Europium-based metal-organic framework and preparation method and application thereof

Abstract

The invention discloses a europium-based metal-organic framework as well as a preparation method and application thereof, and belongs to the technical field of bioassay materials. The preparation method of the europium-based metal-organic framework comprises the following steps: adding europium salt, H4BTA-2OH and ascorbic acid into a binary solution, and sequentially performing ultrasonic treatment, heating and post-treatment to prepare the europium-based metal-organic framework (the molecular formula is {[(CH3) 2NH2] [Eu (BTA-2OH) (H2O) 2]. 4H2O} n). In addition, the invention also discloses an application of the europium-based metal-organic framework in detection of a bacillus anthracis biomarker 2, 6-dipicolinic acid (DPA). The europium-based metal-organic framework Eu-MOF prepared by the method can rapidly detect 2, 6-dipicolinic acid, and has high selectivity and sensitivity, and the excellent fluorescence sensing ability means that the europium-based metal-organic framework Eu-MOF is a potential bacillus anthracis detection material.

Description

Technical Field

[0001] The present invention belongs to the technical field of biometric materials, and particularly relates to a europium-based metal-organic framework and a preparation method and application thereof. Background Art

[0002] Metal-organic frameworks (MOFs) are composed of metal ions / clusters and organic ligands, and have adjustable porous channels, high specific surface areas, and diverse luminescent properties. Therefore, they have wide applications in fields such as gas absorption and separation, magnetic materials, catalysis, conductivity, and fluorescence sensing. Considering that rare earth ions have large Stokes shifts, obvious sharp emissions, and long fluorescence lifetimes, in recent years, rare earth metal-organic frameworks have been widely developed in the sensing field.

[0003] Bacillus anthracis is a bacterium formed by spores and is a microorganism that can cause great harm to both humans and animals. When humans inhale more than 10 4 Bacillus anthracis spores within 24 - 48 hours without effective treatment, serious consequences may occur, even death. 2,6-Pyridinedicarboxylic acid (DPA) accounts for 5 - 15% of the dry mass of bacterial spores and is a unique and specific anthrax biomarker. Therefore, it is imperative to identify germinating spores through efficient and accurate detection methods. So far, a large number of researchers have carried out quantitative analysis on DPA, including high-performance liquid chromatography (HPLC), electrochemical techniques, and surface-enhanced Raman spectroscopy (SERS), etc. However, these quantitative analysis techniques still heavily rely on complex equipment and professional personnel.

[0004] Fluorescence sensing technology has attracted much attention due to its rapid response, easy operation, portability, and high sensitivity. Among many fluorescence sensing technologies, sensors based on metal-organic frameworks (MOF) are particularly prominent, and they usually exhibit excellent sensitivity, selectivity, and repeatability. These excellent properties benefit from the special optical properties of MOF materials, such as sharp emission peaks, long fluorescence lifetimes, and significant Stokes shifts. Especially the development of ratio fluorescence sensing technology, through a self-calibration mechanism, can effectively reduce or eliminate the influence brought by concentration changes, environmental factors, and instrument errors, thereby further improving the accuracy and reliability of detection results. Therefore, this technology is attracting more and more research interest. However, preparing MOF materials with excellent luminescent properties and water stability is still a major challenge.

[0005] Therefore, how to obtain an MOF material with both excellent luminescent properties and water stability to accurately and rapidly detect Bacillus anthracis is a technical problem that needs to be urgently solved by those skilled in the art. Summary of the Invention

[0006] In view of the above technical problems, the present invention provides a europium-based metal-organic framework and its preparation method and application.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] One of the technical solutions of the present invention:

[0009] A preparation method of a europium-based metal-organic framework, comprising the following steps:

[0010] Adding europium salt, H4BTA-2OH and ascorbic acid into a binary solution, and successively performing ultrasonic treatment, heating and post-treatment to prepare a europium-based metal-organic framework (molecular formula {[(CH3)2NH2][Eu(BTA-2OH)(H2O)2]·4H2O} n , simplified as Eu-MOF); wherein, the value of n is not limited, because the degree of polymerization of the europium-based metal-organic framework in the present invention is determined by the specific preparation process and has uncertainty. The europium-based metal-organic framework obtained in the present invention is a mixture, and the value of n can be any value, and its specific numerical range has no influence on the product properties.

[0011] Optionally, the europium salt is Eu(NO3)3·6H2O.

[0012] Optionally, the dosage ratio of Eu(NO3)3·6H2O, H4BTA-2OH, ascorbic acid and the binary solution is: 0.0336 mmol: 0.0254 mmol: 0.25 mmol: 6 mL.

[0013] Optionally, the binary solution is composed of N,N-dimethylformamide (DMF) and deionized water.

[0014] Further, the volume ratio of N,N-dimethylformamide (DMF) to deionized water is 1:1.

[0015] Beneficial effects: The DMF and water solvents used in the synthesis of the present invention are relatively environmentally friendly, and the yield of the prepared europium-based metal-organic framework is as high as 32.5%. Its structure is a single crystal tested by X-ray single crystal.

[0016] Optionally, the time of ultrasonic treatment is 40 min and the ultrasonic power is 360 W.

[0017] Optionally, the conditions during the heating process are: heating at 140 °C for 3 d.

[0018] Optionally, the post-treatment includes cooling, washing and air drying.

[0019] Further, the cooling process is: cooling to room temperature at a rate of 3.1 °C / h.

[0020] The second technical solution of the present invention:

[0021] A europium-based metal-organic framework is prepared by the above preparation method.

[0022] Beneficial effects: The europium-based metal-organic framework synthesized by the present invention has a new three-dimensional structure with mononuclear Eu as the node, where the Eu ion is ten-coordinated (as Figure 1 shown). This structure has good stability and can remain stable below 395 °C and within a pH range of 2-11, and has visible light emission characteristics.

[0023] The third technical solution of the present invention:

[0024] Application of the above-mentioned europium-based metal-organic framework in fluorescence detection of anthrax bacillus marker 2,6-pyridinedicarboxylic acid.

[0025] Optionally, the process of fluorescence detection of anthrax bacillus marker 2,6-pyridinedicarboxylic acid is as follows:

[0026] Grind the above-mentioned europium-based metal-organic framework and prepare it into a suspension, and detect anthrax bacillus marker 2,6-pyridinedicarboxylic acid by fluorescence titration.

[0027] Further, the concentration of the suspension is 0.5 mg / mL.

[0028] Further, the lowest detection limit of the europium-based metal-organic framework for 2,6-pyridinedicarboxylic acid is 0.032 μM.

[0029] Compared with the prior art, the present invention has the following advantages and technical effects:

[0030] The lowest detection limit of the europium-based metal-organic framework prepared by the method of the present invention for 2,6-pyridinedicarboxylic acid reaches 0.032 μM ( Figure 6 in (c)), and at the same time has good anti-interference performance and can be reused at least 8 times. That is, the europium-based metal-organic framework Eu-MOF prepared by the preparation method of the present invention can quickly detect 2,6-pyridinedicarboxylic acid, and has high selectivity and sensitivity. Its excellent fluorescence sensing ability means that it is a potential material for detecting anthrax bacillus. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0032] Figure 1 It is the structure diagram of Eu-MOF obtained in Example 1;

[0033] Among them, (a) is the coordination environment diagram of Eu in Eu-MOF; III (b) is the spatial configuration diagram of Eu in Eu-MOF; (c) is the three-dimensional structure view of Eu-MOF; III

[0034] Figure 2 are the infrared spectra of Eu-MOF and H4BTA-2OH obtained in Example 1;

[0035] Figure 3 are the X-ray powder diffraction patterns of Eu-MOF obtained in Example 1;

[0036] Figure 4 are the PXRD spectra of the solvent stability (a) and pH stability (b) of Eu-MOF obtained in Example 1;

[0037] Figure 5 is the TGA diagram of Eu-MOF obtained in Example 1;

[0038] Figure 6 are the emission spectra (a) of adding different analytes to the Eu-MOF suspension obtained in Example 1, the emission spectra (b) in DPA with different concentrations (the concentration of DPA is 0, 20, 40, 80, 100, 120, 140, 160, 180, 200, 220, 240 μM), and the relationship between the ratio of I 419 / I 618 and the concentration (c);

[0039] Figure 7 is the cyclic experiment diagram of detecting DPA by Eu-MOF obtained in Example 1. Detailed implementation manners

[0040] Now, various exemplary implementation manners of the present invention will be described in detail. This detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention.

[0041] It should be understood that the terms described in the present invention are only for describing specific implementation manners and are not used to limit the present invention. In addition, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0042] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Although this invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of this invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the said documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0043] Without departing from the scope or spirit of this invention, various modifications and variations can be made to the specific embodiments of the description of this invention, which are obvious to those skilled in the art. Other embodiments obtained from the description of this invention are obvious to those skilled in the art. The description and examples of this invention are merely exemplary.

[0044] Regarding the use of "comprising", "including", "having", "containing", etc. herein, they are all open-ended terms, meaning including but not limited to.

[0045] An embodiment of this invention discloses a preparation method of an europium-based metal-organic framework, which includes the following steps:

[0046] Mix Eu(NO3)3·6H2O, H4BTA-2OH, ascorbic acid and a binary solution, after ultrasonic treatment, then heat and post-treat to obtain an europium-based metal-organic framework, denoted as Eu-MOF.

[0047] In some alternative embodiments, the binary solution is composed of N,N-dimethylformamide (DMF) and deionized water, where the volume ratio of DMF to water is 1:1.

[0048] In some alternative embodiments, the ultrasonic treatment time is 40 min and the ultrasonic power is 360 W.

[0049] In some alternative embodiments, the conditions during the heating process are: the heating temperature is 140 °C and the heating time is 3 d.

[0050] In some alternative embodiments, the dosage ratio of Eu(NO3)3·6H2O, H4BTA-2OH, ascorbic acid and the binary solution is: 0.0336 mmol: 0.0254 mmol: 0.25 mmol: 6 mL.

[0051] In some alternative embodiments, the post-treatment includes cooling, washing and air-drying.

[0052] An embodiment of this invention also discloses an europium-based metal-organic framework prepared by the above preparation method and its application in fluorescence detection of the anthrax bacillus marker 2,6-pyridinedicarboxylic acid.

[0053] The "room temperature" in the present invention refers to 20-30°C unless otherwise specified.

[0054] The raw materials used in the present invention are all purchased from the market. Among them, H4BTA-2OH was purchased from Jilin Zhongkexun Company, and the chemical formula is C 34 H 22 O 10 ; Ascorbic acid was purchased from Anaiji Chemical Reagent Company.

[0055] The technical solution of the present invention is further illustrated by the following embodiments.

[0056] Example 1

[0057] A method for preparing a europium-based metal-organic framework comprises the following steps:

[0058] Eu(NO3)3·6H2O (15 mg, 0.0336 mmol), H4BTA-2OH (15 mg, 0.0254 mmol), ascorbic acid (44 mg, 0.25 mmol) and 6 mL of a binary solution of (DMF) and deionized water (V / V=1:1) were mixed and placed in a 25 mL polytetrafluoroethylene stainless steel reactor; ultrasonic treatment was performed at 360 W ultrasonic power for 40 min, and then the mixture was heated at 140°C for 3 days, and then cooled to room temperature at a rate of 3.1°C / h, and then cooled, washed and air-dried to obtain colorless crystals (the yield based on H4BTA-2OH was 32.5%).

[0059] TGA and elemental analysis results: IR (KBr, cm -1 ):3739(w),3614(w),3525(w),3442(w),3332(s),3211(s),1656(s),1584(s),1532(s),1461(w),1411(vs),1253(w),11 99(w)1174(w),1105(w),1075(w),1015(w),852(s),806(s),779(s),759(s),708(s),668(w),517(w),419(w).Elemental analysis(%)calcd for Eu-MOF: C, 50.43; H, 3.97; O, 26.15; N, 1.63. Found: C, 44.404; H, 3.83; O, 20.478; N, 2.818.

[0060] The chemical composition of the europium-based metal-organic framework prepared in the final Example 1 is {[(CH3)2NH2][Eu(BTA-2OH)(H2O)2]·4H2O} n .

[0061] Effect verification

[0062] I. Structural property characterization: The crystal structure of the europium-based metal-organic framework was obtained by X-ray single crystal diffraction technology, and its luminescence properties were detected by infrared, thermogravimetric analysis and spectrometers.

[0063] II. High-efficiency fluorescence detection: The europium-based metal-organic framework synthesized in Example 1 was ground and formulated into a suspension of 0.5 mg / mL. The fluorescence titration test showed that it had a rapid fluorescence detection effect on the anthrax bacillus marker 2,6-pyridinedicarboxylic acid.

[0064] Technical effects

[0065] 1. Detection effect of Eu-MOF on DPA

[0066] In the test, by adding DPA solution to the homogeneous dispersion of Eu-MOF, the sensitivity of Eu-MOF to DPA was deeply studied. After adding DPA, the emission intensity ratio of I 419 / Eu-MOF increased significantly, and the apparent fluorescence color changed from red to blue (as Figure 6 shown in (a)). In the range of 0-220 μM, the luminescence ratio of Eu-MOF showed an ideal linear relationship with the concentration of DPA (as Figure 6 shown in (c)); the LODs (limits of detection) of Eu-MOF were not only significantly lower than the infection dose of endotoxin to the human body, but also better than most reported DPA sensors based on RE-MOF. Therefore, the Eu-MOF prepared in Example 1 of the present invention is an important self-calibrating luminescence sensor that can quickly, conveniently and reliably identify DPA.

[0067] 2. Next, the practical application of Eu-MOF in detecting DPA was explored, demonstrating the potential of Eu-MOF to quickly, directly and truly detect DPA.

[0068] 2-1. Performance characterization:

[0069] Crystal structure:

[0070] The crystal structure of Eu-MOF was characterized by single crystal x-ray diffraction analysis. From Figure 3 it can be seen that Eu-MOF crystallizes in the monoclinic P2 / c space group.

[0071] Figure 1The structural diagram of Eu-MOF obtained in Example 1; among them, (a) is the coordination environment diagram of Eu in Eu-MOF III ; (b) is the spatial configuration diagram of Eu in Eu-MOF III ; (c) is the three-dimensional structure view of Eu-MOF; it can be seen from Figure 1 that the asymmetric unit of Eu-MOF consists of a crystallographically independent Eu(III) ion, a BTA-2OH ligand, two coordinated water molecules, a [(CH3)2NH2] + cation and four lattice water molecules. The Eu(III) ion is coordinated by four carboxylate groups, and these four carboxylate groups come from 4 ligands and two coordinated water molecules. A tetrahedron is constructed according to shape calculation, and the continuous shape measurement (CShM) value is 3.744. The four-site linker of the H4BTA-2OH ligand is completely deprotonated, and the coordination mode of μ 4 -η 1 :η 1 :η 1 :η1:η 1 :η 1 :η 1 :η 1 is adopted. The Eu-O bond lengths are in the normal range between 2.448(5) Å and 2.580(6) Å. Adjacent Eu(III) ions are connected to each other through the carboxylate groups of the H4BTA-2OH ligand to form a two-dimensional layer parallel to the ab plane. The lattice water molecules are located inside the pores and participate in the formation of hydrogen bonds, and the [(CH3)2NH2] + cation is further connected by extensive hydrogen bonds with coordinated water molecules, lattice water molecules, phenolic hydroxyl groups and carboxylate oxygen atoms (O3W-H3WA···O6, O3W-H3WA···O1, O3W-H3WB···O6, O3-H3···O7, O4-H4···O8, O7-H7A···O8, O7-H7B···O3, O8-H8A···O3W, O8-H8B···O2), forming a three-dimensional supramolecular network along the c direction. In Eu-MOF, the porosity of the open channels is about 17.8%.

[0072] Figure 2 are the infrared spectra of Eu-MOF and H4BTA-2OH obtained in Example 1. It can be seen from Figure 2 that the vibration bands of Eu-MOF are significantly different from those of H4BTA-2OH, indicating the synergy between Eu-MOF and H4BTA-2OH.

[0073] Figure 3 is the X-ray powder diffraction pattern of Eu-MOF obtained in Example 1; as Figure 3As shown, the simulated diffraction peaks of Eu-MOF are consistent with the measured X-ray diffraction peaks, indicating that Eu-MOF is a pure phase.

[0074] Figure 4 PXRD spectra of the Eu-MOF obtained in Example 1 for solvent stability (a) and pH stability (b); as Figure 4 shown in (a), the XRD spectra of the Eu-MOF prepared in Example 1 after soaking in different solvents for 24 h are in agreement with the simulation results, indicating that the compound has high stability in common solvents.

[0075] In addition, to study the stability of Eu-MOF under different acid-base conditions, the XRD spectra of its powder after soaking in different acid-base solutions for 24 h were analyzed. The results are as Figure 4 shown in (b). It can be seen that the Eu-MOF obtained in Example 1 is stable in the pH range of 2 - 13. Therefore, Eu-MOF has high stability under ordinary solvents and acid-base conditions.

[0076] 2-2. Thermogravimetric test:

[0077] Thermogravimetric analysis (TGA) of Eu-MOF was carried out to study the thermal stability of Eu-MOF under a nitrogen atmosphere. Figure 5 The TGA diagram of the Eu-MOF obtained in Example 1 is shown. As Figure 5 can be seen from it, the weight loss of Eu-MOF is divided into three stages. The first weight loss occurs at about 139 °C, corresponding to the removal of four lattice water molecules (the measured weight loss is 8.7%, and the calculated value is 8.4%). The second weight loss occurs between 139 °C and 345 °C, corresponding to the removal of two coordinated water molecules (the measured weight loss is 4.3%, and the calculated value is 4.2%). The organic framework remains stable before 395 °C, indicating that the europium metal-organic framework (Eu-MOF) has good thermal stability, laying a solid foundation for future research on water-assisted proton conduction.

[0078] 2-3. Detection of DPA

[0079] Specifically, it includes the following steps:

[0080] Figure 6 Emission spectra (a) of adding different analytes to the Eu-MOF suspension obtained in Example 1, emission spectra (b) in different concentrations of DPA, and the relationship between the ratio of I 419 / I 618 and concentration at different concentrations (c);

[0081] As Figure 6As shown in (a), 5 μL of different analytes with a concentration of 0.2 mol / L were added. After adding potential interfering substances, it was found that in 2 mL Eu-MOF suspension, after adding 5 μL of DPA with a concentration of 0.2 mol / L, the fluorescence intensity at 618 nm decreased significantly, while the fluorescence intensity did not change much in other cases. By monitoring the fluorescence intensity ratio (I 419 / I 618 ), indicating that it has significant potential in sensing DPA. Anti-interference experiments also show that it has good selectivity, anti-interference ability and relatively fast response (~3min) to DPA.

[0082] like Figure 6 As shown in (b), in-depth sensitivity study found that after adding DPA, the I 419 / I 618 The luminescence ratio increased significantly, and the luminescence ratio was linearly related to the DPA concentration.

[0083] like Figure 6 As shown in (c), by different concentrations of I 419 / I 618 The relationship between the ratio and concentration was fitted to obtain the lowest detection limit of 0.032 μM. The LOD (limit of detection) of Eu-MOF was much lower than the infectious dose of bacterial endotoxins to the human body, which is better than most DPA sensors based on RE-MOF.

[0084] Figure 7 This is a cyclic experimental diagram of the Eu-MOF obtained in Example 1 for detecting DPA. It can be seen from the figure that after detecting DPA, the Eu-MOF is recovered by centrifugation, washed with ethanol and dried. After 8 detection cycles, the luminescence intensity remains almost unchanged, and the recyclability and stability are ideal.

[0085] The above are only preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for preparing a europium-based metal-organic framework, characterized in that: The following steps are involved: Europium salt, H4BTA-2OH and ascorbic acid are added to a binary solution, and ultrasonic treatment and hydrothermal reaction are performed in sequence to prepare a europium-based metal-organic framework.

2. The method for preparing a europium-based metal-organic framework according to claim 1, characterized in that: The europium salt is Eu(NO3)3·6H2O.

3. The method for preparing a europium-based metal-organic framework according to claim 2, characterized in that: The usage ratio of Eu(NO3)3·6H2O, H4BTA-2OH, ascorbic acid and binary solution is: 0.0336mmol:0.0254mmol:0.25mmol:6mL.

4. The method for preparing a europium-based metal-organic framework according to claim 3, characterized in that: The binary solution consists of N,N-dimethylformamide and water.

5. The method for preparing a europium-based metal-organic framework according to claim 1, characterized in that: The ultrasonic treatment time was 40 min, and the ultrasonic power was 360 W.

6. The method for preparing a europium-based metal-organic framework according to claim 1, characterized in that: The temperature of the hydrothermal reaction is 140° C. and the time is 3 days.

7. A europium-based metal-organic framework, characterized in that The invention is prepared by the preparation method according to any one of claims 1 to 6.

8. Use of the europium-based metal-organic framework as claimed in claim 7 in fluorescent detection of anthrax Bacillus marker 2,6-pyridinedicarboxylic acid.

9. The use of the europium-based metal-organic framework according to claim 8 in fluorescent detection of anthrax Bacillus marker 2,6-pyridinedicarboxylic acid, characterized in that: The process of fluorescent detection of anthrax bacillus marker 2,6-pyridinedicarboxylic acid is as follows: The europium-based metal-organic framework is ground and prepared into a suspension, and the anthrax Bacillus marker 2,6-pyridinedicarboxylic acid is detected by fluorescence titration.

10. The use of the europium-based metal-organic framework according to claim 8 in fluorescent detection of anthrax Bacillus marker 2,6-pyridinedicarboxylic acid, characterized in that: The minimum detection limit of the europium-based metal-organic framework for 2,6-pyridinedicarboxylic acid is 0.032 μM.

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