Preparation of visible-light response type photochromic iodine-doped bismuth oxybromide catalyst and application of photocatalytic oxidation of ethylbenzene to synthesize acetophenone

Abstract

The invention provides preparation and application of a visible-light response type photochromic iodine-doped bismuth oxybromide catalyst, and belongs to the field of preparation and application of photocatalysts. The iodine-doped bismuth oxybromide BiOBr0. 92I0. 08 is synthesized by a hydrothermal method, and has the characteristics of high purity, simple structure, good stability, good dispersity and the like. The obtained product can be deeply colored within 15 seconds under illumination of 450 nm, and fades in air; and rapid coloring and color fading can be realized under ultraviolet irradiation. The conversion number (TON) of the BiOBr < 0.98 > I < 0.02 > nanosheet for photocatalytic oxidation of ethylbenzene reaches up to 274000 mol.g, which is 7 times that of the BiOBr nanosheet. The method has the advantages of low synthesis cost, no pollution, suitability for large-scale industrial production and the like, and can be applied to photocatalytic oxidation of ethylbenzene.

Description

Technical Field

[0001] This invention relates to the preparation and application of a visible light responsive photochromic iodine-doped bismuth oxybromide catalyst, belonging to the field of photocatalyst preparation and application. Background Technology

[0002] Currently, overexploitation of fossil resources and an increasingly severe ecological environment have led humanity to face the most serious energy and environmental crisis in history. Under mild conditions, the conversion of volatile organic compounds such as ethylbenzene into high-value organic intermediates via CH bond activation offers a sustainable pathway for chemical synthesis and environmental protection. However, the C(sp) group in ethylbenzene... 3 The activation of the CH bond faces significant challenges due to its high bond strength and low polarity. Therefore, achieving CH bond activation under mild conditions has become a key focus and challenge in green organic synthesis. Photocatalysis, which converts light energy into chemical energy, has enormous application potential in carbon dioxide reduction, advanced environmental pollution treatment, and green organic synthesis, and has received considerable attention from the scientific community in recent years.

[0003] In photocatalysts, solid solution photocatalysts generally exhibit better photocatalytic performance than single-component photocatalysts because their band structure is easily tunable. Notably, the BiOBr developed by Wang et al. 0.85 I 0.15 Solid solutions exhibit excellent photocatalytic activity in the degradation of p-chlorophenol, mainly due to their expanded visible light absorption range, elevated valence band position, and efficient charge separation resulting from the synergistic effect between solid solution components and oxygen vacancies. (Wang, Q.; Liu, Z.; Liu, D.; Wang, G.; Yang, M.; Cui, F.; Wang, W., Ultrathin Two-Dimensional BiOBr) x I 1-x Solid Solution with Rich Oxygen Vacancies for EnhancedVisible-Light-Driven Photoactivity in Environmental Remediation. Appl. Catal. B Environ.(2018, 236, 222-232.) Cao et al. demonstrated that photochromic photocatalysts can effectively improve photocatalytic performance due to the enhanced charge separation caused by photochromism. Despite progress in photocatalysis, photochromism is difficult to achieve under >450 nm visible light irradiation. (Cao, X.; Huang, A.; Liang, C.; Chen, H.; Han, T.; Lin, R.; Peng, Q.; Zhuang, Z.; Shen, R.; Chen, H.; Yu, Y.; Chen, C.; Li, Y., xiing Lattice Disorder on a Photocatalyst: Photochromic BiOBr Nanosheets Enhance Activation of Aromatic CH Bonds via Water Oxidation.) J. Am. Chem. Soc. 2022, 144 (8), 3386-3397.)

[0004] Therefore, the development of a visible light-responsive photochromic iodine-doped bismuth oxybromide catalyst for the photocatalytic oxidation of ethylbenzene to acetophenone has significant scientific and practical application value. Summary of the Invention

[0005] To address the shortcomings of existing photocatalysts, this invention provides a method for preparing a visible light-responsive photochromic iodine-doped bismuth oxybromide catalyst, which can be applied to the photocatalytic oxidation of ethylbenzene to acetophenone.

[0006] Iodine doping optimizes BiOBr 1-x I x The band structure of the nanosheets enriches the generation of oxygen vacancies, resulting in significant photochromic behavior under 450 nm light irradiation. The photochromic-induced coloration states can suppress the recombination of photogenerated carriers, thereby improving the utilization rate of light energy. With the development of BiOBr... 1-x I x The enhanced photochromic properties of nanosheets, improved carrier separation efficiency, and significantly enhanced photooxidation activity of CH bonds reveal a positive correlation between photochromism and photocatalytic performance. (BiOBr) 0.98 I 0.02 The catalytic performance of the nanosheets is 7 times that of the original BiOBr. This work highlights a green and sustainable strategy and provides new insights into optimizing CH bond activation by modulating the photochromic effect.

[0007] The technical solution of the present invention is as follows:

[0008] Preparation of a visible-light-responsive photochromic iodine-doped bismuth oxybromide catalyst, with the structural formula BiOBr 0.98 I 0.02 It is characterized by an ultrathin structure and abundant oxygen vacancies, with a size of 17-65 nm and a thickness of ~3.0 nm, and includes the following steps:

[0009] (1) Mixing and stirring: Add the surfactant to the water and stir it completely with a magnetic stirrer. Then add bismuth nitrate pentahydrate to the water and stir it evenly. Then add a mixture containing a certain proportion of bromine source and iodine source. Dissolve it by strong ultrasound and then stir it evenly with magnetic force to obtain a mixed solution.

[0010] (2) Hydrothermal reaction: The mixed solution obtained in step (1) is reacted at 125-165℃ for 3-12 h to obtain the reaction solution;

[0011] (3) Washing and centrifugation: The reaction solution obtained in step (2) is washed and centrifuged several times to obtain the visible light responsive iodine-doped bismuth oxybromide material.

[0012] According to a preferred embodiment of the present invention, the surfactant in step (1) is polyvinylpyrrolidone (K30) and mannitol; the mass ratio of polyvinylpyrrolidone to bismuth source is 0.6~2:1. The mass ratio of mannitol to bismuth source is 1~2:1.

[0013] According to a preferred embodiment of the present invention, step (1) requires 30-90 ml of deionized water to dissolve the mixture of 1 mmol bismuth pentahydrate and 1 mmol bromine and iodine sources.

[0014] According to a preferred embodiment of the present invention, the bromine source in step (1) is sodium bromide, potassium bromide or calcium bromide.

[0015] According to a preferred embodiment of the present invention, the iodine source in step (1) is sodium iodide, potassium iodide or calcium iodide.

[0016] According to a preferred embodiment of the present invention, the molar ratio of iodine to bromine and iodine in the iodine source in step (1) is 1~8:100.

[0017] According to a preferred embodiment of the present invention, the magnetic stirring time in step (1) is 30~65 min.

[0018] According to a preferred embodiment of the present invention, the hydrothermal reaction temperature in step (2) is 135-165℃ and the hydrothermal reaction time is 4-12 h.

[0019] According to a preferred embodiment of the present invention, the detergent in step (3) is anhydrous ethanol or acetone; the optimal volume ratio of anhydrous ethanol or acetone to deionized water in the mixed solvent is 5:1, the centrifugation time is 8 min, and the rotation speed is 11000 r / min.

[0020] According to the present invention, the application of the above-mentioned visible light responsive photochromic iodine-doped bismuth oxybromide catalyst is as follows:

[0021] More preferably, the visible light responsive photochromic iodine-doped bismuth oxybromide catalyst can be used in fields such as photocatalysis and carbon dioxide reduction.

[0022] The technical features and beneficial effects of this invention are as follows:

[0023] 1. The hydrothermal reaction used in this invention has a simple process flow, uses deionized water as a solvent which is inexpensive and has a low cost; no toxic or harmful gases are generated during the synthesis process, which is beneficial to environmental protection and large-scale industrial production.

[0024] 2. The visible-light-responsive photochromic iodine-doped bismuth oxybromide catalyst prepared in this invention has a size of 17-65 nm, which is small, allows for good dispersion in water, high purity, simple structure, and good stability. Furthermore, the iodine-doped bismuth oxybromide photochromic catalyst exhibits clear and distinct coloration after 15 seconds of 450 nm light irradiation. Compared to ultraviolet light, visible light is not only less harmful to organisms and has lower energy, but also has significant advantages such as being less likely to cause side reactions and photodegradation within the color-changing system. The developed visible-light-responsive photochromic iodine-doped bismuth oxybromide catalyst is used for the selective oxidation of C(sp) of ethylbenzene. 3 Bi )-H. Photochromic effect induced by Bi 3+ / Bi (3-δ) + It can serve as an electron trapping center to capture and store photogenerated electrons, thereby enhancing the separation and transfer efficiency of charge carriers.

[0025] In the selective photocatalytic oxidation of ethylbenzene using a visible-light-responsive photochromic iodine-doped bismuth oxybromide catalyst, the C(sp) of the valence band holes in the semiconductor oxidizes ethylbenzene. 3 The formation of a benzyl radical from )-H is a key step in the reaction. Furthermore, BiOBr... 1-x I x Nanosheets possess abundant oxygen vacancies, which facilitate the absorption and activation of O2 by photogenerated electrons and oxygen vacancies. The interaction between O2 and photogenerated electrons generates superoxide radicals (O2-). ∙ ⁻). O2 ∙ ⁻ Benzyl radicals are oxidized to peroxy radicals, which then undergo dehydration to produce the target product, acetophenone. Iodine doping optimizes BiOBr... 1-x I xThe band structure of the nanosheets enriches the generation of oxygen vacancies, resulting in significant photochromic behavior under 450 nm light irradiation, thus enabling BiOBr... 0.98 I 0.02 The photocatalytic oxidation of ethylbenzene using nanosheets achieved a high conversion number (TON) of 274,000 µmol·g⁻¹, which is seven times that of BiOBr nanosheets. This work paves the way for the design of activated and oxidized C(sp) ethylbenzene nanosheets by modulating the photochromic effect. 3 The catalysts of )-H provide a new strategy.

[0026] 3. The present invention utilizes photocatalytic oxidation of C(sp) of hydrocarbons. 3 The photocatalytic conversion of ethylbenzene to acetophenone (H₂O) yields high-value chemical or pharmaceutical intermediates, including aldehydes, ketones, and epoxides, which are crucial in the chemical industry and organic synthesis. This study provides an efficient and promising method for the photocatalytic production of acetophenone from ethylbenzene. Attached Figure Description

[0027] Figure 1 It is BiOBr 1-x I x X-ray diffraction (XRD) pattern of nanosheets.

[0028] Figure 2 BiOBr prepared in the examples 0.98 I 0.02 TEM image of nanosheets.

[0029] Figure 3 a, b, and c are BiOBr 1-x I x High-resolution XPS spectra of I 3d, Br 3d, and O 1s; Figure 3 d represents the BiOBr prepared in the example. 1-x I x ESR spectra before and after illumination.

[0030] Figure 4 Photograph of the visible light responsive iodine-doped bismuth oxybromotriene photochromic material powder prepared for the example.

[0031] Figure 5 The UV-vis spectra of BiOBr powder during (a) the coloring process under 450 nm light and (b) the fading process in ambient air are shown, where the horizontal axis represents wavelength and the vertical axis represents absorbance.

[0032] Figure 6 For BiOBr 0.99 I 0.01UV-vis spectra of powder during (a) coloring process under 450 nm light and (b) fading process in ambient air, where the horizontal axis represents wavelength and the vertical axis represents absorbance.

[0033] Figure 7 For BiOBr 0.98 I 0.02 UV-vis spectra of powder during (a) coloring process under 450 nm light and (b) fading process in ambient air, where the horizontal axis represents wavelength and the vertical axis represents absorbance.

[0034] Figure 8 For BiOBr 0.96 I 0.04 UV-vis spectra of powder during (a) coloring process under 450 nm light and (b) fading process in ambient air, where the horizontal axis represents wavelength and the vertical axis represents absorbance.

[0035] Figure 9 For BiOBr 0.92 I 0.08 The UV-vis spectra of the powder during the coloring process under (a) 450 nm light and (b) fading process in ambient air, where the horizontal axis represents wavelength and the vertical axis represents absorbance.

[0036] Figure 10 a is different from BiOBr 1-x I x The TON and photochromic properties of ethylbenzene converted to acetophenone under the action of a catalyst; Figure 10 b is the BiOBr prepared in the example. 0.98 I 0.02 The change of TON of ethylbenzene with light irradiation time under the action of nanosheet catalyst; Figure 10 c is the free radical capture experiment of the example under standard conditions; Figure 10 d is BiOBr and BiOBr 0.98 I 0.02 ESR diagram of nanosheets under 450 nm light irradiation in the presence of O2 and DMPO, where the horizontal axis represents magnetic field strength and the vertical axis represents signal strength.

[0037] Figure 11 In the example of BiOBr 0.98 I 0.02 Mechanism study of photocatalytic oxidation of ethylbenzene using nanosheets. Detailed Implementation

[0038] The present invention will be further described below with reference to specific embodiments and accompanying drawings, but is not limited thereto.

[0039] In addition, the experimental methods described in the following embodiments are conventional methods unless otherwise specified; the reagents and materials described are commercially available unless otherwise specified.

[0040] Example

[0041] Synthesis of a visible light-responsive photochromic iodine-doped bismuth oxybromide catalyst: The catalyst is prepared by a hydrothermal method, including the following steps:

[0042] (1) Mixing and stirring: Dissolve 0.6 g mannitol in 30 mL of deionized water, then add 0.6 g polyvinylpyrrolidone (K30), stir for 15 min, then add 0.485 g bismuth nitrate pentahydrate, continue stirring until bismuth nitrate pentahydrate is completely dissolved, then slowly add 4.90 mL of 0.2 mol / L sodium bromide aqueous solution and 0.10 mL of sodium iodide aqueous solution dropwise, sonicate to mix, and then magnetically stir for 40 min to obtain a mixed solution;

[0043] (2) Hydrothermal reaction: The mixed solution obtained in step (1) is placed in a 50 mL polytetrafluoroethylene reactor and reacted at 160 °C for 6 h. After the reaction is completed, the solution is naturally cooled to room temperature to obtain the reaction solution.

[0044] (3) Washing and centrifugation: Filter the reaction solution obtained in step (2), and wash the precipitate by alternating centrifugation with water and acetone 3 times (the volume ratio of reaction solution to acetone is 1:5) to obtain the visible light responsive iodine-doped bismuth oxybromide photochromic material.

[0045] (4) Photocatalytic reaction: 3 mL of ethylbenzene and 10 mg of photocatalyst were added to the photocatalytic reaction tube. Before irradiation, the resulting mixture was stirred evenly. Then, under oxygen conditions, the mixture was irradiated at room temperature with a 450 nm LED lamp (100 W) for 15 h. Finally, the reaction product acetophenone was obtained.

[0046] The XRD pattern of the visible-light-responsive photochromic iodine-doped bismuth oxybromide catalyst prepared in this embodiment, as measured by X-ray diffraction, is shown below. Figure 1 As shown, it conforms to the tetragonal phase structure of BiOBr. No BiOI peak was observed, possibly due to the low I content. For comparison, BiOBr with I / Bi precursor ratios of 0%, 1%, 4%, and 8%... 1-x I x Nanosheets and BiOBr 0.98 I 0.02 The tetragonal phase of the nanosheets is consistent with that of typical samples.

[0047] BiOBr 0.98 I 0.02 Transmission electron microscopy images of nanosheets as follows Figure 2As shown in figure a, its size is 17-65 nm. Figure 2 b shows that the thickness of the nanosheets is 2.7-4.1 nm, confirming the ultrathin structure of the nanosheets.

[0048] I 3d spectrum ( Figure 3 a) The peak values ​​for I3d3 / 2 and I3d5 / 2 are 630.09 eV and 618.60 eV, respectively, and the intensity increases with increasing iodine doping level. With increasing iodine doping concentration, in BiOBr... 1-x I x The slight shift in the BrXPS peak observed in the nanosheets is likely due to the interaction between different halogen atoms. Figure 3 b). O 1s spectrum ( Figure 3 c) shows that the peaks at 529.60, 530.98, and 532.33 eV belong to Bi-O bonds, oxygen atoms surrounding oxygen vacancies, and adsorbed oxygen (such as hydroxyl groups or O2 molecules), respectively. The results indicate that BiOBr and BiOBr... 0.99 I 0.01 BiOBr 0.98 I 0.02 BiOBr 0.96 I 0.04 and BiOBr 0.92 I 0.08 The oxygen vacancy peak area ratios of the nanosheets were 48.31%, 55.24%, 59%, 60.97%, and 62.23%, respectively. With increasing iodine content, the prominence of the O 1s peak associated with oxygen vacancies increased, indicating that iodine doping promoted the formation of these vacancies. Figure 3 The ESR test of d further proves BiOBr 0.92 I 0.08 Oxygen vacancies exist within the nanosheets, and the number of oxygen vacancies increases after light exposure. Oxygen vacancies are beneficial to BiOBr. 0.92 I 0.08 Improved catalytic performance of nanosheets.

[0049] The color conversion photograph of the visible light-responsive iodine-doped bismuth oxybromide photochromic material powder prepared in this embodiment is shown below. Figure 4 As shown, it can be colored by irradiating with 450 nm light for 15 s, changing from a faded state (light yellow) to a colored state, and macroscopically it appears grayish-black after coloring.

[0050] Prepared BiOBr 0.92 I 0.08 Nanosheets exhibit unique photochromic behavior, BiOBr 1-x I xNanosheets (x = 0, 0.01, 0.02, 0.04, 0.08) rapidly changed color from light yellow to black after 15 seconds of 450nm light illumination. The color initially intensified and then decreased with increasing iodine doping ratio. Among these, BiOBr... 0.92 I 0.08 Nanosheets have the darkest hue. Figure 5-9 ).

[0051] from Figure 10 From this, we can conclude that BiOBr 0.98 I 0.02 The nanosheets achieved a TON of 60776 µmol·g⁻¹ for ethylbenzene within 6 hours, approximately 7 times that of BiOBr. After 15 hours of light irradiation (λ=450 nm), the TON for ethylbenzene reached 274000 µmol·g⁻¹. Figure 10 b). By Figure 10 As can be seen from the CD, this photocatalytic reaction is a free radical reaction, O2 ∙- , h + , e - Benzyl radicals play an important role in this catalytic reaction.

[0052] Based on various characterization and experimental results, BiOBr 0.98 I 0.02 The photochromic effect of nanosheets plays a crucial role in the photocatalytic oxidation of ethylbenzene to acetophenone. The corresponding photocatalytic mechanism is proposed as follows. (BiOBr) 0.98 I 0.02 Nanosheets generate photogenerated electrons and holes when irradiated with blue light. The photogenerated holes activate the C(sp) group of ethylbenzene. 3 )-H generates a benzyl radical. Simultaneously, BiOBr... 0.98 I 0.02 Oxygen vacancies in the nanosheets serve as active sites for O2 adsorption, promoting O2 activation and formation through oxygen vacancies and photochromism. •- The final product is acetophenone ( Figure 11 ).

[0053] It can be concluded that BiOBr 0.98 I 0.02 The improved catalytic performance of nanosheets is due to the fact that the solid solution formed by trace amounts of iodine doping broadens the absorption of visible light and increases oxygen vacancies. The resulting photochromic effect acts as an electron-capturing center to capture photogenerated electrons, thereby enhancing the separation efficiency of photogenerated charges.

[0054] Comparative Example 1

[0055] The synthesis of a visible light responsive photochromic iodine-doped bismuth oxybromide catalyst, as described in Example 1, involved preparing undoped BiOBr nanosheets by changing the molar amounts of sodium bromide and sodium iodide under the same conditions.

[0056] Comparative Example 2

[0057] The synthesis of a visible-light-responsive photochromic iodine-doped bismuth oxybromide catalyst was carried out as described in Example 1. Under the same conditions, the molar amounts of sodium bromide and sodium iodide were changed to prepare a BiOBr catalyst with an I / Bi precursor ratio of 1%. 0.99 I 0.01 Nanosheets.

[0058] Comparative Example 3

[0059] The synthesis of a visible-light-responsive photochromic iodine-doped bismuth oxybromide catalyst was carried out as described in Example 1. Under the same conditions, the molar amounts of sodium bromide and sodium iodide were changed to prepare a BiOBr catalyst with an I / Bi precursor ratio of 4%. 0.96 I 0.04 Nanosheets.

[0060] Comparative Example 4

[0061] The synthesis of a visible-light-responsive photochromic iodine-doped bismuth oxybromide catalyst was carried out as described in Example 1. Under the same conditions, the molar amounts of sodium bromide and sodium iodide were varied to prepare a BiOBr catalyst with an I / Bi precursor ratio of 8%. 0.92 I 0.08 Nanosheets.

[0062] A comparison of Comparative Examples 1, 2, 3, 4 and Examples shows that the TON value first increases and then decreases with increasing iodine doping ratio, where BiOBr... 0.98 I 0.02 The nanosheets exhibited the highest acetophenone yield (274,000 µmol·g⁻¹), which is 7 times that of undoped BiOBr nanosheets. Furthermore, the photochromic effect and the TON value showed the same trend.

Claims

1. A visible-light-responsive photochromic iodine-doped bismuth oxybromide catalyst and its application in the photocatalytic oxidation of ethylbenzene to acetophenone, characterized in that, The steps include the following: (1) Mixing and stirring: Add surfactant and bismuth nitrate pentahydrate to water, stir evenly, then add a mixture containing a certain proportion of bromine source and iodine source, dissolve by strong ultrasound, and then stir evenly by magnetic force to obtain a mixed solution; (2) Hydrothermal reaction: The mixed solution obtained in step (1) is reacted at 125-165 °C for 3-12 h to obtain the reaction solution; (3) Washing and centrifugation: The reaction solution obtained in step (2) is washed and centrifuged several times to obtain visible light responsive iodine-doped bismuth oxybromide nanoparticles. (4) Photocatalytic reaction: 3 mL of ethylbenzene, 10 mg of photocatalyst, and a magnetic magnet were added to the photocatalytic reaction tube. Then, the mixture was irradiated with a 450 nm LED lamp (100 W) at room temperature for 15 h under oxygen conditions. After the reaction, acetophenone was obtained by centrifugation and rotary evaporation.

2. The preparation method of a visible light responsive iodine-doped bismuth oxybromophotochromic material according to claim 1, characterized in that, In step (1), the surfactants are polyvinylpyrrolidone (K30) and mannitol; the mass ratio of polyvinylpyrrolidone to bismuth source is 0.6~2:

1. The mass ratio of mannitol to bismuth source is 1~2:

1.

3. The preparation method of a visible light responsive iodine-doped bismuth oxybromophotochromic material according to claim 1, characterized in that, In step (1), for a mixture of 1 millimole of bismuth nitrate pentahydrate and 1 millimole of bromine and iodine sources, 30-90 ml of deionized water is required for dissolution.

4. The preparation method of a visible light responsive iodine-doped bismuth oxybromide photochromic material according to claim 1, characterized in that, In step (1), the bromine source is sodium bromide, potassium bromide, or calcium bromide.

5. The preparation of a visible light-responsive iodine-doped bismuth oxybromide photochromic material according to claim 1, characterized in that, In step (1), the iodine source is sodium iodide, potassium iodide, or calcium iodide.

6. The preparation method of a visible light responsive iodine-doped bismuth oxybromophotochromic material according to claim 1, characterized in that, In step (1), the molar ratio of iodine to bromine and iodine in the iodine source is 1~4:

100.

7. The preparation of a visible light-responsive iodine-doped bismuth oxybromide photochromic material according to claim 1, characterized in that, The magnetic stirring time in step (1) is 30~65 min.

8. The preparation of a visible light-responsive iodine-doped bismuth oxybromide photochromic material according to claim 1, characterized in that, In step (2), the hydrothermal reaction temperature is 135-165 ℃ and the hydrothermal reaction time is 4-12 h.

9. The preparation of a visible light-responsive iodine-doped bismuth oxybromophotochromic material according to claim 1, characterized in that, In step (3), the detergent is anhydrous ethanol or acetone; the optimal volume ratio of anhydrous ethanol or acetone to deionized water in the mixed solvent is 5:1, the centrifugation time is 8 min, and the rotation speed is 11000 r / min.

10. The application of the visible light-responsive iodine-doped bismuth oxybromide photochromic material according to claim 1, characterized in that, With BiOBr 1-x I x The enhanced photochromic properties of nanosheets, improved carrier separation efficiency, and significantly enhanced photooxidation activity of CH bonds reveal a positive correlation between photochromism and photocatalytic performance.

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