Coordination-Promoted Bio-Catechol Electro-Reforming toward Sustainable Polymer Production.

ABSTRACT

Sustainable polymer production is essential for a carbon-neutral society. cis,cis-Muconic acid is attracting growing interest as a biomass-derived platform molecule with direct access to adipic acid and terephthalic acid, prominent monomers of commercial polymers. Here, a sustainable route of electro-reforming biorenewable catechol to cis,cis-muconic acid with concurrent H2 production has been proposed. By using a CuO foam electrode, a high cis,cis-muconate yield of 90% and a high faradaic efficiency of 87% can be achieved under ambient conditions without external oxidant. Zn2+ coordination with the catechol is central to the yield and selectivity. In a combinatory analysis via steady-state electrochemical kinetics, in situ spectroscopy, and theoretical calculation, we revealed that the reaction ensemble of catechol electrooxidation involves three major processes of polymerization, ring cleavage, and depolymerization, in which Zn2+ coordination is highly effective in delaying polymerization and promoting ring cleavage toward cis,cis-muconate. The catecholate coordinated to the Zn2+ cations reallocated its electron density with partial structural deformation to accelerate the electron transfer and facilitate the OH- nucleophilic attack. A practical two-electrode system was eventually demonstrated to efficiently and stably electro-reform catechol into isolable cis,cis-muconic acid and hydrogen, providing solutions for polymer sustainability via utilizing alternative biomass resources and electrified processes.