Nonporous, phosphorescent cross-linked poly-
mers (Ru-CP and Ir-CP) were synthesized via Pd-catalyzed
Sonogashira cross-coupling reactions between tetra(p-ethynyl-
phenyl)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 m2/g for Ru-CP and 2.7 m2/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 bromo-
acetate. An efficient light-harvesting mechanism, which involves
collection of photons by exciting the 3MLCT 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.
