Preparation method of ligand exchange-based im-mil-101-so3na material and humidity sensor

Abstract

The application discloses a preparation method of IM-MIL-101-SO3Na material based on ligand exchange and a humidity sensor, relates to the technical field of sensors, and aims to solve the technical problem that the existing humidity sensor cannot meet real-time monitoring requirements due to slow response and recovery speed. The humidity sensor comprises a substrate, interdigital electrodes and a sensing layer. One or more pairs of interdigital electrodes are arranged on any surface of the substrate, and the surface of the interdigital electrodes is provided with the sensing layer. The sensing layer is IM-MIL-101-SO3Na material based on ligand exchange. The application aims to provide a humidity sensor with the sensing layer material being the IM-MIL-101-SO3Na material, and provides a preparation method of the IM-MIL-101-SO3Na material.

Description

Technical Field

[0001] This invention relates to the field of sensor technology, and more specifically, to a method for preparing IM-MIL-101-SO3Na material based on ligand exchange and a humidity sensor. Background Technology

[0002] Humidity indicates the dryness or wetness of air, that is, the amount of water vapor contained in the air. Humidity monitoring plays an important role in agricultural production, industrial manufacturing, and health monitoring.

[0003] Existing humidity detection or monitoring technologies mainly include spectroscopic methods, chromatographic methods, and humidity sensor methods. Among these, spectroscopic and chromatographic methods are costly, complex to operate, and cannot provide real-time detection, thus limiting their application scenarios. Existing humidity sensors mainly come in different types, such as resistive, capacitive, impedance, mass, and optical. However, regardless of the type, the core of a humidity sensor is a humidity-sensitive material, and the physicochemical properties of this material greatly affect the humidity-sensitive characteristics of the sensor. Existing humidity-sensitive materials are mainly made of polymers, oxides, carbon materials, and MXene, etc. When these materials are applied to humidity sensors, the response and recovery speeds are relatively slow, failing to meet the requirements of real-time monitoring. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing IM-MIL-101-SO3Na material based on ligand exchange and a humidity sensor, to solve the technical problem that existing humidity sensors cannot meet the requirements of real-time monitoring due to slow response and recovery speeds. In view of this, this invention is achieved through the following solution.

[0005] In a first aspect, the present invention provides a humidity sensor, comprising a substrate, interdigitated electrodes, and a sensing layer; one or more pairs of interdigitated electrodes are disposed on any surface of the substrate, and the sensing layer is disposed on the surface of the interdigitated electrodes; the sensing layer is an IM-MIL-101-SO3Na material based on ligand exchange.

[0006] Compared with existing technologies, the humidity sensor of the present invention significantly improves the sensor's performance by setting one or more pairs of interdigitated electrodes on the surface of a substrate, and by depositing the interdigitated electrodes on the surface of the interdigitated electrodes with the aforementioned IM-MIL-101-SO3Na material based on ligand exchange. This improvement is achieved through the combined effect of the interdigitated electrode arrangement and the characteristics of the sensing layer material. The present invention solves the technical problem that existing humidity sensors, due to their slow response and recovery speeds, cannot meet the requirements for real-time monitoring.

[0007] Furthermore, in the humidity sensor of the present invention, the interdigitated electrode includes a graphite carbon interdigitated electrode, a gold interdigitated electrode, and a silver interdigitated electrode;

[0008] The substrate includes a ceramic substrate and a polyethylene terephthalate substrate.

[0009] Furthermore, in the humidity sensor of the present invention, 1 to 5 pairs of interdigital electrodes are disposed on the surface of the substrate.

[0010] Secondly, the present invention provides a method for preparing the sensing layer in the above-mentioned humidity sensor, namely the above-mentioned ligand exchange-based IM-MIL-101-SO3Na material, comprising:

[0011] A chromium source, sodium 2-sulfonate terephthalic acid, and tetramethylammonium hydroxide aqueous solution are added to water and mixed evenly to obtain a mixed solution; the molar ratio of sodium 2-sulfonate terephthalic acid to chromium source is 1:(0.5~5).

[0012] The temperature of the mixed solution is controlled at 100~200℃ and kept at that temperature for 12~36 hours, then dried to obtain MIL-101-SO3Na material;

[0013] The MIL-101-SO3Na material and the substitution ligand were added to the solvent and dispersed evenly.

[0014] The temperature of the solvent is controlled at 100~200℃, and the mixture is continuously stirred and kept at the temperature for 2~16 hours, then dried to obtain IM-MIL-101-SO3Na material.

[0015] Each 50-200 mg of MIL-101-SO3Na material requires 5-10 mmol of replacement ligands; the replacement ligands include fumaric acid, imidazole-4,5-dicarboxylic acid, 3,5-pyrazoledicarboxylic acid and 2,5-dimercaptoterephthalic acid.

[0016] Compared with the prior art, the beneficial effects of the preparation method of IM-MIL-101-SO3Na material based on ligand exchange of the present invention are the same as the beneficial effects of the humidity sensor described in the above technical solution, and will not be repeated here.

[0017] Furthermore, in the preparation method of the IM-MIL-101-SO3Na material based on ligand exchange of the present invention, the concentration of the tetramethylammonium hydroxide aqueous solution is 5~25wt%;

[0018] And / or, in the mixed solution, the volume ratio of the tetramethylammonium hydroxide aqueous solution to water is 1:(100~500).

[0019] Furthermore, in the preparation method of the IM-MIL-101-SO3Na material based on ligand exchange of the present invention, the solvent includes water, acetonitrile, and N'N Dimethylformamide;

[0020] And / or,

[0021] The chromium sources include chromium chloride, chromium nitrate, and chromium acetate.

[0022] Furthermore, in the preparation method of the IM-MIL-101-SO3Na material based on ligand exchange of the present invention, during the process of adding the MIL-101-SO3Na material and replacing the ligand in the solvent, the volume of solvent required for each 50-200 mg of MIL-101-SO3Na material is 10-100 mL.

[0023] Furthermore, in the preparation method of the IM-MIL-101-SO3Na material based on ligand exchange of the present invention, after controlling the temperature of the mixed solution to 100~200℃ and keeping it at that temperature for 12~36 hours, and before the drying, the method further includes:

[0024] The mixed solution is cooled to room temperature, and the mixed solution contains a first solid;

[0025] The mixed solution in the first solid is removed by a detergent, which includes water, ethanol and methanol.

[0026] Furthermore, in the preparation method of the IM-MIL-101-SO3Na material based on ligand exchange of the present invention, the step of controlling the temperature of the solvent to 100~200℃, continuously stirring and keeping it at that temperature for 2~16 hours, and before the drying, further includes:

[0027] The solvent is cooled to room temperature, and the solvent contains a second solid;

[0028] The solvent in the second solid is removed by a detergent, which includes water, ethanol, and methanol. Attached Figure Description

[0029] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:

[0030] Figure 1 This is a schematic diagram of the interdigitated electrodes on the substrate in Embodiment 1 of the present invention;

[0031] Figure 2 This is a schematic diagram of the sensor layer being disposed on the surface of the interdigitated electrode in Embodiment 1 of the present invention;

[0032] Figure 3 This is a schematic diagram of the interdigitated electrodes on the substrate in Embodiment 2 of the present invention;

[0033] Figure 4 This is a schematic diagram of the sensor layer being disposed on the surface of the interdigitated electrode in Embodiment 2 of the present invention;

[0034] Figure 5 The X-ray diffraction pattern of the IM-MIL-101-SO3Na material in Example 5 of this invention;

[0035] Figure 6 The infrared spectrum of the IM-MIL-101-SO3Na material in Example 5 of this invention;

[0036] Figure 7 The X-ray photoelectron spectrum of the IM-MIL-101-SO3Na material in Example 5 of this invention;

[0037] Figure 8 This is a schematic diagram of the humidity sensing characteristic curve of the humidity sensor in Embodiment 5 of the present invention.

[0038] Figure 9 The humidity hysteresis curve of the humidity sensor in Embodiment 5 of the present invention is shown.

[0039] Figure 10 This is a schematic diagram of the humidity sensor's response recovery curve to humidity in Embodiment 5 of the present invention;

[0040] Figure 11 This is a schematic diagram of the cyclic response curve of the humidity sensor to humidity in Embodiment 5 of the present invention;

[0041] Figure 12 This is a schematic diagram illustrating the long-term stability of the humidity sensor in Embodiment 5 of the present invention;

[0042] exist Figures 1 to 4 In the attached figures, the labels are:

[0043] 1. Substrate; 2. Interdigitated electrodes; 3. Sensing layer. Detailed Implementation

[0044] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0045] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to that other component.

[0046] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified. "Several" means one or more, unless otherwise explicitly specified.

[0047] Existing humidity detection or monitoring technologies mainly include spectroscopic methods, chromatographic methods, and humidity sensor methods. Among these, spectroscopic and chromatographic methods are costly, complex to operate, and cannot provide real-time detection, thus limiting their application scenarios. Existing humidity sensors mainly come in different types, such as resistive, capacitive, impedance, mass, and optical. However, regardless of the type, the core of a humidity sensor is a humidity-sensitive material, and the physicochemical properties of this material greatly affect the humidity-sensitive characteristics of the sensor. Existing humidity-sensitive materials are mainly made of polymers, oxides, carbon materials, and MXene, etc. When these materials are applied to humidity sensors, the response and recovery speeds are relatively slow, failing to meet the requirements of real-time monitoring.

[0048] To address the aforementioned technical problems, in a first aspect, the present invention provides a humidity sensor, comprising a substrate, interdigitated electrodes, and a sensing layer; one or more pairs of interdigitated electrodes are disposed on any surface of the substrate, and the sensing layer is disposed on the surface of the interdigitated electrodes; the sensing layer is a ligand exchange-based IM-MIL-101-SO3Na material.

[0049] By employing the above technical solution, the humidity sensor of the present invention significantly improves its performance through the combined effect of the interdigitated electrodes and the characteristics of the sensing layer material. This is achieved by setting one or more pairs of interdigitated electrodes on the surface of the substrate, and by depositing the interdigitated electrodes on the surface of the interdigitated electrodes with the aforementioned IM-MIL-101-SO3Na material based on ligand exchange. The above technical solution of the present invention solves the technical problem that existing humidity sensors, due to their slow response and recovery speeds, cannot meet the requirements for real-time monitoring.

[0050] Secondly, the present invention also provides a method for preparing the above-mentioned ligand exchange-based IM-MIL-101-SO3Na material, comprising:

[0051] A chromium source, sodium 2-sulfonate terephthalic acid, and tetramethylammonium hydroxide aqueous solution are added to water and mixed evenly to obtain a mixed solution; the molar ratio of sodium 2-sulfonate terephthalic acid to chromium source is 1:(0.5~5).

[0052] The temperature of the mixed solution is controlled at 100~200℃ and kept at that temperature for 12~36 hours, then dried to obtain MIL-101-SO3Na material;

[0053] The MIL-101-SO3Na material and the substitution ligand were added to the solvent and dispersed evenly.

[0054] The temperature of the solvent is controlled at 100~200℃, and the mixture is continuously stirred and kept at the temperature for 2~16 hours, then dried to obtain IM-MIL-101-SO3Na material.

[0055] Each 50-200 mg of MIL-101-SO3Na material requires 5-10 mmol of replacement ligands; the replacement ligands include fumaric acid, imidazole-4,5-dicarboxylic acid, 3,5-pyrazoledicarboxylic acid and 2,5-dimercaptoterephthalic acid.

[0056] In the preparation method of the IM-MIL-101-SO3Na material based on ligand exchange of the present invention, a chromium source, sodium 2-sulfonate terephthalic acid and tetramethylammonium hydroxide aqueous solution are added to water (which can be deionized water), and the mixed solution is kept at a temperature of 100~200℃ for 12~36 hours to obtain the MIL-101-SO3Na material through reaction. In this process, a chromium source provides metal ions, which undergo a coordination reaction with sodium 2-sulfonate terephthalic acid to generate MIL-101-SO3Na. The sodium sulfonate group (-SO3Na) imparts certain hydrophilic properties to the material. In the above process, the tetramethylammonium hydroxide aqueous solution provides an alkaline source for the reaction. On the one hand, it can increase the reaction rate; on the other hand, compared with the reaction temperature required without the addition of tetramethylammonium hydroxide aqueous solution, the required reaction temperature is significantly reduced after adding a certain volume of tetramethylammonium hydroxide aqueous solution (in one embodiment of the present invention, the required reaction temperature without the addition of tetramethylammonium hydroxide aqueous solution is 250°C, and the required reaction temperature after optimization with the addition of tetramethylammonium hydroxide aqueous solution can be reduced to 120°C). This achieves energy saving and improves operational safety. The above reaction process can be carried out in a hydrothermal reactor. Furthermore, the above process has yielded the MIL-101-SO3Na material. A solvent is selected, and the above MIL-101-SO3Na material and the substitution ligand are added to the solvent. The mixture is stirred continuously and kept at a temperature of 100~200℃ for 2~16 hours. During this process, the substitution ligand further undergoes an exchange reaction with some of the original ligands in MIL-101-SO3Na (sodium 2-sulfonate terephthalic acid), thereby generating IM-MIL-101-SO3Na. Furthermore, in the above technical solution, the substitution ligands include fumaric acid, imidazole-4,5-dicarboxylic acid, 3,5-pyrazoledicarboxylic acid, and 2,5-dimercaptoterephthalic acid. By limiting the type of substitution ligands and the substitution time, this invention can control the structural defects or degree of defects of the prepared IM-MIL-101-SO3Na material, as well as its surface properties (such as hydrophilicity and proton conductivity), so that the humidity sensor prepared using this IM-MIL-101-SO3Na material has the characteristics of fast response speed and fast recovery speed, and realizes the real-time monitoring function.For example, the stirring rate can be 300-1000 rpm; in another example, the stirring rate can be 300 rpm, 600 rpm, or 1000 rpm. For example, in the process of controlling the temperature of the mixed solution to 100-200°C and maintaining it at that temperature for 12-36 hours, the temperature can be 100°C, 120°C, 140°C, 160°C, 180°C, or 200°C; the holding time can be 12 hours, 20 hours, 24 hours, 28 hours, 32 hours, or 36 hours. For example, in the process of controlling the temperature of the solvent to 100-200°C and maintaining it at that temperature for 2-16 hours, the temperature can be 100°C, 120°C, 140°C, 160°C, 180°C, or 200°C; the holding time can be 2 hours, 6 hours, 8 hours, 10 hours, 12 hours, or 16 hours. Through the above technical solutions of the present invention, the technical problem that existing humidity sensors cannot meet the requirements of real-time monitoring due to slow response and recovery speeds is solved.

[0057] It should be understood that in the preparation method of the IM-MIL-101-SO3Na material based on ligand exchange of the present invention, in order to control the reaction rate of chromium source and sodium 2-sulfonate terephthalic acid within a reasonable range and effectively reduce the required reaction temperature, the concentration of the above-mentioned tetramethylammonium hydroxide aqueous solution and the mixing ratio of tetramethylammonium hydroxide aqueous solution to water should also be controlled within a reasonable range. For example, the concentration of the tetramethylammonium hydroxide aqueous solution can be 5~25wt%, and the volume ratio of the tetramethylammonium hydroxide aqueous solution to water in the mixed solution can be 1:(100~500). In another example, the concentration of the tetramethylammonium hydroxide aqueous solution can be 5wt%, 10wt%, 15wt%, or 25wt%, and the volume ratio of the tetramethylammonium hydroxide aqueous solution to water can be 1:100, 1:200, 1:300, or 1:500.

[0058] It should also be understood that in the preparation method of the ligand exchange-based IM-MIL-101-SO3Na material of the present invention, in order to control the degree of defect (the material needs to have a certain degree of defect) and particle size of the prepared IM-MIL-101-SO3Na material within a reasonable range, so that the humidity sensor prepared using the IM-MIL-101-SO3Na material has the characteristics of fast response speed and fast recovery speed, the type of solvent and the type of chromium source, as well as the mixing ratio of MIL-101-SO3Na material and solvent, should also be controlled within a reasonable range; for example, the solvent includes water (which can be deionized water), acetonitrile, and N'NDimethylformamide, wherein the chromium source includes chromium chloride, chromium nitrate, and chromium acetate, and during the process of adding the MIL-101-SO3Na material and the substitution ligand to the solvent, the required solvent volume is 10-100 mL for every 50-200 mg of MIL-101-SO3Na material; as another example, the solvent may be water, acetonitrile, or... N'N Dimethylformamide, wherein the chromium source is chromium chloride, chromium nitrate or chromium acetate (i.e. the chromium source is provided by chromium chloride, chromium nitrate or chromium acetate), and the volume of solvent required for each 50 mg, 100 mg or 200 mg of MIL-101-SO3Na material is 10 mL, 50 mL or 100 mL.

[0059] As one possible implementation, in the preparation method of the IM-MIL-101-SO3Na material based on ligand exchange of the present invention, after controlling the temperature of the mixed solution to 100~200℃ and holding it at that temperature for 12~36 hours, and before the drying, the method further includes:

[0060] The mixed solution is cooled to room temperature, and the mixed solution contains a first solid;

[0061] The mixed solution in the first solid is removed by a detergent, which includes water, ethanol and methanol.

[0062] In the preparation method of the IM-MIL-101-SO3Na material based on ligand exchange of the present invention, after the above-mentioned heat preservation for 12 to 36 hours, the above-mentioned first solid is obtained. However, the first solid exists simultaneously with the mixed solution. Cooling the mixed solution to room temperature and removing the mixed solution from the first solid with a detergent can effectively improve the purity of the first solid (the detergent removes residual solvent and reactants). For example, the detergent can be water, ethanol or methanol. When water, ethanol or methanol is used as the detergent, the detergent can be completely evaporated during the drying process, and the first solid after drying is in powder form.

[0063] As one possible implementation, in the preparation method of the IM-MIL-101-SO3Na material based on ligand exchange of the present invention, the process of controlling the temperature of the solvent to 100~200℃, continuously stirring and maintaining the temperature for 2~16 hours, and before the drying, further includes:

[0064] The solvent is cooled to room temperature, and the solvent contains a second solid;

[0065] The solvent in the second solid is removed by a detergent, which includes water, ethanol, and methanol.

[0066] In the preparation method of the IM-MIL-101-SO3Na material based on ligand exchange of the present invention, after continuous stirring and heating for 2 to 16 hours, the above-mentioned second solid is obtained. However, the second solid exists simultaneously with the reaction solvent. Cooling the solvent to room temperature and removing the mixed solution in the second solid with a detergent can effectively improve the purity of the second solid (the detergent removes residual solvent and reactants). For example, the detergent can be water, ethanol or methanol. When water, ethanol or methanol is used as the detergent, the detergent can be completely evaporated during the drying process, and the dried second solid is in powder form.

[0067] It should also be understood that during the drying process of the first solid (i.e., MIL-101-SO3Na material) and the second solid (i.e., IM-MIL-101-SO3Na material), in order to improve the drying efficiency (or reduce the drying time) and avoid excessively high temperatures from damaging the structure of the first solid (i.e., MIL-101-SO3Na material) or the second solid (i.e., IM-MIL-101-SO3Na material), the drying temperature should be controlled within a reasonable range. For example, the drying temperature can be 25~80°C; in another example, the drying temperature can be 25°C, 45°C, 65°C or 80°C.

[0068] To better understand the present invention, the following specific embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0069] Unless otherwise specified, all raw materials used in the following examples are commercially available.

[0070] Example 1

[0071] This embodiment provides a humidity sensor; please refer to [link / reference]. Figure 1 and Figure 2 The humidity sensor includes a substrate, interdigitated electrodes, and a sensing layer. Three pairs of interdigitated electrodes are disposed on any surface of the substrate, and the sensing layer is disposed on the surface of the interdigitated electrodes. The sensing layer is an IM-MIL-101-SO3Na material based on ligand exchange. Specifically, in this embodiment, the interdigitated electrodes are gold interdigitated electrodes, and the substrate is a ceramic substrate. Figure 1 This example exemplifies the substrate of the humidity sensor in this embodiment, and the interdigitated electrodes arranged in a ring on the substrate. Figure 2 This exemplifies the arrangement of the sensing layer on the surface of the interdigital electrode in this embodiment, specifically demonstrating the arrangement of the layered structure of the ligand exchange-based IM-MIL-101-SO3Na material on the surface of the interdigital electrode. Figure 2 It can be seen that three pairs of interdigital electrodes are disposed on the substrate. Figure 2 Each pair of adjacent interdigitated electrodes is considered a pair.

[0072] Example 2

[0073] Firstly, this embodiment provides a humidity sensor; please refer to [link to relevant documentation]. Figure 3 and Figure 4 The humidity sensor includes a substrate, interdigitated electrodes, and a sensing layer. A pair of interdigitated electrodes are disposed on any surface of the substrate, and the sensing layer is disposed on the surface of each interdigitated electrode. The sensing layer is a ligand exchange-based IM-MIL-101-SO3Na material. Specifically, in this embodiment, the interdigitated electrodes are silver interdigitated electrodes, and the substrate is a polyethylene terephthalate (PET) substrate. Figure 3 The substrate of the humidity sensor in this embodiment is exemplarily illustrated, as well as the arrangement of a pair (two) interdigitated electrodes disposed on the substrate. Figure 4 This exemplifies the way the sensing layer is disposed on the surface of the interdigital electrode in this embodiment, that is, it exemplifies the way the layered structure of the ligand exchange-based IM-MIL-101-SO3Na material is disposed on the surface of the interdigital electrode.

[0074] Secondly, this embodiment provides a method for preparing the above-mentioned ligand exchange-based IM-MIL-101-SO3Na material, including:

[0075] S100: Dissolve 0.5 mmol of chromium chloride and 1 mmol of sodium 2-sulfonate terephthalic acid in deionized water, and add tetramethylammonium hydroxide aqueous solution to the deionized water. Mix well to obtain a mixed solution.

[0076] The concentration of the tetramethylammonium hydroxide aqueous solution is 10 wt%, and the volume ratio of the tetramethylammonium hydroxide aqueous solution to deionized water is 1:100.

[0077] S200, the mixed solution from step S100 is transferred into a hydrothermal reactor and reacted continuously at a temperature of 100°C for 12 hours;

[0078] S300: After the reaction in step S200 is completed, the mixed solution is cooled to room temperature, filtered, and the filter cake is washed with deionized water until the residual mixed solution is removed. It is then dried at a temperature of 25°C to obtain the MIL-101-SO3Na material.

[0079] S400: Weigh 50 mg of MIL-101-SO3Na material from step S300 and disperse it in 10 mL of deionized water. Add 5 mmol of fumaric acid ligand to the deionized water and disperse it evenly.

[0080] S500: Transfer the deionized water from step S400 into the reactor and react continuously at 100°C for 2 hours.

[0081] S600: After the reaction in step S500 is completed, deionized water is cooled to room temperature, filtered, and the filter cake is washed with deionized water until the residual mixed solution is removed. The cake is then dried at 25°C to obtain IM-MIL-101-SO3Na material.

[0082] Example 3

[0083] In a first aspect, this embodiment provides a humidity sensor, which includes a substrate, interdigitated electrodes, and a sensing layer. Three pairs of interdigitated electrodes are disposed on any surface of the substrate, and the sensing layer is disposed on the surface of the interdigitated electrodes. The sensing layer is made of IM-MIL-101-SO3Na material based on ligand exchange, and the interdigitated electrodes in this embodiment are graphite carbon interdigitated electrodes. The structure of the humidity sensor in this embodiment and the material of the substrate are the same as those in Embodiment 1.

[0084] Secondly, this embodiment provides a method for preparing the above-mentioned ligand exchange-based IM-MIL-101-SO3Na material, including:

[0085] S100: Dissolve 5 mmol of chromium acetate and 1 mmol of sodium 2-sulfonate terephthalic acid in deionized water, and add tetramethylammonium hydroxide aqueous solution to the deionized water. Mix well to obtain a mixed solution.

[0086] The concentration of the tetramethylammonium hydroxide aqueous solution is 10 wt%, and the volume ratio of the tetramethylammonium hydroxide aqueous solution to deionized water is 1:500.

[0087] S200, the mixed solution from step S100 is transferred into a hydrothermal reactor and reacted continuously at a temperature of 200°C for 36 hours.

[0088] S300: After the reaction in step S200 is completed, the mixed solution is cooled to room temperature, filtered, and the filter cake is washed with deionized water until the residual mixed solution is removed. It is then dried at a temperature of 50°C to obtain the MIL-101-SO3Na material.

[0089] S400: Weigh 200 mg of MIL-101-SO3Na material from step S300 and disperse it in 100 mL of acetonitrile. Add 10 mmol of 3,5-pyrazole dicarboxylic acid ligand to the acetonitrile and disperse it evenly.

[0090] S500: The acetonitrile from step S400 is transferred into the reactor and reacted continuously at 200°C for 16 hours.

[0091] S600: After the reaction in step S500 is completed, the deionized water is cooled to room temperature, filtered, and the filter cake is washed with deionized water until the residual mixed solution is removed. The cake is then dried at 50°C to obtain the IM-MIL-101-SO3Na material.

[0092] Example 4

[0093] In a first aspect, this embodiment provides a humidity sensor, which includes a substrate, interdigitated electrodes, and a sensing layer. Three pairs of interdigitated electrodes are disposed on any surface of the substrate, and the sensing layer is disposed on the surface of the interdigitated electrodes. The sensing layer is a ligand exchange-based IM-MIL-101-SO3Na material, and the interdigitated electrodes in this embodiment are silver interdigitated electrodes. The structure of the humidity sensor in this embodiment is the same as that in Embodiment 1.

[0094] Secondly, this embodiment provides a method for preparing the above-mentioned ligand exchange-based IM-MIL-101-SO3Na material, including:

[0095] S100: Dissolve 2 mmol of chromium nitrate and 1 mmol of sodium 2-sulfonate terephthalic acid in deionized water, and add tetramethylammonium hydroxide aqueous solution to the deionized water. Mix well to obtain a mixed solution.

[0096] The concentration of the tetramethylammonium hydroxide aqueous solution is 10 wt%, and the volume ratio of the tetramethylammonium hydroxide aqueous solution to deionized water is 1:200.

[0097] S200, the mixed solution from step S100 is transferred into a hydrothermal reactor and reacted continuously at a temperature of 150°C for 20 hours.

[0098] S300: After the reaction in step S200 is completed, the mixed solution is cooled to room temperature, filtered, and the filter cake is washed with ethanol until the residual mixed solution is removed. It is then dried at a temperature of 60°C to obtain the MIL-101-SO3Na material.

[0099] S400, weigh 150 mg of the MIL-101-SO3Na material from step S300 and disperse it in 50 mL of water. N'N In dimethylformamide, N'N Add 7.5 mmol of 2,5-dimercaptoterephthalic acid ligand to dimethylformamide and disperse evenly;

[0100] S500, the step S400 N'N Dimethylformamide was transferred into the reactor and reacted continuously at 120°C for 4 hours.

[0101] After the reaction in step S500 is completed, the deionized water is cooled to room temperature, filtered, and the filter cake is washed with ethanol to remove the residual mixed solution. It is then dried at 60°C to obtain the IM-MIL-101-SO3Na material.

[0102] Example 5

[0103] In a first aspect, this embodiment provides a humidity sensor, which includes a substrate, interdigitated electrodes, and a sensing layer. Three pairs of interdigitated electrodes are disposed on any surface of the substrate, and the sensing layer is disposed on the surface of the interdigitated electrodes. The sensing layer is an IM-MIL-101-SO3Na material based on ligand exchange. The structure of the humidity sensor in this embodiment, as well as the types of the substrate and interdigitated electrodes, are the same as those in Embodiment 1.

[0104] Secondly, this embodiment provides a method for preparing the above-mentioned ligand exchange-based IM-MIL-101-SO3Na material, including:

[0105] S100: Dissolve 1 mmol of chromium nitrate and 1 mmol of sodium 2-sulfonate terephthalic acid in deionized water, and add tetramethylammonium hydroxide aqueous solution to the deionized water. Mix well to obtain a mixed solution.

[0106] The concentration of the tetramethylammonium hydroxide aqueous solution is 10 wt%, and the volume ratio of the tetramethylammonium hydroxide aqueous solution to deionized water is 1:300.

[0107] S200, the mixed solution from step S100 is transferred into a hydrothermal reactor and reacted continuously at a temperature of 120°C for 24 hours.

[0108] S300: After the reaction in step S200 is completed, the mixed solution is cooled to room temperature, filtered, and the filter cake is washed with methanol until the residual mixed solution is removed. It is then dried at a temperature of 80°C to obtain the MIL-101-SO3Na material.

[0109] S400, weigh 100 mg of MIL-101-SO3Na material from step S300 and disperse it in 20 mL of... N'N In dimethylformamide, N'N Add 6 mmol of imidazole-4,5-dicarboxylic acid ligand to dimethylformamide and disperse evenly;

[0110] S500, the step S400 N'N Dimethylformamide was transferred into a reaction vessel and reacted continuously at 160°C for 12 hours.

[0111] S600: After the reaction in step S500 is completed, deionized water is cooled to room temperature, filtered, and the filter cake is washed with methanol to remove residual mixed solution. It is then dried at 80°C to obtain IM-MIL-101-SO3Na material.

[0112] According to Examples 1 to 5 above, various humidity sensors were obtained, and different sensing layers were set for each humidity sensor. These different sensing layers were achieved using various preparation conditions of IM-MIL-101-SO3Na materials. As mentioned earlier, the performance of the humidity sensor of the present invention can be significantly improved by the combined effect of the interdigitated electrode arrangement and the characteristics of the sensing layer material. It should be noted that the characteristics of the sensing layer material are mainly determined by its raw material composition and the specific structure of the IM-MIL-101-SO3Na material. Furthermore, after obtaining the IM-MIL-101-SO3Na material in the above examples, its structure was characterized. Since the structures of the IM-MIL-101-SO3Na materials in Examples 2 to 5 are roughly the same, the following description will use the IM-MIL-101-SO3Na material of Example 5 as an example. Please refer to [link / reference]. Figure 5 X-ray diffraction experiments were conducted on the MIL-101-SO3Na and IM-MIL-101-SO3Na materials of Example 5. The characterization results show that after ligand replacement of the MIL-101-SO3Na material, the X-ray diffraction pattern of the resulting IM-MIL-101-SO3Na material changed, with a wider half-width at half-maximum. This indicates that the structure of the IM-MIL-101-SO3Na material has changed compared to the MIL-101-SO3Na material, and that it has more structural defects (which are reflected in the different peak positions and peak angles in the figure).

[0113] Further, please refer to Figure 6 Similarly, taking Example 5 as an example, infrared spectroscopy experiments were conducted on the MIL-101-SO3Na material and the IM-MIL-101-SO3Na material of Example 5, and the results are as follows. Figure 6 As shown, according to Figure 6 It can be seen that the infrared spectrum of the IM-MIL-101-SO3Na material obtained after ligand substitution of MIL-101-SO3Na material contains absorption peaks of imidazole ring and sulfonate, indicating that the substitution ligand (imidazole-4,5-dicarboxylic acid) successfully replaced part of the ligand (sodium terephthalic acid 2-sulfonate) in MIL-101-SO3Na material.

[0114] Furthermore, taking Example 5 above as an example, X-ray photoelectron spectroscopy experiments were performed on the MIL-101-SO3Na material and the IM-MIL-101-SO3Na material of Example 5. Please refer to [link to relevant documentation]. Figure 7 ,according to Figure 7 It can be seen that after ligand substitution, the spectrum of the resulting IM-MIL-101-SO3Na material shows a distinct N1s peak, while the S2p peak almost disappears, indicating that most of the sulfonic acid ligands in the MIL-101-SO3Na material are replaced. In summary... Figures 5 to 7 As can be seen from the description, the preparation method of IM-MIL-101-SO3Na material based on ligand exchange of the present invention successfully prepared IM-MIL-101-SO3Na material.

[0115] Furthermore, Embodiments 1 to 5 above each provide a humidity sensor, which includes a substrate, interdigitated electrodes, and a sensing layer; one or more pairs of interdigitated electrodes are disposed on any surface of the substrate, and the sensing layer is disposed on the surface of the interdigitated electrodes; the sensing layer is an IM-MIL-101-SO3Na material based on ligand exchange. After obtaining the humidity sensors of Embodiments 1 to 5 above, their performance was tested respectively. Since the performance of the humidity sensors obtained in Embodiments 1 to 5 is roughly the same, the following description will take the humidity sensor of Embodiment 5 as an example; in summary, the response value of the humidity sensor obtained in Embodiment 5 is R=Z0 / Z 95 Where Z0 is the impedance value of the sensor at 0%RH (%RH represents relative humidity), the test voltage is 1 volt AC, and the frequency is 1000 Hz. 95 The impedance value of the sensor at 95% RH; the response / recovery time is the time it takes for the sensor's impedance signal to reach 90% of its change; the hysteresis is the maximum difference on the horizontal axis between the sensor's adsorption and desorption curves. For details, please refer to [link to relevant documentation]. Figure 8 , Figure 8 The humidity sensor's humidity-sensitive characteristic curve is shown. It can be seen that the sensor's impedance value varies under different humidity conditions; the higher the relative humidity, the lower the impedance value. Within a humidity range of 0–95%RH, the sensor's response value is 220,000, indicating its applicability as a wide-range, high-response humidity sensor. Please refer to [link to relevant documentation]. Figure 9 , Figure 9 The hysteresis curve of this humidity sensor is shown. The humidity environment of the sensor was continuously switched within the range of 0%RH–95%RH–0%RH. The impedance values ​​of the humidity sensor between the adsorption and desorption curves were compared. The hysteresis was 1.0%RH, indicating good durability. Please refer to [link to relevant documentation]. Figure 10 , Figure 10The response and recovery curves of this humidity sensor are shown. When the humidity environment changes from 0%RH to 95%RH, the impedance value of the humidity sensor reaches 90% of the impedance signal change after 1.7 seconds. When the humidity environment changes from 95%RH to 0%RH, the impedance value of the humidity sensor reaches 90% of the impedance signal change after 1.3 seconds. The response / recovery time of this humidity sensor is 1.7 / 1.3 seconds, indicating that it can be applied to humidity sensors with fast response / recovery. Please refer to the respective parameters. Figure 11 and Figure 12 , Figure 11 The cyclic response curve of the humidity sensor between 0%RH and 95%RH is shown. It can be seen that within 360s, the humidity sensor switches between 0%RH and 95%RH multiple times, and the impedance value of the humidity sensor changes accordingly, indicating that it has excellent cyclic stability. Figure 12 The impedance values ​​of the sensor were displayed over 150 days under different humidity conditions. The impedance values ​​of the humidity sensor did not change significantly over these 150 days, indicating excellent long-term stability. In summary... Figures 8 to 12 As can be seen from the description, the humidity sensor of the present invention has the characteristics of fast response, fast recovery, high response, low hysteresis, and high stability.

[0116] In the above technical solutions of the present invention, for the MIL-101-SO3Na material, MIL is an abbreviation for Materials of Institute Lavoisier, belonging to a series of metal-organic framework materials, and MIL-101 represents the 101st member in this series; for the IM-MIL-101-SO3Na material, similarly, MIL is an abbreviation for Materials of Institute Lavoisier, belonging to a series of metal-organic framework materials, MIL-101 represents the 101st member in this series, and IM represents the imidazole group contained in the material.

[0117] In the description of the above embodiments, specific features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.

[0118] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A humidity sensor, characterized in that, It includes a substrate, interdigitated electrodes, and a sensing layer; one or more pairs of interdigitated electrodes are disposed on any surface of the substrate, and the sensing layer is disposed on the surface of the interdigitated electrodes; the sensing layer is an IM-MIL-101-SO3Na material based on ligand exchange; IM represents the imidazole group contained in the material.

2. The humidity sensor according to claim 1, characterized in that, The interdigitated electrodes include graphite carbon interdigitated electrodes, gold interdigitated electrodes, and silver interdigitated electrodes. The substrate includes a ceramic substrate and a polyethylene terephthalate substrate.

3. The humidity sensor according to claim 2, characterized in that, The substrate surface is provided with 1 to 5 pairs of interdigital electrodes.

4. A method for preparing the IM-MIL-101-SO3Na material based on ligand exchange for the humidity sensor according to claim 1, characterized in that, include: Add a chromium source, sodium 2-sulfonate terephthalic acid, and an aqueous solution of tetramethylammonium hydroxide to water, mix well, and obtain a mixed solution; The molar ratio of sodium 2-sulfonate terephthalic acid to chromium source is 1:(0.5~5). The temperature of the mixed solution is controlled at 100~200℃ and kept at that temperature for 12~36 hours, then dried to obtain MIL-101-SO3Na material; The MIL-101-SO3Na material and the substitution ligand were added to the solvent and dispersed evenly. The temperature of the solvent is controlled at 100~200℃, and the mixture is continuously stirred and kept at the temperature for 2~16 hours, then dried to obtain IM-MIL-101-SO3Na material. Each 50-200 mg of MIL-101-SO3Na material requires 5-10 mmol of replacement ligands; the replacement ligands include fumaric acid, imidazole-4,5-dicarboxylic acid, 3,5-pyrazoledicarboxylic acid and 2,5-dimercaptoterephthalic acid.

5. The method for preparing IM-MIL-101-SO3Na material based on ligand exchange according to claim 4, characterized in that, The concentration of the tetramethylammonium hydroxide aqueous solution is 5-25 wt%; And / or, in the mixed solution, the volume ratio of the tetramethylammonium hydroxide aqueous solution to water is 1:(100~500).

6. The method for preparing IM-MIL-101-SO3Na material based on ligand exchange according to claim 5, characterized in that, The solvent includes water, acetonitrile, and N,N-dimethylformamide; And / or, The chromium sources include chromium chloride, chromium nitrate, and chromium acetate.

7. The method for preparing IM-MIL-101-SO3Na material based on ligand exchange according to claim 6, characterized in that, During the process of adding the MIL-101-SO3Na material and the replacement ligand to the solvent, the volume of solvent required is 10-100 mL for every 50-200 mg of MIL-101-SO3Na material.

8. The method for preparing IM-MIL-101-SO3Na material based on ligand exchange according to claim 7, characterized in that, The process of controlling the temperature of the mixed solution to 100~200℃ and maintaining it at that temperature for 12~36 hours, and before the drying process, further includes: The mixed solution is cooled to room temperature, and the mixed solution contains a first solid; The mixed solution in the first solid is removed by a detergent, which includes water, ethanol and methanol.

9. The method for preparing IM-MIL-101-SO3Na material based on ligand exchange according to claim 7, characterized in that, The process of controlling the temperature of the solvent to 100~200℃, continuously stirring and maintaining the temperature for 2~16 hours, and prior to the drying process, further includes: The solvent is cooled to room temperature, and the solvent contains a second solid; The solvent in the second solid is removed by a detergent, which includes water, ethanol, and methanol.

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