Reactive 3D printed silanized cellulose nanofiber aerogels for solar-thermal regulatory cooling

Abstract

Polymer aerogels exhibit promise as solar-thermal co-management materials, offering combined thermal insulation and solar scattering characteristics. However, challenges persist in their large-scale preparation and pore structure tailoring. Herein, a polymethylsilsesquioxane interwoven cellulose nanofiber aerogel scaffold with improved interlayer interfaces and tunable pore sizes is prepared via reactive 3D printing. The resulting 3D-printed aerogel scaffold exhibits minimal volume shrinkage during freeze-drying and significantly enhanced interlayer interfaces, demonstrating superior fatigue resistance and impressive environmental resilience. The significantly decreased pore sizes in the aerogel scaffold greatly enhance full solar scattering through the Mie scattering mechanism. Utilized as a hydrophobic and flame-retardant solar–thermal regulatory cooler, the aerogel scaffold demonstrates a solar reflectance of 94.2 % and an atmospheric window emissivity of 95.6 %. The aerogel scaffold achieves a cooling power of 72.2 W m⁻² with an average sub-ambient cooling of 5.8 °C under direct sunlight.