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.

以混合过渡金属（transition-metal, TM）配合物、碱金属阳离子或卤阴离子作为结构导向剂，我们制备了两类二维（2D）层状无机-有机杂化溴化银，并对其结构进行了表征：其通式分别为K[TM(2,2'-联吡啶)3]2Ag6Br11（TM = Ni(1)、Co(2)、Zn(3)、Fe(4)）与[TM(2,2'-联吡啶)3]2Ag13Br17（TM = Ni(5)、Co(6)、Zn(7)、Fe(8)）。化合物1~4具有由AgBr4四面体单元构成的[Ag3Br7]次级结构基元所组装而成的二维微孔阴离子[Ag6Br11]5–层状结构；化合物5~8则包含由一维[Ag8Br12]与[Ag5Br8]链构建而成的二维[Ag13Br16]3–层状结构。过渡金属配合物染料的光敏化作用使得目标化合物呈现出窄带隙半导体行为，其可调谐带隙范围为1.73~2.71 eV，这一特性赋予该类材料在可见光照射下对有机污染物优异且稳定的光催化降解活性。基于自由基捕获实验与电子能带结构计算开展的光催化机理研究表明，过渡金属配合物阳离子凭借其出色的光生载流子分离能力，在光催化活性与光化学稳定性中发挥了关键作用。本研究提供了一类新型可见光驱动光催化剂，推动了二维层状材料与半导体光催化特性在同一种杂化d10过渡金属卤化物中的整合应用。