As an emerging high-energy compound, 3-nitro-1,2,4-triazol-5-one (NTO) is used in military explosives and rocket propellants. However, the strong acidic corrosion of NTO, and the high sensitivity and poor thermostability of its salts, severely restrict their practical applications. Therefore, a novel strategy to design and construct energetic covalent organic frameworks (COFs) is proposed in this study. We have successfully prepared a two-dimensional crystalline energetic COF (named ECOF-1) assembled from triaminoguanidine salt, in which NTO anions are trapped in the porous framework via the ionic interaction and hydrogen bonds. The results show that ECOF-1 exhibits superior thermal stability than energetic salt of NTO. It also exhibits insensitivity and excellent heat of detonation of 7,971.71 kJ·kg⁻¹. ECOF-1 greatly inhibits the corrosiveness of NTO. In prospect, energetic COFs are promising as a functional platform to design high-energy and insensitive energetic materials.