Porous organic frameworks with mesopores and [Ru(bpy)3]2+ ligand built-in as a highly efficient visible-light heterogeneous photocatalyst

Abstract

A mesoporous [Ru(bpy)₃]²⁺ (bpy = 2,2′-bipyridine) ligand based porous organic polymer (Ru-POP) has been synthesized via a bottom-up strategy. The excellent light absorption properties, high BET surface area, wide openings, and interconnected mesopores of Ru-POP ensured its excellent photocatalytic activity in visible-light driven green synthesis of 2-substituted benzimidazole. The Ru-POP catalyst could be recycled and reused 12 times for the photosynthesis of 2-phenyl-benzimidazole without obvious loss of the catalytic activity. Moreover, compared with the previously reported photoactive POPs, Ru-POP has extremely high catalytic activity with the highest TOF value (121.3 h⁻¹) in a photocatalyzing aza-Henry reaction. It is clearly demonstrated that the mesopores in Ru-POP are very important for improving the catalytic efficiency through increasing the accessibility of catalytic sites and facilitating the mass transport process, adhering well to the principles of structure–property–activity relationships.