Impact of Pore Size and Defects on the Selective Adsorption of Acetylene in Alkyne-Functionalized Nickel(II)-Pyrazolate-Based MOFs

Abstract

C₂ H₂ /CO₂ separation is a highly challenging process as a consequence of their similar physicochemical properties. In this work we have explored, by static and dynamic gas sorption techniques and computational modelling, the suitability of a series of two isoreticular robust Ni(II)pyrazolate-based MOFs, bearing alkyne moieties on the ligand backbones, for C₂ H₂ /CO₂ separation. The results are consistent with high adsorption capacity and selectivity of the essayed systems towards C₂ H₂ molecules. Furthermore, a post-synthetic treatment with KOH ethanolic solution gives rise to linker vacancy defects and incorporation of extraframework potassium ions. Creation of defects is responsible for increased adsorption capacity for both gases, however, strong interactions of the cluster basic sites and extraframework potassium cations with CO₂ molecules are responsible for a lowering of C₂ H₂ over CO₂ selectivity.

Keywords: breakthrough curves; carbon capture; computational modelling; gas separation; temperature swing adsorption.