Light-driven hydrogen evolution with carbon quantum dots and an oligoether-bearing [FeFe]‑hydrogenase mimic in...

Carbon quantum dots (CQDs) have emerged as potential nanocrystal photosensitizer for solar light-driven hydrogen (H₂) production in aqueous solution. Herein, we report the first combination of CQDs with diiron subsite mimic of [FeFe]‑hydrogenases for light-driven H₂ generation in aqueous solution. To this end, a new oligoether-bearing diiron azadithiolato complex [Fe{μ-(SCH₂)₂CH₂}(CO)₅{CNC₆H₄NHC(O)C₆H₂[(OCH₂CH₂)₃OCH₃]₃}] (2), which may be considered as a water-soluble [FeFe]‑hydrogenase mimic, was successfully prepared from isonitrile-coordinated diiron precursor mimic [Fe{μ-(SCH₂)₂CH₂}(CO)₅ {CNC₆H₄NH₂}] (1). Further, a hydrogenase-inspired photocatalytic H₂ production system has been established in an aqueous acetonitrile solution (H₂O-MeCN, v/v = 30:1) containing mimic 2 as catalyst, CQDs as photosensitizer, ascorbic acid (H₂A) as electron sacrificial donor, and Triton X-100 as dispersant. The result has shown that (i) this system is photocatalytically active for aqueous H₂ evolution when light (λ > 380 nm) is irradiated and (ii) the H₂ production efficiency depends on the pH value of solution and the concentrations of CQDs, catalyst as well as H₂A. Notably, a possible mechanism for the photocatalytic H₂ generation by CQDs and mimic 2 is proposed by using ultraviolet-visible (UV-vis) absorption, fluorescence emission, fluorescence lifetime, linear sweep voltammetry (LSV), and cyclic voltammetry (CV). All in all, this work will provide a new and promising strategy to promoting the efficient conversion of solar energy into hydrogen energy using nanocrystal CQDs and synthetic [FeFe]‑hydrogenase mimic.