Polynuclear Cd^II Polymers: Crystal Structures, Topologies, and the Photodegradation for Organic Dye Contaminants

To systematically explore the effect of polynuclear complexes on photocatalytic degradation of the organic dyes, a series of coordination complexes containing Cd II clusters, formulated as {[Cd 3 L 2 (H 2 O) 5 ]·H 2 O} n ( 1 ), {[Cd 3 L 2 (hbmb)(H 2 O) 2 ]·2.5H 2 O} n ( 2 ), {[Cd 3 L 2 (btbb)(H 2 O) 2 ]·2EtOH·1.5H 2 O} n ( 3 ), and {[Cd 6 L 4 (bipy) 2 (H 2 O) 6 ]·3H 2 O} n ( 4 ) (H 3 L = 3,4-bi(4-carboxyphenyl)-benzoic acid, hbmb = 1,1′-(1,6-hexane)bis(2-methylbenzimidazole), btbb = 1,4-bis(2-(4-thiazolyl)benzimidazole-1-ylmethyl)benzene, 4,4′-bipy = 4,4′-bipyridine), have been designed and synthesized. Complex 1 based on trinuclear Cd II clusters exhibits a new (3,3,6)-connected 3D framework. 2 belongs to a (3,3,8,8)-connected tfz-d topology net with pillar-layered frameworks assembled by two kinds of trinuclear Cd II clusters. 3 is a 3D pillar-layered framework, which features a (3,8)-connected tfz-d net based upon one kind of trinuclear Cd II cluster. 4 presents a new 3D (3,6,10)-connected framework with dinuclear and tetranuclear clusters. The photocatalytic properties of complexes 1 – 4 have been studied in detail. Remarkably, 1 – 4 all reveal good photocatalytic activity in MB/MO degradation. The optical energy gap calculated by the diffuse reflectivity spectra of 1 – 4 are consistent with their degradation rates. Moreover, the experimental results further demonstrate that the cluster complexes containing different kinds of nuclei may exert different impact on the decomposition of disparate organic dyes.