Revealing an Unexpected Chemical Reactivity of Boron Nitride to H2O and Alkane Molecules.

Abstract

Herein, substantial experimental evidence reveals the unexpected chemical reactivity of inert hexagonal boron nitride (h-BN) to H2O, CH4, and C2H6 under mild conditions. H2O molecules dissociate at B-N edge sites and insert into the B-N bond even under ambient conditions. Detailed spectroscopic characterization shows this process protonates nitrogen sites and hydroxylates boron sites, forming N-H and B-OH groups. Ultimately, the NH4+ and B(OH)4- ions are released into water as the final products of nitrogen protonation and boron hydroxylation. This reactivity is significantly enhanced at the oxygen-doped B-N edges. Theoretical simulations reveal that strong orbital interactions between the H (1s) orbitals of H2O and the B (2p)/N (2p) orbitals of the B-N edge produce significant chemical stress at the adsorption sites, promoting the dissociation and subsequent insertion of H2O into the B-N bonds. Furthermore, we show that CH4 and C2H6 can be oxidized to CO and trace CH3OH in water over boron nitride at mild temperatures without an additional oxidant. The 18O isotope-tracing experiment confirms that the oxygen in the boron nitride matrix is responsible for the activation and oxidation of the C-H bond of CH4 and C2H6. Simultaneously, the released NH4+ and B(OH)4- ions provide a reaction microenvironment enabling the thermodynamically spontaneous hydration of formed CO to formate. These findings fundamentally challenge the long-standing paradigm of h-BN as a chemically inert material under mild conditions.