Accelerated Uptake of CO ₂ Catalyzed by Immobilized Thermophilic Carbonic Anhydrase on Dispersed Aminated Mesoporous Silica

Efficient and durable biocatalysts are important for sustainable CO₂ capture technologies, but enzyme stability often limits their use under harsh process conditions. Here, we evaluate carbonic anhydrases (CAs) adsorbed onto aminated mesoporous SBA-15 as biocatalysts for CO₂ capture under the hypothesis of adsorption-induced thermal stabilization. Carbonic anhydrase from the thermophilic bacterium <i>Persephonella marina</i> (pmCA) and commercial bovine erythrocyte carbonic anhydrase (bCA) were used. Enzyme adsorption isotherms for pmCA and bCA onto the aminated SBA-15 were established, along with desorption tests. Adsorbed and free pmCA and bCA were incubated at 40-90 °C for 14 d. The structural integrity and possibility of amine leaching of the incubated (90°, 14 d) aminated SBA-15 were analyzed by X-ray diffraction (XRD) and NMR spectroscopy. The reaction product speciation in CO₂-loaded catalyzed and uncatalyzed dispersions was monitored using infrared (IR) spectroscopy. The maximum enzyme adsorption capacities were established to be 1.4 ± 0.2 g pmCA·g-aminated SBA-15^-1 and 2.1 ± 0.5 g bCA·g-aminated SBA-15^-1, with no detectable desorption. Adsorbed pmCA and bCA maintained high activity for 14 d at 40-65 °C and for 4 d at 90 °C, whereas free enzymes lost activity within 4 d at all temperatures. The XRD patterns of the heat-treated (90 °C, 14 d) aminated SBA-15 indicated a full collapse of the mesostructure. IR spectroscopy confirmed enhanced HCO₃^- formation in the presence of immobilized CA. Overall, enzyme adsorption onto the aminated SBA-15 significantly improved the thermal stability and activity of pmCA and bCA compared to the free enzymes, demonstrating the potential of adsorbed CAs for biocatalysis.