Long rigid ligand induced basket-type phosphomolybdate photo-/electro-catalytic materials

Abstract

Long rigid ligand induced two basket-type inorganic–organic hybrid materials, (H₄btb)₂[Sr⊂P₆Mo^V₂Mo^VI₁₆O₇₃]·2H₂O (1) and (H₄bbtb)(H₂bbtb)₄[{Fe^III(H₂O)₄Na(H₂O)₂}{Sr⊂P₆Mo^V₂Mo^VI₁₆O₇₃}₂]·2H₂O (2) (btb = 4,4-bis(1-H-1,2,4-triazol-1-yl)biphenyl, bbtb = 1,4-bis(benzotriazol-1-3-ly) benzene), have been hydrothermally synthesized and fully characterized. Compounds 1 and 2 contain 2-electron reduced basket-type polyoxoanion {Sr⊂P₆Mo^V₂Mo^VI₁₆O₇₃} (abbreviated as {P₆Mo₁₈O₇₃}) as a basic cluster unit. In compound 1, adjacent btb molecules are parallel to each other and interconnect via π–π interactions to form two kinds of dimeric ligand units, which are further linked alternately via weak interactions to yield a unique pure organic double chain. The basket cluster grafts onto the chain in the ABAB mode via intensive hydrogen bond interactions leading to an organic–inorganic supramolecular layer along the [011] direction. Meanwhile, each basket polyoxoanion connects to two adjacent basket cages via supramolecular interactions to form a 1D supramolecular chain along the [001] direction. The 2D layer and 1D chains intersect with each other to form a 3D network with basket cages as junctions. Compound 2 is a dimeric string connected by {Na(H₂O)₂} and {Fe(H₂O)₄} units, and is the first basket dimer chain linked by a mixed metal linker. The protonated ligand bbtb connects adjacent dimeric chains to yield a 2D supramolecular layer and a 3D network via extensive supramolecular interactions. They display dual functions of electrocatalytic properties and efficient photocatalytic performance for the degradation of refractory dye Azon Phloxine (AP) under UV light.