Preparation method and application of alkaline earth metal modified covalent organic framework material

Abstract

The invention provides a preparation method of an alkaline earth metal post-modified covalent organic framework (COF) material and CO2 / N2 separation application thereof. The method is suitable for the technical fields of new material preparation and gas adsorption separation. Alkaline-earth metal ions are introduced into channels of the COF material through a post-modification method, so that a COF pore skeleton is kept, and rich CO2 adsorption sites are provided. The preparation method has the advantages of simple process, short synthesis period, adjustable alkaline earth metal ion concentration and the like. The prepared material shows good CO2 / N2 adsorption separation capability.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation of new materials and gas adsorption separation, and specifically relates to a method for preparing a covalent organic framework material modified with an alkaline earth metal group by a grinding method and an application thereof. Background Art

[0002] Covalent organic frameworks (COFs) are a type of crystalline porous materials constructed by strong organic covalent bonds and composed of light elements such as H, B, C, N and O. Unlike general copolymers that construct irregular amorphous structures through strong covalent bonds, COFs are synthesized through reversible condensation reactions and have high order and crystallinity.

[0003] COF materials not only have the basic properties of crystalline porous materials, such as pre-designed structures, high permanent porosity, periodic frameworks, structural and chemical adjustability, but also have the properties of organic polymers, such as large conjugated systems, and are excellent conductive materials. In addition, COF materials with parallel stacking structures have open channels, which are conducive to electron transfer. This makes COF materials have great application potential in the field of gas adsorption and separation.

[0004] In recent years, the functional modification of COFs skeleton using different substituents is the main method to regulate its structure. Sulfonic acid group has strong polarity, and its introduction can make the surface of COFs material have more polar sites. The introduction of alkaline earth metal ions can increase the active sites on the surface of COFs material, thereby increasing the interaction between COFs material and CO2 molecules, thus achieving efficient adsorption and separation of gas.

[0005] The present invention prepares a covalent organic framework material modified with alkaline earth metal groups based on a grinding method combined with an alkaline earth metal post-modification method, and applies the material to CO2 / N2 adsorption and separation. Summary of the invention

[0006] The purpose of the present invention is to provide a novel alkaline earth metal modified COFs material and apply it in the field of CO2 / N2 adsorption separation.

[0007] The purpose of the present invention is achieved by the following technical solutions: On the one hand, the present invention provides a method for preparing a COFs material containing a sulfonic acid group by pre-synthesizing the COFs material by a grinding method, and then preparing the COFs material by post-modification with an alkaline earth metal, comprising the following steps:

[0008] (1) reacting o-phenylenediamine sulfonate with p-toluenesulfonic acid to prepare a diamine salt crystal containing a sulfonic acid group;

[0009] (2) The diamine salt crystals and 2,4,6-trihydroxy-1,3,5-benzenetricarboxaldehyde are uniformly mixed and then mechanically ground for 10 to 20 minutes, a small amount of deionized water is added, and the grinding is continued for 1 to 2 hours to obtain a sludge, and the sample is washed 3 to 5 times with N,N-dimethylformamide, acetone and methanol respectively, and the sludge is heated at 80 to 100° C. to obtain a red powder, which is a covalent organic framework material containing a sulfonic acid group, and the expression is TpPa-SO3H;

[0010] (3) The obtained sulfonic acid group-containing covalent organic framework material is added to an alkali metal salt solution and stirred for 4 to 5 hours. After washing with deionized water, the solution is vacuum dried at 100° C. for 12 hours to obtain an alkaline earth metal-modified covalent organic framework material, expressed as TpPa-SO3R(R:Mg, Ca).

[0011] In a preferred technical implementation scheme, the molar ratio of the 2,4,6-trihydroxy-1,3,5-benzenetricarboxaldehyde used in step (2) to the diamine salt crystals and p-toluenesulfonic acid is 1:1.5:5-10; and the amount of deionized water added is 50-100 μL.

[0012] In a preferred technical embodiment, the alkaline earth metal salt solution is one of a magnesium acetate solution and a calcium acetate solution.

[0013] In a preferred technical embodiment, the molar ratio of the alkaline earth metal salt to the o-phenylenediamine sulfonate is 1 to 1.5:1.

[0014] The alkaline earth metal group-modified covalent organic framework material of the present invention is used for CO2 / N2 adsorption separation.

[0015] The TpPa-SO3R (R: Mg, Ca) material for CO2 / N2 adsorption separation provided by the present invention has the following advantages in preparation and application:

[0016] (1) The present invention uses a mechanical grinding method to prepare a covalent organic framework containing sulfonic acid groups, expressed as TpPa-SO3H. Compared with the traditional solvothermal method, the synthesis cycle is shorter and no organic solvent is required, which is both economical and environmentally friendly.

[0017] (2) The present invention introduces alkaline earth metal ions into the COF pore surface through alkaline earth metal post-modification, thereby increasing the COF material's active sites for CO2 adsorption while maintaining a high yield.

[0018] (3) The TpPa-SO3R (R: Mg, Ca) material prepared in the present invention has high stability and exhibits high CO2 / N2 adsorption and separation performance, providing a new material for the industrial application of gas adsorption and separation. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0020] Figure 1 The synthetic route of the alkaline earth metal modified covalent organic framework material of the present invention;

[0021] Figure 2 The XRD spectrum of the alkaline earth metal modified covalent organic framework material of the present invention;

[0022] Figure 3 This is the infrared spectrum of the alkaline earth metal modified covalent organic framework material of the present invention;

[0023] Figure 4 It is a N2 adsorption-desorption curve diagram of the alkaline earth metal modified covalent organic framework material of the present invention;

[0024] Figure 5 This is the CO2 / N2 adsorption curve of the alkaline earth metal modified covalent organic framework material of the present invention. DETAILED DESCRIPTION

[0025] The present invention is further described below in conjunction with specific embodiments, but the present invention is not limited to these embodiments.

[0026] Example 1: Preparation of covalent organic framework material TpPa-SO3Mg modified by alkaline earth metal magnesium

[0027] This example is the preparation of the covalent organic framework material TpPa-SO3Mg modified with alkaline earth metal magnesium. Figure 1 As shown, the specific preparation method is: react o-phenylenediamine sulfonate with p-toluenesulfonic acid to form diamine salt crystals; uniformly mix the above diamine salt crystals and 2,4,6-trihydroxy-1,3,5-benzenetricarboxaldehyde and then grind them mechanically for 10 to 20 minutes, drop 100 μL of deionized water, and continue grinding for 1 to 2 hours to obtain a sludge, wash the sample with N,N-dimethylformamide, acetone and methanol for 3 to 5 times, heat the sludge at 80 to 100 ° C, and obtain a red powder, which is a covalent organic framework material containing sulfonic acid groups, expressed as TpPa-SO3H. Add 90 mg of the synthesized TpPa-SO3H to 100 mL of 4.5 mol L -1 The product was added to a magnesium acetate solution, stirred for 4 to 5 hours, washed with deionized water, placed in a vacuum oven, and dried at 100°C for 12 hours to obtain TpPa-SO3Mg.

[0028] Example 2: Preparation of covalent organic framework material TpPa-SO3Ca modified with alkaline earth metal calcium

[0029] This example is the preparation of the covalent organic framework material TpPa-SO3Ca modified with alkaline earth metal calcium. Figure 1 As shown, the specific preparation method is: react o-phenylenediamine sulfonate with p-toluenesulfonic acid to form diamine salt crystals; uniformly mix the above diamine salt crystals and 2,4,6-trihydroxy-1,3,5-benzenetricarboxaldehyde and then grind them mechanically for 10 to 20 minutes, drop 100 μL of deionized water, and continue grinding for 1 to 2 hours to obtain a sludge, wash the sample with N,N-dimethylformamide, acetone and methanol for 3 to 5 times, heat the sludge at 80 to 100 ° C, and obtain a red powder, which is a covalent organic framework material containing sulfonic acid groups, expressed as TpPa-SO3H. Add 90 mg of the synthesized TpPa-SO3H to 100 mL of 4.5 mol L -1 The product was added to a calcium acetate solution, stirred for 4 to 5 hours, washed with deionized water, placed in a vacuum oven, and dried at 100°C for 12 hours to obtain TpPa-SO3Ca.

[0030] Figure 2 The X-ray diffraction (XRD) patterns of TpPa-SO3H and TpPa-SO3R (R: Mg, Ca) prepared in Examples 1 and 2 were obtained, with a scanning range of 3° to 40° and a scanning speed of 5° min -1 , TpPa-SO3H and TpPa-SO3R (R: Mg, Ca) both showed obvious diffraction characteristic peaks at 2θ of 4.61° and 26.27°, indicating that TpPa-SO3H and TpPa-SO3R (R: Mg, Ca) were successfully synthesized.

[0031] Figure 3 The Fourier transform infrared spectra (FT-IR) of TpPa-SO3H and TpPa-SO3R (R: Mg, Ca) prepared in Examples 1 and 2 are shown in Table 1. -1 The three characteristic absorption peaks at correspond to the three stretching vibrations of the O=S=O bond, which proves the successful introduction of sulfonic acid groups into the COFs skeleton.

[0032] Figure 4 The N2 adsorption-desorption curves of TpPa-SO3R (R = Mg, Ca) prepared in Examples 1 and 2 are shown in Table 1. The specific surface areas of TpPa-SO3R (R = Mg, Ca) are calculated to be 81 m 2 / g and 82m 2 / g. Since the diameter of Ca ions is larger than that of Mg ions, the pore size of the Mg-modified material is smaller than that of the Ca-modified material.

[0033] Figure 5Adsorption curves of TpPa-SO3H and TpPa-SO3R (R: Mg, Ca) prepared in Examples 1 and 2 for CO2 and N2. At the two test temperatures of 273K and 298K, the adsorption of CO2 by TpPa-SO3R (R: Mg, Ca) was significantly improved compared with that of TpPa-SO3H, indicating that the alkaline earth metal post-modification successfully enhanced the adsorption selectivity of CO2. The adsorption of CO2 and N2 differed greatly, indicating good CO2 / N2 separation ability.

Claims

1. Preparation of an alkaline earth metal modified covalent organic framework material, characterized in that: The specific steps include: (1) p-Toluenesulfonic acid and p-phenylenediamine sulfonate were mixed and ground for 10 minutes, and then 2,4,6-trihydroxy-1,3,5-benzenetricarboxaldehyde was added and ground for 20 minutes. During the process, 100 μL of deionized water was added dropwise, and then heated and dried at 150°C for 10 minutes to obtain a covalent organic framework material containing a sulfonic acid group, which was expressed as TpPa-SO3H; (2) The obtained sulfonic acid group-containing covalent organic framework material is added to an alkaline earth metal salt solution and stirred for 4 to 5 hours. After washing with deionized water, the solution is vacuum dried at 100° C. for 12 hours to obtain an alkaline earth metal-modified covalent organic framework, expressed as TpPa-SO3R(R:Mg, Ca).

2. The preparation method according to claim 1, characterized in that: The molar ratio of 2,4,6-trihydroxy-1,3,5-benzenetricarboxaldehyde to p-toluenesulfonic acid and p-phenylenediamine sulfonate in step (1) is 1:1.5:

10.

3. The preparation method according to claim 1, characterized in that: The alkaline earth metal salt solution in step (2) is one of a magnesium acetate solution and a calcium acetate solution.

4. The preparation method according to claim 1, characterized in that: The molar ratio of the alkaline earth metal salt to the covalent organic framework containing sulfonic acid groups in step (2) is 1 to 1.5:

1.

5. Application of a covalent organic framework material modified with an alkaline earth metal group according to any one of claims 1 to 4 in CO2 / N2 separation.

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