Bimetal gas-sensitive material, gas-sensitive sensor and preparation method and application of bimetallic gas-sensitive material and gas-sensitive sensor

Abstract

The invention belongs to the field of gas-sensitive sensors, and particularly relates to a bimetallic gas-sensitive material, a gas-sensitive sensor and a preparation method and application of the bimetallic gas-sensitive material. According to the rapid synthesis method of the high-quality bimetallic gas-sensitive material, the first metal hydrate and the second metal hydrate are added to be treated together with the organic amine, the organic amine is a deprotonation agent, the high-quality MOF material can be prepared at the room temperature for two hours, meanwhile, the size is scaled to the nanoscale, and the high-quality bimetallic gas-sensitive material is obtained. Gas test data shows that a gas sensitive sensor prepared from the gas sensitive material has excellent selectivity and relatively high sensing response to carbon dioxide gas, and can meet the requirements of carbon dioxide gas detection.

Description

Technical Field

[0001] The present application belongs to the field of gas sensors, and specifically relates to a bimetallic gas-sensitive material, a gas sensor, and a preparation method and application thereof. Background Art

[0002] Carbon dioxide, as an important component of the Earth's atmosphere, is also considered the most important factor causing global warming, accounting for 76% of the greenhouse effect. Due to anthropogenic carbon dioxide emissions, the concentration of carbon dioxide in the outdoor atmosphere has increased by about 30% since the pre-industrial era, increasing at a rate of about 1.5ppm per year. In addition, in indoor environments, high carbon dioxide concentrations can cause adverse health effects such as headaches, fatigue, eye symptoms, chronic asthma, bronchitis, sore throat, respiratory symptoms, etc. In order to make better use of carbon dioxide and effectively curb global warming, people are working hard to develop carbon dioxide gas sensors that can detect a wide range of carbon dioxide concentrations while having high response and high accuracy.

[0003] Carbon dioxide gas has stable chemical properties and is an inert gas, so its detection is significantly limited. Among them, quartz crystal microbalance mass sensor is one of the most attractive technologies, with high sensitivity and fast response. The working principle of quartz crystal microbalance mass sensor is based on the change of crystal oscillation frequency caused by the change of surface mass. Furthermore, quartz crystal microbalance mass sensor has high accuracy and flexibility, and can be connected with other devices, such as microprocessors and other control devices, as a means of environmental control system.

[0004] While the quartz crystal microbalance mass sensor alone cannot be used directly as a gas sensor, it must be treated by surface modification in order to be selective for carbon dioxide gas. Therefore, the advancement of materials with high carbon dioxide adsorption capacity and their integration with quartz crystal microbalance mass sensors are expected to become a reliable method for carbon dioxide detection in applied research. Metal-organic frameworks (MOFs), as a new type of inorganic-organic hybrid materials, have broad application prospects in gas separation and storage, catalysis, drug delivery, and sensing. Among these MOF materials, Mg2(dobpdc) shows a robust hexagonal channel decorated with high-density open metal sites in the case of complete removal of coordinated solvent molecules, thus providing a superior platform for gas adsorption and separation. Mg2(dobpdc) is currently the best performing carbon dioxide capture adsorbent at post-combustion pressure, which is due to the high-density arrangement of open metal sites on its one-dimensional channels.

[0005] Therefore, the existing metal gas-sensitive materials used for carbon dioxide detection still have the problems of low sensitivity and poor repeatability in selective detection. Summary of the invention

[0006] Based on this, an embodiment of the present application provides a bimetallic gas-sensitive material, which has high sensitivity and high repeatability for selective detection of carbon dioxide.

[0007] On the one hand, the present application provides a method for preparing a bimetallic gas-sensitive material, comprising the following steps:

[0008] A first metal hydrate, an organic synthesis intermediate and an organic solvent are mixed to obtain a first mixture; and the first mixture, a second metal hydrate and an organic amine are stirred to obtain a second mixture.

[0009] The second mixture is washed and filtered, the precipitate is collected, and vacuum dried to obtain a bimetallic gas-sensitive material.

[0010] One of the first metal hydrate and the second metal hydrate is selected from magnesium nitrate hexahydrate, and the other is selected from at least one of zinc nitrate hexahydrate, zinc acetate tetrahydrate and zinc chloride hexahydrate.

[0011] In one embodiment, the mass ratio of the magnesium nitrate hexahydrate to the zinc nitrate hexahydrate is (3.3-3.6):1.

[0012] In one embodiment, the organic synthesis intermediate includes 2,5-dihydroxyphthalic acid.

[0013] In one embodiment, the mass ratio of the magnesium nitrate hexahydrate to the 2,5-dihydroxyphthalic acid is (2.3-2.5):1.

[0014] In one embodiment, the mass ratio of the zinc nitrate hexahydrate to the 2,5-dihydroxyphthalic acid is (2.3-2.5):1.

[0015] In one embodiment, the organic solvent includes N,N-dimethylformamide and / or methanol.

[0016] In one embodiment, the volume ratio of the N,N-dimethylformamide to the methanol is (54-56):45.

[0017] In one embodiment, the organic amine includes one or more of triethylamine and ammonia water.

[0018] In one embodiment, the stirring treatment conditions include: a rotation speed of 900 r / min~950 r / min, and a time of 1 h~2 h.

[0019] In one embodiment, the washing treatment conditions include: washing with a mixed solution of N,N-dimethylformamide and methanol for 2 to 4 times.

[0020] In one embodiment, the vacuum drying treatment conditions include: heating to 100°C~120°C at a rate of 8°C / min~2.2°C / min, and keeping warm for 12~14h.

[0021] On the other hand, the present application provides a bimetallic gas-sensitive material, which is prepared by the above-mentioned method for preparing the bimetallic gas-sensitive material.

[0022] The present application also provides a gas sensor, at least part of which includes the above-mentioned bimetallic gas-sensitive material.

[0023] In one embodiment, it includes a quartz crystal substrate, a metal electrode and a carbon dioxide sensitive layer; 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 at least partially prepared by using the bimetallic gas-sensitive material mentioned above, and the carbon dioxide sensitive layer can absorb carbon dioxide gas.

[0024] Another aspect of the present application provides a method for preparing a gas sensor, comprising the following steps:

[0025] The bimetallic gas-sensitive material is mixed with deionized water to prepare a coating;

[0026] The coating is applied to the surface of a substrate containing a metal electrode to cover the metal electrode, and then dried.

[0027] In one embodiment, the mass volume ratio of the gas-sensitive material to the deionized water is (0.8 mg~2 mg): 1 mL.

[0028] In one embodiment, the coating method includes spraying or dripping.

[0029] In one embodiment, the drying process is carried out at a temperature of 60° C. to 70° C. and for a time of 10 h to 14 h.

[0030] On the other hand, the present application provides the use of the above-mentioned bimetallic gas-sensitive material or the above-mentioned gas-sensitive sensor in the selective detection of carbon dioxide gas.

[0031] The present application also provides a method for detecting carbon dioxide, comprising the following steps:

[0032] The gas sensor is placed in a chamber with an inert gas atmosphere for 10 to 15 minutes, and the gas to be tested is injected into the chamber. After the gas to be tested fully reacts with the gas sensor, a gas-sensitive response curve is obtained.

[0033] The details of one or more embodiments of the present application are set forth in the description which follows, and other features, objects, and advantages of the present application will be apparent from the description and its claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present application and to more completely understand the present application and its beneficial effects, the following is a brief introduction to the drawings required for 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.

[0035] Figure 1 This is a scanning electron microscope image of the gas-sensitive material prepared in Example 1;

[0036] Figure 2 is the X-ray diffraction pattern of the gas-sensitive material prepared in Example 1;

[0037] Figure 3 This is a scanning electron microscope image of the gas-sensitive material prepared in Comparative Example 1;

[0038] Figure 4 The gas sensors prepared in Examples 1 to 3 and Comparative Example 1 were tested at 20° C. with a carbon dioxide concentration of 1000 ppm;

[0039] Figure 5 To test Examples 1 to 3 and Comparative Example 1 with 8 interfering gases including carbon dioxide at 20°C;

[0040] Figure 6 The gas sensors prepared in Examples 1 to 3 and Comparative Example 1 were subjected to full spectrum testing in a 1000-10000 ppm carbon dioxide atmosphere at 20°C. DETAILED DESCRIPTION

[0041] Below in conjunction with embodiment and example, the application is further described in detail.It should be understood that these embodiments and examples are only used to illustrate the application and are not used to limit the scope of the application, and the purpose of providing these embodiments and examples is to make the understanding of the disclosure of the application more thorough and comprehensive.It should also be understood that the application can be implemented in many different forms, is not limited to the embodiment and example described herein, and those skilled in the art can make various changes or modifications without violating the connotation of the application, and the equivalent form obtained also falls within the protection scope of the application.In addition, in the description below, a large number of specific details are given in order to provide a more comprehensive understanding of the application, and it should be understood that the application can be implemented without one or more of these details.

[0042] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0043] the term

[0044] Unless otherwise specified or incompatible herewith, the terms and phrases used herein shall have the following meanings:

[0045] The terms "and / or", "or / and", and "and / or" used in this article include any one of two or more related listed items, and also include any and all combinations of related listed items, and the arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. It should be noted that when at least three items are connected by at least two conjunctions selected from "and / or", "or / and", and "and / or", it should be understood that in this application, the technical solution undoubtedly includes technical solutions that are all connected by "logical and", and undoubtedly includes technical solutions that are all connected by "logical or". For example, "A and / or B" includes three parallel solutions of A, B and A+B. For example, the technical solution of "A, and / or, B, and / or, C, and / or, D" includes any one of A, B, C, and D (that is, the technical solution that is all connected by "logical OR"), and also includes any and all combinations of A, B, C, and D, that is, the combination of any two or any three of A, B, C, and D, and also includes the combination of four of A, B, C, and D (that is, the technical solution that is all connected by "logical AND").

[0046] In the present application, "plurality", "multiple", "multiple times", "multiples", etc., unless otherwise specified, refer to a number greater than 2 or equal to 2. For example, "one or more" means one or greater than or equal to two.

[0047] As used herein, "combination thereof", "any combination thereof", "any combination thereof" etc. include all suitable combinations of any two or more of the listed items.

[0048] Herein, the “suitable” mentioned in “suitable combination”, “suitable method”, “any suitable method”, etc., shall be based on the ability to implement the technical solution of this application, solve the technical problems of this application, and achieve the expected technical effects of this application.

[0049] In the present application, "further", "further", "particularly" and the like are used for descriptive purposes to indicate differences in content, but should not be construed as limiting the scope of protection of the present application.

[0050] In this application, "optionally", "optional", and "optional" mean optional or dispensable, that is, any one of the two parallel schemes of "yes" or "no". If multiple "options" appear in a technical solution, unless otherwise specified and there is no contradiction or mutual restriction, each "optional" is independent.

[0051] In the present application, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0052] In the present application, when it comes to numerical intervals (i.e., numerical ranges), unless otherwise specified, the optional numerical distribution is considered continuous within the above numerical interval, and includes the two numerical endpoints (i.e., the minimum and maximum values) of the numerical range, and each numerical value between the two numerical endpoints. Unless otherwise specified, when the numerical interval only refers to the integers within the numerical interval, it includes the two endpoint integers of the numerical range, and each integer between the two endpoints. In this article, it is equivalent to directly listing each integer, such as t is an integer selected from 1 to 10, indicating that t is any integer selected from the integer group consisting of 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10. In addition, when multiple ranges are provided to describe features or characteristics, these ranges can be combined. In other words, unless otherwise specified, the ranges disclosed herein should be understood to include any and all sub-ranges included therein.

[0053] The temperature parameters in this application, unless otherwise specified, are allowed to be either constant temperature treatment or to vary within a certain temperature range. It should be understood that the constant temperature treatment allows the temperature to fluctuate within the accuracy range controlled by the instrument. Fluctuations within the range of ±5°C, ±4°C, ±3°C, ±2°C, and ±1°C are allowed.

[0054] In the present application, % (w / w) and wt% both represent weight percentage, % (v / v) refers to volume percentage, and % (w / v) refers to mass volume percentage.

[0055] All documents mentioned in this application are cited as references in this application, just as each document is cited as reference separately. Unless they conflict with the invention purpose and / or technical solution of this application, the cited documents involved in this application are cited with all contents and all purposes. When the cited documents are involved in this application, the definitions of relevant technical features, terms, nouns, phrases, etc. in the cited documents are also cited. When the cited documents are involved in this application, the examples and preferred methods of the cited relevant technical features can also be incorporated into this application as references, but are limited to the implementation of this application. It should be understood that when the cited content conflicts with the description in this application, the present application shall prevail or be modified adaptively according to the description of this application.

[0056] On the one hand, the present application provides a method for preparing a bimetallic gas-sensitive material, comprising the following steps:

[0057] The first metal hydrate, the organic synthesis intermediate and the organic solvent are mixed to obtain a first mixture. The first mixture, the second metal hydrate and the organic amine are stirred to obtain a second mixture.

[0058] The second mixture is washed and filtered, the precipitate is collected, and vacuum dried to obtain a bimetallic gas-sensitive material.

[0059] One of the first metal hydrate and the second metal hydrate is selected from magnesium nitrate hexahydrate, and the other is selected from at least one of zinc nitrate hexahydrate, zinc acetate tetrahydrate and zinc chloride hexahydrate.

[0060] For example, in one specific example, the first metal hydrate is selected from magnesium nitrate hexahydrate, and the second metal hydrate is selected from zinc nitrate hexahydrate; in another specific example, the first metal hydrate is selected from zinc nitrate hexahydrate, and the second metal hydrate is selected from at least one of zinc nitrate hexahydrate, zinc acetate tetrahydrate and zinc chloride hexahydrate.

[0061] In a specific example, the organic synthesis intermediate includes 2,5-dihydroxyphthalic acid.

[0062] Alternatively, the organic solvent includes N,N-dimethylformamide and methanol.

[0063] In a specific example, the volume ratio of N,N-dimethylformamide to methanol is (54-56):45; for example, the volume ratio of N,N-dimethylformamide to methanol is 54:45, 55:45 or 56:45.

[0064] In a specific example, the mass ratio of magnesium nitrate hexahydrate to zinc nitrate hexahydrate is (3.3-3.6) 1; for example, the mass ratio of magnesium nitrate hexahydrate to zinc nitrate hexahydrate is 3.3:1, 3.4:1, 3.5:1 or 3.6:1.

[0065] In a specific example, the mass ratio of magnesium nitrate hexahydrate to 2,5-dihydroxyphthalic acid is (2.3-2.5):1; for example, the mass ratio of magnesium nitrate hexahydrate to 2,5-dihydroxyphthalic acid is 2.3:1, 2.4:1 or 2.5:1.

[0066] In a specific example, the mass ratio of zinc nitrate hexahydrate to 2,5-dihydroxyphthalic acid is (2.3-2.5): 1. For example, the mass ratio of zinc nitrate hexahydrate to 2,5-dihydroxyphthalic acid is 2.3:1, 2.4:1 or 2.5:1.

[0067] Optionally, the organic amine includes triethylamine or ammonia. Among them, triethylamine is a deprotonating agent, which can prepare high-quality MOF materials in two hours at room temperature and scale the size to nanoscale.

[0068] In a specific example, the stirring speed is 900r / min~950r / min, and the time is 1h~2h; in a specific embodiment, the stirring speed is 900r / min, and in another specific embodiment, the stirring speed is 950r / min. It is not difficult to understand that in other specific embodiments, the stirring speed is 910 r / min, 920 r / min, 930r / min, 940 r / min, and the time is 1h, 1.5h or 2h.

[0069] In a specific example, the washing process includes: washing with a mixed solution of N,N-dimethylformamide and methanol for 2 to 4 times; wherein the volume ratio of N,N-dimethylformamide to methanol is (54 to 56):45; for example, the volume ratio of N,N-dimethylformamide to methanol is 54:45, 55:45 or 56:45, and the washing times are 2, 3 or 4 times.

[0070] In a specific example, the vacuum drying process includes: heating to 100°C~120°C at a rate of 1.8°C / min~2.2°C / min, and keeping warm for 12~14 hours. For example, heating to 100°C, 110°C or 120°C at a rate of 1.8°C / min, 1.9°C / min, 2.0°C / min, 2.1°C / min, 2.2°C / min, and keeping warm for 12 hours, 13 hours or 14 hours.

[0071] On the other hand, the present application provides a bimetallic gas-sensitive material, wherein the bimetallic gas-sensitive material is prepared using the above-mentioned method for preparing the bimetallic gas-sensitive material.

[0072] The present application also provides a gas sensor, at least part of which includes the above-mentioned bimetallic gas-sensitive material.

[0073] In a specific example, it includes a quartz crystal substrate, a metal electrode and a carbon dioxide sensitive layer; 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 at least partially prepared by using the above-mentioned bimetallic gas-sensitive material, and the carbon dioxide sensitive layer can absorb carbon dioxide gas.

[0074] Another aspect of the present application provides a method for preparing a gas sensor, comprising the following steps:

[0075] The bimetallic gas-sensitive material is mixed with deionized water to prepare a coating;

[0076] The coating is applied to the electrode surface of the sensor and dried to prepare a bimetallic gas-sensitive material sensor. Specifically, the following steps are included: a solution obtained by mixing and dispersing the gas-sensitive material and deionized water is drop-coated on the electrode surface of the quartz crystal microbalance sensor to obtain a carbon dioxide gas-sensitive sensor, and the prepared sensor is dried in an oven to form a sensing layer.

[0077] In a specific example, the mass volume ratio of the gas sensitive material to deionized water is (0.8 mg~2 mg):1 mL; for example, the volume ratio is 0.8 mg:1 mL, 1 mg:1 mL, 1.2 mg:1 mL, 1.4 mg:1 mL, 1.6 mg:1 mL, 1.8 mg:1 mL or 2 mg:1 mL.

[0078] In a specific example, the coating method includes spraying or dripping.

[0079] Optionally, in the dripping step, a 0.1 μL to 2.5 μL pipette is used for slow dripping.

[0080] In a specific example, the temperature of the drying process is 60°C to 70°C, for example, the temperature is 60°C, 62°C, 64°C, 66°C, 68°C or 70°C.

[0081] On the other hand, the present application provides the use of the above-mentioned gas-sensitive material or the above-mentioned gas-sensitive sensor in the selective detection of carbon dioxide gas.

[0082] On the other hand, the present application also provides a method for detecting carbon dioxide, comprising the following steps:

[0083] The gas sensor is placed in a chamber with a nitrogen atmosphere for 10 to 15 minutes, and a specific concentration of the test gas is injected into the chamber through a dynamic gas distribution system. After the test gas fully reacts with the gas sensor, a gas-sensitive response curve is obtained.

[0084] The present application provides a method for rapid synthesis of high-quality bimetallic gas-sensitive material Mg / Zn (dobpdc), by adding a first metal hydrate and a second metal hydrate and treating them together with an organic amine, wherein the organic amine is a deprotonating agent, a high-quality MOF material can be prepared at room temperature within two hours, and the size can be scaled to the nanoscale.

[0085] From an industrial and environmental point of view, the synthesis method carried out at room temperature is more attractive because no energy input is required during the MOF formation process. Reduced-size MOF particles have advantages over bulk phase MOF in the fields of catalysis, chemical sensing and gas separation because they have short diffusion paths and large surface areas, which accelerate the mass transfer of guest molecules and make it easier to obtain catalytic active sites. At the same time, compared with monometallic Mg2(dobpdc), bimetallic Mg / Zn(dobpdc) can provide higher carbon dioxide absorption and higher adsorption heat, which is due to the synergistic effect of the two metals as open sites. Gas test data show that the gas sensor prepared using this gas-sensitive material has excellent selectivity and high sensing response to carbon dioxide gas, which can meet the needs of carbon dioxide gas detection.

[0086] The embodiments of the present application will be described in detail below in conjunction with examples. It should be understood that these examples are only used to illustrate the present application and are not intended to limit the scope of the present application. The experimental methods for which specific conditions are not specified in the following examples are preferably referred to the guidance provided in the present application, and can also be based on the experimental manual or normal conditions in this area, can also be based on the conditions recommended by the manufacturer, or refer to experimental methods known in the art.

[0087] In the following specific embodiments, the measured parameters of raw material components may have slight deviations within the range of weighing accuracy unless otherwise specified. For temperature and time parameters, acceptable deviations caused by instrument test accuracy or operation accuracy are allowed.

[0088] It should be understood that in the various embodiments of the present application, the size of the serial numbers of the above-mentioned processes does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0089] Quartz crystal microbalance: purchased from Beijing Chenjing Electronics Co., Ltd., with a base frequency of 10 MHz, composed of AT-cut quartz crystal (8 mm in diameter) covered with silver electrodes (5 mm in diameter) on both sides.

[0090] 2,5-Dihydroxyphthalic acid (molecular formula: C 14 H 10 O6) (purity ≥98.0%): purchased from Shanghai MacLean Biochemical Technology Co., Ltd.

[0091] Magnesium nitrate hexahydrate (molecular formula: Mg(NO3)2·6H2O) (purity ≥ 98.0%): purchased from Shanghai McLean Biochemical Technology Co., Ltd. Zinc nitrate hexahydrate (molecular formula: Zn(NO3)2·6H2O) (purity ≥ 98.0%): purchased from Shanghai McLean Biochemical Technology Co., Ltd. Zinc acetate tetrahydrate (molecular formula: (CH3COO)2Zn·4H2O) (purity ≥ 98.0%): purchased from Shanghai McLean Biochemical Technology Co., Ltd. Zinc chloride hexahydrate (molecular formula: ZnCl2·4H2O) (purity ≥ 98.0%): purchased from Shanghai McLean Biochemical Technology Co., Ltd.

[0092] Anhydrous ethanol: purchased from Chengdu Kelong Chemical Reagent Factory.

[0093] N,N-Dimethylformamide: purchased from Chengdu Kelong Chemical Reagent Factory.

[0094] Triethylamine: purchased from Chengdu Kelong Chemical Reagent Factory.

[0095] Carbon dioxide detector: purchased from Mansfield Company, UK.

[0096] Frequency counter: purchased from Keysight Technologies, Inc., USA.

[0097] Electric constant temperature drying oven: purchased from Kangheng Instrument Co., Ltd.

[0098] Pipette: purchased from Shanghai Guangzheng Medical Instrument Co., Ltd.

[0099] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in the art can be used. The raw materials or instruments used are all conventional products that can be obtained commercially, including but not limited to the raw materials or instruments used in the examples of this application.

[0100] Example 1

[0101] This embodiment provides a method for preparing a gas-sensitive material, and the steps are as follows:

[0102] (1) 0.256 g of magnesium nitrate hexahydrate and 0.137 g of 2,5-dihydroxyphthalic acid were mixed in a mixed solution of N,N-dimethylformamide and methanol; wherein the volume of N,N-dimethylformamide and methanol was 50 mL in total, and the volume ratio of N,N-dimethylformamide to methanol was 55:45 (v / v).

[0103] (2) 0.074 g of zinc nitrate hexahydrate was mixed with the mixture of step (1) and 0.5 mL of triethylamine, and stirred vigorously at a speed of 900 r / min to 950 r / min for 1 h to 2 h, and then stirred at 20 ° C to 30 ° C for 2 h.

[0104] (3) After synthesis, the precipitated metal organic framework crystals were collected by centrifugation at 8000r / min and redispersed in fresh N,N-dimethylformamide. After filtration, white powder was obtained. Then, the mixture was washed three times with a mixture of N,N-dimethylformamide and methanol, with a volume ratio of N,N-dimethylformamide to methanol of 55:45 (v / v). After filtration, the mixture was immersed in methanol, and the methanol was changed once a day for three consecutive days. After filtration, the mixture was vacuum dried at 100°C for 12h to obtain the final bimetallic gas sensitive material Mg / Zn (dobpdc) sample.

[0105] The scanning electron microscope image of the gas-sensitive material prepared in Example 1 is as follows: Figure 1 Its X-ray diffraction pattern is shown in Figure 2 shown.

[0106] Example 2

[0107] This embodiment provides a method for preparing a gas-sensitive material, and the steps are as follows:

[0108] (1) 0.037 g of zinc nitrate hexahydrate and 0.137 g of 2,5-dihydroxyphthalic acid were mixed in a mixed solution of N,N-dimethylformamide and methanol, wherein the total volume of N,N-dimethylformamide and methanol was 50 mL, and the volume ratio of N,N-dimethylformamide to methanol was 55:45 (v / v).

[0109] (2) 0.288 g of magnesium nitrate hexahydrate was mixed with the mixture of step (1) and 0.5 mL of triethylamine, and stirred vigorously at a speed of 900 r / min to 950 r / min for 1 h to 2 h, and then stirred at 20 ° C to 30 ° C for 2 h.

[0110] (3) After synthesis, the metal organic framework crystals were collected by centrifugation at a speed of 8000 r / min and redispersed in fresh N,N-dimethylformamide, and filtered to obtain white powder. Then, the mixture was washed three times with a mixture of N,N-dimethylformamide and methanol, with a volume ratio of N,N-dimethylformamide to methanol of 55:45 (v / v), filtered and immersed in methanol, and the methanol was changed once a day for 3 consecutive days. After filtering, it was vacuum dried at 100°C for 12 hours to obtain the final bimetallic gas sensitive material Mg / Zn (dobpdc) sample.

[0111] Example 3

[0112] This embodiment provides a method for preparing a gas-sensitive material, and the steps are as follows:

[0113] (1) 0.224 g of magnesium nitrate hexahydrate and 0.135 g of 2,5-dihydroxyphthalic acid were mixed in a mixed solution of N,N-dimethylformamide and methanol; wherein the volume of N,N-dimethylformamide and methanol was 50 mL in total, and the volume ratio of N,N-dimethylformamide to methanol was 55:45 (v / v).

[0114] (2) 0.112 g of zinc acetate tetrahydrate was mixed with the mixture of step (1) and 0.5 mL of triethylamine, and stirred vigorously at a speed of 900 r / min-950 r / min for 1 h-2 h, and then stirred at 20° C.-30° C. for 2 h.

[0115] (3) After synthesis, the metal organic framework crystals were collected by centrifugation at 8000 r / min and redispersed in fresh N,N-dimethylformamide, and filtered to obtain white powder. Then, the mixture was washed three times with a mixture of N,N-dimethylformamide and methanol, with a volume ratio of N,N-dimethylformamide to methanol of 55:45 (v / v), filtered and immersed in methanol, with the methanol replaced once a day for three consecutive days. After filtering, the mixture was vacuum dried at 100 °C for 12 h to obtain the final bimetallic gas sensitive material Mg / Zn (dobpdc) sample.

[0116] Example 4

[0117] This embodiment provides a method for preparing a gas sensor, the steps are as follows:

[0118] Disperse 1 mg of the gas-sensitive material obtained in Example 1 in 1 mL of deionized water to obtain a dispersion, and then use a pipette to apply the dispersion on the substrate surface of a quartz crystal microbalance. Place the coated sensor in a constant temperature drying oven at 60°C and dry it for 2 hours to form a sensing layer, thereby obtaining a gas sensor.

[0119] Example 5

[0120] This embodiment provides a method for preparing a gas sensor, the steps are as follows:

[0121] Disperse 2 mg of the gas-sensitive material obtained in Example 2 in 2 mL of deionized water to obtain a dispersion, and then use a pipette to apply the dispersion on the electrode substrate surface of a quartz crystal microbalance. Place the coated sensor in a constant temperature drying oven at 60°C and dry it for 2 hours to form a sensing layer, thereby obtaining a gas sensor.

[0122] Example 6

[0123] This embodiment provides a method for preparing a gas sensor, the steps are as follows:

[0124] Disperse 1 mg of the gas-sensitive material obtained in Example 2 in 1 mL of deionized water to obtain a dispersion, and then use a pipette to apply the dispersion on the electrode substrate surface of a quartz crystal microbalance. Place the coated sensor in a constant temperature drying oven at 60°C and dry it for 1.8 hours to form a sensing layer, thereby obtaining a gas sensor.

[0125] Comparative Example 1

[0126] This comparative example provides a method for preparing a single metal gas sensor. Compared with Example 1, zinc nitrate hexahydrate is not added.

[0127] (1) 0.256 g of magnesium nitrate hexahydrate and 0.137 g of 2,5-dihydroxyphthalic acid were mixed in a mixed solution of N,N-dimethylformamide and methanol; wherein the volume of N,N-dimethylformamide and methanol was 50 mL in total, and the volume ratio of N,N-dimethylformamide to methanol was 55:45 (v / v).

[0128] (2) Quickly add 0.5 mL of triethylamine to the solution while stirring vigorously, and then continue stirring at 20℃~30℃ for 2 h.

[0129] (3) After synthesis, the metal organic framework crystals were collected by centrifugation and redispersed in fresh N,N-dimethylformamide. A white powder was obtained after filtration. Then, it was washed three times with a mixed solution of N,N-dimethylformamide and methanol, with a volume ratio of N,N-dimethylformamide to methanol of 55:45 (v / v), filtered and immersed in methanol, with the methanol replaced once a day for three consecutive days. After filtration, it was vacuum dried at 100°C for 12 hours to obtain the final monometallic Mg2(dobpdc) sample;

[0130] The scanning electron microscope image of the gas-sensitive material prepared in this comparative example 1 is as follows Figure 3 shown.

[0131] Comparative Example 2

[0132] This comparative example provides a method for preparing a single metal gas-sensitive material. Compared with Example 1, this comparative example does not add magnesium nitrate hexahydrate.

[0133] (1) 0.074 g of zinc nitrate hexahydrate and 0.137 g of 2,5-dihydroxyphthalic acid were mixed in a mixed solution of N,N-dimethylformamide and methanol; the total volume of N,N-dimethylformamide and methanol was 50 mL, and the volume ratio of N,N-dimethylformamide to methanol was 55:45 (v / v).

[0134] (2) Quickly add 0.5 mL of triethylamine to the solution while stirring vigorously, and then continue stirring at 20℃~30℃ for 2 h.

[0135] (3) After synthesis, the precipitate and metal organic framework crystals were collected by centrifugation at 8000 r / min and redispersed in fresh N,N-dimethylformamide. A white powder was obtained after filtration. Then, the mixture was washed three times with a mixture of N,N-dimethylformamide and methanol, filtered and immersed in methanol, and the methanol was changed once a day for three consecutive days. After filtration, it was vacuum dried at 100 °C for 12 h to obtain the final monometallic Mg2(dobpdc) sample mixture, which was washed three times.

[0136] Comparative Example 3

[0137] This comparative example also provides a method for preparing a gas sensor:

[0138] 1 mg of the gas-sensitive material obtained in Comparative Example 1 was dispersed in 1 mL of deionized water to obtain a dispersion, which was then applied to the electrode surface of a quartz crystal microbalance using a pipette, and the coated sensor was placed in a constant temperature drying oven at 60° C. and dried for 2 h to form a sensing layer, thereby obtaining a gas sensor.

[0139] Verification results:

[0140] 1. Response of gas sensor to carbon dioxide gas

[0141] The gas-sensitive performance test was carried out at room temperature of 20°C using a carbon dioxide detector and a frequency counter. First, the gas sensor was exposed to a chamber containing a 100% nitrogen atmosphere for 10 min to 15 min, and then a specific concentration of the test gas was injected into the chamber through the dynamic gas distribution system. After the test gas and the gas sensor fully reacted, the gas sensor was exposed to a nitrogen atmosphere and the time and frequency values ​​were recorded to obtain the gas-sensitive response curve and make a standard detection model.

[0142] like Figure 4As shown in a~d in the figure, the gas sensors prepared in Examples 1~3 and Comparative Example 1 were tested with a carbon dioxide concentration of 1000ppm at 20°C. It can be seen that the response value of the gas sensor obtained in Example 1 is 140, which proves that the gas sensor prepared in the present application can sensitively detect carbon dioxide gas at room temperature and has excellent response characteristics.

[0143] 2. Selectivity of gas sensors for carbon dioxide gas

[0144] At the optimal working temperature of 20° C., the gas sensors prepared in Examples 1 to 3 and Comparative Example 1 were tested with 8 interfering gases including carbon dioxide gas. The 8 gases are acetone, methanol, ethanol, nitrogen, methane, nitrogen dioxide, hydrogen and carbon dioxide.

[0145] The results are as follows Figure 5 As shown, the responses of the gas sensors prepared in Examples 1 to 3 and Comparative Example 1 to carbon dioxide gas are significantly higher than those of the other seven interfering gases. The frequency change values ​​of Examples 1 to 3 in carbon dioxide detection are significantly higher than those of Comparative Example 1, which proves that the sensor prepared in the present application has a higher selectivity for carbon dioxide gas.

[0146] 3. Repeatability of gas sensor response to carbon dioxide gas

[0147] The gas sensors prepared in Examples 1 to 3 and Comparative Example 1 were subjected to full spectrum testing in a 1000 ppm to 10000 ppm carbon dioxide atmosphere at 20°C.

[0148] The results are as follows Figure 6 As shown in a~d in the figure, it can be seen that the gas sensor prepared in the present application has a good response to carbon dioxide gas of different concentrations and has good practical application value.

[0149] Based on the above performance test results, the optimal operating temperature of the gas sensor prepared in Example 1 of the present application is 20°C, and the response value to 1000ppm carbon dioxide gas is 140Hz at the optimal operating temperature, and it has excellent selectivity. Compared with Comparative Example 1, although the method of Mg2 (dobpdc) without Zn ion doping is simpler, its responsiveness, gas selectivity and repeatability to carbon dioxide gas are not as good as those of the sensor prepared in Example 1 of the present application.

[0150] The above-described embodiments only express several implementation methods of the present application, which is convenient for understanding the technical solution of the present application in detail, but it cannot be understood as a limitation on the scope of protection of the patent application. It should be pointed out that for ordinary technicians in this field, without departing from the concept of the present application, several deformations and improvements can be made, which all belong to the protection scope of the present application. In addition, it should be understood that after reading the above-mentioned teaching content of the present application, the technicians in this field can make various changes or modifications to the present application, and the equivalent forms obtained also fall within the protection scope of the present application. It should also be understood that the technical solutions obtained by the technicians in this field through logical analysis, reasoning or limited experiments on the basis of the technical solutions provided in the present application are all within the protection scope of the claims attached to the present application. Therefore, the protection scope of the patent of the present application shall be based on the content of the attached claims, and the description and drawings can be used to explain the content of the claims.

Claims

1. A method for preparing a bimetallic gas-sensitive material, characterized in that: The following steps are involved: Mixing a first metal hydrate, an organic synthesis intermediate and an organic solvent to obtain a first mixture; stirring the first mixture, a second metal hydrate and an organic amine to obtain a second mixture; and, washing the second mixture, filtering it, collecting the precipitate, and vacuum drying it to obtain a bimetallic gas-sensitive material; One of the first metal hydrate and the second metal hydrate is selected from magnesium nitrate hexahydrate, and the other is selected from at least one of zinc nitrate hexahydrate, zinc acetate tetrahydrate and zinc chloride hexahydrate.

2. The method for preparing a bimetallic gas-sensitive material according to claim 1, characterized in that: The mass ratio of the magnesium nitrate hexahydrate to the zinc nitrate hexahydrate is (3.3-3.6):1; and / or The organic synthesis intermediate includes 2,5-dihydroxyphthalic acid.

3. The method for preparing a bimetallic gas-sensitive material according to claim 2, characterized in that: The mass ratio of the magnesium nitrate hexahydrate to the 2,5-dihydroxyphthalic acid is (2.3-2.5):1; and / or The mass ratio of the zinc nitrate hexahydrate to the 2,5-dihydroxyphthalic acid is (2.3-2.5):

1.

4. The method for preparing a bimetallic gas-sensitive material according to any one of claims 1 to 3, characterized in that: The method includes one or more of the following features: (1) The organic solvent comprises N,N-dimethylformamide and / or methanol, and the volume ratio of the N,N-dimethylformamide to the methanol is (54-56):45; (2) The organic amine includes one or more of triethylamine and ammonia water; (3) The stirring conditions include: a rotation speed of 900 r / min to 950 r / min and a time of 1 h to 2 h; (4) The washing treatment conditions include: washing with a mixed solution of N,N-dimethylformamide and methanol for 2 to 4 times; (5) The conditions of the vacuum drying treatment include: heating to 100°C~120°C at a rate of 1.8°C / min~2.2°C / min, and keeping the temperature for 12~14 hours.

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

6. A gas sensor, characterized in that: At least a portion of the gas sensor comprises the bimetallic gas-sensitive material according to claim 5.

7. The gas sensor according to claim 6, characterized in that: It comprises a quartz crystal substrate, a metal electrode and a carbon dioxide sensitive layer; the metal electrode is connected to the quartz crystal substrate; The carbon dioxide sensitive layer is arranged on the quartz crystal substrate and covers the metal electrode, wherein the carbon dioxide sensitive layer is at least partially prepared by using the bimetallic gas-sensitive material according to claim 5, and the carbon dioxide sensitive layer can absorb carbon dioxide gas.

8. A method for preparing a gas sensor, characterized in that: The following steps are involved: Mixing the bimetallic gas-sensitive material according to claim 5 with deionized water to prepare a coating; The coating is applied to the surface of a substrate containing a metal electrode to cover the metal electrode, and then dried.

9. The method for preparing a gas sensor according to claim 8, characterized in that: The method includes one or more of the following features: (1) The mass volume ratio of the gas-sensitive material to the deionized water is (0.8 mg to 1.2 mg): 1 mL; (2) The coating method includes spraying or dripping; (3) The drying temperature is 60°C to 70°C and the drying time is 10h to 14h.

10. Use of the bimetallic gas-sensitive material according to claim 5 or the gas-sensitive sensor according to any one of claims 6 to 7 in the selective detection of carbon dioxide gas.

11. A method for detecting carbon dioxide, characterized in that: The following steps are involved: The gas sensor according to any one of claims 6 to 7 is placed in a chamber with an inert gas atmosphere for 10 to 15 minutes, and the gas to be tested is injected into the chamber. After the gas to be tested fully reacts with the gas sensor, a gas-sensitive response curve is obtained.

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