Pd@in2o3-nio nanocomposite based on a MOF derivative, preparation method and application

Abstract

The application discloses a MOF-derived Pd@In2O3-NiO nanocomposite material, a preparation method and application, relates to the technical field of gas detection, and mainly comprises the following steps: synthesizing an In / Ni bimetallic organic framework hierarchical porous nanoflower structure through a cation exchange method, and distributing Pd on the surface of the hierarchical porous nanoflower structure. The application realizes high selectivity response to hydrogen at room temperature, thereby avoiding the risk of accidents caused by introduction of a heat source due to high working temperature, reducing the power consumption of the sensor, further expanding the application range and applicable scenarios of the metal oxide semiconductor hydrogen sensor, and providing a feasible new method for intrinsic safety type room temperature hydrogen sensor design.

Description

Technical Field

[0001] This invention relates to the field of gas detection technology, and in particular to MOF-derived Pd@In2O3-NiO nanocomposite materials, their preparation methods, and applications. Background Technology

[0002] Hydrogen (H2), with its renewable and environmentally friendly advantages, is considered an ideal clean energy source for the future. However, its widespread application faces significant safety challenges: on the one hand, hydrogen's low density (approximately 0.090 g / L) and small molecular dynamics diameter (approximately 0.289 nm) make it prone to leakage; on the other hand, it is colorless and odorless, making leaks undetectable by sensory means. Furthermore, hydrogen is highly explosive when exposed to fire at concentrations of 4.0% to 75% (by volume) in the air, posing an extremely high risk. Therefore, developing reliable hydrogen sensors is of irreplaceable importance for the safety detection and monitoring of the entire hydrogen energy industry chain.

[0003] Current technologies for hydrogen detection mainly encompass electrochemical, semiconductor, thermal conductivity, optical, and quartz crystal microbalances (QCM). However, each of these technologies faces its own limitations in widespread adoption: electrochemical sensors suffer from short lifespans and high costs; optical sensors rely on precision optical paths, resulting in complex and costly maintenance; and thermal conductivity sensors are constrained by manufacturing processes, making cost reduction difficult. Among these, metal-oxide-semiconductor (MOS) sensors, due to their high sensitivity, low cost, and fast response, are commercially mature and widely used in environmental monitoring, industrial safety, and other fields. However, due to limitations in their sensing mechanisms, semiconductor gas sensors still suffer from high operating temperatures, susceptibility to ignition sources, high power consumption, and poor selectivity, significantly limiting their application in complex industrial scenarios. Furthermore, traditional MOS materials exhibit poor selectivity for hydrogen. The deepening application of hydrogen energy has exposed the limitations of traditional sensors in terms of adaptability: they often struggle to simultaneously achieve room temperature operation, high selectivity, and intrinsic safety. Therefore, in the face of the future development of hydrogen energy, the research and development of intrinsically safe sensors that can operate stably at room temperature and accurately identify hydrogen has important scientific research value and is also a core infrastructure construction project for the safe and stable development of the hydrogen energy industry ecosystem. Summary of the Invention

[0004] Based on the technical problems existing in the background technology, this invention proposes a MOF-derived Pd@In2O3-NiO nanocomposite material, its preparation method and application, which achieves a high selective response to hydrogen at room temperature, thereby avoiding the risk of accidents caused by the introduction of heat sources at high operating temperatures, and reducing the power consumption of the sensor. This further expands the application range and applicable scenarios of metal oxide semiconductor hydrogen sensors, and provides a feasible new method for the design of intrinsically safe room temperature hydrogen sensors.

[0005] This invention proposes a MOF-derived Pd@In2O3-NiO nanocomposite material, which synthesizes a hierarchical porous nanoflower structure of In / Ni bimetallic organic framework via cation exchange method, with Pd distributed on the surface of the porous nanoflower structure.

[0006] This invention proposes a method for preparing MOF-derived Pd@In2O3-NiO nanocomposites, the nanocomposites of which are as described above, and the method steps are as follows:

[0007] S1: Nickel source and terephthalic acid are mixed and reacted in a solvent. The product after reaction is dried and sintered to obtain Ni-MOF composite material.

[0008] S2: Dissolve polyvinylpyrrolidone in ethanol, then add Ni-MOF composite material, stir evenly at room temperature, let stand, and obtain intermediate product by centrifugation, washing and drying;

[0009] S3: Dissolve the intermediate product in ethanol, then add an indium source to react and obtain a bimetallic In / Ni-MOF composite material;

[0010] S4: Palladium source and bimetallic In / Ni-MOF composite material were dissolved in ethanol and reacted under ultraviolet light. After reaction, the mixture was centrifuged, washed, dried and sintered to obtain MOF-derived Pd@In2O3-NiO nanocomposite material.

[0011] Preferably, the nickel source in S1 is Ni(NO3)2·6H2O; the solvent is a mixed solution of ethylene glycol and DMF.

[0012] Preferably, the molar ratio of nickel source to terephthalic acid in S1 is 1:2-4; the reaction conditions are: temperature 150-200℃, time 12-18h; the sintering conditions are: temperature 600-700℃, sintering time 2-3h, heating rate 2-4℃ / min.

[0013] Preferably, the polyvinylpyrrolidone in S2 has a molecular weight of K-30; the mass ratio of polyvinylpyrrolidone to Ni-MOF composite material is 2.5-3:1.

[0014] Preferably, the indium source in S3 is In(NO3)3·4.5H2O; the molar ratio of indium source to nickel source is 0.1-0.3:1.

[0015] Preferably, the reaction conditions in S3 are: after mixing and stirring evenly, let stand at 60-80℃ for 12-24 hours.

[0016] Preferably, the palladium source in S4 is PdCl2; the molar ratio of palladium source to nickel source is 0.01-0.1:1.

[0017] Preferably, the reaction conditions in S4 are: under ultraviolet light irradiation with a wavelength of 250-260nm and a power of 15-19W, the reaction is carried out at room temperature for 12-24 hours; the sintering conditions are: temperature of 600-700℃, sintering time of 2-3 hours, and heating rate of 2-4℃ / min.

[0018] This invention proposes an application of MOF-derived Pd@In2O3-NiO nanocomposite material in a hydrogen sensor, the nanocomposite material being described above; the hydrogen sensor can detect hydrogen at room temperature.

[0019] Beneficial technical effects of the present invention:

[0020] This invention utilizes the porous properties of metal-organic framework (MOF) materials to uniformly immobilize Pd catalytic elements. The resulting MOF-derived Pd@In₂O₃ / NiO metal oxide semiconductor gas-sensitive material, obtained through carbonization and sintering, possesses a hierarchical porous structure template based on an In / Ni bimetallic organic framework. This material exhibits advantages such as uniform Pd catalytic distribution and a large specific surface area. By utilizing Pd doping to enhance the specific response to hydrogen, a high selectivity for hydrogen at room temperature is achieved, providing a feasible method for designing intrinsically safe room-temperature hydrogen sensors. Specifically:

[0021] (1) The material synthesis method is simple, the preparation process is clear, and the repeatability is strong. The overall preparation process of gas-sensitive materials has the advantages of being simple and flexible.

[0022] (2) The In / Ni bimetallic organic framework hierarchical porous structure template was used as the substrate material for synthesis. On the one hand, the ultra-high specific surface area provides more binding sites for oxygen adsorption on the material surface; on the other hand, the high porosity and the hierarchical porous structure of the material with both micropores and mesopores further promote the adsorption of oxygen molecules on the material surface and the diffusion inside the material.

[0023] (3) Due to the uniform doping of the catalytic metal Pd, the sensor’s response performance to hydrogen is greatly improved, which can promote the decomposition of surface adsorbed oxygen. The resulting chemically adsorbed oxygen ions will be distributed in large quantities on the surface of the semiconductor material due to their overflow effect, and react with more target gas molecules, thereby increasing the sensor’s initial resistance in air and improving the response value to hydrogen.

[0024] The method of this invention has the advantages of simple sensor preparation process and high selective response to low concentration hydrogen at room temperature, and has broad prospects in the future to meet the huge demand for intrinsically safe hydrogen sensors in multiple scenarios. Attached Figure Description

[0025] Figure 1 This is a flowchart of the preparation method of MOF-derived Pd@In2O3-NiO composite material proposed in this invention.

[0026] Figure 2 The images shown are scanning electron microscope (SEM) images proposed in this invention; (a) is the Ni-MOF composite material prepared in Example 1 before sintering, (b) is the bimetallic In / Ni-MOF composite material prepared in Example 2 before sintering, (c) is the Pd-modified bimetallic In / Ni-MOF composite material prepared in Example 3 before sintering, (d) is the MOF-derived NiO composite material prepared in Example 1 after sintering, (e) is the MOF-derived In2O3 / NiO composite material prepared in Example 2 after sintering, and (f) is the Pd-modified MOF-derived In2O3 / NiO composite material prepared in Example 3 after sintering.

[0027] Figure 3 The images are transmission electron microscope (TEM) images of the Pd-modified MOF-derived In2O3 / NiO composite material prepared in Example 3 of this invention; where (a) is a transmission electron microscope image of the Pd-modified MOF-derived In2O3 / NiO nanoflowers, and (b) is a high-resolution transmission electron microscope image of the Pd-modified MOF-derived In2O3 / NiO nanoflower monomer particles.

[0028] Figure 4 XRD data of the MOF-derived NiO, In2O3 / NiO and Pd@In2O3 / NiO composite materials prepared in this invention;

[0029] Figure 5 The nitrogen adsorption-desorption curves proposed in this invention are shown in the inset (the inset is the corresponding BJH pore size distribution curve); where (a) is the MOF-derived NiO composite material prepared in Example 1, and (b) is the Pd-modified MOF-derived In2O3 / NiO composite material prepared in Example 3.

[0030] Figure 6 The dynamic response-recovery curve of the hydrogen sensor prepared by the present invention using MOF-derived NiO, In2O3 / NiO and Pd@In2O3 / NiO composite materials at room temperature (25°C) to 200 ppm hydrogen is shown.

[0031] Figure 7 The graphs show the dynamic response / recovery characteristics of the hydrogen sensor prepared by the present invention using MOF-derived In2O3 / NiO and Pd@In2O3 / NiO composite materials at room temperature (25°C); where (a) represents 20-400 ppm and (b) represents 500-2000 ppm.

[0032] Figure 8 The concentration-response linear fitting curve of the hydrogen sensor prepared by the present invention using MOF-derived In2O3 / NiO and Pd@In2O3 / NiO composite materials at room temperature (25°C) is shown.

[0033] Figure 9 The graph shows the repeatability test of the hydrogen sensor prepared by the present invention using MOF-derived In2O3 / NiO and Pd@In2O3 / NiO composite materials at room temperature (25°C) for 200 ppm hydrogen.

[0034] Figure 10 This is a graph showing the long-term stability test of the hydrogen sensor prepared by the present invention using MOF-derived In2O3 / NiO and Pd@In2O3 / NiO composite materials at room temperature (25°C) against 200 ppm hydrogen for 35 days.

[0035] Figure 11 The graph shows the response value of the hydrogen sensor prepared by the present invention using MOF-derived In2O3 / NiO and Pd@In2O3 / NiO composite materials to 200ppm hydrogen at room temperature (25°C) as a function of relative humidity.

[0036] Figure 12 This is a selective test diagram of the hydrogen sensor prepared by the present invention using MOF-derived NiO, In2O3 / NiO and Pd@In2O3 / NiO composite materials at room temperature (25°C). Detailed Implementation

[0037] The present invention will be further explained below with reference to specific embodiments.

[0038] The scanning electron microscope involved in this invention is a GeminiSEM450 field emission scanning electron microscope from Zeiss GmbH, Germany; the transmission electron microscope is a TalosF200X from FEI; the XRD experiment is performed using a Smartlab multifunctional rotating target X-ray diffractometer; ultraviolet light can be achieved by using a xenon lamp source with an external 365nm filter or a 365nm LED ultraviolet light bead source.

[0039] Example 1

[0040] Weigh 0.29 g of Ni(NO3)2·6H2O and 0.34 g of terephthalic acid (C8H6O4), and add them sequentially to a 100 mL beaker containing a mixed solution of ethylene glycol and DMF in a 1:1 volume ratio. Stir at 550 rpm for 8 hours at room temperature until a homogeneous suspension is obtained. Transfer the homogeneous suspension to a 100 mL hydrothermal reactor with a polytetrafluoroethylene liner and react at 160 °C for 12 hours.

[0041] After centrifuging the obtained solid precipitate for 10 min to purify it, it was washed with deionized water and ethanol. The washing and centrifugation were repeated 3 times to remove impurities. The purified solid product was placed in a vacuum oven at 70℃ and dried for 12 h to obtain the dried precursor.

[0042] The dried precursor was transferred into a quartz boat and placed in a muffle furnace for direct sintering in air atmosphere. Specifically, it was annealed at 650°C for 2 hours with a heating rate of 2°C / min to obtain a MOF-derived NiO olive-green product (Ni-MOF composite material). Figure 2 As shown.

[0043] Figure 2 Part (a) is a scanning electron microscope (SEM) image of the Ni-MOF prepared in this embodiment. Figure 2 Part (d) shows the scanning electron microscope (SEM) image of the MOF-derived NiO prepared in this embodiment. It can be found that the structure of the nanospheres and nanoflowers of NiO and MOF-derived NiO materials obtained after direct sintering has collapsed significantly, mainly due to the decomposition and carbonization of the organic ligands in the MOF at high temperature.

[0044] Example 2

[0045] Weigh 0.5 g of PVP (K30) and add it to a beaker containing 40 mL of anhydrous ethanol. Sonicate for 5 minutes and stir at room temperature for 30 minutes. Add the Ni-MOF composite material synthesized in Example 1 to the well-stirred ethanol solution of PVP. Stir at 550 rpm for 1 hour at room temperature, then allow to stand at room temperature for 12 hours. Centrifuge the separated solutions at 9000 rpm and wash the precipitate obtained by centrifugation multiple times with deionized water and ethanol (ethanol as the final washing agent). Place the precipitate in a vacuum drying oven and dry at 70°C for 8 hours. The dried product is the Ni-MOF pretreated with PVP.

[0046] The obtained solid was added to a beaker containing 40 mL of anhydrous ethanol. After stirring at room temperature for 30 minutes, a certain amount of In(NO3)3·4.5H2O was added, and stirring was continued at room temperature for 1 hour. The homogeneous reaction solution was then allowed to stand for 24 hours at a constant temperature of 60°C to allow Ni to precipitate. 2+ With In 3+ Complete the cation exchange reaction.

[0047] After cation exchange, the layered solution was purified by centrifugation for 10 min, and then washed with ethanol. The washing and centrifugation were repeated 3 times to remove impurities. The purified solid product was placed in a vacuum oven at 70℃ and dried for 12 h to obtain the dried bimetallic In / Ni-MOF.

[0048] The dried precursor was transferred into a quartz boat and placed in a muffle furnace for direct sintering in air atmosphere. Specifically, it was annealed at 650°C for 2 hours with a heating rate of 2°C / min to obtain MOF-derived In2O3 / NiO nanocomposite material.

[0049] Figure 2 Part (b) is a scanning electron microscope (SEM) image of the bimetallic In / Ni-MOF prepared in this embodiment before sintering. Figure 2 Part (e) shows the scanning electron microscope (SEM) image of the MOF-derived In₂O₃ / NiO composite material prepared in this embodiment after sintering. It can be seen that the MOF-derived In₂O₃ / NiO material maintains a relatively regular nanoflower morphology after sintering, thus indicating that Ni… 2+ With In 3+ The cation exchange that occurs can, to some extent, inhibit the collapse of the hierarchical porous structure of MOF-based materials during high-temperature sintering, which is beneficial to the maintenance of the hierarchical porous structure after sintering.

[0050] Example 3

[0051] Reference Figure 1 Palladium chloride powder (PdCl2) and the unsintered bimetallic In / Ni-MOF synthesized in Example 2 were weighed according to a palladium source to nickel source molar ratio of 0.05:1 and added to a beaker containing 40 mL of anhydrous ethanol. The mixture was stirred at room temperature for 1 hour to obtain a uniformly dispersed reaction solution.

[0052] The resulting homogeneous solution was irradiated with ultraviolet light at a fixed wavelength of 254 nm and reacted at 16 W for 12 hours. The reaction was carried out at room temperature, and the mixture was stirred at a constant speed of 300 rpm throughout the reaction to ensure uniform modification of the Pd element on the In / Ni-MOF surface.

[0053] After purification by centrifugation for 10 min following UV-assisted modification, the solution was washed with ethanol and the washing and centrifugation were repeated 3 times to remove impurities. The purified solid product was then dried in a vacuum oven at 70℃ for 12 h to obtain dried Pd-doped bimetallic In / Ni-MOF.

[0054] The dried precursor was transferred into a quartz boat and placed in a muffle furnace for direct sintering in air atmosphere. Specifically, it was annealed at 650°C for 2 hours with a heating rate of 2°C / min to obtain Pd-doped MOF-derived In2O3 / NiO nanocomposite material.

[0055] Figure 2 Part (c) is a scanning electron microscope (SEM) image of the Pd-modified bimetallic In / Ni-MOF prepared before sintering in this embodiment. Figure 2 Part (f) is a scanning electron microscope (SEM) image of the sintered Pd-modified MOF-derived In2O3 / NiO composite material prepared in this embodiment. It can be seen that, compared with the MOF-derived In2O3 / NiO prepared in Example 2, due to the modification of Pd element, the MOF-derived Pd@In2O3 / NiO material nanoflowers prepared in this embodiment further exhibit a hollow nanoflower structure, and adhesion begins to occur between the nanoflower particles, resulting in an overall increase in surface density.

[0056] Figure 3 The image shows a transmission electron microscope (TEM) image of the Pd-modified MOF-derived In2O3 / NiO composite material prepared in this embodiment. The image reveals that the nanoflower material has a distinct hollow structure, which is beneficial for increasing the specific surface area of ​​the material. To characterize the chemical composition of the nanoflowers, the entire nanoflower monomer was selected as the imaging region for high-resolution transmission electron microscopy (HRTEM) testing. Inverse Fourier transform (IFFT) analysis of the obtained images revealed lattice spacings of 0.244 nm, 0.151 nm, 0.295 nm, and 0.225 nm, corresponding to the NiO (111), NiO (220), In2O3 (222), and Pd (111) crystal planes, respectively.

[0057] The composite materials prepared in Examples 1-3 were subjected to XRD analysis, and the results are as follows: Figure 4 As shown. The characteristic diffraction peaks located at ca.2θ=38.28°, 43.30° and 63.22° correspond to the (111), (200) and (220) crystal planes of NiO, respectively, indicating that all materials are NiO with a trigonal rhombohedral structure. The standard PDF is JCPDS no.44-1159. Furthermore, the characteristic diffraction peaks located at ca.2θ=21.60°, 30.51°, 35.78°, 50.95° and 60.62° correspond to the (211), (222), (400), (440) and (622) crystal planes of In2O3, respectively, indicating that the In2O3 in the MOF-derived In2O3 / NiO and Pd@In2O3 / NiO samples are all cubic manganese iron oxide structures. The standard PDF is JCPDS no.06-0416

[126] . Furthermore, the characteristic diffraction peaks located near ca.2θ = 40.12° and 40.66° correspond to the (111) and (200) crystal planes of Pd, respectively, and the standard PDF is JCPDS no. 87-0654. No other impurity peaks were observed in the figure, and all diffraction peaks had high intensity, indicating that the samples in this series have good purity and crystallinity.

[0058] The nitrogen adsorption-desorption curves of the composite materials prepared in Examples 1 and 3 were measured, and the results are as follows: Figure 5 As shown, the MOF-derived NiO material prepared in Example 1 exhibited significant structural collapse during high-temperature sintering, while the MOF-derived Pd@In2O3 / NiO material prepared in Example 3 maintained a well-preserved pore structure. Specifically, according to IUPAC classification, due to the inconsistency between nitrogen adsorption and desorption curves and the absence of a clear saturation adsorption plateau, the BET curve of the MOF-derived NiO material prepared in Example 1 can be classified as a Type IV isothermal adsorption characteristic, with a hysteresis loop type of H3. This indicates that the pore structure in the sample is mainly mesoporous and macroporous. In contrast, the BET curves of the MOF-derived Pd@In2O3 / NiO material prepared in Example 3 all exhibited Type I isothermal adsorption characteristics, indicating that the main pore composition types in both groups of samples are primarily micropores and mesopores.

[0059] Take 30 mg of the composite material prepared in Examples 1-3 respectively, mix with 1 mL of terpineol, and sonicate for 1 h to disperse evenly. Take 25 μL of the dispersion solution and drop it onto the gold interdigital electrode, and place it in an oven at 70 °C to dry for 12 h. Place the dried gold interdigital electrode with the above composite material into a muffle furnace, heat it to 400 °C at a heating rate of 5 °C / min in air atmosphere and sinter for 4 h, and then let it cool naturally to room temperature. After scraping off the excess covering material at both ends of the sintered gold interdigital electrode, place it in an air environment at 350 °C for 5 days to obtain a hydrogen sensor.

[0060] The dynamic response-recovery curves of the hydrogen sensor prepared using the composite materials of Examples 1-3 at room temperature (25°C) to 200 ppm hydrogen are shown below. Figure 6 As shown in the figure, the hydrogen sensor prepared with the MOF-derived In2O3 / NiO composite material of Example 2 has a response time of 192.8 s and a recovery time of 237.5 s for 200 ppm hydrogen, while the hydrogen sensor prepared with the MOF-derived Pd@In2O3 / NiO composite material of Example 3 has a response time of t... res and recovery time t rec The response and recovery times were 100.2 s and 168.5 s, respectively, which are 48.03% and 29.05% shorter than those of the hydrogen sensor prepared from MOF-derived In₂O₃ / NiO composite material. This indicates that the introduction of the noble Pd metal can effectively reduce the response and recovery times of the metal oxide semiconductor material to hydrogen. This demonstrates that the MOF-derived Pd@In₂O₃ / NiO nanocomposite material proposed in this invention has advantages for room temperature hydrogen detection.

[0061] Figure 7The dynamic response / recovery characteristic curves of hydrogen sensors prepared by the MOF-derived In₂O₃ / NiO composite material of Example 2 and the MOF-derived Pd@In₂O₃ / NiO composite material of Example 3 at room temperature (25°C) are shown. It can be seen that both sensors exhibit good responses to hydrogen in a wide range of 20–2000 ppm, and the response value increases with increasing hydrogen concentration. Specifically, the Pd@In₂O₃ / NiO sensor shows a response of 1.22 to 20 ppm hydrogen and a response as high as 18.72 to 2000 ppm hydrogen. Since a reliable gas sensor has a response value standard of Ra / Rg ≥ 1.2, the experimental detection limit of the Pd@In₂O₃ / NiO sensor can be determined to be 20 ppm. This demonstrates the application potential of the MOF-derived In₂O₃ / NiO and Pd@In₂O₃ / NiO nanocomposites proposed in this invention in low-concentration hydrogen detection scenarios, paving the way for the development of low-concentration hydrogen detection at room temperature.

[0062] Figure 8 The concentration-response linear fitting curves of the hydrogen sensors prepared using the MOF-derived In2O3 / NiO composite material of Example 2 and the MOF-derived Pd@In2O3 / NiO composite material of Example 3 at room temperature (25°C) show a good functional relationship. This proves that the MOF-derived In2O3 / NiO and Pd@In2O3 / NiO nanocomposite sensors prepared by the method of this invention have the ability to calibrate and determine gas concentrations in practical applications. Furthermore, 300 data points were selected from the initial resistance (Ra) baseline of the sensor as samples to calculate its standard deviation, and the concentration-response curve was linearly fitted. Substituting these values ​​into equations (1) and (2), the theoretical estimates of the detection limits of the In2O3 / NiO and Pd@In2O3 / NiO sensors were obtained, which are 79.08 ppm and 24.33 ppm, respectively.

[0063] (1)

[0064] (2)

[0065] In the formula, S represents the original signal noise; S represents the amplitude of the response value; N represents the number of test samples; This is the theoretical minimum detection limit; Let be the slope of the sensor concentration-response fitted line.

[0066] Figure 9Five rounds of repeatability tests were conducted at room temperature (25°C) on hydrogen sensors prepared using the MOF-derived In2O3 / NiO composite material of Example 2 and the MOF-derived Pd@In2O3 / NiO composite material of Example 3 for 200 ppm hydrogen. Figure 10 A 35-day long-term stability test showed that both sensors exhibited excellent repeatability and reversibility for a common concentration of 200 ppm hydrogen. The 35-day long-term stability test graph revealed that all sensors showed relatively low overall fluctuations, indicating that the sensors made from the gas-sensitive material prepared in this invention possess good long-term stability.

[0067] Figure 11 The graph shows the response values ​​of hydrogen sensors prepared using the MOF-derived In₂O₃ / NiO composite material of Example 2 and the MOF-derived Pd@In₂O₃ / NiO composite material of Example 3 to 200 ppm hydrogen at room temperature (25°C) as a function of relative humidity. As can be seen from the graph, the sensor exhibits the highest response under dry conditions, and the response value gradually decreases with increasing relative humidity. When the relative humidity reaches 75%RH, the sensor's response value to 200 ppm hydrogen decreases significantly, reaching 75.21% of that under dry conditions. Since the decrease in the sensor's response value with increasing relative humidity is relatively gradual, the hydrogen sensors prepared using the MOF-derived In₂O₃ / NiO and Pd@In₂O₃ / NiO materials prepared in this invention exhibit good moisture resistance.

[0068] Figure 12 The chart shows the selectivity test results of the hydrogen sensors prepared using the composite materials from Examples 1-3 at room temperature (25°C). It can be seen that the selectivity of the MOF-derived NiO, In2O3 / NiO, and Pd@In2O3 / NiO material sensors differs for 200 ppm of methane (CH4), carbon monoxide (CO), ethanol (EtOH), methanol (MeOH), ethylene (C2H4), and acetone (ACE). The NiO sensor exhibits the highest response value to CO (1.14), the In2O3 / NiO sensor shows the highest response to EtOH (1.49), while the Pd@In2O3 / NiO sensor demonstrates an extremely high response to H2 (3.52), significantly higher than its response values ​​to other interfering gases. This demonstrates the great application potential of the method proposed in this invention in situations requiring singular detection of hydrogen.

[0069] Although embodiments of this application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application. The scope of this application is defined by the appended claims and their equivalents, all of which should be included within the protection scope of this application.

Claims

1. A Pd@In2O3-NiO nanocomposite based on MOF derivatization, characterized in that, The In / Ni bimetallic organic framework hierarchical porous nanoflower structure is synthesized by a cation exchange method, and Pd is distributed on the surface of the hierarchical porous nanoflower structure. The preparation method of the nanocomposite is as follows: S1: a nickel source and terephthalic acid are mixed and reacted in a solvent, and the product after the reaction is dried and sintered to obtain a Ni-MOF composite material; S2: polyvinylpyrrolidone is dissolved in ethanol, and then the Ni-MOF composite material is added, stirred uniformly at room temperature, and then placed, centrifuged, washed, and dried to obtain an intermediate product; S3: the intermediate product is dissolved in ethanol, and then an indium source is added for reaction to obtain a bimetallic In / Ni-MOF composite material; S4: a palladium source and the bimetallic In / Ni-MOF composite material are dissolved in ethanol, and reacted under ultraviolet light irradiation, and then centrifuged, washed, dried, and sintered to obtain a Pd@In2O3-NiO nanocomposite based on MOF derivation.

2. A method for preparing a Pd@In2O3-NiO nanocomposite based on MOF derivatization, the nanocomposite being as claimed in claim 1, characterized in that, The method steps are as follows: S1: a nickel source and terephthalic acid are mixed and reacted in a solvent, and the product after the reaction is dried and sintered to obtain a Ni-MOF composite material; S2: polyvinylpyrrolidone is dissolved in ethanol, and then the Ni-MOF composite material is added, stirred uniformly at room temperature, and then placed, centrifuged, washed, and dried to obtain an intermediate product; S3: the intermediate product is dissolved in ethanol, and then an indium source is added for reaction to obtain a bimetallic In / Ni-MOF composite material; S4: a palladium source and the bimetallic In / Ni-MOF composite material are dissolved in ethanol, and reacted under ultraviolet light irradiation, and then centrifuged, washed, dried, and sintered to obtain a Pd@In2O3-NiO nanocomposite based on MOF derivation.

3. The method for preparing Pd@In2O3-NiO nanocomposite based on MOF derivative according to claim 2, characterized in that, In S1, the nickel source is Ni(NO3)2·6H2O; and the solvent is a mixed solution of ethylene glycol and DMF.

4. The method for preparing Pd@In2O3-NiO nanocomposite based on MOF derivative according to claim 2, characterized in that, In S1, the molar ratio of the nickel source to terephthalic acid is 1:2-4; the reaction conditions are as follows: temperature 150-200℃, time 12-18h; and the sintering conditions are as follows: temperature 600-700℃, sintering time 2-3 hours, and heating rate 2-4℃ / min. 5.The method for preparing MOF-derived Pd@In2O3-NiO nanocomposites according to claim 2, characterized in that, In S2, the molecular weight of the polyvinylpyrrolidone is K-30; and the mass ratio of the polyvinylpyrrolidone to the Ni-MOF composite material is 2.5-3:

1.

6. The method for preparing Pd@In2O3-NiO nanocomposite based on MOF derivative according to claim 2, characterized in that, In S3, the indium source is In(NO3)3·4.5H2O; and the molar ratio of the indium source to the nickel source is 0.1-0.3:

1.

7. The method for preparing Pd@In2O3-NiO nanocomposite based on MOF derivative according to claim 2, characterized in that, In S3, the reaction conditions are as follows: after being mixed and stirred uniformly, the mixture is placed at 60-80℃ for 12-24h.

8. The method for preparing MOF-derived Pd@In2O3-NiO nanocomposite according to claim 2, characterized in that, In S4, the palladium source is PdCl2; and the molar ratio of the palladium source to the nickel source is 0.01-0.1:

1. 9.The method for preparing MOF-derived Pd@In2O3-NiO nanocomposites according to claim 2, characterized in that, In S4, the reaction conditions are as follows: under ultraviolet light irradiation with a wavelength of 250-260nm and a power of 15-18W, the reaction is carried out at room temperature for 10-12 hours; and the sintering conditions are as follows: temperature 600-700℃, sintering time 2-3 hours, and heating rate 2-4℃ / min.

10. Use of a Pd@In2O3-NiO nanocomposite material derived from MOF in a hydrogen sensor, characterized in that, The nanocomposite is as claimed in claim 1; and the hydrogen sensor can detect hydrogen at room temperature.

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