Nature-inspired solar evaporator based on polyzwitterionic hydrogels with reversible salinity adaptability for high-efficiency euryhaline solar desalination

Enhancing water convection to dilute surface brine has proven effective in suppressing salt precipitation during interfacial solar evaporation (ISE), but excessive water transport often leads to heat loss. Herein, we develop a zwitterionic poly(sulfobetaine methacrylate) (PSBMA) hydrogel-based ISE system that self-regulates water transport across a wide salinity range. The hydrogel exhibits a tunable swelling ratio and reduced water evaporation enthalpy due to a strong anti-polyelectrolyte effect, enabling efficient water evaporation with minimal thermal loss. Numerical simulations show that the salt-binding capacity of the hydrogel induces a reversed salt concentration gradient, which enhances both water pumping and backward salt diffusion. This mechanism prevents salt accumulation and ensures consistent evaporation. As a result, the system achieves a stable water evaporation rate exceeding 2.0 kg m −2  h −1 across salinities from 0 to 20 wt%, maintaining long-term performance without salt crystallization or structural degradation. This work demonstrates a promising strategy for designing self-adaptive evaporators with both high energy efficiency and excellent salt resistance across varying saline conditions.