Emergent Molecular Assembly Research Unit

Topological bonds assemble to form porous crystals

Our unit succeeded for the first time in synthesizing crystals by precisely arranging catenane molecules (topological bonds), which are chains of two ring-shaped molecules, and metal ions three dimensionally through coordination bonds. The crystal structure was examined using single crystal X-ray structural analysis, and it was found that more than 90% of the crystal is composed of catenane molecules, that it has a structure with micropores, and that it changes its structure with changes in temperature. Furthermore, it was revealed that the crystal changes its shape when force is applied from the outside and recovers its original shape when the force is removed, showing rubber-like properties despite its crystalline nature. This is expected to lead to the application of innovative porous materials that can absorb and desorb gas molecules, such as carbon dioxide, by pinching and releasing them with a finger.

An elastic porous crystal with a Densely Catenated Backbone

Photoresponsive Porous Crystals

Metal–organic frameworks (MOFs) are porous materials constructed from metal ions and organic ligands, and their various types of pores can be applied to gas storage, separation, catalysis, etc. In general, MOFs that readily take in guest molecules do not readily release them, and there is often a trade-off between taking in and releasing guest molecules. We are challenging this long-standing dilemma for porous materials by developing MOFs composed of diarylethene derivatives, photoreactive molecules. The MOFs can be disassembled into solution by UV light irradiation and reconstructed by visible light irradiation, which enables the highly effective release and uptake of various guest molecules.

Photochemically Crushable and Regenerative Porous Crystals