Size-Dependent Catalytic Activity of Palladium Nanoparticles Decorated on Core–Shell Magnetic Microporous Organic Networks

Abstract

It is of supreme importance to develop recyclable and green heterogeneous catalysts due to their potential to reduce environmental impact and reduce costs associated with their use. Hence, in this research, an initial development was made of a core–shell magnetic structure composed of Fe3O4 and a microporous organic network (MON), followed by the physical absorption of palladium nanoparticles (NPs) onto the outer surface of this shell substance. The results of TEM and EDX analyses indicated that Pd NPs of varying sizes, which were produced by using different reducing agents, were evenly bound to the MON shell materials. The use of PiFM and XPS analyses provided evidence that there was effective bonding between Pd nanoparticles and the amine groups present on the surface of MON materials. Besides, the successful immobilization of palladium NPs was also approved by N2 adsorption/desorption analyses with the decrease of the surface from 328 to 227 m2/g after palladium inclusion. The prepared nanoheterogeneous catalysts can catalyze the C–C formation in mild conditions, green solvents, and short reaction times with good to excellent yields. The results revealed that the catalyst with smaller palladium NPs sized 1–5 nm and in medium abundance has better catalytic performance toward C–C formation, compared to those with bigger Pd NPs sized 5–15 nm and in both low and high Pd contents.