Ligand and Metal Effects on the Stability and Adsorption Properties of an Isoreticular Series of MOFs Based on T-Shaped Ligands and Paddle-Wheel Secondary Building Units.

Abstract

The synthesis of stable porous materials with appropriate pore size and shape for desired applications remains challenging. In this work a combined experimental/computational approach has been undertaken to tune the stability under various conditions and the adsorption behavior of a series of MOFs by subtle control of both the nature of the metal center (Co2+ , Cu2+ , and Zn2+ ) and the pore surface by the functionalization of the organic linkers with amido and N-oxide groups. In this context, six isoreticular MOFs based on T-shaped ligands and paddle-wheel units with ScD0.33 topology have been synthesized. Their stabilities have been systematically investigated along with their ability to adsorb a wide range of gases (N2 , CO2 , CH4 , CO, H2, light hydrocarbons (C1 -C4 )) and vapors (alcohols and water). This study has revealed that the MOF frameworks based on Cu2+ are more stable than their Co2+ and Zn2+ analogues, and that the N-oxide ligand endows the MOFs with a higher affinity for CO2 leading to excellent selectivity for this gas over other species.