Metal–Organic Frameworks as High Explosives: A New Concept for Energetic Materials

Abstract

In memory of Malcolm M. Renfrew coordination polymers · energetic materials · heat of detonation · metal-organic frameworks · porous structures Metal-organic frameworks (MOFs) represent a fascinating class of porous crystalline materials with ordered pores and channels. [1] In general, they can be readily prepared by the self-assembly of metal ions or metal-containing clusters with organic ligands through coordination bonds between metal center and organic linker. Because of their intriguing structures and unique properties, the investigation of MOFs has attracted considerable interest, and their potential applications have been explored in various fields, such as gas storage, catalysis, molecular sensing, separation, and nonlinear optical materials. [2,3] Recently, several investigators have demonstrated the possibility of using nitrogen-rich MOFs as high explosives. [4,5] Although they remain to be systematically exploited, the exceptional energetic performance of several reported energetic MOFs has revealed their great potential as new-generation high explosives.The concept of energetic metal-organic polymers is not strictly new. In the field of energetic materials, a great number of metal-based explosives, including metal salts and complexes, have been used as initiating primary explosives for many decades; many are composed of metal ions (including Pb 2+ and Ag + ) and energetic anions (such as N 3 À and NO 3 À ) or energetic ligands (e.g., hydrazine). In the case of energetic bidentate or multidentate ligands, many energetic metalorganic frameworks can be formed through coordination interactions between metal ions and energetic ligands. By virtue of this strategy, a variety of energetic MOFs with diverse structures and topologies have been synthesized and utilized as energetic materials for commercial and military applications, [6][7][8][9] although they have not been called "energetic MOFs" in the literature. Depending upon the metal ion geometry and the binding mode of the bridging energetic ligands, the network structures of energetic MOFs can be designed in one, two, or three dimensions (1D, 2D, or 3D; Figure 1). Apart from metal ions and ligand geometries, other factors, such as temperature, solvent, pH, and stoichiometry, may also play a significant role in modulating the network topologies and the dimensionalities of the target energetic MOFs. In this sense, the concept of designing energetic MOFs as high explosives has provided a unique architectural platform for developing new-generation energetic materials.Recently, in pursuit of greener energetic materials, an interesting energetic metal-organic coordination polymer of zinc(II) hydrazine azide, [Zn(N 2 H 4 ) 2 (N 3 ) 2 ] n , was reported. [10] This material has a 1D framework structure, in which the Zn II ion is hexacoordinated with two azido ligands by m 1 -azido bridges and four hydrazine molecules, which act as bidentate ligands. The nitrogen content of this energetic 1D MOF material is 65.6 %, and its heat of combustion is 5.45 MJ kg À1 . By ...

3D Co(II, III) mixed-valence metal-organic framework affording field-induced slow magnetic relaxation

“…Much recent research has focused on MOFs that contain nitrogen-rich heterocyclic ligands and non-toxic metal ions as newgeneration green primary explosives become a new concept for energetic materials [7][8][9][10]. In our recent work [11], we obtained two MOF-based energetic compounds that present an ingenious design for guest-dependent energy and sensitivity of 3D MOF-based energetic compound and also offer a practical strategy for the storage and transportation of high-energy materials.…”

Synthesis and Characterization of Tetrahedral Zinc(II) Complexes with 3, 6,7‐Triamino‐7H‐[1, 2,4]triazolo[4, 3‐b][1, 2,4]triazole as Nitrogen‐Rich Ligand

“…[5] In the area of energetic materials, the formation of transition metal complexes is continuously gaining importance. [6] When designing new energetic materials, the desired properties of the explosive need to be customized to specific applications.…”

Eco-friendly energetic complexes based on transition metal nitrates and 3,4-diamino-1,2,4-triazole (DATr)

“…Considerable attention has been drawn to nontoxic metal coordination compounds based on nitrogen-rich heterocyclic groups [5][6][7][8][9][10][11], owing to their multiple structures [12,13], and energetic properties. Nitrogen-rich heterocyclic compounds are mainly azole-based compounds, such as triazoles [6,[14][15][16][17], tetrazoles [4,[18][19][20][21][22], and their derivatives [3,13,[23][24][25][26][27][28][29][30].…”