Since the black powder, the first known explosive, was discovered by ancient Chinese in the seventh century, people have been finding powerful, stable, reliable and low-cost energetic materials for military equipment and civil industry. To obtain a better explosive performance, an efficient strategy is to load unstable chemical bonds [1][2][3], as well as to combine fuel with oxidizer components in a proper ratio for achieving sufficient combustion and rapid detonation [4][5][6]. An effective way is to incorporate fuel and oxidizer properties into a single molecule [7], as demonstrated by a series of classical organic nitro group/nitrogen-rich molecules, such as trinitrotoluene (TNT), pentaerythritol tetranitrate (PETN), cyclotrimethylene trinitramine (RDX), cyclotetramethylene tetranitramine (HMX), hexanitrohexaazaisowurtzitane (CL-20) and octanitrocubane (ONC) (Fig. S1). Loading more nitro groups and higher structural tension into a single molecule does improve explosive performance, but usually leads to complicated and not cost-effective synthetic procedures. By a trade-off of detonation performance and cost, HMX is regarded as the best military high-energetic explosives nowadays [7], although it is neither the most powerful one nor the cheapest one.Parallel to the intensive studies on molecule engineering on the backbone of nitrogen-rich organic energetic molecules [8,9], the exploration of advanced energetic materials extends to the crystal engineering on their energetic co-crystals [10-13], energetic salts [14][15][16][17][18][19][20], as well as coordination polymers or metal-organic frameworks [21][22][23][24][25][26][27]. The essential strategy is to control the intermolecular packing/linkage of the energetic organic fuel and oxidizer components in crystals by non-covalent interactions to modify/enhance the explosive performance and/or to reduce the sensitivity to a practicable level. However, for a specific energetic molecular component, it is highly challenging to predict/engineer the crystal structure of its co-crystals, salts, or metal-organic frameworks [10], and the examples with good detonation performance, high stability and low cost are still scarce.Here we present a promising solution, i.e., assembly of both low-cost organic fuel and oxidizer components into a closely packed, high-symmetry ternary compounds (vide infra), to achieve advanced energetic materials with a nice combination of high explosive power, high stability, and low cost. The presented materials belong to the so-called molecular perovskites [28] with a general formula of ABX 3 , which topologically mimic the cubic structure of the very well-known inorganic perovskites, the simplest high-symmetry structure for ternary compounds, but have at least one organic molecular component (usually A component). Recently, molecular perovskites have attracted growing attention, as illustrated by the extensive studies on methyl-ammonium lead iodide for high performance solar cells [29][30][31][32], and the phase transitions together with the ...

Metal-free energetic materials generally have the advantages of high gas yield and metal-free residue after combustion or explosion, enabling them to be widely used as explosives and propellant components. As part of a series of our investigations on ABX 3 molecular perovskite high-energetic materials, here we report five new metal-free members, (H 2 A)[NH 4 (ClO 4 ) 3 ], by using different organic cations H 2 A 2+ , i.e., 1-hydroxy-1,4diazabicyclo[2.2.2]octane-1,4-diium for DAP-O4, piperazine-1,4-diium for PAP-4, 1methyl-piperazine-1,4-diium for PAP-M4, homopiperazine-1,4-diium for PAP-H4, and 1methyl-1,4-diazabicyclo-[2.2.2]octane-1,4-diium for DAP-M4, respectively. Together with the previously reported member, (H 2 dabco)[NH 4 (ClO 4 ) 3 ] (DAP-4, H 2 dabco 2+ = 1,4diazabicyclo[2.2.2]octane-1,4-diium), these six metal-free molecular perovskite high-energetic materials provide nice instances to fine-tune the oxygen balance, crystal density, thermal stability, and detonation performance, by changing the A-site organic cations solely. The density functional theory (DFT) calculations and the Kamlet−Jacob (K−J) equation suggested that improving the oxygen balance while keeping the spherical shape of the organic cations to match the anionic cage in these metal-free energetic materials facilitates obtaining a better detonation performance, providing an important clue for designing advanced practicable high-energetic materials. It is worth noting that three compounds (PAP-4, PAP-H4, and DAP-O4) are expected to exceed the performances of RDX as both explosive and propellant, in which DAP-O4 has the highest detonation heat (6.21 kJ mol −1 ), detonation velocity (8.900 km s −1 ), and detonation pressure (35.7 GPa), as well as a higher specific impulse value (262 s).

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In recent years, molecular perovskite energetic materials have attracted more attention because of their simple synthesis processes, high thermal stabilities, excellent performances, and great significance as a design platform for energetic materials. To explore the possibility of the application of molecular perovskite energetic materials in heat-resistant explosives, four silver­(I)-based molecular perovskite energetic compounds, (H2A)­[Ag­(ClO4)3], where H2A = piperazine-1,4-diium (H2pz2+) for PAP-5, 1-methyl-piperazine-1,4-diium (H2mpz2+) for PAP-M5, homopiperazine-1,4-diium (H2hpz2+) for PAP-H5, and 1,4-diazabicyclo[2.2.2]­octane-1,4-diium (H2dabco2+) for DAP-5, were synthesized by a one-pot self-assembly strategy and structurally characterized. The single-crystal structures indicated that PAP-5, PAP-M5, and DAP-5 possess cubic perovskite structures while PAP-H5 possesses a hexagonal perovskite structure. Differential thermal analyses showed that their onset decomposition temperatures are >308.3 °C. For PAP-5 and DAP-5, they have not only exceptional calculated detonation parameters (D values of 8.961 and 8.534 km s–1 and P values of 42.4 and 37.9 GPa, respectively) but also the proper mechanical sensitivity (impact sensitivities of ≤10 J for PAP-5 and 3 J for DAP-5 and friction sensitivities of ≤5N for both PAP-5 and DAP-5) and thus are of interest as potential heat-resistant primary explosive components.