Metal-organic framework-derived iron-europium oxide material, preparation method, application and gas sensor thereof

Abstract

This application relates to the field of sensor technology and provides a metal-organic framework-derived iron-europium oxide material, its preparation method, application, and gas sensor. The metal-organic framework-derived iron-europium oxide material comprises a metal-organic framework-derived iron oxide and europium oxide doped into the metal-organic framework-derived iron oxide. The material morphology of the metal-organic framework-derived iron-europium oxide material includes an octahedral structure. The metal-organic framework-derived iron-europium oxide material disclosed in this application exhibits high sensitivity to formaldehyde and rapid response recovery.

Description

Technical Field

[0001] The present application relates to the field of sensor technology, and in particular to a metal organic framework-derived iron-europium oxide material, a preparation method thereof, an application thereof, and a gas sensor. Background Art

[0002] Harmful gases in indoor environmental pollutants include formaldehyde, benzene, and ammonia. For example, long-term exposure to formaldehyde can adversely affect human health. Traditionally, metal oxide semiconductor (MOS) resistive sensors have been used to detect formaldehyde concentrations. However, these sensors, made from materials like zinc oxide and tin dioxide, are susceptible to interference from other gases during detection. This results in poor accuracy and makes it difficult to detect low-concentration formaldehyde. Summary of the Invention

[0003] Based on this, an embodiment of the present application provides a metal-organic framework-derived iron-europium oxide material capable of accurately detecting formaldehyde concentration, as well as its preparation method, application, and gas sensor.

[0004] In a first aspect, the present application provides a metal-organic framework-derived iron-europium oxide material, which includes a metal-organic framework-derived iron oxide and europium oxide doped in the metal-organic framework-derived iron oxide. The material morphology of the metal-organic framework-derived iron-europium oxide material includes an octahedral structure.

[0005] In some embodiments, the molar ratio of iron to europium in the metal-organic framework-derived iron-europium oxide material is (0.85-2.6):1.

[0006] In some embodiments, the mass proportion of iron in the metal-organic framework-derived iron-europium oxide material is 30% to 40%.

[0007] In some embodiments, the mass proportion of europium element in the metal-organic framework-derived iron-europium oxide material is 40% to 50%.

[0008] In some embodiments, the volume average particle size Dv50 of the metal organic framework derived iron-europium oxide material is 100 nm to 800 nm.

[0009] In a second aspect, the present application provides a method for preparing a metal organic framework-derived iron-europium oxide material, the preparation method comprising:

[0010] providing a first solution comprising an Fe-based metal-organic framework material;

[0011] mixing a europium source with the first solution and aging the mixture to obtain an intermediate material;

[0012] After calcining the intermediate material, the metal organic framework-derived iron-europium oxide material is prepared.

[0013] In some embodiments, the organic ligand contained in the Fe-based metal-organic framework material includes at least one of a terephthalic acid group, a trimellitic acid group, a 2-aminoterephthalic acid group, and a 2-hydroxyterephthalic acid group.

[0014] In some embodiments, the europium source includes at least one of EuCl3·6H2O, Eu2(CO3)3, and Eu(NO3)3·6H2O.

[0015] In some embodiments, the molar ratio of the iron element in the Fe-based metal-organic framework material to the europium element in the europium source is (0.85-2.6):1.

[0016] In some embodiments, the molar concentration of the europium source is 0.025 mol / L to 0.075 mol / L.

[0017] In some embodiments, the molar concentration of the Fe-based metal-organic framework material is 0.06 mol / L to 0.07 mol / L.

[0018] In some embodiments, the aging temperature is 20° C. to 40° C., and the aging time is 10 h to 15 h.

[0019] In some embodiments, the calcination temperature is 300° C. to 400° C., and the calcination time is 0.5 h to 1.5 h.

[0020] In some embodiments, the method for preparing the Fe-based metal-organic framework material comprises:

[0021] A second solution containing a ligand material and an iron source is provided, and the Fe-based metal organic framework material is obtained after a hydrothermal reaction.

[0022] Optionally, the ligand material includes at least one of terephthalic acid, trimellitic acid, 2-aminoterephthalic acid and 2-hydroxyterephthalic acid; further optionally, the ligand material includes terephthalic acid and trimellitic acid, and the molar ratio of the terephthalic acid to the trimellitic acid is (2~2.5):1.

[0023] Optionally, the iron source includes FeCl3·6H2O.

[0024] Optionally, the temperature of the hydrothermal reaction is 100° C. to 150° C., and the time is 20 h to 30 h.

[0025] In a third aspect, the present application provides a use of the metal organic framework-derived iron-europium oxide material as described in the first aspect in the preparation of a gas sensor.

[0026] In a fourth aspect, the present application provides a gas sensor, which includes a substrate, a heating plate, an interdigitated electrode and a gas-sensitive material layer stacked in sequence, and the gas-sensitive material layer includes the metal-organic framework-derived iron-europium oxide material as described in the first aspect and / or the metal-organic framework-derived iron-europium oxide material prepared by the preparation method of the metal-organic framework-derived iron-europium oxide material as described in the second aspect.

[0027] In some embodiments, the gas sensor further includes a covalent organic framework material layer disposed on the surface of the gas-sensitive material layer.

[0028] Optionally, the material of the covalent organic framework material layer comprises a covalent organic material, the node group contained in the covalent organic material comprises Tp, and the connecting group comprises Ma.

[0029] Compared with traditional technologies, this application has at least the following beneficial effects:

[0030] This application utilizes a metal-organic framework-derived iron-europium oxide material with an octahedral structure. This material exhibits excellent crystallinity, resulting in a large surface area and numerous active sites. This results in high sensitivity and rapid response recovery, enabling accurate detection of low formaldehyde concentrations while remaining resistant to interference from other gases. Furthermore, the three-dimensional structure maintains excellent dispersion and structural stability, contributing to the long-term operational stability of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is an SEM image of the metal-organic framework-derived iron-europium oxide material prepared in Example 1 of the present application;

[0032] Figure 2 Schematic diagram of the preparation of the gas-sensitive material layer and the covalent organic framework material layer in the gas sensor in Example 1 of the present application;

[0033] Figure 3 Optimal operating temperature curves of the gas sensors in Example 1, Example 2, Example 3, and Comparative Example 2 of the present application;

[0034] Figure 4 This is a response recovery curve diagram of the gas sensor in Example 1 of the present application;

[0035] Figure 5 This is a comparison chart of the sensitivity of Example 1 and Example 7 of the present application at different humidity levels;

[0036] Figure 6This is a response curve diagram of the gas sensor in Example 1 of the present application to different concentrations of formaldehyde. DETAILED DESCRIPTION

[0037] Below in conjunction with embodiment and example, the application is further described in detail These embodiment and example are only used to illustrate the application and are not used to limit the scope of the application, and the purpose of providing these embodiment and example is to make the understanding of the disclosure of the application more thorough and comprehensive. It should also be understood that the application can be implemented in many different forms and is not limited to the embodiment and example described herein. Those skilled in the art can make various changes or modifications without violating the connotation of the application, and the equivalent form obtained also falls within the protection scope of the application. In addition, in the description below, a large amount of specific details are given in order to provide a more complete understanding of the application, and it should be understood that the application can be implemented without one or more of these details.

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application.

[0039] In this application, the terms "optionally," "optional," and "optional" mean optional or dispensable, i.e., they refer to either option being selected from two parallel options: "with" or "without." If a technical solution contains multiple "optional" clauses, each "optional" clause is independent unless otherwise specified and there are no contradictions or constraints.

[0040] In this application, the terms "first" and "second" in "the first aspect" and "the second aspect" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or quantity, nor should they be understood as implicitly indicating the importance or quantity of the technical features indicated. Furthermore, "first" and "second" serve only as non-exhaustive enumeration and description and should be understood not to constitute a closed-ended limitation on quantity.

[0041] In this application, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0042] In this application, when referring to a numerical interval (i.e., a numerical range), unless otherwise specified, the distribution of the optional numerical values ​​within the numerical interval is deemed to be continuous and includes the two numerical endpoints of the numerical interval (i.e., the minimum and maximum values), as well as each numerical value between the two numerical endpoints. Unless otherwise specified, when a numerical interval refers only to integers within the numerical interval, it includes the two endpoint integers of the numerical range, as well as each integer between the two endpoints, which is equivalent to directly listing each integer. When multiple numerical ranges are provided to describe a feature or characteristic, these numerical ranges can be combined. In other words, unless otherwise specified, the numerical ranges disclosed in this application should be understood to include any and all subranges included therein. The "numerical value" in the numerical interval can be any quantitative value, such as a number, percentage, ratio, etc. "Numerical interval" is broadly allowed to include quantitative intervals such as percentage intervals, ratio intervals, and ratio intervals.

[0043] All documents mentioned in this application are cited as references in this application, just as each document is cited as reference separately. Unless they conflict with the application purpose and / or technical solution of this application, the cited documents involved in this application are cited in their entirety and for all purposes. When cited documents are involved in this application, the definitions of relevant technical features, terms, nouns, phrases, etc. in the cited documents are also cited. When cited documents are involved in this application, the examples and preferred embodiments of the cited relevant technical features may also be incorporated into this application as references, but are limited to the ability to implement this application. It should be understood that when the cited content conflicts with the description in this application, the present application shall prevail or be adaptively amended according to the description in this application.

[0044] In traditional technology, the gas-sensitive materials in formaldehyde gas sensors are made of materials such as zinc oxide and tin dioxide. During the formaldehyde detection process, due to the influence of the initial redox reaction between the adsorbed oxygen and the semiconductor surface, it is easily interfered by other gases during the detection process, affecting the detection accuracy of formaldehyde and making it difficult to detect low-concentration formaldehyde.

[0045] In a first aspect, the present application provides a metal-organic framework-derived iron-europium oxide material, which includes a metal-organic framework-derived iron oxide and europium oxide doped in the metal-organic framework-derived iron oxide. The material morphology of the metal-organic framework-derived iron-europium oxide material includes an octahedral structure.

[0046] This application utilizes a metal-organic framework-derived iron-europium oxide material with an octahedral structure. This material exhibits excellent crystallinity, resulting in a large surface area and numerous active sites. This results in high sensitivity and rapid response recovery, enabling accurate detection of low formaldehyde concentrations while remaining resistant to interference from other gases. Furthermore, the three-dimensional structure maintains excellent dispersion and structural stability, contributing to the long-term operational stability of the device.

[0047] It is understood that the metal-organic framework-derived iron oxide in this application refers to iron oxide nanocrystals prepared by pyrolysis of iron metal-organic framework materials, which have a high specific surface area and active site density.

[0048] In some embodiments, the molar ratio of iron to europium in the metal-organic framework-derived iron-europium oxide material is (0.85-2.6):1, for example, 0.85:1, 0.9:1, 1.0:1, 1.2:1, 1.4:1, 1.6:1, 1.8:1, 2.0:1, 2.2:1, 2.4:1 or 2.6:1.

[0049] In some embodiments, the mass proportion of iron element in the metal organic framework derived iron-europium oxide material is 30% to 40%, for example, it can be 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39% or 40%.

[0050] In some embodiments, the mass proportion of europium element in the metal organic framework-derived iron-europium oxide material is 40% to 50%, for example, it can be 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49% or 50%.

[0051] As described above, the present application selects the contents of iron and europium in the metal organic framework-derived iron-europium oxide material so that the gas-sensitive material has the characteristics of high sensitivity and fast response.

[0052] In some embodiments, the metal-organic framework-derived iron-europium oxide material has a volume average particle size Dv50 of 100 nm to 800 nm, for example, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, or 800 nm. The volume average particle size selected in this application provides the gas-sensing material with high sensitivity and fast response.

[0053] A second aspect of the present application provides a method for preparing a metal-organic framework-derived iron-europium oxide material, the preparation method comprising:

[0054] providing a first solution comprising an Fe-based metal-organic framework material;

[0055] mixing a europium source with the first solution and aging the mixture to obtain an intermediate material;

[0056] After calcining the intermediate material, the metal organic framework-derived iron-europium oxide material is prepared.

[0057] This application uses Lewis acid etching to synthesize intermediate materials, forming a metal-organic framework-derived iron-europium oxide material with an octahedral structural morphology. The preparation method is simple, and the resulting material is uniform and has good crystallinity. This gives the gas-sensing material a large specific surface area and a large number of active sites, resulting in high sensitivity and rapid response recovery. It can accurately detect low formaldehyde concentrations and is not susceptible to interference from other gases. At the same time, the three-dimensional structure maintains good dispersion and structural stability, which is beneficial to the long-term operational stability of the device.

[0058] In some embodiments, the organic ligand contained in the Fe-based metal-organic framework material includes at least one of a terephthalic acid group, a trimellitic acid group, a 2-aminoterephthalic acid group, and a 2-hydroxyterephthalic acid group.

[0059] In some embodiments, the europium source includes at least one of EuCl3·6H2O, Eu2(CO3)3, and Eu(NO3)3·6H2O.

[0060] In some embodiments, the molar ratio of the iron element in the Fe-based metal-organic framework material to the europium element in the europium source is (0.85~2.6):1, for example, it can be 0.85:1, 0.9:1, 1.0:1, 1.2:1, 1.4:1, 1.6:1, 1.8:1, 2.0:1, 2.2:1, 2.4:1 or 2.6:1.

[0061] In some embodiments, the molar concentration of the europium source is 0.025 mol / L to 0.075 mol / L, for example, 0.025 mol / L, 0.035 mol / L, 0.045 mol / L, 0.055 mol / L, 0.065 mol / L, or 0.075 mol / L.

[0062] In some embodiments, the molar concentration of the Fe-based metal-organic framework material is 0.06 mol / L~0.07 mol / L, for example, it can be 0.060 mol / L, 0.061 mol / L, 0.062 mol / L, 0.063 mol / L, 0.064 mol / L, 0.065 mol / L, 0.066 mol / L, 0.067 mol / L, 0.068 mol / L, 0.069 mol / L or 0.070 mol / L.

[0063] In some embodiments, the aging temperature is 20°C to 40°C.

[0064] In some embodiments, the aging time is 10 hours to 15 hours, for example, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours or 15 hours.

[0065] In some embodiments, the calcination temperature is 300°C to 400°C, for example, 300°C, 310°C, 320°C, 330°C, 340°C, 350°C, 360°C, 370°C, 380°C, 390°C or 400°C.

[0066] In some embodiments, the calcination time is 0.5 h to 1.5 h, for example, 0.5 h, 0.6 h, 0.7 h, 0.8 h, 0.9 h, 1.0 h, 1.1 h, 1.2 h, 1.3 h, 1.4 h or 1.5 h.

[0067] In some embodiments, the method for preparing the Fe-based metal-organic framework material comprises:

[0068] A second solution containing a ligand material and an iron source is provided, and the Fe-based metal organic framework material is obtained after a hydrothermal reaction.

[0069] Optionally, the molar ratio of the ligand material to the iron source is (0.9-1.1):1.

[0070] Optionally, the ligand material includes at least one of terephthalic acid, trimellitic acid, 2-aminoterephthalic acid and 2-hydroxyterephthalic acid.

[0071] Further optionally, the ligand material includes terephthalic acid and trimellitic acid, and the molar ratio of the terephthalic acid to the trimellitic acid is (2-2.5):1, for example, it can be 2.0:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1 or 2.5:1.

[0072] Optionally, the iron source includes FeCl3·6H2O.

[0073] Optionally, the temperature of the hydrothermal reaction is 100°C to 150°C, for example, 100°C, 110°C, 120°C, 130°C, 140°C or 150°C.

[0074] Optionally, the hydrothermal reaction time is 20 h to 30 h, for example, 20 h, 21 h, 22 h, 23 h, 24 h, 25 h, 26 h, 27 h, 28 h, 29 h or 30 h.

[0075] The third aspect of the present application provides a use of the metal organic framework-derived iron-europium oxide material as described in the first aspect in the preparation of a gas sensor.

[0076] In a fourth aspect, the present application provides a gas sensor, which includes a substrate, a heating plate, an interdigitated electrode and a gas-sensitive material layer stacked in sequence, wherein the gas-sensitive material layer includes the metal-organic framework-derived iron-europium oxide material as described in the first aspect and / or the metal-organic framework-derived iron-europium oxide material prepared by the preparation method of the metal-organic framework-derived iron-europium oxide material as described in the second aspect.

[0077] In some embodiments, the gas sensor further includes a covalent organic framework material layer disposed on the surface of the gas-sensitive material layer.

[0078] Optionally, the covalent organic framework material layer comprises a covalent organic material, wherein the node group contained in the covalent organic material includes Tp (2,4,6-trihydroxy-1,3,5-benzenetricarboxaldehyde group), and the linking group includes Ma (m-phenylenediamine group). It is understood that the covalent organic framework material layer in the present application has a porous structure and a high specific surface area, and covalent organic materials (COFs) with other node groups and linking groups can also be used to improve the resistance of the covalent organic framework material layer to humidity interference.

[0079] Further optionally, the material of the covalent organic framework material layer comprises a modified covalent organic material. It is understood that the hydrophobicity, etc. can be improved by modifying the covalent organic material.

[0080] In some embodiments, the thickness of the gas-sensitive material layer in the gas sensor is 0.05 mm to 0.15 mm.

[0081] In some embodiments, the thickness of the covalent organic framework material layer in the gas sensor is 0.02 mm to 0.03 mm.

[0082] In some embodiments, the method for preparing the covalent organic material comprises:

[0083] adding water to the third solution containing the node monomer;

[0084] Then, a fourth solution containing a linking monomer is added and the solution is left at room temperature for a period of time to obtain the modified covalent organic material.

[0085] Optionally, the node monomer includes Tp. The solvent in the third solution may be dichloromethane.

[0086] Optionally, the concentration of the node monomer in the third solution is 0.001 mmol / mL to 0.002 mmol / mL.

[0087] Optionally, the volume of water added to the third solution is 50% to 70% of the volume of the third solution.

[0088] Optionally, the volume of the fourth solution added to the third solution is 90% to 110% of the volume of the third solution.

[0089] Optionally, the concentration of the linker monomer in the fourth solution is 0.0015 mmol / mL to 0.0025 mmol / mL.

[0090] Optionally, the linking monomer includes Ma. The solvent in the fourth solution may be water.

[0091] Optionally, the storage time at room temperature is 4 to 6 days.

[0092] Exemplarily, a method for preparing the modified covalent organic material is provided, comprising the following steps:

[0093] dissolving the node monomer in dichloromethane to obtain a third solution;

[0094] dissolving the linking monomer in water to obtain a fourth solution;

[0095] Water is added to the third solution, and then the fourth solution is added. After standing at room temperature for a period of time, the aldehyde amine is condensed to obtain a modified covalent organic material.

[0096] Exemplarily, a method for preparing the above-mentioned gas sensor is provided, comprising the following steps:

[0097] Providing MEMS sensor substrates;

[0098] Coating a slurry containing a metal organic framework-derived iron-europium oxide material on the heating area of ​​the MEMS sensor substrate so that it completely covers the surface of the interdigital electrode, and then drying and performing an aging treatment to obtain the gas-sensitive material layer;

[0099] A solution containing a covalent organic framework material is coated on the surface of the gas-sensitive material layer, and a covalent organic framework material layer is formed after drying.

[0100] Optionally, the drying temperature is room temperature.

[0101] Optionally, the aging treatment temperature is 200° C. to 250° C., and the aging time is 12 h to 24 h.

[0102] The embodiments of the present application will be described in detail below with reference to the examples. It should be understood that these examples are intended to illustrate the present application only and are not intended to limit the scope of the present application. The experimental methods for which specific conditions are not specified in the following examples are preferably referred to the guidance provided in the present application, and can also be based on the experimental manuals or conventional conditions in this area, or according to the conditions recommended by the manufacturer, or with reference to experimental methods known in the art.

[0103] Example 1

[0104] (1) Preparation of Fe-based metal-organic framework materials

[0105] 1.3 mmol of a ligand material was dispersed in 20 mL of deionized water, wherein the ligand material included terephthalic acid and trimellitic acid in a molar ratio of 7:3; 1.3 mmol of FeCl3·6H2O was then added and stirred for 30 minutes to prepare a second solution;

[0106] The second solution was sealed in a hydrothermal reactor and subjected to a hydrothermal reaction at 120° C. for 24 hours. After cooling to room temperature, the product was collected by centrifugation and washed with deionized water to prepare an Fe-based metal organic framework material.

[0107] (2) Preparation of metal-organic framework-derived iron-europium oxide materials

[0108] The Fe-based metal organic framework material prepared in the above step (1) is dispersed in 5 mL of deionized water to obtain a first solution;

[0109] 1 mmol of EuCl3·6H2O was added to the first solution and stirred for 15 min. After aging for 12 h, the solution was washed with deionized water and collected by centrifugation to obtain an intermediate material.

[0110] The intermediate material was calcined at 350 ° C for 1 h to prepare the metal organic framework derived iron-europium oxide material, as shown in the SEM image. Figure 1 shown.

[0111] (3) Gas sensor

[0112] A substrate for a MEMS structure sensor based on a multi-layer micro-hotplate is provided. A heating plate and interdigital electrodes are provided on the substrate. The substrate has a size of 1.0 mm × 1.0 mm × 0.5 mm, and the size of the heating area is 0.3 mm × 0.3 mm.

[0113] The metal organic framework derived iron-europium oxide material (denoted as EuFe-MOS) prepared in step (2) above was ground for 10 min, and then the powder was mixed with deionized water in an agate mortar to form a paste, and then ground again for 10 min. Figure 2As shown, the slurry was dipped into a capillary and dropped onto the interdigital electrode in the center of the MEMS chip, so that it completely covered the surface of the interdigital electrode. After drying at room temperature for 1.5 hours, it was aged at 230°C for 18 hours to form a gas-sensitive material layer with a thickness of 0.1 mm on the interdigital electrode.

[0114] For example Figure 2 As shown, 2.0 μL of TpMa-COF (a covalent organic framework formed by aldehyde-amine condensation reaction of 2,4,6-trihydroxy-1,3,5-benzenetricarboxaldehyde as a node monomer and m-phenylenediamine) was taken with a pipette and drop-coated on the device surface. It was dried at room temperature for 48 hours to form a covalent organic framework material layer with a thickness of 0.025 mm to prepare a gas sensor.

[0115] Example 2

[0116] A metal organic framework-derived iron-europium oxide material and a gas sensor were prepared according to the method of Example 1, except that 0.5 mmol of EuCl 3 ·6H 2 O was added to the first solution.

[0117] Example 3

[0118] A metal organic framework-derived iron-europium oxide material and a gas sensor were prepared according to the method of Example 1, except that 1.5 mmol of EuCl 3 ·6H 2 O was added to the first solution.

[0119] Example 4

[0120] A metal organic framework-derived iron-europium oxide material and a gas sensor were prepared according to the method of Example 1, except that the aging time was 5 h.

[0121] Example 5

[0122] A metal organic framework-derived iron-europium oxide material and a gas sensor were prepared according to the method of Example 1, except that the aging time was 20 h.

[0123] Example 6

[0124] A metal organic framework-derived iron-europium oxide material and a gas sensor were prepared according to the method of Example 1, except that the calcination temperature was 450°C.

[0125] Example 7

[0126] A metal organic framework-derived iron-europium oxide material and a gas sensor were prepared according to the method of Example 1, except that the gas sensor did not have a covalent organic framework material layer on the surface of the gas-sensitive material layer.

[0127] Comparative Example 1

[0128] (1) Preparation of metal-organic framework-derived iron-europium oxide materials

[0129] 1.3 mmol of a ligand material was dispersed in 20 mL of deionized water, wherein the ligand material included terephthalic acid and trimellitic acid in a molar ratio of 7:3; then 1.3 mmol of FeCl3·6H2O and 0.5 mmol of EuCl3·6H2O were added and stirred for 30 minutes to prepare a second solution;

[0130] The second solution was sealed in a hydrothermal reactor and subjected to a hydrothermal reaction at 120° C. for 24 hours. After cooling to room temperature, the product was collected by centrifugation and washed with deionized water to prepare a metal organic framework-derived iron-europium oxide material.

[0131] (2) Gas sensor

[0132] A gas sensor was prepared according to the method of Example 1, except that the gas-sensitive material layer used the metal organic framework-derived iron-europium oxide material prepared in step (1).

[0133] Comparative Example 2

[0134] A gas sensor was prepared according to the method of Example 1, except that the gas sensitive material in Example 1 was replaced by α-Fe2O3.

[0135] Performance testing:

[0136] S1. Place the gas sensor in the dynamic gas distribution system chamber, connect the device heating electrode to a constant voltage power supply, and connect the signal electrode to a resistance measuring device;

[0137] S2. Start the dynamic gas distribution system, start to pass background gas, and change the voltage applied to both ends of the gas sensor heating electrode by adjusting the constant pressure heating source;

[0138] S3. After the baseline resistance of the gas sensor stabilizes, record the resistance value Ra and start passing the gas to be tested mixed with the target gas;

[0139] S4. After the gas sensor response reaches a stable state, record the resistance value Rg and start passing background gas;

[0140] S5. The sensitivity Ra / Rg of the gas sensor to formaldehyde is obtained by testing.

[0141] (1) Optimal operating temperature, sensitivity, response time, and recovery time

[0142] During the test, the gas to be tested was 10ppm formaldehyde and the background gas was air with 0% relative humidity. The sensitivity of the gas sensor to 10ppm formaldehyde at different operating temperatures was tested to obtain the optimal operating temperature and corresponding sensitivity of the gas sensor. The test results are shown in Table 1. The optimal operating temperature curves of Example 1, Example 2, Example 3 and Comparative Example 2 are shown in Table 1. Figure 3 As shown, the response of Example 1 to 10 ppm formaldehyde has an optimal operating temperature of 235° C. and a sensitivity of 4.3.

[0143] The response time is the time required for the device resistance value to change by 90% during the response phase, and the recovery time is the time required for the device resistance to change by 90% during the recovery phase. The test results of the gas sensor of Example 1 are shown in FIG. Figure 4 As shown in the figure, the response time is 57s and the recovery time is 394s.

[0144] (2) Impact of environmental humidity

[0145] The gas sensors of Example 1 and Example 7 were tested for sensitivity to formaldehyde concentration of 10 ppm under different relative humidity background gases at the optimal operating temperature. The test results are as follows: Figure 5 As shown, it can be seen that the present application can effectively resist the influence of environmental humidity on formaldehyde concentration detection by setting a covalent organic framework material layer.

[0146] (3) Response to different concentrations of formaldehyde

[0147] The gas sensor was tested at the optimal working temperature and the background gas was 40% relative humidity air to measure the response under different formaldehyde concentrations. Figure 6 The gas sensor of the present application has a good response to formaldehyde gas in the concentration range of 0.5ppm to 50ppm, and can effectively detect formaldehyde gas below the international safety standard. Because the present application forms a covalent organic framework material layer on the surface of the gas-sensitive material layer, it blocks the diffusion of gas molecules, thereby reducing the sensitivity of the gas-sensitive material. While achieving moisture resistance, it also maintains good gas-sensing properties.

[0148] Table 1

[0149] serial number Sensitivity (10ppm formaldehyde, 0%RH) Response time (s) Recovery time (s) Example 1 4.3 57 394 Example 2 3.4 65 420 Example 3 2 78 470 Example 4 3.7 68 450 Example 5 3.5 65 430 Example 6 4.2 65 420 Example 7 4.4 11 30 Comparative Example 1 2.4 105 1250 Comparative Example 2 1.1 457 2370

[0150] The above tests show that:

[0151] (1) From Example 1 and Examples 2-3, it can be seen that the present application adjusts the content of europium and iron to ensure the number of activation centers in the gas-sensitive material, thereby improving the sensitivity.

[0152] (2) Comparing Example 1 with Examples 4-5, it can be seen that the present application controls the aging time, ensures the particle size of the gas-sensitive material, increases the specific surface area, and thus has higher sensitivity.

[0153] (3) Comparing Example 1 with Example 6, it can be seen that the present application controls the calcination temperature to ensure the surface morphology of the gas-sensitive material, thereby improving the sensitivity and response recovery speed of the gas-sensitive material.

[0154] (4) Compared with Example 7, Example 1 combined Figure 5 It can be seen that the present application still has high sensitivity under high ambient humidity by setting a covalent organic framework material layer, thereby having good resistance to ambient humidity interference. It is understandable that when the ambient humidity is 0%, since the covalent organic framework material layer is covered on the surface of the gas-sensitive material layer, it will have a certain impact on gas detection, so the response time and recovery time of Example 1 will be slightly worse than those of Example 7, but further compared with other gas-sensitive materials, such as Comparative Example 1 and Comparative Example 2, the gas-sensitive material of the present application has better sensitivity, faster response time and recovery time. This is because the present application adopts a metal organic framework-derived iron-europium oxide material with an octahedral structural morphology, which has good crystallinity, so that the gas-sensitive material has a larger specific surface area and more active sites, thereby having the characteristics of high sensitivity and fast response recovery.

[0155] (5) Comparison of Example 1 with Comparative Examples 1-2 shows that the metal-organic framework-derived iron-europium oxide material with an octahedral structure and good crystallinity used in this application provides the gas-sensitive material with a large specific surface area and a large number of active sites, thereby exhibiting high sensitivity and rapid response recovery, enabling accurate detection of low formaldehyde concentrations and being less susceptible to interference from other gases. Furthermore, the three-dimensional structure maintains good dispersion and structural stability, which is beneficial to the long-term operational stability of the device.

[0156] In summary, this application has at least the following features:

[0157] (1) The metal-organic framework-derived iron-europium oxide material of this application has an octahedral structure, can have good selectivity for formaldehyde, can effectively resist interference from other gases, has high sensitivity and a low detection concentration limit.

[0158] (2) The gas sensor of the present application has good air permeability and hydrophobicity by arranging a covalent organic framework material layer on the surface of the gas-sensitive material layer, thereby avoiding the influence of environmental water vapor on the gas-sensitive material and improving the gas sensor's anti-interference ability to environmental humidity.

[0159] (3) The gas sensor in this application can adopt a MEMS structure to reduce the device volume, thereby effectively reducing the overall power consumption of the device.

[0160] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0161] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, and such modifications and improvements fall within the scope of protection of the present application. Therefore, the scope of protection of the present application shall be determined by the appended claims.

Claims

1. A metal organic framework derived iron-europium oxide material, characterized in that: The metal organic framework derived iron-europium oxide material comprises a metal organic framework derived iron oxide and europium oxide doped in the metal organic framework derived iron oxide, and the material morphology of the metal organic framework derived iron-europium oxide material comprises an octahedral structure; The preparation method of the metal organic framework derived iron-europium oxide material comprises: Providing a first solution containing an Fe-based metal-organic framework material, wherein the organic ligand contained in the Fe-based metal-organic framework material includes at least one of a terephthalic acid group, a trimellitic acid group, a 2-aminoterephthalic acid group, and a 2-hydroxyterephthalic acid group; mixing a europium source with the first solution and aging the mixture to obtain an intermediate material; After calcining the intermediate material, the metal organic framework-derived iron-europium oxide material is prepared.

2. The metal organic framework derived iron-europium oxide material according to claim 1, characterized in that The metal organic framework derived iron-europium oxide material satisfies at least one of the following conditions: (1) The molar ratio of iron to europium in the metal organic framework-derived iron-europium oxide material is (0.85-2.6):1; (2) The mass proportion of iron in the metal organic framework-derived iron-europium oxide material is 30% to 40%; (3) The mass proportion of europium in the metal organic framework-derived iron-europium oxide material is 40% to 50%; (4) The volume average particle size Dv50 of the metal organic framework-derived iron-europium oxide material is 100 nm to 800 nm.

3. A method for preparing the metal organic framework-derived iron-europium oxide material according to claim 1 or 2, characterized in that: The preparation method comprises: Providing a first solution containing an Fe-based metal-organic framework material, wherein the organic ligand contained in the Fe-based metal-organic framework material includes at least one of a terephthalic acid group, a trimellitic acid group, a 2-aminoterephthalic acid group, and a 2-hydroxyterephthalic acid group; mixing a europium source with the first solution and aging the mixture to obtain an intermediate material; After calcining the intermediate material, the metal organic framework-derived iron-europium oxide material is prepared.

4. The method for preparing a metal organic framework-derived iron-europium oxide material according to claim 3, wherein: The europium source includes at least one of EuCl3·6H2O, Eu2(CO3)3 and Eu(NO3)3·6H2O.

5. The method for preparing a metal organic framework-derived iron-europium oxide material according to claim 3, wherein: The method for preparing the metal organic framework-derived iron-europium oxide material further satisfies at least one of the following conditions: (1) The molar ratio of the iron element in the Fe-based metal organic framework material to the europium element in the europium source is (0.85-2.6):1; (2) The molar concentration of the europium source is 0.025 mol / L to 0.075 mol / L; (3) The molar concentration of the Fe-based metal organic framework material is 0.06 mol / L~0.07 mol / L.

6. The method for preparing a metal organic framework-derived iron-europium oxide material according to claim 3, wherein: The method for preparing the metal organic framework-derived iron-europium oxide material further satisfies at least one of the following conditions: (1) The aging temperature is 20°C to 40°C, and the aging time is 10h to 15h; (2) The calcination temperature is 300°C to 400°C, and the calcination time is 0.5h to 1.5h.

7. The method for preparing a metal organic framework-derived iron-europium oxide material according to any one of claims 3 to 6, wherein: The preparation method of the Fe-based metal organic framework material comprises: A second solution containing a ligand material and an iron source is provided, and the Fe-based metal organic framework material is obtained after a hydrothermal reaction.

8. The method for preparing a metal organic framework-derived iron-europium oxide material according to claim 7, wherein: The ligand material includes at least one of terephthalic acid, trimellitic acid, 2-aminoterephthalic acid and 2-hydroxyterephthalic acid.

9. The method for preparing a metal organic framework-derived iron-europium oxide material according to claim 8, wherein: The ligand material includes terephthalic acid and trimellitic acid, and the molar ratio of the terephthalic acid to the trimellitic acid is (2-2.5):

1.

10. The method for preparing a metal organic framework-derived iron-europium oxide material according to claim 7, wherein: The iron source includes FeCl3·6H2O.

11. The method for preparing a metal organic framework-derived iron-europium oxide material according to claim 7, wherein: The temperature of the hydrothermal reaction is 100° C. to 150° C., and the time is 20 h to 30 h.

12. Use of the metal organic framework-derived iron-europium oxide material according to claim 1 or 2 in the preparation of a gas sensor.

13. A gas sensor, characterized in that: The gas sensor comprises a substrate, a heating plate, an interdigitated electrode and a gas-sensitive material layer stacked in sequence, and the gas-sensitive material layer comprises the metal-organic framework-derived iron-europium oxide material according to claim 1 or 2.

14. The gas sensor according to claim 13, wherein The gas sensor further includes a covalent organic framework material layer arranged on the surface of the gas-sensitive material layer.

15. The gas sensor according to claim 14, wherein The material of the covalent organic framework material layer comprises a covalent organic material, the node groups contained in the covalent organic material comprise a 2,4,6-trihydroxy-1,3,5-benzenetricarboxaldehyde group, and the connecting groups comprise a m-phenylenediamine group.

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