Structural variability, topological analysis and photocatalytic properties of neoteric Cd(ii) coordination polymers based on semirigid bis(thiazolylbenzimidazole) and different types of carboxylic acid linkers

Abstract

A series of novel Cd^II coordination complexes, formulated as {[Cd(btbb)_0.5(p-phda)]·H₂O}_n (1), [Cd(btbb)_0.5(oba)]_n (2), {[Cd₂(btbb)(m-bdc)₂(H₂O)]·2H₂O}_n (3), {[Cd(btbb)_0.5(btec)_0.5(H₂O)]·2H₂O}_n (4), [Cd(btbb)_0.5(o-bdc)]_n (5) and {[Cd₂(btbb)(bptc)(H₂O)]·4H₂O}_n (6) (btbb = 1,4-bis(2-(4-thiazolyl)benzimidazol-1-ylmethyl)benzene, H₂phda = phenylenediacetic acid, H₂oba = 4,4′-oxybis(benzoic acid), m-H₂bdc = 1,3-benzenedicarboxylic acid, H₄btec = 1,2,4,5-benzenetetracarboxylate, o-H₂bdc = 1,2-benzenedicarboxylic acid, H₄bptc = 3,3′,4,4′-benzophenone tetracarboxylic acid), have been obtained by solvothermal/hydrothermal reactions for the exploration of efficient photocatalytic degradation of organic dye pollutants. Complex 1 features a 6-connected 3D pcu α-Po primitive cubic topology net with the point symbol 4¹²·6³. Interestingly, complexes 2, 3 and 5 contain left- and right-handed helical chains (2: a 2-fold interpenetrating 3D architecture with {4¹²·6³}-pcu topology network; 3: a (3,6)-connected net with a vertex symbol (4²·5⁴·6⁶·7·8²)(4·6²); 5: a (3,4)-connected 3,4L83 topology net with point symbol (4²·6)(4²·6³·8)). Complex 4 exhibits a (3,4)-connected 3,4T48 topology net with point symbol (8⁴·10²)(8·10²), while complex 6 possesses a (3,5)-connected 3,5L2 topology with the point symbol (4²·6)(4²·6⁷·8). Furthermore, the photophysical studies indicate that the relatively narrow optical energy gaps of complexes 1–6 (<2.30 eV) calculated from the diffuse reflectivity spectra reflect their outstanding semiconductive nature. The photocatalytic properties of complexes 1–6 were studied in detail, and the results demonstrate their good photocatalytic activities in methylene blue (MB) degradation reactions, especially for complexes 3, 4 and 6 (3: 91.4%, 4: 92.7%, 6: 86.7%).