ZnO-coated C-ZIF composite gas sensitive material as well as preparation method and application thereof
Through the ZnO@C-ZIF composite material, the self-stacking problem of ZnO nanosheets was solved, the transmission channels and active sites were enhanced, and a highly sensitive and stable ethanol gas sensor was realized, which is suitable for industrial and environmental monitoring.
Patent Information
- Application Number
- CN202510615466.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-14
- Publication Date
- 2025-09-16
AI Technical Summary
Existing ZnO two-dimensional nanosheets are easy to stack, resulting in blocked transmission channels, low active site utilization, and poor moisture resistance, which limits their application in ethanol gas sensors.
Using ZnO@C-ZIF composite materials, ZnO@ZIF-8 was synthesized by a hydrothermal method, followed by low-temperature heat treatment under Ar atmosphere to form a carbonaceous layer to support ZnO nanosheets, avoiding self-stacking, and promoting charge carrier transport through the porous structure and heterojunction of C-ZIF, enhancing active sites, and maintaining high responsiveness under high humidity.
The ethanol gas sensor has achieved low operating temperature, high sensitivity and high stability, and has excellent moisture resistance, making it suitable for industrial production, environmental monitoring and human respiration monitoring.
Smart Images
Figure CN120651918A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of functional materials and relates to gas detection materials, in particular to a ZnO@C-ZIF composite gas sensitive material and a preparation method and application thereof. Background Art
[0002] As a common volatile organic compound, ethanol has important applications in industrial production, environmental monitoring, and human respiratory monitoring. It is a key indicator for judging safety standards and health conditions. Therefore, it is very necessary to design a low-temperature, stable, and moisture-resistant ethanol gas sensor.
[0003] Metal oxide semiconductors (MOSs) have attracted considerable attention due to their ease of preparation, low cost, compact size, low energy consumption, stable performance, and excellent oxidative catalytic activity. Zinc oxide (ZnO) has become a research hotspot due to its excellent synthesis and sensing properties. However, ZnO two-dimensional nanosheets are prone to stacking due to van der Waals forces, which affects internal transport channels and reduces the utilization of active sites. Their poor moisture resistance also limits sensor performance. Liu et al. synthesized a ZnO@ZIF-8 composite using ZIF-8 as a support layer, addressing the self-stacking issue of ZnO nanosheets. At 80% humidity, the response to 50 ppm ethanol was reduced by approximately 22%. Wei et al. synthesized Ce-doped MOF:ZnO nanostructures, which exhibited a response of 146.32 to n-butanol under high humidity conditions. Yao et al. synthesized a ZnO@ZIF-CoZn material by coating a ZnO nanowire array with a ZIF-CoZn film. In the relative humidity (RH) range of 0-90%, the sensitivity to 10 ppm acetone remains at around 5. Although the research has improved the gas sensing performance, insufficient moisture resistance, long response / recovery time and poor stability still limit its practical application. Summary of the Invention
[0004] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a ZnO@C-ZIF composite gas sensitive material with high sensitivity, low operating temperature, high stability and excellent moisture resistance, as well as a preparation method and application thereof.
[0005] In order to achieve the above object, the present invention adopts the following technical solutions:
[0006] A method for preparing a ZnO@C-ZIF composite gas-sensitive material comprises the following steps:
[0007] Step 1: dissolving zinc salt and urea in distilled water at a molar ratio of 1:(1.5-2.5) and stirring thoroughly to obtain a precursor solution, wherein the urea concentration is 0.5-1.0 mol / L;
[0008] Step 2: The precursor solution is placed in a reactor, placed in an oven at 100-140°C for hydrothermal reaction for 2-8 hours, then taken out for centrifugal washing and drying to obtain a ZnO nanosheet precursor, and the ZnO nanosheet precursor is placed in a muffle furnace at a heating rate of 1-5°C / min from room temperature to 450-650°C and then kept warm for 1-4 hours to obtain ZnO porous nanosheets;
[0009] Step 3: Take the ZnO porous nanosheets and 2-methylimidazole prepared in step 2 at a molar ratio of (1-5):1, dissolve the ZnO porous nanosheets in distilled water to obtain a solution A with a concentration of 0.2-1.0 mol / L, and dissolve 2-methylimidazole in N,N-dimethylformamide to obtain a solution B with a concentration of 0.1-1.0 mol / L. Under stirring, slowly add solution A dropwise to solution B and stir until the mixture is uniformly mixed. Then, place the mixture in a hydrothermal kettle at 60-80°C and heat for 12-36 hours. After the end, centrifuge, wash, and dry to obtain ZnO@ZIF-8 powder;
[0010] Step 4: The ZnO@ZIF-8 powder prepared in step 3 is evenly dispersed in a quartz porcelain boat, covered with a quartz cover, placed in a tube furnace, and heated from room temperature to 450-650°C at a heating rate of 1-5°C / min under an inert atmosphere and kept warm for 1-4 hours to obtain a ZnO@C-ZIF composite gas sensitive material.
[0011] The present invention also has the following technical features:
[0012] Preferably, the zinc salt includes either zinc nitrate or zinc acetate.
[0013] Preferably, the sufficient stirring in step 1 and step 3 is stirring with a magnetic stirrer for 10 to 30 minutes.
[0014] Preferably, the filling ratio of the reactor in step 2 is 50-70%.
[0015] Preferably, the centrifugal washing in step 2 is performed by alternating ethanol and water until the mixture becomes neutral, and the centrifugal washing in step 3 is performed by alternating methanol until the mixture becomes neutral.
[0016] Preferably, the drying in step 2 and step 3 is performed by placing the product in a vacuum drying oven at 50-70° C. for 12-24 hours.
[0017] The present invention also protects a ZnO@C-ZIF composite gas sensitive material prepared by the method as described above and its application in an ethanol gas sensor.
[0018] Compared with the prior art, the present invention has the following technical effects:
[0019] The present invention first synthesizes ZnO@ZIF-8 by a simple hydrothermal method. Subsequently, ZnO@ZIF-8 is used as a substrate and subjected to low-temperature heat treatment in an Ar atmosphere to substantially retain its framework. ZIF-8 is pyrolyzed to form a carbonaceous layer tightly covering the ZnO surface, effectively acting as a support layer for multilayer ZnO nanosheets, avoiding agglomeration and self-stacking, facilitating carrier transport and providing more active sites, which can effectively solve the self-stacking problem of two-dimensional nanosheets. At the same time, the exposed protrusions of C-ZIF have a hierarchical porous structure, thereby providing more active sites and can also react with Z nO forms a heterojunction, promoting the transport of charge carriers, facilitating the adsorption and screening of gas molecules, and improving sensitivity to ethanol gas. Furthermore, the abundant organic carbon in C-ZIF partially pyrolyzes under the action of temperature, allowing the C-ZIF framework to connect together to form a C-ZIF layer, thus acting as a "moisture-proof umbrella" for the material, allowing it to maintain high response even in high humidity. The ZnO@C-ZIF composite gas-sensitive material prepared by the present invention has low operating temperature, high sensitivity, high stability, and excellent moisture resistance, meeting practical requirements and having good environmental compatibility.
[0020] The preparation method of the present invention has safe process, mild reaction conditions and high repeatability. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Figure 1 SEM images of the ZnO@ZIF-8 precursor prepared in Example 2 and the ZnO@C-ZIF composite gas-sensitive materials prepared in Examples 1-3;
[0022] Figure 2 XRD patterns of the ZnO@ZIF-8 precursor prepared in Example 2 and the ZnO@C-ZIF composite gas-sensitive materials prepared in Examples 1-3;
[0023] Figure 3 This is the gas-sensing performance curve of the ZnO@C-ZIF composite gas-sensitive material prepared in Example 2 to 50 ppm ethanol;
[0024] Figure 4 Gas-sensing performance curve of the ZnO@C-ZIF composite gas-sensitive material prepared in Example 2 to 50 ppm ethanol at different humidity levels;
[0025] Figure 5 This is the long-term stability curve of the ZnO@C-ZIF composite gas sensitive material prepared in Example 2. DETAILED DESCRIPTION
[0026] The specific contents of the present invention are further explained in detail below with reference to the embodiments.
[0027] Example 1:
[0028] This embodiment provides a method for preparing a ZnO@C-ZIF composite gas-sensitive material, comprising the following steps:
[0029] Step 1: Dissolve zinc nitrate and urea in distilled water at a molar ratio of 1:1.5 and stir with a magnetic stirrer for 10 minutes to obtain a precursor solution, wherein the urea concentration is 0.5 mol / L;
[0030] Step 2: The precursor solution is charged into a reactor with a filling ratio of 50%, and the reactor is placed in an oven at 100°C for hydrothermal reaction for 8 hours. The precursor is then taken out and centrifuged and washed with ethanol and water until neutral, and placed in a vacuum drying oven at 70°C for 12 hours to obtain a ZnO nanosheet precursor. The ZnO nanosheet precursor is placed in a muffle furnace and heated from room temperature to 650°C at a heating rate of 5°C / min and then kept warm for 1 hour to obtain a ZnO porous nanosheet;
[0031] Step 3: Take the ZnO porous nanosheets and 2-methylimidazole prepared in step 2 at a molar ratio of 1:1, dissolve the ZnO porous nanosheets in distilled water to obtain a solution A with a concentration of 0.2 mol / L, and dissolve 2-methylimidazole in N,N-dimethylformamide to obtain a solution B with a concentration of 0.1 mol / L. Under stirring, slowly add solution A dropwise to solution B and stir with a magnetic stirrer for 10 minutes until the mixture is evenly mixed. Then, place the mixture in a hydrothermal kettle and hydrothermally heat at 80°C for 12 hours. After the end, centrifuge and wash with methanol until neutral, and place it in a vacuum drying oven at 70°C for 12 hours to obtain ZnO@ZIF-8 powder;
[0032] Step 4: The ZnO@ZIF-8 powder prepared in step 3 is evenly dispersed in a quartz porcelain boat, covered with a quartz cover, placed in a tube furnace, and heated from room temperature to 650°C at a heating rate of 5°C / min under an inert atmosphere and kept warm for 1 hour to obtain a ZnO@C-ZIF composite gas sensitive material.
[0033] Example 2:
[0034] This embodiment provides a method for preparing a ZnO@C-ZIF composite gas-sensitive material, comprising the following steps:
[0035] Step 1: Dissolve zinc nitrate and urea in distilled water at a molar ratio of 1:2 and stir with a magnetic stirrer for 20 minutes to obtain a precursor solution, wherein the urea concentration is 0.8 mol / L;
[0036] Step 2: The precursor solution is charged into a reactor with a filling ratio of 60%, and the reactor is placed in an oven for hydrothermal reaction at 120°C for 5 hours. The precursor is then taken out and centrifuged and washed with ethanol and water until neutral, and placed in a vacuum drying oven at 60°C for 18 hours to obtain a ZnO nanosheet precursor. The ZnO nanosheet precursor is placed in a muffle furnace and heated from room temperature to 550°C at a heating rate of 3°C / min and then kept warm for 2 hours to obtain a ZnO porous nanosheet;
[0037] Step 3: Take the ZnO porous nanosheets and 2-methylimidazole prepared in step 2 at a molar ratio of 2:1, dissolve the ZnO porous nanosheets in distilled water to obtain a solution A with a concentration of 1.0 mol / L, and dissolve 2-methylimidazole in N,N-dimethylformamide to obtain a solution B with a concentration of 1.0 mol / L. Under stirring, slowly add solution A dropwise to solution B and stir with a magnetic stirrer for 30 minutes until the mixture is evenly mixed. Then, place the mixture in a hydrothermal kettle at 70°C and heat for 24 hours. After the end, centrifuge and wash with methanol until neutral, and place it in a vacuum drying oven at 60°C for 18 hours to obtain ZnO@ZIF-8 powder;
[0038] Step 4: The ZnO@ZIF-8 powder prepared in step 3 is evenly dispersed in a quartz porcelain boat, covered with a quartz lid, placed in a tube furnace, and heated from room temperature to 550°C at a heating rate of 3°C / min under an inert atmosphere and kept warm for 2 hours to obtain a ZnO@C-ZIF composite gas sensitive material.
[0039] Example 3:
[0040] This embodiment provides a method for preparing a ZnO@C-ZIF composite gas-sensitive material, comprising the following steps:
[0041] Step 1: Dissolve zinc acetate and urea in distilled water at a molar ratio of 1:2.5 and stir with a magnetic stirrer for 30 minutes to obtain a precursor solution, wherein the urea concentration is 1.0 mol / L;
[0042] Step 2: The precursor solution is charged into a reactor with a filling ratio of 70%, and the reactor is placed in an oven for hydrothermal reaction at 140°C for 2 hours. The precursor is then taken out and washed alternately by centrifugation with ethanol and water until neutral, and placed in a vacuum drying oven at 50°C for 24 hours to obtain a ZnO nanosheet precursor. The ZnO nanosheet precursor is placed in a muffle furnace and heated from room temperature to 450°C at a heating rate of 1°C / min and then kept warm for 4 hours to obtain a ZnO porous nanosheet;
[0043] Step 3: Take the ZnO porous nanosheets and 2-methylimidazole prepared in step 2 at a molar ratio of 5:1, dissolve the ZnO porous nanosheets in distilled water to obtain a solution A with a concentration of 0.8 mol / L, and dissolve 2-methylimidazole in N,N-dimethylformamide to obtain a solution B with a concentration of 0.6 mol / L. Under stirring, slowly add solution A dropwise to solution B and stir with a magnetic stirrer for 20 minutes until the mixture is evenly mixed. Then, place the mixture in a hydrothermal kettle at 60°C and heat for 36 hours. After the end, centrifuge and wash with methanol until neutral, and place it in a vacuum drying oven at 50°C for 24 hours to obtain ZnO@ZIF-8 powder;
[0044] Step 4: The ZnO@ZIF-8 powder prepared in step 3 is evenly dispersed in a quartz porcelain boat, covered with a quartz lid, placed in a tube furnace, and heated from room temperature to 450°C at a heating rate of 1°C / min under an inert atmosphere and kept warm for 4 hours to obtain a ZnO@C-ZIF composite gas sensitive material.
[0045] Figure 1 SEM images of the ZnO@ZIF-8 precursor prepared in Example 2 and the ZnO@C-ZIF composite gas sensitive materials prepared in Examples 1-3; Figure 1 As can be seen in (c, d), ZIF-8 was successfully in situ grown on the porous ZnO nanosheets, and a carbon layer was formed after pyrolysis and carbonization of ZIF-8.
[0046] Figure 2 The XRD patterns of the ZnO@ZIF-8 precursor prepared in Example 2 and the ZnO@C-ZIF composite gas sensitive materials prepared in Examples 1-3 are shown in FIG. Figure 2 It can be seen that after low-temperature treatment, the (112), (013), and (222) crystal planes representing ZIF-8 disappear. This is because the ZIF-8 support layer is pyrolyzed and carbonized, leaving only a certain framework, and the Zn particles therein are deposited on the carbon layer; the peaks of the ZnO crystal plane belonging to hexagonal wurtzite exist in the ZnO@C-ZIF composite gas sensitive material, which proves the presence of ZnO in the composite material; in addition, Zn particles are deposited on the carbon layer, which is also the reason why the characteristic peaks representing ZnO are enhanced before and after low-temperature carbonization treatment.
[0047] Figure 3 The gas-sensing performance curve of the ZnO@C-ZIF composite gas-sensitive material prepared in Example 2 to 50 ppm ethanol; Figure 3 As shown in the figure, the ZnO@C-ZIF composite gas sensitive material prepared by the present invention has a high responsiveness of 51.46 at a low working temperature of 240°C.
[0048] Figure 4 The gas-sensing performance curve of the ZnO@C-ZIF composite gas-sensitive material prepared in Example 2 to 50 ppm ethanol at different humidity levels; Figure 4 It can be seen that the ZnO@C-ZIF composite gas sensitive material still has excellent gas sensing performance in a higher humidity environment (70% RH), proving that it has good moisture resistance.
[0049] Figure 5 This is the long-term stability curve of the ZnO@C-ZIF composite gas sensitive material prepared in Example 2. Figure 5 It can be seen that the response fluctuation of the ZnO@C-ZIF composite gas sensitive material is less than 12.5% after long-term operation, proving that it has good long-term stability.
[0050] Other implementation examples are not listed here. Without departing from the concept of the present invention, deductions or replacements made by those skilled in the art shall fall within the protection scope of the present invention.
Claims
1. A method for preparing a ZnO@C-ZIF composite gas sensitive material, characterized in that: The following steps are involved: Step 1: dissolving zinc salt and urea in distilled water at a molar ratio of 1:(1.5-2.5) and stirring thoroughly to obtain a precursor solution, wherein the urea concentration is 0.5-1.0 mol / L; Step 2: The precursor solution is placed in a reactor, placed in an oven at 100-140°C for hydrothermal reaction for 2-8 hours, then taken out for centrifugal washing and drying to obtain a ZnO nanosheet precursor, and the ZnO nanosheet precursor is placed in a muffle furnace at a heating rate of 1-5°C / min from room temperature to 450-650°C and then kept warm for 1-4 hours to obtain ZnO porous nanosheets; Step 3: Take the ZnO porous nanosheets and 2-methylimidazole prepared in step 2 at a molar ratio of (1-5):1, dissolve the ZnO porous nanosheets in distilled water to obtain a solution A with a concentration of 0.2-1.0 mol / L, and dissolve 2-methylimidazole in N,N-dimethylformamide to obtain a solution B with a concentration of 0.1-1.0 mol / L. Under stirring, slowly add solution A dropwise to solution B and stir until the mixture is uniformly mixed. Then, place the mixture in a hydrothermal kettle at 60-80°C and heat for 12-36 hours. After the end, centrifuge, wash, and dry to obtain ZnO@ZIF-8 powder; Step 4: The ZnO@ZIF-8 powder prepared in step 3 is evenly dispersed in a quartz porcelain boat, covered with a quartz cover, placed in a tube furnace, and heated from room temperature to 450-650°C at a heating rate of 1-5°C / min under an inert atmosphere and kept warm for 1-4 hours to obtain a ZnO@C-ZIF composite gas sensitive material.
2. The method for preparing the ZnO@C-ZIF composite gas sensitive material according to claim 1, wherein: The zinc salt includes either zinc nitrate or zinc acetate.
3. The method for preparing the ZnO@C-ZIF composite gas sensitive material according to claim 1, wherein: The sufficient stirring in step 1 and step 3 is stirring for 10 to 30 minutes using a magnetic stirrer.
4. The method for preparing the ZnO@C-ZIF composite gas sensitive material according to claim 1, wherein: The filling ratio of the reactor in step 2 is 50-70%.
5. The method for preparing the ZnO@C-ZIF composite gas sensitive material according to claim 1, wherein: The centrifugal washing in step 2 is performed by alternately washing with ethanol and water until the mixture becomes neutral. The centrifugal washing in step 3 is performed by alternately washing with methanol until the mixture becomes neutral.
6. The method for preparing the ZnO@C-ZIF composite gas sensitive material according to claim 1, wherein: The drying in step 2 and step 3 is carried out by placing the mixture in a vacuum drying oven at 50-70° C. for 12-24 hours.
7. A ZnO@C-ZIF composite gas sensitive material prepared by the method according to any one of claims 1 to 6.
8. Use of the ZnO@C-ZIF composite gas sensitive material according to claim 7 in an ethanol gas sensor.