Adsorptive removal and catalytic performance of metal-organic frameworks containing mixed azolium-bipyridine ligand

Abstract

Two ligands, 1, 3-bis(4-carboxyphenyl)imidazolium chloride and 4, 4-bipyridine, were employed to prepare nickel and zinc azolium based MOFs, Ni-MOF and Zn-MOF by the mixed ligand solvothermal approach. The positively charged azolium moieties in the imidazolium linker resulted in a charged environment in the as-synthesized frameworks. As a result, Ni-MOF and Zn-MOF demonstrated preferential adsorption of CO₂ over methane molecules in the gas phase adsorption due to the higher quadruple moment of CO₂, which interacts more with the positively charged frameworks. Besides, in aqueous media, Ni-MOF and Zn-MOF exhibited incredible adsorption efficiency for anionic dyes. In the following, Ni-MOF was metallated at the carbene site of the azolium linker to generate the novel heterogeneous catalyst Pd/Ni-MOF, which was successfully applied for Sonogashira and Suzuki-Miyaura coupling reactions without losing its activity after three cycles.