Cadmium-BINOL Metal-Organic Framework for the Separation of Alcohol Isomers

The large-scale isolation of specific isomers of amyl alcohols for applications in the chemical, pharmaceutical, and biochemical industries represents a challenging task due to the physicochemical similarities of these structural isomers. The homochiral metal-organic framework cadmium-BINOL (BINOL=1,1'-bi-2-naphthol) is suitable for the separation of pentanol isomers, combining adsorption selectivities above 5 with adsorption capacities of around 4.5 mol kg^-1 . Additionally, a slight ability for separation of racemic mixtures of 2-pentanol is also detected. This behavior is explained based on matching shapes, strength of host-guest interactions, and on the network of hydrogen bonds. The last of these explains both the relative success and shortfalls of prediction methods at high loadings (ideal adsorbed solution theory) or at low coverage (separation factors), which are therefore useful here at a qualitative level, but not accurate in quantitative terms. Finally, the high selectivity of cadmium-BINOL for 1-pentanol over its isomers offers prospects for practical applications and some room for optimizing conditions.