Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599, United States.
ACS Appl Mater Interfaces. 2012 Apr;4(4):2288-94. doi: 10.1021/am3003445. Epub 2012 Mar 27.
Nonporous, phosphorescent cross-linked polymers (Ru-CP and Ir-CP) were synthesized via Pd-catalyzed Sonogashira cross-coupling reactions between tetra(p-ethynylphenyl)methane and dibrominated Ru(bpy)(3)(2+) or Ir(ppy)(2)(bpy)(+), respectively. The resultant particulate cross-linked polymer (CP) materials have very high catalyst loadings (76.3 wt % for Ru-CP and 71.6 wt % for Ir-CP), and are nonporous with negligibly small surface areas (2.9 m(2)/g for Ru-CP and 2.7 m(2)/g for Ir-CP). Despite their nonporous nature, the insoluble CP materials serve as highly active and recyclable heterogeneous photocatalysts for a range of organic transformations such as aza-Henry reaction, aerobic amine coupling, and dehalogenation of benzyl bromoacetate. An efficient light-harvesting mechanism, which involves collection of photons by exciting the (3)MLCT states of the phosphors and migration of the excited states to the particle surface, is proposed to account for the very high catalytic activities of these nonporous CPs. Steady-state and time-resolved emission data, as well as the reduced catalytic activity of Os(bpy)(3)(2+)-doped Ru-CPs supports efficient excited state migration for the CP frameworks. This work uncovers a new strategy in designing highly efficient photocatalysts based on light-harvesting cross-linked polymers.
无孔磷光交联聚合物（Ru-CP 和 Ir-CP）是通过 Pd 催化的 Sonogashira 交叉偶联反应，分别将四（对乙炔基苯基）甲烷与二溴化 Ru(bpy)(3)(2+)或 Ir(ppy)(2)(bpy)(+)偶联得到的。所得的颗粒状交联聚合物（CP）材料具有非常高的催化剂负载量（Ru-CP 为 76.3wt%，Ir-CP 为 71.6wt%），并且是无孔的，比表面积极小（Ru-CP 为 2.9m²/g，Ir-CP 为 2.7m²/g）。尽管它们是无孔的，但不溶性 CP 材料可用作各种有机转化的高效且可回收的多相光催化剂，如氮杂 Henry 反应、有氧胺偶联和溴乙酸苄酯的脱卤化反应。提出了一种有效的光收集机制，其中涉及磷光体的（3）MLCT 态激发光子的收集以及激发态向颗粒表面的迁移，以解释这些无孔 CP 的非常高的催化活性。稳态和时间分辨发射数据以及 Os(bpy)(3)(2+)掺杂 Ru-CPs 的催化活性降低支持 CP 框架中激发态的有效迁移。这项工作揭示了一种基于光收集交联聚合物设计高效光催化剂的新策略。
