Energetic Bimetallic MOF: A Promising Promoter for Ionic Liquid Hypergolic Ignition

Area of Science:

• Materials Science
• Inorganic Chemistry
• Energetic Materials

Background:

• Metal-organic frameworks (MOFs) offer tunable structures for diverse applications.
• Hypergolic propellants require efficient ignition promoters for rapid combustion.
• Bimetallic MOFs can exhibit synergistic catalytic effects not seen in monometallic systems.

Purpose of the Study:

• To synthesize and characterize a novel bimetallic MOF, CoNi(EIM)2(DCA)2 (1), using energetic 1-ethylimidazole (EIM) and dicyandiamide (DCA) ligands.
• To investigate the structural differences between the bimetallic MOF (1) and its corresponding monometallic compounds (2 and 3).
• To evaluate the performance of the bimetallic MOF as a hypergolic promoter for ionic liquid propellants.

Main Methods:

• Facile synthesis of bimetallic and monometallic MOFs.
• Single-crystal X-ray diffraction for structural analysis.
• SEM-EDS elemental mapping for composition verification.
• Thermal stability and sensitivity testing.
• Hypergolic ignition delay time measurements.
• Differential scanning calorimetry (DSC) for thermal decomposition analysis.

Main Results:

• A 3D reticular architecture was confirmed for the bimetallic MOF (1), distinct from the mononuclear coordination of monometallic compounds (2 and 3).
• Bimetallic MOF (1) demonstrated good thermal stability, insensitivity to mechanical stimuli, and high energetic density.
• Compound (1) significantly reduced the ignition delay time of 1-butyl-3-methylimidazolium dicyanamide (BMIM DCA) from 53 ms to 37 ms, outperforming (2) and (3).
• DSC analysis revealed that (1) effectively catalyzed BMIM DCA thermolysis, lowering decomposition temperature and activation energy by 16.3%.

Conclusions:

• The synthesized bimetallic MOF (1) exhibits superior catalytic activity in promoting hypergolic ignition compared to monometallic analogues.
• The synergistic effect of the bimetallic composition is crucial for enhancing the catalytic performance.
• This study highlights the potential of bimetallic MOFs as advanced energetic materials for hypergolic applications.