A solvent ‘squeezing’ strategy to graft ethylenediamine on Cu3(BTC)2 for highly efficient CO2/CO separation

Abstract Highly efficient separation of residual carbon dioxide (CO 2 ) from syngas, mainly composed of carbon monoxide (CO) and hydrogen (H 2 ), could not only make its utilization more energetically efficient but also avoid catalysts poisoning in some industrial applications. In the attempts to address this issue, it is acknowledged that CO 2 /CO separation is the vital step since H 2 is a nonpolar molecules, difficult to be polarized and could be easily separated from CO 2 . Herein, we report a novel strategy to graft basic ethylenediamine (ED) molecules onto porous metal–organic frameworks (MOFs) as solid adsorbents for CO 2 /CO separation via solvent ‘squeezing’ approach, in which Cu 3 (BTC) 2 (BTC = 1,3,5-benzenetricarboxylate) MOF was employed as the pristine MOF. Surprisingly, the ED-grafted Cu 3 (BTC) 2 shows unprecedented enhancement of CO 2 /CO selectivity of 226% at 273 K and 861% at 298 K, respectively, in comparison with the solvent-free Cu 3 (BTC) 2 . Moreover, despite the large isosteric heats of adsorption of CO 2 on the ED-grafted Cu 3 (BTC) 2 , it could be easily regenerated at moderate temperature. This work provides an efficient and facile method to functionalize MOFs for CO 2 capture.