Two 2D Layered P₄Mo₆ Clusters with Potential Bifunctional Properties: Proton Conduction and CO₂ Photoreduction

Two hourglass-type molybdophosphate hybrids with the formulas [Cd(H 2 O) 2 DABT] 4 [Cd(H 7 P 4 Mo 6 O 31 ) 2 ]·19H 2 O ( 1 ) and (C 2 H 5 OH)(C 3 H 5 N 2 ) 6 [Co 3 (H 6 P 4 Mo 6 O 31 ) 2 ]·H 2 O ( 2 ) (DABT= 3,3′-diamino-5,5′-bis(1H-1,2,4-triazole)) have been successfully designed and synthesized via a hydrothermal method. Structure analysis revealed that the inorganic moieties in compounds 1 and 2 are made up of hourglass-type {M[P 4 Mo 6 ] 2 } (M = Cd/Co) structure, which were constructed by two (P 4 Mo 6 ) units with single transition metal (TM) (Cd/Co) atom as the central metal. The {M[P 4 Mo 6 ] 2 } (M = Cd/Co) structures were then further connected by TM to constitute a 2D layered structure. Surprisingly, under the condition of 60 °C and 98% RH, compounds 1 and 2 exhibited excellent proton conductivity of 1.35 × 10 –3 and 3.78 × 10 –3 S cm –1, respectively. Furthermore, compound 2 can act as heterogeneous catalyst for CO 2 photoreduction, which indicates that it may be a bifunctional POM-based material with great promise.