Azo-MOFs showing controllable framework flexibility and consequently fine-tuned photomechanical crystal motion

Photo-response molecular-scale movement has been well developed in azobenzene photochromic molecules. However, material capable of converting this molecular-scale movement to macroscopic work remains a formidable challenge. Here, we describe an exquisite photomechanical effect observed in an azobenzene-Gd(III) MOF. The single crystal of this material displays complex motion including walking, rolling, self-rotating, swing, and finally popping, dependent on the exposed time under UV and the size of the crystals. Consequently, this functional material gives the direct and impressive evidence to support the potential of MOF material in photomechanical motion.