Biohybrid architectures featuring immobilized metallic nanoparticles for catalytic carbon-carbon bond formation

Small crystalline spherical metal nanoparticles were synthesized using an enzyme-induced formation method. For this purpose, lipases immobilized on graphene flakes were used, obtaining graphene-enzyme-metal nanoparticles hybrids (G/Enzyme/s@MetalNPs). Commercial lipases (T. lanuginosus lipase, C. antarctica B lipase, C. rugosa lipase) were combined with different metal salts (Cu, Pd) to prepare heterogeneous catalysts under different systems (single-enzyme/single-metal, dual-enzyme/single-metal and dual-enzyme/dual-metal) at room temperature in aqueous media. Metal nanoparticles size and metal species was influenced by the enzymatic systems used, obtaining from 2 nm to around 10 nm average diameter size nanoparticles, and in the case of Pd, obtaining metallic species or even containing PdO species in the case of using CRL in the bienzymatic system. These hybrid catalysts were tested in C-C bond forming reactions, including C-H activation and Suzuki-Miyaura coupling, under different reaction conditions. In the C-H activation, the hybrid catalysts showed high selectivity for the C-2 arylation. The use of the double-enzyme/single-metal hybrid (G/TLL/CRL@PdNPs) resulted in superior catalytic performance compared to the single-enzyme/single-metal system G/TLL@PdNPs, achieving > 95% product yield in pure methanol at room temperature, with a TOF value of 14.26 h-1. In contrast, G/TLL@PdNPs hybrid showed the greatest activity in the Suzuki-Miyaura reaction with bromoarenes, to selectively produce biphenyl in a water/acetonitrile mixture at 45 °C.