Abstract
The unique and complex heat release processes of dianthracene-based molecular solar thermal energy storage compounds were elucidated by comprehensive solid-state analyses of their chemical and physical changes using isothermal time-dependent DSC, PXRD, and solid-state NMR. Our study reveals that dianthracenes undergo chemical dissociation, formation of a mixed intermediate phase, and phase transition to the final anthracene crystal, during the triggered energy release process. The solid-state kinetic analysis shows auto-catalyzed cycloreversion and heat release from the energy storage compounds, which is facilitated by the partially cooperative transformation of molecules in the crystalline state. The chemical and physical transformations contribute to the overall energy release to different extents, unveiled by the calculation of lattice energy and dissociation energy changes during the cycloreversion. The fundamental insights into the solid-state transformations will aid in designing advanced energy storage materials and controlling energy release processes.