poor electrical conductivity and stability limit their application in aqueous electrolytes, and this problem can be solved by compounding with conductive carbon carriers. Therefore, developing an ideal immobilization technology to achieve fast electron transfer and maximize the inherent activity of molecular catalysts is of great significance for the realization of efficient CO2RR, but achieving this goal is still challenging.

[0003] Currently, the commonly used method for immobilizing molecular catalysts on carbon carriers is to use the planar π macrocyclic ligand to form a non-covalent π-π stacking with the sp 2 However, this relatively weak non-covalent interaction may result in slow electron transfer and insufficient stability of the composite, and the catalytic performance still has a large room for improvement. In addition, super-large conjugated pyrene substituents are introduced into the ligand to enhance the conjugation effect and effectively improve the catalytic activity and durability of the heterogeneous molecular catalyst; but relying solely on this physical interaction, it is difficult to achieve single-molecule dispersion of the molecular catalyst and controllable adjustment of the microenvironment of the metal center. If the metal center in the molecular catalyst is axially coordinated with the functional groups on the carbon carrier, a molecularly dispersed active site can be achieved, and this coordination effect can modulate the metal electronic configuration of the heterogeneous molecular catalyst, thereby promoting the adsorption and activation of intermediates and improving the catalytic performance. Unfortunately, there are few studies on the use of functionalized multi-walled carbon nanotubes (MWCNT) to anchor molecular catalysts through axial coordination and enhanced π-π conjugation. Therefore, it is particularly important and urgent to use a dual combination strategy to construct immobilized molecular catalysts to achieve efficient CO2RR and to further explore the correlation between intermolecular forces, charge transfer and metal electronic structure. In view of this, the present application is proposed. SUMMARY

[0004] The present application aims to provide a functionalized carbon nanotube supported cobalt molecular complex composite as well as a preparation method and application thereof.

[0005] In order to achieve the above-mentioned purpose, the solution of the present application is as follows:

[0006] A preparation method of a functionalized carbon nanotube supported cobalt molecular complex composite, specifically comprising the following steps:

[0007] (1) 4-bromo-2,2':6',2":6",2":6"' -tetra-pyridine, 4-acetamidobenzoic acid, tetrakis(triphenylphosphine)palladium and a base are added into a mixed solution composed of methanol and water, after heating and refluxing, the solvent is removed, the obtained solid is washed to obtain N-(4-([2,2':6',2":6",2":6"' -tetra-pyridine]-4-yl)phenyl)-acetamide, then N-(4-([2,2':6',2":6",2":6"' -tetra-pyridine]-4-yl)phenyl)-acetamide is added into a methanol hydrogen chloride solution to hydrolyze to obtain 4-([2,2':6',2":6",2":6"' -tetra-pyridine]-4-yl)phenylamine hydrochloride;

[0008] (2) 1-pyrene butyric acid, benzotriazol-1-yl-oxytripyrrolidinophosphonium hexafluorophosphate and N,N-diisopropyl ethylamine are added into dry N,N-dimethyl formamide to stir to obtain a mixed solution, 4-([2,2':6',2":6",2":6"' -tetra-pyridine]-4-yl)phenylamine hydrochloride obtained in step (1) is added into the obtained mixed solution, after continuous reaction, the obtained solid is washed and dried to obtain a ligand N-(4-([2,2':6',2":6",2":6"' -tetra-pyridine]-4-yl)phenyl)-pyrene butyric amide;

[0009] (3) the ligand N-(4-([2,2':6',2":6",2":6"' -tetra-pyridine]-4-yl)phenyl)-pyrene butyric amide obtained in step (2) and a cobalt salt are added into methanol, after stirring and reaction, the solvent is removed, the obtained solid is washed to obtain a cobalt metal complex;

[0010] (4) the cobalt metal complex obtained in step (3) and functionalized carbon nanotubes are added into a mixed solution composed of ethanol and ethylene glycol, after the obtained mixture is uniformly dispersed, a nafion solution is added to obtain the functionalized carbon nanotube supported cobalt molecular complex composite.

[0011] Preferably, in step (1), the molar ratio of 4-bromo-2,2':6',2":6",2":6"' -tetra-pyridine and 4-acetamidobenzoic acid is 6:7; the volume ratio of methanol to water in the mixed solution is 10:1; the concentration of hydrogen chloride in the methanol hydrogen chloride solution is 1-3 mol / L; the base is one of anhydrous sodium carbonate, anhydrous potassium carbonate or anhydrous cesium carbonate.

[0012] Preferably, the molar ratio of 1-pyrene butyric acid, benzotriazol-1-yl-oxytripyrrolidinophosphonium hexafluorophosphate, N,N-diisopropylethylamine and 4-([2,2':6',2":6",2"' -Tetrapyridyl]-4-yl) aniline hydrochloride in step (2) is 6:1:20:5.

[0013] Preferably, the cobalt salt in step (3) is selected from one of cobalt perchlorate, cobalt chloride, cobalt bromide, cobalt nitrate or cobalt sulfate.

[0014] Preferably, the carbon nanotube in step (4) is one of unmodified carbon nanotube, amino-modified carbon nanotube or carboxyl-modified carbon nanotube.

[0015] An N-(4-([2,2':6',2":6",2"' -Tetrapyridyl]-4-yl)phenyl)-pyrene butyramide ligand, the structural formula of the ligand is as follows:

[0016]

[0017] A metal cobalt complex containing N-(4-([2,2':6',2":6",2"' -Tetrapyridyl]-4-yl)phenyl)-pyrene butyramide ligand, the main structural formula of the complex is as follows:

[0018]

[0019] A functionalized carbon nanotube supported cobalt molecular complex composite, the composite is composed of a metal cobalt complex containing N-(4-([2,2':6',2":6",2"' -Tetrapyridyl]-4-yl)phenyl)-pyrene butyramide ligand and carbon nanotube.

[0020] Preferably, the mass ratio of the metal cobalt complex containing N-(4-([2,2':6',2":6",2"' -Tetrapyridyl]-4-yl)phenyl)-pyrene butyramide ligand and carbon nanotube is 1:1-60:1.

[0021] Application of the aforementioned functionalized carbon nanotube supported cobalt molecular complex composite in electrocatalytic CO2 reduction.

[0022] The principle of the original functionalized carbon nanotube supported cobalt molecular complex composite catalyst provided by the application is as follows:

[0023] The functionalized carbon nanotube supported cobalt molecular complex composite provided by the present application mainly uses a double binding force design concept, that is, a new cobalt-based molecular complex is designed and synthesized and is supported on a functionalized carbon nanotube to realize efficient and stable electrocatalytic CO2RR. Specifically, the method provided by the present application prepares 4-([2,2':6',2'':6'',2''':6''' -quaterpyridine]-4-yl) aniline hydrochloride (qpy-Ph-NH2·HCl) ligand through a Suzuki coupling reaction, then performs amidation reaction with 1-pyrene butyric acid to prepare N-(4-([2,2':6',2'':6'',2''':6''' -quaterpyridine]-4-yl)phenyl)-pyrene butyric amide (qpy-pyr) ligand, and finally reacts with a metal cobalt salt to obtain a cobalt molecular complex with a peripherally modified pyrene group. Next, by selecting a suitable functionalized carbon nanotube, the cobalt molecular complex is closely anchored and the electronic beneficial microenvironment is modulated. It should be particularly pointed out that selecting a suitable supporting technology is the key to exciting the inherent activity of the molecular catalyst and realizing controllable electronic structure modulation. The present application uses a synergistic π-π coupling and coordination bonding strategy to realize the heterogenization of the cobalt molecular complex. The advantages of this are as follows: on the one hand, the peripheral pyrene group of the molecular complex strengthens the affinity with the carbon carrier; on the other hand, the carbon nanotube modification group as the first coordination site can effectively coordinate with the cobalt molecular complex in the axial direction, realize loading of more electrochemically active cobalt complexes, and promote interface electron transfer, and finally can reduce the reaction energy barrier by changing the microelectronic environment of the cobalt complex.

[0024] The functionalized carbon nanotube supported cobalt molecular complex composite catalyst and the preparation method thereof provided by the present application have the following advantages:

[0025] (1) The method provided by the present application uses a π-π coupling and coordination bonding double binding force supporting strategy to obtain a functionalized carbon nanotube supported cobalt molecular complex composite catalyst with high efficiency and high stability. The faradic efficiency of the obtained catalyst applied to CO2RR can be as high as 97.5%, and the turnover frequency can be as high as 79 s -1 .

[0026] (2) The method provided by the present application uses a brand-new supporting strategy to break through the limitations of low catalytic efficiency and poor stability of conventional molecular catalysts, so that the catalytic performance of the cheap cobalt center exceeds that of the noble metal center, opens up a new way for the preparation and efficient use of device-based molecular electrocatalysts, and has good industrial application prospect.

[0027] (3) The preparation method of the functionalized carbon nanotube supported cobalt molecular complex composite catalyst provided by the present application also has the advantages of mild reaction conditions and simple operation. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 This is a high-resolution mass spectrum of the cobalt molecular complex.

[0029] Figure 2 High-resolution transmission electron microscopy image (a) and energy spectrum (be) of Coqpy-pyr-MO.

[0030] Figure 3 This is the X-ray photoelectron spectrum of the complex of Coqpy-pyr-MO and cobalt molecule.

[0031] Figure 4 This is the Co 2p X-ray photoelectron spectrum of the Coqpy-pyr-MO and cobalt molecular complex.

[0032] Figure 5 Comparison of the linear voltammetric curves of Coqpy-pyr-MO, Coqpy-pyr-MC and Coqpy-pyr-MN in CO2 atmosphere.

[0033] Figure 6 Comparison of the CO2RR catalytic performance of Coqpy-pyr-MO and Coqpy-MO under different potential conditions.

[0034] Figure 7 This is the long-term electrocatalytic CO2RR stability test curve of Coqpy-pyr-MO. DETAILED DESCRIPTION

[0035] The present invention will be described in detail below with reference to the accompanying drawings and examples. It should also be understood that the following examples are only used to further illustrate the present invention and are not to be construed as limiting the scope of protection of the present invention. The specific mass, reaction time, temperature, process parameters, etc. in the examples are only examples within the appropriate ranges, and any non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention fall within the scope of protection of the present invention.

[0036] Unless otherwise specified, all reagents used were commercial reagents and were not further purified before use.

[0037] Example 1

[0038] The preparation method of the cobalt molecular complex Coqpy-pyr is as follows:

[0039] (1) 117 mg of 4-bromo-2,2':6',2":6",2"' -terpyridine, 63 mg of 4-acetamidobenzoic acid, 17.3 mg of tetrakis(triphenylphosphine)palladium, and 159 mg of anhydrous sodium carbonate were added to 10 mL of a methanol / water (10:1) mixture, and the reaction was heated under reflux for 24 h under argon. After removing the solvent, the resulting product was washed with water (1 mL) and isopropanol (1 mL) in this order to produce N-(4-([2,2':6',2":6",2"' -terpyridine]-4-yl)phenyl)acetamide (qpy-Ph-NHAc). The resulting qpy-Ph-NHAc was added to 1 mL of a 2 M methanolic hydrogen chloride solution, and hydrolysis was performed at room temperature for 1 h to produce 4-([2,2':6',2":6",2"' -terpyridine]-4-yl)phenylamine hydrochloride (qpy-Ph-NH2-HCl) as a yellow solid.

[0040] (2) 35 mg of 1-pyrenebutyric acid, 104 mg of benzotriazol-1-yl-oxytripyrrolidinophosphonium hexafluorophosphate (PyBOP), and 52 mg of N,N-diisopropylethylamine (DIEA) were added to 5 mL of dry DMF, and the resulting mixture was stirred at room temperature for 12 h under argon. Then, 43.7 mg of qpy-Ph-NH2-HCl produced in step (1) was added, and the reaction was performed for 72 h. After removing the DMF, the resulting solid was washed with water (1 mL) and isopropanol (1 mL) in this order. Finally, the resulting solid was dried to produce the ligand N-(4-([2,2':6',2":6",2"' -terpyridine]-4-yl)phenyl)pyrenebutyramide (qpy-pyr) in a yield of 60 mg (89%). The solid qpy-pyr was dissolved in DMSO-d6 to perform1H NMR spectroscopy, and the results were as follows: 1H NMR (400 MHz, DMSO-d6): δ 10.24 (s, 1H), 8.93 (s, 1H), 8.85-8.79 (m, 3H), 8.77 (d, J = 8.0 Hz, 1H), 8.70 (d, J = 8.0 Hz, 1H), 8.62 (d, J = 8.0 Hz, 1H), 8.52 (d, J = 8.0 Hz, 1H), 8.45 (d, J = 8.0 Hz, 1H), 8.31-8.221 (m, 5H), 8.15 (d, J = 4.0 Hz, 2H), 8.08 (d, J = 8.0 Hz, 2H), 8.05-7.99 (m, 3H), 7.86 (d, J = 4.0 Hz, 2H), 7.57 (t, J = 8.0 Hz, 1H), 3.43 (d, J = 8.0 Hz, 2H), 2.55 (d, J = 8.0 Hz, 2H), 2.16 (d, J = 8.0 Hz, 2H). The hydrogen nuclear magnetic resonance spectrum confirmed that qpy-pyr was successfully synthesized.

[0041] (3) 33 mg of qpy-pyr ligand was ultrasonically dispersed with 24 mg of CoCl2·6H2O in 20 mL of methanol, and then the obtained mixture was stirred at room temperature for 48 h. After the reaction was completed, the organic solvent was removed by rotary evaporation, and the obtained solid was washed with water (1 mL), isopropyl alcohol (1 mL), and dichloromethane (1 mL) in sequence. The metal cobalt complex (Coqpy-pyr) was a yellow solid, and the final product was 30 mg (37%). High resolution mass spectrometry was performed on Coqpy-pyr, and the results were as follows: ESI-MS (m / z): [Coqpy-pyr 2+ +HCO2 - ] + : Theoretical value: 775.1994; Test value: 775.1974. The elemental analysis results were as follows: C 46 H 36 Cl2CoN5O 2.5 (Coqpy-pyr·1.5H2O) Theoretical content (detection content): C, 66.67 (66.69), H, 4.38 (4.16), N, 8.45 (8.49), which confirmed that Coqpy-pyr was successfully synthesized.

[0042] Example 2

[0043] The preparation method of the functionalized carbon nanotube supported cobalt molecular complex composite 1 is as follows: 1.5 mg of carboxyl modified functionalized carbon nanotube (CNT-O) is dispersed in 1.28 mL of a mixture of ethylene glycol / ethanol (V=1:1), and ultrasonic treatment is performed for 30 minutes to obtain a dispersion of CNT-O; 200 μL of Coqpy-pyr-containing ethylene glycol / ethanol (V=1:1) dispersion (1 mg / mL) is added to the dispersion of CNT-O, and the mixture is ultrasonically dispersed for 30 minutes to obtain a catalyst / CNT-O mixture; finally, 20 μL of Nafion solution is added, and ultrasonic dispersion is continued for 30 minutes to prepare the functionalized carbon nanotube supported cobalt molecular complex composite (catalyst ink). 200 μL of the catalyst ink is uniformly dropped on carbon paper (1.0×1.0 cm 2 ), and then the carbon paper is baked and dried in an infrared oven for 5 minutes, and the obtained electrode material is named Coqpy-pyr@CNT-O. Coqpy-pyr@CNT-O is characterized; Figure 2 The transmission electron microscopy (TEM) image and energy dispersive spectroscopy (EDS) spectrum of Coqpy-pyr@CNT-O are shown in FIG. 2. It can be seen from the figure that no agglomerated cobalt clusters are observed, indicating that the cobalt complex is monodispersed on the surface of CNT-O. Figure 3 The XPS survey spectrum of Coqpy-pyr@CNT-O and Coqpy is shown in FIG. 3. It can be seen from the figure that the XPS spectrum confirms the coexistence of C, O, N and Co elements in the composite. Figure 4 The Co 2p XPS fine spectrum of Coqpy-pyr@CNT-O and Coqpy is shown in FIG. 4. It can be seen from the figure that the Co 2p spectrum of Coqpy has two peaks at 780.7 and 796.1 eV, which correspond to Co 2+ 2p 3 / 2 and Co 2p 1 / 2 of Coqpy, respectively; compared with the original Coqpy, the positive shift of the Co 2p binding energy of Coqpy-pyr@CNT-O indicates that there is a strong electronic interaction between the molecular catalyst and CNT-O, resulting in an increase in the valence state of Co sites.

[0044] Example 3

[0045] The prepared electrode material Coqpy-pyr@CNT-O was used as the working electrode to carry out the electrocatalytic CO2 reduction reaction. The steps are as follows: using 0.5 M KHCO3 aqueous solution as the electrolyte, the electrocatalytic CO2 reduction reaction was carried out in a customized air-tight single-chamber cell. Before electrolysis, the electrolysis cell was purged with CO2 (99.999%) for at least 50 minutes. In the long-term electrolysis test, the CO2 was continuously introduced into the electrolysis cell using a mass flow controller, and the flow rate was maintained at 20 mL / min. The cell was equipped with a saturated calomel electrode and a platinum wire as the reference electrode and the counter electrode, respectively. The gaseous products were analyzed by gas chromatography (Agilent HP 7820A, TCD detector), and the liquid products were tested by ion chromatography (Dionex). The Faraday efficiency (FE) of CO and H2 was calculated by the following formula:

[0046] wherein 2 is the number of electrons required to generate CO and H2, n is the number of moles of products, F is the Faraday constant (96485 C mol -1 ), and Q is the total charge (C) passed through the sample during the CO2 reduction process.

[0047] The linear voltammetry curve of Coqpy-pyr@CNT-O is shown in Figure 5 From the figure, it can be seen that Coqpy-pyr@CNT-O catalyzes CO2 RR to exhibit a relatively positive starting potential and a relatively large current density, proving the promoting effect of CNT-O axial coordination. The results of the electrocatalytic CO2 RR performance of Coqpy-pyr@CNT-O under different potential conditions are shown in Figure 6 From the figure, it can be seen that Coqpy-pyr@CNT-O presents a relatively high CO Faraday efficiency and current density, confirming the promoting effect of the peripheral pyrene group on improving the catalytic performance. The long-term stability test graph of Coqpy-pyr@CNT-O electrocatalytic CO2 RR is shown in Figure 7 From the figure, it can be seen that the catalytic current density and the Faraday efficiency of CO generation of Coqpy-pyr@CNT-O remain stable, proving its excellent structural stability.

[0048] Comparative Example 1

[0049] The preparation method of the functionalized carbon nanotube supported cobalt molecular complex composite 2 is as in Reference Example 2, except that the carboxyl-modified functionalized carbon nanotube is replaced by a functionalized carbon nanotube MWCNT (CNT) without a modification group, and the remaining steps are the same as in Example 2; the obtained electrode material is named as Coqpy-pyr@CNT.

[0050] The prepared electrode material was tested for electrocatalytic CO2 reduction reaction performance according to the method in Reference Example 3, except that Coqpy-pyr@CNT-O was replaced by Coqpy-pyr@CNT, and the remaining steps were the same as in Example 3. The linear voltammetry curve of Coqpy-pyr@CNT is shown in Figure 5 .

[0051] Comparative Example 2

[0052] The preparation method of the functionalized carbon nanotube supported cobalt molecular complex composite 3 was according to Reference Example 2, except that the carboxyl-modified functionalized carbon nanotube was replaced by an amino-modified functionalized carbon nanotube MWCNT(CNT-N), and the remaining steps were the same as in Example 2. The obtained electrode material was named Coqpy-pyr@CNT-N.

[0053] The prepared electrode material was tested for electrocatalytic CO2 reduction reaction performance according to the method in Reference Example 3, except that Coqpy-pyr@CNT-O was replaced by Coqpy-pyr@CNT-N, and the remaining steps were the same as in Example 3. The linear voltammetry curve of Coqpy-pyr@CNT-N is shown in Figure 5 .

[0054] Comparative Example 3

[0055] The preparation method of the cobalt molecular complex / carbon nanotube composite 4 was as follows: 1.5 mg of carboxyl-modified MWCNT(CNT-O) was dispersed in 1.28 mL of a mixture of ethylene glycol / ethanol(V=1:1) to obtain a dispersion liquid after ultrasonic treatment for 30 minutes. 200 μL of Coqpy ethylene glycol / ethanol(V=1:1) dispersion liquid(1 mg / mL) was added to the dispersion liquid of CNT-O, and then the mixture was ultrasonically treated for 30 minutes to obtain a catalyst / CNT-O mixture liquid. Finally, 20 μL of Nafion solution was added, and ultrasonic treatment was performed for 30 minutes to obtain a final catalyst ink. 200 μL of the ink was uniformly dropped on carbon paper(1.0×1.0 cm 2 ), and dried in an infrared oven for 5 minutes. The obtained electrode material was named Coqpy@CNT-O.

[0056] The prepared electrode material was tested for electrocatalytic CO2 reduction reaction performance according to the method in Reference Example 3, except that Coqpy-pyr@CNT-O was replaced by Coqpy@CNT-O, and the remaining steps were the same as in Example 3. The electrocatalytic CO2 RR performance of Coqpy@CNT-O under different potential conditions is shown in Figure 6 .

[0057] The above merely describes preferred embodiments of the present application, but the scope of protection of the present application is not limited thereto, and any modification, equivalent replacement and improvement made on the basis of the overall concept of the present application shall fall within the scope of protection of the present application.

Claims

1. A method for preparing a functionalized carbon nanotube-supported cobalt molecule complex, characterized in that: The specific steps include: (1) adding 4-bromo-2,2':6',2":6",2"'-tetrapyridine, 4-acetamidophenylboronic acid, tetrakis(triphenylphosphine)palladium and a base to a mixture of methanol and water, heating under reflux and removing the solvent, washing the resulting solid to prepare N-(4-([2,2':6',2":6",2"'-tetrapyridine]-4-yl)phenyl)-acetamide, and then adding N-(4-([2,2':6',2":6",2"'-tetrapyridine]-4-yl)phenyl)-acetamide to a methanolic hydrogen chloride solution for hydrolysis to prepare 4-([2,2':6',2":6",2"'-tetrapyridine]-4-yl)aniline hydrochloride; (2) adding 1-pyrenebutyric acid, benzotriazole-1-yl-oxytripyrrolidinophosphine hexafluorophosphate and N,N-diisopropylethylamine to dry N,N-dimethylformamide and stirring to obtain a mixed solution, adding 4-([2,2′:6′,2″:6″,2″′-tetrapyridine]-4-yl)aniline hydrochloride obtained in step (1) to the obtained mixed solution, continuing the reaction, and washing and drying the obtained solid to obtain the ligand N-(4-([2,2′:6′,2″:6″,2′"-tetrapyridine]-4-yl)phenyl)-pyrenebutamide; (3) adding the ligand N-(4-([2,2′:6′,2″:6″,2″′-tetrapyridine]-4-yl)phenyl)-pyrenebutamide and cobalt salt prepared in step (2) to methanol, stirring the reaction, removing the solvent, and washing the resulting solid to obtain a metal cobalt complex; (4) adding the metal cobalt complex and functionalized carbon nanotubes prepared in step (3) into a mixed solution consisting of ethanol and ethylene glycol, and adding nafion solution after the obtained mixture is evenly dispersed to obtain the functionalized carbon nanotube-supported cobalt molecular complex complex.

2. The method for preparing the functionalized carbon nanotube-supported cobalt molecule complex according to claim 1, characterized in that: The molar ratio of 4-bromo-2,2':6',2":6",2'"-tetrapyridine and 4-acetamidophenylboronic acid in step (1) is 6:7; the volume ratio of methanol to water in the mixed solution is 10:1; the concentration of hydrogen chloride in the methanol hydrogen chloride solution is 1-3 mol / L; and the base is one of anhydrous sodium carbonate, anhydrous potassium carbonate or anhydrous cesium carbonate.

3. The method for preparing the functionalized carbon nanotube-supported cobalt molecule complex according to claim 1, characterized in that: The molar ratio of 1-pyrenebutyric acid, benzotriazole-1-yl-oxytripyrrolidinophosphine hexafluorophosphate, N,N-diisopropylethylamine and 4-([2,2′:6′,2″:6″,2′″-tetrapyridine]-4-yl)aniline hydrochloride described in step (2) is 6:1:20:

5.

4. The method for preparing the functionalized carbon nanotube-supported cobalt molecule complex according to claim 1, characterized in that: The cobalt salt described in step (3) is selected from one of cobalt perchlorate, cobalt chloride, cobalt bromide, cobalt nitrate or cobalt sulfate.

5. The method for preparing the functionalized carbon nanotube-supported cobalt molecule complex according to claim 1, characterized in that: The carbon nanotubes described in step (4) are one of unmodified carbon nanotubes, amino-modified carbon nanotubes or carboxyl-modified carbon nanotubes.

6. An N-(4-([2,2′:6′,2″:6″,2′″-tetrapyridine]-4-yl)phenyl)-pyrenebutanamide ligand, characterized by: The structural formula of the ligand is as follows:

7. A metal cobalt complex containing an N-(4-([2,2′:6′,2″:6″,2″′-tetrapyridine]-4-yl)phenyl)-pyrenebutanamide ligand, characterized in that: The main structural formula of the complex is as follows:

8. A functionalized carbon nanotube-supported cobalt molecule complex, characterized by: The complex consists of a metal cobalt complex containing N-(4-([2,2':6',2":6",2"'-tetrapyridine]-4-yl)phenyl)-pyrenebutanamide ligand and carbon nanotubes.

9. The functionalized carbon nanotube-supported cobalt molecule complex according to claim 8, characterized in that: The mass ratio of the metal cobalt complex containing N-(4-([2,2′:6′,2″:6″,2″′-tetrapyridine]-4-yl)phenyl)-pyrenebutanamide ligand to the carbon nanotube is 1:1 to 60:

1.

10. Use of the functionalized carbon nanotube-supported cobalt molecular complex prepared by the method according to claims 1-6 or the functionalized carbon nanotube-supported cobalt molecular complex according to claims 8-9 in electrocatalytic CO2 reduction.

Images