Dual-mode transport of molecular oxygen in a membrane containing a cobalt porphyrin complex as a fixed carrier

Molecular oxygen transport through a polymeric membrane is found to be augmented by the addition of [α,α′,α″,α‴-meso-tetrakisis-(o- pivalamidophenyl)porphinato]cobalt[II]-1-methylimidazole (CoPIm) complex, which forms an oxygen adduct rapidly and reversibly. The oxygen-binding rate and equilibrium constants for the Co complex in the membrane, i.e., a fixed carrier, were measured spectroscopically in situ. The oxygen permeability of the membrane containing CoPIm increased with decreasing upstream oxygen pressure, which is in accordance with a dual-mode transport model. The oxygen-binding parameters determined spectroscopically, were_adequate for an approximate analysis in terms of this model. The permeability ratio (P_O2/P_N2) was greater than 10 in the membrane containing a large amount of CoPIm.