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

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.