Selective Oxidation of 5-Hydroxymethylfurfural to 2,5-Furandicarboxylic Acid Using O₂ and a Photocatalyst of Co-thioporphyrazine Bonded to g-C₃N₄

Abstract

Selective oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) is one of the key reactions for producing chemical commodities from biomass and their derivatives. The challenge for this reaction is to develop an efficient catalytic process that can be conducted under mild conditions (room temperature and atmospheric pressure, using oxygen molecules in air as the oxidant) and a recyclable catalyst. Herein we report a photocatalyst of cobalt thioporphyrazine (CoPz) dispersed on g-CN (abbreviated as CoPz/g-CN), which exhibits excellent catalytic activity toward the selective oxidation of HMF into FDCA under simulated sunlight using oxygen molecules in air as a benign oxidant. For example, an FDCA yield of 96.1% in an aqueous solution at pH = 9.18 is achieved at ambient temperature and air pressure. At lower pH (4.01), the product generated is 2,5-diformylfuran. Hence, it is possible to control the reaction outcome by control of the pH of the reaction system. g-CN itself is not a suitable catalyst for the selective oxidation because under the experimental conditions g-CN generates hydroxyl radicals that initiate processes that oxidize HMF directly to CO and HO. CoPz on the other hand activates O to give singlet oxygen (O), which more controllably oxidizes HMF to FDCA albeit at a more moderate yield (36.2%). The strong interaction between the CoPz and g-CN in the CoPz/g-CN catalyst is experimentally evidenced, which not only improves accessibility of the CoPz sites and makes the catalyst recyclable but also disables the hydroxyl radical generation by g-CN and promotes O generation on the CoPz sites, significantly enhancing the catalytic performance. This study demonstrates the potential for efficient non-noble metal photocatalysts for organic transformations driven by sunlight.

Designing a 0D/2D S‐Scheme Heterojunction over Polymeric Carbon Nitride for Visible‐Light Photocatalytic Inactivation of Bacteria

“…Here the 5,5-dimethyl-l-pyrroline N-oxide (DMPO) can be used to trap the hydroxyl radicals (COH) and superoxide radicals (CO 2 À ), producing the DMPO-COH and DMPO-CO 2 À adducts,r espectively. [32] As shown in Figure 7a,b,n o EPR signal can be observed in the blank experiments, suggesting that the DMPO molecules have no paramagnetic response.F or pure CeO 2 photocatalytic system, the typical peaks of DMPO-COH adducts can obviously observed, whereas the peak intensity of DMPO-CO 2 À adducts is very weak. These results indicate that the CeO 2 photocatalyst is favorable for producing hydroxyl radicals (COH) rather than superoxide radicals (CO 2 À ), which is attributed to its more positive oxidation potential (2.31 V) than the potential of H 2 O/COH (ca.…”

Beyond Artificial Photosynthesis: Prospects on Photobiorefinery

“…For example, Xu et al. used cobalt thioporphyrazine (CoPz) dispersed on g‐C 3 N 4 as a catalyst for HMF‐to‐FDCA conversion . The reaction was tested under simulated sunlight using O 2 molecules in air as an oxidant in aqueous solution (pH 9.18).…”

Highly Efficient Oxidation of 5‐Hydroxymethylfurfural to 2,5‐Furandicarboxylic Acid with Heteropoly Acids and Ionic Liquids

“…A series of non‐noble‐metal catalysts were employed for the HMF oxidation . Zhu and co‐workers first prepared a photocatalyst, CoPz/g‐C 3 N 4 , and used Na 2 B 4 O 7 solution, which led to excellent yields of FDCA . Mn–Co bimetallic oxides with different Mn/Co molar ratios were prepared, and nanoscale center‐hollow hexagon MnCo 2 O 4 spinels presented highest activity among all other Mn–Co oxides, with a FDCA yield of 70.9 % .…”

“…[5a, 14] Zhu and co-workers first prepared ap hotocatalyst, CoPz/g-C 3 N 4 ,a nd used Na 2 B 4 O 7 solution, which led to excellenty ields of FDCA. [15] Mn-Co bimetallic oxidesw ith different Mn/Com olar ratios were prepared, andn anoscale center-hollow hexagon MnCo 2 O 4 spinels presented highest activity among all other Mn-Co oxides, with aF DCA yield of 70.9 %. [5a] Hayashi et al successfully synthesized MnO 2 with different crystal structures and demonstrated thath igh-surface-area b-MnO 2 presented suitable catalytic activity for the selectiveo xidation of HMF to FDCA.…”