Hydrogen separation membranes are a critical component
in the emerging
hydrogen economy, offering an energy-efficient solution for the purification
and production of hydrogen gas. Inspired by the recent discovery of
monolayer covalent fullerene networks, here we show from concentration-gradient-driven
molecular dynamics that quasi-square-latticed monolayer fullerene
membranes provide the best pore size match, a unique funnel-shaped
pore, and entropic selectivity. The integration of these attributes
renders these membranes promising for separating H<sub>2</sub> from
larger gases such as CO<sub>2</sub> and O<sub>2</sub>. The ultrathin
membranes exhibit excellent hydrogen permeance as well as high selectivity
for H<sub>2</sub>/CO<sub>2</sub> and H<sub>2</sub>/O<sub>2</sub> separations,
surpassing the 2008 Robeson upper bounds by a large margin. The present
work points toward a promising direction of using monolayer fullerene
networks as membranes for high-permeance, selective hydrogen separation
for processes such as water splitting.