Nano MOF (Metal Organic Framework) framework material as well as preparation method and application thereof

Abstract

The invention discloses a nano MOF (Metal Organic Framework) framework material, which is a ZnO-coated In2O3 nano material. Wherein the In < 2 > O < 3 > is of a nano rod-shaped structure, and the ZnO is nano particles; the ZnO is loaded on the surface of the In2O3 in a dotted manner; and an n-n heterojunction is formed between the ZnO and the In2O3. The MEMS gas sensor based on the point-modified rod-shaped ZnO-coated In2O3 nano material, which is prepared by the invention, shows excellent sensitivity and selectivity and low detection lower limit on acetone.

Description

Technical Field

[0001] This application relates to the technical field of gas sensors, and particularly relates to a nano MOF framework material, a preparation method thereof, and an application thereof. Background Art

[0002] Metal-organic frameworks (MOFs), also known as coordination compounds (PCCs), have pores with a diameter range from 0 (non-porous) to 9.8 nm, and are excellent materials with pore sizes between zeolites and mesoporous silica. MOFs have adjustable pore structures, ultra-high surface areas, and a variety of organic-inorganic hybrid combinations. Therefore, in the past two decades, they have achieved rapid development in various applications, such as gas adsorption / separation, catalysis, chemical sensing, energy storage, and conversion. MOF materials have a large specific surface area, which is beneficial to the diffusion of gas molecules and provides a large number of sensing adsorption sites, and have great potential in organic volatile compound (VOCs) sensors.

[0003] Gas sensors are an effective means for monitoring toxic and harmful gases and have characteristics such as portability and miniaturization. Among them, the basic sensing mechanism of metal oxide semiconductor (MOS) sensors is based on the shift of the surface chemical adsorption oxygen reaction equilibrium. According to the type of sensitive material, MOS can be divided into n-type and p-type, and different types show different sensitive behaviors towards the same measured gas. For example: when the sensitive material is exposed to an oxidizing gas, the gas species acts as an acceptor, and the resistance of the n-type semiconductor increases, while the resistance of the p-type semiconductor decreases; when exposed to a reducing gas, the gas species acts as a donor, and the resistance of the n-type semiconductor decreases, while the resistance of the p-type semiconductor increases.

[0004] MOS gas sensors operate under high-temperature (100 - 450 °C) conditions, and the heating process will cause some problems, such as the aggregation and coarsening of nanoparticles, which reduce the long-term stability, increase the heater, resulting in an increase in manufacturing cost and high power consumption. Among them, the power consumption limits the integration of MOS-based gas sensors into some important portable devices.

[0005] Currently, the sensitivity of many single-material gas sensors, such as ZnO gas sensors and In2O3 gas sensors, to acetone is lower than that of composite materials. Therefore, inventing composite material gas sensors is of certain significance for improving the sensitivity of sensors. Summary of the Invention

[0006] In order to solve the above deficiencies in the art, this application aims to provide a nano MOF framework material, a preparation method thereof, and an application thereof.

[0007] According to one aspect of this application, a nano MOF framework material is provided, including ZnO@In2O3 nano materials;

[0008] Among them, In2O3 has a nanorod-like structure and ZnO has nanoparticles;

[0009] ZnO is dot-loaded on the surface of In2O3;

[0010] An n-n heterojunction is formed between ZnO and In2O3.

[0011] According to some embodiments of the present application, the particle size of the ZnO is 28.05 - 37.94 nm;

[0012] The size of the In2O3 is 1700 - 1800 nm in length and 101 - 106 nm in width.

[0013] According to another aspect of the present application, there is also provided a method for preparing a nano MOF framework material, including:

[0014] Adding In(NO3)3 hydrate, Zn(NO3)2·6H2O, and 1,4-benzenedicarboxylic acid to a solvent in proportion and mixing them for reaction to obtain a MOF structure;

[0015] Drying to obtain a ZnO@In2O3 precursor;

[0016] Grinding and annealing to obtain ZnO@In2O3 nanomaterials.

[0017] According to some embodiments of the present application, the molar ratio of the In(NO3)3 hydrate to Zn(NO3)2·6H2O, based on In and Zn, is (2 - 8):1;

[0018] According to some embodiments of the present application, the molar ratio of the In(NO3)3 hydrate to Zn(NO3)2·6H2O, based on In and Zn, is 4:1.

[0019] According to some embodiments of the present application, the solvent is a mixture of ethanol and DMF;

[0020] According to some embodiments of the present application, the volume ratio of ethanol to DMF is (2 - 1):1.

[0021] According to some embodiments of the present application, the temperature of the mixing reaction is 90 - 110 °C; the reaction time is 11 - 13 hours; the reaction heating rate is 1 - 2 °C / min.

[0022] According to some embodiments of the present application, the MOF structure needs to be washed and centrifuged 2 - 3 times.

[0023] According to some embodiments of the present application, the drying temperature is 70 - 80 °C;

[0024] Preferably, the annealing temperature is: 400 - 450 °C; the annealing time is: 4 - 6 h.

[0025] According to another aspect of the present application, there is provided an application of the above-mentioned nano MOF framework material and / or the nano MOF framework material prepared by the above method in a MEMS gas sensor.

[0026] According to another aspect of the present application, there is provided an application of the above-mentioned nano MOF framework material and / or the nano MOF framework material prepared by the above method in a device for detecting acetone gas.

[0027] Compared with the prior art, the present application has at least the following beneficial effects:

[0028] In the present application, ZnO@In2O3 nanomaterials synthesized by a two-step method of hydrothermal method and calcination method using MIL-68(In) as a template have a rod-like morphology modified with nanoparticles.

[0029] The rod-shaped ZnO@In2O3 nanomaterials based on point modification in the present application can realize the regulation of the electrical properties, energy band structure and corresponding gas-sensing performance of the sensitive material, providing an effective idea for the development of VOCs gas sensors. In the present application, the MOF used as a template / precursor can be transformed into a more stable metal oxide. At the same time, the advantages of the MOF porous material such as a larger surface area, high porosity, adjustable morphology and uniform heteroatom doping will improve the sensitive performance of the material. In the present application, ZnO@In2O3 nanomaterials are synthesized by a hydrothermal method using MIL-68(In) as a template. Each component of the composite material has its own advantages and forms a cooperative relationship, thereby improving the gas-sensing performance to acetone.

[0030] The MEMS gas sensor based on the rod-shaped ZnO@In2O3 nanomaterials with point modification prepared in the present application shows excellent sensitivity, selectivity and low detection limit to acetone.

[0031] The MEMS gas sensor based on the rod-shaped ZnO@In2O3 nanomaterials with point modification in the present application integrates the gas sensor based on MOS materials into the MEMS platform, having the advantages of miniaturization, portability, low power consumption, etc. And its preparation method is simple, which can realize the miniaturization of the gas sensor, and the working temperature is low, which can reduce the power consumption of the gas sensor. Description of the Drawings

[0032] Figure 1 It is a schematic structural diagram of the ZnO@In2O3 nanomaterial of the exemplary embodiment of the present application.

[0033] Figure 2Schematic diagram of the MEMS gas sensor structure prepared with ZnO@In2O3 nanomaterials according to the exemplary embodiments of the present application.

[0034] Figure 3 SEM image, TEM image and HRTEM image of the ZnO@In2O3 nanomaterials according to the exemplary embodiments of the present application.

[0035] Figure 4 XRD patterns of pure In2O3 and ZnO@In2O3 nanomaterials.

[0036] Figure 5 Sensitivity of the sensor of the present application to 10 ppm acetone at different operating temperatures.

[0037] Figure 6 Sensitivity-concentration gradient characteristic curves of the embodiments of the present application and Comparative Example 1 to acetone gas at 190°C.

[0038] Figure 7 Selectivity of the sensor in Embodiment 1 of the present application to different gases at 190°C for 10 ppm.

[0039] Figure 8 Stability test of the sensor in Embodiment 1 of the present application to 10 ppm acetone at 190°C.

[0040] Figure 9 Response-recovery characteristic curve of the sensor in Embodiment 1 of the present application to 10 ppm acetone gas at 190°C. Detailed implementation manners

[0041] Next, the technical solutions of the present application will be clearly and completely described in conjunction with the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0042] It should be particularly noted that similar replacements and modifications made to the present application are obvious to those skilled in the art, and they are all considered to be included in the present application. Relevant personnel can obviously make changes or appropriate changes and combinations to the methods and applications described herein without departing from the content, spirit and scope of the present application to implement and apply the technology of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments.

[0043] Unless otherwise specified in the present application, all are carried out according to conventional conditions or conditions recommended by the manufacturer. For the raw materials or excipients used, and for the reagents or instruments used, if the manufacturer is not specified, they are all conventional products that can be obtained commercially.

[0044] The present application will be described in detail below.

[0045] Acetone is a common volatile organic compound and is widely used in different industrial fields. At the same time, it is harmful to human life and health. Therefore, it is very important to realize a sensitive and selective sensor to identify acetone.

[0046] The ZnO@In2O3 nanomaterial of the present application uses In2O3 as the framework and loads ZnO particles.

[0047] The ZnO@In2O3 nanomaterial synthesized by the hydrothermal method with MIL-68(In) as the template in the present application is prepared into ZnO@In2O3 nanomaterials with ZnO doped In2O3 according to different ratios, showing a rod-like structure modified with nanoparticles. It is used to improve the gas-sensing performance to acetone.

[0048] The ZnO@In2O3 nanomaterial prepared by doping In2O3 with ZnO in the present application forms an n-n heterojunction on the nanorods. At the same time, the rod-like structure modified with nanoparticles provides a larger specific surface area. The MEMS gas sensor based on the rod-like ZnO@In2O3 nanomaterial with point modification (such as Figure 2 ) shows excellent sensitivity to acetone. This good performance is attributed to the rod-like morphology modified with nanoparticles and abundant oxygen vacancies.

[0049] Figure 2 In (a): 1 is the interdigital electrode (materials such as Pt, Au, etc.), 2 is the insulating layer (materials such as silicon oxide, silicon nitride, etc.), 3 is the heating electrode, and 4 is the substrate (materials such as silicon wafers, glass, quartz, etc.). Figure 2 (b) is the size diagram of the interdigital electrode of the MEMS sensor. Figure 2 (c) is the physical diagram of the MEMS gas sensor, where 1 is the coated ZnO@In2O3 nanomaterial.

[0050] The rod-like morphology modified with nanoparticles increases the specific surface area and porosity of the material;

[0051] For n-type semiconductor oxides, when the MEMS gas sensor of the ZnO@In2O3 nanomaterial is placed in air, adsorbed oxygen O 2- is formed on the material surface through physical adsorption and chemical adsorption, and a depletion layer is formed on the material surface. When the sensor contacts an organic (VOCs) gas at a certain appropriate operating temperature, the gas molecules will be adsorbed on the sensor surface and react with the chemically adsorbed oxygen on the sensitive material surface, causing the captured electrons to be released to the sensitive material, reducing the width of the electron depletion layer and increasing the electron concentration, which is manifested as a decrease in the resistance value of the gas-sensitive element. Define the sensitivity S of the sensor, where Ra is the resistance between two electrodes of the sensor in air, R g is the resistance between two electrodes of the sensor after contacting the gas to be measured. For n-type semiconductor oxides in reducing gases, S = R a / R g , and in oxidizing gases, S = R g / R a .

[0052] The MEMS gas sensor based on MOS nanomaterials realizes the miniaturization of the gas sensor and has a low operating temperature, which can reduce the power consumption of the sensor.

[0053] Example 1

[0054] Preparation of ZnO@In2O3 nanomaterials in this application:

[0055] According to the ratio of In to Zn of 4:1, 0.3032 g (1.008 mmol) of In(NO3)3·4.5H2O, 0.074844 g (0.252 mmol) of Zn(NO3)2·6H2O, and 0.179 g (1.08 mmol) of 1,4-terephthalic acid (H2BDC) were successively added to 20 mL of ethanol and 20 mL of DMF (N,N-dimethylformamide), and stirred for 30 - 90 min until completely dissolved;

[0056] The obtained solution was transferred to a reaction kettle and heated in a muffle furnace at a heating temperature of 100 °C for 12 hours, with a heating rate of 1 °C / min. After natural cooling to room temperature, a precipitate was formed;

[0057] The generated precipitate was washed and centrifuged with ethanol and DMF multiple times to obtain a metal-organic framework structure; it was dried overnight in an oven at 80 °C to obtain a ZnO@In2O3 precursor;

[0058] The precursor was ground into powder, placed in a ceramic boat, and annealed at 450 °C for 6 hours to obtain dot-modified rod-shaped ZnO@In2O3 nanomaterials, denoted as ZnO@In2O3-1.

[0059] Preparation of MEMS gas sensor:

[0060] Take a MEMS device with interdigital electrodes, ultrasonically clean it with deionized water and ethanol, and blow it dry with a nitrogen gun;

[0061] Take an appropriate amount of ZnO@In2O3-1 nanomaterials and mix them with deionized water to form a uniform slurry, and spray the uniformly configured slurry on the surface of the MEMS device with a dispensing system to form a nanomaterial film;

[0062] After the nanomaterials are dried, the MEMS device coated with the nanomaterials is placed in a muffle furnace for heat treatment. The heat treatment temperature is 300 °C, and the holding time is 2 hours. After the cavity cools down to room temperature, it is taken out to obtain a MEMS gas sensor based on the dot-modified rod-shaped ZnO@In2O3-1 nanomaterials.

[0063] Example 2

[0064] The fabrication process of a MEMS gas sensor based on the dot-modified rod-shaped ZnO@In2O3-2 nanomaterials is as follows:

[0065] 0.2527 g (0.84 mmol) of In(NO3)3·4.5H2O, 0.12474 g (0.42 mmol) of Zn(NO3)2·6H2O, and 0.179 g (1.08 mmol) of 1,4-benzenedicarboxylic acid (H2BDC) are successively added to 20 mL of ethanol and 20 mL of DMF (N,N-dimethylformamide) according to the In:Zn ratio of 2:1, and stirred for 30 - 90 min until completely dissolved;

[0066] The resulting solution is transferred to a reaction kettle and heated in a muffle furnace at a heating temperature of 100 °C for 12 hours with a heating rate of 1 °C / min. After natural cooling to room temperature, a precipitate is formed; the formed precipitate is washed and centrifuged with ethanol and DMF multiple times to obtain a metal-organic framework structure, and then dried overnight in an oven at 80 °C to obtain a ZnO@In2O3 precursor;

[0067] The precursor is ground into powder, placed in a ceramic boat, and annealed at 450 °C for 6 hours to obtain the dot-modified rod-shaped ZnO@In2O3 nanomaterials, denoted as ZnO@In2O3-2.

[0068] Fabrication of the MEMS gas sensor:

[0069] The preparation method is the same as that in Example 1, except that the material is ZnO@In2O3-2.

[0070] Example 3

[0071] The fabrication process of a MEMS gas sensor based on the dot-modified rod-shaped ZnO@In2O3-3 nanomaterials is as follows:

[0072] 0.3248 g (1.08 mmol) of In(NO3)3·4H2O, 0.05346 g (0.18 mmol) of Zn(NO3)2·6H2O, and 0.179 g (1.08 mmol) of 1,4-benzenedicarboxylic acid (H2BDC) were successively added to 20 mL of ethanol and 20 mL of DMF (N,N-dimethylformamide) according to the In:Zn ratio of 6:1, and stirred for 30 - 90 min until completely dissolved;

[0073] The resulting solution was transferred to a reaction kettle and heated in a muffle furnace at a heating temperature of 100 °C for 12 hours with a heating rate of 1 °C / min. After natural cooling to room temperature, a precipitate was formed; the formed precipitate was washed and centrifuged with ethanol and DMF multiple times to obtain a metal-organic framework structure, and then dried overnight in an oven at 80 °C to obtain a ZnO@In2O3 precursor;

[0074] The precursor was ground into a powder, placed in a ceramic boat, and annealed at 450 °C for 6 hours to obtain a point-modified rod-shaped ZnO@In2O3 nanomaterial, denoted as ZnO@In2O3-3.

[0075] Fabrication of MEMS gas sensor:

[0076] The preparation method was the same as that in Example 1, except that the material was ZnO@In2O3-3.

[0077] Example 4

[0078] The fabrication process of a MEMS gas sensor based on a point-modified rod-shaped ZnO@In2O3-4 nanomaterial is as follows:

[0079] 0.3369 g (1.12 mmol) of In(NO3)3·4.5H2O, 0.04158 g (0.14 mmol) of Zn(NO3)2·6H2O, and 0.179 g (1.08 mmol) of 1,4-benzenedicarboxylic acid (H2BDC) were successively added to 20 mL of ethanol and 20 mL of DMF (N,N-dimethylformamide) according to the In:Zn ratio of 8:1, and stirred for 30 - 90 min until completely dissolved;

[0080] The resulting solution was transferred to a reaction kettle and heated in a muffle furnace at a heating temperature of 100 °C for 12 hours with a heating rate of 1 °C / min. After natural cooling to room temperature, a precipitate was formed; the formed precipitate was washed and centrifuged with ethanol and DMF multiple times to obtain a metal-organic framework structure, and then dried overnight in an oven at 80 °C to obtain a ZnO@In2O3 precursor;

[0081] The precursor was ground into powder, placed in a ceramic boat, and annealed at 450 °C for 6 hours to obtain the dot-modified rod-shaped ZnO@In2O3 nanomaterial, denoted as ZnO@In2O3-4.

[0082] Preparation of MEMS gas sensor:

[0083] The preparation method was the same as that in Example 1, except that the material was ZnO@In2O3-4.

[0084] Comparative Example 1

[0085] Preparation of gas sensor of In2O3 rod-shaped nanomaterial (without doping ZnO):

[0086] 0.179 g (1.08 mmol) of 1,4-benzenedicarboxylic acid (H2DBC) was added to 60 mL of DMF (N,N-dimethylformamide), and stirred vigorously to obtain a transparent solution;

[0087] The above solution was ultrasonically dispersed and dissolved in 0.481 g (1.26 mmol) of In(NO3)3·4.5H2O. The resulting solution was transferred to a reaction kettle and heated in a muffle furnace at a heating temperature of 100 °C for 4 hours with a heating rate of 1 °C / min; after natural cooling to room temperature, a white precipitate was formed. The white precipitate was washed and centrifuged three times with DMF and ethanol, and dried overnight in an oven at 80 °C to obtain the MIL-68(In) precursor;

[0088] The product was ground into powder, placed in a ceramic boat, and annealed at 450 °C for 4 hours. The finally obtained light yellow product was the In2O3 rod-shaped nanomaterial.

[0089] Preparation of MEMS gas sensor:

[0090] The preparation method was the same as that in Example 1, except that the material was In2O3 rod-shaped nanomaterial.

[0091] Comparative Example 2

[0092] Preparation of In2O3@ZnO nanomaterial with ZnO as the skeleton:

[0093] Preparation of In2O3@ZnO nanomaterial with ZnO as the skeleton:

[0094] 0.50 g of In(NO3)3·4.5H2O, 0.10 mL of 2% mass fraction dilute hydrochloric acid, and 0.10 mL of 30% mass fraction hydrogen peroxide solution were successively added to 20 mL of deionized water, and stirred at room temperature for 90 min until completely dissolved.

[0095] Using helium as the carrier gas (helium flow rate: 500 sccm), the obtained solution was subjected to ultrasonic spray pyrolysis at a pyrolysis temperature of 700 °C for 2 h. The obtained product was alternately washed 5 times with deionized water and ethanol, and then dried at 70 °C. After drying, the product was calcined at 600 °C for 4 h to obtain In2O3 microsphere powder; then 0.5 g of the obtained In2O3 microsphere powder and 2 g of PVP-K30 were successively added to 20 mL of deionized water and stirred for 90 min until completely dissolved. The obtained product was alternately washed 5 times with deionized water and ethanol; the obtained product was added to 20 mL of methanol solution containing 0.5 g of Zn(NO3)2·6H2O and 0.5 g of dimethylimidazole and allowed to stand at room temperature for 5 h. The obtained In2O3@ZIF-8 was alternately washed 5 times with deionized water and ethanol and then dried at 70 °C. After drying, the product was calcined at 600 °C for 4 h to obtain a core-shell structured In2O3@ZnO composite sensitive material with adjustable shell thickness.

[0096] Preparation method of gas sensor:

[0097] An appropriate amount of core-shell structured In2O3@ZnO composite nano-sensitive material and isopropanol were uniformly mixed at a mass ratio of 0.5:1 to form a coating slurry. A small amount of the slurry was dipped with a brush and coated on the outer surface of the ceramic tube to form a nano-material sensitive layer with a thickness of 20 μm, and the gold electrode was completely covered; the coated ceramic tube was sintered at 250 °C for 2 h, and a nickel-chromium alloy heating wire with a resistance value of 35 Ω was passed through the inside of the Al2O3 ceramic tube to provide heat, and then the gold electrode and the nickel-chromium alloy heating wire were welded to a general side-heated hexagonal tube socket through platinum wire leads; thus, a gas sensor of the core-shell structured In2O3@ZnO composite nano-sensitive material was obtained; the inner diameter of the ceramic tube was 0.7 mm, the outer diameter was 1.2 mm, and the length was 4.5 mm; the width of a single gold electrode was 0.45 mm, the thickness was 0.13 μm, and the distance between the two gold electrodes was 0.55 mm; the platinum wire lead led out from the gold electrode had a length of 5 mm.

[0098] Comparative Example 3

[0099] Preparation of ZIF-8 derivative ZnO sensitive material:

[0100] First, 0.5 g of Zn(NO3)2·6H2O and 0.5 g of dimethylimidazole were added to 20 mL of methanol solution and allowed to stand at room temperature for 6 h. The obtained product was alternately washed 5 times with deionized water and ethanol and then dried at 70 °C. After drying, the product was calcined at 600 °C for 4 h to obtain ZIF-8 derivative ZnO sensitive material.

[0101] Preparation method of gas sensor:

[0102] An appropriate amount of the ZIF-8 derivative ZnO sensitive material and isopropanol were uniformly mixed at a mass ratio of 0.5:1 to form a coating slurry. A small amount of the slurry was dipped with a brush and coated on the outer surface of the ceramic tube to form a sensitive layer of nanomaterial with a thickness of 20 μm, and it completely covered the gold electrode; the coated ceramic tube was sintered at 250 °C for 2 h, and a nickel-chromium alloy heating wire with a resistance value of 35 Ω was passed through the inside of the Al2O3 ceramic tube to provide heat, and then the gold electrode and the nickel-chromium alloy heating wire were welded to a general side-heated hexagonal tube socket through platinum wire leads; thus, a gas sensor of the ZIF-8 derivative ZnO sensitive material was obtained; the inner diameter of the ceramic tube was 0.7 mm, the outer diameter was 1.2 mm, and the length was 4.5 mm; the width of a single gold electrode was 0.45 mm, the thickness was 0.13 μm, and the distance between the two gold electrodes was 0.55 mm; the platinum wire leads led out from the gold electrode had a length of 5 mm.

[0103] Experimental Example

[0104] 1. The SEM images, TEM images, and HRTEM images of Examples 1-4 and Comparative Examples 1-3 were detected respectively.

[0105] As Figure 3 shown, Figure 3 (a) is the SEM image of Comparative Example 1, (f) is the SEM image of Comparative Example 2, (e) is the SEM image of Comparative Example 3, (b) is the SEM image of the Example, (c) is the TEM image of the Example, and (d) is the HRTEM image of the Example. The structures of Examples 2-3 are the same as that of Example 1, only the doping ratios are different.

[0106] It can be seen that the rod-like surface of the ZnO@In2O3 nanomaterial is modified by nanoparticles, which is doped ZnO. Figure 3 (d) depicts the lattice fringes with interplanar spacings of 0.1926 nm and 0.2901 nm, corresponding to the (102) crystal plane of ZnO and the (222) crystal plane of In2O3 respectively.

[0107] 2. The XRD patterns of the nanomaterials of Example 1 and Comparative Example 1 were detected respectively.

[0108] As Figure 4 shown, the X-ray powder (XRD) characterizations of the pure In2O3 nanomaterial and ZnO@In2O3 nanomaterial obtained in Comparative Example 1 and Example 1 show that the XRD peaks of the ZnO@In2O3 nanomaterial after annealing have the characteristic peaks of two materials, hexagonal zinc oxide and cubic indium oxide.

[0109] 3. The sensitivity of the sensor in Example 1 of the present application to 10 ppm acetone at different working temperatures was tested.

[0110] As Figure 5As shown, the optimal operating temperature of the sensor in Example 1 is 190°C, and it shows a good sensitivity of 11.03 to 10 ppm of acetone.

[0111] The sensor of this application can detect 10 ppm of acetone at 150 - 210°C. At 190°C, the gas sensor has the best response to acetone.

[0112] 4. Detect the sensitivity-concentration gradient characteristic curves of Examples 1 - 4 and Comparative Examples 1 - 3 of this application to acetone gas at the optimal temperature.

[0113] As Figure 6 shown, when all devices are at 190°C, it can be seen from the sensitivity-gas concentration function curve for 0.2 - 10 ppm of acetone that the sensitivity of the sensor increases with the increase of acetone concentration.

[0114] In Example 1, when the operating temperature is 190°C, the lower limit of acetone concentration that can be detected is 0.2 ppm, and the corresponding sensitivity is 1.963.

[0115] In Example 2, when the operating temperature is 190°C, the lower limit of acetone concentration that can be detected is 1 ppm, and the corresponding sensitivity is 1.04.

[0116] In Example 3, when the operating temperature is 190°C, the lower limit of acetone concentration that can be detected is 2 ppm, and the corresponding sensitivity is 1.01.

[0117] In Example 4, when the operating temperature is 190°C, the lower limit of acetone concentration that can be detected is 1 ppm, and the corresponding sensitivity is 0.99.

[0118] For Comparative Example 1, when the operating temperature is 190°C, the lower limit of acetone concentration that can be detected is 1 ppm, and the corresponding sensitivity is 0.66.

[0119] For Comparative Example 2, when the operating temperature is 190°C, the lower limit of acetone that can be detected is 5 ppm, and the corresponding sensitivity is 2.32. For Comparative Example 3, when the operating temperature is 190°C, the lower limit of acetone that can be detected is 5 ppm, and the corresponding sensitivity is 1.92. It can be seen that compared with the comparative examples, the sensors in the examples of this application have a lower detection limit and higher sensitivity.

[0120] 5. Detect the selectivity of the sensor of Example 1 of this application to different gases at the optimal operating temperature of 190°C for 10 ppm.

[0121] As Figure 7As shown, the bar chart of the responses of the sensor in Example 1 to 10 ppm of different gases (ethanol, nitric oxide, nitrogen dioxide, ammonia, acetone) at the optimal operating temperature of 190°C. It can be seen from the figure that the sensor in Example 1 has the highest sensitivity to 10 ppm of acetone, which is 11.0326.

[0122] 6. Stability test of the sensor prepared in Example 1 of this application for 10 ppm of acetone at 190°C.

[0123] As Figure 8 shown, the sensitivity of the sensor prepared in Example 1 to 10 ppm of acetone at the operating temperature of 190°C was tested for 30 days. The test was carried out in the atmospheric environment for 30 consecutive days. The sensitivity of the sensor remained relatively stable, and the fluctuation range was maintained within 80%. Thus, it can be seen that the sensor exhibits good stability.

[0124] 7. Response-recovery characteristic curve of the sensor prepared in Example 1 of this application for 10 ppm of acetone gas at 190°C.

[0125] As Figure 9 shown, the response-recovery curve of the sensor prepared in Example 1 at the operating temperature of 190°C. The sensor exhibits the best gas-sensing characteristics and has a fast response time of 50 s.

[0126] The description of the above embodiments is only used to help understand the method and its core idea of this application. It should be noted that for those of ordinary skill in the art of this technology, without departing from the principle of this application, several improvements and modifications can still be made to this application, and these improvements and modifications also fall within the protection scope of the claims of this application.

Claims

1. A nano MOF framework material, characterized in that It includes ZnO@In2O3 nanomaterials; Among them, In2O3 is in a nanorod structure, and ZnO is in nanoparticles; ZnO is dot-like loaded on the surface of In2O3; An n-n heterojunction is formed between ZnO and In2O3.

2. The nano-MOF framework material according to claim 1, wherein The particle size of the ZnO is 28.05 - 37.94 nm; The size of the In2O3 is length: 1700 - 1800 nm, width: 101 - 106 nm.

3. A preparation method of a nano MOF framework material, characterized in that, It includes: Adding In(NO3)3 hydrate, Zn(NO3)2·6H2O, and 1,4-benzenedicarboxylic acid into a solvent in proportion and mixing them for reaction to obtain a MOF structure; Drying to obtain a ZnO@In2O3 precursor; Grinding and annealing to obtain ZnO@In2O3 nanomaterials.

4. The preparation method according to claim 3, wherein The molar ratio of the In(NO3)3 hydrate to Zn(NO3)2·6H2O, calculated based on In and Zn, is (2 - 8):1; Preferably, it is 4:

1.

5. The preparation method according to claim 4, characterized in that, The solvent is a mixture of ethanol and DMF; Preferably, the volume ratio of the ethanol to DMF is (2 - 1):

1.

6. The preparation method according to claim 5, characterized in that, The temperature of the mixing reaction is: 90 - 110 °C; the reaction time is: 11 - 13 hours; the reaction heating rate is: 1 - 2 °C / min.

7. The preparation method according to claim 3, characterized in that, The MOF structure needs to be washed and centrifuged 2 - 3 times.

8. The preparation method according to claim 7, characterized in that, The drying temperature is: 70 - 80 °C; Preferably, the annealing temperature is: 400 - 450 °C; the annealing time is: 4 - 6 h.

9. Application of the nano MOF framework material as described in claim 1 or 2, and / or, the nano MOF framework material prepared by the method as described in any one of claims 3 - 8 in a MEMS gas sensor.

10. Application of the nano MOF framework material as described in claim 1 or 2, and / or, the nano MOF framework material prepared by the method as described in any one of claims 3 - 8 in a device for detecting acetone gas.

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