Rare earth metal europium skeleton, preparation method thereof and application thereof in starting detection of cadmium ions and collaborative closing response of copper ions and glutamic acid

Abstract

The invention relates to the technical field of fluorescence sensing, in particular to a rare earth metal europium skeleton, a preparation method thereof and application of the rare earth metal europium skeleton in starting detection of cadmium ions and cooperative closing response of copper ions and glutamic acid. The rare earth metal europium skeleton is prepared through a one-pot solvothermal reaction, the rare earth metal europium skeleton is a europium (III) coordination polymer, the chemical formula of the europium (III) coordination polymer is [Eu (bppc) 3 (H2O) 4]. 5H2O, and the molecular formula of the europium (III) coordination polymer is C42H24EuN15O15. The preparation method has the advantages of being simple in process, convenient to operate, high in yield, good in reproducibility and the like. The rare earth metal europium skeleton prepared by the invention has better fluorescence property, shows high selectivity and high sensitivity to glutamic acid, and can effectively detect glutamic acid through a fluorescence quenching phenomenon.

Description

Technical Field

[0001] The present invention relates to the technical field of fluorescence sensing, and particularly to a rare earth metal europium framework, a preparation method thereof, and an application for turn-on detection of cadmium ions and synergistic turn-off responses to copper ions and glutamic acid. Background Art

[0002] Amino acids are crucial for maintaining normal physiological functions of humans, of great significance to human life and health, and play important roles in the ecosystem and industrial development, affecting human life, the natural environment, and social progress in all aspects. Glutamic acid, as a key amino acid, plays important roles in biology, ecology, industry, and the environment. It is not only an important raw material for protein synthesis but also serves as the main excitatory neurotransmitter in the central nervous system, participating in physiological processes such as learning and memory. Microorganisms in the soil can utilize glutamic acid to decompose organic substances, release nutrients required for plant growth, promote plant growth and development, and thus maintain the stability of the ecosystem. Glutamic acid is the main component of monosodium glutamate, can significantly enhance the flavor of food, participate in drug synthesis, and is used to treat certain diseases. Glutamic acid can be decomposed by microorganisms in the natural environment, participate in the material cycle, and reduce the pressure on the environment caused by waste to a certain extent. At the same time, the reasonable use of glutamic acid-related products, such as amino acid fertilizers, can reduce the use of chemical fertilizers and is beneficial to environmental protection.

[0003] Excessive glutamic acid can also bring many harms. In terms of human health, excessive intake of glutamic acid may disrupt the excitatory-inhibitory balance of the nervous system, over-stimulate nerve cells, and cause discomfort symptoms such as headache, dizziness, and fatigue. Long-term excessive intake may also be related to nervous system diseases, such as Alzheimer's disease and Parkinson's disease. For people with allergic constitutions, excessive glutamic acid may also trigger allergic reactions, such as skin itching, redness, and shortness of breath. In the ecological environment, if a large amount of glutamic acid-containing waste is directly discharged without treatment, it may lead to eutrophication of water bodies, excessive growth of algae, and destruction of the aquatic ecological balance. Therefore, establishing an effective glutamic acid detection method is crucial for protecting the ecosystem and human health.

[0004] Metal elements show differential concentration distribution characteristics in different geological regions of the world. Some metals play important roles in maintaining ecological balance and promoting biological growth, while heavy metals pose serious threats to the health of animals, plants, and humans. Particularly noteworthy is that transition metal ions (including but not limited to Cr 7 ⁺, Cr 5 ⁺, Hg²⁺, Fe²⁺, Fe³⁺, Cu²⁺, Co²⁺, Ni²⁺, Pb²⁺, etc.) can induce in vivo oxidative stress reactions, leading to increased lipid peroxidation, DNA damage, and damage to the functions of the kidney / reproductive / central nervous system. Among them, Cd²⁺ and Cr 4⁺It has been identified as a Group 1 human carcinogen by the International Agency for Research on Cancer (IARC). For divalent metal ions commonly present in the drinking water system, even at low concentrations, they can still cause chronic pathological changes. Taking Cu²⁺ as an example, according to the drinking water standard of the US Environmental Protection Agency (EPA), its safety threshold is limited to 1.3 ppm. Exceeding this limit will cause potential damage to the respiratory system, gastrointestinal tract, and blood system. This toxicity mechanism is closely related to the accumulation characteristics and redox activity of metal ions in organisms. Based on the bioaccumulation characteristics of the above heavy metal ions and the low-concentration toxicity mechanism, developing a highly sensitive analytical method with a detection limit at the ppb level to achieve precise identification and quantitative analysis of target metal ions has become a core technical link in the field of environmental monitoring. The establishment of this detection system not only provides data support for pollutant tracing but also lays a methodological foundation for the construction of an ecological risk early warning system.

[0005] Currently, the methods for amino acid and ion detection mainly include high-performance liquid chromatography (HPLC), enzymatic methods, electrochemical analysis methods, and spectrophotometry. These methods have the disadvantages of expensive equipment, professional personnel, cumbersome sample pretreatment, high cost, harsh storage conditions, poor sensitivity and selectivity, and are easily interfered by colored substances or substances that can react with reagents. Fluorescent sensing technology has the characteristics of high sensitivity, easy operation, fast response, high selectivity, and low cost and has been studied. Currently, many coordination polymers for amino acid and metal ion detection have been developed. However, most of the reported probe molecules are based on transition metal complexes. Although lanthanide metal complexes have unique advantages such as narrow emission spectra, high optical stability, and biodegradability, due to the high coordination number of lanthanide metal ions, relatively few studies have been conducted on them. Therefore, the construction of fluorescent probes based on rare earth complexes remains an important focus of current research. Based on fluorescent sensing, using lanthanide metal complexes for amino acid and metal ion detection has the advantages of high sensitivity, good selectivity, rapid detection, relatively simple detection process, and can remain stable within a wide range of pH and temperature. This innovative strategy has greatly promoted the development of amino acid and ion detection technologies. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a rare earth metal europium skeleton, its preparation method, and an application for the detection of cadmium ions and the synergistic response of copper ions and glutamic acid based on the deficiencies of the above-mentioned prior art. Its coordination polymer is [Eu(bppc) 3 (H 2 O) 4 ·5H 2O. The coordination polymer has a mononuclear structure with europium(III) as the center, forming a nine-coordinate structure. Strong hydrogen bonding between the oxygen atoms of coordinated water molecules and the carboxyl oxygen atoms of the ligand connects adjacent europium(III) to form a one-dimensional Z-shaped chain structure, and the one-dimensional chains are further connected into a two-dimensional supramolecular structure through π…π interactions between the side pyrazine rings.

[0007] The present invention provides a rare earth metal europium skeleton, and the chemical formula of the rare earth metal europium skeleton is [Eu(bppc) 3 (H 2 O) 4 ·5H 2 O, where the ligand bppc - is deprotonated Hbppc, and the Hbppc is 2,6-bis(2-pyrazinyl)pyridine-4-carboxylic acid. The single molecular formula of the rare earth metal europium skeleton is C 42 H 24 EuN 15 O 15 .

[0008] The present invention provides a preparation method of the above rare earth metal europium skeleton, comprising the following steps: S1. Dissolve 2,6-bis(2-pyrazinyl)pyridine-4-carboxylic acid and europium metal salt in deionized water to obtain a mixed solution, add NaOH solution to adjust the pH value of the mixed solution, and then obtain a reaction product through a solvothermal reaction; S2. Wait for the reaction product obtained in S1 to cool and crystallize naturally, and then obtain the rare earth metal europium skeleton through washing and drying.

[0009] According to the preparation method provided by the present invention, the europium metal salt in S1 is Eu(NO 3 ) 3 . 6H 2 O.

[0010] According to the preparation method provided by the present invention, the molar ratio of 2,6-bis(2-pyrazinyl)pyridine-4-carboxylic acid to europium metal salt in S1 is 0.1~0.15 mmol: 0.05~0.1 mmol.

[0011] According to the preparation method provided by the present invention, the pH value of the mixed solution in S1 is 6~6.5.

[0012] According to the preparation method provided by the present invention, the temperature of the hydrothermal reaction in S1 is 180 °C, the heating rate of the temperature in the hydrothermal reaction is 4~6 °C / h, the solvothermal reaction is carried out in a sealed reaction kettle, and the time of the solvothermal reaction is 4~5 d.

[0013] According to the preparation method provided by the present invention, the drying conditions in S2 are as follows: drying in a constant temperature drying oven at 80 °C for 2 h.

[0014] The present invention also provides an application of the above rare earth metal europium framework for the turn-on detection of cadmium ions and the synergistic turn-off response to copper ions and glutamic acid. The rare earth metal europium framework can effectively detect L-glutamic acid, Cu 2+ and Cd 2+ in water.

[0015] The present invention has the following advantages compared with the prior art: The present invention prepares a rare earth metal europium framework by a one-pot solvothermal reaction. The rare earth metal europium framework is a europium(III) coordination polymer, and the chemical formula of the europium(III) coordination polymer is [Eu(bppc) 3 (H 2 O) 4 ·5H 2 O, and its molecular formula is C 42 H 24 EuN 15 O 15 . This preparation method has the advantages of simple process, convenient operation, high yield and good reproducibility.

[0016] The rare earth metal europium framework prepared by the present invention has good fluorescence properties, shows a turn-on detection for cadmium ions and a synergistic turn-off response to copper ions and glutamic acid, shows high selectivity and high sensitivity to glutamic acid, can effectively detect glutamic acid through the fluorescence quenching phenomenon, and the contents of Cu 2+ and Cd 2+ in water. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is the coordination environment diagram of europium(III) in the europium(III) coordination polymer; Figure 2 is the one-dimensional structure diagram of the europium(III) coordination polymer; Figure 3 is the two-dimensional structure diagram of the europium(III) coordination polymer; Figure 4 is the powder X-ray diffraction pattern of the europium(III) coordination polymer; Figure 5 is the fluorescence lifetime diagram of the europium(III) coordination polymer; Figure 6 is the emission spectrum diagram of the europium(III) coordination polymer in different amino acids; Figure 7 is the intensity comparison diagram of the europium(III) coordination polymer in different amino acids; Figure 8Emission spectra of europium(III) coordination polymer at different glutamic acid concentrations; Figure 9 Linear fitting graphs of europium(III) coordination polymer at different glutamic acid concentrations.

[0018] Figure 10 Emission spectra of europium(III) coordination polymer in different ions; Figure 11 Intensity comparison graphs of europium(III) coordination polymer in different ions; Figure 12 Emission spectra of europium(III) coordination polymer in different concentrations of Cu 2+ ; Figure 13 Linear fitting graphs of europium(III) coordination polymer in different concentrations of Cu 2+ ;

[0019] Figure 14 Emission spectra of europium(III) coordination polymer in different concentrations of Cd 2+ ; Figure 15 Linear fitting graphs of europium(III) coordination polymer in different concentrations of Cd 2+ ; Detailed implementation methods

[0020] Example 1 This example provides a preparation method for a rare earth metal europium framework, and the specific steps are as follows: S1. Dissolve 0.1 mmol of ligand 2,6-bis(2-pyrazinyl)pyridine-4-carboxylic acid (Hbppc) and 0.1 mmol of metal salt Eu(NO 3 ) 3 . 6H 2 O in 10 mL of deionized water to obtain a mixed solution. Add NaOH solution to adjust the pH value of the mixed solution to 6, and then transfer the mixed solution to a high-pressure reaction kettle. The temperature in the high-pressure reaction kettle is raised to 180 °C at a heating rate of 4 °C / h for a total of 4 d for hydrothermal reaction to obtain a reaction product; The structural formula of Hbppc is:

[0021] S2. Wait for the reaction product obtained in S1 to cool and crystallize naturally, and then obtain white crystal powder after washing with absolute ethanol and vacuum filtration. Place it in an oven at 80 °C for 2 h for drying to obtain a rare earth metal europium framework [Eu(bppc) 3 (H 2 O)4 ·5H 2 O, with a yield of 35%.

[0022] Example 2 This example provides a method for preparing a rare earth metal europium framework, and the specific steps are as follows: S1. Dissolve 0.15 mmol of the ligand 2,6-bis(2-pyrazinyl)pyridine-4-carboxylic acid and 0.1 mmol of the metal salt Eu(NO 3 ) 3 . 6H 2 O in 10 mL of deionized water to obtain a mixed solution. Add NaOH solution to adjust the pH value of the mixed solution to 6.2, and then transfer the mixed solution to a high-pressure reaction kettle. After the temperature in the high-pressure reaction kettle is raised to 180 °C at a heating rate of 4 °C / h, carry out a solvothermal reaction for a total of 4 days to obtain a reaction product; S2. Wait for the reaction product obtained in S1 to cool and crystallize naturally, and then obtain a white crystal powder after washing with absolute ethanol and vacuum filtration. Place it in an oven at 80 °C and dry it at a constant temperature for 2 h to obtain a rare earth metal europium framework, europium(III) coordination polymer [Eu(bppc) 3 (H 2 O) 4 ·5H 2 O, with a yield of 42.3%.

[0023] Example 3 This example provides a method for preparing a rare earth metal europium framework, and the specific steps are as follows: S1. Dissolve 0.10 mmol of the ligand 2,6-bis(2-pyrazinyl)pyridine-4-carboxylic acid and 0.05 mmol of the metal salt Eu(NO 3 ) 3 . 6H 2 O in 10 mL of deionized water to obtain a mixed solution. Add NaOH solution to adjust the pH value of the mixed solution to 6.5, and then transfer the mixed solution to a high-pressure reaction kettle. After the temperature in the high-pressure reaction kettle is raised to 180 °C at a heating rate of 5 °C / h, carry out a solvothermal reaction for a total of 5 days to obtain a reaction product; S2. Wait for the reaction product obtained in S1 to cool and crystallize naturally, and then obtain a white crystal powder after washing with absolute ethanol and vacuum filtration. Place it in an oven at 60 °C and dry it at a constant temperature for 3 h to obtain a rare earth metal europium framework, europium(III) coordination polymer [Eu(bppc) 3 (H 2 O) 4 ·5H 2O, with a yield of 59.2%.

[0024] Example 4 This comparative example provides a method for preparing a rare earth metal europium framework, and the specific steps are as follows: S1. Dissolve 0.15 mmol of the ligand 2,6-bis(2-pyrazinyl)pyridine-4-carboxylic acid and 0.05 mmol of the metal salt Eu(NO 3 ) 3 . 6H 2 O in 10 mL of deionized water to obtain a mixed solution. Add NaOH solution to adjust the pH value of the mixed solution to 6.5, and then transfer the mixed solution to a high-pressure reaction kettle. After the temperature in the high-pressure reaction kettle is heated to 180 °C at a heating rate of 5 °C / h, carry out a solvothermal reaction for 5 days to obtain a reaction product; S2. Wait for the reaction product obtained in S1 to cool and crystallize naturally, and then obtain a white crystal powder after washing with absolute ethanol and vacuum filtration. Place it in an oven at 80 °C and dry it at a constant temperature for 2 h to obtain a rare earth metal europium framework, europium(III) coordination polymer [Eu(bppc) 3 (H 2 O) 4 ·5H 2 O, with a yield of 48.8%.

[0025] Example 5 Take the europium(III) coordination polymer prepared in Example 3 for further characterization, and the process is as follows: (1) Determination of the crystal structure of the rare earth metal europium framework Select a single crystal of the coordination polymer with a clean, smooth surface, no concave surface, and no cracks. At a temperature of 293(2) K, use a BRDUKER SMART APEX-II CCD X-ray single crystal diffractometer, use graphite monochromated Mo-Kα (wavelength of 0.71073 Å) rays, and collect diffraction data in a ω-φ scanning mode. All data are corrected by empirical absorption, and the crystal structure is solved by the direct method. The anisotropic parameters and the coordinates of all non-hydrogen atoms are refined by the least squares method. The F2 is refined using the SHELXTL-97 program, and the hydrogen atom coordinates are obtained by theoretical calculation methods.

[0026] The detailed crystal determination data are shown in Table 1, the important bond length and bond angle data are shown in Table 2, and the crystal structure is shown in Figures 1 to 3 .

[0027] Table 1 Main crystallographic data of europium(III) coordination polymerization

[0028] Among them, R1 =∑(||Fo|-|Fc||) / ∑|Fo|, wR 2 =[∑w(Fo 2 -| Fc 2 ) 2 / ∑w(Fo) 2 1 / 2 ; Table 2 Important bond lengths (Å) and bond angles (°) of europium(III) coordination polymer

[0029] In Table 1, a, b, and c represent the edge lengths of the crystal along the three crystallographic axes, and α, β, and γ represent the angles between the a and b, a and c, and b and c axes, respectively; Z Z is the number of molecules per unit cell; the diffraction index range of the restraint factor is (h, k, l); F (000) is the number of electrons in the unit cell; Θ is the Θ angle range for data collection; Final R indices I >2σ( I )] is the residual factor R value for observable diffraction points; R is the non-weighted goodness-of-fit factor; R 1 and wR 2 are both weighted goodness-of-fit factors; In the first row of Table 2, Eu1 refers to Eu atom 1 in the single crystal of europium(III) coordination polymer, O5 refers to O atom 5 in the single crystal of europium(III) coordination polymer, and Eu1-O5 represents the bond length between Eu atom 1 and O atom 5, with a bond length of 2.398 ± 4, where 4 is the standard deviation; O(5)-Eu(1)-O(9) represents the bond angle between O atom 5, Eu atom 1, and O atom 9, with a bond angle of 135.86 ± 15; Other data in the table can be obtained by analogy.

[0030] The europium(III) coordination polymer forms a nine-coordinate structure with europium(III) as the center and forms a one-dimensional Z-shaped chain structure through hydrogen bonds between the carboxyl oxygen atoms of the ligand and the oxygen atoms of the coordinated water molecules. The Z-shaped chain structure further undergoes π…π interactions between the side pyrazine rings.

[0031] (2) Phase purity characterization of the rare earth metal europium skeleton The powder of the europium(III) coordination polymer was characterized by XRD using the instrument Bruker / D8Advance. The characterization results are shown in Figure 4 , indicating that it has reliable phase purity, providing a guarantee for its fluorescence sensing application.

[0032] ​(2)Fluorescence Lifetime Characterization of Europium Metal Skeleton The fluorescence lifetime of the europium(III) coordination polymer was characterized using the Hitachi FLS-1000 instrument. The characterization results are shown in Figure 5 , indicating that it has a relatively high fluorescence lifetime, providing support and guarantee for its fluorescence sensing applications.

[0033] Example 6 Weighed 2 mg of the ground europium(III) coordination polymer prepared in Example 3 and immersed it in 1 mL of different amino acid solutions (amino acids: glycine, L-isoleucine, L-serine, L-alanine, L-cysteine, L-tryptophan, L-arginine, and L-glutamic acid) with a concentration of 0.01 mol / L and 4 mL of ultrapure water. After ultrasonic treatment and standing, the clear supernatant was taken for luminescence studies at room temperature.

[0034] At an excitation wavelength of 325 nm, the emission intensities of the europium(III) coordination polymer in different amino acids were measured and repeated three times as parallel experiments. It can be seen that when L-glutamic acid is present, the luminescence intensity of the complex decreases significantly. This phenomenon indicates that the europium(III) coordination polymer has an obvious fluorescence quenching effect on L-glutamic acid. Therefore, L-glutamic acid can be effectively detected through fluorescence quenching. The results are shown in Figure 6 and Figure 7 as shown.

[0035] Example 7 Weighed 2 mg of the ground europium(III) coordination polymer prepared in Example 3 and immersed it in a mixed solution of 0.01 moL / L L-glutamic acid with different volumes and deionized water. After ultrasonic treatment and standing, the clear supernatant was taken for luminescence studies at room temperature.

[0036] At an excitation wavelength of 325 nm, the emission intensities of the europium(III) coordination polymer at different L-glutamic acid concentrations were measured and repeated three times as parallel experiments. The results are shown in Figure 8 as shown. The numerical values of the above different emission intensities were subjected to fitting analysis and calculation, and the obtained fitting graph has a good linear relationship (R 2 > 0.9), and the results are shown in Figure 9 as shown. By calculating using the formula for the detection limit, it was found that the europium(III) coordination polymer can detect the minimum L-glutamic acid concentration of 4.29 μM (0.63 mg / L).

[0037] Example 8 Weighed 20 mg of the ground europium(III) coordination polymer prepared in Example 3 and immersed it in 1 mL of different metal solutions (Ag + , Li+ , Na + , Cu 2+ , Co 2+ , Ni 2+ , Ga 2+ , Ba 2+ , Mg 2+ , Hg 2+ , Zn 2+ ,Cd 2+ , Mn 2+ and Pb 2+ ), and in 4 mL of ultrapure water. After ultrasonic treatment and standing, the clear supernatant was taken for luminescence studies at room temperature.

[0038] At an excitation wavelength of 325 nm, the emission intensities of the europium(III) coordination polymer in different amino acids were measured and repeated three times as parallel experiments. It can be seen that when Cu 2+ is present, the luminescence intensity of the complex decreases significantly. When Cd 2+ is present, the luminescence intensity of the complex increases significantly. This phenomenon indicates that the europium(III) coordination polymer has an obvious fluorescence quenching phenomenon for Cu 2+ and an obvious fluorescence enhancement phenomenon for Cd 2+ . Therefore, L-glutamic acid can be effectively detected by fluorescence quenching. The results are as shown in Figure 10 and Figure 11 .

[0039] Example 9 Weigh 2 mg of the ground europium(III) coordination polymer prepared in Example 3 and immerse it in a mixed solution of 0.01 moL / L, different volumes of Cu 2+ or Cd 2+ and deionized water. After ultrasonic treatment and standing, the clear supernatant was taken for luminescence studies at room temperature.

[0040] At an excitation wavelength of 325 nm, the emission intensities of the europium(III) coordination polymer with different Cu 2+ or Cd 2+ concentrations were measured and repeated three times as parallel experiments. The results are as shown in Figure 12 , Figure 13 . The numerical values of the above different emission intensities were subjected to fitting analysis and calculation, and the obtained fitting graph had a good linear relationship (R 2 > 0.9). The results are as shown in Figure 14 , Figure 15 .

[0041] By calculating through the formula of the detection limit, it can be obtained that the europium(III) coordination polymer can detect the minimum Cu 2+ or Cd2+ The concentrations are 0.64 μM and 10.51 μM respectively.

[0042] It can be seen therefrom that the europium(III) coordination polymer prepared by the present invention can effectively detect L-glutamic acid, Cu 2+ and Cd 2+ contents in water.

[0043] The above are only the preferred embodiments of the present invention and do not impose any limitations on the present invention. Any simple modifications, changes, and equivalent changes made to the above embodiments according to the technical essence of the invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A rare earth metal europium framework, characterized in that: The chemical expression of the rare earth metal europium skeleton is [Eu(bppc)3(H2O)4]·5H2O, wherein the ligand bppc - is a deprotonated Hbppc, wherein the Hbppc is 2,6-bis(2-pyrazinyl)pyridine-4-carboxylic acid, and the single molecular formula of the rare earth metal europium skeleton is C 42 H 24 E 15 O 15 .

2. A method for preparing the rare earth metal europium framework as claimed in claim 1, characterized in that: The following steps are involved: S1, dissolving 2,6-bis(2-pyrazinyl)pyridine-4-carboxylic acid and europium metal salt in deionized water to obtain a mixed solution, adding a NaOH solution to adjust the pH value of the mixed solution, and then performing a solvothermal reaction to obtain a reaction product; S2. The reaction product obtained in S1 is cooled and crystallized naturally, and then washed and dried to obtain a rare earth metal europium skeleton.

3. The method for preparing the rare earth metal europium framework according to claim 2, characterized in that: The europium metal salt in S1 is Eu(NO3)3 . 6H2O.

4. The method for preparing the rare earth metal europium framework according to claim 2, characterized in that: The molar ratio of 2,6-bis(2-pyrazinyl)pyridine-4-carboxylic acid to europium metal salt in S1 is 0.1-0.15 mmol: 0.05-0.1 mmol.

5. The method for preparing the rare earth metal europium framework according to claim 2, characterized in that: The pH value of the mixed solution in S1 is 6 to 6.

5.

6. The method for preparing the rare earth metal europium framework according to claim 2, characterized in that: The temperature of the hydrothermal reaction in S1 is 180°C, the temperature rise rate in the hydrothermal reaction is 4-6°C / h, the solvent thermal reaction is carried out in a sealed reactor, and the time of the solvent thermal reaction is 4-5 days.

7. The method for preparing the rare earth metal europium framework according to claim 2, characterized in that: The drying conditions described in S2 are: drying in a constant temperature drying oven at a temperature of 80°C for 2 h.

8. An application of the rare earth metal europium framework as claimed in claim 1 to detect cadmium ions and coordinately shut down the response of copper ions and glutamate, characterized in that: The rare earth metal europium skeleton can effectively detect L-glutamic acid, Cu 2+ and Cd 2+ The content.

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