In Situ Synthesized Silica‐Supported Co@N‐Doped Carbon as Highly Efficient and Reusable Catalysts for Selective Reduction of Halogenated Nitroaromatics

Abstract

Silica-supported Co@N-doped carbon (Co@CN/SiO 2) catalysts were first prepared by a one-step impregnation with a mixed solution of cobalt nitrate, glucose and urea, followed by in situ carbonization and reduction. The Co@CN/SiO 2 catalysts were investigated for the selective reduction of nitro aromatics to the corresponding anilines using hydrazine hydrate. The Co@CN/ SiO 2-500 carbonized at 500°C exhibited the highest catalytic activity and excellent stability without any decay of activity after 6 cycles for the reduction of nitrobenzene. Both metallic Co atoms and CoÀ N species formed in the Co@CN/SiO 2 catalysts were active, but the CoÀ N species were dominant active sites. The high activities of the Co@CN/SiO 2 catalysts were attributed to the synergistic effect between the Co and N atoms, promoting heterolytic cleavage of hydrazine to form H + /H À pairs. Representative examples demonstrated that the Co@CN/ SiO 2-500 could completely transform various halogen-substituted nitro aromatics to the corresponding halogenated anilines with high TOFs and selectivity of > 99.5 %.

An intriguing tetranuclear Rh-based polyoxometalate for the reduction of nitroarene and oxidation of aniline

“…1,2 However, less-controllable reaction selectivity, use of transition metal catalysts (e.g., Pb and Pt), and harsh reaction conditions are still ongoing challenges in the conventional methods of synthesizing anilines. 3,4 Although the conversion of nitrobenzene to aniline has gotten a lot of attention in recent years, it also faces environmental and economic obstacles. 5,6 Thus, developing a photo-catalyst with a suitable energy level capable of efficiently triggering the reduction of nitrobenzene to aniline under visible light illumination possesses considerable research interest under these circumstances.…”

Expanding the interlamellar spacing of biomass-derived hybrids with intercalated nanotubes for enhanced oxygen reduction reaction

“…4c, the Co 2p spectra of these samples were divided into three peaks centered at 778.5 eV, 780.8 eV, and 785.5 eV, corresponding to metallic Co, Co 2+ , and a satellite peak derived from Co 2+ , respectively. 33,50 Co 2+ with a binding energy of 780.8 eV was reported to be due to Co-N bonds, corresponding to the appearance of Co-N in the N 1s energy level. 30,51,52 Thereafter, the relative percentage of Co 2+ and metallic Co in Co@NC and Co@NC-CNT calculated according to their area is 26.7%, 2.2 at% and 42.7%, 2.8 at%, respectively, indicating that most cobalt atoms on the surface of the catalysts exist in the oxidized state.…”

A uniformly anchored zirconocene complex on magnetic reduced graphene oxide (rGO@Fe3O4/ZrCp2Clx(x= 0, 1, 2)) as a novel and reusable nanocatalyst for synthesis ofN-arylacetamides and reductive-acetylation of nitroarenes

“…60 In this context, heterogenization of metal catalysts through the immobilization of transition metals species on solid supporters is the widely used strategy in organic synthesis. [61][62][63][64][65][66][67][68] Furthermore, the catalytic formation of amide bonds is one of the most intended procedures in the synthesis of various organic compounds including polymers, agrochemicals, pharmaceuticals and fragrances. 69 Due this, acetylation of arylamines and reductive-acetylation of aromatic nitro compounds by acetic anhydride are the commonly used strategies for the preparation of N-arylacetamides.…”

“…60 In this context, heterogenization of metal catalysts through the immobilization of transition metals species on solid supporters is the widely used strategy in organic synthesis. 61–68…”