Bio-inspired cobalt catalyst enables natural-sunlight-driven hydrogen production from aerobic neutral aqueous solution

Abstract

Hetero-axial cobalt complexes are known for their oxygen-tolerant photocatalytic hydrogen production activity, mostly in organic solvents. Here, variable combinations of peripheral basic groups are explicitly positioned around an existing complex framework to generate an enzyme-inspired minimal outer coordination sphere (OCS) scaffold. This catalyst design strategy yields a series of water-soluble, upgraded versions of imidazole-linked cobaloximes. The presence of fringe protic functionalities ensures the formation of a dynamic and water-mediated proton relay. This appended proton relay allows us to probe imidazole-bound cobaloxime in pure aqueous conditions. It exhibits highly efficient electrocatalytic (TOF ?4,900 s?1) and photocatalytic (TON ?12,000) hydrogen production in neutral water compared to its relatively moderate performance in organic media. The catalyst retains its activity (TON ?22), even under natural sunlight (sunny day in Gandhinagar) in aerobic aqueous solution, emphasizing the importance of OCS features for producing robust, natural-condition-ready, synthetic catalysts.