Polyethylenimine-Modified Membranes for CO2 Capture and in Situ Hydrogenation

Enzymatic CO2 reduction can provide value-added chemicals from greenhouse gases at ambient temperature and pressure. However, poor solubility of CO2 results in a low conversion rate. In this work, polyethylenimine (PEI) was attached onto the surface of poly(acrylic acid)-grafted (PAA-grafted) polyethylene membranes, and then, the membranes were used in an integrated process of CO2 capture and in situ hydrogenation. Modification conditions were optimized with a surface amino group density of PEI-modified membranes as the characteristic parameter, and then, SEM, FTIR, and XPS analyses were conducted. The effect of PEI-modified membranes on enzyme-catalyzed CO2 conversion to formic acid, regeneration conditions, and reusability were studied. The results show that when the grafting ratio of PAA increased, surface amino group density of PEI-modified membranes increased up to 6.00 × 10–7 mol/cm2 and then kept constant. The optimum modification time, temperature, and PEI concentration were 40 min, 40 °C, and 0.3...