Reactivity of a model of B(3)P(3)-doped nanographene with up to three CO(2) molecules

The reactivity of a B(3)P(3)-doped hexa-cata-hexabenzocoronene, as a model of nanographene (B(3)P(3)-NG), towards carbon dioxide was studied at the DFT M06-2X/6-311++G(3df,3pd)//M06-2X/6-31+G* level of theory. This compound can be classified as a poly-cyclic poly-Frustrated Lewis Pair (FLP) system, as it presents more than one Lewis Acid/Lewis Base pair on its surface, making the capture of several carbon dioxide molecules possible. Two scenarios were considered to fully characterize the capture of CO(2) by this multi-FLP system: (i) fixation of three CO(2) molecules sequentially one by one; and (ii) simultaneous contact of three CO(2) molecules with the B(3)P(3)-NG surface. The resulting adducts were analyzed as function of activation barriers and the relative stability of the CO(2) capture. A cooperativity effect due to the π-delocalization of the hexa-cata-hexabenzocoronene is observed. The fixation of a CO(2) molecule modifies the electronic properties. It enhances the capture of additional CO(2) molecules by changing the acidy and basicity of the rest of the boron and phosphorus atoms in the B(3)P(3)-NG system.