Bioinspired and Biodegradable Hydrothermally Treated Cellulose Nanocrystal Aerogels for High Efficiency Solar Steam Generation and Sustainable Water Purification

Abstract Access to clean water is crucial for human survival, yet a significant portion of the global population continues to face challenges from water scarcity and contamination. Traditional water purification methods such as desalination and distillation are energy‐intensive, necessitating the adoption of green alternatives to reduce greenhouse gas emissions and mitigate global warming. High‐efficiency solar steam generation has emerged as a promising solution. Although many solar evaporators have shown impressive evaporation rates, construction of these using only sustainable materials remains challenging. Inspired by the microstructure of natural wood, a series of hydrothermally‐treated cellulose nanocrystal aerogels (HTCAs) is proposed as efficient and eco‐friendly solar steam generators. The HTCAs are prepared through a one‐pot hydrothermal treatment, avoiding the use of hazardous chemicals, and entirely based on sustainable cellulose nanocrystals. They present low tortuosity porous microstructures and exhibit high evaporation rate (1.70 kg m −2 h −1 under 1 sun irradiation) with low water evaporation enthalpy (841 ± 35 J g −1 ). Integration with advanced water purification techniques also demonstrates their effectiveness in removing contaminants. This strategy mimics the microstructure of wood through unidirectional freeze‐drying and offers a sustainable pathway to biodegradable solar steam generators, potentially alleviating the global water scarcity within the carbon neutrality framework.