Highly selective oxygen transport through a cobalt porphyrin liquid membrane

The facilitated transport of oxygen in a liquid membrane containing [meso-α,α,α,α-tetrakis(o-pivalamidophenyl) porphyrinatocobalt(II)]-laurylimidazole (CoP) as an oxygen carrier leads to high permeability and permselectivity of oxygen against nitrogen. The oxygen permeation was properly analyzed by a dual-mode model and using the oxygen-binding constants spectroscopically determined, to give permeation parameters of the membrane such as the diffusion coefficient (D_CoP) of the CoP mobile carrier and the physical diffusion coefficient of oxygen. D_CoP was in accordance with that electrochemically determined. The facilitated permeation was represented by the product of the CoP concentration and D_CoP in the membrane solution. D_CoP decreased with solution viscosity and increased with the measured temperature. High oxygen permeability (10^-7 cm³(STP) cm cm^-2 s^-1 cmHg^-1) was observed, e.g. for the membrane of the 31 wt % CoP methylanisole solution at 10 °C, where the facilitation factor and the oxygen/nitrogen permselectivity were over 20 and 40, respectively.