Bio-Inspired Self-Assembly of Enzyme-Micelle Systems for Semi-Artificial Photosynthesis

Abstract

Supramolecular surfactants provide a versatile platform to construct systems for solar fuel synthesis, for example via the self-assembly of amphiphilic photosensitizers and catalysts into diverse supramolecular structures. However, the utilization of amphiphilic photosensitizers in solar fuel production has predominantly focused on yielding gaseous products, such as molecular hydrogen (H2), carbon monoxide (CO), and methane (CH4) with turnover numbers (TONs) of synthetic catalysts typically in the range of hundreds to thousands. Inspired by biological lipid-protein interactions, we present herein a bio-hybrid assembly strategy that utilizes photosensitizers as surfactants to form micellar scaffolds that interface with enzymes, namely hydrogenases and formate dehydrogenases, for semi-artificial photosynthesis. Specifically, surfactants with a tris(2,2’-bipyridine)ruthenium(II) head group provide high photocatalytic activity upon association with the enzymes as their positively charged [Ru(bpy)3]2+ complex electrostatically interacts with the enzymes favorably to enable direct electron transfer at the micelle-enzyme interface. Time-resolved absorption and emission spectroscopy support the beneficial charge carrier dynamics of the reductively quenched [Ru(bpy)3]+ species when the enzymes are introduced in the micellar solution. Thus, a biohybrid concept is introduced for solar fuel synthesis using a biomimetic enzyme-micellar system, providing also a platform for other photocatalytic transformations using enzymes in the future.