Eu-Tb-In-MOF material based on double fluorescence emission sources as well as preparation method and application of Eu-Tb-In-MOF material

Abstract

The invention discloses a preparation method of an Eu-Tb-In-MOF material based on a dual fluorescence emission source type, and the preparation method specifically comprises the following steps: under a closed condition, uniformly mixing terbium nitrate hexahydrate, europium nitrate hexahydrate, indium nitrate pentahydrate, an organic ligand, N, N-dimethylformamide and acetonitrile, then adjusting the pH value of a mixed solution, and carrying out solvothermal reaction, washing, filtering and drying to obtain the Eu-Tb-In-MOF material. The invention also discloses an application of the Eu-Tb-In-MOF material in identification of heavy metal ions Cr in a water environment. The Cr (VI) ions in the water environment are detected through fluorescence quenching sensing, excellent high selectivity is shown, and interference of other single and mixed anions and cations in the water environment can be resisted.

Description

Technical Field

[0001] The present invention belongs to the technical field of fluorescent material preparation, and in particular relates to a Eu-Tb@In-MOF material based on a dual fluorescent emission source type, a preparation method of the Eu-Tb@In-MOF material, and an application of the Eu-Tb@In-MOF material. Background Art

[0002] Hexavalent chromium is widely used as a highly effective mordant in the textile printing and dyeing industry. However, after being discharged with industrial wastewater, it enters the aquatic environment in a highly soluble state and spreads throughout the ecosystem due to its strong mobility. This substance is classified as a Class I carcinogen by the WHO due to its strong carcinogenic and mutagenic properties, and domestic drinking water standards have a strict limit of 0.05 mg / L. Cr(VI) ions are highly soluble in water and have a strong diffusion capacity. Their concentrations in environmental water bodies are often at trace levels and coexist with other ions, making their effective identification and accurate detection extremely challenging. Currently, the detection of hexavalent chromium ions typically uses complex spectroscopic methods or electrochemical detection methods, but these technologies are not only expensive and difficult to operate, but also require calibration and skilled operators to achieve stable long-term performance. Therefore, it is of great value to develop simple and economical detection methods for the qualitative identification and quantitative detection of Cr(VI) ions.

[0003] Metal-organic frameworks (MOFs) are self-assembled organic units and metal nodes, exhibiting unique high porosity, tunable spatial structure, and functional properties. They also provide a suitable platform for accommodating guest molecules and further post-modification. Luminescent MOFs have been identified as potential photochemical probes for fluorescent sensing of various analytes, exhibiting luminescent responses (wavelength or intensity changes) upon interaction with the target analytes. Fluorescent probes constructed using a single rare earth ion anchored to an In-MOF exhibit a single source of emission signal susceptible to interference from external factors, resulting in insufficient sensing accuracy. By constructing highly water-stable MOFs and introducing dual fluorescence sources, a ratiometric fluorescence sensor is constructed, demonstrating high sensitivity, high detection accuracy, high selectivity, and anti-interference capabilities, enabling efficient fluorescent sensing of target analytes. Summary of the Invention

[0004] The first purpose of the present invention is to provide a Eu-Tb@In-MOF material based on a dual fluorescence emission source type, which solves the problems of low sensitivity and poor anti-interference ability of existing MOFs fluorescent materials in detecting the presence of heavy metal ions in water environments.

[0005] The second object of the present invention is to provide a method for preparing the above-mentioned Eu-Tb@In-MOF material based on dual fluorescence emission sources.

[0006] The third object of the present invention is to provide an application of the above-mentioned Eu-Tb@In-MOF material based on a dual fluorescence emission source type in identifying heavy metal ions Cr (VI) in an aqueous environment.

[0007] The technical solution adopted by the present invention is a preparation method of Eu-Tb@In-MOF material based on a dual fluorescence emission source type, specifically: Under closed conditions, terbium nitrate hexahydrate, europium nitrate hexahydrate, indium nitrate pentahydrate, organic ligand, N,N-dimethylformamide, and acetonitrile are evenly mixed, and then the pH of the mixture is adjusted, the molar ratio of terbium nitrate hexahydrate and europium nitrate hexahydrate is adjusted, a solvent thermal reaction is carried out, and the mixture is washed, filtered, and dried to obtain the Eu-Tb@In-MOF material.

[0008] The present invention is also characterized in that: The solvothermal reaction time is 24 - 72 h, and the solvothermal reaction temperature is 100 - 130 °C.

[0009] The organic ligand is 2,4,6-tris(4-carboxyphenyl)-1,3,5-triazine.

[0010] The molar ratio of terbium nitrate hexahydrate, europium nitrate hexahydrate, indium nitrate pentahydrate and 2,4,6-tris(4-carboxyphenyl)-1,3,5-triazine is 0.5-10:0.5-10:1-5:1; and a nitric acid solution is added dropwise to adjust the pH of the mixed solution to 3-5.

[0011] Another technical solution adopted by the present invention is to prepare the Eu-Tb@In-MOF material based on the preparation method of the Eu-Tb@In-MOF material with dual fluorescence emission sources.

[0012] The beneficial effects of this invention are that the Eu-Tb@In-MOF material of the present invention has a simple preparation process, mild reaction conditions, high product yield and good reproducibility. The synthesized product is a colorless, long, rod-shaped material, which has the potential for industrial production. It detects Cr(VI) ions in aqueous environments through fluorescence quenching sensing, demonstrating excellent selectivity and high detection accuracy, and is resistant to interference from other single and mixed anions and cations in the aqueous environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1a X-ray powder diffraction patterns of Eu-Tb@In-MOF with different ratios of the present invention (the inset is the fluorescence emitted by the corresponding material under ultraviolet light); Figure 1b : The CIE chromaticity diagram of Eu-Tb@In-MOF with different ratios of the present invention; Figure 2a Eu of the present invention 0.36 Tb0.64 @Scanning electron microscope image of In-MOF material; Figure 2b For Eu 0.36 Tb 0.64 @Energy spectrum analysis diagram of C element in In-MOF material; Figure 2c For Eu 0.36 Tb 0.64 @Energy spectrum analysis diagram of O element in In-MOF material; Figure 2d For Eu 0.36 Tb 0.64 @Energy spectrum analysis diagram of Eu element in In-MOF material; Figure 2e For Eu 0.36 Tb 0.64 @Energy spectrum analysis diagram of Tb element in In-MOF material; Figure 2f For Eu 0.36 Tb 0.64 @Energy spectrum analysis diagram of N element in In-MOF material; Figure 2g For Eu 0.36 Tb 0.64 @Energy spectrum analysis diagram of In element in In-MOF material; Figure 3 Eu of the present invention 0.36 Tb 0.64 @Infrared spectrum of In-MOF material; Figure 4 Eu of the present invention 0.36 Tb 0.64 @Full spectrum of X-ray photoelectron spectrum of In-MOF material; Figure 5a Eu of the present invention 0.36 Tb 0.64 High-resolution X-ray photoelectron spectroscopy of C1s of @In-MOF material; Figure 5b Eu of the present invention 0.36 Tb 0.64 High-resolution X-ray photoelectron spectroscopy of O1s of @In-MOF material; Figure 5c Eu of the present invention 0.36 Tb 0.64 High-resolution X-ray photoelectron spectroscopy of N1s of @In-MOF material; Figure 6 Eu of the present invention 0.36 Tb 0.64@In-MOF material fluorescence excitation and emission spectra; Figure 7 Eu of the present invention 0.36 Tb 0.64 @The fluorescence emission intensity diagram corresponding to different concentrations of In-MOF material suspensions; Figure 8a To Eu 0.36 Tb 0.64 Different cations and CrO4 were added to the aqueous suspension of In-MOF material. 2− and Cr2O7 2− Fluorescence quenching efficiency diagram after 4 ℃; Figure 8b To Eu 0.36 Tb 0.64 Different anions and CrO4 were added to the aqueous suspension of In-MOF material. 2− and Cr2O7 2− Fluorescence quenching efficiency diagram after 4 ℃; Figure 9a To Eu 0.36 Tb 0.64 @In-MOF material with different concentrations of CrO4 2- Fluorescence intensity evolution diagram after ; Figure 9b To Eu 0.36 Tb 0.64 @In-MOF material added with different concentrations of CrO4 2- The concentration and fluorescence intensity ratio (I 545 / I 617 )’s piecewise linear relationship graph; Figure 10a To Eu 0.36 Tb 0.64 @In-MOF material added with different concentrations of Cr2O7 2- Fluorescence intensity evolution diagram of ; Figure 10b To Eu 0.36 Tb 0.64 @In-MOF material added with different concentrations of Cr2O7 2- The concentration and fluorescence intensity ratio (I 545 / I 617 )’s piecewise linear relationship graph; Figure 11a To Eu 0.36 Tb 0.64 @In-MOF material testing with different concentrations of CrO4 2- The anti-interference ability diagram of fluorescence quenching response to a single cation; Figure 11b To Eu 0.36Tb 0.64 @In-MOF material testing with different concentrations of CrO4 2- The anti-interference ability diagram of fluorescence quenching response to a single anion; Figure 11c To Eu 0.36 Tb 0.64 @In-MOF material testing with different concentrations of CrO4 2- The anti-interference ability diagram of the fluorescence quenching response to mixed anions or mixed cations; Figure 12a To Eu 0.36 Tb 0.64 @In-MOF material testing adds different concentrations of Cr2O7 2- The anti-interference ability diagram of fluorescence quenching response to a single cation; Figure 12b To Eu 0.36 Tb 0.64 @In-MOF material testing adds different concentrations of Cr2O7 2- The anti-interference ability diagram of fluorescence quenching response to a single anion; Figure 12c To Eu 0.36 Tb 0.64 @In-MOF material testing adds different concentrations of Cr2O7 2- Graph showing the anti-interference ability of fluorescence quenching response to mixed anions or mixed cations. DETAILED DESCRIPTION

[0014] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0015] The present invention is based on the dual fluorescence emission source type Eu-Tb@In-MOF material, using high valence In 3+ The ion is coordinated with an aromatic tricarboxylic acid-based ligand, specifically 2,4,6-tris(4-carboxyphenyl)-1,3,5-triazine; and at the same time anchors Eu 3+ and Tb 3+ , construct MOFs materials with high water stability; Compared to the full XPS spectrum of the original In-MOF, Eu-Tb@In-MOF exhibits characteristic peaks of Eu 3d at 1138 eV and 1168 eV, and characteristic peaks of Tb 3d at 1245 eV and 1278 eV. The binding energies of oxygen atoms in the original In-MOF are 531.96 eV and 533.54 eV, while those in Eu-Tb@In-MOF shift to 531.66 eV and 534.04 eV, indicating the formation of Eu‒O and Tb‒O bonds in Eu-Tb@In-MOF.

[0016] Lanthanide ions (Ln 3+ ) has the characteristics of narrow-band emission, long lifetime, high color purity and large Stokes shift. 3+ and Tb 3+ They are anchored to the originally non-luminescent In-MOF. The aromatic organic ligands of In-MOF can move toward the anchored Eu through the "antenna effect" under light excitation. 3+ and Tb 3+ For efficient energy transfer. 3+ and Tb 3+ The oxophilicity of Ln enables it to be firmly anchored to the carboxyl O atoms of In-MOF through post-synthetic modification, which provides a basis for the induction of Ln anchoring on MOFs through the “antenna effect” and photoinduced electron transfer mechanism. 3+ Luminescence, and then fluorescence sensing detection of target analytes, provides a feasible and effective strategy. Among the many rare earth ions, Eu 3+ and Tb 3+ With large intrinsic quantum yield and narrow energy gap, Tb 5 D4 / 7 F6 (14800 cm -1 ) and Eu 5 D0 / 7 F6 (12300 cm -1 ), can improve the total luminescence yield of Eu-Tb@In-MOF materials and avoid non-radiative transitions. 3+ At 545 nm ( 5 D4→ 7 F5), Tb 3+ At 617 nm ( 5 D0→ 7 The strongest fluorescence emission signals are at F2 and F3, respectively. These two fluorescence emission bands are far apart and do not overlap. This feature provides a key guarantee for ratiometric fluorescence sensing of target analytes using dual fluorescence signal sources, overcoming external environmental interference and improving detection accuracy.

[0017] The present invention is based on a preparation method of a dual-fluorescence emission source type Eu-Tb@In-MOF material, specifically: Under closed conditions, terbium nitrate hexahydrate, europium nitrate hexahydrate, indium nitrate pentahydrate, an organic ligand H3L, namely 2,4,6-tris(4-carboxyphenyl)-1,3,5-triazine, N,N-dimethylformamide, and acetonitrile are uniformly mixed, and then a nitric acid solution is added dropwise to the mixture to adjust the pH of the mixed solution to 3-5. After that, a solvothermal reaction is carried out, and the mixture is repeatedly washed with fresh DMF, filtered, and dried to obtain a Eu-Tb@In-MOF material. The solvothermal reaction time is 24-72 h, and the solvothermal reaction temperature is 100-130°C; The molar ratio of terbium nitrate hexahydrate, europium nitrate hexahydrate, indium nitrate pentahydrate and 2,4,6-tris(4-carboxyphenyl)-1,3,5-triazine is 0.5-10:0.5-10:1-5:1.

[0018] The volume ratio of N,N-dimethylformamide to acetonitrile is 3:1; the mass fraction of nitric acid solution is 63.01%; The Eu-Tb@In-MOF material based on dual fluorescence emission sources has high sensitivity, high selectivity and anti-interference ability; and has a highly specific recognition ability for Cr (VI) ions, and can accurately detect target ions in complex ionic environments. Its recognition of Cr (VI) ions is fluorescence quenching recognition.

[0019] By introducing dual fluorescence sources (double rare earth ions) into the In-MOF framework to construct a ratiometric fluorescence sensor, Cr (VI) ions can be detected using the intensity ratio of the emission peaks from two independent signal sources rather than a single absolute intensity sensor, significantly improving the sensitivity and accuracy of detection through self-calibration.

[0020] Example 1 The present invention is based on a preparation method of a dual-fluorescence emission source type Eu-Tb@In-MOF material, specifically: Under closed conditions, terbium nitrate hexahydrate and europium nitrate hexahydrate are first added, and then indium nitrate pentahydrate and organic ligand H3L, namely 2,4,6-tris(4-carboxyphenyl)-1,3,5-triazine, N,N-dimethylformamide, and acetonitrile are added and mixed evenly. Then, nitric acid solution is added dropwise to the mixture and reacted under solvent thermal conditions to obtain Eu. 0.36 Tb 0.64 @In-MOF material.

[0021] The molar ratio of terbium nitrate hexahydrate to europium nitrate hexahydrate is 16:9; the molar ratio of indium nitrate pentahydrate to organic ligand H3L is 10:3; the volume ratio of N,N-dimethylformamide to acetonitrile is 3:1; the mass fraction of the nitric acid solution is 63.01%; Specifically: 8.02 mg of terbium nitrate hexahydrate to 14.49 mg of europium nitrate hexahydrate, 3 mL of N,N-dimethylformamide and 1 mL of acetonitrile for every 30.1 mg of indium nitrate pentahydrate and 13.24 mg of the organic ligand 2,4,6-tris(4-carboxyphenyl)-1,3,5-triazine; 19.5 mg of Eu 0.36 Tb 0.64 @In-MOF was evenly dispersed in 3 mL of distilled water to obtain 6500 mg / L of Eu0.36 Tb 0.64 @In-MOF aqueous suspension, fluorescence intensity tested on a fluorescence spectrophotometer.

[0022] Add 3 mL of 6500 mg / L Eu 0.36 Tb 0.64 @In-MOF water suspension was added to the cuvette of 50 μL of single / mixed nitrate X(NO3) at the same concentration. n (X = Cu 2+ Cr 3+ 、Al 3+ 、Cd 2+ 、Fe 3+ Mg 2+ 、Na + , Pb 2+ and K + ) or potassium salt K n X' (X' = SO4 2- 、SCN - 、F - 、NO2 - , I - 、Cl - Br - and IO3 - ) and CrO4 2− and Cr2O7 2− The aqueous solution was tested by fluorescence spectrophotometer to verify the CrO4 2− 、Cr2O7 2− Selectivity of fluorescence sensing.

[0023] In the fluorescence sensing evolution process, potassium chromate (K2CrO4) and potassium dichromate (K2Cr2O7) were used as the source of Cr(VI) (CrO4 2- and Cr2O7 2- ), take 50 μL of different concentrations of CrO4 2− and Cr2O7 2− The solution was added to the quartz cuvette containing 3 mL of suspension. Then, the fluorescence spectrophotometer was used to record the CrO4 2− and Cr2O7 2− The sensitivity of the detection was verified by analyzing the details of the fluorescence intensity evolution of the photochemical sensor caused by the reaction.

[0024] In the anti-interference experiment, 50 μL of CrO4 of the same concentration was taken. 2− + X(NO3) n / K n X' or Cr2O7 2 + X(NO3) n / Kn The X' mixed solution was added with 3 mL of Eu with a concentration of 6500 mg / L 0.36 Tb 0.64 @In-MOF cuvette to verify and compare its anti-interference ability.

[0025] The Eu-Tb@In-MOF of the present invention has a dual fluorescence emission source. The material is a colorless long rod-shaped material. The In metal MOF material has a three-dimensional structure of a double interlaced grid. Specifically, a basic unit of In-MOF contains 3 In III ions, 2 TATB 3- Ligand, 2 HCOO - , 1 DMF molecule. In in In-MOF III With ligand L 3- The carboxyl groups in the III The ions are all seven-coordinated, of which four oxygen atoms come from two independent deprotonated carboxyl oxygen atoms in H3L, two oxygen atoms each come from the deprotonated formic acid molecules generated by the decomposition of DMF in the solvent thermal reaction, and the other oxygen atom comes from the oxygen atom of the solvent DMF molecule. 3- The connectors are connected to 3 In III The ion center forms a three-dimensional single network structure; two identical single networks are interpenetrated and combined to further form a double interpenetrating three-dimensional structural framework. The technical solution of the present invention proves that the prepared Eu 0.36 Tb 0.64 @In-MOF has a highly specific recognition ability for Cr(VI) ions and can accurately detect target ions in complex ionic environments. Its recognition of Cr(VI) ions is fluorescence quenching recognition.

[0026] Example 2 The present invention is based on a preparation method of a dual-fluorescence emission source type Eu-Tb@In-MOF material, specifically: First, add 0.64 mmol of terbium nitrate hexahydrate and 0.36 mmol of europium nitrate hexahydrate, then add 30.1 mg of indium nitrate pentahydrate and 13.24 mg of organic ligand H3L, namely 2,4,6-tris(4-carboxyphenyl)-1,3,5-triazine, 3 mL of N,N-dimethylformamide, and 1 mL of acetonitrile, and mix them evenly. Then, add 280 μL of nitric acid solution dropwise to the mixture, react under solvent thermal conditions, and then seal it in a 20 mL small glass bottle. Cool naturally to room temperature to obtain colorless rod-shaped crystals of Eu. 0.36 Tb 0.64 @In-MOF material.

[0027] Example 3 The present invention is based on a preparation method of a dual-fluorescence emission source type Eu-Tb@In-MOF material, specifically: First, add 0.68 mmol of terbium nitrate hexahydrate and 0.32 mmol of europium nitrate hexahydrate, then add 30.1 mg of indium nitrate pentahydrate and 13.24 mg of organic ligand H3L, namely 2,4,6-tris(4-carboxyphenyl)-1,3,5-triazine, 3 mL of N,N-dimethylformamide, and 1 mL of acetonitrile, and mix them evenly. Then, add 280 μL of nitric acid solution dropwise to the mixture, react under solvent thermal conditions, and then seal it in a 20 mL small glass bottle. Cool naturally to room temperature to obtain white rod-shaped crystals of Eu. 0.32 Tb 0.68 @In-MOF material.

[0028] Eu of Eu-Tb@In-MOF obtained in the above embodiment 3+ and Tb 3+ The optimization of the ion doping ratio is as follows: In order to obtain a stronger Eu 3+ and Tb 3+ Fluorescence emission characteristic peaks, the optimal doping ratio was explored from n = 0.22: 0.78 to n = 0.38: 0.62 to obtain Eu-Tb@In-MOF with strong dual emission source signals required for ratiometric fluorescence sensing of Cr(VI). Figure 1a The X-ray powder diffraction patterns of the materials after refinement show that their diffraction peaks are well maintained and the luminescent colors correspond to the coordinate colors of the CIE chromaticity diagram ( Figure 1b ). The following characterization is based on Eu 0.36 Tb 0.64 @In-MOF is a ratiometric fluorescent sensing material for analysis.

[0029] Figure 2a The scanning electron microscope image is Figure 2b-2g The energy spectrum analysis spectrum of each element shows that Eu 0.36 Tb 0.64 @In-MOF still maintains the same long rod shape as In-MOF. The elemental energy spectrum analyzer measures the element composition and distribution. It is clear that Eu and Tb are evenly distributed on In-MOF, which shows that Eu 0.36 Tb 0.64 Successful synthesis of @In-MOF.

[0030] Figure 3 The spectrum shows that at 1680 cm -1 The peak intensity of the tensile vibration at the position of the α-Hydroxy-L-Y-P-MoF is significantly weakened, which is speculated to be due to the coordination effect with the oxygen atom on the ligand carboxylic acid.0.36 Tb 0.64 @In-MOF at 3432 cm -1 The peak at 3748 cm -1 and 3841cm -1 Two new signal peaks appeared, indicating that Eu 3+ and Tb 3+ Chemical reaction occurs between the carboxyl oxygen atoms of In-MOF.

[0031] Figure 4 The spectrum shows that compared with the original In-MOF XPS full spectrum, Eu 0.36 Tb 0.64 @In-MOF showed characteristic peaks of Eu 3d at 1138 eV and 1168 eV, and characteristic peaks of Tb 3d at 1245 eV and 1278 eV. The interaction between the two was further analyzed by high-resolution elemental mapping. Figure 5a 、 Figure 5b 、 Figure 5c As shown, the binding energies of oxygen atoms in the original In-MOF are 531.96 eV and 533.54 eV, and the binding energies of Eu 0.36 Tb 0.64 @In-MOF oxygen atom binding energy shifted to 531.66eV and 534.04eV, indicating that Eu 0.36 Tb 0.64 @Forming of Eu‒O and Tb‒O bonds in In-MOF.

[0032] To Eu 0.36 Tb 0.64 @In-MOF fluorescence characteristics were analyzed, such as Figure 6 As shown in Figure 2, there are 6 emission peaks under the excitation of 369 nm. Among them, 490 nm ( 5 D4→ 7 F6), 545 nm ( 5 D4→ 7 F5), 586 nm ( 5 D4→ 7 F4) is Tb 3+ The characteristic peak of 617nm ( 5 D0→ 7 F2), 651 nm ( 5 D0→ 7 F3) and 699 nm ( 5 D0→ 7 F4) is Eu 3+ The characteristic peak of Tb 3+ The characteristic peak is 622 nm ( 5 D4→7 F3) and Eu 3+ The characteristic peak is 592 nm ( 5 D0→ 7 F1) guess is with 617 nm ( 5 D0→ 7 F2) and 586nm ( 5 D4→ 7 F4) absorbs overlap and disappears.

[0033] In order to better carry out the fluorescence detection experiment, Eu 0.36 Tb 0.64 The concentration of @In-MOF aqueous suspension was studied. Figure 7 As shown in the figure, among a series of concentrations, the emission intensity corresponding to 6500 mg / L was the highest, so this concentration was used for subsequent experiments.

[0034] Use a single anion aqueous solution with the same ion concentration as that in actual water (such as KnX1, where X1 is SO4 2- 、SCN - 、F - 、NO2 - , I - 、Cl - Br - and IO3 - ) and single cation aqueous solutions (such as X2(NO3) n , where X2 is Cu 2+ Cr 3+ 、Al 3+ 、Cd 2+ 、Fe 3+ Mg 2+ 、Na + , Pb 2+ and K + ) as potential interfering ions. 50 μL of the above single ion solution was added to 3 mL of Eu 0.36 Tb 0.64 @In-MOF water suspension was mixed in a quartz cuvette and a series of two-component solutions were formed after uniform mixing. The fluorescence emission intensity of these two-component solutions showed only slight or negligible changes. However, when K n X1 or X2 (NO3) n When 50 μL of Cr(VI) solution is used with the same concentration, Figure 8a 、 Figure 8b As shown, Eu 0.36 Tb 0.64The fluorescence of @In-MOF is almost completely quenched. The prepared fluorescent probe has highly specific recognition ability for Cr(VI) ions and can accurately detect target ions in complex ionic environments.

[0035] Example 4 like Figure 9a As shown, with the CrO4 2- The concentration of Eu 0.36 Tb 0.64 All emission peaks of @In-MOF gradually decreased until the concentration reached 253.25 μM, completely quenching the fluorescence with a quenching efficiency of 98%. In order to better analyze the relationship between fluorescence intensity and Cr(VI) concentration, the strongest emission peak intensity of Tb (I 545 ) and the strongest emission peak intensity of Eu (I 617 ) ratio I 545 / I 617 The relative change of Eu 0.36 Tb 0.64 The initial emission peak intensity of @In-MOF is less than 1000. In order to more significantly show the signal change, this study chose to use the exponential function of the ratio of the two emission peak intensities as the vertical axis to enhance the readability of the ratio change; the horizontal axis corresponds to the concentration of Cr(VI). Figure 9b As shown, it was found that in different concentration ranges, I 545 / I 617 Function of CrO4 2- The concentration of CrO4 in water samples is in a piecewise linear relationship. 2- The concentration of CrO4 is between 0 and 42.522 μM, and the relationship between the concentration and the ratio of the two emission peaks is linear, that is, y = 4.25602 + 0.53788x, with a correlation coefficient of 0.931. 2- The concentration of α-aminobutyric acid ranged from 42.522 to 253.25 μM. The relationship between the concentration and the ratio was y = 2.52176 + 1.60467x, with a correlation coefficient of 0.9748. The calculated quenching constant was 1.301 × 10 5 L / mol, and the detection limit was 7.41 ppb.

[0036] Example 5 like Figure 10a As shown, with the Cr2O7 2- With the increasing concentration, Eu 0.36 Tb 0.64 The fluorescence emission peak intensity of @In-MOF shows a continuous downward trend. 2-When the concentration reached 253.25 μM, the fluorescence signal almost completely disappeared. Figure 10b As shown, when detecting Cr2O7 in water samples 2- When the concentration is in the range of 0 ~ 28.1 μM, the functional relationship between the concentration and the emission peak ratio shows a good linear relationship, the linear equation is y = 4.53156 + 0.41543x, and the correlation coefficient is 0.993. 2- When the concentration ranged from 28.1 to 445.79 μM, the relationship between the concentration and the ratio was in accordance with the equation y = 2.90634 +0.17613x, with a correlation coefficient of 0.98213. The calculated Stern-Volmer quenching constant was 1.1447 ×10 5 L / mol, detected at 8.62 ppb.

[0037] Example 6 In order to evaluate the performance of the fluorescence sensor in a complex ion environment, a single anion (such as SO4 2- 、SCN - 、F - 、NO2 - , I - 、Cl - Br - IO3 - ) or a single cation (such as Cu 2+ Cr 3+ 、Al 3+ 、Cd 2+ 、Fe 3+ Mg 2+ 、Na + , Pb 2+ , K + ) or a 50 μL aqueous solution containing the above anions, cations or their mixtures. These single anions, cations or multi-ion mixtures were added to 3 mL of the aqueous suspension and mixed thoroughly to ensure a uniform solution. Whether it is a single ion system or a designed mixed ion system, Eu 0.36 Tb 0.64 The fluorescence emission intensity of @In-MOF showed a certain degree of attenuation, but the attenuation was relatively weak. However, when the same concentration of Cr2O7 was introduced into these systems, the fluorescence emission intensity of @In-MOF showed a certain degree of attenuation, but the attenuation was relatively weak. 2- and CrO4 2- The fluorescence intensity decreases rapidly and significantly when 0.36 Tb 0.64 @In-MOF can be used in a variety of foreign single cations ( Figure 11a 、 Figure 12a ), single anion ( Figure 11b 、 Figure 12b ) and mixed ionic species ( Figure 11c 、 Figure 12c ) interference, accurately identify and detect target Cr(VI) ions.

Claims

1. A method for preparing a dual-fluorescence emission source Eu-Tb@In-MOF material, characterized in that: Specifically: Under closed conditions, terbium nitrate hexahydrate, europium nitrate hexahydrate, indium nitrate pentahydrate, organic ligand, N,N-dimethylformamide, and acetonitrile are mixed evenly, and then the pH of the mixture is adjusted, a solvent thermal reaction is carried out, and the mixture is washed, filtered, and dried to obtain Eu-Tb@In-MOF material.

2. The method for preparing the Eu-Tb@In-MOF material based on a dual fluorescence emission source type according to claim 1, characterized in that: The solvothermal reaction time is 24 - 72 h, and the solvothermal reaction temperature is 100 - 130 °C.

3. The method for preparing the Eu-Tb@In-MOF material based on a dual fluorescence emission source type according to claim 1, wherein: The organic ligand is 2,4,6-tris(4-carboxyphenyl)-1,3,5-triazine.

4. The method for preparing the Eu-Tb@In-MOF material based on a dual fluorescence emission source type according to claim 1, wherein: The molar ratio of terbium nitrate hexahydrate, europium nitrate hexahydrate, indium nitrate pentahydrate and 2,4,6-tris(4-carboxyphenyl)-1,3,5-triazine is 0.5-10:0.5-10:1-5:

1.

5. The method for preparing the Eu-Tb@In-MOF material based on a dual fluorescence emission source type according to claim 1, wherein: Nitric acid solution was added dropwise to adjust the pH of the mixture to 3-5.

6. The Eu-Tb@In-MOF material prepared by the method for preparing the Eu-Tb@In-MOF material based on dual fluorescence emission sources according to any one of claims 1 to 5.

7. Use of the dual-fluorescence emission source-based Eu-Tb@In-MOF material according to claim 6 in identifying heavy metal ions Cr in an aqueous environment.

8. The use according to claim 7, characterized in that The recognition of heavy metal ions Cr is through fluorescence quenching.

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