Hydrothermal Assembly, Structural Multiplicity, and Catalytic Knoevenagel Condensation Reaction of a Series of Coordination Polymers Based on a Pyridine-Tricarboxylic Acid.

A pyridine-tricarboxylic acid, 5-(3',5'-dicarboxylphenyl)nicotinic acid (Hdpna), was employed as a adjustable block to assemble a series of coordination polymers under hydrothermal conditions. The seven new coordination polymers were formulated as [Co(Hdpna)(dpey)]·HO (), [Zn(dpna)(phen)] (), [Co(dpna)(2,2'-bipy)] (), [Zn(dpna)(2,2'-bipy)] (), [Co(dpna)(4,4'-bipy)(HO)]·2HO (),[Co(bpb)(HO)][Co(dpna)(HO)]·3HO (), and [Mn(dpna)(dpea)] (), wherein 1,2-di(4-pyridyl)ethylene (dpey), 1,10-phenanthroline (phen), 2,2'-bipyridine(2,2'-bipy),4,4'-bipyridine(4,4'-bipy),1,4-bis(pyrid-4-yl)benzene (bpb), and 1,2-di(4-pyridyl)ethane (dpea) were employed as auxiliary ligands. The structural variation of polymers - spans the range from a 2D sheet (-, , and ) to a 3D metal-organic framework (MOF, ). Polymers - were investigated as heterogeneous catalysts in the Knoevenagel condensation reaction, leading to high condensation product yields (up to 100%) under optimized conditions. Various reaction conditions, substrate scope, and catalyst recycling were also researched. This work broadens the application of Hdpna as a versatile tricarboxylate block for the fabrication of functional coordination polymers.