Strong acoustic meta-aerogels enabled by nanoconfined directional freezing and in-situ polymerization

Achieving low-frequency and broadband sound absorption in mechanically robust, space-efficient structures remains a central challenge in acoustic materials design. Here we report a nanoconfined freezing-assisted in situ polymerization strategy that enables the construction of acoustic meta-aerogels with hierarchical nano–micro–macro architectures. Under nanoconfinement, calcium–aluminosilicate hydrate nanoparticles nucleate and assemble along aligned microchannels, where nanoporous calcium–aluminosilicate hydrate phases anchored to the channel walls induce adsorption–desorption hysteresis, thereby generating a resonant-cavity-like acoustic response that enhances low-frequency absorption. This multiscale configuration, featuring aligned microscopic channels reinforced by strongly bonded calcium–aluminosilicate hydrate nanoparticles, facilitates efficient load transfer and structural integrity while promoting interfacial energy dissipation. The resulting aerogels exhibit low density ( ~ 50 mg cm-³), high compressive strength ( ~ 1.88 MPa), and high toughness ( ~ 959 kJ m-³), together with pronounced low-frequency absorption and broadband performance, with a noise reduction coefficient of 0.85 and sound absorption coefficient of 1.00 at 550 Hz, outperforming existing materials of comparable thickness. More broadly, this work establishes a general nanoconfined design strategy for engineering hierarchical acoustic materials, bridging nanoscale interfacial processes with macroscopic functionality and offering a versatile platform for multifunctional porous materials design. This study reports cement-based meta-aerogels made by nanoconfined freezing-assisted in situ polymerization, with hierarchical pores that form resonant cavities for strong low-frequency absorption, mechanical robustness and scalable fabrication.