Highly facilitated permeation and enrichment of oxygen from air through a polyvinylimidazole membrane ligated with cobaltporphyrin that kinetically interacts with oxygen†

A dense and tough membrane of cobalt tetraphenylporphyrin (CoTPP) and poly(1-vinylimidazole-co-octyl methacrylate) (OIm) is prepared on a porous support. The oxygen permeability coefficient and oxygen/nitrogen permselectivity reach 10 Barrer and >110, respectively, at a pressure difference between the feed side and permeate side of 2 cmHg. The membrane with a diameter of 10 cm enriches oxygen from dried air to an oxygen concentration >60% through a one-shot permeation process. The reversible but kinetically very active interaction between oxygen molecules and the CoTPP fixed in the OIm membrane is analyzed while the membrane is under high oxygen pressure or low temperature using spectroscopy techniques including laser-flash photolysis: i.e. 920 cmHg for the half of the CoTPP interacted with oxygen and extremely rapid oxygen-releasing rate constant of approximately 10⁶ s⁻¹, when extrapolated at room temperature. The enhanced oxygen diffusivity is discussed for the oxygen permeation facilitated through the membrane.