Syntheses, crystal structures, and water adsorption behaviors of jungle-gym-type porous coordination polymers containing nitro moieties

NO2 containing dicarboxylate bridging ligands, nitroterephthalate (bdc-NO2) and 2,5-dinitroterephthalate (bdc-(NO2)2), afford porous coordination polymers, {[Zn2(bdc-NO2)2(dabco)].solvents}n (2 contains solvents) and {[Zn2(bdc-(NO2)2)2(dabco)].solvents}n (3 contains solvents). Both compounds form jungle-gym-type regularities, where a 2D square grid composed of dinuclear Zn2 units and dicarboxylate ligands is bridged by dabco molecules to extend the 2D layers into a 3D structure. In 2 contains solvents and 3 contains solvents, a rectangle pore surrounded by eight Zn2 corners contains two and four NO2 moieties, respectively. Thermal gravimetry (TG) and X-ray powder diffraction (XRPD) measurements reveal that both compounds maintain the frameworks regularities without guest molecules and with solvents such as MeOH, EtOH, i-PrOH, and Me2CO. Adsorption measurements reveal that dried 2 and 3 adsorb H2O molecules to be {[Zn2(bdc-NO2)2(dabco)].4H2O}n (2 contains 4H2O) and {[Zn2(bdc-(NO2)2)2(dabco)].6H2O}n (3 contains 6H2O), showing the pore hydrophilicity enhancement caused by NO2 group introduction. - Graphical abstract: Two hydrophilic porous coordination polymers, [Zn2(bdc-NO2)2(dabco)]n (2, bdc-NO2=nitroterephthalate, dabco=1,4-diazabicyclo[2.2.2]octane) and [Zn2(bdc-(NO2)2)2(dabco)]n (3, bdc-(NO2)2=2,5-dinitroterephthalate), have been synthesized and characterized by single X-ray analyses, thermal gravimetry, and adsorption measurements.