A bidirectional rod-like metal organic framework material and a preparation method and application thereof
By employing solvent modification and orientation control strategies, unidirectional rod-shaped MOFs were reconstructed into bidirectional rod-shaped MOFs, solving the problems of single pore structure and insufficient low-pressure benzene adsorption capacity of existing MOFs. This resulted in highly efficient benzene capture, making it suitable for air purification and industrial waste gas treatment.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-30
- Publication Date
- 2026-04-10
Smart Images
Figure CN121405971B_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application relates to the technical field of metal organic framework material synthesis, in particular to a bidirectional rod-shaped metal organic framework material and a preparation method and application thereof. BACKGROUND
[0002] As a kind of porous crystalline material formed by assembling organic ligand and metal ion or metal secondary building unit (SBU), metal organic framework (MOF) has broad application prospects in gas adsorption separation, energy conversion, photocatalysis and other fields due to its high specific surface area, adjustable pore structure and rich functional sites. Among them, rod-shaped MOFs constructed by infinitely extended rod-shaped SBUs have become a research hotspot in the field of gas adsorption separation due to their unique interlocking inhibition and breathing effect.
[0003] In the prior art, in the synthesis process of most rod-shaped MOFs, the SBUs of the rod-shaped MOFs are arranged in a single parallel direction to form a single one-dimensional (1D) channel, which limits the diversity of the pore structure and the optimization of the adsorption performance. MOFs with multi-orientation rod-shaped SBUs lack rational design and synthesis strategies due to the difficulty in accurately controlling and predicting the configuration of the rod-shaped SBUs.
[0004] In addition, benzene, as a volatile organic compound (VOC) with high volatility and strong carcinogenicity and teratogenicity, poses a serious threat to human health and the ecological environment, and it is urgent to develop porous materials with high trace benzene capture performance. The existing rod-shaped MOFs (such as MOF-74, BUT-66, etc.) have limited adsorption capacity for benzene under low pressure conditions, which is difficult to meet the actual application requirements.
[0005] Therefore, it is of important academic value and practical application significance to develop a method for rationally controlling the orientation of rod-shaped SBUs and constructing MOF materials with novel pore structures, and to realize high-efficiency capture of benzene under low pressure. SUMMARY
[0006] The purpose of the present application is to provide a bidirectional rod-shaped metal organic framework material and a preparation method and application thereof, to realize the directional reconstruction of rod-shaped SBUs from single direction to bidirectional, and to obtain MOF materials with smaller channel openings, higher porosity and excellent low-pressure benzene adsorption performance.
[0007] To achieve the above purpose, the present application provides a preparation method of a bidirectional rod-shaped metal organic framework material, comprising the following steps:
[0008] Proportionally, disperse zinc nitrate hexahydrate and 2-hydroxyterephthalic acid in N,N-dimethylformamide, seal, and react at 90-100 DEG C for 5-7 days to obtain an octahedral crystal, i.e. single crystal CCNUF-74;
[0009] N,N-dimethylformamide washing, acetonitrile solvent exchange, step-by-step vacuum activation treatment at 20-40℃, heating at 110-130℃ under vacuum for 10-15h, to obtain the activated CCNUF-74.
[0010] Preferably, the zinc nitrate hexahydrate and the 2-hydroxyterephthalic acid are proportionally dispersed in N,N-dimethylformamide, sealed, and incubated at 95℃ for 6 days to obtain octahedral crystals, i.e., single-crystal CCNUF-74.
[0011] N,N-dimethylformamide washing, acetonitrile solvent exchange, step-by-step vacuum activation treatment at 20-40℃, heating at 110-130℃ under vacuum for 10-15h, to obtain the activated CCNUF-74.
[0012] Preferably, the zinc nitrate hexahydrate, the 2-hydroxyterephthalic acid and the N,N-dimethylformamide are used in a ratio of 0.227mmol:0.111mmol:1.0mL.
[0013] Preferably, the N,N-dimethylformamide washing is performed at least three times.
[0014] Preferably, the acetonitrile solvent exchange is performed three times a day for at least 6 days.
[0015] Preferably, the step-by-step vacuum activation treatment specifically comprises:
[0016] The solid product is maintained at 30, 25, 20, 15, 10, 5, 3 and 1kPa pressure for 30min respectively.
[0017] The application also provides a single-crystal CCNUF-74 material.
[0018] Preferably, the single-crystal CCNUF-74 material crystallizes in a tetragonal space group P41212, and the Zn-O-based rod-like SBUs are arranged in a bidirectional isomorphism along the crystal axes a and b.
[0019] The single-crystal CCNUF-74 material has a pore opening size of 8.9Å×10.7Å and 8.0Å×5.1Å, a porosity of 69.5%, and a BET specific surface area of 980m 2 / g.
[0020] The application also provides a use of a single-crystal CCNUF-74 material in benzene capture.
[0021] Preferably, at 298K, P / P 0=0.005, the single-crystal CCNUF-74 material has an adsorption capacity for benzene of 2.46mmolg -1 ; at 298K,P / P 0=0.01, the adsorption amount of single crystal CCNUF-74 material to benzene is 3.09 mmol g -1 .
[0022] Therefore, the application adopts the above-mentioned bidirectional rod-shaped metal organic framework material, its preparation method and application, and has the following beneficial effects:
[0023] The application proposes a rod-shaped SBU orientation regulation strategy based on solvent modification, realizes in-situ introduction of formate anions and accurate regulation of ligand twist angle by removing water in the reaction system, successfully reconfigures the unidirectional rod-shaped MOF (CPM-74) into the bidirectional rod-shaped MOF (CCNUF-74), and realizes rational design and synthesis of multi-orientation rod-shaped MOFs for the first time.
[0024] The single crystal CCNUF-74 prepared by the application has a unique bidirectional orthogonal rod-shaped SBU structure, forms a three-dimensional interconnected channel network, has smaller channel openings and higher porosity compared with CPM-74, provides a structural basis for efficient adsorption of low-pressure benzene, and can be widely applied to trace benzene capture scenes such as indoor air purification and industrial waste gas treatment.
[0025] The application has simple process, mild conditions and strong repeatability, does not need complex equipment, and is beneficial to large-scale production and practical application popularization.
[0026] The technical scheme of the application will be further described in detail below with the aid of drawings and examples. DETAILED DESCRIPTION
[0027] Figure 1 is a synthesis route schematic diagram of the embodiment one and the comparative example one of the bidirectional rod-shaped metal organic framework material and the preparation method and application of the application;
[0028] Figure 2 is an SXRD result diagram of the embodiment one and the comparative example one of the bidirectional rod-shaped metal organic framework material and the preparation method and application of the application, wherein (a) is the structure of the rod-shaped SBU in CPM-74 and CCNUF-74, color identification: gray is carbon (C), red is oxygen (O), blue, cyan and purple are zinc (Zn), and yellow is hydrogen (H); (b) is a comparison of the ligand twist angle in CPM-74 and CCNUF-74, the twist angle of the carboxylic acid group in OBDC is defined as: the dihedral angle between the plane (green triangle) formed by two carboxyl carbon atoms and hydroxyl oxygen atoms and the carboxylic acid group plane (yellow and orange triangle);
[0029] Figure 3is an optical microscope image of a bidirectional rod-shaped metal organic framework material and a preparation method and application embodiment one and comparative example one to comparative example five of the present application, wherein (a) is comparative example one, (b) is comparative example three, (c) is comparative example four, (d) is comparative example five, (e) is comparative example two, and (f) is embodiment one;
[0030] Figure 4 is a PXRD pattern of a bidirectional rod-shaped metal organic framework material and a preparation method and application embodiment one and comparative example one to comparative example five of the present application, wherein (a) is comparative example one to comparative example five, and (b) is embodiment one;
[0031] Figure 5 is a benzene adsorption test result of a bidirectional rod-shaped metal organic framework material and a preparation method and application embodiment one of the present application, wherein (a) is a N2 adsorption isotherm under 77K conditions, and (b) is a benzene vapor adsorption isotherm under 298K conditions;
[0032] Figure 6 is a grand canonical Monte Carlo (GCMC) simulation result graph of a bidirectional rod-shaped metal organic framework material and a preparation method and application embodiment one and comparative example one of the present application, wherein (a) is a simulated benzene adsorption isotherm and an experimental benzene adsorption isotherm of embodiment one, and (b) is a simulated benzene adsorption isotherm of embodiment one and comparative example one;
[0033] Figure 7 is an SXRD graph of a benzene molecule adsorption site of a bidirectional rod-shaped metal organic framework material and a preparation method and application embodiment one of the present application. DETAILED DESCRIPTION
[0034] The technical solutions of the present application are further described below through the drawings and embodiments.
[0035] Unless otherwise defined, the technical terms or scientific terms used in the present application shall have the usual meanings understood by those skilled in the art to which the present application belongs.
[0036] Embodiment one
[0037] A single crystal CCNU F-74 material is prepared by the following method:
[0038] Zinc nitrate hexahydrate (Zn(NO3)2·6H2O, 67.5 mg, 0.227 mmol) and 2-hydroxyterephthalic acid (H3OBDC, 20.25 mg, 0.111 mmol) are dissolved in 1.0 mL of N,N-dimethylformamide (DMF), and the solution is placed in a 4 mL reaction bottle. After the reaction bottle is sealed, it is placed in a 95°C oven for reaction for 6 days to obtain an octahedral crystal.
[0039] The product was washed three times with DMF to collect the solid product, which was then solvent-exchanged with acetonitrile (three times a day for 6 days). Next, it was subjected to gradual vacuum treatment at 30°C (maintained for 30 min at pressures of 30, 25, 20, 15, 10, 5, 3 and 1 kPa respectively). Finally, the sample was heated at 120°C under vacuum for 12 hours to obtain the activated product.
[0040] Comparative Example 1
[0041] A CPM-74 material ([Zn4(OH)2(OBDC)2], H3OBDC = 2-hydroxyterephthalic acid) is prepared as follows:
[0042] Zn(NO3)2·6H2O (7.75 mg, 0.026 mmol), H3OBDC (2.35 mg, 0.013 mmol), DMF (543 μL), N,N-dibutylformamide (DBF, 150 μL), water (129 μL), isopropanol (iPrOH, 165 μL), and tetrapropylammonium hydroxide (TPAOH, 13 μL) were stirred and mixed in a 4 mL reaction flask. The reaction flask was then sealed and placed in an oven at 120 °C for 24 h to obtain rod-shaped crystals.
[0043] like Figure 1 As shown, in CPM-74, the dihedral angle (collectively referred to as the carboxyl torsion angle) between the carboxyl group on the OBDC ligand and the central plane COC exhibits slight distortion. Due to the inherent flexibility of the OBDC ligand, these torsion angles can be further increased, thereby achieving the directional reconstruction of rod-shaped SBUs from unidirectional to bidirectional. The strategy of increasing the torsion angle of the ligand to achieve orientation regulation of rod-shaped SBUs and obtain a bidirectional rod-shaped structure was employed. The introduction of formic acid significantly altered the torsion angle of the ligand, ultimately forming a novel three-dimensional channel structure with orthogonally arranged rod-shaped SBUs. In CCNUF-74, rod-shaped SBUs labeled with different colors have the same structure but different orientations, while the different colors of the ligands represent differences in their torsion angles. Color coding: gray represents carbon atoms, red represents oxygen atoms, blue or green polyhedra represent zinc atoms, and yellow and orange rods represent ligands.
[0044] Comparative Example 2
[0045] A polycrystalline CCNUF-74 material is prepared by the following method:
[0046] Zn(NO3)2·6H2O (7.75 mg, 0.026 mmol), H3OBDC (2.35 mg, 0.013 mmol), DMF (543 μL), DBF (150 μL), iPrOH (165 μL) and TPAOH (13 μL) were mixed in a 4 mL reaction flask and then sealed and placed in an oven at 120 °C for 24 h to obtain a colorless powder.
[0047] Comparative Example 3
[0048] The difference from Comparative Example 1 is that the amount of water added was reduced to 90 μL.
[0049] Comparative Example 4
[0050] The difference from Comparative Example 1 is that the amount of water added was reduced to 60 μL.
[0051] Comparative Example 5
[0052] The difference from Comparative Example 1 is that the amount of water added was reduced to 30 μL.
[0053] Test
[0054] 1. Single-crystal X-ray diffraction (SXRD) analysis was performed on the materials obtained in Example 1 and Comparative Example 1. The results are as follows: Figure 2 As shown.
[0055] Depend on Figure 2 It is known that CCNUF-74 crystallizes in the tetragonal crystal system, space group P41212, and its bidirectional isomorphic Zn-O rod-shaped SBUs are arranged along the crystal axes a and b. The asymmetric unit of this structure contains four crystallographically independent Zn atoms. 2+ The structure consists of ions, two fully deprotonated OBDC ligands, a formate anion, a bridging μ-OH group, and an N,N-dimethylformamide (DMF) molecule or water molecule present due to disorder. Zn1 adopts a tetrahedral coordination configuration, coordinating with three carboxylic acid oxygens and one μ-OH; Zn2 forms an octahedral configuration through coordination with three carboxylic acid oxygens, one phenolic oxygen, one μ-OH, and one formate; Zn3 has a five-coordinate tetrapyramidal configuration, combining two carboxylic acid oxygens, two μ-OH, and one formate; and Zn4 forms a tetrahedral coordination through one carboxylic acid oxygen, one phenolic oxygen, one μ-OH, and one DMF or water molecule. Compared to CPM-74, the distance between adjacent Zn2 and Zn3 ions within the rod-shaped SBU in CCNUF-74 is increased to approximately 3.123 Å, providing space for bridging the formate, while the smaller μ-OH cannot bridge these sites. Adjacent ZnO... n(n = 4, 5 or 6) units form a zigzag Zn-O chain by sharing vertices or edges. The formula of CPM-74 is [Zn4(OH)2(OBDC)2], while that of CCNUF-74 is [Zn4(OH)(OBDC)2(HCOO)], differing in that the latter replaces μ-OH with formate.
[0056] In CCNUF-74, the torsion angles of the carboxylate groups of half of the OBDC ligands increase significantly (from 5.15° and 27.57° in CPM-74 to 23.83° and 39.92°, respectively), leading to the formation of two sets of rod-like SBUs that are identical in chemical composition but orthogonal to each other. Some of the OBDC ligands that originally lined the pore walls are redirected to the center of the channels, reducing the size of the pore windows. Because the length of the ligand is fixed, the dihedral angle between the Zn-O chain and the ligand decreases from 63.8° in CPM-74 to 49.4° and 46.6° in CCNUF-74, shortening the perpendicular distance between adjacent chains. This reduction in inter-chain distance, combined with the structural feature of the ligands being more exposed to the pore environment, collectively leads to a significant contraction of the channel openings. At the same time, the bidirectional orientation of the rod-like SBUs facilitates the formation of a three-dimensionally interconnected channel network in CCNUF-74. As a result, the channel openings in CCNUF-74 (8.9 Å x 10.7 Å and 8.0 Å x 5.1 Å) are smaller than those in CPM-74 (13.3 Å x 13.3 Å), but still maintain a high porosity of 69.5% (compared to 56.3% for CPM-74). Moreover, the difference in torsion angles of the rod-like SBUs and OBDC ligands results in a topological network in CCNUF-74 that is completely different from that in CPM-74. This result validates the feasibility and effectiveness of the orientation regulation strategy for constructing multidirectional rod-like MOF structures by regulating the torsion angles of the ligands.
[0057] 2. The materials obtained in Example 1 and Comparative Examples 1-5 were subjected to powder X-ray diffraction (PXRD) analysis, and the results are shown in FIGS. 1-5, respectively. Figure 3 Figure 4
[0058] Figure 3 Figure 4 It was found that when 129 μL of water was added, light gray rod-shaped crystals were obtained, which were confirmed as the CPM-74 phase by powder X-ray diffraction (PXRD) analysis. When the water content was reduced to 90 μL, the product was a mixture of rod-shaped crystals and polycrystalline powder, and the PXRD spectrum still corresponded to the CPM-74 phase. When the water content was further reduced to 60 μL and 30 μL, only polycrystalline powder was obtained, and the PXRD peak intensity further decreased, indicating that the crystal quality continued to deteriorate. When no water was added at all, although the product was still polycrystalline powder, the characteristic diffraction peaks of CPM-74 completely disappeared, and only the diffraction peaks corresponding to CCNUF-74 were observed, indicating that a complete phase transition had occurred. These results indicate that small changes in water content can significantly affect the phase transition process: higher water content is conducive to the formation of CPM-74, while a completely anhydrous environment promotes the assembly of the CCNUF-74 phase. To obtain high-quality CCNUF-74 single crystals, a colorless octahedral crystal was finally obtained. The good agreement between the experimental and simulated PXRD spectra confirmed the bulk purity of the CCNUF-74 crystal.
[0059] 3. The permanent porosity analysis and benzene vapor adsorption test were performed on the material obtained in Example 1. The results are as follows: Figure 5 As shown.
[0060] Depend on Figure 5 As shown in (a), CCNUF-74 exhibits a value of 980m. 2 The BET specific surface area per g is approximately equal to the theoretical value of 1690 m². 2 There is a certain deviation in / g. This difference may be related to the significant increase in the ligand torsion angle, which leads to a decrease in the stability of the framework structure.
[0061] Depend on Figure 5 As shown in (b), CCNUF-74 operates in the low-pressure region ( P / P (0 < 0.01) The benzene vapor adsorption capacity shows a steep upward trend, which is typical micropore filling behavior and suitable for trace benzene capture. Specifically, in P / P When α = 0.005, the adsorption capacity reaches 2.46 mmol g. -1 , P / P When 0 = 0.01, it further increased to 3.09 mmol g. -1 It exhibits excellent low-pressure adsorption capacity. As pressure increases, the adsorption capacity gradually approaches saturation, with a maximum adsorption capacity of approximately 4.04 mmol g. -1 Although the measured BET specific surface area of CCNUF-74 is significantly lower than the theoretical value, it still exhibits a high low-pressure benzene adsorption capacity, indicating a strong affinity and good size matching between the pore structure and benzene molecules.
[0062] 4. Giant canonical Monte Carlo (GCMC) simulations were performed on the materials obtained in Example 1 and Comparative Example 1. The results are as follows: Figure 6as shown.
[0063] From Figure 6 It is known that the simulated benzene saturated adsorption capacity of CCNUF-74 is significantly higher than the experimental value, which is consistent with the trend that the theoretical BET specific surface area is greater than the experimental value. More importantly, the calculated adsorption capacity of CCNUF-74 is superior to that of CPM-74, whether under low pressure or saturated conditions. This performance difference is mainly due to two factors: first, unlike the one-dimensional straight-through pore of CPM-74, CCNUF-74 has smaller pore openings and a zigzag channel structure, which enhances the host-guest interaction through multi-site strong bonding between benzene molecules (especially under low pressure conditions); second, the three-dimensional pore network of CCNUF-74 gives it higher overall porosity and more abundant accessible pore space, thus improving the total adsorption capacity.
[0064] 5. The material obtained in Example 1 was soaked in benzene for one week and its structure was resolved by single crystal X-ray diffraction (SXRD), as shown in Figure 7 .
[0065] Benzene molecules are anchored by the network structure through C-H···O (3.43-4.6 Å) interaction and further stabilized by C-H···π (2.28 Å) interaction, and this synergistic effect enhances the host-guest affinity. This specific interaction is the key mechanism for the material to exhibit significant benzene adsorption capacity at low pressure.
[0066] Therefore, the present application uses the above-mentioned bidirectional rod-shaped metal organic framework material, its preparation method and application, realizes the directional reconfiguration of rod-shaped SBUs from unidirectional to bidirectional, and obtains a MOF material with smaller pore opening, higher porosity and excellent low-pressure benzene adsorption performance.
[0067] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application and not to 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 for preparing a bidirectional rod-like metal-organic framework material, characterized in that, The method comprises the following steps: proportionally, zinc nitrate hexahydrate and 2-hydroxyterephthalic acid are dispersed in N,N-dimethylformamide, sealed, and reacted at a constant temperature of 90-100℃ for 5-7 days to obtain octahedral crystals, i.e. single crystal CCNUF-74; N,N-dimethylformamide washing, acetonitrile solvent exchange, step-by-step vacuum treatment at 20-40℃, and heating at 110-130℃ under vacuum for 10-15h to obtain activated CCNUF-74; The use ratio of the zinc nitrate hexahydrate, the 2-hydroxyterephthalic acid and the N,N-dimethylformamide is 0.227mmol:0.111mmol:1.0mL; The step-by-step vacuum treatment specifically comprises: The solid product is kept at a pressure of 30, 25, 20, 15, 10, 5, 3 and 1kPa respectively for 30min.
2. The method of claim 1, wherein the method is a method of preparing a bidirectional rod-like metal organic framework material. The N,N-dimethylformamide washing is performed at least three times.
3. The method of claim 1, wherein the method further comprises: The acetonitrile solvent exchange is performed three times a day for at least 6 days. 4.A single crystal CCNUF-74 material prepared by the preparation method of the bidirectional rod-shaped metal organic framework material according to any one of claims 1-3.
5. A single crystal CCNU F-74 material according to claim 4, wherein: The single crystal CCNUF-74 material is crystallized in a tetragonal space group P41212, and bidirectional isomorphic Zn-O-based rod-shaped SBUs are arranged along the crystal axes a and b; The single crystal CCNU F-74 material has channel opening sizes of 8.9 A x 10.7 A and 8.0 A x 5.1 A, a porosity of 69.5%, a BET specific surface area of 980 m 2 / g. 6.A use of a single crystal CCNUF-74 material prepared by the preparation method of the bidirectional rod-shaped metal organic framework material according to any one of claims 1-3 in benzene capture.