Dynamic Pendulum Effect of an Exceptionally Flexible Pillared-Layer Metal-Organic Framework†

Main observation and conclusion Magnifying the controllable directional motions of molecular machines to the macroscopic levels is a significant topic for chemists. Flexible metal-organic frameworks with long-range order and responsive structural transformation under external stimuli may be an appropriate platform for achieving the target. By taking advantage of the single-crystal to single-crystal manner of soft porous crystals, we utilize single-crystal X-ray diffraction to directly observe the dynamic structural inversion of a new three-fold interpenetrated pillared-layer metal-organic framework [Co(edba)(bpy)] (MCF-83, H(2)edba = 4,4'-(ethyne-1,2-diyl)dibenzoic acid, bpy = 4,4'-bipyridine). More interestingly, the dynamic inversions of the pillars and layers are selectively guest-controllable and independent, allowing precise control of the directional shape changes, which is the key of constructing intelligent materials to accomplish a complex task. The mechanism is further studied by combining the X-ray diffraction analyses, sorption measurements and molecular simulations.