Zinc-based MOF (Metal Organic Framework) material with triangular prism type metal clusters and preparation method of zinc-based MOF material

Abstract

The invention belongs to the technical field of adsorption separation materials, and particularly discloses a zinc-based MOF material with triangular prism type metal clusters and a preparation method thereof.The preparation method comprises the following steps that S1, zinc nitrate hexahydrate and 1, 3, 5-tri (4-carboxyl phenyl) benzene are dissolved in N, N-diethyl formamide and deionized water; placing in a reaction bottle, sealing, carrying out heat treatment, and cooling the system to room temperature to obtain colorless needle-like crystals; and washing, activating, and collecting a product to obtain the WUST-4. According to the zinc-based MOF material with the triangular prism type metal clusters and the preparation method of the zinc-based MOF material, a network topology structure based on the triangular prism type Zn4O clusters is formed, and the benzene adsorption performance is shown under low pressure through multiple non-covalent interaction; the key function of solvent-mediated conformational engineering in expanding the structural diversity of MOFs based on deformable SBUs and flexible ligands is disclosed, and a new path is opened up for directional design of novel functional MOFs.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of adsorption separation materials, and particularly to a zinc-based MOF material with a triangular prism type metal cluster and a preparation method thereof. BACKGROUND

[0002] Metal-organic frameworks (MOFs) are crystalline porous materials assembled from inorganic secondary building units (SBUs) and organic linkers through strong coordination bonds. By rationally designing building units with well-defined geometry, symmetry, and connectivity, a wide variety of framework materials with predictable topology and customized pores can be constructed. Guided by reticular chemistry, SBU and linker engineering strategies have enabled the synthesis of MOFs with diverse topologies and functionalities, which have promoted their applications in gas adsorption / separation, energy storage, catalysis, and sensing.

[0003] The generation of MOF isomers with different topologies through different conformations of linkers provides a new way for the construction of new structures. This conformational change can be achieved by utilizing the different geometry or symmetry of flexible linkers, or by introducing steric hindrance groups to regulate the conformation of the linkers, but the synthesis of MOFs based on metal clusters with variable configuration and unchanged connectivity is still a great challenge. Among the numerous high-connectivity SBUs, Zn4O SBU is one of the most common metal clusters in MOF assembly, which is known for its construction of topologically diverse superporous materials. For example, it can be assembled with tricarboxylic acid H3BTB ligand to obtain the representative superporous material MOF-177 with qom topology.

[0004] Benzene, as one of the most toxic volatile organic compounds (VOCs), poses a serious threat to the environment and health even at trace concentrations. In the prior art, MOF-177 with high specific surface area and adjustable pore structure as an adsorbent has certain effect in capturing various toxic pollutants including benzene, but its adsorption performance of trace benzene and benzene at low pressure still needs to be enhanced. SUMMARY

[0005] The purpose of the present application is to provide a zinc-based MOF material with a triangular prism type metal cluster and a preparation method thereof, to form a network topology based on a triangular prism type Zn4O cluster, to realize excellent benzene adsorption performance at low pressure through multiple non-covalent interactions, and to reveal the key role of solvent-mediated conformational engineering in expanding the structural diversity of MOFs based on deformable SBUs and flexible linkers, thereby opening up a new path for the directional design of new functional MOFs.

[0006] To achieve the above-mentioned purpose, the present application provides a preparation method of a zinc-based MOF material with a triangular prism type metal cluster, comprising the following steps: S1, proportionally mix N,N-diethylformamide and deionized water to obtain a mixed solution A; S2, proportionally mix zinc nitrate hexahydrate and 1,3,5-tris(4-carboxyphenyl) benzene in the mixed solution A obtained in S1 to obtain a mixed solution B; S3, place the mixed solution B obtained in S2 in a reaction bottle, seal and perform heat treatment, and after the system is cooled to room temperature, colorless needle-shaped crystals are obtained; S4, wash the colorless needle-shaped crystals obtained in S3 with a detergent, activate the crystals, collect the product, and obtain WUST-4.

[0007] Preferably, in S1, the volume ratio of the N,N-diethylformamide to the deionized water is 10:1-5.

[0008] Preferably, in S1, the volume ratio of the N,N-diethylformamide to the deionized water is 10:3.

[0009] Preferably, in S2, the molar ratio of the zinc nitrate hexahydrate to the 1,3,5-tris(4-carboxyphenyl) benzene is 35:9.

[0010] Preferably, in S2, the amount ratio of the 1,3,5-tris(4-carboxyphenyl) benzene to the mixed solution A is 8.0 mg:5.2 mL.

[0011] Preferably, in S3, the heat treatment is specifically as follows: After the reaction bottle is sealed, it is placed in an oven at 80-90 for 18-26 hours.

[0012] Preferably, in S4, the detergent is N,N-dimethylformamide, and the washing is performed at least 3 times.

[0013] Preferably, in S4, the activation treatment is specifically as follows: Solvent replacement is performed with methanol three times a day for three days, and then the activated WUST-4 is obtained by vacuum heating at 80 or 200 for 12 hours.

[0014] The application provides a zinc-based MOF material with a triangular prism type metal cluster.

[0015] Preferably, the material is a hexagonal crystal space group P-62c, the material includes a triangular prism type Zn4O cluster and a trident BTB ligand, the Zn4O cluster includes two tetrahedral coordination, two octahedral coordination Zn 2+ ions, forming a novel three-dimensional network structure, i.e. a (3,6)-connected topological network, and the three-dimensional network structure is along cThe one-dimensional channel is formed in the axial direction with a diameter of 18 The one-dimensional channel has a narrow region surrounded by a BTB benzene ring on the channel wall.

[0016] The application further provides application of the zinc-based MOF material with the tricornered prism type metal cluster in benzene adsorption.

[0017] Therefore, the zinc-based MOF material with the tricornered prism type metal cluster and the preparation method thereof have the following beneficial effects: The application successfully prepares the isomer WUST-4 of MOF-177 by fine regulation and control of a synthesis solvent, and the two have the same 6-connected Zn4O cluster and trident BTB ligand, but WUST-4 forms a unique network topology structure due to the geometric configuration difference of the Zn4O cluster and the conformation change of the BTB ligand, in particular, the Zn4O cluster in WUST-4 significantly deforms to present a twisted tricornered prism configuration instead of a typical octahedral configuration. The synergistic effect of the conjugated group and the coordination unsaturated Zn 2+ site, WUST-4 exhibits excellent benzene adsorption performance at low pressure through multiple non-covalent interactions, reveals the key role of solvent-mediated conformation engineering in expanding the structural diversity of MOFs based on deformable SBUs and flexible ligands, and opens up a new path for the directional design of novel functional MOFs.

[0018] The technical solutions of the application are further described in detail below with the aid of the drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 is the structure and topology graph of the zinc-based MOF material with the tricornered prism type metal cluster and the preparation method thereof according to the application, embodiment one (right) and comparative example one (left), atom color: C gray, O red, Zn blue, and hydrogen atoms are omitted; Figure 2 is the configuration graph of the zinc-based MOF material with the tricornered prism type metal cluster and the preparation method thereof according to the application, embodiment one (below) and comparative example one (above), wherein (a) is the configuration of the Zn4O cluster, and (b) is the configuration of the BTB ligand, and the out-of-plane bending angle measurement schematic diagram (green mark measurement site) is shown; Figure 3 is the PXRD spectrum of the zinc-based MOF material with the tricornered prism type metal cluster and the preparation method thereof according to the application, embodiment one to embodiment two and comparative example one; Figure 4 is the thermogravimetric analysis graph of the zinc-based MOF material with the tricornered prism type metal cluster and the preparation method thereof according to the application, embodiment one; Figure 5is the benzene adsorption result graph of the embodiment one and comparative example one of the zinc-based MOF material with a triangular prism type metal cluster and the preparation method thereof, wherein (a) is the 77K nitrogen adsorption-desorption isotherm of WUST-4, (b) is the pore size distribution of WUST-4, (c) is the benzene vapor adsorption isotherm of WUST-4 and MOF-177 at 298K, and (d) is the adsorption performance logarithmic coordinate comparison of WUST-4 and MOF-177 in a low partial pressure area; Figure 6 is the simulated benzene adsorption isotherm and the experimental benzene adsorption isotherm of the embodiment one of the zinc-based MOF material with a triangular prism type metal cluster and the preparation method thereof; Figure 7 is the structural model of the interaction between the embodiment one of the zinc-based MOF material with a triangular prism type metal cluster and the preparation method thereof and benzene molecules, C-H 配体 … 苯 , C-H 苯 … 羧基 , Zn 2+ … 苯 and C-H 苯 … 配体 The interactions are respectively marked with green, orange, pink and blue, wherein (a) is to show the distribution of benzene molecules at the binding sites , , , (b) is the host-guest interaction of benzene molecules at the sites , (c) is the host-guest interaction of benzene molecules at the sites , and (d) is the host-guest interaction of benzene molecules at the sites . Figure 8 is the structural model of the interaction between the embodiment one of the zinc-based MOF material with a triangular prism type metal cluster and the preparation method thereof and benzene molecules, C-H 配体 … 苯 , C-H 苯 … 羧基 , Zn 2+ … 苯 , C-H 苯 … 配体 and π 苯 -π 配体 interactions are respectively marked with green, orange, pink, blue and purple, wherein (a) is the host-guest interaction of other benzene molecules at the sites , and (b) is the host-guest interaction of other benzene molecules at the sites host-guest interactions at the sites of other benzene molecules, host-guest interactions at the sites of other benzene molecules; Figure 9 is a structural model of the interaction between the zinc-based MOF material with a triangular prism type metal cluster of the present application and benzene molecules. DETAILED DESCRIPTION

[0020] The technical solutions of the present application are further described below through the drawings and examples.

[0021] Unless otherwise defined, the technical terms or scientific terms used in the present application shall have the usual meanings understood by those with ordinary skills in the art to which the present application belongs.

[0022] Example 1 A zinc-based MOF material, named WUST-4, is prepared by using DEF solvent and controllably introducing H2O, and DEF / H2O=10:3 (volume ratio), and the preparation method is as follows: Zinc nitrate hexahydrate (Zn(NO3)2·6H2O, 20.8 mg, 0.07 mmol) and 1,3,5-tris(4-carboxyphenyl)benzene (H3BTB, 8.0 mg, 0.018 mmol) are dissolved in N,N-dimethylformamide (DEF, 4.0 mL) and deionized water (1.2 mL), and the mixed solution is placed in a 20 mL reaction bottle. After the reaction bottle is sealed, it is placed in an 85 oven for 24 hours. After the system is cooled to room temperature, colorless needle-shaped crystals are obtained, and the product is collected by washing with N,N-dimethylformamide (DMF) three times, solvent replacement with methanol three times a day for three days, and then activated at 80 or 200 conditions (the material for elemental analysis and thermal gravimetric analysis is 80 activated, and the material for gas adsorption is 200 activated), vacuum heating for 12 hours to obtain activated WUST-4. The yield based on H3BTB calculation is 46%.

[0023] Example 2 A zinc-based MOF material, which is different from example 1, is that DEF / H2O=10:1.

[0024] The preparation method is as follows: Zinc nitrate hexahydrate (Zn(NO3)2-6H2O, 20.8 mg, 0.07 mmol) and 1,3,5-tris(4-carboxyphenyl)benzene (H3BTB, 8.0 mg, 0.018 mmol) were dissolved in N,N-dimethylformamide (DEF, 4.0 mL) and deionized water (0.4 mL), and the mixed solution was placed in a 20 mL reaction bottle. After sealing, the reaction bottle was placed in an 85 oven for 24 hours. After the system cooled to room temperature, the crystalline phase product was obtained, and washed with N,N-dimethylformamide (DMF) three times to collect the product, obtaining a mixed crystal phase of needle-shaped crystals (i.e., WUST-4) and block-shaped crystals (i.e., MOF-177).

[0025] Comparative Example One A MOF-177 material was prepared using a pure DEF solvent system, and the preparation method was as follows: Zinc nitrate hexahydrate (Zn(NO3)2-6H2O, 20.0 mg, 0.067 mmol) and 1,3,5-tris(4-carboxyphenyl)benzene (H3BTB, 5.0 mg, 0.011 mmol) were dissolved in 1.0 mL of N,N-dimethylformamide (DEF), and the mixed solution was placed in a 4 mL reaction bottle. After sealing, the reaction bottle was placed in an 85 oven for 24 hours. After the system cooled to room temperature, the crystalline phase product was obtained, and washed with N,N-dimethylformamide (DMF) three times to collect the product, obtaining a mixed crystal phase of needle-shaped crystals (i.e., WUST-4) and block-shaped crystals (i.e., MOF-177).

[0026] Test Test 1. Structure Analysis The products of Example One~Example Two and Comparative Example One were subjected to single crystal X-ray diffraction (SXRD), powder X-ray diffraction (PXRD) and thermogravimetric analysis, and the results are shown in Figures 1-4 .

[0027] In Zn4O-MOFs, the metal cluster can exhibit different degrees of geometric deformation, but basically maintains an octahedral configuration. Notably, the multiple coordination modes of Zn 2+ ions (such as tetrahedral, square pyramidal and octahedral) allow significant geometric deformation to occur without changing the connection number, which provides a new idea for the topological diversification of MOFs. By precisely controlling the solvent system in the synthesis of MOF-177, a new type of Zn4O-MOF material, WUST-4, was successfully prepared.

[0028] Single crystal X-ray diffraction showed that WUST-4 belongs to the hexagonal crystal system space group P-62c. As shown in Figure 3 , PXRD verified the phase purity of WUST-4, as shown in Figure 4 , thermogravimetric analysis showed that its thermal stability reached 400 .like Figure 1 As shown, although it, like MOF-177, is composed of Zn4O clusters and BTB ligands, there are significant differences in the geometry and connection methods of the building blocks. The Zn4O clusters in WUST-4 consist of two tetrahedral and two octahedral Zn... 2+ The Zn4O cluster in MOF-177 consists of four tetrahedral coordinated Zn atoms. 2+ This unique Zn4O cluster, through its connection with six BTB ligands, forms a 6-connection node with a twisted triangular prism geometry. Ultimately, the three-dimensional network constructed by the Zn4O cluster and BTB ligands extends along... c The axial direction forms a diameter of approximately 18 The structure features one-dimensional channels with narrow "traps" formed by BTB benzene rings visible on the channel walls. Topological analysis reveals a novel (3,6)-connected network topology. This unique configuration arises from the synergistic effect of ligand migration and solvent coordination. Due to the geometric deformation of the Zn4O cluster and the conformational change of the BTB ligands, WUST-4 exhibits an unprecedented (3,6)-connected topological network.

[0029] like Figure 2 The diagram shows the coordination environment of the metal clusters in WUST-4 and MOF-177. Ideally, the Zn4O(COO)6 secondary building unit (SBU) has an octahedral configuration, with six carboxylic acid carbon atoms located at the vertices of the octahedron, and the bond angle (COC) between adjacent carboxylic acid carbon atoms and the central oxygen atom is 90°. (e.g., MOF-5). In some Zn4O-MOFs, topological constraints may cause bond angles to deviate from the ideal value (10). Within a certain range, slight deformation occurs (such as in MOF-177). However, the maximum deviation of the COC bond angle in WUST-4 reaches 30.20 degrees. This significantly altered the cluster's geometry. The study found that this deformation originated from the migration of carboxylic acid ligands and the cooperative coordination of water molecules. Simultaneously, to satisfy the Zn... 2+ The optimal coordination configuration resulted in varying degrees of ligand rotation, ultimately leading to a twisted triangular prism configuration of the Zn4O cluster. Besides the differences in the metal clusters, the flexible BTB ligands also exhibited different configurations in the two MOFs. In WUST-4, the benzoic acid group had the smallest out-of-plane bending angle relative to the central benzene ring, at 170.70°. Compared to MOF-177 (176.28), The SBU becomes more distorted. Therefore, the deformation of the SBU and the flexibility of the ligands together lead to the formation of the unique topology of WUST-4.

[0030] 2. Benzene vapor adsorption analysis Nitrogen adsorption tests and pore size calculations were performed on the product of Example 1, and benzene vapor adsorption experiments were conducted on the products of Example 1 and Comparative Example 1.

[0031] Depend on Figure 5 From (c), we can see that at 298K, the relative pressure ( P / P Under conditions up to 0.9, single-component benzene adsorption isotherms were tested on the activated WUST-4. The material exhibited typical Type I isotherm characteristics: the benzene adsorption capacity increased sharply in the low-pressure region, and... P / P It gradually reaches saturation at approximately 0.02. WUST-4 at 298K and P / P The saturated benzene adsorption capacity at a concentration of 0.9 is 5.5 mmol g. -1 It is lower than the 18.2 mmol g of MOF-177. -1 This difference can be attributed to the higher porosity of MOF-177 (its Langmuir specific surface area reaches 4500 m²). 2 g -1 ).Depend on Figure 5 As shown in (d), WUST-4 operates in the low-pressure region (approximately 0.02). P / P 0: 4.10 mmol g -1 It showed superior performance compared to MOF-177 (0.32 mmol g). -1 The study examined the benzene adsorption performance of WUST-4, revealing its potential in trace benzene adsorption. The low-pressure benzene adsorption performance of WUST-4 was comparable to that of similar high-performing adsorbents under similar conditions. This demonstrates that although WUST-4 and MOF-177 share similar structural units, they exhibit completely different benzene adsorption behaviors.

[0032] like Figure 6 As shown, a grand canonical Monte Carlo (GCMC) simulation was performed to reveal the binding sites of benzene molecules in WUST-4. At 298 K, the simulated benzene adsorption isotherm... P / P When 0 < 0.03, the result is consistent with the experimental results, but slightly higher than the experimental value in the higher pressure range. P / P When θ = 0.02, the simulated benzene adsorption capacity is 3.80 mmol g. -1 , compared with the experimental value of 4.10 mmol g -1 The results are largely consistent. The calculated saturated benzene adsorption capacity is 6.50 mmol g. -1 Slightly higher than the experimental result (5.5 mmol g) -1 ).

[0033] As Figures 7-8 shown by GCMC simulations, three different benzene binding sites (site - site ) were identified in WUST-4. In site 配体 ··· , the benzene molecule is partially confined in a "trap" on the channel wall surface, interacting with the benzene ring of the adjacent ligand and the carboxylate oxygen atoms through C-H 苯 ···O 苯 ··· 羧基 interactions (distances 2.692-3.695 ). Sites and are located on the channel surface: site is adjacent to the Zn4O cluster, forming Zn 2+ ··· 苯 interactions (distances 4.941-5.594 ), while C-H 苯 ··· 配体 (2.687 ), C-H 苯 ···O 羧基 (2.661-3.709 ), and C-H 苯 ··· 配体 interactions (3.937 ) are also present; site is associated with the ligand, stabilized by C-H 苯 ··· 配体 (3.233-3.475 ), C-H 苯 ···O 羧基 (2.786-3.192 ), and 苯 - 配体 interactions (3.702 ). In addition, guest-guest interactions between benzene molecules through C-H 苯 ··· 苯 interactions (2.928-3.735 ) were observed.

[0034] In contrast, as Figure 9 ​​​​​​​As shown, the benzene molecules in MOF-177 mainly interact with the C-H 苯 ··· 配体 (3.367 ), C-H 苯 ···O 羧基 (2.889-3.310 ) and 苯 - 配体 (4.357 ) are located near the BTB ligands. It can be seen that the more abundant non-covalent interactions between WUST-4 and benzene molecules together promote its efficient benzene capture at low pressure.

[0035] Therefore, the application adopts the above-mentioned zinc-based MOF material with a triangular prism type metal cluster and a preparation method thereof, forms a network topology structure based on a triangular prism type Zn4O cluster, and exhibits excellent benzene adsorption performance at low pressure through multiple non-covalent interactions, reveals the key role of solvent-mediated conformational engineering in expanding the structural diversity of MOFs based on deformable SBUs and flexible ligands, and opens up a new path for the directional design of new functional MOFs.

[0036] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application rather than limit them, although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that: it can still modify or equivalently replace the technical solutions of the present application, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present application.

Claims

1. A method of preparing a zinc-based MOF material having a trigonal prism type metal cluster, characterized by, The method comprises the following steps: S1, mixing N,N-diethylformamide and deionized water in a certain proportion to obtain a mixed solution A; S2, dissolving zinc nitrate hexahydrate and 1,3,5-tris(4-carboxyphenyl) benzene in the mixed solution A obtained in S1 in a certain proportion to obtain a mixed solution B; S3, placing the mixed solution B obtained in S2 in a reaction bottle, sealing and then performing heat treatment, and obtaining colorless needle-shaped crystals after the system is cooled to room temperature; S4, washing the colorless needle-shaped crystals obtained in S3 with a detergent, activating and treating, collecting the product, and obtaining WUST-4.

2. The method for preparing a zinc-based MOF material with triangular prism-shaped metal clusters according to claim 1, characterized in that, In S1, the volume ratio of the N,N-diethylformamide to the deionized water is 10:1-5.

3. The method for preparing a zinc-based MOF material with triangular prism-shaped metal clusters according to claim 2, characterized in that, In S1, the volume ratio of the N,N-diethylformamide to the deionized water is 10:

3.

4. The method for preparing a zinc-based MOF material with triangular prism-shaped metal clusters according to claim 1, characterized in that, In S2, the molar ratio of the zinc nitrate hexahydrate to the 1,3,5-tris(4-carboxyphenyl) benzene is 35:

9.

5. The method for preparing a zinc-based MOF material with triangular prism-shaped metal clusters according to claim 1, characterized in that, In S2, the dosage ratio of the 1,3,5-tris(4-carboxyphenyl) benzene to the mixed solution A is 8.0 mg:5.2 mL.

6. The method for preparing a zinc-based MOF material with triangular prism-shaped metal clusters according to claim 1, characterized in that, In S3, the heat treatment is specifically as follows: The reaction vial was sealed and placed in an 80-90 oven for 18-26 hours.

7. The method for preparing a zinc-based MOF material with triangular prism-shaped metal clusters according to claim 1, characterized in that, In S4, the detergent is N,N-dimethylformamide, and the washing is performed at least 3 times.

8. The method for preparing a zinc-based MOF material with triangular prism-shaped metal clusters according to claim 1, characterized in that, In S4, the activation treatment is specifically as follows: The solvent was replaced with methanol three times a day for three days, then the sample was heated under vacuum at 80 °C for 12 hours to obtain activated WUST-4. or 200 hours under vacuum to obtain activated WUST-4.

9. A zinc-based MOF material with a triangular prism type metal cluster prepared by the method according to any one of claims 1-8.

10. The zinc-based MOF material having a triangular prism-shaped metal cluster of claim 9, wherein, The material is hexagonal space group P-62c, the material includes a triangular prism type Zn4O cluster and a trident BTB ligand, the Zn4O cluster includes two tetrahedral coordination, two octahedral coordination Zn 2+ Ions, forming a novel three-dimensional network structure, that is, a (3, 6)-connected topological network, which forms a one-dimensional channel with a diameter of 18 c A narrow region surrounded by a BTB benzene ring on the channel wall of the one-dimensional channel.

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