Metal organic framework material, preparation method and application thereof

Abstract

The application discloses a kind of metal organic framework material and its preparation method and application, belong to mycotoxin detection technical field.The iron-based metal organic framework MIL-101 (Fe) is synthesized by solvothermal method, and is surface modified using TMCS, to obtain TMCS-MIL-101 (Fe) adsorbent.The material effectively improves the surface properties of the material under the premise of not destroying the original framework structure of MIL-101 (Fe), with good thermal stability and dispersibility.Adsorption experiment shows that under the conditions of adsorbent dosage 0.8 mg·mL ‑1 , pH 7.0 and temperature 333K, the removal rate of OTA can reach 95%, and the process is non-uniform surface multi-site adsorption.Molecular docking analysis reveals that OTA and TMCS-MIL-101 (Fe) form multiple non-covalent interactions through hydrogen bonding, π-π stacking and electrostatic interaction.In addition, the adsorbent achieves 87% and 72% OTA removal rate in simulated rapeseed oil and peanut meal system respectively, providing a new idea for constructing efficient mycotoxin adsorption material.

Description

Technical Field

[0001] This invention relates to the field of fungal toxin detection technology, specifically to a metal-organic framework material, its preparation method, and its application. Background Technology

[0002] In recent years, the contamination of grains and common animal feed by mycotoxins has become an increasingly prominent problem, posing a major challenge that urgently needs to be addressed globally. Statistics show that approximately 25% of global food crops are contaminated with mycotoxins annually. Ochratoxin A (OTA) is a toxic secondary metabolite primarily produced by various Aspergillus and Penicillium fungi, and is one of the most prevalent mycotoxins contaminating agricultural products worldwide. OTA is commonly detected in oilseeds, grains, coffee, wine, dried fruits, spices, and their derivatives. Due to its chemical stability, strong heat resistance, and persistence under various storage conditions, OTA can survive most routine food processing and refining processes, thus accumulating along the food chain. Toxicological studies have shown that OTA has significant nephrotoxicity, hepatotoxicity, immunosuppressive effects, and reproductive toxicity; long-term exposure is associated with an increased risk of Balkan endemic kidney disease and cancer. Therefore, the International Agency for Research on Cancer (IARC) has classified OTA as a Group 2B possible human carcinogen. To protect public health, many countries and regions worldwide have established strict limits for OTA residues. Despite some progress in existing removal methods, the persistence of OTA contamination in food and feed systems remains a problem that urgently needs to be addressed.

[0003] To reduce OTA contamination, various detoxification methods have been explored, including physical removal, chemical degradation, and biotransformation. Adsorption technology has attracted significant attention due to its ease of operation, rapid processing, and minimal impact on food quality. Various adsorbents (such as activated carbon, clay minerals, biochar, and polymer resins) have been used to remove OTA or other fungal toxins. While activated carbon has a high specific surface area, it often suffers from poor selectivity and regeneration difficulties. Clay adsorbents have limited adsorption capacity and may interact non-specifically with food components, leading to nutrient loss. Polymer resins are effective but expensive and pose risks related to chemical stability and safety. These limitations severely restrict their application in complex food systems, especially in the edible oil sector. In model vegetable oil systems where triglycerides are the primary solvent, the enrichment of impurities / polar molecules on the adsorption surface and hydrogen bonding are affected by the solvent environment and interfacial structure, thus altering adsorption and mass transfer behavior. Therefore, there is a need to develop advanced adsorbent materials that combine high capacity, high selectivity, reusability, and adaptability to various food matrices.

[0004] Metal-organic frameworks (MOFs) are a rapidly developing class of porous crystalline materials formed by the coordination of metal ions or clusters with organic ligands. With their ultra-high specific surface area, tunable pore size, regular pore structure, and diverse surface chemical properties, MOFs have become potential adsorbents for removing food contaminants. Existing studies have used various MOFs to adsorb and remove contaminants with different physicochemical properties, covering fluorides, tetracyclines, and Pb in matrices such as tea, milk, and apple juice. 2+ Among numerous MOF systems, MOFs constructed with different metal centers exhibit significant differences in stability, biosafety, and adsorption performance. However, in complex food matrices, traditional MOFs often face problems such as insufficient dispersibility and limited interfacial interactions, thus affecting the full realization of their adsorption performance. Therefore, developing MOF materials with both good stability and interfacial adaptability is crucial for achieving efficient removal of OTA from complex systems. Summary of the Invention

[0005] In view of this, the present invention provides a metal-organic framework material, its preparation method and application. The metal-organic framework material uses MIL-101(Fe) as the basic framework and uses trimethylchlorosilane (TMCS) to modify its surface in order to regulate the surface properties of the material and improve its dispersibility and interfacial adaptability in complex systems.

[0006] The present invention achieves the above objectives through the following technical solutions: In a first aspect, the present invention provides a method for preparing a metal-organic framework material, comprising the following steps: Preparation of S1. MIL-101(Fe) FeCl3•6H2O and H2BDC were dissolved in DMF solution, transferred to an autoclave for heating and reaction. After the reaction was completed, the mixture was cooled, centrifuged, and the solid was collected. The solid was purified with ethanol and dried to obtain MIL-101(Fe). S2. Preparation of TMCS-MIL-101(Fe) The MIL-101(Fe) obtained in step S1 was dispersed in anhydrous toluene. Under inert gas protection, TMCS was added for reflux reaction. After the reaction was completed, the product was washed and dried to obtain TMCS-MIL-101(Fe), which is a metal-organic framework material.

[0007] Furthermore, the heating reaction in step S1 is carried out at 100-120°C for 10-30 h.

[0008] Furthermore, in step S1, the ethanol is purified by double treatment with ethanol at 50-70℃ for 2-4 hours.

[0009] Furthermore, in step S2, the reflux reaction temperature is 70-90℃ and the time is 5-7 h.

[0010] Furthermore, step S2 involves washing with distilled water and ethanol 2-4 times each.

[0011] Furthermore, in step S2, the drying process involves first vacuum drying at 70-90℃ for 7-9 hours, followed by drying at 100-120℃ for 11-13 hours.

[0012] Secondly, the present invention provides a metal-organic framework material, which is prepared by any of the above-described methods for preparing a metal-organic framework material.

[0013] Thirdly, the present invention provides the application of a metal-organic framework material as described above in the removal of ochratoxin A.

[0014] Furthermore, the metal-organic framework material is contacted with a sample containing ochratoxin A to adsorb ochratoxin A from the sample.

[0015] Furthermore, the sample is peanut meal, soybean meal, walnut meal, or edible oil; the adsorption conditions are: 0.8 mg / mL of metal-organic framework material, pH 7.0, and temperature 333 K.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention synthesizes MIL-101(Fe) via a solvothermal method, and then modifies its surface with trimethylchlorosilane to prepare the TMCS-MIL-101(Fe) adsorbent. This material effectively improves the surface properties of the material without destroying the original framework structure of MIL-101(Fe), exhibiting uniform particle size distribution, good dispersibility, and good thermal stability below 180℃. Adsorption experiments show that with an adsorbent dosage of 0.8 mg•mL... -1 Under conditions of pH 7.0 and temperature 333 K, the material achieved a removal rate of 95% for ochratoxin A. The adsorption kinetics conformed to a pseudo-second-order kinetic model, and the adsorption isotherm followed the Freundlich model, indicating that the process is a non-uniform surface multi-site adsorption. Thermodynamic analysis showed that the adsorption process was spontaneously endothermic. Molecular docking analysis revealed that OTA and TMCS-MIL-101(Fe) formed multiple non-covalent interactions through hydrogen bonding, π–π stacking, and electrostatic interactions. Furthermore, the material achieved OTA removal rates of 87% and 72% in simulated rapeseed oil and peanut meal systems, respectively, demonstrating good potential for practical application. This invention provides a new approach for the development of highly efficient mycotoxin adsorbent materials. Attached Figure Description

[0017] Figure 1 Schematic diagrams of MIL-101(Fe) and TMCS-MIL-101(Fe) prepared in this invention and their adsorption behavior in rapeseed oil and peanut meal systems.

[0018] Figure 2 The structural characterization diagrams of MIL-101(Fe) and TMCS-MIL-101(Fe) prepared in this invention are shown below. (A) is the SEM image of MIL-101(Fe), (BC) is the SEM image of TMCS-MIL-101(Fe), (D) is the PXRD pattern of MIL-101(Fe) and TMCS-MIL-101(Fe), (E) is the FTIR spectrum of MIL-101(Fe) and TMCS-MIL-101(Fe), (F) is the particle size distribution of TMCS-MIL-101(Fe), (G) is the TGA curve of TMCS-MIL-101(Fe), (H) is the XPS image of TMCS-MIL-101(Fe), (I) is the C1s spectrum of TMCS-MIL-101(Fe), and (J) is the O2 spectrum of TMCS-MIL-101(Fe). 1s spectrum, (K) is the Fe 2p spectrum of TMCS-MIL-101(Fe), (L) is the Si 2p spectrum of TMCS-MIL-101(Fe).

[0019] Figure 3 The process of TMCS-MIL-101(Fe) adsorbing OTA prepared in this invention is shown in the following figures: (A) is the linear equation of OTA concentration-fluorescence intensity fitting; (B) is the effect of temperature on adsorption effect; (C) is the effect of adsorbent dosage on adsorption effect; (D) is the adsorption effect of TMCS-MIL-101(Fe) on OTA in solution at different pH values; (E) is the stability of TMCS-MIL-101(Fe) at different pH values ​​evaluated by PXRD; and (F) is the effect of adsorption time on adsorption effect.

[0020] Figure 4 This is a cyclic adsorption diagram of OTA adsorbed by TMCS-MIL-101(Fe) prepared in this invention.

[0021] Figure 5 The isotherm model and kinetic model for OTA adsorption by TMCS-MIL-101(Fe) prepared in this invention are shown below, where (A) is the fitted linear equation of the Langmuir model, (B) is the fitted linear equation of the Freundlich model, (C) is the fitted linear equation of the pseudo-first-order kinetic model, and (D) is the fitted linear equation of the pseudo-second-order kinetic model.

[0022] Figure 6The diagram shows the molecular conformations, where (A) represents the binding mode of TMCS-MIL-101(Fe) and OTA (conformation 1), (a) is the three-dimensional structure of the complex, (b) is the electrostatic potential distribution on the material surface, (c) is the detailed binding mode diagram of the complex, and (B) is the electrostatic potential analysis of the interacting molecules; (C) represents the binding mode of TMCS-MIL-101(Fe) and OTA (conformation 2), where (a) is the three-dimensional structure of the complex, (b) is the electrostatic potential distribution on the material surface, (c) is the detailed binding mode diagram of the complex, and (D) is the electrostatic potential analysis of the interacting molecules. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention. It should be noted that, unless otherwise specified, all chemical reagents involved in this invention are purchased through commercial channels.

[0024] The reagents and chemicals used in the following examples: Ochratoxin A standard (≥98%), ferric chloride hexahydrate (FeCl3•6H2O, analytical grade), terephthalic acid (H2BDC, 99%), N,N-dimethylformamide (DMF, anhydrous), trimethylchlorosilane (TMCS, 98%), methanol and ethanol (chromatographic grade), sodium hydroxide and hydrochloric acid (guaranteed purity) were purchased from Maclean's Biochemical Co., Ltd. (Shanghai, China). Rapeseed oil was purchased from the local market (Shandong, China). Phosphate-buffered saline (0.01 M, pH 7.0) was prepared in our laboratory.

[0025] The main instruments used in the following embodiments: The fluorescence intensity of OTA was measured at excitation and emission wavelengths of 333 nm and 460 nm using an Infinite Eplex microplate reader (Tecan Group Ltd., Switzerland). The morphology of the prepared materials was observed using a field emission scanning electron microscope (FEG-SEM) (SU8010, Hitachi, Japan) at an accelerating voltage of 5.0 kV. The crystal structure of the synthesized MOFs was characterized by powder X-ray diffraction (PXRD) using a D8 ADVANCE diffractometer (Bruker, Germany) in conjunction with Cu Kα radiation. After vacuum drying, the samples were pressed into pellets, and Fourier transform infrared (FT-IR) spectra were recorded using an IRTracer-100 spectrometer (Shimadzu, Japan). The thermal stability of the materials was analyzed by thermogravimetric analysis (TGA) using a TGA2 analyzer (Mettler-Toledo, Switzerland) within a temperature range of 30–800°C. The surface elemental composition and chemical state of the samples were further analyzed using X-ray photoelectron spectroscopy (XPS) on an ESCALAB 250Xi spectrometer (Thermo Fisher Scientific, USA).

[0026] Example 1 A method for preparing a metal-organic framework material includes the following steps: Preparation of S1. MIL-101(Fe) 2.45 mmol of FeCl3•6H2O and 1.24 mmol of H2BDC were dissolved in 15 mL of DMF solution, transferred to an autoclave, and heated at 110 °C for 20 hours. After the reaction was completed, the mixture was slowly cooled in an oven, and the brown solid was recovered by centrifugation. The solid was purified by double treatment with ethanol at 60 °C for 3 hours and then dried in an oven at 70 °C for 30 minutes to 1 hour to obtain MIL-101(Fe). S2. Preparation of TMCS-MIL-101(Fe) 1.0 g of MIL-101(Fe) obtained in step S1 was dispersed in 50 mL of anhydrous toluene. 0.5 mL of TMCS was added dropwise under nitrogen protection. The mixture was refluxed at 80 °C for 6 h. The product was washed three times each with distilled water and ethanol, dried under vacuum at 80 °C for 8 h, and then dried at 110 °C for 12 h to obtain TMCS-MIL-101(Fe), which is the metal-organic framework material.

[0027] MIL-101(Fe) is prepared by a modified hydrothermal method, using FeCl3•6H2O as a metal node and terephthalic acid as an organic linker molecule to construct a metal-organic framework with a porous structure. Through surface modification, MIL-101(Fe) can better perform its adsorption of OTA.

[0028] Depend on Figure 1 As can be seen, this invention first synthesizes MIL-101(Fe) using FeCl3•6H2O and H2BDC as raw materials via a solvothermal method at 110℃. Then, MIL-101(Fe) is reacted with trimethylchlorosilane (TMCS) to obtain TMCS-MIL-101(Fe) through surface modification. The TMCS-MIL-101(Fe) prepared by this invention can be used as an adsorbent in rapeseed oil and peanut meal systems to achieve the adsorption and removal of ochratoxin A through ultrasonication and stirring.

[0029] Example 2: Characterization of materials The MIL-101(Fe) and TMCS-MIL-101(Fe) prepared in Example 1 were systematically characterized by SEM, PXRD, FTIR, DLS, TGA, and XPS. 1. SEM characterization like Figure 2 As shown in Figure A, MIL-101(Fe) exhibits a typical octahedral shape, good particle size uniformity, and a surface with typical porous texture characteristics of MOF materials, consistent with the classic morphological characteristics of the MIL-101 series materials. Further SEM characterization of TMCS-MIL-101(Fe) was performed. Figure 2 (B and 2C), the edges and vertices of the octahedron of the material become rounded, and the organic layer covering results in a softer profile.

[0030] 2. PXRD characterization like Figure 2 As shown in Figure D, the crystal X-ray diffraction (PXRD) pattern of the synthesized MIL-101(Fe) material is consistent with the characteristic peak parameters of the crystal structure reported in the literature (MIL-101(Fe)@Ag rapid synergistic antimicrobial and biosafety evaluation of nanomaterials, Molecules, 27 (2022) 3497), located at 2θ values ​​of 8.9°, 10.2°, 10.6°, and 19.5°, respectively, and without any impurity peak interference. This result confirms that the synthesized material has high crystallinity and its crystal structure is consistent with the target MIL-101(Fe). The characteristic diffraction peaks of MIL-101(Fe) before and after TMCS modification are preserved, indicating that the modification process did not destroy the crystal framework structure of MIL-101(Fe). Compared to the unmodified sample, the diffraction peak intensity of TMCS-MIL-101(Fe) decreased slightly, which is attributed to lattice distortion and reduced X-ray scattering caused by the grafting of TMCS molecules on the crystal surface.

[0031] 3. FTIR characterization like Figure 2 As shown in E, multiple characteristic peaks appeared in the Fourier transform infrared spectrum, corresponding to the structural functional groups of MIL-101(Fe), at 1580 cm⁻¹. -1 and 1385 cm -1 For benzene ring skeletal vibration and carboxylate symmetric stretching, 540 cm -1 The Fe-O bond vibration at 1250 cm⁻¹ confirmed the coordination structure. -1 The new absorption peak at 2960 cm⁻¹ corresponds to the characteristic stretching vibration of the -Si(CH₃)₃ group, while the peak at 2960 cm⁻¹ corresponds to the characteristic stretching vibration of the -Si(CH₃)₃ group. -1 and 1380 cm -1 The enhanced vibrational signal of the CH bond indicates that the surface modification was successfully performed.

[0032] 4. DLS characterization Dynamic light scattering (DLS) Figure 2 F) Data shows that the particle diameter distribution of TMCS-MIL-101(Fe) exhibits a unimodal characteristic, with the particle size mainly distributed between 200-1000 nm and an average particle size of about 600 nm, indicating that the material has a low degree of particle agglomeration and good dispersibility in the dispersion system.

[0033] 5. TGA characterization Thermogravimetric analysis (TGA) curves show the weight loss of TMCS-MIL-101(Fe) as a function of temperature. Figure 2 The results (G) show that the mass of TMCS-MIL-101(Fe) remains essentially unchanged below 180℃, then gradually decreases, and the skeleton begins to collapse after 500℃. This indicates that the TMCS-MIL-101(Fe) structure exhibits good stability at temperatures not exceeding 180℃, ensuring the material's performance in higher temperature environments.

[0034] 6. XPS characterization The surface chemical composition and elemental valence states of TMCS-MIL-101(Fe) were analyzed by X-ray photoelectron spectroscopy (XPS). Figure 2The C 1s and O 1s signals are relatively strong, mainly originating from the terephthalic acid ligands in the MIL-101(Fe) framework. The appearance of the Fe 2p peak confirms the presence of the iron cluster, while the appearance of the Si 2p peak is direct evidence that trimethylchlorosilane (TMCS) was successfully grafted onto the MIL-101(Fe) surface, indicating that MIL-101(Fe) has completed surface modification. The characteristic peaks of the C 1s, O 1s, Fe 2p, and Si 2p orbitals are clearly observed in the high-resolution spectrum. All spectra are charged and corrected based on the C 1s binding energy (284.80 eV). In the C 1s spectrum ( Figure 2 I), the C=C bond at 284.80 eV mainly corresponds to the carbon atom on the benzene ring of terephthalic acid in MIL-101(Fe) and the carbon on the methyl group in the TMCS modification layer; the CO bond at 286.14 eV belongs to the carbon atom connected to oxygen in the carboxyl group of the ligand; the characteristic peak at 288.82 eV belongs to the C=O bond, which is the characteristic peak of the carboxyl group (-COOH) in the terephthalic acid ligand, proving that the organic skeleton structure of TMCS-MIL-101(Fe) remains intact. Correspondingly, the O1s spectrum ( Figure 2 J) showed contributions corresponding to C=O and CO at 531.96 eV and 533.68 eV, respectively. These contributions mainly originated from the carboxyl oxygen in the terephthalic acid ligand, which is the organic part constituting the MOF framework. In the Fe 2p high-resolution spectrum ( Figure 2 In K), the characteristic peaks at 711.77 eV and 725.11 eV are attributed to Fe. 3+ Fe 2p 3 / 2 and Fe 2p 1 / 2 The orbital, binding energy position, and peak shape indicate that the iron in TMCS-MIL-101(Fe) is mainly in the form of trivalent iron (Fe3+). 3+ The iron exists in the form of ), while distinct satellite peaks are observed at 716.56 eV and 729.58 eV, further confirming the oxidation state of iron in the MOF structure and proving that the valence state of MIL-101(Fe) did not change during TMCS modification. Furthermore, Figure 2 L shows that the Si 2p orbitals at 100.61 eV and 101.72 eV correspond to Si 2p orbitals, respectively. 3 / 2 and Si 2p 1 / 2 This confirms that TMCS underwent a coupling reaction with the MIL-101(Fe) surface, forming silicon-oxygen bonds (Si-O-Fe or Si-O-Si) or retaining silicon-carbon bonds, thus successfully coating the MOF particle surface with a silane layer.

[0035] Example 3: Adsorption performance investigation and condition optimization 1. Establishment of a fluorescence quantitative method for OTA To systematically evaluate the adsorption performance of TMCS-MIL-101(Fe) for OTA and to achieve accurate determination of OTA content, a fluorescence quantitative analysis method for OTA was first established, and further optimization of adsorption conditions was carried out based on this method.

[0036] First, the ochratoxin A standard was serially diluted with methanol to prepare concentrations of 0.001, 0.005, 0.01, 0.05, 0.1, 0.3, 0.5, and 1 µg / mL. -1 A standard solution of OTA was prepared. Its fluorescence intensity was measured at an excitation wavelength of 333 nm and an emission wavelength of 460 nm. Each concentration point was measured in triplicate to establish a standard curve of OTA concentration-fluorescence intensity. The results showed that within the range of 0.001–1 µg / mL... -1 Within the specified concentration range, OTA concentration and fluorescence intensity showed a good linear relationship, with the linear regression equation being y = 20203x + 2351.2 and the correlation coefficient R0. 2 =0.996 ( Figure 3 A) indicates that this method can be used for the quantitative analysis of OTA content in samples. Based on this standard curve, the OTA concentration in the sample extract was determined and calculated.

[0037] 2. Optimization of adsorption conditions Based on this, in order to obtain the best adsorption effect of TMCS-MIL-101(Fe) on OTA, the effects of factors such as temperature, adsorbent dosage and pH on OTA removal rate were further investigated.

[0038] To investigate the effect of temperature on OTA adsorption, the OTA removal rate of TMCS-MIL-101(Fe) was tested at 273, 288, 303, 318, and 333 K. Figure 3 As shown in Figure B, the removal rate of OTA increases with increasing temperature, reaching 95% at 333K (60℃), indicating that the adsorption of OTA on TMCS-MIL-101(Fe) is an endothermic process. Figure 3 C shows the change in OTA adsorption efficiency with increasing adsorbent dosage (TMCS-MIL-101(Fe)). As the adsorbent dosage increases, the removal rate of OTA by TMCS-MIL-101(Fe) gradually increases, reaching a maximum at 0.8 mg / mL. -1 The process tends to stabilize, with a removal rate of approximately 95%.

[0039] The pH of the solution environment has a significant impact on the performance of TMCS-MIL-101(Fe) and its OTA adsorption efficiency. Therefore, this study tested the OTA adsorption performance of TMCS-MIL-101(Fe) within a pH range of 2-14. The results showed that ( Figure 3 (D) As the solution pH approaches neutral, the removal rate of OTA by TMCS-MIL-101(Fe) increases accordingly; when the pH exceeds 10, a significant change in the detection signal occurs. Further analysis using PXRD (…) Figure 3 E) It was found that the crystal structure of TMCS-MIL-101(Fe) changed significantly under pH conditions of 12-14, indicating that the material underwent partial structural damage in a strongly alkaline environment, resulting in abnormal adsorption performance. Therefore, the material exhibits the best adsorption performance and structural stability under neutral conditions.

[0040] Depend on Figure 3 As shown by F, the adsorption process proceeds rapidly in the initial stage (0-1 min), and then gradually reaches equilibrium after about 10 min. To further determine the recyclability of OTA adsorbed by TMCS-MIL-101(Fe), this study conducted cyclic adsorption tests, such as... Figure 4 As shown, when the adsorbent dosage is 2 mg / mL -1 At that time, its adsorption capacity for OTA remained high even after 6 cycles, indicating that it has good cycling stability. Further comparison with previously reported OTA adsorbents (Table 1) shows that TMCS-MIL-101(Fe) exhibits better overall advantages in terms of adsorption capacity and cycling stability, especially achieving a good balance between adsorption capacity and cycling stability, demonstrating its application advantages as an OTA adsorbent.

[0041] Table 1 Comparison of OTA removal performance of different adsorbents The reference for the OTA removal performance of Pep-MPA-RCMs (peptide-modified cellulose microspheres) is: Peptides-modified cellulose microspheres for adsorption of ochratoxin A: Performance and mechanism, Sep. Purif. Technol., 350 (2024) 127764. The reference for the OTA removal performance of date palm kernel powder is: Date palm kernel powder as a cost-effective bio-adsorbent for ochratoxin A and aflatoxins removal from wheat flour used as food, Biomass Convers. Biorefin., 16 (2026)5. The reference for the OTA removal performance of Fe3O4@PDA MIPs is: Polydopamine-based molecularly imprinting polymers on magnetic nanoparticles for recognition and enrichment of ochratoxins prior to their determination by HPLC, Microchim. Acta, 185(2018) 300. The reference for the OTA removal performance of nano-Fe3O4@CTS is: Removal Capacity and Mechanism of Modified Chitosan for Ochratoxin A Based on Rapid Magnetic Separation Technology, Foods, 14 (2025) 666. The reference for the OTA removal performance of activated carbon is: In vitro adsorption of aflatoxin B1, ochratoxin A, and zearalenone by micronized grape stems and olive pomace in buffer solutions, Mycotoxin Res., 35 (2019) 243-252. The reference for the OTA removal performance of CS / Pal composite is: Preparation and characterization of chitosan / palygorskite for the adsorption of ochratoxin A, Appl. Clay Sci., 277 (2025) 107951. Example 4: Analysis of Adsorption Behavior and Mechanism To elucidate the adsorption behavior and mechanism of OTA by TMCS-MIL-101(Fe), this embodiment comprehensively analyzes the adsorption process from three aspects: adsorption thermodynamics, adsorption isotherm and kinetic characteristics, and further explores its molecular mechanism in conjunction with the changes in interfacial electrical properties.

[0042] First, the energy characteristics of the adsorption process were analyzed using thermodynamic parameters. As shown in Table 2, the value of ΔS is 65.82 J•mol. -1 •K -1 The value of ΔH is 13.96 kJ•mol. -1 Therefore, the adsorption process is endothermic (ΔH>0), and increasing the temperature favors adsorption. ΔG is negative at all temperatures, and its absolute value increases with increasing temperature, indicating that the process is spontaneous and that higher temperatures are more conducive to adsorption. Based on this, the adsorption behavior is further described using an adsorption isotherm model. Figure 5 (A and 5B, Table 3) The results show that the correlation coefficient (R) obtained by the Freundlich model is... 2 The Freundlich model's value is significantly higher than that of the Langmuir model, indicating that the Freundlich model can more reasonably describe the adsorption behavior in this system. This result suggests that the surface of the TMCS-MIL-101(Fe) material may be heterogeneous, with adsorption sites exhibiting multiple energy distributions. The Freundlich constant n > 1 further indicates that the adsorption of OTA on the material surface is a favorable adsorption process, and that strong interaction forces exist during adsorption. This heterogeneous multi-site adsorption characteristic provides a structural basis for the synergistic action of multiple mechanisms.

[0043] Table 2 Thermodynamic parameters of OTA adsorption process in TMCS-MIL-101(Fe) Table 3. Parameters of the adsorption isotherm equation for OTA adsorption on TMCS-MIL-101 (Fe) The adsorption rate and control steps were further analyzed using a kinetic model. Figure 5 (C and 5D, Table 4) Adsorption kinetics elucidates the adsorption rate and adsorption equilibrium time of the adsorbate on the adsorbent. The results show that the goodness of fit R of the pseudo-second-order kinetic model is [value missing]. 2 The results are significantly higher than those of the pseudo-first-order model, indicating that the adsorption process is mainly controlled by surface adsorption sites and interfacial interactions, and may involve interfacial interactions such as hydrogen bonding, thus affecting the adsorption rate.

[0044] Table 4. Adsorption kinetics parameters of TMCS-MIL-101(Fe) for OTA adsorption The combined thermodynamic, isothermal, and kinetic analyses indicate that the adsorption of OTA by TMCS-MIL-101(Fe) is not dominated by a single mechanism, but rather by the synergistic effect of multiple interactions. The Freundlich model reveals a non-uniform surface structure that provides the basis for multi-site adsorption, Zeta potential analysis confirms the involvement of electrostatic interactions, and kinetic results suggest the presence of strong interactions during adsorption. However, the system is still dominated by a combination of non-covalent interactions. Therefore, it can be inferred that multiple non-covalent interactions, including electrostatic interactions, hydrogen bonding, and π-π stacking, collectively promote the adsorption and stable binding of OTA on the material surface.

[0045] Example 5: Analysis of the Combination Pattern Based on Theoretical Calculation Based on the aforementioned analysis of adsorption behavior and mechanism, this study further explored the interaction between TMCS-MIL-101(Fe) and OTA at the molecular scale by combining molecular docking and quantum chemical calculations. Since the crystal structure of TMCS-MIL-101(Fe) is not included in CCDC, MIL-101(Cr) (ID: 605510) was used as a template, with Cr replaced by Fe, to construct a TMCS-MIL-101(Fe) cluster model. Optimization was performed at the B3LYP / 6-311G× level using Gaussian 16 software. The OTA structure, after optimization at the same level, was docked using Autodock Vina 4.0. The two optimal conformations (pose1, pose2) were used for IRI (Independent Gradient Model) analysis in Multiwfn 3.7, and the results were graphically processed using PyMOL 1.9.3 software. The results show that OTA can stably enter the pore structure of TMCS-MIL-101(Fe) through various non-covalent interactions such as hydrogen bonding, π–π stacking, and electrostatic interactions. Figure 6 This result is consistent with the results of adsorption thermodynamics and kinetic analysis, further confirming that the adsorption process is driven by multiple synergistic effects.

[0046] 1. Conformation 1 Among the multiple possible conformations obtained by molecular docking, conformation 1 with the optimal binding energy was selected as representative. Its binding mode and key interactions were systematically analyzed to reveal the stabilization mechanism of OTA in the TMCS-MIL-101(Fe) channels. In conformation 1, multiple non-covalent interactions are formed between OTA and TMCS-MIL-101(Fe), resulting in a highly stable complex structure. Figure 6(A and 6B). The carboxyl and phenolic hydroxyl groups on the OTA molecule form a stable hydrogen bond network with the carboxyl groups on the terephthalic acid ligand in the TMCS-MIL-101(Fe) structure. The two representative hydrogen bond distances measured are approximately 2.9 Å and 1.9 Å, respectively, both within the typical range of strong hydrogen bond distances. Simultaneously, there is a significant π-π conjugation between the aromatic ring in the OTA molecule and the aromatic ring of the terephthalic acid ligand in TMCS-MIL-101(Fe). Furthermore, extensive van der Waals and hydrophobic interactions exist between the hydrophobic framework of OTA and the hydrophobic aromatic fragments on the inner wall of TMCS-MIL-101(Fe), further enhancing the stability of the complex. Electrostatic potential analysis shows that ( Figure 6 (B) In the OTA molecule, negatively charged regions preferentially align with relatively electron-deficient or polar regions within the framework, while the hydroxyl hydrogen atoms approach electron-rich oxygen atoms, thus promoting hydrogen bond formation. These results indicate that hydrogen bonding, π–π interactions, van der Waals interactions, and electrostatic interactions collectively promote the stable adsorption of OTA.

[0047] 2. Conformation 2 To further verify the binding stability of OTA in the TMCS-MIL-101(Fe) channels and compare the interaction differences under different conformations, a comparative analysis was conducted on conformation 2, which has the second-best energy. The overall binding mode of conformation 2 is similar to that of conformation 1. Figure 6 C and 6D are also located near the TMCS-MIL-101(Fe) cavity, but the orientation and local interactions of the OTA molecules differ slightly. In conformation 2, OTA still forms multiple hydrogen bonds with the carboxyl groups or other polar groups of TMCS-MIL-101(Fe) through the carboxyl and hydroxyl groups, but the combination of hydrogen bond donors and acceptors and the specific geometric parameters are changed, with some bond lengths extending to 2.4-3.2 Å, indicating a slight weakening of the interaction. π–π stacking still exists, but the orientation of the aromatic rings changes from parallel to "edge-face" or cross-arrangement, resulting in a slightly higher vdW energy (-10.21 kcal·mol⁻¹). -1 Nevertheless, hydrophobic stacking and van der Waals interactions remain the main sources of energy contribution in this conformation, ensuring relatively stable OTA retention within the TMCS-MIL-101(Fe) channels. Furthermore, OTA in this conformation is primarily distributed near the channel inlets and hydrophobic regions, exhibiting good compatibility with the channel structure and showing little exposure to the solvent environment, indicating a strong OTA encapsulation capability of the material. Electrostatic potential analysis ( Figure 6D) Further, it is shown that the degree of electronic complementarity in conformation 2 is reduced compared to conformation 1. The negatively charged regions of OTA fail to achieve optimal matching with the electron-depleted sites in the framework, while the proximity of the hydroxyl hydrogen to the electron-rich oxygen atom is weakened, resulting in a reduction in hydrogen bonding and electrostatic interactions. Nevertheless, the conformation as a whole still maintains good binding stability, indicating that TMCS-MIL-101(Fe) can achieve effective adsorption of OTA through multiple orientations.

[0048] Example 6: Analysis of actual samples Grains and oilseeds are highly susceptible to contamination by toxin-producing fungi such as *Aspergillus ochraceus* and *Aspergillus carbonarius* during storage and transportation, leading to the accumulation of OTA (over-the-counter oxidase). Due to its high chemical stability, OTA can migrate into edible oils during subsequent oil processing, posing a serious threat to human health. In OTA-contaminated edible oils, high levels of hydrophobic triglycerides significantly hinder the dispersion of conventional hydrophilic adsorbents, severely limiting their adsorption performance. Therefore, improving the dispersibility of materials in the oil phase while maintaining their adsorption capacity is of significant practical value for the efficient removal of OTA from edible oils.

[0049] Based on the above studies on adsorption performance and mechanism of action, in order to further evaluate the feasibility of TMCS-MIL-101(Fe) in practical complex matrices, this embodiment constructs a simulated rapeseed oil and peanut meal contamination system and conducts a comprehensive analysis of its adsorption performance.

[0050] Add OTA standard solution to the sample to prepare a contamination model (10 μg·mL⁻¹). -1 The rapeseed oil sample was thoroughly mixed at room temperature before use and ultrasonically treated to improve the uniformity of OTA dispersion in the oil phase. Adsorbent was then added according to a predetermined ratio for adsorption experiments. The peanut meal sample was pulverized and sieved before use, and a certain volume of buffer solution was added to form a suspension system to promote OTA release. Adsorption was performed under suitable conditions, followed by centrifugation. The supernatant was then analyzed using a fluorescence method (λ). ex =333 nm, λ em The OTA content was determined by measuring 460 nm, and its concentration and removal rate were calculated according to the standard curve. All experiments were performed in triplicate.

[0051] Under the same experimental conditions, the adsorption performance of the material in a real matrix was evaluated through three parallel spiking experiments. The results showed that in the simulated rapeseed oil system, the average removal rate of OTA was 87%, corresponding to a unit adsorption capacity of 11.62 mg·g⁻¹. -1In the peanut meal system, the average removal rate of OTA was 72%, corresponding to a unit adsorption capacity of 9.22 mg·g. -1 Each experimental result was the average of three parallel determinations, with a relative standard deviation (RSD) of less than 5%, indicating that the method has good repeatability and stability. Simultaneously, parallel determinations of the samples were performed using high-performance liquid chromatography (HPLC), and the results showed no significant difference from those of this method (p>0.05), further validating the reliability of the adsorption detection system (Table 5). These results demonstrate that TMCS-MIL-101(Fe) not only possesses excellent adsorption performance but also exhibits good methodological reliability and practical application potential, providing effective technical support for the efficient removal of OTA from edible oils and related agricultural products.

[0052] Table 5. Detection of OTA concentration in real samples using fluorescence method and high performance liquid chromatography-mass spectrometry. In summary, this invention successfully prepared a TMCS-modified MIL-101(Fe) adsorbent and systematically evaluated its adsorption performance and mechanism of action for OTA. The results show that TMCS modification improves the surface properties of the material without destroying the MIL-101(Fe) framework, resulting in better adsorption capacity and application stability in complex food systems. Under optimized conditions, the material achieved a maximum OTA removal rate of 95%, indicating its excellent detoxification potential. The adsorption process conforms to a pseudo-second-order kinetic model and a Freundlich isotherm model, indicating that OTA adsorption on the material surface involves multiple synergistic interactions and exhibits a non-uniform surface characteristic with uneven energy distribution. Thermodynamic parameters further confirm that this process is a spontaneous endothermic adsorption. Molecular-level analysis shows that hydrogen bonding, π–π stacking, and electrostatic interactions jointly promote the stable binding of OTA on the TMCS-MIL-101(Fe) surface. Meanwhile, the material achieved OTA removal rates of 87% and 72% in simulated rapeseed oil and peanut meal, respectively. This invention demonstrates that the TMCS modification strategy can effectively improve the adsorption performance of MIL-101(Fe) for OTA and provides a new design idea for constructing highly efficient mycotoxin adsorbent materials.

[0053] The present invention and its embodiments have been described above. This description is not restrictive, and the embodiments shown are only one of the embodiments of the present invention. The actual structure is not limited to this. In conclusion, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the present invention, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing a metal-organic framework material, characterized in that, Includes the following steps: Preparation of S1. MIL-101(Fe) FeCl3•6H2O and H2BDC were dissolved in DMF solution, transferred to an autoclave for heating and reaction. After the reaction was completed, the mixture was cooled, centrifuged, and the solid was collected. The solid was purified with ethanol and dried to obtain MIL-101(Fe). S2. Preparation of TMCS-MIL-101(Fe) The MIL-101(Fe) obtained in step S1 was dispersed in anhydrous toluene. Under inert gas protection, TMCS was added for reflux reaction. After the reaction was completed, the product was washed and dried to obtain TMCS-MIL-101(Fe), which is a metal-organic framework material.

2. The method for preparing a metal-organic framework material according to claim 1, characterized in that, The heating reaction in step S1 is carried out at 100-120℃ for 10-30 h.

3. The method for preparing a metal-organic framework material according to claim 1, characterized in that, In step S1, the ethanol is purified by double treatment with ethanol at 50-70℃ for 2-4 hours.

4. The method for preparing a metal-organic framework material according to claim 1, characterized in that, In step S2, the reflux reaction temperature is 70-90℃ and the time is 5-7 h.

5. The method for preparing a metal-organic framework material according to claim 1, characterized in that, Step S2 washing involves washing with distilled water and ethanol 2-4 times each.

6. The method for preparing a metal-organic framework material according to claim 1, characterized in that, In step S2, the drying process involves first vacuum drying at 70-90℃ for 7-9 hours, and then drying at 100-120℃ for 11-13 hours.

7. A metal-organic framework material, characterized in that, It is prepared by the method for preparing a metal-organic framework material according to any one of claims 1-6.

8. The application of the metal-organic framework material as described in claim 7 in the removal of ochratoxin A.

9. The application according to claim 8, characterized in that, The metal-organic framework material is brought into contact with a sample containing ochratoxin A to adsorb ochratoxin A from the sample.

10. The application according to claim 9, characterized in that, The samples were peanut meal, soybean meal, walnut meal, or edible oil.

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