One-dimensional rare-earth La-MOFs coordinated with hexamethylenetetramine-Co MOFs derived highly efficient catalyst for cascade reaction of nitroarenes with alcohols☆

Abstract

A composite metal-organic frameworks (MOFs) structure, designated as Co-hmta@La-salen, was synthesized through coordination interactions between a one-dimensional lanthanum MOFs (La-salen) with high density of uncoordinated imine (–CH=N–) groups and a cobalt-based MOFs (Co-hmta) structure prepared using hydrogen bonding stacking with hexamethylenetetramine (hmta) as the organic ligand. Subsequently, the Co-hmta@La-salen composite was chosen as a template for the pyrolysis process to synthesize a La(OH)3 supported metallic Co catalyst incorporating carbon-nitrogen (Co/La(OH)3-CN-hmta) catalyst. The catalytic results show that Co/La(OH)3-CN-hmta (54% and 46% selectivity for aniline and N-phenylbenzylamine, respectively) displays superior cascade performance compared to classic Co/La(OH)3-CN-nit catalyst (69% and 31% selectivity for aniline and N-phenylbenzylamine, respectively). Moreover, the kinetic test results indicate that N-alkylation is the rate-limiting step of the overall cascade reaction. The Co/La(OH)3-CN-hmta catalyst can be separated from the reaction system using a magnet, and it also exhibits good cyclic stability. All of these suggest that the “MOFs plus MOFs via coordination” templating method can be employed as an efficient strategy for the preparation of supported catalysts.