In Situ Generated Boron Peroxo as Mild Oxidant in Propane Oxidative Dehydrogenation Revealed by Density Functional Theory Study.

Boron-based materials catalyzing oxidative dehydrogenation is emerging as a promising protocol for efficient conversion of light alkanes to olefins, while the origin of its remarkable selectivity remains unclear. By means of density functional theory calculations, this work addresses the crucial role of boron peroxo as the mild oxidant in propane ODH: (1) Surface boron peroxo species can be generated in situ in the presence of peroxo species, preferably at the >B-O-B< sites of the zigzag edge, and show high activity to dehydrogenate propane (ΔG⧧ = 13.5 kcal/mol, ΔG = 8.9 kcal/mol). (2) The >B-O-O· site shows high discriminability of secondary H over primary H of the propane molecule, leading to significantly higher yield of iso-propyl (CH3CHCH3) than n-propyl (CH3CH2CH2); thus, propene formation is favored over deep oxidation. This provides physical insights into the origin of the remarkable olefin selectivity in the boron-containing ODH catalytic systems.