Abstract
Y(btc) (btc = 1,3,5-benzenetricarboxylate) is a metal-organic framework that exhibits significant adsorption of industrially-relevant gases such as H2, CH4, and O2. Previous studies have noted a surprising lack of close interactions between the adsorbed guest molecules and Y, despite the apparent availability of a “bare-metal” binding site. We have extended our previous work in a detailed investigation of the adsorption behaviours of CO2, CD4, and O2 in Y(btc) over a range of concentrations using in situ neutron powder diffraction methods. The O–Y–O bond angles enclosing the bare-metal site are found to change considerably depending on the type and quantity of guest molecules present. Multiple binding sites are found for each guest species, and the largest changes in O–Y–O angles are accompanied by changes in the filling sequences of the binding sites, pointing to an important interplay between guest-induced framework distortions and binding site accessibility. These results suggest the potential for coordinatively flexible rare-earth metal centres to promote guest-selective binding in metal-organic frameworks.
Highlights
The atomic-scale understanding of gas-sorption mechanisms in porous solid sorbents has become a focus of major research efforts in recent times, driven in particular by the need for efficient gas separators in many energy-related applications
H2 [13,14], we present an analysis of the Y coordination environment in Y(btc) and its behaviour in of the Y coordination environment in Y(btc) and its behaviour in the presence of different guest species the presence of different guest species and concentrations, with a view to understanding how metal-organic frameworks (MOFs)
It is typically expected that the bare-metal sites of a with the available Y bare-metal sites, with the closest interaction distances occurring for sites ACO2 coordination framework should provide guest molecules, quadrupolar CO2 molecules, and CCO2 at 4.16(9) and 4.640(10) Å, respectively
Summary
The atomic-scale understanding of gas-sorption mechanisms in porous solid sorbents has become a focus of major research efforts in recent times, driven in particular by the need for efficient gas separators in many energy-related applications. MOFsIncontaining rare-earth maygeometry display more of the and the fixed network upon topology of the linker molecules both serve maintain thenumber flexibility in metal their centre coordination geometry removal of the solvent due to to the greater overall structure of the MOF without significant changes to the framework geometry in the vicinity of satisfactory geometries adopted by these large metal ions [10,11,12]. One such example is Y(btc) of the metal centre.
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