Co(II), Ni(II),\nMn(II), and Cd(II) Coordination Polymers\nConstructed with Tetracarboxylic Linker: Syntheses, Structural Investigations,\nand Catalytic Application

Eight transition metal coordination polymers were synthesized\nvia\nhydrothermal methods utilizing primary ligand [1,1′:3′,1″-terphenyl]-3,3″,5,5″-tetracarboxylic\nacid (H<sub>4</sub>tpta) alongside auxiliary ligands including phenanthroline\n(phen), 2,2′-bipyridine (bipy), pyridine (py), 1,4-bis(pyrid-4-yl)benzene\n(bpb), 1,2-di(4-pyridyl)ethylene (dpe), and bis(4-pyridyl)amine (bpa).\nThe synthesis yielded three 1D and five 3D coordination polymers,\nwhich were formulated as [Ni<sub>2</sub>(μ<sub>4</sub>-tpta)(phen)<sub>2</sub>(H<sub>2</sub>O)<sub>4</sub>]<sub><i>n</i></sub>·6<i>n</i>H<sub>2</sub>O (<b>1</b>) [Co<sub>2</sub>(μ<sub>4</sub>-tpta)(bipy)<sub>2</sub>(H<sub>2</sub>O)<sub>4</sub>]<sub><i>n</i></sub>·8<i>n</i>H<sub>2</sub>O (<b>2</b>), [Ni<sub>2</sub>(μ<sub>4</sub>-tpta)(bipy)<sub>2</sub>(H<sub>2</sub>O)<sub>4</sub>]<sub><i>n</i></sub>·7<i>n</i>H<sub>2</sub>O (<b>3</b>), [Ni<sub>2</sub>(μ<sub>6</sub>-tpta)(py)<sub>3</sub>(μ-H<sub>2</sub>O)(H<sub>2</sub>O)]<sub><i>n</i></sub>·2<i>n</i>H<sub>2</sub>O (<b>4</b>), [Cd<sub>2</sub>(μ<sub>6</sub>-tpta)(μ-bpb)]<sub><i>n</i></sub>·<i>n</i>H<sub>2</sub>O (<b>5</b>), [M<sub>2</sub>(μ<sub>6</sub>-tpta)(μ-dpe)<sub>2</sub>]<sub><i>n</i></sub>·3<i>n</i>H<sub>2</sub>O [M = Co (<b>6</b>),\nMn (<b>7</b>)], and [Co<sub>2</sub>(μ<sub>6</sub>-tpta)(μ-bpa)<sub>2</sub>]<sub><i>n</i></sub>·2<i>n</i>H<sub>2</sub>O (<b>8</b>). These coordination polymers were meticulously\nanalyzed using standard methodologies to investigate their topological\nstructures and catalytic properties. Remarkably, Co(II) coordination\npolymer <b>8</b> demonstrated remarkable activity in the Henry\nreaction with benzaldehydes, attaining elevated yields under optimal\nconditions. Moreover, it demonstrated remarkable stability, high efficiency,\nand excellent reusability as a heterogeneous catalyst. This work explores\nthe application of H<sub>4</sub>tpta as the flexible tetracarboxylate\nlinker for the synthesis of functional coordination polymers.