Two three-dimensional polyanionic clusters [M(P4Mo6)2] (M = Co, Zn) exhibiting excellent photocatalytic CO2 reduction performance

Abstract

Two captivating {P₄Mo₆}-based compounds, formulated as (H₂bbi)₂{[Co₂(bbi)][Co_2.33(H₂O)₄][H_9.33CoP₈Mo₁₂O₆₂]}·4H₂O (1) and (H₂bbi){[Zn(Hbbi)]₂[Zn_0.75(bbi)][K₂Zn(H₂O)₄][H_8.5ZnP₈Mo₁₂O₆₂]} (2) [bbi = 1,1′-(1,4-butanediyl)bis(imidazole)], were successfully synthesized under hydrothermal conditions. Structural analysis demonstrates that compounds 1 and 2 are constructed from hourglass-shaped structures [M(P₄Mo₆O₃₁)₂]ⁿ⁻ (M = Co, Zn), which are all made up of molybdophosphates and one transition metal ion as the central connecting node. Compounds 1 and 2 feature three-dimensional (3D) frameworks, which are all connected to form a 3D structure by metal ions and bbi ligands. More interestingly, compound 1 exhibits higher catalytic activity than 2 in CO₂ photoreduction due to the suitable energy band structure of Co species in {P₄Mo₆} clusters. The CO yield was 3261 μmol g⁻¹ with high selectivity in 8 h for compound 1 in photocatalytic CO₂ reduction, which is highly promising in the photocatalytic field. Additionally, the photoluminescence properties of 2 were investigated.