Amphiphilic Polycarbonate Micellar Rhenium Catalysts for Efficient Photocatalytic CO₂ Reduction in Aqueous Media

A triblock amphiphilic polymer derived from the copolymerization of CO₂ and epoxides containing a bipyridine rhenium complex in its backbone is shown to effectively catalyze the visible-light-driven reduction of CO₂ to CO. This polymer provides uniformly spherical micelles in aqueous solution, where the metal catalyst is sequestered in the hydrophobic portion of the nanostructured micelle. CO₂ to CO reduction occurs in an efficient visible-light-driven process in aqueous media with turnover numbers up to 110 (>99 % selectivity) in the absence of a photosensitizer, which is a 37-fold enhancement over the corresponding molecular rhenium catalyst in organic solvent. Notably, the amphiphilic polycarbonate micelle rhenium catalyst suppresses H₂ generation, presumably by preventing deactivation of the active catalytic center by water.