Thiol-functionalized metal-organic framework materials, methods of making and using the same

Abstract

The application discloses a thiol-functionalized metal organic framework material and a preparation method and application thereof, and aims at the urgent demand of efficient adsorption of radioactive iodine, combines supergravity synthesis technology with a post-synthesis modification strategy, and successfully prepares the thiol-functionalized metal organic framework material IRMOF-3-SH.The research of the application proves that the supergravity method can quickly synthesize the MOF material with regular crystal form and uniform particle size by strengthening the mass transfer and nucleation process, and further obtains the thiol-functionalized IRMOF-3-SH through the supergravity post-synthesis modification method, so that the iodine adsorption capacity is significantly improved to 3.00 g·g ‑1 , which is increased by 46% compared with the unmodified material, and the excellent cycle stability is exhibited.

Description

Technical Field

[0001] This invention belongs to the field of high-efficiency adsorption technology of radioactive iodine, specifically relating to thiol-functionalized metal-organic framework materials, their preparation methods, and applications. Background Technology

[0002] The statements herein provide only background information in relation to this invention and do not necessarily constitute prior art.

[0003] Nuclear energy, as a highly efficient and clean energy source, occupies an increasingly important position in the global energy structure. However, the development of the nuclear industry generates radioactive iodine (such as...) 129 I and 131 I) Due to its high volatility, once leaked into the environment, volatile iodine will persist in the ecosystem for a long time, posing a significant threat to human health and the environment. Currently, there are two strategies for capturing volatile iodine: wet scrubbing and solid-state adsorption. Wet scrubbing has drawbacks such as high operating costs and the generation of other wastes. In contrast, solid-state adsorption is widely used due to its simplicity, high efficiency, and low pollution. The adsorption of radioactive iodine mainly focuses on the development of adsorbent materials; therefore, developing highly efficient iodine capture and adsorption materials has become a cutting-edge research topic and an urgent technological need in the field of nuclear safety.

[0004] In recent years, researchers have focused on developing various iodine adsorbent materials, including activated carbon, zeolites, and metal-organic frameworks (MOFs). Among these, MOFs, with their high porosity, large surface area, and tunable properties, exhibit excellent adsorption performance in capturing gaseous iodine. Some classic MOF materials, such as ZIF-8 and HKUST-1, have demonstrated superior iodine adsorption capabilities. Existing technology discloses that ZIF-8 achieves an iodine adsorption capacity of 1.25 g·g⁻¹ through channel immobilization and surface adsorption. -1 The adsorption capacity of the ZIF-8 is relatively large, with I2 effectively confined within the sodalite cage. Studies have shown that the performance of adsorbents hinges on the design and regulation of active sites, whose density and affinity directly determine adsorption capacity, selectivity, and kinetic performance. For MOF materials, post-hydrothermal synthesis (PSM) technology has become an effective strategy for constructing highly active site adsorbents to improve active site density and efficiency. Since iodine is a highly electronegative atom, it readily attracts electrons to form shared electron pairs. Therefore, the introduced active sites should be able to form a strong inductive effect with the highly electronegative I2. Active sites such as electron-rich groups (e.g., aromatic rings, azo groups), coordinated unsaturated metal sites, and polar functional groups (e.g., hydroxyl, amino groups) significantly enhance adsorption through mechanisms such as charge transfer, coordination, or halogen bond formation with iodine molecules.

[0005] However, traditional hydrothermal synthesis methods typically involve high reaction temperatures and long reaction times, resulting in MOF materials with uncontrollable morphology and size, and limited crystallinity. This limits the study of their structure-property relationships and creates an urgent need for synthesis methods that can simultaneously achieve active site design and morphology control.

[0006] Supergravity technology is a highly efficient process enhancement technique that provides an innovative solution for preparing MOF adsorbents with regular and uniform dimensions.

[0007] However, how to prepare metal-organic framework materials with high iodine adsorption capacity and easy preparation process remains a goal pursued by those skilled in the art. Summary of the Invention

[0008] In view of the shortcomings of the existing technology, the purpose of this invention is to provide thiol-functionalized metal-organic framework materials, their preparation methods and applications.

[0009] To achieve the above objectives, the present invention provides the following technical solution:

[0010] In a first aspect, the present invention provides a method for preparing thiol-functionalized metal-organic framework materials. First, zinc salt and ligands having both amino (NH2) and carboxyl (COOH) groups are reacted under hypergravity conditions. Then, the resulting product undergoes a thiolization reaction under hypergravity conditions.

[0011] In some embodiments of the present invention, the preparation method includes the following steps: Step 1: Dissolve the zinc salt in an organic solvent, and dissolve the ligand containing both amino and carboxyl groups in the organic solvent. Mix the two solutions by stirring. Dissolve triethylamine in the organic solvent and add it to the two solution system to obtain a mixed solution. React under hypergravity conditions to obtain the intermediate IRMof-3. ; Step 2, the intermediate IRMof-3 obtained in Step 1 It is mixed with mercaptoacetic acid in an organic solvent and reacted under hypergravity conditions.

[0012] In the preparation method provided by the present invention, a ligand with amino and carboxyl groups is first combined with zinc to synthesize an intermediate. Then, the amino group in the intermediate undergoes a condensation reaction with the carboxyl group in the added mercaptoacetic acid to achieve mercapto functionalization, thereby achieving a stronger chemical adsorption effect on iodine.

[0013] Triethylamine in IRMof-3 In the synthesis, it mainly plays a dual role of "deprotonation" and "crystal growth modulation". Triethylamine can effectively remove the proton from the carboxyl group of the ligand, converting it into a highly reactive carboxylate anion (-COO). - ), thus with Zn2+ Rapid coordination drives the formation of Zn4O metal clusters and MOF frameworks. Furthermore, it can buffer free Zn in the reaction system through reversible coordination. 2+ This slows down the nucleation rate, allowing the crystal to grow slowly and orderly, which helps to obtain crystals with high crystallinity and large size. At the same time, this buffering effect also helps to suppress side reactions or structural interference that may be caused by amino groups on the ligands, guiding the reaction to generate thermodynamically stable target topological structures.

[0014] In some embodiments of the present invention, the final product obtained is IRMof-3-SH. It has an open cubic pore system. The amino and thiol functional groups modified on the inner wall of its pores serve as strong adsorption sites, specifically capturing iodine molecules through electron donor-acceptor interactions, thereby achieving efficient adsorption.

[0015] In step 1, the zinc salt is zinc nitrate and its hydrate. Compared to other anions, it is more conducive to the formation of pure Zn4O metal cluster nodes with a specific topological structure.

[0016] In step 1, the organic solvent is ethanol.

[0017] In step 1, the ligand containing both amino and carboxyl groups is 2-aminoterephthalic acid.

[0018] In step 1, the molar ratio of the zinc salt to the ligand is 1.5-1.8:2.

[0019] In step 1, the molar ratio of zinc salt to triethylamine is 1:98.7-111.3.

[0020] In step 2, the intermediate IRMof-3 The mass ratio of mercaptoacetic acid to thioglycolic acid is 1:5.5-5.9.

[0021] In steps 1 and 2, the hypergravity level should not be lower than 64.

[0022] In some embodiments of the present invention, the hypergravity level is 64-179.

[0023] In a second aspect, the present invention provides a metal-organic framework material obtained by the method for preparing thiol-functionalized metal-organic framework materials described in the first aspect.

[0024] Thirdly, the present invention provides the application of the metal-organic framework material described in the second aspect in iodine adsorption.

[0025] This invention combines supergravity synthesis technology with post-synthetic modification strategies to introduce thiol groups containing amino polar functional groups into IRMof-3 containing lone pair electrons, thereby synthesizing IRMof-3-SH with controllable morphology and precise functionalization of active sites. This study investigates the effects of thiol-based synthesis on iodine adsorption performance and mechanisms. First, it compares and analyzes the differences in morphology, structure, and iodine adsorption performance between IRMof-3 synthesized by the traditional hydrothermal method and the centrifugal method, revealing the advantages of the centrifugal synthesis method in improving product performance. Further, through post-centrifugal synthesis modification, thiol-active sites are introduced into IRMof-3. Finally, the effects of thiol-modified IRMof-3-SH are investigated. The influence of -SH on iodine adsorption performance is investigated, and the adsorption mechanism of iodine by -SH is revealed in detail. This invention combines supergravity synthesis technology with post-synthetic modification to develop a high-performance iodine adsorbent synthesis strategy, synthesizing high-performance IRMOF-3-SH. The study revealed the important role of -SH in the iodine adsorption process, ultimately providing support for the efficient adsorption of radioactive iodine in nuclear accidents.

[0026] This invention successfully developed a thiol-functionalized IRMOF-3-SH based on supergravity reaction technology. Materials and systematic studies have confirmed its excellent performance in radioactive iodine capture. The hypergravity synthesis method, by tearing the reaction solution into micron-sized reaction units through high-speed rotation, significantly enhances the mass transfer process, resulting in the preparation of IRMOF-3. It exhibits a regular cubic morphology, uniform particle size distribution, and a higher specific surface area (984 m²·g). -1 This laid an ideal foundation for subsequent functionalization. Based on this, a thiol functional group was introduced using a post-hypergravity modification method to obtain IRMOF-3-SH. The material not only maintains a good crystal structure, but the thiol groups can also modify the surface properties of the material, forming coordination bonds or hydrogen bonds with the adsorbed molecules or ions, thereby increasing the iodine adsorption capacity to 3.00 g·g. -1 Compared to the unfunctionalized IRMof-3 The material exhibited a 46% improvement in performance and demonstrated excellent cycling stability (retaining 79% capacity after 6 cycles). Mechanistic studies revealed that the performance enhancement stemmed from stronger electronic interactions between the thiol functional groups and iodine: Crystal orbital Hamiltonian population (COHP) analysis quantitatively revealed the bonding characteristics of the SI bond (-ICOHP = 0.000485), with a bonding strength approximately 2.5 times that of the Ni interaction. Combined with charge transfer mechanisms confirmed by XPS analysis, it was clarified that multiple sites in the material, including S and N, interact with I through effective charge transfer and the formation of polyiodide anions, achieving efficient adsorption and stable fixation of iodine. This work not only confirms the synergistic effect of hypergravity synthesis and thiol functionalization but also provides crucial theoretical guidance for designing high-performance radioactive iodine adsorbents at the electronic structure level.

[0027] The beneficial effects achieved by one or more embodiments of the present invention described above are as follows: 1. This application provides thiol-functionalized metal-organic framework materials, based on a combination of supergravity synthesis technology and post-synthetic modification strategies, to obtain thiol-functionalized IRMOF-3-SH. The obtained metal-organic framework material exhibits an iodine adsorption capacity as high as 3.00 g·g⁻¹. -1 (Compared to IRMof-3) (Increased by 46%).

[0028] 2. Compared with the hydrothermal synthesis method commonly used in the preparation of metal-organic frameworks in existing technologies, the advantages of the supergravity method used in this invention include: 2.1, improved reaction efficiency, significantly shortened synthesis time (12 h → 1 h), resulting in increased yield and enabling the synthesis of more high-efficiency adsorbents in a short time; 2.2, achieving precise and controllable synthesis of particle size and morphology, enabling the reproducible and large-scale preparation of MOF nanocrystals with extremely narrow particle size distribution and highly uniform morphology; 2.3 Building upon 2.2, the use of the supergravity method makes it easier to achieve continuous production and scale-up. When scaling up production, it is only necessary to increase the number or size of the rotating bed modules in parallel without changing the internal micro-mixing environment. Therefore, seamless connection can be easily achieved from laboratory to pilot-scale to industrial production, and product quality remains consistent, making it very suitable for the future industrial continuous production of MOFs.

[0029] 3. In the metal-organic framework material provided by this invention, COHP analysis reveals that strong SI bonding is the main reason for efficient adsorption. Mechanistic studies, through crystal orbital Hamiltonian population analysis, quantitatively reveal the existence of strong bonding interactions between SI atoms, with a bonding strength 2.5 times that of Ni interaction. Combined with XPS and other characterization, it confirms the synergistic adsorption of iodine through multiple mechanisms, including charge transfer between S, N, and other sites. This technology provides a new synthetic strategy and theoretical basis for developing high-performance radioactive iodine adsorbent materials.

[0030] 4. The metal-organic framework material provided by this invention has regular crystal structure, uniform particle size, and good thermal stability, providing an effective solution for the adsorption of radioactive iodine under high temperature conditions. Attached Figure Description

[0031] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0032] Figure 1 The IRMof-3-SH provided by this invention The synthetic route.

[0033] Figure 2 Characterization of IRMOF-3 products synthesized by conventional hydrothermal and hypergravity methods; (a) SEM image of IRMOF-3 synthesized by conventional hydrothermal method, (bd) IRMOF-3 synthesized under different hypergravity levels. The SEM images are shown, where (a) has a scale bar of 1 μm and (bd) has a scale bar of 4 μm.

[0034] Figure 3 The structure characterization and performance testing of IRMOF-3 synthesized by traditional hydrothermal and supergravity methods are shown in (a) XRD, (b) N2 adsorption-desorption test, and (c) adsorption performance.

[0035] Figure 4 The results show (a) N2 adsorption-desorption test, (b) XRD, and (c, d) SEM of IRMOF-3-SH, where the scale bar in (c) is 1 μm and the scale bar in (d) is 4 μm.

[0036] Figure 5 It is IRMof-3-SH The structural characteristics include (a) thermogravimetric analysis, (b) infrared spectroscopy, and (c) XPS analysis.

[0037] Figure 6 It is IRMof-3-SH The adsorption and desorption properties of the MOF, including (a) adsorption capacity, (b) MOF iodine adsorption capacity, (c) pseudo-first-order kinetics, (d) pseudo-second-order kinetics, (e) iodine desorption capacity, and (f) adsorption cycle.

[0038] Figure 7 It is IRMof-3-SH The adsorption mechanism; (a) FT-IR, (b) XPS full spectrum, (c) XPS energy spectrum of I 3d, (d) high-resolution XPS energy spectrum of O, (e) high-resolution XPS energy spectrum of N, and (f) high-resolution XPS energy spectrum of S.

[0039] Figure 8 Mechanism analysis; including (a) HOMO-LUMO analysis, (b) COHP analysis of NI in I2@IRMOF-3, and (c) I2@IRMOF-3-SH. COHP analysis of SI.

[0040] Figure 9 IRMof-3-SH synthesized using a supergravity method SEM-EDS analysis, scale bar in figure is 4 μm.

[0041] Figure 10 It is the Webber-Morris internal diffusion model.

[0042] Figure 11 It is I2@IRMOF-3-SH Thermogravimetric analysis results.

[0043] Figure 12 This is a schematic diagram illustrating the preparation method, iodine adsorption performance, and mechanism provided by the present invention. Detailed Implementation

[0044] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0045] The present invention will be further described below with reference to the embodiments.

[0046] Experimental methods 1. Hypergravity technology In this embodiment, a centrifuge is used to simulate a hypergravity field. The ratio of the hypergravity horizontal centrifugal acceleration to the gravitational acceleration is calculated as follows: ; ; .

[0047] in, ω It is angular velocity (rad / s). r It is the centrifugal radius (m). r 1 and r 2 represents the inner and outer radii (m) of the reaction zone. g It is the acceleration due to gravity (9.8 m). 2 ·g -1 ), n It is the rotational speed (rpm) of the supergravity rotor.

[0048] 2. Iodine adsorption performance test The iodine adsorption performance and cyclic adsorption performance of MOFs were evaluated by gravimetric method, and the kinetic mechanism was explored using pseudo-first-order kinetic equations, pseudo-second-order kinetic equations and Webber-Morris internal diffusion equations.

[0049] 2.1 The iodine adsorption experiment was conducted using the gravimetric method. The specific steps are as follows: 1) Take two clean 2 mL open glass bottles, place them in a desiccator to dry for 2 hours, take them out and cool them, and label them 1 and 2 for later use. Weigh the open glass bottles with different numbers respectively.

[0050] 2) Take two wide-mouth bottles of equal size, wash them, put them in a drying oven and dry for 2 hours. After cooling, label them 1 and 2 for later use.

[0051] 3) Add a certain amount of iodine to each of the two wide-mouth bottles, and then add a certain amount of MOFs (about 50 mg) to each of the No. 1 and No. 2 open-mouth glass bottles. Weigh the total mass of the open-mouth glass bottles and the sample, put them into the wide-mouth bottles according to their numbers, and seal all the wide-mouth bottles tightly.

[0052] 4) Place the sealed wide-mouth bottle in a constant temperature chamber and let it stand for a period of time. After taking it out, measure and record the total mass of the sample after adsorption at different times.

[0053] 5) Repeat the above steps until the total mass of the sample no longer changes.

[0054] 6) Calculate the amount of iodine vapor captured.

[0055] Iodine adsorption capacity Q (g·g) -1 ) Calculate using the following formula.

[0056]

[0057] Among them, here, w 1 and w 2 refers to the mass before and after MOF captures iodine.

[0058] The data were fitted using pseudo-first-order and pseudo-second-order dynamic models. The mathematical equations of the pseudo-first-order dynamic model are as follows.

[0059]

[0060] k 1 is the pseudo-first-order kinetic rate constant (h) -1 ), t q represents the reaction time (h). t and q e The adsorption amount per unit volume (g·g) at time t and equilibrium are respectively. -1 The mathematical equations of the pseudo-second-order dynamic model are as follows.

[0061]

[0062] k 2 is the pseudo-second-order kinetic rate constant (g·g -1 ·h -1 By plotting ln(q) respectively e -q t For t and t / q t For a straight line with respect to t, the theoretical equilibrium adsorption capacity q can be obtained from the slope and intercept of the line. e And the values ​​of the rate constants k1 and k2.

[0063] To determine whether diffusion is the rate-limiting step in the adsorption of volatile iodine by MOFs, this invention employs an intraparticle diffusion model because the pseudo-first-order and pseudo-second-order kinetic models used are insufficient to elucidate the diffusion mechanism involved. The mathematical equations of the Webber-Morris intraparticle diffusion model are as follows.

[0064]

[0065] k i The diffusion rate constant within the particle (g·g) -1 ·h -0.5 ), C This is the intercept.

[0066] 2.2 Cyclic Adsorption-Desorption Performance Test First, the desorption behavior of the iodine-loaded adsorbent was evaluated using thermogravimetric analysis (TGA) to determine the optimal desorption temperature. Based on the TGA results, the iodine release capacity was then determined gravimetrically at a selected temperature of 150 °C. In a typical desorption experiment, accurately weighed iodine-loaded adsorbent was placed in a 2 mL glass vial. This vial was then placed in a sealed larger container and transferred to an oven maintained at 150 °C. To monitor the desorption process, the vial was periodically removed, cooled to room temperature in a desiccator, and accurately weighed. After each desorption cycle, the regenerated adsorbent was dried, and subsequent iodine adsorption experiments were performed under the same conditions as the initial experiment. The complete adsorption-desorption-regeneration process was repeated six times consecutively to evaluate the cyclic stability and reusability of the material.

[0067] 3. Characterization methods The size and morphology of the MOF were recorded using scanning electron microscopy (SEM, JEOL JSM-7610F Plus and FEI QUANTA-450). Powder X-ray diffraction (PXRD) patterns were obtained using a SmartLab X-ray diffractometer (Cu Kα source, 5° / min). Fourier transform infrared spectroscopy (FT-IR, Nicolet 6700) was performed in the 400–4000 cm⁻¹ range, and the material surface area and pore structure were determined using an autosorb iQ physical adsorption analyzer from Quantachrome, USA. Thermogravimetric analysis (TGA) was performed on a TGA / SDTA-851 instrument under a nitrogen atmosphere. X-ray photoelectron spectroscopy (XPS) was performed using an AXIS Ultrabld instrument.

[0068] 4. Calculation methods and models All calculations were performed using Materials Studio software. Geometric optimization was performed using Dmol. 3 The module is complete, employing density functional theory (DFT) based on the generalized gradient approximation (GGA). It uses the Perdew-Burke-Ernzerhof (PBE) functional, combined with TS-DFT dispersion correction. The convergence criterion is set as follows: energy tolerance of 1.0 × 10⁻⁶. -5 The maximum force is 0.002 Ha / Å, the maximum displacement is 0.005 Å, and the maximum number of iterations is 500.

[0069] The adsorption process was simulated using the grand canonical Monte Carlo (GCMC) method with the Metropolis sampling algorithm, where the probability of adsorbate molecule creation and disappearance is equal. Electrostatic interactions were handled using the Ewald summation method, while van der Waals interactions were described using an atom-based summation method.

[0070] 5. Test reagents and materials 2-Aminoterephthalic acid (Aladdin Reagent Co., Ltd.), mercaptoacetic acid (Aladdin Reagent Co., Ltd.), zinc nitrate hexahydrate (Tianjin Damao Chemical Reagent Co., Ltd.), anhydrous ethanol (Tianjin Fuyu Fine Chemical Co., Ltd.), dichloromethane (Shandong Tianming Biotechnology Development Co., Ltd.), triethylamine (Xilong Scientific Co., Ltd.).

[0071] Example 1 The preparation method provided by this invention, and the schematic diagram of iodine adsorption performance and mechanism are as follows: Figure 12 As shown. It includes the following steps: IRMOF-3 The supergravity synthesis: 0.05 g Zn(NO3)2·6H2O was dissolved in 20 mL ethanol, and 0.036 g 2-aminoterephthalic acid was dissolved in 20 mL ethanol. The two solutions were mixed for 30 min under magnetic stirring. 2 mL triethylamine was added to 20 mL ethanol and then slowly added to the mixed solution. The mixed solution was transferred to a centrifuge tube, and the centrifuge speed was adjusted to regulate the supergravity level. The mixture was vigorously mixed and reacted at room temperature for 30 min. In this embodiment, the supergravity level was adjusted by changing the centrifuge speed. A speed of 1200 rpm corresponded to a supergravity level of 64, a speed of 1600 rpm corresponded to a supergravity level of 108, and a speed of 2000 rpm corresponded to a supergravity level of 179. The product was collected and centrifuged (9000 rpm). The product was dried in a vacuum drying oven at 120 °C for 8 h and named IRMOF-3. .

[0072] IRMOF-3-SH Supergravity synthesis: The synthesis route is as follows Figure 1 As shown, take 0.3 g of IRMOF-3. Add the contents to a beaker, along with 1.3 mL of mercaptoacetic acid and 20 mL of dichloromethane (DCM). Transfer the mixture to a centrifuge tube, adjust the hypergravity level to 179, and vigorously mix and react at room temperature for 1 h. Collect the product and centrifuge (9000 rpm). Dry the product in a vacuum drying oven at 120 °C for 8 h, naming it IRMOF-3-SH. Its single-unit structural formula is: .

[0073] Comparative Example 1 Traditional synthesis of IRMOF-3: 0.05 g Zn(NO3)2·6H2O is dissolved in 20 mL of ethanol, and 0.036 g 2-aminoterephthalic acid (H2ABDC) is dissolved in 20 mL of ethanol. The two solutions are mixed in a beaker, and 2 mL of triethylamine is added to the 20 mL of ethanol. The triethylamine diffuses into the solution of zinc nitrate and H2ABDC, causing H2ABDC to deprotonate and react with Zn. 2+ The reaction was carried out by slowly adding the mixture to the mixed solution under magnetic stirring, stirring at 70 °C for 90 min, collecting the mixture by centrifugation (9000 rpm), and drying it in a vacuum drying oven at 120 °C for 12 h.

[0074] Traditional synthesis of IRMOF-3-SH: 0.3 g of IRMOF-3 was added to a beaker, along with 1.3 mL of mercaptoacetic acid and 20 mL of dichloromethane (DCM), and the mixture was stirred for 12 h. The product was collected by centrifugation, and after solid-liquid separation, the solid was dried in a vacuum oven at 120 °C for 12 h.

[0075] Comparative Example 2 Synthesis method of MOF-5: 1.664 g Zn(NO3)2·6H2O and 0.358 g terephthalic acid were dissolved in 40 mL DMF, stirred and poured into a hydrothermal reactor. The reaction was carried out at 130 ℃ in an oven for 8 h to obtain crystals. The crystals were washed several times and then washed with methanol. The solution was soaked for 3 days, and the solution was changed every 24 h. The crystals were collected by centrifugation (9000 rpm) and dried in a vacuum drying oven at 120 ℃ for 12 h.

[0076] Experimental Example 1 1. Product characterization results Figure 2 SEM images from the Chinese image show IRMof-3 synthesized via conventional hydrothermal synthesis and centrifugal synthesis. As the rotational speed gradually increased from 1200 rpm to 2000 rpm and the high gravity level (HGL) increased from 64 to 179, the particles gradually exhibited a distinct cubic morphology with uniform particle size (≤1 μm) and slightly smaller than MOFs synthesized by conventional hydrothermal methods (1-3 μm). The particle boundaries were also clearer. This may be because the high-speed rotation induced the reactant solution to tear into countless smaller reaction units. These smaller micro-units acted as microreactors to enhance molecular mixing and mass transfer, accelerate the nucleation of reactants, and form more uniform particles.

[0077] IRMof-3 prepared at hypergravity level 179 As a typical product, subsequent testing was conducted, and the results are as follows: Figure 3The XRD pattern of α showed obvious crystal characteristic diffraction peaks at 2θ = 6.7°, 10.3°, 16.5° and 18.8°, corresponding to its (200), (220), (420) and (440) crystal planes, respectively, indicating that the IRMof-3 synthesized by the hypergravity method in a short time... It has a good crystal structure with few impurity peaks and no change in crystal structure. Figure 3 Figure b shows the IRMof-3 synthesized by the supergravity method. The N2 adsorption-desorption curve shows a BET specific surface area of ​​984 m². 2 g -1 Slightly larger than conventionally hydrothermally synthesized IRMof-3 (921m). 2 g -1 ). Figure 3 The image shows the adsorption performance of IRMOF-3 synthesized by the supergravity method and conventional hydrothermal synthesis for iodine. The adsorption capacity for iodine is 2.06 g·g. -1 Greater than IRMof-3 (1.96 g·g) -1 The adsorption rate was 0.086 g·g⁻¹. -1 ·h -1 Greater than IRMof-3 (0.065 g·g) -1 ·h -1 ).

[0078] Figure 4 In section a, IRMof-3-SH is shown. N2 adsorption-desorption curves, IRMOF-3-SH Its specific surface area is 875 m² 2 ·g -1 The BET specific surface area is greater than that of IRMof-3-SH (792 m²). 2 ·g -1 ). Figure 4 SEM images of C and D show that the IRMOF-3-SH particles failed to maintain a good cubic morphology and had blurred boundaries. The particles are uniform in size and maintain a good cubic morphology with clear particle boundaries. EDS qualitative analysis indicates that IRMOF-3-SH... The existence of S in the middle ( Figure 9 ). Figure 4 In the middle b, IRMof-3-SH and IRMof-3-SH XRD comparisons revealed that IRMof-3-SH could be synthesized in a short time using the hypergravity method. It has a good crystal structure.

[0079] Figure 5The text in the image shows IRMof-3-SH. Thermogravimetric analysis showed that after temperatures exceeded approximately 408 °C, the mass rapidly decreased until complete decomposition, which is due to the IRMOF-3-SH... The gradual fragmentation of the crystal framework, producing metal oxides and carbides, until the mass returns to near-stabilization, indicates that IRMOF-3-SH It has good thermal stability.

[0080] Figure 5 The b in the middle displays IRMof-3-SH The infrared spectrum at 2575 cm⁻¹ -1 The characteristic absorption peak of -SH appears at 1590 cm⁻¹. -1 The presence of a characteristic absorption peak for the -NH-CO amide bond indicates the formation of the amide bond, while the 1120 cm⁻¹ peak... -1 The weakening of the CN peak confirms that the -NH2 group of IRMof-3 undergoes a condensation reaction with the COOH group of thioglycolic acid, resulting in IRMof-3-SH. Successfully synthesized.

[0081] Figure 5 c is used as IRMof-3-SH XPS full-spectrum scanning clearly showed the presence of S, which matched the thiol functional groups introduced into the material, synergistically confirming the successful synthesis of the target product at the level of surface elemental composition.

[0082] 2. Adsorption performance and cyclic adsorption performance IRMof-3-SH was tested at 75 °C. The adsorption capacity at different times showed that the amount of iodine adsorbed was 3.00 g·g. -1 ( Figure 6 (a). By investigating the currently reported adsorption capacity of iodine by MOFs ( Figure 6 In b, there are 1 YS-1, 2 MIL-53-SH, 3 Ui0-67, 4 Fe-Cu-BTC, 5 MOF-5, 6 Zn-MOF-3, 7 Ui0-66, and 8 Cu. 2+ -MOF-303, 9 Cu 0-MOF-303, 10MOF-867, 11 Ui0-66-F, 12 MFM-300(AI), 13 Th-Ui0-66, 14 UiO-66-NH-BD, 15 ZF-8, 16Zn-MOF-1, 17 UiO-66-NH-TD, 18 MFM-300(VII), 19 NU-1000, 20 HKU ST-1, 21 medi-MOF-1, 22 Zn-ABTC, 23 a(T)-SCNU-Z6, 24 Zn-MOF-2, 25 MOF-808, 26 IRMOF-3-SH ), discovered that the IRMof-3-SH of the present invention It is at a relatively high level; compared to IRMof-3 The increase was 46%, which may be due to IRMof-3-SH It has additional thiol active sites, which enhance the adsorption capacity of MOFs for iodine.

[0083] For IRMof-3-SH The adsorption of iodine was kinetically fitted by [the following]. Figure 6 As can be seen from C, D in 6 and Table 1, IRMOF-3-SH The adsorption process of iodine is more consistent with the pseudo-second-order kinetic model (higher correlation coefficient, R0). 2 =0.99), and also shows a good correlation with pseudo-first-order dynamics (R = 0.99). 2 =0.98), indicating that the adsorption process involves both physical and chemical adsorption, with chemical adsorption being dominant. IRMOF-3-SH The internal diffusion model of iodine adsorption process is as follows: Figure 10 As shown, it involves two steps. The first is a rapid step, influenced by boundary layer effects, where iodine diffuses into IRMOF-3-SH. The outer surface, the second step is a slower internal diffusion process.

[0084] Table 1 IRMOF-3-SH Kinetic parameters of iodine adsorption

[0085] Figure 11 Display I2@IRMOF-3-SH Thermogravimetric analysis revealed that the adsorbent began to lose weight at 120 °C, so 150 °C was chosen as the desorption temperature for iodine. Figure 6 Quantitative testing of I2@IRMOF-3-SH at 150 ℃ The iodine desorption capacity at different times was found to be I2@IRMOF-3-SH The final weight loss rate was 71.9%, and the desorption amount was 2.87 g·g. -1 This differs from the adsorption capacity, possibly because the high temperature of 150 °C cannot completely desorb I₂, and iodine reacts with IRMOF-3-SH. They have strong interaction forces. After 6 cycles of adsorption ( Figure 6 (f), the adsorbent can still maintain a high adsorption performance (79%).

[0086] 3. Research on adsorption mechanisms IRMof-3-SH before and after adsorption FT-IR spectra such as Figure 7 As shown in Figure a, iodine and functionalized IRMof-3-SH An electron transfer mechanism may be involved between NH-C=O and -SH. The characteristic absorption peak of -SH extends from 2575 cm⁻¹. -1 Moved to 2578 cm -1 The characteristic absorption peak of the -NH-CO amide bond is from 1590 cm⁻¹ -1 Moved to 1592 cm -1 The bending vibration absorption peak of -NH increases from 1684 cm⁻¹ -1 The transfer to 1688 cm -1 These results indicate that IRMof-3-SH The thiol group introduced in the process may have an inductive effect on iodine adsorption. Among them, the S in -SH is a better electron-losing group, which is involved in electron transfer or sharing and exhibits better adsorption performance.

[0087] Figure 7 XPS energy dispersive spectroscopy analysis of iodine-loaded IRMof-3-SH indicates that... The presence of significant characteristic peaks in the I 3d region confirms the effective capture of iodine. High-resolution I 3d energy dispersive spectroscopy (EDS) Figure 7 c) The double peaks at 630.4 eV and 618.5 eV correspond to I3. - The peaks at 632.1 eV and 620.5 eV are attributed to physically adsorbed I₂, revealing the coexistence mechanism of polyiodide anions and elemental iodine. The formation of the polyiodide complex also alters the electron density in the aromatic ring of the organic linker, leading to a positive shift in the O 1s peak. Figure 7 (d). IRMof-3-SH The XPS characteristics of N 1s consist of two peaks ( Figure 7The peaks (e) appear at 399.1 eV and 399.7 eV, respectively, corresponding to the NH groups of the amino and amide groups, C-NH and NC=O, respectively. After iodine adsorption, the peak intensity and binding energy changed, with a significant positive shift in the corresponding peaks, indicating that the lone pair electrons of the amino and amide groups are shifted towards the σ-axis of I₂. Orbital shift, forming n→σ Charge transfer bond. Figure 7 The XPS data in the image show XPS peaks for the thiol S 2p group, at 168.2 eV and 169.5 eV respectively, while the characteristic peaks for the thio group change to 168.4 eV and 169.6 eV after iodine adsorption. These XPS evidences systematically reveal the charge transfer interaction between iodine and N / O / S sites in the material and Zn. 2+ with I - The electrostatic synergistic adsorption mechanism jointly drives the efficient immobilization of iodine.

[0088] According to advanced molecular orbital theory, the HOMO-LUMO energy difference drives the adsorption process in MOFs. The smaller the HOMO, the more difficult it is for the adsorbent to lose electrons; the smaller the LUMO, the easier it is to gain electrons. A smaller band gap (Eg) results in higher adsorbent activity and easier adsorption. Since iodine is a highly electronegative molecule, adsorbents with good electron-losing ability may exhibit good adsorption performance for iodine. Figure 8 Figure a shows IRMof-3 and IRMof-3-SH HOMO and LUMO, of which IRMof-3-SH The HOMO value is -0.1849 eV, which shows better electron loss capability compared to IRMof-3, and a smaller band gap (0.0254 eV), indicating that IRMof-3-SH It may produce stronger chemisorption. Overall, calculations using HOMO and LUMO indicate that IRMof-3-SH... It may produce stronger chemisorption with iodine than IRMOF-3.

[0089] Further analysis using crystal orbital Hamiltonian population (COHP) was employed to quantitatively assess the nature and strength of the interaction between adsorption sites (N or S atoms) and I atoms at the electronic structure level. Specifically, for IRMof-3 materials ( Figure 8In (b), the COHP curve between the N atom in the amino group (-NH2) and the adsorbed I atom shows a positive value in the main energy range, with an integral COHP of 0.000195. The positive COHP value clearly indicates antibonding interaction, meaning that the occupied state formed between the N and I atomic orbitals has a destabilizing effect on the bond between N and I. This suggests that during the adsorption of iodine by IRMOF-3, it is difficult for strong, localized covalent bonds to form between the amino group and iodine; the adsorption may mainly rely on weak charge transfer, electrostatic interactions, or van der Waals forces. However, the thiol-functionalized IRMOF-3-SH... in the material ( Figure 8 In section c), the COHP curve between S and I atoms shows a significant negative value, with the integral -ICOHP reaching 0.000485. This negative COHP value directly corresponds to bonding interactions; the electron cloud effectively accumulates in the internuclear region between S and I, forming a stable chemical bond, thus significantly reducing the overall energy of the system. Furthermore, the absolute value of the integral -ICOHP indicates that the strength of the S-I interaction (0.000485) is approximately 2.5 times that of the Ni-I antibonding interaction (0.000195), quantitatively confirming that the anchoring ability of the S site for I is far superior to that of the N site. In summary, analysis of COHP at the electronic structure level reveals that in IRMof materials, the S atom in the thiol group (-SH) forms a strong and stable bond with I, thus becoming a more efficient and stable iodine-capturing site than the N atom in the amino group (-NH2).

[0090] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing thiol-functionalized metal-organic framework materials, characterized in that, First, zinc salt and ligands with both amino and carboxyl groups are reacted under hypergravity conditions. Then, the resulting product undergoes a thiolation reaction under hypergravity conditions.

2. The method for preparing the thiol-functionalized metal-organic framework material according to claim 1, characterized in that, Includes the following steps: Step 1: Dissolve the zinc salt in an organic solvent, and dissolve the ligand containing both amino and carboxyl groups in the organic solvent. Mix the two solutions by stirring. Dissolve triethylamine in the organic solvent and add it to the two solution system to obtain a mixed solution. React under hypergravity conditions to obtain the intermediate IRMof-3. ; Step 2, the intermediate IRMof-3 obtained in Step 1 It is mixed with mercaptoacetic acid in an organic solvent and reacted under hypergravity conditions.

3. The method for preparing the thiol-functionalized metal-organic framework material according to claim 1, characterized in that, In step 1, the zinc salt is zinc nitrate and its hydrate.

4. The method for preparing the thiol-functionalized metal-organic framework material according to claim 1, characterized in that, In step 1, the ligand containing both amino and carboxyl groups is 2-aminoterephthalic acid.

5. The method for preparing the thiol-functionalized metal-organic framework material according to claim 1, characterized in that, In step 1, the molar ratio of the zinc salt to the ligand is 1.5-1.8:

2.

6. The method for preparing the thiol-functionalized metal-organic framework material according to claim 1, characterized in that, In step 1, the molar ratio of zinc salt to triethylamine is 1:98.7-111.

3.

7. The method for preparing the thiol-functionalized metal-organic framework material according to claim 1, characterized in that, In step 2, the intermediate IRMof-3 The mass ratio of mercaptoacetic acid to thioglycolic acid is 1:5.5-5.

9.

8. The method for preparing the thiol-functionalized metal-organic framework material according to claim 1, characterized in that, In steps 1 and 2, the hypergravity level is not lower than 64; preferably, the hypergravity level is 64-179.

9. The metal-organic framework material obtained by the method for preparing thiol-functionalized metal-organic framework materials according to any one of claims 1-8.

10. The application of the metal-organic framework material of claim 9 in iodine adsorption.

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