Two novel nickel cluster substituted polyoxometalates: syntheses, structures and their photocatalytic activities, magnetic behaviors, and proton conduction properties

Two novel nickel cluster substituted polyoxometalates (POMs), H 7 Na 19 (H 2 O) 26 {Ni 12 (OH) 9 (PO 4 ) 4 (A-α-SiW 9 O 34 )[W 4 O 10 (OH)(PO 2 (OH) 2 ) 2 (A-α-SiW 9 O 34 ) 2 ]}·4C 2 H 8 N·27H 2 O ( 1 ) and H 26.5 K 2.5 Na(H 2 O) 16 [Ni 6 (OH)(BO 3 ) 2 (dien) 2 (B-α-SiW 10 O 37 ) 2 ] 2 ·24H 2 O ( 2 ) (dien = diethylenetriamine), have been successfully prepared. 1 is a Ni 12 -substituted POM comprised of a novel {Ni 12 (OH) 9 (PO 4 ) 4 } core, an A-α-{SiW 9 O 34 } unit and an uncommon {W 4 O 10 (OH)[PO 2 (OH) 2 ] 2 (A-α-SiW 9 O 34 ) 2 } fragment. 2 is a Ni 6 -substituted sandwich-type POM constructed from two B-α-{SiW 10 O 37 } units and an unusual boat-like {Ni 6 (OH)(BO 3 ) 2 (dien) 2 } cluster. Photocatalytic study reveals that 2 shows a moderate catalytic activity in visible-light-driven CO 2 reduction reactions. Additionally, the magnetic behaviors and the proton conduction performances of the compounds were investigated. A Ni 12 -substituted POM and a Ni 6 -substituted POM have been synthesized and characterized. The compounds show a moderate catalytic activity in visible-light-driven CO 2 reduction reactions, and can serve as potential proton conduction materials.