A multi-FLP approach for CO2 capture: investigating nitrogen, boron, phosphorus and aluminium doped nanographenes and the influence of a sodium cation

Abstract

The reactivity of B₃N₃-doped hexa-cata-hexabenzocoronene (B₃N₃-NG), Al₃N₃-NG, B₃P₃-NG and Al₃P₃-NG, models of doped nanographenes (NGs), towards carbon dioxide was studied with density functional theory (DFT) calculations at the M06-2X/6-311++G(3df,3pd)//M06-2X/6-31+G* level of theory. The NG systems exhibit a poly-cyclic poly-frustrated Lewis pair (FLP) nature, featuring multiple Lewis acid/Lewis base pairs on their surface enabling the capture of several CO₂ molecules. The capture of CO₂ by these systems was investigated within two scenarios: (A) sequential capture of up to three CO₂ molecules and (B) capture of CO₂ molecules in the presence of a sodium cation. The resulting adducts were analyzed in terms of the activation barriers and relative stabilities. The presence of aluminium atoms changes the asynchrony of the reaction favoring the aluminium-oxygen bond and influences the regioselectivity of the multi-capture. A cooperative effect is predicted due to π-electron delocalization, with the sodium cation stabilizing the stationary points and favoring the addition of CO₂ to the NGs.