Azaboratrane as an exceptionally potential organocatalyst for the activation of CO2 and coupling with epoxide

PIO and IBO analysis to unravel the hidden details of the CO2 sequestration mechanism of aromatically tempered N/B-based IFLPs

Enhancing the catalytic reactivity of Frustrated Lewis Pairs (FLPs) in various activities such as CO2 activation and sequestration has recently gained interest among researchers around the globe. A recent investigation showed the use of aromaticity as a tool to modulate the catalytic behaviour of FLPs, establishing a whole new dimension in this area. In this work, aromatically tempered N/B-based intramolecular frustrated Lewis Pairs (IFLPs) are proposed for CO2 sequestration. Density functional theory (DFT)-based calculations were carried out to probe the reaction mechanism. The detailed mechanistic investigation was carried out using intrinsic reaction coordinate (IRC), principal interacting orbital (PIO), intrinsic bond orbital (IBO) and natural bonding orbital (NBO) analyses. The results show that aromatic gain in the system at the basic sites lowers the activation barrier, whereas the antiaromatic gain results in increased activation energy. The sequestration mechanism was found to be an asynchronous concerted mechanism, and polar solvents result in higher asynchronicity. This work, for the first time, reports asynchronicity in the catalytic behavior of aromatically tempered IFLPs, which can be crucial to designing better IFLPs for CO2 sequestration.

Unprecedented Activation of CO2 by α-Amino Boronic Acids

Efficient and environmentally benign transformation of carbon dioxide (CO2) into valuable chemicals is mainly obstructed by the lack of suitable catalysts. To date, various catalysts have already been investigated for the conversion of CO2 molecules, but still finding metal-free, simple, and environment-friendly catalysts is a topic of utmost interest among researchers. Thus, in this regard, the present work projects α-amino boronic acids (AABs) as a metal-free and simple catalyst for CO2 activation. The density functional theory (DFT)-based calculations have been carried out to explore the catalytic potential of AABs. The detailed electronic structure analysis of the considered AABs unveils the catalytic similarities with frustrated Lewis pairs (FLPs) in a gas phase. Interestingly, a peculiar catalytic action of AABs has been observed in the presence of solvents. The contrasting catalytic behavior of AABs in solvents has been extensively investigated by employing principal interacting orbital (PIO), intrinsic bond orbital (IBO), and natural bond orbital (NBO) analyses along the reaction paths. The results of the orbital studies provide concrete ground for the observed reaction mechanism. Further, the energetic analysis of the reaction of CO2 with AABs reveals that <5 kcal/mol energy is required for activation in a solvent phase, and the formed adducts are readily active. These observations show that AABs can be considered as an efficient catalyst for CO2 activation.

Boron based intramolecular heterocyclic frustrated Lewis pairs as organocatalysts for CO2 adsorption and activation

The massive increase in the amount of carbon dioxide (CO₂ ) in the atmosphere has led to serious environmental problems. One of the best ways to tackle this problem is the CO₂ capture and its utilization as a C1 carbon source for the production of industrially valuable chemicals. But the thermodynamic stability of the CO₂ molecule poses a great challenge in its transformation. Since the last two decades, various metal-based and organic catalysts have been developed for the adsorption and activation of CO₂ . Among all the catalysts the Frustrated Lewis pairs (FLPs) have been shown great potential in CO₂ capture and conversion. Thus, in the present work, Intramolecular Frustrated Lewis pairs (IFLP) based on N-Heterocycles with boron group functionalization at the α-position to N has been theoretically investigated for CO₂ activation. Thorough orbital analysis has been carried out to investigate the reactivity of the proposed catalytic systems. The result shows that the considered IFLPs are capable of activating CO₂ with minimum energy requirements. The CO₂ activation energy range between 8 and 14 kcal/mol. The non-polar solvent was found to be the suitable medium for the reaction. Also, the reversibility of the adducts formed with the IFLPs can be controlled by appropriate substitution at B atom in the IFLPs.