<p>Molecular perovskite energetic materials are a new class of thermally insensitive high-energy systems which have high enthalpy release during thermal decomposition, making them suitable as energetic additives to propellants and explosives. Catalytic decomposition of 1,4-diazabicyclo [2.2.2] octane-1,4-diium ammonium triperchlorate (DAP-4) molecular perovskite, aiming to reduce its ignition delay, is currently a very active research topic. In the present work, we investigated the catalytic effect of nano copper oxide–graphitic carbon nitride (CuO/g-C₃N₄) composites on the thermal decomposition of DAP-4. The nano copper oxide (CuO) was synthesised in the presence of graphitic carbon nitride (g-C₃N₄) and anchored in situ onto g-C₃N₄ layers, which could prevent the agglomeration of nano copper oxide. The characterisations of DAP-4 and nano CuO/g-C₃N₄ composites were conducted using Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS) and surface area analyser. The dispersion of nano CuO on g-C₃N₄ surface resulting in a high surface area for the nano CuO/g-C₃N₄ composites. Among the different compositions of nano CuO/g-C₃N₄ employed, the 5 mass% of 75:25 nano CuO/g-C₃N₄ was found to be the best catalyst for DAP-4 decomposition in terms of lowering of peak decomposition (by 64 ⁰C) and enhanced the enthalpy released during DAP-4 decomposition.</p> Graphical abstract <p></p>