Alkane–OH Hydrogen Bond Formation and Diffusion Energetics of n-Butane within UiO-66

Abstract

Hydrocarbon diffusion and binding within porous molecular networks are critical to catalysis, separations, and purification technologies. Fundamental insight into n-butane uptake and mobility within a new class of materials for separations, metal−organic frameworks (MOFs), has been gained through in situ infrared spectroscopy. These ultrahigh vacuum (UHV) based measurements revealed that adsorption of n-butane within UiO-66 proceeds through the formation of hydrogen bonds between the alkane molecules and hydroxyl groups located at the inorganic node of UiO-66. Modeling the gas transport of n-butane with Fick's second law yielded diffusion coefficients at several temperatures. The Arrhenius parameter for the activation energy of diffusion was found to be 21.0 ± 1.2 kJ/mol. These studies have further shown that the rate-determining step for diffusion is likely the dissociation of n-butane from a binding site located within the tetrahedral pores of UiO-66.

Bifurcated Dihydrogen Bonding in the Uptake of Gas-Phase Diborane on Silica

“…All experiments were conducted in a custom UHV instrument which has been described in detail in other publications by our group . Sample materials were mounted on a manipulator in the center of the main vacuum chamber for positioning and temperature control.…”

“…All experiments were conducted in a custom UHV instrument which has been described in detail in other publications by our group. 35 Sample materials were mounted on a manipulator in the center of the main vacuum chamber for positioning and temperature control. Power leads connected to an external power supply in conjunction with a liquid-nitrogen reservoir in contact with the sample holder allow for fine control over the sample temperature between 78 and 1000 K. Commercial semiconductor-grade B 2 H 6 was delivered to the chamber via a high-purity manifold and capillary doser array, the outlet of which is positioned within 1 cm of the sample.…”

Dielectric Spectroscopy of Water Dynamics in Functionalized UiO-66 Metal-Organic Frameworks

“…In such systems, incomplete water filling of the pores is common and therefore water-surface interactions are promoted causing system-dependent alterations in the dynamical behavior of the confined water [39]. BDC linkers of the non-functionalized UiO-66 are hydrophobic, but the H-bond formation of the confined water molecules with hydroxy groups located at the inorganic nodes may be possible, similar to reported n-butane binding in these MOFs [41] and water molecules in the MIL-53 [42]. The functionalization of the BDC linker with polar F and NH 2 groups introduces additional possible H-bonding sites in the framework resulting in the increased water-surface interactions.…”

Investigating the Process and Mechanism of Molecular Transport within a Representative Solvent-Filled Metal–Organic Framework

“…Despite a wealth of investigations on gas-phase diffusion in MOFs, − studies in solution, ,, which would be more relevant to some heterogeneous catalysis processes, are relatively limited. Jee et al found that the diffusivity of coumarin molecules in In­(III)-based zeolitic MOFs in DMF is 2 orders of magnitude smaller than in bulk solution, implying the importance of geometric confinement for this system.…”