Urea-based flexible dicarboxylate linkers for three-dimensional metal-organic frameworks

The metal-organic frameworks (MOFs) 3D-[Mn-2(L1)(2)(DMF)]center dot 2DMF (1), 3D-[Cd-2(L2)(2)(DMF)(3)] (3), [Zn-2(L2)(2)(DMF)(3)] (4) and 3D-[Mn-2(L2)(2)(DMF)(3)] (5) are the first examples of three-dimensional metal-organic networks constructed from a single ditopic dicarboxylate linker (i. e., without bridging co-ligands) with an urea group in the linker axis (L1(2) = 4,4'-(carbonylbis(azanediyl)) dibenzoate; L2(2) = 4,4'-( carbonylbis(azanediyl))bis(3-methylbenzoate), DMF = dimethylformamide). From Cd2+ and L1(2) a 1D coordination polymer 1D-[Cd(L1)(DMF)(3)] (2) is formed. The urea group is engaged in hydrogen bonding with the C(4)[R-2(1) (6)] motif to an oxygen atom of a DMF solvent (in 1) or a metal-coordinated carboxylate group (in 3-5). Network 1 has infinite channels with parallelepiped cross sections and 30% solvent-filled volume. The 3 D frameworks 3-5 are of diamond (6,6), dia topology with a single framework having large voids with 17.6 angstrom and 19.7 angstrom nodal separation. Thus, four symmetry-related nets interpenetrate, organized via H-bonds in the C(4)[R-2(1) (6)] motif, still leaving about 50% solvent-filled void volume in the fourfold interpenetrated structure. (C) 2017 Elsevier B.V. All rights reserved.