CN112357906A

CN112357906A - Nitrogen-doped monomodal ultramicropore carbon nanosheet synthesized by in-situ amorphous cobalt template method, and method and application thereof

Info

Publication number: CN112357906A
Application number: CN202011259848.8A
Authority: CN
Inventors: 杨正龙
Original assignee: Tongji University
Current assignee: Tongji University
Priority date: 2020-11-12
Filing date: 2020-11-12
Publication date: 2021-02-12

Abstract

The invention relates to a method for synthesizing nitrogen-doped monomodal ultramicropore carbon nanosheets by using an in-situ amorphous cobalt template method, and a method and application thereof, wherein P4VP and CoCl are used₂·6H₂O as a raw material, Co²⁺Form Co-P with P4VP4VP in Co²⁺From Co-P4VP, P4VP was converted to Co-NDC by Cl^‑Inducing and Co-N bond confinement effect to induce the formation of amorphous Co nanoclusters, coating the amorphous Co nanoclusters in the carbon nanosheets converted from P4VP, and removing the amorphous Co nanoclusters through acid etching to form Co-NDPC with ultramicropores with the pore diameter of 0.5 +/-0.05 nm. Compared with the prior art, the method effectively avoids the defects of corrosivity, poor safety, complex process and the like existing in the traditional activation method or template method, and the synthesized Co-NDPC is CH with a very good application prospect₄/C₂H₂/C₂H₆/C₃H₈/CO₂/N₂Adsorbing the separating agent.

Description

Nitrogen-doped monomodal ultramicropore carbon nanosheet synthesized by in-situ amorphous cobalt template method, and method and application thereof

Technical Field

The invention belongs to the technical field of gas adsorption separation materials, and particularly relates to a nitrogen-doped unimodal ultramicropore carbon nanosheet synthesized by an in-situ amorphous cobalt template method, a method and application thereof.

Background

Natural gas is composed mainly of methane (CH)₄70-90%) and acetylene (C)₂H₂) Ethane (C)₂H₆) Propane (C)₃H₈) Carbon dioxide (CO)₂) And the like, and is one of the most important energy and chemical raw materials in the industrial society. E.g. CH₄Having the highest specific heating value (55.7kJ/g) is considered to be one of the most promising energy candidates in the future; c₂H₆And C₃H₈Dehydrogenation and C₂H₂Hydrogenation is an industrial production C₂H₄And C₃H₆Of a main raw material, and C₂H₄And C₃H₆But also is a basic chemical for producing bulk commodities such as polypropylene, polyester, polyethylene and the like. Based on the specificity of each component, other components in the natural gas are mixed with CH₄The separation has very important significance for realizing the high-efficiency utilization of resources. In addition, fossil fuel combustion produces CO₂The emission is the main cause of greenhouse effect, which causes global warming, glacier melting and sea level rise, and is one of the biggest environmental problems facing human in this century. Although the combustion products of natural gas are cleaner than coal and oil, it still emits significant amounts of CO₂. Therefore, how to capture and separate CO in flue gas₂Also has important research significance. Furthermore, CO is utilized₂The direct preparation of industrial products such as carbon monoxide, methanol, ethylene, ethanol and the like by electrocatalysis reduction is one of the current research hotspots₂The capture and separation of the protein have great economic value and prospect.

The low-temperature rectification separation of natural gas and the absorption of flue gas alkali liquor are the classical methods for solving the problems. However, the rectification separation has complex process and large energy consumption, and the alkali liquor absorption has difficult regeneration and is not beneficial to CO₂The subsequent utilization problem. The adsorption separation has simple operation process, energy saving, high efficiency and easy regenerationAnd the like are considered as the most promising alternative technologies. The adsorbent is the core of the technology and determines the separation efficiency of the whole process. Nitrogen-doped porous carbon (NDPCs) have the advantages of rich raw materials, stable physicochemical properties, strong weather resistance, low cost and the like, and are considered to be one of the most promising adsorbents. Therefore, the development of high performance NDPCs has been the focus and difficulty of adsorption separation engineering. In this regard, Zhang et al [ Wang J, Krishna R, Yang T, et al, Nitrogen-rich micropous carbons for high selectivity section of light hydrocarbons [ J].Journal of Materials Chemistry A 2016,4:13957-13966]Nitrogen-doped porous carbon NCA 700 is synthesized by KOH activation of a nitrogen-rich polymer precursor. At 298K and 1bar, NCA 700 vs. C₂H₂、C₂H₆And C₃H₈Adsorption capacity of (2) and corresponding x/CH₄IAST selectivity reaches 6.39(47.1), 7.59(65.7) and 11.56 mmol.g^-1(501.9). Liang et al [ Liang W, Zhang Y, Wang X, et al. alpha. high surface area activated porous carbonates for the effective adsorption of methane and ethylene [ J].Chemical Engineering Science 2017,162:192-202]Porous carbon A-AC-3 is synthesized by KOH activated asphalt. At 298K and 1bar, A-AC-3 is opposite to C₂H₆And C₃H₈Adsorption capacity of (2) and corresponding x/CH₄IAST selectivity reached 7.09(16.9) and 11.34 mmol. multidot.g^-1(88.8). Ashourirad et al [ Ashourirad B, Sekizkardes A K, Altaraweh S, et al].Chemistry of Materials 2015,27:1349-1358]Nitrogen-doped porous carbon CPC 550 was prepared by KOH activation of a benzimidazole crosslinked polymer. CO of CPC 550 at 298K and 1bar₂Adsorption capacity and corresponding CO₂/N₂IAST selectivities of 5.8 and 59 mmol-g, respectively^-1. Furthermore, Aijaz et al [ Aijaz A, Fujiwara N, Xu Q. from metal-organic frame to nitro-depleted nanopowders carbons: high CO₂ uptake and efficient catalytic oxygen reduction[J].Journal of the American Chemical Society 2014,136:6790-6793]Reported that ZIF-8 is used as a templateAnd preparation of precursor Nitrogen doped porous carbon NC700 with 3.1 mmol. multidot.g at 273K and 1bar^-1Adsorption amount of (2) and CO of 59₂/N₂And (4) selectivity. Singh et al [ Singh D K, Krishna K S, Harish S, et al. No. more HF: teflon-assisted ultra removal of silicon to product high-surface-area structured carbon for Enhanced CO₂ Capture and supercapacitor performance[J].Angewandte Chemie International Edition 2016,55:2032-2036]Reported as SiO₂Ordered mesoporous carbon JCN-1 to CO prepared by template method₂Adsorption amount and CO of₂/N₂IAST selectivities of 3.5 and 7 mmol-g, respectively^-1。

The applicant has found that although high adsorption capacity nitrogen doped porous carbon materials can be obtained by KOH activation, the randomness of the activation reaction results in carbon materials obtained by the method generally having a discrete pore size distribution, which in turn results in a lower effective utilization of the pore structure. In addition, the strong corrosiveness of KOH and the low yield of the activation method limit the practical application possibility. The precise synthesis of the sub-nanometer template in the template method is the biggest bottleneck of the application of the method. Therefore, the development of a safer and more efficient carbon-based adsorbent synthesis method has very important significance for gas adsorption separation engineering.

Disclosure of Invention

The invention aims to provide a method for synthesizing nitrogen-doped monomodal ultramicropore carbon nanosheets by an in-situ amorphous cobalt template method, and a method and application thereof. Effectively avoids the defects of corrosivity, poor safety, complex process and the like existing in the traditional activation method or template method, and the synthesized Co-NDPC is CH with great application prospect₄/C₂H₂/C₂H₆/C₃H₈/CO₂/N₂Adsorbing the separating agent.

The purpose of the invention can be realized by the following technical scheme:

the invention provides a method for synthesizing nitrogen-doped monomodal ultramicropore carbon nanosheets by using an in-situ amorphous cobalt template method, wherein poly 4-vinylpyridine (P4VP) and cobalt chloride hexahydrate (CoCl)₂·6H₂O) as raw material, Co²⁺Form a thermally stable intermediate Co-P4VP with P4VP, in Co²⁺Under the catalytic action of the catalyst, P4VP in the Co-P4VP is converted into carbon nanosheet Co-NDC in the pyrolysis process, and Cl is introduced in the pyrolysis process^-Inducing and Co-N bond confinement effect to induce the formation of amorphous Co nanoclusters, wrapping the amorphous Co nanoclusters in the P4VP converted carbon nanosheets, removing the amorphous Co nanoclusters through subsequent acid etching to form ultramicropore nitrogen-doped porous carbon Co-NDPC with ultramicropores with the diameters of 0.5 +/-0.05 nm, namely synthesizing the nitrogen-doped monomodal ultramicropore carbon nanosheets through the in-situ amorphous cobalt template method.

Preferably, the method comprises the steps of:

(a) mixing P4VP and CoCl₂·6H₂O is respectively dissolved in the solvent to obtain P4VP solution and CoCl₂Solution, P4VP solution was added slowly to CoCl with stirring₂Obtaining a mixed solution in the solution, and drying the mixed solution after vacuum rectification to obtain a thermal stability intermediate Co-P4 VP;

(b) carbonizing Co-P4VP in nitrogen atmosphere, and naturally cooling to room temperature to obtain carbon nanosheet Co-NDC;

(d) washing the Co-NDC subjected to acid washing with deionized water to neutrality, filtering to obtain a filter cake, and drying the filter cake to obtain the ultramicropore nitrogen-doped porous carbon Co-NDPC with ultramicropores with the pore diameter of 0.5 +/-0.05 nm, namely the nitrogen-doped monomodal ultramicropore carbon nanosheet synthesized by the in-situ amorphous cobalt template method.

Preferably, in step (a), said P4VP is reacted with CoCl₂·6H₂The mass ratio of O is 0.1-1.0: 0.5 to 5.0; co in thermal stable intermediate Co-P4VP²⁺The atomic mol ratio of the solvent to the N is 2, and the solvent is absolute ethyl alcohol.

Preferably, in the step (b), the carbonization temperature is 500-900 ℃; the carbonization time is 2-4 h; the heating rate is 2.5-7.5 ℃ per minute^-1。

Preferably, in the step (c), the acid solution is 0.5-2.5M HCl solution, and the stirring time is 12-36 h.

Preferably, in the step (d), the drying temperature is 40-80 ℃ and the drying time is 12-36 h.

The invention provides a nitrogen-doped monomodal ultramicropore carbon nanosheet synthesized by an in-situ amorphous cobalt template method, and the nitrogen-doped monomodal ultramicropore carbon nanosheet is obtained by the method.

Preferably, the nitrogen-doped monomodal ultramicropore carbon nanosheet has a carbon nanosheet network structure, and the specific surface area is 500-1500 m² g^-1The volume of the micro-pores is 0.25-0.75 cm³·g^-1The nitrogen doping amount is 3-15 at%, and the unimodal pore size distribution of 0.5 +/-0.05 nm is formed.

Further preferably, the nitrogen-doped monomodal ultramicropore carbon nanosheet has a unique carbon nanosheet network structure and a specific surface area of 900-1200 m²·g^-1The micropore volume is 0.45-0.55 cm³·g^-1The nitrogen doping amount is 10-12 at%, and the unimodal pore size distribution of 0.5 +/-0.05 nm is formed.

The third aspect of the invention provides application of the in-situ amorphous cobalt template method in synthesis of nitrogen-doped monomodal ultramicropore carbon nanosheets, and the nitrogen-doped monomodal ultramicropore carbon nanosheets are used as adsorbents for C₂H₂、C₂H₆、C₃H₈And CO₂And has x/CH₄And CO₂/N₂IAST selectivity, said x comprising C₂H₂、C₂H₆、C₃H₈Or CO₂。

Compared with the prior art, the invention has the following beneficial effects:

1. the invention introduces Co²⁺Form thermally stable intermediates Co-P4VPs with P4VP, in Co²⁺The P4VP in the Co-P4VPs can be converted into carbon and Co in the pyrolysis process²⁺Is critical to the carbon conversion of P4 VP. Furthermore, by Cl^-Inducing and Co-N bond confinement effect to induce the formation of amorphous Co nanoclusters, coating the uniform ultra-small amorphous Co nanoclusters in the carbon nanosheets converted from P4VP, and removing the Co nanoclusters through a subsequent acid etching process to form ultra-micropores (approximately equal to 0.5nm) with uniform pore size. The invention avoids the defects of pore-forming by the traditional activation method and template method.

2. The nitrogen-doped unimodal ultramicropore carbon nano is synthesized by the in-situ amorphous cobalt template method prepared by the inventionThe rice flake (Co-NDPC) has a unique carbon nanosheet network structure and a high specific surface area (900-1200 m)² g^-1) The volume of the micro pores is 0.45-0.55 cm³·g^-1High nitrogen doping amount (10-12 at%), unimodal pore size distribution (0.5 +/-0.05 nm) and the like. As adsorbent, at 298K and 1bar, Co-NDPC showed an ultra-high C₂H₂、C₂H₆、C₃H₈And CO₂The adsorption capacities were 6.7, 5.9, 7.4 and 5.6 mmol/g, respectively^-1Corresponding x/CH₄(x＝C₂H₂、C₂H₆、C₃H₈Or CO₂). And CO₂/N₂The IAST selectivity is respectively as high as 75.3, 65.9, 1743.6, 11.4 and 74.7, and the method has high application value in the field of gas adsorption separation.

3. The invention effectively avoids the defects of corrosivity, poor safety, complex process and the like of the traditional activation method or template method, and the synthesized Co-NDPC is CH with great application prospect₄/C₂H₂/C₂H₆/C₃H₈/CO₂/N₂Adsorbing the separating agent.

Drawings

FIG. 1 is a schematic diagram of the preparation of Co-NDPC according to the present invention;

FIG. 2 is a topographical feature of Co-NDPC-700 of the present invention: (a, b) SEM images; (c) SEM-mapping; (d-f) TEM images at different magnifications;

FIG. 3 is (a) Co-NDPC-500; (b) Co-NDPC-600; (c) Co-NDPC-800; (d) SEM image of Co-NDPC-900;

FIG. 4 shows (a) N of Co-NDPCs₂Adsorption isotherms; (b) NLDFT pore size distribution curve.

Detailed Description

A method for synthesizing nitrogen-doped monomodal ultramicropore carbon nanosheets by using an in-situ amorphous cobalt template method is characterized in that poly-4-vinylpyridine (P4VP) and cobalt chloride hexahydrate (CoCl)₂·6H₂O) as raw material, Co²⁺Form a thermally stable intermediate Co-P4VP with P4VP, in Co²⁺Under the catalytic action of Co-P4VP, P4VP in the pyrolysis processIs converted into carbon nano-sheet Co-NDC, and is subjected to Cl passing in the pyrolysis process^-Inducing and Co-N bond confinement effect to induce the formation of amorphous Co nanoclusters, wrapping the amorphous Co nanoclusters in the P4VP converted carbon nanosheets, removing the amorphous Co nanoclusters through subsequent acid etching to form ultramicropore nitrogen-doped porous carbon Co-NDPC with ultramicropores with the diameters of 0.5 +/-0.05 nm, namely synthesizing the nitrogen-doped monomodal ultramicropore carbon nanosheets through the in-situ amorphous cobalt template method.

More specifically, the method comprises the steps of:

In step (a), P4VP and CoCl are preferred₂·6H₂The mass ratio of O is 0.1-1.0: 0.5 to 5.0; co in thermal stable intermediate Co-P4VP²⁺The atomic mol ratio of the component to the component is 2, and the solvent is absolute ethyl alcohol.

In the step (b), the carbonization temperature is preferably 500-900 ℃; the carbonization time is 2-4 h; the heating rate is 2.5-7.5 ℃ per minute^-1。

In the step (c), the acid solution is preferably 0.5-2.5M HCl solution, and the stirring time is 12-36 h.

In the step (d), the drying temperature is preferably 40-80 ℃ and the time is 12-36 h.

The method for evaluating the gas adsorption separation performance comprises the following steps:

1. static adsorption Capacity test of samples at 0 and 25 deg.C

Sample pair CH at 0 and 25 ℃₄、C₂H₂、C₂H₆、C₃H₈、CO₂And N₂The static adsorption test of (2) is characterized by an Autosorb-iQ2 specific surface area and a pore diameter adsorption instrument. The test range is 0-1 bar, the ice-water mixture is used as a test thermostat at 0 ℃, the water at 25 ℃ is used as a test thermostat at 25 ℃, and the mass of the sample is about 100 mg. The samples were degassed at 250 ℃ for 12h before testing.

Sample cycle stability was evaluated by conducting 5 consecutive adsorption-desorption experiments on an Autosorb-iQ2 adsorber. The sample was degassed just before the start of the first adsorption test and weighed at the end of each desorption to correct for the sample mass. The removal of gas between different cycles depends on the vacuum pumping process of the apparatus.

2. Adsorption data Single Point Langmuir-Freundlich model fitting

b is a temperature-related parameter, which is related as follows:

R＝8.314J mol^-1K^-1.

3. gas adsorption selectivity prediction

The prediction of the adsorption selectivity (S) of the sample for different gases is calculated according to the Ideal Adsorption Solution Theory (IAST) and is calculated according to the following formula:

in the above formula x_iAnd y_iRepresents the molar fraction of i component (i ═ 1,2) in the adsorption and bulk phases, respectively, of the sample at adsorption equilibrium.

The invention is described in detail below with reference to the figures and specific embodiments.

Example 1

A preparation method for synthesizing nitrogen-doped monomodal ultramicropore carbon nanosheets by an in-situ amorphous cobalt template method is characterized by comprising the following steps: a) 0.42g P4VP and 1.903g CoCl₂·6H₂O was dissolved in 100mL of absolute ethanol, and the P4 VP/ethanol solution was added slowly to CoCl with stirring₂·6H₂In O/ethanol solution, stirring for 4h by magnetic force to obtain P4VP/CoCl₂Mixing the ethanol solution; the resulting P4VP/CoCl₂Vacuum rectifying the ethanol mixed solution, and drying in an oven at 60 deg.C for 24h to obtain carbonized precursor Co-P4VP (Co)²⁺a/N atomic molar ratio of 2); b) placing the Co-P4VP precursor in a tube furnace, N₂Heating to carbonization temperature of 500 ℃ in the atmosphere, preserving heat and carbonizing for 3h (heating rate of 5 ℃ C. min)^-1) Naturally cooling to room temperature to obtain a carbonization product Co-NDC-500, wherein 500 represents the carbonization temperature (DEG C); c) adding Co-NDC-500 into 200mL of 1M HCl solution, and magnetically stirring for 24h to remove metallic cobalt; d) washing the Co-NDC washed by the acid with deionized water to be neutral, filtering to obtain a filter cake, and drying the filter cake in an oven at 60 ℃ for 12h to obtain a final product named Co-NDPC-500, wherein 500 represents the carbonization temperature (DEG C). The nitrogen-doped single-peak ultramicropore carbon nanosheet synthesized by the in-situ amorphous cobalt template method is subjected to structure characterization and gas adsorption separation performance test, and the results are shown in tables 1-4.

Example 2

A preparation method for synthesizing nitrogen-doped monomodal ultramicropore carbon nanosheets by an in-situ amorphous cobalt template method is characterized by comprising the following steps: a) 0.42g P4VP and 1.903g CoCl₂·6H₂O was dissolved in 100mL of absolute ethanol, and the P4 VP/ethanol solution was added slowly to CoCl with stirring₂·6H₂In O/ethanol solution, stirring for 4h by magnetic force to obtain P4VP/CoCl₂Mixing the ethanol solution; the resulting P4VP/CoCl₂Vacuum rectifying the ethanol mixed solution, and drying in an oven at 60 deg.C for 24h to obtain carbonized precursor Co-P4VP (Co)²⁺a/N atomic molar ratio of 2); b) placing the Co-P4VP precursor in a tube furnace, N₂Under the atmosphereHeating to the carbonization temperature of 600 ℃, preserving heat and carbonizing for 3h (the heating rate is 5 ℃ C. min)^-1) Naturally cooling to room temperature to obtain a carbonization product Co-NDC-600, wherein 600 represents the carbonization temperature (DEG C); c) adding Co-NDC-600 into 200mL of 1M HCl solution, and magnetically stirring for 24h to remove metallic cobalt; d) washing the Co-NDC washed by the acid with deionized water to be neutral, filtering to obtain a filter cake, and drying the filter cake in an oven at 60 ℃ for 12h to obtain a final product, wherein 600 represents the carbonization temperature (DEG C). The nitrogen-doped single-peak ultramicropore carbon nanosheet synthesized by the in-situ amorphous cobalt template method is subjected to structure characterization and gas adsorption separation performance test, and the results are shown in tables 1-4.

Example 3

A preparation method for synthesizing nitrogen-doped monomodal ultramicropore carbon nanosheets by an in-situ amorphous cobalt template method is characterized by comprising the following steps: a) 0.42g P4VP and 1.903g CoCl₂·6H₂O was dissolved in 100mL of absolute ethanol, and the P4 VP/ethanol solution was added slowly to CoCl with stirring₂·6H₂In O/ethanol solution, stirring for 4h by magnetic force to obtain P4VP/CoCl₂Mixing the ethanol solution; the resulting P4VP/CoCl₂Vacuum rectifying the ethanol mixed solution, and drying in an oven at 60 deg.C for 24h to obtain carbonized precursor Co-P4VP (Co)²⁺a/N atomic molar ratio of 2); b) placing the Co-P4VP precursor in a tube furnace, N₂Heating to 700 ℃ under the atmosphere, preserving heat and carbonizing for 3h (the heating rate is 5 ℃ C. min)^-1) Naturally cooling to room temperature to obtain a carbonization product Co-NDC-700, wherein 700 represents the carbonization temperature (DEG C); c) adding Co-NDC-700 into 200mL of 1M HCl solution, and magnetically stirring for 24h to remove metallic cobalt; d) washing the Co-NDC subjected to acid washing with deionized water to neutrality, filtering to obtain a filter cake, and drying the filter cake in an oven at 60 ℃ for 12 hours to obtain a final product named Co-NDPC-700, wherein 700 represents the carbonization temperature (DEG C). The nitrogen-doped single-peak ultramicropore carbon nanosheet synthesized by the in-situ amorphous cobalt template method is subjected to structure characterization and gas adsorption separation performance test, and the results are shown in tables 1-4.

Example 4

Nitrogen-doped single-peak ultramicropore synthesized by in-situ amorphous cobalt template methodA method for preparing carbon nano-sheets is characterized by comprising the following steps: a) 0.42g P4VP and 1.903g CoCl₂·6H₂O was dissolved in 100mL of absolute ethanol, and the P4 VP/ethanol solution was added slowly to CoCl with stirring₂·6H₂In O/ethanol solution, stirring for 4h by magnetic force to obtain P4VP/CoCl₂Mixing the ethanol solution; the resulting P4VP/CoCl₂Vacuum rectifying the ethanol mixed solution, and drying in an oven at 60 deg.C for 24h to obtain carbonized precursor Co-P4VP (Co)²⁺a/N atomic molar ratio of 2); b) placing the Co-P4VP precursor in a tube furnace, N₂Heating to the carbonization temperature of 800 ℃ in the atmosphere, preserving heat and carbonizing for 3h (the heating rate is 5 ℃ C. min)^-1) Naturally cooling to room temperature to obtain a carbonization product Co-NDC-800, wherein 800 represents the carbonization temperature (DEG C); c) adding Co-NDC-800 into 200mL of 1M HCl solution, and magnetically stirring for 24h to remove metallic cobalt; d) washing the Co-NDC subjected to acid washing with deionized water to neutrality, filtering to obtain a filter cake, and drying the filter cake in an oven at 60 ℃ for 12 hours to obtain a final product named Co-NDPC-800, wherein 800 represents the carbonization temperature (DEG C). The nitrogen-doped single-peak ultramicropore carbon nanosheet synthesized by the in-situ amorphous cobalt template method is subjected to structure characterization and gas adsorption separation performance test, and the results are shown in tables 1-4.

Example 5

A preparation method for synthesizing nitrogen-doped monomodal ultramicropore carbon nanosheets by an in-situ amorphous cobalt template method is characterized by comprising the following steps: a) 0.42g P4VP and 1.903g CoCl₂·6H₂O was dissolved in 100mL of absolute ethanol, and the P4 VP/ethanol solution was added slowly to CoCl with stirring₂·6H₂In O/ethanol solution, stirring for 4h by magnetic force to obtain P4VP/CoCl₂Mixing the ethanol solution; the resulting P4VP/CoCl₂Vacuum rectifying the ethanol mixed solution, and drying in an oven at 60 deg.C for 24h to obtain carbonized precursor Co-P4VP (Co)²⁺a/N atomic molar ratio of 2); b) placing the Co-P4VP precursor in a tube furnace, N₂Heating to 900 deg.C under atmosphere, and carbonizing for 3h (heating rate 5 deg.C. min)^-1) Naturally cooling to room temperature to obtain a carbonization product Co-NDC-900, wherein 900 represents the carbonization temperature (DEG C); c. C) Adding Co-NDC-900 into 200mL of 1M HCl solution, and magnetically stirring for 24 hours to remove metal cobalt; d) washing the Co-NDC subjected to acid washing with deionized water to neutrality, filtering to obtain a filter cake, and drying the filter cake in an oven at 60 ℃ for 12 hours to obtain a final product named Co-NDPC-900, wherein 900 represents the carbonization temperature (DEG C). The nitrogen-doped single-peak ultramicropore carbon nanosheet synthesized by the in-situ amorphous cobalt template method is subjected to structure characterization and gas adsorption separation performance test, and the results are shown in tables 1-4.

Example 6

A preparation method for synthesizing nitrogen-doped monomodal ultramicropore carbon nanosheets by an in-situ amorphous cobalt template method is characterized by comprising the following steps: a) 0.42g P4VP and 1.903g CoCl₂·6H₂O was dissolved in 100mL of absolute ethanol, and the P4 VP/ethanol solution was added slowly to CoCl with stirring₂·6H₂In O/ethanol solution, stirring for 4h by magnetic force to obtain P4VP/CoCl₂Mixing the ethanol solution; the resulting P4VP/CoCl₂Vacuum rectifying the ethanol mixed solution, and drying in an oven at 60 deg.C for 24h to obtain carbonized precursor Co-P4VP (Co)²⁺a/N atomic molar ratio of 2); b) placing the Co-P4VP precursor in a tube furnace, N₂Heating to the carbonization temperature of 700 ℃ in the atmosphere, preserving heat and carbonizing for 3h (the heating rate is 2.5 ℃ C. min)^-1) Naturally cooling to room temperature to obtain a carbonization product Co-NDC-700, wherein 700 represents the carbonization temperature (DEG C); c) adding Co-NDC-700 into 200mL of 1M HCl solution, and magnetically stirring for 24 hours to remove metal cobalt; d) washing the Co-NDC subjected to acid washing with deionized water to neutrality, filtering to obtain a filter cake, and drying the filter cake in an oven at 60 ℃ for 12 hours to obtain a final product named Co-NDPC-700, wherein 700 represents the carbonization temperature (DEG C). And (3) synthesizing the nitrogen-doped monomodal ultramicropore carbon nanosheet by using an in-situ amorphous cobalt template method, and testing the gas adsorption separation performance.

Example 7

A preparation method for synthesizing nitrogen-doped monomodal ultramicropore carbon nanosheets by an in-situ amorphous cobalt template method is characterized by comprising the following steps: a) 0.42g P4VP and 1.903g CoCl₂·6H₂Dissolving O in 100mL of absolute ethanol respectively, and stirring to obtain P4 VP/ethylAlcohol solution was slowly added to CoCl₂·6H₂In O/ethanol solution, stirring for 4h by magnetic force to obtain P4VP/CoCl₂Mixing the ethanol solution; the resulting P4VP/CoCl₂Vacuum rectifying the ethanol mixed solution, and drying in an oven at 60 deg.C for 24h to obtain carbonized precursor Co-P4VP (Co)²⁺a/N atomic molar ratio of 2); b) placing the Co-P4VP precursor in a tube furnace, N₂Heating to the carbonization temperature of 700 ℃ in the atmosphere, preserving heat and carbonizing for 3h (the heating rate is 7.5 ℃ C. min)^-1) Naturally cooling to room temperature to obtain a carbonization product Co-NDC-700, wherein 700 represents the carbonization temperature (DEG C); c) adding Co-NDC-700 into 200mL of 1M HCl solution, and magnetically stirring for 24 hours to remove metal cobalt; d) washing the Co-NDC subjected to acid washing with deionized water to neutrality, filtering to obtain a filter cake, and drying the filter cake in an oven at 60 ℃ for 12 hours to obtain a final product named Co-NDPC-700, wherein 700 represents the carbonization temperature (DEG C). And (3) synthesizing the nitrogen-doped monomodal ultramicropore carbon nanosheet by using an in-situ amorphous cobalt template method, and testing the gas adsorption separation performance.

Example 8

A preparation method for synthesizing nitrogen-doped monomodal ultramicropore carbon nanosheets by an in-situ amorphous cobalt template method is characterized by comprising the following steps: a) 0.42g P4VP and 1.903g CoCl₂·6H₂O was dissolved in 100mL of absolute ethanol, and the P4 VP/ethanol solution was added slowly to CoCl with stirring₂·6H₂In O/ethanol solution, stirring for 4h by magnetic force to obtain P4VP/CoCl₂Mixing the ethanol solution; the resulting P4VP/CoCl₂Vacuum rectifying the ethanol mixed solution, and drying in an oven at 60 deg.C for 24h to obtain carbonized precursor Co-P4VP (Co)²⁺a/N atomic molar ratio of 2); b) placing the Co-P4VP precursor in a tube furnace, N₂Heating to 700 ℃ under the atmosphere, preserving heat and carbonizing for 3h (the heating rate is 5 ℃ C. min)^-1) Naturally cooling to room temperature to obtain a carbonization product Co-NDC-700, wherein 700 represents the carbonization temperature (DEG C); c) adding Co-NDC-700 into 200mL2.5M HCl solution, and magnetically stirring for 24h to remove metallic cobalt; d) washing the Co-NDC after acid washing with deionized water to neutrality, filtering to obtain a filter cake, drying the filter cake in an oven at 60 ℃ for 12h to obtain the final product named Co-NDPC-700, where 700 represents carbonization temperature (. degree. C.). And (3) synthesizing the nitrogen-doped monomodal ultramicropore carbon nanosheet by using an in-situ amorphous cobalt template method, and testing the gas adsorption separation performance.

TABLE 1 texture characteristics and metallic Co content of Co-NDPCs

The element content is as follows: (a) XPS (at%), (b) ICP-AES (wt%).

TABLE 2 examples gas loading at 273 or 298K, 1bar

TABLE 3 example at 298K, 1bar vs. x/CH₄IAST selectivity of (50/50, v/v) binary gas mixture

TABLE 4 example at 298K, 1bar vs. CO₂/N₂(v/v) IAST Selectivity of binary gas mixture

The schematic diagram of the preparation process of Co-NDPC is shown in FIG. 1, and the morphological characteristics of Co-NDPC-700 in FIG. 2 are as follows: (a, b) SEM images; (c) SEM-mapping; (d-f) TEM image. FIG. 3(a) Co-NDPC-500; (b) Co-NDPC-600; (c) Co-NDPC-800; (d) SEM image of Co-NDPC-900. FIG. 4 shows (a) N of Co-NDPCs₂Adsorption isotherms; (b) NLDFT pore size distribution curve.

In summary, as shown in FIGS. 1-4, tables 1-4, with P4VP and CoCl₂·6H₂O is taken as a raw material to successfully synthesize nitrogen-doped monomodal ultramicropore carbon nanosheets (Co-NDPC), and the Co-NDPC is prepared from Co²⁺And P4VP by carbonization, with Cl^-Inducing and Co-N bond confinement effect to induce the formation of amorphous Co nanoclusters, coating the uniform ultra-small amorphous Co nanoclusters in the carbon nanosheets converted from P4VP, and removing the Co nanoclusters through a subsequent acid etching process to form ultra-micropores (approximately equal to 0.5nm) with uniform pore size. The Co-NDPC has a unique carbon nanosheet network structure and a high specific surface area (900-1200 m)² g^-1) The volume of the micro pores is 0.45-0.55 cm³·g^-1High nitrogen doping amount (10-12 at%), unimodal pore size distribution (0.5 +/-0.05 nm) and the like. As adsorbent, at 298K and 1bar, Co-NDPC showed an ultra-high C₂H₂、C₂H₆、C₃H₈And CO₂The adsorption capacities were 6.7, 5.9, 7.4 and 5.6 mmol/g, respectively^-1Corresponding x/CH₄And CO₂/N₂The IAST selectivity was also as high as 75.3, 65.9, 1743.6, 11.4, and 74.7, respectively. The synthesized Co-NDPC is CH with great application prospect₄/C₂H₂/C₂H₆/C₃H₈/CO₂/N₂Adsorbing the separating agent.

The embodiments described above are intended to facilitate the understanding and use of the invention by those skilled in the art. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make improvements and modifications within the scope of the present invention based on the disclosure of the present invention.

Claims

1. The method for synthesizing the nitrogen-doped monomodal ultramicropore carbon nanosheet by using the in-situ amorphous cobalt template method is characterized in that P4VP and CoCl are used₂·6H₂O as a raw material, Co²⁺Form a thermally stable intermediate Co-P4VP with P4VP, in Co²⁺Under the catalytic action of the catalyst, P4VP in the Co-P4VP is converted into carbon nanosheet Co-NDC in the pyrolysis process, and Cl is introduced in the pyrolysis process^-Induction and Co-N bond confinement effect induced amorphous Co nanoclusterForming clusters, enabling the clusters to be coated in the carbon nanosheets converted from P4VP, removing amorphous Co nanoclusters through subsequent acid etching, and forming ultramicropore nitrogen-doped porous carbon Co-NDPC with ultramicropores with the pore diameters of 0.5 +/-0.05 nm, namely synthesizing the nitrogen-doped monomodal ultramicropore carbon nanosheets through the in-situ amorphous cobalt template method.

2. The method for synthesizing nitrogen-doped monomodal ultramicropore carbon nanosheets according to claim 1, comprising the steps of:

(c) adding Co-NDC into an acid solution, stirring, and removing metal cobalt in the solution;

3. The method for synthesizing nitrogen-doped monomodal ultramicropore carbon nanosheets by using in-situ amorphous cobalt templating method according to claim 2, wherein in step (a), P4VP and CoCl are used₂·6H₂The mass ratio of O is 0.1-1.0: 0.5 to 5.0; co in thermal stable intermediate Co-P4VP²⁺The atomic mol ratio of the solvent to the N is 2, and the solvent is absolute ethyl alcohol.

4. The method for synthesizing nitrogen-doped monomodal ultramicropore carbon nanosheets by using the in-situ amorphous cobalt template method according to claim 2, wherein in the step (b), the carbonization temperature is 500-900 ℃; carbon (C)The time for the reaction is 2-4 h; the heating rate is 2.5-7.5 ℃ per minute^-1。

5. The method for synthesizing nitrogen-doped monomodal ultramicropore carbon nanosheets by using the in-situ amorphous cobalt template method according to claim 2, wherein in step (c), the acid solution is 0.5-2.5M HCl solution, and the stirring time is 12-36 h.

6. The method for synthesizing nitrogen-doped monomodal ultramicropore carbon nanosheets by using the in-situ amorphous cobalt template method according to claim 2, wherein in step (d), the drying temperature is 40-80 ℃ and the drying time is 12-36 h.

7. An in-situ amorphous cobalt template method for synthesizing nitrogen-doped monomodal ultramicropore carbon nanosheet, which is characterized by being obtained by the method of any one of claims 1 to 6.

8. The in-situ amorphous cobalt template method for synthesizing nitrogen-doped monomodal ultramicropore carbon nanosheets according to claim 7, wherein the nitrogen-doped monomodal ultramicropore carbon nanosheets have a carbon nanosheet network structure and a specific surface area of 500-1500 m²g^-1The volume of the micro-pores is 0.25-0.75 cm³·g^-1The nitrogen doping amount is 3-15 at%, and the unimodal pore size distribution of 0.5 +/-0.05 nm is formed.

9. The in-situ amorphous cobalt templating method of claim 8, wherein the nitrogen-doped unimodal nanoporous carbon nanoplatelets have a unique carbon nanoplatelet network structure with a specific surface area of 900-1200 m²·g^-1The micropore volume is 0.45-0.55 cm³·g^-1The nitrogen doping amount is 10-12 at%, and the unimodal pore size distribution of 0.5 +/-0.05 nm is formed.

10. Application of in-situ amorphous cobalt template method for synthesizing nitrogen-doped monomodal ultramicropore carbon nanosheets as claimed in any one of claims 7 to 9, wherein the nitrogen-doped monomodal ultramicropore carbon nanosheets are used as adsorbent for C₂H₂、C₂H₆、C₃H₈And CO₂And has x/CH₄And CO₂/N₂IAST selectivity, said x comprising C₂H₂、C₂H₆、C₃H₈Or CO₂。