KR20170063113A - Method for Manufacturing Three-Dimension Porous Graphene - Google Patents

Abstract

The present invention relates to a method for producing a three-dimensional porous graphene, and more particularly, to a method for producing a three-dimensional porous graphene by graphene oxide (GO-ester) containing an ester group and an organic linking material containing an amine group To a method for producing a three-dimensional porous graphene. According to the method for producing a three-dimensional porous graphene according to the present invention, the interlayer distance of graphene can be controlled according to the length of the organic binder, and the specific surface area of the graphene structure can be determined. In addition, the benzoimidazole structure in which an amine group of an organic linking group and an ester group of a graphene oxide are formed by reaction is known to be the easiest chemical structure to store carbon dioxide and hydrogen to date. The preparation method is a one-pot reaction in which reactants are reacted in a single reactor, and is environmentally friendly because it does not use additives such as a catalyst and a surfactant that cause environmental pollution or increase synthesis cost, There is a saving effect.

Description

TECHNICAL FIELD The present invention relates to a three-dimensional porous graphene,

The present invention relates to a method for producing a three-dimensional porous graphene, and more particularly, to a method for producing a three-dimensional porous graphene by graphene oxide (GO-ester) containing an ester group and an organic linking material containing an amine group To a method for producing a three-dimensional porous graphene.

Graphene is a two-dimensional carbon-based macromolecule with a single atomic thickness, which has received considerable attention in recent years due to its excellent mechanical properties (physical stability), chemical properties and electrical properties, and is being used for energy storage devices, nanoelectronics, Is a nanomaterial that can be applied to various applications such as purification and gas storage.

The two-dimensional graphene sheet has the advantage that the gas molecules are adsorbed well due to the π-π resonance structure of the surface. However, due to the van der waals interaction between the π-π resonance structures of the graphene sheet as a whole, The graphene sheet of the present invention coagulates. Therefore, in order to increase the amount of adsorbed gas by graphene, it is necessary to increase the surface area of the graphene sheet and to study the production of graphene having a three-dimensional structure in a two-dimensional graphene sheet, In order to have a high porosity, it is important to control the interlayer distance of the graphene sheet.

In the prior art, Korean Patent No. 1273495 discloses a method of controlling the interlayer distance of graphene oxide by injecting carbon dioxide gas into graphene oxide produced using graphite powder.

In addition, although a method of synthesizing porous graphene using a metal catalyst to produce graphene having a three-dimensional structure is known, an expensive palladium catalyst and a surfactant are required (Rao et al., Chem. Commun In the case of forming a porous graphene structure by performing a CC coupling reaction using graphene oxide and an organic coupling agent using a metal catalyst, a large amount of oxygen functional groups (for example, Oxygen Functional Groups).

In the case of connecting an organic linkage having a diamine group to a graphene oxide without using a catalyst, it is possible to form a benzimidazole structure, but the graphene oxide is directly reacted with an organic linkage, (Y. Cui et al., Nanoscale 5: 8367, 2013) can be confirmed by the fact that a large amount of functional groups (Oxygen Functional Group) remain.

Accordingly, the present inventors have found that the use of a catalyst containing an ester group to produce graphene capable of controlling the interlayer distance of the graphene sheet without using additives such as catalysts and surfactants that cause environmental pollution or increase the synthesis cost When an organic linking material containing graphene oxide (GO-ester) and an amine group is dispersed in a solvent and then reacted to obtain three-dimensional graphene, graphene oxide is produced by converting the -OH group on the surface of graphene oxide to -COO- (RGO) other than GO to obtain a large π-π specific surface area and simultaneously form a large amount of ester group on the graphene surface, and to control the interlayer distance and specific surface area of graphene And it is confirmed that the adsorption (storage) ability of hydrogen and carbon dioxide can be controlled thereby, and the present invention has been completed.

It is an object of the present invention to provide a method for producing a three-dimensional porous graphene capable of controlling the interlayer distance of graphene according to the length of an organic connecting body and without using an additive such as a catalyst and a surfactant.

In order to accomplish the above object, the present invention provides a process for preparing a three-dimensional porous graphene comprising dispersing an organic linking material containing graft-oxide (GO-ester) containing an ester group and an amine group in a solvent and then reacting ≪ / RTI >

The present invention also provides a three-dimensional porous graphene produced by the above method and having a specific surface area of 400 to 800 m ² / g.

The present invention also provides a method of adsorbing carbon dioxide (CO ₂ ) using the three-dimensional porous graphene.

The present invention also provides a carbon dioxide (CO ₂ ) adsorbent containing the three-dimensional porous graphene.

The present invention also provides a method for storing hydrogen (H ₂ ) using the three-dimensional porous graphene.

The present invention also provides a hydrogen (H ₂ ) adsorbent containing the three-dimensional porous graphene.

According to the method for producing a three-dimensional porous graphene according to the present invention, the interlayer distance of graphene can be controlled according to the length of the organic binder, and the specific surface area of the graphene structure can be determined. In addition, the benzoimidazole structure in which an amine group of an organic linking group and an ester group of a graphene oxide are formed by reaction is known to be the easiest chemical structure to store carbon dioxide and hydrogen to date. The preparation method is a one-pot reaction in which reactants are reacted in a single reactor, and is environmentally friendly because it does not use additives such as a catalyst and a surfactant that cause environmental pollution or increase synthesis cost, There is a saving effect.

FIG. 1 is a conceptual diagram showing a method of manufacturing a three-dimensional porous graphene according to an embodiment of the present invention.
FIG. 2 is a Fourier transform infrared spectroscopy (FTIR) analysis result of a three-dimensional porous graphene according to an embodiment of the present invention.
FIG. 3 is an X-ray photoelectron spectroscopy (XPS) analysis result of a three-dimensional porous graphene according to an embodiment of the present invention.
FIG. 4 is a PXRD (Powder X-Ray Diffraction) analysis result of a three-dimensional porous graphene according to an embodiment of the present invention.
5 is an SEM (Scanning Electron Microscope) image of a three-dimensional porous graphene according to an embodiment of the present invention.
FIG. 6 is a TGA (thermogravimetric analysis) analysis result of a three-dimensional porous graphene according to an embodiment of the present invention.
FIG. 7 is a pore-size distribution (PSD) analysis result of a three-dimensional porous graphene according to an embodiment of the present invention.
FIG. 8 is a BET (Brunauer Emmett Teller) analysis result of a three-dimensional porous graphene according to an embodiment of the present invention.
FIG. 9 is a graph showing gas absorption / desorption isotherms of a three-dimensional porous graphene according to an embodiment of the present invention.

The present invention can be all accomplished by the following description. It is to be understood that the following description is only illustrative of preferred embodiments of the invention, but the invention is not necessarily limited thereto. It is to be understood that the accompanying drawings are included to provide a further understanding of the invention and are not to be construed as limiting the present invention. The details of the individual components may be properly understood by reference to the following detailed description of the related description.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In general, the nomenclature used herein is well known and commonly used in the art.

The terms used in this specification can be defined as follows.

"Interlayer distance " means the distance between the graphen sheet and the sheet.

"Organic linkages" control the interlayer distance of graphenes as an organic material that is inserted between the graphene sheet and the sheet.

"Selectivity" is an index of how selectively adsorbent can adsorb only a specific gas in a mixed gas.

In the present invention, when three-dimensional porous graphene is prepared by dispersing an organic linking material containing an ester group and an amine group in a solvent, the distance between layers of graphene And it is confirmed that three-dimensional porous graphene can be produced without using additives such as catalyst and surfactant which cause environmental pollution or increase synthesis cost.

As shown in Fig. 1, a three-dimensional porous graphene was obtained by using an organic linking material containing an ester group and an amine group, such as graft-oxide (GO-ester) containing an ester group.

Accordingly, in one aspect, the present invention relates to a method for producing a three-dimensional porous graphene comprising the step of dispersing an organic linking material containing graft-oxide (GO-ester) containing an ester group and an amine group in a solvent, .

In the present invention, the ester group of the graphene oxide and the amine group of the organic linkage may react to form a benzimidazole structure.

In the present invention, it is preferable not to include a catalyst and a surfactant.

In the present invention, the organic linking material containing an amine group is preferably selected from the group consisting of 3,3 ', 4,4'-tetraaminobiphenyl (3,3', 4,4'-tetraaminobiphenyl) (3,3 ', 4,4'-tetraaminoterphenyl), benzidine, 1,5-diaminonaphthalene, (E) -4,4'- (E) -4,4 '- (diazene-1,2-diyl) dianiline or an organic linkage having a diamine group such as ethylenediamine, 1,6- 1,6-diaminohexane, and 1,8-diaminooctein are preferable.

Hereinafter, the formula of the organic linkage containing the amine group is shown.

3,3 ', 4,4'-tetraaminobiphenyl

3,3 ', 4,4'-tetraaminophenyl

Benzidine

1,5-diaminonaphthalene

(E) -4,4 '- (Diazene-1,2-diyl) dianiline

(N = 2, 6, 8, Ethylenediamine, 1,6-Diaminohexane, 1,8-diaminooctane (1, 8-Diaminoacetyl))

In the present invention, it is preferable that the molar ratio of oxygen is 1: 0.1 to 1: 5, and most preferably 1: 1, for graphene oxide (GO-ester) containing an ester group and an organic linking material containing an amine group Do.

In the present invention, the solvent may be DMF (dimethylformamide), THF (tetrahydrofuran), distilled water, dioxane, ethanol or a mixture thereof.

In the present invention, graphene oxide (GO-ester) containing an ester group is obtained by mixing graphene oxide and triethyl orthoacetate; And dispersing the mixture in p-toluenesufonic acid. Graft-oxide (GO-ester) containing an ester group is obtained by converting graphene oxide (GO) to -COO- (ester group) through a Johnson-Claisen rearrangement and merely converting graphene oxide (GO) It is possible to obtain more reduced RGO than using a linker, obtain a wider and more π-π resonance structure, and form a benzimidazole structure through reaction with an organic linkage containing an amine group do.

In the present invention, graphene oxide (GO-ester) containing an ester group and an organic linking material containing an amine group may be dispersed in an organic solvent and reacted at 60 to 150 ° C for 3 to 5 days. Three-dimensional porous graphene can be produced by one-pot reaction. When the reaction time is shorter than 3 days, the three-dimensional structure is not formed. When the reaction time is more than 5 days, the specific surface area decreases.

Further, the mixture may be further cooled, filtered, washed, and dried to produce three-dimensional porous graphene.

Also, in the present invention, it was confirmed that carbon dioxide or hydrogen can be adsorbed by the three-dimensional porous graphene obtained by dispersing an organic linking material containing an ester group and an amine group containing an ester group in a solvent.

FIGS. 2 to 8 are results of analyzing characteristics of the three-dimensional porous graphenes of the present invention, and FIG. 9 are graphs of gas absorption / desorption isotherms of the three-dimensional porous graphenes of the present invention.

Accordingly, the present invention, in another aspect, relates to a three-dimensional porous graphene produced by the above production method and having a specific surface area of 400 to 800 m ² / g.

In another aspect, the present invention provides a method for adsorbing carbon dioxide (CO ₂ ) using the three-dimensional porous graphene.

The invention also provides in another aspect, the carbon dioxide (CO ₂₎ containing the three-dimensional porous graphene adsorbent.

In another aspect, the present invention provides a method for storing hydrogen (H ₂ ) using the three-dimensional porous graphene.

In another aspect, the present invention provides a hydrogen (H ₂ ) adsorbent containing the three-dimensional porous graphene.

The three-dimensional porous graphene of the present invention can adsorb carbon dioxide or hydrogen. The ester group of graphene oxide reacts with the amine group of the organic linkage to form a benzimidazole structure. To date, the benzimidazole structure has been known to have an easy chemical structure for storing carbon dioxide and hydrogen.

The three-dimensional porous graphene of the present invention exhibited a carbon dioxide adsorption amount of 3.75 mmol / g at 273 K and a maximum adsorption heat of chemical absorption (physical adsorption) of 31.7 kJ / mol. In addition, the hydrogen storage capacity of the 3D porous graphene showed hydrogen adsorption amounts of 77 wt% and 1.2 wt% and hydrogen adsorption heat (physical adsorption) of 7.3 kJ / mol.

Hereinafter, the present invention will be described in more detail with reference to Examples. It will be apparent to those skilled in the art that these embodiments are merely illustrative of the present invention and that the scope of the present invention is not limited to these embodiments.

Example  1: containing an ester group Grapina Of oxide (GO-ester)  Produce

200 mg of graphene oxide (GO) and 156.7 mL of triethyl orthoacetate (98%) are placed in a 200 mL round bottom flask and sonicated for 10 minutes. 7.1 mg of p-toluenesulfonic acid (> 97%) is added to the mixture. The reaction mixture was refluxed at 130 DEG C for 36 hours to obtain a black solution. After cooling to room temperature, the mixture was dispersed in 40 mL of acetone for 10 minutes using an ultrasonic washing machine, and then centrifuged (7800 rpm, 20 minutes) to obtain a precipitate. The step of dispersing in acetone and then centrifuging was repeated twice. In order to remove unreacted starting materials and impurities, the step of dispersing in tetrahydrofuran (THF) in the same manner as above was repeated twice. Suspended and clear liquids were discarded each time. The resulting precipitate was dried in a vacuum atmosphere, and 150 mg of graphene oxide (GO-ester) containing an ester group was obtained.

Example  2: Porosity using GO-ester Grapina  Produce

50 mg of GO-Ester prepared in Example 1 and 128.6 mg of 3,3 ', 4,4'-tetraaminobiphenyl (3,3', 4,4'-tetraaminobiphenyl) as an organic linker were dissolved in dimethylformamide dimethylformamide, DMF) and sonicated for 10 minutes. At this time, the content of GO-ester and tetraaminobiphenyl was in a molar ratio of 1: 1, and the reaction was carried out at 150 ° C for 4 days. After cooling the reaction mixture to room temperature, the resulting precipitate was centrifuged and washed several times with ethanol (100 mL * 3 times) and THF (100 mL * 3 times), and then subjected to Soxhlet extraction ) Ethanol and THF were extracted for 24 hours, respectively. The final product was separated into a black solid and the porous graphene thus prepared was designated 'PGN-1'.

Alternatively, except for the addition of 262 mg of 3,3 ', 4,4'-tetraaminoterphenyl (3,3', 4,4'-tetraaminoterphenyl) as an organic linker in the above-mentioned 'PGN-1' The porous graphene thus prepared was designated as 'PGN-2'.

Example  3: Porosity Grapina  Character analysis

2- (a) is a result of FTIR analysis of porous graphene to confirm the surface functional group of the material. GO shows a broad peak at 3345 cm ^-1 , which means that it contains a large amount of -OH groups, 1725 cm ^-1 peak indicates an ester group (-COO-), and there is little ester group on the GO surface , 1619 cm ^-1 peak means C = C bond. In the case of the GO-ester, the peak (-OH) decreased at 3345 cm ^-1 and the 1725 cm ^-1 peak (-COO-) increased, indicating that the -OH of the graphene surface was converted to the -COO- group Able to know. In addition, it can be confirmed that GO is reduced to RGO by increasing the peak at 1619 cm ^-1 . In the case of PGN-1 and PGN-2, it can be expected that the -COO- of the GO-ester reacted with the diamine of the organic linkage through the disappearance of the 1724 cm ^-1 peak. In addition, Fig. 2- (b) shows the results of the extended FTIR analysis. As a characteristic peak of each of the benzimidazole peaks, PGN-1 and PGN-2 show peaks between the graphene sheet and the organic coupler Benzoimidazole structure was formed.

FIG. 3 and Table 1 are for measuring the amount of bonding between the element and the element (comparing the area of the graph) as a result of XPS analysis of the porous graphene, and the bonding energy is different for each bonding. When GO is modified to GO-ester, it can be seen that the C-OH bond is reduced and the O-C = O bond is abruptly increased, and that the GO is reduced by increasing the C-C bond. In the case of PGN-1 and PGN-2, it was confirmed that the C-N bond was formed together with the increase of the C-C bond, and it was confirmed that the benzimidazole structure was formed by the decrease of the O-C = 0 bond.

Table 2 shows the results of elemental analysis of porous graphene. When the GO content of the GO-ester was compared with that of the GO-ester, it was found that the content of GO-ester decreased rapidly, indicating that the graphene oxide was reduced to secure the π-π resonance structure. As the GO-ester was converted to PGN-1 and PGN-2, the nitrogen content (amine) increased sharply. This indicates that a benzimidazole structure is formed in the three-dimensional porous graphene structure.

4 is a graph showing the PXRD (Powder X-Ray Diffraction) analysis of porous graphene to measure the interlayer distance of graphene. In the case of GO, each graphene sheet was oxidized and separated from graphite to confirm the interlayer distance of about 0.816 nm. When converted to GO-ester, the -OH groups on the GO surface were converted to -COO- It was confirmed that the interlayer distance increased to about 1.3 nm. In addition, PGN-1 and PGN-2 prepared by using organic linkers of different lengths have longer interlayer distances than GO-ester, and it was confirmed that they have an amorphous structure through wide-shaped peaks.

FIG. 5 is an SEM (Scanning Electron Microscope) image of a porous graphene, and cross-sectional SEM images of GO and GO-Ester show that the interlayer distance of graphene sheets is increased. In the case of PGN-1 and PGN-2, it was confirmed that graphene sheets were laminated in different directions to form a three-dimensional porous structure.

FIG. 6 is a graph showing the results of TGA (thermogravimetric analysis) analysis of porous graphene, and the degree of thermal decomposition of the sample is measured as the temperature increases. Fig. 6- (a) is from Air atmosphere, Fig. 6- (b) was conducted an analysis in N ₂ atmosphere, GO and GO-ester was compared to the decomposition at about 200 ℃, the PGN PGN-1 and-2 It was confirmed that it was stable up to 350 ° C.

FIG. 7 shows the pore size distribution and the degree of distribution of the sample as a result of the PSD (pore-size distribution) analysis of the porous graphene. In the case of PGN-1, pores with an average diameter of 0.58 nm were mainly distributed, and PGN-2 showed less pores of 0.58 nm than PGN-1. (3,3 ', 4,4'-tetraaminopurphenyl) used in the preparation of PGN-2 was replaced with the organic linker (3,3', 4,4'- 4'-tetraaminobiphenyl), which is longer than that of the graphene layer.

8 and Table 3 are for checking the specific surface area of the sample as a result of measurement of the BET (Brunauer Emmett Teller) of the porous graphene. The specific surface areas of GO-Ester, PGN-1 and PGN-2 were 76 m ² /, 732 m ² / g and 416 m ² / g, respectively. PGN-1 and PGN- It was confirmed that micro-sized pores were distributed in the range of 0.1 to 0.1. This indicates that the GO-Ester sheet reacted with an organic linkage having an amine group to form a three-dimensional porous graphene. Also, it was confirmed that the shorter the length of the organic connecting material, the larger the specific surface area. This is due to the flexibility of the alpha carbon between the graphene sheet and the ester group, which means that the long organic linkages are tilted between the graphene oxide sheets.

Example  4: Porosity Grapina  gas Adsorption capacity  analysis

FIG. 9 shows the gas absorption / desorption isotherm of the porous graphene, and Table 4 shows the adsorption amount, adsorption heat, and selectivity based on FIG. Carbon dioxide adsorption amount was measured at 273 K and 298 K, respectively. As described above, PGN-1 having the largest specific target had the highest amount of carbon dioxide adsorption (3.75 mmol g ^-1 , 273 K, 1.1 bar) and hydrogen adsorption (1.2 wt% 77K 1.1 bar).

Adsorption heat was calculated using Clausius-Clapeyron Equation.

P = pressure, ΔHν = heat of adsorption, R = gas constant, T = temperature

In particular PGN-1, PGN-2 is 31.0 KJmol ^{-1, -1} 31.7 KJmol eotneunde indicate high carbon dioxide adsorption (physisorption), which is due to the high affinity of the carbon dioxide-benzoimidazole structure of the PGN-1, PGN-2. It also contributes to high hydrogen adsorption heat (PGN-1; 7.3 KJmol- ¹ , PGN-2; 7.3 KJmol- ¹ ).

Gas selectivity is an indicator of how selectively adsorbent can adsorb specific gases in the mixed gas. PGN-1 and PGN-2 exhibit excellent carbon dioxide gas selectivity when compared to GO-Ester in a 273 K gas mixture (carbon dioxide, nitrogen fraction 0.15: 0.85) (GO-Ester 56, PGN- 2 103). This is because PGN-1 and PGN-2 are more adsorbed by the benzimidazole structure than the polar molecules, carbon dioxide.

Table 5 compares the characteristics of the three-dimensional porous graphene (PGN-1) of the present invention and the known porous graphene, wherein PGF-1 and PGF-2 are porous graphene prepared using Pd catalyst (Y. Cui et al., Nanoscale, 5 (2001), 5, 2015, 2014), sGOBIN-1 _DMF was prepared using an organic linker having graphene oxide and a diamine group : 8367, 2013).

Palladium (Pd) and the case of the PGF-1-PGF 2 produced by using a catalyst, respectively, the amount of carbon dioxide adsorbed at ^{273K 1.64 mmol g -1, 1.76 mmol} g -1, 1.26 mmol g ^-1 at 298K, 1.43 mmol g ^{- 1} (31.0 kJ mol ^{- 1} ) was higher than that of PGF-1 (3.75 mmol g ^-1 at 273 K and 2.36 mmol g ^-1 at 298 K) 27.4 kJ mol ^-1 ) and PGF-2 (27.7 kJ mol ^-1 ).

Without using a catalyst, the amount of carbon dioxide adsorbed by sGOBIN prepared using an organic linker having graphene oxide and a diamine group was 3.22 mmol g ^-1 at 273 K. Under the same conditions, PGN-1 could adsorb more carbon dioxide , And the adsorption heat also showed that the adsorption heat of PGN-1 was 31.0 kJ mol ^-1 higher than that of sGOBIN 25.0 kJ mol ^-1 . The sGOBIN is obtained by directly reacting an organic linkage having a diamine group with graphene oxide, which is not graphene oxide containing an ester group like the PGN-1 of the present invention, and many Oxygen groups remain on the graphene surface. Therefore, although both sGOBIN and PGN-1 have a benzimidazole structure, it can be confirmed that PGN-1 has a high specific surface area and a high carbon dioxide adsorption amount and adsorption heat.

The scope of the present invention is defined by the appended claims rather than the detailed description and all changes or modifications derived from the meaning and scope of the claims and their equivalents are to be construed as being included within the scope of the present invention do.

Claims (16)

Dispersing an organic linking material containing graft-oxide (GO-ester) containing an ester group and an amine group in a solvent, and reacting the grafted oxide with an organic solvent.
The method of claim 1, wherein a benzimidazole structure is formed by reacting an ester group of the graphene oxide and an amine group of an organic linking agent.
2. The method of claim 1, wherein the grafting oxide (GO-ester) comprising the ester group comprises: mixing graphene oxide and triethyl orthoacetate; And dispersing the mixture in p-toluenesufonic acid to obtain a three-dimensional porous graphene.
2. The organic electroluminescent device according to claim 1, wherein the organic linking group containing the amine group is at least one selected from the group consisting of 3,3 ', 4,4'-tetraaminobiphenyl (3,3', 4,4'-tetraaminobiphenyl) 4'-tetraaminoterphenyl, benzidine, 1,5-diaminonaphthalene, (E) -4,4'- (Diazene-1,2-diyl) dianiline, ethylenediamine, 1,6-diaminohexane ((E) 1,8-diaminohexane, 1,8-diaminohexane, and 1,8-diaminooctane. The method of manufacturing a three-dimensional porous graphene according to claim 1,
[3] The method according to claim 1, wherein the grafting oxide (GO-ester) containing the ester group and the organic linking material containing an amine group have a molar ratio of oxygen of 1: 0.1 to 1: ≪ / RTI >
The method according to claim 1, wherein the solvent is at least one selected from the group consisting of dimethylformamide (DMF), tetrahydrofuran (THF), distilled water, dioxane, and ethanol.
The method according to claim 1, wherein the catalyst and the surfactant are not contained.
The method of claim 1, wherein the reaction is carried out at 60 to 150 ° C for 3 to 5 days.
The method of claim 1, wherein the reaction is a one-pot reaction.
The method of claim 1, further comprising cooling, filtrating, washing, and drying after completion of the reaction.
10. A three-dimensional porous graphene produced by the method of any one of claims 1 to 10 and having a specific surface area of 400 to 800 m ² / g.
12. The three-dimensional porous graphene according to claim 11, wherein the three-dimensional porous graphene is for adsorbing carbon dioxide.
A method for adsorbing carbon dioxide (CO ₂ ) using the three-dimensional porous graphene of claim 11.
Claim 11 3D Yes porous carbon containing a pin (CO ₂₎ absorbent.
A method for storing hydrogen (H ₂ ) using the three-dimensional porous graphene of claim 11.
A hydrogen (H ₂ ) adsorbent using the three-dimensional porous graphene of claim 11.

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