Manganese-based MOF organic-inorganic hybrid catalyst and preparation method thereof

Abstract

The invention provides a manganese-based MOF (Metal Organic Framework) 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. According to the manganese-based MOF organic-inorganic hybrid catalyst, a prepared manganese-based organic framework material is dispersed in a solution containing an organic monomer and a transition metal oxide, and the organic monomer is subjected to in-situ polymerization on the surface of the manganese-based organic framework material through an initiator and an oxidizing agent; meanwhile, the transition metal oxide and the manganese-based organic framework material are tightly combined, the manganese-based MOF organic-inorganic hybrid catalyst is finally obtained, the manganese-based MOF organic-inorganic hybrid catalyst can quickly and efficiently remove substances such as formaldehyde and methylbenzene in a room, and the material can also be used as a catalyst in hydrogen production through water electrolysis.

Description

Technical Field

[0001] The present invention relates to the field of formaldehyde removal catalysts, and particularly to a manganese-based MOF organic-inorganic hybrid catalyst and a preparation method thereof. Background Art

[0002] Formaldehyde and toluene are the most common and extremely harmful pollutants in indoor air. Formaldehyde, a colorless gas with a strong pungent odor, widely exists in various building materials, furniture, decoration materials, and some textiles. In newly renovated houses, the formaldehyde release period can be as long as 3 - 15 years. Long-term exposure to an environment containing formaldehyde will cause serious damage to the human respiratory, nervous, and immune systems, increasing the risk of diseases such as cancer and leukemia. Toluene is often used as an organic solvent in products such as paints, coatings, and adhesives. It is volatile and will cause anesthetic effects on the central nervous system after entering the human body, causing symptoms such as dizziness, fatigue, and nausea. Long-term exposure may also affect the hematopoietic function.

[0003] Metal-organic framework materials (MOF) are a class of porous materials with a periodic network structure formed by the self-assembly of metal ions or metal clusters and organic ligands. MOF materials have an extremely high specific surface area, adjustable pore size, and rich pore structure, which enable them to exhibit great application potential in the fields of gas adsorption, separation, catalysis, etc. In indoor air purification, MOF materials can remove pollutants such as formaldehyde and toluene through physical adsorption and chemical adsorption. Their high specific surface area and porous structure provide a large number of adsorption sites for pollutants, enabling effective adsorption of harmful substances in indoor air. At the same time, by reasonably designing organic ligands and metal nodes, functional groups with specific functions can be introduced to enhance the chemical adsorption and catalytic conversion ability of pollutants. In the field of electrolytic water hydrogen production, 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 electrolytic water hydrogen production. In addition, the structural diversity and tailoring ability 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 restricted by external environmental conditions and cannot effectively function in extreme weather or enclosed spaces; although activated carbon adsorption can adsorb formaldehyde and toluene to a certain extent, its adsorption capacity is limited, it is easy to reach saturation and difficult to regenerate, resulting in a short duration of purification effect. Therefore, there is an urgent need to develop an efficient and long-lasting indoor air purification material.

[0005] At present, noble metal catalysts (such as platinum, iridium, etc.) exhibit excellent catalytic performance in hydrogen production by electrolyzing water. However, due to their scarce reserves and high prices, it is difficult to be applied on a large scale. Therefore, finding a catalyst with low price, rich reserves and excellent performance has become a current research hotspot.

[0006] Aiming at the problems existing in the prior art, this application aims to invent a catalyst that can quickly and efficiently remove substances such as formaldehyde and toluene in the room and can be used for hydrogen production by electrolyzing water. Summary of the Invention

[0007] Object of the Invention: The object of the present invention is to provide a manganese-based MOF organic-inorganic hybrid catalyst and its preparation method, which can quickly and efficiently remove substances such as formaldehyde and toluene in the room and can be used as a catalyst for hydrogen production by electrolyzing water.

[0008] Technical Solution of the Present Invention:

[0009] The present invention 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 includes the following steps:

[0013] S1: Take an appropriate amount of 3,4,5-trihydroxybenzoic acid in a beaker, add N,N-dimethylformamide to it, and stir at room temperature until 3,4,5-trihydroxybenzoic acid is completely dissolved to 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, continuously stir for 15-30 minutes, and slowly drop it into solution A prepared in step S1, and continuously stir until it is clear to obtain solution B;

[0015] S3: Then transfer the mixed solution B prepared in step S2 to a high-pressure reaction kettle, heat it at 120-150 °C for 8-16 hours, cool it to room temperature, and centrifuge and 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 °C for 4-8 h 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(NO 3 ) 2 solution with a mass fraction of 30 - 50%.

[0018] Further, the organic monomers are a mixture of 3-(1H-imidazol-1-yl)propanamide and 2-aminoimidazole.

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

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

[0021] This application also provides a preparation method of a manganese-based MOF organic-inorganic hybrid catalyst, which is characterized by including the following steps:

[0022] Step (1): Dissolve the organic monomers 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, wash repeatedly 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 is carried out for 1 - 2 hours.

[0026] The present invention provides a manganese-based MOF organic-inorganic hybrid catalyst. The manganese-based metal-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 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 react with formaldehyde and toluene. The amino group can undergo a nucleophilic addition reaction with formaldehyde to form imine compounds, thereby fixing formaldehyde on the material surface and providing favorable conditions for subsequent catalytic oxidation reactions. 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 into carbon dioxide and water. The manganese-based MOF material and the organic monomer can produce a synergistic catalytic effect with the transition metal oxide. The manganese-based MOF material can provide adsorption sites, making it easier for pollutant molecules to contact the transition metal oxide. The organic monomer can adjust the electronic structure of the catalyst and enhance the catalytic activity of the transition metal oxide through electron transfer or conjugation, thereby improving the catalytic oxidation efficiency of formaldehyde and toluene.

[0027] Beneficial effects:

[0028] The manganese-based MOF organic-inorganic hybrid catalyst provided by the present invention can quickly and efficiently remove substances such as formaldehyde and toluene in the room, and this material can also be used as a catalyst in water electrolysis for hydrogen production. Specific embodiments

[0029] The following will illustrate the present invention in conjunction with specific implementation schemes. It should be noted that the following examples are examples of the present invention and are only used to illustrate the present invention, rather than to limit the present invention. Other combinations and various improvements within the concept of the present invention can be made without departing from the main idea or scope of the present invention.

[0030] Unless otherwise specified, other chemical reagents used in the present invention are all ordinary commercially available analytical pure.

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

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

[0033] S1: Take 5 g of 3,4,5-trihydroxybenzoic acid in a beaker, add 50 mL of N,N-dimethylformamide thereto, and 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 in another beaker, add 50 mL of distilled water thereto, stir until completely dissolved, and then add 2.5 g of a 50% by mass Mn(NO 3 ) 2 solution. After continuously stirring for 30 minutes, slowly drop it into the solution A prepared in step S1, and continuously stir until it becomes clear to obtain solution B;

[0035] S3: Then transfer the mixed solution B prepared in step S2 to a high-pressure reactor, heat it at 120 °C for 10 hours, cool it to room temperature, centrifuge and 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 6 h to prepare 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 in a beaker, add 50 mL of N,N-dimethylformamide thereto, stir at room temperature until 3,4,5-trihydroxybenzoic acid is completely dissolved to obtain solution A;

[0038] S2: Take 5 g of cerium nitrate hexahydrate in another beaker, add 50 mL of distilled water thereto, stir until completely dissolved, and then add 2.5 g of a 30% by mass Mn(NO 3 ) 2 solution. After continuously stirring for 30 minutes, slowly drop it into the solution A prepared in step S1, and continuously stir until it becomes clear to obtain solution B;

[0039] S3: Then transfer the mixed solution B prepared in step S2 to a high-pressure reactor, heat it at 120 °C for 10 hours, cool it to room temperature, centrifuge and 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 6 h to prepare 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 in a beaker, add 50 mL of N,N-dimethylformamide thereto, stir at room temperature until 3,4,5-trihydroxybenzoic acid is completely dissolved to obtain solution A;

[0042] S2: Slowly drop 2.5 g of a 50% by mass Mn(NO 3 ) 2 solution into the solution A prepared in step S1, and continuously stir until it becomes clear to obtain solution B;

[0043] S3: Next, transfer the mixed solution B prepared in step S2 to a high-pressure reactor, heat it at 120 °C for 10 hours. After cooling to room temperature, centrifuge and 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 6 h to obtain the manganese-based metal-organic framework material C.

[0044] Example 1

[0045] Step (1): Dissolve 1 g of 3-(1H-imidazol-1-yl)propanamide and 4 g of 2-aminoimidazole in 100 mL of ethanol solvent, and then disperse 1 g of the manganese-based metal-organic framework material A in the solution of 3-(1H-imidazol-1-yl)propanamide and 2-aminoimidazole, and ultrasonically disperse for 30 minutes.

[0046] Step (2): Add 0.5 g of manganese dioxide, 0.5 g of titanium dioxide, 0.5 g of rhodium oxide, 0.5 g of chromium(III) oxide, 0.5 g of azobisisobutyronitrile, and 2 g of sodium hydroxide to step (1), adjust the reaction temperature to 80 °C, and react for 2 hours.

[0047] Step (3): After the reaction is completed, wash repeatedly with ethanol, and then dry in an oven at 70 °C for 4 hours to obtain the manganese-based MOF organic-inorganic hybrid catalyst.

[0048] Example 2

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

[0050] Example 3

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

[0052] Example 4

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

[0054] Example 5

[0055] The difference between this preparation and Example 1 is that: in step (1), 1 g of manganese-based organic framework material A is replaced by 1 g of manganese-based organic framework material C.

[0056] Comparative Example 1:

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

[0058] Step (2): Add 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 to step (1), adjust the reaction temperature to 80 °C, and react for 2 hours;

[0059] Step (3): After the reaction is completed, wash repeatedly with ethanol, and then dry in an oven at 70 °C for 4 hours to obtain the manganese-based MOF organic-inorganic hybrid catalyst.

[0060] Comparative Example 2:

[0061] Step (1): Dissolve 1 g of 3-(1H-imidazol-1-yl)propanamide and 4 g of 2-aminoimidazole in 100 mL of ethanol solvent, and then disperse 1 g of manganese-based organic framework material A in the organic monomer solution and ultrasonically disperse for 30 minutes;

[0062] Step (2): Add 0.5 g of azobisisobutyronitrile and 2 g of sodium hydroxide to step (1), adjust the reaction temperature to 80 °C, and react for 2 hours;

[0063] Step (3): After the reaction is completed, wash repeatedly with ethanol, and then dry in an oven at 70 °C for 4 hours to obtain the manganese-based MOF organic-inorganic hybrid catalyst.

[0064] Perform the following tests on the manganese-based MOF organic-inorganic hybrid catalysts prepared in the above Examples 1-5 and Comparative Examples 1-2:

[0065] 1. Formaldehyde adsorption experiment: Put 1 L of 40% by mass formaldehyde aqueous solution prepared into a 1 m 3 sealed space, and volatilize at 25 °C until the formaldehyde content no longer changes. Record the initial formaldehyde content in the sealed space at this time. Then, accurately weigh 10 g of the manganese-based MOF organic-inorganic hybrid catalysts prepared in Examples 1-5 and Comparative Examples 1-2 and put them into the sealed space. Use a formaldehyde detector to detect the formaldehyde concentration in the sealed space at intervals of 5, 10, 15, 30, 60, and 120 min, calculate the adsorption amount of the catalyst in 120 min, and thus analyze the average rate of formaldehyde adsorption by the catalyst in 120 min.

[0066] 2. Catalytic oxidation experiment: Formaldehyde gas at a concentration of 10 ppm was introduced into a reactor containing the manganese-based MOF organic-inorganic hybrid catalysts prepared in Examples 1-5 and Comparative Examples 1-2 at a flow rate of 200 mL / min at 25 °C. The gas components after the reaction were detected at the reactor outlet using a gas chromatograph, and the amount of carbon dioxide generated in the outlet gas was analyzed by GC-MS. The carbon dioxide selectivity value S = nCO 2 / n 0 (1 - X)×100%, where nCO 2 refers to the amount of substance of carbon dioxide in the outlet gas of the reactor obtained by GC-MS analysis, and n 0 is the initial amount of substance of formaldehyde gas introduced into the reactor. X represents the conversion rate of formaldehyde gas, and X = (n 0 -n 1 ) / n 0 ×100%, where n 1 is the amount of substance of formaldehyde in the outlet gas of the reactor for formaldehyde gas.

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

[0068] Table 1: Performance test results table

[0069]

[0070] As can be seen from Table 1, the manganese-based MOF organic-inorganic hybrid catalyst prepared by the present invention can quickly and efficiently remove substances such as formaldehyde and toluene in the room, and this material can also be used as a catalyst in water electrolysis for hydrogen production. From the comparison between Example 4 and Example 1, it can be seen that when the mass ratio of 3-(1H-imidazol-1-yl)propanamide to 2-aminoimidazole is unreasonable, it will lead to a slower adsorption rate of formaldehyde by the manganese-based MOF organic-inorganic hybrid catalyst, a smaller adsorption amount in 2 hours, a lower carbon dioxide selectivity, a worse catalytic oxidation effect, a farther starting potential from the theoretical hydrogen evolution potential, a weaker catalytic activity for water electrolysis, and the expected effect cannot be achieved; from the comparison between Example 5 and Example 1, it can be seen that when cerium nitrate hexahydrate is not used in the preparation of the manganese-based organic framework material, it will lead to a slower adsorption rate of formaldehyde by the manganese-based MOF organic-inorganic hybrid catalyst, a smaller adsorption amount in 2 hours, a lower carbon dioxide selectivity, a worse catalytic oxidation effect, a farther starting potential from the theoretical hydrogen evolution potential, a weaker catalytic activity for water electrolysis, and the expected effect cannot be achieved; from the comparison between Comparative Example 1 and Example 1, it can be seen that without adding an organic monomer, it will lead to a slower adsorption rate of formaldehyde by the manganese-based MOF organic-inorganic hybrid catalyst, a smaller adsorption amount in 2 hours, a lower carbon dioxide selectivity, a worse catalytic oxidation effect, a farther starting potential from the theoretical hydrogen evolution potential, a weaker catalytic activity for water electrolysis, and the expected effect cannot be achieved; from the comparison between Comparative Example 2 and Example 1, it can be seen that without adding a transition metal oxide, it will lead to a slower adsorption rate of formaldehyde by the manganese-based MOF organic-inorganic hybrid catalyst, a smaller adsorption amount in 2 hours, a lower carbon dioxide selectivity, a worse catalytic oxidation effect, a farther starting potential from the theoretical hydrogen evolution potential, a weaker catalytic activity for water electrolysis, and the expected effect cannot be achieved.

[0071] The present invention can also have various other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and deformations according to the present invention, but these corresponding changes and deformations should all fall within the protection scope of the appended claims of the present invention.

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.

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

4. The manganese-based MOF organic-inorganic hybrid catalyst according to claim 3, characterized in that: The preparation method of the manganese-based organic framework material, The following steps are involved: 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 thereto, stir until completely dissolved, then add manganese nitrate solution thereto, continue stirring for 15-30 minutes, slowly drip into solution A prepared in step S1, and continue stirring until clarified 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.

5. The manganese-based MOF organic-inorganic hybrid catalyst according to claim 4, characterized in that: The mass ratio of the manganese nitrate solution, cerium nitrate hexahydrate and 3,4,5-trihydroxybenzoic acid is 1:2-4:1-2.

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

7. The manganese-based MOF organic-inorganic hybrid catalyst according to claim 1, characterized in that: The organic monomer is a mixture of 3-(1H-imidazole-1-yl) propionamide and 2-aminoimidazole; the mass ratio of the 3-(1H-imidazole-1-yl) propionamide to 2-aminoimidazole is 1:1.5-5.

8. The manganese-based MOF organic-inorganic hybrid catalyst according to claim 1, characterized in that: The transition metal oxide is a mixture of one or more of manganese dioxide, titanium dioxide, rhodium oxide and chromium trioxide.

9. The method for preparing the manganese-based MOF organic-inorganic hybrid catalyst according to any one of claims 1 to 8, 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.

10. The method for preparing the manganese-based MOF organic-inorganic hybrid catalyst according to claim 9, 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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