CO2 selective 1D double chain dipyridyl-porphyrin based porous coordination polymers

Abstract

Thermal reactions of MnCl(DPyP) (DPyP = 5,15-di(4-pyridyl)-10,20-diphenylporphyrin) as a metalloligand with Co^II and Zn^II ions in dimethylformamide led to neutral one-dimensional (1D) double chain dipyridyl-porphyrin-based porous coordination polymers (PCPs), Co₃(DPyP)₃·4DMF (I) and Zn₃(DPyP)₃·2DMF·4H₂O (II). Both PCPs were structurally characterized by X-ray crystallography. Particularly, the central Mn^III ion in MnCl(DPyP) was transmetallated with Co^II or Zn^II ions and the central Co^II or Zn^II ions were further coordinated to pyridyl groups of neighboring M(DPyP) (M = Co or Zn) porphyrin complexes. PCPs I and II are isostructural and each 1D double chain interacts with another 1D double chain by multiple hydrogen bonding to stabilize the resulting framework. Therefore, solvent-free 1D double chain PCPs have permanent porosity, and the void volumes of the solvent-free I and II are calculated to be 22.6% and 23.0%, respectively. Gas sorption analysis indicated that I and II exhibited selective adsorption of CO₂ at 196 K. Both PCPs exhibited much smaller sorption abilities for N₂ (77 K), H₂ (77 K), and CH₄ (196 K) than CO₂ (196 K). Both PCPs exhibited different PXRD patterns when dried at 373 K, which indicated that the framework transformation of the isostructural M₃(DPyP)₃ type of PCPs strongly depended on the type of central metal ions.