A three-dimensional porous Zn metal-organic framework (UPC-12) with high thermal and chemical stability was isolated in high yield and purity from a hydrothermal reaction. UPC-12 exhibits high selectivity for CO2 due to the formation of hydrogen bonds between CO2 molecules and the -COOH groups exposed inside the channels and the effective pi-pi interactions between CO2 molecules and the pillared bipyridine moieties of the MOF. The adsorption desorption process was studied, for the first time, by both C-13 CP-TOSS NMR spectroscopy and in situ DRIFTS.