C-c single bond connected ionic covalent organic frameworks and methods of making and using the same

Abstract

The present application relates to the technical field of pollutant detection, and in particular to a C-C single bond connected ionic covalent organic framework as well as a preparation method and application thereof.The preparation method is as follows: a C-C single bond connected ionic COF is prepared through an aldol condensation reaction between TMPyP and PDA, and is named as CSBL-COF-4.The present application introduces an ionic reaction monomer into the CSBL-COF-4 skeleton structure, and increases the affinity with an electron-rich amine molecule through electrostatic interaction.Meanwhile, a hydroxyl functional group is introduced into the CSBL-COF-4 structure, and the intramolecular charge transfer (ICT) effect is weakened through the hydrogen bond interaction between the hydroxyl group and the amine molecule, so that the fluorescence on-off detection of the amine molecule is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of pollutant detection, and particularly relates to a C-C single bond connected ionic covalent organic framework and a preparation method and application thereof. BACKGROUND

[0002] Ammonia pollutants have attracted much attention due to their potential threat to human health, including but not limited to causing headaches, skin burns, eye irritation and various respiratory diseases, and in extreme cases, even leading to serious consequences such as bladder cancer. These harmful substances mainly come from the dye, chemical fertilizer and pharmaceutical industries, and have caused significant negative impact on the natural environment. In addition, biological amines produced during food spoilage, such as cadaverine (1,5-diaminopentane) and histamine (2-(1H-imidazol-5-yl)ethylamine), not only affect food quality, but also are important indicators for evaluating food safety and hygiene conditions. Due to the rich electron characteristics of amine molecules, scientists have designed a series of electron-deficient materials, such as carbon dots, activated carbon and metal-organic frameworks (MOFs), aiming to achieve effective detection and capture of these basic amines through Lewis acid-base interaction. However, due to the strong corrosive nature of amine molecules, only a few materials can exhibit sufficient chemical stability while maintaining high affinity. Therefore, the development of electron-deficient materials with high stability and high selectivity for efficient detection of corrosive amines has become a research hotspot and important direction in this field. This not only is the key to improving detection accuracy, but also provides strong technical support for public health and environmental protection.

[0003] Covalent organic frameworks (COFs) have shown wide application prospects in chemical sensing, catalysis and gas adsorption due to their high crystallinity, porosity and excellent chemical stability. Currently, most COF-based amine detectors rely on fluorescence quenching mechanism, which is easily affected by other components in the environment and is not sensitive enough for target analyte detection. In contrast, COF sensors based on fluorescence turn-on are more practical, but such cases are still rare. So far, only a few specially designed COFs have been reported. For example, materials connected by imine bonds and using guanidinium as a building block have been confirmed to be highly sensitive "on" type chemical sensors for amine molecules, which can achieve effective detection at very low concentrations. However, the existing COF materials for amine detection are mainly limited to reversible imine or borate bonds, which have poor chemical stability when encountering strongly corrosive amine molecules, and may cause damage to the material structure. Therefore, the development of new COF materials that not only produce fluorescence "on" response to amine molecules, but also maintain stability and reliability in complex environments, is a problem to be solved. This is of great significance for improving the detection accuracy of amine molecules at trace levels. SUMMARY

[0004] In view of the above problems in the prior art, the present application aims to provide a C-C single bond connected ionic covalent organic framework and a preparation method thereof, and to synthesize stable C-C single bond connected COF and apply it to fluorescence on-off detection of corrosive amines.

[0005] To achieve the above-mentioned purposes, the technical scheme adopted by the present application is as follows:

[0006] On the one hand, a preparation method of a C-C single bond connected ionic covalent organic framework is provided, which prepares a C-C single bond connected ionic COF through an aldol condensation reaction between 5,10,15,20-tetra(4-N-methylpyridyl)-porphyrin (TMPyP) and p-phthalaldehyde (PDA), and the C-C single bond connected ionic COF is named as CSBL-COF-4.

[0007] The method specifically comprises the following steps:

[0008] Step 1, synthesis of TMPyP

[0009] 5,10,15,20-tetra(pyrrol-4-yl)porphyrin and iodomethane are added to DMF, and heated to react to generate crude TMPyP, and then cooled to room temperature. The product is washed with ethanol to remove unreacted iodomethane and other by-products, and dried to remove the solvent in the product to obtain pure TMPyP as a black powder;

[0010] Preferably, in step 1, the molar ratio of 5,10,15,20-tetra(pyrrol-4-yl)porphyrin to iodomethane is 1-2:4-5;

[0011] Preferably, in step 1, the volume ratio of iodomethane to DMF is 1-2:20-25;

[0012] Preferably, in step 1, the temperature for heating reaction is 80-100℃, and the time is 18-20h.

[0013] Preferably, in step 1, the drying temperature is 100-120℃, and the drying time is 10-12h.

[0014] Step 2, synthesis of CSBL-COF-4

[0015] In a thick-walled pressure reaction tube, the mixture of TMPyP and DMF obtained in step 1 was heated to dissolve TMPyP. Then, the mixture of PDA, methanol solution of NaOH and 1,4-dioxane was added dropwise into the above solution, after stirring, the reaction tube was vacuumed three times and sealed by freeze-pumping-thaw degassing, and heated to obtain a black solid mixture (crude product CSBL-COF-4). The solid was collected by centrifugation, and then was immersed and washed in 1,4-dioxane, acetonitrile and tetrahydrofuran in turn in a Soxhlet extractor. Finally, drying was performed to obtain the pure product CSBL-COF-4.

[0016] Preferably, in step 2, the molar ratio of TMPyP and PDA is 1:2;

[0017] Preferably, in step 2, the volume ratio of DMF, methanol solution of NaOH and 1,4-dioxane solution is 2-4:1-2:2-4;

[0018] Preferably, in step 2, the concentration of the methanol solution of NaOH is 0.5-1.5M;

[0019] Preferably, in step 2, the temperature of the heating reaction is 90-110℃, and the time is 92-100h;

[0020] Preferably, in step 2, the stirring time is 2-6h;

[0021] Preferably, in step 2, the washing time is 20-28h for each solvent;

[0022] Preferably, in step 2, the vacuum drying temperature is 110-130℃, and the vacuum drying time is 10-14h;

[0023] Preferably, in step 2, the volume ratio of 1,4-dioxane, acetonitrile and tetrahydrofuran is 1:1:1.

[0024] In another aspect, the application provides the use of the above-mentioned C-C single bond connected ionic covalent organic framework in the fluorescence-on detection of amine molecules.

[0025] The application has the following beneficial effects:

[0026] (1) C4 reaction monomer TMPyP is used for the first time to construct a C-C single bond structure, which to some extent solves the problems of lack of high-stability COFs and difficulty in synthesis. At the same time, the C-C single bond endows CSBL-COF-4 with excellent chemical stability, which can exist stably in 1M NaOH or 1M HCl for 3 days, which greatly ensures its potential for interaction with corrosive amines, and provides a new idea for designing high-stability C-C single bond connected COFs.

[0027] (2) The introduction of abundant ionically active sites in the CSBL-COF-4 framework not only improves the dispersibility of CSBL-COF-4 in water, but also provides a large number of acidic open sites, which enhances the affinity with basic amines through Lewis acid-base interaction.

[0028] (3) The intramolecular charge transfer (ICT) effect from PDA (electron donor) to TMPyP unit (electron acceptor) makes CSBL-COF-4 exhibit red emission in water, which provides the possibility for the fluorescence detection of amine molecules. Since amine compounds can form hydrogen bonds with the hydroxyl functional groups in the CSBL-COF-4 framework and weaken the ICT effect, CSBL-COF-4 can be used for the fluorescence "turn-on" detection of amine molecules. And CSBL-COF-4 shows a lower detection limit for biological amines (histamine) than most previously known BAS detection chemical sensors, providing a new method for the fluorescence "turn-on" trace detection of amine molecules.

[0029] (4) CSBL-COF-4 can be successfully used to monitor the freshness of raw meat samples and shows a significant fluorescence enhancement effect, providing a new way for the real-time detection of the freshness of raw meat samples. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 Schematic diagram for the synthesis of CSBL-COF-4 of embodiment 1 of the present application and fluorescence detection of amine molecules;

[0031] Figure 2 PXRD pattern and structure refinement diagram of CSBL-COF-4 of embodiment 1 of the present application;

[0032] Figure 3 HR-TEM image of CSBL-COF-4 of embodiment 1 of the present application;

[0033] Figure 4 SAED diagram of CSBL-COF-4 of embodiment 1 of the present application;

[0034] Figure 5 FT-IR spectrum of CSBL-COF-4 of embodiment 1 of the present application;

[0035] Figure 6 Solid state 13 C NMR spectrum of CSBL-COF-4 of embodiment 1 of the present application;

[0036] Figure 7 PXRD patterns of CSBL-COF-4 of embodiment 1 of the present application before and after treatment with strong acid and strong base;

[0037] Figure 8SEM image of CSBL-COF-4 of Example 1 of the present application;

[0038] Figure 9 AFM image of CSBL-COF-4 of Example 1 of the present application;

[0039] Figure 10 Fluorescence change image of CSBL-COF-4 of Example 1 of the present application after adding different concentrations of NH3(aq) to the dispersion thereof;

[0040] Figure 11 Column chart of relative fluorescence intensity of CSBL-COF-4 of Example 1 of the present application in the presence of different amine aqueous solutions;

[0041] Figure 12 Column chart of relative fluorescence intensity of CSBL-COF-4 of Example 1 of the present application in the presence of different amine gases;

[0042] Figure 13 Fluorescence response image of CSBL-COF-4 dispersion of Example 1 of the present application after being stored with fresh raw fish slices at 4°C for different time;

[0043] Figure 14 Fluorescence response image of CSBL-COF-4 dispersion of Example 1 of the present application after being stored with fresh raw fish slices at 25°C for different time;

[0044] Figure 15 Fluorescence response image of CSBL-COF-4 dispersion of Example 1 of the present application after being stored with rotten raw fish slices for different time. DETAILED DESCRIPTION

[0045] The specific embodiments of the present application are described below to facilitate the understanding of the present application for those skilled in the art, but it should be clear that the present application is not limited to the scope of the specific embodiments, and for those skilled in the art, any changes that are obvious within the spirit and scope of the present application as defined and determined by the appended claims are obvious, and all the inventions utilizing the concept of the present application are within the scope of protection.

[0046] Example 1

[0047] In a thick-walled pressure reaction tube, 0.05 mmol of TMPyP (59.3 mg) and DMF (3 mL) were heated to 100 °C. Then a mixture of 0.1 mmol of PDA (13.4 mg), 1 mL of NaOH in methanol (1 M) and 1 mL of 1,4-dioxane was gradually added to the above solution, after stirring for 4 hours, a large amount of black precipitate was formed. Then, the reaction tube was vacuumed three times by freeze-pump-thaw technique and sealed. The reaction was continued at 100 °C for 96 hours to give a black solid. The solid was collected by centrifugation, then was immersed in 1,4-dioxane, acetonitrile and tetrahydrofuran in a Soxhlet extractor for 24 hours, respectively. Finally, vacuum dried at 120 °C for 12 hours to give 63% yield of CSBL-COF-4 (45.8 mg).

[0048] Example 2

[0049] In a thick-walled pressure reaction tube, 0.0125 mmol of TMPyP (14.825 mg) and DMF (0.75 mL) were heated to 100 °C. Then a mixture of 0.0025 mmol of PDA (3.35 mg), 0.25 mL of NaOH in methanol (1 M) and 0.25 mL of 1,4-dioxane was gradually added to the above solution, after stirring for 4 hours, a large amount of black precipitate was formed. Then, the reaction tube was vacuumed three times by freeze-pump-thaw technique and sealed. The reaction was continued at 100 °C for 96 hours to give a black solid. The solid was collected by centrifugation, then was immersed in 1,4-dioxane, acetonitrile and tetrahydrofuran in a Soxhlet extractor for 24 hours, respectively. Finally, vacuum dried at 120 °C for 12 hours to give 58% yield of CSBL-COF-4 (10.5 mg).

[0050] Example 3

[0051] In a thick-walled pressure reaction tube, 0.025 mmol of TMPyP (29.65 mg) and DMF (1.5 mL) were heated to 100 °C. Then a mixture of 0.05 mmol of PDA (6.7 mg), 0.5 mL of NaOH in methanol (1 M) and 0.5 mL of 1,4-dioxane was gradually added to the above solution, after stirring for 4 hours, a large amount of black precipitate was formed. Then, the reaction tube was vacuumed three times by freeze-pump-thaw technique and sealed. The reaction was continued at 100 °C for 96 hours to give a black solid. The solid was collected by centrifugation, then was immersed in 1,4-dioxane, acetonitrile and tetrahydrofuran in a Soxhlet extractor for 24 hours, respectively. Finally, vacuum dried at 120 °C for 12 hours to give 61% yield of CSBL-COF-4 (22.1 mg).

[0052] Example 4

[0053] In a thick-walled pressure reaction tube, 0.1 mmol TMPyP (118.6 mg) and DMF (6 mL) were heated to 100 °C. Then, 0.2 mmol PDA (26.8 mg), 2 mL of a 1 M NaOH methanol solution, and 2 mL of a mixture of 1,4-dioxane were gradually added to the above solution. After stirring for 4 hours, a large amount of black precipitate formed. The reaction tube was then evacuated three times using a freeze-evacuation-thawing technique and sealed. The reaction was continued at 100 °C for 96 hours to obtain a black solid. The solid was collected by centrifugation and then washed sequentially with 1,4-dioxane, acetonitrile, and tetrahydrofuran in a Soxhlet extractor for 24 hours. Finally, it was dried under vacuum at 120 °C for 12 hours to obtain CSBL-COF-4 (94.5 mg) in 65% yield.

[0054] Example 5

[0055] In a thick-walled pressure reaction tube, 0.2 mmol TMPyP (237.2 mg) and DMF (12 mL) were heated to 100 °C. Then, a mixture of 0.4 mmol PDA (53.6 mg), 4 mL of NaOH in methanol (1 M), and 4 mL of 1,4-dioxane was gradually added to the above solution. After stirring for 4 hours, a large amount of black precipitate formed. The reaction tube was then evacuated three times using a freeze-evacuation-thawing technique and sealed. The reaction was continued at 100 °C for 96 hours to obtain a black solid. The solid was collected by centrifugation and then washed sequentially with 1,4-dioxane, acetonitrile, and tetrahydrofuran in a Soxhlet extractor for 24 hours. Finally, it was dried under vacuum at 120 °C for 12 hours to obtain CSBL-COF-4 (200.7 mg) in 69% yield.

[0056] The synthetic route of CSBL-COF-4 is as follows: Figure 1 As shown, the CSBL-COF-4 prepared in Example 1 was used for the following tests.

[0057] Depend on Figure 2 It can be seen that the CSBL-COF-4 prepared in Example 1 has high crystallinity and a long-range ordered structure. CSBL-COF-4 belongs to space group P4 (No. 75) and has a tetragonal crystal structure. The interlayer spacing obtained from the simulation of the unit cell parameters is... Theoretical simulations show that CSBL-COF-4 adopts an AA stacking mode, and the simulated PXRD results agree well with experimental data. The cell parameters obtained from the Pawley-refined PXRD results are as follows: α=β=γ=90°, R p and R wpThe values are 2.45% and 1.67%, respectively, which are in good agreement with the experimental results. The peak at 2Θ = 3.4° corresponds to the (1 0 0) crystal plane of CSBL-COF-4, which proves its long-range ordered structure.

[0058] From Figure 3 It can be seen that the lattice fringes of CSBL-COF-4 have a lattice spacing of corresponding to its (0 0 1) crystal plane. From Figure 4 It can be seen that the ordered diffraction spots in the SAED image indicate the single-crystal nature of CSBL-COF-4. In addition, the resolution of the SAED pattern is as high as which indicates that their skeleton structures can still remain stable even under high-energy electron beams. These results further confirm the high crystallinity and high stability of CSBL-COF-4.

[0059] From Figure 5 It can be seen that the disappearance of the peak at 1680 cm -1 (corresponding to the C=0 stretching vibration of PDA) and the appearance of a new characteristic absorption at 3375 cm -1 (corresponding to the stretching vibration of -OH) in the infrared spectrum indicate that the conversion efficiency between TMPyP and PDA is high. From Figure 6 It can be seen that the solid-state 13 C NMR spectrum of CSBL-COF-4 shows chemical shifts at 128 ppm (carbon atoms on the benzene ring), 45 ppm (hydroxyl-substituted carbon atoms), and 36 ppm (saturated carbon atoms connected to N + ions), which further confirms the successful synthesis of CSBL-COF-4.

[0060] From Figure 7 It can be seen that CSBL-COF-4 exhibits excellent chemical stability and can remain stable in 1 M HCl and 1 M NaOH at room temperature for at least three days and maintain structural stability.

[0061] From Figure 8 It can be seen that the morphology of the COF before dispersion is an aggregated state of bulk nanosheets. From Figure 9 It can be seen that these aggregated bulk solids will be exfoliated into nanosheets once dispersed in water. In addition, the CSBL-COF-4 nanosheets have smooth surfaces and uniform thicknesses (2-3 nm) and are composed of a few lamellae. These results indicate that CSBL-COF-4 has excellent water dispersibility, which is mainly attributed to the abundant N + ion sites in the skeleton network. It is worth noting that the abundant N +The ion sites not only increase the water dispersibility of CSBL-COF-4 by electrostatic repulsion to exfoliate into nanosheets, but also provide a large number of open acidic sites to enhance the affinity with basic amine molecules through Lewis acid-base interactions.

[0062] In view of the electron-deficient and Lewis acid nature of CSBL-COF-4, the present application studies its potential as a chemical sensor for detecting basic amine molecules.

[0063] From Figure 10 It can be seen that with the addition of ammonia solution, the red emission of CSBL-COF-4 at 650 nm continues to increase with the increase of ammonia concentration. From Figure 11 It can be seen that CSBL-COF-4 can also be applied to detect organic amine molecules (such as triethylamine, diethylamine, pyridine and hydrazine) produced in industrial production, which further expands the detection range of CSBL-COF-4.

[0064] From Figure 12 It can be seen that the fluorescence emission intensity of the dispersion of CSBL-COF-4 also increases with time when exposed to saturated analyte vapor in a closed state at 25°C, which proves that CSBL-COF-4 can also be used as an ideal platform for gas amine detection.

[0065] During the spoilage of meat, ammonia and biogenic amines (such as histamine or putrescine) will continue to accumulate as meat proteins decompose. Detecting these amines is crucial to ensure the quality of meat. Based on the advantages of CSBL-COF-4 in amine vapor sensing, this embodiment further studies the ability of CSBL-COF-4 to monitor meat spoilage in situ. For the experiment of monitoring the freshness of fish samples, a fresh fish sample was first stored in a sealed beaker to simulate typical storage conditions, and then stored in 4°C and 25°C environments respectively. At the same time, CSBL-COF-4 water dispersion was placed in it, and the freshness change of the fish sample was detected within 2 days, and its fluorescence spectrum was recorded over time.

[0066] From Figure 13 It can be seen that after the fresh fish sample is stored at 4°C for 24h, a significant change in fluorescence intensity can be observed, which proves that the fish sample has begun to rot at this time. From Figure 14 It can be seen that after the fresh fish sample is stored at 25°C for 24h, a more obvious fluorescence intensity enhancement can be observed, which proves that a higher concentration of biogenic amines will be produced in the same time at this temperature compared to 4°C. From Figure 15It can be seen that for the rotten fish sample, CSBL-COF-4 can more quickly identify the degree of deterioration, and these results clearly show that CSBL-COF-4 can detect amines released from deteriorated meat and can be used for freshness detection of such meat products.

[0067] In summary, the present application introduces an ionic reaction monomer into the CSBL-COF-4 skeleton structure, increases the affinity with the electron-rich amine molecules through electrostatic interaction. At the same time, the hydroxyl functional group is introduced into the structure of CSBL-COF-4, and the hydrogen bond interaction between the hydroxyl group and the amine molecules weakens the ICT (Intramolecular Charge Transfer) effect to realize the fluorescence on-off detection of amine molecules.

[0068] It is apparent to those skilled in the art that the present application is not limited to the details of the foregoing exemplary embodiments, and that the present application can be implemented in other specific forms without departing from the spirit or essential characteristics of the present application. Therefore, the embodiments should be considered in all respects as illustrative and not restrictive, and the scope of the present application should be defined by the appended claims rather than the above description, and it is intended to encompass all changes falling within the meaning and range of equivalents of the claims.

[0069] Furthermore, it should be understood that, although the present specification is described in terms of embodiments, not every embodiment contains only one independent technical solution, and the description of the specification is only for the sake of clarity, and those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that those skilled in the art can understand.

Claims

1. A method for preparing a C-C single bond linked ionic covalent organic framework, characterized in that, Preparation of C-C single bond linked ionic COF through the aldol condensation reaction between TMPyP and PDA, named as CSBL-COF-4; Specifically comprising the following steps: The mixture of TMPyP and DMF is heated to dissolve TMPyP, then the mixture of PDA, methanol solution of NaOH and 1,4-dioxane is added dropwise into the above solution, after stirring, the black solid crude product CSBL-COF-4 is obtained through freeze-pumping-thaw degassing, vacuum pumping multiple times and sealing, and heating; the solid is collected by centrifugation, washed and dried to obtain the pure product CSBL-COF-4.

2. The method for preparing an ionic covalent organic framework linked by a C / C single bond according to claim 1, characterized in that, The molar ratio of TMPyP to PDA is 1:

2.

3. The method for preparing an ionic covalent organic framework linked by a C / C single bond according to claim 1, characterized in that, The volume ratio of DMF, methanol solution of NaOH and 1,4-dioxane solution is 2-4:1-2:2-4.

4. The method for preparing an ionic covalent organic framework linked by C / C single bonds according to claim 1, characterized in that, The temperature of heating reaction is 90-110℃, and the time is 92-100h.

5. The method for preparing an ionic covalent organic framework linked by a C / C single bond according to claim 1, characterized in that, Washing with 1,4-dioxane, acetonitrile and tetrahydrofuran in turn, and the washing time is 20-28h for each solvent.

6. The method for preparing an ionic covalent organic framework linked by a C / C single bond according to claim 1, characterized in that, The synthesis method of TMPyP specifically comprises the following steps: TMPyP and methyl iodide are added into DMF, heated to react to generate crude TMPyP, then cooled to room temperature; the product is washed with ethanol to remove unreacted methyl iodide and other by-products, and dried to remove the solvent in the product to obtain the pure product TMPyP.

7. The method for preparing an ionic covalent organic framework linked by a C / C single bond according to claim 6, characterized in that, In the synthesis of TMPyP, the molar ratio of TMPyP to methyl iodide is 1-2:4-5, and the volume ratio of methyl iodide to DMF is 1-2:20-25.

8. The method for preparing an ionic covalent organic framework linked by a C / C single bond according to claim 6, characterized in that, In the synthesis of TMPyP, the temperature of heating reaction is 80-100℃, and the time is 18-20h.

9. A C-C single bond linked ionic covalent organic framework prepared by the method of any one of claims 1-8.

10. The use of the C-C single bond linked ionic covalent organic framework of claim 9 in the fluorescence-on detection of amine molecules.

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