Preparation method of siloxane cluster metal organic framework material and application in propane / propylene reverse separation

Abstract

The application discloses a preparation method of a siloxane cluster metal organic framework material and application thereof in propane / propylene reverse separation, and belongs to the technical field of chemical separation. By introducing Zn8(CH3COO)8-siloxane clusters, a series of metal organic framework materials (MOFs) with C3H8 selective adsorption are constructed. Compared with existing C3H8 selective adsorption MOFs, the MOFs prepared in the application all show significant improvement in six key indicators (adsorption kinetics, desorption kinetics, experimental separation potential Delta q, adsorption enthalpy Q st , cycle efficiency) required for evaluating industrial feasibility. Further, the MOFs obtained in the application can directly collect high-purity C3H6 (>= 99.5%) from a separation tower through a gas cylinder, effectively connecting the bridge between laboratory research and industrial actual application.

Description

Technical Field

[0001] This invention belongs to the field of chemical separation technology, and more specifically relates to a method for preparing a siloxane cluster metal-organic framework material and its application in propane / propylene reverse separation. Background Technology

[0002] Propylene (C3H6) is a core olefin feedstock supporting the development of polymer materials, fine chemicals, and other fields. More than 90% of it needs to be purified to a polymer-grade purity of over 99.5% before it can be used in the production of key products such as polypropylene and propylene oxide. Industrially, propylene is mainly produced through naphtha steam cracking (accounting for about 60%) and propane dehydrogenation (accounting for about 30%). Both processes inevitably introduce propane (C3H8) impurities into the products. Therefore, propylene / propane separation is a core link in the propylene industry chain that determines product quality and production costs.

[0003] The current mainstream industrial technology for propylene / propane separation is cryogenic distillation. Due to the similar physicochemical properties of these two gases, this technology requires continuous operation in a large distillation column with 120-180 trays under harsh conditions of 240-255 K and 0.3-0.6 MPa to achieve effective separation. This process is energy-intensive and costly, which does not align with the chemical industry's trend towards low-carbon and high-efficiency development. Developing energy-efficient alternative separation technologies has become a critical issue that the industry urgently needs to address. Adsorption separation technology based on porous materials offers advantages such as high efficiency, energy saving, and environmental friendliness, and is considered one of the most promising new separation technologies.

[0004] Most current research on metal-organic frameworks (MOFs) and porous materials such as zeolites typically utilizes the strong interactions between polar metal sites and unsaturated propylene molecules, leading to preferential propylene adsorption and efficient propylene / propane positive separation. However, propylene separation materials require multiple adsorption-desorption cycles to obtain high-purity propylene. In contrast, materials that preferentially adsorb propane can directly obtain high-purity propylene through a one-step adsorption process, reducing energy consumption by approximately 40%. However, research in this direction faces two major technological bottlenecks: First, the dipole moment of propane molecules is only 0.08D (far lower than propylene's 0.36D) and lacks unsaturated bonds, making it difficult to form strong interactions with the adsorption sites of MOFs, resulting in extreme difficulty in designing MOFs with high propane adsorption selectivity; second, currently only a few propane-selective MOFs exist, and all are "case-specific syntheses," lacking a generalizable and replicable construction strategy, severely limiting the transformation of such materials from laboratory research to industrial applications. Therefore, researching a general construction design strategy to achieve the synthesis of a series of C3H8 selective MOFs is of great significance. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing siloxane cluster metal-organic framework materials and their application in propane / propylene reverse separation, so as to solve the problems existing in the prior art. This invention constructs a series of MOFs with propane selective adsorption by introducing Zn8(CH3COO)8-siloxane clusters.

[0006] To achieve the above objectives, the present invention provides the following solution:

[0007] One of the technical solutions of this invention is to provide a siloxane cluster metal-organic framework material with the chemical formula Zn8[(MeSiO2)4]2(X)4, wherein X refers to a 2-linked dicarboxylic acid ester linker.

[0008] Preferably, the siloxane cluster is an 8-linked Zn8(CH3COO)8-siloxane cluster, composed of eight Zn atoms, each Zn center adopting a tetrahedral coordination geometry, and associated with two cyclic tetramers [(MeSiO2)4]. 4− The two oxygen atoms are bonded to two oxygen atoms from two dicarboxylic acid ester linkers; the Zn8(CH3COO)8-siloxane cluster is Zn8Si8O 16 Secondary structural unit, wherein each Zn8Si8O 16 The secondary structural unit acts as an 8-connection node, which is bridged by 2 connected dicarboxylic acid ester linkers to form a three-dimensional porous network.

[0009] Preferably, the siloxane cluster metal-organic framework material belongs to the monoclinic crystal system and has a space group of I2 / a.

[0010] The second technical solution of the present invention provides a method for preparing the above-mentioned siloxane cluster metal-organic framework material, comprising the following steps:

[0011] Zinc salt was dissolved in a mixed solution of methyltrimethoxysilane, acetic acid and ethanol to obtain siloxane cluster precursor solution A;

[0012] A rigid dicarboxylic acid ligand is dissolved in a solvent to obtain a mixture B; the siloxane cluster precursor solution A and the mixture B are mixed and reacted to obtain the siloxane cluster-based metal-organic framework material.

[0013] The rigid dicarboxylic acid ligands include bicyclo[1.1.1]pentane-1,3-dicarboxylic acid, bicyclo[2,2,2]octane-1,4-cyclohexanedicarboxylic acid, 2-methyl-1,4-phthalic acid, 2-(trifluoromethyl)terephthalic acid, 2,5-dimethyl-1,4-phthalic acid, 2-methoxyterephthalic acid, 2,5-diethoxyterephthalic acid, 2,2'-dimethyl-[1,1'-biphenyl]-4,4'-dicarboxylic acid, or 4,4'-(perfluoropropane-2,2-diyl)dibenzoic acid.

[0014] Preferably, the molar ratio of acetic acid to methyltrimethoxysilane is 2.8~3.5:1; the molar ratio of zinc salt to methyltrimethoxysilane is 0.5~1.2:1; and the volume ratio of ethanol to methyltrimethoxysilane is 17~27:1.

[0015] Preferably, the zinc salt comprises zinc nitrate.

[0016] Preferably, the molar ratio of the siloxane cluster precursor solution A to the rigid dicarboxylic acid ligand, based on Zn8 units, is 1:2 to 10; the solvent comprises a mixed solvent of N,N-dimethylformamide and triethylamine in a volume ratio of 1:0.2.

[0017] Preferably, the siloxane cluster precursor solution A and the mixture B are mixed by adding the mixture B dropwise to the siloxane cluster precursor solution A at a rate of 1~2 mL / min.

[0018] Preferably, the reaction temperature is 115°C and the reaction time is 48~72h.

[0019] The siloxane cluster-based metal-organic framework materials provided by this invention belong to the orthorhombic crystal system with space group I2 / a. By controlling the substituents of the ligands (such as cycloalkane skeletons, alkyl groups, and fluoroalkyl groups) and the ligand length, the resulting series of materials have a pore size range of 6.5–11.4 Å and a porosity range of 0.52–0.75 μm. 3 / g, and the structure of the zinc siloxane cluster remains intact in all materials. When short-chain linear dicarboxylic esters are used as linkers, a relatively open network structure can be formed, resulting in materials with large cavity pore sizes (10~11.4 Å) and high porosity (0.61~0.75 m). 3 / g). If the linker is further extended, for example using 2,2'-dimethyl-[1,1'-biphenyl]-4,4'-dicarboxylic acid, an interpenetrating framework structure will be formed, resulting in a decrease in porosity (0.52m). 3 / g). Furthermore, if angular linkers are used, such as 4,4'-(perfluoropropane-2,2-diyl)dibenzoic acid, frameworks with different topologies can be constructed with significantly reduced pore sizes (6.5 Å).

[0020] Unlike traditional strategies that enhance alkane selectivity by functionalizing organic linkers with nonpolar groups, this invention proposes a general method to achieve selective adsorption of C3H8 by integrating siloxane clusters into MOFs. Zn8Si8O 16 The triangularly arranged oxygen atoms on the cluster are strong adsorption sites for C3H8 and C3H6. Due to the different spatial orientations of the guest molecules C3H8 and C3H6, C3H8 adsorbs onto Zn8Si8O.16 The confinement interaction of oxygen atoms arranged in a triangular pattern on the cluster is stronger than that between C3H6 and Zn8Si8O. 16 The confined interaction of oxygen atoms arranged in a triangular pattern on the cluster. Therefore, the metal-organic framework material based on Zn8(CH3COO)8-siloxane cluster provided by this invention can selectively adsorb C3H8 from C3H6 / C3H8 mixed components, thereby obtaining high-purity C3H6.

[0021] The third technical solution of this invention provides the application of the above-mentioned siloxane cluster metal-organic framework material in the field of propylene / propane reverse separation.

[0022] The present invention discloses the following technical effects:

[0023] (1) Advantages of general strategy: It breaks through the limitations of the existing propane selective MOFs “case-by-case synthesis” and proposes “Zn8Si8O 16 The strategy of "cluster substitution of different dicarboxylic acid ligands" enables the targeted synthesis of a series of materials. This method allows for flexible control of pore structure and adsorption performance according to industrial separation requirements, providing a universal synthetic route for the design of propane-selective MOFs.

[0024] (2) Separation performance advantages: The C3H8 adsorption capacity of JNU-66-II synthesized in this invention is 137 cm⁻¹. 3 / g) and its separation potential in C3H8 / C3H6 (50 / 50, v / v) mixtures (Δq=28.8cm 3 The values ​​( / g) are the highest reported to date. This material can separate polymer-grade propylene (C3H6) with a purity ≥99.5% from C3H8 / C3H6 mixtures with volume ratios of 5 / 95 and 50 / 50 in a single adsorption step.

[0025] (3) Advantages in kinetics and energy consumption: The C3H8 adsorption diffusion coefficient of JNU-66-II synthesized in this invention is as high as 17.47×10. -6 cm 2 / s (Adsorption capacity reaches 78cm³ within 10 seconds) 3 / g), the desorption diffusion coefficient is 10.4×10 -8 cm 2 / s (desorption rate reaches 98% within 3 minutes), a single adsorption-desorption cycle can be completed in only 4 minutes; its measured adsorption enthalpy (Q) of C3H8 stThe Q of JNU-66-II is only 32.6 kJ / mol, which is significantly lower than the measured adsorption enthalpy of other C3H8 selective MOFs (FDMOF-2 (40.1 kJ / mol), HIAM-402 (40.4 kJ / mol), and PCP-IPA (47.5 kJ / mol)). st The value (32.6 kJ / mol) is significantly lower, which means that less energy is required for the regeneration of JNU-66-II.

[0026] (4) Stability advantage: Under 95% relative humidity, the adsorption performance of JNU-66-II synthesized in this invention did not decrease after 10 experiments; after 3000 C3H8 adsorption-desorption cycles, its adsorption capacity retention rate was still ≥98%.

[0027] (5) Advantages of large scale: Kilogram-level preparation is achieved. The large-scale breakthrough experiment of JNU-66-II at a scale of 0.54 kg showed that 54.6 ± 0.5 g of C3H6 with a purity ≥ 99.5% could be stably collected from the C3H8 / C3H6 (5 / 95, v / v) mixture every 10 cycles, which directly verified the feasibility of the material in industrial applications. Attached Figure Description

[0028] Figure 1 The graph shows the performance indicators of siloxane cluster metal-organic framework materials.

[0029] Figure 2 The crystal structure topology diagram of the siloxane cluster precursor in solution A is shown.

[0030] Figure 3 The crystal structure topology diagram of JNU-66-I;

[0031] Figure 4 The crystal structure topology diagram of JNU-66-II;

[0032] Figure 5 The crystal structure topology diagram of JNU-66-III;

[0033] Figure 6 The crystal structure topology diagram of JNU-66-IV;

[0034] Figure 7 The crystal structure topology diagram of JNU-66-V;

[0035] Figure 8 The crystal structure topology diagram of JNU-67;

[0036] Figure 9 The crystal structure topology diagram of JNU-68;

[0037] Figure 10 The images show powder X-ray diffraction patterns of siloxane cluster metal-organic framework materials, where (a) represents JNU-66-I, (b) represents JNU-66-II, (c) represents JNU-66-III, (d) represents JNU-66-IV, (e) represents JNU-66-V, (f) represents JNU-66-VI, (g) represents JNU-66-VII, (h) represents JNU-67, and (i) represents JNU-68.

[0038] Figure 11 The adsorption-desorption isotherms of N2 at 77 K for siloxane cluster metal-organic framework materials are shown, where (a) is JNU-66-I, (b) is JNU-66-II, (c) is JNU-66-III, (d) is JNU-66-IV, (e) is JNU-66-V, (f) is JNU-66-VI, (g) is JNU-66-VII, (h) is JNU-67, and (i) is JNU-68.

[0039] Figure 12 The adsorption-desorption isotherms of C3H6 and C3H8 based on siloxane cluster metal-organic framework materials at 298 K;

[0040] Figure 13 The measured isothermal adsorption heat Q of C3H6 and C3H8 based on siloxane cluster metal-organic framework materials. st Among them, (a) is JNU-66-I, (b) is JNU-66-II, (c) is JNU-66-III, (d) is JNU-66-IV, and (e) is JNU-66-V;

[0041] Figure 14 The results of adsorption and desorption kinetic tests of JNU-66-II for C3H8 at 298K are presented.

[0042] Figure 15 The figures are separation breakthrough curves based on siloxane cluster metal-organic framework materials, where (a) is the separation breakthrough curve (298K, 1 bar) of C3H6 / C3H8 (v:v = 50:50, total flow rate 1 mL / min) mixed gas based on siloxane cluster metal-organic framework materials, and (b) is the separation breakthrough curve of C3H6 / C3H8 (v:v = 50:50, total flow rate 1 mL / min) mixed gas under different humidity conditions according to JNU-66-II.

[0043] Figure 16 3000 C3H8 adsorption / desorption cycles were performed on JNU-66-II;

[0044] Figure 17The diagram shows the large-scale breakthrough experiment of NU-66-II, where (a) is a schematic diagram of the experimental setup, and (b), (c), and (d) are the results of the large-scale breakthrough experiment.

[0045] Figure 18 The diagram shows the adsorption mechanism of gas molecules C3H6 and C3H8 supported in situ on single crystals for experimental study. In the diagram, (a) and (b) represent JNU-66-III, and (c) and (d) represent JNU-66-IV.

[0046] Figure 19 The diagram shows the adsorption mechanism of in-situ powder-loaded gas molecules C3H6 and C3H8 in an experimental study. (a) represents JNU-66-I, (b) represents JNU-66-II, (c) represents JNU-66-III, (d) represents JNU-66-IV, and (e) represents JNU-66-V.

[0047] Figure 20 Figure 1 shows the results of in-situ infrared-supported gas molecules C3H6 and C3H8. In this figure, (a) represents the results of JNU-66-III adsorbing C3H8, and (b) represents the results of JNU-66-III adsorbing C3H6.

[0048] Figure 21 The figure shows the experimental results of in-situ Raman-supported gas molecules C3H6 and C3H8. In the figure, (a) represents the experimental results of JNU-66-III adsorbing C3H8, and (b) represents the experimental results of JNU-66-III adsorbing C3H6.

[0049] Figure 22 The figure shows the experimental results of in-situ differential scanning calorimetry for loading gas molecules C3H6 and C3H8. Detailed Implementation

[0050] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0051] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0052] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0053] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0054] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0055] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0056] The main raw materials and their sources in the various embodiments of this invention are as follows:

[0057] Bicyclo[1,1,1]pentane-1,3-dicarboxylic acid, CAS No.: 56842-95-6, Chemical formula: C7H8O4;

[0058] Bicyclo[2,2,2]octane-1,4-cyclohexanedicarboxylic acid, CAS No.: 711-02-4, Chemical Formula: C 10 H 14 O4;

[0059] 2-Methyl-1,4-phthalic acid, CAS No.: 5156-01-4, Chemical formula: C9H8O4;

[0060] 2-(trifluoromethyl)terephthalic acid, CAS No.: 1483-47-2, Chemical formula: C9H5F3O4;

[0061] 2,5-Dimethyl-1,4-phthalic acid, CAS No.: 6051-66-7, Chemical Formula: C 10 H 10 O4;

[0062] 2-Methoxyterephthalic acid, CAS No.: 5156-00-3, Chemical Formula: C9H8O5;

[0063] 2,5-Diethoxyterephthalic acid, CAS No.: 105338-33-8, Chemical Formula: C 12 H 14 O6;

[0064] 2,2'-Dimethyl-[1,1'-biphenyl]-4,4'-dicarboxylic acid, CAS No.: 117490-52-5, Chemical Formula: C 16 H 14 O4;

[0065] 4,4'-(perfluoropropane-2,2-diyl)dibenzoic acid, CAS No.: 1171-47-7, Chemical Formula: C 17 H 10 F6O4;

[0066] Zn(NO3)2·6H2O, CAS No.: 10196-18-6, Chemical Formula: N2O6Zn;

[0067] N,N-Dimethylformamide (DMF), CAS No.: 68-12-2, Chemical Formula: C3H7NO;

[0068] Acetic acid (HOAc), CAS No.: 64-19-7, Chemical formula: C2H4O2;

[0069] Ethanol (EtoH), CAS No.: 64-17-5, Chemical Formula: C2H6O;

[0070] Triethylamine, CAS No.: 121-44-8, Chemical Formula: C6H 15 N;

[0071] All of the above raw materials are commercially available conventional chemical raw materials, and all are of laboratory analytical grade.

[0072] Unless otherwise specified, all other raw materials used are commercially available products, and the source of these commercially available products does not affect the technical effect of this invention.

[0073] Unless otherwise specified, the room temperature involved in this invention is 25±5℃.

[0074] Example 1

[0075] This embodiment provides a specific preparation process for siloxane cluster metal-organic framework materials:

[0076] MeSi(OMe)3 (4.3 mL, 30.2 mmol), HOAc (5.2 mL, 90.7 mmol), and Zn(NO3)2·6H2O (6.0 g, 20.1 mmol) were mixed and dissolved in 75 mL of anhydrous ethanol and stirred at room temperature for 30 minutes. Then, DMF (41.4 mL), triethylamine (8.4 mL, 60 mmol), and bicyclo[1,1,1]pentane-1,3-dicarboxylic acid (1.87 g, 12.0 mmol) were added. The solution gradually became turbid within 10 minutes. After stirring for another hour, the reaction mixture was transferred to a 350 mL sealed glass bottle and heated at 115 °C for 48 hours. After the reaction was complete, the mixture was cooled to room temperature, and the resulting crystals were collected and washed with DMF and acetone to obtain the metal-organic framework material JNU-66-I.

[0077] MeSi(OMe)3 (3.225 mL, 22.65 mmol), HOAc (3.9 mL, 68 mmol), and Zn(NO3)2·6H2O (4.5 g, 15.075 mmol) were mixed and dissolved in 56.25 mL of anhydrous ethanol and stirred at room temperature for 30 minutes. Then, DMF (31.05 mL), triethylamine (6.3 mL, 45 mmol), and bicyclo[2,2,2]octane-1,4-cyclohexanedicarboxylic acid (1.784 g, 9 mmol) were added. The solution gradually became turbid within 10 minutes. After stirring for another hour, the reaction mixture was transferred to a 350 mL sealed glass bottle and heated at 115 °C for 48 hours. After the reaction was complete, the mixture was cooled to room temperature, and the resulting crystals were collected and washed with DMF and acetone to obtain the metal-organic framework material JNU-66-II.

[0078] MeSi(OMe)3 (3.225 mL, 22.65 mmol), HOAc (3.9 mL, 68 mmol), and Zn(NO3)2·6H2O (4.5 g, 15.075 mmol) were mixed and dissolved in 56.25 mL of anhydrous ethanol and stirred at room temperature for 30 minutes. Then, DMF (28 mL), triethylamine (5.6 mL, 40 mmol), and 2-methyl-1,4-phthalic acid (2.16 g, 12 mmol) were added. The solution gradually became turbid within 10 minutes. After stirring for another hour, the reaction mixture was transferred to a 350 mL sealed glass bottle and heated at 115 °C for 48 hours. After the reaction was complete, the mixture was cooled to room temperature, and the resulting crystals were collected and washed with DMF and acetone to obtain the metal-organic framework material JNU-66-III.

[0079] MeSi(OMe)3 (4.3 mL, 30.2 mmol), HOAc (5.2 mL, 90.7 mmol), and Zn(NO3)2·6H2O (6.0 g, 20.1 mmol) were mixed and dissolved in 75 mL of anhydrous ethanol, and stirred at room temperature for 30 minutes. Then, DMF (41.4 mL), triethylamine (8.4 mL, 60 mmol), and 2-(trifluoromethyl)terephthalic acid (4.21 g, 18 mmol) were added. The solution gradually became turbid within 10 minutes. After stirring for another hour, the reaction mixture was transferred to a 350 mL sealed glass bottle and heated at 115 °C for 48 hours. After the reaction was complete, the mixture was cooled to room temperature, and the resulting crystals were collected and washed with DMF and acetone to obtain the metal-organic framework material JNU-66-IV.

[0080] MeSi(OMe)3 (2.15 mL, 15.6 mmol), HOAc (2.6 mL, 45.35 mmol), and Zn(NO3)2·6H2O (3.0 g, 10.05 mmol) were mixed and dissolved in 37.5 mL of anhydrous ethanol and stirred at room temperature for 30 minutes. Then, DMF (20.7 mL), triethylamine (4.2 mL, 30 mmol), and 2,5-dimethyl-1,4-phthalic acid (2.33 g, 12 mmol) were added. The solution gradually became turbid within 10 minutes. After stirring for another hour, the reaction mixture was transferred to a 350 mL sealed glass bottle and heated at 115 °C for 48 hours. After the reaction was complete, the mixture was cooled to room temperature, and the resulting crystals were collected and washed with DMF and acetone to obtain the metal-organic framework material JNU-66-V.

[0081] MeSi(OMe)3 (2.15 mL, 15.6 mmol), HOAc (2.6 mL, 45.35 mmol), and Zn(NO3)2·6H2O (3.0 g, 10.05 mmol) were mixed and dissolved in 37.5 mL of anhydrous ethanol and stirred at room temperature for 30 minutes. Then, DMF (20.7 mL), triethylamine (4.2 mL, 30 mmol), and 2-methoxyterephthalic acid (2.35 g, 12 mmol) were added. The solution gradually became turbid within 10 minutes. After stirring for another hour, the reaction mixture was transferred to a 350 mL sealed glass bottle and heated at 115 °C for 48 hours. After the reaction was complete, the mixture was cooled to room temperature, and the resulting crystals were collected and washed with DMF and acetone to obtain the metal-organic framework material JNU-66-VI.

[0082] MeSi(OMe)3 (2.15 mL, 15.6 mmol), HOAc (2.6 mL, 45.35 mmol), and Zn(NO3)2·6H2O (4.5 g, 15.075 mmol) were mixed and dissolved in 56.25 mL of anhydrous ethanol and stirred at room temperature for 30 minutes. Then, DMF (20.7 mL), triethylamine (4.2 mL, 30 mmol), and 2,5-diethoxyterephthalic acid (2.288 g, 9 mmol) were added. The solution gradually became turbid within 10 minutes. After stirring for another hour, the reaction mixture was transferred to a 350 mL sealed glass bottle and heated at 115 °C for 48 hours. After the reaction was complete, the mixture was cooled to room temperature, and the resulting crystals were collected and washed with DMF and acetone to obtain the metal-organic framework material JNU-66-VII.

[0083] MeSi(OMe)3 (2.15 mL, 15.6 mmol), HOAc (2.6 mL, 45.35 mmol), and Zn(NO3)2·6H2O (3.0 g, 10.05 mmol) were mixed and dissolved in 37.5 mL of anhydrous ethanol and stirred at room temperature for 30 minutes. Then, DMF (41.4 mL), triethylamine (8.4 mL, 60 mmol), and 2,2'-dimethyl-[1,1'-biphenyl]-4,4'-dicarboxylic acid (2.16 g, 8 mmol) were added. The solution gradually became turbid within 10 minutes. After stirring for another hour, the reaction mixture was transferred to a 350 mL sealed glass bottle and heated at 115 °C for 48 hours. After the reaction was complete, the mixture was cooled to room temperature, and the resulting crystals were collected and washed with DMF and acetone to obtain the metal-organic framework material JNU-67.

[0084] MeSi(OMe)3 (4.3 mL, 30.2 mmol), HOAc (5.2 mL, 90.7 mmol), and Zn(NO3)2·6H2O (6.0 g, 20.1 mmol) were mixed and dissolved in 75 mL of anhydrous ethanol and stirred at room temperature for 30 minutes. Then, DMF (41.4 mL), triethylamine (8.4 mL, 60 mmol), and 4,4'-(perfluoropropane-2,2-diyl)benzoic acid (3.14 g, 8 mmol) were added. The solution gradually became turbid within 10 minutes. After stirring for another hour, the reaction mixture was transferred to a 350 mL sealed glass bottle and heated at 115 °C for 48 hours. After the reaction was complete, the mixture was cooled to room temperature, and the resulting crystals were collected and washed with DMF and acetone to obtain the metal-organic framework material JNU-68.

[0085] Figure 2 This is a topological diagram of the crystal structure of the siloxane cluster precursor in solution A. Figure 3This is the crystal structure topology diagram of JNU-66-I. Figure 4 This is the crystal structure topology diagram of JNU-66-II. Figure 5 This is the crystal structure topology diagram of JNU-66-III. Figure 6 This is the crystal structure topology diagram of JNU-66-IV. Figure 7 This is the crystal structure topology diagram of JNU-66-V. Figure 8 This is the crystal structure topology diagram of JNU-67. Figure 9 This is the crystal structure topology diagram of JNU-68.

[0086] 1. Structural characterization of the material obtained in Example 1:

[0087] (1) Single crystal experiments: Crystallographic data of synthesized JNU-66-I, JNU-66-II, JNU-66-III, JNU-66-IV, JNU-66-V, JNU-66-VI, JNU-66-VII, JNU-67, and JNU-68 samples were collected at 100 K using an XtaLAB PROMM007-DW (Cu / Mo) X-ray generator and a HyPix-6000HE hybrid photon counting (HPC) detector (Rigaku Corporation, Japan, CuKα,λ=1.54056Å). The results are shown in Tables 1, 2, and 3. X-ray single-crystal diffraction data were collected in ω-scan mode on an XtaLAB PRO MM007-DW single-crystal diffractometer system. The X-ray generator used was RA-Micro7HF-MR-DW (Cu / Mo), and the detector was HyPix-6000HE HybridPhoton Counting (HPC).

[0088] Table 1. Crystallographic data of synthesized JNU-66-I, JNU-66-II, and JNU-66-III samples.

[0089] JNU-66-I JNU-66-II JNU-66-III CCDC number 2448668 248669 2486670 Empirical molecular formula <![CDATA[C 54 A 72 O 48 Si 12 Zn 12 ]]> <![CDATA[C 72 A 108 O 49 Si 12 Zn 12 ]]> <![CDATA[C 66 A 72 O 48 Si 12 Zn 12 ]]> Space Group <![CDATA[I2 / a]]> <![CDATA[I2 / a]]> <![CDATA[I2 / a]]> Crystal system monoclinic monoclinic monoclinic temperature 100 K 100 K 100 K a (Å) 29.7238 (7) 33.3523 (6) 31.7821 (3) b (Å) 39.6794 (10) 41.4614 (7) 42.2299 (4) c (Å) 31.4049 (6) 31.2272 (5) 33.2478 (3) α (deg) 90 90 90 β (deg) 93.215 92.6960 93.6906 γ (deg) 90 90 90 <![CDATA[V (Å) 3 ]]> 36981.4 (15) 43134.2 (13) 44531.2 (7) Z 8 8 8 <![CDATA[Theoretical density / g / cm 3 > 0.937808 0.886722 0.821809 <![CDATA[Absorption coefficient / mm -1 > 2.826 2.459 2.366 Final R R1=0.0619 R1=0.0742 R1=0.0562 [I>2 sigma (I)] wR1=0.1823 wR1=0.2242 wR1=0.1734 GooF 1.032 0.918 1.087 Completeness 100% 100% 99% radiation source Copper (Cu) Copper (Cu) Copper (Cu)

[0090] Table 2. Crystallographic data of the synthesized JNU-66-IV, JNU-66-V, and JNU-66-VI samples.

[0091] JNU-66-IV JNU-66-V JNU-66-VI CCDC number 2448675 248676 2448677 Empirical molecular formula <![CDATA[C 66 A 54 F 18 O 48 Si 12 Zn 12 ]]> <![CDATA[C 72 A 84.5 O 48 Si 12 Zn 12 ]]> <![CDATA[C 66 A 72 O 54 Si 12 Zn 12 ]]> Space Group <![CDATA[I2 / a]]> <![CDATA[I2 / a]]> <![CDATA[I2 / a]]> Crystal system monoclinic monoclinic monoclinic temperature 100 K 100 K 100 K a (Å) 31.8302 (4) 31.8290 (3) 31.4723 (3) b (Å) 42.4148 (5) 42.2501 (4) 41.7698 (6) c (Å) 33.1541 (4) 33.1728 (2) 33.7872 (5) α (deg) 90 90 90 β (deg) 93.8680 94.2520 92.6726 γ (deg) 90 90 90 <![CDATA[V (Å) 3 ]]> 44658.4 (9) 44487.3 (7) 44368.1 (10) Z 8 8 8 <![CDATA[Theoretical density / g / cm 3 > 0.915792 0.847909 0.853572 <![CDATA[Absorption coefficient / mm -1 > 2.519 2.378 2.407 Final R R1=0.0935 R1=0.0689 R1=0.0839 [I>2 sigma (I)] wR1=0.2752 wR1=0.2122 wR1=0.2881 GooF 1.100 1.106 1.125 Completeness 99% 100% 100% radiation source Copper (Cu) Copper (Cu) Copper (Cu)

[0092] Table 3. Crystallographic data of the synthesized JNU-66-VII, JNU-67, and JNU-68 samples.

[0093] JNU-66-VII JNU-67 JNU-68 CCDC number 2448679 2448680 2448678 Empirical molecular formula <![CDATA[C 168 A 216 O 120 Si 24 Zn 24 ]]> <![CDATA[C 434 A 435 O 196 Si 48 Zn 48 ]]> <![CDATA[C 38 H 30 F 12 O 17 Si4Zn4]]> Space Group <![CDATA[I2 / a]]> <![CDATA[I2 / a]]> <![CDATA[I2 / a]]> Crystal system monoclinic monoclinic monoclinic temperature 100 K 100 K 100 K a (Å) 31.8546 (3) 38.7711 (5) 15.5786 (2) b (Å) 42.8203 (3) 39.4498 (6) 44.0454 (5) c (Å) 33.0465 (4) 39.5524 (5) 53.1862 (5) α (deg) 90 60.2290 (10) 90 β (deg) 94.2402 67.5480 (10) 90 γ (deg) 90 60.6770 (10) 90 <![CDATA[V (Å) 3 ]]> 44952.8 (9) 45007.4 (12) 36494.5 (7) Z 4 1 16 <![CDATA[Theoretical density / g / cm 3 > 0.945450 0.979438 0.990450 <![CDATA[Absorption coefficient / mm -1 > 2.438 2.415 2.263 Final R R1=0.1025 R1 = 0.1152 R1 = 0.0723 [I>2 sigma (I)] wR1=0.2758 wR1 = 0.2990 wR1 = 0.2246 GooF 1.065 1.120 1.063 Completeness 96% 99% 99.4% radiation source Copper (Cu) Copper (Cu) Copper (Cu)

[0094] The crystal structure topology of siloxane cluster metal-organic framework materials is shown in the figure below. Figures 2-9 As shown, JNU-66-I, JNU-66-II, JNU-66-III, JNU-66-IV, and JNU-66-V have the same structure, all using 8-linked zinc siloxane clusters as structural nodes and 2-linked dicarboxylic acid esters as linkers. When the linkers are further extended, for example using 2,2'-dimethyl-[1,1'-biphenyl]-4,4'-dicarboxylic acid, an interpenetrating framework (JNU-67) is formed. If angle-restricted linkers are used, such as 4,4'-(perfluoropropane-2,2-diyl)benzoic acid, a framework with a different topology, JNU-68, can be constructed.

[0095] 2. Performance testing was performed on the material obtained in Example 1:

[0096] Figure 10 The images show powder X-ray diffraction (PXRD) spectra of siloxane cluster metal-organic framework materials, where (a) represents JNU-66-I, (b) JNU-66-II, (c) JNU-66-III, (d) JNU-66-IV, (e) JNU-66-V, (f) JNU-66-VI, (g) JNU-66-VII, (h) JNU-67, and (i) JNU-68. Figure 10 As can be seen, the synthesized JNU-66-I, JNU-66-II, JNU-66-III, JNU-66-IV, JNU-66-V, JNU-66-VI, JNU-66-VII, JNU-67, and JNU-68 samples are in good agreement with the simulated PXRD spectra, proving that each sample has high phase purity.

[0097] The N2 adsorption of Zn8(CH3COO)8-siloxane cluster metal-organic framework materials was tested at 77 K using a Micromeritics ASAP 2020 Plus Accelerated Surface Area and Porosimetry adsorption analyzer. The N2 isotherm adsorption curves are shown below. Figure 11 As shown. Figure 11 The images show the N2 adsorption-desorption isotherms at 77 K for siloxane cluster metal-organic framework materials, where (a) represents JNU-66-I, (b) JNU-66-II, (c) JNU-66-III, (d) JNU-66-IV, (e) JNU-66-V, (f) JNU-66-VI, (g) JNU-66-VII, (h) JNU-67, and (i) JNU-68. Figure 11It can be seen that the pore size range of siloxane cluster metal-organic framework materials is 6.5~11.4 Å, and the porosity ranges from 0.52~0.75 μm. 3 / g.

[0098] Isothermal adsorption curves of C3H6 and C3H8 at 298 K based on siloxane cluster metal-organic framework materials are shown below. Figure 12 As shown. Figure 12 The figure shows the adsorption-desorption isotherms of C3H6 and C3H8 based on siloxane cluster metal-organic frameworks at 298 K. As can be seen from the figure, JNU-66-I, JNU-66-II, JNU-66-III, JNU-66-IV, JNU-66-V, and JNU-68 all exhibit higher C3H8 adsorption capacities than C3H6, directly demonstrating that this series of MOFs has a stronger affinity for C3H8, providing key performance support for achieving reverse separation of propylene / propane. Under the standard test conditions of 298 K and 1.0 bar, JNU-66-II achieved a C3H8 adsorption capacity of 137 cm⁻¹. 3 / g, significantly superior to currently reported C3H8 selective MOF materials. JNU-67 exhibits low C3H8 adsorption selectivity in the low-pressure range (<0.3 bar), while losing selectivity in the high-pressure range (>0.3 bar).

[0099] The isothermal adsorption heats of C3H8 and C3H6 in the synthesized JNU-66-I, JNU-66-II, JNU-66-III, JNU-66-IV, and JNU-66-V samples were determined by differential scanning calorimetry (DSC), and the results are as follows: Figure 13 As shown. Figure 13 The measured isothermal adsorption heat Q of C3H6 and C3H8 based on siloxane cluster metal-organic framework materials. st Among them, (a) is JNU-66-I, (b) is JNU-66-II, (c) is JNU-66-III, (d) is JNU-66-IV, and (e) is JNU-66-V. As shown in the figure, JNU-66-I, JNU-66-II, JNU-66-III, JNU-66-IV, and JNU-66-V all exhibit a higher isothermal adsorption heat of C3H8 than that of C3H6. This energy difference indicates that JNU-66-II has a preferential adsorption affinity for C3H8, while also having lower regeneration energy consumption, meeting the requirements for low regeneration energy consumption in industrial applications.

[0100] The kinetic adsorption and desorption behavior of C3H8 on JNU-66-II was determined by gravimetric method. The results are as follows: Figure 14 As shown. Figure 14The figure shows the adsorption and desorption kinetics of C3H8 by JNU-66-II at 298 K. As can be seen from the figure, the adsorption capacity of C3H8 by JNU-66-II reaches 78 cm⁻¹ within 10 seconds. 3 / g, the adsorption-diffusion coefficient of C3H8 was obtained by quantitative calculation as 17.47×10. -6 cm 2 / s; Within 3 minutes, the adsorbed C3H8 release rate was approximately 98%, and the corresponding desorption diffusion coefficient was estimated to be 10.4 × 10⁻⁶. - 8 cm 2 / s.

[0101] The synthesized JNU-66-I, JNU-66-II, JNU-66-III, JNU-66-IV, and JNU-66-V samples were subjected to breakthrough experiments of C3H8 / C3H6 mixed components at room temperature. Specifically, 1.0 g of activated JNU-66-I, JNU-66-II, JNU-66-III, JNU-66-IV, and JNU-66-V series samples were packed into a custom-made stainless steel column (3.15 mm inner diameter × 200 mm length), and the void space was filled with silica cotton. The adsorbent was activated in situ in the column at 353 K and high vacuum (5–6 μmHg) for 12 hours. After activation, helium gas was introduced at a flow rate of 20 mL / min to purge the adsorbent. Then, the helium flow was stopped, and a C3H8 / C3H6 (50:50, v:v) mixed gas was allowed to flow into the column (total flow rate of the mixed gas was 1 mL / min). The results are as follows Figure 15 As shown.

[0102] Depend on Figure 15 As shown in (a), JNU-66-I, JNU-66-II, JNU-66-III, JNU-66-IV, and JNU-66-V can all efficiently separate C3H8 / C3H6 (50:50, v / v) gas mixtures, with C3H6 penetrating the column first, directly yielding high-purity C3H6. Among all materials, JNU-66-II exhibits the best performance, with the largest breakthrough window, achieving a C3H6 (≥99.5%) yield as high as 19.4 cm⁻¹. 3 / g.

[0103] To further evaluate the effect of water vapor on the separation performance of JNU-66-II, breakthrough experiments were conducted under different humidity conditions. The results are presented by... Figure 15 As shown in (b), the breakthrough curves of C3H8 / C3H6 (50:50, v / v) were almost identical under different relative humidity (RH), indicating that water vapor had minimal impact on the separation performance of JNU-66-II.

[0104] To evaluate its long-term stability under actual operating conditions, we conducted 3000 C3H8 adsorption / desorption cycles on the JNU-66-II material. The results showed that its adsorption capacity remained stable with almost no significant decrease (e.g., ...). Figure 16 ).

[0105] Considering the scalability of JNU-66-II synthesis and its excellent separation potential, a large-scale breakthrough experiment was further conducted on 0.54 kg of JNU-66-II and a gas cylinder collector. The experimental setup is shown in the figure below. Figure 17 As shown in (a). The specific experimental procedure was as follows: In the early stage of the experiment, 0.54 kg of JNU-66-II was synthesized and activated by solvothermal method. An experimental apparatus containing a stainless steel fixed bed adsorption column, a gas chromatography detection system and an 8L gas cylinder collection system was built. Two volume ratios of C3H8 / C3H6 mixed gas, 50 / 50 and 5 / 95, were prepared. During the experiment, the mixed gas was introduced at a flow rate of 60 mL / min. The outlet gas concentration was monitored in real time by gas chromatography to obtain the breakthrough curve. Polymer-grade C3H6 with a purity ≥99.5% was collected. After adsorption saturation, the cycle was completed by vacuum regeneration. The results are as follows. Figure 17 As shown in (b), (c), and (d).

[0106] Depend on Figure 17 As shown in (b), at a temperature of 298 K, a C3H8 / C3H6 (50 / 50) mixed gas can be passed through 0.54 kg of JNU-66-II material to obtain propylene with a purity of ≥99.5%.

[0107] Depend on Figure 17 As shown in (c), at a temperature of 298 K, a C3H8 / C3H6 (5 / 95) mixed gas can be passed through 0.54 kg of JNU-66-II material to obtain propylene with a purity of ≥99.5%.

[0108] Depend on Figure 17 As shown in (d), when the C3H8 / C3H6 mixed gas ratio is 5 / 95, and the experiment is carried out continuously for 10 times at a flow rate of 60 mL / min, an average of 54.6 ± 0.5 g of high-purity propylene (≥99.5%) can be obtained each time.

[0109] The study achieved an average yield of 54.6 g of high-purity C3H6 (≥99.5%) from a C3H8 / C3H6 (5:95, v / v) mixture in 10 consecutive trials. This result marks the first time that propylene purification using a kilogram-scale adsorbent combined with gas cylinder collection has been achieved, directly verifying the feasibility of industrial application.

[0110] 3. Mechanism explanation for the material properties obtained in Example 1:

[0111] (1) In-situ single crystal experiments: JNU-66 series crystals (JNU-66-III, JNU-66-IV) were exposed to the corresponding gases (C3F6 and C3F8) at room temperature and about 1 bar for 3 hours to load the gas, and then their single crystal data were collected at the same low temperature of 100K. The results showed that only JNU-66-III and JNU-66-V obtained high-quality data that could be used for structural analysis. The binding sites of C3H8 and C3H6 were determined by atomic occupancy and equivalent isotropic displacement parameter (U eq The crystal structure was determined using the Olex2 platform and ShelXT program. The structure was solved using the eigenphase method, and refined using the least squares method. The analytical results are as follows: Figure 18 As shown. By Figure 18 It can be seen that both C3H8 and C3H6 molecules preferentially bind to Zn8Si8O. 16 The O atom sites with surface triangular coordination show that C3H8 forms 3 CH∙∙∙O hydrogen bonds with O atoms (bond length 2.68~2.82 Å), while C3H6 forms only 2 CH∙∙∙O hydrogen bonds (bond length 2.91~3.05 Å), proving that C3H8 has a stronger interaction with the framework and providing direct structural evidence for the preferential adsorption of C3H8.

[0112] (2) In-situ powder X-ray diffraction experiment: In this experiment, in-situ X-ray powder diffraction (PXRD) analysis was performed using a Panalytical Empyrean equipped with a 1Der detector and a Cu X-ray tube (λ=1.54056Å), and gas adsorption experiments were conducted using an AntonPaar TTK 600 in-situ heating stage. C3H6 or C3H8 was introduced into the sample chamber through a BELSORP-MAX X volumetric adsorption device until the pressure reached 100 kPa. After adsorption equilibrium was reached, the PXRD pattern was recorded. The analysis of the results of the in-situ powder X-ray diffraction experiment showed that after adsorption of C3H8 or C3H6, the main peak position of the JNU-66 series materials (including JNU-66-I, JNU-66-II, JNU-66-III, JNU-66-IV, JNU-66-V) did not shift significantly (2θ deviation <0.1°), proving that the framework structure was stable; Rietveld refinement showed that ( Figure 19 The binding site for C3H8 or C3H6 in JNU-66-I, JNU-66-II, JNU-66-III, JNU-66-IV, and JNU-66-V is Zn8Si8O. 16 Near the O atom site.

[0113] (3) In-situ infrared spectroscopy experiment: The analysis was performed using a Bruker INVENIO-S Fourier transform infrared spectrometer equipped with a liquid nitrogen-cooled mercury cadmium telluride (MCT-A) detector. 20 mg of sample was uniformly placed into a sample cup of the Harrick in-situ sample cell. Before measurement, the sample was activated under vacuum at 433 K for 1 h, and then cooled to 298 K. During the measurement, C3H6 or C3H8 was introduced at a flow rate of 10 mL / min. Infrared spectra were recorded at time intervals of 0, 1, 2, 4, 6, 8, 10, 14, 18, 22, 30, and 40 minutes. The results are as follows: Figure 20 As shown. By Figure 20 It can be seen that after adsorbing C3H8, JNU-66-III has a 1577 cm⁻¹ diameter. -1 (v) as COO - ) and 906cm -1 (v) as The peak intensity of Si-O-Zn gradually increases with adsorption time and is greater than that of C3H6, proving that C3H8 and Zn8Si8O 16 It has a stronger effect and provides spectroscopic evidence for the preferential adsorption of C3H8.

[0114] (4) In-situ Raman spectroscopy experiment: In-situ Raman spectroscopy analysis was performed using a Horiba LabRAM HR Evolution spectrometer. 20 mg of sample was placed in the in-situ sample cell of a Linkam THCELL-600. The sample was activated under vacuum at 433 K for 1 hour, and then cooled to 298 K. During the measurement, C3H6 or C3H8 was introduced at a flow rate of 2 mL / min. Raman spectra were recorded at time intervals of 0, 1, 5, 9, 13, 17, 23, 29, and 35 minutes. The results are as follows: Figure 21 As shown. By Figure 21 It can be seen that the 1442 cm⁻¹ of JNU-66-III when adsorbing C₃H₈ is... -1 (v) s COO - ) and 786 cm -1 The intensity of the (Si-O-Si) peak gradually decreases with increasing adsorption time, and the decrease is greater than that of the peak intensity when C3H6 is adsorbed, indicating that C3H8 has a more significant effect on the frame vibration. This is consistent with the in-situ FTIR results and together confirms the preferential adsorption characteristics of C3H8.

[0115] (5) Differential scanning calorimetry experiment: The experiment was conducted using a simultaneous thermal analyzer (STA 449 F3 Jupiter, NETZSCH, Germany). 8.0 mg of sample was placed in an aluminum dish and purged at 298 K with a helium flow rate of 20 mL / min for 6 hours. Subsequently, C3H6 or C3H8 was introduced at a flow rate of 50 mL / min, and the heat flow was monitored in real time. Replacing the 2-methyl terephthalate linker in JNU-66-III with 2-methoxy terephthalate yielded a structurally isomorphic skeleton (JNU-66-VI), whose Zn8Si8O 16 The steric hindrance around the cluster is enhanced, increasing spatial crowding. Further synthesis of another isomorphic framework (JNU-66-VII) using a larger 2,5-diethoxyterephthalate ester as a linker, where Zn8Si8O 16 The clusters were almost completely enclosed. Differential scanning calorimetry (DSC) analysis results showed that ( Figure 22 Compared with JNU-66-III, JNU-66-VI showed a decrease in selectivity for C3H8 relative to C3H6, while JNU-66-VII almost lost its selective adsorption capacity for C3H8.

[0116] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0117] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A siloxane cluster metal-organic framework material, characterized in that, Chemical formula: [Zn8[(MeSiO2)4]2(X)4] n wherein X refers to a 2-linked dicarboxylic acid linker; The siloxane cluster is an 8-connected Zn8(CH3COO)8-siloxane cluster consisting of eight Zn atoms, each Zn center adopting a tetrahedral coordination geometry, binding to two oxygen atoms from two cyclic tetramers [(MeSiO2)4] 4− and two oxygen atoms from two dicarboxylic acid linkers; the Zn8(CH3COO)8-siloxane cluster is a Zn8Si8O 16 secondary building unit, wherein each Zn8Si8O 16 secondary building unit serves as an 8-connected node bridged by 2-connected dicarboxylic acid linkers, forming a three-dimensional porous network; The siloxane cluster-based metal organic framework material belongs to a monoclinic system and has a space group I2 / a. The dicarboxylic acid in the 2-connected dicarboxylic acid linker is provided by bicyclo[1.1.1]pentane-1,3-dicarboxylic acid, bicyclo[2,2,2]octane-1,4-cyclohexanedicarboxylic acid, 2-methyl-1,4-benzenedicarboxylic acid, 2-(trifluoromethyl)terephthalic acid or 2,5-dimethyl-1,4-benzenedicarboxylic acid.

2. The method for preparing a siloxanecage-based metal-organic framework material according to claim 1, characterized in that, The method comprises the following steps: dissolving a zinc salt in a mixed solution of methyltrimethoxysilane, acetic acid and ethanol to obtain a siloxane cluster precursor solution A; dissolving a rigid dicarboxylic acid ligand in a solvent to obtain a mixed solution B; mixing the siloxane cluster precursor solution A and the mixed solution B to obtain the siloxane cluster-based metal organic framework material through reaction; The rigid dicarboxylic acid ligand comprises bicyclo[1.1.1]pentane-1,3-dicarboxylic acid, bicyclo[2,2,2]octane-1,4-cyclohexanedicarboxylic acid, 2-methyl-1,4-benzenedicarboxylic acid, 2-(trifluoromethyl)terephthalic acid or 2,5-dimethyl-1,4-benzenedicarboxylic acid.

3. The method of claim 2, wherein, The molar ratio of the acetic acid and the methyltrimethoxysilane is 2.8-3.5:1; the molar ratio of the zinc salt and the methyltrimethoxysilane is 0.5-1.2:1; and the volume ratio of the ethanol and the methyltrimethoxysilane is 17-27:

1.

4. The preparation method according to claim 2, characterized in that, The zinc salt comprises zinc nitrate.

5. The preparation method according to claim 2, characterized in that, The molar ratio of the siloxane cluster precursor solution A (calculated based on Zn8 units) and the rigid dicarboxylic acid ligand is 1:2-10; and the solvent comprises a mixed solvent of N,N-dimethylformamide and triethylamine at a volume ratio of 1:0.

2.

6. The preparation method according to claim 2, characterized in that, The mixing manner of the siloxane cluster precursor solution A and the mixed solution B is that the mixed solution B is added dropwise into the siloxane cluster precursor solution A at a rate of 1-2 mL / min.

7. The preparation method according to claim 2, characterized in that, The reaction temperature is 115°C and the reaction time is 48-72 h.

8. Application of the siloxane cluster-based metal organic framework material in claim 1 in the field of propylene / propane reverse separation.

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