Sensitive material, gas sensitive element, preparation method, sensor and detection method

Abstract

The invention discloses a gas sensor sensitive material and a preparation method thereof, a quartz crystal microbalance gas sensor and a preparation method thereof, a carbon dioxide sensor and a carbon dioxide detection method. The quartz crystal microbalance gas sensor prepared by the invention has good moisture resistance, simple manufacturing process, simple structure, small size, and can be integrated, and can realize real-time monitoring of carbon dioxide, with high monitoring sensitivity and good reproducibility.

Description

Technical Field

[0001] The present application relates to the technical field of gas sensors and their preparation, and in particular to a gas sensor sensitive material and a preparation method thereof, a quartz crystal microbalance gas sensor and a preparation method thereof, a carbon dioxide sensor and a carbon dioxide detection method. Background Art

[0002] Carbon dioxide (CO2) is the main component of the air, and its content in the atmosphere is relatively stable. Excessive emissions of carbon dioxide will aggravate global warming and trigger a series of serious environmental problems, such as rising sea levels and frequent extreme weather, which will have a huge impact on the earth's ecosystem. When the concentration of carbon dioxide in the atmosphere is too high, it will also cause many harms to the human body, such as symptoms such as difficulty breathing, dizziness, fatigue, etc., and in extreme cases it may even endanger life. For plants, excessively high concentrations of carbon dioxide will inhibit the normal growth and development of plants and affect the ecological balance.

[0003] By detecting carbon dioxide, we can timely understand the carbon dioxide concentration level in a specific environment. In the atmospheric environment, the carbon dioxide concentration level detected can help scientists to deeply study the trends and laws of climate change and provide a scientific basis for the formulation of response strategies; in indoor environments, carbon dioxide detection can ensure the air quality of people's living and working places and protect people's health; in some closed spaces such as basements and mines, real-time detection of carbon dioxide can prevent people from being harmed by excessive carbon dioxide concentration; in large-scale operations requiring anesthesia, real-time monitoring of carbon dioxide exhaled by the human body can reflect the operation of the human respiratory system; in the agricultural field, carbon dioxide detection helps to reasonably regulate the gas environment in the greenhouse and optimize plant growth conditions; for industrial production processes, detecting carbon dioxide concentration can help companies better control emissions, achieve the goal of energy conservation and emission reduction, and contribute to environmental protection. It can be seen that carbon dioxide detection is of great significance for protecting human health, maintaining ecological balance, and responding to climate change.

[0004] Currently, the methods for detecting carbon dioxide gas include spectroscopy, chromatography, electrochemistry, and quartz crystal microbalance gas sensors (QCM). Spectroscopy, chromatography, and electrochemistry have the problems of high cost, susceptibility to temperature and humidity, and poor selectivity. Quartz crystal microbalance sensors are easily disturbed by humidity. Summary of the invention

[0005] Based on this, it is necessary to provide a quartz crystal microbalance gas sensor and a preparation method thereof. The quartz crystal microbalance gas sensor of the present invention has good moisture resistance, simple manufacturing process, simple structure, small size, and can be integrated. It can realize real-time monitoring of carbon dioxide, is basically not affected by humidity, has high monitoring sensitivity, and good reproducibility.

[0006] An embodiment of the present application provides a method for preparing a sensitive material of a gas sensor.

[0007] A method for preparing a gas sensor sensitive material comprises the following steps:

[0008] Adding zirconium oxychloride octahydrate or zirconium tetrachloride and 2,5-dihydroxyterephthalic acid to a first solvent, mixing to obtain a first precursor solution, and reacting the first precursor solution under predetermined conditions to obtain a metal organic framework material MOF-804 dispersion;

[0009] Centrifuging the metal organic framework material MOF-804 dispersion, removing the supernatant, and collecting the first precipitate at the bottom;

[0010] Furthermore, the first precipitate is washed and then vacuum dried to obtain a yellow solid powdery metal organic framework material MOF-804.

[0011] In some embodiments, the mass volume ratio of the zirconium oxychloride octahydrate or zirconium tetrachloride, the 2,5-dihydroxyterephthalic acid, and the first solvent is: (0.01 g~1 g): (0.04 g~2 g): (200 mL~2000 mL).

[0012] In some embodiments, the first solvent includes N,N-dimethylformamide.

[0013] In some of the embodiments, when the first precursor solution is reacted under predetermined conditions to obtain a metal organic framework material MOF-804 dispersion, the predetermined conditions are: setting the reaction temperature to 120° C. to 150° C. and the reaction time to 24 h to 48 h.

[0014] In some of the embodiments, when the metal organic framework material MOF-804 dispersion is centrifuged, the obtained metal organic framework material MOF-804 dispersion is placed in a centrifuge, the centrifugal speed is set to 8000 rpm~10000 rpm, and the centrifugal time is 5 min~15 min.

[0015] In some embodiments, when the first precipitate is washed and then vacuum dried, the obtained first precipitate is washed with methanol and placed in a vacuum drying oven, the vacuum drying temperature is set at 60°C~80°C, and the vacuum drying time is not less than 12 h.

[0016] An embodiment of the present application provides a method for preparing a sensitive material of a gas sensor.

[0017] A method for preparing a gas sensor sensitive material comprises the following steps:

[0018] adding ionic liquid 1-butyl-3-methylimidazole bis(trifluoromethylsulfonyl)imide to the second solvent and mixing to obtain a second precursor solution;

[0019] Adding the metal organic framework material MOF-804 to the second precursor solution, stirring to obtain a metal organic framework material-ionic liquid MOF@[BMIM][TFSI] dispersion;

[0020] Centrifuging the metal organic framework material-ionic liquid MOF@[BMIM][TFSI] dispersion, removing the supernatant, and collecting the second precipitate at the bottom;

[0021] And, the second precipitate is vacuum dried to obtain a yellow solid metal organic framework-ionic liquid composite material MOF@[BMIM][TFSI].

[0022] In some of the embodiments, the mass volume ratio of the ionic liquid 1-butyl-3-methylimidazole bis(trifluoromethylsulfonyl)imide to the second solvent is: (0.05 g~1 g): (10 mL~20 mL).

[0023] In some embodiments, the second solvent includes methanol.

[0024] In some of the embodiments, the metal organic framework material MOF-804 is added to the second precursor solution at a loading amount of 0.1 wt% to 5 wt%.

[0025] In some of the embodiments, when the metal organic framework material MOF-804 is added to the second precursor solution, it is placed at 20° C. to 30° C. and stirred for 12 h to 24 h.

[0026] In some of the embodiments, when the metal organic framework material-ionic liquid MOF@[BMIM][TFSI] dispersion is centrifuged, the metal organic framework material-ionic liquid MOF@[BMIM][TFSI] dispersion is placed in a centrifuge, the centrifugal speed is set to 8000 rpm~10000 rpm, and the centrifugation time is 5 min~15 min.

[0027] In some of the embodiments, when the second precipitate is vacuum dried, the second precipitate is placed in a vacuum drying oven, the vacuum drying temperature is set at 60° C. to 80° C., and the vacuum drying time is not less than 12 h.

[0028] An embodiment of the present application provides a sensitive material for a gas sensor.

[0029] A gas sensor sensitive material is prepared by using the above-mentioned method for preparing the gas sensor sensitive material.

[0030] An embodiment of the present application provides a method for preparing a quartz crystal microbalance gas sensor.

[0031] A method for preparing a quartz crystal microbalance gas sensor comprises the following steps:

[0032] Adding zirconium oxychloride octahydrate and 2,5-dihydroxyterephthalic acid to a first solvent, mixing to obtain a first precursor solution; drying the first precursor solution to obtain a metal organic framework material MOF-804 dispersion; centrifuging the metal organic framework material MOF-804 dispersion, removing the supernatant, and collecting a first precipitate at the bottom; washing the first precipitate and performing vacuum drying to obtain a yellow solid powder of the metal organic framework material MOF-804;

[0033] And, adding the ionic liquid 1-butyl-3-methylimidazole bis(trifluoromethylsulfonyl)imide to the second solvent, mixing to obtain a second precursor solution; adding the metal organic framework material MOF-804 to the second precursor solution, stirring to obtain a metal organic framework material-ionic liquid MOF@[BMIM][TFSI] dispersion; centrifuging the metal organic framework material-ionic liquid MOF@[BMIM][TFSI] dispersion, removing the supernatant, and collecting a second precipitate at the bottom; vacuum drying the second precipitate to obtain a yellow solid metal organic framework-ionic liquid composite material MOF@[BMIM][TFSI];

[0034] Adding the metal organic framework material MOF-804 and / or the metal organic framework-ionic liquid composite material MOF@[BMIM][TFSI] into a third solvent, and performing ultrasonic dispersion to prepare a sensitive layer material dispersion;

[0035] The sensitive layer material dispersion is coated on the surface of a quartz crystal substrate connected to a metal electrode and covers the metal electrode, and is vacuum dried to form a carbon dioxide sensitive layer.

[0036] In some of the embodiments, before coating the sensitive layer material dispersion on the surface of a quartz crystal substrate having a metal electrode connected to the surface, the following steps are also included: ultrasonically cleaning the quartz crystal substrate having a metal electrode connected to the surface with acetone, ethanol and water in turn, with the ultrasonic cleaning time being 20 min to 30 min, and introducing dry nitrogen for drying.

[0037] In some embodiments, the third solvent includes anhydrous ethanol or water.

[0038] In some embodiments, the ultrasonic dispersion time is 10 min to 20 min.

[0039] In some of the embodiments, the concentration of the dispersion of the sensitive layer material is 0.5 mg / mL to 2 mg / mL.

[0040] In some of the embodiments, the volume of the sensitive layer material dispersion coating is 0.5 μL~3 μL.

[0041] In some of the embodiments, after the sensitive layer material dispersion is coated on the surface of a quartz crystal substrate connected to a metal electrode and covers the metal electrode, during vacuum drying, the vacuum drying temperature is set to 60° C.~80° C. and the vacuum drying time is set to 1 h~2 h.

[0042] An embodiment of the present application also provides a quartz crystal microbalance gas sensor.

[0043] A quartz crystal microbalance gas sensor is prepared by adopting the above preparation method.

[0044] An embodiment of the present application also provides a quartz crystal microbalance gas sensor.

[0045] A quartz crystal microbalance gas sensor comprises a quartz crystal substrate, a metal electrode and a carbon dioxide sensitive layer, wherein the metal electrode is connected to the quartz crystal substrate, and the carbon dioxide sensitive layer is arranged on the quartz crystal substrate and covers the metal electrode, wherein the carbon dioxide sensitive layer is prepared by using a gas sensor sensitive material containing at least a metal organic framework material MOF-804 and / or a metal organic framework-ionic liquid composite material MOF@[BMIM][TFSI], and the carbon dioxide sensitive layer can absorb carbon dioxide gas.

[0046] In some of the embodiments, the preparation material of the quartz crystal substrate is an AT-cut quartz wafer, and the fundamental frequency of the AT-cut quartz wafer is 6 MHz, 8 MHz or 10 MHz.

[0047] In some embodiments, the metal electrode is made of gold or silver.

[0048] In some embodiments, the metal electrode is in the shape of a circular structure or a ring structure.

[0049] In some of the embodiments, the cross-sectional diameter of the metal electrode is 0.5 cm to 1.0 cm.

[0050] An embodiment of the present application also provides a carbon dioxide sensor.

[0051] A carbon dioxide sensor comprises a quartz crystal microbalance gas sensing element prepared by the above-mentioned preparation method, or comprises the above-mentioned quartz crystal microbalance gas sensing element.

[0052] An embodiment of the present application also provides a carbon dioxide detection method.

[0053] A method for detecting carbon dioxide, using the above-mentioned carbon dioxide sensor, comprises the following steps:

[0054] The carbon dioxide sensor is connected to a test instrument and placed in an experimental space, so that the carbon dioxide sensitive layer on the carbon dioxide sensor absorbs carbon dioxide gas in the experimental space and changes the vibration frequency of the quartz crystal substrate of the carbon dioxide sensor;

[0055] The concentration of carbon dioxide gas in the experimental space is controlled by nitrogen gas to change from 100% to 0 in sequence;

[0056] Control the vibration frequency value of the quartz crystal substrate when the test instrument measures several different carbon dioxide gas concentration values, and calculate the response value of the quartz crystal microbalance gas sensor according to the vibration frequency value; wherein the response value S of the quartz crystal microbalance gas sensor is equal to f g -f0, where f g is the vibration frequency value of the quartz crystal microbalance gas sensor under carbon dioxide gas, f0 is the vibration frequency value of the quartz crystal microbalance gas sensor under nitrogen atmosphere; obtain the corresponding relationship between the response value and the carbon dioxide gas concentration: set the carbon dioxide gas concentration of 100%, 60%, 40%, 20% and 0 as sampling points, test at least 3 groups of corresponding response values ​​at each sampling point and obtain the average response value, take the carbon dioxide gas concentration as the abscissa and the corresponding average response value as the ordinate, and use the linear curve obtained by linear fitting as the working curve of the test instrument;

[0057] Furthermore, the carbon dioxide sensor is connected to a test instrument and placed in a test space, the test instrument is controlled to measure the vibration frequency value of the quartz crystal substrate, the response value of the quartz crystal microbalance gas sensor is calculated according to the vibration frequency value, and the carbon dioxide concentration in the test space is obtained according to the response value and the working curve.

[0058] The quartz crystal microbalance gas sensor prepared by the preparation method of the quartz crystal microbalance gas sensor comprises a quartz crystal substrate, a metal electrode and a carbon dioxide sensitive layer. The carbon dioxide sensitive layer is prepared by using a gas sensor sensitive material containing at least a metal organic framework material MOF-804 and / or a metal organic framework-ionic liquid composite material MOF@[BMIM][TFSI]. The carbon dioxide sensitive layer can absorb carbon dioxide gas. The basic frequency of the quartz crystal substrate is 6 MHz, 8 MHz or 10 MHz. When the carbon dioxide concentration changes, the molecular weight of carbon dioxide gas adsorbed by the metal organic framework material and / or the metal organic framework-ionic liquid composite material in the carbon dioxide sensitive layer will increase, and the vibration frequency of the quartz crystal substrate will change. By measuring the vibration frequency value of the quartz crystal microbalance gas sensor in real time, the response value of the quartz crystal microbalance gas sensor can be obtained by calculation, thereby obtaining the corresponding relationship between the response value and the concentration of the gas to be measured and establishing a detection model. In practical applications, as long as the response value of the quartz crystal microbalance gas sensor in the measured space is measured, the carbon dioxide gas concentration in the current measured gas can be obtained through the above detection model to achieve the detection of carbon dioxide gas. After experimental verification, the quartz crystal microbalance gas sensor of the present application has good moisture resistance, simple manufacturing process, small size and can be integrated, and has practical application significance. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application, and those skilled in the art can obtain other drawings based on these drawings without creative work.

[0060] In order to more completely understand the present application and its beneficial effects, the following description will be given in conjunction with the accompanying drawings. In the following description, the same reference numerals represent the same parts.

[0061] Figure 1 This is a scanning electron microscope image of the gas sensor material MOF-804 prepared in Example 1 of the present invention;

[0062] Figure 2 The X-ray diffraction pattern of the gas sensor material MOF-804 prepared in Example 1 of the present invention;

[0063] Figure 3 This is a scanning electron microscope image of the gas sensor material MOF@[BMIM][TFSI] prepared in Example 3 of the present invention;

[0064] Figure 4X-ray diffraction pattern of MOF@[BMIM][TFSI], a sensitive material of a gas sensor prepared in Example 3 of the present invention;

[0065] Figure 5 X-ray diffraction pattern of MOF@[BMIM][TFSI], a sensitive material of a gas sensor prepared in Example 4 of the present invention;

[0066] Figure 6 The quartz crystal microbalance gas sensor based on the gas sensor sensitive material MOF-804 prepared in Example 5 of the present invention is placed at 0, 20%, 40%, 60%, 80%, 85%, 90% and 95% relative humidity (RH) and the continuous response curve of carbon dioxide gas with a concentration of 50000 ppm is introduced;

[0067] Figure 7 This is an optical photograph of the quartz crystal substrate of the quartz crystal microbalance gas sensor described in Example 5 of the present invention;

[0068] Figure 8 The quartz crystal microbalance gas sensor prepared in Example 6 of the present invention based on the gas sensor sensitive material MOF-804@[BMIM][TFSI] is placed at 0, 20%, 40%, 60%, 80%, 85%, 90% and 95% RH, and the continuous response curve of the carbon dioxide gas with a concentration of 50000ppm is introduced;

[0069] Fig. 9 The quartz crystal microbalance gas sensor based on the gas sensor sensitive material MOF-804 prepared in Example 6 of the present invention and the quartz crystal microbalance gas sensor based on the gas sensor sensitive material MOF-804@[BMIM][TFSI] prepared in Example 7 are placed at 0, 20%, 40, 60%, 80%, 85%, 90% and 95% RH and the sensitivity is compared when 50000 ppm carbon dioxide gas is introduced. DETAILED DESCRIPTION

[0070] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific embodiments disclosed below.

[0071] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0072] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0073] In the description of the present invention, "several" means more than one, "many" means more than two, "greater than", "less than", "exceed", etc. are understood to exclude the number itself, and "above", "below", "within", etc. are understood to include the number itself. If there is a description of "first" or "second", it is only used for the purpose of distinguishing the technical features, and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0074] In this article, "optionally", "optional", "optional" means optional, that is, it means to be selected from any of the two parallel solutions of "yes" or "no". If there are multiple "optional" in a technical solution, unless otherwise specified and there is no contradiction or mutual restriction, each "optional" is independent. In this application, the descriptions such as "optionally contain" and "optionally include" mean "contain or not contain".

[0075] In the present invention, unless otherwise stated, the sum of the parts of each component in the composition can be 100 parts by weight. Unless otherwise specified, the basis of the percentages (including weight percentages) of the present invention is the total weight of the composition. In addition, "wt%" herein means mass percentage, and "at%" means atomic percentage.

[0076] In this article, unless otherwise stated, each reaction step may be carried out in the order described herein or may not be carried out in the order described herein. For example, other steps may be included between each reaction step, and the order of the reaction steps may also be appropriately swapped. This can be determined by the technician based on common knowledge and experience. Preferably, the reaction method herein is carried out sequentially.

[0077] In the present application, when it comes to a numerical interval (i.e., a numerical range), unless otherwise specified, the distribution of the optional numerical values ​​in the numerical interval is considered to be continuous, and includes the two numerical endpoints (i.e., the minimum and maximum values) of the numerical interval, and each numerical value between the two numerical endpoints. Unless otherwise specified, when the numerical interval only refers to an integer in the numerical interval, it includes the two endpoint integers of the numerical range, and each integer between the two endpoints, which is equivalent to directly listing each integer. When multiple numerical ranges are provided to describe features or characteristics, these numerical ranges can be combined. In other words, unless otherwise specified, the numerical range disclosed in the present application should be understood to include any and all sub-ranges included therein. The "numerical value" in the numerical interval can be any quantitative value, such as a number, a percentage, a ratio, etc. "Numerical interval" allows for a broad range of quantitative intervals such as percentage intervals, ratio intervals, and ratio intervals.

[0078] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0079] The embodiment of the present application provides a quartz crystal microbalance gas sensor to solve at least one of the following technical problems existing in the prior art: (1) spectroscopy, chromatography, and electrochemical methods have the problems of high cost, susceptibility to temperature and humidity, and poor selectivity; (2) the detection results of the quartz crystal microbalance sensor are easily disturbed by humidity.

[0080] The quartz crystal microbalance gas sensor will be described below in conjunction with the accompanying drawings. The quartz crystal microbalance gas sensor of the present application can be used for real-time monitoring of carbon dioxide, has high monitoring sensitivity, good moisture resistance, and has application value. In the present invention, the quartz crystal microbalance gas sensor realizes real-time monitoring of carbon dioxide by detecting the change in the frequency signal output by the quartz crystal microbalance. In order to more clearly illustrate the structure of the quartz crystal microbalance gas sensor, the quartz crystal microbalance gas sensor will be introduced below in conjunction with the accompanying drawings.

[0081] An embodiment of the present application provides a method for preparing a sensitive material of a gas sensor.

[0082] A method for preparing a gas sensor sensitive material comprises the following steps:

[0083] Zirconium oxychloride octahydrate or zirconium tetrachloride and 2,5-dihydroxyterephthalic acid are added to a first solvent, mixed to obtain a first precursor solution, and the first precursor solution is reacted under predetermined conditions to obtain a metal organic framework material MOF-804 dispersion.

[0084] The metal organic framework material MOF-804 dispersion is centrifuged, the supernatant is removed, and the first precipitate at the bottom is collected.

[0085] The first precipitate is washed and then vacuum dried to obtain a yellow solid powdery metal organic framework material MOF-804, namely, a sensitive material for a gas sensor.

[0086] In some of the embodiments, the mass volume ratio of zirconium oxychloride octahydrate or zirconium tetrachloride, 2,5-dihydroxyterephthalic acid, and the first solvent is: (0.01 g ~ 1 g): (0.04 g ~ 2 g): (200 mL ~ 2000 mL). For example, in one specific example, the mass volume ratio of zirconium oxychloride octahydrate or zirconium tetrachloride, 2,5-dihydroxyterephthalic acid, and the first solvent is: 0.01 g: 0.04 g: 200 mL; for example, in another specific example, the mass volume ratio of zirconium oxychloride octahydrate or zirconium tetrachloride, 2,5-dihydroxyterephthalic acid, and the first solvent is: 1 g: 2 g: 2000 mL.

[0087] In some embodiments, the first solvent includes N,N-dimethylformamide (DMF).

[0088] In some embodiments, when the first precursor solution is reacted under predetermined conditions to obtain a metal organic framework material MOF-804 dispersion, the predetermined conditions are: setting the reaction temperature to 120°C~150°C, and the reaction time to 24h~48h. In a specific example, the value of the reaction temperature includes but is not limited to: 120°C, 130°C, 140°C, 150°C or a range between any two of the foregoing, and correspondingly, the value of the reaction time includes but is not limited to: 24h, 32h, 40h, 48h or a range between any two of the foregoing. It should be noted that when the reaction temperature is increased, the reaction time is correspondingly reduced, and the reaction temperature and reaction time can be set according to actual needs.

[0089] In some of the embodiments, when the metal organic framework material MOF-804 dispersion is centrifuged, the obtained metal organic framework material MOF-804 dispersion is placed in a centrifuge, the centrifugal speed is set to 8000 rpm~10000 rpm, and the centrifugal time is 5 min~15 min. For example, the centrifugal speed is set to 8000 rpm, 9000 rpm, 10000 rpm or a range between any two of the foregoing, and the centrifugal time is 5 min, 10 min or 15 min. It should be noted that when the centrifugal speed is increased, the centrifugal time is correspondingly reduced, and the centrifugal speed and the centrifugal time can be set according to actual needs to achieve the purpose of complete separation.

[0090] In some embodiments, when the first precipitate is washed and then vacuum dried, the first precipitate is washed with methanol and then placed in a vacuum drying oven, the vacuum drying temperature is set to 60°C to 80°C, and the vacuum drying time is not less than 12 hours. For example, the vacuum drying temperature is 60°C, 70°C, 80°C, or a range between any two of the foregoing, and the vacuum drying time is 12 hours, 24 hours, or overnight.

[0091] An embodiment of the present application provides a method for preparing a sensitive material of a gas sensor.

[0092] A method for preparing a gas sensor sensitive material comprises the following steps:

[0093] The ionic liquid 1-butyl-3-methylimidazole bis(trifluoromethylsulfonyl)imide is added into the second solvent and mixed to obtain a second precursor solution.

[0094] The metal organic framework material MOF-804 is added into the second precursor solution and stirred to obtain a metal organic framework material-ionic liquid MOF@[BMIM][TFSI] dispersion.

[0095] The metal organic framework material-ionic liquid MOF@[BMIM][TFSI] dispersion was centrifuged, the supernatant was removed, and the second precipitate at the bottom was collected.

[0096] The second precipitate is vacuum dried to obtain a yellow solid metal organic framework-ionic liquid composite material MOF@[BMIM][TFSI], i.e., a sensitive material for a gas sensor.

[0097] In some of the embodiments, the mass volume ratio of the ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BMIM][TFSI]) to the second solvent is: (0.05 g~1 g): (10 mL~20 mL). For example, in one specific example, the mass volume ratio of the ionic liquid to the second solvent is: 0.05 g:10 mL; in another specific example, the mass volume ratio of the ionic liquid to the second solvent is: 1 g:20 mL.

[0098] In some of these embodiments, the second solvent includes methanol.

[0099] In some embodiments, the metal organic framework material MOF-804 is added to the second precursor solution at a loading amount of 0.1 wt% to 5 wt%. The loading amount of the metal organic framework material MOF-804 added to the second precursor solution can be 0.1 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt% or a range between any two of the foregoing.

[0100] In some embodiments, when the metal organic framework material MOF-804 is added to the second precursor solution, it is stirred at 20°C to 30°C for 12 h to 24 h. For example, in a specific example, the stirring temperature is 20°C, 23°C, 26°C, 30°C, or any range between the foregoing, and the stirring time is 12 h, 16 h, 22 h, 24 h, or any range between the foregoing.

[0101] In some of the embodiments, when the metal organic framework material-ionic liquid MOF@[BMIM][TFSI] dispersion is centrifuged, the metal organic framework material-ionic liquid MOF@[BMIM][TFSI] dispersion is placed in a centrifuge, the centrifugal speed is set to 8000 rpm~10000 rpm, and the centrifugal time is 5 min~15 min. For example, the centrifugal speed is set to 8000 rpm, 9000 rpm, 10000 rpm or a range between any two of the foregoing, and the centrifugal time is 5 min, 10 min or 15 min. It should be noted that when the centrifugal speed is increased, the centrifugal time is correspondingly reduced. The centrifugal speed and the centrifugal time can be set according to actual needs to achieve the purpose of complete separation.

[0102] In some embodiments, when the second precipitate is subjected to vacuum drying, the second precipitate is placed in a vacuum drying oven, the vacuum drying temperature is set to 60°C to 80°C, and the vacuum drying time is not less than 12 hours. For example, the vacuum drying temperature is 60°C, 70°C, 80°C, or a range between any two of the foregoing, and the vacuum drying time is 12 hours, 24 hours, or overnight.

[0103] An embodiment of the present application provides a sensitive material for a gas sensor.

[0104] A gas sensor sensitive material is prepared by using the above-mentioned method for preparing the gas sensor sensitive material.

[0105] Exemplarily, a method for preparing a quartz crystal microbalance gas sensor comprises the following steps:

[0106] A yellow solid powdery metal organic framework material MOF-804 is prepared by any of the above methods and set aside.

[0107] A yellow solid metal organic framework-ionic liquid composite material MOF@[BMIM][TFSI] is prepared by any of the above methods and set aside.

[0108] The metal organic framework material MOF-804 and / or the metal organic framework-ionic liquid composite material MOF@[BMIM][TFSI] are added into the third solvent, ultrasonically dispersed, and prepared into a sensitive layer material dispersion.

[0109] The sensitive layer material dispersion is coated on the surface of a quartz crystal substrate connected to a metal electrode and covers the metal electrode, and is vacuum dried to form a carbon dioxide sensitive layer, thereby obtaining a quartz crystal microbalance gas sensor based on the metal organic framework material MOF-804, or a quartz crystal microbalance gas sensor based on the metal organic framework-ionic liquid composite material MOF@[BMIM][TFSI], or a quartz crystal microbalance gas sensor based on the metal organic framework material MOF-804 and the metal organic framework-ionic liquid composite material MOF@[BMIM][TFSI].

[0110] In some of the embodiments, before coating the sensitive layer material dispersion on the surface of the quartz crystal substrate having the metal electrode connected to the surface, the following steps are also included:

[0111] The quartz crystal substrate with a metal electrode on the surface was ultrasonically cleaned with acetone, ethanol and water in turn, with the ultrasonic cleaning time being 20 min to 30 min each, and then dried by passing dry nitrogen.

[0112] In some embodiments, the third solvent includes anhydrous ethanol or water.

[0113] In some embodiments, the ultrasonic dispersion time is 10 min to 20 min. For example, in a specific example, the ultrasonic dispersion time is 10 min, 12 min, 15 min, 18 min, 20 min, or a range between any two of the foregoing.

[0114] In some embodiments, the concentration of the dispersion of the sensitive layer material is 0.5 mg / mL to 2 mg / mL. For example, in a specific example, the concentration of the dispersion of the sensitive layer material is 0.5 mg / mL, 0.5 mg / mL, 0.8 mg / mL, 1 mg / mL, 1.2 mg / mL, 1.5 mg / mL, 1.8 mg / mL, 2 mg / mL, or a range between any two of the foregoing.

[0115] In some embodiments, the volume of the sensitive layer material dispersion liquid applied is 0.5 μL to 3 μL. For example, in a specific example, the volume of the sensitive layer material dispersion liquid applied is 0.5 μL, 0.8 μL, 1 μL, 1.5 μL, 2 μL, 2.5 μL, 3 μL, or a range between any two of the foregoing.

[0116] In some embodiments, after the sensitive layer material dispersion is coated on the surface of a quartz crystal substrate connected to a metal electrode and covers the metal electrode, during vacuum drying, the vacuum drying temperature is set to 60°C to 80°C, and the vacuum drying time is 1 h to 2 h. For example, in a specific example, the vacuum drying temperature is 60°C, 70°C, 80°C, or a range between any two of the foregoing, and the vacuum drying time is 12 h, 24 h, or overnight.

[0117] An embodiment of the present application also provides a quartz crystal microbalance gas sensor.

[0118] A quartz crystal microbalance gas sensor is prepared by adopting the above preparation method.

[0119] An embodiment of the present application also provides a quartz crystal microbalance gas sensor.

[0120] A quartz crystal microbalance gas sensor comprises a quartz crystal substrate, a metal electrode and a carbon dioxide sensitive layer, wherein the metal electrode is connected to the quartz crystal substrate, and the carbon dioxide sensitive layer is arranged on the quartz crystal substrate and covers the metal electrode, wherein the carbon dioxide sensitive layer is prepared by using a gas sensor sensitive material containing at least a metal organic framework material MOF-804 and / or a metal organic framework-ionic liquid composite material MOF@[BMIM][TFSI], and the carbon dioxide sensitive layer can absorb carbon dioxide gas.

[0121] In some of the embodiments, the material of the quartz crystal substrate is an AT-cut quartz wafer, and the fundamental frequency of the AT-cut quartz wafer is 6 MHz, 8 MHz, or 10 MHz.

[0122] In some embodiments, the metal electrode is made of gold or silver.

[0123] In some of the embodiments, the metal electrode is in the shape of a circular structure or a ring structure.

[0124] In some embodiments, the cross-sectional diameter of the metal electrode is 0.5 cm to 1.0 cm. For example, in a specific example, the cross-sectional diameter of the metal electrode is 0.5 cm, 0.8 cm, 1 cm, or a range between any two of the foregoing.

[0125] An embodiment of the present application also provides a carbon dioxide sensor.

[0126] A carbon dioxide sensor comprises a quartz crystal microbalance gas sensing element prepared by the above-mentioned preparation method, or comprises the above-mentioned quartz crystal microbalance gas sensing element.

[0127] An embodiment of the present application also provides a carbon dioxide detection method.

[0128] A method for detecting carbon dioxide, using the above-mentioned carbon dioxide sensor, comprises the following steps:

[0129] After the carbon dioxide sensor is connected to the test instrument and placed in the experimental space, the carbon dioxide sensitive layer on the carbon dioxide sensor absorbs the carbon dioxide gas in the experimental space and causes the vibration frequency of the quartz crystal substrate of the carbon dioxide sensor to change.

[0130] Nitrogen was used to control the concentration of carbon dioxide in the experimental space from 100% to 0.

[0131] Control the vibration frequency value of the quartz crystal substrate when the test instrument measures several different carbon dioxide gas concentration values, and calculate the response value of the quartz crystal microbalance gas sensor according to the vibration frequency value; wherein the response value S of the quartz crystal microbalance gas sensor is equal to fg -f0, where f g is the vibration frequency value of the quartz crystal microbalance gas sensor under carbon dioxide gas, f0 is the vibration frequency value of the quartz crystal microbalance gas sensor under nitrogen atmosphere; obtain the corresponding relationship between the response value and the carbon dioxide gas concentration: set the carbon dioxide gas concentration of 100%, 60%, 40%, 20% and 0 as sampling points, test at least 3 groups of corresponding response values ​​at each sampling point and obtain the response average value, take the carbon dioxide gas concentration as the abscissa and the corresponding response average value as the ordinate, and use the linear curve obtained by linear fitting as the working curve of the test instrument.

[0132] The carbon dioxide sensor is connected to a test instrument and placed in a test space. The test instrument is controlled to measure the vibration frequency value of the quartz crystal substrate. The response value of the quartz crystal microbalance gas sensor is calculated according to the vibration frequency value. The carbon dioxide concentration in the test space is obtained according to the response value and the working curve.

[0133] The quartz crystal microbalance gas sensor prepared by the preparation method of the quartz crystal microbalance gas sensor comprises a quartz crystal substrate, a metal electrode and a carbon dioxide sensitive layer. The carbon dioxide sensitive layer is prepared by using a gas sensor sensitive material containing at least a metal organic framework material MOF-804 and / or a metal organic framework-ionic liquid composite material MOF@[BMIM][TFSI]. The carbon dioxide sensitive layer can absorb carbon dioxide gas. The basic frequency of the quartz crystal substrate is 6 MHz, 8 MHz or 10 MHz. When the carbon dioxide concentration changes, the molecular weight of carbon dioxide gas adsorbed by the metal organic framework material and / or the metal organic framework-ionic liquid composite material in the carbon dioxide sensitive layer will increase, and the vibration frequency of the quartz crystal substrate will change. By measuring the vibration frequency value of the quartz crystal microbalance gas sensor in real time, the response value of the quartz crystal microbalance gas sensor can be obtained by calculation, thereby obtaining the corresponding relationship between the response value and the concentration of the gas to be measured and establishing a detection model. In practical applications, as long as the response value of the quartz crystal microbalance gas sensor in the measured space is measured, the carbon dioxide gas concentration in the current measured gas can be obtained through the above detection model to achieve the detection of carbon dioxide gas. After experimental verification, the quartz crystal microbalance gas sensor of the present application has good moisture resistance, simple manufacturing process, small size and can be integrated, and has practical application significance.

[0134] Example 1

[0135] This embodiment provides a sensitive material for a gas sensor.

[0136] The gas sensor sensitive material of this embodiment is prepared by the following preparation method to obtain the gas sensor sensitive material, which includes the following steps:

[0137] (1) 0.25 g of zirconium oxychloride octahydrate (ZrOCl2·8H2O) and 0.5 g of 2,5-dihydroxyterephthalic acid (DHTA) were added to 400 mL of a first solvent, N,N-dimethylformamide (DMF), to obtain a first precursor solution. The first precursor solution was reacted at a reaction temperature of 120 °C and a reaction time of 48 h to obtain a metal organic framework material MOF-804 dispersion.

[0138] (2) The metal organic framework material MOF-804 dispersion obtained in step (1) is placed in a centrifuge for centrifugal treatment, the centrifugal speed is set to 8000 rpm, the centrifugal time is set to 15 min, the supernatant is removed, and the first precipitate at the bottom is collected.

[0139] (3) The first precipitate obtained in step (2) was washed with methanol and then placed in a vacuum drying oven for vacuum drying. The vacuum drying temperature was set to 60° C. and vacuum dried overnight to obtain about 0.65 g of a yellow solid powder of a metal organic framework material MOF-804.

[0140] See also Figure 1 As shown, Figure 1 This is a scanning electron microscope image of the gas sensor sensitive material MOF-804 prepared in Example 1. The prepared gas sensor sensitive material MOF-804 is a tetradecahedron with a size of about 450 nm.

[0141] Example 2

[0142] This embodiment provides a sensitive material for a gas sensor.

[0143] The gas sensor material of this embodiment is prepared by the following preparation method, which comprises the following steps:

[0144] (1) 0.5 g of zirconium oxychloride octahydrate (ZrOCl2·8H2O) and 1 g of 2,5-dihydroxyterephthalic acid (DHTA) were added to 800 mL of a first solvent, N,N-dimethylformamide (DMF), to obtain a first precursor solution.

[0145] (2) The first precursor solution obtained in step (1) is placed in an oven and reacted at a reaction temperature of 150° C. and a reaction time of 24 h to obtain a metal organic framework material MOF-804 dispersion.

[0146] (3) The MOF-804 dispersion obtained in step (2) was placed in a centrifuge for centrifugal treatment. The centrifugal speed was set to 10,000 rpm and the centrifugal time was set to 5 min. The supernatant was removed and the first precipitate at the bottom was collected.

[0147] (4) The first precipitate obtained in step (3) was washed with methanol and then placed in a vacuum drying oven for vacuum drying. The vacuum drying temperature was set to 60° C. and vacuum dried overnight to obtain about 1.3 g of a yellow solid powder of metal organic framework material MOF-804.

[0148] See also Figure 2 As shown, Figure 2 The X-ray diffraction pattern of the gas sensor material MOF-804 prepared in Example 1 of the present invention is shown in FIG. Figure 2 It can be seen that the successful synthesis of the gas sensor sensitive material MOF-804 in this application is proved.

[0149] Example 3

[0150] This embodiment provides a sensitive material for a gas sensor.

[0151] The gas sensor material of this embodiment is prepared by the following preparation method, which comprises the following steps:

[0152] (1) The preparation method of Example 1 was used to prepare a yellow solid powdered metal organic framework material MOF-804.

[0153] (2) Add 0.3 g of ionic liquid 1-butyl-3-methylimidazole bis(trifluoromethylsulfonyl)imide ([BMIM][TFSI]) to 10 mL of the second solvent methanol to obtain a second precursor solution.

[0154] (3) The metal organic framework material MOF-804 obtained in step (1) was added to the second precursor solution obtained in step (2) at a loading amount of 0.5 wt%, and the mixture was stirred at 25 °C for 24 h to obtain a metal organic framework material - ionic liquid MOF@[BMIM][TFSI] dispersion.

[0155] (4) The metal organic framework material-ionic liquid MOF@[BMIM][TFSI] dispersion obtained in step (3) was placed in a centrifuge for centrifugation, the centrifugal speed was set to 8000 rpm, the centrifugation time was set to 10 min, the supernatant was removed, and the second precipitate at the bottom was collected.

[0156] (5) The second precipitate obtained in step (4) was placed in a vacuum drying oven for vacuum drying, the vacuum drying temperature was set to 60 °C, and vacuum drying was performed overnight to obtain about 0.3 g of a yellow solid metal organic framework-ionic liquid composite material MOF@[BMIM][TFSI]; see Figure 3 As shown, Figure 3This is a scanning electron microscope image of the gas sensor material MOF@[BMIM][TFSI] prepared in Example 3 of the present invention. The prepared gas sensor material MOF@[BMIM][TFSI] is a tetradecahedron with a size of about 500 nm. Figure 4 As shown, Figure 4 This is the X-ray diffraction pattern of the gas sensor sensitive material MOF@[BMIM][TFSI] prepared in Example 3. The peak position corresponds to that of MOF-804 prepared in Example 1, proving that the presence of [BMIM][TFSI] does not affect the crystal form of the gas sensor sensitive material MOF-804.

[0157] Example 4

[0158] This embodiment provides a sensitive material for a gas sensor.

[0159] The gas sensor material of this embodiment is prepared by the following preparation method, which comprises the following steps:

[0160] (1) The preparation method of Example 1 was used to prepare a yellow solid powdered metal organic framework material MOF-804.

[0161] (2) Add 0.5 g of ionic liquid 1-butyl-3-methylimidazole bis(trifluoromethylsulfonyl)imide ([BMIM][TFSI]) to 10 mL of the second solvent methanol to obtain a second precursor solution.

[0162] (3) The metal organic framework material MOF-804 obtained in step (1) was added to the second precursor solution obtained in step (2) at a loading amount of 1 wt%, and the mixture was stirred at 25 °C for 24 h to obtain a metal organic framework material - ionic liquid MOF@[BMIM][TFSI] dispersion.

[0163] (4) The metal organic framework material-ionic liquid MOF@[BMIM][TFSI] dispersion obtained in step (3) was placed in a centrifuge for centrifugation, the centrifugal speed was set to 10,000 rpm, the centrifugation time was set to 5 min, the supernatant was removed, and the second precipitate at the bottom was collected.

[0164] (5) The second precipitate obtained in step (4) was placed in a vacuum drying oven for vacuum drying, the vacuum drying temperature was set to 60 °C, and vacuum drying was performed overnight to obtain about 0.5 g of a yellow solid metal organic framework-ionic liquid composite material MOF@[BMIM][TFSI]; see Figure 5 As shown, Figure 5The X-ray diffraction pattern of the gas sensor sensitive material MOF@[BMIM][TFSI] prepared in Example 4 of the present invention has a peak position corresponding to that of the metal organic framework material MOF-804 prepared in Example 1, proving that the presence of [BMIM][TFSI] does not affect the crystal form of the metal organic framework material MOF-804.

[0165] Example 5

[0166] This embodiment provides a quartz crystal microbalance gas sensor.

[0167] The quartz crystal microbalance gas sensor of this embodiment is prepared by the following preparation method, which comprises the following steps:

[0168] (1) Preparation of gas sensor sensitive material: The preparation method of Example 1 is used to prepare a yellow solid powder metal organic framework material MOF-804 for later use.

[0169] (2) The quartz crystal substrate with the metal electrode on the surface was ultrasonically cleaned with acetone, ethanol and water in turn, with the ultrasonic cleaning time being 20 min to 30 min, and then dried by passing dry nitrogen. The quartz crystal substrate was AT-cut quartz crystal with a base frequency of 10 MHz; the metal electrode was a silver electrode with a diameter of 0.8 mm and a circular shape.

[0170] (3) The metal organic framework material MOF-804 obtained in step (1) was added to the third solvent anhydrous ethanol and ultrasonically dispersed for 20 min to prepare a sensitive layer material dispersion with a concentration of 1 mg / mL.

[0171] (4) Take 2 μL of the dispersion of the sensitive layer material prepared in step (3), apply it on the surface of the quartz crystal substrate and cover the metal electrode, place it in a vacuum drying oven for vacuum drying, set the vacuum drying temperature to 60 °C, and the vacuum drying time to 2 h to obtain a quartz crystal microbalance gas sensor based on the metal organic framework material MOF-804; see Figure 6 As shown, Figure 6 The quartz crystal microbalance gas sensor based on the metal organic framework material MOF-804 prepared in Example 5 was placed at 0, 20%, 40%, 60%, 80%, 85%, 90% and 95% relative humidity (RH) and introduced with a concentration of 50000 ppm of carbon dioxide gas. Figure 6 It can be seen that with the change of relative humidity in the test environment, the sensitivity of the quartz crystal microbalance gas sensor is 12, 18, 29, 51, 60, 105, 142 and 160 respectively.

[0172] See also Figure 7 As shown, Figure 7 This is an optical photograph of the quartz crystal substrate of the quartz crystal microbalance gas sensor of Example 5 of the present invention.

[0173] Example 6

[0174] This embodiment provides a quartz crystal microbalance gas sensor.

[0175] The quartz crystal microbalance gas sensor of this embodiment is prepared by the following preparation method, which comprises the following steps:

[0176] (1) Preparation of gas sensor sensitive material: The preparation method of Example 3 was used to prepare a yellow solid metal organic framework-ionic liquid composite material MOF@[BMIM][TFSI] for later use.

[0177] (2) The quartz crystal substrate with the metal electrode on the surface was ultrasonically cleaned with acetone, ethanol and water in turn, with the ultrasonic cleaning time of 20 min each, and then dried by passing dry nitrogen. The quartz crystal substrate was AT-cut quartz crystal with a base frequency of 10 MHz; the metal electrode was a silver electrode with a diameter of 0.7 mm and a circular shape.

[0178] (3) The metal organic framework-ionic liquid composite material MOF@[BMIM][TFSI] obtained in step (1) was added to the third solvent anhydrous ethanol and ultrasonically dispersed for 20 min to prepare a sensitive layer material dispersion with a concentration of 1 mg / mL.

[0179] (4) Take 2 μL of the dispersion of the sensitive layer material prepared in step (3), coat it on the surface of the quartz crystal substrate and cover the metal electrode, place it in a vacuum drying oven for vacuum drying, set the vacuum drying temperature to 60 °C, and the vacuum drying time to 2 h to obtain a quartz crystal microbalance gas sensor based on the metal organic framework-ionic liquid composite material MOF@[BMIM][TFSI]. See Figure 8 As shown, Figure 8 The quartz crystal microbalance gas sensor based on the metal organic framework-ionic liquid composite material MOF-804@[BMIM][TFSI] prepared in Example 6 of the present invention is placed at 0, 20%, 40%, 60%, 80%, 85%, 90% and 95% RH and is introduced with a continuous response curve of 50000 ppm carbon dioxide gas; Figure 8It can be seen that with the change of relative humidity in the test environment, the sensitivity of the quartz crystal microbalance gas sensor is 130, 170, 183, 194, 213, 214, 217 and 220 respectively.

[0180] See also Fig. 9 As shown, Fig. 9 The quartz crystal microbalance gas sensor based on the metal organic framework material MOF-804 prepared in Example 6 and the quartz crystal microbalance gas sensor based on the metal organic framework-ionic liquid composite material MOF-804@[BMIM][TFSI] prepared in Example 7 were placed at 0, 20%, 40, 60%, 80%, 85%, 90% and 95% RH and the sensitivity was compared when the carbon dioxide gas with a concentration of 50000 ppm was introduced; Fig. 9 It can be seen that as the relative humidity of the test environment changes, the sensitivity of the quartz crystal microbalance gas sensor based on the metal organic framework-ionic liquid composite material MOF-804@[BMIM][TFSI] to 50,000 ppm carbon dioxide changes less, proving its better moisture resistance.

[0181] Example 7

[0182] This embodiment provides a quartz crystal microbalance gas sensor.

[0183] The quartz crystal microbalance gas sensor of this embodiment is prepared by the following preparation method, which comprises the following steps:

[0184] (1) Preparation of gas sensor sensitive material: The preparation method of Example 4 was used to prepare a yellow solid metal organic framework-ionic liquid composite material MOF@[BMIM][TFSI] for later use.

[0185] (2) The quartz crystal substrate with the metal electrode on the surface was ultrasonically cleaned with acetone, ethanol and water in turn, with the ultrasonic cleaning time of 20 min each, and then dried by passing dry nitrogen. The quartz crystal substrate was AT-cut quartz crystal with a base frequency of 10 MHz; the metal electrode was a silver electrode with a diameter of 0.8 mm and a circular shape.

[0186] (3) The metal organic framework-ionic liquid composite material MOF@[BMIM][TFSI] obtained in step (1) was added to the third solvent anhydrous ethanol and ultrasonically dispersed for 20 min to prepare a sensitive layer material dispersion with a concentration of 1.5 mg / mL.

[0187] (4) 1 μL of the dispersion of the sensitive layer material prepared in step (3) was taken and coated on the surface of the quartz crystal substrate and covered with the metal electrode, and then placed in a vacuum drying oven for vacuum drying. The vacuum drying temperature was set to 60 °C and the vacuum drying time was set to 1 h to obtain a quartz crystal microbalance gas sensor based on the metal organic framework-ionic liquid composite material MOF@[BMIM][TFSI].

[0188] In summary, compared with the conventional technology, the quartz crystal microbalance gas sensor of the present invention has at least the following beneficial effects:

[0189] (1) The gas sensor proposed in the present invention uses metal organic framework materials and / or metal organic framework-ionic liquid composite materials as the sensitive materials of the gas sensor to modify the surface of the metal electrode. The experimental raw materials are easy to obtain, the synthesis method is simple, and it is easy to promote.

[0190] (2) The quartz crystal microbalance gas sensor based on metal organic framework materials and / or metal organic framework-ionic liquid composite materials proposed in the present invention has good moisture resistance, simple manufacturing process, small size and can be integrated, and has practical application significance.

[0191] (3) The quartz crystal microbalance gas sensor prepared by the present invention based on metal organic framework materials and / or metal organic framework-ionic liquid composite materials has better detection effect than the bare electrode and the quartz crystal microbalance gas sensor modified with other sensitive materials reported so far, and can be used for actual sample detection.

[0192] (4) The quartz crystal microbalance gas sensor based on metal organic framework materials and / or metal organic framework-ionic liquid composite materials prepared by the present invention can detect carbon dioxide at room temperature, has high sensitivity and good reproducibility, and has a good linear response relationship to different concentrations of carbon dioxide gas, which can realize quantitative detection of carbon dioxide concentration and has practical application value.

[0193] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0194] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0195] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing a sensitive material of a gas sensor, characterized in that: The gas sensor material prepared by the preparation method is a tetradecahedron, and the preparation method of the gas sensor material comprises the following steps: Adding zirconium oxychloride octahydrate and 2,5-dihydroxyterephthalic acid into a first solvent, mixing to obtain a first precursor solution, wherein the mass ratio of the zirconium oxychloride octahydrate to the 2,5-dihydroxyterephthalic acid is (0.25 g to 0.5 g): (0.5 g to 1 g), reacting the first precursor solution under predetermined conditions to obtain a metal organic framework material MOF-804 dispersion; Centrifuging the metal organic framework material MOF-804 dispersion, removing the supernatant, and collecting the first precipitate at the bottom; and The first precipitate is washed and then vacuum dried to obtain a yellow solid powder metal organic framework material MOF-804; adding ionic liquid 1-butyl-3-methylimidazole bis(trifluoromethylsulfonyl)imide to the second solvent and mixing to obtain a second precursor solution; Adding the metal organic framework material MOF-804 to the second precursor solution, stirring to obtain a metal organic framework material-ionic liquid MOF@[BMIM][TFSI] dispersion; Centrifuging the metal organic framework material-ionic liquid MOF@[BMIM][TFSI] dispersion, removing the supernatant, and collecting the second precipitate at the bottom; and The second precipitate is vacuum dried to obtain a yellow solid metal organic framework-ionic liquid composite material MOF@[BMIM][TFSI].

2. The method for preparing a gas sensor material according to claim 1, characterized in that: The method for preparing the gas sensor sensitive material also satisfies at least one of the following conditions: (1) The mass volume ratio of the zirconium oxychloride octahydrate, the 2,5-dihydroxyterephthalic acid, and the first solvent is: (0.25 g~0.5 g): (0.5 g~1 g): (200 mL~2000 mL); (2) The first solvent includes N,N-dimethylformamide; (3) When the first precursor solution is reacted under predetermined conditions to obtain a metal organic framework material MOF-804 dispersion, the predetermined conditions are: setting the reaction temperature to 120°C to 150°C and the reaction time to 24 h to 48 h; (4) When the MOF-804 dispersion is centrifuged, the obtained MOF-804 dispersion is placed in a centrifuge and the centrifugal speed is set to 8000 rpm. 10000 rpm, centrifugation time 5min~15min; (5) When the first precipitate is washed and then vacuum dried, the first precipitate is washed with methanol and placed in a vacuum drying oven, the vacuum drying temperature is set at 60°C to 80°C, and the vacuum drying time is not less than 12 h.

3. The method for preparing a gas sensor material according to claim 1, characterized in that: The method for preparing the gas sensor sensitive material also satisfies at least one of the following conditions (1) The mass volume ratio of the ionic liquid 1-butyl-3-methylimidazole bis(trifluoromethylsulfonyl)imide and the second solvent is: (0.05 g~1 g): (10 mL~20 mL); (2) the second solvent includes methanol; (3) The metal organic framework material MOF-804 is added to the second precursor solution at a loading amount of 0.1 wt% to 5 wt%; (4) When adding the metal organic framework material MOF-804 to the second precursor solution, stirring at 20°C to 30°C for 12 h to 24 h; (5) When the metal organic framework material-ionic liquid MOF@[BMIM][TFSI] dispersion is centrifuged, the metal organic framework material-ionic liquid MOF@[BMIM][TFSI] dispersion is placed in a centrifuge, the centrifugal speed is set to 8000 rpm~10000 rpm, and the centrifugal time is 5 min~15 min; (6) When the second precipitate is subjected to vacuum drying treatment, the second precipitate is placed in a vacuum drying oven, the vacuum drying temperature is set to 60°C to 80°C, and the vacuum drying time is not less than 12 hours.

4. A gas sensor sensitive material, characterized in that: The gas sensor is prepared by the method for preparing the gas sensor material according to any one of claims 1 to 3.

5. A method for preparing a quartz crystal microbalance gas sensor, characterized in that: The steps include: Adding the metal organic framework-ionic liquid composite material MOF@[BMIM][TFSI] according to any one of claims 1 to 3 into a third solvent, and ultrasonically dispersing the mixture to prepare a dispersion of a sensitive layer material; and The sensitive layer material dispersion is coated on the surface of a quartz crystal substrate connected to a metal electrode and covers the metal electrode, and is vacuum dried to form a carbon dioxide sensitive layer, thereby obtaining a quartz crystal microbalance gas sensor based on a metal organic framework-ionic liquid composite material MOF@[BMIM][TFSI].

6. The method for preparing the quartz crystal microbalance gas sensor according to claim 5, characterized in that: The method for preparing the quartz crystal microbalance gas sensor also satisfies at least one of the following conditions: (1) The third solvent includes anhydrous ethanol or water; (2) The ultrasonic dispersion time is 10 min to 20 min; (3) The concentration of the dispersion of the sensitive layer material is 0.5 mg / mL to 2 mg / mL; (4) The volume of the sensitive layer material dispersion liquid applied is 0.5 μL~3 μL; (5) After the sensitive layer material dispersion is coated on the surface of a quartz crystal substrate connected to a metal electrode and covers the metal electrode, a vacuum drying temperature is set at 60°C to 80°C and a vacuum drying time is set at 1 h to 2 h during vacuum drying. (6) Before coating the sensitive layer material dispersion on the surface of a quartz crystal substrate having a metal electrode connected to the surface, the method further includes the following steps: ultrasonically cleaning the quartz crystal substrate having a metal electrode connected to the surface with acetone, ethanol and water in turn, with the ultrasonic cleaning time being 20 min to 30 min, and introducing dry nitrogen for drying.

7. A quartz crystal microbalance gas sensor, characterized in that: Prepared by the preparation method according to any one of claims 5 to 6; The quartz crystal microbalance gas sensor comprises a quartz crystal substrate, a metal electrode and a carbon dioxide sensitive layer, wherein the metal electrode is connected to the quartz crystal substrate, and the carbon dioxide sensitive layer is arranged on the quartz crystal substrate and covers the metal electrode, wherein the carbon dioxide sensitive layer is prepared by using a gas sensor sensitive material of a metal organic framework-ionic liquid composite material MOF@[BMIM][TFSI], and the carbon dioxide sensitive layer can absorb carbon dioxide gas.

8. A carbon dioxide sensor, characterized in that: The invention relates to a quartz crystal microbalance gas sensor prepared by the preparation method described in any one of claims 5 to 6, or a quartz crystal microbalance gas sensor described in claim 7.

9. A method for detecting carbon dioxide, characterized in that: The carbon dioxide sensor according to claim 8 comprises the following steps: The carbon dioxide sensor is connected to a test instrument and placed in an experimental space, so that the carbon dioxide sensitive layer on the carbon dioxide sensor absorbs carbon dioxide gas in the experimental space and changes the vibration frequency of the quartz crystal substrate of the carbon dioxide sensor; The concentration of carbon dioxide gas in the experimental space is controlled by nitrogen gas to change from 100% to 0 in sequence; Control the vibration frequency value of the quartz crystal substrate when the test instrument measures several different carbon dioxide gas concentration values, and calculate the response value of the quartz crystal microbalance gas sensor according to the vibration frequency value; wherein the response value S of the quartz crystal microbalance gas sensor is equal to f g- f0, where f g is the vibration frequency value of the quartz crystal microbalance gas sensor under carbon dioxide gas, f0 is the vibration frequency value of the quartz crystal microbalance gas sensor under nitrogen atmosphere; obtain the corresponding relationship between the response value and the carbon dioxide gas concentration: set the carbon dioxide gas concentration of 100%, 60%, 40%, 20% and 0 as sampling points, test at least 3 groups of corresponding response values ​​at each sampling point and obtain the average response value, take the carbon dioxide gas concentration as the abscissa and the corresponding average response value as the ordinate, and use the linear curve obtained by linear fitting as the working curve of the test instrument; and The carbon dioxide sensor is connected to a test instrument and placed in a test space. The test instrument is controlled to measure the vibration frequency value of the quartz crystal substrate. The response value of the quartz crystal microbalance gas sensor is calculated according to the vibration frequency value. The carbon dioxide concentration in the test space is obtained according to the response value and the working curve.

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