We found that the molar content of cage C could be switched between ~0% and ~17% reversibly without noticeable fatigue. Whereas the fraction of C stabilized by Z-2 is modest, these results constitute a unique example of using light to reversibly interconvert between two isomers of a cage that does not respond to light. As such, this system is conceptually similar to previous reports on controlling self-assembly of non-photoresponsive nanoparticles using light by placing them in light-switchable environments.