Porous Organic Cages CC3 and CC2 as Adsorbents for the Separation of Carbon Dioxide from Nitrogen and Hydrogen

The selective capture of carbon dioxide over nitrogen and hydrogen is of great industrial interest in flue gas and hydrogen purification, respectively. Microporous adsorbents are highly suitable materials to preferentially adsorb gases. In particular, porous organic cages (POCs) with tunable hierarchically ordered micropores, high surface area, and thermodynamic affinity for CO2make them appealing candidates for these applications. Herein, we demonstrate that two prototypical POCs denoted as CC3 and CC2 with a limiting pore aperture of 3.6 Å can selectively separate CO2from N2and H2. For CC3 adsorption selectivities as high as ∼8 and ∼20 for CO2/N2and CO2/H2, respectively, were observed. For CC2 adsorption selectivities as high as ∼9 and ∼35 for CO2/N2and CO2/H2, respectively, were observed. Interestingly, the adsorption selectivity of the studied gases correlated linearly with polarizability ratio.