Post-synthetic ligand functionalization of defect-engineered MOF-74

Abstract

Although the IRMOF-74 is one of the most studied metal-organic frameworks (MOFs), due to the difficulty of the covalent modification of organic linkers, the functionalization of MOF is mostly limited to the dative modification of the monodendate solvent site of the framework. For the first time, we report the preparation of defect-engineered IRMOF-74(Ni)-I through fragmented linker strategy, the functionalization of the fragmented linker through post-synthetic covalent modification, and the subsequent post-synthetic metal insertion. The defect-engineered IRMOF-74(Ni)-I was synthesized according to the procedure used for IRMOF-74(Ni)-I, but the mixed ligands, 2,5-dihydoxy-1,4-benzenedicarboxylic acid (H4DOBDC) and a salicylic acid derivative containing an amino residue, were used instead of pure H4DOBDC. The amino residues in the defect-engineered MOF were further functionalized via post-synthetic covalent modification by using Schiff base condensation reaction between the amino residues of the fragmented ligands and pyridine aldehyde. A subsequent post-synthetic insertion of palladium resulted in the complexation of the covalently modified linkers and the palladium metal ions in the framework. The MOF showed very efficient and size-selective recyclable catalytic performance for Suzuki-Miyaura coupling reaction.