A CdSO4-Type 3D Metal Organic Framework Showing Coordination Dynamics on Cu2+ Axial Sites: Vapochromic Response and Guest Sorption Selectivity

A unique 2-fold interpenetrated CdSO4 coordination network of the formula {[Cu-2(4-mpmd)(2)(CH3OH)(4)(opd)(2)]center dot 2H(2)O [4-pmpmd = N,Ni'-bis(4-pyridylmethyl)phenyldiimide; opd = o-phthalic acid] has been synthesized and characterized by IR spectra, thermogravimetric (TG) analyses, elemental analyses, and single crystal and powder X-ray diffraction methods. The metal organic framework (MOF) exhibits reversible dehydration and rehydration in a singlecrystal-to-single-crystal (SC-SC) process. Moreover, the dehydrated material, having coordinatively unsaturated Cu2+ sites, can encapsulate CH3OH molecules with a color change, again in a reversible SC SC fashion, and shows selective adsorption of CO2 over N-2 and H-2. This feature of obvious color variation induced by the presence of small hydroxylic molecules is highly promising for detecting hydroxylic molecules through a simple sensing mechanism. In addition, the MOP selectively interacts with hydroxylic guests and shows sorption selectivity for water, methanol, ethanol, and n-propanol over benzene guests. Notably, this compound shows complete selectivity in adsorption for n-propanol over 2-propanol owing to the effect of shape exclusion.