Heterogenized cobalt oxide catalysts for nitroarene reduction by pyrolysis of molecularly defined complexes

Abstract

Molecularly well-defined homogeneous catalysts are known for a wide variety of chemical transformations. The effect of small changes in molecular structure can be studied in detail and used to optimize many processes. However, many industrial processes require heterogeneous catalysts because of their stability, ease of separation and recyclability, but these are more difficult to control on a molecular level. Here, we describe the conversion of homogeneous cobalt complexes into heterogeneous cobalt oxide catalysts via immobilization and pyrolysis on activated carbon. The catalysts thus produced are useful for the industrially important reduction of nitroarenes to anilines. The ligand indirectly controls the selectivity and activity of the recyclable catalyst and catalyst optimization can be performed at the level of the solution-phase precursor before conversion into the active heterogeneous catalyst.

Green synthesis of nitriles using non-noble metal oxides-based nanocatalysts

“…Similarly, pyrolyzed metal salts on carbon without any phenanthroline ligand present gave only slight conversion (Table 1, entries 22-28). Notably, pyrolysis of metal-phenanthroline complexes showed varying catalytic activities (Table 1 [32][33][34][35]. To demonstrate the recycling of the catalyst, Co 3 O 4 -NGr/C was used for the benchmark reaction.…”

“…Last year, we reported the preparation of nanoscale cobalt and iron oxides, which constitute excellent catalysts for highly selective hydrogenation process 33,34 . We also showed that pyrolysis of metal acetatenitrogen ligated complexes on carbon leads to the formation of nanoscale metal oxides (Co 3 O 4 -NGr/C; Fe 2 O 3 -NGr/C), which are surrounded by nitrogen-doped graphene layers (NGr).…”

“…In the last decade, the development of non-noble metal-based catalysts [28][29][30][31] , especially nanomaterials [32][33][34] , for organic synthesis has become a prime topic and is crucial for the advancement of green and sustainable industrial processes. Last year, we reported the preparation of nanoscale cobalt and iron oxides, which constitute excellent catalysts for highly selective hydrogenation process 33,34 .…”

Magnetically Separable and Sustainable Nanostructured Catalysts for Heterogeneous Reduction of Nitroaromatics

“…Commercially, the reduction of nitroaromatics carried out in the gas phase using a nickel, copper or iron catalyst in the presence of various proton sources produces a large amount of wastes, which are environmentally undesirable [6]. In addition, high temperature and hydrogen pressure are other restrictions associated with these catalytic processes [7]. The classical methods for the hydrogenation of nitro compounds use various homogeneous transition-metal catalysts, e.g., Pd, Pt, Ru, etc.…”

Chemo‐selective reduction of nitro and nitrile compounds using Ni nanoparticles immobilized on hyperbranched polymer‐functionalized magnetic nanoparticles

“…Ni, Co, Fe and Cu metals or oxides). [47][48][49][50][51][52] To take advantage of these characteristics and also as a part of our ongoing research programme on the design of new catalysts for the development of useful and green synthetic methodologies, [15,16,[53][54][55][56][57][58][59] herein, we report a dendritic magnetic catalyst based on Ni(0) nanoparticles, an inexpensive non-noble metal, for selective hydrogenation of nitro and nitrile compounds in the presence of various reducible substituents such as carboxylic acid, ketone, aldehyde and halogen to the respective amines using NaBH 4 as the reducing agent in the aqueous phase. …”