2,5-furandicarboxylic acid (FDCA) is one of the most important bio-sourced building blocks and several routes have been reported for its synthesis. FDCA is presumed to be an ideal green alternative to terephthalate, which is one of the predominant monomers in polymer industry. This Minireview concerns the synthesis of FDCA by using various carboxylation reactions and discusses the synthesis of FDCA starting from furoic acid and CO 2 and using different catalytic and stoichiometric processes. This process is of high interest, as it avoids the glucose isomerization step and selectivity issues observed during the 5-hydroxymethylfurfural oxidation step of the current alternative route to FDCA. Discussion focuses on the main parameters that govern selectivity and activity in the carboxylation processes. Moreover, various previously described processes, such as the Henkel reaction and enzymatic, homogeneous catalytic, and photoelectrocatalytic processes, are also discussed.

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Hybrid catalysis, which combines chemo‐ and biocatalytic benefits, is an efficient way to address green chemistry principles. 5‐Hydroxymethylfurfural (HMF) is a versatile building block in numerous industrial applications. To date, few studies have described the production of its amine derivatives and their polymers. Finding a good methodology to directly transform HMF to 5‐aminomethyl‐2‐furancarboxylic acid (AMFC) therefore represents an important challenge. After selecting the best oxidation catalyst for HMF conversion to 5‐aldehyde‐2‐furancarboxylic acid and immobilizing a transaminase onto a solid carrier, we implemented the first one‐pot/two‐steps hybrid catalytic process to produce AMFC (77 % yield); this is the most efficient AMFC catalytic production method from HMF reported to date. This process also produced 2,5‐furandicarboxylic acid (21 % yield) as a major secondary product that can be applied to polymer syntheses such as polyethylene furanoate. Herein, we report a novel way to access new biosourced polymers based on HMF oxidized and aminated derivatives.

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Covalent organic frameworks (COFs) is a rapidly developing field in material chemistry. However, COFs still have very limited applications due to the absence of functional groups. In this work, we demonstrate the efficient way for the synthesis of crystalline composite based on phosphotungstic acid and 2D imine CIN-1 type of COF. Heteropolyacid behaves as structure directing agent and it is stabilized between the layers of COF. The composite material shows a layered-sheet arrangement of large imine network layers with sizes up to 1.5 μm. Owing to the strong interaction of heteropolyacid with COF, the resultant material shows high activity and stability with no leaching during acid-catalyzed esterification reaction.

Plasmon-driven chemical transformation has become a promising approach for enhancing sluggish electrocatalytic reactions.

In this paper, Raman spectroscopy is used as a tool to study the mechanism of furfural oxidation using H2O2 as a reagent on gold nanoparticles (NPs) supported on hydrotalcites (HTs). This reaction was repeated, under the same conditions, but with different reaction times in a parallel multireactor system. The reaction media were analyzed using a macro device associated with a multipass cell permitting us to enhance the Raman signal by reflecting the laser beam 3 times. The Raman spectra showed the conversion of furfural to furoic acid without any chemical intermediates, thus privileging a direct pathway. Combining the results of the catalytic tests with those of the Raman study, the mechanism of furfural oxidation to furoic acid using gold NPs supported on HTs is proposed. The key points of this mechanism were found to be as follows: (i) the in situ formation of a base, originating from the Mg leaching from the HT support, initiates the oxidation of furfural by deprotonation; (ii) H2O2 used as a reagent in the solution increases the catalytic activity by its dissociation to form hydroxide ions; and (iii) the oxidation of furfural occurs on the surface of gold NPs and leads to higher furoic acid yield.

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