A bimetallic MOF-derived In 2 O 3 / Fe 2 O 3 Heterogeneous gas-sensitive materials, preparation methods and applications

Abstract

This invention proposes a bimetallic MOF-derived In 2 O 3 / Fe 2 O 3 Heterogeneous gas-sensitive materials, preparation methods, and applications. This invention features a simple and low-cost preparation process. It involves preparing a metal-organic framework In / Fe-MOF, and subsequently deriving In materials with n-n type heterostructures. 2 O 3 / Fe 2 O 3 Heterogeneous gas-sensitive materials utilize heterojunctions to create more oxygen vacancies, increasing the number of active sites and thus the concentration of adsorbed oxygen participating in the sensing reaction. Furthermore, the unique hollow porous structure provides even more adsorbed oxygen for gas diffusion and adsorption, further enhancing the gas-sensing effect on CO and improving the performance of pure In. 2 O 3 The gas-sensitive material exhibits an extremely high response to CO, along with excellent repeatability and selectivity. It can be used for highly sensitive CO detection, which is of significant practical importance for monitoring and real-time CO detection in industrial production activities.

Description

A bimetallic MOF-derived In2O3 / Fe2O3 heterostructure gas-sensitive material, its preparation method and application. Technical Field

[0001] This invention belongs to the field of semiconductor metal oxide functional materials and gas sensing technology, specifically relating to a bimetallic MOF-derived In2O3 / Fe2O3 heterostructure gas sensing material, its preparation method, and its application. Background Technology

[0002] Carbon monoxide (CO), a colorless, odorless, and highly toxic gas, is a major component of automobile engine exhaust, plant smoke, gunpowder smoke, and incomplete combustion products in industrial production. On one hand, engine exhaust, plant smoke, and gunpowder smoke are typical interfering agents in battlefield environments, and the presence of CO strongly interferes with the performance of gas detection equipment. On the other hand, CO's toxicity stems from the strong adsorption capacity of hemoglobin in human blood, which significantly reduces the partial pressure of oxygen in the blood, allowing people to unknowingly inhale excessive amounts, leading to poisoning symptoms such as headache, shortness of breath, and even death. Therefore, timely and accurate CO monitoring is of paramount importance. In recent decades of research, metal oxide-based gas sensors have been considered one of the most promising gas detection devices due to their low cost, real-time monitoring capabilities, and simple fabrication methods. Among them, In₂O₃, as a typical n-type semiconductor material with a direct band gap of 3.65 eV, low resistivity, and high catalytic activity, is one of the best materials for detecting toxic and harmful gases and has received considerable attention in CO gas-sensitive detection.

[0003] Metal-organic frameworks (MOFs) have attracted considerable attention due to their abundant porous structures, high specific surface area, and structural regularity. Furthermore, MOFs can serve as multifunctional self-sacrificing templates and precursors, yielding a wealth of MOF-derived metal oxides, which hold broad application prospects in supercapacitors, lithium-ion batteries, and gas sensors. In recent years, researchers have prepared bimetallic organic frameworks by doping two metal ions into the MOF structure, which can be derived into metal oxide composites to enhance the gas-sensing performance of these materials, showing potential applications in gas sensing. Summary of the Invention

[0004] (a) Technical problems to be solved

[0005] This invention proposes a bimetallic MOF-derived In2O3 / Fe2O3 heterostructure gas-sensitive material, its preparation method, and its application, in order to solve the technical problem of low CO response value of pure In2O3 gas-sensitive materials.

[0006] (II) Technical Solution

[0007] To address the aforementioned technical problems, this invention proposes a bimetallic MOF-derived In2O3 / Fe2O3 heterostructure gas-sensitive material. This In2O3 / Fe2O3 heterostructure gas-sensitive material is composed of hollow nanotube-shaped In2O3 and Fe2O3 nanoparticles surrounding it, forming an n-type heterostructure between In2O3 and Fe2O3 that facilitates electron transport.

[0008] Furthermore, this invention also proposes a method for preparing a bimetallic MOF-derived In2O3 / Fe2O3 heterostructure gas-sensitive material. The preparation method involves using indium nitrate hexahydrate and anhydrous ferric chloride as raw materials, terephthalic acid as an organic ligand, and N,N dimethylformamide as a solvent. An In / Fe-MOF precursor is prepared by a one-step solvothermal method, and then heat-treated in an air atmosphere to obtain an In2O3 / Fe2O3 heterostructure gas-sensitive material with an N,N heterostructure, consisting of hollow nanotube-shaped In2O3 and Fe2O3 nanoparticles surrounding it.

[0009] Furthermore, the preparation method specifically includes the following steps:

[0010] Preparation of S1.In / Fe-MOF: Terephthalic acid was dispersed in NN dimethylformamide, then indium nitrate hexahydrate and anhydrous ferric chloride were added. After ultrasonic dispersion and dissolution for 30 min, a mixed solution was obtained. The bimetallic organic framework In / Fe-MOF precursor was obtained by a one-step solvothermal method.

[0011] S2. Preparation of In2O3 / Fe2O3 heterostructure gas-sensitive material: The prepared In / Fe-MOF precursor was subjected to high-temperature heat treatment in air atmosphere to obtain In2O3 / Fe2O3 heterostructure gas-sensitive material.

[0012] Further, in step S1, the molar ratio of terephthalic acid and indium nitrate hexahydrate to anhydrous ferric chloride is 1:4, and the In:Fe molar ratio of the solution obtained after dissolution is (2-6):1.

[0013] Furthermore, in step S1, the solvothermal reaction temperature is 90℃~120℃, and the reaction time is 3h~5h; after the reaction, the mixture is centrifuged and washed with deionized water and anhydrous ethanol, respectively, and then dried.

[0014] Further, in step S2, the In / Fe-MOF precursor is calcined at 450℃ to 550℃ for 3 to 5 hours at a heating rate of 0.5℃ / min to 5℃ / min.

[0015] Furthermore, this invention also proposes a method for preparing a gas-sensitive element. The method involves mixing an In2O3 / Fe2O3 heterostructure gas-sensitive material with deionized water to form an In2O3 / Fe2O3 heterostructure gas-sensitive material slurry; coating the In2O3 / Fe2O3 heterostructure gas-sensitive material slurry onto an Ag-Pd electrode; and allowing it to dry naturally at room temperature to obtain the gas-sensitive element.

[0016] Further, the In2O3 / Fe2O3 heterostructure gas-sensitive material was added to agate mortar, deionized water was added and the mixture was ground to form an In2O3 / Fe2O3 heterostructure gas-sensitive material slurry; the In2O3 / Fe2O3 heterostructure gas-sensitive material slurry was then applied to the Ag-Pd electrode using a paint pen.

[0017] Furthermore, this invention also proposes an application of a bimetallic MOF-derived In2O3 / Fe2O3 heterostructure gas-sensitive material, applying the In2O3 / Fe2O3 heterostructure gas-sensitive material to gas sensing and detection.

[0018] Furthermore, the In2O3 / Fe2O3 heterostructure gas-sensitive material was used to detect CO at 200℃~300℃.

[0019] (III) Beneficial Effects

[0020] This invention proposes a bimetallic MOF-derived In₂O₃ / Fe₂O₃ heterostructure gas-sensitive material, its preparation method, and its applications. The preparation process is simple and low-cost. By preparing a metal-organic framework In / Fe-MOF, an In₂O₃ / Fe₂O₃ heterostructure gas-sensitive material with an n-type heterojunction is obtained. The formation of the heterojunction provides the material with more oxygen vacancies, increasing the number of active sites and thus increasing the concentration of adsorbed oxygen participating in the sensing reaction. Furthermore, the unique hollow porous structure provides more adsorbed oxygen for gas diffusion and adsorption, further improving the gas-sensing effect on CO. This enhances the CO response of pure In₂O₃ gas-sensitive materials, exhibiting extremely high response and excellent repeatability and selectivity for CO. It can be used for highly sensitive CO detection, which has significant practical implications for monitoring and real-time CO detection in industrial production activities. Attached Figure Description

[0021] Figure 1 shows the XRD diffraction patterns of a series of In2O3 / Fe2O3 heterostructure gas-sensitive materials prepared with different indium-iron molar ratios;

[0022] Figure 2 is a scanning electron microscope (SEM) image of the In2O3 / Fe2O3 heterostructure gas-sensitive material prepared in Example 2;

[0023] Figure 3 is a transmission electron microscope (TEM) image of the In2O3 / Fe2O3 heterostructure gas-sensitive material prepared in Example 2;

[0024] Figure 4 shows the Raman spectra of the In2O3 / Fe2O3 heterostructure gas-sensitive materials prepared in Examples 1-3;

[0025] Figure 5 shows the fluorescence visible spectrum of the In2O3 / Fe2O3 heterostructure gas-sensitive material prepared in Example 2;

[0026] Figure 6 is a line graph showing the response of the In2O3 / Fe2O3 heterostructure gas-sensitive materials prepared in Examples 1-3 to 200ppm CO gas in the temperature range of 220-300℃.

[0027] Figure 7 shows the response curve of the In2O3 / Fe2O3 heterostructure gas-sensitive material prepared in Example 2 to 200-1ppm CO at 260℃;

[0028] Figure 8 shows the response curve of the In2O3 / Fe2O3 heterostructure gas-sensitive material prepared in Example 2 to 200ppm CO at 260℃.

[0029] Figure 9 shows the response curves of the In2O3 / Fe2O3 heterostructure gas-sensitive material prepared in Example 2 to 200 ppm CO and four other interfering gases at 260 °C. Detailed Implementation

[0030] To make the objectives, contents, and advantages of the present invention clearer, the specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples.

[0031] Example 1

[0032] Preparation of In₂O₃ / Fe₂O₃ heterostructure gas-sensitive material with an indium-iron molar ratio of 2:1

[0033] S1. Weigh 0.1062g of terephthalic acid (H2BDC) and ultrasonically disperse it in 60ml of N-N dimethylformamide (DMF) until it is completely dissolved.

[0034] S2. Add 0.4g of indium nitrate hydrate (In(NO3)3·4.5H2O) and 0.043g of anhydrous ferric chloride (FeCl3) to the solution in step S1, and continue sonicating for 30 minutes until completely dissolved.

[0035] S3. Transfer the solution obtained in step S2 to the reaction vessel and react at 100°C for 4 hours.

[0036] S4. After the reactor has cooled naturally, the product is collected by centrifugation, washed three times with deionized water and anhydrous ethanol, and dried overnight at 60°C to obtain the bimetallic organometallic In / Fe-MOF precursor material.

[0037] S5. The bimetallic metal-organic framework obtained in step S4 is laid flat on a ceramic crucible and calcined in a groom furnace at 500℃ (1℃ / min) for 4 hours to obtain an In2O3 / Fe2O3 heterostructure gas-sensitive material.

[0038] Example 2

[0039] The preparation of the In2O3 / Fe2O3 heterostructure gas-sensitive material with an indium-iron molar ratio of 4:1 was the same as in Example 1, except that the proportion of raw materials was changed, namely, 0.4g of indium nitrate hydrate (In(NO3)3·4.5H2O) and 0.021g of anhydrous ferric chloride (FeCl3) were used.

[0040] Example 3

[0041] The preparation of the In2O3 / Fe2O3 heterostructure gas-sensitive material with an indium-iron molar ratio of 6:1 was the same as in Example 1, except that the proportion of raw materials was changed, namely, 0.4g of indium nitrate hydrate (In(NO3)3·4.5H2O) and 0.0135g of anhydrous ferric chloride (FeCl3) were used.

[0042] Example 4

[0043] Fabrication of a gas-sensitive material sensor based on an In₂O₃ / Fe₂O₃ heterostructure with an indium-iron molar ratio of 4:1.

[0044] The manufacturing process of gas-sensitive components is as follows:

[0045] S1. Weigh 4 mg of In2O3 / Fe2O3 heterostructure gas-sensitive material into an agate mortar, add 800 μL of deionized water, and grind it into a slurry with appropriate strength.

[0046] S2. Apply the slurry to the cleaned Ag-Pd electrode (14mm×7mm) with a paint pen and allow it to air dry at room temperature to obtain a gas sensor.

[0047] Before testing, the gas sensor should be continuously aged at 260°C for 12 hours to make the molecular structure of the material more compact and obtain better test results.

[0048] The sensitivity is calculated by using the resistance value (Rg) of the material in the target gas and the resistance value (Ra) of the material in the air environment, and defining the gas-sensitive response value as S = (Rg / Ra).

[0049] Figure 1 shows the XRD diffraction patterns of the In2O3 / Fe2O3 heterostructure gas-sensitive materials obtained in Examples 1-3. The figure shows that the diffraction peaks at 21.5°, 30.6°, 35.5°, 41.6°, 45.7°, 51.1°, and 60.7° are consistent with the standard In2O3 spectrum (PDF#89-4595), corresponding to the (211), (222), (400), (332), (431), (440), and (622) crystal planes of cubic In2O3, respectively, and no other impurity peaks were found. The peak at 35.5° is consistent with the (110) crystal plane of hematite Fe2O3, proving that the In2O3 / Fe2O3 composite material was successfully synthesized in this invention.

[0050] As can be seen from SEM (Figure 2) and TEM (Figure 3), the In2O3 / Fe2O3 heterostructure gas-sensitive material has a hollow structure with a large number of pores. The In2O3 maintains the hollow porous nanotube morphology with a diameter of about 200 nm, while the tubular In2O3 is surrounded by a layer of Fe2O3 nanoparticles with a certain thickness.

[0051] The Raman results in Figure 4 show that the Raman characteristic peaks of cubic phase In2O3 and hematite Fe2O3 coexist, further proving the successful synthesis of the In2O3 / Fe2O3 composite material.

[0052] Figure 5 shows the fluorescence spectra of the three In2O3 / Fe2O3 materials at an excitation wavelength of 340 nm. Compared with In-Fe-2 and In-Fe-6 gas-sensitive materials, the emission peak intensity of In-Fe-4 is relatively low, indicating that the recombination rate of photogenerated electron-hole pairs inside it is weak, and the generated electron-hole pairs are effectively separated, providing a greater number of charge carriers.

[0053] Figure 6 shows the response of the gas sensors obtained in Examples 1-3 to 200 ppm CO at 220-300℃. The results clearly show that the curve trend between the operating temperature and the gas response value is an inverted V-shape. By analyzing the response values ​​of the three groups of samples to CO gas, the optimal operating temperature of the In2O3 / Fe2O3 composite gas sensor was determined to be 260℃, among which the response value of In-Fe-4 to CO gas was as high as 33.7.

[0054] Figure 7 shows the response curve of the In₂O₃ / Fe₂O₃ heterostructure gas-sensitive material prepared in Example 2 to 200 ppm CO at 260 °C. It can be seen that the response value increases significantly with increasing CO concentration. More notably, the detection limit of the In-Fe₄ sensor is 1 ppm, indicating that this sensor is an ideal candidate for practical CO detection.

[0055] Figure 8 shows the response curve of the In2O3 / Fe2O3 heterostructure gas-sensitive material prepared in Example 2 to 200ppm CO at 260℃. It can be clearly seen that the response time to reach 33.7 is 23s, and the recovery time is 76s. The rapid response and recovery speed is due to the porous structure and large specific surface area of ​​the material.

[0056] Figure 9 shows the response curves of the In2O3 / Fe2O3 heterostructure gas-sensitive material prepared in Example 2 to 200ppm CO and four other interfering gases at 260℃. The results clearly show that In-Fe-4 has significant selectivity for CO and can achieve a complete response to CO in complex gas environments.

[0057] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a bimetallic MOF-derived In₂O₃ / Fe₂O₃ heterostructure gas-sensitive material, characterized in that, The preparation method is as follows: using indium nitrate hexahydrate and anhydrous ferric chloride as raw materials, terephthalic acid as organic ligand, and N / N dimethylformamide as solvent, an In / Fe-MOF precursor is prepared by a one-step solvothermal method. After heat treatment in an air atmosphere, an In2O3 / Fe2O3 heterostructure gas-sensitive material with an N / N heterostructure is obtained, consisting of hollow nanotube-shaped In2O3 and Fe2O3 nanoparticles surrounding it. Specifically, the method includes the following steps: S1. Preparation of In / Fe-MOF: Terephthalic acid is dispersed in N / N dimethylformamide, then indium nitrate hexahydrate and anhydrous ferric chloride are added, and the mixture is heated for 30 minutes. The mixture was ultrasonically dispersed and dissolved to obtain a mixed solution; a one-step solvothermal method was used to obtain the bimetallic organic framework In / Fe-MOF precursor; wherein the molar ratio of terephthalic acid and indium nitrate hexahydrate to anhydrous ferric chloride was 1:4, and the In:Fe molar ratio of the solution obtained after dissolution was (2~6):1; S2. Preparation of In2O3 / Fe2O3 heterostructure gas-sensitive material: The prepared In / Fe-MOF precursor was calcined in air at 450℃~550℃ for 3~5h at a heating rate of 0.5℃ / min~5℃ / min to obtain the In2O3 / Fe2O3 heterostructure gas-sensitive material.

2. The method for preparing In2O3 / Fe2O3 heterostructure gas-sensitive material as described in claim 1, characterized in that, In step S1, the solvothermal reaction temperature is 90℃~120℃, and the reaction time is 3h~5h; after the reaction, the mixture is centrifuged and washed with deionized water and anhydrous ethanol, respectively, and then dried.

3. A bimetallic MOF-derived In₂O₃ / Fe₂O₃ heterostructure gas-sensitive material, characterized in that, The bimetallic MOF-derived In2O3 / Fe2O3 heterostructure gas-sensitive material is prepared by the method described in claim 1 or 2. The In2O3 / Fe2O3 heterostructure gas-sensitive material is composed of hollow nanotube-shaped In2O3 and Fe2O3 nanoparticles surrounding it, and an n-type heterostructure that is conducive to electron transport is formed between In2O3 and Fe2O3.

4. A method for preparing a gas-sensitive element, characterized in that, The preparation method is as follows: the bimetallic MOF-derived In2O3 / Fe2O3 heterostructure gas-sensitive material of claim 3 is mixed with deionized water to form an In2O3 / Fe2O3 heterostructure gas-sensitive material slurry; the In2O3 / Fe2O3 heterostructure gas-sensitive material slurry is coated on an Ag-Pd electrode and naturally dried at room temperature to obtain a gas-sensitive element.

5. The preparation method according to claim 4, characterized in that, In2O3 / Fe2O3 heterostructure gas-sensitive material was mixed with agate mortar, deionized water was added and the mixture was ground to form an In2O3 / Fe2O3 heterostructure gas-sensitive material slurry. The In2O3 / Fe2O3 heterostructure gas-sensitive material slurry was then applied to the Ag-Pd electrode using a paint pen.

6. An application of a bimetallic MOF-derived In₂O₃ / Fe₂O₃ heterostructure gas-sensitive material, characterized in that, The bimetallic MOF-derived In2O3 / Fe2O3 heterostructure gas-sensitive material of claim 3 is applied to gas sensing and detection, and the In2O3 / Fe2O3 heterostructure gas-sensitive material is used to detect CO at 200℃~300℃.

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