High-pressure 2D nanoreactors for organic reactions

Abstract: 

Chemical reactions conducted at high pressures provide opportunities for realising new synthesis chemistries and achieving novel states of matter. Many industrial chemical reactors operate at pressures of few thousand atmospheres but facile application of very high pressures (>1 GPa), where interesting reactions can occur and new materials can be realized, is challenging. Confinement of reactants within nanoscale spaces of low dimensional materials (pores such as zeolites and metal organic frameworks and carbon nanotubes) has been shown to provide non-equilibrium conditions for synthesis of novel molecules3 and tuning of chemical reactivity. While few studies have reported chemistry within zero dimensional pores and one dimensional nanotubes, organic reactions in confined spaces between 2D materials have yet to be explored. In this talk, I will demonstrate that reactants confined between atomically thin sheets of graphene or hexagonal boron nitride experience pressures as high as 7 GPa, which allows the propagation of solvent-free organic reactions that ordinarily do not occur under standard conditions. Specifically, we show that cyclodehydrogenation of hexaphenylbenzene without catalysts as a proof of concept and oxidative polymerisation of dopamine into sheet-like crystalline structure are enabled by the effective high pressure experienced by the reactants between the graphene layers. The graphene/polydopamine/graphene reaction results in a novel composite material that possesses higher Young’s modulus (430 GPa) than pure graphene layers (300 GPa) and an exceptionally low water vapor transmission rate of < 0.1 g-m-2-day-1 – nearly an order of magnitude lower than the state-of-the-art water-diffusion barriers for graphene and hBN. Our results demonstrate a facile, general approach for performing new high-pressure chemistry based on confinement of reactants within graphene layers that provides opportunities for realizing new materials with extraordinary properties.