Zn Single-Atom Catalysts Enable the Catalytic Transfer Hydrogenation of α,β-Unsaturated Aldehydes

Abstract

Highly active nonprecious-metal single-atom catalysts (SACs) toward catalytic transfer hydrogenation (CTH) of α,βunsaturated aldehydes are of great significance but still are deficient. Herein, we report that Zn−N−C SACs containing Zn−N 3 moieties can catalyze the conversion of cinnamaldehyde to cinnamyl alcohol 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 heterogeneous catalysts for the CTH reaction. Isotopic labeling, in situ FT-IR spectroscopy, and DFT calculations indicate that reactants, coabsorbed at the Zn sites, proceed CTH via a "Meerwein−Ponndorf− Verley" mechanism. DFT calculations also reveal that the high activity over Zn−N 3 moieties stems 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 reactions and thus provide a promising approach to explore the advanced SACs for high-value-added chemicals.

Regulating Second-Shell Coordination in Cobalt Single-Atom Catalysts toward Highly Selective Hydrogenation

“…The hydrogenation behavior of p -CNB over the Co-SACs, including Co 1 N 4 , Co 1 N 4 –S L , and Co 1 N 4 –S M , was further evaluated using DFT calculations. − According to the calculated subreaction free energy and rate-determining reaction step (Figure S21), the hydrogenation of the NO 2 group in p -CNB was established, which proceeded via *ONO → *ONOH → *ON (+H 2 O) → *ONH → *ONHH → NH 2 (+*OH → H 2 O), where * stands for the adsorption on Co-SACs (Figure a). When p -CNB approached the Co-SACs, the oxygen atom of NO 2 was much preferable to be adsorbed by the Co atom, compared with the Cl atom (Figure S22).…”