Series of Cadmium-Organic Frameworks Based on Mixed Flexible and Rigid Ligands: Single-Crystal-to-Single-Crystal Transformations, Sorption, and Luminescence Properties.

Here, we present a series of Cd(II) coordination polymers containing two types of ligands: sterically rigid terephthalate derivatives (bdc-NO and bdc-Br) and flexible bis(2-methylimidazolyl)propane (bmip). The combination of two types of ligands is used to obtain and characterize compounds by single crystal and powder X-ray diffraction, FT-IR, elemental analysis, and TGA. Guest exchange results in structural transformations. 2-fold interpenetrated ·DMF and ·DMF rapidly undergo to 4-fold interpenetrated ·EtO, ·EtOH, and ·HO, or ·EtO, respectively. Also, changes in the coordinating numbers and length of the ,'-donor bmip ligand were observed according to single crystal X-ray analysis. Activated guest-free compounds [Cd(bdc-NO)(bmip)] () and [Cd(bdc-Br)(bmip)] () are shown to be porous with a BET surface area of 103 and 283 m·g, respectively. Moreover, both compounds demonstrate gate-opening behavior of ethylene adsorption isotherms at low pressures (<1 bar) and highly selective adsorption of benzene over cyclohexane or lower alcohols. Also, both compounds demonstrate a strong dependence of the maximum of the photoluminescence emission on an excitation wavelength. As a result, the photoluminescence color changes from white to red and from blue to red through green and yellow for compounds and , respectively, with excitation wavelength changing from 360 to 540 nm.