Efficient Electroenzymatic Cascade Catalysis for Ortho-Selective Chlorination of Phenol

The integration of enzymatic catalysis and electrocatalysis is promising for developing new green techniques for chemical production; however, how to coordinate the two processes for one-pot cascade reactions is a challenge. In this work, the electrocatalytic reduction of O2 to H2O2 by a reduced graphene oxide (rGO)/polyethylenimine (PEI) composite to initiate an enzymatic reaction by ionic liquid modified chloroperoxidase (CPO-ILEMB) is presented. The whole cascade process is very efficient due to the four strategies, including avoiding the inactivation of CPO through the competitive reaction of oxidant (H2O2), utilizing nanoproximity effects to construct substrate diffusion channels, fine-tuning the microenvironment of the enzymatic active site by ILEMB to increase the electron transfer efficiency as well as enhance the stability, and improving the selectivity of the 2e-ORR (oxidation reduction reaction) of rGO by PEI. The cascade efficiency is enhanced 5.5 times compared to manually adding H2O2, and 2.3 times compared to free CPO. Moreover, the rapid generation of intermediate (compounds I and X) and the orientation of substrate lead to ortho-selectivity of phenol chlorination.