Five d¹⁰ 3D Metal−Organic Frameworks Constructed From Aromatic Polycarboxylate Acids and Flexible Imidazole-Based Ligands

Five new metal−organic frameworks, namely, [Cd(HIDC)(bix)] n ( 1 ), [Cd 2 (BDC) 2 (mbix)H 2 O] n ( 2 ), [Cd(HBTEC)(H 2 bix) 0.5 ] n ( 3 ), [Cd(BTEC)(H 2 mbix)] n ( 4 ), and [Zn(BTEC) 0.5 (mbix)] n ( 5 ) (H 3 IDC = imidazole 4,5-dicarboxylic acid, H 2 BDC = 1,4-benzenedicarboxylate, H 4 BTEC = 1,2,4,5-benzenetetracarboxylate, bix = 1,4-bis(imidazol-1-ylmethyl)-benzene, and mbix = 1,3-bis(imidazol-1-ylmethyl)-benzene), have been synthesized under hydrothermal conditions by employing mixed ligands of various carboxylic acids with bix (or mbix). Coordination polymer 1 is a 3-fold-interpenetrated diamondoid network. Particularly, in 1 there occur triple-stranded helices based on Cd ions and bix ligands when viewed along b axis. Coordination polymer 2 is a 2D infinite layer framework, which is further interconnected by hydrogen-bond interactions leading to a 3D supramolecular architecture. Both 3 and 4 feature a 3D open framework with protonated bix (or mbix) locating in the channels, and the 3D open frameworks can be rationalized as a zeolite ABW topology for 3 and pts net for 4 . Coordination polymer 5 also has a 3D architecture, and the topological study shows that its framework features a 3D four-connected (6 4 8 2 )(6 6 ) net. The photoluminescent properties of the coordination polymers were investigated. All of these coordination polymers exhibited intense fluorescent emissions in the solid state at room temperature.