A Microporous Organic Copolymer for Selective CO₂ Capture under Humid Conditions

A cross-linked microporous organic copolymer, termed KFUPM-2, was synthesized through a Friedel-Crafts alkylation polymerization of phenothiazine, pyrrole, and p-formaldehyde in the presence of iron(III) chloride catalyst. KFUPM-2 was demonstrated to have intrinsic permanent microporosity with a Brunauer-Emmett-Teller surface area of 352 m² g^-1 and a high capacity (39.1 cm³ g^-1 at 273 K and 760 Torr) and affinity (Q_st = 34 kJ mol^-1 and CO₂/N₂ selectivity of 51) toward CO₂ as a result of its nitrogen-rich structure. To demonstrate its practical applicability, breakthrough measurements were performed using a gas mixture that mimicked the composition of an industrial flue gas stream (CO₂/N₂ = 20/80% v/v with 91% relative humidity). Accordingly, KFUPM-2 was shown to have an ultrahigh CO₂ dynamic capacity (32 cm³ g^-1 at 298 K) in the presence of water and was demonstrated recyclable over at least 10 cycles with mild regeneration conditions needed between each cycle.