Carbonic Anhydrase Enzyme-MOFs Composite with a Superior Catalytic Performance to Promote CO₂ Absorption into Tertiary Amine Solution

Abstract

Carbonic anhydrase (CA) enzyme-based absorption technology for CO₂ capture has been intensively investigated. The main issue related to this novel technology is the activity and stability of the CA enzyme under the typical flue gas conditions. To address this issue, CA enzymes were embedded into zeolitic imidazolate framework (ZIF-L) nanoparticles to synthesize a novel CA/ZIF-L-1 composite. The composite exhibited a superior apparent catalytic activity (1.5 times higher) for CO₂ absorption compared with their free counterparts, which was due to the synergistic enhancement of CO₂ adsorption by support ZIF-L and enzymatic catalysis. The analyses of Fourier transform infrared spectroscopy and circular dichroism revealed that the CA enzyme's secondary structure was not significantly varied during the CA/ZIF-L-1 preparation, resulting in a high enzyme activity retention. Moreover, the CA/ZIF-L-1 possessed a high thermal stability and reusability due to the structural rigidity and confinement of ZIF-L scaffolds. Compared with the free enzyme, its thermal stability was improved by approximately 100% at 40 °C. After six cycles of reuse, CA/ZIF-L-1 still retained a relative activity of 134%. Therefore, the CA/ZIF-L-1 can be a good candidate to promote the CO₂ capture in industrial application.