Scaffold and Guest Regulation Metal-free Laser-Responsive Energetic Ionic Salts: Functional Construction and Transformation

Laser initiation offers a safer and more controllable alternative to conventional initiation methods, with laser-responsive materials serving as the fundamental platform for such functional conversion. However, existing laser-responsive energetic compounds often rely on heavy metals and suffer from poor safety profiles, significantly limiting their practical deployment. The development of metal-free laser-responsive materials remains largely unexplored. This study introduces a design strategy that enables the construction and transformation of laser-responsive functions in metal-free energetic ionic salts (EISs) through the synergistic regulation of their oxygen balance via a fused-ring scaffold and guest ions. Following this strategy, a metal-free EIS (ES-1) was synthesized from a [5,1-c][1,2,4]pyrazolotriazine ring and a ClO4– anion. Subsequent transformations yielded ES-2 via guest anion exchange (ClO4– to NO3–) and ES-3 through functionalization. The distinct crystal packing, thermal stability, and energetic properties of ES-1, ES-2, and ES-3, as determined by X-ray diffraction and DSC-TG, validate the viability of this component-level functional tuning approach. Rapid laser-initiation tests and high-speed photography confirmed that ES-1 undergoes a deflagration-to-detonation transition (DDT) under 980 nm near-infrared laser irradiation, with a delay time of 185 ms. In contrast, ES-2 exhibited excellent moisture resistance but negligible laser sensitivity, whereas ES-3 displayed pronounced hygroscopicity due to an excessive proportion of oxygen-related contacts, which effectively masked its intrinsic laser responsiveness. These results uncover structure–property relationships governed by scaffold and guest regulation, and underscore the critical role of oxygen balance in regulating photoresponsive activity, energy output, and environmental stability. This work provides a practical framework for designing next-generation, environmentally friendly, metal-free laser initiators.