Taming cyclo-pentazolate anions with a hydrogen-bonded organic framework

Because of its high energy, aromaticity, and carbon- and hydrogen-free structure, the cyclo-pentazolate anion (c-N5) has attracted increasing attention as a potential polynitrogen structural unit for next-generation high energy density materials. However, the poor thermal stability of c-N5-based compounds has limited their development. Here, a hydrogen-bonded organic framework (HOF) is shown to self-assemble with and stabilize c-N5, positioning c-N5 in the pores of the framework through symmetrical c-N5 hydrogen bonds as the main stabilizing factors. These interactions yield an onset decomposition temperature of 153 °C for the c-N5@HOF portion, exceeding the typical thermal stabilities of c-N5 derivatives (<135 °C). This approach suggests a path toward c-N5-based materials with enhanced stabilities and improved performance.