Variation of CO2 adsorption in isostructural Cd(ii)/Co(ii) based MOFs by anion modulation

Abstract

A potential multidentate tris-pyridyl ligand has been synthesized, and later employed for the tailoring of four isostructural cadmium(II)/cobalt(II) two dimensional (2D) metal organic frameworks, [[M(dmpt)₂(X)₂]·xS]_n, where S = solvent, M = Cd²⁺, (X = NO₃⁻ (1), Br⁻ (2), I⁻ (3)); M = Co²⁺ (X = Cl⁻ (4)), dmpt = 4′-(3,4-dimethoxyphenyl)-4,2′:6′,4′′-terpyridine. These complexes have been characterized by infrared (IR) spectroscopy, elemental analysis, thermogravimetric analysis (TGA) and powder X-ray diffraction (PXRD) and single crystal X-ray diffraction analyses. Single crystal X-ray diffraction analysis reveals that the complexes (1–4) are isostructural and crystallize in the monoclinic C2/c space group. They possess similar structural features such as metal-coordination environment, network topology, π⋯π interactions and exhibit a 2D uninodal 4⁴-sql topology with slightly tuned cavities. In complexes 1–4, the [[M(dmpt)₂(X)₂]·xS] coordination monomer acts as the building block, building 2D layers which are further stacked up via Van der Waals interactions into a three-dimensional (3D) framework. The effect of weak interactions on the structural dynamics of the systems has also been studied. Furthermore, a gas adsorption study of these complexes demonstrates that they are affected by the impact of directing anions inside the pores.