Multi‐Scale Bionic Structure Constructs Biomass Flame‐Retardant Thermal Insulation Foam Material

ABSTRACT Amid intensifying environmental and energy pressures, sustainable thermal‐insulation materials that also provide effective fire protection are increasingly needed for buildings. Cellulose‐based foams are promising candidates for building‐envelope applications; however, their practical deployment is hindered by limited fire performance, inadequate structural stability, and complex processing. Here, we propose a multiscale biomimetic strategy inspired by mussel adhesion and hierarchical brick‐and‐mortar architectures. Polydopamine is introduced as an interfacial bridging layer to uniformly immobilize bentonite nanosheets within a cellulose network, enabling the fabrication of high‐efficiency flame‐retardant cellulose‐based biomimetic foam (CBF) through aqueous mechanical foaming and ambient‐pressure drying. The resulting CBF exhibits low thermal conductivity alongside improved flame retardancy and environmental compatibility. A cradle‐to‐grave life‐cycle assessment further indicates lower greenhouse‐gas emissions and reduced toxicity‐related impacts than conventional petroleum‐derived foams, while retaining recyclability and biodegradability. Collectively, these results establish a green, scalable route to high‐performance, degradable thermal‐insulation materials for safer and more energy‐efficient buildings.