Preparation and application of a chiral MOF-based fluorescent probe

Abstract

The application discloses preparation and application of a high-performance chiral MOF-based fluorescent probe and belongs to the field of functional metal organic framework materials. A chiral luminescent MOF material based on binaphthol skeleton is prepared by coordinating and assembling pyridine functionalized binaphthol ligands with zinc ions. The crystal material is simple in synthesis method, can be prepared on a large scale, is stable in structure and can exist stably in water, and has a significant fluorescence enhancement property with chiral compounds, so that a new MOF-based fluorescent probe material with potential use value is provided for chiral molecules in an aqueous solution.

Description

Technical Field

[0001] This invention belongs to the field of functional metal-organic framework materials technology, specifically relating to a method for preparing a novel chiral metal-organic framework material based on a binaphthol skeleton and its fluorescent recognition application for highly selective and sensitive recognition of amino acid enantiomer molecules. Background Technology

[0002] Chiral compounds play a crucial role in life activities within natural ecosystems. Studies have found that different enantiomers within chiral compounds can lead to variations in their activity in living organisms. For example, the thalidomide drug molecule contains enantiomers with opposite configurations, resulting in significant differences in its pharmacological activity and toxicity. A lack of sufficient understanding and effective detection methods for such chiral compounds could potentially have incalculable consequences in clinical applications. Therefore, developing a highly selective and sensitive method for identifying different enantiomers of chiral compounds is a vital and challenging task.

[0003] In recent years, chiral recognition technology based on enantiomeric fluorescence sensing has demonstrated unparalleled advantages over techniques such as high-performance liquid chromatography (HPLC), circular dichroism spectroscopy (CD), and electrophoresis due to its rapid response, high sensitivity, low cost, and ease of operation. Chiral metal-organic frameworks (MOFs) in luminescent crystalline form have become ideal fluorescent probe materials for enantiomeric selective recognition due to their abundant porosity, ordered pore structure, large specific surface area, and diverse functional groups. Furthermore, the "confining effect" and "pre-enrichment effect" formed by the regularly shaped pores in the MOF framework structure can maximize the dynamic response of the recognition site to chiral guest molecules, achieving high selectivity and high sensitivity for the recognition of low-concentration analytes.

[0004] However, to truly transform the enormous potential of luminescent MOFs in fluorescence detection into practical applications, the following limitations must be overcome: 1) the stability of crystalline materials in aqueous solvents to facilitate the recognition and detection of water-soluble chiral molecules; 2) the directed synthesis of MOFs with multiple active sites to facilitate the highly selective recognition of chiral compounds; and 3) further improvements in the luminescence properties of MOFs to ensure the stability of fluorescence response signal transmission and amplification during the recognition of target organic molecules.

[0005] In this invention, we prepared a chiral luminescent MOF material based on a binaphthol framework by coordinating and assembling a pyridine-functionalized binaphthol ligand with zinc ions. This crystalline material has a simple synthesis method, can be prepared on a large scale, is structurally stable, and can exist stably in water. It exhibits significant fluorescence enhancement properties with chiral compounds, providing a novel MOF-based fluorescent probe material with potential applications for chiral molecules in aqueous solutions. Summary of the Invention

[0006] The purpose of this invention is to provide a novel method for preparing axially chiral metal-organic framework materials and their application in fluorescence recognition of amino acid enantiomers with high selectivity and sensitivity. This chiral metal-organic framework material is assembled from a pyridine-linked tetradentate axially chiral binatol organic ligand coordinated with zinc(II) ions. It exhibits good stability and luminescence properties, abundant pore structure and chiral interaction sites, and demonstrates high enantioselectivity for amino acid molecules in aqueous solution.

[0007] The objective of this invention can be achieved through the following technical solutions:

[0008] A method for preparing a chiral MOF-based fluorescent probe includes: forming the chiral metal-organic framework material using a solvothermal method;

[0009] Specifically, it includes the following steps:

[0010] A certain amount of chiral ligand (S)-L and zinc nitrate were weighed and dissolved in an aqueous solution of 1,4-dioxane. The mixture was then reacted at a constant temperature to form a chiral metal-organic framework material.

[0011] The structure of the chiral ligand (S)-L is as follows:

[0012] ;

[0013] Full name: (S)-4,4',4'',4'''-(2,2'-diethoxy[1,1'-binaphthyl]-4,4',6,6'-tetramethyl)tetrapyridine.

[0014] Preferably, the molar ratio of the chiral ligand to zinc nitrate is 1:(4-6).

[0015] Preferably, the zinc nitrate is zinc nitrate hexahydrate.

[0016] Preferably, the volume ratio of 1,4-dioxane to water is 10:(0.5-1).

[0017] Preferably, the reaction temperature is 95-105℃ and the reaction time is 10-16 hours.

[0018] Preferably, post-treatment is performed after the reaction is completed, including washing and vacuum drying.

[0019] Preferably, the washing process includes washing with acetone and water alternately multiple times.

[0020] Preferably, the vacuum drying conditions are: temperature 80-100℃, time 6-8 hours.

[0021] Another object of the present invention is to provide the application of the metal-organic framework material as a chiral fluorescent probe in the recognition of chiral amino acids and chiral benzyl alcohol.

[0022] The chiral amino acids and chiral benzyl alcohols are arginine, proline, leucine, 1-phenylethanol, etc.

[0023] The fluorescence testing conditions were as follows: deionized water was used as the solvent system, and the concentration of the chiral metal-organic framework suspension was 5.0 × 10⁻⁶. -4 mol / L, at excitation wavelength λ ex =350 nm, slit: 10 / 10 nm, chiral amino acids and chiral benzyl alcohol were identified by fluorescence spectroscopy.

[0024] Experiments have shown that at 5×10 -4 At low concentrations of mol / L, the aforementioned chiral metal-organic frameworks can be used as chiral recognition fluorescent probes to perform qualitative and semi-quantitative analysis of enantiomeric composition.

[0025] The invention prepares a chiral metal-organic framework material based on a binaphthol skeleton, which exhibits good stability and luminescence properties in aqueous solution. Furthermore, its ordered chiral porous structure can undergo host-guest interactions with proline, arginine, leucine, and 1-phenylethanol, achieving highly selective and sensitive enantiomeric recognition, and retains good crystalline state even after cycling.

[0026] The beneficial effects of this invention are:

[0027] 1. The chiral metal-organic framework material provided by this invention has a novel structure and possesses high water stability, a single chiral characteristic, and good luminescence properties, making it easy to store and use.

[0028] 2. The chiral metal-organic framework material provided by this invention has multiple interaction sites within its chiral channels, enabling host-guest interactions with proline, arginine, leucine, and 1-phenylethanol, achieving highly selective and sensitive fluorescent recognition of chiral enantiomers. Therefore, it has potential applications in the detection of chiral molecules in aqueous solutions.

[0029] 3. The solvothermal reaction used in the preparation of the chiral metal-organic framework material provided by this invention is simple to operate, has a high crystal yield, and can be prepared on a large scale. Attached Figure Description

[0030] The invention will now be further described with reference to the accompanying drawings.

[0031] Figure 1 The single-chiral ligand in the example ( S (a) 1H NMR and (b) 1C NMR spectrum of )-L;

[0032] Figure 2 Crystal structure diagram of the chiral metal-organic framework material prepared in Example 1;

[0033] Figure 3 The pXRD pattern of the chiral metal-organic framework material prepared in Example 1;

[0034] Figure 4 Thermogravimetric curves of the chiral metal-organic framework material prepared in Example 1;

[0035] Figure 5 The ligand prepared in Example 1 ( S Solid-state fluorescence spectra of )-L and metal-organic framework materials;

[0036] Figure 6 The graph shows the fluorescent titration data of arginine in aqueous solution by the chiral metal-organic framework material prepared in Example 2.

[0037] Figure 7 The graph shows the fluorescent titration data of proline in aqueous solution by the chiral metal-organic framework material prepared in Example 3.

[0038] Figure 8 The graph shows the fluorescence titration data of the chiral metal-organic framework material prepared in Example 5 on 1-phenylethanol in aqueous solution.

[0039] Figure 9 The image shows the fluorescent titration data of leucine in aqueous solution by the chiral metal-organic framework material prepared in Example 4. Detailed Implementation

[0040] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0041] The chiral ligands used in the following embodiments ( S)-L is prepared through the following steps:

[0042] S1. will ( S Naphthol (CAS: 18531-99-2), bromoethane, potassium carbonate, and acetone were mixed and refluxed under an inert gas atmosphere for 5-10 hours. After the reaction was completed, the mixture was cooled, some of the solvent was removed, and the mixture was diluted with water and stirred for 5-10 hours. The mixture was then filtered and washed with distilled water to obtain intermediate 1. The reaction formula is as follows:

[0043] ;

[0044] S2. Intermediate 1 was mixed with dichloromethane, and liquid bromine was added dropwise at -5°C to 5°C. After the addition was complete, the mixture was allowed to return to room temperature for further reaction. After the reaction was complete, excess bromine was quenched with sodium thiosulfate aqueous solution, the organic phase was separated, dried, and distilled under reduced pressure to obtain the crude product. The crude product was then purified by column chromatography to obtain intermediate 2. The molar ratio of intermediate 1 to liquid bromine was 1:5. The reaction formula is as follows:

[0045] ;

[0046] S3. The intermediate 2,4-pyridineboronic acid pinacol ester, potassium phosphate trihydrate, and tetrakis(triphenylphosphine)palladium were added to N,N-dimethylformamide as raw materials, and reacted at 95-105℃ for 1-5 days under an inert gas atmosphere. After the reaction, the crude product was obtained by vacuum distillation, and the chiral ligand was obtained by column chromatography. S The molar ratio of intermediate 2,4-pyridineboronic acid pinacol ester (CAS: 181219-01-2), potassium phosphate trihydrate, and tetrakis(triphenylphosphine)palladium is 1:6:6:0.2; the reaction formula is as follows:

[0047] ;

[0048] like Figure 1 As shown, this is the chiral ligand ( S The proton and carbon spectra of )-L.

[0049] Example 1

[0050] Chiral metal-organic framework materials are synthesized via a solvothermal method, including the following steps:

[0051] Weigh the chiral ligands ( S 56 mg (0.086 mmol) of 1,4-dioxane was dissolved in 10 mL of 1,4-dioxane. Zinc nitrate hexahydrate (102.40 mg, 0.34 mmol) was then weighed and dissolved in 0.5 mL of deionized water. The solution was sonicated for 5 min to ensure complete dissolution and uniform dispersion. The mixture was sealed in a 20 mL reaction flask and reacted at 100 °C for 12 hours to obtain pale yellow octahedral crystals.

[0052] The crystal sample of the crystalline material was subjected to diffraction at 193 K using a single-crystal diffractometer. The crystal structure was then refined using the Olex2 structural analysis software. See [link to specific structure]. Figure 2 The purity of the overall prepared samples was confirmed by X-ray powder diffraction.

[0053] After naturally cooling to room temperature, the mother liquor was removed, and the crystal sample was collected. It was then washed three to four times with deionized water and acetone, and dried under vacuum at 80°C for 6 hours to obtain high-quality chiral metal-organic framework materials with a yield of 80%.

[0054] like Figures 3-5 The figure shown is a performance characterization diagram of the chiral metal-organic framework material prepared in the example.

[0055] The structure of the chiral metal-organic framework material prepared in Example 1 is as follows: Figure 2 As shown. The prepared chiral metal-organic framework material crystallizes in a tetragonal chiral space I41, and the asymmetric unit contains two ligands ( S )-L, three zinc ions and six water molecules. The zinc ions adopt a six-coordinate mode, coordinating with the nitrogen atoms on the four pyridine groups and the oxygen atoms on the two water molecules. The ligands in this asymmetric unit employ two coordination modes: one ligand ( S All nitrogen atoms on the pyridine group of the )-L ligand participate in coordination, forming a (4,4) interconnected three-dimensional network with zinc ions; nitrogen atoms on the pyridine group of the other ligand participate in coordination, forming a (4,2) interconnected three-dimensional network with zinc ions, while the remaining two nitrogen atoms are in a free state, providing additional interaction sites in the pores that can interact with guest molecules.

[0056] Example 2

[0057] Fluorescent titration of D / L-arginine using chiral metal-organic frameworks:

[0058] The chiral metal-organic framework material obtained during the process was thoroughly ground, and 3.0 mg was weighed and dispersed in 2 mL of deionized water. The mixture was sonicated for 20 minutes to ensure a uniform distribution and prepare a suspension. Then, an aqueous solution (1 × 10⁻⁶) of arginine containing D- or L-enantiomers was added dropwise to the suspension. -2 (mol / L), and its fluorescence intensity was tested. For example... Figure 6 As shown, the prepared chiral metal-organic framework exhibits a significant fluorescence enhancement effect with the addition of arginine solution. Furthermore, due to the chiral channels, the host-guest interaction of the chiral metal-organic framework with L-arginine becomes more pronounced. The enantioselectivity EF is calculated to be 16.04 using the Benesi-Hildebrand equation.

[0059] Example 3

[0060] Fluorescent titration of D / L-proline using chiral metal-organic frameworks:

[0061] The chiral metal-organic framework material obtained during the process was thoroughly ground, and 3.0 mg was weighed and dispersed in 2 mL of deionized water. The mixture was sonicated for 20 minutes to ensure a uniform distribution and prepare a suspension. Then, an aqueous solution of proline containing D- or L-enantiomers (1 × 10⁻⁶) was added dropwise to the suspension. -2 (mol / L), and its fluorescence intensity was tested. For example... Figure 7 As shown, the prepared chiral metal-organic framework exhibits a significant fluorescence enhancement effect with the dropwise addition of proline solution. Furthermore, due to the chiral channels, the host-guest interaction of the chiral metal-organic framework with L-proline becomes more pronounced. The enantioselectivity EF is calculated to be 16.44 using the Benesi-Hildebrand equation.

[0062] Example 4

[0063] Fluorescent titration of D / L-leucine using chiral metal-organic frameworks:

[0064] The chiral metal-organic framework material obtained during the process was thoroughly ground, and 3.0 mg was weighed and dispersed in 2 mL of deionized water. The mixture was sonicated for 20 minutes to ensure a uniform distribution and prepare a suspension. Then, an aqueous solution of proline containing D- or L-enantiomers (1 × 10⁻⁶) was added dropwise to the suspension. -2 (mol / L), and its fluorescence intensity was tested. For example... Figure 9 As shown, the prepared chiral metal-organic framework exhibits a significant fluorescence enhancement effect with the addition of leucine solution. Furthermore, due to the chiral channels, the host-guest interaction of the chiral metal-organic framework with L-leucine becomes more pronounced. The enantioselectivity EF is calculated to be 1.97 using the Benesi-Hildebrand equation.

[0065] Example 5

[0066] Fluorescent titration of R / S-1-phenylethanol using chiral metal-organic frameworks:

[0067] The chiral metal-organic framework material obtained during the process was thoroughly ground, and 3.0 mg was weighed and dispersed in 2 mL of deionized water. The mixture was sonicated for 20 minutes to ensure a uniform distribution and prepare a suspension. Then, an aqueous solution of 1-phenylethanol containing R- or S-enantiomers (1 × 10⁻⁶) was added dropwise to the suspension. -2 (mol / L), and its fluorescence intensity was tested. For example... Figure 8As shown, the prepared chiral metal-organic framework exhibits a significant fluorescence enhancement effect with the dropwise addition of 1-phenylethanol solution. Furthermore, due to the chiral channels, the host-guest interaction of the chiral metal-organic framework with S-1-phenylethanol becomes more pronounced. The enantioselectivity EF is calculated to be 3.85 using the Benesi-Hildebrand equation.

[0068] In summary, the above embodiments are based on a novel and stable chiral metal-organic framework material. X-ray crystallography results show that the material exhibits a triple interpenetrating structure with internal chiral channels capable of accommodating small organic molecules. A series of fluorescence titration experiments demonstrate that the crystal channels of the material can undergo host-guest chemical interactions with organic molecules such as amino acids and 1-phenylethanol, leading to enhanced fluorescence. Furthermore, further fluorescence titration studies show that the material's binding affinity to one enantiomer is significantly higher than that to another, enabling specific recognition. This invention provides a simple, feasible, highly selective, and highly sensitive method for recognizing chiral molecules in aqueous solutions.

[0069] The above detailed embodiments provide a specific description of the analytical methods involved in this invention. It should be noted that the above description is only intended to help those skilled in the art better understand the methods and ideas of this invention, and is not intended to limit the scope of the invention. Without departing from the principles of this invention, those skilled in the art can make appropriate adjustments or modifications to this invention, and such adjustments and modifications should also fall within the protection scope of this invention.

Claims

1. A method for preparing a chiral MOF-based fluorescent probe, characterized in that, The method comprises the following steps: forming the chiral metal organic framework material by a solvothermal method; specifically comprising the following steps: weighing a certain amount of a chiral ligand (S)-L and zinc nitrate, dissolving them in an aqueous solution of 1,4-dioxane, and reacting at a constant temperature to form a chiral metal organic framework material; wherein the chiral ligand (S)-L has the following structure: ； Full name: (S)-4,4',4'',4'''-(2,2'-diethoxy[1,1'-binaphthalene]-4,4',6,6'-tetrayl)tetrapyridine.

2. The method for preparing a chiral MOF-based fluorescent probe according to claim 1, characterized in that, The molar ratio of the chiral ligand to zinc nitrate is 1:(4-6).

3. The method for preparing a chiral MOF-based fluorescent probe according to claim 1, characterized in that, The zinc nitrate is zinc nitrate hexahydrate.

4. The method for preparing a chiral MOF-based fluorescent probe according to claim 1, characterized in that, The volume ratio of 1,4-dioxane to water is 10:(0.5-1).

5. The method for preparing a chiral MOF-based fluorescent probe according to claim 1, characterized in that, The reaction temperature is 95-105 DEG C, and the reaction time is 10-16 hours.

6. The method for preparing a chiral MOF-based fluorescent probe according to claim 1, characterized in that, After the reaction is completed, post-treatment is performed, which includes washing and vacuum drying.

7. The application of a chiral MOF-based fluorescent probe prepared by the method of any one of claims 1-6 in identifying chiral amino acids and chiral benzyl alcohol.

8. Use according to claim 7, characterized in that, The chiral amino acids and chiral benzyl alcohol include arginine, proline, leucine, and 1-phenylethanol.

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