Adsorption and Separation of Organic Six-Membered Ring Analogues on Neutral Cd(II)-MOF Generated from Asymmetric Schiff-Base Ligand

A new CdL2-MOF was synthesized based on an asymmetric Schiff-base ligand LH, which is obtained by condensation of 5-formyl-8-hydroxyquinoline and 3-pyridinecarboxylic acid hydrazide. A series of organic six-membered ring analogues, namely, 1,4-dioxane, cyclohexane, cyclohexene, benzene, cyclohexanone, and cyclohexanol, can be absorbed by the CdL2 porous framework in liquid-phase to generate Gn⊂CdL2 (n = 1 and 2) host−guest complexes. In addition, the CdL2 host framework displays different affinity for these six-membered ring substrates and can effectively separate them under mild conditions (i.e., 1, 4-dioxane > cyclohexane > cyclohexene and benzene > cyclohexanone > cyclohexanol). The empty CdL2 displays strong green-yellow emission. Furthermore, these host−guest systems show an interesting guest-driven luminescent emission, and the emission intensities of these guest-loaded complexes are effectively reduced.