Rational Preparation of Atomically Precise Non-Alkyl Tin-Oxo Clusters with Theoretical to Experimental Insights into Electrocatalytic CO2 Reduction Applications

Abstract

Tin oxides (SnO2) have been widely utilized in electronics, nanolithography, and catalysis. As the atomically precise models of SnO2, tin-oxo clusters (TOCs) not only provide opportunities for mechanism studies, but they also extend potential applications through structural modulation. However, to date, most of the reported TOCs belong to alkyl organotin complexes, which are usually toxic to the human body and the active sites are difficult to expose for catalysis. In this work, we successfully developed a green synthesis directly using SnCl4 as precursors to prepare unprecedented non-alkyl TOCs. Unlike the former alkyl TOCs with Sn–C bond (inert), the surface of the obtained TOCs is completely functionalized by Cl ions and pyrazole ligands (active). Both density functional theory (DFT) calculations and electrocatalytic experiments indicated that the non-alkyl Sn10 cluster presented better CO2 reduction reaction (CO2RR) activity than the classical alkyl-Sn12 cluster. Moreover, to get further insights into the active center for CO2RR, an isostructural Ti-substituted cluster of Sn4Ti6 with only Sn–Cl bonds was prepared. The comparable electrocatalytic CO2RR activities between Sn10–(Cl, pyrazole) and Sn4Ti6–Cl confirmed the critical active roles of Sn–Cl sites. This work will benefit the future design of SnO2 materials with environmentally friendly applications in CO2 conversion.