Ratio-type rare earth functionalized covalent organic framework fluorescent probe as well as preparation method and application thereof

Abstract

The invention relates to a ratio type rare earth functionalized covalent organic framework fluorescent probe as well as a preparation method and application thereof. The fluorescent probe comprises a covalent organic framework and rare earth ions, the covalent organic framework comprises a first connector and a second connector; the first connector is 3, 3 ''-dihydroxy-[1, 1 ': 4', 1''-terphenyl]-4, 4 ''-dialdehyde, and the second connector is 3, 3''-dihydroxy-[1, 1 ': 4', 1 ''-terphenyl]-4, 4''-dialdehyde; the rare earth ions are scandium ions. The prepared fluorescent probe can detect enrofloxacin, norfloxacin and pefloxacin in the environment, and compared with other fluorescent probes, the fluorescent probe has higher resistance to changes of external environmental factors, and the recognition result is more accurate and reliable; and the preparation method is simple, high in product yield and suitable for batch production and application.

Description

Technical Field

[0001] The invention relates to the technical field of environmental detection, and in particular to a ratiometric rare earth functionalized covalent organic framework fluorescent probe and a preparation method and application thereof. Background Art

[0002] Since their discovery, antibiotics have played a vital role in human production and life. In terms of disease prevention and treatment, as well as in animal husbandry and aquaculture, the use of antibiotics has greatly reduced the incidence of disease and mortality. However, the antibiotics used in the treatment process are not fully absorbed and utilized by humans and animals. In addition, the overuse of antibiotics has caused these substances to appear frequently in the environment and in organisms, which has led to a series of environmental and health problems. For example, the emergence of drug-resistant genes has reduced the effectiveness of antibiotic treatment, and the residues of antibiotics in water and soil have changed the biochemical characteristics, thereby affecting the structure of biological populations.

[0003] Commonly used antibiotics include quinolones, macrolides, sulfonamides and tetracyclines. Among them, quinolones have received special attention due to their wide variety and wide use. Enrofloxacin, norfloxacin and pefloxacin, as third-generation quinolone antibacterial drugs, are widely used in the prevention and treatment of bacterial diseases in livestock, poultry and aquatic animals. However, due to their low metabolism and absorption rates in animals, antibiotics are easily left in the environment, causing serious environmental pollution and ecological damage. Therefore, in the face of this potential ecological and health risk, effective pollution control measures are urgently needed, and early detection of antibiotics provides the necessary basis and direction for related governance. In this context, the efficient identification of enrofloxacin, norfloxacin and pefloxacin is particularly important, especially the use of sensitive, convenient, economical and suitable for on-site detection technology, which has important practical significance.

[0004] At present, a variety of detection technologies have been widely used in antibiotic detection, such as high performance liquid chromatography-electrospray ionization tandem mass spectrometry (HPLC-ESI-MS / MS), capillary electrophoresis, micellar liquid chromatography and surface acoustic wave sensing. However, these methods usually require complex sample pretreatment and rely on expensive instruments and equipment. Therefore, the development of low-cost and easy-to-operate on-site monitoring technologies has become the current research focus. Among the many detection technologies, the fluorescent probe method has gradually stood out with its advantages of portability, sensitivity and high specificity, becoming an ideal choice for antibiotic detection.

[0005] CN112816448A discloses a fluorescence detection method for rapid detection of tetracycline in food, by preparing carbon quantum dots and thioglycolic acid modified cadmium telluride quantum dots (CQDs / TGA-CdTe QDs) solution as a ratio fluorescence probe. The invention uses monohydrated citric acid as a carbon source and reduced glutathione as a nitrogen / sulfur source. First, CQDs and red luminescent TGA-CdTe QDs are synthesized by a hydrothermal method, and then CQDs and TGA-CdTe QDs are mixed together in a certain proportion to prepare a CQDs / TGA-CdTe QDs ratio fluorescence probe. The probe can greatly eliminate the interference of the external environment with the help of its own dual fluorescence self-reference effect, and achieve more accurate quantitative detection, but the use of heavy metal cadmium will undoubtedly also cause pollution to the environment, and improper use may even affect one's own health.

[0006] CN118956390A discloses a fluorescent probe for detecting gatifloxacin and its application in food. A new type of biomatrix-derived carbon quantum dots was prepared using bear bile powder as a precursor, and a highly selective fluorescence sensing platform was constructed, which was successfully used to detect gatifloxacin in milk and honey. The color of the system changes from blue fluorescence to green fluorescence under ultraviolet light. By establishing the linearity between the fluorescence signal intensity and the gatifloxacin concentration, sensitive detection of gatifloxacin is achieved, and the detection limit can be as low as 3μg / L. However, the raw materials for the preparation are limited in source and expensive, and more importantly, the color change is not obvious, and the naked eye identification of the solution produces a large error.

[0007] CN118063787A discloses a metal organic framework fluorescent probe for specific detection of tetracycline antibiotics and its preparation method, which can realize the qualitative and quantitative detection of tetracycline, and has the advantages of rapid, simple, good selectivity, high sensitivity, etc., for the identification and detection of three different antibiotics, and the preparation method of the material is simple, high purity, and good activity. However, the material is a single quenching type detection of the identification object, which is very susceptible to interference from external substances and causes measurement errors.

[0008] Therefore, it is of great significance to develop more fluorescent probe strategies for detecting antibiotics, especially those for quinolone antibiotics. Summary of the invention

[0009] In order to solve the above technical problems, the present invention provides a ratiometric rare earth functionalized covalent organic framework fluorescent probe and its preparation method and application. The present invention protects rare earth ions and weakens the influence of other interferences by coordinating scandium ions with covalent organic frameworks, and has more sensitive and portable detection of enrofloxacin, norfloxacin and pefloxacin in water.

[0010] To achieve this object, the present invention adopts the following technical solutions:

[0011] In a first aspect, the present invention provides a ratiometric rare earth functionalized covalent organic framework fluorescent probe, the fluorescent probe comprising a covalent organic framework and a rare earth ion; the covalent organic framework comprising a first linker and a second linker;

[0012] The first linker is 3,3"-dihydroxy-[1,1':4',1"-terphenyl]-4,4"-dialdehyde; and the rare earth ion is a scandium ion.

[0013] The covalent organic framework in the present invention has highly adjustable pore structure and surface characteristics, good stability, high specific surface area and accessible porosity, multifunctionality and adjustability, and strong fluorescence emission, and can play a role of fluorescence reference in the detection process; at the same time, rare earth ions such as scandium ions can sensitize and enhance the fluorescence of organic molecules. Therefore, the present invention provides protection for rare earth ions through the coordination of the covalent organic framework and the scandium ions, and also plays a certain pore blocking role, which reduces the influence of other interferents, so that the fluorescent probe has higher sensitivity and selectivity in fluorescence sensing.

[0014] As a preferred technical solution of the present invention, the second linker includes any one of 1,3,5-tri(4-aminophenyl)benzene, 1,3,5-tri(4-formylphenyl)benzene, 1,3,5-trihydroxybenzene or 1,3,5-triaminobenzene.

[0015] In a second aspect, the present invention provides a method for preparing the fluorescent probe as described in the first aspect, the preparation method comprising:

[0016] (1) 1,4-phenylenediboronic acid and 4-bromo-2-hydroxybenzaldehyde are mixed, and then an alkali solution and a first catalyst are added to react, and after the reaction, the pH is adjusted for solid-liquid separation to obtain a first linker;

[0017] (2) mixing the second linker with the first linker and adding a second catalyst to react, and performing solid-liquid separation after the reaction to obtain a covalent organic framework precursor;

[0018] (3) The covalent organic framework precursor is mixed with a scandium salt and subjected to a coordination reaction, and solid-liquid separation is performed after the reaction to obtain the ratiometric rare earth functionalized covalent organic framework fluorescent probe.

[0019] The preparation technology route of the fluorescent probe in the present invention is: 1,4-phenylenediboronic acid and 4-bromo-2-hydroxybenzaldehyde are subjected to Suzuki coupling reaction to obtain a first linker 3,3"-dihydroxy-[1,1':4',1"-terphenyl]-4,4"-dialdehyde. Subsequently, 1,3,5-tri(4-aminophenyl)benzene (a second linker) and 3,3"-dihydroxy-[1,1':4',1"-terphenyl]-4,4"-dialdehyde are used as precursors to achieve condensation of aldehyde groups and amino groups under hydrothermal conditions to form a covalent organic framework (COF) material COF-3 with a crystalline form, and then a probe COF-3-Sc is obtained by anchoring trivalent scandium ions on the COF structure.

[0020] As a preferred technical solution of the present invention, the 1,4-phenyldiboric acid and 4-bromo-2-hydroxybenzaldehyde in step (1) are mixed in an organic solvent.

[0021] Preferably, the organic solvent comprises any one of methanol, ethanol, toluene, tetrahydrofuran or anhydrous acetonitrile, or a combination of at least two thereof. Typical but non-limiting examples include methanol and ethanol, toluene and tetrahydrofuran, methanol and anhydrous acetonitrile, and the like.

[0022] Preferably, the alkali solution comprises potassium carbonate and / or potassium phosphate.

[0023] Preferably, the first catalyst comprises tetrakis(triphenylphosphine)palladium or palladium acetate.

[0024] As a preferred technical solution of the present invention, the reaction in step (1) is carried out under a protective atmosphere.

[0025] Preferably, the protective atmosphere comprises nitrogen and / or argon.

[0026] Preferably, the reaction temperature is 50-80°C, for example 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, etc., but is not limited to the listed values. Other unlisted values ​​within the above numerical range are also applicable, and 60-80°C is more preferably used.

[0027] Preferably, the reaction time is 12-24h, for example 12h, 14h, 16h, 18h, 20h, 22h, 24h, etc., but is not limited to the listed values. Other unlisted values ​​within the above numerical range are also applicable, and more preferably 20h-24h.

[0028] Preferably, the pH adjustment specifically includes: adjusting the pH of the solution to be acidic to generate a precipitate.

[0029] Preferably, after the solid-liquid separation, the solid is washed and dried to obtain a first connector.

[0030] Preferably, the washing is carried out using methanol and water.

[0031] As a preferred technical solution of the present invention, in step (2), the second linker and the first linker are mixed in an organic solvent.

[0032] Preferably, the organic solvent comprises any one of 1,4-dioxane, dimethyl sulfoxide or dimethylformamide or a combination of at least two thereof, and typical but non-limiting examples thereof include 1,4-dioxane and dimethyl sulfoxide, 1,4-dioxane and dimethylformamide, and dimethyl sulfoxide and dimethylformamide.

[0033] Preferably, the second catalyst comprises acetic acid.

[0034] As a preferred technical solution of the present invention, the reaction in step (2) is carried out under a protective atmosphere.

[0035] Preferably, the protective atmosphere comprises nitrogen and / or argon.

[0036] Preferably, the reaction temperature is 60-120°C, for example 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, 110°C, 120°C, etc., but is not limited to the listed values, and other unlisted values ​​within the above numerical range are also applicable, and 90-120°C is further preferred.

[0037] Preferably, the reaction time is 3-5 d, for example 3 d, 3.5 d, 4 d, 4.5 d, 5 d, etc., but is not limited to the listed values. Other values ​​not listed in the above numerical range are also applicable, and 3 d is more preferred.

[0038] Preferably, the solid-liquid separation is followed by washing and drying to obtain a covalent organic framework precursor.

[0039] Preferably, the washing is performed with tetrahydrofuran and ethanol at least three times.

[0040] As a preferred technical solution of the present invention, the mass ratio of the covalent organic framework precursor to the scandium salt in step (3) is 1:(0.5-2), for example, 1:0.5, 1:0.8, 1:1, 1:1.2, 1:1.5, 1:1.8, 1:2, etc., but is not limited to the listed values. Other values ​​not listed within the above numerical range are also applicable, and more preferably 1:(0.5-1).

[0041] Preferably, the scandium salt includes any one of scandium chloride hexahydrate, scandium nitrate, scandium sulfate, scandium trifluoromethanesulfonate or scandium oxide, or a combination of at least two thereof. Typical but non-limiting examples include scandium chloride hexahydrate and scandium nitrate, scandium sulfate and scandium trifluoromethanesulfonate, scandium sulfate and scandium oxide, scandium chloride hexahydrate and scandium oxide, etc.

[0042] As a preferred technical solution of the present invention, in step (3), the covalent organic framework precursor and the scandium salt are mixed in an organic solvent.

[0043] Preferably, the organic solvent is anhydrous acetonitrile.

[0044] Preferably, the temperature of the coordination reaction is 60-80°C, for example 60°C, 65°C, 70°C, 75°C, 80°C, etc., but is not limited to the listed values. Other unlisted values ​​within the above numerical range are also applicable, and 60°C is more preferably.

[0045] The coordination reaction time is 6-24h, for example 6h, 9h, 12h, 15h, 18h, 21h, 24h, etc., but is not limited to the listed values. Other values ​​not listed in the above numerical range are also applicable, and 18-24h is more preferably used.

[0046] Preferably, after the solid-liquid separation, the solid is washed and dried to obtain a ratiometric rare earth functionalized covalent organic framework fluorescent probe.

[0047] Preferably, the washing is performed by rinsing with anhydrous ethanol.

[0048] In a third aspect, the present invention provides a use of the fluorescent probe as described in the first aspect, wherein the fluorescent probe is used to detect quinolone antibiotics.

[0049] Preferably, the quinolone antibiotic comprises any one of enrofloxacin, norfloxacin or pefloxacin, or a combination of at least two of them. Typical but non-limiting examples include: enrofloxacin and norfloxacin, enrofloxacin and pefloxacin, and norfloxacin and pefloxacin.

[0050] Compared with the prior art, the present invention has at least the following beneficial effects:

[0051] (1) The present invention prepares a linker 3,3"-dihydroxy-[1,1':4',1"-terphenyl]-4,4"-dialdehyde with aggregation-induced emission effect through a one-step simple Suzuki coupling reaction. The preparation process is simple to operate and the product yield is high;

[0052] (2) The present invention provides protection for rare earth ions through the coordination of the covalent organic framework and the scandium ions, while also playing a certain role in pore blocking, thereby reducing the impact of other interfering substances;

[0053] (3) The fluorescent probe of the present invention can specifically identify the quinolone antibiotics enrofloxacin, norfloxacin and pefloxacin. Compared with the common "turn-off" or "turn-on" fluorescent probes, it is more resistant to changes in external environmental factors and the identification results are more accurate and reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 This is a schematic diagram of the synthesis of the first linker 3,3"-dihydroxy-[1,1':4',1"-terphenyl]-4,4"-dialdehyde.

[0055] Figure 2 These are the H-NMR spectrum (a) and C-NMR spectrum (b) of the first linker 3,3”-dihydroxy-[1,1':4',1”-terphenyl]-4,4”-dialdehyde.

[0056] Figure 3 This is the aggregation-induced emission of the first linker 3,3"-dihydroxy-[1,1':4',1"-terphenyl]-4,4"-dialdehyde.

[0057] Figure 4 This is a schematic diagram of the synthesis of the covalent organic framework precursor COF-3.

[0058] Figure 5 This is a comparison of the Fourier infrared spectra of the ligand and COF-3 before and after the synthesis of the covalent organic framework material.

[0059] Figure 6 This is the powder XRD spectrum of the covalent organic framework precursor COF-3.

[0060] Figure 7 These are the scanning electron microscopy (SEM) (a) and transmission electron microscopy (TEM) images (b) of the covalent organic framework precursor COF-3.

[0061] Figure 8 This is the fluorescence emission spectrum of COF-3 under 365nm excitation light.

[0062] Fig. 9 This is a schematic diagram of the construction of the fluorescent probe COF-3-Sc.

[0063] Fig.10 This is the distribution of elements in the transmission electron microscope TEM image of the fluorescent probe COF-3-Sc and the EDS test image.

[0064] Fig.11 This is the XPS comparison chart of O1s in the covalent organic framework COF-3 and the fluorescent probe COF-3-Sc.

[0065] Fig.12The fluorescence spectra of the fluorescent probe COF-3-Sc changed under different concentrations of enrofloxacin (a), norfloxacin (b) and pefloxacin (c). DETAILED DESCRIPTION

[0066] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and through specific implementation methods. However, the following examples are only simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0067] Example 1

[0068] This embodiment provides a method for preparing a ratiometric rare earth functionalized covalent organic framework fluorescent probe, the preparation method comprising:

[0069] (1) 1,4-phenylenediboronic acid (414.4 mg, 2.5 mmol) and 4-bromo-2-hydroxybenzaldehyde (1.005 g, 5 mmol) were dispersed in 50 ml of methanol solution, and potassium carbonate solution (2 M, 15 mL) and tetrakis(triphenylphosphine)palladium (56 mg) were added. The mixture was reacted at 50° C. for 24 h under nitrogen protection. After the reaction, the pH was adjusted to acidic to produce a precipitate. After solid-liquid separation, the mixture was washed with methanol and water and dried to obtain the first linker 3,3”-dihydroxy-[1,1':4',1”-terphenyl]-4,4”-dialdehyde;

[0070] (2) 1,3,5-tris(4-aminophenyl) (17.6 mg, 0.05 mmol) and 3,3"-dihydroxy-[1,1':4',1"-terphenyl]-4,4"-dialdehyde (23.9 mg, 0.075 mmol) were dissolved in a mixed solution of 1,4-dioxane and dimethyl sulfoxide (10 mL, 4:1), 0.2 mL of acetic acid was added, and the mixture was reacted at 60 °C for 3 days under nitrogen protection. After solid-liquid separation, the mixture was washed with tetrahydrofuran and ethanol for at least three times, and dried to obtain the covalent organic framework precursor COF-3;

[0071] (3) COF-3 (50 mg) was uniformly dispersed in 20 mL of acetonitrile solution by ultrasound, and scandium chloride hexahydrate (25 mg) was added. The mixture was condensed and refluxed at 60°C for 24 h. After the reaction, the solid and liquid were separated, and the mixture was rinsed with ethanol and dried to obtain the fluorescent probe COF-3-Sc.

[0072] Example 2

[0073] This embodiment provides a method for preparing a ratiometric rare earth functionalized covalent organic framework fluorescent probe, the preparation method comprising:

[0074] (1) 1,4-phenylenediboronic acid (414.4 mg, 2.5 mmol) and 4-bromo-2-hydroxybenzaldehyde (1.005 g, 5 mmol) were dispersed in 50 ml of methanol solution, and potassium carbonate solution (2 M, 15 mL) and tetrakis(triphenylphosphine)palladium (56 mg) were added. The mixture was reacted at 60° C. for 20 h under nitrogen protection. After the reaction, the pH was adjusted to acidic to produce a precipitate. After solid-liquid separation, the mixture was washed with methanol and water and dried to obtain the first linker 3,3”-dihydroxy-[1,1':4',1”-terphenyl]-4,4”-dialdehyde;

[0075] (2) 1,3,5-tris(4-aminophenyl) (17.6 mg, 0.05 mmol) and 3,3"-dihydroxy-[1,1':4',1"-terphenyl]-4,4"-dialdehyde (23.9 mg, 0.075 mmol) were dissolved in a mixed solution of 1,4-dioxane and dimethyl sulfoxide (10 mL, 4:1), 0.2 mL of acetic acid was added, and the mixture was reacted at 90 °C for 3 days under nitrogen protection. After solid-liquid separation, the mixture was washed with tetrahydrofuran and ethanol for at least three times, and dried to obtain the covalent organic framework precursor COF-3;

[0076] (3) COF-3 (50 mg) was uniformly dispersed in 20 mL of acetonitrile solution by ultrasound, and scandium chloride hexahydrate (50 mg) was added. The mixture was condensed and refluxed at 60°C for 18 h. After the reaction, the solid and liquid were separated, and the mixture was rinsed with ethanol and dried to obtain the fluorescent probe COF-3-Sc.

[0077] Example 3

[0078] This embodiment provides a method for preparing a ratiometric rare earth functionalized covalent organic framework fluorescent probe, the preparation method comprising:

[0079] (1) 1,4-phenylenediboronic acid (414.4 mg, 2.5 mmol) and 4-bromo-2-hydroxybenzaldehyde (1.005 g, 5 mmol) were dispersed in 50 ml of methanol solution, and potassium carbonate solution (2 M, 15 mL) and tetrakis(triphenylphosphine)palladium (56 mg) were added. The mixture was reacted at 70° C. for 16 h under nitrogen protection. After the reaction, the pH was adjusted to acidic to produce a precipitate. After solid-liquid separation, the mixture was washed with methanol and water and dried to obtain the first linker 3,3”-dihydroxy-[1,1':4',1”-terphenyl]-4,4”-dialdehyde;

[0080] (2) 1,3,5-tris(4-aminophenyl) (17.6 mg, 0.05 mmol) and 3,3"-dihydroxy-[1,1':4',1"-terphenyl]-4,4"-dialdehyde (23.9 mg, 0.075 mmol) were dissolved in a mixed solution of 1,4-dioxane and dimethyl sulfoxide (10 mL, 4:1), 0.2 mL of acetic acid was added, and the mixture was reacted at 120 °C for 3 days under nitrogen protection. After solid-liquid separation, the mixture was washed with tetrahydrofuran and ethanol for at least three times, and dried to obtain the covalent organic framework precursor COF-3;

[0081] (3) COF-3 (50 mg) was uniformly dispersed in 20 mL of acetonitrile solution by ultrasound, and scandium chloride hexahydrate (100 mg) was added. The mixture was condensed and refluxed at 70°C for 12 h. After the reaction, the solid and liquid were separated, and the mixture was rinsed with ethanol and dried to obtain the fluorescent probe COF-3-Sc.

[0082] Example 4

[0083] This embodiment provides a method for preparing a ratiometric rare earth functionalized covalent organic framework fluorescent probe, the preparation method comprising:

[0084] (1) 1,4-phenylenediboronic acid (414.4 mg, 2.5 mmol) and 4-bromo-2-hydroxybenzaldehyde (1.005 g, 5 mmol) were dispersed in 50 ml of methanol solution, and potassium carbonate solution (2 M, 15 mL) and tetrakis(triphenylphosphine)palladium (56 mg) were added. The mixture was reacted at 80° C. for 12 h under nitrogen protection. After the reaction, the pH was adjusted to acidic to produce a precipitate. After solid-liquid separation, the mixture was washed with methanol and water and dried to obtain the first linker 3,3”-dihydroxy-[1,1':4',1”-terphenyl]-4,4”-dialdehyde;

[0085] (2) 1,3,5-tris(4-aminophenyl) (17.6 mg, 0.05 mmol) and 3,3"-dihydroxy-[1,1':4',1"-terphenyl]-4,4"-dialdehyde (23.9 mg, 0.075 mmol) were dissolved in a mixed solution of 1,4-dioxane and dimethyl sulfoxide (10 mL, 4:1), 0.2 mL of acetic acid was added, and the mixture was reacted at 150 °C for 3 days under nitrogen protection. After solid-liquid separation, the mixture was washed with tetrahydrofuran and ethanol for at least three times, and dried to obtain the covalent organic framework precursor COF-3;

[0086] (3) COF-3 (50 mg) was uniformly dispersed in 20 mL of acetonitrile solution by ultrasound, and scandium chloride hexahydrate (150 mg) was added. The mixture was condensed and refluxed at 80°C for 8 h. After the reaction, the solid and liquid were separated, and the mixture was rinsed with ethanol and dried to obtain the fluorescent probe COF-3-Sc.

[0087] Example 5

[0088] This embodiment provides a method for preparing a ratiometric rare earth functionalized covalent organic framework fluorescent probe, which is different from Embodiment 1 only in that the reaction temperature of step (1) is 80° C., and the rest is the same as Embodiment 1.

[0089] Example 6

[0090] This embodiment provides a method for preparing a ratiometric rare earth functionalized covalent organic framework fluorescent probe, which is different from Embodiment 1 only in that the reaction time of step (2) is 4 days, and the rest is the same as Embodiment 1.

[0091] Example 7

[0092] This embodiment provides a method for preparing a ratiometric rare earth functionalized covalent organic framework fluorescent probe, which is different from Embodiment 2 only in that the reaction time of step (2) is 1 day, and the rest is the same as Embodiment 2.

[0093] Example 8

[0094] This embodiment provides a method for preparing a ratiometric rare earth functionalized covalent organic framework fluorescent probe, which is different from Embodiment 2 only in that the reaction temperature of step (2) is 30° C., and the rest is the same as Embodiment 2.

[0095] Example 9

[0096] This embodiment provides a method for preparing a ratiometric rare earth functionalized covalent organic framework fluorescent probe, which is different from Embodiment 2 only in that the amount of scandium chloride hexahydrate added in step (3) is 10 mg, and the rest is the same as Embodiment 2.

[0097] Comparative Example 1

[0098] This comparative example provides a method for preparing a ratiometric rare earth functionalized covalent organic framework fluorescent probe, which is different from Example 2 only in that europium chloride hexahydrate is added in step (3), and the rest is the same as Example 2.

[0099] Comparative Example 2

[0100] This comparative example provides a method for preparing a ratiometric rare earth functionalized covalent organic framework fluorescent probe, which differs from Example 2 only in that step (1) is omitted, and in step (2), 1,3,5-tri(4-aminophenyl)benzene and 2,6-pyridinedicarboxaldehyde are used to react to synthesize a covalent organic framework precursor, and the rest is the same as Example 2.

[0101] Performance Testing

[0102] The fluorescent probe COF-3-Sc prepared in Examples 1-9 and Comparative Examples 1 and 2 was used to detect and identify enrofloxacin, norfloxacin and pefloxacin, respectively. The specific test method is as follows:

[0103] Detection of enrofloxacin: 5 mg of the fluorescent probe COF-3-Sc prepared in Examples 1-9 and Comparative Examples 1 and 2 were weighed and dispersed in 1 mL of dimethyl sulfoxide to prepare a 5 mg / mL fluorescent probe stock solution; 40 μL of the fluorescent probe stock solution was taken in a cuvette, and then 1.95 mL of deionized water was added; then 10 μL of enrofloxacin solutions of different concentrations were added dropwise to make the enrofloxacin concentrations in the system 5 μM, 10 μM, 15 μM, 20 μM and 25 μM, respectively. After reacting for 10 minutes, a spectral test was performed under 330 nm excitation light to detect the ratio of different materials at 430 nm and 556 nm, and then the slope K value was obtained by curve fitting.

[0104] The detection and identification test methods of norfloxacin and pefloxacin are as described above, and the test results are shown in Table 1.

[0105]

[0106]

[0107] The slope K reflects the fluorescence change of the probe to the antibiotic. The larger the K value, the more sensitive the sensing of the antibiotic in the system. The reaction temperature and time during the synthesis process directly affect the crystal spatial structure of the COFs material. The ordered spatial structure is conducive to the smooth sensing. 3+ The content of Sc directly affects the sensitization luminescence to antibiotics, so 3+ The amount of addition should be able to fully coordinate with the binding sites in COFs.

[0108] It can be seen from Examples 1-6 that, under the condition of ensuring that the reaction proceeds fully, increasing the reaction time, temperature and Sc 3+ The amount of will not have a significant impact on the detection efficiency; and by comparing Example 2 and Example 7-9, it can be seen that the reaction time, temperature and Sc 3+ Insufficient addition will affect the sensing performance of the material.

[0109] By comparing Example 2 with Comparative Example 1, it can be seen that the use of Eu 3+ The fluorescent probe prepared by the coordinated covalent organic framework has poor sensing performance for antibiotics, mainly because Eu 3+It is not possible to enhance the luminescence of the three antibiotics at 430nm. Instead, the energy absorbed by norfloxacin among the three is used to sensitize itself to emit light at 612nm through the antenna effect. For enrofloxacin and pefloxacin, they can only rely on their own weaker fluorescence to produce contrast, and the sensing performance is reduced. For norfloxacin, since the luminescence at 612nm is very close to the luminescence wavelength of the covalent organic framework, it is also impossible to produce effective ratiometric detection.

[0110] By comparing Example 2 with Comparative Example 2, it can be seen that although the covalent organic framework synthesized in Comparative Example 2 can also be combined with Sc 3+ However, the prepared fluorescent probe has poor sensing performance for antibiotics, mainly because the covalent organic framework precursor synthesized by this method cannot emit light by itself and can only rely on Sc 3+ The enhanced antibiotics produced a single fluorescence enhanced emission at 430 nm, which was not effective for ratiometric detection.

[0111] In addition, according to Example 2, while ensuring good detection results, the conditions for preparing the material are also milder, avoiding waste of time, energy and materials. Therefore, considering the preparation efficiency and detection ability comprehensively, the material obtained in Example 2 was used for corresponding tests.

[0112] The material obtained in Example 2 is characterized accordingly and illustrated with reference to the figures.

[0113] In the early stage of material preparation, a first linker 3,3"-dihydroxy-[1,1':4',1"-terphenyl]-4,4"-dialdehyde ( Figure 1 ). Subsequently, its structure was determined through nuclear magnetic resonance hydrogen and carbon spectra ( Figure 2 ). The test found that the first linker can be dissolved in dimethyl sulfoxide, but difficult to dissolve in water. When the first linker is dissolved in dimethyl sulfoxide, almost no fluorescence is generated. When different proportions of water are added to the system, the first linker gradually precipitates and the fluorescence of the system continues to increase ( Figure 3 Then we used 1,3,5-tris(4-aminophenyl) and 3,3"-dihydroxy-[1,1':4',1"-terphenyl]-4,4"-dialdehyde to successfully construct the covalent organic framework precursor COF-3 ( Figure 4 ).

[0114] Afterwards, the covalent organic framework precursor COF-3 was characterized and tested accordingly. Figure 5 As shown in the figure, the FITR results show that after the first step of Schiff base reaction, the amino vibration peak (3420 cm -1 and 3345cm-1 ) and 3,3"-dihydroxy-[1,1':4',1"-terphenyl]-4,4"-dialdehyde (1668cm -1 ) could not be observed, and the C=N bond (1618cm -1 ), indicating that the amino and aldehyde groups have been successfully combined to form the covalent organic framework precursor COF-3.

[0115] like Figure 6 As shown, the PXRD test confirmed that the material was crystalline, and the test results showed that the material had a strong crystal diffraction peak at 2θ=2.0°, thereby further confirming the synthesis of the covalent organic framework precursor COF-3. Figure 7 The scanning electron microscope and transmission electron microscope images of COF-3 show that COF-3 is a uniformly dispersed spherical structure. It is important that COF-3 material produces strong fluorescence emission at 556nm under the excitation of ultraviolet light, which provides a basis for the construction of ratiometric fluorescent probes ( Figure 8 ).

[0116] Finally, the scandium ions were fixed on COF-3 by electrostatic adsorption and van der Waals forces ( Fig. 9 ). The energy spectrum analysis test of transmission electron microscope shows that after the reaction, Sc 3+ The Sc-O bond was uniformly dispersed in COF-3, and XPS test also verified the formation of Sc-O bond, indicating that COF-3-Sc was successfully prepared ( Fig.10 and Fig.11 ).

[0117] When enrofloxacin, norfloxacin and pefloxacin are coordinated with trivalent scandium, the rigid structure of the molecule is further increased and the fluorescence is further enhanced. 3+ While providing support and protection, it can also serve as a reference fluorescence. The test results show that COF-3-Sc is a ratiometric test for the three antibiotics. As the concentration of the antibiotics increases, the fluorescence intensity around 430nm further increases; and the fluorescence of the COF-3-Sc material at 556nm will also slightly increase due to the fluorescence resonance energy transfer (FRET) effect, but the color of the entire system changes from orange to purple due to the dominant role of the internal filter effect (IFE). Fig.12 ).

[0118] In summary, the present invention provides a ratiometric rare earth functionalized covalent organic framework fluorescent probe and a preparation method and application thereof. The first linker is synthesized by a one-step Suzuki coupling reaction, the method is simple, and the product yield is high. The covalent organic framework and the scandium ions are coordinated to provide protection for the rare earth ions while also playing a certain pore blocking role, thereby reducing the influence of other interferents, thereby achieving more sensitive and portable detection of enrofloxacin, norfloxacin and pefloxacin in water.

[0119] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A ratiometric rare earth functionalized covalent organic framework fluorescent probe, characterized in that: The fluorescent probe comprises a covalent organic framework and a rare earth ion; the covalent organic framework comprises a first linker and a second linker; The first linker is 3,3"-dihydroxy-[1,1':4',1"-terphenyl]-4,4"-dialdehyde; and the rare earth ion is a scandium ion.

2. The fluorescent probe according to claim 1, characterized in that The second linker includes any one of 1,3,5-tri(4-aminophenyl)benzene, 1,3,5-tri(4-formylphenyl)benzene, 1,3,5-trihydroxybenzene or 1,3,5-triaminobenzene.

3. A method for preparing a fluorescent probe as claimed in claim 1 or 2, characterized in that: The preparation method comprises: (1) 1,4-phenylenediboronic acid and 4-bromo-2-hydroxybenzaldehyde are mixed, and then an alkali solution and a first catalyst are added to react, and after the reaction, the pH is adjusted for solid-liquid separation to obtain a first linker; (2) mixing the second linker with the first linker and adding a second catalyst to react, and performing solid-liquid separation after the reaction to obtain a covalent organic framework precursor; (3) The covalent organic framework precursor is mixed with a scandium salt and subjected to coordination reaction, and solid-liquid separation is performed after the reaction to obtain the ratiometric rare earth functionalized covalent organic framework fluorescent probe.

4. The preparation method according to claim 3, characterized in that: The 1,4-phenylenediboronic acid and 4-bromo-2-hydroxybenzaldehyde described in step (1) are mixed in an organic solvent; Preferably, the organic solvent comprises any one or a combination of at least two of methanol, ethanol, toluene, tetrahydrofuran or anhydrous acetonitrile; Preferably, the alkali solution comprises potassium carbonate and / or potassium phosphate; Preferably, the first catalyst comprises tetrakis(triphenylphosphine)palladium or palladium acetate.

5. The preparation method according to claim 3 or 4, characterized in that: The reaction in step (1) is carried out under a protective atmosphere; the reaction temperature is 50-80° C., preferably 60-80° C.; Preferably, the reaction time is 12-24h, preferably 20h-24h; Preferably, the pH adjustment specifically includes: adjusting the pH of the solution to be acidic to generate a precipitate; Preferably, the solid-liquid separation is followed by washing and drying to obtain a first connector; Preferably, the washing is carried out using methanol and water.

6. The preparation method according to any one of claims 3 to 5, characterized in that: Step (2) the second linker and the first linker are mixed in an organic solvent; Preferably, the organic solvent comprises any one or a combination of at least two of 1,4-dioxane, dimethyl sulfoxide or dimethylformamide; Preferably, the second catalyst comprises acetic acid.

7. The preparation method according to any one of claims 3 to 6, characterized in that: The reaction in step (2) is carried out under a protective atmosphere; the reaction temperature is 60-120° C., preferably 90-120° C.; Preferably, the reaction time is 3-5 days; Preferably, the solid-liquid separation is followed by washing and drying to obtain a covalent organic framework precursor; Preferably, the washing is performed with tetrahydrofuran and ethanol at least three times.

8. The preparation method according to any one of claims 3 to 7, characterized in that: In step (3), the mass ratio of the covalent organic framework precursor to the scandium salt is 1:(0.5-2), preferably 1:(0.5-1); Preferably, the scandium salt includes any one of scandium chloride hexahydrate, scandium nitrate, scandium sulfate, scandium trifluoromethanesulfonate or scandium oxide, or a combination of at least two thereof.

9. The preparation method according to any one of claims 3 to 8, characterized in that: Step (3) the covalent organic framework precursor is mixed with a scandium salt in an organic solvent; Preferably, the organic solvent is anhydrous acetonitrile; Preferably, the temperature of the coordination reaction is 60-80°C; the time of the coordination reaction is 6-24h, preferably 18-24h; Preferably, after the solid-liquid separation, the solid is washed and dried to obtain a ratiometric rare earth functionalized covalent organic framework fluorescent probe; Preferably, the washing is performed by rinsing with anhydrous ethanol.

10. A use of the fluorescent probe as claimed in claim 1 or 2, characterized in that: The fluorescent probe is used to detect quinolone antibiotics; Preferably, the quinolone antibiotics include any one of enrofloxacin, norfloxacin or pefloxacin, or a combination of at least two of them.

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