Hollow MOF Immobilized Formate Dehydrogenase and Carbonic Anhydrase for Electroenzymatic CO2 Reduction

The main challenges in electroenzymatic CO2 reduction are the low solubility of CO2 and the high cost of the cofactor. Inspired by eukaryotic cell structures, this study designed a hollow zeolite imidazole framework (H-ZIF-8) with the dual functions of capturing CO2 and immobilizing dual enzymes. This platform was coupled with electrochemical cofactor (reduced nicotinamide adenine dinucleotide, NADH) regeneration for enzymatic CO2 reduction. The hollow structure of ZIF-8 retained the activity of formate dehydrogenase (FDH) and carbonic anhydrase (CA) in the obtained FDH&CA@H-ZIF-8, while achieving efficient CO2 reduction using substrate enrichment by CA and ZIF-8. 2-Hydroxy-1,4-naphthoquinone (HNQ) served as an electron mediator in the electrocatalytic step. The electroenzymatic system produced 3.12 mM formate within 3 h, which was 7.3 times that of the free enzyme system. Meanwhile, the immobilized enzyme retained 80.1% of the initial enzyme activity after 8 reuse cycles with high storage stability. This strategy provided an effective platform for addressing the limitations of CO2 solubility and cofactor regeneration in enzymatic CO2 conversion.