(64i) Elucidation of an Enzyme-like Reaction Mechanism at a Polymer Electrocatalyst

Naturally evolved biological catalysts accomplish numerous difficult reactions with much greater speed and specificity than human-made materials. Replicating these characteristics in an artificial catalyst would revolutionize many industrial processes, but this goal has remained elusive in most cases. Biological catalysts achieve these impressive properties by sequestering reactants in a molecular scale pocket, enabling strong control over reaction thermodynamics. Most abiotic materials have comparatively limited influence over the chemical environment of reacting molecules, limiting their ability to mimic enzymes. Here, we develop and characterize a polymer electrocatalyst with enzyme-like control over reaction thermodynamics. This material, imidazolium-functionalized poly-3-hexylthiophene (P3HT-Im⁺), enables rapid electron transfer to the biological electron carrier flavin mononucleotide (FMN) via a mechanism previously restricted to enzymes. We discover that this property arises because P3HT-Im⁺ envelops reactants in molecular-scale cavities, altering the stability of reaction intermediates to promote a desired reaction pathway in a mechanism reminiscent of enzyme binding sites. We further demonstrate that these cavities form because of the relatively weak association between polymer side chains, which arises from the unique electronic structure of the imidazolium pendant group. By connecting the structure of P3HT-Im⁺ to its catalytic properties, we uncover a new mechanism of electrocatalysis which can be applied to rationally design new enzyme-like materials.