Capture and Sequestration of CO2 by Human Carbonic Anhydrase Covalently Immobilized onto Amine-Functionalized SBA-15

Human carbonic anhydrase (HCA) was immobilized onto mesoporous SBA-15 surfaces that had been covalently functionalized using one of three amine compounds, namely, tris(2-aminoethyl)amine (TAEA), tetraethylenepentamine (TEPA), and octa(aminophenyl)silsesquioxane (OAPS). Amine functionalization over SBA-15 was characterized by XRD, FE-SEM, BET analysis, and 29 Si and 13 C CP MAS NMR spectroscopy. HCA immobilization was verified by FT-IR spectroscopy. The catalytic activity toward hydrolysis of p -nitrophenylacetate ( p -NPA) was calculated for free and immobilized HCA. The k cat values for HCA/TEPA/SBA-15, HCA/TAEA/SBA-15, and HCA/OAPS/SBA-15 were found to be 7182, 7368, and 7569 M –1 s –1, respectively. The activities of immobilized HCA were retained even after long-term storage, exposure to high temperatures, and reuse for 40 cycles. For comparison, CO 2 hydration and sequestration were measured in the presence of both free and immobilized HCA. Importantly, the CO 2 conversion efficiency was calculated using the ion chromatography method. The CO 2 capture efficiency of immobilized HCA was 36 times higher than that of free HCA, and 75% of the initial enzymatic activity was retained through 40 cycles.