A two-dimensional covalent organic framework material and its preparation method and application

Abstract

The present invention discloses a two-dimensional covalent organic framework material and a preparation method and application thereof. The preparation method comprises the following steps: placing 2,5-dimethoxybenzene-1,4-diformaldehyde, tetrakis(4-aminophenyl)ethylene, an acetic acid aqueous solution, and a first solution in an ampoule under inert gas protection, performing ultrasonication, and then refrigerating and cyclically pumping gas to prepare a two-dimensional organic framework material containing a Schiff base structure; the present invention adopts 2,5-dimethoxybenzene-1,4-diformaldehyde and tetrakis(4-aminophenyl)ethylene as precursors, introduces a simple imine bond structure into the covalent organic framework material, and compared with common small molecule fluorescent probes, the covalent organic framework material has a large specific surface area (353.13 m 2 / g), high sensitivity (228nM), and fast response time (50s); based on its superior recognition performance, it was applied to the detection of stannous ions in food cans, realizing the first application of covalent organic framework materials in the food field.

Description

Technical Field

[0001] The present invention belongs to the field of food testing, and in particular relates to a two-dimensional covalent organic framework material and a preparation method and application thereof. Background Art

[0002] Tin (Sn) is one of the essential trace elements for the human body. It has an important impact on various physiological activities of the human body and affects life and health. Lack of Sn can cause protein and nucleic acid metabolism disorders and hinder human growth and development. On the contrary, excessive intake or inhalation of Sn can cause adverse symptoms such as dizziness, diarrhea, nausea, etc., leading to a decrease in serum calcium levels. In daily life, Sn is present in various canned food packaging and oral filling materials. This is an item that must be checked in canned food hygiene inspections. According to the regulations of the Food and Agriculture Organization of the United Nations / World Health Organization (FAO / WHO), the maximum limit of tin in canned food is 250 mg / kg. Therefore, in order to ensure food safety, Sn in canned food must be 250 mg / kg. 2+ Detection is becoming increasingly important.

[0003] At present, the commonly used methods for determining the tin content in food are spectrophotometry, hydride generation atomic fluorescence spectrometry, atomic absorption spectrometry, and inductively coupled plasma emission spectrometry. These methods have the disadvantages of high detection limit and complex operation, resulting in large detection deviation and high cost. Therefore, the Sn 2+ New methods for ion detection are of great significance. Summary of the Invention

[0004] The purpose of the present invention is to provide a two-dimensional covalent organic framework material and its preparation method and application, so as to obtain Sn with high sensitivity, good selectivity and simple operation. 2+ Ion Detection Materials and Methods.

[0005] The present invention adopts the following technical solution: a two-dimensional covalent organic framework material, whose structural formula is:

[0006]

[0007] A method for preparing a two-dimensional covalent organic framework material, the synthesis route of which is:

[0008]

[0009] Furthermore, under the protection of inert gas, 2,5-dimethoxybenzene-1,4-dicarbaldehyde, tetrakis(4-aminophenyl)ethylene, an acetic acid aqueous solution, and the first solution were placed in an ampoule, and ultrasonicated, and then refrigerated and circulated to obtain a two-dimensional organic framework material containing a Schiff base structure;

[0010] The first solution is any one of N,N-dimethylformamide, N,N-dimethylacetamide, acetonitrile, dioxane, mesitylene, n-butanol, o-dichlorobenzene, and toluene, or a combination of two or more thereof.

[0011] Furthermore, the usage ratio of 2,5-dimethoxybenzene-1,4-dicarbaldehyde:tetrakis(4-aminophenyl)ethylene: acetic acid aqueous solution: the first solution is 0.15 mmol: 0.07 mmol: (0.1-0.5) mL: (1-5) mL.

[0012] Furthermore, the reaction conditions are: ultrasonication for 10-30 minutes, refrigeration cycle vacuuming for 3-9 times, and reaction at 80-150° C. for 3-8 days.

[0013] An application of a two-dimensional covalent organic framework material, the two-dimensional covalent organic framework material is used to detect the concentration of stannous ions in food cans, wherein the two-dimensional covalent organic framework material is obtained by any preparation method of claims 1-5.

[0014] Furthermore, when detecting the concentration of stannous ions in canned food, the detection method consists of the following steps:

[0015] Step 1: Take the solid matter of the food can and treat it at high temperature in a tube furnace.

[0016] Step 2: Dissolve with concentrated hydrochloric acid, then dilute with distilled water and NaOH.

[0017] Step 3: Transfer the diluted solution to the calibration flask and add aluminum to make Sn 4+ Reduced to Sn 2+ , to obtain the test solution,

[0018] Step 4: Prepare a stannous ion standard solution and obtain a linear relationship curve.

[0019] Step 5: Immerse the two-dimensional covalent organic framework material in the test solution, test its fluorescence intensity with a fluorescence spectrometer, and substitute it into the linear relationship curve to calculate the Sn content in the canned food sample. 2+ concentration.

[0020] The beneficial effects of the present invention are:

[0021] 1. The present invention uses 2,5-dimethoxybenzene-1,4-dicarbaldehyde and tetrakis(4-aminophenyl)ethylene as precursors, and prepares a two-dimensional organic framework material in a one-step process under the action of an acetic acid aqueous solution and a first solution;

[0022] 2. The material obtained by the present invention has a great influence on Sn 2+ Has specific recognition ability, encounters Sn 2+ There will be obvious fluorescence changes, and the fluorescence intensity is similar to Sn 2+The concentration has a good linear relationship, which can achieve Sn in food cans 2+ Qualitative and quantitative analysis of Sn in food 2+ The detection has important application prospects;

[0023] 3. The present invention uses 2,5-dimethoxybenzene-1,4-dicarboxaldehyde and tetra(4-aminophenyl)ethylene as precursors to introduce a simple imine bond structure into a covalent organic framework material. Compared with ordinary small molecule fluorescent probes, it has a large specific surface area (353.13m 2 / g), high sensitivity (228nM), and fast response time (50s); based on its superior recognition performance, it was applied to the detection of stannous ions in food cans, realizing the first application of covalent organic framework materials in the food field. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 XRD (actual value, theoretical value) and stacking pattern diagram of COF material in the present invention;

[0025] Figure 1 (a) PXRD refined curve and actual test PXRD curve of COF;

[0026] Figure 1 (b) is the difference between the refined curve and the actual test curve;

[0027] Figure 1 (c) PXRD simulation curve of single-hole-AB stacking structure;

[0028] Figure 1 (d) PXRD simulation curve of single-hole-AA stacking structure;

[0029] Figure 1 (e) PXRD simulation curve of double-pore-AB stacking structure;

[0030] Figure 1 (f) PXRD simulation curve of double-pore-AA stacking structure;

[0031] Figure 1 (g) is a schematic diagram of the single-hole-AA stacking structure;

[0032] Figure 1 (h) is a schematic diagram of a single-hole-AB stacking structure;

[0033] Figure 1 (i) Schematic diagram of the double-hole-AA stacking structure;

[0034] Figure 1 (j) is a schematic diagram of the double-hole-AB stacking structure;

[0035] Figure 2 Characterization and basic performance of the COF material in the present invention;

[0036] Figure 2 (a) N2 adsorption / desorption isotherms of COF;

[0037] Figure 2 (b) is a scanning electron microscope image of COF;

[0038] Figure 2 (c) is the infrared spectrum of COF;

[0039] Figure 2 (d) is the XPS spectrum of COF;

[0040] Figure 2 (e) is the high-resolution XPS spectrum of N1s of COF;

[0041] Figure 2 (f) is the thermogravimetric curve of COF;

[0042] Figure 3 The fluorescence performance spectrum of the COF material in the present invention;

[0043] Figure 3 (a) UV-absorption spectrum, fluorescence excitation spectrum, and fluorescence emission spectrum of COF;

[0044] Figure 3 (b) Ion recognition and ion coexistence maps of COF;

[0045] Figure 3 (c) COF to Sn 2+ Fluorescence titration and linear relationship diagram;

[0046] Figure 3 (d) COF to Sn 2+ The time response graph of

[0047] Figure 4 COF to Sn 2+ Recognition mechanism diagram. DETAILED DESCRIPTION

[0048] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0049] Covalent organic frameworks (COFs) are a new type of porous crystalline material composed of structural units connected by strong covalent bonds. COFs have the advantages of low mass density, high stability, large specific surface area, and controllable pore structure. Their rational design and directional synthesis have attracted widespread attention. More importantly, COFs materials can replicate multiple identical binding sites throughout the framework. When a single binding event occurs at a site, the signal can be effectively transmitted and amplified through the framework. The large specific surface area is conducive to molecular binding, making the reaction faster and more accurate. Therefore, the development of COFs in ion detection is changing with each passing day. However, most crystalline COFs materials are used as fluorescent chemical sensors for the detection of Cu 2+ 、Fe 3+ 、Hg 2+ 、Pd 2+ wait.

[0050] The present invention discloses a two-dimensional covalent organic framework material, the structural formula of which is:

[0051]

[0052] The synthetic route of the preparation method of the two-dimensional covalent organic framework material of the present invention is:

[0053]

[0054] The present invention also discloses a method for preparing a two-dimensional covalent organic framework material. Under the protection of an inert gas, 2,5-dimethoxybenzene-1,4-dicarbaldehyde, tetrakis(4-aminophenyl)ethylene, an acetic acid aqueous solution, and a first solution are placed in an ampoule, ultrasonicated, and then refrigerated and circulated to obtain a two-dimensional organic framework material containing a Schiff base structure.

[0055] The first solution is any one of N,N-dimethylformamide, N,N-dimethylacetamide, acetonitrile, dioxane, mesitylene, n-butanol, o-dichlorobenzene, and toluene, or a combination of two or more thereof.

[0056] The usage ratio of 2,5-dimethoxybenzene-1,4-dicarbaldehyde:tetrakis(4-aminophenyl)ethylene: acetic acid aqueous solution: the first solution is 0.15 mmol: 0.07 mmol: (0.1-0.5) mL: (1-5) mL.

[0057] Preferably, the usage ratio of 2,5-dimethoxybenzene-1,4-dicarbaldehyde:tetrakis(4-aminophenyl)ethylene: acetic acid aqueous solution: the first solution is 0.15 mmol: 0.07 mmol: 0.1 mL: (2-3) mL.

[0058] The reaction conditions are as follows: ultrasonic treatment for 10-30 minutes, refrigeration cycle vacuuming for 3-9 times, and reaction at 80-150° C. for 3-8 days.

[0059] Preferably, the reaction conditions are: ultrasonication for 10 minutes, refrigeration cycle vacuuming 3-5 times, and reaction at 120-150° C. for 5-6 days.

[0060] After the reaction is completed, the two-dimensional organic framework material is washed 3-6 times and then dried in a vacuum oven for 6-12 hours, wherein the washing solvent is selected from any one of acetone, methanol, ethanol, tetrahydrofuran, and toluene, or a combination of two or more thereof.

[0061] The present invention also discloses an application of a two-dimensional covalent organic framework material, which is used to detect the concentration of stannous ions in food cans, wherein the two-dimensional covalent organic framework material is obtained by the above-mentioned preparation method.

[0062] The two-dimensional covalent organic framework material of the present invention is used to detect the concentration of stannous ions in food cans. The detection method comprises the following steps:

[0063] Step 1: Take the solid matter of the food can and treat it at high temperature in a tube furnace.

[0064] Step 2: Dissolve with concentrated hydrochloric acid, then dilute with distilled water and NaOH.

[0065] Step 3: Transfer the diluted solution to the calibration flask and add aluminum to make Sn 4+ Reduced to Sn 2+ , to obtain the test solution,

[0066] Step 4: Prepare a stannous ion standard solution and obtain a linear relationship curve.

[0067] Step 5: Immerse the two-dimensional covalent organic framework material in the test solution, test its fluorescence intensity with a fluorescence spectrometer, and substitute it into the linear relationship curve to calculate the Sn content in the canned food sample. 2+ concentration.

[0068] Example 1

[0069] Under the protection of inert gas, a mixed system containing 2,5-dimethoxybenzene-1,4-dicarbaldehyde, tetrakis(4-aminophenyl)ethylene, acetic acid aqueous solution and o-dichlorobenzene was placed in an ampoule, ultrasonicated for 10 minutes to disperse the system, refrigerated and evacuated 5 times, sealed and reacted at 120°C for 5 days to prepare a two-dimensional organic framework material containing a Schiff base structure.

[0070] The usage ratio of 2,5-dimethoxybenzene-1,4-dicarbaldehyde:tetrakis(4-aminophenyl)ethylene: acetic acid aqueous solution: solvent I is 0.15 mmol: 0.07 mmol: 0.1 mL: 3 mL.

[0071] After the reaction was completed, the product mixture was washed with acetone and tetrahydrofuran three times each, and dried in a vacuum oven for 10 hours to obtain 51.4 mg of a two-dimensional organic framework material COF with a yield of 87%.

[0072] Figure 1 The XRD patterns (actual and theoretical values) and stacking patterns of the COF material of the present invention are shown. The COF structure was simulated using Materials Studio, and AA and AB stacking structures were simulated for possible single and double pores, respectively. The PXRD patterns of the simulated structures were obtained, and compared with the experimentally obtained PXRD patterns. The PXRD patterns of the single-pore-AB stacking structure were basically consistent with those of the experimentally obtained structure, indicating that this method can synthesize a single-pore-AB stacking COF model.

[0073] Figure 2 Characterization and basic performance of the COF material in the present invention; the sample was degassed at 100 ° C for 10 hours and activated. The nitrogen adsorption and desorption isotherms of the COF structure were measured from 0 to 1 atm at 77 K. The specific surface area was 353.13 m 2 / g, and the pore size distribution was derived from the adsorption data using a nonlocal density functional theory model, with an average pore size of 2.34 nm.

[0074] The morphology of the sample was observed by thermal field emission scanning electron microscopy, and the COF material showed irregular spherical particles with uniform distribution.

[0075] The bonding of COF structure was studied by Fourier transform infrared spectroscopy (FT-IR), which belongs to the amino group of raw material (3360 cm -1 ) and aldehyde groups (2870 cm -1 ) has basically disappeared, and the peak at 1667cm -1 The characteristic peak of the imine bond appeared, indicating that the COF material was successfully prepared.

[0076] By performing X-ray photoelectron spectroscopy on the COF structure, a C=N bond was found in the fine spectrum of N, indicating that the COF structure was successfully prepared.

[0077] The sample was heated from room temperature to 1000°C at a heating rate of 10°C / min under argon atmosphere for thermogravimetric analysis, and its thermal decomposition temperature was found to be 430°C, indicating that the synthesized COF material has good thermal stability.

[0078] Figure 3The fluorescence performance spectrum of the COF material in the present invention is as follows; the COF material was evenly dispersed in an acetonitrile solution and subjected to UV and fluorescence tests. The UV spectrum peaked at 321 nm, while the optimal excitation and emission peaks of the fluorescence were located at 396 nm and 461 nm, respectively. Ion recognition and ion competition experiments were performed on it and it was found that it has a strong affinity for Sn 2+ Ions have good recognition ability, adding Sn 2+ The fluorescence was significantly enhanced, and this enhancement showed a good linear relationship in the range of 0μM to 100μM. 2 =0.9968. In addition, COF materials have a 2+ The response is very fast and reaches stability within 50 seconds.

[0079] Example 2

[0080] like Figure 4 As shown, the concentration of stannous ions in food cans was detected using the two-dimensional organic framework material prepared in Example 1, and the steps consisted of the following steps:

[0081] Step 1:

[0082] Take 2.0g of the solid matter from luncheon meat, canned fish, and canned kidney beans, and treat it at 600℃ in a tube furnace for 4-8h.

[0083] Step 2:

[0084] Dissolve it with 10 mL of concentrated hydrochloric acid, and then dilute it to 50 mL with distilled water and 1 mol / L NaOH, and the pH is about 6.

[0085] Step 3:

[0086] Take 0.5mL of the dilution solution and transfer it to a 25mL calibration flask. Add 0.02g of aluminum to make Sn 4+ Reduced to Sn 2+ , to obtain the test solution.

[0087] Step 4:

[0088] The prepared covalent organic framework material COF was immersed in different concentrations of stannous ion standard samples and taken out after 1-5 minutes; its fluorescence intensity was tested by fluorescence spectrometer; different concentrations of Sn 2+ The fluorescence intensity of COF and Sn 2+ The linear relationship curve of concentration: y = 176655.679 + 27800.121x; where x represents Sn 2+ concentration, y represents the fluorescence intensity of COF. 2+The detection limit is y=3σ / k=228 nM, where k is the slope of the standard curve equation and σ is the standard deviation of the blank COF fluorescence intensity.

[0089] Step 5:

[0090] The covalent organic framework material COF prepared in Example 1 was immersed in the test solution and taken out after 1 minute; its fluorescence intensity was measured by fluorescence spectrometer, and the value was substituted into the standard curve in step 4 for calculation to determine the Sn content in the canned food sample. 2+ The results are shown in Table 1.

[0091] Table 1 Sn in canned food 2+ Detection

[0092]

[0093] Example 3

[0094] Under the protection of inert gas, a mixed system containing 2,5-dimethoxybenzene-1,4-dicarbaldehyde, tetrakis(4-aminophenyl)ethylene, aqueous acetic acid solution, mesitylene and n-butanol was placed into an ampoule, and the system was dispersed by ultrasonication for 10 minutes. The system was refrigerated and evacuated three times, sealed and reacted at 120°C for 6 days to prepare a two-dimensional organic framework material containing a Schiff base structure.

[0095] The usage ratio of the 2,5-dimethoxybenzene-1,4-dicarbaldehyde:tetrakis(4-aminophenyl)ethylene: acetic acid aqueous solution: mesitylene and n-butanol is 0.15 mmol: 0.07 mmol: 0.1 mL: 2 mL.

[0096] After the reaction, the product mixture was washed with acetone and methanol three times each, and dried in a vacuum oven for 8 hours to obtain 46.1 mg of two-dimensional organic framework material COF with a yield of 78%.

[0097] Example 4

[0098] Under the protection of inert gas, a mixed system containing 2,5-dimethoxybenzene-1,4-phthalaldehyde, tetrakis(4-aminophenyl)ethylene, aqueous acetic acid solution and n-butanol was placed in an ampoule, ultrasonicated for 10 minutes to disperse the system, refrigerated and evacuated three times, sealed and reacted at 150°C for 6 days to prepare a two-dimensional organic framework material containing a Schiff base structure.

[0099] The usage ratio of the 2,5-dimethoxybenzene-1,4-dicarbaldehyde:tetrakis(4-aminophenyl)ethylene: acetic acid aqueous solution: n-butanol is 0.15 mmol: 0.07 mmol: 0.1 mL: 3 mL.

[0100] After the reaction was completed, the product mixture was washed with acetone and methanol three times each, and dried in a vacuum oven for 8 hours to obtain 44.3 mg of two-dimensional organic framework structure material COF with a yield of 75%.

[0101] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A two-dimensional covalent organic framework material, characterized in that Its structural formula is: ； The two-dimensional covalent organic framework material is prepared by the following method: Under inert gas protection, 2,5-dimethoxybenzene-1,4-dicarbaldehyde, tetrakis(4-aminophenyl)ethylene, an acetic acid aqueous solution, and the first solution are placed in an ampoule, ultrasonicated, and then subjected to refrigeration cycle pumping to obtain the two-dimensional covalent organic framework material; Wherein, the first solution is any one or a combination of two or more of mesitylene, n-butanol, and o-dichlorobenzene; The usage ratio of the 2,5-dimethoxybenzene-1,4-dicarbaldehyde:tetrakis(4-aminophenyl)ethylene: acetic acid aqueous solution: the first solution is 0.15 mmol: 0.07 mmol: (0.1-0.5) mL: (1-5) mL; The reaction conditions are as follows: ultrasonic treatment for 10-30 minutes, refrigeration cycle vacuuming for 3-9 times, and reaction at 80-150° C. for 3-8 days.

2. The use of the two-dimensional covalent organic framework material according to claim 1 in detecting the concentration of stannous ions in food cans, characterized in that: The detection method consists of the following steps: Step 1: Take the solid matter of the food can and treat it at high temperature in a tube furnace. Step 2: Dissolve with concentrated hydrochloric acid, then dilute with distilled water and NaOH. Step 3: Transfer the diluted solution to the calibration flask and add aluminum to make Sn 4+ Reduced to Sn 2+ , to obtain the test solution, Step 4: Prepare a stannous ion standard solution and obtain a linear relationship curve. Step 5: Immerse the two-dimensional covalent organic framework material in the test solution, test its fluorescence intensity with a fluorescence spectrometer, and substitute it into the linear relationship curve to calculate the Sn content in the canned food sample. 2+ concentration.

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