Tuning the energy barrier of water exchange reactions on Al(iii) by interaction with the single-walled carbon nanotubes

Abstract

The limiting dissociative (D) and interchange dissociative (I_d) water exchange pathways on Al(III) inside and outside single-walled carbon nanotubes (SWCNTs) were modelled using ONIOM calculations with density functional theory, and the influence of SWCNTs on both D and I_d pathways was examined. The interchange dissociative water exchange pathway was revealed, in which the zigzag SWCNTs (13,0), (14,0) and (15,0) with the same length were modelled for interaction. The results indicate that the confinement effect of SWCNTs on the energy barriers is strong when the reaction takes place inside SWCNTs with small diameter relative to reaction complexes, and varies heavily along with the change of diameters of SWCNTs. The results also indicate that SWCNTs act as trans-activating ligand to effectively lower the energy barriers of both D and I_d pathways outside SWCNTs. The interaction between aluminium-water complexes and SWCNTs can effectively lower the energy barriers in general and may accelerate the reaction rates, which has great importance for the influence of carbon nanotubes on dissolution and transformation rates of minerals such as aluminium (hydr)oxide.