Zn-single atom catalysts enable the catalytic transfer hydro-genation of α,β-unsaturated aldehydes

Abstract

Abstract Highly active non-precious metal single-atom catalysts (SACs) toward catalytic transfer hydrogenation (CTH) of α, β-unsaturated aldehydes is of great significance, but still is deficient. Herein, we report that the Zn-N-C SACs containing ZnN3 moieties can catalyze the cinnamaldehyde (CAL) to cinnamyl alcohol (COL) with a conversion of 95.5% and selectivity of 95.4% under a mild temperature and atmospheric pressure, which is the first case of Zn species-based catalysts for the CTH reaction. More impressively, the catalytic activity is dependent on the coordination number of the active Zn-metal atoms, and the optimized Zn-N-C SACs even outperformed most of the reported precious metals-based catalysts in catalytic performance. Isotopic labeling and in situ FT-IR spectroscopy indicate that two reactants were co-absorbed at the Zn sites to proceed CTH via a "Meerwein-Ponndorf-Verley" mechanism, which is supported by the DFT calculations. DFT calculations also reveal that the outstanding catalytic activity of ZnN3 moieties stemmed from the suitable adsorption energy and favorable reaction energy of the rate-determining step at the Zn active sites. Our findings demonstrate that Zn-N-C SACs hold extraordinary activity toward CTH of α, β-unsaturated aldehydes, and thus provide a promising approach to explore the advanced SACs for achieving high value-added chemicals.