Assembly of photocatalytic micelles. Systems that self-assemble into functional supramolecular structures are attractive targets, but they are also hard to optimise due to the numerous interdependent variables. This is exemplified herein with amphiphilic self-assembly of molecular components for photocatalytic CO2 reduction. The system exploits the tuneability of molecular components to functionalise a CO2 reduction catalyst and photosensitiser with alkyl tails and enable supramolecular assembly into micelles. The catalyst and photosensitiser are cationic complexes, to which alkyl tails were added to the periphery to render them amphiphilic while preserving the metal coordination environment and functionality. For the catalyst, cobalt tetra-methylpyridinium porphyrin (CoPyPC1) is an active catalyst for CO2-to-CO conversion in aqueous media, and was made amphiphilic by replacing the methyl groups with hexadecyl groups (CoPyPC16; Fig ). A ruthenium tris-bipyridine was selected as it is a prototypical photosensitiser previously used for photocatalytic CO2 reduction with cobalt porphyrins and amphiphilic variants are known. To minimise additional functional groups, one bipyridine ligand was functionalised with two heptadecyl groups (RubpyC17; Fig ). In both cases, characterisation of the complexes was consistent with previous reports and the UV-Vis spectra showed minimal changes to max to indicate that the coordination environment was preserved (details in experimental section). For photocatalytic studies, the water-insoluble [CoPyPC16](PF6)4 was solubilised in micelles from a MeCN stock solution into aqueous CO2-saturated phosphate solution (pH 6.3; MeCN removed in CO2 purging step).