Enzyme-Induced Nanocavity Formation in Leaf-Shaped Zeolitic Imidazolate Frameworks for Functional Entrapment of Carbonic Anhydrase.

Abstract

Immobilizing carbonic anhydrases for CO₂ hydration holds great promise for efficient carbon capture. However, understanding how immobilization affects enzyme activity and host material structure is crucial for advancing this strategy. Here, we investigate the structural and functional consequences of entrapping <i>Persephonella marina</i> carbonic anhydrase (PmCA) within leaf-shaped zeolitic imidazolate frameworks (ZIF-L). Our results reveal that PmCA retains its activity - and, therefore, its structural integrity - after entrapment. Interestingly, while ZIF-L retains its crystallinity, the presence of ∼5-nm nanocavities suggests a structural adaptation of the framework to accommodate the enzyme. Considering the size mismatch between the pore size of ZIF-L (∼5 Å) and the diameter of PmCA (∼5 nm), the formation of such cavities is likely associated with defect generation and surface-mediated incorporation rather than conventional pore diffusion. By integrating detailed structural analysis with functional assay, this study uncovers insights into the underlying structural phenomenon, advancing our understanding on enzyme-incorporated biocatalytic systems.