Vanadium-based metal-organic framework material, preparation method and application thereof

Abstract

The application provides a vanadium-based metal organic framework material and a preparation method and application thereof, and belongs to the technical field of metal organic framework materials.The vanadium-based metal organic framework material is a three-dimensional framework structure formed by connecting one-dimensional vanadium-oxygen chains and square acid ligands through coordination bonds.The preparation method of the vanadium-based metal organic framework material comprises the following steps: adding a vanadium source and an organic ligand into an acidic aqueous solution to perform a solvothermal reaction, and obtaining the vanadium-based metal organic framework material, wherein the organic ligand is square acid.The vanadium-based metal organic framework material provided by the application can be used for separating straight-chain alkanes and isomers thereof.

Description

Technical Field

[0001] This invention relates to the field of metal-organic framework materials technology, specifically to a vanadium-based metal-organic framework material, its preparation method, and its application. Background Technology

[0002] High-purity n-hexane (nHEX) is a key solvent widely used in important fields such as pharmaceuticals, polymer manufacturing, electronic equipment manufacturing, vegetable oil extraction, and food processing.

[0003] In the preparation of nHEX, the purity of crude nHEX prepared by traditional distillation process is usually only 60-80%. In addition to the target product linear nHEX, the crude product also contains structural isomers with similar physical properties to nHEX, including single-branched isomers such as 2-methylpentane (2MP) and 3-methylpentane (3MP), as well as dibranched isomers such as 2,3-dimethylbutane (23DMB) and 2,2-dimethylbutane (22DMB). At the same time, cyclic impurities with C6 skeletons such as benzene (Bz), cyclohexane (Cya), and cyclohexene (Cxe) are also mixed into the crude nHEX because their physical properties are similar to those of nHEX.

[0004] To meet the higher purity requirements of specific industrial applications for nHEX, advanced purification technologies such as precision distillation, extractive distillation, and adsorption separation based on porous materials have been developed, surpassing traditional distillation. However, these existing purification strategies all have inherent limitations and are difficult to align with sustainable development goals. Precision distillation and extractive distillation are not only energy-intensive but also require complex and expensive equipment. Adsorption separation technologies using 5A zeolite and modified activated carbon as adsorbents are limited by the adsorption capacity and selectivity of the adsorbents; for example, 5A zeolite adsorbs only 90 mg / g of nHEX at 150°C. Therefore, developing adsorbents with both high adsorption capacity and high selectivity, while addressing the high energy consumption problem of existing technologies, has become a pressing technical challenge in this field. This is particularly important for meeting the practical needs of rapidly developing industries such as pharmaceuticals and clean energy batteries. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a vanadium-based metal-organic framework material, its preparation method, and its applications, aiming to at least partially solve the above-mentioned technical problems. The specific technical solution provided by this invention is as follows.

[0006] As a first aspect of the present invention, a vanadium-based metal-organic framework material is provided, wherein the vanadium-based metal-organic framework material is a three-dimensional framework structure formed by one-dimensional vanadium-oxygen chains and squaric acid ligands connected by coordination bonds.

[0007] As a second aspect of the present invention, a method for preparing a vanadium-based metal-organic framework material is provided, comprising: adding a vanadium source and an organic ligand to an acidic aqueous solution for a solvothermal reaction to obtain a vanadium-based metal-organic framework material, wherein the organic ligand is squaric acid.

[0008] As a third aspect of the present invention, an application of a vanadium-based metal-organic framework material in the separation of straight-chain alkanes and their isomers is provided.

[0009] In this embodiment of the invention, a vanadium-based metal-organic framework material with a three-dimensional framework structure, formed by a one-dimensional vanadium-oxygen chain linked to a squaric acid ligand via coordination bonds, is constructed. Its unique structural design endows the vanadium-based metal-organic framework material with excellent selective adsorption performance of straight-chain alkanes and their isomers, enabling precise identification and efficient adsorption of straight-chain alkanes. Furthermore, the vanadium-based metal-organic framework material also possesses excellent thermal stability, air stability, chemical stability, and mechanical stability. Even after molding and processing, it maintains excellent adsorption performance, which surpasses that of existing industrial benchmark materials. Therefore, it has broad application prospects in the separation and purification of straight-chain alkanes and their isomers, and can meet the separation needs of actual industrial production.

[0010] In the embodiments of the present invention, the preparation method of vanadium-based metal-organic framework materials adopts a solvothermal reaction in an acidic aqueous solution system, which is simple, easy to control, and conducive to large-scale preparation. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the cross-sectional structure of the vanadium-based metal-organic framework material in an embodiment of the present invention;

[0012] Figure 2 for Figure 1 A schematic diagram of the longitudinal section structure of the vanadium-based metal-organic framework material shown in the figure;

[0013] Figure 3 for Figure 1 A schematic diagram of the three-dimensional structure of the vanadium-based metal-organic framework material shown in the figure;

[0014] Figure 4 The X-ray diffraction patterns of V-SA and V-SA-ACT in Embodiment 1 of the present invention are shown below.

[0015] Figure 5 In Example 1 of this invention, the pore volume and pore size distribution of V-SA-ACT were derived from the HK model based on the CO2 adsorption data of V-SA-ACT at 195K.

[0016] Figure 6 The above are X-ray diffraction patterns of V-SA-ACT powder in different solvents in Example 1 of this invention.

[0017] Figure 7 This is a single-component adsorption isotherm diagram of V-SA-ACT for hexane isomers at 303 K in Example 1 of the present invention;

[0018] Figure 8 This is a single-component adsorption isotherm diagram of V-SA-ACT for hexane isomers at 423 K in Example 1 of the present invention;

[0019] Figure 9 This is a test graph showing the cyclic performance of V-SA-ACT for the adsorption of n-hexane at 303K in Example 1 of the present invention;

[0020] Figure 10 This is a test graph showing the cyclic performance of V-SA-ACT for the adsorption of n-hexane at 423K in Example 1 of the present invention;

[0021] Figure 11 This is the chromatographic breakthrough curve of V-SA-ACT at 303K for an equimolar ternary mixture in Example 1 of the present invention;

[0022] Figure 12 This is the chromatographic breakthrough curve of V-SA-ACT at 393K for an equimolar ternary mixture in Example 1 of the present invention;

[0023] Figure 13 Chromatographic breakthrough cycle curve of V-SA-ACT at 423 K for an equimolar ternary mixture in Example 1 of this invention;

[0024] Figure 14 This is a single-component adsorption isotherm diagram of V-SA-ACT at 303K and 423K in Example 1 of the present invention;

[0025] Figure 15 This is a single-component adsorption isotherm diagram of V-SA-ACT for butane isomers at 303 K in Example 1 of the present invention;

[0026] Figure 16 These are powder X-ray diffraction patterns of V-SA before and after the air thermal stability test in Example 1 of the present invention;

[0027] Figure 17 This is a graph showing the CO2 isothermal adsorption curves of V-SA at 298K before and after the air thermal stability test in Example 1 of the present invention.

[0028] Figure 18 The image shows the powder X-ray diffraction patterns of V-SA before and after the air stability test in Example 1 of this invention.

[0029] Figure 19 This is a graph showing the CO2 isothermal adsorption curves of V-SA at 298K before and after the air stability test in Example 1 of the present invention.

[0030] Figure 20 These are powder X-ray diffraction patterns of V-SA before and after chemical stability testing in Example 1 of this invention;

[0031] Figure 21 This is a CO2 isothermal adsorption curve of V-SA at 298K before and after the chemical stability test in Example 1 of the present invention;

[0032] Figure 22 The image shows the powder X-ray diffraction patterns of V-SA before and after the mechanical stability test in Example 1 of this invention.

[0033] Figure 23 This is a standardized curve of the crystallization rate (with pressure as the variable) of the V-SA sample before and after the mechanical stability test in Example 1 of the present invention;

[0034] Figure 24 The image shows the powder X-ray diffraction patterns of V-SA before and after the mechanical stability test in Example 1 of this invention.

[0035] Figure 25 These are powder X-ray diffraction patterns of V-SA at different temperatures in Example 1 of this invention;

[0036] Figure 26 This is a thermogravimetric analysis diagram of V-SA in Embodiment 1 of the present invention;

[0037] Figure 27 Images of V-SA-shaping formed in embodiments of the present invention;

[0038] Figure 28 The isothermal adsorption curves of CO2 at 195K for V-SA, V-SA-2, and V-SA-shaping prepared in the embodiments of the present invention are shown.

[0039] Figure 29 The isothermal adsorption curves of V-SA and V-SA-shaping prepared in the embodiments of the present invention and zeolite 5A in n-hexane at 423 K are shown.

[0040] Figure 30 The above are powder X-ray diffraction patterns of V-SA and samples from Comparative Examples 1-5 in Example 1 of this invention. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0042] Metal-organic frameworks (MOFs) offer a promising technological platform for improving the separation of straight-chain alkanes and their isomers (e.g., n-hexane and its isomers, n-pentane and its isomers, n-butane and its isomers) due to their high compositional tunability, diverse pore environments, and strong structural adaptability. In recent years, several MOFs have been reported to achieve efficient separation of n-hexane and its isomers. However, most reported MOFs focus on the simultaneous adsorption of nHEX and single-branched isomers (2MP / 3MP) at room temperature via size exclusion mechanisms, while also collecting dibranched isomers, aiming to improve research octane number (RON) and prepare high-quality fuels. The core drawback of these MOFs lies in their insufficient precision in pore structure design, making it impossible to distinguish the differences in size and configuration between nHEX and single-branched isomers, thus hindering the preparation of high-purity nHEX. Clearly, designing and synthesizing MOFs with suitable pore size and configuration to achieve efficient separation of nHEX from single-branched isomers requires more precise control over pore characteristics than simply "excluding dibranched isomers." Furthermore, while some reported MOFs exhibit the ability to separate nHEX from 2MP and 3MP at operating temperatures above 100°C, their adsorption capacity for nHEX decreases significantly with increasing temperature. Simultaneously, the local flexibility of the MOF structure itself enhances its adsorption of 2MP or 3MP under high-temperature conditions, leading to a substantial decrease in separation selectivity.

[0043] In summary, to date, no alternative porous material has been found that can achieve adsorption capacity and selectivity comparable to the benchmark material 5A zeolite under actual separation conditions at 150℃ and above.

[0044] Based on this, the present invention provides a vanadium-based metal-organic framework material, which aims to overcome the technical difficulty of existing adsorbent materials in effectively separating n-hexane and its isomers, n-pentane and its isomers, and n-butane and its isomers under high temperature conditions. This vanadium-based metal-organic framework material can overcome the limitations of traditional technologies and has high adsorption capacity, high separation selectivity and excellent high temperature stability, providing reliable material support for the efficient separation of n-hexane and its isomers, n-pentane and its isomers, and n-butane and its isomers.

[0045] Figure 1 This is a schematic diagram of the cross-sectional structure of the vanadium-based metal-organic framework material in an embodiment of the present invention; Figure 2 for Figure 1 A schematic diagram of the longitudinal section structure of the vanadium-based metal-organic framework material shown in the figure; Figure 3 for Figure 1 The diagram shows a three-dimensional structural schematic of the vanadium-based metal-organic framework material.

[0046] As a first aspect of the present invention, a vanadium-based metal-organic framework material is provided, such as Figures 1-3As shown, vanadium-based metal-organic framework materials are three-dimensional framework structures formed by one-dimensional vanadium-oxygen chains and squaric acid ligands connected by coordination bonds.

[0047] In this embodiment of the invention, a vanadium-based metal-organic framework material with a three-dimensional framework structure is constructed by connecting a one-dimensional vanadium-oxygen chain and a squaric acid ligand via coordination bonds. Due to its unique structural design, the vanadium-based metal-organic framework material is endowed with excellent selective adsorption performance of straight-chain alkanes and their isomers, which can achieve accurate identification and efficient adsorption of straight-chain alkanes.

[0048] In some embodiments, the three-dimensional frame structure has one-dimensional channels. Further, the aperture of the one-dimensional channels is 3-7 Å.

[0049] like Figure 1 , Figure 2 As shown, in the vanadium-based metal-organic framework material of the present invention, the "one-dimensional vanadium-oxygen chain" is not a simple linear arrangement of -VOVO- chain structure, but a rigid chain framework formed by orderly connection of vanadium-oxygen coordination octahedra as basic units and bridging oxygen atoms along the one-dimensional direction. Figure 1 This demonstrates the orderly connection between the one-dimensional vanadium-oxygen chain and the squaric acid ligands; each vanadium center, in addition to participating in the intrachain backbone construction through bridging oxygen, also coordinates with the oxygen atoms of four squaric acid ligands. Simultaneously, the four oxygen atoms of each squaric acid ligand connect to four different vanadium centers, thereby precisely crosslinking the one-dimensional vanadium-oxygen chain and constructing... Figure 2 The three-dimensional frame structure shown is formed within the three-dimensional frame. Figure 3 The one-dimensional channel is shown. The one-dimensional chain-like framework composed of vanadium-oxygen octahedrons and bridging oxygen atoms endows vanadium-based metal-organic framework materials with excellent structural rigidity, ensuring the crystallization stability and structural regularity of the three-dimensional framework, and effectively avoiding defects such as collapse and coordination disorder that are prone to occur in traditional simple vanadium-oxygen chain structures. Figure 3 The one-dimensional pore size shown can be precisely controlled by this coordination structure to achieve compatibility with straight-chain alkane molecules. The size sieving effect of the pores enables efficient separation of straight-chain alkanes and their isomers (isomers of straight-chain alkanes are difficult to enter the pores due to their spatial structure). The stable three-dimensional framework structure not only supports the structural stability of the pores in practical applications but also facilitates the molding and processing of vanadium-based metal-organic framework materials. This solves the problem of balancing separation performance and structural stability in some metal-organic framework materials, providing a high-performance adsorbent material with wide applicability in the separation of straight-chain alkanes and their isomers.

[0050] As a second aspect of the present invention, a method for preparing a vanadium-based metal-organic framework material is provided, comprising: adding a vanadium source and an organic ligand to an acidic aqueous solution for a solvothermal reaction to obtain a vanadium-based metal-organic framework material, wherein the organic ligand is squaric acid.

[0051] In this embodiment of the invention, an acidic aqueous solution is used as the reaction medium to prepare vanadium-based metal-organic framework materials via a solvothermal reaction. Compared with the organic solvents commonly used in the preparation of traditional metal-organic frameworks, the acidic aqueous solution system has advantages such as readily available raw materials, low cost, environmental friendliness, and high operational safety. Simultaneously, the acidic environment promotes the uniform dissolution of the vanadium source and the regulation of its coordination activity, ensuring the coordination reaction between the vanadium source and the squaric acid ligand, which is conducive to the formation of well-structured, highly crystalline one-dimensional vanadium-oxygen chains and three-dimensional framework structures. The solvothermal reaction conditions are easily controlled, and the process has good repeatability, enabling the stable preparation of vanadium-based metal-organic framework materials with specific one-dimensional channels. This avoids problems such as impure product phases and insufficient crystallinity that are prone to occur under heterogeneous reactions or harsh conditions. Furthermore, this preparation process does not require complex equipment and can achieve large-scale production, providing process feasibility support for the industrial application of vanadium-based metal-organic framework materials. At the same time, the prepared vanadium-based metal-organic framework materials can stably maintain their structural stability and adsorption separation performance, matching the application requirements in actual industrial scenarios.

[0052] In some embodiments, the vanadium source is selected from vanadium pentoxide and vanadium acetylacetonate. The acidic aqueous solution is prepared by mixing an organic acid with water. The organic acid is selected from at least one of acetic acid, propionic acid, and isobutyric acid. The volume ratio of the organic acid to water is 2-5:1.

[0053] In some embodiments, the molar ratio of vanadium source to organic ligand is 1:1-2.7. The mass ratio of vanadium source to acidic aqueous solution is 1:3-1200.

[0054] In some embodiments, the reaction temperature of the solvothermal reaction is 150-180°C, and the reaction time is 24-72 h.

[0055] In this embodiment of the invention, the selected vanadium source is adapted to an acidic aqueous solution system, which can effectively release the vanadium centers with coordination activity, forming a suitable coordination reaction basis with squaric acid as an organic ligand. The acidic aqueous solution prepared with a specific organic acid and water can stably control the acidic environment of the reaction system, promoting both the uniform dispersion and dissolution of the vanadium source and ensuring the structural stability and coordination activity of the squaric acid ligand. The precise setting of the ratios of vanadium source to organic ligand and vanadium source to acidic aqueous solution ensures sufficient contact between reactants and orderly coordination reactions, avoiding problems such as impure product phases and insufficient crystallinity caused by ligand residues or excessive reactants. The temperature and time range of the solvothermal reaction ensures a thorough and gentle reaction, promoting the complete formation of one-dimensional vanadium-oxygen chains and three-dimensional framework structures, and obtaining a highly crystalline product. The synergistic combination of the above parameters gives this preparation process excellent repeatability and stability, enabling the continuous preparation of vanadium-based metal-organic framework materials with regular structures and consistent performance. Furthermore, the strong adaptability of raw materials and the environmentally friendly system provide a reliable process guarantee for the large-scale preparation and industrial application of vanadium-based metal-organic framework materials.

[0056] Specifically, the present invention provides a method for preparing vanadium-based metal-organic framework materials, comprising: thoroughly mixing an organic acid and water to obtain an acidic aqueous solution; adding a vanadium source and an organic ligand to the acidic aqueous solution, stirring evenly, carrying out a solvothermal reaction at 150-180°C, and obtaining the vanadium-based metal-organic framework material after post-treatment after the reaction is completed.

[0057] The post-treatment process includes filtration, washing, and drying. Washing can be performed using any one of anhydrous methanol, ethanol, or acetone, followed by drying.

[0058] As a third aspect of the present invention, an application of a vanadium-based metal-organic framework material in the separation of straight-chain alkanes and their isomers is provided.

[0059] In some embodiments, the straight-chain alkane includes any one of n-butane, n-pentane, and n-hexane.

[0060] In this embodiment of the invention, the application of the vanadium-based metal-organic framework (MOF) material in the separation of straight-chain alkanes and their isomers utilizes the three-dimensional framework constructed by precise coordination and the structure of regular one-dimensional channels. This allows for the precise identification and efficient adsorption of straight-chain alkanes such as n-butane, n-pentane, and n-hexane through the size sieving effect of the channels. Simultaneously, because the spatial structure of the isomers of straight-chain alkanes is insufficiently compatible with the channels, they are difficult to adsorb, thus achieving efficient separation of straight-chain alkanes and their isomers. Combined with the excellent thermal, mechanical, and chemical stability of the vanadium-based MOF material, it maintains structural and adsorption performance stability during the separation process. Even after molding and processing, it maintains good separation performance, effectively avoiding the low separation efficiency problems caused by structural deactivation and insufficient selectivity in traditional separation materials. Furthermore, it meets the requirements of continuous operation and reusability in industrial separation scenarios, providing an efficient and stable solution for the large-scale and precise separation of straight-chain alkanes and their isomers, and possessing significant industrial application value.

[0061] Furthermore, before performing the separation of straight-chain alkanes and their isomers, the vanadium-based metal-organic framework (MOF) material needs to be activated. The core purpose of this activation is to remove residual water, acids, and low-boiling-point organic solvents such as anhydrous methanol, ethanol, and acetone from the pores of the MOF material, thereby clearing the pores and reserving effective pore volume to ensure the high efficiency of the subsequent hydrocarbon adsorption and separation process. The activation treatment can be performed using either of the following methods: firstly, vacuum drying at 120-200℃ and a vacuum degree of 0.001-0.1 torr for 2-12 hours; secondly, placing the MOF material in an oven and treating it continuously at 100-250℃ for at least 10 minutes.

[0062] In summary, this invention provides a vanadium-based metal-organic framework material, its preparation method, and its applications. The preparation method is simple, safe, and reliable, and can stably prepare vanadium-based metal-organic framework materials with high crystallinity and excellent thermal, mechanical, and chemical stability. Vanadium-based metal-organic framework materials, with their unique three-dimensional framework structure and precisely controlled one-dimensional micropores, possess the core capability to accurately identify and separate n-butane and its isomers, n-pentane and its isomers, and n-hexane and its isomers, which are extremely similar in size and shape. Compared to existing technologies such as 5A zeolite, this provides a new technical path for developing more efficient, highly selective, and energy-saving hydrocarbon purification solutions. It not only effectively solves traditional problems in the field of hydrocarbon separation but also injects new vitality into technological innovation and industrial upgrading in this field, possessing significant practical application value and broad industrialization prospects.

[0063] The present invention will be further illustrated below through embodiments and related test experiments. In the following detailed description, numerous specific details are set forth for ease of explanation to provide a comprehensive understanding of the embodiments of the present invention. However, it will be apparent that one or more embodiments may be practiced without these specific details. Moreover, the details in the following embodiments can be arbitrarily combined to form other feasible embodiments without conflict. All instruments, consumables, and reagents used in the following embodiments are commercially available unless otherwise specified.

[0064] Example 1

[0065] This embodiment 1 provides a vanadium-based metal-organic framework material, and the specific preparation process is as follows.

[0066] Take 1 mL of water, 3.25 mL of acetic acid, and 0.75 mL of propionic acid, and mix them thoroughly to obtain 5 mL of acidic aqueous solution. Add 1.824 g of squaric acid to this acidic aqueous solution and stir at room temperature until the squaric acid is fully dissolved; then add 1.092 g of vanadium pentoxide and continue stirring until the system is homogeneous. Transfer the above mixture to a 25 mL reaction vessel, seal it, and place the reaction vessel in a 150℃ oven for a constant temperature reaction for 24 h. After the reaction is completed, allow the reaction vessel to cool naturally to room temperature, and then collect, wash, and dry the product in the vessel to obtain the vanadium-based metal-organic framework material (denoted as V-SA).

[0067] Furthermore, the adsorption performance of the V-SA sample prepared in Example 1 was tested. Before testing, the V-SA needed to be activated; the activated sample was designated V-SA-ACT. The specific activation procedure was as follows: V-SA was vacuum-dried at 180°C under dynamic vacuum conditions for 2 hours to complete the activation.

[0068] Figure 4 The X-ray diffraction patterns of V-SA and V-SA-ACT in Embodiment 1 of the present invention are shown.

[0069] from Figure 4 It can be seen that the X-ray diffraction peaks of V-SA and V-SA-ACT are significantly different, corresponding to their different crystal systems and space groups: V-SA belongs to the orthorhombic crystal system with space group Pnma; V-SA-ACT belongs to the monoclinic crystal system with space group P21 / c. Comparing their unit cell volumes, the unit cell volume of V-SA (724.08 Å) is significantly larger. 3 The unit cell volume is greater than that of V-SA-ACT (685.97 Å). 3 This indicates that the unit cell of V-SA shrinks after activation treatment, resulting in a decrease in the corresponding pore size. This change in pore size is more suitable for the size of n-hexane, enabling specific adsorption of n-hexane.

[0070] Figure 5 In Example 1 of this invention, the pore volume and pore size distribution of V-SA-ACT were derived from the HK model based on the CO2 adsorption data of V-SA-ACT at 195K.

[0071] from Figure 5 As can be seen, this figure presents the pore volume and pore size distribution derived from the HK model based on V-SA-ACT CO2 adsorption data at 195 K. Calculations using the HK model show that the average pore size of V-SA-ACT is 0.4335 nm (approximately 4.36 Å), the most probable pore size is 0.4344 nm, and the micropore volume is 0.02045 cm³. 3 / g. Based on the definition of "pores with a pore size of less than 7 Å" for ultramicropores, the pore size of V-SA-ACT (4.36 Å) falls within the range of ultramicropore sizes. Therefore, it can be clearly stated that V-SA-ACT is an ultramicroporous metal-organic framework (MOF) material.

[0072] To test the structural stability of V-SA-ACT under different solvent environments, the following tests were conducted. V-SA-ACT was immersed in solvents such as acetonitrile (MECN), n-hexane (nHEX), acetone (ace), and dichloromethane (DCM) under a nitrogen atmosphere. After immersion for 24 hours, the samples were filtered and separated, then rapidly transferred to a powder X-ray diffraction (PXRD) apparatus for structural analysis. Routine PXRD data acquisition was performed using a Rigaku Miniflex diffractometer equipped with Cu Kα radiation (λ=1.54059Å) for basic structural characterization and diffraction peak comparison.

[0073] Figure 6 The image shows the powder X-ray diffraction patterns of V-SA-ACT in different solvents in Example 1 of this invention.

[0074] from Figure 6 It can be seen that the PXRD diffraction peaks of V-SA-ACT after immersion in different solvents such as acetone, acetonitrile, ethyl acetate, dichloromethane, and n-hexane all showed slight shifts or intensity changes compared to the unimmersed original sample. This phenomenon corresponds to the slight adjustment of the V-SA-ACT crystal structure caused by different solvent molecules entering the V-SA-ACT channels, proving that the framework of this V-SA-ACT material is not a rigid structure, but rather has significant framework stretching and flexibility in response to external solvent molecule stimulation, and can adapt to the size of different molecules through adaptive deformation of the channels.

[0075] To test the adsorption performance and cycling stability of V-SA-ACT for n-hexane at different temperatures, the following tests were conducted. V-SA-ACT samples were placed at 303 K and 423 K, and single-component adsorption equilibrium isotherms of hexane isomers (n-hexane (nHEX), 2,2-dimethylbutane (22DMB), 2,3-dimethylbutane (23DMB), 2-methylpentane (2MP), 3-methylpentane (3MP)) and benzene (BZ) and cyclohexane vapors were collected using a Belsarp Max X analyzer. Simultaneously, multiple cycling tests of V-SA-ACT for n-hexane adsorption at 303 K and 423 K were performed to verify its cycling stability. It should be noted that all solvents underwent degassing treatment through five freeze-pump-thaw cycles before the adsorption tests.

[0076] Figure 7This is a single-component adsorption isotherm diagram of V-SA-ACT at 303 K for the hexane isomer in Example 1 of the present invention. Figure 8 This is a single-component adsorption isotherm diagram of V-SA-ACT for hexane isomers at 423 K in Example 1 of the present invention. Figure 9 This is a test graph showing the cyclic performance of V-SA-ACT for the adsorption of n-hexane at 303K in Example 1 of the present invention. Figure 10 This is a test graph showing the cyclic performance of V-SA-ACT for the adsorption of n-hexane at 423K in Example 1 of the present invention.

[0077] from Figure 7 , Figure 8 It can be seen that V-SA-ACT has a significantly higher adsorption capacity for n-hexane (nHEX) at 303K and 423K than components such as 22DMB, 23DMB, 2MP, 3MP, BZ and cyclohexane, demonstrating high adsorption selectivity for n-hexane. At the same time, comparing the adsorption curves at different temperatures, V-SA-ACT still maintains effective adsorption capacity for n-hexane under high temperature (423K) conditions.

[0078] from Figure 9 , Figure 10 It can be seen that after five consecutive n-hexane adsorption-desorption cycles at 303K and 423K, V-SA-ACT did not show significant loss in adsorption capacity. This result confirms that V-SA-ACT has high structural and adsorption stability, and also means that this vanadium-based metal-organic framework material is easier to recycle and reuse in practical applications, and has good potential for industrial applications.

[0079] To test the separation performance of V-SA-ACT for mixtures of n-hexane and its isomers under actual separation conditions, the following tests were conducted. A laboratory-scale fixed-bed reactor was used, and multi-component column breakthrough measurements were performed at 303 K, 393 K, and 423 K.

[0080] The specific operation is as follows: 0.82g of V-SA sample was packed into a quartz column (inner diameter 4.0mm × length 300mm), and the voids inside the column were filled with glass wool treated with silane; the adsorbent was first purged with a helium flow of 20mL / min, and then the V-SA sample was activated overnight at 453K to obtain the V-SA-ACT sample; after activation, the helium flow was turned off, and another dry helium flow was turned on at the same time. An equimolar mixture of n-hexane (nHEX, 2.92mL), 3-methylpentane (3MP, 2.06mL), and 2,2-dimethylbutane (22DMB, 1.285mL) was introduced at a rate of 1mL / min to conduct a column breakthrough experiment.

[0081] Figure 11This is the chromatographic breakthrough curve of V-SA-ACT against an equimolar ternary mixture at 303K in Example 1 of the present invention. Figure 12 This is the chromatographic breakthrough curve of V-SA-ACT against an equimolar ternary mixture at 393K in Example 1 of the present invention. Figure 13 The chromatographic breakthrough cycle curve of V-SA-ACT against an equimolar ternary mixture at 423 K in Example 1 of this invention.

[0082] from Figure 11 , Figure 12 It can be seen that under the conditions of 303K and 393K, the breakthrough curves (C / C0) of branched isomers such as 22DMB and 3MP rapidly rise to 1.0, indicating that these branched isomers can be quickly eliminated by V-SA-ACT; while the breakthrough curve of n-hexane (nHEX) remains at C / C0=0 for a long time, and only shows a significant increase in the later stage. This phenomenon shows that V-SA-ACT can effectively separate nHEX from branched isomers, which is completely consistent with the high selective adsorption results of the material for nHEX in the single-component adsorption experiment.

[0083] from Figure 13 It can be seen that after three consecutive penetration measurements under the same conditions, the penetration curves of different cycles are basically consistent, demonstrating good experimental repeatability. This also confirms that V-SA-ACT has excellent regeneration performance and recycling capability.

[0084] To test the adsorption performance of V-SA-ACT on n-pentane, the following tests were conducted. Before the tests, the solvent containing the pentane isomers (n-pentane and 2-methylbutane (2MB)) was degassed through five cycles of freezing-pumping-thawing to ensure the accuracy of the adsorption tests. Using a Belsarp Max X analyzer, single-component adsorption equilibrium isotherm data for n-pentane and 2-methylbutane vapors were collected at 303K and 423K.

[0085] Figure 14 This is a single-component adsorption isotherm diagram of V-SA-ACT at 303K and 423K in Example 1 of the present invention for the pentane isomer.

[0086] from Figure 14 It can be seen that V-SA-ACT exhibits significant adsorption capacity for straight-chain n-pentane under both 303K and 423K conditions (especially at 303K); while for the branched isomer 2-methylbutane (2MB), the adsorption capacity remains close to zero. This result directly proves that V-SA-ACT has precise selectivity—adsorbing only straight-chain n-pentane and not its branched isomers.

[0087] To test the adsorption performance of V-SA-ACT for n-butane and isobutane, the following tests were conducted. Single-component adsorption equilibrium isotherms for the two butane isomers were measured using dedicated analytical instruments: the single-component adsorption equilibrium isotherm for n-butane was acquired using a BSD-660C A6C analyzer, and the single-component adsorption equilibrium isotherm for isobutane was measured using a BSD-660MC A3MC analyzer.

[0088] Figure 15 This is a single-component adsorption isotherm of V-SA-ACT on butane isomers at 303 K in Example 1 of the present invention.

[0089] from Figure 15 It can be seen that V-SA-ACT exhibits a significant adsorption capacity for straight-chain n-butane, and the adsorption capacity gradually stabilizes with increasing pressure; while for iso-butane, a branched isomer, the adsorption capacity remains close to zero. This result clearly demonstrates that V-SA-ACT has high structure selectivity—adsorbing only straight-chain n-butane and not branched isomers of butane.

[0090] To investigate the effect of temperature on the structural integrity and performance stability of V-SA, the following tests were conducted. 250 mg of V-SA sample was heated in air for 1 h at different temperatures and then activated under dynamic vacuum at 423 K for 2 h. The crystallinity and adsorption performance of the V-SA sample were characterized by powder X-ray diffraction (PXRD) and gas adsorption. PXRD data were collected using a Rigaku Miniflex diffractometer equipped with Cu Kα radiation (λ = 1.54059 Å) for basic characterization and comparative analysis of the V-SA sample's crystal structure. CO2 single-component adsorption isotherms were acquired at 298 K using a Micromeritics 3Flex analyzer to assess the stability of the V-SA sample's adsorption performance.

[0091] Figure 16 This is a powder X-ray diffraction pattern of V-SA before and after the air thermal stability test in Example 1 of the present invention. Figure 17 This is a CO2 isothermal adsorption curve of V-SA at 298K before and after the air thermal stability test in Example 1 of the present invention.

[0092] from Figure 16 It can be seen that after V-SA was heated in air at 50℃, 100℃, 150℃, 200℃ and 250℃, the position and intensity of its PXRD diffraction peaks remained consistent, indicating that even after heating at 250℃, the sample still maintained good crystallinity.

[0093] from Figure 17 It can be seen that the CO2 single-component adsorption isotherm trend of V-SA after heating at different temperatures at 298K is similar to that of the original sample, and the adsorption amount does not show a significant decrease.

[0094] comprehensive Figure 16 and Figure 17 The results show that V-SA can maintain good crystallinity and stable CO2 adsorption performance after treatment in an air environment at 250℃, proving that it has high air thermal stability.

[0095] To investigate the effects of air on the structural integrity and performance stability of V-SA, the following tests were conducted. V-SA samples were exposed to ambient air for extended periods, with samples taken at predetermined intervals (e.g., one week) (each sample being 250 mg), and activated under dynamic vacuum at 423 K for 2 hours. The crystallinity and adsorption performance of the V-SA samples were characterized by powder X-ray diffraction (PXRD) and gas adsorption. PXRD data were collected using a Rigaku Miniflex diffractometer equipped with Cu Kα radiation (λ=1.54059 Å) for basic characterization and comparative analysis of the V-SA sample crystal structure; CO2 single-component adsorption isotherms were acquired using a Micromeritics 3Flex analyzer at 298 K to assess the stability of the V-SA sample adsorption performance.

[0096] Figure 18 This is a powder X-ray diffraction pattern of V-SA before and after air stability testing in Example 1 of the present invention. Figure 19 This is a CO2 isothermal adsorption curve of V-SA at 298K before and after the air stability test in Example 1 of the present invention.

[0097] from Figure 18 It can be seen that after V-SA was exposed to ambient air for 2 and 3 weeks, the position and intensity of its PXRD diffraction peaks were basically the same as those of the original sample, indicating that even after long-term exposure to air, the sample still maintained good crystallinity.

[0098] from Figure 19 It can be seen that the CO2 single-component adsorption isotherms of V-SA after 2 and 3 weeks of air exposure are highly consistent with the trend of the original sample, and the adsorption amount does not show a significant decrease.

[0099] comprehensive Figure 18 and Figure 19The results show that V-SA maintains stable crystallinity and CO2 adsorption performance after long-term air exposure, proving that it has high air stability. This characteristic makes it exhibit good resistance to hydrolysis in air, which is in stark contrast to the previously reported vanadium-based metal-organic frameworks (V-MOFs) and demonstrates superior environmental adaptability.

[0100] To investigate the effects of different chemical reagents on the structural integrity and adsorption performance of V-SA, the following tests were conducted. 250 mg of V-SA sample was immersed in five different chemical reagents: ethanol, acetone, N,N-dimethylformamide (DMF), acetonitrile (MeCN), and methanol (MeOH), at room temperature for 24 h. After treatment, the sample was collected by filtration and activated under dynamic vacuum at 423 K for 2 h. The crystallinity and adsorption performance of the V-SA sample were characterized by powder X-ray diffraction (PXRD) and gas adsorption. PXRD data were collected using a Rigaku Miniflex diffractometer equipped with Cu Kα radiation (λ=1.54059 Å) for basic characterization and comparative analysis of the V-SA sample's crystal structure. CO2 single-component adsorption isotherms were acquired using a Micromeritics 3Flex analyzer at 298 K to assess the stability of the V-SA sample's adsorption performance.

[0101] Figure 20 This is a powder X-ray diffraction pattern of V-SA before and after chemical stability testing in Example 1 of the present invention. Figure 21 This is a CO2 isothermal adsorption curve of V-SA at 298K before and after the chemical stability test in Example 1 of the present invention.

[0102] from Figure 20 It can be seen that after V-SA was soaked in ethanol, acetone, DMF, MeCN and MeOH, the position and intensity of its PXRD diffraction peaks were basically the same as those of the original sample, indicating that the V-SA sample still maintained good crystallinity under the action of different chemical reagents.

[0103] from Figure 21 It can be seen that the CO2 single-component adsorption isotherm of V-SA after treatment with the above chemical reagents at 298K is highly consistent with the trend of the original sample, and the adsorption amount does not show significant decay.

[0104] comprehensive Figure 20 and Figure 21 The results show that V-SA maintains stable crystallinity and CO2 adsorption performance after being soaked in various chemical reagents, proving that it has high chemical stability.

[0105] To investigate the effect of externally applied pressure on the structural integrity and adsorption performance of V-SA, the following tests were conducted. 80 mg of V-SA sample was subjected to pressure applied at 0–24 tonnes / cm using a hydraulic press. 2 The uniaxial compressive force was gradually increased within a certain range. After compression treatment, the sample particles were ground uniformly and activated in a dynamic vacuum environment at 423 K for 2 h. The crystallinity and adsorption performance of the V-SA samples were characterized by powder X-ray diffraction (PXRD) and gas adsorption. PXRD data were collected using a Rigaku Miniflex diffractometer equipped with Cu Kα radiation (λ=1.54059Å). The full width at half maximum (FWHM) of the first sharp peak of the original sample was used as a reference to normalize and compare the broadening of the first sharp peak of the samples after different pressure treatments. CO2 single-component adsorption isotherms were acquired at 298 K using a Micromeritics 3Flex analyzer to evaluate the stability of the adsorption performance of the V-SA samples.

[0106] Figure 22 This is a powder X-ray diffraction pattern of V-SA before and after mechanical stability testing in Example 1 of the present invention. Figure 23 This is a standardized curve of the crystallization rate (with pressure as the variable) of the V-SA sample before and after the mechanical stability test in Example 1 of the present invention. Figure 24 This is a powder X-ray diffraction pattern of V-SA before and after mechanical stability testing in Example 1 of the present invention.

[0107] from Figure 22 It can be seen that V-SA ranges from 0 to 24 tonne / cm 2 After uniaxial compression treatment, the position and intensity of its PXRD diffraction peaks were basically consistent with those of the original sample, indicating that the sample still maintained excellent crystallinity even under different levels of pressure.

[0108] from Figure 23 It can be seen that as the pressure increases from 0 to 24 tonne / cm 2 The crystallization rate of V-SA remained close to 1.0 with only slight fluctuations, further confirming the stability of its crystal structure under pressure.

[0109] from Figure 24 It can be seen that the position and intensity of the PXRD diffraction peaks of V-SA treated with different pressures maintain excellent consistency, proving that it has high mechanical stability.

[0110] Considering the crucial role of the mechanical stability of MOF crystal structure in the molding process for large-scale applications, it can be seen that V-SA, after being compressed under different pressures, maintains both excellent crystallinity and stable CO2 adsorption performance, proving that it has high mechanical stability and can adapt to the molding and processing requirements in actual industrial scenarios.

[0111] To evaluate the thermal stability of V-SA under different temperature conditions, powder X-ray diffraction (PXRD) was performed using a Rigaku SmartLab diffractometer with a Cu Kα radiation source (radiation wavelength λ = 1.54178 Å). PXRD characteristic data at different temperatures were collected to analyze the effect of temperature changes on the material's crystal structure. Further thermogravimetric analysis (TGA) was conducted on V-SA using a Mettler Toledo thermal analyzer in an oxygen atmosphere at a heating rate of 5 °C / min.

[0112] Figure 25 The image shows powder X-ray diffraction patterns of V-SA at different temperatures in Example 1 of this invention.

[0113] from Figure 25 It can be seen that the position and intensity of the PXRD diffraction peaks of V-SA remain excellently consistent under different temperature conditions, including 25℃, 50℃, 75℃, 100℃, 125℃, 150℃, 175℃, 200℃, 225℃, 250℃, and 275℃. Even at 275℃, it still maintains excellent crystallinity, which directly proves that the V-SA sample possesses excellent thermal stability.

[0114] Figure 26 This is a thermogravimetric analysis diagram of V-SA in Embodiment 1 of the present invention.

[0115] from Figure 26 It can be seen that V-SA exhibits only a slight weight loss before the temperature rises to approximately 200℃; when the temperature reaches around 200℃, the weight decreases in stages and then stabilizes, with no significant change in weight observed further as the temperature rises to 800℃. This indicates that V-SA can maintain relative structural stability even at high temperatures, further demonstrating its excellent thermal stability.

[0116] Example 2

[0117] This embodiment 2 provides a vanadium-based metal-organic framework material, and the specific preparation process is as follows.

[0118] Take 2 mL of water, 6.5 mL of acetic acid, 0.5 mL of propionic acid, and 1 mL of isobutyric acid, and mix them thoroughly to obtain 10 mL of acidic aqueous solution. Add 0.026 g of squaric acid to this acidic aqueous solution and stir at room temperature until the squaric acid is completely dissolved; then add 0.011 g of vanadium pentoxide and continue stirring until the system is homogeneous. Transfer the above mixture to a 25 mL reaction vessel, seal it, and place the reaction vessel in a 150 °C oven for a constant temperature reaction for 72 h. After the reaction is completed, allow the reaction vessel to cool naturally to room temperature, and then collect, wash, and dry the product in the vessel to obtain a vanadium-based metal-organic framework material (denoted as V-SA-2).

[0119] Figure 27 This is an image of the V-SA-shaping molding prepared in an embodiment of the present invention.

[0120] To meet specific application requirements, the V-SA sample obtained in Example 1 was molded according to the structure of 5A molecular sieve. The specific molding process is as follows: A binder (including but not limited to polyvinyl alcohol (PVA), used in an amount of 10 wt% of the V-SA sample mass) and a dispersion medium of ethanol were mixed using a hand-made pot granulator. During the mixing process, the required amount of ethanol was sprayed into the system to promote particle growth, ultimately obtaining particles with a wide size distribution. The particles were then sieved, and particles with a 5mm specification were selected and tumbled using a tumbler mill to improve the sphericity of the particles, obtaining the molded sample (e.g., ...). Figure 27 As shown in the figure, it is denoted as V-SA-shaping.

[0121] To investigate the CO2 adsorption performance of V-SA samples in different forms, the following tests were conducted. The CO2 single-component adsorption isotherms of the V-SA samples were measured using a BSD-660M A3M|B3M analyzer; the CO2 single-component adsorption isotherms of the V-SA-2 sample were measured using a BSD-660MG A3MG analyzer; and the CO2 single-component adsorption isotherms of the V-SA-shaping sample were measured using a BSD-660MC A3MC analyzer.

[0122] Figure 28 The image shows the isothermal adsorption curves of CO2 at 195 K for V-SA, V-SA-2, and V-SA-shaping prepared in the embodiments of the present invention.

[0123] from Figure 28It can be seen that the V-SA-shaping sample exhibits similar CO2 adsorption isotherm characteristics to the original V-SA sample, and the adsorption capacities of both are at the same level. This experimental result fully confirms that the molding process used is significantly effective—it can effectively avoid the blockage of accessible pores in the V-SA material by binder molecules, ensuring the permeability of the material channels. In addition, both the original V-SA sample and the V-SA-2 sample exhibit regular and ideal CO2 single-component adsorption isotherms, further demonstrating the stability and reliability of the adsorption performance of this series of materials.

[0124] To investigate the n-hexane adsorption performance of V-SA samples in different forms, the following tests were conducted. V-SA samples were activated under dynamic vacuum at 453 K for 2 h before testing. V-SA-shaping samples were activated under dynamic vacuum at 453 K for 6 h before testing. Zeolite 5A samples were activated under dynamic vacuum at 473 K for 2 h before testing.

[0125] Figure 29 The image shows the isothermal adsorption curves of V-SA and V-SA-shaping prepared in the embodiments of the present invention, as well as zeolite 5A, on n-hexane at 423 K.

[0126] from Figure 29 It can be seen that the hexane adsorption isotherm trends of the V-SA sample and the V-SA-shaping sample at 423 K are highly consistent, and the adsorption capacity is at the same level. This indicates that the molding process did not significantly affect the hexane adsorption performance of the material, demonstrating the good molding scalability of V-SA. Combined with the previous experimental results, it can be seen that the material still maintains the specific selective performance of "adsorbing only straight-chain hexane (nHEX) and not adsorbing branched isomers".

[0127] Meanwhile, as a benchmark adsorbent material in industrial applications, zeolite 5A exhibits significantly lower hexane adsorption capacity at the same temperature (423 K) compared to the V-SA series samples. Quantitative comparison shows that the adsorption capacity of V-SA is 1.56 times that of zeolite 5A. This result fully demonstrates that V-SA not only possesses excellent selective adsorption capacity for straight-chain alkanes and good molding and processing performance, but its adsorption capacity is also superior to that of the existing industrial benchmark material zeolite 5A, showing significant application potential and substitution value in practical industrial separation scenarios.

[0128] Furthermore, to investigate the effects of different preparation processes, samples of Comparative Examples 1 to 5 were prepared and subjected to powder X-ray diffraction tests.

[0129] To further investigate the influence of different preparation process parameters on the material structure, this invention designed and prepared a series of samples, from Comparative Example 1 to Comparative Example 5. The crystal structure of each comparative example sample was systematically characterized and compared by powder X-ray diffraction (PXRD) to clarify the correlation between the preparation process and the material structure.

[0130] Comparative Example 1

[0131] Take 1 mL of water and 4 mL of acetic acid, and mix them thoroughly to obtain 5 mL of acidic aqueous solution. Add 0.684 g of squaric acid to this acidic aqueous solution and stir at room temperature until the squaric acid is completely dissolved; then add 0.546 g of vanadium pentoxide and continue stirring until the system is thoroughly mixed. Transfer the above mixture to a 25 mL reaction vessel, seal it, and place the reaction vessel in a 150 °C oven for 72 h of constant temperature reaction. After the reaction is completed, allow the reaction vessel to cool naturally to room temperature, and then collect, wash, and dry the product in the vessel to obtain the final sample of Comparative Example 1.

[0132] Comparative Example 2

[0133] Take 1 mL of water and 4 mL of acetic acid, and mix them thoroughly to obtain 5 mL of acidic aqueous solution. Add 0.57 g of squaric acid to this acidic aqueous solution and stir at room temperature until the squaric acid is completely dissolved; then add 0.364 g of vanadium pentoxide and continue stirring until the system is thoroughly mixed. Transfer the above mixture to a 25 mL reaction vessel, seal it, and place the reaction vessel in a 120 °C oven for 72 h of constant temperature reaction. After the reaction is completed, allow the reaction vessel to cool naturally to room temperature, and then collect, wash, and dry the product in the vessel to obtain the final sample of Comparative Example 2.

[0134] Comparative Example 3

[0135] Take 1 mL of water, 3 mL of acetic acid, and 1 mL of propionic acid, and mix them thoroughly to obtain 5 mL of acidic aqueous solution. Add 0.3705 g of squaric acid to this acidic aqueous solution and stir at room temperature until the squaric acid is completely dissolved; then add 0.424 g of VOSO4·xH2O and continue stirring until the system is thoroughly mixed. Transfer the above mixture to a 25 mL reaction vessel, seal it, and place the reaction vessel in a 150℃ oven for a constant temperature reaction for 72 h. After the reaction is completed, allow the reaction vessel to cool naturally to room temperature, and then collect, wash, and dry the product in the vessel to obtain the final sample of Comparative Example 3.

[0136] Comparative Example 4

[0137] Add 0.684 g of squaric acid to 5 mL of acetic acid and stir at room temperature until the squaric acid is completely dissolved. Then add 0.546 g of vanadium pentoxide and continue stirring until the system is homogeneous. Transfer the mixture to a 25 mL reaction vessel, seal it, and place the vessel in a 150 °C oven for 72 h. After the reaction is complete, allow the reaction vessel to cool naturally to room temperature. Collect the product in the vessel by suction filtration, wash, and dry it to obtain the final sample of Comparative Example 4.

[0138] Comparative Example 5

[0139] Take 1 mL of water and 4 mL of formic acid, and mix them thoroughly to obtain 5 mL of acidic aqueous solution. Add 0.684 g of squaric acid to this acidic aqueous solution and stir at room temperature until the squaric acid is completely dissolved; then add 0.546 g of vanadium pentoxide and continue stirring until the system is thoroughly mixed. Transfer the above mixture to a 25 mL reaction vessel, seal it, and place the reaction vessel in a 150 °C oven for 72 h of constant temperature reaction. After the reaction is completed, allow the reaction vessel to cool naturally to room temperature, and then collect, wash, and dry the product in the vessel to obtain the final sample of Comparative Example 5.

[0140] Figure 30 The above are powder X-ray diffraction patterns of V-SA and samples from Comparative Examples 1-5 in Example 1 of this invention.

[0141] from Figure 30 It can be seen that the PXRD diffraction peaks of the V-SA sample in Example 1 are sharp and intense, with regular peak shapes, indicating excellent crystallinity and a single phase. However, the PXRD patterns of the samples in Comparative Examples 1-5 show significant differences from the V-SA sample. In Comparative Example 1, in addition to the characteristic peaks of V-SA, impurity peaks appeared in the diffraction pattern, proving that when the key ratio parameters in the preparation process deviate from the range of the examples, the purity of the product phase decreases, making it impossible to obtain a single pure phase of V-SA. The diffraction pattern of Comparative Example 2 did not show the characteristic peaks of V-SA, but instead exhibited diffraction signals of other phases, indicating that adjusting the preparation temperature to a range not specified in the examples would trigger a phase transformation, preventing the formation of the target product V-SA. The diffraction pattern of Comparative Example 3 showed ligand-related characteristic peaks, but no obvious V-SA characteristic peaks, proving that when a metal source other than those specified in the examples was used, the reaction could not proceed sufficiently, resulting in a large number of ligands remaining unparticipated in the coordination reaction. In the diffraction pattern of Comparative Example 4, even though some diffraction peaks similar to V-SA appeared, their peak shapes were broadened and their intensities were significantly reduced. This indicates that using an acidic aqueous solution (not used in the examples) as a solvent severely affects the crystallinity of the product, leading to a decrease in crystallinity. The diffraction pattern of Comparative Example 5 also did not show the characteristic peaks of V-SA, but instead corresponded to other phases. This further proves that when the type or ratio of the acidic aqueous solution solvent deviates from the settings of the examples, it leads to a change in the phase composition of the reaction system, making it impossible to prepare the target V-SA product.

[0142] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. 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 method for preparing a vanadium-based metal-organic framework material, characterized in that, include: A vanadium-based metal-organic framework material was obtained by adding a vanadium source and an organic ligand to an acidic aqueous solution and carrying out a solvothermal reaction. The organic ligand is squaric acid; The vanadium source is selected from either vanadium pentoxide or vanadium acetylacetonate. The acidic aqueous solution is prepared by mixing organic acid and water; The organic acid is selected from at least one of acetic acid, propionic acid, and isobutyric acid; The molar ratio of the vanadium source to the organic ligand is 1:1-2.7; The mass ratio of the vanadium source to the acidic aqueous solution is 1:3-1200; The solvothermal reaction is carried out at a temperature of 150-180℃ for 24-72 hours.

2. A vanadium-based metal-organic framework material prepared by the method described in claim 1, characterized in that, The vanadium-based metal-organic framework material is a three-dimensional framework structure formed by one-dimensional vanadium-oxygen chains and squaric acid ligands connected by coordination bonds. The three-dimensional frame structure has one-dimensional channels.

3. The vanadium-based metal-organic framework material according to claim 2, characterized in that, The aperture of the one-dimensional channel is 3-7 Å.

4. The application of a vanadium-based metal-organic framework material as described in any one of claims 2-3 in the separation of straight-chain alkanes and their isomers.

5. The application according to claim 4, characterized in that, The straight-chain alkane includes any one of n-butane, n-pentane, and n-hexane.

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