Synthesis and characterization of high-energy anti-perovskite compounds Cs3X[B12H12] based on cesium dodecahydro-closo-borate with molecular oxoanions (X- = [NO3]-, [ClO3]- and [ClO4]-)

Abstract

Three novel anti-perovskite compounds, formulated as Cs3X[B12H12] (X = [NO3], [ClO3], and [ClO4]), were successfully synthesized through the direct mixing of aqueous solutions containing Cs2[B12H12] and CsX (X: [NO3], [ClO3], [ClO4]), followed by isothermal evaporation. All three compounds crystallize in the orthorhombic space group Pnma, exhibiting relatively similar unit-cell parameters (e.g., Cs3[ClO3][B12H12]: a = 841.25(5) pm, b = 1070.31(6) pm, c = 1776.84(9) pm). The crystal structures were determined using single-crystal X-ray diffraction, revealing a distorted hexagonal anti-perovskite order for each. Thermal analysis indicated that the placing oxidizing anions X into the 3 Cs+ + [B12H12]2 blend leads to a reduction in the thermal stability of the resulting anti-perovskites Cs3X[B12H12] as compared to pure Cs2[B12H12], so thermal decomposition commences at lower temperatures, ranging from 320 to 440 C. Remarkably, the examination of the energy release through DSC studies revealed that these compounds are capable of setting free a substantial amount of energy, up to 2000 J/g, upon their structural collapse under an inert-gas atmosphere (N2). These three compounds represent pioneering members of the first ever anti-perovskite high-energy compounds based on hydro-closo-borates.