Hexagonal boron nitride (h-BN), also known as white graphene, is well known for its chemical inertness. Recent studies indicate that functionalization of h-BN can tune its physico-chemical properties, including its electrical conductivity. Here we propose a method for the functionalization of h-BN flakes with various oxygen functionalities to make a graphite oxide analogue of h-BN, with a view to develop cross-linked, low-density (∼40 mg cm⁻³), and porous h-BN solids, as have been recently well cited for graphene and graphite oxide. For the first time, a macro-porous low density h-BN monolith foam is developed via a single step template free chemical route followed by a lyophilisation process. h-BN is known for its high thermal stability, and here oil adsorption by the foam (∼2 g g⁻¹) and complete burning of the adsorbed oil without disrupting the h-BN skeleton were demonstrated indicating the flexibility of tuning the morphology of the h-BN in bulk, like graphite, without losing its inherent physical properties, opening new avenues for h-BN in the energy and environment related fields.

Low-density nanostructured foams are often limited in applications due to their low mechanical and thermal stabilities. Here we report an approach of building the structural units of three-dimensional (3D) foams using hybrid two-dimensional (2D) atomic layers made of stacked graphene oxide layers reinforced with conformal hexagonal boron nitride (h-BN) platelets. The ultra-low density (1/400 times density of graphite) 3D porous structures are scalably synthesized using solution processing method. A layered 3D foam structure forms due to presence of h-BN and significant improvements in the mechanical properties are observed for the hybrid foam structures, over a range of temperatures, compared with pristine graphene oxide or reduced graphene oxide foams. It is found that domains of h-BN layers on the graphene oxide framework help to reinforce the 2D structural units, providing the observed improvement in mechanical integrity of the 3D foam structure.

A novel vertical non-van der Waals (non-vdW) heterostructure of graphene and hexagonal boron nitride (G/hBN) is realized and its application in direct four-electron oxygen reduction reaction (ORR) in alkaline medium is established.