Selective CO2 Fixation to Styrene Oxide by Ta-Substitution of Lindqvist-Type [(Ta,Nb)6O19]8− Clusters

Metal oxide clusters composed of group 5 metal ions, such as Nb and Ta, exhibit catalytic activities for CO2 fixation to styrene (SO) due the highly negative natural bonding charge terminal O atoms that could work activation sites. In this study, tetrabutylammonium (TBA) salts [TaxNb6−xO19]8− (TBA-TaxNb6−x, x = 0–6) were prepared Ta-substitution effect on properties TBA-TaxNb6−x SO was investigated. We found TBA-Ta1Nb5 shows highest carbonate (SC) selectivity (95%) among TBA-TaxNb6−x, although conversion monotonously increases with incremental Ta substitution amount. The under various conditions in situ X-ray absorption fine structure measurements reveal is activated both sites coordinated (terminal OTa) ONb) sites, whereas proceeds OTa and/or bridge are connected Ta. Density functional theory (DFT) calculations preferentially adsorbs compared other ONb base conclude selective at without a crucial factor high SC SO.