Abstract
We report a series of p-functionalized phenylbenzoxazoles that offer a remarkable energy storage, exceeding 300 J/g, for the first time among intermolecular cycloaddition-based molecular solar thermal energy storage systems. The [2+2] photocycloaddition of phenylbenzoxazoles generate diazetidine cycloadducts that store energy for up to 23 years in the solid state and release energy upon triggered cycloreversion. The solid-state phase transition contributes to increasing overall energy storage densities, and the dearomative cycloaddition process is revealed to be critical for maximizing the intrinsic energy storage capacities. The solvent-assisted cycloreversion is also used to accelerate the energy release from the emerging molecular scaffold.