Two 1D Anderson-Type Polyoxometalate-Based Metal–Organic Complexes as Bifunctional Heterogeneous Catalysts for CO₂ Photoreduction and Sulfur Oxidation

Abstract

Sulfur oxides from the combustion of petrol and excessive emissions of carbon dioxide (CO2) are currently the main causes of environmental pollution. Considerable interest has been paid to solving the challenge, and catalytic reactions seem to be the desired choice. Due to the high density of Lewis acid active sites, polyoxometalates are considered to be the ideal choice for these catalytic reactions. Herein, two captivating polyoxometalate-based metal–organic complexes, formulated as [Co(H2O)2DABT]2[CrMo6(OH)5O19] ({Co-CrMo6}) and [Zn(H2O)2DABT]2[CrMo6(OH)5O19] ({Zn-CrMo6}) (DABT = 3,3′-diamino-5,5′-bis(1H-1,2,4-triazole)) were successfully obtained under hydrothermal conditions. The structural analysis demonstrates that {Co-CrMo6} and {Zn-CrMo6} are isostructural with two different transition metal (Co/Zn) ions based on quadridentate Anderson-type [CrMo6(OH)5O19]4– polyanions. A fan-shaped unit of {Co-CrMo6}/{Zn-CrMo6} is linked to generate a one-dimensional (1D) ladder-like structure. Intriguingly, benefitting from rich Co centers with a suitable energy band structure, {Co-CrMo6} displays better photocatalytic activity than {Zn-CrMo6} for converting CO2 into CO, endowing the CO formation of 1935.3 μmol g–1 h–1 with high selectivity. Meanwhile, {Co-CrMo6} also exhibits a satisfactory removal rate of 99% for oxidizing dibenzothiophene at 50 °C, which suggests that {Co-CrMo6} may be utilized as a potential dual functional material with immense prospects in photocatalytic CO2 reduction and sulfur oxidation for the first time.