Influence of Defects in Boron Nitride Nanotubes in the Adsorption of Molecules. Insights from B3LYP-D2*Periodic Simulations

The adsorption of H2O, NH3 and HCOOH as polar molecules and C6H6 and CH4 as non-polar ones on a series of zig-zag (6,0) single-walled boron nitride nanotubes (BNNTs) both being defect-free (P_BNNT) and containing defects at the nanotube walls has been studied by means of B3LYP-D2* periodic calculations. We focused on defects derived from monovacancies of B (N-rich_BNNT) and N (B-rich_BNNT) atoms and also on Stone-Wales defects (SW_BNNT). The adsorption of polar molecules with defective BNNTs is generally based on dative interactions and H-bonding, and their adsorption energies strongly depend on the type of BNNT. N-rich_BNNT is the most reactive nanotube towards adsorption of polar molecules, as in all cases deprotonation of the polar molecules is spontaneously given upon adsorption. The strength in the adsorption energies is followed by B-rich_BNNT, SW_BNNT and P_BNNT. Adsorption of non-polar molecules is mainly dictated by dispersion interactions, and, accordingly, the adsorption energies are almost constant for a given molecule irrespective of the type of nanotube.