Immobilized carbonic anhydrase on mesoporous cruciate flower-like metal organic framework for promoting CO2 sequestration

Abstract

CO₂ capture by immobilized carbonic anhydrase (CA) has become an alternative and environmental friendly approach in CO₂ sequestration technology. However, the immobilized CA usually exhibits low CO₂ sequestration efficiency due to no gas adsorption function for the conventional CA supports. Metal organic frameworks (MOFs) are an excellent material for gas adsorption and enzyme immobilization. Herein, a combined immobilization system of CA and ZIF-8 with cruciate flower-like morphology for CO₂ adsorption was prepared for the first time by adsorbing CA onto ZIF-8. The immobilization efficiency was greater than 95%, and the maximum activity recovery reached 75%, indicating the highly efficient immobilization process. The resultant CA@ZIF-8 composites exhibited outstanding thermostability, the tolerance against denaturants, and reusability compared with free CA. Furthermore, we demonstrated for the first time that the shape of ZIF-8 could be controlled by adjusting concentrations of Zn²⁺ ions at the high concentration of 2-methylimidazole (1 M). More importantly, we also demonstrated the applicability of the CA@ZIF-8 composites to the sequestration of CO₂ in carbonate minerals. The yields of the CaCO₃ obtained by using CA@ZIF-8 composites were 22-folds compared to free CA. Thus, this CA@ZIF-8 composite can be successfully used as a robust biocatalyst for sequestration of CO₂.

Keywords: CO(2) sequestration; CaCO(3); Carbonic anhydrase; Immobilization; ZIF-8.