Ti-MOF-based nano material, preparation method thereof and application of Ti-MOF-based nano material in methylene blue dye adsorption

Abstract

The invention belongs to the technical field of preparation and application of metal organic framework adsorption materials, and particularly relates to a Ti-MOF-based nanometer material, a preparation method thereof and application of the Ti-MOF-based nanometer material in methylene blue dye adsorption, and a hierarchical pore Ti-MOF-based nanometer methylene blue adsorbent rich in oxygen vacancies is constructed by means of a temperature regulation and control ligand pyrolysis strategy. Adsorption performance tests show that the adsorbent has high adsorption capacity and high adsorption rate on methylene blue, due to the fact that hierarchical pores in the adsorbent promote diffusion and mass transfer of methylene blue, and oxygen vacancies enhance electronegativity of the surface of the adsorbent and provide more adsorption active sites.

Description

Technical Field

[0001] The present invention relates to the technical field of metal-organic framework crystal materials, and particularly relates to a Ti-MOF-based nanomaterial, a preparation method thereof, and an application thereof in the adsorption of methylene blue dye. Background Art

[0002] Organic dyes are widely used in various industries, including textiles, paper, food additives, paints, and leather. However, approximately 15% of these dyes are discharged in the form of waste liquid, posing a serious threat to human health and ecological balance. Compared with anionic dyes, cationic dyes are more toxic because they easily interact with negatively charged cell membranes, thus causing potential diseases. Methylene Blue (MB) is a typical cationic dye with carcinogenic risks and is widely used industrially, and it needs to be fully treated before being discharged into the environment.

[0003] Currently, the main methods for treating dye wastewater include adsorption, membrane separation, catalytic degradation, and chemical oxidation. Among them, the adsorption method is an efficient dye removal method in wastewater treatment. This is due to many factors, including its cost-effectiveness, ease of implementation, and no secondary pollution. The adsorbent is the core component of the adsorption method, but most reported dye adsorbents still have problems such as low adsorption capacity, slow adsorption rate, difficulty in co-adsorption, and narrow pH application range, making continuous dye removal impossible. Therefore, designing efficient co-adsorbing adsorbents within a wide pH range is a huge challenge. Compared with traditional adsorbents, metal-organic frameworks (MOFs) have a large specific surface area and high porosity, and have received considerable attention in the adsorption field. However, MOFs usually have pore diameters in the micropore range (<2 nm), while the size of organic dyes often exceeds 2 nm. This exacerbates the mass transfer resistance, hinders the full contact between dye molecules and adsorption sites, and limits their adsorption capacity and rate. Therefore, preparing MOFs with larger pore diameters is crucial for improving their adsorption ability. Summary of the Invention

[0004] The purpose of the present invention is to provide a Ti-MOF-based nanomaterial, a preparation method thereof, and an application thereof in the adsorption of methylene blue dye.

[0005] Based on the linker defect engineering strategy, the present invention proposes a novel hierarchical Ti-MOF material with oxygen vacancies to achieve efficient and continuous adsorption. First, by utilizing the coordination ability difference and steric hindrance effect between 2-aminoterephthalic acid and terephthalic acid, a dual-ligand Ti-MOF (D-MIL-125(Ti)) was constructed. Second, by selectively removing the ligands and metal clusters with weak thermal stability at high temperature, D-MIL-125(Ti) was transformed into an HD-MIL-125(Ti) material with hierarchical pores and oxygen vacancies.

[0006] In the first aspect, the present invention provides a preparation method of a Ti-MOF-based nanomaterial, comprising the following steps: S1. Divide the mixed solution of DMF and methanol into two equal parts. Add terephthalic acid and 2-aminoterephthalic acid ligands to one part, and add a titanium source to the other part. After ultrasonic dissolution, carry out a solvothermal reaction, and after the reaction is completed, cool and wash; S2. Heat the D-MIL-125(Ti) material obtained in S1 under a nitrogen atmosphere to obtain an HD-MIL-125(Ti) nanomaterial.

[0007] Further, the volume ratio of DMF to methanol is 27:3.

[0008] Further, the molar ratio of terephthalic acid to 2-aminoterephthalic acid is 1:1; the addition ratio of terephthalic acid to the titanium source is 5 mmol:1.8 ml.

[0009] Further, the titanium source is one of isopropyl titanate, n-butyl titanate, and titanium chloride.

[0010] Further, the reaction conditions of S1 are: react at 150 °C for 48 h.

[0011] Further, the reaction conditions of S2 are: heat at a heating rate of 2 °C min -1 -5 °C min -1 to 280 °C - 380 °C and maintain for 3 h.

[0012] In the second aspect, the present invention further provides a Ti-MOF-based nanomaterial prepared by any of the above preparation methods.

[0013] In the third aspect, the present invention further provides the application of the above Ti-MOF-based nanomaterial in the adsorption of methylene blue dye.

[0014] Compared with the prior art: the present invention has the following technical effects: (1) The Ti-MOF-based nanomaterials prepared by the present invention have a large specific surface area and a hierarchical pore structure, with the coexistence of micropores and mesopores, overcoming the limitation of the small pore size (<2 nm) of traditional MOFs and promoting the diffusion and adsorption of macromolecular dyes.

[0015] The present invention introduces oxygen vacancies through a pyrolysis strategy, enhancing the surface electronegativity of the material, strengthening the electrostatic interaction with cationic dyes (such as MB), and increasing the density of active sites at the same time.

[0016] (2) The Ti-MOF-based nanomaterials prepared by the present invention exhibit excellent adsorption performance for methylene blue (MB), with a maximum adsorption capacity of 525.7 mg·g⁻¹, and the adsorption equilibrium can be achieved within 10 minutes. This benefits from its hierarchical pore structure that accelerates the diffusion and mass transfer of dye molecules, while oxygen vacancies enhance the surface negativity and provide more active sites. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a flowchart of a preparation method of an HD-MIL-125(Ti) material provided by the present invention; Figure 2 It is an X-ray electron diffraction pattern of D-MIL-125(Ti), D-MIL-125(280), and D-MIL-125(380) prepared by the present invention; Figure 3 It is a thermogravimetric spectrum of D-MIL-125(Ti), D-MIL-125(280), and D-MIL-125(380) prepared by the present invention; Figure 4 It is an infrared curve graph of D-MIL-125(Ti), D-MIL-125(280), and D-MIL-125(380) prepared by the present invention; Figure 5 It is a scanning electron microscope and transmission electron microscope image of D-MIL-125(Ti), D-MIL-125(280), and D-MIL-125(380) materials prepared by the present invention; Figure 6 It is an N2 adsorption-desorption isotherm and pore size distribution curve graph of D-MIL-125(Ti), D-MIL-125(280), and D-MIL-125(380) materials prepared by the present invention; Figure 7 It is an XPS spectrum of D-MIL-125(Ti), D-MIL-125(280), and D-MIL-125(380) materials: (a) full spectrum, (b) Ti 2p fine spectrum, (c) O 1s fine spectrum, (d) electron paramagnetic resonance (EPR) spectrum; Figure 8The physical picture of the removal of methylene blue by the material prepared in this invention; Figure 9 The comparison chart of the removal efficiency of methylene blue by the D-MIL-125(Ti), D-MIL-125(280) and D-MIL-125(380) materials prepared in this invention: (a) Comparison among different adsorbents, (b) Comparison among different adsorbents at 1 minute, (c) Comparison under different pH conditions, (d) Isoelectric point of D-MIL-125(280).

[0018] Figure 10 (a) is the adsorption kinetic curve of D-MIL-125(280) material, (b) Pseudo-first-order (PFO) and (c) Pseudo-second-order (PSO) kinetic models.

[0019] Figure 11 (a) Langmuir and Freundlich adsorption isotherms of D-MIL-125(280) material, (b) Linear fitting of Langmuir model, (c) Van’t Hoff thermodynamic curve, (d) Comparison of the maximum adsorption capacity (qm) between D-MIL-125(280) and other adsorbents, (e) Application evaluation of D-MIL-125(280) in actual water samples.

[0020] Figure 12 (a) The repeatable adsorption performance of D-MIL-125(280) for methylene blue (MB), (b) XRD spectrum of D-MIL-125(280)-MB and (c) Scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) analysis; Figure 13 (a) XPS full spectrum of the sample, (b) S 2p, (c) Ti 2p, (d) O 1s, (e) N 1s fine spectrum, (f) Fourier transform infrared (FTIR) spectra of D-MIL-125(280), MB and D-MIL-125(280)-MB; Figure 14 The schematic diagram of the adsorption mechanism between D-MIL-125(280) and MB is shown. Specific implementation mode

[0021] See Figure 1 , this invention provides a preparation method of Ti-MOF-based nanomaterials, including the following steps: S1. Divide the mixed solution of DMF and methanol into two equal parts. Add terephthalic acid and 2-aminoterephthalic acid ligand to one part, and add a titanium source to the other part. After ultrasonic dissolution, carry out a solvothermal reaction. After the reaction is completed, cool and wash; the titanium source is one of isopropyl titanate, n-butyl titanate, and titanium chloride.

[0022] S2. Heat the D-MIL-125(Ti) material obtained in S1 under a nitrogen atmosphere to obtain the HD-MIL-125(Ti) nanomaterial.

[0023] Example 1 A preparation method of a Ti-MOF-based nanomaterial, comprising the following steps: S1. Mix 27 mL of DMF and 3 mL of methanol and divide them into two equal parts. Add 5 mmol of terephthalic acid and 5 mmol of 2-aminoterephthalic acid to one part, and add 1.8 mL of isopropyl titanate to the other part. After ultrasonic treatment to ensure complete dissolution, mix the two parts and transfer them to a 100 mL stainless steel autoclave lined with polytetrafluoroethylene, and then heat at 150 °C in an oven for 48 h. After cooling, wash with DMF and methanol to obtain D-MIL-125(Ti); S2. Put 500 mg of D-MIL-125(Ti) into a crucible and heat it to 280 °C at a heating rate of 2.5 °C min -1 under a continuous N2 flow rate and maintain for 3 h to obtain the D-MIL-125(280) nanomaterial.

[0024] Example 2 A preparation method of a Ti-MOF-based nanomaterial, comprising the following steps: S1. Mix 27 mL of DMF and 3 mL of methanol and divide them into two equal parts. Add 5 mmol of terephthalic acid and 5 mmol of 2-aminoterephthalic acid to one part, and add 1.8 mL of isopropyl titanate to the other part. After ultrasonic treatment to ensure complete dissolution, mix the two parts and transfer them to a 100 mL stainless steel autoclave lined with polytetrafluoroethylene, and then heat at 150 °C in an oven for 48 h. After cooling, wash with DMF and methanol to obtain D-MIL-125(Ti); S2. Put 500 mg of D-MIL-125(Ti) into a crucible and heat it to 380 °C at a heating rate of 2.5 °C min -1 under a continuous N2 flow rate and maintain for 3 h to obtain the D-MIL-125(380) nanomaterial.

[0025] Material Characterization The D-MIL-125(Ti) and HD-MIL-125(Ti) nanomaterials obtained in the above Examples 1-2 were characterized by XRD, TGA, SEM, TEM, and N2 adsorption-desorption isotherms asFigures 2 - 5 as shown

[0026] Figure 2 is an XRD pattern, indicating that D-MIL-125(Ti) has diffraction peaks at 6.8°, 9.5°, 9.7°, 11.6°, 16.6°, etc., confirming its successful synthesis and good crystallinity. When the pyrolysis temperature rises to 280 °C, the peak intensity decreases due to the decarboxylation reaction of the ligand. When the temperature further rises to 380 °C, the characteristic peak at 6.8° disappears, indicating that significant structural changes occur due to the decarboxylation of a large amount of ligand.

[0027] Figure 3 is a TGA curve, indicating that D-MIL-125(Ti) remains stable below 150 °C. The 12% weight loss is due to the removal of free water, and the weight loss between 100 - 160 °C is attributed to the escape of residual solvents and unreacted substances in the pores. The decarboxylation process (corresponding to the decomposition of NH2BDC) starts at 280 °C, and the weight loss between 350 - 400 °C is related to the decomposition of H2BDC. Mild decarboxylation treatment at 280 °C can introduce oxygen vacancies without destroying the framework structure. According to the calculation of the residual weight, the mass ratio of NH2BDC to H2BDC in D-MIL-125(Ti) is 1.6.

[0028] Figure 4 is an infrared curve, indicating that stretching vibrations of O-H bonds or N-H bonds of amino groups are observed in the range of 3300 - 3600 cm⁻¹. The characteristic peaks between 1400 - 1700 cm⁻¹ correspond to the vibrations of carboxylate groups. Among them, the peak at 1537 cm⁻¹ belongs to the vibration of the C=O bond, and the peak at 1259 cm⁻¹ is the stretching vibration of the C-N bond in aromatic amines. The peak at 960 cm⁻¹ indicates the stretching vibration of the Ti-O-C bond. For D-MIL-125(280), due to the cleavage of the C-O bond, the peak intensities at 1537 and 1259 cm⁻¹ decrease significantly, while the vibration amplitude in the range of 800 - 400 cm⁻¹ reflects the presence of the O-Ti-O bond. When the pyrolysis temperature rises to 380 °C, some characteristic peaks disappear, but the carbon skeleton of the benzene ring group remains. The broad peak at 630 cm⁻¹ indicates the formation of crystalline TiO2. These results prove that a hierarchical porous Ti-MOF material with oxygen vacancies was successfully constructed through the decomposition of organic ligands at 280 °C.

[0029] Figure 5 are scanning electron microscopy and transmission electron microscopy images, indicating that the morphology of the adsorbent is characterized by scanning electron microscopy (SEM). Figure 5 a - c show that the samples exhibit a complete dodecahedral morphology. As the pyrolysis temperature increases, the surface of the material gradually becomes rough, which is attributed to the particle growth and aggregation processes induced by the decomposition of organic ligands. Figure 5The transmission electron microscopy (TEM) images of d-e further confirmed that D-MIL-125(Ti), D-MIL-125(280), and D-MIL-125(380) all maintained an icosahedral structure. It is worth noting that there is a rich pore structure inside D-MIL-125(280), which provides favorable conditions for its excellent adsorption performance. Experiments showed that the pyrolysis treatment did not have a significant impact on the overall morphology of the material.

[0030] Figure 6 Are the adsorption-desorption isotherm and pore size distribution curves, indicating that: Figure 6 And Table 1 studied the effect of pyrolysis temperature on the specific surface area and pore size of the samples through N2 adsorption-desorption isotherms. In the relative pressure range of 0.8 - 1.0, the isotherm of D-MIL-125(Ti) was of type I with a small hysteresis loop ( Figure 6 a), indicating that the material was mainly composed of micropores, and this feature could be further verified by Figure 6 the pore size distribution curve of c. The isotherm of D-MIL-125(280) presented a mixed type I / IV ( Figure 6 b), indicating the coexistence of micropores and a small amount of mesopores. The data in Table 1 showed that although the SBET of D-MIL-125(280) decreased significantly, its pore volume was basically equivalent to that of D-MIL-125(Ti). When the pyrolysis temperature rose to 380 °C, the N2 adsorption-desorption isotherm of the material changed to type III non-porous ( Figure 6 b). As shown in Table 1, its specific surface area, pore volume, and average pore size all decreased sharply, which was attributed to the decomposition of a large number of ligands and particle agglomeration during the heat treatment process. These results indicated that D-MIL-125(280) had the characteristics of a hierarchical porous structure. The existence of hierarchical pores in MOF materials could effectively promote the mass transfer rate during the adsorption process.

[0031] Figure 7 Is the XPS full spectrum, indicating that: As Figure 7 shown in a, all samples contained C, N, O, and Ti elements. The Ti 2p spectrum was deconvoluted ( Figure 7 b), and it was found that the characteristic peaks at 458.6 eV (Ti 2p3 / 2) and 464.4 eV (Ti 2p1 / 2) were attributed to Ti 4 ⁺, and the pyrolysis treatment did not change the chemical state of Ti. The O 1s spectrum ( Figure 7 c) showed that oxygen existed in the form of lattice oxygen (529.6 eV) and oxygen vacancies (531.3 eV). As the pyrolysis temperature increased, the content of oxygen vacancies (OVs) increased significantly. Figure 7 The electron paramagnetic resonance (EPR) spectrum (g = 2.003) of d further confirmed the existence of oxygen vacancies, and these defect sites might become active centers for dye adsorption.

[0032] Based on the above analysis, it can be inferred that by partially removing the organic ligands in D-MIL-125(Ti), a hierarchical structure with coexisting micropores and mesopores can be formed in this material. In addition, when the sample is pyrolyzed in a nitrogen atmosphere, oxygen vacancies are generated inside the material. Based on the synergistic effect of the hierarchical pores and oxygen vacancies, HD-MIL-125 shows broad application prospects in the adsorption field.

[0033] The prepared HD-MIL-125(Ti) nanomaterial was subjected to an adsorption test for methylene blue dye performance ( Figure 8 ).

[0034] As Figure 9 shown in a, D-MIL-125 pyrolyzed at 280 °C exhibited the best adsorption performance, and it could completely remove 200 mg L⁻¹ of methylene blue (MB) within 1 minute. Its adsorption efficiency was 2.2 times and 172.4 times that of D-MIL-125(Ti) and D-MIL-125(380), respectively ( Figure 9 b). This phenomenon is attributed to the synergistic effect of its micro-mesoporous hierarchical structure and abundant oxygen vacancies.

[0035] Effect of solution pH on adsorption performance Solution pH is a key factor affecting dye adsorption because it significantly affects the dye removal efficiency by regulating the surface charge density of the adsorbent. As Figure 9 shown in c, 1 g L⁻¹ of D-MIL-125(280) could completely remove 200 mg L⁻¹ of MB within the experimental pH range, but the adsorption rate showed a trend of first increasing and then decreasing with the change of pH. When pH = 6, MB could be completely removed within 1 minute. Therefore, this pH value was selected for subsequent experiments to study the influence of other variables. Through Figure 9 the zero charge point (pHPZC) analysis of d, it can be seen that when the solution pH > 1, the surface of D-MIL-125(280) is negatively charged. Since MB is a cationic dye, the negative charge on the adsorbent surface can promote the efficient adsorption of dye molecules through electrostatic attraction.

[0036] Study on adsorption kinetic mechanism To analyze the adsorption mechanism, the adsorption kinetic behavior of D-MIL-125(280) was systematically analyzed. As Figure 10 shown in a, when the adsorption capacities reached 200, 300, and 400 mg·g⁻¹ respectively, the corresponding adsorption equilibrium times were 3, 7, and 9 minutes. By fitting the experimental data to the pseudo-first-order kinetic model (PFO, Figure 10 b) and the pseudo-second-order kinetic model (PSO, Figure 10c), and combined with the fitting parameters in Table 2, it can be seen that the correlation coefficient of the PSO model (R² = 0.998) is significantly higher than that of the PFO model (R² = 0.952). This result indicates that the adsorption process of methylene blue (MB) on D-MIL-125(280) follows the pseudo-second-order kinetic law, confirming that its essence is a process dominated by chemical adsorption (such as surface coordination or electron transfer).

[0037] Adsorption Isotherm and Thermodynamic Studies Adsorption isotherms are crucial for understanding the interaction mechanism between adsorbent and adsorbate and system optimization. As Figure 11 shown in a, isotherm data were obtained through a 10-minute adsorption experiment, and non-linear fittings were performed using the Langmuir model (Ce / q vs. Ce) and the Freundlich model (log q vs. log Ce) respectively (charts are inserted). The R² value of the Langmuir model (0.984) is significantly higher than that of the Freundlich model (0.522), indicating that the adsorption process conforms to the characteristics of monolayer adsorption. In addition, the maximum adsorption capacity calculated by the Langmuir model (qm, cal. = 525.7 mg g⁻¹) is in good agreement with the experimental value (qm,exp. = 524.2 mg g⁻¹), verifying the reliability of the model. Figure 11 The R² of the linearly fitted Langmuir model in b reaches 0.999, further confirming its applicability.

[0038] Adsorption Thermodynamic Studies Evaluating the spontaneity of the adsorption process is crucial for practical applications. In this invention, the thermodynamic properties of methylene blue (MB) on D-MIL-125(280) were investigated through adsorption experiments at 298 K (25 °C), 308 K (35 °C), and 318 K (45 °C). Based on the linear relationship between lnK 0 and 1 / T ( Figure 11 c and the inserted table), thermodynamic parameters such as ΔH 0 (enthalpy change), ΔG 0 (Gibbs free energy change), and ΔS 0 (entropy change) were calculated. The negative value of ΔG 0 indicates that the adsorption process can occur spontaneously, and D-MIL-125(280) is feasible in practical applications; the positive value of ΔH 0 shows that this adsorption is an endothermic reaction, so the adsorption capacity increases significantly with the increase in temperature. The positive value of ΔS 0 indicates an increase in the disorder degree at the solid-liquid interface during the adsorption process, reflecting the strong affinity of D-MIL-125(280) for MB molecules.

[0039] As Figure 11As shown in Fig. d, the maximum adsorption capacity (qm = 525.7 mg·g⁻¹) and the shortest equilibrium time (10 minutes) of D-MIL-125(280) at 298 K are significantly better than those of classical MOF materials such as MIL-125(Ti), NH2-MIL-125(Ti), UiO-66, and NH2-UiO-66. The qm value is improved by 2-3 orders of magnitude compared with the reference materials, which is attributed to the synergistic effect of hierarchical pores and oxygen vacancies.

[0040] Verification of application in actual water bodies D-MIL-125(280) was applied to actual water samples such as deionized water, tap water, Chahe River water, and Jianhe River water in Dezhou area ( Figure 11 Fig. e). 1 g / L of D-MIL-125(280) achieved complete removal of 200 mg / L of MB, but the adsorption rate in actual water bodies decreased by about 15-20% compared with laboratory conditions, which may be related to the presence of competitive ions such as Na⁺ and Ca²⁺ in the water body. The results indicate that D-MIL-125(280) still has excellent potential for treating dye wastewater in complex water quality environments.

[0041] Recycling performance test In this invention, 0.1 M methanol / HCl (volume ratio 4:1) was used to desorb methylene blue (MB) from D-MIL-125(280). Acidic methanol can weaken the electrostatic interaction between the dye and the adsorbent, and at the same time, the methanol solvent promotes the dissolution of the dye. As Figure 12 shown in Fig. a, the MB removal efficiency still remained 87% after 6 cycles. Figure 12 XRD analysis in Fig. b shows that the crystallinity of the material did not change significantly after adsorbing MB. Figure 12 The elemental distribution map of D-MIL-125(280)-MB in Fig. c shows that Ti, O, and S elements are evenly distributed, confirming the successful adsorption of MB. The above results prove the excellent stability and regenerability of D-MIL-125(280).

[0042] Analysis of adsorption mechanism Figure 13 The appearance of the S 2p peak in Fig. a-b confirmed the loading of MB after adsorption. High-resolution XPS spectra ( Figure 13 Figs. c-e) show that after adsorbing MB, the peak positions of Ti 2p and N 1s did not shift, while the O 1s peak showed a red shift, indicating that oxygen vacancies play a key role in the adsorption of MB. Figure 13The FTIR spectrum of f showed that the characteristic peaks of MB appeared at 886 and 1600 cm⁻¹ for D-MIL-125(280)-MB, confirming its successful adsorption. In addition, the following significant changes occurred in the spectrum after adsorption: the O-H stretching vibration peak shifted from 3440 cm⁻¹ to 3400 cm⁻¹, indicating that the deprotonated O-H group participated in adsorption through electrostatic interaction; the shift of the aromatic ring vibration peak (1620→1610 cm⁻¹) was due to the π-π stacking effect between the adsorbent and the planar six-membered ring structure of MB; the amino N-H shear vibration peak shifted from 1631 cm⁻¹ to 1613 cm⁻¹, indicating the existence of hydrogen bond interaction between D-MIL-125(280) and MB molecules.

[0043] Based on XPS, FTIR and zeta potential analysis, Figure 14 showed the adsorption mechanism of D-MIL-125(280) and MB, mainly including: the multiple synergistic effects of electrostatic attraction (surface negative charge and cationic dye), π-π stacking (aromatic ring interaction), hydrogen bond interaction (amino and hydroxyl groups) and oxygen vacancy coordination (defect sites capturing dye molecules).

Claims

1. A preparation method of a Ti-MOF-based nanomaterial, characterized in that: It includes the following steps: S1. Divide the mixed solution of DMF and methanol into two equal parts. Add terephthalic acid and 2-aminoterephthalic acid ligand to one part, and add a titanium source to the other part. After ultrasonic dissolution, carry out a solvothermal reaction. After the reaction ends, cool and wash; S2. Heat the D-MIL-125(Ti) material obtained in S1 under a nitrogen atmosphere to obtain the HD-MIL-125(Ti) nanomaterial.

2. The preparation method of the Ti-MOF-based nanomaterial according to claim 1, characterized in that: The volume ratio of DMF to methanol is 27:

3.

3. The preparation method of the Ti-MOF-based nanomaterial according to claim 1, wherein: The molar ratio of terephthalic acid to 2-aminoterephthalic acid is 1:1; the addition ratio of terephthalic acid to the titanium source is 5 mmol:1.8 ml.

4. The preparation method of the Ti-MOF-based nanomaterial according to claim 1, wherein: The titanium source is one of isopropyl titanate, n-butyl titanate, and titanium chloride.

5. The preparation method of the Ti-MOF-based nanomaterial according to claim 1, characterized in that: The reaction conditions for S1 are: react at 150 °C for 48 h.

6. The preparation method of the Ti-MOF-based nanomaterial according to claim 1, wherein: The reaction conditions of S2 are as follows: heating at a heating rate of 2 °C min -1 -5 °C min -1 to 280 °C - 380 °C and maintaining for 3 h.

7. A Ti-MOF-based nanomaterial prepared by the preparation method according to any one of claims 1-6, characterized in that: The Ti-MOF-based nanomaterial has hierarchical pores and oxygen vacancies.

8. Application of a Ti-MOF-based nanomaterial prepared by the preparation method according to any one of claims 1-6 in the adsorption of methylene blue dye.

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