Size-Tunable Carbon-Doped Ni Nanoparticles for Switchable Reductive Amination of Biomass-Derived Carbonyl Compounds to Primary Amines and Secondary Imines

Reductive aminations of biomass-derived carbonyl compounds, an industrially important class of reactions applied for green and sustainable production of valuable amines/imines, often suffer from problems of selectivity toward the target product and reusability of the catalyst. Herein, we develop a facile strategy to synthesize two carbon-doped Ni catalysts with particle sizes of 7.5 and 47.5 nm, respectively, over which the selectivity in the reductive amination of biomass-derived carbonyl compounds is completely switched between primary amines (>96% yield, 7.5 nm) and secondary imines (>97% yield, 47.5 nm). The synthesis is derived from the confined pyrolysis of Ni-Al layered double hydroxides (NiAl-LDH) grafted on hollow polymer nanospheres (HPS), in which the HPS play four roles (i.e., template, reductant, carbon resource, and Ni size controller). The two catalysts exhibit excellent stability due to the existence of surface Ni-C-x species. Reductive aminations over these two catalysts have a broad substrate scope and can be scaled up to the gram level, indicating the potential for industrial applications.