Design of Molecular Crystals toward Crystalline Molecular Machines: Rotors, Gears, and Motors

Crystalline molecular machines provide a promising platform for integrating dynamic molecular motion into nanoscale solid-state materials, where motion can be programmed, triggered, and harnessed for functional output. This perspective highlights recent advances in the design of crystalline molecular materials that support controlled molecular motion with a focus on three key types: rotors, gears, and motors. We discuss strategies to enable internal rotational freedom, realize mechanically correlated motion, and achieve molecular motion driven by external stimuli. By bridging molecular-level design with long-range crystalline order, these systems open new avenues for the development of molecular-based dynamic crystalline materials with engineered mechanical responses.