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.