A metal organic framework crystal material, a preparation method and application thereof

Abstract

The present application relates to the field of temperature measurement, in particular to a kind of metal organic framework crystal material and its preparation method and application.The present application provides a kind of metal organic framework crystal material, wherein the crystal material is connected body 2,6-di (2,4-dicarboxyphenyl) -4- (phenyl) pyridine and Zn (II) connected with the crystal material with periodic three-dimensional network structure.The metal organic framework crystal material provided by the present application still keeps the afterglow characteristic under the condition of smaller particle size, and the charging time is shorter;At the same time, the decay time of the metal organic framework crystal material of the present application is seconds, and the light source only needs ordinary ultraviolet semiconductor light source, and the camera can record the time / color of afterglow decay, as the basis for temperature judgment, which greatly reduces the temperature measurement cost and simplifies the measurement process;In addition, the metal organic framework crystal material of the present application can be synthesized below 120 DEG C, which reduces the production cost and danger.

Description

Technical Field

[0001] This invention relates to the field of temperature measurement, and in particular to a metal-organic framework crystal material, its preparation method, and its application. Background Technology

[0002] In the field of measurement and control, it is often necessary to measure the surface temperature of the object being measured. Currently, there are three commonly used temperature measurement technologies: The first is to install thermocouples on the model surface to measure intermittent point temperatures through the thermoelectric effect. However, thermocouple temperature measurement technology can only perform point measurements. To obtain a more comprehensive temperature distribution, many measurement points need to be set up with thermocouple equipment, which places a significant burden on economic costs and assembly work. The second is to use infrared thermal imaging technology to measure the surface temperature distribution of the model by utilizing the infrared radiation from the model surface. However, in low-temperature environments, the infrared radiation from the model surface is relatively small, which reduces the accuracy and resolution of infrared thermal imaging, and reduces the sensitivity and accuracy of temperature measurement. The third is to use temperature-sensitive paint (TSP). A temperature-sensitive probe is mixed with a polymer to form a temperature-sensitive paint, which is then applied to the model surface. This temperature-sensitive probe can convert temperature changes into changes in luminous intensity or luminous lifetime, and the surface temperature distribution of the measured area can be measured through a non-contact optical measurement method. This method of temperature measurement using luminescent materials can achieve comprehensive temperature measurement of the model surface and maintain a strong signal at low temperatures, making it well-suited for temperature measurement applications in low-temperature environments.

[0003] However, there are some drawbacks to the method of measuring temperature through luminescent materials: (1) Inorganic long-afterglow materials are affected by trap distribution and quantum size effect. The smaller the particle size of the system, the weaker the long-afterglow luminescence intensity and duration. That is, the retention of the afterglow characteristics of materials with small particle size is not good. In addition, inorganic long-afterglow materials usually have deep traps and require a long charging time (about 3 minutes) to obtain the maximum afterglow luminescence and duration. (2) Most afterglow system luminescent materials are inorganic oxide matrix doped with rare earth ions, which are expensive, may be toxic, and the synthesis process may require high temperature above 800℃, resulting in high production energy consumption. (3) Fluorescent temperature sensors based on changes in luminescence intensity are subject to system errors caused by the drift and fluctuation of the excitation system, which reduces the measurement accuracy. Temperature sensors based on luminescence lifetime can avoid errors caused by the light source and sample state (amount of substance, thickness, crystallinity, etc.) in principle. However, measuring luminescence lifetime (nanosecond to millisecond) requires expensive CCD cameras and pulsed light sources, which have high usage costs and application thresholds. In fact, the light source lifetime may also be detected and mistakenly identified as a signal from the sample, affecting the results. Summary of the Invention

[0004] In view of this, the present invention provides a metal-organic framework crystal material, its preparation method, and its application. The metal-organic framework crystal material provided by the present invention retains its afterglow characteristics even with a small particle size, and has a short charging time. Furthermore, the decay time of the metal-organic framework crystal material of the present invention is on the order of seconds, requiring only a common ultraviolet semiconductor light source. A camera can record the afterglow decay time / color as a basis for temperature determination, greatly reducing temperature measurement costs and simplifying the measurement process. In addition, the metal-organic framework crystal material of the present invention can be synthesized below 120°C, reducing production costs and risks.

[0005] This invention provides a metal-organic framework crystal material, wherein the crystal material is a crystal material with a periodic three-dimensional network structure formed by linking 2,6-bis(2,4-dicarboxyphenyl)-4-(phenyl)pyridine and Zn(II).

[0006] The present invention also provides a method for preparing the metal-organic framework crystal material described in the above technical solution, comprising the following steps:

[0007] A) Preparation of solution:

[0008] Method 1:

[0009] Zinc salt and 2,6-bis(2,4-dicarboxyphenyl)-4-(phenyl)pyridine were dissolved in a solvent to obtain a solution;

[0010] Method 2:

[0011] A solution was obtained by mixing zinc salt, 2,6-bis(2,4-dicarboxyphenyl)-4-(phenyl)pyridine, solvent, and polyvinylpyrrolidone.

[0012] B) The solution obtained in step A) is subjected to heat treatment, and then cooled to crystallize, to obtain a metal-organic framework crystal material.

[0013] Preferably, in step B), the heat treatment temperature is 90–120°C and the time is 1–5 days.

[0014] Preferably, in step A), the zinc salt is at least one of zinc nitrate, zinc sulfate, zinc acetate, and zinc chloride.

[0015] Preferably, in the first method, the molar ratio of the zinc salt to 2,6-bis(2,4-dicarboxyphenyl)-4-(phenyl)pyridine is (1-5):1;

[0016] In the second method, the molar ratio of the zinc salt to 2,6-bis(2,4-dicarboxyphenyl)-4-(phenyl)pyridine is (1-5):1.

[0017] Preferably, in step A), the solvent is a mixture of water and N,N-dimethylformamide, or a mixture of water, ethanol and N,N-dimethylformamide.

[0018] Preferably, in the mixed solvent of water and N,N-dimethylformamide, the volume ratio of water to N,N-dimethylformamide is 2:(3-8);

[0019] In the mixed solvent of water, ethanol and N,N-dimethylformamide, the volume ratio of water, ethanol and N,N-dimethylformamide is 2:1:(3-8).

[0020] Preferably, step B) specifically includes: heat-treating the solution obtained in step A), then cooling it, separating the solid and liquid to obtain crystals, and then washing and drying them to obtain a metal-organic framework crystal material.

[0021] This invention also provides an application for temperature measurement using a low-temperature long-afterglow material, wherein the low-temperature long-afterglow material is the metal-organic framework crystal material described in the above technical solution or the metal-organic framework crystal material prepared by the preparation method described in the above technical solution.

[0022] Preferably, the temperature measurement process includes:

[0023] S1. Establish a statistical model:

[0024] Excite low-temperature long-afterglow materials to emit light, record the afterglow decay process at different temperatures, and statistically analyze the correspondence between the indicator quantity and temperature.

[0025] Wherein, the indicated quantity is afterglow color and / or afterglow decay time;

[0026] S2, Optical non-contact measurement:

[0027] The object being tested is excited to emit light, and the resulting indicated value is compared with the statistical results in step S1 to obtain the corresponding temperature.

[0028] This invention provides a metal-organic framework (MOF) crystal material, wherein the crystal material is a periodic three-dimensional network structure formed by linking 2,6-bis(2,4-dicarboxyphenyl)-4-(phenyl)pyridine and Zn(II). This invention also provides a method for preparing the above-mentioned MOF crystal material, and its application as a low-temperature long afterglow material for temperature measurement. The MOF crystal material provided by this invention retains its afterglow characteristics even with a small particle size, and has a short charging time; optimal afterglow emission is obtained after 2 seconds of 310nm–375nm ultraviolet irradiation, making it suitable for temperature measurement. Meanwhile, the decay time of the metal-organic framework crystal material of this invention is on the order of seconds. Only a common ultraviolet semiconductor light source is needed, and a camera can record the decay time / color of the afterglow as a basis for temperature judgment, greatly reducing temperature measurement costs and simplifying the measurement process. Furthermore, this invention uses the aforementioned metal-organic framework crystal material as a low-temperature afterglow material for temperature measurement, allowing the use of afterglow color changes and duration to indicate temperature. The afterglow properties are independent of the light source system, avoiding the influence of light source differences on the results. Because the emission range and afterglow range are different, the on and off states of the light source can be clearly distinguished. A common camera can record the afterglow color and duration, reducing usage costs and application barriers. In addition, the metal-organic framework crystal material of this invention can be synthesized below 120°C, reducing production costs and risks. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0030] Figure 1 A schematic diagram of the asymmetric structural unit in the metal-organic framework crystal material provided by the present invention;

[0031] Figure 2 A schematic diagram of the crystal structure of the metal-organic framework crystal material provided by the present invention; wherein... Figure 2 (a) and Figure 2 (b) are schematic diagrams of the crystal structure at different coordinate positions;

[0032] Figure 3 The XRD pattern of the metal-organic framework crystal material of this invention is shown below.

[0033] Figure 4 This is a SEM image of the metal-organic framework crystal material of the present invention;

[0034] Figure 5This is a graph showing the afterglow decay time variation of the metal-organic framework crystal material of the present invention under different charging times at 375 nm ultraviolet light.

[0035] Figure 6 This is a scan of the afterglow decay kinetics of the metal-organic framework crystal material of the present invention; wherein, the insertion... Figure I The graph shows the change in luminescence intensity over time during the charging phase. Figure II This is a schematic diagram showing how the intensity of afterglow decay changes over time.

[0036] Figure 7 This is a diagram showing the afterglow decay of the metal-organic framework crystal material of the present invention at temperatures ranging from 80 to 260 K.

[0037] Figure 8 This is a schematic diagram illustrating the relationship between the afterglow color and temperature change of the metal-organic framework crystal material of the present invention; wherein, Figure 8 (a) is a schematic diagram of the afterglow color at different temperatures. Figure 8 (b) Normalized afterglow emission spectrum at temperatures of 80–200 K. Figure 8 (c) is a schematic diagram of the maximum emission wavelength of the afterglow at temperatures of 80–200K;

[0038] Figure 9 This is a schematic diagram illustrating the relationship between the afterglow decay time and temperature of the metal-organic framework crystal material of the present invention; wherein, Figure 9 (a) is the afterglow decay curve after charging for 5 minutes at temperatures of 80–260 K; Figure 9 (b) Statistical graphs showing the time required for the afterglow intensity to reach 2%, 1%, 0.5%, and 0.2% of the maximum luminous intensity and to coincide with the background signal at temperatures ranging from 80K to 260K; Figure 9 (c) is a statistical chart showing the percentage of afterglow decay at 0.2s, 0.4s, 0.6s, 0.8s and 1s after the irradiation source is turned off at temperatures of 80–260K.

[0039] Figure 10 This is the afterglow spectrum of the metal-organic framework crystal material of the present invention measured at 80K using a fiber optic spectrometer. Detailed Implementation

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0041] The term “and / or” as used herein includes any and all combinations of one or more of the related listed items.

[0042] In this document, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when a range refers to an integer, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0043] In this article, when referring to units for data ranges, if the unit is only followed by the right endpoint, it indicates that the units for the left and right endpoints are the same. For example, 90~120℃ means that the units for the left endpoint "90" and the right endpoint "120" are both in degrees Celsius.

[0044] This document only specifically discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, just as any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and be combined with any other point or single value or with other lower or upper limits to form an unspecified range.

[0045] This invention provides a metal-organic framework crystal material, wherein the crystal material is a crystal material with a periodic three-dimensional network structure formed by linking 2,6-bis(2,4-dicarboxyphenyl)-4-(phenyl)pyridine and Zn(II).

[0046] Metal-organic framework (MOF) crystal materials refer to crystal materials with a periodic three-dimensional network structure formed by connecting organic ligands (or linkers) with metal ions / metal clusters. In this invention, the linker in the MOF crystal material is 2,6-bis(2,4-dicarboxyphenyl)-4-(phenyl)pyridine, whose structure is shown in formula (1). Its source is not particularly limited; it can be a commercially available product, such as one provided by Jinan Henghua Technology Co., Ltd. In this invention, the metal in the MOF crystal material is Zn(II); Zn(II) represents the +2 oxidation state of zinc in the compound. Framework crystal materials are three-dimensional network structures formed by linkers connecting metal ions according to a certain structure. The asymmetric structural units within them are as follows: Figure 1 As shown. Its crystal structure is as follows. Figure 2 As shown.

[0047]

[0048] In this invention, the crystal structure of the metal-organic framework crystal material is as follows: monoclinic crystal system; space group C2 / c; cell parameters are: β=91(1)°, α=γ=90°, Z=190.

[0049] In this invention, the metal-organic framework crystal material may also contain solvent molecules. Solvents are used in the preparation of the crystal material, and the crystal material is dried after synthesis. The solvent adhering to its surface is almost negligible. However, other solvents may participate in the crystal material. Specifically, part of the solvent acts as guest molecules, randomly distributed in the pores of the framework material, while another part participates in the coordination with the unsaturated Zn (partially evaporates and detaches after drying, making it impossible to determine the precise location and quantity). Therefore, in this invention, the chemical formula of the metal-organic framework crystal material can be represented by formula (2): C 54+3y H 26+2x+7y N 2+y O 16+x+y Zn3 equation (2), where x≥0, y≥0; x and y are determined by the solvent molecules that may exist in the crystal material. Their distribution in the crystal is random and related to factors such as the synthesis batch, storage environment and time. It is difficult to quantify them precisely and has little impact on the material properties. Therefore, they can be expressed inaccurately as C 54 H 26 N2O 16 Simplified representation of Zn3.

[0050] The present invention also provides a method for preparing the metal-organic framework crystal material described in the above technical solution, comprising the following steps:

[0051] A) Preparation of solution:

[0052] Method 1:

[0053] Zinc salt and 2,6-bis(2,4-dicarboxyphenyl)-4-(phenyl)pyridine were dissolved in a solvent to obtain a solution;

[0054] Method 2:

[0055] A solution was obtained by mixing zinc salt, 2,6-bis(2,4-dicarboxyphenyl)-4-(phenyl)pyridine, solvent, and polyvinylpyrrolidone.

[0056] B) The solution obtained in step A) is subjected to heat treatment, and then cooled to crystallize, to obtain a metal-organic framework crystal material.

[0057] [Regarding step A]:

[0058] Method 1:

[0059] Zinc salt and 2,6-bis(2,4-dicarboxyphenyl)-4-(phenyl)pyridine were dissolved in a solvent to obtain a solution.

[0060] In this invention, the zinc salt is preferably at least one selected from zinc nitrate, zinc sulfate, zinc acetate, and zinc chloride, and more preferably zinc nitrate. The zinc nitrate is preferably Zn(NO3)3·6H2O.

[0061] In this invention, the structure of 2,6-bis(2,4-dicarboxyphenyl)-4-(phenyl)pyridine is shown in formula (1) (see above for details).

[0062] In this invention, the preferred molar ratio of the zinc salt to 2,6-bis(2,4-dicarboxyphenyl)-4-(phenyl)pyridine is (1-5):1, specifically 1:1, 2:1, 3:1, 4:1, or 5:1.

[0063] In this invention, the solvent is preferably a mixture of water and N,N-dimethylformamide, or a mixture of water, ethanol, and N,N-dimethylformamide. Specifically, in the mixture of water and N,N-dimethylformamide, the volume ratio of water to N,N-dimethylformamide is preferably 2:(3-8), specifically 2:3, 2:4, 2:5, 2:6, 2:7, or 2:8. In the mixture of water, ethanol, and N,N-dimethylformamide, the volume ratio of water, ethanol, and N,N-dimethylformamide is preferably 2:1:(3-8), specifically 2:1:3, 2:1:4, 2:1:5, 2:1:6, 2:1:7, or 2:1:8.

[0064] In this invention, there are no particular limitations on the ratio of the reaction raw materials (i.e., zinc salt and 2,6-bis(2,4-dicarboxyphenyl)-4-(phenyl)pyridine) to the solvent, as long as the raw materials are fully and uniformly dissolved. Specifically, the preferred ratio of zinc salt to solvent is 1 mmol:(10-100) mL.

[0065] In this invention, there are no special restrictions on the dissolution temperature of zinc salt and 2,6-bis(2,4-dicarboxyphenyl)-4-(phenyl)pyridine in the solvent; it can be carried out at room temperature, specifically 15–25°C. The raw materials and solvent are mixed evenly until completely dissolved to obtain a solution.

[0066] Method 2:

[0067] A solution was prepared by mixing zinc salt, 2,6-bis(2,4-dicarboxyphenyl)-4-(phenyl)pyridine, solvent, and polyvinylpyrrolidone.

[0068] In this invention, the zinc salt is preferably at least one selected from zinc nitrate, zinc sulfate, zinc acetate, and zinc chloride, and more preferably zinc nitrate. The zinc nitrate is preferably Zn(NO3)3·6H2O.

[0069] In this invention, the structure of 2,6-bis(2,4-dicarboxyphenyl)-4-(phenyl)pyridine is shown in formula (1) (see above for details).

[0070] In this invention, the preferred molar ratio of the zinc salt to 2,6-bis(2,4-dicarboxyphenyl)-4-(phenyl)pyridine is (1-5):1, specifically 1:1, 2:1, 3:1, 4:1, or 5:1.

[0071] In this invention, the solvent is preferably a mixture of water and N,N-dimethylformamide, or a mixture of water, ethanol, and N,N-dimethylformamide. Specifically, in the mixture of water and N,N-dimethylformamide, the volume ratio of water to N,N-dimethylformamide is preferably 2:(3-8), specifically 2:3, 2:4, 2:5, 2:6, 2:7, or 2:8. In the mixture of water, ethanol, and N,N-dimethylformamide, the volume ratio of water, ethanol, and N,N-dimethylformamide is preferably 2:1:(3-8), specifically 2:1:3, 2:1:4, 2:1:5, 2:1:6, 2:1:7, or 2:1:8.

[0072] In this invention, there are no particular limitations on the ratio of the reaction raw materials (i.e., zinc salt and 2,6-bis(2,4-dicarboxyphenyl)-4-(phenyl)pyridine) to the solvent, as long as the raw materials are fully and uniformly dissolved. Specifically, the preferred ratio of zinc salt to solvent is 1 mmol:(10-100) mL, and more specifically, it can be 0.2 mmol:8 mL.

[0073] In this invention, the preferred ratio of zinc salt to polyvinylpyrrolidone is 0.05 mol:(30-60) mg, more preferably 0.05 mol:50 mg. The introduction of polyvinylpyrrolidone in this invention can improve the crystal morphology and make the crystals more uniform.

[0074] In this invention, there are no particular restrictions on the temperature at which the zinc salt, 2,6-bis(2,4-dicarboxyphenyl)-4-(phenyl)pyridine, solvent, and polyvinylpyrrolidone are mixed and dissolved; the process can be carried out at room temperature, specifically 15–25°C. After the above materials are mixed evenly until completely dissolved, a solution is obtained.

[0075] [Regarding step B]:

[0076] B) The solution obtained in step A) is subjected to heat treatment, and then cooled to crystallize, to obtain a metal-organic framework crystal material.

[0077] In this invention, the heat treatment temperature is preferably 90–120°C, specifically 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, or 120°C, more preferably 100°C. The heat treatment time is preferably 1–5 days, specifically 1 day, 2 days, 3 days, 4 days, or 5 days, more preferably 3 days. The first method of heat treatment is carried out in a high-temperature, high-pressure reactor; specifically, after obtaining the solution in step A), it is placed in a high-temperature, high-pressure reactor and kept at the aforementioned heat treatment temperature for the aforementioned duration. For the first heat treatment method, the heat treatment time is more preferably 2–5 days. The second method of heat treatment is heating and reflux; specifically, after obtaining the solution in step A), a reflux device is connected, and heating and reflux treatment is performed. In the second heat treatment method, it is preferable to add a stirring magnetic stirrer to the solution and heat the reaction while stirring. For the second treatment method, the heat treatment time is more preferably 24 hours to 48 hours.

[0078] After the above heat treatment, 2,6-bis(2,4-dicarboxyphenyl)-4-(phenyl)pyridine reacts with zinc salt, and 2,6-bis(2,4-dicarboxyphenyl)-4-(phenyl)pyridine and Zn(II) are linked together to form a crystalline material with a periodic three-dimensional network structure.

[0079] In this invention, after the above heat treatment, cooling and crystallization are performed. Preferably, the cooling is performed at room temperature, specifically 15–25°C. Crystallization gradually occurs during the heat treatment and cooling process, resulting in a solution containing crystals. Then, solid-liquid separation is performed to obtain crystals. The method of solid-liquid separation is not particularly limited and can be any conventional method in the art, such as filtration. In this invention, after obtaining the crystals, washing and drying are preferred. The solvent used for washing can be water and / or a volatile organic solvent. The drying is preferably vacuum drying. The drying temperature is preferably 60–90°C, specifically 60°C, 70°C, 80°C, 90°C, more preferably 80°C. The drying time is preferably 1–3 hours, specifically 1 hour, 2 hours, 3 hours, more preferably 2 hours. After the above treatment, a metal-organic framework crystal material is obtained. The asymmetric structural units in the obtained metal-organic framework crystal material are as follows: Figure 1 As shown, the crystal structure of the obtained metal-organic framework crystal material is as follows: Figure 2 As shown.

[0080] This invention also provides an application for temperature measurement using low-temperature long-afterglow materials, wherein the low-temperature long-afterglow material is the metal-organic framework crystal material described in the above technical solution or the metal-organic framework crystal material prepared by the preparation method described in the above technical solution.

[0081] In this invention, preferably, the temperature measurement process includes:

[0082] S1. Establish a statistical model:

[0083] Excite low-temperature long-afterglow materials to emit light, record the afterglow decay process at different temperatures, and statistically analyze the correspondence between the indicator quantity and temperature.

[0084] Wherein, the indicated quantity is afterglow color and / or afterglow decay time;

[0085] S2, Optical non-contact measurement:

[0086] The object being tested is excited to emit light, and the resulting indicated value is compared with the statistical results in step S1 to obtain the corresponding temperature.

[0087] Regarding step S1:

[0088] In this invention, the preferred method for exciting the low-temperature long-afterglow material to emit light is ultraviolet irradiation. The afterglow phenomenon of the metal-organic framework crystal material provided by this invention can be observed after irradiation with a 310nm / 365nm / 375nm near-ultraviolet lamp for 2 seconds at a low temperature. The afterglow spectrum can be measured by a CCD fiber optic spectrometer, and the afterglow decay time can be observed by a research-type fluorescence spectrometer and a camera.

[0089] In this invention, the afterglow decay process is recorded at different temperatures. The recording medium can be a spectrometer or a camera. The preferred different temperatures are 80–260 K.

[0090] In this invention, when statistically analyzing the correspondence between indicated quantities and temperature, the selected indicated quantities are preferably afterglow color and / or afterglow decay time. That is, the afterglow decay process is recorded at different temperatures, and the changes in the indicated quantities (afterglow color and / or decay time) with temperature variations are statistically analyzed. For example, the metal-organic framework crystal material of this invention, after 2 seconds of 375nm ultraviolet irradiation at 80K, exhibits green afterglow emission with a broadband emission peak at 520nm, and an afterglow duration of approximately 6-7 seconds. When the afterglow decay process is recorded using a camera at temperatures ranging from 80 to 260K, it can be observed that as the temperature increases from 80K to 260K, the afterglow decay time shortens from approximately 7 seconds to within 0.5 seconds, and the afterglow color changes from green to yellow. Therefore, both decay time and color can indicate temperature changes. This invention uses afterglow color and / or afterglow decay time as indicated quantities, statistically analyzes the correspondence between temperature and the aforementioned indicated quantities, and proposes a temperature measurement method based on afterglow decay time / afterglow color.

[0091] Regarding step S2:

[0092] After establishing the statistical model in step S1, actual temperature measurement is performed. Specifically, the object under test is excited to emit light, and an indication is obtained (specifically, the afterglow decay is recorded, and the afterglow color and / or afterglow decay time are indicated). The obtained indication is compared with the statistical results of step S1 to obtain the corresponding temperature, thus realizing the temperature measurement of the object.

[0093] As can be seen, this invention proposes a temperature measurement method based on afterglow decay time / afterglow color. Specifically, the temperature measurement method based on afterglow decay time proposes two strategies: 1. Statistically calculate the time required for the afterglow intensity to decay to a certain percentage at different temperatures. 2. Statistically calculate the percentage decrease in afterglow intensity after the light source is turned off for a certain period at different temperatures. The statistical results of the above two methods are shown below. Figure 9 As shown in the figure and Table 1-2, by calculating the time required for the afterglow to decay to a fixed percentage, or the percentage of afterglow decay at a fixed time, and comparing it with the statistical test results, the ambient temperature (low temperature environment) can be measured optically in a non-contact manner.

[0094] Table 1: Statistics on the time required for the afterglow signal to decay to 2%, 1%, 0.5%, and 0.2% at different temperatures.

[0095]

[0096] Table 2: Statistics on the percentage attenuation of afterglow signal after turning off the light source for 0.2s, 0.4s, 0.6s, 0.8s, and 1s at different temperatures.

[0097]

[0098] The temperature measurement method of the present invention can perform optical non-contact measurement of ambient temperature (low temperature environment), wherein the temperature of the low temperature environment can be 80-260K.

[0099] Compared with the prior art, the present invention has the following beneficial effects:

[0100] 1. In existing technologies, inorganic long-afterglow materials are affected by trap distribution and quantum size effects; the smaller the particle size of the system, the weaker the intensity and duration of long-afterglow luminescence. However, the metal-organic framework crystal material provided by this invention retains its afterglow characteristics even with a small particle size. Existing inorganic long-afterglow materials typically have deep traps, requiring a relatively long charging time (approximately 3 minutes) to achieve maximum afterglow luminescence and duration. In contrast, the metal-organic framework crystal material provided by this invention has a shorter charging time; optimal afterglow emission is achieved after 2 seconds of 310nm–375nm ultraviolet irradiation, which is suitable for temperature measurement.

[0101] 2. In existing technologies, most afterglow systems are inorganic oxide matrices doped with rare earth ions, which are expensive and potentially toxic; moreover, the synthesis process may require temperatures above 800°C, resulting in high energy consumption. This invention uses organic ligands and inexpensive zinc to synthesize the system at temperatures below 120°C, reducing production costs and risks.

[0102] 3. In existing technologies, when using afterglow materials for temperature measurement, fluorescence temperature sensors based on changes in luminescence intensity are susceptible to system errors caused by drift and fluctuations in the excitation system, reducing measurement accuracy. Temperature sensors based on luminescence lifetime can theoretically avoid errors caused by the light source and sample conditions (amount, thickness, crystallinity, etc.), but measuring luminescence lifetime (nanoseconds to milliseconds) requires expensive CCD cameras and pulsed light sources. Furthermore, the light source lifetime may also be detected and mistakenly interpreted as a signal from the sample. This invention uses afterglow color change and duration to indicate temperature. The afterglow properties are independent of the light source system, avoiding the influence of light source differences on the results. Because the luminescence and afterglow regions are different, the on / off state of the light source can be clearly distinguished. An ordinary camera can record the afterglow color and duration, reducing usage costs and application barriers. In summary, this invention uses afterglow materials with decay times on the order of seconds, requires only a common ultraviolet semiconductor light source, and a camera can record the afterglow decay time / color as a basis for temperature judgment, significantly reducing temperature measurement costs and simplifying the measurement process.

[0103] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims of the present invention.

[0104] Example 1

[0105] 1. Preparation of metal-organic framework crystal materials

[0106] A) Zn(NO3)3·6H2O and 2,6-bis(2,4-dicarboxyphenyl)-4-(phenyl)pyridine were mixed in a molar ratio of 4:1 and then dissolved in a mixed solvent of water-ethanol-N,N-dimethylformamide (v / v / v = 2 / 1 / 5). The mixture was stirred until completely dissolved to obtain a solution.

[0107] B) The solution was sealed in a high-temperature and high-pressure reactor and placed in an oven at 100°C for 3 days. After cooling to room temperature, it was removed and filtered to obtain flaky, aggregated crystalline samples. Then, it was washed three times with water and ethanol respectively, and dried under vacuum at 80°C for 2 hours to obtain 8.5 mg of pale yellow / yellow-green crystals.

[0108] 2. Characterization and Testing

[0109] (1) XRD characterization

[0110] The crystalline material obtained in Example 1 was characterized by X-ray diffraction, and the results are as follows: Figure 3 As shown.

[0111] (2) SEM characterization

[0112] The crystal material obtained in Example 1 was characterized by SEM, and the results are as follows: Figure 4 As shown, the average particle size of the obtained crystal material is less than 5 μm.

[0113] (3) Charging time test and afterglow decay dynamics scan

[0114] The afterglow decay of the crystal material obtained in Example 1 under different charging times under 375nm ultraviolet light is as follows: Figure 5 As shown, the afterglow decay time varies little when the charging time is between 2 seconds and 5 minutes. Figure 6 Insert Figure II This indicates that the luminous intensity reaches its maximum value 2 seconds after the start of charging, therefore the minimum charging time is 2 seconds.

[0115] The afterglow decay kinetics of the crystal material obtained in Example 1 was tested, and the results are as follows: Figure 6 As shown, the luminescence intensity at the 500nm emission point after 3 minutes of 365nm ultraviolet irradiation at 80K is normalized. Figure I The fitted curves show that the afterglow decay conforms to the bimolecular ionization recombination law. Figure II This indicates that under ultraviolet irradiation, the excited state undergoes ionization, i.e., a charging process, reaching its maximum in 1 to 1.5 seconds. Furthermore, the crystal material of this invention, after 30 seconds of 375 nm ultraviolet irradiation at 80 K, exhibits green afterglow emission, with a broadband emission peak in the 500 nm to 520 nm range, covering the 420 nm to 700 nm spectrum, and the afterglow lasts for approximately 6 to 7 seconds. Figure 10 As shown.

[0116] As can be seen from (2)-(3) above, the crystal material obtained by this invention has a small particle size (average particle size less than 5 μm); at 80 K, after 30 s of 375 nm ultraviolet irradiation, green afterglow emission can be observed, with a broadband emission peak in the range of 500 nm to 520 nm, covering the spectrum of 420 nm to 700 nm, and the afterglow duration is about 6 to 7 s, proving that the metal-organic framework crystal material provided by this invention still maintains its afterglow characteristics even with a small particle size. In addition, the metal-organic framework crystal material provided by this invention has a short charging time, and the optimal afterglow emission is obtained after 2 s of 310 nm to 375 nm ultraviolet irradiation.

[0117] (4) Afterglow attenuation test

[0118] The afterglow decay phenomenon of the crystal material obtained in Example 1 was recorded using a camera at temperatures ranging from 80 to 260 K. The results are as follows: Figure 7 As shown, it can be seen that as the temperature increases (from 80K to 260K), the afterglow decay time shortens (from about 7s to within 0.5s), and the afterglow color changes (gradually changing from green to yellow). Therefore, based on the correspondence between temperature and afterglow decay time / color, a temperature measurement method based on afterglow decay time / color is proposed.

[0119] (5) Temperature measurement based on afterglow color indication

[0120] The afterglow color and temperature changes of the crystalline material obtained in Example 1 were investigated, and the results are as follows: Figure 8 As shown, where, Figure 8 (a) is a schematic diagram of the afterglow color at different temperatures. Figure 8 (b) Normalized afterglow emission spectrum at temperatures of 80–200 K. Figure 8 (c) is a schematic diagram of the maximum emission wavelength of the afterglow at temperatures of 80–200 K. It can be seen that the afterglow spectrum redshifts and the wavelength becomes longer as the temperature increases, and the emission color gradually changes from green to yellow (the color of the afterglow gradually changes from green at 80 K–140 K to yellowish-green at 140 K–180 K, and then to yellow at 180 K–260 K). Based on this, the approximate temperature range can be intuitively determined by the color of the afterglow at a certain temperature. Figure 8 (b)-(c) show the correspondence between the afterglow spectrum and the maximum emission wavelength measured at different temperatures and the temperature. The temperature can be measured based on the maximum emission wavelength or color change of the afterglow.

[0121] (6) Afterglow decay time indication temperature measurement

[0122] The afterglow decay time and temperature variation of the crystal material obtained in Example 1 were investigated, and the results are as follows: Figure 9 As shown, where, Figure 9 (a) is a graph showing the afterglow decay curves after charging for 5 minutes at temperatures ranging from 80 to 260 K. Figure 9 (b) Statistical graphs showing the time required for the afterglow intensity to reach 2%, 1%, 0.5%, and 0.2% of the maximum luminous intensity and to coincide with the background signal at temperatures ranging from 80K to 260K (statistical data can be found in Table 1 above). Figure 9 (c) is a statistical graph showing the percentage of afterglow decay at 0.2s, 0.4s, 0.6s, 0.8s, and 1s after the irradiation source was turned off at temperatures ranging from 80 to 260K (statistical data can be found in Table 2 above). Among them, Figure 9(a) shows the afterglow decay curves after the material is charged for 5 minutes at different temperatures. The time from when the light source is turned off until the afterglow signal and the background (Black) completely overlap can be considered as the afterglow decay time. For example, the afterglow decay time is 6.36s at 90K and 5.44s at 100K. The time from when the light source is turned off until the afterglow brightness cannot be observed is considered the decay time. The shorter the photo interval, the higher the measurement accuracy. After irradiating the sample with a 375nm ultraviolet light source for 3 minutes at a certain temperature, the afterglow of the sample is photographed at regular intervals. The shorter the camera photo interval, the higher the measurement accuracy. Alternatively, video recording can also be used to record the afterglow decay process. By comparing the decay time and afterglow color with experimental data, the temperature can be measured. It can be seen that by calculating the time required for the afterglow to decay to a fixed percentage, or the percentage of afterglow decay at a fixed time, and comparing it with statistical experimental results, optical non-contact measurement of ambient temperature (low temperature environment) can be performed.

[0123] Example 2

[0124] A) Zn(NO3)3·6H2O and 2,6-bis(2,4-dicarboxyphenyl)-4-(phenyl)pyridine are mixed in a molar ratio of 1:1 and then dissolved in a mixed solvent of water-ethanol-N,N-dimethylformamide (v / v / v = 2 / 1 / 5). The mixture is stirred until completely dissolved to obtain a solution.

[0125] B) The solution was sealed in a high-temperature and high-pressure reactor and placed in an oven at 100°C for 3 days. After cooling to room temperature, it was removed and filtered to obtain flaky and aggregated crystalline samples. Then, it was washed three times with water and ethanol respectively, dried under vacuum at 80°C for 2 hours, and 52.2 mg of pale yellow / yellow-green crystals were obtained.

[0126] Example 3

[0127] A) Zn(NO3)3·6H2O and 2,6-bis(2,4-dicarboxyphenyl)-4-(phenyl)pyridine are mixed in a molar ratio of 2:1 and then dissolved in a mixed solvent of water-ethanol-N,N-dimethylformamide (v / v / v = 2 / 1 / 5). The mixture is stirred until completely dissolved to obtain a solution.

[0128] B) The solution was sealed in a high-temperature and high-pressure reactor and placed in an oven at 100°C for 3 days. After cooling to room temperature, it was removed and filtered to obtain flaky, aggregated crystalline samples. Then, it was washed three times with water and ethanol respectively, dried under vacuum at 80°C for 2 hours, and 29.8 mg of pale yellow / yellow-green crystals were obtained.

[0129] Example 4

[0130] A) Zn(NO3)3·6H2O and 2,6-bis(2,4-dicarboxyphenyl)-4-(phenyl)pyridine were mixed in a molar ratio of 3:1 and then dissolved in a mixed solvent of water-ethanol-N,N-dimethylformamide (v / v / v = 2 / 1 / 5). The mixture was stirred until completely dissolved to obtain a solution.

[0131] B) The solution was sealed in a high-temperature and high-pressure reactor and placed in an oven at 100°C for 3 days. After cooling to room temperature, it was removed and filtered to obtain flaky, aggregated crystalline samples. Then, it was washed three times with water and ethanol respectively, dried under vacuum at 80°C for 2 hours, and 15.6 mg of pale yellow / yellow-green crystals were obtained.

[0132] Example 5

[0133] A) Zn(NO3)3·6H2O and 2,6-bis(2,4-dicarboxyphenyl)-4-(phenyl)pyridine are mixed in a molar ratio of 4:1 and then dissolved in a mixed solvent of water and N,N-dimethylformamide (v / v = 2 / 5). The mixture is stirred until completely dissolved to obtain a solution.

[0134] B) The solution was sealed in a high-temperature and high-pressure reactor and placed in an oven at 100°C for 3 days. After cooling to room temperature, it was removed and filtered to obtain flaky, aggregated crystalline samples. Then, it was washed three times with water and ethanol respectively, dried under vacuum at 80°C for 2 hours, and 7.2 mg of pale yellow / yellow-green crystals were obtained.

[0135] Example 6

[0136] A) Zn(NO3)3·6H2O and 2,6-bis(2,4-dicarboxyphenyl)-4-(phenyl)pyridine were mixed in a molar ratio of 5:1 and then dissolved in a mixed solvent of water-ethanol-N,N-dimethylformamide (v / v / v = 2 / 1 / 5). The mixture was stirred until completely dissolved to obtain a solution.

[0137] B) The solution was sealed in a high-temperature and high-pressure reactor and placed in an oven at 100°C for 3 days. After cooling to room temperature, it was removed and filtered to obtain flaky, aggregated crystalline samples. Then, it was washed three times with water and ethanol respectively, dried under vacuum at 80°C for 2 hours, and 4.1 mg of pale yellow / yellow-green crystals were obtained.

[0138] Example 7

[0139] A) Zn(NO3)3·6H2O and 2,6-bis(2,4-dicarboxyphenyl)-4-(phenyl)pyridine were mixed in a molar ratio of 5:2 and then dissolved in a mixed solvent of water-ethanol-N,N-dimethylformamide (v / v / v = 2 / 1 / 5). The mixture was stirred until completely dissolved to obtain a solution.

[0140] B) After placing a magnetic stir bar in the solution, the mixture was placed in a round-bottom flask and connected to a reflux reflux apparatus. After refluxing at 100°C for 24 hours, crystal precipitation was observed. After cooling to room temperature, the mixture of mother liquor and sample was removed and filtered to obtain flaky, aggregated crystalline samples. Then, the samples were washed three times with water and ethanol respectively, dried under vacuum at 80°C for 2 hours, and 21.4 mg of pale yellow / yellow-green crystals were obtained.

[0141] Example 8

[0142] A) Zn(NO3)3·6H2O and 2,6-bis(2,4-dicarboxyphenyl)-4-(phenyl)pyridine were mixed at a molar ratio of 0.2 mmol and 0.05 mmol, respectively, and then dissolved in a mixed solvent of water-ethanol-N,N-dimethylformamide (v / v / v = 2 mL / 1 mL / 5 mL). 50 mg of polyvinylpyrrolidone was added, and the mixture was stirred until completely dissolved to obtain a solution.

[0143] B) After placing a magnetic stir bar in the solution, the mixture was placed in a round-bottom flask and connected to a reflux reflux apparatus. After refluxing at 100°C for 24 hours, crystal precipitation was observed. After cooling to room temperature, the mixture of mother liquor and sample was removed and filtered to obtain flaky, aggregated crystalline samples. Then, the samples were washed three times with water and ethanol respectively, dried under vacuum at 80°C for 2 hours, and 9.8 mg of pale yellow / yellow-green crystals were obtained.

[0144] The crystal materials obtained in Examples 2-8 were subjected to afterglow emission tests according to the test method in Example 1. The results showed that, similar to Example 1, the crystal materials obtained in Examples 2-8 exhibited green afterglow emission after approximately 30 seconds of 375nm ultraviolet irradiation at 80K. The spectrum showed a broadband emission peak in the range of 500nm to 520nm, covering the spectral range of 420nm to 700nm, and the afterglow duration was approximately 6-7 seconds. As the ambient temperature increased, the afterglow duration shortened, the afterglow emission color gradually turned yellow, and the afterglow spectrum gradually red-shifted. Based on the correspondence between temperature and afterglow decay time / color, a temperature measurement method based on afterglow decay time / color can be proposed.

[0145] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of these embodiments are merely to aid in understanding the method and core ideas of the present invention, including the best mode, and to enable any person skilled in the art to practice the present invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that those skilled in the art can make various improvements and modifications to the present invention without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims. The scope of protection of this patent is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements similar to those expressed in the claims, or if they include equivalent structural elements that are not substantially different from those expressed in the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. An application for temperature measurement using low-temperature long-afterglow materials, characterized in that, The low-temperature long afterglow material is a metal-organic framework crystal material; The crystal material in the metal-organic framework crystal material is a crystal material with a periodic three-dimensional network structure formed by linking 2,6-bis(2,4-dicarboxyphenyl)-4-(phenyl)pyridine and Zn(II). The crystal structure of the metal-organic framework crystal material is as follows: monoclinic system; space group C2 / c; cell parameters: a=22.7108(6)Å, b=29.2405(7)Å, c=22.9120(6)Å, β= , α=γ= Z=190; The chemical formula of the metal-organic framework crystal material can be represented by formula (2): C 54+3y H 26+2x+7y N 2+y O 16+x+y Zn3 Equation (2), where x≥0, y≥0.

2. The application according to claim 1, characterized in that, The temperature measurement process includes: S1. Establish a statistical model: Excite low-temperature long-afterglow materials to emit light, record the afterglow decay process at different temperatures, and statistically analyze the correspondence between the indicator quantity and temperature. Wherein, the indicated quantity is afterglow color and / or afterglow decay time; S2, Optical non-contact measurement: The object being tested is excited to emit light, and the resulting indicated value is compared with the statistical results in step S1 to obtain the corresponding temperature.

3. The application according to claim 1, characterized in that, The preparation method of the metal-organic framework crystal material includes the following steps: A) Preparation of solution: Method 1: Zinc salt and 2,6-bis(2,4-dicarboxyphenyl)-4-(phenyl)pyridine were dissolved in a solvent to obtain a solution; Method 2: A solution was obtained by mixing zinc salt, 2,6-bis(2,4-dicarboxyphenyl)-4-(phenyl)pyridine, solvent, and polyvinylpyrrolidone. B) The solution obtained in step A) is subjected to heat treatment, and then cooled to crystallize, to obtain a metal-organic framework crystal material.

4. The application according to claim 3, characterized in that, In step B), the heat treatment temperature is 90~120℃ and the time is 1~5 days.

5. The application according to claim 3, characterized in that, In step A), the zinc salt is at least one of zinc nitrate, zinc sulfate, zinc acetate, and zinc chloride.

6. The application according to claim 3, characterized in that, In Method 1, the molar ratio of the zinc salt to 2,6-bis(2,4-dicarboxyphenyl)-4-(phenyl)pyridine is (1~5):1; In the second method, the molar ratio of the zinc salt to 2,6-bis(2,4-dicarboxyphenyl)-4-(phenyl)pyridine is (1~5):

1.

7. The application according to claim 3, characterized in that, In step A), the solvent is a mixture of water and N,N-dimethylformamide, or a mixture of water, ethanol and N,N-dimethylformamide.

8. The application according to claim 7, characterized in that, In the mixed solvent of water and N,N-dimethylformamide, the volume ratio of water to N,N-dimethylformamide is 2:(3~8); In the mixed solvent of water, ethanol and N,N-dimethylformamide, the volume ratio of water, ethanol and N,N-dimethylformamide is 2:1:(3~8).

9. The application according to claim 3, characterized in that, Step B) specifically includes: heat-treating the solution obtained in step A), then cooling it, separating the solid and liquid to obtain crystals, and then washing and drying them to obtain metal-organic framework crystal materials.

Images