Visible light responsive photocatalyst, and preparation method and application thereof

Abstract

The application provides a visible light response type photocatalyst, which comprises a titanium oxygen cluster, an organic skeleton and an amino group connected to the organic skeleton, the titanium oxygen cluster is connected to the organic skeleton through a coordination bond, and a porous crystal structure is formed; the organic skeleton is 2-amino terephthalic acid, and the amino group serves as a visible light response group; the visible light response type photocatalyst is in a granular form, and the particle size of the visible light response type photocatalyst is not less than 180 microns. In the application, 2-amino terephthalic acid is used as a ligand, the molecular structure of the ligand comprises a carboxyl group for connecting the titanium oxygen cluster and an amino group as a visible light response group, the amino group is an inherent structural part of the ligand, is bonded to an organic component part of the porous crystal framework in situ and synchronously in the framework forming process, so that one-step synchronous construction of the amino functionalization and the framework structure is realized, the plugging of an external modifier to the material pores is avoided, the specific surface area is improved, and the photocatalytic reaction efficiency and long-term cycle stability are improved.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, specifically to a visible light responsive photocatalyst, its preparation method, and its application. Background Technology

[0002] Photocatalysts are semiconductor materials with photocatalytic functions. They can generate highly oxidizing substances (such as hydroxyl radicals and superoxide radicals) under light irradiation. They can be used to decompose organic compounds, some inorganic compounds, bacteria and viruses, etc., and have important applications in the field of environmental remediation, especially in the purification of organic wastewater.

[0003] For the treatment of organic pollutants, such as dyeing and printing wastewater, traditionally, wide-bandgap semiconductor photocatalysts, such as titanium dioxide (TiO2), have been widely used. Although these materials have high redox capabilities, their large intrinsic bandgap means that their light absorption threshold is usually less than 387 nm, thus requiring ultraviolet light to drive the process. They are almost unable to utilize the visible light portion of the solar spectrum, which has the highest energy content, resulting in low solar energy conversion efficiency. Currently, titanium-based metal-organic framework materials such as MIL-125(Ti) have been developed. This material is composed of titanium oxide clusters and terephthalic acid ligands. Although it has a regular pore structure, its light response range is still in the ultraviolet region. Post-modification is needed to extend its light response range to the visible light region. However, the post-modification process often leads to problems such as pore blockage, decreased specific surface area, and limited mass transfer. Furthermore, the post-modified components are prone to detachment, affecting the catalyst's cycle stability. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this application provides a visible light responsive photocatalyst, its preparation method, and its application.

[0005] This application discloses a visible light responsive photocatalyst, comprising a titanium oxide cluster, an organic framework, and an amino group attached to the organic framework. The titanium oxide cluster and the organic framework are connected by coordination bonds to form a porous crystal structure. The organic framework is 2-aminoterephthalic acid, and the amino group serves as a visible light responsive group. The visible light responsive photocatalyst is particulate, and the particle size of the visible light responsive photocatalyst is not less than 180 micrometers.

[0006] This application also discloses a method for preparing a visible light responsive photocatalyst, comprising the following steps: S1: Tetrabutyl titanate and 2-aminoterephthalic acid are dissolved in a first solvent to obtain tetrabutyl titanate solution and 2-aminoterephthalic acid solution, respectively; S2: 2-aminoterephthalic acid solution is added dropwise to tetrabutyl titanate solution at a rate of 0.5 mL / min to 2 mL / min to obtain a mixed solution; S3: The mixed solution is placed in a reaction vessel and reacted at 150℃ to 180℃ for 48 to 72 hours; S4: After centrifugation, washing and drying, a visible light responsive photocatalyst is obtained.

[0007] Preferably, the first solvent comprises N,N-dimethylformamide and methanol, wherein the volume ratio of N,N-dimethylformamide to methanol is 1:1.

[0008] Preferably, the ratio of the volume of the first solvent used to dissolve tetrabutyl titanate to the molar number of tetrabutyl titanate is equal to the ratio of the volume of the first solvent used to dissolve 2-aminoterephthalic acid to the molar number of 2-aminoterephthalic acid.

[0009] Preferably, the amount of the first solvent is 3000~15000 mL / mol Ti.

[0010] Preferably, the molar ratio of tetrabutyl titanate to 2-aminoterephthalic acid is 1:(0.9~1.1).

[0011] Preferably, in step S3, the temperature is programmed to rise to 150°C~180°C at a rate of 1°C-3°C / min.

[0012] This application also discloses the application of a visible light responsive photocatalyst in the degradation of methyl orange in wastewater.

[0013] Preferably, a visible light-responsive photocatalyst is added to wastewater containing methyl orange, with a light source wavelength of not less than 420 nm and a light source intensity of 100~200 mW / cm². 2 It is carried out under the illumination of a visible light source.

[0014] The beneficial effects of this application are as follows: by using 2-aminoterephthalic acid as a ligand, its molecular structure simultaneously contains a carboxyl group for linking the titanium oxide cluster and an amino group as a visible light responsive group. After a solvothermal reaction, the carboxyl group in 2-aminoterephthalic acid coordinates with the titanium oxide cluster generated by the hydrolysis of tetrabutyl titanate to form a porous crystal framework. The amino group, as an inherent structural part of the ligand, is simultaneously and in situ bonded to become an organic component of the porous crystal framework during the framework formation process. This achieves one-step simultaneous construction of amino functionalization and framework structure. Compared with traditional post-modification processes, it avoids the blockage of material pores by exogenous modifiers, increases the specific surface area, and improves the photocatalytic reaction efficiency and long-term cycling stability.

[0015] Meanwhile, this application obtained block particles with a particle size of not less than 180 micrometers through symmetrical solvent matching and programmed temperature control, which makes the visible light responsive photocatalyst of this application directly recyclable with an 80-mesh sieve. After being recycled 5 times, the degradation rate is still greater than 92%, which solves the industry problem of difficult separation and recycling of powdered catalysts and realizes the simple and recyclable utilization of visible light responsive photocatalysts. Attached Figure Description

[0016] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings: Figure 1 This is a flowchart illustrating the preparation method of the visible light responsive photocatalyst in the examples; Figure 2 The XRD patterns of the visible light responsive photocatalysts in Examples 1 and 6 are shown. Figure 3 The degradation kinetics curves of 20 mg / L methyl orange solution under different catalyst dosages in Example 1 are shown. Figure 4 This is another degradation kinetic curve of 20 mg / L methyl orange solution under different catalyst dosages in Example 1; Figure 5 The degradation kinetics curves of 10 mg / L methyl orange solution under different catalyst dosages in Example 1 are shown. Figure 6 This is another degradation kinetic curve of 10 mg / L methyl orange solution under different catalyst dosages in Example 1; Figure 7 This is a comparison chart of the degradation rate of methyl orange each time it was used 5 times in Example 6. Detailed Implementation

[0017] The following drawings disclose several embodiments of this application. For clarity, many practical details will be described in the following description. However, it should be understood that these practical details should not be used to limit this application. That is, in some embodiments of this application, these practical details are not essential. In addition, for the sake of simplicity, some conventional structures and components will be shown in the drawings in a simple schematic manner.

[0018] It should be noted that all directional indications in the embodiments of this application, such as up, down, left, right, front, back, etc., are only used to explain the relative positional relationship and movement of the components in a specific posture as shown in the attached figure. If the specific posture changes, the directional indication will also change accordingly.

[0019] Furthermore, the use of terms such as "first" and "second" in this application is for descriptive purposes only and does not specifically refer to any order or sequence, nor is it intended to limit this application. They are merely used to distinguish components or operations described using the same technical terms and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the technical solutions of various embodiments can be combined with each other, but only if they are feasible for those skilled in the art. If a combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed in this application.

[0020] To further understand the content, features, and effects of this application, the following embodiments are provided, and detailed descriptions are given in conjunction with the accompanying drawings.

[0021] Example 1: Reference Figure 1 , Figure 1 The flowchart below shows the preparation method of the visible light responsive photocatalyst in this embodiment. The preparation method of the visible light responsive photocatalyst in this embodiment includes the following steps: S1: Tetrabutyl titanate and 2-aminoterephthalic acid are dissolved separately in a first solvent to obtain tetrabutyl titanate solution and 2-aminoterephthalic acid solution. In specific applications, tetrabutyl titanate and 2-aminoterephthalic acid are pre-dissolved to ensure that both are fully dispersed in the first solvent before mixing, forming a homogeneous and stable precursor solution. Specifically, tetrabutyl titanate is dissolved in the first solvent and magnetically stirred at room temperature for 30 minutes until a homogeneous and transparent solution is formed. 2-Aminoterephthalic acid is dissolved in the first solvent and stirred in a constant temperature water bath until completely dissolved.

[0022] S2: Add 2-aminoterephthalic acid solution dropwise to tetrabutyl titanate solution at a rate of 0.5 mL / min to 2 mL / min to obtain a mixed solution. In practical applications, by gradually adding the solution, the supersaturation of the reaction interface can be precisely controlled, explosive nucleation can be suppressed, and directional epitaxial growth of crystals can be promoted, thereby obtaining bulk products with significantly increased size.

[0023] S3: Place the mixed solution in a reaction vessel and react at 150℃~180℃ for 48~72 hours.

[0024] S4: Visible light responsive photocatalyst is obtained after centrifugation, washing and drying.

[0025] By using 2-aminoterephthalic acid as a ligand, whose molecular structure simultaneously contains a carboxyl group for linking titanium oxide clusters and an amino group as a visible light responsive group, after a solvothermal reaction, the carboxyl group in 2-aminoterephthalic acid coordinates with the titanium oxide clusters generated by the hydrolysis of tetrabutyl titanate to form a porous crystal framework. The amino group, as an inherent structural part of the ligand, is simultaneously and in situ bonded to become an organic component of the porous crystal framework during the framework formation process. This achieves one-step simultaneous construction of amino functionalization and framework structure. Compared with traditional post-modification processes, this avoids the blockage of material pores by exogenous modifiers, increases the specific surface area, and improves the photocatalytic reaction efficiency and long-term cycling stability.

[0026] Preferably, the first solvent comprises N,N-dimethylformamide and methanol, wherein the volume ratio of N,N-dimethylformamide to methanol is 1:1. In specific applications, the volumes of N,N-dimethylformamide (DMF) and anhydrous methanol are equal. This symmetrical solvent matching process ensures that the titanium source (tetrabutyl titanate) and the organic ligand (2-aminoterephthalic acid) are in a solvent environment with completely identical chemical properties before the reaction, providing a basis for the uniform and orderly growth of crystals and facilitating the subsequent acquisition of bulk products.

[0027] Preferably, the amount of the first solvent is 3000~15000 mL / mol Ti. In specific applications, the two portions of the first solvent used to dissolve the titanium source and the organic ligand should not only maintain the same N,N-dimethylformamide to methanol volume ratio (i.e., 1:1), but also have the same unit molar volume of solute solvent. That is, the amount of the first solvent used to dissolve tetrabutyl titanate is controlled within the range of 3000~15000 mL / mol Ti. To achieve symmetrical solvent matching, the ratio of the volume of the other portion of the first solvent used to dissolve 2-aminoterephthalic acid to the molar amount of 2-aminoterephthalic acid is equal to the ratio of the volume of the first solvent used to dissolve tetrabutyl titanate to the molar amount of titanium. By maintaining this precise matching of solvent amounts, it is ensured that the titanium source and the organic ligand are in a system with completely consistent chemical environment and concentration conditions in the initial stage of the reaction, thereby synergistically regulating crystal growth kinetics, promoting the formation of uniformly sized bulk products, and ultimately achieving excellent and stable photocatalytic performance.

[0028] Preferably, the molar ratio of tetrabutyl titanate to 2-aminoterephthalic acid is 1:(0.9~1.1).

[0029] Preferably, in step S3, the mixed solution obtained in step S2 is transferred to a polytetrafluoroethylene-lined high-pressure reactor, sealed, and placed in an oven. The temperature is then programmed to rise to 150°C–180°C at a rate of 1°C–3°C / min, and reacted at this temperature for 48–72 hours. In practical applications, a programmed temperature rise rate of 1–3°C / min can control the heating rate of the reaction system, avoiding a sudden increase in the reaction rate due to excessively rapid heating, which could lead to explosive nucleation. This allows the crystals to grow slowly and uniformly at a relatively low supersaturation level, resulting in large and concentrated blocky particles.

[0030] Preferably, the ratio of the volume of the first solvent used to dissolve tetrabutyl titanate to the molar number of tetrabutyl titanate is equal to the ratio of the volume of the first solvent used to dissolve 2-aminoterephthalic acid to the molar number of 2-aminoterephthalic acid. In practical applications, by maintaining this ratio of solvent volume matching, it is ensured that the titanium source and the organic ligand are in a completely symmetrical chemical environment and concentration conditions during the reaction stage. This synergistically regulates crystal growth kinetics, promotes the formation of uniformly sized bulk products, and obtains a visible light-responsive photocatalyst with excellent photocatalytic performance. In other words, symmetrical solvent matching ensures that the titanium source and ligand are in the same concentration environment at the initial stage of the reaction, providing a basis for uniform nucleation, while temperature programming further regulates crystal growth kinetics and inhibits secondary nucleation. Both work together to promote the formation of uniformly sized and regularly morphologically regular bulk crystal products.

[0031] Preferably, in step S4, the centrifugation speed is 8000~10000 rpm, and methanol is used for washing. Specifically, after the reaction in step S3 is completed, the high-pressure reactor is allowed to cool naturally to room temperature. The product suspension is then removed, centrifuged at 8000~10000 rpm, and the solid is collected. The obtained solid is washed with anhydrous methanol: 50 mL of fresh methanol is added each time, the mixture is ultrasonically dispersed for 5 minutes, centrifuged, and the supernatant is discarded. This process is repeated a total of 3 times.

[0032] Preferably, in step S4, the washed solid is placed in a vacuum drying oven and dried at 60°C for 12 hours to obtain the visible light responsive photocatalyst NH2-MIL-125(Ti), which is a light yellow blocky solid.

[0033] Example 2: The visible-light-responsive photocatalyst in this embodiment comprises a titanium oxide cluster, an organic framework, and amino groups attached to the organic framework. The titanium oxide cluster and the organic framework are connected by coordination bonds to form a porous crystal structure. The organic framework is 2-aminoterephthalic acid, with the amino group serving as the visible-light-responsive group. The visible-light-responsive photocatalyst is particulate, and its particle size is not less than 180 micrometers. In specific applications, the titanium oxide cluster is formed by the hydrolysis and condensation of tetrabutyl titanate, serving as a metal cluster acting as a structural node. The organic framework is 2-aminoterephthalic acid, with carboxyl groups at both ends of its molecule connected to the titanium oxide cluster, forming the main supporting structure of the porous crystal framework. It can be understood that the amino group, serving as the visible-light-responsive group, is an inherent part of the 2-aminoterephthalic acid ligand, in situ integrated during framework formation, becoming an intrinsic electronic component of the material. This allows the material's band structure to be directly and effectively modulated through the lone pair electrons of the amino group, intrinsically extending the light response range from the ultraviolet region to the visible light region, thereby achieving efficient and stable visible-light photocatalytic activity. Meanwhile, by avoiding the introduction of exogenous components through post-modification, the catalyst's pore structure remains intact and unobstructed, maintaining a high specific surface area and ensuring sufficient contact between the reactants and the active sites.

[0034] Preferably, the visible light-responsive photocatalyst in this embodiment is in the form of bulk particles. In practical applications, after the photocatalytic reaction is completed, efficient solid-liquid separation and recovery can be achieved directly and simply through a sieve, simplifying the catalyst recycling process, reducing subsequent catalyst separation costs, and avoiding the problems of easy loss and difficult recovery of traditional nano or micron-sized powder catalysts in continuous flow catalytic systems. Furthermore, the particle size of the visible light-responsive photocatalyst is not less than 180 micrometers, enabling it to be stably retained by an 80-mesh standard sieve, further improving the catalyst separation efficiency.

[0035] Example 1: The visible light responsive photocatalyst in this embodiment was prepared by the following steps: S1: Take 3.4g of tetrabutyl titanate (0.01mol) and place it in the first container. Add the first solvent, which consists of 15mL of N,N-dimethylformamide (DMF) and 15mL of anhydrous methanol. Stir magnetically at room temperature for 30 minutes to obtain a uniform and transparent tetrabutyl titanate solution. Separately, take 1.81g of 2-aminoterephthalic acid (0.01mol) and place it in the second container. Add the first solvent, which consists of 15mL of DMF and 15mL of anhydrous methanol. Stir in a 40℃ water bath until completely dissolved to obtain a 2-aminoterephthalic acid solution.

[0036] S2: Under constant temperature and continuous stirring conditions at 25℃, 2-aminoterephthalic acid solution was slowly added dropwise to tetrabutyl titanate solution at a rate of 1 mL / min to obtain a mixed solution.

[0037] S3: Transfer the mixed solution to a 100 mL PTFE-lined high-pressure reactor, seal it, and place it in an oven. Proceed to 160 °C at a rate of 2 °C / min, and react at 160 °C for 60 hours. After the reaction is complete, allow the reactor to cool naturally to room temperature, and then remove the product suspension.

[0038] S4: Centrifuge the product suspension at 9000 rpm for 12 minutes and collect the solid. Wash the obtained solid with anhydrous methanol: each time, add 50 mL of fresh methanol, sonicate for 5 minutes, centrifuge, discard the supernatant, and repeat this process a total of 3 times. Place the washed product in a vacuum drying oven and dry at 60℃ for 12 hours to obtain the light yellow blocky solid product, the visible light responsive photocatalyst NH2-MIL-125(Ti).

[0039] Example 2: The difference between the preparation steps of the visible light responsive photocatalyst in this embodiment and those in Example 1 is that the volume ratio of N,N-dimethylformamide to methanol in the first solvent in this embodiment is adjusted to 2:1, while the other steps are the same, and the total volume of the first solvent is the same as in Example 1, which is 30 mL.

[0040] Example 3: The difference between the preparation steps of the visible light responsive photocatalyst in this embodiment and those in Example 1 is that, in this embodiment, step S3 involves transferring the mixed solution to a 100 mL polytetrafluoroethylene-lined high-pressure reactor, sealing it, and placing it in an oven. The temperature is then programmed to rise to 150 °C at a rate of 2 °C / min, and the reaction is carried out at 150 °C for 60 hours. After the reaction is complete, the reactor is allowed to cool naturally to room temperature, and the product suspension is removed. The remaining steps are the same.

[0041] Example 4: The difference between the preparation steps of the visible light responsive photocatalyst in this embodiment and those in Example 1 is that, in this embodiment, step S3 involves transferring the mixed solution to a 100 mL polytetrafluoroethylene-lined high-pressure reactor, sealing it, and placing it in an oven. The temperature is then programmed to rise to 160 °C at a rate of 2 °C / min, and the reaction is carried out at 160 °C for 48 hours. After the reaction is complete, the reactor is allowed to cool naturally to room temperature, and the product suspension is removed. The remaining steps are the same.

[0042] Example 5: The difference between the preparation steps of the visible light responsive photocatalyst in this embodiment and those in Example 1 is that, in this embodiment, step S1 involves placing 3.4 g of tetrabutyl titanate (0.01 mol) in a first container, adding a first solvent composed of 15 mL of N,N-dimethylformamide (DMF) and 15 mL of anhydrous methanol, and magnetically stirring at room temperature for 30 minutes to obtain a uniform and transparent tetrabutyl titanate solution; separately, placing 1.63 g of 2-aminoterephthalic acid (0.009 mol) in a second container, adding a first solvent composed of 13.5 mL of DMF and 13.5 mL of anhydrous methanol, and stirring in a 40°C water bath until completely dissolved to obtain a 2-aminoterephthalic acid solution. The remaining steps are the same.

[0043] The catalytic performance of 0.1 g of the visible light responsive photocatalysts from Examples 1 to 5 was tested. The catalytic performance test steps are as follows: 0.1 g of the visible light responsive photocatalyst was added to 100 mL of methyl orange (MO) solution (20 mg / L) and placed in a photocatalytic reactor. A 300 W xenon lamp equipped with a 420 nm cutoff filter (light intensity 150 mW / cm²) was used. After reacting for 120 min under magnetic stirring, the suspension was taken from the reaction system and centrifuged to obtain the supernatant. The absorbance at 464 nm was measured using a UV-Vis spectrophotometer, and the MO degradation rate was calculated. The test results are shown in Table 1.

[0044] 0.05 g, 0.1 g, and 0.15 g of the visible light-responsive photocatalyst from Example 1 were added to 100 mL of methyl orange (MO) solution (20 mg / L) and placed in a photocatalytic reactor. A 300 W xenon lamp equipped with a 420 nm cutoff filter (150 mW / cm²) was used, and the reaction was carried out under magnetic stirring. Suspensions were collected from the reaction system at 10 min, 20 min, 30 min, and 40 min, and centrifuged to obtain the supernatant. The absorbance at 464 nm was measured using a UV-Vis spectrophotometer to obtain the MO degradation kinetic curves. (Refer to...) Figure 3 and Figure 4 .

[0045] 0.05 g, 0.1 g, and 0.15 g of the visible light-responsive photocatalyst from Example 1 were added to 100 mL of methyl orange (MO) solution (10 mg / L) and placed in a photocatalytic reactor. A 300 W xenon lamp equipped with a 420 nm cutoff filter (150 mW / cm²) was used, and the reaction was carried out under magnetic stirring. Suspensions were collected from the reaction system at 10 min, 20 min, 30 min, and 40 min, and the supernatant was obtained by centrifugation. The absorbance at 464 nm was measured using a UV-Vis spectrophotometer to obtain the MO degradation kinetic curves. (Refer to...) Figure 5 and Figure 6 .

[0046] Example 6: The visible light-responsive photocatalyst from Example 1, after being recovered through an 80-mesh sieve for catalytic performance testing, was soaked in anhydrous methanol for 3 hours to remove surface-adsorbed organic matter, and then vacuum-dried at 60°C. The dried visible light-responsive photocatalyst was then added to 100 mL of methyl orange (MO) solution (20 mg / L) and placed in a photocatalytic reactor. A 300 W xenon lamp equipped with a 420 nm cutoff filter (light intensity 150 mW / cm²) was used, and the reaction was carried out for 120 min under magnetic stirring. This process was repeated five times before the visible light-responsive photocatalyst underwent catalytic performance testing and XRD analysis. The test results are shown in Table 1. Figure 2 and Figure 7 As shown.

[0047] Example 7: The difference between the preparation steps of the visible light-responsive photocatalyst in this embodiment and those in Example 1 is that the total amount of the first solvent used in this embodiment is 8000 mL / mol Ti. Specifically, it includes the following steps: S1: Take 3.4g of tetrabutyl titanate (0.01mol) and place it in the first container. Add a mixed solvent consisting of 40mL N,N-dimethylformamide (DMF) and 40mL anhydrous methanol (total solvent 80mL). Stir magnetically at room temperature for 30 minutes to obtain a uniform and transparent tetrabutyl titanate solution. Separately, take 1.81g of 2-aminoterephthalic acid (0.01mol) and place it in the second container. Add a mixed solvent consisting of 40mL DMF and 40mL anhydrous methanol (total solvent 80mL). Stir in a 40℃ water bath until completely dissolved to obtain a 2-aminoterephthalic acid solution.

[0048] S2: Under constant temperature and continuous stirring conditions at 25℃, 2-aminoterephthalic acid solution was slowly added dropwise to tetrabutyl titanate solution at a rate of 1 mL / min to obtain a mixed solution.

[0049] S3: Transfer the mixed solution to a 100 mL PTFE-lined high-pressure reactor, seal it, and place it in an oven. Proceed to 160 °C at a rate of 2 °C / min, and react at 160 °C for 60 hours. After the reaction is complete, allow the reactor to cool naturally to room temperature, and then remove the product suspension.

[0050] S4: Centrifuge the product suspension at 9000 rpm for 12 minutes and collect the solid. Wash the obtained solid with anhydrous methanol: each time, add 50 mL of fresh methanol, sonicate for 5 minutes, centrifuge, discard the supernatant, and repeat this process a total of 3 times. Place the washed product in a vacuum drying oven and dry at 60℃ for 12 hours to obtain the light yellow blocky solid product, the visible light responsive photocatalyst NH2-MIL-125(Ti).

[0051] Example 8: The difference between the preparation steps of the visible light responsive photocatalyst in this embodiment and those in Example 1 is that the total amount of the first solvent used in this embodiment is 10000 mL / mol Ti. Specifically, it includes the following steps: S1: Take 3.4g of tetrabutyl titanate (0.01mol) and place it in the first container. Add a mixed solvent consisting of 50mL N,N-dimethylformamide (DMF) and 50mL anhydrous methanol (total solvent 100mL). Stir magnetically at room temperature for 30 minutes to obtain a uniform and transparent tetrabutyl titanate solution. Separately, take 1.81g of 2-aminoterephthalic acid (0.01mol) and place it in the second container. Add a mixed solvent consisting of 50mL DMF and 50mL anhydrous methanol (total solvent 100mL). Stir in a 40℃ water bath until completely dissolved to obtain a 2-aminoterephthalic acid solution.

[0052] S2: Under constant temperature and continuous stirring conditions at 25℃, 2-aminoterephthalic acid solution was slowly added dropwise to tetrabutyl titanate solution at a rate of 1 mL / min to obtain a mixed solution.

[0053] S3: Transfer the mixed solution to a 150 mL PTFE-lined high-pressure reactor, seal it, and place it in an oven. Proceed to 160 °C at a rate of 2 °C / min, and react at 160 °C for 60 hours. After the reaction is complete, allow the reactor to cool naturally to room temperature, and then remove the product suspension.

[0054] S4: Centrifuge the product suspension at 9000 rpm for 12 minutes and collect the solid. Wash the obtained solid with anhydrous methanol: each time, add 50 mL of fresh methanol, sonicate for 5 minutes, centrifuge, discard the supernatant, and repeat this process a total of 3 times. Place the washed product in a vacuum drying oven and dry at 60℃ for 12 hours to obtain the light yellow blocky solid product, the visible light responsive photocatalyst NH2-MIL-125(Ti).

[0055] Example 9: The difference between the preparation steps of the visible light-responsive photocatalyst in this embodiment and those in Example 1 is that the total amount of the first solvent used in this embodiment is 15000 mL / mol Ti. Specifically, it includes the following steps: S1: Take 3.4g of tetrabutyl titanate (0.01mol) and place it in the first container. Add a mixed solvent consisting of 75mL N,N-dimethylformamide (DMF) and 75mL anhydrous methanol (total solvent 150mL). Stir magnetically at room temperature for 30 minutes to obtain a uniform and transparent tetrabutyl titanate solution. Separately, take 1.81g of 2-aminoterephthalic acid (0.01mol) and place it in the second container. Add a mixed solvent consisting of 75mL DMF and 75mL anhydrous methanol (total solvent 150mL). Stir in a 40℃ water bath until completely dissolved to obtain a 2-aminoterephthalic acid solution.

[0056] S2: Under constant temperature and continuous stirring conditions at 25℃, 2-aminoterephthalic acid solution was slowly added dropwise to tetrabutyl titanate solution at a rate of 1 mL / min to obtain a mixed solution.

[0057] S3: Transfer the mixed solution to a 200 mL PTFE-lined high-pressure reactor, seal it, and place it in an oven. Proceed to 160 °C at a rate of 2 °C / min, and react at 160 °C for 60 hours. After the reaction is complete, allow the reactor to cool naturally to room temperature, and then remove the product suspension.

[0058] S4: Centrifuge the product suspension at 9000 rpm for 12 minutes and collect the solid. Wash the obtained solid with anhydrous methanol: each time, add 50 mL of fresh methanol, sonicate for 5 minutes, centrifuge, discard the supernatant, and repeat this process a total of 3 times. Place the washed product in a vacuum drying oven and dry at 60℃ for 12 hours to obtain the light yellow blocky solid product, the visible light responsive photocatalyst NH2-MIL-125(Ti).

[0059] Comparative Example 1: The visible light-responsive photocatalyst in this comparative example was prepared using the following steps: S1: Obtain unmodified MIL-125(Ti).

[0060] S2: Place MIL-125(Ti) in a solution containing aminosilane and react at 80°C for 12 hours.

[0061] S3: After centrifugation, washing, and drying, an amino-modified visible light responsive photocatalyst was obtained, denoted as AM-MIL-125(Ti).

[0062] Take 0.1g of each of the visible light responsive photocatalysts from Examples 1, 7, 8, 9 and Comparative Example 1 for catalytic performance testing. The catalytic performance testing steps are as follows: Take 0.1g of the visible light responsive photocatalyst and add it to 100mL of methyl orange (MO) solution (20mg / L), place it in a photocatalytic reactor, and use a 300W xenon lamp equipped with a 420nm cutoff filter (light intensity 150mW / cm²). 2 After reacting under magnetic stirring for 120 min, the suspension was taken from the reaction system and centrifuged to obtain the supernatant. The absorbance at 464 nm was measured using a UV-Vis spectrophotometer, and the MO degradation rate was calculated. Simultaneously, the BET specific surface area was determined using nitrogen adsorption-desorption, and the optical band gap was calculated using UV-Vis diffuse reflectance spectroscopy. The test results are shown in Table 2.

[0063] Table 1: Performance Comparison of Examples 1-6 and Comparative Example 1

[0064] Table 2: Performance Comparison of Examples 1, 7-9 and Comparative Example 1

[0065] As shown in Table 1, the visible light responsive photocatalyst of Example 1 has a high specific surface area (1250 m²). 2 It exhibits significant visible light response (narrow bandgap to 2.8 eV) and excellent photocatalytic activity (degradation rate >96% in 120 minutes). In Example 2, compared to Example 1, the proportion of DMF in the first solvent was increased. Although a catalyst could still be formed, the product was in powder form, failing to form an ideal bulk structure. Furthermore, the catalytic activity and specific surface area of ​​the product decreased. This result confirms that a 1:1 volume ratio of DMF to methanol in the first solvent is the preferred condition for obtaining highly active bulk materials. In Example 3, compared to Example 1, the reaction temperature was lowered to 150°C, resulting in less sufficient crystal growth compared to Example 1. The product was microcrystalline (<50 μm), although the specific surface area and catalytic activity remained at a high level (1100 μm). 2 / g, degradation rate 88.1%), but lower than Example 1. Compared with Example 1, Example 4 shortened the reaction time to 48 hours. Although the product yield and photocatalytic activity were lower than Example 1, its degradation rate remained above 90%, indicating that the reaction could be basically completed in 48 hours. However, extending the reaction time helps to obtain more mature crystals with better performance. In Example 5, the molar ratio of titanium source to ligand was adjusted (1:0.9), and a blocky solid product was still obtained, with a specific surface area (1220 m²). 2The molar ratio (g) and degradation rate (93.7%) are close to those of Example 1, indicating that a high-performance catalyst can be obtained within this molar ratio range (1:0.9–1.1), further verifying the stability and applicability of the process. Compared with Example 1, the visible light responsive photocatalyst of Example 6 maintained a degradation rate of 92.7% for MO after being reused 5 times, with its specific surface area and optical band gap remaining essentially unchanged. This indicates that it has excellent chemical and structural stability in the visible light photocatalysis process. Combining the XRD test results of Examples 1 and 6, it can be seen that the diffraction peaks of the two are basically consistent, further verifying the chemical stability, structural integrity, and recyclability of Example 1.

[0066] Comparative Example 1, prepared by the conventional post-modification method, has a high specific surface area (1350 m² / g), but its optical band gap is as wide as 3.4 eV, and its degradation rate under the same visible light conditions is only 68.5%. This further confirms that the strategy of introducing amino groups in situ through 2-aminoterephthalic acid ligands to construct a functionalized framework in one step has significant advantages in expanding the photoresponse range and improving photocatalytic activity.

[0067] Table 2 shows that when the amount of the first solvent varies within the range of 3000~15000 mL / mol Ti, it is possible to successfully prepare particles with a blocky morphology (particle size >180 μm) and a high specific surface area (>1230 m²). 2 The NH2-MIL-125(Ti) photocatalyst exhibits a narrow optical band gap (approximately 2.8 eV) and excellent visible light photocatalytic activity (degradation rate >95.5% after 120 minutes). This means that even when the initial solvent concentration is increased from 3000 mL / mol Ti to 8000, 10000, or even 15000 mL / mol Ti, the product morphology, specific surface area, band gap, and degradation rate do not show significant deterioration, with the degradation rate remaining between 95.8% and 96.2%. This demonstrates that the preparation method of this application has good process tolerance and stability over a wide range of solvent concentrations. Comparative Example 1, prepared using a conventional post-modification method, has a higher specific surface area (1350 m² / g) than the aminated MIL-125(Ti) prepared using a conventional post-modification method. 2 / g), but its optical band gap is as wide as 3.4eV, and the degradation rate under the same visible light conditions is only 68.5%, which is much lower than that of Examples 1-9. This further confirms the significant advantages of the strategy of introducing amino groups in situ through 2-aminoterephthalic acid ligands and constructing functionalized frameworks in one step in expanding the photoresponse range and improving photocatalytic activity, and it is independent of the change in solvent amount.

[0068] In summary, by using 2-aminoterephthalic acid as a ligand, whose molecular structure simultaneously contains a carboxyl group for linking the titanium oxide cluster and an amino group as a visible light responsive group, after a solvothermal reaction, the carboxyl group in 2-aminoterephthalic acid coordinates with the titanium oxide cluster generated by the hydrolysis of tetrabutyl titanate to form a porous crystal framework. The amino group, as an inherent structural part of this ligand, simultaneously and in situ bonds to become an organic component of the porous crystal framework during framework formation. This achieves one-step simultaneous construction of amino functionalization and framework structure. Compared with traditional post-modification processes, this avoids the clogging of material pores by exogenous modifiers, increases the specific surface area, and improves photocatalytic reaction efficiency and long-term cycling stability. Furthermore, this embodiment obtains block particles with a particle size of not less than 180 micrometers through symmetrical solvent matching and programmed temperature control, allowing the visible light responsive photocatalyst to be directly recovered using an 80-mesh sieve. After five cycles, the degradation rate remains greater than 92%, solving the industry problem of difficult separation and recovery of powdered catalysts and realizing the simple and recyclable utilization of visible light responsive photocatalysts.

[0069] The above description is merely an embodiment of this application and is not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. A visible light-responsive photocatalyst, characterized in that, include: The photocatalyst comprises a titanium oxide cluster, an organic framework, and an amino group attached to the organic framework, wherein the titanium oxide cluster and the organic framework are connected by coordination bonds to form a porous crystal structure; the organic framework is 2-aminoterephthalic acid, and the amino group serves as a visible light responsive group; the visible light responsive photocatalyst is particulate, and the particle size of the visible light responsive photocatalyst is not less than 180 micrometers.

2. A method for preparing a visible light-responsive photocatalyst as described in claim 1, characterized in that, Includes the following steps: S1: Tetrabutyl titanate and 2-aminoterephthalic acid are dissolved in the first solvent to obtain tetrabutyl titanate solution and 2-aminoterephthalic acid solution, respectively. S2: The 2-aminoterephthalic acid solution is added dropwise to the tetrabutyl titanate solution at a rate of 0.5 mL / min to 2 mL / min to obtain a mixed solution; S3: Place the mixed solution in a reaction vessel and react at 150℃~180℃ for 48~72 hours; S4: Visible light responsive photocatalyst is obtained after centrifugation, washing and drying.

3. The method for preparing a visible light-responsive photocatalyst according to claim 2, characterized in that, The first solvent comprises N,N-dimethylformamide and methanol, wherein the volume ratio of N,N-dimethylformamide to methanol is 1:

1.

4. The method for preparing a visible light-responsive photocatalyst according to claim 2, characterized in that, The ratio of the volume of the first solvent used to dissolve tetrabutyl titanate to the number of moles of tetrabutyl titanate is equal to the ratio of the volume of the first solvent used to dissolve 2-aminoterephthalic acid to the number of moles of 2-aminoterephthalic acid.

5. The method for preparing a visible light-responsive photocatalyst according to claim 2, characterized in that, The amount of the first solvent used is 3000~15000 mL / mol Ti.

6. The method for preparing a visible light-responsive photocatalyst according to claim 2, characterized in that, The molar ratio of tetrabutyl titanate to 2-aminoterephthalic acid is 1:(0.9~1.1).

7. The method for preparing a visible light-responsive photocatalyst according to claim 2, characterized in that, In step S3, the temperature is programmed to rise to 150℃~180℃ at a rate of 1℃-3℃ / min.

8. The application of the visible light responsive photocatalyst as described in claim 1 in the degradation of methyl orange in wastewater.

9. The application of the visible light-responsive photocatalyst according to claim 8 in the degradation of methyl orange in wastewater, characterized in that, The visible light responsive photocatalyst was added to wastewater containing methyl orange, and the light source wavelength was not less than 420 nm and the light source intensity was 100~200 mW / cm². 2 It is carried out under the illumination of a visible light source.

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