Chemodynamic therapy (CDT) is an emerging treatment strategy that inhibits tumor growth by catalyzing the generation of reactive oxygen species (ROS), such as hydroxyl radicals (center dot OH), using specific nanomaterials. Herein, we have developed a new class of iron-based nanomaterials, i.e., iron-based borides (FeB), using the superchaotropic effect of a boron cluster (closo-[B12H1212-) and organic ligands, followed by high-temperature calcination. Experimental data and theoretical calculations revealed that FeB nanoparticles exhibit a Fentonlike effect, efficiently decomposing hydrogen peroxide into center dot OH and thus increasing the concentration of ROS. FeB nanomaterials demonstrate excellent catalytic performance, efficiently generate ROS, and exert significant antitumor effects in cell experiments and animal models. Therefore, FeB nanomaterials have