Preparation of a metal-organic framework material with a confined trimetallic active center and photosynthesis of urea

Abstract

This invention relates to the preparation of a metal-organic framework (MOF) material with confined trimetallic active centers and its catalytic performance in the artificial photosynthesis of urea. A trimetallic synergistic catalytic MOF is provided to address the problem of MOFs' difficulty in photocatalytic urea production. Methods: 1. Preparation of NH2-MIL-125(Ti / Ce); 2. Preparation of Cu-NH2-MIL-125(Ti / Ce). This invention first dopes cerium into NH2-MIL-125(Ti), and then coordinates the amino group of NH2-MIL-125(Ti / Ce) with copper, thereby increasing the electron transfer rate during the photocatalytic process and achieving a high photocatalytic urea yield for Cu-NH2-MIL-125(Ti / Ce). In this invention, the photocatalytic urea yield of Cu-NH2-MIL-125(Ti / Ce) is 400 μg gcat. ‑1 .

Description

Technical Field

[0001] This invention relates to a metal-organic framework with the combined action of three metals to adsorb and activate carbon dioxide and nitrogen, ultimately yielding the product urea. Background Technology

[0002] Industrial urea production primarily relies on the coupled reaction of NH3 and CO2 under harsh conditions (100-150℃, 15-25MPa), resulting in high energy consumption, multiple cycles, and enormous ammonia consumption (accounting for 80% of total ammonia production), causing additional energy and environmental problems. Theoretically, designing a direct route based on nitrogen as a feedstock and green electricity input would be a key step in overcoming this obstacle. Fortunately, the rapid development of clean and sustainable photo / electrocatalytic N2 or CO2 reduction technologies in recent years promises to achieve green urea synthesis via a direct nitrogen feedstock route. In the field of electrocatalysis, research on synthesizing clean, moderate-yield urea using N2 and CO2 as feedstocks has begun to emerge. However, electrocatalysis requires the separation and purification of the generated urea from complex electrolytes. Solar-powered routes to convert nitrogen, carbon dioxide, and water into urea offer another promising alternative for urea production, as it can be directly used by plants without geographical limitations. Therefore, artificial photocatalytic synthesis of urea is considered a cleaner and more direct technology.

[0003] This study designed a photocatalyst using metal-organic frameworks (MOFs). MOFs have a wide range of applications in catalysis, gas storage, and molecular sieving due to their large specific surface area, ordered porous structure, and tunable organic linkers or metal clusters. In recent years, the application of MOFs as photocatalysts has attracted considerable interest. Among them, MIL-125(Ti) stands out due to its unique chemical, mechanical, and thermal stability. Therefore, this study introduced Ce metal into the metal cluster of NH2-MIL-125(Ti) and coordinated Cu metal at its -NH2 position to enhance its electron transfer rate, thereby achieving the photocatalytic production of urea. Summary of the Invention

[0004] The purpose of this invention is to solve the problem of photocatalytic synthesis of urea using existing materials, and to provide a method for preparing a metal-organic framework with the combined action of three metals and its application in photocatalytic synthesis of urea.

[0005] The preparation method of a metal-organic framework material with trimetallic interaction according to the present invention is carried out by the following steps:

[0006] I. Preparation of NH2-MIL-125(Ti / Ce): Ce(NO3)3·6H2O was added to a 50ml beaker containing DMF and methanol and sonicated for 20min to dissolve it, denoted as solution A. Subsequently, 2-aminoterephthalic acid was added to a 100ml beaker containing a certain amount of DMF and methanol, and sonicated for 20min, denoted as solution B. Solution B was stirred on a magnetic stirrer for 30min. Then, a certain amount of solution A was added to solution B, and stirring continued. Tetrabutyl titanate was then added to the above mixed solution, and stirring continued. The mixture was then transferred to a 100ml reaction vessel and heated at 120–150℃ for 12–24h. The product was washed with DMF and ethanol and then vacuum dried for 24h to obtain NH2-MIL-125(Ti / Ce).

[0007] II. Preparation of Cu-NH2-MIL-125(Ti / Ce): Copper acetate was added to a 100ml beaker containing ethanol. The dried NH2-MIL-125(Ti / Ce) was added to the above solution. After stirring at room temperature for 2 hours, the mixture was washed several times with ethanol. The resulting solid was dried under vacuum to obtain Cu-NH2-MIL-125(Ti / Ce).

[0008] The amount of 2-aminoterephthalic acid mentioned in step one is 1.038g;

[0009] The amounts of DMF and methanol mentioned in step one are both 5 ml;

[0010] The amount of Ce(NO3)3·6H2O mentioned in step one is 200mg;

[0011] The amount of solution A added to solution B in step one is 0.3255 ml;

[0012] The amount of tetrabutyl titanate added in step one is 0.6 ml;

[0013] After transferring it into a 100ml high-temperature and high-pressure reactor as described in step one, it was heated at 130℃ for 24 hours;

[0014] The mass of copper acetate mentioned in step two is 180 mg;

[0015] The volume of ethanol mentioned in step two is 28 ml;

[0016] The input mass of NH2-MIL-125(Ti / Ce) in step two is 110 mg;

[0017] The beneficial effects of this invention are:

[0018] This invention utilizes a solvothermal method to successfully synthesize NH2-MIL-125(Ti / Ce) material using cerium nitrate hexahydrate, 2-aminoterephthalic acid, and tetrabutyl titanate as raw materials. However, this material exhibits poor light absorption, resulting in a urea photosynthesis yield of only 100 μg gcat. -1 Therefore, this invention synthesizes a trimetallic MOF material, Cu-NH2-MIL-125(Ti / Ce), by coordinating Cu with the amino groups in the aforementioned MOF material through room-temperature stirring. This material effectively improves light absorption performance and electron transfer rate, thereby enhancing the photocatalytic urea production performance. The photosynthetic urea yield of Cu-NH2-MIL-125(Ti / Ce) material is 400-420 μg / kg. -1 . Attached Figure Description

[0019] Figure 1 Comparison of X-ray powder diffraction patterns of NH2-MIL-125(Ti / Ce) and Cu-NH2-MIL-125(Ti / Ce) materials;

[0020] Figure 2 The qualitative spectrum of the diazine derivative generated after the colorimetric reaction of the photocatalytic product (urea);

[0021] Figure 3 The graph shows the performance of photocatalytic synthesis of urea using NH2-MIL-125(Ti / Ce) and Cu-NH2-MIL-125(Ti / Ce) materials. Detailed Implementation

[0022] The present invention will be further illustrated below with examples. These examples are only for illustrating the method of the present invention and do not limit the scope of application of the present invention in any way.

[0023] Example 1: The preparation of a metal-organic framework material with trimetallic interaction according to this embodiment is carried out according to the following steps:

[0024] I. Preparation of NH2-MIL-125(Ti / Ce): 200 mg Ce(NO3)3·6H2O was added to a 50 ml beaker containing 5 ml DMF and 5 ml methanol. The solution was dissolved by sonication at 40 kHz for 20 min, and this solution was labeled as solution A. Subsequently, 1.038 g 2-aminoterephthalic acid was added to a 100 ml beaker containing 5 ml DMF and 5 ml methanol. After sonication for 20 min, this solution was labeled as solution B. Solution B was stirred on a magnetic stirrer for 30 min. Then, 0.32551 ml of solution A was added to solution B, and stirring was continued for another 30 min. Subsequently, 0.6 ml of tetrabutyl titanate was added to the above mixed solution, and the mixture was stirred for 30 min. Then, it was transferred to a 100 ml reaction vessel and heated at 130 °C for 24 h. After the temperature dropped to room temperature, the product was washed with DMF and ethanol and then vacuum dried for 24 h to obtain NH2-MIL-125(Ti / Ce).

[0025] II. Preparation of Cu-NH2-MIL-125(Ti / Ce): 180 mg of copper acetate was added to a 100 ml beaker containing 28 ml of ethanol and sonicated at 40 kHz for 15 min to form a homogeneous solution. 110 mg of the dried NH2-MIL-125(Ti / Ce) was added to the above solution and stirred at room temperature for 2 h. The mixture was then washed several times with ethanol. The resulting solid was placed in a vacuum drying oven at 80 °C for 12 h to obtain Cu-NH2-MIL-125(Ti / Ce).

[0026] The following experiments were conducted to verify the beneficial effects of the present invention:

[0027] To investigate the photocatalytic synthesis of urea using NH2-MIL-125(Ti / Ce) and Cu-NH2-MIL-125(Ti / Ce) materials, their visible light photocatalytic urea synthesis performance was tested using the following method. The test procedure was as follows: 10 mg of NH2-MIL-125(Ti / Ce) and 10 mg of Cu-NH2-MIL-125(Ti / Ce) were used as photocatalysts, and deionized water was used as the reaction solution. The mixture was ultrasonicated for 30 min at an ultrasonic frequency of 40 kHz to form a homogeneous suspension. The suspension was then poured into a reactor, and a mixture of nitrogen and carbon dioxide (N2 / CO2 = 85% / 15%) was introduced for 30 min to purge the air from the reactor and fill it with the mixture. Then, using a xenon lamp as the light source, after 10 hours of illumination, the resulting suspension was filtered through a 1 mL syringe with a filter tip to remove the catalyst, and the liquid was collected. A colorimetric reagent was added to the collected 1 mL of the test liquid, and after thorough mixing, it was placed in an oven at 100℃ for 15 minutes. After cooling to room temperature, it was analyzed using a UV-Vis spectrophotometer. Figure 3As shown, NH2-MIL-125(Ti / Ce) exhibits low efficiency in photocatalytic urea synthesis, with a yield of only 100 μg / g. cat -1 The photocatalytic performance of Cu-NH2-MIL-125(Ti / Ce) material in urea synthesis was improved, with a urea yield of 400 μg / g. cat -1 .

[0028] The colorimetric reagents mentioned above are two solutions. Solution A is prepared by placing 5 mg of diacetyl monooxime and 100 mg of thiourea in a 250 ml beaker, adding 150 ml of ultrapure water, and sonicating for 10 min to ensure complete dissolution. The solution is then transferred to a 1 L brown volumetric flask and diluted to 1 L with ultrapure water. Solution B is a mixture of 25 mg ferric chloride, 75 ml concentrated sulfuric acid, 25 ml concentrated phosphoric acid, and 150 ml ultrapure water. The specific procedure for the urea colorimetric reaction is as follows: Take 1 ml of the test solution and place it in a 10 ml glass vial. Add 1 ml of solution A and 2 ml of solution B to the vial, mix thoroughly, and then place it at 100°C for 15 min. After cooling to room temperature, analyze using a UV-Vis spectrophotometer.

Claims

1. The application of a metal-organic framework material with confined trimetallic active centers in the photocatalytic synthesis of urea, characterized in that, The preparation of metal-organic framework materials with confined trimetallic active centers is carried out according to the following steps: I. Preparation of NH2-MIL-125(Ti / Ce): Ce(NO3)3·6H2O was added to a 50ml beaker containing DMF and methanol and sonicated for 20min to dissolve it, which was recorded as solution A; then, 2-aminoterephthalic acid was added to a 100ml beaker containing DMF and methanol and sonicated for 20min, which was recorded as solution B; Place solution B on a magnetic stirrer and stir for 30 minutes. Then add solution A to solution B and continue stirring. Tetrabutyl titanate was then added to the resulting mixed solution, and the mixture was stirred continuously. The solution was then transferred to a 100 ml reactor and heated at 120-150 °C for 12-24 h. The product was washed with DMF and ethanol and then dried under vacuum for 12 h to obtain NH2-MIL-125(Ti / Ce). II. Preparation of Cu-NH2-MIL-125(Ti / Ce): Copper acetate was added to a 100ml beaker containing ethanol. The dried NH2-MIL-125(Ti / Ce) was added to the copper acetate solution. After stirring at room temperature for 2 hours, the mixture was washed several times with ethanol. The resulting solid was dried under vacuum to obtain Cu-NH2-MIL-125(Ti / Ce). The mass ratio of NH2-MIL-125(Ti / Ce) to copper acetate was 1:1.

63.

2. The application according to claim 1, characterized in that... In step one, the amount of methanol and DMF is 5 ml each.

3. The application according to claim 1, characterized in that... In step one, the amount of 2-aminoterephthalic acid is 1.038g.

4. The application according to claim 1, characterized in that... In step one, the heating temperature is 130℃ and the heating time is 24 hours.

5. The application according to claim 1, characterized in that... In step one, the amount of solution A added to solution B is 0.3255 ml.

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