Study On The C-C Coupling Reactions Catalyzed By Novel Nanomaterials Supported Palladium Catalysts

The palladium catalyzed Suzuki-Miyaura cross-coupling reaction is very versatile route to construct biaryl units in organic chemistry. Traditional Suzuki reaction is performed mostly with homogeneous catalyst. However, the low efficiency in separation and subsequent recycling of homogeneous transition metal catalysts remains a scientific challenge. Conversely, heterogeneous catalysts can be easily separated from the reaction systems and reused. A number of solid materials, such as mesoporous silica, zeolites, and polymers, have been used as catalysts for C-C coupling reactions. However, these materials have one or more limitations in terms of stability, catalytic efficiency, and recyclability. Therefore, it is still attractive to explore efficient heterogeneous Pd catalyst for the coupling reactions.Graphene(G) has attracted tremendous research attention since its discovery in 2004.Owing to their unique physical, chemical properties, graphene-based materials might be promising candidates for catalysts or catalyst supports. At the sametime, as a novel class of nanoporous materials, metal-organic frameworks(MOFs) have received significant attention in recent years mainly due to their tunable pore sizes, high specific surface areas,and designable framework structures. In this paper, Pd nanoparticls supported on graphene and MOFs were fabricated and used as efficient catalyst for the Suzuki coupling reaction.The main content in this thesis is as follows:(1) SBA-15 supported graphene-palladium catalyst(Pd/G/SBA-15) was prepared and used as an efficient catalyst for Suzuki cross-coupling reaction. Pd/G/SBA-15 was characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy and infrared spectra. The integration of SBA-15 with graphene-palladium can enhance the stability of graphene-palladium naoparticles and reduce the irreversible agglomerates of graphene. The yields of the products were in the range from 81% to 99.5%.(2) Pd supported on polyamine modified graphene oxide(GO-NH2-Pd2+) was fabricated.A series of biphenyl compounds were synthesized through the Suzuki–Miyaura reaction using GO-NH2-Pd2+ as catalyst. The yields of the products were in the range of 71%- 95%.The catalyst can be readily recovered and reused at least 10 consecutive cycles without significant loss its catalytic activity.(3) An N-heterocyclic carbine-palladium complex(NHC-Pd2+) was immobilized ontothe surface of graphene oxide via a chemical bonding method. The result demonstrated that the GO supported NHC-Pd2+ can act as an efficient catalyst for Suzuki-Miyaura coupling reactions. The yields of the products were in the range of 83%- 96%. The catalyst can be readily recovered and reused at least 6 consecutive cycles without any significant loss in catalytic activity.(4) Well dispersed palladium nanoparticles were successfully encapsulated in the cages of a metal–organic framework, MIL-101, by using a “double solvents” method. Such a fabrication method can effectively avoid the aggregation of palladium nanoparticles on the external surfaces of MIL-101. The as-prepared catalyst, Pd@MIL-101, exhibited high catalytic activity toward the Suzuki–Miyaura and Heck cross-coupling reactions. The catalyst can be readily recovered and reused at least 5 consecutive cycles without significant loss its catalytic activity.