A photocatalytic material with a baseball-like structure, and a preparation method and application thereof

Abstract

This invention discloses a baseball-shaped photocatalytic material, its preparation method, and its application, belonging to the field of photocatalytic ammonia synthesis technology. The baseball-shaped photocatalytic material comprises rod-shaped FeMOF and spherical MnMOF. The baseball-shaped photocatalytic material uses rod-shaped FeMOF as a substrate, with spherical MnMOF grown on top of the rod-shaped FeMOF. The spherical MnMOF contains acetate ions. The preparation method involves dissolving an iron source and a manganese source in a solvent, adding an organic ligand, and ultrasonically treating the mixture, followed by a hydrothermal reaction. The manganese source is manganese acetate tetrahydrate. This invention's baseball-shaped photocatalytic material, through the uniform growth of spherical MnMOF on rod-shaped FeMOF, forms an electron-hole conversion channel, thereby enhancing the electron-hole transport rate, improving the photocatalytic performance of the bimetallic organic framework structure, and significantly increasing the yield of photocatalytic ammonia synthesis.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of photocatalytic synthesis of ammonia, and particularly relates to a photocatalytic material with a baseball-shaped structure and a preparation method and application thereof. BACKGROUND

[0002] In recent years, carbon neutrality has become a consensus in response to global climate change. Today, one of the shackles of carbon neutrality is industrial ammonia (NH3) synthesis, which emits 3% of the world's carbon dioxide and consumes 2% of the world's energy every year. Photocatalytic ammonia synthesis heralds a fascinating vision of using zero-carbon emissions and low-energy solar energy to convert nitrogen (N2) into NH3. However, as the first step in the conversion of nitrogen to ammonia, the activation of nitrogen requires an ultra-high energy to break the first bond of the N-N triple bond (410 kJ -1 ), which is a key problem that needs to be urgently addressed.

[0003] Metal-organic frameworks (MOFs) are porous materials assembled from metal ions or inorganic clusters and organic linkers using strong bonds with permanent porosity, especially biocompatible MOFs. However, there are still many deficiencies in the current metal-organic frameworks for photocatalytic synthesis of ammonia, such as some MOFs (such as the IRMOF series) cannot effectively drive the nitrogen reduction reaction (NRR) due to the fast electron-hole recombination rate and low utilization rate of photo-generated charges. At the same time, the metal nodes of some MOFs (such as HKUST-1) are excessively wrapped by ligands, hindering the contact of N2 molecules with active sites. Therefore, how to improve the performance of metal-organic frameworks for photocatalytic synthesis of ammonia has become a difficult problem that needs to be overcome by those skilled in the art. SUMMARY

[0004] In order to solve the problems presented in the background art, the purpose of the present application is to provide a photocatalytic material with a baseball-shaped structure and a preparation method and application thereof. The photocatalytic material with a baseball-shaped structure provided by the present application has a rod-shaped structure of FeMOF and a heterojunction of MnMOF generated from manganese acetate and organic ligands, which promotes the migration of photo-generated electrons to the rod-shaped structure of FeMOF and inhibits recombination. In addition, the high specific surface area and microporous-mesoporous structure of the rod-shaped structure of FeMOF promote N2 adsorption and expose Fe 2+ / Fe 3+ redox sites on the surface of FeMOF.

[0005] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows: on the one hand, the present application provides a photocatalytic material with a baseball-shaped structure, which includes a rod-shaped structure of FeMOF and a spherical structure of MnMOF.

[0006] The light catalytic material of the baseball-shaped structure takes a FeMOF of a rod-shaped structure as a substrate, and a MnMOF of a spherical structure is grown on the FeMOF of the rod-shaped structure.

[0007] The MnMOF of the spherical structure contains acetate ions.

[0008] In another aspect, the present application provides a preparation method of the light catalytic material of the baseball-shaped structure, comprising the following steps:

[0009] The iron source and the manganese source are dissolved in a solvent, then an organic ligand is added and ultrasonic treatment is performed, and then a hydrothermal reaction is performed to obtain the light catalytic material of the baseball-shaped structure.

[0010] The manganese source is manganese acetate tetrahydrate ((CH3COO)2Mn·4H2O).

[0011] The reaction mode changes, which affects the bonding of the metal source and the organic ligand, affects the morphology of the final product, and further affects the adsorption of N2 activity and reduces the photocatalytic nitrogen fixation performance. If the ultrasonic treatment is replaced by stirring, the morphology of the FeMnMOF material will be damaged when stirring, which makes it difficult to adsorb on the outside of the FeMOF when generating a heterojunction subsequently, and affects the photocatalytic effect.

[0012] Further, the iron source is iron chloride hexahydrate (FeCl3·6H2O) or iron nitrate nonahydrate (Fe(NO3)3·9H2O).

[0013] Further, the organic ligand includes 2-amino terephthalic acid (NH2-H2BDC) or terephthalic acid (H2BDC).

[0014] Further, the solvent includes N,N-dimethylformamide (DMF) or methanol (CH3OH).

[0015] Further, the molar ratio of the organic ligand to the iron source is 1:1.

[0016] Further, the molar ratio of the organic ligand to the manganese source is 1:3.

[0017] Further, the dosage ratio of the metal source (manganese source and iron source) to the solvent is 4 mmol:50 mL.

[0018] Further, the power of the ultrasonic treatment is 100W-300W, the frequency of the ultrasonic treatment is 10-40Hz, the temperature of the ultrasonic treatment is 10-25℃, and the time of the ultrasonic treatment is 0.5h-1h.

[0019] Further, the temperature of the hydrothermal reaction is 110-180℃, and the time of the hydrothermal reaction is 12-24h. If the reaction temperature is too high (higher than 180℃), the skeleton of the solid product will be destroyed.

[0020] In another aspect, the application provides a use of the baseball-shaped structure photocatalytic material or the baseball-shaped structure photocatalytic material prepared by any one of the preparation methods in photocatalytic synthesis of ammonia.

[0021] For the numerical ranges in the present application, it should be understood that each intermediate value between the upper limit and the lower limit of the range is also specifically disclosed. The intermediate values in any stated value or range, and each smaller range between any other stated values or intermediate values in the stated range are also included in the present application. The upper limit and the lower limit of these smaller ranges can be independently included or excluded from the range.

[0022] Compared with the prior art, the present application has the following beneficial effects:

[0023] (1) In the preparation method of the baseball-shaped structure photocatalytic material, the manganese source is manganese acetate tetrahydrate, and the performance of the MnMOF is enhanced by doping acetate ions in the MnMOF and utilizing the synergistic effect of the acetate ions.

[0024] (2) The preparation method of the baseball-shaped structure photocatalytic material is simple, low in cost and environmentally friendly, and the prepared baseball-shaped structure photocatalytic material has a stable and porous double-metal organic framework structure.

[0025] (3) The baseball-shaped structure photocatalytic material is composed of the MnMOF in a spherical structure uniformly grown on the FeMOF in a rod-like structure to form a channel for conversion of electrons and holes, so as to enhance the electron and hole transport rate and the photocatalytic performance of the double-metal organic framework structure, and the yield of photocatalytic synthesis of ammonia is significantly improved. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 SEM image of the baseball-shaped structure photocatalytic material prepared in Example 1 of the present application;

[0027] Figure 2 SEM image of the octahedral structure photocatalytic material prepared in Comparative Example 1 of the present application;

[0028] Figure 3 SEM image of the laminar structure photocatalytic material prepared in Comparative Example 2 of the present application;

[0029] Figure 4 SEM image of the photocatalytic material prepared in Comparative Example 3 of the present application;

[0030] Figure 5 This is a SEM image of the photocatalytic material prepared in Comparative Example 4 of this invention;

[0031] Figure 6 This is a SEM image of the photocatalytic material prepared in Comparative Example 5 of this invention;

[0032] Figure 7 The image shows a comparison of the photocatalytic ammonia synthesis performance of the photocatalytic materials prepared in Example 1 and Comparative Examples 1-7 of this invention. Detailed Implementation

[0033] To better understand the content of this invention, the following detailed description is provided in conjunction with specific implementation methods. However, the scope of protection of this invention is not limited to the following embodiments.

[0034] The raw materials and reagents used in the specific embodiments of this invention are all commercially available products.

[0035] Any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0036] Example 1

[0037] Preparation of baseball-shaped photocatalytic materials:

[0038] 1 mmol FeCl3·6H2O and 3 mmol (CH3COO)2Mn·4H2O were dissolved in 50 mL DMF, and then 1 mmol 2-NH2-H2BDC was added. The mixture was sonicated for 1 h, and then placed in an oven and heated to 110 °C for 24 h to obtain a baseball-shaped photocatalytic material, denoted as 1:3FeMnMOF.

[0039] Electron microscopy was performed on the photocatalytic material with a baseball-like structure, and the results are as follows: Figure 1 As shown. From Figure 1 As can be seen, the morphology of 1:3FeMnMOF is that of rod-shaped elongated spheres.

[0040] Comparative Example 1

[0041] Preparation of octahedral photocatalytic materials:

[0042] 1 mmol FeCl3·6H2O was dissolved in 50 mL DMF, then 1 mmol NH2-H2BDC was added, and the mixture was sonicated for 1 h. The mixture was then placed in an oven and heated to 110 °C for 24 h to obtain an octahedral photocatalytic material, denoted as FeMOF.

[0043] Electron microscopy was performed on the octahedral photocatalytic material, and the results are as follows: Figure 2 As shown. From Figure 2As can be seen, pure FeMOF has an octahedral morphology.

[0044] Comparative Example 2

[0045] Preparation of layered photocatalytic materials:

[0046] 3 mmol (CH3COO)2Mn·4H2O was dissolved in 50 mL DMF, then 1 mmol NH2-H2BDC was added, and the mixture was sonicated for 1 h. The mixture was then placed in an oven and heated to 110 °C for 24 h to obtain a layered photocatalytic material, denoted as MnMOF.

[0047] Electron microscopy was performed on the layered photocatalytic material, and the results are as follows: Figure 3 As shown. From Figure 3 As can be seen, pure MnMOF is lamellar.

[0048] Comparative Example 3

[0049] Preparation of photocatalytic materials:

[0050] 1 mmol FeCl3·6H2O and 1 mmol (CH3COO)2Mn·4H2O were dissolved in 50 mL DMF, and then 1 mmol NH2-H2BDC was added. The mixture was sonicated for 1 h, and then placed in an oven and heated to 110 °C for 24 h to obtain the photocatalytic material, denoted as 1:1 FeMnMOF.

[0051] Electron microscopy was performed on the photocatalytic material, and the results are as follows: Figure 4 As shown. From Figure 4 As can be seen, after compounding with 1 mmol of manganese source, its morphology is irregular granular.

[0052] Comparative Example 4

[0053] Preparation of photocatalytic materials:

[0054] 1 mmol FeCl3·6H2O and 2 mmol (CH3COO)2Mn·4H2O were dissolved in 50 mL DMF, and then 1 mmol NH2-H2BDC was added. The mixture was sonicated for 1 h, and then placed in an oven and heated to 110 °C for 24 h to obtain the photocatalytic material, denoted as 1:2FeMnMOF.

[0055] Electron microscopy was performed on the photocatalytic material, and the results are as follows: Figure 5 As shown. From Figure 5 As can be seen, after compounding with 2 mmol of manganese source, its morphology is irregular granular, and the irregular granules become larger.

[0056] Comparative Example 5

[0057] Preparation of photocatalytic materials:

[0058] 1 mmol FeCl3·6H2O and 4 mmol (CH3COO)2Mn·4H2O were dissolved in 50 mL DMF, and then 1 mmol NH2-H2BDC was added. The mixture was sonicated for 1 h, and then placed in an oven and heated to 110 °C for 24 h to obtain the photocatalytic material, denoted as 1:4FeMnMOF.

[0059] Electron microscopy was performed on the photocatalytic material, and the results are as follows: Figure 6 As shown. From Figure 6 As can be seen, after combining with 4 mmol of manganese source, the morphology is regular spherical, which is the morphology of MnMOF, and no rod-shaped FeMOF was observed.

[0060] Comparative Example 6

[0061] Preparation of photocatalytic materials:

[0062] 1 mmol FeCl3·6H2O and 3 mmol MnCl2·4H2O were dissolved in 50 mL DMF, and then 1 mmol NH2-H2BDC was added. The mixture was sonicated for 1 h, and then placed in an oven and heated to 110 °C for 24 h to obtain the photocatalytic material, denoted as Cl-FeMnMOF.

[0063] Comparative Example 7

[0064] Preparation of photocatalytic materials:

[0065] 1 mmol FeCl3·6H2O and 3 mmol (CH3COO)2Mn·4H2O were dissolved in 50 mL DMF, and then 1 mmol NH2-H2BDC was added. The mixture was stirred for 1 h, and then placed in an oven and heated to 110 °C for 24 h to obtain the photocatalytic material, denoted as S-FeMnMOF.

[0066] BET tests were performed on the 1:3 FeMnMOF prepared in Example 1, the FeMOF prepared in Comparative Example 1, and the MnMOF prepared in Comparative Example 2. The specific surface area, pore volume, and pore size results are shown in the table below.

[0067]

[0068] The photocatalytic materials prepared in Example 1 and Comparative Examples 1-7 were used to conduct photocatalytic ammonia synthesis experiments. The specific steps included:

[0069] 50 mg of photocatalyst material was added to 100 mL of ultrapure water. N2 was first introduced under dark reaction conditions until saturation. After adsorption saturation, a 300 W xenon lamp with a 420 nm filter was used for illumination. During illumination, 5 mL of solution was drawn every 10 minutes using a 5 mL syringe, and the absorbance of the solution at different time intervals at 420 nm wavelength was measured using a UV-Vis spectrophotometer. The calibration curve for ammonia was then determined using the Nessler reagent method: y = 0.00142 + 0.12074x. This curve indicates that the absorbance of the sample at 420 nm wavelength is similar to that of NH4+. + There is a strong linear relationship between the concentrations of ions. Finally, the ammonium yield was calculated, and the results are as follows: Figure 7 As shown. From Figure 7 As can be seen from the data, 1:3FeMnMOF exhibits the best performance.

[0070] The above description is only a specific embodiment of the present invention and not all embodiments. Any equivalent modifications made by those skilled in the art to the technical solutions of the present invention by reading the present invention specification shall be covered by the claims of the present invention.

Claims

1. A method for preparing a baseball-shaped photocatalytic material, characterized in that, Includes the following steps: Iron and manganese sources are dissolved in a solvent, then an organic ligand is added and ultrasonically treated, followed by a hydrothermal reaction to obtain the baseball-shaped photocatalytic material. The manganese source is manganese acetate tetrahydrate; The molar ratio of the organic ligand to the iron source is 1:1; The molar ratio of the organic ligand to the manganese source is 1:3; The hydrothermal reaction temperature is 110-180℃, and the hydrothermal reaction time is 12-24h; The baseball-shaped photocatalytic material includes rod-shaped FeMOF and spherical MnMOF. The baseball-shaped photocatalytic material uses a rod-shaped FeMOF as a substrate, and the spherical MnMOF is grown on the rod-shaped FeMOF.

2. The preparation method according to claim 1, characterized in that, The iron source is ferric chloride hexahydrate or ferric nitrate nonahydrate.

3. The preparation method according to claim 1, characterized in that, The organic ligands include 2-aminoterephthalic acid or terephthalic acid.

4. The preparation method according to claim 1, characterized in that, The ultrasonic treatment has a power of 100W-300W, a frequency of 10-40Hz, a temperature of 10-25℃, and a duration of 0.5h-1h.

5. A photocatalytic material with a baseball-like structure, characterized in that, It is prepared by any one of the preparation methods described in claims 1-4.

6. The application of the baseball-shaped photocatalytic material according to claim 5 in photocatalytic ammonia synthesis.

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