Transition-Metal-Complex Cationic Dyes Photosensitive to Two Types of 2D Layered Silver Bromides with Visible-Light-Driven Photocatalytic Properties

With mixed transition-metal (TM) complex, alkali-metal cations, or halogen anions as structure-directing agents, two types of two-dimensional (2D) layered inorganic–organic hybrid silver bromides were prepared and structurally characterized as K[TM(2,2-bipy)3]2Ag6Br11 (TM = Ni (1), Co (2), Zn (3), Fe (4)) and [TM(2,2-bipy)3]2Ag13Br17 (TM = Ni (5), Co (6), Zn (7), Fe (8)). Compounds 1–4 feature 2D microporous anionic [Ag6Br11]5– layers composed of [Ag3Br7] secondary building units based on AgBr4 tetrahedral units, and compounds 5–8 contain 2D [Ag13Br16]3– layers built from the one-dimensional complex [Ag8Br12] and [Ag5Br8] chains. The photosensitization of TM complex dyes led to the narrow semiconducting behaviors with tunable band gaps of 1.73–2.71 eV for the title compounds, which result in excellent and stable photocatalytic degradation activities over organic pollutants under visible-light irradiation. The studies of photocatalytic mechanism based on radical-trapping experiments and electronic band structural calculation show that the TM complex cations play important roles in the photocatalytical activities and photochemical stabilities due to their excellent separating abilities for photogenerated carriers. This technique affords one new type of visible-light-driven photocatalyst and facilitates the integration of 2D layered materials and semiconducting photocatalytic properties into one hybrid d10 TM halogenide.