Porous hydrogen bond organic framework fluorescent probe for detecting 3-nitropropionic acid as well as preparation method and application of porous hydrogen bond organic framework fluorescent probe

Abstract

The invention belongs to the technical field of hydrogen bond organic frameworks, and particularly relates to a porous hydrogen bond organic framework fluorescent probe for 3-nitropropionic acid detection and a preparation method and application thereof, and the porous hydrogen bond organic framework fluorescent probe is constructed by 2 ', 7'-dichlorofluorescein and 4, 4 '-azopyridine. The porous hydrogen bond organic framework fluorescent probe can realize quantitative detection of 3-nitropropionic acid, and has the characteristics of simplicity in operation, high sensitivity, good selectivity, high response speed, low detection limit and the like.

Description

Technical Field

[0001] This invention belongs to the field of hydrogen-bonded organic framework technology, and specifically relates to a porous hydrogen-bonded organic framework fluorescent probe for the detection of 3-nitropropionic acid, its preparation method and application. Background Technology

[0002] Food spoilage is a global problem. Ingesting food contaminated with mycotoxins (toxic secondary metabolites produced by fungi, commonly known as mold) poses a risk of poisoning to humans and animals. Globally, at least 2% of food is contaminated with mold each year, causing significant economic losses. Among various toxic mycotoxins, 3-nitropropionic acid (3-NPA), a secondary metabolite produced by *Fusarium moniliforme* in moldy sugarcane, is commonly found in moldy sugarcane, grains, and other agricultural products and has been identified as a pathogen causing poisoning events. This toxin is closely associated with poisoning events in humans and animals and can lead to Huntington's disease-like symptoms, central nervous system dysfunction, and brain damage in children. As a potent neurotoxin, 3-NPA can cause cellular energy metabolism disorders by inhibiting succinate dehydrogenase (SDH) in mitochondria, leading to oxidative stress and neuronal death, which in turn can cause central nervous system dysfunction, and in severe cases, even brain damage or death. 3-NPA contamination in food is particularly prevalent in warm and humid regions, and it is a significant pathogen causing food poisoning incidents. Because it is difficult to detect early signs of mold or spoilage, cases of fatal food poisoning caused by 3-NPA due to accidental ingestion of moldy sugarcane still occur frequently. Currently, the Chinese national standard (GB 2761-2017) stipulates a maximum limit of 40 μg / kg for 3-NPA in food. Therefore, developing highly sensitive and selective methods for detecting 3-NPA is of great significance for ensuring food safety and public health.

[0003] Hydrogen-bonded organic frameworks (HOFs) are crystalline porous materials composed of organic building blocks (OBUs) interacting through hydrogen bonds. Besides hydrogen bonds, other intermolecular forces such as π-π interactions, van der Waals forces, and electrostatic interactions play crucial roles in the construction and stabilization of HOFs. In recent years, as an emerging porous framework material, HOFs have shown broad application prospects in gas adsorption, separation, guest molecule recognition, drug delivery, and proton conduction. HOFs used for fluorescence sensing need to possess permanent porous spaces to achieve specific recognition, and the captured analytes should be able to interact closely with the host HOFs to alter their fluorescence properties. Studying the precise molecular structure and conformation of HOFs helps to explore their response mechanisms to analytes. Since 3-NPA contains multiple hydrogen bond binding sites, it is expected to form specific composite structures with HOFs, causing changes in HOF fluorescence. Therefore, developing a HOF-based fluorescence sensor with high sensitivity and selectivity using 3-NPA is feasible and necessary. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a porous hydrogen-bonded organic framework fluorescent probe for the detection of 3-nitropropionic acid, its preparation method and application, which gives 3-NPA the advantages of simple operation, high sensitivity, good selectivity, fast response speed and low detection limit.

[0005] This invention provides a porous hydrogen-bonded organic framework fluorescent probe for the detection of 3-nitropropionic acid, constructed from 2',7'-dichlorofluorescein and 4,4'-azopyridine, with the chemical formula C. 30 H 17 Cl2N4O5 was named HOF-DCF-abp.

[0006] Furthermore, the single-crystal structure of the porous hydrogen-bonded organic framework fluorescent probe is triclinic, space group P-1, with the following unit parameters: a = 10.79 Å, b = 11.08 Å, c = 12.89 Å, α = 79.59°, β = 68.60°, γ = 70.74°, V = 1353.61 Å. 3 .

[0007] Furthermore, the 2',7'-dichlorofluorescein and 4,4'-azopyridine form a two-dimensional network through intermolecular hydrogen bonding interactions, and a three-dimensional porous hydrogen-bonded organic framework through layer-to-layer π-π interactions.

[0008] Furthermore, the porous hydrogen-bonded organic framework fluorescent probe is a crystalline porous material with a pore size of 5-7 nm.

[0009] This invention provides a method for preparing the above-mentioned porous hydrogen-bonded organic framework fluorescent probe, comprising the following steps: dissolving 2',7'-dichlorofluorescein and 4,4'-azopyridine in a methanol / water mixed solvent system, and preparing the porous hydrogen-bonded organic framework fluorescent probe by a solvothermal synthesis method.

[0010] Preferably, the mass ratio of 2',7'-dichlorofluorescein to 4,4'-azopyridine is 10:7.

[0011] Preferably, the reaction temperature of the solvothermal synthesis method is 140 ± 5 ℃, and the reaction time is 72 ± 12 hours.

[0012] More preferably, the reaction temperature of the solvothermal synthesis method is 140 °C and the reaction time is 72 hours.

[0013] Preferably, the volume ratio of methanol to water in the methanol / water mixed solvent system is 3:2-5:3.

[0014] More preferably, the volume ratio of methanol to water in the methanol / water mixed solvent system is 5:3.

[0015] Preferably, the porous hydrogen-bonded organic framework is a needle-shaped orange-yellow crystal.

[0016] The present invention also provides an application of the above-mentioned porous hydrogen-bonded organic framework fluorescent probe in the detection of 3-nitropropionic acid.

[0017] Furthermore, the application specifically involves dispersing the porous hydrogen-bonded organic framework fluorescent probe in water to form a suspension, thereby achieving qualitative and quantitative detection of 3-NPA through the fluorescence quenching effect.

[0018] Preferably, the concentration of the suspension is 0.30-0.36 g / L, and the detection limit is less than 6.6 μM.

[0019] Beneficial effects.

[0020] (1) This invention utilizes a solvothermal synthesis method to successfully develop a novel porous hydrogen-bonded organic framework material (HOF-DCF-abp), which can be used as a fluorescent probe for detecting 3-NPA. The preparation process is simple, the obtained material has excellent stability and is easy to operate, showing broad application prospects.

[0021] (2) The HOF-DCF-abp fluorescent probe in this invention can perform qualitative and quantitative analysis of trace 3-NPA in solution. It has the characteristics of rapid response, low detection limit and high selectivity. It is an ideal choice with great potential for real-time monitoring of 3-NPA and has significant practical value in related fields such as chemistry and biology. Attached Figure Description

[0022] Figure 1 This is a structural diagram of HOF-DCF-abp obtained in Example 1.

[0023] Figure 2 The thermogravimetric curve of HOF-DCF-abp obtained in Example 1 is shown.

[0024] Figure 3 The image is a transmission electron microscope (TEM) image of HOF-DCF-abp obtained in Example 1.

[0025] Figure 4 The nitrogen isothermal adsorption-desorption curves of HOF-DCF-abp obtained in Example 1 are shown.

[0026] Figure 5 The fluorescence spectra of HOF-DCF-abp obtained in Example 1 in 3-NPA solutions of different concentrations are shown.

[0027] Figure 6 This is a fitted curve showing the relationship between the fluorescence emission intensity of the HOF-DCF-abp fluorescent probe obtained in Example 1 and the concentration of 3-NPA.

[0028] Figure 7 The data represents the selection of the quenching response of the HOF-DCF-abp fluorescent probe obtained in Example 1 to 3-NPA.

[0029] Figure 8 The FT-IR spectra of HOF-DCF-abp, HOF-DCF-abp+3-NPA and 3-NPA obtained in Example 1 are shown. Detailed Implementation

[0030] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0031] The method for preparing porous hydrogen-bonded organic frameworks in this invention, through optimization of reaction conditions, determined the key reaction parameters for obtaining high-yield, highly crystalline needle-like orange-yellow single crystals. The optimization process mainly focused on core factors such as solvent composition, reaction temperature, and reaction time.

[0032] Solvent composition optimization: First, single solvents (methanol, ethanol, water, acetonitrile, N,N-dimethylformamide, etc.) and mixed solvent systems in different proportions were investigated. Experiments revealed that the methanol / water mixed solvent system was crucial for the crystallization of the target product. When using pure methanol or pure water, no crystalline product was obtained, or only an amorphous precipitate was produced. Further optimization of the methanol / water volume ratio was conducted. Various ratios (V...) were tested.甲醇 :V 水 = 4:1, 3:2, 1:1, 2:3, 1:4). The results show that when the volume ratio of methanol to water is 3:2-5:3 (preferably 5:3), needle-like orange-yellow crystals with uniform morphology and optimal crystallinity can be obtained. This ratio range can effectively balance the solubility of the reactants and the crystal nucleation / growth rate. Too low or too high water content will lead to inhibited crystal growth or the formation of impurity phases.

[0033] Reaction temperature optimization: at a determined preferred solvent ratio (V 甲醇 :V 水 The effects of different reaction temperatures (e.g., 100 ℃, 120 ℃, 130 ℃, 140 ℃, 150 ℃, 160 ℃) on crystal formation were investigated at a ratio of 5:3. The study found that below 130 ℃, the reaction rate was too slow, making it difficult to form complete crystals or only yielding microcrystals; above 150 ℃, the products were prone to decomposition or carbonization, resulting in darker crystal color and irregular morphology. The optimal reaction temperature was determined to be 140 ℃. At this temperature, the reaction kinetics were suitable, promoting sufficient and slow crystal growth, ultimately yielding large, well-formed, and high-purity needle-like orange-yellow single crystals.

[0034] Reaction time optimization: at the optimal solvent ratio (V 甲醇 :V 水 The effects of different reaction times (e.g., 1 day, 2 days, 3 days, 4 days, and 5 days) on crystal quality and yield were investigated under the conditions of a 5:3 ratio and a reaction temperature (140 ℃). When the reaction time was less than 2 days, crystal growth was incomplete, resulting in smaller crystals and lower yield. When the reaction time exceeded 4 days, crystal size growth was not significant, and there was a risk of crystal fusion or slight dissolution. The optimal reaction time was determined to be 3 days, which is sufficient to ensure that the crystals complete the nucleation and growth process, achieving the ideal size and crystallinity, while avoiding unnecessary energy consumption and potential side reactions.

[0035] Example 1

[0036] This embodiment prepares a porous hydrogen-bonded organic framework fluorescent probe based on optimized reaction conditions, specifically including the following steps: 2',7'-dichlorofluorescein (10 mg) and 4,4'-azopyridine (7 mg) are weighed and dissolved in a methanol / water mixed solvent system (5 mL methanol, 3 mL water). The solution is then sealed in a polytetrafluoroethylene liner, and finally the liner is placed in a stainless steel reactor and placed in an oven at 140 °C for 3 days. After cooling to room temperature, needle-shaped orange-yellow crystals are obtained, denoted as HOF-DCF-abp.

[0037] The structure of the synthesized HOF-DCF-abp was analyzed, and the following results were obtained: Figure 1The structure shown is constructed from 2',7'-dichlorofluorescein and 4,4'-azopyridine through intermolecular hydrogen bonds and π-π interactions, forming a three-dimensional porous structure. Figure 2 As shown, the thermal stability of HOF-DCF-abp from room temperature to 800 °C was investigated by thermogravimetric analysis (TGA). The TGA curves indicate that solvent molecules in the structure were removed at 130-220 °C. These test results demonstrate that HOF-DCF-abp possesses good structural and thermal stability.

[0038] Transmission electron microscopy image of HOF-DCF-abp as shown below Figure 3 As shown, HOF-DCF-abp exhibits a blocky structure with uniform distribution, smooth surface, and uniform size. Nitrogen isothermal adsorption-desorption data ( Figure 4 The results show that HOF-DCF-abp is a mesoporous material, and the pore size of HOF-DCF-abp is calculated to be 5.6 nm according to density functional theory.

[0039] To investigate the fluorescence response of HOF-DCF-abp to 3-NPA, thoroughly ground HOF-DCF-abp was dispersed in water and sonicated to obtain a suspension with a concentration of 0.33 g / L. Figure 5-6 As shown, the emission intensity of HOF-DCF-abp significantly decreased upon gradual addition of 3-NPA solution to the HOF-DCF-abp suspension. When 30 μM of 3-NPA was added to the HOF-DCF-abp suspension, the fluorescence quenching efficiency was 86%. Experimental results indicate that the detection limit of this fluorescent probe material for 3-NPA is 6.6 μM, and it exhibits good detection performance for 3-NPA in the concentration range of 12-150 μM, demonstrating that this fluorescent probe can quantitatively detect 3-NPA. Therefore, this fluorescent probe has significant application value for the quantitative detection of 3-NPA produced in moldy sugarcane.

[0040] from Figure 7 It can be seen that HOF-DCF-abp exhibits significantly better selectivity and fluorescence quenching response to 3-nitropropionic acid than common organic acids and sugars (serine, alanine, glucose, fructose, sucrose).

[0041] Characterization by FT-IR ( Figure 8 This confirms that the HOF-DCF-abp material, after adsorbing 3-NPA, reaches a focal length of 1728.2 cm⁻¹. -1A new characteristic absorption peak appears, which is attributed to the stretching vibration of the carbonyl group (C=O) in 3-NPA. This phenomenon proves that 3-NPA has been successfully adsorbed into the material, and that its carbonyl group has undergone specific hydrogen bonding interaction with the pyridine nitrogen atom at the active site in the HOF-DCF-abp framework, thereby achieving highly selective detection of this molecule.

[0042] In summary, the HOF-DCF-abp used in this invention, as a fluorescent probe, gradually reduces the intensity of its green luminescent center (530 nm) after interaction with 3-NPA, thus achieving quantitative detection of 3-NPA produced in moldy sugarcane. The porous hydrogen-bonded organic framework fluorescent probe provided by this invention exhibits good linearity in sensing 3-NPA, with high selectivity and a low detection limit. Furthermore, the fluorescent probe in this invention is characterized by low dosage, simple synthesis process, and high operability, thus possessing broad application prospects.

Claims

1. A porous hydrogen-bonded organic framework fluorescent probe for the detection of 3-nitropropionic acid, characterized in that, The porous hydrogen-bonded organic framework fluorescent probe is constructed from 2',7'-dichlorofluorescein and 4,4'-azopyridine.

2. The porous hydrogen-bonded organic framework fluorescent probe according to claim 1, characterized in that, The porous hydrogen-bonded organic framework fluorescent probe has a single-crystal structure in the triclinic system, space group P-1, with the following unit parameters: a = 10.79 Å, b = 11.08 Å, c = 12.89 Å, α = 79.59°, β = 68.60°, γ = 70.74°, V = 1353.61 Å. 3 .

3. The porous hydrogen-bonded organic framework fluorescent probe according to claim 1, characterized in that, The porous hydrogen-bonded organic framework fluorescent probe is a crystalline porous material with a pore size of 5-7 nm.

4. A method for preparing a porous hydrogen-bonded organic framework fluorescent probe, characterized in that, The preparation method includes the following steps: dissolving 2',7'-dichlorofluorescein and 4,4'-azopyridine in a methanol / water mixed solvent system, and preparing a porous hydrogen-bonded organic framework fluorescent probe by solvothermal synthesis.

5. The method for preparing a porous hydrogen-bonded organic framework fluorescent probe according to claim 4, characterized in that, The mass ratio of 2',7'-dichlorofluorescein to 4,4'-azopyridine is 10:

7.

6. The method for preparing the porous hydrogen-bonded organic framework fluorescent probe according to claim 4, characterized in that, The reaction temperature of the solvothermal synthesis method is 140 ± 5 ℃, the reaction time is 72 ± 12 hours, and the volume ratio of methanol to water in the methanol / water mixed solvent system is 3:2-5:

3.

7. The application of a porous hydrogen-bonded organic framework fluorescent probe as described in claim 1 in the detection of 3-nitropropionic acid.

8. The application according to claim 7, characterized in that, The porous hydrogen-bonded organic framework fluorescent probe is dispersed in water to form a suspension, and qualitative and quantitative detection of 3-nitropropionic acid is achieved through fluorescence quenching effect.

9. The application according to claim 8, characterized in that, The concentration of the suspension was 0.30-0.36 g / L, and the detection limit was less than 6.6 μM.

Images