Non-interpenetrated Cu-based MOF constructed from a rediscovered tetrahedral ligand

A systematic expansion of the well-known non-interpenetrated and robust MOF-11 was accomplished through a rediscovery of the ligand tetrakis(4-carboxyphenyl)adamantane (L). The combination of a rigid tetrahedral L and copper(II) paddle-wheel secondary building unit (SBU) resulted in a stable non-interpenetrated metal–organic framework, UOF-1 (UOF = University of Otago framework), with the predicted PtS topology. This MOF exhibits permanent porosity, as established by X-ray diffraction (XRD) and gas adsorption studies. This low-density open framework possesses one open-metal site per Cu(II) cation which could be accessed by employing appropriate activation techniques such as the use of supercritical CO2 (s-CO2) or dry CH2Cl2. CO2 gas displayed higher affinity towards activated UOF-1 than CH4 and N2 gases at room temperature and low pressure. UOF-1 displayed excellent selectivity for CO2 over N2 of 52 : 1 at practical operating conditions of 15 : 85 CO2 : N2 mixture at 273 K and 1 bar.