Exploring the potential of nanosized oxides of zinc and tin as recyclable catalytic components for the synthesis of cyclic organic carbonates under atmospheric CO2 pressure

Nanomaterials based on tin (IV) oxide (SnO2) and zinc oxide (ZnO) were investigated in the search for active, environmentally benign, and inexpensive materials for the crucial reaction of CO2 cycloaddition to epoxides to afford cyclic carbonates. In particular, nanoparticles (NPs), nanorods (NRs), nanosheets (NSs) and microplates (µPLs) were prepared and used in combination with small amounts of TBAI (tetrabutylammonium iodide) as the nucleophile. Different from the general case of metal oxides, often requiring harsh reaction conditions, the most active compound in this study, SnO2-NPs, served as an active material for the cycloaddition of CO2 to several terminal epoxides under atmospheric pressure at moderate temperatures (60–80 °C) and could also be employed for converting internal epoxides under harsher conditions. Importantly, SnO2-NPs could also be used in the presence of impure CO2 feeds (20% methane in CO2) resembling low calorific landfill gas and could be recycled and reused. Overall, SnO2-NPs represent a promising, readily available, and inexpensive metal oxide-based material to produce cyclic carbonates under atmospheric CO2 pressure.