A circularly polarized luminescent metal-organic framework material and its preparation method and application

Abstract

The present invention discloses a circularly polarized luminescent metal-organic framework material, its preparation method, and application, belonging to the technical field of organic luminescent materials. The preparation method of the metal-organic framework material of the present invention comprises the following steps: adding zinc halide, alkaline earth metal salt, 2,5-dimethylimidazole-4-carboxaldehyde, and chiral cyclohexanediamine to a solvent, heating and reacting, and obtaining the metal-organic framework material. The metal-organic framework material prepared by the present invention is a chiral metal-organic framework material containing an internal helical chain, has high crystallinity, and has excellent circularly polarized luminescence performance. Its luminescence asymmetry factor (g lum ) and fluorescence quantum yield (Φ PL ) can be regulated and optimized by doping with alkaline earth metal salts, and the operation is very flexible.

Description

Technical Field

[0001] The present invention relates to the technical field of organic luminescent materials, and in particular to a circularly polarized luminescent metal organic framework material and a preparation method and application thereof. Background Art

[0002] Metal-organic frameworks (MOFs) are self-assembled from metal ions and organic ligands through coordination bonds. Chiral MOFs with fluorescence properties exhibit great application potential in the field of circularly polarized luminescence (CPL) due to the optical phenomenon of unequal intensities of left-handed and right-handed circularly polarized light caused by their chiral structure. Currently, the circularly polarized luminescence performance of most chiral MOF materials does not meet the requirements of practical applications. It is difficult to prepare MOFs with both high efficiency and high asymmetric luminescence factor (g lum ) circularly polarized luminescent materials is a difficulty in this field.

[0003] At present, the main strategies for preparing high-level circularly polarized luminescent materials based on metal organic frameworks are chiral molecular surface self-assembly and host-guest encapsulation strategies. Among them, chiral molecular surface self-assembly usually refers to replacing the original ligands on the surface of the material to introduce chiral ligands to induce circularly polarized luminescence or modifying chiral luminescent molecules on the surface of MOF to amplify the circularly polarized luminescence asymmetry factor through orderly arrangement. The host-guest encapsulation strategy embeds or encapsulates the luminescent units (such as quantum dots and nanoclusters) into the confined space of the chiral metal organic framework, and uses the chiral microenvironment of the metal organic framework to induce the circularly polarized luminescence activity of the luminophore. However, the chiral molecular surface self-assembly and host-guest encapsulation strategies have the following disadvantages: 1) the synthesis steps are complicated and the cost is high; 2) the structural stability is poor; 3) the chiral transfer efficiency is low, resulting in g lum4) low values; 5) reduced quantum yield; and 6) poor material compatibility (existing circularly polarized luminescent materials are essentially composite materials, resulting in poor material compatibility). The main reasons for these shortcomings are as follows: both chiral molecular surface self-assembly and host-guest encapsulation strategies require precise control over the introduction of chiral ligands or the assembly of the framework structure, involving complex co-assembly and in situ synthesis steps; mechanical deformation or environmental changes in the encapsulated material may cause the chiral microenvironment to be destroyed; when introducing chirality through ligand exchange, the coupling between the chiral center and the luminescent unit may be weak, resulting in insufficient chiral induction efficiency; encapsulation or ligand modification may introduce non-radiative transition pathways, limiting the performance of the luminescent material; and long-term use of ligand exchange or encapsulation materials may lead to ligand shedding or framework collapse, resulting in poor stability. Furthermore, there is a strategy for preparing continuous chiral MOF thin films using liquid phase epitaxial growth for direct detection of circularly polarized light, but this strategy is only applicable to a small number of pillar-type metal-organic frameworks and suffers from demanding preparation conditions. Therefore, simpler methods for creating metal-organic frameworks with high levels of circularly polarized luminescence performance are urgently needed. Summary of the Invention

[0004] The purpose of the present invention is to provide a circularly polarized luminescent metal organic framework material and its preparation method and application, so as to solve the problems existing in the above-mentioned prior art.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] One of the technical solutions of the present invention is a method for preparing a circularly polarized luminescent metal-organic framework material, comprising the following steps:

[0007] Zinc halide, alkaline earth metal salt, 2,5-dimethylimidazole-4-carboxaldehyde and chiral cyclohexanediamine are added into a solvent and heated for reaction to obtain the metal organic framework material.

[0008] Furthermore, the zinc halide includes at least one of ZnCl2, ZnBr2 and ZnI2.

[0009] Furthermore, the alkaline earth metal in the alkaline earth metal salt includes at least one of Mg, Ca, Sr and Ba.

[0010] The method of the present invention can regulate the circularly polarized luminescence properties of metal organic framework materials through metal (alkaline earth metal) doping strategy, providing a simple and universal strategy for developing CPL materials with excellent performance. Specifically, it is obtained by doping alkaline earth metal salts and optimizing the luminescence asymmetry factor (g lum ) and fluorescence quantum yield (Φ PL ), that is, circularly polarized luminescence performance.

[0011] Furthermore, the solvent comprises an aprotic solvent and a protic solvent in a volume ratio of 2:1;

[0012] The aprotic solvent includes N,N-dimethylformamide or N,N-diethylformamide;

[0013] The protic solvent includes methanol or ethanol.

[0014] Using N,N-dimethylformamide and methanol in a volume ratio of 2:1 as solvent, a metal-organic framework material with good crystalline phase can be obtained.

[0015] Furthermore, the molar ratio of the total molar amount of the zinc halide and the alkaline earth metal salt to the molar amount of 2,5-dimethylimidazole-4-carboxaldehyde and chiral cyclohexanediamine is 0.05:0.04:0.02.

[0016] Furthermore, the heating reaction temperature is 100-120° C., and the time is 72 hours.

[0017] Furthermore, the preparation method further includes cooling to room temperature and washing after the heating reaction.

[0018] Furthermore, the washing comprises washing with DMF and methanol respectively.

[0019] The second technical solution of the present invention: a metal organic framework material prepared by the above preparation method.

[0020] The third technical solution of the present invention: an application of the above-mentioned metal organic framework material as a circularly polarized luminescent material.

[0021] The present invention discloses the following technical effects:

[0022] (1) The present invention prepares a metal-organic framework material with significant circularly polarized luminescence properties through a simple one-pot synthesis method.

[0023] (2) The preparation method of the present invention is simple and does not require complicated post-modification or pre-synthesis steps, and a crystalline product with a single chirality can be directly obtained. In addition, the ligand used in the present invention is simple and easy to obtain, and is prepared by a one-pot method, and multi-component raw materials are introduced in situ, which simplifies the reaction steps, reduces costs, and has universal applicability.

[0024] (3) The metal organic framework material prepared by the present invention is a chiral metal organic framework material containing a helical chain inside (which has the function of chirality transmission and amplification, specifically: the inherent chirality of the helical chain (such as composed of chiral ligands or metal helical centers) can be transmitted to the entire MOF framework through spatial arrangement, so that the non-chiral components follow the helical symmetry and form a chiral environment. The chirality of the local helical unit can be amplified by the long-range ordered framework structure, significantly enhancing the overall chiral response of the material. It has high crystallinity and excellent circularly polarized luminescence performance. Its luminescence asymmetry factor (g lum ) and fluorescence quantum yield (Φ PL ) can be regulated and optimized by doping with alkaline earth metal salts, and the operation is very flexible.

[0025] (4) The present invention synthesized a series of MOF materials with different helical chains based on zinc metal salts and chiral diamines, and obtained materials with high luminescence quantum yield (Φ PL ) and the asymmetry factor (g lum ) of CPL metal-organic framework materials.

[0026] (5) The metal organic framework material prepared by the present invention is an intrinsic material and can exhibit excellent circularly polarized luminescence performance without being compounded with other materials. Therefore, there is no problem of poor material compatibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0028] Figure 1 Schematic diagram of the preparation process of metal organic framework materials;

[0029] Figure 2 Powder X-ray diffraction data of MOF P / M-ZnCa-1, MOF P / M-ZnCa-2, MOF P / M-ZnCa-3, and MOFP / M-ZnCa-4 prepared in Examples 1 to 4, where (a) is P-ZnCa-1, P-ZnCa-2, P-ZnCa-3, and P-ZnCa-4, and (b) is M-ZnCa-1, M-ZnCa-2, M-ZnCa-3, and M-ZnCa-4;

[0030] Figure 3Solid-state circular dichroism (CD) spectra of MOF P / M-ZnCa-1, MOF P / M-ZnCa-2, MOF P / M-ZnCa-3, and MOFP / M-ZnCa-4 prepared in Examples 1 to 4;

[0031] Figure 4 Solid-state circularly polarized luminescence (CPL) spectra of MOF P / M-ZnCa-1, MOF P / M-ZnCa-2, MOF P / M-ZnCa-3, and MOFP / M-ZnCa-4 prepared in Examples 1 to 4, where (a) is the solid-state circularly polarized luminescence spectrum and (b) is the luminescence asymmetry factor;

[0032] Figure 5 Powder X-ray diffraction data of MOF P / M-ZnMg-1 prepared in Example 5;

[0033] Figure 6 Solid-state circular dichroism (CD) spectrum of MOF P / M-ZnMg-1 prepared in Example 5;

[0034] Figure 7 Solid-state circularly polarized luminescence (CPL) spectrum of MOF P / M-ZnMg-1 prepared in Example 5;

[0035] Figure 8 Powder X-ray diffraction data of MOF P / M-ZnSr-1 prepared in Example 6;

[0036] Figure 9 Solid-state circular dichroism (CD) spectrum of MOF P / M-ZnSr-1 prepared for Example 6;

[0037] Figure 10 Solid-state circularly polarized luminescence (CPL) spectrum of MOF P / M-ZnSr-1 prepared in Example 6;

[0038] Figure 11 Powder X-ray diffraction data of MOF P / M-ZnBa-1 prepared in Example 7;

[0039] Figure 12 Solid-state circular dichroism (CD) spectrum of MOF P / M-ZnBa-1 prepared in Example 7;

[0040] Figure 13 Solid-state circularly polarized luminescence (CPL) spectrum of MOF P / M-ZnBa-1 prepared in Example 7;

[0041] Figure 14 Solid-state circularly polarized luminescence (CPL) spectrum of P / M-Zn prepared in Comparative Example 1;

[0042] Figure 15 Solid-state circularly polarized luminescence (CPL) spectrum of P-ZnCd-1 prepared in Comparative Example 2;

[0043] Figure 16 XRD patterns of P / M-ZnCa-4 prepared in Example 4 after being placed in air for 3 days or immersed in different solvents for 3 days;

[0044] Figure 17 Schematic diagram of the structure of MOF before and after calcium doping, where a is the 3D structure view of P-Zn observed along the c-axis, b is the triple right-handed helical chain of P-Zn, c is the 3D structure view of P-ZnCa observed along the c-axis (randomly freely distributed metal ions), and d is the triple right-handed helical chain of P-ZnCa. DETAILED DESCRIPTION

[0045] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0046] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any intermediate value within a stated value or stated range and any other stated value or intermediate value within the stated range is also encompassed by the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0047] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0048] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be exemplary only.

[0049] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0050] It should be pointed out that the matters not described in detail in the present invention are conventional operating means in this field and are not the focus of the present invention.

[0051] In a first aspect, the present invention provides a method for preparing a circularly polarized luminescent metal-organic framework material, comprising the following steps:

[0052] Zinc halide (ZnX2), alkaline earth metal salt (MX2), 2,5-dimethylimidazole-4-carboxaldehyde and chiral cyclohexanediamine are mixed, dissolved in a mixed solvent of N,N-dimethylformamide (DMF) and methanol, heated under closed conditions for reaction, and then cooled to room temperature. The crystals are washed, filtered, and collected to obtain a metal organic framework material.

[0053] In a specific embodiment of the present invention, M is an alkaline earth metal Mg 2+ , Ca 2+ 、Sr 2+ 、Ba 2+ At least one of; X is at least one of Cl, Br, I.

[0054] In a specific embodiment of the present invention, the volume ratio of N,N-dimethylformamide (DMF) to methanol is 2:1.

[0055] In a specific embodiment of the present invention, the molar ratio of the total molar amount of zinc halide and alkaline earth metal salt to the molar amount of 2,5-dimethylimidazole-4-carboxaldehyde and chiral cyclohexanediamine is 0.05:0.04:0.02.

[0056] In a specific embodiment of the present invention, the heating reaction temperature is 100-120° C. and the time is 72 hours.

[0057] In a specific embodiment of the present invention, washing comprises washing with DMF and methanol, respectively.

[0058] In a specific embodiment of the present invention, the sealed condition is provided by a sealed hard glass tube.

[0059] The schematic diagram of the preparation process of metal organic framework materials is shown in Figure 1 .

[0060] In a second aspect, the present invention provides a metal organic framework material prepared by the above preparation method.

[0061] In a third aspect, the present invention provides an application of the metal organic framework material as a circularly polarized luminescent material.

[0062] In a specific embodiment of the present invention, the room temperature is 25°C.

[0063] In the embodiments of the present invention, if specific conditions are not specified, conventional conditions or conditions recommended by the manufacturer are followed. All raw materials, reagents, etc. used without specifying the manufacturer are conventional products that can be purchased commercially.

[0064] In a specific embodiment of the present invention, powder X-ray diffraction data were collected on a UItimal in-situ high-temperature X-ray diffractometer, with a Cu target, room temperature, a scanning range of 3 to 40 deg, and a scanning speed of 10.0 deg min -1 The simulated powder X-ray diffraction patterns were converted from the single crystal structures using Mercury software.

[0065] In a specific embodiment of the present invention, solid-state circular dichroism (CD) spectra are measured using a MOS-500 circular dichroism spectrometer, and the specific method includes: KBr pellet, slit of 2 nm, exposure time of 1 s, and scanning range of 200-600 nm.

[0066] In a specific embodiment of the present invention, solid-state circularly polarized luminescence (CPL) spectra are measured using a CPL-300 circularly polarized luminescence spectrometer. The specific method includes: evenly distributing an appropriate amount of sample on a transparent quartz glass plate and measuring the CPL signal of the sample at room temperature. The scanning range is 355-700 nm.

[0067] In a specific embodiment of the present invention, the absolute quantum yield is measured using an absolute quantum yield meter Hamamatsu C11347-11. The specific method includes: taking an appropriate amount of sample and placing it in a quartz sample tank, and performing the test at room temperature.

[0068] Example 1

[0069] Preparation method of a circularly polarized luminescent metal-organic framework material (MOF P / M-ZnCa-1):

[0070] ZnCl2 (4.77 mg, 0.035 mmol), CaCl2 (1.66 mg, 0.015 mmol), chiral cyclohexanediamine (2.28 mg, 0.02 mmol), and 2,5-dimethylimidazole-4-carbaldehyde (5.0 mg, 0.04 mmol) were mixed and dissolved in 3.0 mL of a mixed solvent of N,N-dimethylformamide (DMF) and methanol (the volume ratio of DMF to methanol was 2:1). The mixture was sealed in a Pyrex glass tube and heated in an oven at 100°C for 72 hours. The mixture was then cooled to room temperature at a rate of 5°C / h and washed with DMF and methanol, respectively. The yellow rod-shaped crystals were collected by filtration to obtain the metal-organic framework material with a yield of 60.2% (2.87 mg).

[0071] Example 2

[0072] Preparation method of a circularly polarized luminescent metal-organic framework material (MOF P / M-ZnCa-2):

[0073] ZnCl2 (3.4 mg, 0.025 mmol), CaCl2 (2.77 mg, 0.025 mmol), chiral cyclohexanediamine (2.28 mg, 0.02 mmol), and 2,5-dimethylimidazole-4-carboxaldehyde (5.0 mg, 0.04 mmol) were mixed and dissolved in 3.0 mL of a mixed solvent of N,N-dimethylformamide (DMF) and methanol (the volume ratio of DMF to methanol was 2:1). The mixture was sealed in a Pyrex glass tube and heated in an oven at 100°C for 72 hours. The tube was then cooled to room temperature at a rate of 5°C / h and washed with DMF and methanol, respectively. The yellow rod-shaped crystals were collected by filtration to obtain the metal-organic framework material with a yield of 55.2% (1.87 mg).

[0074] Example 3

[0075] Preparation method of a circularly polarized luminescent metal-organic framework material (MOF P / M-ZnCa-3):

[0076] ZnCl2 (2.73 mg, 0.02 mmol), CaCl2 (3.3 mg, 0.03 mmol), chiral cyclohexanediamine (2.28 mg, 0.02 mmol), and 2,5-dimethylimidazole-4-carboxaldehyde (5.0 mg, 0.04 mmol) were mixed and dissolved in 3.0 mL of a mixed solvent of N,N-dimethylformamide (DMF) and methanol (the volume ratio of DMF to methanol was 2:1). The mixture was sealed in a Pyrex glass tube and heated in an oven at 100°C for 72 hours. The mixture was then cooled to room temperature at a rate of 5°C / h, washed with DMF and methanol, respectively, and filtered to collect yellow rod-shaped crystals, which were the metal-organic framework material with a yield of 50.2% (1.37 mg).

[0077] Example 4

[0078] Preparation method of a circularly polarized luminescent metal-organic framework material (MOF P / M-ZnCa-4):

[0079] ZnCl2 (2.0 mg, 0.015 mmol), CaCl2 (3.88 mg, 0.035 mmol), chiral cyclohexanediamine (2.28 mg, 0.02 mmol), and 2,5-dimethylimidazole-4-carbaldehyde (5.0 mg, 0.04 mmol) were mixed and dissolved in 3.0 mL of a mixed solvent of N,N-dimethylformamide (DMF) and methanol (the volume ratio of DMF to methanol was 2:1). The mixture was sealed in a Pyrex glass tube and heated in an oven at 100°C for 72 hours. The mixture was then cooled to room temperature at a rate of 5°C / h and washed with DMF and methanol, respectively. The yellow rod-shaped crystals were collected by filtration to obtain the metal-organic framework material with a yield of 40.6% (0.812 mg).

[0080] The powder X-ray diffraction data of MOF P / M-ZnCa-1 (M-ZnCa-1, P-ZnCa-1), MOF P / M-ZnCa-2 (M-ZnCa-2, P-ZnCa-2), MOF P / M-ZnCa-3 (M-ZnCa-3, P-ZnCa-3) and MOF P / M-ZnCa-4 (M-ZnCa-4, P-ZnCa-4) prepared in Examples 1 to 4 are shown in FIG. Figure 2 , solid-state circular dichroism (CD) spectrum see Figure 3 , solid-state circularly polarized luminescence (CPL) spectrum see Figure 4 .

[0081] Figure 2 (a) shows P-ZnCa-1, P-ZnCa-2, P-ZnCa-3 and P-ZnCa-4, and (b) shows M-ZnCa-1, M-ZnCa-2, M-ZnCa-3 and M-ZnCa-4.

[0082] Figure 4 (a) is the solid-state circularly polarized luminescence spectrum; (b) is the luminescence asymmetry factor.

[0083] from Figure 2 It can be seen from the figure that the crystal phases of the metal organic framework materials prepared in Examples 1 to 4 are very uniform and free of impurity crystal phases.

[0084] from Figure 3 It can be seen that the metal organic framework materials prepared in Examples 1 to 4 produce mirror Cotton effects at 330 nm and 390 nm, respectively, which is consistent with their opposite chirality.

[0085] from Figure 4 It can be seen that the metal organic framework materials prepared in Examples 1 to 4 all exhibit CPL response in the wavelength range of 450 to 650 nm.

[0086] Example 5

[0087] Preparation method of a circularly polarized luminescent metal-organic framework material (MOF P / M-ZnMg-1):

[0088] ZnCl2 (2.0 mg, 0.015 mmol), MgCl2 (3.33 mg, 0.035 mmol), chiral cyclohexanediamine (2.28 mg, 0.02 mmol), and 2,5-dimethylimidazole-4-carboxaldehyde (5.0 mg, 0.04 mmol) were mixed and dissolved in 3.0 mL of a mixed solvent of N,N-dimethylformamide (DMF) and methanol (the volume ratio of DMF to methanol was 2:1). The mixture was sealed in a Pyrex glass tube and heated in an oven at 100°C for 72 hours. The tube was then cooled to room temperature at a rate of 5°C / h and washed with DMF and methanol, respectively. The yellow rod-shaped crystals were collected by filtration to obtain the metal-organic framework material with a yield of 35.6% (0.712 mg).

[0089] The powder X-ray diffraction data of the metal organic framework materials (P-ZnMg-1, M-ZnMg-1) prepared in Example 5 are shown in Figure 5 , solid-state circular dichroism (CD) spectrum see Figure 6 , solid-state circularly polarized luminescence (CPL) spectrum see Figure 7 .

[0090] from Figure 5 It can be seen from the figure that the crystal phase of the metal organic framework material prepared in Example 5 is very uniform and free of impurity crystal phase.

[0091] from Figure 6 As can be seen from the figure, the metal organic framework material prepared in Example 5 produces a mirror Cotton effect at 335 nm and 400 nm, which is consistent with their opposite chirality.

[0092] from Figure 7 It can be seen from the figure that the metal organic framework material prepared in Example 5 exhibits CPL response in the wavelength range of 450-650 nm.

[0093] Example 6

[0094] Preparation method of a circularly polarized luminescent metal-organic framework material (MOF P / M-ZnSr-1):

[0095] ZnCl2 (2.0 mg, 0.015 mmol), SrCl2 (5.55 mg, 0.035 mmol), chiral cyclohexanediamine (2.28 mg, 0.02 mmol), and 2,5-dimethylimidazole-4-carbaldehyde (5.0 mg, 0.04 mmol) were mixed and dissolved in 3.0 mL of a mixed solvent of N,N-dimethylformamide (DMF) and methanol (the volume ratio of DMF to methanol was 2:1). The mixture was sealed in a Pyrex glass tube and heated in an oven at 100°C for 72 hours. The mixture was then cooled to room temperature at a rate of 5°C / h and washed with DMF and methanol, respectively. The yellow rod-shaped crystals were collected by filtration to obtain the metal-organic framework material with a yield of 41.3% (0.826 mg).

[0096] The powder X-ray diffraction data of the metal organic framework materials (P-ZnSr-1, M-ZnSr-1) prepared in Example 6 are shown in Figure 8 , solid-state circular dichroism (CD) spectrum see Figure 9 , solid-state circularly polarized luminescence (CPL) spectrum see Figure 10 .

[0097] from Figure 8 It can be seen from the figure that the crystal phase of the metal organic framework material prepared in Example 6 is very uniform and free of impurity crystal phase.

[0098] from Figure 9 As can be seen from the graph, the metal organic framework material prepared in Example 6 produces a mirror Cotton effect at 335 nm and 400 nm, which is consistent with their opposite chirality.

[0099] from Figure 10 It can be seen that the metal organic framework material prepared in Example 6 exhibits CPL response in the wavelength range of 450~650 nm.

[0100] Example 7

[0101] Preparation method of a circularly polarized luminescent metal-organic framework material (MOF P / M-ZnBa-1):

[0102] ZnCl2 (2.0 mg, 0.015 mmol), BaCl2 (7.29 mg, 0.035 mmol), chiral cyclohexanediamine (2.28 mg, 0.02 mmol), and 2,5-dimethylimidazole-4-carbaldehyde (5.0 mg, 0.04 mmol) were mixed and dissolved in 3.0 mL of a mixed solvent of N,N-dimethylformamide (DMF) and methanol (the volume ratio of DMF to methanol was 2:1). The mixture was sealed in a Pyrex glass tube and heated in an oven at 100°C for 72 hours. The mixture was then cooled to room temperature at a rate of 5°C / h and washed with DMF and methanol, respectively. The yellow rod-shaped crystals were collected by filtration to obtain the metal-organic framework material with a yield of 45.6% (0.912 mg).

[0103] The powder X-ray diffraction data of the metal organic framework materials (P-ZnBa-1, M-ZnBa-1) prepared in Example 7 are shown in Figure 11 , solid-state circular dichroism (CD) spectrum see Figure 12 , solid-state circularly polarized luminescence (CPL) spectrum see Figure 13 .

[0104] from Figure 11 It can be seen that the crystal phase of the metal organic framework material prepared in Example 7 is very uniform and has no impurity crystal phase.

[0105] from Figure 12 As can be seen from the figure, the metal organic framework material prepared in Example 7 produces a mirror Cotton effect at 335 nm, which is consistent with their opposite chirality.

[0106] from Figure 13 It can be seen from the figure that the metal organic framework material prepared in Example 7 exhibits CPL response in the wavelength range of 450~650 nm.

[0107] The absolute quantum yields of the metal organic framework materials prepared in Examples 1 to 7 are shown in Table 1.

[0108] Table 1 Absolute quantum yield

[0109] Grouping Fluorescence quantum yield PLQY (%) <![CDATA[Asymmetry factor | g lum |]]> P / M-ZnCa-1 (Example 1) 20.6(19.8) <![CDATA[9×10 -3 (9×10 -3 )]]> P / M-ZnCa-2 (Example 2) 25.0(23.2) 0.023(0.023) P / M-ZnCa-3 (Example 3) 42.3(42.3) 0.035(0.035) P / M-ZnCa-4 (Example 4) 51.4(52.9) 0.045(0.045) P / M-ZnMg-1 (Example 5) 37.7(36.0) 0.018(0.018) P / M-ZnSr-1 (Example 6) 26.9(27.4) 0.012(0.012) P / M-ZnBa-1 (Example 7) 19.0(19.8) 0.010(0.010)

[0110] The data outside the brackets in Table 1 are data of the P configuration, and the data inside the brackets are data of the M configuration.

[0111] Comparative Example 1

[0112] A preparation method for a circularly polarized luminescent metal-organic framework material (P / M-Zn):

[0113] ZnCl2 (6.8 mg, 0.05 mmol), 2,5-dimethylimidazole-4-carboxaldehyde (5.0 mg, 0.04 mmol), and chiral cyclohexanediamine (2.28 mg, 0.02 mmol) were mixed and dissolved in 3.0 mL of a mixed solvent of N,N-dimethylformamide (DMF) and methanol (the volume ratio of DMF to methanol was 2:1). The mixture was sealed in a Pyrex glass tube and heated in an oven at 100°C for 72 hours. The mixture was then cooled to room temperature at a rate of 5°C / h, washed with DMF and methanol, respectively, and filtered to collect yellow rod-shaped crystals, which were the metal-organic framework material with a yield of 66.2% (4.5 mg).

[0114] The solid-state circularly polarized luminescence (CPL) spectrum of P / M-Zn prepared in Comparative Example 1 is shown in Figure 14 .

[0115] P / M-Zn prepared in Comparative Example 1 |g lum |≈1.5×10 -3 , the circularly polarized luminescence effect is not good.

[0116] Comparative Example 2

[0117] Preparation method of a circularly polarized luminescent metal-organic framework material (MOF P-ZnCd-1):

[0118] ZnCl2 (2.0 mg, 0.015 mmol), CdCl2 (5.55 mg, 0.03 mmol), chiral cyclohexanediamine (2.28 mg, 0.02 mmol), and 2,5-dimethylimidazole-4-carboxaldehyde (5.0 mg, 0.04 mmol) were mixed and dissolved in 3.0 mL of a mixed solvent of N,N-dimethylformamide (DMF) and methanol (the volume ratio of DMF to methanol was 2:1). The mixture was sealed in a Pyrex glass tube and heated in an oven at 100°C for 72 hours. The mixture was then cooled to room temperature at a rate of 5°C / h and washed with DMF and methanol, respectively. The yellow rod-shaped crystals were collected by filtration to obtain the metal-organic framework material with a yield of 25.6% (0.512 mg).

[0119] The solid-state circularly polarized luminescence (CPL) spectrum of P / M-Zn prepared in Comparative Example 2 is shown in Figure 15 .

[0120] The results showed that the wavelength range of 450~650 nm was insufficient to obtain detectable CPL signals.

[0121] Comparative Example 3

[0122] The same as Example 1, except that the solvents used were N,N-dimethylacetamide (DMA) and methanol (the volume ratio of DMA to methanol was 2:1).

[0123] The method of this comparative example could not produce a metal organic framework material, but a yellow clear solution was obtained, and no crystals could be obtained.

[0124] Effect Example 1

[0125] The P / M-ZnCa-4 prepared in Example 4 was placed in air for 3 days and then subjected to X-ray diffraction test, or was immersed in different solvents for 3 days and then filtered and dried and then subjected to X-ray diffraction test. The results are shown in FIG. Figure 16 .

[0126] Figure 16 DMSO is dimethyl sulfoxide, acetone is acetone, H2O is water, CH3OH is methanol, C2H5OH is ethanol, CH3CN is acetonitrile, DMF is N,N-dimethylformamide, air is air, and As-synthesized is the newly synthesized P / M-ZnCa-4.

[0127] from Figure 16 It can be seen that the P / M-ZnCa-4 prepared in Example 4 maintains excellent stability in most organic solvents, and there is no deintercalation of doped ions or dissociation of the framework structure.

[0128] Effect Example 2

[0129] Schematic diagram of the structure of MOF before and after calcium doping is shown in Figure 17 , Figure 17 Figure a shows the 3D structure of P-Zn observed along the c-axis, Figure b shows the triple right-handed helical chain of P-Zn, Figure c shows the 3D structure of P-ZnCa observed along the c-axis (randomly distributed metal ions), and Figure d shows the triple right-handed helical chain of P-ZnCa. Zn is cyan; Ca is orange; Cl is green; C is gray; and N is blue.

[0130] from Figure 17 As can be seen from Figures a and b in the figure, the connection between the ligands is mainly through the coordination of zinc ions. Each zinc ion forms a tetrahedral coordination environment with three nitrogen atoms and a chloride ion around it. In P-Zn, the imidazole group acts as a bridging ligand to connect Zn 2+ The ions link up to form a triple helical chain with right-handed rotation.

[0131] It can be seen from Figures c and d that Zn 2+ and Ca 2+The coordination environment of Zn is composed of three nitrogen atoms and one chlorine atom, forming a tetrahedral coordination geometry. 2+ The metal center also contains a small amount of Ca 2+ , sharing the same coordination environment with each other, and the coordination number is 4. The imidazole and metal ions in the framework are arranged alternately in an orderly manner, maintaining the inherent right-handed P helical chain and spatial chirality.

[0132] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for preparing a circularly polarized luminescent metal-organic framework material, characterized in that: The steps are: Adding zinc halide, alkaline earth metal salt, 2,5-dimethylimidazole-4-carboxaldehyde and chiral cyclohexanediamine into a solvent, heating and reacting to obtain the metal organic framework material; The chiral cyclohexanediamine is chiral 1,2-cyclohexanediamine; The solvent is N,N-dimethylformamide and methanol in a volume ratio of 2:1; The molar ratio of the total molar amount of the zinc halide and the alkaline earth metal salt to the molar amount of 2,5-dimethylimidazole-4-carboxaldehyde and chiral cyclohexanediamine is 0.05:0.04:0.

02.

2. The preparation method according to claim 1, characterized in that The zinc halide is at least one of ZnCl2, ZnBr2 and ZnI2.

3. The preparation method according to claim 1, characterized in that The alkaline earth metal in the alkaline earth metal salt is at least one of Mg, Ca, Sr and Ba.

4. The preparation method according to claim 1, characterized in that The heating reaction temperature is 100° C. to 120° C., and the reaction time is 72 hours.

5. The preparation method according to claim 1, characterized in that It also includes cooling to room temperature and washing after heating the reaction.

6. The preparation method according to claim 5, characterized in that The washing includes washing with DMF and methanol, respectively.

7. A metal organic framework material prepared by the preparation method according to any one of claims 1 to 6.

8. Use of the metal organic framework material according to claim 7 as a circularly polarized luminescent material.

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