Tailoring the structure, pH sensitivity and catalytic performance in Suzuki–Miyaura cross-couplings of Ln/Pd MOFs based on the 1,1′-di(p-carboxybenzyl)-2,2′-diimidazole linker

Abstract

An array of heterobimetallic Pd/Ln MOFs (1-4) with Sm, Eu, Tb, Dy as preferred metal nodes and 1,1'-di(p-carboxybenzyl)-2,2'-diimidazole (H2L) as a fairly suitable bifunctional organic linker have been synthesized, fully characterized and tested as catalysts in cross-coupling reactions. These robust MOFs, ensuring a uniform distribution of Pd, showed excellent stability in air and high catalytic activity in Suzuki-Miyaura reactions conducted in neat water, neat ethanol as well as water-ethanol mixture. Depending on the solvent, complex 1 could be effectively recycled 4-8 times without significant loss of catalytic activity. Importantly, this complex was found to be pH responsive in a reversible way, enabling convenient recovery from acidic aqueous solutions, indicating good recyclability as well as environment-friendly separation of the metal residues after the reaction.