Selectively strong molecular adsorption on boron nitride monolayer induced by transition metal substrate

We studied adsorption of several molecules (CO, CO2, H2O, N2O, NO, NO2, and O2) on hexagonal boron nitride (h-BN) monolayers supported on transition metal (TM) surfaces, using density functional calculations. We observed that all the molecules bind very weakly on the pristine h-BN, with binding energies in the range of 0.02–0.03 eV. Interestingly, however, when h-BN is supported on the TM surface, NO2 and O2 become strongly chemisorbed on h-BN, with binding energies of >1 eV, whereas other molecules still physisorbed, with binding energies of ∼0.1 eV at most. The electron transfer from TM to pz states of h-BN played a substantial role in such strong bindings of NO2 and O2 on h-BN, as these molecules possess unpaired electrons that can interact with pz states of h-BN. Such selective molecular binding on h-BN/TM originates from the peculiar distribution of the spin-polarized highest occupied and lowest unoccupied molecular orbitals of NO2 and O2. Strong molecular adsorption and high selectivity would make the h-BN/TM system possible for a variety of applications such as catalysts and gas sensors.