Preparation method and application of cadmium metal-organic framework material

Abstract

The invention discloses a preparation method and application of a cadmium metal-organic framework material, and belongs to the technical field of functional materials. The chemical formula of the cadmium metal-organic framework material is {[Cd2 (L) 2H2O] 2 (H2O)}. (4H2O). (DMF), and L is deprotonated 4, 4 '-(2-(1H-pyrazole-4-alkyl)-1H-imidazole-4, 5-dialkyl) dibenzoic acid. The cadmium metal-organic framework material has a specific crystal structure and space structure, is high in synthesis purity and good in stability, and can be used for detecting fluazinam pesticides. Quantitative detection of fluazinam can be realized through fluorescence intensity detection, the lowest limit value of detection is 1.68 mu M, and semi-quantitative detection of fluazinam can be conveniently and quickly realized through colorimetric detection on a paper-based device.

Description

Technical Field

[0001] The invention relates to the technical field of functional materials, and in particular to a preparation method and application of a cadmium metal-organic framework material. Background Art

[0002] Fluazinam is an effective broad-spectrum fungicide belonging to the pyridinamine class. It plays a key role in pest prevention and food preservation and is widely used in medicine, agriculture, water treatment, diet and cosmetics. However, the indiscriminate use of fluazinam will lead to environmental pollution, which will then accumulate in the human body through the food chain and pose a major threat to human health. Chronic and subchronic toxicity studies have clearly demonstrated the harmful effects of fluazinam on important organs such as the liver, stomach, eyes, lungs and brain, and may also induce dermatitis and asthma in humans.

[0003] With increasing attention, various analytical techniques, including gas chromatography, high-performance liquid chromatography, gas chromatography-mass spectrometry, and liquid chromatography-tandem mass spectrometry, have been used to detect fluazinam. Although these methods have good sensitivity and accuracy, they also have the disadvantages of time-consuming detection procedures, complex operations, and high costs, which limit their development and application. In recent decades, various sensors have been widely used in food and environmental testing due to their high sensitivity and portability. Metal-organic frameworks (MOFs), as a potential sensor material, have attracted attention due to their structural and functional diversity. It is necessary to develop high-performance metal-organic framework materials that can be used to detect fluazinam. Summary of the invention

[0004] The purpose of the present invention is to provide a preparation method and application of a cadmium metal-organic framework material to solve the problems existing in the above-mentioned prior art.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] One of the technical solutions of the present invention: a cadmium metal-organic framework material, the chemical formula of which is {[Cd2(L)2H2O]2(H2O)}·(4H2O)·(DMF), wherein L is deprotonated (losing two H atoms) 4,4′-(2-(1H-pyrazole-4-alkyl)-1H-imidazole-4,5-dialkyl)dibenzoic acid;

[0007] The crystal structure parameters of the cadmium metal-organic framework material include:

[0008] The space group is Pī and the unit cell parameters are α=90.000°, β=107.696°, and γ=90.000°.

[0009] Furthermore, the molecular formula of the cadmium metal-organic framework material is Cd4C 83H 69 O 24 N 17 .

[0010] Furthermore, the framework structure of the cadmium metal-organic framework material is: the asymmetric unit ([Cd2(L)2H2O] part, the molecular formula is Cd2C 40 H 26 O9N8) consists of two Cd 2+ ion, two organic ligands and a coordinated water molecule. Cd1 adopts a six-coordination mode, with an average Cd1-O bond length of 2.791A, of which 4 oxygen atoms come from the carboxyl groups of 2 organic ligands, and 2 nitrogen atoms come from two pyrazole rings. Cd2 exhibits a five-coordination mode, with an average Cd2-O bond length of 2.791A, of which 3 oxygen atoms come from the carboxyl groups of 2 organic ligands, 1 oxygen atom comes from water, and 1 nitrogen atom comes from the pyrazole ring. The tested pore size distribution is represented by values ​​such as 18.03714, 17.11764, 16.19876, 13.65568, and 10.85791, and the porosity can reach 0.93425. The schematic diagram of the secondary building unit structure of the cadmium metal-organic framework material is shown in Figure 2 shown.

[0011] The second technical solution of the present invention: The preparation method of the above-mentioned cadmium metal-organic framework material is characterized by comprising the following steps:

[0012] 4,4′-(2-(1H-pyrazole-4-alkyl)-1H-imidazole-4,5-dialkyl)dibenzoic acid (abbreviated as H2L), cadmium salt and a mixed solvent of N,N-dimethylformamide (DMF) and water are mixed and heated to react to obtain the cadmium metal-organic framework material; the structural formula of the 4,4′-(2-(1H-pyrazole-4-alkyl)-1H-imidazole-4,5-dialkyl)dibenzoic acid is as shown in Formula I (molecular formula is C 20 H 14 O4N4):

[0013]

[0014] Furthermore, the molar ratio of the 4,4′-(2-(1H-pyrazole-4-alkyl)-1H-imidazole-4,5-dialkyl)dibenzoic acid and the cadmium salt is 3:10; the volume ratio of N,N-dimethylformamide to water in the mixed solvent is 3:1; the temperature of the heating reaction is 90° C. and the time is 72 hours.

[0015] Furthermore, the cadmium salt is cadmium nitrate (Cd(NO3)2).

[0016] Furthermore, the specific operation of mixing 4,4′-(2-(1H-pyrazole-4-alkyl)-1H-imidazole-4,5-dialkyl)dibenzoic acid (abbreviated as H2L), cadmium salt and a mixed solvent of N,N-dimethylformamide (DMF) and water is: adding H2L to a mixed solvent of N,N-dimethylformamide and water to prepare an H2L solution with a concentration of 0.010 g / mL (0.03 mmol / mL); adding Cd(NO3)2 to a mixed solvent of N,N-dimethylformamide and water to prepare a Cd(NO3)2 solution with a solubility of 0.012 g / mL (0.05 mmol / mL); and mixing the H2L solution and 2 mL of Cd(NO3)2 solution in a volume ratio of 1:2.

[0017] Furthermore, after the heating reaction is completed, the process also includes naturally cooling to room temperature, filtering, washing, and drying.

[0018] Furthermore, the preparation method of the 4,4′-(2-(1H-pyrazole-4-alkyl)-1H-imidazole-4,5-dialkyl)dibenzoic acid comprises:

[0019] Methyl 4,4'-oxalyldibenzoate, 4-formylpyrazole and ammonium acetate are suspended in acetic acid at room temperature, and then refluxed for reaction. After the reaction is completed, the reaction system is poured into water and stirred at room temperature to obtain the 4,4'-(2-(1H-pyrazole-4-alkyl)-1H-imidazole-4,5-dialkyl)dibenzoic acid.

[0020] Furthermore, the usage ratio of 4,4'-oxalyl dibenzoic acid methyl ester, 4-formyl pyrazole, ammonium acetate and acetic acid is 0.02 mol: 0.034 mol: 0.2 mol: 250 mL; the temperature of the reflux reaction is 120° C., and the time is 8 h.

[0021] Furthermore, the stirring time is 30 minutes.

[0022] Furthermore, the volume ratio of the acetic acid to the water used when the reaction system is poured into water after the reaction is completed is 1:2.

[0023] Furthermore, after the stirring is completed, the process further includes filtering and collecting the precipitate, washing with water, and drying.

[0024] Furthermore, the drying temperature is 100° C. and the drying time is 12 hours.

[0025] The third technical solution of the present invention: application of the above-mentioned cadmium metal-organic framework material in the detection of fluazinam.

[0026] The fourth technical solution of the present invention: a quantitative detection method of fluazinam (fluorescence detection), comprising the following steps: adding the above-mentioned cadmium metal-organic framework material to fluazinam standard solutions of different concentrations, and then testing the fluorescence intensity under the excitation of 365nm light, and drawing a standard curve according to the concentration of the fluazinam standard solution and the fluorescence intensity at the corresponding concentration and the fluorescence intensity when the concentration of the fluazinam standard solution is 0; adding the above-mentioned cadmium metal-organic framework material in the test sample, and then testing the fluorescence intensity under the excitation of 365nm light, substituting the fluorescence intensity corresponding to the test sample into the standard curve to obtain the concentration of fluazinam in the test sample.

[0027] Significant fluorescence quenching can be observed in cadmium metal-organic framework materials in the fluorescence detection of fluazinam, which may come from the competitive absorption mechanism of dynamic quenching and excitation energy.

[0028] Technical solution five of the present invention: A method for preparing a paper-based device for semi-quantitative detection of fluazinam, comprising the following steps: mixing a binder, a preservative and water, heating and stirring until completely dissolved to obtain a gel; adding the above-mentioned cadmium metal-organic framework material to the gel, dispersing it evenly, to obtain a gel dispersion of the cadmium metal-organic framework material; uniformly coating the gel dispersion of the cadmium metal-organic framework material on a paper-based carrier, drying, to obtain the paper-based device for semi-quantitative detection of fluazinam.

[0029] Furthermore, the binder includes polyvinyl alcohol and / or triethanolamine; the preservative includes methyl paraben and / or methyl 4-hydroxybenzoate.

[0030] The addition of binder is helpful to improve the uniformity of paper-based device, and the addition of preservative is helpful to improve the stability of paper-based device without affecting the detection performance.

[0031] Furthermore, when the binder is polyvinyl alcohol and triethanolamine, and the preservative is methyl paraben and methyl 4-hydroxybenzoate, the dosage ratio of the polyvinyl alcohol, methyl paraben, methyl 4-hydroxybenzoate, triethanolamine, water and cadmium metal-organic framework material is 0.04g:0.002g:0.002g:0.05mL:1.95mL:60mg.

[0032] Technical solution six of the present invention: A paper-based device for semi-quantitative detection of fluazinam prepared by the above preparation method.

[0033] Technical solution seven of the present invention: A semi-quantitative detection method (colorimetric detection) of fluazinam, comprising the following steps: dropping fluazinam standard solutions of different concentrations onto the above-mentioned paper-based device for semi-quantitative detection of fluazinam, and collecting color information of fluazinam standard solutions of different concentrations on the paper-based device; dropping a sample to be tested onto the above-mentioned paper-based device for semi-quantitative detection of fluazinam, collecting color information of the sample to be tested on the paper-based device, and comparing it with the color information of fluazinam standard solutions of different concentrations on the paper-based device to obtain the concentration range of fluazinam in the sample to be tested.

[0034] When different concentrations of fluazifamine are dropped onto a paper-based device (test paper) made of cadmium metal-organic framework material, a color change from colorless to brick red can be observed with the naked eye. The mechanism of this color change may be the catalytic mechanism of the active sites on the cadmium metal-organic framework material (the active sites on the metal-organic framework material catalyze the oxidation reaction of fluazifamine, resulting in the unique "brick red" color change of fluazifamine).

[0035] The present invention discloses the following technical effects:

[0036] The present invention provides a cadmium metal-organic framework material, which has a specific crystal structure and spatial structure, high synthetic purity, good stability, and can be used for the detection of fluazinam pesticide. Significant fluorescence quenching can be observed in the fluorescence detection of fluazinam, and quantitative detection of fluazinam can be achieved through fluorescence intensity detection, and the minimum limit of detection is 1.68 μM.

[0037] Furthermore, when different concentrations of fluazinam are dropped onto a paper-based device (test paper) made of cadmium metal-organic framework material, a color change from colorless to brick red can be observed with the naked eye. The semi-quantitative detection of fluazinam can be achieved conveniently and quickly through colorimetric detection on the paper-based device.

[0038] In summary, the cadmium metal-organic framework material of the present invention has broad application prospects in the field of pesticide detection and has potential value in enhancing food safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0040] Figure 1 is the hydrogen spectrum of the organic ligand H2L prepared in Example 1;

[0041] Figure 2This is a schematic diagram of the secondary building unit structure of the cadmium metal-organic framework material prepared in Example 2;

[0042] Figure 3 is the X-ray powder diffraction pattern of the cadmium metal-organic framework material prepared in Example 2;

[0043] Figure 4 TGA (black) and DTG (red) curves of the cadmium metal-organic framework material prepared in Example 2;

[0044] Figure 5 The UV-visible absorption spectra of cadmium metal-organic framework material, fluazinam and a mixture of the two;

[0045] Figure 6 The fluorescence photos of cadmium metal-organic framework materials detecting different concentrations of fluazinam under ultraviolet light;

[0046] Figure 7 This is the standard curve for the quantitative detection of fluazinam using cadmium metal-organic framework materials;

[0047] Figure 8 Detection of the colorimetric signal changes of different concentrations of fluazinam for cadmium metal-organic framework materials. DETAILED DESCRIPTION

[0048] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0049] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0050] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0051] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to the skilled artisan. The present invention description and examples are exemplary only.

[0052] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0053] All raw materials used in the specific implementation of the present invention are common commercial products. The specific information of the raw materials used to prepare the organic ligand H2L is as follows:

[0054] 4,4'-oxalyl dibenzoic acid methyl ester: molecular formula is C 18 H 14 O6, structural formula The CAS number is 66553-02-4;

[0055] 4-Formylpyrazole: molecular formula is C4H4N2O, structural formula is The CAS number is 35344-95-7.

[0056] The room temperature involved in the specific implementation manner of the present invention specifically refers to 20-30°C.

[0057] Example 1

[0058] The preparation steps of organic ligand H2L are as follows:

[0059] A mixture of 6.52 g (0.02 mol) of methyl 4,4'-oxalyl dibenzoate, 3.28 g (0.034 mol) of 4-formyl pyrazole and 15.4 g (0.2 mol) of ammonium acetate was suspended in 250 mL of acetic acid at room temperature to obtain a mixed system. Then, the mixed system was refluxed at a temperature of 120°C for 8 h. When the temperature was cooled to room temperature, the obtained slightly yellow solution was poured into 500 mL of water and stirred at room temperature for 30 min. The precipitate was collected by filtration, washed with water, and dried at 100°C for 12 h to obtain an organic ligand material H2L.

[0060] The hydrogen spectrum of the organic ligand material H2L prepared in this embodiment is as follows: Figure 1 As shown, the chemical shift 2.5ppm is the peak of deuterated dimethyl sulfoxide, 3.3ppm is the peak of deuterated dimethyl sulfoxide water. 7.59-8.00ppm are the eight hydrogens at positions 3 and 4 on the benzene ring. 8.15ppm is the hydrogen at position 2 of the imidazole ring, and the chemical shift 12.62ppm is the hydrogen at position 1 of the heterocycle. The chemical shift 13.01ppm is the active hydrogen of the hydroxyl group on the amino and carboxyl groups.

[0061] Example 2

[0062] The preparation steps of cadmium metal-organic framework materials are as follows:

[0063] The organic ligand H2L prepared in Example 1 is added to a mixed solvent formed by mixing N,N-dimethylformamide and water in a volume ratio of 3:1 to prepare a H2L solution with a concentration of 0.010 g / mL (0.03 mmol / mL); Cd(NO3)2 is added to a mixed solvent formed by mixing N,N-dimethylformamide and water in a volume ratio of 3:1 to prepare a Cd(NO3)2 solution with a solubility of 0.012 g / mL (0.05 mmol / mL); 1 mL of H2L solution and 2 mL of Cd(NO3)2 solution are mixed in a 5 mL screw-top glass bottle, sealed, and placed in an oven at 90°C for heating to react for 72 hours. After the reaction is completed, it is naturally cooled to room temperature, and the crystalline product is collected by filtration. The obtained crystalline product is washed with water and ethanol until the solution becomes transparent, and then dried at room temperature to obtain a cadmium metal-organic framework material (abbreviated as HBU-169, with a yield of 83% based on H2L).

[0064] Test Example 1

[0065] 1. X-ray single crystal diffraction

[0066] 30 mg of the sample obtained in Example 2 was picked and placed on an Agilent SuperNova X-ray single crystal diffractometer, and tested at 150 K using Cu / Ka rays as the diffraction light source, and data empirical absorption correction was completed using the instrument's own program. The final structure analysis and refinement were performed using the Superflip analysis method of the Olex2 software package, during which all non-hydrogen atoms were identified using the full matrix least squares method and anisotropic refinement was completed.

[0067] Figure 2 This is a schematic diagram of the secondary building block structure of the cadmium metal-organic framework material. Figure 2 It can be seen that the asymmetric unit ([Cd2(L)2H2O] part, the molecular formula is Cd2C 40 H 26 O9N8) consists of two Cd 2+ions, two organic ligands and a coordinated water molecule. Cd1 adopts a six-coordination mode, with an average Cd1-O bond length of 2.791A, of which 4 oxygen atoms come from the carboxyl groups of 2 organic ligands, and 2 nitrogen atoms come from 2 pyrazole rings. Cd2 exhibits a five-coordination mode, with an average Cd2-O bond length of 2.791A, of which 3 oxygen atoms come from the carboxyl groups of 2 organic ligands, 1 oxygen atom comes from water, and 1 nitrogen atom comes from the pyrazole ring. The tested pore size distribution is represented by values ​​such as 18.03714, 17.11764, 16.19876, 13.65568, and 10.85791, and the porosity can reach 0.93425. In addition, there is a water molecule between the two asymmetric units in the form of crystal water.

[0068] More specific crystal structure analysis data are shown in Table 1:

[0069] Table 1 Crystal structure analysis data of cadmium metal-organic framework materials

[0070]

[0071] The molecular formula resolved by X-ray single crystal diffraction differs from the molecular formula corresponding to the chemical formula of HBU-169 {[Cd2(L)2H2O]2(H2O)}·(4H2O)·(DMF) by the (4H2O)·(DMF) part. This is because the (4H2O)·(DMF) part is free on the surface of the asymmetric unit. Based on the accuracy of X-ray single crystal diffraction and other factors, the free solvent cannot be resolved into the molecular formula.

[0072] Figure 3 is the X-ray powder diffraction pattern of the cadmium metal-organic framework material, Figure 3 It can be seen that the PXRD pattern of the cadmium metal-organic framework material is similar to the corresponding simulation pattern, indicating that its phase purity is high.

[0073] 2. Thermogravimetric analysis

[0074] Thermogravimetric analysis was performed in a nitrogen atmosphere at 100-700 °C (100 mL min -1 ) was performed on the HBU-169 sample obtained in Example 2. The TGA (black) and DTG (red) curves of HBU-169 are shown in Figure 4 As shown. Figure 4 It can be seen that the first weight loss zone is about 60-111℃, and the weight decreases by 3.20% ， This is due to the loss of adsorbed water molecules (calculated weight loss rate is 3.37%). The second weight loss zone is about 111-167℃, and the weight loss is 3.24%. ，This is due to the loss of adsorbed DMF, proving that there is indeed a free (4H2O)·(DMF) moiety in the chemical formula of HBU-169. The third weight loss zone is approximately 168-315 °C, with a weight loss of 11.40%, which can be attributed to the partial decomposition of the organic linker. The fourth decomposition zone starts at 315 °C, which can be attributed to the decomposition of the organic linker, resulting in crystal collapse.

[0075] Test Example 2

[0076] Figure 5 is the UV-visible absorption spectra of cadmium metal-organic framework materials, fluazinam and their mixture, Figure 5 It can be seen that no new peaks appeared in the comparative analysis of the UV-visible absorption spectra, and the UV-visible absorption spectrum of fluazinam overlapped with that of the cadmium metal-organic framework material, proving the possibility of fluorescence quenching between fluazinam and the cadmium metal-organic framework material through the competitive absorption mechanism of dynamic quenching and excitation energy.

[0077] Application Example 1

[0078] Fluorescence Qualitative Detection of Fluazinam Using Cadmium Metal-Organic Framework Materials

[0079] Add equal volumes of different concentrations of fluazinam standard solutions (0 mol / L, 10 - 4 mol / L、10 -3 mol / L、10 -2 mol / L) to simulate the presence of pesticides, and then drip an equal volume of 1 mg / mL cadmium metal-organic framework material (prepared in Example 2) dispersion onto the surface of cabbage leaves where the fluazinam standard solution was dripped, and then irradiated with a 365 nm ultraviolet lamp to observe the fluorescence on the surface of the cabbage sample.

[0080] The results are as follows Figure 6 As shown, (a) is 0 mol / L, (b) is 10 -4 mol / L, (c) is 10 - 3 mol / L, (d) is 10 - 2 mol / L, the circled part is the part where the standard solution of fluazinam was added; Figure 6 It can be seen that the cadmium metal-organic framework material itself has fluorescence. The higher the concentration of fluazinam, the weaker the fluorescence of the cadmium metal-organic framework material, indicating that the concentration of fluazinam will affect the fluorescence intensity of the metal-organic framework.

[0081] Application Example 2

[0082] Fluorescence Quantitative Detection of Fluazinam Using Cadmium Metal-Organic Framework Materials

[0083] A 1 mg / mL cadmium metal-organic framework material dispersant was prepared in an ethanol solution using a cadmium metal-organic framework material sample (prepared in Example 2). Fluazinam powder was dissolved in an ethanol solution to prepare fluazinam standard solutions of different concentrations (concentrations were 10, 20, 50, 99, 196, 291, and 385 μM, respectively). 1 mL of cadmium metal-organic framework material dispersant was added to a quartz cuvette, and fluazinam standard solutions of different concentrations were added to the cuvette, respectively. The fluorescence intensity under the excitation of 365 nm light was recorded at room temperature, and each experiment was repeated 3 times, and the results were averaged. The efficiency of fluorescence quenching was evaluated using the Stern-Volmer (SV) equation: (I0 / I)=Ksv[A]+1, and the quenching rate equation: (I0-I) / I0×100(%), where I0 represents the fluorescence intensity before adding the fluazinam standard solution, I represents the fluorescence intensity after adding the fluazinam standard solution, [A] represents the fluazinam concentration, and Ksv represents the quenching coefficient.

[0084] With fluazinam concentration as the horizontal axis and I0 / I-1 as the vertical axis, a curve was drawn and calibrated to obtain a standard curve such as Figure 7 As shown by Figure 7 It can be seen that the linear range of fluorescence detection of fluazinam by cadmium metal-organic framework material is 10-385 μM, the linear equation is y=0.2099+0.0172x (x is the concentration of fluazinam; y is I0 / I-1), and the minimum limit is 1.68 μM.

[0085] Application Example 3

[0086] Colorimetric Detection of Fluazinam Using Cadmium Metal-Organic Framework Materials

[0087] Polyvinyl alcohol (0.04 g), nipac methyl ester (0.002 g), methyl 4-hydroxybenzoate (0.002 g), triethanolamine (0.05 mL) and deionized water (1.95 mL) were mixed in a 10 mL glass vial. The mixture was heated and stirred at 90 ° C until it was completely dissolved to obtain a transparent gel. Subsequently, 60 mg of HBU-169 prepared in Example 2 was added to the gel, ultrasonically treated for 10 min, and vortexed for 5 min to ensure uniform dispersion to obtain a gel dispersion of HBU-169. The gel dispersion of HBU-169 was then evenly coated on a quantitative filter paper (coating thickness of 1 mm) with a glass triangular rod and dried in an oven at 60 ° C for 10 min. A paper-based device (test paper) for detecting fluazinam was obtained.

[0088] The detection process is as follows: add 10 μL of fluazinam standard solution of different concentrations (1, 2.5, 5, 7.5, 10, 12.5, 15 and 17.5 mM) to the prepared test paper (add the corresponding concentration of fluazinam standard solution to ordinary quantitative filter paper as a blank control). Observe the response and changes of color development. When the color no longer changes, take a photo with a mobile phone. Figure 8 As shown ( Figure 8 Only concentrations of 1, 2.5, 5, 7.5, 10 and 17.5 mM are shown, of which the upper part is the color development on the test paper, and the lower part is the color development on the ordinary quantitative filter paper (blank control group). Figure 8 It can be seen that as the concentration of fluazinam increases, the color change from colorless to brick red can be observed by the naked eye. Then use the color recognizer on the smartphone to identify the color presented on the test strip in the photo. After capturing each color, the image is immediately converted into RGB channels (red, green, and blue), and the converted color information is a specific RGB value (R represents red, G represents green, and B represents blue, each corresponding to a specific value, and then the average of the three is taken), and then the collected color information is used for on-site semi-quantitative analysis of fluazinam (the concentration range of fluazinam in the test solution is determined based on the average value of the RGB values ​​converted from the test solution and the average value of the RGB values ​​converted from the fluazinam standard solutions of different concentrations, for example, if the RGB average value of the test solution is between the RGB average values ​​of the fluazinam standard solutions with concentrations of 5 and 7.5 mM, then the concentration of fluazinam in the test solution is judged to be between 5 and 7.5 mM).

[0089] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A cadmium metal-organic framework material, characterized in that: The chemical formula is {[Cd2(L)2H2O]2(H2O)}·(4H2O)·(DMF), wherein L is deprotonated 4,4′-(2-(1H-pyrazol-4-alkyl)-1H-imidazole-4,5-dialkyl)dibenzoic acid; The crystal structure parameters of the cadmium metal-organic framework material include: The space group is Pī and the unit cell parameters are α=90.000°, β=107.696°, and γ=90.000°.

2. The method for preparing a cadmium metal-organic framework material according to claim 1, characterized in that: The following steps are involved: 4,4′-(2-(1H-pyrazole-4-alkyl)-1H-imidazole-4,5-dialkyl)dibenzoic acid, cadmium salt, and a mixed solvent of N,N-dimethylformamide and water are mixed and heated for reaction to obtain the cadmium metal-organic framework material; the structural formula of the 4,4′-(2-(1H-pyrazole-4-alkyl)-1H-imidazole-4,5-dialkyl)dibenzoic acid is shown in Formula I:

3. The method for preparing a cadmium metal-organic framework material according to claim 2, characterized in that: The molar ratio of the 4,4′-(2-(1H-pyrazole-4-alkyl)-1H-imidazole-4,5-dialkyl)dibenzoic acid and the cadmium salt is 3:10; the volume ratio of N,N-dimethylformamide and water in the mixed solvent is 3:1; the temperature of the heating reaction is 90° C. and the time is 72 hours.

4. Use of the cadmium metal-organic framework material as claimed in claim 1 in the detection of fluazinam.

5. A quantitative detection method for fluazinam, characterized in that: The following steps are involved: The cadmium metal-organic framework material according to claim 1 is respectively added to fluazinam standard solutions of different concentrations, and then the fluorescence intensity is tested under the excitation of 365nm light, and a standard curve is drawn according to the concentration of the fluazinam standard solution and the fluorescence intensity at the corresponding concentration and the fluorescence intensity when the concentration of the fluazinam standard solution is 0; the cadmium metal-organic framework material according to claim 1 is added to the test sample, and then the fluorescence intensity is tested under the excitation of 365nm light, and the fluorescence intensity corresponding to the test sample is substituted into the standard curve to obtain the concentration of fluazinam in the test sample.

6. A method for preparing a paper-based device for semi-quantitative detection of fluazinam, characterized in that: The following steps are involved: A binder, a preservative and water are mixed, and heated and stirred until completely dissolved to obtain a gel; the cadmium metal-organic framework material according to claim 1 is added to the gel, and dispersed evenly to obtain a gel dispersion of the cadmium metal-organic framework material; the gel dispersion of the cadmium metal-organic framework material is evenly coated on a paper-based carrier, and dried to obtain the paper-based device for semi-quantitative detection of fluazinam.

7. A paper-based device for semi-quantitative detection of fluazinam prepared according to the preparation method of claim 6.

8. A semi-quantitative detection method for fluazinam, characterized in that: The method comprises the following steps: dripping fluazinam standard solutions of different concentrations onto the paper-based device for semi-quantitative detection of fluazinam as claimed in claim 7, and collecting color information of the fluazinam standard solutions of different concentrations on the paper-based device; dripping a sample to be tested onto the paper-based device for semi-quantitative detection of fluazinam as claimed in claim 7, and collecting color information of the sample to be tested on the paper-based device, and comparing the color information of the fluazinam standard solutions of different concentrations on the paper-based device to obtain the concentration range of fluazinam in the sample to be tested.

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