Electroenzymatic CO₂ Reduction Through Hollow Covalent Organic Framework-Immobilized Enzyme With Neutral Red-Modified...

To meet the global pursuit of carbon neutrality, electroenzymatic reduction of CO₂ has been a potential technology that can convert CO₂ into useful chemicals or fuels. However, the low solubility of CO₂ in water inhibits the reaction rate, and free enzyme suffers from poor stability and reusability and requires the expensive cofactor NADH. Herein, a spherical covalent organic framework (COF) TPB-DMTP was synthesized for both CO₂ enrichment and enzyme immobilization. The electron mediator neutral red was covalently attached to a carbon paper electrode for electrochemical NADH regeneration, thereby avoiding damage to the enzyme. The constructed electrocatalytic NADH regeneration was coupled with enzyme-catalyzed CO₂ reduction. After immobilizing formate dehydrogenase (FDH) in the COF, the CO₂ was enriched near the enzyme molecules, and the stability and reusability of enzyme were enhanced. The optimized system produced up to 2.312 mM formate, which was 4.01 times that of the free enzyme system.