Metal–Organic\nFrameworks for the Adsorptive Removal of Gaseous Aliphatic Ketones

Abstract

Recent\nresearch endeavors have established metal–organic frameworks\n(MOFs) as suitable platforms for the adsorptive removal of various\nenvironmental pollutants. In this regard, the sorptive performances\nof four MOFs (MOF-199, UiO-66, UiO-66-NH₂, and Co-CUK-1)\nwere investigated against two gaseous aliphatic ketones (methyl ethyl\nketone (MEK) and methyl isobutyl ketone (MiBK)) at a low partial pressure\n(0.1 Pa). Activated carbon was utilized as a reference commercial\nsorbent. The 10% breakthrough volume (BTV10) values for MEK decreased\nin the following order: MOF-199 (4772 L atm g^–1)\n> activated carbon (224 L atm g^–1) > UiO-66-NH₂ (106 L atm g^–1) > UiO-66 (53 L atm g^–1) > Co-CUK-1 (16 L atm g^–1).\nIn case of MiBK, the relative ordering in BTV10 was consistently maintained\nwhile showing noticeable increases in its magnitude: MOF-199 (7659\nL atm g^–1) > activated carbon (816 L atm g^–1) > UiO-66-NH₂ (304 L atm g^–1) > UiO-66 (150 L atm g^–1) > Co-CUK-1 (31\nL atm g^–1). The superiority of MOF-199 was confirmed\ntoward the adsorptive removal of gaseous aliphatic ketones. For a\nbinary mixture of ketones, the BTV10 values of MOF-199 were reduced\nconsiderably for MEK and MiBK (in comparison to single component sorption)\nsuch as 1579 and 3969 L atm g^–1, respectively, reflecting\ncompetitive inhibition of the adsorption process. Theoretical simulations\nbased on density functional theory (DFT) elucidated the involvement\nof highly favorable coordination between the carbonyl group present\nin ketone molecules and the uncoordinated Cu­(II) sites in the MOF-199\nstructure (Lewis acidic centers). Interestingly, MOF-199 maintained\nappreciable performance toward the mixture of ketones up to 5 cycles\nto support its practical merit.