Atomically dispersed Zn-NxCy sites on N-doped carbon for catalytic transfer hydrogenation of ethyl levulinate into γ-valerolactone

Abstract

Catalytic transfer hydrogenation (CTH) of biomass-derived carbonyl compounds provides a viable strategy to synthesize high value-added chemicals and biofuels, for which the development of efficient catalysts still remains a formidable challenge. Here, we report a Zn-based single-atom catalyst (Zn/NC-950), prepared by pyrolysis of ZIF-8 at 950 °C, for the CTH of ethyl levulinate to γ-valerolactone (GVL). This catalyst exhibited excellent performance, affording a GVL selectivity of 95.3 % at an ethyl levulinate conversion of 100 %, using isopropanol as the hydrogen source at 200 °C and autogenous pressure. The structural characterization and theoretical calculation demonstrate that such extraordinary efficacy of the Zn/NC-950 catalyst is attributed to the dual Zn-N3C1 and Zn-N2C2 sites of low Zn oxidation states, which work synergistically to generate the active hydrogen species and activate the carbonyl bonds, respectively. This work provides a rationale for the precise design of the non-noble metal single-atom catalysts efficient for the biomass valorization.