A pair of 3D homochiral metal–organic frameworks: spontaneous resolution, single-crystal-to-single-crystal transformation and selective adsorption properties

Abstract

A novel achiral hexacarboxylic ligand L was synthesized. Spontaneous resolution occurred during the reaction of L with Eu(NO₃)₃ to produce a pair of enantiomers of 1a and 1b with a formula of [EuL(NO₃)₃(H₂O)]·13H₂O, which possesses 1D chiral open channels formed by triple-stranded helical chains. When heated to 60 °C, 1a releases coordinated and partial lattice H₂O molecules to give a complex of [EuL(NO₃)₃]·4H₂O (1a′), accompanied by a single-crystal-to-single-crystal transformation from 1a to 1a′, with the space group changing from P2₁ to P3₁2. The dehydrated 1 can selectively adsorb water over organic solvents and exhibits reversible water adsorption upon dehydration and hydration.