Preparation method of imine pyridine COF fluorescent probe and application of imine pyridine COF fluorescent probe in detection of Cu 2+ ​

Abstract

The present invention discloses a preparation method of an iminopyridine COF fluorescent probe and its 2+ The detection application comprises the following steps: dispersing amino monomer (TA) and aldehyde monomer (PD) in an organic solvent, ultrasonically treating, using glacial acetic acid as a catalyst, repeatedly freezing and thawing, and then passing N2 for degassing, heating the container in a vacuum seal for reaction, cooling to room temperature after the reaction is complete, washing, and drying the product to obtain an iminopyridine COF (COF-TAPD) fluorescent probe. The COF-TAPD fluorescent probe of the present invention realizes the detection of Cu in water. 2+ The probe has excellent stability, anti-interference ability and low detection limit, with a LOD of 7.63nM. After five cycles of use, it still maintains more than 85% of the fluorescence response ability, and is effective in detecting heavy metal Cu in water. 2+ It has good practical application potential.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of covalent organic framework materials, and particularly relates to synthesis of a covalent organic framework fluorescent probe and application of the covalent organic framework fluorescent probe to detection of Cu 2+ in water. BACKGROUND

[0002] With the acceleration of global industrialization, a large amount of industrial wastewater is generated, which contains toxic heavy metal ions such as Fe 3+ , Cu 2+ and Hg 2+ . These ions enter the ecological cycle through the biological chain and finally accumulate in the human body, causing damage to the organs and threatening life and health. Therefore, it is of great importance to develop efficient and reliable sensing materials for the detection of heavy metal ions in water to ensure the safety of human life.

[0003] In the detection of heavy metal ions, commonly used methods include ultraviolet spectrophotometry, fluorescence method and atomic absorption method. However, the ultraviolet spectrophotometry has low sensitivity and is easily interfered by sample color, turbidity or fluorescent substances; the atomic absorption method has high equipment cost and needs complex pretreatment steps. In comparison, the fluorescence method is more attractive in the detection of metal ions due to its high sensitivity, excellent selectivity, non-destructive detection and fast response, and becomes a more preferred analysis method.

[0004] COFs materials have attracted much attention due to their structural diversity and high designability. Generally, COFs use rigid planar structures of aromatic derivatives as synthetic monomers, and the extension of conjugated electrons in the framework and the ordered stacking structure not only provide a stable framework, but also endow the material with unique luminescent properties. It is worth noting that the optical properties of fluorescent COFs depend largely on the choice of building units and the connection mode. At present, COF fluorescent probes have been successfully applied to the detection of heavy metal ions in water and have shown excellent potential for practical application. For example, Wu et al. synthesized a hydrazine-containing COF at room temperature, which was used for the detection and removal of Cu 2+ in water, and the Cu 2+maximum adsorption capacity of 203 mg / g, and LOD of 47.8 nM. [Wu X, Zhang Y, Wang F, et al. Room-temperature synthesis of a covalent organic framework with hydrazine linkages for sensitive fluorescent detecting and renewable removing of copper ions [J]. Optical Materials, 2023, 140: 113873.] and Wei et al. synthesized hydrazone-based crystalline H-COF-1 and H-COF-2 using a solvothermal method, in which H-COF-1 has a LOD of 233 nM for Cu 2+ in water, and H-COF-2 has a LOD of 74 nM. [Dongxue W, Yuwei Z, Ce X, et al. Luminescence covalent organic frameworks for metal ions detection via turntable sites [J]. Microporous and Mesoporous Materials, 2024, 366112938-.] Chinese application (patent) no. CN202110170647.9 discloses a fluorescent COF material responsive to Cu 2+ , which also has a sensitive fluorescent response to Cu 2+ with a linear range of 0.02-0.2 μM. Although many COF fluorescent probes for detecting Cu 2+ have been developed, there are still some deficiencies that need to be improved. For example, the COF fluorescent probes reported in the above documents and patents have high detection limits, narrow linear ranges, and weak anti-interference ability.

[0005] The present application first synthesizes an imine pyridine covalent organic framework (COF-TAPD) fluorescent probe for detecting Cu 2+ in water by one-pot synthesis of amino monomers (TA) and aldehyde monomers (PD) through Schiff base reaction. The imine pyridine COF fluorescent probe prepared in the present application has strong anti-interference ability, high sensitivity, and can realize efficient and rapid detection of Cu 2+ with a linear range of 0.1-7.0 μM and a LOD of 7.63 nM, which has important practical significance and broad application prospects. SUMMARY

[0006] It is necessary to develop effective sensing materials to detect Cu 2+It has important practical significance. The developed COF fluorescent probe for Cu 2+ The COF fluorescent probe for detecting Cu 2+ The COF fluorescent probe for detecting Cu 2+ has high sensitivity, excellent anti-interference ability and reusability, and meets the needs of efficient and rapid detection of Cu

[0007] In order to achieve the purpose of the present application, the technical scheme adopted by the present application is:

[0008] The present application provides a preparation method of a COF fluorescent probe for detecting Cu 2+ The preparation method of the COF fluorescent probe for detecting Cu

[0009] In some embodiments, the molar ratio of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and 5,5'-(1,4-phenylene) bis(pyridine-2-carboxaldehyde) is 3:2.

[0010] In some embodiments, the organic solvent is tetrahydrofuran, the concentration of glacial acetic acid is 6M, and the volume ratio of tetrahydrofuran and glacial acetic acid is (1-2):(0.06-0.15), preferably, the volume ratio of tetrahydrofuran and glacial acetic acid is 1:0.1.

[0011] In some embodiments, 3-5 cycles of freezing-vacuumizing-thawing processes are required before the reaction to keep the reaction system in a vacuum state; preferably, 3 cycles of freezing-vacuumizing-thawing processes are performed.

[0012] In some embodiments, the reaction temperature is 100-120 DEG C, and the reaction time is 3 days. Preferably, the reaction temperature is 120 DEG C.

[0013] In some embodiments, the washing solvent includes but is not limited to acetonitrile, 1,4-dioxane, N,N-dimethylformamide, ethanol, tetrahydrofuran, acetone, and methanol commonly used organic solvents; preferably, the order of the washing agent from small to large in polarity is tetrahydrofuran, acetone, and methanol.

[0014] In some embodiments, the vacuum drying temperature is 50-80℃, and the drying time is 10-24 hours; preferably, the vacuum drying temperature is 60℃, and the drying time is 12 hours.

[0015] The present application also relates to the application of the COF fluorescent probe prepared by the above method in detecting heavy metal Cu 2+ ; preferably, the COF-TAPD fluorescent probe dispersion solvent is ethanol. 2+ .

[0016] In some embodiments, the COF-TAPD fluorescent probe dispersion solvent includes but is not limited to ethanol, acetonitrile, 1,4-dioxane, N,N-dimethylformamide, and water; preferably, the COF-TAPD fluorescent probe dispersion solvent is ethanol.

[0017] In some embodiments, the concentration of the COF-TAPD fluorescent probe dispersion is (0.05-0.2) mg / mL; preferably, the concentration of the COF-TAPD fluorescent probe dispersion is 0.2 mg / mL.

[0018] In some embodiments, the pH of the COF-TAPD fluorescent probe detection solution is 3-6; preferably, the pH of the COF-TAPD fluorescent probe detection solution is 4.

[0019] Compared with the prior art, the present application has the advantages and beneficial effects that:

[0020] (1) The COF-TAPD fluorescent probe material has high crystallinity, excellent chemical stability, and good reusability.

[0021] (2) The COF-TAPD fluorescent probe has high selectivity and sensitivity, a wide linear range, a low detection limit, and excellent anti-ion interference ability. 2+ (3) The COF-TAPD fluorescent probe shows fluorescence weakening after reacting with Cu 2+ , realizes rapid detection of Cu 2+ , and has practical application value and potential.

[0022] (3) The COF-TAPD fluorescent probe shows fluorescence weakening after reacting with Cu 2+ , realizes rapid detection of Cu 2+ , and has practical application value and potential. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a scanning electron microscope image of the COF-TAPD fluorescent probe of the present application;

[0024] Figure 2 is the infrared spectrum of the COF-TAPD fluorescent probe of the present application;

[0025] Figure 3 is the X-ray powder diffraction pattern of the COF-TAPD fluorescent probe of the present application;

[0026] Figure 4 is the fluorescence stability diagram of the COF-TAPD fluorescent probe of the present application;

[0027] Figure 5 is the fluorescence emission intensity change diagram of the COF-TAPD fluorescent probe of the present application before and after adding different metal ions;

[0028] Figure 6 is the fluorescence emission intensity change diagram of the COF-TAPD fluorescent probe of the present application in the presence of Cu 2+ and other metal ions;

[0029] Figure 7 is the quenching efficiency diagram of the COF-TAPD fluorescent probe of the present application under different pH values of Cu 2+ ;

[0030] Figure 8 is the fluorescence emission spectrum diagram of the COF-TAPD fluorescent probe of the present application for different copper salts;

[0031] Figure 9 is the fluorescence emission intensity change diagram of the COF-TAPD fluorescent probe of the present application before and after adding different concentrations of Cu 2+ ;

[0032] Figure 10 is the repeated use performance research diagram of the COF-TAPD fluorescent probe of the present application. Specific embodiments

[0033] The specific embodiments of the present application are further described in detail in conjunction with the accompanying drawings in the examples, and the following examples are used to illustrate the present application, but do not limit the application range and expansion of the present application.

[0034] Example 1: Preparation of a covalent organic framework fluorescent probe

[0035] (1) The preparation reaction of the COF-TAPD fluorescent probe is as follows:

[0036]

[0037] (2) The preparation steps of the COF-TAPD fluorescent probe are as follows:

[0038] Firstly, 21.2 mg of TA (0.3 mmol) and 25.9 mg of PD (0.2 mmol) were placed in a heat-resistant long glass tube; 1 mL of tetrahydrofuran was added as a solvent and ultrasonic treatment was performed for 2 min to obtain a dispersion liquid; then 0.1 mL of glacial acetic acid (6M) was added dropwise; the glass tube was frozen in liquid nitrogen and connected to a double-tube pump to vacuum, and then the glass tube was transferred to a methanol reagent for thawing; the freezing-pumping-thawing cycle operation was repeated 3 times, and the glass tube was sealed with a flame gun; after thawing at room temperature, the glass tube was placed in a 120°C oven and reacted for 72 h. After the reaction was cooled to room temperature, centrifugal separation was performed, and the solvents were washed with polar solvents from small to large, and tetrahydrofuran, acetone and methanol were washed several times until the washing liquid was colorless; vacuum drying was performed at 60°C for 12 h to obtain a brown-yellow product (COF-TAPD).

[0039] The morphology of the prepared COF-TAPD fluorescent probe was analyzed by scanning electron microscopy, and the results are shown in Figure 1 . COF-TAPD shows a typical layered stacking structure.

[0040] The synthesis of the prepared COF-TAPD fluorescent probe was analyzed by infrared spectroscopy, and the results are shown in Figure 2 . The characteristic peaks of N-H (3300-3400 cm -1 ) stretching vibration of amino monomer (TA) and C=O (1710 cm -1 ) of aldehyde monomer (PD) have disappeared. At the same time, a new characteristic peak of C=N bond stretching vibration appears at 1610 cm -1 , indicating that COF-TAPD is successfully prepared.

[0041] The crystal structure of the prepared COF-TAPD fluorescent probe was analyzed by XRD, and the results are shown in Figure 3 . COF-TAPD appears a sharp diffraction peak near 2.0° in the range of 2θ = 2-10°, which corresponds to the reflection phenomenon of (100) crystal plane, fully proving the excellent crystallinity of COF-TAPD.

[0042] The stability of COF-TAPD fluorescent probe was explored by continuously measuring the fluorescence emission intensity of COF-TAPD fluorescent probe in solution, and the fluorescence emission intensity at λ = 355 nm was measured at λ = 305 nm, and the results are shown in Figure 4 . The fluorescence emission intensity of COF-TAPD fluorescent probe in ethanol solution remained stable within 72 hours, indicating that COF-TAPD fluorescent probe has excellent fluorescence stability.

[0043] Example 2:

[0044] (1) Selectivity of COF-TAPD fluorescent probe

[0045] In order to study the fluorescence response of COF-TAPD fluorescent probe to different heavy metal ions, Zn 2+ 、Co 2+ 、Cd 2 + , Ca 2+ Mg 2+ 、Mn 2+ 、A1 3+ Cr 3+ 、Fe 3+ 、Ni + and Cu 2+ The following experiments were conducted for 11 metal ions: First, 1 mL of COF-TAPD fluorescent probe dispersion (0.2 mg / mL) was taken into a centrifuge tube, and then 1 mL of each of the 11 metal ions (2 × 10 - 5 mol / L), excited at λ = 305nm and measured the fluorescence emission intensity at λ = 355nm. The obtained data were analyzed to analyze the change of fluorescence intensity and determine whether the COF-TAPD fluorescent probe was selective. Figure 5 As shown, under the same concentration of metal ions, only Cu 2+ The fluorescence of COF-TAPD fluorescent probe was obviously quenched, which fully proved that COF-TAPD fluorescent probe was sensitive to Cu 2+ Has excellent selectivity.

[0046] (2) Anti-interference property of COF-TAPD fluorescent probe

[0047] By adding Cu into the COF-TAPD fluorescent probe dispersion 2+ Anti-interference experiments were conducted with other metal ions to explore whether other metal ions interfere with the interaction between COF-TAPD fluorescent probe and Cu 2+ The experimental process is as follows: add 1 mL of COF-TAPD fluorescent probe dispersion (0.2 mg / mL) to the centrifuge tube and then add 0.5 mL of Cu 2+ Solution (4×10 -5 mol / L), and then 0.5 mL of the other 10 metal ion solutions (4×10 -5 mol / L), and after mixing evenly, the fluorescence value of the mixture was immediately measured. Figure 6 As shown, compared with the presence of only Cu 2+ The situation, Cu 2+ When coexisting with 10 other metal ions, it still has a good quenching effect on the COF-TAPD fluorescent probe, proving that the COF-TAPD fluorescent probe has good anti-interference ability.

[0048] Example 3:

[0049] The fluorescence response of the COF-TAPD fluorescent probe to Cu 2+ under different pH conditions was explored, and the results are shown in Figure 7 . The quenching effect of the COF-TAPD fluorescent probe on Cu 2+ under slightly acidic and slightly basic conditions was poor, and when pH > 7, the quenching efficiency was almost below 20%. The quenching effect of the COF-TAPD fluorescent probe was best at pH = 4.

[0050] Example 4:

[0051] Four copper salts with different anions, CuSO4·5H2O, Cu(NO3)2·3H2O, CuBr2, and CuCl2·2H2O, were selected to explore whether the anions interfere with the fluorescence response of the COF-TAPD fluorescent probe to Cu 2+ . The experimental process was as follows: 1 mL of COF-TAPD fluorescent probe dispersion (0.2 mg / mL) was added to a centrifuge tube, and then 1 mL of CuSO4·5H2O, Cu(NO3)2·3H2O, CuBr2, and CuCl2·2H2O solutions (2×10 -5 mol / L) were added to the centrifuge tube, respectively. After mixing well, the fluorescence value of the mixture was immediately determined. The results are shown in Figure 8 . Different anion copper salts had no significant difference in the quenching effect of the COF-TAPD fluorescent probe, indicating that the anions did not interfere with the fluorescence response of the COF-TAPD fluorescent probe to Cu 2+ .

[0052] Example 5:

[0053] The fluorescence response of the COF-TAPD fluorescent probe to different concentrations of Cu 2+ was explored, and the experimental process was as follows: 1 mL of COF-TAPD fluorescent probe dispersion (0.2 mg / mL) was added to a centrifuge tube, and 1 mL of Cu 2+ solution with different concentrations was added to the centrifuge tube to make the test concentration 1×10 -7 mol / L, 5×10 -7 mol / L, 1×10 -6 mol / L, 2×10 -6 mol / L, 3×10 -6 mol / L, 4×10 -6 mol / L, 6×10 -6 mol / L, 7×10 -6 mol / L, 8×10 -6 mol / L, 9×10 -6 mol / L, and 1×10 -5mol / L、1.2×10 -5 mol / L、1.5×10 -5 mol / L, 2×10 -5 mol / L, 2.5×10 -5 mol / L and 3×10 -5 mol / L, and measure the fluorescence emission spectrum. The results are as follows Figure 9 As shown, with Cu 2+ As the concentration of copper ions increases, the fluorescence emission intensity of the COF-TAPD fluorescent probe gradually weakens. When the copper ion concentration is 10 μM, the fluorescence is almost completely quenched ( Figure 9 a) Fluorescence intensity of the fluorescent probe and Cu in the range of 0.1-7.0 μM 2+ The concentration is linearly related ( Figure 9 b) The regression equation is y = -0.11x + 0.99, R 2 The kinase activity was 0.996 and the LOD was 7.63 nM.

[0054] Example 6:

[0055] In order to explore the reusability of COF-TAPD fluorescent probe, the experimental process is as follows: take 1 mL of the prepared COF-TAPD fluorescent probe dispersion (0.2 mg / mL) in a centrifuge tube, and then add 1 mL of Cu 2+ Solution (2×10 -5 mol / L), and immediately measure the fluorescence value of the mixed solution. After the measurement, add EDTA-2Na and Cu 2+ The COF-TAPD fluorescent probe was recovered by centrifugation, washed several times and dried under vacuum at 60°C. The dried fluorescent probe was used to prepare the dispersion and the preparation-measurement-recovery-drying steps were repeated five times. Figure 10 As shown in the figure, after 5 cycles of use, the COF-TAPD fluorescent probe 2+ The fluorescence response rate can still be maintained above 85%, proving that the COF-TAPD fluorescent probe has excellent reusability and practical application value.

Claims

1. A method for preparing an iminopyridine COF fluorescent probe, characterized in that: Using the fluorescent amino monomer 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and the N-containing aldehyde monomer 5,5'-(1,4-phenylene)bis(pyridine-2-carboxaldehyde) as building blocks, a C=N-linked iminopyridine COF (COF-TAPD) fluorescent probe was synthesized via a solvothermal Schiff base reaction for the detection of Cu in water. 2+ .

2. The preparation method according to claim 1, characterized in that The amino monomer and the aldehyde monomer are dispersed in an organic solvent. The mixture is ultrasonically treated and then degassed by repeated freezing and thawing with N2 using glacial acetic acid as a catalyst. The reaction vessel is vacuum-sealed for heating reaction. After the reaction is cooled to room temperature, the product is washed and dried to obtain the COF-TAPD fluorescent probe.

3. The preparation method according to claim 2, wherein: The molar ratio of the amino monomer 2,4,6-tris(4-aminophenyl)-1,3,5-triazine to the aldehyde monomer 5,5'-(1,4-phenylene)bis(pyridine-2-carboxaldehyde) is 3:

2.

4. The preparation method according to claim 2, wherein: The organic solvent is tetrahydrofuran, the concentration of the glacial acetic acid is 6M, and the volume ratio of the tetrahydrofuran to the glacial acetic acid is (1-2):(0.06-0.15).

5. The preparation method according to claim 2, wherein: Before the reaction, 3-5 freeze-vacuum-thaw cycles are required to keep the reaction system in a vacuum state.

6. The preparation method according to claim 2, wherein: The reaction temperature is 100-120° C., and the reaction time is 3 days.

7. The preparation method according to claim 2, characterized in that: The washing solvent is acetonitrile, 1,4-dioxane, N,N-dimethylformamide, ethanol, tetrahydrofuran, acetone, and methanol, and then vacuum drying is performed at 50-80° C. for 10-24 hours.

8. The COF-TAPD fluorescent probe prepared according to the preparation method of claim 2 is used to detect Cu 2+ The application is characterized by: The COF-TAPD fluorescent probe was added to the solvent and stirred to obtain a probe dispersion with a concentration of (0.05-0.2) mg / mL. The COF-TAPD probe dispersion was added to the test sample and its fluorescence emission intensity was measured at an excitation wavelength of λ=305 nm. The fluorescence intensity was weakened at 355 nm, indicating the presence of Cu in the test solution. 2+ .

9. The COF-TAPD fluorescent probe according to claim 8 is used to detect Cu 2+ The application is characterized by: The COF-TAPD fluorescent probe dispersion solvent is ethanol, acetonitrile, 1,4-dioxane, N,N-dimethylformamide, and water; the pH range of the COF-TAPD fluorescent probe detection solution is 3-6.

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