Ambient-temperature constructing modification-free superhydrophobic melamine@polyurea aerogels with stable network for broadband sound absorption in humid environments

Aerogels that effectively absorb noise provide a highly promising way to improve human living environments. However, maintaining stable broadband sound absorption performance under humid conditions remains challenging. Moreover, demanding fabrication requirements, complicated surface modification procedures, and inherent fragility are urgent to be solved. Herein, we present a mild modification-free strategy for fabricating superhydrophobic melamine@polyurea (ME@PUA) aerogels with stable porous structures and extraordinary noise-reduction capability by combining a template-assisted method with crosslinking-induced phase separation. The template skeleton’s self-supporting function, coupled with hydrogen bonding interactions from ME and PUA, constructs a robust three-dimensional network structure, achieving ambient-temperature drying. Furthermore, superhydrophobicity and acoustic properties are simultaneously achieved during ambient-temperature gelation due to the synergistic interaction between the PUA's material properties and the skeletal microstructure. This approach eliminates the need for low-temperature refrigerants and specialized drying equipment, while not increasing preparation time. The as-obtained ME@PUA aerogels, characterized by a novel porous architecture integrating core-shell structures and coral-like structures, have ultralow density (25.55 mg cm −3 ), superhydrophobicity (water contact angle >150°), low thermal conductivity (35 mW m −1 K −1 ), excellent flexibility (99% elastic recovery after deformation), and broadband sound absorption (NRC up to 0.50). Notably, ME@PUA aerogels maintain stable NRC after exposure to an extremely humid environment (80% RH) for 168 h or after 80% strain compression. This readily achievable, scalable, and reproducible synthesis approach provides a promising pathway for advancing the development of organic aerogels designed for stable noise reduction in humid environments.