Rare Three-Dimensional Uranyl-Biphenyl-3,3'-disulfonyl-4,4'-dicarboxylate Frameworks: Crystal Structures, Proton Conductivity, and Luminescence.

Due to the intrinsic coordination preference of the linear uranyl unit, uranyl-organic frameworks (UOFs) are generally prone to exhibiting low-dimensional structures. Reactions of uranyl nitrate with biphenyl-3,3'-disulfonyl-4,4'-dicarboxylic acid dipotassium salt (KHBPDSDC) under different conditions led to three UOFs, namely, {(MeNH)[K(UO)(μ-O)(μ-OH)(μ-OH)(BPDSDC)(HO)]·4DMF} (), {[K(UO)(μ-O)(BPDSDC)(HO)]} (), and {(MeNH)[K(UO)(BPDSDC)(HO)]} (). Compounds and contain one-dimensional (1D) ribbon structures formed from UO units bridged by μ-O atoms and carboxylate groups. The 1D ribbons in are linked by K atoms to form a two-dimensional (2D) layer, which is further pillared by the biphenyl units to give a three-dimensional (3D) framework. For , the oxygen atoms of UO units in each 1D ribbon bridge the K atoms to form four -[K-O-K]- infinite chains located above and below the ribbon. The 1D ribbons in are bridged by sulfonate groups to generate a 3D substructure featuring 1D channels occupied by biphenyl moieties. In , each mononuclear [(UO)(COO)] unit is bridged by three K atoms to form a 3D substructure featuring 1D small left-handed and large righted helical channels occluded by biphenyl moieties. Compound exhibits an excellent proton conductivity with the highest conductivity of 1.07 × 10 S cm. The inner walls of 1D channels of are full of the hydrophilic sulfonate groups, which boost enrichment of the guest water molecules, thus resulting in a high proton conductivity. Finally, temperature dependence of fluorescent studies showed that compounds and display the characteristic uranyl emissions. This work presents the elegant examples of the rarely explored 3D UOFs and expands the potentials of UOFs.