Electroenzymatic CO2 reduction using dual enzymes encapsulated in Zn-MOF-74

The capture and conversion of CO 2 to valuable products has garnered significant attention. The electroenzymatic reduction of CO 2 is of particular interest owing to its high selectivity and yield. However, this process is hindered by various challenges, such as the low CO 2 solubility in water and the requirement for efficient cofactor regeneration. In this work, we developed a green, water-based, room-temperature synthesis of Zn-MOF-74 for enzyme immobilization. Formate dehydrogenase (FDH) and carbonic anhydrase (CA) are co-encapsulated within the Zn-MOF-74 framework to create a dual enzyme cascade system. This strategy effectively enhances enzyme proximity, stability, and reusability to subsequently promote the enzyme cascade reaction efficiency. Additionally, the adsorption of CO 2 by CA improves the solubility of CO 2 in water. NADH regeneration is achieved using an electron mediator, 2-hydroxy-1-naphthoquinone. The optimized electroenzymatic system achieved a formate yield of 3.01 mM within 3 h, 4.98 times higher than that of the pristine free enzyme system and 2.27 times higher than the free enzyme system with NADH regeneration. Schematic illustration of electroenzymatic CO 2 reduction by Zn-MOF-74 encapsulated dual enzyme (FDH&CA@Zn-MOF-74) • Mild preparation of MOF immobilized FDH and CA for dual enzyme cascade system. • The adsorption of CO 2 was enhanced by Zn-MOF-74 and CA. • Immobilized enzymes had high stability and reusability. • NADH regeneration combined with enzymatic reactions for efficient CO 2 reduction. • Co-immobilization shortened the spatial distance of enzymes to enhance reaction.