Unusual Metallic Microporous Boron Nitride Networks

Two metallic zeolite-like microporous BN crystals with all-sp² bonding networks are predicted from an unbiased structure search based on the particle-swarm optimization (PSO) algorithm in combination with first-principles density functional theory (DFT) calculations. The stabilities of both microporous structures are confirmed via the phonon spectrum analysis and Born–Oppenheimer molecular dynamics simulations with temperature control at 1000 K. The unusual metallicity for the microporous BN allotropes stems from the delocalized p electrons along the axial direction of the micropores. Both microporous BN structures entail large surface areas, ranging from 3200 to 3400 m²/g. Moreover, the microporous BN structures show a preference toward organic molecule adsorption (e.g., the computed adsorption energy for CH₃CH₂OH is much more negative than that of H₂O). This preferential adsorption can be exploited for water cleaning, as demonstrated recently using porous boron BN nanosheets (Nat. Commun. 2013, 4, 1777).