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.