Selective adsorption of CO 2 /CH 4 and CO 2 /N 2 within a charged metal–organic framework

Presented here is a new ultramicroporous metal–organic framework (MOF) formulated as [Zn 3 L 2 (HCOO) 1.5 ][(CH 3 ) 2 NH 2 ] 1.5 · x DMF, 1 (H 3 L = 9-(4-carboxy-phenyl)-9 H -carbazole-3,6-dicarboxylic acid), DMF = N,N -dimethylformamide, consisting of an anionic framework and two types of interlaced one-dimensional channels with 0.42 and 0.79 nm diameters respectively, in which the larger channels accommodate protonated dimethylamine as the counter cations. Gas sorption analysis of N 2 , CO 2 and CH 4 was investigated and the isotherms exhibit reversible thermodynamic behaviours without hysteresis desorption, evidencing framework rigidity and permanent porosity of solvent-free 1 . The synergistic effect of the open ultramicropores and dimethylamine cations may lead to high efficiency separation of CO 2 from CH 4 and N 2 . According to the Toth model, the selectivity of CO 2 /CH 4 and CO 2 /N 2 was calculated to be 96 and 37, respectively. This effort will give rise to a new conception to tailor the charged MOF for high efficiency CO 2 adsorption and separation.