Fluorescent boron quantum dot photocatalyst as well as preparation method and application thereof

Abstract

The invention discloses a fluorescent boron quantum dot photocatalyst and a preparation method and application thereof.The preparation method comprises the steps that organic boric acid and organic amine which are low in price and easy to obtain serve as boron sources or heteroatom precursors, reaction is conducted in an organic solvent, separation and purification are conducted, and then fluorescent boron quantum dots are prepared. The synthesized boron quantum dot has the advantages of cheap and easily available raw materials, simple and efficient reaction method, high yield, convenience in post-treatment, suitability for amplified production, photoluminescence characteristic, good water solubility, low toxicity, environmental friendliness, good biocompatibility and the like, and is suitable for large-scale production. And the boron quantum dot can catalyze C-H oxidation / cyclization reaction of enaminone, and has a certain application prospect.

Description

Technical Field

[0001] The invention relates to a quantum dot photocatalyst and a preparation method and application thereof, and in particular to a fluorescent boron quantum dot photocatalyst and a preparation method and application thereof. Background Art

[0002] In 2004, Xu et al. (J.Am.Chem.Soc., 2004, 126, 12736) from the University of South Carolina discovered and synthesized luminescent carbon nanoparticles for the first time during the preparation and purification of single-walled nanotubes by arc discharge. Since then, various nanomaterials have emerged, such as carbon quantum dots, semiconductor quantum dots, and boron quantum dots.

[0003] Semiconductor quantum dots, such as zinc sulfide, cadmium sulfide, cadmium telluride and zinc selenide, are severely limited in their application in biomarkers and medical fields because they contain heavy metal elements. The hazards of these heavy metals to human health and the environment have aroused widespread concern. Therefore, the development of metal-free quantum dots with good biocompatibility, low toxicity and environmental protection properties has become an important research hotspot in recent years. The biggest feature of boron quantum dots is that they do not contain heavy metal components, which makes them significantly different in properties from typical semiconductor quantum dots (such as cadmium sulfide, zinc selenide, etc.). Boron quantum dots not only have the characteristics of photoluminescence, but also have good water solubility and biocompatibility. At the same time, they have low toxicity, are easy to functionalize, meet environmental protection requirements, and have a wide range of raw materials and low cost.

[0004] Because of this, boron quantum dots have gradually attracted the attention of more and more researchers in many fields such as photoelectric conversion, photocatalysis, light-emitting devices, fluorescence imaging, chemical sensors, biosensors and nanomedicine, and have become an important research direction in the current field of nanomaterial science. It is worth mentioning that biocompatibility and low toxicity are two basic conditions for nanomaterials in biological applications. Compared with traditional heavy metal quantum dots (such as cadmium sulfide, zinc selenide and cadmium telluride), boron quantum dots are environmentally friendly and non-toxic because their main components are boron and nitrogen, and will not cause leakage of toxic elements in biological applications. This unique property makes boron quantum dots more friendly to organisms and the environment, thus laying a good foundation for their wide application in bioanalysis, drug delivery, cell imaging and diagnosis, and showing broad prospects.

[0005] Li et al. reported a simple and effective method to successfully prepare size-controlled boron nitride quantum dots by combining ultrasonic treatment-assisted liquid exfoliation technology with solvent heating process (Small, 2015, 11, No. 48, 6491–6499). et al. reported the process of exfoliating boron quantum dots using fixed ultrasound in a pressurized ultrasonic reactor (Sci. Adv. Mater., 6, 1–11, 2014). Rajesh Kumar et al. reported a simple, scalable and single-step effective synthesis route, which uses high-intensity ultrasound treatment in the liquid phase and the exfoliation of boron quantum dots in the H3PO4 liquid medium to manufacture boron quantum dots through a top-down approach (Journal of Alloys and Compounds 683 (2016) 38e45). Xue et al. successfully prepared fluorescent monolayer boron nitride-based quantum dots by hydrothermal method, cutting bulk materials with the assistance of alkaline solution (RSC Adv., 2016, 6, 79090). Allwood et al. made a breakthrough by proposing a novel method in which semi-finished quantum dots prepared under high temperature conditions were cooled in a vacuum and then treated with ultrasound in an ethanol / water solution, and the remaining impurities were removed by filtration / centrifugation and the use of cation exchange resin. Finally, boron quantum dots were successfully obtained (Small, 2014, 10, 60–65). Liu et al. reported a new method in which bulk BN powder was first exfoliated into nanosheets by ultrasonic treatment. The obtained nanosheet suspension was then degassed with N2 for 30 minutes to remove oxygen from the nanosheet dispersion, and then the dispersion was solvothermally treated at 180 ° C for 10 hours to further cut the nanosheets into the required nitrogen-containing boron quantum dots (Adv. Optical Mater. 2017, 1600661).

[0006] Generally speaking, there are two strategies for making boron quantum dots: "top-down" and "bottom-up" processes. The "top-down" process involves cutting large-sized bulk boron-containing nanosheets into small-sized boron quantum dots by physical exfoliation or chemical tailoring methods. These methods mainly include liquid exfoliation, solvothermal / hydrothermal treatment, and ion intercalation. The mechanism of this process is that the oxygen-containing functional groups formed during the reaction can produce certain defects in the boron quantum dots, which can be used as reaction sites for crushing the nanosheets into boron quantum dots. The "bottom-up" process is related to the use of some simple organic or inorganic materials as precursors under certain conditions through chemical assembly. The typical methods of the "bottom-up" process are hydrothermal / solvothermal synthesis and microwave radiation, which have the advantages of easy modification and doping. However, the above preparation processes are not easy to prepare on a large scale and have high requirements for experimental instruments. Summary of the invention

[0007] Purpose of the invention: The present invention aims to provide a boron quantum dot photocatalyst having many advantages such as photoluminescence properties, good water solubility, low toxicity, easy functionalization, environmental friendliness, good biocompatibility, and a preparation method and use thereof.

[0008] Technical solution: The preparation method of the fluorescent boron quantum dot photocatalyst described in the present invention comprises: adding one or more organic molecular boron sources and organic amines into a solvent, reacting at 100-250°C for 8-12 hours, purifying after the reaction, and obtaining a fluorescent boron quantum dot photocatalyst.

[0009] Preferably, the reaction temperature is 180°C and the reaction time is 12h.

[0010] Further, the organic molecular boron source is an organic boronic acid and / or an organic boronic acid containing a carboxyl group, the organic boronic acid is phenylboric acid or a substituted phenylboric acid, selected from at least one of 4-chlorophenylboric acid, 4-fluorophenylboric acid, 4-methoxyphenylboric acid, 4-formylphenylboric acid, 2-chlorophenylboric acid, 2-fluorophenylboric acid, 3-chlorophenylboric acid, 3-bromophenylboric acid or p-carboxyphenylboric acid; the organic amine is at least one of propylamine, butylamine, pentylamine, ethylenediamine, propylenediamine, butylenediamine, pentylenediamine, p-phenylenediamine, m-phenylenediamine, o-phenylenediamine, m-phenylenediamine, urea, thiourea and acrylamide.

[0011] Furthermore, the solvent is at least one of dimethyl sulfoxide, water, formamide, N-methylformamide, N,N-dimethylformamide, and N,N-dimethylacetamide; and the molar concentration of the organic molecular boron source in the solvent is 0.01 to 1M.

[0012] Furthermore, the size of the boron quantum dot photocatalyst is 2 to 20 nm, and the luminescence range is 300 to 700 nm.

[0013] The boron quantum dot photocatalyst can be used to catalyze the CH oxidation / cyclization of enaminones to synthesize polysubstituted oxazoles.

[0014] The method for synthesizing polysubstituted oxazoles through CH oxidation / cyclization of enaminones comprises the following steps: using enaminones 1 as a starting material, using boron quantum dots as a photocatalyst, reacting under light and room temperature conditions, and realizing CH oxidation / cyclization of enaminones to synthesize polysubstituted oxazoles in one step to generate compound 2.

[0015] The synthetic route is shown in the following reaction formula:

[0016]

[0017] in,

[0018] R1 is a benzene ring, a substituted or unsubstituted benzene ring or a benzo five-membered heterocyclic ring, and the substituent is selected from at least one of halogen, C1-C6 alkoxy, C1-C6 alkyl, halogen-substituted C1-C6 alkyl, and furan.

[0019] Preferably, the benzo five-membered heterocyclic ring is

[0020] R2 is a benzene ring, a substituted or unsubstituted benzene ring or a five-membered heterocyclic ring, and the substituent is selected from at least one of halogen, C1-C6 alkoxy, C1-C6 alkyl, halogen-substituted C1-C6 alkyl, and thiophene.

[0021] Preferably, the benzo five-membered heterocyclic ring is

[0022] Furthermore, the molar ratio of the enaminone 1 to the base is 1:0.5 to 1:2.

[0023] Furthermore, the wavelength of the light source of the illumination is 390 to 600 nm (preferably 390 to 500 nm); the reaction solvent is one or more of water, dimethyl sulfoxide, N,N-dimethylformamide, tetrahydrofuran, toluene, acetonitrile, methanol, 1,2-dichloroethane, and 1,4-dioxane; the reaction time is 40 to 48 hours; and the reaction atmosphere is air and / or oxygen.

[0024] Furthermore, the base is potassium carbonate, cesium carbonate, lithium carbonate, sodium carbonate, potassium phosphate, potassium tert-butoxide or lithium tert-butoxide.

[0025] The size of the prepared boron quantum dots is 2 to 20 nm; the luminescence range of the prepared boron quantum dots is 300 to 700 nm.

[0026] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0027] (1) The raw materials for synthesized boron quantum dots are cheap and readily available, the reaction method is simple and efficient, the yield is high, the post-processing is convenient, and it is suitable for scale-up production;

[0028] (2) The prepared boron quantum dots have many advantages, such as photoluminescence, good water solubility, low toxicity, easy functionalization, environmental friendliness, and good biocompatibility;

[0029] (3) Boron quantum dots are miscible with solvents, and the active catalytic components can be evenly dispersed in the solvent, which can effectively promote the occurrence of photoreactions;

[0030] (4) The prepared boron quantum dots can be used as photocatalysts to avoid the residue of heavy metals in the product, which is in line with the purpose of green chemistry;

[0031] (5) The prepared boron quantum dots can be used as a new type of photocatalyst to catalyze the CH oxidation / cyclization of enaminones to synthesize polysubstituted oxazoles. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is the XPS image of the boron quantum dots prepared in Example 1;

[0033] Figure 2This is the XRD spectrum of the boron quantum dots prepared in Example 1;

[0034] Figure 3 This is the UV-vis full spectrum of the boron quantum dots prepared in Example 1;

[0035] Figure 4 This is the FT-IR spectrum of the boron quantum dots prepared in Example 1. DETAILED DESCRIPTION

[0036] The technical solution of the present invention is further described below in conjunction with the accompanying drawings.

[0037] Example 1

[0038] Preparation of Boron Quantum Dot 1 (Bor-QD1): Weigh 830 mg of p-carboxyphenylboric acid and 600 mg of urea, then add 10 ml of N,N-dimethylformamide in a sealed tube, react at 180°C for 12 hours. After the reaction is completed, cool to room temperature, concentrate under reduced pressure to remove the solvent, and purify the residue by silica gel flash chromatography, concentrate and dry to obtain 650 g of light yellow solid powder. Figure 1-4 They are XPS graph, XRD spectrum, UV-vis full spectrum and FT-IR spectrum of boron quantum dot 1 respectively.

[0039] Example 2

[0040] Preparation of Boron Quantum 2 (Bor-QD2) dots: Weigh 610 mg of phenylboric acid and 600 mg of urea, then add 10 ml of N,N-dimethylformamide in a sealed tube, react at 180°C for 12 hours. After the reaction is completed, cool to room temperature, concentrate under reduced pressure to remove the solvent, and purify the residue by silica gel flash chromatography, concentrate and dry to obtain 800 g of light yellow-green solid powder.

[0041] Example 3

[0042] Preparation of Boron Quantum 3 (Bor-QD3) dots: Weigh 829 mg of phenylboric acid and 600 mg of urea, then add 10 ml of N,N-dimethylformamide in a sealed tube, react at 180°C for 12 hours. After the reaction is completed, cool to room temperature, concentrate under reduced pressure to remove the solvent, and purify the residue by silica gel flash chromatography, concentrate and dry to obtain 600 g of light green solid powder.

[0043] Application Example 1

[0044]

[0045] Weigh 1a (80 mg, 0.3 mmol), Cs2CO3 (98 mg, 0.3 mmol), Bor-QD2 (25 mg) in a photoreaction tube, add 3 ml of DMF solvent, stir evenly at room temperature, and place under 10W 495 nm LEDs for reaction. Thin layer chromatography is used to detect the reaction progress. After the reaction is completed, ethyl acetate is used to extract and collect the organic phase, then dried over anhydrous sodium sulfate, filtered, and the volatile components are removed by rotary evaporator. The crude mixture is separated by silica gel column chromatography, and the eluent is petroleum ether (60-90 ° C) / ethyl acetate = 15:1, v / v) to obtain a white solid 2a (51 mg, separation yield 61%). The target product is confirmed by nuclear magnetic resonance spectroscopy.

[0046] Application Example 2

[0047]

[0048] Weigh 1b (77 mg, 0.3 mmol), Cs2CO3 (98 mg, 0.3 mmol), Bor-QD2 (25 mg) in a photoreaction tube, add 3 mL of DMF solvent, stir evenly at room temperature, and place under 10W 495 nm LEDs for reaction. Thin layer chromatography is used to detect the reaction progress. After the reaction is completed, ethyl acetate is used to extract and collect the organic phase, which is then dried over anhydrous sodium sulfate, filtered, and the volatile components are removed by rotary evaporator. The crude mixture is separated by silica gel column chromatography, and the eluent is petroleum ether (60-90 ° C) / ethyl acetate = 15:1, v / v) to obtain a white solid 2b (76 mg, separation yield 57%). The target product is confirmed by nuclear magnetic resonance spectroscopy.

[0049] Application Example 3

[0050]

[0051] Weigh 1c (98 mg, 0.3 mmol), Cs2CO3 (98 mg, 0.3 mmol), Bor-QD2 (25 mg) in a photoreaction tube, add 3 mL of DMF solvent, stir evenly at room temperature, and place under 10W 495 nm LEDs for reaction. Thin layer chromatography is used to detect the reaction progress. After the reaction is completed, ethyl acetate is used to extract and collect the organic phase, which is then dried over anhydrous sodium sulfate, filtered, and the volatile components are removed by rotary evaporator. The crude mixture is separated by silica gel column chromatography, and the eluent is petroleum ether (60-90 ° C) / ethyl acetate = 15:1, v / v) to obtain a white solid 2c (40 mg, separation yield 41%). The target product is confirmed by nuclear magnetic resonance spectroscopy.

[0052] Application Example 4

[0053]

[0054] Weigh 1d (81 mg, 0.3 mmol), Cs2CO3 (98 mg, 0.3 mmol), Bor-QD2 (25 mg) in a photoreaction tube, add 3 mL of DMF solvent, stir evenly at room temperature, and place under 10W 495 nm LEDs for reaction. Thin layer chromatography is used to detect the reaction progress. After the reaction is completed, ethyl acetate is used to extract and collect the organic phase, which is then dried over anhydrous sodium sulfate, filtered, and the volatile components are removed by rotary evaporator. The crude mixture is separated by silica gel column chromatography, and the eluent is petroleum ether (60-90 ° C) / ethyl acetate = 15:1, v / v) to obtain a white solid 2d (43 mg, separation yield 50%). The target product is confirmed by nuclear magnetic resonance spectroscopy.

[0055] Application Example 5

[0056]

[0057] Weigh 1e (77 mg, 0.3 mmol), Cs2CO3 (98 mg, 0.3 mmol), Bor-QD2 (25 mg) in a photoreaction tube, add 3 mL of DMF solvent, stir evenly at room temperature, and place under 10W 495 nm LEDs for reaction. Thin layer chromatography is used to detect the reaction progress. After the reaction is completed, ethyl acetate is used to extract and collect the organic phase, which is then dried over anhydrous sodium sulfate, filtered, and the volatile components are removed by rotary evaporator. The crude mixture is separated by silica gel column chromatography, and the eluent is petroleum ether (60-90 ° C) / ethyl acetate = 15:1, v / v) to obtain a white solid 2e (29 mg, separation yield 38%). The target product is confirmed by nuclear magnetic resonance spectroscopy.

[0058] Application Example 6

[0059]

[0060] Weigh 1f (84 mg, 0.3 mmol), Cs2CO3 (98 mg, 0.3 mmol), Bor-QD2 (25 mg) in a photoreaction tube, add 3 mL of DMF solvent, stir evenly at room temperature, and place under 10W 495 nm LEDs for reaction. Thin layer chromatography is used to detect the reaction progress. After the reaction is completed, ethyl acetate is used to extract and collect the organic phase, which is then dried over anhydrous sodium sulfate, filtered, and the volatile components are removed by rotary evaporator. The crude mixture is separated by silica gel column chromatography, and the eluent is petroleum ether (60-90 ° C) / ethyl acetate = 15:1, v / v) to obtain a white solid 2f (36 mg, separation yield 43%). The target product is confirmed by nuclear magnetic resonance spectroscopy.

[0061] Application Example 7

[0062]

[0063] Weigh 1g (98mg, 0.3mmol), Cs2CO3 (98mg, 0.3mmol), Bor-QD2 (25mg) in a photoreaction tube, add 3ml DMF solvent, stir evenly at room temperature, and place under 10W 495nm LEDs for reaction, and detect the reaction progress by thin layer chromatography. After the reaction is completed, extract with ethyl acetate and collect the organic phase, then dry with anhydrous sodium sulfate, filter, and remove volatile components with a rotary evaporator. The crude mixture is separated by silica gel column chromatography, and the eluent is petroleum ether (60-90℃) / ethyl acetate = 15:1, v / v) to obtain 2g (45mg, separation yield 46%) of white solid. The target product is confirmed by nuclear magnetic resonance spectroscopy.

[0064] Application Example 8

[0065]

[0066] Weigh 1h (81 mg, 0.3 mmol), Cs2CO3 (98 mg, 0.3 mmol), Bor-QD2 (25 mg) in a photoreaction tube, add 3 ml of DMF solvent, stir evenly at room temperature, and place under 10W 495 nm LEDs for reaction. Thin layer chromatography is used to detect the reaction progress. After the reaction is completed, ethyl acetate is used to extract and collect the organic phase, then dried over anhydrous sodium sulfate, filtered, and the volatile components are removed by rotary evaporator. The crude mixture is separated by silica gel column chromatography, and the eluent is petroleum ether (60-90 ° C) / ethyl acetate = 15:1, v / v) to obtain a white solid 2h (35 mg, separation yield 41%). The target product is confirmed by nuclear magnetic resonance spectroscopy.

[0067] Application Example 9

[0068]

[0069] Weigh 1i (84 mg, 0.3 mmol), Cs2CO3 (98 mg, 0.3 mmol), Bor-QD (25 mg) in a photoreaction tube, add 3 mL of DMF solvent, stir evenly at room temperature, and place under 10W 495 nm LEDs for reaction, and thin layer chromatography to detect the reaction progress. After the reaction is completed, extract with ethyl acetate and collect the organic phase, then dry with anhydrous sodium sulfate, filter, and remove volatile components with a rotary evaporator. The crude mixture is separated by silica gel column chromatography, and the eluent is petroleum ether (60-90 ° C) / ethyl acetate = 15:1, v / v) to obtain a white solid 2i (35 mg, separation yield 40%). The target product is confirmed by nuclear magnetic resonance spectroscopy.

[0070] Characterization data of typical compounds

[0071] (2-(4-methoxyphenyl)oxazol-5-yl)benzyl ketone, white solid (2a), 1 H NMR (400MHz, CDCl3) δ8.11(d,J=8.9Hz,2H),7.96(d,J=6.6Hz,2H),7.81(s,1H) ,7.61(t,J=6.9Hz,1H),7.56–7.44(m,2H),6.98(d,J=8.7Hz,2H),3.85(s,3H). 13 C NMR (100MHz, CDCl3) δ181.5,165.1,162.7,148.7,138.1,137.2,133.2,129.5,129.0,128.8,118.9,114.5,55.6.

[0072] (2-(4-Fluorophenyl)oxazol-5-yl)benzyl ketone, white solid (2b), 1 H NMR (400MHz, CDCl3) δ8.24–8.16(m,2H),8.02–7.95(m,2H),7.84(s,1H),7.65(t,J=7.4Hz,1H),7.54(t,J=7.6Hz,2H),7.20(t,J=8.7Hz,2H). 13 C NMR(100MHz, CDCl3)δ181.50,167.74–162.31(m,J=237.5Hz),149.14,137.76,136.97 ,133.41,129.95(d,J=9.1Hz),129.07,128.92,122.70(d,J=3.3Hz),116.58,116.36.

[0073] (2-(2-Bromophenyl)oxazol-5-yl)benzyl ketone, white solid (2c),1 H NMR (400MHz, CDCl3) δ8.11-8.60(m,3H),7.97(s,1H),7.76(dd,J=8.0,1.3Hz,1H),7.65(t,J =7.4Hz,1H),7.54(t,J=7.6Hz,2H),7.46(td,J=7.6,1.3Hz,1H),7.37(td,J=7.7,1.8Hz,1H). 13 C NMR (100MHz, CDCl3) δ181.5,163.0,149.5,136.9,136.6,135.0,133.6,132.5,132.2,129.3,128.9,127.7,127.3,121.7.

[0074] (2-(3-Chlorophenyl)oxazol-5-yl)benzyl ketone, white solid (2d), 1 H NMR(400MHz, CDCl3)δ8.16(t,J=1.9Hz,1H),8.08–8.03(m,1H),7.99–7.95(m,2H),7.85(s, 1H),7.64(t,J=7.4Hz,1H),7.54(t,J=7.7Hz,2H),7.51–7.46(m,1H),7.43(t,J=7.9Hz,1H). 13 C NMR (100MHz, CDCl3) δ181.4,163.4,149.3,137.6,136.8,135.3,133.5,132.0,130.4,129.1,128.9,127.9,127.5,125.6.

[0075] Phenyl(2-(thiophen-2-yl)oxazol-5-yl)methanone, white solid (2e), 1 H NMR (400MHz, CDCl3) δ8.01–7.94(m,2H),7.91(dd,J=3.7,1.2Hz,1H),7.81(s,1H),7.68–7.61(m,1H),7.58–7.50(m,3H),7.18(dd,J=5.0,3.8Hz,1H). 13 C NMR (100MHz, CDCl3) δ181.3,161.1,148.6,137.9,137.0,133.4,131.1,130.6,129.1,128.9,128.7,128.6.

[0076] (4-Methoxyphenyl)(2-phenyloxazol-5-yl)methanone, white solid (2f), 1H NMR (400MHz, CDCl3) δ8.17(dd,J=7.9,1.7Hz,2H),8.03(d,J=8.9Hz,2H),7.85(s,1H),7.49(d,J=7.5Hz,3H),7.01(d,J=8.9Hz,2H),3.88(s,3H). 13 C NMR (100MHz, CDCl3) δ180.0,164.4,163.9,149.3,136.8,131.8,131.5,129.6,129.1,127.5,126.4,114.1,55.6.

[0077] (4-bromophenyl)(2-phenyloxazol-5-yl)methanone, white solid (2 g), 1 H NMR (400MHz, CDCl3) δ8.16 (dd, J=8.0, 1.7Hz, 2H), 7.92–7.82 (m, 3H), 7.68 (d, J=8.6Hz, 2H), 7.57–7.47 (m, 3H). 13 CNMR (100MHz, CDCl3) δ180.3,165.0,148.9,137.8,135.6,132.2,132.2,130.6,129.2,128.5,127.6,126.2.

[0078] (3-Chlorophenyl)(2-phenyloxazol-5-yl)methanone, white solid (2h), 1 H NMR (400MHz, CDCl3) δ8.18(dd,J=8.1,1.6Hz,2H),7.97(t,J=1.9Hz,1H),7.88(d,J=9.0Hz,2H),7.61(ddd,J=8.0,2.1,1.1Hz,1H),7.56–7.45(m,4H). 13 C NMR (100MHz, CDCl3) δ180.0,165.2,148.8,138.4,138.2,135.2,133.3,132.2,130.2,129.2,127.7,127.2,126.2.

[0079] Benzo[d][1,3]dioxol-5-yl(2-phenyloxazol-5-yl)methanone, white solid (2i), 1H NMR(400MHz,CDCl3)δ8.17(dd,J=8.0,1.7Hz,2H),7.85(s,1H),7.66(dd,J=8.2,1.7Hz,1H),7.54–7.47(m,4H),6.92(d,J=8.1 Hz,1H),6.08(s,2H). 13 C NMR(100 MHz,CDCl3)δ179.6,164.6,152.3,149.2,148.4,137.0,131.9,131.3,129.1,127.5,126.4,125.6,109.1,108.3,102.2.

Claims

1. A method for preparing a fluorescent boron quantum dot photocatalyst, characterized in that: The method comprises: adding one or more organic molecular boron sources and organic amine into a solvent, reacting at 100-250°C for 8-12 hours, purifying after the reaction, and obtaining a fluorescent boron quantum dot photocatalyst.

2. The method for preparing the fluorescent boron quantum dot photocatalyst according to claim 1, characterized in that: The organic molecular boron source is organic boronic acid and / or organic boronic acid containing a carboxyl group.

3. The method for preparing the fluorescent boron quantum dot photocatalyst according to claim 2, characterized in that: The organic boronic acid is phenylboric acid or substituted phenylboric acid, selected from at least one of 4-chlorophenylboric acid, 4-fluorophenylboric acid, 4-methoxyphenylboric acid, 4-formylphenylboric acid, 2-chlorophenylboric acid, 2-fluorophenylboric acid, 3-chlorophenylboric acid, 3-bromophenylboric acid or p-carboxyphenylboric acid; the organic amine is at least one of propylamine, butylamine, pentylamine, ethylenediamine, propylenediamine, butylenediamine, pentylenediamine, p-phenylenediamine, m-phenylenediamine, o-phenylenediamine, m-phenylenediamine, urea, thiourea and acrylamide.

4. The method for preparing the fluorescent boron quantum dot photocatalyst according to claim 1, characterized in that: The solvent is at least one of dimethyl sulfoxide, water, formamide, N-methylformamide, N,N-dimethylformamide, and N,N-dimethylacetamide, and the molar concentration of the organic molecular boron source in the solvent is 0.01-1M.

5. A fluorescent boron quantum dot photocatalyst, characterized in that: The catalyst is prepared by the preparation method according to any one of claims 1 to 4. The size of the boron quantum dot photocatalyst is 2 to 20 nm, and the luminescence range of the boron quantum dot photocatalyst is 300 to 700 nm.

6. Use of the boron quantum dot photocatalysis according to claim 5 in one-step CH oxidation / cyclization of enaminones to synthesize polysubstituted oxazoles.

7. The use according to claim 6, characterized in that: The method for synthesizing polysubstituted oxazoles by CH oxidation / cyclization of enaminones comprises the following steps: using enaminones 1 as a starting material, using boron quantum dots as a photocatalyst, reacting under light, room temperature, and alkaline conditions to achieve the generation of oxazoles in one step to generate compound 2; The synthetic route is shown in the following reaction formula: in, R1 is a benzene ring, a substituted or unsubstituted benzene ring or a benzo five-membered heterocyclic ring, and the substituent is selected from at least one of halogen, C1-C6 oxy, C1-C6 alkyl, halogen-substituted C1-C6 alkyl, and furan; R2 is a benzene ring, a substituted or unsubstituted benzene ring or a five-membered heterocyclic ring, and the substituent is selected from at least one of halogen, C1-C6 alkoxy, C1-C6 alkyl, halogen-substituted C1-C6 alkyl, and thiophene.

8. The use according to claim 7, characterized in that: The molar ratio of the enaminone 1 to the base is 1:0.5 to 1:

2.

9. The use according to claim 7, characterized in that: The wavelength of the light source of the illumination is 390-500 nm, the reaction solvent is N,N-dimethylformamide, the reaction time is 40-48 hours; and the reaction atmosphere is air and / or oxygen.

10. The use according to claim 7, characterized in that: The base is potassium carbonate, cesium carbonate, lithium carbonate, sodium carbonate, potassium phosphate, potassium tert-butoxide or tert-butanol.

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