Insight on the Contribution of Plasmons to Gold‐Catalyzed Solar‐Driven Selective Oxidation of Glucose under Oxygen

Abstract

With the increasing concerns about pollution and reduction of energy demands, the use of solar energy to drive chemical transformations is becoming increasingly attractive. Within the context of sustainability, sunlight‐driven organic transformation of biomass feedstock, such as free carbohydrates, to obtain high added‐value products is an important topic in which the recent progress should contribute to the development of solar biorefineries. Among the variety of photocatalysts, gold nanoparticles (NPs) loaded onto large bandgap semiconductors represent the state of the art. Such catalysts are known to accelerate the targeted reaction upon plasmonic excitation. In addition, as noble metal NPs, they also hold an additional role related to surface catalysis, which has been exploited for aerobic oxidation of free sugars. Nevertheless, the respective contribution of each role during transformation is not well established. Herein, the enhancement of the O2‐mediated oxidation of free sugars using Au NPs on CeO2 under standard air mass 1.5G illumination conditions is reported. The results highlight that the plasmonic contribution of Au NPs is totally annihilated and this enhancement stems solely from a thermal activation process induced by NIR radiation from standard white‐light conditions.

Gold-Catalyzed Oxidative Transformation of Free Sugars into Biobased Platform Molecules

“…Moreover the supporting material of the gold nanoparticles is known to affect the overall catalyst properties. Our previous experiences, − as well as recent literature, showed that Au/CeO 2 exhibits excellent properties for aerobic oxidation of free sugars. For this reason, ceria was chosen as a support in this study.…”

“…Particularly, the oxidation of the anomeric position of free sugars using gold nanoparticles (Au NPs) as the catalyst has been widely investigated. − In aqueous conditions using O 2 or H 2 O 2 as the oxidant, free sugars are selectively converted into corresponding aldonate salts or aldonic acids, identified as promising biobased chemical platforms to replace those currently derived from the petroleum . Among others, we contributed to this topic by demonstrating that alternative activation pathways such as microwave or photocatalysis − were effective to enhance both the conversion yield and the reaction selectivity. Nevertheless, the subsequent transformation of the oxidized derivative (aldonic acid or aldonate salt) is unfavored due to the weak reactivity of the carbonyl group, for which an activating group is generally needed. − Sugar lactones, activated derivatives, represent a viable alternative to overcoming this issue and are widely used as building blocks for glycoconjugate synthesis.…”

Plasmonics: A Versatile Toolbox for Heterogeneous Photocatalysis

“…Nevertheless, either with CeO 2 alone or without catalyst, oxidative cleavage was observed instead of the desired controlled oxidation. [ 151 ] Moreover, conversion under irradiation is two times higher than that under dark conditions. Experimental evidence suggests that for this catalytic system, aerobic photocatalyzed oxidation of glucose is due to thermal effects and not to charge separation processes in CeO 2 or the generation of hot carriers on Au NPs.…”

Sustainable production of high-value gluconic acid and glucaric acid through oxidation of biomass-derived glucose: A critical review

“…Despite the decreased TOF after five cycles, the conversion and selectivity remained high, indicating excellent reusability of this catalyst. The use of O 2 as the oxidant was also studied for Au/CeO 2 -photocatalyzed glucose oxidation (Golonu et al, 2020). The reaction may be driven by the thermal effect induced by near-infrared radiation, instead of UV-promoted excitation of CeO 2 or visible photon-activated SPR effect of Au nanoparticles.…”