Preparation and photocatalytic nitrogen fixation application of PMo12 modified MIL-101 (Fe) composite material

Abstract

The invention discloses preparation and photocatalytic nitrogen fixation application of a PMo12 modified MIL-101 (Fe) composite material, and belongs to the technical field of photocatalytic nitrogen reduction. The preparation method of the PMo12 modified MIL-101 (Fe) composite material comprises the following steps: mixing an iron source, terephthalic acid and Keggin type POM, and reacting to obtain the PMo12 modified MIL-101 (Fe) composite material, the Keggin type POM is H3PMo12O40, and the Keggin type POM is H3PMo12O40. MIL-101 (Fe) is used as a main framework, Keggin type POM is used as a functional object, a solvothermal method is adopted for assembling and compounding, the problems of light energy utilization rate, photon-generated carrier compounding and the like can be solved through introduction of POM, and therefore the photocatalytic nitrogen fixation effect is improved. In addition, POM is used as an electron repeater and can store and transfer electrons and provide rich electron activated inert N2, so that the yield of the target product NH4 < + > is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of photocatalytic nitrogen reduction, and more specifically relates to a PMo 12 Preparation of modified MIL-101(Fe) composite materials and their application in photocatalytic nitrogen fixation. Background Art

[0002] Ammonia (NH3), as a key chemical raw material and hydrogen energy carrier, holds an irreplaceable strategic position in agricultural production and industrial manufacturing. Currently, industrial ammonia synthesis relies primarily on the Haber-Bosch process, which involves the catalytic synthesis of nitrogen and hydrogen under high temperature and pressure. While this technology allows for large-scale production, it suffers from significant drawbacks such as high energy consumption and associated high carbon dioxide emissions. This high-carbon, high-energy production model runs counter to the concept of sustainable development. Therefore, the development of new environmentally friendly ammonia synthesis technologies has become a key focus in the field of energy chemistry.

[0003] Photocatalytic nitrogen reduction offers a new approach to clean ammonia synthesis. This technology mimics the mechanism of natural photosynthesis, utilizing inexhaustible solar energy to drive the synthesis of ammonia from nitrogen and hydrogen at ambient temperature and pressure. However, the dissociation of the strong covalent bonds in nitrogen molecules requires overcoming significant energy barriers and limited reactive sites. Therefore, the development of novel photocatalysts with high charge carrier separation efficiency and excellent nitrogen activation capabilities is crucial.

[0004] Metal-organic frameworks (MOFs) are crystalline porous materials composed of metal cluster nodes and organic ligands. Their periodically arranged metal cluster nodes, rich in unoccupied d-orbital active sites, are considered ideal media for biomimetic design of nitrogenase-like catalytic systems, connecting N2 molecule binding sites with the FeMo cofactor. Therefore, they have attracted considerable attention in the study of artificial nitrogenase-like catalytic systems. However, while the organic ligands in MOFs can generate photogenerated electrons through light harvesting and, through structural design, achieve electron transfer pathways similar to those in Fe proteins, the lack of structural units similar to P clusters leads to severe recombination of photogenerated electron-hole pairs, which greatly limits the catalytic efficiency of light-driven biomimetic nitrogen fixation. Therefore, the development of highly efficient photocatalytic nitrogen fixation catalysts is of great significance. Summary of the Invention

[0005] The purpose of the present invention is to provide a PMo 12 The preparation of modified MIL-101 (Fe) composite materials and their application in photocatalytic nitrogen fixation are used to solve the problems existing in the above-mentioned prior art and realize the preparation of photocatalytic nitrogen fixation catalysts with high catalytic efficiency.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] One of the technical solutions of the present invention: providing a PMo12 The preparation method of the modified MIL-101(Fe) composite material comprises the following steps:

[0008] The iron source, terephthalic acid and Keggin type POM are mixed and reacted to obtain the PMo 12 Modified MIL-101(Fe) composites;

[0009] The Keggin type POM is H3PMo 12 O 40 .

[0010] Preferably, the PMo 12 The specific steps of the preparation method of the modified MIL-101(Fe) composite material are as follows:

[0011] The iron source is dissolved in a solvent to obtain a mixed solution; the mixed solution, terephthalic acid and Keggin type POM are mixed and reacted to obtain the PMo 12 Modified MIL-101 (Fe) composite material; the Keggin type POM is H3PMo 12 O 40 .

[0012] Preferably, the solvent comprises one or more of N,N-dimethylformamide, ethanol and water.

[0013] Preferably, the iron source comprises one or more of ferric chloride, ferric nitrate and ferric sulfate.

[0014] Preferably, the usage ratio of the iron source, terephthalic acid and Keggin-type POM is 4-6 mmol: 1-2 mmol: 150-200 mg.

[0015] Preferably, the reaction temperature is 100-120° C. and the reaction time is 20-24 h.

[0016] Preferably, the reaction further comprises washing and drying steps after completion.

[0017] The second technical solution of the present invention is to provide PMo prepared by the above preparation method. 12 Modified MIL-101(Fe) composite materials.

[0018] The third technical solution of the present invention: providing the above-mentioned PMo 12 Application of modified MIL-101(Fe) composite materials in the field of photocatalytic nitrogen fixation.

[0019] A fourth technical solution of the present invention provides a method for improving the efficiency of a nitrogen reduction reaction in synthesizing ammonia by a photocatalytic nitrogen reduction reaction, comprising the following steps:

[0020] With the above PMo 12 The modified MIL-101(Fe) composite material was used as a catalyst for photocatalytic nitrogen reduction reaction to synthesize ammonia.

[0021] The technical mechanism of the present invention is as follows:

[0022] Polyoxometalates (POMs), a class of transition metal polyoxyanion nanoclusters with atomic-level precision, exhibit unique electron transfer properties when combined with MOFs to form supramolecular assemblies. POMs can act as "electron relays," enabling rapid and reversible transfer of multiple electrons while maintaining structural synergy with MOFs. This property effectively mimics the electron regulation function of the P cluster in nitrogenase. At the same time, the polyoxygen clusters of POMs, with their strong electronegativity, can continuously attract electrons from the metal clusters of MOFs. This not only enhances the metal node d orbitals to adsorb N2 and promote the excitation of more electrons, but also realizes a N2 activation mechanism similar to that of biological nitrogenase by stimulating the directional transfer of occupied d orbital electrons to the N-Nπ* antibonding orbital.

[0023] The present invention utilizes the Fe cluster node of MIL-101(Fe) to simulate the electron transfer / storage unit and anchors the Keggin type PMo through covalent bonds. 12 A well-defined Fe-O-Mo interface serves as both the core catalytic site and electron relay. This design achieves a division of labor between the electron transfer pathway and the active site, overcoming the critical challenge of severe carrier recombination in MOF-based materials. Based on this synergistic effect, the MOF-POM composite system exhibits a high degree of similarity to nitrogenase in terms of electron transfer pathway simulation, active site construction, and biomimetic catalytic mechanism, providing an important theoretical foundation for the development of a catalytic platform that mimics biological nitrogen fixation.

[0024] The PMo of the present invention 12 When the modified MIL-101(Fe) composite material is used in the field of photocatalytic nitrogen fixation, the photocatalytic nitrogen reduction reaction uses ultrapure water and N2 as raw materials, and the composite material PMo 12 @MIL-101(Fe) has high catalytic activity. 12 Formed a bridging structure (such as Figure 8 As shown in Figure 2), MIL-101(Fe) itself can expand the visible light absorption range. In addition, the bridging structure causes the photogenerated electrons on MIL-101(Fe) to be transferred to PMo in a directional manner. 12 On with PMo 12 The introduction of POM can solve the problems of light energy utilization and photogenerated carrier recombination, thereby improving the photocatalytic nitrogen fixation effect.

[0025] Terephthalic acid, as a ligand, has the function of adjusting the pore size of MOF and is irreplaceable. If it is replaced with other ligands, the bridge structure described in the present invention cannot be formed. 12 The preparation parameters of the modified MIL-101(Fe) composite material have a significant influence on the formation of the bridging structure. A bridging structure can be formed under the preparation parameters determined by the present invention. However, if the preparation parameters exceed the range defined by the present invention, other structures will be generated (such as a POM / MOF physically mixed isolated dispersed structure, a POM confined in the MOF pore structure, or a heterogeneous mixed structure of POM aggregates and MOF), which will lead to the inability to form a bridging structure and a significant decrease in the photocatalytic nitrogen fixation effect.

[0026] The present invention discloses the following technical effects:

[0027] This invention, based on the design concept of a nitrogenase-inspired photocatalyst, utilizes MIL-101(Fe) as the main framework and a Keggin-type POM as the functional guest. Using a solvothermal method, the POM is assembled and composited with the MIL-101(Fe) support via a transcovalent bond. The composite is then applied to ammonia synthesis via a photocatalytic nitrogen reduction reaction. This synthesis process requires minimal equipment, produces minimal pollution, and can be easily performed at room temperature.

[0028] Photocatalytic nitrogen reduction reaction uses ultrapure water and N2 as raw materials, and the composite material PMo 12 @MIL-101(Fe) has high catalytic activity. 12 A bridging structure is formed, and MIL-101(Fe) itself can expand the visible light absorption range. In addition, the bridging structure causes the photogenerated electrons on MIL-101(Fe) to be transferred to PMo in a directional manner. 12 On with PMo 12 The introduction of POM can solve the problems of light energy utilization and photogenerated carrier recombination, thereby improving the photocatalytic nitrogen fixation effect. In addition, POM can store and transfer electrons as an electron relay, providing abundant electron-activated inert N2, thereby increasing the target product NH4 + yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 XRD patterns of MIL-101(Fe) and the composite materials prepared in Examples 1 to 4;

[0030] Figure 2 Fourier transform infrared spectra of MIL-101(Fe) and the composite materials prepared in Examples 1 to 4;

[0031] Figure 3The photocatalytic performance diagram of MIL-101(Fe) and the composite materials prepared in Examples 1 to 4;

[0032] Figure 4 For PMo in Example 5 12 @Photocatalytic performance cycle diagram of MIL-101(Fe) composite material;

[0033] Figure 5 NH4 is produced by the reaction system in Example 6 + of 1 HNMR spectrum;

[0034] Figure 6 PMo in Example 7 12 @MIL-101(Fe) photocatalytic oxygen production performance diagram;

[0035] Figure 7 For PMo 12 @MIL-101(Fe) photocatalytic performance diagram under different conditions;

[0036] Figure 8 MIL-101(Fe) and PMo 12 Model diagram of @MIL-101(Fe), where (a) is MIL-101(Fe), (b) and (c) are PMo 12 @MIL-101(Fe). DETAILED DESCRIPTION

[0037] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0038] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. The intermediate value within any stated value or stated range, and each smaller range between any other stated value or intermediate value within the stated range, is also encompassed within the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0039] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0040] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be illustrative only.

[0041] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0042] It should be pointed out that the matters not described in detail in the present invention are conventional operating means in this field and are not the focus of the present invention.

[0043] Unless otherwise specified, the raw materials used in the following examples of the present invention are all commercially available products, and the sources of the commercially available products do not affect the technical effects of the present invention.

[0044] Unless otherwise specified, the room temperature referred to in the present invention is 25±5°C.

[0045] Example 1

[0046] S1: At room temperature, dissolve FeCl₃·6H₂O (0.811 g, 5 mmol) in 60 mL of N,N-dimethylformamide (DMF). Ultrasonicate until completely dissolved, forming a yellow solution. Subsequently, add terephthalic acid (0.249 g, 1.5 mmol) to the mixture and continue stirring for 30 min.

[0047] S2: Transfer the mixed solution obtained in step S1 to a reactor and maintain it at 110°C for 24 hours. After the reaction is complete, cool it to room temperature and centrifuge it at 8000 rpm. Wash the solid product three times with acetone and anhydrous ethanol alternately, and finally dry it in a vacuum oven at 80°C for 12 hours.

[0048] S3: Grind the powder obtained in step S2 and put it into a sample tube for later use. The prepared sample is named MIL-101(Fe).

[0049] Example 2

[0050] S1: FeCl3·6H2O (0.811 g, 5 mmol) was weighed and dissolved in 60 mL of N,N-dimethylformamide (DMF) at room temperature and ultrasonicated until completely dissolved to form a yellow solution. Subsequently, terephthalic acid (0.249 g, 1.5 mmol) and 200 mg of H3PMo 12 O 40 Add the above mixed solution and continue stirring for 30 minutes.

[0051] S2: Transfer the mixed solution obtained in step S1 to a reactor and maintain it at 110°C for 24 hours. After the reaction is complete, cool it to room temperature and centrifuge it at 8000 rpm. Wash the solid product three times with acetone and anhydrous ethanol alternately, and finally dry it in a vacuum oven at 80°C for 12 hours.

[0052] S3: Grind the powder obtained in step S2 and put it into a sample tube for later use. The prepared sample is named PMo 12 @MIL-101(Fe).

[0053] Example 3

[0054] S1: FeCl3·6H2O (0.811 g, 5 mmol) was weighed and dissolved in 60 mL of N,N-dimethylformamide (DMF) at room temperature and ultrasonicated until completely dissolved to form a yellow solution. Subsequently, terephthalic acid (0.249 g, 1.5 mmol) and 200 mg of H3PW were added. 12 O 40 Add the above mixed solution and continue stirring for 30 minutes.

[0055] S2: Transfer the mixed solution obtained in step S1 to a reactor and maintain it at 110°C for 24 hours. After the reaction is complete, cool it to room temperature and centrifuge it at 8000 rpm. Wash the solid product three times with acetone and anhydrous ethanol alternately, and finally dry it in a vacuum oven at 80°C for 12 hours.

[0056] S3: Grind the powder obtained in step S2 and put it into a sample tube for later use. The prepared sample is named PW 12 @MIL-101(Fe).

[0057] Example 4

[0058] S1: FeCl3·6H2O (0.811 g, 5 mmol) was weighed and dissolved in 60 mL of N,N-dimethylformamide (DMF) at room temperature and ultrasonicated until completely dissolved to form a yellow solution. Subsequently, terephthalic acid (0.249 g, 1.5 mmol) and 200 mg of H4SiW 12 O 40Add the above mixed solution and continue stirring for 30 minutes.

[0059] S2: Transfer the mixed solution obtained in step S1 to a reactor and maintain it at 110°C for 24 hours. After the reaction is complete, cool it to room temperature and centrifuge it at 8000 rpm. Wash the solid product three times with acetone and anhydrous ethanol alternately, and finally dry it in a vacuum oven at 80°C for 12 hours.

[0060] S3: Grind the powder obtained in step S2 and put it into a sample tube for later use. The prepared sample is named SiW 12 @MIL-101(Fe).

[0061] The MIL-101(Fe) and PMo obtained in Examples 1 to 4 12 @MIL-101(Fe), PW 12 @MIL-101(Fe) and SiW 12 @MIL-101(Fe) was structurally analyzed by X-ray diffraction and Fourier transform infrared spectroscopy, such as Figure 1 and Figure 2 shown.

[0062] Figure 1 XRD patterns of MIL-101(Fe) and the composite materials prepared in Examples 1 to 4;

[0063] Figure 2 Fourier transform infrared spectra of MIL-101(Fe) and the composite materials prepared in Examples 1 to 4.

[0064] Depend on Figure 1 It can be seen that the composite material PMo 12 @MIL-101(Fe), SiW 12 @MIL-101(Fe) and PW 12 The diffraction peaks of @MIL-101(Fe) are consistent with the crystal structure of MIL-101(Fe), and no three POM (H3PMo 12 O 40 、H3PW 12 O 40 、H4SiW 12 O 40 ), which indicates that the addition of POM does not affect the crystal structure of MIL-101(Fe). The chemical bonding properties of the three composites were characterized by FT-IR.

[0065] like Figure 2 As shown, H3PMo 12 O 40The characteristic absorption peak signals are located at 1065, 962, 872 and 787 cm -1 , belonging to Mo=O, PO, Mo-O in turn b -Mo and Mo-O c -Mo bond vibration mode. Similarly, for H4SiW 12 O 40 , at 979, 925, 880 and 784 cm -1 Typical absorption peaks appear at the b -W and WO c -W bond vibration mode. For H3PW 12 O 40 , at 1085, 984, 892 and 807 cm -1 Characteristic absorption peak signals appear at the points corresponding to W=O, PO, and WO b -W and WO c -W bond vibration mode. The carrier MIL-101(Fe) is at 1597, 1505 and 1393 cm -1 Characteristic absorption peaks appear at the 300 nm and 300 nm positions, corresponding to the C=O asymmetric vibration, benzene ring skeletal vibration, and C=O symmetric vibration modes of terephthalic acid, respectively. Skeletal vibration signals of MIL-101(Fe) and characteristic vibration bands of POM molecules were also detected in the three composites, demonstrating that both the POM molecules and MIL-101(Fe) maintained their original chemical structures during the composite synthesis process, without undergoing structural dissociation.

[0066] Example 5

[0067] A 300W xenon lamp (PLS-SXE 300, Beijing Perfect Light Co., Ltd.) was used as the light source, and the reaction temperature of the photocatalytic reaction was maintained at 25°C. 30 mg of the photocatalysts MIL-101 (Fe), PMo 12 @MIL-101(Fe), SiW 12 @MIL-101(Fe) and PW 12 @MIL-101(Fe) was placed in a quartz reactor and 100 mL of ultrapure water was added. Ultrasonic treatment was performed for 3 minutes to uniformly disperse the photocatalyst. Before irradiation, the suspension was stirred in the dark with N2 for 30 minutes to allow the adsorption and desorption of N2 on the photocatalyst surface to reach equilibrium. The xenon lamp was then turned on to irradiate the reactor, and N2 was continuously introduced at a gas flow rate of 80 mL / min. 5 mL of the reaction solution was taken at regular intervals and centrifuged to remove the photocatalyst. The concentration of ammonia in the reaction solution was determined by ion chromatography. The results are shown in Figure 2. Figure 3 shown.

[0068] Figure 3 The photocatalytic performance diagram of MIL-101(Fe) and the composite materials prepared in Examples 1 to 4.

[0069] Depend on Figure 3 It can be seen that the photocatalysts MIL-101(Fe), PMo 12 @MIL-101(Fe), SiW 12 @MIL-101(Fe) and PW 12 The ammonia generation rates of @MIL-101(Fe) were 8.75 μmol·g -1 cat ·h -1 , 50.29 μmol·g -1 cat ·h -1 、36.33μmol·g -1 cat ·h -1 and 20.72 μmol·g -1 cat ·h -1 The performance difference mainly comes from the fact that molybdenum-based heteropolyacids exhibit stronger adsorption and activation capabilities for nitrogen molecules than tungsten-based heteropolyacids. They promote the dissociation of N≡N bonds by enhancing the chemical adsorption strength of N2 molecules, thereby improving the nitrogen reduction efficiency and ultimately exhibiting better catalytic activity.

[0070] The photocatalyst PMo with the best performance obtained in Example 2 12 @MIL-101(Fe) was subjected to 6 cycles of testing according to the test procedure of Example 5, with an interval of 1 hour between each cycle test. The cycle test results are shown in the figure below. Figure 4 shown.

[0071] Figure 4 For PMo in Example 5 12 @Photocatalytic performance cycle diagram of MIL-101(Fe) composite material.

[0072] Depend on Figure 4 It can be seen that PMo 12 The photocatalytic cycle performance of @MIL-101(Fe) remained basically unchanged, further demonstrating that the photocatalyst has good stability.

[0073] Example 6

[0074] In order to verify the photocatalytic nitrogen fixation reaction of NH4 +The source of nitrogen was determined by isotope labeling. The experimental design was as follows: a 300W xenon lamp (PLS-SXE 300, Beijing Perfect Light Co., Ltd.) was used as the light source, and the reaction temperature of the photocatalytic reaction was maintained at 25°C. 30 mg of the photocatalyst PMo prepared in Example 2 was weighed. 12 @MIL-101(Fe) was placed in a quartz reactor and 100 mL of ultrapure water was added. Ultrasonication was performed for 3 minutes to uniformly disperse the photocatalyst. Before irradiation, the suspension was stirred with N2 in the dark for 30 minutes to allow the adsorption and desorption of N2 on the photocatalyst surface to reach equilibrium. The photocatalytic reaction system was vacuumed and filled with argon three times to eliminate environmental nitrogen pollution. 15 N2 or 14 N2 to normal pressure. After the photocatalytic reaction is completed, 30 mL of the reaction solution is filtered through a 0.22 μm water filter membrane, concentrated sulfuric acid is added to adjust the pH value to 2, and then concentrated to 10 mL using a rotary evaporator. At the same time, 600 μL of the concentrate is added to a 5 mm NMR sample tube, and 20 μL of D2O (99.99%, Sigma-Aldrich) is added thereto as a lock field reagent and mixed for 30 seconds. The analysis and test are performed using an AVANCE NEO 500M nuclear magnetic resonance spectrometer. The results are as follows Figure 5 shown.

[0075] Figure 5 NH4 is produced by the reaction system in Example 6 + of 1 HNMR spectrum.

[0076] Depend on Figure 5 It can be observed that the coupling constant J = 75Hz 15 NH4 + The doublet peak and the triplet peak with a coupling constant of J = 53 Hz are attributed to 14 NH4 + , which verifies that NH4 + It comes from N2 molecules. This proves that the photocatalyst obtained by the present invention can be used to synthesize ammonia through photocatalytic nitrogen reduction reaction.

[0077] Example 7

[0078] The photocatalytic nitrogen fixation process (i.e. the process of synthesizing ammonia by photocatalytic nitrogen reduction reaction) is often accompanied by the generation of O2. 12@MIL-101(Fe) powder was dispersed in 100 mL of ultrapure water and placed in a photocatalytic reaction device. A carrier gas purge was then initiated, followed by irradiation with a 300W xenon lamp. The generated gas was monitored online using a gas chromatograph with a TCD thermal conductivity detector and high-purity nitrogen as the carrier gas. The photocatalytic oxygen production was monitored by gas chromatography for 3 hours, with measurements taken every hour. The results are shown in the figure. Figure 6 shown.

[0079] Figure 6 PMo in Example 7 12 @Photocatalytic oxygen production performance diagram of MIL-101(Fe).

[0080] Depend on Figure 6 It can be seen that the amount of O2 generated was 50.08 μmol·g -1 cat ·h -1 , while the ammonia yield under nitrogen atmosphere was 61.44 μmol·g -1 cat ·h -1 Theoretically, the NH4 + / O2 is 4 / 3, the actual photocatalytic reaction is NH4 + and O2 production is close to this ratio, which indicates that the simulated enzyme photocatalyst PMo 12 @MIL-101(Fe) produces photogenerated electrons to reduce N2 to NH4 + , and the photogenerated holes oxidize H2O into O2 and H + It is also proved that the photocatalyst obtained by the present invention can be used to synthesize ammonia by photocatalytic nitrogen reduction reaction.

[0081] Example 8

[0082] To verify the PMo 12 The photocatalytic performance of @MIL-101(Fe) was tested under different conditions as follows: The photocatalytic experimental system consists of a xenon lamp light source (300W), a quartz photoreactor, a constant temperature circulation device and a vacuum filtration device. The specific operation is as follows: Accurately weigh 30mg of photocatalyst PMo 12@MIL-101(Fe) powder was mixed with 100mL ultrapure water in a quartz photoreactor and ultrasonically dispersed for 5 minutes to ensure uniform dispersion of the photocatalyst. For photocatalytic experiments in different atmospheres, the specified gas (high-purity N2, high-purity Ar and air (Air)) was introduced into the reaction system at a rate of 5sccm for 30 minutes, the constant temperature circulation system was started to maintain a constant temperature environment of 25°C, and the magnetic stirrer speed was set to 400r / min. The xenon lamp power supply was adjusted to a working current of 15A and positioned at a vertical distance of 10cm from the liquid surface for irradiation. After the reaction was completed, a vacuum filtration device (equipped with a 0.22μm water filter membrane) was used to achieve solid-liquid phase separation and product detection. For performance testing in a dark environment (Dark), the irradiation operation steps were omitted, and the remaining steps were the same as above. The results are as follows Figure 7 shown.

[0083] Depend on Figure 7 It can be seen that PMo 12 @MIL-101(Fe) No NH4 detected in dark conditions or argon atmosphere + The production of NH4 + The amount of NH4 generated increases linearly with the illumination time. + The cumulative production amounts were 177.11 μmol·g -1 cat ·h -1 and 150.89 μmol·g -1 cat ·h -1 , with performance in nitrogen higher than in air. This suggests that as nitrogen purity increases, its photocatalytic performance improves accordingly. Furthermore, it was confirmed that the photocatalyst can fix nitrogen in air, and that other small gas molecules do not affect its performance.

[0084] Example 9

[0085] To verify the H3PMo 12 O 40 The dosage of PMo 12 @MIL-101(Fe) photocatalytic performance was tested as follows:

[0086] First, prepare PMo 12 @MIL-101(Fe): The difference between the preparation process and Example 2 is that the H3PMo 12 O 40 The dosages were 250 mg and 100 mg respectively, and the others were the same as in Example 2.

[0087] Secondly, for different H3PMo 12 O 40The PMo obtained at the dosage of 12 The ammonia generation rate of @MIL-101(Fe) was tested, and the specific testing process was the same as in Example 5. The results are as follows: 12 O 40 When the dosage was 250 mg and 100 mg, respectively, the ammonia generation rate was 20.36 μmol·g -1 cat ·h -1 and 25.23 μmol·g -1 cat ·h -1 .

[0088] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0089] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A PMo 12 The preparation method of the modified MIL-101(Fe) composite material is characterized in that: The steps include: The iron source, terephthalic acid and Keggin type POM are mixed and reacted to obtain the PMo 12 Modified MIL-101(Fe) composites; The Keggin type POM is H3PMo 12 O 40 .

2. The preparation method according to claim 1, characterized in that The steps include: The iron source is dissolved in a solvent to obtain a mixed solution; the mixed solution, terephthalic acid and Keggin type POM are mixed and reacted to obtain the PMo 12 Modified MIL-101(Fe) composite materials.

3. The preparation method according to claim 2, characterized in that The solvent includes one or more of N,N-dimethylformamide, ethanol and water.

4. The preparation method according to claim 1 or 2, characterized in that The iron source includes one or more of ferric chloride, ferric nitrate and ferric sulfate.

5. The preparation method according to claim 1 or 2, characterized in that The usage ratio of the iron source, terephthalic acid and Keggin type POM is 4-6 mmol: 1-2 mmol: 150-200 mg.

6. The preparation method according to claim 1 or 2, characterized in that The reaction temperature is 100-120° C. and the reaction time is 20-24 hours.

7. The preparation method according to claim 1 or 2, characterized in that After the reaction is completed, the steps of washing and drying are further included.

8. PMo prepared by the preparation method according to any one of claims 1 to 7 12 Modified MIL-101(Fe) composite materials.

9. The PMo according to claim 8 12 Application of modified MIL-101(Fe) composite materials in the field of photocatalytic nitrogen fixation.

10. A method for improving the efficiency of nitrogen reduction reaction in synthesizing ammonia by photocatalytic nitrogen reduction reaction, characterized in that: The steps include: The PMo according to claim 8 12 The modified MIL-101(Fe) composite material was used as a catalyst for photocatalytic nitrogen reduction reaction to synthesize ammonia.

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