Immobilization of a Pd(ii)-containing N-heterocyclic carbene ligand on porous organic polymers: efficient and recyclable catalysts for Suzuki–Miyaura reactions

Abstract

Palladium coordinated with N-heterocyclic carbene-functionalized porous organic polymers (Pd@POPs) was successfully prepared via Scholl coupling reaction and a successive immobilization method. The protocol features simple reaction conditions, easy separation, high yield and low cost. The structure and composition of Pd@POPs were characterized by N₂ sorption, TGA, FT-IR, SEM, EDX, TEM, XPS and ICP. Then the obtained heterogeneous catalysts were applied in Suzuki–Miyaura coupling reaction to evaluate their catalytic performance. The Pd@POPs displayed high catalytic activity for the Suzuki–Miyaura coupling reaction in an EtOH/H₂O solvent. A 0.03 mol% Pd loading was sufficient for the reaction with a high turnover number (TON) of 3220. Moreover, the catalyst was easily recovered and reused for at least six consecutive cycles without obvious loss of its initial activity.