Phyllosilicate‐derived Nickel‐cobalt Bimetallic Nanoparticles for the Catalytic Hydrogenation of Imines, Oximes and N‐heteroarenes

Abstract

The development of cost-effective, noble metal-free catalytic systems for the hydrogenation of unsaturated aliphatic, aromatic, and heterocyclic compounds is fundamental for future valorization of general feedstock. With this aim, we report here the preparation of highly dispersed bimetallic Ni/Co nanoparticles (NPs), by a one-pot deposition-precipitation of Ni and Co phases onto mesoporous SBA-15 silica. By adjusting the chemical composition in the starting mixture, three supported catalysts with different Ni to Co weight ratios were obtained, which were further subjected to treatments under reducing conditions at high temperatures. Characterization of the resulting solids evidenced a homogenous distribution of Ni and Co elements forming the NPs, the best results being obtained for Ni/Co-2 : 2 samples, for which 50 wt.% Ni-50 wt.% Co NPs are found located on the surface of the residual phyllosilicate. Ni/Co-2 : 2, presenting the best performances for the hydrogenation of 2-methyl-quinoline, was further evaluated in the catalytic hydrogenation of selected imines, oximes and Nheteroarenes. Due to the high dispersion of bimetallic NiÀ Co NPs, excellent properties (activity and selectivity) in the conversion of the selected substrates are reported.

Encapsulating Cobalt into N-Doping Hollow Frameworks for Efficient Cascade Catalysis

“…In view of many byproducts generated during the chemical synthesis process, developing a high-performance catalytic system is of great demand and arouses wide attention. − Consequently, there is an urgent need to design and synthesize catalysts with high activity and selectivity. − In this regard, the non-noble metal catalysts, such as Fe- and Co-based materials, have attracted enormous interest due to their low cost and high selectivity in comparison to the precious metal-based catalysts. − Nowadays, unremitting efforts have been devoted to selective hydrogenation reactions using inexpensive metal-based catalysts. , Especially, the selective hydrogenation of azacyclo compounds with heterogeneous cobalt or other metal-based catalysts using H 2 as well as alternative transfer hydrogen resources has been studied. This priority of the heterogeneous catalytic system is because the heterogeneous catalysts can be easily separated from the reaction system, although the structure of the catalysts is ambiguous to precisely recognize at atomic levels. , Well-dispersed non-noble metal nanoparticles supported by nitrogen-doped porous carbon have attracted growing interest due to their well confirmable structure. − …”

“…7−10 Nowadays, unremitting efforts have been devoted to selective hydrogenation reactions using inexpensive metalbased catalysts. 11,12 Especially, the selective hydrogenation of azacyclo compounds with heterogeneous cobalt or other metalbased catalysts using H 2 as well as alternative transfer hydrogen resources has been studied. This priority of the heterogeneous catalytic system is because the heterogeneous catalysts can be easily separated from the reaction system, although the structure of the catalysts is ambiguous to precisely recognize at atomic levels.…”

Catalytic Reduction of Oximes to Hydroxylamines: Current Methods, Challenges and Opportunities

“…Recently in 2020, Ciotonea et al developed a heterogeneous catalyst based on bimetallic Ni/Co nanoparticles highly dispersed onto mesoporous SBA-15 silica (Scheme 5). [39] The catalyst was prepared in one step with the optimal Ni to Co weight ratios being 1 : 1. It showed excellent chemoselectivity and good performance in the hydrogenation of three differently substituted ketoximes 17 i-k, including arylketoximes 17 i, j that are problematic to reduce with Pt-catalysts.…”

“…Their facile separation from the product and recovery makes them attractive for large‐scale applications. [ 32 , 33 ] Up to date, the competent ones for oxime reduction contain either platinum[ 34 , 35 , 36 , 37 , 38 ] or nickel plus cobalt bimetallic mixtures, [39] and all use hydrogen gas as reductant. These systems have only achieved moderate catalytic efficiencies (up to 290 TON), which devaluates their advantages.…”

Cu Nanoclusters Anchored on the Metal–Organic Framework for the Hydrolysis of Ammonia Borane and the Reduction of Quinolines

“…On the other hand, hydrides of N-heteroarenes, which are obtained by the hydrogenation of aromatics, play an important role in the agrochemical and pharmaceutical industries. − Recently, a heterogeneous catalysis system applied in such processes undergo rapid development. − Notably, catalysts supported by noble metals, such as Ru, Rh, and Ir, provide a good catalytic platform and are successfully used in different aromatic hydrogenation reactions. − However, most of the studies on these processes concentrate on a simple model reaction. , The molecules often have more intricate structures in practical industry applications. Consequently, rational design and synthesis of supported metal catalysts with superb mass enrichment combined with excellent active sites are of equal importance for the catalytic reactions in pharmaceutical industries.…”