A single-crystal-to-single-crystal transformation affording photochromic 3D MORF crystals

Metal-Organic Framework (MOF) type crystals in which rigid, viologen-based pillars are surrounded by cucurbit[7]uril (CB[7]) macrocycles are described. These Metal-Organic Rotaxane Frameworks (MORF) are obtained by desolvation of a crystal precursor featuring a network already near-optimal toward 3D Metal-Ligand reticulation and show reversible photochromism.