CN113502505B - Azide porphyrin ligand, metalloporphyrin/carbon composite material and application of water electrolysis - Google Patents

Abstract

The invention discloses an azinyl porphyrin ligand, a metal porphyrin complex/carbon composite material and an application of electrolytic water, wherein the structural formula of the ligand is as follows:

the ligand can be coordinated with various metal ions to obtain a stable metalloporphyrin complex, and an azide group on the molecule of the ligand can be covalently connected with an alkynyl group modified on the carbon nano tube in an azide-alkynyl cycloaddition mode, so that various metalloporphyrin complexes are immobilized on the carbon nano material. The invention firstly applies different metalloporphyrin complexes/carbon composite materials as a catalyst for cathodic hydrogen evolution and a catalyst for anodic oxygen evolution to electrocatalytic water decomposition respectively, the stability of the catalyst in the electrocatalytic water decomposition process is good, and the catalytic current density reaches 10mA/cm ² The required voltage is less than that of commercial platinum carbon and iridium carbon catalysts with equal loading.

Description

A kind of azide porphyrin ligand and metalloporphyrin/carbon composite material and water electrolysis application

technical field

The invention belongs to the technical field of electrocatalytic decomposition of water for hydrogen production, and in particular relates to an A3B _- type azide porphyrin ligand, and a metalloporphyrin complex based on the ligand is immobilized through an azide-alkynyl cycloaddition reaction On carbon nanomaterials, it is used for electrocatalytic water splitting to produce hydrogen and oxygen.

Background technique

The energy problem is one of the three major problems in the world today. As an ideal new energy source in the future, the development of hydrogen energy has become a focus of attention. Electrocatalytic water splitting for hydrogen production is an ideal process for converting electrical energy into chemical energy, but the two half-reactions of water splitting (hydrogen evolution reaction and oxygen evolution reaction) are slow due to the limitation of kinetics, so it is necessary to seek Efficient catalyst to promote the occurrence of the reaction.

In the field of organic small molecule catalysis, porphyrin ligands can coordinate with various metal ions to form various metalloporphyrin complexes due to their rigid and stable coordination environment, thus enriching the redox properties of metalloporphyrin complexes , so it can be used in the study of electrocatalytic hydrogen-producing half-reaction or oxygen-producing half-reaction (Chem. Rev. 2017, 117, 3717-3797). However, considering the low solubility of metal complexes in aqueous solution, which greatly reduces the catalytic conductivity, molecules are usually loaded on carbon nanomaterials to realize metalloporphyrin complex-functionalized carbon nanocomposites (ACS Catal.2017, 7, 8033-8041).

SUMMARY OF THE INVENTION

The object of the present invention is to provide an azide porphyrin ligand capable of coordinating with a variety of transition metal ions, and a metalloporphyrin complex based on the ligand and an alkynyl-modified carbon nanomaterial through an azide-alkynyl group A cycloaddition reaction covalently linked metalloporphyrin complex/carbon composite material provides an application for the composite material at the same time.

For the above purpose, the structural formula of the azide porphyrin ligand used in the present invention is as follows:

The preparation method of the above-mentioned azide porphyrin ligand is: using dichloromethane as a solvent, 4-azidobenzaldehyde, pentafluorobenzaldehyde, pyrrole, boron trifluoride ether, 2,3-dichloro-5, The molar ratio of 6-dicyano-1,4-benzoquinone (DDQ) is 1:3:4:1.6:3, and the reaction is stirred in the dark, and after the reaction is completed, separation and purification are performed to obtain the azide porphyrin ligand.

The metalloporphyrin complex/carbon composite material of the present invention is a metalloporphyrin complex formed by coordinating any metal among manganese, iron, cobalt, nickel and copper with the azide porphyrin ligand, and a modified alkyne The carbon nanotubes of the base are formed by covalent connection by means of azide-alkynyl cycloaddition, and its preparation method consists of the following steps:

Step 1. Preparation of Metalloporphyrin Complexes

The azide porphyrin ligand, metal precursor and 2,6-lutidine were added to N,N-dimethylformamide, and the reaction was performed under argon at 50 to 160 °C for 0.5 to 12 h in the dark, and the reaction was completed. After separation and purification, the metalloporphyrin complex with the following structural formula is obtained;

In the formula, M represents any one of Mn, Fe, Co, Ni, and Cu, and the corresponding metal precursors are manganese acetate, ferrous chloride, cobalt acetate, nickel acetate, and copper acetate in turn.

Step 2. Preparation of alkynyl-modified carbon nanotubes

Add carbon nanotubes and 4-ethynylaniline into hydrochloric acid, and ultrasonically disperse evenly, then add sodium nitrite aqueous solution at 0 to 5 °C and ultrasonically disperse evenly, then add iron powder, and ultrasonicate for 1 to 1.5 hours; use excess dilute sulfuric acid The residual iron powder is removed, filtered, washed, and dried to obtain alkynyl-modified carbon nanotubes.

Step 3. Preparation of metalloporphyrin complexes/carbon composites

The carbon nanotubes and metalloporphyrin complexes modified with alkynyl groups were added to N,N-dimethylformamide, dispersed uniformly by ultrasonic, and stirred at 70 to 90 °C for 10 to 12 hours, and the metalloporphyrin/carbon complex was obtained. material, namely obtain manganese porphyrin complex/carbon composite or iron porphyrin complex/carbon composite or cobalt porphyrin complex/carbon composite or nickel porphyrin complex/carbon composite or copper porphyrin complex/ carbon composite.

In the above step 1, the molar ratio of the azide porphyrin ligand to the metal precursor and 2,6-lutidine is preferably 1:10-12:0.15-0.20.

In the above step 2, preferably the molar ratio of 4-ethynylaniline to sodium nitrite is 1:1-1.2, and the mass ratio of carbon nanotubes to 4-ethynylaniline is 1:8-12.

In the above step 3, it is preferable that the mass ratio of the alkynyl-modified carbon nanotube and the metalloporphyrin complex is 1:1-1.2.

The metalloporphyrin complex/carbon composite material of the present invention can be used to catalyze the electrolysis of water for hydrogen production and oxygen production, and the specific usage mode is as follows: the above-mentioned iron porphyrin complex/carbon composite material and cobalt porphyrin complex/carbon composite material are respectively used as catalysts Loaded on the electrode, the electrode loaded with iron porphyrin complex/carbon composite material was used as the cathode, and the electrode loaded with cobalt porphyrin complex/carbon composite material was used as the anode, and water was electrolyzed in 1.0 mol/L KOH solution.

The beneficial effects of the present invention are as follows:

1. The azide porphyrin ligands of the present invention can coordinate with different transition metal ions to form metalloporphyrin complexes. The metalloporphyrin complex can be covalently connected and immobilized on the carbon nanomaterial through an azide-alkynyl cycloaddition reaction with a carbon nanomaterial modified with an alkynyl group to form a metalloporphyrin complex/carbon composite material. The construction of this immobilization method not only realizes the heterogeneous catalysis of various metalloporphyrin complexes, but also has the excellent high conductivity, large specific surface area and good chemical stability of carbon nanomaterials.

2. For the first time in the present invention, a metalloporphyrin complex/carbon composite material is formed into a ^two -electrode system for electrocatalytic water splitting to produce hydrogen and oxygen at the same time. The voltage is lower than that of commercial platinum-carbon and iridium-carbon catalysts with the same loading.

3. The azide porphyrin ligand and metalloporphyrin complex/carbon composite material of the present invention have the characteristics of simple and easy-to-obtain raw materials, mild reaction conditions, simple operation, etc. in synthesis; in terms of catalytic electrolysis of water, the catalyst dosage is low, and the catalytic conditions It is easy to control and has good catalyst stability.

Description of drawings

Figure 1 is the synthetic route of metalloporphyrin/carbon composites.

Figure 2 is the infrared spectrum of 1-Mn@CNT.

Figure 3 is the infrared spectrum of 1-Fe@CNT.

Figure 4 is the infrared spectrum of 1-Co@CNT.

Figure 5 is the infrared spectrum of 1-Ni@CNT.

Figure 6 is the infrared spectrum of 1-Cu@CNT.

Figure 7 is a diagram of electrocatalytic water splitting of 1-Fe@CNT||1-Co@CNT with platinum carbon and iridium carbon with the same loading.

Detailed ways

The present invention is further described in detail below with reference to the accompanying drawings and embodiments, but the protection scope of the present invention is not limited to the following embodiments.

Example 1

Preparation of azide porphyrin ligands

In a 500 mL round-bottomed flask equipped with a magnetic stirring bar, 300 mL of dichloromethane was added, followed by 181.2 mg (1.2 mmol) of 4-azidobenzaldehyde, 444 μL (3.6 mmol) of pentafluorobenzaldehyde, and 333 μL (4.8 mmol) Pyrrole, after stirring for 5 min, 200 μL (1.6 mmol) of boron trifluoride ether was added dropwise, and stirred for 45 min in the dark, then 0.817 g (3.6 mmol) of DDQ was added, and stirring was continued for 1 h. Separation by thin-layer chromatography (using a mixture of petroleum ether and dichloromethane with a volume ratio of 2:1 as a developing solvent), and then rotary evaporation under reduced pressure to remove the solvent to obtain a purple solid, namely azide porphyrin ligand, referred to as porphyrin Ligand 1, chemically named 5-(4-azidophenyl)-10,15,20-tris(perfluorophenyl)porphyrin, has a yield of 14.8%, and the structural characterization data are as follows:

¹ H NMR (400 MHz, CDCl ₃ ): δ [ppm]=9.01-8.78 (m, 8H), 8.20 (d, J=8.2 Hz, 2H), 7.47 (d, J=8.0 Hz, 2H), -2.85 (s,2H).

HRMS (ESI) m/z: C ₄₄ H ₁₅ F ₁₅ N ₇ , [M+H] ⁺ , theoretical value 926.1144; found value 926.1143.

Example 2

1. Preparation of manganese porphyrin complexes

In a 50 mL round-bottomed flask equipped with a magnetic stirring bar, 15 mL of N,N-dimethylformamide was added, followed by 29.6 mg (0.032 mmol) of porphyrin ligand 1, 78.4 mg (0.32 mmol) of manganese acetate tetrahydrate, 20 μL 2, 6-lutidine, refluxed at 110 °C for 12 h in the dark under argon. The N,N-dimethylformamide was removed by rotary evaporation under reduced pressure, washed three times with dichloromethane and saturated aqueous sodium chloride solution, collected the organic phase, dried with anhydrous sodium sulfate, rotary evaporated to remove dichloromethane, and then used Tetrahydrofuran was recrystallized to obtain a dark brown-yellow solid, namely a manganese porphyrin complex (denoted as 1-Mn).

HRMS (ESI) m/z: C ₄₄ H ₁₂ F ₁₅ N ₇ Mn, [M] ⁺ , theoretical value 978.0290; found value 978.0289.

2. Preparation of carbon nanotubes with modified alkynyl groups

Add 70 mL of 0.5M hydrochloric acid solution to a 200 mL round-bottomed flask, add 30 mg of carbon nanotubes (CNTs) and 305 mg (2.6 mmol) of 4-ethynylaniline, sonicate for 30 min, and add 15 mL (2.6 mmol) of aqueous sodium nitrite solution at 0°C Sonicate for 30 min, then add 500 mg of iron powder and sonicate for 1 h. Excessive dilute sulfuric acid was used to remove the residual iron powder, followed by washing with water, ethanol, and acetone in sequence until the filtrate was colorless, and finally dried at room temperature to obtain alkynyl-modified CNTs.

3. Preparation of manganese porphyrin complexes/carbon composites

Add 20 mL of N,N-dimethylformamide to a 50 mL round-bottomed flask, add 10 mg of alkynyl-modified CNTs and 10 mg of 1-Mn, sonicate for 10 min, stir at 85 °C for 12 h, collect by centrifugation, and re-disperse in 2 In methyl chloride, centrifuged for several times to collect, washed away unreacted 1-Mn, and dried at room temperature in the dark to obtain a manganese porphyrin complex/carbon composite material (denoted as 1-Mn@CNT).

The obtained product was characterized by infrared spectroscopy. As shown in Fig. 2, 1-Mn has a characteristic peak of azide at 2100cm ^-1 . After reacting with CNTs modified with alkynyl group, the characteristic peak of azide disappeared, and 1- The infrared spectra of Mn@CNT and 1-Mn are in one-to-one correspondence between 1800cm ^-1 and 600cm ^-1 , which proves that 1-Mn is successfully covalently attached to CNTs.

Example 3

1. Preparation of iron porphyrin complexes

In a 50mL round-bottomed flask equipped with a magnetic stirring bar, 15mL of N,N-dimethylformamide was added, followed by 29.6mg (0.032mmol) of porphyrin ligand 1, 40.6mg (0.32mmol) of ferrous chloride, 20μL of 2 , 6-lutidine, under argon, 110 ℃ dark and reflux reaction for 3h. The N,N-dimethylformamide was removed by rotary evaporation under reduced pressure, washed three times with dichloromethane and an aqueous saturated sodium chloride solution, and then three times with dichloromethane and an aqueous solution of dilute hydrochloric acid. It was dried with sodium sulfate, dichloromethane was removed by rotary evaporation, and then recrystallized with tetrahydrofuran to obtain a dark brown solid, namely iron porphyrin complex (referred to as 1-Fe), which was stored at low temperature and protected from light. The yield was 75%. Data are as follows:

HRMS(ESI)m/z:C ₄₄ H ₁₂ F ₁₅ N ₇ Fe,[M] ⁺ , theoretical value 979.0259; observed value 979.0247.

2. Preparation of carbon nanotubes with modified alkynyl groups

This step is the same as step 2 of Example 2.

3. Preparation of iron porphyrin complexes/carbon composites

Add 20 mL of N,N-dimethylformamide to a 50 mL round-bottomed flask, add 10 mg of alkynyl-modified CNTs and 10 mg of 1-Fe, sonicate for 10 min, stir at 85 °C for 12 h, collect by centrifugation, and re-disperse in two In methyl chloride, centrifuged for several times to collect, washed away unreacted 1-Fe, and dried at room temperature in the dark to obtain iron porphyrin complex/carbon composite material (denoted as 1-Fe@CNT). It can be seen from Figure 3 that 1-Fe was successfully covalently attached to CNTs.

Example 4

1. Preparation of cobalt porphyrin complexes

In a 50 mL round-bottomed flask equipped with a magnetic stirring bar, 15 mL of N,N-dimethylformamide was added, followed by 29.6 mg (0.032 mmol) of porphyrin ligand 1, 79.7 mg (0.32 mmol) of cobalt acetate tetrahydrate, 20 μL 2, 6-Lutidine was reacted under argon at 110 °C for 3 h in the dark. The N,N-dimethylformamide was removed by rotary evaporation under reduced pressure, washed three times with dichloromethane and saturated aqueous sodium chloride solution, collected the organic phase, dried with anhydrous sodium sulfate, rotary evaporated to remove dichloromethane, and then used Tetrahydrofuran was recrystallized to obtain a reddish-brown solid, that is, a cobalt porphyrin complex (denoted as 1-Co).

HRMS (ESI) m/z: C ₄₄ H ₁₂ F ₁₅ N ₇ Co, theoretical value 982.0241; found value 982.0227.

2. Preparation of carbon nanotubes with modified alkynyl groups

This step is the same as step 2 of Example 2.

3. Preparation of cobalt porphyrin complexes/carbon composites

Add 20 mL of N,N-dimethylformamide to a 50 mL round-bottomed flask, add 10 mg of alkynyl-modified CNTs and 10 mg of 1-Co, sonicate for 10 min, stir at 85°C for 12 h, collect by centrifugation, and re-disperse in two In methyl chloride, centrifuged for several times to collect, washed away unreacted 1-Co, and dried at room temperature in the dark to obtain a cobalt porphyrin complex/carbon composite (denoted as 1-Co@CNT). It can be seen from Figure 4 that 1-Co was successfully covalently attached to CNTs.

Example 5

1. Preparation of nickel porphyrin complexes

In a 50mL round-bottomed flask equipped with a magnetic stirring bar, 15mL of N,N-dimethylformamide was added, followed by 29.6mg (0.032mmol) of porphyrin ligand 1, 79.6mg (0.32mmol) of nickel acetate tetrahydrate, 20μL2 , 6-lutidine, and react under argon at 160 °C for 1 h in the dark. The N,N-dimethylformamide was removed by rotary evaporation under reduced pressure, washed three times with dichloromethane and saturated aqueous sodium chloride solution, collected the organic phase, dried with anhydrous sodium sulfate, rotary evaporated to remove dichloromethane, and then used Tetrahydrofuran was recrystallized to obtain a reddish-brown solid, namely nickel porphyrin complex (denoted as 1-Ni), which was stored in the dark at low temperature, and its yield was 80%. The structural characterization data were as follows:

¹ H NMR (400 MHz, CDCl ₃ ): δ [ppm]=8.82-8.69 (m, 8H), 8.57 (d, J=8.1 Hz, 2H), 8.18 (d, J=8.2 Hz, 2H).

2. Preparation of carbon nanotubes with modified alkynyl groups

This step is the same as step 2 of Example 2.

3. Preparation of nickel porphyrin complexes/carbon composites

Add 20 mL of N,N-dimethylformamide to a 50 mL round-bottomed flask, add 10 mg of alkynyl-modified CNTs and 10 mg of 1-Ni, sonicate for 10 min, stir at 85°C for 12 h, collect by centrifugation, and re-disperse in two In methyl chloride, centrifuged for several times to collect, washed away the unreacted 1-Ni, and dried at room temperature in the dark to obtain a nickel porphyrin complex/carbon composite material (denoted as 1-Ni@CNT). It can be seen from Figure 5 that 1-Ni was successfully covalently attached to CNTs.

Example 6

1. Preparation of copper porphyrin complexes

In a 50 mL round-bottomed flask equipped with a magnetic stirring bar, 15 mL of N,N-dimethylformamide was added, followed by 29.6 mg (0.032 mmol) of porphyrin ligand 1, 63.9 mg (0.32 mmol) of copper acetate monohydrate, 20 μL 2, 6-Lutidine was reacted under argon at 50 °C for 30 min in the dark. The N,N-dimethylformamide was removed by rotary evaporation under reduced pressure, washed three times with dichloromethane and saturated aqueous sodium chloride solution, collected the organic phase, dried with anhydrous sodium sulfate, rotary evaporated to remove dichloromethane, and then used Tetrahydrofuran was recrystallized to obtain a reddish-brown solid, that is, a copper porphyrin complex (denoted as 1-Cu), which was stored at low temperature and protected from light. The yield was 95%.

HRMS (ESI) m/z: C ₄₄ H ₁₃ F ₁₅ N ₇ Cu, [M+H] ⁺ , theoretical value 987.0283; found value 987.0301.

2. Preparation of carbon nanotubes with modified alkynyl groups

This step is the same as step 2 of Example 2.

3. Preparation of copper porphyrin complexes/carbon composites

Add 20 mL of N,N-dimethylformamide to a 50 mL round-bottomed flask, add 10 mg of alkynyl-modified CNTs and 10 mg of 1-Cu, sonicate for 10 min, stir at 85 °C for 12 h, collect by centrifugation, and re-disperse in two In methyl chloride, centrifuged for several times to collect, washed away unreacted 1-Cu, and dried at room temperature in the dark to obtain a copper porphyrin complex/carbon composite material (denoted as 1-Cu@CNT). It can be seen from Figure 6 that 1-Cu was successfully covalently attached to CNTs.

Example 7

Application of Metalloporphyrin Complexes/Carbon Composites in Catalytic Water Electrolysis for Hydrogen and Oxygen Production

Add 3 mg of 1-Fe@CNT and 20 μL of 5% Nafion to 1 mL of N,N-dimethylformamide, sonicate until dispersed uniformly, take 3 μL of the mixed suspension and drop it evenly on the surface of the clean glassy carbon electrode, and dry it at room temperature. A 1-Fe@CNT-loaded electrode was obtained. 1-Co@CNT-loaded electrodes were prepared in the same way.

A two-electrode system 1-Fe@CNT||1-Co@CNT was formed by using the electrode loaded with 1-Fe@CNT as the cathode and the electrode loaded with 1-Co@CNT as the anode, in 1.0M KOH solution with a scan rate of 10mV The total hydrolysis experiment was carried out under the condition of /s. At the same time, the platinum carbon with the same loading was used as the cathode, and the iridium carbon was used as the anode. The experimental results are shown in Figure 7.

It can be seen from Fig. 7 that when the current density reaches 10 mA/cm ² , the required voltage of 1-Fe@CNT||1-Co@CNT is 2.18 V, the required voltage of Pt/C||Ir/C is 2.39 V, and the required voltage of 1- Fe@CNT||1-Co@CNT is 210 mV smaller than Pt/C||Ir/C, that is, the catalytic current density of 1-Fe@CNT||1-Co@CNT in electrocatalytic water splitting reaches 10 mA/cm When ² , the required voltage is less than the Pt/C||Ir/C of the same load, indicating that the performance of the bi-electrode catalytic water electrolysis for hydrogen production and oxygen production prepared by using the metalloporphyrin complex/carbon composite material of the present invention as a catalyst is better than that of platinum carbon. , The performance of iridium carbon double electrode is good.

Claims (5)

1. The application of metalloporphyrin complex/carbon composite material in catalytic electrolysis of water for hydrogen production and oxygen production, the specific usage is as follows: iron porphyrin complex/carbon composite material and cobalt porphyrin complex/carbon composite material are used as The catalyst is supported on the electrode, the electrode loaded with iron porphyrin complex/carbon composite material is used as the cathode, and the electrode loaded with cobalt porphyrin complex/carbon composite material is used as the anode, and water is electrolyzed in 1.0mol/L KOH solution; The iron porphyrin complex/carbon composite material is a metalloporphyrin complex formed by coordinating iron metal and an azide porphyrin ligand, and is formed by azide-alkynyl cycloaddition with a carbon nanotube modified with an alkynyl group. form covalently linked; The cobalt porphyrin complex/carbon composite material is a metalloporphyrin complex formed by coordinating cobalt metal and an azide porphyrin ligand, and the carbon nanotube modified with an alkynyl group is added through an azide-alkynyl cycloaddition. form covalently linked; The structural formula of the azide porphyrin ligand is shown below:

2. the application of metalloporphyrin complex/carbon composite material according to claim 1 in the catalytic electrolysis of water for hydrogen production and oxygen production, it is characterized in that, described iron porphyrin complex/carbon composite material is coordinated with cobalt porphyrin The material/carbon composite was prepared by the following steps: Step 1. Preparation of Metalloporphyrin Complexes The azide porphyrin ligand, metal precursor and 2,6-lutidine were added to N,N-dimethylformamide, and the reaction was performed under argon at 50 to 160 °C for 0.5 to 12 h in the dark, and the reaction was completed. After separation and purification, the metalloporphyrin complex with the following structural formula is obtained;

In the formula, M represents any one of Fe and Co, and the corresponding metal precursors are ferrous chloride and cobalt acetate in turn; Step 2. Preparation of alkynyl-modified carbon nanotubes Add carbon nanotubes and 4-ethynylaniline into hydrochloric acid, and ultrasonically disperse evenly, then add sodium nitrite aqueous solution at 0 to 5 °C and ultrasonically disperse evenly, then add iron powder, and ultrasonicate for 1 to 1.5 hours; use excess dilute sulfuric acid Remove residual iron powder, filter, wash, and dry to obtain alkynyl-modified carbon nanotubes; Step 3. Preparation of metalloporphyrin complexes/carbon composites Add the carbon nanotubes and metalloporphyrin complexes modified with alkynyl groups into N,N-dimethylformamide, disperse them uniformly by ultrasonic, and stir at 70-90 °C for 10-12 hours to obtain metalloporphyrin/carbon composites , that is, the iron porphyrin complex/carbon composite material or the cobalt porphyrin complex/carbon composite material is obtained. 3. the application of metalloporphyrin complex/carbon composite material according to claim 2 in catalytic electrolysis of water for hydrogen production and oxygen production, it is characterized in that: in step 1, described azide porphyrin ligand and metal precursor The molar ratio of 2,6-lutidine is 1:10～12:0.15～0.20. 4. the application of metalloporphyrin complex/carbon composite material according to claim 2 in catalytic electrolysis of water for hydrogen production and oxygen production, it is characterized in that: in step 2, described 4-ethynyl aniline and sodium nitrite are mixed The molar ratio is 1:1-1.2, and the mass ratio of carbon nanotubes to 4-ethynylaniline is 1:8-12. 5. the application of metalloporphyrin complex/carbon composite material according to claim 2 in catalytic electrolysis of water for hydrogen production and oxygen production, it is characterized in that: in step 3, the carbon nanotube and the metalloporphyrin of described modified alkyne group The mass ratio of the morpholine complexes is 1:1 to 1.2.

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