A two-dimensional photoluminescent cadmium(II) coordination polymer containing a new coordination mode of pyridine-2,3-dicarboxylate: Synthesis, structure and molecular simulations for gas storage and separation applications

A novel two-dimensional (2D) coordination polymer, [Cd(μ-pydc)(2-meim)]n (1) (pydc = pyridine-2,3-dicarboxylate, 2-meim = 2-methylimidazole) was synthesized and characterized by spectral methods (FT-IR and photoluminescence), elemental analysis, thermal analysis (TG, DTG and DTA) and single crystal X-ray diffraction techniques. Complex 1 displays a 2D layer structure through the linkage of bridging carboxyl oxygen and pyridine nitrogen atoms of the pydc ligand. Each Cd(II) center exhibits a distorted octahedral coordination environment with four carboxylate oxygen atoms and two nitrogen atoms from the pydc and 2-meim ligands. In 1, the pydc ligand exhibits a new coordination mode. The distances of adjacent Cd(II) atoms are 3.679 and 7.742 Å. The 2D layers are further linked by C–H⋯π and π⋯π stacking to construct a 3D supramolecular structure. In order to assess the potential of 1 in gas storage and gas separation applications, molecular simulations were performed. Furthermore, 1 exhibits blue photoluminescence in the solid state at room temperature.

Graphical abstractA two dimensional Cd(II)-pyridine-2,3-dicarboxylate (pydc) coordination polymer has been synthesized and structurally characterized. An X-ray crystallographic study of 1 revealed that the pydc ligand adopts a new coordination mode. The most striking feature of 1 is that it exhibits a selectivity of 4 for CH4 over H2, which makes it a potential candidate for gas separation applications. Complex 1 exhibits blue fluorescent emission bands in the solid state at room temperature.Figure optionsDownload full-size imageDownload as PowerPoint slide