Atomically Dispersed Co Clusters Anchored on N‐doped Carbon Nanotubes for Efficient Dehydrogenation of Alcohols and Subsequent Conversion to Carboxylic Acids

Abstract

The catalytic dehydrogenation of readily available alcohols to high value‐added carbonyl compounds is a research hotspot with scientific significance. Most of the current research about this reaction is performed with noble metal‐based homogeneous catalysts of high price and poor reusability. Herein, highly dispersed Co‐cluster‐decorated N‐doped carbon nanotubes (Co/N‐CNTs) were fabricated via a facile strategy and used for the dehydrogenation of alcohols with high efficiency. Various characterization techniques confirmed the presence of metallic Co clusters with almost atomic dispersion, and the N‐doped carbon supports also enhanced the catalytic activity of Co clusters in the dehydrogenation reaction. Aldehydes as dehydrogenation products were further transformed in situ to carboxylic acids through a Cannizzaro‐type pathway under alkaline conditions. The reaction pathway of the dehydrogenation of alcohols was clearly confirmed by theoretical calculations. This work should provide an effective and simple approach for the accurate design and synthesis of small Co‐clusters catalysts for the efficient dehydrogenation‐based transformation of alcohols to carboxylic acids under mild reaction conditions.

Ni(OH)2 nanoparticles as a recyclable catalyst in acceptorless dehydrogenation of alcohols to acids/acid salts under aerobic conditions

“…Although the yield of benzoic acid can be improved by employing a heterogeneous Pd/C catalyst, [24] it needs to carry out the reaction in reduced pressure to realize optimal yields of products and thus it provided an operational difficulty to perform the reaction. Moreover, the reaction can easily be carried out in the presence of catalytic systems such as ZnO, [26] in‐situ generated Ag nanoparticles, [29] magnetic Ag nanoparticles, [28] zeolite imidazolate framework‐8, Co‐clusters decorated with N‐doped carbon nanotube (Co/N‐CNTs), [27,33] palladium nanoparticles supported on NiO, [32] self‐supported Ru‐NHC single site catalyst [14k] in the presence of either NaOH or KOH base. Remarkably, a graphene‐supported Ru‐NHC catalytic system has been employed to synthesize a multitude of acids from corresponding alcohols in an aqueous basic medium [14l] .…”

“…Moreover, cumbersome synthetic protocols for the catalysts and the requirement of expensive ligands are serious drawbacks associated with these catalytic systems. Hence, to mitigate these issues, a few heterogeneous catalytic systems of Pd, [24] Rh, [25] Ru, [14k] Zn, [26] Co, [27,33] and in-situ generated Ag nanoparticles [28,29] have been employed for the synthesis of acids from corresponding primary alcohols via an acceptorless dehydrogenation strategy. However, these catalytic protocols required either high catalyst loadings (20 mol % of Rh in Rh/C) or high temperature (164 °C), and an excess amount of base (up to 4 equivalents KOH) to achieve efficiency.…”

Anchoring Ru Active Sites on N−CNTs for an Improved One‐pot Cellobiose Conversion

“…Doping Carbon materials with heteroatom N is verified to be an important and effective way to enhance the metal-support interaction in CNT-supported catalysts and improve the catalytic performances in reactions. [13][14][15][16][17] Dong et al [18][19][20] prepared a series of N-doped nano-carbon materials to anchor metal species (Ru and Co) and verified that these N modified catalysts had a higher catalytic performance than the non-modified catalysts in biomass conversion. The most common way used to obtain N-doped CNT was chemical vapor deposition (CVD) method up to now, however, this method usually needs high reaction temperature and toxic chemicals to dope N during the synthesis process which would limit its wide application because of the non-environmental effect.…”

“…Doping Carbon materials with heteroatom N is verified to be an important and effective way to enhance the metal‐support interaction in CNT‐supported catalysts and improve the catalytic performances in reactions [13–17] . Dong et al [18–20] . prepared a series of N‐doped nano‐carbon materials to anchor metal species (Ru and Co) and verified that these N modified catalysts had a higher catalytic performance than the non‐modified catalysts in biomass conversion.…”

Zn Single-Atom Catalysts Enable the Catalytic Transfer Hydrogenation of α,β-Unsaturated Aldehydes

“…Nowadays, 3d transition-metal-related catalysts, including Fe, Co, Ni, Cu, and Mn, have been widely explored for the CTH reaction because of their unique electronic structure and structure flexibility. − However, their catalytic performances are still far lower than those of precious-metal catalysts. Compared with other 3d transition metals, such as Cu, Co, and Ni, and other precious metals, the Zn element is much more cost-effective owing to its abundant reserves on Earth .…”