Dual-mode light-responsive chitosan-based hybrid hydrogel for efficient solar-driven water evaporation and multifunctional water purification.

Porous hydrogel-based evaporators are emerging as promising platforms for interfacial solar steam generation (SSG), yet their practical implementation is hindered by suboptimal solar energy utilization, low evaporation rate, and poor biofouling resistance. Herein, a dual-mode light-responsive g-C3N4/MXene@chitosan (CM/CH) hybrid hydrogel, capable of harnessing both photothermal and photodynamic pathways under light irradiation, was rationally engineered by embedding g-C3N4/MXene heterostructures into a chitosan-based network via Zn2+-mediated ionic crosslinking. This system integrates light-triggered heat generation and reactive oxygen species production, along with the intrinsic antimicrobial properties of chitosan, thereby ensuring rapid and complete bacterial eradication in contaminated water. Moreover, abundant hydrophilic functional groups further contribute to the formation of hydrogen-bonded networks with water molecules, facilitating efficient water transport and reducing evaporation enthalpy. As a result, the CM/CH hydrogel exhibits an excellent water evaporation rate of 2.98 kg m-2 h-1 with a solar-to-vapor efficiency of 97.4% under 1 sun simulated irradiation. More importantly, it maintains an efficient evaporation performance under natural solar illumination (⁓0.066 W cm-2), achieving an evaporation rate of 1.97 kg m-2 h-1 with a corresponding solar-to-vapor efficiency of 96.2%. Furthermore, owing to its robust biofouling resistance and superior mechanical properties, the hydrogel maintains an evaporation efficiency above 91% even after 15 days of outdoor exposure. It also efficiently desalinates, eliminates heavy metal ions, and degrades organic dyes, enabling effective multi-contaminant treatment and demonstrating its potential as a reliable solar-driven water purification platform.