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⊃solvents) and {[Zn2(bdc-(NO2)2)2(dabco)]·solvents}n (3⊃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⊃solvents and 3⊃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⊃4H2O) and {[Zn2(bdc-(NO2)2)2(dabco)]·6H2O}n (3⊃6H2O), showing the pore hydrophilicity enhancement caused by NO2 group introduction.