Spatially harnessing oxygenase enables paired and ultraselective electrooxidative waste depolymerization.

Abstract

Electrooxidative C - C bond cleavage often encounters poor regioselectivity and low efficiency in conventional single-anode systems. Here, we deliberately customize a bipolar enzymic electrocatalyst HM@MM-MWCNT featuring medium-spin Fe^III sites by covalently anchoring natural hemin (HM) to carboxylated multi-walled carbon nanotubes (MWCNT) cross-linked by melamine (MM) that further axially coordinates the single-atom Fe. HM@MM-MWCNT can trigger the complete oxidative upcycling of diverse lignin and plastic derivatives concurrently on two electrodes to exclusively afford organic acids with yields reaching >95% (cathode) and >92% (anode), double to quadruple that of state-of-the-art electrodes. The axial MM switches Fe^III from a high-spin to medium-spin state, boosting directional C_β - H activation activity of cathodic Fe^III - O₂^•- and anodic Fe^IV = O species. Additionally, in-situ formed Fe^III - OOH and Fe^III - OH with weaker Fe-O bonding enabled by axial coordination can facilitate the dissociation of *OOH and *OH, respectively, for the subsequent coupling with the substrate C_β• generated by dehydrogenation, eventually achieving paired and selective C_α - C_β bond scission. Bipolar co-depolymerization of corn stover lignin furnishes aromatic monomers in a total yield, and its techno-economic analysis highlights low production costs. Spatially customizing enzymic electrodes with self-adaptive active species enables bipolar co-oxidation, doubling electrosynthesis efficiency for upgrading waste carbon sources.