Preparation method of ultra-microporous metal-organic framework and its application in propylene and propane adsorption separation

Abstract

A method for preparing an ultra-microporous metal-organic framework (MOF) and its application in propylene and propane adsorption separation, belonging to the technical field of crystalline materials, is disclosed. The MOF is derived from the organic ligands D-camphoric acid, 3-amino-1,2,4-triazole, and anhydrous zinc acetate via a solvothermal reaction in N,N-dimethylformamide and tetrafluoroboric acid. Gas adsorption studies have shown that this MOF has the potential to separate propylene and propane gas molecules.

Description

Technical Field

[0001] The present invention belongs to the technical field of crystalline materials, and the technology relates to metal-organic coordination polymer materials. The invention is characterized by a zinc metal-based organic framework material, a preparation method and its application in propylene and propane adsorption separation. Background Art

[0002] The separation of propane / propylene mixtures is an important and challenging task in the petrochemical industry. In industry, it is difficult to separate molecules with similar physical / chemical properties, and high-energy-consuming low-temperature distillation technology is usually required. The main disadvantage of distillation is that it is only based on the principle of volatility. Although its process is simple, the energy utilization efficiency of this technology is low. Replacing distillation with relatively low-energy-consuming processes can significantly save energy. Adsorption and membrane separation methods have great prospects in gas separation. The key is the design and construction of porous functional materials. These materials can distinguish these molecules through different mechanisms, depending on their intrinsic structural characteristics. Therefore, academia and industry are now researching and developing porous materials to separate low-carbon hydrocarbons through adsorption or membrane separation technology, improve the efficiency of the separation process and save energy.

[0003] Metal-organic frameworks (MOFs) are a new type of porous functional material. They are crystalline materials with a periodic network structure formed by metal nodes (metal ions or clusters) and organic ligands connected by coordination bonds. Due to their high porosity, large specific surface area, and adjustable pore size and properties, MOFs have potential applications in many fields such as adsorption separation, gas storage, sensing, and catalysis. In the application of gas adsorption separation, the use of MOFs for the separation of light hydrocarbons has been widely studied. There are two main methods to achieve the separation of light hydrocarbons: (1) functionalizing the organic ligands of MOFs with polar functional groups; (2) introducing unsaturated metal sites on the surface of MOF pores. Although some MOFs have been reported to be promising for the separation of propylene and propane, the construction of these MOFs uses very complex organic ligands and requires tedious steps to synthesize. The construction of new MOFs using simple, readily available and inexpensive ligands coordinated with metal centers and their application in the separation of propylene and propane has important academic significance and practical value. Summary of the Invention

[0004] The present invention aims to synthesize a metal organic framework material using a simple and readily available organic ligand and use the metal organic framework material for the separation of C3H6 / C3H8.

[0005] The present invention synthesizes a zinc-based metal-organic framework material based on two simple and easily available organic ligands, (1R,3S)-1,2,2-trimethyl-1,3-cyclopentanedicarboxylic acid (D-camphoric acid, H2CAM) and 3-amino-1,2,4-triazole (HATZ).

[0006] The metal organic framework crystallizes in the orthorhombic system with space group P21212 and unit cell parameters: The chemical formula is Zn3C 28 H 45 N5O 11 .

[0007] The single crystal structure analysis of the metal organic framework shows that its smallest asymmetric unit is composed of two independent zinc ions, a D-camphorate ion CAM 2- , two deprotonated 3-amino-1,2,4-triazole (ATZ - ), one N,N-dimethylformamide (DMF) molecule. Each zinc ion is tetrahedral with three ATZ - and a CAM 2- Ligand coordination, each ATZ - The ligand is linked to three zinc ions, each CAM 2- The ligand bridges two zinc ions; the zinc ions and ATZ - The alternating connection of ligands forms a two-dimensional layered structure, CAM 2- Ligands pillar these two-dimensional layers, forming the three-dimensional framework structure of the MOF.

[0008] The structural formulas of the two organic ligands are shown below:

[0009]

[0010] The method for synthesizing the metal organic framework material of the present invention comprises the following steps:

[0011] Under sealed conditions, organic ligands D-camphoric acid and 3-amino-1,2,4-triazole react with anhydrous zinc acetate Zn(CH3COO)2 in a mixed solution of DMF and tetrafluoroboric acid to obtain crystals of the metal organic framework through solvothermal reaction.

[0012] It is further preferred that the molar ratio of the organic ligand to the metal salt, i.e., HATZ:D-camphoric acid:Zn(CH3COO)2, is 2:5:1, and every 0.05 mmol of Zn(CH3COO)2 corresponds to 2 mL of DMF, 0.01-0.03 mL of tetrafluoroboric acid and 0.3 mL of H2O. The temperature of the thermal reaction is 120°C-130°C, and the reaction time is 48-72 hours.

[0013] The present invention is used for separating a C3H6 / C3H8 gas mixture and can be used for complete 100% separation. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is the minimum asymmetric unit diagram of the metal-organic framework.

[0015] Figure 2 Schematic diagram of the three-dimensional structure of the metal-organic framework.

[0016] Figure 3 To prove the X-ray powder diffraction pattern of the metal organic framework.

[0017] Figure 4 This is the adsorption diagram of the metal organic framework material for C3H6 and C3H8 at 298K. Specific implementation methods

[0018] The present invention will be further described below with reference to the examples, but the present invention is not limited to the following examples.

[0019] Example 1

[0020] The organic ligand (0.024 mmol HATZ and 0.010 mmol D-camphoric acid) and Zn(CH3COO)2 (0.05 mmol) were mixed in 2.0 mL of N,N-dimethylformamide, 0.15 mL of tetrafluoroboric acid was added, and the mixture was sealed in a vial. A thermal reaction at 120°C for 72 hours yielded the metal-organic framework crystals.

[0021] Example 2

[0022] The organic ligand (0.024 mmol HATZ and 0.010 mmol D-camphoric acid) and Zn(CH3COO)2 (0.05 mmol) were mixed in 2.0 mL of N,N-dimethylformamide, 0.13 mL of tetrafluoroboric acid was added, and the mixture was sealed in a vial. A thermal reaction at 130°C for 24 hours yielded the metal-organic framework crystals.

[0023] The test results of the products obtained in the above examples are the same, as shown below:

[0024] (1) Determination of crystal structure:

[0025] Select crystals with regular shape, smooth surface and appropriate size, collect crystal data on a Rigaku Supernova CCD diffractometer equipped with a graphite monochromatic enhanced Cu-Kα radiation source at room temperature, and then analyze and refine the crystal structure. Figures 1 to 2 The crystallographic data are shown in Table 1.

[0026] Table 1 Crystallographic data of metal organic framework materials

[0027]

[0028] Figure 1 The structural diagram shows that there are two independent zinc ions in the minimum asymmetric unit, and each zinc ion is connected in a different way.

[0029] Figure 2 The structure of the metal organic framework is composed of D-camphorate ions CAM 2- For the column, zinc ions and ATZ - The layers obtained by alternating ligand connections form a columnar structure.

[0030] Figure 3 is the X-ray powder diffraction pattern of the MOF.

[0031] (2) Gas adsorption test

[0032] Figure 4 This is the single-component adsorption diagram of C3H6 and C3H8 of the material of the present invention at 298K, in which the adsorption amount of C3H6 is greater than that of C3H8, indicating that the material has the ability to separate C3H6 / C3H8.

[0033] The above content is only a preferred embodiment of the present invention, but the present invention should not be limited to the content disclosed in this embodiment. Therefore, any equivalent or modified content that does not depart from the spirit disclosed in the present invention shall fall within the scope of protection of the present invention.

Claims

1. An ultra-microporous metal-organic framework, characterized in that: It is a zinc-based metal organic framework material, and its organic ligands are (1R, 3S)-1,2,2-trimethyl-1,3-cyclopentanedicarboxylic acid (D-camphoric acid H2CAM) and 3-amino-1,2,4-triazole HATZ. The structural formula of the organic ligand is shown below: The metal organic framework crystallizes in the orthorhombic system with a space group of P21212 and unit cell parameters of a=14.0603(6)Å, b=14.1504(5)Å, c=8.7464(2)Å. The chemical formula is Zn3C 28 H 45 N5O 11 ; Single crystal structure analysis of the metal-organic framework shows that the smallest asymmetric unit is composed of two independent zinc ions, a D-camphorate ion and a CAM. 2- , two deprotonated 3-amino-1,2,4-triazole ATZ - , one N, N-dimethylformamide DMF molecule; each zinc ion is tetrahedral with three ATZ - and a CAM 2- Ligand coordination, each ATZ - The ligand is linked to three zinc ions, each CAM 2- The ligand bridges two zinc ions; the zinc ions and ATZ - The alternating connection of ligands forms a two-dimensional layered structure, CAM 2- The ligands pillar these two-dimensional layers, forming a three-dimensional framework structure; The synthesis method of the ultramicroporous metal organic framework comprises the following steps: Under sealed conditions, organic ligands D-camphoric acid and 3-amino-1,2,4-triazole reacted with anhydrous zinc acetate Zn(CH3COO)2 in a mixed solution of DMF and tetrafluoroboric acid to obtain the metal-organic framework crystals through solvothermal reaction; The molar ratio of the organic ligand to the metal salt, i.e., HATZ:D-camphoric acid:Zn(CH3COO)2, is 2.4:1:

5. Every 0.05 mmol of Zn(CH3COO)2 corresponds to 2 mL of DMF and 0.13 mL or 0.15 mL of tetrafluoroboric acid. The solvothermal reaction temperature is 120°C-130°C, and the reaction time is 48-72 hours.

2. Use of the ultra-microporous metal-organic framework according to claim 1 in separating a C3H6 / C3H8 gas mixture, characterized in that: Achieve complete 100% separation.

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