Challenging the Limits of the Oxygen Balance of a Pyrazole Ring

•A high-crystal-density 1-trinitromethyl-3,4,5-trinitropyrazole was synthesized for the first time.•The target compound has high oxygen balance (+18.1 %), excellent thermal stability (160 ℃), and high specific impulse (Isp: 243 s), which is a potential energetic oxidiser.•One kind of N-alkylation reagents (diazoacetone) was used in the research field of energetic materials.