Circularly polarized luminous metal organic framework material as well as preparation method and application thereof

Abstract

The invention discloses a circularly polarized light-emitting metal organic framework material as well as a preparation method and application thereof, and belongs to the technical field of organic light-emitting materials. The preparation method of the metal organic framework material comprises the following steps: adding zinc halide, alkaline earth metal salt, 2, 5-dimethylimidazole-4-formaldehyde and chiral cyclohexanediamine into a solvent, and heating for reaction to obtain the metal organic framework material. The prepared metal organic framework material is a chiral metal organic framework material internally containing a spiral chain, has high crystallinity and excellent circular polarization luminescence performance, the luminescence asymmetry factor (glum) and the fluorescence quantum yield (phi PL) of the metal organic framework material can be regulated, controlled and optimized by doping alkaline earth metal salt, and the operation is very flexible.

Description

Technical Field

[0001] The present invention relates to the technical field of organic light-emitting materials, and particularly to a metal-organic framework material with circularly polarized luminescence, a preparation method thereof, and an application thereof. Background Art

[0002] Metal-organic frameworks (MOFs) are formed by the self-assembly of metal ions and organic ligands through coordination bonds. Chiral metal-organic frameworks combined with fluorescence properties have shown 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 the chiral structure. At present, the circularly polarized luminescence performance of most chiral metal-organic framework materials still fails to meet the requirements of practical applications. Preparing a circularly polarized luminescence material with both high-efficiency luminescence and a high dissymmetry factor (g lum ) is a difficult point in this field.

[0003] Currently, the main strategies for preparing high-level metal-organic framework circularly polarized luminescence materials are two approaches: chiral molecular surface self-assembly and host-guest encapsulation strategies. Among them, chiral molecular surface self-assembly usually refers to replacing the original ligand on the material surface to introduce a chiral ligand to induce circularly polarized luminescence or modifying the chiral luminescent molecule on the surface of the MOF to amplify the circularly polarized luminescence dissymmetry factor through ordered arrangement. The host-guest encapsulation strategy embeds or encapsulates luminescent units (such as quantum dots, nanoclusters) into the confined space of the chiral metal-organic framework, and utilizes the chiral microenvironment of the metal-organic framework to induce the circularly polarized luminescence activity of the luminescent body. However, the chiral molecular surface self-assembly and host-guest encapsulation strategies have the following disadvantages: 1) The synthesis steps are complex and the cost is high; 2) The structural stability becomes poor; 3) The chiral transfer efficiency is low, resulting in g lumThe values are not high; 4) The quantum yield is reduced; 5) Poor material compatibility (existing circularly polarized luminescent materials are basically composite materials, so the material compatibility is poor). The main reasons for the above disadvantages are as follows: Both the self-assembly on the chiral molecular surface and the host-guest encapsulation strategy require precise control of the introduction of chiral ligands or the assembly of the framework structure, involving complex co-assembly and in-situ synthesis steps; The chiral microenvironment may be damaged when the encapsulating material undergoes mechanical deformation or environmental changes; 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 paths, limiting the performance of the luminescent body; The long-term use of ligand exchange or encapsulating materials may cause ligand detachment or framework collapse, with poor stability; In addition, there is also a strategy of using liquid-phase epitaxial growth to prepare continuous chiral MOF films for directly detecting circularly polarized light, but this strategy is only applicable to the preparation of a few column-layered metal-organic framework materials and has the problem of harsh preparation conditions. Therefore, there is an urgent need for a method to create metal-organic framework materials with high-level circularly polarized luminescent properties in a simpler way. Summary of the Invention

[0004] The object of the present invention is to provide a metal-organic framework material with circularly polarized luminescence, 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: A preparation method of a metal-organic framework material with circularly polarized luminescence, comprising the following steps:

[0007] Adding zinc halide, alkaline earth metal salt, 2,5-dimethylimidazole-4-carbaldehyde and chiral cyclohexanediamine into a solvent, heating and reacting to obtain the metal-organic framework material.

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

[0009] Further, 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 luminescent properties of metal-organic framework materials through a metal (alkaline earth metal) doping strategy, providing a simple and universal strategy for developing CPL materials with excellent properties. Specifically, it is obtained by doping alkaline earth metal salts, and the luminescence dissymmetry factor (g lum ), and the fluorescence quantum yield (Φ PL ), that is, the circularly polarized luminescent properties.

[0011] Further, the solvent includes an aprotic solvent and a protic solvent with 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 with a volume ratio of 2:1 as the solvent, a metal-organic framework material with good crystal phase can be obtained.

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

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

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

[0018] Further, the washing includes 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 metal-organic framework material as a circularly polarized luminescence material.

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

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

[0023] (2) The preparation method of the present invention is simple, without complex post-modification or pre-synthesis steps, and can directly obtain a crystalline product with a single chirality; moreover, the ligands used in the present invention are simple and easily available, prepared by a one-pot method, and multi-component raw materials are introduced in-situ, simplifying the reaction steps, reducing the cost, and having universality.

[0024] (3) The metal-organic framework material prepared by the present invention is a chiral metal-organic framework material containing helical chains inside (which has the function of chiral transfer and amplification. Specifically, the inherent chirality of the helical chain (such as composed of chiral ligands or metal helical centers) can be transferred to the entire MOF framework through spatial arrangement, enabling achiral components to follow helical symmetry and form a chiral environment. The chirality of local helical units can be amplified through the long-range ordered framework structure, significantly enhancing the overall chiral response) with high crystallinity and excellent circularly polarized luminescence properties. Its luminescence dissymmetry factor (g lum ) and fluorescence quantum yield (Φ PL ) can be regulated and optimized by doping 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 CPL metal-organic framework materials with high luminescence quantum yield (Φ PL ) and dissymmetry factor (g lum ).

[0026] (5) The metal-organic framework material prepared by the present invention is an intrinsic material and can exhibit excellent circularly polarized luminescence properties 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 technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0028] Figure 1 It is a schematic diagram of the preparation process of the metal-organic framework material;

[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 MOF P / 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 circular dichroism (CD) spectra of MOF P / M-ZnCa-1, MOF P / M-ZnCa-2, MOF P / M-ZnCa-3, and MOF P / M-ZnCa-4 prepared in Examples 1-4;

[0031] Figure 4 Solid circularly polarized luminescence (CPL) spectra of MOF P / M-ZnCa-1, MOF P / M-ZnCa-2, MOF P / M-ZnCa-3, and MOF P / M-ZnCa-4 prepared in Examples 1-4, where (a) is the solid 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 circular dichroism (CD) spectrum of MOF P / M-ZnMg-1 prepared in Example 5;

[0034] Figure 7 Solid 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 circular dichroism (CD) spectrum of MOF P / M-ZnSr-1 prepared in Example 6;

[0037] Figure 10 Solid 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 circular dichroism (CD) spectrum of MOF P / M-ZnBa-1 prepared in Example 7;

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

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

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

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

[0044] Figure 17 Schematic diagrams of the structures of the MOF before and after doping with calcium. Among them, a is a 3D structural view of P-Zn observed along the c-axis direction, b is a triple right-handed helical chain of P-Zn, c is a 3D structural view of P-ZnCa observed along the c-axis direction (randomly and freely distributed metal ions), and d is a triple right-handed helical chain of P-ZnCa. Detailed implementation manners

[0045] 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 rather as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention.

[0046] It should be understood that the terms used in the present invention are only for describing specific implementation manners and are not used to limit the present invention. Additionally, 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.

[0047] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation 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 related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0048] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific implementation manners of the present invention specification, which are obvious to those skilled in the art. Other implementation manners obtained from the specification of the present invention are obvious to those skilled in the art. The specification and examples of the present invention are only exemplary.

[0049] Regarding the terms "comprising", "including", "having", "containing", etc. used herein, they are all open-ended terms, meaning including but not limited to.

[0050] It should be noted that the parts not described in detail in the present invention are all conventional operation means in the art and are not the focus of the present invention.

[0051] In the first aspect of the present invention, a preparation method of a metal-organic framework material with circularly polarized luminescence is provided, including the following steps:

[0052] Mix zinc halide (ZnX2), alkaline earth metal salt (MX2), 2,5-dimethylimidazole-4-carbaldehyde and chiral cyclohexanediamine, dissolve them in a mixed solvent of N,N-dimethylformamide (DMF) and methanol, heat and react under closed conditions, then cool to room temperature, wash, filter, and collect the crystals to obtain the 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+ ; and at least one of X is at least one of Cl, Br, and 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 amounts of 2,5-dimethylimidazole-4-carbaldehyde and chiral cyclohexanediamine is 0.05:0.04:0.02.

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

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

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

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

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

[0061] In the third aspect of the present invention, an application of the above metal-organic framework material as a circularly polarized luminescence material is provided.

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

[0063] In the specific embodiments of the present invention, unless otherwise specified, the conditions are carried out according to conventional conditions or the conditions recommended by the manufacturer. The raw materials, reagents, etc. without indicating the manufacturer can be obtained as conventional products through commercial purchase.

[0064] In the specific embodiments of the present invention, the powder X-ray diffraction data is collected on a UItimal in-situ high-temperature X-ray diffractometer, with a Cu target, at room temperature, scanning range: 3 - 40 deg, and a scanning speed of 10.0 deg min -1 The simulated powder X-ray diffraction pattern is obtained by conversion based on the single crystal structure through Mercury software.

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

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

[0067] In the specific embodiments of the present invention, the absolute quantum yield is measured using an absolute quantum yield instrument Hamamatsu C11347-11. The specific method includes: taking an appropriate amount of the sample and placing it in a quartz sample cell for testing at room temperature.

[0068] Example 1

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

[0070] Mix 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), dissolve them in a mixed solvent of 3.0 mL of N,N-dimethylformamide (DMF) and methanol (the volume ratio of DMF to methanol is 2:1), seal in a Pyrex glass tube, heat in an oven at 100 °C for 72 hours, then cool to room temperature at a rate of 5 °C / h, wash with DMF and methanol respectively, filter, and collect the yellow rod-shaped crystals, which are the metal-organic framework material, with a yield of 60.2% (2.87 mg).

[0071] Example 2

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

[0073] Mix 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-carbaldehyde (5.0 mg, 0.04 mmol), dissolve them in a mixed solvent of 3.0 mL N,N-dimethylformamide (DMF) and methanol (the volume ratio of DMF to methanol is 2:1), seal it in a Pyrex glass tube, heat it in an oven at 100 °C for 72 hours, then cool it to room temperature at a rate of 5 °C / h, wash it with DMF and methanol respectively, filter, and collect the yellow rod-shaped crystals, which are the metal-organic framework material, and the yield is 55.2% (1.87 mg).

[0074] Example 3

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

[0076] Mix 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-carbaldehyde (5.0 mg, 0.04 mmol), dissolve them in a mixed solvent of 3.0 mL N,N-dimethylformamide (DMF) and methanol (the volume ratio of DMF to methanol is 2:1), seal it in a Pyrex glass tube, heat it in an oven at 100 °C for 72 hours, then cool it to room temperature at a rate of 5 °C / h, wash it with DMF and methanol respectively, filter, and collect the yellow rod-shaped crystals, which are the metal-organic framework material, and the yield is 50.2% (1.37 mg).

[0077] Example 4

[0078] Preparation method of a metal-organic framework material with circularly polarized luminescence (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 a mixed solvent of 3.0 mL 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, then cooled to room temperature at a rate of 5 °C / h, washed with DMF and methanol respectively, filtered, and yellow rod-shaped crystals were collected, which were metal-organic framework materials 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 Figure 2 , and the solid-state circular dichroism (CD) spectra are shown in Figure 3 , and the solid-state circularly polarized luminescence (CPL) spectra are shown in Figure 4 .

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

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

[0083] It can be seen from Figure 2 that the crystal phases of the metal-organic framework materials prepared in Examples 1 to 4 are very uniform and there are no impurity crystal phases.

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

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

[0086] Example 5

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

[0088] Mix 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-carbaldehyde (5.0 mg, 0.04 mmol), dissolve them in a mixed solvent of 3.0 mL N,N-dimethylformamide (DMF) and methanol (the volume ratio of DMF to methanol is 2:1), seal in a Pyrex glass tube, heat in an oven at 100 °C for 72 hours, then cool to room temperature at a rate of 5 °C / h, wash with DMF and methanol respectively, filter, and collect the yellow rod-shaped crystals, which are 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 and the solid-state circular dichroism (CD) spectra are shown in Figure 6 and the solid-state circularly polarized luminescence (CPL) spectra are shown in Figure 7 .

[0090] It can be seen from Figure 5 that the crystal phase of the metal-organic framework material prepared in Example 5 is very uniform and there is no impurity crystal phase.

[0091] It can be seen from Figure 6 that the metal-organic framework materials prepared in Example 5 produce mirror-image Cotton effects at 335 nm and 400 nm, which is consistent with their opposite chirality.

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

[0093] Example 6

[0094] Preparation method of a metal-organic framework material with circularly polarized luminescence (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 a mixed solvent of 3.0 mL 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, then cooled to room temperature at a rate of 5 °C / h. It was washed with DMF and methanol respectively, filtered, and the yellow rod-shaped crystals were collected, which were 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 , and the solid-state circular dichroism (CD) spectra are shown in Figure 9 , and the solid-state circularly polarized luminescence (CPL) spectra are shown in Figure 10 .

[0097] It can be seen from Figure 8 that the crystal phases of the metal-organic framework materials prepared in Example 6 are very homogeneous and there are no impurity crystal phases.

[0098] It can be seen from Figure 9 that the metal-organic framework materials prepared in Example 6 produced mirror-image Cotton effects at 335 nm and 400 nm, which is consistent with their opposite chirality.

[0099] It can be seen from Figure 10 that the metal-organic framework materials prepared in Example 6 showed CPL responses in the wavelength range of 450 - 650 nm.

[0100] Example 7

[0101] A preparation method of a circularly polarized luminescence 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 a mixed solvent of 3.0 mL 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, then cooled to room temperature at a rate of 5 °C / h. It was washed with DMF and methanol respectively, filtered, and yellow rod-shaped crystals were collected, which were 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 , and the solid-state circular dichroism (CD) spectra are shown in Figure 12 , and the solid-state circularly polarized luminescence (CPL) spectra are shown in Figure 13 .

[0104] It can be seen from Figure 11 that the crystal phases of the metal-organic framework materials prepared in Example 7 are very homogeneous and there are no impurity crystal phases.

[0105] It can be seen from Figure 12 that the metal-organic framework materials prepared in Example 7 produced mirror-image Cotton effects at 335 nm, which is consistent with their opposite chirality.

[0106] It can be seen from Figure 13 that the metal-organic framework materials prepared in Example 7 showed CPL responses in the wavelength range of 450 - 650 nm.

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

[0108] Table 1 Absolute quantum yields

[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 the data of the P configuration, and the data inside the brackets are the data of the M configuration.

[0111] Comparative Example 1

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

[0113] ZnCl2 (6.8 mg, 0.05 mmol), 2,5-dimethylimidazole-4-carbaldehyde (5.0 mg, 0.04 mmol), and chiral cyclohexanediamine (2.28 mg, 0.02 mmol) were mixed and dissolved in a mixed solvent of 3.0 mL 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, then cooled to room temperature at a rate of 5 °C / h, washed with DMF and methanol respectively, filtered, and yellow rod-shaped crystals were collected, 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] For P / M-Zn prepared in Comparative Example 1, the |g lum |≈1.5×10 -3 , and the circularly polarized luminescence effect is not good.

[0116] Comparative Example 2

[0117] A preparation method of a circularly polarized luminescence 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-carbaldehyde (5.0 mg, 0.04 mmol) were mixed and dissolved in a mixed solvent of 3.0 mL 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, then cooled to room temperature at a rate of 5 °C / h, washed with DMF and methanol respectively, filtered, and yellow rod-shaped crystals were collected, which were 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] It was found that in the wavelength range of 450 - 650 nm, a detectable CPL signal could not be obtained.

[0121] Comparative Example 3

[0122] Same as Example 1, with the only difference being that the solvent used is N,N-dimethylacetamide (DMA) and methanol (the volume ratio of DMA to methanol is 2:1).

[0123] Using the method of this comparative example, the metal-organic framework material cannot be obtained. Instead, a yellow clear solution is obtained, and crystals cannot be obtained.

[0124] Effect Example 1

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

[0126] Figure 16 In , 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 as-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 situation of doping ion deintercalation and framework structure dissociation.

[0128] Effect Example 2

[0129] The schematic structural diagrams of the MOF before and after doping with calcium are shown in Figure 17 , Figure 17 In , Figure a is a 3D structural view of P-Zn observed along the c-axis direction, Figure b is a triple right-handed helical chain of P-Zn, Figure c is a 3D structural view of P-ZnCa observed along the c-axis direction (randomly and freely distributed metal ions), and Figure d is a triple right-handed helical chain of P-ZnCa. Among them, Zn is cyan; Ca: orange; Cl, green; C, gray; N, blue.

[0130] From Figure 17 Figures a and b in it can be seen that the connection mode between ligands is mainly through the coordination of zinc ions. Each zinc ion forms a tetrahedral coordination environment with three surrounding nitrogen atoms and one chlorine ion. In P-Zn, the imidazole group acts as a bridging ligand, connecting the Zn 2+ ions to form a right-handed triple helical chain.

[0131] From Figures c and d, it can be seen that Zn 2+ and Ca 2+The coordination environment consists of three nitrogen atoms and one chlorine atom, forming a tetrahedral coordination geometry. The crystal structure not only contains Zn 2+ The metal center also contains a small amount of Ca 2+ , sharing the same coordination environment with each other and both having a coordination number of 4. In the framework, imidazoles and metal ions are arranged alternately in an orderly manner, maintaining the inherent right-handed P-helical chain and space chiral structure.

[0132] The embodiments described above are only descriptions of the preferred modes of the present invention and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A preparation method of a metal-organic framework material with circularly polarized luminescence, characterized in that, It includes the following steps: Adding zinc halide, alkaline earth metal salt, 2,5-dimethylimidazole-4-carbaldehyde and chiral cyclohexanediamine into a solvent, heating for reaction to obtain the metal-organic framework material.

2. The preparation method according to claim 1, characterized in that, The zinc halide includes 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 includes at least one of Mg, Ca, Sr and Ba.

4. The preparation method according to claim 1, wherein The solvent includes an aprotic solvent and a protic solvent with a volume ratio of 2:1; and / or, the aprotic solvent includes N,N-dimethylformamide or N,N-diethylformamide; and / or, the protic solvent includes methanol or ethanol.

5. The preparation method according to claim 1, wherein The molar ratio of the total molar amount of the zinc halide and the alkaline earth metal salt to the molar amounts of 2,5-dimethylimidazole-4-carbaldehyde and chiral cyclohexanediamine is 0.05:0.04:0.

02.

6. The preparation method according to claim 1, wherein, The temperature of the heating reaction is 100°C to 120°C, and the time is 72 hours.

7. The preparation method according to claim 1, wherein It also includes cooling to room temperature and washing after the heating reaction.

8. The preparation method according to claim 7, characterized in that, The washing includes washing with DMF and methanol respectively.

9. A metal-organic framework material prepared by the preparation method according to any one of claims 1 to 8.

10. An application of the metal-organic framework material according to claim 9 as a circularly polarized luminescent material.

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