Chiral porphyrin-based COF nanosheet and its preparation method and application

Abstract

This invention belongs to the technical field of chiral nanomaterials, specifically relating to chiral porphyrin-based COF nanosheets, their preparation method, and applications. The invention utilizes a sonochemical room-temperature ultrasonic synthesis method, using isomers of phenylethylamine to induce the preparation of ultrathin chiral porphyrin-based COF nanosheets. These nanosheets exhibit uniform thickness, good crystallinity, and large lateral dimensions. These chiral nanosheets exhibit opposite circular dichroism (CD) spectral signals and can be used as chiral solid-state fluorescence detectors to detect enantiomers of the same chiral compound.

Description

Technical Field

[0001] The present invention belongs to the technical field of chiral nanomaterials, and in particular relates to a chiral porphyrin-based COF nanosheet and a preparation method and application thereof. Background Art

[0002] Covalent organic frameworks (COFs) are a new class of lightweight porous materials with large specific surface area, adjustable periodic pores, designable and predictable structure, and a thermodynamically stable framework with long-range order.

[0003] Since their initial report in 2005, covalent organic frameworks (COFs) have garnered widespread attention. The successful separation of monolayer graphene has provided significant insights into this field, spurring renewed interest in the design and synthesis of two-dimensional polymers. Compared to bulk materials, ultrathin nanosheets offer several advantages: substrate molecules and electrons with lower diffusion / transport barriers can more easily access active sites on the material surface during reactions; they facilitate the modification and regulation of materials by doping with metal atoms or clusters; and their improved dispersibility in solvents facilitates chemical reactions such as catalysis and recognition. As an important branch of the field, two-dimensional ultrathin COFs have demonstrated exceptional performance in numerous fields, including drug separation, photoelectrocatalysis, chemical energy storage, and semiconductor fabrication.

[0004] Chirality, as one of the most important properties of nature, is widely present on Earth. Chiral functionalization is of great significance to biomedicine and materials. Chiral COFs have been shown to be effective in the recognition and separation of chiral substances. In fact, there are many studies on chiral COFs, and their preparation strategies mainly include direct synthesis, chiral induced synthesis and post-modification. Chiral induction is to change the mirror symmetry of the module by adding chiral molecules to the building block. Compared with the direct synthesis method, the chiral induction method gets rid of the difficulty of synthesizing chiral molecules in the early stage; compared with the post-modification method, it avoids the damage to the framework structure caused by subsequent processing; chiral induced synthesis as an ideal method has great exploration value.

[0005] Most COFs currently prepared are synthesized under solvothermal conditions, and their microscopic morphology often exhibits a blocky stack of sheets. The preparation of chiral COFs is also subject to numerous limitations: one reason is the difficulty in constructing chiral ligands, and another is that some chiral modules undergo spatial twisting at the high temperatures of solvothermal reactions. The large-scale, high-yield production of chiral ultrathin COF nanosheets remains a significant challenge, limiting the exploration of the unique functionalities and broad application potential of this class of materials. Summary of the Invention

[0006] In view of the problems existing in the prior art, the present invention provides a chiral porphyrin-based COF nanosheet and a preparation method and application thereof.

[0007] The present invention is achieved through the following technical solutions:

[0008] A chiral porphyrin-based COF nanosheet having a basic structural unit shown in formula I;

[0009] , named COF-367.

[0010] Formula I

[0011] The chiral porphyrin-based COF nanosheets have a uniform thickness of 3-4 nm and a large lateral size of micrometer level.

[0012] The second object of the present invention is to provide a method for preparing the chiral porphyrin-based COF nanosheets, comprising the following steps:

[0013] S1. Dissolve 5,10,15,20-tetrakis(4-aminophenyl)porphyrin (H2TAPP) and terephthalaldehyde (BPDA) in a mixed solvent of mesitylene and ethanol and thoroughly mix them by ultrasonication to form a uniform dispersion. This uniformity facilitates the subsequent reaction and avoids agglomeration or incomplete reaction.

[0014] S2. Add chiral organic ligand: (S)-(-)-1-phenylethylamine (S-PEA) or (R)-(+)-1-phenylethylamine (R-PEA), shake well to form a uniform dispersion;

[0015] S3, add 6 mol / L acetic acid aqueous solution, place in ultrasonic cleaner and continue ultrasonication for 8 hours;

[0016] S4. After the reaction is completed, solid-liquid separation is performed to obtain a dark purple fluffy solid, which is the chiral porphyrin-based COF nanosheet.

[0017] Furthermore, in step S1, the molar ratio of 5,10,15,20-tetrakis(4-aminophenyl)porphyrin to terephthalaldehyde is 1:2; the volume ratio of mesitylene to ethanol in the mixed solvent is 1:1; and the amount of the mixed solvent added is 1 mL of the mixed solvent for every 0.01 mmol of 5,10,15,20-tetrakis(4-aminophenyl)porphyrin.

[0018] Furthermore, in step S2, the molar ratio of the chiral organic ligand (S)-(-)-1-phenylethylamine or (R)-(+)-1-phenylethylamine to 5,10,15,20-tetrakis(4-aminophenyl)porphyrin is (10-40):1.

[0019] Furthermore, in step S3, the volume ratio of the 6 mol / L acetic acid aqueous solution to the mixed solvent is 1: 10. The acetic acid aqueous solution can not only adjust the pH of the reaction environment but also act as a reaction catalyst, promoting the binding of porphyrin and ligand while maintaining the stability of the reactants.

[0020] Furthermore, in step S4, the material is collected by high-speed centrifugation at 8000 rpm for 5 minutes and washed 3-5 times with tetrahydrofuran and ethanol, respectively, to remove unreacted organic ligand molecules and soluble fragments, thereby obtaining a dark purple fluffy solid. High-speed centrifugation and washing with tetrahydrofuran and ethanol can remove unreacted organic ligand molecules and other soluble fragments, thereby improving the purity of the final product and preventing interference from impurities.

[0021] The present invention also provides the application of the chiral porphyrin-based COF nanosheet as a chiral solid fluorescence detector in identifying the enantiomers of 1,2-cyclohexanediamine.

[0022] Furthermore, when an ethanol solution of (1S,2S)-1,2-cyclohexanediamine or (1R,2R)-1,2-cyclohexanediamine was added to the ethanol dispersion of the chiral porphyrin-based COF nanosheets, the fluorescence intensity of the system was enhanced to varying degrees.

[0023] Compared with the prior art, the present invention has the following technical effects:

[0024] (1) The present invention adopts a sonochemical room-temperature ultrasonic synthesis method. Compared with the traditional solvothermal method, this method is more economical and convenient, and it also effectively avoids the axial π-π stacking of COFs and the spatial torsion of chiral ligands caused by high temperature. Based on the dynamic reversible properties of the imine bond, chirality is induced in the COF-367 module, and continuous ultrasonication is performed at room temperature to achieve the preparation of chiral nanosheets. This method for synthesizing ultrathin two-dimensional chiral porphyrin-based COF nanosheets based on chirality induction under room-temperature ultrasonication is universal and simple to process.

[0025] (2) The ultrathin chiral porphyrin-based COF nanosheet material is a dark purple fluffy solid with uniform thickness, good crystallinity and large lateral size.

[0026] (3) During the preparation process, the chiral COF-367 nanosheets induced by isomers of phenylethylamine have opposite circular dichroism (CD) signals.

[0027] (4) The chiral porphyrin-based COF nanosheet material can be used as a chiral solid fluorescence detector to detect enantiomers of the same chiral compound.

[0028] (5) The chiral ultrathin nanosheet material has good dispersibility and can be evenly dispersed in ethanol solvent to serve as a chiral fluorescence detector to detect chiral 1,2-cyclohexanediamine, which has the function of identification and identification. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 HR-TEM image of S40-COF367 NSs obtained in Example 1;

[0030] Figure 2 HR-TEM image of R40-COF367 NSs obtained in Example 1;

[0031] Figure 3 FT-IR spectrum of S40-COF367 NSs obtained in Example 1;

[0032] Figure 4 FT-IR spectrum of R40-COF367 NSs obtained in Example 1;

[0033] Figure 5 TEM image of S40-COF367 NSs obtained in Example 1;

[0034] Figure 6 TEM image of R40-COF367 NSs obtained in Example 1;

[0035] Figure 7 This is the SEM image of S40-COF367 NSs obtained in Example 1;

[0036] Figure 8 This is the SEM image of R40-COF367 NSs obtained in Example 1;

[0037] Figure 9 AFM image of S40-COF367 NSs obtained in Example 1;

[0038] Figure 10 is the AFM image of R40-COF367 NSs obtained in Example 1;

[0039] Figure 11 This is the UV-vis spectrum of S / R40-COF367 NSs obtained in Example 1;

[0040] Figure 12 This is the UV-vis spectrum of S / R30-COF367 NSs obtained in Example 2;

[0041] Figure 13 This is the UV-vis spectrum of S / R20-COF367 NSs obtained in Example 3;

[0042] Figure 14 This is the UV-vis spectrum of S / R10-COF367 NSs obtained in Example 4;

[0043] Figure 15 This is the UV-vis spectrum of COF367 NSs obtained in Example 5;

[0044] Figure 16 CD spectrum of S / R40-COF367 NSs obtained in Example 1;

[0045] Figure 17 CD spectrum of S / R30-COF367 NSs obtained in Example 2;

[0046] Figure 18 CD spectrum of S / R20-COF367 NSs obtained in Example 3;

[0047] Figure 19 CD spectrum of S / R10-COF367 NSs obtained in Example 4;

[0048] Figure 20 CD spectrum of COF367 NSs obtained in Example 5;

[0049] Figure 21 is the fluorescence emission spectrum of S40-COF367 NSs dispersion after adding (R)-(+)-1-phenylethylamine;

[0050] Figure 22 is the fluorescence emission spectrum of S40-COF367 NSs dispersion after adding (S)-(-)-1-phenylethylamine;

[0051] Figure 23 Based on Figure 21 and 22 The fluorescence enhancement curve of S40-COF367 NSs detecting chiral 1,2-cyclohexanediamine is plotted;

[0052] Figure 24 is the fluorescence emission spectrum of R40-COF367 NSs dispersion after adding (R)-(+)-1-phenylethylamine;

[0053] Figure 25 is the fluorescence emission spectrum of R40-COF367 NSs dispersion after adding (S)-(-)-1-phenylethylamine;

[0054] Figure 26 Based on Figure 24 and 25The fluorescence enhancement curve of R40-COF367 NSs detecting chiral 1,2-cyclohexanediamine is plotted. DETAILED DESCRIPTION

[0055] The present invention will be further described below with reference to the embodiments.

[0056] Example 1

[0057] S1. Weigh two portions of 5,10,15,20-tetrakis(4-aminophenyl)porphyrin (6.75 mg, 0.01 mmol) and terephthalaldehyde (4.2 mg, 0.02 mmol) and add them to glass vials. Add 1 mL of a mixed solvent of mesitylene and ethanol to each vial and mix thoroughly by ultrasonication to form a uniform dispersion.

[0058] S2. Add chiral organic ligands separately: add (S)-(-)-1-phenylethylamine (52 μL, 0.4 mmol) to one portion and (R)-(+)-1-phenylethylamine (52 μL, 0.4 mmol) to the other portion, and shake to form a uniform dispersion.

[0059] S3. Add 100 μL of 6 mol / L acetic acid aqueous solution respectively, place in an ultrasonic cleaner and continue ultrasonication at room temperature for 8 h.

[0060] S4. After the reaction is completed, the material is collected by high-speed centrifugation at 8000 rpm for 5 minutes and washed with tetrahydrofuran and ethanol for 3-5 times respectively to remove unreacted organic ligand molecules and soluble fragments to obtain a dark purple fluffy solid, which is the chiral porphyrin-based COF nanosheet material, named S40-COF367 NSs and R40-COF367 NSs.

[0061] Example 2

[0062] S1. Weigh two portions of 5,10,15,20-tetrakis(4-aminophenyl)porphyrin (6.75 mg, 0.01 mmol) and terephthalaldehyde (4.2 mg, 0.02 mmol) and add them to glass vials. Add 1 mL of a mixed solvent of mesitylene and ethanol to each vial and mix thoroughly by ultrasonication to form a uniform dispersion.

[0063] S2. Add chiral organic ligands separately: add (S)-(-)-1-phenylethylamine (39 μL, 0.3 mmol) to one portion and (R)-(+)-1-phenylethylamine (39 μL, 0.3 mmol) to the other portion, and shake to form a uniform dispersion.

[0064] S3. Add 100 μL of 6 mol / L acetic acid aqueous solution respectively, place in an ultrasonic cleaner and continue ultrasonication at room temperature for 8 h.

[0065] S4. After the reaction is completed, the material is collected by high-speed centrifugation at 8000 rpm for 5 minutes and washed with tetrahydrofuran and ethanol for 3-5 times respectively to remove unreacted organic ligand molecules and soluble fragments to obtain a dark purple fluffy solid, which is the chiral porphyrin-based COF nanosheet material, named S30-COF367 NSs and R30-COF367 NSs.

[0066] Example 3

[0067] S1. Weigh two portions of 5,10,15,20-tetrakis(4-aminophenyl)porphyrin (6.75 mg, 0.01 mmol) and terephthalaldehyde (4.2 mg, 0.02 mmol) and add them to glass vials. Add 1 mL of a mixed solvent of mesitylene and ethanol to each vial and mix thoroughly by ultrasonication to form a uniform dispersion.

[0068] S2. Add chiral organic ligands separately: add (S)-(-)-1-phenylethylamine (26 μL, 0.2 mmol) to one portion and (R)-(+)-1-phenylethylamine (26 μL, 0.2 mmol) to the other portion, and shake to form a uniform dispersion.

[0069] S3. Add 100 μL of 6 mol / L acetic acid aqueous solution respectively, place in an ultrasonic cleaner and continue ultrasonication at room temperature for 8 h.

[0070] S4. After the reaction is completed, the material is collected by high-speed centrifugation at 8000 rpm for 5 minutes and washed with tetrahydrofuran and ethanol for 3-5 times respectively to remove unreacted organic ligand molecules and soluble fragments to obtain a dark purple fluffy solid, which is the chiral porphyrin-based COF nanosheet material, named S20-COF367 NSs and R20-COF367 NSs.

[0071] Example 4

[0072] S1. Weigh two portions of 5,10,15,20-tetrakis(4-aminophenyl)porphyrin (6.75 mg, 0.01 mmol) and terephthalaldehyde (4.2 mg, 0.02 mmol) and add them to glass vials. Add 1 mL of a mixed solvent of mesitylene and ethanol to each vial and mix thoroughly by ultrasonication to form a uniform dispersion.

[0073] S2. Add chiral organic ligands separately: add (S)-(-)-1-phenylethylamine (13 μL, 0.1 mmol) to one portion and (R)-(+)-1-phenylethylamine (13 μL, 0.1 mmol) to the other portion, and shake to form a uniform dispersion.

[0074] S3. Add 100 μL of 6 mol / L acetic acid aqueous solution respectively, place in an ultrasonic cleaner and continue ultrasonication at room temperature for 8 h.

[0075] S4. After the reaction is completed, the material is collected by high-speed centrifugation at 8000 rpm for 5 minutes and washed with tetrahydrofuran and ethanol for 3-5 times respectively to remove unreacted organic ligand molecules and soluble fragments to obtain a dark purple fluffy solid, which is the chiral porphyrin-based COF nanosheet material, named S10-COF367 NSs and R10-COF367 NSs.

[0076] Example 5

[0077] S1. Add 5,10,15,20-tetrakis(4-aminophenyl)porphyrin (6.75 mg, 0.01 mmol) and terephthalaldehyde (4.2 mg, 0.02 mmol) into a glass vial. Add 1 mL of a mixed solvent of mesitylene and ethanol and mix thoroughly by ultrasonication to form a uniform dispersion.

[0078] S2. Add 100 μL of 6 mol / L acetic acid aqueous solution and place in an ultrasonic cleaner for continuous ultrasonication at room temperature for 8 h.

[0079] S3. After the reaction is completed, solid-liquid separation is performed to obtain an ahiral porphyrin-based COF nanosheet material, named COF367 NSs.

[0080] Chiral COF nanosheets were synthesized by room-temperature ultrasonic chiral induction using a chiral modulator. However, the addition of an excessive amount of chiral modulator caused the majority of the aldehyde ligands in the reaction system to preferentially react with chiral amino groups, thereby forming fragmented organic polymers. Experimental results confirmed that the addition of more than 40 equivalents of (S)-(-)-1-phenylethylamine or (R)-(+)-1-phenylethylamine relative to 5,10,15,20-tetrakis(4-aminophenyl)porphyrin resulted in extremely low COF nanosheet yields. Most of the solids obtained after the reaction were dissolved and removed by tetrahydrofuran, and the small amount of material obtained lacked a significant circular dichroism signal.

[0081] Characterize the morphology of the material:

[0082] The morphologies of the materials obtained in Examples 1-5 are the same and are characterized as follows:

[0083] (1) The HR-TEM images of S40-COF367 NSs and R40-COF367 NSs obtained in Example 1 are shown in Figure 2. Figure 1 and Figure 2 As shown, it is shown that the target COF material has been successfully prepared in this embodiment, and the COF material has long-range order.

[0084] (2) The FT-IR spectra of S40-COF367 NSs and R40-COF367 NSs obtained in Example 1 are shown in FIG. Figure 3 and Figure 4 As shown, compared with the monomer, the material has a -1 Obvious characteristic peaks appeared on the left and right, which were attributed to the C=N stretching vibration peaks, indicating the successful synthesis of COF.

[0085] (3) TEM images of S40-COF367 NSs and R40-COF367 NSs obtained in Example 1 are shown in FIG. Figure 5 and Figure 6 As shown, both materials have large lateral dimensions at the micron level and uniform ultra-thin radial thickness.

[0086] (4) The SEM images of S40-COF367 NSs and R40-COF367 NSs obtained in Example 1 are shown in FIG. Figure 7 and Figure 8 As shown, it shows that the material has ultra-thin radial thickness and good dispersibility.

[0087] (5) The AFM images of S40-COF367 NSs and R40-COF367 NSs obtained in Example 1 are shown in Figure 2. Figure 9 and Figure 10 As shown, the material has large lateral dimensions reaching the micrometer level and a uniform thickness of about 3-4 nanometers.

[0088] The materials obtained in Examples 1-5 were subjected to UV absorption and CD spectroscopy tests:

[0089] (1) The UV-vis spectrum of S / R40-COF367 NSs obtained in Example 1 is shown in FIG. Figure 11 As shown, it shows that the material has good light absorption in the wavelength range of 300-750nm, and the maximum ultraviolet absorption occurs at around 450nm.

[0090] (2) The UV-vis spectrum of S / R30-COF367 NSs obtained in Example 2 is shown in FIG. Figure 12 As shown, it shows that the material has good light absorption in the wavelength range of 300-750nm, and the maximum ultraviolet absorption occurs at around 450nm.

[0091] (3) The UV-vis spectrum of S / R20-COF367 NSs obtained in Example 3 is shown in FIG. Figure 13 As shown, it shows that the material has good light absorption in the wavelength range of 300-750nm, and the maximum ultraviolet absorption occurs at around 460nm.

[0092] (4) The UV-vis spectrum of S / R100-COF367 NSs obtained in Example 4 is shown in FIG. Figure 14 As shown, it shows that the material has good light absorption in the wavelength range of 300-750nm, and the maximum ultraviolet absorption occurs at around 430nm.

[0093] (5) The UV-vis spectrum of COF367 NSs obtained in Example 5 is shown in FIG. Figure 15 As shown, it shows that the material has good light absorption in the wavelength range of 300-750nm, and the maximum ultraviolet absorption occurs at around 450nm.

[0094] (6) The CD spectrum of S / R40-COF367 NSs obtained in Example 1 is shown in FIG. Figure 16 As shown, the two materials have CD signals with similar intensities but are mirror images of each other, indicating that the two structures induced by chirality have a certain mirror symmetry in space.

[0095] (7) The CD spectrum of S / R30-COF367 NSs obtained in Example 2 is shown in FIG. Figure 17 As shown, the two materials have CD signals with similar intensities but are mirror images of each other, indicating that the two structures induced by chirality have a certain mirror symmetry in space.

[0096] (8) The CD spectrum of S / R20-COF367 NSs obtained in Example 3 is shown in FIG. Figure 18 The two materials have CD signals with similar intensities but are mirror images of each other, indicating that the two structures induced by chirality have a certain mirror symmetry in space.

[0097] (9) The CD spectrum of S / R100-COF367 NSs obtained in Example 4 is shown in FIG. Figure 19 As shown, the two materials have CD signals with similar intensities but are mirror images of each other, indicating that the two structures induced by chirality have a certain mirror symmetry in space.

[0098] (10) The CD spectrum of COF367 NSs obtained in Example 5 is shown in FIG. Figure 20 As shown, the material has no obvious CD spectrum signal, indicating that the material prepared without the presence of a chiral inducing agent does not have chiral characteristics.

[0099] Example 6

[0100] Application of the S40-COF367 NSs nanosheets obtained in Example 1 for fluorescence detection of chiral substances:

[0101] Under an excitation wavelength of 415 nm, the maximum fluorescence emission peak of S40-COF367 NSs is at 660 nm. S40-COF367 NSs nanosheets were dispersed in ethanol. Six 5 μL ethanol dispersions of (1S,2S)-1,2-cyclohexanediamine (0.1 mol / L) were added to each 2.5 mL of the S40-COF367 NSs ethanol dispersion. Fluorescence intensity changes were monitored.

[0102] Under the same conditions, 5 μL of 0.1 mol / L (1R,2R)-1,2-cyclohexanediamine ethanol dispersion was added to 2.5 mL of S40-COF367 NSs ethanol dispersion in batches, and the changes in fluorescence intensity were detected in time. A total of 6 additions were made.

[0103] Comparison of the changes in the maximum fluorescence emission peak of S40-COF367NSs after adding equal amounts of (1S,2S)-1,2-cyclohexanediamine and (1R,2R)-1,2-cyclohexanediamine. Although the position of the maximum fluorescence emission peak did not change, the intensity of the fluorescence emission peak was enhanced to varying degrees. For specific results, refer to Figure 21 and 22 , Figure 21 This is the fluorescence emission spectrum of S40-COF367 NSs dispersion after adding (R)-(+)-1-phenylethylamine. Figure 22 The fluorescence emission spectrum of S40-COF367 NSs dispersion after adding (S)-(-)-1-phenylethylamine shows that the fluorescence response ability of S40-COF367 NSs to (1S,2S)-1,2-cyclohexanediamine and (1R,2R)-1,2-cyclohexanediamine is significantly different.

[0104] The fluorescence enhancement curve is drawn using the maximum fluorescence emission peak intensity at 660 nm, and the equation is defined as I / I0=K EC [X] + 1, where I / I0 is the ratio of the maximum fluorescence intensity before and after the addition of the analyte, [X] is the concentration of the analyte, and K EC is the fluorescence enhancement efficiency. Figure 23 For S40-COF367 NSs, the fluorescence enhancement efficiency K EC[（S,R）-Dia] =0.21L / mmol; Under different amounts of (1R,2R)-1,2-cyclohexanediamine, the fluorescence enhancement efficiency K EC[（S,S）-Dia] =0.10L / mmol; selectivity coefficient α (α=K EC[（S,R）-Dia] / K EC[（S,S）-Dia] ) is 2.1. This demonstrates that S40-COF367 NSs responds more significantly to (1R, 2R)-1,2-cyclohexanediamine.

[0105] Example 7

[0106] Application of the R40-COF367 NSs obtained in Example 1 for fluorescence detection of chiral substances:

[0107] Under an excitation wavelength of 415 nm, the maximum fluorescence emission peak of R40-COF367 NSs is at 660 nm. The nanosheets were dispersed in ethanol. Six 5 μL ethanol dispersions of (1S,2S)-1,2-cyclohexanediamine (0.1 mol / L) were added to each 2.5 mL R40-COF367 NSs ethanol dispersion in batches. Fluorescence intensity changes were monitored.

[0108] Under the same conditions, 5 μL of 0.1 mol / L (1R,2R)-1,2-cyclohexanediamine ethanol dispersion was added in batches to 2.5 mL of R40-COF367 NSs ethanol dispersion, and the changes in fluorescence intensity were detected in time. This was added a total of 6 times.

[0109] Comparison of the changes in the maximum fluorescence emission peak of R40-COF367NSs after adding equal amounts of (1S,2S)-1,2-cyclohexanediamine and (1R,2R)-1,2-cyclohexanediamine. Although the position of the maximum fluorescence emission peak did not change, the intensity of the fluorescence emission peak was enhanced to varying degrees. For specific results, refer to Figure 24 and Figure 25 , indicating that the fluorescence response ability of R40-COF367 NSs to (1S,2S)-1,2-cyclohexanediamine and (1R,2R)-1,2-cyclohexanediamine is significantly different.

[0110] The fluorescence enhancement curve is drawn using the maximum fluorescence emission peak intensity at 660 nm, and the equation is defined as I / I0=K EC [X] + 1, where I / I0 is the ratio of the maximum fluorescence intensity before and after the addition of the analyte, [X] is the concentration of the analyte, and K EC is the fluorescence enhancement efficiency. Figure 26 For R40-COF367 NSs, the fluorescence enhancement efficiency K EC[（R,S）-Dia] =0.28L / mmol; Under different amounts of (1R,2R)-1,2-cyclohexanediamine, the fluorescence enhancement efficiency K EC[（R,R）-Dia] =0.13L / mmol; selectivity coefficient α (α=K EC[（R,S）-Dia] / K EC[（R,R）-Dia] ) is 2.2. It is proved that R40-COF367 NSs responds more significantly to (1S,2S)-1,2-cyclohexanediamine.

Claims

1. A method for preparing chiral porphyrin-based COF nanosheets, characterized in that: The steps include: S1. Dissolve 5,10,15,20-tetrakis(4-aminophenyl)porphyrin H2TAPP and 4,4'-biphenyldicarboxaldehyde in a mixed solvent of mesitylene and ethanol, and thoroughly mix by ultrasonication to form a uniform dispersion; S2. Add chiral organic ligand: (S)-(-)-1-phenylethylamine or (R)-(+)-1-phenylethylamine, shake well to form a uniform dispersion; S3, add 6 mol / L acetic acid aqueous solution, place in ultrasonic cleaner and continue ultrasonication for 8 hours; S4. After the reaction is completed, solid-liquid separation is performed to obtain a dark purple fluffy solid, which is the chiral porphyrin-based COF nanosheet; In step S2, the molar ratio of the chiral organic ligand (S)-(-)-1-phenylethylamine or (R)-(+)-1-phenylethylamine to 5,10,15,20-tetrakis(4-aminophenyl)porphyrin is (10-40):1; The chiral porphyrin-based COF nanosheet has a basic structural unit shown in Formula I; , named COF-367; Formula I The chiral porphyrin-based COF nanosheets have a uniform thickness of 3-4 nm and a large lateral size of micrometer level; The chiral porphyrin-based COF nanosheet is used to identify the enantiomers of 1,2-cyclohexanediamine.

2. The method for preparing chiral porphyrin-based COF nanosheets according to claim 1, wherein: In step S1, the molar ratio of 5,10,15,20-tetrakis(4-aminophenyl)porphyrin to 4,4'-biphenyldicarboxaldehyde is 1:2; the volume ratio of mesitylene to ethanol in the mixed solvent is 1:1; and the amount of the mixed solvent added is 1 mL of the mixed solvent for every 0.01 mmol of 5,10,15,20-tetrakis(4-aminophenyl)porphyrin.

3. The method for preparing chiral porphyrin-based COF nanosheets according to claim 1, wherein: In step S3, the volume ratio of the 6 mol / L acetic acid aqueous solution to the mixed solvent is 1:

10.

4. The method for preparing chiral porphyrin-based COF nanosheets according to claim 1, wherein: In step S4, the material was collected by high-speed centrifugation at 8000 rpm for 5 minutes, and washed with tetrahydrofuran and ethanol 3-5 times, respectively, to remove unreacted organic ligand molecules and soluble fragments, to obtain a dark purple fluffy solid.

5. The method for preparing chiral porphyrin-based COF nanosheets according to claim 1, wherein: When an ethanol solution of (1S,2S)-1,2-cyclohexanediamine or (1R,2R)-1,2-cyclohexanediamine is added to the ethanol dispersion of the chiral porphyrin-based COF nanosheets, the fluorescence intensity of the system is enhanced to varying degrees.

Images