Molecular dynamic crystals conveniently combine flexibility required for mechanical reconfiguration, strength for effective translation of elastic energy, and long-range order of mechanically coupled molecules for rapid conversion of disordered motion (heat) or photons (light) into ordered motion (work). By direct measurement of the actuation force generated by crystals of a thermosalient solid, here we describe the first direct quantification of the work performed and energy conversion that can be accomplished by using dynamic crystals as supramolecular actuators. Upon reversible alpha-to-gamma phase transition, crystals of (phenylazophenyl)palladium hexafluoroacetylacetonate of submillimeter to millimeter size exert forces in the range of 1-100 mN upon longitudinal and lateral expansion. This work translates to a volumetric power density of about 1-3 MW m(-3) and efficiency comparable to the existing multicomponent actuators.