Cr (VI) oxygen anion specific fluorescent probe based on zinc coordination polymer as well as preparation and application of Cr (VI) oxygen anion specific fluorescent probe

Abstract

The invention relates to the technical field of fluorescent sensors, in particular to a Cr (VI) oxygen anion specific fluorescent probe based on a zinc coordination polymer as well as preparation and application of the Cr (VI) oxygen anion specific fluorescent probe. A traditional detection means for hexavalent Cr (VI) is high in equipment dependence, long in detection period and high in operation specialization degree. In order to solve the technical problems, the invention provides the Cr (VI) oxygen anion specific fluorescent probe based on the zinc coordination polymer, and the Cr (VI) oxygen anion specific fluorescent probe is a complex formed by metal zinc ions and 4-(3-methyl-1H-pyrazole) benzoate. According to the present invention, the Cr2O7 < 2-> and CrO4 < 2-> anions have the selective quenching effect on the complex, the qualitative and quantitative treatment can be performed on the Cr2O7 < 2-> and CrO4 < 2-> in the sample to be detected according to the principle, the detection limit is less than 0.2 [mu] M, and compared with the traditional detection method, the sensitivity, the selectivity and the anti-interference performance are excellent;

Description

Technical Field

[0001] The present invention relates to the technical field of fluorescent sensors, and in particular to a Cr(VI) oxygen anion specific fluorescent probe based on a zinc coordination polymer and a preparation and application thereof. Background Art

[0002] As global environmental protection and healthy consumption awareness deepen, the ecological safety of leather products has become a core issue in the industry. Although the current mainstream chrome tanning process gives leather excellent properties, the residual hexavalent Cr (VI), often in the form of CrO4 2- 、Cr2O7 2- The existence of Cr(VI) in its various forms is strictly restricted due to its strong carcinogenicity and persistent environmental toxicity. Although traditional detection methods such as chromatography-mass spectrometry and spectral analysis have high accuracy, they have bottlenecks such as strong equipment dependence, long detection cycle, and high degree of operational specialization, making it difficult to meet the rapid screening needs of trace Cr(VI) in industrial production.

[0003] In comparison, fluorescence sensing technology triggers fluorescence signal changes (quenching / enhancement effect) through the specific interaction between probe materials and targets, and has three core advantages:

[0004] (1) It can achieve ultra-sensitive detection at the ppm level and accurately identify Cr(VI) in complex matrices;

[0005] (2) Short response time and support for real-time on-site monitoring;

[0006] (3) The equipment has significant potential for portability, which can significantly reduce testing costs.

[0007] This technology has demonstrated important application value in areas such as environmental water monitoring and leather product quality control, providing innovative solutions for building a green industrial chain.

[0008] Metal-organic coordination polymers (CPs) are an emerging class of highly crystalline coordination polymers that are self-assembled with organic ligands around a single metal ion or metal ion cluster. Metal-organic coordination polymers exhibit unique properties due to their inherent crystallinity, porosity, structural diversity, and tunability, and have shown unique advantages in the field of fluorescence sensing. In recent years, based on the fluorescence properties of metal-organic coordination polymers, using them as probe materials to identify toxic chemical species and biological entities has been considered an effective method. The probe material is simple to prepare, has high selectivity and sensitivity, is easy to operate, and can be recycled. Summary of the invention

[0009] Problems existing in the prior art are as follows: For traditional detection methods of hexavalent Cr(VI), there are problems such as strong equipment dependence, long detection cycle, and high degree of operation specialization, making it difficult to meet the rapid screening requirements of trace Cr(VI) in industrial production. To address the above technical problems, the present invention provides a Cr(VI) oxygen anion-specific fluorescent probe based on a zinc coordination polymer, which is a complex formed by metal zinc ions and L ligand, with the structural formula [Zn(L)2]n, where the L - is 4-(3-methyl-1H-pyrazolyl)benzoate, n≥1, and n is an integer.

[0010] Preferably, the Cr(VI) oxygen anion-specific fluorescent probe belongs to the monoclinic system and crystallizes in the monoclinic space group C2 / m with Z = 4. Lattice parameters: α = 90°, β = 96.09(3)°, γ = 90°.

[0011] A method for preparing a Cr(VI) oxygen anion-specific fluorescent probe based on a zinc coordination polymer includes the following steps:

[0012] (1) Dissolve Zn(II) salt, L ligand, and imidazole in deionized water, and stir evenly to obtain a turbid liquid;

[0013] (2) Transfer the turbid liquid to a heat-resistant reaction vessel for sealing, then place the heat-resistant reactor in a high temperature for constant temperature reaction. After the reaction is completed, cool to room temperature to obtain colorless block crystals;

[0014] (3) The obtained colorless block crystals are successively subjected to solid-liquid separation, washed with water, and dried to obtain the target product.

[0015] Preferably, the Zn(II) salt includes one or a combination of two or more of zinc sulfate, zinc acetate, zinc nitrate, and zinc chloride.

[0016] Preferably, in step (1), the molar ratio of Zn(II) salt to L ligand and imidazole is 1.3-1.8:0.9-1.2:1.

[0017] Preferably, the mass ratio of L ligand to deionized water is 1:150-400.

[0018] Preferably, the constant temperature reaction temperature in step (2) is 140-160 °C.

[0019] Preferably, when the volume of the turbid liquid in step (2) < 25 mL, transfer the turbid liquid to a heat-resistant glass tube for sealing, then place it in an oven at 140-160 °C for constant temperature reaction for 48-96 h. After the reaction is completed, cool to room temperature at 3-10 °C / h to obtain colorless block crystals.

[0020] Preferably, when the volume of the turbid liquid in step (2) ≥ 25 mL, the obtained turbid liquid is heated to reflux for 12 - 36 h. After the reaction ends, it is naturally cooled to room temperature to obtain colorless block crystals.

[0021] Preferably, in step (3), the drying temperature is 50 - 80 °C and the drying time is 12 - 24 h.

[0022] A fluorescence sensor uses the above-mentioned Cr(VI) oxygen anion-specific fluorescence probe as its fluorescence probe to perform trace detection on hexavalent Cr ions in a solution containing Cr(VI).

[0023] The present invention has the following beneficial effects:

[0024] The obtained Cr(VI) oxygen anion-specific fluorescence probe of the present invention has good fluorescence intensity and stability, and can qualitatively and quantitatively detect trace Cr2O7 2- and CrO4 2- anions in water, with a detection limit as low as below 0.2 μM. Compared with existing detection methods, it shows more excellent sensitivity, selectivity, anti-interference ability, and recyclability. Description of the Drawings

[0025] Figure 1 : One-dimensional chain schematic diagram of the obtained Cr(VI) oxygen anion-specific fluorescence probe in Example 1 of the present invention.

[0026] Figure 2 : Infrared spectrum diagram of the obtained Cr(VI) oxygen anion-specific fluorescence probe in Example 1 of the present invention.

[0027] Figure 3 : X-ray powder diffraction pattern of the obtained Cr(VI) oxygen anion-specific fluorescence probe in Example 1 of the present invention.

[0028] Figure 4 : Thermogravimetric curve diagram of the obtained Cr(VI) oxygen anion-specific fluorescence probe in Example 1 of the present invention.

[0029] Figure 5 : Fluorescence excitation and emission spectrum diagram of the obtained Cr(VI) oxygen anion-specific fluorescence probe in Example 1 of the present invention.

[0030] Figure 6 : Fluorescence intensity effect diagram of anti-interference anions of the obtained Cr(VI) oxygen anion-specific fluorescence probe in Example 1 of the present invention.

[0031] Figure 7 : Fluorescence response spectrum diagram of the obtained Cr(VI) oxygen anion-specific fluorescence probe in Example 1 of the present invention to different concentrations of Cr2O7 2- ions.

[0032] Figure 8 : The fluorescence intensity ratio based on the S-V equation of the Cr(VI) oxyanion-specific fluorescent probe obtained in Example 1 of the present invention and the linear relationship diagram of the Cr2O7 2- ion concentration.

[0033] Figure 9 : The fluorescence response spectrum diagram of the Cr(VI) oxyanion-specific fluorescent probe obtained in Example 1 of the present invention for CrO4 2- ions with different concentrations

[0034] Figure 10 : The fluorescence intensity ratio based on the S-V equation of the Cr(VI) oxyanion-specific fluorescent probe obtained in Example 1 of the present invention and the linear relationship diagram of the CrO4 2- ion concentration.

[0035] Figure 11 : The repeated recognition effect diagram of the Cr(VI) oxyanion-specific fluorescent probe obtained in Example 1 of the present invention for Cr2O7 2- ions in water, where the vertical axis is the luminescence intensity and the horizontal axis is the number of cycles.

[0036] Figure 12 : The repeated recognition effect diagram of the Cr(VI) oxyanion-specific fluorescent probe obtained in Example 1 of the present invention for CrO4 2- ions in water, where the vertical axis is the luminescence intensity and the horizontal axis is the number of cycles. Detailed implementation manners

[0037] The present invention will be described in detail below with reference to the embodiments. However, it should be understood that the following embodiments are only illustrative examples of the implementation manners of the present invention, rather than limiting the scope of the present invention.

[0038] 4-(3-Methyl-4-carboxy-1H-pyrazole) benzoic acid in the following embodiments of the present invention is prepared according to the method described in paragraphs

[0026] -

[0027] of the specification of Chinese invention patent CN 116969890A.

[0039] Zn-CP in the attached drawings of the specification of the present invention represents the Cr(VI) oxyanion-specific fluorescent probe.

[0040] Example 1

[0041] A Cr(VI) oxyanion-specific fluorescent probe based on a zinc coordination polymer, and its preparation method is as follows:

[0042] (1) At room temperature, Zn(NO3)2·6H2O (0.15 mmol, 0.0447 g), 4-(3-methyl-4-carboxy-1H-pyrazole)benzoic acid (0.1 mmol, 0.0246 g) and imidazole (0.1 mmol, 0.0068 g) were dissolved in 8 mL of deionized water to obtain a white turbid solution;

[0043] (2) The obtained white turbid solution was transferred to a 25 mL heat-resistant glass tube with a polytetrafluoroethylene lid and reacted in an oven at 150 °C for 72 h. After the reaction, it was cooled to room temperature at a rate of 5 °C / h to obtain a reaction solution containing colorless block crystals;

[0044] (3) The reaction solution containing colorless block crystals was filtered, washed with water 4 times, and dried at 50 °C for 18 h to obtain a Cr(VI) oxyanion-specific fluorescent probe, yield: 73.11%.

[0045] Example 2

[0046] A Cr(VI) oxyanion-specific fluorescent probe based on a zinc coordination polymer, and its preparation method is as follows:

[0047] (1) At room temperature, Zn(CH3COO)2·2H2O (0.13 mmol, 0.0285 g), 4-(3-methyl-4-carboxy-1H-pyrazole)benzoic acid (0.09 mmol, 0.0222 g) and imidazole (0.1 mmol, 0.0068 g) were dissolved in 7.5 mL of deionized water to obtain a white turbid solution;

[0048] (2) The obtained white turbid solution was transferred to a 25 mL heat-resistant glass tube with a polytetrafluoroethylene lid and reacted in an oven at 145 °C for 72 h. After the reaction, it was cooled to room temperature at a rate of 3 °C / h to obtain a reaction solution containing colorless block crystals;

[0049] (3) The reaction solution containing colorless block crystals was filtered, washed with water 4 times, and dried at 60 °C for 15 h to obtain a Cr(VI) oxyanion-specific fluorescent probe, yield: 70.54%.

[0050] Example 3

[0051] A Cr(VI) oxyanion-specific fluorescent probe based on a zinc coordination polymer, and its preparation method is as follows:

[0052] (1) At room temperature, ZnCl2 (0.16 mmol, 0.0218 g), 4-(3-methyl-4-carboxy-1H-pyrazole)benzoic acid (0.12 mmol, 0.0295 g) and imidazole (0.1 mmol, 0.0068 g) were dissolved in 10.5 mL of deionized water to obtain a white turbid solution;

[0053] (2) Transfer the obtained white turbid solution to a 25 mL heat-resistant glass tube with a polytetrafluoroethylene cap, react in an oven at 155 °C for 96 h. After the reaction is completed, cool it to room temperature at a rate of 8 °C / h to obtain a reaction solution containing colorless block crystals;

[0054] (3) Filter the obtained reaction solution containing colorless block crystals, wash it with water 4 times, and dry it at 80 °C for 12 h to obtain a Cr(VI) oxyanion-specific fluorescent probe, yield: 78.92%.

[0055] Example 4

[0056] (1) At room temperature, sequentially add Zn(NO3)2·6H2O (1.3 mmol, 0.3867 g), 4-(3-methyl-4-carboxy-1H-pyrazol) benzoic acid (1.0 mmol, 0.2462 g), imidazole (1.0 mmol, 0.0681 g) and 40 mL of deionized water into a round-bottom flask, and stir for 30 min to obtain a white turbid solution;

[0057] (2) Heat the obtained white turbid solution under reflux in an oil bath for 12 h to obtain a reaction solution;

[0058] (3) Filter the obtained reaction solution, wash it 4 times with 10 mL of deionized water, and dry it at 60 °C for 18 h to obtain a Cr(VI) oxyanion-specific fluorescent probe, yield: 85.24%.

[0059] Example 5

[0060] (1) At room temperature, sequentially add Zn(CH3COO)2·2H2O (1.8 mmol, 0.3951 g), 4-(3-methyl-4-carboxy-1H-pyrazol) benzoic acid (1.2 mmol, 0.2955 g), imidazole (1.0 mmol, 0.0681 g) and 60 mL of deionized water into a round-bottom flask, and stir for 30 min to obtain a white turbid solution;

[0061] (2) Heat the obtained white turbid solution under reflux in an oil bath for 15 h to obtain a reaction solution;

[0062] (3) Filter the obtained reaction solution, wash it 5 times with 20 mL of deionized water, and dry it at 70 °C for 15 h to obtain a Cr(VI) oxyanion-specific fluorescent probe, yield: 90.13%.

[0063] Example 6

[0064] (1) At room temperature, ZnCl2 (1.5 mmol, 0.2044 g), 4-(3-methyl-4-carboxy-1H-pyrazole) benzoic acid (0.9 mmol, 0.2216 g), imidazole (1.0 mmol, 0.0681 g) and 55 mL of deionized water were successively added to a round-bottom flask, and stirred for 30 min to obtain a white turbid solution;

[0065] (2) The obtained white turbid solution was heated under reflux in an oil bath for 24 h to obtain a reaction solution;

[0066] (3) The obtained reaction solution was filtered, washed 5 times with 20 mL of deionized water, and dried at 80 °C for 18 h to obtain a Cr(VI) oxyanion-specific fluorescent probe, yield: 86.37%.

[0067] Comparative Example 1 was the same as Example 1, except that in Comparative Example 1, imidazole was replaced with an equal amount of DMF. The specific steps were as follows:

[0068] A Cr(VI) oxyanion-specific fluorescent probe based on a zinc coordination polymer, and its preparation method is as follows:

[0069] (1) At room temperature, Zn(NO3)2·6H2O (0.15 mmol, 0.0447 g), 4-(3-methyl-4-carboxy-1H-pyrazole) benzoic acid (0.1 mmol, 0.0246 g) and DMF (0.1 mmol) were dissolved in 8 mL of deionized water to obtain a white turbid solution;

[0070] (2) The obtained white turbid solution was transferred to a 25 mL heat-resistant glass tube with a polytetrafluoroethylene lid, and reacted in an oven at 150 °C for 72 h. After the reaction was completed, it was cooled to room temperature at a rate of 5 °C / h to obtain a reaction solution;

[0071] (3) The obtained reaction solution was filtered, washed four times with water, and dried at 50 °C for 18 h. The obtained solid product did not belong to the monoclinic system with Z = 4, and the product was a white solid powder.

[0072] Comparative Example 2 was the same as Example 4, except that in Comparative Example 2, imidazole was replaced with an equal amount of DMF. The specific steps were as follows:

[0073] (1) At room temperature, Zn(NO3)2·6H2O (1.3 mmol, 0.3867 g), 4-(3-methyl-4-carboxy-1H-pyrazole) benzoic acid (1.0 mmol, 0.2462 g), DMF (1.0 mmol) and 40 mL of deionized water were successively added to a round-bottom flask, and stirred for 30 min to obtain a white turbid solution;

[0074] (2) The obtained white turbid solution was placed in an oil bath at 140 °C for reflux reaction for 12 h to obtain a reaction solution;

[0075] (3) The obtained reaction solution was filtered, washed 4 times with 10 mL of deionized water, and dried at 60 °C for 18 h. The obtained solid product did not belong to the monoclinic system with Z = 4, and the product was a white solid powder.

[0076] Performance test

[0077] 1. The Cr(VI) oxyanion-specific fluorescent probes obtained in Examples 1-6 of the present invention were the same, only the yields were different. Now, the Cr(VI) oxyanion-specific fluorescent probe obtained in Example 1 of the present invention was subjected to X-ray single crystal diffraction analysis, and the test results are as shown in the attached Figure 1 description. L - The N atom on the pyrazole ring and the carboxylate group connected to the benzene ring in the ligand ion both participated in coordination. Two L - ligand ions connected Zn1 and Zn1B through monodentate bridging and O,O’-chelation to form a one-dimensional coordination chain [Zn(L)2] n .

[0078] 2. The Cr(VI) oxyanion-specific fluorescent probe obtained in Example 1 of the present invention was subjected to infrared spectroscopy analysis. The test results are as shown in the attached Figure 2 description. The characteristic peak at 3000-2800 cm -1 corresponded to the stretching vibration of the saturated C-H alkyl chain. The characteristic peak at 1680-1580 cm -1 belonged to the stretching vibration of C=O. The absorption band near 1269 cm -1 corresponded to the symmetric stretching vibration of -COO-. 1522 cm -1 and 1418 cm -1 were part of the aromatic skeleton vibration.

[0079] 3. At room temperature, the Cr(VI) oxyanion-specific fluorescent probes obtained in Examples 1 and 4 were subjected to X-ray powder diffraction analysis to analyze the purity of the samples. The test results are as shown in the attached Figure 3 description, and basically corresponded to the simulated peaks of the theoretical single crystal data.

[0080] 4. The Cr(VI) oxyanion-specific fluorescent probe obtained in Example 1 of the present invention was subjected to thermogravimetric analysis. The specific test results are as shown in the attached Figure 4As shown, as the temperature increases, the weight of the fluorescent probe remains basically unchanged in the range of 0 - 340 °C, showing good thermal stability. After that, the remaining structure decomposes continuously until 38.67% of the weight remains undecomposed at 800 °C, indicating that the main skeleton structure of the Cr(VI) oxyanion-specific fluorescent probe has good thermal stability.

[0081] 5. The Cr(VI) oxyanion-specific fluorescent probe obtained in Example 1 of the present invention was subjected to fluorescence emission spectrum detection in an aqueous solution. The test results are as shown in the attached Figure 5 As shown, when the excitation wavelength of the fluorescent probe is 300 nm, the maximum emission wavelength is 348 nm.

[0082] 6. A fluorescence detection experiment was carried out on the Cr(VI) oxyanion-specific fluorescent probe obtained in Example 1 of the present invention. The specific steps are as follows: At room temperature, 30 mg of the Cr(VI) oxyanion-specific fluorescent probe powder sample was put into a ball mill and ground for 5 min, then dispersed in 30 mL of deionized H2O and sonicated for another 30 min to obtain a uniformly dispersed suspension (1 mg / mL). Take 0.1 mL of an aqueous solution of nitrate M(NO3) -2 with a concentration of 5×10 x mol / L (M = Cu, Zn, Ni, Co, Ba, Mn, Ca, K, Pb, Er, Sr, Cd, Hg, Dy, Yb, Ce, Cr, Sm, Na, and Fe; x = 1, 2, and 3) and an aqueous solution of anions (Cl - , Br - , F - , I - , NO3 - , NO2 - , CO3 2- , SO4 2- , PO4 2- , IO3 - , SCN - , Cr2O7 2- and CrO4 2- , with counter cations being K + and Na + ), and they were respectively added to 2 mL of the above suspension. After sonication for 30 s, they were left to stand for 5 min, and the fluorescence emission spectra of different suspensions were measured. The test results are as shown in the attached Figure 6 As shown, the fluorescence intensity of the coordination polymer changed slightly but negligibly after the addition of ions other than Cr2O7 2- and CrO4 2- , while the fluorescence intensity changed significantly after the addition of Cr2O7 2- and CrO4 2-The addition of ions quenches the fluorescence of the fluorescent probe, and the quenching efficiencies reach 98.88% and 98.56% respectively. Therefore, the Cr(VI) oxyanion-specific fluorescent probe obtained in Example 1 has excellent selectivity for the recognition of Cr2O7 2- and CrO4 2- anions.

[0083] 7. Use the Cr(VI) oxyanion-specific fluorescent probe obtained in Example 1 of the present invention for the Cr2O7 2- ion titration experiment. The specific experimental steps are as follows: Take 2 mL of the suspension aqueous solution of the Cr(VI) oxyanion-specific fluorescent probe with a concentration of 1 mg / mL, and successively add 20 μL of the Cr2O7 2- anion aqueous solution (5×10 -3 mol / L). After shaking well for 30 s, immediately detect its fluorescence emission intensity. The test results are shown in the attached Figure 7 and 8 . As the concentration of Cr2O7 2- ions (0 - 0.50 mM) increases continuously, the fluorescence emission intensity of the fluorescent probe weakens continuously. According to the fitting calculation of the S-V equation, the relative fluorescence intensity ratio (I0 / I) - 1 has a linear relationship with in the range of 0 - 0.20 mM, indicating that it can quantitatively detect Cr2O7 2- anions in water at low concentrations. Through linear fitting, K sv (Cr2O7 2- ) = 50.608 mM -1 (approximately 5.06×10 4 M -1 ), R 2 = 0.9825. The detection limit of Zn-CP is calculated to be 0.0953 μM by the formula LOD = 3σ / k.

[0084] 8. Use the Cr(VI) oxyanion-specific fluorescent probe obtained in Example 1 of the present invention for the CrO4 2- ion titration experiment. The specific experimental steps are as follows: Take 2 mL of the suspension aqueous solution of the Cr(VI) oxyanion-specific fluorescent probe with a concentration of 1 mg / mL, and successively add 20 μL of the CrO4 2- anion aqueous solution (5×10 -3 mol / L). After shaking well for 30 s, immediately detect its fluorescence emission intensity. The test results are shown in the attached Figure 9 and 10 . As the concentration of CrO4 2-The concentration of ions (0 - 0.45 mM) increases continuously, and the fluorescence emission intensity of the fluorescent probe weakens continuously. According to the fitting calculation by the S-V equation, the relative fluorescence intensity ratio (I0 / I)-1 and show a linear relationship in the range of 0 - 0.25 mM, indicating that it can quantitatively detect CrO4 in water at low concentrations 2- anions. By linear fitting, K sv (CrO4 2- ) = 24.107 mM -1 (approximately 2.41×10 4 M -1 ), R 2 = 0.9864. The detection limit of Zn-CP is calculated to be 0.2 μM by the formula LOD = 3σ / k.

[0085] 9. Perform an anti-interference experiment analysis on the Cr(VI) oxygen anion-specific fluorescent probe obtained in Example 1 of the present invention. The specific steps are as follows: At room temperature, put 30 mg of the Cr(VI) oxygen anion-specific fluorescent probe powder sample into a ball mill and grind for 5 min, then disperse it in 30 mL of deionized H2O and continue to sonicate for 30 min to obtain a uniformly dispersed suspension (1 mg / mL). Take 0.1 mL of an aqueous solution of nitrate M(NO3) -2 (M = Cu, Zn, Ni, Co, Ba, Mn, Ca, K, Pb, Er, Sr, Cd, Hg, Dy, Yb, Ce, Cr, Sm, Na, and Fe; x = 1, 2, and 3) and an aqueous solution of anions (Cl x , Br - , F - , I - , NO3 - , NO2 - , CO3 - , SO4 2- , PO4 2- , IO3 2- , SCN - , Cr2O7 - and CrO4 2- , with counter cations being K 2- and Na + and Na + ), and add them to 2 mL of the above suspension respectively. After sonication for 30 s, let it stand for 5 min, and test the fluorescence emission spectra of different suspensions. The test results are as shown in the attached Figure 6 of the specification. In the presence of interfering ions (Cl - , Br - , F - , I - , NO3 - , NO2- , CO3 2- , SO4 2- , PO4 2- , IO3 - , SCN - ) In the presence of, the fluorescence probe has almost no influence on the ion recognition of Cr2O7 2- and CrO4 2- ions, indicating that the Cr(VI) oxyanion-specific fluorescence probe obtained in the present invention has good anti-interference ability for the detection of Cr2O7 2- and CrO4 2- ions in water.

[0086] 10. The cyclic stability of the Cr(VI) oxyanion-specific fluorescence probe obtained in Example 1 of the present invention was detected. The specific experimental steps were as follows: Take 2 mL of a suspension aqueous solution of the Cr(VI) oxyanion-specific fluorescence probe with a concentration of 2 mg / mL, and add 0.1 mL of a solution with a concentration of 5×10 -2 mol / L of Cr2O7 2- and CrO4 2- to it respectively. After fully shaking for 30 s, immediately detect its fluorescence emission intensity, then filter, wash with deionized water, and dry at 60 °C for 12 h. Then, the dried Cr(VI) oxyanion-specific fluorescence probe was re-prepared into a suspension aqueous solution with a concentration of 2 mg / mL, and the above operation was repeated 5 times. The test results are shown in the attached instructions Figure 11 and 12 . After the fluorescence probe was used repeatedly for many times, it still had the ability to recognize Cr2O7 2- and CrO4 2- ions in water, indicating that the Cr(VI) oxyanion-specific fluorescence probe obtained in the present invention has good cyclic stability and recyclability.

[0087] Enlightened by the above ideal embodiments according to the present invention, through the above description, relevant staff can completely make various changes and modifications without departing from the technical idea of this invention. The technical scope of this invention is not limited to the content in the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A Cr(VI) oxyanion-specific fluorescent probe based on a zinc coordination polymer, characterized in that, is a complex formed by metal zinc ions and ligand L, with the structural formula [Zn(L)2]n, where L - is 4-(3-methyl-1H-pyrazolyl)benzoate, n≥1, and n is an integer.

2. The Cr(VI) oxyanion-specific fluorescent probe based on a zinc coordination polymer according to claim 1, wherein The Cr(VI) oxyanion-specific fluorescent probe belongs to the monoclinic system and crystallizes in the monoclinic space group C2 / m with Z = 4. The unit cell parameters are: α = 90°, β = 96.09(3)°, γ = 90°.

3. A Cr(VI) oxyanion-specific fluorescent probe based on a zinc coordination polymer according to claim 1, characterized in that, The preparation method comprises the following steps: (1) Dissolve a Zn(II) salt, an L ligand, and imidazole in deionized water. After stirring evenly, a turbid solution is obtained. (2) Transfer the turbid solution to a heat-resistant reaction vessel for sealing. Then, place the heat-resistant reactor in a high-temperature environment for constant-temperature reaction. After the reaction is completed, cool it to room temperature to obtain colorless block crystals. (3) The obtained colorless block crystals are successively subjected to solid-liquid separation, washed with water, and dried to obtain the target product.

4. The Cr(VI) oxyanion-specific fluorescent probe based on a zinc coordination polymer according to claim 3, characterized in that, The Zn(II) salt includes one or a combination of two or more of zinc sulfate, zinc acetate, zinc nitrate, and zinc chloride.

5. A Cr(VI) oxyanion-specific fluorescent probe based on a zinc coordination polymer according to claim 3, characterized in that In step (1), the molar ratio between the Zn(II) salt, the L ligand, and imidazole is 1.3 - 1.8:0.9 - 1.2:

1.

6. The Cr(VI) oxyanion-specific fluorescent probe based on a zinc coordination polymer according to claim 5, wherein The mass ratio of the L ligand to deionized water is 1:150 - 400.

7. A Cr(VI) oxyanion-specific fluorescent probe based on a zinc coordination polymer according to claim 3, characterized in that, The constant-temperature reaction temperature in step (2) is 140 - 160 °C.

8. A Cr(VI) oxyanion-specific fluorescent probe based on a zinc coordination polymer according to claim 3, characterized in that, When the volume of the turbid solution in step (2) < 25 mL, transfer the turbid solution to a heat-resistant glass tube for sealing, and then place it in an oven at 140 - 160 °C for constant-temperature reaction for 48 - 96 h. After the reaction is completed, cool it to room temperature at a rate of 3 - 10 °C / h to obtain colorless block crystals.

9. A Cr(VI) oxyanion-specific fluorescent probe based on a zinc coordination polymer according to claim 3, characterized in that, When the volume of the turbid solution in step (2) ≥ 25 mL, heat the obtained turbid solution to reflux for 12 - 36 h. After the reaction is completed, naturally cool it to room temperature to obtain colorless block crystals.

10. A fluorescence sensor, characterized in that, Using the Cr(VI) oxyanion-specific fluorescent probe described in any one of claims 1 - 9 as its fluorescent probe, perform trace detection on hexavalent Cr ions in a Cr(VI)-containing solution.

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