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 increased attention as a potential polynitrogen structural unit for the research of next-generation high energy density materials. However, the poor thermal stability of c-N₅^--based compounds has become an important factor restricting their development. Here, we show that a hydrogen-bonded organic framework (HOF) self-assembles with and stabilizes c-N₅^-, with c-N₅^- situated in the pores of the resulting framework through the formation of symmetrical c-N₅^- hydrogen bonds as the main stabilizing factors. These factors result in an onset decomposition temperature of 153 °C for the c-N₅^-@HOF portion, which exceeds the thermal stabilities generally observed for c-N₅^--based derivatives of below 135 °C. We envisage that further c-N₅^--based materials with enhanced stabilities and better performance will be developed in the future.