Ce-Zr UiO-66 MOF as recyclable heterogeneous catalyst for selective N-methylation

Metal-organic frameworks (MOFs) are proven heterogeneous recoverable catalysts in a number of organic transformations. However, their role in the reaction of amines with dialkyl carbonates has only been partially investigated. In this paper, the catalytic potential of Ce-Zr UiO-66 MOF towards the N-alkylation of secondary amines with dimethyl carbonate has been investigated. The desired MOF catalyst was prepared by the solvothermal method and its morphology, texture, porosity, functionality, and crystallinity were examined before its catalytic investigation. The MOF consisted of sphere-like particles with a surface area of 272 m2/g and an average pore size of 3.4 nm. Under the optimized conditions, the aromatic and heterocyclic amines yielded the N-methylated derivatives as the sole or the major product in the presence of Ce-Zr UiO-66 MOF. The maximum methylation percentage achieved was 100%. The reaction followed the pseudo-first-order rate kinetics and the heterogeneous bimetallic Ce-Zr UiO-66 MOF was reused four times without any significant activity loss. Thus, the Ce-Zr UiO-66 MOF serves as an efficient, selective, and reusable heterogeneous catalyst in N-methylation reactions.