MIL metal organic framework photocatalyst as well as preparation method and application thereof

Abstract

The invention discloses an MIL metal organic framework photocatalyst and a preparation method and application thereof.The MIL metal organic framework photocatalyst comprises a metal organic framework material which is constructed by metal tungsten and organic ligands and is of a periodic three-dimensional network structure, and the organic ligands comprise at least one of 2-hydroxyterephthalic acid, 2, 3, 4-trimethyl-1, 3, 4-trimethyl-1, 3, 4-trimethyl-1, 3, 4-trimethyl-1, 3, 4-trimethyl-1, 3, 4-trimethyl-1, 3, 4-trimethyl-1, and 2, 5-dihydroxyterephthalic acid and 2-nitroterephthalic acid. The MIL metal organic framework photocatalyst disclosed by the invention has a relatively wide light absorption spectrum and relatively high catalytic efficiency.

Description

Technical Field

[0001] The present application relates to the technical field of metal-organic framework materials, and in particular to a MIL metal-organic framework photocatalyst and its preparation method and application. Background Art

[0002] As one of the important renewable energy sources, solar energy has broad application prospects. Among them, photocatalytic technology (such as carbon dioxide reduction, water decomposition, hydrogen peroxide synthesis, etc.) can significantly reduce the energy consumption of traditional industrial processes by directly using solar energy to drive chemical reactions, and generate clean energy or high-value-added chemicals, which has significant environmental and economic benefits. In recent years, titanium dioxide (TiO2) and graphitic carbon nitride (g-C3N4) have been widely studied for the photocatalytic synthesis of hydrogen peroxide (H2O2) due to their stable chemical properties and photoresponsive characteristics. However, these two types of materials have inherent defects: titanium dioxide has a large band gap and can only absorb ultraviolet light (accounting for 4% of the solar spectrum), resulting in low light utilization efficiency; although graphitic carbon nitride has visible light responsiveness, it has a high carrier recombination rate and limited reaction active sites, resulting in insufficient hydrogen peroxide yield and selectivity.

[0003] MIL (Materials of Institute Lavoisier) materials refer to a series of Metal-Organic Framework (MOF) materials developed by the Institut Lavoisier in France. These materials use transition metal ions as nodes and multidentate organic ligands as connecting units to form porous crystalline materials with regular pore structures through self-assembly. MOF materials have become a new direction in the design of photocatalysts due to their high specific surface area, tunable pore structure and abundant metal active centers. Among them, MOF materials containing tungsten (W) exhibit unique advantages: the 5d electron orbital of tungsten has excellent photoexcitation activity, which can broaden the light absorption range to the visible light region; the periodic structure formed by its metal center and organic ligand provides a high-density active site for the oxygen reduction reaction (ORR).

[0004] Therefore, MIL(W) materials have great potential as photocatalysts, and it is necessary to develop a MIL(W) material photocatalyst. Summary of the Invention

[0005] To overcome the deficiencies of the prior art, the present invention provides a MIL metal-organic framework photocatalyst and a preparation method and application thereof.

[0006] One aspect of the present application discloses a MIL metal-organic framework photocatalyst, which includes a metal-organic framework material with a periodic three-dimensional network structure constructed by metal tungsten and organic ligands, wherein the organic ligands include at least one of the following: 2-hydroxyterephthalic acid, 2,5-dihydroxyterephthalic acid and 2-nitroterephthalic acid.

[0007] In one implementation of the present application, the metal organic framework material has a hexa-coordinated [WO6] 6- Octahedral structure.

[0008] In one implementation of the present application, the metal organic framework material includes at least one of the following:

[0009] Wherein, each W is connected to 6 organic ligands.

[0010] Another aspect of the present application provides a method for preparing a MIL metal-organic framework photocatalyst, comprising: mixing a tungsten salt and an organic ligand, heating the temperature to a preset temperature according to a temperature rising program in an inert gas atmosphere, and maintaining the temperature at the preset temperature for a predetermined time to obtain a metal-organic framework material having a periodic three-dimensional network structure, wherein the MIL metal-organic framework photocatalyst includes the metal-organic framework material, wherein the organic ligand includes at least one of the following: 2-hydroxyterephthalic acid, 2,5-dihydroxyterephthalic acid and 2-nitroterephthalic acid.

[0011] In one implementation of the present application, the tungsten salt is tungsten hexachloride (WCl6).

[0012] In one implementation of the present application, the molar ratio of the tungsten salt to the organic ligand is 1:(3-6).

[0013] In one implementation of the present application, the molar ratio of the tungsten salt to the organic ligand is 1:3.5.

[0014] In one implementation of the present application, the preset temperature is 200-300°C.

[0015] In one implementation of the present application, the preset temperature is 250°C.

[0016] In one implementation of the present application, the temperature rising program is to increase the temperature at a rate of 2 to 6° C. / s.

[0017] In one implementation of the present application, the predetermined time is 10 to 15 hours.

[0018] Another aspect of the present application provides an application of a MIL metal-organic framework photocatalyst in a catalytic reaction, wherein the substrate is water and the product is hydrogen peroxide.

[0019] In one implementation of the present application, the catalytic reaction is driven by light and / or heat.

[0020] In one implementation of the present application, the wavelength of the light driven by the light is 400 to 675 nm.

[0021] The beneficial effects of this application are:

[0022] The MIL metal-organic framework photocatalyst of the present application uses W as the metal, which is beneficial for broadening the light absorption range to the visible light region and providing a high-density active site for the oxygen reduction reaction. In addition, the organic ligand includes at least one of 2-hydroxyterephthalic acid, 2,5-dihydroxyterephthalic acid, and 2-nitroterephthalic acid, which can make the organic ligand more easily combined with the tungsten salt and increase the W loading in the catalyst, thereby further enhancing oxygen adsorption and promoting photocatalytic efficiency, and can form a better [WO6] 6- Crystals can help enhance the absorption of visible light by the catalyst. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of the molecular structure of the MIL metal-organic framework material MIL-2OH-W involved in the embodiments of the present application.

[0024] Figure 2 This is an X-ray diffraction pattern of the MIL metal-organic framework material involved in the embodiment of the present application.

[0025] Figure 3 This is a transmission electron microscope image of the MIL metal-organic framework material involved in the embodiments of the present application.

[0026] Figure 4 This is a scanning electron microscope image of the MIL metal-organic framework material involved in the embodiments of the present application.

[0027] Figure 5 This is the energy dispersion spectrum of the MIL metal-organic framework material MIL-OH-W involved in the embodiments of the present application.

[0028] Figure 6 This is the energy dispersion spectrum of the MIL metal-organic framework material MIL-2OH-W involved in the embodiments of this application.

[0029] Figure 7 This is the energy dispersion spectrum of the MIL metal-organic framework material MIL-NO2-W involved in the embodiments of this application.

[0030] Figure 8 This is an X-ray photoelectron spectrum of the MIL metal-organic framework material involved in the embodiments of the present application.

[0031] Figure 9 This is a UV-visible spectrum of the MIL metal-organic framework material involved in the embodiments of the present application.

[0032] Figure 10 This is the in-situ infrared spectrum of the MIL metal-organic framework material involved in this application.

[0033] Figure 11 This is a diagram showing the electrochemical experimental results of the rotating disk electrode of the MIL metal-organic framework material involved in this application under room temperature and light conditions.

[0034] Figure 12 This is a diagram showing the electrochemical experimental results of the rotating disk electrode of the MIL metal-organic framework material involved in this application under ice water illumination conditions.

[0035] Figure 13 This is an efficiency diagram of the catalytic production of hydrogen peroxide by the MIL metal-organic framework material involved in this application.

[0036] Figure 14 This is an efficiency diagram of the MIL metal-organic framework material involved in this application for catalytic production of hydrogen peroxide under different temperature and light conditions.

[0037] Figure 15 This is a performance comparison chart of the MIL metal-organic framework material and other catalysts involved in this application. DETAILED DESCRIPTION

[0038] The present invention is further described in detail below by specific embodiments in conjunction with the accompanying drawings. In the following embodiments, many detailed descriptions are intended to enable the present application to be better understood. However, those skilled in the art can readily appreciate that some of the features may be omitted in different circumstances, or may be replaced by other materials or methods. In some cases, some operations related to the present application are not shown or described in the specification. This is to avoid the core of the present application being overwhelmed by excessive descriptions, and for those skilled in the art, it is not necessary to describe these related operations in detail. They can fully understand the related operations based on the description in the specification and the general technical knowledge in the art.

[0039] In addition, the features, operations, or characteristics described in the specification may be combined in any appropriate manner to form various embodiments. Furthermore, the steps or actions in the method description may be reordered or adjusted in a manner readily apparent to those skilled in the art. Therefore, the various sequences in the specification and drawings are provided solely for the purpose of clearly describing a particular embodiment and are not intended to be mandatory, unless otherwise specified.

[0040] The following table shows the terms used in this application:

[0041]

[0042]

[0043] Metal-organic frameworks (MOFs) possess active metal centers and an ordered crystal structure, making them promising photocatalysts. Tungsten (W)'s 5d electrons exhibit excellent reactivity and photoexcitation activity. Catalysts containing metallic tungsten are widely used in hydrogen evolution reactions, water splitting, wastewater treatment, photodetectors, and organic synthesis. MIL(W) materials hold great promise as photocatalysts. Further optimization of the catalyst's molecular structure, improvement of the oxygen reduction reaction (ORR) mechanism for hydrogen peroxide generation, and enhanced hydrogen peroxide generation efficiency could lead to further breakthroughs in catalyst performance.

[0044] In view of this, the present application creatively proposes a MIL metal-organic framework photocatalyst, its preparation method and application. The MIL metal-organic framework photocatalyst of the present application has a high hydrogen peroxide generation rate, and the hydroxyl groups in the organic ligands undergo reversible oxygen free radical structural transformation, which can provide additional hydrogen peroxide generation pathways and further improve the catalytic efficiency.

[0045] The MIL metal organic framework photocatalyst of this application has the following advantages: (1) a large amount of W element loaded on the catalyst; (2) high W 4,5+ The unsaturated coordination state has a strong affinity for oxygen and chemical adsorption; (3) the absorption of visible light is enhanced (TEM results show that 2-hydroxy / 2,5-dihydroxyterephthalic acid forms a better [WO6] 6- crystals, thereby enhancing their optical absorption); (4) additional reaction sites provided by the hydroxyl functional groups.

[0046] The present application provides a MIL metal-organic framework photocatalyst, which includes a metal-organic framework material.

[0047] In a specific embodiment, the metal organic framework material is a material having a periodic three-dimensional network structure constructed from metal tungsten (W) and organic ligands.

[0048] In one embodiment, the organic ligand includes at least one of 2-hydroxyterephthalic acid, 2,5-dihydroxyterephthalic acid, and 2-nitroterephthalic acid.

[0049] In one embodiment, the metal organic framework material has a hexa-coordinated [WO6] 6- Octahedral structure.

[0050] In one embodiment, the metal organic framework material comprises at least one of the following:

[0051]

[0052] Wherein, each W is connected to 6 organic ligands. MIL-OH-W, MIL-2OH-W and MIL-NO2-W are the names of the above three materials in this application.

[0053] Figure 1 Schematic diagram of the molecular structure of the MIL metal organic framework material MIL-2OH-W involved in the embodiment of this application. Figure 1 As shown, MIL-2OH-W has [WO6] 6- Octahedral structure, connected with organic ligands to form a three-dimensional MOF structure.

[0054] It should be noted that for organic ligands such as 2-hydroxyterephthalic acid or 2,5-dihydroxyterephthalic acid (MIL-OH-W or MIL-2OH-W), the organic ligand with a reducing functional group (-OH) on the benzene ring is easy to combine with tungsten salts (such as WCl6) and greatly increase the loading of W element. In addition, TEM images show that the tungsten-based metal-organic framework materials (MIL-OH-W and MIL-2OH-W) formed by 2-hydroxyterephthalic acid and 2,5-dihydroxyterephthalic acid have better [WO6] 6- crystals, thereby enhancing the absorption of the catalyst in the visible light band.

[0055] In a specific embodiment, in the MIL-OH-W material of the present application, the proportion of oxygen vacancies is 0% to 1%.

[0056] In a specific embodiment, the content of tungsten in the MIL-OH-W material of the present application is 50% to 70%.

[0057] In a specific embodiment, in the MIL-2OH-W material of the present application, the proportion of oxygen vacancies is 20% to 30%.

[0058] In a specific embodiment, the content of tungsten in the MIL-2OH-W material of the present application is 35% to 45%.

[0059] In a specific embodiment, in the MIL-OH-W material of the present application, the proportion of oxygen vacancies is 5% to 10%.

[0060] In a specific embodiment, the content of tungsten in the MIL-OH-W material of the present application is 1% to 3%.

[0061] It should be noted that MIL-OH-W and MIL-2OH-W can not only pass [WO6] 6- Oxygen vacancies in the lattice undergo a photocatalytic reaction to generate hydrogen peroxide (pathway one), and an additional hydrogen peroxide generation pathway (pathway two) can also be driven by the hydroxyl groups on the benzene ring, and this path two can be driven by both light and heat. MIL-OH-W does not have a photothermal synergistic catalytic effect, while MIL-2OH-W has a significant photothermal synergistic catalytic effect.

[0062] The present application also provides a method for preparing a MIL metal-organic framework photocatalyst, comprising: mixing a tungsten salt and an organic ligand, heating the temperature to a preset temperature according to a temperature rising program in an inert gas atmosphere, and maintaining the temperature at the preset temperature for a predetermined time to obtain a metal-organic framework material having a periodic three-dimensional network structure. The MIL metal-organic framework photocatalyst comprises the metal-organic framework material.

[0063] In a specific embodiment, the organic ligand includes at least one of the following: 2-hydroxyterephthalic acid, 2,5-dihydroxyterephthalic acid, and 2-nitroterephthalic acid.

[0064] In one embodiment, the tungsten salt is tungsten hexachloride, and the preparation method involves a dehydrochlorination reaction.

[0065] In a specific embodiment, the molar ratio of the tungsten salt to the organic ligand is 1:(3-6). For example, the molar ratio of the tungsten salt to the organic ligand can be 1:3, 1:4, 1:5 or 1:6.

[0066] In a specific embodiment, the preset temperature is 200-300° C. For example, the preset temperature may be 200° C., 210° C., 220° C., 230° C., 240° C., 250° C., 260° C., 270° C., 280° C., 290° C., or 300° C.

[0067] In one embodiment, the temperature is raised at a rate of 2 to 6° C. / min. For example, the temperature may be raised at a rate of 2° C. / min, 3° C. / min, 4° C. / min, 5° C. / min, or 6° C. / min.

[0068] In a specific embodiment, the predetermined time is 10 to 15 hours. For example, the predetermined time can be 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, or 15 hours.

[0069] The present application also provides an application of a MIL metal-organic framework photocatalyst or a metal-organic framework material in a catalytic reaction.

[0070] In one embodiment, in the catalytic reaction, the substrate is water and the product is hydrogen peroxide.

[0071] In one embodiment, the catalytic reaction is driven by light and / or heat. In other words, the catalytic reaction can be driven by light, heat, or a combination of light and heat.

[0072] In a specific embodiment, the light driven by the optical method is visible light, and the wavelength of the visible light ranges from 380 nm to 740 nm.

[0073] In a specific embodiment, the wavelength of the light driven by the light may be 400-675 nm.

[0074] In a specific embodiment, the light driven by the light is white light, for example, a light source generated by the sun, an incandescent lamp, a white light LED, etc.

[0075] In a specific embodiment, the light power can be 80-150 mW / cm 2 For example, the illumination power can be 80mW / cm 2 , 100mW / cm 2 , 120mW / cm 2 or 150mW / cm 2 .

[0076] In a specific embodiment, the catalytic reaction conditions for MIL-OH-W may include the following: illumination and a temperature of 0-50°C (preferably 0°C), and no illumination and a temperature of 30-50°C (preferably 40°C). It should be noted that MIL-OH-W can be driven by light or heat, but illumination and temperature increase do not have a synergistic effect.

[0077] In a specific embodiment, the catalytic reaction conditions for MIL-2OH-W may include the following: illumination and a temperature of 0-50°C (preferably 40°C), and no illumination and a temperature of 30-50°C (preferably 40°C). It should be noted that MIL-2OH-W can be driven by light or heat, and illumination and temperature increase can synergistically improve its catalytic efficiency.

[0078] In a specific embodiment, the catalytic reaction conditions of MIL-NO2-W can be: light irradiation and a temperature of 0-50° C. (preferably room temperature, i.e., 25° C.) It should be noted that MIL-NO2-W can only be driven by light.

[0079] The present invention is further described in detail below by means of specific examples. The following examples are only provided to further illustrate the present invention and should not be construed as limiting the present invention. In the present examples, unless otherwise specified, the reagents and instruments used are all commercially available, and the experimental procedures are all carried out in accordance with the product instructions or conventional experimental specifications.

[0080] Example

[0081] 1. Preparation of MIL Metal-Organic Framework Materials

[0082] The tube furnace was evacuated using a vacuum pump, and argon was slowly introduced at a gas flow rate of 50 sccm. Tungsten hexachloride (WCl6) was mixed with different organic ligands (2-hydroxyterephthalic acid / 2,5-dihydroxyterephthalic acid / 2-nitroterephthalic acid) at a molar ratio of 1:3.5 (600 mg:964 / 1049 / 1118 mg). Under an argon atmosphere, the temperature was raised to 250°C within one hour for dehydrochlorination reaction. The temperature was then maintained for 12 hours and naturally cooled to room temperature to obtain three final products, each with the following structural formulas. In this example, these three products are named MIL-OH-W, MIL-2OH-W, and MIL-NO2-W:

[0083]

[0084] Among them, each W (tungsten) atom is surrounded by 6 O (oxygen) atoms, forming an octahedral structure. Each W is connected to six organic ligands (2-hydroxyterephthalic acid / 2,5-dihydroxyterephthalic acid / 2-nitroterephthalic acid). The structure continues to extend outward and finally forms a three-dimensional MOF structure.

[0085] 2. Structural characterization of catalysts:

[0086] The three materials prepared above, MIL-OH-W, MIL-2OH-W and MIL-NO2-W, and the materials recovered after the photocatalytic reaction of these three materials were detected by X-ray diffraction (XRD). Figure 2 This is the X-ray diffraction pattern of the MIL metal organic framework material involved in the embodiment of this application, where the peaks marked by squares are the planes composed of tungsten atoms, and the peaks marked by triangles are the planes composed of oxygen atoms. The XRD peaks confirm that the three catalysts have hexa-coordinated [WO6] 6- Octahedral structure. MIL-2OH-W exhibits four distinct lattice peaks, while MIL-OH-W and MIL-NO2-W exhibit slightly weaker peaks. Samples recovered after the photocatalytic reaction exhibit photostability, with no significant changes in lattice peaks.

[0087] The three materials prepared above, MIL-OH-W, MIL-2OH-W and MIL-NO2-W, were observed by transmission electron microscopy (TEM). Figure 3 This is a transmission electron micrograph of the MIL metal-organic framework material used in the examples of this application. Crystal plane analysis further confirms the [WO6]6-octahedral structure. Two crystal planes were observed for both MIL-OH-W and MIL-2OH-W, while only one was observed for MIL-NO2-W. The (-1,1,2) and (2,-2,0) crystal planes were clearly visible for the MIL-2OH-W catalyst, while only the (2,-2,0) crystal plane was observed for the MIL-NO2-W catalyst. This is likely due to the low W loading on MIL-NO2-W (see EDS results) and the irregular structure.

[0088] The three materials prepared above, MIL-OH-W, MIL-2OH-W and MIL-NO2-W, and the materials recovered after the photocatalytic reaction of these three materials were observed by scanning electron microscopy (SEM). Figure 4 This is a scanning electron microscope image of the MIL metal-organic framework material involved in the embodiment of the present application, showing that the catalyst particle size is about micron-level, and there is no obvious change in the microscopic morphology of the material before and after the photocatalytic reaction.

[0089] The element distribution of the three materials prepared above - MIL-OH-W, MIL-2OH-W and MIL-NO2-W - was analyzed by energy dispersive spectroscopy (EDS). Figure 5 This is the energy dispersion spectrum of the MIL metal organic framework material MIL-OH-W involved in the embodiment of this application, Figure 6 This is the energy dispersion spectrum of the MIL metal organic framework material MIL-2OH-W involved in the embodiment of this application, Figure 7 This is the energy dispersion spectrum of the MIL metal-organic framework material MIL-NO2-W involved in the embodiments of the present application. It shows that MIL-OH-W contains 59.18wt% tungsten, MIL-2OH-W contains 38.69%wt tungsten, and MIL-NO2-W contains 1.48%wt tungsten. W is evenly distributed in the catalyst particles, and most of the chlorine is removed through the dehydrochlorination reaction, so the W element is able to form new chemical bonds with the O on the organic ligand. A high proportion of W element loading can greatly increase the number of photocatalytic reaction centers, thereby improving the efficiency of hydrogen peroxide generation.

[0090] The spectra of the three materials prepared above, MIL-OH-W, MIL-2OH-W and MIL-NO2-W, were analyzed by X-ray photoelectron spectroscopy (XPS). Figure 8This is the X-ray photoelectron spectrum of the MIL metal organic framework material involved in the embodiment of this application. The WO bond peak of O1s XPS in the figure proves the successful combination of metal tungsten and organic ligands; at the same time, the number of -OH in the molecule of each catalyst is calculated by CO, OH, and C=O peaks (deconvolution peak area): 0.714 in MIL-OH-W, indicating that the oxygen vacancy content is extremely low, close to 0; 2.48 in MIL-2OH-W, and the oxygen vacancy ratio is about 24%; 0.1758 in MIL-NO2-W, and the oxygen vacancy ratio is about 8.79%. High W 4,5+ The unsaturated coordination state enhances the chemical adsorption of oxygen, and its strong affinity for oxygen further promotes the ORR (redox reaction) required to produce hydrogen peroxide. In addition, the XPS spectrum of the catalyst collected after the reaction showed that the catalyst structure had not changed significantly.

[0091] 3. Catalyst Performance Characterization

[0092] Absorption wavelength analysis of catalyst:

[0093] The absorption spectra of 2-hydroxyterephthalic acid, 2,5-dihydroxyterephthalic acid, 2-nitroterephthalic acid, MIL-OH-W, MIL-2OH-W and MIL-NO2-W were analyzed by UV-visible spectroscopy. Figure 9 The UV-visible spectra of the MIL metal-organic framework materials involved in the examples of this application show that the three catalysts have certain absorption in the visible wavelength range, which is beneficial to enhancing the photochemical reaction performance of the catalysts.

[0094] Analysis of catalytic mechanism of catalyst:

[0095] The three materials prepared above, MIL-OH-W, MIL-2OH-W and MIL-NO2-W, were analyzed by in situ FTIR spectroscopy in water (H2O) and deuterated water (D20), respectively. Figure 10This is the in situ infrared spectrum of the MIL metal-organic framework material involved in this application. The FTIR absorption peak of the deuterium-containing functional group is approximately 400-500 wavenumbers smaller than the H absorption peak. Two reaction sites were observed: ① at the WO site, involving the formation of O=CO---(H); and ② at the –OH site on the benzene ring, where the –OH is oxidized by O2 to form an oxygen radical (–O·) and then reduced back to –OH by H2O. The negative peak at approximately 1100 represents the shedding of the –OH on the benzene ring; the positive peaks at approximately 1150 (in H2O) and approximately 671.12 (in D2O) represent the formation of O=CO---(H); and the positive peaks at approximately 610 and 620 represent the newly formed -OD on the benzene ring. The unstable peak at approximately 1200 is caused by the hydrolysis of O=COC=O, generating a new CO bond. It is the strongest in MIL-NO2-W because it is primarily composed of organic ligands. Peaks at approximately 1200 can also be observed in MIL-OH-W and MIL-2OH-W, but they are much smaller and disappear as the reaction ends.

[0096] The three materials prepared above - MIL-OH-W, MIL-2OH-W and MIL-NO2-W - were analyzed by rotating disk electrode (RDE) electrochemical experiments. The RDE experiment was divided into two parts, namely room temperature lighting conditions and ice water lighting conditions. Figure 11 This is a diagram showing the electrochemical experimental results of the rotating disk electrode of the MIL metal organic framework material involved in this application under room temperature and light conditions. Figure 12 This is the result of the rotating disk electrode electrochemical experiment of the MIL metal organic framework material involved in this application under ice water illumination conditions. The electron transfer number of MIL-OH-W is between 3 and 4 at room temperature and 0°C, and the selectivity deteriorates again after cooling and removing some hydroxyl conversion pathways. The electron transfer number of MIL-2OH-W is extremely low at room temperature, between 1 and 2, which is caused by the good synergistic catalysis of light (two electron transfer) and heat (single electron transfer). After cooling and removing some hydroxyl conversion pathways, the electron transfer number is around 2, that is, most of the reaction is around [WO6] 6- The center's two-electron photocatalytic process, it is worth noting that this does not mean that its hydrogen peroxide generation selectivity is close to 100%, because the photoinduced hydroxyl conversion process on the benzene ring can still occur under 0 ° C light conditions, and the n value appears around 2 is the result of a small amount of 4-electron transfer (oxygen to water) and a small amount of single-electron transfer balance.

[0097] The above results show that the catalyst can be used to 6- The oxygen vacancies in the lattice undergo photocatalytic reaction to generate hydrogen peroxide, and an additional hydrogen peroxide generation pathway can also be carried out through the hydroxyl groups on the benzene ring (except for MIL-NO2-W which does not contain hydroxyl groups on the benzene ring), and this pathway can be driven by light / heat at the same time.

[0098] Analysis of catalytic performance of catalyst:

[0099] a) The three materials prepared above were added as catalysts into a 50 mL round-bottom flask. 50 mg of the catalyst was dissolved in 7.5 mL of deionized water. 2 The reaction was carried out using magnetic stirring under white light irradiation. The effective wavelength range of white light was 400-675 nm. 1 mL of the reaction solution was taken after 10 min, 20 min, 30 min, and 1 h of reaction, and the concentration of hydrogen peroxide was titrated with 0.01 mol / L potassium permanganate solution. Figure 13 This is a graph showing the efficiency of the MIL metal-organic framework materials involved in this application for catalytic production of hydrogen peroxide. The results show that under room temperature, air, neutral pH, and light conditions, 50 mg of MIL-OH-W, MIL-2OH-W, or MIL-NO2-W catalysts in 7.5 mL of deionized water can produce hydrogen peroxide at rates of 405,000, 1,500,000, and 750,000 μmol·h, respectively. -1 ·g -1 ·L -1 MIL-NO2-W produced a high amount of hydrogen peroxide in the first 10 minutes but subsequently decomposed rapidly. This was likely due to the strong oxidizing functional group -NO2, which decomposed hydrogen peroxide. Furthermore, compared to the catalyst MIL(W) (described in patent CN118480185A), the catalyst in this application exhibited significantly improved catalytic efficiency.

[0100] b) The catalytic performance of the catalyst was studied under different light / temperature conditions.

[0101] The two hydrogen peroxide production pathways were analyzed under different light / temperature conditions to evaluate the effects of light / heat on the two catalytic pathways. Figure 14This is a graph showing the efficiency of the MIL metal-organic framework (MOF) material involved in this application for catalytic production of hydrogen peroxide under different temperatures and illumination conditions, with the vertical axis representing the amount of hydrogen peroxide in the reaction solution. By comparing the hydrogen peroxide production of two catalysts containing -OH groups on the benzene ring (MIL-OH-W and MIL-2OH-W) in the dark with that of MIL-NO2-W, which does not contain -OH groups, it was found that the pathway for the conversion of hydroxyl groups on the benzene ring to hydrogen peroxide increased with increasing temperature. By comparing the hydrogen peroxide production at different temperatures under illumination, the authors evaluated whether the three catalysts exhibited synergistic photothermal catalysis. The results showed that the photothermal catalysis of MIL-OH-W was not synergistic, likely due to its lack of oxygen vacancies. When heated and illuminated, the W metal center did not absorb a large amount of oxygen, but instead accumulated hydrogen peroxide for decomposition. In contrast, the photothermal catalysis of MIL-2OH-W was highly synergistic. MIL-NO2-W lacks additional hydroxyl groups on its benzene ring, while the nitro group has strong oxidizing properties, which promotes the decomposition of hydrogen peroxide under illumination and elevated temperatures.

[0102] c) comparing the catalytic performance of other hydrogen peroxide catalysts in existing research with the catalyst of the present application, Figure 15 This is a performance comparison chart of the MIL metal organic framework material and other catalysts involved in this application. The vertical axis QE refers to quantum efficiency. Where n(H2O2) is the amount of hydrogen peroxide, ф is the photon flux of the light source, and T is the reaction time. The results show that the catalyst of the present application has outstanding performance compared with other hydrogen peroxide photocatalysts.

[0103] The above content is a further detailed description of the present application in conjunction with specific implementation methods, and the specific implementation of the present application cannot be considered to be limited to these descriptions. For ordinary technicians in the technical field to which the present application belongs, several simple deductions or substitutions can be made without departing from the concept of the present application.

Claims

1. A MIL metal-organic framework photocatalyst, characterized in that: The MIL metal-organic framework photocatalyst includes a metal-organic framework material having a periodic three-dimensional network structure constructed by metal tungsten and organic ligands, wherein the organic ligands include at least one of the following: 2-hydroxyterephthalic acid, 2,5-dihydroxyterephthalic acid and 2-nitroterephthalic acid.

2. The MIL metal-organic framework photocatalyst according to claim 1, characterized in that: The metal organic framework material has a hexa-coordinated [WO6] 6- Octahedral structure.

3. The MIL metal-organic framework photocatalyst according to claim 1 or 2, characterized in that: The metal organic framework material includes at least one of the following: Wherein, each W is connected to 6 organic ligands.

4. A method for preparing a MIL metal-organic framework photocatalyst, characterized in that: include: A tungsten salt and an organic ligand are mixed, the temperature is raised to a preset temperature according to a temperature rising program in an inert gas atmosphere, and the temperature is maintained at the preset temperature for a predetermined time to obtain a metal organic framework material having a periodic three-dimensional network structure. The MIL metal organic framework photocatalyst includes the metal organic framework material, wherein the organic ligand includes at least one of the following: 2-hydroxyterephthalic acid, 2,5-dihydroxyterephthalic acid and 2-nitroterephthalic acid.

5. The preparation method according to claim 4, characterized in that The tungsten salt is tungsten hexachloride.

6. The preparation method according to claim 4, characterized in that The molar ratio of the tungsten salt to the organic ligand is 1:(3-6); Preferably, the molar ratio of the tungsten salt to the organic ligand is 1:3.

5.

7. The preparation method according to claim 4, characterized in that The preset temperature is 200-300°C; Preferably, the preset temperature is 250°C; Preferably, the temperature rising program is to increase the temperature at a rate of 2 to 6°C / min.

8. The preparation method according to claim 4, characterized in that The predetermined time is 10 to 15 hours.

9. Use of the metal organic framework material according to any one of claims 1 to 3 in a catalytic reaction, characterized in that: In the catalytic reaction, the substrate is water and the product is hydrogen peroxide.

10. The use according to claim 9, characterized in that The catalytic reaction is driven by light and / or heat; Preferably, the wavelength of the light driven by the light is 400-675 nm.

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