Co-adsorption of CO molecules at the open ends of MgO nanotubes

Equilibrium geometries, stabilities, and electronic properties of the adsorption of a CO molecule along with two or three CO co-adsorptions at the open ends of MgO nanotubes have been investigated through density functional calculations. It was found that the interaction of CO molecule with ends of the tube is much stronger than that of with its exterior surface. It was also found that adsorption of the second CO molecule at the end of the tube is independent of the first adsorbed CO molecule, while the prior adsorption process impacts the third adsorption. This phenomenon was described based on the frontier molecular orbital analysis, showing that the third CO molecule has to interact with high energetic unoccupied orbitals instead of the LUMO. Furthermore, it was revealed that similar to CO adsorption on the exterior surface of the tube, the adsorption at its open ends is electronically harmless.