Lanthanide metal organic framework material, fluorescence sensor, preparation method of lanthanide metal organic framework material and application of lanthanide metal organic framework material and fluorescence sensor in pesticide detection

Abstract

The invention belongs to the technical field of metal organic framework materials, and relates to a lanthanide series metal organic framework material, a fluorescent sensor, a preparation method of the fluorescent sensor and application of the fluorescent sensor in pesticide detection. The preparation method of the lanthanide series metal organic framework material comprises the following steps: taking lanthanide series metal salt and an organic ligand as raw materials, and then adopting a solvothermal method to obtain the lanthanide series metal organic framework material, the organic ligand is 1, 4-naphthalic acid or 2, 6-naphthalic acid. The lanthanide series metal organic framework material is prepared from an organic ligand with an isomeride and lanthanide series metal salt through a solvothermal method, lanthanide series metal ions are effectively sensitized to emit light through an antenna effect, the fluorescence quantum yield and the luminous intensity are improved, the signal-to-noise ratio of the lanthanide series metal organic framework material is further improved, and the 2, 4-difluoro-2, 4-difluoro-2, 4-difluoro-2, 4-difluoro-2, 4-difluoro-2, 4-difluoro-2, 4-difluoro-2, 4- and the detection of the 2, 6-dichloro-4-nitroaniline has high sensitivity and accuracy.

Description

Technical Field

[0001] This invention belongs to the field of metal-organic framework materials technology, and relates to a lanthanide metal-organic framework material, a fluorescence sensor, its preparation method, and its application in pesticide detection. Background Technology

[0002] Pesticides are an indispensable part of agricultural production, playing a crucial role in protecting crops from pests, diseases, and weeds. In particular, 2,6-dichloro-4-nitroaniline, a broad-spectrum pesticide, is commonly used to control wheat powdery mildew, cotton boll rot, and fruit / vegetable diseases. However, 2,6-dichloro-4-nitroaniline decomposes slowly, and its residues can persist in soil and water environments for a long time, thus it is classified as a Class III hazardous pesticide. Therefore, there is an urgent need to develop an effective method for detecting 2,6-dichloro-4-nitroaniline.

[0003] To date, common detection methods for nitroaniline pesticides include high-performance liquid chromatography (HPLC), gas chromatography (GC), and liquid chromatography-tandem mass spectrometry (LC-MS / MS). For example, patent document CN116124929A describes a method for simultaneously determining trace amounts of dinitrobenzene, diaminotoluene, and nitroaniline in a phenylenediamine reduction solution using liquid chromatography. However, these methods require complex sample pretreatment and expensive instruments, significantly limiting their application in pesticide detection. In contrast, fluorescence detection methods based on sensing materials have gained increasing attention in the field of pollutant detection due to their low cost, ease of operation, and short response time.

[0004] Currently, reported sensing materials can be broadly categorized into metal-organic frameworks (MOFs), covalent organic materials, carbon dot materials, and small molecule fluorescent probes. Among these, MOF-based fluorescent probes have attracted increasing attention due to their inherent properties (e.g., tunable structure, tunable pore size, and different fluorescence emission mechanisms). MOFs achieve adsorption or recognition of target pesticides by stabilizing metal sites with good coordination capabilities and organic ligands, thus enabling detection. In existing technologies, the metals used in constructing MOFs include transition metals or rare earth metals. Due to the inherent properties of metal ions and the corresponding functional guidance of MOFs, rare earth MOFs possess excellent luminescent properties such as strong emission peaks, long luminescence lifetimes, and high luminescence efficiency, making them more advantageous in fluorescence detection. However, rare earth metal ions exhibit weak absorption of excitation light due to the Laporte rule-forbidden 4f-4f transitions, resulting in low luminescence efficiency. This, in turn, reduces the fluorescence quantum yield and luminescence intensity of target pesticides, affecting the sensitivity of the detection results and significantly limiting their application in fluorescence sensing. Summary of the Invention

[0005] To address the technical problem that in existing rare earth metal-organic framework materials, rare earth metal ions have weak absorption of excitation light due to the Laporte rule-forbidden 4f-4f transition, resulting in low luminescence efficiency, which in turn reduces the fluorescence quantum yield and luminescence intensity of the target pesticide, thus affecting the sensitivity of the detection results, this invention provides a lanthanide metal-organic framework material, a fluorescence sensor, its preparation method, and its application in pesticide detection.

[0006] This invention utilizes an organic ligand with isomers and lanthanide metal ions to prepare lanthanide metal-organic framework materials via a solvothermal method. By effectively sensitizing the luminescence of lanthanide metal ions through the "antenna effect," the fluorescence quantum yield and luminescence intensity are improved, thereby enhancing the signal-to-noise ratio of the lanthanide metal-organic framework materials. The materials exhibit high sensitivity and accuracy in the detection of 2,6-dichloro-4-nitroaniline.

[0007] The technical concept of this invention is: in lanthanide metal-organic framework materials, sensitizing lanthanide metal ions (Ln) is achieved by rationally selecting organic ligands. 3+ Lanthanide metal ions are effectively sensitized through an "antenna effect," thereby significantly enhancing their luminescence performance. Specifically, when an organic ligand absorbs excitation light of an appropriate wavelength, it is excited from the ground state (S0) to the singlet state (S1). Then, according to Reinhoudt's rule of thumb, when the band gap (ΔE1) between S0 and S1 exceeds 5000 cm⁻¹... 1 At this time, the transition from S1 to the triplet state (T1) is more likely to occur (intersystem crossing, ISC). Furthermore, when T1 and Ln... 3+ The band gap (ΔE2) between excited ion states is greater than 3500 cm. 1 At this time, further energy transfer from T1 to lanthanide metal ions will be successfully achieved, thereby enabling sensitization of lanthanide metal ions through the "antenna effect" of organic ligands in lanthanide metal-organic framework materials.

[0008] To achieve the above objectives and inventive concept, the technical solution adopted by this invention is as follows: A method for preparing lanthanide metal-organic framework materials includes the following steps: Lanthanide metal-organic framework materials are obtained by using lanthanide metal salts and organic ligands as raw materials and then employing a solvothermal method; the organic ligands are 1,4-naphthalenedicarboxylic acid or 2,6-naphthalenedicarboxylic acid.

[0009] Further specified, the molar ratio of the lanthanide metal salt to the organic ligand is 2:(1-5).

[0010] Further specifying, the lanthanide metal salts contain lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, or lutetium.

[0011] To further define the specific process for obtaining lanthanide metal-organic framework materials using the solvothermal method, the process is as follows: lanthanide metal salts and organic ligands are dissolved in a solvent to carry out a coordination reaction; then cooled and dried to obtain the lanthanide metal-organic framework materials.

[0012] Further specifying, the solvent is one or more of dimethylacetamide, N,N-dimethylformamide, methanol, ethanol, and water.

[0013] Further specifying the conditions for the coordination reaction, the conditions are: temperature 100±10℃, time 12-72 hours.

[0014] A lanthanide metal-organic framework material, obtained by any of the preparation methods described herein.

[0015] A fluorescence sensor comprising the aforementioned lanthanide metal-organic framework material.

[0016] The application of the lanthanide metal-organic framework material or the fluorescence sensor described herein in pesticide detection.

[0017] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention uses two isomers (1,4-naphthalenedicarboxylic acid or 2,6-naphthalenedicarboxylic acid) to prepare lanthanide metal-organic framework materials via a solvothermal method with lanthanide metal salts. Both organic ligands can effectively sensitize Eu through the "antenna effect". 3+ The luminescence of ions enables the prepared lanthanide metal-organic framework materials to exhibit excellent red luminescence properties, demonstrating superior performance in fluorescence sensing for detecting pesticide pollutants.

[0018] 2. Through density functional theory calculations, this invention further demonstrates that 1,4-naphthalenedicarboxylic acid and 2,6-naphthalenedicarboxylic acid can effectively sensitize lanthanide metal ions. Furthermore, the emission spectra of the two lanthanide metal-organic framework materials were measured using fluorescence spectroscopy. The differences in their fluorescence intensity and the fluorescence quantum yield results are consistent with the density functional theory calculations, verifying the rationality of the material design.

[0019] 3. This invention further discusses the sensing performance of two lanthanide metal-organic framework materials for the pesticide 2,6-dichloro-4-nitroaniline through fluorescence sensing experiments. The results show that, at the same low concentration (10-60 μmol), the detection limits of the two lanthanide metal-organic framework materials for 2,6-dichloro-4-nitroaniline are between 4.430 μmol and 13.15 μmol, achieving efficient detection of low concentrations of 2,6-dichloro-4-nitroaniline.

[0020] 4. This invention selects 1,4-naphthoic acid and 2,6-naphthoic acid ligands with isomers, and reasonably adjusts the luminescence intensity and fluorescence quantum yield of the obtained lanthanide metal-organic framework material, thereby achieving higher sensitivity and lower detection limit for the pesticide 2,6-dichloro-4-nitroaniline. Attached Figure Description

[0021] Figure 1 This is the synthetic route for the lanthanide metal-organic framework material in Example 1; Figure 2 This is the synthetic route for the lanthanide metal-organic framework material in Example 2; Figure 3 These are morphology images of the lanthanide metal-organic framework materials in Examples 1 and 2; Figure 4 EDS images of the lanthanide metal-organic framework materials in Examples 1 and 2; Figure 5 X-ray diffraction and infrared spectra of the lanthanide metal-organic framework materials in Examples 1 and 2; Figure 6 For organic ligands 1,4-naphthalenedicarboxylic acid and 2,6-naphthalenedicarboxylic acid, the effect of Eu... 3+ Schematic diagram of ion antenna effect and excitation and emission spectra of lanthanide metal-organic framework materials in Examples 1 and 2; Figure 7 The results of the selectivity and anti-interference experiments of the lanthanide metal-organic framework materials in Examples 1 and 2 are as follows; Figure 8 The results are from the fluorescence titration experiments of the lanthanide metal-organic framework materials in Examples 1 and 2. Detailed Implementation

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this disclosure. Rather, they are merely examples of methods consistent with some aspects of the invention as detailed in the appended claims.

[0024] The terminology used in this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular forms “a,” “the,” and “the” used in this invention and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any and all possible combinations of one or more of the associated listed items.

[0025] In the description of this application, it should be understood that the numerical labels before the steps do not indicate the order of the steps, but are only used to facilitate the description of this application and to distinguish each step, and therefore should not be construed as a limitation of this application.

[0026] This invention discloses a method for preparing lanthanide metal-organic framework materials, comprising the following steps: Lanthanide metal-organic framework materials are obtained by using lanthanide metal salts and organic ligands as raw materials and then employing a solvothermal method; the organic ligands are 1,4-naphthalenedicarboxylic acid or 2,6-naphthalenedicarboxylic acid.

[0027] Preferably, in the lanthanide metal salt, the lanthanide metal is lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, or lutetium. The lanthanide metal salt is a nitrate.

[0028] The molar ratio of lanthanide metal salt to organic ligand is 2:(1-5). For example, the molar ratio of lanthanide metal salt to organic ligand is 2:1, 2:3 or 2:5.

[0029] The specific process of obtaining lanthanide metal-organic framework materials by the solvothermal method in this invention is as follows: lanthanide metal salts and organic ligands are dissolved in a solvent to carry out a coordination reaction; then cooled and dried to obtain lanthanide metal-organic framework materials.

[0030] Preferably, the solvent is one or more of dimethylacetamide, N,N-dimethylformamide, methanol, ethanol, and water. More preferably, the solvent is N,N-dimethylformamide.

[0031] Preferably, the conditions for the coordination reaction are: a temperature of 100±10℃ and a time of 12-72 hours.

[0032] The present invention also provides a lanthanide metal-organic framework material, which is obtained by the above preparation method.

[0033] The present invention also provides a fluorescence sensor comprising a lanthanide metal-organic framework material.

[0034] The present invention also provides an application of lanthanide metal-organic framework materials or fluorescent sensors, which is to realize the detection of pesticides using lanthanide metal-organic framework materials or fluorescent sensors.

[0035] The technical solutions protected by the present invention will be described below with several examples.

[0036] It should be noted that, unless otherwise specified, the chemicals, reagents and other raw materials used in the following examples are all analytical grade and purchased from the market.

[0037] It should be noted that, unless otherwise specified, the operations and detection methods used in the following embodiments are all conventional operations and detection methods in the field.

[0038] Example 1 See Figure 1 The lanthanide metal-organic framework material provided in this embodiment is prepared by the following steps: Lanthanide metal salt Eu(NO3)·6H2O (89.23 mg, 0.2 mmol) and organic ligand 1,4-naphthalenedicarboxylic acid (64.86 mg, 0.3 mmol) were dissolved in 6 mL of N,N-dimethylformamide (DMF), transferred to a stainless steel reactor with a polytetrafluoroethylene liner, and heated in an oven at 100 °C for 72 hours. After cooling to room temperature, colorless transparent crystals were collected and dried at room temperature. The resulting solid product was a lanthanide metal-organic framework material, named Eu-1,4-NDC.

[0039] Example 2 See Figure 2 The lanthanide metal-organic framework material provided in this embodiment is prepared by the following steps: Weigh out 44.8 mg (0.1 mmol) of lanthanide metal salt Eu(NO3)3·6H2O and 32.5 mg (0.15 mmol) of organic ligand 2,6-naphthalenedicarboxylic acid, and dissolve them in a mixed solution of N,N-dimethylformamide (4 mL), methanol (2 mL), and water (1 mL). Then, transfer the mixed solution to a stainless steel reactor lined with polytetrafluoroethylene and heat it in an oven to 95 °C for 12 hours. After naturally cooling to room temperature, collect the colorless, transparent crystals and allow them to dry naturally. The resulting solid product is the lanthanide metal-organic framework material, named Eu-2,6-NDC.

[0040] It should be noted that the lanthanide metal salt Eu(NO3)3·6H2O in Examples 1 and 2 above can be replaced with Tb(NO3)3·6H2O, Sm(NO3)3·6H2O, Nd(NO3)3·6H2O, La(NO3)3·6H2O or other lanthanide metal nitrates.

[0041] Example 3 The purpose of this embodiment is to provide a fluorescence sensor comprising the lanthanide metal-organic framework materials prepared in Examples 1 and 2.

[0042] Fluorescent sensors can be categorized into suspension-type sensors or thin-film solid-phase sensors. Suspension-type sensors disperse lanthanide metal-organic framework (Ln-MOF) powder in water, ultrasonically dispersed to create a homogeneous suspension, and are directly used for the detection of liquid-phase pesticide samples. Thin-film solid-phase sensors mix lanthanide metal-organic framework (Ln-MOF) powder with conventional membrane support materials, coat the mixture onto a glass slide, and are used for the detection of solid-phase pesticide samples.

[0043] Furthermore, the performance of the lanthanide metal-organic framework materials (Eu-1,4-NDC and Eu-2,6-NDC) prepared in Examples 1 and 2 was tested and studied through the following experiments.

[0044] Experiment 1: Scanning Electron Microscope Eu-1,4-NDC and Eu-2,6-NDC prepared in Examples 1 and 2 above were used as test samples. The morphology of the synthesized materials was studied using scanning electron microscopy images. The results... Figure 3 and Figure 4 As shown.

[0045] See Figure 3 In samples a and b, Eu-1,4-NDC exhibits a blocky morphology; elemental distribution analysis by energy dispersive spectroscopy shows that C, O, and Eu are uniformly distributed in the prepared Eu-1,4-NDC material. Figure 3 c).

[0046] Figure 4 In the images, a and b show that Eu-2,6-NDC is elongated in shape. Furthermore, elemental composition information was obtained using EDS images. For example... Figure 4 The elemental distribution of c in the energy scattering spectrometer shows that C, O, and Eu are uniformly distributed on the Eu-2,6-NDC surface.

[0047] Experiment 2: Powder X-ray diffraction and infrared spectroscopy Eu-1,4-NDC and Eu-2,6-NDC prepared in Examples 1 and 2 above were used as test samples, and their powder X-ray diffraction and infrared spectra were measured respectively. The results are as follows: Figure 5 As shown.

[0048] Figure 5 a and Figure 5 Powder X-ray diffraction patterns of Eu-1,4-NDC and Eu-2,6-NDC were measured. The results showed that the prepared Eu-1,4-NDC and Eu-2,6-NDC exhibited good agreement with the simulated diffraction peaks, indicating that the prepared Eu-1,4-NDC and Eu-2,6-NDC materials possessed good phase purity. Figure 5 As shown in b, the infrared spectra of the organic ligands 1,4-H2NDC and Eu-1,4-NDC were measured. Compared with the organic ligand at 1663 cm⁻¹, the infrared spectra of the organic ligands are significantly different. -1 The C=O stretching vibration peak at [location missing], and the C=O stretching vibration peak of Eu-1,4-NDC shift to a lower wavenumber of 1652 cm⁻¹. -1 This is attributed to the coordination of Eu with -COOH. For example... Figure 5 As shown in d, compared to organic ligands at 1691 cm⁻¹ -1 The C=O stretching vibration peak at Eu-2,6-NDC shifted to 1683 cm⁻¹. -1 This indicates that the carboxylic acid of the organic ligand reacts with Eu. 3+ Coordination bonds were successfully formed between the metal centers.

[0049] Based on the combined results of scanning electron microscopy, powder X-ray diffraction, and infrared spectroscopy characterization, it is shown that materials Eu-1,4-NDC and Eu-2,6-NDC were successfully prepared.

[0050] Experiment 3: Study on the luminescent properties of Eu-1,4-NDC and Eu-2,6-NDC materials Density functional theory was used to calculate the pairings of two organic ligands with Eu. 3+ The "antenna effect" of ions, the result is as follows Figure 6 As shown.

[0051] like Figure 6 As shown in figure a, the singlet state S1 of the organic ligands 1,4-naphthalenedicarboxylic acid (1,4-NDC) and 2,6-naphthalenedicarboxylic acid (2,6-NDC) are 32654 cm⁻¹, respectively. 1 and 32068 cm 1 The triplet T1 values ​​are 20866 cm⁻¹. 1 and 20900 cm 1Therefore, in Eu-1,4-NDC, the values ​​of ΔE1 and ΔE2 are calculated to be 11788 cm⁻¹. 1 (>5000 cm) 1 ) and 3566 cm 1 (>3500 cm) 1 The values ​​of ΔE1 and ΔE2 in Eu-2,6-NDC are calculated to be 11168 cm. 1 (>5000 cm) 1 ) and 3600 cm 1 (>3500 cm) 1 This demonstrates that the energy of the organic ligands 1,4-naphthalenedicarboxylic acid and 2,6-naphthalenedicarboxylic acid can be transferred to Eu. 3+ Ions, thereby achieving Eu 3+ Effective sensitization of ions. This result was further confirmed by the fluorescence emission spectra of Eu-1,4-NDC and Eu-2,6-NDC ( Figure 6 b and Figure 6 c) has been verified.

[0052] Eu-1,4-NDC and Eu-2,6-NDC prepared in Examples 1 and 2 above were used as test samples, and fluorescence spectroscopy and fluorescence quantum yield were measured respectively. Figure 6 As shown in b, the fluorescence spectrometry results of Eu-1,4-NDC at the optimal excitation wavelength of 340 nm were obtained. 3+ The characteristic emission peaks of the ion at 593 nm, 617 nm, and 652 nm correspond to Eu, respectively. 3+ Ionic 5 D0→ 7 F J (J=1, 2, 3) transition. For example... Figure 6 As shown in c, Eu-2,6-NDC at the optimal excitation wavelength of 358 nm, Eu 3+ The characteristic emission peaks of the ion at 594 nm, 617 nm, 653 nm, and 701 nm correspond to Eu, respectively. 3+ Ionic 5 D0→ 7 F J(J=1, 2, 3, 4) transitions. Based on the fluorescence intensities of Eu-1,4-NDC and Eu-2,6-NDC at 617 nm (6329 and 5536 respectively, both being the strongest emission peaks), this invention selected these characteristic peaks as the sensing signal monitoring index. Furthermore, the fluorescence quantum yields of Eu-1,4-NDC and Eu-2,6-NDC were measured to be 3.84% and 1.31%, respectively.

[0053] Experiment 3: Fluorescence sensing study of the pesticide 2,6-dichloro-4-nitroaniline using Eu-1,4-NDC and Eu-2,6-NDC materials. The Eu-1,4-NDC and Eu-2,6-NDC prepared in Examples 1 and 2 above were used as test samples, and fluorescence sensing experiments were performed respectively. The results are as follows: Figure 7 and 8 As shown.

[0054] The specific procedures for the selectivity and anti-interference experiments are as follows: Before fluorescence testing, the Eu-1,4-NDC or Eu-2,6-NDC (10.00 mg) sample prepared above was dispersed in 10 mL of ethanol and sonicated for 30 minutes to prepare a 1 mg / mL Eu-1,4-NDC or Eu-2,6-NDC suspension. The sensing experiment involved adding 2 mL of Eu-1,4-NDC or Eu-2,6-NDC suspension to a quartz cuvette at room temperature. Then, 1 mL of a 400 μmol / L pesticide solution (thiamethoxam, TMX; carbendazim, CBZ; glyphosate, GLY; thiabendazim, TBZ; atrazine, ATZ; quinclorac, QNC; fipronil, FIP; dinotefuran, DNF; chlorpyrifos, DCN) was added, and the mixture was thoroughly mixed. The changes in fluorescence emission intensity were recorded at an excitation wavelength of 340 nm or 358 nm to study the selectivity of Eu-1,4-NDC and Eu-2,6-NDC. Figure 7 a and Figure 7 As shown in c, the results indicate that both Eu-1,4-NDC and Eu-2,6-NDC exhibit good selectivity for the detection of the pesticide 2,6-dichloro-4-nitroaniline.

[0055] In addition, to evaluate the anti-interference ability of lanthanide metal-organic framework materials in detecting the pesticide 2,6-dichloro-4-nitroaniline, the changes in fluorescence intensity before and after the addition of eight other pesticides and 2,6-dichloro-4-nitroaniline to Eu-1,4-NDC and Eu-2,6-NDC were measured. Figure 7 b and Figure 7The experimental data from d show that even with interference from other pesticides, the recognition of the target analyte 2,6-dichloro-4-nitroaniline by the prepared Eu-1,4-NDC and Eu-2,6-NDC is not affected, which strongly demonstrates that Eu-1,4-NDC and Eu-2,6-NDC have good anti-interference ability.

[0056] To systematically evaluate the detection sensitivity of Eu-1,4-NDC and Eu-2,6-NDC for the pesticide 2,6-dichloro-4-nitroaniline, a fluorescence titration experiment was performed. The results are shown in [reference needed]. Figure 8 .

[0057] like Figure 8 As shown in (a) and (c), the fluorescence intensity of Eu-1,4-NDC and Eu-2,6-NDC gradually decreased with increasing concentration of the pesticide 2,6-dichloro-4-nitroaniline.

[0058] Using the Stern-Volmer equation (I0 / I = K) SV [M] + 1) The relationship between the concentration of 2,6-dichloro-4-nitroaniline and the emission peak intensity of Eu-1,4-NDC was further discussed. The fluorescence intensity of the Eu-1,4-NDC suspension without the addition of 2,6-dichloro-4-nitroaniline was the blank sample, and its fluorescence intensity was recorded as I0.

[0059] In the Stern-Volmer equation: I0 is the fluorescence intensity, I is the fluorescence intensity of the Eu-1,4-NDC suspension after the addition of 2,6-dichloro-4-nitroaniline; K SV The quenching constant (M) -1 [M] represents the concentration of 2,6-dichloro-4-nitroaniline.

[0060] The experimental data analysis results show that: (1) See Figure 8 (b) In the range of 10–60 μmol / L, I0 / I⁻¹ showed a linear relationship with DCN concentration: I0 / I = 0.01701 × [M] + 1 (linear fitting correlation coefficient R₀). 2 =0.995, K SV =1.701×10 4 M -1 (Standard deviation SD = 0.02512). Based on the formula LOD = 3SD / K SV The calculated detection limit is 4.430 μmol / L.

[0061] (2) See Figure 8(d) In the low concentration range of 10–60 μmol / L, the linear fit between I0 / I⁻¹ of Eu⁻²,⁶-NDC and the DCN concentration is I0 / I = 0.01904 × [M] + 1 (linear fit correlation coefficient R₀). 2 =0.958, K SV =1.904×10 4 M -1 (Standard deviation SD = 0.08347), the detection limit was calculated to be 13.15 μmol / L.

[0062] Fluorescence sensing results showed that, at the same low concentration, both Eu-1,4-NDC and Eu-2,6-NDC had low limits of detection for 2,6-dichloro-4-nitroaniline, with Eu-1,4-NDC having a limit of detection that was nearly 2.968 times smaller than that of Eu-2,6-NDC.

[0063] Furthermore, by comparing the detection limits of existing metal-organic framework materials (fluorescent MOF materials) for the pesticide 2,6-dichloro-4-nitroaniline (see Table 1), the advantages of the fluorescence sensing of the present invention in pesticide detection are demonstrated.

[0064] Table 1. Detection limits of fluorescent MOF materials for the pesticide 2,6-dichloro-4-nitroaniline. The comparison shows that, through the rational selection of organic ligands, the present invention can effectively enhance the fluorescence intensity and fluorescence quantum yield of lanthanide metal-organic framework materials, thereby improving the sensitivity and accuracy of the sensor for 2,6-dichloro-4-nitroaniline.

[0065] It should be noted that the above performance tests were performed using the lanthanide metal-organic framework materials prepared in Examples 1 and 2 as the subjects. When the lanthanide metal salts (Eu(NO3)3·6H2O) in Examples 1 and 2 are replaced with other lanthanide metals, the resulting lanthanide metal-organic framework materials exhibit the same performance. By utilizing the "antenna effect" of organic ligands in the lanthanide metal-organic framework materials, the sensitization of lanthanide metal ions is achieved, thereby improving the fluorescence quantum yield and fluorescence intensity, and realizing the high-sensitivity detection of the pesticide 2,6-dichloro-4-nitroaniline.

[0066] The above embodiments are merely illustrative examples of the implementation of the technical solution of the present invention. The experiments described above are merely illustrative. Any situation that can be understood and implemented by those skilled in the art without creative effort is within the scope of the technical concept of the present invention.

Claims

1. A method for preparing a lanthanide metal-organic framework material, characterized in that, Includes the following steps: Lanthanide metal-organic framework materials are obtained by using lanthanide metal salts and organic ligands as raw materials and then employing a solvothermal method; the organic ligands are 1,4-naphthalenedicarboxylic acid or 2,6-naphthalenedicarboxylic acid.

2. The method for preparing lanthanide metal-organic framework materials according to claim 1, characterized in that, The molar ratio of the lanthanide metal salt to the organic ligand is 2:(1-5).

3. The method for preparing lanthanide metal-organic framework materials according to claim 1, characterized in that, In the lanthanide metal salts, the lanthanide metals are lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, or lutetium.

4. The method for preparing lanthanide metal-organic framework materials according to claim 1, characterized in that, The specific process for obtaining lanthanide metal-organic framework materials using the solvothermal method is as follows: lanthanide metal salts and organic ligands are dissolved in a solvent to carry out a coordination reaction; then cooled and dried to obtain the lanthanide metal-organic framework materials.

5. The method for preparing lanthanide metal-organic framework materials according to claim 4, characterized in that, The solvent is one or more of dimethylacetamide, N,N-dimethylformamide, methanol, ethanol, and water.

6. The method for preparing lanthanide metal-organic framework materials according to claim 4, characterized in that, The conditions for the coordination reaction are: temperature 100±10℃ and time 12-72 hours.

7. A lanthanide metal-organic framework material, characterized in that, Obtained by the preparation method described in any one of claims 1-6.

8. A fluorescence sensor, characterized in that, It includes the lanthanide metal-organic framework material as described in claim 7.

9. The application of the lanthanide metal-organic framework material of claim 6 or the fluorescence sensor of claim 7 in pesticide detection.

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