Reactivity of a model of B3P3-doped nanographene with up to three CO2 molecules.

The reactivity of a B3P3-doped hexa-cata-hexabenzocoronene, as a model of nanographene (B3P3-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 CO2 by this multi-FLP system: (i) fixation of three CO2 molecules sequentially one by one; and (ii) simultaneous contact of three CO2 molecules with the B3P3-NG surface. The resulting adducts were analyzed as function of activation barriers and the relative stability of the CO2 capture. A cooperativity effect due to the π-delocalization of the hexa-cata-hexabenzocoronene is observed. The fixation of a CO2 molecule modifies the electronic properties. It enhances the capture of additional CO2 molecules by changing the acidy and basicity of the rest of the boron and phosphorus atoms in the B3P3-NG system.