Ab initio and density functional G2M(MP2)//B3LYP/6-311+G(d) calculations have been carried out to investigate the potential energy surface for the B + CO2 BO + CO reaction. The most favorable reaction pathway has been shown to be B+CO2 (0.0 kcal/mol) --> TS1 (19.2 kcal/mol) --> trans-BOCO (-25.1 kcal/mol) --> TS2 (-22.0 kcal/ mol) --> BO + CO (-64.0 kcal/mol) --> OBCO (-75.6 kcal/mol). The results explain observation of OBCO as the major reaction product in the earlier matrix isolation experiments, where this molecule was likely been produced through secondary recombination of the primary BO and CO products. (C) 2003 Published by Elsevier Science B.V.