Covalent organic framework material for CO2 / C2H2 reverse separation as well as preparation method and application of covalent organic framework material

Abstract

The invention discloses a covalent organic framework material for CO2 / C2H2 reverse separation and a preparation method and application thereof, and the preparation method specifically comprises the following steps: adding a ligand containing nitrogen atoms and a ligand containing boron atoms into a solvent, ultrasonically mixing uniformly, placing in a drying oven for solvothermal reaction, cooling to room temperature, filtering, washing with 1, 4-dioxane for several times, and drying to obtain the covalent organic framework material for CO2 / C2H2 reverse separation. The covalent organic framework material is obtained. The covalent organic framework (COFs) material disclosed by the invention can efficiently and selectively adsorb CO2 and shows good reverse adsorption performance, acetylene is obtained through one-step separation, the purity of acetylene is remarkably improved, and the loss of acetylene in the adsorption process is reduced. In addition, the material has good stability, can be recycled for multiple times, and is simple in synthesis step, low in energy consumption, small in pollution and good in application prospect.

Description

Technical Field

[0001] The present invention belongs to the field of covalent organic framework materials, and in particular relates to a covalent organic framework material for CO2 / C2H2 inversion separation and a preparation method thereof, and also relates to the application of the covalent organic framework material. Background Art

[0002] Covalent organic frameworks (COFs) are ordered crystalline porous materials composed of light elements (such as carbon, hydrogen, oxygen, nitrogen, boron, and silicon) linked by covalent bonds. These materials have attracted considerable attention for their highly ordered porous structures and customizable chemical compositions. They have shown promising applications and enormous potential in a variety of fields, including gas adsorption and separation, catalysis, sensing, energy storage and conversion, and environmental remediation.

[0003] Acetylene (C2H2) is not only the main fuel gas, but also one of the most widely used precursors in the petrochemical industry. In industry, the production process of acetylene through partial combustion of methane or cracking of hydrocarbons will inevitably produce CO2 impurities. Since C2H2 and CO2 have similar kinetic diameters, The carbonyl groups C2H2 and CO2 have different boiling points (C2H2, 189.3K; CO2, 194.7K), making them difficult to separate by conventional means. Therefore, the selective separation and removal of CO2 is a bottleneck that needs to be solved urgently. Currently, the separation of C2H2 and CO2 is mostly achieved through selective adsorption on porous materials. Typically, the π electrons at the functional sites of the porous material form hydrogen bonds with the relatively acidic and polarizable C2H2, preferentially adsorbing C2H2, and then desorbing it to obtain higher-purity C2H2. However, this process is complex, has multiple operational procedures, and is costly.

[0004] Covalent organic frameworks (COFs) have multiple interactions in their structures, such as hydrogen bonds, which enable the selective adsorption of a variety of different gas molecules. Their pore structure can also be precisely controlled through molecular design, and they have potential applications in the field of carbon dioxide (CO2) / acetylene (C2H2) inversion separation. However, COFs lack stability and are difficult to meet the separation requirements of various gas mixtures. Therefore, the development of new COFs with high stability and high selectivity to adsorb CO2 and achieve CO2 / C2H2 inversion separation is of great theoretical and practical significance. Summary of the Invention

[0005] The first object of the present invention is to provide a method for preparing a covalent organic framework material for CO2 / C2H2 inversion separation, so as to achieve efficient separation of carbon dioxide (CO2) and acetylene (C2H2).

[0006] The second object of the present invention is to provide the above covalent organic framework material, which has good stability.

[0007] The third object of the present invention is to provide an application of a covalent organic framework material in the separation process of CO2 and C2H2, to achieve reverse selective adsorption (highly selective adsorption of CO2) in the separation process of carbon dioxide and acetylene, and to obtain acetylene in one step.

[0008] The technical solution adopted by the present invention is a method for preparing a covalent organic framework material for CO2 / C2H2 inversion separation, specifically: adding a ligand containing a nitrogen atom and a ligand containing a boron atom to a solvent, mixing them evenly by ultrasonication, placing them in an oven for solvent thermal reaction, cooling to room temperature and then filtering, washing several times with 1,4-dioxane, and drying to obtain a covalent organic framework material.

[0009] The present invention is also characterized in that:

[0010] The ligand containing a nitrogen atom is 4-carboxyphenylboronic acid (CPBA), the ligand containing a boron atom is 1,4-diazabicyclo[2.2.2]octane (DABCO), and the mass ratio of 4-carboxyphenylboronic acid to 1,4-diazabicyclo[2.2.2]octane is 3-7:47.

[0011] The solvent is a mixture of 1,4-dioxane and formic acid, with a volume ratio of 82-88:1.

[0012] The mass ratio of the ligand containing nitrogen atoms to the solvent is 2-6:10000.

[0013] The ultrasonic power is 200-600W, and the ultrasonic time is 15-20min.

[0014] The solvent thermal reaction time is 24-48 hours, the solvent thermal reaction temperature is 90-110° C. The drying temperature is 20-25° C., and the drying time is 0.5-1 hour.

[0015] The beneficial effects of the present invention are:

[0016] (1) The covalent organic framework material for CO2 / C2H2 inversion separation synthesized by the present invention is specifically a crystalline porous covalent organic framework material based on B←N bond, with 4-carboxyphenylboronic acid and 1,4-diazabicyclo[2.2.2]octane as two ligands as raw materials. Three molecules of carboxyphenylboronic acid form a six-membered ring through BO covalent bonds, and the hexacyclic borane (B3O3) is combined with 1,4-diazabicyclo[2.2.2]octane molecules through B←N coordination bonds, and further assembled through hydrogen bonds and π-π stacking interactions to form a porous framework structure with good stability;

[0017] (2) The present invention uses 4-carboxyphenylboronic acid and 1,4-diazabicyclo[2.2.2]octane as raw materials to synthesize a crystalline porous covalent organic framework material based on B←N bond through a solvothermal method in one step. The process is simple, energy consumption is low, and pollution is small.

[0018] (3) The crystalline porous covalent organic framework material based on B←N bond synthesized by the present invention preferentially adsorbs CO2 during the adsorption separation process of C2H2 and CO2, showing good reversal adsorption performance and high selectivity, and can directly obtain C2H2, realizing the one-step separation of CO2 and C2H2, which not only improves the purification efficiency of acetylene, but also improves the purity of acetylene and reduces the loss of acetylene during the adsorption process;

[0019] (4) The inverse separation of carbon dioxide and acetylene using the covalent organic framework material of the present invention can be carried out at lower temperature and pressure, with low energy consumption, low operating cost, and good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a pore size distribution diagram of the porous covalent organic framework material of Example 1;

[0021] Figure 2 The porous covalent organic framework material of Example 1 is a N2 adsorption isotherm at 77K and CO2 at 195K;

[0022] Figure 3 The C2H2 adsorption isotherms of the porous covalent organic framework material of Example 1 at 298K and 273K are shown;

[0023] Figure 4 This is a penetration curve diagram (1) of the porous covalent organic framework material of Example 1;

[0024] Figure 5 This is the penetration curve diagram (2) of the porous covalent organic framework material of Example 1;

[0025] Figure 6 This is a diagram of the penetration cycle experiment of the porous covalent organic framework material in Example 1. DETAILED DESCRIPTION

[0026] The present invention will be described in detail below with reference to specific embodiments and the accompanying drawings.

[0027] The preparation method of the covalent organic framework material for CO2 / C2H2 inversion separation of the present invention is specifically as follows:

[0028] A ligand containing a nitrogen atom and a ligand containing a boron atom are added to a solvent, mixed uniformly by ultrasonication, placed in an oven for solvothermal reaction, cooled to room temperature, filtered, washed several times with 1,4-dioxane, and dried to obtain a covalent organic framework material;

[0029] The ligand containing a nitrogen atom is 4-carboxyphenylboronic acid, the ligand containing a boron atom is 1,4-diazabicyclo[2.2.2]octane, and the mass ratio of 4-carboxyphenylboronic acid to 1,4-diazabicyclo[2.2.2]octane is 3-7:47;

[0030] The solvent is a mixture of 1,4-dioxane and formic acid, and the volume ratio of 1,4-dioxane to formic acid is 82-88:1;

[0031] The mass ratio of the ligand containing nitrogen atoms to the solvent is 2-6:10000;

[0032] The ultrasonic power is 200-600W, and the ultrasonic time is 15-20min;

[0033] The solvent thermal reaction time is 24-48h, and the solvent thermal reaction temperature is 90-110℃;

[0034] The drying temperature is 20-25°C and the drying time is 0.5-1h.

[0035] Example 1

[0036] The method for preparing a covalent organic framework material for CO2 / C2H2 inversion separation of the present invention comprises the following steps:

[0037] In step 1, 14.9 mg (0.09 mmol) of 4-carboxyphenylboronic acid (CPBA) and 1.7 mg (0.015 mmol) of 1,4-diazabicyclo[2.2.2]octane (DABCO) were weighed and added to a 10 mL glass bottle. Then, 3 mL of 1,4-dioxane and 35 L of formic acid were added thereto, and the mixture was sonicated until the solution was clear.

[0038] Step 2: transfer the clarified solution obtained in step 1 into a hydrothermal reactor, place it in a 90° C. oven and heat it for 48 hours to obtain colorless needle-shaped crystals.

[0039] Step 3: Cool the crystals obtained in step 2 to room temperature, filter them, wash them with pure 1.4-dioxane, and dry them at room temperature to obtain a crystalline porous covalent organic framework material based on B←N bonds.

[0040] Example 2

[0041] In order to characterize the microporous structure of the covalent organic framework material obtained in Example 1, the present invention was tested by a specific surface area / pore size distribution instrument. The results are as follows: Figure 1As shown, the horizontal axis represents the pore width (in angstroms), and the vertical axis represents the change in pore volume per unit pore width change (in cm 3 g-1 ). According to the pore volume distribution of the material at different pore widths, it can be seen that the pores of the material obtained in Comparative Example 1 are mainly concentrated in the area of about As the pore width increases, the pore volume distribution function value gradually decreases, indicating that The size is the dominant pore size of the material.

[0042] Example 3

[0043] In order to characterize the specific surface area of the covalent organic framework material obtained in Example 1 and its adsorption performance for CO2 and C2H2, the present invention conducted N2 adsorption experiments, CO2 adsorption experiments and C2H2 adsorption experiments. The results are as follows Figure 2 and Figure 3 As shown. Under 77K conditions, N2 adsorption experiments proved the permanent porosity of the porous covalent organic framework material obtained in Example 1. Under low pressure (P / P0<0.01), the adsorption capacity of the porous covalent organic framework material obtained in Example 1 increased rapidly, and the saturated adsorption capacity was 8.30cm 3 g -1 The Brunauer-Emmett-Teller (BET) and Langmuir specific surface areas of the material were 291.81 and 383.30 m2, respectively, obtained by fitting the adsorption data. 2 g -1 At 195K, the adsorption of CO2 by the porous covalent organic framework material obtained in Example 1 showed type I isothermal adsorption, with a saturated absorption capacity of 776.62 cm 3 g -1 , indicating that the porous material obtained in Example 1 has good adsorption performance for CO2.

[0044] Example 4

[0045] In order to test the selectivity of the covalent organic framework material obtained in Example 1 for carbon dioxide adsorption, a dynamic penetration test was conducted when the partial pressure of the C2H2 and CO2 mixed gas was C2H2 / CO2=50 / 50. The results are shown in FIG. Figure 4 After 1.1 g of activated porous material sample was loaded into the packed column, the column was heated at 2.5 mL min -1A mixture of C2H2 and CO2 (C2H2 / CO2 = 50 / 50) was introduced at a flow rate of 1.5 s. C2H2 was first detected at 1155.6 s, while CO2 had a retention time of 297.2 s and a breakthrough interval of 141.6 s. Pure C2H2 was directly obtained during this process, demonstrating that the porous material exhibits excellent inverse adsorption performance in the separation of carbon dioxide and acetylene.

[0046] Example 5

[0047] In order to simulate the actual application scenario, the partial pressure of the C2H2 and CO2 mixed gas was changed to C2H2 / CO2=90 / 10, and the material obtained in Example 1 was further subjected to the penetration test. The results are as follows: Figure 5 As shown in the figure, the retention times of C2H2 and CO2 are 230.7 and 382.1s respectively, and the breakthrough interval is 151.4s, showing a separation performance similar to that when C2H2 / CO2=50 / 50;

[0048] Example 6

[0049] Finally, the porous material obtained in Example 1 was subjected to five penetration cycle experiments. Figure 6 As shown, the results show that there is no obvious change in performance, which indicates that the porous material has good stability and the advantages of reusability.

[0050] The covalent organic framework material of the present invention can efficiently and selectively adsorb CO2, directly obtain C2H2, and realize the one-step separation of CO2 and C2H2. It not only improves the purification efficiency of acetylene, but also significantly improves the purity of acetylene and reduces the loss of acetylene during the adsorption process. At the same time, the covalent organic framework material has good stability and can be recycled and reused multiple times. In addition, the inverse separation of carbon dioxide and acetylene using the covalent organic framework material of the present invention can be carried out at lower temperatures and pressures, with low energy consumption and low operating costs.

Claims

1. A method for preparing a covalent organic framework material for CO2 / C2H2 inversion separation, characterized in that: Specifically, a ligand containing a nitrogen atom and a ligand containing a boron atom are added to a solvent, mixed evenly by ultrasound, placed in an oven for solvent thermal reaction, cooled to room temperature and then filtered, washed several times with 1,4-dioxane, and dried to obtain a covalent organic framework material.

2. The method for preparing a covalent organic framework material for CO2 / C2H2 inversion separation according to claim 1, characterized in that: The nitrogen-containing ligand is 4-carboxyphenylboronic acid; the boron-containing ligand is 1,4-diazabicyclo[2.2.2]octane; and the mass ratio of 4-carboxyphenylboronic acid to 1,4-diazabicyclo[2.2.2]octane is 3-7:

47.

3. The method for preparing a covalent organic framework material for CO2 / C2H2 inversion separation according to claim 1, characterized in that: The solvent is a mixture of 1,4-dioxane and formic acid in a volume ratio of 82-88:

1.

4. The method for preparing a covalent organic framework material for CO2 / C2H2 inversion separation according to claim 1, characterized in that: The mass ratio of the ligand containing nitrogen atoms to the solvent is 2-6:10000.

5. The method for preparing a covalent organic framework material for CO2 / C2H2 inversion separation according to claim 1, characterized in that: The ultrasonic power is 200-600W, and the ultrasonic time is 15-20min.

6. The method for preparing a covalent organic framework material for CO2 / C2H2 inversion separation according to claim 1, characterized in that: The solvent thermal reaction time is 24-48h, and the solvent thermal reaction temperature is 90-110°C.

7. The method for preparing a covalent organic framework material for CO2 / C2H2 inversion separation according to claim 1, characterized in that: The drying temperature is 20-25°C and the drying time is 0.5-1h.

8. A covalent organic framework material prepared by the method for preparing a covalent organic framework material for CO2 / C2H2 inversion separation according to any one of claims 1 to 7.

9. Use of the covalent organic framework material for CO2 / C2H2 inversion separation according to any one of claims 1 to 7 in the process of separating CO2 and C2H2.

Images