In-situ growth of ZnO@ZIF-71 / WO3 composite material, preparation method and application thereof

Abstract

The application provides an in-situ growth ZnO@ZIF-71 / WO3 composite material and a preparation method and application thereof, and aims at solving the problem that a WO3 sensor is greatly affected by humidity in application. The application provides the preparation method of the ZnO@ZIF-71 / WO3 composite material, WO3 nanosheets are grown on the surface of a ceramic tube by using an in-situ growth method, then ZnO nanorods are in-situ synthesized on the surface, and ZIF-71 films are synthesized by taking ZnO as a Zn source, and finally the ZnO@ZIF-71 / WO3 composite material is obtained. By constructing a 1D / 2D composite multi-level structure, the surface performance of the material is enhanced, and by means of the hydrophobic effect of the ZIF-71 film, the problem that the WO3-based composite material is greatly affected by humidity in practical application is improved. The sensitive material shows super-high selectivity, high sensitivity, fast response and recovery speed, and good stability and humidity resistance to NO2 gas.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of semiconductor gas sensors, and particularly relates to an in-situ grown ZnO@ZIF-71 / WO3 composite material and a preparation method and application thereof. BACKGROUND

[0002] Nitrogen oxides are one of the most common polluting gases in the atmosphere, which can pollute the living environment, atmosphere and soil of human beings, and is the main cause of acid rain, global warming, photochemical smog and the like. NO2 is a red-brown gas with a pungent odor, which can be inhaled into the human body through the respiratory tract to cause damage to the respiratory system and lung tissue, stimulate the respiratory mucosa to cause dry cough, nausea and other adverse symptoms, and can also cause bronchitis, pulmonary edema, and even affect the central nervous system to cause neurasthenia, syncope and other phenomena, greatly endangering human health. Therefore, it is particularly important to design a gas sensor for rapid and real-time detection of NO2 gas in the environment.

[0003] A gas sensor is a component that senses the gas components in the atmosphere, collects signals and converts them into electrical signals to feed back to human beings. It has attracted widespread attention from researchers due to its portability, simple preparation, low cost, high sensitivity and other characteristics. WO3, as a typical n-type wide-bandgap semiconductor, is widely studied and used in gas sensors due to its low price, good chemical stability and good response to a variety of gases. However, WO3 sensors are usually greatly affected by humidity in practical applications, and are prone to damage due to hydroxyl poisoning in high humidity environments. For example, the application publication CN113860374A discloses a flower-shaped nano WO3 gas-sensitive material, and the prepared gas sensor has the advantages of low working temperature, high sensitivity and good selectivity, but the humidity resistance of the sensor is not improved, and the working temperature, sensitivity and selectivity still have optimization space. In addition, the preparation method of traditional gas-sensitive components usually adopts the method of coating nano powder, but the artificial coating process can easily cause uneven coating, uncontrollable thickness, damage to the morphology during slurry preparation, particle stacking, poor combination of materials and ceramic tube, and other shortcomings. In the long-term use process, the components will have the phenomena of powder falling, poor consistency and repeatability, and great influence of humidity, which greatly limits its practical application value. Therefore, it is urgent to develop a NO2 gas sensor suitable for low concentration detection, high response and high selectivity, fast response and recovery rate, and certain humidity resistance. SUMMARY

[0004] In response to the technical problems that WO3 sensors are greatly affected by humidity, have high operating temperatures, low sensitivity and poor selectivity in practical applications, the present invention proposes an in-situ grown ZnO@ZIF-71 / WO3 composite material, its preparation method and application. By constructing a 1D / 2D multi-level structure, the transfer of electrons is accelerated, the sensitivity is significantly improved, and the moisture resistance is improved by forming a ZIF-71 hydrophobic layer on the ZnO / WO3 surface. The prepared ZnO@ZIF-71 / WO3 composite material has the advantages of good moisture resistance, low operating temperature, good selectivity and high sensitivity, and also has the characteristics of fast response recovery speed and good long-term stability.

[0005] In order to achieve the above object, the technical solution of the present invention is achieved as follows:

[0006] The invention discloses an in-situ grown ZnO@ZIF-71 / WO3 composite material. The ZnO@ZIF-71 / WO3 gas-sensitive material is constructed layer by layer on a ceramic tube by an in-situ growth method. The ZnO@ZIF-71 / WO3 composite material is composed of one-dimensional ZnO@ZIF-71 nanorods in-situ grown on the surface of two-dimensional WO3 ultra-thin nanosheets. The WO3 nanosheets have a thickness of 8 to 20 nm, and the ZnO nanorods have a length of 500 to 1000 nm and a diameter of 50 to 150 nm.

[0007] A method for preparing an in-situ grown ZnO@ZIF-71 / WO3 composite material comprises the following steps:

[0008] Step one: accurately weigh a certain amount of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer (P123) into a mixed solvent of anhydrous ethanol (EtOH) and water, stir for 10-30 min to completely dissolve P123 to form a homogeneous mixed solution, then weigh a certain amount of tungsten hexachloride (WCl6) into the above mixed solution, stir for 15-30 min until WCl6 is completely dissolved to form a homogeneous solution, the mass ratio of P123 to WCl6 is 1:(1-5), the addition amount of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer in the mixed solution is 6-20 mg / mL, and the mass ratio of anhydrous ethanol to water is (15-40):1. Put a clean ceramic tube into the above solution for 2-4 min, take it out and dry, then immerse it again, repeat the immersion for 3-5 times to fully adsorb, then transfer the adsorbed ceramic tube and the precursor solution into a reaction kettle for hydrothermal reaction, in particular, the ceramic tube should be suspended in the center of the solution during the hydrothermal reaction instead of being deposited at the bottom of the solution; the reaction temperature is 110-150°C, and the reaction time is 80-240 min. After natural cooling, the ceramic tube is taken out and washed repeatedly with anhydrous ethanol, then dried and annealed at a temperature of 300-450°C with a heating rate of 1-3°C / min and a holding time of 2-4 h; thus a ceramic tube with WO3 nanosheets grown thereon is obtained.

[0009] Step two: weigh a certain amount of zinc acetate dihydrate (Zn(CH3COO)2·2H2O) into a certain molar concentration of sodium hydroxide (NaOH) solution, stir for 15-20 min until Zn(CH3COO)2·2H2O is completely dissolved to form a clear zinc acetate dihydrate solution, and then put the ceramic tube obtained in step one into the above zinc acetate dihydrate solution for 3-5 times of adsorption, each time for 3 min. Then add a certain amount of cetyltrimethylammonium bromide (CTAB) to the above zinc acetate dihydrate solution, heat it at 60-65°C to completely dissolve it, and then transfer the solution and the ceramic tube with WO3 nanosheets grown thereon into a polytetrafluoroethylene-lined high-pressure reaction kettle for hydrothermal reaction, in which the ceramic tube should be suspended in the center of the solution during the hydrothermal reaction instead of being deposited at the bottom of the solution; after natural cooling, the ceramic tube is taken out and washed repeatedly, dried at 50°C, and annealed to obtain in-situ grown ZnO / WO3 composite material.

[0010] Step three: weigh a certain amount of 4,5-dichloroimidazole into a solution of DMF and H2O with a certain ratio, and then transfer the ZnO / WO3 composite material obtained in step two and the solution into a reaction kettle for hydrothermal reaction, in which the ceramic tube should be suspended in the center of the solution during the hydrothermal reaction instead of being deposited at the bottom of the solution; after cooling, the ceramic tube is taken out and washed with DMF to obtain in-situ grown ZnO@ZIF-71 / WO3 composite material.

[0011] Preferably, the concentration of sodium hydroxide in the second step is 0.15-0.3 mol / L, the molar ratio of Zn(CH3COO)2·2H2O and CTAB is 1:(10-12), and the concentration of zinc acetate dihydrate in the zinc acetate dihydrate solution is 1.38-2.8 mg / mL.

[0012] Preferably, the hydrothermal reaction conditions in the second step are 130-150 DEG C for 8-12 h, and the hydrothermal temperature in the third step is 60-85 DEG C for 2-4 h.

[0013] Preferably, the annealing process in the second step is carried out in an air atmosphere, the annealing temperature is 300-450 DEG C, the heating rate is 1 DEG C / min-3 DEG C / min, and the holding time is 2-4 h.

[0014] Application of in-situ grown ZnO@ZIF-71 / WO3 composite material in real-time detection of NO2.

[0015] Preferably, the ZnO@ZIF-71 / WO3 composite material grown on the ceramic tube is made into a ZnO@ZIF-71 / WO3 gas sensor for real-time detection of NO2, and the steps are as follows: the ZnO@ZIF-71 / WO3 composite material is directly welded on a black hexagonal base, a Ni-Cr heating wire is welded on the hexagonal base by passing through the ceramic tube, and the in-situ grown ZnO@ZIF-71 / WO3 gas sensor is prepared after aging at room temperature for 5 days.

[0016] The beneficial effects of the present application are as follows:

[0017] The present application adopts the mode of in-situ growth of ZnO@ZIF-71 / WO3 composite material, which is beneficial to the close combination between the layers of gas-sensitive materials, and also makes the sensitive material layer and the ceramic tube closely combined, and the preparation method is simple, which saves the manual coating process, has good repeatability, and reduces the operation error in the process of manually coating the gas-sensitive material.

[0018] (1) Low working temperature: the present application constructs a multi-level structure of one-dimensional ZnO nanorod grown on the surface of two-dimensional WO3 nanosheet, forms a ZnO / WO3 heterojunction, significantly reduces the resistance of the composite material, has a higher activation energy at a lower temperature, promotes the adsorption of oxygen molecules at a lower temperature, and the prepared ZnO / WO3 and ZnO@ZIF-71 / WO3 sensors exhibit excellent response to NO2 at 180 DEG C, which reduces the working temperature.

[0019] (2) selectivity: the ZnO@ZIF-71 / WO3 gas sensor described in the application has high selectivity to NO2 and low or no sensitivity to other gases, such as benzene, toluene, xylene, anhydrous ethanol, isopropanol, n-butanol, acetone, formaldehyde, triethylamine, ammonia, formamide, aniline and nitrogen dioxide;

[0020] (3) high sensitivity: the ZnO@ZIF-71 / WO3 gas sensor provided by the application has a large specific surface area, rich active sites and defects, and the formation of ZnO / WO3 heterojunction and the synergistic effect between multiple materials greatly improve the sensitivity. The composite material has excellent response to 100ppm of NO2 gas at 180℃, and the response value to 100ppm of NO2 gas is 947.96, which is 3.07 times that of ZnO / WO3 gas sensor and 12.12 times that of pure WO3 gas sensor;

[0021] (4) fast response and recovery speed: the in-situ grown ZnO@ZIF-71 / WO3 gas sensor described in the application has a response time of 39s and a recovery time of 6s to 100ppm of NO2 gas at 180℃, which is mainly due to the rapid contact of NO2 gas molecules with the two-dimensional WO3 surface along the one-dimensional ZnO nanorod tip, and the unique pore structure of ZIF-71 also provides a way for the diffusion of gas molecules;

[0022] (5) good long-term stability: the ZnO@ZIF-71 / WO3 composite material described in the application grows ZnO@ZIF-71 / WO3 gas sensitive layer on the surface of Al2O3 ceramic tube by in-situ growth, eliminating the coating process of traditional semiconductor gas sensor and avoiding the problem of poor stability caused by loose combination of gas sensitive layer material and ceramic tube substrate. Moreover, the in-situ growth method uniformly grows a thin and uniform functional layer in the solution, which also helps the rapid adsorption and desorption process of gas molecules and materials, thereby improving the stability of the material. The prepared material can maintain high response value for a month;

[0023] (6) good moisture resistance: the ZnO@ZIF-71 / WO3 composite material described in the application utilizes the hydrophobic property of ZIF-71 to block the entry of part of the water molecules, and the rough surface formed by the one-dimensional ZnO grown on the nanosheet also blocks the contact of some water molecules with the WO3 surface, greatly improving the moisture resistance of WO3. The ZnO@ZIF-71 / WO3 composite material shows good moisture resistance under a series of humidity environments, and still has a high response value when the humidity is as high as 85%RH.

[0024] The 1D / 2D composite multistage structure in the application improves the specific surface area and surface roughness of the material, and further improves the adsorption and desorption rate of the material surface, greatly improves the moisture resistance by virtue of the unique pore structure and hydrophobic characteristics of the ZIF-71 material itself, and expands the practical value of pure WO3 for NO2 detection. The gas sensor disclosed in the application has the characteristics of high sensitivity, good selectivity, fast response and recovery, good stability and good moisture resistance when used for NO2 gas detection, and has good repeatability, simple preparation process and low cost. The problems of poor stability, long response and recovery time, poor repeatability and poor moisture resistance in the detection of NO2 gas caused by uneven manual coating, too thick gas sensitive layer or poor combination of gas sensitive material and ceramic tube are solved. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor.

[0026] Figure 1 SEM images of different materials obtained in Example 1; (a, b) in-situ grown WO3 nanosheets; (c, d) ZnO / WO3 composite material; (e, f) ZnO@ZIF-71 / WO3 composite material.

[0027] Figure 2 Sensitivity curves of the gas sensor of different materials obtained in Example 1 to 100ppm NO2 at different working temperatures.

[0028] Figure 3 Dynamic response curve of the in-situ grown ZnO@ZIF-71 / WO3 gas sensor obtained in Example 1 to 100ppm NO2 at 180 DEG C.

[0029] Figure 4 Dynamic response curve of the in-situ grown ZnO@ZIF-71 / WO3 gas sensor obtained in Example 1 to different concentrations of NO2 gas at 180 DEG C.

[0030] Figure 5 Linear fitting curve of the in-situ grown ZnO@ZIF-71 / WO3 gas sensor obtained in Example 1 to different gas concentrations and sensitivity.

[0031] Figure 6 Long-term stability curve of the in-situ grown ZnO@ZIF-71 / WO3 gas sensor obtained in Example 1 to 100ppm NO2 gas at 180 DEG C.

[0032] Figure 7 Selectivity of different materials gas sensor obtained in Example 1 to different interference gases.

[0033] Figure 8 Humidity stability of in-situ growth ZnO@ZIF-71 / WO3 gas sensor to 100ppm NO2 gas. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative labor are within the protection scope of the present application.

[0035] Example 1

[0036] A preparation method of an in-situ growth ZnO@ZIF-71 / WO3 composite material, comprising the following steps:

[0037] (1) 0.2g of P123 is weighed and dissolved in a mixed solution of 16.5mL of anhydrous ethanol and 0.5mL of water, and stirred for 10min to form a uniform solution. Then, 0.4g of WCl6 is weighed and dissolved in the above mixed solution, and stirred for 30min to form a uniform solution. A clean ceramic tube is immersed in the above solution for 3min, taken out and dried, and then immersed repeatedly for 5 times. Subsequently, the ceramic tube is hung in the center of a polytetrafluoroethylene reaction kettle, and the solution is transferred to a high-pressure reaction kettle lined with polytetrafluoroethylene and reacted at 110℃ for 2h. After natural cooling, the ceramic tube is taken out and washed repeatedly with anhydrous ethanol. After drying, annealing treatment is performed, the annealing temperature is 400℃, the heating rate is 2℃ / min, and the holding time is 2h. Thus, in-situ growth WO3 nanosheets are prepared.

[0038] (2) Weigh 0.0626 g of zinc acetate dihydrate (Zn(CH3COO)2·2H2O) and dissolve it in 30 mL of sodium hydroxide (0.225 mol / L) solution, and stir thoroughly for 15 min until the Zn(CH3COO)2·2H2O is completely dissolved to form a clear solution. Then, put the ceramic tube with WO3 nanosheets grown in step (1) into the above solution for adsorption for 3 times, each time for 3 min. Then, add 1.2464 g of CTAB into the above solution, and heat it at 60°C until it is completely dissolved. Then, transfer the solution and the WO3 nanosheets adsorbed ceramic tube into a polytetrafluoroethylene-lined autoclave for hydrothermal reaction. The ceramic tube is hung in the center of the solution. The reaction temperature is 140°C, and the reaction time is 12 h. After the reaction, the ceramic tube is taken out and washed repeatedly, and then dried at 50°C. Subsequently, annealing is performed at an annealing temperature of 400°C, with a heating rate of 2°C / min and a holding time of 2 h, to obtain in-situ grown ZnO / WO3 composite material.

[0039] (3) Weigh 0.04 g of 4,5-dichloroimidazole and dissolve it in a mixed solution of 12 mL of DMF and 4 mL of H2O. Then, transfer the ceramic tube obtained in step (2) and the solution into a reaction kettle for hydrothermal reaction at 70°C for 2 h. After cooling, the in-situ grown ZnO@ZIF-71 / WO3 composite material is obtained by washing with DMF.

[0040] The ceramic tubes with in-situ grown WO3 nanosheets, ZnO / WO3 composite material and ZnO@ZIF-71 / WO3 composite material obtained in steps (1), (2) and (3) are respectively welded to a hexagonal base, and then packaged and aged to obtain ZnO / WO3 and ZnO@ZIF-71 / WO3 gas sensitive sensors.

[0041] Figure 1 The SEM images of different materials prepared in Example 1 are shown in Figure 1 As can be seen from (a, b), the WO3 nanosheets are uniformly grown vertically on the surface of the ceramic tube. Figure 1 As can be seen from (c, d), the ZnO nanorods are uniformly grown on the surface of the WO3 to form a 1D / 2D multi-level structure. Figure 1 As can be seen from (e, f), the growth of ZIF-71 does not change the morphology of the original ZnO / WO3 composite material, but the diameter of the ZnO nanorods is reduced and the surface becomes rough, indicating that part of the ZnO is dissolved to generate ZIF-71. Gas sensitive research is carried out on the gas sensitive elements of the several different materials prepared.

[0042] Figure 2The sensitivity curves of the in-situ grown pure WO3, ZnO / WO3 and ZnO@ZIF-71 / WO3 gas sensors prepared in Example 1 to 100 ppm NO2 gas at different working temperatures. It can be seen from Figure 2 that the sensitivities of the three prepared gas sensors to NO2 gas increase first and then decrease with the increase of working temperature. The WO3 gas sensor shows the highest response to NO2 gas at 210°C, while the ZnO / WO3 and ZnO@ZIF-71 / WO3 gas sensors show excellent response to NO2 gas at 180°C, which significantly reduces the working temperature of the pure WO3 gas sensor. It can also be seen from the figure that the sensitivity of the ZnO@ZIF-71 / WO3 gas sensor prepared by the application to NO2 gas is higher than that of the other two gas sensors.

[0043] Figure 3 The dynamic response curve of the ZnO@ZIF-71 / WO3 gas sensor in Example 1 at the optimal working temperature of 180°C and the NO2 gas concentration of 100 ppm. It can be seen from Figure 3 that the ZnO@ZIF-71 / WO3 gas sensor has a short response and recovery time to NO2 gas, with a response time of 39 s and a recovery time of 6 s.

[0044] Figure 4 The dynamic response curve of the ZnO@ZIF-71 / WO3 gas sensor obtained in Example 1 at a working temperature of 180°C to NO2 gas of different concentrations. It can be seen from Figure 4 that the sensitivity of the gas sensor increases with the increase of the concentration of NO2 gas, indicating that the prepared sensor has good reversibility. In addition, it can be seen from the linear fitting curve between the gas of different concentrations and the sensitivity Figure 5 that the sensor has a good linear relationship in the test range of 1-100 ppm.

[0045] Figure 6 The long-term stability curve of the ZnO@ZIF-71 / WO3 gas sensor obtained in Example 1 at a working temperature of 180°C and a NO2 gas concentration of 100 ppm. It can be seen from Figure 6 that after one week or one month of use, the gas sensor can still quickly recover to the initial sensitivity, indicating that the gas sensor has good consistency and stability during long-term use, i.e. the gas sensor has good repeatability and stability during the detection of NO2 gas.

[0046] Figure 7The gas sensitive sensors of different materials prepared in Example 1 were subjected to gas sensitive test on benzene, toluene, xylene, anhydrous ethanol, isopropanol, n-butanol, acetone, formaldehyde, triethylamine, ammonia, formamide, aniline, nitrogen dioxide 13 kinds of gases. The response value of oxidizing gas is defined as positive value, and the response value of reducing gas is defined as negative value. As can be seen from the figure, the three prepared sensors all show ultra-high selectivity to NO2 gas, and the response to other gases is poor, and the selectivity of the ZnO@ZIF-71 / WO3 gas sensitive sensor prepared by the application to NO2 gas is obviously better than that of the other two gas sensitive elements.

[0047] Figure 8 The relative sensitivity curves of the gas sensitive sensors of different materials obtained in Example 1 at a working temperature of 180℃ to different humidity can be seen that the prepared element still has a high response in the test under high humidity, and the ZnO@ZIF-71 / WO3 gas sensitive element still has 62.75% of the original response value under the condition of relative humidity of 85% RH, while the response value of pure WO3 is only 31.54% of the original value. It can be seen that the ZnO@ZIF-71 / WO3 gas sensitive sensor significantly improves the humidity resistance of the WO3-based gas sensitive sensor and has good humidity resistance.

[0048] Example 2

[0049] A preparation method of in-situ grown ZnO@ZIF-71 / WO3 composite material, comprising the following steps:

[0050] (1) 0.2g P123 is weighed and dissolved in a mixed solution of 16.5mL anhydrous ethanol and 0.5mL water, and stirred thoroughly for 10min, and P123 is completely dissolved to form a uniform solution, then 0.4g WCl6 is weighed and dissolved in the above mixed solution, and stirred thoroughly for 30min, and WCl6 is completely dissolved to form a uniform solution, a clean ceramic tube is placed in the above solution for adsorption for 3min, taken out and dried, then immersed repeatedly for 5 times, then the ceramic tube is hung in the center of a polytetrafluoroethylene reaction kettle, and the solution is transferred to a high-pressure reaction kettle lined with polytetrafluoroethylene to immerse the ceramic tube, and reacted at 110℃ for 2h, and after natural cooling, the ceramic tube is taken out, washed repeatedly with anhydrous ethanol and dried, then annealed at 400℃ with a temperature rising rate of 3℃ / min for 2h to obtain in-situ grown WO3 nanosheets.

[0051] (2) 0.0835 g of zinc acetate dihydrate (Zn(CH3COO)2·2H2O) was weighed into 30 mL of a sodium hydroxide (0.3 mol / L) solution, and stirred thoroughly for 15 min until the Zn(CH3COO)2·2H2O was completely dissolved to form a clear solution. The ceramic tube with WO3 nanosheets grown in step (1) was repeatedly adsorbed in the above solution for 3 times, and then 1.6619 g of CTAB was added to the above solution and completely dissolved by slightly heating at 60°C. The solution and the ceramic tube with WO3 nanosheets grown after adsorption were then transferred into a polytetrafluoroethylene-lined autoclave for hydrothermal reaction. The ceramic tube was hung in the center of the solution, the reaction temperature was 130°C, and the reaction time was 12 h. After natural cooling, the ceramic tube was taken out, washed and dried at 50°C, and then annealed. The annealing temperature was 350°C, the heating rate was 1°C / min, and the holding time was 3 h. An in-situ grown ZnO / WO3 composite material was obtained.

[0052] (3) 0.04 g of 4,5-dichloroimidazole was weighed into a mixed solution of 12 mL of DMF and 4 mL of H2O, and then the ceramic tube obtained in step (2) was transferred into the reaction kettle together with the solution for hydrothermal reaction at 70°C for 2 h. After cooling, the in-situ grown ZnO@ZIF-71 / WO3 composite material was obtained by washing with DMF.

[0053] The in-situ grown WO3, ZnO / WO3 and ZnO@ZIF-71 / WO3 ceramic tubes prepared in steps (1), (2) and (3) were respectively welded to a hexagonal base, and encapsulated and aged to obtain in-situ grown WO3, ZnO / WO3 and ZnO@ZIF-71 / WO3 gas sensitive sensors.

[0054] Example 3

[0055] A method for preparing an in-situ grown ZnO@ZIF-71 / WO3 composite material, comprising the following steps:

[0056] (1) 0.2 g of P123 was weighed into a mixed solution of 16.5 mL of anhydrous ethanol and 0.5 mL of water, and stirred thoroughly until the P123 was completely dissolved to form a uniform solution. Then, 0.4 g of WCl6 was weighed into the above mixed solution, and stirred thoroughly for 30 min until the WCl6 was completely dissolved to form a uniform solution. A clean ceramic tube was immersed in the above solution for 3 min, taken out and dried, and then repeatedly immersed for 5 times. Then, the ceramic tube was hung in the center of a polytetrafluoroethylene reaction kettle, and the solution was transferred into a polytetrafluoroethylene-lined autoclave to immerse the ceramic tube. The reaction was carried out at 110°C for 2 h. After natural cooling, the ceramic tube was taken out, repeatedly washed with anhydrous ethanol and dried. Then, annealing treatment was performed. The annealing temperature was 400°C, the heating rate was 1°C / min, and the time was 2 h. An in-situ grown WO3 nanosheet was obtained.

[0057] (2) Weigh 0.0417 g of zinc acetate dihydrate (Zn(CH3COO)2·2H2O) into 30 mL of sodium hydroxide (0.15 mol / L) solution, stir well until Zn(CH3COO)2·2H2O is completely dissolved, forming a clear solution, and then place the ceramic tube with WO3 nanosheets grown in step (1) into the above solution for adsorption 3 times, 3 min each time, then add 0.6923 g of CTAB to the above solution, and heat it at 60°C to completely dissolve, then transfer the solution and the adsorbed WO3 ceramic tube to a polytetrafluoroethylene-lined high-pressure reaction kettle for hydrothermal reaction, with the ceramic tube hanging in the center of the solution, the reaction temperature is 150°C, and the reaction time is 8 h. After natural cooling, the ceramic tube is taken out and washed clean and dried at 50°C, then annealed, the annealing temperature is 450°C, the heating rate is 2°C / min, and the holding time is 2 h, to obtain in-situ grown ZnO / WO3 composite material.

[0058] (3) Weigh 0.04 g of 4,5-dichloroimidazole into 12 mL of a mixed solution of DMF and 4 mL of H2O, then transfer the ceramic tube obtained in step (2) and the solution into a reaction kettle for hydrothermal reaction at 60°C for 4 h, and then take it out and wash it with DMF to obtain in-situ grown ZnO@ZIF-71 / WO3 composite material.

[0059] The in-situ grown WO3, ZnO / WO3 and ZnO@ZIF-71 / WO3 ceramic tubes prepared in steps (1), (2) and (3) are respectively welded to a hexagonal base, and then packaged and aged to obtain in-situ grown WO3, ZnO / WO3 and ZnO@ZIF-71 / WO3 gas sensitive sensors.

[0060] Example 4

[0061] A method for preparing in-situ grown ZnO@ZIF-71 / WO3 composite material, comprising the following steps:

[0062] (1) 0.2 g of P123 was weighed into a mixed solution of 16.5 mL of anhydrous ethanol and 0.5 mL of water, and after being fully stirred for 15 min, the P123 was completely dissolved to form a uniform solution. Then 0.4 g of WCl6 was weighed into the above mixed solution, and after being fully stirred for 20 min, the WCl6 was completely dissolved to form a uniform solution. A clean ceramic tube was placed in the above solution for adsorption for 3 min, taken out and dried, and then immersed repeatedly for 4 times. Subsequently, the ceramic tube was suspended in the center of a polytetrafluoroethylene reaction kettle, and the solution was transferred to a high-pressure reaction kettle lined with polytetrafluoroethylene to immerse the ceramic tube. The reaction was carried out at 130℃ for 2 h. After natural cooling, the ceramic tube was taken out and repeatedly rinsed with anhydrous ethanol. Subsequently, annealing treatment was performed at an annealing temperature of 400℃ and a temperature rise rate of 2℃ / min, and the holding time was 2 h. Thus, in-situ grown WO3 nanosheets were prepared.

[0063] (2) 0.0626 g of zinc acetate dihydrate (Zn(CH3COO)2·2H2O) was weighed into 30 mL of a sodium hydroxide (0.3 mol / L) solution, and after being fully stirred for 20 min, the Zn(CH3COO)2·2H2O was completely dissolved to form a clear solution. The ceramic tube with WO3 nanosheets grown in step (1) was placed in the above solution for repeated adsorption. Subsequently, 1.1433 g of CTAB was added to the above solution, and the solution was completely dissolved by slightly heating at 60℃. Then, the solution and the adsorbed WO3 ceramic tube were transferred together to a high-pressure reaction kettle lined with polytetrafluoroethylene for hydrothermal reaction. The ceramic tube was suspended in the center of the solution. The reaction temperature was 150℃, and the reaction time was 10 h. After natural cooling, the ceramic tube was taken out and repeatedly rinsed. Drying was performed at 50℃. Subsequently, annealing was performed at an annealing temperature of 400℃ and a temperature rise rate of 3℃ / min, and the holding time was 2 h. Thus, in-situ grown ZnO / WO3 composite material was prepared.

[0064] (3) 0.04 g of 4,5-dichloroimidazole was weighed into a mixed solution of 13.5 mL of DMF and 2.5 mL of H2O. Subsequently, the ceramic tube obtained in step (2) was transferred together with the solution into a reaction kettle for hydrothermal reaction at 70℃ for 2 h. After cooling, the in-situ grown ZnO@ZIF-71 / WO3 composite material was obtained by rinsing with DMF.

[0065] The in-situ grown WO3, ZnO / WO3 and ZnO@ZIF-71 / WO3 ceramic tubes prepared in steps (1), (2) and (3) were respectively welded to a hexagonal base. Packaging and aging were performed, and thus in-situ grown WO3, ZnO / WO3 and ZnO@ZIF-71 / WO3 gas sensitive sensors were prepared.

[0066] Example 5

[0067] A method for preparing in-situ grown ZnO@ZIF-71 / WO3 composite material, comprising the following steps:

[0068] (1) 0.2 g of P123 was weighed into a mixed solution of 16.5 mL of anhydrous ethanol and 0.5 mL of water, and stirred thoroughly for 20 min, and the P123 was completely dissolved to form a uniform solution. Then 0.4 g of WCl6 was weighed into the mixed solution, and stirred thoroughly for 30 min, and the WCl6 was completely dissolved to form a uniform solution. A clean ceramic tube was immersed in the solution for 3 min, taken out and dried, and then immersed repeatedly for 3 times. Subsequently, the ceramic tube was hung in the center of a polytetrafluoroethylene reaction kettle, and the solution was transferred to a high-pressure reaction kettle lined with polytetrafluoroethylene to immerse the ceramic tube. The reaction was carried out at a temperature of 110°C for 2 h, and after natural cooling, the ceramic tube was taken out, washed repeatedly with anhydrous ethanol and dried, and then annealed at an annealing temperature of 400°C with a temperature rising rate of 2°C / min and a holding time of 2 h, to obtain in-situ grown WO3 nanosheets.

[0069] (2) 0.0626 g of zinc acetate dihydrate (Zn(CH3COO)2·2H2O) was weighed into 30 mL of a sodium hydroxide (0.3 mol / L) solution, and stirred thoroughly for 20 min, and the Zn(CH3COO)2·2H2O was completely dissolved to form a clear solution. The ceramic tube with WO3 nanosheets grown thereon obtained in step (1) was immersed in the solution for 3 times, each time for 3 min. Then 1.0914 g of CTAB was added to the solution, and the solution was heated at 60°C to completely dissolve the CTAB. Subsequently, the solution and the WO3 ceramic tube after adsorption were transferred to a high-pressure reaction kettle lined with polytetrafluoroethylene for hydrothermal reaction. The ceramic tube was hung in the center of the solution, and the reaction was carried out at a temperature of 140°C for 10 h. After natural cooling, the ceramic tube was taken out, washed repeatedly and dried at 50°C. Subsequently, annealing was carried out at an annealing temperature of 350°C with a temperature rising rate of 1°C / min and a holding time of 3 h, to obtain in-situ grown ZnO / WO3 composite material.

[0070] (3) 0.1 g of 4,5-dichloroimidazole was weighed into a mixed solution of 12 mL of DMF and 4 mL of H2O. Subsequently, the ceramic tube obtained in step (2) was transferred to the reaction kettle together with the solution for hydrothermal reaction at 85°C for 2 h. After cooling, the in-situ grown ZnO@ZIF-71 / WO3 composite material was obtained by washing with DMF.

[0071] The in-situ grown WO3, ZnO / WO3 and ZnO@ZIF-71 / WO3 ceramic tubes obtained in steps (1), (2) and (3) were respectively welded to a hexagonal base, and encapsulated and aged, to obtain in-situ grown WO3, ZnO / WO3 and ZnO@ZIF-71 / WO3 gas sensitive sensors.

[0072] Example 6

[0073] A preparation method of in-situ grown ZnO@ZIF-71 / WO3 composite material, comprising the following steps:

[0074] (1) 0.2 g of P123 was weighed and dissolved in a mixed solution of 16.5 mL of anhydrous ethanol and 0.5 mL of water, and stirred for 20 min until P123 was completely dissolved to form a uniform solution. Then 0.4 g of WCl6 was weighed and dissolved in the above mixed solution, and stirred for 30 min until WCl6 was completely dissolved to form a uniform solution. A clean ceramic tube was placed in the above solution for adsorption for 3 min, taken out and dried, and then immersed repeatedly for 5 times. Subsequently, the ceramic tube was hung in the center of the solution in a polytetrafluoroethylene reaction kettle, and the solution was transferred to a high-pressure reaction kettle lined with polytetrafluoroethylene for reaction at 110℃ for 2 h. After natural cooling, the ceramic tube was taken out, washed repeatedly with anhydrous ethanol and dried, and then annealed at an annealing temperature of 400℃ and a heating rate of 2℃ / min for 2 h. Thus, in-situ grown WO3 nanosheets were prepared.

[0075] (2) 0.0626 g of zinc acetate dihydrate (Zn(CH3COO)2·2H2O) was weighed and dissolved in a 0.3 mol / L sodium hydroxide (NaOH) solution, and stirred for 20 min until Zn(CH3COO)2·2H2O was completely dissolved to form a clear solution. The ceramic tube with WO3 nanosheets grown in step (1) was placed in the above solution for adsorption for 3 times, each time for 3 min. Then 1.2464 g of CTAB was added to the above solution, and heated at 60℃ to completely dissolve it. Subsequently, the solution and the adsorbed WO3 ceramic tube were transferred together to a high-pressure reaction kettle lined with polytetrafluoroethylene for hydrothermal reaction. The ceramic tube was hung in the center of the solution, and the reaction was carried out at a temperature of 140℃ for 12 h. After natural cooling, the ceramic tube was taken out, washed repeatedly and dried at 50℃. Subsequently, annealing was carried out at an annealing temperature of 400℃ and a heating rate of 2℃ / min for 2 h. Thus, in-situ grown ZnO / WO3 composite material was prepared.

[0076] (3) 0.08 g of 4,5-dichloroimidazole was weighed and dissolved in a mixed solution of 12 mL of DMF and 4 mL of H2O. Subsequently, the ceramic tube obtained in step (2) was transferred together with the solution to a reaction kettle for hydrothermal reaction at 70℃ for 4 h. After cooling, the in-situ grown ZnO@ZIF-71 / WO3 composite material was obtained by washing with DMF.

[0077] The in-situ grown WO3, ZnO / WO3 and ZnO@ZIF-71 / WO3 ceramic tubes prepared in steps (1), (2) and (3) were respectively welded to a hexagonal base, and encapsulated and aged. Thus, in-situ grown WO3, ZnO / WO3 and ZnO@ZIF-71 / WO3 gas sensitive sensors were prepared.

[0078] Example 7

[0079] A preparation method of in-situ grown ZnO@ZIF-71 / WO3 composite material, comprising the following steps:

[0080] (1) 0.32 g of P123 was weighed and dissolved in a mixed solution of 15 mL of anhydrous ethanol and 1 mL of water, and stirred for 10 min until P123 was completely dissolved to form a uniform solution. Then 0.32 g of WCl6 was weighed and dissolved in the above mixed solution, and stirred for 30 min until WCl6 was completely dissolved to form a uniform solution. A clean ceramic tube was placed in the above solution for adsorption for 3 min, taken out and dried, and then immersed repeatedly for 5 times. Subsequently, the ceramic tube was hung in the center of a polytetrafluoroethylene reaction kettle, and the solution was transferred to a high-pressure reaction kettle lined with polytetrafluoroethylene to immerse the ceramic tube. The reaction was carried out at 130℃ for 80 min. After natural cooling, the ceramic tube was taken out, washed repeatedly with anhydrous ethanol and dried. Then, annealing treatment was carried out at 450℃ with a heating rate of 3℃ / min for 2 h to obtain in-situ grown WO3 nanosheets.

[0081] (2) 0.0835 g of zinc acetate dihydrate (Zn(CH3COO)2·2H2O) was weighed and dissolved in 30 mL of sodium hydroxide (0.3 mol / L) solution, and stirred for 15 min until Zn(CH3COO)2·2H2O was completely dissolved to form a clear solution. The ceramic tube with WO3 nanosheets grown in step (1) was placed in the above solution and adsorbed repeatedly for 3 times. Then 1.6619 g of CTAB was added to the above solution and completely dissolved by slightly heating at 60℃. Then the solution and the ceramic tube with WO3 nanosheets grown after adsorption were transferred together to a high-pressure reaction kettle lined with polytetrafluoroethylene for hydrothermal reaction. The ceramic tube was hung in the center of the solution. The reaction was carried out at a temperature of 130℃ for 12 h. After natural cooling, the ceramic tube was taken out, washed clean and dried at 50℃. Then annealing was carried out at a temperature of 300℃ with a heating rate of 1℃ / min for 4 h to obtain in-situ grown ZnO / WO3 composite material.

[0082] (3) 0.0396 g of 4,5-dichloroimidazole was weighed and dissolved in a mixed solution of 12 mL of DMF and 6 mL of H2O. Then the ceramic tube obtained in step (2) was transferred together with the solution into a reaction kettle for hydrothermal reaction at 70℃ for 3 h. After cooling, the in-situ grown ZnO@ZIF-71 / WO3 composite material was obtained by washing with DMF.

[0083] Example 8

[0084] A preparation method of in-situ grown ZnO@ZIF-71 / WO3 composite material, comprising the following steps:

[0085] (1) take 0.246g P123 and dissolve in 40mL anhydrous ethanol and 1mL water mixed solution, fully stir for 10min, P123 completely dissolves to form a uniform solution, then take 1.23g WCl6 and dissolve in the above mixed solution, fully stir for 30min, WCl6 completely dissolves to form a uniform solution, put a clean ceramic tube into the above solution and adsorb for 3min, take out and dry, then immerse repeatedly for 5 times, then hang the ceramic tube in the center of a polytetrafluoroethylene reaction kettle, and transfer the solution to a polytetrafluoroethylene lined high-pressure reaction kettle to immerse the ceramic tube, react at 150℃ for 240min, take out the ceramic tube after natural cooling, rinse repeatedly with anhydrous ethanol and dry, then anneal at 300℃ with a temperature rising rate of 1℃ / min for 4h to obtain in-situ grown WO3 nanosheets.

[0086] (2) take 0.0835g of zinc acetate dihydrate (Zn(CH3COO)2·2H2O) and dissolve in 30mL sodium hydroxide (0.3mol / L) solution, fully stir for 15min, Zn(CH3COO)2·2H2O completely dissolves to form a clear solution, put the ceramic tube with WO3 nanosheets grown in step (1) into the above solution and adsorb repeatedly for 3 times, then add 1.6619g of CTAB to the above solution, completely dissolve by slightly heating at 60℃, then transfer the solution and the ceramic tube with WO3 nanosheets grown after adsorption to a polytetrafluoroethylene lined high-pressure reaction kettle for hydrothermal reaction, the ceramic tube is hung in the center of the solution, the reaction temperature is 130℃, and the reaction time is 12h, take out the ceramic tube after natural cooling, rinse clean and dry at 50℃, then anneal, the annealing temperature is 300℃, the temperature rising rate is 1℃ / min, and the holding time is 4h, to obtain in-situ grown ZnO / WO3 composite material.

[0087] (3) take 0.07g of 4,5-dichloroimidazole and dissolve in 12mL DMF and 2mL H2O mixed solution, then transfer the ceramic tube obtained in step (2) and the solution to a reaction kettle for hydrothermal reaction at 70℃ for 3h, take out after cooling and rinse with DMF to obtain in-situ grown ZnO@ZIF-71 / WO3 composite material.

[0088] The above only describes preferred embodiments of the present application and is not intended to limit the present application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. In-situ grown ZnO@ZIF-71 / WO3 composite material, characterized in that: The ZnO@ZIF-71 / WO3 composite material is constructed layer by layer on the ceramic tube by in-situ growth, and is composed of one-dimensional ZnO nanorod grown in-situ on the surface of two-dimensional WO3 ultrathin nanosheet, wherein the WO3 nanosheet has a thickness of 8-20 nm, the ZnO nanorod has a length of 500 nm-1000 nm and a diameter of 50-150 nm, and the ZIF-71 material is synthesized on the surface of the ZnO by taking the ZnO as Zn source, so as to obtain the ZnO@ZIF-71 / WO3 multi-level structure material, wherein the size of the ZnO@ZIF-71 nanorod still remains at a length of 500 nm-1000 nm and a diameter of 50-150 nm; The preparation of the in-situ grown ZnO@ZIF-71 / WO3 composite material comprises the following steps: (1) WO3 nanosheet is grown vertically on the surface of the ceramic tube by in-situ growth method by taking polyethylene oxide-polypropylene oxide-polyethylene oxide triblock polymer and tungsten hexachloride as raw materials, so as to obtain the ceramic tube with grown WO3 nanosheet; (2) ZnO nanorod structure is synthesized in-situ on the surface of the ceramic tube with grown WO3 nanosheet by taking zinc acetate dihydrate as raw material, so as to obtain the in-situ grown ZnO / WO3 composite material; (3) ZIF-71 film is synthesized by taking the ZnO in the ZnO / WO3 composite material as Zn source and taking 4,5-dichloroimidazole as raw material, so as to obtain the in-situ grown ZnO@ZIF-71 / WO3 composite material; The specific process of the step (2) is that: zinc acetate dihydrate is dissolved in sodium hydroxide solution to obtain zinc acetate dihydrate solution, the ceramic tube with grown WO3 nanosheet obtained in the step (1) is adsorbed in the zinc acetate dihydrate solution for 3-5 times, each time for 2-4 min, then cetyltrimethylammonium bromide is added in the zinc acetate dihydrate solution to completely dissolve it, then the ceramic tube is transferred into a reaction kettle together with the solution to perform hydrothermal reaction, the ceramic tube is hung in the center of the solution during the hydrothermal reaction, and the cooled ceramic tube is washed after the reaction, and is annealed after drying to obtain the in-situ grown ZnO / WO3 composite material; The specific process of the step (3) is that: 4,5-dichloroimidazole is dissolved in a mixed solution of DMF and H2O to obtain 4,5-dichloroimidazole solution, the volume ratio of DMF to H2O is (2-6):1, and the concentration of 4,5-dichloroimidazole in the 4,5-dichloroimidazole solution is 2.2-6.3 mg / mL; the ceramic tube with grown ZnO / WO3 composite material obtained in the step (2) is transferred into a reaction kettle together with the solution to perform hydrothermal reaction, the ceramic tube is hung in the center of the solution during the hydrothermal reaction, the hydrothermal temperature is 60-85 ℃, the reaction time is 2-4 h, and the in-situ grown ZnO@ZIF-71 / WO3 composite material is obtained after washing after cooling. 2.The in-situ grown ZnO@ZIF-71 / WO3 composite material according to claim 1, characterized in that: The specific process of step (1) is as follows: the poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock polymer is dissolved in a mixed solution of anhydrous ethanol and water, and fully stirred to completely dissolve the poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock polymer, then WCl6 is dissolved in the mixed solution, and fully stirred until WCl6 is completely dissolved, a clean ceramic tube is placed in the solution for adsorption for 2-4 min, taken out to dry, then immersed again, and the above steps are repeated for 3-5 times, then the adsorbed ceramic tube and the precursor solution are transferred to a reaction kettle for hydrothermal reaction, the ceramic tube is suspended in the center of the solution during the hydrothermal reaction, and after the reaction is completed, the solution is naturally cooled, repeatedly washed with anhydrous ethanol, dried, and then annealed to obtain in-situ grown WO3 nanosheets. 3.The in-situ grown ZnO@ZIF-71 / WO 3 composite material of claim 2, characterized in that: In step (1), the mass ratio of the poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock polymer to WCl6 is 1:(1-5), the mass ratio of anhydrous ethanol to water in the mixed solution is (15-40):1, and the addition amount of the poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock polymer in the mixed solution is 6-20 mg / mL. 4.The in-situ grown ZnO@ZIF-71 / WO3 composite material according to claim 3, characterized in that: In step (1), the hydrothermal reaction temperature is 110-150 ℃, and the reaction time is 80-240 min; in step (1), the annealing temperature is 300-450 ℃, the heating rate is 1-3 ℃ / min, and the holding time is 2-4 h. 5.The in-situ grown ZnO@ZIF-71 / WO3 composite material of claim 4, characterized in that: In step (2), the concentration of sodium hydroxide in the sodium hydroxide solution is 0.15-0.3 mol / L, and the molar ratio of zinc acetate dihydrate to cetyltrimethylammonium bromide is 1:(10-12); the concentration of zinc acetate dihydrate in the zinc acetate dihydrate solution is 1.38-2.8 mg / mL; in step (2), the hydrothermal reaction temperature is 130-150 ℃, and the reaction time is 8-12 h. 6.The in-situ grown ZnO@ZIF-71 / WO 3 composite material of claim 5, characterized in that: In step (2), the annealing temperature is 300-450 ℃, the heating rate is 1-3 ℃ / min, and the holding time is 2-4 h.

7. The in-situ grown ZnO@ZIF-71 / WO3 composite material in claim 1 is applied to real-time detection of NO2.

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