Two bimetal-doped (Fe/Co, Mn) polyoxometalate-based hybrid compounds for visible-light-driven CO 2 reduction.

Two polyoxometalate (POM)-based hybrid compounds have been successfully designed and constructed by the hydrothermal method with molecular formulas [K(H 2 O) 2 FeII0.33Co 0.67 (H 2 O) 2 (DAPSC)] 2 {[FeII0.33Co 0.67 (H 2 O)(DAPSC)] 2 [FeII0.33Co 0.67 (H 2 O) 4 ] 2 [Na 2 FeIII4P 4 W 32 O 120 ]}·21.5H 2 O (1), and [Na(H 2 O) 2 FeII0.33Mn 0.67 (H 2 O) 2 (DAPSC)] 2 {[FeII0.33Mn 0.67 (H 2 O)(DAPSC)] 2 [FeII0.33Mn 0.67 (H 2 O) 4 ] 2 [Na 2 FeIII4P 4 W 32 O 120 (H 2 O) 2 ]}·24H 2 O (2) (DAPSC = 2,6-diacetylpyridine bis-(semicarbazone)), respectively. Structural analysis revealed that 1 and 2 consisted of metal-organic complexes containing DAPSC ligands with dumbbell-type inorganic clusters, iron-cobalt (iron-manganese) and some other ions. By utilizing a combination of strongly reducing {P 2 W 12 } units and bimetal-doped centres the CO 2 photoreduction catalytic capacity of 1 and 2 was improved. Notably, the photocatalytic performance of 1 was much better than that of 2. In CO 2 photoreduction, 1 exhibited CO selectivity as high as 90.8%. Furthermore, for 1, the CO generation rate reached 6885.1 μmol g -1 h -1 at 8 h with 3 mg, and its better photocatalytic performance was presumably due to the introduction of cobalt and iron elements to give 1 a more appropriate energy band structure. Further recycling experiments indicated that 1 was a highly efficient CO 2 photoreduction catalyst, which could still possess catalytic activity after several cycles.