Synergistic solar-magnetic desalination via covalently anchored Fe₃O₄/hydrogel composites

Synergistic photothermal-magnetothermal activation overcomes environmental interference (e.g., cloud cover) that critically limits solar evaporator efficiency, enabling robust all-weather vapor generation. Herein, we demonstrate in-situ synthesis of a covalently integrated Fe₃O₄/hydrogel composite via ice-templating and interfacial covalent bonding engineering. Si-O-Fe bonds anchor KH-570 onto Fe₃O₄, enabling copolymerization of surface-grafted methacryloyloxy groups with acrylamide monomers for covalent network grafting, while programmed gravitational sedimentation yields a hierarchical porous hydrophilic magnetic gel solar interfacial evaporator (MSE) with magnetothermal interface. This architecture reduces evaporation enthalpy, achieving 2.33 kg m −2  h −1 under 1 sun. Significantly, synergistic activation by an alternating magnetic field and 1 sun irradiation boosts the evaporation rate for 3.5 wt% saline water to 2.94 kg m −2  h −1 . This work establishes the magnetothermal-photothermal synergy within the covalently integrated MSE as an effective material design paradigm for all-weather solar desalination.