A kind of MOFs derived Zn-Fe oxide heterojunction nanocomposite and its application

Abstract

The application discloses a kind of Zn-Fe oxide heterojunction nanocomposite based on MOFs derivation and application thereof, amino terephthalic acid is dissolved with FeCl3·6H2O in dimethylformamide solution;Ethanol solution is dropped into the above-mentioned solution, is moved into reaction kettle after mixing uniformly, is washed after centrifugal washing after heating reaction, and is obtained Fe-MOF precursor by drying;Precursor is dissolved with PVP in methanol solution, is moved into reaction kettle after adding Zn (NO3) 2·6H2O and stirring uniformly, and precursor solution is obtained;Terephthalic acid is dissolved in dimethylformamide / dimethyl sulfoxide mixed solution;Drop into precursor solution, move into reaction kettle and heat reaction to collect white product, centrifugal, clean, and anneal after drying to obtain MOFs derived Fe-Zn oxide gas sensitive material.Provide a new idea for preparing MOFs derived Zn-Fe oxide heterojunction nanocomposite using Fe-MOF as template and subsequent Zn-MOF annealing process.The material has good sensitivity to triethylamine, with fast response speed, high sensitivity, low working temperature and good selectivity.

Description

Technical Field

[0001] This invention belongs to the field of gas-sensitive sensing materials technology, specifically relating to MOFs-derived Zn-Fe oxide heterojunction nanocomposites and their applications. Background Technology

[0002] Triethylamine (TEA), as a volatile organic compound, is widely used in catalysts, organic solvents, and antibacterial agents. Due to its excellent physicochemical properties, it is also extensively used in chemical experiments. However, TEA has a strong pungent odor and is toxic, potentially causing significant harm to human skin, respiratory system, and central nervous system. Exposure to open flames, strong oxidizers, or high temperatures at certain concentrations of TEA can even cause explosions, posing a significant threat to industrial production and daily life safety. Therefore, rapid and accurate real-time monitoring of TEA concentration is crucial, and the development of TEA sensor materials is urgently needed.

[0003] Currently, various methods have been developed and reported for the detection of TEA gases, including electrochemical analysis, gas / liquid / solid chromatography, conductive polymer sensors, and luminescent gas sensors. While these methods offer good stability and high accuracy, their high cost, complex procedures, and long detection cycles limit their practical application in TEA gas detection. Resistive sensors based on metal-oxide-semiconductor (MOS) nanostructures have attracted considerable attention due to their low cost, simple fabrication process, portability, and excellent sensor performance. Iron-based oxide semiconductor materials are among the most studied MOS materials. Nanomaterials, with their extremely large specific surface area and tiny microstructure, are prone to special effects such as volume effects, quantum effects, and surface tunneling effects. This leads to significant changes in the physicochemical properties of nanomaterials compared to conventional macroscopic materials, resulting in various applications for nanoscale iron-based oxide semiconductors, including photocatalysis, magnetic materials, and gas-sensitive sensing materials.

[0004] Metal-organic frameworks (MOFs) or their derivatives are widely considered promising gas-sensitive materials with applications in various fields. However, the limited composition, structure, and morphology of individual MOFs restrict their advanced performance and applications. In recent years, MOF derivatives synthesized using MOFs as templates through economical and simple hydrothermal and co-precipitation annealing methods have been continuously studied due to their excellent properties. In most cases, two or more MOF-derived composite materials can be successfully constructed using similar crystal topologies, forming heterocrystalline structures. To achieve superior gas sensing, a simple, economical, and feasible research strategy for the epitaxial growth of MOF-derived MOS functional material nanostructures remains a significant challenge. Furthermore, the concentration of metal ions and the ratio of organic ligands can be used to rationally design the MOF structure. Simultaneously, the migration and deletion processes of MOF atoms / ions, as well as the lack of oxygen atoms, can introduce more oxygen vacancies into MOFs, thereby giving MOS gas sensors superior gas-sensing performance. Summary of the Invention

[0005] The purpose of this invention is to improve the overall performance of existing gas sensors by providing a MOF-derived Zn-Fe oxide heterojunction nanocomposite material and its application.

[0006] The MOF-derived Zn-Fe oxide heterostructure nanocomposite material was prepared by the following method:

[0007] 1) Dissolve 4-6 mmol of aminoterephthalic acid and 2-4 mmol of FeCl3·6H2O in 80-100 ml of dimethylformamide solution;

[0008] 2) Under continuous magnetic stirring, 80-100 ml of ethanol solution was added dropwise to the solution in step 1). After stirring evenly, the solution was transferred to a reaction vessel, heated to react, and then centrifuged and washed with alcohol and water respectively to obtain the Fe-MOF precursor.

[0009] 3) Dissolve 0.01g-0.1g of Fe-MOF precursor and 0.01g-0.1g of PVP in 10ml of methanol solution, mix well, and then add 0.01-1.08g of Zn(NO3)2·6H2O and stir until homogeneous;

[0010] 4) Dissolve 2–4 mmol of terephthalic acid in a mixed solution of 10–30 ml of dimethylformamide and 0–20 ml of dimethyl sulfoxide, and stir until homogeneous;

[0011] 5) Slowly add the terephthalic acid solution prepared in step 4) to the solution prepared in step 3), stir evenly and let stand for 45 min, then transfer to a reaction vessel, heat and collect the white product, centrifuge and wash with ethanol and water respectively, dry, and anneal at 450-550℃ for 2-4 h at a rate of 3-6℃ / min to obtain MOFs-derived Zn-Fe oxide heterostructure nanocomposite material.

[0012] Step 1) contains 4.5–5.5 mmol of aminoterephthalic acid, 3–3.5 mmol of FeCl3·6H2O, and 85–95 ml of dimethylformamide.

[0013] The volume ratio of the ethanol solution in step 2) to the dimethylformamide solution in step 1) is 1:1.

[0014] Step 2) involves heating the reaction at a temperature of 80–90°C and holding it at that temperature for 10–14 hours.

[0015] Step 3) The mass ratio of the Fe-MOF precursor to PVP is 1:1.

[0016] Step 4) The volume ratio of dimethylformamide to dimethyl sulfoxide solution is 2:1.

[0017] Step 5) involves heating the reaction at a temperature of 120–140°C for 2–6 hours.

[0018] Step 5) The heating rate is 5℃ / min, and the temperature is raised to 500℃ for annealing for 3 hours.

[0019] Step 3) The mass ratio of the Fe-MOF precursor to zinc nitrate is 2:1, 1:1.6, 2:5, 1:7.2, or 1:1.08.

[0020] The preparation method of the triethylamine sensor includes: adding deionized water to the MOFs-derived Zn-Fe oxide heterojunction nanocomposite material as described in claim 1, grinding it into a paste, uniformly coating it on the ceramic plate with electrodes, air-drying it, and then heating it at a constant temperature of 80-220℃ for 8-12 hours.

[0021] The MOF-derived Zn-Fe oxide heterostructure nanocomposite material is used in gas sensing, where the gas is triethylamine.

[0022] This invention provides a MOF-derived Zn-Fe oxide heterostructure nanocomposite material and its application. The preparation process of the Zn-Fe oxide nanocomposite material includes: 1) dissolving aminoterephthalic acid and FeCl3·6H2O in dimethylformamide solution; 2) adding ethanol solution dropwise to the solution in step 1) under continuous magnetic stirring, mixing, transferring to a reaction vessel, heating and reacting, centrifuging and washing, and drying to obtain Fe-MOF precursor; 3) dissolving the precursor in step 2) and PVP in methanol solution, mixing, adding Zn(NO3)2·6H2O and stirring evenly; 4) dissolving terephthalic acid in a dimethylformamide / dimethyl sulfoxide mixed solution; 5) slowly adding the terephthalic acid solution prepared in step 4) dropwise to the solution prepared in step 3), mixing, standing for 45 min, transferring to a reaction vessel, heating and reacting to collect the white product, centrifuging and washing with ethanol and water respectively, drying and annealing to obtain MOF-derived Fe-Zn oxide gas-sensitive material. This invention provides a novel approach for preparing MOF-derived Zn-Fe oxide heterostructure nanocomposites using Fe-MOF as a template and a subsequent Zn-MOF annealing process. Results show that the MOF-derived Zn-Fe oxide heterostructure nanocomposite-based triethylamine gas sensor prepared in this invention exhibits excellent sensitivity to the volatile organic compound triethylamine, characterized by fast response, high sensitivity, low operating temperature, and good selectivity. Attached Figure Description

[0023] Figure 1 Field emission electron microscopy (SEM) images (ae) and HRTEM images (fj) of MOFs-derived Zn-Fe oxide heterostructure nanocomposites F1, ZZF2, ZZF3, ZZF4, and ZZ5;

[0024] Figure 2 X-ray diffraction (XRD) pattern of MOFs-derived Zn-Fe oxide heterojunction nanocomposite F1-ZZ5;

[0025] Figure 3 a) Dynamic response curves of F1-ZZ5-based gas sensors to 50ppm TEA for four consecutive cycles at their respective optimal operating temperatures; b) Repeatability response curves of F1-ZZ5-based gas sensors; c) Dynamic response recovery curves of the ZZF4 sample with the highest response value.

[0026] Figure 4 a) Response curve of F1-ZZ5-based gas sensor to 50ppm TEA within the operating temperature range; b) Response curve of F1-ZZ5 to different gases.

[0027] Figure 5a) Dynamic response curves of the F1-ZZ5-based gas sensor to different concentrations of TEA at their respective optimal temperatures; bc) Response values ​​of the F1-ZZ5-based gas sensor to different concentrations of TEA and their polynomial fitting curves. Detailed Implementation

[0028] Example 1

[0029] The specific preparation method of MOF-derived Zn-Fe oxide heterostructure nanocomposites is as follows:

[0030] 1) Dissolve 5.1 mmol of aminoterephthalic acid and 3.3 mmol of FeCl3·6H2O in 90 ml of dimethylformamide solution;

[0031] 2) Under continuous magnetic stirring, 90 ml of ethanol solution was added dropwise to the solution in step 1), mixed well, and then transferred to a reaction vessel. After heating at 85 °C for 12 h, the mixture was centrifuged and washed three times with alcohol and water respectively, and dried at 60 °C for 10 h to obtain the Fe-MOF precursor.

[0032] 3) Dissolve 0.1g of Fe-MOF precursor and 0.1g of PVP in 10ml of methanol solution, mix well, and then add 0.05g of Zn(NO3)2·6H2O and stir until homogeneous;

[0033] 4) Dissolve 3.3 mmol of terephthalic acid in a mixed solution of 20 ml dimethylformamide and 10 ml dimethyl sulfoxide, and stir until homogeneous;

[0034] 5) The terephthalic acid solution prepared in step 4) was slowly added dropwise to the solution prepared in step 3). After mixing and standing for 45 min, it was transferred to a reaction vessel and heated at 130 °C for 4 h. The white product was collected, centrifuged and washed three times with ethanol and water respectively, dried at 60 °C for 10 h, and then annealed at 500 °C for 3 h with the temperature increased at 5 °C / min to obtain MOFs-derived Zn-Fe oxide heterostructure nanocomposite material F1.

[0035] The preparation method of MOFs-derived Zn-Fe oxide-based triethylamine gas sensor includes: adding deionized water to the MOFs-derived Zn-Fe oxide heterojunction nanocomposite material F1, grinding it into a paste, and then uniformly coating it onto the ceramic plate with electrodes welded to the base. After air drying, the base is connected to the CGS-8 gas-sensitive testing system and heated at 140℃ for 12 hours.

[0036] Example 2: MOF-derived Zn-Fe oxide heterostructure nanocomposites

[0037] The MOF-derived Zn-Fe oxide heterostructure nanocomposite material is prepared as follows: In step 3), 0.1 g of Fe-MOF precursor and 0.1 g of PVP prepared in the previous step are dissolved in 10 ml of methanol solution and 0.16 g of Zn(NO3)2·6H2O, and stirred evenly. The remaining steps are the same as in Example 1; the MOF-derived Zn-Fe oxide heterostructure nanocomposite material ZZF2 is obtained.

[0038] The preparation method of MOFs-derived Zn-Fe oxide-based triethylamine gas sensor includes: adding deionized water to ZZF2, a MOFs-derived Zn-Fe oxide heterojunction nanocomposite material, grinding it into a paste, and then uniformly coating it onto a ceramic plate with electrodes welded to the base. After air drying, the base is connected to a CGS-8 gas-sensitive testing system and heated at 140°C for 12 hours.

[0039] Example 3: MOF-derived Zn-Fe oxide heterostructure nanocomposites

[0040] The MOF-derived Zn-Fe oxide heterostructure nanocomposite material is prepared as follows: In step 3), 0.1 g of Fe-MOF precursor and 0.1 g of PVP prepared in the previous step are dissolved in 10 ml of methanol solution and 0.25 g of Zn(NO3)2·6H2O, and stirred evenly. The remaining steps are the same as in Example 1; the MOF-derived Zn-Fe oxide heterostructure nanocomposite material ZZF3 is obtained.

[0041] The preparation method of MOFs-derived Zn-Fe oxide-based triethylamine gas sensor includes: adding deionized water to ZZF3, a MOFs-derived Zn-Fe oxide heterojunction nanocomposite material, grinding it into a paste, and then uniformly coating it onto a ceramic plate with electrodes welded to the base. After air drying, the base is connected to a CGS-8 gas-sensitive testing system and heated at 140°C for 12 hours.

[0042] Example 4: MOF-derived Zn-Fe oxide heterostructure nanocomposites

[0043] The MOF-derived Zn-Fe oxide heterostructure nanocomposite material is prepared as follows: In step 3), 0.1g of Fe-MOF precursor and 0.1g of PVP prepared in the previous step are dissolved in 10ml of methanol solution and 0.72g of Zn(NO3)2·6H2O, and stirred evenly. The remaining steps are the same as in Example 1; the MOF-derived Zn-Fe oxide heterostructure nanocomposite material ZZF4 is obtained.

[0044] The preparation method of MOFs-derived Zn-Fe oxide-based triethylamine gas sensor includes: adding deionized water to ZZF4, a MOFs-derived Zn-Fe oxide heterojunction nanocomposite material, grinding it into a paste, and then uniformly coating it onto a ceramic plate with electrodes welded to the base. After air drying, the base is connected to a CGS-8 gas-sensitive testing system and heated at 140°C for 12 hours.

[0045] Example 5: MOF-derived Zn-Fe oxide heterostructure nanocomposites

[0046] The MOF-derived Zn-Fe oxide heterostructure nanocomposite material is prepared as follows: In step 3), 0.1g of Fe-MOF precursor and 0.1g of PVP prepared in the previous step are dissolved in 10ml of methanol solution and 1.08g of Zn(NO3)2·6H2O, and stirred evenly. The remaining steps are the same as in Example 1; the MOF-derived Zn-Fe oxide heterostructure nanocomposite material ZZ5 is obtained.

[0047] The preparation method of MOFs-derived Zn-Fe oxide-based triethylamine gas sensor includes: adding deionized water to ZZ5, a MOFs-derived Zn-Fe oxide heterojunction nanocomposite material, grinding it into a paste, and then uniformly coating it onto a ceramic plate with electrodes welded to the base. After air drying, the base is connected to a CGS-8 gas-sensitive testing system and heated at 140℃ for 12 hours.

[0048] Examples 1-5 are MOF-derived Zn-Fe oxide heterostructure nanocomposites F1, ZZF2, ZZF3, ZZF4, and ZZ5, respectively. The sample designations F1-ZZF5 are based on HRTEM and XRD test results, where Z represents ZnO or ZnFe2O4 phase, and F represents Fe2O3 phase. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to observe the particle size and atomic-level resolution images of the samples. X-ray diffraction was used to characterize the materials, obtaining the material composition information for F1-ZZ5. Gas sensors were fabricated using composite materials F1, ZZF2, ZZF3, ZZF4, and ZZ5. The optimal operating temperature for 50 ppm TEA was tested within the range of 100℃ to 220℃. Experimental results showed that the optimal operating temperature for F1 and ZZF2 was 120℃, for ZZF3 it was 110℃, and for ZZF4 and ZZ5 it was 180℃, with ZZF4 exhibiting the highest response value at its optimal operating temperature. At this temperature, ZZF4 responded to 50 ppm TEA in 1 second, with a response value of 44.9. Simultaneously, the selectivity of the F1-ZZ5 gas sensors was measured, revealing good selectivity for TEA compared to acetone, trimethylamine, ammonia, ethanol, formaldehyde, and aniline. Four cycles of dynamic response value measurements for 50 ppm TEA were performed on the sensors at their optimal operating temperatures. The results showed that all sensors maintained approximately the same response curve, indicating good repeatability among the five sensors. By measuring TEA gas concentrations ranging from 0.1 to 200 ppm, it was found that ZZF4 exhibited response values ​​of 1.41 and 1.73 for 0.5 ppm and 1 ppm TEA, respectively, demonstrating its ability to detect low concentrations of TEA. Furthermore, polynomial fitting was performed on the gas response curves of the sensors at different concentrations, yielding R² values ​​of 0.997, 0.998, 0.994, 0.998, and 0.997, respectively. The gas sensors derived from MOFs-based Zn-Fe oxide heterojunction nanocomposite materials maintained approximately linear response values ​​to different concentrations of TEA gas.

[0049] Figure 1 ae provides SEM images of F1-ZZF, and fj corresponds to HRTEM images of the samples. The images show that F1 is a single phase of Fe2O3, ZZF2, ZZF3 and ZZF4 are three phases of ZnO, Fe2O3 and ZnFe2O4, and ZZ5 is a two-phase material of ZnO and ZnFe2O4. Figure 2The XRD patterns of the composite materials are shown, where the peak value of iron oxide is represented by a triangle, the peak value of zinc ferrite by a rhombus, and the peak value of zinc oxide by a pentagram. All the standard cards corresponding to F1-ZZ5 show significant peak values, and the results are well-matched with the standard cards for iron oxide (JCPDS No. 33-0664), zinc ferrite (JCPDS No. 22-1012), and zinc oxide (JCPDS No. 36-1451). The gas-sensing performance of the sensor was measured using the CGS-8 intelligent gas-sensing analysis system. The concentration of the target gas was configured using the static gas mixing method according to Formula 1. Under normal operating conditions (25±2℃, 20±10%RH), the steady-state resistance value R of the sensor was collected in both the air cylinder and the target gas cylinder. a and R g The response time is the time required for the sensor to reach 90% of its response value. After the reaction, the device is moved back to the air bottle, and its response value is calculated as shown in Formula 2. The recovery time is the time required for the sensor resistance value to recover to its steady-state resistance value in the air bottle after being moved back to the air bottle.

[0050] C = 22.4 × d × p × V1 × 1000 / M × V2 (Formula 1)

[0051] S=R a / R g Formula 2

[0052] Figure 3 The repeatability and response curves of the ab-based MOFs-derived Zn-Fe oxide heterojunction nanocomposite gas sensor show that the sensor has good repeatability. Figure 3 c is a single dynamic recovery curve of the ZZF4 sensor with the highest response value. The curve shows that the sensor has a high response value (44.9) and a fast response time (1s). Figure 4 'a' represents the response value measured by each sensor within its operating temperature range, with the optimal operating temperature indicated by an asterisk. Figure 4 b represents the sensor's response to other common interfering gases such as acetone and ethanol. The data in the bar chart shows that the F1-ZZF4 sensor's response to TEA is more than 50% higher than that of other gases, indicating good selectivity. The ZZF5 sensor has a relatively high response to TEA, but it is only more than 20% higher than that of other gases, showing poorer selectivity compared to the F1-ZZF4 sensor. Figure 5 The dynamic response recovery curves of the sensor to different concentrations of TEA show that the sensor has a low detection limit and good recovery performance in high concentrations of target gas, and has good linearity in response to different concentrations of TEA gas.

Claims

1. A MOF-derived Zn-Fe oxide heterostructure nanocomposite material, prepared by the following method, comprising: 1) Dissolve 4-6 mmol of aminoterephthalic acid and 2-4 mmol of FeCl3·6H2O in 80-100 ml of dimethylformamide solution and stir until homogeneous; 2) Under continuous magnetic stirring, 80-100 ml of ethanol solution was added dropwise to the solution in step 1). After stirring evenly, the solution was transferred to a reaction vessel, heated to react, and then centrifuged and washed with alcohol and water respectively to obtain the Fe-MOF precursor. 3) Dissolve 0.01g-0.1g of Fe-MOF precursor and 0.01g-0.1g of PVP in 10ml of methanol solution, mix well, and then add 0.01-1.08g of Zn(NO3)2·6H2O and stir until homogeneous; 4) Dissolve 2–4 mmol of terephthalic acid in a mixed solution of 10–30 ml of dimethylformamide and 0–20 ml of dimethyl sulfoxide, and stir until homogeneous; 5) Slowly add the terephthalic acid solution prepared in step 4) to the solution prepared in step 3), stir evenly and let stand for 45 min, then transfer to a reaction vessel, heat and collect the white product, centrifuge and wash with ethanol and water respectively, dry, and anneal at 450-550℃ for 2-4 h at a rate of 3-6℃ / min to obtain MOFs-derived Zn-Fe oxide heterostructure nanocomposite material.

2. The MOF-derived Zn-Fe oxide heterostructure nanocomposite material according to claim 1, characterized in that: Step 1) contains 4.5–5.5 mmol of aminoterephthalic acid, 3–3.5 mmol of FeCl3·6H2O, and 85–95 ml of dimethylformamide.

3. The MOF-derived Zn-Fe oxide heterostructure nanocomposite material according to claim 2, characterized in that: The volume ratio of the ethanol solution in step 2) to the dimethylformamide solution in step 1) is 1:

1.

4. The MOF-derived Zn-Fe oxide heterostructure nanocomposite material according to claim 3, characterized in that: Step 2) involves heating the reaction at a temperature of 80–90°C and holding it at that temperature for 10–14 hours.

5. The MOF-derived Zn-Fe oxide heterostructure nanocomposite material according to claim 3, characterized in that: Step 3) The mass ratio of Fe-MOF precursor to PVP is 1:

1.

6. The MOF-derived Zn-Fe oxide heterostructure nanocomposite material according to claim 4, characterized in that: Step 4) The volume ratio of dimethylformamide to dimethyl sulfoxide solution is 2:

1.

7. The MOF-derived Zn-Fe oxide heterostructure nanocomposite material according to claim 5, characterized in that: Step 5) involves heating the reaction at a temperature of 120–140°C for 2–6 hours. The heating rate is 5℃ / min, and the temperature is raised to 500℃ for annealing for 3 hours.

8. A MOF-derived Zn-Fe oxide heterostructure nanocomposite material according to claim 1, 2, 3, 4, 5, 6 or 7, characterized in that: Step 3) The mass ratio of the Fe-MOF precursor to zinc nitrate is 2:1, 1:1.6, 2:5, 1:7.2 or 1:1.

08.

9. The application of the MOFs-derived Zn-Fe oxide heterojunction nanocomposite material as described in claim 1 in the preparation of a sensor for detecting triethylamine.

10. The application according to claim 9, characterized in that: A MOFs-derived Zn-Fe oxide heterostructure nanocomposite material was added to deionized water, ground into a paste, and then uniformly coated onto a ceramic plate with electrodes. After air drying, it was heated at a constant temperature of 80–220°C for 8–12 hours to obtain a MOFs-derived Zn-Fe oxide-based triethylamine gas sensor.

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