Preparation of an ultrafast, visualized volatile amine response sensor based on covalent organic framework materials
By embedding pyridinium linker units into covalent organic framework materials, TPCH-mOBPy+ materials were prepared, solving the problem of porosity reduction in traditional methods and realizing rapid and visualized volatile amine sensing and food freshness monitoring.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- JIANGNAN UNIV
- Filing Date
- 2023-08-04
- Publication Date
- 2026-06-19
AI Technical Summary
Traditional post-modification methods introduce triggers into covalent organic framework materials, which leads to a decrease in porosity, making it difficult to achieve efficient volatile amine sensing, and the lack of suitable building blocks results in insufficient sensing characteristics.
By using a bottom-up synthesis method, pyridinium linker units are embedded into a covalent organic framework material to form a two-dimensional layered TPCH-mOBPy+ material. The electrostatic interaction between the TPCH-mOBPy+ and volatile amines induces a reversible fluorescence change, thus avoiding porosity loss.
It achieves visualized volatile amine detection with millisecond-level response speed, has a stable material structure, can monitor biogenic amines in the food spoilage process in real time, and provides non-contact quantitative assessment of meat freshness.
Smart Images
Figure CN117164790B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the fabrication of an ultrafast, visualized volatile amine response sensor based on covalent organic framework materials, belonging to the field of stimulus-responsive chemical sensing materials technology. Background Technology
[0002] Nitrogen-containing volatile amines, such as ammonia, methylamine, aniline, and biogenic amines, are easily released and / or generated during chemical production, environmental changes, and food spoilage, and can have serious effects on human health, such as gastrointestinal poisoning, headaches, and palpitations. Highly sensitive, visualized, online, and real-time sensing platforms are essential and necessary to reduce the harm of volatile amines to human health and limit the exponential growth of global food safety problems. Currently, due to the indirect and inefficient interactions between sensors and molecules, assessing amines at the molecular level and constructing an efficient signal recognition-translation protocol remain pressing problems for these sensors. Summary of the Invention
[0003] [Technical Issues]
[0004] Traditional post-modification methods for introducing "triggers" into covalent organic framework materials to respond to foreign molecules have various drawbacks. For example, they can lead to a decrease in porosity and further weaken host-guest interactions, ultimately making it difficult to achieve the desired sensing performance. Furthermore, due to the lack of suitable building blocks, designing the framework structure of covalent organic framework materials to endow them with ideal sensing properties remains a significant challenge.
[0005] [Technical Solution]
[0006] To address the above-mentioned technical problems, this invention proposes a method for designing and fabricating a volatile amine sensor based on a covalent organic framework material that features visualized color changes, structural stability, and reversibility.
[0007] Covalent organic framework materials, as a class of porous and finely tuned crystalline materials linked by covalent bonds, have been widely used in chemical separation, catalysis, batteries, and sensing systems. Among them, SP... 2Carbon-conjugated covalent organic frameworks (CFOs) possess a rigid framework and an extended in-plane π-conjugated network. Due to their high specific surface area and abundant active units, they hold promise as ideal platforms for constructing molecular sensors based on CFOs. To develop molecular sensors based on porous materials, functional "triggers," i.e., recognition units, are typically post-modified as side chains on the pore / channel surface. However, this post-modification strategy, which grafts guest components into the channels, significantly reduces the specific surface area of the CFO and drastically decreases sensing efficiency. A "bottom-up" synthesis approach, embedding the recognition unit into the framework rather than on the side chain, avoids porosity loss and allows for greater conversion efficiency in recognizing guest molecules. In the building blocks of such CFOs, pyridine-containing linkers provide π-electron defects in the framework and enhance the interaction between the CFO and electron-rich chemical species. Based on this, this invention embeds such pyridine-containing linkers into the framework of a CFO, creating an electron-deficient framework "trigger" that responds to electron-rich molecules such as volatile amines. Based on the special properties of pyridine monomers, this invention prepares a sensing platform that can be applied to the sensing of volatile gaseous amines.
[0008] One objective of this invention is to provide a covalent organic framework material with a volatile amine response. This is achieved by introducing a volatile amine recognition unit into the framework. Specifically, a pyridinium linker (2,2'-bipyridine-5,5'-dicarboxaldehyde) with defective ion properties is condensed with 1,3,5-tris(4-cyanomethylbenzene)benzene via a Knoevenagel condensation reaction, forming a covalent organic framework material with a two-dimensional layered structure, denoted as TPCH-mOBPy. + .
[0009] This covalent organic framework material exhibits reversible fluorescence color and intensity changes upon contact with gaseous amines, and its chemical structure remains stable. The fragment structure of this material is as follows:
[0010]
[0011] Among them, X - It is an anion, selected from: sulfate, chloride, and phosphate.
[0012] The second objective of this invention is to provide a method for preparing the above-mentioned volatile amine-responsive covalent organic framework material, comprising the following steps:
[0013] (1) Using 2,2'-bipyridine-5,5'-dicarboxaldehyde and 1,3,5-tris(4-cyanomethylbenzene)benzene as reactants, adding reaction solvent and catalyst to obtain a first mixture, and then subjecting the mixture to ultrasonic treatment to obtain a second mixture;
[0014] (2) The container containing the second mixed solution is transferred to a reaction vessel and subjected to three freeze-thaw degassing treatments to obtain the third mixed solution;
[0015] (3) Heat the third mixed solution in a high-temperature oil bath until the final product mixture is obtained;
[0016] (4) Centrifuge the final product mixture to retain the solid product. The obtained solid product is then washed with solvent, extracted by Soxhlet and vacuum dried to obtain solid powder.
[0017] (5) Disperse the solid powder in an acid solution, let it stand and heat it, and then centrifuge and dry it to obtain the covalent organic framework material with volatile amine response.
[0018] In one embodiment of the present invention, the molar ratio of the molecular module of 2,2'-bipyridine-5,5'-dicarboxaldehyde and 1,3,5-tris(4-cyanomethylbenzene)benzene in step (1) is (2-5):(1-2); specifically, 3:2 can be selected.
[0019] In one embodiment of the present invention, the reaction solvent in step (1) is a mixture of dioxane, n-butanol and acetonitrile, wherein the volume ratio of dioxane, n-butanol and acetonitrile is (20-30):(10-20):1; specifically, 24:16:1.
[0020] In one embodiment of the present invention, the catalyst in step (1) is a 1-5 mol / L aqueous solution of 1,8-diazabicyclo-bicyclo(5,4,0)-7-undecene; specifically, a 4 mol / L aqueous solution of 1,8-diazabicyclo-bicyclo(5,4,0)-7-undecene may be selected.
[0021] In one embodiment of the present invention, the freeze-thaw degassing process in step (2) is as follows: the Shrek reaction tube containing the reactants is subjected to freezing in a 77K liquid nitrogen bath, negative pressure extraction, thawing, and degassing in sequence, and this process is repeated three times.
[0022] In one embodiment of the present invention, the static heating time in step (3) is 60-90 hours; specifically, 72 hours may be selected.
[0023] In one embodiment of the present invention, the solvent washing process in step (4) is specifically as follows: wash twice with 0.1 mol / L hydrochloric acid aqueous solution, dioxane, and tetrahydrofuran in sequence, and the volume of the washing solvent used each time is 5 mL.
[0024] In one embodiment of the present invention, the concentration of the acid solution in step (5) is 2 mol / L.
[0025] In one embodiment of the present invention, the time for static heating in step (5) is 20 - 30 hours; specifically, 24 hours can be selected.
[0026] The present invention also provides the application of the above-mentioned volatile amine-responsive covalent organic framework material in the field of food detection.
[0027] The present invention also provides a method for visually detecting food freshness, which is to uniformly coat the above-mentioned volatile amine-responsive covalent organic framework material on a substrate to form a uniform mixed matrix membrane, and then paste it into a container containing food to observe the fluorescence change.
[0028] In one embodiment of the present invention, if the fluorescence changes from red to yellow-green, spoilage has occurred.
[0029] The present invention also provides a method for quantitatively evaluating / monitoring the freshness of meat, which is to uniformly coat the above-mentioned volatile amine-responsive covalent organic framework material on a substrate to form a uniform mixed matrix membrane, and then paste it into a container containing meat samples, and collect the RGB values of the fluorescence colors of the covalent organic framework material in different meat spoilage states, as well as the corresponding TVBN values; a quantitative model is obtained by linearly correlating the TVBN value with the G / R value.
[0030] In one embodiment of the present invention, the freshness of meat is measured according to the level of TVB-N, that is, the TVBN of fresh meat is less than 12 mg / 100 g, the TVVBN value of slightly spoiled and barely qualified meat is between 12 - 25 mg / 100 g, and the TVBN value of inedible and spoiled meat is greater than 25 mg / 100 g.
[0031] In one embodiment of the present invention, the G / R value has a good linear relationship with the logarithmic content of TVB-N in meat samples stored at 25°C, that is, for fish: R 2 = 0.9987, for shrimp: R 2 = 0.9917. Among them, when the G / R value ≤ 0.14 ± 0.01, it is fresh meat; when 0.14 ± 0.01 < G / R value ≤ 0.43 ± 0.01, the meat has slight spoilage and is barely qualified; when the G / R value > 0.43 ± 0.01, the meat is spoiled and inedible.
[0032] [Beneficial Effects]
[0033] The structure of this type of covalent organic framework material with volatile amine response includes an electron acceptor unit, namely a protonated pyridine unit, and an electron donor unit, namely a benzene ring, which are bridged by carbon-carbon double bonds. This acceptor-donor structure enables a strong intramolecular charge transfer process and produces weak red fluorescence. When the protonated pyridine unit in the structure comes into contact with a volatile amine molecule, this intramolecular charge transfer process is hindered by the electrostatic interaction between the protonated pyridine and the volatile amine. Due to this hindered process, the fluorescence color of the material undergoes a blue shift, and the fluorescence intensity is significantly increased. The covalent organic framework material with volatile amine response described in this invention has good volatile amine recognition function and produces a clear color change from red to yellow-green that is visible to the naked eye. It is structurally stable, has a millisecond-level response, and can be applied to the real-time monitoring of volatile amines in the atmospheric environment and biogenic amines produced during food spoilage.
[0034] This invention establishes a non-contact quantitative method for assessing / monitoring meat freshness based on this specific covalent organic framework material. This method does not damage meat products and can quickly and accurately predict TVBN levels and assess food freshness. Attached Figure Description
[0035] Figure 1 This is the infrared spectrum of the covalent organic framework material and its synthetic unit.
[0036] Figure 2 These are the chromaticity diagrams and fluorescence spectra of the covalent organic framework material in response to volatile ammonia gas at different concentrations.
[0037] Figure 3 This is a graph showing the fluorescence intensity changes of the covalent organic framework material in response to alternating ammonia and hydrogen chloride gases.
[0038] Figure 4 This is a response time diagram of the covalent organic framework material to ammonia and hydrogen chloride gases.
[0039] Figure 5 These are photo comparisons of the application of this covalent organic framework material in monitoring food freshness.
[0040] Figure 6 This is a semi-quantitative evaluation model diagram of the covalent organic framework material on total volatile basic nitrogen in food. Detailed Implementation
[0041] The following describes preferred embodiments of the present invention. It should be understood that these embodiments are for better explanation of the invention and are not intended to limit the invention. Furthermore, the experimental methods used in the following embodiments are conventional methods unless otherwise specified; the materials and reagents used are commercially available. Many specific details are set forth in the following description to provide a thorough understanding of the invention. However, the invention may be practiced in other ways than those described herein, and therefore, the invention is not limited to the specific embodiments disclosed in the following specification.
[0042] A general combinatorial design strategy for covalent organic framework materials with volatile amine response is provided, namely, the presence of electron-deficient protonated pyridine units in the covalent organic framework material. The electron-deficient sites can generate electrostatic interactions with external electron-rich volatile amines, inhibiting the intramolecular charge transfer process of the covalent organic framework material, resulting in a visual change in fluorescence color from red to yellow-green, and significantly improving the fluorescence intensity. The reaction rate is on the order of milliseconds, which can provide a substrate material for the preparation of a fluorescent sensor for visualizing volatile amines.
[0043] Example 1
[0044] This embodiment provides a covalent organic framework material TPCH-mOBPy with volatile amine sensing capabilities. + Preparation method
[0045] A mixture was prepared by mixing 0.12 mmol of 2,2'-bipyridine-5,5'-dicarboxaldehyde, 0.08 mmol of 1,3,5-tris(4-cyanomethylbenzene)benzene, 1.2 mL of dioxane, 0.8 mL of n-butanol, 0.05 mL of acetonitrile, and 0.5 mL of a 4 mol / L aqueous solution of 1,8-diazabicyclo-bicyclo(5,4,0)-7-undecene. The mixture was ultrasonically dispersed for 10 minutes and transferred to a 5 mL Shrek reaction tube. The mixture was subjected to three freeze-thaw cycles for degassing, and then the reaction tube was heated in a 120°C oil bath for 72 hours. After the reaction, the reaction tube was allowed to cool naturally to room temperature, and centrifugation yielded a yellow powder. The obtained solid was further heated in a 2 mol / L sulfuric acid solution in an 80°C oil bath for 24 hours and dried at 80°C to obtain the covalent organic framework material TPCH-mOBPy. + Infrared spectral characterization is shown in [reference needed]. Figure 1 .
[0046] Example 2
[0047] The volatile amine sensing ability of the covalent organic framework material obtained in Example 1 was tested using ammonia solutions of different concentrations as test subjects. Figure 2As shown, different concentration points were set at 0, 0.1, 0.5, 1, 2, 5, 8, 12, 15, and 17 μmol / L. The sample was held for 5 minutes at each concentration point, and after removal, fluorescence spectroscopy was performed, and a chromaticity diagram was plotted. Figure 2 As shown. Figure 2 The study demonstrated that the fluorescence intensity of the covalent organic framework material gradually increased with increasing ammonia concentration, exhibiting a good linear relationship between fluorescence intensity and ammonia concentration. Furthermore, with increasing ammonia solution concentration, the maximum emission wavelength of the obtained covalent organic framework material blue-shifted from 600 nm to 550 nm, showcasing a visually apparent transition from red to yellow-green.
[0048] Example 3
[0049] The cyclic stability of the covalent organic framework material obtained in Example 1 was tested. The test results are as follows: Figure 3 As shown, after five alternating ammonia gas sensing cycles, the material's sensing performance did not show a significant difference compared to the initial test, and it still exhibited good reversibility.
[0050] Example 4
[0051] The volatile amine response rate of the covalent organic framework material obtained in Example 1 was tested. Ammonia gas at 60 ppm was used as a representative target substance, and fluorescence intensity was used as the indicator. Figure 4 As shown, when the covalent organic framework material provided by the present invention comes into contact with ammonia, the fluorescence intensity reaches its maximum within 1 second, exhibiting a millisecond-level response speed.
[0052] Example of effect
[0053] The covalent organic framework material obtained in Example 1 was used to monitor food freshness, with biogenic amines produced during food spoilage as indicators. Figure 5 As shown, the covalent organic framework material obtained in Example 1 was uniformly coated on one side of Scotch tape to form a uniform mixed matrix film, which was then attached to the inside of the lid of the petri dish to monitor and evaluate the freshness of fish and shrimp meat on-site without damaging the samples. Figure 5 The images show photographs of fish and shrimp samples stored at 25°C and -20°C. When shrimp meat was stored at 25°C, the fluorescence color of the covalent organic framework material turned orange after 12 hours and bright yellow after 36 hours. For fish meat, the fluorescence color of the covalent organic framework material turned bright yellow after only 24 hours of storage at 25°C, and no fluorescence change was observed in either fish or shrimp meat samples after 48 hours of storage at -20°C.
[0054] To conduct intelligent evaluation and monitoring of food freshness, the red / green / blue (RGB) values of the fluorescence color of covalent organic framework materials during the spoilage process of meat, as well as the total volatile basic nitrogen (TVBN) values of the samples under different storage conditions, were collected. The TVBN value has a direct relationship with the freshness of food. That is, under constant storage conditions, the freshness of meat can be measured according to the level of TVB-N. Specifically, the TVBN of fresh meat is less than 12 mg / 100 g, the TVVBN value of slightly spoiled and barely qualified meat is between 12 - 25 mg / 100 g, and the TVBN value of inedible and rotten meat is greater than 25 mg / 100 g. As Figure 6 shown, the G / R value has a good linear relationship with the logarithmic content of TVB-N in meat samples stored at 25 °C. That is, for fish: R 2 = 0.9987, and for shrimp: R 2 = 0.9917. Moreover, when the G / R value ≤ 0.14 ± 0.01, it is fresh meat; when 0.14 ± 0.01 < G / R value ≤ 0.43 ± 0.01, the meat is slightly spoiled and barely qualified; when the G / R value > 0.43 ± 0.01, the meat is rotten and inedible. Therefore, the RGB output of the fluorescence color of the self-made covalent organic framework material of the present invention can be used in a formula to predict the TVBN level and evaluate food freshness.
[0055] The above results fully demonstrate that the covalent organic framework material with volatile amine sensing ability provided by the present invention has excellent reversibility, stability, and rapid responsiveness, and has good development prospects in application fields such as food spoilage sensing and monitoring of volatile amines in the environment.
[0056] Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Anyone familiar with this technology can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be defined by the claims.
Claims
1. A covalent organic framework material with volatile amine responsiveness, characterized in that, This is achieved by introducing volatile amine recognition units into the framework. Specifically, the pyridine linker 2,2'-bipyridine-5,5'-dicarboxaldehyde, which has electron-deficient properties, is condensed with 1,3,5-tris(4-cyanomethylbenzene)benzene via a Knauven-Gail condensation reaction, forming a covalent organic framework material with a two-dimensional layered structure, denoted as TPCH-mOBPy. + ; The fragment structure of the covalent organic framework material is as follows: ， Among them, X - It is an anion, selected from: sulfate, chloride, and phosphate.
2. A method for preparing the volatile amine-responsive covalent organic framework material of claim 1, characterized in that, It includes the following steps: (1) Using 2,2'-bipyridine-5,5'-dicarboxaldehyde and 1,3,5-tris(4-cyanomethylphenyl)benzene as reaction raw materials, adding a reaction solvent and a catalyst thereto to obtain a first mixed solution, and performing ultrasonic treatment on the mixed solution to obtain a second mixed solution; (2) Transferring the second mixed solution into a reaction vessel and performing three freeze-thaw degassing treatments to obtain a third mixed solution; (3) Placing the third mixed solution in a high-temperature oil bath and standing for heating to obtain a final product mixed solution; (4) Performing a centrifugation separation operation on the final product mixed solution, retaining the solid product, and subjecting the obtained solid product to solvent washing, Soxhlet extraction, and vacuum drying steps to obtain a solid powder; (5) Dispersing the solid powder into an acid solution, standing for heating, and then centrifuging and drying to obtain the covalent organic framework material with volatile amine response.
3. The method according to claim 2, characterized in that, The molar ratio of the molecular module of 2,2'-bipyridine-5,5'-dicarboxaldehyde and 1,3,5-tris(4-cyanomethylphenyl)benzene in step (1) is (2-5):(1-2).
4. The method according to claim 2, characterized in that, The reaction solvent in step (1) is a mixed system of dioxane, n-butanol, and acetonitrile, and the volume ratio of dioxane, n-butanol, and acetonitrile is (20-30):(10-20):
1.
5. The method according to any one of claims 2-4, characterized in that, The catalyst in step (1) is an aqueous solution of 1,8-diazabicyclo-bicyclo(5,4,0)-7-undecene at 1-5 mol / L.
6. Application of the covalent organic framework material with volatile amine response described in claim 1 in the field of food detection.
7. A method for visually detecting the freshness of food, characterized in that, It is to uniformly coat the covalent organic framework material with volatile amine response described in claim 1 on a substrate to form a uniform mixed matrix membrane, and then paste it into a container containing food to observe the fluorescence change.
8. A method for quantitatively assessing / monitoring meat freshness, characterized in that, It is to uniformly coat the covalent organic framework material with volatile amine response described in claim 1 on a substrate to form a uniform mixed matrix membrane, and then paste it into a container containing a meat sample, and collect the RGB values of the fluorescence colors of the covalent organic framework material in different meat deterioration states, as well as the corresponding TVBN values; a quantitative model is obtained by linearly correlating the TVBN value with the G / R value.
9. The method according to claim 8, characterized in that, When the G / R value ≤ 0.14 ± 0.01, it is fresh meat; when 0.14 ± 0.01 < G / R value ≤ 0.43 ± 0.01, the meat has slight decay and is barely qualified; when the G / R value > 0.43 ± 0.01, the meat is decayed and inedible.