Three-dimensional ordered macroporous gas sensitive material, preparation method and application thereof

Abstract

The application discloses a kind of gas-sensitive materials based on three-dimensional ordered macroporous and its preparation method and application, and belongs to gas sensing material technical field, wherein, the preparation method of the gas-sensitive material includes the following steps: self-assembly forms three-dimensional ordered polymethyl methacrylate microsphere template;Three-dimensional ordered macroporous Pb-ZIF-8 is prepared by polymethyl methacrylate microsphere template method;CsPbBr3 is confined crystallization in the channel of three-dimensional ordered macroporous Pb-ZIF-8, and gas-sensitive material is prepared.The gas-sensitive material prepared by the application can be used for preparing nitrogen dioxide gas-sensitive element, and the nitrogen dioxide gas-sensitive element can detect the change of element resistance signal under light excitation, can realize the high sensitivity, high selectivity and repeatability detection of room temperature environment nitrogen dioxide gas, and has wide application prospect in environmental monitoring field.

Description

Technical Field

[0001] This invention relates to the field of gas sensing materials technology, specifically a gas-sensitive material based on three-dimensional ordered macropores, its preparation method, and its application. Background Technology

[0002] Nitrogen dioxide (NO2) is a typical harmful gas, mainly originating from vehicle exhaust, fossil fuel combustion, and industrial emissions. It not only contributes to acid rain and photochemical smog, damaging the ecological environment, but also poses a significant threat to human health; even at low concentrations, long-term exposure can cause respiratory diseases and lung damage. Therefore, developing gas sensors capable of efficiently and rapidly detecting low concentrations of NO2 is crucial for environmental monitoring and public safety.

[0003] Metal halide perovskite materials, such as CsPbBr3, have attracted widespread attention in fields such as photodetectors and light-emitting diodes due to their excellent photoelectric properties. Studies have shown that they also exhibit potential in room-temperature light-assisted gas sensing; photoexcitation can significantly increase their carrier concentration, thereby enhancing their response to gases such as NO2. However, pure CsPbBr3 materials suffer from problems such as low specific surface area, easy aggregation, and poor long-term stability, which severely limit their practical application in gas sensors.

[0004] Metal-organic frameworks (MOFs), especially ZIF-8, possess large specific surface areas, well-ordered pore structures, and good thermal / chemical stability. Using MOFs as a support for CsPbBr3 not only effectively disperses and stabilizes CsPbBr3 nanoparticles but also leverages their porous structure to pre-enrich NO2 gas, thereby improving sensor sensitivity. However, the microporous structure of traditional ZIF-8 limits rapid gas diffusion and the loading of large molecules.

[0005] Therefore, how to overcome the shortcomings of existing technologies and develop a CsPbBr3-based composite material with high specific surface area, fast gas mass transfer capability and excellent stability to achieve high-performance detection of NO2 is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] The purpose of this invention is to provide a gas-sensitive material based on three-dimensional ordered macropores, its preparation method, and its application, so as to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A method for preparing a gas-sensitive material based on three-dimensional ordered macropores includes the following steps:

[0009] Based on the polymerization reaction of methyl methacrylate monomer, a three-dimensional ordered polymethyl methacrylate microsphere template is formed through self-assembly;

[0010] Zinc source and 2-methylimidazole were dissolved in a first organic solvent, and lead salt solution was added to obtain a first precursor solution; polymethyl methacrylate template was immersed in the first precursor solution, then removed, dried, and crystallized; then the polymethyl methacrylate microsphere template was removed to obtain three-dimensional ordered macroporous Pb-ZIF-8.

[0011] Cesium source and three-dimensional ordered macroporous Pb-ZIF-8 were dissolved in a second organic solvent and mixed with oleic acid and oleylamine to obtain a second precursor solution. The mixed second precursor solution was then added dropwise to toluene to generate CsPbBr3, which was then confined and crystallized within the pores of the three-dimensional ordered macroporous Pb-ZIF-8. After centrifugation and drying, the gas-sensitive material was obtained.

[0012] Furthermore, the step of forming a three-dimensionally ordered polymethyl methacrylate microsphere template through self-assembly based on the polymerization reaction of methyl methacrylate monomers specifically includes:

[0013] Methyl methacrylate was washed with a 10-20 mg / mL sodium hydroxide aqueous solution to remove the polymerization inhibitor, and purified methyl methacrylate was obtained.

[0014] The purified methyl methacrylate was dissolved in deionized water containing polyvinylpyrrolidone and stirred in an oil bath at 85-95°C to obtain a mixture. Subsequently, an aqueous solution of potassium persulfate and azobisisobutyronitrile were added to the mixture and stirred to obtain a polymethyl methacrylate microsphere colloidal suspension.

[0015] The polymethyl methacrylate microsphere colloidal suspension obtained from the reaction was centrifuged, the precipitate was collected and dried to obtain polymethyl methacrylate microspheres.

[0016] Polymethyl methacrylate microspheres were dispersed in a first organic solvent, ultrasonicated, and then vacuum filtered. The resulting filter cake was then vacuum dried to obtain a three-dimensionally ordered polymethyl methacrylate microsphere template.

[0017] Furthermore, the first organic solvent is methanol.

[0018] Furthermore, the zinc source is zinc nitrate hexahydrate, and its mass ratio with 2-methylimidazole is (8-8.3):(6.5-7); the lead salt solution is a 0.5-0.6 g / mol lead nitrate solution.

[0019] Further, the steps of immersing the polymethyl methacrylate template in the first precursor solution, then removing it for drying and crystallization treatment specifically include:

[0020] The polymethyl methacrylate template was immersed in the first precursor solution, degassed under vacuum, and soaked for several hours to obtain the soaked composite.

[0021] The soaked composite was removed, vacuum dried, and then transferred to a mixed solvent of methanol and ammonia for vacuum degassing. Finally, it was vacuum heated at 40-60°C to promote the crystallization of macroporous Pb-ZIF-8.

[0022] Furthermore, the cesium source is CsBr; the second organic solvent is N,N-dimethylformamide.

[0023] Another objective of this invention is to provide a gas-sensitive material based on three-dimensional ordered macropores prepared by the above-described method.

[0024] Another object of the present invention is to provide a nitrogen dioxide gas-sensitive element, comprising a substrate and a gas-sensitive layer formed on the substrate, wherein the gas-sensitive layer comprises the above-mentioned gas-sensitive material based on three-dimensional ordered macropores.

[0025] Furthermore, the preparation method of the nitrogen dioxide gas-sensitive element includes the following steps:

[0026] The gas-sensitive material is mixed with toluene and then thoroughly ground to obtain a slurry;

[0027] The slurry is drop-coated onto an LED, which consists of, from bottom to top, a transparent conductive glass substrate, a hole transport layer, a perovskite light-emitting layer, an electron transport and hole blocking layer, a buffer layer, and a metal cathode layer, to obtain a sensor element.

[0028] The prepared sensor element is subjected to aging treatment to obtain the nitrogen dioxide gas-sensitive element.

[0029] Another object of the present invention is to provide an application of the above-mentioned gas-sensitive material based on three-dimensional ordered macropores or the above-mentioned nitrogen dioxide gas-sensitive element in the quantitative detection of nitrogen dioxide.

[0030] This invention provides a gas-sensitive material based on three-dimensional ordered macroporous structures, prepared by a polymethyl methacrylate microsphere template method. It possesses a regularly arranged macroporous structure, with the ZIF-8 framework providing high specific surface area and gas enrichment capacity. CsPbBr3 nanomaterials generate photogenerated carriers under LED excitation and adsorb nitrogen dioxide. The synergistic effect of these two components significantly enhances the sensitivity to nitrogen dioxide gas, effectively improving the sensitivity, selectivity, and stability of the device. This gas-sensitive material can be used to fabricate nitrogen dioxide gas-sensitive elements. The fabrication process is simple, and the resulting nitrogen dioxide gas-sensitive elements detect changes in resistance signals under photoexcitation, achieving highly sensitive, selective, and repeatable detection of nitrogen dioxide gas at room temperature. It has broad application prospects in the field of environmental monitoring. Attached Figure Description

[0031] Figure 1 The image shows a scanning electron microscope (SEM) image of a gas-sensitive material based on three-dimensional ordered macropores obtained according to an embodiment of the present invention; in the image, a and b are SEM images with different magnification ratios.

[0032] Figure 2 This is a transmission electron microscope (TEM) image of a gas-sensitive material based on three-dimensional ordered macropores obtained in an embodiment of the present invention.

[0033] Figure 3 The dynamic resistance curve of the nitrogen dioxide gas-sensitive element prepared in an embodiment of the present invention to low concentration (1-15 ppb) NO2 under photoexcitation.

[0034] Figure 4 The dynamic resistance curve of the nitrogen dioxide gas-sensitive element prepared in the embodiment of the present invention under photoexcitation for high concentrations (20-500ppm) of NO2.

[0035] Figure 5 The repeatability curve of the nitrogen dioxide gas-sensitive element prepared in the embodiment of the present invention under photoexcitation for 10 ppm NO2.

[0036] Figure 6 The bar chart shows the response of gas-sensitive elements prepared from conventional Zif-8 / CsPbBr3, pure CsPbBr3, and macroporous Zif-8 / CsPbBr3 to 10 ppb NO2, as provided in Comparative Examples 1-2 and Example 1. Detailed Implementation

[0037] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0038] Combining CsPbBr3 with macroporous ZIF-8 can enhance the stability of CsPbBr3 and its sensing response to target gases by leveraging the confinement effect and adsorption enrichment capacity of macroporous ZIF-8. Therefore, designing and fabricating ZIF-8 with a three-dimensional ordered macroporous structure and combining it with CsPbBr3 combines the multiple advantages of rapid mass transfer in macroporous structures, high specific surface area adsorption of MOFs, and high photoelectric response of perovskites, making it an ideal strategy for developing high-performance room-temperature photoexcited NO2 gas sensors.

[0039] Specifically, in one embodiment of the present invention, a gas-sensitive material based on three-dimensional ordered macropores is provided, which can be applied to a nitrogen dioxide gas-sensitive element of a gas sensor. The preparation method of the gas-sensitive material specifically includes the following steps:

[0040] S1. Synthesis of three-dimensional ordered polymethyl methacrylate (PMMA) microsphere templates: 40-60 mL of methyl methacrylate (MMA) was washed multiple times with an equal volume of 10-20 mg / mL NaOH aqueous solution to remove polymerization inhibitors, resulting in purified MMA. The purified MMA was dissolved in 500-700 mL of deionized water containing 0.05-0.15 g of polyvinylpyrrolidone, and stirred in an oil bath at 85-95℃ for 0.5 hours to obtain a mixture. Subsequently, potassium persulfate aqueous solution (0.2-0.4 g potassium persulfate dissolved in 60 mL of water) and 0.03-0.04 g azobisisobutyronitrile (AIB) particle size modifier were added to the mixture, and the mixture was stirred vigorously at 300-500 rpm to continue the reaction. The resulting milky white PMMA microsphere colloidal suspension was centrifuged at 2000-4000 rpm. The precipitate was collected, dried at 40-60℃, and washed multiple times with methanol to obtain PMMA microspheres with an average diameter of approximately 100-200 nm. 1-3 g of the obtained PMMA microspheres were dispersed in 100 mL of methanol and sonicated to obtain a dispersion. The dispersion was then vacuum filtered, and the resulting filter cake was vacuum dried at 40-60℃ to obtain a three-dimensionally ordered PMMA microsphere template.

[0041] S2. Preparation of three-dimensional ordered macroporous Pb-ZIF-8: Dissolve 8-8.3 g of zinc nitrate hexahydrate and 6.5-7 g of 2-methylimidazole in 30-50 mL of methanol, sonicate, and then add 0.5-0.6 g / mL of lead nitrate solution to obtain the first precursor solution. After thorough stirring, immerse a PMMA microsphere template prepared in step S1 into the first precursor solution and degas under vacuum to ensure complete wettation of the template by the precursor. Immerse the PMMA microsphere template at room temperature and pressure. The soaked composite was obtained; the soaked composite was removed and vacuum dried at 40-60℃, and the resulting composite fragments were transferred to a mixed solvent of equal volume of methanol and ammonia, degassed under vacuum, and then vacuum heated at 40-60℃ for 1 hour to promote the crystallization of macroporous Pb-ZIF-8; the crystallized product was repeatedly washed with N,N-dimethylformamide and chloroform to remove the PMMA microsphere template, and finally washed with methanol and dried to obtain three-dimensional ordered macroporous Pb-ZIF-8.

[0042] S3. Dissolve 0.03-0.08 g of CsBr and 0.03-0.08 g of the three-dimensional ordered macroporous Pb-ZIF-8 prepared above in 1 mL of N,N-dimethylformamide, respectively, and sonicate. Then, take 0.3-0.8 mL of the N,N-dimethylformamide solution of Pb-ZIF-8, mix it with 0.5-1 mL of the N,N-dimethylformamide solution of CsBr, 0.05-0.15 mL of oleic acid, and 0.03-0.08 mL of oleylamine, and stir to obtain the second precursor solution. Then, add the mixed second precursor solution dropwise to 2-4 mL of toluene to generate CsPbBr3, and allow CsPbBr3 to crystallize confined within the pores of the three-dimensional ordered macroporous Pb-ZIF-8. After centrifugation and drying, the gas-sensitive material can be obtained.

[0043] In another embodiment of the present invention, a nitrogen dioxide gas-sensitive element is also provided, including a substrate and a gas-sensitive layer formed on the substrate, wherein the gas-sensitive layer includes the gas-sensitive material based on three-dimensional ordered macropores as described above.

[0044] Specifically, the preparation method of this nitrogen dioxide gas-sensitive element includes the following steps: mixing the gas-sensitive material with toluene and grinding it thoroughly to obtain a slurry; drop-coating the slurry onto an LED consisting of, from bottom to top, a transparent conductive glass substrate, a hole transport layer, a perovskite light-emitting layer, an electron transport and hole blocking layer, a buffer layer, and a metal cathode layer to obtain a sensor element; and subjecting the prepared sensor element to an aging treatment to obtain the nitrogen dioxide gas-sensitive element. When this nitrogen dioxide gas-sensitive element is used to detect NO2 gas, it achieves quantitative detection of NO2 concentration by detecting changes in the resistance signal of the element.

[0045] Unless otherwise specified, all raw materials used in the following embodiments are commercially available products and can be purchased through commercial channels. The invention will be described in detail below through specific embodiments in practical applications.

[0046] Example 1: This example provides a gas-sensitive material based on three-dimensional ordered macroporous structures, the preparation method of which specifically includes the following steps:

[0047] S1. Synthesis of three-dimensionally ordered polymethyl methacrylate (PMMA) microsphere templates: 50 mL of methyl methacrylate (MMA) was washed six times with an equal volume of 15 mg / mL NaOH aqueous solution to remove polymerization inhibitors, resulting in purified MMA. The purified MMA was dissolved in 600 mL of deionized water containing 0.1 g polyvinylpyrrolidone, placed in a round-bottom flask, and stirred in an oil bath at 90 °C for 0.5 hours to obtain a mixture. Subsequently, potassium persulfate aqueous solution (0.3 g potassium persulfate dissolved in 60 mL of water) and azobisisobutyronitrile (0.036 g) as a particle size modifier were added to the mixture, and the mixture was stirred vigorously at 400 rpm for 2 hours. The resulting milky white PMMA microsphere colloidal suspension was centrifuged at 3000 rpm for 2 hours. The precipitate was collected, dried at 50 °C, and washed six times with methanol to obtain PMMA microspheres with an average diameter of approximately 150 nm. 2g of the obtained PMMA microspheres were dispersed in 100mL of methanol and sonicated to obtain a dispersion. The dispersion was then vacuum filtered, and the resulting filter cake was vacuum dried at 50℃ for 24 hours to obtain a three-dimensional ordered PMMA microsphere template.

[0048] S2. Preparation of three-dimensional ordered macroporous Pb-ZIF-8: 8.15 g of zinc nitrate hexahydrate and 6.75 g of 2-methylimidazole were dissolved in 40 mL of methanol, sonicated, and then 0.56 g / mL of lead nitrate solution was added to obtain the first precursor solution. After thorough stirring, a PMMA microsphere template prepared in step S1 was immersed in the first precursor solution and degassed under vacuum for 30 minutes to ensure complete wettation of the template by the precursor. The PMMA microsphere template was then soaked at room temperature and pressure for 12 hours to obtain… The soaked composite was removed and vacuum dried at 50°C for 12 hours to obtain composite fragments. These fragments were then transferred to a mixed solvent of methanol and ammonia in equal volumes and degassed under vacuum for 10 minutes. The mixture was then vacuum heated at 50°C for 10 hours to promote the crystallization of macroporous Pb-ZIF-8. The crystallized product was repeatedly washed 10 times with N,N-dimethylformamide and chloroform to remove the PMMA microsphere template. Finally, it was washed with methanol and dried to obtain three-dimensional ordered macroporous Pb-ZIF-8.

[0049] S3. Dissolve 0.05 g of CsBr and 0.05 g of the three-dimensional ordered macroporous Pb-ZIF-8 prepared above in 1 mL of N,N-dimethylformamide (DMF) and sonicate for 10 minutes. Then, take 0.3 mL of the Pb-ZIF-8 DMF solution, mix it with 1 mL of the CsBr DMF solution, 0.1 mL of oleic acid, and 0.05 mL of oleylamine, and stir for 10 minutes. Slowly add the mixed solution dropwise to 3 mL of toluene under vigorous stirring to obtain a suspension. Centrifuge the obtained suspension at 10000 rpm for 10 minutes, collect the powder, and vacuum dry it at 50 °C for 10 hours to obtain the three-dimensional ordered macroporous Zif-8 / CsPbBr3 composite material, which is the gas-sensitive material.

[0050] Example 2: This example provides a method for preparing a nitrogen dioxide gas-sensitive element, which includes the following steps:

[0051] S1. Mix 0.1g of the three-dimensional ordered macroporous Zif-8 / CsPbBr3 composite material prepared in Example 1 with 10mL of toluene and grind for 30 minutes to obtain a uniform slurry;

[0052] S2. Dissolve 1 mmol of cesium acetate and 0.33 mmol of cerium acetate in 10 ml of octadecene, 1.5 ml of oleic acid and 1.5 ml of oleylamine, transfer to a three-necked flask, react at 150 °C under nitrogen for 1 hour, then raise the temperature to 230 °C and hold for 1 minute. Quickly inject 2 mmol of trimethylbromosilane and hold for 1 minute. Immerse the three-necked flask in an ice-water mixture to cool to room temperature. Centrifuge the reaction mixture at 9500 r / min for 8 minutes, discard the supernatant, dissolve the precipitate in 3 ml of toluene, sonicate, let stand for 12 h, and then collect the supernatant to obtain the Cs3CeBr6 perovskite supernatant. Thin strip electrodes were etched onto a transparent conductive glass substrate, followed by spin-coating of a hole transport layer using PEDOT:PSS material with a thickness of 2-10 nm. Next, a prepared Cs3CeBr6 perovskite supernatant was spin-coated. 60-80 μL of the supernatant was pipetted onto the center of the substrate, and spin-coating was performed at 2000 rpm for 30 seconds. Afterward, the supernatant was transferred to an organic evaporation chamber, and the vacuum level was allowed to reach 2-3 × 10⁻⁶. -5 At Pa, an electron transport and hole blocking layer is deposited by evaporation using TPBi material. The evaporation rate is controlled at 0.05-0.1 nm / s, and the thickness is controlled at 40-50 nm. Then, a composite metal cathode layer composed of LiF and Ag is deposited sequentially under vacuum. The evaporation rate of lithium fluoride (LiF) is controlled at 0.05-0.01 nm / s, and the evaporation rate of silver (Ag) is controlled at 0.3-0.6 nm / s, thus obtaining the LED substrate.

[0053] S3. Take 10µL of the slurry obtained in step S1 and drop it onto the LED substrate. Let it dry naturally to form a gas-sensitive layer with a thickness of 5-30μm, thus obtaining the sensor element.

[0054] S4. The sensor element obtained in step S3 is aged at room temperature for 3 days to obtain a nitrogen dioxide gas-sensitive element. This nitrogen dioxide gas-sensitive element can be used to detect NO2 gas under room temperature LED excitation, and the quantitative detection of NO2 concentration is achieved by detecting the change in the resistance signal of the sensing element.

[0055] Example 3: This example provides a method for detecting NO2 gas concentration using a nitrogen dioxide gas-sensitive element, specifically including the following steps:

[0056] The nitrogen dioxide gas-sensitive element prepared in Example 2 was connected to the detection circuit and placed in the gas chamber. Air was introduced, and after the baseline stabilized, NO2 gas of different concentrations was introduced. The resistance of the prepared nitrogen dioxide gas-sensitive element was read under the equilibrium state of air and NO2 gas concentrations, and the resistance data of the element was recorded using the CGS-8 intelligent gas-sensitive analysis system.

[0057] Comparative Example 1: This comparative example provides a method for preparing a conventional Zif-8 / CsPbBr3 composite material, specifically including the following steps:

[0058] S1. Synthesis of conventional ZIF-8: 3g of zinc nitrate hexahydrate and 6.75g of 2-methylimidazole were dissolved in 100mL of methanol respectively; then the two solutions were mixed and stirred thoroughly for 5 minutes, and aged at room temperature for 12 hours; the resulting precipitate was collected by centrifugation, washed four times with methanol, and dried at 50℃ for 12 hours to obtain conventional ZIF-8 powder.

[0059] S2. Preparation of conventional ZIF-8 / CsPbBr3: The preparation method is the same as step S3 in Example 1, except that conventional ZIF-8 powder is used instead of three-dimensional ordered macroporous Pb-ZIF-8. Furthermore, following the same method as in Example 3, the obtained conventional ZIF-8 / CsPbBr3 composite material is used to fabricate a gas-sensitive element.

[0060] Comparative Example 2: This comparative example provides a method for preparing pure CsPbBr3 material, as follows:

[0061] 0.085 g CsBr, 0.147 g PbBr2, 0.1 mL oleic acid, and 0.05 mL oleylamine were sequentially dissolved in 10 mL of N,N-dimethylformamide. This homogeneous solution was then poured into 100 mL of toluene under stirring for 5 minutes. The product was collected by centrifugation, washed twice with toluene, and dried under vacuum to obtain pure CsPbBr3 powder. Furthermore, the obtained pure CsPbBr3 material was fabricated into a gas-sensitive element using the same method as in Example 3.

[0062] Performance Testing: I. Scanning electron microscope images of the Zif-8 / CsPbBr3 composite material (gas-sensitive material) prepared in Example 1 above are shown below. Figure 1 As shown in the figure, the gas-sensitive material prepared in this embodiment of the invention exhibits a regular macroporous structure with a pore size of approximately 200 nm.

[0063] II. Transmission electron microscopy (TEM) images of the Zif-8 / CsPbBr3 composite material prepared in Example 1 above are shown below. Figure 2 As shown in the figure, CsPbBr3 quantum dots are distributed within the channels of the macroporous ZIF-8.

[0064] III. The resistance change curve of the nitrogen dioxide gas-sensitive element prepared in Example 3 above for low concentration (1-15 ppb) NO2 gas is shown in Figure 3. Figure 3 As shown in the figure, the resistance signal increases in NO2 gas, exhibiting a good detection limit at low concentrations.

[0065] IV. The response recovery curves of the nitrogen dioxide gas sensor prepared in Example 3 above to high concentrations (20-500 ppm) of NO2 are as follows: Figure 4 As shown in the figure, the sensitivity of the gas-sensitive element increases with the increase of NO2 gas concentration, and it exhibits good response recovery characteristics.

[0066] V. The repeatability curve of the nitrogen dioxide gas sensor prepared in Example 3 above for 100 ppm NO2 is as follows: Figure 5 As shown in the figure, the gas sensor maintains a stable response value over 18 air-NO2 cycles, demonstrating its good repeatability.

[0067] six, Figure 6 The figures shown are bar charts illustrating the response of gas-sensitive elements prepared from conventional Zif-8 / CsPbBr3, pure CsPbBr3, and macroporous Zif-8 / CsPbBr3 to 10 ppb NO2, as provided in Comparative Examples 1-2 and Example 1. The comparison shows that the gas-sensitive element prepared from three-dimensional ordered macroporous Zif-8 / CsPbBr3 provided in this embodiment of the invention exhibits the highest sensitivity (response) to NO2.

[0068] In summary, the three-dimensional ordered macroporous Zif-8 / CsPbBr3 composite material prepared in the embodiments of the present invention, with its unique structural and compositional advantages, achieves high sensitivity, high selectivity and repeatability detection of NO2 gas under room temperature photoexcitation, and has broad application prospects in the field of environmental monitoring.

[0069] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification.

Claims

1. A method for preparing a gas-sensitive material based on three-dimensional ordered macroporous structures, characterized in that, Includes the following steps: Based on the polymerization reaction of methyl methacrylate monomer, a three-dimensional ordered polymethyl methacrylate microsphere template is formed through self-assembly; Zinc source and 2-methylimidazole were dissolved in a first organic solvent, and lead salt solution was added to obtain a first precursor solution; polymethyl methacrylate template was immersed in the first precursor solution, then removed, dried, and crystallized; then the polymethyl methacrylate microsphere template was removed to obtain three-dimensional ordered macroporous Pb-ZIF-8. Cesium source and three-dimensional ordered macroporous Pb-ZIF-8 were dissolved in a second organic solvent, respectively, and then mixed with oleic acid and oleylamine to obtain a second precursor solution. The mixed second precursor solution was then added dropwise to toluene to generate CsPbBr3, which was then confined and crystallized within the pores of the three-dimensional ordered macroporous Pb-ZIF-8. After centrifugation and drying, the gas-sensitive material was obtained.

2. The method for preparing gas-sensitive materials based on three-dimensional ordered macroporous structures according to claim 1, characterized in that, The steps involved in forming a three-dimensionally ordered polymethyl methacrylate microsphere template through self-assembly based on the polymerization reaction of methyl methacrylate monomers specifically include: Methyl methacrylate was washed with a 10-20 mg / mL sodium hydroxide aqueous solution to remove the polymerization inhibitor, and purified methyl methacrylate was obtained. The purified methyl methacrylate was dissolved in deionized water containing polyvinylpyrrolidone and stirred in an oil bath at 85-95°C to obtain a mixture. Subsequently, an aqueous solution of potassium persulfate and azobisisobutyronitrile were added to the mixture and stirred to obtain a polymethyl methacrylate microsphere colloidal suspension. The polymethyl methacrylate microsphere colloidal suspension obtained from the reaction was centrifuged, the precipitate was collected and dried to obtain polymethyl methacrylate microspheres. Polymethyl methacrylate microspheres were dispersed in a first organic solvent, ultrasonicated, and then vacuum filtered. The resulting filter cake was then vacuum dried to obtain a three-dimensionally ordered polymethyl methacrylate microsphere template.

3. The method for preparing gas-sensitive materials based on three-dimensional ordered macroporous structures according to claim 1 or 2, characterized in that, The first organic solvent is methanol.

4. The method for preparing gas-sensitive materials based on three-dimensional ordered macroporous structures according to claim 3, characterized in that, The zinc source is zinc nitrate hexahydrate, and its mass ratio with 2-methylimidazole is (8-8.3):(6.5-7); the lead salt solution is a 0.5-0.6 g / mol lead nitrate solution.

5. The method for preparing gas-sensitive materials based on three-dimensional ordered macroporous structures according to claim 1, characterized in that, The steps of immersing a polymethyl methacrylate template in a first precursor solution, followed by drying and crystallization, specifically include: The polymethyl methacrylate template was immersed in the first precursor solution, degassed under vacuum, and soaked for several hours to obtain the soaked composite. The soaked composite was removed, vacuum dried, and then transferred to a mixed solvent of methanol and ammonia for vacuum degassing. Finally, it was vacuum heated at 40-60°C to promote the crystallization of macroporous Pb-ZIF-8.

6. The method for preparing gas-sensitive materials based on three-dimensional ordered macroporous structures according to claim 1, characterized in that, The cesium source is CsBr; the second organic solvent is N,N-dimethylformamide.

7. A gas-sensitive material based on three-dimensional ordered macropores prepared by the preparation method according to any one of claims 1-6.

8. A nitrogen dioxide gas-sensitive element, comprising a substrate and a gas-sensitive layer formed on the substrate, characterized in that, The gas-sensitive layer comprises the gas-sensitive material based on three-dimensional ordered macropores as described in claim 7.

9. The nitrogen dioxide gas-sensitive element according to claim 8, characterized in that, The method for preparing the nitrogen dioxide gas-sensitive element includes the following steps: The gas-sensitive material is mixed with toluene and then thoroughly ground to obtain a slurry; The slurry is drop-coated onto an LED, which consists of, from bottom to top, a transparent conductive glass substrate, a hole transport layer, a perovskite light-emitting layer, an electron transport and hole blocking layer, a buffer layer, and a metal cathode layer, to obtain a sensor element. The prepared sensor element is subjected to aging treatment to obtain the nitrogen dioxide gas-sensitive element.

10. The application of a gas-sensitive material based on three-dimensional ordered macropores as described in claim 7 or a nitrogen dioxide gas-sensitive element as described in any one of claims 8-9 in the quantitative detection of nitrogen dioxide.

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