Microcrystalline Cellulose-Supported Gold Nanoparticle Catalysts for Homocoupling of Phenylboronic Acids

A solid-grinding strategy for the large-scale synthesis of solid microcrystalline cellulose (MCC)-supported gold nanoparticle (NP) catalysts without using solvents and a sophisticated purification technique is reported. In contrast to typical solution-based methods, the deposition of high loading of gold NPs with greater uniformity on native MCC polymers without chemical modifications was achieved rapidly by manual grinding. The Fourier transform infrared (FT-IR) study revealed that the abundant hydroxyl functional groups present on the MCC support could effectively hold tiny gold NPs through hydrogen bonding between the -OH groups of MCC and gold NPs, thereby making the MCC-supported gold NPs stable heterogeneous catalysts. Thus, the Au/MCC catalyst exhibits higher catalytic activity and selectivity toward homocoupling of phenylboronic acids into corresponding biphenyls in water under air. Compared to other solid-supported gold NP catalysts, the MCC-supported gold catalysts showed greater catalytic activity and selectivity in the homocoupling of phenylboronic acids. The kinetics study on the homocoupling reaction catalyzed by Au/MCC reveals that the catalysts possess much lower apparent activation energy than the reported gold catalysts. Thus, the present sustainable approach may inspire more studies on the design of renewable biopolymer matrix-supported gold NPs in a large scale for heterogeneous catalysis.