Precise Modulation of Surface Layer Dynamics for Tunable Flowability and Gas Absorption Properties of Molecular Porous Liquids

Porous liquids (PLs) have improved the understanding of the porous properties of matter; however, rational tuning of the viscosities and gas absorption properties of PLs lag far behind the explosive growth of PL applications. Herein, neat molecular PLs are constructed by grafting polymers onto the surface of 2 nm molecular nanocages with precisely tuned graft densities and molecular weights Mws. The flowability of the PLs showed a non‐monotonic dependence on the Mw of the polymers due to the interplay between the surface confinement effect and polymer chain entanglements, enabling optimization of their viscosities, similar to those of conventional liquids. The surface layer dynamics and gas absorption kinetics are quantified, correlation between the two properties is confirmed, and gas permeation process is regulated by surface layer dynamics. From the understanding of the structure–property relationship, the surface layer grafting densities are tuned to promote surface layer dynamics to achieve improved gas sorption performance.