MOFs with PCU Topology for the Inclusion of One-Dimensional Water Cages: Selective Sorption of Water Vapor, CO2, and Dyes and Luminescence Properties

A rigid pyridine-3,5-bis(5-azabenzimidazole) ligand (L) and linear dicarboxylate sodium terephthalate (TPA) with Cd(II), Zn(II), and Co(II) under solvothermal conditions afforded water stable and nitrogen-rich MOFs with general formulas [Cd2L2(TPA)(2)]center dot 12H(2)O}(n), 1, [Zn4L4(TPA)(4)] center dot(DMF)center dot 16H(2)O}(n), 2, and {[Co2L2(TPA)(2)]center dot 12H(2)O}(n), 3, respectively. These MOFs are found to contain doubly interpenetrated pm networks with hydrophilic channels. The networks are propagated by M-2(CO2)(2) SBUs (intermetallic distances 4.0 angstrom) which leads to the formation of a two-dimensional grid structure of metal-terephthalate. The shape of grids varies from rhomboidal to squaric depending on the presence of a metal center. The channels of these MOFs are occupied by the one-dimensional water cages. In the pcu network, each cuboid is found to have, dimensions of similar to 12.5 angstrom as width and 18.5 angstrom as length. They have shown an excellent ability for water vapor sorption (180-225 cc/g at 298 K). Further, CO2 is found to be the preferred sorbent (70 cc/g at 273 K) over N-2. They were also shown to be capable of dye (methylene blue and crystal violet) removal from aqueous solutions through adsorption. Further, Cd(II) and Zn(II) MOFs are found to exhibit solid state luminescence properties.