Triple Framework Interpenetration and Immobilization of Open Metal Sites within a Microporous Mixed Metal–Organic Framework for Highly Selective Gas Adsorption

A three-dimensional triply interpenetrated mixed metal–organic framework, Zn₂(BBA)₂(CuPyen)·G_<i>x</i> (<b>M’MOF-20</b>; BBA = biphenyl-4,4′-dicarboxylate; G = guest solvent molecules), of primitive cubic net was obtained through the solvothermal reaction of Zn­(NO₃)₂, biphenyl-4,4′-dicarboxylic acid, and the salen precursor Cu­(PyenH₂)­(NO₃)₂ by a metallo-ligand approach. The triple framework interpenetration has stabilized the framework in which the activated <b>M’MOF-20a</b> displays type-I N₂ gas sorption behavior with a Langmuir surface area of 62 m² g^–1. The narrow pores of about 3.9 Å and the open metal sites on the pore surfaces within <b>M’MOF-20a</b> collaboratively induce its highly selective C₂H₂/CH₄ and CO₂/CH₄ gas separation at ambient temperature