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

NO 2 containing dicarboxylate bridging ligands, nitroterephthalate (bdc-NO 2) and 2,5-dinitroterephthalate (bdc-(NO 2) 2), afford porous coordination polymers, {[Zn 2(bdc-NO 2) 2(dabco)]· solvents} n ( 2⊃ solvents) and {[Zn 2(bdc-(NO 2) 2) 2(dabco)]· solvents} n ( 3⊃ solvents). Both compounds form jungle-gym-type regularities, where a 2D square grid composed of dinuclear Zn 2 units and dicarboxylate ligands is bridged by dabco molecules to extend the 2D layers into a 3D structure. In 2⊃ solvents and 3⊃ solvents, a rectangle pore surrounded by eight Zn 2 corners contains two and four NO 2 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 Me 2CO. Adsorption measurements reveal that dried 2 and 3 adsorb H 2O molecules to be {[Zn 2(bdc-NO 2) 2(dabco)]·4H 2O} n ( 2⊃4H 2O) and {[Zn 2(bdc-(NO 2) 2) 2(dabco)]·6H 2O} n ( 3⊃6H 2O), showing the pore hydrophilicity enhancement caused by NO 2 group introduction. Two hydrophilic porous coordination polymers, [Zn 2(bdc-NO 2) 2(dabco)] n ( 2, bdc-NO 2=nitroterephthalate, dabco=1,4-diazabicyclo[2.2.2]octane) and [Zn 2(bdc-(NO 2) 2) 2(dabco)] n ( 3, bdc-(NO 2) 2=2,5-dinitroterephthalate), have been synthesized and characterized by single X-ray analyses, thermal gravimetry, and adsorption measurements.