Functionalized metal organic framework material for water / heavy water separation as well as preparation method and application of functionalized metal organic framework material

Abstract

The invention relates to the technical field of metal organic framework materials (MOF) and isotope separation, in particular to a functionalized metal organic framework material for water / heavy water separation and a preparation method and application thereof. The metal organic framework material is a porous crystal material which is formed by coordination self-assembly of metal ions and V-shaped organic ligands and has a periodic network structure; the V-shaped organic ligand is a V-shaped dicarboxylic acid organic ligand modified by an oxygen-containing functional group designed through topological functionalization. According to the metal organic framework material, through topological functional design of a V-shaped organic ligand, a space confinement channel and a high-density oxygen active site are integrated in the same MOF material, and an ideal model system is provided for identification of water isotopes; according to the metal organic framework material, the framework structure flexibility, the pore channel confinement effect and the molecular recognition capability can be synergistically regulated and controlled, so that efficient recognition and separation of water / heavy water are realized.

Description

Technical Field

[0001] This invention relates to the fields of metal-organic framework (MOF) materials and isotope separation technology, specifically to a functionalized metal-organic framework material based on V-type organic ligand topological functionalization, which has spatially confined channels and high-density oxygen sites, its preparation method, and its application in water / heavy water (H2O / D2O) separation. Background Technology

[0002] Heavy water (D2O) holds an irreplaceable strategic position in the field of nuclear energy as a neutron moderator, coolant, and potential fuel for nuclear fusion reactions in nuclear reactors. It also plays a crucial role in scientific research such as isotope tracing and neutron scattering. However, the abundance of heavy water in nature is extremely low (approximately 0.015%), and the fact that water (H2O) and heavy water (D2O) have nearly identical molecular sizes and thermodynamic properties makes their separation a highly challenging technical problem. Currently, the cryogenic distillation method mainly used in industry suffers from high energy consumption, low efficiency, and large equipment requirements, necessitating the development of new, efficient, and scalable separation technologies.

[0003] Metal-organic frameworks (MOFs) have shown great potential in gas adsorption and separation due to their tunable structure, high specific surface area, and precisely designable pore environment. Current research mainly focuses on amplifying the diffusion differences between H₂O and D₂O by introducing open metal sites, utilizing framework flexibility, or constructing spatially confined channels to achieve the separation of water and heavy water. However, the separation efficiency of these strategies still needs improvement. Summary of the Invention

[0004] Studies have shown that oxygen-containing functional groups (such as hydroxyl groups, ether oxygen bonds, and crown ethers) are sensitive to the strength of isotopic hydrogen bonds, and D2O can form stronger hydrogen bond interactions with them than H2O. Therefore, the synergistic design of these highly recognizable oxygen-containing functional groups with the spatially confined channels of MOFs is key to achieving efficient water isotope recognition.

[0005] This invention provides a functionalized metal-organic framework material with spatially confined channels and high-density oxygen sites constructed based on the topological functionalization of V-type organic ligands, as well as its preparation method and applications. The metal-organic framework material achieves synergistic regulation of the framework structure flexibility, pore confinement effect and molecular recognition ability through the topological functionalization design of V-type organic ligands, which is beneficial to the efficient recognition and separation of water / heavy water by the metal-organic framework material.

[0006] The objective of this invention is achieved through the following technical solution: A metal-organic framework material, wherein the metal-organic framework material is a porous crystalline material with a periodic network structure formed by coordination self-assembly of metal ions and V-type organic ligands; wherein the V-type organic ligands are V-type dicarboxylic acid organic ligands modified with oxygen-containing functional groups through topological functionalization design.

[0007] According to an embodiment of the present invention, the V-type dicarboxylic acid organic ligand is a topologically functionalized organic ligand. By regulating the density and distribution of oxygen-containing functional groups on the V-type dicarboxylic acid organic ligand, the synergistic regulation of the framework structure flexibility, pore confinement effect and molecular recognition ability can be achieved.

[0008] According to an embodiment of the present invention, the oxygen-containing functional group is selected from at least one of ether oxygen bond (-O-), hydroxyl-functionalized ether chain, or cyclic crown ether unit.

[0009] According to an embodiment of the present invention, the V-type organic ligand is a V-type dicarboxylic acid organic ligand containing a cyclic crown ether unit, a V-type dicarboxylic acid organic ligand containing an ether oxygen bond (-O-), or a V-type organic ligand containing a hydroxyl-functionalized ether chain.

[0010] According to an embodiment of the present invention, the V-type organic ligand is selected from at least one of 1,3-bis(p-carboxyphenoxy)propane (H2ProBDC), 4,4'-(propane-1,3-dioxy)bis(3-hydroxybenzoic acid) (H2Pro(OH)2BDC), and 4,4'-dicarboxy-dibenzo-14-crown-4 (H2DB14C4). In a specific embodiment of the present invention, the V-type organic ligand is 4,4'-dicarboxy-dibenzo-14-crown-4 (H2DB14C4).

[0011] According to an embodiment of the present invention, the metal ion is selected from at least one transition metal ion, preferably Ni. 2+ Fe 3+ Mo 6+ Mn 2+ Ti 4+ Cu 2+ Zn 2+ or Co 2+ In one specific embodiment of the present invention, the metal ion is Cu. 2+ .

[0012] According to an embodiment of the present invention, the molar ratio of the metal ion to the V-type organic ligand is 1:1-5, for example, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5 or 1:5.

[0013] According to an embodiment of the present invention, the metal-organic framework material has pores with spatial confinement effect, and the inner surface of the pores is distributed with a high density of oxygen sites.

[0014] According to an embodiment of the present invention, the pore size of the metal-organic framework material is 0.6-1 nm, for example, 0.6 nm, 0.7 nm, 0.8 nm, 0.83 nm, 0.9 nm or 1 nm; the pore size of the metal-organic framework material matches the dynamic diameter of water and heavy water molecules, which is beneficial for forming a spatial confinement effect.

[0015] According to an embodiment of the present invention, the oxygen-containing functional groups in the metal-organic framework material can induce the formation of a unique hydrogen bond network within the spatially confined pores of the metal-organic framework material, and combined with the adaptive adjustment of the pores, achieve selective capture and recognition of D2O.

[0016] This invention also provides a method for preparing the above-mentioned metal-organic framework material, comprising the following steps: (1) Dissolve the metal salt and V-type organic ligand in a mixed solvent of organic solvent and water to obtain a reaction solution; (2) The reaction solution from step (1) is placed in a sealed reaction vessel and subjected to a solvothermal reaction to obtain the metal-organic framework material.

[0017] According to an embodiment of the present invention, in step (1), the organic solvent is N,N-dimethylformamide (DMF), and the volume ratio of DMF to water in the mixed solvent is 1:1-5, for example, 1:1, 1:2, 1:3, 1:4 or 1:5.

[0018] According to an embodiment of the present invention, in step (1), the metal salt is at least one of nickel nitrate, ferric nitrate, ammonium molybdate, manganese nitrate, tetrabutyl titanate, copper nitrate, zinc nitrate, or cobalt nitrate.

[0019] According to an embodiment of the present invention, in step (1), the definition of the V-type organic ligand is as described above.

[0020] According to an embodiment of the present invention, in step (1), the molar ratio of the metal salt and the V-type organic ligand is 1:1-5, for example, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5 or 1:5.

[0021] According to an embodiment of the present invention, in step (2), the temperature of the solvothermal reaction is 60-90°C, for example 60°C, 70°C, 80°C or 90°C; and the time of the solvothermal reaction is 24-72 hours, for example 24 hours, 48 ​​hours or 72 hours.

[0022] According to an embodiment of the present invention, in step (2), after the solvothermal reaction is completed, post-processing steps such as cooling, filtration, washing, and drying are also included.

[0023] The present invention also provides the application of the above-mentioned metal-organic framework materials in water / heavy water separation.

[0024] According to an embodiment of the present invention, the metal-organic framework material can be used as an adsorbent to achieve the separation of H2O and D2O; preferably, the separation of H2O and D2O is achieved by utilizing the preferential recognition and adsorption selectivity of the metal-organic framework material for D2O.

[0025] The present invention also provides a method for separating water / heavy water, the method comprising the following steps: The metal-organic framework material described above is activated; the activated metal-organic framework material adsorbs H2O and D2O respectively, thereby achieving the separation of H2O and D2O.

[0026] According to an embodiment of the present invention, the activation treatment is, for example, vacuum heating at 120-150°C for 6-18 hours, or vacuum heating at 140°C for 12 hours.

[0027] According to an embodiment of the present invention, the metal-organic framework material exhibits an adsorption selectivity of up to 1.43 for D2O / H2O, demonstrating preferential recognition of heavy water, which differs from conventional materials that preferentially adsorb water.

[0028] The beneficial effects of this invention are: 1. Pioneering collaborative design strategy: This invention is the first to integrate spatially confined channels and high-density oxygen active sites (especially crown ether structures) into the same MOF material through the topological functionalization of V-type organic ligands, providing an ideal model system for the identification of water isotopes.

[0029] 2. Superior separation performance: The functionalized MOF material prepared in this invention achieves preferential recognition of heavy water, with an adsorption selectivity of up to 1.43 for D2O / H2O. This performance stems from the synergistic effect of the strong hydrogen bond network induced by oxygen-containing functional groups (such as crown ethers) and the spatially confined pores, enabling precise control of HD exchange behavior.

[0030] 3. High structural tunability: By simply changing the type of functional group on the V-type organic ligand (ether oxygen bond (-O-), hydroxyl-functionalized ether chain or cyclic crown ether unit), the local distribution of oxygen sites, conformational freedom and hydrogen bond strength in the pore can be systematically controlled, providing a broad regulatory space for optimizing separation performance.

[0031] 4. Clear mechanism and strong guidance: This invention reveals the mechanism by which "oxygen-containing functional group-induced hydrogen bond network" and "spatial confinement pore adaptability" synergistically determine the adsorption and exchange behavior of water isotopes through multi-scale in-situ characterization, providing general design guidance for the development of porous materials for other challenging isotope separation. Attached Figure Description

[0032] Figure 1 The structural formulas of the V-type organic ligands used in Examples 1-3 of this invention are as follows: a. 1,3-bis(p-carboxyphenoxy)propane (H2ProBDC) (Example 1), b. 4,4'-(propane-1,3-dioxy)bis(3-hydroxybenzoic acid) (H2Pro(OH)2BDC) (Example 2), c. 4,4'-dicarboxy-dibenzo-14-crown-4 (H2DB14C4) (Example 3).

[0033] Figure 2 The X-ray powder diffraction (PXRD) pattern of IPE-10 prepared in Example 1 of this invention.

[0034] Figure 3 The X-ray powder diffraction (PXRD) pattern of IPE-11 prepared in Example 2 of this invention.

[0035] Figure 4 The X-ray powder diffraction (PXRD) pattern of IPE-12 prepared in Example 3 of this invention.

[0036] Figure 5 This is a single-crystal structure diagram of IPE-10 prepared in Example 1 of the present invention.

[0037] Figure 6 This is a single-crystal structure diagram of IPE-11 prepared in Example 2 of the present invention.

[0038] Figure 7 This is a single-crystal structure diagram of IPE-12 prepared in Example 3 of the present invention.

[0039] Figure 8 A comparison of the adsorption isotherms of IPE-10 prepared in Example 1 of this invention for H2O and D2O vapors at 298K.

[0040] Figure 9 A comparison of the adsorption isotherms of IPE-11 prepared in Example 2 of this invention for H2O and D2O vapors at 298K.

[0041] Figure 10 A comparison of the adsorption isotherms of IPE-12 prepared in Example 3 of this invention for H2O and D2O vapors at 298K. Detailed Implementation

[0042] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention, and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0043] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0044] Example 1: Synthesis of IPE-10, a MOF material containing flexible ether oxygen bonds 1) Weigh out 3 mg of V-type dicarboxylic acid ligand (H2ProBDC) containing flexible ether oxygen bond (-O-) and 11 mg of Cu(NO3)2·XH2O and add them to a glass bottle; 2) Add DMF (0.4 mL) and water (1 mL) to the glass bottle; 3) Place the glass bottle in an ultrasonic bath and sonicate for 10 minutes; 4) Place the glass bottle in an oven and heat at 80°C for 30 hours; 5) After cooling to room temperature, a large number of light blue crystals are generated. The solid product is collected by centrifugation and washed multiple times with DMF and acetonitrile. 6) Vacuum dry overnight in an oven at 140℃ to obtain IPE-10 sample.

[0045] Example 2: Synthesis of IPE-11, a MOF material containing hydroxyl-functionalized ether chains 1) Weigh out 3 mg of V-type dicarboxylic acid ligand (H2Pro(OH)2BDC) and 11 mg of Cu(NO3)2·XH2O containing hydroxyl-functionalized ether chains and add them to a glass bottle; 2) Add DMF (0.4 mL) and water (1 mL) to the glass bottle; 3) Place the glass bottle in an ultrasonic bath and sonicate for 10 minutes; 4) Place the glass bottle in an oven and heat at 80°C for 30 hours; 5) After cooling to room temperature, a large number of light green crystals are generated. The solid product is collected by centrifugation and washed multiple times with DMF and acetonitrile. 6) Vacuum dry overnight in an oven at 140℃ to obtain IPE-11 sample.

[0046] Example 3: Synthesis of crown ether functionalized MOF material IPE-12 1) Weigh out V-type crown ether ligand H2DB14C4 (3 mg) and Cu(NO3)2·XH2O (11 mg) and add them to a glass bottle; 2) Add DMF (0.5 mL) and water (0.2 mL) to the glass bottle; 3) Place the glass bottle in an ultrasonic bath and sonicate for 10 minutes; 4) Place the glass bottle in an oven and heat at 80°C for 30 hours; 5) After cooling to room temperature, a large number of light green crystals are generated. The solid product is collected by centrifugation and washed multiple times with DMF and acetonitrile. 6) Vacuum dry overnight in an oven at 140℃ to obtain IPE-12 sample.

[0047] Structural characterization: Single-crystal X-ray diffraction analysis shows (see...) Figure 2-4 The selected ligands successfully constructed the target metal-organic framework structure, and the resulting product was a novel highly crystalline MOF material. At the same time, the product had one-dimensional confined channels with oxygen atoms provided by oxygen-containing functional groups densely arranged on the inner wall of the channels.

[0048] Figure 5 This is a single-crystal structure diagram of IPE-10 prepared in Example 1 of the present invention. Figure 6 This is a single-crystal structure diagram of IPE-11 prepared in Example 2 of the present invention. Figure 7 This is a single-crystal structure diagram of IPE-12 prepared in Example 3 of the present invention. From... Figure 5 As can be seen, the MOF material IPE-10 containing flexible ether oxygen bonds exhibits spatially confined pores and a specific distribution of oxygen sites. From... Figure 6 It can be seen from the data that the MOF material IPE-11, containing hydroxyl-functionalized ether chains, exhibits spatially confined pores and oxygen site distribution. From... Figure 7 As can be seen, the crown ether functionalized MOF material IPE-12 exhibits spatially confined pores and the distribution of crown ether oxygen sites.

[0049] Application Example 1: Water / Heavy Water Vapor Adsorption Separation Performance Test The MOF samples (approximately 30 mg) prepared in Examples 1-3 were activated under vacuum at 140 °C for 12 hours, and their adsorption isotherms for H2O and D2O vapors were tested at 298 K using a vapor adsorption apparatus.

[0050] The results show (see Figure 8-10The IPE-12 material prepared in Example 3 exhibited preferential adsorption of D2O throughout the entire test pressure range. Its D2O / H2O adsorption selectivity was calculated to be as high as 1.43. The selectivity of the IPE-10 material prepared in Example 1 and the IPE-11 material prepared in Example 2 was lower than that of the IPE-12 material. This indicates that the crown ether structure and the unique hydrogen bonding environment formed within the spatially confined pores are key to achieving highly selective heavy water recognition.

[0051] Application Example 2: Cyclic Stability Test The IPE-12 material tested in Case 1 was regenerated (vacuum activation at 140℃ for 12 hours), and the adsorption test was repeated twice. The results showed that after two cycles, the D2O saturated adsorption capacity and separation selectivity of the IPE-12 material did not decrease significantly, demonstrating its excellent regeneration performance and structural stability.

[0052] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A metal-organic framework material, wherein, The metal-organic framework material is a porous crystalline material with a periodic network structure formed by coordination self-assembly of metal ions and V-type organic ligands; the V-type organic ligands are V-type dicarboxylic acid organic ligands modified with oxygen-containing functional groups through topological functionalization design.

2. The metal-organic framework material according to claim 1, wherein, The oxygen-containing functional group is selected from at least one of ether oxygen bond, hydroxyl-functionalized ether chain, or cyclic crown ether unit.

3. The metal-organic framework material according to claim 2, wherein, The V-type organic ligand is selected from at least one of 1,3-bis(p-carboxyphenoxy)propane, 4,4'-(propane-1,3-dioxy)bis(3-hydroxybenzoic acid), and 4,4'-dicarboxy-dibenzo-14-crown-4.

4. The metal-organic framework material according to claim 1, wherein, The metal ions are selected from Ni. 2+ Fe 3+ Mo 6+ Mn 2+ Ti 4+ Cu 2+ Zn 2+ or Co 2+ .

5. The metal-organic framework material according to claim 4, wherein, The molar ratio of the metal ion to the V-type organic ligand is 1:1-5.

6. A method for preparing the metal-organic framework material according to any one of claims 1-5, comprising the following steps: (1) Dissolve the metal salt and V-type organic ligand in a mixed solvent of organic solvent and water to obtain a reaction solution; (2) The reaction solution from step (1) is placed in a sealed reaction vessel and subjected to a solvothermal reaction to obtain the metal-organic framework material.

7. The preparation method according to claim 6, wherein, In step (1), the organic solvent is N,N-dimethylformamide, and the volume ratio of N,N-dimethylformamide to water in the mixed solvent is 1:1-5; In step (1), the molar ratio of the metal salt to the V-type organic ligand is 1:1-5; In step (2), the temperature of the solvothermal reaction is 60-90℃; the time of the solvothermal reaction is 24-72 hours.

8. The application of the metal-organic framework material according to any one of claims 1-5 in water / heavy water separation.

9. A method for separating water / heavy water, wherein, The method includes the following steps: The metal-organic framework material according to any one of claims 1-5 is activated; the activated metal-organic framework material adsorbs H2O and D2O respectively to achieve the separation of H2O and D2O.

10. The separation method according to claim 9, wherein, The activation treatment is vacuum heating at 120-150℃ for 6-18 hours.

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