Unveiling the Obscure Potential of O-Carborane Based IFLPs for CO Sequestration.

Sequestering carbon dioxide (CO) from the atmosphere is necessary to achieve a sustainable environment. However, the thermodynamic stability of the CO molecule poses a significant challenge to its capture, necessitating catalysts that can overcome this stability. The emergence of frustrated Lewis pairs (FLPs) has opened a new dimension in the development of organocatalysts for CO capture and utilization. To date, various FLPs have been developed for CO sequestration, yet the quest for robust FLPs continues. Based on the intriguing electronic effects of the carborane polyhedral, o-carboranes can be projected as a versatile bridging unit for intramolecular FLPs (IFLPs). In the present work, o-carborane based IFLPs i. e., 1-Al(CH)-2-P(CH)-1,2-C2BH, 1-B(CH)-2-P(CH)-1,2-CBH, 1-Al(CH)-2-N(CH)-1,2-CBH, 1-P(CH)-2-B(CH)-1,2-CBH abbreviated as AlP, BP, AlN and BN have been proposed for the activation of CO molecule. The density functional theory (DFT) based calculations and thorough orbital analysis have been carried out to extensively study the electronic structure of the o-carborane unit. The proposed IFLPs were systematically compared with their corresponding phenyl bridged analogues to assess the effect of o-carborane bridging unit on the reactivity of the acidic and basic sites. The results show that the o-carborane supported IFLPs are more reactive towards CO than the phenyl bridged IFLPs. Also, placing the basic site on the B atom at the 4 position of the o-carborane bridge rather than the C atom at the 2 position results in more reactive IFLPs.