Pseudomorphic Replacement Driven Construction of Hierarchical Homostructured CL‐20 Core‐Shell Architectures for Safety Improvement

ABSTRACT Hierarchical homostructured core‐shell architectures (HHCS) integrate the advantages of maintaining high energy density and enhancing interfacial stability. However, their rational design and controllable construction remain significantly challenging. Herein, we propose a self‐limiting surface pseudomorphic replacement strategy mediated by localized solvation regulation, enabling the precise construction of HHCS of ε‐2,4,6,8,10,12‐hexanitro‐2,4,6,8,10,12‐hexaazaisowurtzitane (ε‐CL‐20). Specifically, a γ‐butyrolactone (γ‐BL)/H 2 O mixed solvent system induces a selective surface dissolution—recrystallization process on ε‐CL‐20 crystals, forming a stable CL‐20∙γ‐BL solvate (S γ‐BL ) layer. This layer undergoes interfacially induced nucleation on the crystal surface and exhibits self‐limiting growth while preserving the morphology of the parent crystal, thereby enabling a morphology‐preserving pseudomorphic replacement process. Upon thermal treatment, solvent removal and solid‐state rearrangement facilitate the conversion of the outer solvate shell into the CL‐20 phase, yielding a homogeneous shell with hierarchical nanoporous features. The resulting HHCS of CL‐20 exhibits a remarkable enhancement in safety performance: its impact sensitivity value increases from 2.5 to 12 J, while the packing density decreases by only 4.85%. Importantly, the core‐shell structure consists solely of ε‐CL‐20, with no heterogeneous materials. This work presents an interfacial‐engineering strategy that provides new theoretical and methodological insights for the safety‐oriented design and structural regulation of high‐energy molecular crystals.