Construction of five Zn(ii)/Cd(ii) coordination polymers derived from a new linear carboxylate/pyridyl ligand: design, synthesis, and photocatalytic properties

Abstract

Solvothermal reactions of Cd(OAc)₂/Zn(OAc)₂ with a new ligand, (pyridin-3-yl)methyl 4-(2-(4-((pyridin-3-yl)methoxy)phenyl)diazenyl)benzoate (L1), under different templates via an in situ ligand transformation reaction produced five coordination polymers, [CdL₂(H₂O)]_n (1), [Cd_1.5L₃]_n (2), [Cd₂L₄]_n (3), [(ZnL₂)·H₂O]_n (4) and {[Zn(1,3-BDC)(L1)]·MeCN·0.5H₂O}_n (5), where HL = 4-(2-(4-((pyridin-3-yl)methoxy)phenyl)diazenyl)benzoic acid, 1,3-H₂BDC = 1,3-benzenedicarboxylic acid. Compound 1 is a three-dimensional (3D) wave-like structure constructed from 4-connected Cd(II) nodes and L⁻ linkers. Compounds 2 and 3 bear similar 2D networks built from metallocyclic [Cd₄L₄] units. Compound 4 features a wrinkled 2D layer based on metallocyclic [Zn₄L₄] units. Compound 5 has a novel 1D single-wall metal–organic nanotube (SWMONT) in which the 1,3-BDC ligands act as linkers to connect the [Zn₂(L1)₂] rings. The results reveal that the different templates have a significant effect on the final structures. Compounds 1–5 exhibited relatively high photocatalytic activity towards the degradation of methylene blue (MB) in aqueous solution under UV-Vis irradiation. The kinetics of the catalytic photodegradation reactions and the stabilities of photocatalysts were also investigated.