In situ-grown active transition metal-functionalized MOF via solvent-free mechanochemical conditions as effective catalyst for the preparation of carbamates from organic azides with amines and anilines

Abstract

The solvent-free synthesis of MOF represents a promising and environmentally benign protocol. This paper outlines a green one-pot mechanochemical method for the synthesizing of UiO-66 in the absence of solvent, along with the implantation of three different metals (Cu, Ni, and Pd) into the defect sites. The materials have proven to be effective catalysts in the transformation between azidocarbonate and amines/anilines in moderate to excellent isolated yields (up to 94%), exhibiting better advantages compared with the exiting methodologies. More interestingly, Cu and Ni exhibited very good catalytic performance towards primary and secondary amines, respectively. It also should be noted that high yield was still observed after six cycles. Our work presents a novel and straightforward strategy for the preparation of secondary and tertiary carbamates in an unprecedented fashion, greatly enriched the toolbox for the synthetic community. Moreover, the combination of experimental studies and density functional theory (DFT) calculations gave more insight and evidence for the mechanism. Accompanied by the advantages of the effective and recyclable catalyst, the broad substrate scope, good functional group tolerance, and excellent reaction yields made the established method attractive in heterogeneous catalysis and the carbamates synthesis.