High‐Spin States of Manganese(III) Enable Robust Cold‐Adapted Activity of MnO2 Nanozymes

Abstract Developing novel cold‐adapted nanozymes and elucidating their mechanisms of action remains a great challenge. Inspired by natural oxidases that utilize high‐spin and high‐valent metal‐oxygen intermediates to achieve high efficiency at low temperatures, in this study, a series of MnO x nanomaterials with varied valence and spin states are synthesized. The activity assay revealed that the oxygen vacancy‐engineered ε ‐MnO 2 nanozyme displayed excellent cold‐adapted oxidase‐like properties, and no observable activity loss is observed in the temperature range of −20 to 45 °C. The superior performance is attributed to the high‐spin Mn(III)–O species coupled with its induced Jahn–Teller effect, which facilitates the dissociation and activation of oxygen at low temperatures. As a proof of concept, an excellent cold‐adapted δ ‐MnO 2 nanozyme can be obtained using Mn 3 O 4 as the precursor by regulating the spin state of Mn(III). Moreover, a novel and effective degradation strategy for corn stalk at low temperature is built based on the robust cold‐adapted oxidase‐like activity of ε ‐MnO 2 . These results not only provide new insights for the rational design of cold‐adapted nanozymes but also broaden the application of nanozymes in low‐temperature industrial processes.