Post-cycloaddition modification of a porous MOF for improved GC separation of ethanol and water

An olefin-containing pyridinium derivative, 1-(4-carboxybenzyl)-4-[2-(4-pyridyl)-vinyl]-pyridinium chloride (HBCbpeCl) has been introduced into a novel 2D metal-organic framework with rare right- and left-handed spiral nanotubular channels arranged alternately in the structure. The 1D channel is modified by positively-charged pyridinium segments, which shows high affinities to Lewis basic molecules such as methanol, ethanol, and water vapor. Additionally, the BCbpe molecules in the structure have been directed through cation-π interactions to be aligned antiparallel to each other with the CC double bond arranged properly for [2 + 2] photocycloaddition, which can be triggered to undergo structural transformation from 2D to 3D. This post-cycloaddition modification strategy has been used to separate alcohols and water, which includes a successful adjustment of large tailor-made channels by the [2 + 2] cycloaddition reaction. The gas-chromatographic separation experiments show that ethanol can be better separated from water through a column filled with a post-cycloaddition modified sample than the as-synthesized one.