LAUSR

Flexible metal-organic frameworks (MOFs) are highly attractive porous crystalline materials presenting structural changes when exposed to external stimuli, the mechanism of which is often difficult to glean, owing to their complex and dynamic nature. Herein, we report a flexible, interpenetrated Zr-MOF, NU-1401, composed of rare 4-connected Zr6 nodes and tetratopic naphthalenediimide (NDI)-based carboxylate linkers. The intra-framework pore opening deformation and inter-framework motions, when subjected to different solvent molecules, are investigated by single-crystal X-ray diffraction. It is shown that the distance and overlap angle between the stacked NDI pairs in the entangled structure can be finely tuned, and the interactions between NDI and solvent molecules lead to a solvochromism property. Furthermore, the presence of electron-deficient NDI units and Lewis acidic Zr(IV) site in the interpenetrated porous structure offers high density of adsorption sites for ammonia molecules, resulting in high uptake at low pressures.