Nano-pyramid-type Co-ZnO/NC for hydrogen transfer cascade reaction between alcohols and nitrobenzene

A nano pyramid-like catalyst, Co-ZnO/NC, in which cobalt single atoms are deposited on highly dispersed ZnO nanoparticles supported by nitrogen-doped carbon, was prepared, and it exhibited excellent catalytic performance toward the catalytic hydrogen transfer cascade reaction between alcohols and nitro-compounds, which meets atom-economical and green requirements for obtaining imines. [Display omitted] •A hierarchical nano-pyramid Co-ZnO/NC was designed and obtained by a facile method.•Co single atoms were deposited on ZnO nanoparticles supported on nitrogen doped carbon.•Co-ZnO is state-of-the-art non-noble-metal catalyst toward imine synthesis by CHT cascade reaction.•Co SAs supported on ZnO reduced the reaction energy barrier of hydroxyl dehydrogenation. The catalytic hydrogen transfer (CHT) cascade reaction between alcohols and nitro- compounds meets green chemistry yet involves high catalyst requirements. Herein, a hierarchical nano-pyramid structure, in which cobalt single atoms (Co SAs) are deposited on highly dispersed ZnO nanoparticles supported by nitrogen-doped carbon (denoted as Co-ZnO/NC), was designed and obtained through pyrolysis of ZnCo-ZIF. The catalyst exhibited excellent catalytic performance toward the CHT cascade reaction, achieving a high nitrobenzene conversion (94 %), imine selectivity (97 %), and turnover frequency (8.8 h−1). This nano-pyramid is a state-of-the-art non-noble-metal catalyst and is comparable to noble-metal catalysts. Experimental and DFT results revealed that the Co SAs supported on ZnO reduced the reaction energy barrier of hydroxyl dehydrogenation, the first and rate-determining step in this heterogeneous catalysis. Furthermore, Co-ZnO/NC exhibits good recyclability and universality. Our findings offer a new catalyst for Schiff base synthesis and aid understanding of the roles of Zn in ZIF-derived carbon catalysts.