Creation of Nickel-Based Active Species within a Macroreticular Acidic Resin: A Noble-Metal-Free Heterogeneous Catalyst for Visible-Light-Driven H2 Evolution from Water

An acidic resin bearing -SO3 functional groups within its macroreticular structure acts as an efficient support for in situ formation of a noble-metal-free Ni-based catalyst responsible for visible-light-driven H-2 production from water. Characterization by means of XAFS revealed that simple ion-exchange of the resin with a trinuclear Ni complex, Ni(NiL2)(2)C(l)2 (L = beta-mercaptoethylamine), affords monomeric Ni(II) species involving beta-mercaptoethylamine and aqua ligands in an octahedral coordination geometry, which is easily transformed into real active species containing a TEOA ligand during the initial induction period of the photocatalytic reaction. Such in situ-generated Ni species offer a simple and efficient photocatalytic system whose activity is five times greater than that of its homogeneous counterpart, enabling efficient H-2 production when xanthene dye is employed as a visible-light-responsive photosensitizer. The acidity of the resins as well as beta-mercaptoethylamine and the TEOA ligands were found to be key factors in achieving efficient catalytic performance. Moreover, leaching and agglomeration of the active Ni species were not observed, and the recovered catalyst could be recycled without significant loss of activity.