Cross-linked graphene networks

1. A method of producing an aerogel or xerogel comprising graphene, graphene oxide or a mixture thereof, comprising the steps of: a) dispersing graphene, graphene oxide or a mixture thereof in a solvent compatible therewith; b) cross-linking said graphene, graphene oxide or a mixture thereof by use of a coupling agent via functional groups present, on the graphene and/or the graphene oxide, or with a linking molecule comprising at least two functional sites capable of reacting with the surface of said graphene and/or graphene oxide, to form a covalently cross-linked gel network, wherein said coupling agent is selected from the group consisting of N,N′-dicyclohexylcarbodiimide (DCC), N,N′-diisopropylcarbodiimide (DIC), ethyl-(N′,N′-dimethylamino)propylcarbodiimide hydrochloride (EDC), 4-(N,N-dimethylamino) pyridine (DMAP), (benzotriazol-1-yloxy)tris(dimethylamino)phosphonium hexafluorophosphate (BOP), (benzotriazol-1-yloxy)tripyrrolidinophosphonium hexafluorophosphate, bromotripyrrolidinophosphonium hexafluorophosphate, 0-(benzotriazol-1-yl)-N,N,N′,N′-tetramethyluronium hexafluorophosphate (HBTU), O-(benzotriazol-1-yl)-N,N,N′,N′-tetramethyluronium tetrafluoroborate (TBTU), 0-(7-azabenzotriazol-1-yl)-N,N,N′,N′-tetramethyluronium hexafluorophosphate (HATU), 0-(6-chlorobenzotriazol-1-yl)-N,N,N′,N′-tetramethyluronium hexafluorophosphate (HCTU), 0-(3,4-Dihydro-4-oxo-1,2,3-benzotriazine-3-yl)-N,N,N′,N′ tetramethyluronium tetrafluoroborate (TDBTU), 3-(diethylphosphoryloxy)-1,2,3 benzotriazin-4(3H)-one (DEPBT) and carbonyldilmidazole (CDI), and mixtures thereof; and c) removing said solvent to produce a cross-linked aerogel or xerogel with a solvent content of less than 10%.

2. The method according to claim 1 , wherein said cross-linking is carried out directly on the graphene pristine surface with a molecule selected from the group consisting of bis(diazonium) salts and multifunctional molecules suitable for 1,3-dipolar cycloadditions or Bingel condensations, or by the reduction of the graphenes followed by the reaction of the graphenes with an electrophilic cross-linking molecule.

3. The method according to claim 1 , further comprising the step of capping residual functional groups on the graphenes prior to the removal of the solvent.

4. The method according to claim 1 , wherein said solvent is selected from the group consisting of dimethyl formamide, benzene, dichloromethane, chlorobenzene, dichlorobenzene, chloroform, toluene, xylene, dioxane, dimethylsulfoxide, tetrahydrofuran, amide solvents and mixtures thereof.

5. The method according to claim 1 , wherein said removal of solvent is carried out by solvent exchange with at least one solvent having lower surface tension than the solvent used in step (a).

6. The method according to claim 5 , wherein said solvent exchange is carried out using acetone, followed by C 3 -C 10 hydrocarbon, siloxane or fluorinated C 3 -C 10 hydrocarbon.

7. A method of producing an aerogel or xerogel comprising graphene, graphene oxide or a mixture thereof, comprising the steps of: a) dispersing graphene, graphene oxide or a mixture thereof in a solvent compatible therewith; b) cross-linking said graphene, graphene oxide or a mixture thereof via functional groups present on the graphene and/or the graphene oxide, or with a linking molecule comprising at least two functional sites capable of reacting with the surface of said graphene and/or graphene oxide, to form a covalently cross-linked gel network, wherein said cross-linking is carried out directly on the graphene pristine surface with a molecule selected from the group consisting of bis(diazonium) salts and multifunctional molecules suitable for 1,3-dipolar cycloadditions or Bingel condensations, or by the reduction of the graphenes followed by the reaction of the graphenes with an electrophilic cross-linking molecule; and c) removing said solvent to produce a cross-linked aerogel or xerogel with a solvent content of less than 10%.

8. The method according to claim 7 , wherein said cross-linking is achieved by using a coupling agent or by a dehydration step.

9. The method according claim 8 , wherein said cross-linking is formed using a coupling agent which is selected from the group consisting of N,N′-dicyclohexylcarbodiimide (DCC), N,N′-diisopropylcarbodiimide (DIC), ethyl-(N′,N′-dimethylamino)propylcarbodiimide hydrochloride (EDC), 4-(N,N-dimethylamino) pyridine (DMAP), (benzotriazol-1-yloxy)tris(dimethylamino)phosphonium hexafluorophosphate (BOP), (benzotriazol-1-yloxy)tripyrrolidinophosphonium hexafluorophosphate, bromotripyrrolidinophosphonium hexafluorophosphate, 0-(benzotriazol-1-yl)-N,N,N′,N′-tetramethyluronium hexafluorophosphate (HBTU), O-(benzotriazol-1-yl)-N,N,N′,N′-tetramethyluronium tetrafluoroborate (TBTU), 0-(7-azabenzotriazol-1-yl)-N,N,N′,N′-tetramethyluronium hexafluorophosphate (HATU), 0-(6-chlorobenzotriazol-1-yl)-N,N,N′N′-tetramethyluronium hexafluorophosphate (HCTU), 0-(3,4-Dihydro-4-oxo-1,2,3-benzotriazine-3-yl)-N,N,N′,N′ tetramethyluronium tetrafluoroborate (TDBTU), 3-(diethylphosphoryloxy)-1,2,3 benzotriazin-4(3H)-one (DEPBT) and carbonyldilmidazole (CDI), and mixtures thereof.

10. The method according to claim 7 , further comprising the step of capping residual functional groups on the graphenes prior to the removal of the solvent.

11. The method according to claim 7 , wherein said solvent is selected from the group consisting of dimethyl formamide, benzene, dichloromethane, chlorobenzene, dichlorobenzene, chloroform, toluene, xylene, dioxane, dimethylsulfoxide, tetrahydrofuran, amide solvents and mixtures thereof.

12. The method according to claim 7 , wherein said removal of solvent is carried out by solvent exchange with at least one solvent having lower surface tension than the solvent used in step (a).

13. The method according to claim 12 , wherein said solvent exchange is carried out using acetone, followed by C 3 -C 10 hydrocarbon, siloxane or fluorinated C 3 -C 10 hydrocarbon.