N-butanol sensing material and preparation method thereof

Abstract

The application discloses a n-butanol sensing material and a preparation method thereof, and belongs to the technical field of semiconductor metal oxide gas sensors. First, In2O3 hexagonal hollow tubes and single-atom catalyst Zn x Co1-N-C nanoparticles are respectively prepared, and then a hexagonal hollow tube-shaped Zn x Co1-N-C / In2O3 composite sensing material is prepared by using a mechanical mixing method, and the sensing material is prepared into a gas sensor. At an optimal operating temperature of 240 DEG C, the gas sensor assembled from the Zn7Co1-N-C / In2O3 material with a zinc-cobalt molar ratio of 7:1 has the best performance, the response time of the gas sensor to 0.5ppm n-butanol is 43s, the recovery time is 200s, the response and recovery sensitivity of the gas sensor to n-butanol with different concentrations are good, the response value is as high as 145.0 at a concentration of 5ppm, and the composite sensing material has excellent selectivity to n-butanol and good practical application value.

Description

Technical fields:

[0001] This invention belongs to the field of semiconductor metal oxide gas sensor technology, specifically involving the development of a hexagonal hollow tubular Zn x Co1-NC / In2O3 composite sensing material; gas sensors assembled from this material exhibit high sensing performance for n-butanol. Background technology:

[0002] Semiconductor metal oxide gas sensors have attracted widespread attention due to their advantages such as low cost, low power consumption, portability, and ease of operation, and are commonly used for the detection of various gases. n-Butanol is a colorless, transparent liquid with a pungent odor. Industrially, it is widely used as an organic solvent in many paints and surfactants. Prolonged exposure to n-butanol gas can cause adverse symptoms such as dizziness, anesthesia, drowsiness, and corneal damage. Therefore, there is an urgent need to develop a highly responsive and selective n-butanol gas sensor. Several gas sensors for detecting n-butanol have been reported. Patent (CN115326888A) "A method for preparing a liquid-phase synthesized n-butanol gas sensor" describes a gas sensor based on AuLaFeO3 material prepared using liquid-phase synthesis, with a response value of 115 for 100 ppm n-butanol at 225℃. Patent (CN117368273A) "An ultrafast n-butanol gas sensor based on CdS / Ag2S composite nanomaterials and its preparation method" describes a n-butanol sensor based on CdS / Ag2S composite nanomaterials prepared using a hydrothermal method, with a response value of 24.5 for 100 ppm n-butanol at 200℃. Patent (CN118032875A) "A high-sensitivity n-butanol gas-sensitive material and its preparation method and application" describes a 1 wt% Pd Ho2S gas sensor prepared using electrospinning. 0.9 Sm 0.1 The FeO3 gas sensor has a response value of 11.38 for 1.0 ppm n-butanol at 220℃. Although significant progress has been made in the research of n-butanol gas sensors, it is still necessary to further improve the sensitivity and selectivity of the sensor.

[0003] Indium oxide (In₂O₃) is a typical n-type semiconductor with a wide bandgap (3.5–3.7 eV), high conductivity, and good thermal stability, making it a promising candidate for gas sensing applications. Forming composite materials is one method to enhance gas-sensing performance. For example, patent (CN108545777A) "An antimony-cerium modified molybdenum disulfide / indium oxide quaternary gas-sensing material and its preparation method" prepared an Sb / Ce-MoS₂ / In₂O₃ gas-sensing material via a hydrothermal method. The gas sensor prepared using this material showed a response value of 64.2 for 50 ppm ethanol at 260°C. However, the prepared composite material is complex and costly. This invention first synthesizes two MOF materials, MIL-68(In) and Co-doped ZIF-8, using a simple oil bath method, and then calcines them to obtain In₂O₃ hexagonal hollow tubes and ZnO₂ hollow tubes, respectively. x Co1-NC nanoparticles, after characterization, showed that Zn x In Co1-NC, Co is anchored to the C substrate in a single-atom form, coordinated with N. The aforementioned In2O3 hexagonal hollow tube and the single-atom catalyst Zn... x Co1-NC nanoparticles are then mechanically mixed to obtain Zn. x Co1-NC / In2O3 composite sensing material. According to research, no composite sensing material combining a single-atom catalyst and a sensing material substrate has been reported for use in gas sensors. Importantly, this composite sensing material exhibits a high response value to n-butanol, exceeding currently reported values, good selectivity, low preparation cost, and a simple composite method, making it suitable for large-scale production. It is an excellent n-butanol sensing material. Summary of the Invention:

[0004] The present invention describes a hexagonal hollow tubular Zn x The Co1-NC / In2O3 composite sensing material was first prepared by an oil bath method using hexagonal prism-shaped MIL-68(In) and nanoparticle-shaped Co-ZIF-8. Then, it was calcined under air and nitrogen atmospheres respectively to obtain hexagonal hollow tubular In2O3 sensing material and single-atom catalyst Zn. x Co1-NC nanoparticles were then combined with the other two components using mechanical stirring to obtain the final product. The specific preparation steps are as follows:

[0005] 1. Preparation of a n-butanol sensing material

[0006] (1) Dissolve 180-220 mg of indium nitrate hydrate and 180-220 mg of terephthalic acid in 100-140 ml of N,N-dimethylformamide, heat and stir in an oil bath at 100-140 °C for 55-75 min, then centrifuge to obtain MIL-68(In), dry, and place the dried MIL-68(In) in a muffle furnace at 450-550 °C for 1-3 h to obtain In2O3, which is a light yellow powder, for later use;

[0007] (2) Dissolve 0.9–1.0 g of zinc nitrate hydrate and 0.2–0.3 g of cobalt(III) acetylacetonate in 80–120 ml of methanol, and label this solution A; then dissolve 1.4–1.8 g of dimethylimidazole and 1.5–2.5 ml of n-butylamine in 80–120 ml of methanol, and label this solution B; quickly pour solution B into solution A, stir well, react at 60 °C for 24 h, then centrifuge to obtain Co-ZIF-8, dry it, grind it into powder, and set it aside for later use;

[0008] (3) Dissolve 0.45–0.55 g of the powder obtained in step (2) and 0.45–0.55 g of dimethylimidazole in 20–30 ml of methanol, transfer to a 50–100 ml reaction vessel, and react at 120–160 °C for 2–6 h. Then centrifuge and dry to obtain Zn. x Co1-NC precursor, a purple powder, is prepared for later use;

[0009] (4) Place the purple powder obtained in step (3) into a tube furnace, purge with nitrogen, and calcine at 900–1100°C for 0.5–1.5 h to obtain black powder Zn. x Co1-NC, for later use;

[0010] (5) Take 15-45 mg of the pale yellow In2O3 powder obtained in step (1) and the black Zn obtained in step (4). x Mix 15–45 mg of Co1-NC powder, add to 40–60 mL of deionized water, ultrasonically disperse, stir at room temperature for 2–4 hours, centrifuge and dry to obtain the final product, hexagonal hollow tubular Zn. x Co1-NC / In2O3 composite sensing material.

[0011] 2. A method for preparing a gas sensor based on the above-mentioned sensing material.

[0012] The gas sensor involved in this invention adopts a side-heated structure, and the specific process is as follows: 15-25 mg of Zn xCo1-NC / In2O3 composite sensing material is mixed with 2-3 drops of terpineol and ground clockwise in an agate mortar for 5-15 minutes to form a uniform slurry. The slurry is then evenly coated onto the surface of a ceramic tube with a brush to form a thin sensing material coating. After natural drying, it is welded onto a base and subsequently aged at 220-260℃ for 12-36 hours to produce a side-heated sintered gas sensor. Figure 1 As shown. Attached image description:

[0013] Figure 1 Schematic diagram of the fabricated gas sensor;

[0014] Figure 2 The image shown is a scanning electron microscope (SEM) image of In2O3 obtained in Example 1.

[0015] Figure 3 The image shown is a transmission electron microscope (TEM) image of Zn7Co1-NC obtained in Example 1.

[0016] Figure 4 The image shows a scanning electron microscope (SEM) image of the final product Zn7Co1-NC / In2O3 obtained in Example 1.

[0017] Figure 5 The image shown is a HAADF image of Zn7Co1-NC double spherical aberration corrected transmission electron microscope obtained in Example 1.

[0018] Figure 6 The EXAFS spectrum of Zn7Co1-NC obtained in Example 1;

[0019] Figure 7 The graph shows the response value of the gas sensors prepared based on the sensing materials of Examples 1, 2, 3, 4, and 5 to 1 ppm n-butanol as a function of operating temperature.

[0020] Figure 8 The graph shows the resistance of the gas sensor prepared based on the sensing material of Example 1 as a function of operating temperature when it responds to 1 ppm n-butanol.

[0021] Figure 9 The response recovery time diagram of the gas sensor prepared based on the sensing material of Example 1 to 0.5 ppm n-butanol is shown.

[0022] Figure 10 The response recovery curves of the gas sensor prepared based on the sensing material of Example 1 to different concentrations of n-butanol are shown.

[0023] Figure 11 The graph shows the sensitivity test performance of the gas sensor prepared based on the sensing material of Example 1 at the optimal operating temperature for 5 ppm of methanol, formaldehyde, ammonia, n-butanol, ethanol, acetone, and isopropanol. Detailed implementation method:

[0024] The present invention will be specifically described below with reference to embodiments, enabling those skilled in the art to implement it after reading this specification, wherein Embodiment 1 is a preferred embodiment. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0025] Example 1: A method for preparing a n-butanol sensing material (Zn7Co1-NC / In2O3, preferred method)

[0026] (1) Dissolve 200 mg of indium nitrate hydrate and 200 mg of terephthalic acid in 120 ml of N,N-dimethylformamide, heat and stir in an oil bath at 120 °C for 65 min, then centrifuge to obtain MIL-68(In), dry, and place the dried MIL-68(In) in a muffle furnace and calcine at 500 °C for 2 h to obtain In2O3, which is a light yellow powder, for later use;

[0027] (2) Dissolve 0.9352g of zinc nitrate hydrate and 0.2513g of cobalt(III) acetylacetonate in 100ml of methanol, and label it as solution A; then dissolve 1.621g of dimethylimidazole and 1.95ml of n-butylamine in 100ml of methanol, and label it as solution B; quickly pour solution B into solution A and stir evenly, react at 60℃ for 24h, then centrifuge to obtain Co-ZIF-8, dry it, grind it into powder, and set it aside for later use;

[0028] (3) Take 0.5g of the powder obtained in step (2) and 0.5g of dimethylimidazolium and dissolve it in 25ml of methanol. Transfer it to a 50ml reaction vessel and react at 140℃ for 4h. Then centrifuge and dry to obtain Zn7Co1-NC precursor, which is a purple powder, for later use.

[0029] (4) Place the purple powder obtained in step (3) into a tube furnace, pass nitrogen gas through it, and calcine at 1000℃ for 1 hour to obtain black powder Zn7Co1-NC for later use.

[0030] (5) Take 30 mg of the light yellow In2O3 powder obtained in step (1) and 30 mg of the black Zn7Co1-NC powder obtained in step (4), add 50 mL of deionized water, ultrasonically disperse, stir at room temperature for 3 h, centrifuge and dry to obtain the final product hexagonal hollow tubular Zn7Co1-NC / In2O3 composite sensing material.

[0031] Figure 2 The image shows a scanning electron microscope (SEM) image of In2O3 obtained in Example 1, which shows a hexagonal hollow tubular morphology with a length of about 6 μm and a pore diameter of about 1 μm.

[0032] Figure 3 The image shown is a transmission electron microscope (TEM) image of Zn7Co1-NC obtained in Example 1, showing particles with a size of 20-30 nm.

[0033] Figure 4 The image shows a scanning electron microscope (SEM) image of the final product Zn7Co1-NC / In2O3 obtained in Example 1. The morphology remains a hexagonal hollow tubular shape, with a length of about 6 μm and a pore size of about 1 μm. Many fine particles are attached to the surface.

[0034] Figure 5 The image shows a HAADF transmission electron microscope image of Zn7Co1-NC with double spherical aberration correction obtained in Example 1. The bright spots in the image represent Co single atoms.

[0035] Figure 6 The image shows the EXAFS spectrum of Zn7Co1-NC obtained in Example 1. The peaks in the image represent the scattering paths of Co-N, and no Co-Co peaks were observed, indicating that Co did not aggregate but existed in the sample as single Co atoms coordinated with N.

[0036] Example 2: A method for preparing a n-butanol sensing material (Zn5Co1-NC / In2O3)

[0037] (1) Dissolve 200 mg of indium nitrate hydrate and 200 mg of terephthalic acid in 120 ml of N,N-dimethylformamide, heat and stir in an oil bath at 120 °C for 65 min, then centrifuge to obtain MIL-68(In), dry, and place the dried MIL-68(In) in a muffle furnace and calcine at 500 °C for 2 h to obtain In2O3, which is a light yellow powder, for later use;

[0038] (2) Dissolve 0.9352g of zinc nitrate hydrate and 0.3518g of cobalt(III) acetylacetonate in 100ml of methanol, and label it solution A; then dissolve 1.621g of dimethylimidazole and 1.95ml of n-butylamine in 100ml of methanol, and label it solution B; quickly pour solution B into solution A and stir evenly, react at 60℃ for 24h, then centrifuge to obtain Co-ZIF-8, dry it, grind it into powder, and set it aside for later use;

[0039] (3) Take 0.5g of the powder obtained in step (2) and 0.5g of dimethylimidazolium and dissolve it in 25ml of methanol. Transfer it to a 50ml reaction vessel and react at 140℃ for 4h. Then centrifuge and dry to obtain Zn5Co1-NC precursor, which is a purple powder, for later use.

[0040] (4) Place the purple powder obtained in step (3) into a tube furnace, pass nitrogen gas through it, and calcine at 1000℃ for 1 hour to obtain black powder Zn5Co1-NC for later use.

[0041] (5) Take 30 mg of the light yellow In2O3 powder obtained in step (1) and 30 mg of the black Zn5Co1-NC powder obtained in step (4), add them to 50 mL of deionized water, disperse them by ultrasonication, stir at room temperature for 3 h, centrifuge and dry to obtain the final product, hexagonal hollow tubular Zn5Co1-NC / In2O3 composite sensing material.

[0042] Example 3: A method for preparing a n-butanol sensing material (Zn9Co1-NC / In2O3)

[0043] (1) Dissolve 200 mg of indium nitrate hydrate and 200 mg of terephthalic acid in 120 ml of N,N-dimethylformamide, heat and stir in an oil bath at 120 °C for 65 min, then centrifuge to obtain MIL-68(In), dry, and place the dried MIL-68(In) in a muffle furnace and calcine at 500 °C for 2 h to obtain In2O3, which is a light yellow powder, for later use;

[0044] (2) Dissolve 0.9352g of zinc nitrate hydrate and 0.1955g of cobalt(III) acetylacetonate in 100ml of methanol, and label it solution A; then dissolve 1.621g of dimethylimidazole and 1.95ml of n-butylamine in 100ml of methanol, and label it solution B; quickly pour solution B into solution A and stir evenly, react at 60℃ for 24h, then centrifuge to obtain Co-ZIF-8, dry it, grind it into powder, and set it aside for later use;

[0045] (3) Take 0.5g of the powder obtained in step (2) and 0.5g of dimethylimidazole and dissolve them in 25ml of methanol. Transfer the solution to a 50ml reaction vessel and react at 140℃ for 4h. Then centrifuge and dry to obtain Zn9Co1-NC precursor, which is a purple powder, for later use.

[0046] (4) Place the purple powder obtained in step (3) into a tube furnace, pass nitrogen gas through it, and calcine at 1000℃ for 1 hour to obtain black powder Zn9Co1-NC for later use.

[0047] (5) Take 30 mg of the light yellow In2O3 powder obtained in step (1) and 30 mg of the black Zn9Co1-NC powder obtained in step (4), add them to 50 mL of deionized water, disperse by ultrasonication, stir at room temperature for 3 h, centrifuge and dry to obtain the final product, hexagonal hollow tubular Zn9Co1-NC / In2O3 composite sensing material.

[0048] Example 4: A method for preparing a n-butanol sensing material (In2O3)

[0049] 200 mg of indium nitrate hydrate and 200 mg of terephthalic acid were dissolved in 120 ml of N,N-dimethylformamide. The mixture was heated and stirred in an oil bath at 120 °C for 65 min, and then centrifuged to obtain MIL-68(In). The MIL-68(In) was dried and then calcined in a muffle furnace at 500 °C for 2 h to obtain the final product In2O3, which is a pale yellow powder.

[0050] Example 5: A method for preparing a n-butanol sensing material (ZIF-8-NC / In2O3 without Co)

[0051] (1) Dissolve 200 mg of indium nitrate hydrate and 200 mg of terephthalic acid in 120 ml of N,N-dimethylformamide, heat and stir in an oil bath at 120 °C for 65 min, then centrifuge to obtain MIL-68(In), dry, and place the dried MIL-68(In) in a muffle furnace and calcine at 500 °C for 2 h to obtain In2O3, which is a light yellow powder, for later use;

[0052] (2) Dissolve 0.9352g of zinc nitrate hydrate in 100ml of methanol, and denote it as solution A; then dissolve 1.621g of dimethylimidazole and 1.95ml of n-butylamine in 100ml of methanol, and denote it as solution B; quickly pour solution B into solution A and stir evenly, react at 60℃ for 24h, then centrifuge to obtain ZIF-8, dry it, grind it into powder, and set it aside for later use;

[0053] (3) Take 0.5g of the powder obtained in step (2) and 0.5g of dimethylimidazole and dissolve them in 25ml of methanol. Transfer the solution to a 50ml reaction vessel and react at 140℃ for 4h. Then centrifuge and dry to obtain ZIF-8-NC precursor, which is a white powder, for later use.

[0054] (4) Place the white powder obtained in step (3) into a tube furnace, pass nitrogen gas through it, and calcine at 1000℃ for 1 hour to obtain black powder ZIF-8-NC for later use.

[0055] (5) Take 30 mg of the light yellow In2O3 powder obtained in step (1) and 30 mg of the black ZIF-8-NC powder obtained in step (4), add them to 50 mL of deionized water, disperse them by ultrasonication, stir at room temperature for 3 h, centrifuge and dry to obtain the final product, hexagonal hollow tubular ZIF-8-NC / In2O3 composite sensing material.

[0056] Example 6: Fabrication of a Gas Sensor

[0057] (1) Take 18mg of the product prepared in the above example and put it into an agate mortar. Add 1-2 drops of terpineol and grind clockwise for 10 minutes to form a slurry. Use a brush to take an appropriate amount of slurry and coat it on the outer surface of a commercially available ceramic tube to form a thin sensing material coating. After it dries naturally, first use high-performance solder wire to weld the dried ceramic tube on the base, and then pass the heating wire through the ceramic tube and solder it with solder wire.

[0058] (2) The prepared sensor was placed on an aging table and aged at 240°C for 24 hours to obtain gas sensors with different sensing materials.

[0059] Example 7: Sensing Performance Test of Gas Sensor

[0060] The gas sensor characteristics were tested using the static gas mixing method. The response values ​​of gas sensors made of different sensing materials to 1 ppm n-butanol were measured using a GGS-8 gas-sensitive analysis system within an operating temperature range of 200℃ to 280℃, as shown in the curves. Figure 7 The resistivity of the product Zn7Co1-NC / In2O3 obtained under optimal preparation conditions versus 1 ppm n-butanol as a function of operating temperature is shown in the figure below. Figure 8 ,from Figure 7 It can be seen that the response values ​​of different gas sensors to 1 ppm n-butanol increase as the operating temperature decreases, but from... Figure 8 It can be seen that as the temperature decreases, the recovery time of the gas sensor's resistance value gradually increases. Considering practical applications, 240℃ is selected as the optimal operating temperature. Figure 7 As can be seen, the Zn7Co1-NC / In2O3 gas sensor with a zinc-cobalt molar ratio of 7:1 exhibits an excellent response value of 35.5 for n-butanol at this operating temperature, a significant improvement compared to In2O3 (4.1) and the Co-free ZIF-8-NC / In2O3 (5.1). Its response recovery time is as follows... Figure 9 As shown, the response time to n-butanol is 43 s, and the recovery time is 200 s. Furthermore, Figure 10 The response recovery time curves for different concentrations of n-butanol are shown. It can be seen that the response recovery is sensitive to different concentrations of n-butanol, and the response values ​​have a good linear relationship. At a concentration of 5 ppm, the response value is as high as 145.0. Similarly, using the static gas mixing method, the response values ​​of the gas sensor prepared from Zn7Co1-NC / In2O3 material with a zinc-cobalt molar ratio of 7:1 to other organic compounds were tested using a GGS-8 gas-sensitive analysis system. Figure 11 The response values ​​at 240℃ to 5 ppm of methanol, formaldehyde, ammonia, n-butanol, ethanol, acetone, and isopropanol were shown to be 30.3, 11.5, 1.4, 145.0, 44.8, 50.3, and 58.7, respectively. Figure 11 The test results show that the Zn7Co1-NC / In2O3 gas sensor with a zinc-cobalt molar ratio of 7:1 has good selectivity for the detection of n-butanol.

[0061] Table 1. Response values ​​of 1 ppm n-butanol at 240°C for Examples 1 to 5

[0062]

[0063] This invention first prepares In2O3 hexagonal hollow tubes and single-atom catalyst Zn, respectively. x Co1-NC nanoparticles were then mechanically mixed to obtain Zn with different zinc-cobalt molar ratios as described in the examples. x Co1-NC / In2O3 composite sensing materials were used to fabricate gas sensors. Response tests were conducted on 1 ppm n-butanol at different operating temperatures. Combined with resistance response recovery analysis, the optimal operating temperature was determined to be 240℃, and the response values ​​at this temperature are shown in Table 1. It can be seen that the Zn7Co1-NC / In2O3 composite sensing material with a zinc-cobalt molar ratio of 7:1 exhibits the highest response value to n-butanol, making it the preferred option. Its response time to n-butanol is 43 s, and its recovery time is 200 s. It demonstrates sensitive response recovery to different concentrations of n-butanol, and the response values ​​show a good linear relationship, reaching a high response value of 145.0 at a concentration of 5 ppm. In addition, the Zn7Co1-NC / In2O3 composite sensing material was tested at 240℃ for 5 ppm of methanol, formaldehyde, ammonia, n-butanol, ethanol, acetone, and isopropanol, with response values ​​of 30.3, 11.5, 1.4, 145.0, 44.8, 50.3, and 58.7, respectively, indicating that the Zn7Co1-NC / In2O3 composite sensing material has good selectivity for n-butanol.

Claims

1. A method for preparing a n-butanol sensing material, characterized in that, The process includes the following steps: (1) Dissolve 180–220 mg of indium nitrate hydrate and 180–220 mg of terephthalic acid in 100–140 mL of N,N-dimethylformamide, heat and stir in an oil bath at 100–140 °C for 55–75 min, then centrifuge to obtain MIL-68, dry it, and calcine the dried MIL-68 in a muffle furnace at 500 °C for 2 h to obtain In2O3, which is a light yellow powder; (2) Dissolve 0.9–1.0 g of zinc nitrate hydrate and 0.2–0.3 g of cobalt acetylacetonate III in 80–120 mL of methanol, and denote it as solution A; then dissolve 1.4–1.8 g of dimethylimidazole and 1.5–2.5 mL of n-butylamine in 80–120 mL of methanol, and denote it as solution B; quickly pour solution B into solution A and stir evenly, and react at 60 °C for 24 hours. h, then centrifuge to obtain Co-ZIF-8, dry, and grind into powder; (3) Take 0.45~0.55 g of the powder obtained in step (2) and 0.45~0.55 g of dimethylimidazolium and dissolve in 20~30 mL of methanol, transfer to a 50~100 mL reaction vessel, react at 120~160℃ for 2~6 h, then centrifuge and dry to obtain Zn x Co1-NC precursor, where x equals 7, 5, or 9, is a purple powder; (4) The purple powder obtained in step (3) is placed in a tube furnace, nitrogen is introduced, and it is calcined at 900-1100℃ for 0.5-1.5 h to obtain black powder Zn. x Co1-NC, where x equals 7, 5, or 9; (5) Take 15–45 mg of the pale yellow In2O3 powder obtained in step (1) and the black Zn obtained in step (4). x Mix 15–45 mg of Co1-NC powder, add 40–60 mL of deionized water, ultrasonically disperse, stir at room temperature for 2–4 h, centrifuge and dry to obtain the final product, hexagonal hollow tubular Zn. x Co1-NC / In2O3 composite sensing material, where x equals 7, 5, or 9.

2. The method for preparing a n-butanol sensing material as described in claim 1, characterized in that: (1) Dissolve 200 mg of indium nitrate hydrate and 200 mg of terephthalic acid in 120 mL of N,N-dimethylformamide, heat and stir in an oil bath at 120 °C for 65 min, then centrifuge to obtain MIL-68, dry it, and calcine the dried MIL-68 in a muffle furnace at 500 °C for 2 h to obtain In2O3, which is a light yellow powder; (2) Dissolve 0.9352 g of zinc nitrate hydrate and 0.2513 g of cobalt acetylacetone III in 100 mL of methanol, and denote it as solution A; then dissolve 1.621 g of dimethylimidazole and 1.95 mL of n-butylamine in 100 mL of methanol, and denote it as solution B; quickly pour solution B into solution A and stir evenly, react at 60 °C for 24 h, then centrifuge to obtain Co-ZIF-8, dry it, and grind it into powder; (3) Take 0.5 g of the powder obtained in step (2) and 0.5 g of dimethylimidazole and dissolve it in 25 mL of N,N-dimethylformamide. (3) Transfer 1 mL of methanol to a 50 mL reaction vessel and react at 140 °C for 4 h. After centrifugation and drying, the Zn7Co1-NC precursor is obtained as a purple powder. (4) Place the purple powder obtained in step (3) into a tube furnace, pass nitrogen gas through it, and calcine at 1000 °C for 1 h to obtain black powder Zn7Co1-NC. (5) Take 30 mg of the light yellow In2O3 powder obtained in step (1) and 30 mg of the black Zn7Co1-NC powder obtained in step (4), add 50 mL of deionized water, disperse by ultrasonication, stir at room temperature for 3 h, centrifuge and dry to obtain the final product, hexagonal hollow tubular Zn7Co1 NC / In2O3 composite sensing material.

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