Lewis Acid–Base Self-Assembly toward Insensitive Energetic Cocrystals with Sandwich-like Layered Structures

The development of HEDMs (High Energy Density Materials) that simultaneously possess high energy density and low sensitivity remains a significant challenge. Herein, we design two novel insensitive energetic cocrystals based on TTO (2,4,6-triamino-1,3,5-triazine-1-oxide), NTO (3-nitro-1,2,4-triazole-5-one), and TNBI (4,4′,5,5′-tetranitro-2,2′-bi-1H-imidazole). TTO-NTO and TTO-TNBI fabricated through a rational Lewis acid–base self-assembly strategy using planar precursor molecules. Single-crystal X-ray diffraction analyses reveal that both cocrystals adopt a distinctive sandwich-like layered architecture, featuring alternating columns of TTO and counterpart molecules (NTO or TNBI) connected via extensive intermolecular hydrogen bonds. Notably, protonation of the TTO molecule was observed in the cocrystals, which plays a crucial role in stabilizing the layered assemblies. Combined theoretical analyses including electrostatic potential (ESP) mapping, Hirshfeld surface studies, and the independent gradient model based on Hirshfeld partition (IGMH), quantitatively elucidate that hydrogen bonding dominates the intermolecular interactions, while significant π–π contributions further enhance stability. Both cocrystals exhibit high calculated detonation performances (D: 7980–8054 m/s; P: 23.58–26.36 GPa), positive heat of formation, and excellent low sensitivity (IS > 40 J, FS > 360 N), surpassing the performance of the precursor TTO. Thermal analyses indicate two-stage decomposition patterns with onset temperatures lower than those of the individual components, likely due to reduced crystal density. This work not only presents two promising insensitive energetic candidates but also validates the feasibility of Lewis acid–base self-assembly as a potent strategy for the rational design of advanced energetic cocrystals with balanced properties.