Oxygen selective iron and cobalt-metalloporphyrin polymers - Extraordinary selectivity at low temperature

Oxygen binding properties of a recent class of porphyrin-based porous organic polymers (POPs) were investigated. POPs containing iron (Fe-POP) and cobalt (Co-POP) were synthesized, characterized and evaluated. Adsorption studies under ambient and cryogenic conditions (91-303 K) were studied. Interestingly, these POPs showed selective adsorption of O2 over N2 of up to 1.3 at 273 K, and most significantly, the oxygen uptake was found to be stable and reversible over the range of temperatures studied. Furthermore, the polymers also exhibited a molecular sieving effect, which showed increasing nitrogen exclusion between 110 K and 160 K and led to an extraordinary O2:N2 selectivity of up to 14.7 at 91 K. The high oxygen loading (13 wt% at 1 atm) together with the high selectivity suggests great potential for use of these materials in hybrid adsorption-cryogenic air separation systems.