Scalable Synthesis of Ultrathin Silica Nanosheets for Applications in Thermal‐Management Aerogels and Flexible Composite Films

ABSTRACT Silica nanosheets (SiO 2 NSs) hold great promise for advanced thermal protection applications because of their exceptional thermal and chemical stability. However, their development has been hindered by challenges in scalable synthesis and structural integration for specialized applications. Herein, we report a facile and scalable wet‐chemical strategy for producing high‐quality and ultrathin SiO 2 NSs with lateral dimension more than 5 μm and thickness of ∼2 nm. After graphene oxide (GO)‐templated thermal treatment, the mechanical stiffness of the SiO 2 NSs was significantly enhanced from 60.9 to 76.1 GPa. Leveraging their unique ultrathin and large lateral properties, the ultralight SiO 2 NSs aerogel was achieved via a bidirectional freeze‐casting technique. The aerogel demonstrates excellent fire resistance and high‐temperature tolerance, maintaining its structure upon direct exposure to 1200°C flames. Furthermore, the integration of SiO 2 NSs into a polycaprolactone (PCL) matrix has enabled the development of a large‐area and flexible fire‐retardant composite film, which exhibits an exceptional flame self‐extinguishing time of 2 s and mechanical flexibility. This work offers a scalable platform for fabricating functional SiO 2 NSs‐based materials and paves the way for their potential application in energy devices, aerospace protection, and flexible electronics.