Conjugated microporous polymer with quinoxaline diol as recognition group, preparation method and application thereof

Abstract

The present invention belongs to the technical field of fluorescence sensors and provides a conjugated microporous polymer with quinoxaline diol as a recognition group, a preparation method thereof, and an application thereof. The present invention uses C6H6Br2N2S and sodium borohydride to react to prepare an intermediate compound 1, which is then reacted with oxalic acid to prepare an intermediate compound 2, which is then subjected to a coupling reaction with 2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine under the action of a catalyst to prepare a conjugated microporous polymer CMP. The conjugated microporous polymer prepared by the present invention is sensitive to Ag. + and MnO4 ‑ It has high selectivity and high sensitivity. The fluorescence intensity of CMP solution at 450nm is similar to that of Ag. + / MnO4 ‑ The concentrations showed a linear relationship, and the detection limits were 2.5×10 ‑6 mol·L ‑1 and 7.4×10 ‑6 mol·L ‑1 The CMP prepared by the present invention is suitable for Ag + or MnO4 ‑ Conduct testing.

Description

Technical Field

[0001] The present invention relates to the technical field of fluorescence sensors, and in particular to a conjugated microporous polymer using quinoxaline diol as a recognition group, a preparation method and application thereof. Background Art

[0002] Silver ion is a common cation that is widely used in catalysis, production of coins, batteries, photoelectric tubes, bearing parts, gels, professional bandages, implantable prostheses, ureters, and drinking water disinfection. About 2,500 tons of silver are discharged into the environment from industry each year, of which 150 tons are precipitates from wastewater. The negative impact of silver ions on the environment, especially organisms, has also attracted great attention. It is reported that silver ions can bind to amines, imidazoles, and adenylate groups of various metabolites, thereby inactivating them. Silver ions can replace Ca in hydroxyapatite in bones. 2+ and Zn 2+ Excessive exposure to silver may lead to blood silver (argyria) and urine silver excretion, heart dilatation, growth retardation and liver degenerative changes.

[0003] Due to its strong oxidizing properties, permanganate has a wide range of applications. For example, in chemical production, it is used as an oxidizing agent for the production of saccharin, vitamin C, isoniazid, and benzoic acid; in medicine, it is used for cleaning, disinfection, and fungicide; in water purification and wastewater treatment, it is used as a water treatment agent to oxidize hydrogen sulfide, phenols, iron, manganese, and various organic and inorganic pollutants, control odor, and decolorize; and in laboratories, it is often used as a colorimetric developer for developing thin-layer chromatography bands. Permanganate is used extensively in these areas, and when released into the environment, it quickly enters the biosphere and hydrosphere, posing a serious threat to organisms, ecosystems, and human health and safety.

[0004] Currently, most methods used to detect silver ions and permanganate require expensive instruments and specialized operators, and the procedures are complex, making on-site testing impossible. Therefore, there is a need to develop a fast, efficient, simple, and on-site method for detecting silver ions and permanganate.

[0005] Conjugated microporous polymers, also known as Conjugated Microporous Polymers (CMPs), are a new type of porous microporous material with a stable π-π conjugated nano-skeleton spatial network structure. Since its discovery in 2007, it has had broad application prospects in catalysis, energy storage, fluorescence sensing, separation, etc. due to its flexible and designable structure, adjustable pore size properties, and adjustable optical properties. Some CMPs have fluorescent properties themselves, but they can be quenched under the action of ions to identify specific ions, which is also a method for detecting some elements. The document "Synthesis of New Porous Organic Polymers and Research on Their Fluorescence Sensing Properties" (Zhang Chao, Jilin University, 2024) discloses a new conjugated microporous organic polymer (TPA-Bp). Experiments have found that Fe 3+ and Fe 2+ will quench the fluorescence of TPA-Bp. 3+ The detection limit was 1.02×10 - 5 mol·L -1 , Fe 2+ The detection limit was 5.37×10 -6 mol·L -1 TPA-Bp is expected to be used as a Fe 3+ and Fe 2+ Detection of fluorescence sensors.

[0006] At present, there is no report on the use of conjugated microporous polymers with quinoxaline diol as the recognition group for the detection of silver ions and permanganate. Summary of the Invention

[0007] The purpose of the present invention is to solve the above problems and provide a conjugated microporous polymer with quinoxaline diol as a recognition group, a preparation method and application thereof. + and MnO4 - It has high selectivity and high sensitivity and can be used to detect silver ions or permanganate in solution.

[0008] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0009] A conjugated microporous polymer with quinoxaline diol as a recognition group, the conjugated microporous polymer is denoted as CMP, and its structure is shown in formula (I):

[0010]

[0011] The present invention also provides a method for preparing a conjugated microporous polymer using quinoxaline diol as a recognition group, wherein 2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine and 2,3-dihydroxy-5,8-dibromo-quinoxaline are used as monomers and polymerized through a coupling reaction to obtain a conjugated microporous polymer shown in formula (I).

[0012] In the present invention, preferably, the specific steps of the coupling reaction are as follows:

[0013] 2,3-dihydroxy-5,8-dibromo-quinoxaline and 2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine are weighed in a molar ratio of 1 to 1.5:1 and placed in a reaction container. Catalysts tetrakis(triphenylphosphine)palladium and cuprous iodide are added to the reaction container, and the reaction container is degassed with nitrogen. Toluene is injected into the reaction container, and at the same time, the instrument is started for stirring to perform nitrogen degassing. Triethylamine is then injected into the reaction container and nitrogen degassing is performed. After the nitrogen degassing is completed, the reaction temperature is raised to 78 to 82° C., and while maintaining nitrogen protection, a cover is used to avoid light and the reaction is continued for 40 to 55 hours. After the reaction is completed, the reaction container is cooled to room temperature, washed, and then subjected to Soxhlet extraction with methanol. The product is dried to obtain the conjugated microporous polymer.

[0014] In the present invention, preferably, the 2,3-dihydroxy-5,8-dibromo-quinoxaline is prepared by the following method: oxalic acid and 1,4-dibromo-2,3-diaminobenzene are weighed in a molar ratio of 1:1 to 1.3, and respectively dissolved with hydrochloric acid; the two solutions are mixed in a reaction vessel, heated under reflux for a period of time; after cooling to room temperature, the obtained precipitate is separated by filtration, washed with water and dried to obtain the final product 2,3-dihydroxy-5,8-dibromo-quinoxaline.

[0015] In the present invention, preferably, the 1,4-dibromo-2,3-diaminobenzene is prepared by the following method: 4,7-dibromobenzo[c]-1.2.5-thiadiazole and sodium borohydride are weighed in a molar ratio of 1:10 to 15, dissolved in anhydrous ethanol, and added to a reaction vessel of a reflux reaction device; then a small amount of cobalt chloride hexahydrate is added to carry out a reflux reaction; after the reflux is completed, the reaction vessel is cooled to room temperature; after the solution is filtered and separated, the filtrate is spin-dried and water is added, and then dichloromethane is added for extraction, and the extract is collected in a conical flask; finally, anhydrous sodium carbonate is added, the upper opening is wrapped with a paper towel, and the mixture is left for about 1 hour. After the solvent is evaporated, 1,4-dibromo-2,3-diaminobenzene is obtained.

[0016] In the present invention, preferably, the amounts of tetrakis(triphenylphosphine)palladium and cuprous iodide used are 1% and 0.4% of the mass of 2,3-dihydroxy-5,8-dibromo-quinoxaline, respectively.

[0017] In the present invention, preferably, the reflux reaction time is 2 to 3 hours.

[0018] The present invention also provides an application of the conjugated microporous polymer, specifically referring to using the conjugated microporous polymer as a fluorescent sensor for Ag in solution. + or MnO4 - Detection.

[0019] In the present invention, preferably, the Ag + or MnO4 - The detection method used is:

[0020] (1) Prepare a CMP mother solution of a certain concentration using DMF as solvent and test its fluorescence intensity I0. + or MnO4 - The solution was added to the conjugated microporous polymer mother solution and mixed, the fluorescence intensity I was tested, and (I0-I) / I0 was calculated; Ag was continued to be added dropwise. + or MnO4 - Solution, test the fluorescence intensity I of the mixed solution, repeat several times, establish (I0-I) / I0 and the Ag content in the solution to be tested + or MnO4 - The linear relationship between the concentration of

[0021] (2) Under the same conditions as step (1), the sample solution to be tested is added to the CMP mother solution, and the fluorescence intensity I of the mixed solution is detected. The linear relationship obtained in step (1) is used to calculate the Ag content in the sample solution to be tested. + or MnO4 - concentration.

[0022] In the present invention, preferably, the fluorescence intensity is tested at 450 nm.

[0023] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0024] 1. The present invention uses 4,7-dibromobenzo[c]-1.2.5-thiadiazole (C6H6Br2N2S) to react with sodium borohydride to obtain intermediate compound 1, and then the intermediate compound 1 is reacted with oxalic acid to obtain intermediate compound 2. The intermediate compound 2 is then coupled with 2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine in the presence of a palladium catalyst to obtain a conjugated microporous polymer CMP. The preparation method of the present invention has the advantages of simple operation, low cost, good synthesis effect and high yield.

[0025] 2. The conjugated microporous polymer CMP product prepared by the present invention is fluffy and is a special amorphous material. + and MnO4 -It has high selectivity and high sensitivity. The fluorescence intensity of CMP at 450nm is similar to that of Ag. + / MnO4 - The concentration is linearly related, y (Ag+) =0.00576x-0.00143, R 2 =0.994;y (MnO4 - )=0.037x-1.65,R 2 =0.996; Ag + The quenching constant K SV =1.5×10 4 , limit of detection (LOD) = 2.5 × 10 -6 mol·L -1 ;MnO4 - Ion quenching constant K SV =5.1×10 3 , limit of detection (LOD) = 7.4 × 10 -6 mol·L -1 The CMP prepared by the present invention is suitable for Ag + or MnO4 - Perform specific testing. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 FT-IR spectrum of the conjugated microporous polymer CMP synthesized in Example 1;

[0027] Figure 2 This is a diagram of the physical shape of the conjugated microporous polymer CMP synthesized in Example 1;

[0028] Figure 3 This is a scanning electron microscope image of the conjugated microporous polymer CMP synthesized in Example 1;

[0029] Figure 4 This is the X-ray diffraction pattern of the conjugated microporous polymer CMP synthesized in Example 1;

[0030] Figure 5 This is the nuclear magnetic resonance spectrum of the intermediate compound 2 synthesized in Example 1;

[0031] Figure 6 This is the nuclear magnetic resonance spectrum of the synthesized conjugated microporous polymer CMP;

[0032] Figure 7 This is a comparison of the fluorescence intensity after adding different metal cations to CMP;

[0033] Figure 8 This is a graph showing the change in fluorescence intensity after adding different concentrations of cations to CMP;

[0034] Figure 9 is a bar graph showing the fluorescence quenching percentage of CMP after the addition of metal cations;

[0035] Figure 10 This is the result of Ag+ anti-interference experiment;

[0036] Figure 11 Adding low concentration of Ag to CMP + The fluorescence change graph afterward;

[0037] Figure 12 This is the fluorescence intensity change diagram of CMP at different pH;

[0038] Figure 13 This is a fluorescence photo of CMP after adding anions;

[0039] Figure 14 Fluorescence intensity changes when different anions are added to CMP;

[0040] Figure 15 Adding MnO4 to CMP - a is the actual change diagram, b is the ultraviolet spectrum diagram.

[0041] Figure 16 is the fluorescence quenching percentage of CMP after adding anions;

[0042] Figure 17 This is the result of CMP's anti-interference experiment for different anions;

[0043] Figure 18 Adding low concentration MnO4 to CMP - The fluorescence change graph afterward;

[0044] Figure 19 Ag + Results of anti-interference experiments (for anions);

[0045] Figure 20 Several typical ions and Ag in CMP + / MnO4 - The relative intensity of fluorescence quenching. DETAILED DESCRIPTION

[0046] Below in conjunction with the embodiment of the present invention, the technical scheme of the present invention is clearly and completely described, it is obvious that the embodiment described is only a part of embodiment of the present invention, rather than all embodiments. Based on the embodiment in the present invention, all other embodiments obtained by those of ordinary skill in the art without paying creative work premise all fall within the scope of protection of the present invention. In the present invention, unless otherwise specified, all raw material components are commercially available commodities well known to those skilled in the art.

[0047] The conjugated microporous polymer with quinoxaline diol as the recognition group is denoted as CMP, and its structure is shown in formula (I):

[0048]

[0049] In an embodiment of the present invention, the preparation method of CMP is as follows: 2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine and 2,3-dihydroxy-5,8-dibromo-quinoxaline are used as monomers and polymerized by coupling reaction to obtain a conjugated microporous polymer represented by formula (I). The preparation route is as follows:

[0050]

[0051] Among them, the synthesis route of intermediate compound 2 (2,3-dihydroxy-5,8-dibromo-quinoxaline) is as follows:

[0052]

[0053] First, 4,7-dibromobenzo[c]-1.2.5-thiadiazole and sodium borohydride are weighed in a molar ratio of 1:10-15, dissolved in anhydrous ethanol, and added to a reaction vessel of a reflux reaction device; then a small amount of cobalt chloride hexahydrate is added to carry out a reflux reaction; after the reflux is completed, the reaction vessel is cooled to room temperature; after the solution is filtered and separated, the filtrate is dried and water is added, and then dichloromethane is added for extraction, and the extract is collected in a conical flask; finally, anhydrous sodium carbonate is added, the upper opening is wrapped with a paper towel, and the mixture is left for about 1 hour. After the solvent is evaporated, the intermediate compound 1 (1,4-dibromo-2,3-diaminobenzene) is obtained.

[0054] Oxalic acid and 1,4-dibromo-2,3-diaminobenzene were weighed in a molar ratio of 1:1 to 1.3 and dissolved separately with hydrochloric acid; the two solutions were mixed in a reaction vessel and heated under reflux for a period of time; after cooling to room temperature, the resulting precipitate was separated by filtration, washed with water, and dried to obtain intermediate compound 2 (2,3-dihydroxy-5,8-dibromo-quinoxaline).

[0055] 1. Preparation Example

[0056] Example 1

[0057] The conjugated microporous polymer using quinoxaline diol as a recognition group comprises the following steps:

[0058] (1) Preparation of intermediate compound 1: 1.0385 g of 4,7-dibromobenzo[c]-1.2.5-thiadiazole and 1.3224 g of sodium borohydride were weighed in a molar ratio of 1:10, dissolved in 60 ml of anhydrous ethanol, and added to the flask of a reflux reaction apparatus; then 0.008 g of cobalt chloride hexahydrate was added, and the mixture was placed in a reflux apparatus for reflux reaction for 3 h; after the reflux was completed, the flask was cooled to room temperature; after the solution was filtered and separated, the filtrate was dried and 100 ml of water was added, and dichloromethane was added in small amounts several times, and the mixture was extracted and collected in a conical flask; finally, anhydrous sodium carbonate was added, the upper opening was wrapped with a paper towel, and the mixture was left for 1 hour. After the solvent was evaporated, intermediate compound 1, i.e., 1,4-dibromo-2,3-diaminobenzene, was obtained with a yield of 3.6811 g and a yield of 81.4%;

[0059] (2) Preparation of intermediate compound 2 (2,3-dihydroxy-5,8-dibromo-quinoxaline): 0.3784 g of oxalic acid and 1.1443 g of intermediate compound 1 were weighed at a molar ratio of 1:1 and dissolved in 10 ml of hydrochloric acid respectively; the two solutions were mixed in a flask and heated under reflux for 2 h; after cooling to room temperature, the resulting precipitate was separated by filtration, washed with water, and dried to obtain intermediate compound 2, i.e., 2,3-dihydroxy-5,8-dibromo-quinoxaline, with a yield of 0.7884 g and a yield of 61.8%;

[0060] (3) Preparation of CMP: 0.5 g of 2,3-dihydroxy-5,8-dibromo-quinoxaline and 0.396 g of raw material M [2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine] were weighed in a molar ratio of 1.5:1 and placed in a three-necked flask. 0.0052 g of tetrakis(triphenylphosphine)palladium and 0.0020 g of cuprous iodide were added to the three-necked flask and degassed with nitrogen for 20 min. 6 mL of toluene was injected into the three-necked flask and the stirring was started. The nitrogen degassed process was continued for 10 min. 6 mL of triethylamine was injected into the three-necked flask and the stirring was continued for 10 min. Degas with nitrogen. After degassing, raise the reaction temperature to 80°C and continue the reaction for 48 hours under a nitrogen atmosphere, shielded from light, and covered. After the reaction, cool the three-necked flask to room temperature and sequentially wash with dichloromethane, acetone, distilled water, and methanol. Perform Soxhlet extraction with methanol for 72 hours. Place the product in a vacuum drying oven at 50°C and dry for 24 hours. The yield of the product, CMP, is 0.6598 g, with a yield of 73.3%.

[0061] Example 2

[0062] The conjugated microporous polymer using quinoxaline diol as a recognition group comprises the following steps:

[0063] (1) Preparation of intermediate compound 1: 1.0385 g of 4,7-dibromobenzo[c]-1.2.5-thiadiazole and 1.5868 g of sodium borohydride were weighed in a molar ratio of 1:12, dissolved in 60 ml of anhydrous ethanol, and added to a flask of a reflux reaction apparatus; then 0.008 g of cobalt chloride hexahydrate was added, and the mixture was placed in a reflux apparatus for reflux reaction for 3 h; after the reflux was completed, the flask was cooled to room temperature; after the solution was filtered and separated, the filtrate was dried and 100 ml of water was added, and dichloromethane was added in small amounts several times, and the mixture was extracted and collected in a conical flask; finally, anhydrous sodium carbonate was added, the upper opening was wrapped with a paper towel, and the mixture was left for 1 hour. After the solvent was evaporated, intermediate compound 1, i.e., 1,4-dibromo-2,3-diaminobenzene, was obtained with a yield of 3.6811 g and a yield of 81.4%;

[0064] (2) Preparation of intermediate compound 2 (2,3-dihydroxy-5,8-dibromo-quinoxaline): 0.3784 g of oxalic acid and 1.3732 g of intermediate compound 1 were weighed at a molar ratio of 1:1.2, and each was dissolved in 10 ml of hydrochloric acid; the two solutions were mixed in a flask and heated under reflux for 2 h; after cooling to room temperature, the resulting precipitate was separated by filtration, washed with water, and dried to obtain intermediate compound 2, i.e., 2,3-dihydroxy-5,8-dibromo-quinoxaline;

[0065] (3) Preparation of CMP: 0.4 g of 2,3-dihydroxy-5,8-dibromo-quinoxaline and 0.396 g of raw material M [2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine] were weighed in a molar ratio of 1.2:1 and placed in a three-necked flask. 0.0041 g of tetrakis(triphenylphosphine)palladium and 0.0016 g of cuprous iodide were added to the three-necked flask and degassed with nitrogen for 20 min. 6 mL of toluene was injected into the three-necked flask and the stirring was started. The nitrogen degassed process was continued for 10 min. 6 mL of triethylamine was injected into the three-necked flask and the stirring was continued for 10 min. Degas with nitrogen. After degassing, raise the reaction temperature to 78°C and, while maintaining a nitrogen atmosphere and shielding from light, continue the reaction for 55 hours. After the reaction, cool the three-necked flask to room temperature and sequentially wash with dichloromethane, acetone, distilled water, and methanol. Perform Soxhlet extraction with methanol for 72 hours. Place the product in a vacuum drying oven at 50°C and dry it for 24 hours to obtain the CMP product.

[0066] Example 3

[0067] The conjugated microporous polymer using quinoxaline diol as a recognition group comprises the following steps:

[0068] (1) Preparation of intermediate compound 1: 1.0385 g of 4,7-dibromobenzo[c]-1.2.5-thiadiazole and 1.9836 g of sodium borohydride were weighed in a molar ratio of 1:15, dissolved in 60 ml of anhydrous ethanol, and added to the flask of a reflux reaction apparatus; then 0.008 g of cobalt chloride hexahydrate was added, and the mixture was placed in a reflux apparatus for reflux reaction for 3 h; after the reflux was completed, the flask was cooled to room temperature; after the solution was filtered and separated, the filtrate was dried and 100 ml of water was added, and dichloromethane was added in small amounts several times, and the mixture was extracted and collected in a conical flask; finally, anhydrous sodium carbonate was added, the upper opening was wrapped with a paper towel, and the mixture was left for 1 hour. After evaporation of the solvent, intermediate compound 1, i.e., 1,4-dibromo-2,3-diaminobenzene, was obtained with a yield of 3.6811 g and a yield of 81.4%;

[0069] (2) Preparation of intermediate compound 2 (2,3-dihydroxy-5,8-dibromo-quinoxaline): 0.3784 g of oxalic acid and 1.1443 g of intermediate compound 1 were weighed at a molar ratio of 1:1.3 and dissolved in 10 ml of hydrochloric acid respectively; the two solutions were mixed in a flask and heated under reflux for 2 h; after cooling to room temperature, the resulting precipitate was separated by filtration, washed with water, and dried to obtain intermediate compound 2, i.e., 2,3-dihydroxy-5,8-dibromo-quinoxaline, with a yield of 0.7884 g and a yield of 61.8%;

[0070] (3) Preparation of CMP: 0.32 g of 2,3-dihydroxy-5,8-dibromo-quinoxaline and 0.396 g of raw material M [2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine] were weighed in a molar ratio of 1:1 and placed in a three-necked flask. 0.0032 g of tetrakis(triphenylphosphine)palladium and 0.0013 g of cuprous iodide were added to the three-necked flask and degassed with nitrogen for 20 min. 6 mL of toluene was injected into the three-necked flask and the instrument was stirred for 10 min. 6 mL of triethylamine was injected into the three-necked flask and degassed with nitrogen for 10 min. Degas with nitrogen. After degassing, raise the reaction temperature to 82°C and continue the reaction for 40 hours under nitrogen protection, using a cover to protect from light. After the reaction, cool the three-necked flask to room temperature and wash with dichloromethane, acetone, distilled water, and methanol in sequence. Perform Soxhlet extraction with methanol for 72 hours. Place the product in a vacuum drying oven at 50°C and continue drying the product CMP for 24 hours.

[0071] Example 4

[0072] The conjugated microporous polymer is used as a fluorescent sensor for Ag in solution. + The detection method used is:

[0073] (1) Prepare 0.01 mg mL using DMF as solvent -1The fluorescence intensity I0 of CMP mother solution was tested at 450nm. + The solution was added to the conjugated microporous polymer mother solution and mixed. The fluorescence intensity I was measured at 450 nm and (I0-I) / I0 was calculated. Ag was added dropwise. + Solution, test the fluorescence intensity I of the mixed solution, repeat several times, establish (I0-I) / I0 and the Ag content in the solution to be tested + or MnO4 - The linear relationship between the concentration of

[0074] (2) Under the same conditions as step (1), the sample solution to be tested is added to the CMP mother solution, and the fluorescence intensity I of the mixed solution is detected. The linear relationship obtained in step (1) is used to calculate the Ag content in the sample solution to be tested. + concentration.

[0075] Example 5

[0076] The conjugated microporous polymer is used as a fluorescent sensor for MnO4 in solution. - The detection method used is:

[0077] (1) Take a certain concentration of conjugated microporous polymer mother solution and test its fluorescence intensity I0 at 450nm. - The solution was added to the conjugated microporous polymer mother liquor and mixed, the fluorescence intensity I was measured at 450nm, and (I0-I) / I0 was calculated; MnO4 was added dropwise. - The fluorescence intensity I of the mixed solution was tested at 450nm, and the fluorescence intensity was repeatedly determined to establish the relationship between (I0-I) / I0 and the MnO4 - The linear relationship between the concentration of

[0078] (2) Under the same conditions as step (1), the sample solution to be tested is added to the CMP mother solution, and the fluorescence intensity I of the mixed solution is detected. The linear relationship obtained in step (1) is used to calculate the MnO4 content in the sample solution to be tested. - concentration.

[0079] 2. Characterization of Materials

[0080] 1. Fourier transform infrared spectroscopy (FTIR) analysis

[0081] Figure 1 The FTIR spectrum of the prepared conjugated microporous polymer CMP is shown in the figure. -1The characteristic absorption peak at 1352cm is attributed to the vibration absorption peak of the benzene ring skeleton in the intermediate compound 2. The characteristic absorption peak in the structure of the raw material M is not obvious. It may be due to the influence of the noise signal in the environment, which leads to the fact that this group of characteristic peaks at 1352cm is not obvious in the CMP structure. -1 The characteristic absorption peak of disappeared, proving that -C-Br- in intermediate compound 2 disappeared. Intermediate compound 2 combined with raw material M to successfully prepare conjugated microporous polymer CMP.

[0082] 2. Physical shape and scanning electron microscopy (SEM) analysis

[0083] Figure 2 Figure 1 is a diagram of the physical shape of the polymer. It can be observed that the polymer CMP is a reddish-brown powder. Figure 3 This is a scanning electron microscope image of CMP. It can be seen that CMP has a good fluffy feeling, indicating that the pore size is large.

[0084] 3. X-ray diffraction (XRD) analysis

[0085] Figure 4 The XRD pattern of CMP shows distinct and sharp diffraction peaks at 2θ = 14.2° and 26.7°, and several diffraction peaks of varying sizes appear near 2θ = 21.3°. Combined with the scanning electron microscopy image, the polymer is fluffy and irregularly arranged, indicating that CMP is a special amorphous material.

[0086] 4. Solid-state NMR characterization

[0087] The polymers were characterized at the molecular level using solid-state nuclear magnetic resonance spectroscopy. The solid-state nuclear magnetic resonance spectra of intermediate compound 2 and CMP are shown in Figure 5 and Figure 6 .from Figure 5 It can be seen that the chemical shift of hydrogen on carbon 5 and carbon 6 on the benzene ring is at 7.67ppm. Figure 6 As can be seen, the C=N (number 1) on the triazine and quinoxaline rings is assigned to 183.7 ppm, the CN (number 2) on the quinoxaline ring is assigned to 145.3 ppm, the Cs 3, 4, and 5 on the benzene ring have chemical shifts of 133.4, 130.3, and 125.6 ppm, respectively, and the alkynyl (number 6, -C≡C-) has a chemical shift of 77.1 ppm. These data indicate that the porous polymer was successfully prepared.

[0088] 2. Performance Testing

[0089] 1. Preparation of relevant solutions:

[0090] 0.01 mg mL -1 Preparation of CMP mother solution

[0091] Accurately weigh 0.001 g of the CMP powder prepared in Example 1 using an electronic balance, place it in a beaker, and add N,N-dimethylformamide (DMF) as a solvent to dissolve it. Stirring and ultrasonic treatment can be performed during dissolution. Then transfer it to a volumetric flask, adjust the volume, and label it with the solution name, concentration, and preparation date. The resulting solution is used as a mother liquor for later use.

[0092] 10 -3 mol·L -1 Preparation of cationic solution

[0093] Calculate the mass of the required compound solute, accurately weigh it using an electronic balance, place the compound in a beaker, and add ultrapure water (H2O) as a solvent to dissolve it. If you encounter insoluble substances, you can perform ultrasonic treatment. Then transfer it to a volumetric flask, make up the volume, and label it, indicating the solution name, concentration, and preparation date. The resulting solution is the various ion solutions used subsequently.

[0094] 2. Selective sensitivity experiment of cations

[0095] Preparation of cationic solution: Use an analytical balance to accurately weigh a certain amount of metal ion-containing compounds and dissolve them in ultrapure water (H2O) to form multiple 10 -3 mol·L -1 The cation solution is ready for use. The compounds used are: Cd(NO2)2·4H2O, Ni(NO3)2·6H2O, FeCl3·6H2O, MnSO4·H2O, CoCl2·6H2O, BaCO3, Cr(NO3)3·9H2O, CuSO4·5H2O, MgCl2·6H2O, AgSO4, FeSO4·7H2O, CaCl2·4H2O, AlCl3·6H2O, Pb(NO3)2.

[0096] Add 2 mL of 0.01 mg mL into the centrifuge tube. -1 CMP mother solution, then add 20μL of each metal cation solution, observe the changes in fluorescence intensity in each centrifuge tube under the irradiation of a portable UV analyzer (365nm), and take photos for comparison. Figure 7 As shown in the figure, by comparing with the blank group without any cations added, it was found that most metal cations had almost no effect on the fluorescence intensity of CMP, a small number of metal cations could enhance the fluorescence intensity of CMP, and Ag + The addition of can almost quench the fluorescence of CMP. By comparing the pictures, such obvious quenching phenomenon can be concluded that CMP has a strong effect on Ag. + selection sensitivity.

[0097] 2. Chemical sensing of metal cations by CMP

[0098] Still use the above-prepared CMP mother solution with a mass concentration of 10 -2 mg·mL -1 ; Prepared to contain (K + 、Na + 、Ba 2+ Mg 2+ , Ca 2+ 、Ag + 、Cu 2+ 、Fe 2+ 、Mn 2+ 、Ni 2+ 、Co 2+ Cr 3+ 、Zn 2+ 、Cd 2+ 、Fe 3+ ) cation solution, the concentration is 10 -3 mol·L -1 The fluorescence intensity was detected using a fluorescence spectrophotometer.

[0099] Ag, where quenching is most obvious + For example, add 3 mL of mother solution to the cuvette, use a fluorescence photometer to measure the fluorescence intensity as I0, then gradually add silver ion solution, shake it to mix it thoroughly, and then measure its fluorescence intensity as I. Repeat this operation until the fluorescence intensity of CMP no longer changes or changes very slightly.

[0100] Based on the above experiments, the content of the solution to which each metal cation is added can be set to 0, 20, 40, 60, 80, and 100 μL. In order to eliminate the interference of H2O, we also conducted the above experiment. The results are as follows Figure 8 As shown in the comparison chart, we can see that H2O can increase the fluorescence intensity of CMP, but the range is not large; with the increase of the concentration of many cations, the fluorescence intensity of CMP has no obvious change; in the above experiment, we observed the Ag + The conclusion that it has a significant quenching effect on CMP is also established.

[0101] From this we can conclude that CMP materials are + There is no specific selection function, and it has no substantial effect on the research of CMP sensing performance. + As the concentration increases, the fluorescence intensity of the CMP gradually decreases until all the fluorescence phenomena almost disappear completely. This is the effect of CMP on Ag. + The result of specific selection.

[0102] 3. Calculation of the quenching percentage of CMP after adding metal cations

[0103] The quenching percentage refers to an indicator that can intuitively compare the quenching effects of different metal cations on the polymer material at the same concentration, and can more accurately express the specific expression ability of the polymer material for metal cations.

[0104] The formula for fluorescence quenching percentage is:

[0105] Quenching percentage (%) = (I0-I) / I0×100%

[0106] I0 refers to the fluorescence intensity of the polymer stock solution without the addition of analytes, and I refers to the fluorescence intensity after the addition of different analytes.

[0107] The comparison of the quenching percentage of CMP after adding metal cations is shown in the figure below. Figure 9 As shown, add 10 -3 mol·L -1 Cation (100 μL), Ag + The quenching of CMP can reach 100%, which fully proves that the polymer material can effectively inhibit the quenching of silver ions (Ag + ) specific selection. At the same ion concentration, it is followed by copper ions (Cu 2+ )13%, ferrous ion (Fe 2+ )12%, manganese ion (Mn 2+ )12%, and there are also some ions that can enhance the fluorescence intensity of polymer materials, such as calcium ions (Ca 2+ ), magnesium ions (Mg 2+ ), iron ions (Fe 3+ ), H2O. The remaining other ions have little quenching effect on the polymer material.

[0108] 4. Competition experiments with metal cations

[0109] In previous experiments, we have clearly known that polymer materials have a strong effect on Ag + To better understand the degree of specific selection, we set up a competition experiment.

[0110] The experimental steps are as follows: take the mass concentration of 10 -2 mg·mL -1 3mL of CMP mother solution was placed in a cuvette and a concentration of 10 -3 mol·L -1 100 μL of metal cation solution was added and its fluorescence intensity was measured by fluorescence photometer. The fluorescence intensity at this time was the effect of a single metal cation on the CMP. Finally, Ag with the same concentration and content was added. +, and detect the fluorescence intensity again. We can draw a comparison chart based on the changes in fluorescence intensity twice, and see more intuitively the effect of polymer materials on Ag under complex conditions. + The anti-interference ability of the detection is strong. Figure 10 , we can see that among many metal cations, polymer materials have the best + single selectivity.

[0111] 5. CMP for Ag + Sensitivity testing

[0112] We all know that when determining whether a polymer can be used as a fluorescent sensor material, one important factor to consider is sensitivity. In the following experiment, we will use the limit of detection (LOD) to express the sensitivity of the polymer material to the analyte.

[0113] Quenching constant (K SV ) formula is:

[0114] I0 / II=K SV ·[Q], formula (1)

[0115] [Q] refers to the concentration of the polymer suspension, K SV is the quenching constant.

[0116] The formula for the detection limit is:

[0117] LOD=3δ / K SV , formula (2)

[0118] δ is the calculated standard deviation obtained from 10 measurements of the fluorescence of the polymer stock solution.

[0119] S=Sqrt[(∑(Xi-X) 2 ) / (N-1)], formula (3)

[0120] Xi represents the sample data, X represents the mean of the sample data, and N represents the number of sample data.

[0121] Take the mass concentration as 10 -2 mg·mL -1 CMP mother solution, test its fluorescence intensity I0 at 450nm, and Ag + The solution was added to the CMP mother solution and mixed, and the fluorescence intensity I at 450 nm was measured and calculated to obtain (I0-I) / I0; Ag was added dropwise. + The fluorescence intensity I of the mixed solution at 450nm was tested repeatedly to establish the relationship between (I0-I) / I0 and the Ag content in the solution to be tested. + The results are shown in Figure 11 .

[0122] From the above Figure 11 a It can be seen that CMP has a great influence on Ag + It has very good sensitivity and provides a very good entry point for the future exploration and application of polymer materials. Figure 11 b It can be seen that the addition of Ag + The fluorescence intensity changes after Ag + The concentration showed an excellent linear relationship (R 2 =0.994). The linear equation is y (Ag+) =0.00576x-0.00143, R 2 =0.994, Ag + The quenching constant K SV =1.5×10 4 , the detection limit is (LOD) = 2.5 × 10 -6 mol·L -1 .

[0123] 6. Effect of pH value

[0124] In order to explore the tolerance of the polymer and to investigate whether the fluorescence intensity of the polymer changes under different pH environments, we conducted the following experiment: Buffer solutions with pH values ​​of 2, 4, 6, 8, and 10 were prepared by mixing hydrochloric acid and potassium hydroxide. 3 mL of each solution was accurately measured using a pipette and placed in a cuvette to create different pH environments. Finally, 500 μL of CMP mother solution was added and the solution was placed in a fluorescence photometer to measure the fluorescence intensity. The results are shown in Figure 2. Figure 12 As shown, in an acidic environment, the peak value of the curve gradually decreases, reaching its highest value at pH 6. In an alkaline environment, however, the curve changes little; in fact, the fluorescence intensity is weakest at pH 7. This is because the addition of H2O to create a pH 7 environment dilutes the concentration of the mother solution to a certain extent.

[0125] 7. Anion selective sensitivity test

[0126] The experimental steps are basically the same as those of metal cations. We selected (B4O7 2- WO4 2- 、S 2- 、Cr2O7 2- 、S2O3 2- 、MnO4 - 、F - Br - 、NO2 - 、HSO4 - 、CO3 2- 、HCO3 - 、Cl - 、SO42- ) ion solution was preliminarily tested and the results were photographed as shown in Figure 13 As shown. Through visual observation, it was found that when MO4 - , the fluorescence intensity becomes weaker. To explore this issue in more depth, we next use a fluorescence photometer to detect changes in fluorescence intensity.

[0127] 8. Chemical sensing of anions by CMP

[0128] The operation is similar to that of cations, and the results are as follows Figure 14 As shown in the histogram, it can be clearly seen that with the continuous increase of anion concentration, most anions have a very small effect on CMP, and the degree of change in fluorescence intensity is very small; while it is observed that MnO4 - , which makes the fluorescence intensity of CMP change significantly. When the added concentration reaches 33μM, the fluorescence intensity suddenly decreases. This experiment can be used to test the selective detection of MnO4 by fluorescent probes. - possibility.

[0129] But MnO4 - , it appears purple-red in the solution. In order to prove whether this color has an effect on the CMP fluorescence phenomenon, we conducted a demonstration. First, 3 mL of CMP mother solution was added to the cuvette, and then potassium permanganate solution was added. The results are shown in Figure 2. Figure 15 a, with the MnO4 - As the concentration increases, the color of the solution in the cuvette becomes darker. Figure 15 b is the corresponding UV spectrum, an elliptical peak appears in the 300-400nm range, as MnO4 - With the increase of concentration, a blue shift occurs and the absorption intensity becomes weaker and weaker until the peak disappears. From this, it can be inferred that MnO4 - The color itself has no effect on the CMP fluorescence intensity.

[0130] 9. Anion quenching percentage

[0131] like Figure 16 As shown in Figure 2, when 700 μL of anion solution was added, the quenching percentage of CMP by most anions was around 25%, and the one that had the greatest impact on the fluorescence intensity was MnO4 - 87.7%, followed by Cr2O7 2- 49.9%, followed by NO3 - 35%. Through experimental research, it was confirmed that the CMP can efficiently detect MnO4 - .

[0132] 10. Anion competition experiment

[0133] Even if CMP has a great influence on MnO4 - It has good selectivity and sensitivity, but if it is really used in practice in the future, there are many uncontrollable factors. For this reason, we need to conduct anion anti-interference tests on CMP. -2 mg·mL -1 3mL of CMP mother solution was placed in a cuvette and a concentration of 10 -3 mol·L -1 100 μL of anion solution was added and its fluorescence intensity was measured by fluorescence photometer. The fluorescence intensity at this time was the effect of a single anion on the CMP. Finally, MnO4 with the same concentration and content was added. - , and detect the fluorescence intensity again. We can draw a comparison chart based on the changes in fluorescence intensity twice, and see more intuitively the effect of polymer materials on MnO4 under complex conditions. - The anti-interference ability of the detection is strong. Figure 17 As shown, many anions also showed an effect on CMP at the beginning, but in the second step, it was found that when MnO4 - The addition of MnO4 increases the intensity of quenching, and almost drops to about 20% of the original fluorescence intensity. This experiment shows that the sudden decrease in CMP fluorescence intensity is mainly due to the addition of MnO4 - and is not affected by other anions.

[0134] 11. CMP to MnO4 - Sensitivity test

[0135] Similar to Ag + For the test, we used low concentration of MnO4 - ions, a dropwise addition experiment was conducted on the CMP mother solution, and the fluorescence intensity was detected by a fluorescence photometer to describe the effect of the polymer material on MnO4 - The detection sensitivity of Figure 18 a shows that as MO4 - With the increase of concentration, the fluorescence intensity of the polymer material became weaker and weaker until 650 μL MnO4 was added. - , the fluorescence intensity change is almost the same, we can think that it has reached the maximum limit. Figure 18 b It can be seen that with the increase of MO4 - There is a good linear relationship between the increase of concentration and the decrease of CMP fluorescence intensity (R 2 =0.996), y (MnO4 -)=0.037x-1.65,R 2 =0.996; MnO4 - Ion quenching constant K SV =5.1×103 , limit of detection (LOD) = 7.4 × 10 -6 mol·L -1 . This shows that the polymer material has a great influence on the MnO4 - Good sensitivity.

[0136] 12. Ag + Anti-interference experiment (for anions)

[0137] Through the above experiments, we have learned that Ag + The fluorescence intensity of the polymer material can be reduced, while Ag + It can also combine with some anions to form precipitation, so in the next experiment, we will explore, in the first Ag + Under the premise of existence, adding different anions separately will have no effect on the polymer material.

[0138] The concentration of the mother solution used is still 10 -2 mg·mL -1 , Ag + The concentration is 10 -3 mol·L -1 , anion concentration is 0.1 mol·L -1 .

[0139] Add 3mL of mother solution to the cuvette and measure its initial fluorescence intensity; then add Ag + 100μL of solution was added and the fluorescence intensity at this time was measured; finally, 300μL of anion solution was added and the final fluorescence intensity was measured. By comparing the fluorescence intensities at different stages, it was concluded that Figure 19 .

[0140] pass Figure 19 , we found that adding Ag + When the fluorescence intensity decreases, the addition of other anions will increase the already decreased fluorescence intensity. 2- Br - 、Cl - ), can recover to about 40% of the initial strength; and MnO4 - Can be in Ag + On the premise of quenching the polymer material, the material tends to be completely quenched, reflecting the dual quenching ability of these two ions.

[0141] 13. Relative intensity of fluorescence quenching

[0142] Calculate and compare the quenching constants of polymer CMP for different cations. The results are shown in Figure 20 As shown in a, polymer CMP has an effect on Ag +The quenching constant of Ag can be as low as 1000 times that of other ions and as high as 3500 times. Such clear data comparison can further highlight the effect of polymer CMP on Ag. + The sensitivity of the polymer material to Ag is much higher than that of other ions, which further illustrates the sensitivity of the polymer material to Ag. + The excellent selectivity of the material has laid a good experimental data foundation for further exploration of the material.

[0143] Calculate and compare the quenching constants of polymer CMP for different cations. The results are shown in Figure 20 As shown in b, CMP has an effect on MnO4 - The quenching constant can be as low as 50 times that of other ions and as high as 120 times, which is lower than the above Ag + data, but it still shows the effect of polymer materials on MnO4 - Excellent selectivity.

[0144] The above description is a detailed description of the preferred embodiments of the present invention, but the embodiments are not intended to limit the scope of the patent application of the present invention. Any equivalent changes or modifications completed under the technical spirit suggested by the present invention should fall within the patent scope covered by the present invention.

Claims

1. A conjugated microporous polymer with quinoxaline diol as a recognition group, characterized in that: The conjugated microporous polymer is denoted as CMP, and its structure is shown in formula (I): （Ⅰ）。 2. The method for preparing a conjugated microporous polymer with quinoxaline diol as a recognition group according to claim 1, characterized in that: A conjugated microporous polymer represented by formula (I) is obtained by polymerization through coupling reaction using 2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine and 2,3-dihydroxy-5,8-dibromo-quinoxaline as monomers.

3. The preparation method according to claim 2, wherein: The specific steps of the coupling reaction are as follows: 2,3-dihydroxy-5,8-dibromo-quinoxaline and 2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine are weighed in a molar ratio of 1-1.5:1 and placed in a reaction vessel. Catalysts tetrakis(triphenylphosphine)palladium and cuprous iodide are added to the reaction vessel, and the reaction vessel is degassed with nitrogen. Toluene is injected into the reaction vessel while stirring the instrument to degas the reaction vessel. Triethylamine is then injected into the reaction vessel to degas the reaction vessel. After the nitrogen degassing is completed, the reaction temperature is raised to 78-82° C., and while maintaining nitrogen protection, a cover is used to avoid light and the reaction is continued for 40-55 hours. After the reaction is completed, the reaction vessel is cooled to room temperature, washed, and then subjected to Soxhlet extraction with methanol. The product is dried to obtain the conjugated microporous polymer.

4. The preparation method according to claim 2, wherein: The 2,3-dihydroxy-5,8-dibromo-quinoxaline is prepared by the following method: oxalic acid and 1,4-dibromo-2,3-diaminobenzene are weighed in a molar ratio of 1:1 to 1.3, and each is dissolved in hydrochloric acid; the two solutions are mixed in a reaction vessel, heated under reflux for a period of time; after cooling to room temperature, the resulting precipitate is separated by filtration, washed with water, and dried to obtain 2,3-dihydroxy-5,8-dibromo-quinoxaline.

5. The preparation method according to claim 4, characterized in that: The 1,4-dibromo-2,3-diaminobenzene is prepared by the following method: 4,7-dibromobenzo[c]-1,2,5-thiadiazole and sodium borohydride are weighed in a molar ratio of 1:10-15, dissolved in anhydrous ethanol, and added to a reaction vessel of a reflux reaction device; then a small amount of cobalt chloride hexahydrate is added to carry out a reflux reaction; after the reflux is completed, the reaction vessel is cooled to room temperature; after the solution is filtered and separated, the filtrate is dried, water is added, and dichloromethane is added for extraction, and the extract is collected in a conical flask; finally, anhydrous sodium carbonate is added, the upper opening is wrapped with a paper towel, and the mixture is left for 1 hour. After the solvent is evaporated, 1,4-dibromo-2,3-diaminobenzene is obtained.

6. The preparation method according to claim 3, wherein: The amounts of tetrakis(triphenylphosphine)palladium and cuprous iodide used are 1% and 0.4% of the mass of 2,3-dihydroxy-5,8-dibromo-quinoxaline, respectively.

7. The preparation method according to claim 5, characterized in that: The reflux reaction time is 2 to 3 hours.

8. The use of the conjugated microporous polymer according to claim 1, characterized in that: The conjugated microporous polymer was used as a fluorescent sensor for Ag in solution. + or MnO4 - Detection.

9. The use according to claim 8, characterized in that The Ag + or MnO4 - The detection method used is: (1) Prepare a certain concentration of CMP mother solution using DMF as solvent, test its fluorescence intensity I0, and + or MnO4 - The solution was added to the CMP mother solution and mixed, the fluorescence intensity I was tested, and (I0-I) / I0 was calculated; Ag was continued to be added dropwise. + or MnO4 - Solution, test the fluorescence intensity I of the mixed solution, repeat several times, establish (I0-I) / I0 and the Ag content in the solution to be tested + or MnO4 - The linear relationship between the concentration of (2) Under the same conditions as step (1), add the sample solution to be tested to the CMP mother solution, detect the fluorescence intensity I of the mixed solution, and use the linear relationship obtained in step (1) to calculate the Ag content in the sample solution to be tested. + or MnO4 - concentration.

10. The use according to claim 9, characterized in that: The fluorescence intensity was measured at 450 nm.

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