Introduction of Protonated Sites on Exfoliated, Large-Area Sheets of Hexagonal Boron Nitride.

Hexagonal boron nitride (h-BN) sheets possess an exclusive set of properties, including wide energy band gap, high optical transparency, high dielectric breakdown strength, high thermal conductivity, UV cathodoluminescence, and pronounced thermochemical stability. However, functionalization of large h-BN layers has remained a challenge due to their chemical resistance and unavailable molecular-binding sites. Here we report on the protonation of h-BN via treatment with chlorosulfonic acid that not only exfoliates "large" h-BNs (up to 10 000 μm) at high yields (∼23%) but also results in their covalent functionalization by introducing four forms of aminated nitrogen (N) sites within the h-BN lattice: sp-delocalized and sp-quaternary protonation on internal N sites (>N═ and >NH-) and pyridinic-like protonation on the edge N sites (═NH- and -NH-).