A fluorescent metal organic framework material, a preparation method thereof and a method for detecting content of magnetic substances in a secondary battery negative electrode material

Abstract

The application provides a fluorescent metal organic framework material, a preparation method thereof and a detection method of magnetic substance content in a secondary battery negative electrode material, and belongs to the technical field of metal organic framework materials. The chemical formula of the fluorescent metal organic framework material is Ln2L3xH2O, wherein the inorganic metal center Ln is at least one of lanthanide metals, the organic ligand L has a diphenic acid structure, and x is 0-3. The fluorescent metal organic framework material has specific response to Fe 3+ and Cr 3+ magnetic substances, and exhibits the characteristics of rapidness, high selectivity and high sensitivity, and can detect the magnetic substances through an ultraviolet fluorescence (UV-vis) method.

Description

Technical Field

[0001] This application belongs to the field of metal-organic framework materials technology, specifically relating to a fluorescent metal-organic framework material and its preparation method, as well as a method for detecting the content of magnetic materials in secondary battery anode materials. Background Technology

[0002] Lithium-ion batteries, as a new type of rechargeable battery, are widely used in transportation, electronic products, energy storage, military, and aerospace fields. Currently, lithium-ion batteries primarily use graphite as the main negative electrode material. However, the manufacturing process of negative electrode materials generates magnetic substances such as iron, chromium, and their oxides, which may increase the battery's self-discharge and, in severe cases, cause a short circuit. Therefore, magnetic substance detection is an important part of negative electrode material testing.

[0003] The "Test Method for Magnetic Foreign Matter Content in Lithium-ion Battery Electrode Materials" issued by the Ministry of Industry and Information Technology in 2022 specifies a method for determining the magnetic foreign matter content in lithium-ion battery electrode materials through magnetic separation-rinsing-digestion-inductively coupled plasma atomic emission spectrometry. This method is applicable to the detection of magnetic foreign matter content in lithium-ion battery positive and negative electrode powder materials and their slurries, binders, conductive agents, and other auxiliary materials, with a measurement range between 10 μg / kg and 5000 μg / kg.

[0004] However, relying on only one detection method is too simplistic, and it is necessary to develop new detection methods for detecting the content of magnetic materials in the negative electrode materials of secondary batteries. Summary of the Invention

[0005] This application aims to at least partially address one of the technical problems in related technologies. To this end, embodiments of this application propose a fluorescent metal-organic framework material and its preparation method, as well as a method for detecting the content of magnetic materials in secondary battery anode materials.

[0006] The first aspect of this application provides a fluorescent metal-organic framework material with the chemical formula Ln2L3·xH2O, wherein the inorganic metal center Ln is at least one of the lanthanides, the organic ligand L has a biphenyl acid structure, and x is 0 to 3.

[0007] In some embodiments, the fluorescent metal-organic framework material belongs to the tetragonal crystal system with space group P4 / ncc.

[0008] In some embodiments, the biphenyl acid structure is at least one selected from biphenylcarboxylic acid, 3,3'-dihydroxy-4,4'-biphenylcarboxylic acid, and 3,3'-dimethyl-4,4'-biphenylcarboxylic acid.

[0009] The second aspect of this application provides a method for preparing a fluorescent metal-organic framework material, comprising the following steps:

[0010] S11. Mix the lanthanide metal nitrate, the organic ligand, and the organic solvent to obtain the precursor solution;

[0011] S21. After subjecting the precursor solution to a hydrothermal reaction, cool it to room temperature to obtain crystals;

[0012] S31. The crystal is washed and dried to obtain the fluorescent metal-organic framework material of the first aspect of this application.

[0013] In some embodiments, in step S11, the molar ratio of the lanthanide metal nitrate to the organic ligand is (0.4–0.6):1.

[0014] In some embodiments, in step S11, the organic solvent is at least one of N,N-dimethylformamide, N,N-dimethylacetamide, and N,N-diethylformamide.

[0015] In some embodiments, in step S21, the holding temperature of the hydrothermal reaction is 80–160°C; and / or, the holding time of the hydrothermal reaction is 12–48 h.

[0016] In some embodiments, in step S21, the cooling is performed using natural cooling.

[0017] In some embodiments, the natural cooling time is 12 to 24 hours.

[0018] In some embodiments, in step S31, the solvent used for washing is the same type of organic solvent as in step S11.

[0019] In some embodiments, in step S31, the drying is performed using vacuum drying.

[0020] In some embodiments, the vacuum drying time is 12 to 24 hours.

[0021] A third aspect of this application provides a method for detecting the content of magnetic materials in a secondary battery negative electrode material. The method uses a fluorescent metal-organic framework material from the first aspect of this application to detect the content of magnetic materials in a test solution. The magnetic materials include Fe. 3+ and / or Cr 3+ .

[0022] In some embodiments, the detection method includes the following steps:

[0023] S12. Grind the fluorescent metal-organic framework material to obtain fluorescent metal-organic framework material powder; disperse the fluorescent metal-organic framework material powder in deionized water to obtain fluorescent metal-organic framework material solution;

[0024] S22. The negative electrode material is mixed with anhydrous ethanol to obtain a negative electrode material dispersion; a clean magnetic rod is placed into the negative electrode material dispersion to allow the magnetic rod to fully adsorb the magnetic material therein; the magnetic rod with adsorbed magnetic material is removed and washed, and the washed magnetic rod with adsorbed magnetic material is mixed with aqua regia, which digests the magnetic material to obtain a digestion solution; the digestion solution is subjected to acid removal and then cooled to room temperature to obtain a magnetic material solution;

[0025] S32. Establish a standard curve between the concentration of magnetic material and fluorescence intensity, and fit it to obtain the Stern-Volmer equation;

[0026] S42. Mix the magnetic material solution and the fluorescent metal-organic framework material solution, and adjust the volume to obtain the test solution; use a fluorescence spectrometer to test the fluorescence intensity of the test solution, and substitute the fluorescence intensity of the test solution into the Stern-Volmer equation to calculate the molar concentration c of the magnetic material in the test solution. 磁 ;

[0027] S52. Calculate the content ω of magnetic material in the negative electrode material. 磁 ω 磁 The unit is wt%.

[0028] ω 磁 =m 磁 / m 负极材料 =c 磁 ×V 待测溶液 ×M 磁 / m 负极材料 ,

[0029] Among them, c 磁 This represents the molar concentration of the magnetic substance in the test solution, expressed in mol / L.

[0030] V 待测溶液 The volume of the solution to be tested is in liters (L).

[0031] M 磁 This refers to the molar mass of the magnetic material, expressed in g / mol.

[0032] m 负极材料 The mass of the negative electrode material is expressed in grams (g).

[0033] Compared with related technologies, the advantages and technical effects of the embodiments of this application are as follows:

[0034] The fluorescent metal-organic framework material of the first aspect of this application has an inorganic metal center Ln that is at least one of the lanthanides, and an organic ligand L that has a biphenyl dicoxide structure. It exhibits high fluorescence emission efficiency and fluorescence stability, and when used for fluorescence detection of metal ions, it will affect Fe... 3+ and Cr 3+ Magnetic materials produce a fluorescence quenching effect on Fe 3+ and Cr 3+ Magnetic materials exhibit specific responses, demonstrating rapid, highly selective, and highly sensitive characteristics. They can be detected in secondary battery anode materials using ultraviolet fluorescence (UV-vis) method, thus expanding the detection methods for magnetic materials.

[0035] The preparation method of the second aspect of this application obtains fluorescent metal-organic framework materials through a hydrothermal reaction. The synthesis method is simple, easy to operate, and convenient for large-scale production. Moreover, the obtained fluorescent metal-organic framework materials are effective against Fe... 3+ and Cr 3+ The detection of magnetic materials exhibits the characteristics of being rapid, highly selective, and highly sensitive. Magnetic materials in secondary battery anode materials can be detected using ultraviolet fluorescence (UV-vis) method, thus expanding the detection methods for magnetic materials.

[0036] Because the fluorescent metal-organic framework material of the first aspect of this application is used, the detection method of the third aspect of this application can detect the content of magnetic materials in the negative electrode material of secondary batteries by ultraviolet-fluorescence (UV-vis) method, which is fast and has high selectivity and sensitivity. Attached Figure Description

[0037] Figure 1 The fluorescence intensity of the fluorescent metal-organic framework material prepared in Example 1 is measured in a series of standard solutions of varying concentrations. Figure 1 The concentration shown is Fe in the standard solution. 3+ The concentration.

[0038] Figure 2 The above is a Stern-Volmer linear / nonlinear plot of fluorescence intensity data of the fluorescent metal-organic framework material prepared in Example 1 in a series of standard solutions of different concentrations, where a is Fe 3+ Stern-Volmer linear plots were created from fluorescence intensity data of standard solutions with concentrations below 500 μM, where b represents Fe. 3+ Stern-Volmer nonlinear plots were created from fluorescence intensity data in standard solutions with concentrations below 700 μM. Detailed Implementation

[0039] The embodiments of this application are described in detail below, with examples of these embodiments illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application.

[0040] Fluorescent metal-organic frameworks (LMOFs), as an important branch of metal-organic frameworks (MOFs), possess excellent fluorescence emission properties, along with unique MOF characteristics such as high porosity, large specific surface area, strong adsorption capacity, tunable pore size, and mild preparation conditions. These advantages make them suitable as high-performance photochemical materials and have wide applications in fluorescence sensing and bioimaging. The inventors believe it is possible to design a fluorescent metal-organic framework material with specific responsiveness to magnetic substances in anode materials, thereby enabling the detection of magnetic substance content in secondary battery anode materials using ultraviolet fluorescence (UV-vis) spectroscopy.

[0041] In view of this, the first aspect of the present application provides a fluorescent metal-organic framework material with the chemical formula Ln2L3·xH2O, wherein the inorganic metal center Ln is at least one of the lanthanides, the organic ligand L has a biphenyl acid structure, and x is 0 to 3.

[0042] The fluorescent metal-organic framework material of the first aspect of this application has an inorganic metal center Ln that is at least one of the lanthanides, and an organic ligand L that has a biphenyl dicoxide structure. It exhibits high fluorescence emission efficiency and fluorescence stability, and when used for fluorescence detection of metal ions, it will affect Fe... 3+ and Cr 3+ Magnetic materials produce a fluorescence quenching effect on Fe 3+ and Cr 3+ Magnetic materials exhibit specific responses, demonstrating rapid, highly selective, and highly sensitive characteristics. They can be detected in secondary battery anode materials using ultraviolet fluorescence (UV-vis) method, thus expanding the detection methods for magnetic materials.

[0043] If the inorganic metal center is not a lanthanide metal, or the organic ligand does not have a biphenyl alkane structure, the resulting metal-organic framework material may not exhibit the fluorescence properties described above.

[0044] In some embodiments, the fluorescent metal-organic framework material belongs to the tetragonal crystal system with space group P4 / ncc. Fluorescent metal-organic framework materials that satisfy this crystal form and space group exhibit better fluorescence stability and higher detection sensitivity.

[0045] In some embodiments, the biphenyl acid structure is at least one selected from biphenylcarboxylic acid, 3,3'-dihydroxy-4,4'-biphenylcarboxylic acid, and 3,3'-dimethyl-4,4'-biphenylcarboxylic acid. Organic ligands having the aforementioned biphenyl acid structure are beneficial for improving the fluorescence stability and detection sensitivity of fluorescent metal-organic framework materials.

[0046] The second aspect of this application provides a method for preparing a fluorescent metal-organic framework material, comprising the following steps:

[0047] S11. A precursor solution is obtained by mixing a lanthanide metal nitrate, an organic ligand, and an organic solvent.

[0048] S21. After subjecting the precursor solution to a hydrothermal reaction, cool it to room temperature to obtain crystals;

[0049] S31. The crystal is washed and dried to obtain the fluorescent metal-organic framework material of the first aspect of the present application.

[0050] The preparation method of the second aspect of this application obtains fluorescent metal-organic framework materials through a hydrothermal reaction. The synthesis method is simple, easy to operate, and convenient for large-scale production. Moreover, the obtained fluorescent metal-organic framework materials are effective against Fe... 3+ and Cr 3+ The detection of magnetic materials exhibits the characteristics of being rapid, highly selective, and highly sensitive. Magnetic materials in secondary battery anode materials can be detected using ultraviolet fluorescence (UV-vis) method, thus expanding the detection methods for magnetic materials.

[0051] In some embodiments, in step S11, the molar ratio of lanthanide nitrate to organic ligand can be (0.4–0.6):1, for example, 0.4:1, 0.42:1, 0.44:1, 0.46:1, 0.48:1, 0.5:1, 0.52:1, 0.54:1, 0.56:1, 0.58:1, 0.6:1, etc. When the molar ratio of lanthanide nitrate to organic ligand is too low, the reaction between the lanthanide nitrate and organic ligand will be incomplete. When the molar ratio of lanthanide nitrate to organic ligand is too high, impurities with other metal-ligand ratios will be generated.

[0052] In some embodiments, in step S11, the organic solvent may be at least one of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA), and N,N-diethylformamide (DEF).

[0053] In some embodiments, the holding temperature for the hydrothermal reaction in step S21 can be 80–160°C, such as 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, etc. When the holding temperature for the hydrothermal reaction is too low, it is not conducive to the reaction and the fluorescent metal-organic framework material cannot be prepared. When the holding temperature for the hydrothermal reaction is too high, it is not conducive to the purity control of the fluorescent metal-organic framework material, and by-products may be generated.

[0054] In some embodiments, the holding time for the hydrothermal reaction in step S21 is 12–48 hours, for example, 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 22 hours, 24 hours, 26 hours, 28 hours, 30 hours, 32 hours, 34 hours, 36 hours, 38 hours, 40 hours, 42 hours, 44 hours, 46 hours, 48 ​​hours, etc. If the holding time for the hydrothermal reaction is too short, it is not conducive to the complete reaction. If the holding time for the hydrothermal reaction is too long, the reaction has already been basically completed, and further heating has little effect.

[0055] The preparation method of the second aspect of this application does not have any particular limitation on the cooling method used in step S21. For example, it can be at least one of natural cooling, air cooling, and water cooling. In some embodiments, natural cooling can be used in step S21. Natural cooling is sufficient for this step, as it is simple to operate.

[0056] In some embodiments, in step S21, the cooling is performed by natural cooling, and the natural cooling time can be 12 to 24 hours, such as 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 22 hours, 24 hours, etc.

[0057] The preparation method of the second aspect of this application does not have any particular limitation on the type of solvent used for washing in step S31, as long as it can remove any potentially excessive lanthanide nitrates or organic ligands adhering to the crystal. For example, the solvent used for washing in step S31 can be at least one of N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA), and N,N-diethylformamide (DEF).

[0058] In step S31, the solvent used for washing can be the same as or different from the organic solvent used in step S11. Preferably, in some embodiments, the solvent used for washing in step S31 is the same as the organic solvent used in step S11, which can avoid introducing impurities into the crystal during the washing process.

[0059] In some embodiments, in step S31, the drying is performed using vacuum drying. Vacuum drying can achieve low-temperature drying; moreover, the reduction in oxygen partial pressure avoids oxidative deterioration of the crystals.

[0060] In some embodiments, in step S31, the drying is carried out by vacuum drying, and the vacuum drying time can be 12 to 24 hours, such as 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 22 hours, 24 hours, etc.

[0061] A third aspect of this application provides a method for detecting the content of magnetic materials in a secondary battery negative electrode material. The method uses a fluorescent metal-organic framework material from the first aspect of this application to detect the content of magnetic materials in a test solution. The magnetic materials include Fe. 3+ and / or Cr 3+ .

[0062] Because the fluorescent metal-organic framework material of the first aspect of this application is used, the detection method of the third aspect of this application can detect the content of magnetic materials in the negative electrode material of secondary batteries by ultraviolet-fluorescence (UV-vis) method, which is fast and has high selectivity and sensitivity.

[0063] For example, the detection method may specifically include the following steps:

[0064] S12. Grind the fluorescent metal-organic framework material of the first aspect of the present application to obtain fluorescent metal-organic framework material powder; disperse the fluorescent metal-organic framework material powder in deionized water to obtain fluorescent metal-organic framework material solution;

[0065] S22. Mix the negative electrode material with anhydrous ethanol to obtain a negative electrode material dispersion; place a clean magnetic rod into the negative electrode material dispersion to allow the magnetic rod to fully adsorb the magnetic material; remove the magnetic rod that has adsorbed the magnetic material and wash it, then mix the washed magnetic rod with aqua regia to digest the magnetic material and obtain a digestion solution; remove the acid from the digestion solution and then cool it to room temperature to obtain a magnetic material solution.

[0066] S32. Establish a standard curve between the concentration of magnetic material and fluorescence intensity, and fit it to obtain the Stern-Volmer equation;

[0067] S42. Mix the magnetic material solution and the fluorescent metal-organic framework material solution, and bring the volume to a final volume to obtain the test solution; use a fluorescence spectrometer to measure the fluorescence intensity of the test solution, and substitute the fluorescence intensity of the test solution into the Stern-Volmer equation to calculate the molar concentration c of the magnetic material in the test solution. 磁 ;

[0068] S52. Calculate the content ω of magnetic material in the negative electrode material. 磁 ω 磁 The unit is wt%.

[0069] ω 磁 =m 磁 / m 负极材料 =c 磁 ×V 待测溶液 ×M 磁 / m 负极材料 ,

[0070] Among them, c 磁 This represents the molar concentration of the magnetic substance in the test solution, expressed in mol / L.

[0071] V 待测溶液 The volume of the solution to be tested is in liters (L).

[0072] M 磁 This refers to the molar mass of the magnetic material, expressed in g / mol.

[0073] m 负极材料 The mass of the negative electrode material is expressed in grams (g).

[0074] It should be noted that in the detection method of the third aspect of the embodiments of this application, fluorescence intensity refers to fluorescence emission intensity.

[0075] In some embodiments, in step S32, a mother liquor containing magnetic material can be prepared. Different volumes of the mother liquor are mixed with equal volumes of fluorescent metal-organic framework material solution, and after being brought to a final volume, standard solutions containing different concentrations of magnetic material are obtained. The fluorescence intensity of this series of standard solutions is tested using a fluorescence spectrometer. A standard curve between the concentration of magnetic material and fluorescence intensity is established, and the Stern-Volmer equation is obtained by fitting the curve. When testing the fluorescence intensity of a series of standard solutions, as the concentration of magnetic material increases, the fluorescence intensity of the standard solutions gradually decreases until it disappears, indicating that the magnetic material has a fluorescence quenching effect on the fluorescent metal-organic framework material.

[0076] In some embodiments, in step S32, the Stern-Volmer equation is I o / I=Ksv[Q]+1, where I o Let I be the fluorescence intensity of a standard solution with a magnetic material concentration of 0, and let [Q] be the fluorescence intensity of a standard solution with a magnetic material concentration other than 0. Let [Q] be the concentration of the magnetic material in the standard solution, and K be the quenching constant of the magnetic material. K is used to quantitatively evaluate the sensing efficiency of fluorescent metal-organic framework materials; a larger K value indicates a higher quenching efficiency of the magnetic material on the fluorescent metal-organic framework material. Calculations show that the magnetic material (Fe...)... 3+ Cr 3+ The quenching constant K reaches 3.18 × 10⁻⁶. 3 M -1The above demonstrates that the fluorescent metal-organic framework material of the first aspect of this application has a high sensitivity and high selectivity for fluorescence detection of magnetic materials.

[0077] This application is described in detail below with reference to the embodiments and accompanying drawings.

[0078] Example 1:

[0079] 0.05 mmol of europium nitrate hexahydrate (Eu(NO3)3·6H2O), 0.1 mmol of biphenyl dicarboxylic acid, and 5 mL of DMF were weighed sequentially and added to a 20 mL glass bottle. After stirring uniformly for 1 h, the contents were transferred to a reaction vessel and sealed. The mixture was heated at 100 °C for 48 h and then allowed to cool naturally to room temperature. After the reaction was completed, the crystals were collected, washed with DMF, and vacuum dried for 24 h to obtain the fluorescent metal-organic framework material Ln2L3·xH2O, where Ln is Eu, L is biphenyl dicarboxylic acid, and x is 1. This fluorescent metal-organic framework material belongs to the tetragonal crystal system with space group P4 / ncc.

[0080] The fluorescent metal-organic framework material obtained in Example 1 was used to detect the content of magnetic materials in lithium-ion battery anode materials. The following steps were followed:

[0081] (1) The fluorescent metal-organic framework material was ground to obtain fluorescent metal-organic framework material powder; the fluorescent metal-organic framework material powder was dispersed in deionized water to obtain a fluorescent metal-organic framework material solution with a concentration of 2 mmol / L.

[0082] (2) The negative electrode material of lithium-ion battery is mixed with anhydrous ethanol to obtain a negative electrode material dispersion; a clean magnetic rod is placed in the negative electrode material dispersion to allow the magnetic rod to fully adsorb the magnetic material therein; the magnetic rod adsorbed with magnetic material is taken out and washed, and the washed magnetic rod adsorbed with magnetic material is placed in a beaker, 10 mL of aqua regia and 50 mL of ultrapure water are added, and the aqua regia digests the magnetic material to obtain a digestion solution; the above beaker is placed on an electric heating plate and boiled open for 30 min, during which the beaker is shaken several times, and after boiling for 30 min, the heating is stopped and cooled to room temperature; all the digestion solution in the above beaker is transferred to a volumetric flask, and the magnetic rod and the inner wall of the beaker are washed with a small amount of ultrapure water. The washing solution is also poured into the volumetric flask, diluted with ultrapure water to 100 mL, and shaken well to obtain a magnetic material solution.

[0083] (3) ①Preparation of Fe 3+ The mother liquor was taken in different volumes and mixed with 100 μL of the fluorescent metal-organic framework material solution obtained in step (1). Deionized water was added to bring the volume to 10 mL to obtain solutions containing different concentrations of Fe. 3+Standard solutions of (0 μM, 50 μM, 100 μM, 150 μM, 200 μM, 250 μM, 300 μM, 350 μM, 400 μM, 450 μM, 500 μM, 550 μM, 600 μM, 650 μM, 700 μM) were used. These standard solutions were irradiated with ultraviolet light at 500–700 nm using a fluorescence spectrometer to obtain the fluorescence intensity of each standard solution.

[0084] Figure 1 The fluorescence intensity of the fluorescent metal-organic framework material prepared in Example 1 is measured in a series of standard solutions of varying concentrations. Figure 1 The concentration shown is Fe in the standard solution. 3+ The concentration.

[0085] Figure 2 The above are Stern-Volmer linear / nonlinear plots plotted from the fluorescence intensity data of the fluorescent metal-organic framework material prepared in Example 1 in a series of standard solutions of different concentrations. Figure a shows the fluorescence intensity data of Fe... 3+ Stern-Volmer linear plots were generated from fluorescence intensity data of standard solutions with concentrations below 500 μM. Figure b shows the fluorescence intensity data of Fe. 3+ Stern-Volmer nonlinear plots were created from fluorescence intensity data in standard solutions with concentrations below 700 μM.

[0086] ② Establish a standard curve between the concentration of magnetic material and fluorescence intensity, and fit it to obtain the Stern-Volmer equation. The Stern-Volmer equation is I... o / I=Ksv[Q]+1, where I o For Fe 3+ The fluorescence intensity of a standard solution with a concentration of 0, where I represents Fe. 3+ The fluorescence intensity of a standard solution with a non-zero concentration, where [Q] represents the Fe concentration in the standard solution. 3+ The concentration of Fe, K is the concentration of Fe 3+ The quenching constant is calculated to be K = 3.18 × 10⁻⁶. 3 M -1 .

[0087] (4) Mix the magnetic material solution obtained in step (2) with 100 μL of the fluorescent metal-organic framework material solution obtained in step (1), and add deionized water to make up to 10 mL to obtain the test solution; irradiate the test solution with ultraviolet light at 500–700 nm using a fluorescence spectrometer to obtain the fluorescence intensity of the test solution. Substitute the fluorescence intensity of the test solution into the Stern-Volmer equation obtained in step (3) to calculate the molar concentration c of the magnetic material in the test solution. 磁 = 35.7 μmol / L.

[0088] (5) Calculate the magnetic material Fe in the negative electrode material of lithium-ion batteries. 3+ ω content 磁 ω 磁 The unit is wt%.

[0089] ω 磁 =m 磁 / m 负极材料 =c 磁 ×V 待测溶液 ×M 磁 / m 负极材料 =5×10 -7 wt%

[0090] Among them, c 磁 This represents the molar concentration of the magnetic substance in the test solution, expressed in mol / L.

[0091] V 待测溶液 The volume of the solution to be tested is expressed in liters (L).

[0092] M 磁 This refers to the molar mass of the magnetic material, expressed in g / mol.

[0093] m 负极材料 This refers to the mass of the lithium-ion battery anode material, expressed in grams (g).

[0094] Example 2:

[0095] 0.05 mmol of terbium nitrate hexahydrate (Tb(NO3)3·6H2O), 0.1 mmol of biphenyl dicarboxylic acid, and 5 mL of DMA were weighed sequentially and added to a 20 mL glass bottle. After stirring uniformly for 1 h, the contents were transferred to a reaction vessel and sealed. The mixture was heated at 120 °C for 24 h and then allowed to cool naturally to room temperature. After the reaction was complete, the crystals were collected, washed with DMA, and vacuum dried for 24 h to obtain the fluorescent metal-organic framework material Ln2L3·xH2O, where Ln is Tb, L is biphenyl dicarboxylic acid, and x is 1. This fluorescent metal-organic framework material belongs to the tetragonal crystal system with space group P4 / ncc.

[0096] The detection method for magnetic materials in lithium-ion battery anode materials is the same as that in Example 1, except that the fluorescent metal-organic framework material obtained in this example is used; step (3) calculates K = 5.3 × 10 3 M -1 c obtained in step (4) 磁 The concentration is 71.4 μmol / L, and the ω obtained in step (5) is... 磁 1×10 -6 wt%.

[0097] Example 3:

[0098] 0.05 mmol of lanthanum nitrate hexahydrate La(NO3)3·6H2O, 0.1 mmol of biphenyl dicarboxylic acid, and 5 mL of DEF were weighed sequentially and added to a 20 mL glass bottle. After stirring uniformly for 1 h, the contents were transferred to a reaction vessel and sealed. The mixture was heated at 80 °C for 72 h and then naturally cooled to room temperature. After the reaction was completed, the crystals were collected, washed with DEF, and vacuum dried for 24 h to obtain the fluorescent metal-organic framework material Ln2L3·xH2O, where Ln is La, L is biphenyl dicarboxylic acid, and x is 2. This fluorescent metal-organic framework material belongs to the tetragonal crystal system with space group P4 / ncc.

[0099] The detection method for magnetic materials in lithium-ion battery anode materials is the same as that in Example 1, except that the fluorescent metal-organic framework material obtained in this example is used; step (3) calculates K = 7.2 × 10 3 M -1 c obtained in step (4) 磁 The concentration is 17.9 μmol / L, and the ω obtained in step (5) is... 磁 2.5×10 -7 wt%.

[0100] Example 4:

[0101] 0.05 mmol of yttrium nitrate hexahydrate Y(NO3)3·6H2O, 0.1 mmol of biphenyl dicarboxylic acid, and 5 mL of DMF were weighed sequentially and added to a 20 mL glass bottle. After stirring uniformly for 1 h, the contents were transferred to a reaction vessel and sealed. The mixture was heated at 100 °C for 48 h and then naturally cooled to room temperature. After the reaction was completed, the crystals were collected, washed with DMF, and vacuum dried for 24 h to obtain the fluorescent metal-organic framework material Ln2L3·xH2O, where Ln is Y, L is biphenyl dicarboxylic acid, and x is 2. This fluorescent metal-organic framework material belongs to the tetragonal crystal system with space group P4 / ncc.

[0102] The detection method for magnetic materials in lithium-ion battery anode materials is the same as that in Example 1, except that the fluorescent metal-organic framework material obtained in this example is used; step (3) calculates K = 6.8 × 10 3 M -1 c obtained in step (4) 磁 The concentration is 35.7 μmol / L, and the ω obtained in step (5) is... 磁 5×10 -7 wt%.

[0103] Comparative Example 1:

[0104] 0.05 mmol of cadmium nitrate hexahydrate (Cd(NO3)3·6H2O), 0.1 mmol of biphenyl dicarboxylic acid, and 5 mL of DMF were weighed sequentially and added to a 20 mL glass bottle. After stirring evenly for 1 h, the contents were transferred to a reaction vessel and sealed. The mixture was heated at 100 °C for 48 h and then allowed to cool naturally to room temperature. After the reaction was complete, the crystals were collected, washed with DMF, and vacuum dried for 24 h to obtain the metal-organic framework material.

[0105] The metal-organic framework material obtained in this comparative example does not exhibit fluorescent properties.

[0106] Comparative Example 2:

[0107] 0.05 mmol of zinc nitrate hexahydrate (Zn(NO3)3·6H2O), 0.1 mmol of biphenyl dicarboxylic acid, and 5 mL of DMF were weighed sequentially and added to a 20 mL glass bottle. After stirring evenly for 1 h, the contents were transferred to a reaction vessel and sealed. The mixture was heated at 100 °C for 48 h and then allowed to cool naturally to room temperature. After the reaction was complete, the crystals were collected, washed with DMF, and vacuum dried for 24 h to obtain the metal-organic framework material.

[0108] The metal-organic framework material obtained in this comparative example does not exhibit fluorescent properties.

[0109] Comparative Example 3:

[0110] 0.05 mmol of europium nitrate hexahydrate (Eu(NO3)3·6H2O), 0.1 mmol of 6-quinolinecarboxylic acid, and 5 mL of DMF were weighed sequentially and added to a 20 mL glass bottle. After stirring uniformly for 1 h, the contents were transferred to a reaction vessel and sealed. The mixture was heated at 100 °C for 48 h and then allowed to cool naturally to room temperature. After the reaction was complete, the crystals were collected, washed with DMF, and vacuum dried for 24 h to obtain the metal-organic framework material.

[0111] The metal-organic framework material obtained in this comparative example does not exhibit fluorescent properties.

[0112] In this application, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0113] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A fluorescent metal-organic framework material, characterized in that, The fluorescent metal-organic framework material has the chemical formula Ln2L3·xH2O, wherein the inorganic metal center Ln is at least one of the lanthanides, the organic ligand L has a biphenyl acid structure, and x is 0 to 3.

2. The fluorescent metal-organic framework material according to claim 1, characterized in that, The fluorescent metal-organic framework material belongs to the tetragonal crystal system with space group P4 / ncc.

3. The fluorescent metal-organic framework material according to claim 1, characterized in that, The biphenyl acid structure is at least one selected from biphenyl dicarboxylic acid, 3,3'-dihydroxy-4,4'-biphenyl dicarboxylic acid, and 3,3'-dimethyl-4,4'-biphenyl dicarboxylic acid.

4. The method for preparing the fluorescent metal-organic framework material according to any one of claims 1 to 3, characterized in that, Includes the following steps: S11. Mix the lanthanide metal nitrate, the organic ligand, and the organic solvent to obtain the precursor solution; S21. After subjecting the precursor solution to a hydrothermal reaction, cool it to room temperature to obtain crystals; S31. The crystal is washed and dried to obtain the fluorescent metal-organic framework material.

5. The preparation method according to claim 4, characterized in that, In step S11, the molar ratio of the lanthanide metal nitrate to the organic ligand is (0.4-0.6):

1.

6. The preparation method according to claim 4, characterized in that, In step S11, the organic solvent is at least one of N,N-dimethylformamide, N,N-dimethylacetamide, and N,N-diethylformamide.

7. The preparation method according to claim 4, characterized in that, In step S21, the holding temperature of the hydrothermal reaction is 80-160°C; and / or, the holding time of the hydrothermal reaction is 12-48 hours.

8. The preparation method according to claim 4, characterized in that, In step S21, the cooling is performed using natural cooling. Optionally, the natural cooling time is 12 to 24 hours; Optionally, in step S31, the solvent used for washing is the same type of organic solvent as in step S11; Optionally, in step S31, the drying is performed using vacuum drying. Optionally, the vacuum drying time is 12 to 24 hours.

9. A method for detecting the content of magnetic materials in a secondary battery negative electrode material, characterized in that, The fluorescent metal-organic framework material according to any one of claims 1 to 3 is used to detect the test solution containing magnetic substances, wherein the magnetic substances include Fe. 3+ and / or Cr 3+ .

10. The detection method according to claim 9, characterized in that, Includes the following steps: S12. Grind the fluorescent metal-organic framework material to obtain fluorescent metal-organic framework material powder; disperse the fluorescent metal-organic framework material powder in deionized water to obtain fluorescent metal-organic framework material solution; S22. The negative electrode material is mixed with anhydrous ethanol to obtain a negative electrode material dispersion; a clean magnetic rod is placed into the negative electrode material dispersion to allow the magnetic rod to fully adsorb the magnetic material therein; the magnetic rod with adsorbed magnetic material is removed and washed, and the washed magnetic rod with adsorbed magnetic material is mixed with aqua regia, which digests the magnetic material to obtain a digestion solution; the digestion solution is subjected to acid removal and then cooled to room temperature to obtain a magnetic material solution; S32. Establish a standard curve between the concentration of magnetic material and fluorescence intensity, and fit it to obtain the Stern-Volmer equation; S42. Mix the magnetic material solution and the fluorescent metal-organic framework material solution, and adjust the volume to obtain the test solution; use a fluorescence spectrometer to test the fluorescence intensity of the test solution, and substitute the fluorescence intensity of the test solution into the Stern-Volmer equation to calculate the molar concentration c of the magnetic material in the test solution. 磁 ; S52. Calculate the content ω of magnetic material in the negative electrode material. 磁 ω 磁 The unit is wt%. ω 磁 =m 磁 / m 负极材料 =c 磁 ×V 待测溶液 ×M 磁 / m 负极材料 , Among them, c 磁 This represents the molar concentration of the magnetic substance in the test solution, expressed in mol / L. V 待测溶液 The volume of the solution to be tested is in liters (L). M 磁 This refers to the molar mass of the magnetic material, expressed in g / mol. m 负极材料 The mass of the negative electrode material is expressed in grams (g).

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