Solvent-assisted ligand exchange (SALE) for the enhancement of epoxide ring-opening reaction catalysis based on three amide-functionalized metal–organic frameworks

Abstract

TMU-49. These structures were achieved by layering the compounds via hydrothermal reaction. Moreover, the ability of these structures to act as catalysts was evaluated using the methanolysis reaction of epoxides. To increase the MOF catalytic efficiency, we designed the N1,N3-di (pyridine-4-yl) malonamide linker (S) as a malonamide pillar ligand, which contains an acidic hydrogen that is suitable for catalyzing an epoxide ring-opening reaction and therefore enhancing the catalytic activity. As the synthesis of the MOF structure with this linker was not successful, we designed three new structures by incorporating different percentages of S linkers by exchanging the acylamide functional group with malonamide via the SALE pathway. The acylamide functional group was successfully replaced and produced daughter MOFs TMU-49S, TMU-50S and TMU-51S. PXRD and NMR spectroscopy confirmed that the S linker was incorporated into the acylamide-MOF structure. The obtained materials TMU-49S, TMU-50S and TMU-51S are isostructural with their parent frameworks. The S spacer significantly improved the catalytic properties of the MOF compounds in the ring-opening reaction of epoxides, with TMU-50S showing a 98% catalytic efficiency after incorporating the S linker. The catalysts could be recycled without any significant loss in the catalytic efficiency.