Thiophenebenzimidazole / titanium oxide heterojunction photocatalyst and its preparation method and application

Abstract

The present invention discloses a thiophene benzimidazole / titanium oxide heterojunction photocatalyst and its preparation method and application. First, using 2,5-thiophenedicarboxaldehyde and p-fluoro-o-phenylenediamine as raw materials, a benzimidazole ring-closing reaction is carried out under the synergistic oxidation of hydrogen peroxide and ammonium cerium nitrate, and then reacted with hexyl bromide to generate a compound thiophene benzimidazole (TBM-F), the molecular structure of which is shown in Formula 1. Then, the compound TBM-F and titanium oxide (TiO2) are prepared by ultrasonic impregnation according to different mass ratios to obtain a heterojunction photocatalyst. After TBM-F and TiO2 are combined, the spectral absorption range of the catalyst is expanded and the light energy utilization efficiency of the photocatalyst is improved. At the same time, the construction of the heterojunction can quickly transfer photogenerated carriers and hinder the recombination of photogenerated electrons and holes. When the mass ratio of TBM-F and TiO2 is 1:2, the photocatalytic degradation efficiency of phenol can reach up to 32.82%, which is more than doubled compared to the efficiency of a single TiO2 catalyst under the same conditions. #imgabs0#

Description

Technical Field

[0001] The present invention belongs to the field of photocatalysts, and in particular relates to a thiophenebenzimidazole / titanium oxide heterojunction photocatalyst and a preparation method and application thereof. Background Art

[0002] Photocatalysis can directly utilize sunlight as an energy source, and its reaction conditions are relatively mild, making it considered a green and sustainable technology. Semiconductor materials, such as metal oxides like titanium oxide, are the most common solar photocatalysts. However, due to their wide band gaps, most reported semiconductor photocatalysts are only active in the ultraviolet region, leaving 43% of solar energy in the visible light region unusable. Therefore, there is an urgent need to expand the light absorption wavelength range of catalysts and increase solar energy utilization. At the same time, current photocatalytic applications still face challenges such as the easy recombination of photogenerated electrons and holes, difficulty in regulating redox activity, and poor stability, which seriously restrict the application of photocatalytic technology. Heterojunction construction has been proven to be one of the most promising approaches for preparing advanced photocatalysts, as it is feasible and effective for electron-hole pair separation, while also improving the material's visible light absorption properties and regulating its band gap.

[0003] Small molecule organic conjugated compounds have good absorption in the visible light region, and the energy band position of the compound can be adjusted through molecular design. Therefore, constructing a heterojunction photocatalytic structure with titanium oxide can optimize the photocatalyst's light energy utilization efficiency, regulate the redox ability of the photogenerated electrons and holes, quickly transfer the photogenerated electrons, and hinder the recombination of the photogenerated electrons and holes, thereby improving the photocatalytic efficiency. Summary of the Invention

[0004] One of the purposes of the present invention is to provide a method for preparing a thiophenebenzimidazole / titanium oxide heterojunction photocatalyst.

[0005] The second object of the present invention is to provide a thiophenebenzimidazole / titanium oxide heterojunction photocatalyst prepared by the above preparation method.

[0006] The third object of the present invention is to provide the application of the above-mentioned thiophenebenzimidazole / titanium oxide heterojunction photocatalyst in the degradation of phenol.

[0007] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] In a first aspect, the present invention provides a method for preparing a thiophenebenzimidazole / titanium oxide heterojunction photocatalyst, comprising the following steps:

[0009] S1: Synthesis of small molecule organic conjugated compound thiophene benzimidazole (TBM-F):

[0010] The reactants 2,5-thiophenedicarboxaldehyde and 4-fluoro-o-phenylenediamine were first dissolved in acetonitrile at a ratio of 1:2.2 and stirred to dissolve. The mixture was then heated to 60°C and maintained for 30-50 minutes. An acetonitrile solution containing 30% hydrogen peroxide and ceric ammonium nitrate was then slowly added, and the mixture was allowed to react under reflux for 4-5 hours. The precipitate was collected, dried, and added to dimethyl sulfoxide. The mixture was heated and stirred until the solution became clear, and sodium hydride was slowly added in batches. The mixture was heated continuously and maintained at 70°C for 30-50 minutes. Hexyl bromide was dissolved in dimethyl sulfoxide and slowly added to the reaction system. The mixture was heated to 90°C and stirred for 3-4 hours. After the reaction was completed, the mixture was cooled and filtered, and the filtrate was purified to obtain the final product TBM-F.

[0011] S2: Preparation of TBM-F / TiO2 heterojunction photocatalyst:

[0012] The organic matter TBM-F and TiO2 are mixed in an anhydrous ethanol solution in a certain mass ratio, and then ultrasonically reacted for 20 minutes. The solution is then evaporated to dryness and placed in an oven at 80-90°C for 20-30 minutes to obtain a TBM-F / TiO2 heterojunction photocatalyst.

[0013] Preferably, the filtrate purification step comprises extracting with dichloromethane, washing with saturated brine, and drying over anhydrous magnesium sulfate; after further filtration, the filtrate is transferred to a rotary evaporator, an appropriate amount of silica gel is added, and rotary evaporation is performed. The silica gel is then scraped off, placed in a crucible to dry, and separated and purified by column chromatography.

[0014] Preferably, the eluent used for column chromatography purification is a mixed solvent of n-hexane and ethyl acetate in a volume ratio of 10:1.

[0015] Preferably, the mass ratio of TBM-F to TiO2 in step S2 is 1:1-8.

[0016] More preferably, the mass ratio of TBM-F to TiO2 in step S2 is 1:2.

[0017] In a second aspect, the present invention provides a thiophenebenzimidazole / titanium oxide heterojunction photocatalyst prepared by the above preparation method.

[0018] In a third aspect, the present invention provides the above-mentioned thiophenebenzimidazole / titanium oxide heterojunction photocatalyst for photocatalytic degradation of phenol in wastewater.

[0019] Compared to existing technologies, the conjugated organic small molecule TBM-F prepared in this invention absorbs light in the visible range. When combined with TiO2, this expands the catalyst's spectral absorption range and improves the photocatalyst's light energy utilization efficiency. Furthermore, the heterojunction structure rapidly transfers photogenerated charge carriers, hindering the recombination of photogenerated electrons and holes, thereby enhancing photocatalytic efficiency. After six hours of illumination, this TBM-F / TiO2 heterojunction photocatalyst achieved a maximum phenol degradation rate of 32.82%, more than doubling the photocatalytic efficiency compared to TiO2 alone. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is the SEM image of TBM-F / TiO2 heterojunction photocatalyst.

[0021] Figure 2 Visible light absorption spectra of TiO2 and TBM-F / TiO2.

[0022] Figure 3 Fluorescence spectra of TiO2 and TBM-F / TiO2.

[0023] Figure 4 This is the efficiency diagram of photocatalytic degradation of phenol under different TBM-F / TiO2 ratios. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present invention are clearly and completely described below with reference to the accompanying drawings and specific embodiments, but are not limited thereto.

[0025] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available products with a purity of analytical grade or higher.

[0026] Example 1: Synthesis of CO fluorescent probe molecules

[0027] S1: Synthesis of small molecule organic conjugated compound thiophene benzimidazole (TBM-F):

[0028] The reactants, 2,5-thiophenedicarboxaldehyde (1 mmol, 0.134 g) and 4-fluoro-o-phenylenediamine (2.2 mmol, 0.237 g), were dissolved in acetonitrile at a ratio of 1:2.2 and stirred until dissolved. The mixture was heated to 60°C and held for 30 minutes. A 30% hydrogen peroxide solution (4 mmol, 4 mL) and cerium ammonium nitrate (1 mmol, 0.548 g) in acetonitrile were then slowly added and allowed to react under reflux for 4 hours. The resulting precipitate was filtered, air-dried, and poured into a round-bottom flask. Dimethyl sulfoxide (DMSO) was added and heated with stirring. Once the solution became clear, 0.49 g (10 mmol) of sodium hydride was slowly added in portions. Heating was continued, maintaining the temperature at 70°C for 30 minutes. 0.33 g (2 mmol) of bromohexane was dissolved in 10 mL of DMSO and slowly added to the round-bottom flask. The temperature was raised to 90°C and stirred for 3 hours. After the reaction is complete, cool and filter. The filtrate is extracted with dichloromethane, washed with saturated brine, and dried over anhydrous magnesium sulfate. After further filtration, the filtrate is transferred to a rotary evaporator, an appropriate amount of silica gel is added, and rotary evaporation is performed. The silica gel is then scraped off and placed in a crucible to dry. Separate and purify the product using column chromatography, using a 10:1 v / v mixture of n-hexane and ethyl acetate as the eluent. This yields the final product, TBM-F.

[0029] The reaction route is as follows:

[0030]

[0031] Its structural characterization data are as follows:

[0032] H NMR spectrum: 1 H NMR (600MHz, Chloroform-d): δ7.70(s,2H),7.50(dd,J=9.2,2.4Hz,1H),7.35-7.32(m,1H),7.11(td,J=9.2,2.4Hz,2H),4.42(d t,J=24.0,7.8Hz,4H),1.94(qd,J=9.1,8.5,6.5Hz,4H),1.48-1.41(m,4H),1.40-1.27(m,9H),0.90(td,J=5.9,4.9,3.3Hz,6H);

[0033] Infrared spectrum: IR:KBr, (cm -1 ):2980(aromatic ring CH), 1698(C=N), 1390(CN), 1003(CF).

[0034] S2: Preparation of TBM-F / TiO2 heterojunction photocatalyst:

[0035] The organic matter TBM-F and TiO2 were weighed in a mass ratio of 1:2, mixed in anhydrous ethanol solution, and then ultrasonically reacted for 20 minutes. The solution was then placed in a rotary evaporator, the solvent was dried, and then placed in an oven at 80°C for 20 minutes to obtain a TBM-F / TiO2 heterojunction photocatalyst. The SEM morphology of the catalyst is shown in Figure 2. Figure 1 shown.

[0036] Figure 2 The visible light absorption spectra of TiO2 and TBM-F / TiO2 are shown in Figure 2. It can be seen that the organic TBM-F absorbs in the visible light range. After compounding with TiO2, it expands the spectral absorption range of the catalyst and improves the light energy utilization efficiency of the photocatalyst.

[0037] Figure 3 The fluorescence spectra of TiO2 and TBM-F / TiO2 are shown below. As can be seen, after the TiO2 and TBM-F recombine, the fluorescence intensity decreases, indicating that photogenerated carriers are transferred from TiO2 to TBM-F. Therefore, this TBM-F / TiO2 heterojunction catalyst can rapidly transfer photogenerated electron carriers, hindering the recombination of photogenerated electrons and holes, thereby improving photocatalytic efficiency.

[0038] The heterojunction photocatalyst was transferred to a 50mL photoreactor tube, into which a certain amount of calibrated phenol solution was added for photocatalytic degradation of phenol. After 6 hours of illumination under a 500W xenon lamp, the phenol degradation rate reached 32.82%, which is twice the photocatalytic efficiency of TiO2 alone and three times that of TBM-F alone. Figure 4 shown.

[0039] Example 2

[0040] Different from Example 1, the mass ratio of TBM-F to TiO2 is 1:1, and the degradation rate of phenol is 21.44%.

[0041] Example 3

[0042] Different from Example 1, the mass ratio of TBM-F to TiO2 is 1:4, and the degradation rate of phenol is 31.62%.

[0043] Example 4

[0044] Different from Example 1, the mass ratio of TBM-F to TiO2 is 1:6, and the degradation rate of phenol is 20.20%.

[0045] Example 5

[0046] Different from Example 1, the mass ratio of TBM-F to TiO2 is 1:8, and the degradation rate of phenol is 18.15%.

[0047] The above description is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with this technical field within the technical scope disclosed by the present invention and within the spirit and principles of the present invention should be covered by the scope of protection of the present invention.

Claims

1. A method for preparing a thiophenebenzimidazole / titanium oxide heterojunction photocatalyst, characterized in that: Here are the steps: S1: Synthesis of small molecule organic conjugated compound thiophenebenzimidazole TBM-F: The reactants, 2,5-thiophenedicarboxaldehyde and 4-fluoro-o-phenylenediamine, were first dissolved in acetonitrile at a molar ratio of 1:2.2 and stirred to dissolve. The mixture was then heated to 60°C and maintained for 30-50 minutes. An acetonitrile solution containing 30% hydrogen peroxide and ceric ammonium nitrate was then slowly added, and the mixture was allowed to react under reflux for 4-5 hours. The precipitate was collected, dried, and added to dimethyl sulfoxide. The mixture was heated and stirred until the solution became clear, and sodium hydride was slowly added in batches. The mixture was heated continuously and maintained at 70°C for 30-50 minutes. Hexyl bromide was dissolved in dimethyl sulfoxide and slowly added to the reaction system. The temperature was raised to 90°C and stirred for 3-4 hours. After the reaction was completed, the mixture was cooled and filtered, and the filtrate was purified to obtain the final product, TBM-F. S2: Preparation of TBM-F / TiO2 heterojunction photocatalyst: The organic matter TBM-F and TiO2 are mixed in an anhydrous ethanol solution in a certain mass ratio, and then ultrasonically reacted for 20 minutes. The solution is then evaporated to dryness and placed in an oven at 80-90°C for 20-30 minutes to obtain a TBM-F / TiO2 heterojunction photocatalyst.

2. The method for preparing a thiophenebenzimidazole / titanium oxide heterojunction photocatalyst according to claim 1, characterized in that: The filtrate purification steps include extracting with dichloromethane, washing with saturated brine, and drying with anhydrous magnesium sulfate; after filtering again, transferring the filtrate to a rotary evaporator, adding an appropriate amount of silica gel, and performing rotary evaporation; then scraping off the silica gel, placing it in a crucible to dry, and separating and purifying it by column chromatography.

3. The method for preparing a thiophenebenzimidazole / titanium oxide heterojunction photocatalyst according to claim 2, characterized in that: The eluent used for column chromatography purification was a mixed solvent of n-hexane and ethyl acetate in a volume ratio of 10:

1.

4. The method for preparing a thiophenebenzimidazole / titanium oxide heterojunction photocatalyst according to claim 1, characterized in that: The mass ratio of TBM-F to TiO2 in step S2 is 1:1-8.

5. The method for preparing a thiophenebenzimidazole / titanium oxide heterojunction photocatalyst according to claim 4, characterized in that: The mass ratio of TBM-F to TiO2 in step S2 is 1:

2.

6. A thiophenebenzimidazole / titanium oxide heterojunction photocatalyst, characterized in that: Prepared according to the preparation method according to any one of claims 1 to 5.

7. The thiophenebenzimidazole / titanium oxide heterojunction photocatalyst according to claim 6 is used for photocatalytic degradation of phenol in wastewater.

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