Reveal the Alignment of Defects in a Metal-Organic Framework with Tunable Flexibility

Abstract Crystalline materials are often considered to have rigid periodic lattices while soft materials are associated with flexibility and non-periodicity. The continuous evolution of metal-organic frameworks (MOFs) has erased the boundaries between these two distinct conceptions. Flexibility, disorder and defects have been found to be abundant in MOF materials with imperfect crystallinity, and their intricate interplay is poorly understood due to the limited strategies for characterizing disordered structures. Here, we apply advanced nuclear magnetic resonance (NMR) spectroscopy to elucidate the mesoscale structures in a defective MOF with a partially disordered lattice. We show that engineered defects can tune the degree of lattice flexibility by combining both ordered and disordered compartments. The one-dimensional alignment of defects is the key for the reversible topological transition.