Cocrystal,
ionic salt, and coordination polymer had prompted the
development of propellants, explosives, and pyrotechnics. However,
the difference between their formation based on the same coformer
has rarely been studied. 5,5′-Bis(trinitromethyl)-3,3′-bi-1H-1,2,4-triazole (BTNMBT) is perchlorate-free, favorable
to scale-up, and a green energetic oxidizer with high physical performance
(oxygen balance: +18.4%, IS: 22.5 J, FS: 252 N, D: 9073 m s–1, P: 36.2 GPa). To investigate the influence of different
coformers on the formation of BTNMBT’s cocrystal, ionic salt,
and metal–organic framework, organic acid as well as organic
and inorganic bases with different dissociation constants (pK
a) were theoretically studied. In this work,
two energetic cocrystals, energetic ionic salt, and energetic metal–organic
framework were synthesized based on BTNMBT. For their formation, the
basic principle is found as follows: (i) when the pK
a value of organic base is far lower than both pK
a values of hydrogen-protons in organic acid,
the reaction systems are prone to forming cocrystals; (ii) if the
pK
a value of the selected organic base
is higher than that of one of the hydrogen-protons in organic acid
but lower than that of the other one, a 1:1 energetic ionic salt appears;
(iii) the 1:2 type of energetic ionic salt (or coordination polymer)
can form when the pK
a value of corresponding
base is higher than values of both hydrogen-protons in organic acid.
Among these shapes of derivatives, the coordination polymer form of
BTNMBT not only exhibits good detonation performance (D: 8872 m s–1), but also shows positive oxygen balance
(+18.2%) and high thermal stability (T
d: 180 °C) comparable to those of AP and superior to those of
ADN. These discoveries can assist the design and preparation of other
promising energetic materials toward future high-performing energy
applications.