Bio-based cyclic poly(2,5-furylene vinylene) from 2,5-Diformylfuran via McMurry coupling and its palladium nanoparticle hybrids for electrocatalytic applications

Cyclic poly(2,5-furylene vinylene) (cPFV) is a novel cyclic furan-based π-conjugated oligomer synthesized through the McMurry reductive homocoupling of 2,5-diformylfuran (DFF), a biosourced derivative of 5-hydroxymethylfurfural (HMF). Owing to the renewable origin of HMF from carbohydrate or lignocellulosic feedstocks, DFF acts as a bio-based C6 platform to transfer renewable carbon atoms into the furan-vinylene linkages of cPFV that can be thus described as a novel bio-derived conjugated cyclic polymer. McMurry polymerization provides a straightforward and operationally simple route to conjugated C C bonds, relying on inexpensive and commercially available TiCl4/Zn reagents based on relatively abundant elements. The overall approach combines a biosourced monomer with a robust and accessible reductive coupling strategy, enabling the preparation of a structurally unprecedented cyclic π-conjugated material. Importantly, the formation of the cPFV structure represents the key novelty of this material, since this topology eliminates chain-end effects and provides an extended π-conjugated system with potential electronic and supramolecular properties different from those of conventional linear furan-vinylene oligomers. 1H, 13C NMR, UV–Vis, FT-IR and MALDI mass spectrometry supported the formation of highly symmetric cyclic structure composed of 8–16 furylene-vinylene units, with a predominant E -configuration of the vinylene linkage. cPFV exhibits excellent thermal stability with decomposition temperature higher than 300 °C in nitrogen atmosphere. Palladium nanoparticles (PdNPs) of ∼12 nm were homogeneously deposited onto cPFV to obtain the hybrid nanocomposite PdNPs@cPFV which was used to prepare electrodes by drop-casting suspensions of PdNPs@cPFV in water onto a glassy carbon support. These electrodes were then applied in electrocatalytic dihydrogen oxidation (HOR) and evolution (HER) reactions; onset potentials of −0.15 V and + 0.13 V vs RHE were respectively measured for the two reactions. This work introduces a novel promising renewable and conductive organic support of metal nanoparticles for the development of efficient hybrid electrocatalysts.