A functional group functionalized mil-53 type metal organic framework adsorbent and its application in lithium extraction and lithium isotope separation

Abstract

The application discloses a kind of functional group functional MIL-53 type metal organic framework adsorbents and its application in lithium extraction and lithium isotope separation, preparation steps: (1) metal salt and functional group substituted terephthalic acid are added into solvent, mixed uniformly, add hydrofluoric acid;Precursor suspension is obtained;(2) hydrothermal reaction or solvothermal reaction, metal ion in metal salt and the functional group substituted terephthalic acid occur coordination self-assembly, and the crude product is obtained;Centrifugal separation, washing, solvent exchange, drying;(3) activation, and the adsorbent is obtained.The application has the advantages of material structure designable, pore microenvironment controllable, adsorption site optimizable, mild operating conditions, relatively fast adsorption rate, renewable use and the like.The application provides a new solid-phase separation idea for Li 6 Li / 7 Li isotope adsorption fractionation and enrichment, and plays a role in lithium resource recovery, salt lake brine lithium extraction, lithium-containing wastewater treatment and lithium isotope enrichment.

Description

Technical Field

[0001] This invention belongs to the technical fields of lithium resource extraction, adsorption and separation materials, metal-organic framework materials, lithium isotope separation and resource utilization of salt lake brine, specifically involving functionalized MIL-53 type metal-organic framework adsorbents, their preparation methods and applications. Background Technology

[0002] Lithium is a key strategic resource supporting the development of new energy batteries, energy storage devices, and nuclear energy-related materials. With the rapid development of electric vehicles and grid energy storage industries, global lithium demand continues to grow. Natural lithium resources mainly include hard-rock lithium deposits and liquid lithium resources. Liquid lithium resources, such as salt lake brines, underground brines, and geothermal brines, have considerable reserves and are considered an important source for alleviating the supply-demand imbalance of lithium resources. However, in liquid lithium resources, Li... + Usually with Na + K + Ca 2+ Mg 2+ These coexisting ions, especially in brines with a high magnesium-to-lithium ratio, are present simultaneously, particularly Mg. 2+ High concentration and with Li + The similarity in hydration characteristics makes the efficient and selective separation of lithium a significant challenge.

[0003] Existing liquid lithium extraction technologies mainly include evaporation precipitation, solvent extraction, membrane separation, electrochemical methods, and adsorption methods. Among them, evaporation precipitation has a long cycle time and poor adaptability to brines with high magnesium-to-lithium ratios; solvent extraction poses risks such as organic phase loss, equipment corrosion, and environmental impact; membrane separation is susceptible to membrane fouling, concentration polarization, and long-term stability limitations. Although electrochemical methods have advantages such as high selectivity and process controllability, they usually rely on specific lithium insertion / delithiation electrode materials and are easily affected by electrode structure degradation, side reactions, interface passivation, interference from coexisting ions, and energy consumption variations. Furthermore, their long-term cycling stability and large-scale operation in complex brine systems still require further improvement.

[0004] In contrast, adsorption methods offer advantages such as mild operating conditions, low energy consumption, and renewable materials, making them a promising lithium extraction technology. Currently, common lithium adsorption materials include manganese-based ion sieves, titanium-based ion sieves, and aluminum-based stroma adsorbents. However, these materials still suffer from issues such as metal leaching, insufficient framework stability, slow mass transfer rates, and sensitivity to brine composition, requiring further improvement in overall performance.

[0005] 6 Li / 7 The separation of Li isotopes is also of great significance in the nuclear industry and future energy fields. 6 Li can be used in tritium breeding and fusion energy systems. 7 Lithium (Li) can serve as an important lithium source for pH adjustment in nuclear reactor coolants. In natural lithium...6 Li abundance was low, and 6 Li and 7 Lithium (Li) differs only in mass; their chemical properties are extremely similar, making separation challenging. Traditional lithium isotope separation methods, such as lithium amalgamation, while industrialized, pose serious environmental and health risks. Alternative methods, such as crown ether extraction and electrochemical separation, still face problems such as limited separation factors, insufficient mass transfer efficiency, or complex processes. Therefore, developing novel solid-phase adsorption materials with tunable structures, environmental friendliness, and the potential for both lithium-ion adsorption and lithium isotope separation is of significant application value.

[0006] Metal-organic frameworks (MOFs) possess advantages such as designable metal nodes, tunable ligand functional groups, controllable pore structure, and engineerable microenvironment within the pores. However, existing MOF adsorbents for liquid lithium extraction still have certain shortcomings: the pore walls of traditional MOFs are mostly composed of carboxylic acid skeletons or relatively neutral organic ligands, resulting in a limited number of effective lithium recognition sites within the pores. They also lack sufficient highly lithium-affinity coordination or polar interaction sites such as oxygen, nitrogen, and fluorine, leading to limitations in their ability to effectively target hydrated Lithium. + Its specific binding ability is insufficient.

[0007] Therefore, developing MOF adsorbents with tunable structures, excellent adsorption performance, and potential for lithium isotope separation, especially functionalized MIL-53 type metal-organic framework adsorbents, is of great significance for lithium resource extraction and lithium isotope enrichment. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of the prior art and provide a functionalized MIL-53 type metal-organic framework adsorbent.

[0009] The second objective of this invention is to provide a method for preparing a functionalized MIL-53 type metal-organic framework adsorbent.

[0010] A third objective of this invention is to provide the application of functionalized MIL-53 type metal-organic framework adsorbents in lithium extraction.

[0011] The fourth objective of this invention is to provide an application of a functionalized MIL-53 type metal-organic framework adsorbent in lithium isotope separation.

[0012] The technical solution of this invention is summarized as follows: The preparation method of functionalized MIL-53 type metal-organic framework adsorbent includes the following steps: (1) Add the metal salt and functionally substituted terephthalic acid to the solvent, mix well, and add hydrofluoric acid to obtain a precursor suspension; the solvent is selected from water, N,N-dimethylformamide, N,N-dimethylacetamide, acetonitrile, methanol, ethanol, ethylene glycol and acetone. (2) The precursor suspension is subjected to hydrothermal or solvothermal reaction to allow the metal ions in the metal salt to coordinate with the functionalized terephthalic acid to self-assemble, thereby obtaining a functionalized MIL-53 type metal-organic framework crude product; centrifugation, washing of the solid with detergent, solvent exchange, and drying to obtain the dried product. (3) The dried material is activated to obtain a functionalized MIL-53 type metal-organic framework adsorbent.

[0013] Preferably, the molar ratio of the metal salt, functionally substituted terephthalic acid, and hydrofluoric acid is 1:0.5~2:0.5~2, and the ratio of the metal salt to the solvent is 1 g:20-60 mL.

[0014] Preferably, the metal ion in the metal salt is Fe. 3+ .

[0015] The functional group in the terephthalic acid that is substituted with the functional group is monosubstituted or disubstituted, and the functional group is hydroxyl, amino, fluorine, chlorine, bromine, nitro or trifluoromethyl.

[0016] Preferably, the hydrothermal reaction temperature is 100–220 °C, and the hydrothermal reaction time is 6–72 h.

[0017] Preferably, the temperature of the solvothermal reaction is 100–220 °C, and the reaction time is 6–72 h.

[0018] Preferably, the activation is vacuum thermal activation, atmospheric pressure thermal activation, or inert atmosphere thermal activation.

[0019] The functionalized MIL-53 type metal-organic framework adsorbent prepared by the above preparation method.

[0020] The application of the functionalized MIL-53 type metal-organic framework adsorbent with the above-mentioned functional groups in lithium extraction.

[0021] The application of the functionalized MIL-53 metal-organic framework adsorbent with the above-mentioned functional groups in lithium isotope separation.

[0022] Advantages of this invention: The functionalized MIL-53 metal-organic framework adsorbent of this invention directly adsorbs and enriches lithium ions in lithium-containing aqueous solutions. It offers advantages such as designable material structure, tunable pore microenvironment, optimized adsorption sites, mild operating conditions, rapid adsorption rate, and recyclability. Compared to traditional lithium isotope separation methods that commonly involve lithium amalgam, complex extraction, ion exchange, or high-energy-consuming separation processes, this invention further utilizes the flexible pore confinement effect, oxygen-containing site activity, metal node regulation, and Fe–F related interaction sites of MOF materials to provide… 6 Li / 7 This method offers a novel solid-phase separation approach for lithium isotope adsorption fractionation and enrichment. It holds promise for applications in lithium resource recovery, lithium extraction from salt lake brine, lithium-containing wastewater treatment, and lithium isotope enrichment, providing a new material foundation and methodological approach for efficient, green, and controllable lithium extraction and isotope separation technologies.

[0023] This invention discloses the application of functionalized MIL-53 metal-organic framework adsorbents in lithium extraction and lithium isotope separation. These materials benefit from the flexible and tunable pore structure, designable metal nodes, and modifiable ligand functional groups of the MIL-53 MOF, making them suitable for lithium extraction and isotope separation. + A specific adsorption microenvironment is provided to achieve the adsorption and enrichment of lithium ions in lithium-containing aqueous solutions. Experimental results show that the lithium adsorption performance of MIL-53-type MOFs can be effectively improved through a continuous optimization route of "metal center screening – ligand functionalization". MIL-53(Fe) was selected as the preferred parent material, and hydroxyl functionalization can enhance the adsorption of lithium ions by oxygen-containing sites within the pores. + The interaction between the two resulted in an equilibrium lithium adsorption capacity of 26.58 mg·g. -1 Furthermore, NH2-MIL-53 (Fe) has a maximum lithium isotope separation factor of 1.072. Attached Figure Description

[0024] Figure 1 The XRD patterns of the MIL-53 series adsorbents are shown.

[0025] Figure 2 A comparison chart of lithium adsorption capacity of MIL-53 series materials.

[0026] Figure 3 XRD patterns of functionalized MIL-53 type metal-organic framework adsorbents: a. Single electron-withdrawing substituents; b. Double electron-withdrawing substituents; c. Electron-donating substituents.

[0027] Figure 4 Comparison of lithium adsorption capacity of functionalized MIL-53 metal-organic framework adsorbents.

[0028] Figure 5 Lithium isotope separation performance of MIL-53 with different metal nodes.

[0029] Figure 6 Lithium isotope separation performance of MIL-53 (Fe) modified with different functional groups. Detailed Implementation

[0030] The present invention will be further described below with reference to specific embodiments.

[0031] Compare with Example 1 The preparation method of MIL-53 series adsorbents includes the following steps: (1) Take the metal salt (MCl3, where M is Al) 3+ Ga 3+ ,Sc 3+ Cr 3+ Fe 3+ V 3+ or In 3+ Add terephthalic acid and terephthalic acid to a solvent (water), mix well, and add hydrofluoric acid to obtain a precursor suspension; the molar ratio of metal salt, terephthalic acid and hydrofluoric acid is 1:1:1, and the ratio of metal salt to solvent is 1 g:40 mL; (2) The precursor suspension was subjected to a hydrothermal reaction (the hydrothermal reaction temperature was 150 °C and the hydrothermal reaction time was 24 h) to allow the metal ions in the metal salt to coordinate with the terephthalic acid for self-assembly, thereby obtaining a crude product of the MIL-53 type metal-organic framework; the solid was separated by centrifugation, washed with detergent (water), solvent exchanged (the solvent used for solvent exchange was ethanol), and dried (the drying temperature was 90 °C and the drying time was 12 h) to obtain the dried product; (3) The dried material was vacuum thermally activated (activation temperature 150 °C, activation for 12 h) to remove residual solvent and moisture from the pores, and the XRD patterns of the MIL-53 series adsorbents (MIL-53(Al), MIL-53(Ga), MIL-53(Sc), MIL-53(Cr), MIL-53(Fe), MIL-53(V), MIL-53(In)) are shown in the figure. Figure 1 (The comparison example yielded a synthetic result.) Example 1 The preparation method of functionalized MIL-53 type metal-organic framework adsorbent includes the following steps: (1) Add the metal salt (FeCl3·6H2O) and the functionally substituted terephthalic acid (2-hydroxyterephthalic acid) to the solvent (water), mix well, and add hydrofluoric acid to obtain a precursor suspension; the molar ratio of the metal salt, the functionally substituted terephthalic acid and hydrofluoric acid is 1:1:1, and the ratio of the metal salt to the solvent is 1 g:40 mL; (2) The precursor suspension was subjected to a hydrothermal reaction (the hydrothermal reaction temperature was 150 °C and the hydrothermal reaction time was 24 h; a solvothermal reaction could also be performed under the same conditions as the hydrothermal reaction) to allow the metal ions in the metal salt to coordinate with the functionalized terephthalic acid to undergo self-assembly, thereby obtaining a functionalized MIL-53 type metal-organic framework crude product; the solid was separated by centrifugation, washed with detergent (water), solvent exchanged (the solvent used was ethanol), and dried at 90 °C for 12 h to obtain the dried product; (3) The dried material is vacuum thermally activated at a temperature of 150 °C for 12 h to remove residual solvent and moisture from the pores, thereby obtaining a functionalized MIL-53 type metal-organic framework adsorbent, abbreviated as OH-MIL-53(Fe).

[0032] Example 2 The preparation method of functionalized MIL-53 type metal-organic framework adsorbent includes the following steps: (1) Add the metal salt (FeCl3·6H2O) and the functionally substituted terephthalic acid (2-nitroterephthalic acid) to a solvent (a mixed solvent of N,N-dimethylformamide and N,N-dimethylacetamide in a volume ratio of 1:1), mix well, and add hydrofluoric acid to obtain a precursor suspension; the molar ratio of the metal salt, the functionally substituted terephthalic acid and hydrofluoric acid is 1:0.5:0.5, and the ratio of the metal salt to the solvent is 1g:20mL; (2) The precursor suspension was subjected to a hydrothermal reaction (the hydrothermal reaction temperature was 120 °C and the hydrothermal reaction time was 36 h; a solvothermal reaction could also be performed under the same conditions as the hydrothermal reaction) to allow the metal ions in the metal salt to coordinate with the functionalized terephthalic acid to undergo self-assembly, thereby obtaining a functionalized MIL-53 type metal-organic framework crude product; the product was centrifuged, washed with detergent (N,N-dimethylformamide), solvent exchanged (acetonitrile was used), and dried at 50 °C for 24 h to obtain the dried product; (3) Vacuum thermal activation of the dried material at a temperature of 80 °C for 48 h, or at atmospheric pressure or inert atmosphere (with the same activation conditions as vacuum thermal activation) to remove residual solvent and moisture from the pores, thereby obtaining functionalized MIL-53 type metal-organic framework adsorbent NO2-MIL-53(Fe).

[0033] Example 3 The preparation method of functionalized MIL-53 type metal-organic framework adsorbent includes the following steps: (1) Add the metal salt (FeCl3·6H2O) and the functionally substituted terephthalic acid (2-aminoterephthalic acid) to the solvent (acetonitrile), mix well, and add hydrofluoric acid to obtain a precursor suspension; the molar ratio of the metal salt, the functionally substituted terephthalic acid and hydrofluoric acid is 1: 2:2, and the ratio of the metal salt to the solvent is 1 g: 60 mL; (2) The precursor suspension was subjected to a hydrothermal reaction (the hydrothermal reaction temperature was 180 °C and the hydrothermal reaction time was 12 h; a solvothermal reaction could also be performed under the same conditions as the hydrothermal reaction) to allow the metal ions in the metal salt to coordinate with the functionalized terephthalic acid to undergo self-assembly, thereby obtaining a functionalized MIL-53 type metal-organic framework crude product; the solid was separated by centrifugation, washed with detergent (methanol), solvent exchanged (acetone was used), and dried at 120 °C for 6 h to obtain the dried product; (3) Vacuum thermal activation of the dried material at a temperature of 250 °C for 2 h, or at atmospheric pressure or inert atmosphere (with the same activation conditions as vacuum thermal activation) to remove residual solvent and moisture from the pores, thereby obtaining the functionalized MIL-53 type metal-organic framework adsorbent NH2-MIL-53(Fe).

[0034] Example 4 The preparation method of functionalized MIL-53 type metal-organic framework adsorbent includes the following steps: (1) Add the metal salt (FeCl3·6H2O) and the functionally substituted terephthalic acid (2-trifluoromethylterephthalic acid) to the solvent (a mixture of methanol and ethanol in a volume ratio of 1:1), mix well, and add hydrofluoric acid to obtain a precursor suspension; the molar ratio of the metal salt, the functionally substituted terephthalic acid and hydrofluoric acid is 1:1.5:1.5, and the ratio of the metal salt to the solvent is 1 g:50 mL; (2) The precursor suspension was subjected to a hydrothermal reaction (the hydrothermal reaction temperature was 100 °C and the hydrothermal reaction time was 72 h; a solvothermal reaction could also be performed under the same conditions as the hydrothermal reaction) to allow the metal ions in the metal salt to coordinate with the functionalized terephthalic acid to undergo self-assembly, thereby obtaining a functionalized MIL-53 type metal-organic framework crude product; the solid was separated by centrifugation, washed with detergent (acetone), and solvent exchanged (the solvent used was a 1:1 volume ratio ethanol-methanol mixture), and dried at 70 °C for 20 h to obtain the dried product; (3) Activate the dried material (vacuum thermal activation, activation temperature 100 °C, time 24 h, or normal pressure thermal activation or inert atmosphere thermal activation, activation conditions are the same as vacuum thermal activation) to remove residual solvent and moisture in the pores and obtain functionalized MIL-53 type metal-organic framework adsorbent CF3-MIL-53(Fe).

[0035] Example 5 The preparation method of functionalized MIL-53 type metal-organic framework adsorbent includes the following steps: (1) Add the metal salt (FeCl3·6H2O) and functionally substituted terephthalic acid (2-fluoroterephthalic acid, or 2-chloroterephthalic acid, 2-bromoterephthalic acid) to a solvent (a mixture of ethylene glycol and acetone in a volume ratio of 1:1), mix well, and add hydrofluoric acid to obtain a precursor suspension; the molar ratio of the metal salt, functionally substituted terephthalic acid and hydrofluoric acid is 1:1.4:1.4, and the ratio of the metal salt to the solvent is 1g:40mL; (2) The precursor suspension was subjected to a hydrothermal reaction (the hydrothermal reaction temperature was 220 °C and the hydrothermal reaction time was 6 h; a solvothermal reaction could also be performed under the same conditions as the hydrothermal reaction) to allow the metal ions in the metal salt to coordinate with the functionalized terephthalic acid to undergo self-assembly, thereby obtaining a functionalized MIL-53 type metal-organic framework crude product; the product was centrifuged, washed with detergent (50% ethanol aqueous solution), solvent exchanged (acetonitrile was used as the solvent), and dried at 110 °C for 10 h to obtain the dried product; (3) Activate the dried material (vacuum thermal activation, activation temperature 180 °C, time 6 h, or normal pressure thermal activation or inert atmosphere thermal activation, activation conditions are the same as vacuum thermal activation) to remove residual solvent and moisture in the pores, and obtain functionalized MIL-53 type metal-organic framework adsorbents F-MIL-53(Fe), Cl-MIL-53(Fe) or Br-MIL-53(Fe).

[0036] See Figure 3 .

[0037] Example 6 Application of functionalized MIL-53 metal-organic framework adsorbents in lithium extraction.

[0038] Prepare a 1.0 g / L LiCl aqueous solution as a simulated lithium-containing solution.

[0039] 20 mg of MIL-53 (M) prepared in the control example and NO2-MIL-53 (Fe), OH-MIL-53 (Fe), CF3-MIL-53 (Fe), NH2-MIL-53 (Fe), F-MIL-53 (Fe), Cl-MIL-53 (Fe), and Br-MIL-53 (Fe) prepared in each example were weighed and added to 20 mL of simulated lithium-containing solution. Adsorption was carried out at 25 °C with shaking at a rate of 140 rpm for 24 h. After adsorption, the supernatant was filtered through a microporous membrane to obtain the test solution. 1 mL of the simulated lithium-containing solution and the test solution were added to 100 mL volumetric flasks and diluted to the mark with deionized water. The lithium concentration was determined using ICP-OES, and the lithium adsorption capacity of the metal-organic framework adsorbent was calculated using the formula. (See [reference]). Figure 2 and Figure 4 .

[0040] Example 7 Application of functionalized MIL-53 metal-organic framework adsorbents in lithium isotope separation.

[0041] Formulated with natural abundance 6 Li and 7 LiCl aqueous solution was used as the raw solution for lithium isotope separation, in which Li + The concentration was 1 g / L. 20 mg of MIL-53 (M) prepared in the control example and NO2-MIL-53 (Fe), OH-MIL-53 (Fe), CF3-MIL-53 (Fe), NH2-MIL-53 (Fe), F-MIL-53 (Fe), Cl-MIL-53 (Fe), and Br-MIL-53 (Fe) prepared in each example were weighed and added to 20 mL of lithium isotope separation stock solution. The mixture was shaken and adsorbed at 25 °C at a shaking rate of 140 rpm for 24 h. After adsorption, the supernatant was filtered through a microporous membrane to obtain the test solution. 100 μL of both the lithium isotope separation stock solution and the test solution were added to 100 mL volumetric flasks and diluted to the mark with deionized water. The concentrations were determined by ICP-MS. 6 Li and 7 The signal intensity or isotopic abundance of Li was calculated. 6 Li / 7 Li isotope segregation factor. See Figure 5 and Figure 6 .

Claims

1. A method for preparing a functionalized MIL-53 type metal-organic framework adsorbent, characterized in that: Includes the following steps: (1) Add the metal salt and functionalized terephthalic acid to the solvent, mix well, and add hydrofluoric acid to obtain a precursor suspension; (2) The precursor suspension is subjected to hydrothermal or solvothermal reaction to allow the metal ions in the metal salt to coordinate with the functionalized terephthalic acid to self-assemble, thereby obtaining a functionalized MIL-53 type metal-organic framework crude product; centrifugation, washing of the solid with detergent, solvent exchange, and drying to obtain the dried product. (3) The dried material is activated to obtain a functionalized MIL-53 type metal-organic framework adsorbent.

2. The preparation method according to claim 1, characterized in that... The molar ratio of the metal salt, functionally substituted terephthalic acid, and hydrofluoric acid is 1:0.5~2:0.5~2, and the ratio of the metal salt to the solvent is 1 g:20-60 mL.

3. The preparation method according to claim 1 or 2, characterized in that, The metal ions in the metal salt are selected from Fe. 3 + .

4. The preparation method according to claim 1, characterized in that... The functional group in the terephthalic acid that is substituted with the functional group is monosubstituted or disubstituted, and the functional group is hydroxyl, amino, fluorine, chlorine, bromine, nitro or trifluoromethyl.

5. The preparation method according to claim 1, characterized in that... The hydrothermal reaction temperature is 100–220 °C, and the hydrothermal reaction time is 6–72 h.

6. The preparation method according to claim 1, characterized in that... The temperature of the solvothermal reaction is 100–220 °C, and the reaction time is 6–72 h.

7. The preparation method according to claim 1, characterized in that... The activation is vacuum thermal activation, atmospheric pressure thermal activation, or inert atmosphere thermal activation.

8. A functionalized MIL-53 type metal-organic framework adsorbent prepared by the preparation method according to any one of claims 1-7.

9. The application of the functionalized MIL-53 type metal-organic framework adsorbent of claim 8 in lithium extraction.

10. The application of the functionalized MIL-53 type metal-organic framework adsorbent of claim 8 in lithium isotope separation.

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