Controlled Immobilization of a Palladium Complex/Laccase Hybrid into a Macrocellular Siliceous Host

Abstract

This study investigates the site-directed immobilization of a hybrid catalyst bearing a biquinoline-based-Pd(II) complex (1) and a robust laccase within cavities of a silica foam to favor veratryl alcohol oxidation. We performed the grafting of 1 at a unique surface located lysine of two laccase variants, either at closed (1�UNIK 157 ) or opposite position (1�UNIK 71 ) of the enzyme oxidation site. After immobilization into the cavities of silica monoliths bearing hierarchical porosity, we show that catalytic activity is dependent on the orientation and loading of each hybrid, 1�UNIK 157 being twice as active than 1�UNIK 71 (203 TON vs 100 TON) when operating under continuous flow. These systems can be reused 5 times, with an operational activity remaining as high as 40 %. We show that the synergy between 1 and laccase can be tuned within the foam. This work is a proof of concept for controlling the organization of a heterogeneous hybrid catalyst using a Pd/laccase/silica foam.