Hierarchical Biogenic-Based Thermal Insulation Foam

Biogenic-based foam, renowned for its sustainable and eco-friendly properties, is emerging as a promising thermal insulating material with the potential to significantly enhance energy efficiency and sustainability in building applications. However, its relatively high thermal conductivity, large-pore configurations, and energy-intensive manufacturing processes hinder its widespread use. Here, we report on the scalable, one-pot synthesis of biogenic foams achieved by integrating recycled paper pulp and in situ nanoporous silica formation, resulting in a hierarchical structure comprising both micropores and nanopores. Ambient solvent-exchange drying can preserve the pore structure by reducing the capillary forces during the drying process. The resulting flame-retardant and hydrophobic foam exhibits low density (0.110 g/cm 3 ), ideal porosity (70.69%), excellent thermal conductivity (0.033 W/(m·K)), and impressive compressive strength (1.48 MPa at 80% strain). This recyclable biogenic foam, with its hierarchical pore structure and environmental durability, shows great potential for energy-efficient building applications.