Defective mil-53(al)-no2 material, preparation method and application and detection platform thereof

Abstract

The present application belongs to the technical field of tailored defect materials with unsaturated aluminum sites, and particularly relates to a defective MIL-53(Al)-NO2 material, a preparation method and application thereof, and a detection platform. Through the synergistic effect of effective pore filling, strong host-guest interaction and enhanced charge transfer capacity, the material realizes high adsorption capacity of naringin q max , 186.88mgg ‑ ¹) and sensitive fluorescence detection (detection limit, 6.0 μg L ‑ ¹), and the performance is better than that of other reported materials.

Description

Technical Field

[0001] This invention belongs to the field of customized defect-type materials with unsaturated aluminum sites, and particularly relates to a MIL-53(Al)-NO2 material, its preparation method, application, and testing platform. Background Technology

[0002] The efficient separation and sensitive detection of bioactive flavonoids are crucial for drug quality control, the development of nutritional supplements, and biological research. Naringin, a abundant and representative dihydroflavonoid glycoside found in citrus peel, has attracted widespread attention due to its diverse bioactivities and significant pharmacological properties, including antioxidant, antibacterial, antiviral, anti-inflammatory, anticancer, and cardioprotective effects. To date, various adsorbents have been designed and applied to the adsorption and purification of naringin, such as boric acid affinity materials, molecularly imprinted polymers, macroporous resins, metal-organic frameworks (MOFs), and MOF / covalent organic framework hybrids. MOFs, formed by the self-assembly of metal nodes and multidentate organic ligands, possess significant potential in separation, biomedicine, catalysis, and sensing due to their high specific surface area, abundant binding sites, and structural tunability. Although these adsorbents exhibit good performance in adsorption and separation, they typically lack intrinsic signal transduction capabilities, thus limiting their use as sensors for detecting naringin. On the other hand, the detection methods for naringin mainly rely on high performance liquid chromatography and electrochemical techniques, which often require complex pretreatment and precise operation.

[0003] Fluorescence sensing, particularly the "on" strategy, offers a promising alternative for naringin detection due to its rapid response, high sensitivity, and real-time imaging capabilities. However, to our knowledge, no studies have yet been reported in the field on the adsorption and detection of flavonoids (let alone naringin).

[0004] Therefore, designing a bifunctional naringin material that integrates separation and fluorescence detection capabilities remains a challenging yet very important task. Summary of the Invention

[0005] Based on the requirements for the separation and detection of naringin and metal-organic frameworks (MOFs) and covalent organic framework hybrid materials, this invention designs a defective MIL-53(Al)-NO2 material for naringin, along with its preparation method and applications. The aim is to solve the problems of complex pretreatment for detection and the lack of research in the field of fluorescence sensing.

[0006] To achieve the above objectives, the present invention provides a defective MIL-53(Al)-NO2 material, wherein Al³⁺ is present in the defective MIL-53(Al)-NO2 material. +The molar ratio of / BDC-NO2 is 2:1-4:1; the defective MIL-53(Al)-NO2 material contains mesopores with a pore size of 2.0-7.0 nm; the mass percentage of missing links in the defective MIL-53(Al)-NO2 material is 14-27% of the total mass of the defective MIL-53(Al)-NO2 material.

[0007] Naringin has a C6-C3-C6 flavanone backbone and a disaccharide unit, with a molecular size of 2.25 × 0.58 × 1.36 nm (the molecular structure of naringin is shown in the attached figure). Figure 1 (As shown). Therefore, ideal MOFs for the separation and detection of naringin should possess the following characteristics: (1) a mesoporous structure with a suitable pore size (≥1.9 nm) to accommodate naringin; (2) high surface area and abundant active sites (e.g., unsaturated metal sites for coordination, functionalized aromatic linkers for π-π and / or hydrogen bonding interactions) to enhance naringin binding; and (3) sensing and transduction units capable of converting host-guest interactions into readable optical signals. MIL-101(Fe) has been shown to have excellent adsorption capacity for naringin (120.1 mg / g). - ¹), which is attributed to its mesoporous cage-like structure (2.9–3.4 nm) and the π-π interaction between naringin and the linker (1,4-terephthalic acid, BDC). However, the micropore window (1.2 nm) of MIL-101(Fe) somewhat restricts the diffusion of naringin, and to our knowledge, this material cannot be used for the detection of naringin. Notably, Al³ + It can coordinate with the 4-C=O and 5-OH groups of naringin to form a charge-transfer complex with enhanced fluorescence. This indicates a mesoporous structure and abundant unsaturated Al³⁺. + Al-MOFs with coordination sites and strong host-guest interactions show promise for simultaneously achieving naringin adsorption and sensing.

[0008] MIL-53(Al) with electron-withdrawing group –NO2 (MIL-53(Al)-NO2, pore size approximately 0.85 nm) has one-dimensional rhombic channels, Al³ + Enhanced Lewis acidity at the site and stronger non-covalent host-guest interactions result in improved gas adsorption performance. However, its microporous nature hinders the diffusion and accessibility of naringin into the framework. To address this size exclusion problem, a defect strategy using monocarboxylic acids (such as formic acid, acetic acid, and benzoic acid) as competitive modulators is commonly employed to introduce mesopores (2-50 nm) and increase adsorption capacity. Furthermore, the high density of oxygen vacancies resulting from the absence of linkers can significantly enhance sensing performance.

[0009] This application provides a strategy for constructing defective MIL-53(Al)-NO2 (MIL-53(Al)-NO2-D3 being the most preferred) by controlling the synthetic conditions. This is achieved through the introduction of mesoporous pore size, electron-withdrawing BDC-NO2 groups, and unsaturated Al³⁺. + The synergistic effect of the coordination sites together achieves the best performance in the adsorption and detection of naringin.

[0010] Preferably, the defective MIL-53(Al)-NO2 material contains electron-withdrawing BDC-NO2 groups and unsaturated Al³⁺ groups. + Coordination site.

[0011] Under the same technical concept, the present invention also provides a method for preparing defective MIL-53(Al)-NO2 material, comprising the following steps: S1. Dissolve Al(NO3)3 and BDC-NO2 in DMF, wherein the molar ratio of Al(NO3)3 to BDC-NO2 is 2:1-4:1; stir ultrasonically until the solid is completely dissolved to obtain a mixed solution; S2. The mixed solution is solvothermal treated at 120-160℃ for 3-12h; after cooling to room temperature, the pale yellow precipitate obtained by centrifugation is washed with water and ethanol respectively, and the product is dried overnight in a vacuum oven at 40-80℃ to obtain defective MIL-53(Al)-NO2 material.

[0012] Preferably, the solvothermal treatment in step S2 takes place in a reaction tube lined with polytetrafluoroethylene, and the washing with water and ethanol is performed at least three times.

[0013] Under the same technical concept, the present invention also provides an application of a defective MIL-53(Al)-NO2 material, which is used for the adsorption and sensing of naringin.

[0014] Preferably, the adsorption of naringin specifically includes: suspending the defective MIL-53(Al)-NO2 material in a naringin acetonitrile solution to obtain a suspension; after the suspension is shaken to reach equilibrium, collecting the defective MIL-53(Al)-NO2 material by centrifugation, washing with acetonitrile, and ultrasonically extracting to obtain an eluent; filtering the eluent through a filter membrane to obtain the eluted naringin.

[0015] Preferably, the solid-liquid ratio of the defective MIL-53(Al)-NO2 material to the naringin acetonitrile solution is 1:5 to 1:10; the oscillation includes oscillation at 283-318 K for 300-400 min; the ultrasonic extraction includes ultrasonic extraction in 30 mL of ethanol at 283-318 K for 5-15 min; and the filter membrane is a 0.22 μm filter membrane.

[0016] Preferably, the sensing for naringin specifically includes: dispersing defective MIL-53(Al)-NO2 material in naringin acetonitrile solutions of different concentrations and incubating; obtaining fluorescence spectra in the range of excitation wavelength 365 nm and emission wavelength 390-600 nm.

[0017] Preferably, the solid-liquid ratio of the defective MIL-53(Al)-NO2 material to the naringin acetonitrile solution is 1:5 to 1:15; the incubation is carried out at 283-318K for 40-60 minutes.

[0018] Under the same technical concept, the present invention also provides a defective MIL-53(Al)-NO2 material detection platform, wherein the defective MIL-53(Al)-NO2 material detection platform uses defective MIL-53(Al)-NO2 material as a fluorescent signal detection reagent for naringin.

[0019] The above-described solution of the present invention has the following beneficial effects: (1) This invention provides a defective MIL-53(Al)-NO2 material, which achieves a high adsorption capacity for naringin through the synergistic effect of effective pore design, strong host-guest interaction, and enhanced charge transfer capability. q max 186.88mgg - ¹) and sensitive fluorescence detection (detection limit, 6.0 μg / L) - ¹), outperforming other reported materials; (2) This invention also provides a solution for the application of defective MIL-53(Al)-NO2 material in both adsorption and sensing of naringin, which can fill the long-standing research gap in the field of materials capable of adsorbing and detecting naringin. Attached Figure Description To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1This is a schematic diagram of the chemical structure of naringin; Figure 2 A schematic diagram illustrating the structure and mechanism of Al-MOFs materials used for the adsorption and detection of naringin; Figure 3 The structural characterization of Al-MOFs samples includes: (A) PXRD pattern; (B) SEM image; (C) FTIR spectrum; (D) N2 adsorption-desorption isotherm; (E) pore size distribution map; (F) TGA curve under argon atmosphere (inset is defect level bar chart); and (G) EPR spectrum. Figure 4 Schematic diagrams of the adsorption of naringin on MIL-53(Al)-NO2, MIL-53(Al)-NO2-D3 and MIL-53(Al)-NO2-FA (A, C, E: top view; B, D, F: side view). Figure 5 To investigate the adsorption and detection mechanism of naringin. (A, B) Optimized configuration and binding energy of naringin adsorbed on MIL-53(Al)-NO2-D3 and MIL-53(Al)-NO2-FA, and (C, D) surface electrostatic potential analysis; (E) Adsorption capacity of naringin and (F) F0) / F0 value; (F) pore size, defect level, oxygen vacancies, binding energy, adsorption capacity, and (F) A diagram showing the relationship between F0 and F0; Figure 6 FTIR spectra of MIL-53(Al)-NO2-D3, MIL-53(Al)-NO2-D3@naringin and naringin; Figure 7 Surface electrostatic potential analysis of MIL-53(Al)-NO2-D3(A) and MIL-53(Al)-NO2-FA(B); Figure 8 The images show the spectra and adsorption curves of the adsorption capacity of Al-MOFs for naringin; where (A) is the standard curve of UV-vis absorption spectroscopy used to calculate the adsorption capacity of Al-MOFs for naringin; and (B) is the adsorption curve of Al-MOFs (10 μg / mL). - ¹) concentration-dependent adsorption capacity curves; (C–E)Al-MOFs (0.2 mg / mL) - ¹) Adding naringin (540 μg / L) - ¹) Fluorescence spectra before and after; Figure 9 In Example 3, (A)Al³ + A schematic diagram illustrating the effect of the / BDC-NO2 molar ratio and (B) heating time on the adsorption capacity of the synthesized Al-MOFs; Figure 10The adsorption performance of naringin on MIL-53(Al)-NO2-D3 is shown. (A) Kinetic adsorption curve at 308 K; (B) Intraparticle diffusion model; (C) Equilibrium adsorption at 298 K, 308 K and 318 K; (D) Adsorption capacity after six adsorption-desorption cycles; (E) Selective adsorption capacity. Figure 11 The pseudo-first-order, pseudo-second-order, and Elovich model fitting curves are shown for the adsorption of naringin on MIL-53(Al)-NO2-D3. Figure 12 The following are the fitting curves of (A) Langmuir and Freundlich models and (B) Temkin model for the adsorption of naringin on MIL-53(Al)-NO2-D3. Figure 13 The desorption rates of naringin eluted from MIL-53(Al)-NO2-D3 were determined by different elution solvents over three cycles. Figure 14 Example 3 shows the HPLC-UV standard curves for naringin before and after purification; (A) is the HPLC-UV standard curve for naringin; (B) are the HPLC-UV spectra of crude naringin and naringin purified by MIL-53(Al)-NO2-D3. Figure 15 Fluorescence spectra of different reaction systems in Example 4: (1) MIL-53(Al)-NO2-D3+ naringin, (2) Al³ + + Naringin (concentration same as in (1)), (3)Al³ + + naringin (concentration is 40 times that in (2)), (4) BDC-NO2+ naringin, (5) MIL-53(Al)-NO2-D3; Figure 16 The fluorescence intensity of MIL-53(Al)-NO2-D3 and naringin after incubation at different (A) MIL-53(Al)-NO2-D3 concentrations, (B) incubation times, and (C) reaction temperatures; Figure 17 The images show fluorescence detection of naringin. (A) Fluorescence spectra of the MIL-53(Al)-NO2-D3-based detection system after adding different concentrations of naringin; (B) Calibration curve; (C) Response specificity after adding potential interfering substances; (D) Comparison of fluorescence detection analysis and HPLC-UV detection results. Detailed Implementation

[0021] To make the technical problems, solutions, and advantages of this invention clearer, a detailed description will be provided below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0022] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0023] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a locking connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0024] Reagents and Instruments Acetonitrile (99.9%, HPLC), N,N-dimethylformamide (DMF, 99%, AR), ethanol (99%, AR), methanol (99%, AR), formic acid (99%, AR), 2-nitro-1,4-phthalic acid (BDC-NO2, 98%, AR), salicylic acid (SA, 99%, AR), and hydroquinone (HQ, 99%, AR) were purchased from Shanghai Maclean Biochemical Technology Co., Ltd. (Shanghai, China). Naringin (98%, AR), noriheptacortin (98%, AR), quercetin (98%, AR), and rutin (98%, AR) were purchased from Shanghai Yuanye Biotechnology Co., Ltd. (Shanghai, China). Naringin (58.5%, AR) was kindly provided by Lianyuan Kanglu Biotechnology Co., Ltd. (Lianyuan, China). Leucine (99%, BR), alanine (Ala, 99%, BR), L-serine (99%, BR), histidine (His, 99%, BR), Al(NO3)3·9H2O (99%, AR), KCl (99%, AR), FeCl3·6H2O (97%, AR), CaCl2 (96%, AR), ZnSO4·7H2O (99%, AR), MgSO4·7H2O (98%, AR), Na2SO4 (99%, GR), and CoCl2 (99%, AR) were purchased from Aladdin Industries, Inc. (Shanghai, China). The 0.22 μm filter membrane was purchased from Tianjin Jinghua Co., Ltd. (Shanghai, China).

[0025] The morphology and dimensions of the material were characterized using a JSM-7900F scanning electron microscope (JEOL Ltd., Japan, 5kV). Powder X-ray diffraction data were acquired using a MiniFlex 600 powder X-ray diffractometer (Rigaku Ltd., Japan). The Brunauer-Emmett-Teller specific surface area and pore volume were measured using N2 adsorption-desorption experiments on a KuboX1000 (Beijing Bio-Tech Electronics Technology Co., Ltd., China). Pore size distribution data were obtained using nonlocal density functional theory. Thermogravimetric analysis was performed using a TGA2 thermogravimetric analyzer (Mettler-Toledo Ltd., Switzerland) in an Ar atmosphere (240 mL min). - ¹), the temperature test range is 35℃ to 800℃, and the heating rate is 3℃ / min. -¹. Surface functional group characterization was performed on a Fourier transform infrared spectrometer (PerkinElmer, USA). UV-Vis absorption spectra were acquired on a UV-2600 UV-Vis spectrophotometer (Shimadzu Corporation, Japan). Fluorescence spectra were obtained on an FL-7000 fluorescence spectrophotometer (Hitachi Corporation, Japan). High-performance liquid chromatography (HPLC) analysis was performed on an Agilent 1260 series system (Agilent Technologies, USA). A Waters SunFire-C18 column (250 mm × 4.6 mm inner diameter, 5 μm, Waters Corporation, USA) was used for analysis at 30 °C. The mobile phase consisted of acetonitrile (A) and 0.1% (v / v) formic acid aqueous solution (B), with a gradient elution program of: 0–3 min, 10% A; 3–8 min, 10–20% A; 8–15 min, 20–40% A. The flow rate was 0.8 mL / min. - ¹, the injection volume was 10 μL, and the detection wavelength was 282 nm.

[0026] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0027] Example 1: This embodiment provides a method for preparing defective MIL-53(Al)-NO2-D3: Al(NO3)3·9H2O (2.0820 g, 5.55 mM) and BDC-NO2 (0.3905 g, 1.85 mM) were dissolved in DMF (40 mL), and the solution was ultrasonically stirred until the solid was completely dissolved. The solution was then transferred to a reaction tube (100 mL) lined with polytetrafluoroethylene and solvothermal treated at 130 °C for 4 hours. After cooling to room temperature, the resulting pale yellow precipitate was separated by centrifugation, washed three times with water and ethanol, and the product was dried overnight in a vacuum oven at 60 °C to obtain the defective MIL-53(Al)-NO2-D3 material.

[0028] Comparative Example 1: As a comparison, Comparative Example 1 also synthesized and evaluated pristine MIL-53(Al)-NO2 and MIL-53(Al)-NO2-FA (prepared using FA as a modifier); schematic diagrams of the defective MIL-53(Al)-NO2-D3 material, pristine MIL-53(Al)-NO2, and MIL-53(Al)-NO2-FA used for naringin adsorption and detection in Example 1 are shown below. Figure 2 As shown; Preparation of MIL-53(Al)-NO2-FA: After Al(NO3)3·9H2O and DMF are mixed evenly, formic acid (262 μL, 6 mM) is added and stirred for 30 minutes. Then BDC-NO2 is added. Subsequent steps are the same as for MIL-53(Al)-NO2.

[0029] Synthesis of the original MIL-53(Al)-NO2 (non-defective type): Al(NO3)3·9H2O (0.2251 g, 0.60 mM) and BDC-NO2 (0.1267 g, 0.60 mM) were dissolved in DMF (30 mL) and ultrasonically stirred until the solid was completely dissolved. The solution was then transferred to a reaction tube (100 mL) lined with polytetrafluoroethylene and solvothermal treated at 180 °C for 12 hours. After cooling to room temperature, the pale yellow precipitate obtained by centrifugation was washed three times with water and ethanol, and the product was dried overnight in a vacuum oven at 60 °C.

[0030] Defect level calculation Theoretically, in order to form MIL-53(Al)-NO2, one Al2 center coordinates with two BDC-NO2 ligands, and the calculated mass loss of BDC-NO2 is 26.9%. According to the TGA results, the weight losses of MIL-53(Al)-NO2-D3, MIL-53(Al)-NO2-FA, and MIL-53(Al)-NO2 during the second decomposition stage were 20.2%, 23.6%, and 27.2%, respectively. Therefore, their respective missing linker numbers were calculated to be 24.9%, 12.3%, and -1.1%.

[0031] MIL-53(Al)-NO2-D3:(1 (20.2% ÷ 26.9%) × 100% = 24.9% MIL-53(Al)-NO2-FA:(1 (23.6% ÷ 26.9%) × 100% = 12.3%; MIL-53(Al)-NO2:(1 27.2% ÷ 26.9%) × 100% = 1.1%; Actual experimental results show that the mass loss percentage of connectants in defect-free MIL-53(Al)-NO2 is 27.2%. Using defect-free MIL-53(Al)-NO2 as a reference, the actual percentages of missing connectants are calculated to be 25.7% and 13.2%, respectively: MIL-53(Al)-NO2-D3:(1 (20.2% ÷ 27.2%) × 100% = 25.7%; MIL-53(Al)-NO2-FA:(1 (23.6% ÷ 27.2%) × 100% = 13.2%; Adsorption experiment (1) Adsorption isotherm analysis The adsorption behavior of naringin on MIL-53(Al)-NO2-D3, MIL-53(Al)-NO2-FA, and MIL-53(Al)-NO2 was evaluated by static binding experiments. First, 5.0 mg each of MIL-53(Al)-NO2-D3, MIL-53(Al)-NO2-FA, and MIL-53(Al)-NO2 (hereinafter referred to as Al-MOFs) were mixed with different concentrations (…). C Mix 50 mL of naringin solution (0). After shaking in a constant temperature shaker for 360 minutes, filter the solution through a 0.22 μm filter membrane and measure the ultraviolet absorbance at 282 nm by UV-vis analysis.

[0032] equilibrium adsorption capacity q e (mgg - ¹) Calculate using the following formula: (1) in C e (unit: mg / L) - ¹) is the concentration of naringin after adsorption equilibrium; V This represents the volume of the naringin solution; m The mass of MOFs is represented by . The pseudo-first-order, pseudo-second-order, and Elovich kinetic model fitting parameters for the adsorption of naringin on MIL-53(Al)-NO2-D3 are shown in Table 1.

[0033] The adsorption results of naringin on MIL-53(Al)-NO2-D3 were obtained using Langmuir, Freundlich, and Temkin isotherm models (equilibrium adsorption capacity). q e The concentration of naringin after adsorption equilibrium C e The fitting process is performed as follows: The Langmuir model: (2) The Freundlich model: (3) The Temkin model: (4) in q m (mgg - ¹) represents the theoretical isotherm saturation adsorption capacity of naringin on MIL-53(Al)-NO2-D3. (Lmg -¹) is the Langmuir isotherm constant related to the affinity of the binding site. k F [(mgg –1 (mgL) –1 ) –1 / n [] is the Freundlich affinity constant, which is related to the adsorption capacity. n It is a heterogeneity factor related to the adsorption strength of the adsorbent ( n >1 indicates preferential adsorption. n <1 indicates multilayer adsorption). RT / b It is the Temkin constant (related to the heat of adsorption). k T is the Temkin adsorption equilibrium constant.

[0034] (2) Adsorption thermodynamics The standard Gibbs free energy (Δ) was calculated. G 0 kJmol - ¹) Standard entropy change (Δ) S 0 Jmol - ¹K - ¹) and standard enthalpy change (Δ H 0 kJmol - ¹) The adsorption of naringin was studied using thermodynamic parameters. Δ G 0 Calculate using formula (5): (5) in R (8.314 Jmol) - ¹K - ¹) is the ideal gas constant. T (K) is temperature. Kc (Lg - ¹) represents the thermodynamic equilibrium constant, which can be calculated using formula (6): (6) H 0 and S 0 It can be calculated using formula (7): (7) (3) Adsorption kinetics study The adsorption kinetics experiment was conducted as follows: MIL-53(Al)-NO2-D3 (10 mg) was reacted with naringin acetonitrile solution (100 mL, 150.0 mg / L). - ¹) Mixing. Shake in a 308K isothermal shaker, collect samples (2 mL) at preset time intervals, filter through a 0.22 μm filter membrane, and analyze using a UV-Vis spectrophotometer. Obtain the concentration of naringin at different time points (…). C t mg / L - ¹), adsorption capacity at different time intervals ( q t ,mgg - ¹) It can be calculated using the following formula: (8) in C 0 (mg / L) - ¹) is the initial concentration of naringin. V (L) is the volume of the solution. m (g) is the amount of MIL-53(Al)-NO2-D3 used.

[0035] Four kinetic models (pseudo-first-order kinetics, pseudo-second-order kinetics, Elovich model, and intraparticle diffusion model) were used to fit the adsorption kinetic data and to study the adsorption process of naringin on MIL-53(Al)-NO2-D3.

[0036] Quasi-first-order dynamic model: (9) Quasi-second-order dynamic model: (10) Elovich model: (11) Intraparticle diffusion model: (12) in q e (mgg - ¹) is the equilibrium adsorption capacity of naringin. k 1(min - ¹) and k 2(gmg - ¹min - ¹) are the rate constants of the pseudo-first-order and pseudo-second-order dynamic models, respectively; kp (mgg - ¹min - ¹ / ²) represents the diffusion rate constant of naringin. C i (mgg - ¹) is a constant related to the thickness of the MIL-53(Al)-NO2-D3 boundary layer.

[0037] (4) Calculation method Density functional theory calculations were performed using the AdsorptionLocator module in Materials Studio 2020 to elucidate the adsorption mechanism of naringin on Al-MOFs. A finite, aperiodic cluster model was constructed to represent local segments of the Al-MOF structure, focusing on its key unsaturated coordination of Al³⁺. + Site and BDC-NO2 environment. These cluster models and the geometry of the naringin molecule were first optimized. The most stable adsorption configuration and its binding energy (Δ) were determined using the simulated annealing algorithm in AdsorptionLocator. E ads The simulation was conducted with one naringin molecule placed in each cluster. Interatomic interactions were described using the COMPASSIII force field. Considering the aperiodic model, both electrostatic and van der Waals energies were calculated using a group-based summation method. Atomic charges were determined through a force field distribution scheme to ensure system charge neutrality.

[0038] The binding energy is calculated as follows: Δ E ads = E total –( E MOFs + E Naringin (13) in E total It is the potential energy of the optimized adsorption complex. E MOFs and E Naringin These represent the energies of the separated Al-MOF clusters and the naringin molecule, respectively. Δ E ads The larger the negative value, the stronger the adsorption interaction, which is more thermodynamically favorable (e.g., Al-O interaction, hydrogen bonding, π-π stacking).

[0039] Results and Discussion Synthesis and structural identification of Al-MOF By adjusting parameters, such as Al³ + Types of salts and solvents, Al³ + By adjusting the molar ratio of linker to solvent, reaction temperature, and time, Al-MOFs with different framework structures (e.g., MIL-53, MIL-101, CAU-1, MOF-235) can be obtained. N , NIn dimethylformamide (DMF) solution, MIL-101(Al) can dissolve and recrystallize, transforming into the MIL-53(Al) phase. Here, MIL-53(Al)-NO2-D3 was synthesized by reacting Al(NO3)3 (5.55 mM) and BDC-NO2 (1.85 mM) in DMF (40 mL) under solvothermal conditions at 130 °C for 4 hours. The resulting pale yellow solid exhibited powder X-ray diffraction peaks at 8.5°, 14.8°, and 17.1°. Figure 3 A), corresponding to the (011), (101), and (022) crystal planes. These peaks are highly consistent with those of MIL-53(Al)-NO2-FA, the original MIL-53(Al)-NO2, and the simulated macroporous phase of MIL-53(Al), indicating that they maintain an isomorphic framework despite different synthesis conditions. Notably, the characteristic diffraction peaks of MIL-53(Al)-NO2-D3 are broader and less intense, indicating reduced crystallinity due to the formation of numerous defects. Furthermore, scanning electron microscopy images show that MIL-53(Al)-NO2-D3 has a cubic morphology with a wrinkled surface and smaller particle size (e.g., ...). Figure 3 B), indicating that a lower BDC-NO2 ratio modulates framework crystallization and produces more missing linkages. The Fourier transform infrared spectra of the three Al-MOFs show similar stretching vibrations, with typical –COO (1421 and 1615 cm⁻¹) values. - ¹) and Al–O (585cm - ¹) Absorption band, simultaneously O–H (2500-3200cm) - ¹) and –COOH(1700cm - ¹) Disappearance of spectral bands (e.g.) Figure 3 C. This indicates that BDC-NO2 successfully coordinates with Al and there are no missing cluster defects. The N2 adsorption-desorption isotherm of MIL-53(Al)-NO2-D3 is type IV, and its Brunauer... Emmett Teller's specific surface area is 368.6 m²g. - ¹, mainly mesoporous structure (pore size 2.34 nm), significantly higher than the original MIL-53(Al)-NO2 (BET specific surface area 78.9 m²g). - ¹, micropore size 0.77 nm) Figure 3 D and 3E). Furthermore, the BET specific surface area of ​​MIL-53(Al)-NO2-FA (749.9 m²g) - ¹) and aperture (2.39 nm) Figure 3D and 3E) are in excellent agreement with previous findings. Clearly, the missing linker strategy can be engineered to construct mesoporous structures with high specific surface areas. Thermogravimetric analysis results are as follows: Figure 3 As shown in Figure F, the second weightlessness region (200-500℃) corresponds to the decomposition of the frame. The defective structure exhibits reduced thermal stability. According to TGA calculations, the missing connective defect level of MIL-53(Al)-NO2-D3 is 25.7%, exceeding that of MIL-53(Al)-NO2-FA (13.2%). Figure 3 (F illustration) and reported MIL-53(Al) (<19%) prepared using different modifiers. Defects in MIL-53(Al)-NO2-D3 originate from a low BDC-NO2 ratio, leading to the absence of the entire linker and thus generating more missing linker defects. Furthermore, the type of vacancy was determined by electron paramagnetic resonance measurements ( Figure 3 G), in g A stronger signal was observed in MIL-53(Al)-NO2-D3 at =2.008, indicating the presence of abundant oxygen vacancies. MIL-53(Al)-NO2-FA showed a small number of oxygen vacancies, which may be due to the interaction between FA and Al³⁺. + This is due to coordination. Overall, the pore structure of Al-MOFs can be controlled by changing the synthesis conditions. MIL-53(Al)-NO2-D3 possesses a mesoporous structure, high specific surface area, and abundant unsaturated Al³⁺. + The open site may provide sufficient adsorption capacity for naringin and enable sensitive fluorescence detection.

[0040] Table 1. Fitting parameters of pseudo-first-order, pseudo-second-order, and Elovich kinetic models for the adsorption of naringin on MIL-53(Al)-NO2-D3.

[0041] Table 2. Fitting parameters for the intraparticle diffusion model of naringin adsorbed on MIL-53(Al)-NO2-D3.

[0042] Table 3. Fitting parameters of Langmuir, Freundlich, and Temkin isotherm models for the adsorption of naringin on MIL-53(Al)-NO2-D3.

[0043] Table 4. Thermodynamic parameters of naringin adsorption on MIL-53(Al)-NO2-D3

[0044] Example 2: Purification of crude naringin product using defective MIL-53(Al)-NO2 material: MIL-53(Al)-NO2-D3 (25.0 mg) from Example 1 was suspended in a naringin acetonitrile solution (89.5 mg / L). - ¹, 58.5%, 50 mL). After reaching equilibrium by shaking at 308 K for 360 min, MIL-53(Al)-NO2-D3 was collected by centrifugation, washed with acetonitrile, and then ultrasonically extracted in ethanol (30 mL) at 308 K for 10 min to elute the adsorbed naringin. The eluent was filtered through a 0.22 μm filter membrane and analyzed by HPLC-UV.

[0045] Fluorescence sensing of naringin by defective MIL-53(Al)-NO2 materials: The MIL-53(Al)-NO2-D3 (500 μL, 0.8 mg / mL) from Example 1 was used. - ¹) Dispersed at different concentrations (50–570 μg / L) - The sample was incubated in 1.5 mL of a naringin acetonitrile solution at 308 K for 50 minutes. Fluorescence spectra were obtained in the range of 390-600 nm for excitation and emission.

[0046] Comparative Example 2: The purification and sensing methods were consistent with those in Example 2, and the original MIL-53(Al)-NO2 and MIL-53(Al)-NO2-FA prepared in Comparative Example 1 were purified and sensed.

[0047] Theoretical calculations were performed to predict the molecular-level interaction between Al-MOFs and naringin, and the pore structure was modeled based on BET and TGA results. Figure 3 and Figure 4 As shown, Figure 4 Schematic diagrams showing the adsorption of naringin on MIL-53(Al)-NO2, MIL-53(Al)-NO2-D3, and MIL-53(Al)-NO2-FA (A, C, E: top views; B, D, F: side views). The mesoporous structures of MIL-53(Al)-NO2-D3 and MIL-53(Al)-NO2-FA facilitate the diffusion of naringin into the internal pores for binding and adsorption. In contrast, the narrower pore size of MIL-53(Al)-NO2 hinders mass transfer and diffusion.

[0048] Investigation on the adsorption and detection mechanism of naringin The binding energy of naringin on MIL-53(Al)-NO2-D3 was calculated to be -3.86 eV (e.g., Figure 5A), compared to the binding energy on MIL-53(Al)-NO2-FA (-3.22 eV, Figure 5 A more negative B indicates a stronger thermodynamic driving force for its binding. This adsorption process involves pore-filling effects, hydrogen bonds, π-π stacking, and Al-O coordination interactions. Figure 4 , Figure 5 A and Figure 5 B). The uniform blue shift of Al-O stretching vibrations in the FTIR spectrum is due to the interaction between MIL-53(Al)-NO2-D3 and naringin in Al³⁺. + Evidence was provided that chemisorption occurred at the site. Figure 6 Furthermore, the charge density difference calculation results visually demonstrate that the electronegativity of the –NO2 group and the abundant oxygen vacancies in MIL-53(Al)-NO2-D3 lead to Al³ + Nodes generate more electronic defects ( Figure 7 Furthermore, surface electrostatic potential analysis quantified the Al³⁺ content in MIL-53(Al)-NO₂-D₃ after naringin adsorption. + The net charge transfer is 0.014e, while in MIL-53(Al)-NO2-FA it is 0.006e ( Figure 5 (C and D). The greater charge transfer between MIL-53(Al)-NO2-D3 and naringin may activate the fluorescence signal, thus enabling more sensitive naringin detection. In summary, theoretical calculations determine that MIL-53(Al)-NO2-D3 is the most promising candidate material for naringin adsorption and detection. The comparison of adsorption and fluorescence response performance clearly shows the following order: MIL-53(Al)-NO2-D3 > MIL-53(Al)-NO2-FA > MIL-53(Al)-NO2( Figure 5 E, Figure 8 This trend is consistent with theoretical calculations. Compared to MIL-53(Al)-NO2-FA, MIL-53(Al)-NO2-D3, with its lower BET surface area, exhibits higher adsorption and better detection performance, indicating that specific surface area is not the decisive factor. Figure 5 As shown in the summary figure of F, MIL-53(Al)-NO2-D3 has a suitable mesoporous structure, higher defect level and oxygen vacancies, and enhanced binding energy, thereby improving the adsorption and detection performance of naringin.

[0049] Adsorption performance study The adsorption performance of MIL-53(Al)-NO2-D3 for naringin in acetonitrile solution was evaluated. At 308 K, naringin reached its maximum adsorption capacity (186.88 mg / g) within 180 minutes. - ¹) 92%, and it takes 360 minutes to reach saturation ( Figure 9A). The pseudo-first-order kinetic model fits the adsorption kinetic data better, with a rate constant of 0.01607 min. - ¹, R The value is 0.9973; Figure 10 The adsorption performance of naringin on MIL-53(Al)-NO2-D3 is shown. (A) Kinetic adsorption curve at 308 K; (B) Intraparticle diffusion model; (C) Equilibrium adsorption at 298 K, 308 K, and 318 K; (D) Adsorption capacity after six adsorption-desorption cycles; (E) Selective adsorption capacity. Furthermore, the transport process of naringin within the pores of MIL-53(Al)-NO2-D3 was investigated using an intraparticle diffusion model. Figure 9 As shown in A and Table 2, the adsorption process involves three distinct stages, with the larger ones... k p1 and k p2 Constants (16.27 and 2.195 mgg) - ¹min –1 / 2 This indicates a rapid surface and pore diffusion rate. Therefore, MIL-53(Al)-NO2-D3 with accessible pore size promotes the diffusion of naringin. The adsorption capacity of naringin on MIL-53(Al)-NO2-D3 increases with increasing naringin concentration and incubation temperature. Figure 9 B). From Figure 9 B Figure 11 As can be clearly seen from Table 3, the Langmuir and Temkin models provide a better fit, indicating monolayer adsorption at non-uniform sites, a characteristic of defective MOFs. Negative Δ G and positive Δ S Δ H The values ​​indicate that this chemisorption process is spontaneous, disordered, and endothermic (Table 4). It is noteworthy that MIL-53(Al)-NO2-D3... q max Superior to previously reported porous adsorbents (Table 5). After eluting bound naringin with ethanol (desorption rate 99.3%), the regenerated MIL-53(Al)-NO2-D3 retained 93.0% of its adsorption capacity after six adsorption-desorption cycles. Figure 12 Subsequently, the commercially available crude naringin product (purity determined by HPLC-UV) was treated with MIL-53(Al)-NO2-D3, and the purity of naringin after elution increased to 93.7%. Figure 13 These results demonstrate that MIL-53(Al)-NO2-D3 has great potential for the selective adsorption and purification of naringin in practical applications.

[0050] Table 5 Comparison of the maximum adsorption capacity of reported adsorbents for naringin

[0051] Table 6 Comparison of naringin detection methods

[0052] Table 7. Spiked recovery results of naringin in commercial crude products

[0053] Example 3: The preparation method in this embodiment is partially the same as that in Example 1, and is divided into two groups: Group A: The remaining preparation methods are consistent with Example 1, the only difference being the setting of Al³. + The molar ratio of BDC-NO2 is 1:1, 2:1, 3:1, 4:1, or more. Group B: The remaining preparation methods are consistent with those in Example 1, except that the heating time is set to 2, 4, 5, 7, 9, or 12 hours.

[0054] Figure 9 In Example 3, (A)Al³ + A schematic diagram illustrating the effect of the / BDC-NO2 molar ratio and (B) heating time on the adsorption capacity of the synthesized Al-MOFs. MIL-53(Al)-NO2-D3 was identified as the most effective material after optimization of key synthesis parameters, highlighting the ability to regulate Al³⁺ adsorption capacity. + The importance of the / BDC-NO2 molar ratio.

[0055] Figure 14 For Example 3, HPLC-UV (Waters SunFire-C18 (250 mm × 4.6 mm i.d., 5 μm) column was used to elute naringin before and after purification. The mobile phase was acetonitrile (A) - 0.1% formic acid gradient elution: 10% A (0) 3min), 10 20%A(3 8min), 20 40%A(8 15 min; Flow rate: 0.8 mL / min 1; Injection volume: 10 μL; Detection wavelength: 282 nm) Determination of standard curve; Among them, (A) HPLC-UV determination standard curve of naringin; (B) HPLC-UV spectra of crude naringin and naringin purified by MIL-53(Al)-NO2-D3.

[0056] Example 4: Detection Performance Study The fluorescence detection performance of naringin based on MIL-53(Al)-NO2-D3 was systematically studied.

[0057] The fluorescence detection performance of naringin based on MIL-53(Al)-NO2-D3 was investigated using MIL-53(Al)-NO2-D3 as the fluorescence detection material. To study the fluorescence emission spectra of MIL-53(Al)-NO2-D3 compared to other materials, the following groups of detection materials were selected for separate testing and analysis: Figure 15 Fluorescence spectra of different reaction systems in Example 4: (1) MIL-53(Al)-NO2-D3+ naringin, (2) Al³ + + Naringin (concentration same as in (1)), (3)Al³ + + naringin (concentration is 40 times that in (2)), (4) BDC-NO2+ naringin, (5) MIL-53(Al)-NO2-D3; like Figure 15 As shown, MIL-53(Al)-NO2-D3 initially showed no fluorescence signal, but after the addition of naringin, a distinct emission peak appeared at 495 nm under 365 nm excitation. More importantly, under the same conditions (the same concentration as MIL-53(Al)-NO2-D3 + naringin), Al³ + No fluorescence emission was observed in the naringin solution; even when Al³ was added... + With a 40-fold increase in concentration, Al³ + The fluorescence intensity of naringin was still significantly lower than that of MIL-53(Al)-NO2-D3+naringin. Therefore, the MOF structure facilitated efficient fluorescence signal transduction. Subsequently, the concentration of MIL-53(Al)-NO2-D3 (0.2 mg / mL) was optimized. - ¹), Incubation temperature (308K) and time (50min) Figure 16 Under optimized parameters, as the concentration of naringin increased from 60 to 540 μg / L... - ¹, the fluorescence intensity increased linearly (*y*=0.4130*x*+89.67, R ² = 0.9965 Figure 17 (A and B). The detection limit (3σ / S, where σ is the fluorescence value of 11 blank samples and S is the slope of the linear equation) was determined to be 6.0 μg / L. - ¹, lower than reported fluorescence, HPLC, and electrochemical methods (Table 6). Furthermore, MIL-53(Al)-NO2-D3 exhibits a specific response to naringin, unaffected by metal ions, amino acids, and structural analogs. Figure 17The presence of C indicates good anti-interference ability. The high precision of the method was demonstrated by evaluating the intraday relative standard deviation (RSD, 3.5%, five parallel measurements) and interday RSD (4.7%, over five consecutive days). Finally, commercially available crude naringin was selected as the actual sample, yielding excellent recoveries (actual detected value / spiked value) (98.7-102.5%) and low RSD (≤4.4%), consistent with HPLC-UV results, with a relative error of less than 1.8%. Figure 17 D (Table 7). Therefore, MIL-53(Al)-NO2-D3 can be used as an excellent fluorescent probe with high sensitivity, selectivity and accuracy for the detection of naringin.

[0058] in conclusion In summary, we successfully synthesized a bifunctional MIL-53(Al)-NO2-D3, achieving highly selective adsorption of naringin (186.88 mg / g). - ¹) and sensitive “on” fluorescence detection (LOD, 6.0 μg / L). - ¹). Theoretical and experimental studies established a clear structure-property relationship and elucidated the potential adsorption and detection mechanisms among MIL-53(Al)-NO2-D3, MIL-53(Al)-NO2-FA, and MIL-53(Al)-NO2. The superior performance of MIL-53(Al)-NO2-D3 stems from the precise regulation of its pore structure: the mesopores (2.34 nm) facilitate pore filling of naringin, and the electron-deficient BDC-NO2 linker can form strong hydrogen bonds and π-π stacking interactions with naringin. + The abundant oxygen vacancies (with a linker defect level of 25.7%) allow for specific coordination and efficient charge transfer with naringin. These synergistic host-guest interactions make MIL-53(Al)-NO2-D3 an excellent adsorbent and fluorescent probe for the purification and detection of naringin in real samples. More broadly, this study paves the way for the rational design and synthesis of high-performance MOFs.

Claims

1. A defective MIL-53(Al)-NO2 material, characterized in that, The defective MIL-53(Al)-NO2 material contains Al³ + The molar ratio of / BDC-NO2 is 2:1-4:1; the defective MIL-53(Al)-NO2 material contains mesopores with a pore size of 2.0-7.0 nm; the mass percentage of missing links in the defective MIL-53(Al)-NO2 material is 14-27% of the total mass of the defective MIL-53(Al)-NO2 material.

2. The defective MIL-53(Al)-NO2 material as described in claim 1, characterized in that, The defective MIL-53(Al)-NO2 material contains electron-withdrawing BDC-NO2 groups and unsaturated Al³⁺. + Coordination site.

3. A method for preparing a defective MIL-53(Al)-NO2 material, characterized in that, Includes the following steps: S1. Dissolve Al(NO3)3 and BDC-NO2 in DMF, wherein the molar ratio of Al(NO3)3 to BDC-NO2 is 2:1-4:1; stir ultrasonically until the solid is completely dissolved to obtain a mixed solution; S2. The mixed solution is solvothermal treated at 120-160℃ for 3-12h; after cooling to room temperature, the pale yellow precipitate obtained by centrifugation is washed with water and ethanol respectively, and the product is dried overnight in a vacuum oven at 40-80℃ to obtain defective MIL-53(Al)-NO2 material.

4. The method for preparing the defective MIL-53(Al)-NO2 material as described in claim 3, characterized in that, The solvothermal treatment described in S2 takes place in a reaction tube lined with polytetrafluoroethylene, and the washing with water and ethanol respectively is performed at least three times.

5. An application of the defective MIL-53(Al)-NO2 material as described in any one of claims 1-2, characterized in that, The defective MIL-53(Al)-NO2 material is used for the adsorption and sensing of naringin.

6. The application of the defective MIL-53(Al)-NO2 material as described in claim 5, characterized in that, The adsorption of naringin specifically includes: suspending the defective MIL-53(Al)-NO2 material in a naringin acetonitrile solution to obtain a suspension; after the suspension is shaken to reach equilibrium, collecting the defective MIL-53(Al)-NO2 material by centrifugation, washing with acetonitrile, and ultrasonically extracting to obtain an eluent; filtering the eluent through a filter membrane to obtain the eluted naringin.

7. The application of the defective MIL-53(Al)-NO2 material as described in claim 6, characterized in that, The solid-liquid ratio of the defective MIL-53(Al)-NO2 material to the naringin acetonitrile solution is 1:5 to 1:10; the oscillation includes oscillation at 283-318K for 300-400 min; the ultrasonic extraction includes ultrasonic extraction in 30 mL of ethanol at 283-318K for 5-15 min; and the filter membrane is a 0.22 μm filter membrane.

8. The application of the defective MIL-53(Al)-NO2 material as described in claim 5, characterized in that, The sensing method for naringin specifically includes: dispersing defective MIL-53(Al)-NO2 material in naringin acetonitrile solutions of different concentrations and incubating it; obtaining fluorescence spectra in the range of excitation wavelength 365 nm and emission wavelength 390-600 nm.

9. The application of the defective MIL-53(Al)-NO2 material as described in claim 8, characterized in that, The solid-liquid ratio of the defective MIL-53(Al)-NO2 material to the naringin acetonitrile solution is 1:5 to 1:15; the incubation is carried out at 283-318K for 40-60 minutes.

10. A defect-type MIL-53(Al)-NO2 material testing platform as described in any one of claims 1-2, characterized in that, The defective MIL-53(Al)-NO2 material detection platform uses defective MIL-53(Al)-NO2 material as a fluorescent signal detection reagent for naringin.

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