Pseudomorphic Replacement Driven Construction of Hierarchical Homostructured CL-20 Core-Shell Architectures for...

Area of Science:

• Materials Science
• Chemical Engineering
• Crystallography

Background:

• Hierarchical homostructured core-shell architectures (HHCS) offer enhanced energy density and interfacial stability.
• The controlled synthesis of HHCS, particularly for high-energy molecular crystals like ε-2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (ε-CL-20), remains a significant challenge.

Purpose of the Study:

• To develop a precise and controllable strategy for constructing HHCS of ε-CL-20.
• To enhance the safety performance of ε-CL-20 while maintaining its energy density and structural integrity.

Main Methods:

• A self-limiting surface pseudomorphic replacement strategy mediated by localized solvation regulation was employed.
• A γ-butyrolactone (γ-BL)/H₂O mixed solvent system induced selective surface dissolution-recrystallization, forming a CL-20∙γ-BL solvate (Sγ-BL) layer.
• Thermal treatment facilitated solvent removal and solid-state rearrangement to form the homogeneous ε-CL-20 shell with hierarchical nanoporous features.

Main Results:

• Precisely constructed HHCS of ε-CL-20 were successfully synthesized, preserving parent crystal morphology.
• The resulting HHCS of ε-CL-20 exhibited significantly improved safety, with impact sensitivity increasing from 2.5 to 12 J.
• Packing density decreased minimally by 4.85%, and the core-shell structure was composed solely of ε-CL-20.

Conclusions:

• The proposed interfacial-engineering strategy provides a novel method for the rational design and structural regulation of high-energy molecular crystals.
• This approach offers new theoretical and methodological insights for developing safer energetic materials.
• The successful synthesis of HHCS of ε-CL-20 demonstrates the potential for enhancing material safety without compromising performance.