Green Energetic Ionic Cocrystals with Ultralow Hygroscopicity via the Cooperative Heterosynthon Strategy

Ionic cocrystals (ICCs) hold significant potential to
enhance performances
for inorganic salts in fields of pharmaceuticals, photoelectricity,
energetic materials, etc. However, the targeted design of ICCs with
specific properties remains challenging. Herein, this work addresses
the critical hygroscopicity of ammonium dinitramide (ADN), a vital
green replacement for ammonium perchlorate (AP), by establishing the
cooperative heterosynthon strategy. Specifically, improved binding
energy in the cluster analysis revealed that moisture sensitivity
originates from synergistic cation–anion interactions, which
guided the identification of 3,4-diaminofurazan (DAF) as the optimal
coformer through subsequent experimental screening. The resulting
ADN/DAF cocrystal achieves unprecedented moisture resistance (critical
relative humidity = 84.0% at 25 °C) among all ADN cocrystals,
enables substitution for AP even surpassing ADN in specific impulse
(272.25 s), and significantly enhances safety performance. Notably,
this cocrystal demonstrates superior manufacturability: utilizing
commercially available coformers and synthesizing via continuous flow
production at the hectogram-scale with >88% yield. Therefore, this
work presents an effective strategy for engineering moisture-resistant
ionic cocrystals as well as showcasing high potential in applications
for green energetic propellants.