Spatially harnessing oxygenase enables paired and ultraselective electrooxidative waste depolymerization

Le résumé fourni par la source

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 FeIII 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 FeIII from a high-spin to medium-spin state, boosting directional Cβ − H activation activity of cathodic FeIII − O2•− and anodic FeIV = O species. Additionally, in-situ formed FeIII − OOH and FeIII − 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 Cβ• generated by dehydrogenation, eventually achieving paired and selective Cα − Cβ 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. Turning mixed waste into useful chemicals is limited by inefficient and poorly controlled oxidation. This study designs iron-based paired electrodes that selectively split key bonds, giving high yields of organic acids and aromatic products.

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