Highly selective adsorption of CO over CO₂ in a Cu(I)-chelated porous organic polymer

Cu(I) species were successfully chelated to nitrogen atoms in a nitrogen-rich porous organic polymer (SNW-1) by mixing with a CuCl solution (Scheme 1). Although pristine SNW-1 adsorbs CO₂ better than CO, Cu(I)-incorporated SNW-1 (nCu(I)@SNW-1) shows selective CO adsorption over CO₂ because of the π-complexation of CO with Cu(I). To the best of our knowledge, this is the first CO/CO₂ selectivity observed for POP-based materials. 1.3Cu(I)@SNW-1 exhibits high CO/CO₂ selectivity (23) at 1 bar and a large CO working capacity (0.6 mmol/g) at 0.1–1 bar. Moreover, the breakthrough and thermogravimetric experiments show that 1.3Cu(I)@SNW-1 can effectively separate CO from CO₂ under dynamic mixture conditions and can be easily regenerated under mild regeneration conditions without heating the column. Furthermore, 1.3Cu(I)@SNW-1 exhibited a good stability under exposure to atmospheric air for 3 h or 9 h. These results suggest that chelating Cu(I) species to a nitrogen-rich porous organic polymer can be an efficient strategy to separate and recover CO from CO/CO₂ mixtures.