Biotemplate Fabrication of S-Modified Cu–Co-Based Nanocomposites for Tandem Hydrogenation of Nitroaromatics

Traditional hydrogenation requires noble metal catalysts and harsh conditions. To overcome these intrinsic drawbacks, herein, sulfur-doped Co₃O₄–CuO/CNS bicomponent nanocomposites were prepared using S-modified chitosan (CNS) as a template via the precipitation method. The experimental results demonstrated that the incorporation of sulfur (S) significantly enhanced the synergistic effect of the Cu–Co-based bimetallic system, thereby improving catalytic activity. Notably, Co₃O₄–CuO/CNS-10 exhibited remarkable catalytic performance in the hydrolytic dehydrogenation of sodium borohydride, achieving a hydrogen generation rate (HGR) of 357.9 mL·min^–1·g^–1_cat. Furthermore, Co₃O₄–CuO/CNS effectively catalyzed the tandem hydrogenation reduction of m-nitrobenzene (m-CNB) to m-nitroaniline (m-CAN) in the presence of sodium borohydride (NaBH₄), as evidenced by an m-CAN yield of up to 99.80% under highly mild conditions. Also, Co₃O₄–CuO/CNS-10 displayed high chemoselectivity and regioselectivity for the reduction of various aromatic nitro compounds containing potential reactive functional groups. The doping of sulfur promotes the bimetallic Cu–Co synergistic effects accompanied by the increases of the Co²⁺/Co³⁺ ratio and enriches oxygen vacancy defects on the surface, thereby enhancing the catalytic activity of the screened heterogeneous catalyst. This work highlights the key role of sulfur and provides an innovative strategy for elevating the catalytic reactivity of bimetallic nanocatalysts.