Metal-Free Molecular Perovskite High-Energetic Materials

Abstract

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).

Room-temperature ferroelectric and ferroelastic orders coexisting in a new tetrafluoroborate-based perovskite

“…[23][24][25][26][27][28][29] For instance, by employing the tetrahedral perchlorate ion (ClO 4 − ), we recently constructed a large family of molecular perovskites being promising practicable high-energetic materials. [30][31][32] Similarly, as another well-known tetrahedral ion, tetrafluoroborate (BF 4 − ) catches increasing attentions with an expectation to serve as bridging ligand for constructing molecular perovskites. Since the first tetrafluoroborate-based perovskite, (H 2 dabco)(NH 4 )(BF 4 ) 3 (H 2 dabco 2+ = 1,4-diazabicyclo[2.2.2]octane-1,4-diium), was reported by Liu et al in 2011, 33 the efforts to date have added five instances.…”

Homopiperazine (Hexahydro-1,4-diazepine)

“…At present, it is commercially available from several major suppliers and it has recently found various applications, including as a component of liquids for CO 2 capture [4] and as a component of various organic and organic/inorganic supramolecular ionic salts and transition metal complexes. In these latter applications, the materials are often characterised by X-ray diffraction and so there are a large number of X-ray structures involving a homopiperazinium dication in salts or mixed salts with, for example, carboxylic acids [5][6][7], potassium perchlorate [8], ammonium perchlorate [9], manganese sulfate oxalate [10], cobalt sulfate [11], zinc phosphate [12], arsenic oxide [13], tellurium phosphate [14], cadmium phosphate [15], cadmium chlorides [16,17], lead bromide [18], bismuth iodide [19], uranium fluoride [20] and uranium sulfate [21]. There are also a significant number of structures in which homopiperazine acts as a bidentate ligand on nickel [22,23], copper [24] and platinum [25][26][27][28].…”

Prospects of Metal‐Free Perovskites for Piezoelectric Applications

“…Most recently, metal‐free perovskites including C 4 N 2 H 12 ‐NH 4 Cl 3 ‐H 2 O, C 6 N 2 H 14 ‐NH 4 Cl 3 , (C 4 N 2 H 12 )(NH 4 Br 3 )‐H 2 O, (C 4 N 2 H 12 )(NH 4 Br 3 )‐H 2 O, hmta‐NH 4 Br 3 , (H 2 DABCO)(NH 4 )[BF 4 ] 3 , (H 2 A)[NH 4 (ClO 4 ) 3 ] (where H 2 A 2+ cations = 1‐hydroxy‐1,4‐diazabicyclo[2.2.2]octane‐1,4‐diium, piperazine‐1,4‐diium, 1‐methyl‐piperazine‐1,4‐diium, homopiperazine‐1,4‐diium, 1‐methyl‐1,4‐diazabicyclo‐[2.2.2]octane‐1,4‐diium), (H 2 DABCO)‐NH 3 OH + ‐(ClO 4 ) 3 , and (H 2 DABCO)‐NH 2 NH 3 + ‐(ClO 4 ) 3 have been successfully synthesized to show their potential in ferroelectric and piezoelectric applications. [ 31,34,78–81 ] A breakthrough on metal‐free organic perovskite ferroelectrics has been reported to include 23 new compounds with a general formula of A(NH 4 )X 3 (A = divalent organic cation and X = Cl, Br, or I). Of these, MDABCO‐NH 4 I 3 has been reported to show a spontaneous polarization of 22 mC cm −2 (close to that of BTO), a high phase transition temperature of 448 K (higher than BTO), and 8 obvious polarization directions.…”