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

Abstract

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]·12H2O}n, 1, {[Zn4L4(TPA)4]·(DMF)·16H2O}n, 2, and {[Co2L2(TPA)2]·12H2O}n, 3, respectively. These MOFs are found to contain doubly interpenetrated pcu networks with hydrophilic channels. The networks are propagated by M2(CO2)2 SBUs (intermetallic distances 4.0 A) 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 ∼12.5 A as width and 18.5 A 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 c...