Enhancing combustion performance of solid propellants using synergistic effect of energetic metal–organic framework with cage-like [Bi6(µ3-O)3(µ3-OH)5] clusters and copper-iron hetero-metallic compound

[Display omitted] •{[Bi6O3(tza)5(NO3)2(OH)5]·H2O}n (Bi-MOF) can be synthesized gently and efficiently.•Bi-MOF has good thermal stability and mechanical insensitivity.•Copper-iron hetero-metallic compound (CuFe-MOF) has good mechanical insensitivity.•Bi-MOF and CuFe-MOF synergistically catalyze thermal decomposition of RDX and HMX.•Bi-MOF and CuFe-MOF synergistically enhance propellants’ combustion performance. This study explores the potential of energetic metal–organic frameworks (E-MOFs) to enhance the combustion performance of solid propellants. A {[Bi6O3(tza)5(NO3)2(OH)5]·H2O}n (Bi-MOF) incorporating the energetic ligand tetrazole-1-acetic acid (Htza) was synthesized and evaluated for structural characteristics and properties. The catalytic thermal decomposition of cyclotrimethylene trinitramine (RDX) and cyclotetramethylene tetranitramine (HMX) by mixed systems was investigated. These systems consisted of Bi-MOF and copper-iron hetero-metallic compound ({[CuFe3O(tza)6(H2O)3]·Cl·(NO3)2·4H2O}n, CuFe-MOF), previously reported by our group in different ratios. The effect of the mixed system with the highest synergy index on the combustion performance of composite modified double-base propellant (RDX-CMDB) and nitrate ester plasticized polyether propellant (HMX-NEPE) was investigated. The impact of varying carbon black (CB) contents on the catalytic performance of the mixed system was also examined. The results showed that Bi-MOF exhibits good thermal stability (Tdec = 226.9 °C) and insensitivity (IS>40 J, FS>360 J). The mixed system, comprising Bi-MOF and CuFe-MOF in a 2:1 ratio (M2), exhibited the highest synergistic indices (3.35 and 3.24) on thermal decomposition for RDX and HMX. RDX-CMDB and HMX-NEPE propellant formulations containing M2 and a small amount of CB exhibited significant improvements in combustion performance. RDX-CMDB propellant exhibited up to an 80.6 % increase in burning rate and up to a 59.6 % reduction in pressure index. The pressure indices of NEPE without and with aluminum were reduced from 0.65 and 0.50 to 0.38 and 0.40, respectively (10–20 MPa, 1–20 MPa). These findings highlight the promise of the mixed system, formed by Bi-MOF and CuFe-MOF, as a potential combustion catalyst for RDX-CMDB and HMX-NEPE propellants.