Spherical Design‐Driven Scalable Solar‐Powered Water Treatment with Salt Self‐Cleaning and Light Self‐Adaptivity

Interfacial solar evaporation, harnessing sunlight to induce water molecule evaporation, holds great promise for sustainable solar energy conversion. However, challenges such as reduced efficiency and instability due to salt accumulation, inadequate water transport, and the high cost of advanced nanostructured solar evaporators collectively hinder the sustainable and large‐scale practical use of this technology. Herein, an eco‐friendly, floatable 3D solar seawater evaporator is developed by innovatively incorporating a lightweight foam ball enclosed in a porous cellulose hydrogel. The 3D evaporator achieves a high water evaporation rate of ≈2.01 kg m −2 h −1 under 1 Sun, owing to its super high photothermal efficiency of 117.9% and efficient internal water transport channels. Even at a 0° simulated solar angle, the 3D evaporator maintains 85.8% of the evaporation rate at a 90° simulated solar angle. Moreover, the salt self‐cleaning capability is realized by the autonomous rotation caused by salt deposition. Particularly, the 3D evaporator can be fabricated over a large area and maintain seawater evaporation performance and structural integrity for 28 days. This study provides novel economically feasible and sustainable large‐scale solutions for interfacial solar‐powered seawater treatment.