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

Abstract

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 × 9) double ring B₁₈ 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.