Modulating energetic performance through decorating nitrogen-rich ligands in high-energy MOFs

Area of Science:

• Materials Science
• Inorganic Chemistry
• Energetic Materials

Background:

• Metal-organic frameworks (MOFs) offer tunable properties for energetic applications.
• Nitrogen-rich ligands are crucial for enhancing the energy density and stability of MOFs.
• Ammonium perchlorate (AP) is a widely used oxidizer in energetic formulations.

Purpose of the Study:

• To synthesize and characterize two novel energetic MOFs, [Ag(tza)]n and [Ag(atza)]n, using tetrazole-1-acetic acid (Htza) and (5-amino-1H-tetrazole-1-yl) acetic acid (Hatza) ligands.
• To evaluate and compare the energetic properties, thermal stability, and sensitivity of the synthesized MOFs.
• To investigate the effect of an amino group on the structure-property relationships of these energetic MOFs and their potential as ammonium perchlorate (AP) additives.

Main Methods:

• Synthesis and characterization of MOFs using X-ray single crystal structure analysis.
• Experimental and theoretical evaluation of energetic properties, including heats of detonation, thermal stability, sensitivity, and detonation performance.
• Determination of nonisothermal thermokinetic parameters using Kissinger and Ozawa methods.
• Calculation of standard molar enthalpies of formation via constant volume combustion energy measurements.
• Assessment of the compounds as additives to promote ammonium perchlorate (AP) thermal decomposition.

Main Results:

• Two 2D layer-like energetic MOFs, [Ag(tza)]n (1) and [Ag(atza)]n (2), were successfully synthesized.
• Both MOFs demonstrated promising energetic properties, including high heats of detonation, thermal stability, and detonation performance.
• The introduction of an amino group in [Ag(atza)]n (2) resulted in varied coordination, altered framework stacking, shorter bond lengths (Ag-O, Ag-Ag, C-N, N-N, N≡N), and consequently, superior heats of detonation and thermostability compared to [Ag(tza)]n (1).
• [Ag(atza)]n (2) exhibited enhanced thermal decomposition promotion of ammonium perchlorate (AP).

Conclusions:

• The amino group in the ligand plays a significant role in tuning the coordination modes, framework structure, and energetic performance of silver-based MOFs.
• [Ag(atza)]n (2) presents superior energetic characteristics and thermal stability, making it a promising candidate for advanced energetic materials.
• This study provides an effective strategy for manipulating the energetic properties and thermal stability of high-energy compounds through ligand modification.