Asymmetric spiral chain Cu-MOF material and preparation method and application thereof

Abstract

The invention discloses an asymmetric helical chain Cu-MOF material and a preparation method and application thereof, the molecular formula of the material is {[CuL2 (H2O) 2]. (NO3) 2 (H2O) 1.5. (CH3OH)} infinity, the ligand L is PhPO (NH4Py) 2, Ph is phenyl, and NH4Py is 4-amino substituted pyridyl; the preparation method of the material comprises the following steps: respectively dissolving 4-aminopyridine and phenylphosphonic dichloride in chloroform, mixing, carrying out reflux treatment, filtering, washing and drying to obtain a ligand L; and respectively dissolving the ligand L and copper nitrate hexahydrate in methanol, adding water, mixing, sealing, standing, filtering, washing and drying to obtain the material. The asymmetric helical chain Cu-MOF material belongs to an achiral space group Cc and a point group m, but due to asymmetric arrangement of a levorotatory helical chain and a dextrorotatory helical chain in a crystal structure, the material shows remarkable chiral optical activity under the condition of not depending on a traditional chiral point group, and the optical activity is regulated and controlled by the thickness.

Description

Technical Field

[0001] The present invention relates to the technical field of functional materials, and more particularly to an asymmetric helical chain Cu-MOF material, its preparation method and applications. Background Art

[0002] Chirality is a property that is of great significance in the optical and biological applications of materials, and has wide applications in the fields of optics, chemistry, biology, etc. In the field of optics, the action of chiral materials on light is manifested as optical activity, that is, they can change the polarization direction of incident light. This property of chiral materials makes them have broad application prospects in the fields of optical devices, polarization information encryption, optical sensing, etc.

[0003] The chiral optical activity of chiral materials is usually closely related to their crystal structures. In particular, chirality usually exists in crystalline materials with a specific symmetry - chiral point group. These materials have chiral optical activity and exhibit optical rotation effects and other optical properties.

[0004] Due to their chiral optical activity, chiral materials have unique advantages in optical applications. However, recent studies have shown that current chiral materials are often limited by chiral point groups and have relatively small chiral optical activity, thus restricting their applications in chiral optics.

[0005] Therefore, how to develop a functional material with significant chiral optical activity is an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide an asymmetric helical chain Cu-MOF material, its preparation method and applications to solve the deficiencies in the prior art.

[0007] To achieve the above purpose, the present invention adopts the following technical solutions:

[0008] An asymmetric helical chain Cu-MOF material, with the molecular formula {[CuL 2 (H 2 O) 2 ·(NO 3 ) 2 ·(H 2 O) 1.5 ·(CH 3 OH)} ∞ , where the ligand L is PhPO(NH 4 Py) 2 , Ph is phenyl, and NH 4 Py is 4-aminopyridine-substituted pyridyl.

[0009] Furthermore, the thickness of the asymmetric spiral chain Cu-MOF material film is 0.5 to 1.5 μm.

[0010] Furthermore, when the thickness of the film is 0.5 to 0.7 μm, it is right-handed and the anisotropy factor is negative, specifically -0.79 to -1.95.

[0011] Furthermore, when the thickness of the film is 0.7 to 1.5 μm, it is left-handed and the anisotropy factor is positive, specifically 0.94 to 1.94.

[0012] A method for preparing the above-mentioned asymmetric spiral chain Cu-MOF material specifically comprises the following steps:

[0013] (1) 4-aminopyridine and chloroform are fully stirred at 0° C. to obtain a 4-aminopyridine suspension;

[0014] (2) stirring and mixing phenylphosphonyl dichloride and chloroform at 0° C. to obtain a phenylphosphonyl dichloride solution;

[0015] (3) adding the 4-aminopyridine suspension dropwise to the phenylphosphonic acid dichloride solution, refluxing for 6 hours, filtering, washing and drying to obtain ligand L;

[0016] (4) stirring and dissolving the ligand L and methanol, and filtering to obtain a ligand L solution;

[0017] (5) stirring and dissolving copper nitrate hexahydrate and methanol, and filtering to obtain a copper nitrate solution;

[0018] (6) The ligand L solution, water and copper nitrate solution are mixed and sealed, and then allowed to stand at room temperature of 25° C. for 4 weeks, filtered, washed and dried to obtain asymmetric helical chain Cu-MOF material crystals.

[0019] Furthermore, in the above step (1), the usage ratio of 4-aminopyridine to chloroform is 11.756 g:200 mL.

[0020] Furthermore, in the above step (2), the usage ratio of phenylphosphonic dichloride to chloroform is 3.475 g:10 mL.

[0021] Furthermore, in the above step (4), the usage ratio of ligand L and methanol is 0.062 g:3 mL.

[0022] Furthermore, in the above step (5), the usage ratio of copper nitrate hexahydrate and methanol is 0.0245 g:3 mL.

[0023] Furthermore, in the above step (6), the usage ratio of ligand L solution, water and copper nitrate solution is 3 mL:3 mL:3 mL.

[0024] The present invention also claims the application of the above-mentioned asymmetric helical chain Cu-MOF material in chiral optics.

[0025] Furthermore, the above-mentioned chiral optics includes circularly polarized light detection, quantum communication, and optical spintronics.

[0026] Furthermore, the method of the above application is as follows: Place the prepared Cu-MOF thin film on the built optical second harmonic generation-circular dichroism (SHG-CD) test system, use a PMT photodetector to collect the optical second harmonic generation (SHG) signals of the Cu-MOF thin film under different circularly polarized lights, and use the asymmetry factor to represent the degree of chirality. Among them, I LCP (2ω) represents the SHG signal intensity under left-handed circularly polarized light (LCP), and I RCP (2ω) represents the SHG signal intensity under right-handed circularly polarized light (RCP).

[0027] According to the above technical solutions, compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] 1. The asymmetric helical chain Cu-MOF material of the present invention belongs to the non-chiral space group Cc and point group m. However, due to the asymmetric arrangement of left-handed and right-handed helical chains in the crystal structure, the material exhibits significant chiral optical activity without relying on traditional chiral point groups, and this optical activity is regulated by the thickness. The reason is that the material has a special structure, in which the cation {[CuL 2 (H 2 O)2] 2+} n main framework, the H-bond arrangements of solvent molecules and nitrate anions all form left-handed or right-handed helical chains, and these two types of left-handed and right-handed helical chains can coincide through slip and mirror symmetry operations.

[0029] 2. The asymmetric helical chain Cu-MOF material of the present invention realizes optical second harmonic generation-circular dichroism. There is an obvious difference in the optical second harmonic signal intensities under left-handed circularly polarized light and right-handed circularly polarized light excitation. Under the excitation of 800 nm polarized light, its anisotropy factor g SHG-CDUp to 1.95, which is much higher than the anisotropy of conventional chiral point group materials, and the anisotropy factor can be regulated by controlling the thickness of the Cu-MOF film, thus enabling it to have broad application prospects in chiral optical applications such as circularly polarized light detection, quantum communication, and optical spintronics.

[0030] 3. The preparation method of the present invention has the advantages of mild conditions and simple operation, and the synthesized Cu-MOF material has the characteristics of a large and easily regulated anisotropy factor.

[0031] 4. It is found that the chiral optical coefficients of Cu-MOF films with different thicknesses are significantly different, among which the highest coefficient reaches 1.95, which is very close to the theoretical maximum chiral optical coefficient of 2 and far exceeds that of general chiral crystals. This means that the material can show obvious differences in LCP and RCP, and has broad applications in chiral optics, especially in the direct detection of circularly polarized light (CPL) based on the SHG-CD effect.

[0032] 5. The asymmetric helical chain Cu-MOF material of the present invention has obvious chiral optical activity and can exhibit a large asymmetry factor at room temperature.

[0033] 6. The asymmetric helical chain Cu-MOF material of the present invention can regulate the asymmetry factor by controlling the film thickness, and this operation method is simple, easy to implement, and highly operable, which has great application potential in chiral optics.

[0034] 7. The asymmetric helical chain Cu-MOF material of the present invention belongs to a non-chiral point group, and its chiral optical activity is not limited to traditional chiral point groups, strongly supporting the theory that non-chiral crystals can generate optical activity and providing a strong experimental evidence for the phenomenon that rare non-chiral crystals have optical activity.

[0035] 8. Non-chiral materials may generate chiral optical activity in specific non-chiral point groups due to reasons such as the anisotropy or asymmetric arrangement of molecules in the crystal. The present invention proposes a special left-handed and right-handed helical chain structure, which can generate chiral optical activity in a specific non-chiral point group m.

[0036] 9. The present invention provides new ideas for the design and application of optically active materials, broadens the types of chiral optically active materials, explores the application potential of non-chiral materials in the optical field, and provides more possibilities for the development of new optical devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 XRD pattern of the asymmetric helical chain Cu-MOF material prepared in Example 1;

[0038] Figure 2 Crystal structure diagram of the asymmetric helical chain Cu-MOF material prepared in Example 1;

[0039] Figure 3 SHG-CD optical path diagram;

[0040] Among them, 1 - femtosecond laser, 2 - energy attenuator, 3 - chopper, 4 - λ / 2 wave plate, 5 - λ / 4 wave plate, 6 - long-pass filter, 7 - mirror, 8 - beam splitter prism, 9 - objective lens, 10 - electrically controlled displacement stage, 11 - sample, 12 - lens, 13 - Glan prism, 14 - band-pass filter, 15 - PMT photodetector;

[0041] Figure 4 Graph of the function relationship between the SHG intensity of two Cu-MOF films with different thicknesses and opposite chirality and the rotation angle of the λ / 4 wave plate;

[0042] Figure 5 For a series of Cu-MOF films with different thicknesses, the g SHG-CD Value comparison diagram;

[0043] Figure 6 Chirality coefficient comparison diagram of some chiral compounds and Cu-MOF films in recent years. Detailed implementation manners

[0044] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0045] Example 1

[0046] Asymmetric helical chain Cu-MOF material, with the molecular formula {[CuL 2 (H 2 O) 2 ·(NO 3 ) 2 ·(H 2 O) 1.5 ·(CH 3 OH)} ∞ , where the ligand L is PhPO(NH 4 Py) 2 , Ph is phenyl, NH 4 Py is 4-aminopyridinyl;

[0047] The preparation method of the above asymmetric helical chain Cu-MOF material specifically includes the following steps:

[0048] (1) 11.756 g of 4-aminopyridine and 200 mL of chloroform were stirred well at 0 °C to obtain a 4-aminopyridine suspension;

[0049] (2) 3.475 g of phenylphosphonic dichloride and 10 mL of chloroform were stirred and mixed at 0 °C to obtain a phenylphosphonic dichloride solution;

[0050] (3) The 4-aminopyridine suspension was added dropwise to the phenylphosphonic dichloride solution. After refluxing for 6 h, it was filtered, washed, and dried to obtain ligand L;

[0051] (4) 0.062 g of ligand L and 3 mL of methanol were stirred and dissolved, and then filtered to obtain a ligand L solution;

[0052] (5) 0.0245 g of copper(II) nitrate hexahydrate and 3 mL of methanol were stirred and dissolved, and then filtered to obtain a copper(II) nitrate solution;

[0053] (6) 3 mL of the ligand L solution, 3 mL of water, and 3 mL of the copper(II) nitrate solution were mixed and sealed. After standing at room temperature of 25 °C for 4 weeks, it was filtered, washed, and dried to obtain crystals of the asymmetric helical chain Cu-MOF material.

[0054] Performance Test

[0055] 1. XRD

[0056] The XRD results of the asymmetric helical chain Cu-MOF material prepared in Example 1 are as Figure 1 shown. It can be seen from Figure 1 that the measured XRD curve is basically consistent with the simulated curve of the CIF file, indicating that the material has good crystallinity and high purity. In addition, through XRD and other crystallographic data calculations, it is found that the material belongs to the Cc space group, m point group, and the point group symmetry is "Cs", and it does not belong to the 11 chiral crystallographic point groups (C 1 、C 2 、D 2 、C 4 、D 4 、C 3 、D 3 、C 6 、D 6 、T and O).

[0057] 2. Crystal Structure

[0058] The crystal structure of the asymmetric helical chain Cu-MOF material prepared in Example 1 is as Figure 2 shown. It can be seen from Figure 2 that the asymmetric arrangement of the left-handed and right-handed helical chains in the crystal structure of the material results in the material having chiral optical activity. Among them, the cation {[CuL2 (H 2 O) 2 2+} n The H-bond arrangements of the main framework, solvent molecules, and nitrate anions all form left-handed or right-handed helical chains, and these two types of helical chains, left-handed and right-handed, can coincide through slip and mirror symmetry operations. This special crystal structure brings significant chiral optical activity to the material.

[0059] 3. SHG-CD Optical Path for Characterizing Asymmetry Factor

[0060] Figure 3 An SHG-CD optical path for studying the chiral optical coefficient of the asymmetric helical chain Cu-MOF material prepared in Example 1 and its application in chiral optics is provided, including a femtosecond laser 1, a variable power attenuator 2, a chopper 3, a λ / 2 waveplate 4, a λ / 4 waveplate 5, a long-pass filter 6, a mirror 7, a beam splitter prism 8, an objective lens 9, an electronically controlled displacement stage 10, a lens 12, a Glan prism 13, a band-pass filter 14, and a PMT photodetector 15.

[0061] In the optical path, the λ / 2 waveplate 4 is used to convert the incident light into linearly polarized light; the λ / 4 waveplate 5 is used to modulate the linearly polarized light into circularly polarized light, providing LCP and RCP; the λ / 4 waveplate 5 is disposed on the electronically controlled rotating stage 10, and by controlling the rotation angle of the λ / 4 waveplate 5 through the electronically controlled rotating stage 10, the linearly polarized light is modulated into laser light with different polarization states such as left-handed circularly polarized light, elliptically polarized light, and right-handed circularly polarized light. Then, by collecting the SHG signal responses of the sample under laser light with different polarization states through the PMT photodetector 15, the signal differences of the chiral sample for different (elliptically) circularly polarized lights can be obtained, and thus the SHG anisotropy factor g characterizing the nonlinear circular dichroism can be calculated. SHG-CD . The electronically controlled displacement stage 10 can move the sample 11 through computer program control, enabling precise movement at the nanometer level of several hundred nanometers. It can perform micro-area scanning on a selected area of the sample 11. By calculating the images scanned under LCP and RCP, the purpose of SHG-CD micro-area imaging of the selected area can be achieved, and the g SHG-CD map can intuitively present the chiral optical activity related to the space of the material.

[0062] ​During the experiment, a laser with a wavelength of 800 nm is emitted from the femtosecond laser 1. After being attenuated to an appropriate energy by the variable optical attenuator 2, the laser is modulated to a certain frequency by the chopper 3, and then adjusted to linearly polarized light in a certain direction by the λ / 2 wave plate 4. After that, it is modulated to (elliptically) circularly polarized light by the λ / 4 wave plate 5. The laser passes through the long-pass filter 6 to filter out stray light, and then is focused on the sample 11 mounted on the electronically controlled displacement stage 10 through the mirror 7, the beam splitter prism 8, and the objective lens 9. The reflected laser passes through the objective lens 9, the beam splitter prism 8, the lens 12, and the Glan prism 13, and then the fundamental frequency light of 800 nm is filtered out by the band-pass filter 14. Finally, the SHG signal of 400 nm is received by the PMT photodetector 15.

[0063] 4. Chiral optical coefficient

[0064] The asymmetric helical chain Cu-MOF material prepared in Example 1 was placed on the blue tape, and the Cu-MOF material was mechanically peeled into Cu-MOF thin films with different thicknesses by repeated pasting. The Cu-MOF thin film used for the application research of chiral optical coefficient in chiral optics was a thin film with better quality. Specifically, the surface of the thin film was flat, and the area of the thin film was significantly larger than the laser spot (more than 5 μm × 5 μm).

[0065] Figure 4 For two Cu-MOF thin films with different thicknesses and opposite chirality (g SHG-CD Asymmetric factor symbol), it is a function relationship diagram of the SHG intensity of the Cu-MOF thin film and the rotation angle of the λ / 4 wave plate 5. The 800 nm laser was randomly irradiated on the selected Cu-MOF thin film, and the circularly polarized light was modulated by the λ / 4 wave plate 5. When the rotation angle was 0° and 180°, it was left-handed circularly polarized light (LCP), and when the rotation angle was 90° and 270°, it was right-handed circularly polarized light (RCP). Figure 4 In the lower left figure of, as the λ / 4 wave plate 5 continuously rotates from 0° to 360°, there is an obvious difference in the SHG intensity of the Cu-MOF thin film under left-handed CPL and right-handed CPL. The SHG intensity under left-handed CPL is less than the SHG intensity under right-handed CPL. At the same time, from Figure 4 it can be calculated that Figure 4 In the lower right figure of, as the λ / 4 wave plate 5 continuously rotates from 0° to 360°, there is an obvious difference in the SHG intensity of the Cu-MOF thin film under left-handed CPL and right-handed CPL. The SHG intensity under left-handed CPL is greater than the SHG intensity under right-handed CPL. At the same time, from Figure 4 it can be calculated that The chiral optical coefficients of Cu-MOF films with these two thicknesses not only significantly exceed those of most chiral crystals discovered so far, but also have the ability to distinguish left and right circularly polarized light better than traditional chiral crystals. At the same time, films with stronger response to left-handed CPL or right-handed CPL signals can be selected according to needs.

[0066] Figure 5 is the g of a series of Cu-MOF films with different thicknesses SHG-CD Comparison chart of values. An 800nm ​​laser is randomly hit at a point on the selected Cu-MOF film. The circularly polarized light is modulated by the λ / 4 wave plate 5. When the rotation angle is 0° and 180°, it is left-handed circularly polarized light (LCP). When the rotation angle is 90° and 270°, it is right-handed circularly polarized light (RCP). As the λ / 4 wave plate 5 rotates continuously from 0° to 360°, a functional relationship between the SHG intensity and the rotation angle of the λ / 4 wave plate 5 can be obtained. The g calculated from Cu-MOF films of different thicknesses is SHG-CD The values ​​are summarized in Figure 5 The upper left illustration shows the SHG-CD When g is positive, the state of SHG signal intensity when LCP and RCP light act on Cu-MOF film. At this time, the SHG intensity under left-handed CPL is greater than that under right-handed CPL. The inset in the lower right corner shows the state of SHG signal intensity when g is positive. SHG-CD When it is negative, the state of SHG signal intensity when LCP and RCP light act on Cu-MOF film, at this time, the SHG intensity under left-handed CPL is less than the SHG intensity under right-handed CPL. It can be seen that the chiral optical coefficients of Cu-MOF films of different thicknesses are different, but Cu-MOF films of different thicknesses have obvious resolution for left-handed CPL and right-handed CPL.

[0067] Figure 6 This is a comparison chart of the chiral coefficients (asymmetry factors) of some chiral compounds and Cu-MOF films in recent years. Figure 6 It can be seen that the Cu-MOF film has a large asymmetry factor and has excellent resolution for left and right circularly polarized light, which is better than general chiral compounds.

[0068] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An asymmetric helical chain Cu-MOF material, characterized in that: The molecular formula is {[CuL2(H2O)2]·(NO3)2·(H2O) 1.5 ·(CH3OH)} ∞ , where the ligand L is PhPO(NH 4 Py)2, Ph is phenyl, NH 4 Py is 4-amino substituted pyridyl.

2. The asymmetric spiral chain Cu-MOF material according to claim 1, characterized in that: The thickness of the film is 0.5 to 1.5 μm.

3. The asymmetric spiral chain Cu-MOF material according to claim 2, characterized in that: When the film thickness is 0.5 to 0.7 μm, it is right-handed and the anisotropy factor is -0.79 to -1.

95.

4. The asymmetric spiral chain Cu-MOF material according to claim 2, characterized in that: When the thickness of the film is 0.7-1.5 μm, it is left-handed and the anisotropy factor is 0.94-1.

94.

5. A method for preparing the asymmetric helical chain Cu-MOF material as claimed in claim 1, characterized in that: The specific steps include: (1) 4-aminopyridine and chloroform are fully stirred at 0° C. to obtain a 4-aminopyridine suspension; (2) stirring and mixing phenylphosphonyl dichloride and chloroform at 0° C. to obtain a phenylphosphonyl dichloride solution; (3) adding the 4-aminopyridine suspension dropwise to the phenylphosphonic acid dichloride solution, refluxing for 6 hours, filtering, washing and drying to obtain ligand L; (4) stirring and dissolving the ligand L and methanol, and filtering to obtain a ligand L solution; (5) stirring and dissolving copper nitrate hexahydrate and methanol, and filtering to obtain a copper nitrate solution; (6) The ligand L solution, water and copper nitrate solution are mixed and sealed, and then allowed to stand at room temperature of 25° C. for 4 weeks, filtered, washed and dried to obtain the asymmetric helical chain Cu-MOF material crystal.

6. The method for preparing an asymmetric spiral chain Cu-MOF material according to claim 5, characterized in that: In step (1), the usage ratio of 4-aminopyridine and chloroform is 11.756 g:200 mL; in step (2), the usage ratio of phenylphosphonic dichloride and chloroform is 3.475 g:10 mL; in step (4), the usage ratio of ligand L and methanol is 0.062 g:3 mL; in step (5), the usage ratio of copper nitrate hexahydrate and methanol is 0.0245 g:3 mL; in step (6), the usage ratio of ligand L solution, water and copper nitrate solution is 3 mL:3 mL:3 mL.

7. An application of the asymmetric spiral chain Cu-MOF material as claimed in claim 1 in chiral optics.

8. The use according to claim 7, characterized in that: The chiral optics includes circularly polarized light detection, quantum communication and optical spin electronics.

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