CN103508434A - Preparation method of boron/nitrogen-doped microporous carbon material - Google Patents

Abstract

The invention relates to a method for preparing a boron-nitrogen-doped microporous carbon material and its gas adsorption performance. Specifically, boron-nitrogen is prepared by using a metal-organic framework compound ZIF-8 and a boron-nitrogen compound as precursors through a high-temperature sintering method Element-doped microporous carbon materials and their adsorption properties for hydrogen, carbon dioxide, nitrogen, and other gases. The preparation steps are as follows: 1) Prepare the porous metal organic framework compound ZIF-8; 2) Confine the boron nitrogen compound (such as ammonia borane) to the inside of the channel of the metal organic framework compound ZIF-8 by solution impregnation; 3) The composite material is calcined at high temperature under an argon atmosphere to prepare a microporous carbon material doped with boron and nitrogen elements. The preparation process of the present invention is simple, and the prepared carbon material realizes the simultaneous doping of boron and nitrogen elements and concentrates the micropore size distribution, and has good hydrogen adsorption performance and selective adsorption performance for carbon dioxide.

Description

A kind of preparation method of boron nitrogen element doped microporous carbon material

technical field

The invention relates to a method for preparing a microporous carbon material doped with boron and nitrogen elements and its gas adsorption performance. Specifically, the metal-organic framework compound ZIF-8 and the boron-nitrogen compound ammonia borane are used as precursors through a high-temperature sintering method The prepared microporous carbon materials doped with boron and nitrogen elements and their adsorption properties of hydrogen, carbon dioxide, nitrogen and other gases.

Background technique

Nanoporous carbon materials have been widely used in gas adsorption and separation, catalyst supports and electrode materials due to their high specific surface area, large pore volume and excellent chemical stability. The methods used to synthesize nanoporous carbon materials mainly include the following: 1) physical and chemical activation; 2) chemical vapor deposition; 3) polymer carbonization; 4) template method, etc. Among them, the template method is widely used because of its easy operation and easy control of the structural properties of materials. Conventional porous materials such as porous silica and porous zeolites have been successfully used as templates to synthesize porous carbon materials. However, due to the characteristics of the pore properties of the current template materials, such as large pore size, uneven pore size distribution, and small template surface area, the prepared porous carbon materials have a small surface area and a wide range of pore size distribution. Finding new and excellent template materials is the key to preparing high-performance porous carbon materials.

On the other hand, due to the characteristics of metal-organic frameworks (MOFs) with adjustable pore size, large specific surface area, and diverse structural compositions, the research on them has been highly valued by researchers from all over the world. Yaghi in the United States (N.L.Rosi, J.Eckert, M.Eddaoudi, D.T.Vodak, J.Kim, M.O'Keeffe and O.M.Yaghi, Science, 2003, 300, 1127-1129), Férey in France (G.Ferey, M.Latroche, C.Serre, F.Millange, T.Loiseau and A.Percheron-Guegan, Chem Commun, 2003, 2976-2977) and other research groups have obtained many achievements in the structure design and performance research of porous metal organic compounds. Compelling research results. At present, a lot of research has been done on the development of the properties of metal organic framework compounds. For example, porous metal-organic compounds have potential applications in gas storage (especially hydrogen storage), gas separation, catalysis, nonlinear optics, magnetism, etc. Porous metal-organic compounds are crystalline polycrystalline materials with regular channel or hole structures constructed by inorganic metal centers and organic functional groups connected to each other through covalent bonds or ionic bonds. Its regular pores can be used as templates and organic ligands can be used as carbon sources. In view of this, we choose metal-organic framework compound (ZIF-8) as the template and precursor to prepare porous carbon materials. In addition, ammonia borane is introduced into the pores through solution impregnation, and boron and nitrogen elements are simultaneously doped after high-temperature calcination.

Contents of the invention

The purpose of the present invention is to provide a preparation method of boron and nitrogen doped microporous carbon material, which has good hydrogen adsorption performance and selective adsorption performance of carbon dioxide.

Another object of the present invention is to provide a method for preparing element-doped porous carbon materials using porous metal organic compounds and boron-nitrogen compounds as precursors.

In order to achieve the above object, the technical scheme adopted in the present invention is:

A method for preparing a microporous carbon material doped with boron and nitrogen elements, the specific preparation process is as follows:

1) Dissolve metal inorganic salts and imidazole ligands in an organic solvent (add 1-20 mmol metal inorganic salts and 70-90 mmol organic imidazole ligands per 200 mL of solvent), the reaction temperature is 10-30 ° C, and the crystallization reaction time is After 10-50 hours, the product was collected, filtered, washed (with water or organic solvent), dried in vacuum at 30-150°C, and activated in vacuum at 200-300°C to obtain ZIF-8.

2) impregnating 0.5-3mol/L ammonia borane solution into ZIF-8 pores to prepare a composite material of metal organic framework compound ZIF-8 confined ammonia borane.

3) Put the composite material of ZIF-8 confined ammonia borane in a high-temperature furnace, use argon atmosphere (gas flow rate is 100-400mL/min), and raise the temperature to 800~ 1200°C, keep at 800~1200°C for 2~10 hours, cool down to room temperature in argon atmosphere.

The gas adsorption and desorption performance test is carried out on the boron and nitrogen element-doped microporous carbon material. The test is carried out on the Absorb-1 physical adsorption instrument of the American Quanta Company, and the specific operation process is as follows:

1) Weigh 0.1-2g of microporous carbon material doped with boron and nitrogen elements, put it into a sample tube, seal it and activate it in vacuum. The activation temperature is 140-300°C, and the activation time is 5-15h.

2) The hydrogen storage test is carried out at a constant temperature under two temperature conditions of 77K and 87K.

3) The carbon dioxide absorption and desorption test is carried out at a constant temperature under two temperature conditions of 273K and 298K.

4) The nitrogen adsorption and desorption test is carried out at a constant temperature under two temperature conditions of 77K and 273K.

5) The methane adsorption test is carried out at a constant temperature under two temperature conditions of 273K and 298K.

The microporous carbon material doped with boron and nitrogen elements has good hydrogen storage performance, and the hydrogen absorption capacity can reach 1.83wt% under the hydrogen pressure conditions of 77K and 820mmHg.

The boron and nitrogen element-doped microporous carbon material has good carbon dioxide selective adsorption performance. Under the pressure conditions of 273K and 780mmHg, each gram of boron and nitrogen element-doped microporous carbon material can absorb ^100cm3 of carbon dioxide. Under the same conditions, nitrogen and The adsorption amount of methane is only 20cm ³ and 45cm ³ .

The present invention has the following advantages:

(1) Using metal-organic framework materials and boron-nitrogen compounds as precursors, a porous carbon material doped with boron-nitrogen elements with a pore size distribution of 0.6-1.2 nm was prepared. The particle size of the carbon material is small and the specific surface area is large, and the preparation process of the invention is simple and easy to operate.

(2) The microporous carbon material doped with boron and nitrogen elements has good gas adsorption performance. Under the conditions of 77K and 820mmHg hydrogen pressure, the hydrogen absorption capacity can reach 1.83wt%. Under the pressure conditions of 273K and 780mmHg, each gram of boron and nitrogen doped microporous carbon materials can absorb 100cm ³ of carbon dioxide, and the adsorption amounts of nitrogen and methane are only 20cm ³ and 45cm ³ under the same conditions.

The preparation process of the present invention is simple, and the prepared carbon material realizes the simultaneous doping of boron and nitrogen elements and concentrates the micropore size distribution, and has good hydrogen adsorption performance and selective adsorption performance for carbon dioxide.

Description of drawings

Fig. 1 is the XRD spectrogram of the ZIF-8 sample prepared in Example 1 of the present invention.

FIG. 2 is an XRD spectrum of a boron and nitrogen-doped microporous carbon material sample prepared in Example 1 of the present invention.

Fig. 3 is the 77K nitrogen physical adsorption and pore size distribution curve of the boron-nitrogen doped microporous carbon material sample prepared in Example 1 of the present invention;

Fig. 4 is the 77K and 87K hydrogen adsorption curves of the boron and nitrogen element doped microporous carbon material sample of Example 2 of the present invention;

Fig. 5 is the 273K carbon dioxide gas adsorption curve of the boron and nitrogen element-doped microporous carbon material sample of Example 3 of the present invention;

Fig. 6 is the 273K methane gas adsorption curve of the boron and nitrogen element-doped microporous carbon material sample of Example 4 of the present invention.

Detailed ways

Example 1

1. Weigh 2.933g of zinc nitrate hexahydrate and 6.489g of dimethylimidazole and dissolve them in 200ml of methanol solution respectively. Stir vigorously for 3h~6h, and stand still overnight. The product was filtered, washed with fresh methanol solution, and vacuumed overnight at 30 °C to prepare a ZIF-8 sample. Apply vacuum at 300°C for 4 hours to obtain the activated ZIF-8 sample.

2. Add 3ml, 2mol/L ammonia borane solution to one gram of activated ZIF-8 sample in an argon atmosphere glove box, ultrasonically impregnate for 5h, and vacuum dry overnight at room temperature. A composite material of ammonia borane and metal-organic framework compound ZIF-8 was prepared.

3. Put the above composite material into a high-temperature furnace, use an argon atmosphere (gas flow rate is 100-400mL/min), raise the temperature to 800-1200°C at a heating rate of 1-10°C/min, and heat it up at 800-1200 °C was kept for 2-10 hours, and cooled to room temperature in an argon atmosphere to prepare a boron-nitrogen-doped microporous carbon material.

It can be seen from Figures 1, 2, and 3 that after high-temperature sintering, the highly crystalline ZIF-8 framework material becomes an amorphous porous carbon material, and the pore size of the material is mainly distributed in the range of 0.6-1.2nm.

Example 2

The 0.4g boron-nitrogen-doped microporous carbon material prepared in Example 1 was placed in a 9mm sample tube of the Absorb-1 physical adsorption instrument of Quanta Corporation, USA, and heated overnight at 200°C in a sealed vacuum. The low-pressure hydrogen adsorption experiment was carried out under two temperature conditions of 77K and 87K.

It can be seen from Figure 4 that under the hydrogen pressure conditions of 77K and 820mmHg, the microporous carbon material doped with boron and nitrogen elements can absorb 204cm ³ of hydrogen gas per gram, and the corresponding mass fraction is 1.83wt%.

Example 3

The microporous carbon material doped with 0.3 g of boron and nitrogen elements prepared in Example 1 was placed in a 9 mm sample tube of the Absorb-1 physical adsorption instrument of Quanta Corporation, USA, and heated in a sealed vacuum at 200 ° C overnight. Under the constant temperature condition of 273K, the low-pressure carbon dioxide adsorption experiment was carried out.

It can be seen from Figure 5 that under the pressure conditions of 273K and 780mmHg, each gram of boron and nitrogen doped microporous carbon material can absorb 100cm ³ of carbon dioxide.

Example 4

The microporous carbon material doped with 0.3 g of boron and nitrogen elements prepared in Example 1 was placed in a 9 mm sample tube of the Absorb-1 physical adsorption instrument of Quanta Corporation, USA, and heated in a sealed vacuum at 200 ° C overnight. The low-pressure methane adsorption experiment was carried out under the temperature condition of 273K.

It can be seen from Figure 6 that under the pressure conditions of 273K and 780mmHg, every gram of boron and nitrogen doped microporous carbon materials can absorb 45cm ³ of methane. Far less than the adsorption capacity of carbon dioxide, so the material has a certain selective adsorption of carbon dioxide.

Claims (5)

1. a preparation method for boron nitrogen-doping micro-pore carbon material, is characterized in that:

Take metal organic frame compound ZIF-8 and boron nitrogen compound ammonia borine prepares by high-temperature sintering process as presoma; Respective material preparation process is:

1) the ammonia borine solution impregnation of 0.5-3mol/L is arrived in ZIF-8 duct, make the matrix material of metal organic frame compound ZIF-8 confinement ammonia borine;

2) matrix material of ZIF-8 confinement ammonia borine is placed in to High Temperature Furnaces Heating Apparatus, adopt argon gas atmosphere, gas flow rate is 100 ~ 400mL/min, temperature rise rate with 1 ~ 10 ° of C/min is warming up to 800 ~ 1200 ° of C from room temperature, at 800 ~ 1200 ° of C, keep 2 ~ 10 hours, in argon gas atmosphere, cool to room temperature, obtain product.

2. the preparation method of boron nitrogen-doping micro-pore carbon material according to claim 1, it is characterized in that: prepare the composite material by adopting solution impregnation of metal organic frame compound ZIF-8 confinement ammonia borine, the quality of dried every gram of ZIF-8 material confinement ammonia borine is between 0.1-0.45 gram.

3. the preparation method of boron nitrogen-doping micro-pore carbon material according to claim 1, is characterized in that:

Metal organic frame compound ZIF-8 preparation process is as follows: metal inorganic salt and glyoxaline ligand are dissolved in organic solvent, every 200mL solvent adds 1～20mmol metal inorganic salt and the organic imidazole ligands of 70～90mmol, temperature of reaction is 10～30 ℃, the crystallization time is 10～50 hours, by product collection, suction filtration, water or organic solvent washing, 30～150 ℃ of vacuum-dryings, 200-300 ℃ of vacuum activating, makes ZIF-8.

4. the preparation method of boron nitrogen-doping micro-pore carbon material according to claim 3, is characterized in that: zinc nitrate hexahydrate is metal inorganic salt used, and methylimidazole is that glyoxaline ligand and methyl alcohol are organic solvent.

5. the preparation method of boron nitrogen-doping micro-pore carbon material according to claim 1, it is characterized in that: the described micro-pore carbon material that synthesizes boron nitrogen-doping, doping when having realized boron nitrogen element to carbon material, the aperture of sample is concentrated and is distributed in 0.6-1.2nm.

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