Mixed-ligand metal-organic framework material, gas sensor and preparation method

Abstract

The present invention relates to the technical field of gas sensors, and in particular to a gas sensor based on a mixed-ligand metal-organic framework material, and a preparation method thereof. The present invention uses a silicon wafer with an oxide layer as a device substrate, on which a vapor-deposited titanium-gold interdigital electrode is attached. The metal-organic framework material particles with mixed ligands are dispersed on the interdigital electrode by a drop-coating method to form a sensor device, and the detection of volatile organic compounds with adjustable signals is realized by regulating the ratio of the two ligands in the metal-organic framework material. The present invention realizes the transformation of semiconductor characteristics based on the regulation of the mixed-ligand ratio, improves the detection accuracy, and has important application prospects in the detection method of volatile organic compounds in exhaled breath.

Description

Technical Field

[0001] The present invention relates to the technical field of gas sensors, and particularly to a mixed-ligand metal-organic framework material-based gas sensor and a preparation method thereof. Background Art

[0002] Volatile organic compounds have the characteristics of low boiling point and high vapor pressure, are volatile under normal temperature and pressure, and are accompanied by strong reactivity. Volatile organic compounds are not only widely used in industrial production, but also some volatile organic compounds in human exhaled breath can be used as biomarkers for related diseases (for example, ethanol in exhaled breath can be used as a biomarker for liver diseases, and acetone can be used as a biomarker for diabetic ketoacidosis). Detecting the content of volatile organic compounds in the production environment and exhaled breath is of great significance for safe production and rapid screening and diagnosis. Therefore, it is crucial to develop a volatile organic compound sensor that can be used at room temperature, has a rapid response, and is easy to operate.

[0003] In addition to metal oxides and multifunctional composite materials, metal-organic framework materials have a large specific surface area, customizable pore structures, flexibly adjustable metal centers and ligand compositions, and a wide range of conductance distributions, and are one of the high-performance functional materials that can be applied to gas sensors.

[0004] In addition to the intrinsic pore structure, the adjustable chemical composition of the mixed-ligand metal-organic framework material can affect the conductance and semiconductor properties of the material, thereby affecting important sensing parameters such as the sensitivity, selectivity, response / recovery time of the gas sensor, and achieving the purpose of optimizing the sensing performance. However, due to the limitations of the microscopic chemical structure, the ligands are single during the synthesis process of the current metal-organic framework materials, and it is difficult to achieve the mixing and regulation of ligands in a crystal structure, so that the performance of the synthesized sensor is single and the performance of the gas sensor cannot be adjusted.

[0005] Tetrathiafulvalene tetracarboxylic acid (abbreviated as [TTF]) and nickel dithienyl tetracarboxylic acid (abbreviated as [NiS4]) have similar molecular structures, which is conducive to the formation of isomorphic metal-organic framework materials. At the same time, they also have very different physical and chemical properties. For example, tetrathiafulvalene and its derivatives are typical p-type semiconductors, while nickel dithienyl has been proven to be an n-type semiconductor. Different physical and chemical properties of the ligands will lead to significantly different sensing performances. Summary of the Invention

[0006] The purpose of the present invention is to provide a mixed-ligand metal-organic framework material-based gas sensor and a preparation method thereof, provide a ligand mixing method, realize the transformation of semiconductor properties based on the regulation of the mixed-ligand ratio, and improve the detection accuracy.

[0007] To solve the above technical problems, the technical solution of the present invention is as follows:

[0008] In a first aspect, a metal-organic framework material based on mixed ligands is provided, where tetrathiafulvalene tetracarboxylic acid TTF and / or nickel dithiolene tetracarboxylic acid NiS4 ligands are mixed in a crystal structure, and the components of the metal-organic framework material are Mn2[TTF] x [NiS4] 1-x , where 0 ≤ x ≤ 1.

[0009] In a second aspect, a preparation method of a metal-organic framework material based on mixed ligands is provided, and the steps include:

[0010] A100: Dissolve a quantitative amount of manganese nitrate tetrahydrate in a mixed solvent containing ethanol and deionized water, and ultrasonically dissolve it to obtain a metal salt solution;

[0011] A200: Dissolve a mixed ligand obtained by mixing tetrathiafulvalene tetracarboxylic acid TTF ligand and nickel dithiolene tetracarboxylic acid NiS4 ligand in a certain ratio in a mixed solvent containing N,N-dimethylformamide and ethanol, and ultrasonically dissolve it to obtain a ligand solution;

[0012] A300: After mixing the metal salt solution and the ligand solution, carry out a heating reaction and then naturally cool to room temperature;

[0013] A400: Rinse with N,N-dimethylformamide and ethanol to obtain the metal-organic framework material Mn2[TTF] x [NiS4] 1-x , where 0 ≤ x ≤ 1.

[0014] Furthermore, in step A100, in the mixed solvent containing ethanol and deionized water, the volume ratio of ethanol to deionized water is 1:1; in the metal salt solution, the mass ratio of manganese nitrate tetrahydrate to the mixed solvent ranges from 1:100 to 3:1000.

[0015] Furthermore, in step A200, in the mixed solution containing N,N-dimethylformamide and ethanol, the volume ratio of N,N-dimethylformamide to ethanol is 3:1; in the ligand solution, the mass ratio of the mixed ligand to the mixed solvent ranges from 1:20 to 1:60.

[0016] Furthermore, when heating in step A300, first heat at 60 °C for 1 hour, then raise the temperature to 80 °C and heat for 24 hours, and naturally cool to room temperature after the reaction ends.

[0017] In a third aspect, a gas sensor based on a metal-organic framework material with mixed ligands is provided. The metal-organic framework material synthesized by the above preparation method of the metal-organic framework material with mixed ligands is coated on the interdigital electrodes of the gas sensor.

[0018] Further, the gas sensor includes: a substrate silicon wafer, titanium-gold interdigital electrodes, a metal-organic framework material, and an aluminum-silicon alloy wire; wherein, the substrate silicon wafer has an oxide layer, the titanium-gold interdigital electrodes are deposited on the substrate silicon wafer, the metal-organic framework material has a mixed ligand ratio and is micro-dispersed on the interdigital electrodes by a drop-coating method to form a sensor device, and the aluminum-silicon alloy wire is used to connect the interdigital electrodes to an external circuit.

[0019] Further, the substrate silicon wafer is a square with a side length of 2.5 cm; the width between the fingers of the interdigital electrodes is 2 μm, and the number of fingers is 10; the length of the aluminum-silicon alloy wire is 1 - 3 cm.

[0020] Fourthly, a preparation method of a gas sensor based on a mixed-ligand metal-organic framework material is provided, and the steps include:

[0021] S100: Prepare a silicon wafer with adhered interdigital electrodes from a silicon wafer with an oxide layer, specifically including:

[0022] Mask the interdigital electrode pattern on the silicon wafer with an oxide layer by ultraviolet lithography, and sequentially deposit metal titanium and metal gold on the silicon wafer by electron beam evaporation. Among them, metal titanium is used as an adhesion layer, and metal gold is used as an electrode material; place the evaporated silicon wafer in acetone, soak it, and perform ultrasonic treatment to remove the metal layer outside the interdigital electrode area, and then rinse the silicon wafer with the interdigital electrodes with acetone and isopropyl alcohol in sequence, and dry it with high-purity nitrogen to obtain a silicon wafer with adhered interdigital electrodes;

[0023] S200: Disperse the metal-organic framework material with adjustable ligand ratio in the form of microparticles on the interdigital electrodes by a drop-coating method to obtain a uniformly distributed metal-organic framework material-based micro-nano device, specifically including:

[0024] Place the silicon wafer with interdigital electrodes obtained in step S100 in a plasma generator and clean it with oxygen plasma, and then heat it;

[0025] Disperse the metal-organic framework material with adjustable ligand ratio in ethanol and perform ultrasonic treatment, and then suck the ethanol dispersion containing the metal-organic framework material with a pipette and drop it on the interdigital electrodes. After the ethanol volatilizes, a uniformly distributed metal-organic framework material-based micro-nano device is obtained; among them, the metal-organic framework material is prepared by the above preparation method of the mixed-ligand metal-organic framework material;

[0026] S300: Connect the source and drain electrodes of the micro-nano device in step S200 to an external circuit through an aluminum-silicon alloy wire to prepare a gas sensor based on a mixed-ligand metal-organic framework material.

[0027] In a fifth aspect, there is provided an application of a gas sensor prepared by the method for preparing a gas sensor based on a mixed-ligand metal-organic framework material as described above in detecting two volatile organic compounds, namely ethanol and acetone.

[0028] The present invention has the following beneficial effects:

[0029] First, based on the similarity and differences in physical and chemical properties between tetrathiafulvalene tetracarboxylic acid (TTF) and nickel dithiolene tetracarboxylic acid (NiS4) structures, the present invention provides a ligand mixing method to achieve control of the ligand ratio and regulation and optimization of the sensing performance for volatile organic compounds; realizing the transformation of the semiconductor properties of the metal-organic framework material based on the regulation of the mixed-ligand ratio, and precisely customizing specific properties such as the sensitivity, detection limit, power consumption, and response / recovery time of the sensor.

[0030] Second, the synthesis method of the metal-organic framework material is simple, the preparation of the sensor device is easy, the cost of a single sensor is low, the power consumption of the sensor is low, and it has high economic value and mass production value;

[0031] Third, a series of metal-organic framework materials with different ligand ratios can be synthesized in batches to form a sensing array, strengthening the pattern recognition of volatile organic compounds;

[0032] Fourth, the gas sensor of the present invention belongs to the category of room-temperature sensors, has little requirement for the test environment, and still has good sensing response in the detection of simulated exhaled breath; it has important application prospects in the detection method of volatile organic compounds in exhaled breath. Description of the Drawings

[0033] Figure 1 It is a flow chart of the method for preparing the metal-organic framework material in the embodiment of the present invention;

[0034] Figure 2 It is a powder XRD pattern of five ligand ratios in the mixed-ligand metal-organic framework material in the embodiment of the present invention;

[0035] Figure 3 It is a schematic structural diagram of the gas sensor based on the mixed-ligand metal-organic framework material in the embodiment of the present invention;

[0036] Figure 4 It is a flow chart of the method for preparing the gas sensor based on the mixed-ligand metal-organic framework material in the embodiment of the present invention;

[0037] Figure 5 It is a response-recovery curve graph of the gas sensors prepared with five typical ligand ratios in the mixed-ligand metal-organic framework material for different concentrations of ethanol and acetone at room temperature;

[0038] Figure 6Response correction curves of gas sensors prepared with five typical ligand ratios in mixed-ligand metal-organic framework materials for different concentrations of ethanol and acetone at room temperature;

[0039] Figure 7 Comparison chart of the response performance of gas sensors prepared with typical ligand ratios in mixed-ligand metal-organic framework materials for 50 ppm ethanol;

[0040] Figure 8 Response-recovery curves of Mn2[NiS4] for different concentrations of ethanol under the condition of simulated exhaled breath as the carrier gas.

[0041] Reference signs: 1, substrate silicon wafer; 2, oxide layer; 3, interdigital electrode; 4, metal-organic framework material; 5, aluminum-silicon alloy wire; 6, external circuit; 601, digital source meter; 602, power supply. Detailed implementation manners

[0042] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0043] Please refer to Figure 1 and Figure 2 , the present invention provides a preparation method of a mixed-ligand-based metal-organic framework material, and the steps include:

[0044] A100: Dissolve a quantitative amount of manganese nitrate tetrahydrate in a mixed solvent containing ethanol and deionized water, and ultrasonically dissolve to obtain a metal salt solution;

[0045] A200: Dissolve a mixed ligand obtained by mixing tetrathiafulvalene tetracarboxylic acid TTF ligand and nickel dithiolene tetracarboxylic acid NiS4 ligand in a certain ratio in a mixed solvent containing N,N-dimethylformamide and ethanol, and ultrasonically dissolve to obtain a ligand solution;

[0046] A300: Mix the metal salt solution and the ligand solution, carry out a heating reaction, and then naturally cool to room temperature;

[0047] A400: Rinse with N,N-dimethylformamide and ethanol to obtain the mixed-ligand metal-organic framework material Mn2[TTF] x [NiS4] 1-x , where 0 ≤ x ≤ 1.

[0048] The following will specifically describe each step in Figure 1 .

[0049] In step A100, in the mixed solvent containing ethanol and deionized water, the volume ratio of ethanol to deionized water is 1:1; in the metal salt solution, the mass ratio of manganese nitrate tetrahydrate to the mixed solvent ranges from 1:100 to 3:1000.

[0050] In the embodiment of this example, step A100 is: Dissolve 6 mg of manganese nitrate tetrahydrate in 1.25 mL of a mixed solution containing ethanol (0.625 mL) and deionized water (0.625 mL), and ultrasonically dissolve for 15 minutes.

[0051] In step A200, in the mixed solution containing N,N-dimethylformamide and ethanol, the volume ratio of N,N-dimethylformamide to ethanol is 3:1; in the ligand solution, the mass ratio of the mixed ligand to the mixed solvent ranges from 1:20 to 1:60.

[0052] In the embodiment of this example, step A200 is: Dissolve 3 mg of a mixed ligand of a certain proportion of tetrathiafulvalene tetracarboxylic acid ligand and nickel dithiolene tetracarboxylic acid ligand in 0.12 mL of a mixed solution containing N,N-dimethylformamide (0.09 mL) and ethanol (0.03 mL), and ultrasonically dissolve for 15 minutes. In the embodiment of this example, five specific embodiments are given for the mixed ligand, namely embodiments a, b, c, d, and e. The mass ratio of tetrathiafulvalene tetracarboxylic acid TTF to nickel dithiolene tetracarboxylic acid NiS4 is different in each embodiment. In embodiment a, the mass ratio of TTF to NiS4 is 3:0. In embodiment b, the mass ratio of TTF to NiS4 is 2.25:0.75. In embodiment c, the mass ratio of TTF to NiS4 is 1.5:1.5. In embodiment d, the mass ratio of TTF to NiS4 is 0.75:2.25. In embodiment e, the mass ratio of TTF to NiS4 is 0:3.

[0053] In the embodiment of this example, step A300 is specifically: Mix the metal salt solution and the ligand solution, shake well, transfer to a 15 mL hard pressure-resistant glass tube, place it in a constant temperature oven, first heat at 60 °C for 1 hour, then raise the temperature to 80 °C and heat for 24 hours. After the reaction is completed, naturally cool to room temperature, and filter to obtain a solid sample.

[0054] In the embodiment of this example, step A400 is specifically: Rinse three times with N,N-dimethylformamide, and then rinse three times with ethanol to obtain the pure metal-organic framework material Mn2[TTF] x [NiS4] 1-x (0 ≤ x ≤ 1). According to the above five embodiments with different mass ratios, the obtained metal-organic framework materials are:

[0055] Embodiment a: Mn2[TTF]

[0056] Example b: Mn2[TTF] 0.78 [NiS4] 0.22

[0057] Example c: Mn2[TTF] 0.49 [NiS4] 0.51

[0058] Example d: Mn2[TTF] 0.24 [NiS4] 0.76

[0059] Example e: Mn2[NiS4]

[0060] The obtained metal-organic framework material was stored in 4 mL of ethanol solvent.

[0061] The present invention also provides a metal-organic framework material based on mixed ligands, which is prepared by the preparation method of the above steps A100 - A400.

[0062] Refer to Figure 3 , the present invention also provides a gas sensor based on a metal-organic framework material with mixed ligands, which is prepared by the preparation method shown in Figure 4 . The gas sensor includes a substrate silicon wafer 1, a titanium-gold interdigital electrode 3, a metal-organic framework material 4, and an aluminum-silicon alloy wire 5; wherein, an oxide layer 2 is provided on the substrate silicon wafer 1, the titanium-gold interdigital electrode 3 is deposited on the substrate silicon wafer 1, the metal-organic framework material 4 is in a mixed ligand ratio and is micro-dispersed on the interdigital electrode 3 by a drop-coating method to form a sensor device, and the aluminum-silicon alloy wire 5 is used to connect the interdigital electrode 3 to an external circuit 6.

[0063] In this embodiment, the oxide layer 2 is silicon oxide. The external circuit 6 includes a digital source meter 601 and a power supply 602 connected to each other. In this example embodiment, the substrate silicon wafer 1 is a square with a side length of 2.5 cm; the finger width of the interdigital electrode 3 is 2 μm, and the number of interdigital fingers is 10; the length of the aluminum-silicon alloy wire 5 is 1 - 3 cm.

[0064] Refer to Figure 4 , the present invention also provides a preparation method of a gas sensor based on a metal-organic framework material with mixed ligands, and the steps include:

[0065] S100: Prepare a silicon wafer with an attached interdigital electrode from a silicon wafer with an oxide layer, specifically including:

[0066] Use a spin coater to evenly coat the photoresist on a silicon wafer with a 275 nm oxide layer. The spin coater rotates at 600 revolutions per minute for 6 seconds in the first stage and 3000 revolutions per minute for 30 seconds in the second stage. Subsequently, place the silicon wafer with the photoresist on a heating stage and heat it at 170 °C for 10 minutes. Pattern the interdigital electrode on the mask on the silicon wafer through ultraviolet lithography technology. Use electron beam evaporation to sequentially deposit 25 nm of metal titanium and 50 nm of metal gold on the silicon wafer. Among them, the interdigital electrode is used to connect the metal-organic framework material and the external circuit; metal titanium serves as an adhesion layer, and metal gold serves as an electrode material.

[0067] Place the evaporated silicon wafer in acetone, soak it, and perform ultrasonic treatment to remove the metal layer outside the interdigital electrode area. Then, rinse the silicon wafer with the interdigital electrode with acetone and isopropyl alcohol successively, and dry it with high-purity nitrogen to obtain a silicon wafer with an adhered interdigital electrode.

[0068] S200: Disperse the metal-organic framework material particles with adjustable ligand ratio on the interdigital electrode by drop coating to obtain a uniformly distributed metal-organic framework material-based micro-nano device, which specifically includes:

[0069] Place the silicon wafer with the interdigital electrode obtained in step S100 in a plasma generator and clean it with oxygen plasma for 15 minutes. Then, place it on a heating stage at 50 °C for standby.

[0070] Disperse the mixed metal-organic framework material with adjustable ligand ratio in ethanol and perform ultrasonic treatment for 10 minutes. Then, use a pipette to aspirate 2 μL of the ethanol dispersion containing the metal-organic framework material and drop it on the interdigital electrode. After the ethanol evaporates, a uniformly distributed metal-organic framework material-based micro-nano device is obtained; among them, the metal-organic framework material is prepared and synthesized by the above metal-organic framework material preparation method.

[0071] S300: Use a wire bonder to connect the source and drain electrodes of the micro-nano device in step S200 to the external circuit through aluminum-silicon alloy wires to fabricate a gas sensor based on the mixed ligand metal-organic framework material.

[0072] The present invention also provides an application of the above gas sensor based on the mixed ligand metal-organic framework material in detecting two volatile organic compounds, ethanol and acetone.

[0073] The working principle is as follows: When the gas sensor based on the mixed-ligand metal-organic framework material is placed in an inert carrier gas, nitrogen, the conductance value of the sensor is stable and there is no response. When volatile organic compounds, ethanol and acetone molecules, are introduced, charge transfer occurs between the ethanol and acetone molecules and the metal-organic framework, changing the conductance of the sensor. Changes in the ratio of tetrathiafulvalene tetracarboxylic acid and nickel dithiolene tetracarboxylic acid in the mixed ligand will cause a transformation in the semiconductor properties of the synthesized metal-organic framework material, resulting in sensing signals with different directions, sensitivities, and detection limits. We define the response of the sensor as where G1 is the conductance of the sensor when ethanol and acetone are introduced, and G0 is the conductance of the sensor in nitrogen.

[0074] The present invention provides a mixed channel in which tetrathiafulvalene tetracarboxylic acid and nickel dithiolene tetracarboxylic acid are mixed in a crystal structure, realizing the transformation of the semiconductor properties of the metal-organic framework material based on the regulation of the mixed-ligand ratio, and precisely customizing specific performances such as the sensitivity, detection limit, power consumption, and response / recovery time of the sensor.

[0075] The present invention uses a silicon wafer with an oxide layer as the device substrate, on which evaporated titanium-gold interdigital electrodes are attached. Metal-organic framework material particles with a specific ligand ratio are dispersed on the interdigital electrodes by drop coating to form a sensor device. By regulating the ratio of the two ligands in the metal-organic framework material, the detection of volatile organic compounds with adjustable signals is achieved, and the detection limit of the prepared sensor can reach 5 ppm. In addition, the sensor device of the present invention has a simple structure, low power consumption, small volume, and a shielding effect on water vapor, and has important application prospects in the detection method of volatile organic compounds in exhaled breath.

[0076] Refer to Figures 5 - 8 , and the performance evaluation is as follows:

[0077] When using the gas sensor based on the mixed-ligand metal-organic framework material of the present invention to detect two volatile organic compounds, ethanol and acetone, as Figure 5 shown, the responses of the sensor all increase with the increase in gas concentration. The minimum detection limits of Mn2[TTF] and Mn2[TTF] 0.78 [NiS4] 0.22 for ethanol and acetone reach 5 ppm and 20 ppm respectively. Among them, when the ratio of nickel dithiolene tetracarboxylic acid reaches 51%, the sensing direction of the volatile organic compounds changes, proving the transformation of the mixed-ligand metal-organic framework material from a p-type semiconductor to an n-type semiconductor and its regulation of the sensing signal. Figure 6 shows the calibration curves of the responses of the gas sensor based on the mixed-ligand metal-organic framework material with respect to the changes in the concentrations of ethanol and acetone. All curves show excellent linear relationships within the test range, and the response gradually increases with the increase in the ratio of nickel dithiolene tetracarboxylic acid in the mixed ligand.Figure 7 Shows a summary of the sensing performance of a gas sensor based on a mixed-ligand metal-organic framework material with a typical ratio. The response and recovery times of the sensor decrease as the proportion of nickel dithiolene tetracarboxylic acid in the mixed ligand increases. The response time and recovery time of Mn2[NiS4] to 50 ppm ethanol reach 32.3 and 23.4 seconds, respectively. In addition, Mn2[TTF] 0.78 [NiS4] 0.22 exhibits the lowest theoretical detection limit, and Mn2[NiS4] exhibits the lowest power consumption and the best water vapor shielding effect. The above results demonstrate the non-linear modulation effect of the ligand synergy of the mixed-ligand metal-organic framework material on the sensing performance.

[0078] Of particular importance is that Figure 8 it is shown that the gas sensor based on the mixed-ligand metal-organic framework material has no response to carbon dioxide, and also exhibits comparable sensing performance in simulated exhaled gas with 80% humidity as when nitrogen is used as the carrier gas, demonstrating the application prospect of the gas sensor based on the mixed-ligand metal-organic framework material in the detection of volatile organic compounds in exhaled breath.

[0079] Parts not involved in the present invention are the same as or implemented by the prior art.

[0080] The above content is a further detailed description of the present invention in combination with specific embodiments, and it cannot be determined that the specific implementation of the present invention is limited only to these descriptions. For those of ordinary skill in the technical field to which the present invention pertains, without departing from the concept of the present invention, several simple deductions or substitutions can still be made, which should all be regarded as belonging to the protection scope of the present invention.

Claims

1. A metal-organic framework material based on mixed ligands, characterized in that The preparation steps include: A100: Dissolve 6 mg of manganese nitrate tetrahydrate in 1.25 mL of a mixed solution containing 0.625 mL of ethanol and 0.625 mL of deionized water, and ultrasonically dissolve for 15 minutes; A200: Dissolve a mixed ligand of 3 mg of tetrathiafulvalene tetracarboxylic acid ligand and nickel dithiolene tetracarboxylic acid ligand in 0.12 mL of a mixed solution containing 0.09 mL of N,N-dimethylformamide and 0.03 mL of ethanol, and ultrasonically dissolve for 15 minutes; the mass ratio of tetrathiafulvalene tetracarboxylic acid ligand to nickel dithiolene tetracarboxylic acid ligand in the aforementioned mixed ligand is 2.25:0.75, 1.5:1.5, or 0.75:2.25; A300: Mix the metal salt solution and the ligand solution, shake well, place it in a 15 mL hard pressure-resistant glass tube, and place it in a constant temperature oven. First, heat it at 60 °C for 1 hour, then raise the temperature to 80 °C and heat for 24 hours. After the reaction is completed, naturally cool it to room temperature, and filter to obtain a solid sample; A400: Rinse with N,N-dimethylformamide and ethanol to obtain a metal-organic framework material of the following mixed ligand: Mn2[TTF] 0.78 [NiS4] 0.22 、Mn2[TTF] 0.49 [NiS4] 0.51 or Mn2[TTF] 0.24 [NiS4] 0.76 。 2. Gas sensor based on a mixed-ligand metal-organic framework material, characterized in that: The interdigital electrodes of the gas sensor are coated with the metal-organic framework material based on the mixed ligand described in claim 1.

3. The gas sensor based on the hybrid ligand metal-organic framework material according to claim 2, characterized in that: The gas sensor includes: a substrate silicon wafer, titanium-gold interdigital electrodes, a metal-organic framework material, and an aluminum-silicon alloy wire; wherein, the substrate silicon wafer has an oxide layer, the titanium-gold interdigital electrodes are evaporated and attached to the substrate silicon wafer, the metal-organic framework material is a mixed ligand and is microscopically dispersed on the interdigital electrodes by a drop-coating method to form a sensor device, and the aluminum-silicon alloy wire is used to connect the interdigital electrodes to an external circuit.

4. The gas sensor based on the hybrid ligand metal-organic framework material according to claim 3, characterized in that: The substrate silicon wafer is a square with a side length of 2.5 cm; the interdigital width of the interdigital electrodes is 2 μm, and the number of interdigital fingers is 10; the length of the aluminum-silicon alloy wire is 1 - 3 cm.

5. Preparation method of gas sensor based on hybrid ligand metal-organic framework material, characterized in that: The steps include S100: Prepare a silicon wafer with attached interdigital electrodes from a silicon wafer with an oxide layer, specifically including: Mask the interdigital electrode pattern on the silicon wafer with an oxide layer by ultraviolet lithography, and sequentially evaporate metal titanium and metal gold on the silicon wafer by electron beam evaporation. Among them, metal titanium is used as an adhesion layer, and metal gold is used as an electrode material; place the evaporated silicon wafer in acetone, soak and ultrasonically treat it to remove the metal layer outside the interdigital electrode area, and rinse the silicon wafer with attached interdigital electrodes with acetone and isopropyl alcohol successively, and dry it with high-purity nitrogen to obtain a silicon wafer with attached interdigital electrodes; S200: Microscopically disperse the metal-organic framework material on the interdigital electrodes by a drop-coating method to obtain a uniformly distributed metal-organic framework material-based micro-nano device, specifically including: Place the silicon wafer with interdigital electrodes obtained in step S100 in a plasma generator and clean it with oxygen plasma, and then heat it; Disperse the metal-organic framework material in ethanol and ultrasonically treat it, and then suck the ethanol dispersion containing the metal-organic framework material with a pipette and drop-coat it on the interdigital electrodes. After the ethanol volatilizes, a uniformly distributed metal-organic framework material-based micro-nano device is obtained; among them, the metal-organic framework material uses the metal-organic framework material based on the mixed ligand described in claim 1; S300: Connect the source and drain electrodes of the micro-nano device in step S200 to an external circuit through aluminum-silicon alloy wires to fabricate a gas sensor based on a hybrid-ligand metal-organic framework material.

6. Application of the gas sensor based on the hybrid-ligand metal-organic framework material prepared by the preparation method according to claim 5 in detecting two volatile organic compounds, ethanol and acetone.

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