Stepless IR Chromism in Ti3C2Tx MXene Tuned by Interlayer Water Molecules

Real‐time control over infrared (IR) radiation of objects is highly desired in a variety of areas such as personal thermal regulation and IR camouflage. This requires the dynamic modulation of IR emissivity in a stepless manner over a wide range (>50%), which remains a daunting challenge. Here, an emissivity modulation phenomenon is reported in stacked 2D Ti3C2Tx MXene nanosheets, from 12% to 68% as the intercalation/discharging of water molecules within the interlayers. The intercalation of water molecules dynamically changes the electronic properties and the complex permittivity in IR frequencies of Ti3C2Tx. This emissivity modulation is a stepless and reversible process without the assistance of any external energy input. Further, intercalating cellulose nanofibers into the Ti3C2Tx interlayers makes this dynamic process highly repeatable. Last, a sweat‐responsive adaptive textile that can improve thermal comfort of human body under changes in metabolic rates and environmental conditions is demonstrated, showing great potential of this mechanism in passive on‐demand radiation modulation. A stepless and reversible emissivity modulation with a broad range (>50%) is revealed in stacked 2D Ti3C2Tx MXene nanosheets as the intercalation/discharging of water molecules in the interlayers. This phenomenon can keep the human body in thermal comfort when changing metabolic rates (≈20%) and environmental temperatures (≈3 °C) and show great potential in on‐demand passive radiation modulation of other applications.