Gradient oxygen-injecting MoS2 nanosheets catalyst boosting reductive C-N coupling of nitroarenes: Mechanistic insight into activity reconstruction

Abstract

It is very appealing to be able to improve the intrinsic activity of a low-cost MoS2 catalyst and broaden the adaptability of substrates in heterogeneous catalytic C-N bond formation from nitro compounds. A gradient oxygen-injection method was used in this study to regulate the electronic structure of the in-plane Mo site in the inert basal plane of the 2H-MoS2 nanosheet, resulting in a remarkable activity reconstruction in the reductive C-N coupling of nitroarenes with aromatic boronic acids. In the lattice of MoS2, gradient oxygen substitution results in structured changes of the in-plane Mo site, including crystal distortion brought on by asymmetric coordination and additive intergrown interfacial MoS2 and MoO3, which in turn contributes to the synergistic highly-active reactive sites of MoS2. Additionally, the interesting secondary activity reconstruction of the catalyst in the toluene solvent during the reaction can replace partial S sites with reactive intermediate oxygen, which results in a subsequent improvement in activity of the used catalyst. The effectiveness of the modified catalyst and the crucial role of the introduced oxygen concentration and alternate position around the Mo site of MoS2 in determining the adsorption and activation of nitro compound were validated through the implementation of various reaction experimental controls and density functional theory calculations. The N-O bond of nitrobenzene was specifically made weaker and easier to break by the addition of adjacent oxygen atoms around the Mo center, which aided the subsequent coupling process. Through altering the coordination environment of the active metal in the reductive coupling reaction of nitroarenes, this work offers some novel findings and new insights into the activity reconstruction of Mo-based catalysts.