Preparation method of novel COF fluorescent probe and application of novel COF fluorescent probe in detection of Cu < 2 + >

Abstract

The invention discloses a preparation method of a novel COF fluorescent probe and application of the novel COF fluorescent probe to detection of Cu < 2 + >. Comprising the following steps: dispersing an amino monomer (TA) and an aldehyde monomer (PD) in an organic solvent, carrying out ultrasonic treatment, repeatedly freezing and thawing by using glacial acetic acid as a catalyst, introducing N2 for degassing, carrying out a heating reaction in a vacuum sealed container, cooling to room temperature after the reaction is completed, washing, and drying the product to obtain the COF-TAPD fluorescent probe. According to the novel COF-TAPD fluorescent probe, efficient and rapid detection of Cu < 2 + > in water is achieved, the probe has excellent stability, anti-interference capacity and low detection limit, the LOD is 7.63 nM, the fluorescent response capacity of 85% or above is still kept after five times of recycling, and the good practical application potential is achieved in the aspect of detecting the heavy metal Cu < 2 + > in water.

Description

Technical Field

[0001] The present invention belongs to the technical field of covalent organic framework materials, and specifically relates to the synthesis of a novel covalent organic framework fluorescent probe and its detection of Cu in water. 2+ detection applications. Background Art

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

[0003] In the detection of heavy metal ions, commonly used methods include ultraviolet spectrophotometry, fluorescence and atomic absorption. However, ultraviolet spectrophotometry has low sensitivity and is easily interfered by sample color, turbidity or fluorescent substances; atomic absorption has high equipment cost and requires complex pre-treatment steps. In contrast, fluorescence is more attractive in metal ion detection due to its high sensitivity, excellent selectivity, non-destructive detection and rapid response, and has become a more popular analytical method.

[0004] COFs materials have attracted much attention due to their structural diversity and high designability. Generally, COFs use aromatic derivatives with rigid planar structures as synthetic monomers. The expansion and ordered stacking structure of conjugated electrons in their skeletons not only provide a stable skeleton, but also give the material unique luminescence properties. It is worth noting that the optical properties of fluorescent COFs depend to a large extent on the selection and connection method of building units. At present, COF fluorescent probes have been successfully used in the detection of heavy metal ions in water, showing excellent practical application potential. For example, Wu et al. synthesized a hydrazine-bonded COF at room temperature for the detection and removal of Cu in water. 2+ , for Cu 2+The maximum adsorption capacity reached 203 mg / g, and the LOD was 47.8 nM. [Wu X, Zhang Y, Wang F, et al. Room-temperature synthesis of a covalent organic frameworkwith hydrazine linkages for sensitive fluorescent detecting and renewableremoving of copper ions[J]. Optical Materials, 2023, 140: 113873.], and Wei et al. used a solvothermal method to synthesize hydrazone-based crystalline H-COF-1 and H-COF-2, among which H-COF-1 was very sensitive to Cu in water. 2+ The LOD of is 233nM, and that of H-COF-2 is 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-.]. The Chinese application (patent) number is CN202110170647.9, which discloses a Cu 2+ The fluorescent COF material responds to Cu 2+ It also has a sensitive fluorescence response with a linear range of 0.02-0.2 μM. 2+ However, there are still some shortcomings that need to be improved. For example, the COF fluorescent probes reported in the above literature and patents have problems such as high detection limit, narrow linear range, and weak anti-interference ability.

[0005] This invention is the first to synthesize Cu in water by a one-pot method using amino monomer (TA) and aldehyde monomer (PD) through Schiff base reaction. 2+ The covalent organic framework fluorescent probe COF-TAPD prepared by the present invention has strong anti-interference ability and high sensitivity, and can realize efficient and rapid detection of Cu 2+ , the linear range is 0.1-7.0 μM, and the LOD is 7.63 nM, which has important practical significance and broad application prospects. Summary of the invention

[0006] Developing effective sensing materials to detect Cu in water 2+It has important practical significance. 2+ The COF fluorescent probes used for detection still have problems such as high detection limit, weak anti-interference ability and poor reusability. The present invention aims to solve the above problems and provides a method for detecting Cu 2+ The novel COF fluorescent probe preparation method is provided. The COF fluorescent probe prepared by the method has high sensitivity, excellent anti-interference ability and reusability, which meets the requirements of efficient and rapid detection of Cu in water. 2+ demand.

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

[0008] The present invention provides a method for detecting Cu 2+ The preparation method of the novel COF fluorescent probe comprises the following steps: using 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and N-atom-containing aldehyde monomer 5,5'-(1,4-phenylene)bis(pyridine-2-carboxaldehyde) as building units, dissolving them in an organic solvent and using glacial acetic acid as a catalyst, ultrasonically treating the mixture, and then repeatedly freezing and thawing and passing N 2 Degassing is performed, and the reaction container is vacuum sealed and heated for reaction. After the reaction is cooled to room temperature, the product is washed and dried to obtain the COF-TAPD fluorescent probe material.

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

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

[0011] In some embodiments, 3-5 freeze-vacuum-thaw cycles are performed before the reaction to keep the reaction system in a vacuum state; preferably, 3 freeze-vacuum-thaw cycles are performed.

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

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

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

[0015] The present invention also relates to the COF fluorescent probe prepared by the above method for detecting heavy metal Cu 2+ In terms of application, COF-TAPD fluorescent probe is added to the dispersion solvent and stirred to obtain a probe dispersion with a concentration of (0.05-0.2) mg / mL; COF-TAPD probe dispersion is added to the test sample, and its fluorescence emission intensity is measured at an excitation wavelength of λ=305nm. The fluorescence intensity weakens at 355nm, indicating the presence of Cu in the test solution. 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 dispersed COF-TAPD fluorescent probe is (0.05-0.2) mg / mL; preferably, the concentration of the COF-TAPD fluorescent probe is 0.2 mg / mL.

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

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

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

[0021] (2) The COF-TAPD fluorescent probe of the present invention is used for Cu 2+ It has high selectivity and sensitivity, wide linear range, low detection limit, and excellent resistance to ion interference.

[0022] (3) COF-TAPD fluorescent probe of the present invention and Cu 2+ After the reaction, the fluorescence weakened, achieving the effect of Cu 2+ The rapid detection shows the practical application value and potential. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0024] Figure 2 is an infrared image of the COF-TAPD fluorescent probe of the present invention;

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

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

[0027] Figure 5 This is a graph showing the change in fluorescence emission intensity of the COF-TAPD fluorescent probe of the present invention before and after adding different metal ions;

[0028] Figure 6 The COF-TAPD fluorescent probe of the present invention is 2+ Fluorescence emission intensity changes under coexistence conditions with other metal ions;

[0029] Figure 7 The COF-TAPD fluorescent probe of the present invention is Cu at different pH values. 2+ Quenching efficiency graph;

[0030] Figure 8 This is the fluorescence emission spectrum of the COF-TAPD fluorescent probe of the present invention quenched by different copper salts;

[0031] Fig. 9 The COF-TAPD fluorescent probe of the present invention is added with different concentrations of Cu 2+ Fluorescence emission intensity before and after change graph and linear graph;

[0032] Fig.10 This is a graph showing the research on the reusability of the COF-TAPD fluorescent probe of the present invention. Specific implementation plan

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

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

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

[0036]

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

[0038] First, 21.2 mg TA (0.3 mmol) and 25.9 mg PD (0.2 mmol) were placed in a heat-resistant long glass tube; 1 mL tetrahydrofuran was added as a solvent and ultrasonically treated for 2 min to obtain a dispersion; then 0.1 mL glacial acetic acid (6 M) was added dropwise; the glass tube was placed in liquid nitrogen and frozen, and a double-row tube was connected to evacuate to vacuum, and then the glass tube was transferred to a methanol reagent for thawing; the freeze-pump-thaw cycle 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℃ oven and reacted for 72 h. After the reaction was cooled to room temperature, it was centrifuged and washed with solvents with increasing polarity, tetrahydrofuran, acetone and methanol several times each until the washing liquid was colorless; vacuum dried at 60℃ 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. Figure 1 As shown. COF-TAPD exhibits a typical layered stacking structure.

[0040] The synthesis of the prepared COF-TAPD fluorescent probe was analyzed by infrared spectroscopy. Figure 2 As shown. The NH (3300~3400 cm -1 ) stretching vibration and the C=O (1710 cm -1 ) have disappeared. At the same time, at 1610 cm -1 A new characteristic peak of C=N bond stretching vibration appeared at , indicating that COF-TAPD was successfully prepared.

[0041] The crystal structure of the prepared COF-TAPD fluorescent probe was analyzed by XRD. Figure 3 shown.

[0042] In the range of 2θ=2~10°, COF-TAPD shows a sharp diffraction peak near 2.0°. This feature corresponds to the reflection phenomenon of the (100) crystal plane, which fully proves the excellent crystallinity of COF-TAPD.

[0043] The stability of the COF-TAPD fluorescent probe was explored by continuously measuring its fluorescence emission intensity in the solution. The fluorescence emission intensity at λ=355 nm was measured by exciting at λ=305 nm. The results are as follows: Figure 4 The fluorescence emission intensity of COF-TAPD fluorescent probe remained stable in ethanol solution for 72 hours, indicating that COF-TAPD fluorescent probe has excellent fluorescence stability.

[0044] Embodiment 2:

[0045] (1) Selectivity of COF-TAPD fluorescent probe

[0046] 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+ A total of 11 metal ions were used for the following experiments: First, 1 mL of COF-TAPD fluorescent probe dispersion (0.2 mg / mL) was taken into a centrifuge tube, and then 1 mL of the 11 metal ions (2×10 -5 mol / L), the fluorescence emission intensity at λ=355 nm was measured by exciting at λ=305 nm, and the change of fluorescence intensity was analyzed by the obtained data to determine whether the COF-TAPD fluorescent probe is selective. The results are shown in Figure 5 As shown in Figure 2, under the same metal ion concentration conditions, 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.

[0047] (2) Anti-interference of COF-TAPD fluorescent probe

[0048] By adding Cu into the COF-TAPD fluorescent probe dispersion 2+ Anti-interference experiments were carried out 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 then the fluorescence value of the mixed solution was measured immediately after mixing evenly. Figure 6 As shown, compared with the presence of only Cu 2+ The situation of 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.

[0049] Embodiment 3:

[0050] The COF-TAPD fluorescence probe was used to investigate the effect of COF-TAPD on Cu under different pH conditions. 2+ The fluorescence response of Figure 7 As shown, under acidic and alkaline conditions, Cu 2+ The quenching effect is poor. When pH > 7, the quenching efficiency is almost below 20%. The COF-TAPD fluorescent probe has the best quenching effect at pH = 4.

[0051] Embodiment 4:

[0052] Select CuSO 4 •5H 2 O, Cu(NO 3 ) 2 •3H 2 O、CuBr 2 and CuCl 2 •2H 2 Four copper salts with different anions were used to investigate whether anions interfere with the COF-TAPD fluorescence probe on Cu 2+ The experimental process is as follows: 1 mL of COF-TAPD fluorescent probe dispersion (0.2 mg / mL) was added to the centrifuge tube, and then 1 mL of CuSO 4 •5H 2 O, Cu(NO 3 ) 2 •3H 2 O、CuBr 2 and CuCl 2 •2H 2 O solution (2×10 -5 mol / L), and then the fluorescence value of the mixed solution was measured immediately after mixing evenly. Figure 8 As shown in the figure, there is no significant difference in the quenching effect of different anionic copper salts on the COF-TAPD fluorescent probe, indicating that anions do not interfere with the COF-TAPD fluorescent probe to Cu 2+ The fluorescence response.

[0053] Embodiment 5:

[0054] To investigate the effect of COF-TAPD fluorescence probe on different concentrations of Cu 2+The experimental process is as follows: 1 mL of COF-TAPD fluorescent probe dispersion (0.2 mg / mL) was added to the centrifuge tube, and 1 mL of different concentrations of Cu 2+ The solution was tested at a concentration of 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、1×10 -5 mol / 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 the fluorescence emission spectrum was measured. The results are as follows Fig. 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 ( Fig. 9 a), Fluorescence intensity of fluorescent probes and Cu in the range of 0.1-7.0 μM 2+ The concentration is linearly related ( Fig. 9 b), the regression equation is y=-0.11x+0.99, R 2 is 0.996 and the LOD is 7.63 nM.

[0055] Embodiment 6:

[0056] 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. Fig.10 As shown in the figure, after 5 cycles of use, the COF-TAPD fluorescence 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. Preparation of a novel COF fluorescent probe and its effect on Cu 2+ The detection application is characterized by: A novel iminopyridine COF (COF-TAPD) fluorescent probe with C=N as the connecting bond was prepared by solvothermal Schiff base reaction using fluorescent amino monomer 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and N-containing aldehyde monomer 5,5'-(1,4-phenylene)bis(pyridine-2-carboxaldehyde) as building blocks 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, and the mixture is ultrasonically treated. Then, glacial acetic acid is used as a catalyst, and the mixture is repeatedly frozen and thawed and degassed by passing N2. 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, characterized in that: In step 2, 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, characterized in that: In step 2, the organic solvent is tetrahydrofuran, the concentration of the glacial acetic acid is 6 M, 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, characterized in that: Before the reaction in step 2, 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, characterized in that: The reaction temperature in step 2 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 in step 2 includes, but is not limited to, acetonitrile, 1,4-dioxane, N,N-dimethylformamide, ethanol, tetrahydrofuran, acetone, methanol and other commonly used organic solvents, and then vacuum dried at 50-80° C. for 10-24 hours.

8. The COF-TAPD fluorescent probe obtained by the preparation method according to claim 2 is used to detect Cu 2+ The application is characterized by: Add COF-TAPD fluorescent probe to the solvent and stir evenly to obtain a probe dispersion with a concentration of (0.05-0.2) mg / mL; add COF-TAPD probe dispersion to the test sample and measure its fluorescence emission intensity at an excitation wavelength of λ=305nm. The fluorescence intensity weakens at 355nm, 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 includes but is not limited to 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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