Carbonate-based solvents have advantages over amines for capturing CO2 from fossil fuel-fired power stations. However, due to slow reaction kinetics, boric acid has been proposed as rate promoter in carbonate-based solvents for reducing CO2 emission. In this work, borate promotion mechanism has been validated and vapor liquid equilibrium for 35 wt% carbonate solutions with 1 wt%, 3 wt% boric acid was investigated at 323 K, 333 K and 343 K. Based on complexation reaction with mannitol, results show that the tetrahydroxy borate ion, B(OH)(4)(-), is considered as a reactive specie toward carbon dioxide absorption. Effect of boric acid and temperature on equilibrium CO2 partial pressures was discussed in the investigated CO2 loading range. (C) 2014 Elsevier B.V. All rights reserved.