Design and Application of Porous Coordination Materials with Soft and Dynamic Nature

Porous materials, including porous carbons, zeolites, and porous coordination polymers (PCPs), are generally recognized as rigid, hard, and fragile substances. However, focusing on their structure and surface at the molecular level, there are various dynamic phenomena and processes such as deformation and reconstruction of the crystal structure as well as molecular motion such as vibration and rotation occurring in the materials. In this account, recent developments of functional PCPs based on a new design approach making use of such dynamic nature of molecular entities are described. A dynamic molecular functionality incorporated into the PCP nanochannel affords precise control of gas diffusion process in the PCP, thus enabling outstanding gas separation and storage capability. In order to visualize the dynamic behavior of PCP, atomic force microscopy was used to observe native surfaces of a PCP crystal, which enabled real-time imaging of the dynamic response of the PCP with a molecular-level resolution. In addition, an interdisciplinary approach that combines porous material chemistry and soft material chemistry, which gives novel porous soft materials with solution/thermal processable feature, is described. This bottom-up design concept that connects dynamic molecular properties to the material functions offers a promising way to the next-generation porous materials.