Selective Oxidation of 5‐Hydroxymethylfurfural to 2,5‐Diformylfuran by Visible Light‐Driven Photocatalysis over In Situ Substrate‐Sensitized Titania

Abstract

Solar energy‐driven processes for biomass valorization are priority for the growing industrialized society. To address this challenge, efficient visible light‐active photocatalyst for the selective oxidation of biomass‐derived platform chemical is highly desirable. Herein, selective oxidation of 5‐hydroxymethylfurfural (HMF) to 2,5‐diformylfuran (DFF) was achieved by visible light‐driven photocatalysis over titania. Pristine titania is photocatalytically inactive under visible light, so an unconventional approach was employed for the visible light (λ=515 nm) sensitization of titania via a formation of a visible light‐absorbing complex of HMF (substrate) on the titania surface. Surface‐complexation of HMF on titania mediated ligand‐to‐metal charge transfer (LMCT) under visible light, which efficiently catalyzed the oxidation of HMF to DFF. A high DFF selectivity of 87 % was achieved with 59 % HMF conversion after 4 h of illumination. The apparent quantum yield obtained for DFF production was calculated to be 6.3 %. It was proposed that the dissociative interaction of hydroxyl groups of HMF and the titania surface is responsible for the surface‐complex formation. When the hydroxyl groups of titania were modified via surface‐fluorination or calcination the oxidation of HMF was inhibited under visible light, signifying that hydroxyl groups are decisive for photocatalytic activity.

Cellulose‐Derived Carbon Dot‐Guided Growth of ZnIn2S4 Nanosheets for Photocatalytic Oxidation of 5‐Hydroxymethylfurfural into 2,5‐Diformylfuran

“…5‐Hydroxymethylfurfural (5‐HMF), derived from the dehydration of C 6 carbohydrates, is a key and versatile bio‐based platform chemical to produce different high value‐added chemicals like 2,5‐diformylfuran (DFF) [14] . DFF is an important monomer of furan‐based biopolymers and broadly served as the intermediates of pharmaceuticals and antifungal agents [15] . Accordingly, appropriate oxidation of 5‐HMF into DFF has drawn increasing interest, and the photocatalytic transformation is an economical, green and mild way with an appreciable selectivity [16] .…”

“…[14] DFF is an important monomer of furan-based biopolymers and broadly served as the intermediates of pharmaceuticals and antifungal agents. [15] Accordingly, appropriate oxidation of 5-HMF into DFF has drawn increasing interest, and the photocatalytic transformation is an economical, green and mild way with an appreciable selectivity. [16] Generally, metal sulfides with narrow bandgaps (e. g., CdS and ZnIn 2 S 4 ) intrinsically have a suitable band configuration with strong reduction and weak oxidation ability, which is appropriate to attain the selective oxidation of 5-HMF into DFF.…”

Titania/chitosan–lignin nanocomposite as an efficient photocatalyst for the selective oxidation of benzyl alcohol under UV and visible light

“…To measure the apparent quantum yield ( Φ ), the photon flux to the photoreactor was determined by potassium ferrioxalate actinometry. 39 The experiment was performed using 0.006 and 0.15 M potassium ferrioxalate solution under UV and visible light, respectively.…”

“…The apparent quantum yield (F) for the Bnald formation is dened as the ratio of the amount of Bnald formed per unit time to the number of photons absorbed by the system per unit time (eqn (4)) To measure the apparent quantum yield (F), the photon ux to the photoreactor was determined by potassium ferrioxalate actinometry. 39 The experiment was performed using 0.006 and 0.15 M potassium ferrioxalate solution under UV and visible light, respectively.…”

Synergistic Modulation of the Separation of Photo‐Generated Carriers via Engineering of Dual Atomic Sites for Promoting Photocatalytic Performance

“…[ 70 ] According to the proposed catalytic mechanism, H 2 O 2 was the main by‐product in the photo‐oxidation of HMF reaction, which could decrease the selectivity by further oxidizing DFF. [ 71 ] Due to the efficient separation of photo‐generated electrons and holes in Cu SAs/p‐CNS, the by‐product H 2 O 2 could be efficiently decomposed to O 2 and H 2 O by the separated photo‐generated holes. [ 72 ] This phenomenon restricted the further oxidation of DFF and bare the generation of side‐products.…”