Two Comparable Isostructural Microporous Metal-Organic Frameworks: Better Luminescent Sensor and Higher Adsorption Selectivity for the Fluorine-Decorated Framework: Isostructural Microporous Metal-Organic Frameworks

Two isostructural 3D metal–organic frameworks (MOFs), {[Zn3(tzba)3(dabco)]·5DMF·3H2O} (1) and {[Zn3(F-tzba)3(dabco)]·5DMA·3H2O} (2) [tzba = 4-(1H-tetrazol-5-yl) benzolate, F-tzba = 2-fluoro-4-(1H-tetrazol-5-yl) benzolate, dabco = triethylenediamine], were solvothermally synthesized from a tetrazolate–carboxylate bifunctional linker and a diamine ligand. The framework contains an uncommon metal–tetrazolate–carboxylate linear trinuclear Zn3(ttaz)3(COO)3 (ttaz = tetrazolyl) cluster, which serves as an eight-connected node to afford a 3D porous network. Both 1 and 2 show strong photoluminescence and selective luminescent quenching for Cu2+ ions and nitrobenzene relative to that shown by other metal ions (e.g., Na+, K+, Mg2+, Ca2+, Mn2+, Co2+, Ni2+, Cd2+, and Pb2+) and organic solvents (e.g., methanol, ethanol, acetonitrile, n-propanol, 2-propanol, ethyl acetate, toluene, dichloromethane, N,N′-dimethylformamide, and N-methylpyrrolidone). It is interesting to find that relative to 1, 2 decorated with F atoms exhibits more efficient luminescent sensing for these two guests. Furthermore, 2 also adsorbs more CO2 and has higher CO2/CH4 adsorption selectivities than 1 under the same conditions, which can be ascribed to the CO2-philic F sites in the pores of 2. These advantages make 2 a promising material in both luminescent sensors and CO2 separation from a CO2/CH4 mixture.