A novel dual-functional EMOFs containing azide ligands: Synergistic enhancement on ignition and combustion properties of boron powders

The applications of boron-based (B) fuels in propulsion and weapon systems are hindered by inefficient combustion and harsh ignition conditions of B particles. Dual-functional energetic metal-organic frameworks (EMOFs) were synthesized on B surface by incorporating azide ligands as secondary ligands to improve the thermal and combustion properties of B particles. Polydopamine (PDA) interfacial layer was constructed between B and EMOFs to strengthen the interface interaction and facilitate the processes of mass and heat transfer. The mechanisms of EMOFs in eliminating the negative effects of oxide film and enhancing B combustion were analyzed. The results illustrate that the expansion of flame front is driven by the micro-explosion effect of azide ligands, and the flame height increases from 0.46 to 67.9 mm. Concurrently, the generated metal oxides alter the oxygen diffusion pathway by adhering to B surface, thereby significantly enhancing the oxidation process of B. The combustion efficiency of B increased from 60.7% to 80.4%, the oxidation temperature lowered by 77 °C, and the flame radiation intensity enhanced by approximately 29%. Crucially, the azide ligands and residual metal oxides exhibit different functions. The azide ligands exhibit the functions of ignition sensitization and micro-explosion at the combustion interface, while the adherent metal oxides promote the efficient oxidation of B particles along two distinct pathways. This innovative strategy of integrating azide ligands and metal oxides offers a novel direction for enhancing the energy release performance of B-based fuels. The low combustion efficiency and high oxygen consumption of boron-based (B) fuel hinder its energy release in energy and weapon systems. In this work, a novel dual-functional energetic metal-organic frameworks (EMOFs) containing azide ligands was designed to improve the thermal and combustion properties of B. Moreover, the influence and mechanism of energetic ligands on B combustion were investigated. • Dual-functional EMOFs containing azide ligands were synthesized and firstly used to enhance the B combustion. • R -MOF (MA) greatly enhances the flame intensity, flame temperature and combustion efficiency of B particles. • The dual-channel oxidation mechanism was proposed to explain the oxidation process of B@ R -MOF (MA) composites.