Carbonic anhydrase (CA) based conversion of CO2 to CaCO3 has been identified as a green and economic strategy to sequester CO2 from flue gas and industrial emissions. The method is, however, cost-intensive as an efficient immobilization method for reusing the enzyme poses a major challenge. In this investigation, the recombinant carbonic anhydrase of polyextremophilic bacterium Bacillus halodurans TSLV1 (rBhCA) has been immobilized on the surface of modified magnetic (silanized) iron oxide nanoparticles (Si-MNPs). The immobilized rBhCA exhibited improvement in alkalistability and retained significantly high activity at elevated temperatures as compared to the free rBhCA. Furthermore, rBhCA immobilized on Si-MNPs could be easily isolated from the reaction by magnetic separation. After 22 repeated uses, the immobilized rBhCA retained 50% of the initial activity and could be stored for 28 days without any loss in activity. rBhCA-Si-MNPs accelerated the onset of CaCO3 precipitation over that of the free enzyme, but the amount of CaCO3 precipitated was not affected, suggesting that the silanized MNPs act as efficient supports for immobilization of CA for utility in CO2 sequestration.