A mediator-free enzyme carbonaceous cathode for bioelectrocatalysis reduction of furfural into furfuryl alcohol

Abstract

The valorization of biomass derivatives into fine chemicals through the electro-enzymatic catalysis combination routes under green chemistry scopes has a promising prospect. However, bottlenecks including poor electron transfer efficiency between the electrode surface and electron mediators, inefficient regeneration of cofactors, and the high cost of enzymes and electron mediators still hindered the realistic applications. Herein, to address the abovementioned technical barriers, an electron mediator free bioelectrocatalytic system that integrates the electrochemical NADH regeneration and enzymatic reaction was suggested based on a novel orderly assembled composite bioelectrode consisted of conjugated structure of a covalent organic frameworks (COFs, namely TpBD) that inside encapsulating co-factor dependent oxidordeuctase. The as-prepared composite bioelectrode was further applied for the highly selective hydrogenation of furfural into furfural alcohol. Results indicated that electron pathway involved in the TpBD conjugated structure guaranteed the effective co-factor regeneration on the composite bioelectrode without the assistant of costly electron mediators, and consequently promoted the enzymatic reduction of furfural. Considerable high furfural conversion (98.94%) was realized accompanied by remarkable furfural alcohol selectivity of 90.13% at -1.4 V (vs Ag/AgCl). The novel composite bioelectrode also showed good stability and reusability. Up to 88.1% of the original furfuryl alcohol selectivity was preserved after 10 times of recycling. This work presents a promising green alternative route for the valorization of furfural, which also shows great potential extending to valorize other renewable biomass derivatives.