A new series of Cd(ii) metal-organic architectures driven by soft ether-bridged tricarboxylate spacers: synthesis, structural and topological versatility, and photocatalytic properties

Two multifunctional, ether-bridged tricarboxylic acids, 2-(4-carboxylphenoxy)terephthalic acid (H(3)cpta) and 2-(3,5-dicarboxylatobenzyloxy)benzoic acid (H(3)dbba), were used as unexplored and highly versatile building blocks for the hydrothermal generation of a novel series of cadmium(ii) metal-organic architectures. These were formulated as [Cd(-Hcpta)(phen)(py)](n) (1), {[Cd-3((5)-cpta)(2)(phen)(3)]8H(2)O}(n) (2), {[Cd-3((5)-cpta)(2)(2,2-bipy)(3)]6H(2)O}(n) (3), {[Cd((3)-cpta)(Hbpa)]2H(2)O}(n) (4), {[Cd-6((4)-cpta)(2)((6)-cpta)(2)(H(2)biim)(2)(H2O)(6)]5H(2)O}(n) (5), [Cd-3((4)-cpta)(2)(-prz)(H2O)(4)](n) (6), {[Cd-3((4)-dbba)(2)(phen)(3)]H2O}(n) (7), and {[Cd-3((3)-dbba)(2)(2,2-bipy)(3)(H2O)(3)]2H(2)O}(n) (8) on the basis of single-crystal X-ray diffraction, elemental analysis, FTIR, PXRD, and TGA data. Products 1-8 were assembled in the presence of N-donor crystallization mediators selected from pyridine (py), 1,10-phenanthroline (phen), 2,2-bipyridine (2,2-bipy), bis(4-pyridyl)amine (bpa), 2,2-biimidazole (H(2)biim), or piperazine (prz). The nature of the crystallization mediator and/or the type of principal tricarboxylate building block have a significant effect on the structural diversity, dimensionality, and topology of the resulting cadmium-organic architectures. These span from 1D (1, 8) and 2D (7) coordination polymers to 3D metal-organic frameworks (2-6) with intricate topologies (3,4,5T64 in 2 and 3, utp (10(3))-d in 4, 3,4,4T9 in 6) that also include unprecedented types in 5 and 7. Besides, MOF 6 features a 3D + 3D two-fold interpenetrated framework. Luminescent and photocatalytic properties of selected materials were investigated, showing that coordination polymer 7 is a promising photocatalyst for the UV-light-driven degradation of methylene blue as a model organic dye pollutant. Moreover, products 7 and 8 are the first examples of structurally characterized coordination compounds derived from H(3)dbba.