NIR light-driven deflagration of energetic copper complexes through photothermal effect

The search for laser-ignitable energetic materials catering to the safety and accuracy requirements in military and civilian affairs is an important yet challenging task. In this work, non-explosive and stable nitro bearing ligands of 3,5-dinitro-4-chlorobenzoic acid (HDNB-Cl) and 3,5-dinitro-4-hydroxybenzoic acid (HDNB-OH) have been adopted as energetic modules and organic building units to assemble with copper ions to construct energetic coordination complexes. The d-d transition introduced by Cu²⁺ endows the as-synthesized compounds to display remarkable absorptions of NIR light, and thus achieve efficient photothermal conversions upon irradiation by an 808 nm laser. As a result, the DNB-Cl based complexes can be laser-ignited and strong deflagration has been observed. The satisfactory thermal stability and tolerance toward friction and electrostatic discharge make them good candidates as laser-ignitable energetic materials. Unlike the conventional energetic materials based on nitrogen-rich organics (e.g., azido, furazan, and heterocyclic compounds), this work reveals that the easily functionalized nitro-bearing carboxylate ligand is an alternative energy module for assembling stable energetic complexes, and the coordination interaction-induced photothermal conversion would be an efficient strategy to achieve laser ignition for the resultant energetic compounds.