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

The reactivity of BN-doped hexa-cata-hexabenzocoronene (BN-NG), AlN-NG, BP-NG and AlP-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 CO molecules. The capture of CO by these systems was investigated within two scenarios: (A) sequential capture of up to three CO molecules and (B) capture of CO 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 CO to the NGs.