Recent Advances in Photocatalytic Oxidation of 5‐Hydroxymethylfurfural

Abstract

Conversion of biomass-derived platform compounds into valueadded chemicals will reduced the current dependence on carbon resources from fossil reserves. In recent years, catalytic oxidation of 5-hydroxymethylfurfural (HMF) has received extensive attention due to the widespread application of 2,5diformylfuran (DFF) and 2,5-furandicarboxylic acid (FDCA). A photocatalyst system is a cost-effective way of O 2 utilization as a green chemical oxidant for HMF oxidation. Moreover, replacement of the kinetically sluggish water oxidation with HMF oxidation can promote hydrogen production during photo water splitting. This review provides a concise and up-to-date overview of photocatalyst systems for HMF oxidation, giving special attention to catalyst material design, product selectivity, mechanistic insight, and catalyst stability. The chemistry discussed in this review is an attempt to provide inspiration for researchers to develop efficient photocatalyst systems for solar biorefinery.

Nb2O5/g‐C3N4 Heterojunction Facilitates 2,5‐Diformylfuran Production via Photocatalytic Oxidation of 5‐Hydroxymethylfurfural under Direct Sunlight Irradiation

“…), however, with a lower selectivity of 53 % through a nearly same HMF conversion (71 %) (Figure 8b‐d). Thus, the heterojunction demonstrated promising by attaining a 1.5 to 3.3‐fold higher product yield than the single photocatalysts and even the literature reports [4b,c,5,32] . Overall, the outstanding performance of the heterojunction can be accounted for the synergism of g‐C 3 N 4 and Nb 2 O 5 species in the efficient separation of e − ‐h + pairs, leaving a higher number of h + for an accelerated and selective HMF oxidation.…”

Progress and Perspectives in Photo‐ and Electrochemical‐Oxidation of Biomass for Sustainable Chemicals and Hydrogen Production

“…As mentioned previously in Section 4.4, HMF oxidation can lead to the production of value-added products such as DFF and FDCA, which are molecules with commercial interests in fields such as pharmaceuticals, polymers or in organic synthesis. [403] Therefore obtaining these chemicals using photocatalysis producing hydrogen as a byproduct has attracted widespread attention within the last years. In this scenario electron-hole pairs generated by photoexcitation of a semiconductor travel toward the surface where electrons reduce H + to H 2 (typically in the metallic cocatalyst) and the holes react with water to form OH radicals or directly with HMF, releasing the oxidation products.…”

Current Advances in the Sustainable Conversion of 5‐Hydroxymethylfurfural into 2,5‐Furandicarboxylic Acid

“…Superoxide and hydroxyl radicals ( * O 2 À and * OH) seem to be the key reactive species in photo-oxidative catalysis in presence of water: the photo-generated electrons can reduce the O 2 molecules to form * O 2 À , and the photo-generated holes may extract electrons from organic substrates or produce * OH. [96] The mechanism of HMF oxidation to FDCA by photocatalysis is still a matter of discussion; however, the stepwise oxidation of HMF to FDCA in alkaline aqueous media, a combination of chemical and electrochemical studies, proposed by Li and Na, is described in Scheme 3. [96] The nucleophilic addition between HMF and a hydroxide ion determines the formation of a diol intermediate.…”

“…[96] The mechanism of HMF oxidation to FDCA by photocatalysis is still a matter of discussion; however, the stepwise oxidation of HMF to FDCA in alkaline aqueous media, a combination of chemical and electrochemical studies, proposed by Li and Na, is described in Scheme 3. [96] The nucleophilic addition between HMF and a hydroxide ion determines the formation of a diol intermediate. In the presence of hydroxide ions and catalysts, HMFCA is formed, which can be further oxidized to FFCA.…”