Alkali halides induced electron-deficient oxygen vacancies on polyoxometalates promoting CO2 hydrogenation

The development of catalysts for the efficient catalytic conversion of CO₂ remains a significant challenge. Herein, a series of alkali halide-modified polyoxometalate (POM) catalysts with substituted Ru single atoms were constructed for efficient CO₂ hydrogenation. Characterization using XRD, ESI-MS, in-situ FT-IR, HAADF-STEM and XAFS confirmed that the single-atom Ru were incorporated into the POM framework. Notably, the introduction of LiCl modulating electron-deficient oxygen vacancies (O_V) on the POM surface can effectively promote the dissociation of H₂. Moreover, the single-atom Ru facilitated the adsorption of CO₂ and formed the bidentate carbonate intermediate (b-CO₃). Then, the reactive hydrogen species on the O_V sites enhanced the selective hydrogenation of CO₂ to CO, thereby promoting the reverse water gas shift (RWGS) reaction. In-situ RWGS reaction FT-IR and DFT calculations jointly revealed the synergistic effect of electron-deficient O_V and single-atom Ru on promoting H₂ dissociation and CO₂ adsorption. In addition, the CO produced from the RWGS reaction can be subsequently utilized in the hydroformylation of olefins using a conventional catalytic system consisting of rhodium complex and phosphine ligands, thereby achieving the conversion of CO₂ into valuable chemicals.