Taming of Trinitromethyl-Oxadiazole to access high density and high oxygen balance via a dual modulation strategy

Abstract

Energetic compounds bearing the trinitromethyl group are garnering broad attraction as potential candidates for a new generation of high energy dense oxidizers. In this work, an effective dual modulation strategy involving both molecular isomerization and crystal morphology control was employed to design and optimize trinitromethyl-oxadiazole with improved comprehensive performance. Utilizing this dual strategy, 3,5-bis(trinitromethyl)-1,2,4-oxadiazole (3) was synthesized, resulting in the formation of two distinct crystal morphologies (needle and sheet) corresponding to two crystal forms (3-a and 3-b). Encouragingly, while maintaining ultra-high oxygen balance (21.73%), 3 achieves impressive densities (1.97–1.98 g/cm3). To our knowledge, the density of 1.98 g/cm3 for 3-a sets a new record among that of nitrogen-rich monocyclic compounds. Notably, practical crystal morphology prediction was creatively introduced to guide the experimental crystallization conditions of 3, increasing the impact sensitivity and friction sensitivity from 1 J and 80 N (3-a) to 10 J and 240 N (3-b), respectively. Additionally, the crystal structural analyses and theoretical calculations were conducted to elucidate the reasons of differences between 3-a and 3-b in density and stability. This work provides an efficient strategy to enhance performance of trinitromethyl derivatives, broadening the path and expanding the toolbox for energetic materials.