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

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-MnO₂ 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-MnO₂ nanozyme can be obtained using Mn₃O₄ 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-MnO₂. 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.