One-Step Conversion of Graphite to Crinkled Boron Nitride Nanofoams for Hydrophobic Liquid Absorption

We describe a robust and scalable method to produce crinkled hexagonal boron nitride (h-BN) nanofoam from graphite in a single-step, leapfrog-like process. The conversion is based on carbothermic reduction and simultaneous nitrogenization of boron oxide and graphite. High-resolution transmission electron microscopy and electron diffraction demonstrate that the final converted h-BN nanofoam is crystalline at the atomic scale but has substantial crinkling of the h-BN sheets at the nanoscale. It also supports a dense network of nanometer-sized pores throughout. The operative conversion mechanism from flat carbon precursors to crinkled boron nitride sheets is proposed. Crinkled h-BN nanofoam shows a surface area over 60 times larger, as compared to the graphitic scaffold, leading to improved oil absorption capabilities (up to 325 wt %).