Carbon nanotubes and graphene have a combination of remarkable properties: lightness, high surface area, good stability, superior thermal and electrical conductivity and high mechanical properties. These properties confer to them an undisputable potential to develop sustainable technologies. Energy and environmental applications are especially concerned since they involve surface phenomena and require high rate interface transfer. Carbon nanomaterials can be considered as a platform for which a targeted chemical modification is able to generate a specific functionality and interactions. This paper describes several types of chemical treatment applied to graphene nanosheets or carbon nanotubes. And some examples of application of these chemically modified carbon nanomaterials are given including support to immobilize enzymes for green chemistry and conductive additive for heat transfer fluids.