Four Cd-Based Metal–Organic Frameworks with Structural Varieties Derived from the Replacement of Organic Linkers

Four three-dimensional (3D) Cd-based metal–organic frameworks (MOFs), [Cd­(pyip)­(dmf)] (1), [Cd­(pyip)­(doa)] (2), [Cd­(pyip)­(pz)] (3) and [Cd­(pyip)­(bipy)­(H2O)0.5] (4) (dmf = N,N′-dimethylformamide, doa = 1,4-dioxane, pz = pyrazine, bipy = 4,4′-bipyridine) have been rationally designed and systematically synthesized by using 5-(pyridine-4-yl)­isophthalic acid (H2pyip) and Cd­(NO3)2·4H2O under solvothermal conditions. Compound 1 possesses a mineral-like 3,6-connected rtl network, and compounds 2–4 exhibit a 3,5-connected interpenetrating hms network constructed with 2-fold layers and bridging coligands pillars (doa, pz, and bipy), respectively. In compounds 2–4, doa, pz, and bipy act as pillars to extend the distance between the two layers from 7.34 to 11.36 Å, and the different conformations and lengths of the coligands have influenced the angles between the bridging ligands and the layers. Additionally, the four compounds exhibit strong luminescent emissions in the solid state at room temperature, and the latter three compounds exhibit robust architectures as evidenced by their permanent porosity and high thermal stability.