阅读说明：本技术 一种用于活化氧气分子的钴基金属有机框架催化剂的制备方法及其应用 (Preparation method and application of cobalt-based metal organic framework catalyst for activating oxygen molecules ) 是由 段春迎 宋靖修 张铁欣 史雨生 李莫尘 于 2020-11-30 设计创作，主要内容包括：本发明属于光催化材料技术领域,一种用于活化氧气分子的钴基金属有机框架催化剂的制备方法及其应用,其中制备方法：是以吡唑配体H_2DPA与金属钴盐中的Co~(2+)作为节点,通过溶剂热法制得用于活化氧气分子的钴基金属有机框架催化剂,其合成路线如下：H_2DPA+Co~(2+)→Co-DPA,金属钴盐选自氯化钴或硝酸钴中的一种。本发明制备的钴基金属有机框架催化剂在光催化活化氧气分子反应中的光电流测试对比图,可以看出,氧气氛围下Co-DPA具有明显增大的光电流响应,表明Co-DPA中还原态的Co具备活化氧气分子的能力。(The invention belongs to the technical field of photocatalytic materials, and relates to a preparation method and application of a cobalt-based metal organic framework catalyst for activating oxygen molecules, wherein the preparation method comprises the following steps: is a pyrazole ligand H 2 DPA and Co in metal cobalt salts 2+ As a node, produced by solvothermal method for activating oxygen moleculesThe cobalt-based metal organic framework catalyst is synthesized by the following steps: h 2 DPA+Co 2+ → Co-DPA, metallic cobalt salt is selected from one of cobalt chloride or cobalt nitrate. The comparative graph of the photocurrent test of the cobalt-based metal organic framework catalyst in the photocatalytic activation oxygen molecule reaction shows that Co-DPA in the oxygen atmosphere has obviously increased photocurrent response, which indicates that the reduced Co in the Co-DPA has the capability of activating oxygen molecules.)

1. A preparation method of a cobalt-based metal organic framework catalyst for activating oxygen molecules is characterized by comprising the following steps: is a pyrazolyl ligand H₂DPA and Co in metal cobalt salts²⁺As nodes, by means of solventsThe cobalt-based metal organic framework catalyst is prepared by a thermal method, and the synthetic route is as follows:

H₂DPA+Co²⁺→Co-DPA；

the metal cobalt salt is selected from one of cobalt chloride or cobalt nitrate;

the pyrazolyl ligand H₂DPA of formula C₂₀H₁₄N₄Having the following (A)

The molecular structural formula of the compound is shown in the specification,

the preparation method of the Co-DPA comprises the following steps:

step 1, mixing lithium perchlorate, silicon dioxide, anthracene and N-bromosuccinimide according to the proportion of l: 6-10: 6-10: adding 13-20 mol ratio of the mixture into a 250mL three-necked bottle, adding 80-120 mL dichloromethane solvent into the bottle, stirring at room temperature for 25-40 min, filtering the obtained yellow mixture, washing the obtained filtrate with deionized water in a separating funnel, and finally performing rotary evaporation on the obtained organic phase filtrate by using a rotary evaporator to obtain yellow powder 9, 10-dibromoanthracene;

step 2, placing the 9, 10-dibromoanthracene, cesium carbonate, tetrakis (triphenylphosphine) palladium and 4-pyrazole boronic acid pinacol ester prepared in the step 1 in a 250mL three-neck flask according to the molar ratio of 1: 5-8: 0.1-0.2: 3-5, and adding N₂Replacing the gas atmosphere in a bottle for three times, adding 10-20 mL of DMF subjected to degassing treatment into the mixture, reacting for 50-80H at 105-115 ℃, pouring the reaction mixture into a 1L beaker after the reaction is finished, adding 500-700 mL of water, continuously stirring for 15-25 min, filtering to obtain a light yellow reaction crude product, dissolving the light yellow reaction crude product into tetrahydrofuran, separating by using column chromatography, and obtaining yellow powder, namely pyrazolyl ligand H, by using a mixed solvent of acetone and n-hexane with the volume ratio of 1:1 as a mobile phase₂DPA；

Step 3, the pyrazolyl ligand H prepared in the step 2₂DPA and CoCl₂·6H₂O or Co (NO)₃)₂·6H₂Adding O into a 7mL glass vial according to the mass ratio of 1: 4-5, adding 2-4 mL DEF and 5-25 muL acetic acid, fully mixing, uniformly stirring, firstly putting the mixture into a hydrothermal autoclave, then putting the hydrothermal autoclave into an oven with a temperature control function, heating for 8-12 hours to raise the temperature to 110-120 ℃, reacting for 72-90 hours, finally cooling to 25 ℃ for 8-12 hours to obtain a purple rod-shaped crystal, filtering, washing with DEF, and drying in the air to obtain the target material Co-based metal organic framework catalyst Co-DPA.

2. Use of a cobalt-based metal-organic framework catalyst prepared according to the process of claim 1 in photocatalytically-activated molecular oxygen reactions.

Technical Field

The invention relates to a preparation method and application of a cobalt-based metal organic framework catalyst for activating oxygen molecules, belonging to the technical field of photocatalytic materials.

Background

Metal-organic frameworks (MOFs) are a highly ordered class of materials with a porous structure assembled by Metal ions and organic ligands through coordination bonds, and many different MOFs over 20000 have been reported so far due to the differences in the geometric shapes, sizes and functional group characteristics of the structural components. The specific surface area is about 1000 to 10000m²The/g varies and significantly exceeds that of traditional porous materials such as zeolite, activated carbon and the like. Meanwhile, the dye has the characteristics of permanent porosity, multiple and variable components and the like, so that the dye can be used for storing dyes (hydrogen, methane and the like) and capturing CO₂The method has wide application in the aspects of activating oxygen molecules, catalyzing and the like.

In recent years, the green sustainable development has attracted more and more attention, and the greening technology for developing oxidation reaction is not slow. Although the traditional metal catalyst has excellent catalytic efficiency, the traditional metal catalyst cannot be recycled, and resource waste and environmental pollution are caused. In the solid material heterogeneous catalyst which is formed in recent years, oxygen molecules can only act with active sites exposed on the surface of the catalyst. Metal-organic frameworks benefit from their porous nature, and internal active sites can also interact with oxygen molecules. Meanwhile, the metal organic framework is a heterogeneous catalyst, can be separated from a reaction system by a relatively convenient method after the reaction is finished, and can be subjected to next catalytic reaction after being cleaned, so that resource waste and environmental pollution are avoided.

Disclosure of Invention

In order to overcome the defects in the prior art, the invention aims to provide a preparation method and application of a cobalt-based metal organic framework catalyst for activating oxygen molecules. At the same time, the reduction state of the macrocyclic anthracene-based ligand is capable of reducing O by taking the macrocyclic anthracene-based ligand and Co with redox activity as a metal center₂Active oxygen species are generated, and Co intermediates with various valence states can further react with the active oxygen species through a Fenton reaction mechanism, so that the mediation of the oxidation reaction of the organic substrate is realized. In the structural design of the heterogeneous catalyst, a nitrogen-containing coordination group with good electron conductivity is used for connecting a photosensitive ligand and a metal center; because the aromatic accumulation of the ligand and the nitrogen-metal cluster have different charge conductivity and photoresponse mechanisms, the efficient charge separation of the ligand aggregation unit and the metal cluster aggregation unit is hopefully realized under the condition of photoexcitation, and O is coupled₂Reduction and organic substrate oxidation to realize O utilization₂The method is a photocatalytic oxidation reaction of a green oxidant to prepare a fine chemical intermediate with a high added value; the heterogeneous nature of the metal organic framework material facilitates catalyst recovery.

In order to achieve the above purpose and solve the problems existing in the prior art, the invention adopts the technical scheme that: a cobalt-based metal-organic frame catalyst for activating oxygen molecule is prepared from pyrazolyl ligand H₂DPA and Co in metal cobalt salts²⁺As a node, the cobalt-based metal organic framework catalyst is prepared by a solvothermal method, and the synthetic route is as follows:

H₂DPA+Co²⁺→Co-DPA；

the metal cobalt salt is selected from one of cobalt chloride or cobalt nitrate;

the pyrazolyl ligand H₂DPA，Molecular formula C₂₀H₁₄N₄Having the following (A)

The molecular structural formula of the compound is shown in the specification,

the preparation method of the Co-DPA comprises the following steps:

step 1, mixing lithium perchlorate, silicon dioxide, anthracene and N-bromosuccinimide according to the proportion of l: 6-10: 6-10: adding 13-20 mol ratio of the mixture into a 250mL three-necked bottle, adding 80-120 mL dichloromethane solvent into the bottle, stirring at room temperature for 25-40 min, filtering the obtained yellow mixture, washing the obtained filtrate with deionized water in a separating funnel, and finally performing rotary evaporation on the obtained organic phase filtrate by using a rotary evaporator to obtain yellow powder 9, 10-dibromoanthracene;

step 2, placing the 9, 10-dibromoanthracene, cesium carbonate, tetrakis (triphenylphosphine) palladium and 4-pyrazole boronic acid pinacol ester prepared in the step 1 in a 250mL three-neck flask according to the molar ratio of 1: 5-8: 0.1-0.2: 3-5, and adding N₂Replacing the gas atmosphere in a bottle for three times, adding 10-20 mL of DMF subjected to degassing treatment into the mixture, reacting for 50-80H at 105-115 ℃, pouring the reaction mixture into a 1L beaker after the reaction is finished, adding 500-700 mL of water, continuously stirring for 15-25 min, filtering to obtain a light yellow reaction crude product, dissolving the light yellow reaction crude product into tetrahydrofuran, separating by using column chromatography, and obtaining yellow powder, namely pyrazolyl ligand H, by using a mixed solvent of acetone and n-hexane with the volume ratio of 1:1 as a mobile phase₂DPA；

Step 3, the pyrazolyl ligand H prepared in the step 2₂DPA and CoCl₂·6H₂O or Co (NO)₃)₂·6H₂Adding O into a 7mL glass vial according to the mass ratio of 1: 4-5, adding 2-4 mL DEF and 5-25 mu L acetic acid, fully mixing and uniformly stirring, firstly putting the mixture into a hydrothermal autoclave, then putting the hydrothermal autoclave into an oven with a temperature control function, raising the temperature to 110-120 ℃ through heating for 8-12 hours, reacting for 72-90 hours, and finally cooling for 8-12 hoursObtaining purple rod-shaped crystals at 25 ℃, filtering, washing with DEF, and drying in the air to obtain the target material Co-based metal organic framework catalyst Co-DPA;

the cobalt-based metal organic framework catalyst prepared by the method is applied to photocatalytic activation of oxygen molecular reaction.

The invention has the beneficial effects that: a preparation method and application of a cobalt-based metal organic framework catalyst for activating oxygen molecules are disclosed, wherein the preparation method comprises the following steps: is a pyrazole ligand H₂DPA and Co in metal cobalt salts²⁺As a node, the cobalt-based metal organic framework catalyst for activating oxygen molecules is prepared by a solvothermal method, and the synthetic route is as follows:

H₂DPA+Co²⁺→Co-DPA；

the cobalt-based metal organic framework catalyst Co-DPA for activating oxygen molecules prepared by the method constructs a separation column accumulation type metal organic framework by means of crystal engineering, wherein an anthracene-based ligand forms a one-dimensional chain with photosensitivity by zigzag type pi-pi accumulation; the Co metal center forms a Co-N-N-Co one-dimensional chain through a pyrazole group at the end position of the ligand; the two one-dimensional chains are arranged in parallel in the metal organic framework, and a pyrazole linking group between the anthracene-based ligand and Co is approximately vertically arranged with the anthracene-based ligand; the structural characteristics ensure that the ligand one-dimensional chain is insulated in a dark state, but can be switched into conduction under the excitation of light to serve as a channel for photoinduced electron transfer, so that efficient charge separation is realized; meanwhile, photoexcitation can also start photoinduced charge transfer from anthracene-based ligand to Co center, and reduced Co species are generated in situ and serve as O₂Activated and reduced active center.

Drawings

FIG. 1 is ligand H prepared in example 1₂Nuclear magnetic resonance spectrum of DPA.

FIG. 2 shows ligand H prepared in example 1₂Uv-vis absorption spectrum of DPA.

FIG. 3 is a schematic diagram of the crystal structure of Co-DPA, the target material of example 1.

FIG. 4 is a solid UV absorption spectrum of Co-DPA, a target material of example 1.

FIG. 5 is a comparison of NIS impedance before and after light irradiation of the Co-DPA target material of example 1.

FIG. 6 is a comparative graph of photocurrent measurements of the target material Co-DPA of example 6 under argon and oxygen atmospheres, respectively.

Detailed Description

The present invention will be further described with reference to the following examples.

Example 1

Anthracene (1.78g, 10mmol), N-bromosuccinimide (3.56g, 20mmol), lithium perchlorate (0.16g, 1.5mmol), silica (0.6g, 10mmol) were added to a 250mL three-necked flask, followed by 100mL of dichloromethane solvent. After stirring at room temperature for 35min, the resulting yellow mixture was filtered and the filtrate was washed with deionized water in a separatory funnel. Finally, the obtained organic phase filtrate is subjected to rotary evaporation by using a rotary evaporator to obtain 3.2g of yellow powder 9, 10-dibromoanthracene;

9, 10-dibromoanthracene (1.098g,3mmol), cesium carbonate (5.868g, 18mmol), tetrakis (triphenylphosphine) palladium (0.5g, 0.43mmol) and 4-pyrazolylboronic acid pinacol ester (2.328g, 12mmol) were weighed into a 250mL three-necked flask with N₂The atmosphere in the bottle was replaced three times. 15mL of DMF which had been degassed was added thereto and reacted at 110 ℃ for 60 hours. After the reaction was completed, the reaction mixture was poured into a 1L beaker, 600mL of water was added and stirring was continued for 15min, followed by filtration to give a crude reaction product in pale yellow color. Dissolving the light yellow reaction crude product in tetrahydrofuran, separating by column chromatography, and collecting the mobile phase with mixed solvent of acetone and n-hexane at volume ratio of 1:1 to obtain yellow powder, i.e. pyrazolyl ligand H₂DPA 0.8 g. The nuclear magnetic resonance spectrum is shown in figure 1, and the ultraviolet-visible absorption spectrum is shown in figure 2.

Weighing 10mg of H₂DPA with 40mg CoCl₂·6H₂O was added to a 7mL glass vial followed by 3mL DEF and 20. mu.L acetic acid. Fully mixing and uniformly stirring, firstly putting the mixture into a hydrothermal high-pressure autoclave, then putting the hydrothermal high-pressure autoclave into a baking oven with a temperature control function, firstly heating for 8 hours to raise the temperature to 110 ℃, reacting for 90 hours, and finally cooling for 10 hours to reach the temperatureAt 25 ℃ to give purple rod-like crystals. And (3) filtering, washing with DEF, and drying in air to obtain the target material Co-DPA 10mg with a yield of 75%, wherein the crystal structure is shown as figure 3, the solid ultraviolet absorption spectrum is shown as figure 4, and the NIS impedance before and after illumination is shown as figure 5.

Example 2

Weighing 10mg of H₂DPA with 40mg CoCl₂·6H₂O was added to a 7mL glass vial followed by 3mL of DEF and 20. mu.L of acetic acid. And (3) fully mixing and uniformly stirring, firstly putting the mixture into a hydrothermal high-pressure autoclave, then putting the hydrothermal high-pressure autoclave into a baking oven with a temperature control function, firstly heating for 8 hours to raise the temperature to 110 ℃, reacting for 90 hours, and finally cooling for 10 hours to 25 ℃ to obtain the purple rod-shaped crystal. And after filtration, washing the catalyst by DEF, and drying the catalyst in air to obtain 9 mg of the target material Co-based metal organic framework catalyst Co-DPA with the yield of 68%.

Example 3

Weighing 10mg of H₂DPA with 45mg Co (NO)₃)₂·6H₂O was added to a 7mL glass vial followed by 3mL of DEF and 20. mu.L of acetic acid. And (3) fully mixing and uniformly stirring, firstly putting the mixture into a hydrothermal high-pressure autoclave, then putting the hydrothermal high-pressure autoclave into a baking oven with a temperature control function, firstly heating for 8 hours to raise the temperature to 110 ℃, reacting for 90 hours, and finally cooling for 10 hours to 25 ℃ to obtain the purple rod-shaped crystal. And after filtering, washing the catalyst by DEF, and drying the catalyst in the air to obtain 8mg of the target material Co-DPA, wherein the yield is 60%.

Example 4

10mg of Co-DPA and benzylamine (32mg, 0.3mmol) were added to the photoreaction tube, and 3mL of acetonitrile solvent was added. An LED with the wavelength of 405nm is used as a light source, and the reaction is carried out for 12h at 30 ℃ in an oxygen atmosphere. The reaction solution was extracted with ethyl acetate, washed with water, dried, concentrated, and the product was isolated by thin layer chromatography and characterized by nuclear magnetism as N-benzyl enamine with 90% yield. This heterogeneous catalytic oxidation allowed for an expansion of the benzylamine substrate as shown in table 1.

TABLE 1

Example 5

To a photoreaction tube, 10mg of Co-DPA and 2-phenyl-1, 2,3, 4-tetrahydroisoquinoline (68.7mg, 0.3mmol) were added, and 3mL of acetonitrile solvent was added. And (3) reacting for 12h under the irradiation of an LED light source with the wavelength of 405nm and the temperature of 30 ℃ in an oxygen atmosphere. The reaction solution was extracted with ethyl acetate, washed with water, dried, concentrated, and the product was isolated by thin layer chromatography, and the product, 1(2H) -isoquinolinone, 3, 4-dihydro-2-phenyl, was characterized by nuclear magnetism in 92% yield. This heterogeneous catalytic oxidation allowed for the development of benzylamine substrates as shown in table 2.

TABLE 2

Example 6

Adding Co-DPA 5mg into ethanol 5mL to obtain suspension, adding Nafin 0.5mL, ultrasonic mixing, and coating on FTO glass surface with coating area of 1cm²And drying, and then clamping the FTO glass on an electrode clamp to serve as a working electrode. The photocurrent test was carried out at CHI 660E electrochemical workstation, using a three-electrode system, an Ag/AgCl electrode as a reference electrode, a platinum sheet as a counter electrode, and a 3M potassium chloride aqueous solution as an electrolyte, and the photocurrent tests were respectively carried out under argon atmosphere and 1atm of oxygen atmosphere at room temperature with a light source of 30W of a 405nm wavelength LED. The comparative graph of the photocurrent test shows that Co-DPA under an oxygen atmosphere has a significantly increased photocurrent response as shown in FIG. 6, which indicates that reduced Co in the Co-DPA has the capability of activating oxygen.