Adsorption of Acetone Vapor by Cu-BTC: An Experimental and Computational Study

We report an experimental and theoretical study of acetone adsorption in the metal–organic framework (MOF) compound Cu-BTC. The isosteric heat of adsorption could be derived experimentally and was found to be −60 kJ mol^–1. This value matches the theoretical data obtained by DFT-based methods at zero coverage. In situ DRIFT measurements allowed us to precisely describe the adsorption steps from zero coverage to saturation. Two main adsorption sites were determined for the adsorption of acetone. The small cavities were found to interact through van der Waals interaction with acetone, while the Cu­(II) site was found to interact with the carbonyl function of acetone. On the basis of the in situ infrared experiments, it was demonstrated that the small cavities were first in interaction with acetone. DFT proved consistent with these findings by giving the energy of interaction in the different sites explored but also by providing calculated infrared spectra of adsorbed acetone in Cu-BTC. Using acetone as a probe allowed showing that dispersive interactions with the pore sites of the Cu-BTC can be dominant among all other interactions. Additionally, the adsorption of acetone in Cu-BTC proved not fully reversible unless exposed to atmospheric moisture

A Comparative IRMPD and DFT Study of Fe³⁺ and UO₂²⁺ Complexation with <i>N</i>‑Methylacetohydroxamic Acid

Iron­(III) and uranyl complexes of <i>N</i>-methylacetohydroxamic acid (NMAH) have been investigated by mass spectrometry, infrared multiphoton dissociation (IRMPD) spectroscopy, and density functional theory (DFT) calculations. A comparison between IRMPD and theoretical IR spectra enabled one to probe the structures for some selected complexes detected in the gas phase. The results show that coordination of Fe³⁺ and UO₂²⁺ by hydroxamic acid is of a very similar nature. Natural bond orbital analysis suggests that bonding in uranyl complexes possesses a slightly stronger ionic character than that in iron complexes. Collision-induced dissociation (CID), IRMPD, and ¹⁸O-labeling experiments unambiguously revealed a rare example of the UO bond activation concomitant with the elimination of a water molecule from the gaseous [UO₂(NMA)­(NMAH)₂]⁺ complex. The UO bond activation is observed only for complexes with one monodentate NMAH molecule forming a hydrogen bond toward one “yl” oxygen atom, as was found by DFT calculations. This reactivity might explain oxygen exchange observed for uranyl complexes