Photothermal--Magnetocaloric Coupled Evaporators for Self-Adaptive Water Evaporation and Oil--Water Purification in Complex Environments

Solar-driven interfacial evaporation is a sustainable approach for freshwater production; however, its reliability is limited by the fluctuating solar intensity and complex water contaminants. This study produces a synergistic strategy that integrates magnetocaloric-mediated thermal compensation within a hierarchically structured aerogel. Iron-based nanoparticles derived from waste self-heating patches are incorporated into a konjac glucomannan/polyvinylpyrrolidone (KPF) aerogel with vertically aligned channels, yielding an adaptive photothermal–magnetocaloric coupled evaporation system capable of operating under diverse conditions. The KPF evaporator achieves an evaporation rate of 4.5 kg m -2 h -1 under one-sun illumination, increasing to 5.6 kg m -2 h -1 upon activation of an alternating magnetic field. Notably, under overcast and low-light conditions, comparable evaporation performance is maintained through magnetic-field-induced energy compensation. Molecular dynamics simulations and Raman spectroscopy reveals that magnetocaloric heating disrupts the ordered hydrogen-bond network of water, increasing the free water content and facilitating evaporation. The intrinsic underwater superoleophobicity of the KPF aerogel enables a coupled interception and evaporation mechanism for high-concentration oily wastewater, achieving a purification efficiency of 99.9%. Moreover, the magnetocaloric-enhanced Marangoni flow promotes salt ion migration, ensuring long-term stability in high-salinity environments. This dual-response strategy provides a universal platform for designing adaptive and efficient water treatment systems.