Topologies of Metal−Organic Frameworks Based on Pyrimidine-5-carboxylate and Unexpected Gas-Sorption Selectivity for CO₂

A simple and multitopic ligand, pyrimidine-5-carboxylate (pmc), has been used to obtain a series of metal−organic frameworks (MOFs) based on Co2+, Cd2+, and Cu2+. The networks possess well-defined topologies of body-centered-cubic, rutile, and interpenetrated NbO structures, respectively. Among those, [Cu(pmc)2] possesses a permanent porosity resulting from straight one-dimensional channels of 5.5 Å free passages. Unexpectedly, this porous MOF displays a highly selective sorption behavior for CO2, and the sorptions of N2, Ar, O2, H2, and CH4 at two different temperatures are found to be negligible. The results of diffraction and spectroscopic analyses exclude framework dynamics or incomplete evacuation as the origin of the gas-sorption selectivity.