A fluorescent Mn-MOF material based on T-type tricarboxylic acid ligand and its preparation method and application

Abstract

The present invention discloses a fluorescent Mn-MOF material based on a T-type tricarboxylic acid ligand, a preparation method and an application thereof. The molecular formula of the fluorescent Mn-MOF material is [(CH3CH2)2NH2][Mn3(HL)(L)(A C )2], the three-dimensional structure of the fluorescent Mn-MOF material includes a one-dimensional spiral metal manganese chain unit, on the same plane, the one-dimensional spiral metal manganese chain units are connected by completely removing the ligands of the hydrogen atoms on the three carboxyl groups to form a layered structure, and the layered structures are connected by removing the ligands of the hydrogen atoms on the two carboxyl groups, and the above connection mode is infinitely extended in the spatial structure to form a three-dimensional porous network structure, in which the uncoordinated terminal carboxylic acid is suspended in the 1D rectangular channel of the network structure. The fluorescent Mn-MOF material can be used in the field of temperature sensing.

Description

Technical Field

[0001] The invention belongs to the technical field of MOF material fluorescence temperature sensing, and specifically relates to a fluorescent Mn-MOF material based on a T-type tricarboxylic acid ligand, and a preparation method and application thereof. Background Art

[0002] Metal-organic frameworks (MOFs), as a new type of porous crystalline material, have attracted widespread attention due to their tunable structure and multi-field applications. In recent years, researchers have focused on studying the "on" or "off" phenomenon of fluorescence through the luminescence properties of different MOFs materials. Among them, one of the main luminescence sources of transition metal-based MOFs materials is the ligand emission center, mainly because the metal center and the organic ligand self-assemble through coordination bonds to reduce the free torsion between the benzene rings in the organic ligands and improve the rigidity of the MOF framework. The rigidity of the MOF structure reduces the non-radiative energy consumption in the solid state, so that the obtained MOF can form a luminescent system and even improve its fluorescence performance and quantum yield. However, the rational design of MOFs materials based on ligand emission centers remains a huge challenge.

[0003] At present, fluorescence temperature measurement, as a new temperature detection technology, has attracted widespread attention for its advantages such as high sensitivity, fast response speed, strong anti-interference ability, and non-contact measurement. Among them, fluorescent MOF materials have unique framework structures and luminescence performance advantages, especially rich luminescence sites, wide emission wavelength range, adjustable structure, and easy functional modification. Therefore, the relationship between the fluorescence intensity ratio and temperature in the MOF structure is used to detect temperature, which provides a broad development space and prospect for the design and development of intelligent fluorescent temperature sensing materials in the future. However, the existing technology lacks the design and construction of fluorescent Mn-MOFs with ligand emission centers to achieve accurate sensing of a wide temperature range. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention provides a fluorescent Mn-MOF material based on T-type tricarboxylic acid ligands and a preparation method and application thereof.

[0005] The present invention is achieved through the following technical solutions:

[0006] A fluorescent Mn-MOF material based on a T-type tricarboxylic acid ligand, wherein the molecular formula of the fluorescent Mn-MOF material is [(CH3CH2)2NH2][Mn3(HL)(L)(A C )2], the ligand of the Mn-MOF material is T-shaped 5-((4-carboxybenzyl)oxy)isophthalic acid, abbreviated as H3L, and the structural formula is as follows:

[0007] In the molecular formula, the HL 2- The L is a ligand anion that removes the hydrogen atoms on the two carboxyl groups. 3- The ligand anion is a ligand anion that removes the hydrogen atoms on the three carboxyl groups. C - is a carboxylate ion, the [(CH3CH2)2NH2] + Derived from the decomposition of N,N-diethylformamide;

[0008] The three-dimensional structure of the fluorescent Mn-MOF material includes one-dimensional spiral metal manganese chain units. On the same plane, the one-dimensional spiral metal manganese chain units are connected by ligands that completely remove the hydrogen atoms on three carboxyl groups to form a layered structure. The layered structures are connected by ligands that remove the hydrogen atoms on two carboxyl groups. The above connection method extends infinitely in the spatial structure to form a three-dimensional porous network structure, in which the uncoordinated terminal carboxylic acids are suspended in the 1D rectangular channels of the network structure.

[0009] Furthermore, the Mn(II) ions in the one-dimensional helical manganese metal chain unit exhibit four coordination modes, namely, the Mn1 ion consists of three carboxylate O atoms of three organic ligands and three Ac - The Mn2 ion is coordinated by three O atoms of the ion, and the Mn2 ion is coordinated by four carboxylate O atoms of four organic ligands and two Ac - The two O atoms of the ion are coordinated, and the Mn3 ion consists of four carboxylate O atoms of three organic ligands and two Ac - The two O atoms of the ion are coordinated, and the Mn4 ion consists of three carboxylate O atoms and two Ac - The two O atoms of the ion are coordinated; adjacent Mn ions form a one-dimensional spiral metal manganese chain unit through bridging oxygen.

[0010] The present invention also provides a method for preparing the fluorescent Mn-MOF material, comprising the following steps:

[0011] Manganese chloride tetrahydrate and ligand 5-((4-carboxybenzyl)oxy)isophthalic acid are added to a mixed solution system of N,N-diethylformamide and glacial acetic acid to carry out a solvent thermal reaction. After the reaction is completed, the solution is naturally cooled to room temperature, filtered, and dried at room temperature to obtain a fluorescent Mn-MOF material.

[0012] Furthermore, in the mixed solution, the molar ratio of the manganese chloride tetrahydrate to the organic ligand H3L is (2.9-3.17):1.

[0013] Furthermore, the volume ratio of N,N-diethylformamide to glacial acetic acid in the mixed solvent is 3:(0.2-0.4).

[0014] Furthermore, the solvent thermal reaction conditions are constant temperature of 125° C. and heating for 1 to 2 days.

[0015] The present invention also provides application of the fluorescent Mn-MOF material in the field of temperature sensing.

[0016] Beneficial effects of the present invention:

[0017] The present invention obtains a fluorescent Mn-MOF material with a novel structure. The fluorescent Mn-MOF material has high phase purity and good thermal stability, and its fluorescence intensity changes with temperature, so it can be used in the field of temperature sensing and the like. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The organic ligand HL of the fluorescent Mn-MOF material prepared in Example 1 2- Connection method.

[0019] Figure 2 The organic ligand L of the fluorescent Mn-MOF material prepared in Example 1 3- Connection method.

[0020] Figure 3 The one-dimensional spiral metal chain unit of the fluorescent Mn-MOF material was prepared in Example 1.

[0021] Figure 4 This is a three-dimensional structural diagram of the fluorescent Mn-MOF material obtained in Example 1.

[0022] Figure 5 This is the X-ray powder diffraction pattern of the fluorescent Mn-MOF material obtained in Example 1.

[0023] Figure 6 This is the thermogravimetric curve of the fluorescent Mn-MOF material obtained in Example 1.

[0024] Figure 7 This is the fluorescence emission spectrum of the fluorescent Mn-MOF material and H3L ligand prepared in Example 1.

[0025] Figure 8 This is the fluorescence emission spectra of the fluorescent Mn-MOF material prepared in Example 1 at different temperatures.

[0026] Fig. 9 This is a linear fitting diagram of the fluorescence emission intensity and temperature of the fluorescent Mn-MOF material prepared in Example 1. DETAILED DESCRIPTION

[0027] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments, but the protection scope of the present invention is not limited to these embodiments.

[0028] Example 1

[0029] Manganese chloride tetrahydrate (0.11 mmol) and organic ligand H3L (0.032 mmol) were added to a mixed solution system of N,N-diethylformamide (3 mL) and glacial acetic acid (0.3 mL). The thermal reaction was placed in a constant temperature drying oven at 125 °C for 1 day and naturally cooled to room temperature to obtain a large amount of colorless long rod-shaped crystals. After filtration and drying at room temperature, the prepared fluorescent Mn-MOF material was obtained with a yield of 0.015 g and a yield of 46.8%.

[0030] Example 2

[0031] Manganese chloride tetrahydrate (0.11 mmol) and organic ligand H3L (0.032 mmol) were added to a mixed solution system of N,N-diethylformamide (3 mL) and glacial acetic acid (0.2 mL). The thermal reaction was placed in a constant temperature drying oven at 125 °C for 1 day and naturally cooled to room temperature to obtain a large amount of colorless long rod-shaped crystals. After filtration and drying at room temperature, the prepared fluorescent Mn-MOF material was obtained with a yield of 0.022 g and a yield of 68.7%.

[0032] Example 3

[0033] The preparation method of the fluorescent Mn-MOF material of the T-type tricarboxylic acid ligand of this embodiment is as follows:

[0034] Manganese chloride tetrahydrate (0.20 mmol) and organic ligand H3L (0.63 mmol) were added to a mixed solution system of N,N-diethylformamide (3 mL) and glacial acetic acid (0.4 mL). The thermal reaction was placed in a constant temperature drying oven and heated at 125 °C for 2 days. After naturally cooling to room temperature, a large amount of colorless long rod-shaped crystals were obtained. After filtration and drying at room temperature, the prepared fluorescent Mn-MOF material was obtained with a yield of 0.050 g and a yield of 80.6%.

[0035] Example 4

[0036] The preparation method of the fluorescent Mn-MOF material of the T-type tricarboxylic acid ligand of this embodiment is as follows:

[0037] Manganese chloride tetrahydrate (0.30 mmol) and organic ligand H3L (0.95 mmol) were added to a mixed solution system of N,N-diethylformamide (3 mL) and glacial acetic acid (0.4 mL). The thermal reaction was placed in a constant temperature drying oven and heated at 125 °C for 2 days. After naturally cooling to room temperature, a large amount of colorless long rod-shaped crystals were obtained. After filtration and drying at room temperature, the prepared fluorescent Mn-MOF material was obtained with a yield of 0.075 g and a yield of 80.2%.

[0038] (1) Crystal structure determination

[0039] Crystal data of fluorescent Mn-MOF material prepared in Example 1

[0040] Data were collected using a Bruker D8 Quest CMOS single crystal diffractometer at 296(2) K. Data were collected using Mo-K monochromated with a graphite monochromator. α (λ = 0.71073 Å) target ray. The crystal structure was solved by direct method using SHELXTL program. The coordinates of all non-hydrogen atoms were first determined by difference function method and least square method, and then the crystal structure was refined by SHELXTL. Since the highly disordered solvent molecules in the crystal structure affect the thermal vibration of atoms in the crystal structure, "SQUEEZE" treatment was performed in the structure. The crystallographic formula does not include solvent molecules and counter ions in the pores. The crystallographic data are shown in Table 1.

[0041] Table 1 Crystallographic data of the metal-organic framework material

[0042]

[0043] Attached Figure 1 This is the connection mode between the T-type tricarboxylic acid anion and the manganese ion in the fluorescent Mn-MOF material, in which the hydrogen atoms on the two carboxyl groups are removed. Figure 2 It is the connection mode of T-type tricarboxylic acid anion and manganese ion in the fluorescent Mn-MOF material, in which the hydrogen atoms on the three carboxyl groups are removed. That is, in the fluorescent Mn-MOF material, the ligand H3L has two forms of coordination, and the uncoordinated terminal carboxylic acid is distributed in the pores of the three-dimensional structure of the fluorescent Mn-MOF material.

[0044] Figure 3 The one-dimensional spiral metal chain unit of the fluorescent Mn-MOF material is prepared in Example 1. The Mn(II) ion in the one-dimensional spiral metal manganese chain unit exhibits four coordination modes, that is, the Mn1 ion is composed of three carboxylate O atoms of three organic ligands and three Ac - The Mn2 ion is coordinated by three O atoms of the ion, and the Mn2 ion is coordinated by four carboxylate O atoms of four organic ligands and two Ac - The two O atoms of the ion are coordinated, and the Mn3 ion consists of four carboxylate O atoms of three organic ligands and two Ac - The two O atoms of the ion are coordinated, and the Mn4 ion consists of three carboxylate O atoms and two Ac - The two O atoms of the ion are coordinated, and the adjacent Mn ions are connected by Ac - The oxygen atoms in the middle bridge to form a one-dimensional spiral metal manganese chain unit.

[0045] Figure 4This is a three-dimensional structural diagram of the fluorescent Mn-MOF material obtained in Example 1. The three-dimensional structure of the fluorescent Mn-MOF material includes a one-dimensional spiral metal manganese chain unit. On the same plane, the one-dimensional spiral metal manganese chain units are connected by ligands that completely remove the hydrogen atoms on three carboxyl groups to form a layered structure. The layered structures are connected by ligands that remove the hydrogen atoms on two carboxyl groups. The above connection method extends infinitely in the spatial structure to form a three-dimensional porous network structure, in which the uncoordinated terminal carboxylic acids are suspended in the 1D rectangular channels of the network structure.

[0046] Figure 5 This is the X-ray powder diffraction pattern of the fluorescent Mn-MOF material prepared in Example 1. It shows that the diffraction peaks of the PXRD spectrum of the crystal sample prepared in this example are highly consistent with the PXRD spectrum of the single crystal structure simulation, indicating that the phase purity of the MOFs material is very high.

[0047] Figure 6 This is a thermogravimetric curve of the fluorescent Mn-MOF material obtained in Example 1, indicating that the fluorescent Mn-MOF material can be stabilized to 276° C. That is, it has a certain thermal stability.

[0048] (2) Solid-state fluorescence emission spectrum of the fluorescent Mn-MOF material prepared in Example 1

[0049] The solid-state fluorescence of the fluorescent Mn-MOF material and H3L ligand was studied at room temperature (see Appendix Figure 7 ). When the excitation wavelength is 381 nm, the H3L ligand shows a very strong fluorescence emission peak at 397 nm, while when the excitation wavelength is 451 nm, the Mn-MOF material shows a very strong fluorescence emission peak at 532 nm. Compared with the fluorescence emission peak of the H3L ligand, the Mn-MOF material has a large red shift of about 140 nm. This phenomenon can be attributed to the fact that after the H3L ligand coordinates with the metal manganese ion, a rigid plane is generated between the benzene rings, which is conducive to the delocalization of π electrons, reduces the energy level between HOMO and LUMO, and causes a large red shift in the Mn-MOF material.

[0050] (3) Fluorescence emission spectra of the fluorescent Mn-MOF material prepared in Example 1 at different temperatures

[0051] At present, it is of great significance to design and prepare MOF fluorescent temperature sensors in a targeted manner. Due to its structural advantages and good fluorescence properties, we studied Mn-MOF materials as thermometers to detect changes in fluorescence intensity over a wide temperature range (100K to 300K). The results of the variable temperature fluorescence spectrum of fluorescent Mn-MOF show that with the increase of temperature, the fluorescence intensity gradually decreases and the maximum emission spectrum does not change with temperature, which indicates that the rigidity of the MOF structure enhances the energy transfer between the organic ligands and the metal center in MOF (see Appendix Figure 8 ). As the temperature decreases, the thermal motion of the organic ligands and uncoordinated carboxyl group molecules in the MOF structure slows down, thereby enhancing the MOF fluorescence intensity. More importantly, the relationship between the emission intensity and temperature (100K to 300K) shows a good linear correlation ( R 2 =0.9688)(see attached Fig. 9 ), indicating that Mn-MOF material is a promising luminescent thermometer.

[0052] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A fluorescent Mn-MOF material based on T-type tricarboxylic acid ligands, characterized in that: The molecular formula of the fluorescent Mn-MOF material is [(CH3CH2)2NH2][Mn3(HL)(L)(A C )2], the ligand of the Mn-MOF material is T-shaped 5-((4-carboxybenzyl)oxy)isophthalic acid, abbreviated as H3L, and the structural formula is as follows: In the molecular formula, the HL 2- The L is a ligand anion that removes the hydrogen atoms on the two carboxyl groups. 3- The ligand anion is a ligand anion that removes the hydrogen atoms on the three carboxyl groups. C - is a carboxylate ion, the [(CH3CH2)2NH2] + Derived from the decomposition of N,N-diethylformamide; The three-dimensional structure of the fluorescent Mn-MOF material includes one-dimensional spiral metal manganese chain units. On the same plane, the one-dimensional spiral metal manganese chain units are connected by ligands that completely remove the hydrogen atoms on three carboxyl groups to form a layered structure. The layered structures are connected by ligands that remove the hydrogen atoms on two carboxyl groups. The above connection method extends infinitely in the spatial structure to form a three-dimensional porous network structure, in which the uncoordinated terminal carboxylic acids are suspended in the 1D rectangular channels of the network structure.

2. The fluorescent Mn-MOF material based on T-type tricarboxylic acid ligand according to claim 1, characterized in that: Furthermore, the Mn(II) ions in the one-dimensional helical manganese metal chain unit exhibit four coordination modes, namely, the Mn1 ion consists of three carboxylate O atoms of three organic ligands and three Ac - The Mn2 ion is coordinated by three O atoms of the ion, and the Mn2 ion is coordinated by four carboxylate O atoms of four organic ligands and two Ac - The two O atoms of the ion are coordinated, and the Mn3 ion consists of four carboxylate O atoms of three organic ligands and two Ac - The two O atoms of the ion are coordinated, and the Mn4 ion consists of three carboxylate O atoms and two Ac - The two O atoms of the ion are coordinated; adjacent Mn ions form a one-dimensional spiral metal manganese chain unit through bridging oxygen.

3. A method for preparing a fluorescent Mn-MOF material based on a T-type tricarboxylic acid ligand as claimed in any one of claims 1 to 2, characterized in that: The steps include: Manganese chloride tetrahydrate and ligand 5-((4-carboxybenzyl)oxy)isophthalic acid are added to a mixed solution system of N,N-diethylformamide and glacial acetic acid to carry out a solvent thermal reaction. After the reaction is completed, the solution is naturally cooled to room temperature, filtered, and dried at room temperature to obtain a fluorescent Mn-MOF material.

4. The method for preparing the fluorescent Mn-MOF material based on T-type tricarboxylic acid ligand according to claim 3, characterized in that: In the mixed solution, the molar ratio of the manganese chloride tetrahydrate to the organic ligand H3L is (2.9-3.17):

1.

5. The method for preparing the fluorescent Mn-MOF material based on T-type tricarboxylic acid ligand according to claim 3, characterized in that: The volume ratio of N,N-diethylformamide to glacial acetic acid in the mixed solvent is 3:(0.2-0.4).

6. The method for preparing the fluorescent Mn-MOF material based on T-type tricarboxylic acid ligand according to claim 3, characterized in that: The solvent thermal reaction conditions are constant temperature of 125° C. and heating for 1 to 2 days.

7. An application of the fluorescent Mn-MOF material based on T-type tricarboxylic acid ligand as described in any one of claims 1 to 2 in the field of temperature sensing.

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