Multi-functional MOF-CNT polymer aerogels: A novel design for low-frequency sound-absorbing and thermal insulation

Absorbing low frequency sound below 500 Hz with ultra-lightweight materials is a key challenge due to the structural homogeneity of existing sound absorbing materials. In order to address the challenge of combining enhanced low frequency sound absorption, mechanical robustness, moisture resistance and thermal insulation, this study proposes a new multiple acoustic material design. Coaxial electrostatic spinning was used to introduce MOF and CNT acoustic additives into the polymer matrix in a single step. The addition of PI and directional freezing then led to the formation of radially aligned lamellar structures within the electrospun fibers and PI polymer aerogel. It was found that PI/CZ-X aerogels with a radical porous structure, nanofibres and acoustic absorbing additives with high MOF-CNT content show excellent low frequency sound absorption properties (up to 0.99 at low frequencies of 500 Hz, 0.5 at low frequencies of 200 Hz and an NRC coefficient of 0.70), excellent thermal insulation properties (thermal conductivity of approximately 24.03 mW/mK), super elasticity (deformation returns to 90 % of its original value after 1000 cycles of compression) and hydrophobic properties (water contact angle of 140°). This work provides an effective strategy to design low-frequency broadband acoustic absorption materials.