Biomass Oxidation: Formyl CH Bond Activation by the Surface Lattice Oxygen of Regenerative CuO Nanoleaves

Abstract

An integrated experimental and computational investigation reveals that surface lattice oxygen of copper oxide (CuO) nanoleaves activates the formyl C-H bond in glucose and incorporates itself into the glucose molecule to oxidize it to gluconic acid. The reduced CuO catalyst regains its structure, morphology, and activity upon reoxidation. The activity of lattice oxygen is shown to be superior to that of the chemisorbed oxygen on the metal surface and the hydrogen abstraction ability of the catalyst is correlated with the adsorption energy. Based on the present investigation, it is suggested that surface lattice oxygen is critical for the oxidation of glucose to gluconic acid, without further breaking down the glucose molecule into smaller fragments, because of C-C cleavage. Using CuO nanoleaves as catalyst, an excellent yield of gluconic acid is also obtained for the direct oxidation of cellobiose and polymeric cellulose, as biomass substrates.

Integrated Experimental and Theoretical Study of Shape-Controlled Catalytic Oxidative Coupling of Aromatic Amines over CuO Nanostructures

“…Because the CuO(111) surface is the most stable surface of CuO, 30,32 it will be the dominant exposed facet of the CuO nanocatalysts. Indeed, the CuO(111) surface was observed in other morphologies of CuO such as nanoleaves, 21 nanocubes, 21 nanowires, 32,52 and nano thin-flims, 53,54 and the predominance of this surface was also evidenced from XRD and HR-TEM images for all CuO morphologies examined in this study. Therefore, the mechanism of oxidative coupling of amine was evaluated computationally using the CuO(111) surface.…”

“…This observation is consistent with the previous findings on the role of the O 3 site of C–H bond dissociation of other substrates on the CuO(111) surface. 18,21 The essential role of surface chemisorbed oxygen on Cu-based catalysts in facilitating the generation of imine has also been demonstrated in other experimental studies. 27,28…”

“…26−28 There are also reports that Cu could be easily converted to the copper oxide phase in O 2 atmosphere. 18,21,29,30 CuO catalysts have also been tested for oxidative coupling of amines to imines; however, their activities have not been optimized to a satisfactory level. 31 In addition, our mechanistic understanding of the formation of imines over these heterogeneous catalysts is insufficient, which impedes efficient development of better catalysts.…”

Nanostructured Metal Catalysts for Selective Hydrogenation and Oxidation of Cellulosic Biomass to Chemicals

“…CuO -200 N 2 100 86 [182] Morphological Control *cellobiose as substrate; X: conversion; S: selectivity Figure 18. TEM images of (a) NiMoO 4 nanofiber electrode (request permission from ref [171i] ), (b) PtCu/TiO 2 catalyst (request permission from ref [174] ) and (c) SEM image for Au on Ni foam electrode (request permission from ref [171j] ) for glucose oxidation .…”

3D hierarchical walnut-like CuO nanostructures: Preparation, characterization and their efficient catalytic activity for CO oxidation

“…1D, 2D and 3D CuO micro/nanostructure have been intensively synthesized [20][21][22][23][24][25][26][27][28][29]30,31]. Most applications of CuO are focused on the catalytic activity for CO oxidation.…”