Heterojunction material, preparation method thereof and application of heterojunction material in photocatalytic reduction of CO2 to generate C2H4

Abstract

The invention discloses a heterojunction material, a preparation method of the heterojunction material and application of the heterojunction material in photocatalytic reduction of CO2 to generate C2H4. The heterojunction material comprises titanium dioxide and a metal organic framework material, wherein M metal nanoparticles are loaded on the surface of the metal organic framework material; in the heterojunction material, the loading capacity of the titanium dioxide is 20%-70%. The M / TiO2 / MFU-41 heterojunction material disclosed by the invention, as a photocatalyst, shows excellent catalytic performance in the aspect of reducing CO2 into C2H4 through photocatalysis, can be used for remarkably improving the photocatalytic activity and the selectivity of producing ethylene, and shows good stability in multiple cycles.

Description

Technical Field

[0001] The present invention relates to the technical field of photocatalytic materials, and particularly relates to a heterojunction material, a preparation method thereof, and an application thereof in photocatalytic reduction of CO2 to produce C2H4. Background Art

[0002] Photocatalytic technology with mild reaction conditions is considered a green and effective method for solving energy and environmental problems because it aims to maximize the utilization of solar energy. In particular, photocatalytic reduction of carbon dioxide driven by solar energy to produce high-value chemicals such as CO, CH4, CH3OH, C2H6, and C2H4 is considered the best way to reduce the content of atmospheric CO2. Among them, ethylene, as the basic raw material of polyolefins, is the most worthy option to be developed. However, compared with C1 products such as CO, photocatalytic reduction of CO2 to produce C2+ products such as ethylene not only requires overcoming a larger energy barrier to form C-C bonds, but also requires oxidative desaturation of C-C single bonds to form C=C double bonds. Currently, there is still a lack of well-established photocatalytic materials.

[0003] Among various photocatalytic materials, the design of heterojunction materials is mainly to broaden the absorption of the solar spectrum and improve the utilization efficiency of solar energy. However, the disadvantage of this method is that it must sacrifice the redox energy efficiency of the catalyst, reduce the reduction potential of the conduction band, weaken the oxidation ability of the valence band, and mainly obtain single-carbon products. To solve this problem, depositing a few percent of metal nanoparticles on heterogeneous catalysts can generate high-energy "hot electrons" through the local surface plasmon resonance effect (LSPR), which is an effective means to convert CO2 into multi-carbon products. This method can use visible light irradiation without reducing the redox potential of the photocatalyst. In addition, TiO2, as a classic inorganic semiconductor, can be used to couple with metal-organic framework materials (MOF) to form a composite catalyst to improve the photocatalytic reduction activity of CO2. Therefore, how to construct a heterojunction material to achieve highly active and highly selective photocatalytic reduction of CO2 to produce ethylene is of great significance. Summary of the Invention

[0004] To solve the above technical problems, the technical solution of the present invention is as follows:

[0005] A heterojunction material, wherein the heterojunction material comprises titanium dioxide and a metal-organic framework material, and M metal nanoparticles are further loaded on the surface of the metal-organic framework material.

[0006] According to an embodiment of the present invention, in the heterojunction material, the loading amount of titanium dioxide is 20%-70%, preferably 30-60 wt%, and further preferably 40-60 wt%.

[0007] According to an embodiment of the present invention, the metal-organic framework material is selected from at least one of MFU-4l and UiO-66.

[0008] According to an embodiment of the present invention, the MFU-4l has a cubic crystal structure.

[0009] According to an embodiment of the present invention, the MFU-4l includes a transition metal and a ligand, the transition metal is located at the tetrahedral coordination and center, and the transition metals at the tetrahedral coordination and center are connected by the ligand.

[0010] According to an embodiment of the present invention, the transition metal ions with tetrahedral coordination in the MFU-4l are selected from at least one of Zn, Cu, and Ni, for example, Zn.

[0011] According to an embodiment of the present invention, in the MFU-4l, the ligand is selected from organic ligands. Preferably, the organic ligand is selected from bis(1H-1,2,3-triazole[4,5-b],[4′,5′-i])dibenzo[1,4]dioxin (H2BTDD).

[0012] According to an embodiment of the present invention, when the transition metal in the MFU-4l is Zn / or Cu, it is denoted as M-MFU-4l. Exemplarily, when the transition metal in the MFU-4l is Zn, it is denoted as Zn-MFU-4l, wherein 4 Zn(II) ions are tetrahedrally coordinated by three triazole-based linkers and one Cl ion, and 1 central Zn(II) ion is coordinated by six linkers. According to an embodiment of the present invention, the M metal in the M metal nanoparticles is selected from at least one of Au, Pt, and Cu.

[0013] According to an embodiment of the present invention, in the heterojunction material, the loading amount of the M metal nanoparticles is 1-15 wt%, preferably 3-10 wt%, and further preferably 5-8 wt%.

[0014] According to an embodiment of the present invention, the diameter of the metal nanoparticles is 10-100 nm, preferably the diameter is 30-80 nm, for example, 60 nm.

[0015] According to a preferred embodiment of the present invention, the heterojunction material includes MFU-4l with a cubic structure, the surface of which is covered with TiO2 particles (for example, TiO2 particles with a diameter of 25 nm) and M metal nanoparticles, and the heterojunction material is denoted as M / TiO2 / MFU-4l; further, the M metal nanoparticles are loaded between the edge of the MFU-4l and TiO2.

[0016] The present invention also provides a preparation method of the above heterojunction material, and the preparation method includes the following steps:

[0017] (1) Dissolve a transition metal salt and an organic ligand in a solvent, add titanium dioxide to obtain a mixed solution, and obtain a composite precursor after a hydrothermal reaction at a constant temperature.

[0018] (2) Mix the composite precursor obtained in step (1) with an M metal salt, and react under light to obtain the heterojunction material.

[0019] According to an embodiment of the present invention, the transition metal salt in step (1) is at least one of soluble zinc salts, copper salts, and nickel salts. Preferably, the zinc salt is, for example, one or several of zinc chloride, zinc iodide, and zinc bromide, such as zinc chloride. Preferably, the copper salt is, for example, copper chloride. Preferably, the nickel salt is, for example, nickel chloride.

[0020] According to an embodiment of the present invention, the organic ligand in step (1) is selected from bis(1H-1,2,3-triazole[4,5-b],[4′,5′-i])dibenzo[1,4]dioxin (H2BTDD).

[0021] According to an embodiment of the present invention, the solvent in step (1) can be at least one of N,N-dimethylacetamide and N-N-dimethylformamide, such as N-N-dimethylformamide.

[0022] According to an embodiment of the present invention, the concentration of the transition metal salt in the mixed solution in step (1) is 10-30 g / L, such as 15 g / L.

[0023] According to an embodiment of the present invention, the concentration of the organic ligand in the mixed solution in step (1) is 1-3 g / L, such as 1.5 g / L.

[0024] According to an embodiment of the present invention, the concentration of titanium dioxide in the mixed solution in step (1) is 0.5-5 g / L, such as 2.5 g / L.

[0025] According to an embodiment of the present invention, in step (1), after obtaining the mixed solution, it can also be ultrasonically treated and stirred, for example, stirred for 1-2 h.

[0026] According to an embodiment of the present invention, the conditions of the hydrothermal reaction at a constant temperature in step (1) include: the reaction temperature is 120-160°C, such as 140°C; the reaction time is 16-20 h, such as 18 h.

[0027] According to an embodiment of the present invention, after obtaining the composite precursor through the hydrothermal reaction at a constant temperature in step (1), the composite precursor can also be subjected to centrifugal washing and / or vacuum drying. Preferably, the washing solvent used for centrifugal washing can be a solvent known in the art, such as N-N-dimethylformamide, methanol, and dichloromethane respectively, and the number of washing times is at least 3 times.

[0028] Preferably, during centrifugal washing, centrifugal conditions known in the art can be selected. For example, the centrifugal speed is 5000 - 10000 r / min, such as 8000 r / min, and the centrifugal time is at least 10 min.

[0029] Preferably, the conditions for the vacuum drying include: the temperature for vacuum drying is 60 - 120 °C, such as 80 °C; the drying time is at least 10 h, such as 12 h.

[0030] According to an embodiment of the present invention, in step (2), mixing means dispersing the composite precursor in an aqueous solution containing a sacrificial agent and an M metal salt, and performing ultrasonic treatment and / or stirring; for example, ultrasonic treatment for at least 20 min and stirring for at least 30 min.

[0031] According to an embodiment of the present invention, the sacrificial agent in step (2) is selected from at least one or several of triethylamine, triethanolamine, and methanol, such as triethylamine.

[0032] According to an embodiment of the present invention, in the M metal salt in step (2), M is selected from at least one of gold, copper, and platinum.

[0033] Preferably, the M metal salt in step (2) is selected from at least one of chloroauric acid, copper chloride, and potassium tetrachloroplatinate.

[0034] According to an embodiment of the present invention, the volume fraction of the sacrificial agent in the aqueous solution in step (2) is 0.01 - 0.10%, such as 0.02%.

[0035] According to an embodiment of the present invention, in the aqueous solution in step (2), the concentration of the M metal salt is 2.0 - 15 g / L, such as 10 g / L.

[0036] According to an embodiment of the present invention, in step (2), after mixing, degassing can also be performed, such as using the bubbling method for degassing. Exemplarily, the bubbling method for degassing includes: introducing an inert gas using the bubbling method to remove air, and the aeration time is, for example, 0.2 - 1.0 h.

[0037] According to an embodiment of the present invention, the light intensity of the light irradiation in step (2) is 0.2 - 0.6 w / cm 2 ,such as 0.3 w / cm 2 。

[0038] According to an embodiment of the present invention, the reaction time under light in step (2) is 0.5 - 2 h, for example, 1 h.

[0039] According to an embodiment of the present invention, the reaction under light in step (2) is carried out under stirring conditions.

[0040] According to an embodiment of the present invention, after obtaining the heterojunction material by the reaction under light in step (2), the heterojunction material can be centrifugally washed and / or vacuum dried.

[0041] Preferably, during centrifugal washing, centrifugation conditions known in the art can be selected. For example, the centrifugation speed is 5000 - 10000 r / min, for example, 8000 r / min; the centrifugation time is at least 10 min.

[0042] Preferably, the drying conditions in step (2) include: the drying temperature is 60 - 120 °C, for example, 80 °C; the drying time is at least 10 h, for example, 12 h.

[0043] The present invention also provides the application of the above-mentioned heterojunction material in photocatalysis.

[0044] The present invention also provides a photocatalyst, and the photocatalyst includes the above-mentioned heterojunction material.

[0045] The present invention also provides the application of the above-mentioned heterojunction material and / or photocatalyst in photocatalysis, preferably for the application in reducing carbon dioxide to produce ethylene.

[0046] The present invention also provides a method for reducing carbon dioxide to ethylene, and the method includes the following steps: dispersing the above-mentioned photocatalyst in a solution containing a sacrificial agent, introducing carbon dioxide, and performing a catalytic reduction reaction under light irradiation to obtain ethylene.

[0047] According to an embodiment of the present invention, the concentration of the photocatalyst in the reaction system is 0.1 - 1 g / L, for example, 0.25 g / L.

[0048] According to an embodiment of the present invention, the solution containing a sacrificial agent includes a sacrificial agent and water, wherein the volume ratio of the sacrificial agent to water is 0.01 - 1:1 - 20, for example, 0.1:20.

[0049] According to an embodiment of the present invention, the sacrificial agent is selected from at least one or several of triethylamine, triethanolamine, and ascorbic acid, for example, triethylamine.

[0050] According to an embodiment of the present invention, in the reaction system, the mass-volume ratio of the photocatalyst to the sacrificial agent is 0.1 - 10 mg:0.01 - 1 mL, for example, 5 mg:0.1 mL.

[0051] According to an embodiment of the present invention, the catalytic reduction reaction is carried out in a photoreactor, such as a light-transmitting reactor.

[0052] According to an embodiment of the present invention, the method of introducing carbon dioxide can be selected from methods known in the art, such as introducing carbon dioxide gas using the bubbling method.

[0053] According to an embodiment of the present invention, the time for introducing carbon dioxide is not specifically limited and can be carried out according to the needs of the catalytic reduction reaction, for example, 0.2 - 1.0 h.

[0054] According to an embodiment of the present invention, the conditions of light irradiation include: the light intensity is 0.1 - 2 w / cm 2 , for example, 0.5 w / cm 2 ; the light irradiation time is at least 0.1 h, for example, more than 1 h.

[0055] According to an embodiment of the present invention, the photocatalyst can reduce carbon dioxide to ethylene under light irradiation, and the yield of ethylene generated is greater than 20 μmol / g / h, for example, 107 μmol / g / h.

[0056] According to an embodiment of the present invention, the selectivity of the heterojunction photocatalyst for photocatalytic reduction of CO2 to ethylene is not less than 30%, for example, 40%, 50%, 60%, 70%, 80%, 90%.

[0057] According to an embodiment of the present invention, the light irradiation can be sunlight or xenon lamp.

[0058] Beneficial effects

[0059] 1) By combining the metal-organic framework MFU-4l and the metal-organic semiconductor TiO2 and further loading metal nanoparticles, the obtained M / TiO2 / MFU-4l heterojunction material can be used as a photocatalyst, which improves the utilization rate of solar energy and enhances the redox ability of the heterojunction material, thus facilitating the hole-dominated oxidation elimination reaction and enabling the conversion of saturated C-C intermediates into C═C bond products.

[0060] 2) The heterojunction photocatalyst of the present invention shows opposite binding abilities to CO and C2H4. The binding ability of the photocatalyst surface to CO is strong, and the binding ability to C2H4 is weak, which is very beneficial for stabilizing the intermediate CO and the surface desorption product C2H4.

[0061] 3) The M / TiO2 / MFU-4l heterojunction material of the present invention exhibits excellent catalytic performance as a photocatalyst in photocatalytic reduction of CO2 to C2H4, can significantly improve the photocatalytic activity and the selectivity for ethylene production, and shows good stability in multiple cycles.

[0062] 4) The preparation method of the photocatalyst of the present invention is simple and easy to operate. Description of the Drawings

[0063] Figure 1 It is the transmission electron microscope image and the corresponding elemental mapping image of Au / TiO2 / MFU-4l prepared in Example 1;

[0064] Figure 2 It is the X-ray diffraction pattern of the catalysts prepared in Example 1 and Comparative Examples 1 and 2;

[0065] Figure 3 It is the performance test chart of photocatalytic reduction of carbon dioxide by different photocatalysts in Application Example 1;

[0066] Figure 4 It is the performance test chart of photocatalytic reduction of carbon dioxide by different photocatalysts in Application Examples 2-6; wherein, a) is Application Example 4; b) is Application Example 2; c) is Application Example 3, d) is Application Example 5, e) is Application Example 6.

[0067] Figure 5 It is the cyclic stability test chart of the Au / TiO2 / MFU-4l photocatalyst prepared in Example 1 for photocatalytic reduction of carbon dioxide. Detailed Embodiments

[0068] The technical solutions of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are only for illustrative explanation of the present invention and should not be construed as limiting the protection scope of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0069] Unless otherwise specified, the raw materials and reagents used in the following embodiments are all commercially available products or can be prepared by known methods.

[0070] Example 1

[0071] A preparation method of a heterojunction photocatalyst Au / TiO2 / MFU-4l is as follows:

[0072] (1) Weigh 1 g of ZnCl2 and 100 mg of H2BTDD and disperse them in 60 mL of N,N-dimethylformamide. Stir ultrasonically for 30 min to make them disperse evenly. Then add 150 mg of TiO2 and stir ultrasonically for 30 min. Transfer the resulting mixed solution to a 100 mL stainless steel autoclave with a PTFE liner and heat it at 140 °C for 18 h. After the reaction is completed, cool it naturally to room temperature, centrifuge to collect the precipitate, and wash it 3 times with N,N-dimethylformamide, methanol, and dichloromethane respectively. Then dry the washed solid under vacuum at 80 °C overnight to obtain 55% TiO2 / MFU-4l, which is usually referred to as TiO2 / MFU-4l.

[0073] (2) Disperse 50 mg of TiO2 / MFU-4l in 200 μL of triethylamine and 50 mL of water. Subsequently, add 10 mg of HAuCl4 to the suspension and ultrasonically treat it for 10 min to make it disperse evenly. Then degas the reaction mixture with argon for 30 min to remove oxygen. Then irradiate the suspension solution under a light intensity of 0.3 W / cm 2 for 60 min. Finally, wash the obtained sample with deionized water and dry it in a vacuum oven at 80 °C for 24 h to obtain the Au / TiO2 / MFU-4l photocatalyst, where the Au content is 8%, the TiO2 content is 55%, and the rest is MFU-4l.

[0074] Example 2

[0075] The preparation method of the photocatalyst Au / TiO2 / Cu-MFU-4l in this example is as follows:

[0076] (1) Weigh 1 g of ZnCl2 and 100 mg of H2BTDD and disperse them in 60 mL of N,N-dimethylformamide. Stir ultrasonically for 30 min to make them disperse evenly. Then add 150 mg of TiO2 and stir ultrasonically for 30 min. Transfer the resulting mixed solution to a 100 mL stainless steel autoclave with a PTFE liner and heat it at 140 °C for 18 h. After the reaction is completed, cool it naturally to room temperature, centrifuge to collect the precipitate, and wash it 3 times with N,N-dimethylformamide, methanol, and dichloromethane respectively. Then dry the washed solid under vacuum at 80 °C overnight to obtain TiO2 / MFU-4l.

[0077] 8.15 mmol of copper chloride and 0.2 g of TiO₂ / MFU-4l were dissolved in 35 ml of N-N-dimethylformamide, and the mixture was ultrasonically stirred for 30 min, and then the reaction mixture was heated at 60 °C for 20 h. Subsequently, fresh N-N-dimethylformamide was used to exchange with the N-N-dimethylformamide in the reactants, then 5.6 mmol of copper chloride was added and heated at 60 °C for 20 h. The precipitate was collected by centrifugation and washed 3 times with N-N-dimethylformamide, methanol and dichloromethane respectively. Then the solid was dried under vacuum at 80 °C overnight to obtain TiO₂ / Cu-MFU-4l.

[0078] (2) Other conditions were the same as in step (2) of Example 1, except that: TiO₂ / MFU-4l in step (2) of Example 1 was replaced with TiO₂ / Cu-MFU-4l obtained in the above step (1) to obtain an Au / TiO₂ / Cu-MFU-4l photocatalyst, wherein the Au content was 8%, the TiO₂ content was 55%, and the rest was Cu-MFU-4l.

[0079] Example 3

[0080] The preparation method of the photocatalyst in this example was basically the same as that in Example 1, except that:

[0081] The addition amount of TiO₂ in step (1) of Example 1, which was 150 mg, was replaced with 100 mg, and other conditions remained unchanged, to obtain an Au / 45%TiO₂ / MFU-4l photocatalyst, wherein the Au content was 8%, the TiO₂ content was 45%, and the rest was MFU-4l.

[0082] Example 4

[0083] The preparation method of the photocatalyst in this example was basically the same as that in Example 1, except that:

[0084] The addition amount of TiO₂ in step (1) of Example 1, which was 150 mg, was replaced with 200 mg, and other conditions remained unchanged, to prepare an Au / 62.5%TiO₂ / MFU-4l photocatalyst, wherein the Au content was 8%, the TiO₂ content was 62.5%, and the rest was MFU-4l.

[0085] Example 5

[0086] The preparation method of the photocatalyst in this example was basically the same as that in Example 1, except that:

[0087] The addition amount of HAuCl₄ in step (2) of Example 1, which was 10 mg, was replaced with 15 mg, and other conditions remained unchanged, to obtain a 12%Au / TiO₂ / MFU-4l photocatalyst, wherein the Au content was 12%, the TiO₂ content was 55%, and the rest was MFU-4l.

[0088] Example 6

[0089] The preparation method of the photocatalyst in this example is basically the same as that in Example 1, except that:

[0090] Replace HAuCl4 in step (2) of Example 1 with CuCl2·6H2O, and keep other conditions unchanged. The Cu / TiO2 / MFU-4l photocatalyst is prepared, in which the Cu content is 8%, the TiO2 content is 55%, and the rest is MFU-4l.

[0091] Comparative Example 1

[0092] Preparation of MFU-4l:

[0093] Weigh 1 g of ZnCl2 and 100 mg of H2BTDD, disperse them in 60 mL of N-N-dimethylformamide, and stir ultrasonically for 30 min to make them evenly dispersed. Transfer the obtained mixed solution to a 100 mL stainless steel autoclave with a polytetrafluoroethylene inner liner, and heat it at 140 °C for 18 h. After the reaction is completed, cool it naturally to room temperature, centrifuge to collect the precipitate, and wash it 3 times with N-N-dimethylformamide, methanol, and dichloromethane respectively. Then dry the washed solid under vacuum at 80 °C overnight to obtain the catalyst MFU-4l.

[0094] Comparative Example 2

[0095] Preparation of the catalyst TiO2 / MFU-4l

[0096] The preparation method of TiO2 / MFU-4l is the same as step (1) in Example 1. In the catalyst TiO2 / MFU-4l, the TiO2 content is 55%, and the rest is MFU-4l.

[0097] Application Example 1

[0098] Photocatalytic carbon dioxide reduction performance test:

[0099] Take 5 mg of the photocatalysts prepared in Example 1 and Comparative Examples 1 and 2 and TiO2 respectively, add 100 μL of triethylamine and 20 mL of water, stir ultrasonically for 10 min to make them evenly dispersed, and then degas the reaction mixture with pure CO2 gas for 30 min to remove oxygen. Then, irradiate the reaction mixture with a simulated solar spectrum light source with a light intensity of 0.3 w / cm 2 and stir to carry out the catalytic reduction reaction. At the same time, maintain the reaction temperature at 25 °C through a circulating water cooler. During the catalytic reaction, take 1 mL of the gaseous product in the reactors of different reaction mixtures respectively, and monitor the products by gas chromatography equipped with FID and TCD detectors.

[0100] Figure 3 Performance test diagrams of photocatalytic carbon dioxide reduction for different photocatalysts. Among them, less carbon dioxide reduction products are generated using Comparative Examples 1, 2 and the TiO2 photocatalyst. However, the heterojunction photocatalyst prepared in Example 1 exhibits excellent C2H4 generation performance, with a C2H4 generation rate of 107.0 μmol / g / h and a selectivity as high as 91.5%.

[0101] Figure 5 It is a test diagram of the cyclic stability of the Au / TiO2 / MFU-4l photocatalyst prepared in Example 1 for photoreducing carbon dioxide. After five cycles, the heterojunction photocatalyst still exhibits good photocatalytic activity, indicating that the prepared heterojunction material has good stability.

[0102] Application Example 2

[0103] The photocatalytic carbon dioxide reduction reaction in this application example is basically the same as that in Application Example 1, except that Au / TiO2 / Cu-MFU-4l of Example 2 is used.

[0104] As Figure 4 shown in b) therein, the ethylene yield obtained by the reaction of Au / TiO2 / Cu-MFU-4l is 38 μmol / g / h at this time, which may be caused by the lack of tetrahedrally coordinated Zn sites in the MFU-4l framework.

[0105] Application Example 3

[0106] The photocatalytic carbon dioxide reduction reaction in this application example is basically the same as that in Application Example 1, except that Cu / TiO2 / MFU-4l of Example 6 is used. As Figure 4 shown in c) therein, after replacing Au nanoparticles with Cu nanoparticles, the ethylene yield is 30 μmol / g / h, indicating that Au in the heterojunction photocatalyst affects the catalytic performance of the photocatalyst.

[0107] Application Example 4

[0108] The photocatalytic carbon dioxide reduction reaction in this application example is basically the same as that in Application Example 1, except that the sacrificial reagent triethylamine in Application Example 1 is replaced with triethanolamine or ascorbic acid. As Figure 4 shown in a) therein, when using other sacrificial agents, a high ethylene selectivity is still achieved.

[0109] Application Example 5

[0110] The photocatalytic carbon dioxide reduction reaction in this application example is basically the same as that in Application Example 1, except that the Au / 45% TiO2 / MFU-4l photocatalyst and Au / 62.5% TiO2 / MFU-4l photocatalyst of Examples 3 and 4 are used respectively. As Figure 4As shown in d), the TiO2 content in the photocatalyst affects the catalytic performance of the photocatalyst.

[0111] Application Example 6

[0112] The photocatalytic carbon dioxide reduction reaction in this application example is basically the same as that in Application Example 1, except that the 12% Au / TiO2 / MFU-4l photocatalyst of Example 5 is used respectively. As Figure 4 shown in e), the Au content in the photocatalyst also affects the catalytic performance of the photocatalyst, but has a relatively small effect on the ethylene selectivity.

[0113] Comparative Application Example 1

[0114] The photocatalytic carbon dioxide reduction reaction in this comparative application example is basically the same as that in Application Example 1, except that blank experiments are carried out under the conditions of introducing argon, without light irradiation, and without adding a catalyst. At this time, no carbon dioxide reduction product is generated.

[0115] The above describes the exemplary embodiments of the present invention. However, the protection scope of this application is not limited to the above embodiments. Any modifications, equivalent replacements, improvements, etc. made by those skilled in the art within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A heterojunction material, characterized in that: The heterojunction material comprises titanium dioxide and a metal organic framework material, and the surface of the metal organic framework material is also loaded with M metal nanoparticles; In the heterojunction material, the loading amount of titanium dioxide is 20%-70%.

2. The heterojunction material according to claim 1, characterized in that: The metal organic framework material is selected from at least one of MFU-41 and UiO-66; And / or, in the heterojunction material, the loading amount of the M metal nanoparticles is 1-15wt%; And / or, the diameter of the metal nanoparticles is 10-100 nm.

3. The method for preparing the heterojunction material according to claim 1 or 2, characterized in that: The preparation method comprises the following steps: (1) dissolving a transition metal salt and an organic ligand in a solvent, adding titanium dioxide to obtain a mixed solution, and subjecting the mixed solution to a constant temperature hydrothermal reaction to obtain a composite precursor; (2) Mixing the composite precursor obtained in step (1) with the M metal salt, and reacting them under light to obtain the heterojunction material.

4. The preparation method according to claim 3, characterized in that: The transition metal salt in step (1) is at least one of a soluble zinc salt, a copper salt and a nickel salt; and / or, the organic ligand in step (1) is selected from bis(1H-1,2,3-triazole[4,5-B],-[4′,5′-I])dibenzo[1,4]dioxin; And / or, the solvent in step (1) is at least one of N,N-dimethylacetamide and NN-dimethylformamide; And / or, the concentration of the transition metal salt in the mixed solution in step (1) is 10-30 g / L; And / or, the concentration of the organic ligand in the mixed solution in step (1) is 1-3 g / L; And / or, the concentration of titanium dioxide in the mixed solution in step (1) is 0.5-5 g / L; And / or, the conditions of the constant temperature hydrothermal reaction in step (1) include: reaction temperature of 120-160° C.; reaction time of 16-20 h.

5. The preparation method according to claim 3, characterized in that: In step (2), mixing refers to dispersing the composite precursor in an aqueous solution containing a sacrificial agent and an M metal salt, and ultrasonicating and / or stirring; And / or, the sacrificial agent in step (2) is selected from at least one of triethylamine, triethanolamine and methanol; And / or, in the M metal salt in step (2), M is selected from at least one of gold, copper and platinum; And / or, the volume fraction of the sacrificial agent in the aqueous solution in step (2) is 0.01-0.10%; And / or, in the aqueous solution in step (2), the concentration of the M metal salt is 2.0-15 g / L; And / or, in step (2), degassing may be performed after mixing.

6. The preparation method according to claim 3, characterized in that: The light intensity of the illumination in step (2) is 0.2-0.6w / cm 2 ; And / or, the reaction time under illumination in step (2) is 0.5 to 2 h; And / or, the reaction under illumination in step (2) is carried out under stirring conditions.

7. Use of the heterojunction material according to claim 1 or 2 in photocatalysis.

8. A photocatalyst, comprising the heterojunction material according to claim 1 or 2.

9. Use of the heterojunction material according to claim 1 or 2 and / or the photocatalyst according to claim 8 in photocatalysis.

10. A method for reducing carbon dioxide to ethylene, characterized in that: The method comprises the following steps: dispersing the photocatalyst according to claim 8 in a solution containing a sacrificial agent, introducing carbon dioxide, and then performing a catalytic reduction reaction under light irradiation to obtain ethylene.

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