The elegance of simplicity: a cost-effective Janus membrane for all-day radiative thermal management inspired by complementary photothermal design†

Passive radiation thermal control technology offers a promising alternative to traditional energy-intensive cooling and heating methods, aiming to improve energy efficiency and environmental sustainability. In this work, we demonstrate that the combination of Nylon66 and MXenes yields complementary radiative properties, enabling dual-mode thermal regulation. Integrating MXenes with a porous Nylon66 membrane featuring a richly textured, coral-like hierarchical architecture adeptly addresses challenges associated with environments that are characterized by extreme thermal disparities. The Nylon66 side, with a solar absorptivity of 0.062 and a mid-infrared emissivity of 0.928, achieves subambient cooling of 14.8 °C during the day and 1.7 °C at night. In contrast, the MXene side, with a solar absorptivity of 0.845 and a mid-infrared emissivity of 0.073, provides heating up to 36.4 °C during the day and 0.5 °C at night. Rapid mode switching via membrane flipping (Δε = 0.843) and MXenes' conductive electrothermal heating for external compensation further expand its applicability. Our straightforward and cost-effective fabrication strategy delivers thermal management performance comparable to more complex systems, offering significant potential for large-scale application in space exploration, architecture, and personal thermal management.