We show that structural changes of a guest molecule can trigger structural transformations of a crystalline host framework. Azobenzene was introduced into a flexible porous coordination polymer (PCP), and cis/trans isomerizations of the guest azobenzene by light or heat successfully induced structural transformations of the host PCP in a reversible fashion. This guest-to-host structural transmission resulted in drastic changes in the gas adsorption property of the host-guest composite, displaying a new strategy for creating stimuli-responsive porous materials.