Confining Co-Based Nanocatalysts by Ultrathin Nanotubes for Efficient Transfer Hydrogenation of Biomass Derivatives

Abstract

Catalytic transfer hydrogenation (CTH) based on non-noble-metal catalysts has emerged as an environmentally friendly way for the utilization of biomass resources. However, the development of efficient and stable non-noble-metal catalysts is crucially challenging due to their inherent inactivity. Herein, a metal–organic framework (MOF)-transformed CoAl nanotube catalyst (CoAl NT160‑H) with unique confinement effect was developed via a “MOF transformation and reduction” strategy, which exhibited excellent catalytic activity for the CTH reaction of levulinic acid (LA) to γ-valerolactone (GVL) with isopropanol (2-PrOH) as the H donor. Comprehensive characterizations and experimental investigations uncovered that the confined effect of the ultrathin amorphous Al2O3 nanotubes could modulate the electronic structure and enhance the Lewis acidity of Co nanoparticles (NPs), thus contributing to the adsorption and activation of LA and 2-PrOH. The synergy between the electropositive Co NPs and Lewis acid–base sites of the CoAl NT160‑H catalyst facilitated the transfer of α-H in 2-PrOH to the C atom of carbonyl in LA during the CTH process via a Meerwein–Ponndorf–Verley mechanism. Moreover, the confined Co NPs embedded on am-Al2O3 nanotubes endowed the CoAl NT160‑H catalyst with superior stability and the catalytic activity was nearly unchanged for at least ten cycles, far surpassing that of the Co/am-Al2O3 catalyst prepared by the traditional impregnation method.

Isomorphic Insertion of Ce(III)/Ce(IV) Centers into Layered Double Hydroxide as a Heterogeneous Multifunctional Catalyst for Efficient Meerwein–Ponndorf–Verley Reduction

“…Both the reduction of carbonyl compounds and the oxidation (dehydrogenation) of alcohols, especially secondary alcohols, are of particular importance from an industrial point of view. Although there are well-established processes for carrying out these basic conversions, these conversions suffer greatly from being time-consuming, wasteful, and requiring isolation/purification steps to remove undesired products and byproducts. , These aspects are far from the requirements of green chemistry, and the emerging demand to optimize the redox economy of the synthesis processes, i.e., to minimize the number of oxidation state changes throughout the process, has led to the golden age of catalytic transfer hydrogenations (CTHs). , Recently, this trend has been further strengthened as CTH reactions play a key role in many catalytic reaction cascades for the conversion of biomass-derived molecules into valuable products, which can greatly contribute to achieving the main goals of the circular economy. − …”