TiO2-mof photocatalyst and preparation method and application thereof

Abstract

The application relates to the technical field of photocatalysts, in particular to a TiO2-MOFs photocatalyst and a preparation method and application thereof, and comprises the following steps: adding TiO2 nanoparticles into deionized water to obtain a solution A through dispersion, adding modified MIL-88A / GO into the solution A to obtain a mixed solution, stirring the mixed solution, washing the mixed solution through centrifugal separation of ethanol and deionized water alternately, and freeze-drying to obtain a modified TiO2-MOFs photocatalyst. Through the compounding of the TiO2 nanoparticles and the modified MIL-88A / GO, the adsorption-catalysis synergistic effect is realized, the modified MIL-88A / GO material has the characteristics of high specific surface area, porosity and controllable pore size, can efficiently adsorb pollutants in organic wastewater, provides a high-concentration reaction environment for the photocatalytic reaction of the TiO2 nanoparticles, and the electron-hole pairs generated under the excitation of photons of the TiO2 nanoparticles as the efficient photocatalyst can quickly oxidize and degrade the adsorbed pollutants.

Description

Technical Field

[0001] This invention relates to the field of photocatalyst technology, specifically to TiO2-MOFs photocatalysts, their preparation methods, and applications. Background Technology

[0002] With the rapid development of science and technology, the discharge of industrial wastewater is increasing, and the composition of toxic and harmful substances in water bodies is complex, making water treatment increasingly difficult. Photocatalysis technology, with its advantages of strong oxidation and low energy consumption, has shown high efficiency in the oxidative degradation of toxic and harmful substances. In recent years, significant progress has been made in the research of photocatalysis technology. When a semiconductor is excited by photons with energy equal to or greater than the band gap, electrons transfer from the valence band to the conduction band and form holes. If recombination does not occur, the electrons and holes that migrate to the semiconductor surface will reduce / oxidize the adsorbed substrate. Metal-organic frameworks (MOFs) are porous network structures with central metal ions as nodes and organic ligands as components. MOF materials have diverse morphologies and structures, and the pore size can be controlled and adjusted. They have unique physical and chemical properties, and MOFs with various structures are applied in many fields such as catalysis and environmental remediation.

[0003] Catalysts such as pure TiO2 nanoparticles and TiO2 / P25, while possessing strong oxidizing and photocatalytic activities, lack porous structures and exhibit extremely weak adsorption capacity for organic pollutants. In actual industrial wastewater (with low pollutant concentrations and dispersed components), it is difficult to form a high-concentration reaction environment on the TiO2 surface, and photogenerated electron-hole pairs struggle to effectively contact pollutants, resulting in low catalytic degradation efficiency and an inability to meet the demands of deep treatment of low-concentration pollutants. Therefore, addressing the problems described above, this invention proposes a TiO2-MOFs photocatalyst, its preparation method, and its applications. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of this invention is to provide TiO2-MOFs photocatalysts, their preparation methods and applications, so as to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] The preparation method of TiO2-MOFs photocatalyst includes the following steps:

[0007] S1. The coordinating precursor solution was reacted at 60-80℃ for 10-12h, and after being washed alternately by centrifugation with ethanol and deionized water and dried, the modified MIL-88A / GO was obtained.

[0008] S2. Add TiO2 nanoparticles to deionized water and disperse for 1-3 hours to obtain solution A. Add modified MIL-88A / GO to solution A to obtain a mixed solution.

[0009] S3. Stir the mixed solution for 2-4 hours, wash it alternately with ethanol and deionized water by centrifugation and dry it to obtain the modified TiO2-MOFs photocatalyst.

[0010] The coordinating precursor solution is prepared through the following steps:

[0011] S11. At 0-5℃, expandable graphite is added to the modified mixed acid, and then potassium permanganate is added to mix and obtain a reaction system. The reaction system is stirred for 10-12h and then hydrogen peroxide is added to obtain a suspension. The suspension is stirred for 2-4h, and then centrifuged and washed with deionized water until the pH of the supernatant is 6-7. The precipitate is collected and dried to obtain modified GO.

[0012] S12. Mix ferric chloride hexahydrate, fumaric acid, and terephthalic acid in a certain proportion, add them to deionized water to prepare precursor solution A, add the modified GO prepared in S11 to precursor solution A, and ultrasonically disperse for 20-30 min to obtain a synergistic coordination precursor solution.

[0013] Furthermore, the TiO2 nanoparticles are prepared through the following steps:

[0014] S21. Dissolve titanium isopropoxide in anhydrous ethanol and stir for 20-30 min until completely dissolved to obtain solution B. Add tetrabutyl titanate coupling agent to solution B and continue stirring for 15 min. Add octylamine and stir evenly to obtain precursor solution B.

[0015] S22. Precursor solution B is refluxed at 60-70℃ for 16-20h to obtain modified precursor solution. The modified precursor solution is filtered and dried at 50-70℃ for 2-4h to obtain modified precursor particles. The modified precursor particles are calcined in the atmosphere at 300-600℃ for 2-4h to obtain TiO2 nanoparticles.

[0016] Furthermore, the modified mixed acid is prepared by the following steps:

[0017] Concentrated sulfuric acid and concentrated phosphoric acid are mixed to form a mixed acid. Aminosulfonic acid is added to the mixed acid and stirred at 0-3℃ for 10-20 minutes until the aminosulfonic acid is completely dissolved to obtain an aminated modified mixed acid. The mass ratio of concentrated sulfuric acid, concentrated phosphoric acid and aminosulfonic acid is (9-11):1:(2-4).

[0018] Furthermore, in step S2, the mass ratio of TiO2 nanoparticles to deionized water is 1:(90-110), and the mass ratio of TiO2 nanoparticles to modified MIL-88A / GO is 1:(1-3).

[0019] Furthermore, in step S11, the mass ratio of expandable graphite to modified mixed acid is 1:(214-288), the mass ratio of potassium permanganate to expandable graphite is (6-7):1, and the mass ratio of hydrogen peroxide to potassium permanganate is (1.5-2.2):1.

[0020] Furthermore, in step S12, the mass ratio of ferric chloride hexahydrate, fumaric acid, and terephthalic acid is 2:(0.8-1.2):(0.1-0.5), the mass ratio of ferric chloride hexahydrate to deionized water is 1:(28-34), and the mass ratio of ferric chloride hexahydrate to modified GO is (5-8):1.

[0021] Furthermore, in step S21, the mass ratio of titanium isopropoxide to anhydrous ethanol is 1:(8-12), the mass ratio of titanium isopropoxide to tetrabutyl titanate coupling agent is (5-8):1, and the mass ratio of titanium isopropoxide to octylamine is 1:(1-1.2).

[0022] Furthermore, in steps S1 and S3, the mass ratio of ethanol to precipitate is (5-10):1, and the mass ratio of deionized water to precipitate is (5-10):1, with alternating washing 3-4 times.

[0023] Furthermore, a TiO2-MOFs photocatalyst was prepared according to the above preparation method.

[0024] Furthermore, the TiO2-MOFs photocatalyst is applied in the degradation of organic wastewater pollutants.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] 1. This invention achieves a synergistic adsorption-catalysis effect by combining TiO2 nanoparticles with modified MIL-88A / GO. The modified MIL-88A / GO material has the characteristics of high specific surface area, porosity, and controllable pore size, which can efficiently adsorb pollutants in organic wastewater and provide a high-concentration reaction environment for the photocatalytic reaction of TiO2 nanoparticles. As a highly efficient photocatalyst, TiO2 nanoparticles can rapidly oxidize and degrade adsorbed pollutants by generating electron-hole pairs under photon excitation, thus solving the problem of weak adsorption capacity or insufficient catalytic reaction sites of single catalysts.

[0027] 2. This invention uses modified GO added during the preparation process as an electron transfer bridge to effectively suppress the recombination of photogenerated electrons and holes in TiO2 nanoparticles, prolong carrier lifetime, and thus improve catalytic reaction efficiency. Attached Figure Description

[0028] Figure 1This is a schematic diagram of the preparation process of the TiO2-MOFs photocatalyst of the present invention;

[0029] Figure 2 This is a schematic diagram of the preparation process of the synergistic coordination precursor solution of the present invention;

[0030] Figure 3 This is a schematic diagram of the preparation process of TiO2 nanoparticles according to the present invention;

[0031] Figure 4 The XRD phase analysis diagrams of the modified TiO2-MOFs photocatalysts in Examples 1-4 are shown.

[0032] Figure 5 The image shows the XRD phase analysis of the modified TiO2-MOFs photocatalyst in Example 1.

[0033] Figure 6 The image shows the FT-IR spectrum of the modified TiO2-MOFs photocatalyst in Example 1.

[0034] Figure 7 Here is an electron microscope image of the modified GO in Example 1;

[0035] Figure 8 This is an electron microscope image of TiO2 from Example 1;

[0036] Figure 9 The image shown is an electron microscope image of the modified MIL-88A / GO in Example 1.

[0037] Figure 10 This is an electron microscope image of the modified TiO2-MOFs photocatalyst in Example 1. Detailed Implementation

[0038] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0039] Please see Figures 1-10 The present invention provides a technical solution:

[0040] Example 1:

[0041] The preparation method of TiO2-MOFs photocatalyst includes the following steps:

[0042] Measure 36.0g of concentrated sulfuric acid and 4.0g of concentrated phosphoric acid, pour them into a three-necked flask, add 13.33g of aminosulfonic acid, and place in an ice-water bath at 2℃ and stir for 15min until completely dissolved to obtain an amino-modified mixed acid.

[0043] Add 0.2g of expandable graphite to the above modified mixed acid, stir at 3℃ for 15min until uniformly dispersed, add 1.2g of potassium permanganate in batches, control the system temperature ≤10℃, raise the temperature to 35℃ after the addition is complete, stir at constant temperature for 11h, add 1.8g of 30% hydrogen peroxide solution dropwise until no bubbles are generated, continue stirring for 3h to obtain a suspension, centrifuge at 8000r / min for 10min, wash repeatedly with deionized water until the pH of the supernatant is 6.5, collect the precipitate, freeze dry at -50℃ and 10Pa for 24h to obtain modified GO;

[0044] Weigh 2.0 g of ferric chloride hexahydrate, 0.8 g of fumaric acid, and 0.1 g of terephthalic acid, add 56.0 g of deionized water, stir to dissolve, add 0.4 g of the modified GO prepared above, ultrasonically disperse at 300 W for 25 min, and then magnetically stir for 4 h to obtain a co-coordination precursor solution. Transfer the co-coordination precursor solution to a hydrothermal reactor, react at 70 °C for 11 h, cool, wash three times with alternating centrifugation with ethanol and deionized water, and freeze-dry for 24 h to obtain modified MIL-88A / GO.

[0045] Weigh 1.0 g of titanium isopropoxide, dissolve it in 8.0 g of anhydrous ethanol, stir for 25 min until completely dissolved, add 0.2 g of tetrabutyl titanate, stir for 15 min, then add 1.0 g of octylamine, stir until homogeneous to obtain precursor solution B, reflux at 65 °C for 18 h, filter with a 0.22 μm filter membrane, dry the filter residue at 60 °C for 3 h to obtain precursor particles, heat to 450 °C at 2 °C / min, calcine for 3 h, and cool with furnace to obtain TiO2 nanoparticles;

[0046] 0.5 g TiO2 nanoparticles were added to 45.0 g deionized water and ultrasonically dispersed for 2 h to obtain solution A. 0.5 g modified MIL-88A / GO was added and magnetically stirred for 3 h. The solution was washed three times by alternating centrifugation with ethanol and deionized water and then freeze-dried for 24 h to obtain the modified TiO2-MOFs photocatalyst.

[0047] Example 2:

[0048] The preparation method of TiO2-MOFs photocatalyst includes the following steps:

[0049] Measure 40.0g of concentrated sulfuric acid and 4.0g of concentrated phosphoric acid, pour them into a three-necked flask, add 11.0g of aminosulfonic acid, and place in an ice-water bath at 2℃ and stir for 15 minutes until completely dissolved to obtain an amino-modified mixed acid.

[0050] Add 0.2g of expandable graphite to the above modified mixed acid, stir at 3°C ​​for 15min until uniformly dispersed, add 1.3g of potassium permanganate in batches, control the system temperature ≤10°C, raise the temperature to 35°C after the addition is complete, stir at constant temperature for 11h, add 2.34g of 30% hydrogen peroxide solution dropwise until no bubbles are generated, continue stirring for 3h to obtain a suspension, the remaining parameters are the same as in Example 1, and modified GO is obtained;

[0051] Weigh 2.0 g of ferric chloride hexahydrate, 1.0 g of fumaric acid, and 0.3 g of terephthalic acid. Add 62.0 g of deionized water and stir to dissolve. Add 0.308 g of the modified GO prepared above. After ultrasonic dispersion at 300 W for 25 min, stir magnetically for 4 h to obtain a co-coordination precursor solution. Transfer the co-coordination precursor solution to a hydrothermal reactor and react at 70 °C for 11 h. After cooling, wash with alternating centrifugation three times with ethanol and deionized water, and freeze-dry for 24 h to obtain modified MIL-88A / GO.

[0052] Weigh 1.0 g of titanium isopropoxide, dissolve it in 10.0 g of anhydrous ethanol, stir for 25 min until completely dissolved, add 0.154 g of tetrabutyl titanate, stir for 15 min, then add 1.1 g of octylamine, stir until homogeneous to obtain precursor solution B, reflux at 65 °C for 18 h, filter with a 0.22 μm filter membrane, dry the filter residue at 60 °C for 3 h to obtain precursor particles, heat to 450 °C at 2 °C / min, calcine for 3 h, and cool with furnace to obtain TiO2 nanoparticles;

[0053] 0.5 g TiO2 nanoparticles were added to 50.0 g deionized water and ultrasonically dispersed for 2 h to obtain solution A. 1.0 g modified MIL-88A / GO was added, and the mixture was magnetically stirred for 3 h. The mixture was washed three times by alternating centrifugation with ethanol and deionized water, and then freeze-dried for 24 h to obtain the modified TiO2-MOFs photocatalyst.

[0054] Example 3:

[0055] The preparation method of TiO2-MOFs photocatalyst includes the following steps:

[0056] Measure 38.5g of concentrated sulfuric acid and 3.5g of concentrated phosphoric acid, pour them into a three-necked flask, add 11.5g of aminosulfonic acid, and place in a 2℃ ice-water bath and stir for 15 minutes until completely dissolved to obtain an amino-modified mixed acid.

[0057] Add 0.25g of expandable graphite to the above modified mixed acid, stir at 3°C ​​for 15min until uniformly dispersed, add 1.625g of potassium permanganate in batches, control the system temperature ≤10°C, raise the temperature to 35°C after the addition is complete, stir at constant temperature for 11h, add 2.925g of 30% hydrogen peroxide solution dropwise until no bubbles are generated, continue stirring for 3h to obtain a suspension, the remaining parameters are the same as in Example 1, and modified GO is obtained;

[0058] Weigh 3.0 g of ferric chloride hexahydrate, 1.35 g of fumaric acid, and 0.6 g of terephthalic acid. Add 93.0 g of deionized water and stir to dissolve. Add 0.462 g of the modified GO prepared above. After ultrasonic dispersion at 300 W for 25 min, stir magnetically for 4 h to obtain a co-coordination precursor solution. Transfer the co-coordination precursor solution to a hydrothermal reactor and react at 70 °C for 11 h. After cooling, wash three times with alternating centrifugation using ethanol and deionized water, and freeze-dry for 24 h to obtain modified MIL-88A / GO.

[0059] Weigh 1.5g of titanium isopropoxide, dissolve it in 15.0g of anhydrous ethanol, stir for 25min until completely dissolved, add 0.231g of tetrabutyl titanate, stir for 15min, then add 1.65g of octylamine, stir evenly to obtain precursor solution B, reflux at 65℃ for 18h, filter with a 0.22μm filter membrane, dry the filter residue at 60℃ for 3h to obtain precursor particles, heat to 450℃ at 2℃ / min, calcine for 3h, and cool with furnace to obtain TiO2 nanoparticles;

[0060] 0.8 g TiO2 nanoparticles were added to 80.0 g deionized water and ultrasonically dispersed for 2 h to obtain solution A. 1.2 g modified MIL-88A / GO was added, and the mixture was magnetically stirred for 3 h. The mixture was washed three times by alternating centrifugation with ethanol and deionized water, and then freeze-dried for 24 h to obtain the modified TiO2-MOFs photocatalyst.

[0061] Example 4:

[0062] The preparation method of TiO2-MOFs photocatalyst includes the following steps:

[0063] Measure 44.0g of concentrated sulfuric acid and 4.0g of concentrated phosphoric acid, pour them into a three-necked flask, add 9.6g of aminosulfonic acid, and place in a 2℃ ice-water bath and stir for 15 minutes until completely dissolved to obtain an amino-modified mixed acid.

[0064] Add 0.2g of expandable graphite to the above modified mixed acid, stir at 3°C ​​for 15min until uniformly dispersed, add 1.4g of potassium permanganate in batches, control the system temperature ≤10°C, raise the temperature to 35°C after the addition is complete, stir at constant temperature for 11h, add 3.08g of 30% hydrogen peroxide solution dropwise until no bubbles are generated, continue stirring for 3h to obtain a suspension, the remaining parameters are the same as in Example 1, and modified GO is obtained;

[0065] Weigh 2.0 g of ferric chloride hexahydrate, 1.2 g of fumaric acid, and 0.5 g of terephthalic acid. Add 68.0 g of deionized water and stir to dissolve. Add 0.25 g of the modified GO prepared above. After ultrasonic dispersion at 300 W for 25 min, stir magnetically for 4 h to obtain a co-coordination precursor solution. Transfer the co-coordination precursor solution to a hydrothermal reactor and react at 70 °C for 11 h. After cooling, wash three times with alternating centrifugation using ethanol and deionized water, and freeze-dry for 24 h to obtain modified MIL-88A / GO.

[0066] Weigh 1.0 g of titanium isopropoxide, dissolve it in 12.0 g of anhydrous ethanol, stir for 25 min until completely dissolved, add 0.125 g of tetrabutyl titanate, stir for 15 min, then add 1.2 g of octylamine, stir until homogeneous to obtain precursor solution B, reflux at 65 °C for 18 h, filter with a 0.22 μm filter membrane, dry the filter residue at 60 °C for 3 h to obtain precursor particles, heat to 450 °C at 2 °C / min, calcine for 3 h, and cool with furnace to obtain TiO2 nanoparticles;

[0067] 0.5 g TiO2 nanoparticles were added to 55.0 g deionized water and ultrasonically dispersed for 2 h to obtain solution A. 1.5 g modified MIL-88A / GO was added, and the mixture was magnetically stirred for 3 h. The mixture was washed three times by alternating centrifugation with ethanol and deionized water, and then freeze-dried for 24 h to obtain the modified TiO2-MOFs photocatalyst.

[0068] Comparative Example 1

[0069] Comparative Example 1 differs from Example 1 in that the modified MIL-88A / GO catalyst is replaced with TiO2 / P25 catalyst, and the remaining steps are exactly the same as in Example 1.

[0070] Comparative Example 2

[0071] Compared to Example 1, Comparative Example 2 omits the TiO2 nanoparticles, but the remaining steps are exactly the same as in Example 1.

[0072] Comparative Example 3

[0073] Comparative Example 3 differs from Example 1 in that the modified GO is replaced with conventional graphene, and the remaining steps are exactly the same as in Example 1.

[0074] Comparative Example 4

[0075] Comparative Example 4 omits the modified GO compared to Example 1, and the remaining steps are exactly the same as in Example 1.

[0076] Eight different photocatalysts were prepared using Examples 1-4 and Comparative Examples 1-4, respectively. The performance of each of the eight photocatalysts was tested under the following conditions: catalyst dosage 0.1 g / L, reaction system volume 50 mL, and light intensity 100 mW / cm². 2 The pollutant was a 100 mg / L Rhodamine B aqueous solution. The sample was irradiated with visible light for 60 min. The degradation effect of the photocatalyst on the pollutant Rhodamine B was tested, and the specific test results are shown in Table 1 below.

[0077] Table 1

[0078]

[0079] As can be seen from the data in Table 1, the modified TiO2-MOFs photocatalysts prepared in Examples 1-4 have significantly better performance than the comparative examples. Furthermore, the compatibility of the component ratios significantly affects the performance. The degradation rate of Rhodamine B by the modified TiO2-MOFs photocatalysts is generally between 93.5% and 97.9%, while the highest degradation rate of Comparative Examples 1-4 is only 75.3% (Comparative Example 1, 450nm light response), and it is below 70% in most scenarios, especially under long-wavelength light (650nm, 790nm), where the degradation rate of the comparative examples drops sharply to below 35.6%, even as low as 21.3% (Comparative Example 4). The modified TiO2-MOFs photocatalyst of this invention has an absolute advantage in degradation efficiency (790nm). Examples 1-4 consistently maintained a degradation rate above 93% across the entire test wavelength range from 380nm (near-ultraviolet) to 790nm (near-infrared), with minimal fluctuations (e.g., Example 3 showed a degradation rate of 97.9% at 380nm and still 96.5% at 790nm). This indicates that the modified TiO2-MOFs photocatalyst can effectively utilize light of different wavelengths, adapting to various scenarios such as natural light and simulated light sources, thus solving the problem of narrow spectral response range in traditional catalysts. In contrast, the comparative examples showed a much wider range of degradation efficiency at longer wavelengths. The activity of the modified MIL-88A / GO decreased significantly under long-term illumination (650nm, 790nm). For example, the degradation rate of Comparative Example 1 was only 21.5% at 790nm, indicating that it can only respond to short-wavelength light, which limits its practical application. The degradation rates of Comparative Example 1 (replacing modified MIL-88A / GO with TiO2 / P25) and Comparative Example 2 (omitting TiO2 nanoparticles) both decreased significantly, confirming the synergistic mechanism of modified MOF adsorption of pollutants + TiO2 photocatalytic degradation. This solves the problem of weak adsorption or insufficient catalytic sites of single catalysts. The activity of Comparative Example 3 (replacing modified GO with conventional graphene) and Comparative Example 4 (omitting modified GO) also decreased significantly. The degradation rate can be significantly worsened, especially at long wavelengths where deactivation is severe. This indicates that modified GO, as an electron transfer bridge, can effectively suppress electron-hole recombination and broaden the spectral response range. It is a core auxiliary component for improving catalytic efficiency and spectral adaptability. The degradation rates of Examples 2 and 3 (96.2%-97.9%) are slightly higher than those of Examples 1 and 4 (93.5%-95.3%), indicating that there is an optimal range for the proportions of each component during preparation (such as the mass ratio of TiO2 to modified MIL-88A / GO, the ratio of ferric chloride hexahydrate to ligands, and the amount of modified GO added). Reasonable control of the proportions can further improve the degradation efficiency.

[0080] Figure 4The XRD phase analysis spectra of the modified TiO2-MOFs photocatalysts in Examples 1-4 are shown. The diffraction peak positions of the modified TiO2-MOFs photocatalysts in Examples 1-4 are similar, indicating that their crystal structures and interplanar spacings are similar. No additional impurity peaks appeared in any of the spectra, and the baselines were stable, indicating that the modified TiO2-MOFs photocatalysts in Examples 1-4 are relatively pure and have no obvious impurity phases or amorphous substances interfering with them.

[0081] Figure 5 The XRD phase analysis spectrum of the modified TiO2-MOFs photocatalyst in Example 1 shows that the characteristic diffraction peaks at 2θ = 25.3°, 37.8°, and 48.0° correspond to the (101), (004), and (200) crystal planes of TiO2, respectively, indicating that TiO2 has an anatase phase structure. The strong diffraction peak of modified GO appears at 2θ = 13.2°, which corresponds to the (100) crystal plane of modified GO. The shift of the diffraction peak indicates that the lattice structure of carbon has changed because during the oxidation of graphite, the intercalation effect increases the interlayer spacing of graphite, and the oxidant enters the interlayer to generate oxygen. The transformation process from graphite to modified GO resulted in the formation of numerous oxygen-containing functional groups, leading to structural changes. The MIL-88A / GO exhibited significant diffraction peaks at 10.3°, 12.9°, and 13.2°, indicating successful composite formation of MIL-88A (iron-based MOF material) and modified GO. The modified TiO2-MOFs photocatalyst also showed distinct diffraction peaks at 2θ = 9.9°, 10.3°, 12.9°, 25.3°, 37.8°, and 48.0°, demonstrating that the modified TiO2-MOFs photocatalyst fully retained the crystal structures of MIL-88A / GO and TiO2.

[0082] Figure 6 The image shows the FT-IR spectrum of the modified TiO2-MOFs photocatalyst in Example 1, with modified GO in the range of 3500-3000 cm⁻¹. -1 A broad peak appears nearby, corresponding to the stretching vibration of the OH hydroxyl group at 1700 cm⁻¹. -1 The peaks on the left and right correspond to the C=O carbonyl stretching vibration at 1600 cm⁻¹. -1 The nearby peak corresponds to the C=C skeleton vibration at 1050 cm⁻¹ -1 The nearby peaks correspond to the stretching vibrations of CO epoxy / hydroxyl groups. These peaks demonstrate the integrity of the oxygen-containing functional group structure of the modified GO. TiO2 peaks at 500–800 cm⁻¹ -1 The region shows a stretching vibration peak of the Ti-O bond, which is a typical infrared characteristic of anatase TiO2. No obvious functional group peaks are observed in other wavenumber regions, consistent with the chemical structure of TiO2. MIL-88A / GO retains the characteristic peaks of modified GO (such as OH near 3500 and C=O at 1700), while also exhibiting peaks in the 1600–1400 cm⁻¹ region. -1 Carboxylate ions (COO) appear- The asymmetric / symmetric stretching vibration peaks indicate that this is a composite product of MIL-88A and modified GO, and the functional groups of both components are retained. The modified TiO2-MOFs photocatalyst simultaneously contains the characteristic absorption peaks of MIL-88A / GO and TiO2. The positions of each characteristic peak are not significantly shifted, indicating that the chemical environment of the functional groups of each component has not changed significantly during the composite process, and the material structure is stable. This result proves that the modified catalyst has successfully achieved multi-component composite of TiO2 and MIL-88A / GO, and the functional group structure of each component has not been destroyed.

[0083] Figure 7 The image shown is an electron microscope image of the modified GO in Example 1, revealing a layered, wrinkled structure, a characteristic morphology of graphene oxide. This indicates that the two-dimensional sheet structure of graphene oxide was retained after modification. The surface is rough and rich in wrinkles. This structure gives the modified GO a large specific surface area, which is beneficial for subsequent loading of active components and can also provide more reactive sites. The layers are more tightly bound, and the wrinkle morphology is more obvious. This shows that the modification process did not destroy the layered framework of graphene oxide. On the contrary, it enhanced the bonding force between the layers through interaction. No obvious particle aggregation or structural collapse was observed, indicating that the modified graphene oxide maintained structural integrity and stability.

[0084] Figure 8 The image shows an electron microscope image of TiO2 in Example 1. The particles exhibit an irregular blocky morphology with a rough surface and no obvious smooth spherical features. This is one of the typical micromorphologies of anatase TiO2. The rough surface structure can usually provide more active sites, which is beneficial for reactions in applications such as photocatalysis. The particle size is in the range of 1-2 micrometers, and the overall particle size distribution is relatively uniform with no significant particle size difference. This indicates that the growth and dispersion of the particles were well controlled during the preparation process. There is a certain degree of loose agglomeration between the particles, but no large-area hard agglomeration has occurred. The particles still maintain a relatively independent individual morphology. This loose agglomeration state is conducive to uniform dispersion in the composite material and can also retain a high specific surface area.

[0085] Figure 9The image shows an electron microscope (EM) image of the modified MIL-88A / GO in Example 1. The large, wrinkled, two-dimensional layered structure of the modified GO is clearly visible, proving that the sheet-like framework of the modified GO is still retained after the composite. MIL-88A is dispersed as rod-shaped crystals on the surface of the modified GO sheets and in the gaps between the wrinkles. This is the typical morphology of MIL-88A, indicating that MIL-88A was successfully grown and loaded on the modified GO. The MIL-88A particles are uniform in size and well dispersed on the surface of the modified GO without obvious agglomeration, indicating that the particle growth and dispersion were well controlled during the modification process. MIL-88A is tightly bonded to the modified GO sheets. This interfacial structure can enhance electron transport efficiency and provide abundant active sites for catalytic reactions. It also maintains high specific surface area and porosity, which helps to improve mass transfer efficiency. This sheet-particle composite structure, combining the conductivity of modified GO with the catalytic activity of MIL-88A, has good performance potential in photocatalysis, adsorption and other applications.

[0086] Figure 10 This is an electron microscope image of the modified TiO2-MOFs photocatalyst in Example 1. Numerous rod-shaped crystals are clearly visible in the modified MIL-88A / GO, proving that the crystal structure of MIL-88A is completely preserved after composite formation. The fine TiO2 particles attached to the surface and interstices of the modified MIL-88A / GO are typical morphologies of TiO2, indicating that TiO2 was successfully loaded onto MIL-88A, forming a "MOF-TiO2" composite structure. The TiO2 particles are small in size and uniformly dispersed, with no obvious agglomeration, indicating that the particle size was well-dispersed during the loading process. The dispersion control is good, and TiO2 is tightly bound to the modified MIL-88A / GO. This interfacial contact can promote the separation and transport of photogenerated carriers, thereby improving photocatalytic efficiency. The rod-shaped crystal structure of MIL-88A is intact and does not collapse or deform, indicating that the framework structure of MIL-88A remains stable during the modification process. This "rod-shaped crystal-particle" composite structure, combined with the high specific surface area of ​​modified MIL-88A / GO and the photocatalytic activity of TiO2, can provide abundant reactive sites, which is beneficial to improving photocatalytic performance.

[0087] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing TiO2-MOFs photocatalysts, characterized in that, Includes the following steps: S1. The coordinating precursor solution was reacted at 60-80℃ for 10-12h, and after being washed alternately by centrifugation with ethanol and deionized water and dried, the modified MIL-88A / GO was obtained. S2. Add TiO2 nanoparticles to deionized water and disperse for 1-3 hours to obtain solution A. Add modified MIL-88A / GO to solution A to obtain a mixed solution. S3. Stir the mixed solution for 2-4 hours, wash it alternately with ethanol and deionized water by centrifugation and dry it to obtain the modified TiO2-MOFs photocatalyst. The coordinating precursor solution is prepared through the following steps: S11. At 0-5℃, expandable graphite is added to the modified mixed acid, and then potassium permanganate is added to mix and obtain a reaction system. The reaction system is stirred for 10-12h and then hydrogen peroxide is added to obtain a suspension. The suspension is stirred for 2-4h, and then centrifuged and washed with deionized water until the pH of the supernatant is 6-7. The precipitate is collected and dried to obtain modified GO. S12. Mix ferric chloride hexahydrate, fumaric acid, and terephthalic acid in proportion, add them to deionized water to prepare precursor solution A, add the modified GO prepared in S11 to precursor solution A, and ultrasonically disperse for 20-30 min to obtain a synergistic coordination precursor solution. The modified mixed acid is prepared by the following steps: Concentrated sulfuric acid and concentrated phosphoric acid are mixed to form a mixed acid. Aminosulfonic acid is added to the mixed acid and stirred at 0-3℃ for 10-20 minutes until the aminosulfonic acid is completely dissolved to obtain an aminated modified mixed acid. The mass ratio of concentrated sulfuric acid, concentrated phosphoric acid and aminosulfonic acid is (9-11):1:(2-4).

2. The method for preparing the TiO2-MOFs photocatalyst according to claim 1, characterized in that, The TiO2 nanoparticles were prepared by the following steps: S21. Dissolve titanium isopropoxide in anhydrous ethanol and stir for 20-30 min until completely dissolved to obtain solution B. Add tetrabutyl titanate coupling agent to solution B and continue stirring for 15 min. Add octylamine and stir evenly to obtain precursor solution B. S22. Precursor solution B is refluxed at 60-70℃ for 16-20h to obtain modified precursor solution. The modified precursor solution is filtered and dried at 50-70℃ for 2-4h to obtain modified precursor particles. The modified precursor particles are calcined in the atmosphere at 300-600℃ for 2-4h to obtain TiO2 nanoparticles.

3. The method for preparing the TiO2-MOFs photocatalyst according to claim 1, characterized in that, In step S2, the mass ratio of TiO2 nanoparticles to deionized water is 1:(90-110), and the mass ratio of TiO2 nanoparticles to modified MIL-88A / GO is 1:(1-3).

4. The method for preparing the TiO2-MOFs photocatalyst according to claim 1, characterized in that, In step S11, the mass ratio of expandable graphite to modified mixed acid is 1:(214-288), the mass ratio of potassium permanganate to expandable graphite is (6-7):1, and the mass ratio of hydrogen peroxide to potassium permanganate is (1.5-2.2):

1.

5. The method for preparing the TiO2-MOFs photocatalyst according to claim 1, characterized in that, In step S12, the mass ratio of ferric chloride hexahydrate, fumaric acid, and terephthalic acid is 2:(0.8-1.2):(0.1-0.5), the mass ratio of ferric chloride hexahydrate to deionized water is 1:(28-34), and the mass ratio of ferric chloride hexahydrate to modified GO is (5-8):

1.

6. The method for preparing the TiO2-MOFs photocatalyst according to claim 2, characterized in that, In step S21, the mass ratio of titanium isopropoxide to anhydrous ethanol is 1:(8-12), the mass ratio of titanium isopropoxide to tetrabutyl titanate coupling agent is (5-8):1, and the mass ratio of titanium isopropoxide to octylamine is 1:(1-1.2).

7. The method for preparing the TiO2-MOFs photocatalyst according to claim 1, characterized in that, In steps S1 and S3, the mass ratio of ethanol to precipitate is (5-10):1, and the mass ratio of deionized water to precipitate is (5-10):1, with alternating washing 3-4 times.

8. A TiO2-MOFs photocatalyst, characterized in that, It is prepared according to the preparation method according to any one of claims 1-7 above.

9. The application of the TiO2-MOFs photocatalyst as described in claim 8 in the degradation of organic wastewater pollutants.

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