Two-dimensional Cd-CP fluorescent probe material, preparation method thereof and application of two-dimensional Cd-CP fluorescent probe material in detection of Cr (VI) oxyanions

Abstract

The invention discloses a two-dimensional Cd-CP fluorescent material, a preparation method thereof and application of the two-dimensional Cd-CP fluorescent material to detection of Cr (VI) oxyanions, and belongs to the technical field of fluorescence sensing. The molecular formula of the Cd-CP fluorescent probe material is [Cd (L) (H2O)] n, wherein an L < 2-> ligand is 1-(4-carboxylate phenyl)-pyrazole-3-formate. The Cd-CP is prepared by the following method: carrying out solvothermal reaction on a ligand 1-(4-carboxyl phenyl)-pyrazole-3, 4-dicarboxylic acid and a Cd (II) salt to synthesize the Cd-CP. The two-dimensional Cd-CP fluorescent probe material is simple in preparation method, high in yield and low in cost, has good fluorescence stability and acid and alkali resistance stability, shows excellent recognition performance when used for detecting CrO4 < 2-> and Cr2O7 < 2-> in a water body, and is good in stability and recoverability and environmentally friendly.

Description

Technical Field

[0001] The present invention belongs to the technical field of fluorescence sensing, and particularly relates to a two-dimensional Cd-CP fluorescent probe material, a preparation method thereof, and an application for identifying and detecting Cr(VI) oxoanions CrO4 2- and Cr2O7 2- applications. Background Art

[0002] During the manufacturing process of coatings and pigments, chromium-containing compounds may be used, resulting in a small amount of Cr(VI) remaining in the products, usually in the form of CrO4 2- or Cr2O7 2- forms. Cr(VI) is recognized as having significant hazards to human health, which may cause skin allergies, respiratory diseases and even cancer. At the same time, it causes persistent pollution to the ecological environment such as water bodies and soils. Therefore, in the detection of harmful substances in coatings and pigments, the detection of Cr(VI) has become the focus of attention of production enterprises and testing institutions. For this reason, there is an urgent need to develop a method that can selectively, rapidly and sensitively detect low-concentration Cr(VI). In recent years, methods for detecting Cr(VI)-containing oxoanions include chromatography, mass spectrometry, spectrophotometry, electrochemistry, and infrared and ultraviolet spectroscopy. However, the high cost and operational complexity of these methods limit their wide application in practice. Fluorescence sensing mainly realizes the qualitative and quantitative detection of target substances by analyzing the fluorescence signal changes caused by the interaction between the analyte and the probe material. This method has the advantages of simple operation, real-time detection, low cost, strong selectivity, high sensitivity, etc., and is widely used in environmental monitoring, biotechnology, food safety, chemical manufacturing and clinical medicine and other fields Metal-organic coordination polymers (CPs) are a class of novel functional materials formed by the self-assembly of metal ions or metal ion clusters with organic ligands through coordination bonds. Metal-organic coordination polymers have unique properties such as high crystallinity, porosity, structural diversity and tunability, which make them show application potential in the fields of materials science, chemical sensing and catalysis. In recent years, based on the fluorescence properties of metal-organic coordination polymers, using them as fluorescent probes for detecting toxic chemicals and biomolecules has become an efficient and environmentally friendly method. Such probe materials are not only simple to prepare, highly selective and sensitive, but also have good reusability and stability. Summary of the Invention

[0003] The object of the present invention is to address the above problems existing in the prior art, and propose a two-dimensional Cd-CP fluorescent probe material, a preparation method thereof, and an application for identifying and detecting Cr(VI) oxoanions (CrO4 2- , Cr2O7 2- ). The Cd-CP fluorescent probe material for CrO4 in water2- and Cr2O7 2- The detection shows high sensitivity, stability, anti-interference ability and recyclability, and the preparation method is simple, low-cost, green and environmentally friendly.

[0004] The present invention firstly provides a two-dimensional Cd-CP fluorescent probe material, and its structural formula is: [Cd(L)(H2O)] n . Where L 2- The ligand is 1-(4-carboxyphenyl)-pyrazole-3-carboxylate, which is formed by high-temperature decarboxylation of self-made 1-(4-carboxyphenyl)-pyrazole-3,4-dicarboxylic acid during the synthesis of Cd-CP. It crystallizes in Z = 2 triclinic space group Pi with cell parameters: a = 6.1551(9) Å, b = 8.0188(15) Å, c = 12.2468(19) Å, α = 83.825(4)°, β = 76.811(3)°, γ = 67.533(3)°.

[0005] Furthermore, a preparation method of the 1-(4-carboxyphenyl)-pyrazole-3,4-dicarboxylic acid is provided, including the following steps: placing 4-(3-methyl-4-carboxy-pyrazole)benzoic acid and KOH in H2O, heating and reacting, adding solid KMnO4 in small amounts and multiple times, and filtering by suction after the reaction. 6 M HCl solution is added dropwise to the obtained filtrate until a solid precipitates, and then filtered by suction, washed and dried to obtain the product 1-(4-carboxyphenyl)-pyrazole-3,4-dicarboxylic acid.

[0006] Among them, the reactant 4-(3-methyl-4-carboxy-pyrazole)benzoic acid is prepared by referring to the method described in Chinese invention patent CN 116969890 A.

[0007] Preferably, the molar ratio of the reactants 4-(3-methyl-4-carboxy-pyrazole)benzoic acid, KOH and KMnO4 is 2:5:16; the molar concentration of imidazole in the reaction solution is 6~12.5 mmol / L.

[0008] Preferably, the oil bath heating reaction temperature is 80 °C and the reaction time is 60 h.

[0009] Preferably, the drying temperature is 65 °C and the drying time is 24 h.

[0010] The present invention further provides a preparation method of the above-mentioned two-dimensional Cd-CP fluorescent probe material, which includes the following specific steps: (1) Dissolve a Cd(II) salt, ligand 1-(4-carboxyphenyl)-pyrazole-3,4-dicarboxylic acid and imidazole in H2O and stir for 30 min to obtain a white suspension; (2) Heat and react the reaction solution obtained in step (1) at a temperature of 140-170 °C, filter, wash and dry the obtained product to obtain the Cd-CP fluorescent probe material.

[0011] Preferably, in step (1), the molar ratio of the Cd(II) salt, ligand 1-(4-carboxyphenyl)-1H-pyrazole-3,4-dicarboxylic acid and imidazole is 1-1.5:0.5-1:0.5-1.

[0012] Preferably, the white suspension reaction solution obtained in step (1) is added into a heat-resistant glass tube with a polytetrafluoroethylene lid and reacted in a programmable temperature oven for 48-96 h.

[0013] Preferably, after the reaction in step (2) is completed, the temperature is decreased at a rate of 3-10 °C / h. After the temperature is decreased to room temperature, the obtained product is filtered, washed and dried to obtain colorless block crystals of Cd-CP.

[0014] Preferably, in step (2), the Cd(II) is divalent cadmium ions, which can be provided by CdCl2, CdSO4, Cd(NO3)2 and their hydrates.

[0015] The present invention also provides the application of the above-mentioned two-dimensional Cd-CP fluorescent probe material as a fluorescent sensor in the detection of Cr(VI) oxyanions (CrO4 2- , Cr2O7 2- ).

[0016] It includes the following specific steps: (1) Grind the two-dimensional Cd-CP fluorescent probe material with a ball mill for 10-20 min to a mesh size of 60-80, prepare a suspension of Cd-CP with a concentration of 0.5-2 mg / mL, and measure its fluorescence excitation and emission spectra; (2) Prepare aqueous solutions of different concentrations of Cr(VI) oxyanions (Cr2O7 2- or CrO4 2- , with counter cations K + and Na + ); (3) Pipette 0.1 mL of the solution in step (2) into 2 mL of the Cd-CP material suspension obtained in step (1), and measure its fluorescence emission intensity; (4) Calculate the linear range according to the S-V equation and obtain the linear fitting equation through linear fitting; (5) Pipette 0.1 mL of the solution to be measured and add it to the 2 mL suspension of the Cd-CP material obtained in step (1), and measure its fluorescence emission intensity. If the fluorescence emission intensity decreases, it indicates that Cr2O7 is contained in the solution to be measured 2- or CrO4 2- , thereby identifying the Cr(VI) oxyanion in the aqueous solution; or substitute it into the linear fitting equation obtained in step (4) to calculate the content of the Cr(VI) oxyanion in the aqueous solution.

[0017] The present invention has the following beneficial effects: The Cd-CP fluorescence probe material provided by the present invention has good fluorescence intensity, excellent thermal stability and acid-base stability, and can qualitatively and quantitatively detect Cr2O7 in water 2- and CrO4 2- anions. Compared with the existing detection methods, it shows excellent sensitivity, selectivity, anti-interference ability and recyclability. Brief Description of the Drawings

[0018] Figure 1 is the 1H NMR spectrum of the ligand 1-(4-carboxyphenyl)-pyrazole-3,4-dicarboxylic acid; Figure 2 is the two-dimensional structure schematic diagram of the two-dimensional Cd-CP fluorescence probe material of the present invention; Figure 3 is the X-ray powder diffraction pattern of the two-dimensional Cd-CP fluorescence probe material of the present invention; Figure 4 is the thermogravimetric curve of the two-dimensional Cd-CP fluorescence probe material of the present invention; Figure 5 is the infrared spectrum of the two-dimensional Cd-CP fluorescence probe material of the present invention; Figure 6 is the fluorescence excitation and emission spectrum of the two-dimensional Cd-CP fluorescence probe material of the present invention; Figure 7 is the PXRD pattern of the two-dimensional Cd-CP fluorescence probe material of the present invention before and after being soaked in aqueous solutions under different pH conditions; Figure 8 is the fluorescence intensity comparison diagram of the two-dimensional Cd-CP fluorescence probe material of the present invention in the presence of interfering anions; Figure 9 is the fluorescence response spectrum of the two-dimensional Cd-CP fluorescence probe material of the present invention to different concentrations of Cr2O7 2- ions; Figure 10The fluorescence intensity ratio based on the S-V equation and Cr2O7 of the two-dimensional Cd-CP fluorescent probe material of the present invention 2- Linear relationship diagram of ion concentration Figure 11 The fluorescence response spectrum of the two-dimensional Cd-CP fluorescent probe material of the present invention to CrO4 ions with different concentrations 2- Ion Figure 12 The fluorescence intensity ratio based on the S-V equation and CrO4 of the two-dimensional Cd-CP fluorescent probe material of the present invention 2- Linear relationship diagram of ion concentration Figure 13 The reproducibility of the two-dimensional Cd-CP fluorescent probe material of the present invention in identifying Cr2O7 ions in water 2- Ion ability Figure 14 The reproducibility of the two-dimensional Cd-CP fluorescent probe material of the present invention in identifying CrO4 ions in water 2- Ion ability Specific embodiments

[0019] The present invention will be further described below in conjunction with specific embodiments and accompanying drawings

[0020] In the following examples of the present invention, 4-(3-methyl-4-carboxy-pyrazole) benzoic acid is prepared according to the method described in Chinese invention patent CN116969890 A

[0021] Synthesis of ligand 1-(4-carboxyphenyl) -pyrazole-3,4-dicarboxylic acid Add 4-(3-methyl-4-carboxy-pyrazole) benzoic acid (6.33 g, 20 mmol), KOH (2.80 g, 50 mmol) and H2O (250 mL) into a 500 mL three-necked round-bottom flask in sequence, heat to 80 °C, and add solid particles of KMnO4 (25.28 g, 160 mmol) in small amounts and multiple times. After reacting for 60 h, filter by suction, and transfer the filtrate to a clean round-bottom flask. Wait for the solution to cool, dropwise add 6 M HCl solution to it and stir continuously until solid precipitates. After filtering by suction, wash with appropriate amount of deionized water and acetone, and dry at 65 °C for 24 h to obtain a light yellow solid product 1-(4-carboxyphenyl) -pyrazole-3,4-dicarboxylic acid, with a yield of 4.81 g and a yield of about 87.07% Figure 1 1H NMR spectrum of ligand 1-(4-carboxyphenyl) -pyrazole-3,4-dicarboxylic acid 1HNMR (500 MHz, DMSO-d6): 8.01 (s, 1H, C3HN2-H), 7.97 (m, 2H, Ar-H), 7.48 (m, 2H, Ar-H) Example 1

[0022] Method for Cd-CP fluorescent probe material, comprising the following steps: Under room temperature conditions, dissolve Cd(NO3)2 . 4H2O (0.15 mmol, 0.0447 g), 1-(4-carboxyphenyl)-pyrazole-3,4-dicarboxylic acid (0.1 mmol, 0.0278 g) and imidazole (0.1 mmol, 0.0068 g) in 8 mL of H2O, and ultrasonicate for 30 min to obtain a white suspension; transfer the obtained suspension to a 25 mL heat-resistant glass tube with a Teflon lid, react in an oven at 150 °C for 72 h, cool the temperature to room temperature at a rate of 3 °C / h to obtain colorless rectangular sheet crystals. Filter, wash with 6 mL of deionized water 2-3 times, dry at 60 °C for 24 h and then weigh. Yield: 55.46%. Example 2

[0023] Under room temperature conditions, dissolve Cd(NO3)2 . 4H2O (0.12 mmol, 0.0358 g), 1-(4-carboxyphenyl)-pyrazole-3,4-dicarboxylic acid (0.08 mmol, 0.0222 g) and imidazole (0.06 mmol, 0.0041 g) in 8 mL of H2O, and ultrasonicate for 30 min to obtain a white suspension; transfer the obtained suspension to a 25 mL heat-resistant glass tube with a Teflon lid, react in an oven at 160 °C for 72 h, and after cooling the temperature to room temperature at a rate of 5 °C / h, colorless rectangular sheet crystals are obtained. Filter, wash with 6 mL of deionized water 2-3 times, dry at 70 °C for 24 h and then weigh. Yield: 52.34%. Example 3

[0024] CdCl2 (0.15 mmol, 0.0275 g), 1-(4-carboxyphenyl)-pyrazole-3,4-dicarboxylic acid (0.08 mmol, 0.0222 g) and imidazole (0.1 mmol, 0.0068 g) were dissolved in 8 mL of H2O, and ultrasonicated for 30 min to obtain a white suspension; the obtained suspension was transferred to a 25 mL heat-resistant glass tube with a Teflon cap, and reacted in an oven at 140 °C for 96 h. After cooling to room temperature at a rate of 3 °C / h, colorless rectangular plate-like crystals were obtained. Filtered, washed 2-3 times with 6 mL of deionized water, dried at 70 °C for 32 h and then weighed. Yield: 50.13%. Example 4

[0025] Under room temperature conditions, CdSO4 (0.13 mmol, 0.0271 g), 1-(4-carboxyphenyl)-pyrazole-3,4-dicarboxylic acid (0.1 mmol, 0.0278 g) and imidazole (0.1 mmol, 0.0068 g) were dissolved in 8 mL of H2O, and ultrasonicated for 30 min to obtain a white suspension; the obtained suspension was transferred to a 25 mL heat-resistant glass tube with a Teflon cap, and reacted in an oven at 165 °C for 72 h. After cooling to room temperature at a rate of 3 °C / h, colorless rectangular plate-like crystals were obtained. Filtered, washed 2-3 times with 6 mL of deionized water, dried at 60 °C for 48 h and then weighed. Yield: 51.67%. Example 5

[0026] Cd(NO3)2 . 4H2O (0.1 mmol, 0.0298 g), 1-(4-carboxyphenyl)-1H-pyrazole-3,4-dicarboxylic acid (0.06 mmol, 0.0167 g) and imidazole (0.06 mmol, 0.0041 g) were dissolved in 8 mL of H2O, and ultrasonicated for 30 min to obtain a white suspension; the obtained suspension was transferred to a 25 mL heat-resistant glass tube with a Teflon cap, and reacted in an oven at 170 °C for 72 h. After cooling to room temperature at a rate of 5 °C / h, colorless rectangular plate-like crystals were obtained. Filtered, washed 2-3 times with 6 mL of deionized water, dried at 65 °C for 36 h and then weighed. Yield: 49.36%.

[0027] The Cd-CP fluorescent probe materials prepared in the above Examples 1-5 are the same, only the yields are different.

[0028] Taking the Cd-CP fluorescent probe material prepared in Example 1 as an example, performance test experiments were carried out.

[0029] As Figure 2As shown, X-ray single crystal diffraction analysis was performed on the Cd-CP fluorescent probe material prepared in the present invention, L 2- The N atom on the pyrazole ring of the ligand ion in Cd-CP did not participate in coordination. While the two carboxyl oxygen atoms on the carboxyl group connected to the pyrazole ring chelated and coordinated with Cd1, one of the carboxyl oxygen atoms also bridged another Cd1E ion to form a [Cd2O2] ring. The carboxylate group on the benzene ring adopted a μ 2-bridging coordination mode to coordinate with Cd1 and Cd1C to form a [Cd2(-CO2)2] ring, and finally formed a μ 4- k :O; k :O’; k :O’’,O’’’; k :O’’’ coordination mode. Under its action, Cd-CP presented a two-dimensional layered structure as Figure 2 shown.

[0030] As Figure 3 shown, at room temperature, X-ray powder diffraction analysis was performed on the Cd-CP fluorescent probe material prepared in the present invention, and its phase purity was tested. It can be seen that a large number of Cd-CP products showed good phase purity, which basically corresponded to the simulated peaks of single crystal data.

[0031] As Figure 4 shown, thermogravimetric analysis was performed on the two-dimensional Cd-CP fluorescent probe material. It can be seen that as the temperature increased, the Cd-CP material basically did not change in the range of 40-200 °C, indicating that the main framework structure of the Cd-CP material had good thermal stability within 200 °C.

[0032] As Figure 5 shown, infrared spectroscopy analysis was performed on the Cd-CP fluorescent probe material prepared in the present invention. As Figure 5 can be seen, the broad absorption peak appearing between 3400-3200 cm⁻¹ indicated the presence of water molecules therein. The absorption peak located at 1600-1400 cm⁻¹ was the stretching vibration peak of aromatic ring C=O, while the absorption peak in the range of 1400-1200 cm⁻¹ was the stretching vibration of C-O of the carboxylate group, and the broad peak appearing at 1200-1100 cm⁻¹ was the stretching vibration of pyrazole ring C-N.

[0033] As Figure 6 shown, fluorescence emission spectrum detection was performed on the two-dimensional Cd-CP fluorescent probe material prepared in the present invention. When the excitation wavelength of the two-dimensional Cd-CP fluorescent probe material was 350 nm, the maximum emission wavelength was 408 nm.

[0034] Figure 7PXRD patterns of the two-dimensional Cd-CP fluorescent probe material before and after being soaked in aqueous solutions under different pH conditions. After soaking in solutions with pH = 1 - 12, the PXRD of the two-dimensional Cd-CP did not change significantly, indicating that this two-dimensional Cd-CP fluorescent probe material has excellent acid and alkali stability.

[0035] The two-dimensional Cd-CP fluorescent probe material prepared in the present invention was subjected to fluorescence detection for its selective quenching experiment on Cr2O7 2- and CrO4 2- ions. As Figure 8 can be seen, after most ions were added, the fluorescence intensity of the Cd-CP fluorescent probe material changed slightly but could be ignored. However, the addition of Cr2O7 2- and CrO4 2- ions caused the fluorescence of Cd-CP to quench, and the quenching efficiencies reached 99.82% and 99.94% respectively. Therefore, Cd-CP showed excellent selectivity for the recognition of Cr2O7 2- and CrO4 2- anions. In the presence of interfering ions, the Cd-CP fluorescent probe material was hardly affected by the recognition of Cr2O7 2- and CrO4 2- ions, indicating that the material has good anti-interference ability for the detection of Cr2O7 2- and CrO4 2- ions in water.

[0036] The fluorescence detection experiment for detecting the concentration of Cr2O7 2- anion is as Figure 9 and Figure 10 shown. As the concentration of Cr2O7 2- ions (0 - 0.50 mM) increased continuously, the fluorescence emission intensity of the Cd-CP fluorescent probe material decreased continuously. According to the fitting calculation of the S-V equation, it can be known that the relative fluorescence intensity ratio ( I 0 / I ) - 1 and showed a linear relationship in the range of 0 - 0.25 mM and increased rapidly after exceeding 0.25 mM, indicating that it can quantitatively detect Cr2O7 2- anions in water at low concentrations. Through linear fitting, K sv (Cr2O7 2- ) = 60.243 mM -1 (approximately 6.02 × 10 4 M -1 ), R 2= 0.9865, and the detection limit is calculated to be 0.752 μM from the formula LOD = 3σ / k The detection limit is calculated to be 0.752 μM.

[0037] Detect CrO4 2- The fluorescence detection experiment of the anion concentration is as Figure 11 and Figure 12 shown. As the concentration of CrO4 2- ions (0 - 0.35 mM) continuously increases, the fluorescence emission intensity of the Cd-CP fluorescent probe material continuously weakens. According to the fitting calculation of the S-V equation, it can be known that the relative fluorescence intensity ratio ( I 0 / I ) - 1 has a linear relationship with in the range of 0 - 0.25 mM and increases rapidly after exceeding 0.25 mM, indicating that it can quantitatively detect CrO4 2- anions in water at low concentrations. Through linear fitting, K sv (CrO4 2- ) = 214.2375 mM -1 (approximately 2.14 × 10 5 M -1 ), R 2 = 0.9827, and the detection limit is calculated to be 0.0211 μM from the formula LOD = 3σ / k The detection limit is calculated to be 0.0211 μM.

[0038] The cyclic stability of the prepared Cd-CP fluorescent probe material of the present invention is detected. As Figure 13 and Figure 14 shown, the two-dimensional Cd-CP fluorescent probe material still has the ability to recognize Cr2O7 2- and CrO4 2- ions in water after being recycled multiple times, indicating that the material has good cyclic stability and recyclability.

[0039] In summary, the present invention designs and synthesizes a novel Cd-CP fluorescent probe material for the detection of Cr2O7 2- and CrO4 2- ions in water. It not only has a fast detection speed, but also shows strong selectivity, sensitivity and anti-interference ability. Moreover, the probe material is simple to prepare, low in cost, less polluting and easy to operate.

[0040] The above-described embodiments are only the preferred experimental schemes of the present invention. It should be noted that for those skilled in the art of operation, there are different ways of expressing the experimental schemes, and appropriate polishing and modification can be made on the basis of the embodiments of the present invention, but all are within the protection scope of the present invention.

Claims

1. A two-dimensional Cd-CP fluorescent probe material, characterized in that: The structural formula of the Cd-CP fluorescent probe is: [Cd(L)(H2O)] n , where L 2- The ligand is 1-(4-carboxyphenyl)-pyrazole-3-carboxylate; the Cd-CP fluorescent probe crystallizes in Z the trigonal crystal system space group Pī with unit cell parameters: a a = 6.1551(9) Å, b b = 8.0188(15) Å, c c = 12.2468(19) Å, α α = 83.825(4)°, β β = 76.811(3)°, γ γ = 67.533(3)°.

2. The two-dimensional Cd-CP fluorescent probe material according to claim 1, wherein: The ligand L 2- is formed by high-temperature decarboxylation of 1-(4-carboxyphenyl)-pyrazole-3,4-dicarboxylic acid during the synthesis of Cd-CP.

3. The two-dimensional Cd-CP fluorescent probe material according to claim 2, wherein: The preparation method of 1-(4-carboxyphenyl)-pyrazole-3,4-dicarboxylic acid comprises the following steps: 4-(3-methyl-4-carboxy-pyrazole) benzoic acid and KOH are placed in H2O, heated for reaction, and solid KMnO4 is added in portions. After the reaction, filtration is carried out by suction; HCl solution is added dropwise to the obtained filtrate until a solid precipitates, and then filtration by suction, washing, and drying are carried out to obtain the product 1-(4-carboxyphenyl)-pyrazole-3,4-dicarboxylic acid.

4. The two-dimensional Cd-CP fluorescent probe material according to claim 3, wherein: The molar ratio of the reactants 4-(3-methyl-4-carboxy-pyrazole) benzoic acid, KOH, and KMnO4 is 2:5:16; and / or the temperature of the heating reaction is 80 °C and the reaction time is 60 h.

5. The preparation method of the two-dimensional Cd-CP fluorescent probe material according to any one of claims 1 to 4, characterized in that: Comprises the following steps: A Cd(II) salt, the ligand 1-(4-carboxyphenyl)-pyrazole-3,4-dicarboxylic acid, and imidazole are dissolved in H2O to obtain a reaction solution; the reaction solution is heated for reaction, and the product is collected, filtered, washed, and dried to obtain the Cd-CP fluorescent probe material.

6. The preparation method of the two-dimensional Cd-CP fluorescent probe material according to claim 5, characterized in that, The molar ratio of the Cd(II) salt, the ligand 1-(4-carboxyphenyl)-pyrazole-3,4-dicarboxylic acid, and imidazole is 1-1.5:0.5-1:0.5-1.

7. The preparation method of the two-dimensional Cd-CP fluorescent probe material according to claim 5, characterized in that, The temperature of the heating reaction is 140-170 °C and the reaction time is 48-96 h.

8. The preparation method of the two-dimensional Cd-CP fluorescent probe material according to claim 7, characterized in that, After the reaction in a programmable temperature-controlled oven, the temperature is decreased to room temperature at a cooling rate of 3-10 °C / h.

9. The two-dimensional Cd-CP fluorescent probe material according to any one of claims 1 to 4 is used for detecting Cr(VI) oxyanions in water.

10. The application according to claim 9, characterized in that: The Cr(VI) oxyanion includes Cr2O7 2- or CrO4 2- , and the application is to detect the fluorescence emission intensity of the two-dimensional Cd-CP fluorescent probe material in a water sample at an excitation wavelength of 350 nm.

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