High CO2 uptake capacity and selectivity in a N-oxide-functionalized 3D Ni(II) microporous metal–organic framework

A three-dimensional (3D) rigid Ni(II) microporous metal–organic framework (MOF), {[Ni(bpdado)(bpe)(H2O)2]·2DMF·2H2O}n (1), has been synthesized upon axially chiral N-Oxide-functionalized 2,2′-bipyridine-3,3′-dicarboxylate-1,1′-dioxide (H2bpdado) ligand with auxiliary rigid linear trans-1,2-bis (4-pyridyl)ethene (bpe) linker. Structural analysis reveals that there exist 1D diamond channels in the framework of 1, decorated with abundant N-Oxide "open donor sites" (ODSs) and vacant carboxyl sites on the pore surfaces. The modification of pyridine-N into the N-oxide group endows the N-oxide group with unique charge-separated plus electron-rich character, which may provide an enhanced affinity towards CO2 molecules. The gas adsorption property of 1' has been investigated by N2, CH4 and CO2, and it exhibits a high capacity and selectivity for CO2 over CH4.