To
combat the water crisis, on-site reclamation of freshwater from
seawater and sewage is urgently desired, in which solar-driven interfacial
evaporation has been recognized as an emerging strategy. However,
potentially costly fabrication, salt accumulation, and contaminant
influence still hinder the real-world application of solar–thermal
evaporators. Herein, a biomass-derived composite aerogel is constructed
through the Schiff base reaction of chitosan and polyethylenimine
and freeze assembly and further loaded with CuS/rGO nanoheterostructures
via a spray stacking strategy. Because of the reverse transport of
vertical-channel arrays, the lower part enables excellent salt-resistant
properties during long-term desalination in parallel to upward water
supply. The upper part promotes the thermal localization by controlling
the spatial distribution of CuS/rGO, providing high solar spectrum
absorption for efficient water evaporation. Notably, the composite
aerogel exhibits great superiority in sewage treatment benefiting
from its adsorption and photocatalytic capabilities, thus harvesting
freshwater resources that meet drinking water standards. The rational
design of this cost-effective evaporator may inspire new paradigms
for boosting the combination of solar–thermal utilization and
freshwater access.