Daytime radiative cooling (DRC) materials offer a sustainable approach to thermal management by exploiting net positive heat transfer to deep space. While such materials typically have a white or mirror-like appearance to maximize solar reflection, extending the palette of available colors is required to promote their real-world utilization. However, the incorporation of conventional absorption-based colorants inevitably leads to solar heating, which counteracts any radiative cooling effect. In this work, efficient sub-ambient DRC (Day: −4 °C, Night: −11 °C) from a vibrant, structurally colored film prepared from naturally derived cellulose nanocrystals (CNCs), is instead demonstrated. Arising from the underlying photonic nanostructure, the film selectively reflects visible light resulting in intense, fade-resistant coloration, while maintaining a low solar absorption (≈3%). Additionally, a high emission within the mid-infrared atmospheric window (>90%) allows for significant radiative heat loss. By coating such CNC films onto a highly scattering, porous ethylcellulose (EC) base layer, any sunlight that penetrates the CNC layer is backscattered by the EC layer below, achieving broadband solar reflection and vibrant structural color simultaneously. Finally, scalable manufacturing using a commercially relevant roll-to-roll process validates the potential to produce such colored radiative cooling materials at a large scale from a low-cost and sustainable feedstock.

Atmospheric water harvesting (AWH) has received tremendous interest because of population growth, limited freshwater resources, and water pollution. However, key challenges remain in developing efficient, flexible, and lightweight AWH materials with scalability. Here, we demonstrated a radiative cooling fabric for AWH via its hierarchically structured cellulose network and hybrid sorption–dewing mechanisms. With 8.3% solar absorption and ∼0.9 infrared (IR) emissivity, the material can drop up to 7.5 °C below ambient temperature without energy consumption via radiative cooling. Water adsorption onto the hydrophilic functional groups of cellulose is dominated by sorption at low relative humidity (RH) and dewing at high RH. The cellulose network provides desirable mechanical properties with entangled high-aspect-ratio fibers over tens of adsorption–extraction cycles. In the field test, the cellulose sample exhibited water uptake of 1.29 kg/kg at 80% RH during the night. The profusion of radiative cooling fabric features desirable cost effectiveness and allows fast deployment into large-scale AWH applications.

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Supramolecular frameworks have been widely synthesized for ion transport applications. However, conventional approaches of constructing ion transport pathways in supramolecular frameworks typically require complex processes and display poor scalability, high cost, and limited sustainability. Here, we report the scalable and cost-effective synthesis of an ion-conducting (e.g., Na + ) cellulose-derived supramolecule (Na-CS) that features a three-dimensional, hierarchical, and crystalline structure composed of massively aligned, one-dimensional, and ångström-scale open channels. Using wood-based Na-CS as a model material, we achieve high ionic conductivities (e.g., 0.23 S/cm in 20 wt% NaOH at 25 °C) even with a highly dense microstructure, in stark contrast to conventional membranes that typically rely on large pores (e.g., submicrometers to a few micrometers) to obtain comparable ionic conductivities. This synthesis approach can be universally applied to a variety of cellulose materials beyond wood, including cotton textiles, fibers, paper, and ink, which suggests excellent potential for a number of applications such as ion-conductive membranes, ionic cables, and ionotronic devices.