Formation of a bi-rhodium boron tube Rh2B18 and its great CO2 capture ability

The geometries, bonding and abilities for CO2 capture of the doubly rhodium-doped boron cluster Rh2B18 are presented. DFT calculations using the TPSSh functional show that the doubly doped Rh2B18 is stable in a high symmetry shape (D-9d) in which two Rh dopants are vertically and oppositely coordinated to nonagonal faces of a (2 x 9) double ring B-18 tube, having the form of a teetotum toy. Bonding of the tube is analysed using different schemes for partition of total electron density (EDI_D, AIM). The high thermodynamic stability of Rh2B18 can be rationalized in terms of its electron distribution in which both Rh atoms share delocalized bonds with B atoms. Molecular dynamic simulations also confirm its stability within a range of temperatures. Exploration of the interaction of gas phase CO2 molecules with Rh2B18 suggests that this tubular structure has a great ability for capture and transformation of carbon dioxide. Formation of two new strong bonds of CO2 with the B-B edges of Rh2B18 favour its capture through a dissociative adsorption mechanism in which a nearly spontaneous dissociation of CO2 into CO and BO groups follows its attachment.