Dopamine/Polyethylenimine-Modified Silica for Enzyme Immobilization and Strengthening of Enzymatic CO₂Conversion

Enzymatic conversion of CO2 to high-value chemicals is a green route of resource reutilization, which is limited by low solubility of CO2 in mild conditions. Here, silica microspheres were first modified by the co-deposition of polyethyleneimine (PEI) and dopamine and the resultant polydopamine (PDA)/PEI-SiO2 was then used as the strengthening material of the enzymatic conversion of CO2 to formate. The initial reaction rate increased from 13.4 to 27.2 times with the loading amount of PDA/PEI-SiO2 increasing from 0.1 to 0.4 g. Following that, PDA/PEI-SiO2 was used as the carrier for the immobilization of carbonic anhydrase (CA). As a result of synergism, the formate synthesis was accelerated up to 48.6 times with a low loading amount of 0.2 g of PDA/PEI-SiO2-CA. Although the promoting effect of PDA/PEI-SiO2 retained only 56.1% after being used once, PDA/PEI-SiO2-CA retained 95.1% activity after 10 cycles of use. It was presumed that CA boosted the impact and reusability of PDA/PEI-SiO2 by improving CO2 desorption. This work is much significant in providing a simple and high-efficiency strategy for process intensification of enzymatic CO2 conversion.