Au-coated CeO2 material based on MOF derivation as well as preparation method and application of Au-coated CeO2 material

Abstract

The invention discloses an Au (at) CeO2 material based on MOF derivation and a preparation method and application thereof, a Ce-based MOFs material (Ce-UiO-66) which is easy to synthesize, low in cost and high in selectivity and quick in response to H2S gas is designed and synthesized, the Ce-based MOFs material serves as a precursor, Au is loaded on the surface of the Ce-UiO-66 material, then heating treatment is conducted, Ce-UiO-66 is converted into a CeO2 material, and the CeO2 material is prepared. Meanwhile, the MOF is tightly combined with Au nanoparticles, so that the Au-coated CeO2 material derived based on the MOF is obtained. According to the invention, the MOF-derived Au-coated CeO2 material is used as a gas sensitive material for preparing a gas sensor for detecting H2S gas, the gas sensor shows high response speed and relatively high sensitivity, and the detection limit is as low as 5ppb.

Description

Technical Field

[0001] The present invention relates to the technical field of gas-sensitive materials, and in particular to a MOF-derived Au@CeO2 material and a preparation method and application thereof. Background Art

[0002] Hydrogen sulfide (H2S) gas is colorless, smells like rotten eggs and is highly toxic. It is the main component of pollutant gases in the current environment. Even in low concentrations of H2S gas, it can cause some negative effects on human health, including throat inflammation, coughing and eye inflammation. When the human body is exposed to high concentrations of H2S gas, the body's discomfort reaction is aggravated, which can lead to paralysis of the central nervous system, difficulty breathing, heart damage and even loss of consciousness. According to relevant health agencies, the human body's exposure limit to H2S gas within 8 hours is 10ppm, and the acceptable concentration range is 20-100ppb. Therefore, building a highly selective and sensitive ppb-ppm level H2S gas sensor is particularly critical for real-time evaluation of environmental quality and protection of human health.

[0003] At present, a variety of materials have been used to prepare semiconductor H2S gas sensors, such as metal oxides (CuO, ZnO, WO3 and Co3O4, etc.), metal oxide heterojunctions (CuO / NiO and In2O3 / ZnO) and metal oxide and graphene oxide composites (SnO2 / rGO). Although these materials have their own advantages, they also face some disadvantages, such as complex preparation process, low structural adjustability, poor selectivity, and slow response time.

[0004] Metal organic framework materials (MOFs) have the advantages of highly controllable pore structure, huge specific surface area, diverse functionalization strategies and good stability, so they are widely used in catalysis, sensing, gas storage and separation. However, studies have found that semiconductor H2S gas sensors prepared using MOFs-based materials often have poor sensitivity and long response time, poor mechanical properties, and due to limitations in sensor type, sensor material performance and signal processing, current gas sensors still face some challenges in terms of selectivity and rapid response. Therefore, it is urgent to use composite material strategies to improve the response performance of MOFs to gas and develop new sensing materials with high selectivity, high stability and high-speed response to meet various detection needs. Summary of the invention

[0005] In order to solve the above technical problems, the purpose of the present invention is to provide a MOF-derived Au@CeO2 material and its preparation method and application. The present invention designs and synthesizes a Ce-based MOFs material (Ce-UiO-66) that is simple to synthesize, low in cost, and has high selectivity and rapid response to H2S gas. It is used as a precursor to first load Au onto the surface of the Ce-UiO-66 material, and then, by heating treatment, the Ce-UiO-66 is converted into a CeO2 material, and at the same time, it is tightly combined with Au nanoparticles to obtain a MOF-derived Au@CeO2 material.

[0006] The above object of the present invention is achieved through the following technical solutions:

[0007] The first aspect of the present invention provides a method for preparing Au@CeO2 material based on MOF derivative, comprising the following steps:

[0008] (1) adding a reducing agent and a compound containing gold element to a Ce-UiO-66 dispersion to react and obtain Au@Ce-UiO-66; the compound containing gold element is selected from one or more of tetrachloroauric acid (HAuCl4), tetrachloroaurate, tetrabromoauric acid and tetrabromoaurate;

[0009] (2) The Au@Ce-UiO-66 obtained in step (1) is subjected to a primary calcination treatment in an air atmosphere at 300-350°C, and the calcined solid is subjected to a secondary calcination treatment in an inert atmosphere at 400-450°C to obtain the MOF-derived Au@CeO2 material.

[0010] The present invention utilizes a specific temperature annealing and an oxidation process to obtain a metal oxide material derived from MOF. The metal oxide material derived from MOF can usually maintain the framework structure of MOF, thereby effectively avoiding the problem of large-scale metal agglomeration, while also maintaining a large specific surface area and obtaining better semiconductor performance, and can be used as a gas-sensitive material for gas sensors.

[0011] The present invention adopts two calcination treatments. The purpose of the first calcination treatment is to calcine Au@Ce-UiO-66 in a relatively low temperature air atmosphere to partially oxidize it, and the second calcination treatment is to calcine it in a relatively high temperature inert atmosphere to completely oxidize it and prevent the skeleton of Ce-UiO-66 from being burned down.

[0012] Furthermore, in step (1), the tetrachloroaurate may be sodium tetrachloroaurate, potassium tetrachloroaurate, ammonium tetrachloroaurate, or the like.

[0013] Furthermore, in step (1), the tetrabromoaurate may be sodium tetrabromoaurate, potassium tetrabromoaurate, or the like.

[0014] Furthermore, in step (1), the concentration of Ce-UiO-66 in the Ce-UiO-66 dispersion is 1-5 mg / mL.

[0015] Furthermore, in step (1), the molar ratio of Ce-UiO-66 to the compound containing gold element is (15-25):1.

[0016] Furthermore, in step (1), the mass ratio of the reducing agent to the compound containing the gold element is 1:(0.3-0.6).

[0017] Furthermore, in step (1), the reducing agent is selected from one or more of oxalic acid, sulfuric acid, ferrous sulfate, sodium citrate, sodium nitrite and sodium borohydride.

[0018] Furthermore, in step (1), the preparation method of Ce-UiO-66 includes the following steps: dissolving the ligand in an organic solvent to obtain a ligand solution; dissolving the cerium salt in a solvent to obtain a cerium salt solution; mixing the ligand solution and the cerium salt solution, and reacting at 90-110°C to obtain the Ce-UiO-66.

[0019] Furthermore, the ligand is selected from one or more of terephthalic acid, 2-aminoterephthalic acid and disodium terephthalate.

[0020] Furthermore, the organic solvent is selected from one or more of N,N-dimethylformamide (DMF), methanol and ethanol.

[0021] Furthermore, the cerium salt may be ammonium cerium nitrate (Ce(NH4)2(NO3)6) or cerium sulfate (cerium sulfate tetrahydrate, Ce(SO4)2·4H2O), preferably ammonium cerium nitrate (Ce(NH4)2(NO3)6).

[0022] Furthermore, the solvent is selected from one or more of a mixed solvent of acetic acid and water, a mixed solvent of sodium acetate and water, and a mixed solvent of oxalic acid and water.

[0023] Furthermore, in step (2), the specific operation of the primary calcination treatment is: in an air atmosphere, heating to 300-350° C. at a heating rate of 1-3° C. / min, and then keeping the temperature for 20-30 min.

[0024] Furthermore, in step (2), the specific operation of the secondary calcination treatment is: in an inert atmosphere, heating to 400-450° C. at a heating rate of 1-3° C. / min, and then keeping the temperature for 20-30 min.

[0025] The second aspect of the present invention provides a MOF-derived Au@CeO2 material prepared by the method described in the first aspect.

[0026] The third aspect of the present invention provides an application of the MOF-derived Au@CeO2 material described in the second aspect, wherein the MOF-derived Au@CeO2 material is used as a gas-sensitive material for preparing a gas sensor.

[0027] Furthermore, it is particularly used for detecting H2S gas.

[0028] Furthermore, the detection limit of the H2S gas sensor is 5 ppb.

[0029] The fourth aspect of the present invention provides a gas sensor, comprising the MOF-derived Au@CeO2 material described in the second aspect.

[0030] Furthermore, the gas sensor is a MEMS gas sensor.

[0031] The MOF-derived Au@CeO2 material prepared by the present invention has good selectivity for H2S gas. At the same time, due to the composite of Au nanoparticles and CeO2, the Au@CeO2 gas-sensitive material exhibits a fast response speed and high sensitivity, which greatly improves the detection performance of Au@CeO2 for H2S gas.

[0032] Beneficial effects of the present invention:

[0033] The present invention designs and synthesizes a Ce-based MOFs material (Ce-UiO-66) which is simple to synthesize, low in cost, highly selective and rapidly responsive to H2S gas. Using Ce-UiO-66 as a precursor, Au is first loaded onto the surface of the Ce-UiO-66 material, and then the Ce-UiO-66 is converted into a CeO2 material by heating treatment. At the same time, the Ce-UiO-66 is tightly combined with Au nanoparticles to obtain an Au@CeO2 material derived from MOF.

[0034] The present invention uses Au@CeO2 material derived from MOF as a gas-sensitive material to prepare a gas sensor for detecting H2S gas. The gas sensor exhibits a fast response speed and high sensitivity, which greatly improves the detection performance of H2S gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a physical picture of the MEMS gas sensor.

[0036] Figure 2 This is the XRD pattern of Ce-UiO-66.

[0037] Figure 3 The XRD diagrams of CeO2 prepared in Comparative Example 1 and Au@CeO2 prepared in Example 1 are shown.

[0038] Figure 4 SEM images of Ce-UiO-66, CeO2 prepared in Comparative Example 1, and Au@CeO2 prepared in Example 1; wherein (a) and (b) are Ce-UiO-66, (c) and (d) are CeO2, and (e) and (f) are Au@CeO2.

[0039] Figure 5 The graphs show the response values ​​of CeO2 sensor, CeO2-Air sensor, Au@CeO2 sensor and Au@CeO2-Air sensor to 1ppm H2S gas at different working temperatures; (a) shows the response values ​​of CeO2-Air sensor and Au@CeO2-Air sensor to 1ppm H2S gas at 660-900℃, and (b) shows the response values ​​of CeO2 sensor and Au@CeO2 sensor to 1ppm H2S gas at 140-300℃.

[0040] Figure 6 The data graphs show the detection performance of CeO2 sensor for H2S gas; wherein, (a) is the response recovery curve of CeO2 sensor for 1-5ppm H2S gas at 260°C, (b) is the response-recovery cyclic test result graph of CeO2 sensor for 1ppm H2S gas, (c) is the linear fitting curve graph of response value and concentration of CeO2 sensor in the range of 1-5ppm H2S gas concentration, and (d) is the response-recovery curve graph of CeO2 sensor for 5ppm H2S gas.

[0041] Figure 7 The data graphs show the detection performance of Au@CeO2 sensor for H2S gas; wherein, (a) is the response recovery curve of Au@CeO2 sensor for 1-5ppm H2S gas at 260°C, (b) is the response-recovery cyclic test result graph of Au@CeO2 sensor for 1ppm H2S gas, (c) is the linear fitting curve graph of response value and concentration of Au@CeO2 sensor in the H2S gas concentration range of 1-5ppm, (d) is the response recovery curve graph of Au@CeO2 sensor for 10-50ppb H2S gas, (e) is the response recovery curve graph of Au@CeO2 sensor for 5ppb H2S gas, and (f) is the response-recovery curve graph of Au@CeO2 sensor for 5ppm H2S gas.

[0042] Figure 8 The selectivity test results of CeO2 sensor and Au@CeO2 sensor for different gases at 1 ppm are shown in Figure 2; (a) is the CeO2 sensor and (b) is the Au@CeO2 sensor. DETAILED DESCRIPTION

[0043] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. 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 related listed items.

[0044] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0045] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods, and the materials, reagents, etc. used are all available from commercial sources unless otherwise specified.

[0046] In the following examples and comparative examples, Ce-UiO-66 was prepared by the following method: 0.083g of terephthalic acid was dissolved in 2.3mL of N,N-dimethylformamide (DMF) to obtain a terephthalic acid solution; 0.274g of Ce(NH4)2(NO3)6 was dissolved in 0.5mL of deionized water and 1.5mL of acetic acid to obtain a cerium ammonium nitrate solution; the terephthalic acid solution and the cerium ammonium nitrate solution were fully dissolved by ultrasonic and then mixed, and the mixture was added to a 20mL gland bottle and sealed, and then placed in a 100°C oven for reaction for 24h. The gland bottle was taken out, cooled to room temperature, and the white solid was separated by centrifugation, washed twice with DMF, deionized water, and ethanol, and finally placed in a 60°C oven for drying for 6h.

[0047] The instrument used in the following embodiments is a MEMS gas sensor prepared by Suzhou Huiwen Nanotechnology Co., Ltd. using an ED09 micro-hotplate.

[0048] Example 1

[0049] The preparation method of Au@CeO2 material based on MOF derivative comprises the following steps:

[0050] (1) 100 mg Ce-UiO-66 was dispersed in 100 mL deionized water and stirred for 30 min using a magnetic stirrer at a speed of 300 r / min. Then 150 μL of HAuCl4 aqueous solution (Au 3+The concentration is 0.1mol / L), and the stirring is continued for 30min. Then, 5mL of NaBH4 aqueous solution (containing 10mg NaBH4, 100mgNaOH) is slowly added to the above mixture. The solution immediately changes color, showing the color of nano-Au at different particle sizes. After stirring for another 1h to fully react, the mixture turns purple. After standing for 1h, the lower precipitate is sucked and washed with deionized water 3 times by suction filtration to obtain Au@Ce-UiO-66.

[0051] (2) 500 mg Au@Ce-UiO-66 was heated to 350°C at a rate of 1°C / min in a muffle furnace air atmosphere, then kept at this temperature for 20 min and naturally cooled. Then, the partially oxidized Au@Ce-UiO-66 was heated to 450°C at a rate of 1°C / min in a tube furnace argon atmosphere, then kept at this temperature for 20 min and naturally cooled to obtain Au@CeO2.

[0052] Comparative Example 1

[0053] A method for preparing CeO2 material comprises the following steps:

[0054] 500 mg of Ce-UiO-66 was heated to 350°C at a rate of 1°C / min in a muffle furnace air atmosphere, then kept at this temperature for 20 minutes and then naturally cooled. Then, the partially oxidized Ce-UiO-66 was heated to 450°C at a rate of 1°C / min in a tube furnace argon atmosphere, then kept at this temperature for 20 minutes and then naturally cooled to obtain CeO2.

[0055] X-ray powder diffraction (XRD) tests were performed on Ce-UiO-66, CeO2 prepared in Comparative Example 1, and Au@CeO2 prepared in Example 1. Figure 2 and Figure 3 As shown, the diffraction peaks of Ce-UiO-66 are consistent with those in the literature, and the diffraction peaks of CeO2 and Au@CeO2 correspond to the PDF standard card, indicating that Au particles are doped into CeO2.

[0056] Ce-UiO-66, CeO2 prepared in Comparative Example 1, and Au@CeO2 prepared in Example 1 were characterized by scanning electron microscopy (SEM). Figure 4 As shown. Figure 4 As can be seen in (a) and (b), Ce-UiO-66 has a unique octahedral structure. After oxidation, the eight faces of CeO2 are concave, but the skeleton of Ce-UiO-66 is still retained, such as Figure 4 As shown in (c) and (d). Figure 4As can be seen in (e) and (f), the nano-Au particles are well attached to CeO2, and the overall skeleton of Ce-UiO-66 is still maintained.

[0057] Comparative Example 2

[0058] A method for preparing a MOF-derived Au@CeO2-Air material is basically the same as Example 1, except that in step (2), 500 mg of Au@Ce-UiO-66 is heated to 450°C at a rate of 1°C / min in an air atmosphere of a muffle furnace, then kept warm for 20 minutes and naturally cooled to obtain Au@CeO2-Air.

[0059] Comparative Example 3

[0060] A method for preparing a CeO2-Air material comprises the following steps:

[0061] 500 mg of Ce-UiO-66 was heated to 450°C at a rate of 1°C / min in an air atmosphere of a muffle furnace, then kept at this temperature for 20 min and cooled naturally to obtain CeO2-Air.

[0062] Application Examples

[0063] The micro hot plate chip manufactured based on MEMS processing technology is model S200-2. Figure 1 As shown, it is composed of a cantilever microstructure integrated with a micro heater and interdigital electrodes, with a plane size of 900μm×900μm, and can provide a heating voltage of 0.5-2.2V (temperature is approximately between 70-410℃). While providing a suitable operating temperature for the gas sensor, it detects the resistance change of the gas-sensitive material. Ethylene glycol is used as a solvent to prepare a glue solution of the gas-sensitive material, and the glue solution of the gas-sensitive material prepared above is sprayed on the substrate of the 200μm×200μm heating area of ​​the micro-hotplate chip by a dispensing method to form a film. After sintering at a temperature of 330℃ for 10 minutes, a MEMS gas sensor is obtained.

[0064] Test Case

[0065] The MEMS gas sensor prepared in the application example is used to detect gas, and the detection method is as follows:

[0066] The MEMS gas sensor is mounted on the ED09 micro hot plate, which is connected to the power workstation. The power supply and software are turned on, and the test system is run first. After the MEMS gas sensor stabilizes the baseline resistance in the air atmosphere, the gas to be tested is introduced, and the atmosphere is maintained for a certain period of time, and then the air atmosphere is restored to obtain a complete response-recovery curve.

[0067] The response values ​​of CeO2-based MEMS gas sensor (referred to as CeO2 sensor), CeO2-Air-based MEMS gas sensor (referred to as CeO2-Air sensor), Au@CeO2-based MEMS gas sensor (referred to as Au@CeO2 sensor) and Au@CeO2-Air-based MEMS gas sensor (referred to as Au@CeO2-Air sensor) to 1ppm H2S gas at different operating temperatures were tested, and the temperature ranges were 660-900℃ and 140-300℃ respectively. The test results are shown in Figure 2. Figure 5 As shown, Figure 5 (a) shows the response values ​​of CeO2-Air sensor and Au@CeO2-Air sensor to 1ppm H2S gas at an operating temperature of 660-900℃. CeO2-Air sensor and Au@CeO2-Air sensor respond only at higher temperatures (660-900℃), and the response values ​​change irregularly with increasing temperature, indicating that the CeO2-Air and Au@CeO2-Air materials obtained by calcining Ce-UiO-66 and Au@Ce-UiO-66 in a non-inert atmosphere have extremely high resistance, and the resistance can only be detected at high temperatures. Moreover, the response value of the sensor to 1ppm H2S gas is low, which is not suitable for practical applications. Figure 5 (b) shows the response values ​​of CeO2 sensor and Au@CeO2 sensor to 1ppm H2S gas at the working temperature of 140-300℃. As the temperature increases, the response values ​​of the sensor to H2S gas increase first and then decrease. The response values ​​of CeO2 sensor and Au@CeO2 sensor at 260℃ are the largest, which are 1.64 and 2.82 respectively. The response of Au@CeO2 sensor to H2S gas is significantly higher than that of CeO2 sensor. The optimal working temperature of both is the same, which is 260℃. Next, a series of tests will be conducted on CeO2 sensor and Au@CeO2 sensor at 260℃.

[0068] The detection performance of CeO2 sensor for H2S gas is studied. The detection results are as follows Figure 6 shown. Figure 6 (a) is the response recovery curve of CeO2 sensor to H2S gas of different concentrations at 260℃. The response values ​​of CeO2 sensor to 1, 2, 3, 4 and 5ppm H2S gas are 1.61, 1.74, 2.09, 2.29 and 2.57 respectively. As the concentration of H2S gas increases, the response value of the sensor also gradually increases. Figure 6 (b) is the response-recovery cyclic test result of the CeO2 sensor to 1ppm H2S gas. The sensor has relatively good response and recovery characteristics to 1ppm H2S gas in five cycles, and the baseline resistance is not much different. Figure 6 (c) is the linear fitting curve of the response value and concentration of the CeO2 sensor in the range of 1-5ppm H2S gas concentration. The response value and concentration of the sensor are fitted by the equation y=0.247x+1.319. The linear correlation coefficient R 2 =0.9812, which is greater than 0.9, so the CeO2 sensor has excellent linearity. Figure 6 (d) is the response-recovery curve of CeO2 sensor to 5ppmH2S gas, from which its response time t can be analyzed. res =12s, recovery time is t rec =246s, with extremely fast response time.

[0069] The detection performance of Au@CeO2 sensor for H2S gas was studied. The detection results are as follows Figure 7 shown. Figure 7 (a) is the response recovery curve of Au@CeO2 sensor to H2S gas of different concentrations at 260℃. The response values ​​of Au@CeO2 sensor to 1, 2, 3, 4 and 5ppm H2S gas are 2.99, 3.81, 5.66, 6.41 and 7.69 respectively. With the increase of H2S gas concentration, the response value of the sensor also gradually increases. The response at all concentrations is higher than that of CeO2 sensor, which reflects the advantage of Au doping in improving the gas detection sensitivity of the sensor. Figure 7 (b) is the response-recovery cyclic test result of Au@CeO2 sensor to 1ppm H2S gas. The sensor has very good response and recovery characteristics to 1ppm H2S gas in five cycles, and the baseline resistance is stable with almost no difference. The stability is better than that of CeO2 sensor. Figure 7 (c) is the linear fitting curve of the response value and concentration of the Au@CeO2 sensor in the range of 1-5ppm H2S gas concentration. The response value and concentration of the sensor are fitted by the equation y=1.2x+1.712. The linear correlation coefficient R 2 =0.9791, which is greater than 0.9, so the Au@CeO2 sensor has excellent linearity. Figure 7 (d) is the response recovery curve of Au@CeO2 sensor to 10-50ppb H2S gas. The response values ​​of Au@CeO2 sensor to 10, 20, 30, 40 and 50ppb H2S gas are 1.03, 1.07, 1.09, 1.12 and 1.14 respectively. It can be seen from the figure that its response recovery curve to 10-50ppb H2S gas has a good regularity. Figure 7(e) is the response recovery curve of the Au@CeO2 sensor to 5ppb H2S gas. It can be observed that it still has a certain response to 5ppb H2S gas. This shows that the sensor has an extremely low detection limit. In comparison, the CeO2 sensor has no response at 50ppb H2S gas concentration. Figure 7 (f) is the response-recovery curve of Au@CeO2 sensor to 5ppm H2S gas, from which its response time t can be analyzed. res =11s, recovery time is t rec =488s, with extremely fast response time, higher than CeO2 sensor.

[0070] Figure 8 The selectivity test results of CeO2 sensor and Au@CeO2 sensor for different gases at 1ppm are shown in the figure. The test gases are ammonia, nitrogen dioxide, formaldehyde, and H2S. Figure 8 The response values ​​of CeO2 sensor and Au@CeO2 sensor to different gases at 1 ppm are shown, indicating that both CeO2 and Au@CeO2 sensors have high selectivity for H2S gas, and the selectivity of Au@CeO2 sensor for H2S gas is more prominent.

[0071] Obviously, the above embodiments of the present invention are only examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Those skilled in the art should understand that other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. An application of Au@CeO2 material derived from MOF, characterized in that: The Au@CeO2 material derived from MOF is used as a gas-sensitive material to prepare a gas sensor; The preparation method of the Au@CeO2 material based on MOF derivative comprises the following steps: (1) adding a reducing agent and a compound containing gold element to a Ce-UiO-66 dispersion to react and obtain Au@Ce-UiO-66; the compound containing gold element is selected from one or more of tetrachloroauric acid, tetrachloroaurate, tetrabromoauric acid and tetrabromoaurate; (2) The Au@Ce-UiO-66 obtained in step (1) is subjected to a primary calcination treatment in an air atmosphere at 300-350°C, and the calcined solid is subjected to a secondary calcination treatment in an inert atmosphere at 400-450°C to obtain the MOF-derived Au@CeO2 material.

2. The use according to claim 1, characterized in that: The gas sensor is used to detect hydrogen sulfide gas.

3. The use according to claim 2, characterized in that: The detection limit of the gas sensor is 5 ppb.

4. The use according to claim 1, characterized in that: In step (1), the concentration of Ce-UiO-66 in the Ce-UiO-66 dispersion is 1-5 mg / mL.

5. The use according to claim 4, characterized in that: In step (1), the molar ratio of Ce-UiO-66 to the compound containing gold element is (15-25):

1.

6. The use according to claim 1, characterized in that: In step (1), the mass ratio of the reducing agent to the compound containing the gold element is 1:(0.3-0.6).

7. The use according to claim 1, characterized in that: In step (1), the preparation method of Ce-UiO-66 includes the following steps: dissolving the ligand in an organic solvent to obtain a ligand solution; dissolving the cerium salt in a solvent to obtain a cerium salt solution; mixing the ligand solution and the cerium salt solution, and reacting at 90-110°C to obtain the Ce-UiO-66.

8. The use according to claim 7, characterized in that: The ligand is selected from one or more of terephthalic acid, 2-aminoterephthalic acid and disodium terephthalate.

9. A gas sensor, characterized in that: Includes MOF-derived Au@CeO2 materials; The preparation method of the Au@CeO2 material based on MOF derivative comprises the following steps: (1) adding a reducing agent and a compound containing gold element to a Ce-UiO-66 dispersion to react and obtain Au@Ce-UiO-66; the compound containing gold element is selected from one or more of tetrachloroauric acid, tetrachloroaurate, tetrabromoauric acid and tetrabromoaurate; (2) The Au@Ce-UiO-66 obtained in step (1) is subjected to a primary calcination treatment in an air atmosphere at 300-350°C, and the calcined solid is subjected to a secondary calcination treatment in an inert atmosphere at 400-450°C to obtain the MOF-derived Au@CeO2 material.

10. The gas sensor according to claim 9, characterized in that The gas sensor is a MEMS gas sensor.

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