Covalent assemblies of graphene and single-walled carbon nanotubes (SWNTs) are known to exhibit interesting morphological features and gas adsorption properties. Combining 1D SWNTs with 2D graphene in assemblies can also lead to novel properties, due to synergies between graphene and SWNTs.

C. N. R. Rao and co-workers, Jawaharlal Nehru Center for Advanced Scientific Research, Jakkur, Bangalore, India, have generated covalent composites of graphene and SWNTs by Sonogashira and EDC {1-ethyl-3-(3-dimethylaminopropyl)carbodiimide)} coupling reactions.

The assemblies obtained by EDC coupling show the formation of amide bonds between amine-functionalized graphene and acid-functionalized SWNTs and have a smaller surface area compared to Sonogashira assemblies. Sonogashira coupling involves iodobenzene functionalization of graphene and SWNTs through diazotization, followed by treatment with 4,4-diethynylbiphenyl linker in presence of Pd⁰ and Cu⁺¹ catalysts.

The composites have high surface areas, with the highest value being 1260 m²/g. CO₂ and H₂ uptake by these assemblies is comparable to those of high-surface-area metal-organic frameworks (MOFs). The high surface area arises from the presence of uniform slit-shaped pores in the assemblies. The assemblies also show superhydrophobicity with a contact angle of 153 to 165°.

• Graphene / Single-Walled Carbon Nanotube Composites Generated by Covalent Cross-Linking,
  K. Pramoda, Ram Kumar, C. N. R. Rao,
  Chem. Asian J. 2015.
  DOI: 10.1002/asia.201500627