Engineering hydrogels towards next-generation multifunctional interfacial solar evaporators beyond seawater desalination

Interfacial solar evaporation has emerged as a promising technology for sustainable freshwater production using renewable green energy to alleviate freshwater shortages. Hydrogels have been regarded as the most effective platform materials for interfacial solar evaporation due to their inherent hydrophilicity and water retention capabilities. This review initially describes the endeavors in molecular and structural engineering of hydrogels to achieve highly efficient interfacial solar evaporation with increased intermediated water content, improved heat confinement and water transport management, salt-resilience and three-dimensional structures. Subsequently, it scrutinizes and discusses the development of hydrogel evaporators with additional functionalities, including stimuli-responsive properties, self-healing, recyclability, disinfection, and volatile organic compound removal abilities for better water purification performance. Furthermore, it summarizes the potential applications of hydrogels in the emerging next-generation interfacial solar evaporators for metal ion extraction, evaporative cooling, and electricity generation beyond seawater desalination. Finally, conclusions are drawn and future perspectives on hydrogel-based systems are proposed. This review will provide insights into engineering hydrogels for achieving highly efficient solar evaporation performance while promoting practical and wideranging applications.