A flexible, porous, cluster-based Zn-pyrazolate-dicarboxylate framework showing selective adsorption properties

Abstract

A flexible Zn-pyrazolate-carboxylate framework [Zn₇O₂(deppy)₂(oba)₄]·2.5DMF·2H₂O (1) (Hdeppy = 3,5-diethyl-4-(4′-pyridyl)pyrazole, H₂oba = 4,4′-oxobisbenzoic acid) was synthesized by solvothermal reaction. Single-crystal X-ray diffraction indicated that 1 possesses a 10-connected bct topological network based on a rare heptanuclear zinc(II) cluster. Comparison of crystal structures of 1 determined at 300 K and 150 K illustrated the conformational flexibility of deppy⁻ ligands. Thermogravimetry analyses and powder X-ray diffraction measurements showed that 1 has high thermal stability and good water stability. Gas and liquid sorption experiments of 1 not only showed stronger adsorption of CO₂ compared with N₂, but also demonstrated highly efficient separation of n-propylbenzene from other C₉H₁₂ alkylbenzene isomers 1,2,4-trimethylbenzene and 1,3,5-trimethylbenzene.