Inorganic–Organic Hybrid Polyoxoniobates: Polyoxoniobate Metal Complex Cage and Cage Framework

Abstract The combination of polyoxoniobates (PONbs) with 3d metal ions, azoles, and organoamines is a general synthetic procedure for making unprecedented PONb metal complex cage materials, including discrete molecular cages and extended cage frameworks. By this method, the first two PONb metal complex cages K 4 @{[Cu 29 (OH) 7 (H 2 O) 2 (en) 8 (trz) 21 ][Nb 24 O 67 (OH) 2 (H 2 O) 3 ] 4 } and [Cu(en) 2 ]@{[Cu 2 (en) 2 (trz) 2 ] 6 (Nb 68 O 188 )} have been made. The former exhibits a huge tetrahedral cage with more than 120 metal centers, which is the largest inorganic–organic hybrid PONb known to date. The later shows a large cubic cage, which can act as building blocks for cage‐based extended assembly to form a 3D cage framework {[Cu(en) 2 ]@{[Cu 2 (trz) 2 (en) 2 ] 6 [H 10 Nb 68 O 188 ]}}. These materials exhibit visible‐light‐driven photocatalytic H 2 evolution activity and high vapor adsorption capacity. The results hold promise for developing both novel cage materials and largely unexplored inorganic–organic hybrid PONb chemistry.