Selective sorption and facilitated transport of oxygen in porphinatocobalt-coordinated polymer membranes

Selective sorption and permeation of molecular oxygen are described for meso-α,α,α,α-tetrakis-(o-pivalamidophenyl) porphinatocobalt(II) (CoP) coordinated polymer membranes (Chart I). Oxygen solubility is ca. 70 times augmented in comparison with that of nitrogen by the CoP loading in the membrane. Sorption isotherms of oxygen for the membranes are analyzed with a dual-mode sorption model to give C_c′ and K. C_c′ (the saturated amount of oxygen reversibly bound to the CoP sorption site) is independent of temperature and increases with the loaded CoP amount into the membrane. K (the oxygen-affinity constant of CoP) agrees with that determined spectroscopically by monitoring the CoP moiety in the membrane. Oxygen permeation through the membrane is facilitated, and the permeability is in accordance with a dual-mode transport model. Substituting the sorption parameters, C_c′ and K, in the model yields diffusion constants of oxygen in the membranes.