Synergistic black phosphorus and cellulose nanofiber aerogels: A breakthrough in flame-retardant and thermal insulation for building applications

Managing thermal energy effectively in buildings is vital for sustainability, particularly in extremely cold climates. Herein, we present an innovative approach to building insulation by leveraging cellulose nanofiber (CNF)/black phosphorus (BP) aerogels with uniquely aligned xylem-like porous structures. This study posits that the synergistic interplay between CNF and BP significantly enhances thermal insulation, photothermal conversion, and flame-retardant capabilities, offering a cutting-edge solution for advanced thermal management. Using a strategic combination of polyethyleneimine and 3-glycidoxypropyltrimethoxysilane as co-additives, lightweight CNF sponge-like aerogels were fabricated via freeze-drying and post-crosslinking techniques. These aerogels achieved exceptional thermal insulation with a remarkably low thermal conductivity of 0.067 W/(m·K). Additionally, they demonstrated superior photothermal performance, reaching 84 °C within just 300 s under one-sun illumination, effectively maintaining a stable microclimate even at −5 °C by combining photothermal conversion and insulation effects. The flame-retardant properties of the CNF/BP aerogels were equally impressive, with total heat release reduced by 71 % compared to conventional crosslinked CNF aerogels. This is attributed to the robust porous char formed through phosphoric acid crosslinking with internal carbon chains. These multifunctional CNF/BP aerogels not only redefine the boundaries of thermal management but also establish a promising pathway for next-generation thermal protection materials.