Gas sorption studies on a microporous coordination polymer assembled from 2D grid layers by strong π-π interactions

The microporous coordination polymer [Co(H2 L)(bipy)0.5 ]⋅2 H2 O (1, bipy=4,4'-bipyridine) was synthesized on the basis of the V-shaped flexible diphosphonate ligand (2,4,6-trimethyl-1,3-phenylene)bis(methylene)diphosphonic acid (H4 L) and the auxiliary bipy ligand under hydrothermal conditions. The structure of this compound was characterized by single-crystal X-ray diffraction. By joining the diphosphonate ligands and bipy through tetrahedral [CoO3 N] clusters, a 2D square grid layered network was formed. Further stacking of these layers on the basis of π-π interactions resulted in a pseudo-3D microporous network with 1D channels running through the a axis. Gas sorption studies for CO2 , H2 , CH4 , N2 , and O2 on this coordination polymer were performed, and the results revealed interesting dynamic and hysteresis sorption behavior toward H2 at low temperature.