Development of super-heat-resistant purine-based coordination polymers for applications in energetic materials

Recent studies highlight the potential of nitrogen-rich, high-energy coordination polymers (CPs) for the development of next-generation energetic materials. Compared to traditional organic explosives, they provide improved density, sensitivity, oxygen balance, and heat of detonation. However, the tuning of high-energy CPs with respect to their energetic properties and the decoding of their structure-function relationship are still in the nascent phase. This work highlights the role of coordination polymerization in tailoring key energetic and physicochemical properties, including density, mechanical insensitivity, and thermal stability. Purine (a naturally occurring and widely available ligand) was used to synthesize two energetic coordination polymers (ECPs): ECP-1 [Ag(L₁)(ClO₄)₂]_<i>n</i> and ECP-2 [Ag(L₂)(NO₃)₂]_<i>n</i>. Crystal structure analysis revealed that ECP-1 forms a wavelike three-dimensional network, while ECP-2 exhibits a solvent-free compact lamellar 3D structure. Both ECPs exhibit excellent thermal stability (<i>T</i>_d = 320.4-405.2 °C) with significantly improved densities (2.36-2.37 g cm^-3), acceptable detonation velocities (6707-7691 m s^-1) and detonation pressures (22.5-32 GPa), while being insensitive to mechanical stimuli (IS = 40 J; FS = 360 N). Additionally, this study provides a pathway for synthesizing novel ECPs based on naturally occurring ligands with dual structures, promoting a balance between energetic performance and safety while offering versatile functionality.