Is the Formation of Poly-CO2 Stabilized by Lewis Base Moieties in N- and S-Doped Porous Carbon?

The polymerization of CO2 by Lewis basic moieties has been recently proposed to account for the high adsorption ability of N and S-doped porous carbon materials formed from the pyrolysis of sulfur or nitrogen containing polymers in the presence of KOH. Ab initio calculations performed on the ideal CO2 tetramer complex LB-(CO2)4 (LB = NH3, H2O, H2S) showed no propensity for stabilization. A weak association is observed using Lewis acid species bound to oxygen (LA = H+, AlF3, AlH3, B4O6); however, the combination of a Lewis acid and base does allow for the formation of polymerized CO2 (i.e., LB-C(O)O-[C(O)O]n-C(O)O-LA). While the presence of acid moieties in porous carbon is well known, and borate species are experimentally observed in KOH activated porous carbon materials, the low stability of the oligomers calculated herein, is insufficient to explain the reported poly-CO2.