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

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.