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 {(PO 3 CH 2 CH 2 PO 3 H) 4 Nb 8 O 16 } 4- ( Nb 8 P 8 ) has been achieved by a one-pot hydrothermal method. The ring is constructed from a tetragonal {Nb 8 O 36 } motif and four {PO 3 CH 2 CH 2 PO 3 H} ligands. Interestingly, Nb 8 P 8 can be joined together via K-H 2 O clusters {K 2 (H 2 O) 4 (OH) 2 } to form one-dimensional chains {[K 2 (H 2 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 [K 2 (H 2 O) 4 (OH) 2 ] Nb 8 P 8 }·3en·H 2 O ( 1 ). 1 exhibits good chemical and thermal stability and has a high water vapor adsorption capacity of ≤224 cm 3 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.