Defect engineering mediated molecules coordination activation for one-pot synthesis of secondary amine over Bi2MoO6 hierarchical microspheres

Bi2MoO6 hierarchical microspheres (BMO-SP) consisting of monolayer nanosheets with abundant surface oxygen defects and unsaturated Mo sites are constructed for the one-pot synthesis of secondary amine via a photocatalytic coupling reaction of nitrobenzene (NB) and benzyl alcohol (BA). The performance of this photocatalyst is 12 times higher than that of bulk Bi2MoO6 (BMO-bulk). Experiment results and density functional theory calculations reveal that surface oxygen defects induce more unsaturated Mo atoms facilitating the coordination activation of NB and BA molecules through the formation of –N–O···Mo and –C–O···Mo coordination, respectively. The surface oxygen defects also promote the separation of photogenerated carriers. More photogenerated holes transfer to the surface for oxidizing the activated BA while the photogenerated electrons are trapped by oxygen defects for reducing NB. Thus, the photocatalytic performance is markedly improved. This work successfully designs an efficient photocatalyst for the tandem reaction via surface defect engineering.