Metal-organic frameworks with dual-ligand strategy and their application in detection of al3+

Abstract

The application belongs to the technical field of metal framework materials and detection probes, and particularly relates to a metal organic framework material with a dual-ligand strategy and application thereof in detection of Al 3+ . A ratio type fluorescent probe with a dual-ligand strategy is designed based on an ESIPT mechanism between the MOF and Al 3+ . Under an excitation wavelength of 270 nm, the prepared MOF has three emission peaks at 515 nm, 605 nm and 620 nm respectively. Al 3+ can not only significantly enhance the fluorescence intensity at 515 nm, but also keep the fluorescence intensity at 620 nm basically unchanged; raw materials include 2,6-pyridinedicarboxylic acid, 2,5-dihydroxyterephthalic acid and europium. The preparation method is simple, the material is easy to obtain, and the prepared MOF has good dispersibility and high stability in aqueous solution, and exhibits excellent luminescent characteristics. The application of the MOF in aluminum ion detection can effectively avoid the interference of the external environment on the detection result, has high sensitivity and selectivity, and simultaneously realizes visual detection based on a smart phone platform.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal framework materials and detection probes, and in particular relates to metal organic framework materials with a dual ligand strategy and their application in Al 3+ Application in detection. Background Art

[0002] As the most abundant metal element in the earth's crust, aluminum is widely used in our daily life, such as food additives, cookware, broad-spectrum fumigants for protecting grain, etc. 3+ It can enter the human body through food and drinking water. Excessive exposure to Al 3+ It can damage the central nervous system, cause Alzheimer's disease, Parkinson's disease, osteoporosis and other diseases, posing a great threat to human health.

[0003] In recent years, luminescence detection has attracted considerable attention due to its advantages, including high sensitivity, good selectivity, convenient detection, and fast response. Numerous fluorescent probes have been developed and proven to be highly effective tools for sensing and detection in healthcare, environmental protection, industrial and agricultural production, security, and defense. Among these various detection methods, fluorescent sensors offer broad application prospects due to their simplicity, high sensitivity, portability, high efficiency, and low cost. Among the numerous photoluminescent sensing materials, lanthanide metal-organic frameworks (Ln-MOFs) possess unique optical properties, including long fluorescence lifetime, high color purity, and large Stokes shift. However, most fluorescent probes exhibit the same fluorescence signal for different analytes, i.e., intensity variations or wavelength shifts within a single emission band. Consequently, cross-interference between different analytes is difficult to avoid. Furthermore, most MOFs are detected in organic solvents, which are environmentally unfriendly. The complex and diverse nature of aqueous environments leads to significant background interference during detection, compromising the accuracy and authenticity of the results. Consequently, efforts are underway to develop Ln-MOFs with enhanced anti-interference capabilities and superior detection performance. Summary of the Invention

[0004] Based on the defects in the prior art, the present invention provides a preparation method and application of Eu-MOF with a dual emission strategy, which not only has a simple synthesis method, but also has the advantages of good water stability, low cost, and visual detection. The present invention can be used for Al 3+ Sensitive detection.

[0005] The present invention is achieved by adopting the following technical solutions:

[0006] A metal-organic framework material with a dual-ligand strategy, wherein the raw materials include 2,6-pyridinedicarboxylic acid (DPA), 2,5-dihydroxyterephthalic acid, and europium.

[0007] Preferably, the molar ratio of 2,6-pyridinedicarboxylic acid (DPA) to 2,5-dihydroxyterephthalic acid is: 0.3:0.2;

[0008] And / or, the europium comprises europium chloride.

[0009] Another object of the present invention is to protect a method for preparing a metal organic framework material with a dual ligand strategy, which comprises fully mixing the above raw materials; reacting at 35°C-40°C, cooling after the reaction, washing, and drying to obtain the material.

[0010] Furthermore, the reaction time is 1h-4h;

[0011] And / or, washing is performed by using ethanol or water multiple times.

[0012] Another object of the present invention is to protect the metal organic framework material with a dual ligand strategy in Al 3+ Application in detection.

[0013] Another object of the present invention is to protect a ratiometric fluorescent probe comprising the above-mentioned metal-organic framework material; preferably, the mass concentration of the metal-organic framework material is 0.01-0.06 mg / mL.

[0014] Another object of the present invention is to protect the above ratiometric fluorescent probe in quantitative detection of Al 3+ The beneficial effects of the present invention are as follows:

[0015] The present invention prepares Eu-MOF by a simple one-step solvent thermal method, such as Figure 1 The preparation method of the present invention is simple, the materials are easy to obtain, and the prepared MOF has good dispersibility and high stability in aqueous solution, showing excellent luminescence properties. 3+ The ESIPT mechanism between them is used to design a ratiometric fluorescent probe with a dual ligand strategy. At an excitation wavelength of 270 nm, the prepared MOF has two emission peaks at 515, 605, and 620 nm, respectively. 3+ The fluorescence intensity at 515 nm can be significantly enhanced, while the fluorescence intensity at 620 nm remains substantially unchanged. 515 / I 620 )With Al 3+ The application of this MOF in aluminum ion detection can effectively avoid the interference of the external environment on the detection results, has high sensitivity and selectivity, and realizes visual detection based on the smartphone platform. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. They are used to explain the present invention together with the embodiments of the present invention and do not constitute a limitation of the present invention.

[0017] Figure 1 Schematic diagram of the preparation and application process of the Eu-MOF ratiometric fluorescent probe with dual emission strategy provided by the present invention;

[0018] Figure 2 is the transmission electron microscopy (TEM) image of Eu-MOF;

[0019] Figure 3 is the scanning electron microscope (SEM) image of Eu-MOF;

[0020] Figure 4 is the fluorescence excitation (Em) spectrum of Eu-MOF and ligand;

[0021] Figure 5 is the fluorescence emission (Ex) spectra of Eu-MOF and ligand;

[0022] Figure 6 I under 250-320nm excitation 515 / I 620 The intensity ratio diagram of

[0023] Figure 7 This is the fluorescence intensity graph of Eu-MOF aqueous solution stored at room temperature for five days;

[0024] Figure 8 is the fluorescence intensity of Eu-MOF aqueous solution stored at room temperature for five days (I 515 / I 620 ) ratio diagram;

[0025] Figure 9 Is to join Al 3+ Fluorescence lifetime diagram of Eu-MOF before and after ions;

[0026] Figure 10 This is the ratio of the fluorescence intensity of Eu-MOF to different ions, where the concentration of metal ions is 20 μM;

[0027] Figure 11 H2DHT, DPA, Eu-MOF and Eu-MOF+Al 3+ Fourier transform infrared spectrum (FT-IR) diagram;

[0028] Figure 12 Join Al 3+ X-ray photoelectron spectroscopy of Eu-MOF before and after ionization;

[0029] Figure 13 Is to join Al3+ X-ray photoelectron spectroscopy of Al 2p of Eu-MOF before and after ionization;

[0030] Figure 14 Is to join Al 3+ X-ray photoelectron spectra of O1s of Eu-MOF before and after ionization;

[0031] Figure 15 is the concentration optimization histogram of Eu-MOF;

[0032] Figure 16 Eu-MOF fluorescent probes for Al 3+ Detection, fluorescence intensity of Al 3+ concentration-response curves;

[0033] Figure 17 is the fluorescence intensity ratio (I 515 / I 620 ) and Al 3+ The linear relationship diagram of concentration; where I 515 and I 620 are the fluorescence intensities of Eu-MOF at 515 nm and 620 nm, respectively;

[0034] Figure 18 Eu-MOF detects different concentrations of Al 3+ Photos of the fluorescent color changes under ultraviolet light;

[0035] Figure 19 It's Al 3+ Linear curve of concentration and G / R value. DETAILED DESCRIPTION

[0036] In order to make the purpose and technical solution of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings. The experimental methods described in the following examples are all conventional methods unless otherwise specified; if no specific techniques or conditions are specified in the examples, they are carried out according to the techniques or conditions described in the literature in the field or according to the product instructions; the reagents and materials described are all commercially available unless otherwise specified.

[0037] Example 1 Preparation method of a visual ratiometric fluorescent probe with dual ligands:

[0038] 1) At room temperature, 50.14 mg of DPA (0.3 mmol) and 39.63 mg of 2,5-dihydroxyterephthalic acid (0.2 mmol) solid powder were dissolved in 15 mL of ethanol solution, and 139 μL of triethylamine solution was added.

[0039] 2) Dissolve 91.5 mg of europium chloride hexahydrate (0.25 mmol) in 5 mL of ultrapure water and sonicate for 5 min until fully dissolved.

[0040] 3) The solutions obtained in 1) and 2) were mixed uniformly in a round-bottom flask and heated in a water bath at 40°C with stirring for 2 h. The resulting suspension was centrifuged and washed, and the washed precipitate was dried in a vacuum drying oven at 40°C for 12 h.

[0041] Example 2 Detection and Analysis of Fluorescent Probe Properties

[0042] Figure 2 This is a transmission electron microscopy (TEM) image of Eu-MOF. The prepared Eu-MOF has good dispersion and uniform size distribution. The average size of Eu-MOF is 224nm.

[0043] Figure 3 This is a scanning electron microscope (SEM) image of the prepared Eu-MOF. It clearly shows that when the DPA / H2DHT ratio is 3:2, the MOF exhibits a regular flaky structure with an average diameter of 224 nm. This structure increases the specific surface area for the reaction, allowing the reaction to proceed more thoroughly.

[0044] Figure 4-5 This is the excitation and emission spectrum of the prepared Eu-MOF. It can be clearly seen from the figure that the excitation wavelength of Eu-MOF is about 270nm, there is a weak fluorescence peak at 515, and there are two fluorescence emission peaks at 605 and 620nm.

[0045] Figure 6 Under 250-320nm excitation, I 515 / I 620 The intensity ratio diagram of I 515 / I 620 The ratio is the smallest.

[0046] Figure 7-8 The stability test of Eu-MOF aqueous solution stored at room temperature for five days is shown in the figure. The fluorescence intensity and fluorescence intensity ratio (I 515 / I 620 ) remains basically unchanged, proving that Eu-MOF has good water stability.

[0047] Example 3 Fluorescent probe for Al 3+ Detection

[0048] Al 3+The fluorescence detection was carried out in a 2 mL centrifuge tube. First, 75 μL (400 μg / mL) of Eu-MOF was mixed with 425 μL of water. Then, 500 μL of different concentrations of Al 3+ After mixing evenly, the mixture was reacted at room temperature for 15 seconds. Finally, the fluorescence spectrum was recorded using an excitation wavelength of 270 nm. 515 / I 620 ) ratio changes in Al 3+ Quantitative detection of .

[0049] Figure 9 With and without Al 3+ ions. Then add Al 3+ Previously, the average fluorescence lifetime of Eu-MOF was 4.559ns, but the addition of Al 3+ ions, the average luminescence lifetime of Eu-MOF becomes 10.99ns. 3+ ions, resulting in an increase in the fluorescence intensity at 515 nm.

[0050] Figure 10 The response degree of Eu-MOF to different ions, where the concentration of metal ions is 20μM. As shown in the figure, Eu-MOF responds differently to different ions, so this fluorescent probe can detect Al with ultra-sensitive sensitivity. 3+ .

[0051] Figure 11 H2DHT, DPA, Eu-MOF and Eu-MOF+Al 3+ The Fourier transform infrared spectrum (FT-IR) of Eu-MOF is shown in the figure. -1 The broadband at 1693 cm-1 disappeared, proving that DPA and H2DHT deprotonated to synthesize MOF. -1 and 1658cm -1 The C=O stretching vibration peak appears at 1623 cm-1, while the Eu-MOF red shifts to 1623 cm-1. -1 Both changes reveal the carboxyl group and Eu 3+ The coordination of ions forms Eu-MOF. -1 The absorption peak appears at , which reflects the stretching vibration of hydroxyl groups. 3+ At 1281cm -1 、1279cm -1 、1280cm -1The absorption peak appears, reflecting the stretching vibration of phenolic hydroxyl. Based on the above phenomenon, it is shown that phenolic hydroxyl is an important reaction site. The adsorption peak position of Eu-MOF is similar to that of Eu-MOF+Al 3+ The adsorption peak positions of Eu-MOF are basically consistent, further proving that the types of functional groups of Eu-MOF do not change significantly during the reaction.

[0052] Figure 12-14 The X-ray photoelectron spectroscopy (XPS) diagram of Eu-MOF and the X-ray photoelectron spectroscopy (XPS) diagram of Al2p and O1s. The XPS diagram shows that there are four elements, C, N, O, Eu, in Eu-MOF. When Al is added 3+ Afterwards, Eu-MOF showed an Al 2p peak at 74.8 eV, proving that Al 3+ Successfully complexed with Eu-MOF. The O1s peak shifted from 531.75eV to 532.2eV, indicating that the O atoms of the H2DHT ligand participated in the complexation with Al 3+ The coordination of phenolic hydroxyl group was proved to be an important reaction site.

[0053] Figure 15 This is the concentration optimization curve of Eu-MOF in the embodiment of the present invention. As can be seen from the figure, when aluminum ions are added to a 30 μg / mL Eu-MOF aqueous solution, the fluorescence intensity (I 515 / I 620 ) has the most obvious change and the best detection effect.

[0054] Figure 16-17 The Eu-MOF with dual emission strategy implemented in the present invention is used to emit Al in the concentration range of 0-40 μM. 3+ The response curve and linear curve of Al 3+ Quantitative detection of Al 3+ With the increase of concentration, the fluorescence intensity of Eu-MOF at 515nm gradually increases, while that at 620nm gradually decreases. 515 / I 620 Follow Al 3+ The concentration of Al 3+ Fluorescence detection is possible. Figure 16 Al 3+ Concentration and I 515 / I 620 The linear curve of the fluorescence intensity ratio at the emission peaks of 515 nm and 620 nm is shown in Figure 2. Figure 17 It can be seen that the Eu-MOF has a great influence on Al 3+ It has good linearity, and the linear range is 0 to 40 μM. It shows that the Eu-MOF with dual emission strategy in the embodiment of the present invention can be successfully applied to the ratio fluorescence detection of Al3+ .

[0055] Figure 18 Detecting different concentrations of Al for Eu-MOF 3+ The fluorescence color change photo under ultraviolet light shows that as Al 3+ With the increase of concentration, the fluorescence color gradually changes from orange-red to green. This shows that the Eu-MOF ratiometric fluorescence probe with dual emission strategy in the present invention can be successfully applied to the ratiometric fluorescence detection of Al 3+ , and can realize visual detection.

[0056] Figure 19 The fluorescence color change photos obtained under UV light are processed in RGB color space through a smartphone application (swatches) to obtain the G / R value and obtain Al 3+ The linear curve of concentration and G / R value. As can be seen from the figure, G / R and Al 3+ It has good linearity with a linear range of 0 to 10 μM, indicating that the Eu-MOF ratiometric fluorescent probe with a dual-emission strategy can be successfully combined with a smartphone platform, making detection more convenient and quick.

[0057] Table 1A1 3+ Recovery rate in actual water samples

[0058]

[0059] Table 1 shows Al 3+ The recovery rates in actual water samples ranged from 95.20% to 97.37%, with a relative standard deviation (RSD) of less than 4.47%. The results showed that the Eu-MOF ratiometric fluorescent probe with dual emission strategy has the potential to realize the detection of Al in actual samples. 3+ Great potential for quantitative determination.

[0060] Of course, the above are merely preferred embodiments of the present method and are not intended to limit the present method. Although the present method has been described in detail with reference to the aforementioned method, those skilled in the art will be able to modify the aforementioned technical solutions or substitute equivalents for some of the technical features. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present method shall be included within the scope of protection of the present invention.

Claims

1. A metal-organic framework material with a dual-ligand strategy in Al 3+ The application of detection is characterized in that The raw materials of the metal organic framework material with a dual ligand strategy include 2,6-pyridinedicarboxylic acid DPA, 2,5-dihydroxyterephthalic acid, and europium; The molar ratio of the 2,6-pyridinedicarboxylic acid DPA, 2,5-dihydroxyterephthalic acid and is 0.3:0.

2.

2. The use according to claim 1, characterized in that The europium includes europium chloride.

3. The use according to claim 1 or 2, characterized in that The raw materials are fully mixed; reacted at 35°C-40°C; cooled after the reaction, washed, and dried to obtain the product.

4. The use according to claim 3, characterized in that Reaction time is 1h-4h; And / or, washing is performed by using ethanol or water multiple times.

5. A ratiometric fluorescent probe for quantitative detection of Al 3+ The application is characterized in that The invention relates to a metal organic framework material with a dual ligand strategy comprising the metal organic framework material according to any one of claims 1 to 4.

6. The use according to claim 5, characterized in that The mass concentration of the metal organic framework material is 0.01-0.06 mg / mL.

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