Data for Redox-Active Biochar Catalysts for Base-Free HMF Oxidation to FDCA: Mechanistic Insights from Inelastic Neutron Scattering

The catalytic oxidation was performed under mild conditions using tert-butyl hydroperoxide as the oxidant and 2,2,6,6 tetramethylpiperidine-1-oxyl (TEMPO) as a co-catalyst. Sulfonation and iron loading modified the surface characteristics and porosity of the biochar while largely maintaining its graphitic structure.

Notably, raw biochar exhibited significant catalytic activity due to naturally occurring iron species inherited from the biomass precursor, without the needed for additional iron loading or sulfonation, and showed good stability and reusability. Increasing iron content enhanced FDCA formation, correlating with the presence of mixed valence Fe²⁺/Fe³⁺ species. Inelastic neutron scattering provided evidence of interactions between HMF and biochar, where the addition of TEMPO alone does not bring about oxidation but gives intermediate species which suggest deprotonation of the HMF as the first chemical interaction.