Oxygen-resistant floatable two-dimensional heterojunction device for photocatalytic carbon dioxide reduction and water purification

Abstract

The invention discloses an oxygen-resistant floatable two-dimensional heterojunction device for photocatalytic carbon dioxide reduction and water purification, which ingeniously integrates photocatalytic carbon dioxide reduction and water purification functions and can float stably. In-MOF nanosheets grow in situ on single-layer graphene oxide by adopting a dynamic regulation and control strategy, and the heterostructure is integrated with a polytetrafluoroethylene membrane by virtue of a suction filtration method, so that the prepared carbon dioxide adsorbent has high adsorption preference on carbon dioxide, and therefore, the carbon dioxide adsorbent shows excellent reduction performance in a low-concentration carbon dioxide environment. Experimental results show that in a simulated combustion waste gas environment, the generation rate of carbon monoxide reaches up to 762.5 [mu] mol g <-1 > h <-1 >, and excellent stability and efficiency are highlighted. Meanwhile, the device can remove pollutants in a real water body, high-efficiency coupling of water quality purification and carbon dioxide conversion is realized, and the application value of the device is greatly expanded.

Description

Technical Field

[0001] The present invention belongs to the field of photocatalytic carbon dioxide reduction, and relates to an oxygen-resistant and floatable two-dimensional heterojunction device for photocatalytic carbon dioxide reduction and water purification, and specifically relates to a two-dimensional heterojunction photocatalyst and a preparation method thereof, and an oxygen-resistant and floatable two-dimensional heterojunction device constructed based on the catalyst, and the application of the device in photocatalytic carbon dioxide reduction and water purification. Background Art

[0002] In recent years, with the continuous increase in the concentration of carbon dioxide in the atmosphere, its significant impact on the environment and climate has become the focus of global attention. Among them, the combustion of fossil fuels, as the main source of carbon dioxide emissions, contributes almost 90% of the total emissions, which is particularly concerning. Photocatalytic carbon dioxide reduction, as a method of directly converting carbon dioxide into fuels and chemicals using solar energy, provides a very promising path to alleviate the problem of carbon dioxide emissions. However, current research on photocatalytic carbon dioxide reduction (CO2RR) is mostly focused on the treatment of high-concentration carbon dioxide gas, which usually involves additional, energy-intensive carbon dioxide capture and concentration steps, rather than directly targeting natural emission sources, such as complex mixtures such as combustion exhaust containing about 12-14% carbon dioxide and 3-5% oxygen. At present, there are two major challenges in the direct use of combustion exhaust for photocatalytic carbon dioxide reduction conversion: one is its relatively low carbon dioxide concentration, and the other is the presence of oxygen. Under the condition of coexistence of oxygen, the competition between the oxygen reduction reaction (ORR) and the carbon dioxide reduction reaction is particularly fierce. Since ORR is more thermodynamically favorable, it seriously restricts the effective implementation of CO2RR. In order to overcome the above-mentioned technical difficulties, especially how to efficiently promote carbon dioxide reduction in an aerobic environment while inhibiting oxygen reduction reactions has become the key to promoting technological innovation in this field.

[0003] On the other hand, compared with thermal catalysis and electrocatalysis, photocatalysis has shown significant advantages, especially in terms of simplicity and flexibility. Photocatalysis directly uses sunlight as a driving force, eliminating the reliance on external complex energy supply and transportation pipelines. This feature also gives photocatalytic reaction devices unparalleled flexibility, allowing them to be easily deployed in various geographical locations and spatial environments without limitation. Summary of the invention

[0004] In order to improve the above technical problems, the present invention provides an innovative two-dimensional heterojunction device, which cleverly integrates the photocatalytic carbon dioxide reduction and water purification functions and can float stably.

[0005] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is as follows:

[0006] An In-MOF / GO material comprises graphene oxide (GO) and an indium-based metal-organic framework In-MOF (Indium-Based Metal-Organic Framework) grown on the graphene oxide (GO).

[0007] According to an embodiment of the present invention, in the In-MOF / GO material, the mass percentage of In-MOF is 10-20%, and exemplary ones are 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19% or 20%.

[0008] According to an embodiment of the present invention, the In-MOF is a nanosheet structure, specifically, the average thickness thereof is 0.5 to 1 nm, exemplified by 0.5 nm, 0.6 nm, 0.7 nm, 0.8 nm, 0.9 nm or 1 nm.

[0009] According to an embodiment of the present invention, the In-MOF forms a face-to-face arrangement on GO. Preferably, C, N, O, and In elements are uniformly dispersed on In-MOF / GO.

[0010] According to an embodiment of the present invention, the graphene oxide (GO) is a single-layer structure. Preferably, the graphene oxide (GO) has a thickness of 1 to 5 nm, exemplified by 1 nm, 2 nm, 3 nm, 3.5 nm, 3.8 nm, 4.0 nm or 5.0 nm.

[0011] The present invention also provides a method for preparing the above-mentioned In-MOF / GO material, comprising growing an indium salt precursor and an organic ligand on graphene oxide (GO) through an in-situ reaction.

[0012] According to an embodiment of the present invention, the reaction mass ratio of the indium salt precursor, the organic ligand, and graphene oxide (GO) is 1:(0.5-2):(2-50), exemplified by 1:1:40, 1:1:20, 1:1:13, 1:1:10 or 1:1:6.7.

[0013] According to an embodiment of the present invention, the indium salt precursor, the organic ligand, and the graphene oxide (GO) are all added to the reaction system in the form of a solution. For example, the indium salt precursor solution, the organic ligand solution, and the graphene oxide (GO) dispersion are prepared respectively, and then the indium salt precursor solution and the organic ligand solution are added to the graphene oxide (GO) dispersion at the same time. Preferably, the indium salt precursor solution and the organic ligand solution are added to the graphene oxide (GO) dispersion at the same time through a dual-channel injection pump. For example, the injection speed of the indium salt precursor solution and the organic ligand solution is, for example, 0.1 to 0.5 mL / h, exemplified by 0.1 mL / h, 0.15 mL / h, 0.2 mL / h, 0.25 mL / h, 0.3 mL / h, 0.4 mL / h, or 0.5 mL / h.

[0014] In one embodiment of the present invention, the concentration of the indium salt precursor solution is 0.1-1 mg / mL, exemplified by 0.1 mg / mL, 0.2 mg / mL, 0.3 mg / mL, 0.4 mg / mL, 0.5 mg / mL, 0.6 mg / mL, 0.7 mg / mL, 0.8 mg / mL, 0.9 mg / mL or 1 mg / mL.

[0015] In one embodiment of the present invention, the concentration of the organic ligand solution is 0.1-1 mg / mL, exemplified by 0.1 mg / mL, 0.2 mg / mL, 0.3 mg / mL, 0.4 mg / mL, 0.5 mg / mL, 0.6 mg / mL, 0.7 mg / mL, 0.8 mg / mL, 0.9 mg / mL or 1 mg / mL.

[0016] In one embodiment of the present invention, the concentration of the graphene oxide (GO) dispersion is 0.1-1 mg / mL, exemplified by 0.1 mg / mL, 0.2 mg / mL, 0.3 mg / mL, 0.4 mg / mL, 0.5 mg / mL, 0.6 mg / mL, 0.7 mg / mL, 0.8 mg / mL, 0.9 mg / mL or 1 mg / mL.

[0017] In one embodiment of the present invention, the solvent used to prepare the indium salt precursor solution, the organic ligand solution and the graphene oxide (GO) dispersion is, for example, one or two of DMF and ethanol; preferably, when the solvent is a composite of two solvents, the volume ratio of the two is 1:(0.5-10); exemplarily 1:3.

[0018] According to an embodiment of the present invention, the indium salt precursor is one or both of indium chloride and indium nitrate.

[0019] According to an embodiment of the present invention, the organic ligand is tetrakis(4-carboxyphenyl)porphyrin (TCPP).

[0020] According to an embodiment of the present invention, the temperature of the in-situ reaction is 80-100°C, exemplarily 90°C; the time of the in-situ reaction is 0-6h, exemplarily 0h, 1h, 2h, 3h, 4h, 6h.

[0021] According to an embodiment of the present invention, the preparation method further comprises a process of performing solid-liquid separation on the reaction system to obtain a reaction product after the reaction is completed. For example, the solid-liquid separation can be performed by means known in the art, such as centrifugation.

[0022] According to an embodiment of the present invention, the preparation method further comprises washing the reaction product obtained by solid-liquid separation. For example, the solvent used for the washing may be ethanol. For another example, the washing may be performed once, twice or more times, preferably three times.

[0023] According to an embodiment of the present invention, the preparation method further comprises drying the washed reaction product. For example, the drying temperature is 60-90° C., exemplarily 60° C. Further, the drying time is 12-24 hours, exemplarily 12 hours.

[0024] The present invention also provides a floatable two-dimensional heterojunction device, which contains the above-mentioned In-MOF / GO material and / or is prepared from the above-mentioned In-MOF / GO material.

[0025] According to an embodiment of the present invention, the floatable two-dimensional heterojunction device further comprises a substrate, on which the above-mentioned In-MOF / GO material is modified.

[0026] According to an embodiment of the present invention, the substrate is, for example, selected from polytetrafluoroethylene membranes (PTFE).

[0027] The present invention also provides a method for preparing the above-mentioned floatable two-dimensional heterojunction device, comprising modifying a solution containing the above-mentioned In-MOF / GO material on a substrate by a suction filtration method.

[0028] According to an embodiment of the present invention, the concentration of the solution containing the above-mentioned In-MOF / GO material is 0.1 to 1 mg / mL, exemplified by 0.1 mg / mL, 0.2 mg / mL, 0.3 mg / mL, 0.4 mg / mL, 0.5 mg / mL, 0.6 mg / mL, 0.7 mg / mL, 0.8 mg / mL, 0.9 mg / mL or 1 mg / mL.

[0029] According to an embodiment of the present invention, the solvent of the solution containing the In-MOF / GO material is, for example, ethanol.

[0030] According to an embodiment of the present invention, the preparation method further comprises drying the substrate modified with the In-MOF / GO material. For example, the drying temperature is 40 to 80°C, and exemplarily 60°C.

[0031] The present invention also provides a photocatalytic system, which contains the above-mentioned In-MOF / GO material and / or the above-mentioned floatable two-dimensional heterojunction device.

[0032] The present invention also provides the use of the above-mentioned In-MOF / GO material and / or the above-mentioned floatable two-dimensional heterojunction device and / or the above-mentioned photocatalytic system in photocatalytic reduction of carbon dioxide and / or water purification.

[0033] According to an embodiment of the present invention, the carbon dioxide comes from a natural emission source, such as a complex mixture of combustion exhaust gas containing about 12-14% carbon dioxide by volume and about 3-5% oxygen by volume.

[0034] The present invention also provides a method for photocatalytic carbon dioxide reduction and water purification, comprising using carbon dioxide as a raw material, the above-mentioned In-MOF / GO material and / or the above-mentioned floatable two-dimensional heterojunction device as a catalyst, and water as a reducing agent, and causing carbon dioxide reduction and water oxidation reactions under light conditions.

[0035] Beneficial effects of the present invention:

[0036] The present invention provides a two-dimensional heterojunction device, which contains the In-MOF / GO material of the present invention and / or is prepared from the In-MOF / GO material of the present invention. The device cleverly integrates the photocatalytic carbon dioxide reduction and water purification functions and can float stably.

[0037] The present invention adopts a kinetic control strategy to in-situ grow In-MOF (specifically a nanosheet structure) on a single layer of graphene oxide (GO) to construct a high-performance two-dimensional heterojunction structure. Subsequently, this heterojunction structure is integrated with a polytetrafluoroethylene membrane (PTFE) by a filtration method to create a unique floating device.

[0038] The device of the present invention has a high degree of adsorption selectivity for carbon dioxide, and thus exhibits excellent reduction performance in a low-concentration carbon dioxide environment. Experimental results show that in a simulated combustion exhaust gas environment (containing 10% carbon dioxide, 20% oxygen and 70% argon), its carbon monoxide generation rate can be as high as 762.5 μmol g -1 h -1, the rate is only reduced by 5% compared with the oxygen-free environment, which highlights its excellent stability and efficiency. More importantly, the device effectively produces hydrogen peroxide while driving the water oxidation reaction, thereby achieving efficient coupling of water purification and carbon dioxide conversion, greatly expanding its application value.

[0039] In addition, when the two-dimensional heterojunction In-MOF / GO of the present invention is used as a catalyst, it is not only chemically stable and cost-effective, but also has easily accessible raw materials. It provides an economically feasible and easy-to-promote strategy for developing carbon dioxide conversion photocatalytic systems suitable for open environments, and is therefore expected to trigger new changes in the field of sustainable energy and environmental protection technologies.

[0040] The present invention attaches In-MOF / GO material as a catalyst to a polytetrafluoroethylene membrane to obtain a device that can float freely on the open water surface, thereby effectively promoting energy conversion processes such as water decomposition and CO2 reduction reaction, and creating a new model of energy conversion on water.

[0041] The design of the present invention greatly enhances the freedom of facility layout, reduces the demand for valuable land resources, and opens up new possibilities for combining water purification with energy production, marking a promising step forward for photocatalytic technology. It provides a new way to implement photocatalytic CO2 reduction reactions in open environments, such as photocatalytic conversion of low-concentration carbon dioxide such as atmospheric air or combustion exhaust. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 a, b, c, d, e, f, and g are schematic diagrams of the preparation process of the In-MOF / GO two-dimensional heterojunction photocatalyst of the present invention and TEM images corresponding to different growth times (0h, 1h, 2h, 3h, 4h, and 6h) of In-MOF on a single layer of graphene oxide (GO);

[0043] Figure 2 It is the powder X-ray diffraction pattern corresponding to different growth times (0h, 1h, 2h, 3h, 4h, 6h) of the In-MOF / GO two-dimensional heterojunction photocatalyst in the present invention;

[0044] Figure 3 It is a high-angle annular dark field image of the In-MOF / GO two-dimensional heterojunction photocatalyst prepared when the growth time is 4 hours in the present invention and the corresponding element distribution map;

[0045] Figure 4 It is a photocatalytic performance diagram of the In-MOF / GO-PTFE two-dimensional heterojunction device as a photocatalyst in the present invention and a comparison diagram compared with other conditions;

[0046] Figure 5It is a comparison diagram of the photocatalytic performance of the In-MOF / GO-PTFE two-dimensional heterojunction device of the present invention as a photocatalyst in the presence of different proportions of oxygen in the environment;

[0047] Figure 6 a and b are respectively a comparison diagram of the In-MOF / GO-PTFE two-dimensional heterojunction device of the present invention as a photocatalyst to produce hydrogen peroxide under different oxygen ratios and its influence on the chemical oxygen demand (COD) in natural water bodies;

[0048] Figure 7 a and b are the photocatalytic performance diagram of the In-MOF / GO-PTFE two-dimensional heterojunction device as a photocatalyst for 5 cycles and the powder X-ray diffraction diagram before and after the cycle in the present invention, respectively;

[0049] Figure 8 a and b are TEM images of the In-MOF / GO-PTFE two-dimensional heterojunction device as a photocatalyst before and after 5 cycles in the present invention, respectively;

[0050] Fig. 9 It is a schematic diagram of the principle of the In-MOF / GO-PTFE two-dimensional heterojunction device of the present invention as a photocatalyst for chemical oxygen demand (COD) in natural water. DETAILED DESCRIPTION

[0051] The technical scheme of the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only exemplary descriptions and explanations of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are included in the scope that the present invention is intended to protect.

[0052] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0053] Example 1

[0054] A method for preparing a floatable two-dimensional heterojunction device comprises the following steps:

[0055] (1) The catalyst In-MOF / GO was synthesized according to the following steps. The specific method is as follows:

[0056] Solutions A and B were prepared first for further use. Solution A: 1 mg In(NO3)3 was dissolved in a mixed solvent of 2 mL DMF / ethanol (V:V=3:1). Solution B: 1 mg tetrakis(4-carboxyphenyl)porphyrin (TCPP) was dissolved in a mixed solvent of 2 mL DMF / ethanol (V:V=3:1). Then, 5 mg GO (monolayer, purchased from Beijing Bailingwei Technology Co., Ltd.) was dispersed in a 25 mL three-necked flask containing a mixed solvent of 10 mL DMF / ethanol (V:V=3:1) by ultrasonic treatment at 40 KHz for 2 minutes. After that, the bottle was covered with a lid, placed in an oil bath, and preheated at 90 ° C for 10 min. Next, a dual-channel syringe pump was used to inject solution A and solution B into the three-necked flask at a rate of 0.25 mL / h. The whole process was stirred, the temperature was maintained at 90°C, and the growth time was 0h, 1h, 2h, 3h, 4h, and 6h (it should be noted that growth 0h means that solution A and solution B were not injected, 1h means that 0.25mL of solution A and solution B were injected, 2h means that 0.5mL of solution A and solution B were injected, 3h means that 0.75mL of solution A and solution B were injected, 4h means that 1mL of solution A and solution B were injected, and 6h means that 1.5mL of solution A and solution B were injected). After the reaction was completed, the product was collected by centrifugation at 8000 rpm for 2min and washed three times with ethanol. Finally, the product was dried under vacuum at 60°C for 12h to obtain In-MOF / GO.

[0057] (2) Weigh 2 mg of the catalyst In-MOF / GO prepared in step (1), disperse it in 10 mL of ethanol, and then filter it onto a polytetrafluoroethylene membrane (PTFE) with a diameter of 3.5 cm, and then dry it at 60° C. to obtain a floating two-dimensional heterojunction device (In-MOF / GO-PTFE).

[0058] Comparative Example 1

[0059] The preparation method of In-MOF is as follows: tetrakis(4-carboxyphenyl)porphyrin (TCPP) (50 mg, 0.07 mmol), In(NO3)3 (46.5 mg, 0.149 mmol) and hexadecyltrimethylammonium bromide (CTAB) (200 mg) are dispersed in deionized water (3.15 mL). The obtained suspension is ultrasonicated at 40 KHz for 10 min at room temperature, then transferred to a 25 mL reactor and heated at 120 ° C for 16 hours. After cooling to room temperature, the product is collected by centrifugation at 8000 rpm for 5 min, then washed twice with N, N-dimethylformamide (DMF) (2×20 mL), washed twice with acetone (2×20 mL), and finally, dried under vacuum conditions at 80 ° C to obtain solid In-MOF.

[0060] Preparation method of a floatable two-dimensional heterojunction device: Weigh 2 mg of In-MOF, disperse it in 10 mL of ethanol, then filter it onto a polytetrafluoroethylene membrane (PTFE) with a diameter of 3.5 cm, and then dry it at 60°C to obtain a floatable two-dimensional heterojunction device (In-MOF-PTFE).

[0061] Comparative Example 2

[0062] The preparation method of In-MOF / GO-ex-situ is as follows: 1 mg of In-MOF prepared in Comparative Example 1 is dispersed in a mixed solution of 2 mL of DMF / ethanol (V:V=3:1). Then 5 mg of graphene oxide (monolayer) is dispersed in a 25 mL three-necked flask containing a mixed solvent of 10 mL of DMF / ethanol (V:V=3:1). Then, the bottle is sealed and preheated at 90°C in an oil bath for 10 min. Under stirring conditions, 1 mL of In-MOF dispersion is injected at a rate of 0.25 mL / h using a single-channel syringe pump. When the reaction is completed, the product is collected by a centrifuge and washed three times with ethanol. Finally, the product is dried under vacuum at 60°C for 12 h to obtain In-MOF / GO-ex-situ.

[0063] Preparation method of a floatable two-dimensional heterojunction device: Weigh 2 mg of In-MOF / GO-ex-situ, disperse it in 10 mL of ethanol, then filter it onto a polytetrafluoroethylene membrane (PTFE) with a diameter of 3.5 cm, and then dry it at 60°C to obtain a floatable two-dimensional heterojunction device (In-MOF / GO-ex-situ-PTFE).

[0064] Comparative Example 3

[0065] Preparation method of floating two-dimensional heterojunction device: 2 mg GO (single layer, purchased from Beijing Bailingwei Technology Co., Ltd.) was weighed and dispersed in 10 mL ethanol, then filtered onto a polytetrafluoroethylene membrane (PTFE) with a diameter of 3.5 cm, and then dried at 60°C to obtain a floating two-dimensional heterojunction device (GO-PTFE).

[0066] 1. Morphology and structure of In-MOF / GO two-dimensional heterojunction photocatalyst.

[0067] The morphology of In-MOF / GO obtained by different growth times (0h, 1h, 2h, 3h, 4h, 6h) of In-MOF on a single layer of graphene oxide (GO) was observed using a HT7700 transmission electron microscope. The results are as follows: Figure 1 As shown in bg in the figure, it was found that In-MOF grew in situ on a monolayer of graphene oxide (GO), and as the growth time increased, In-MOF grew from the initial nucleus into nanosheets, forming a 2D / 2D heterostructure.

[0068] In order to determine the structure of In-MOF / GO, an X-ray diffractometer from Rigaku, Japan, was used for analysis, wherein the X-ray was a Cu target Kα voltage of 40 kV, a current of 100 mA, a step size of 0.2°, and a scanning range of 5° to 50°. The X-ray diffraction patterns of the In-MOF / GO two-dimensional heterojunction photocatalyst obtained at different growth times (0 h, 1 h, 2 h, 3 h, 4 h, 6 h) are shown in Figure 2. Figure 2 As shown. The results show that in the first 2 hours of in-situ growth, since only small In-MOF nuclei were observed on the graphene oxide sheet, there was no new diffraction peak in the XRD spectrum. As the growth time increased, flaky In-MOF appeared on the monolayer graphene oxide (GO), and its characteristic diffraction peak peak was 7.5°, which was attributed to the (021) crystal plane of In-MOF, thus further verifying the successful synthesis of the In-MOF / GO two-dimensional heterojunction photocatalyst.

[0069] 2. The high-angle annular dark field image of In-MOF / GO prepared with a growth time of 4 h and the corresponding element distribution were further measured using a JEOL JEM-F200 microscope at an accelerating voltage of 200 kV. The results are as follows: Figure 3 As shown. The results show that In-MOF forms a face-to-face arrangement on GO, and C, N, O, and In elements are evenly dispersed on In-MOF / GO, which further proves the synthesis of In-MOF / GO two-dimensional heterojunction photocatalyst.

[0070] At 300mw / cm 2 Under full illumination, deionized water and a mixed gas with a volume fraction of 10% carbon dioxide, 20% oxygen and 70% nitrogen were used as reactants for the reactions on both sides, respectively. The photocatalytic performance was tested in a 167mL reactor at normal pressure and room temperature. The floating two-dimensional heterojunction device (In-MOF / GO-PTFE) prepared in Example 1 with a growth time of 4h, the In-MOF-PTFE prepared in Comparative Example 1, the In-MOF / GO-ex-situ-PTFE prepared in Comparative Example 2, and the GO-PTFE prepared in Comparative Example 3 were placed at the bottom of the reactor, and 20mL of water was added thereto to cover the bottom layer of the reactor. Subsequently, a mixed gas with a volume fraction of 10% carbon dioxide, 20% oxygen and 70% argon was introduced thereto for 30 minutes, followed by illumination. The gas phase products were detected using FID and TCD detectors, and the liquid phase products were detected using UV-visible spectroscopy. The results are as follows: Figure 4As shown in Figure 2, In-MOF / GO-PTFE exhibited a significant catalytic advantage compared with other control groups (In-MOF-PTFE, GO-PTFE, and In-MOF / GO-ex-situ-PTFE), with a CO yield of 762.5 μmol g -1 h -1 The selectivity is almost 100%. The CO yield of In-MOF / GO-PTFE is 20.3 and 32.9 times higher than that of In-MOF-PTFE or GO-PTFE, respectively. Compared with the ex situ synthesized In-MOF / GO-ex-situ-PTFE (whose CO yield is 35.2 μmol g -1 h -1 , the selectivity is almost 100%), and the performance also has great advantages, which shows that the two-dimensional heterojunction formed by growing In-MOF on GO through the in-situ growth method in the present invention significantly improves the reaction activity of photocatalytic carbon dioxide.

[0071] The floating two-dimensional heterojunction device (In-MOF / GO-PTFE) prepared when the growth time of Example 1 was 4h was placed at the bottom of the reactor, and 20mL of water was added to cover the bottom of the reactor, and then a mixed gas of carbon dioxide, oxygen and argon was introduced into it for 30min, followed by illumination, and the gas phase product was detected using FID and TCD detectors, and the liquid phase product was detected using UV-visible spectroscopy. By adjusting the proportion of oxygen in the mixed gas (a mixed gas of carbon dioxide, oxygen and argon), the volume proportion of oxygen (it should be noted that the volume proportion of carbon dioxide is 10%, 0% oxygen corresponds to the volume proportion of argon is 90%; 5% oxygen corresponds to the volume proportion of argon is 85%; 10% oxygen corresponds to the volume proportion of argon is 80%; 20% oxygen corresponds to the volume proportion of argon is 70%; 40% oxygen corresponds to the volume proportion of argon is 50%). The photocatalytic carbon dioxide reduction performance is compared, and the results are as follows: Figure 5 As shown, the results show that the catalytic performance is almost unchanged compared with the anaerobic conditions, which strongly proves that In-MOF / GO has good tolerance and efficiency in carbon dioxide reduction under aerobic conditions, and maintains high catalytic activity despite increased oxygen interference. This further proves the strong adaptability of the In-MOF / GO material of the present invention to complex operating scenarios in practical applications.

[0072] At the same time, the oxidation end of In-MOF / GO can also produce hydrogen peroxide. It is worth noting that the content of hydrogen peroxide generated is not affected by the oxygen content in the gas atmosphere. Figure 6As shown in a, since hydrogen peroxide, a reagent widely used in water pollutant degradation and sterilization, is produced on the floatable two-dimensional heterojunction device (In-MOF / GO-PTFE) prepared when the growth time is 4 h in Example 1, the present invention further considers combining aerobic carbon dioxide reduction with water purification to create a photocatalytic system for practical environmental applications.

[0073] Lake water was collected, and the floatable two-dimensional heterojunction floatable device (In-MOF / GO-PTFE) prepared with a growth time of 4 h in the above Example 1 was used instead of deionized water, and a mixed gas with a volume fraction of 10% carbon dioxide, 20% oxygen and 70% argon was used to simulate combustion flue gas. Compared with deionized water, the two-dimensional heterojunction floatable device (In-MOF / GO-PTFE) on the lake water showed the same performance in aerobic photocatalytic reduction of carbon dioxide to CO, indicating that the presence of organic or inorganic matter in the lake water does not interfere with the carbon dioxide reduction activity. More importantly, we monitored the changes in the chemical oxygen demand (COD) of the lake water during the photocatalytic reaction. The COD decreased linearly with the change in illumination time, and the results are as follows. Figure 6 As shown in b, it shows the decomposition of organic pollutants by in situ generated hydrogen peroxide or photogenerated holes. After 6 hours of reaction, the COD of the lake water dropped to below 15 mg / L, which meets the standard of Class I water in China. Therefore, the design of the two-dimensional heterojunction floatable device (In-MOF / GO-PTFE) of the present invention conceptualizes an extremely convenient reaction system suitable for use in a real open water environment.

[0074] The stability of the floatable two-dimensional heterojunction floatable device (In-MOF / GO-PTFE) prepared in Example 1 when the growth time was 4 h was further tested. Figure 7 As shown in a, after 5 cycles and 25 hours of testing, the In-MOF / GO-PTFE catalyst of the present invention maintained an efficiency of 95%. Figure 7 Figure b is the X-ray diffraction pattern of In-MOF / GO-PTFE before and after the cycle. It can be seen from the figure that the structure of In-MOF / GO-PTFE remains consistent before and after the cycle, which shows that the structure of In-MOF / GO-PTFE as a catalyst material of the present invention is stable and not destroyed.

[0075] Figure 8 This is the TEM image of the floatable two-dimensional heterojunction floatable device (In-MOF / GO-PTFE) prepared when the growth time is 4 hours in Example 1 before and after the cycle. It can be seen from the figure that: there is no change in the morphology of In-MOF / GO-PTFE before and after the cycle, which further proves that In-MOF / GO-PTFE has good catalytic stability.

[0076] The above is an explanation of the embodiments of the present invention. However, the present invention is not limited to the above embodiments. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An In-MOF / GO material, characterized in that: The invention comprises graphene oxide (GO) and In-MOF grown on graphene oxide (GO).

2. The In-MOF / GO material according to claim 1, characterized in that In the In-MOF / GO material, the mass percentage of In-MOF is 10-20%. Preferably, the In-MOF is a nanosheet structure; preferably, its average thickness is 0.5 to 1 nm. Preferably, the In-MOF forms a face-to-face arrangement on GO. Preferably, the graphene oxide (GO) is a single-layer structure. Preferably, the graphene oxide (GO) has a thickness of 1 to 5 nm.

3. The method for preparing the In-MOF / GO material according to claim 1 or 2, characterized in that: The preparation method comprises growing an indium salt precursor and an organic ligand on graphene oxide (GO) through an in-situ reaction.

4. The preparation method according to claim 3, characterized in that: The reaction mass ratio of the indium salt precursor, the organic ligand and graphene oxide (GO) is 1: (0.5-2): (2-50). Preferably, the indium salt precursor, organic ligand and graphene oxide (GO) are all added to the reaction system in the form of solution. Preferably, the injection rate of the indium salt precursor solution and the organic ligand solution is 0.1-0.5 mL / h.

5. A buoyant two-dimensional heterojunction device, characterized in that: It contains the In-MOF / GO material according to claim 1 or 2 and / or is prepared from the In-MOF / GO material according to claim 1 or 2.

6. The device according to claim 5, characterized in that The floatable two-dimensional heterojunction device also includes a substrate, on which the In-MOF / GO material is modified.

7. The method for preparing a floatable two-dimensional heterojunction device according to claim 5 or 6, characterized in that: The preparation method comprises modifying a solution containing the In-MOF / GO material according to claim 1 or 2 on a substrate by suction filtration.

8. A photocatalytic system, characterized in that: It contains the In-MOF / GO material described in claim 1 or 2 and / or the floatable two-dimensional heterojunction device described in claim 5 or 6.

9. Use of the In-MOF / GO material according to claim 1 or 2 and / or the floatable two-dimensional heterojunction device according to claim 5 or 6 and / or the photocatalytic system according to claim 8 for photocatalytic reduction of carbon dioxide and / or water purification.

10. A method for photocatalytic carbon dioxide reduction and water purification, characterized in that: The method comprises using carbon dioxide as a raw material, the In-MOF / GO material according to claim 1 or 2 and / or the floatable two-dimensional heterojunction device according to claim 5 or 6 as a catalyst, and water as a reducing agent, and causing carbon dioxide reduction and water oxidation reactions under light conditions.

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