Polyoxometalate-induced 'cage-within-cage' metal-organic frameworks with high efficiency towards CO2 photoreduction

Photocatalytic CO2 reduction (CO2RR) into high-value products is of great significance not only in addressing global warming but also in developing sustainable energy resources. Herein, two novel metal-organic frameworks (MOFs) induced by polyoxometalates (POMs) have been successfully synthesized via a solvothermal method, formulated as {Zn-4(MoO4)(HCO2)(3)(C4H5N2)(3)}center dot DMF (Zn/Mo-MOF) and {Zn2Co2(MoO4)(HCO2)(3)(C4H5N2)(3)}center dot DMF (Zn/Co/Mo-MOF) [DMF = HCON(CH3)(2)]. The single crystal X-ray diffraction (SCXRD) analysis reveals that both MOFs contained MoO42- anions as the building units, which resulted from the decomposition of phosphomolybdic acid (H3PMo12O40). Notably, the cage beta in MOFs was constructed by MoO42- anions, and this cage was located outside and interconnected with independent cage alpha with a sodalite cage-type structure to arrange into a rare cage-within-cage structure. More interestingly, Zn/Co/Mo-MOF exhibited a remarkable CO production rate (38.41 mu mol h(-1)) with a high selectivity of 91.4% for the CO2 photoreduction, which outperforms most of the reported MOF-based photocatalysts. The result of this study demonstrates that the successful introduction of the POM's anions to construct MOFs may open up new opportunities to synthetize highly efficient MOF-based photocatalysts for the CO2 photoreduction.

Automated summary

The study successfully synthesized two novel MOFs, among which Zn/Co/Mo-MOF exhibited remarkable CO production rate and a high selectivity of 91.4% for CO2 photoreduction, outperforming most reported MOF-based photocatalysts.