A cadmium metal-organic framework material with long afterglow properties and its preparation method

Abstract

The present invention relates to the technical field of metal-organic framework crystalline functional materials, and particularly relates to a cadmium metal-organic framework material with long afterglow characteristics and a preparation method thereof. The coordination compound chemical formula of the cadmium metal-organic framework material is [Cd2(D-Cam)2(bidpe)2]·6H2O, wherein bidpe is 4,4'-bis(imidazol-1-yl)diphenyl ether, and D-Cam is deprotonated D-camphoric acid. The preparation method is as follows: cadmium nitrate, 4,4'-bis(imidazol-1-yl)diphenyl ether, and D-camphoric acid are subjected to a solvothermal reaction, followed by cooling, washing, and drying. The preparation method is simple, has good stability, and a high yield. Under room temperature conditions and irradiation with a 365 nm ultraviolet lamp, it shows blue fluorescence emission, and after turning off the ultraviolet light, it shows long green phosphorescence.

Description

Technical Field

[0001] The present invention relates to the technical field of metal-organic framework crystalline functional materials, and particularly relates to a cadmium metal-organic framework material with long afterglow characteristics and a preparation method thereof. Background Art

[0002] So far, the research on inorganic phosphorescent materials has been very mature, but the preparation process of inorganic phosphorescent materials is relatively complex and the materials used are relatively expensive. Compared with inorganic phosphorescent materials, organic room temperature phosphorescent materials have attractive application prospects in many high-tech fields such as bioimaging, optical recording, information storage, and anti-counterfeiting systems due to their low price, simple synthesis, good biocompatibility, flexibility, and easy modification of functional groups. Although many examples of fluorescent Zn(II) and Cd(II) complexes have been reported, phosphorescent materials with afterglow characteristics are still more challenging. Summary of the Invention

[0003] To solve the above technical problems, the present application provides a cadmium metal-organic framework material with long afterglow characteristics. The chemical formula of the metal-organic framework material complex is: [Cd 2 (D-Cam) 2 (bidpe) 2 ·6H 2 O, where bidpe is 4,4'-bis(imidazol-1-yl)diphenyl ether and D-Cam is deprotonated D-camphoric acid. In the structure of the complex, Cd 2+ is hexacoordinated, and Cd 2+ is connected to four oxygen atoms and two nitrogen atoms. These four oxygen atoms come from two deprotonated D-camphoric acids respectively, and the two nitrogen atoms come from two bidpe ligands respectively.

[0004] In the cadmium metal-organic framework material, the bidpe ligand is connected to Cd 2+ to form a one-dimensional chain structure, and the deprotonated D-camphoric acid is connected to Cd 2+ to form a one-dimensional chain structure. The two one-dimensional chain structures are then connected to each other to form a two-dimensional network structure; the complex belongs to the monoclinic system, the space group is P21, and the crystal parameters are α = 90°, β = 113.460(7)°, γ = 90°, Z = 2,

[0005] The present application also provides a preparation method of the above cadmium metal-organic framework material with long afterglow characteristics:

[0006] Under a protective atmosphere (such as nitrogen), 4,4'-dibromodiphenyl ether, imidazole, K 2 CO3 , Cu 2 O was added to 25 - 35 mL of N,N'-dimethylformamide, and the mixture was heated to 155 °C - 165 °C under stirring for reflux reaction for 46 - 50 hours. After the reaction was stopped, it was cooled to room temperature (25 °C, the same below), filtered by suction. 350 - 450 mL of ice-cold distilled water was poured into the filtrate to produce a white solid. After sufficient precipitation, the white solid was filtered out by suction and dried to obtain 4,4'-bis(imidazol-1-yl)diphenyl ether.

[0007] Among them, the molar ratio of 4,4'-dibromodiphenyl ether, imidazole, K 2 CO 3 , Cu 2 O was 9.9 - 10.1:39.9 - 40.1:39.9 - 40.1:0.49 - 0.51;

[0008] The 4,4'-bis(imidazol-1-yl)diphenyl ether, D-camphoric acid and cadmium nitrate prepared above were dissolved in a mixed solvent of N,N’-dimethylformamide and water, and placed in a reaction kettle with a polytetrafluoro inner liner. The reaction was carried out at 105 °C - 115 °C for 46 - 50 hours. After the reaction was completed, it was naturally cooled to room temperature to obtain colorless block crystals.

[0009] Among them, the molar ratio of 4,4'-bis(imidazol-1-yl)diphenyl ether, D-camphoric acid, and cadmium nitrate was 0.09 - 0.11:0.09 - 0.11:0.19 - 0.21.

[0010] The volume ratio of N,N’-dimethylformamide and water was 0.9 - 1.1:0.9 - 1.1.

[0011] The advantages of the present invention are as follows: To meet the requirements of efficient and persistent RTP, specific functional groups with rich lone pair electrons should exist. These functional groups promote the aggregation of triplet excitons from singlet to triplet through the intersystem crossing (ISC) process. At the same time, an ordered molecular packing pattern and a relatively rigid environment are also required, which are crucial for stabilizing triplet excitons and suppressing non-radiative transitions. In this application, by selecting appropriate metal ions and ligands, the complex ideally meets the requirements of efficient and persistent RTP, and shows afterglow characteristics. Under room temperature conditions, under the irradiation of a 365 nm ultraviolet lamp, it shows blue fluorescence emission, and after turning off the ultraviolet light, it shows long green phosphorescence emission. And compared with traditional luminescent MOFs containing precious metals and rare earth elements, the cadmium metal-organic framework material provided by the present invention has low cost, simple preparation method, good stability, and high yield. Description of the Drawings

[0012] Figure 1 It is the structural diagram of the asymmetric unit of the cadmium metal-organic framework material complex prepared in this application;

[0013] Figure 2 The two-dimensional structure diagram of the cadmium metal-organic framework material complex prepared for this application;

[0014] Figure 3 The stacking diagram of the cadmium metal-organic framework material complex prepared for this application;

[0015] Figure 4 The comparison diagram of the X-ray diffraction and simulated diffraction of the cadmium metal-organic framework material complex prepared for this application;

[0016] Figure 5 The thermogravimetric analysis diagram of the cadmium metal-organic framework material complex prepared for this application;

[0017] Figure 6 The emission spectra diagram of the fluorescence and phosphorescence of the cadmium metal-organic framework material complex prepared for this application;

[0018] Figure 7 The phosphorescence decay curve diagram of the cadmium metal-organic framework material complex prepared for this application in air.

[0019] Figure 8 The photo diagram of the cadmium metal-organic framework material complex prepared for this application before and after turning off the ultraviolet light in air. Detailed implementation mode

[0020] The following further illustrates the present invention in conjunction with the accompanying drawings of the specification and specific embodiments, but the embodiments do not limit the present invention in any form. Unless otherwise specified, the reagents and materials used in the following embodiments are all commercially available.

[0021] Example 1

[0022] Preparation of ligand 4,4'-bis(imidazol-1-yl)diphenyl ether:

[0023] Under the protection of a nitrogen atmosphere, 4,4'-dibromodiphenyl ether (10 mmol), imidazole (40 mmol), K 2 CO 3 (40 mmol), Cu 2 O (0.5 mmol) were added to 25 mL of N,N'-dimethylformamide, and the temperature was raised to 155 °C under stirring for reflux reaction for 46 hours. After stopping the reaction, it was cooled to room temperature, filtered by suction. 400 mL of ice-distilled water was poured into the filtrate to produce a white solid. After the precipitation was sufficient, the white solid was filtered out by suction and dried to obtain 4,4'-bis(imidazol-1-yl)diphenyl ether.

[0024] Example 2

[0025] Preparation of ligand 4,4'-bis(imidazol-1-yl)diphenyl ether:

[0026] Under the protection of nitrogen atmosphere, 4,4'-dibromodiphenyl ether (10 mmol), imidazole (40 mmol), K 2 CO 3 (40 mmol), Cu 2 O (0.5 mmol) were added to 35 mL of N,N'-dimethylformamide, and the mixture was heated to 165 °C under stirring and refluxed for 50 hours. After the reaction was stopped, it was cooled to room temperature, filtered by suction. 450 mL of ice-cold distilled water was poured into the filtrate to produce a white solid. After sufficient precipitation, the white solid was filtered out by suction and dried to obtain 4,4'-bis(imidazol-1-yl)diphenyl ether.

[0027] Example 3

[0028] Preparation of cadmium metal-organic framework material complex:

[0029] 4,4'-Bis(imidazol-1-yl)diphenyl ether (0.1 mmol), D-camphoric acid (0.1 mmol) and cadmium nitrate (0.2 mmol) prepared in Example 1 above were dissolved in 6 mL of a mixed solvent of N,N'-dimethylformamide and water, wherein the volume ratio of N,N'-dimethylformamide to water was 0.9:1.1. It was placed in a 25 ml reaction kettle with a polytetrafluoroethylene inner lining and reacted at 110 °C for 48 hours. After the reaction was completed, it was naturally cooled to room temperature to obtain colorless block crystals. The colorless block crystals were filtered and separated, and successively washed and dried to obtain the target product.

[0030] Example 4

[0031] Preparation of cadmium metal-organic framework material complex:

[0032] 4,4'-Bis(imidazol-1-yl)diphenyl ether (0.1 mmol), D-camphoric acid (0.1 mmol) and cadmium nitrate (0.2 mmol) prepared in Example 2 above were dissolved in 5 mL of a mixed solvent of N,N'-dimethylformamide and water, wherein the volume ratio of N,N'-dimethylformamide to water was 1.1:0.9. It was placed in a 25 ml reaction kettle with a polytetrafluoroethylene inner lining and reacted at 110 °C for 48 hours. After the reaction was completed, it was naturally cooled to room temperature to obtain colorless block crystals. The colorless block crystals were filtered and separated, and successively washed and dried to obtain the target product.

[0033] Table 1: Crystallographic data of the target product cadmium metal-organic framework material complex prepared in Example 3

[0034]

[0035] Figure 1Based on the crystallographic data of the cadmium metal-organic framework material complex prepared in Example 3, the structural diagram of the asymmetric unit of the grown crystal is shown by Figure 1 It can be seen that due to the asymmetry of D-camphoric acid, Cd 2+ has two coordination modes, both of which are six-coordinate. One type of Cd 2+ is connected to four oxygen atoms (O3, O4, O5, and O6) and two nitrogen atoms (N8 and N1#2). These four oxygen atoms (O3, O4, O5, and O6) are respectively from two deprotonated D-camphoric acids, and these two nitrogen atoms (N8 and N1#2) are respectively from two bidpe ligands. The other type of Cd 2+ is connected to four oxygen atoms (O7, O8, O9, and O10) and two nitrogen atoms (N4 and N5). These four oxygen atoms (O7, O8, O9, and O10) are respectively from two deprotonated D-camphoric acids, and these two nitrogen atoms (N4 and N5) are respectively from two bidpe ligands;

[0036] Figure 2 The two-dimensional structural diagram of the cadmium metal-organic framework material complex prepared in Example 3 is shown by Figure 2 It can be seen that the bidpe ligand is connected to Cd 2+ to form a one-dimensional chain structure. The deprotonated D-camphoric acid is connected to Cd 2+ to form a one-dimensional chain structure. The two one-dimensional chain structures are then connected to each other to form a two-dimensional network structure;

[0037] Figure 3 The stacking diagram of the cadmium metal-organic framework material complex prepared in Example 3 is shown by Figure 3 It can be seen that the two-dimensional network structure is stacked layer by layer;

[0038] Figure 4 The comparison diagram of the X-ray diffraction and simulated diffraction of the cadmium metal-organic framework material complex prepared in Example 3 (the detected X-ray diffraction pattern is on the top and the experimentally simulated diffraction pattern is on the bottom) is shown by Figure 4 It can be seen that the powder X-ray diffraction pattern coincides with the experimentally simulated diffraction pattern, indicating that the cadmium metal-organic framework material has reliable purity, providing a guarantee for its application as a long-afterglow material;

[0039] Figure 5 The thermogravimetric analysis diagram of the cadmium metal-organic framework material complex prepared in Example 3 is shown by Figure 5 It can be seen that the thermogravimetric analysis characterization of the cadmium metal-organic framework material shows that it remains stable at 290 °C and has thermal stability;

[0040] Figure 6Emission spectra of fluorescence and phosphorescence of the cadmium metal-organic framework material complex prepared in Example 3. It can be seen from Figure 6 that the fluorescence emission peak of the cadmium metal-organic framework material complex is around 445 nm, showing blue emission, and the phosphorescence emission peak of the cadmium metal-organic framework material complex is around 540 nm, showing green emission;

[0041] Figure 7 Phosphorescence decay curve of the cadmium metal-organic framework material complex prepared in Example 3 in air. It can be seen from Figure 7 that the phosphorescence lifetime of the cadmium metal-organic framework material is about 2107.70 ms.

[0042] Figure 8 Photos of the cadmium metal-organic framework material complex prepared in Example 3 in air before and after turning off the ultraviolet light. It can be seen from Figure 8 that the cadmium metal-organic framework material complex shows blue fluorescence emission under the irradiation of a 365 nm ultraviolet lamp in air at room temperature. After turning off the ultraviolet light, the cadmium metal-organic framework material emits visible green phosphorescence for several seconds, and the luminescence disappears after about 2.5 s, indicating that the duration of the afterglow is very long.

[0043] Since the preparation process of the target product in Example 4 is not much different from that in Example 3, the crystals obtained are the same, and thus the relevant detection results are also similar.

Claims

1. Preparation method of cadmium metal-organic framework material with long afterglow property, characterized in that: The steps are as follows: Under a protective atmosphere, add 4,4'-dibromodiphenyl ether, imidazole, K2CO3, and Cu2O into N,N'-dimethylformamide, heat to reflux under stirring, cool to room temperature after stopping the reaction, filter by suction, pour ice distilled water into the filtrate to produce a white solid, filter out the white solid by suction after sufficient precipitation and dry it to obtain 4,4'-bis(imidazol-1-yl)diphenyl ether; Dissolve the prepared 4,4'-bis(imidazol-1-yl)diphenyl ether, D-camphoric acid, and cadmium nitrate in a mixed solvent of N,N’-dimethylformamide and water, carry out a heating reaction, naturally cool to room temperature after the reaction ends, and colorless block crystals can be obtained. Filter and separate the colorless block crystals, and successively carry out washing and drying treatments to obtain the target product; 4,4'-Dibromodiphenyl ether, imidazole, K 2 CO 3 , Cu 2 The molar ratio of O is 9.9 to 10.1: 39.9 to 40.1: 39.9 to 40.1: 0.49 to 0.51; The coordination chemical formula of the cadmium metal-organic framework material is [Cd 2 (D-Cam) 2 (bidpe) 2 •6H 2 O, where bidpe is 4,4'-bis(imidazol-1-yl)diphenyl ether and D-Cam is deprotonated D-camphoric acid. The cadmium complex belongs to the monoclinic system, and the space group is P 21. The crystal parameters are a = 16.6928(10) Å, b = 9.3844(4) Å, c = 19.6627(11) Å, α = 90°, β = 113.460(7)°, γ = 90°, Z = 2, V = 2825.6(3) Å3.

2. The preparation method of the cadmium metal-organic framework material with long afterglow property as described in claim 1, characterized in that: In the complex structure, Cd 2+ is six-coordinated. Cd 2+ is connected to four oxygen atoms and two nitrogen atoms. Among them, the four oxygen atoms are respectively from the four carboxylate oxygen atoms of two deprotonated D-camphoric acids, and the two nitrogen atoms are respectively from the imidazole nitrogen atoms of two bidpe ligands. The bidpe ligands are connected to the Cd 2+ to form a one-dimensional chain structure. The deprotonated D-camphoric acid is connected to the Cd 2+ to form a one-dimensional chain structure. The two one-dimensional chain structures are further connected to form a two-dimensional network structure.

3. The preparation method of the cadmium metal-organic framework material with long afterglow property as described in claim 1, characterized in that: The temperature of the heating reflux is 155°C to 165°C, and the reaction time of the heating reflux is 46 to 50 hours.

4. The preparation method of the cadmium metal-organic framework material with long afterglow property as described in claim 1, characterized in that: The molar ratio of 4,4'-bis(imidazol-1-yl)diphenyl ether, D-camphoric acid, and cadmium nitrate is 0.09 to 0.11: 0.09 to 0.11: 0.19 to 0.

21.

5. The preparation method of the cadmium metal-organic framework material with long afterglow property as described in claim 1, characterized in that: In the mixed solvent, the volume ratio of N,N’-dimethylformamide to water is 0.9 to 1.1: 0.9 to 1.

1.

6. The preparation method of the cadmium metal-organic framework material with long afterglow property as described in claim 1, characterized in that: The temperature of the heating reaction is 105°C to 115°C, and the reaction time of the heating reaction is 46 to 50 hours.

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