This work reports the inherent peroxidase-like properties of Ruthenium (Ru) nanoframes. After templating with Palladium (Pd) seeds, Ru nanoframes with an octahedral shape, average edge length of 6.2 nm, and thickness of 1.8 nm were synthesized in high purity (>95 %) and good uniformity. Using the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) by H2O2 as a model catalytic reaction, the Ru frames were demonstrated to be approximately three times more active than natural peroxidases in catalyzing the formation of colored products. As compared to their natural counterparts, Ru frames have a stronger binding affinity to TMB as well as a weaker binding affinity to hydrogen peroxide during the catalysis. The Ru frames as peroxidase mimics proved to be chemically and thermally stable. This work represents the first demonstration of Ru nanostructure-based peroxidase mimics and is therefore …