C-C single bond connected ionic covalent organic framework and preparation method and application thereof

Abstract

The invention relates to the technical field of pollutant detection, in particular to a C-C single bond connected ionic covalent organic framework and a preparation method and application thereof. The preparation method comprises the following steps: preparing C-C single bond connected ionic COF through aldol condensation reaction between TMPyP and PDA, wherein the ionic COF is named as CSBL-COF-4; according to the invention, an ionic reaction monomer is introduced into a CSBL-COF-4 skeleton structure, and the affinity with electron-rich amine molecules is increased through electrostatic interaction. Meanwhile, a hydroxyl functional group is introduced into a CSBL-COF-4 structure, and an ICT (Intramollar Charge Transfer) effect is weakened through hydrogen bond interaction between hydroxyl and amine molecules, so that fluorescence open type detection on the amine molecules is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of pollutant detection, and in particular to an ionic covalent organic framework connected by a CC single bond, and a preparation method and application thereof. Background Art

[0002] Ammonia pollutants have attracted much attention due to their potential threats to human health, including but not limited to headaches, skin burns, eye irritation, and a variety of respiratory diseases. In extreme cases, they may even lead to serious consequences such as bladder cancer. These harmful substances mainly come from industries such as dyes, fertilizers, and pharmaceuticals, and have a significant negative impact on the natural environment. In addition, biogenic amines produced during food spoilage, such as cadaverine (1,5-diaminopentane) and histamine (2-(1H-imidazole-5-yl)ethylamine), not only affect food quality, but are also important indicators for assessing food safety and sanitation conditions. In view of the electron-rich properties 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 interactions. However, due to the strong corrosiveness of amine molecules themselves, only a few materials can show sufficient chemical stability while maintaining high affinity. Therefore, the development of electron-deficient materials with both high stability and high selectivity for efficient detection of corrosive amines has become a research hotspot and important direction in this field. This is not only the key to improving detection accuracy, but also provides strong technical support for safeguarding public health and environmental protection.

[0003] Covalent organic frameworks (COFs) have shown broad application prospects in many fields such as chemical sensing, catalysis and gas adsorption due to their high crystallinity, porosity and excellent chemical stability. At present, most COFs-based amine detectors rely on fluorescence quenching mechanisms, which are easily affected by other components in the environment and are not sensitive enough for the detection of target analytes. In contrast, COFs sensors based on fluorescence on-type are more practical, but such research cases are still rare. So far, there are only a few specifically designed COFs. For example, materials connected by imine bonds and using guanidine salts as building blocks have been proven to be able to serve as "on-type" chemical sensors with extremely high sensitivity to amine molecules, which can achieve effective detection at extremely low concentrations. However, the connection methods of existing COFs materials for amine detection are mainly limited to reversible imine or borate bonds. Such connections have poor chemical stability when encountering strongly corrosive amine molecules and may cause damage to the material structure. Therefore, the development of new COFs materials that can not only produce a fluorescent "on" response to amine molecules, but also maintain stability and reliability in complex environments is an urgent problem to be solved. This is of great significance for improving the detection accuracy of amine molecules at trace levels. Summary of the invention

[0004] In view of the above-mentioned deficiencies in the prior art, the object of the present invention is to provide an ionic covalent organic framework with CC single bond connection and a preparation method thereof, synthesize a stable CC single bond connection COF and apply it to the fluorescence on-type detection of corrosive amines.

[0005] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is:

[0006] On the one hand, a method for preparing a C-C single-bond linked ionic covalent organic framework is provided, wherein a C-C single-bond linked ionic COF is prepared by an aldol condensation reaction between 5,10,15,20-tetrakis(4-N-methylpyridyl)-porphyrin (TMPyP) and terephthalaldehyde (PDA), and is named CSBL-COF-4.

[0007] The method specifically comprises the following steps:

[0008] Step 1. Synthesis of TMPyP

[0009] 5,10,15,20-tetrakis(pyridin-4-yl)porphyrin and iodomethane are added to DMF, 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 the solvent in the product is dried to obtain pure TMPyP as a black powder;

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

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

[0012] Preferably, in step 1, the heating reaction temperature is 80-100° C. and the time is 18-20 hours.

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

[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 is heated to dissolve TMPyP. Then, a mixture of PDA, a methanol solution of NaOH, and 1,4-dioxane is added dropwise to the above solution. After stirring, the mixture is degassed by freeze-pump-thaw, and the reaction tube is evacuated three times and sealed, and heated to obtain a black solid mixture (crude CSBL-COF-4). The solid is collected by centrifugation and then soaked and washed in a Soxhlet extractor with 1,4-dioxane, acetonitrile, and tetrahydrofuran. Finally, it is dried to obtain pure CSBL-COF-4.

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

[0017] Preferably, in step 2, the volume ratio of DMF, NaOH methanol solution 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 to 1.5 M;

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

[0020] Preferably, in step 2, the stirring time is 2 to 6 hours;

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

[0022] Preferably, in step 2, the vacuum drying temperature is 110 to 130° C., and the vacuum drying time is 10 to 14 hours;

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

[0024] On the other hand, the invention provides an application of the above CC single-bond-connected ionic covalent organic framework in fluorescence-on detection of amine molecules.

[0025] The beneficial effects of the present invention are:

[0026] (1) For the first time, the C4 reactive monomer TMPyP was used to construct a CC single bond structure, which to some extent solved the problem of the lack of high-stability COFs and the difficulty in synthesis. At the same time, the CC single bond gave CSBL-COF-4 excellent chemical stability and it could be stable in 1M NaOH or 1M HCl for 3 days, which greatly ensured its potential to interact with corrosive amines and provided a new idea for the design of highly stable CC single bond-connected COFs.

[0027] (2) Abundant ionic active sites were introduced into the CSBL-COF-4 skeleton, which not only improved the dispersibility of CSBL-COF-4 in water but also provided a large number of acidic open sites, thereby enhancing the affinity with basic amines through Lewis acid-base interactions.

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

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

[0030] Figure 1 Schematic diagram of the synthesis of CSBL-COF-4 and fluorescence detection of amine molecules according to Example 1 of the present invention;

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

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

[0033] Figure 4 is the SAED pattern of CSBL-COF-4 of Example 1 of the present invention;

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

[0035] Figure 6 The solid state of CSBL-COF-4 of Example 1 of the present invention 13 C NMR spectrum;

[0036] Figure 7 The PXRD patterns of CSBL-COF-4 in Example 1 of the present invention before and after strong acid and strong base treatment;

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

[0038] Fig. 9 This is an AFM image of CSBL-COF-4 of Example 1 of the present invention;

[0039] Fig.10 The fluorescence change images of the dispersion of CSBL-COF-4 in Example 1 of the present invention after adding different concentrations of NH3(aq);

[0040] Fig.11 is a bar graph of the relative fluorescence intensity of CSBL-COF-4 in Example 1 of the present invention in the presence of different amine aqueous solutions;

[0041] Fig.12 is a bar graph of the relative fluorescence intensity of CSBL-COF-4 in Example 1 of the present invention in the presence of different amine gases;

[0042] Fig.13 This is a fluorescence response diagram of the CSBL-COF-4 dispersion of Example 1 of the present invention after being stored together with fresh sashimi at 4° C. for different periods of time;

[0043] Fig.14 This is a fluorescence response diagram of the CSBL-COF-4 dispersion of Example 1 of the present invention after being stored together with fresh sashimi at 25° C. for different time periods;

[0044] Fig.15 This is a fluorescence response diagram of the CSBL-COF-4 dispersion of Example 1 of the present invention and rotten sashimi after being stored together for different time periods. DETAILED DESCRIPTION

[0045] The specific implementation modes of the present invention are described below so that those skilled in the art can understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific implementation modes. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations utilizing the concept of the present invention are protected.

[0046] Example 1

[0047] In a thick-walled pressure reaction tube, 0.05 mmol TMPyP (59.3 mg) and DMF (3 mL) were heated to 100 °C. Then, a mixture of 0.1 mmol 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 evacuated three times by freeze-pump-thaw 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 with 1,4-dioxane, acetonitrile and tetrahydrofuran in a Soxhlet extractor for 24 hours. Finally, it was dried in vacuum at 120 °C for 12 hours to obtain CSBL-COF-4 (45.8 mg) with a yield of 63%.

[0048] Example 2

[0049] In a thick-walled pressure reaction tube, 0.0125 mmol TMPyP (14.825 mg) and DMF (0.75 mL) were heated to 100 °C. Then, a mixture of 0.0025 mmol PDA (3.35 mg), 0.25 mL of a methanol solution of NaOH (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 evacuated three times by freeze-pump-thaw 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 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 (10.5 mg) with a yield of 58%.

[0050] Example 3

[0051] In a thick-walled pressure reaction tube, 0.025 mmol TMPyP (29.65 mg) and DMF (1.5 mL) were heated to 100 °C. Then, a mixture of 0.05 mmol PDA (6.7 mg), 0.5 mL NaOH in methanol (1 M) and 0.5 mL 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 evacuated three times by freeze-pump-thaw 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 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 (22.1 mg) with a yield of 61%.

[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, a mixture of 0.2 mmol PDA (26.8 mg), 2 mL of NaOH in methanol (1 M) and 2 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 evacuated three times by freeze-pump-thaw 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 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) with a yield of 65%.

[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 was formed. Then, the reaction tube was evacuated three times by freeze-pump-thaw 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 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) with a yield of 69%.

[0056] The synthetic route of CSBL-COF-4 is shown in Figure 1 As shown, the CSBL-COF-4 prepared in Example 1 was used to carry out the following tests.

[0057] Depend on Figure 2 It can be seen that the CSBL-COF-4 prepared in Example 1 has a high crystallinity and a long-range ordered structure. CSBL-COF-4 belongs to the P4 space group (No. 75) and has a tetragonal crystal structure. The interlayer spacing obtained by the unit cell parameter simulation is The results of theoretical simulation show that CSBL-COF-4 adopts AA stacking mode, and the simulated PXRD is in good agreement with the experimental data. The unit cell parameters obtained from the Pawley refined PXRD results are: 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, proving its long-range ordered structure.

[0058] Depend on 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. Figure 4 It can be seen that the ordered diffraction spots in the SAED image indicate the single crystalline nature of CSBL-COF-4. In addition, the resolution of the SAED pattern is as high as These results further confirm the high crystallinity and stability of CSBL-COF-4.

[0059] Depend on Figure 5 It can be seen that in the infrared spectrum, 1680cm -1 The peak at 3375 cm disappeared (corresponding to the C=O stretching vibration of PDA) and -1 The new characteristic absorption (corresponding to the stretching vibration of -OH) at indicates that the reaction conversion efficiency between TMPyP and PDA is high. Figure 6 It can be seen that the solid 13 In the C NMR spectrum, 128 ppm (carbon atoms on the benzene ring), 45 ppm (carbon atoms substituted by hydroxyl groups), and 36 ppm (carbon atoms with N + The chemical shifts observed at the saturated carbon atoms (ionically linked) further confirmed the successful synthesis of CSBL-COF-4.

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

[0061] Depend on Figure 8 It can be seen that the morphology of COF before dispersion is the aggregation state of large nanosheets. Fig. 9 It can be seen that once dispersed in water, these aggregated block solids will be peeled off to form nanosheets. In addition, the CSBL-COF-4 nanosheets have a smooth surface and uniform thickness (2-3 nm) and are composed of a few sheets. These results show that CSBL-COF-4 has excellent water dispersibility, which is mainly attributed to the rich N + ion sites. It is noteworthy that the abundant N +The ionic sites can not only increase the water dispersibility of CSBL-COF-4 by exfoliating it to form nanosheets through electrostatic repulsion, but also provide a large number of acidic open sites to enhance the affinity with basic amine molecules through Lewis acid-base interactions.

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

[0063] Depend on Fig.10 It can be seen that with the addition of ammonia solution, the red emission of CSBL-COF-4 at 650nm continues to increase with the increase of ammonia concentration. Fig.11 It can be seen that CSBL-COF-4 can also be applied to the detection of 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] Depend on Fig.12 It can be seen that when the dispersion of CSBL-COF-4 is exposed to saturated analyte vapor in a closed state at 25°C, its fluorescence emission intensity will also increase with time, which proves that CSBL-COF-4 can also be used as an ideal platform for gaseous amine detection.

[0065] During the meat spoilage process, as the meat protein decomposes, ammonia and biogenic amines (such as histamine or putrescine) will continue to accumulate. Detecting these amines is crucial to ensuring 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 in in situ monitoring of meat spoilage. For the experiment of monitoring the freshness of fish samples, a piece of fresh fish sample was first stored in a sealed beaker to simulate typical storage conditions, and then stored at 4°C and 25°C respectively. At the same time, a CSBL-COF-4 aqueous dispersion was placed in it, and the freshness changes of the fish samples were detected within 2 days, and their fluorescence spectra were recorded over time.

[0066] Depend on Fig.13 It can be seen that after the fresh fish sample was stored at 4°C for 24 hours, a significant change in fluorescence intensity can be observed, proving that the fish sample has begun to rot. Fig.14 It can be seen that after the fresh fish samples were stored at 25°C for 24 hours, a more obvious increase in fluorescence intensity was observed, proving that a higher concentration of biogenic amines was produced at this temperature compared to 4°C in the same period of time. Fig.15It can be seen that for rotten fish samples, CSBL-COF-4 can identify the degree of deterioration more quickly. These results clearly show that CSBL-COF-4 is capable of detecting amines released from spoiled meat and can be used to detect the freshness of such meat products.

[0067] In summary, the present invention introduces ionic reactive monomers into the CSBL-COF-4 skeleton structure to increase the affinity with electron-rich amine molecules through electrostatic interaction. At the same time, a hydroxyl functional group is introduced into the CSBL-COF-4 structure to weaken the ICT (Intramolecular Charge Transfer) effect through the hydrogen bond interaction between the hydroxyl group and the amine molecules to achieve fluorescence on-type detection of amine molecules.

[0068] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered exemplary and non-restrictive in all respects, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present invention.

[0069] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for preparing an ionic covalent organic framework connected by a CC single bond, characterized in that: The C-C single-bond linked ionic COF named CSBL-COF-4 was prepared by the aldol condensation reaction between TMPyP and PDA; The specific steps include: The mixture of TMPyP and DMF was heated to dissolve TMPyP, and then a mixture of PDA, a methanol solution of NaOH and 1,4-dioxane was added dropwise to the above solution. After stirring, the mixture was degassed by freeze-pump-thaw, vacuumed several times and sealed, and heated to obtain a black solid crude product CSBL-COF-4. The solid was collected by centrifugation, washed, and dried to obtain a pure product CSBL-COF-4.

2. The method for preparing the ionic covalent organic framework connected by CC single bonds according to claim 1, characterized in that: The molar ratio of TMPyP and PDA was 1:

2.

3. The method for preparing the ionic covalent organic framework connected by CC single bonds according to claim 1, characterized in that: The volume ratio of DMF, NaOH methanol solution and 1,4-dioxane solution is 2-4:1-2:2-4.

4. The method for preparing the ionic covalent organic framework connected by CC single bonds according to claim 1, characterized in that: The heating reaction temperature is 90-110°C and the time is 92-100 hours.

5. The method for preparing the ionic covalent organic framework connected by CC single bonds according to claim 1, characterized in that: Soak and wash with 1,4-dioxane, acetonitrile and tetrahydrofuran in sequence, and the washing time is 20 to 28 hours with each solvent.

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

7. The method for preparing an ionic covalent organic framework connected by CC single bonds 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 connected by CC single bonds according to claim 6, characterized in that: In the synthesis of TMPyP, the heating reaction temperature is 80 to 100° C. and the time is 18 to 20 hours.

9. An ionic covalent organic framework connected by CC single bonds prepared by the method according to any one of claims 1 to 8.

10. Use of the CC single-bond-connected ionic covalent organic framework according to claim 9 in fluorescence-on detection of amine molecules.

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