NO2 sensor based on MOF-derived Ni-doped In2O3 core-shell octahedral sensitive material and preparation method of NO2 sensor
A Ni-doped In2O3 core-shell octahedral NO2 sensor was prepared by MOF template method, which solved the problem of poor performance of traditional In2O3-based sensors in high temperature and humid environments, and achieved high sensitivity and strong resistance to moisture in low temperature NO2 detection.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- JILIN UNIVERSITY
- Filing Date
- 2026-01-27
- Publication Date
- 2026-04-21
AI Technical Summary
Traditional In2O3-based NO2 sensors suffer from high operating temperatures, insufficient response to low-concentration gases, and significant performance degradation in humid environments, limiting their practical application in complex environments.
Ni-doped In2O3 core-shell octahedral structures were prepared using the MOF template method. Combined with the electronic modulation effect of Ni doping, Ni-In2O3 sensitive materials with high specific surface area and abundant porosity were prepared through a simple hydrothermal method and pyrolysis process, which can be used to construct NO2 sensors.
It achieves high-sensitivity detection of NO2 concentrations as low as 10 ppb at low temperatures and maintains stable performance within a humidity range of 0–60%, making it suitable for trace NO2 monitoring in complex environments.
Smart Images
Figure CN121899206A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of semiconductor metal oxide gas sensor technology, specifically relating to an NO2 sensor based on MOF-derived Ni-doped In2O3 core-shell octahedral sensitive material and its preparation method. Background Technology
[0002] With the acceleration of industrialization, air pollution has become increasingly prominent, with nitrogen dioxide (NO2) being one of the major pollutants, posing a serious threat to ecosystems and human health. Due to long-term human activities such as fossil fuel combustion and vehicle exhaust emissions, NO2 emissions have continued to rise, causing extremely serious damage to the human living environment. This not only triggers environmental problems such as acid rain and photochemical smog, but also severely harms the human respiratory system. Therefore, developing highly sensitive NO2 gas sensors is of significant practical importance.
[0003] Among various gas sensing technologies, metal-oxide-semiconductor (MOS) sensors have attracted much attention due to their low cost, good stability, and ease of integration. Indium oxide (In2O3), in particular, is considered a highly promising NO2 sensing material due to its wide bandgap, high carrier mobility, and good conductivity. However, traditional In2O3-based sensors generally suffer from problems such as high operating temperatures, insufficient response to low-concentration gases, and significant performance degradation in humid environments, limiting their practical application in complex environments.
[0004] Metal-organic frameworks (MOFs) are porous materials with an infinite lattice, synthesized through coordination chemistry using metal cations and organic ligands. MOF precursors can be pyrolyzed into oxide structures with porous structures, high specific surface areas, and specific morphologies, which facilitates gas diffusion and surface reactions. Furthermore, doping with transition metals (such as nickel) can effectively modulate the electronic structure of In₂O₃, increase surface active sites and oxygen vacancy concentrations, thereby enhancing its adsorption and charge transfer capabilities for target gases. Simultaneously, appropriate doping can significantly suppress the competitive adsorption of water molecules onto the sensitive material, thus improving the sensor's stability in humid environments.
[0005] Based on the above analysis, this invention proposes to prepare Ni-doped In2O3 core-shell octahedral structures using the MOF template method. Combining the structural advantages of In2O3 with the electronic modulation effect of Ni doping, this invention achieves high sensitivity, low detection limit, and high moisture resistance in NO2 sensing performance, providing a new material design and preparation approach for developing practical NO2 sensors suitable for complex atmospheric environments. Summary of the Invention
[0006] The purpose of this invention is to provide an NO2 sensor based on MOF-derived Ni-doped In2O3 core-shell octahedral sensitive material and its preparation method.
[0007] This invention utilizes a MOF-derived Ni-doped In₂O₃ core-shell octahedral sensing material. On one hand, the In₂O₃ derived from the MOF template possesses a high specific surface area, abundant porosity, and a regular core-shell octahedral morphology, providing ample surface reaction sites and efficient diffusion channels for gas molecules. On the other hand, Ni doping not only effectively modulates the electronic structure of In₂O₃, increasing the oxygen vacancy concentration and surface activity, thus significantly enhancing the adsorption of NO₂ molecules, but also effectively suppresses the interference of ambient humidity on the detection signal, improving the sensor's resistance to humidity. These combined effects promote the reaction efficiency between the sensing material and NO₂ gas, shorten the response and recovery times, and improve the material's resistance to humidity interference. This invention prepares an octahedral MOF using a simple hydrothermal method and obtains the Ni-In₂O₃ sensing material through the pyrolysis of the MOF template. The sensor constructed based on this sensitive material can achieve high sensitivity and high selectivity for NO2 concentrations as low as 10 ppb under low-temperature operating conditions of 70°C, and maintain stable performance within a wide humidity range of 0-60%. It provides a reliable solution for trace NO2 monitoring in complex environments and has significant practical value and application prospects.
[0008] The present invention describes an NO2 sensor based on MOF-derived Ni-doped In2O3 core-shell octahedral sensitive material, such as... Figure 1 As shown, the sensor consists of an Al2O3 ceramic tube substrate with parallel annular gold electrodes on its surface, a MOF-derived Ni-doped In2O3 core-shell octahedral sensing material coated on the outer surfaces of the annular gold electrodes and the Al2O3 ceramic tube substrate, and a nickel-chromium alloy heating coil placed inside the Al2O3 ceramic tube; wherein, the MOF-derived Ni-doped In2O3 core-shell octahedral sensing material is obtained by the following steps:
[0009] (1) Dissolve 0.2~0.25g of indium nitrate (In(NO3)3•4.5H2O) and 3~12mg of nickel nitrate (Ni(NO3)2•6H2O) in 25~30mL of N,N-dimethylformamide (DMF) and stir at room temperature for 20~30 minutes to form a homogeneous solution;
[0010] (2) Dissolve 95~100mg of terephthalic acid (H2BDC) in 15~20mL of ethylene glycol and stir at room temperature for 20~30 minutes to form a homogeneous solution;
[0011] (3) Slowly add the solution obtained in step (1) to the solution obtained in step (2), and continue stirring at room temperature for 60-70 minutes to obtain a homogeneous solution;
[0012] (4) Transfer the solution obtained in step (3) to a stainless steel autoclave lined with polytetrafluoroethylene and react at 120~150℃ for 4~6 hours; after the reaction is completed and the autoclave is naturally cooled to room temperature, centrifuge the reaction product, wash the precipitate with deionized water and ethanol alternately several times, and then dry it at 70~90℃ for 10~20 hours to obtain white Ni-In MOF solid powder;
[0013] (5) Calcine the Ni-In MOF solid powder obtained in step (4) in air at 400~600℃ for 1.5~3.0 hours with a heating rate of 1.0~3.0℃ / min. Collect the light yellow powder obtained, which is the MOF-derived Ni-doped In2O3 core-shell octahedral sensitive material.
[0014] The present invention discloses a method for preparing an NO2 sensor based on MOF-derived Ni-doped In2O3 core-shell octahedral sensitive material, the steps of which are as follows:
[0015] (1) Take 10-20 mg of MOF-derived Ni-doped In2O3 core-shell octahedral sensitive material in an agate mortar, add 3-5 drops of ethanol, mix thoroughly and grind to form a uniform paste; then use a fine brush to dip the paste and uniformly coat it on the outer surface of an Al2O3 ceramic tube with two parallel ring-shaped gold electrodes to form a sensitive material film with a thickness of 10-30 μm, ensuring that the sensitive material film completely covers the gold electrodes and the outer surface of the Al2O3 ceramic tube substrate; the Al2O3 ceramic tube has a length of 4.0-4.5 mm, an outer diameter of 1.2-1.5 mm, and an inner diameter of 0.8-1.0 mm; the width of a single ring-shaped gold electrode is 0.4-0.5 mm, the thickness of the gold electrode is 0.1-0.2 mm, and the distance between the two electrodes is 0.5-0.6 mm; a platinum wire lead with a length of 4-6 mm is welded on the gold electrode;
[0016] (2) The Al2O3 ceramic tube coated with the sensitive material film in step (1) is calcined at 200~300℃ for 1.5~3.0 hours to improve the stability of the sensitive material, with a heating rate of 3~5℃ / min; then it is naturally cooled to room temperature; after that, a nickel-chromium alloy heating coil with a resistance of 25~35Ω is inserted into the inner cavity of the Al2O3 ceramic tube as a heating element; finally, the obtained device is welded onto a standard hexagonal tube base, thus obtaining an NO2 sensor based on MOF-derived Ni-doped In2O3 core-shell octahedral sensitive material, with an optimal operating temperature of 70℃.
[0017] The NO2 sensor based on MOF-derived Ni-doped In2O3 core-shell octahedral sensitive material described in this invention has the following advantages:
[0018] (1) The present invention uses a simple solvothermal combined with heat treatment method to prepare sensitive materials, with MOF as precursor and Ni doping introduced. The process is controllable, has good repeatability, and the raw material cost is low, making it suitable for large-scale preparation.
[0019] (2) This invention utilizes the MOF template method to construct In2O3 nanomaterials with a core-shell octahedral structure and abundant pores. Combined with Ni doping to modulate the electronic structure and enhance surface activity, it significantly improves the sensor's sensitivity to NO2 gas, lowers the detection limit, and effectively suppresses humidity interference. It has good application prospects in the field of low-concentration NO2 monitoring.
[0020] (3) Commercially available tubular sensors are used. The device process is simple, the cost is low, and the size is small, making it suitable for mass production. Attached Figure Description
[0021] Figure 1 : A schematic diagram of the structure of an NO2 sensor based on MOF-derived Ni-doped In2O3 core-shell octahedral sensitive material according to the present invention;
[0022] Figure 2 The SEM images of the In2O3 and Ni-In2O3 sensitive materials prepared in Comparative Example 1, Example 1, Example 2, and Example 3, as well as the TEM images of Comparative Example 1 and Example 1, show that the materials all exhibit an octahedral core-shell structure with a size ranging from approximately 0.5 to 1 μm.
[0023] Figure 3 The XRD patterns of In2O3 and Ni-In2O3 sensitive materials prepared in Comparative Example 1, Example 1, Example 2, and Example 3 of this invention show that all diffraction peaks of all samples can be well pointed to the cubic In2O3 standard card.
[0024] Figure 4 The sensitivity curves of the gas sensors prepared in Comparative Example 1, Example 1, Example 2, and Example 3 as a function of temperature are shown. The optimal operating temperature of Comparative Example 1 is 80℃, the optimal operating temperatures of Examples 2 and 1 are 70℃, and the optimal operating temperature of Example 3 is 60℃, indicating that the operating temperature of the sensor can be reduced by increasing the nickel doping content. Compared with the comparative examples, the sensor of Example 1 has the highest sensitivity to NO2, reaching 100 for 200 ppb NO2.
[0025] Figure 5The response recovery curves of the gas sensors prepared in Comparative Example 1 and Example 1 to 200 ppb NO2 at the optimal operating temperature are respectively... Figure 5 (a) and Figure 5 (b); The sensitivity of Comparative Example 1 was 14.1, and the response / recovery time was 533 s / 2087 s; the sensitivity of Example 1 was 100, and the response / recovery time was 357 s / 248 s. The results show that the gas sensor prepared in Example 1 exhibits both higher sensitivity and faster response / recovery speed.
[0026] Figure 6 The concentration gradient curve of NO2 gas for the gas sensor prepared in Example 1 at the optimal operating temperature shows that the sensitivity of the sensor prepared in Example 1 increases with the increase of NO2 concentration and has a low detection limit (10 ppb).
[0027] Figure 7 The selectivity histograms of the gas sensors prepared in Example 1 and Comparative Example 1 for different gases show that both Example 1 and Comparative Example 1 exhibit good selectivity for NO2 and extremely low response to other interfering gases. Example 1 shows a significant increase in the response value to NO2, while the response to other gases remains almost unchanged, proving that its selectivity is further improved.
[0028] Figure 8 The response curves of the gas sensors prepared in Comparative Example 1 and Example 1 to NO2 as a function of relative humidity correspond to the following: Figure 8 (a) and Figure 8 (b) indicates that the sensor in Comparative Example 1 is severely affected by humidity, and its sensitivity drops rapidly when the relative humidity of the environment increases, while the sensor in Example 1 can maintain a stable response to NO2 within a 60% humidity range, proving that its moisture resistance is significantly improved.
[0029] Note: The sensitivity (response value) of a device is defined as the ratio of the resistance between its two gold electrodes in the gas being measured to the resistance in air. The response and recovery time are the time it takes for the sensor's resistance to change to 90% of the total change after the gas environment in which the device is located is changed (from air to NO2 gas or from NO2 gas to air). Detailed Implementation
[0030] Comparative Example 1:
[0031] (1) First, add 200 mg of In(NO3)3•4.5H2O to 26 mL of DMF and stir for 20 minutes at room temperature to form a homogeneous solution;
[0032] (2) Dissolve 97.5 mg of H2BDC in 16 mL of ethylene glycol and stir at room temperature for 20 minutes to form a homogeneous solution;
[0033] (3) Slowly add the solution obtained in step (1) to the solution obtained in step (2) and continue stirring for 1 hour to mix the solution evenly;
[0034] (4) The solution obtained in step (3) was transferred to a stainless steel autoclave lined with polytetrafluoroethylene and kept at 150°C for 4 hours. After natural cooling, the reaction product was centrifuged and washed several times with deionized water and ethanol. The precipitate was then dried at 80°C for 12 hours to obtain white In MOF powder.
[0035] (5) Take the MOF powder obtained in step (4) into a porcelain boat, place it in a muffle furnace, and calcine it at 500°C for 2 hours in an air atmosphere with a heating rate of 2.0°C / min to obtain a pale yellow In2O3 sensitive material with a product mass of 50 mg.
[0036] (6) Take 10 mg of the In2O3 sensitive material obtained in step (5) into an agate mortar, add 3 drops of ethanol, mix thoroughly and grind to form a uniform paste; then use a fine brush to dip the paste and evenly coat it on the outer surface of the Al2O3 ceramic tube with two parallel ring-shaped gold electrodes to form a sensitive film with a thickness of about 20 μm, ensuring that the film completely covers the gold electrodes and the surface of the ceramic tube between the electrodes; the Al2O3 ceramic tube is 4 mm long, with an inner diameter of 0.8 mm and an outer diameter of 1.2 mm, a single ring-shaped gold electrode width of 0.45 mm, a gold electrode thickness of 0.15 mm, and a distance between the two electrodes of 0.55 mm;
[0037] (7) The Al2O3 ceramic tube with the sensitive material coated on the outer surface obtained in step (6) is transferred to a ceramic boat and placed in a muffle furnace. It is calcined in air at 350°C for 2 hours to improve the stability of the sensitive material. After it is naturally cooled to room temperature, a nickel-chromium alloy heating coil with a resistance of 30Ω is passed through the inside of the ceramic tube as a heating wire. A 5mm long platinum wire lead is welded to the gold electrode and the heating wire. Finally, the above device is welded to the hexagonal tube base through the platinum wire lead to prepare the NO2 gas sensor.
[0038] Example 1:
[0039] (1) First, add 200 mg of In(NO3)3•4.5H2O and 6 mg of Ni(NO3)2•6H2O to 26 mL of DMF and stir at room temperature for 20 minutes to form a homogeneous solution;
[0040] (2) Dissolve 97.5 mg of H2BDC in 16 mL of ethylene glycol and stir at room temperature for 20 minutes to form a homogeneous solution;
[0041] (3) Slowly add the solution obtained in step (1) to the solution obtained in step (2) and continue stirring for 1 hour to mix the solution evenly;
[0042] (4) The solution obtained in step (3) was transferred to a stainless steel autoclave lined with polytetrafluoroethylene and kept at 150°C for 4 hours. After the reaction was completed and the autoclave was naturally cooled to room temperature, the reaction product was centrifuged. The reaction product was centrifuged and washed several times with deionized water and ethanol. The precipitate was then dried at 80°C for 12 hours to obtain white Ni-In MOF powder.
[0043] (5) Take the Ni-In MOF powder obtained in step (4) into a porcelain boat, place it in a muffle furnace, and calcine it at 500°C for 2 hours in an air atmosphere with a heating rate of 2.0°C / min to obtain a light yellow core-shell octahedral sensitive material based on MOF-derived Ni-doped In2O3 with a product mass of 50 mg.
[0044] (6) Take 10 mg of the MOF-derived Ni-doped In2O3 core-shell octahedral sensitive material obtained in step (5) in an agate mortar, add 3 drops of ethanol, mix thoroughly and grind to form a uniform paste; then use a fine brush to dip the paste and uniformly coat it on the outer surface of the Al2O3 ceramic tube with two parallel ring-shaped gold electrodes to form a sensitive film with a thickness of about 20 μm, ensuring that the film completely covers the gold electrodes and the outer surface of the Al2O3 ceramic tube substrate; the Al2O3 ceramic tube is 4 mm long, with an inner diameter of 0.8 mm and an outer diameter of 1.2 mm, a single ring-shaped gold electrode width of 0.45 mm, a gold electrode thickness of 0.15 mm, and a distance between the two electrodes of 0.55 mm;
[0045] (7) The Al2O3 ceramic tube with the sensitive material coated on the outer surface obtained in step (6) is transferred to a ceramic boat and placed in a muffle furnace. It is then calcined in air at 350°C for 2 hours to improve the stability of the sensitive material. After naturally cooling to room temperature, a nickel-chromium alloy heating coil with a resistance of 30Ω is passed through the inside of the ceramic tube as a heating wire. A 5mm long platinum wire lead is welded to the gold electrode and the heating wire. Finally, the above device is welded to a hexagonal tube base through the platinum wire lead to prepare an NO2 sensor based on MOF-derived Ni-doped In2O3 core-shell octahedral sensitive material.
[0046] Example 2:
[0047] (1) First, add 200 mg of In(NO3)3•4.5H2O and 3 mg of Ni(NO3)2•6H2O to 26 mL of DMF and stir at room temperature for 20 minutes to form a homogeneous solution;
[0048] (2) Dissolve 97.5 mg of H2BDC in 16 mL of ethylene glycol and stir at room temperature for 20 minutes to form a homogeneous solution;
[0049] (3) Slowly add the solution obtained in step (1) to the solution obtained in step (2) and continue stirring for 1 hour to mix the solution evenly;
[0050] (4) The solution obtained in step (3) was transferred to a stainless steel autoclave lined with polytetrafluoroethylene and kept at 150°C for 4 hours. After natural cooling, the reaction product was centrifuged and washed several times with deionized water and ethanol. The precipitate was then dried at 80°C for 12 hours to obtain white Ni-In MOF powder.
[0051] (5) Take the MOF powder obtained in step (4) into a ceramic boat, place it in a muffle furnace, and calcine it at 500°C for 2 hours in an air atmosphere with a heating rate of 2.0°C / min to obtain a light yellow core-shell octahedral sensitive material based on MOF-derived Ni-doped In2O3 with a product mass of 50 mg.
[0052] (6) Take 10 mg of the MOF-derived Ni-doped In2O3 core-shell octahedral sensitive material obtained in step (5); add 3 drops of ethanol to an agate mortar, mix thoroughly and grind to form a uniform paste; then use a fine brush to dip the paste and uniformly coat it on the outer surface of the Al2O3 ceramic tube with two parallel ring-shaped gold electrodes to form a sensitive film with a thickness of about 20 μm, ensuring that the film completely covers the gold electrodes and the surface of the ceramic tube between the electrodes; the Al2O3 ceramic tube is 4 mm long, with an inner diameter of 0.8 mm and an outer diameter of 1.2 mm, a single ring-shaped gold electrode width of 0.45 mm, a gold electrode thickness of 0.15 mm, and a distance between the two electrodes of 0.55 mm;
[0053] (7) The Al2O3 ceramic tube with the sensitive material on the outer surface obtained in step (6) is transferred to a ceramic boat and placed in a muffle furnace. It is calcined in air at 350°C for 2 hours to improve the stability of the sensitive material. After it is naturally cooled to room temperature, a nickel-chromium alloy heating coil with a resistance of 30Ω is passed through the inside of the ceramic tube as a heating wire. A 5mm long platinum wire lead is welded on the gold electrode and the heating wire. Finally, the above device is welded to the hexagonal tube seat through the platinum wire lead to prepare an NO2 sensor based on MOF-derived Ni-doped In2O3 core-shell octahedral sensitive material.
[0054] Example 3:
[0055] (1) First, add 200 mg of In(NO3)3•4.5H2O and 12 mg of (Ni(NO3)2•6H2O) to 26 mL of DMF and stir at room temperature for 20 minutes to form a homogeneous solution;
[0056] (2) Dissolve 97.5 mg of H2BDC in 16 mL of ethylene glycol and stir at room temperature for 20 minutes to form a homogeneous solution;
[0057] (3) Slowly add the solution obtained in step (1) to the solution obtained in step (2) and continue stirring for 1 hour to mix the solution evenly;
[0058] (4) The solution obtained in step (3) was transferred to a stainless steel autoclave lined with polytetrafluoroethylene and kept at 150°C for 4 hours. After natural cooling, the reaction product was centrifuged and washed several times with deionized water and ethanol. The precipitate was then dried at 80°C for 12 hours to obtain white Ni-In MOF powder.
[0059] (5) Take the MOF powder obtained in step (4) into a ceramic boat, place it in a muffle furnace, and calcine it at 500°C for 2 hours in an air atmosphere with a heating rate of 2.0°C / min to obtain a light yellow core-shell octahedral sensitive material based on MOF-derived Ni-doped In2O3 with a product mass of 50 mg.
[0060] (6) Take 10 mg of the MOF-derived Ni-doped In2O3 core-shell octahedral sensitive material obtained in step (5); add 3 drops of ethanol to an agate mortar, mix thoroughly and grind to form a uniform paste; then use a fine brush to dip the paste and uniformly coat it on the outer surface of the Al2O3 ceramic tube with two parallel ring-shaped gold electrodes to form a sensitive film with a thickness of about 20 μm, ensuring that the film completely covers the gold electrodes and the surface of the ceramic tube between the electrodes; the Al2O3 ceramic tube is 4 mm long, with an inner diameter of 0.8 mm and an outer diameter of 1.2 mm, a single ring-shaped gold electrode width of 0.45 mm, a gold electrode thickness of 0.15 mm, and a distance between the two electrodes of 0.55 mm;
[0061] (7) The Al2O3 ceramic tube with the sensitive material on the outer surface obtained in step (6) is transferred to a ceramic boat and placed in a muffle furnace. It is calcined in air at 350°C for 2 hours to improve the stability of the sensitive material. After it is naturally cooled to room temperature, a nickel-chromium alloy heating coil with a resistance of 30Ω is passed through the inside of the ceramic tube as a heating wire. A 5mm long platinum wire lead is welded on the gold electrode and the heating wire. Finally, the above device is welded to the hexagonal tube seat through the platinum wire lead to prepare an NO2 sensor based on MOF-derived Ni-doped In2O3 core-shell octahedral sensitive material.
Claims
1. A NO2 sensor based on MOF-derived Ni-doped In2O3 core-shell octahedral sensitive material, comprising an Al2O3 ceramic tube substrate with two parallel annular gold electrodes on its surface, a thin film of sensitive material coated on the outer surface of the ceramic tube and the gold electrodes, and a nickel-chromium alloy heating coil placed inside the ceramic tube; characterized in that: The sensitive material is a MOF-derived Ni-doped In₂O₃ core-shell octahedral material, and is prepared through the following steps. (1) Dissolve 0.2~0.25g of indium nitrate and 3~12mg of nickel nitrate in 25~30mL of N,N-dimethylformamide and stir at room temperature for 20~30 minutes to form a homogeneous solution; (2) Dissolve 95-100 mg of terephthalic acid in 15-20 mL of ethylene glycol and stir at room temperature for 20-30 minutes to form a homogeneous solution; (3) Slowly add the solution obtained in step (1) to the solution obtained in step (2), and continue stirring at room temperature for 60-70 minutes to obtain a homogeneous solution; (4) Transfer the solution obtained in step (3) to a stainless steel autoclave lined with polytetrafluoroethylene and react at 120~150℃ for 4~6 hours; after the reaction is completed and the autoclave is naturally cooled to room temperature, centrifuge the reaction product, wash the precipitate with deionized water and ethanol alternately several times, and then dry it at 70~90℃ for 10~20 hours to obtain white Ni-In MOF solid powder; (5) Calcine the Ni-In MOF solid powder obtained in step (4) in air at 400~600℃ for 1.5~3.0 hours with a heating rate of 1.0~3.0℃ / min. Collect the light yellow powder obtained, which is the MOF-derived Ni-doped In2O3 core-shell octahedral sensitive material.
2. The NO2 sensor based on MOF-derived Ni-doped In2O3 core-shell octahedral sensitive material as described in claim 1, characterized in that: The Al2O3 ceramic tube has a length of 4.0~4.5 mm, an outer diameter of 1.2~1.5 mm, and an inner diameter of 0.8~1.0 mm; the width of a single annular gold electrode is 0.4~0.5 mm, the spacing between two gold electrodes is 0.5~0.6 mm, and the thickness of the gold electrode is 0.1~0.2 mm; the thickness of the sensitive material film is 10~30 μm.
3. The method for preparing an NO2 sensor based on MOF-derived Ni-doped In2O3 core-shell octahedral sensitive material as described in claim 1 or 2, comprising the following steps: (1) Take 10~20mg of MOF-derived Ni-doped In2O3 core-shell octahedral sensitive material in an agate mortar, add 3~5 drops of ethanol, mix thoroughly and grind to form a uniform paste; then use a fine brush to dip the paste and evenly coat it on the outer surface of the Al2O3 ceramic tube with two parallel ring gold electrodes to form a sensitive material film, ensuring that the sensitive material film completely covers the gold electrodes and the outer surface of the Al2O3 ceramic tube substrate; (2) The Al2O3 ceramic tube coated with the sensitive material film in step (1) is calcined at 200~300℃ for 1.5~3.0 hours to improve the stability of the sensitive material, with a heating rate of 3~5℃ / min; then it is naturally cooled to room temperature; after that, a nickel-chromium alloy heating coil with a resistance of 25~35Ω is inserted into the inner cavity of the Al2O3 ceramic tube as a heating element; finally, the obtained device is welded onto a standard hexagonal tube base, thus obtaining the NO2 sensor based on MOF-derived Ni-doped In2O3 core-shell octahedral sensitive material.