Preparation method and application of a photo-fenton catalytic material

Abstract

The application is suitable for the field of photo-Fenton water treatment technology, and provides a preparation method and application of a photo-Fenton catalytic material; the method innovatively uses ND as a template, uses ND as a structural framework to support MIL-100(Fe) metal organic framework, thereby constructing MIL / ND, which is used for degrading MB dye wastewater in a photo-Fenton reaction. MIL / ND increases the exposed photo-Fenton active sites on the material, and meanwhile, the built-in electric field formed between the materials effectively hinders the recombination of photo-generated carriers. Moreover, the introduction of ND effectively improves the adsorption capacity of the active sites of Fe and H2O2, reduces the adsorption energy barrier of H2O2, accelerates the circulation of Fe 3+ / Fe 2+ , and meanwhile, forms a stable Fe-O-C structure to promote the generation of •OH, thereby effectively solving the technical problems of low reaction efficiency and slow kinetics of MIL-100(Fe) in traditional photo-Fenton.

Description

Technical Field

[0001] This invention belongs to the field of photo-Fenton water treatment technology, and particularly relates to a method for preparing and applying a photo-Fenton catalytic material. Background Technology

[0002] Photo-Fenton technology, as an advanced derivative of the traditional Fenton reaction, has become a cutting-edge field in advanced oxidation process research due to its superior degradation efficiency and significantly reduced operating costs in the treatment of recalcitrant organic wastewater. However, the actual application effect of this technology is highly dependent on the performance of the photo-Fenton catalytic material.

[0003] Most catalysts currently suffer from key defects such as insufficient stability and low recycling efficiency, directly leading to engineering bottlenecks in photo-Fenton reaction systems, including slow reaction kinetics and limited processing efficiency. Among numerous candidate materials, iron-based metal-organic frameworks (Fe-MOFs) have attracted much attention due to their unique porous crystal structure formed by the self-assembly of metal nodes and organic ligands. While MIL-100(Fe) possesses a regular pore structure and excellent H2O2 activation characteristics, it still faces two major technical challenges in practical photo-Fenton applications: First, under photoexcitation conditions, the photogenerated carrier recombination rate of Fe-O clusters in the material is too high, resulting in low electron-hole pair separation efficiency, which severely restricts the efficiency of Fe reaction. 3+ / Fe 2+ The cyclic kinetics and the generation rate of hydroxyl radicals (·OH) are affected; secondly, the insufficient number of coordinated unsaturated metal active sites in the material itself, coupled with the limitations of the reaction interface and the activation ability of H2O2, jointly weaken the overall reaction efficiency of the photo-Fenton system. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing and applying photo-Fenton catalytic materials, thereby addressing the problems mentioned in the background art.

[0005] The present invention is implemented as follows: a method for preparing a photo-Fenton catalytic material includes the following steps:

[0006] Step 1: Weigh out ferric chloride hexahydrate (FeCl3·6H2O) and 1,3,5-benzenetricarboxylic acid (H3BTC) in a 1:1 molar ratio, add them to a beaker containing deionized water, and stir to form a homogeneous mixture.

[0007] Step 2: Prepare catalytic materials using ND (size 5-30 nm) as templates. First, calculate the required mass of ND based on the mass of Fe and the mass ratio of ND:MIL-100(Fe) = 1:160. Then, add the required ND to the above mixture and continue stirring to ensure that the ND is uniformly dispersed in the MIL-100(Fe) precursor solution.

[0008] Step 3: Transfer the orange-yellow mixture (the product of Step 2) to a high-pressure reactor and place it in an oven for heating to allow MIL-100(Fe) to grow in situ on the ND surface; after the reaction is complete, cool to room temperature, then pour the product into a beaker and wash it multiple times with a 1:1 volume ratio of water and ethanol mixture, and let it stand to precipitate.

[0009] Step 4: Finally, put the washed precipitate into an oven to dry, and grind it to obtain an orange-yellow solid powder, which is the ND skeleton support MIL-100(Fe) material.

[0010] In a further technical solution, in step 1, accurately weigh 0.378 g of FeCl3·6H2O and 0.272 g of H3BTC, add them to a beaker containing 10 mL of deionized water, and stir with a magnetic stirrer for 30 minutes to form a uniform mixture.

[0011] In a further technical solution, in step 2, the mass of Fe is 78.26 mg and the mass of ND required is 0.49 mg.

[0012] In a further technical solution, in step 2, an ND of a certain size is added to the mixture in step 1, and the stirring time is 20 minutes.

[0013] In a further technical solution, in step 3, the product of step 2 is transferred to a high-pressure reactor and placed in an oven. The temperature of the oven is set to 130°C and the reaction time is 72 hours. Then, the product is washed three times with a 1:1 water and ethanol mixture solution. The settling time is 6 hours.

[0014] In a further technical solution, in step 4, the drying temperature of the oven is 80°C.

[0015] Another objective of this invention is to provide an application of a photo-Fenton catalytic material, which is based on the ND framework-supported MIL-100(Fe) material prepared by the above method, and uses the ND framework-supported MIL-100(Fe) material as a catalytic material in photo-Fenton technology to treat recalcitrant industrial wastewater.

[0016] A further technical solution involves applying the ND skeleton support MIL-100(Fe) material to photo-Fenton treatment of MB recalcitrant dye wastewater.

[0017] This invention provides a method for preparing and applying a photo-Fenton catalytic material. This method innovatively uses ND as a template, employing ND as a structural framework to support a MIL-100 (Fe) metal-organic framework, thereby constructing a high-performance MIL / ND framework-supported catalytic material for the degradation of MB dye wastewater in photo-Fenton reactions. The MIL / ND combination increases the number of exposed photo-Fenton active sites on the material, while the built-in electric field formed between the materials effectively hinders the recombination of photogenerated carriers. Furthermore, the introduction of ND effectively enhances the adsorption capacity of Fe active sites for H2O2, lowers the H2O2 adsorption energy barrier, and accelerates the degradation of Fe... 3+ / Fe 2+ The cycle simultaneously forms a stable Fe-OC structure, promoting •OH generation. In optical Fenton technology, MIL / ND not only improves the separation efficiency of photogenerated carriers but also suppresses e-. - / h + The composite process also enhances the exposure of Fe active sites and the generation of •OH, solving the technical challenges of low reaction efficiency and slow kinetics of MIL-100(Fe) in traditional photo-Fenton reactions. The prepared catalytic material not only has high efficiency in degrading MB, but is also inexpensive and easier to commercialize. Attached Figure Description

[0018] Figure 1 Degradation mechanisms during MB removal from MIL / ND materials;

[0019] Figure 2 The preparation process of MIL / ND;

[0020] Figure 3 To simulate the photo-Fenton degradation reaction system of MB under sunlight;

[0021] Figure 4 The electrolyte prepared for electrochemical testing;

[0022] Figure 5 This is a three-electrode system assembled for electrochemical testing;

[0023] Figure 6 Microscopic images of MIL-100(Fe) and MIL / ND (where a is a TEM image of MIL-100(Fe), b is a TEM image of MIL / ND, and c is an elemental mapping of MIL / ND).

[0024] Figure 7The nitrogen adsorption / desorption isotherms and pore size distribution curves for the three samples are shown (where a is the nitrogen adsorption / desorption isotherm and b is the pore size distribution curve).

[0025] Figure 8 Raman spectra of MIL / ND and pure MIL-100(Fe) at different ratios (where a is the Raman spectrum of 0.49 MIL / ND and pure MIL-100(Fe), and b is the Raman spectrum of 7.83 MIL / ND, 0.98 MIL / ND and 1.96 MIL / ND).

[0026] Figure 9 Infrared and XRD spectra of ND, MIL-100(Fe) and MIL / ND (where a is the infrared spectrum and b is the XRD spectrum).

[0027] Figure 10 The full scan XPS spectrum of MIL / ND and the high-resolution XPS spectra of Fe, O and C elements in MIL / ND are shown (where a is the full scan XPS spectrum of MIL / ND, and b, c and d are the high-resolution XPS spectra of Fe, C and O elements in MIL / ND, respectively).

[0028] Figure 11 The cell diagrams of MIL / ND and MIL-100(Fe) and the HOMO and LUMO diagrams of MIL / ND are shown (where a is the cell diagram of MIL / ND and MIL-100(Fe), and b is the HOMO and LUMO diagram of MIL / ND).

[0029] Figure 12 Impedance plots and transient photocurrent plots for ND, MIL-100(Fe), and MIL / ND (where a is the impedance plot and b is the transient photocurrent plot).

[0030] Figure 13 The CV and LSV curves for ND, MIL-100(Fe) and MIL / ND are shown (where a is the CV curve and b is the LSV curve).

[0031] Figure 14 The images show the UV-Vis spectra and corresponding Tauc curves of different catalysts, as well as the Mott-Schottky curves in 1M KOH solution (where a is the UV-Vis spectrum, b is the corresponding Tauc curve, and c is the Mott-Schottky curve in 1M KOH solution).

[0032] Figure 15The active sites of MIL-100(Fe), ND, and MIL / ND at different scan rates, and the Cdl of each sample (where a is the active site of MIL-100(Fe) at different scan rates, b is the active site of ND at different scan rates, c is the active site of MIL / ND at different scan rates, and d is the Cdl of each sample).

[0033] Figure 16 MB degradation was performed using different ratios of MIL / ND and different catalysts (where a represents different ratios of MIL / ND and b represents different catalysts).

[0034] Figure 17 The fluorescence intensity of •OH generated by MIL / ND in 2-hydroxyterephthalic acid and the photogenerated electron transfer of MIL / ND under the influence of the built-in electric field are shown in Figure 1 (where a is the fluorescence intensity of •OH generated by MIL / ND in 2-hydroxyterephthalic acid and b is the photogenerated electron transfer of MIL / ND under the influence of the built-in electric field).

[0035] Figure 18 The effects of different catalysts on the photo-Fenton degradation of MB under dark conditions and under conditions without hydrogen peroxide (where a represents dark conditions and b represents conditions without hydrogen peroxide).

[0036] Figure 19 The effect of different doses of MIL / ND on MB degradation;

[0037] Figure 20 The effect of MIL / ND on the photo-Fenton degradation of MB with different initial concentrations;

[0038] Figure 21 The effect of different pH values ​​on the photo-Fenton degradation of MB solution;

[0039] Figure 22 The effect of different doses of H2O2 on the photo-Fenton degradation of MB;

[0040] Figure 23 The TOC change curves for MB degradation by MIL / ND and the cyclic experiments of MB degradation by MIL / ND photo-Fenton (where a is the TOC change curve for MB degradation and b is the cyclic experiment of MB degradation by photo-Fenton).

[0041] Figure 24 For in Cl - SO4 2- and HCO3 - The effect of MIL / ND on the photo-Fenton degradation of MB in the presence of Cl (where a is the value of MIL / ND in the presence of Cl) - Given that b exists in SO4 2- In the presence of HCO3, c represents the presence of HCO3. -(Existing below)

[0042] Figure 25 For ethylenediaminetetraacetic acid (h + ), tert-butanol (•OH), ethanol (•OH and SO4) 2- ) and benzoquinone (•O2) - Radical capture experiments of MIL / ND in the presence of ethylenediaminetetraacetic acid (where a represents the presence of ethylenediaminetetraacetic acid, b represents the presence of tert-butanol, c represents the presence of ethanol, and d represents the presence of benzoquinone).

[0043] Figure 26 The PDOS of Fe 3d orbitals in MIL / ND (where a is d xy d yz and d xz b is and );

[0044] Figure 27 COHP represents the CO and C-Fe bonds in MIL / ND (where a is a CO bond and b is a C-Fe bond).

[0045] Figure 28 Gibbs free energy and d-band center for the formation of ·OH in MIL-100(Fe) and MIL / ND (where a is the Gibbs free energy for the formation of ·OH and b is the d-band center).

[0046] Figure 29 The process of generating •OH in MIL / ND and the process of generating •OH in MIL-100(Fe) (where a is the process of generating •OH in MIL / ND and b is the process of generating •OH in MIL-100(Fe).

[0047] Figure 30 The mechanism of enhancing the photo-Fenton degradation of MB by the MIL / ND skeleton support material. Detailed Implementation

[0048] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0049] The specific implementation of the present invention will be described in detail below with reference to specific embodiments.

[0050] like Figure 2 The image shows a method for preparing a photo-Fenton catalytic material according to an embodiment of the present invention. The material is synthesized in one step and specifically includes the following steps:

[0051] Step 1: Accurately weigh 0.378 g of FeCl3·6H2O and 0.272 g of 1,3,5-benzenetricarboxylic acid (H3BTC, pyromellitic acid), add them to a beaker containing 10 mL of deionized water, and stir with a magnetic stirrer for 30 minutes to form a homogeneous mixture.

[0052] Step 2: Prepare the catalytic material using 20 nm nanodiamond (ND) nanoparticles as a template. First, based on the mass of Fe (78.26 mg) and the ND:MIL-100(Fe) ratio of 1:160 (mass ratio), calculate the required mass of ND to be 0.49 mg. Then, add 0.49 mg of ND to the above mixture and continue stirring for 20 minutes to ensure that the ND is uniformly dispersed in the MIL-100(Fe) precursor solution.

[0053] Step 3: Transfer the orange-yellow mixture (the product of Step 2) to a high-pressure reactor and place it in an oven. React at 130°C for 72 hours to allow MIL-100(Fe) to grow in situ on the ND surface. After the reaction is complete, cool to room temperature, then pour the product into a beaker and wash three times with 40 mL of water and 40 mL of alcohol. Let it stand for 6 hours to precipitate.

[0054] Step 4: Finally, put the washed precipitate into an oven at 80℃ to dry. The orange-yellow solid powder obtained by grinding is the ND skeleton support MIL-100(Fe) material, which is named 0.49 MIL-100(Fe) / ND (abbreviated as 0.49 MIL / ND).

[0055] In this embodiment of the invention, the method strictly controls the proportions according to a 1:1 molar ratio (0.378 g FeCl3·6H2O and 0.272 g H3BTC), which is more conducive to the formation of high-purity MIL-100(Fe). The reaction is carried out at 130℃ for 72 hours (mild conditions, long-term crystallization). Low-temperature, long-time reaction may be more conducive to slow crystal growth and reduce defects. Using ND as a template and structural framework, MIL-100(Fe) grows in situ on its surface and is supported by it, forming a stable framework-supported structure. This material is used as a catalyst in photo-Fenton technology to treat recalcitrant industrial wastewater (such as dye wastewater and antibiotic wastewater), providing advanced purification of biochemically treated wastewater to meet discharge or reuse standards. Its core advantages are its extremely high degradation rate (99.9% degradation in 20 minutes), extremely high stability (92.4% performance after 8 cycles), and low cost, making it a high-performance material for efficiently treating recalcitrant dye wastewater.

[0056] The degradation mechanism of this material in photo-Fenton treatment of MB recalcitrant dye wastewater is as follows: Figure 1 As shown.

[0057] like Figure 3 As shown, in a preferred embodiment of the present invention, the standard reaction system is constructed and its catalytic performance is evaluated as follows:

[0058] Using nitric oxide (MB) as the target pollutant, the photo-Fenton performance of ND, MIL-100(Fe), and catalysts with different MIL / ND ratios was investigated. A 500W xenon lamp was used as the visible light source. In the photo-Fenton degradation experiment, 10 mg of MB was first dissolved in 1 L of water to prepare a 10 mg / L MB solution. Then, 10 mg of catalyst was added to 80 mL of the 10 mg / L MB solution, along with 100 μL of 30% H2O2. The mixture was placed under a xenon lamp for photo-Fenton degradation, with continuous stirring while maintaining solution homogeneity and controlling the reaction temperature. After the reaction started, samples were collected every 5 minutes and centrifuged at 4000 rpm for 7 min. The results were analyzed using a UV-Vis spectrophotometer at λ... max The absorbance of the supernatant was measured at 664 nm. MB concentration was determined, and degradation efficiency was calculated. All experiments were performed in triplicate to minimize potential errors. In the experiment studying the photo-Fenton degradation effect of MB under dark conditions, other experimental conditions in the standard reaction system remained unchanged; only the xenon lamp was turned off, and the reaction platform was covered with an opaque black cloth to avoid external light sources.

[0059] MB removal rate The calculation formula is as follows:

[0060] ;

[0061] in, This is the initial concentration of MB. It is a moment The concentration of MB at any given time.

[0062] In a preferred embodiment of the present invention, the working electrode for electrochemical testing is prepared as follows:

[0063] First, cut a 1 cm × 2 cm piece of carbon cloth. Then, weigh 0.100 g of catalyst, 0.024 g of polyvinylidene fluoride (PVDF), and 0.024 g of conductive carbon black. The mass ratio of catalyst, PVDF, and conductive carbon black should be between 8:2:2 and 8:1:1. Take 4-6 mL of N,N-dimethylformamide (liquid) and mix the three materials to dissolve them into a uniformly dispersed solution. Use a pipette to take an appropriate amount of the mixed solution and drop it onto the carbon cloth. Place the carbon cloth in an oven at 60-80 ℃ for 5-10 min. Remove the carbon cloth with the catalyst fixed on it and roll it with a rolling pin with a force of 20-30 N to make the catalyst bond with the carbon cloth more tightly. Place the rolled carbon cloth in an oven at 60-80 ℃ for 15-20 minutes until it is dry. The catalyst is completely fixed on the carbon cloth and tightly bonded. Repeat the above steps three times until all catalysts and additives are fixed on the carbon cloth.

[0064] The electrolyte is prepared as follows:

[0065] Weigh 3.500g of sodium sulfate pentahydrate using a 0.01% balance, then dissolve it in a beaker containing 25 mL of deionized water. Place the beaker containing the Na₂SO₄·5H₂O solution on a magnetic stirrer and stir for 10-20 minutes until the solution is clear and free of turbidity. The final electrolyte is as follows: Figure 4 As shown.

[0066] The three-electrode system is assembled as follows:

[0067] The experiment requires a three-electrode system (working electrode, auxiliary electrode, and reference electrode) and an electrolytic cell system. The prepared carbon cloth coated with the sample is fixed onto the working electrode, with the loading controlled at 1 mg / cm³. 2 The electrode was placed in a 0.5 M Na₂SO₄·5H₂O electrolyte along with a platinum wire auxiliary electrode and a HgO reference electrode. The assembled three-electrode system is shown below. Figure 5 As shown.

[0068] In this embodiment of the invention, the prepared MIL / ND, a highly efficient and stable framework-supported photo-Fenton catalyst with ND as a template, not only exhibits high MB degradation efficiency but also boasts low material cost, making its commercialization more likely. Using the ND framework-supported MIL-100(Fe) MIL / ND catalyst as a photo-Fenton catalyst enhances the MB degradation effect and significantly improves the degradation efficiency.

[0069] Table 1. Comparison of MB removal rates with other catalytic materials

[0070]

[0071] Table 1 shows a comparison of the performance of different catalytic materials in photo-Fenton degradation of MB. The catalytic material MIL / ND prepared in this patent can achieve an MB removal rate of 99.9% and a TOC mineralization rate of 78.1% within just 20 minutes, and still maintains a high degradation efficiency of 92.4% after 8 cycles. These examples demonstrate that the MB removal efficiency of MIL / ND is not only far higher than that of other iron-based and metal catalysts, but also that the removal time is much shorter than that of other catalytic materials. This not only demonstrates the excellent performance and ultra-high removal rate of MIL / ND in MB removal, but also showcases the application potential of MIL / ND in practical industry.

[0072] The following are several specific examples to verify the effectiveness of this method.

[0073] Example 1: Preparation and characterization of catalytic materials;

[0074] (1) Preparation of the catalytic material MIL-100(Fe):

[0075] Accurately weigh 0.378 g of FeCl3·6H2O and 0.272 g of H3BTC, with a molar ratio of 1:1. Add the two raw materials to a beaker containing 10 mL of deionized water and stir with a magnetic stirrer at room temperature for 30 minutes until homogeneous. After 30 minutes, transfer the resulting orange-yellow mixed solution to a stainless steel autoclave lined with polytetrafluoroethylene, seal it, and place it in an oven. React at a constant temperature of 130℃ for 72 hours to allow MIL-100(Fe) crystals to grow fully. After the reaction, allow the autoclave to cool naturally to room temperature, and transfer the product to a beaker. Add 40 mL of deionized water and 40 mL of anhydrous ethanol, disperse by ultrasonication for 10 minutes, and let stand for 6 hours to allow the product to precipitate fully. Remove the supernatant and wash three times to remove unreacted organic ligands and metal ions. Dry the precipitate in an oven at 80℃ for 12 hours, then grind it into a fine powder to obtain orange-yellow MIL-100(Fe) powder.

[0076] (2) Preparation of the catalyst material MIL / ND:

[0077] The material was synthesized using a one-step method. First, 0.378 g of FeCl3·6H2O and 0.272 g of H3BTC were accurately weighed and added to a beaker containing 10 mL of deionized water. The mixture was stirred with a magnetic stirrer for 30 minutes to form a homogeneous solution. Next, the catalytic material using ND as a template was prepared. Based on the mass of Fe (78.26 mg) and the ND:MIL-100(Fe) ratio of 1:160 (mass ratio), the required mass of ND was calculated to be 0.49 mg. Then, 0.49 mg of ND was added to the mixture, and stirring was continued for 20 minutes to ensure uniform dispersion of ND in the MIL-100(Fe) precursor solution. After 20 minutes, the orange-yellow mixture was transferred to a high-pressure reactor and placed in an oven. The reaction was carried out at 130°C for 72 hours, allowing MIL-100(Fe) to grow in situ on the ND surface. After the reaction was complete, the mixture was cooled to room temperature. The product was then poured into a beaker and washed three times with 40 mL of water and 40 mL of alcohol. The mixture was allowed to stand for 6 hours to precipitate. Finally, the washed precipitate was dried in an oven at 80°C. The resulting orange-yellow solid powder was the ND framework-supported MIL-100(Fe) material, which was named 0.49 MIL-100(Fe) / ND (abbreviated as 0.49 MIL / ND).

[0078] To investigate the effect of ND content on catalytic performance, 0.24 mg (1:320), 0.98 mg (1:80), 1.96 mg (1:40), and 7.83 mg (1:10) of ND were added, yielding 0.24 MIL-100(Fe) / ND, 0.98 MIL-100(Fe) / ND, 1.96 MIL-100(Fe) / ND, and 7.83 MIL-100(Fe) / ND, respectively. All samples were prepared using the same steps, differing only in the amount of ND added to ensure comparability. All MIL-100(Fe) / ND ratios are abbreviated as MIL / ND.

[0079] (3) Characterization of three catalytic materials: ND, MIL-100(Fe), and MIL / ND;

[0080] The morphology and microstructure of MIL-100(Fe) and MIL / ND were systematically characterized using field emission scanning electron microscopy (SEM, MAGELLAN-400). Figure 6As can be seen, MIL-100(Fe) exhibits a well-dispersed and irregularly shaped flake pattern. MIL / ND successfully inherits the monodispersity of MIL-100(Fe). Furthermore, a large number of fine, uniformly distributed black ND particles are clearly observed adhering to the surface of the MIL-100(Fe) particles. This morphological feature strongly confirms that ND successfully serves as a template, providing skeletal support and thus forming a stable skeletal-supported catalytic material, MIL / ND. Figure 6 b). The varying sizes of MIL-100(Fe) particles in the figure may be due to the use of an aqueous preparation method, while some larger particles may originate from the aggregation and growth of MOF crystals under high local concentration conditions during synthesis. Energy-dispersive X-ray (EDX) spectroscopy further determined the elemental distribution of MIL / ND, with Fe, O, and C elements uniformly distributed in almost the same positions, indicating that a stable and uniform skeletal support structure has been formed between MIL-100(Fe) and ND. Figure 6 c). This synergistic effect not only verifies the effective addition of ND, but also suggests that it may have a regulatory effect on the electronic structure of MIL-100(Fe), which helps to construct an excellent photogenerated electron transport channel and provides structural protection for the separation of photoelectron-hole pairs in the subsequent photoFenton reaction.

[0081] To further understand how the specific surface area and pore size distribution of a catalyst directly affect its ability to adsorb pollutants and the accessibility of active sites, a nitrogen adsorption-desorption test (Micromeritics ASAP 2460) system was used to characterize the specific surface area and pore structure of the material. Analysis of the test data using the BET method and DFT pore model yielded the following important findings: Figure 7 As shown in Figure a, ND exhibits a typical Type II isotherm, while MIL-100(Fe) and MIL / ND both exhibit typical Type III isotherms. The ND sample shows the highest specific surface area (295.126 m²). 2 The specific surface area ( / g) indicates its highly porous nature. MIL-100(Fe) has a relatively low specific surface area of ​​only 54.506 m² / g, indicating its high porosity. 2 / g. The specific surface area of ​​MIL / ND was significantly increased to 221.400 m². 2 The concentration of ND was significantly increased compared to pure MIL-100(Fe), indicating that ND effectively supported the porosity in the MIL-100(Fe) structure, thereby increasing its specific surface area, reaction contact surface, and thus exposing more active sites. Figure 7The pore size distribution curves (b) show that the most likely pore size of MIL / ND is 3.315 nm, significantly smaller than that of MIL-100(Fe) (5.584 nm) and ND (11.106 nm). This pore size reduction can be attributed to the ND framework being supported within and on the surface of MIL-100(Fe), exhibiting a certain degree of embedding and causing partial pore shrinkage. This microstructural modulation helps to form denser photogenerated electron channels and a more efficient space utilization environment, thereby promoting rapid separation of photogenerated electrons and holes, suppressing their recombination behavior, enhancing the utilization efficiency of photogenerated carriers, and thus improving photoFenton catalytic performance.

[0082] To further investigate the interaction mechanism between the ND framework and the MIL-100(Fe) metal-organic framework, Raman spectroscopy was used to systematically characterize three catalysts. The tests were conducted using a 532 nm laser source with power controlled at 5 mW to avoid thermal damage to the samples, and the scanning range was 100–3200 cm⁻¹. -1 The resolution is 2 cm. -1 Characterization results showed that MIL-100(Fe) and MIL / ND at 460 cm⁻¹ -1 The characteristic peak at that location is attributed to the Fe-O-Fe bridging vibration ( Figure 8 a). After the introduction of ND, MIL / ND reached 1350cm. -1 (D peak) and 1580 cm -1 The presence of typical ND-characteristic peaks at the (G peak) confirms successful ND loading and framework support for MIL-100(Fe). These peaks are also attributed to the vibrations of the C=C bonds in the benzene ring of MIL-100(Fe). The I(D) / I(G) ratio is close to 1, indicating a high defect density in ND, which helps accelerate electron migration and optimize photoelectron dynamics. With increasing ND content, the overall intensity of the MIL / ND Raman peaks significantly increases, and the peak shapes change significantly, indicating that the addition of ND alters the molecular structure of MIL-100(Fe). Figure 8 b). The 0.49 MIL / ND sample performed best, indicating that the interface coupling was strongest at this ratio.

[0083] To analyze the chemical structure and crystal composition characteristics of three catalysts—MIL-100(Fe), ND, and MIL / ND—systematic characterization was performed using X-ray diffraction (XRD, 6000 Shimadzu, Kyoto, Japan) and Fourier transform infrared spectroscopy (FT-IR, IFS 66V / S). The results showed that the FT-IR spectrum of MIL-100(Fe) was within the range of 3390 cm⁻¹. -1 and 717 cm -1There are two characteristic peaks at each location, which are caused by the stretching vibrations of the -OH and CH groups, respectively. Figure 9 a). Furthermore, the peak location is between 1300 and 1700 cm. -1 Absorption bands associated with carboxylic acid groups can be observed within this range. The 1610 cm⁻¹ band is one such band. -1 and 1410 cm -1 These characteristic peaks are attributed to the stretching vibrations of the C=O and CO bonds, respectively. These characteristic peaks are generally preserved in MIL / ND, indicating that the framework structure remains intact. However, the peak intensity is significantly reduced, suggesting that the carboxylic acid ligands in MIL-100(Fe) may be coupled with the C=C bonds on the ND surface. This bonding behavior helps to construct an efficient photogenerated electron transfer pathway, promoting rapid carrier migration and separation, thereby improving the efficiency of photo-Fenton degradation of MB. Figure 9 b shows the XRD pattern of the prepared catalyst. The sharp, strong diffraction peaks of pure MIL-100(Fe) indicate good crystallinity of the sample. The characteristic peaks at 10.2°, 11.1°, 18.3°, 20.1°, 24.2°, and 27.7° are consistent with previous reports, indicating the successful synthesis of these MIL-100(Fe) materials. The MIL / ND catalyst exhibits similar diffraction peak characteristics to MIL-100(Fe), indicating that its framework structure is well preserved. However, the ND diffraction peaks are significantly weakened, presumably due to the lower ND content. Furthermore, compared to MIL-100(Fe), the characteristic peaks of MIL / ND are broadened and weakened, demonstrating that the successful synthesis of MIL / ND can be confirmed by the changes and disappearance of diffraction peaks.

[0084] X-ray photoelectron spectroscopy (XPS) provides crucial evidence for elucidating the chemical state and interfacial bonding mechanism of MIL / ND catalytic materials. Therefore, the elemental composition and chemical environment of the material surface were tested using a Thermo Scientific ESCALAB 250Xi XPS instrument, and the data were analyzed in depth. Full-scan XPS spectra revealed that MIL / ND contains three elements: Fe, C, and O. Figure 10 a). In the high-resolution spectrum of Fe 2p, both 2p¹ / ² (773.6 eV) and 2p³ / ² (760.7 eV) point to Fe. 3+ Oxidized state ( Figure 10 b). The satellite peak at 768.2 eV reflects Fe 3+ Its low spin characteristic indicates that it has strong redox capabilities, which is beneficial for electron transfer processes in photo-Fenton reactions. Figure 10 c shows the high-resolution C 1s spectrum, further revealing multiple carbon environments in MIL / ND. The 285.0 eV corresponds to the sp... of the ligand benzene ring. 2-C exhibits its conjugated π-electron structure, which is advantageous as an electron donor. The 285.9 eV C-C bond originates from ND, indicating the presence of defect states on the ND surface, which helps to enhance the electron density. - / h + Separation efficiency. The carboxyl group at 289.4 eV originates from the -COOH structure on the MIL-100(Fe) organic ligand. These carboxyl structures enhance the loading capacity and electron transport capability of ND for MIL-100(Fe), thereby improving the Fenton reaction efficiency. The peak at 532.4 eV in the O 1s spectrum is attributed to the C=O or COC bond, originating from the MOF framework structure of MIL-100(Fe). Figure 10 d). Therefore, XPS results indicate that the introduction of the ND framework not only stabilizes Fe in MIL-100(Fe) 3+ The presence of this state also promotes the effective separation of electron transport paths and photogenerated carriers, thereby enhancing the photo-Fenton catalytic ability of MIL / ND.

[0085] Example 2: MIL-100(Fe) faces two major limitations: first, photogenerated carriers are prone to recombination, leading to a decrease in actual reaction efficiency; second, Fe has a limited number of active sites, restricting its efficient utilization of oxidants and continuous •OH generation. Therefore, relying solely on a single MOF framework is insufficient to meet the requirements of efficient photo-Fenton catalysis. To elucidate the regulation of the electronic structure of MIL-100(Fe) by ND and its role in photoelectronic behavior, unit cell models of MIL / ND and pure MIL-100(Fe) were constructed using Materials Studio and Vesta. Figure 11 a). The positions of Fe 1 and O 2 in MIL / ND are consistent with the corresponding atoms in MIL-100(Fe), ensuring the structural comparability of the systems. Figure 11 b represents the frontier molecular orbital distribution of MIL / ND. The results show that the electron cloud of the highest occupied molecular orbital (HOMO) is mainly concentrated between the Fe-O bridges of MIL / ND, indicating that this region is the main source region for photogenerated electrons and has good photoresponse capability. Meanwhile, the lowest occupied molecular orbital (LUMO) orbitals are concentrated in ND and the connecting sites. This means that under illumination, electrons tend to jump from MIL-100(Fe) to the ND surface, thereby effectively achieving electron-hole separation, suppressing recombination, improving electron utilization efficiency, and further enhancing the catalytic activity of the photo-Fenton reaction.

[0086] Example 3: To demonstrate the excellent charge transport performance and catalytic activity of the MIL / ND catalyst during MB degradation, the interfacial charge transfer resistance (Rct) was measured using electrochemical impedance spectroscopy (EIS) on a Shanghai Chenhua CHI660E electrochemical workstation. Combined with cyclic voltammetry (CV) analysis of redox characteristics, photocurrent testing to evaluate carrier separation efficiency, and Mott-Schottky curve analysis to study the band structure, the interfacial charge transport characteristics of the MIL / ND catalyst were systematically studied. Before testing, the assembled three-electrode system was allowed to stand at an open-circuit potential until it stabilized. Then, the frequency range was set to 100-1000 kHz, and a small sinusoidal perturbation signal with an amplitude of 10 mV was used for scanning. Real-time monitoring of the Nyquist plot ensured data quality. After testing, the obtained impedance data was analyzed using Oringe software. The entire testing process required environmental shielding and was repeated three times to ensure data reproducibility, with the error controlled within 5%. For cyclic voltammetry and linear sweep voltammetry (LSV) tests, the parameters are the same as for EIS tests, except for the parameter settings (initial setting is 0 V as the center, a range is set, initial setting is -2 V, highest point is set to 2 V, lowest point is set to -2 V, and termination is set to 2 V; then, after clicking start, the range is adjusted at any time according to the test curve. The CV scan rate is usually 5-100 mV / s; LSV uses unidirectional linear sweep, and the scan rate is generally 1-10 mV / s). Transient photocurrent testing requires special light source control, using periodic illumination (with light protection every 20 seconds) to study the photoelectric response characteristics of the material. Current changes must be recorded synchronously during illumination to evaluate the photogenerated carrier separation efficiency of the catalyst. All tests must be performed in the same electrolyte system and with the same three-electrode configuration to ensure data comparability.

[0087] The impedance characteristics of MIL / ND, MIL-100(Fe), and ND were analyzed by electrochemical impedance spectroscopy. Figure 12 (a) The figure shows that the 0.49 MIL / ND ratio has the smallest semicircle, indicating the lowest charge transfer resistance and the highest electron transport efficiency, which is beneficial for the separation of photogenerated electron-hole pairs. This is attributed to the fact that the introduction of an appropriate amount of ND enhances the conductivity of the material and introduces moderate surface defects, which helps electron migration and the exposure of active sites. However, excessive ND content may lead to agglomeration, hindering electron transport and photoresponse. Instantaneous photocurrent response diagram ( Figure 12(b) This further validates the above inference. MIL-100(Fe) exhibits the lowest photocurrent intensity, indicating its weak photocatalytic activity. The addition of ND significantly enhances the photocurrent, especially at 0.49 MIL / ND, demonstrating optimal photogenerated electron-hole separation efficiency and photocatalytic performance. This is because the ND framework supports MIL-100(Fe), providing more active sites and constructing efficient electron transport pathways. Secondly, an appropriate amount of ND can form a good reaction interface with MIL-100(Fe), while a higher ND ratio may cause light shielding or interface blockage, reducing performance.

[0088] To further understand the electrochemical performance of the materials, cyclic voltammetry (CV) and linear sweep voltammetry (LSV) curves of three comparative materials were measured. MIL-100(Fe) exhibited the smallest current response and a large redox potential difference (1.167 V / -0.627 V), reflecting its low electrochemical activity, which may limit its catalytic performance for H2O2. ND alone possessed good electron transport capabilities, with redox peaks at 1.234 V and -0.468 V (1.234 V / -0.468 V), but ND alone showed limited adsorption and catalytic activity for H2O2. In contrast, MIL / ND had the smallest redox potential difference (1.031 V and -0.179 V) and the highest current density. Figure 13 a). This indicates that its reaction polarization is smaller, resulting in higher electrochemical activity and a faster charge transfer rate, which is beneficial for electron transfer from ND to MIL-100(Fe). By comparing the LSV curves of ND, MIL-100(Fe), and MIL / ND, it was found that at the same applied potential, MIL / ND exhibits a significantly enhanced current density response ( Figure 13 (b) This characteristic directly benefits the sustained generation of •OH in the photo-Fenton reaction, thereby improving the degradation efficiency of MB. More importantly, MIL / ND exhibits a lower overpotential in the reduction potential range, indicating that the introduction of ND effectively optimizes the electron transport capability of the material and promotes Fe degradation. 3+ / Fe 2+ The cycle rate is the key mechanism by which the photo-Fenton system maintains high catalytic activity.

[0089] Example 4: To investigate the light absorption characteristics of the framework support material MIL / ND and its role in the photo-Fenton degradation of MB, ultraviolet-visible diffuse reflectance spectroscopy (DRS) was performed using a Shimadzu U-2600i UV-Vis spectrometer. First, the dried powder sample was uniformly filled into the sample cell, using BaSO4 as a 100% reflectance reference standard. The test wavelength range was set to 200-700 nm, covering the ultraviolet to visible light region. The scan speed was set to low, and the slit width was adjusted to 2 nm to ensure resolution. Each sample was tested three times to ensure data reliability. Furthermore, the DRS data also revealed whether the introduction of ND formed a new energy level structure in the new catalytic material. These results corroborated the electrochemical test data, jointly explaining the excellent photocatalytic performance of MIL / ND.

[0090] like Figure 14 a shows the light absorption characteristics of ND, MIL-100(Fe), and MIL / ND samples in the UV-Vis diffuse reflectance spectrum. ND itself has a wide bandgap, with absorption mainly concentrated in the UV region and weak absorbance, indicating its limited absorption capacity in the visible light region. MIL-100(Fe), on the other hand, shows significant absorption in both the UV and visible regions, especially in the 300-500 nm range, indicating a strong photoresponse capability of the Fe center. Compared to ND and MIL-100(Fe), the absorption spectrum of MIL / ND shows a redshift and increased absorption intensity. The E2 and B absorption peaks are located between 200-300 nm, corresponding to π→π* transitions or the benzene ring and carboxyl group structure on the ligand. The absorption peak near 450 nm originates from the LMCT in the Fe-OC structure. The ligand field absorption between 500–700 nm may originate from the Fe... 3+ The dd transition reflects the photoresponse characteristics of the Fe center.

[0091] The band gap energy of a material can be approximately calculated using the Tauc formula, as follows:

[0092] ;

[0093] In the formula: The absorption coefficient is... It is a constant. Let be Planck's constant. For light frequency, This represents the band gap energy of the material.

[0094] like Figure 14 b is Follow The changing curve, with the outer dashed line representing the band gap energy. The band gaps of MIL-100(Fe) and ND are 2.27 eV and 2.42 eV, respectively, while the band gap of the framework support material MIL / ND decreases to 1.92 eV. The narrower band gap of MILND broadens the range of absorbed light, enhances visible light absorption, and accelerates photogenerated electrons. - and h + The ability to separate makes it easier to stimulate more e in VB. - Entering CB, thus benefiting h + The conduction band positions of MIL-100(Fe) and ND were calculated to be -0.49 V (vs. RHE) and -0.4 V (vs. RHE) respectively, based on the Mott-Schottky (MS) curve. Figure 14 c), according to The calculated valence band (VB) potentials are approximately 1.78 V and 2.02 V, respectively. This band matching ensures effective excitation of MIL / ND under light irradiation, and electron transport with Fe. 3+ / Fe 2+ The rapid cycling significantly improves the degradation efficiency of the photo-Fenton reaction.

[0095] Example 5: To test the number of active sites on the material surface, cyclic voltammetry was used to measure the electrochemical responses of three materials at different scan rates. Before testing, the assembled three-electrode system was allowed to stand at an open-circuit potential until the potential stabilized. Then, the scan potential range was set to -1.00 to 1.00 V, and the scan potential range was adjusted according to the data results. After adjustment, tests were conducted at six scan rates: 20, 40, 60, 80, 100, and 120 mV / s, with each rate repeated three times. By analyzing the linear relationship between the redox peak current and the square root of the scan rate, and combining the electrochemical double-layer capacitance (Cdl) calculation, it was found that the introduction of ND in MIL / ND effectively increased the number of electrochemical active sites and improved charge transport performance.

[0096] Experiments revealed that the area under the curve for MIL-100(Fe) was relatively small, indicating that it has fewer active sites, which limits the performance of the photo-Fenton reaction. Figure 15 a). The weak response of the ND curve indicates that the activity of ND alone is not high. Figure 15 b). The CV area of ​​MIL / ND is significantly increased ( Figure 15 c), and showed a good linear relationship with increasing scan rate, indicating that the synergistic effect of MIL-100(Fe) and ND effectively improved the number of active sites and utilization efficiency. Further, the electrochemical active surface area (ECSA) of each sample was measured by electrochemical double-layer capacitance. Figure 15d). Calculations showed that the Cdl value of MIL / ND was significantly greater than that of MIL-100(Fe) and ND, approximately 12 times that of MIL-100(Fe). A higher Cdl value indicates an increase in reactive sites, which positively promotes the sustained photo-Fenton reaction that degrades MB.

[0097] Example 6: To evaluate the photo-Fenton degradation performance of MIL / ND, a photo-Fenton degradation experiment of MB was conducted under constructed standard simulated sunlight conditions. In an 80 mL standard system, the degradation rate of 0.49 MIL / ND reached 99.9%, significantly better than other ratio samples. Figure 16 a). This is because an appropriate amount of ND ensures the effective utilization of Fe sites and the full activation of H2O2, thereby enhancing the •OH generation capacity and accelerating MB degradation. Excessive ND, however, may cover the active sites of MIL-100 (Fe), hindering light absorption and creating an electron transport barrier, which is detrimental to the photo-Fenton degradation of MB. Comparative experiments further confirm that MIL / ND has a synergistic enhancing effect ( Figure 16 b). While MIL-100(Fe) exhibits some degradation ability, it is limited by the electron migration rate and the number of Fe active sites. ND has almost no degradation ability. Compared to MIL-100(Fe), MIL / ND increased the degradation rate of MB by 10.9%. This is because MIL / ND binds Fe from MIL-100(Fe). 3+ The active site and ND's excellent electron transport properties effectively suppress e - / h + The composite efficiency is improved, which in turn increases the decomposition of H2O2 and the generation of •OH, thereby enhancing the degradation efficiency of MB by photo-Fenton degradation.

[0098] Example 7: To determine the •OH concentration on the surface of the MIL / ND photocatalyst, terephthalic acid (PTA) was used as a probe molecule. The fluorescence intensity of its derivative, 2-hydroxyterephthalic acid, was detected to track •OH generation. A 300 mL sodium terephthalate solution was prepared, containing 0.01 M NaOH and 20 ppm terephthalic acid. 30 mL of this solution was then taken, and 0.05 g of the MIL / ND catalyst was added. After stirring for 30 minutes, the suspension reached adsorption-desorption equilibrium. Simulated sunlight was then applied, and 1 mL samples were taken at 0, 5, 10, 15, and 20 minutes, and each sample was filtered once using a syringe filter. Finally, the samples were diluted 5-fold, and the fluorescence spectra were acquired using a fluorescence spectrophotometer under excitation conditions of λ = 315 nm. The fluorescence intensity of the characteristic emission peak at λ = 426 nm was recorded. The test results are as follows: Figure 17As shown in Figure a, the spectral intensity of MIL / ND gradually increased with the reaction time increasing to 20 min, indicating that it had the highest •OH yield, thus achieving the best MB photo-Fenton degradation effect at 20 min. The highest photo-Fenton degradation rate of MIL / ND is due to the high carrier mobility of ND transferring electrons to MIL-100(Fe) under static conditions, thereby constructing a built-in electric field, ultimately achieving charge balance and significantly improving the separation and migration efficiency of photogenerated carriers. Figure 17 b).

[0099] Example 8: To systematically study the influence mechanism of MIL / ND on MB degradation performance, a series of controlled variable experiments were designed under standard photo-Fenton reaction conditions. The efficacy relationship was revealed by precisely controlling key reaction parameters. For example... Figure 18 a. To verify the effectiveness of the photo-Fenton reaction, a comparative experiment was conducted under dark conditions. The results showed that the degradation rates of all three photo-Fenton materials were below 0.62% under dark conditions. However, the degradation rate of MIL / ND was still higher than that of pure MIL-100(Fe) and ND. This is mainly because H2O2 acts as a lone pair electron donor, filling the vacancies in Fe. z 2 Orbitals, forming σ coordination of O-Fe. And in Lewis acidic Fe... 3+ The center triggers a limited non-photo-Fenton reaction to generate •OH, which then participates in the degradation reaction. Figure 18 b found that even under H2O2-free conditions, 0.49 MIL / ND could achieve 18.7% MB degradation. This is likely due to the generation of trace amounts of H2O2 within the system, which participates in the reaction, indicating that MIL / ND possesses certain catalytic activity in the photo-Fenton reaction.

[0100] Figure 19 The effect of different doses of MIL / ND on MB degradation was investigated. The results showed that the degradation rate initially increased and then decreased with increasing MIL / ND dose. 10 mg of MIL / ND exhibited the best degradation effect, while 15 mg and 20 mg of MIL / ND slightly reduced the degradation rate. This is because at 5 mg, MIL / ND has fewer active sites, resulting in a lower rate of •OH formation and thus a slower degradation rate. At 10 mg, MIL / ND provided sufficient active sites, and the catalytic efficiency of the photo-Fenton reaction reached its optimal state. However, at 15 mg and 20 mg, increased solution turbidity and decreased transmittance may occur, thereby inhibiting light absorption and leading to a decrease in the degradation rate.

[0101] Figure 20The degradation effect of MB at different initial concentrations was demonstrated. At both 5 and 10 mg / L, MIL / ND achieved almost complete degradation (99.9%). Due to the limited number of available photo-Fenton active sites on the MIL / ND surface, lower MB concentrations resulted in a higher proportion of MB dye molecules that could be efficiently oxidized per unit time, thus exhibiting a higher degradation rate. As the MB concentration increased, the generated •OH groups in the system were relatively insufficient, limiting the reaction rate. Considering both degradation effect and experimental operability, the degradation efficiency of MIL / ND was best at an MB concentration of 10 mg / L.

[0102] from Figure 21 The degradation of MB initially increased and then decreased with increasing pH. MB degradation was most efficient under acidic and neutral conditions, especially at pH 7, where the degradation rate reached its highest. This is likely because the photo-Fenton reaction achieves an optimal balance between the formation rate and stability of •OH under neutral conditions, promoting efficient MB degradation. While an acidic environment may facilitate Fe degradation... 3+ Reduction, but too low a pH will inhibit the formation of •OH and induce Fe. 3+ Precipitation limits the reaction. The oxidizing power of •OH is weakened under alkaline conditions, which also hinders the reaction. This indicates that MIL / ND is suitable for a wider pH range and has greater application potential in neutral environments, superior to traditional materials such as 8% Ag / AgBr / ferric hydroxide.

[0103] Based on the results of different H2O2 dosages, it was found that as the H2O2 dosage increased, the MB degradation rate first increased and then tended to stabilize. Figure 22 When the H2O2 addition reached 100 μL, further increasing it to 120 μL had limited effect on improving the degradation rate, indicating that the system was approaching saturation. An appropriate amount of H2O2 can provide sufficient ·OH, improving the efficiency of the photo-Fenton reaction. However, excessive H2O2 may undergo side reactions with ·OH, thus consuming the effective oxidant and weakening the oxidizing activity. Considering both reaction efficiency and resource utilization, 100 μL was determined to be the optimal addition amount.

[0104] Example 9: To accurately evaluate the mineralization capacity of MIL / ND in the degradation of MB, a total organic carbon analyzer (TOC-L CPH, Shimadzu) was used for systematic testing. The specific method is as follows: Under standard photo-Fenton reaction conditions (10 mg catalyst, 80 mL of 10 mg / L MB solution, 100 μL of 30% H2O2), 5 mL samples were taken every 5 minutes, filtered through a 0.22 μm filter membrane, and the TOC value of the solution was measured. The results showed that the mineralization degree of MB by MIL / ND was 78.0%, while the mineralization degree of MB by MIL-100(Fe) was 55.0% (…). Figure 23a). MIL / ND showed significantly better mineralization of MB than MIL-100(Fe), indicating that most of the degradation products of MB were water and carbon dioxide, with only a small amount existing in the form of organic carbon. This conclusion fully demonstrates the deep oxidation capacity and practical application potential of MIL / ND under simulated sunlight conditions. To systematically evaluate the stability and recycling performance of MIL / ND in practical applications, a cyclic degradation experiment was conducted. Each experiment was conducted under standard photo-Fenton reaction conditions for 20 minutes. After the reaction was completed, the remaining material was recovered by centrifugation. The recovered material was repeatedly washed with deionized water 2-3 times, then dried at 60°C for 12 hours and collected. The recovered material was then subjected to photo-Fenton degradation treatment again. After repeating the photo-Fenton degradation experiment 8 times, it was found that the degradation efficiency of MIL / ND for MB remained at 92.4% ( Figure 23 b). This result indicates that MIL / ND exhibits extremely high chemical stability and can be repeatedly used for MB degradation.

[0105] Example 10: To systematically evaluate the anti-interference capability of MIL / ND in a real wastewater environment, three common water-borne inorganic anions were selected: chloride ions (Cl... - ), sulfate ions (SO4) 2- ) and bicarbonate ions (HCO3) - In the experiment, different concentrations of sodium chloride, sodium sulfate, and sodium bicarbonate were added to a solution with constant initial conditions and a pH of 7. The solution was placed under a xenon lamp for photo-Fenton degradation for 20 minutes, and the concentration of MB was measured every 5 minutes. Figure 24 a showed Cl - The effect on MB degradation efficiency. Compared to the situation without Cl... - and different concentrations of Cl - Under these conditions, Cl was found - It has virtually no impact on photo-Fenton degradation. Figure 24 b found that in the absence of SO4 2- and different concentrations of SO4 2- Under the given conditions, the degradation curves almost overlap, indicating that SO4 2- It exhibits good inertness in the system and does not significantly interfere with the photo-Fenton reaction process. This may be because MIL / ND, as a photo-Fenton catalyst, can exhibit high stability and selectivity under certain conditions. Figure 24 The results showed that HCO3 - The addition of bicarbonate significantly inhibited the degradation of MB. This may be because the pH of the solution changes from acidic to alkaline after the addition of bicarbonate, leading to a decrease in the oxidizing power of ·OH.

[0106] Example 11: To investigate the main reactive substances in the reaction system, a free radical quenching experiment was conducted. Ethylenediaminetetraacetic acid, tert-butanol, and benzoquinone were used as h... + •OH and •O2 - Ethanol is used as a quencher for both •OH and •O2. - Quenching. Under standard photo-Fenton reaction conditions, four quenchers were added to the system individually. After running for 20 minutes, samples were taken every 5 minutes to determine the degradation efficiency of MB, ultimately identifying the main active substances involved in the degradation process. The results are as follows: Figure 25 a is h + The quenching experiment revealed that the degradation rate of MB decreased rapidly with increasing ethylenediaminetetraacetic acid (EDTA) concentration, especially at high concentrations where the reaction was significantly inhibited. This is due to H... + The equilibrium between and •OH is then shown by the equation:

[0107] ;

[0108] Figure 25 Tables b and 25c investigated the effects of the ·OH quencher tert-butanol and the multifunctional free radical quencher ethanol, respectively. Increased tert-butanol concentration significantly reduced the degradation rate of MB, indicating that ·OH is the major active species in the MIL / ND system. While increased ethanol concentration also reduced the degradation rate of MB, its inhibitory effect was weaker than that of tert-butanol. This suggests that in addition to quenching ·OH free radicals, SO42- also plays a role. 2- Free radicals. Figure 25 d. Further utilize benzoquinone as •O2 - The quencher. The results showed that the addition of benzoquinone also slightly inhibited the degradation of MB. This indicates that •O2 - In the MIL / ND system, ·OH also participated in the photo-Fenton process, but its contribution was lower than that of ·OH. Based on the analysis of the participation of various active species, a comparison of the quenching effects of tert-butanol and ethanol shows that ·OH is the main active species for degrading MB in the MIL / ND system, and ·O2... - It then acts as an auxiliary species, enhancing the system's oxidation capacity.

[0109] Example 12: In order to more clearly elucidate the essential mechanism of efficient MB degradation achieved by MIL / ND in the photo-Fenton system, density functional theory was used to systematically analyze its electronic structure and interfacial bonding characteristics. Figure 26 a- Figure 26 b. The study found that the spin-up and spin-down orbitals in Fe3d orbitals are essentially symmetrical, and the d orbital splitting is relatively small, indicating that Fe is in a low-spin state. Low-spin Fe typically possesses a higher crystal field stability energy (CSE) and stronger electron binding ability, which helps enhance the Fe center's ability to control electron transfer processes, thereby accelerating Fe... 3+ / Fe2+ The cycle rate between them. In the photo-Fenton reaction, this low-spin characteristic can more efficiently activate H2O2 to produce ·OH, thereby accelerating the degradation rate of MB.

[0110] Further chemical bonding orbital analysis (COHP) revealed the key bonding behavior at the MIL / ND interface. COHP results showed a high number of bonding orbitals with low energy distribution, thus forming stable and strong σ bonds, which facilitated the separation of photogenerated carriers. Figure 27 a). C-Fe bonds exhibit higher-energy bonding characteristics. Although some antibonding states are close to the Fermi level, bonding orbitals still dominate overall. Figure 27 (b) This indicates that the C-Fe bond forms a structure dominated by π-type electronic coupling, which facilitates rapid electron transfer at the interface. Furthermore, from the perspective of orbital interactions, electrons mainly move from the C 2p orbital to the Fe t orbital. 2g Orbital transitions further lead to σ-π conjugation. This not only endows Fe with structural stability but also makes it a highly efficient electron acceptor center, significantly enhancing the charge migration capability at the MIL / ND interface. PDOS and COHP results demonstrate that low-spin Fe in the MIL / ND interface effectively improves the utilization efficiency of photogenerated electrons by enhancing electron binding and transport capabilities. Meanwhile, the stable CO and C-Fe bonding structure provides a solid guarantee for carrier separation and migration, further promoting the efficient generation of ·OH radicals and significantly enhancing the photo-Fenton reaction performance.

[0111] Example 13: To reveal the essential reason for the enhanced ·OH generation ability of MIL / ND in the photo-Fenton system from a thermodynamic perspective, the Gibbs free energy changes of key reaction steps were calculated using density functional theory. For example... Figure 28 As shown in figure a, the maximum Gibbs free energy for the photo-Fenton catalytic oxidation of ·OH by MIL / ND is 0.57 eV, while that by MIL-100(Fe) is 0.65 eV. This means that MIL / ND can generate ·OH more efficiently, thus enhancing the photo-Fenton activity. This also indicates that ND, acting as a framework support, modulates the electronic structure of the Fe center, lowers the activation barrier, and accelerates the Fe… 3+ / Fe 2+ Cycle. The initial free energies of both MIL / ND and MIL-100(Fe) are 0 eV. Subsequently, H2O2 adsorbs onto *, *H2O2 reacts and loses an ·OH atom to participate in the photo-Fenton reaction, forming *OH. Then, *OH absorbs an etomidium. - and h + *H₂O is formed, and then one H₂O molecule returns to the initial state. The reaction pathway is as follows: Figure 29 As shown in a and 29b, the reaction process is as follows:

[0112] ;

[0113] ;

[0114] ;

[0115] ;

[0116] The d-band center of MIL / ND (-0.883 eV) is closer to the Fermi level than that of MIL-100(Fe) (-1.071 eV). Figure 28 b). This indicates that the introduction of ND enhances the electron-attracting ability of Fe, which helps to improve the ability of Fe active sites to capture and transfer reaction electrons, thereby accelerating the reaction. 3+ / Fe 2+ The cycle enhances the efficiency of the photo-Fenton reaction.

[0117] Example 14: MIL / ND exhibits excellent catalytic performance in the photo-Fenton degradation of MB. The mechanism can be analyzed from two aspects: electronic structure regulation and interfacial synergistic effects between the framework support materials of MIL-100(Fe) supported by ND. Firstly, the Fe in MIL-100(Fe)... 3+ In the low-spin state, its d orbitals are significantly split, and electrons preferentially occupy the low-energy t orbitals. 2g The orbital structure reduces the probability of spin transitions and enhances redox activity. Its strong coordination environment further reduces Fe... 3+ Its reduction potential makes it more readily react with H₂O₂ to generate •OH radicals. The introduction of ND provides abundant sp⁻¹. 2 / sp 3 Hybridized electronic states not only enhance Fe 3+ / Fe 2+ The increased electron transfer efficiency between the electrons effectively suppressed the recombination of photogenerated carriers, thus improving the utilization rate of reaction electrons. Theoretical calculations further revealed that the introduction of ND significantly lowered the energy barrier for H2O2 adsorption, enhanced the cycling activity of Fe, and increased the reaction rate. Under illumination, MIL / ND can efficiently absorb photons, exciting electrons to transition from the valence band to the conduction band to form electrons. - / h + Yes. The high conductivity of ND promotes the rapid separation and directional transfer of photogenerated electrons, synergistically accelerating the reduction reaction of H2O2 and Fe. 3+ / Fe 2+ The recycling of •OH effectively increases the yield of •OH and achieves complete mineralization of MB.

[0118] Furthermore, the system's excellent charge separation capability is also attributed to the built-in electric field induced by the Fermi level difference between ND and MIL-100(Fe). For example... Figure 30 As shown, the band arrangement further confirms the influence of the built-in electric field on e. - / h + The ND component promotes efficient separation. Simultaneously, the σ-electronic structure of ND, through strong hybridization coupling with the d orbitals of the Fe center, expands the charge migration path and improves electron utilization efficiency. Frontier molecular orbital analysis shows that ND modulates the HOMO / LUMO energy level distribution of MIL-100(Fe), lowers the electron transition barrier, and accelerates the photo-Fenton reaction. From the reaction process, MIL / ND is excited to generate photogenerated electrons and holes under illumination, and then the photogenerated electrons transition from the organic ligand to Fe via the LMCT mechanism. 3+ Promote Fe 2+ The regeneration process generates holes that participate in the photo-Fenton reaction to degrade and mineralize MB. Subsequently, the photo-Fenton reaction generates •OH, which continuously attacks MB, ultimately degrading and mineralizing it into H2O and CO2. Meanwhile, valence bond and acid-base ion theory further indicate that Fe... 3+ The σ-type coordination with H2O2 helps stabilize the formation of intermediates and maintain the persistence of the photo-Fenton reaction.

[0119] ;

[0120] ;

[0121] ;

[0122] ;

[0123] .

[0124] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a photo-Fenton catalytic material, characterized in that, Includes the following steps: Step 1: Weigh FeCl3·6H2O and 1,3,5-benzenetricarboxylic acid H3BTC in a 1:1 molar ratio, add them to a beaker containing deionized water, and stir to form a homogeneous mixture. Step 2: Prepare a catalytic material using nanodiamond ND as a template. First, calculate the required mass of ND based on the mass of Fe and the mass ratio of ND:MIL-100(Fe) = 1:

160. Then, add the required ND to the above mixture and continue stirring to ensure that the ND is uniformly dispersed in the MIL-100(Fe) precursor solution. Step 3: Transfer the product from Step 2 to a high-pressure reactor and place it in an oven for heating to allow MIL-100(Fe) to grow in situ on the ND surface; after the reaction is complete, cool to room temperature, then pour the product into a beaker and wash it multiple times with a 1:1 volume ratio of water and ethanol mixture, and allow it to stand to precipitate. Step 4: Finally, put the washed precipitate into an oven to dry, and grind it to obtain an orange-yellow solid powder, which is the ND skeleton support MIL-100(Fe) material.

2. The method for preparing the photo-Fenton catalytic material according to claim 1, characterized in that, In step 1, accurately weigh 0.378 g of FeCl3·6H2O and 0.272 g of H3BTC, add them to a beaker containing 10 mL of deionized water, and stir with a magnetic stirrer for 30 minutes to form a homogeneous mixture.

3. The method for preparing the photo-Fenton catalytic material according to claim 2, characterized in that, In step 2, the mass of Fe is 78.26 mg, and the mass of ND required is 0.49 mg.

4. The method for preparing the photo-Fenton catalytic material according to claim 3, characterized in that, In step 2, ND with a size of 5-30 nm is added to the mixture from step 1, and the mixture is stirred for 20 minutes.

5. The method for preparing the photo-Fenton catalytic material according to claim 4, characterized in that, In step 3, the product from step 2 is transferred to a high-pressure reactor and placed in an oven. The oven temperature is set to 130°C and the reaction time is 72 hours. Then, the product is washed 3-5 times with a 1:1 volume ratio of water and ethanol. The product is allowed to stand for precipitation for 6 hours.

6. The method for preparing the photo-Fenton catalytic material according to claim 5, characterized in that, In step 4, the drying temperature of the oven is 80°C.

7. An application of a photo-Fenton catalytic material, comprising an ND framework-supported MIL-100(Fe) material prepared based on the preparation method of the photo-Fenton catalytic material according to any one of claims 1-6, characterized in that, The ND framework supporting MIL-100(Fe) material is used as a catalyst in photo-Fenton technology to treat recalcitrant industrial wastewater.

8. The application of the photo-Fenton catalytic material according to claim 7, characterized in that, The ND skeleton supporting MIL-100(Fe) material was applied to the photo-Fenton treatment of methylene blue MB recalcitrant dye wastewater.

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