Efficient and Selective Photocatalytic Transformation of CO2 to CO with Mo6 Clusters Supported on Fe-Doped g‑C3N4.

The carbon dioxide reduction reaction (CO2RR) driven by sunlight is expected to become a sustainable way of producing high-value compounds in the future. To achieve this goal, affordable and efficient photocatalysts still need to be discovered. In this work, we show that near-IR luminescent octahedral molybdenum iodido clusters decorated with isonicotinato ligands, (Bu4N)2[Mo6I8(O2CC5H4N)6] (Mo6), once combined with iron-doped carbon nitride (Fe-g-C3N4), provide the Mo6/Fe-g-C3N4 nanostructured materials, which are able to photocatalytically produce carbon monoxide (CO) from CO2 with high efficiency and selectivity. In a plausible mechanism, the Mo6 cluster acts as a photosensitizer, and its pyridine groups interact coordinatively with the embedded iron atoms, thus promoting the electronic conduction to the catalytic iron sites of the nanohybrid. The materials were characterized analytically, texturally, structurally, and spectroscopically using techniques such as inductively coupled plasma (ICP), specific surface area measurements, UV-vis-NIR diffuse reflectance spectra (DRS), powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM) coupled with energy-dispersive X-ray spectroscopy (EDS), and photoluminescence. The CO2RR studies showed that this association induces a change in the selectivity and a significant increase in CO production compared to that produced separately by the Mo clusters and graphitic precursors. Considering the versatility of this building block strategy for preparing multicomponent hybrid nanomaterials, molybdenum metal clusters are regarded as promising catalysts for creating eco-friendly and cost-effective photocatalysts for the CO2RR.