Synthesis of biphenyl via sustainable Suzuki-Miyaura coupling reaction using mesoporous MCF-supported tin-palladium nanoparticles

Abstract

The current work presents a novel approach to synthesizing monometallic palladium (Pd) and bimetallic tin-palladium (Sn-Pd) nanoparticles anchored to mesostructured cellular foam silica (MCF). The monometallic catalyst Pd@MCF was prepared by the impregnation method, whereas the bimetallic catalyst Pd@MCF(Sn) was prepared by a green electroless reduction method. Our findings demonstrate that the bimetallic Sn-Pd nanoparticles produced through green electroless reduction exhibit no aggregation or clustering, and possess high and uniform dispersion, smaller average particle size and a narrower distribution of particle size than Pd nanoparticles obtained via impregnation. The synthesis of Pd@MCF(Sn) used tin as one of the metallic components of the catalyst and also as a reducing agent rather than conventionally used harmful reducing agents in the electroless reduction method. Remarkably, the introduction of tin into the catalyst system also displays a synergistic effect in the Suzuki-Miyaura coupling (SMC) reaction. The monometallic Pd@MCF catalyst was outperformed by the bimetallic Pd@MCF(Sn) catalyst in terms of catalytic activity for SMC reaction of phenylboronic acid with iodobenzene to produce biphenyl without using toxic reagents, organic solvents, costly phosphine ligands or protective atmospheres. This study also explored and optimized the factors controlling the reaction rate, offering insightful information to improve the production of biphenyl. The reaction follows a second-order kinetics with an apparent activation energy of 8.2 Kcal/mol by applying the Langmuir-Hinshelwood-Hougen-Watson (LHHW) mechanism. Here, we present a promising strategy for formulating a highly effective and eco-friendly catalyst for sustainable production of biphenyl using Suzuki-Miyaura coupling reaction.