An open-type colorimetric fluorescent covalent organic polymer and preparation and application thereof

Abstract

This invention belongs to the field of fluorescent detection materials technology, specifically disclosing an open-type colorimetric fluorescent covalent organic polymer and its preparation and application. The preparation includes the following steps: dissolving 4,4',4''-(1,3,5-triazine-2,4,6-triyl)tris(2,6-dimethylaniline) and trialdehyde-resorcinol in 1,4-dioxane; uniformly adding acetic acid via ultrasonication; degassing three times using a refrigerated pump followed by heating reaction; sequentially washing with tetrahydrofuran and dichloromethane using a Soxhlet washing method; drying; passing through a 200-mesh sieve; and dry grinding. This invention utilizes the aforementioned open-type colorimetric fluorescent covalent organic polymer and its preparation and application. This open-type colorimetric fluorescent covalent organic polymer reacts sensitively with aminourea and 3,5-dinitro-2-hydroxyphenylenehydrazine, and can be used in open-type fluorescent chemical sensors to reduce the influence of other impurities on the detection results, thereby improving the detection sensitivity.

Description

Technical Field

[0001] This invention belongs to the field of fluorescent detection materials technology, specifically relating to an on-type colorimetric fluorescent covalent organic polymer and its preparation and application. Background Technology

[0002] Nitrofurans (NFs) are a class of inexpensive and highly effective synthetic broad-spectrum antibiotics. Common examples include nitrofurantoin (NFT), furazolidone (FZD), nitrofurazone (NZF), nifurosol (NFS), and furazolidone (FTD), which are widely used to treat Gram-related bacterial infections. Although NFs have potential teratogenic, carcinogenic, and mutagenic effects, and are prohibited drugs in the EU, the US, and China, some manufacturers still illegally add them.

[0003] NFs are rapidly metabolized in the body, and their metabolites bind to proteins to form complexes that can remain in the body for months. The metabolites corresponding to NFT, FZD, NZF, NFS, and FTD are 1-aminohydantoin (AHD), 3-amino-2-oxazolidinone (AOZ), aminourea (SEM), 3,5-dinitro-2-hydroxyphenylenehydrazine (DNSAH), and 3-amino-5-morpholinomethyl-2-oxazolidinone (AMOZ), respectively. Because NF metabolites have potential mutagenic and carcinogenic effects, these complexes are difficult to degrade using common food processing methods, and they are passed through the food chain. In a weakly acidic environment, the metabolites can be released from the protein-bound complexes, thus posing a threat to human health. Since the parent drugs of NFs are rapidly metabolized in animals and their direct residues are extremely low, making direct detection difficult, while the bound residues of their metabolites exhibit stability and dose-dependent characteristics, monitoring the content of nitrofuran metabolites in animal-derived foods can indirectly reflect the usage and residue levels of the parent drugs.

[0004] Currently, methods for detecting nitrofuran metabolites include high-performance liquid chromatography (HPLC), liquid chromatography-mass spectrometry (LC-MS), and enzyme-linked immunosorbent assay (ELISA). However, chromatographic methods are time-consuming and expensive, and on-site detection is difficult; ELISA is cumbersome, and the stability of enzymes is easily affected by interference, which limits its widespread application in daily life. Therefore, there is an urgent need to develop a rapid and sensitive detection method for monitoring the residues of nitrofuran metabolites in animal-derived products to ensure food supply safety.

[0005] Fluorescence detection offers advantages such as high sensitivity, ease of operation, and real-time imaging. Common fluorescent materials include semiconductor quantum dots (QDs), carbon dots (CDs), and nanomaterials. However, QDs are often toxic due to the presence of heavy metal ions, and CDs cannot be purified due to their small particle size. Therefore, there is a need in this field to develop an on-off colorimetric fluorescent covalent organic polymer, its preparation, and its applications, which can effectively solve the above problems. Summary of the Invention

[0006] The purpose of this invention is to provide an open-type colorimetric fluorescent covalent organic polymer, its preparation and application. The open-type colorimetric fluorescent covalent organic polymer prepared by this invention reacts sensitively with aminourea and 3,5-dinitro-2-hydroxyphenylenehydrazine, and can be used in open-type fluorescent chemical sensors to reduce the influence of other impurities on the detection results, thereby improving the detection sensitivity.

[0007] To achieve the above objectives, the present invention provides a method for preparing an on-type colorimetric fluorescent covalent organic polymer, comprising the following steps: Step S1: Dissolve 4,4',4''-(1,3,5-triazine-2,4,6-triyl)tris(2,6-dimethylaniline) and trialdehyde phloroglucinol in 1,4-dioxane to obtain a mixture; Step S2: After the mixture is homogenized by the first ultrasonication, 12M acetic acid is added and the mixture is subjected to a second ultrasonic catalysis at 25°C to obtain the reaction product. Step S3: After degassing the reaction product three times by circulating it through a refrigeration pump, the product is heated to obtain the material. Step S4: The material is sequentially washed with tetrahydrofuran and dichloromethane using a Soxhlet washing process. Step S5: After Soxhlet washing, the product is dried under a vacuum of -100 kPa, passed through a 200-mesh sieve, dry-ground, and then passed through another 200-mesh sieve to obtain an open-type colorimetric fluorescent covalent organic polymer.

[0008] Preferably, in step S1, the mass ratio of 4,4',4''-(1,3,5-triazine-2,4,6-triyl)tris(2,6-dimethylaniline) to trialdehyde phloroglucinol is 2.1:1; and the mass-to-volume ratio of trialdehyde phloroglucinol to 1,4-dioxane is 10.5 mg / mL.

[0009] Preferably, in step S2, the frequency of the first and second ultrasounds is 40kHz, the power of the ultrasounds is 300W, and the duration of the ultrasounds is 20min. The volume ratio of acetic acid to 1,4-dioxane is 1:10.

[0010] Preferably, in step S3, the degassing via the refrigeration pump specifically involves: placing the reaction vessel containing the reaction product in an environment of liquid nitrogen freezing solvent at a temperature of -196°C until no liquid remains; then evacuating the vessel under a vacuum of -0.1 MPa for 1 minute; and finally thawing the reaction vessel in hot water at a temperature of 100°C until no solid remains in the reaction vessel.

[0011] Preferably, in step S3, the heating temperature is 120°C and the heating time is 3 days.

[0012] Preferably, in step S4, both tetrahydrofuran and dichloromethane are AR-grade solvents. The soxhlet washing temperature for tetrahydrofuran is 100°C, and the soxhlet washing temperature for dichloromethane is 75°C. Each solvent is used for soxhlet washing for 24 hours, and the solvent is replaced every 6 hours.

[0013] Preferably, in step S5, the drying temperature is 60°C and the drying time is 12 hours.

[0014] The present invention also provides an open-type colorimetric fluorescent covalent organic polymer prepared by means of an open-type colorimetric fluorescent covalent organic polymer.

[0015] This invention also provides the application of an open-type colorimetric fluorescent covalent organic polymer in the fluorescence detection of nitrofuran metabolites.

[0016] Preferably, nitrofuran metabolites include aminourea and 3,5-dinitro-2-hydroxyphenylhydrazine.

[0017] This invention utilizes the aforementioned open-type colorimetric fluorescent covalent organic polymer, its preparation, and its application, with the following beneficial effects: (1) Covalent organic polymers (COPs) are a class of porous nanomaterials composed of light elements (C, B, H, O, N, etc.) connected by strong covalent bonds, possessing characteristics such as large specific surface area and tunable pore size. The open-type colorimetric fluorescent covalent organic polymer in this invention increases the contact opportunity with the analyte through its large specific surface area, and the tunable pore size allows for the pre-enrichment of the analyte. Furthermore, the open-type colorimetric fluorescent covalent organic polymer in this invention can also be functionalized to achieve fluorescence sensing of specific analytes based on their characteristics.

[0018] (2) The open-type colorimetric fluorescent covalent organic polymer in this invention reacts with nitrofuran metabolites through a photoinduced electron transfer effect. The open-type colorimetric fluorescent covalent organic polymer reduces the influence of other impurities on the detection results of the open-type fluorescent chemical sensor, thereby improving detection sensitivity. Furthermore, the shift in the fluorescence emission peak of the open-type colorimetric fluorescent covalent organic polymer in this invention provides bidirectional verification of the experimental results. This is currently the first known fluorescent COPs material for detecting nitrofuran metabolites (SEM, DNSAH).

[0019] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0020] Figure 1The sensitivity of the covalent organic polymer prepared at different synthesis times with SEM and DNSAH is shown in Experiment 1 of the present invention, which describes an open-type colorimetric fluorescent covalent organic polymer and its preparation and application. Figure 2 The image shows the sensitivity of the covalent organic polymer prepared at different synthesis temperatures in Experiment 1 of this invention, in reaction with SEM and DNSAH. Figure 3 This is a sensitivity diagram of the reaction between the covalent organic polymer prepared at different catalyst concentrations and SEM and DNSAH in Experiment Example 1 of the present invention, which describes an open-type colorimetric fluorescent covalent organic polymer and its preparation and application. Figure 4 This is a scanning electron microscope image of the open-type colorimetric fluorescent covalent organic polymer prepared in Example 2 of the present invention, which is described in Experimental Example 2. Figure 5 This is a graph showing the sensitivity detection results of the open-type colorimetric fluorescent covalent organic polymer prepared in Example 2 of the present invention as the SEM concentration increases. Figure 6 This invention relates to an open-type colorimetric fluorescent covalent organic polymer, its preparation, and its application. Example 2 concerns F. max / F0 and Δλ with C SEM The fitted standard curve plot; Figure 7 This is a graph showing the sensitivity detection results of the open-type colorimetric fluorescent covalent organic polymer prepared in Example 2 of the present invention as the concentration of DNSAH increases. Figure 8 This invention relates to an open-type colorimetric fluorescent covalent organic polymer, its preparation, and its application. Example 2 concerns F. max / F0 and Δλ with C DNSAH The fitted standard curve plot; Figure 9 This is an optimized detection time diagram of the open-type colorimetric fluorescent covalent organic polymer prepared in Example 2 of the present invention, which is described in Experimental Example 2. Figure 10 This is a graph showing the effect of fluorescence irradiation stability of the open-type colorimetric fluorescent covalent organic polymer prepared in Example 2 of the present invention. Detailed Implementation

[0021] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0022] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0023] In the experimental examples of this invention, acetonitrile was used as the solvent to prepare SEM and DNSAH standard solutions of different concentrations. Under optimal conditions, the wavelength measurement range was set to 395-700 nm, and the values ​​and trends of the optimal fluorescence emission peak were recorded. According to formulas (1) and (2), a colorimetric response platform for SEM and DNSAH detection was constructed using the obtained data.

[0024] F max / F0=K1C+b1(1) Δλ=K2C+b2(2; Where C represents the concentration of the target analyte, K represents the slope of the calibration curve, and F... max λ represents the value of the optimal emission peak, F0 represents the value of the emission peak of the pure material, λ represents the shift value of the fluorescence emission peak, and b represents the intercept of the calibration curve.

[0025] Example The preparation of an on-type colorimetric fluorescent covalent organic polymer includes the following steps: Step S1: Dissolve 66.15 mg of 4,4',4''-(1,3,5-triazine-2,4,6-triyl)tris(2,6-dimethylaniline) and 31.5 mg of trialdehyde phloroglucinol in 3 mL of 1,4-dioxane to obtain a mixture; Step S2: After sonicating the mixture for 20 minutes at a frequency of 40 kHz and a power of 300 W, add 0.3 mL of 12 M acetic acid and sonicate it for 20 minutes at a frequency of 40 kHz and a power of 300 W to obtain the reaction product. Step S3: After degassing the reaction product three times by circulating it through a refrigeration pump, heat it at 120°C for 3 days to obtain the material. Specifically, the degassing process using a refrigeration pump involves placing the reaction vessel containing the reaction products in a liquid nitrogen freezing solvent environment at a temperature of -196°C until no liquid remains; then evacuating the vessel under a vacuum of -0.1 MPa for 1 minute; finally, thawing the reaction vessel in hot water at a temperature of 100°C until no solid remains in the reaction vessel; repeating the degassing process using a refrigeration pump three times.

[0026] Step S4: The material is sequentially washed with tetrahydrofuran and dichloromethane using a Soxhlet washing process. Tetrahydrofuran and dichloromethane are both AR-grade solvents. The Soxhlet washing temperature for tetrahydrofuran is 100°C, and the Soxhlet washing temperature for dichloromethane is 75°C. Each solvent is subjected to Soxhlet washing for 24 hours, and the solvent is replaced every 6 hours.

[0027] Step S5: After Soxhlet washing, the product is dried under a vacuum of -100 kPa at a temperature of 60°C for 12 hours. After dry grinding through a 200-mesh sieve, it is then passed through another 200-mesh sieve to obtain the open-type colorimetric fluorescent covalent organic polymer (fluorescent COPs).

[0028] Comparative Example 1 The preparation of a covalent organic polymer includes the following steps: Step S1: Dissolve 66.15 mg of 4,4',4''-(1,3,5-triazine-2,4,6-triyl)tris(2,6-dimethylaniline) and 31.5 mg of trialdehyde phloroglucinol in 3 mL of 1,4-dioxane to obtain a mixture; Step S2: After sonicating the mixture for 20 minutes at a frequency of 40 kHz and a power of 300 W, add 0.3 mL of 12 M acetic acid and sonicate it for 20 minutes at a frequency of 40 kHz and a power of 300 W to obtain the reaction product. Step S3: After degassing the reaction product three times by circulating it through a refrigeration pump, the product is heated at 120°C for 1 day and 2 days respectively to obtain the materials. Specifically, the degassing process using a refrigeration pump involves placing the reaction vessel containing the reaction products in a liquid nitrogen freezing solvent environment at a temperature of -196°C until no liquid remains; then evacuating the vessel under a vacuum of -0.1 MPa for 1 minute; finally, thawing the reaction vessel in hot water at a temperature of 100°C until no solid remains in the reaction vessel; repeating the degassing process using a refrigeration pump three times.

[0029] Step S4: The material is sequentially subjected to Soxhlet washing with tetrahydrofuran and dichloromethane. Tetrahydrofuran and dichloromethane are both AR-grade solvents. The Soxhlet washing temperature for tetrahydrofuran is 100°C, and the Soxhlet washing temperature for dichloromethane is 75°C. Each solvent is subjected to Soxhlet washing for 24 hours, and the solvent is replaced every 6 hours.

[0030] Step S5: After Soxhlet washing, the product is dried under a vacuum of -100 kPa at a temperature of 60°C for 12 hours. After dry grinding through a 200-mesh sieve, the covalent organic polymers are obtained.

[0031] Comparative Example 2 The preparation of a covalent organic polymer includes the following steps: Step S1: Dissolve 66.15 mg of 4,4',4''-(1,3,5-triazine-2,4,6-triyl)tris(2,6-dimethylaniline) and 31.5 mg of trialdehyde phloroglucinol in 3 mL of 1,4-dioxane to obtain a mixture; Step S2: After sonicating the mixture for 20 minutes at a frequency of 40 kHz and a power of 300 W, add 0.3 mL of 12 M acetic acid and sonicate it for 20 minutes at a frequency of 40 kHz and a power of 300 W to obtain the reaction product. Step S3: After degassing the reaction product three times by circulating it through a refrigeration pump, the product was heated at 110℃ and 150℃ for 3 days respectively to obtain the materials. Specifically, the degassing process using a refrigeration pump involves placing the reaction vessel containing the reaction products in a liquid nitrogen freezing solvent environment at a temperature of -196°C until no liquid remains; then evacuating the vessel under a vacuum of -0.1 MPa for 1 minute; finally, thawing the reaction vessel in hot water at a temperature of 100°C until no solid remains in the reaction vessel; repeating the degassing process using a refrigeration pump three times.

[0032] Step S4: The material is sequentially subjected to Soxhlet washing with tetrahydrofuran and dichloromethane. Tetrahydrofuran and dichloromethane are both AR-grade solvents. The Soxhlet washing temperature for tetrahydrofuran is 100°C, and the Soxhlet washing temperature for dichloromethane is 75°C. Each solvent is subjected to Soxhlet washing for 24 hours, and the solvent is replaced every 6 hours.

[0033] Step S5: After Soxhlet washing, the product is dried under a vacuum of -100 kPa at a temperature of 60°C for 12 hours. After dry grinding through a 200-mesh sieve, the covalent organic polymers are obtained.

[0034] Comparative Example 3 The preparation of a covalent organic polymer includes the following steps: Step S1: Dissolve 66.15 mg of 4,4',4''-(1,3,5-triazine-2,4,6-triyl)tris(2,6-dimethylaniline) and 31.5 mg of trialdehyde phloroglucinol in 3 mL of 1,4-dioxane to obtain a mixture; Step S2: After sonicating the mixture for 20 minutes at a frequency of 40 kHz and a power of 300 W, add 0.3 mL of 6 M, 9 M, and 15 M acetic acid respectively, and sonicate for 20 minutes at a frequency of 40 kHz and a power of 300 W respectively to obtain the reaction products. Step S3: After degassing the reaction products three times by circulating them through a refrigeration pump, the products are heated at 120°C for 3 days to obtain the materials. Specifically, the degassing process using a refrigeration pump involves placing the reaction vessel containing the reaction products in a liquid nitrogen freezing solvent environment at a temperature of -196°C until no liquid remains; then evacuating the vessel under a vacuum of -0.1 MPa for 1 minute; finally, thawing the reaction vessel in hot water at a temperature of 100°C until no solid remains in the reaction vessel; repeating the degassing process using a refrigeration pump three times.

[0035] Step S4: The material is sequentially subjected to Soxhlet washing with tetrahydrofuran and dichloromethane. Tetrahydrofuran and dichloromethane are both AR-grade solvents. The Soxhlet washing temperature for tetrahydrofuran is 100°C, and the Soxhlet washing temperature for dichloromethane is 75°C. Each solvent is subjected to Soxhlet washing for 24 hours, and the solvent is replaced every 6 hours.

[0036] Step S5: After Soxhlet washing, the product is dried under a vacuum of -100 kPa at a temperature of 60°C for 12 hours. After dry grinding through a 200-mesh sieve, the covalent organic polymers are obtained.

[0037] Comparative Example 4 The preparation of a covalent organic polymer includes the following steps: Step S1: Dissolve 66.15 mg of 4,4',4''-(1,3,5-triazine-2,4,6-triyl)tris(2,6-dimethylaniline) and 31.5 mg of trialdehyde phloroglucinol in 3 mL of 1,4-dioxane to obtain mixture A; Step S2: After sonicating the mixture at a frequency of 40 kHz and a power of 300 W for 20 minutes, mixture B is obtained. Step S3: After degassing mixture B three times by circulating it through a refrigeration pump, it is heated at 120°C for 3 days to obtain the material. Specifically, the degassing process using a refrigeration pump involves placing the reaction vessel containing the reaction products in a liquid nitrogen freezing solvent environment at a temperature of -196°C until no liquid remains; then evacuating the vessel under a vacuum of -0.1 MPa for 1 minute; finally, thawing the reaction vessel in hot water at a temperature of 100°C until no solid remains in the reaction vessel; repeating the degassing process using a refrigeration pump three times.

[0038] Step S4: The material is sequentially washed with tetrahydrofuran and dichloromethane using a Soxhlet washing process. Tetrahydrofuran and dichloromethane are both AR-grade solvents. The Soxhlet washing temperature for tetrahydrofuran is 100°C, and the Soxhlet washing temperature for dichloromethane is 75°C. Each solvent is subjected to Soxhlet washing for 24 hours, and the solvent is replaced every 6 hours.

[0039] Step S5: After Soxhlet washing, the product is dried under a vacuum of -100 kPa at a temperature of 60°C for 12 hours. After dry grinding through a 200-mesh sieve, the covalent organic polymer is obtained.

[0040] Experimental Example 1 The covalent organic polymers prepared in Examples 1-4 and Comparative Examples 1-4 were used in fluorescence detection of nitrofuran metabolites (SEM, DNSAH) to conduct sensitivity experiments.

[0041] The experimental results show that the sensitivity of the reaction between covalent organic polymers and SEM and DNSAH is affected by the synthesis parameters, including the material synthesis time (e.g., Figure 1 As shown), the synthesis temperature (e.g.) Figure 2 (as shown) and catalyst concentration (e.g.) Figure 3 The influence of (as shown in the figure). Analysis shows that in the embodiments of the present invention, under the conditions of synthesis temperature of 120℃ for 3 days and catalyst concentration of 12M, the synthesized fluorescent COPs react most sensitively with SEM and DNSAH.

[0042] Experiment Example 2 (1) The fluorescent COPs prepared in the examples were characterized.

[0043] like Figure 4 As shown, the fluorescent COPs prepared in the examples are irregularly stacked sheet-like structures.

[0044] (2) Sensitive detection of the fluorescent COPs prepared in the examples.

[0045] Using SEM and DNSAH at concentrations of 0-50 mg / L as targets, respectively, they were reacted with 0.5 mg / mL of fluorescent COPs. The changes in the intensity and position of the fluorescence emission peaks of the fluorescent COPs with increasing SEM and DNSAH concentrations were observed to evaluate the performance of the fluorescent COPs colorimetric sensor for quantitative analysis of SEM and DNSAH.

[0046] like Figure 5 As shown, the intensity of the fluorescence emission peak of fluorescent COPs gradually increases with increasing SEM concentration, and the fluorescence emission peak of fluorescent COPs gradually blue-shifts with increasing SEM concentration. Figure 6 As shown, we obtain information about F. max / F0 and Δλ with C SEM The fitted standard curve.

[0047] Similarly, such as Figure 7 As shown, the intensity of the fluorescence emission peak of fluorescent COPs increases with increasing DNSAH concentration, and a blue shift occurs simultaneously. Figure 8 As shown, we obtain information about F. max / F0 and Δλ with C DNSAH The fitted standard curve plot.

[0048] In summary, the open-type colorimetric sensor using fluorescent COPs (open-type colorimetric fluorescent covalent organic polymers) prepared in the embodiments of the present invention is a promising tool for detecting SEM and DNSAH.

[0049] (3) The detection time of the fluorescent COPs prepared in the example was optimized.

[0050] 0.5 mg / mL of fluorescent COPs were reacted with SEM and DNSAH at specific concentrations, respectively, and detected every 5 minutes. The results were obtained by observing the F... max The changes in / F0 and Δλ over time were used to determine the optimal reaction time for the detection of SEM and DNSAH by fluorescent COPs.

[0051] like Figure 9 As shown, for SEM and DNSAH, basically after reacting with fluorescent COPs for 15 min, F max / F0 and Δλ are basically in equilibrium, so in order to save reaction time, the reaction time of fluorescent COPs with SEM and DNSAH is 15 min.

[0052] (4) The fluorescence stability of the fluorescent COPs prepared in the examples was detected.

[0053] The material was continuously irradiated under a light-protected ultraviolet lamp for 120 minutes, and the intensity and position of the optimal emission peak were measured every 5 minutes to evaluate the fluorescence irradiation stability of the fluorescent COPs.

[0054] like Figure 10 As shown, the fluorescence emission peak intensity and shift of the fluorescent COPs remained essentially unchanged, proving that the fluorescent COPs (on-type colorimetric fluorescent covalent organic polymers) prepared in the embodiments of the present invention have good fluorescence stability.

[0055] Therefore, the present invention employs the above-mentioned open-type colorimetric fluorescent covalent organic polymer and its preparation and application. The open-type colorimetric fluorescent covalent organic polymer prepared by this method reacts sensitively with aminourea and 3,5-dinitro-2-hydroxyphenylenehydrazine, and can be used in open-type fluorescent chemical sensors to reduce the influence of other impurities on the detection results, thereby improving the detection sensitivity.

[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. The application of an open-type colorimetric fluorescent covalent organic polymer in the fluorescence detection of nitrofuran metabolites, characterized in that, A method for preparing an open-type colorimetric fluorescent covalent organic polymer includes the following steps: Step S1: Dissolve 4,4',4''-(1,3,5-triazine-2,4,6-triyl)tris(2,6-dimethylaniline) and trialdehyde phloroglucinol in 1,4-dioxane to obtain a mixture; Step S2: After the mixture is homogenized by the first ultrasonication, 12M acetic acid is added and the mixture is subjected to a second ultrasonic catalysis at 25°C to obtain the reaction product. Step S3: After degassing the reaction product three times by circulating it through a refrigeration pump, the product is heated to obtain the material. Step S4: The material is sequentially washed with tetrahydrofuran and dichloromethane using a Soxhlet washing process. Step S5: After Soxhlet washing, the product is dried under a vacuum of -100 kPa, passed through a 200-mesh sieve, dry-ground, and then passed through another 200-mesh sieve to obtain an open-type colorimetric fluorescent covalent organic polymer. In step S3, the temperature of the heating reaction is 120°C, and the heating reaction time is 3 days. Nitrofuran metabolites are selected from aminourea and 3,5-dinitro-2-hydroxyphenylhydrazine.

2. The application according to claim 1, characterized in that: In step S1, the mass ratio of 4,4',4''-(1,3,5-triazine-2,4,6-triyl)tris(2,6-dimethylaniline) to trialdehyde phloroglucinol is 2.1:1; the mass-to-volume ratio of trialdehyde phloroglucinol to 1,4-dioxane is 10.5 mg / mL.

3. The application according to claim 2, characterized in that: In step S2, the frequency of the first and second ultrasounds is 40kHz, the power of the ultrasounds is 300W, and the duration of the ultrasounds is 20min. The volume ratio of acetic acid to 1,4-dioxane is 1:

10.

4. The application according to claim 1, characterized in that, In step S3, the degassing process using the refrigeration pump is as follows: the reaction vessel containing the reaction product is placed in a liquid nitrogen freezing solvent environment at a temperature of -196°C and frozen until there is no liquid; then, a vacuum is drawn for 1 minute at a vacuum degree of -0.1 MPa; and then the reaction vessel is placed in hot water at a temperature of 100°C to thaw until there is no solid in the reaction vessel.

5. The application according to claim 1, characterized in that: In step S4, both tetrahydrofuran and dichloromethane are AR-grade solvents. The Soxhlet washing temperature for tetrahydrofuran is 100°C, and the Soxhlet washing temperature for dichloromethane is 75°C. Each solvent is subjected to Soxhlet washing for 24 hours, and the solvent is replaced every 6 hours.

6. The application according to claim 1, characterized in that: In step S5, the drying temperature is 60℃ and the drying time is 12 hours.

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