Accessibility of grafted functional groups limits reactivity of covalent graphene derivatives

Graphene derivatives are an emerging and important class of promising materials because they can bear a wide variety of functional groups, rendering them suitable for a plethora of applications, ranging from energy storage to sensorics. Further functionalisation of these materials requires a thorough understanding of their reactivity at the molecular level because the organic functional groups are close to an effectively infinite surface, which may affect their reactivity. Nitrile groups grafted on a graphene can be easily hydrolysed to carboxyl groups, but they are resistant to reduction by LiAlH4. Here, we combine theoretical and experimental methods to explain the resistance of CN groups grafted on the graphene surface in terms of the limited accessibility of these groups for the reduction agent. We highlight that such mechanistic aspects, i.e., steric hindrance of the reaction centres and surface-solvent interactions, play a crucial role in the reactivity of 2D materials.