Unveiling the Obscure Potential of O-Carborane Based IFLPs for CO₂ Sequestration

Sequestering carbon dioxide (CO₂) from the atmosphere is necessary to achieve a sustainable environment. However, the thermodynamic stability of the CO₂ 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 CO₂ capture and utilization. To date, various FLPs have been developed for CO₂ 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(CH₃)₂-2-P(CH₃)₂-1,2-C2B₁₀H₁₀, 1-B(CH₃)₂-2-P(CH₃)₂-1,2-C₂B₁₀H₁₀, 1-Al(CH₃)₂-2-N(CH₃)₂-1,2-C₂B₁₀H₁₀, 1-P(CH₃)₂-2-B(CH₃)₂-1,2-C₂B₁₀H₁₀ abbreviated as AlP, BP, AlN and BN have been proposed for the activation of CO₂ 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 CO₂ than the phenyl bridged IFLPs. Also, placing the basic site on the B atom at the 4^th position of the o-carborane bridge rather than the C atom at the 2^nd position results in more reactive IFLPs.