Self-Template Evolution Toward Hierarchically Hollow Spherulites of Energetic Materials for Safety Control and...

The hierarchical hollow structure can endow functional materials with concerning performances, whereas its rational design remains challenging, especially for organic molecules. Herein, a novel strategy of self-template evolution is presented to construct hollow spherulites (HSs) for energetic organic materials with controllable safety and enhanced combustion, utilizing the mechanism of pseudomorphic replacement coupled with Ostwald ripening. Specifically, the spherulites of thermodynamically metastable β-2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (β-CL-20) as the self-template spontaneously evolves into the HSs of CL-20-based inclusion compounds in solution, during which the dissolution of β-CL-20 and the crystallization of CL-20-based inclusion compounds are spatiotemporally correlated, enabling pseudomorphic replacement preserving the spherulitic structure, and cavities are formed inside via Ostwald ripening. Moreover, the conversion rates and the mediating solvent cause different locations of cavities, with two cases exhibited. The hollow-core spherulites of CL-20-formic acid exhibit controllable safety through manipulating micro-/nanostructures, and the hollow-spoke spherulites of CL-20-CO₂ can be the efficient carrier to composite with oxidants, enhancing combustion with increases of 23.2% in pressure duration effect, 9.8% in peak pressure, and 3.3% in pressurization rate. This work offers a novel route to construct hierarchical hollow energetic crystals with enhanced performance and puts insight into the design of hierarchical hollow crystals for broad material systems.