An Organodiphosphate-Containing Polyoxoniobate Ring and Its Assembly into a Three-Dimensional Framework through Hydrogen Bonding.

In this work, a novel organodiphosphate-containing inorganic-organic hybrid polyoxoniobate (PONb) ring {(PO3 CH2 CH2 PO3 H)4 Nb8 O16 }4- ( Nb 8 P 8 ) has been achieved by a one-pot hydrothermal method. The ring is constructed from a tetragonal {Nb8 O36 } motif and four {PO3 CH2 CH2 PO3 H} ligands. Interestingly, Nb 8 P 8 can be joined together via K-H2 O clusters {K2 (H2 O)4 (OH)2 } to form one-dimensional chains {[K2 (H2 O)4 (OH)2 ] Nb 8 P 8 } n and further linked by {Cu(en)2 }2+ (en = ethylenediamine) complexes, resulting in a three-dimensional supramolecular framework {[Cu(en)2 ]2 [K2 (H2 O)4 (OH)2 ] Nb 8 P 8 }·3en·H2 O ( 1 ). 1 exhibits good chemical and thermal stability and has a high water vapor adsorption capacity of ≤224 cm3 g-1 (22.71 mol·mol-1 ) at 298 K, outperforming most of the known polyoxometalate-based materials. Impedance measurements prove that 1 can transfer protons with moderate conductivity. This study not only contributes to the structural diversity of organodiphosphate-containing PONbs and PONb rings but also provides a reference for the development of PONb-based materials with unique performance.