Highly Selective Oxygen/Nitrogen Separation Membrane Engineered Using a Porphyrin-Based Oxygen Carrier

Air separation is very important from the viewpoint of the economic and environmental advantages. In this work, defect-free facilitated transport membranes based on poly(amide-12-b-ethylene oxide) (Pebax-2533) and tetra(p-methoxylphenyl)porphyrin cobalt chloride (T(p-OCH₃)PPCoCl) were fabricated in systematically varied compositions for O₂/N₂ separation. T(p-OCH₃)PPCoCl was introduced as carriers that selectively and reversibly interacted with O₂ and facilitated O₂ transport in the membrane. The T(p-OCH₃)PPCoCl had good compatibility with the Pebax-2533 via the hydrogen bond interaction and formed a uniform and thin selective layer on the substrate. The O₂ separation performance of the thin film composite (TFC) membranes was improved by adding a small amount of the T(p-OCH₃)PPCoCl and decreasing the feed pressure. At the pressure of 0.035 MPa, the O₂ permeability and O₂/N₂ selectivity of the 0.6 wt % T(p-OCH₃)PPCoCl/Pebax-2533 was more than 3.5 times that of the Pebax-2533 TFC membrane, which reached the 2008 Robeson upper bound. It provides a candidate membrane material for O₂/N₂ efficient separation in moderate conditions.