Facile Preparation of Superelastic and Ultralow Dielectric Boron Nitride Nanosheet Aerogels via Freeze-Casting Process

As a structural analogue of graphene, boron nitride nanosheets (BNNSs) have attracted ever-growing research interest in the past few years, due to their remarkably mechanical, electrical, and thermal properties. The preparation of BNNS aerogels is considered to be one of the most effective approaches for their practical applications. However, it has remained a great challenge to fabricate BNNS aerogels with superelasticity by a facile method. Here, we report the preparation of BNNS aerogels via a facile method involving polymer-assisted cross-linking and freeze-casting strategies. The resulting aerogels exhibit a well-ordered and anisotropic microstructure, leading to anisotropic superelasticity, high compressive strength, and excellent energy absorption ability. The unique microstructure also endows the aerogels with ultralow dielectric constant (1.24) and loss (∼0.003). The successful fabrication of such fascinating materials paves the way for application of BNNSs in energy-absorbing services, catalyst carrier, and environmental remediation, etc.