Enhanced electroenzymatic CO2 reduction by a multifunctional ZIF-8 layer on silica nanoflower with immobilized enzyme

Abstract

Carbon capture, utilization and storage have become a hot topic in recent years, and enzymatic CO2 reduction benefits from high selectivity, high efficiency and mild conditions making it promising. However, the low solubility of CO2, poor stability of free enzyme and high cost of coenzyme limit the application. Therefore, mesoporous silica nanoflower (SNF) was used to immobilize formate dehydrogenase (FDH) by electrostatic adsorption followed by the coating of a multifunctional zeolitic imidazolate framework (ZIF-8) layer by sequential coating of Zn2+ and 2-methylimidazole (2-MeIm), thus obtaining a novel integrated nanocatalyst ZIF-8@FDH@SNF. Regulated by controlling the ratio of ligands, the ZIF-8 coating layer not only protected the enzyme and prevented leakage, but also increased the local CO2 concentration using the imidazole group of ZIF-8 which improved the CO2 adsorption by 34.5% compared with SNF. And the expensive NADH was regenerated by the coupled electrocatalysis. The optimized integrated nanocatalyst showed excellent stability and reusability. Highly efficient electroenzymatic CO2 reduction was achieved with 1.38 mM formate yield after 3 h, 48.4% higher than that without ZIF-8 layer.