Bifunctional Portable Powder for Freshwater Production With Moisture Harvesting and Undrinkable Water Purification

Abstract Freshwater scarcity threatens human survival, particularly in extreme environments like deserts, oceans, and space. Compatible atmospheric water harvesting and undrinkable water purification offer an affordable approach to solving freshwater scarcity in these extreme environments. Nonetheless, developing composite sorbent to attain efficient atmospheric water harvesting and undrinkable water purification remains challenging. Hence, a portable hybrid hygroscopic powder (HLC powder) consisting of hydroxypropyl chitosan, dibenzaldehyde‐functional poly(ethylene glycol), lithium chloride (LiCl), and nano carbon black is proposed. The HLC powder with optimized LiCl load can capture moisture from the air, showing a high water uptake of 1.76 g g⁻¹ at 34% relative humidity (RH) and appropriate over a wide humidity from 34% to 75% RH. pH‐responsive sol‐gel transition induced by Schiff base bonds transforms the HLC solution into hydrogel, inhibiting hydrated salt leakage. Meanwhile, to achieve efficient undrinkable water purification, the LiCl‐free hybrid powder is utilized to convert the undrinkable water, including seawater, dye water, and human urine, to photothermal hydrogel evaporators with low evaporation enthalpies and high evaporation rates ranging from 1.81 to 2.05 kg m⁻² h⁻¹ under one sun. This strategy establishes a new path to conveniently obtaining freshwater, breaking hydrological restrictions.