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

Abstract

The invention relates to the technical field of sensors, and provides a metal organic framework derived iron-europium oxide material, a preparation method and application thereof and a gas sensor, 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, the material morphology of the metal organic framework derived iron-europium oxide material comprises an octahedral structure. The metal organic framework derived iron-europium oxide material has the characteristics of high sensitivity to formaldehyde, fast response and recovery and the like.

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 and a preparation method, application and gas sensor thereof. Background Art

[0002] Harmful gases in indoor environmental pollutants include formaldehyde, benzene and ammonia. For example, long-term exposure to an environment containing formaldehyde gas will have an impact on human health. In traditional technology, metal oxide semiconductor resistive sensors are used to detect the formaldehyde concentration in the environment. However, gas-sensitive materials made of zinc oxide, tin dioxide and other materials are easily interfered by other gases during the detection process, resulting in poor accuracy in formaldehyde detection concentration and difficulty in detecting 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 a preparation method, application and gas sensor thereof.

[0004] In a first aspect, the present application provides a metal-organic framework-derived iron-europium oxide material, wherein 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.

[0005] In some embodiments, the molar ratio of iron element to europium element 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 the europium source with the first solution and aging 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 phthalic acid and trimellitic acid, and the molar ratio of the phthalic 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 the traditional technology, this application has at least the following beneficial effects:

[0030] The present application uses a metal organic framework derived iron-europium oxide material including an octahedral structural morphology, which has good crystallinity, so that the gas-sensitive material has a large specific surface area and more active sites, thus having the characteristics of high sensitivity and fast response recovery, and can accurately detect low formaldehyde concentrations, and is not easily interfered by other gases. At the same time, the three-dimensional structure can maintain good dispersion and structural stability, which is conducive to the long-term working stability of the device. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0032] Figure 2 This is a schematic diagram of preparing 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 The optimal operating temperature curve diagram of the gas sensor 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 sensitivity comparison diagram 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 the embodiments and examples, the present application is further described in detail. These embodiments and examples are only used to illustrate the present application and are not used to limit the scope of the present application. The purpose of providing these embodiments and examples is to make the understanding of the disclosure of the present application more thorough and comprehensive. It should also be understood that the present application can be implemented in many different forms, and is not limited to the embodiments and examples described herein. Those skilled in the art can make various changes or modifications without violating the connotation of the present application, and the equivalent form obtained also falls within the protection scope of the present application. In addition, in the description below, a large number of specific details are given in order to provide a more comprehensive understanding of the present application. It should be understood that the present 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 belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0039] In this application, "optionally", "optional", and "optional" mean optional or dispensable, that is, any one of the two parallel schemes of "yes" or "no". If multiple "options" appear in a technical solution, unless otherwise specified and there is no contradiction or mutual restriction, each "optional" is independent.

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

[0041] In the present 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 the present application, when it comes to a numerical interval (i.e., a numerical range), unless otherwise specified, the distribution of the optional numerical values ​​in the numerical interval is considered to be continuous, and includes the two numerical endpoints (i.e., the minimum and maximum values) of the numerical interval, and each numerical value between the two numerical endpoints. Unless otherwise specified, when the numerical interval only refers to an integer in the numerical interval, it includes the two endpoint integers of the numerical range, and each integer between the two endpoints, which is equivalent to directly listing each integer. When multiple numerical ranges are provided to describe features or characteristics, these numerical ranges can be combined. In other words, unless otherwise specified, the numerical range disclosed in the present application should be understood to include any and all sub-ranges included therein. The "numerical value" in the numerical interval can be any quantitative value, such as a number, a percentage, a ratio, etc. "Numerical interval" allows for a broad range of 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 with all contents and all purposes. When the 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 the cited documents are involved in this application, the examples and preferred methods of the cited relevant technical features can also be incorporated into this application as references, but are limited to the implementation of 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 modified adaptively according to the description of this application.

[0044] In traditional technology, the gas-sensitive materials in formaldehyde gas sensors are made of zinc oxide, tin dioxide and other materials. 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 it is difficult to detect low-concentration formaldehyde.

[0045] The first aspect of 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] The present application uses a metal organic framework derived iron-europium oxide material including an octahedral structural morphology, which has good crystallinity, so that the gas-sensitive material has a large specific surface area and more active sites, thus having the characteristics of high sensitivity and fast response recovery, and can accurately detect low formaldehyde concentrations, and is not easily interfered by other gases. At the same time, the three-dimensional structure can maintain good dispersion and structural stability, which is conducive to the long-term working stability of the device.

[0047] It is understood that the metal organic framework derived iron oxide in the present 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, 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.

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

[0052] In some embodiments, the volume average particle size Dv50 of the metal organic framework derived iron-europium oxide material is 100nm~800nm, for example, it can be 100nm, 200nm, 300nm, 400nm, 500nm, 600nm, 700nm or 800nm. The volume average particle size of the material selected in the present application is selected as above, so that the gas-sensitive material has the characteristics of high sensitivity and fast response.

[0053] The 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 the europium source with the first solution and aging to obtain an intermediate material;

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

[0057] The present application adopts Lewis acid etching method to synthesize intermediate materials, which can form metal organic framework derived iron-europium oxide materials with octahedral structural morphology. The preparation method is simple, and the prepared material has good uniformity and good crystallinity, so that the gas-sensitive material has a large specific surface area and more active sites, thus having the characteristics of high sensitivity and fast response recovery, and can accurately detect low formaldehyde concentrations, and is not easily interfered by other gases. At the same time, the three-dimensional structure can maintain good dispersibility and structural stability, which is conducive to the long-term working 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 h to 15 h, for example, 10 h, 11 h, 12 h, 13 h, 14 h or 15 h.

[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 phthalic acid and trimellitic acid, and the molar ratio of the phthalic 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, it can be 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 material of the covalent organic framework material layer comprises a covalent organic material, the node group contained in the covalent organic material comprises Tp (2,4,6-trihydroxy-1,3,5-benzenetricarboxaldehyde group), and the linking group comprises Ma (meta-phenylenediamine group). It can be 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 (Covalent Organic Frameworks, 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 and the like 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 connecting monomer is added and left to stand 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 linking 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 being left 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 electrodes, and performing an aging treatment after drying 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 time is 12h to 24h.

[0102] The embodiments of the present application will be described in detail below in conjunction with examples. It should be understood that these examples are only used to illustrate the present application 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 manual or normal conditions in this area, can also be based on the conditions recommended by the manufacturer, or refer 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 is dispersed in 20 mL of deionized water, wherein the ligand material includes terephthalic acid and trimellitic acid in a molar ratio of 7:3; then 1.3 mmol of FeCl3·6H2O is added and stirred for 30 minutes to prepare a second solution;

[0106] The second solution was sealed in a hydrothermal reactor, and a hydrothermal reaction was carried out 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] Dispersing the Fe-based metal organic framework material prepared in the above step (1) 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 a metal organic framework-derived iron-europium oxide material, as shown in the SEM image. Figure 1 shown.

[0111] (3) Gas sensor

[0112] A substrate of a MEMS structure sensor based on a multi-layer micro-hotplate is provided, a heating plate and interdigital electrodes are arranged on the substrate, the size of the substrate is 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 is dripped on the interdigital electrode in the center of the MEMS chip with a capillary to completely cover the surface of the interdigital electrode. After drying at room temperature for 1.5 hours, it is 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 an aldehyde-amine condensation reaction between 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. The mixture was dried at room temperature for 48 hours to form a covalent organic framework material layer with a thickness of 0.025 mm, and a gas sensor was prepared.

[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 EuCl3·6H2O 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 EuCl3·6H2O 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 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 min 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 is prepared according to the method of Example 1, except that the gas sensitive material layer adopts the metal organic framework derived iron-europium oxide material prepared in the above 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 Test:

[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 passing the 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 is stable, the resistance value Ra is recorded, and the gas to be tested mixed with the target gas is started to flow;

[0139] S4. After the gas sensor response reaches a stable state, the resistance value Rg is recorded and the background gas is started to flow;

[0140] S5. Test and obtain the sensitivity Ra / Rg of the gas sensor to formaldehyde.

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

[0142] During the test, the gas to be tested was 10 ppm formaldehyde, and the background gas was air with 0% relative humidity. The sensitivity of the gas sensor to 10 ppm formaldehyde at different working temperatures was tested to obtain the optimal working temperature and corresponding sensitivity of the gas sensor. The test results are shown in Table 1, where the optimal working temperature curves of Example 1, Example 2, Example 3 and Comparative Example 2 are shown in Table 1. Figure 3 As shown, the optimal operating temperature of Example 1 to 10 ppm of formaldehyde is 235° C., and the sensitivity reaches 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 as follows: Figure 4 As shown, 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 working 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 placed at the optimal operating temperature and the background gas was 40% relative humidity air, and the response under different formaldehyde concentrations was tested. The formaldehyde response of the gas sensor of Example 1 is as follows: Figure 6 The gas sensor of the present application has a good response to formaldehyde gas in the concentration range of 0.5ppm~50ppm, and can effectively detect formaldehyde gas below the international safety standard. Since the present application forms a covalent organic framework material layer on the surface of the gas-sensitive material layer, it will block the diffusion of gas molecules, thereby reducing the sensitivity of the gas-sensitive material, achieving moisture resistance while ensuring good gas-sensitive properties.

[0148] Table 1

[0149]

[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) Compared with Examples 4-5, Example 1 shows that the present invention controls the aging time, ensures the particle size of the gas-sensitive material, increases the specific surface area, and thus has a higher sensitivity.

[0153] (3) Compared 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 is combined with 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, thus 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 that of Example 7, but further compared with other gas-sensitive materials, such as Comparative Examples 1 and 2, the gas-sensitive material of the present application has better sensitivity, faster response time and recovery time. This is because the present application uses 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) Compared with Comparative Examples 1-2, Example 1 shows that the metal organic framework derived iron-europium oxide material with an octahedral structure morphology used in this application has good crystallinity, so that the gas-sensitive material has a large specific surface area and more active sites, thereby having the characteristics of high sensitivity and fast response recovery, and can accurately detect low formaldehyde concentrations, and is not easily interfered by other gases. At the same time, the three-dimensional structure can maintain good dispersibility and structural stability, which is beneficial to the long-term working 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 the present 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) In the gas sensor of the present application, a covalent organic framework material layer is arranged on the surface of the gas-sensitive material layer, so that the gas sensor has good air permeability and hydrophobicity, 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 size, thereby effectively reducing the overall power consumption of the device.

[0160] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described 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 only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be construed as limiting the scope of the application. It should be noted that, for a person of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached 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 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 comprises an octahedral structure.

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 element to europium element 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 100nm~800nm.

3. A method for preparing a metal organic framework derived iron-europium oxide material, characterized in that: The preparation method comprises: Providing a first solution comprising an Fe-based metal-organic framework material; Mixing the europium source with the first solution and aging 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 the metal organic framework derived iron-europium oxide material according to claim 3, characterized in that: The method for preparing the metal organic framework derived iron-europium oxide material satisfies at least one of the following conditions: (1) 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; (2) The europium source includes at least one of EuCl3·6H2O, Eu2(CO3)3 and Eu(NO3)3·6H2O.

5. The method for preparing the metal organic framework derived iron-europium oxide material according to claim 3, characterized in that: The method for preparing the metal organic framework derived iron-europium oxide material also 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 the metal organic framework derived iron-europium oxide material according to claim 3, characterized in that: The method for preparing the metal organic framework derived iron-europium oxide material also 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 the metal organic framework derived iron-europium oxide material according to any one of claims 3 to 6, characterized in that: The preparation method of the Fe-based metal organic framework material comprises: Providing a second solution comprising a ligand material and an iron source, and obtaining the Fe-based metal organic framework material after a hydrothermal reaction; 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 phthalic acid and trimellitic acid, and the molar ratio of the phthalic acid to the trimellitic acid is (2-2.5):1; Optionally, the iron source includes FeCl3·6H2O; Optionally, the temperature of the hydrothermal reaction is 100° C. to 150° C., and the time is 20 h to 30 h.

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

9. A gas sensor, characterized in that: The gas sensor comprises a substrate, a heating plate, an interdigitated electrode and a gas-sensitive material layer which are stacked in sequence, wherein the gas-sensitive material layer comprises the metal-organic framework-derived iron-europium oxide material according to claim 1 or 2 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 according to any one of claims 3 to 7.

10. The gas sensor according to claim 9, characterized in that The gas sensor further comprises a covalent organic framework material layer disposed on the surface of the gas-sensitive material layer; 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.

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