Organic hybrid material UIO-66-NH2-coated UIO-66-(OH) 2, preparation method and application thereof, gas sensor and application thereof

Abstract

The invention relates to the field of gas detection, and discloses an organic hybrid material UIO-66-NH2 (at) UIO-66-(OH) 2, a preparation method and application thereof, a gas sensor and application of the gas sensor, the organic hybrid material UIO-66-NH2 (at) UIO-66-(OH) 2 comprises UIO-66-(OH) 2, and the surface of the UIO-66-(OH) 2 is modified with UIO-66-NH2. The organic hybrid material has a nano-porous structure, has a relatively high specific surface area, can effectively adsorb and enrich H2, CO and other target gas molecules, and improves the interaction rate between the gas and the sensing material, so that the rapid and high-precision detection of the transformer oil dissolved gas is realized.

Description

Technical Field

[0001] The present invention relates to the field of gas detection, and particularly to an organic hybrid material UIO-66-NH2@UIO-66-(OH)2, its preparation method and application, a gas sensor and its application. Background Art

[0002] As a core equipment of the power grid, the operation status of power equipment transformers being observable, measurable, and controllable is crucial for the safe and stable operation of the power grid. The on-line monitoring technology for dissolved gases in oil can effectively diagnose whether there are faults such as overheating and discharge in transformers by measuring and analyzing the component content of dissolved gases in transformer oil. However, when diagnosing transformer faults with the existing on-line monitoring technology for dissolved gases in oil, false alarms and missed alarms often occur, posing a threat to the safe operation of the power grid. The main reasons include insufficient design accuracy at the factory of the device and great difficulty in operation and maintenance affected by environmental factors, etc.

[0003] Therefore, there is an urgent need for an on-line monitoring device for dissolved gases in transformer oil with high speed, high precision, and high stability to solve the bottleneck of the existing technology and ensure the safe and stable operation of the main equipment of the power grid. Summary of the Invention

[0004] The purpose of the present invention is to overcome the problem that false alarms and missed alarms often occur when diagnosing transformer faults with the existing on-line monitoring technology for dissolved gases in oil, and to provide an organic hybrid material UIO-66-NH2@UIO-66-(OH)2, its preparation method and application, a gas sensor and its application. This organic hybrid material has a nanoporous structure and a relatively high specific surface area, can effectively adsorb and enrich target gas molecules such as H2 and CO, and improve the interaction rate between the gas and the sensing material, so as to achieve rapid and high-precision detection of dissolved gases in transformer oil.

[0005] In order to achieve the above purpose, on the one hand, the present invention provides an organic hybrid material UIO-66-NH2@UIO-66-(OH)2, and the organic hybrid material UIO-66-NH2@UIO-66-(OH)2 includes UIO-66-(OH)2, and UIO-66-NH2 is surface-modified on the UIO-66-(OH)2.

[0006] The organic hybrid material UIO-66-NH2@UIO-66-(OH)2 of the present invention is in the shape of nanoporous rhombic particles, with a particle size of 200 - 300 nm and a specific surface area of 1100 - 1200 m 2 / g.

[0007] On the second aspect, the present invention provides a preparation method of the above organic hybrid material UIO-66-NH2@UIO-66-(OH)2, and the preparation method includes the following steps:

[0008] Mix a zirconium salt, 2-aminoterephthalic acid, UIO-66-(OH)2 and a solvent, stir and then carry out a hydrothermal reaction. After the hydrothermal reaction is completed, carry out solid-liquid separation. Wash and dry the solid obtained after solid-liquid separation to obtain the organic hybrid material UIO-66-NH2@UIO-66-(OH)2.

[0009] The zirconium salt used in the present invention is selected from one or more of zirconium chloride, zirconium nitrate and zirconium carbonate; in a specific embodiment, the zirconium salt used is zirconium chloride.

[0010] Further preferably, the weight ratio of the zirconium salt, 2-aminoterephthalic acid and UIO-66-(OH)2 is 1:1-1.5:1-2.

[0011] Among them, the zirconium salt serves as a metal source, 2-aminoterephthalic acid provides an organic ligand, and UIO-66-(OH)2 serves as a template agent. The combination of the three can form a material with a nanoporous structure and a high specific surface area, which is beneficial to the adsorption and detection of gas molecules. Using the three as reaction raw materials and controlling the dosage ratio within the above range can jointly participate in the reaction to generate the organic hybrid material UIO-66-NH2@UIO-66-(OH)2 with excellent gas sensing performance.

[0012] The solvent in the present invention contains N,N-dimethylformamide and acetic acid, and the volume ratio of N,N-dimethylformamide to acetic acid is 2:1-2; N,N-dimethylformamide has good solubility and helps the uniform mixing of raw materials; acetic acid participates in the reaction and affects the structure and performance of the product; controlling the dosage of the two within this range can dissolve the reaction raw materials and form a suitable reaction environment.

[0013] Further, the weight-to-volume ratio of the zirconium salt to the solvent is 1 g:40-80 mL; controlling the dosage ratio of the zirconium salt and the solvent within this range is beneficial to the full dissolution of the zirconium salt and the formation of a suitable concentration.

[0014] In a preferred case, mix the zirconium salt, 2-aminoterephthalic acid, UIO-66-(OH)2 and the solvent, stir at room temperature and then carry out a hydrothermal reaction, wherein the stirring time is 10-30 min.

[0015] The room temperature referred to in the present invention means 20-30 °C.

[0016] In a preferred embodiment, the conditions of the hydrothermal reaction include: a temperature of 80 to 120 °C and a time of 4 to 12 h; under these conditions, it is ensured that the reactants can fully react to form a stable organic hybrid material structure, while avoiding a decrease in material performance caused by too high a temperature and too long a time. The main process of the hydrothermal reaction is a chemical reaction that occurs at high temperature in a sealed autoclave for the reactants, and through this process, an organic hybrid material with high crystallinity and good dispersibility can be obtained.

[0017] In a preferred case, the method for solid-liquid separation in the present invention can be centrifugation or filtration. Further, in a specific embodiment, the method for solid-liquid separation is filtration.

[0018] After the hydrothermal reaction, since there will be unreacted and residual reaction raw materials on the surface of the solid obtained after solid-liquid separation and inside the pores, in order to remove these residual reaction raw materials and avoid affecting the material performance, it is also necessary to fully wash the solid obtained after solid-liquid separation. Preferably, methanol is used for washing. Therefore, the specific operations for washing and drying the solid obtained after solid-liquid separation in the present invention include: mixing the solid obtained after solid-liquid separation with methanol (the amount of methanol only needs to completely immerse the solid obtained after solid-liquid separation), then stirring at room temperature for 12 to 24 h (to ensure complete removal of the residual unreacted substances), then filtering to obtain a solid complex, and drying the solid complex at 60 to 120 °C for 12 to 24 h.

[0019] Further, the UIO-66-(OH)2 used in the present invention can be obtained commercially or prepared by itself. In a specific embodiment, the UIO-66-(OH)2 used in the present invention is prepared by itself. The preparation method of the UIO-66-(OH)2 includes: mixing a zirconium salt, 2-hydroxyterephthalic acid, and a mixed solvent, stirring at room temperature for 10 to 30 min and then carrying out a heat preservation reaction. After the heat preservation reaction is completed, filtration is carried out to obtain a solid phase material. Mix the solid phase material with methanol (similarly, the amount of methanol only needs to completely immerse the solid phase material), then stir at room temperature for 12 to 24 h (similarly, in order to remove the residual reaction raw materials and avoid affecting the material performance, it is necessary to fully wash the solid phase material obtained after filtration), then filter to obtain a solid product, and dry the solid product at 60 to 120 °C for 12 to 24 h to obtain UIO-66-(OH)2.

[0020] In the preparation method of UIO-66-(OH)2, the weight ratio of the zirconium salt to 2-hydroxyterephthalic acid is 1:1 to 2.

[0021] Preferably, the mixed solvent contains N,N-dimethylformamide and acetic acid, and the volume ratio of N,N-dimethylformamide to acetic acid is 3:2 to 3.

[0022] Further, in the preparation method of UIO-66-(OH)2, the weight-to-volume ratio of the zirconium salt to the mixed solvent is 1 g: 40-60 mL.

[0023] Among them, the conditions for the heat preservation reaction include: the temperature is 110-140 °C and the time is 4-12 h.

[0024] In the present invention, by first synthesizing UIO-66-(OH)2 as a template agent, and then growing a layer of UIO-66-NH2 on the surface of the UIO-66-(OH)2 solid particles through in-situ self-assembly measurement, the organic hybrid material UIO-66-NH2@UIO-66-(OH)2 is formed.

[0025] The third aspect of the present invention provides an application of the above-mentioned organic hybrid material UIO-66-NH2@UIO-66-(OH)2 in a gas sensor.

[0026] The fourth aspect of the present invention provides a gas sensor, and the surface of the ceramic tube electrode of the gas sensor is coated with the above-mentioned organic hybrid material UIO-66-NH2@UIO-66-(OH)2.

[0027] Further, the gas sensor device structure adopted in the present invention is a side-heating type, and the specific preparation method of the gas sensor includes: mixing the above-mentioned organic hybrid material UIO-66-NH2@UIO-66-(OH)2 and water to obtain a slurry with a concentration of 3-5 wt%;

[0028] Clean the ceramic tube electrode, then dry it, coat the slurry on the surface of the dried ceramic tube electrode to obtain a ceramic tube electrode coated with the slurry, calcine the ceramic tube electrode coated with the slurry, then insert a nickel-chromium alloy heating wire into the calcined ceramic tube electrode, weld the four platinum wires on the calcined ceramic tube electrode to four feet of a six-pin socket, and then weld the nickel-chromium alloy heating wire to the other two feet of the six-pin socket to obtain a gas sensor.

[0029] In a specific embodiment, the inner diameter of the ceramic tube electrode used in the present invention is 0.8 mm, the outer diameter is 1.2 mm, the length is 5 mm, and the width of the gold electrode is 0.5 mm.

[0030] In the present invention, it is preferably to perform ultrasonic cleaning on the ceramic tube electrode with absolute ethanol to remove surface impurities.

[0031] In the preparation method of the gas sensor, the conditions for drying include: the temperature is 60-80 °C and the time is 12-24 h.

[0032] Among them, the dosage of the coated slurry only needs to ensure that the thickness of the organic hybrid material UIO-66-NH2@UIO-66-(OH)2 coated on the surface of the ceramic tube electrode in the finished gas sensor is 100-300 nm.

[0033] In the present invention, the calcination treatment can enhance the stability and gas-sensing performance of the sensitive layer. Therefore, in order to maintain good gas-sensing performance, the conditions of the calcination include: the temperature is 150-300 °C, and the time is 1-3 h.

[0034] Since MOF, as a metal-organic hybrid material, exhibits significant advantages when used as a gas-sensing material for detecting dissolved gases in transformer oil. MOF materials have diverse structures and pore sizes, which can be easily controlled by adjusting the synthesis conditions, so that they have a large specific surface area and an ultra-high porosity. These characteristics enhance the advantages of MOF as a gas-sensing material because it can more effectively adsorb and enrich gas molecules, improving the detection sensitivity. Based on this, in the present invention, a certain amount of zirconium metal salt and 2-hydroxyterephthalic acid are used as reaction raw materials, dissolved and mixed in a specific mixed solvent, and then reacted under high-temperature conditions to obtain the UIO-66-(OH)2 product. Using the above-prepared UIO-66-(OH)2, zirconium metal salt and 2-aminoterephthalic acid as reaction raw materials, and also under specific solvent and reaction conditions, UIO-66-NH2@UIO-66-(OH)2 is prepared by double hydrothermal synthesis. The obtained UIO-66-NH2@UIO-66-(OH)2 is mixed with an appropriate amount of deionized water to prepare a slurry, which is uniformly coated on the ceramic tube electrode to form a sensitive layer film. After calcination treatment, the stability and gas-sensing performance of the sensitive layer are enhanced. Finally, the heating wire and the electrode are welded to the base to complete the assembly of the sensor.

[0035] The organic hybrid material UIO-66-NH2@UIO-66-(OH)2 of the present invention exhibits excellent gas-sensing performance for H2 and CO. Its high specific surface area and rich pore structure enable the material surface to have more adsorption sites, which can effectively adsorb and enrich target gas molecules such as H2 and CO. When the target gas molecules are adsorbed on the material surface, they will interact with the sensing material, resulting in a change in the electronic structure inside the material, and then causing a change in the resistance of the gas sensor. This resistance change can be converted into an electrical signal for output, thereby realizing the detection of the target gas. Since the UIO-66-NH2@UIO-66-(OH)2 material has a high adsorption capacity and response speed for gas molecules such as H2 and CO, the gas sensor can achieve rapid and high-precision detection of these gases.

[0036] The fifth aspect of the present invention provides an application of the above gas sensor in the detection of H2 and CO.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] The present invention prepares a novel organic hybrid material UIO-66-NH2@UIO-66-(OH)2 by a dual hydrothermal synthesis method. This material combines the advantages of UIO-66-NH2 and UIO-66-(OH)2, has a higher specific surface area, forms abundant active sites, significantly enhances the catalytic activity on the material surface, and thus enhances its performance as a gas-sensitive material.

[0039] Since UIO-66-NH2@UIO-66-(OH)2 has a high specific surface area and can more effectively adsorb and enrich gas molecules, the prepared gas-sensitive sensor has high detection accuracy for target gases such as H2 and CO, can quickly and accurately detect gases such as H2 and CO dissolved in transformer oil, effectively improves the detection sensitivity, can timely discover most of the hidden dangers and defects inside the transformer, and has great significance for ensuring the safe and stable operation of power equipment. Brief Description of the Drawings

[0040] Figure 1 is a schematic diagram of the preparation of the organic hybrid material UIO-66-NH2@UIO-66-(OH)2 of the present invention;

[0041] Figure 2 is the SEM image of the organic hybrid material UIO-66-NH2@UIO-66-(OH)2 obtained in Example 1;

[0042] Figure 3 is the XRD pattern of the organic hybrid material UIO-66-NH2@UIO-66-(OH)2 obtained in Example 1;

[0043] Figure 4 is the N2 adsorption-desorption isotherm of the organic hybrid material UIO-66-NH2@UIO-66-(OH)2 obtained in Example 1;

[0044] Figure 5 is the response curve of the gas-sensitive sensor obtained in Example 1 to 5 ppm H2 at different operating temperatures;

[0045] Figure 6 is the response curve of the gas-sensitive sensor obtained in Example 1 to 5 ppm CO at different operating temperatures. Detailed Description of the Invention

[0046] The following detailed description of the specific embodiments of the present invention is provided in conjunction with the accompanying drawings and examples. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the present invention.

[0047] The endpoints and any values in the ranges disclosed herein are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0048] In addition, the technical solutions between the various embodiments provided by the present invention can be combined with each other, but it must be based on the ability of those of ordinary skill in the art to implement. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0049] The preparation schematic diagram of the organic hybrid material UIO-66-NH2@UIO-66-(OH)2 of the present invention is as Figure 1 shown.

[0050] The room temperature in the following examples all refers to 25 °C.

[0051] Example 1

[0052] (1) Mix N,N-dimethylformamide and acetic acid evenly according to a volume ratio of 3:2 to obtain a mixed solvent. Weigh 1 g of zirconium salt (zirconium chloride) and 1 g of 2-hydroxyterephthalic acid and dissolve them in 50 mL of the mixed solvent, and mix them. Stir at room temperature for 15 min. After mixing evenly, transfer it to a polytetrafluoroethylene high-pressure reaction kettle for heat preservation reaction. The conditions of the heat preservation reaction include: the temperature is 120 °C and the time is 6 h. After the heat preservation reaction is completed, filter to obtain a white solid material. Add the white solid material to 100 mL of methanol and mix, and then stir at room temperature for 12 h to remove the remaining unreacted metal salts and organic substances. Then filter to obtain a solid product. Put the solid product in an oven at 80 °C and dry it for 12 h to obtain pure UIO-66-(OH)2;

[0053] (2) Mix N,N-dimethylformamide and acetic acid evenly in a volume ratio of 2:1 to obtain a solvent. Weigh 1 g of zirconium salt (zirconium chloride), 1 g of 2-aminoterephthalic acid, and 1 g of UIO-66-(OH)2 obtained in step (1), add them to 50 mL of the solvent and mix. Stir at room temperature for 15 min. After mixing evenly, transfer to a polytetrafluoroethylene autoclave for hydrothermal reaction. The conditions of the hydrothermal reaction include: temperature is 90 °C, time is 12 h. After the hydrothermal reaction, filter. Add the obtained white solid to 100 mL of methanol and mix, then stir at room temperature for 12 h to remove residual unreacted metal salts and organic substances. Then filter to obtain a solid complex. Place the solid complex in an oven at 80 °C and dry for 12 h to obtain a pure organic hybrid material UIO-66-NH2@UIO-66-(OH)2;

[0054] (3) Mix the organic hybrid material UIO-66-NH2@UIO-66-(OH)2 obtained in step (2) and deionized water to obtain a uniform slurry with a concentration of 5 wt%.

[0055] (4) Use absolute ethanol to ultrasonically clean the ceramic tube electrode (the inner diameter of the ceramic tube electrode is 0.8 mm, the outer diameter is 1.2 mm, the length is 5 mm, and the width of the gold electrode is 0.5 mm) to remove surface impurities, and then dry. The drying conditions include: temperature is 60 °C, time is 12 h. Uniformly coat the slurry obtained in step (3) on the surface of the dried ceramic tube electrode to obtain a ceramic tube electrode coated with the slurry. Place the ceramic tube electrode coated with the slurry in a muffle furnace and calcine at 200 °C for 2 h. Then insert a nickel-chromium alloy heating wire into the calcined ceramic tube electrode. Weld the four platinum wires on the calcined ceramic tube electrode to four pins of a six-pin socket with a soldering iron, and then weld the nickel-chromium alloy heating wire to the other two pins of the six-pin socket to obtain a gas sensor A1. The thickness of the organic hybrid material UIO-66-NH2@UIO-66-(OH)2 coated on the surface of the ceramic tube electrode in the gas sensor A1 is 100 nm.

[0056] Example 2

[0057] Implement according to the method of Example 1, the difference is that in step (1), weigh 1 g of zirconium salt (zirconium chloride) and 2 g of 2-hydroxyterephthalic acid to obtain a gas sensor A2.

[0058] Example 3

[0059] Implement according to the method of Example 1, the difference is that in step (2), weigh 1 g of zirconium salt (zirconium chloride), 1 g of 2-aminoterephthalic acid, and 2 g of UIO-66-(OH)2 obtained in step (1) to obtain a gas sensor A3.

[0060] Comparative Example 1

[0061] Implemented according to the method of Example 1, except that the UIO-66-(OH)2 obtained in step (1) was directly used instead of the organic hybrid material UIO-66-NH2@UIO-66-(OH)2 to obtain the gas sensor D1.

[0062] Comparative Example 2

[0063] Implemented according to the method of Example 1, except that UIO-66-NH2 was directly prepared instead of the organic hybrid material UIO-66-NH2@UIO-66-(OH)2 to obtain the gas sensor D2; the preparation method of UIO-66-NH2 is as follows:

[0064] N,N-dimethylformamide and acetic acid were mixed evenly according to a volume ratio of 2:1 to obtain a solvent. 1 g of zirconium salt (zirconium chloride) and 1 g of 2-aminoterephthalic acid were weighed and added to 50 mL of the solvent and mixed. After stirring at room temperature for 15 min and mixing evenly, it was transferred to a polytetrafluoroethylene autoclave for hydrothermal reaction. The conditions of the hydrothermal reaction included: the temperature was 90 °C and the time was 12 h. After the hydrothermal reaction, filtration was carried out. The white solid obtained after filtration was added to 100 mL of methanol and mixed, and then stirred at room temperature for 12 h to remove the remaining unreacted metal salts and organic substances. Then filtration was carried out to obtain a solid complex. The solid complex was placed in an oven at 80 °C and dried for 12 h to obtain UIO-66-NH2.

[0065] Test Example 1

[0066] The organic hybrid material UIO-66-NH2@UIO-66-(OH)2 obtained in step (2) of Example 1 was subjected to SEM detection, and the SEM image is as Figure 2 shown, from Figure 2It can be seen from [the figure] that the prepared organic hybrid material UIO-66-NH2@UIO-66-(OH)2 has a particle size of 200 - 300 nm. A smaller particle size means a shorter diffusion path for gas molecules inside the material, which helps to accelerate the interaction rate between gas molecules and the sensing material. Therefore, the sensor can respond faster to changes in gas concentration and shorten the response time. It can also be clearly seen from the SEM image that these particles exhibit a nano-porous rhombic structure, which is a unique morphological feature of the UIO-66 series of materials. These porous structures not only increase the specific surface area of the material, providing more active sites for the adsorption and reaction of gas molecules, but also further promote the diffusion and transmission of gas molecules inside the material. In addition, the surface of the particles in the figure is modified by a thin layer of substance, which is the successful modification of the surface of UIO-66-(OH)2 by UIO-66-NH2. This modification not only improves the surface properties of the material, such as hydrophilicity and chemical stability, but also may enhance the interaction force between the material and target gas molecules by introducing amino functional groups, thus improving the sensitivity and selectivity of the sensor.

[0067] Test Example 2

[0068] The obtained organic hybrid material UIO-66-NH2@UIO-66-(OH)2 in step (2) of Example 1 was subjected to XRD detection, and the XRD pattern is as Figure 3 shown, Figure 3 It can be seen that the prepared organic hybrid material UIO-66-NH2@UIO-66-(OH)2 has good crystallinity and phase purity, and UIO-66-NH2 was successfully modified on the surface of UIO-66-(OH)2.

[0069] Test Example 3

[0070] Detect the N2 adsorption - desorption isotherm of the organic hybrid material UIO - 66 - NH2@UIO - 66-(OH)2 obtained in step (2) of Detection Example 1. The specific operation is as follows: First, place the organic hybrid material UIO - 66 - NH2@UIO - 66-(OH)2 obtained in step (2) of Example 1 in a specific surface area and porosity analyzer test device. Subsequently, conduct degassing treatment on the organic hybrid material UIO - 66 - NH2@UIO - 66-(OH)2 at 120 °C to remove the impurity gases adsorbed on the surface of the organic hybrid material UIO - 66 - NH2@UIO - 66-(OH)2. Then, introduce nitrogen as the adsorbate into the test system. By precisely controlling the partial pressure of nitrogen, gradually increase the nitrogen concentration, and record the adsorption amount of nitrogen by this composite material at different nitrogen concentrations. After completing the measurement of the adsorption process, gradually decrease the nitrogen concentration and conduct the measurement of the desorption process, recording the release amount of nitrogen during the desorption process. By plotting the relationship curve between the adsorption amount and the nitrogen partial pressure, the N2 adsorption - desorption isotherm of the organic hybrid material UIO - 66 - NH2@UIO - 66-(OH)2 is obtained.

[0071] The N2 adsorption - desorption isotherm is as Figure 4 shown. From Figure 4 it can be seen that the specific surface area of the organic hybrid material UIO - 66 - NH2@UIO - 66-(OH)2 is as high as 1154 m 2 / g. A high specific surface area means that there are more adsorption sites on the material surface, which can more effectively adsorb target gas molecules (such as H2, CO). This increases the interaction opportunities between gas molecules and the sensor sensing element, thereby improving the sensitivity of the sensor. In gas - sensitive materials, the reaction between gas molecules and the sensing element usually occurs on the material surface. The high specific surface area provides more reaction sites, enabling the reaction rate to be increased, and thus accelerating the response speed of the sensor to the target gas.

[0072] Test Example 4

[0073] As the target gas molecules are adsorbed on the surface of the gas - sensitive sensor, electrons transfer from the sensor material to the target molecules, resulting in a change in the resistance of the gas - sensitive sensor. This change can be converted into an electrical signal for output, thereby realizing the detection of the target gas. This test example evaluates the gas - sensitive performance of the gas - sensitive sensor to the oil - dissolved gases H2 and CH4 in power equipment.

[0074] Detect the response curve of gas sensor A1 to 5 ppm H2: First, place gas sensor A1 in a test chamber with a controllable atmosphere. Subsequently, inject a mixed gas with a hydrogen concentration of 5 ppm into the test chamber through an accurate gas flow controller (usually using nitrogen or air as the balance gas). At the same time, use a high-precision temperature and humidity control system to maintain the stability and consistency of the test environment, detect the response values of gas sensor A1 to 5 ppm H2 at different temperatures respectively, and obtain the response curve, as Figure 5 shown.

[0075] Detect the response curve of gas sensor A1 to 5 ppm CO: First, place gas sensor A1 in a test chamber with a controllable atmosphere. Subsequently, inject a mixed gas with a CO concentration of 5 ppm into the test chamber through an accurate gas flow controller (usually using nitrogen or air as the balance gas). At the same time, use a high-precision temperature and humidity control system to maintain the stability and consistency of the test environment, detect the response values of gas sensor A1 to 5 ppm CO at different temperatures respectively, and obtain the response curve, as Figure 6 shown.

[0076] From Figure 5 and Figure 6 it can be seen that as the temperature increases, the response value of gas sensor A1 shows a trend of first increasing and then decreasing. The response values of gas sensor A1 to H2 and CO reach the maximum values of 69 and 29 respectively when the working temperature is 90 °C;

[0077] Among them, the response value is calculated using the calculation formula for n-type semiconductor gas sensors: S = R g / R a , S is the response value, R g is the resistance value of the gas sensor in air, and R a is the resistance value of the gas sensor in the gas to be measured;

[0078] According to the same method, the response curves of gas sensors A2 - A3 and gas sensors D1 - D2 to 5 ppm H2 and 5 ppm CO were detected respectively. It was found that the trends of the response curves of gas sensors A2 - A3 and gas sensors D1 - D2 to 5 ppm H2 and 5 ppm CO are similar to those of gas sensor A1 to 5 ppm H2 and 5 ppm CO, that is, as the temperature increases, the response value of the gas sensor shows a trend of first increasing and then decreasing, and when the working temperature is 90 °C, the response value reaches the maximum. The specific maximum response values are shown in Table 1.

[0079] Table 1

[0080]

[0081]

[0082] As can be seen from the results in Table 1, the sensor in Example 1 has the highest response values to H2 and CO, which are 69 and 29 respectively. This is due to its precise raw material mass ratio, optimized reaction conditions and unique composite structure design. In contrast, the response values in Example 2 and Example 3 decreased slightly by adjusting the raw material mass ratio. For Comparative Example 1 and Comparative Example 2, the sensitivity decreased significantly due to the change of the gas-sensitive material, indicating that the composite structure of the organic hybrid material UIO-66-NH2@UIO-66-(OH)2 prepared by the present invention plays an important role in improving the sensor sensitivity.

[0083] It should be understood that the parts not detailed in this specification belong to the prior art.

[0084] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. An organic hybrid material UIO-66-NH2@UIO-66-(OH)2, characterized in that: The organic hybrid material UIO-66-NH2@UIO-66-(OH)2 includes UIO-66-(OH)2, and the surface of the UIO-66-(OH)2 is modified with UIO-66-NH2.

2. The organic hybrid material UIO-66-NH2@UIO-66-(OH)2 according to claim 1, characterized in that: The organic hybrid material UIO-66-NH2@UIO-66-(OH)2 has a particle size of 200-300 nm and a specific surface area of ​​1100-1200 m 2 / g.

3. A method for preparing the organic hybrid material UIO-66-NH2@UIO-66-(OH)2 according to claim 1 or 2, characterized in that: The preparation method comprises the following steps: Zirconium salt, 2-aminoterephthalic acid, UIO-66-(OH)2 and solvent are mixed, stirred and subjected to hydrothermal reaction. After the hydrothermal reaction, solid-liquid separation is performed. The solid obtained after solid-liquid separation is washed and dried to obtain the organic hybrid material UIO-66-NH2@UIO-66-(OH)2.

4. The preparation method according to claim 3, characterized in that: The zirconium salt is selected from one or more of zirconium chloride, zirconium nitrate and zirconium carbonate; The weight ratio of the zirconium salt, 2-aminoterephthalic acid and UIO-66-(OH)2 is 1:1-1.5:1-2; The solvent contains N,N-dimethylformamide and acetic acid, wherein the volume ratio of N,N-dimethylformamide to acetic acid is 2:1-2; The weight volume ratio of the zirconium salt to the solvent is 1 g:40-80 mL.

5. The preparation method according to claim 3 or 4, characterized in that: The stirring time is 10 to 30 minutes; The conditions of the hydrothermal reaction include: temperature of 80 to 120° C. and time of 4 to 12 hours; The specific operation of washing and drying the solid obtained after solid-liquid separation includes: mixing the solid obtained after solid-liquid separation with methanol, then stirring for 12 to 24 hours, then filtering to obtain a solid composite, and drying the solid composite at 60 to 120° C. for 12 to 24 hours.

6. The preparation method according to claim 3, characterized in that: The preparation method of UIO-66-(OH)2 includes: mixing zirconium salt, 2-hydroxyterephthalic acid and a mixed solvent, stirring for 10 to 30 minutes and then performing a heat preservation reaction, filtering after the heat preservation reaction to obtain a solid phase material, mixing the solid phase material with methanol, and then stirring for 12 to 24 hours, followed by filtering to obtain a solid product, and drying the solid product at 60 to 120°C for 12 to 24 hours to obtain UIO-66-(OH)2.

7. The preparation method according to claim 6, characterized in that: The weight ratio of the zirconium salt to 2-hydroxyterephthalic acid is 1:1-2; The mixed solvent contains N,N-dimethylformamide and acetic acid, wherein the volume ratio of N,N-dimethylformamide to acetic acid is 3:2-3; The weight volume ratio of the zirconium salt to the mixed solvent is 1 g: 40-60 mL; The conditions of the heat preservation reaction include: temperature of 110-140° C. and time of 4-12 hours.

8. Use of the organic hybrid material UIO-66-NH2@UIO-66-(OH)2 described in claim 1 or 2 in a gas sensor.

9. A gas sensor, characterized in that: The surface of the ceramic tube electrode of the gas sensor is coated with the organic hybrid material UIO-66-NH2@UIO-66-(OH)2 described in claim 1 or 2.

10. Use of the gas sensor according to claim 9 in H2 and CO detection.

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