A manganese-based MOF organic-inorganic hybrid catalyst and a method for preparing the same

Abstract

The application provides a manganese-based MOF organic-inorganic hybrid catalyst and a preparation method thereof. The manganese-based MOF organic-inorganic hybrid catalyst is synthesized from a manganese-based organic framework material, an organic monomer and a transition metal oxide; the manganese-based MOF organic-inorganic hybrid catalyst disperses the prepared manganese-based organic framework material in a solution containing the organic monomer and the transition metal oxide, and makes the organic monomer in-situ polymerize on the surface of the manganese-based organic framework material through an initiator and an oxidant, while the transition metal oxide is closely combined with the manganese-based organic framework material, so that the manganese-based MOF organic-inorganic hybrid catalyst is finally obtained; the manganese-based MOF organic-inorganic hybrid catalyst can quickly and efficiently remove indoor formaldehyde, toluene and other substances, and the material can also be used as a catalyst in water electrolysis hydrogen production.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of aldehyde removal catalysts, in particular to a manganese-based MOF organic-inorganic hybrid catalyst and a preparation method thereof. BACKGROUND

[0002] Formaldehyde and toluene are the most common and harmful pollutants in indoor air. Formaldehyde, as a colorless gas with strong irritating odor, is widely present in various building materials, furniture, decoration materials and some textiles. In newly renovated houses, the formaldehyde release period can last for 3-15 years. Long-term exposure to environments containing formaldehyde can cause serious damage to the respiratory system, nervous system and immune system of the human body, increasing the risk of cancer, leukemia and other diseases. Toluene is often used as an organic solvent in products such as paint, coating and adhesive. It has volatility and can cause narcotic effects on the central nervous system after entering the human body, causing dizziness, fatigue, nausea and other symptoms. Long-term exposure can also affect hematopoietic function.

[0003] Metal-organic framework (MOF) is a kind of porous material with periodic network structure formed by self-assembly of metal ions or metal clusters and organic ligands. MOF materials have extremely high specific surface area, adjustable pore size and rich pore structure, which makes them have great application potential in gas adsorption, separation, catalysis and other fields. In the aspect of indoor air purification, MOF materials can remove formaldehyde, toluene and other pollutants through physical and chemical adsorption. Its high specific surface area and porous structure provide a large number of adsorption sites for pollutants, which can effectively adsorb harmful substances in indoor air. At the same time, by reasonably designing organic ligands and metal nodes, groups with specific functions can be introduced to enhance the chemical adsorption and catalytic conversion capacity of pollutants. In the field of hydrogen production by electrolysis of water, MOF materials also have unique advantages. Their rich active sites and adjustable electronic structure can promote the adsorption and activation of water molecules, reduce the overpotential of the reaction, and improve the efficiency of hydrogen production by electrolysis of water. In addition, the structural diversity and tailorability of MOF materials enable them to be compounded with other materials to form hybrid catalysts with more excellent performance.

[0004] Traditional indoor air purification methods, such as ventilation and activated carbon adsorption, have certain limitations. Ventilation is limited by external environmental conditions and cannot effectively function in extreme weather or closed spaces; activated carbon adsorption can adsorb formaldehyde and toluene to some extent, but has limited adsorption capacity, is difficult to regenerate and has short purification effect duration. Therefore, there is an urgent need to develop an efficient and long-lasting indoor air purification material.

[0005] Currently, noble metal catalysts (such as platinum, iridium, etc.) exhibit excellent catalytic performance in the electrolysis of water to produce hydrogen, but due to their scarcity and high price, it is difficult to be applied on a large scale. Therefore, finding a kind of catalyst with low price, abundant reserves and excellent performance has become the current research hotspot.

[0006] In view of the problems existing in the prior art, the present application aims to provide a catalyst capable of quickly and efficiently removing indoor formaldehyde, toluene and other substances, which can be used for the electrolysis of water to produce hydrogen. SUMMARY

[0007] The purpose of the present application is to provide a manganese-based MOF organic-inorganic hybrid catalyst and a preparation method thereof, which can quickly and efficiently remove indoor formaldehyde, toluene and other substances, and can be used as a catalyst for the electrolysis of water to produce hydrogen.

[0008] The technical scheme of the present application is as follows:

[0009] The present application provides a manganese-based MOF organic-inorganic hybrid catalyst, which is synthesized from a manganese-based organic framework material, an organic monomer and a transition metal oxide.

[0010] Further, the mass ratio of the manganese-based organic framework material, the organic monomer and the transition metal oxide is 1:5-8:1.5-2.

[0011] Further, the raw materials for preparing the manganese-based organic framework material include manganese nitrate solution, cerium nitrate hexahydrate and 3,4,5-trihydroxybenzoic acid.

[0012] Further, the preparation method of the manganese-based organic framework material comprises the following steps:

[0013] S1: Take an appropriate amount of 3,4,5-trihydroxybenzoic acid in a beaker, add N,N-dimethylformamide to it, stir at room temperature until the 3,4,5-trihydroxybenzoic acid is completely dissolved, and obtain solution A;

[0014] S2: Take an appropriate amount of cerium nitrate hexahydrate in another beaker, add an appropriate amount of distilled water to it, stir until completely dissolved, then add manganese nitrate solution to it, continue stirring for 15-30 minutes, then slowly drop solution A prepared in step S1 into it, and continue stirring until clear to obtain solution B;

[0015] S3: Then transfer the mixed solution B prepared in step S2 to a high-pressure reaction kettle, heat at 120-150℃ for 8-16 hours, cool to room temperature, then centrifugally wash the obtained solid product with N,N-dimethylformamide and ethanol respectively, and dry the product obtained after washing in an oven at 65-80℃ for 4-8h to prepare the manganese-based organic framework material.

[0016] Further, the mass ratio of the manganese nitrate solution, cerium nitrate hexahydrate and 3,4,5-trihydroxybenzoic acid is 1:2-4:1-2.

[0017] Further, the manganese nitrate solution is a Mn(NO3)2 solution with a mass fraction of 30-50%.

[0018] Further, the organic monomer is a mixture of 3-(1H-imidazol-1-yl)propionamide and 2-aminoimidazole.

[0019] Further, the mass ratio of the 3-(1H-imidazol-1-yl)propionamide and 2-aminoimidazole is 1:1.5-5.

[0020] Further, the transition metal oxide is a mixture of one or more of manganese dioxide, titanium dioxide, rhodium oxide and chromium sesquioxide.

[0021] The application also provides a preparation method of a manganese-based MOF organic-inorganic hybrid catalyst, characterized in that it comprises the following steps:

[0022] Step (1): Dissolve the organic monomer in an ethanol solvent, and then disperse the manganese-based organic framework material in the organic monomer solution and ultrasonically disperse for 15-30 minutes;

[0023] Step (2): Add the transition metal oxide, initiator and sodium hydroxide in step (1), adjust the reaction temperature, and react for a period of time.

[0024] Step (3): After the reaction is completed, repeatedly wash with ethanol, and then dry in an oven at 60-100°C for several hours to obtain the manganese-based MOF organic-inorganic hybrid catalyst.

[0025] Further, the reaction temperature in step (2) is 60-80°C, and the reaction time is 1-2 hours.

[0026] The present application provides a manganese-based MOF organic-inorganic hybrid catalyst, the manganese-based organic framework material (MOF) has a high specific surface area and a rich pore structure. These pores can provide physical adsorption sites for adsorbing formaldehyde and toluene molecules. The metal sites in the manganese-based MOF material and the hydroxyl groups and carboxyl groups on the organic ligand 3,4,5-trihydroxybenzoic acid can chemically adsorb formaldehyde and toluene. The imidazole group and amino group in the organic monomer can chemically react with formaldehyde and toluene, and the amino group can undergo nucleophilic addition reaction with formaldehyde to generate an imine compound, thereby fixing formaldehyde on the surface of the material and providing favorable conditions for subsequent catalytic oxidation reaction. Transition metal oxides have variable oxidation states and can participate in redox reactions. Taking manganese dioxide as an example, in the presence of oxygen, manganese dioxide can act as a catalyst to oxidize formaldehyde to carbon dioxide and water. The manganese-based MOF material and the organic monomer can produce synergistic catalysis with the transition metal oxide, and the manganese-based MOF material can provide adsorption sites to make the pollutant molecules more easily contact with the transition metal oxide. The organic monomer can adjust the electronic structure of the catalyst, enhance the catalytic activity of the transition metal oxide through electron transfer or conjugation, and thereby improve the catalytic oxidation efficiency of formaldehyde and toluene.

[0027] Advantages:

[0028] The manganese-based MOF organic-inorganic hybrid catalyst provided by the present application can quickly and efficiently remove indoor formaldehyde, toluene and other substances, and the material can also be used as a catalyst for hydrogen production by electrolysis of water. DETAILED DESCRIPTION

[0029] The present application will be described below in conjunction with specific embodiments. It should be noted that the following examples are examples of the present application and are only used to illustrate the present application, but not to limit the present application. Other combinations and various modifications within the concept of the present application can be made without departing from the spirit or scope of the present application.

[0030] Unless otherwise specified, other chemical reagents used in the present application are commercially available and are of analytical purity.

[0031] 3-(1H-Imidazol-1-yl)propanamide has a CAS number of 43115-74-8; azobisisobutyronitrile is purchased from Shandong Jinyueyuan New Material Co., Ltd.

[0032] Preparation of manganese-based organic framework material A:

[0033] S1: Take 5g of 3,4,5-trihydroxybenzoic acid in a beaker, add 50mL of N,N-dimethylformamide to it, stir at room temperature until the 3,4,5-trihydroxybenzoic acid is completely dissolved, to obtain solution A;

[0034] S2: Take 10 g of cerium nitrate hexahydrate into another beaker, add 50 mL of distilled water to it, stir until completely dissolved, then add 2.5 g of Mn(NO3)2 solution with a mass fraction of 50% to it, continue stirring for 30 minutes, then slowly drop the solution A prepared in step S1 into it, and continue stirring until clear to obtain solution B;

[0035] S3: Then transfer the mixed solution B prepared in step S2 into a high-pressure reaction kettle, heat at 120°C for 10 hours, cool to room temperature, then centrifugally wash the obtained solid product with N,N-dimethylformamide and ethanol respectively, and dry the product obtained after washing in an oven at 75°C for 6h to prepare the manganese-based organic framework material A.

[0036] Preparation of manganese-based organic framework material B:

[0037] S1: Take 5 g of 3,4,5-trihydroxybenzoic acid into a beaker, add 50 mL of N,N-dimethylformamide to it, stir at room temperature until the 3,4,5-trihydroxybenzoic acid is completely dissolved to obtain solution A;

[0038] S2: Take 5 g of cerium nitrate hexahydrate into another beaker, add 50 mL of distilled water to it, stir until completely dissolved, then add 2.5 g of Mn(NO3)2 solution with a mass fraction of 30% to it, continue stirring for 30 minutes, then slowly drop the solution A prepared in step S1 into it, and continue stirring until clear to obtain solution B;

[0039] S3: Then transfer the mixed solution B prepared in step S2 into a high-pressure reaction kettle, heat at 120°C for 10 hours, cool to room temperature, then centrifugally wash the obtained solid product with N,N-dimethylformamide and ethanol respectively, and dry the product obtained after washing in an oven at 75°C for 6h to prepare the manganese-based organic framework material B.

[0040] Preparation of manganese-based organic framework material C:

[0041] S1: Take 5 g of 3,4,5-trihydroxybenzoic acid into a beaker, add 50 mL of N,N-dimethylformamide to it, stir at room temperature until the 3,4,5-trihydroxybenzoic acid is completely dissolved to obtain solution A;

[0042] S2: Slowly drop 2.5 g of Mn(NO3)2 solution with a mass fraction of 50% into the solution A prepared in step S1, and continue stirring until clear to obtain solution B;

[0043] S3: Then the mixed solution B prepared in step S2 is transferred to a high-pressure reaction kettle, heated at 120°C for 10 hours, and after cooling to room temperature, the obtained solid product is centrifugally washed with N,N-dimethylformamide and ethanol respectively, and the product obtained after washing is dried in an oven at 75°C for 6h, to prepare a manganese-based organic framework material C.

[0044] Example 1

[0045] Step (1): 1g of 3-(1H-imidazol-1-yl)propanamide, 4g of 2-aminoimidazole are dissolved in 100mL of ethanol solvent, and then 1g of manganese-based organic framework material A is dispersed in the solution of 3-(1H-imidazol-1-yl)propanamide and 2-aminoimidazole, and ultrasonic dispersion is performed for 30 minutes;

[0046] Step (2): 0.5g of manganese dioxide, 0.5g of titanium dioxide, 0.5g of rhodium oxide, 0.5g of chromium sesquioxide, 0.5g of azobisisobutyronitrile, 2g of sodium hydroxide are added in step (1), and the reaction temperature is adjusted to 80°C, and the reaction is performed for 2 hours;

[0047] Step (3): After the reaction is completed, repeated washing with ethanol is performed, and then drying in an oven at 70°C for 4 hours, to prepare a manganese-based MOF organic-inorganic hybrid catalyst.

[0048] Example 2

[0049] The difference between the present preparation and Example 1 is that in step (1), 1g of 3-(1H-imidazol-1-yl)propanamide, 4g of 2-aminoimidazole, and 1g of manganese-based organic framework material A are replaced by 2g of 3-(1H-imidazol-1-yl)propanamide, 4g of 2-aminoimidazole, and 1g of manganese-based organic framework material B.

[0050] Example 3

[0051] The difference between the present preparation and Example 1 is that in step (2), 0.5g of manganese dioxide, 0.5g of titanium dioxide, 0.5g of rhodium oxide, and 0.5g of chromium sesquioxide are replaced by 1g of rhodium oxide and 0.5g of chromium sesquioxide.

[0052] Example 4

[0053] The difference between the present preparation and Example 1 is that in step (1), 1g of 3-(1H-imidazol-1-yl)propanamide and 4g of 2-aminoimidazole are replaced by 2g of 3-(1H-imidazol-1-yl)propanamide and 2g of 2-aminoimidazole.

[0054] Example 5

[0055] The preparation is different from Example 1 in that 1 g of manganese-based organic framework material A is replaced by 1 g of manganese-based organic framework material C in step (1).

[0056] Comparative Example 1:

[0057] Step (1): 1 g of manganese-based organic framework material A was dispersed in 100 mL of ethanol solvent and ultrasonically dispersed for 30 minutes.

[0058] Step (2): 0.5 g of manganese dioxide, 0.5 g of titanium dioxide, 0.5 g of rhodium oxide, 0.5 g of chromium sesquioxide, 0.5 g of azobisisobutyronitrile, and 2 g of sodium hydroxide were added in step (1), the reaction temperature was adjusted to 80°C, and the reaction was carried out for 2 hours.

[0059] Step (3): After the reaction was completed, the manganese-based MOF organic-inorganic hybrid catalyst was prepared by repeatedly washing with ethanol and then drying in an oven at 70°C for 4 hours.

[0060] Comparative Example 2:

[0061] Step (1): 1 g of 3-(1H-imidazol-1-yl)propionamide and 4 g of 2-aminoimidazole were dissolved in 100 mL of ethanol solvent, and then 1 g of manganese-based organic framework material A was dispersed in the organic monomer solution and ultrasonically dispersed for 30 minutes.

[0062] Step (2): 0.5 g of azobisisobutyronitrile and 2 g of sodium hydroxide were added in step (1), the reaction temperature was adjusted to 80°C, and the reaction was carried out for 2 hours.

[0063] Step (3): After the reaction was completed, the manganese-based MOF organic-inorganic hybrid catalyst was prepared by repeatedly washing with ethanol and then drying in an oven at 70°C for 4 hours.

[0064] The manganese-based MOF organic-inorganic hybrid catalysts prepared in Examples 1-5 and Comparative Examples 1-2 above were tested as follows:

[0065] 1. Formaldehyde adsorption experiment: A 1L formaldehyde aqueous solution with a mass fraction of 40% was placed in a 1m 3 closed space, and volatilized at 25°C until the formaldehyde content no longer changed. The initial formaldehyde content in the closed space was recorded. Then, 10 g of the manganese-based MOF organic-inorganic hybrid catalyst prepared in Examples 1-5 and Comparative Examples 1-2 was accurately weighed and placed in the closed space. The formaldehyde concentration in the closed space was detected using a formaldehyde detector at intervals of 5, 10, 15, 30, 60, and 120 minutes, and the adsorption amount of the catalyst in 120 minutes was calculated to analyze the average rate of formaldehyde adsorption by the catalyst in 120 minutes.

[0066] 2. Catalytic oxidation experiment: 10 ppm of formaldehyde gas was passed into the reactor containing the manganese-based MOF organic-inorganic hybrid catalyst prepared in Examples 1-5 and Comparative Examples 1-2 at a flow rate of 200 mL / min at 25°C, and the composition of the gas after the reaction was detected at the outlet of the reactor using a gas chromatograph. The amount of carbon dioxide generated in the outlet gas was analyzed by GC-MS, and the carbon dioxide selectivity value S = nCO2 / n0(1-X) x 100% was calculated, where nCO2 is the amount of substance of carbon dioxide in the outlet gas obtained by GC-MS analysis, n0 is the initial amount of substance of formaldehyde gas passed into the reactor, X represents the conversion rate of formaldehyde gas, X = (n0-n1) / n0 x 100%, and n1 is the amount of substance of formaldehyde in the outlet gas of the reactor.

[0067] 3. Hydrogen production performance test by electrolysis of water: The manganese-based MOF organic-inorganic hybrid catalyst prepared in Examples 1-5 and Comparative Examples 1-2 was mixed with polyvinyl alcohol at a ratio of 1:1 and then coated on a conductive titanium substrate at a loading of 1 mg / cm 2 A three-electrode system was used, and the prepared working electrode, reference electrode (Ag / AgCl), and counter electrode (platinum sheet electrode) were placed in an electrolytic cell, and an electrolyte (0.5 M HSO solution) was added. LSV testing was performed in an alkaline electrolyte from -1.2 V to 0.2 V vs. RHE (reversible hydrogen electrode) at a certain scan rate (5 mV / s), and the initial potential was recorded. The closer the initial potential to the theoretical hydrogen evolution potential, the better the catalytic activity of the catalyst. The theoretical hydrogen evolution potential in an alkaline electrolyte is -0.828 V vs. RHE.

[0068] Table 1: Performance test results

[0069]

[0070] It can be seen from Table 1 that the manganese-based MOF organic-inorganic hybrid catalyst prepared in the application can quickly and efficiently remove indoor formaldehyde, toluene and other substances, and the material can also be used as a catalyst for hydrogen production by electrolysis of water. It can be seen from the comparison between Example 4 and Example 1 that when the mass ratio of 3-(1H-imidazol-1-yl)propionamide and 2-aminoimidazole is unreasonable, the adsorption rate of the manganese-based MOF organic-inorganic hybrid catalyst for formaldehyde will be slow, the 2-hour adsorption amount will be small, the carbon dioxide selectivity will be low, the catalytic oxidation effect will be poor, the initial potential distance from the theoretical hydrogen evolution potential will be far, the water electrolysis catalytic activity will be weak, and the expected effect cannot be achieved. It can be seen from the comparison between Example 5 and Example 1 that when the manganese-based organic framework material is prepared without using cerium nitrate hexahydrate, the adsorption rate of the manganese-based MOF organic-inorganic hybrid catalyst for formaldehyde will be slow, the 2-hour adsorption amount will be small, the carbon dioxide selectivity will be low, the catalytic oxidation effect will be poor, the initial potential distance from the theoretical hydrogen evolution potential will be far, the water electrolysis catalytic activity will be weak, and the expected effect cannot be achieved. It can be seen from the comparison between Comparative Example 1 and Example 1 that without adding an organic monomer, the adsorption rate of the manganese-based MOF organic-inorganic hybrid catalyst for formaldehyde will be slow, the 2-hour adsorption amount will be small, the carbon dioxide selectivity will be low, the catalytic oxidation effect will be poor, the initial potential distance from the theoretical hydrogen evolution potential will be far, the water electrolysis catalytic activity will be weak, and the expected effect cannot be achieved. It can be seen from the comparison between Comparative Example 2 and Example 1 that without adding a transition metal oxide, the adsorption rate of the manganese-based MOF organic-inorganic hybrid catalyst for formaldehyde will be slow, the 2-hour adsorption amount will be small, the carbon dioxide selectivity will be low, the catalytic oxidation effect will be poor, the initial potential distance from the theoretical hydrogen evolution potential will be far, the water electrolysis catalytic activity will be weak, and the expected effect cannot be achieved.

[0071] The application can also have other various embodiments, and those skilled in the art can make various corresponding changes and modifications according to the application without departing from the spirit and essence of the application. However, these corresponding changes and modifications should all belong to the protection scope of the claims attached to the application.

Claims

1. A manganese-based MOF organic-inorganic hybrid catalyst, characterized in that: The manganese-based MOF organic-inorganic hybrid catalyst is synthesized from a manganese-based organic framework material, an organic monomer, and a transition metal oxide; The raw materials for preparing the manganese-based organic framework material include manganese nitrate solution, cerium nitrate hexahydrate, and 3,4,5-trihydroxybenzoic acid; The method for preparing the manganese-based organic framework material comprises the following steps: S1: Take an appropriate amount of 3,4,5-trihydroxybenzoic acid in a beaker, add N,N-dimethylformamide thereto, and stir at room temperature until 3,4,5-trihydroxybenzoic acid is completely dissolved to obtain solution A; S2: Take an appropriate amount of cerium nitrate hexahydrate in another beaker, add an appropriate amount of distilled water, stir until completely dissolved, then add manganese nitrate solution, continue stirring for 15-30 minutes, and then slowly add dropwise to solution A prepared in step S1, and continue stirring until clear to obtain solution B; S3: Then, the mixed solution B prepared in step S2 is transferred to a high-pressure reactor, heated at 120-150° C. for 8-16 hours, cooled to room temperature, and the obtained solid product is centrifugally washed with N,N-dimethylformamide and ethanol, respectively, and the washed product is dried in an oven at 65-80° C. for 4-8 hours to obtain a manganese-based organic framework material; The mass ratio of the manganese nitrate solution, cerium nitrate hexahydrate, and 3,4,5-trihydroxybenzoic acid is 1:2-4:1-2; The organic monomer is a mixture of 3-(1H-imidazol-1-yl)propionamide and 2-aminoimidazole; The mass ratio of the 3-(1H-imidazol-1-yl)propionamide and 2-aminoimidazole is 1:1.5-5; The transition metal oxide is a mixture of one or more of manganese dioxide, titanium dioxide, rhodium oxide, and chromium trioxide.

2. The manganese-based MOF organic-inorganic hybrid catalyst according to claim 1, characterized in that The mass ratio of the manganese-based organic framework material, the organic monomer, and the transition metal oxide is 1:5-8:1.5-2.

3. The manganese-based MOF organic-inorganic hybrid catalyst according to claim 1, characterized in that The manganese nitrate solution is a Mn(NO3)2 solution with a mass fraction of 30-50%.

4. The method for preparing the manganese-based MOF organic-inorganic hybrid catalyst according to any one of claims 1 to 3, characterized in that: The following steps are involved: Step (1): dissolving the organic monomer in an ethanol solvent, and then dispersing the manganese-based organic framework material in the organic monomer solution, and ultrasonically dispersing for 15-30 minutes; Step (2): adding transition metal oxide, initiator, and sodium hydroxide in step (1), adjusting the reaction temperature, and reacting for a period of time; Step (3): After the reaction is completed, the mixture is repeatedly washed with ethanol and then dried in an oven at 60-100° C. for several hours to obtain the manganese-based MOF organic-inorganic hybrid catalyst.

5. The method for preparing a manganese-based MOF organic-inorganic hybrid catalyst according to claim 4, characterized in that: The reaction temperature of step (2) is 60-80°C and the reaction time is 1-2 hours.

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