Storage of CO 2 into Porous Coordination Polymer Controlled by Molecular Rotor Dynamics

Design to store gas molecules, such as CO 2 , H 2 , and CH 4 , under low pressure is one of the most important challenges in chemistry and materials science. Herein, we describe the storage of CO 2 in the cavities of a porous coordination polymer (PCP) using molecular rotor dynamics. Owing to the narrow pore windows of PCP, CO 2 was not adsorbed at 195 K. As the temperature increased, the rotors exhibited rotational modes; such rotations dynamically expanded the size of the windows, leading to CO 2 adsorption. The rotational frequencies of the rotors ( k ≈10 −6  s) and correlation times of adsorbed CO 2 ( τ ≈10 −8  s) were elucidated via solid‐state NMR studies, which suggest that the slow rotation of the rotors sterically restricts CO 2 diffusion in the pores. This restriction results in an unusually slow CO 2 mobility close to solid state ( τ ≥10 −8  s). Once adsorbed at room temperature, CO 2 is robustly stored in the PCP under vacuum at 195–233 K because of the steric hindrance of the rotors. We also demonstrate that this mechanism can be applied to the storage of CH 4 .