Provided are energetic materials of low vapor pressure in the form of ionic liquids having fuel and oxidizer ions including, substituted pyridinium or imidazolium cations paired with nitrato-, perchlorato-, or nitramido-based anions, to form such ionic liquids or salts. The salts of the present invention are low melting and have essentially little or no vapor pressure over a wide temperature range. The salts of this invention are thus an important breakthrough since they can serve as high-performing monopropellants which are not complex mixtures and have no vapor toxicity. Such salts also find use as munitions, liquid explosives, reaction media for the synthesis of other high-energy materials, and as plasticizers.