Selective Electrocatalytic Oxidation of Biomass-derived 5-Hydroxymethylfurfural (HMF) to 2,5-Diformylfuran (DFF): From Mechanistic Investigations to Catalyst Recovery

The catalytic transformation of bio-derived compounds, specifically 5-hydroxymethyfurfural (HMF), into value-added chemicals may provide sustainable alternatives to crude oil and natural gas based products. HMF can be obtained from fructose and successfully converted to 2,5-diformylfuran (DFF) by an environmental-friendly organic electrosynthesis performed in an ElectraSyn reactor, using cost-effective and sustainable graphite (anode) and stainless steel (cathode) electrodes in an undivided cell, without the need for conventional precious metal electrodes. In this work, we perform the electrocatalysis of HMF using green solvents such as acetonitrile, γ-valerolactone, as well as PolarClean that is used in electrocatalysis for the first time. The reaction parameters, and the synergistic effects of the TEMPO catalyst and 2,6-lutidine base are explored both experimentally and through computation modelling. The molecular design and synthesis of a size-enlarged C3-symmetric tris-TEMPO catalyst are also performed to facilitate a sustainable reaction work-up via nanofiltration. The obtained performance is then compared with those obtained by heterogeneous TEMPO alternatives recovered via an external magnetic field and microfiltration. Results show that our new method of electrocatalytic oxidation of HMF to DFF can be achieved with excellent selectivity, good yield, and excellent catalyst recovery.