Biomimetic multifunctional material: Bidirectional-freezing-mediated hierarchically ordered nanocellulose material...

Biomass-derived solar evaporators offer a promising solution to freshwater scarcity, yet conventional designs often suffer from limited evaporation rates. Inspired by the structure of Thalia dealbata stems, we prepared a TEMPO-oxidized cellulose nanofiber evaporation material (TPP-B) featuring a biomimetic "layer-bridge" porous architecture via bidirectional freeze-casting combined with in-situ polymerization of polypyrrole and incorporation of poly(sodium 4-styrenesulfonate). The bidirectional freezing-induced architecture endows TPP-B with efficient thermal localization, high compressive strength, reduced evaporation enthalpy, and notable salt tolerance. Under 1 sun irradiation, TPP3-B achieves an evaporation rate of 3.40 ± 0.16 kg m^-2 h^-1 with 98.6 ± 2.2% energy efficiency, while steadily generating electricity. Increasing the evaporator height to 15 mm enhances the cold evaporation zone and thermal localization, achieving an ultrahigh evaporation rate of 4.34 ± 0.22 kg m^-2 h^-1. Life cycle assessment confirms the low carbon footprint (8.03 kg CO₂ eq. kg^-1) of TPP3-B, highlighting its environmental advantage. This work offers a sustainable strategy for coupled water-energy challenges.