(588dc) Aqueous Porous Liquids with Enhanced Gas Capacities and Kinetics

Porous liquids are stable solutions or dispersions of porous solids within a liquid while effectively excluding the liquid from the pores. Porous liquids have been traditionally designed with sterically hindered solvents to prevent the insertion of solvent within the porous solids. Alternatively, recent efforts rely on dispersing microporous frameworks in simpler solvents like water. In this work we present a unique strategy to construct macroporous water by selectively incorporating hydrophilicity on the surfaces of hydrophobic hollow carbon spheres (HCS). Specifically, we show that the stable dispersion surface ionized HCS in water while retaining the inherent porosity. Gas adsorption measurements show the increased gas capacities (~6×) compared to pure solvents. We further confirm the presence of empty pores with neutron diffraction experiments. The electrocatalytic conversion of small gas molecules in aqueous electrolytes is limited by the concentration and diffusion rate of gas molecules in water. In this case, macroporous water exhibited 6 times gas uptake to nonporous (pure) water. We further show the enhancement in diffusivity of gases in porous liquids due to the hierarchical porous structure of the carbon with PFG-NMR experiments. By leveraging the high gas capacity and enhanced diffusion kinetics, the limiting diffusion current of oxygen reduction reaction (ORR) in macroporous water is 2 times that in nonporous water, offering promising prospects for sustainable energy conversion technologies.