A ti-mof-based nanomaterial, a preparation method thereof and application thereof in methylene blue dye adsorption

Abstract

The application belongs to the technical field of metal organic framework adsorption material preparation and application, and particularly relates to a Ti-MOF-based nanomaterial, a preparation method thereof and application of the Ti-MOF-based nanomaterial in methylene blue dye adsorption. The application constructs a multi-porous Ti-MOF-based methylene blue adsorbent rich in oxygen vacancies by means of a temperature-regulated ligand pyrolysis strategy. The adsorption performance test shows that the adsorbent has a high adsorption capacity and a fast adsorption rate for methylene blue, because the multi-porous structure promotes the diffusion mass transfer of methylene blue, and the oxygen vacancies enhance the negative electric property of the adsorbent surface and provide more adsorption active sites.

Description

Technical Field

[0001] This invention relates to the field of metal-organic framework crystal materials technology, and in particular to a Ti-MOF-based nanomaterial, its preparation method, and its application in the adsorption of methylene blue dye. Background Technology

[0002] Organic dyes are widely used in various industries, including textiles, papermaking, food additives, paints, and leather. However, approximately 15% of these dyes are discharged as wastewater, posing a serious threat to human health and ecological balance. Compared to anionic dyes, cationic dyes are more toxic because they readily interact with negatively charged cell membranes, potentially causing disease. Methylene blue (MB) is a typical example of a cationic dye with carcinogenic risks, widely used in industry, and requires thorough treatment before being released into the environment.

[0003] Currently, the main methods for treating dye wastewater include adsorption, membrane separation, catalytic degradation, and chemical oxidation. Among these, adsorption is a highly efficient method for dye removal in wastewater treatment. This is due to many factors, including its cost-effectiveness, ease of implementation, and lack of secondary pollution. The adsorbent is the core component of adsorption methods, but most reported dye adsorbents still suffer from 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 highly efficient co-adsorption adsorbents over a wide pH range is a significant challenge. Compared to traditional adsorbents, metal-organic frameworks (MOFs) have a large specific surface area and high porosity, attracting considerable attention in the adsorption field. However, MOFs typically have pore sizes within the micropore range (<2 nm), while the size of organic dyes often exceeds 2 nm. This exacerbates mass transfer resistance, hindering sufficient contact between dye molecules and adsorption sites, and limiting their adsorption capacity and rate. Therefore, preparing MOFs with larger pore sizes is crucial for improving their adsorption capacity. Summary of the Invention

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

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

[0006] In a first aspect, the present invention provides a method for preparing Ti-MOF-based nanomaterials, comprising 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 titanium source to the other part. After ultrasonic dissolution, carry out a solvothermal reaction. After the reaction is completed, cool and wash. S2. The D-MIL-125(Ti) material obtained in S1 is heated under a nitrogen atmosphere to obtain HD-MIL-125(Ti) nanomaterials.

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

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

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

[0010] Furthermore, the reaction conditions for S1 are: 150℃ for 48 hours.

[0011] Furthermore, the reaction conditions for S2 are: at 2°C for [time missing] min [time missing] -1 -5°Cmin -1 Heat to 280°C-380°C at a heating rate and maintain for 3 hours.

[0012] Secondly, the present invention also provides a Ti-MOF-based nanomaterial prepared by any of the above preparation methods.

[0013] Thirdly, the present invention also provides the application of the above-mentioned Ti-MOF-based nanomaterials 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 this invention have a large specific surface area and a hierarchical pore structure with micropores and mesopores coexisting, which overcomes the limitation of small pore size (<2 nm) of traditional MOFs and promotes the diffusion and adsorption of macromolecular dyes.

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

[0016] (2) The Ti-MOF-based nanomaterials prepared in this invention exhibit excellent adsorption performance for methylene blue (MB), with a maximum adsorption capacity of 525.7 mg·g⁻¹, and adsorption equilibrium is reached within 10 minutes. This is due to its hierarchical porous structure, which accelerates the diffusion and mass transfer of dye molecules, while oxygen vacancies enhance the surface negative charge and provide more active sites. Attached Figure Description

[0017] Figure 1 A flowchart illustrating a method for preparing HD-MIL-125(Ti) material provided by this invention; Figure 2 X-ray electron diffraction patterns of D-MIL-125(Ti), D-MIL-125(280) and D-MIL-125(380) prepared in this invention; Figure 3 Thermogravimetric spectra of D-MIL-125(Ti), D-MIL-125(280) and D-MIL-125(380) obtained in this invention; Figure 4 Infrared curves of D-MIL-125(Ti), D-MIL-125(280) and D-MIL-125(380) obtained by the present invention; Figure 5 Scanning electron microscope (SEM) and transmission electron microscope (TEM) images of the D-MIL-125(Ti), D-MIL-125(280) and D-MIL-125(380) materials prepared in this invention; Figure 6 The N2 adsorption-desorption isotherms and pore size distribution curves of the D-MIL-125(Ti), D-MIL-125(280) and D-MIL-125(380) materials prepared in this invention are shown. Figure 7 XPS spectra of D-MIL-125(Ti), D-MIL-125(280) and D-MIL-125(380): (a) full spectrum, (b) Ti 2p fine spectrum, (c) O 1s fine spectrum, (d) electron paramagnetic resonance (EPR) spectrum; Figure 8This is a photograph of the material prepared according to the present invention for removing methylene blue. Figure 9 The following is a comparison 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 between different adsorbents, (b) Comparison of different adsorbents at 1 minute, (c) Comparison under different pH conditions, (d) Isoelectric point of D-MIL-125(280).

[0018] Figure 10 (a) shows the adsorption kinetics curves of D-MIL-125(280) material, (b) shows the pseudo-first-order (PFO) and (c) shows the 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 maximum adsorption capacity (qm) of D-MIL-125(280) with other adsorbents, (e) evaluation of the application of D-MIL-125(280) in actual water samples.

[0020] Figure 12 (a) Repeatable adsorption performance of D-MIL-125(280) for methylene blue (MB), (b) XRD pattern of D-MIL-125(280)-MB and (c) Scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) analysis; Figure 13 (a) Full XPS 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 A schematic diagram of the adsorption mechanism between D-MIL-125(280) and MB is shown. Detailed Implementation

[0021] See Figure 1 This invention provides a method for preparing Ti-MOF-based nanomaterials, comprising 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 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, or titanium chloride.

[0022] S2. The D-MIL-125(Ti) material obtained in S1 is heated under a nitrogen atmosphere to obtain HD-MIL-125(Ti) nanomaterials.

[0023] Example 1: A method for preparing Ti-MOF-based nanomaterials, comprising the following steps: S1. Mix 27 mL of DMF and 3 mL of methanol and divide into two equal portions. Add 5 mmol of terephthalic acid and 5 mmol of 2-aminoterephthalic acid to one portion, and add 1.8 mL of isopropyl titanate to the other portion. After sonication to ensure complete dissolution, mix the two portions and transfer them to a 100 mL stainless steel autoclave lined with polytetrafluoroethylene. Then heat at 150 °C for 48 h in a drying oven. After cooling, wash with DMF and methanol to obtain D-MIL-125(Ti). S2. Place 500 mg of D-MIL-125(Ti) in a crucible and incubate at 2.5°C for min. -1 The heating rate was increased to 280°C under continuous N2 flow and maintained for 3 hours to obtain D-MIL-125(280) nanomaterials.

[0024] Example 2: A method for preparing Ti-MOF-based nanomaterials, comprising the following steps: S1. Mix 27 mL of DMF and 3 mL of methanol and divide into two equal portions. Add 5 mmol of terephthalic acid and 5 mmol of 2-aminoterephthalic acid to one portion, and add 1.8 mL of isopropyl titanate to the other portion. After sonication to ensure complete dissolution, mix the two portions and transfer them to a 100 mL stainless steel autoclave lined with polytetrafluoroethylene. Then heat in a drying oven at 150 °C for 48 h. After cooling, wash with DMF and methanol to obtain D-MIL-125(Ti). S2. Place 500 mg of D-MIL-125(Ti) in a crucible and incubate at 2.5°C for min. -1 The heating rate was increased to 380°C under continuous N2 flow and maintained for 3 hours to obtain D-MIL-125(380) nanomaterials.

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

[0026] Figure 2 The XRD pattern shows that D-MIL-125(Ti) exhibits diffraction peaks at 6.8°, 9.5°, 9.7°, 11.6°, and 16.6°, confirming its successful synthesis and good crystallinity. When the pyrolysis temperature is increased to 280°C, the peak intensity decreases due to the decarboxylation reaction of the ligands. When the temperature is further increased to 380°C, the characteristic peak at 6.8° disappears, indicating that extensive decarboxylation of the ligands leads to significant structural changes.

[0027] Figure 3 The TGA curves show that D-MIL-125(Ti) remains stable below 150℃. The 12% weight loss is due to the removal of free water, while the weight loss between 100-160℃ is attributed to the escape of residual solvent and unreacted substances from the pores. Decarboxylation (corresponding to NH₂BDC decomposition) begins at 280℃, and the weight loss between 350-400℃ is related to H₂BDC decomposition. Mild decarboxylation at 280℃ introduces oxygen vacancies without damaging the framework structure. Based on the residual weight, the mass ratio of NH₂BDC to H₂BDC in D-MIL-125(Ti) is 1.6.

[0028] Figure 4 The infrared curves show that OH bond stretching vibrations or amino NH bond vibrations are observed in the 3300-3600 cm⁻¹ range. Characteristic peaks between 1400-1700 cm⁻¹ correspond to the vibrations of carboxylate groups. The peak at 1537 cm⁻¹ is attributed to C=O bond vibrations, and the peak at 1259 cm⁻¹ is the stretching vibration of the CN bond in aromatic amines. The peak at 960 cm⁻¹ indicates the stretching vibration of the Ti-OC bond. For D-MIL-125(280), the peak intensities at 1537 and 1259 cm⁻¹ are significantly reduced due to the breaking of the CO bond, while the vibration amplitude in the 800-400 cm⁻¹ range reflects the presence of the O-Ti-O bond. When the pyrolysis temperature rises to 380℃, some characteristic peaks disappear, but the carbon skeleton of the benzene ring group is still retained. The broad peak at 630 cm⁻¹ indicates the formation of crystalline TiO₂. These results demonstrate that hierarchical porous Ti-MOF materials with oxygen vacancies were successfully constructed by decomposing organic ligands at 280 °C.

[0029] Figure 5 The images show scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images, demonstrating that the morphology of the adsorbent was characterized by scanning electron microscopy (SEM). Figure 5 Ac shows that the sample exhibits a complete decahedral morphology. As the pyrolysis temperature increases, the material surface gradually becomes rough, which is attributed to the particle growth and aggregation process induced by the decomposition of organic ligands. Figure 5Transmission electron microscopy (TEM) images further confirmed that D-MIL-125(Ti), D-MIL-125(280), and D-MIL-125(380) all maintain a decahedral structure. Notably, D-MIL-125(280) exhibits a rich porous structure, which provides favorable conditions for its excellent adsorption performance. Experiments showed that pyrolysis treatment did not significantly affect the overall morphology of the material.

[0030] Figure 6 The adsorption-desorption isotherms and pore size distribution curves show that: Figure 6 Table 1 shows the effect of pyrolysis temperature on the specific surface area and pore size of the samples, investigated using N2 adsorption-desorption isotherms. Within the relative pressure range of 0.8–1.0, the isotherms for D-MIL-125(Ti) exhibit a type I pattern with a small hysteresis loop. Figure 6 a) indicates that the material is predominantly microporous, a characteristic that can be observed through... Figure 6 The pore size distribution curve of c further verifies this. The isotherm of D-MIL-125(280) shows a mixed type of I / IV. Figure 6 b), indicating the simultaneous presence of micropores and a small number of mesopores. Table 1 data shows 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℃, the N2 adsorption-desorption isotherm of the material transformed into a type III nonporous type ( Figure 6 (b) As shown in Table 1, its specific surface area, pore volume, and average pore size all decreased sharply, which is attributed to the decomposition of a large number of ligands and particle agglomeration during the heat treatment process. These results indicate that D-MIL-125(280) has a hierarchical porous structure. The presence of hierarchical channels in MOF materials can effectively promote the mass transfer rate during the adsorption process.

[0031] Figure 7 The XPS full spectrum indicates that: Figure 7 As shown in figure a, all samples contain C, N, O, and Ti elements. Peak fitting was performed on the Ti 2p spectrum ( Figure 7 (b) The characteristic peaks at 458.6 eV (Ti 2p3 / 2) and 464.4 eV (Ti 2p1 / 2) were found to be attributed to Ti. 4 ⁺, and the pyrolysis treatment did not change the chemical state of Ti. O 1s spectrum ( Figure 7 c) shows that oxygen exists in the form of lattice oxygen (529.6 eV) and oxygen vacancies (531.3 eV). The content of oxygen vacancies (OVs) increases significantly with increasing pyrolysis temperature. Figure 7 The electron paramagnetic resonance (EPR) spectrum of d (g=2.003) further confirmed the presence of oxygen vacancies, which may become active centers for dye adsorption.

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

[0033] The performance of the prepared HD-MIL-125(Ti) nanomaterials was tested by adsorption analysis for methylene blue dye. Figure 8 ).

[0034] like Figure 9 As shown in Figure a, D-MIL-125 pyrolyzed at 280°C exhibited the best adsorption performance, completely removing 200 mg L⁻¹ of methylene blue (MB) within 1 minute. Its adsorption efficiencies were 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 its micro-mesoporous hierarchical structure and the synergistic effect of abundant oxygen vacancies.

[0035] Effect of solution pH on adsorption performance Solution pH is a key factor affecting dye adsorption, as it significantly influences dye removal efficiency by regulating the surface charge density of the adsorbent. For example... Figure 9 As shown in Figure c, 1 g L⁻¹ of D-MIL-125(280) completely removed 200 mg L⁻¹ of MB within the experimental pH range, but the adsorption rate first increased and then decreased with pH. MB was completely removed within 1 minute at pH = 6; therefore, this pH value was chosen for subsequent experiments to investigate the effects of other variables. Figure 9 Analysis of the zero charge point (pHPZC) of d revealed that the surface of D-MIL-125(280) was negatively charged when the solution pH>1. 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] Adsorption kinetics mechanism study To elucidate the adsorption mechanism, the adsorption kinetics of D-MIL-125(280) were systematically analyzed. For example... Figure 10 As shown in Figure a, when the adsorption capacity reaches 200, 300, and 400 mg·g⁻¹, the corresponding adsorption equilibrium times are 3, 7, and 9 minutes, respectively. The experimental data were then fitted with a pseudo-first-order kinetic model (PFO). Figure 10 b) and the pseudo-second-order dynamical 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 pseudo-second-order kinetics, confirming that its essence is a process dominated by chemisorption (such as surface coordination or electron transfer).

[0037] Adsorption isotherms and thermodynamic studies Adsorption isotherms are crucial for understanding the interaction mechanism between adsorbents and adsorbates, and for system optimization. For example... Figure 11 As shown in figure a, isotherm data were obtained through a 10-minute adsorption experiment, and nonlinear fitting was performed using the Langmuir model (Ce / q vs. Ce) and the Freundlich model (log q vs. log Ce), respectively (see figures and tables). The R² value of the Langmuir model (0.984) was 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 high agreement with the experimental value (qm, exp. = 524.2 mg g⁻¹), verifying the reliability of the model. Figure 11 The Langmuir model with linear fitting in b achieves an R² of 0.999, further confirming its applicability.

[0038] Adsorption thermodynamics studies The spontaneous assessment of the adsorption process is crucial for practical applications. This invention investigates the thermodynamic properties of methylene blue (MB) on D-MIL-125 (280) through adsorption experiments at 298 K (25 °C), 308 K (35 °C), and 318 K (45 °C). Based on lnK... 0 Linear relationship with 1 / T ( Figure 11 c and interpolation), ΔH was calculated. 0 (Enthalpy change), ΔG 0 (Gibbs free energy change) and ΔS 0 Thermodynamic parameters such as entropy change. ΔG 0 A negative value indicates that the adsorption process can proceed spontaneously, and that D-MIL-125(280) is feasible in practical applications; ΔH 0 A positive value indicates that the adsorption is an endothermic reaction, therefore the adsorption capacity increases significantly with increasing temperature. ΔS 0 A positive value indicates an increase in the degree of disorder at the solid-liquid interface during adsorption, reflecting the strong affinity of D-MIL-125(280) for MB molecules.

[0039] like Figure 11As shown in Figure d, D-MIL-125(280) exhibits significantly better maximum adsorption capacity (qm = 525.7 mg·g⁻¹) and shortest equilibrium time (10 min) at 298 K than classic MOF materials such as MIL-125(Ti), NH₂-MIL-125(Ti), UiO-66, and NH₂-UiO-66. Its qm value is 2-3 orders of magnitude higher than the comparative materials, attributed to the synergistic effect of hierarchical pores and oxygen vacancies.

[0040] Real-world water application verification D-MIL-125 (280) was applied to actual water samples from Dezhou area, including deionized water, tap water, Chahe River water, and Jianhe River water. Figure 11 e). 1 g / L D-MIL-125(280) completely removed 200 mg / L MB, but the adsorption rate in actual water bodies decreased by about 15-20% compared to laboratory conditions, possibly due to the presence of competing ions such as Na⁺ and Ca²⁺ in the water. These results indicate that D-MIL-125(280) still possesses excellent potential for treating dye wastewater in complex water environments.

[0041] Cyclic performance test This invention uses 0.1 M methanol / HCl (volume ratio 4:1) to desorb methylene blue (MB) from D-MIL-125(280). The acidic methanol weakens the electrostatic interaction between the dye and the adsorbent, while the methanol solvent promotes dye dissolution. Figure 12 As shown in a, the MB removal efficiency remained at 87% after 6 cycles. Figure 12 XRD analysis of b showed that the crystallinity of the material did not change significantly after MB adsorption. Figure 12 The elemental distribution map of D-MIL-125(280)-MB c shows that Ti, O, and S elements are uniformly distributed, confirming the successful adsorption of MB. The above results demonstrate the excellent stability and regenerability of D-MIL-125(280).

[0042] Adsorption mechanism analysis Figure 13 The appearance of the S 2p peak in ab confirms the loading of MB after adsorption. High-resolution XPS spectra ( Figure 13 The results showed that after MB adsorption, the Ti 2p and N 1s peaks did not shift, while the O 1s peak showed a red shift, indicating that oxygen vacancies play a key role in MB adsorption. Figure 13The FTIR spectrum of f showed that D-MIL-125(280)-MB exhibited characteristic MB peaks at 886 and 1600 cm⁻¹, confirming its successful adsorption. Furthermore, the following significant changes occurred in the spectrum after adsorption: the OH stretching vibration peak shifted from 3440 cm⁻¹ to 3400 cm⁻¹, indicating that the deprotonated OH 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 NH shear vibration peak shifted from 1631 cm⁻¹ to 1613 cm⁻¹, indicating the presence of hydrogen bonds between D-MIL-125(280) and MB molecules.

[0043] Based on XPS, FTIR and zeta potential analysis Figure 14 The adsorption mechanism of D-MIL-125(280) with MB was demonstrated, which mainly includes multiple synergistic effects such as electrostatic attraction (negative surface charge and cationic dye), π-π stacking (aromatic ring interaction), hydrogen bonding (amino and hydroxyl groups) and oxygen vacancy coordination (defect sites capture dye molecules).

Claims

1. A method for preparing Ti-MOF-based nanomaterials, characterized in that: 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 titanium source to the other part. After ultrasonic dissolution, carry out a solvothermal reaction. After the reaction is completed, cool and wash. S2. The D-MIL-125(Ti) material obtained in S1 is heated under a nitrogen atmosphere to obtain HD-MIL-125(Ti) nanomaterials; The reaction conditions for S2 are: at 2°C for min. -1 -5°Cmin -1 Heat to 280°C at a rising rate and maintain for 3 hours; The Ti-MOF-based nanomaterials have hierarchical channels and oxygen vacancies.

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

3.

3. The method for preparing Ti-MOF-based nanomaterials according to claim 1, characterized in that: The molar ratio of terephthalic acid to 2-aminoterephthalic acid is 1:1; the addition ratio of terephthalic acid and titanium source is 5 mmol: 1.8 ml.

4. The method for preparing Ti-MOF-based nanomaterials according to claim 1, characterized in that: The titanium source is one of isopropyl titanate, n-butyl titanate, or titanium chloride.

5. The method for preparing Ti-MOF-based nanomaterials according to claim 1, characterized in that: The reaction conditions for S1 are: 150℃ for 48 hours.

6. A Ti-MOF-based nanomaterial prepared by the preparation method according to any one of claims 1-5, characterized in that: The Ti-MOF-based nanomaterials have hierarchical pores and oxygen vacancies.

7. The application of a Ti-MOF-based nanomaterial prepared by any one of claims 1-5 in the adsorption of methylene blue dye.

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