Plastic Pores for Switchable and Optimized Adsorption Behaviors

Similar to conventional solids, porous materials have
demonstrated
rigid and flexible behaviors. Here, we show that flexible pores can
be not just elastic but also plastic. By variation of the hydrogen-bonding
ability and steric hindrance of ligand side groups, the energy difference
and barrier between metastable states of a porous framework are fine-tuned
to enable the plastic behavior. All metastable pore structures can
transform to the target ones in atmospheres of the target guests with
sufficiently high pressures, and all shaped pores can remain unchanged
after guest removal, resulting in optimized host–guest recognitions
for the target guests. Up to a 6-fold increase of adsorption selectivity
and 9-fold increase of purification productivity for CO2 capture and coalmine CH4 upgrading, and even inversion
of CO2/C2H2 selectivity, have been
achieved by reversible pore-shaping of a single plastic-pore adsorbent.
The realization of plastic pores creates an opportunity for on-demand
switching of adsorption and separation functions with optimized performances.