Dual-crosslinked and dual-networked hydrogels with high mechanical properties for cost-effective solar water desalination and purification

High solar evaporation efficiency combined with enhanced desalination and antifouling performance is key in the application of the solar-driven interfacial water evaporation (SIWE) technology. In this study, we have designed a dual-crosslinked and dual-networked hydrogel (CSH) for interfacial solar vapor generation (ISVG). Through adjusting the proportions of matrix components and balancing the degree of crosslinking between cellulose and epichlorohydrin, it is feasible to obtain the hybrid hydrogel with elastic behaviors. The resulted hydrogel has a porous structure enabling the transport of water molecules, while the doped component of iron-based metal–organic frameworks provides this hydrogel with strong light absorbance, achieving an evaporation rate of 2.52 kg·m−2·h−1 under 1 kW·m−2 solar irradiation and an evaporation efficiency of 89.32%. The porosity also creates salt resistance through capillary forces. Practical applications of such CSH hydrogels in the field of seawater desalination and wastewater purification are conducted under outdoor light conditions, and the concentrations of metal ions are revealed to be reduced by orders of magnitude below the WHO threshold ones, while pigments are found to be absent from the condensate contained in the treated wastewater.